ABSTRACT. The study of the occurrence, fate and effects of micro- and nanoplastics (MNPs) has its origins in the field of environmental analysis, with the first observations of MNPs reported for the aquatic (marine) environment. Gradually, the idea has taken hold that we as humans are also exposed to these tiny particles. While it was already difficult to reliably quantify MNPs in environmental matrices, accurately measuring the multitude of polymer materials in different sizes and shapes in human samples proved to be a major challenge, although this field is developing very rapidly. Currently, pyrolysis gas chromatography mass spectrometry (Py-GC-MS) is the most promising technique, partially due to its throughput, but also due to its suitability to study particle sizes in the nanometer range, depending on the sample preparation. The power and potential of Py-GC-MS has already been amply demonstrated in other areas of research, such as forensics, material sciences, biomass conversion and also for the analysis of organic materials in artworks and archaeological artifacts. Building on best practices from these fields, we explored the application of Py-GC-MS to address the complexity of measuring MNPs in human blood. Recently, we have been working on the development of our methodology by enhancing the quality and reliability of our data. Initially, method development was hindered by the limited availability of suitable analytical standards and the absence of certified reference materials which still are lacking. This has led us to study the quantification reliability in relationship to the choice of pyrolysis settings and pyrolysis markers, as well as the choice of analytical standards of different particle sizes and characteristics like endcapping, tacticity, chain braining. Furthermore, we prepared our own internal reference materials for quality assurance and quality control. We used multivariate and machine-learning techniques to identify the most robust set of variables for polymer identification and quantification, while minimizing the impact of co-pyrolysis and matrix effects. Finetuning the enzymatic and chemical digestion protocols and the sequential cleanup steps supported the overall method performance. Apart from instrumental and sample preparation aspects, background contamination control is one of the most important factors to obtain reliable quantitative exposure data. In addition, sample quality is key: typically, archived samples in human biobanks are stored in plastic containers. To assess whether these valuable samples can be used for retrospect analysis and epidemiological studies, contamination of the sample with the container material have been studied. In the meantime, based on our lessons learned, we are expanding our working area to other fields of exposure assessment, with sample preparation methods tuned for cow and human breast milk and human organs in order to study the distribution of MNPs in the human body. With our efforts, we aim to contribute to the advancement of human internal exposure assessment, and to help unravel the eventual causality between MNP exposure and adverse health outcomes.

ABSTRACT. Pyrolysis is a strategic enabling technology in biorefinery concepts, offering a flexible multi-product platform for the simultaneous production of biochar, bio-oil and gaseous fuels. However, the mechanisms governing biochar stabilization during pyrolysis are still predominantly interpreted in terms of final temperature, while the role of heating rate (HR) and solid residence time (t) at the final temperature remains insufficiently elucidated. These parameters directly influence the devolatilization dynamics, secondary reactions, degree of aromatization and establishment of “turbostratic” order, and the interaction between organic carbon and mineral matter, particularly in feedstocks with markedly different ash contents such as forestry and herbaceous residues [1]. This study aims at investigating the effect of HR and t at different final temperatures in both slow and fast pyrolysis regimes (∼0.1−1 °C/s and ∼100−1000 °C/s, respectively) on the chemical and physical properties of the biochar, with a focus on those related to its persistence. Poplar and giant reed, differing in the content of both organic components and ash, were selected as representatives of different classes of residual biomasses, namely woody and herbaceous biomasses. The biomass samples underwent pyrolysis tests experiencing different thermal histories (HR and t) representative of the operating conditions typical of slow and fast pyrolysis in the temperature range 500-700 °C. The experimental campaign was carried out in a thermogravimetric analyzer and in bench-scale batch reactors (Figure 1). The chemical and structural properties of the produced biochars (H/C ratio, chemical functionalities, structural order) [2] were analysed and discussed in relation to their implications for biochar persistence. In parallel, the liquid and gaseous products were characterised through chromatographic techniques [3] to provide deeper insight into the transformation pathways of organic carbon within the solid matrix. By addressing the combined effects of solid residence time and heating rate on biochar physicochemical properties linked to persistence, this study contributes to a more mechanistic understanding of pyrolysis within integrated biorefineries and supports the rational design of processes that optimize both energy co-products and long-term carbon sequestration performance.

Figure 1 – Reactors for (a) slow and (b) fast pyrolysis tests

References: [1] Giudicianni et al., 2020. Inherent metal elements in biomass pyrolysis: a review. Energy fuels, 35(7), 5407-5478. [2] M. Bartoli et al., 2022. Effect of heating rate and feedstock nature on electrical conductivity of biochar and biochar-based composites. Appl. Energy Combust. Sci., 12, 100089. [3] Gargiulo et al., 2022. Insights about the effect of composition, branching and molecular weight on the slow pyrolysis of xylose-based polysaccharides. J Anal. Appl. Pyrolysis, 161, 105369.

ABSTRACT. Hemp is a fast-growing annual plant cultivated worldwide for use in multiple sectors. Hemp fibres are used for textiles and paper production, seeds for food and animal feed, shives are applied in construction materials, and flowers and leaves, through the extraction of cannabidiol (CBD), serve the pharmaceutical industry. In Western Europe, hemp cultivation is primarily focused on CBD production, leaving the remaining stem components, such as fibres and shives, as low-value by-products or waste. These untreated stems are commonly applied as fertilizer or used for energy generation, although such uses provide limited added value. Alternatively, this biomass could be incorporated into value-added processes in line with circular economy and sustainability principles. Growing societal interest in renewable resources and biobased materials as substitutes for fossil-based products has encouraged the exploration of new biomass valorization pathways. One promising approach for upgrading hemp residues is their thermochemical conversion into biochar. The physical and chemical characteristics of biochar can be tailored through adjustments in feedstock selection and process parameters. Slow pyrolysis is an effective technology for biochar production and is suitable for a wide range of biomass types. However, although higher pyrolysis temperatures generally enhance biochar quality, they also reduce solid yield while increasing gas production, resulting in significant quantities of volatile by-products. Efficient utilization of these by-products is therefore essential to improve the overall sustainability and efficiency of the biochar production process. This study focuses on the characterization and valorization of residual hemp biomass through slow pyrolysis. The volatile products generated during hemp carbonization were analyzed using several analytical techniques (TGA, UV–VIS, TLC, Flash Prep-LC, UHPLC, and QTOF-MS) to understand pyrolysis mechanisms and identify the chemical compounds formed. The process yielded 29% solid carbon and produced gaseous emissions rich in phenolic and furanic compounds, which were collected in four temperature-dependent fractions (F1: 20–150 °C, F2: 150–250 °C, F3: 250–400 °C, and F4: 400–1000 °C). The condensed liquids were further separated into subfractions via flash chromatography. The total phenolic content varied among fractions but showed no direct correlation with either increasing temperature or decreasing pH. Nevertheless, fractions F1, F3, and F4 contained predominantly phenolic compounds, such as guaiacyl and syringyl derivatives originating from lignin decomposition, and demonstrated antioxidant activity. A positive relationship was observed between pyrolysis temperature and detectable phenolic content, reflecting the sequential thermal degradation of hemp’s chemical constituents. Overall, a comprehensive understanding of the chemical profile of hemp pyrolysis products enables the identification of viable valorization pathways and highlights the economic potential of this currently underexploited biomass.

ABSTRACT. The pyrolysis of lignocellulosic biomass plays a key role in the development of sustainable thermochemical routes for the production of renewable fuels, chemicals, and carbonaceous materials. However, the intrinsic complexity of this feedstock poses significant challenges to the development of kinetic models capable of predicting devolatilization behavior and product speciation for real biomasses. Lignocellulosic biomass is composed of cellulose, hemicellulose, and lignin, found in highly variable proportions. While the pyrolysis of these individual components has been widely investigated, it is still debated whether in mixtures these constituents behave independently, or synergistic effects are present. This unresolved issue impacts the ultimate goal of describing the pyrolysis behavior of real biomass pyrolysis, questioning whether it can be described as the simple superposition of the kinetics of its main components, considered as independent sub-reactive systems. This study starts with the experimental investigation of rice husk pyrolysis by thermogravimetric analysis coupled with mass spectrometry (TG–MS), providing detailed information on devolatilization behavior and product speciation. The rice husk sample was then characterized through chemical fractionation allowing the quantification of its constituents. The pyrolysis behaviours of the single constituents were then combined as the weighted sum of their contributions according to the fractionation results and directly compared with the experimental evidence obtained for rice husk. The comparison shows that the additive approach satisfactorily reproduces both the overall devolatilization profile and the main trends in product speciation, with only minor discrepancies. However, the limits of validity of this hypothesis are still unclear. For this reason, physical mixtures of single biomass components were used as a tool to investigate the boundaries of additive behavior and to identify possible systems in which interactions become relevant. Binary and ternary mixtures of cellulose, hemicellulose, and lignin were studied by TG–MS and the experimental behavior of the mixtures was systematically compared with the predicted one, obtained as the weighted sum of the individual component contributions. The results indicate that the additivity assumption holds for most of the investigated systems, especially for mixtures involving only cellulose and hemicelluloses, which show devolatilization profiles and product yields very close to the additive predictions. Deviations become more evident in mixtures containing lignin and are particularly pronounced for the cellulose–lignin system, which exhibits increased char formation, a shift of the main devolatilization peak toward higher temperatures, and a reduced volatile release. The ternary mixture shows trends consistent with those observed in the binary systems, confirming that the main source of non-additive behavior lies in the cellulose–lignin interaction region. Overall, this work provides a quantitative assessment of whether the kinetics of cellulose, hemicellulose and lignin can be used as independent building blocks to describe the pyrolysis behavior of real biomasses and single components mixtures. Experiments showed discrepancies between the two scenarios, suggesting the onset of different physicochemical phenomena. Further measurements with advanced mixtures (e.g. pelletization, ball milling) are ongoing. These results can help in defining the domain of applicability of the additive hypothesis in kinetic models and support their reliable use for predictive simulations of complex lignocellulosic feedstocks.

ABSTRACT. Pyrolysis coupled with gas chromatography–mass spectrometry (Py–GC–MS) is widely used for the characterisation of solid and insoluble materials that are difficult to introduce directly into GC–MS systems, including polymers, paper, and other complex matrices.

However, pyrograms generated from these materials are often highly complex, with extensive coelution observed when using one-dimensional gas chromatography (1DGC). In addition, detailed manual comparison of individual peaks becomes impractical, particularly when screening recycled materials of diverse composition.

In this study, pyrolysis coupled with comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (Py–GC×GC–TOF MS) is applied to improve the separation of complex materials. The additional chromatographic dimension enhances resolution of coeluting compounds and provides clearer grouping of compound classes, enabling more straightforward sample characterisation.

To efficiently handle the high data density, we employ tile-based chemometric methods, which divide the 2D chromatograms into manageable segments (“tiles”) for automated, statistically robust comparison. This method highlights meaningful compositional differences between samples, reduces the need for labor-intensive manual inspection, and allows systematic analysis of subtle variations across multiple materials.

By combining Py–GC×GC–TOF MS with chemometric analysis, this methodology offers a systematic approach for characterising, comparing, and assessing the quality of complex solid materials, including tyres, plastics, and paper. It is particularly valuable for evaluating recycled or waste-derived materials, supporting sustainable material management.

ABSTRACT. Microplastics (MPs), defined as plastic particles ranging from1 µm to 5 mm, are found scattered across various environments, impacting resident biota. Their hazard lies not only in their physical dimensions but also in their chemical additives used during manufacturing. Agriculture significantly contributes to the proliferation of these pollutants through the intensive use of mulching films, irrigation systems, and greenhouse coverings. To mitigate MP accumulation, the European Union, through Commission Delegated Regulation (EU) 2024/2787 [1], promotes replacing conventional mulching plastics with biodegradable materials. However, bioplastics often fail to degrade completely under natural conditions, leading to the emergence of biodegradable microplastics (BMPs). This study investigates the presence of MPs in agricultural soils from Almería (Spain), which hosts the highest concentration of greenhouses in Europe. A wide range of both conventional polymers and biopolymers was determined, including polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), nylon-6 (N6), polycarbonate (PC), polyethylene terephthalate (PET), polyurethane (PU), polystyrene (PS), as well as polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polycaprolactone (PCL) and poly-3-hydroxybutyrate (P3HB). A pre-digestion step using Fenton reagents (H2O2 and FeSO4·7H2O) was employed to reduce organic matter, followed by density separation with ZnCl2. A double density separation was performed to ensure accurate MP recovery. After separation, samples were filtered through cellulose nitrate filter (1 µm). Finally, filters were homogenized using a cryomill and submitted for analysis. After that, a novel analytical method was applied using thermoanalytical techniques as an alternative to traditional spectroscopic methods like FTIR or Raman. The approach employs pyrolysis and gas chromatography coupled with mass spectrometry (Py-GC/MS) in Selected Ion Monitoring (SIM) mode to identify and quantify the MPs evaluated. The optimized method was fully validated evaluating selectivity, linearity, recovery and precision. Validation performance was adequate for most compounds with values ranging from 0.05 to 0.25 mg. Finally, the method was applied to the analysis of 20 agricultural soils from different origins: greenhouse and extensive fields. Samples showed a clear trend, finding a high prevalence of PP and PE, suggesting a connection between agricultural practices and the MPs found. In addition, some biopolymers were also found, such as PLA, highlighting the importance of monitoring such compounds.

This publication is part of project PID2022-137122OB-I00, funded by MICIU/AEI/10.13039/501100011033/ and ERDF, EU. Encarnación López Rodríguez acknowledge grant FPU21/00858, funded by MICIU/AEI/10.13039/501100011033 and ESF+. Jesús Marín Sáez acknowledges the Andalusian government, the Counselling of University, Investigation and Innovation (CUII) and European Social Fund plus (Andalusia ESF+ 2021–2027) for financial support (POST_2024_00151).

[1] European Commission. Delegated Regulation (EU) 2024/2787 of 23 July 2024 amending Regulation (EU) 2019/1009 of the European Parliament and of the Council regarding the inclusion of mulch plastics in category 9 of constituent materials. 2024. https://doi.org/10.2873/23399

ABSTRACT. A new analytical procedure for the quantification of small amount of polyethylene (PE) in compostable bioplastics blends using evolved gas analysis coupled with mass spectrometry (EGA-MS) is here reported. In recent years, the production of compostable bioplastics has become a key aspect for the ecological transition. Bioplastics are increasingly replacing conventional plastic items, in particular disposable plastic products such as shopping bags or packaging1. Bioplastics are produced as blends of many components and small amount of non-biodegradable polymers, mainly PE, are added to improve properties and reduce production costs. European standards, as EN 13432:2002, establish that the maximum allowed amount of PE in compostable bioplastic blends is 1% in weight of the final product2. Quantification of PE in bioplastic formulation is fundamental to ensure conformity with regulations, but no standardized analytical protocol is available. Recent literature showed that analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS)3 is a suitable technique to quantify small amounts of PE in complex blends. However, the technique is time-intensive and can rarely match the time pressure of bioplastic production plants or industrial composting facilities. In this study, we propose a faster method based on EGA-MS. It allows the quantification of small amounts of PE to be done thanks to an innovative strategy based on a mid-run split switch, which increases the signal of PE despite its low content (Figure 1). The method was developed using bioplastic blends with known amounts of PE, specifically produced for this study. Once developed, the method was tested on commercially compostable shopping bags, and the results were compared with those obtained by Py-GC/MS. We also improved this methodology by switching the mass spectrometer off when bioplastics exit the system and then turning it on only for PE analysis: this allows us to preserve the instrument and to make the analysis faster. Both the methods are robust, efficient, and suitable to perform rapid quantification of PE even for large sample numbers.

Figure 1: Ion thermogram at m/z 71 for sample 0% PE, 1.0% PE, 5.01% PE

References: 1. Coralli, I., Rombolà, A. G. & Fabbri, D. Analytical pyrolysis of the bioplastic PBAT poly(butylene adipate-co-terephthalate). J Anal Appl Pyrolysis 181, (2024). 2. Rizzarelli, P. et al. Determination of polyethylene in biodegradable polymer blends and in compostable carrier bags by Py-GC/MS and TGA. J Anal Appl Pyrolysis 117, 72–81 (2016). 3. Mattonai, M. et al. Quantification of polyethylene in biodegradable plastics by analytical pyrolysis-based methods with GC split modulation. J Anal Appl Pyrolysis 191, (2025).

ABSTRACT. Ekotrend has developed a new low-temperature biomass pyrolysis technology using PyroFriction technology, i.e. liquid-phase pyrolysis employing a cavitation pump. The process is carried out at a temperature of approximately 300–350 °C; however, the actual process temperature, which cannot be directly measured, is most likely several tens of degrees higher due to intense friction forces and the collapse of cavitation bubbles. The technology is capable of processing any type of biomass with a moisture content below 20% and a particle size below 5 mm. To date, production-scale tests have been conducted using straw, wood sawdust, pistachio shells, pomegranate peels, and sunflower husks. There is also potential for processing plastic waste; however, this is not currently the subject of research. The process is supported by commercial catalysts such as zeolite 4A, as well as naturally occurring mineral substances present in the feedstock. The main products of the process are high-quality bio-oil and biochar, and the relatively low process temperature results in a negligible amount of gaseous products. After 12 years of experience, the company is preparing to convert a demonstration plant with a capacity of 1 tonne of biomass per hour into a fully commercial installation with higher throughput.

ABSTRACT. Nowadays, catalytic co-hydropyrolysis of biomass and plastic is considered an enjoyable process for obtaining value-added precursors for obtaining sustainable aviation fuel production. Thus, some potential catalysts derived from a Chilean natural zeolite after an acid treatment (HCl, 2.4 M) and metal impregnation with Ni, Co, and Ni/Co were evaluated for upgrading evolved volatile pyrolysis streams. Then, the aim was to explore how acid modification and metal incorporation influenced the structural, acidic, and textural properties of the obtained catalysts and their influence on the chemical distribution of evolved gases during co-hydropyrolysis of Chilean Oak and HDPE/LDPE, using an analytical pyrolysis system coupled to gas chromatography–mass spectrometry (Py-GC/MS). The Py-GC/MS system provides rapid screening of gaseous chemical composition, enabling assessment of catalytic effects through detailed identification of chemical species, including hydrocarbons, oxygenates, aromatics, and fuel-range fractions. Such a setup (Py-GC/MS) enabled reliable comparisons of catalyst contributions, accounting for negligible mass-transfer limitations and secondary reactions, and allowing data recollection for mechanistic interpretation of catalytic performance.

The acid treatment of the Chilean natural zeolite (ZN) led to a notable increase in surface area (from 213 to 439 m²/g) and enhanced mesoporosity, resulting in a higher Si/Al ratio (+33%), as confirmed by N₂ physisorption and XRF. Moreover, the modification also removed aluminium (extra-framework and framework) and decreased the concentrations of inorganic impurities (Na, Ca, Fe, Mg, K), thereby improving acid site accessibility. SEM-EDX analysis revealed increased surface roughness, enlarged pores, and homogeneous distribution of the impregnated metals on the modified zeolite (ZH2.4). XRD analysis confirmed that the crystalline structure was not affected by acid treatment and metal impregnation. Thus, monometallic catalysts showed NiO and Co₃O₄ reflections. In contrast, the bimetallic NiCo/ZH2.4 catalyst additionally exhibited characteristic peaks of the mixed spinel phase NiCo₂O₄, suggesting structural integration of Ni and Co.

Furthermore, the H₂-TPR profiles of NiCo/ZH2.4 exhibited an intense and readily accessible reduction feature, likely due to hydrogen spillover and the formation of mixed-metal phases. Additionally, NH₃-TPD experiments confirmed that metal incorporation modified the surface’s acidity: Ni promoted medium-strength acidity, Co preserved strong acid sites, and NiCo/ZH2.4 presented a balanced acid distribution favourable for bifunctional acid–metal reactions. Py-GC/MS runs at 550°C showed that NiCo/ZH2.4 catalyst substantially enhanced hydrocarbon production, specifically alkanes, while reducing oxygenated compound families. This catalyst exhibited the highest selectivity toward Jet Fuel–type hydrocarbon fractions, evidencing a strong acid–metal synergy. Thus, registered results indicate that applied pre-treatments (acid modification and bimetallic impregnation) successfully improve catalytic performance in biomass/plastic co-hydropyrolysis. Finally, among all samples, the NiCo/ZH2.4 catalyst exhibited remarkable physicochemical properties and product selectivity, consolidating its potential for sustainable aviation fuel production using mixed waste feedstocks in thermochemical processes.

ABSTRACT. Paper sludge (PS) is a solid waste generated in large quantities by the papermaking industry. PS contains fine minerals and lignocellulosic biomass, which can be recycled to recover circular minerals and produce bio-based chemicals. This contribution presents our latest study on the ex-situ catalytic pyrolysis of PS to bio-based benzene, toluene, and xylene (bio-BTX) in a newly developed staged free-fall reactor using three commercial catalysts, including E-cat, Pt/Al2O3, and H-ZSM-5. The pyrolysis liquid products were analyzed in detail by GC-TCD, GC-FID, GC×GC-FID, elemental analysis, Karl Fischer (KF) titration, total acid number (TAN), and gel permeation chromatography (GPC). The fresh, used, and regenerated catalysts were characterized by BET, NH₃-TPD, TGA, and XRD. Reaction-regeneration cycles were performed to investigate the catalyst reusability after regeneration. Results showed that H-ZSM-5 catalyst exhibited the highest BTX carbon yields of 4.14 C.%, compared to 1.84 C.% for Pt/Al2O3, 1.46 C.% for E-cat, and 0.39 C.% for no catalysts. TAN of the oil phase decreased from 171 mgKOH gsample-1 for Pt/Al2O3 to 108 mgKOH gsample-1 for H-ZSM-5, in accordance with the decreased concentration of the free fatty acids in the oil phase from 14.6 wt.% for Pt/Al2O3 to 0.5 wt.% for H-ZSM-5 catalyst. This indicates that H-ZSM-5 can effectively convert oxygenated intermediates, e.g., free fatty acids, into BTX. A techno-economic assessment (TEA) showed that the bio-BTX yield was one of the most important factors influencing the economic viability. This study presents an industrially feasible technical method for the ex-situ catalytic pyrolysis of PS to produce BTX and supports the development of sustainable catalysis in the field of circular carbon conversions.

ABSTRACT. A machine learning (ML) and optimisation tool is developed to improve the maximum quantity of pyrolysis oil produced from plastic waste. This is based on an extensive, curated experimental dataset of 148 trials across eight types of plastic, using both ultimate and proximate analytical methods, along with operational conditions including temperature, residence time, and heating rate. The four ML models: Gaussian Process Regression (GPR), Support Vector Machine, Random Forest, and Decision Tree were used in combination with Genetic Algorithm (GA) and Particle Swarm Optimisation (PSO) for selecting features and determining hyperparameters. Results show that GPR with GA outperforms all other combinations, achieving a coefficient of determination (R2) of 0.912 on the training set and 0.827 on the test set, and substantially lower root mean squared error than the other combinations. Partial Dependence, Sobol Sensitivity Indices and Shapley Additive Explanations (SHAP) demonstrate that the most influential factors controlling the variation in yield are carbon content, volatile matter, and temperature, whereas high oxygen content, fixed carbon, moisture, and excess heat can significantly reduce liquid yields. Monte Carlo simulations provide an estimated mean predicted yield of approximately 42% with relatively large but stable predictive interval estimates. Additionally, a graphical user interface for predicting independent laboratory experiments and literature studies was successfully implemented, utilising the GA-GPR combination model, with errors of less than about 6%, demonstrating potential for application. Overall, this work demonstrates a transparent, data-driven methodology for selecting relevant features, calibrating ML models, and estimating uncertainty for plastic pyrolysis, and establishes a platform for transferring these tools to develop a real-time optimiser and integrate them into larger datasets and environmental assessments.

ABSTRACT. The rising production of plastic waste has driven the search for effective utilization routes. Pyrolysis offers a promising solution to converting waste plastic into available high-value products, fuels or chemicals. To increase the quality and durability of plastics, various additives are used, such as pigments, stabilizers, fillers and others, which positively affect the properties of plastics. However, at the end of the plastic life cycle, additives may positively or negatively affect the yield and quality of pyrolysis products. In this study, the most common plastics and additives were selected, and the influence of naturally occurring additives on the yield and quality of products during thermo-catalytic pyrolysis over HZSM-5 was evaluated. Waste plastics commonly contain a combination of different additives, so this study also examines the influence of the additive’s combination. In the thermo-catalytics pyrolysis of waste plastic mixtures, additives can lead to catalyst deactivation through the reduction of acid-site activity. Nevertheless, additive combinations may relieve these negative effects while allowing controlled enhancement or suppression of aromatic compound formation. The exception is carbon black, which significantly increased the formation of monoaromatic hydrocarbons.

ABSTRACT. In 2024 alone, global plastic production reached approximately 430.9 million tonnes, yet less than 10% is recycled globally. While mechanical recycling is effective for clean, single-polymer streams, it performs poorly for mixed and contaminated plastics, which are typical for e.g. municipal waste. Chemical recycling, particularly pyrolysis, has therefore emerged as a necessary alternative, offering a practical compromise between economic viability and product quality. However, scaling pyrolysis reactors to industrial capacities remains challenging, largely due to the prohibitive cost of large-scale experimentation. As a result, numerical simulation has become indispensable for reactor design and process optimization, although many existing models rely on oversimplified representations of polymer conversion. A critical but frequently overlooked factor in plastic pyrolysis modeling is the inherently low thermal conductivity of polymers. In industrial applications, shredded plastic particles typically range from millimeters to centimeters in size and effectively behave like thermal insulators. Consequently, overall conversion is governed not only by intrinsic reaction kinetics but also by intra-particle heat conduction. Despite this physical reality, most computational studies employ homogeneous (0D) particle models that assume uniform internal temperature. This assumption neglects the dominant, rate-limiting role of internal heat transfer and can lead to substantial errors for predicting reactor performance. In this work, we address this limitation by systematically quantifying the predictive error of the 0D assumption through direct comparison with a particle-resolved model (1D) that explicitly captures internal temperature gradients. The results show that the conventional 0D model consistently overestimates both particle heating and conversion rates. Moreover, this discrepancy is not constant: it increases markedly with particle size, reactor temperature, and external heat transfer coefficient, conditions typical of industrial reactors, under which the assumption of thermal uniformity breaks down entirely. We propose a novel correction framework to bridge the gap between the computational efficiency of lumped-capacitance (0D) models and the physical fidelity of particle-resolved simulations. By analyzing the 0D model's error relative to the Pyrolysis number (Py) and Biot number (Bi), we derive a correction factor that accounts for intra-particle thermal lag. This factor reduces the heating rate predicted by the 0D model to align with particle-resolved solutions. The magnitude of this correction is modeled by fitting the discrepancy between the two approaches as a function of Py and Bi. This new model allows the 0D approach to replicate the accuracy of particle-resolved simulations while requiring a fraction of the computational cost. This advancement is particularly valuable for three-dimensional Euler-Lagrange simulations of large-scale reactors, where resolving the internal temperature profiles for millions of particles is computationally prohibitive. Ultimately, the proposed methodology offers a broadly transferable framework for the accurate modeling of other thermally-driven particle conversion processes where internal gradients are significant, such as biomass pyrolysis and solid fuel combustion, thereby facilitating more reliable virtual prototyping of next-generation recycling technologies.

