Apparently, it's cheaper and more efficient to extract the hydrogen from wee wee than water, making a hydrogen powered motor car more viable.
So, that's what Fletcher was doing when he wee'd into the petrol tank of the prison van in the Porridge movie

Just think how far you'd be able to go in your car after a night out on the old beer (waiting long enough to sober up, obviously!). At least it'll stop landlords piping it all straight back into the barrels in the cellar anyway.
Story here: http://www.rsc.org/chemistryworld/News/ ... 070902.asp