LARAMIE, Wyo. -- Coal is an important part of developing hydrogen as a fuel source, but progress must be made in capturing and storing the greenhouse gases that occur in making hydrogen from coal, speakers at an energy conference said Wednesday.

Hydrogen is a clean burning fuel that can be produced from coal, water, natural gas and biomass. Proponents of using hydrogen as fuel say it can help address climate change and U.S. energy security.

Carl Bauer, director of the U.S. Energy Department's National Energy Technology Laboratory, said hydrogen has been taken for granted and is beginning to be recognized as a solution to climate change.

Gov. Dave Freudenthal, who addressed the conference on Wednesday, welcomed the development of hydrogen as one of many sources of energy that will be needed to meet the growing demands for power.

''What I wanted to emphasize to them was that clearly, this question about a hydrogen economy is both intriguing and important but that, fundamentally, we need to rethink our approach to energy and look toward a diverse set of technologies and a diverse set of strategies,'' Freudenthal said later Wednesday.

The United States has the largest estimated recoverable reserves of coal in the world, and Wyoming, with its massive coal deposits in the Powder River Basin, is the leading coal producing state in the nation.

Hydrogen is not yet produced commercially from coal, but Bauer and other speakers at this week's hydrogen conference said coal is the most reliable, cheap and plentiful source for hydrogen production now.

There is plenty of water available, but it takes huge amounts of electricity to make hydrogen from water, Bauer said. Other sources of electric generation, such as wind and solar, are not as reliable and as cheap as coal, he said.

''We want the hydrogen from some source that is economically viable so that we can use it to a higher value application of the energy someplace else,'' Bauer said.

Hydrogen can be produced from coal through gasification, which also produces carbon dioxide, a major greenhouse gas. Research is being done to find an economical way to capture and store carbon dioxide on a commercial-size scale.

As concerns grow about a warming world climate, advocates of hydrogen point to its zero emissions when used to power vehicles.

If hydrogen can be produced from coal with little pollution, hydrogen could then be used to supplant gasoline, which is another source of carbon dioxide pollution when used to power engines.

But speakers at the conference sponsored by the University of Wyoming in association with the Mountain States Hydrogen Business Council acknowledged that hydrogen faces many challenges, including developing it into affordable and reliable fuel for vehicles and battling misinformation about its safety.