DETROIT (AP) Fuel cell technology is "the holy grail the breakthrough" if it works, GM president and CEO Rick Wagoner told an industry conference.

But even with the partnership announced last week between the federal government and automakers to develop them, it could be a long time before drivers are able to trade in gas guzzlers for hydrogen breathers.

Fuel cells, first used by NASA in the space program, create electricity through a chemical reaction between hydrogen and oxygen. If pure hydrogen is used as a fuel, the only emission is water vapor.

However, hydrogen is an extremely flammable gas, requiring heavy tanks that can withstand collisions. The industry is working to develop lighter tanks that also are crash-worthy.

The alternative to hydrogen is more easily available fuels, such as gasoline, methanol, propane or natural gas. But using those fuels requires an extra piece of equipment called a reformer to extract hydrogen from them, adding heat, cost and weight. The vehicles produce some polluting emissions, although to a lesser extent than internal combustion engines.

The other major challenge to what automakers call "a hydrogen society" is a lack of a refueling infrastructure, or hydrogen filling stations.

One of the goals of the partnership announced at the North American International Auto Show last week, called Freedom CAR, is to develop such an infrastructure.