Promoting anaerobic co-digestion of sewage sludge and food waste with different types of conductive materials: Performance, stability, and underlying mechanism.

In this research, we investigated and compared the effects of three widely used conductive materials, e.g., zero-valent iron (Fe), magnetite (FeO), and biochar on the performance, stability, and in-depth mechanism during the anaerobic co-digestion process of sewage sludge and food waste. Among the three conductive materials, Fe could achieve the highest cumulative methane production of 394.0 mL/g volatile solids (VS) , which was 1.24-fold and 1.17-fold higher than that receiving FeO and biochar. The mechanistic studies indicated that compared to the FeO and biochar groups, Fe could significantly enhance the release of soluble protein, polysaccharide, and dissolved organic matters, the degradation of volatile fatty acids and VS, and the activities of key enzymes and direct interspecies electron transfer (DIET). Consequently, the methane yield and digestate dewaterability were notably improved. Collectively, these findings will offer suggestions of the preferable conductive materials in the anaerobic co-digestion process for decision makers.