Tubular Microbial Fuel Cells for Efficient Electricity Generation

TLDR

Lower efficiency of wastewater‑treating MFCs is due to non‑readily biodegradable organics and competing electron acceptors such as sulfate, and sustainable open‑air cathodes are essential for practical deployment. The study aims to improve MFC performance by enhancing conversion of non‑rapidly biodegradable material and directing anode flow toward the electrode rather than alternative acceptors. The authors present a tubular, single‑chambered, continuous MFC with a granular graphite anode and ferricyanide cathode that achieves high power outputs. The MFC achieved maximal net anodic power outputs of 90 W m⁻³ for acetate and 66 W m⁻³ for glucose, with Coulombic efficiencies of 75 % and 59 % respectively, and converted up to 96 % of organic matter to electricity when treating wastewater.

Abstract

A tubular, single-chambered, continuous microbial fuel cell (MFC) that generates high power outputs using a granular graphite matrix as the anode and a ferricyanide solution as the cathode is described. The maximal power outputs obtained were 90 and 66 W m-3 net anodic compartment (NAC) (48 and 38 W m-3 total anodic compartment (TAC)) for feed streams based on acetate and glucose, respectively, and 59 and 48 W m-3 NAC for digester effluent and domestic wastewater, respectively. For acetate and glucose, the total Coulombic conversion efficiencies were 75 ± 5% and 59 ± 4%, respectively, at loading rates of 1.1 kg chemical oxygen demand m-3 NAC volume day-1. When wastewater was used, of the organic matter effectively removed (i.e., 22% at a loading of 2 kg organic matter m-3 NAC day-1), up to 96% was converted to electricity on a Coulombic basis. The lower overall efficiency of the wastewater-treating reactors is related to the presence of nonreadily biodegradable organics and the interference of alternative electron acceptors such as sulfate present in the wastewater. To further improve MFCs, focus has to be placed on the enhanced conversion of nonrapidly biodegradable material and the better directing of the anode flow toward the electrode instead of to alternative electron acceptors. Also the use of sustainable, open-air cathodes is a critical issue for practical implementation.