Harnessing Carbonaceous materials' multifaceted roles for enhanced anaerobic digestion performance

Anaerobic digestion (AD) is a promising approach for generating sustainable bioenergy from organic wastes. However, it encounters numerous challenges, such as high ammonia concentration, low temperature, and volatile fatty acid accumulation, which inhibit AD processes. Carbonaceous materials (CMs), such as granular activated carbon (GAC), possess high porosity, large specific surface area, excellent electrical conductivity, and abundant surface functional groups, enabling them to serve multiple roles in AD and enhance AD performance. In this study, we provided a comprehensive review and analysis of the mechanisms by which properties of CMs impact AD, including acting as carriers for microbial colonization, buffering pH, serving as effective adsorbents, stimulating extracellular secretions, and promoting direct and mediated interspecies electron transfer (DIET and MIET). In particular, we concentrated on the profound impact of functional groups on the surface of CMs (e.g., quinones, flavins, phenazines, and their derivatives), as well as the significant influence of extracellular secretions (e.g., quorum sensing molecules and vitamins) to address existing knowledge gaps. Additionally, we presented the challenges and prospects of CMs-based AD with the aim of inspiring future research and practical applications.