Upscaling of Microbial Electrolysis Cell Integrating Microbial Electrosynthesis: Insights, Challenges and Perspectives

Abstract

Recent development of microbial electrochemical technologies has allowed microbial electrosynthesis (MES) of organic molecules with microbial electrolysis cell treating waste organic matter. An electrolytic cell with a MES cathode (ME-ME cell) can produce soluble organic molecules with higher market price than biomethane, and thus satisfy both economic and environmental interest. However, the sustainability of bioanode activity could become a major concern. In this work, a 15-liter ME-ME reactor was designed with specific electrode configurations. An electrochemical model was established to assess the feasibility and possible performance of the design, considering the “aging” effect of the bioanode. The reactor was then built and operated for performance evaluation as well as bioanode regeneration assay. Biowaste from an industrial deconditioning platform was used as substrate for bioanode. The COD removal rate in the anodic chamber reached 0.83 g day-1 L-1 of anolyte and the anodic coulombic efficiency reached 98.6%. Acetate was produced with a rate of 0.53 g day-1 L-1 of catholyte, reaching a maximum concentration of 8.3 g L-1. A potential difference was applied between the bioanode and biocathode independent of reference electrodes. The active biocathode was dominated by members of the Genus Pseudomonas, rarely reported so far for MES activity.

Enhanced performance of microbial electrolysis cells using microstructured electrodes

“…This biofilm formation contributes immensely to the electric charge transport resistance after an operation of several months. Similar but less prominent biofilm formation has been found on anodes as well [19–22].…”

“…Two processes are responsible for the reduced charge conversion which is accordingly found in similar works. First, a thin carbonate film develops at the surface that significantly reduces the electrical conductivity and second, the contact to the water-based biomass in the reactor leads to the formation of a biofilm also suppressing the electrical conductivity [19][20][21][22][23][24][25][26]. The biofilm covers the surface by a physisorption process and can therefore be removed by classical mechanical cleaning.…”

“…One the one hand, it is found that chemical surface reactions lead to the formation of carbonate layers on electrodes in microbial electrolysis cells [23][24][25][26]. In addition, mass transport initiated by the electric field in the electrolyte in many cases leads to the formation of weakly bound biofilms consisting of microorganisms and water [19][20][21][22]. The fact that a twostage drop of the electrical current is observed supports the idea that the two steps refer to these two kinds of films that might develop during operation.…”

Ammonium as a Carbon-Free Electron and Proton Source in Microbial Electrosynthesis Processes

“…A potentiostat drives the electrons from anode to cathode. However, electro-active biofilm may grow on the anode surface and may catalyze oxidation reactions [18,19]. Whether this reduces the potential requirement of ammonium oxidation has not yet been investigated.…”

Improving the Cathodic Biofilm Growth Capabilities of Kyrpidia spormannii EA-1 by Undirected Mutagenesis

“…There are, however, several drawbacks that this technology has to overcome. First, the number of applicable electroautotrophic biocatalysts is so far rather small and most of them belong to the group of methanogens or acetogens [ 4 , 5 ]. These organisms are often strictly anaerobic and genetic engineering is either not possible or very laborious.…”