Biochar has been considered as a promising material to enhance the anaerobic digestion of organic wastes, whereas the critical mechanism of biochar promoting interspecies electron transfer is still unclear. The study presented here performed a side-by-side comparison of the three types of biochar (BC300, BC400, and BC500, the pyrolytic temperatures) with the different properties in enhancing the anaerobic digestion of kitchen wastes. The results showed that, in the presence of biochar with the properties of the higher electrical conductance but less redox-active organic functional groups (BC500), the improved performances involved in methane production rates (673.6 mL/d vs 956.8 mL/d) and organic removal efficiencies (69.9% vs 76.4%) were lower than that in the presence of biochar with the properties of the lower electrical conductance but more redox-active organic functional groups (BC400). Biochar (BC400) with the properties of more redox-active organic functional groups enriched the higher abundance of Petrimonas species and Anaerolineaceae capable of electron transfer to the conductive materials than biochar (BC500) with the properties of the higher electrical conductance. The study proposed a strategy of engineering a better anaerobic digestion of kitchen wastes via optimizing the pyrolytic temperature of biochar to form more redox-active organic functional groups as possible. (c) 2020 Elsevier Ltd. All rights reserved.