American coal generation plunged to a 44-year low in 2019, as utilities closed plants and temporarily shut down others. Power sector carbon dioxide emissions fell 10% as a result, one of the largest annual declines ever.
And yet for all the industry's woes, coal plants remained the largest individual sources of CO2 in America. Even as many plants struggled, big utilities continued to churn out electricity and pump carbon dioxide into the atmosphere.
Collectively, coal plants are running less than ever before. Their usage rate nationwide fell below 50% for the first time in 2019, according to the Department of Energy.
But many of the country's largest plants continued to run more than half the year. Those are the plants that tend to be found on this list: the top 10 largest carbon emitters in America.
Together, these plants generated 152 million metric tons of carbon dioxide last year, or almost 9% of U.S. power sector emissions. That's the amount of greenhouse gases that would be created by 33 million cars over a year.
"The transition is clearly underway, and yet there is still a lot of ground to cover," said Julie McNamara, who tracks the power sector at the Union of Concerned Scientists. "The churn of switching from a coal-dominated system is not playing out evenly."
The top 10 list is telling in several ways. First, it represents a measure of economic health. Just one plant on this list is scheduled for retirement over the next decade, and it's a partial shutdown. There is also only one plant with a usage rate below 50%, the threshold below which coal plants tend to face economic difficulty.
America's top emitters tend to be relatively young coal plants. Most were built in the 1970s and '80s, noted Emily Grubert, a professor who studies the power sector at the Georgia Institute of Technology.
As large plants, they tend to benefit from economies of scale that have helped them weather a challenging power market in recent years. Perhaps ironically, they may have benefited from environmental regulations instituted during the Obama administration, when utilities spent millions of dollars to install controls to address mercury and other air pollutants.
Utilities may be loath to turn off those plants until their investments are paid off, Grubert said.
"It is a cautionary tale of what happens when you use side channels to get to climate [policy]," she said.
Costa Samaras, a professor who studies the power sector at Carnegie Mellon University, noted that emissions from power plants have trended down in recent decades. But continued emissions from large coal plants represent a long-term challenge for U.S. climate policy. America's top emitters in 2019 are still running much of the time, despite record-low natural gas prices and stiff competition from renewables, he said.
Pointing to Oak Grove, a recently built Texas coal plant and the 10th-largest emitter last year, he asked, "When will that plant generate its last megawatt-hour? 2050? 2060?"
Now for the list. Each heading includes several characteristics of each plant, beginning with their emissions rank compared with other coal facilities in the U.S. Then comes the plant's owner, the location of the facility, its emissions in 2019, followed by its emissions over the last decade. We also include the plant's capacity factor, or the amount of time it ran in 2019.
James H. Miller Jr. Electric Generating Plant
Owner: Southern Co.
Emissions in 2019: 20,965,151 metric tons
Emissions 2009-19: 241,244,075
Capacity factor in 2019: 76%
James H. Miller Jr. has been the top carbon dioxide emitter in the U.S. since 2015, when it took the title from its fellow Southern electricity generator, Plant Scherer. As coal plants around the country struggle, Miller has not posted a usage rate worse than 73% in the last five years. Southern shows no signs of closing the plant down, despite a pledge to achieve "no to low" carbon emissions by midcentury. The Atlanta-based utility told E&E News last year it would run its large coal plants as long as they remain economic (Climatewire, Sept. 25, 2019).
Monroe Power Plant
Owner: DTE Energy Co.
Emissions in 2019: 16,599,356 metric tons
Emissions 2009-19: 190,135,174
Capacity factor in 2019: 57%
DTE has embarked on a plan to overhaul its power plant fleet by retiring its coal units in favor of natural gas and renewables (Climatewire, Oct. 26, 2018).
Except for one.
Monroe is the lone DTE coal plant not destined for the scrap heap. Michigan regulators recently approved a plan to keep the facility open until 2040. In 2019, Monroe accounted for 39% of DTE's power generation and about half of its CO2 emissions.
Colstrip Steam Electric Station
Owners: Talen Energy, Puget Sound Energy, PacifiCorp, Northwestern Energy, Avista Corp.
Emissions in 2019: 15,617,378 metric tons
Emissions 2009-19: 174,309,520
Capacity factor in 2019: 73%
Colstrip is the star of a Western soap opera about the future of the region's power grid. The plant has long sent electricity to consumers in the Pacific Northwest, but utilities there now want to cut ties as lawmakers in Washington state and Oregon seek to phase down the use of coal and reduce emissions. The local Montana utility, Northwestern Energy, is attempting to buy their stake while the plant's operator, Talen Energy, has signaled that it's open to replacing its colleagues from the Pacific Northwest.
