AUSTIN, Texas — Coal ash — the chalky remnants of coal that has been burned for fuel — has been piling up across the United States for decades. But new research led by The University of Texas at Austin has found that the national coal ash supply contains enough rare earth elements to significantly bolster the national supply without any new mining.
“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 are a group of 17 elements that are essential for modern technology. They are also necessary for the energy transition to lower carbon fuels, with these elements being put to use in solar panels, batteries, magnets and other energy technologies.
However, the United States relies almost entirely on imports for its rare earth element supply. About 75% come from China — which poses potential problems in a world of complex supply chains and geopolitical tensions.
The new research found that there could be as much as 11 million tons of rare earth elements in accessible coal ash in the United States, which is nearly 8 times the amount that the U.S. currently has in domestic reserves, according to the researchers.
The study is the first study to tally up national coal ash resources. The researchers estimate that $8.4 billion worth of rare earth elements could be extracted from the accessible supply of coal ash.
The results were published in the International Journal of Coal Science & Technology. The U.S. Department of Energy is also applying the study’s methodology to conduct its own national assessment of coal ash resources.
Even though the level of rare earth elements in coal ash is relatively low when compared with those mined from geological deposits, the fact that the ash is readily available in large quantities makes it an attractive resource, said co-author Davin Bagdonas, a research scientist at the University of Wyoming.
“There’s huge volumes of this stuff all over the country,” Bagdonas said. “And the upfront process of extracting the (mineral host) is already taken care of for us.”
The researchers found that about 70% of the coal ash produced from 1985 to 2021 — a total of about 1,873 million tons — is potentially recoverable, with the material stored in landfills, ponds and offsite storage areas. The rest of the coal ash has been sold and used by other industries, such as cement production and road construction.
Coal ash contains different levels of rare earth elements depending on where it originates. Place of origin also affects how much of the rare earth elements can be extracted.
For example, ashes from Appalachian Basin coal contain the highest amounts of rare earth elements, with an average value of 431 milligrams per kilogram. But only 30% of the rare earth elements it contains can be extracted. In contrast, coal from the Powder River Basin has the lowest average value of rare earth elements at 264 milligrams per kilogram, but it has an extractability of about 70%.
While rare earth elements tend to be heavier, and less likely to go up the flue, natural coal burning has put a lot of crap into lungs of birds, beasts and humans for centuries, whether out of smokestacks, stoves or fireplaces.
Coal ash also contains radioactive uranium and thorium. The coal bed has acted as a giant groundwater filter for millions of years, and burning it concentrates such impurities by ~10 x. However, rare earth ores also often contain relatively high levels of fissile elements. Thorium especially is chemically analogous to REEs, plus spontaneous fission often creates them as fission products. Even though natural uranium is not particularly radioactive, and thorium even less so (their chemical toxicity, on par with lead, is more of an issue), their presence in an ore body throws all sorts of spanners into the licencing works – especially for the heavier REEs, usually found together with thorium. That’s one reason China dominates the field – they’re not so fussy about where they find it. The main reason, though, is that they’re all so chemically similar (due to the electron orbital characteristics that make them valuable in the first place), that they take a lot of very messy processes to separate. So far, the rest of the world has been happy to let the Chinese take that environmental hit – the whole industry was only worth about 12 billion dollars last year, versus ~1.5 trillion for steel.
[Just a general comment: I’m sure John is more than aware of this.]
Holding some radioactive materials in your hand vs. breathing in particles makes all the difference in toxicity. The depth of the epidermis is sufficient to block α particles, while inhaling α emitters puts them in direct contact with living tissue.
I’m sure China does not publish the cancer rates for miners. (Though with the horrible levels of coal smoke most citizens have had to live with over the last few decades, there probably isn’t that much difference between the lungs of miners and the citizens of Beijing, cancer-wise.)
Apparently China’s big city air has improved remarkably in the last decade. Good news for the inhabitants, though Jim Hansen reckons less sulfur in the atmosphere is taking the handbrake off for global warming.
The US shaming China a bit by posting air-quality readings taken from the roof of the Beijing embassy helped goose the CCP into really addressing a lot of that pollution. And yeah, ending acid rain unmasks the warming, but I think that’s a positive tradeoff as long as we keep decarbonizing.
I live in a dispersed Superfund site based on refining ores for rare earths and having the resulting spoil get sold or given away for fill on construction projects – thorium is the main radionuclide still present and it gets dug up fairly regularly on new projects. Any foundation work or even exploratory digging in my area includes mandated radiation readings in the hole.
But coal ash sometimes gets re-used anyway (like the stuff above did), but what’s still in contained ash storage, especially along rivers and lake edges, does need better disposal as we continue into increasingly-floody climates everywhere. If there’s enough demand for what’s in the ash to drive extraction, and that helps pay for more proper disposal of the remainder of the ash, it’s all to the good. We’d been processing from that rare earth mine in California until we sent the polluting to China, and that doesn’t seem a perfect choice today, either. If we’re going to live by possible contaminants, it’s sort of responsible to do at least some of the risky processing inside our borders.
But “we’re” NOT decarbonizing. Ditching coal and replacing it with gas is the 2nd worst possible action because it reduces aerosols but keeps increasing GHGs, but it’s what “we’re” doing.
Obviously the problem is…you guessed it, Wetiko-caused capitalism and cruelty (sorry for the redundancy). And by falling for the lunatic right wing’s lies and repeatedly voting them into office (where, in the US, the lunatics then destroy what little democracy existed, with gerrymandering, voter suppression, etc) SOME people allow the far right to retain power no matter what most people want. So SOME people invite even more corruption in the most pervasively but silently corrupt country in the world.
Deregulation of everything, no matter how destructive—in fact the more destructive the closer it comes to satisfying their insatiable nihilism, cruelty, and addiction to domination—is the way to get the least healthy, least ecological—but cheapest! and most profitable!—mining and manufacturing. We begin to heal the Earth, and civilization, by radically equalizing and fully democratizing, but without beginning a strong multifaceted global, US-centered program to heal Wetiko it’s extremely unlikely we’ll prevent catastrophic ecological, psychological, social, and political collapse.
Dispelling Wetiko: Breaking the Curse of Evil, by Paul Levy
It might have been shame, but the increased looming medical costs for the population (including the filthy lungs of people who didn’t smoke cigarettes) must have been motivation, too.