Sub-bituminous coal, also known as black lignite, falls between lignite and bituminous coal, as per the classification system used in the United States and Canada. Geologically, it is a young coal, having formed anywhere from 251 million years ago to the present.
When dry and free of ash, sub-bituminous coal contains 42- to 52-percent carbon; its calorific value ranges from 19 to 26 megajoules per kilogram, the Encyclopaedia Britannica states. In terms of appearance, it is dark brown to black and is brighter than lignite, which often has a woody structure rather than a compact shine. Some sub-bituminous coal looks exactly like bituminous coal to the naked eye.
One advantage of sub-bituminous coal is that it contains less water than lignite and is therefore harder, a characteristic that makes it more suitable for transportation and storage. However, sub-bituminous coal’s sulfur content is sometimes lower than 1 percent, well below the level found in bituminous coal. That means more sub-bituminous coal than bituminous coal must be burned to create the same amount of energy. Even so, many power plants have switched to sub-bituminous coal as bituminous coal’s high sulfur content is environmentally problematic.
Sub-bituminous coal production
Nearly half of the world’s proven coal reserves are sub-bituminous coal and lignite. The five countries with the largest proven reserves of these types of coal are Romania, Australia, the United Kingdom, Turkey and France, NationMaster states.
More specifically, Romania has 107,922 million tonnes, Australia has 52,300 million tonnes, the UK has 21,944 million tonnes, Turkey has 17,879 million tonnes and France has 6,556 million tonnes. In contrast, proven reserves in US, which produces a fair amount of sub-bituminous coal, sit at just 3,107 million tonnes.
In the US, sub-bituminous coal is plentiful in the Powder River Basin, which spans Wyoming and Montana. In fact, according to the US Energy Information Administration, in 2012, the top 10 coal-producing mines in the US all contained sub-bituminous coal and were all located in the Powder River Basin. At the top of the list by tonnage was the North Antelope Rochelle mine, which put out more than 100 million tonnes that year.
3 sub-bituminous coal producers
Despite its low reserves of sub-bituminous coal, the US is home to a number of significant producers of the fuel. Here’s a look at three of them:
- Peabody Energy (NYSE:BTU), the world’s largest private coal company, owns the North Antelope Rochelle mine, the Caballo mine and the Rawhide mine, all of which are located in the Powder River Basin. Altogether, Peabody owns nearly 9 billion tons of proven and probable coal reserves, as well as majority interests in 28 coal operations in the US and Australia, as per its website.
- Arch Coal (NYSE:ACI), the second-largest overall producer in the Southern Powder River Basin, owns the Black Thunder and Coal Creek mines, also situated in the Powder River Basin. Overall, the company is in charge of 3.3 billion tons of reserves in that region.
- Low-sulfur sub-bituminous coal producer Cloud Peak Energy (NYSE:CLD) owns the Antelope and Cordero Rojo mines in Northeast Wyoming, as well as the Spring Creek mine in Southeast Montana. The coal Cloud Peak produces is shipped largely to utilities throughout the US, as well as to industrial consumers in Asia via the Westshore terminal in British Columbia.