Could the remnants of coal combustion hold the key to unlocking a vast supply of critical rare-earth elements? Recent findings suggest that the ash left behind by burning fossil fuels might be an unexploited resource, valued at billions of dollars, right under our noses.
According to a 2024 study, geologists have estimated that the waste ash from coal used in power plants could contain rare-earth elements worth up to US$165 billion, with as much as $97 billion being feasibly recoverable. This revelation, spearheaded by researchers from the University of Texas at Austin, presents a unique opportunity for the United States to harness a domestic supply of these essential elements, reducing reliance on imported materials.
“This really exemplifies the ‘trash to treasure’ mantra,” says geologist Bridget Scanlon of the Jackson School of Geosciences. “We’re basically trying to close the cycle and use waste and recover resources in the waste, while at the same time reducing environmental impacts.” Source
Rare earth elements (REEs) consist of 17 elements, including the 15 lanthanides, yttrium, and scandium. These are classified as “critical minerals” in the US, indispensable for industries like batteries, wind turbines, electric vehicles, and smartphones. Despite their importance, the US largely relies on imports for its REEs, with around 70 percent sourced from China. Learn more about rare earth elements
Recent research highlights that the US power plants’ coal-ash waste, totaling 52 billion tons since the 1950s, could be a hidden reserve of REEs. Coal, formed from ancient plant matter, contains trace amounts of various materials. While these are too minute for extraction from unburnt coal, the combustion process leaves behind non-combustible materials, including clay minerals, quartz, and concentrated REEs.
Concentrations of REEs in coal ash are significantly higher—4 to 10 times—than in raw coal, albeit lower compared to commercial ores. However, since the coal ash is already mined, refining it bypasses the need for additional extraction efforts.
Geologists, led by Scanlon and Robert Reedy, analyzed decades of data on ash composition, extraction efficiency, and storage locations across the US. They estimate that accessible coal-ash deposits from 1985 to 2021 could contain 11 million tons of REEs, nearly eight times the current US reserves. The theoretical value of these REEs in all US coal ash is about $56 billion, with $14 billion accessible and $8.4 billion feasibly extractable.
Incorporating yttrium and scandium into the assessment raises the potential total value of the coal ash to $165 billion, with $97 billion recoverable. Read the full study here
Currently, methods for extracting these elements are still under investigation, but the potential rewards have garnered significant interest from both scientists and the US government. “In addition to enhancing energy security in the US through development of REE resources, the economic value of producing these REEs could help offset the costs of remediation of unlined ash landfills or ponds in environmentally vulnerable areas,” the researchers conclude.
The potential for REE resource development from coal ash should be evaluated globally in nations where coal ash is available.
Scientists are also exploring alternative sources for rare earth elements. Extinct volcanoes and certain plant species have shown potential for yielding these valuable minerals. For instance, some plants naturally extract and store REEs from metallic soils.
“Rare earth elements are critical metals for clean energy and high-tech applications, yet their supply faces environmental and geopolitical challenges,” notes Liuqing He from the Chinese Academy of Sciences. “Phytomining, a green strategy using hyperaccumulator plants to extract metals from soil, offers potential for sustainable REE supply but remains underexplored.” More on this research
While the pursuit of these resources is ongoing, the critical nature of rare earth elements ensures that their extraction remains a pivotal focus for future technological and environmental advancements.
Original Story at www.sciencealert.com