Considerations for application of granular activated carbon as capacitive bioanode in Bioelectrochemical Systems

In the last decades, the research in Microbial Fuel Cells (MFCs) has expanded from electricity production and wastewater treatment to remediation technologies, chemicals production and low power applications. More recently, capacitors have been implemented to boost the power output of these systems when applied as wastewater treatment technology. Specifically, the use of granular capacitive materials (e.g. activated carbon granules) as bioanodes has opened up new opportunities for reactor design and upscaling of the technology. One of the main features of these systems is that charge and discharge processes can be separated, which offers multiple advantages over more conventional reactor types. In the manuscript, we discuss several aspects to consider for the application of capacitive granules as bioanodes in MFCs and other bioelectrochemical systems, as well as the recent advances that have been made in applying these granules in various reactor systems. We discuss the granule properties that are key to determine system operation and performance, and show that biofilm growth is highly dependent on the efficiency of discharge.