Life cycle assessment of a medium commercial scale biogas plant and nutritional assessment of effluent slurry

The present study is addressing the life cycle assessment of a novel design multi-digester anaerobic bioenergy plant. Notably the impacts regarding bioenergy generation and utilization of bioenergy and digestate are reviewed with reference to three different feed stocks used and experimented in this typical plant i.e. slurries of; 100% cow-dung, 75% cow-dung+25% potato-pulp and 100% potato-pulp respectively. The results depicted that concentrations of NPK and heavy metals (Cu, Ni, Mn and Fe) were highest in feedstock comprising 75% cow-dung+25% potato-pulp. The comparative LCA of said feed stocks was further deliberated in three representative environmental impact categories i.e. climate change potential (CO2 equivalent), fresh-water eutrophication potential (Phosphorous equivalent) and acidification potential (SO2 equivalent). The results revealed that feedstock comprising 100% cow-dung had highest savings in-terms of climate change i.e. 70 kg, lowest acidification potential i.e. 5 kg and considerably more fresh-water eutrophication potential i.e. 0.022 kg. The second best proven feedstock was 100% potato-pulp having potentials regarding climate change, acidification and fresh-water eutrophication as; 70.5 kg, 6.5 kg and 0.021 kg respectively. Whereas the feedstock comprising 75% cow-dung+25% potato-pulp had the highest comparative life cycle impacts i.e. 200 kg, 6.9 kg and 0.034 kg against climate change, acidification and fresh-water eutrophication categories.