agricultural uses
Scientists at Northwestern University in the United States have developed a pocket-sized fuel cell powered by soil microbes. This device harvests energy created by the microbial activity in soil and demonstrates strong performance for low-power applications in both wet and dry conditions. The compact unit, about the size of a small book, relies on bacteria in the earth to generate electricity instead of traditional chemicals.
The invention offers a sustainable alternative to conventional batteries, which often become electronic waste containing toxic and flammable chemicals that can harm the environment.
agricultural uses
Researchers tested this fuel cell by using it to power agricultural sensors that monitor soil moisture. The system also demonstrated the ability to sense touch, a capability that could assist in tracking animals.
“These batteries use microbes to break down the soil and convert that small energy release into power for the sensors. As long as there is organic carbon in the soil for the microbes to process, the fuel cell could potentially run for a very long time”, say the researchers.
Battery image
The sensor included a small antenna enabling wireless communication and data transfer to a nearby base station. The fuel cell operated in both dry and wet environments and delivered power surpassing similar technologies by roughly 120 percent.
In recent years, precision agriculture has surged in popularity as a way to raise crop yields. This approach relies on detailed measurements of soil moisture, nutrients, and contaminant levels to guide decisions that improve crop health. It typically requires a broad, distributed network of electronic devices capable of continuously collecting environmental data.
A different geometry is the key to success
Professor Bill Yen and his team at Northwestern University undertook a two-year effort to develop a practical and reliable soil-based microbial fuel cell. They created four variants, compared them, and tracked each system’s data for nine months before testing the best-performing prototype in an outdoor garden. The breakthrough lay in the device geometry, which differed from traditional designs.
During testing, the team chose a vertical design over parallel anode and cathode configurations. The anode was made from carbon felt, and the cathode from an inert conductive metal. This geometry proved effective in both dry and waterlogged conditions.
System diagram
The device features a vertical form that sits flush with the soil surface. A 3D-printed lid on top keeps debris out, while a small top opening allows for continuous airflow. The lower end of the cathode stays beneath the surface to stay moistened by surrounding soil, and a waterproof cover permits breathing during floods. The unit generates energy well beyond what its sensors require and endures large swings in soil moisture.
Researchers note that all components of the earth battery can be sourced from common hardware stores. The next goal is to develop a soil-based battery made entirely from biodegradable materials.
“These microbes are ubiquitous; they live in soil everywhere”, stated a lead author from Northwestern. “We can use straightforward engineering to capture their electricity. This energy won’t power entire cities, but it can provide small, steady amounts of power for practical applications.” (Source: ACM Digital Library, DOI: 10.1145/3631410)
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