Thermophilic solid-state anaerobic digestion of solid waste residues from palm oil mill industry for biogas production

Thermophilic solid-state anaerobic digestion (SS-AD) of biomass from palm oil mill industry, including empty fruit bunches (EFB), oil palm fronds (OPF) and oil palm trunks (OPT) were investigated under different feedstock-to-inoculum ratios (F:I), carbon-to-nitrogen ratios (C:N) and total solids contents (TS). The optimal condition for biogas production was achieved at F:I ratio of 2:1, C:N ratio of 40:1 and TS content of 16%. The highest methane yield from EFB, OPF and OPT were 223, 207 and 161 m3 CH4 tonne−1 VS, respectively. Bacterial community structure in thermophilic SS-AD of oil palm biomass was dominated by Thermoanaerobacterium sp. and Clostridium sp. Archaeal community structure was dominated by Methanosaeta sp. and Methanoculleus sp. The highest methane production of 45 m3 CH4 tonne−1 fresh biomass was achieved from EFB. Solid waste residues from palm oil mill industry have great potential for methane production via thermophilic SS-AD.