U.S. power plant fleet emissions have declined for the third year in a row in 2017, according to an S&P Global Market Intelligence analysis of the U.S. Environmental Protection Agency's Continuous Emissions Monitoring System, or CEMS, data.
Carbon dioxide, or CO2, emissions were down 3.9% year over year, at 1.92 billion tons in 2017, while nitrogen oxide, or NOx, emissions were 11.7% lower over the same period, at 2.17 billion pounds.
CO2 and NOx are products of fossil fuel combustion that, among other sources, contribute to the potential for global warming by trapping heat in the atmosphere. Due to differences in reporting methodology among companies, unit-level information was used to extrapolate owner-level emissions data.
The steady declines in emissions are in line with the annual findings of the International Energy Agency, or IEA, which contrasted the decrease in U.S. emissions with a global growth in 2017. According to the IEA, shrinking electricity demand and more production from renewable energy resources were the main drivers of decreased CO2 emissions in the U.S.
Emissions reductions occurred despite the U.S. Supreme Court's stay in February 2016 of the proposed Clean Power Plan, after critics of the rule argued that the EPA overstepped its jurisdiction by allowing states to require actions outside the fence line of power plants subject to the regulation. The EPA on Aug. 21 unveiled a scaled-back replacement, called the Affordable Clean Energy, or ACE, rule, which would give states wide leeway in regulating their own CO2 emissions.
Emissions by company
The 10 companies with the largest CO2 and NOx emissions in 2017 accounted for a little over 40.3% of the total U.S. emissions. Nine of the 10 companies with the largest amount of CO2 emissions were also the largest emitters of NOx in 2017.
Vistra Energy Corp. led the list of both CO2 and NOx emitters in 2017, emitting 156.3 million tons of CO2, or 8.2% of the U.S. total, and 154.1 million lbs of NOx, or 7.1% of the total. That result might be different for 2018 as Vistra in early 2018 retired nearly 4,400 MW of coal-fired generating capacity, all in Texas. The company currently owns approximately 14,358 MW of nameplate coal capacity.
Duke Energy Corp. accounted for the second-largest emissions in both cases at about 105.1 million tons of CO2, or 5.5% of the total, and 124.3 million lbs of NOx, or 5.7% of the total. Duke Energy owns roughly 18,822 MW of coal-fired generating capacity, but in a March 22 report outlined its goal of curbing CO2 emissions by 72% by 2050 against 2010 levels by eliminating all existing coal generation.
Southern Co. had the third-largest amount of CO2 emissions, about 105.0 million tons, also about 5.5% of the total, but the fifth-largest amount of NOx emissions, at about 81.1 million lbs. Southern Co. owns nearly 14,938 MW of coal-fired generation capacity, and on April 9 announced that it will transition its entire power generation fleet to low- and no-carbon technologies by 2050.
American Electric Power Co. Inc. emitted 109.7 million lbs of NOx, or 5.1% of the total, and 82.1 million tons of CO2, coming in the third spot in terms of NOx emissions but in fourth place in terms of CO2 emissions. The company currently owns about 15,440 MW of coal-fired generating capacity, and on Feb. 6 unveiled plans to reduce emissions from its power plants by 80% by 2050, cutting CO2 emissions to 33 million metric tons from 167 million metric tons in 2000, through increased natural gas generation, as well as heavy investments in renewable generation and advanced technologies, among others.
Under the new ACE rule, the EPA has proposed to define the "best system of emissions reduction" for existing coal-fired power plants as on-site, heat-rate efficiency improvements. EPA Acting Administrator Andrew Wheeler said the ACE rule would only require changes within the fence line of existing power plants, and not force an accelerated shift to renewables.
Although the plan's ultimate impact on emissions is unclear, Moody's Investors Service vice president Toby Shea said that "economics — not regulation — will continue to be the primary driver of coal plant shutdowns."
About 23,700 MW of U.S. coal-fired capacity is slated for retirement through 2032, and plant operators in their initial reactions to the new emissions rule maintained their retirement timelines.
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