Enhanced biogas production efficiency of kitchen waste by anaerobic co-digestion and pretreatment

Anaerobic fermentation (AF) can effectively dispose of kitchen waste (KW) without the shortcomings of traditional methods such as incineration and sanitary landfill. However, KW has a high organic content, which easily leads to acidification and ammonia inhibition during digestion. To mitigate this issue, anaerobic co-digestion (AnCoD) with other substrates helps to adjust the carbon to nitrogen ratio (C/N) and enhance the stability of the reaction system. The hydrolysis of substrate is the rate-determining step in AF, prompting the adoption of necessary pretreatment methods to accelerate substrate hydrolysis. Among physical, chemical, and enzymatic pretreatments, the latter is more efficient. And the enzymatic pretreatment does not need additional equipment or reagents. Therefore, coupling enzyme treatment before AnCoD received more attention. In this review, we conduct a comparative analysis of the biogas production efficiency of enzymatic pretreatment against other pretreatment methods. The challenges and strategies concerning enzymatic pretreatment coupled with AnCoD system were discussed. Finally, the pilot-scale study and industrial application for KW co-digestion are also analyzed. Graphical abstract