Recent advances of carbon-based additives in anaerobic digestion: A review

Anaerobic digestion (AD) is one of the paramount technologies for organic wastes treatment. However, there still remain intractable issues including low digestibility and sluggish reaction kinetics in its practical implementation, leading to limited bio-product production. Recently, carbon-based additives (CAs) have aroused great attentions for enhanced AD performance by establishing direct interspecies electron transfer (DIET) and adjusting the functional microorganisms due to their large specific surface area and high conductivity. However, such inherent physicochemical capabilities of CAs and its specific role in AD have not been fully exploited. In this review, we detailedly summarize the research advances of biochar and activated carbon (AC) as additives in AD system, which are combed in terms of structure construction of CAs, macro-behaviors of CAs, micro-mechanisms of CAs and hybrid strategy. Finally, perspectives regarding future modification and application of CAs in AD system are also discussed.