Design approach and performance of a scalable granular packed bed biofilter for electro-fermentation

Bioelectrochemical systems (BES) represent a promising technology for the production of energy, energy carriers, and chemicals; however, their implementation in industrial applications faces significant challenges related to scalability. In this study, we introduce a novel, scalable, single-chamber BES in which the working electrode is realised as a packed bed of electrically conductive equal-sized spheres made from a graphite-polymer composite. The reactor has a total volume of 3.56 L and a packed bed volume of 1.66 L with an electrode surface area of 1.06 m². A model microbial electrolysis / electro-fermentation of lactate to acetate was catalysed by the exoelectrogenic bacterium Shewanella oneidensis, achieving a maximum current density of 430 mA m$^{-2}$ at an anode potential of 300 mV relative to the standard hydrogen electrode.