Evaluation of Biogas Performance and Process Stability from Food, Kitchen, and Fruit/Vegetable Waste by Mono-, Co-, and Tridigestion

With the increase of municipal solid waste (MSW), multiple sources of waste are simultaneously digested by anaerobic digestion (AD), which can be an environmentally friendly waste disposal and energy recovery method. In this study, using food waste (FW), kitchen waste (KW), and fruit/vegetable waste (FVW) as substrates, the biogas production and performance of anaerobic mono-, co-, and tridigestion systems were evaluated. The results showed that the highest biogas and methane yields were 614.8 and 354.51 mL/gVS, respectively, and were observed in the tridigestion of FW/KW/FVW (5:2:3). Anaerobic tridigestion has a higher synergistic effect on biogas and methane production compared with codigestion. In the monodigestion of FW, volatile fatty acid (VFA) accumulation and pH reduction were observed in the digester, but these effects could be effectively alleviated via the tridigestion of FW/KW/FVW. The microbial community structure analysis revealed that the dominant bacteria were Chloroflexi and Bacteroidetes and that hydrogenotrophic methanogenesis was the main methanogenic pathway for methane production. The tridigestion enriched Methanosaeta, which as an acetate-utilizing methanogen could enhance the acetoclastic methanogenic pathway. This finding suggests that anaerobic tridigestion is an efficient way to improve system stability and biomass energy production.