ABSTRACT. Several technologies are available for the upgrading of biogas produced during the anaerobic digestion (AD) of biowaste. The main aim is the gas cleaning from CO₂ with subsequent concentration of CH₄ up to minimum 95-96% to obtain biomethane for grid injection or/and transport use. Biomethane substitutes natural gas and can contribute to the EU objectives of 10% of biofuel for transport within year 2020. Generally the upgrading technologies available on the market are economically sustainable only for large plants (>300-500 Nm³/hour of entering biogas), thus the development of low cost solutions devoted to small biogas plants - or for processing the surplus biogas which cannot be converted to power - seems to be a topic of interest. Previous projects carried out by the University of Florence since 2010 showed the capacity of bottom ash from a municipal solid waste incineration (MSWI) to capture the CO₂ present in the landfill gas (Mostabuer et al., 2014; Lombardi et al., 2016). As an alternative to MSWI bottom ash, in alpine regions the availability of ash deriving from the combustion of wood biomass, generally carried out in district heating plants, represents an opportunity to better use this kind of waste before final disposal.

In the present work wood ash (WA) generated by the combustion of wood in a central heating plant was used to capture CO₂ from laboratory simulated biogas, with the aim to evaluate its application for biomethane production. 
The results of preliminary tests carried out by at laboratory scale are presented. The process was realized in a static single-stage reactor, made of a fixed bed of WA crossed by a gas flow rate of simulated gas, as a mixture of 45-48% CO₂ (in volume) and N₂ as remaining amount, to simulate the composition of biogas from AD (N₂ substituting CH₄ for safety reasons; CH₄ does not react with ashes as neither N₂ does).

The results showed a very good removal of CO₂, which was about 100% in the first 30 hours of the tests. With respect to other typologies of ash used in the cited previous projects the capacity of WA to capture the CO₂ seems to be higher, reaching in the reported test values higher than 120 g of captured CO₂ per kg of dry WA.

ABSTRACT. The separate collection of recyclables waste in Italian municipalities (including biowaste, packaging waste, WEEEs and others) has reached a quota of 45.2% of all MSW managed in Italy in 2014 (29.66Mtons/yr), with a rather stable total production of waste (CIC, 2016). In Italy, the number of Anaerobic Digestion plants has constantly increased in the last decade. By 2015, 46 AD-plants have been realized a total authorized capacity of about 2 million tons of biowaste. Italy being the third world producer of biogas, the economic valuation of the option of purifying biogas and obtaining biomethane is currently a major line of inquiry. This study was carry out with an anaerobic laboratory scale reactor filled with OFMSW (organic fraction from separate collection of municipal solid waste, biowaste), in order to evaluate its performance in terms of energy recovery. The study was performed under the LIFE+ project Biomether (www.biomether.it) on the promotion of biomethane in Emilia-Romagna region for vehicles use, as substitute of fossil fuel, and to integrate the natural gas in domestic, commercial and industrial consumption.

The aim of the contribution is to evaluate the feasibility and efficiency of biogas production from “biowaste juice”. It was sampled in a full-scale plant after treatment with a centrifugal separator machine, from which an organic liquid fraction (juice) was obtain, cleaned from inert (such as glass, plastic, wood). The dry matter content (10.3%) obtained by the treatment makes it easy to use in anaerobic digestion plant. The process was carried out in mesophilic conditions (40 °C), with an average volumetric organic rate (OLR) of 2.9 kg m³d^-1 and the average hydraulic retention time (HRT) was 29 days.

The methane yield on raw materials, an important parameter for the sizing of an anaerobic digestion plant that operates on “biowaste juice” was 30 m³ t^-1. The methane percentage measured in biogas produced was good, 67%, due to the high level of organic matter present in biowaste and the absence of unwanted fractions. The production in methane has reached good values equal to 387 Nm³tVS^-1.The pre-treatment process of the OFMSW, separating the solid phase, allows to send only the liquid phase to the anaerobic digester thereby avoiding that in the digestate are present large quantities of inert solid substance or not convertible into biogas, resulting in lower production digestate material difficult to treat. The results of the laboratory test confirm that the quality of the biogas is satisfactorily, and that the production rate may be considered economically interesting.

ABSTRACT. This paper investigates the mass balance and economic performance of a material recovery plant located in Rodengo Saiano, in the Northern Italy. The plant is owned by Linea Energia, a business unit of LGH, Linea Group Holding. LGH is a multi-utility working in the area of Brescia, Cremona, Crema, Lodi and Pavia and Linea Energia is the business unit working in the sector of energy production. 

Rodengo Saiano plant is composed of one composting section and one energy recovery section. Composting section has a treatment capacity of 33,000 tons per year of: yard wastes from gardens; green waste from parked and wooden packaging. The composting section has two kinds of output: compost and woodchips. Woodchips are burned in the energy generation section, which is based on an air – cooled moving grate furnace with integrated an Organic Rankine Cycle. At maximum continuous rating (MCR) condition the plant produces a gross electric power of 1 MW. The composting section is based on open air windrow process, without forced aeration, a technology typically used in garden waste composting process. Compost produced from green waste has wide use in floriculture and agriculture; however, composting process has high operating costs, and its economic sustainability depends strongly from tariffs payed by municipal and private collectors.

