A greener car, powered by ...a steam engine? That's the hope of Glynne Bowsher and his compatriots at the British Steam Car Challenge as they develop a vehicle which uses an external combustion engine, not an internal-combustion one, in order to reduce emissions (mostly NOx, with some CO2 benefit). Their engine uses the same principles as the great steam-engines of yore, but with modern technology and propane fuel instead of coal or wood.
It may sound wacky, but these are no amateurs here: Bowsher was 'Mechanical Designer of Richard Noble's ThrustSSC, the current holder of the absolute World Land Speed Record and the first car to break the sound barrier on land." The BBC had a thorough article (with pictures) on the project a week ago. I can't say I'm hugely optimistic about the car's potential, but it's good that people are exploring every possible avenue.