Sizes of Anode and Cathode Affect Electricity Generation in Rice Paddy-Field Microbial Fuel Cells

Abstract

Rice paddy-field microbial fuel cells (RPF-MFCs) are devices that exploit rhizosphere bacteria to generate electricity from soil organic matter, including those excreted from roots. Previous stu-dies have examined factors affecting electric outputs from RPF-MFCs and demonstrated that RPF-MFC was able to generate electricity up to 80 mW • m −2 (based on the projected area of anode). The present study operated RPF-MFCs with different sizes of anodes and cathodes and examined how electrode sizes affected electricity generation. We show that anodes are the limiting factor for electricity generation immediately after commencing the operation, while cathodes become the limiting factor after anode performances are sufficiently increased. RPF-MFC achieved the maxi-mum power density of 140 mW • m −2 (based on the projected area of anode), when the cathode is sufficiently larger than the anode. Results suggest that the cathode needs to be improved for eli-citing the maximum capacity of rhizosphere bacteria for electricity generation in RPF-MFC.