Bioenergy from anaerobic digestion plants: Energy and environmental assessment of a wide sample of Italian plants

This study assesses the energy and environmental performances of electricity produced from Italian anaerobic digestion coupled with combined heat and power plants. The Life Cycle Assessment methodology is applied to a set of plants characterised by different power sizes (from 100 to 999 kW) and feedstock compositions (variable rates of agricultural products and by-products). Then, the average eco-profile of the produced electricity is compared with electricity produced by the national grid and photovoltaic panels. The analysis allows detection of the combinations of size and feedstock with the lowest impacts. They correspond to small and medium plants mainly fed by organic by-products. In addition, compared to electricity from the grid, the average biogas electricity is characterised by the lowest contribution in impacts categories, such as abiotic depletion potential and ozone layer depletion potential, while largest in acidification and eutrophication. Focusing on global warming potential and cumulative energy demand fossil, the impacts of average biogas electricity (155 kgCO2eq/MWh and 172 MJ/MWh) are about 35 % and 38 % of that generated by the grid. Furthermore, it could generate 47 % less of the impact in the abiotic depletion elements category of the solar system. To enhance the farms' environmental and economic sustainability and balance the electric grid, these outcomes point out that biogas electricity produced from the agriculture and livestock sector can contribute to the decarbonisation and self-sufficiency of European countries. The results strictly depend on the operative conditions and can aid policymakers at the global level in improving the energy supply security and sustainability. Further, they provide reliable information to stakeholders to select the most sustainable solution, according to the feedstock type, power supply, and management.