Researchers led by Northwestern University have developed a fuel cell that uses microorganisms naturally found in soil to generate electricity. The device, about the size of a paperback book, generates small amounts of electricity by capturing the energy released when these microorganisms break down organic matter in dirt.
This soil power system is designed to power underground sensors used in precision agriculture and environmental monitoring. This is a battery that could potentially replace traditional batteries, which contain toxic and flammable materials, rely on complex global supply chains, and contribute to increased e-waste.
Power the sensor without batteries
To demonstrate its functionality, the team used a fuel cell to measure soil moisture and operate a sensor that detects contact. This touch-sensing ability could be useful in monitoring the movement of wildlife, such as animals passing through fields. The system also includes a small antenna that reflects existing radio frequency signals and transmits data wirelessly, keeping energy usage extremely low.
The device proved reliable across a wide range of conditions. The system worked in both dry soil and flooded environments and produced more sustained power than similar systems, lasting approximately 120% longer.
This research Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable, and Ubiquitous Technologies.. The researchers also published designs, tutorials, and simulation tools to help others build on their research.
Why soil microbes are important to the Internet of Things
“The number of Internet of Things (IoT) devices continues to grow,” said Bill Yen, a Northwestern University graduate who led the work. “If we imagine a future where we have trillions of these devices, they can’t all be made with lithium, heavy metals, and toxins that are dangerous to the environment. We need to find alternatives that can provide lower amounts of energy to power distributed networks of devices. Seeking Solutions In doing so, we turned to soil microbial fuel cells, which use specialized microorganisms to break down soil and use that small amount of energy to power the sensor.As long as there is organic carbon in the soil that the microorganisms can break down, the fuel cell could last forever.”
Microbial fuel cells, often called MFCs, function like batteries. They contain an anode, a cathode, and an electrolyte, but instead of a chemical reaction, they rely on bacteria that naturally release electrons. As these electrons move through the system, an electric current is generated.
“These microbes are ubiquitous. They already live in soil everywhere,” said George Wells of Northwestern, senior author of the study. “We can use a very simple design system to recover power. We’re not going to power an entire city with this energy. But we can recover small amounts of energy to fuel practical low-power applications.”
Challenges of solar-powered and battery-powered sensors
Precision agriculture relies on large networks of sensors that continuously track soil conditions such as moisture, nutrients, and pollutants. These data help farmers make more informed decisions and improve crop yields.
However, powering these sensors is a major challenge. Batteries eventually wear out and need to be replaced, which is not practical on large farms. Solar panels can also be unreliable because they get dirty, require sunlight, and require space.
“If you want to install the sensor outdoors, such as on a farm or in a wetland, you will need to install a battery or collect solar energy,” Yen said. “Solar panels don’t work well in dirty environments because they’re covered in dirt, they don’t work unless the sun is out, and they take up a lot of space. Batteries also run out of power, which makes it difficult. Farmers aren’t going to walk around a 100-acre farm to change batteries and dust their solar panels on a regular basis.”
The researchers instead focused on harvesting energy directly from the soil itself, turning the environment into a power source.
Why did early microbial fuel cells fail?
Soil-based microbial fuel cells have been around since 1911, but have struggled to achieve consistent performance. These systems require both moisture and oxygen to function properly, but maintaining them underground is difficult, especially in dry conditions.
“Although MFC has existed as a concept for more than a century, its unreliable performance and low output power have hindered efforts toward practical implementation, especially in low-humidity environments,” Yen said.
New design improves performance
To address these issues, the team spent two years developing and testing various designs. They compared four versions, collected nine months of performance data, and tested them outdoors before choosing the final prototype.
The breakthrough came through a change in geometry. The new design places the anode and cathode vertically rather than parallel to each other.
An anode made of carbon felt (a cheap and plentiful conductor for capturing microbial electrons) is placed horizontally beneath the soil. The cathode is made of a conductive metal and extends perpendicular to the surface.
This structure helps solve multiple problems at once. The top of the device remains exposed to air, ensuring a steady oxygen supply. At the same time, the lower part remains buried in moist soil, maintaining hydration even in dry conditions. A protective cap prevents debris from entering, and a small air chamber allows airflow.
This design also improves resilience when flooded. The waterproof coating allows the cathode to continue functioning, and the vertical layout allows the cathode to gradually dry after the water recedes.
Deliver superior results in real-world situations
The final prototype performed well in a wide range of soil conditions, from moderately dry soil (41% water by volume) to fully submerged environments. On average, they generated 68 times more power than was required to operate the sensor.
These results suggest that this system can withstand deployment in real agricultural fields and natural environments.
Ongoing research and future possibilities
Interest in microbial fuel cells has continued to grow since this study was first published. Researchers are working to improve efficiency, stability, and materials, including exploring biodegradable designs that can further reduce environmental impact.
The Northwestern team notes that all parts of the system can be sourced from common hardware materials. They are now aiming to create a fully biodegradable version that avoids complex supply chains and conflict minerals.
“The COVID-19 pandemic has made us all aware of how crises can disrupt global electronics supply chains,” said study co-author Josiah Hester, a former Northwestern University faculty member now at Georgia Tech. “We want to build devices using local supply chains and low-cost materials to make computing accessible to all communities.”
Although the technology is not intended to power large-scale systems, it could play an important role in supporting low-energy devices across agriculture, environmental monitoring, and the expanding Internet of Things.
Important points
- Scientists have developed a new fuel cell that uses naturally occurring soil microorganisms to generate electricity.
- The system can track soil moisture and power underground sensors that detect movement and contact.
- It continues to operate in a wide range of conditions, from dry soil to fully flooded environments.
- This technology could provide a cleaner alternative to batteries for sensors used in precision agriculture.
The study, “Soil Powered Computing: An Engineer’s Guide to Practical Soil Microbial Fuel Cell Design,” was supported by the National Science Foundation (Award Number CNS-2038853), the Agriculture and Food Research Initiative of the USDA National Institute of Food and Agriculture (Award Number 2023-67021-40628), the Alfred P. Sloan Foundation, VMware Research, and 3M.
