Additives can effectively improve the anaerobic digestion performance. In this work, we have investigated the effect of seven carbon materials as additives on the biogas yield, the total chemical oxygen demand (CODt) removal rate and the digestate stability. These carbon materials have larger Brunauer-Emmett-Teller (BET) specific surface area of 580-824 m(2)/g and uniform pore volume of 0.54-0.64 m(3)/g. Adding carbon into AD systems can significantly improve the biogas yield (380-502 mL/g TS) and CODt removal rate (51.39%-67.81%) by 30-70% and 74-129%, respectively, compared to the reference system (CK, control check, 294 mL/g TS and 29.55%). Carbon additives with higher BET specific surface area are responsible for improving the AD efficiency by providing sites where substrate accumulate and thereby promote high localized substrate concentrations. Significant improvement in the AD efficiency can be microscopically attributed to the methanogenesis promoted by the conductive carbon that can facilitate direct interspecies electron transfer between fermenting bacteria and methanogens, accelerating syntrophic acetate metabolism and biogas yield. These carbon materials developed are excellent additives in AD for improving the biogas yield, CODt degradation, the stability and the fertilizer utilization of the digestate. These increased properties lead to more efficient use of the waste feedstock in biogas systems. (C) 2018 Elsevier Ltd. All rights reserved.