EXPERIMENTAL UTILIZATION OF URINE TO RECHARGE SOIL MICROBIAL FUEL CELL FOR CONSTANT POWER GENERATION

Abstract

The simplicity of the soil-based microbial fuel cells (MFCs) makes them very attractive, as perhaps, the only natural components they need to run are nutrient-rich soil combined with water to form mud. However, the MFC will cease to produce electricity when the soil runs out of its nutrient-rich characteristics and bacteria. It is against this background that this study is designed to study the possible utilization of urine to recharge soil MFCs that have run out of their nutrient-rich characteristics. The mud-watt MFC was utilized for this study. It was run continuously for forty days when the power output was nearly zero. Fresh urine was then introduced into the soil and the power output determined. The initial (24 hours after set-up) open-circuit voltage (OCV) was 219 mV. A maximum OCV of 731 mV was obtained on day 14 of this study. The OCV of the MFC was 7.31 mV on day 40 prior to the ejection of urine into the soil. Twenty four hours after the ejection of urine, the OCV was 360 mV and rose to 407 mV forty-eight hours later. The OCV remained constant at this value for fifteen days after which urine was re-injected. The voltage drop across seven external loads also showed a similar trend. This study has demonstrated that fresh urine can be successfully utilized to recharge a soil-based MFC that has run out of its nutrient rich characteristics.