Dr. Ioannis Ieropoulos of the Bristol Robotics Laboratory has specialised in producing electricity from the most unlikely of sources using microbial fuel cells (MFCs). Now he's taken that to the next level, managing to harness power from pee - definitely one of the more unlikely places you'd look for electricity.
The Microbial Fuel Cell uses microorganisms to turn organic matter into electricity. The microbes placed onto these cells produce electricity as a by-product of their life cycle, so the more urine they eat, the more electricity they create for longer periods of time.
The actual output is small at the moment, and they've only been able to accumulate low levels for shot periods of time; but this is the first time they've been able to directly charge a phone battery with it, making for a breakthrough.
"Using the ultimate waste product as a source of power to produce electricity is about as eco as it gets." Dr. Ieropoulos commented. “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."
While he imagines a future where urine will be used to power our homes, I can see a more immediate use in developing countries. If there's already a pee-powered generator, why not power other devices instead!
Source: Bristol Robotics Laboratory