Microbial Electrosynthesis for Biogas Upgradation by CO2 Utilization: Evaluating the Scalability of the Process

The depletion of fossil fuel reserves, the abundance of organic waste, and the accelerating global transition toward renewable energy underscore the need for sustainable bioenergy solutions. Biogas has emerged as a promising alternative energy source with strong potential to address the intertwined challenges of climate change, waste management, and energy security. However, its high CO2 content substantially lowers its calorific value, necessitating upgrading prior to use as a transportation or grid fuel. Conventional biogas upgrading techniques are often energy- and chemical-intensive and typically vent the separated CO2 back into the atmosphere, undermining their environmental benefit. Microbial electrosynthesis (MES) offers a sustainable alternative by biologically utilizing the CO2 fraction of biogas for the production of value-added compounds. In MES, electroactive microbes catalyze CO2 reduction using electrons derived from renewable electricity, generating acetic acid in the liquid phase and methane in the gas phase, thereby producing dual products from a single biogas feed. This chapter evaluates the viability of MES for biogas upgrading in a liter-scale (L-scale) system, providing an overview of conventional upgrading technologies and elucidating the operational principles of MES. Results from the scaled reactor demonstrate that optimization of electrode materials, electrochemical conditions, and process parameters significantly enhances CO2 utilization and methane enrichment in the upgraded biogas. The findings also highlight the critical bottlenecks, including energy demand, material costs, and process scalability, that must be overcome to enable the commercial deployment of MES as a next-generation, carbon-neutral biogas upgrading technology.