ABSTRACT. Bark is an abundant forestry by-product that is commonly downcycled or burned for energy, despite its heterogeneous composition and high mineral content, which can limit its combustion performance. At the same time, bark is chemically rich, containing high amounts of lignin and polyphenolic extractives, which enables cascade schemes where valuable extractives are recovered first, and the residual solid is upgraded through pyrolysis. In this study, the focus is on the biochar step of a cascaded valorisation route for oak (Quercus robur) bark and evaluating how upstream extraction pretreatments affect the composition and structure of the resulting biochar. Residual bark solids obtained after (i) hot-water extraction, (ii) ultrasound-assisted hydroalcoholic extraction (water–ethanol), and (iii) alkaline aqueous extraction (1% NaOH) were dried and carbonized by slow pyrolysis in a tubular furnace under nitrogen (300 L h⁻¹) at 800 °C for 30 min (heating rate 1500 °C h⁻¹). The produced biochars were mechanically ground and sieved (106 µm mesh) to homogenize the fraction used for analysis. Biochars are characterized via proximate analysis (volatiles/ash), CHNO elemental analysis, N₂ physisorption (BET surface area; BJH pore size), laser-diffraction particle sizing, and FTIR-ATR to qualitatively assess surface functionalities. Across pretreatments, carbon contents fall in the 68–72% range with low H and N (±1%), while ash contents remain comparatively high (13–16%). Textural properties are moderate, with BET surface areas about 19–55 m²g⁻¹ and average pore widths in the mesoporous range (±6–19 nm). Alkaline pretreatment tends to yield a more carbonized material (higher C, lower O) but with higher ash and lower developed surface area, while the solvent-based routes can increase surface area and larger average pores. FTIR spectra are consistent with high-temperature carbonization, showing limited intensity of oxygenated functional group bands. Overall, the study supports pretreatment-guided tailoring of bark-derived biochars within a cascade biorefinery framework. Ongoing work is increasing replication and benchmarking adsorption/soil-relevant performance to establish robust structure–function relationships for environmental and materials applications.

ABSTRACT. Thermal ejection may play a key role in the formation of primary volatiles from biomass fast pyrolysis. As the first in the field, this study proposes a new method based on the tracers that are only present in the ejected aerosols or the evaporated vapours, in order to determine the true yields of the ejected aerosols and the evaporated vapours in the condensable volatiles (so-called tar) produced from cellulose pyrolysis in a wire mesh reactor at 600 °C and 1 – 1000 K/s. The results show that some non-volatile compounds (i.e., cellotriosan, cellotetraosan and cellopentaosan) are only present in the ejected aerosols with similar collection efficiencies, while volatile compounds such as 5-hydroxymethylfurfural are only present in the evaporated vapours with high collection efficiencies (>90%). Consequently, the true yields of the ejected aerosols and the evaporated vapours can be determined using those key compounds as “tracers”. The results show that the true yield of the ejected aerosols from cellulose pyrolysis continuously increases from 29% at 1 K/s to 57% at 1000 K/s, accompanied by the continuous decrease in the true yield of the evaporated vapours from 43% at 1 K/s to 28% at 1000 K/s. The total primary tar yield of cellulose pyrolysis still increases with the heating rate (from 72% at 1 K/s to 86% at 1000 K/s), with the contribution of the ejected aerosols increasing from 40% at 1 K/s to 67% at 1000 K/s. The data clearly demonstrate the key role of thermal ejection in the formation of condensable volatiles during cellulose pyrolysis, greatly influencing the yield and composition of tar generated from cellulose pyrolysis. Overall, the results of this study provide significant insights into the formation mechanisms of primary volatiles during cellulose/biomass pyrolysis.

ABSTRACT. Molten salt pyrolysis of biomass is a promising approach for producing clean and renewable energy by combining solar-driven molten salt heat storage with thermochemical conversion of biomass. Pyrolysis of large-particle biomass offers many advantages in practical applications. However, during pyrolysis, heat and mass transfer behavior inside the particles cannot be ignored. This study investigated the product composition and product distribution characteristics during the pyrolysis process of large-particle biomass in molten salt. The influence of molten salt on the physical and chemical structure of biochar from the core to the outer layer was analyzed layer-by-layer by micro computed tomography and temperature programmed oxidation techniques. The evolution mechanism of products during the molten salt pyrolysis of large-particle biomass was also analyzed. The results indicate that the excellent heat transfer efficiency of molten salt promoted the pyrolysis of large biomass particles and increased the aromatic condensation degree of biochar. Compared with traditional pyrolysis, molten salt pyrolysis afforded higher yields of biochar and pyrolysis gas, as well as lower yields of bio-oil. In particular, the catalytic reforming effect of molten salt on volatile matter further reduced the yield of bio-oil and increased the yield of combustible gases such as H2 and CO. Moreover, the etching effect of the molten salt on the biochar resulted in a more porous structure, and led to a 24 % increase in the total pore count across various regions of the biomass particles during molten salt-assisted pyrolysis. There was a 70 % reduction in pores with a volume exceeding 10 mm3, and a 46 % increase in pores with a volume of less than 2.2 mm3. This study can promote the development of pyrolysis technology and help to promote biomass energy utilization technology.

ABSTRACT. Levoglucosenone (LGO) is a highly functionalized biomass-derived platform molecule that can be produced from cellulose via catalytic pyrolysis or secondary upgrading of a primary product from its non-catalytic pyrolysis, levoglucosan. Owing to its enone structure, LGO has attracted considerable attention as a precursor for a wide range of value-added chemicals including polymers. While various catalytic systems have been proposed to enhance LGO formation, reported studies generally rely on slow pyrolysis conditions. In contrast, fast heating and high-temperature continuous pyrolysis often result in significantly lower LGO yields. From the viewpoint of reactor design and process intensification, understanding the thermal stability of LGO in the gas phase is essential for improving its recovery under fast pyrolysis conditions. In this study, the gas-phase thermal stability of LGO was systematically investigated using a continuous-flow reactor. A flow-type reaction system consisting of an evaporation zone and a reaction zone was employed. Liquid LGO was vaporized and continuously supplied to the reaction zone under a controlled flow of inert carrier gas. The reaction temperature and residence time were varied over a wide range to evaluate their effects on LGO recovery. At temperatures below 200 °C, LGO was almost completely recovered regardless of residence time, indicating high thermal stability under mild conditions. However, LGO recovery decreased markedly with increasing temperature and residence time. At 300 °C, the recovery dropped below 80% within tens of seconds, while at 400 °C, nearly complete loss of LGO occurred within only a few seconds. Similar trends were observed when the inert gas nitrogen was replaced by steam, hydrogen, or carbon dioxide as the carrier gas, suggesting that the observed LGO loss was not strongly dependent on gas atmosphere. Notably, negligible amounts of permanent gases were detected below 400 °C, and coke deposition on the reactor wall was minimal. Instead, a substantial fraction of LGO was converted into condensable products that were not detectable by general GC analysis. Gel permeation chromatography revealed the presence of products with molecular weights higher than that of LGO, indicating the formation of heavy liquid species. These results suggest that LGO predominantly undergoes gas-phase addition or polymerization reactions rather than thermal cracking. Given the high reactivity of the enone moiety, intermolecular reactions between the α and β carbon atoms of LGO molecules are likely responsible for the rapid loss of LGO in the gas phase, although the details have yet to be clarified. Based on kinetic analysis of the obtained data, the results demonstrate that appropriate control of temperature and residence time is critical to suppress gas-phase reactions of LGO. The findings provide important guidelines for reactor design and operating conditions, indicating that high-yield continuous production of LGO is achievable even under fast heating and continuous pyrolysis, provided that gas-phase degradation is effectively minimized.

ABSTRACT. The growing global energy demand and persistent reliance on fossil resources underscore the critical need for sustainable carbon materials derived from renewable biomass. Biochar, a carbon-rich solid produced via pyrolysis, presents a low-emission alternative to conventional petrochemical carbons. Its electrical conductivity, essential for applications in energy storage, sensing, and environmental technologies, is governed by its graphitic structure, which is intrinsically linked to the biomass feedstock and thermal treatment parameters. This study systematically investigates the structural and electrical evolution of biochars produced from pine, beech, and rice husk through controlled slow pyrolysis (500–900°C under N₂) followed by CO₂ activation. A comprehensive multi-technique characterization approach was employed to correlate material properties with performance. This included textual analysis (N₂ physisorption), morphological assessment (Scanning Electron Microscopy, SEM), structural ordering evaluation (X-ray Diffraction, XRD, and Raman spectroscopy), and elemental analysis. A pivotal aspect of the work is the direct comparison of electrical conductivity for different biochars at the same apparent density, which provides a standardized basis for evaluating their intrinsic conductive performance. Electrical properties were precisely measured under varying compressive loads using a novel coupled impedance–compression analysis, providing unique insights into the mechano-electrical coupling within biochar networks. The results demonstrate that a lignin-rich feedstock (pine) combined with high-temperature pyrolysis and activation yields a biochar (PI900-Act) with a hierarchical pore network, enhanced graphitic domain size, and exceptional electrical conductivity (770 S/m at an apparent density of 700 kg/m³). In contrast, the high silica content in rice husk biochar impedes both textural development and conductivity. The innovative application of impedance–compression coupling reveals the structure-property relationships under mechanical stress. These findings provide a definitive framework for designing functional, sustainable carbon materials with tailored conductivity, directly supporting circular economy strategies by valorizing biomass residues into high-value alternatives for conductive composites, EMI shielding, and advanced electrochemical applications.

ABSTRACT. Micro- and nanoplastics (MNPs) are omnipresent, even in the most remote places on Earth. At the same time, reports of MNPs in the human body are increasing exponentially. The main exposure routes are ingestion and, above all, inhalation. People spend most of their time indoors, predominately in their homes. Characterization of indoor air exposure to MNPs is essential to contextualize internal human measurements and assess their environmental plausibility. Accordingly, exposure levels, composition, spatial and behavioral determinants require detailed evaluation. Passive sampling was performed in 105 households in Utrecht, the Netherlands and surrounding areas within a 50 km radius. Petri dishes were placed in elevated positions for dust collection twice within a period of three months. Samples, replicates and blanks were analyzed for MNP composition and mass with reactive Py-GC/MS after Fenton oxidation. Accompanying questionnaires captured sociodemographic, behavioral, and household factors, and environmental data were linked to sampling locations. Spatial and household-level determinants of MNP deposition rates were examined using multivariable mixed-effects linear regression. All samples contained MNPs reported as clusters related to the respective quantifiable homo polymers and accordingly include copolymers on a proportional basis. Most prominent was the polyethylene terephthalate cluster (C-PET), with rates between 0.37 and 170 µg/m²/day (mean 27.2) which accounted for almost 80% of total polymer deposition. It was followed by the clusters of polypropylene (C-PP) and polyethylene (C-PE) representing a significantly lower proportion of total polymer deposition with 6% each. Less prominent clusters were polystyrene (C-PS), polymethyl methacrylate (C-PMMA), polycarbonate (C-PC) and polyamide (C-PA6). A subset of samples (n=40) was analyzed for tire wear particles. Very few samples had levels which exceeded the LOD, suggesting a minor role, if any, of tire abrasion in the household dust samples examined. The polyvinylchloride cluster was excluded from the results due to severe interferences of natural fibres. Prior to pyrolysis, the prepared sample filters were inspected microscopically. This revealed a significant proportion of fibres. Most likely the high proportions of C-PET, and C-PP to a lesser extent, were attributed to household and clothing textiles. Multivariable linear regression (Figure 1) was used to assess associations for specific polymer clusters with potential determinants of exposure. Higher deposition was observed in multi-person households and in autumn and winter compared to summer. However, more living space per person, was associated with lower deposition. Specific household sources and sinks were identified: curtains in the living room were associated with higher C-PP deposition; vacuuming, with higher C-PC; and dryer use, with lower C-PP. Higher levels of C-PMMA and C-PS were associated with environmental conditions, including urbanicity and ultrafine particle concentrations, respectively. Besides identification of some key determinants, qualitative and quantitative data will be related to published outdoor and indoor deposition. In addition, the observed pattern is compared and discussed with that from a selection of previously published human samples.

Figure 1. Heatmap (multiple regression) of geometric mean ratios (GMRs) for associations between determinants of exposure and MNP concentrations. *significant (p < 0.05), .marginally significant (p < 0.1) associations.

ABSTRACT. Plastics and microplastics are ubiquitous in the global environment, drawing increasing attention due to their adverse environmental impacts. Particles originating from tyre abrasion represent a substantial share of the microplastic pollution, mainly pronounced in traffic-dominated and urban environments. Following their release, several environmental processes encompassing for instance mechanical abrasion, and physicochemical degradation such as UV-irradiation. The latter mechanisms can lead to pronounced changes in the chemical fingerprint and functional characteristics of tire wear particles (TWPs), hence their overall impact has not been elucidated. This knowledge gap is predominantly originating from the complex analytical approach required to tackle these heterogeneous samples. Conventional pyrolysis coupled to gas chromatography mass spectrometry (Py-GC-MS) is seen as the go to strategy to characterize TWPs by identifying its polymer-specific marker compounds. However, due to the sample complexity, Py-GC-MS faces limitations in resolving power, restricting research to unravel the full chemical fingerprint of TWPs. Comprehensive two-dimensional gas chromatography hyphenated with analytical pyrolysis and time-of-flight mass spectrometry (Py-GCxGC-ToFMS) can present a potential solution to overcome the conventional shortcomings. In the current study, human-produced TWPs were artificially aged using a weathering chamber with UV-irradiation, and every week a subsample was taken for four weeks. The pristine and aged TWPs were subsequently analysed using Py-GCxGC-ToFMS, revealing a temporal alteration pattern in the relative abundance of characteristic pyrolysis compound groups obtained in the 2D pyrograms. This outcome supports the hypothesis that UV-irradiation can induce degradation of TWPs altering their chemical composition, and in turn complicating accurate quantification. In conclusion, such non-targeted screening approaches are of major importance for tracing degradation products and acquiring reliable TWP data for environmental mitigation strategies.

The authors acknowledge the COST Action ICPLASTIC CA23131 ISO compatible, efficient and reproducible protocols/equipment for mICro-nanoPLASTIC detection through machine-learning – ICPLASTIC, supported by COST (European Cooperation in Science and Technology), and the Fonds de la Recherche Scientifique (FNRS) for financial support of the current study.

ABSTRACT. Environmental pollution caused by microplastics has become an issue of increasing public concern. In recent years, atmospheric microplastics have increasingly been reported, attracting growing scientific and public interest, and the development of analytical methods to track their behavior is now an urgent task. In our previous studies, atmospheric particulate matter was collected on quartz fiber filters, and a portion of the collected samples was directly introduced into a pyrolysis gas chromatography–mass spectrometry (Py-GC/MS) system to quantify trace amounts of polymer components. Using this approach, we successfully demonstrated the quantitative determination of polymer species such as polypropylene, polystyrene, and styrene–butadiene rubber. However, in the quantitative analysis of polyvinyl chloride (PVC), the large hydrogen chloride signal typically observed during pyrolysis is strongly influenced by matrix components and therefore does not function reliably as evidence for the presence of PVC. Although many researchers use naphthalene as a marker compound, this issue may be addressed by clarifying the behavior of hydrogen chloride generated during the pyrolysis of PVC in matrices inevitably introduced during atmospheric sampling as well as in real atmospheric particulate matter, and by elucidating how these matrices affect the responses of marker compounds such as naphthalene. In this study, the peak behavior of hydrogen chloride in atmospheric particulate matter collected on quartz fiber filters was analyzed, and the validity of the quantitative method was evaluated through spike-and-recovery experiments using real atmospheric samples. In this presentation, we will present the results of this study, including the analytical results of PVC contents in size-classified atmospheric particulate matter (PM>10, PM2.5–10, and PM2.5).

ABSTRACT. In this study, we quantified plastic content in foraminifera tests to evaluate their suitability as tools for time-resolved plastic pollution studies in the marine environment. Foraminifera are unicellular marine organisms capable of producing shell-like agglomerates known as tests using seawater particles. Suspended plastic particles might be incorporated into these tests and protected from environmental degradation. This makes foraminifera tests potential bio-archives of plastic pollution, with a better spatial resolution compared to marine sediments. However, information on the plastic content in either fresh or historical foraminifera tests is lacking in the literature. Here, four historical foraminifera tests (1911–1952) from different oceans were retrieved from a museum collection and plastic contents were quantified by analytical pyrolysis-GC-MS. The tests were ground and analyzed without further pretreatment. A new tool that allows splitless injection of pyrolyzates into the chromatographic system was used to increase instrumental sensitivity. In addition, matrix-matched calibration was performed using a plastic reference mixture with calcium carbonate as solid dispersant. Peaks from the organic linings of the tests were detected in the pyrograms and constituted potential interferents for some of the pyrolysis markers of polymers. Therefore, a careful selection was made of polymers for which reliable quantitative data could be provided, and discussion of the results was limited to these polymers. Results revealed the presence of polyethylene, polystyrene, and polyethylene terephthalate, in amounts consistent with plastic production history and age of the samples (Figure 1). While the sample pool is not big enough to draw definitive conclusions, these results indicate that fresh and historical foraminifera tests are promising resources to build time-resolved plastic pollution patterns in marine environments.

Figure 1. Left – Total ion pyrogram of a test sample (a) and extracted ion pyrograms showing pyrolytic markers for polyethylene (b), polystyrene (c) and polyethylene terephthalate (d). Right, top – quantitative results. Right, bottom – microscopy images of the samples.

ABSTRACT. Hydropyrolysis (hydrogen pyrolysis or HyPy) is a comprehensive method for the isolation and quantification of the carbonaceous fraction of biochar that is environmentally stable over extended (centennial) timescales (McBeath et al 2015). It has been shown to strongly correlate with both widely used bulk compositional metrics such as atomic H/C ratio, and also novel indirect parameters such as solid-state electrical conductivity (Hagemann et al., 2025). It has the advantage of being able to isolate a fraction of consistent thermal stability which is also defined on a molecular basis as being composed of >7 aromatic rings. In addition, the fraction which is potentially environmentally labile can also be recovered and subsequently characterised by gas chromatography mass spectrometry. This fraction, composed of smaller aromatic clusters, together with alkyl moieties and breakdown products of the lignocullulosic material derived from the biochar feedstock, can, together with the quantification of the residual stable ployaromatic carbon fraction (SPAC) allow for the feedstock and process conditions of the biochar to be assessed. It may also provide a methodology for assessing the extent of alteration of biochars once they have been exposed to environmental degradation.

Here we describe the characterisation of the labile fraction of a range of wood biochars produced under different process conditions, and hence of markedly different stability, as assessed by both their SPAC content and atomic H/C ratio. As shown in the Figure, for relatively low temperature biochars with a consequent low degree of condensation (H/C ratio of 1.07) and SPAC of 13% the labile fraction consisted of a high abundance of PAH compounds of between 2 and 7 rings, together with their alkyl substituted homologs, and some phenolic species. With increasing temperature, and consequent increased degree of condensation (H/C = 0.46; SPAC 66%), the recovered products were restricted to just the parent PAHs, although still spanning the 2-7 ring size range. For highly stable biochars (H/C = 0.21; SPAC = 94%), the concentration of products was much reduced, and comprised only of 3 and 4 ring structures. It is thought that rather than being cleaved from the biochar structure itself these were condensation products, thermally desorbed from the biochar during HyPy that had condensed onto the char surface during production. In addition we also report on the characterisation of the labile fraction of biochars that had been part of an agricultural field trail 13 years ago, to assess how the labile fraction may change after environmental exposure.

References

McBeath AV, Wurster CM, Bird MI. 2015. Influence of feedstock properties and pyrolysis conditions on biochar carbon stability as determined by hydro¬gen pyrolysis. Biomass Bioenergy 73, 155–73.

Hagemann N, Schmidt HP, Buchelia TD, Grafmueller G, Vosswinkel S, Herdegen V, Meredith W, Uguna CN and Snape CE. 2025. Proxies for use in biochar decay models: Hydropyrolysis, electric conductivity, and H/Corg molar ratio. PLoS One 20, e0330206.

ABSTRACT. Micro- and nanoplastics (MNPs) are increasingly recognized as emerging contaminants with potential implications for human health. However, detecting and quantifying MNPs in human biological matrices remains a substantial analytical challenge due to their particle nature, the complexity of the matrix, and the high risk of cross‑contamination arising from their pervasive presence. Among human samples, biological fluids such as breast milk and bile represent particularly relevant matrices for human exposure assessment: breast milk reflects maternal transfer pathways and early‑life exposure, while bile plays a key role in the excretion of exogenous substances entering the body via ingestion. Despite their importance, these matrices are highly complex and diverse, characterized by varying and often high contents of proteins, lipids and other endogenous compounds. These factors demand analytical approaches that provide high specificity and sensitivity, together with robust contamination control. Pyrolysis–gas chromatography–mass spectrometry (Py‑GC‑MS) offers a powerful and reliable strategy for MNP analysis, as it provides polymer‑specific chemical fingerprints derived from characteristic thermal degradation pathways. However, the complexity of biological fluids can introduce co‑pyrolysis effects, leading to altered marker profiles or interferences with pyrolysis products originating from matrix constituents. The main aim of this study was the development and validation of Py‑GC‑MS methods tailored for the analysis of MNPs in human biological fluids such as breast milk and bile. Given the heterogeneity of the target matrices, we developed matrix‑specific digestion procedures designed to efficiently remove organic material while preserving polymer integrity. Each digestion workflow was optimized to guarantee high recoveries and minimal matrix effects. For each targeted polymer, pyrolysis markers were selected to reduce interferences and co‑pyrolysis artefacts. The final protocols were successfully validated, following international validation guidelines, for human bile and human breast milk, demonstrating reliable performance for six commonly encountered polymers: polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polymethyl methacrylate (PMMA). Application of the validated methods to samples collected from donors confirmed their suitability for the detection and quantification of MNPs in real human matrices. This work highlights the essential role of Py‑GC‑MS in advancing MNP exposure assessment, offering a versatile and sensitive analytical approach. The developed methods provide a crucial foundation for future studies investigating human uptake, distribution, and potential health impacts of MNPs pollution.

ABSTRACT. The seeking of alternative routes for green marine fuel production has accelerated due to recent regulations that aim to reduce toxic gas emissions, particularly sulfur oxides (SOₓ). Bio-oil can be considered a promising alternative to fossil-based marine fuels because of its carbon neutrality and naturally low sulfur content. However, it cannot be used directly in engines due to its poor fuel quality. The high oxygen content of bio-oil reduces its calorific value and stability, while its high acidity causes corrosion problems in engines. Therefore, an upgrading step is necessary to improve the fuel properties of bio-oil and make it suitable for blending or co-refining with conventional marine fuels. Hydrodeoxygenation (HDO) is one of the most effective upgrading methods, aiming to remove oxygen from bio-oil under hydrogen flow in the presence of a catalyst. In this study, slow pyrolysis oil is produced from cherry plum waste and then upgraded through HDO under different conditions using nickel oxide and noble metal catalysts. The bio-oil is pyrolyzed in a continuously operated screw reactor at 500°C under constant 10 NL/min N2 flow with 5 min solid residence time. The char, oil, and gas yields are 29.4 wt.%, 38.6 wt.%, and 32 wt.%, respectively. In this study, three different conditions are applied: 1) Mild HDO was performed at 250 °C and 80 bar; 2) Deep HDO was carried out at 330 °C and 80 bar; 3) two-step HDO process, first applying the mild HDO conditions and following deep HDO. The upgraded products were characterized by several analyses such as GC-FID, GC-TCD, and CHNS to evaluate the influence of reaction severity and catalyst type on the physicochemical properties of the resulting fuels. This study demonstrates that reaction severity is the primary driver of bio-oil upgrading, while catalyst type mainly controls product selectivity and gas formation pathways. Increasing temperature from 250 °C to 330 °C strongly enhanced deoxygenation. The O/C ratio decreased from 0.29 to 0.21 after mild stabilization and to 0.05 after deep HDO. Deoxygenation is lower for the two-step HDO compared to direct deep HDO (ca. O/C = 0.19). The lowest gas yields (̴ 12 wt.%) were obtained with the two-step HDO, indicating more controlled oxygen removal. Under mild conditions, oxygen is mainly removed via decarboxylation, leading to CO2 formation (ca. 3 vol%) with about 1 vol% methane production. Under deep HDO, hydrogenation–hydrogenolysis and decarboxylation are the main pathways, while very low CO formation (̴ 0.1 vol%) indicates negligible decarbonylation. The two-step process restores CO2 as a dominant oxygen-removal pathway and limits excessive cracking, resulting in moderate C1–C3 formation. Overall, mild HDO alone is insufficient for producing fuel-grade oils but is essential for stabilizing highly reactive oxygenated species. Deep HDO is required for significant oxygen removal, but when applied directly it sacrifices liquid yield through excessive gas formation. A staged HDO strategy that first stabilizes and then deeply deoxygenates bio-oil provides the best balance between oxygen removal, liquid yield, and product quality, making it a promising route for producing marine-fuel-range liquids from bio-oils.

ABSTRACT. Two microalgae strains, Chlorella sorokiniana and Chlorella vulgaris, were subject to hydrothermal liquefaction (HTL). The resulting HTL biocrudes were then upgraded via hydrotreatment (HDT), using a sulfided NiW/Al2O3 catalyst, with samples collected after 0, 2.5, 5, and 8 hours of reaction. The heavy fractions from these distinct HTL biocrudes and HDT bio-oils were subsequently characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). These analyses yielded thousands of distinct molecular formulae, corresponding to CHON, CHN, CHO, and CH compound classes. The lipids present in algae were converted by HTL into long chain acids and CHN, CHO, CHNO compounds. Through deoxygenation and denitrogenation reactions, a large amount of alkanes and aromatics were obtained. However, a significant population of refractory species was identified, mainly in Chlorella sorokiniana HDT oils. This strain is defined by its higher content of carbohydrates that yield Maillard reaction products, along with algal proteins. These high-mass species were formed during HDT and are therefore better characterized by FT-ICR MS than by gas chromatography (GC). Furthermore, analysis of the treated bio-oil obtained after a short HDT time exhibited the lowest unsaturation level, likely due to reaction between the fatty chains and amino acids. In summary, the FT-ICR MS approach combined with multivariate statistical analyses, proved to be highly complementary to GC analyses. It enabled to decipher the molecular complexity of the heavy fraction of the HTL biocrudes and HDT bio-oils, clarified the influence of the microalgae strain on the HDT efficiency, and provided meaningful insight into the reactions occurring during the early stages of the upgrading process.

ABSTRACT. This study investigates the catalytic pyrolysis of chicken wing bones residues to improve yield and quality of the by-products. The work focuses on the use of novel catalysts produced from chicken bone waste, supporting the valorization of cooked poultry residues. Biochar obtained from the pyrolysis of chicken bones was further modified with HZSM-5 zeolite and nickel to enhance catalytic activity. Experiments were performed using chicken wings bones residues as feedstock. The main goal was to evaluate catalyst efficiency, product distribution, and the potential reuse of the catalysts. When biochar-based catalyst was used, the average yields were approximately 42% biochar, 31% bio-oil, and 22% gas. For HZSM5, mean yields were about 45% biochar, 29% bio-oil, and 21% gas. Gas analysis showed that, for both catalysts, the main components were hydrogen, carbon monoxide, carbon dioxide, methane, acetylene, ethylene, and a high fraction of butane, with smaller amounts of other light hydrocarbons. When biochar-based catalyst was used, the dominant compound classes in the bio-oil were carboxylic acids, amides, nitriles, aromatic compounds, and nitrogen-containing aromatics. In contrast, bio-oils obtained with HZSM5 contained a broader range of compounds, including alkanes, alkenes, aromatic compounds, amides, carboxylic acids, nitriles, amines, and esters. Overall, the results show that chicken bone-derived catalysts are effective in catalytic pyrolysis and offer a promising route for the sustainable conversion of cooked bone waste into valuable products.

ABSTRACT. Biomass-derived green hydrogen is a promising route toward carbon-neutral energy. This work presents an integrated catalytic pyrolysis strategy that realizes H2 generation and selective aromatic production using a Fe-Ni-CaO/C catalyst under 600 ℃. Performance validation results demonstrated the superior efficacy of the Fe-Ni-CaO/C catalyst: the biomass-based hydrogen yield reached 345.3 mL/g, which is 19.93% and 99.66% higher than that of the Fe-CaO/C and Fe/C catalysts, respectively, marking a significant breakthrough in low-energy hydrogen production from biomass. Additionally, the catalyst achieved 100% conversion of heavy oil fractions in pyrolysis oil and 100% selectivity toward high-value benzene and toluene. Systematic parameter optimization shows that the tri-metallic synergistic system outperforms single-metal and dual-metal counterparts in catalytic activity; a 2:1 feedstock-to-catalyst mass ratio achieved a balance between raw material conversion and target product selectivity. Characterization and DFT analysis reveal that Fe-Ni redox coupling facilitates C–H bond activation and continuous H2 evolution, while controlled carbon-chain scission governs aromatic upgrading. This study establishes a mechanistic and scalable framework for low-energy catalytic biomass valorization, advancing sustainable hydrogen and bio-aromatic production.

