Exploring the mechanisms of supplemented CO2 in enhancing methane production in anaerobic digestion process, a review.

Anaerobic digestion (AD) is a sustainable technology that converts organic waste into renewable energy while reducing greenhouse gas emissions. Recent studies suggest that adding CO₂ to the AD process can improve methane production through different mechanisms. This review examines four key ways CO₂ supplementation can enhance methane yield: (1) direct conversion of CO₂ into acetate by homoacetogens, (2) direct methanation of CO₂ by hydrogenotrophic methanogens, (3) improved breakdown of organic material due to higher enzyme activity, and (4) better digester conditions through pH regulation and reduced ammonia toxicity. By analyzing microbial interactions and process improvements, this paper highlights knowledge gaps and the need for further research to optimize CO₂ addition in different operational settings. These findings are expected to contribute to the development of cost-effective and efficient AD systems that support energy recovery and environmental sustainability.