The U.S. Environmental Protection Agency (EPA) is expected to impose a limit on greenhouse gas emissions from new power plants, a strict new regulation that could prevent conventional coal-fired power plants from being built. In new rules to be announced as soon as Tuesday, the EPA will require that new power plants generate no more than 1,000 pounds of carbon dioxide per megawatt of electricity produced. While the typical natural gas plant — which emits 800 to 859 pounds of CO2 per megawatt — would meet the new requirement, coal plants, with an average of 1,768 pounds of CO2 per megawatt, would fail to meet the standard, according to the Washington Post. The rules would exempt coal plants that are already permitted and scheduled to begin construction within a year. About 20 additional projects are seeking permits, two of which would meet the new standard because they would employ pollution control technologies. Michael Brune, executive director of the Sierra Club, hailed the rule, saying the it marked the “end of an era” during which coal has provided about 40 percent of U.S. electricity.