Saturday, November 10, 2012

A good idea frought with other problems...electricity from urine

"Maker Faire Africa: Schoolgirls Create Urine-Powered Generator"


Philippa Warr

November 9th, 2012


According to the Maker Faire blog, the girls’ invention takes the urine and uses urea electrolysis to generate hydrogen, which can then be used to power a generator.

The blog doesn’t offer too much in the way of fine detail regarding the process, but the steps of the system outlined describe the urine being added to an electrolytic cell to separate out the hydrogen. The hydrogen would then be purified via a water filter and any moisture could be removed by passing the hydrogen through a cylinder of liquid borax. The final stage would be using the hydrogen to power a generator and create electricity.

While the idea of using human waste as a power source is very attractive, the prototype device will have a number of potential problems to contend with before it can become a reality — not least the fact that it may not be capable of creating a net gain in terms of electricity.

The electrolysis of urea to generate the hydrogen requires an electrical input. As such the urine cannot be used to create electricity in an area without an existing power supply.

“It’s a wonderful idea and really encouraging to see people working to convert waste products to something useful, but considering the required inputs I’d be surprised if the overall gain was positive,”
said Oliver Warr, a researcher at the University of Manchester. “If there was an alternative method of generating the hydrogen, such as microbial, that would be better.”

Another consideration would be the longevity of the device: “Urine isn’t just composed of urea,” explains Warr. “There are a lot of salts as well. Electrolysis of salt water creates more hydrogen but also chlorine, which could combine with the hydrogen to form hydrochloric acid — not good for the long-term health of a generator’s innards!”
These issues, coupled with the complexities of storing hydrogen safely, mean the generator may not be an immediately marketable prospect, but it demonstrates the potential for using the abundant resource that is urine to create valuable products.

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