Edwardsport, a “capture-ready” Duke Energy coal plant, is scheduled to begin commercial operation this year. The plant, in Edwardsport, Ind., will cook coal into a fuel gas and could be retrofitted to capture carbon dioxide released in that conversion. But Duke, the builder, has no plan to capture the carbon dioxide and no place to sequester it for now. It is exempted from the new rule because construction began five years ago.

The plant cost nearly $3 billion to build, about $1 billion over budget, and carbon capture would cost $380 million, not counting storage.

Only two other major carbon capture projects are on the drawing boards in the United States. Neither is affected directly by low natural gas prices. But the ebbing interest in coal-fired construction may signal that even if the technology works well, there may be few commercial projects where it could be deployed.

One is FutureGen 2.0, a $1.6 billion plan to burn coal in oxygen, generating exhaust gas that is pure carbon dioxide, and pumping it into geologic formations thousands of feet below the earth’s surface.

The Recovery Act of 2009 is covering $1 billion of the cost of the project, which is in Meredosia, Ill. But the project, originally expected to be running by 2015, has run into a variety of bureaucratic problems and is now scheduled to be in service in 2017, barring further delays. An earlier version, FutureGen, was rejected by the Energy Department in 2008 to save money.

The other venture is the Southern Company’s Kemper County project in Mississippi, which will turn coal into a cleaner gas and use it to power a turbine. The captured carbon dioxide is expected to be sold and travel through a pipeline to Texas, where it will be pumped under ground to force oil out of old oil fields, a process known as enhanced oil recovery.