Direct Conversion Fuel Cell of Urine in Animal Wastes and Its Condition Monitoring Sensors for Efficient Water Usage in Agriculture

Abstract

Over one billion tons of agricultural (e.g. manure), municipal (e.g. biosolids), and industrial (e.g. coal combustion products) wastes with potential uses in agriculture are generated annually in the United States according to the National Agricultural Statistics Service [1]. An annual global production of about 40 billion liters of urine from farm animals is estimated. If urine by humans is added to that figure, 6.5 trillion liters are produced every year. Many of these materials are spread, sprayed or otherwise applied to agricultural land because of the benefits they provide. These benefits include: providing a nutrient source for crops; improving soil chemical, physical and biological properties; improving soil water storage and use; reducing movement of contaminants to water and air; and reducing production costs and energy use. However, improperly managed manure and other byproducts can pose a threat to soil, water and air quality, and to human and animal health. To prevent environmental pollution, it is important to treat them before release with minimal power consumption. For example, in activated sludge process, which is conventional wastewater treatment process, 1kWh/kg carbohydrate of energy is required [2]. If we can recover and use it for wastewater treatment, total power consumption for wastewater treatment will be reduced, and further, if the amount of recovered energy exceeds the amount of required energy for wastewater treatment, energy can be obtained from wastewater. In this project, we demonstrates very efficient and scalable direct urine fuel cells without the use of bacteria to mitigate animal waste, as well as generate electricity from wastewater. Unlike common microbial fuel cells that use electrons produced by bacterial metabolism [3], the proposed fuel cell is to harvest electrons directly from urea in urine by converting urea into H2O, CO2 and N2. Newly engineered electrodes and electrolytes were developed for efficient and rapid electricity generation. Since the mechanisms relating to direct conversion of urea have still not been understood entirely, our condition monitoring sensors will be re-engineered to measure chemical species generated by reactions between animal wastewater and fuel cells. The performance of the fuel cell is enhanced by developing unique sensing probes to monitor conditions of the reactors and animal wastes. Electrochemical sensors based on hierarchically nanostructured functional metal oxides. The measurement of gas and liquid environment of animal waste is demonstrated by addressing sensitivity, sensitivity and response time.