In this paper workflow, internal logistic and mass flow and balance of the composting section are described. The specific costs of each activity are determined and analyzed.

ABSTRACT. Energy recovery from waste materials has been practiced for decades.  The recent focus on the environment and sustainable energy production has increased the awareness toward using waste, in particular municipal solid waste (MSW), for base load energy generation.  This has also led to an increase in the development and demonstration of new technologies to convert waste to valuable products such as liquid fuels and chemicals.  The heterogeneous nature of the waste streams necessitates the use of novel designs and materials to ensure robust performance and long term operation. 

Recently we have examined a number of gasification and pyrolysis processes that range from non-recycled plastics to very wet wastes.  This presentation will compare the material and energy balances of some unique pilot scale units that convert waste streams to energy and fuels.  Quantitative comparisons, along with emission measurements will be discussed and put into context compared to conventional waste to energy systems.

ABSTRACT. Thermal conversion of waste-derived fuels is gaining a clear role in the general frame of the circular economy as one pathway to close the recycle loop when a material or chemical recycle is impossible or economically unfeasible. Sewage sludge derived from the treatment of urban wastewaters is currently facing rapidly increasing production volumes and severe restrictions of the conventional disposal options: thermal conversion stems out as the most viable strategy, entailing large reduction of the sludge volume and thermal destruction of the toxic organic constituents. In the frame of thermochemical processing of waste-derived fuels, pyrolysis/gasification presents several advantages over the direct waste-to-energy combustion path, mostly related to the generation of syngas and condensable species which can be easily transported, burned or even exploited in gas-to-liquid fuel or chemical processes.

The present study addresses the development of a process for oxy-pyrolysis of sewage sludge in a rotary kiln converter. The aim of the process is the production of syngas from devolatilization of a waste-derived fuel, with oxygen playing the role of promoting autothermal operation of the pyrolyzer by controlled oxidation of volatile compounds. The specific concern of the study is the assessment of the effectiveness of staged oxygen feeding, as opposed to localized feeding at the reactor inlet, as a tool to selectively promote desired secondary reactions occurring in gas phase, like partial oxidation of tars. The converter consists of a rotary kiln in which the oxidizer is fed at multiple coordinates along the reactor axis, so as to obtain a reactant contacting pattern resembling that of a Zwietering reactor. The reactor is modelled at steady state using a 1.5D frame. Material and energy balances are set up considering a semi-lumped kinetic mechanism that was purposely developed to represent the complex chemical pathways of the solid fuel, of the gaseous compounds, of different tar components and of soot. Model results are analyzed with a focus on the effect of axial staging of the oxidizer on the quality of the produced gas and on the performance of the reactor.

ABSTRACT. The world increasingly need of greater varieties of raw materials and minerals, this leads to take action to promote the recovery of Critical Raw Materials (CRMs). According to the new European mining management vision and with the EU pillars, the European Raw Materials strategy must lay the foundations for a European policy of production of strategic raw materials that raises extraction mining option, promoting recovery of CRM from recycling, provide incentives for study and research at European level for the introduction of elements and alternative technologies and encourage the creation of a European Innovation Partnership for and the dissemination of new technologies. The waste resulting from the extraction and processing of stones, can be disposed of in authorized landfills, but properly treated and recovered, might find relocation on the market as "secondary raw material".

The following research is therefore aimed at the characterization of sludge, to determine which treatments (for normal industrial practice) can be applied to sludge in order to avoid the dangerous substances derived from the wear of cutting tools. The investigation was conducted on sludge from cutting with diamond wire, diamond saw blades, and mixed sludge. The tests performed are: particle size analysis, chemical analysis, wet magnetic separation, diffraction and SEM analysis. Magnetic separation is carried out in order to obtain two secondary materials: very fine-grained mineral fraction and metals fraction. The study performed is useful for evaluating the possible reuses of both the metal (containing CRM), and the mineral part, through the implementation of a proactive waste management strategy in order to avoid a subsequent environmental degradation.

This study is part of the WeCARE commitment (Wastes from Construction industry As a ResourcE) recognized by EIP Raw Material, which involve several European institutions, with the common aim of seeking a solution to recover and recycle sludge from construction industry and in particular processing stone.

ABSTRACT. The increase in carbon fiber reinforced polymer usage makes tackling the challenges of their disposal unavoidable. The high production costs make fiber recycling desirable over disposal. Reclaiming the fibers from their polymer matrix however is not without challenges. With chemical, mechanical and thermal processes available, thermal processes are so far favored by the industry. 

Pyrolysis leads to a decay of the polymer matrix, but may also leave solid carbon residues on the fiber. These residues prevent fiber sizing and thereby reuse in new materials. In the state of the art, these residues are removed with oxygen. This however may damage the fiber’s tensile strength. In order to avoid damaging the fibers oxidizing non-oxygen atmospheres, especially carbon dioxide and water vapor, were used, to reduce the char residues from carbon fibers while causing minimal or no fiber damage. 

