Pilot-scale of biohythane production from palm oil mill effluent by two-stage thermophilic anaerobic fermentation

The pilot-scale of two-stage thermophilic (55 degrees C) for biohythane production from palm oil mill effluent (POME) was operated at hydraulic retention time (HRT) of 2 days and organic loading rate (OLR) of 27.5 gCOD/L.d) for first stage and HRT of 10 days and OLR of 5.5 gCOD/L.d for second stage. Biohythane production rate was 1.93 L-gas/L.d with biogas containing 11% H-2, 37% CO2, and 52% CH4. Recirculation of methane effluent mixed with POME at a ratio of 1:1 can control pH in the first stage at an optimal range of 5.0-6.5. Microbial community in hydrogen stage dominated by Thermoanaerobacterium sp., while methane stage dominated by Methanosarcina sp. The H-2/CH4 ratio of biohythane was 0.13-0.18 which suitable for vehicle fuel. Biohythane production from POME could be promising cleaner biofuel with flexible and controllable H-2/CH4 ratio. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.