Papers by Francesco Di Maria
An LCA (Life Cycle Analysis) was realized for different residual waste management scenarios in a ... more An LCA (Life Cycle Analysis) was realized for different residual waste management scenarios in a given urban area. The analysis was performed by evaluating the environmental impacts and the potential of the conservation of the resources. The results show that the disposal of the residual waste in landfill, even if the waste has been biostabilized before, is always disadvantageous in comparison with the scenarios with energy recovery. The use of Solid Recovered Fuel in the cement plants, in substitution for coal, results to be advantageous. Recycling of metals, coming from mechanical selection, is a significant benefit for the environment.
Different management options of the organic fraction (OF) generated in a given urban area were an... more Different management options of the organic fraction (OF) generated in a given urban area were analyzed by a life cycle assessment (LCA) approach for different source segregation (SS) intensities ranging from 0% up to 52%. Best management options for the different SS values were represented by the presence of incineration for processing the amount of OF remaining in the residual waste (ROF). The introduction of aerobic treatment and/or of anaerobic digestion (AD) for processing the SSOF leads to relevant environmental impact reduction even if the difference between the two options results quite negligible. A noticeable role is played by the amount of renewable energy recoverable from AD. An increase of about 50% of the biogas generated from the AD in the scenario with SS=52% with incineration of ROF leads to a global environmental gain.
Energy Procedia, 2014
The possibility of recovering the heat ejected with the exhaust air arising from the aerobic conv... more The possibility of recovering the heat ejected with the exhaust air arising from the aerobic conversion of organic waste for feeding a micro organic Rankine cycle (ORC) was investigated. This heat was upgraded by the combustion of a given amount of solid recovered fuel (SRF). The exhaust air rate ejected by the aerobic process ranged from 40 to 95 kg/day per each tonne/day of waste processed and the temperature ranged, respectively, from 340 K to 330 K. Calculations refer to a typical aerobic treatment facility able to process 20,000 tonnes of organic waste per year. Maximum efficiency in the utilization of the heat produced by the combustion of SRF, ranging from 14 % to 22 %, was achieved for ORC operating at a compression ratio from 1.5 to 2.5 and exhaust air temperatures from about 340 to 350 K. Operating the ORC with compression ratios higher than 3.5 and exhaust air temperatures of about 510 K, the power output ranged from about 9 to 12 kW. In these conditions, for the size of the facility investigated, the efficiency of the utilization of the heat generated by the combustion of SRF was from 4 % to 7 % higher than the ORC thermodynamic efficiency.
The global gaseous emissions produced by landfilling the Mechanically Sorted Organic Fraction (MS... more The global gaseous emissions produced by landfilling the Mechanically Sorted Organic Fraction (MSOF) with different weeks of Mechanical Biological Treatment (MBT) was evaluated for an existing waste management system. One MBT facility and a landfill with internal combustion engines fuelled by the landfill gas for electrical energy production operate in the waste management system considered. An experimental apparatus was used to simulate 0, 4, 8 and 16 weeks of aerobic stabilization and the consequent biogas potential (Nl/kg) of a large sample of MSOF withdrawn from the full-scale MBT. Stabilization achieved by the waste was evaluated by dynamic oxygen uptake and fermentation tests. Good correlation coefficients (R 2 ), ranging from 0.7668 to 0.9772, were found between oxygen uptake, fermentation and anaerobic test values. On the basis of the results of several anaerobic tests, the methane production rate k (year À1 ) was evaluated. k ranged from 0.436 to 0.308 year À1 and the bio-methane potential from 37 to 12 N m 3 /tonne, respectively, for the MSOF with 0 and 16 weeks of treatment. Energy recovery from landfill gas ranged from about 11 to 90 kW h per tonne of disposed MSOF depending on the different scenario investigated. Life cycle analysis showed that the scenario with 0 weeks of pre-treatment has the highest weighted global impact even if opposite results were obtained with respect to the single impact criteria. MSOF pre-treatment periods longer than 4 weeks showed rather negligible variation in the global impact of system emissions.
