If asked what would be a great power source for mobile phones, it’s a fair bet that most people wouldn't make urine their first choice. But that's exactly what a group of scientists at Bristol Robotics Laboratory in the UK have done. As part of a project to find new ways to provide electricity for small devices in emergency situations and developing countries they have created a new fuel cell system powered by pee.

The key to this rather unorthodox way of powering a phone is a microbial fuel cell (MFC) that converts organic matter directly into electricity. Inside the MFC, there are a mixture of ordinary anaerobic microorganisms that release electrons as they feed – in this case, on the urine. The technology has been under development for 30 years, but because of problems in scaling up the technology to provide significant amounts of power, it has yet to find widespread commercial application. However, it is possible to attain practical levels of power when several small MFCs are stacked and wired together.

The Bristol experiment used 12 ceramic cylinders 10.2 cm (4 in) long wired with a cathode and an anode. These cylinders were stacked in sets of three with each stack acting as a cascade. Urine was introduced into the first cylinder of each cascade and as the organisms fed on it, they generated electricity. This was repeated in the second and then the third cylinder before the urine was collected in a waste flask. Since the output of even three cylinders was very small, four cascades were hooked together like batteries to produce sufficient current to charge a mobile phone battery.

The purpose of the experiment was to demonstrate that it is possible to build a practical MFC system that could be mass produced, while also showing that urine could be a practical fuel to provide power for such a device.

“We are very excited as this is a world first, no one has harnessed power from urine to do this so it's an exciting discovery,” says Doctor Ioannis Ieropoulos from the University of the West of England (UWE Bristol), which came together with the University of Bristol to form the Bristol Robotics Laboratory. “Using the ultimate waste product as a source of power to produce electricity is about as eco as it gets.”

According to the scientists involved in the project, using urine for fuel may sound a bit disgusting, but it is an inexhaustible resource that people always have available. This makes it excellent for powering emergency communications and it even has the potential to generate power for showers, lighting and razors in domestic bathrooms.

“One product that we can be sure of an unending supply is our own urine,” says Ieropoulos. “By harnessing this power as urine passes through a cascade of microbial fuel cells, we have managed to charge a Samsung mobile phone. The beauty of this fuel source is that we are not relying on the erratic nature of the wind or the sun; we are actually reusing waste to create energy.”

He went on to say that, “So far the microbial fuel power stack that we have developed generates enough power to enable SMS messaging, web browsing and to make a brief phone call. Making a call on a mobile phone takes up the most energy but we will get to the place where we can charge a battery for longer periods. The concept has been tested and it works – it's now for us to develop and refine the process so that we can develop MFCs to fully charge a battery.”

The results of the research were published in the Journal of Physical Chemistry Chemical Physics.

The video below explains how the urine-powered fuel cell works.

Source: UWE Bristol