Enhancement of Food Waste Thermophilic Anaerobic Digestion with Supplementing Spent Mushroom Substrate: Synergistic Effect and Stability

In order to explore the co-digestion performance of food waste (FW) and spent mushroom substrate (SMS) under high temperature anaerobic conditions, the effects of FW and SMS co-digestion at different mixing ratios on methane production were investigated. Results shown that the co-digestion of FW and SMS had a positive synergistic effect [synergy index (SI) = 106.87-131.09% > 100%], and when the mixing ratio of FW/SMS (volatile solid basis) was 7:3, the methane production of the co-digestion system increased by 15.92% and 69% compared with the single fermentation of FW and SMS, respectively. Simulation results of first-order kinetic model and modified Gompertz model shown that the co-digestion of FW and SMS exhibited the highest hydrolysis rate constant (0.102 day-1) and shortest lag-phase time (4.90 days). Experimental results also demonstrate that co-digestion had lower total/free ammonia nitrogen, suitable pH and alkalinity value, and faster system stability compared with single fermentation. Therefore, co-digestion of FW and SMS to produce methane has certain technical feasibility.