Enhancing methane production and microbial community dynamics by removing phenolic compounds from palm oil mill effluent

This study evaluates the impact of phenolic compound removal from raw Palm Oil Mill Effluent (POME) on methane production in anaerobic digestion. Experiments were conducted at both small and large scales under controlled anaerobic conditions (37 °C, pH 7.0). In small-scale trials, the optimal inoculum: raw POME: extracted POME ratio of 5:0:1 resulted in a maximum cumulative methane yield of 559.80 mL-CH₄/g-VS, which was 2.68 times higher than the 5:1:0 ratio. The maximum methane production rate (MMPR) increased from 24.72 to 125.90 mL-CH₄/g-VS·day following phenolic compound removal. Microbial community analysis revealed a shift in dominant species, with Methanosaeta increasing from 88.75 % on Day 3–97.36 % on Day 15, enhancing acetoclastic methanogenesis. Large-scale trials confirmed the trend, with methane yield reaching 1221.00 mL-CH₄/g-VS for the 5:0:1 ratio, approximately 7.7 times higher than that of the 5:1:0 ratio (158.50 mL-CH₄/g-VS). The removal of more than 93 % of phenolic compounds not only improved methane production but also reduced digestate toxicity, enabling safer environmental discharge. The extraction system generated 3882.89 m³ of methane per batch, yielding 1037.67 USD, significantly outperforming the non-extraction system (1143.32 m³, 305.54 USD). Despite higher initial costs, the improved methane yield suggests strong economic viability. These findings demonstrate that phenolic compound removal significantly enhances methane yield and process efficiency, providing a sustainable and scalable strategy for biogas production from POME, contributing to environmental sustainability and resource recovery.