ABSTRACT. Eucalyptus is an invasive biomass species due to its fast growing and self-proliferation, which makes it a renewable and abundant resource. Its low ash content and composition make it an interesting source of high value-added products such as phenolic compounds. Catalytic pyrolysis of eucalyptus is especially remarkable for its ability to enhance selectivity towards oxygenated compounds. It has been demonstrated that hierarchical zeolites lead to the decomposition of heavy oligomers coming from the biomass, improving the bio-oil quality and boosting the proportion of phenolic compounds in the bio-oil1. Previous studies show that increasing the pressure in catalytic pyrolysis enhances the selectivity of zeolites towards compounds of interest for bio-oil upgrading2. In this context, this study is focused on the effect of pressure on the catalytic performance of both commercial (H-BETA) and hierarchical (h-H-BETA) BETA zeolites in eucalyptus pyrolysis. The experiments were carried out under nitrogen atmosphere in a fixed-bed reactor operating at 550 ºC for thermal eucalyptus decomposition and 450 ºC for catalytic vapour upgrading, using a catalyst/biomass ratio of 0.2 and operating pressures of 1 and 6 bar. The resulting char, bio-oil* (water-free basis), water, permanent gases, and coke (the latter just for catalytic tests) were analysed using different techniques to assess conversion efficiency and products selectivity. By comparison, in the non-catalytic test (NC), increasing the pressure reduced the bio-oil* yield and increased the char yield, due to the slower vaporization rate of liquid products coming from primary thermal degradation reactions, leading to the formation of secondary char. In the case of the catalytic tests the bio-oil* yield was reduced because of the increased water and coke production. Gas production is enhanced by the increasing pressure in both thermal and catalytic tests, due to the severe cracking and decarboxylation reactions. Consequently, in thermal reactions, the increased pressure provoked a decrease in the detected matter quantified by GC-MS of the bio-oil*. The pressure showed a strong influence on the light compounds in the bio-oil*, leading to the cracking of the lightest species and promoting the formation of non-condensable gases such as CO and CO₂. These trends indicate a higher degree of cracking affecting a fraction of the oligomers derived from pyrolysis, resulting in a more homogeneous distribution of lower molecular weight compounds. Although increasing pressure is not favourable in thermal reactions, its positive effect can be observed in catalytic reactions, where an improvement in bio-oil* quality in terms of a higher selectivity towards the target compounds in the detected fraction occurs. The higher pressure boosted the production of AR and O-AR with the use of H-BETA. This effect was improved with the h-H-BETA zeolite, showing an increase in the concentration of the above compounds and promoting lignin oligomers conversion to O-AR which exhibit numerous industrial applications.

Figure 1. Bio-oil* family compounds obtained in the eucalyptus catalytic pyrolysis over commercial and hierarchical H-Beta zeolites at different pressures.

1. Ávila, M. I. et al. Catal. Today 456, 115343 (2025). 2. Artillo, F. et al. Ind. Crops Prod. 194, 116313 (2023).

ABSTRACT. Hydrothermal liquefaction (HTL) of tannery sludge (TS), carried out in hot pressurized water (ca. 200–375°C and 40–200 bar), enables the conversion of TS into bio-crude, as target product, together with a gaseous, solid, and aqueous co-products, while not aiming at a complete oxidation of the organic matrix, potentially preventing the oxidation of chromium to its more harmful hexavalent form [1]. However, HTL-derived bio-crude often contains high O, N, and S content, leading to poor fuel properties. To mitigate these limitations, Fe, Zn and MgCl₂ were in-situ added during HTL to improve bio-crude quality [2]. Experiments were conducted in a 500 mL batch autoclave reactor at 350°C for 10min with 20% (percentages are by weight) of dry sludge and active phase loadings of 5–50%, (1–10% of loaded slurry). The feedstock and HTL products were characterized by ash content, elemental analysis, and higher heating value (HHV). For Zn-assisted HTL (the only case reported, for brevity), the gas phase was analyzed by micro-GC at 20% and 50% of Zn loadings to determine the gas composition and estimate the aqueous-phase product yield. This enabled the evaluation of the gas-phase HHV and the associated energy recovery (ERG), which contributes to the total energy recovery (ERTOT) of the HTL process. Table 1 reports HTL product yields, and the characterization of bio-crude and gas obtained from Zn-assisted tests. Raising the Zn concentration up to 25%, the bio-crude and gas yield slightly increase and the aqueous phase yield decreases, while a subsequent increase in Zn concentration leads to a decrease in these phases in favor of the solid residue. Compared to the TS (34.4% C, 4.8% H, 2.7% N, 3.2% S, 13.9% O, and HHV of 16.7 MJ/kg), the C and H content of bio-crude increases and N and S content decreases, with HHV almost doubled. Compared to the test without active phases, C and H contents increased with Zn loading, peaking at 20% and decreasing thereafter. The nitrogen content remains nearly unchanged compared to the test without active phase. Sulphur content generally decreases with increasing active phase concentration, likely due to ZnS formation during HTL, which promotes deoxygenation reactions [3]. The HHV increases with Zn concentration, peaking at 32.7 MJ/kg and 51.3% energy recovery at 20% Zn, before decreasing at 50% Zn. Regarding the gas phase characterization, hydrogen production was higher at 50% Zn than at 20% Zn. The HHV values of 13.8 MJ/kg and 23.9 MJ/kg were obtained for the 20% and 50% Zn tests, corresponding to ERG increases of 6.6% and 10% relative to bio-crude alone and resulting in ERTOT of 57.9% and 56.1%, respectively.

Table 1. Yields (Y) on dry basis (db) and properties of the bio-crude and gas phase obtained with Zn-assisted HTL tests. S=solid; G=gas; BC=bio-crude; AP=aqueous phase. References

[1] F. Di Lauro, M. Balsamo et al., Fuel, 399 (2025) 135595. [2] C. Prestigiacomo, J. Zimmermann et al., Fuel Processing Technology, 237 (2022) 107452. [3] Q. Zhou, S. Yang et al., Applied Catalysis B: Environmental, 282 (2021) 119603.

ABSTRACT. This is not a traditional research paper. It is a keynote-style submission aimed at reflecting on the path from laboratory innovation to commercial implementation — from the first presentations at PYRO 2006 to today’s global efforts to deploy pyrolysis at industrial scale.

In 2004, I had the opportunity to present the early scientific foundations of microwave-induced pyrolysis as part of my work at the Department of Chemical Engineering and Biotechnology at the University of Cambridge. That research became the basis for Enval, a spin-out company that developed a modular process for recycling complex flexible packaging using microwave energy. Today, that same technology is being deployed at scale by Greenback Recycling Technologies, which acquired Enval and is building a global network of advanced recycling plants.

This presentation will tell the story of how one of the many concepts shared at PYRO conferences became a functioning, commercial reality — and why that journey has been neither straightforward nor complete. Beyond describing the process itself, I will focus on the wider picture: what it means to apply pyrolysis in the real world, what works, what doesn’t, and where the gaps remain between academic knowledge and operational success.

At the heart of the talk will be a reflection on the current state of the pyrolysis sector. A few years ago, the promise of chemical recycling attracted intense interest from regulators, brand owners, and investors alike. Dozens of start-ups emerged; many secured funding, while others have since disappeared. Today, we find ourselves at a crossroads. Many of the brand owners who made bold pledges about recycled content have softened or abandoned them. Demand for recycled polymers — especially from pyrolysis oil — is far lower than expected. At the same time, the petrochemical sector is navigating oversupply, volatile margins, and declining public support, making offtake agreements and long-term partnerships far more difficult to secure.

Meanwhile, pyrolysis companies like ours continue to face technical and regulatory hurdles: from traceability and certification of outputs (e.g. mass balance under ISCC) to emissions compliance, feedstock variability, and customer hesitancy. Policymakers still struggle to define where pyrolysis fits in the recycling hierarchy, and investment into the sector has become more cautious.

In this context, I hope to offer a practitioner’s perspective that complements the technical research presented at PYRO 2026. While the science remains critical, this talk is about what happens when the reactor moves from the lab bench to the factory floor — and what the academic community can do to help accelerate that transition.

If the goal of our field is to build a bridge between science and sustainability, then I hope this keynote can serve as a case study in what it means to try to cross it.

ABSTRACT. Despite its promise, pyrolysis remains challenging to implement for mixed plastic waste recycling. For instance, high-density polyethylene (HDPE) is one of the most abundant polyolefins in plastic waste and an ideal candidate for pyrolysis oil production due to its high volatile matter content (>90 wt.%)[1],[2]; however, when co-pyrolyzed with other plastics like polyethylene terephthalate (PET), the obtained oil yields are lower than its theoretical values [1]. Therefore, the purpose of this study is to better understand the effects of the co-pyrolysis of PET and HDPE on oil yields and their quality. Experiments were conducted in a stainless-steel semi-batch tubular reactor at 440 °C using PET mixtures ranging from 5 to 20 wt.%. Analysis of the composition and molecular weight distribution of the condensable products were performed using GPC, GC-MS, and FTIR. Gas product was analyzed by GC, while the purity of terephthalic acid (TPA) was analyzed by HPLC and FTIR. The results demonstrate a proportional decrease in oil yield with increasing PET content of the feed. This decrease in oil yield was expected, as no oil is produced when PET is pyrolyzed alone. However, the oil yield obtained during co-pyrolysis is lower than the expected value from HDPE depolymerization, indicating that some products derived from HDPE pyrolysis may undergo some kind of aromatization (e.g., benzene, toluene, PAHs). Nonetheless, the aromatization process is not limited to the gas and solid phases. FT-IR analysis reveals that the first four oil samples — collected after 15, 30, 60, and 90 minutes of reaction — also contain aromatic and arene compounds, whose concentration decreases over time. This behavior is consistent with the earlier onset of PET pyrolysis compared to HDPE. In addition to aromatic species, FTIR spectra show the presence of oxygenated compounds in the oil, whose concentration likewise decreases with reaction time. The presence of oxygenated and aromatic compounds undoubtedly lowers the quality of the pyrolysis oil; however, this drawback is partially offset by the enhanced recovery of terephthalic acid (TPA). During these experiments, approximately 55 wt.% of TPA was recovered, mainly in the tubing (≈39 wt.%), with a maximum recovery of 70 wt.% achieved when 5 wt.% PET was present in the feed mixture. Furthermore, HPLC analysis revealed that the TPA collected in the tubing exhibits a purity exceeding 95%, in comparison to the TPA present in the oil phase, which appears to undergo secondary reactions, as indicated by the presence of 3–5 additional peaks in the HPLC chromatograms. When compared with pyrolysis of pure PET, where only 7 wt.% TPA is recovered, these results clearly demonstrate that PET–HDPE co-pyrolysis, although unfavorable for the oil quality, offers a significant opportunity for the recovery of a valuable chemical.

[1] S. D. Anuar Sharuddin, et al., “A review on pyrolysis of plastic wastes,” May 01, 2016, Elsevier Ltd. doi: 10.1016/j.enconman.2016.02.037. [2] M. Kusenberg et al., “Opportunities and challenges for the application of post-consumer plastic waste pyrolysis oils as steam cracker feedstocks: To decontaminate or not to decontaminate?,” Feb. 01, 2022, Elsevier Ltd. doi: 10.1016/j.wasman.2021.11.009.

ABSTRACT. This study investigates the multi-stage (stepwise) thermochemical conversion of polyethylene (PE) and polyvinyl chloride (PVC) using distinct reactor configurations. The multi-stage processes were designed as either a two-stage system, consisting of an auger reactor connected to a fluidized bed reactor, or a three-stage system incorporating a tar-reforming reactor connected in series downstream of the fluidized bed reactor.

For PE, experiments were conducted using the two-stage process with a feed capacity of 500 g/h, aiming to maximize the direct production of light olefins (C₂–C₄). The results demonstrated that preheating the PE to 300 °C in the first-stage auger reactor prior to the main reaction in the fluidized bed enhanced the light olefin yield by 6–8 wt% compared to direct feeding into the fluidized bed reactor.

In the case of PVC, the three-stage process with a feed capacity of 500 g/h was employed to induce dehydrochlorination in the first stage. This approach aimed to convert chlorine in PVC into HCl for extraction prior to entering the fluidized bed reactor, thereby mitigating downstream contamination. The dechlorinated PVC pyrolysis char subsequently underwent steam gasification in the fluidized bed reactor, followed by continuous tar reforming to generate hydrogen-rich, low-tar syngas. Experimental results confirmed that 98 wt% of the total chlorine balance was pre-extracted in the auger reactor. Furthermore, depending on the operating temperature of the tar-reforming reactor, a maximum hydrogen yield of 89 g kg⁻¹ PVC was achieved.

The primary significance of this research lies in demonstrating that a simple stepwise thermal approach can effectively remove problematic substances from PVC while maintaining stable operating conditions, as well as enhance target product yields (e.g., light olefins in the PE study). Furthermore, this study contributes by proposing process configurations optimized for specific feedstock characteristics and by providing essential inventory data for future process scale-up and expansion assessments.

ABSTRACT. Fast pyrolysis is regarded as a promising pathway for the chemical recycling of waste plastics due to its high heating rate and potential to suppress secondary reactions [1]. However, most supporting evidence is derived from idealized reactors, whereas industrial practice commonly employs rotary-kiln or horizontal reactors with distinct heat and mass transfer [2]. In this study, three representative operations of the rotary-kiln reactors with different heating rates (Figure 1) were investigated, including a slow heating rate of about 6 °C min-1 by programmed heating of the furnace (together with the reactor and plastics), an intermediate heating rate of about 32 °C min-1 by inserting the reactor (together with plastics) into a preheated furnace, and a relatively fast heating of about 100 °C min-1 by loading the plastics to the preheated reactor. Pyrolysis of three types of waste plastics including PP, PE, and PS were studied at temperatures of 450, 500, and 550 °C. The pyrolysis products, including gas, liquid oil, and solid char were analyzed by GC-TCD, GC-FID, SimDis, GPC, XRF, TGA, and elemental analysis. Results of the pyrolysis at 500 °C (Figure 1) indicated that heating rate had a minor influence on the liquid oil yields of 58-60 wt.% for PP, 64-66 wt.% for PE, and 78-83 wt.% for PS. However, the product quality was significantly affected by the heating rate. Compared to slow heating, fast heating resulted in a decreased average molecular weight of liquid oil (e.g., from 2407 to 1566 g mol-1, for PE pyrolysis); a transition from waxy liquid to semi-fluid oil; and an increased selectivity of the product (e.g., styrene, from 46.8% to 58.0% for PS pyrolysis). With the comprehensive analysis of the mass/carbon balance and product property, this contribution is a very good reference for the applied pyrolysis of plastics.

ABSTRACT. Plastic waste generation is a major concern, as it is continuously increasing around the world, with waste being usually incinerated, disposed of in landfills or released into the environment. Therefore, the promotion of recycling strategies is a key aspect for contributing to sustainability. In particular, thermochemical valorization routes with integrated CO2 capture are very promising due to their potential for producing highly pure H2 with limited CO2 emissions. In this work, the conversion of HDPE, PP, PS and PET to hydrogen through a two-step pyrolysis-reforming process was studied based on thermodynamics. Plastics were first pyrolyzed in a spouted bed reactor using steam as fluidizing agent, and the volatiles generated were directed towards the sorption enhanced steam reforming step. CaO was used as sorbent, and it was found that in the temperature range that allowed full CO2 capture (400-600 °C), maximum H2 production (pure H2) according to stoichiometry was attained (0.43 kgH2 kg-1plastic for the HDPE and PP, 0.38 kgH2 kg-1plastic for the PS and 0.15 kgH2 kg-1plastic for the PET). Above 600 °C, the promotion of the CaCO3 decomposition led to lower H2 production and purity, with the sorption enhancing effect being negligible at 800 °C. The steam to plastic ratio was also evaluated (0.5-4 range), and it was concluded that it had a minimal effect on H2 as long as there was enough steam according to stoichiometry (2.57 kgH2O kg-1plastic for the HDPE and PP, 2.77 kgH2O kg-1plastic for the PS and 0.99 kgH2O kg-1plastic for the PET). It implied that the driving force of the CO2 capture in the reaction network was sufficient for converting all the pyrolysis volatiles to H2. Finally, and using the HDPE case as reference, the conversion of the CaCO3 formed into syngas and CaO by recirculating a fraction of the H2 produced was evaluated. It was identified that the optimum conditions were a CaCO3 regeneration temperature of 750 °C and a ratio between the H2 fed to the regeneration step and the H2 produced of 0.61. Under optimum conditions (pyrolysis temperature of 500 °C, reforming temperature between 400 and 600 °C and steam to plastic ratio higher than 2.57 (stoichiometric value)), 0.43 kgH2 kg-1HDPE were produced. By feeding 0.26 kgH2 kg-1HDPE to the CaCO3 regeneration step (750 °C), 1.36 kgsyngas kg-1HDPE were generated, converting 60 % of the CO2 released from the CaCO3. In conclusion, these results are evidence of the potential of this pyrolysis-reforming process for converting plastic waste into valuable products with low CO2 emissions.

ABSTRACT. Solar assisted fast pyrolysis can reduce the bio-oil carbon foot print via renewable energy. In PySOLO project, we evaluate particulate heat carriers (PHCs) and fluidized bed operating windows, using electrical heating to reproduce solar boundary conditions. Experiments were performed in a TRL4 bubbling fluidized bed unit (35 runs) under inert N2 using pine chips. Bed temperature and pressure drop were continuously monitored to ensure stable fluidization and steady state. Three PHCs, silica sand, bauxite and olivine, were tested, spanning inert to potentially catalytic behavior. Products were quantified as char, condensable liquids and permanent gases. Liquids were analyzed by GC-MS, while gases were analyzed by GC (H2, CH4, CO, CO2 and C1–C4 hydrocarbons). Operating ranges were: BedT= 400-550 °C, PHCT= 450-650 °C, and 3–9×Vmf (u/umf), with a PHC:biomass ratio of 3:1 and 19:1. Additionally, the heat to be provided by the PHC and thus its mass flow rate (for different ΔT defined as PHCT − BedT) (was quantified by isolating each contribution (reaction heat, gas heating, biomass + moisture heating, and losses) using the Creck fluidized bed model integrated in Aspen Plus. The calculations assumed, biomass at 70 °C with 10% moisture, biomass flow 0.66 kg h-1, fluidizing gas/biomass 3.5 kg kg-1 and bed losses 1% of biomass LHV. Under solar operation, the PHC:biomass ratio sets the thermal buffering capacity required to decouple heat delivery from biomass conversion and maintaining fast pyrolysis heating rates, Figure 1a. Screening results highlight that PHC selection and hydrodynamics must be co-designed. With bauxite, replicate tests at BedT=450 °C, PHCT=550 °C and 5×Vmf yielded 20, 50, 25 wt% (solid, liquid, gases) showed robustness (σ < 3.4). Olivine showed signs of catalytic vapor cracking but presented attrition related operability limitations, thus silica and bauxite were prioritized. The model derived high ratio condition was experimentally validated with silica at 19:1, BedT=450 °C, PHCT=600 °C (ΔT=150°C), 7×Vmf, yields were 17.3, 53.6, 24.1 wt% (solid, liquid, gases) mass balance closure 95 wt% and steady state operation, fully comparable to the reference silica case at 3:1 (BedT=450 °C, PHCT=550 °C, 7×Vmf, yields: 18.2, 54, 22.9 wt% (solids, liquid, gases), Figure 1b. Figure 1. a) Theoretical silica sand:biomass mass ratio calculated with Creck model (Aspen plus integrated) as a function of pyrolysis temperature for different ΔT values (difference between PHCT and BedT); b) Product yields for silica at BedT = 450 °C, 7×Vmf: reference (PHC:biomass 3:1, PHCT = 550 °C) vs solar relevant condition (PHC:biomass 19:1, PHCT = 600 °C; ΔT = 150 °C). The results show that PHC:biomass ratio can be increased to solar relevant levels (19:1) without penalizing yields, provided that PHC selection and fluidization ensure thermal homogeneity and rapid heat transfer. Funding disclaimer: Funded by the European Union (Pysolo project: 101118270). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Climate, Infrastructure and Environment Executive Agency (CINEA). Neither the European Union nor the granting authority can be held responsible for them.

ABSTRACT. The catalytic co-hydropyrolysis of biomass and plastic residues represents a promising pathway for producing value-added hydrocarbons suitable as precursors for sustainable aviation fuels. In this study, a Chilean natural zeolite was modified by acid treatment with HCl (2.4 M) and subsequently impregnated with Ni, Co, and Ni–Co to develop acid–metal catalysts tailored for upgrading volatile pyrolysis streams. The objective was to assess how acid modification and metal incorporation influence the structural, acidic, and textural properties of the catalysts and their impact on the chemical distribution of volatile products from the co-hydropyrolysis of Chilean oak (biomass) and HDPE-LDPE(plastics). To evaluate the catalytic influence on product distribution, all co-hydropyrolysis experiments were carried out using an analytical pyrolysis system coupled to gas chromatography–mass spectrometry (Py-GC/MS). This technique enabled rapid screening of catalytic effects by providing detailed identification of the volatile compounds generated, including hydrocarbons, oxygenates, aromatics, and fuel-range fractions. The Py-GC/MS setup allowed consistent comparison between catalysts while minimizing mass-transfer limitations and secondary reactions, making it a suitable tool for mechanistic interpretation of catalytic behavior. Acid treatment of the natural zeolite (ZN) generated a substantial increase in surface area (from 213 to 439 m²/g), enhanced mesoporosity, and a higher Si/Al ratio (~33% increase), as confirmed by N₂ physisorption and XRF. This modification removed extra-framework and framework aluminum and decreased the concentration of inorganic impurities (Na, Ca, Fe, Mg, K), improving acid site accessibility. SEM-EDX analysis revealed increased surface roughness, enlarged pores, and homogeneous distribution of the impregnated metals on the modified zeolite (ZH2.4). XRD analysis showed that the zeolite crystalline structure was preserved after acid treatment and metal impregnation. Monometallic catalysts displayed NiO and Co₃O₄ reflections, while the bimetallic NiCo/ZH2.4 catalyst additionally exhibited characteristic peaks of the mixed spinel phase NiCo₂O₄, suggesting structural integration of both metals. H₂-TPR profiles indicated that NiCo/ZH2.4 had the most intense and easily accessible reduction features, likely due to hydrogen spillover and the formation of mixed metal phases. NH₃-TPD experiments showed that metal incorporation modulated surface acidity: Ni promoted medium-strength acidity, Co preserved strong acid sites, and NiCo/ZH2.4 presented a balanced acid distribution favorable for bifunctional acid–metal reactions. Py-GC/MS analysis of the co-hydropyrolysis products at 550 °C demonstrated that the NiCo/ZH2.4 catalyst significantly enhanced hydrocarbon formation, especially alkanes, while markedly reducing oxygenated compound families. This catalyst showed the highest selectivity toward Jet Fuel–type hydrocarbon fractions, evidencing a strong acid–metal synergy in volatile upgrading. Overall, the results indicate that combining acid modification with bimetallic impregnation effectively boosts catalytic performance in biomass/plastic co-hydropyrolysis. The NiCo/ZH2.4 catalyst exhibited superior physicochemical properties and product selectivity, highlighting its potential for sustainable aviation fuel precursor production from mixed waste feedstocks.

ABSTRACT. Pyrolysis is a key technical means for the clean and efficient utilization of biomass. However, the high oxygen content of biomass leads to a large amount of water and CO₂ in its pyrolysis products. How to in-situ utilize these water and CO₂ to improve bio-oil quality and reduce CO₂ emissions during biomass utilization is crucial, with the core lying in matching the reforming reaction temperature with the CO₂/steam release temperature. In this study, the catalytic adsorption performance of CaO was enhanced by regulating its physicochemical properties and constructing a bimetallic sequential catalytic system, realizing the simultaneous adsorption and conversion of water and CO₂ to improve bio-oil quality. Furthermore, DFT calculations, isotope tracing, and other techniques were employed to reveal the mechanism of CaO's dynamic participation in the pyrolysis process and the catalytic pyrolysis upgrading mechanism of the CaO-based catalytic system.

ABSTRACT. Sugar measurements during fermentation showed a maximum ethanol concentration of 0.46 ± 0.05 g/L after 72 h. The physicochemical characterization of corn cob biomass and its fermented residue revealed overall consistency, with differences attributed to compositional changes induced by biochemical conversion. Thermogravimetric analysis identified 500 °C as the optimal temperature for pyrolysis, yielding the highest liquid fractions (63% for raw corn cob and 54% for fermented residue). At this temperature, bio-oil from raw corn cob showed a higher abundance of value-added compounds, such as furfuryl alcohol and acetic acid, compared to the fermented residue. Catalytic pyrolysis of the fermented residue reduced liquid yield (36%) due to deoxygenation reactions, increasing gas production (40%) and CO/CO₂ concentrations, while enhancing phenolic compounds and reducing ketones and acids. Biochar obtained may be further evaluated for advanced materials or bioremediation. Overall, the hybrid bio–thermocatalytic conversion route demonstrates strong potential for sustainable waste valorization aligned with the United Nations Sustainable Development Goals.

ABSTRACT. The catalytic pyrolysis of lipid-based biomass, such as non-edible vegetable oils, offers a promising route for producing sustainable aviation fuel (SAF) and high-value chemicals such as benzene, toluene, and xylene (BTX) However, achieving precise selectivity toward targeted hydrocarbons remains a fundamental challenge in catalyst design. Through a systematic evaluation of zeolite catalysts, the ex-situ pyrolysis of oleic acid was studied in a continuous fixed-bed reactor at 550 °C to achieve precise control over product selectivity. Non-catalytic pyrolysis of oleic acid afforded a high bio-oil yield (>80 wt%) with a broad, non-selective product spectrum. In contrast, zeolites enabled targeted transformations. H-ZSM-5, leveraging its strong acid sites and shape selectivity, exhibited exceptional performance for BTX production, achieving 81% selectivity and a stable yield of 37.3 wt.% over 8 h without significant deactivation. This catalyst also demonstrated robustness with real feedstocks, affording a 28 wt.% BTX yield from castor oil. Meanwhile, MCM-41, MCM-41 favored milder cracking, preserving a higher liquid yield of 57.1 wt.% with inherent selectivity toward C8–C16 alkanes/alkenes. Strategic modification of MCM-41 with Ni and Mo further enhanced SAF-precursor selectivity, increasing the C8–C16 fraction from 12% to 28%. This improvement is attributed to optimized metal-support interactions and tailored acid sites that promote deoxygenation and mild cracking while suppressing excessive aromatization. These results underscore the critical role of zeolite design in directing lipid pyrolysis toward distinct product streams. Ongoing work expands this study to diverse fatty acid profiles and employs advanced characterization techniques (e.g., structure/acidity/coke analysis) to elucidate deactivation mechanisms and refine catalyst stability. This integrated approach establishes a versatile pathway for converting renewable lipids into bio-aromatics and SAF components, advancing the circular bio-economy.

