BMW showed off a hydrogen-powered 7-series sedan at the 2008 SAE World Congress in Detroit that actually emits less carbon monoxide than are found in the air around it. This means the engine breaks down or converts the carbon monoxide it takes in. The emissions tests, run by Argonne Laboratories, also show a similar reduction in nonmethane organic gases. The vehicle's other emissions are all so low that standard automobile emissions testing wouldn't have detected them.
This particular demonstration vehicle uses a 6-liter combustion engine that uses hydrogen as fuel, burning it in the cylinders and, according to BMW, delivering performance on par with a standard gas-powered 7-series. Most hydrogen cars from other automakers use fuel cells to generate electricity. Currently, BMW has been handing its Hydrogen 7 sedan, a car with a dual-fuel hydrogen and gas system, over to various celebrities and decision influencers, such as J.D. Power III. But the new demonstration vehicle only uses hydrogen for fuel. BMW doesn't consider the car a prototype, and won't be building more on the same scale as the Hydrogen 7.