Fluidized and fixed granular beds of activated carbon as electrodes in microbial electrochemical technologies

So far, microbial electrochemical technologies (METs) are hardly applied in practice due to their limited current densities and constraints regarding upscaling. Granular-activated carbon (GAC) has unique features as electrode materials to move toward the upscaling of these systems. This chapter gives an overview of the most significant intrinsic properties of GAC and how those determine the type of interaction with electroactive bacteria. Another important aspect for the upscaling of MET is their operation modes, that is, intermittent or continuous. This chapter includes a performance description and outputs of the two main reactor designs using GAC as electrode materials: fixed- and fluidized-bed reactors. These will be discussed for bioanodes and cathodes in microbial fuel cells (MFC) but also for biocathodes in microbial electrolysis cells (MEC) and microbial electrosynthesis cells (MES). Finally, a general comparison will be given about the two main granular bed reactor configurations, highlighting their main advantages and drawbacks.