Role of organic loading rate in bioenergy generation from palm oil mill effluent in a two-stage up-flow anaerobic sludge blanket continuous-stirred tank reactor

This contribution presents the technical possibilities for continuous hydrogen and methane production using an optinium organic loading rate of palm oil mill effluent in a two-stage reactor at a thermophilic temperature of 55 degrees C. The influence of four organic loading rates, namely, 30, 40, 50, and 60 kg COD/(m(3) d) for hydrogen production and 8.3, 10.2, 13.1, 15.8 kg COD/(m(3) d) for methane production, were investigated. Hydrogen production was controlled in an up-flow anaerobic sludge blanket reactor at a constant hydraulic retention time of 12 h. The maximum hydrogen content, volumetric hydrogen production rate and hydrogen yield were found to be 45%, 2.5 L H-2/d and 33.48 mL H-2/g COD, respectively, at the organic loading rate of 50 kg COD/(m(3) d). The effluent from the hydrogenogenic reactor was further digested into methane in the continuous stirred tank reactor at a hydraulic retention time of 5 d. The maximum volumetric methane production rate and methane yield were 10.58 L CH4/d. and 0.11 m(3) CH4/kg COD, respectively, at an organic loading rate of 13.1 kg COD/(m(3) d). A total chemical oxygen demand removal of 91% was achieved in this two-stage process. The scientific contribution of this two-stage technology with an optimized organic loading rate may play a significant role in degrading palm oil mill effluent and developing an energy-efficient strategy for waste management. (C) 2016 Elsevier Ltd. All rights reserved.