Holistic Life Cycle Assessment of a biogas-based electricity generation plant in a pig farm considering co-digestion and an additive

This study aims to perform an LCA of the co-digestion of pig manure with two co-substrates (corn silage and elephant grass) and an additive (biochar) to produce biogas for electricity generation. Four scenarios were defined: considering only the digestion of pig manure (Base scenario); co-digestion of pig manure with elephant grass-silage (scenario II); co-digestion of pig manure with corn silage (scenario III), and digestion of pig manure with biochar as an additive (scenario IV). The biogas produced was used for electricity generation in a cogen-eration system. The thermal energy obtained from the cogeneration system was used to heat the substrate, maintain a mesophilic digestion temperature (38 C), and heat the pig stalls. Digestate was considered an organic fertilizer in this analysis. Scenario III presented the worst results for most of the impact categories considered in the LCA, with only a positive impact on ozone depletion (ODP). Scenario II presented a lower impact than Scenario III. Using co-substrates and additives in the digestion of pig manure has allowed a considerable increase in electricity production. However, the environmental impacts of using co-substrates are significant in most impact categories, mainly due to the use of fossil fuels in the chain of silage production.