Rare earth minerals: The peril and promise of coal ash Image By EPN Staff A recent study led by researchers at the University of Texas estimates the coal ash stored around the United States contains 11 million tons of rare earth elements worth approximately $8.4 billion. That coal ash contains rare earth elements – crucial to modern products – has long been known, but the September 2024 study seems to be the first to catalog the possibilities and put a dollar figure on them. Why it matters Accessing these elements isn’t easy, and so far researchers haven’t hit upon a cost-effective process. But multiple studies are underway, some funded by federal grants, and the issue is a huge one for U.S. manufacturers and the military, in part because the lion’s share of these important elements come from China. Rare earths are a collection of 17 metallic elements with similar chemical properties, and the United States imports some 80% of its supply, according to the Department of Energy. They’re not actually rare worldwide, but concentrated deposits are rare, making them difficult to mine and refine. They have a wide range of uses. Cerium, for example, is used in catalytic converters. Neodymium and praseodymium are used in electric vehicle motors. The United States has trace deposits of these elements, but the extraction process is – as Popular Mechanics described it in June – “environmentally nasty.” There appears to be only one active rare earth mine in the United States, and it’s in California. Context about coal ash Coal ash, a byproduct of burning coal for energy, has “long been considered a potential source” of these elements, according to the U.S. Geological Survey, and the United States has roughly 2 billion tons of ash, according to the Department of Energy. The University of Texas study put the recoverable amount of ash stored in the United States at about 1.8 billion tons. That ash is poisonous, and multiple lawsuits and criminal charges have been filed over storage issues, but the ash has some uses, including in making concrete. Acids and membranes can be used to pull rare earths out of the coal ash, but the acids are expensive, and the rare earths are miniscule, meaning most of the poisonous coal ash waste stream remains, West Virginia University Water Research Institute Director Paul Ziemkiewicz told CNN last year. That leaves questions about who deals with the ash once it's processed. The bigger picture Scientists have talked about mining rare earths from coal ash and other coal waste for decades. Penn State, in a university magazine published in 2022, said its researchers identified these elements in coal 70 years earlier: “In 1952, Edward Steidle, dean of what was then the College of Mineral Industries, wrote, ‘By the year 2000 we will not be wasting our coal ash, in which geochemists have shown there is a notable concentration of rare elements, such as germanium and rare earths. We will be recovering these elements.'" Multiple efforts are underway to make the removal process viable at scale. The University of Texas said in April that its researchers had developed a new method, "opening up new avenues for gathering rare earth elements amid global trade tensions." The Department of Energy has funded multiple projects, including studies at the University of Kentucky, West Virginia University, Penn State University and with Microbeam Technologies in Grand Forks, North Dakota, as well as research based at Caltech and the University of Utah. Additional details Coal ash from different types of coal has different concentrations of rare Earth elements. The University of Texas study, which also included researchers from the University of Wyoming and the University of Kentucky, found that ash from coal mined in the Appalachian Basin had the highest amounts, though only 30% of the rare earth elements it contains can be extracted. Coal from the Powder River Basin in Wyoming and Montana has the lowest average value of rare earth elements of the coal ash studied, the researchers said, but an extractability of about 70%.
