Evaluation of anaerobic digestion of palm oil mill effluent (POME) using different sludges as inoculum

Abstract

Inoculum plays a crucial role in the start of anaerobic digestion. This study evaluates the impact of two different inocula on the anaerobic digestion of Palm Oil Mill Effluent (POME). Inoculum A, sourced from a Wastewater Treatment Plant's anaerobic digester, and Inoculum B, from a palm oil extraction industry's oxidation lagoon, were compared. Acidogenic and methanogenic activity tests, using glucose and sodium acetate respectively, were conducted for each inoculum. After the activity test were carried out, the anaerobic digestion of POME was evaluated with each inoculum at two different temperatures (25 and 35 °C). Metataxonomic identification was performed on the microbial communities. Results show that Inoculum A had better acidogenic and methanogenic activities and led to a faster methane production and higher methane yields. The highest methane yields observed with Inoculum A were 490 N mL CH₄/g VS at 25 °C and 508.9 N mL CH₄/g VS at 35 °C, respectively. The presence of Clostridium spp. as a dominant genus and the dominance of strict anaerobes over facultative anaerobes in the microbial community, seems to favor the anaerobic digestion of POME.