DELIGNIFICATION METHODS FOR EMPTY FRUIT BUNCH CO-SUBSTRATE IN POME ANAEROBIC DIGESTION: AN EXPERIMENTAL COMPARATIVE ANALYSIS

Abstract

Empty fruit bunch (EFB) enhances biogas production in the anaerobic digestion of palm oil mill effluent (POME) by acting as a co-substrate. Yet, lignin in EFB inhibits the performance boost. Therefore, EFB was delignified before using it as a co-substrate as much as 4%. This study compared three delignification techniques using the pairwise comparison method: Bacterial, chemical, and hydrothermal. Three parameter variations were selected for each method, namely bacterial concentration, molar concentration, and temperatures. Chemical delignification at a NaOH concentration of 2 M yielded the largest production of biogas and methane (302.0 and 153.8 mL, respectively), followed by hydrothermal at 180°C (260.0 and 83.8 mL, respectively). Although bacterial delignification required a long time (2 weeks), it was the simplest to implement and yielded the largest lignin reduction. However, the bacterial method yielded lower biogas (103-204 mL) than hydrothermal and chemical, probably because of lower hemi-and cellulose contents. Based on biogas and methane yield, production hazards, preparation time, and required infrastructure, chemical delignification was selected as the best method because of its gas production, followed closely by hydrothermal due to its efficiency and safety.