Inventing a new device with the ability to produce endless energy from soil

A new fuel cell harnesses energy from soil-dwelling microbes to power sensors, harvesting nearly unlimited energy from the soil.

According to Isna, citing New Atlas, a team from Northwestern University has shown a new way to produce electricity. They introduced a device the size of a book that sits on top of the soil and collects the force generated by microbes breaking down the soil (as long as there is carbon in the soil).

Microbial fuel cells, as their name suggests, have been around for over 100 years. They work a bit like a battery, with an anode, cathode and electrolyte, but instead of taking electricity from a chemical source, they work with bacteria that naturally donate electrons to nearby conductors.

This newly invented fuel cell relies on the ubiquitous natural microbes in the soil to generate energy.

Powered by soil, this device is a good alternative to the batteries of underground sensors used for precision agriculture.

A microbial fuel cell (MFC) or biological fuel cell is a biochemical system that produces electricity by mimicking the activity of bacteria that occurs in nature. A microbial fuel cell is a type of biochemical fuel cell system that generates electrical current by diverting electrons produced from microbial oxidation of reduced compounds (also known as fuel or electron donors) on the anode to oxidizing compounds (called (also known as an oxidizing agent or electron acceptor) is produced on the cathode through an external electrical circuit.

Fuel cells can be divided into two general categories “intermediate and non-intermediate”. The first fuel cells that appeared in the early 20th century used a mediator, which was a chemical substance that transferred electrons from the bacteria in the cell to the anode. Non-intermediate fuel cells emerged in the 1970s. In this type of fuel cell, bacteria usually have electrochemically active proteins such as cytochromes on their outer membrane that can transport electrons directly to the anode.

Northwestern University researchers note the durability of their powerful fuel cell and have demonstrated its ability to withstand various environmental conditions, including dry soil and flood-prone areas.

The issue until now has been to supply them with water and oxygen while they are buried in the soil. Although these devices have existed as a concept for more than a century, their uncertain performance and low output power have hampered efforts to put them to practical use, says Bill Yen, a graduate student at Northwestern University and head of the project. especially in low humidity conditions had stopped.

So the team set out to create several new designs aimed at providing cells with continuous access to oxygen and water, and succeeded with a cartridge-shaped design that sits vertically on a horizontal disk.

A disk-shaped carbon felt anode sits horizontally at the bottom of the device and goes deep into the soil, where it can capture electrons as microbes break down the soil.

Meanwhile, the conductive metal cathode is placed vertically above the anode. Therefore, the lower part goes deep enough to access the moisture of the deep soil, while the upper part is level with the ground surface, and a fresh air gap runs the entire length of the electrode, and a protective cap on top prevents it from falling. It becomes dust and waste and cuts off the cathode's access to oxygen. Part of the cathode is also covered with a water-insulating material, so that when water is present, a hydrophobic part of the cathode is still in contact with oxygen for the fuel cell to work.

The researchers used a waterproof material on the surface of the cathode, which allows it to work even during flooding and ensures gradual drying after immersion in water.

“These microbes are everywhere,” says George Wells, senior author of the study. They live everywhere in the soil now, and we can use very simple engineered systems to get electricity from them. We're not going to power entire cities with this energy, but we can capture very small amounts of energy to fuel essential, low-consumption applications.

Also, the chemicals left over from the batteries can potentially seep into the soil. While this new technology is an environmentally friendly alternative that reduces the environmental concerns associated with the hazardous components of batteries and is also non-combustible.

The design performed consistently well in tests at varying levels of soil moisture, from completely waterlogged to relatively dry, and produced, on average, about 68 times more energy than its sensors needed to operate. It was also strong enough to survive extreme changes in soil moisture.

As with other sources of long-term electricity generation, such as diamond beta-voltaic batteries made using nuclear waste, the amount of electricity produced here is not enough to start a car or power a smartphone, but rather to power small sensors. so that they can work for a long time without needing to replace the battery regularly.

In addition, the researchers attached the soil sensor to a small antenna to enable wireless communication. This allowed the fuel cell to transmit data to a nearby station by reflecting existing radio frequency signals.

It is noteworthy that this soil fuel cell has a 120% better performance than similar technology.

Bill Yen says: If we imagine a future with trillions of devices, we cannot make them all from lithium, heavy metals and toxins that are dangerous for the environment. We need to find alternatives that can provide small amounts of energy to power a decentralized network of devices. In our search for a solution, we turned to soil microbial fuel cells, which use special microbes to break down soil and use that small amount of energy. As long as there is organic carbon in the soil for microbes to break down, our fuel cell can potentially survive.

Therefore, sensors like these can be very useful for farmers looking to monitor various soil elements including moisture, nutrients, pollutants, etc., and to use a technology-based precision agriculture approach. So if you put several devices of this type around your farm, they can generate data for you for years, maybe even decades.

It should be mentioned that according to the research team, all the components of this device can be purchased from hardware stores. So there is no problem in the supply chain or materials for widespread commercialization of this product.

This research was published in the ACM journal on Interactive, Mobile, Wearable and Ubiquitous Technologies.