U.S. coal ash holds tons of rare-earth elements worth $8.4 billion

Coal ash is the chalky leftovers from a fuel that’s been our mainstay for centuries. Now, it’s something of a hot issue, considering that it’s been accumulating across the nation for decades.

A new study, led by researchers from The University of Texas at Austin, unearthed a hidden treasure in these mounds of ash – a large supply of rare-earth elements that could significantly beef up the national supply and reduce the need for new mining operations.

From trash to treasure

“This really exemplifies the ‘trash to treasure’ mantra,” said co-lead author Bridget Scanlon, a research professor at UT’s Bureau of Economic Geology at 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.”

Rare-earth elements, a group of 17 pivotal chemical soldiers, are the backbone of our modern tech-dependent world. These unseen heroes also play a critical part in our energy transition towards lower carbon fuels, as they are used in solar panels, batteries, magnets and a host of other energy technologies.

Rare-earth dilemma

The United States is heavily dependent on imports – about 75% – for these strategic elements, and most of it is from China. It’s a risky situation, given the convoluted labyrinth of global supply chains and rising geopolitical tensions.

But UT Austin’s trailblazing study provides a ray of hope. A whopping 11 million tons of rare-earth elements could be up for grabs in easily accessible coal ash piles; this represents nearly eight times the amount currently hoarded in U.S. domestic reserves.

This study, the first to take stock of our national coal ash resources, estimates that $8.4 billion worth of these elements could be unearthed from this accessible coal ash treasure.

Moreover, the U.S. Department of Energy is keen to apply this new methodology to conduct its own assessment of national coal ash resources.

Building value from coal ash

Though the levels of rare earth elements in coal ash are low compared to traditional geological sources, the sheer volume of readily available coal ash makes it a promising resource.

“There’s huge volumes of this stuff all over the country. And the upfront process of extracting the (mineral host) is already taken care of for us,” said co-author Davin Bagdonas, a research scientist at the University of Wyoming.

The scientists discovered that from 1985 to 2021, nearly 70% of coal ash produced, amounting to 1,873 million tons, could potentially be recovered.

This ash is largely stored in landfills, ponds, and offsite storage areas. The rest has been sold off and put to use by other industries, such as in cement production and road construction.

Coal ash origin affects the content

The coal ash’s place of origin impacts the concentration of rare-earth elements it contains, and the quantity that can be extracted.

Ashes from Appalachian Basin coal contain the highest amounts of rare-earth elements (an average of 431 milligrams per kilogram), but only about 30% of it can be extracted.

On the other hand, coal from the Powder River Basin has a lower average rare-earth content (264 milligrams per kilogram), but nearly 70% of it can be extracted.

Implementing the strategy

Chris Young, the Chief Strategy Officer at Element USA, a company that extracts critical minerals from waste, sees this new research as further proof of coal ash’s potential.

“The idea of getting rare-earth elements out of tailings (mining by-products) just makes a lot of sense. It’s a common-sense approach,” he said. “The challenge is to convert that common-sense approach to an economic approach.”

The study’s promising results have sparked a surge in industry interest. Element USA is moving its analytical lab and pilot equipment to Austin to leverage the mineral expertise at The University of Texas and provide students with hands-on experience in critical mineral research and careers.

The funding for this research was raised by the U.S. Department of Energy’s Office of Fossil Energy and Carbon Management, and the Jackson School of Geosciences.

The study’s other co-authors include Robert Reedy, J. Richard Kyle, and Kristine Uhlman from the Bureau, James Hower from the University of Kentucky, and independent consultant Dennis James.

The research is published in the International Journal of Coal Science & Technology.

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