Soil Microbes Could Be Harnessed to Provide Power for Sensors

Computer scientists from UC San Diego have demonstrated how bacteria in soil can produce electricity to drive low-power sensors and other devices. Current agriculture sensors are powered by batteries, solar cells or wind generators, which have their drawbacks as batteries need to be changed or recharged periodically, and renewable energy platforms can become damaged by farm equipment. Microbial fuel cells (MFCs), on the other hand, are self-contained, eliminating the need for above-ground structures and can be buried beneath till depths, mitigating damage.

The researchers designed their MFC using readily available hardware, including a Magical Microbes' MudWatt fuel cell, an ADP5021 development kit and an E Ink display, which provides 100 μW of power at around 500 mV. The display was used to represent an example of a periodic, energy-intensive load, which approximates how a sensor load can be intermittently powered to garner soil information several times per day.

The team ultimately want to use biodegradable, self-contained MFCs and circuitry that can melt away overtime to eradicate the need to retrieve dead sensors. It should also be noted that while all microbes can generate energy, scientists are interested in a family of anaerobic bacteria known as Geobacter, which reduce heavy metal toxicity in soil, furthering the MFC's green footprint.

"Our most immediate applications are in agricultural settings, trying to create closed-loop controls," stated assistant professor Pat Pannuto. "First for watering, but eventually for fertilization and treatment: sensing nitrates, nitrogen, phosphorous, potassium. This could help us understand how to limit runoff and other effects."

Beyond farm monitoring, the scientists are looking to deploy the MFC sensors in wetlands and other environments to monitor pollutants.