20 Years of Microbial Electrochemical Technologies: From Lab to Full Scale

Two decades after Geobacter was found to be the key actor for electric current generation in a sediment, real applications for removing environmental pollutants (electrobioremediation) have been developed after intense multidisciplinary research (Tucci et al 2021). Wastewater (ww) has been certainly the most tested matrix for hosting Microbial Electrochemical Technologies (MET) due to the potential conversion of the chemical energy contained in organic pollutants into electrical power. However, we needed roughly ten years to realize Microbial Fuel Cells could not compete with commercial solutions based on renewables energies. Despite this bottleneck researchers in the field have developed a plethora of devices and applications with electromicrobiology as key actor. In a wastewater context, the largest electrobioremediation strategy so far corresponds to a solution so-called METland®, where electrochemical concepts are integrated in already existing wastewater treatment solution: the constructed wetlands (Peñacoba-Antona et al. 2022). The hybrid solution is indeed a biofilter made of electroconductive sustainable materials to enhance microbial oxidation of pollutants and reduce the footprint of this nature-based solution as low as 50 m2 for treating ww from 1000 pe. The system has evolved to modular construction so it can be used as plug and play solutions for treating also industrial water from oil&gas, food&beverage, automotive and pharma sectors to name a few. Solid electrodes (eg. rods, plates, granules, and felts) are typically used as electroconductive materials to support biofilm growth in conventional microbial electrochemistry, diffusion and migration processes could limit the performance for optimal biodegradation rates. To overcome such limitation, we developed a game changer: the microbial electrochemical fluidized bed reactor (ME-FBR). Core element is a fluidlike electrode to minimize mass transfer and energy limitations while simultaneously enhancing the activity of both electroactive planktonic and electroactive biofilms in the bioreactor. Indeed, a fluid-like anode has been shown to be efficient for removing organic pollutants and nitrogen from industrial brewery wastewater. Moreover, MEFBR allow to develop a nutrient recovery strategy by culturing purple phototrophic bacteria to transform brewery wastewater into protein source and bioplastics (Muniesa et al., 2025), or even fixed CO2 to bioelectrosynthesized acetate (Llorente et al. 2024). Finally, electrobioremediation generate “useful electrons” that may drive desalination if performed devices calles Microbial Desalination Cells. So, MDC represents a hybrid concept in which energy from an organic pollutants can be directly used in a passive device to produce fresh water (i.e. indirect use of energy). MDC technology has been extensively studied in order to increase the desalinated water production while maintaining low energy requirements resulting in the first full-scale demonstration of MDC technology (Ramirez et al. 2022).