Technological Approaches for the Capture and Reuse of Biogenic Carbon Dioxide Towards Sustainable Anaerobic Digestion

Anaerobic digestion (AD) produces renewable energy but releases biogenic CO2 and generates digestate requiring management. This paper evaluates four emerging pathways for CO2 capture and reuse in AD systems: (1) in situ CO2 conversion to CH4 via microbial electrolysis cells (MECs), (2) hydrogenotrophic CO2 methanation using green hydrogen, (3) enzymatic CO2 capture coupled with autotrophic algae cultivation, and (4) digestate pyrolysis with syngas biomethanation. Each pathway is assessed in terms of technical feasibility, biocatalyst performance, system configuration, and key implementation challenges. Integrated scenarios demonstrate up to 98% CO2 emission reduction, substantial bioenergy yield improvements, and enhanced nutrient and biomass recovery compared to conventional AD. MEC-based and hydrogenotrophic pathways show the highest energy efficiency, while algae-based systems provide added bioproduct valorization. The remaining limitations include cost, process integration, and scale-up. The study defines development priorities to advance zero-emission AD technologies for the agri-food and waste management sectors.