Kinetic modelling and simulation of bioanode and biocathode in a bioelectrochemical cell for carbon dioxide reduction

Abstract

Bioelectrochemical systems (BESs) have garnered extensive research attention for their biosynthesis and environmental remediation applications. One of the challenges to upscaling BES for carbon dioxide (CO2) methanation is energy-efficient process development. Investigations are ongoing to determine the relationship between the yield of electroactive microorganisms, the key candidates for electrochemical reactions with external electricity input. Consequently, simulating processes, particularly with biocathode for biosynthesis and bioanode for remediation, gives crucial insights for designing efficient BESs. The framework for establishing Nernst-Monod equations for modeling BES, starts from bioanode, where anode respiring bacteria (ARB) oxidize organic carbon compounds to CO2, and generate the proton (H+). In this work, kinetic modeling was applied to calculate the biomass yield of ARBs corresponding to the applied anodic voltage. The generated CO2 and H+ from the anode determined the biomass yield of electroactive methanogens and acetogens on the cathode. Two biofilm models were established for anodic and cathodic biofilm growth in the Aquasim simulation tool. Results showed that the concentration of organic carbon compound (acetate) available for ARB, had a significant impact on the biofilm thickness and biomass concentration on the biofilm, especially at +0.3 V. The optimum anode voltage which released the highest CO2 and H+, was +0.3 V. The anodic and cathodic biofilm thickness reached 3 mm and 55 µm, respectively, at +0.3 V and 10 g.L-1 acetate input to the anode chamber. Moreover, methanogens surpassed acetogens on the biocathode for CO2 reduction to methane rather than acetate. In addition, acetate consumption rate by ARB at anode was remarkably faster than acetate production at cathode.