WASHINGTON - For years, scientists have had a straightforward idea for taming global warming. They want to take the carbon dioxide that spews from coal-burning power plants and pump it back into the ground.
President Bush is for it, and has talked up the virtues of "clean coal." All three candidates to succeed him favor the approach. So do many other members of Congress. Coal companies are for it. Many environmentalists favor it.
But in January, the government canceled its support for what was supposed to be a showcase project, a plant at a carefully chosen site in Illinois where there was coal, access to the power grid, and soil underfoot that backers said could hold the carbon dioxide for eons.
Perhaps worse, in the last few months, utility projects in Florida, West Virginia, Ohio, Minnesota and Washington state that would have made it easier to capture carbon dioxide have all been canceled or thrown into regulatory limbo.
"It's a total mess," said Daniel M. Kammen, director of the Renewable and Appropriate Energy Laboratory at the University of California, Berkeley.
"Coal's had a tough year," said John Lavelle, head of a business at General Electric Co. that makes equipment for processing coal into a form from which carbon can be captured.
Many of these projects were derailed by the short-term pressure of rising construction costs. But scientists say the result could be a long-term disaster.
Plans to combat global warming generally assume that continued use of coal is unavoidable for at least several decades. Therefore, starting as early as 2020, forecasters assume that carbon dioxide emitted by new power plants will have to be captured and stored underground to cut down on global-warming gases in the atmosphere.
Yet considerable research is still needed to be certain the technique would be safe, effective and affordable.
Scientists need to figure out which kinds of rock and soil formations are best at absorbing carbon dioxide. They need to be sure the gas will not bubble back to the surface. They need to find optimal designs for new power plants so as to cut costs. And some complex legal questions need to be resolved, such as who would be liable if such a project polluted the groundwater or caused other damage far from the power plant.
Major corporations sense the possibility of a profitable new business, and GE signed a partnership Wednesday with Schlumberger Ltd., the Houston oil field services company, to advance the technology of carbon capture and sequestration.
But only a handful of small projects survive, and the recent cancellations mean that most of this work has come to a halt.
The highest-profile failure involved a project known as FutureGen, which Bush announced in 2003: a utility consortium was going to build a plant in Mattoon, Ill., testing the most advanced techniques for converting coal to a gas, capturing pollutants, and burning the gas for power. The carbon dioxide would have been compressed and pumped underground into deep soil layers.
In January the government pulled out after projected costs nearly doubled, to $1.8 billion. The government feared the costs would go even higher. A bipartisan effort is afoot on Capitol Hill to save FutureGen, but the project is on life support.
The government had to change its approach, said Clarence Albright Jr., Energy Department undersecretary, to "limit taxpayer exposure to the escalating cost."
The Energy Department is trying to cut a deal with a utility that is already planning a new power plant. The government would offer subsidies to add a segment to the plant dedicated to capturing and injecting carbon dioxide, as long as the utility bore much of the risk of cost overruns.
It is unclear whether any utility will agree to such a deal. The power companies, in fact, have been busy pulling back from coal-burning power plants of all types, amid rising costs and political pressure.