Enhancement of Biogas Production and Archaeal Diversity during Anaerobic Digestion of Bacterially Pretreated Coconut (Cocos nucifera L) Coir

Growing demand for renewable energy and sustainable waste management has increased interest in anaerobic digestion of lignocellulosic biomass. However, efficient conversion of such substrates remains limited by their complex structure, particularly the recalcitrant lignin–cellulose matrix, which restricts microbial accessibility and results in low hydrolysis efficiency. Coconut coir, a widely available agricultural waste, is particularly resistant to biodegradation, thereby limiting its potential as a feedstock for high-yield biogas production. This study aimed to enhance biogas production from coconut coir lignocellulosic biomass through pretreatment with cellulose-degrading bacteria. Over 150 days, the biogas production process was evaluated using standard protocols. Initial screening of bacteria from poultry feces revealed very high cellulose hydrolytic capacities, ranging from 9 to 11 mm. The identified bacteria included Bacillus megaterium, Bacillus licheniformis, Lactobacillus plantarum, Bacillus cereus, and Bacillus subtilis. Coconut coir was pretreated with a consortium of these bacteria, buffered with plantain peel ash solution, and inoculated with aged cow dung for anaerobic digestion. A control digester without bacterial pretreatment was also maintained. The total biogas yield in the control digester at the end of 150 days digestion was 67,105 mL, whereas the pretreated substrate produced 88,355 mL. The mean methane content was 45 ± 25% in the control and 56 ± 17% in the pretreated substrate, indicating a significantly higher methane yield in the pretreated substrate (p < 0.05). Sequencing of PCR products amplified using universal 16S rRNA primers generated 244, 240 sequences, of which 236, 200 (97%) were identified as bacterial, 2,443 (1%) as archaeal, and 5,597 (2.3%) remained unclassified. The bacterial pretreatment of coconut coir enhanced both biogas volume and methane yield and influenced the abundance and diversity of the methanogenic archaeal community. These findings suggest that utilizing cellulose-degrading bacteria from poultry feces and an organic buffering agent can significantly improve biogas production and methane content, providing a sustainable approach to biomass utilization.