Modelling a bioelectrochemical cell from a physics perspective

Abstract

Bioelectrochemical cells utilize bacteria in order to extract electricity from organic compounds, for example found in wastewater streams. This process occurs within a thin layer of bacterial cells, the biofilm, on either the anode or cathode. Using a physics based modelling approach, four main processes in the (anode) biofilm are considered; ionic transport coupled to acid-base reactions, biochemical conversion of acetate species, electron transfer to a network of conductive pili, and charge transport through the pili towards the electrode. Results obtained by De Lichtervelde et al. [Physical Review applied, vol. 12, no. 1, p. 014 018, 2019] are replicated, showing a reproducibility of the model. These results indicate that an accumulation of protons within the biofilm limits the current that can be extracted from the bioelectrochemical cell. Based on the electric potential profile within the biofilm, the question arises if the local electroneutrality condition can be used within these kinds of systems. To investigate this, a first attempt in adding the Poisson equation to the system is made. Based on length-scale considerations, the results obtained from using the local electroneutrality condition seem reliable, but the potential profile should be interpreted with caution.