A comparative life cycle assessment of biofertilizer production towards sustainable utilization of anaerobic digestate

Direct application of anaerobic digestate to agricultural soil has major environmental threats. Therefore, this study evaluates and compares four scenarios of digestate utilization as the first life cycle assessment (LCA) study conducted on these four scenarios. The four scenarios included (i) biofertilizer pellets (BFPs), (ii) biocompost (BC), (iii) liquid biofertilizer (LBF), and (iv) powder biofertilizer (PBF). The results showed that the LBF scenario was the best treatment choice, achieving environmental benefits in five of the ten impact categories examined; the highest was the marine aquatic ecotoxicity category (-141,304.03 kg 1,4-DB-eq./tonne digestate). Contrarily, the scenario with the least environmental benefits was the BC scenario in which it contrib-uted to emissions in five categories; the most notable was the contribution to the global warming category with 25.68 kg CO2-eq./tonne digestate. However, all the studied scenarios achieved environmental gains compared to the chemical fertilizers, and the top three emission reduction categories were marine aquatic ecotoxicity, global warming, and human toxicity. This study provides a valuable reference and inventory data for digestate treatment options. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.