Bituminous Coal

Use and Composition

Bituminous coal is burned for steel production rather than electricity production. Bituminous coal may also be referred to as metallurgical coal or coking coal. This coal is ideal for steelmaking because it has a carbon content of 70–90%, low impurities, and is dense in energy. Bituminous coal is dense yet brittle, dark brown to black in color, and possibly has a shiny appearance. Because it is brittle, coal rocks can fragment, creating smaller particles that can then be uplifted into the atmosphere by winds or motion, for example, on moving train cars.

Other components of coal are its volatile matter, which refers to compounds that evaporate when coal is heated. The volatile matter content determines whether coal can be used in steelmaking, partly distinguishing bituminous coal from other types of coal. Relevant for steelmaking, coal should have low amounts of phosphorus (P) and sulfur (S), which lead to impurities in the steel.

Relevant for the health impacts of our exposure to coal, bituminous coal, and other types of coal, contain so-called chalcophile, meaning "sulfur-loving," elements. Chalcophiles include toxic metals such as lead (Pb), selenium (Se), arsenic (As), cadmium (Cd), and mercury (Hg), which are known cause cancer and other adverse health effects even at very low levels.

Geological Formation

Bituminous coal was formed in ancient tropical swamps 300 million years ago and is mined today in locations that include the coal seams of the Appalachian Basin in West Virginia. These swamps were home plants such as scale, seed ferns, and true ferns, which thrived in the waterlogged, organic matter-rich conditions that are needed for coal formation. When these plants died, a thick bed of peat was created on the swamp floor. The peat bed lacked oxygen, i.e., the layer was anaerobic, facilitating coal formation through a process known as coalification. Coalification occurs over millions of years, with the layers of peat continually compressed by local sediments and rocks. The pressure and heat of this overlaying process converts peat to lignite, a form of low-quality coal.

Moving forward to 100 million years ago, sea level rose and intruded into freshwater peat bogs (i.e, peat containers). For the Appalachian region, this was done by the Western Interior Seaway, a massive water body that split North America in half. Sulfur (S) in seawater are then fixed onto the fresh lignite and sulfur-fixing bacteria, adding sulfur into the mixture. These cyclical fluctuations are called cyclothems, intercepting layers of marine shale, sandstone and limestone to the coalbed. This layer continues to be squeezed with more moisture removed and then baked up to 100-200^oC as the Earth shifts (i.e., tectonic processes). The heat during this period drove out moisture, concentrated carbon, and formed the ‘bitumen’ that gave way to high-rank coal formation, and move up from lignite to anthracite [6].

Of all the Appalachian Basin, WV stands out with the most extensive and economically viable region for bituminous coal subsidence [7]. This subsidence refers to gradual sinking of Earth’s crustal layer, creating vast spaces for peat accumulation. Therefore, these 100-feet sink holes could accumulate more coal without too much disruption, creating over 100 distinct coal seams over millennia. This geological setting gave bituminous coal here, especially in WV, the quality needed to fuel the industrial growth across eastern United States. Metallurgical, low-volatile bituminous coal from No.3 Pocahontas (Pocahontas formation), Beckley and Sewell (New River Formation) remains vital for industrial activities over eastern U.S. [8].

Coal mined in the Appalachian Basin is transported by rail to major East Coast ports for global distribution, including the Port of Virginia, which consists of the Dominion Terminal Associates and Kinder Morgan Bulk Terminals in Southeast Newport News and the Norfolk Southern Terminal in Lambert's Point, Norfolk, as well as Curtis Bay in Baltimore, Maryland.

Documents

• Senior et al., Toxic Substances from Coal Combustion—A Comprehensive Assessment, 2001
• Milici et al., Bituminous Coal Production in the Appalachian Basin: Past, Present, and Future, Chapter D.3 of Coal and Petroleum Resources in the Appalachian Basin: Distribution, Geologic Framework, and Geochemical Character, Edited by Ruppert and Ryder, Professional Paper 1708-D.3, U.S. Department of the Interior, U.S. Geological Survey, 2014
• Tewalt et al., Coal Assessments and Coal Research in the Appalachian Basin, Chapter D.4 of Coal and Petroleum Resources in the Appalachian Basin: Distribution, Geologic Framework, and Geochemical Character, Edited by Ruppert and Ryder, Professional Paper 1708-D.4, U.S. Department of the Interior, U.S. Geological Survey, 2014