ABSTRACT. Environmental concerns related to global warming are accelerating the transition from fossil fuels toward renewable energy sources, with hydrogen expected to play a key role in future energy systems. Despite this, H2 is still mainly produced from fossil fuels, which has motivated the development of sustainable alternatives such as biomass thermochemical conversion [1]. In this context, the integration of biomass fast pyrolysis with in-line oxidative steam reforming (P-OSR) represents an efficient route for H2 production, enabling autothermal operation while improving catalyst stability [2]. Ni-based catalysts are particularly attractive due to their high activity, although their susceptibility to coke deposition remains a challenge [3]. Therefore, this work investigates the performance of Ni-based catalysts in the P-OSR with the aim of maximizing H2 production under autothermal conditions. Pine sawdust serves as the biomass feed in a laboratory-scale plant comprising two in-line reactors: a conical spouted bed reactor (CSBR) for pyrolysis (500 °C) and a fluidized bed reactor for OSR of the resulting volatiles (600 °C). Ni/Al₂O₃, Ni/ZrO₂, and Ni/SiO₂ catalysts are employed to convert the biomass pyrolysis volatiles into H2. The runs were conducted with continuous biomass feeding (1 g·min⁻¹), a steam-to-biomass (S/B) ratio of 3, and a space-time of 15 gcat·min·gvolatiles⁻¹. The results obtained in this process at zero time on stream give evidence of the high influence of catalyst support on process performance. For Ni/Al2O3 catalyst, almost full conversion as well as a H2 yield over 90% was attained, which is related to the suitable properties of this support as are high surface area and proper Ni dispersion. However, Ni/SiO2 and Ni/ZrO2 evidenced lower initial activity (conversion of 88.5 and 84.5%, respectively). Thus, H2 production decreased as follows: Ni/Al2O3 (9.5 wt%) > Ni/ZrO2 (6.1 wt%) > Ni/SiO2 (5.3 wt%). The carbon conversion and H2 yield decreased with time on stream for all three catalysts due to coke deposition on the catalytic surface. Ni/Al₂O₃ demonstrated the highest stability, maintaining higher H2 yield throughout the reaction. Ni/ZrO₂ exhibited the fastest decline in volatile conversion (it decreased from 84.5 to 58.8% for 18 min on stream), leading to higher yields of by-products compared to Ni/Al2O3 and Ni/SiO₂ catalysts. As regards Ni/SiO2 catalyst, it presents a suitable stability, maintaining a stable conversion during 60 min on stream and then decreasing to 55.7% for 81 min on stream. This fact can be ascribed to the basic nature of SiO2 support, which hinders coke formation. In view of these results, it can be concluded that the Ni/Al2O3 catalyst is the best one in terms of initial activity and stability, leading to a high H2 production (9.5 wt%). Moreover, the process proposed is a promising alternative for sustainable hydrogen production from biomass.

ABSTRACT. Preparation of two-dimensional carbon materials through biomass pyrolysis is of great significance for the high value utilization of biomass. But, biomass-derived 2D carbon materials are prone to agglomeration at elevated temperatures. Herein, we propose a method for coproducing carbon nanosheets and methanol-rich oil in a potassium chloride-lithium chloride (KCl-LiCl) liquid phase environment. Results showed that carbon nanosheets featuring a low layer thickness of 21.3 nm were produced through pyrolysis at 800 ◦C with the assistance of KCl-LiCl, which is lower than that of commercial carbon nanosheets (100 nm). In addition, methanol-rich oils with a selectivity of 98 % were prepared under the same conditions. The temperature and molten salt ratio can change the thickness of carbon nanosheets and the selectivity of methanol. Moreover, we propose a Molten salt catalytic mechanism for intercalation stripping. The KCl-LiCl etched the carbon surface and intercalated into the carbon layers, while molten salt ions covalently bonded with carbonyl and aldehyde groups on the carbon surface. These interactions facilitated cross-linking between the carbon layers, leading to the exfoliation and formation of carbon nanosheets.

ABSTRACT. Improving the efficiency and stability of biomass cyclic catalytic pyrolysis has become a recent research focus. This study details the effects of hydrochloric acid and acetic acid washing pretreatments and Mo-modified HZSM-5 on hydrocarbon production during five cyclic catalytic pyrolysis cycles of sweet sorghum stalk (SSS). The results showed that acid-washing pretreatments significantly increased hydrocarbon yields. Hydrochloric and acetic acid washing raised the volatile matter content to 78.89% and 77.86%, and the higher heating value (HHV) increased by 45.00% and 37.27%, respectively. Mo/HZSM-5 also enhanced hydrocarbon selectivity and stability. Nevertheless, the combination of acetic acid washing and Mo/HZSM-5 exhibited superior performance after five pyrolysis cycles, with hydrocarbon selectivity remaining as high as 14.22% compared with only 4.31% for raw SSS. This study proposes an integrated strategy combining acid-washing pretreatment and metal-modified HZSM-5 as a sustainable and feasible method to enhance hydrocarbon production from biomass pyrolysis.

ABSTRACT. The present study reports the results of an extensive experimental campaign carried out within the framework of the European “BioPhenom” project (Grant Agreement No: 101135107), aimed at developing sustainable pathways to produce bio-based phenolic compounds. Phenols are among the most important classes of aromatic compounds in the chemical industry, serving as key intermediates for the manufacture of a wide range of value-added products. Since phenol production relies on fossil resources (e.g., the energy- intensive cumene process [1]), the development of renewable and low-carbon routes for phenol production is of great environmental and industrial relevance. Fast pyrolysis of lignocellulosic biomass represents a promising technology for the sustainable production of phenolic compounds. This process is feedstock-flexible, using lignin-rich agricultural residues and industrial by-products, and directly produces phenolic intermediates within pyrolysis bio-oils. These bio-oils contain both monomeric phenols and polyphenolic oligomers derived from lignin depolymerization. While monomeric phenols are of high industrial interest due to their direct applicability, their concentration in conventional pyrolysis oils is typically low, whereas the dominant phenolic fraction consists of high-molecular-weight, oxygen-rich oligomers commonly referred to as pyrolytic lignin, which limits their direct valorization. In this work, thermal and catalytic pyrolysis experiments were performed using lignin-rich Olive Stone residues as feedstock in a laboratory-scale fluidized bed reactor. The tests were carried out at 400, 500, and 600 °C with a gas residence time of approximately 1 s, to assess the influence of operating conditions on product yields and composition. To enhance the yield and selectivity towards monomeric phenols while suppressing the formation of heavy oxygenated by-products, a calcined dolomite catalyst was employed as bed material. Dolomite was selected due to its low cost, non-toxicity and minimal environmental impact, and its basic properties, which are favorable for selective phenolic production [2]. The effect of the weight hourly space velocity on product distribution and quality was also investigated. The pyrolysis products were characterized by continuous online gas analysis and chemical analysis of the condensed bio-liquid. GC-MS was used to identify and estimate the relative abundance of volatile and semi-volatile compounds, while Karl Fischer titration, Folin-Ciocâlteu assay, and total acid number (TAN) analysis were applied to quantify water content, total (poly)phenols, and acidity, respectively. In addition, bio-char samples were characterized in terms of textural, morphological, and chemical properties to evaluate their potential for further valorization. Results demonstrate that the use of calcined dolomite significantly improves the selectivity of pyrolysis towards phenol-rich bio-oils. Under optimized conditions, the resulting bio-oils exhibit a simplified chemical composition mainly consisting of phenols and ketones, along with reduced oxygen content and acidity. Overall, these findings highlight the potential of catalytic fast pyrolysis of OS as a viable and sustainable route for the production of bio-based phenolic compounds.

Figure 1. GC-MS peak area (%) for vapors produced over: (a) sand, (b) 100 wt.% and (c) 60wt.% calcinated dolomite, at 400, 500 and 600 °C.

[1] L.M.J. Sprakel and B. Schuur, Journal of Chemical Thermodynamics 162 (2021) 106577. [2] M. Tawalbeh, et al., Journal of Environmental Management 299 (2021) 113597.

ABSTRACT. Mitigating atmospheric CO2 accumulation justifies the development of sustainable processes focused on key molecular building blocks that do not rely on high-emission fossil feedstocks. In this context, catalytic co-hydropyrolysis (CCo-HyPy) of biomass and plastics offers an attractive route for converting waste resources into monoaromatic hydrocarbons (MAHs); however, its efficiency remains tightly constrained by the need for a carefully tailored, exigent catalyst design. Commonly, such processes use synthetic zeolites such as ZSM-5, which incorporate Brønsted and Lewis acid sites within strictly microporous frameworks, thereby enabling efficient coupling between furanic intermediates derived from biomass and olefinic fragments originating from plastics to obtain monoaromatics. Nevertheless, their high acidity and restricted porosity promote polycyclic aromatic hydrocarbon (PAH) formation and rapid coke deposition, ultimately reducing MAH selectivity. Herein, a metal-organic framework was employed as a sacrificial precursor to generate thermo-metallically transformed Ni0/Al2O3-C catalysts integrating accessible acid sites, oxophilic domains and well-dispersed Ni0 hydrogenation centres. This thermo-metallic restructuring enhances mesoporosity and surface chemistry, enabling a systematic assessment of how structural evolution governs catalytic performance and product distribution in CCo-HyPy. The pristine support (MIL-53(Al)) was impregnated by incipient wetness with 5, 10 and 15 wt% Ni and subsequently subjected to controlled thermolysis at 650 °C and 800 °C under flowing N2 for 2 h, after which the resulting structures were reduced in H2 at 500 °C for 2 h and characterised by XRD, NH3-TPD and N2 physisorption. CCo-HyPy experiments were conducted at 600 °C and 100 psi H2 in a Py-GC/MS system, with product selectivity semi-quantified using relative abundance (RA), and synthetic ZSM-5 used as a benchmark. XRD confirms the formation of metallic Ni, with reflection intensities increasing as Ni loading increases, while the support remains predominantly amorphous. Progressive Ni incorporation suppresses strong acid sites, whereas weak acidity is maximised at 10 wt% Ni and medium-strength acidity peaks at 15 wt%, consistent with partial masking or neutralisation of high-energy acid centres by dispersed Ni0 species. The bare support exhibits nearly constant BTEX selectivity across thermolysis temperatures, whereas the introduction of 5 wt% Ni approximately doubles selectivity and renders it insensitive primarily to thermolysis conditions. In contrast, higher Ni loadings result in a pronounced decrease in BTEX selectivity at 650 °C, followed by partial recovery at 800 °C, reflecting enhanced hydrogenolysis and hydrogenation activity that diverts unsaturated intermediates towards saturated aliphatics. Consequently, the 5 wt% Ni catalyst achieves BTEX selectivity comparable to that of ZSM-5, with only a marginal reduction (-6.5%), while simultaneously suppressing PAH formation by approximately 11%. Overall, optimal monoaromatic production is achieved at low Ni loadings, where thermo-metallic modification of the MOF-derived framework establishes a favourable metal-acid balance. In contrast, higher loadings disrupt this balance and compromise MAH selectivity during biomass-plastic CCo-HyPy.

ABSTRACT. Catalytic pyrolysis of lignocellulosic biomass has been extensively studied as a strategic route for the production of bio-oil and high-value-added compounds. However, crude bio-oil exhibits significant technical limitations, such as high oxygen and water content, high acidity, low thermal stability, and low heating value. These drawbacks preclude its direct application and necessitating advanced catalytic upgrading methods [1].

Catalytic pyrolysis is proposed as an alternative to enhance bio-oil quality while circumventing the need for hydrodeoxygenation. This review identifies two primary operational configurations: in situ, where the catalyst is mixed with the biomass to interact directly with pyrolytic vapors within the reactor, thereby minimizing undesirable secondary reactions; and ex situ, where the catalytic upgrading occurs in a separate downstream bed, facilitating precise control over reaction parameters and catalyst regeneration [3]. Furthermore, multi-stage systems combining Al-MCM-41, HZSM-5, and ZrO2 have been employed, demonstrating significant improvements in both quality and yield [2].

Operational parameters—including temperature, heating rate, residence time, and the biomass-to-catalyst ratio—alongside the reactor configuration (e.g., fixed bed, circulating fluidized bed, or auger reactor) govern the overall yield and product composition. Fast pyrolysis, characterized by high heating rates and temperatures near 500 °C, maximizes liquid yield (with reported values up to 75%) [3]. Conversely, higher temperatures promote aromatization but concurrently increase gas production and secondary cracking. Furthermore, a low biomass-to-catalyst ratio tends to maximize deoxygenation at the expense of liquid yield due to enhanced gas and coke formation [4].

Among acidic zeolites, HZSM-5 is particularly distinguished by its high selectivity toward Benzene, Toluene, and Xylene (BTX) and its robust deoxygenation capacity, both attributed to its Brønsted acidity and microporous structure. However, its inherent microporosity promotes pore plugging due to coke formation, limiting long-term stability. Consequently, hierarchical, hollow, and mesoporous zeolites (e.g., Hollow (30)-TP, HRCHY HBeta) and micro/mesoporous composites (H-ZSM-5/Al-MCM-41) have been developed to enhance molecular accessibility and diffusion. These structural modifications have achieved aromatic selectivities exceeding 78% in specific cases [2, 4].

The review also examines bifunctional catalysts promoted with transition and noble metals, which enhance deoxygenation, aromatization, and coking resistance. Notably, bimetallic systems such as Pt-Ni/γ-Al2O3 have demonstrated high efficiency in the production of jet-fuel-range hydrocarbons. Furthermore, low-cost alternatives—including CaO, MgO, Na2CO3/γ-Al2O3, dolomite, and activated carbon—effectively reduce bio-oil acidity and oxygen content, albeit at the expense of total liquid yield [5].

Finally, this review identifies critical challenges, including coke formation and catalytic deactivation, the inherent trade-off between bio-oil quality and yield, and the lack of standardized experimental data reporting, which complicates comparative analysis and industrial scaling [5]. In summary, while catalytic pyrolysis of lignocellulosic biomass presents promising pathways for high-value bio-oil production, further optimization, standardization, and scale-up efforts remain essential.

References

[1] Chong, Y. Y., et al. (2019). JEM, 247, 38–45. https://doi.org/10.1016/j.jenvman.2019.06.049 [2] Jin, Y., et al. (2024). Energy, 295. https://doi.org/10.1016/j.energy.2024.131029 [3] Reza, M. S., et al. (2023). Energies, 16, 14, 5547. https://doi.org/10.3390/en16145547 [4] Chaihad, N., et al. (2021). Bioresource Technology, 341. https://doi.org/10.1016/j.biortech.2021.125874 [5] Chen, X., et al. (2019). Fuel Processing Technology, 196, 106180. https://doi.org/10.1016/j.fuproc.2019.106180

ABSTRACT. In Colombia, the annual generation of 10.86 MTon of sugarcane bagasse (SCB), characterized by a higher heating value (HHV) of 13.0 MJ/kg, underscores a significant opportunity for energy valorization through pyrolysis [1]. This study investigates the efficiency of bio-oil production from SCB using clinoptilolite (CLI), a cost-effective natural zeolite, modified with various acidifying agents (H2SO4, H3PO4, and NH4Cl). Prior to thermochemical conversion, the biomass was disinfected using a 2 vol. % H2O2 solution for 12 hours at 25 °C. The catalytic modification involved ion exchange processes: treatment with 1.0 N H2SO4 (CLI-SA) and H3PO4 (CLI-PA) for 24 hours at room temperature, and 1.0 N NH4Cl (CLI-AC) under reflux for 3 hours.

Pyrolysis experiments were executed at 475 °C for 5 minutes under a nitrogen atmosphere (60 mL/min) with a 5 wt.% catalyst load. Comprehensive characterization, including indirect titration for acidity and GC-MS for bio-oil composition, revealed that CLI-PA yielded the most favorable results, achieving a 65.1% liquid yield and an HHV of 20.5 MJ/kg. Notably, this natural catalyst outperformed the synthetic ZSM5 benchmark, which produced a lower yield (46.5%) and energy content (16.8 MJ/kg). Furthermore, natural zeolite demonstrated a superior sustainability profile, featuring a 43-fold cost advantage and a 6-fold reduction in environmental impact compared to ZSM5. These findings position the proposed catalytic process as a robust and eco-friendly alternative for the sustainable recovery of agro-industrial waste.

References

[1] M. N. Puteri, L. T. Gew, H. C. Ong, and L. C. Ming, “Biomass-to-biohydrogen conversion: Comprehensive analysis of processes, environmental, and economic implications,” Sep. 01, 2025, Elsevier Ltd. doi: 10.1016/j.biombioe.2025.107943.

ABSTRACT. The increasing accumulation of plastic waste, particularly polyolefins such as polypropylene (PP), represents a growing environmental and technological challenge. Polyolefins account for more than 50% of the global plastic waste stream [1]. Among available waste management strategies, chemical recycling has attracted considerable attention as a route for recovering valuable products from waste plastics. In this context, pyrolysis enables the conversion of polymer waste into hydrocarbon mixtures that may be used as petrochemical feedstocks or components of transportation fuels. However, further development of this approach requires a better understanding of polymer degradation mechanisms and the role of catalysts in directing product distribution toward desirable fuel-range fractions. The present study investigates the thermal and catalytic pyrolysis of polypropylene using β-zeolite as a catalyst. Particular attention was paid to degradation pathways leading to hydrocarbons within typical fuel fractions. Experiments were carried out using complementary analytical techniques: pyrolysis–gas chromatography–mass spectrometry (Py-GC-MS) and pyrolysis combined with Fourier transform infrared spectroscopy (Py-FT-IR). These methods enabled identification of compounds formed during PP decomposition, evaluation of the chemical character of the resulting mixtures, and interpretation of possible reaction mechanisms involved in polymer degradation. β-Zeolite was selected due to its developed pore structure and the presence of acidic active sites known to promote cracking reactions and facilitate the transformation of polymer chains into lighter hydrocarbons. The obtained pyrolysis products were grouped according to carbon number into four fractions corresponding to conventional fuel ranges: C1–C4 (refinery gases), C5–C10 (gasoline range), C11–C15 (kerosene and light diesel range), and C15+ (heavier hydrocarbons). Additionally, the chemical character of the compounds was analyzed, with emphasis on aromatic, olefinic, and paraffinic hydrocarbons. This enables a preliminary assessment of the potential applicability of the resulting mixtures as blending components for conventional fuels. The results show that thermal degradation of polypropylene produces a wide range of hydrocarbons, with olefins representing a significant fraction of the products. Their formation is mainly associated with random chain scission followed by β-scission reactions during polymer decomposition. The presence of β-zeolite significantly influences the process by enhancing cracking reactions and promoting secondary transformations on acidic catalyst sites, including isomerization and hydrogen transfer reactions. Consequently, the product distribution shifts toward lighter hydrocarbon fractions with noticeable changes in the relative proportions of olefins and paraffins. Overall, the results provide insight into the relationship between polypropylene degradation pathways and the formation of hydrocarbons within fuel-range fractions, contributing to a better understanding of the potential use of polyolefin pyrolysis products in refinery processes or fuel blending.

Acknowledgements: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101086071, project name “CUPOLA — Carbon-neutral pathways of recycling marine plastic waste”. Support was also provided by the Ministry of Science and Higher Education in Poland through the program "PMW grant no. 5863/HE/2024/2 (no. W52/HE/2024).

ABSTRACT. Catalytic pyrolysis represents a cornerstone technology for the valorization of complex feedstocks, where the structural efficiency of the zeolite catalyst is paramount. To enhance catalytic performance while simplifying synthesis, this research establishes a robust template-free hydrothermal route for the production of hierarchical NaY nanozeolites. By systematically unraveling the synergistic interplay between gel composition and kinetic parameters, we successfully tailored the crystallization pathways to maximize textural properties suitable for industrial applications. The results reveal a distinct correlation between system dilution and crystal size, where an optimized H₂O/SiO₂ ratio of ~19.6 yielded ultra-small primary crystallites of 12 nm. Furthermore, the implementation of a multi-stage thermal protocol (incorporating a nucleation step at 80 °C) inhibited Ostwald ripening, resulting in a highly uniform morphology of interconnected nanocrystalline aggregates. Comprehensive characterization via XRD, FTIR, SEM, and advanced N₂ physisorption confirms the development of a superior hierarchical architecture. The optimized nanozeolites exhibit high specific surface areas (> 600 m²/g) and exceptional total pore volumes up to 0.844 cm³/g, merging intrinsic FAU microporosity with extensive interparticular mesoporosity. This specific architecture ensures optimal accessibility to active sites, making these materials highly effective candidates for demanding catalytic pyrolysis and upgrading reactions.

ABSTRACT. The pyrolytic decomposition behavior of ammonium nitrate (AN) and AN–nanothermite composites was investigated. A nanothermite composed of a fuel mixture (Al and Mg) and iron oxide nanoparticles supported on nitrogen-reduced graphene oxide (NGO@nFe₂O₃) ,synthesized via a one-step hydrothermal process and subsequently coated with nitrocellulose (NC). This mixture was used as a catalyst for AN, in proportions ranging of 7%. The resulting energetic formulations (AlMg-NGO@nFe₂O₃-NC/AN) were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), and oxygen bomb calorimetry. The kinetic parameters of AN decomposition were determined from thermogravimetric data using integral isoconversional methods, including the Kissinger–Akahira–Sunose (it-KAS) and Flynn–Wall–Ozawa (it-FWO) models.FTIR analysis confirmed that the chemical structure of the nitrocellulose-coated nanothermite corresponds to a physical mixture, indicating the successful synthesis of the composite. The combined kinetic and calorimetric results demonstrate the strong catalytic effectiveness of the AlMg/NGO@nFe₂O₃/NC system in promoting the thermal decomposition of ammonium nitrate (AN) and enhancing its energetic performance.

ABSTRACT. Spray pyrolysis is a simple and cost-effective process that has been widely applied to the synthesis of carbon-based composite microspheres with diverse compositions. In addition, spray pyrolysis enables the generation of micron-sized droplets with controlled precursor ratios, allowing the synthesis of catalysts with uniformly distributed components at specific molar ratios. In this study, Cu catalysts supported on CeO2-ZrO2 were synthesized using spray pyrolysis and applied to the reverse water–gas shift (RWGS) reaction. An enhancement in oxygen storage capacity (OSC) was found to positively influence catalytic activity, and Cu-CeO2-ZrO2 catalysts prepared at different calcination temperatures exhibited similar trends in both OSC and catalytic performance. Consequently, these results demonstrate that superior OSC properties of the catalyst can be translated into enhanced activity in the RWGS reaction.

ABSTRACT. The reverse water-gas shift (RWGS) reaction is a promising route for syngas production via CO2 valorization. However, the endothermic RWGS reaction faces strong competition with the methanation at low temperatures, limiting the simultaneous achievement of high activity and selectivity. To address these challenges, high entropy oxide (HEO) was applied as a catalyst for the RWGS reaction, leveraging its excellent thermal stability and tunable redox properties. Spray pyrolysis method allows precise compositional control, leading to the formation of structurally stable oxide catalysts. All catalysts were synthesized via spray pyrolysis, and among the three prepared catalysts, the CoNiCuZn catalyst exhibited the highest catalytic activity and stability, which can be attributed to its unique structural characteristics.

ABSTRACT. Biomass catalytic fast pyrolysis (CFP) is a promising process but its development is still hampered by the formation of coke which reduces the carbon selectivity of the process to the targeted aromatic hydrocarbons. It is important to better understand the effect of zeolite structure on the mechanisms of coke deposit and how this coke deposit poison the active sites (Bronsted sites, BAS). In our article [1] and in this poster, we provide a systematic comparison of various zeolites: mordenite (MOR), beta (*BEA) and ZSM-5 (MFI) with different hierarchization methods (NaOH, HF, NH4F). The effect of crystal size has been also studied for *BEA. These zeolites were tested with a constant biomass to catalyst ratio of 0.8 in a double fixed bed reactor which enables to decouple biomass pyrolysis and ex-situ volatiles conversion. The formation of volatiles species was monitored on-line by photoionization mass spectrometry. Aromatic hydrocarbons were also quantified by GC/MS-FID. The spent catalysts were analysed by pyridine probe (for acidity), FTIR (for coke composition) and N2 sorption (for porous structure). The structure of mordenite with a two dimensional network of channels and weak connections between the channels leads to a fast deactivation by pores blocking even after different hierarchization methods. The hierarchical MFI (obtained by mild desilication with NaOH) was the best selective zeolite towards aromatic hydrocarbons. The selectivity towards aromatics and coke formation depends on the shape of canals but not on the H+ cage environment. *BEA promotes the diffusion of species to BAS in larger pores than MFI but it leads to a lower shape-selectivity than MFI, especially after partial deactivation by coke.

[1] Pinard et al., Energy & Fuels 38 (15), 14351-14364, 2024

ABSTRACT. The thermochemical conversion of organic waste into value-added chemicals is a promising strategy for achieving resource circularity and reducing environmental burdens associated with waste disposal. Among various conversion routes, catalytic pyrolysis has attracted significant attention due to its ability to selectively upgrade complex organic feedstocks into high-value hydrocarbons. Conventional microporous zeolites, such as ZSM-5, are widely used in catalytic pyrolysis due to their strong Brønsted acidity and shape-selective pore structures, which are effective for promoting cracking, deoxygenation, and aromatization reactions. However, their strictly microporous channels impose significant diffusion limitations when processing bulky oxygenated intermediates derived from organic waste. These limitations often result in incomplete vapor upgrading, rapid coke formation, and catalyst deactivation, ultimately restricting aromatic yields and long-term catalytic stability. Nanosponge zeolites offer a promising alternative by incorporating a hierarchical pore architecture that combines intrinsic micropores with interconnected meso- and macroporous networks. This structural modification enhances molecular accessibility to active acid sites and facilitates the transport of large pyrolysis-derived molecules within the catalyst framework. As a result, nanosponge zeolites can alleviate diffusion resistance, suppress secondary condensation reactions, and mitigate coke deposition while maintaining the intrinsic catalytic functionality of the zeolite framework. These features make nanosponge zeolites particularly suitable for upgrading complex and oxygen-rich pyrolysis vapors generated from organic waste. During catalytic pyrolysis, the nanosponge zeolite facilitates cracking, deoxygenation, and aromatization reactions, promoting the conversion of oxygen-rich pyrolysis vapors into mono-aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylenes. Overall, this work highlights the potential of nanosponge zeolite catalysts for the efficient catalytic pyrolysis of organic waste and demonstrates their applicability for producing aromatic-rich hydrocarbon streams. The findings provide insight into catalyst design strategies for waste-to-chemicals technologies and contribute to the development of sustainable thermochemical conversion processes.

ABSTRACT. The continuous demand for fossil resources has resulted in greenhouse gas emissions, environmental degradation, and depletion of non-renewable feedstocks. As a sustainable alternative, catalytic co-pyrolysis of biomass and waste plastics has emerged as a promising approach for producing carbon-circulated aromatic hydrocarbons (BTX: benzene, toluene, xylene). This study aims to elucidate and optimise the catalytic reaction pathways that maximise BTX yields from the simultaneous conversion of woody biomass and plastic wastes. Particular attention is given to the interactions between biomass-derived furans and plastic-derived olefins, which are central to two key mechanisms: the furan–olefin Diels–Alder pathway and the hydrocarbon pool mechanism. The former enhances BTX selectivity through effective deoxygenation via dehydration reactions, while the latter promotes aromatic hydrocarbon formation by utilising olefins as hydrogen donors. These synergistic pathways reduce coke formation, improve catalyst stability, and enhance the overall efficiency of BTX production. ZSM-5 based catalysts were further tailored through metal incorporation and acidity modulation, enabling improved control over product selectivity and resistance to deactivation. The results demonstrate that catalytic co-pyrolysis can overcome the limitations of processing biomass or plastics alone, offering a viable strategy for upgrading heterogeneous waste streams into high-value aromatics. This work highlights the scientific basis for catalytic co-pyrolysis as a pathway to resource circulation and carbon neutrality within the chemical industry.

Acknowledgements: This study was supported by National Research Foundation of Korea (RS-2024-00341143, RS-2024-00416414) and also supported by the Ministry of the Environment’s waste resource energy recycling professional training project (YL-WE-22-001).

