For years, the term "clean coal" seemed to be an oxymoron. America's most-plentiful fossil fuel was plagued with air pollution problems, in recent years made more difficult by tighter air quality standards. Devices to clean power plant exhaust, called scrubbers, have been used for decades, but lingering air pollution issues associated with coal have seen the power industry favoring natural gas.

Now, however, a combination of rising costs for other sources of energy and new, advanced technologies might result in a brighter future for coal.

Burning coal has been undeniably dirty, despite the ability of scrubbers to remove most of the pollutants from power-plant exhaust. A new concept, called coal gasification, solves air pollution issues by extracting the coal's energy in the form of synthetic gas.

An advanced form of coal gasification uses steam to clean the coal and remove pollutants. Then, the clean gas is burned in a turbine to produce electricity and the hot exhaust is used in a secondary process to boil water to power steam turbines that also make electricity. This "combine cycle" not only utilizes clean coal, but also maximizes the efficiency of the process by adding the secondary generation feature.

To further reduce air pollution associated with coal, the carbon dioxide produced in this process is captured and essentially recycled by injection into oil wells to help coax more oil from existing wells. The captured carbon dioxide also can be used in a similar fashion in coal seams to push more usable methane gas.

The changing economics of the global energy markets is likely to encourage and accelerate more clean coal development. Coal is abundant in several regions of the United States (some estimates suggest a 200-year supply), but its pollution byproducts have long been a problem - and seemed to doom coal to a shrinking role in the future.

Despite the fact that coal-fired power plants produce 52 percent of America's electricity, natural gas has in recent decades been the preferred fuel for power plants. Another option, nuclear energy, is only now emerging from the setbacks associated with Three Mile Island. But due to lingering waste storage issues and public memories of past plant failures, its future remains unclear.

Coal, however, is benefiting from not only the latest gasification technologies, but also the recent run-up in the price of both oil and natural gas. Some energy experts are beginning to see coal as the fossil fuel of the future for the United States. Some of the expanding price advantages of coal can be used to pay for the more-expensive gasification process.

Two coal gasification plants are planned by American Electric Power Co. (AEP) for sites along the Ohio River. If these new power plants live up to expectations in terms of technology and efficiency, they could usher in a new age for coal. If coal gasification works as demonstration projects suggest it will, and if prices of competing fuels such as petroleum and natural gas remain high, there could be a renewed interest in expanding the mining of U.S. coal reserves - sometimes described as America's Middle East in terms of energy potential.

This could be particularly good news for the eastern United States, where higher-sulfur coal had lost ground to low-sulfur coal from western states, due to stricter environmental regulations. The gasification technology would allow hydrogen to be extracted and burned to make the steam that powers turbines and generators. Michael Morris, chairman and chief executive officer of AEP, talked to BusinessWeek magazine about his company's planned coal gasification plants, saying, "These facilities would be as clean as gas-fired generators from the get-go, no matter how impure or sulfurous the coal is."

After decades as the ugly stepsister to natural-gas and petroleum-fired power plants, it's encouraging to see the new potential for coal to provide clean power from plentiful and domestically available resources.

Longer-term, renewable energy sources must play a greater role in the U.S., but until then, coal's future looks bright.

- J.L.W.III