<Li> Coal: 13,787 </Li> <P> Coal - fired electric power generation emits around 2,000 pounds (900 kg) of carbon dioxide for every megawatt - hour (MWh) generated, which is almost double the carbon dioxide released by natural gas - fired generation . Because of this higher carbon efficiency of natural gas generation, as the fuel mix in the United States has changed to reduce coal and increase natural gas generation, carbon dioxide emissions have unexpectedly fallen . Those measured in the first quarter of 2012 were the lowest of any recorded for the first quarter of any year since 1992 . </P> <P> Combined cycle power generation using natural gas is currently the cleanest available source of power using hydrocarbon fuels, and this technology is widely and increasingly used as natural gas can be obtained at increasingly reasonable costs . Fuel cell technology may eventually provide cleaner options for converting natural gas into electricity, but as yet it is not price - competitive . Locally produced electricity and heat using natural gas powered Combined Heat and Power plant (CHP or Cogeneration plant) is considered energy efficient and a rapid way to cut carbon emissions . </P> <P> Natural gas generated power has increased from 740 TWh in 1973 to 5140 TWh in 2014, generating 22% of the worlds total electricity . Approximately half as much as generated with coal . Efforts around the world to reduce the use of coal has led some regions to switch to natural gas . </P>

Where does natural gas come from in the united states