In this project, we designed, built, and tested a specially fabricated device that uses micro-organisms naturally found in soil to generate electricity and power wireless soil moisture sensors. These microbes live throughout all soil and sediment on the earth. Some of the particular microbe species have the unique ability to release electrons outside their bodies as part of their respiration process. The device utilizes these special microbe species in soil to generate electricity. The device is comprised of two electrodes, an anodic (noncorrosive stainless steel mesh) and a cathode (ferricyanide). The anode is placed within the mud where the electrogenic microbes can grow, while the cathode is placed on top exposing it to oxygen in the air. When placed in soil, the electrode pair generates an electrical potential. Multiple cells were fabricated and placed in parallel to increase the power output. The data was compiled into Minitab software and used to analyze the influence of each variable, and if any interaction between the variables. Voltage production observed ranged from 0.12 to 0.33 volts, and the voltage was step up to 5v to charge a capacitor as a sensor power supply. The device is inexpensive and completely passive, requiring no external power input.
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