Option of treatment scenario for food waste anaerobic digestion by-products based on comprehensive evaluation and scenario promotion benefits analysis

Anaerobic digestion technology is widely used to treat food waste. However, this technology produces nutrient-rich by-products including biogas slurry (BS), biogas residue (BR), and three-phase oil extraction residues, which currently have no sustainable treatment methods, so there is an urgent need to explore a way out for their treatment. The purpose of this study is to explore sustainable path for the treatment food waste anaerobic digestion by-product. This study established three hypothetical food waste anaerobic digestion by-product treatment scenarios: (1) scenario 1 (S1): BS sewage treatment, BR incineration; (2) scenario 2 (S2): BS land application, BR composting; (3) scenario 3 (S3): BS sewage treatment, BR composting. In the three scenarios, the three-phase oil extraction residues are used for fly maggot breeding, and the produced frass was used for composting. Based on MFA and economic performance analysis, the scenario with the highest resource recovery rate and profit is selected, and then it is assumed that the scenario would be promoted in Jiangsu area (JS area) and Suzhou (SZ), Wuxi (WX), Changzhou (CZ) (collectively referred to as the SXC area) in 2030. The benefits of scenario promotion are calculated based on the food waste yield in 2030 calculated by the forecasting model. The analysis results show that S2 has the highest nutrient recovery rate and economic benefits. Therefore, we believe that S2 is the best choice under this study. After the promotion of S2, JS area would replace 5.3% of chemical fertilizer applications, and save $148 million and $12.2 million in sewage treatment costs and incineration costs, respectively. SXC area would replace 25.3%, 26.4%, and 12.6% of chemical fertilizer applications, respectively, and save $22.8 million, $12.2 million, and $8.42 million in sewage treatment costs, $1.87 million, $1.09 million, and $0.7 million incineration disposal costs, respectively. JS and SXC areas all reduce 26.5% of total nitrogen non-point source pollution, and the profit increased by 3.8 times compared with traditional rice planting.