ABSTRACT. Polylactic acid (PLA) is often regarded as a biodegradable plastic, but it decomposes poorly under normal conditions and is mostly disposed of together with conventional plastic waste. To address this limitation, catalytic co-pyrolysis of polylactic acid (PLA) and high-density polyethylene (HDPE) was investigated to enhance deoxygenation and aromatic hydrocarbon formation. Non-catalytic co-pyrolysis showed strong synergistic suppression of oxygenates due to hydrogen transfer from HDPE-derived intermediates. Zeolite catalysts further promoted aromatization, with HZSM-5 (HZ) exhibiting high BTEX selectivity owing to its strong acidity and shape-selective micropores. To overcome diffusion limitations of bulky PLA-derived intermediates, hierarchical HZ catalysts were prepared by alkaline desilication using NaOH (N-HZ) or NaOH combined with TEAOH (TE-HZ) or TPAOH (TP-HZ). Compared with the parent HZ, which produced a BTEX area of 377.3 × 106, alkali-treated catalysts exhibited enhanced mesoporosity and increased acidity, leading to improved oxygenate removal and aromatic hydrocarbon formation. During catalytic co-pyrolysis, hierarchical catalysts significantly promoted decarbonylation, as evidenced by increased CO formation in the gas phase, due to facilitated transport of bulky PLA-derived oxygenates to accessible acid sites of catalysts. While N-HZ showed a slightly reduced BTEX signal (354.0 × 106) due to weakened shape selectivity and enhanced secondary alkylation, TE-HZ and TP-HZ exhibited higher BTEX production, reaching 396.8 × 106 and 430.1 × 106, respectively, owing to their well-regulated micro–mesoporous structures combined with increased surface area, pore volume, and acidity. Acknowledgement: This work was supported by National Research Foundation of Korea (RS-2024-00341143, RS-2024-00416414).

ABSTRACT. A hybrid catalyst combining nitrogen-doped reduced graphene oxide and α-Fe₂O₃ (N-rGO@Fe₂O₃) was synthesized through a facile one-step hydrothermal method, yielding a well structured material confirmed by extensive characterization. Its catalytic performance was investigated in the thermal decomposition of ammonium nitrate (AN). A composite containing 3 wt% of the hybrid material (N-rGO@Fe₂O₃/AN) was prepared using a recurrent spray-coating technique to ensure homogeneous distribution. Thermal analyses, including thermogravimetric (TG) and differential scanning calorimetric (DSC) methods, were used to evaluate the influence of N-rGO@Fe₂O₃ on the decomposition process, while isoconversional kinetic approaches provided Arrhenius parameters and the critical ignition temperature. The presence of the hybrid catalyst led to a notable improvement in AN decomposition behavior, reducing the activation energy by 41% and the oxygen bomb calorimetry measurements revealed an increase of 1,440 J·g⁻¹ in the calorific value of AN after surface modification with N-rGO@Fe₂O₃, indicating enhanced energy release.

ABSTRACT. Nano-cellulose nitrate has attracted increasing interest due to its unique physicochemical properties and potential energetic applications. In this study, the thermal decomposition kinetics of nano-cellulose nitrate were systematically investigated and compared with those of conventional (macro-scale) cellulose nitrate. Nano-cellulose was synthesized via a bacterial route, ensuring high purity and controlled nanoscale morphology. Thermogravimetric analysis (TGA) was employed to study the decomposition behavior under non-isothermal conditions. Kinetic parameters were determined using two model-free isoconversional methods, namely the iterative Kissinger–Akahira–Sunose (IT-KAS) and the iterative Flynn–Wall–Ozawa (IT-FWO) approaches. The results reveal a noticeable decrease of approximately 5% in the apparent activation energy for nano-cellulose nitrate compared to its macro-scale counterpart, indicating enhanced thermal reactivity associated with nanoscale effects. Furthermore, the decomposition process of nano-cellulose nitrate follows a different reaction model, g(α), highlighting a change in the dominant decomposition mechanism induced by nanostructuring. These findings demonstrate that size reduction at the nanoscale significantly influences the thermal decomposition kinetics and mechanisms of cellulose nitrate, providing valuable insights for its safe handling and potential energetic applications.

ABSTRACT. This study investigates the catalytic co-pyrolysis of Miscanthus (MT) and polystyrene (PS) over Zn-Fe co-modified HZSM-5/MCM-41 molecular sieves to produce aromatics. Various characterization techniques, including transmission electron microscopy, X-ray diffraction, Brunauer-mmett-Teller analysis, and ammonia temperature-programmed desorption, were used to analyze the catalysts. Py-GC/MS was employed to study the pyrolysis of MT and PS separately, together, catalytically, and non-catalytically, and to evaluate the catalysts. The experimental results show that all catalysts significantly increase the proportion of aromatics in the pyrolysis products. Under the action of 2wt% Zn-2wt% Fe-HZSM-5/MCM-41, Zn and Fe exhibit a notable synergistic effect, with the proportion (93.47%) and yield (1.01×109) of aromatics (AHs) reaching the maximum values. Oxygenated compounds, except for furan, drop to 0%. The synergy between Zn and Fe enhances the proportion of polycyclic aromatic hydrocarbons (PAHs) while suppressing the content of monoaromatic hydrocarbons (MAHs). Furthermore, after nine cycles of using 2wt% Zn-2wt% Fe-HZSM-5/MCM-41, the proportion of AHs decreases to 84.1%, which is lower than that in the non-catalytic pyrolysis of MTPS, indicating deactivation has occurred. This study provides a new approach for the recycling of MT and waste PS.

ABSTRACT. Abstract Thermo-catalytic methane pyrolysis has introduced a promising route for the simultaneous production of hydrogen and solid carbon without direct CO2 emissions. In this work, pyrolysis-derived carbon produced in a stainless-steel-based catalytic reactor is systematically characterized to assess its structural diversity and application potential. Scanning electron microscopy (SEM) analyses reveal the coexistence of multiple carbon morphologies, including agglomerated amorphous sub-micron particles, spheroidal carbon, and filamentous nanotube-like structures, indicating heterogeneous growth mechanisms driven by local catalytic conditions. Energy dispersive X-ray spectroscopy (EDS) confirms high carbon purity (typically >90 wt.%), with minor Fe- and Ni-based residues originating from the catalytic stainless steel, which may be advantageous for metallurgical integration. X-ray diffraction patterns show predominantly amorphous carbon with distinct graphitic (002) reflections near 26°, whose intensity and sharpness depend strongly on post-collection physical separation. Fine carbon powders exhibit sharper (002) peaks and reduced background noise compared to mixed flake-powder fractions, indicating locally enhanced structural order and partial graphitization. These results demonstrate that carbon quality can be significantly refined through morphology-based separation without altering synthesis conditions. The combined structural and compositional analysis highlights the versatility of methane pyrolysis-derived carbon and its tunability for targeted applications, including ironmaking reductants, carburizing agents, catalysis, and energy-related materials, supporting the role of methane pyrolysis as a circular and sustainable industrial process.

ABSTRACT. The surge in generation of medical waste, particularly plastic based waste needs immediate and sustainable eradication sustainable techniques due to its environmental and community health risk. The findings of this experimental study provide a strong basis for advancing microwave assisted catalytic pyrolysis into practical waste to resources solutions. These technologies are designed to be compliant, energy efficient, and resilient, supporting the needs of modern health care system while addressing regulatory, environmental, and operational challenges. They align with emerging frameworks for circular bioenergy and materials recovery, offering scalable approaches to global medical waste management infrastructure. Microwave assisted pyrolysis is gaining attention as a viable method for converting complex plastic waste into valuable products. In this study, the medical feedstock comprising PP, PE, PS and PVC, from syringes, IV bags, tubing, and packaging was rigorously pretreated, decontaminated and homogenized. Microwave-assisted pyrolysis of mixed medical waste plastics was carried out employing activated carbon as the microwave susceptor, alongside four different catalytic materials as activated alumina, iron powder, natural zeolite, and regenerated zinc oxide at fixed microwave power input of 450 W, reaching final temperature up to 600 °C. End products yield distribution confirms catalyst selection fundamentally determines cracking severity, secondary reforming, and product selectivity. With activated alumina, extensive β-scission and deoxygenated occurred, delivering lighter hydrocarbon fractions while limiting wax. Iron powder catalyzed in situ reforming and aromatization, markedly increasing H₂ and CO yields via dehydrogenation and cracking. Natural zeolite achieved shape selective monoaromatics production, though pore clogging and acid catalyzed condensation led to higher coke deposition. ZnO demonstrated intermediate acidic properties coupled with redox-active characteristics, facilitating balanced liquid production with suppressed coke formation while minimizing undesired carbon deposition and enhancing catalyst durability across repeating microwave assisted treatment cycles. Gas phase composition characterization confirms the enrich presence of hydrogen, methane, and light olefins when iron and ZnO were employed as catalytic additives, highlighting their effectiveness in generating syngas-type, energy-dense mixtures from medical plastic residues. The condensed liquid primarily consists aliphatic and aromatic hydrocarbons, exhibiting a lower proportion of heteroatom-containing compounds relative to uncatalyzed microwave pyrolysis underscoring the upgrading potential of the applied catalysts. The solid carbonaceous char residue exhibited increased fixed carbon content with improved chemical and physical properties for cyclical application as an auxiliary heating medium. This research establishes a novel approach combining affordable, regenerable catalytic materials with microwave-assisted processing for therapeutic polymer valorization, confirming operational viability, ecological compatibility, and commercial promise for distributed resource recovery networks within medical facility frameworks. Findings provide a scalable blueprint for circular economy implementation in high-risk waste streams, aligning with UN SDGs 3, 7, 12, and 13.

ABSTRACT. Marine plastic pollution constitutes a global environmental crisis, with an estimated concentration of at least 268,940 Mg of plastic particles in the oceans, primarily originating from riverine flows reaching 1.15–2.41 million Mg annually. In particular, polymer waste containing polyesters (PET) and polyolefins (PP, PE) does not undergo biodegradation and poses a permanent threat to aquatic ecosystems. Simultaneously, modern chemical recycling technologies can convert heterogeneous polymer mixtures into aromatic and aliphatic hydrocarbons with significant market potential. However, the application of conventional catalysts at the industrial scale may encounter economic and logistical barriers related to their sourcing and regeneration. The study conducted within the CUPOLA project focused on catalytic pyrolysis of marine polymer waste, utilising catalysts derived from waste processing, which represent a fundamental paradigm shift in resource thinking.

The catalysts used in this study were waste-derived materials, namely the solid residue from the gasification of sunflower husks (SH) and tomato processing waste (TW), as well as the commercial catalyst. SH and TW ashes were characterised by a composition dominated by alkali and alkaline earth metal oxides, primarily CaO and K₂O, accompanied by significant amounts of phosphates and sulphates (P₂O₅, SO₃). This chemical composition indicates a predominance of basic/neutralising properties and suggests a strong potential to bind acidic and halogen-containing species during pyrolysis.

These catalysts demonstrate potential for converting heterogeneous polymer mixtures without their preliminary sorting, maintaining the principles of circular economy by avoiding the challenges associated with sourcing pure materials. The application of such catalysts can additionally minimise multi-stage separation processes, which traditionally generate substantial operational costs and additional process waste streams.

The experimental section of the study encompassed catalytic pyrolysis of heterogeneous marine polymer waste at temperatures ranging from 400 to 600°C using analytical pyrolysis with chromatographic separation and mass detection (Py-GC-MS) with various waste-derived catalysts, followed by detailed product analysis and determination of possible directions for their subsequent utilisation. The results were compared with commercially available catalysts such as unmodified ZSM-5 and catalytically active forms of ZSM-5 in various modification variants (NH₄/ZSM-5, Ni-ZSM-5). The conversion yields obtained from the waste-derived catalysts reached 70–78% total conversion, with selectivity toward aromatic compounds (benzene, toluene, and xylenes) of approximately 52%, representing 10–20% higher compared to the commercially unmodified ZSM-5 catalyst, which achieved merely up to 30–40% BTEX compounds for PP and PET, respectively.

Such products constitute a precursor to a further purification process enabling subsequent steps to obtain products applicable in polymer synthesis, aircraft fuels with reduced sulphur content, and speciality chemicals. The study thus aligns with the broader vision of the European Green Deal, transforming the economy toward more sustainable and circular models, supported equally by European Union directives such as the Circular Economy Action Plan.

Acknowledgement

This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101086071, project name "CUPOLA — Carbon-neutral pathways of recycling marine plastic waste". This research was funded in part by the National Science Centre, Poland [Grant no. 2023/51/B/ST8/01531].

ABSTRACT. Carbon fibre reinforced plastics (CFRP) are extensively employed in the transport and energy sectors owing to their outstanding mechanical performance and high strength-to-weight ratio, which contribute to reduced fuel consumption and lower CO₂ emissions during service life. As their use expands across aircraft structures, automotive components, and recreational boats, the amount of CFRP waste expected in the coming decades is rapidly increasing. Despite their strategic importance, end-of-life management of CFRP remains challenging, as consolidated and economically viable recycling routes are still scarce. Among the different CFRP recycling technologies proposed, pyrolysis has emerged as a particularly promising option. This thermochemical route allows the decomposition of the polymeric matrix in an oxygen-free environment, enabling the recovery of high-value carbon fibres with minimal structural damage. At the same time, the resin is converted into a mixture of permanent gases and condensable vapours. While considerable research efforts have been devoted to optimising fibre recovery and preserving fibre properties, the effective valorisation of the volatile products generated during CFRP pyrolysis has received considerably limited attention, especially with regard to their conversion into hydrogen rich gas streams. In this work, the influence of different cracking catalysts, concretely zeolites, on hydrogen production during the pyrolysis of CFRP waste is investigated. Experiments were conducted using a two-stage reactor configuration, consisting of a primary pyrolysis reactor followed by a second fixed-bed catalytic reactor. The volatile products released during CFRP pyrolysis were directed to the catalytic stage, where they were subjected to further cracking and reforming reactions over the selected zeolites. A range of zeolite frameworks with different pore architectures, textural properties and Si/Al ratios was examined in order to establish correlations between catalyst characteristics, gas composition, hydrogen yield and overall performance. The experimental results demonstrate that the incorporation of a zeolitic catalytic stage substantially modifies the product distribution compared to non-catalytic pyrolysis. In particular, the presence of zeolites enhances gas formation and increases hydrogen production. This behaviour is mainly associated with the intensification of secondary cracking reactions of the pyrolysis vapours within the catalytic bed, which promotes the breakdown of heavier species into lighter gaseous compounds. As a result, hydrogen concentration in the product gas increases, while the formation of heavy hydrocarbons and high boiling condensable fraction is significantly suppressed. To sum up, this study demostrates the strong potential of zeolite-based catalytic upgrading for transforming CFRP-derived pyrolysis vapours into hydrogen-rich gas streams. These findings support the development of integrated recycling approaches that combine high-quality carbon fibre recovery with energy and chemical valorisation of the polymeric fraction, contributing to more sustainable end-of-life management of composite materials.

ABSTRACT. The management and disposal of plastic waste is an escalating challenge, with the EU alone producing over 29 million tons of post-consumer plastics annually [1]. Gasification presents a promising thermochemical pathway for converting plastic waste into synthesis gas (syngas), allowing for the processing of mixed plastics alongside energy recovery. Syngas primarily contains H₂, CO, CO₂, CH₄, and light hydrocarbons (C₂–C₅) [2], with its composition influenced by factors such as the oxidizing agent, temperature, and oxidant to plastic ratio. However, syngas can also carry contaminants, including halogenated and sulfur compounds, nitrogen species, tars, and trace organics like dioxins and furans, which can impede its downstream utilization [3]. Within the EU-funded SURPLAS project (Marie Skłodowska-Curie Actions), this work investigates plastic waste gasification, focusing on the impact of steam and catalysts on product yields, contaminant mitigation, and syngas optimization for applications such as Fischer–Tropsch (FT) synthesis.

This study specifically examines the steam gasification of plastic waste under both catalytic and non-catalytic conditions, focusing on syngas composition, product yields, and tar reduction. Experiments were conducted at 850 °C in a continuous-flow fluidized-bed reactor, using either inert bed material or a commercial nickel based catalyst, with and without steam. Gas products were collected and analyzed offline via gas chromatography. Feed and carrier gas flow rates were optimized (0.8 g/min PE, 2.7 L/min N₂) to maximize gaseous product yields while minimizing condensable organics.

Steam addition significantly increased H₂ and CO concentrations while decreasing CH₄, adjusting the H₂/CO ratio from 21.2 to 3.4, approaching the ideal range for FT synthesis. The incorporation of the catalyst dramatically reduced tar formation from 17.12 wt.% to 0.3 wt.% and increased total gas yield from 60.2 wt.% to 84.0 wt.%, attributed to enhanced reforming, water–gas shift reactions, and catalytic tar cracking.

These findings demonstrate that catalytic steam gasification of PE waste can produce high-quality syngas suitable for synthetic fuels and other downstream applications, supporting energy recovery and circular economy strategies.

Future work will investigate water–gas shift catalysts under varied conditions to further optimize syngas composition and minimize contaminants, as well as, assess the effects of incorporating other types of plastic waste.

Figure 1. Schematic representation of the experimental set-up

[1] Plastics Europe – The facts 2020; [www.plasticseurope.org] [2] C. Wu, P.T. Williams, Int J Hydrogen Energy 2010; 949-957 – 35 [3] PJ. Woolcock, RC. Brown, Biomass Bioenergy 2013;52:54–84.

ABSTRACT. Various types of biomass as a renewable and sustainable feedstock have attracted increased attention as precursors for activated carbons synthesis lately. Activated carbons can be synthesized from numerous precursors such as wood and its components and residues, e.g. industrial lignins or black liquor, nut shells, straw, peat, etc. Use of biomass in the production of carbon materials has several advantages, including low cost, abundance, and environmental friendliness. Chemical activation is a widespread approach to obtain activated carbons with the highly developed porosity, and it is possible to synthesize activated carbons with a specific surface close to theoretical limits for this type of materials. The main factors influencing total porosity, pore size distribution, surface groups functionality and nature of internal pore structure of the activated carbons can be summarized as follows: precursor nature, type of pretreatment (carbonization or hydrothermal treatment), activation temperature, nature of activation agent, activation agent impregnation ratio, taking into account that their combination can work in synergy and used for the fine tuning of desired properties.

This work is dedicated to the study of the influence of the above mentioned parameters on the properties of activated carbons. Various biomass-based precursors, including number of wood species, such as alder, birch, eucalyptus, oak, and pine, were tested to demonstrate how the choice raw materials can influence porosity. Two types of pretreatment, conventional slow pyrolysis and hydrothermal treatment, were tested to show the influence and the importance of carbonization methodology. Activation temperatures in the range 600-800 C and three common activation agents (NaOH, KOH and H3PO4) at various addition rates has been studied as well. The resulting activated carbons were characterized using nitrogen sorption at 77K, ultimate analysis, SEM, etc.

It is worth noting here that in some cases, biomass-based precursors have a certain hierarchical structure, which can contribute to the formation of the necessary porous material during the activation process, and thus tailored for the further application of the synthesized carbons as electrodes in supercapacitors, for oxygen reduction reactions in fuel cells, hydrogen evolution reactions, or as catalysts or catalyst substrates for other processes. Another possibility for further development of necessary properties is doping of activated carbons with various heteroatoms or transitional metals.

This study was funded by Horizon Europe Framework Programme, ARMS project, under grant agreement No 101120677, as part of Graphene Flagship initiative which works to advance technologies that rely on graphene and other 2D materials.

ABSTRACT. A substantial amount of spent nuclear graphite generates after the decommissioning of high-temperature gas-cooled reactors and molten salt reactors. The bromination mechanisms were estimated by density functional theory for the trace metallic radionuclides triggered by HBr on a nuclear graphite surface in an enhanced thermal treatment. The existence of defects affected both the adsorption and the diffusion of metallic nuclides on surfaces. Ni, Cs and Eu adatoms were adsorbed preferably at the defective surface, and the defective sites enhanced the adsorption of metallic nuclides. The presence of HBr could promote the diffusion properties of 59Ni, 134Cs and 152Eu on defective surfaces. The absorption energies of 59Ni and 152Eu on the single vacancy (SV) were -698.8 and -202.9 kJ/mol, respectively, which were substantially larger than those on the double vacancy (DV) and the pristine surface. Moreover, the absorption energy of 134Cs on the DV was -341.2 kJ/mol, which was far greater than that on the pristine and SV surfaces. Based on the energy barrier of the rate-determining step, the recovery of Ni and Eu by bromination was more difficult than that of Cs. The bromination of Ni, Cs and Eu on the surface of defective graphite was all described by the second order reaction model. The most stable adsorption site in single vacancy existed for Ni and Eu atoms, while that emerged in double vacancy for Cs atom. The bromination roasting approach was feasible for recovery of 59Ni, 134Cs and 152Eu from nuclear graphite. Bromination reaction pathways of 59Ni, 152Eu and 134Cs followed the sequence: Ni → NiBr → NiBr2, Eu → EuBr → EuBr2, Cs → CsBr. The bromination of three metallic nuclides on the defective surfaces all obeyed the Eley-Rideal mechanism. The study would contribute to fundamental data for the design of enhanced thermal treatment systems for decommissioned nuclear graphite.

ABSTRACT. This study investigates the hydrothermal carbonization (HTC) of wet sewage sludge as a thermochemical pretreatment prior to plasma gasification. The impact of reaction temperature and residence time on hydrochar yield and properties are examined, with particular emphasis on their suitability for syngas production and nutrients recovery during subsequent treatment in a plasma torch. The combined application of HTC and plasma gasification advances the current state of the art on the treatment of organic waste streams from wastewater treatment plants, aiming to maximize the value creation from this challenging biomass.

Hydrothermal carbonization of centrifuged, digested sewage sludge is performed at reaction temperatures of 180, 210, and 240 °C and residence times of 2 and 4 h, using a constant water to biomass ratio of 7. Initial experiments are performed in small 30-mL autoclave reactors heated in an electric oven and subsequently scaled up to a 450-mL stainless-steel mechanically stirred autoclave reactor under identical process conditions. The resulting hydrochars are analyzed through elemental and proximate analyses to determine their composition and higher heating value (HHV), while hydrochar yields are calculated through mass balance techniques. Metal and mineral contents are quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES), with a specific focus on phosphorus (P) to calculate P recovery yields.

Previous studies on HTC of non-thickened digested sewage sludge with a total solids content of 4.1 % were carried out in 30 mL autoclave reactors at temperatures between 180 and 220 °C and residence times of 2 and 4 h, resulting in promising average char yields (57.6 – 72.2 %) and phosphorus recovery efficiencies (79.9 – 89.3 %), with HHV values ranging between 8.5 and 9.0 MJ/kg. The present study builds on this work by exploring a broader temperature range, increased reactor scale, and higher solid content in the biomass, enabling a more comprehensive assessment of hydrochar properties.

Based on the experimental outcomes, an optimization criterion for further conversion in plasma torches will be determined, based on the following features: carbon enrichment, energy yield, hydrochar production, and mineral recovery yields. In addition, this approach may be extended to the treatment of industrial sewage sludge containing persistent xenobiotics such as PFAS, offering potential pathways for contaminant stabilization within the char followed by high‑temperature destruction during plasma gasification.

ABSTRACT. The main aim of the present study is to assess the feasibility of a self-sustained process within an innovative auger pyrolyzer (SPYRO), targeting biochar production, and to increase plant throughput through autothermal operation. To the author’s knowledge, autothermal operation has been achieved and validated in various reactors, such as fluidized and fixed bed reactors. However, it has not yet been investigated in auger reactors. Despite auger reactors present a simple design, the heat transfer is a limiting factor for scaling up. Therefore, this work deals with the experimental investigation of poplar oxidative slow pyrolysis (OSP) within an innovative patented auger reactor, which was designed to facilitate the introduction of air into the cylinder. In this work autothermal pyrolysis is proposed as a solution to overcome the heat exchange limitation of allothermal reactors. Firstly, OSP trials were performed at a poplar flow rate of 1.5 kg/h, temperature of 500 °C and solid residence time of 30 min, at distinct amount of air injected into the reactor. An increase in the air flow rate led to an increase in gas and reaction water yields and a decrease in organics yield, whereas char yield was almost preserved at 25 wt%. Autothermal operation was experimentally achieved at an equivalence ratio (ER) of 0.05 ± 0.03. In this condition, partial oxidation of products provided the enthalpy for pyrolysis while reactor heaters were only used to overcome thermal losses. Without countering thermal losses in this manner, pilot pyrolyzers would require operation at very high equivalence ratios to overcome thermal losses. These would result in excessive consumptions of pyrolysis products and inaccurate performance predictions for industrial-scale reactors. Autothermal operation led to a decrease of 7 wt% in organics yield compared to conventional pyrolysis. On the other hand, yields of reaction water and gas increased by 4 wt% and 8.6 wt%, respectively, while char yield was almost preserved at 24.7 wt%. These outcomes suggested that during autothermal operation the heat for the process was mainly provided by volatiles oxidation rather than char oxidation. In addition, it led to a decrease of 3.4% and 3.9% in the energies retained in the oily and aqueous phases, respectively, compared to conventional pyrolysis. On the other hand, gas energy increased by 3.5%, while the energy retained in the char was almost preserved and equal to 42 wt%. The total energy content of the pyrolysis products decreased by 2%, since volatiles were partially oxidized to provide heat for the process. Finally, the intensification of OSP was performed by increasing both biomass and air flow rates while keeping constant the ER slightly above 0.05. Autothermal operation made possible a three-fold increase in feedstock throughput for this reactor, resulting in a 3.1-fold increase in biochar, a 2.0-fold increase in oil phase, a 3.6-fold increase in aqueous phase, and an 8.8-fold increase in gas compared to allothermal operation, while maintaining constant electric consumptions and yield of products. Therefore, autothermal operation enabled smaller reactors to handle much higher throughputs compared to heat transfer-dependent reactors of similar size.

ABSTRACT. Nuclear graphite serves as an indispensable core material for the fourth-generation advanced nuclear energy systems such as high-temperature gas-cooled reactors (HTGRs) and molten salt reactors (MSRs). During the irradiation service period, nuclear graphite will adsorb and accumulate various radionuclides, which would encounter severe challenges to its subsequent treatment and disposal after decommissioning. At present, the technology is still immature for efficient and thorough decontamination of decommissioned nuclear graphite. The synchronous deep removal of multiple impurities embedded in the graphite matrix has become a key bottleneck restricting the safe treatment and resource utilization of nuclear graphite. Therefore, in this study a multi-halogen synergistic roasting technology was proposed for removing radionuclides from decommissioned nuclear graphite, aiming to systematically evaluate the removal mechanism and regulation effect of this technology on all impurities in decommissioned nuclear graphite. The effect of single additive (NH₄Cl) and the composite additive (NH₄F-NH₄Cl) was compared on the overall volatilization rate of main impurities such as Ca, Mg, Sr, V and U. The composite additive was able to significantly enhance the overall volatilization efficiency of target elements in decommissioned nuclear graphite by virtue of the fluorine-chlorine synergistic complementary effect. In addition, a Back Propagation (BP) neural network model optimized by the Particle Swarm Optimization (PSO) algorithm was developed constructed, establishing a nonlinear mapping relationship between process parameters (three composite additives: NH₄F-NH₄Cl, NH₄F-NH₄Br and NH₄Cl-NH₄Br and their dosage, as well as roasting temperature) and volatilization rate. On this basis, the Non-dominated Sorting Genetic Algorithm Ⅱ (NSGA-Ⅱ) was introduced for multi-objective optimization to screen out the optimal process scheme that could balance the maximization of volatilization rate and the minimization of energy consumption. The overall volatilization rate of elements in nuclear graphite ramped up with the rise of temperature and additive dosage. when the temperature was over the critical threshold (1427 ℃), it became the core driving factor dominating element volatilization, while the regulatory effect of composite additive ratio on the volatilization process greatly weakened. When the mass ratio of additive to graphite was close to 2:1, the supply of halide ions in the system was sufficient to fully remove the impurities in graphite. NH₄F-NH₄Cl additive was identified as the optimal halogenating additive combination. The findings could provide important theoretical basis and direction for the harmless and effective disposal of decommissioned nuclear graphite.

