EIA report shows U.S. electric CO2 emissions decline as generation mix transitions from coal to natural gas

Published on June 11, 2021 by Chris Galford

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Although changing prices could alter the picture to come, the U.S. Energy Information Administration (EIA) reported this week that the electric power sector’s CO2 emissions have tumbled over the past 15 years as the generation mix has transitioned from coal to natural gas and renewables.

In 2005, coal made up 50 percent of U.S. electricity generation, but by 2019, it had dropped to less than half that — 23 percent. As coal waned, natural gas waxed, increasing from 19 percent of generation in 2005 to 38 percent in 2019. This, in particular, contributed to a large, 32 percent drop in emissions over the period. By 2019, the sector produced 1,724 million metric tons of CO2, compared to the 2,544 MMmt produced in 2005.

A side-by-side comparison in 2019 showed that coal-fired generation produced 2,257 pounds of CO2 per megawatt-hour (MWh), against the 976 pounds per MWh produced by natural gas.

While this has been good for the environment, in the short term, this trend could go the other way. The EIA’s most recent Short-Term Energy Outlooks report predicts higher natural gas prices, meaning more coal usage and less natural gas usage is likely this year.

Renewables usage is expected to continue climbing all the while. In 2005, this umbrella term of sources accounted for just 9 percent of total U.S. generation. In 2019, it rose to 18 percent, largely thanks to wind and solar growth. Nuclear generation, however, has remained consistent over the years, making up approximately 20 percent of U.S. generation in both 2005 and 2019.

The EIA called out the shift to natural gas being the most profound driver of CO2 emissions declines in the sector, though. Of the 819 million metric tons of CO2 emissions shed over the years, nearly 532 million metric tons (65 percent) could be attributed to the ascension of natural gas generation. Approximately 248 million metric tons (30 percent) could be attributed to the increase in renewable generation. The rest could be credited largely to decreased petroleum-fired generation.