Sludge-based iron-carbon composite mediators enhanced simultaneous utilization of anaerobic sludge and biogas slurry in anaerobic digestion coupled with microbial electrolysis cell.

To achieve the simultaneous recycling of biogas slurry and anaerobic sludge, the sludge was used to synthesize sludge-based iron-carbon composite mediators (SICM), which were applied to enhance the performance of anaerobic digestion coupled with microbial electrolysis cell (AD-MEC) for biogas slurry degradation. By comparing four preparation methods, it was found that SICM oxygen-containing functional groups and different valence states of iron in SICM played active roles in facilitating electron transfer. Fe@C-B had the best performance of biogas slurry degradation, achieving a COD removal rate of 86.99 %. The methane yield for Fe@C was the greatest at 301.6 mL/gCOD. SICM enhanced AD-MEC performance through selective enrichment of key functional microorganisms such as Fastidiosipila, norank_f_Anaerolineaceae, Geobacter and Methanosaeta. This study demonstrated the feasibility of simultaneously converting biogas slurry into energy and recycling anaerobic sludge, also offering both theoretical and technical support for the sustainable development of biogas projects.