Life Cycle Assessment and Cost-Benefit Analysis as Combined Economic-Environmental Assessment Tools: Application to an Anaerobic Digestion Plant

In the present study, using Life Cycle Assessment (LCA) and Cost-Benefit Analysis (CBA), we assess the economic-environmental performance of an anaerobic digestion (AD) plant, fed by cultured crops (i.e., maize and wheat), in Italy. The biogas generated by the AD plant is used for the production of electricity, imputed into the Italian energy grid. The LCA evaluated potential greenhouse gas (GHG) emissions, measured via Carbon Footprint (CF), while the CBA analysed the financial and economic profiles via the Net Present Value (NPV) and Internal Rate of Return (IRR) indicators. The strength of combining these methodologies is the joint examination of the financial and social-environmental performance of the plant. The results of the CBA are complemented with the GHG emissions avoided by producing electricity from biogas. The CF of 0.28 kg CO(2)eq.kWh(-1) of electricity produced is mainly due to the nitrogen fertilizers involved in the production of the additional feedstock matrix (i.e., maize flour). In the CBA, the negative financial NPV and the financial IRR, which is lower than the discount rate applied, highlight the inability of the net revenue to repay the initial investment. Regarding the social desirability, the economic analysis, enriched by the LCA outcomes, shows a positive economic performance, demonstrating that the combination of information from different methodologies enables wider consideration for the anaerobic digestion plant. In line with the Italian Recovery and Resilience Plan's aim to strongly increase the exploitation of renewable resources, an AD plant fed by dedicated crops could valorise the marginal uncultivated land, obtaining energy without consuming land for food production. Moreover, this AD plant could contribute to the creation of repeatable small-scale energy production systems able to sustain the demand of local communities.