Still even under ideal recycling conditions, a production based fiber shortening will occur with every new life-cycle. Fiber disposal pathways will therefore always be necessary. Utilizing the energy stored within the fibers, thermal disposal is favorable, but aggravated by thermal fiber fragmentation.

ABSTRACT. Biowaste separate collection and recycling plays as a driver of increasing importance when addressing the overall Municipal Solid Waste performances in Italy, as recently confirmed by the Italian Environment Agency (ISPRA) through its report on MSW management in 2015. The recycling sector counts over 300 facilities in operation, characterized by a growing technological and layout diversity, above all thanks to the introduction of Anaerobic Digestion as an integration of the traditional composting process.

The new challenges to take on in order to strengthen both reliability and competitiveness of biowaste sector are increasingly related to the improvement of biowaste quality (the main role being played by the separate collection services), the optimization of recycling processes and the diversification of the final products achievable, which range from fertilizers (soil improvers, growing media, inorganic fertilizers) to the products deriving from anaerobic digestion (biogas, biomethane).

Starting from the experience gained by the Italian Composting and Biogas Association (CIC) – above all focused on the evolution of the quality of biowaste taken to the recycling facilities, and on the quality of compost labeled as “CIC quality compost” – the presentation aims at foreseeing the tendencies on the diversification of the products generated by biowaste recycling facilities, increasingly shaped as actual biorefineries.

ABSTRACT. Nowadays the selection and the treatment of the glass waste is implemented in processing plants where, through sorting the foreign bodies and separation from Pb crystal, opaque bodies and the metals, a secondary raw material (SRM) - named cullet - is obtained, suitable for glass products and a glassy waste (glass waste ²) still not accepted by the glass factories. While the recovery of primary glass waste is already spread and technological known, the secondary glass waste (glass waste²) is recovered by few companies in Italy from some years. Consequently the recovery of the waste of this secondary recovery process of glass waste is new (glass waste³) and therefore to optimize, in order to reach an economic and sustainable industrial process solution.
With the aim of optimizing the plant of SASIL already existing for the recovery of the “glass waste³”, innovative technologies have been studied and executed. The major difficulty is in the automatic separation of materials as plastic lightweight, synthetic stoppers and cork stoppers that can nowadays find a market. In particular, the solved problem is the separation for materials whose density is < 1, using non-impacting methods. The particle distribution and characterization of the waste in entrance in plant and the products obtained in different stage of treatment have been used to dimension the new plant and to suggest new kind of treatment. Among the innovative process suggested two density separation have been performed:

- separation by means jig concentrators;

- separation of new method of bath suction.

In this research the jig concentrator, at difference of the previous research don’t use floatation principle but only fluid motion (without chemical addition and collectors). The same is for the “bath suction apparatus” that it needs only of water to execute the separation. The separation of efficiencies are major than 80% both  for jig concentrators, for the separation of  heavy plastic and glass from plastic lightweight and  synthetic stoppers and cork stoppers, and for bath suction apparatus that led to separate plastic lightweight from synthetic stoppers and cork stoppers. On the base of laboratory results, a new treatment plant has been designed and economic evaluation have been made. The materials to be trade as secondary raw materials (SRM) are about 87.5% of the total feeding and they are glass, plastic lightweight, ferrous metals, non-ferrous metals, synthetic stoppers and cork stoppers. These percentage should be related to the high amount of this kind of waste to be valorised (glass waste ³), landfilled in the plant in Italy and ready to be recovered, after the implementation of the right industrial technology.

ABSTRACT. The present work concerns the evaluation of MSWI solid residues reuse as partial replacement of natural aggregates for concrete production. The residues studied are: bottom ash derived from two mass-burning kilns (MB(A) and MB(B)) that treat MSW; exhausted sand and bottom ash derived from a fluidized-bed incinerator (FB(C)) that receive MSW-derived solid recovered fuel (SRF).

The bottom ash derived from MB(A) were pre-treated by means sieving and iron removal processes; moreover, additional washing was applied. Sieving and iron removal processes with a subsequent ageing (for two months) were performed on the bottom ash derived from MB(B). Natural aggregate was partially replaced (with a weight percentage from 7% to 40%) with different residues for the production of some concrete mixtures, casted adopting different types or dosages of residues and two different type of cement. Regarding the mechanical characterization of concrete mixtures, the use of 400 kg/m³ (corresponding to 23% of natural aggregate replacement) of bottom ash from fluidized-bed reactor (with the use of CEM42.5R) showed the best results: in this case concrete mixtures could be classified in concrete class C16/20, suitable for structural elements made of reinforced concrete.

The results of the leaching test showed that only the washed bottom ash from the mass-burning kiln could be reused following the simplified procedures according to Ministerial Decree 186/2006. For the exhausted sand derived from the fluidized-bed incinerator, the release of some pollutants (especially chromium and arsenic) was higher than the other residues. As concerns the leaching behaviour, concrete mixtures containing the residues derived from fluidized-bed reactor showed a release of pollutants higher than the other mixtures.