ABSTRACT. This study centres biochar as the key pyrolysis product, evaluating pinewood biochar as a partial Portland cement replacement in cementitious grouts and examining how curing environment governs performance when biochar is combined with supplementary cementitious materials (SCMs) to reduce clinker demand. Although biochar is often discussed mainly as an environmental amendment, its porous, carbonaceous structure and surface chemistry can also influence hydration kinetics, moisture transport and cracking behaviour in cement-based materials. If these interactions are managed through mix design and curing, biochar offers a route to lower-carbon binders while introducing a stable carbon phase into long-life infrastructure. Here, we focus on practical formulation space for pumpable grouts and on curing conditions that are realistic for field placement, linking fresh-state workability and setting to longer-term mechanical and durability indicators.

Our proof-of-concept work showed that adding biochar consistently reduced initial flow and increased flow loss over 30 minutes. This behaviour is consistent with water uptake into the biochar pore network and higher particle friction and it was more pronounced when slag and biochar were combined due to their higher overall surface-area demand. Moderate biochar incorporation (≤15% wt.%) maintained workable mixes (typically <25 wt.% loss of spread) while enabling meaningful clinker reduction. In hardened grouts, curing environment was decisive: sealed air curing increased compressive strength by from 25 to 80 wt.% relative to unsealed curing by limiting moisture loss and carbonation-related decalcification, particularly in SCM-rich systems. Under sealed air curing, many mixes with ≥60 wt.% Portland cement achieved at least 75% wt.% of the reference strength, whereas high biochar contents (25 wt.%) depressed compressive strength under unsealed curing (typically 20–40% lower), consistent with dilution and increased matrix porosity. In contrast, flexural behaviour was more composition-sensitive; slag–biochar combinations frequently improved modulus of rupture (up to ~15%), consistent with crack-bridging and toughening from carbonaceous inclusions. Biochar-containing mixes tended to show slightly lower sorptivity (pore connectivity) but higher absorption at high dosages (total open porosity). Carbonation depth increased as clinker content decreased, but remained limited (<5 mm) when Portland cement content was ≥55 wt.%.

The results also showed that pyrolysis-derived biochar can function simultaneously as a carbon-sequestering filler and a microstructural modifier in grout systems, provided dosage and curing are designed together. Because the pinewood biochar was highly carbonaceous (85.1 wt.% C) and retained a porous surface area after grinding (8.3 m² g⁻¹), it represents a stable, functional carbon phase rather than an inert filler, with clear potential for incorporation into long-life construction materials. This provides a credible, higher-value utilisation route for pyrolysis chars beyond land application, while supporting clinker reduction when biochar is combined with SCMs. Practical formulations were achieved at ≤10 wt.% biochar with balanced SCM contents, while higher biochar levels require sealed curing (or equivalent moisture management) to retain strength and durability.

ABSTRACT. Fast pyrolysis of lignocellulosic residues produces a solid char fraction whose high volatile content and limited structural stability restrict its valorization beyond energy use. Within the Horizon Europe project ABATE, we investigated a thermal stabilization pathway to upgrade fast‑pyrolysis char (FP‑char) derived from sawdust (SD) and forest residues (FR). FP‑chars were pelletized and subjected to slow‑pyrolysis at 500 °C in a pilot plant, generating pilot‑scale stabilized chars (PSS‑chars). A comprehensive analytical dataset was collected to characterize the structural, compositional, and microstructural evolution induced by stabilization. Proximate and ultimate analyses quantified significant chemical shifts, with H/Corg molar ratios decreasing from 0.82 (SD) and 0.53 (FR) to 0.33 and 0.37, respectively. Thermogravimetric analysis (TGA) revealed substantial depletion of thermolabile fractions, and reflectance microscopy provided direct evidence of carbon structural reorganization, with inertinite content increasing from 7.9 % to 44.6 % (SD) and 5.1 % to 47.7 % (FR), indicating a transition toward highly condensed aromatic domains. Microstructural characterization by N₂ physisorption showed moderate increases in BET surface area, while water‑holding capacity measurements revealed slight reductions, consistent with pelletization‑induced densification. Organic contaminant analysis (PAH16, PCDD/F, PCB) confirmed concentrations well below EU limits, with PAH16 at 0.97–2.06 mg/kg. Overall, thermal stabilization at 500 °C significantly enhances FP‑char permanence, transforming a labile co‑product into a structurally robust carbonaceous material. The high degree of recalcitrance already achieved (H/Corg < 0.4; inertinite > 40 %) suggests that increasing the maximum process temperature, e.g. toward 600 °C, may unlock additional improvements in carbon stability, increasing further the inertinite content. This treatment broadens potential applications, including carbon removal certification pathways and soil‑related deployment where long‑term carbon persistence supports both agronomic value and carbon accounting functions.

ABSTRACT. Biochar as a value-added pyrolysis product converts lignocellulosic residues into a stable, carbon-rich material that can be traded and used across agriculture, remediation and materials markets. Its quality can vary widely because pyrolysis is carried out using different feedstocks and operating conditions. As a result, biochar from different biomass batches, sites or harvesting seasons may show clear differences in properties that matter for use and sale, including carbon content, ash and nutrient levels, pH and surface chemistry. This variability is a growing challenge for biochar quality assurance and certification. Current certification routes typically rely on representative sampling, laboratory analysis and audit-based checks, which can be expensive and slow and may miss variation within biochar batches. To scale certification with market growth, producers need faster ways to check product quality during production and before shipping. Hyperspectral imaging (HSI) can support biochar certification by providing a quick, non-destructive check of product consistency. When paired with machine learning (ML) and artificial intelligence (AI), HSI data can screen key quality indicators and identify batches that may need confirmatory laboratory testing, strengthening routine quality control.

We present a UK-Viet Nam study where wood-based feedstocks from Viet Nam were converted to biochar by pyrolysis and then assessed in the UK to support biochar quality control and certification. Biochar samples produced across 300-600 °C were scanned using a near-infrared HSI system collecting 168 spectral bands over 884-1726 nm . This provided a fast, non-destructive way to capture chemistry-related signals and detect variation across the sample surface. After standardising the spectra, we trained predictive models for key elemental parameters (C, H, N and O). For single-wood biochar, strong performance was achieved even with a small dataset (<50 samples), reaching prediction scores up to R² = 0.998 for elemental composition. When multiple wood sources were combined, advanced models maintained good performance, supporting robust screening across mixed-feedstock biochar and reflecting real supply-chain conditions.

Our preliminary results show that combining HSI with ML and AI provides a practical, fast screening method for pyrolysis biochar. The HSI signal can be converted into simple, numerical quality indicators that support routine checks, batch sorting and tighter process control without disrupting production. For certification, this approach can sit alongside standard laboratory testing by reducing repeat analyses, identifying batches that may not meet the required quality, and keeping a simple digital record for tracking and reporting as biochar is traded more widely. Next steps will expand the multi-feedstock training set (including additional UK–Viet Nam samples), improve model transfer between instruments and sites, and run Round Robin inter-laboratory comparisons to benchmark HSI systems and modelling pipelines and move towards harmonised, reproducible rapid-assessment methods.

ABSTRACT. CO2 activation is a thermochemical process used to transform raw biochar into a high-performance material, often referred to as activated biochar. In this work, the biochar produced from spruce wood was activated using CO2 as activated agent at 700 and 900 °C. The untreated biochar and CO2 activated biochar were characterized using a combination of analytical techniques. The mass yield from activation experiments indicated CO2 activation removes residual tars and volatile organic compounds trapped in the biochar pores during initial pyrolysis. As the activation were conducted at 900 °C, CO release was more intensive where CO2 starts etching the carbon. The concentration of CO in the effluent gas rises as the Boudouard reaction becomes more favorable, leading to more significant burn-off of material. As the activation temperature increases, the carbon matrix is consumed by the CO2 gasification reaction. This leads to a relative enrichment of most inorganic elements. The FTIR analyses indicate that more oxygen-containing functional groups formed on the surface of biochar after CO2 activation. It can enhance the biochar’s affinity for specific reactants or pollutants. The SEM-EDS analysis results showed, CO2 activation etches away the carbon matrix, exposing inorganic element (e.g., Ca and K) naturally present in the biochar. It leads Ca and K move from the internal bulk to the surface of the pores created by CO2, making them more accessible for catalytic reactions. In addition, the temperature is the critical threshold that dictates the chemical state of these inorganic elements, particularly calcium, which is most abundant inorganic element in the studied biochar. The XRD analysis results revealed that, at low activation temperature 700°C, the carbonation effect is more evident as for example CaO or MgO produced during initial heating can react with the CO2 atmosphere to form carbonates. For the biochar after activation at 900 °C, both calcium carbonate and oxide were detected. The latter was formed due to decomposition of the calcium carbonate, which is highly significant for using the activated biochar as catalyst.

ABSTRACT. Auger reactors represent an interesting alternative for the pyrolysis of biomass. Research focused mainly on the mass throughput and the power requirements of horizontal, inclined, or vertical screw conveyors. Knowledge of the residence time would be beneficial for simple modeling of auger reactors, especially with heat-carriers and could be used for the design and scale-up of these types of reactors [1]. Literature on residence time is rather sparse and therefore still not well understood, and often an ideal plug flow is assumed to predict the solid residence time. Nachenius et al. measured the residence time of four different materials for a single screw conveyor and created a model to predict the mean residence time that took not only the frequency but also the volumetric throughput into account [2]. This showed a good prediction for the tested geometry and materials. However, the current methods are not able predict the actual residence time of screws with larger pitches and underestimate them significantly. Also the influence of the ratio between the particle size and clearance on the residence time is often not taken into account. Therefore the aim of this was to create new methods to predict the mean residence time of a wider range of pitches that also take other parameters into account, such as e.g. the clearance. With the help of Discrete Element Method various pitches were investigated and two new models were developed, by combining the ideal plug flow and the work of Nachenius et. al. with the transport efficiency that was investigated in earlier work. [3, 4]. This showed good predictions the own simulations and experiments, as well as for various screw conveyors from literature and can be used to model the pyrolysis in an auger reactor.

References [1] S. Papari, K. Hawboldt, Development and Validation of a Process Model To Describe Pyrolysis of Forestry Residues in an Auger Reactor, Energy & Fuels 31 (10) (2017) 10833–10841. doi:10.1021/acs.energyfuels.7b01263 [2] R. Nachenius, T. Van De Wardt, F. Ronsse, W. Prins, Residence time distributions of coarse biomass particles in a screw conveyor reactor, Fuel Processing Technology 130 (2015) 87–95. doi:10.1016/j.fuproc.2014.09.039.

[3] W. Peters, Schnellentgasung von Steinkohlen, Habilitationsschrift RWTH Aachen, 1963. [4] E. Aschenbrenner, A. Funke, Numerical Validation of a Screw Conveyor Design Method, Energy & Fuels 38 (14) (2024) 13019–13028. doi:10.1021/acs.energyfuels.4c00189.

ABSTRACT. Wind turbine blades are typical thermosetting composites characterized by high chemical stability and a highly crosslinked three-dimensional network structure. The fiber reinforcement accounts for more than 60% of the total mass, making end-of-life blades a potential resource rich in high-value glass fibers. During pyrolysis of waste wind turbine blades, cracking products from the resin matrix exert an erosive effect on the glass fibers, damaging the structural integrity of the fiber surface, inducing microcracks and surface defects, and consequently reducing the mechanical strength of recycled fibers. This study systematically investigates the evolution of mechanical strength and the transformation behavior of the intrinsic surface structure of recycled glass fibers under high-temperature pyrolysis–oxidation conditions. Results show that at a pyrolysis temperature of 500 °C, the epoxy matrix undergoes complete depolymerization and volatilization, resulting in carbon deposition and axial microcracks on the fiber surface. Consequently, the tensile strength decreases from 2969.54 MPa to 2151.52 MPa, accompanied by a reduction in the Weibull modulus, indicating a defect-dominated failure mechanism. Subsequent oxidation treatment in the range of 300–500 °C reveals a distinct performance transition. Under moderate oxidation conditions (350–400 °C), the initially continuous and dense carbon layer gradually transforms into discrete carbon residues and is ultimately removed (weight loss increasing from 1.27% to 3.06%). Correspondingly, the tensile strength increases to 2724.92 MPa, achieving 91.7% of the original fiber strength. Between 400 and 450 °C, the fibers enter a transitional stage characterized by declining mechanical performance. When the oxidation temperature exceeds 450 °C, high-temperature oxidative cleavage of the Si–O–Si network occurs, and structural degradation features such as corrosion pits and cracks appear on the fiber surface, leading to a significant decrease in tensile strength to 1964.92 MPa. Overall, this work elucidates the synergistic mechanism of “pyrolytic depolymerization for resin removal – moderate oxidation for decarbonization and release of interfacial constraints – excessive oxidation inducing glass network degradation.” The evolutionary pathway of fiber performance—from damage initiation to strength recovery and finally structural deterioration—is clarified, and 350–400 °C is identified as the critical oxidation window for maximizing strength retention.

ABSTRACT. The sustainable valorization of biomass-derived waste streams is a critical challenge in advancing circular bioeconomy strategies while reducing environmental burdens. Fast pyrolysis of lignocellulosic feedstocks generates complex aqueous phases that can contain up to 30 % of the initial carbon as soluble oxygenated organics. These streams are often treated as wastewater, resulting in carbon loss and increased treatment costs. Integrating pyrolysis with downstream catalytic processes, particularly aqueous phase reforming (APR), offers a promising route to produce renewable hydrogen and light hydrocarbons. However, the efficiency and selectivity of APR is strongly dependent on the chemical composition of the feed, which is highly variable and poorly understood for real pyrolytic waters. A wide range of organics commonly present in pyrolytic process waters can poison catalysts, promote fouling, or trigger undesired side reactions, making comprehensive characterization of these streams a prerequisite for effective catalyst design and process optimization.

In this study, five representative aqueous fractions derived from fast pyrolysis of agricultural and forestry residues were comprehensively analyzed using advanced analytical techniques. Chromatographic methods (GC-FID, HPLC-UV, HPLC-RI, headspace and direct injection GC-MS) were combined with elemental analysis, ICP-OES, and physicochemical measurements to quantify various organics, inorganic species, and bulk properties.

Results revealed wide variability in water content (23.6–80.9 wt%), carbon content (9.2–48.4 wt%), and acidity (pH 2.1–3.2), strongly influenced by feedstock type, pyrolysis severity and separation method. High concentrations of reactive oxygenates such as glycolaldehyde (up to 67 g/L) and hydroxyacetone (up to 30 g/L) reinforced the potential of these aqueous streams for catalytic conversion via APR. The detection of thermally unstable or polymerization-prone species such as levoglucosan, furans, and phenolics indicated the need for stabilization strategies (e.g., mild hydrogenation) to suppress coke formation during APR. Inorganic analysis revealed significant levels of K, Mg and S, particularly in wheat straw-derived samples, which may poison reforming catalysts or accelerate sintering.

These findings demonstrate that APR catalyst development for pyrolytic waters cannot rely on simplified model compounds or generic assumptions about feed quality. Instead, tailored valorization APR strategies must address the high oxygen content, acidity, and presence of reactive species in pyrolytic aqueous phases. The resulting compositional fingerprints provide essential input parameters for designing APR catalysts that achieve high conversion efficiency with minimal deactivation. Ultimately, coupling detailed characterization with targeted APR catalyst engineering will facilitate thermochemical–catalytic upgrading routes for sustainable fuel production.

ABSTRACT. Hydrogen storage systems have become of great interest particularly especially for those that conjugate a high storage capacity together with high safety standards. Chemical storage using amino borane has attracted a great interest and ammonia borane is playing a major role in the field due to the hydrogen storage capacity up to 19 wt%. Nevertheless, the hydrogen evolution from ammonia borane is a matter of great complexity and hydrolytic methods represent the simpler way to approach it. Actually, the ammonia borane hydrolysis is carried out by using complex catalysts not containing critical raw materials and/or noble metals. In the present work, we report the production of iron based heterogeneous catalyst support onto biochar derived pig manure. The complexity of this waste stream was very helpfully to provide an active surface for the anchoring of iron nanoparticles and promoting the hydrogen evolution form hydrolysis of ammonia borane reaching a conversion of 98.3 % at 50 ◦C with an iron loading of 10 wt%. The catalytic system reduced the activation energy of the reaction up to 51 % increasing the kinetic constant of the reaction of one order of magnitude. Furthermore, the stability of the catalytic system was preserved after three cycles without appreciable changes.

ABSTRACT. Corn is one of the most widely produced raw materials globally. According to the literature, corn grain production in the EU alone exceeds 61 million tones in 2023 (Pacuar et l., 2025). This suggests a meaningful possibility that corn cob residues could serve as a viable feedstock for biochar production and future applications. Corn stalk waste has been analyzed in terms of three components: corn stalk wall, corn stalk spongy core, and leaves. Experiments were carried out for final carbonization temperatures of 450, 550 and 650ºC using laboratory scale batch reactor. First stage of experimental investigations showed that biochar from the corn stalk wall is characterized by its lower volatile (19.5%) content than biochar from leaves and the spongy core (27.5% and 27.2% ) and higher fixed carbon content, which reached 65.6% and 52.2 and 49.7% for leaves and the spongy core respectively. The first stage of experimental investigation showed that carbonization of the mixture of corn stalk waste is characterized by a similar caloric value of the obtained gases (3.08-3.67 MJ/kg). However, the analysis of the calorific value of the entire volatile fraction (tar + gases) indicates that increasing the temperature of corn stalk carbonization t from 450 to 650 °C results in an increase in the total calorific value of the products from 2.5 MJ/kg to 7 MJ/kg. Characterization of the obtained biochars showed that low content of fixed carbon and high ash content, indicates that obtained biochar samples cannot be used to produce barbecue products. However, thermogravimetric analysis of the biochar samples suggested that the biochar produced at a carbonization temperature of 650 °C may exhibit a relatively high calorific value and combust in a manner similar to that of a commercial charcoal briquette. These results indicate that the obtained biochars may be used as additive for the formation of fuels intended for combustion. An important aspect of biochar application is its potential use in wastewater treatment, particularly for the removal of pharmaceutical contaminants. Adsorption experiments were conducted over a 24 h test. The evaluation of biochars derived from corn stalk waste indicated that biochar produced at a carbonization temperature of 450 °C adsorbed approximately 21% of ibuprofen from an aqueous solution with an initial concentration of 100 mg L⁻¹. In contrast, chemical modification of the biochar using a 1 M HCl solution enhanced the adsorption efficiency to 81%. These results suggest that biochars derived from corn stalk waste may be suitable for application in wastewater treatment processes.

Financial support for this study was provided by National Science Centre. Poland. OPUS 25. Nr. 2023/49/B/ST8/02136/R – “Experimental research and modeling of contaminant transformation processes in biochar-sand filters”

ABSTRACT. Carbonaceous materials are highly promising for post-lithium energy-storage devices, particularly aqueous zinc hybrid supercapacitors (ZHSCs). However, conventional carbon-based cathodes suffer from limited capacity and sluggish ion transport, restricting the achievable energy density and efficiency of ZHSCs.1 Developing sustainable, high-performance alternatives is therefore critical. Here, we investigate biomass-derived hard carbons (BHCs) from almond tree pruning residues (AT) and almond shells (AS)—non-edible agricultural by-products abundantly generated during almond cultivation and processing—as low-cost cathode materials. Valorisation of these residues aligns with circular-economy principles while enabling the production of functional carbons with tuneable surface chemistry, structural diversity, and cost-effective synthesis.2 The study systematically examines the influence of precursor morphology, activation strategy, and electrochemical configuration on the resulting electrochemical performance. The precursors (AT and AS) were converted into hard carbons via hydrothermal pre-treatment followed by chemical activation using K2CO3 or KOH, generating hierarchical porous materials, as illustrated in Figure 1. HTC significantly enhanced surface area and porosity by opening the lignocellulosic matrix, facilitating deeper penetration of the activating agent and increasing ion-accessible sites. AT-derived carbons exhibited the highest surface areas (1461–1494 m2 g–1) and mesopore volumes (up to 0.068 cm3 g–1) surpassing AS-derived materials. This reflects how AT is more reactive, in contrast to the denser and lignified structure of AS, as confirmed by thermal and morphological analysis. Mild K2CO3 activation achieved high carbon recovery (ca. 19 wt. %), outperforming harsher KOH routes by limiting excessive burn-off. Figure 1. Schematic of hard carbon synthesis from almond residues Electrochemical testing confirmed the superior performance of AT-derived hard carbons. The best-performing K2CO3-treated sample delivered a specific capacity of 142 mAh g–1 at 0.1 A g–1 and maintained 92 % capacity retention over 2 000 cycles at 10 A g–1. Its enhanced performance is attributed to hierarchical porosity, higher mesopore volume, and oxygen-rich surface chemistry. This improves electrolyte wetting, reduces ion-diffusion resistance, and enables mixed electric double-layer and pseudo-capacitive charge storages. Overall, these findings establish a sustainable and scalable strategy for converting almond-based agricultural residues into high-performance hard carbons for next-generation aqueous ZHSCs. Precursor selection and pre-treatment are decisive: the morphology and chemical composition of AT favour pore development and activation efficiency, while hydrothermal pre-treatment promotes hierarchical porosity and introduces O-containing moieties on surface leading to improved rate capability and cycling stability. References: (1) Ramavath, J. N.; et al. J. Electrochem. Soc. 2021, 168, 010538. (2) Yang, L.; et al. J. Mater. Chem. A 2022, 10, 24208–24215.

ABSTRACT. The temporal evolution of gas composition during biomass gasification offers important insight into reaction mechanisms and process dynamics. Monitoring key gaseous species such as oxygen (O2) and carbon dioxide (CO2) makes it possible to identify distinct operational phases, including initial oxidation and subsequent gasification under sub-stoichiometric conditions. This study analyzes gas concentration profiles measured during a gasification run to clarify the transition between these stages and to evaluate the influence of biomass fuel properties on reaction behavior. At the beginning of the process, oxygen concentrations remain close to atmospheric levels (~21 vol.%), indicating that the reactor initially contains air. As gasification starts, a rapid decrease in O₂ concentration is observed, reflecting oxygen consumption through partial oxidation reactions. These reactions are essential for providing the heat required to sustain endothermic gasification processes. Although oxygen levels drop to very low values, they do not remain at zero, confirming operation under sub-stoichiometric conditions characteristic of gasification rather than complete combustion. Simultaneously, CO2 concentrations increased sharply, reaching peak values of 15-16 vol.% shortly after the O2 minimum (1.5 vol.%). This peak corresponds to the initial oxidation stage, during which part of the biomass carbon is oxidized to CO2, contributing significantly to reactor temperature rise. The presence of two CO2 curves suggests differences related to fuel type, measurement location, or experimental conditions, resulting in variations in peak intensity and temporal behavior. Following this peak, CO2 concentrations gradually decline, signaling a transition from oxidation-dominated reactions to gasification reactions. As oxygen becomes scarce, CO2 is increasingly consumed through secondary reactions, particularly the Boudouard reaction, which converts CO2 into CO. This process explains the sustained decrease in CO₂ levels despite the continued presence of carbonaceous material. Differences in the decay rates of the CO2 curves indicate variations in fuel reactivity and composition. More heterogeneous biomass, such as trimming residues, tends to sustain CO2 production and consumption over a longer period, whereas more homogeneous fuels like eucalyptus wood show sharper peaks and faster declines due to more uniform reaction kinetics. In the final stage of the process, oxygen concentrations increased and recovered to 19 vol.% slightly below their initial values, indicating depletion of reactive fuel and the end of active gasification. At this point, CO2 levels reach low, quasi-steady values, suggesting that most carbon has been converted or remains in a less reactive solid form. Overall, the gas profiles illustrate the typical two-stage behavior of biomass gasification: an initial partial oxidation phase followed by a reduction-dominated gasification phase. The observed differences between fuels highlight the significant influence of biomass properties on gasification dynamics and performance.

Acknowledgements The authors acknowledge Fundação para a Ciência e a Tecnologia, I.P. (Portuguese Foundation for Science and Technology) under grant UID/05064/2025 (https://doi.org/10.54499/UID/05064/2025), and H2DRIVEN Green Agenda, reference C644923817-00000037.

ABSTRACT. Biochar is a carbon-rich material obtained from thermochemical processes such as pyrolysis, torrefaction and gasification, conducted under sub-stoichiometric conditions. Its physicochemical characteristics—including carbon content, surface area, porosity, pH, nutrient composition and cation exchange capacity—are strongly dependent on feedstock type and processing parameters. These variations determine the potential performance of biochars in environmental and energy-related contexts.

Biochars produced at elevated temperatures, particularly through thermal gasification processes above 700 °C, typically exhibit higher aromaticity, increased carbon content and enhanced surface area, largely due to the removal of volatile compounds and the development of porous structures. However, in gasification systems biochar is generated as a secondary product, resulting in comparatively lower yields. Thermal gasification involves partial oxidation using limited amounts of gasifying agents, producing gaseous, liquid and solid fractions. While extensive literature exists on the energetic aspects of biomass gasification using diverse feedstocks, the properties and potential valorisation pathways of gasification-derived biochars remain comparatively underexplored.

Olive pomace is an abundant agro-industrial residue in Mediterranean regions and represents a relevant case study for examining the theoretical relationships between feedstock composition, gasification conditions and resulting biochar properties. From a conceptual standpoint, the porous structure of biochar—spanning micro- to nanopores—and the presence of surface functional groups underpin its interaction with organic and inorganic species. These characteristics are commonly associated with adsorption phenomena and are influenced by production temperature, residence time and post-processing strategies.

From a theoretical perspective, biochars have been widely discussed in the literature in relation to carbon sequestration mechanisms, soil carbon stability and long-term persistence in terrestrial systems. Additionally, their structural and surface properties have been analysed in the context of gas purification, catalyst support materials and hydrogen-related technologies, where porosity and surface chemistry play a critical role. Biochars have also been described as carbonaceous adsorbents for aqueous systems, with hydrophobicity and surface functionality governing interactions with organic pollutants and emerging contaminants.

This contribution provides a comprehensive theoretical discussion on the properties of biochars derived from the thermal gasification of olive pomace, emphasising structure–property relationships, compliance with international biochar quality frameworks and potential valorisation concepts. The work aims to consolidate existing knowledge and identify research gaps regarding gasification-derived biochars, supporting future studies focused on their role within circular bioeconomy and sustainable thermochemical conversion systems. Acknowledgements The authors acknowledge Fundação para a Ciência e a Tecnologia, I.P. (Portuguese Foundation for Science and Technology) under grant UID/05064/2025 (https://doi.org/10.54499/UID/05064/2025).

ABSTRACT. This study, developed within the framework of the Interreg AIHRE project (Analysis and Promotion of Renewable H₂ in the POCTEP region), investigates the integration of in-situ CO2 capture using CaO during biomass gasification is a promising route to reduce carbon emissions while maintaining process efficiency. However, the influence of CaO loading on sorbent utilisation efficiency remains insufficiently understood. In this study, the effect of CaO addition on gas composition and CO2 capture performance during pruning biomass gasification was investigated, with particular attention to oxygen (O2) and carbon dioxide (CO2) concentration profiles. Experiments were conducted using pruning alone and pruning mixed with 10 wt% and 20 wt% CaO. Gas concentrations were continuously monitored, and CO2 capture was quantified by mass balance, while char conversion was independently evaluated. Results show that char conversion was essentially identical for all cases, indicating that CaO addition did not affect the overall extent of char oxidation. However, significant differences were observed in the gas-phase composition. In the absence of CaO, CO2 concentration increased rapidly after ignition and reached peak values close to 10%, reflecting the full release of CO2 from biomass oxidation into the gas phase. Correspondingly, the O2 concentration exhibited the largest decrease, attributable to both oxygen consumption and dilution by accumulated CO2. When CaO was added, CO2 concentrations were markedly reduced throughout the reaction. The maximum CO2 concentration decreased to approximately 4–5% for both CaO loadings, confirming effective in-situ CO2 capture via carbonation. Quantitative analysis showed that the addition of 10 wt% CaO resulted in the highest CO2 capture, corresponding to 42% of the total CO2 produced on a mass basis, while 20 wt% CaO captured 39%. Despite the higher sorbent loading, the increase in CaO content did not lead to a proportional enhancement in CO2 capture. The O2 concentration profiles reflected these trends. In the presence of CaO, higher O2 concentrations were measured compared to pruning alone, despite identical char conversion. This behavior is attributed to the removal of CO2 from the gas phase, which increases the relative molar fraction of O2 rather than indicating a reduction in oxidation reactions. The similarity of the O2 profiles for 10 wt% and 20 wt% CaO is consistent with their comparable gas-phase CO2 concentrations. The lower CO2 capture efficiency observed at higher CaO loading suggests a limitation in sorbent utilization. Possible explanations include diffusion resistance through the CaCO3 product layer, reduced gas–solid contact efficiency, and partial deactivation or agglomeration of excess CaO. These factors limit the effective participation of additional CaO once carbonation becomes kinetically or mass-transfer controlled. Overall, this study demonstrates that CaO addition significantly alters gas composition during pruning biomass gasification by enabling in-situ CO2 capture without affecting char conversion. The authors acknowledge Fundação para a Ciência e a Tecnologia, I.P. (Portuguese Foundation for Science and Technology) under grant UID/05064/2025, the HYFUELUP project under grant agreement no. 101084148 and AIHRE project, reference 0093-AIHRE-6-E, co-financed by the European Regional Development Fund (ERDF) through the Interreg V-A Spain - Portugal Cooperation Programme (POCTEP) 2021- 2027.

