A car that runs on methane gas produced by human waste has been launched and its makers claim drivers cannot tell the difference. The Bio-Bug has been converted by a team of British engineers to be powered by biogas, which is produced from human waste at sewage works across the country. Excrement flushed down the lavatories of just 70 homes is enough to power the car for 10,000 miles - the equivalent of one average motoring year.