The anaerobic digestion of palm oil mill effluent (POME) was carried out under mesophilic (37 degrees C) and thermophilic (55 degrees C) conditions without long-time POME storage in order to compare the performance of each condition in the field of Sumatra Island, Indonesia. The anaerobic treatment system was composed of anaerobic hybrid reactor and anaerobic baffled filter. Raw POME was pretreated by screw decanter to reduce suspended solids and residual oil. The total COD removal rate of 90-95% was achieved in both conditions at the OLR of 15 kg [COD]/m(3)/d. The COD removal in thermophilic conditions was slightly better, however the biogas production was much higher than that in the mesophilic one at high OLR. The organic contents in pretreated POME were highly biodegradable in mesophilic under the lower OLRs. The biogas production was 13.5-20.0 l/d at the 15 kg [COD]/m(3)/d OLR, and the average content of carbon dioxide was 5-35% in both conditions. (C) 2014 Elsevier Ltd. All rights reserved.