Optimization and microbial community analysis for production of biogas from solid waste residues of palm oil mill industry by solid-state anaerobic digestion

•Solid-state anaerobic digestion (SS-AD) of oil palm biomass was studied.•Optimal conditions for methane production was 16% TS, C:N of 30:1 and F:I of 2:1.•The highest methane production of 77.8 m3 CH4 ton−1 biomass was achieved from EFB.•Bacteria community in SS-AD was dominated by Ruminococcus sp. and Clostridium sp.•Archaea community in SS-AD was dominated by Methanoculleus sp.

This study investigated the improvement of biogas production from solid-state anaerobic digestion (SS-AD) of oil palm biomass by optimizing of total solids (TS) contents, feedstock to inoculum (F:I) ratios and carbon to nitrogen (C:N) ratios. Highest methane yield from EFB, OPF and OPT of 358, 280 and 324 m3 CH4 ton−1 VS, respectively, was achieved at TS content of 16%, C:N ratio of 30:1 and F:I ratio of 2:1. The main contribution to methane from biomass was the degradation of cellulose and hemicellulose. The highest methane production of 72 m3 CH4 ton−1 biomass was achieved from EFB. Bacteria community structure in SS-AD process of oil palm biomass was dominated by Ruminococcus sp. and Clostridium sp., while archaea community was dominated by Methanoculleus sp. Oil palm biomass has great potential for methane production via SS-AD.