The immense cost for cleaning up coal would be equivalent to building two nuclear power plants every year.

That finding comes from a report sponsored by the U.S. Department of Energy; the state's utilities reviewed it this week.

"Based on the findings of this report, it seems unlikely geologic carbon capture and storage is a viable option in North Carolina," said Progress Energy spokeswoman Dana Yeganian. "That doesn't mean that we are rejecting sequestration outright. It just means we would need to look at other options -- offshore, pipelines -- and the issues and costs associated with them to make it work here."

The report was prepared for Duke Energy, Progress Energy and others to identify underground geologic sites where carbon dioxide could be injected as a solution to global warming. Researchers concluded that the Carolinas lack the proper geology to trap the gas forever and would instead require hundreds of miles of pipelines to deliver the gas to Kentucky, West Virginia and offshore sites from Cape Hatteras to Georgia. Such a pipeline network could cost $4 billion to build.

Progress Energy and Duke Energy are responsible for most of the 77 million tons of carbon dioxide generated by power plants each year in the Carolinas. The odorless, nonflammable gas accounts for 60 percent of global warming emissions.

Carbon sequestration is in its infancy and at least a decade away from commercial application, experts say.

The bulk of the cost of carbon sequestration comes from the industrial process required to separate the gas from coal or from its emissions, and then to compress the gas into liquid form. According to some calculations, carbon sequestration would increase the cost of electricity from coal-fired power plants by as much as 80 percent. The impact could dramatically alter the economics of power in this state, where half the electricity comes from coal-fired plants.

Coal-fired power plants have become the focus of carbon sequestration efforts because they are the principal emitters, followed by automobiles, office buildings and residential homes. In recent decades, modern industry has devised technologies for trapping pollutants such as fly ash, mercury, sulphur and nitrogen oxides, leaving carbon dioxide as the remaining obstacle to turning coal into a clean fuel.

Some in the electric industry are making carbon sequestration the cornerstone of an energy policy dependent on coal. Duke Energy, one of the nation's top producers of carbon dioxide, is reviewing whether it will build a new coal-fired plant west of Charlotte that would emit about 5.5 million tons of carbon dioxide into the atmosphere every year.

"In the Carolinas and across the nation, we believe utility-scale carbon storage and capture technology for large base load power plants is expected to be available in 10 to 15 years," said Duke Energy spokeswoman Marilyn Lineberger.

Typically, capturing CO2 and compressing it into liquid form represent about 80 percent of the cost of carbon sequestration. Moving the CO2 liquid by pipeline and injecting it underground account for the remainder of the cost, said Howard Herzog, a principal research engineer at the Massachusetts Institute of Technology who studies carbon sequestration.

The study of CO2 sequestration potential in the Carolinas will be available at www.secarbon.org.

"Potential Sinks for Geologic Storage of Carbon Dioxide Generated in the Carolinas" was prepared for the Southern States Energy Board and Electric Power Research Institute on behalf of Duke Energy, Progress Energy and other utilities.

The executive summary can be accessed from the online version of this article at www.newsobserver.com.