Improvement of anaerobic digestion containing sulfur with conductive materials: Focusing on recent advances and internal biological mechanisms

Conductive materials application in anaerobic digestion containing sulfur gains increasing attention due to their multifunctional effects in promoting substrate degradation, methane production, and hydrogen sulfide production control. However, a comprehensive understanding of biological mechanisms that conductive materials promote anaerobic digestion containing sulfur has yet to be achieved. This paper reviews recent advances and internal biological mechanisms on conductive materials enhancing anaerobic digestion containing sulfur. Related literatures were searched on web of science, systematically summarized, compared, and analyzed. Direct interspecies electron transfer (DIET), quorum sensing, and enhancement of microbial tolerance to sulfides are identified as critical biological mechanisms. On this basis, the current work presents a unique insight into the potential connection between DIET and quorum sensing. Furthermore, the influences of conductive materials on microbial metabolism are comprehensively evaluated, including organic carbon metabolism, sulfur metabolism, and methanogenic metabolism. Finally, current challenges and future research directions are pointed out. This work is of great importance for guiding and elucidating the biological mechanisms of conductive materials to improve anaerobic digestion containing sulfur.