Coal ash, the leftover material from burning coal for energy, has been piling up in the United States for decades.
But researchers at The University of Texas at Austin have discovered that this waste contains a hidden treasure: enough rare earth elements to significantly boost the nation’s supply without needing new mining operations.
Rare earth elements are a group of 17 metals that are essential for modern technologies, including solar panels, batteries, and magnets.
These materials are also critical for the transition to cleaner energy.
However, the U.S. currently imports almost all of its rare earth supply, with about 75% coming from China. This dependence creates risks due to global supply chain issues and political tensions.
According to the study, published in the International Journal of Coal Science & Technology, the coal ash in the U.S. contains an estimated 11 million tons of rare earth elements.
That’s nearly eight times the current reserves in the country.
The researchers estimate that this hidden supply could be worth $8.4 billion if extracted.
“This really shows the value of turning waste into resources,” said Bridget Scanlon, a research professor at UT Austin. “Not only can we recover these important elements, but we can also reduce the environmental impact of coal ash.”
Why coal ash?
Coal ash is an attractive source because it’s already collected and stored in large amounts across the country.
From 1985 to 2021, about 1.9 billion tons of coal ash were produced, with around 70% of it stored in landfills and ponds.
The extraction process is easier because the coal has already been burned, leaving the rare earth elements concentrated in the ash.
Different regions produce coal ash with varying levels of rare earth elements. For instance:
- Coal ash from the Appalachian Basin has the highest concentration, with 431 milligrams of rare earth elements per kilogram. However, only about 30% of the elements can be extracted.
- In contrast, Powder River Basin coal ash contains fewer rare earth elements (264 milligrams per kilogram) but has a higher extractability rate of 70%.
The study lays the groundwork for using coal ash as a resource. While extraction technologies are still being developed, pilot projects, like one at the National Energy Technology Lab, are testing methods to recover rare earth elements from coal ash.
“This research provides the foundation for future projects,” said Scanlon. Companies like Element U.S. are already exploring how to scale up operations and train workers for this emerging industry.
By transforming waste into a valuable resource, coal ash could play a key role in creating a sustainable and secure supply of rare earth elements in the U.S.
