Optimizing anaerobic digestion of palm oil mill effluent (POME) with biochar: Synergistic impact of biochar addition and kinetic analysis

This study investigates the synergistic potential of biochar to improve Palm Oil Mill Effluent (POME) treatment through anaerobic digestion (AD) under mesophilic conditions, focusing on the effects of biochar dosage (0.5 to 2.0 g), feed-to-inoculum (FI) ratio (0.16 to 1.00), and organic loading (OL) (1.20 to 5.45 g VS/L) on AD performance. The synergistic addition of biochar significantly enhanced the conversion of organic matter into biogas, resulting in 45.0 % higher biogas production, 73.3 % greater methane yield, and a 98.2 % increase in VS removal compared to POME mono-digestion. A Central Composite Design (CCD) within the Response Surface Methodology (RSM) framework was used optimize the process conditions to ensure effective biodegradation and high methane yield with the lowest biochar dosage. The optimal conditions included a low biochar dosage of 0.5 g (equivalent to 2 g/L of reactor volume), a low FI ratio of 0.266, and a high OL of 4.536 g VS/L. These conditions were validated in duplicate, resulting in 2950 mL of biogas, with a methane yield of 0.355 L/g VS and a VS removal of 95.1 %. The Transference Function Model (TFM) was identified as the most accurate kinetic model for predicting methane yield, demonstrating minimal error. • Synergistic biochar addition enhances POME anaerobic digestion efficiency. • Biogas production, methane yield, and VS removal increased by 45 %, 73 %, and 98 %. • RSM optimization identifies cost-effective biochar dosage and conditions.