Rare Earth Elements from Coal
Coal and coal preparation products are also potential sources of rare-earth elements. REEs are a group of elements (shown in purple on the periodic table below) unknown to most people. They include the lanthanide series elements (cerium through lutetium), yttrium, and scandium. Although relatively unheard of, rare earth elements are very important in our modern technological world, because they are used in a variety of products people use every day, including televisions and cellphones.
China currently produces most of the world's REEs (85 percent). They used to export large quantities of REEs to other countries ; in 2000, more than 90 percent of the REEs used in the United States were from China ( Haxel and others, 2002). Now, however, China is using most of what they produce domestically. As Chinese sources have diminished, world demand has increased. The U.S. Government and many manufacturing companies are looking for new domestic sources of REEs. One of those sources may be coal and coal waste.
Link to U.S. NETL’s Rare-Earth Element Poster.
REEs occur in very small trace amounts in coals and coal byproducts. Trace amounts are measured in microscopic concentrations of 100 parts per million or less. However, small amounts can be concentrated by large-scale mining and preparation. In fact, a recent study suggests that Appalachian coal bed refuse may contain one of the largest REE resources in the United States (Taggart and others, 2016).
Much work is ongoing to discover the highest commercial concentrations of REEs in specific coal beds and specific coal byproducts. The Department of Mining Engineering, Center for Applied Energy Research, and Kentucky Geological Survey, all at the University of Kentucky, are testing Kentucky- mined coals and coal byproducts for their REE content and concentration, and testing the potential for commercial extraction of REEs from coal and coal byproducts. Professor Rick Honaker of the Department of Mining Engineering at UK was awarded a $1 million research grant from the U.S. Department of Energy’s National Energy Technology Laboratory to develop a mobile pilot plant for the recovery of REEs from coal. In addition, Professor Jim Hower of UK’s Center for Applied Energy Research is collaborating on several grants to test methods to recover REEs from coal combustion residues and from the Fire Clay coal in eastern Kentucky. The Fire Clay coal has relatively high REE concentrations in some areas because it contains a volcanic ash bed, which may have been the source of its REEs (Hower and others, 1999).
Other Uses of Coal:
- Coal for Electricity Generation
- Coal to Make Coke and Steel
- Coal for Industry and Residential Markets
- Coal for Specialty Products and Chemicals
Rare Earth Elements from Coal References
- Crowley, S.S., Stanton, R.W., and Ryer, T.A., 1989, The effects of volcanic ash on the maceral and chemical composition of the C coal bed, Emery Coal Field, Utah: Organic Geochemistry, v. 14, p. 315– 331.
- Haxel, G.B., Hedrick, J.B., and Hendley, J.W., II, 2002, Rare earth elements —Critical resources for high technology: U.S. Geological Survey Fact Sheet 87-02, 4 p.
- Hower, J.C., Granite, E.J., Mayfield, D.B., Lewis, A.S., and Finkelman, R.B., 2016, Notes on contributions to the science of rare earth element enrichment in coal and coal combustion byproducts: Minerals, v. 6, no. 32, 9 p.
- Hower, J.C., Ruppert, L.F., and Eble, C.F., 1999, Lanthanide, yttrium, and zirconium anomalies in the Fire Clay coal bed, eastern Kentucky: International Journal of Coal Geology, v. 39, p. 141– 153.
- Mayfield, D.B., and Lewis, A.S., 2013, Environmental review of coal ash as a resource for rare earth and strategic elements: Proceedings of the 2013 World Ash Conference, Lexington, Ky., April 2013, 10 p.
- Seredin, V.V., 2010, A new method for primary evaluation of the outlook for rare earth element ores: Geology of Ore Deposits, v. 52, p. 428 –433.
- Seredin, V.V., and Dai, S., 2012, Coal deposits as a potential alternative source for lanthanides and yttrium: International Journal of Coal Geology, v. 94, p. 67– 93.
- Taggart, R.K., Hower, J.C., Dwyer, G.S., and Hsu-Kim, H., 2016, Trends in rare earth element content of U.S.-based coal combustion fly ashes: Environmental Science and Technology, v. 50, no. 11, p. 5919– 5926.
- U.S. National Technology Laboratory , 2016, Rare earth elements: https://www.netl.doe.gov/File%20Library/Research/Coal/Rare%20Earth%20Elements/REE-Project-Portfolio-2016.pdf.