Biomethane enhancement using reduced graphene oxide in anaerobic digestion of municipal solid waste

•The effect of rGO addition on the semi-continuous AD of OfMSW was investigated.•110% CH4 production increase observed via rGO addition.•rGO addition promote DIET at acetoclastic pathway.•Syntrophic bacterium became more abundant via rGO addition. The present research investigated the impact of reduced graphene oxide (rGO) addition on the semi-continuous anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) in the range of 0.5–10 gVolatileSolid(VS)/Lreactorday organic loading rates (OLR). Adding rGO enhanced the rate and yield of biomethane production, and the maximum biomethane increment rate was obtained as 110% at an OLR of 4.0 gVS/Lreactorday. However, after increasing the OLR to 6 gVS/Lreactorday, there was a dramatic decrease in biomethane production because of volatile fatty acid (VFA) accumulation. Methanotrix is the predominant archaeal genus at OLRs lower than 6 gVS/Lreactorday in reactors (89–97%). An increment in biomethane production was associated with the higher abundance of the Methanothrix genus in the rGO-supported reactor (rG) than in the control reactor (rC).