Unlocking anaerobic digestion potential via extracellular electron transfer by exogenous materials: Current status and perspectives.

[Display omitted] • Exogenous materials enhance anaerobic digestion by boosting extracellular electron transfer (EET). • Different promotion mechanisms in anaerobic digestion are summarized. • Conductivity and redox reaction are the predominant ways exogenous materials mediate EET. • Different EET facilitation mechanisms promote different stages of anaerobic digestion. • Individual materials may promote EET through multiple mechanisms. The efficiency of energy transfer among microorganisms presents a substantial hurdle for the widespread implementation of anaerobic digestion techniques. Nonetheless, recent studies have demonstrated that enhancing the extracellular electron transfer (EET) can markedly enhance this efficiency. This review highlights recent advancements in EET for anaerobic digestion and examines the contribution of external additives to fostering enhanced efficiency within this context. Diverse mechanisms through which additives are employed to improve EET in anaerobic environments are delineated. Furthermore, specific strategies for effectively regulating EET are proposed, aiming to augment methane production from anaerobic digestion. This review thus offers a perspective on future research directions aimed at optimizing waste resources, enhancing methane production efficiency, and improving process predictability in anaerobic digestion. [ABSTRACT FROM AUTHOR]