ABSTRACT. Using pyrolysis oils as blend components in marine residual fuels offers a practical route to introduce renewable carbon into shipping without requiring full chemical upgrading of the bio-liquid, as shipping faces tightening greenhouse-gas and pollutant requirements. Any candidate blend must still behave as a high-energy-density fuel compatible with existing engines, storage and bunkering. Woody-biomass intermediate pyrolysis oils can be produced from lignocellulosic residues, but their direct use is limited by high acidity, water content and chemical instability, which create handling, storage and engine-compatibility risks. This study therefore applies a certification-led framework in which fuel properties are benchmarked against ISO 8217:2024 bio-residual grades, treating the specification as an engineering ‘acceptance gate’ rather than reporting blend properties in isolation.

Two pine-wood intermediate pyrolysis oils were produced in a continuous, oxygen-depleted Pyrotest™ system at 500 °C using different residence times (PO-500-20 and PO-500-40). The oils were characterised using ASTM methods for water, net heat of combustion, total acid number, viscosity, density, flash point, ash and elemental content, supported by GC–MS speciation. The neat oils contained about 8–10 vol% water and exhibited high acidity (total acid number 49-70 mg KOH g⁻¹), confirming they are not suitable as drop-in marine fuels. Four ternary blends were then prepared with a fixed 30 vol% pyrolysis oil fraction and variable waste-cooking-oil biodiesel and n-butanol fractions (10–20 vol% butanol), selected to balance ignition quality and cold-flow. All blends remained homogeneous after 48 h and (when benchmarked against ISO 8217) achieved RF20-relevant viscosity and density with acceptable ignition quality (CCAI). Acidity was reduced into the specification range (2 mg KOH g⁻¹, below the 2.5 limit), sulphur and key metals were below detection and energy content remained in the mid-30 MJ kg⁻¹ range with a pour point around −15 °C.

The results demonstrate that intermediate pyrolysis oils are valuable blendstocks for low-sulphur marine residual fuels when developed through a certification-relevant lens, and that low-severity blending with biodiesel and a higher alcohol can deliver broad ISO 8217:2024 alignment across most measured properties. Meeting the 60 °C minimum flash point needs close control of alcohol content and blend variability to keep storage and handling safe. Water content also depended strongly on n-butanol level: blends with 10 vol% butanol were 0.37-0.38 vol% (near the 0.5 vol% limit), while 20 vol% butanol increased water to 0.71-0.74 vol%. In some blends, accelerated aged sediment reached 0.30-0.50% m/m, exceeding the 0.10% m/m limit, which is consistent with carry-over of fine solids and ageing during storage.

Next stages of our research will focus on practical mitigation measures, including upstream oil cleaning (hot filtration, centrifugation or electrostatic precipitation), drying and tighter blend control, followed by longer-term storage tests, materials compatibility checks and engine-scale validation under representative marine conditions.

ABSTRACT. Bamboo is an abundant, renewable lignocellulosic material whose hierarchical porosity, anisotropic structure, and mechanical robustness make it an attractive template for bio based functional devices. In this study, we investigate the evolution of magnetic and paramagnetic properties in untreated and Fe impregnated bamboo subjected to slow pyrolysis across a wide heat treatment temperature range (300–1000 °C). Bamboo-derived biochar (BB) monoliths were produced from Dendrocalamus giganteus under nitrogen, with parallel series prepared with and without FeCl₃ impregnation to assess the synergistic effects of iron incorporation and thermal transformation. X ray diffraction analysis revealed progressive graphitization at high temperatures, leading to turbostratic, graphene like domains consistent with enhanced electrical conductivity, especially in biochars treated at 800 and 1000 °C. These findings align with previous demonstrations of bamboo-derived carbons as promising electrodes for microfluidic heaters, lithium ion batteries, and sodium ion batteries. Magnetic characterization via vibrating sample magnetometry (VSM) showed the onset of clear ferromagnetic like behavior beginning at 600 °C. The S shaped hysteresis loops suggest the presence of ferro or ferrimagnetic contributions arising either from trace iron naturally present in the pristine bamboo (~0.2 wt%, confirmed via ICP OES and XRF) or from defect induced magnetism associated with disordered graphitic domains. FeCl₃ impregnated bamboo pyrolyzed under the same conditions exhibited a small enhanced magnetic signatures. Raman analysis confirmed the coexistence of carbon D/G bands with characteristic peaks of magnetite (Fe₃O₄), indicating in situ formation of iron oxide nanophases. Electron paramagnetic resonance (EPR) spectroscopy further revealed two paramagnetic species: (i) persistent free radicals (PFRs) centered on aromatic carbon (g = 2.0037, ~8 × 10¹⁸ spins g⁻¹), and (ii) signals attributable to superparamagnetic iron nanoparticles (g ≈ 2.020). The coexistence of carbon based PFRs and iron based magnetic nanodomains suggests a hybrid mechanism for redox activity, magnetization, and potential catalytic behavior. The combined magnetic response, electrical conductivity, and radical stability highlight pyrolyzed bamboo as a multifunctional, sustainable carbon platform. These properties unlock new prospects for magnetically assisted water remediation, flow reactor oxidation processes, and smart carbon architectures where magnetic separation, radical reactivity, and conductivity are simultaneously desirable.

References: [1] O.G.Pandoli et al.,, Pivotal Contribute of EPR‐Characterized Persistent Free Radicals in the Methylene Blue Removal by a Bamboo‐Based Biochar‐Packed Column Flow System, ChemCatChem 16 (2024). [2] O.G.Pandoli et al., Permanent free radicals in bamboo biochar-based flow bed reactor: a sustainable solution for dye degradation via adsorption and radical oxidation. Accepted for publication on Catalysis Science & Technology (2025) [3] O.G.Pandoli et al., 3D conductive monolithic carbons from pyrolyzed bamboo for microfluidic self-heating system, Carbon N Y (2023) 118214 [4] O.G.Pandoli et al., Untreated bamboo biochar as anode material for sustainable lithium ion batteries, Biomass Bioenergy 193 (2025) 107511

ABSTRACT. Municipal wastewater treatment produces massive quantities of digestate, a highly recalcitrant residue that remains after anaerobic stabilization of sewage sludge. Current management practices, such as thermal drying for use in cement kilns or incineration, are energetically intensive and overlook the potential for circular valorisation. This study proposes an innovative revalorization pathway for biologically-stabilized sewage sludge digestate by integrating Hydrothermal Carbonization (HTC) and intermediate pyrolysis within a Hybrid Thermochemical-Biological (HTB) framework.

The research evaluates the performance of the HTC-Py coupling to transform poorly bioavailable digestate into a platform of fermentable intermediates. The feedstock consists of thermally dried digestate (≈ 98% TS) and digestate slurry (≈7% TS) obtained from an advanced biological municipal wastewater treatment facility in Istanbul. HTC experiments are conducted in a 100 mL high-pressure reactor at temperatures ranging from 180 to 240 °C with retention times between 30 and 240 minutes under autonomous pressure. The resulting hydrochars and dried raw digestate are then subjected to intermediate pyrolysis in a sealed tubular furnace under nitrogen flow. The pyrolysis thermal profile utilizes a 10 °C heating rate to reach target temperatures between 350 and 550 °C, followed by a 15–30 minute hold time.

To systematically assess the redistribution of chemical energy and the enhancement of bioavailability, a Chemical Oxygen Demand (COD) approach is employed as the primary monitoring parameter. This methodology allows for a direct comparison of thermochemical depolymerization efficiency against conventional hydrolysis, tracking how "chemical energy" is partitioned into solid (biochar), liquid (WS), and gaseous (syngas) fractions. Preliminary results indicate that hydrothermal treatment and/or intermediate pyrolysis can effectively increase the soluble organic fraction of anaerobically treated sewage sludge (i.e. sewage sludge digestate).

Furthermore, this study includes a systematic, data-based analytical literature review of digestate-derived pyrolysis products to establish a comparative framework for process optimization. By combining HTC’s ability to dissolve hemicellulose-like fractions and minerals with the selective depolymerization of pyrolysis, this integrated approach aims to "unlock" recalcitrant organic matter. While the thermochemical performance remains the focus, the obtained intermediates are ultimately designed to serve as accessible substrates for downstream anaerobic bioconversion, facilitating the production of value-added end-products such as bio-fuels, green-chemical, and bio-materials within a circular bioeconomy.

ABSTRACT. The rapid increase in waste, including municipal waste, industrial waste, agricultural and agroforestry waste, has become a serious environmental problem due to improper disposal methods. The use of agroforestry waste for biochar production and its application in environmental remediation has been progressing in recent years. The current study is focused on the production of porous carbon biochar from agroforestry biomass waste. In this study, rubber fig (Ficus elastica) leaves, an agroforestry waste biomass, were used as a precursor to produce biochar. Biochar was synthesised using a fixed-bed reactor under an inert nitrogen atmosphere at two different temperatures, 550°C and 750°C, with a controlled heating rate of 10°C/min. The pyrolysis process resulted in biochar yields of approximately 100g and 70g at 550°C and 750°C, respectively. This indicates that 550°C was the optimum temperature resulting in a higher yield. Further, to enhance the biochar’s surface properties (surface area, pore volume), chemical activation was carried out using potassium hydroxide. Preliminary test such as proximate and ultimate analyses, were carried out to find the physicochemical and elemental composition of the biochar samples. Further characterisation techniques, such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, and scanning electron microscopy (SEM), were undertaken to observe the functional group, structural, and morphological properties of the prepared biochar. This work will facilitate in converting waste biomass into value-added materials to produce porous carbon material, which could be applied in wastewater treatment techniques to achieve sustainable development goals (SDGs 6, 14 and 15) .

ABSTRACT. In the conventional chemical looping gasification (CLG) process, H2 content in the product gas typically does not exceed 40 vol.% with the usual range of H2/CO ratios from 0.7 to 1.6. Moreover, the tar is inevitable. Further composition adjustments and purification are necessary for the synthesis of aviation fuel and chemicals. To address these limitations, a staged chemical looping gasification (SCLG) process has been developed, decoupling gasification into two distinct stages: high-temperature pyrolysis (stage 1) and gasification of the solid residues (stage 2). This process is shown in the fig.1, the devolatilization reactions responsible for tar generation and the redox reactions that increase CO2 content in the gas product are isolated and conducted in stage 1. Stage 2 focuses on steam gasification of char and the upgrading of syngas using an oxygen carrier (OC). The core of the process involves establishing a pre-gasifier for stage 1 and a gasifier for stage 2, both designed for continuous operation. The bed material circulates sequentially through these reactors, with each reactor maintaining independent reaction atmospheres, allowing for optimal conditions for the respective reactions. Using pine sawdust as the feedstock and metallurgical slag as the OC, the decoupling gasification performance of this system was evaluated. Experimental results indicate that high-temperature pyrolysis gas contains more CO and less CO₂ due to the metallurgical slag carrier's superior CO selectivity. The tar produced during high-temperature pyrolysis primarily consists of polycyclic aromatic hydrocarbons and naphthalene derivatives, followed by monocyclic aromatic hydrocarbons and phenolic compounds, with minor amounts of furan compounds. As temperature increased, tar content decreased by 48% (from 21.2 g/Nm³ to 11.0 g/Nm³), with reductions in polycyclic aromatic hydrocarbons, phenols, and furan compounds, while naphthalene derivatives and monocyclic aromatic hydrocarbons increased. This shift stems from heightened oxygen carrier activity at elevated temperatures, which promotes tar cracking, catalytic cracking, and lattice oxygen oxidation. Tar removal becomes markedly effective when temperatures exceed 800°C. Additionally, significant amounts of calcium and iron, along with trace magnesium in the metallurgical slag, all of which play crucial roles in the process. Solid products from high-temperature pyrolysis include unreacted char and partially reduced oxygen carriers. The XRD patterns reveal trace amounts of metallic Fe and FeO phases. Steam is introduced for gasification. The gasifier temperature is a critical factor influencing the composition and yield of the product gas, as it affects the reaction rate within the gasifier and the effectiveness of reducing oxygen carriers in enhancing gas quality. Below 750°C, H₂ dominates the product gas (exceeding 96% by volume), but it drops sharply to 76% as the temperature rises, while the contents of CO and CO₂ show the opposite trend. Under gasifier conditions 850°C and steam-to-carbon mass ratio of 1.12, a hydrogen-rich syngas with H2 concentration of 74.0 vol.% and dry gas yield of 0.46 Nm3/kg was produced, with no detectable tar.

ABSTRACT. The development of sustainable electrode materials from biomass precursors has gained increasing attention for next-generation energy storage systems. In this context, hard carbons (HCs) have emerged as a promising electrode materials for hybrid capacitors due to its favorable charge storage mechanisms [1]. However, their practical implementation in hybrid capacitors is still limited by intrinsic challenges, including relatively low initial Coulombic Efficiency, complex solid electrolyte interphase formation and a strong dependence of electrochemical behavior on microstructural and surface chemical properties [1]. In fact, the choice of the most appropriate carbon precursor is pivotal in determining the final properties of HCs. Lignin-rich precursors are particularly suitable for HCs production, because they promote disordered structures with enlarged interlayer spacing and good structural stability, beneficial for ion storage [2]. Among the variety of carbon precursors, the waste biomass hazelnut shells (HS) represents a promising and abundant feedstock, although its use for HCs synthesis remains scarcely explored [2-4]. The present work aims to investigate the potential of HS-derived HCs as negative electrodes for lithium-ion capacitors, with particular attention to the influence of precursor treatment on the electrochemical performances in full-cell configurations [2-4]. For this purpose, the effects of different mild pre-treatments, including water washing, particle size selection, acid treatment and hydrothermal carbonization, applied to the pristine HS biomass before the final pyrolysis step were investigated on the electrochemical performances of the resulting HC materials in a full-device configuration. All the synthesized HCs were initially evaluated through electrochemical tests in half-cell configurations. Then, the most performing HCs were subsequently employed in full-cell devices. In all cases, the HCs were employed as anode materials, while an activated carbon derived from HS was used as the cathode material. Definitely, the final goal of this work was to develop sustainable hybrid energy storage devices, by integrating waste-derived materials into full-cell configurations for real electrochemical systems applications.

ABSTRACT. Four carbonaceous xerogels were prepared via a sol-gel route followed by pyrolysis, using furfural and m-substituted phenols as precursors. The drying and pyrolysis processes were investigated by thermogravimetric analysis (TGA) and thermomechanical analysis (TMA) up to 1,000 °C. The resulting materials were further characterized by scanning electron microscopy (SEM) and evaluated for adsorption of methylene blue, iodine, and phenol. TGA revealed total mass losses during pyrolysis in the range of 49–52 %, while volumetric losses measured by TMA ranged from 50–62 %. Prior pyrolysis, the drying step showed water removal up to ~100 °C with mass losses of 5.7–7.6 %. Pyrolysis proceeded in two distinct stages: (i) release of volatile compounds up to ~220–260 °C with mass losses of 4.1–11.4 %, and (ii) carbonization up to 1,000 °C with mass losses of 40.2–45.9 %. Mechanically, shrinkage patterns corresponded well with TGA mass losses, although slight shifts were observed: sample contraction during drying occurred around 100 °C in both TMA and TGA, whereas shrinkage during pyrolysis appeared at lower temperatures, likely due to differences in heating rates (10 °C min⁻¹ for TGA vs. 1 °C min⁻¹ for TMA). SEM images revealed that the samples shared a similar morphology, consisting of small, interconnected spherical particles. Adsorption capacities were determined as 0.04–0.15 mmol g⁻¹ for methylene blue, 1.54–1.75 mmol g⁻¹ for iodine, and 0.77–0.92 mmol g⁻¹ for phenol.

ABSTRACT. Carbon molecular sieve (CMS) is a carbonaceous adsorbent with an uniform and narrow pore size distribution, and be used for separation and purification of gases. The gas separation performance of CMS is mainly determined by its micropore volume and the micropore size, and the microporous structure is mainly affected by carbonization, activation and chemical vapor deposition during the preparation process. Based on the principle that the liquid spontaneously wets the surface of porous material to remove the gas adsorbed in the porous material, the theoretical model and derivation process were given, and the spontaneous liquid gas imbibition (SLGI) method has been applied to the preparation of the CMS. The SLGI depends on not only the porous structure of the adsorbent, but also the gas molecule (we call it gas probe) adsorbed in the pores and the liquid molecule (liquid probe) used to displace the gas. For both gas and liquid probe, they could only enter the pores of the sizes larger than their molecular kinetic diameters. The molecular probe method provides a useful way to get the pore structure information. The intermediate products of carbonization, activation and chemical vapor deposition under varied reaction conditions have been characterized by SLGI. The results show that, when the C2H5OH-N2 probe system is used in the carbonization stage, samples with larger pore volumes and pore sizes can be selected. The suitable carbonization condition is carbonization temperature 800°C and holding time 30 min. During activation, the micropore volume of the sample has been developed, and at the same time, the micropore size has increased. At this time, the difference in the H2O-N2/O2 probe system was used to determine the appropriate activation conditions. The optimized activation condition is: activation temperature 830°C and water flow rate 0.35 mL/min. The performance of laboratory CMS prepared by SLGI guidance is close to that of commercial CMSs. SLGI can more sensitively and accurately and rapidly express the micropore structure differences of the samples both qualitatively and quantitatively. Therefore, the SLGI method holds promise as a generalizable technique for the assessment of solid products in thermal pyrolysis. According to the different characteristics of the target products at different stages, a suitable liquid-gas probe system was selected to evaluate the pore structure changes.

ABSTRACT. Heated tobacco products (HTPs) are designed to heat tobacco without inducing combustion, making the accurate characterization of the boundary between thermal degradation and combustion a critical issue for both scientific understanding and product design. However, identifying this boundary in biomass systems remains challenging due to the coexistence of multiple physico-chemical processes and the absence of clear, operationally meaningful indicators. Existing approaches for determining heating-combustion boundaries, such as ignition point measurements and nitrogen-oxygen stable isotope tracing, are either poorly suited to the specific physical structure of HTPs or involve complex experimental procedures, which limits their practical applicability. In this study, a thermal-analysis-based method is proposed to characterize the heating-combustion boundary in fixed-bed biomass systems. The method identifies a temperature inflection point associated with changes in thermal behaviour, providing a simple, reproducible, and physically interpretable indicator of the transition from heating-dominated to combustion-influenced regimes. Using this approach, the effects of oxygen concentration, heating rate, and feed gas flow rate on the position of the temperature inflection point were systematically investigated. The results show that increasing oxygen concentration and heating rate causes the temperature inflection point to shift toward earlier stages of the heating process, indicating an enhanced contribution of oxidative reactions to the overall thermal behaviour. The validity of the proposed method was further evaluated through comparative characterization of homogeneous biomass samples using industrial analysis, elemental analysis, and the conventional ignition point method based on TG method. The consistency of the results supports the reliability of the inflection-point-based approach. This study provides a practical and physically meaningful framework for characterizing the heating–combustion boundary in biomass systems and offers methodological support for the thermal design and assessment of heated tobacco products.

ABSTRACT. Pyrolysis is a thermochemical process in which a material undergoes decomposition in absence of oxidising agents. When realised in a fluidised bed reactor, an upward flow of inert gas (e.g. N2) is applied to create a suspension of the substrate mixed with bed particles. Such a solution improves the overall heat transfer of the system and results in a higher efficiency of the process, as compared to a fixed bed operation.

In our work, we present the analysis of products (biochar, gas and tar) of pyrolysis experiments performed at different temperatures (500°C, 700°C, 900°C). As feedstock, pine and birch wood samples sourced from a post-industrial site polluted with Pb and Zn were used. The experiments were carried out in a fluidised bed mode, with quartz sand as the bed material, in a laboratory-scale BIOTA plant (Biogenic, Innovative and Optimized Thermochemistry Apparatus), operating at TU Wien.

In each case, the composition of the produced gas was measured on-line throughout the reaction. Tar samples were captured simultaneously (in accordance with a standardised method) and later analysed qualitatively by means of GC-MS. To describe the surface chemistry of the obtained biochars, various methods were implemented, including ATR-FTIR and XPS. From a structural point of view, Raman spectroscopy was used to investigate the biochars’ graphitisation degree. Morphology and surface area of the pores were determined based on CO2 and N2 adsorption isotherms, measured at 273 K and 77 K, respectively. Additionally, to trace the fate of the contaminants present in the biomass, ICP-OES analyses of the biochars and tar samples were performed.

Acknowledgments: This research is a part of the project “Processes for metal-to-char encapsulation” supported by the Austrian Science Fund (FWF), project number I 5404-N and National Science Centre (Poland), project No. 2020/39/I/ST8/01484 (OPUS).

ABSTRACT. Anaerobic digestion (AD) plays a key role in this waste valorization because it converts biomass residues into biogas, a mixture of methane (CH4) and carbon dioxide (CO2). Biogas represents a renewable energy source, that can be upgraded for applications such as transports or converted into heat and electricity1. However, only the easily degradable fraction of the feedstock is converted into biogas, while the recalcitrant components are accumulated in the digestate, resulting in a loss of potential energy production. To remove this bottleneck the application of hybrid Pyrolysis-Anaerobic Digestion (PyAD) on digestate can break refractory lignocellulosic structures through thermal degradation, producing smaller compounds accessible to anaerobic bacteria2, allowing to convert digestate into additional biomethane, biochar and water insoluble byproducts 3. This study evaluates a Py-AD configuration where biochar, gas and WS are subjected to AD and water insoluble fraction is used as source for energy rich fuels or bitumen for road paving. Digestate was subjected to slow pyrolysis at 450°C under CO₂; products were quantified to provide a detailed mass and COD balances. On mass basis, the pyrolysis of digestate converted the feedstock mainly into char (>60%), followed by WS fraction and syngas with 22.7% and 13%, respectively. On COD basis, most of the initial COD was recovered into the liquid fractions, with 32.9% in WS and 45.3% in WI, whereas biochar and syngas retained only a small fraction of the initial COD (about 14% and 6.6%, respectively). Mass and COD losses were below 3%, indicating a good closure balance. At the beginning of the experiment, WS fraction was co-fed to the bioreactor with chickpea flour to acclimate the microbial community. The chickpea flour-WS ratio was gradually reduced until reaching 100% WS. In the second part of the experiment, WS was co-fed with acetic acid which was used to mimic acetic acid production observed in the conducted syngas experiment. Biomethane conversion increased to 80% but dropped to 20% once the bioreactor was fed with 100% WS suggesting the inhibitory effect of the WS on microbial consortia. In the second phase, acetic acid was co-fed with WS fraction and the biomethane conversion increased again, suggesting that co-feeding with abundant and easily degradable feedstock is required when dealing with WS. Because WS represents the main substrate and may exhibit inhibitory effects, this fraction was for the first time characterized in detail at the molecular level. Using derivatization technique coupled to GC-MS, it was possible to investigate the molecular composition of WS fraction of bio-oil. The silylation technique improves chromatographic separation and stabilizes reactive analytes allowing to resolve up to 300 compounds, which is close to the theoretical limit of a capillary GC column. This allowed to quantify and tentatively identify about 65% of the organic compounds present in pyrolysis liquid.

ABSTRACT. The combustion state of cigars was of great significance to the quality of smoke and consumption experience. To enhance the smoking quality of cigar and optimize the design parameters of cigar, this study systematically investigates the effects of dry basis density, moisture content, and puff volume on the morphology and temperature distribution of cigar combustion cone, based on a rapid detection and characterization method for the temperature distribution of the cigar combustion cone. The results shown that: The dry basis density shows a strong positive correlation with both the morphology of the combustion cone (length, penetration depth, volume (V0)) and its temperature distribution (average volume temperature (Tm), maximum temperature (Tmax)). A higher moisture content increases the length and Tm of combustion cone. However, the intermediate moisture content (12%) results in the largest V0 alongside the lowest Tmax, suggesting that moisture regulates the intensity of combustion through phase change heat absorption during puffing. Increasing the puff volume directly expands the length and penetration depth of combustion cone, while also raising the Tm. Once the puff volume exceeds a certain threshold, the V0 and Tmax no longer increase significantly, indicating that the combustion has entered a stable and fully developed state. The study aims to provide a theoretical basis for cigar density control, combustion performance evaluation, and process optimization, with the goal of effectively regulating the combustion cone status and reducing the risk of internal combustion.

ABSTRACT. Pyrolysis is a central process in thermal conversion technologies and plays a governing role in solid-fuel aerospace propulsion systems. In both solid and hybrid rocket motors, pyrolysis constitutes the primary mechanism by which condensed-phase materials are transformed into gaseous species that sustain gas-phase combustion. The characteristics of pyrolysis—namely decomposition pathways, kinetics, and product distribution—directly affect fuel regression rates, flame structure, and combustion efficiency. For this reason, a detailed thermo-chemical characterization of solid fuels, with specific focus on pyrolysis phenomena, is essential for the development of advanced propulsion concepts. In hybrid rocket propulsion, the coupling between heat feedback from the flame and pyrolysis at the solid fuel surface controls the generation rate and composition of gaseous fuel species. Unlike conventional solid propellants, where oxidizer and fuel are premixed, hybrid systems rely entirely on pyrolysis-driven mass transfer from the solid phase to the reacting flow. Consequently, the efficiency and stability of hybrid combustion are intrinsically linked to the thermal degradation behavior of the solid fuel. Insufficient pyrolysis rates, unfavorable melting/decomposition windows or volatiles composition may result in reduced regression rates and incomplete combustion. Recent research has increasingly focused on the pyrolysis of non-traditional polymeric materials, including thermoplastics and bio-based polymers, as alternative solid fuels. These materials offer advantages in terms of processability, reduced toxicity, and compatibility with additive manufacturing, while also enabling more sustainable material sourcing. Polylactic acid (PLA) is a biodegradable thermoplastic polymer extensively used in additive manufacturing that has recently emerged as a candidate solid fuel for hybrid aerospace propulsion. Its molecular structure suggests a well-defined thermal response, making it a suitable model material for investigating the interplay between thermal transitions, pyrolysis onset, and volatile release. In this work, PLA is characterized through a combination of differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG), and analytical pyrolysis coupled with gas chromatography–mass spectrometry (Py-GC/MS). DSC measurements were performed to identify thermal transitions such as melting behavior, and possible pre-decomposition phenomena, providing insight into the thermal stability and heat flow associated with structural changes in the polymer. TG/DTG analysis was used to determine mass loss profiles, decomposition onset temperatures, and apparent reaction rates under controlled heating conditions. Py-GC/MS enabled the identification and quantification of volatile and condensable species released during thermal degradation, offering detailed information on pyrolysis pathways and product distribution. The results indicate that PLA undergoes a reproducible pyrolytic decomposition over a relatively narrow temperature range, preceded by well-defined thermal transitions. The pyrolysis process yields a significant fraction of low-molecular-weight combustible species, including acetaldehyde, which are expected to play a key role in sustaining homogeneous combustion when adequately mixed with common hybrid rocket oxidizers. While these laboratory-scale experiments do not directly reproduce the complex thermo-fluid-dynamic conditions of an operating hybrid rocket motor, they represent essential input for pyrolysis-driven combustion modeling. Overall, this study emphasizes pyrolysis as the key link between material properties and combustion behavior, supporting the assessment of PLA as a solid fuel for hybrid propulsion systems governed by pyrolysis-controlled mass transfer.

