Fuel cells vs cleaner petrol engines: weighing up the pros and cons

Fuel cells have been put forward as the solution to poor air quality and global warming - but conventional petrol engines are also poised for a significant clean-up. One recent life-cycle study found that, on greenhouse gas emissions, some fuel cell systems would perform scarcely any better than advanced petrol engines.Using electricity from the standard generating mix would produce even more CO₂ than reforming. But using electricity from renewable sources opens the door to a carbon-free source of hydrogen and breaks the link with hydrocarbons.Germany's Federal Environment Agency has evaluated "well-to-wheel" emissions from fuel cell vehicles running on hydrogen from different sources - on-board reforming of methanol; direct hydrogen from steam reforming of natural gas; and direct hydrogen from renewables. It compared them with the performance of a conventional internal combustion engine and an ultra-low emission vehicle (ULEV) meeting the stringent Euro 4 emission limits which will be in force in 2005. ¹