A national environmental group is proposing a plan to reduce carbon pollution from power plants across the country.The Natural Resources Defense Council’s proposalis one the group says the federal government could implement under the existing Clean Air Act—and thus, wouldn’t need Congressional action. It advocates for reducing carbon dioxide emissions from existing power plants.Right now, these existing power plants are already subjected to a number of new regulations—like upcoming limits on mercury and other toxic pollutants. New power plants will have to comply with carbon limits, but there aren’t any limits on carbon from existing plants.The NRDCis touting its plan as flexible. Director of Climate and Clean Air Dan Lashof says the plan would set different target rates for different states.“States which currently rely heavily on coal will not have to meet the same target emissions rates in 2020 or 2025 as states that have a cleaner generation mix at the beginning,” he said, though noted those states would have to get their emissions closer to the cleaner states over that period.Lashof says coal technology like carbon capture and sequestration could be one way some states comply with the hypothetical proposal.“Our analysis suggests that there would be some role for it,” he said. “It doesn’t play a major role in our case, mainly because energy efficiency is cheaper.”The reductions could also be achieved by earning credits for renewable energy or energy efficiency programs.The NRDC estimates the cost to comply with the plan will be $4 billion in 2020, but it will provide anywhere from $25 to $60 billion in benefits.