Search

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]

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]

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]