Natural gas powers the four-fuel-cell system, each cell capable of producing 200 kilowatts of electricity.

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Also a type of electric vehicle, a fuel-cell car takes hydrogen gas and converts it into electricity, while emitting only water vapor.

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Some even dream of using natural gas to make hydrogen which would power fuel-cell cars, though advocates admit that these are still a long way off.

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It is powered by a hydrogen fuel-cell engine, which converts hydrogen gas into energy.

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Earlier this week, Honda produced the first commercial hydrogen fuel-cell vehicles, which will rely on natural gas-derived hydrogen for fuel and will be leased for use in Los Angeles.

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Little, a consultancy that has investigated the matter, the running costs to a driver of a fuel-cell car that gets its hydrogen from natural gas would be comparable to those of one that used clean petrol.

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So, a hydrogen fuel-cell car even running ... on hydrogen derived from natural gas cuts that carbon emission by 60%.

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