Enhancing the renewable power output of microbial fuel cells by applying an electric field

Abstract. Microbial Fuel Cells (MFCs) convert renewable organic feedstock directly into electricity by reduction and oxidation of the feedstock through the bio-catalytic, anaerobic metabolism of anode-reducing bacterial consortia harvested from bovine rumen fluid. MFCs show promise in applications such as electricity generation from energy crops, wastewater treatment, and desalination. Currently, low power densities limit the commercial applications of microbial fuel cells. High internal resistance is often cited as one of the most limiting factors in microbial fuel cell performance. One source of internal resistance is the diffusion time required for cations to flow from the fuel cell's anode to its cathode. Studies on internal resistance of microbial fuel cells have focused on fuel cell design, external resistance, substrate and oxidizer flow rates, and cathodic reactions. The goal of all of these modifications is to cause cations to reach the cathode electrode faster, which in turn decreases internal resistance and increases power density. The hypothesis of this study is that microbial fuel cell performance can be enhanced by applying an electric field across the fuel cell. The application of this field would result in multiple effects; specifically, the acceleration of cation diffusion, increased feedstock catabolic rates, and faster electron transport. All of these factors should significantly decrease the internal resistance of the fuel cell as evidenced by an increase in output current and power density. Results will include power density curves, derived internal resistance values, and quantitative analysis of three reaction kinetics loss categories: activation losses, ohmic losses, and mass transport losses. Overcoming the limitations caused by low power density is key to proving that the microbial fuel cell can be a viable renewable energy technology.