Methane Production Potential of Oil Palm Decanter Cake and Hydrothermal Pretreatments

Oil palm decanter cake (OPDC) is generated from the clarification and purification during the palm oil production process, which highly contained lignocellulosic compounds. It could be used as feedstock in anaerobic digestion (AD) for renewable energy production. However, lignocellulosic materials are recalcitrance to directly utilize. High potential of anaerobic seeds sludge and hydrothermal pretreatment for enhance the CH₄ production were investigated. Anaerobic seeds sludge from palm oil mill effluent (POME), cow manure (CM), and pig manure (PM) were collected and tested by biochemical methane potential assay. CM inoculum exhibited the highest maximum CH₄ production and maximum CH₄ production rate at 350 mL·g^-1VS and 11.25 mL·g^-1VS·d^-1, respectively, with short lag phase (3.4 d). Two hydrothermal pretreatment processes were conducted on OPDC, hot water (HW) and hot compress water (HCW) conditions. The solubilization of lignocellulose compoment was observed. The HW pretreatment could enhance the CH₄ production higher than HCW at 20%, while HCW was only at 3.6% compare to non-pretreated sample. CM inoculum showed a promsing inoculum for CH₄ produciton of OPDC. In addition, HW pretreatment cause solubilization and disruption of OPDC lignocellulose structure, leading to enhance the hydrolysis of lignocellulose and convert into CH₄.