(418c) A Computational Model for Microbial Electrosynthesis of Organic Compounds in Reverse Microbial Fuel Cells

Noticeably increased emissions of carbon dioxide as a result of industrial development in recent decades have been attracted more attention to combat and prevent the devastating effects. So to find a way to get rid of harmful greenhouse gases seems necessary. Carbon dioxide is formed the main greenhouse gas. In reverse microbial fuel cells, which compared to microbial fuel cells perform conversely, bacteria, using electrons which are transferred to cathode from anode or from an external energy source, transform CO₂ and H₂O to organic compounds during a process which is like photosynthesis. These organic compounds can be transformed to fuel by themselves. In the present study, modeling of microbial-electrosynthesis to produce organic compounds is presented based on direct conduction of electrons in biofilms. The output of the present model includes the changes of the substrate concentration, electric potential, the distribution of active bacteria in the biofilm, the time variation of the current density, and the thickness of the biofilm. In this model, Coulombic efficiency is a function of substrate concentration and cathode potential.  For CO₂ substrate and Sporomusa ovata species, the increase of the substrate concentration leads to the decrease of Coulombic efficiency, increase of current density and increase of biofilm thickness and increase of cathodic voltage surface leads to the increase of Coloumbic efficiency and decrease of current density. Because the electrical conductivity of Sporomusa ovata biofilm is very high, most part of microbial fuel cell resistances with this microbial community and CO₂ substrate come from the resistance of mass transfer. Coulombic efficiency is short because of ohmic and cathodic resistances in the performance of cell. The maximum Coulombic efficiency was revealed to be  %75 in the concentration of  0.025 mmol cm^-3  and %55 in the cathodic voltage surface of  -0.3 V, thus, we can achieve a high range of acetate production by creating an optimal state in this concentration and potential.