Now, in what may be a case of taking it a bit too far, researchers at the University of West England, Bristol, have invented a wearable energy-generation system powered solely by human urine.
The paper, headed by Associate Professor Ioannis Ieropoulos and alluringly titled ‘Self-sufficient Wireless Transmitter Powered by Foot-pumped Urine Operating Wearable MFC,’ appears in the science journal Bioinspiration & Biomimetics.
The mechanism essentially consists of a sock lined with tubes of microbial fuel cells (MFCs) into which urine is systematically pumped and then removed. In order to generate power, all you need to do is rely on the pressure of your foot against the ground to pulse the liquid throughout the tubes as you walk.
Urine is abundant in nitrogen and phosphorous, key nutrients on which the microbes feed. Other less mentionable human waste is also rich in these nutrients, so if you were worried about sticking your foot into a pee-lined sock, don’t worry; these other wastes could be substituted to achieve the same results.
As the microbes devour the nitrogen and phosphorous, they release electrons, which are then taken up by the fuel cells to produce electricity.
In a previous study, the team effectively powered a mobile phone using only urine, but they wanted to replicate their results in the form of a wearable device.
“We also wanted the system to be entirely self-sufficient,” Ieropoulos said, “running only on human power — using urine as fuel and the action of the foot as the pump.”
Admittedly, none of this sounds particularly viable as a marketable product, and with a maximum achievable power of only 110 microwatts, the system itself doesn’t generate enough electricity to be of significant aid. So why subject yourself to the potential gross-factor?
For one, it would work anywhere, any time, in any weather, when other energy sources like solar may fail. In this regard, it could be a unique and appealing option for hikers and mountaineers who risk solitary treks across inaccessible tracts of wilderness.
“This work opens up possibilities of using waste for powering portable and wearable electronics,” said Ieropoulos. “For example, recent research shows it should be possible to develop a system based on wearable MFC technology to transmit a person’s coordinates in an emergency situation. At the same time this would indicate proof of life since the device will only work if the operator’s urine fuels the MFCs.”