Scientists are developing a new Earth-powered fuel cell that lasts forever

A team of researchers led by Northwestern University has developed a new fuel cell that harvests energy from microbes that live in dirt.

The ground-based technology is about the size of a typical paper book and can power underground sensors used in precision agriculture and green infrastructure. It potentially provides a sustainable, renewable alternative to batteries, which contain toxic and flammable chemicals that end up in landfills, littering contentious supply chains and contributing to the growing e-waste problem.

To test the new fuel cell, the researchers used it to power sensors that measure soil moisture and detect touch — a capability that could be useful for tracking transient animals. To enable wireless communication, the researchers equipped the ground-based sensor with a small antenna to transmit data to a nearby base station by reflecting existing radio frequency signals.

Not only did the fuel cell work in wet and dry conditions, but its performance exceeded comparable technology by 120%.

The research is published today (Jan. 12) in the Proceedings of the Association for Computing Machinery in Interactive, Mobile, Wearable, and Universal Technologies. Study authors also publish all designs, tutorials, and simulation tools so others can use and build on the research.

“The number of devices connected to the Internet of Things (IoT) is constantly increasing,” said Northwestern University graduate student Bill Yen who led the work. “If we envision a future with these trillions of devices, we won’t be able to build every one of them with lithium, heavy metals, and toxins that threaten the environment. We need to find alternatives that use less of this energy to power a decentralized network of devices. amount can provide. In our search for a solution, we looked at soil microbial fuel cells, which use special microbes to break down the soil and use that small amount of energy in energy sensors. If there is organic carbon present and the microbes in the soil decompose, Fuel cells could potentially last forever.

“These germs are everywhere. “They actually live in the ground everywhere,” said George Wells of Northwestern University, a senior author of the study. can gather a small amount of energy for

Wells is an associate professor of civil and environmental engineering at Northwestern’s McCormick School of Engineering. Now the Ph.D. Yin, a graduate student at Stanford University, started the project while working in Wells’ lab as an undergraduate.

Solution for a dirty job

In recent years, farmers around the world have increasingly adopted precision agriculture as a strategy to improve crop yields. The technology-based approach relies on measuring specific moisture, nutrient and pollutant levels in the soil to make decisions to improve crop health. It requires a large and distributed network of electronic devices to continuously collect environmental data.

“If you want to deploy a sensor in the wilderness, on a farm or in a wetland, all you need to do is install a battery or collect solar energy,” Yin said. “Solar panels don’t work well in dirty environments because they’re covered in dirt, they don’t work when the sun isn’t shining and they take up a lot of space. Batteries are also a challenge because they run out of power.” Farmers don’t regularly walk around 100-acre farms replacing batteries or dusting solar panels.

To overcome these challenges, Wells, Owen and their collaborators wondered if they could instead harvest energy from the existing environment. “We can extract energy from the soil that farmers already observe,” Yin said.

“Frustrated Effort”

When they debuted in 1911, soil-based microbial fuel cells (MFCs) functioned like a battery—with an anode, cathode, and electrolyte. But instead of using chemicals to generate electricity, MFCs harvest electricity from bacteria that naturally release electrons to nearby conductors. As these electrons flow from the anode to the cathode, they form a circuit.

After being removed from the ground for study, the fuel cell is covered in dirt. Photo credit: Bill Yen/Northwestern University

However, for microbial fuel cells to function continuously, they must be moist and oxygenated, which is difficult to bury underground in dry soil.

“Although MSCs have been around as a concept for more than a century, their unreliable performance and low production capacity have frustrated efforts to put them into practice, especially under low humidity conditions,” Yin said.

successful technology

Given these challenges, Yin and his team embarked on a two-year journey to develop a practical and reliable ground-based MFC cell. His journey included creating – and comparing – four different versions. First, the researchers collected nine months of data on the performance of each design. They then tested their final version in an outdoor park.

The highest performing prototype performed well in both dry conditions and underwater environments. The secret to his success: his strategy. Instead of the traditional design where the anode and cathode are parallel to each other, the winning fuel cell used an orthogonal design.

The anode is made of carbon felt (a readily available and inexpensive conductor for capturing micro-electrons) and is positioned horizontally on the soil. The cathode is made of an inert, conductive metal and is mounted vertically above the anode.

Although the entire device is buried, the vertical design ensures that the upper part is flush with the ground surface. The device has a 3D printed cover on top that prevents dirt from getting inside. The empty air chamber running along the top hole and the cathode allows a constant flow of air.

The lower end of the cathode is positioned deep below the surface, ensuring that it remains moist from the surrounding moist soil, even as the topsoil dries out in sunlight. The researchers coated parts of the cathode with a waterproof material so it could breathe during flooding. After a potential flood, the vertical design allows the cathode to dry gradually, rather than all at once.

On average, this resulted in the fuel cell generating 68 times more electricity than needed to power its sensors. It was also robust enough to withstand large changes in soil moisture—from slightly dry (41% water by volume) to completely submerged.

Making computing accessible to everyone

All of the components for soil-based MFCs can be purchased at local hardware stores, the researchers say. Next, they plan to develop a soil-based MFC made entirely from biodegradable materials. Both designs bypass complex supply chains and avoid the use of conflict minerals.

“With this COVID-19 “We’ve all become aware of how a crisis can disrupt the global electronics supply chain,” said study co-author Josiah Hester, a former Northwestern University faculty member who now works at the Georgia Institute of Technology. “We want to create devices that can use local supply chains and low-cost materials to make computing accessible to all communities.”

References: Bill Yen, Laura Glave, Luis Gutierrez, Veluthi Sahinidis, Sadie Bernstein, John Madden, Steven Taylor, Colin Josephson, Pat Panuto, Weitao Shuai, George Wells, Nivedita Arora, and Josiah Hester, “Soil-Driven Computing,” January 11. … 2024, Proceedings of the ACM on Interactive, Mobile, Wearable and Pervasive Technologies.
doi: 10.1145/3631410

The research was supported by the National Science Foundation (Award No. CNS-2038853), the Agriculture and Food Research Initiative of the USDA National Institute of Food and Agriculture (Award No. 2023-67021-40628), and the Alfred P. was supported by Sloan. Foundation, VMware Research and 3M.