Determination of the suitability of urine as substrate in a power generating soil microbial fuel cell

Abstract

Urine has been identified as a suitable substrate in Microbial Fuel Cells (MFC). However, its possible utilization in a soil-based Membrane-less Single Chamber Microbial Fuel Cell (MSCMFC) has, hitherto, not been reported. This study used the mud-watt MFC vessel inoculated with mud prepared from topsoil, and was operated across seven external loads for 19 days (456 hours) without adding any substrate to the soil. Urine was fed into the cell in four duration time, after the MFC output stabilized. For comparison, a fresh set up (control MFC) was made and operated under the same condition of temperature (27+3°C), but without the addition of urine. The performances of the MFCs were examined over seven external loads of resistances 4670Ω, 2190Ω, 1000Ω, 470Ω, 220Ω, 100Ω, and 47Ω. The Urine treated MFC and the control MFC both produced initial peak power output of 5.62μW. Both MFCs produced close values of power outputs up to the point of adding urine. At the final stage, the peak power output of the MFC treated with urine was 246.77μW; whereas the corresponding values for the control MFC were 0.007μW. This study showed that fresh (untreated) human urine can be successfully utilized as fuel in a soil-based MFC for the production of electrical energy for varied external loads.