By Tom W.

I think you should invent a car that runs on frozen blocks of liquid Nitrogen. You could make it from one Hidrogen atom, one Nitrogen atom and three Oxigen atoms at -210 degrees celsious. It would be incredibly green as Hidrogen, Oxigen and Nitrogen are all natural gasses. It evapourates at 20 degrees celsious and can be pressurized to commence propulsion when a gap to the exhaust pipe is opened.