Comparative effect of conductive and dielectric materials on methanogenesis from highly concentrated volatile fatty acids

[Display omitted] •AD of concentrated VFA is greatly enhanced by stainless steel mesh and carbon fiber.•Electrogenic Ureibacillus, Limnochordia, Coprothermobacter, Ca. Caldatribacterium.•Short thick pili-like structures 150 nm in width correlate with ECM and enhanced AD. Various conductive materials and their dielectric counterparts were used to get deeper insights into contribution of direct interspecies electron transfer (DIET) in improving methanogenesis from highly concentrated volatile fatty acids (12.5 g/L). Potential CH4 yield, maximum CH4 production rate and lag phase were significantly (up to 1.4, 3.9 and 2.0 times, respectively) improved with addition of stainless-steel mesh (SM) and carbon felt (CF) compared to both control and dielectric counterparts (p