Bioelectrochemical power-to-gas (BEP2G) is a new electromethanogenesis technology in which carbon dioxide (CO2) and electricity are converted directly into methane (CH4) on electrodes colonized by methanogenic microorganisms from the Archaea domain. The analysis of production rates and estimation of energy input show that BEP2G can in principle become an attractive alternative to both biochemical methanogenesis and thermochemical methanation (Sabatier process), operating with pools of microorganisms selected from biogas plants or natural anaerobic environments. Microbial electromethanogenesis can be effectively combined with the conventional anaerobic digestion (AD) process by using either CO2-rich gases from biogas plants (and performing methane upgrading) or CO2-rich industrial waste gases; in this way, it helps solve the emissions issue and store otherwise wasted energy.

However, there are still many technological issues to be solved to make BEP2G economically and industrially competitive with other more mature energy storage systems. Indeed, bioelectrochemical systems are still experimented mainly at the laboratory level. To bring BEP2G technology to a pre-competitive industrial level, high-surface area porous biocompatible materials (such as appropriately functionalized biogenic-derived charcoal) are being investigated on which to maximize interaction with microorganisms while minimizing resistance to charge transfer and diffusive mass transportation. Other critical issues involve optimizing the design and configuration of bioreactors to make the technology reproducible on a large scale. In recent years, numerous research activities have aimed at achieving these goals.

This report describes the most promising results and motivates the experimental programs planned in the ongoing System Research. In particular, the opportunity to experiment with syntropy between bacteria and hyperthermophilic Archaea is suggested, taking a cue from the natural behavior of these microorganisms in extreme, CO2-rich natural environments. Furthermore, the opportunity to experiment with innovative electrode materials is stressed, for example multicomposites based on biogenic carbon functionalized with hydroxyapatite, which could make BEP2G technology scalable in a circular economy logic.