The concept of powering a car on waste products has been around for a while, and indeed it's an idea that's very attractive for a sustainable fuel future. Why let waste go to waste?

Scientists have already explored methane power harnessed by the gases that escape from good old "number twos", but how about a better idea? A 'number one' idea, if you like...

Well, a firm in Athens, Ohio and students at Ohio University have been exploring ways to produce clean energy from human urine and to prove their technology works the team has constructed a small car powered by pee.

Most of what you find in your average number one really is waste as far as the experiment is concerned, as 99 percent is water and therefore not an obvious power source. The other percent is where the interest lies. Urea contains a lot of hydrogen, and extracting this can provide the power.

E-3 Technologies, the Athens-based firm, is developing the technology as its 'green box'. There are several methods by which urea could be collected, such as small units in public toilets and workplaces, or larger collectors working at wastewater treatment plants.

While the technology won't let you pee in your gas tank just yet, the idea of using waste to produce energy is certainly one we're keeping an eye on.

[40 29 TV, image by flickr user Koffiemetkoek]