Consequential Life Cycle Assessment of electricity production from biogas in Italy

In Italy, an increasing number of Anaerobic Digestion (AD) plants fed with agricultural feedstock has been detected to meet the European goals for Renewable Energy Sources (RES) production. AD is one of the most promising technologies for RES production, especially when wastes are used as feed instead of dedicated crops. However, the economic subsidy framework encouraged to invest in highly productive plants fed with dedicated crops. Since the economic subsidy has already been reduced, it can be expected its end in the future, thus potentially making the plants’ feeding with dedicated crops uneconomic. This study aims at evaluating the consequences of the potential deletion of the subsidy framework for AD production plants. Consequential life cycle assessment (cLCA) was implemented to evaluate the environmental effects of: (i) substituting dedicated crops in the feeding mix with pig and cow slurry; (ii) closing plants fed with dedicated crops and substituting the related renewable energy production with non-renewable one from the national energy mix. When cereal silages are substituted by animal slurry the environmental performances of agricultural AD plants are improved for two reasons. First, the avoided slurry storage at farm in traditional open tanks reduces the emissions of pollutants (e.g., methane, ammonia and dinitrogen monoxide) and, secondarily, the higher efficiency of the digestate nitrogen reduces the consumption of mineral fertilisers for crops cultivation. The outcomes of this study can be a valuable support for policy makers to drive the future towards a more sustainable energetic production.