Urine-powered battery offers cheap energy source

Dr. Mirella Di Lorenzo with her urine-powered microbial fuel cell(Credit: University of Bath)

When most people think of bacteria and urine together, chances are good they think of a not-so-pleasant infection. For researchers at the University of Bath however, unifying these two thoughts led to the development of a battery that could harness "pee power" to bring energy to parts of the world that might not otherwise have access to it.

Working with colleagues from Queen Mary University of London and the Bristol Bioenergy Centre, the Bath researchers came up with a type of microbial fuel cell (MFC) that is powered by human urine.

MFC's are devices that use bacteria to perform reduction/oxidation reactions on organic material like banana skins or, in this case, urine. When such a reaction occurs, electrons are swapped around between molecules and electricity is produced. By causing this reaction to take place in a closed system with an anode and a cathode, a battery is formed. Earlier this month, researchers in the Netherlands demonstrated a bacteria-based battery using this basic principle that they were able to charge and recharge multiple times. That battery used acetate to cause the reaction to take place. For this new battery, urine serves as the fuel.

The benefits of using urine in an MFC includes the fact that it's a free, available-everywhere substance that's readily usable – there is no need to wait for anything to decompose, as is the case with other bacterial sources like food waste. While we've seen a urine-based battery before, the size and price tag of this latest pee-based MFC is a marked improvement. The batteries themselves cost just £1-2 each, and the substance they need to run on is obviously free, so they could help impoverished area get the resources they need to power important technologies like well pumps or lights.

Using urine-based batteries is also a great example of extreme recycling – a waste product that would otherwise be lost is harnessed, put through a MFC and turned into useful energy without any of the pollution associated with other fuel sources like the burning of fossil fuels.

"Microbial fuel cells can play an important role in addressing the triple challenge of finding solutions that support secure, affordable, and environmentally sensitive energy, known as the 'energy trilemma,'" said University of Bath's Dr. Mirella Di Lorenzo, who is a co-author of a paper detailed the findings published earlier this year in the journal Electrochimica Acta. "There is no single solution to this 'energy trilemma' apart from taking full advantage of available indigenous resources, which include urine."

The next step for the researchers is to figure out how to up the energy output of the urine-based MFCs. They've already discovered that by extending the electrodes in the cell from 4 to 8 mm, power output increased tenfold, and that stacking the batteries could produce even greater electrical output.








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