The U.S. electric power sector has cut its carbon dioxide emissions by 32 percent compared to 2005, according to the latest report from the federal Energy Information Administration.
The shift away from a once-predominant coal-fired mix to natural gas and renewables lead to the carbon reduction. In 2019, according to the EIA, the U.S. electric power sector produced 1,724 million metric tons of CO2, compared with 2,544 MMmt 14 years earlier.
In 2005, coal account for 50 percent of U.S. generation capacity, while it was closer to 20 percent last year. Gas-fired power, meanwhile, rose from 19 percent to 38 percent in 2019.
PE covers all of the power generation portfolio
This long-term change may slow or reverse temporarily. The EIA earlier forecast that higher natural gas prices may lead to less gas-fired power and a rally in coal-fired generation this year, while renewables will grow its share into 2022.
When generating electricity, coal emits significantly more CO2 than natural gas, according to the EIA data. In 2019, coal-fired generation produced 2,257 pounds of CO2 per MWh of electricity. Natural gas-fired generation produced less than half that amount at 976 pounds of CO2/MWh.
The amount of CO2 produced when a fuel is burned depends on a fuel’s carbon content. Coal produces more CO2 per unit of energy than natural gas does when burned. Coal consumption for electricity generation produces 209 pounds of CO2 per million British thermal units (MMBtu), compared with 117 pounds of CO2/MMBtu for natural gas.
Natural gas-fired generators, especially those that operate in a combined-cycle configuration, are also more efficient than coal-fired generators. On average, natural gas-fired generators produce electricity with significantly less energy input than coal, also helping to lower CO2 emissions.
In 2019, the conversion efficiency for natural gas-fired generation was 7,731 Btu per kilowatthour (Btu/kWh) and 10,551 Btu/kWh for coal-fired generation.
The increased use of renewables has also reduced emissions from generating electricity in the United States. In 2005, 9% of the electricity generated in the United States came from renewable sources. The renewable share of generation rose to 18% in 2019, largely driven by growth in wind and solar generation.
Nuclear generation, a zero-emission energy source, made up about 20% of U.S. generation in both 2005 and 2019, according to the EIA.