Current Status of Food Waste Anaerobic Digestion and Challenges in Carbon Source Production in China
Resource utilization of food waste is a key measure for implementing waste classification and constructing zero-waste cities in China. However, the technical route based on anaerobic digestion currently faces developmental bottlenecks. In this study, engineering-scale facilities located in Northeast, North, Northwest, and Southeast China were selected, and material flow analysis was employed to comprehensively assess the current status of anaerobic digestion of food waste. The results indicated that, during the pretreatment stage, both leachate and organic slurry from all surveyed regions exhibited high COD/TN ratios, and the leachate contained high concentrations of lipids. Following three-phase (oil-water-solid) separation, the oil recovery rate could reach over 98%. Anaerobic digestion of each ton of food waste from the four regions generated approximately 70 to 80 Nm³ of biogas, while simultaneously producing liquid digestate accounting for 69% to 80% of the total mass and solid digestate accounting for 2.7% to 3.6%. However, the annual continuous production of digestate was not aligned with the seasonal demand for land use, thereby restricting the pathway for resource utilization. Converting food waste into an external carbon source can significantly enhance its resource utilization efficiency, with the economic benefits increasing by more than 203% compared to the methanogenesis pathway. The selection of the carbon source production technology route should be comprehensively determined by taking into account factors such as the specific nitrogen removal requirements of the target wastewater treatment process, the quality requirements for the carbon source products, and the substitution rate of commercial carbon sources.