Emissions from Coal

From a National Environmental Trust report on "Sources of Greenhouse Gases in the United States":

Coal accounts for about half of electricity generation in terms of kilowatt hours, but 83% of carbon dioxide emissions from the electricity sector, the largest piece of the pie in terms of U.S. greenhouse gas emissions.

Natural gas, in contrast, generates nearly 20% of the country’s electricity but is responsible for 12% of emissions in this sector because it is a less carbon-intensive fuel.