In the meantime, two of Colstrip's four units closed this year as part of a settlement with environmental groups. Those units represented 27% of Colstrip's emissions last year. So this might be the last time Colstrip makes the top 10 list, but it is likely to remain a significant emitter for at least several years.
Labadie Energy Center
Owner: Ameren Corp.
Emissions in 2019: 15,508,284 metric tons
Emissions 2009-19: 183,372,871
Capacity factor in 2019: 68%
Ameren has committed to cutting emissions 80% of 2005 levels by 2050. But like many utilities with climate goals on this list, Ameren does not plan to retire its largest emitter for decades to come. Two of Labadie's four units will close in 2036, according to the utility's most recent integrated resource plan. The two remaining units are slated to be shut down in 2042. Labadie represented 58% of Ameren's emissions last year.
Owners: Oglethorpe Power Corp.; Southern; NextEra Energy Inc.; JEA; Municipal Electric Authority of Georgia; city of Dalton, Ga.
Emissions in 2019: 15,053,635 metric tons
Emissions 2009-19: 233,913,974
Capacity factor in 2019: 40%
Plant Scherer may be the most economically challenged plant in the top 10. Its usage has steadily declined since 2014, and it only ran 40% of the time in 2019. But Plant Scherer is the largest coal plant in America, with a net summer capacity of 3,440 megawatts. So even at 40%, it still generates a lot of power and produces tons of CO2.
Gen. James M. Gavin Power Plant
Owner: Lightstone Generation LLC
Emissions in 2019: 14,258,008 metric tons
Emissions 2009-19: 184,010,725
Capacity factor in 2019: 59%
American Electric Power Co. sold Gavin to two private equity firms behind Lightstone Generation in 2016. The plant has been relatively competitive in PJM Interconnection LLC, the gas-saturated power market stretching from Maryland to Illinois. Its usage rose from 59% in 2016 to 67% and 68% in 2017 and 2018, respectively. It fell to 59% last year.
Gavin is the first merchant power generator on this list. Its higher-ranked counterparts are operated by regulated monopolies, which offer a degree of insulation from market pressures. Merchant plants like Gavin are more susceptible to changes in market conditions.
Martin Lake Power Plant
Owners: Vistra Energy Corp.
Emissions in 2019: 13,898,033 metric tons
Emissions 2009-19: 182,496,723
Capacity factor in 2019: 58%
Martin Lake has survived Texas' historically low natural gas prices and a large injection of wind in recent years, both of which are positive signs for the plant's future. The Electric Reliability Council of Texas, the grid operator serving much of Texas, has slim reserve margins after Vistra Energy closed three large coal plants in the state. But with a lot of wind and solar in the Texas pipeline, the electricity market remains difficult to predict.
Prairie State Energy Campus
Owners: Nine public power authorities across eight Midwestern states have a stake in Prairie State.
Emissions in 2019: 13,859,542 metric tons
Emissions 2009-19: 86,050,027
Capacity factor in 2019: 85%
Prairie State is the newest plant on this list, having rumbled online in 2012. The plant experienced a difficult start to life, including questions over its construction costs and an accident that damaged one of its units in 2014. But its usage has climbed steadily in the years since. And as Prairie State's usage has risen, so, too, has its CO2 emissions.
In 2014, it emitted roughly 9.8 million tons. Last year, its emissions were almost 13.9 million.
W.A. Parish Generating Station
Owner: NRG Energy Inc.
Emissions in 2019: 13,611,580
Emissions 2009-19: 184,413,104
Capacity factor in 2019: 65%
W.A. Parish is the largest coal plant west of the Mississippi River. It is perhaps best known as home to the Petra Nova carbon capture and sequestration project, which captures 90% of emissions off a 240-MW slipstream. Still, Petra Nova only covers part of the emissions for one of Parish's eight units. The plant's four coal and four gas units make it one of the largest emitters in America.
Oak Grove Power Plant
Owner: Vistra Energy Corp.
Emissions in 2019: 13,495,543 metric tons
Emissions 2009-19: 129,888,551
Capacity factor in 2019: 85%
Gas prices spiked in the first decade of the 21st century, prompting the last wave of coal plant construction in the United States. Prairie State was one of the last big coal plants to come online. Oak Grove was another. Its two units rumbled to life in 2010 and 2011. At 1,665 MW, it's smaller than its counterparts on this list. But it ran more than 80% of the year between 2015 and 2019, which accounts for its spot here.