CORRECTION

This article originally stated that Duke Energy releases 40 tons of carbon dioxide in the Carolinas each year. The correct figure is 40 million tons.

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Duke Energy is set to begin construction today on the state's first new coal-burning power plant in a quarter century, even as opponents consider new strategies to block the project.

State environmental regulators Tuesday cleared the way for the electric utility to begin construction on the $2.4 billion Cliffside power plant in the Appalachian foothills, about 50 miles west of Charlotte.

In what officials say is the nation's first attempt to regulate a utility's carbon dioxide emissions, the state air permit will require Duke Energy to reduce greenhouse gas emissions by shutting down its oldest and dirtiest coal-burning power plants. Some date to the 1920s.

Coal plants are a leading source of carbon dioxide, the gas that is thought to be contributing to the planet's rising temperature.

The air permit issued by the state's Division of Air Quality blindsided environmental organizers, who had vowed to keep fighting Cliffside until Duke Energy suffered a financial setback or bowed to public pressure and cancelled the project.

"This final permit is just so different from what we were expecting," said Gudrun Thompson, a lawyer in Chapel Hill with the Southern Environmental Law Center, an advocacy group that is fighting Cliffside with nine other environmental organizations.

"We had been operating on the assumption that the final permit would be similar to the draft permit, and there are some important differences," Thompson said.

What's next?

The environmental organizations are regrouping to assess whether a legal challenge is still feasible. They have 60 days to appeal the Division of Air Quality's ruling.

The draft air permit had been issued in August and was subject to hundreds of comments from the public, interest groups and government agencies. The National Park Service warned that Cliffside would harm air quality and visibility at the Great Smoky Mountains National Park.

Even if one legal avenue is cut off, activists vow to continue to stage protests and conduct civil disobedience.

"It's not over," said Jim Warren, director of N.C. Waste Awareness and Reduction Network, a Durham group that has run full-page newspapers ads urging Duke Energy to scrap the coal plant. "There will be a variety of opposition tactics -- some of it will be legal, some of it's going to be public demonstrations."

The Division of Air Quality's director, Keith Overcash, said Duke Energy's proposed Cliffside power-generating plant will have "state of the art [pollution] controls" and is "almost as efficient as you can get for any coal-burning operation."

Duke Energy, which is based in Charlotte, expects construction to take about four years and require 1,600 workers.

Cliffside would have an output capacity of 800 megawatts and would emit about 6 million tons of carbon dioxide a year, equivalent to about 1 million automobiles. Duke Energy agreed to shut down older coal-burning power plants with a total combined capacity of 1,000 megawatts by 2018.

Mothballing the aging coal plants would offset about two-thirds of Cliffside's greenhouse gas emissions. Duke Energy would make up for the rest of the carbon dioxide by operating planned nuclear plants that would emit no greenhouse gases and would allow the company to idle other coal-burning power plants.

The goal is to make Cliffside "carbon neutral" by keeping the company's total carbon dioxide output flat. Duke Energy's operations in the Carolinas release about 40 tons of carbon dioxide into the atmosphere every year.

Closing old plants

Duke Energy had previously planned to close the older power plants, but now the utility has committed to a schedule and agreed to monitoring of emissions, Overcash said.

"They are canceling out the emissions from the new unit by shutting down the old units," Overcash said.

Duke Energy, which has seen the project's cost double in the past year, is eager to begin the project before costs for labor and equipment rise again.

The utility has 2.3 million customers in the Carolinas, a region that is growing by about 50,000 new customers each year. The company also has applied to build new nuclear reactors and natural gas power plants to meet growing energy demand. And the utility is exploring renewable sources such as solar power and conservation programs as part of its energy mix.

But environmental activists fear that a major coal-burning plant will stymie the development of energy alternatives.

"It will commit us to a carbon-intensive future," said Stephen Smith, director of the Southern Alliance for Clean Energy. "This is very much a battle over public opinion."