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Coal Production & Mining

Wyoming remains the most prolific coal-producing state in the nation, producing 304 million short tons (MT) in 2018, a decrease of 4 percent from the 316 MT produced in 2017. Annually, Wyoming’s coal mines account for 40 percent of all U.S. coal production. Wyoming’s large surface coal mines are the most efficient in the nation, with an average recovery factor of 92 percent (DOE-EIA, 2015). Statewide, the average production of coal per employee is 25.7 short tons per hour. This is the highest productivity in the nation and more than double the productivity of the next top coal-producing state.

Between 1865 and January 1, 2019, more than 11.9 billion short tons of coal had been mined in Wyoming, most of it in the last 20 years. The highest coal production year for Wyoming was 2008, with 466.3 MT mined.

Sixteen coal mines are in operation in Wyoming, located in three counties: Campbell, Lincoln, and Sweetwater. The majority of the coal, however, is produced from 11 mines in Campbell County. Fifteen of the mines extract coal through surface mining techniques, and one underground mine operates in Sweetwater County.

The table below shows Wyoming coal production in short tons, by county, and by method of mining for 2018 (Source: Wyoming State Inspector of Mines, 2019).

County	2018 production	Underground mine	Surface mine	Total mines
Campbell	293,462,565	-	293,462,565	12
Lincoln	4,016,923	-	4,016,923	1
Sweetwater	6,708,114	2,210,433	4,497,681	3
Total	304,187,602	2,210,433	301,977,169	16

Coal Distribution

More than 91 percent of the coal mined in Wyoming is shipped via rail to 29 other states. The largest consumers of Wyoming coal are coal-fired power plants in Texas, Missouri, and Illinois. Most of the coal is used for steam to generate electricity at power plants, but a small amount is used at industrial plants and commercial facilities

Powder River Basin Mining

In the Powder River Basin coal field—the most prolific in the world—coal is mined from two major coal seams, the Anderson and Canyon coals. This coal occurs in the Paleocene-age (65 to 55 million years ago) Tongue River Member of the Fort Union Formation. The mineable subbituminous coal seams in the Fort Union Formation are 60 to 80 feet thick, with a moisture content between 20 and 30 percent, and contain less than 6 percent ash and 0.5 percent sulfur. Powder River Basin (PRB) coal also includes beds in the Eocene-age Wasatch Formation, where exploration drilling has encountered coal seams greater than 200 feet thick.

Coal is mined in the PRB at a rate of 12 tons per second, filling between 50 to 70 coal trains per day. Seven of the nation’s 10 largest coal mines operate in the Wyoming part of the PRB. The largest coal mine is the Peabody Energy North Antelope Rochelle Complex, which produced more than 98 million tons in 2018.

Rapid growth in Wyoming's coal industry during the latter part of the 1970s resulted from the development of large-scale open-pit surface mines in the Powder River Basin (PRB). Development of the abundant coal resources in the PRB was driven by amendments to the Clean Air Act of 1974 and the following energy crisis. The continuous growth of coal production in Wyoming resulted from a growing national demand for low-cost, low-sulfur steam-coal, as well as technological advances in engineering and mining practice, large-scale development of mining and rail infrastructure, and the great abundance of thick, mineable coal resources in the PRB.

The PRB also has more than 1,500 square miles of reddish clinker rock, which is mined for use as aggregate in construction and decorative applications. Clinker beds are layers of sedimentary rock that have been altered by the burning of an adjacent coal seam. Outcrops of coal exposed at the surface can be ignited by lightning strikes or brush fires. These fires can spread across a coal bed and into the subsurface, burning for hundreds of years. As they burn, they heat up the surrounding rock, altering it and in some cases melting the rock. Recent age-dating suggests that these clinker beds are between 1.1 Ma to 10 ka in age (Heffern and others, 2007). These clinker beds can be up to 180 feet thick.

Quarterly Coal Production
Excel file containing Wyoming's quarterly coal mine production and employment according to MSHA (Last update: fourth quarter, 2019).