Activated carbon is known to enhance methane formation in anaerobic reactors via interspecies electron transfer between fermentative bacteria and methanogenic archaea. Biochar, a by-product of biomass pyrolysis process, could also perform similar functions due to its conductive properties and the presence of redox active moieties. Hence, this study was conducted to evaluate the effectiveness of different types of activated carbons and biochars on anaerobic digestion. Biochars obtained from canola meal, switchgrass and Ashe juniper were tested for methane production from both glucose and aqueous phase of bio-oil generated via hydrothermal liquefaction of algae. The results suggested that absorbents enhanced methane production. Furthermore, biochars synthesized at intermediate temperatures significantly increased methane yield and reduced the lag time required for methane formation. In addition, the results suggested that the redox active moieties such as quinones and phenazines in biochars are responsible for electron transport, which ultimately enhanced methane production.