Anaerobic co-digestion of food waste and excess sludge by humus composites: Characteristics and microbial community structure

Volatile fatty acids (VFA) produced during the anaerobic co-digestion (Co-AD) an Manual removal of impurities such as bones, fish spines, napkins, etc., after collection at the food waste collection sited hydrolysis of food waste (FW) and excess sludge (ES) are important factors affecting the stability of the digestion and biogas production. This study aimed to use humus composites (HS) to mediate the Co-AD system of FW and ES, investigate their effects on VFA conversion, and analyze the microbial community structure using high-throughput sequencing technology to reveal the mechanism of action of HS in mediating the Co-AD system from a microbial perspective. The amount of HS was positively correlated with the accumulation of VFA produced by the hydrolysis of co-digested substrates, and in the Co-AD system with 5.00 g/L HS, the accumulation of VFA increased by approximately 1.1 times, whereas the pH and oxidation reduction potential of the system tended to be in the benign range, offering a favoring condition for enhancing the stability of the system. The biogas production increased by 46.3 % compared with that of the blank group. HS significantly increased the relative abundance values of Synergistota, a mutualistic symbiont with acetic acid-producing bacteria, and Proteobacteria, a mutualistic symbiont with methanogenic bacteria, thus promoting VFA conversion and strengthening the Co-AD efficacy of FW and ES. This study provides a simple and effective method to improve the Co-AD efficacy of FW and ES, as well as a new approach for the anaerobic resource treatment of other organic solid wastes. • Organic substrate transformation in humus composites-mediated anaerobic co-digestion system is defined. • Humus composites mediate the anaerobic co-digestion system, and volatile fatty acids and biogas yields are increased. • Humus composites promoted environmental balance in the anaerobic co-digestion system. • Synergistota and Proteobacteria were the dominant phyla in the anaerobic co-digestion system.