Soil-powered fuel cell powers water purifier

Technology News | November 3, 2020

By Nick Flaherty

Medical Electronics Energy Harvesting

Researchers in Bath, UK have developed a fuel cell powered by microbes in the soil that can be used to generate clean drinking water.

The team of chemical and electrical engineers at the University of Bath has demonstrated a cheap, simple soil microbial fuel cell (SMFC) that can be buried in the earth to power a water purifier. The proof-of-concept design was demonstrated during field testing in North-East Brazil and showed that SMFCs can purify about three litres of water per day, enough to cover a person’s daily water needs.

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The project is a collaboration with a team of geographers from Universidade Federal do Ceará and a team of chemists from Universidade Federal do Rio Grande do Norte.

Testing took place in Icapuí, a fishing village located in a remote semi-arid location where the main source of drinking water is rainwater and access to a reliable power network is scarce.

The system, developed by staff from Bath’s Department of Chemical Engineering and Department of Electronic & Electrical Engineering, consists of two carbon-based electrodes 4cm apart and connected to an external circuit. The anode is buried inside the soil while the cathode is exposed to air on the soil surface.

Microbes populate the surface of the anode and consume organic compounds present in soil, generate electrons. These electrons are transferred to the anode and travel to the cathode via the external circuit, generating enough current to charge a 600 mAh battery in 8.5 hours. This was within within 12 percent of the current produced in the lab and can be used to treat 1.4 litres of water.

A single SMFC unit costs just a few pounds, which could be further reduced with mass production and with the use of local resources for the electrode fabrication.

The need for sustainable water purification in the area stems from the fact that the main supply of water is from precipitation, which needs to be chlorinated to be drinkable. A stack of several SMFCs can be used to power an electrochemical reactor for water treatment.

The technology, installed at the EEF Professora Mizinha of Icapuí primary school, creates a small amount of power, which can be used to purify up to 2.8 litres of water a day.

“Using soil microbial fuel cell technology to treat a family’s daily water needs is already achievable in laboratory conditions, but doing so outdoors and with a system that requires minimal maintenance is much trickier, and this has previously proven a barrier to microbial fuel cells being considered effective. This project shows that SMFCs have true potential as a sustainable, low-energy source,” said Dr Mirella Di Lorenzo, who led the project.

“We’re addressing the issue of water scarcity and energy security in North-East Brazil, which is a semi-arid area. We sought a sustainable way to treat water effectively and make it drinkable. Rainwater is the main source of drinking water in the area, but this is not sterile – our approach in this work points to a way we could solve the issue.

“Another important element of our project is education around sustainable technologies. The field work was performed together with primary school pupils and their teachers. They were trained on the system’s working principles, installation and maintenance.”

Further research is needed to scale-up its capacity. The project, which is funded by Research England under the Global Challenges Research Fund (GCRF) frame and by The Brazilian National Council for Scientific and Technological Development, has now been granted further funds to continue its work and improve the design and efficiency of the fuel cells.

www.bath.ac.uk

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