By 2030, the world population will reach 8.6 billion, increasing energy demand by 30%. This population growth will also amplify global organic waste production. To tackle these challenges, anaerobic digestion (AD) offers an innovative and resilient solution, treating organic waste streams while producing renewable energy in energy-rich biogas and digestate, a high-value-added bio-fertilizer.
In a recent study, we enriched the AD process with carbon dioxide to boost biomethane production and assess degradation kinetics and methanogenic pathway evolution. Carbon dioxide enrichment improved 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 increased the methane production rate and surpassed the lag phase. No antagonistic effects were observed with carbon dioxide enrichment after applying the feedstocks. Increased methane production and a significant reduction in chemical oxygen demand confirm the impact of carbon dioxide enrichment on inoculum digestion.
Isotope analysis showed increased δ2H-CH4 values by approximately 36 mU compared to non-enriched inoculum, implying enhanced hydrogenotrophic methanogenesis. Carbon dioxide enrichment significantly enhances biomethane production and digestion efficiency in anaerobic digestion, offering a sustainable solution for large-scale plant operations. Importantly, biogas plants already produce CO2, making this method both cost-effective and widely applicable, with successful trials on digestates from municipal wastewater treatment and agricultural feedstock.
