Turning Waste into Resources for Rare Earth Element Production in the Gulf Coast Basin
Quantifying rare earth element (REE) resources within the U.S. is critical because the U.S. is heavily reliant on REE imports from China, resulting in a supply chain highly vulnerable to disruption. REEs are crucial for many energy-related technologies, including wind turbines and electric vehicles, and are vital to national defense.
In 2021, the Department of Energy (DOE) developed the Carbon Ore, Rare Earth, and Critical Mineral (CORE-CM) Initiative to quantify and support production of REE resources within the U.S. In a study led by the Bureau’s Bridget Scanlon, the Gulf Coast Basin was one of eight coal basins evaluated during this program. The CORE-CM program expanded the feedstocks considered from coal and coal ash to include other potential feedstocks in these basins.
Mapping of coal resources in the Gulf Coast Basin shows that there are 83 billion metric tons (gigatonnes, Gt) of coal in the upper 90 m (300 ft) of the Gulf Coast Basin. REE concentrations in coal are similar to average concentrations in the Earth’s crust, with local hotspots up to 15 times crustal levels. The REEs can be readily extracted (about 60–90% extractable) with environmentally benign weak acid because they are associated with organics in these brown coals (lignite) similar to lignites in the Williston Basin in North Dakota. The contained value of REEs as oxides in these coals is estimated to total $266 billion based on 83 Gt of coal. The value of REEs that are critical for permanent magnets account for about 80% of the total value of REEs.
Coal ash from power plants represents another important waste resource that could be used for REE extraction. REEs in coal ash from Gulf Coast lignites have about 4 times higher median concentration of REEs than coal because REEs are nonvolatile and remain in the ash after the coal is burned. However, the extractability of REEs from coal ash is much lower (about 30%) and requires stronger acids than used for extracting REEs from coal. The value of REEs from coal ash derived from lignite in the Gulf Coast area total $1.15 billion, based on 0.26 Gt of ash that is potentially accessible at power plants (not sold or used). REEs used for permanent magnets also account for about 80% of the value of the total REEs from the ash.
Red mud or bauxite residue is generated when bauxite is processed for aluminum at five sites along the Gulf Coast in about a 1:1 ratio. Processing of bauxite that was imported from Jamaica resulted in red mud with very high concentrations of REEs, more than 10 times crustal concentrations. The estimated value of REEs from the red mud at the Copano site in Texas (about 150 million tonnes) is estimated to be $3.4 billion, assuming 30% extractability. REEs for permanent magnets account for about 80% of the value of the REEs. When scandium (at 10 times crustal levels) is included with the REEs, the value increases to $8.7 billion. Coproducts can also be generated from red mud which has additional aluminum and up to 50% iron. Some of the red mud storage areas in the Gulf Coast are within meters of sea level and are vulnerable to storm surge.
Heavy mineral sands along the Gulf Coast are also a byproduct of sand production to support hydraulic fracturing. Preliminary analyses of these sands indicates that physical processing to concentrate the heavy minerals can result in REE levels exceeding 1% (10,000 ppm). Sand mining areas in Texas have substantial resources that could provide heavy mineral concentrates.
Additional feedstocks for REEs and critical minerals in the Gulf Coast include zeolite and graphite, and also produced water from oil and gas production that contains lithium.
The Gulf Coast Basin is highly suitable for developing REEs because of the feedstocks available and the fact that the REE processing industry is already growing, with active involvement from ElementUSA and Lynas Rare Earths. Also, the coastal location is ideally suited for importing feedstocks from other regions to expand the program.
Turning waste to resources, such as coal ash, red mud, and frac sands, will benefit REE supply security in the U.S. and could also benefit the environment in the Gulf Coast by offsetting remediation costs.
The Bureau’s Brent Elliott will be leading the CORE-CM Phase II evaluation of Gulf Coast REEs. To watch a recent webinar featuring Drs. Scanlon and Elliott, entitled, “Assessment of Critical Minerals and Rare Earth Elements in the Gulf Coast Basin,” please see:
