Wired for energy: Electromethanogenesis redefining anaerobic digestion

The present state of energy scarcity and the intensified greenhouse impact resulting from carbon dioxide emissions have prompted significant apprehension over the capture and utilization of carbon dioxide. The utilization of exoelectrogenic bacteria within an electrochemical framework has positioned microbial electrolysis cells (MECs) as a promising alternative for the bioelectrochemical conversion of CO₂ into low-carbon electro fuels such as CH₄. By employing this approach, not only may CO₂ be sequestered, but it also presents an opportunity to harness and utilize energy. The integration of a MEC with a traditional anaerobic digester (AD) is employed in the novel process of electromethanogenesis, facilitating the production of bio-methane. Following the discovery that both cathodic and anodic bacteria possess the capability to generate methane, subsequent research endeavours were undertaken to enhance the efficiency of this process. This was achieved by optimizing several parameters, including microbial species selection, biofilm formation, substrate sources, and electrode surface characteristics. The intriguing nature of microbial composition in MECs as biocatalysts, along with their remarkable capacity to assimilate various essential nutrients, renders them highly captivating. As a result of extensive research conducted in this particular domain, a multitude of MECs have been devised to facilitate the biodegradation of organic compounds and the subsequent generation of hydrogen. This paper undertakes a comprehensive assessment of the existing MEC-AD vaccination and launch methods. Subsequently, the system design and scale-up details are provided, along with pertinent information regarding the selected electrode materials, their respective surface areas, and surface chemistry, as well as the inter-electrode spacing.