Modelling bio-electrosynthesis in a reverse microbial fuel cell to produce acetate from CO₂and H₂O

Abstract

Bio-electrosynthesis is one of the significant developments in reverse microbial fuel cell technology which is potentially capable of creating organic compounds by combining CO2 with H2O. Accordingly, the main objective in the current study was to present a model of microbial electrosynthesis for producing organic compounds (acetate) based on direct conduction of electrons in biofilms. The proposed model enjoys a high degree of rigor because it can predict variations in the substrate concentration, electrical potential, current density and the thickness of the biofilm. Additionally, coulombic efficiency was investigated as a function of substrate concentration and cathode potential. For a system containing CO2 as the substrate and Sporomusa ovata as the biofilm forming microorganism, an increase in the substrate concentration at a constant potential can lead to a decrease in coulombic efficiency as well as an increase in current density and biofilm thickness. On the other hand, an increase in the surface cathodic voltage at a constant substrate concentration may result in an increase in the coulombic efficiency and a decrease in the current density. The maximum coulombic efficiency was revealed to be 75% at a substrate concentration of 0.025 mmol cm(-3) and 55% at a surface cathodic voltage of -0.3 V producing a high range of acetate production by creating an optimal state in the concentration and potential intervals. Finally, the validity of the model was verified by comparing the obtained results with related experimental findings.

Understanding the interdependence of operating parameters in microbial electrosynthesis: a numerical investigation

“…However past research on MES has extensively focused on experimental studies, and barring a few numerical investigations, modeling and simulation remain mostly neglected. [19][20][21][22][23][24] Pinto et al 22 proposed a multi-population dynamic model of a microbial electrolysis cell (MEC) and derived an expression for the hydrogen production rate at the chemical cathode based on MEC current and specific cathode efficiency. The bacterial population at the anode is assumed to consist of fermentative, electricigenic, methanogenic acetoclastic, and methanogenic hydrogenophilic microorganisms, whose metabolic activity and growth rates are described using multiplicative Monod kinetics.…”

“…Though this model is not derived for MES directly and does not consider any biocatalyst at the cathode, it serves as a good starting point for more comprehensive numerical models for different microbial electrochemical cells. 22 Kazemi et al 23 used the conductive biofilm approach and modeled the biocathode in an MES to study the bioelectrosynthesis of acetate by CO 2 reduction. The rate of microbial reduction at the cathode is described using a Nernst-Monod expression assuming that the biofilm matrix conducts electrons from the cathode to the biofilm bacteria.…”

Modelling the simultaneous production and separation of acetic acid from CO2 using an anion exchange membrane microbial electrosynthesis system

“…These models can predict energy consumption, concentrations, and operational time amongst other parameters . Several models have been developed for bioelectrochemical systems (BESs), including one for the MES of CO 2 to acetate which could predict substrate concentration, electrical potential, current density and biofilm thickness . But, no one has investigated MES and electroseparation simultaneously, which is why we developed our model.…”

A Review of Modeling Bioelectrochemical Systems: Engineering and Statistical Aspects

“…The ODE stereotypes were modified to enrich the mathematical expressions of mass balance and substrate diffusion between the interface of biofilm and bulk solution, to simulate the biological activity inside the biofilm [44,81]. The model is able to simulate the performance of reverse MFC, especially the biofilm thickness and acetate production rate in the cathode [81].…”

“…The ODE stereotypes were modified to enrich the mathematical expressions of mass balance and substrate diffusion between the interface of biofilm and bulk solution, to simulate the biological activity inside the biofilm [44,81]. The model is able to simulate the performance of reverse MFC, especially the biofilm thickness and acetate production rate in the cathode [81]. The conception of finite difference approach was applied to make ODEs workable to simulate the mass diffusion and the impact of pH change on the substrate consumption and biofilm performance attached on the electrode (Figure 4) [44].…”