Precision agriculture uses sensors to monitor soil and help farmers improve yields. However, powering these sensors with continuous, uninterrupted power is challenging due to limited battery capacity and limited development of renewable power. To help address farmers' power needs, Northwestern University researchers have developed a fuel cell the size of a paperback book that captures energy as microbes break down organic matter, powering underground sensors for agriculture and environmental monitoring.
In the study, published in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies, the team showed that a microbial fuel cell (MFC) could power sensors to measure soil moisture and detect touch, enabling the monitoring of wildlife movement within a field. The device worked reliably in both dry and flooded soil and outperformed similar systems, lasting 120% longer.
"If we imagine a future with trillions of [IoT] devices, we cannot build every one of them out of lithium, heavy metals, and toxins that are dangerous to the environment. We need to find alternatives that can provide low amounts of energy to power a decentralized network of devices,” said Bill Yen, a Northwestern alum who led the research team.
MFCs generate electricity using bacteria in soil. As these bacteria break down organic matter, they naturally release electrons, which create a small electric current. These microbes can be found everywhere and harnessed with simple devices to generate small amounts of electricity for low-energy applications.
Past soil-based microbial fuel cells have often failed due to insufficient moisture in the operating area. After spending two years testing designs, the team achieved a breakthrough by arranging the anode and cathode perpendicularly rather than in parallel. The carbon anode lies horizontally beneath the soil, and the cathode, made of a conductive metal, extends vertically to the surface.
With this configuration, the device's top remains exposed to air, ensuring a steady oxygen supply. At the same time, the lower portion stays buried in moist soil, maintaining hydration even during dry conditions. A protective cap prevents debris from entering, while a small air chamber allows airflow. The design also improves resilience during flooding. A waterproof coating keeps the cathode functioning, and the vertical layout helps it dry gradually as water recedes.
The final prototype performed well across a wide range of soil conditions, from moderately dry soil (41% water by volume) to fully submerged environments. On average, it generated 68 times more power than required to run its sensors.
Today, researchers are working to improve the efficiency, stability, and materials of MFCs, including exploring biodegradable designs that could further reduce environmental impact. While the technology is not intended to power large systems, it could play an important role in supporting low-energy devices across agriculture, environmental monitoring, and the expanding Internet of Things.
