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In this study, the effect of gasifying agent and bed material on the performance of the co-gasification of a mixture of coal, plastic waste, and wood was investigated. The experimental runs were carried out in a lab-scale bubbling fluidized bed reactor utilizing air, oxygen-enriched air, a mixture of air and steam, and a mixture of oxygen and carbon dioxide as reactant gases, while silica sand, olivine, and a mixture of olivine and dolomite as bed materials were used. The results indicated that both gasifying agent and bed material strongly affect the gas composition and, as a consequence, the process performance. In particular, the test with oxygen-enriched air and silica sand provided a producer gas with the highest heating value (9.32 MJ/Nm3), while the best performance in terms of gas yield (2.98 Nm3/kg) and tar reduction (−94.5%) was obtained by utilizing the air/steam mixture and olivine. As regards tar composition, it was observed that the most abundant and recalcitrant tar substance groups are naphthalenes and PAHs. On the other hand, phenols and furans appear to be the most sensitive groups to the effect of gasifying agent and bed material. [ABSTRACT FROM AUTHOR]

Hydrochar, carbon-rich material produced during the thermochemical processing of biomass, is receiving increased attention due to its potential value as soil amendment. It can increase agroforestry systems' productivity through direct and indirect effects on growth and soil quality. Hydrochar may also directly help mitigate climate change by sequestering stable carbon compounds in the soil and perhaps indirectly through increased C uptake by trees. In this research, we aim to evaluate how the application of hydrochar produced by two feedstock types, Cynara cardunculus L. (Hc) residuals and sewage sludge (Hs), and in two different doses (3 and 6 kg m−2) could improve the growth and water use efficiency of Populus alba L., a fast-growing tree species largely used in agroforestry as bioenergy crops and in C sequestration. We considered five plants per treatment, and we measured apical growth, secondary growth, leaf area and intrinsic water use efficiency in each plant for the whole growing season from February to October 2022. Our results highlighted that hydrochar applications stimulate the growth and water use efficiency of plants and that the double dose (6 kg m−2) of both hydrochars, and particularly Hc, had positive effects on plant performance, especially during extremely hot periods. Indeed, the year 2022 was characterized by a heat wave during the summer period, and this condition allowed us to evaluate how plants, growing in soils amended with hydrochar, could perform under climate extremes. Our findings showed that the control plants experienced severe damage in terms of dried stems and dried leaves during summer 2022, while hydrochar applications reduced these effects. [ABSTRACT FROM AUTHOR]

Nowadays, the decarbonization of the sector of energy and the transformation of the whole economy chain in climate-neutral economy are targets in the political agenda of more than 50 Countries. The replacing of carbonbased fuels with hydrogen is one of the main ways to reach the decarbonization of the energy sector and reducing of impact on climate. Anyway, the production of hydrogen by recurring to electrolysis of the water molecules requires a large energy amount so that its sustainability must be increased by realizing more efficient system or synergy with other industrial sectors such as clean energy recovery. Possible well recognized sources of sustainable energy are biomasses, solar, and wind; in this paper an additional resource, a biowaste produced by anthropic activity, the sewage sludge, is considered as a possible source of energy for green hydrogen on the basis of a life-cycle perspective: the avoided burdens of landfill and incineration of sludges balance the low efficiency of the overall system for hydrogen production. The paper illustrates a model that combines biowaste treatment with hydrogen production. The mathematical model of the system allowed to calculate the mass balance and the feedstock energies distribution. The output variables of the model are hydrogen yield, electricity to the grid (surplus), and CO2 sequestrated; the input data to the model are the biowaste mass rate (and the composition), the power demand for hydrogen production by electrolysis and the electricity and heat consumption of the plant. The model results demonstrated that the hydrothermal carbonization of the given biowaste, that is sewage sludge from a waste-water treatment plant and the enriched air gasification of the resulted hydrochar converted into biofuel allowed to produce about 20kg/h of green hydrogen by covering all the energy demand of the plant, both heat, and electricity. [ABSTRACT FROM AUTHOR]