The energetic performance of an ORC system fueled by the heat generated from the integrated aerob... more The energetic performance of an ORC system fueled by the heat generated from the integrated aerobic/ anaerobic treatment of organic waste was analyzed. The temperature and heat content of the exhaust air arising from the aerobic treatment were increased by the combustion of the biogas produced by the anaerobic digestion of a fraction of the same waste. On the basis of the amount of excess air exploited in the process, for each tonne of organic waste treated, it was possible to produce from 30 to 90 kg of exhaust air per day with a mean temperature ranging from 330 to 340 K. By processing from 0.5% to 16% of the whole organic waste in an anaerobic digestion section instead of the aerobic one, it was possible to increase the exhaust air temperature from 340 to 510 K, leading to an increase in the ORC size from about 0.05 to about 1 W/tonne/year. The best energetic utilization of the biogas was achieved for ORC compression ratios from 1.5 to 2 and for maximum air temperatures from 335 to 340 K. In these conditions, by using a micro-ORC system (i.e. <15 kW), it was possible to convert about 20% of the energy content of the biogas into electrical energy.
The energetic exploitation of the organic fraction of municipal solid waste treated in an existin... more The energetic exploitation of the organic fraction of municipal solid waste treated in an existing Mechanical Biological Treatment plant was found to be successful by the Solid State Anaerobic Digestion. The amount of inoculum used per tonne of waste for starting the anaerobic process was shown to have a relevant effect on both biogas and biomethane production. For a waste-to-inoculum ratio ranging from 1:1 to 1:3 (w/w), the energy production increased from about 100 kWh/tonne to about 380 kWh/tonne of waste organic fraction. Consequently, the investment costs also rise, going from about 180 € to more than 370 €/tonne of treated municipal solid waste organic fraction. The economic optimization analysis showed that the waste-to-inoculum ratio that minimized the treatment cost, ranged from 1:1.5 to 1:2.5, being strongly influenced by the plant size (i.e. electrical efficiency) and by the Green Certificate value. Considering the cost of producing electrical energy, the optimum ratio was 1:2, leading to a cost of 0.26 €/kWh, during the investment period, and of 0.14 €/kWh after the investment period.
Waste Management, 2014
Life cycle analysis of several waste management scenarios for an Italian urban area was performed... more Life cycle analysis of several waste management scenarios for an Italian urban area was performed on the basis of different source segregation collection (SS) intensities from 0% up to 52%. Source segregated waste was recycled and or/recovered by composting. Residual waste management options were by landfilling, incineration with energy recovery or solid recovered fuel (SRF) production to substitute for coal. The increase in fuel and materials consumption due to increase in SS had negligible influence on the environmental impact of the system. Recycling operations such as incineration and SRF were always advantageous for impact reduction. There was lower impact for an SS of 52% even though the difference with the SS intensity of 35% was quite limited, about 15%. In all the configurations analyzed, the best environmental performance was achieved for the management system producing SRF by the biodrying process.
Waste Management & Research, 2013
The bioreactor environment for the mechanically sorted organic fraction (MSOF) of residual munici... more The bioreactor environment for the mechanically sorted organic fraction (MSOF) of residual municipal solid waste was simulated for a period of 300 days. A closed-loop system was implemented for analysing the leachate purification process due to its recirculation through MSOF. Maximum concentrations of Cu, Zn and Ni in the leachate were about 60, 20 and 15 mg L −1 , whereas Pb and Cr were about 5.5 and 7 mg L −1 . About 60 days from the start of recirculation these concentrations dropped to < 1 mg L −1 . Chemical (COD) and biological oxygen demand (BOD 5 ) dropped, respectively, by about 50 and 80%, achieving a COD-to-BOD 5 ratio > 7. Volatile fatty acids, which were about 10 g L −1 , fell to about 3.5 g L −1 whereas biomethane production was about 34 NL kg TS −1 . As expected, recirculation under strictly anaerobic conditions gave minor benefits in reducing nitrogen and ammonium which reached final concentrations of about 4 and 3.8 g L −1 , respectively.
International Journal of Energy Research, 2003
International Journal of Energy Research, 2001
International Journal of Energy Research, 1999
International Journal of Energy Research, 2004
Applied Thermal Engineering, 2005
Saving energy and money is one of the main concerns of many industrial and service firms. Reducin... more Saving energy and money is one of the main concerns of many industrial and service firms. Reducing energy consumption means reducing environmental impact, related to the considered activity, and in some cases this entails also economical benefits. Environmental impact reduction becomes of main importance if the device operates in a nature reserve.
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Papers by Francesco Di Maria