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Publication | 10 January 2019

Environmental assessment of electricity produced in biogas plants using alternative feedstocks

Achieving Bioeconomy objectives requires exploring alternative use of feedstocks and biomass valorisation towards the optimisation of benefits while minimising environmental impact. The present study aims at comparing different feedstock to unveil burdens and benefits associated to their Anaerobic Digestion (AD). AD has been recognized as an effective process to produce renewable energy while contributing to reduce the GHG emissions. It can use different feeding mix, chosen primarily in function of maximization of profit according to technical and economical feasibility of process. However, although the best environmental performance is achieved when the biogas plants are fed with crop residues, livestock manure and agro-industrial byproducts, cereal silages are by far the most used feedstock.The rapid expansion of biogas production in Europe is largely due to the feed-in-tariffs (FiT) schemes available in 29 countries. For example, in Italy, until 2013, electricity generators are paid 280 € per MWh generated using biogas produced in AD plants smaller than 1 MW. However, the FiT scheme in Italy has recently been changed, reducing the subsidy for electricity by 15%-30% and introducing payments for utilization of heat and other co-products. In this context, this study aims to assess, using the LCA (Life Cycle Assessment) approach, the environmental impact of electricity produced in biogas plants fed with increasing share of agro-industrial by-products. To this purpose four different feeding mix were compared with a reference scenario where the biogas plants is fed with cereal silages (mainly maize silage) and, secondarily, with animal manure (pig and cattle slurry). The alternative feeding mix involve the digestion of by-products from the processing of tomato (skins), potatoes (peels, skins and green tomatoes), olive (pomace) and grapevine (marc). For the different feedstock, the specific biogas production was evaluated by means of lab scale tests.

Environmental assessment of electricity produced in biogas plants using alternative feedstocks
English
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