Mathematical model of a microbial electrosynthesis cell for the conversion of carbon dioxide into methane and acetate

CO2 conversion to methane and short-chain carboxylic acids in a microbial electrosynthesis cell (MESC) is an emerging approach for combining CO2 sequestration with the production of valuable commodities from a renewable source of carbon. While the production of CH4 and carboxylic acids, such as acetate, was demonstrated in several studies, process scale-up requires a simulation tool for a thorough system analysis, optimization, and a techno-economic assessment. The dynamic mathematical model developed in this work simulates the production of H-2 via electrochemical and bio-electrochemical pathways and the formation of CH4 and acetate from CO2 at the MESC cathode taking into account the non-linear dynamics of microbial growth and CO2 conversion, the effects of various operating conditions, and CO2 transport between the MESC electrode compartments. Furthermore, the model simulates the growth of the three key biomass populations of acetogenic, methanogenic and electroactive microorganisms. Parameter identification followed by model validation demonstrated a reasonable agreement between the model predictions and the experimental results. The model was used to predict changes in CH4 and acetate production in response to changing MESC operating conditions.