Evaluation of the co‐fermentation potential of different types of food waste combined with low organic matter waste activated sludge

Abstract Background To address the disposal challenges of low‐organic‐matter waste activated sludge (WAS) and food waste (FW) while enhancing resource recovery, this study systematically investigated the co‐fermentation of WAS with distinct types of FW. Result Results demonstrated that co‐fermentation significantly outperformed mono‐fermentation in both hydrolysis and acidification. Specifically, the protein‐rich system (with tofu residue) achieved optimal hydrolysis (protein: 832.24 mg COD/L; polysaccharides: 123.68 mg COD/L), whereas the carbohydrate‐rich system (with rice) yielded the highest short‐chain fatty acids (SCFAs) production (3842.95 mg COD/L). Mechanistically, substrate composition dictated microbial community succession and metabolic pathways. In the carbohydrate‐rich system, the boosted α‐glucosidase activity and selective enrichment of carbohydrate‐fermenting bacteria ( Erysipelothrix ) facilitated robust substrate‐level phosphorylation and acetate production, driving superior acidification. Conversely, the protein‐rich system stimulated protease activity and enriched protein‐degrading anaerobes ( Proteiniclasticum and Tissierella ), which enhanced the hydrolysis of macromolecular proteins but directed the metabolic flux towards amino acid degradation rather than high‐yield SCFAs biosynthesis. Conclusion In summary, the carbohydrate‐rich co‐fermentation system demonstrated the greatest potential for SCFAs bioconversion and resource utilization. These findings provide a customizable paradigm for directing microbial metabolism through FW sorting, thereby advancing the circular bioeconomy via waste biorefinery. © 2026 Society of Chemical Industry (SCI).