The main role of a waste management plan is to define which is the combination of waste management strategies and method needed to collect and manage the waste in such a way to ensure a given set of targets is reached. Objectives have to be sustainable and realistic, consistent with the environmental policies and regulations and monitored to verify the progressive achievement of the given targets. To get the aim, the setting up and quantification of indicators can allow the measurement of efficiency of a waste management system. The quantification of efficiency indicators requires the developing of a material flow analysis over the system boundary, from waste collection to secondary materials selling, processing and disposal. The material flow analysis has been carried out with reference to a case study for which a reliable, time- and site-specific database was available. The material flow analysis allowed the evaluation of the amount of materials sent to recycling, to landfilling and to waste-to-energy, by highlighting that the sorting of residual waste can further increase the secondary materials amount. The utilisation of energy recovery to treat the low-grade waste allows the maximisation of waste diversion from landfill with a low production of hazardous ash. A preliminary economic balance has been carried out to define the gate fee of the waste management system that was in the range of 84–145 € t−1 without including the separate collection cost. The cost of door-by-door separate collection, designed to ensure the collection of five separate streams, resulted in 250 € t−1 ±30%. [ABSTRACT FROM AUTHOR]

The effect of fuel composition on gasification process performance was investigated by performing mass and energy balances on a pre-pilot scale bubbling fluidized bed reactor fed with mixtures of plastic waste, wood, and coal. The fuels containing plastic waste produced less H2, CO, and CO2 and more light hydrocarbons than the fuels including biomass. The lower heating value (LHV) progressively increased from 5.1 to 7.9 MJ/Nm3 when the plastic waste fraction was moved from 0% to 100%. Higher carbonaceous fines production was associated with the fuel containing a large fraction of coal (60%), producing 87.5 g/kgFuel compared to only 1.0 g/kgFuel obtained during the gasification test with just plastic waste. Conversely, plastic waste gasification produced the highest tar yield, 161.9 g/kgFuel, while woody biomass generated only 13.4 g/kgFuel. Wood gasification showed a carbon conversion efficiency (CCE) of 0.93, while the tests with two fuels containing coal showed lowest CCE values (0.78 and 0.70, respectively). Plastic waste and wood gasification presented similar cold gas efficiency (CGE) values (0.75 and 0.76, respectively), while that obtained during the co-gasification tests varied from 0.53 to 0.73. [ABSTRACT FROM AUTHOR]

Abstract: Gasification processes can play a key role in the clean energy production from fossil and non-conventional fuels because of its transformation in a synthetic gas (syngas) rich in hydrogen and carbon monoxide. Fluidized bed reactors, both bubbling and circulating, allow to use a catalytic or reacting solid material in partial or total substitution of the bed in order to promote the dehydrogenation of the fuel. Depending on the operating conditions of reactor and of fuel type, the catalyst has a strong influence on the hydrogen yield; otherwise, the effect of catalyst add to a fluidized bed can decrease during the experimental run due to its progressive deactivation. The experimental tests demonstrated that the utilization of olivine as bed material, recognized in the literature as a good catalyst for gasification process of biomass and plastics, improves the dehydrogenation of the recycled polyethylene used as fuel by producing a hydrogen-rich syngas and a coke layer on the bed particles. The tests also indicated that the olivine was not capable to catalyse the dehydrogenation process for long time because of loss of metals diffused and linked to the carbonaceous solid (coke). A Substance Flow Analysis has been applied to the experimental data in order to evaluate the Hydrogen Recovery Efficiency for the gasification tests and to follow the repartition of metals (Fe, Ni, Mg) in the input/output streams and in the bed. The limited duration of the steady state regime as observed during the tests with olivine indicated a progressive reduction of the catalytic action correlated to the loss of metals. In other words, the use of olivine allows to obtain very high hydrogen concentration in the producer gas but for a limited time and without the possibility to recover its catalytic capacity by thermal or mechanical regeneration due to the progressive loss of metals responsible of polymer dehydrogenation. This experimental result is strictly correlated to the utilization of polyethylene as fuel. This evidence has been confirmed by analysis on olivine and fines elutriated by the reactor and showed, in this work, by a material balance on metals. [Copyright &y& Elsevier]

Abstract: The effect of oxygen-enriched air during fluidized bed co-gasification of a mixture of coal, plastics and wood has been investigated. The main components of the obtained syngas were measured by means of on-line analyzers and a gas chromatograph while those of the condensate phase were off-line analysed by means of a gas chromatography–mass spectrometer (GC–MS). The characterization of condensate phase as well as that of the water used as scrubbing medium completed the performed diagnostics. The experimental results were further elaborated in order to provide material and substances flow analyses inside the plant boundaries. These analyses allowed to obtain the main substance distribution between solid, gaseous and condensate phases and to estimate the conversion efficiency of carbon and hydrogen but also to easily visualise the waste streams produced by the process. The process performance was then evaluated on the basis of parameters related to the conversion efficiency of fuels into valuable products (i.e. by considering tar and particulate as process losses) as well as those related to the energy recovery. [Copyright &y& Elsevier]

