Today's coal-burning power plants are among the dirtiest sources of fossil fuel power. Gasification power plants-huge pressure cookers that convert coal into a stew of superheated gases that power a turbine-release fewer pollutants than conventional coal plants but still emit vast amounts of carbon dioxide, the leading cause of global warming. Research on cheap carbon dioxide removal, though, is gathering steam-and could make coal gasification a nearly zero-emission fossil fuel power source.

Research funded by the U.S. Department of Energy and a consortium of  companies, including ChevronTexaco, British Petroleum (BP), and Royal Dutch/Shell, is yielding one of the most promising methods for improving coal gasification: metal-ceramic membranes that  only allow hydrogen to pass through, effectively trapping carbon dioxide. The compressed carbon dioxide gas can then be piped off to underground repositories or other permanent storage sites.

Anthony Sammells, president of Eltron Research-the Boulder, CO, company that developed the technology-says the membranes are 10 times more efficient than competing experimental membranes. That means the membranes approach the efficiency levels needed for commercialization of the technology, says Gary J. Stiegel, the gasification technologies program manager at the Department of Energy's National Energy Technology Lab in Pittsburgh. By September 2004, Eltron Research hopes to move its membrane testing from lab-scale devices to pilot-scale reactors.

If the tests succeed, coal gasification plants could emerge as the cheapest ultralow-emission fossil fuel power plants, trouncing oil or gas plants that use scrubbers and pressurizers to remove carbon dioxide, says Cliff Lowe, an engineer with ChevronTexaco in Richmond, CA.