ABSTRACT. The transition toward a bio-economy, in line with the EU 2030 targets, requires enhanced and more efficient utilization of biomass and alternative renewable resources. Slow pyrolysis is a mature technology suitable for large-scale processing of lignocellulosic feedstocks, producing biochar alongside valuable co-product, namely bio-oil, a precursor of biofuel and chemicals, and a gaseous phase. One strategy for energetically supporting pyrolysis, particularly in the case of decentralised units and mobile installations dedicated to biochar production, is to integrate the pyrolysis unit with a proper burner capable of oxidizing pyrolysis vapors and recirculating the exhaust (containing a mixture of N2, CO2, H2O) to the pyrolysis unit. Different atmospheres can affect product yield and properties. However, steam and CO2 have been widely studied primarly as gasifying or activating agents at high temperatures [1]. Recently, there has been growing interest in the exploration and use of CO2 also under pyrolysis conditions [1], whereas few studies are devoted to the presence of steam and its effect on biochar [2]. Steam plays a role not only in the extraction of volatile compounds, resulting in a well-developed porous structure and active sites on the surface of biochar, but it also strongly influences reaction pathways in the formation of liquid compounds in the early stage of hemicellulose decomposition [3]. Herein, a parametric study is presented to investigate the effect of H₂O concentration in an N₂ carrier gas during the pyrolysis of poplar at different final temperatures. Preliminary results show that the nature of the pyrolysis atmosphere influences the products yields. In particular, at increasing temperatures, the presence of pure steam leads to a reduction in biochar yield compared to pure nitrogen, while promoting the formation of gaseous and liquid products due to intensified devolatilization and secondary cracking. Under inert conditions and lower steam concentration, higher temperatures produced biochar with greater aromaticity, higher carbon content, and lower oxygen levels, characteristics favorable for long-term carbon sequestration. Increasing the steam ratio in the composition of the pyrolysis atmosphere, the reactive action of steam further reduces biochar yield through gasification reactions, enriching the gas composition in CO, CH4, and H₂.

ABSTRACT. As a critical renewable energy source, biomass utilization is hindered by two major challenges: inherently low energy density and poor grindability. During torrefaction process, oxygen is removed through water vaporization and cracking of oxygen-containing functional groups presenting in biomass, thereby raising the energy density of the obtained biochar. The depolymerization or breakdown of cellulose and hemicellulose structures in biomass also enhance the grindability of biochar. In this work, a fluidized bed oxidative-torrefaction process was designed to torrefy pine wood pellets and produce biochar with superior grindability. The results of comparative experiments at a feeding rate of 1 kg/h under varied operating parameters demonstrated that as the operating temperature and O2 concentration in fluidizing reagent increased, the yield of biochar gradually decreased and the grindability of produced biochar obviously improved. The content of oxygen in biochar greatly decreased, proving that the fluidized bed flash-torrefaction increases the energy density of biomass used as a fuel or a raw feedstock for other thermochemical conversions such as gasification. Additionally, the tested oxidative torrefaction exhibited excellent continuous operation stability, and enabled the steady production of biochar, thus providing an effective solution to the upgrading of biomass.

Reference [1] M. Zhang, K. Yang, C. Wang, et al, Oxidative torrefaction of biomass in a fluidized bed for preparation of the biochar with high grindability, Fuel 407 (2025) 137403. [2] C. Zhang, S. Ho, W. Chen, et al, Oxidative torrefaction of biomass nutshells: Evaluations of energy efficiency as well as biochar transportation and storage, Applied Energy 235 (2019) 428-441. [3] C. Wang, F. Liu, L. Zhu, et al, Two-stage fluidized bed gasification enhanced with oxidative pyrolysis for low-tar producer gas from biomass, Fuel 363 (2024) 130839. [4] R. Nachenius, T. van de Wardt, F. Ronsse, et al, Torrefaction of pine in a bench-scale screw conveyor reactor, Biomass and Bioenergy 79 (2015) 96-104. [5] D. Chen, F. Chen, K. Cen, et al, Upgrading rice husk via oxidative torrefaction: Characterization of solid, liquid, gaseous products and a comparison with non-oxidative torrefaction, Fuel 275 (2020) 117936.

ABSTRACT. Solid–fluid reactive systems are fundamental to thermochemical biomass conversion technologies such as pyrolysis and gasification. Further progress in these processes requires a detailed understanding of the coupled transport, reaction, and structural evolution phenomena occurring at the scale of individual particles, which may govern reactor performance [1]. In pyrolysis reactors, particle-scale heat and mass transfer strongly interact with chemical reactions and evolving material properties, directly affecting conversion rates and product yields [1]. However, resolv-ing intra-particle dynamics remains computationally expensive, and most reactor-scale models therefore rely on simplified particle representations.

Spatially resolved continuum particle models provide detailed descriptions of intra-particle temperature gradients and transport–reaction coupling but typically assume isotropic properties, uniform boundary conditions, and idealized particle geometries. These assumptions do not generally hold for biomass, due to its hierarchical structure, anisotropic pore network, and non-spherical shape. Pore-resolved studies have demonstrated the importance of intra-particle anisotropic transport during pyrolysis and gasification [2-5], but their computational cost limits their applicability to very small systems.

To bridge the gap between physical fidelity and computational efficiency, this work presents a three-dimensional, pore-informed, continuum particle model for biomass pyrolysis. The model incorporates pore-informed and direction-dependent transport properties, derived from pore-resolved simulations, to account for the influence of pore network on heat and mass transport, as well as on transport-chemistry interactions during pyrolysis. This approach enables spatially resolved predictions of intra-particle temperature and conversion at a computational cost suitable for practical simulations and integration into multiphase reactor models.

Model development and validation are supported by a dedicated experimental campaign measuring internal (several intra-particle positions) and surface particle (with phosphor thermometry) temperatures during pyrolysis. The impact of anisotropic intra-particle pore structure is addresed by comparing natural with densified particles, both using beech wood. Experiments are perfor-med under constant heating rates, representative of slow pyrolysis, and under rapid, isothermal heating conditions relevant to industrial reactors.

The combined experimental and simulation results demonstrate the critical role of particle anisotropy and heating mode on intra-particle transport and pyrolysis behavior, providing a physically grounded and computationally efficient pathway for improved particle-scale modeling in biomass pyrolysis.

[1] P. N. Ciesielski, M. B. Pecha, N. E. Thornburg, M. F. Crowley, X. Gao, O. Oyedeji, H. Sitaraman, N. Brunhart-Lupo, Energy & Fuels 35 (18) (2021) 14382–14400. doi:10.1021/acs.energyfuels.1c02163.

[2] M. F. Crowley, H. Sitaraman, J. Klinger, F. Usseglio-Viretta, N. E. Thornburg, N. Brun-hart-Lupo, M. B. Pecha, J. H. Dooley, Y. Xia, P. N. Ciesielski, Frontiers in Energy Rese-arch 10 (2022). doi:10.3389/fenrg.2022.850630.

[3] A. Dernbecher, S. Bhaskaran, N. Vorhauer-Huget, J. Seidenbecher, S. Gopalkrishna, L. Briest, A. Dieguez-Alonso, Particuology 98 (2025) 172–190. doi:10.1016/j.partic.2025.01.006.

[4] M. F. Crowley, R. Seiser, M. A. S. Posada, J. C. Maya, F. Chejne, H. Sitaraman, F. Usseglio-Viretta, A. K. Starace, P. N. Ciesielski, Energy & Fuels (2025). doi:10.1021/acs.energyfuels.5c04362.

[5] D. Liang, S. Singer, Proceedings of the Combustion Institute 39 (3) (2023) 3293–3302. doi:10.1016/j.proci.2022.07.098.

ABSTRACT. (a) Both first authors

Pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) is a widely used technique for analyzing synthetic polymers and copolymers due to its strong structural identification capabilities. It enables direct analysis, requires very small sample amounts, and provides a chemical fingerprint that allows identification of polymeric materials based on their degradation products. Py-GC/MS is particularly effective for identifying unknown polymers, characterizing copolymer compositions, and studying organic additives even at low concentrations. In addition, pyrolysis is well-suited for investigating aging phenomena, thermal degradation, and the analysis of microplastics in complex matrices. However, the information obtained is most often limited to low-molecular-weight pyrolysis products (< 200 Da), and the low-resolution mass spectrometers commonly employed offer restricted analytical performance. While semi-quantitative information on comonomer distributions can be obtained for copolymers, polymer chain length information remains inaccessible. We have recently developed in our laboratory two novel online methodologies for the analysis of thermo-desorption (TD) and pyrolysis (Py) products of synthetic polymers coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). These approaches enable precise identification of the nature and distribution of high-molecular-weight products (up to ~1,500 Da) generated during thermo-desorption and pyrolysis processes, exploiting the ultra-high resolving power and mass accuracy of FT-ICR MS. The first methodology couples a thermal desorption/pyrolysis (TD/Py) device to FT-ICR MS using direct analysis in real time (DART) as the ionization technique. It was applied to two poly(vinylidene fluoride) (PVDF) samples. Below 400 °C, distributions of the smallest oligomers (Mₙ ≈ 600 Da) were observed, enabling end-group identification and clear differentiation between the two PVDF materials. The detection of specific pyrolysis products for one sample demonstrated that it was a poly(VDF-co-HFP) copolymer containing 5.1% hexafluoropropylene (HFP), in good agreement with the comonomer content determined by ¹⁹F NMR spectroscopy. The second methodology enables online analysis of fast polymer pyrolysis products by combining an FT-ICR MS instrument with a modified direct introduction probe (DIP) operated under atmospheric pressure chemical ionization (APCI). A controlled gas flow within the DIP glass capillary allows fine control of the residence time of generated species in the pyrolysis zone. At the same time, a micro-thermocouple in direct contact with the sample provides real-time monitoring of temperature evolution. Comparison with an empty capillary reveals endothermic processes intrinsic to polymer pyrolysis. Application to polystyrene (PS) samples demonstrated a strong dependence of pyrolysis product distributions on polymer chain length. While styrene oligomers containing up to approximately twelve monomer units were detected for all samples, only low-Mₙ PS led to significant observation of end-group-containing species, either intact (TD) or degraded (Py). Principal component analysis enabled discrimination between end-group-related compounds and products arising from thermal chain degradation. The relative distribution of these two compound families correlated with PS molar mass and shows promise for determining Mₙ values below 10 kDa.

ABSTRACT. In pyrograms of high-density polyethylene (HDPE), hydrocarbon peaks eluting above C14 often show abnormal peak appearance. As shown in Figure 1 a), a distinctive leading edge appears in a series of triplet peaks. Despite the long history of capillary GC, this phenomenon has been unsolved for more than four decades. Similar abnormal peak appearance is also observed for mid-boiling point hydrocarbons in the C20 to C30 range in chromatograms measured by the conventional split injection of liquid samples. In this study, we examined the mechanism of this phenomenon based on HDPE pyrograms and explored practical countermeasures.

HDPE samples were pyrolyzed at 600 ºC. Measurements were carried out using a GC/MS system with a micro-furnace pyrolyzer (EGA/PY-3030D, Frontier Laboratories Ltd.) which was directly interfaced with the GC injector. The GC oven temperature was programmed from 40 °C (2 min hold) to 350 °C at 20 °C/min (13 min hold). A packed GC insert was used, filled with either Chromosorb W coated with PDMS or α-alumina as the packing material. A deactivated pre-column (SMC; 0.25 mm i.d., 0.25 to 8 m length, same as above) was connected to a metal capillary separation column (5% diphenyl polysiloxane, 30 m length, 0.25 mm i.d., 0.25 µm film, same as above). Peak resolution and reproducibility were evaluated by EIC (m/z 82) of C21 diene (C21”) and monoene (C21’).

Acceptable peak separation was obtained for the sample amount of 0.3 mg or less, because higher loadings cause non-uniform introduction of pyrolyzates into the separation column. Therefore, all subsequent measurements were carried out for a sample amount of 0.3 mg. The effects of GC insert packing material and the length of SMC on the abnormal peak appearance were then examined. Under the optimized conditions (using an α-alumina-packed insert and a 2 m SMC), the peak shapes beyond C14 improved significantly as shown in Figure 1 b). Furthermore, the reproducibility of the C21 diene peak area improved from 7.57 % obtained under conventional conditions to 0.68 % after optimization. These results demonstrate that the abnormal peak appearance observed in HDPE pyrograms originates from the sample introduction process and can be effectively mitigated by combining an α-alumina-packed insert with SMC, which also enhanced the peak area reproducibility of hydrocarbons in the mid-boiling point range.

ABSTRACT. Wind turbine blades (WTB), made of fiber reinforced composites, have a typical lifespan of 20 years, post which they are dumped in landfills. Pyrolysis helps in recycling WTB by converting the polymeric foam and resin portion into pyrolysis oil and gas, while leaving the fibers and char in solid phase. In this study, waste WTB samples from three different installations were analyzed using analytical pyrolysis hyphenated with gas chromatograph/mass spectrometer (Py-GC/MS) to understand the pyrolysis reaction pathways, pyrolysate composition and resource recovery potential. The samples were characterized for their proximate and elemental composition, functional groups and morphology using microscopic and spectroscopic methods. Pyrolysis was carried out at different temperatures, viz., 450 °C, 550 °C, 650 °C, 750 °C. Formation of aromatic acids, phenolics and aromatic hydrocarbons were observed from polyethylene terephthalate foam, epoxy resin and polyester resin portions respectively. The results demonstrated that in the case of resins, temperature is not a significant factor while in the case of polymeric foam, lower temperatures result in high selectivity to specific products such as benzoic acid. Catalytic pyrolysis using HZSM-5 zeolite catalyst produced aromatic hydrocarbons such as benzene, toluene and ethylbenzene. More interesting results on the product quantification and distribution under different temperatures and catalyst loading will be discussed. Life cycle assessment of different recycling methods demonstrated that pyrolysis and chemical recycling provide significant environmental benefits. Energy sources, viz. grid vs wind vs other renewables, were found to have decisive impact on the environmental offsets.

ABSTRACT. Microalgae are highly promising feedstocks for the production of biofuels and platform chemicals due to their broad availability, rapid growth and high photosynthetic efficiency. Pyrolysis is one of the most widely used methods for converting microalgae into valuable products [1]. However, microalgae-derived bio-oil typically exhibits high oxygen and nitrogen contents and a broad product distribution, including long-chain and short-chain fatty acids, hydrocarbons, esters, light oxygenates, and nitrogenated compounds, which significantly limit their suitability for use as fuel or as a pool of chemicals. As an alternative, catalytic hydropyrolysis integrates pyrolysis and a partial degree of hydroprocessing into a single unit operation, overcoming the main limitations of conventional pyrolysis [2]. In this work, we investigate the catalytic hydropyrolysis of Chlorella Vulgaris (CV) at relatively mild H2 pressures (6 bar), significantly lower than those typically reported in the literature, thus enhancing the technical and economic viability of the process. Specifically, the activity of different bifunctional Pd-based catalysts (5 wt%) supported on ZrO₂, TiO₂, and ZSM‑5 is evaluated. As observed in Figure 1A, all catalytic systems reduce bio‑oil yields, particularly Pd/TiO₂ and Pd/ZSM‑5, which promote the formation of gaseous products and water. Catalyst incorporation leads to a substantial reduction of the oxygen content (<2 wt%); however, the nitrogen amount remains almost invariable (8 wt%), still limiting its application as fuel. Accordingly, the presence of oxygenated compounds such as esters, oxygenated aromatics, and light oxygenates is strongly reduced compared to the thermal experiment (see Figure 1 B), while nitrogenated compounds formed through protein breakdown are the predominant products. Among the catalysts, Pd/ZrO₂ reduces the GC-MS non-detected fraction share (mainly formed by oligomers and heavy species that cannot be detected by this technique and produces the most homogeneous distribution of nitrogenates, primarily monoaromatic pyrrole‑derived species. Additionally, it increases the formation of aromatic and aliphatic hydrocarbons compared to Pd/TiO₂ and Pd/ZSM‑5.

References 1. T.F. Widawati, B.P. Pancasakti, D.H. Kinanthi, H. Sudibyo, M.A. Budiman, Resources Chemicals and Materials, 2025, 100150. 2. P. Duan, X. Bai, Y. Xu, A. Zhang, F. Wang, L. Zhang, J. Miao, Bioresource Technology, 136, 2013, 626-634. Acknowledgments The authors gratefully acknowledge the financial support from MICIU/AEI (10.13039/501100011033) and ERDF/EU under Grant Agreement No. PID2023-147355OB-C21 (HYPY-CAT) and Grant PIPF-2022/ECO-25620 funded by Comunidad de Madrid.

ABSTRACT. Rising global energy demands and the environmental consequences of fossil fuel consumption have intensified the search for sustainable biofuels. Rapid pyrolysis serves as a promising thermochemical route for converting lignocellulosic residues into renewable liquid fuels, yet its efficiency depends on the development of low-cost catalytic systems. This study addresses the valorization of sugarcane bagasse (SCB), an agro-industrial waste with high energy potential, by using ilmenite (FeTiO3) as a geocatalyst. Ilmenite, a semiconductor mineral present in alluvial gold mining waste, offers a cost-effective alternative for promoting circular economy models.

To mitigate mass and heat transfer limitations, both the SCB and ilmenite were processed to particle sizes below 75 um. Granulometric analysis of the raw ilmenite showed a monomodal distribution, with 81.34% of particles concentrated between 106 and 180 um. A critical finding was the impact of thermal modification: calcination increased the total acidity of the ilmenite more than five-fold, from 80.31 umol/g to 451.8 umol/g. This enhanced acidity is essential for providing the Lewis and Brønsted acid sites necessary for cracking and deoxygenation reactions [1].

The catalytic activity was evaluated using non-isothermal thermogravimetric analysis [2]. As demonstrated in Figure 1, the inclusion of 20% ilmenite significantly reduced the activation energy (E) required for SCB decomposition, particularly at conversion degrees (alpha) exceeding 50%. These results confirm that thermally modified ilmenite effectively facilitates biomass valorization by lowering kinetic barriers, supporting its use as a sustainable catalyst for bio-oil production.

References

[1] Xiong, X., Yang, Z., & Ouyang, H. (2011). Study on character of ilmenite modified by thermal treatment. Advanced Materials Research, 284–286, 2090–2093. https://doi.org/10.4028/WWW.SCIENTIFIC.NET/AMR.284-286.2090

[2] Pretell, V., & Erazo, R. (2020). Catalytic pyrolysis of the empty fruit bunches of the oil palm and the sugarcane bagasse: Non-isothermal thermogravimetric kinetic analysis. Proceedings of the LACCEI International Multi-Conference for Engineering, Education and Technology, July, 27–31. https://doi.org/10.18687/LACCEI2020.1.1.69

ABSTRACT. Pyrolysis of lignocellulosic biomass like bamboo yields aromatic oxygenates like Phenol, guaiacol and other phenolic derivatives. The presence of intrinsic oxygen in the chemical structure of the oil compounds hinders its usage as biofuel. Therefore, hydrodeoxygenation (HDO) using catalysts or by co-pyrolysis with hydrogen rich plastics like polystyrene (PS) are two of the many effective methods for upgrading bio-derived oils into valuable biofuels with less oxygen content. In this study both of these methods are used and thereby conventional co-pyrolysis of bamboo with polystyrene (PS) was performed using modified red mud catalysts in ex-situ mode. Along with the many metal oxides like Fe2O3, Al2O3, SiO2, TiO2, CaO, Na2O already present in red mud pivotal transition metals like Nickel, Cobalt and Molybdenum that are well-known for deoxygenation, hydrogenation properties were doped with red mud to enhance its catalytic activity. BET surface studies revealed the mesoporous nature of modified red mud catalysts which are desirable for giving higher oil yield. HHVs of biomass and polymer feedstock were 17.7 and 42 MJ/Kg respectively. HHV of the chars were found to be in the range of 31.2 MJ/Kg. Overall, it was observed that calcined red mud and Ni-RM catalysts gave higher oil yield.

ABSTRACT. Mineral fillers are widely used in consumer plastics to enhance processability, improve mechanical properties, and reduce cost [1]. Within a recycling context, however, mineral impurities complicate mechanical recycling, which is primarily suited for feedstocks of higher purities. Chemical recycling via pyrolysis is more tolerant toward contamination and thus suited to process mineral-containing plastics [2]. Understanding the influence of minerals is thus necessary for optimizing pyrolysis-based recycling processes, particularly because knowledge of the pyrolysis behavior of plastics in the presence of minerals is limited. Accordingly, this study investigates the pyrolysis of polystyrene (PS) in the presence of minerals. PS is extensively used in the construction sector as expanded polystyrene (EPS) in external thermal insulation composite systems (ETICS) [3]. During pyrolysis, PS predominantly depolymerizes to the monomer styrene and its oligomers [4]. PS-based ETICS usually contain minerals from mortar and paint layers, such as calcite (CaCO3) and anhydrite (CaSO4). Pyrolytic decomposition of pure PS and PS-composites containing minerals is described using thermogravimetric analysis (TGA). A shift in the PS-decomposition step is used as an indicator for mineral-induced effects. Complementary semi-quantitative analysis of primary pyrolysis products, with focus on styrene, was performed using a microgram-pyrolyzer coupled to gas chromatography-mass spectrometry (Py-GC-MS). The quasi-instantaneous heating in the Py-GC-MS allows for investigations on the effects of minerals as well as temperature. Derivative thermogravimetric (DTG) profiles of PS alongside PS-composites containing mineral fillers are depicted in Figure 1. Normalization to the PS fraction allows for direct comparison. The results show that high concentrations of calcite and anhydrite shift peak PS decomposition to a higher temperature, indicating a stabilization effect, potentially via delaying the unzipping of the polymer chain. This effect is reduced at lower mineral concentrations.

Figure 1: DTG of pure PS compared to PS-composites containing different minerals, normalized to the PS fraction.

Py-GC-MS results, normalized to the PS fraction, show that anhydrite does not significantly impact the styrene yield, whereas the presence of calcite increases the styrene yield from 47 to 53 area% at 550 °C. In combination with TGA, the results suggest that calcite and anhydrite stabilize different radical intermediates, altering the product distribution. At 650 °C, however, the yield in the presence of calcite (58 area%) is comparable to that of PS (59 area%), indicating that the thermal decomposition outweighs the stabilization effect of calcite. The stabilization of different intermediates and its implications will be discussed in more detail in the conference presentation.

[1] A.A. Ahmad Fauzi, A.F. Osman, A.A. Alrashdi, Z. Mustafa, K.A. Abdul Halim, On the Use of Dolomite as a Mineral Filler and Co-Filler in the Field of Polymer Composites: A Review, Polymers 14 (2022) 2843. https://doi.org/10.3390/polym14142843. [2] A. Schade, M. Melzer, S. Zimmermann, T. Schwarz, K. Stoewe, H. Kuhn, Plastic Waste Recycling─A Chemical Recycling Perspective, ACS Sustainable Chem. Eng. 12 (2024) 12270–12288. https://doi.org/10.1021/acssuschemeng.4c02551. [3] Plastics Europe, The Circular Economy for Plastics - A European Analysis, 2024. https://plasticseurope.org/knowledge-hub/the-circular-economy-for-plastics-a-european-analysis-2024/ (accessed January 7, 2026). [4] I.M. Maafa, Pyrolysis of Polystyrene Waste: A Review, Polymers (Basel) 13 (2021). https://doi.org/10.3390/polym13020225.

ABSTRACT. The increasing production of plastics and inadequate management of plastic waste have led to severe environmental issues. Mechanical recycling is primarily effective for mono-fraction thermoplastics streams, whereas chemical recycling can handle mixed or contaminated feedstocks. Among current chemical recycling processes, pyrolysis offers an attractive balance of environmental impact, economic feasibility, and product quality.

Plastic pyrolysis converts polymeric feedstocks into smaller molecules at intermediate to high temperatures in the absence of oxygen. A major challenge to industrial deployment is process scale-up, where the coupled multi‑scale physicochemical phenomena remain insufficiently understood. Large‑scale experiments alone are time‑consuming and costly, making numerical simulations a cost‑effective complement. Nevertheless, the effects of operating conditions on competing chemical reactions, heat and mass transfer—and their consequences for product composition—are rarely reported, particularly with respect to different feeding modes.

In this study, we conduct Eulerian-Lagrangian CFD simulations of polypropylene (PP) pyrolysis in a laboratory‑scale fluidized‑bed reactor, which is used in experimental investigations. To reduce computational cost, PP pyrolysis is represented by a five‑lump kinetic model, in which complex intermediates and final products are grouped into five pseudo‑components based on boiling point: plastics (P), wax (W), heavy fraction (HF), light fraction (LF), and gas (G). The simulations consider the pyrolysis of PP particles with different sizes and systematically examine the effects of reactor temperature (T_R), particle size (d_p), and feeding mode (batch-wise and continuous) on product yields.

The investigation starts with a simulation at T_R=505°C under batch-wise feeding, LF is the major product with a yield of 67.4 wt%, followed by G (29.6 wt%) and HF (3 wt%). A characteristic time‑scale analysis indicates that pyrolysis reactions are rate‑determining under the investigated conditions (t_R = 210 s, t_heating = 10 s). When the T_R is increased by 20°C, the LF yield decreases to 56.7 wt%, while the G yield increases to 40.9 wt% and the HF yield remains nearly unchanged. This trend is consistent with the different activation energies of the competing pathways that generate each product (Ea(W->LF) = 100 kJ/mol, Ea(W->G) = 249 kJ/mol). Subsequent simulations varying d_p from 1.5 to 2.5 mm show that increasing particle size reduces the specific surface area (1/d_p), thereby diminishing external heat transfer rates and increasing the t_heating from 9 to 14 s. However, because the overall process is kinetics‑controlled within the examined conditions, these changes in heat transfer have no significant impact on product distribution.

This work elucidates role of operating conditions and modes in plastic pyrolysis through particle‑level analysis, clarifies their ultimate impact on product distribution, provides guidance for process optimization. Moreover, the modeling method is also appliable to more poorly mixing reactors, where kinetics may no longer be rate‑limiting, thereby enabling quantitative analysis of real systems beyond the laboratory-scale.

ABSTRACT. Plastics are essential materials, yet current end-of-life management practices remain inadequate, resulting in significant losses within the plastics economy and continued dependence on fossil resources. In Europe in 2022, most of the 26.9% of plastic waste recycled was recovered through mechanical recycling; however the effectiveness of mechanical recycling is limited by a reliance on clean, well-sorted streams. Consequently, to achieve a circular plastics economy, complementary recycling methods are needed to process mixed and contaminated plastic waste streams. Pyrolysis is well-suited to address this deficiency.

This work investigates how branching in polyethylene (PE) influences pyrolysis behavior and product distributions. Two grades of linear low-density polyethylene (LLDPE) with short-chain branching, two grades of low-density polyethylene (LDPE) with short- and long- chain branching, and one grade of high-density polyethylene (HDPE) with minimal branching, provided by SABIC, were pyrolyzed at 500 and 600 °C. Samples were pyrolyzed using a micropyrolysis unit coupled to an analytical system featuring comprehensive two-dimensional gas chromatography (GC×GC) with parallel detectors, enabling quantification via Flame Ionization Detection (FID) and compound identification through Time-of-Flight Mass Spectrometry (TOF-MS). The most remarkable difference in the distribution of products, by carbon number, was an increase in C5 and C6 products from LLDPE pyrolysis. The yields of low molecular weight products, in particular products in the desirable naphtha range, were impacted more significantly by temperature than by the presence of branching in the feedstock. These insights inform how feedstock composition and process conditions shape pyrolysis product profiles, supporting future optimization of chemical recycling processes.