In the Campania region, an area in the south of Italy with 5.7 million inhabitants and a production of about 7,900 tonnes of municipal solid waste per day, an emergency situation was created by inappropriate waste management policy and practice. In order to support decisions regarding future solutions for this crisis, reliable, transparent, and impartial strategies and concepts are needed. For this purpose, six waste management scenarios have been defined and quantitatively assessed by means of substance flow analysis (SFA). The scenarios are based on firm objectives and recent legislation for waste management and take into account regional waste production and composition as well as existing waste treatment infrastructure. They are evaluated and compared with the status quo in view of reaching the goals of waste management. For each scenario, the following material flows were quantified: wastes that would be sent to different processes, such as those of mechanical-biological treatment, incineration, or anaerobic digestion; treatment residues (in mass and volume) to be diverted to landfills; materials recoverable by recycling processes; and energy obtainable by waste-to-energy and anaerobic digestion plants. The results demonstrate that a future waste management system that is based on a combination of more recycling, thermal treatment, anaerobic digestion, and improved landfilling reaches the objectives of waste management much more closely than the present, inadequate system. [ABSTRACT FROM AUTHOR]

This article discusses the use of olivine in the gasification of plastic waste. Olivine acts as a catalyst to reduce the hydrocarbon presence and increase the thermal efficiency of synthetic gases (syngas). Syngas is produced from plastics using a bubbling fluidized bed air-gasification process. A laboratory gasification plant for polyethylene pellets was used to measure the effect of olivine in carbon mitigation. The chemical stages of this mitigation process are described. The significance of developing new gasification technologies for waste management purposes is noted.

Investigates the overall environmental performances of mechanical recycling of plastic containers in Italy. Environmental burdens of plastic waste management options; Comparison of the system with conventional options of landfilling or incineration, feedstock recycling, low-temperature fluidized bed pyrolysis and high-pressure hydrogenation; Environmental performance of plastic waste management schemes.

Biological treatments such as anaerobic digestion and composting are known to be the most widespread methods to deal with Organic Fraction of Municipal Solid Waste (OFMSW). The production of biogas, a mix of methane and carbon dioxide, is worth but alone cannot solve the problems of waste disposal and recovery; moreover, the digestate could be stabilized by aerobic stabilization, which is one of the most widespread methods. The anaerobic digestion + composting integration converts 10% to 14% of the OFMSW into biogas, about 35–40% into compost and 35–40% into leachate. The economic sustainability could be rather increased by integrating the whole system with lactic acid production, because of the high added value and by substituting the composting process with the hydrothermal carbonization process. The assessment of this integrated scenario in term of mass balance demonstrates that the recovery of useful products with a potentially high economic added value increases, at the same time reducing the waste streams outgoing the plant. The economic evaluation of the operating costs for the traditional and the alternative systems confirms that the integration is a valid alternative and the most interesting solution is the utilization of the leachate produced during the anaerobic digestion process instead of fresh water required for the hydrothermal carbonization process. [ABSTRACT FROM AUTHOR]

Organic Rankine Cycle (ORC) power plants are characterized by high efficiency and flexibility, as a result of a high degree of maturity. These systems are particularly suited for recovering energy from low temperature heat sources, such as exhaust heat from other plants. Despite ORCs having been assumed to be appropriate for stationary power plants, since their layout, size and weight constraints are less stringent, they represent a possible solution for improving the efficiency of propulsion systems for road transportation. The present paper investigates an ORC system recovering heat from the exhaust gases of an internal combustion engine. A passenger car with a Diesel engine was tested over a Real Driving Emission (RDE) cycle. During the test exhaust gas mass flow rate and temperature have been measured, thus calculating the enthalpy stream content available as heat addition to ORC plant in actual driving conditions. Engine operating conditions during the test were discretized with a 10-point grid in the engine torque–speed plane. The ten discretized conditions were employed to evaluate the ORC power and the consequent engine efficiency increase in real driving conditions for the actual Rankine cycle. N-pentane (R601) was identified as the working fluid for ORC and R134a was employed as reference fluid for comparison purposes. The achievable power from the ORC system was calculated to be between 0.2 and 1.3 kW, with 13% system efficiency. The engine efficiency increment ranged from 2.0% to 7.5%, with an average efficiency increment of 4.6% over the RDE test. [ABSTRACT FROM AUTHOR]