We’ve covered poop-to-plastic, so naturally it’s time to talk about turning pee into power. This proposition comes by way of the Royal Chemistry Society’s Chemistry World, and if it sounds like an April Fool’s joke, we assure you, the article is dated 31 October 2011 and the study it is based on – by researchers at the University of West of England – is published in the journal Physical Chemistry Chemical Physics.

The story here is really all about finding a new way to drive microbial fuel cells. MFCs, as they’re known, are devices that use bacteria to oxidize organic matter to produce an electric current. MFCs have been bubbling in the background of biomass energy research, popping into mainstream discussion only occasionally – one lone story shows up in the vast EarthTechling database, about the Navy’s effort to use marine organisms to fuel an MFC for possible use in unmanned underwater vessels.

microbial fuel cell using urine
image via Shutterstock

The charm of MFCs is their ability to turn what the Bristol researchers call “too-wet-to-burn low-grade organic matter” into electricity – with no greenhouse gases emitted. Researchers trying to advance this fuel cell technology have played with carbohydrates, fatty acids, alcohols and whatnot as fuels, but apparently nobody had tried urine – cheap and abundant urine, it goes without saying. And what do you know, the Bristol boys found that the uric acid, creatinine and small peptide molecules found in urine, catalyzed by some of the same bacteria used in wastewater treatment plants, actually worked: In the anaerobic environment of the fuel cell’s anode chamber, the bacteria transfer the electrons obtained by breaking down the urine to an electrode, beginning the current-generating process.

The researchers found that a fuel cell fed 25 ml of unprocessed urine could produce current output of 0.25 mA, continuously for three days, before beginning to fall off. Very encouraging stuff. Of course, there are questions: Do people want to separate out their urine? Is the MFC-urine process economically viable? Whatever the answers to those questions might be, the researchers – Ioannis Ieropoulos, John Greenman and Chris Melhuish – conclude their paper with the rather impassioned insistence that their work has real-world applications.

“This is not another MFC study that simply demonstrates the utilisation of a substrate, but it is the first report that urine can be an abundant fuel for electricity generation,” they write. “The impact from this could be enormous, not only for the wastewater treatment industry, but also for people as a paradigm shift in the way of thinking about waste. With an annual global production rate of trillions of litres, this is a technology that could help change the world.”

The paper, “Urine utilisation by microbial fuel cells; energy fuel for the future,” is available online for registered RSCPublishing users (registration is free).

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