Comparative environmental and economic life cycle assessment of dry and wet anaerobic digestion for treating food waste and biogas digestate

Anaerobic digestion (AD) has proven to be a promising option for food waste (FW) management, due to the significant potential of recovering energy from waste. In this study, the environmental and economic impacts of six scenarios for FW and biogas digestate management in Shenzhen, China, were evaluated using life cycle assessment (LCA) and life cycle cost (LCC) analysis. GaBi model was employed to perform LCA on the basis of CML 2001 methodology, while LCC analysis was conducted using net present value to evaluate the economic efficiency. Results showed that dry AD coupled with biogas digestate incineration not only exhibited the best net environmental benefits with the reduction of 195 kg CO2 per ton of FW, but also appeared to be the most economically feasible option with the lowest LCC (446.223 thousand CNY). With respect to the FW treatment technology, dry AD scenarios exhibited better environmental benefits associated with global warming, human toxicity, marine aquatic ecotoxicity and photochemical ozone creation potential, compared to those in wet AD. Regarding post treatment for biogas digestate, incineration appeared to be the best option compared to the landfill and compost. Moreover, sensitivity analysis indicated that dry AD coupled with biogas digestate incineration exhibited least vulnerable to the change in biogas production environmentally. The outcomes of this study will contribute to developing the optimal FW management strategy for mitigating the environmental and economic impacts in terms of both environmental and economic sustainability.