Comparison of electricity production using water vs. air-cathode microbial fuel cell technologies

Although current densities generated by microbial fuel cells are low, the sizes of the cathode and proton exchange membrane (PEM) relative to the anode size are important factors in maximum power output. MFC were constructed with PEM having three different surface areas (3.5, 6.2, or 30.6 sq cm). For a fixed and equal anode and cathode surface areas (22.5 sq cm), the power density normalized to the anode surface area increased with the PEM size in the order: 45 mw/sq m (3.5 sq cm), 68 mw/sq m (6.2 sq cm), and 190 mw/sq m (30.6 sq cm). This resulted from changes in internal resistance as increasing the PEM surface area from 3.5 to 30.6 sq cm decreased the resistance from 1110 to 89.2 ohm. Power output was predictable in this system based on the relative sizes of the PEM, anode, and cathode as demonstrated by a good fit to an empirical equation. This is an abstract of a paper presented at the 230th ACS National Meeting (Washington, DC 8/28/2005-9/1/2005).