http://en.wikipedia.org/wiki/Hydrogen_fuel
So, first we make ze methane, zen we process into hydrogen, zen we sell it, we put it in ze car/plane and zoom, we all drives/flies round luvvely jubbley and all we make is ze oxygen and ze water.. is simples yes?
And for ze local itty bitty car for the short drive we fill up wiz ze methane at ze local garage, where we make ze methane out of ze rubbish we throws away yes?
And ze poo we poo down ze lav yes? And zen we get ze lovely clean water out of ze biodigester, and we puts it through ze reed bed into the canal system yes, and all the lovelly jubbly boats get to go catching ze fish in ze canal, and ze heavy traffic off ze road, because we use ze waterways instead yes? Then we digs up some of ze tarmacs in ze towns, so we gets our parks back for ze birdies and ze nice picnics?