The intriguing effect of CO2 enrichment in anaerobic digestion
Mohammad Javad Bardi, Felix Müller, Daniela Polag, Nigus Gabbiye Habtu, Konrad Koch
Abstract
• Impact of CO 2 enrichment on biomethane production, degradation kinetics, and methanogenic pathways studied. • Methane yield increased by 53%-77% after CO 2 enrichment of inoculum. • CO 2 enrichment led to lag phase increasing up to 3.1 times. • Higher COD reduction due to CO 2 enrichment led to significantly enhanced methane production. • Δ 2 H-CH 4 values increased by 36 mU, indicating intensified hydrogenotrophic methanogenesis. This study explores carbon dioxide enrichment in anaerobic digestion to boost biomethane production and assess degradation kinetics and methanogenic pathway evolution. Carbon dioxide enrichment was found to improve inoculum digestion, supplying additional energy for methanogenic archaea. The methane yield of blank inocula increased by 53 % to 77 % after carbon dioxide enrichment. Although further digestion of inoculum residues took longer, rapid adaptation led to an increased methane production rate that surpassed the lag phase. No antagonistic effects were observed with carbon dioxide enrichment after applying the feedstocks. Increased methane production, along with a significant reduction in chemical oxygen demand, confirms the impact of carbon dioxide enrichment on inoculum digestion. Isotope analysis showed an increase in δ 2 H-CH 4 values by approximately 36 mU compared to non-enriched inoculum, implying intensified hydrogenotrophic methanogenesis. Carbon dioxide enrichment significantly enhances biomethane production and digestion efficiency in anaerobic digestion, offering a sustainable solution for large-scale plant operations.