Highlights

• University of Texas researchers estimate up to $165 billion worth of rare earth elements, yttrium, and scandium in US coal ash.
• $97 billion of these elements are potentially recoverable under optimistic scenarios.
• $8.4 billion are potentially recoverable under conservative assumptions.
• Coal ash from 1950-2021 has concentrated REEs 4-10 times higher than original coal.
• 5.3 gigatons of ash have been generated, with 69% potentially accessible from storage sites across the Appalachian, Illinois, and Powder River basins.
• Recovery faces a critical bottleneck: while coal ash offers a domestic REE resource, China continues to control the separation and processing capacity.
• Realizing strategic value requires massive US investment in midstream infrastructure, regulatory clarity, and community engagement.

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A team led by geoscientist Robert C. Reedy (opens in a new tab) at the Bureau of Economic Geology (opens in a new tab), Jackson School of Geosciences, University of Texas at Austin (opens in a new tab), with senior collaborator Bridget R.Scanlon (opens in a new tab) and partners from the University of Wyoming, University of Kentucky, and US industry, has put a dollar figure on something most Americans never think about: coal ash.

In a major open-access study in the International Journal of Coal Science & Technology, the authors estimate that the waste ash left behind from decades of US coal-fired power generation could host up to US$165 billion worth of rare earth elements plus yttrium and scandium (REEYSc) in total. Under optimistic technical assumptions, around US$97 billion of that might be recoverable.

Using more conservative extraction efficiencies and focusing on ash that is both present and accessible today, they still see about US$8.4 billion in recoverable rare earth oxides—an intriguing, if complex, “trash to treasure” proposition in a world where China dominates rare earth processing.

How the Researchers Counted the Coal-Ash Treasure

For lay readers, coal ash is the fine, glassy powder (fly ash) and heavier bottom material left after coal is burned in power plants. When coal burns, the combustible parts—carbon, hydrogen, sulfur—go up the stack as gases. What remains is a concentrated residue of non-combustible material such as clay minerals, quartz, and trace metals, including rare earths. Because most of the coal’s mass disappears as smoke, REEs end up 4–10 times more concentrated in the ash than in the original coal.

Reedy and colleagues did not drill new holes or build pilot plants. Instead, they assembled a national-scale data mosaic from:

• Historical coal production and consumption records (USGS, EIA, FERC) from 1950–2021
• Power-plant reports on coal deliveries, ash content, and ash disposition (sold, stored, or dumped)
• Published datasets on REE concentrations in coal ash from major US coal basins
• 2020 rare earth oxide price benchmarks

They linked the chain: coal mines → power plants → ash amounts → ash disposition (sold vs stored) → REE concentrations → theoretical value, basin by basin. This is a classic resource assessment, not a mine plan: it estimates how much might be there, and roughly where, but not whether it can be produced economically in today’s market.

What They Found: Billions of Tons of Ash, Billions in Potential REEs

Some key quantitative takeaways, translated for a broad audience:

• From 1950 to 2021, the US produced about 52 gigatons of coal, generating an estimated ≈5.3gigatons of ash (roughly 10% of the coal by weight).

• Between 1985 and 2021, about 69% of that ash is considered “potentially accessible” for REE recovery because it was stored in landfills, ponds, or stockpiles, rather than sold into cement, wallboard, or road fill.

• Most of the relevant ash comes from three basins:

  • Appalachian Basin
  • Illinois Basin
  • Powder River Basin (PRB)

Ash from Appalachian coals tends to be richer in total REEYSc (around 585 mg/kg) than PRB ash(around 330 mg/kg). However, PRB ash is much easier to leach, with assumed extraction efficiencies of ~70%, compared with ~30% for Appalachian and Illinois ashes, because of differences in ash chemistry.

Using 2020 rare earth oxide prices, the team estimates:

• About US$56 billion in REO value in all US coal ash (lanthanides only)
• About US$41 billion in ash that is both present and physically accessible
• About US$8.4 billion after applying realistic extraction efficiencies to that accessible ash

When yttrium and scandium are added to the picture, the headline theoretical number rises to ~US$165 billion, with roughly US$97 billion considered recoverable in a best-case technical scenario.

What This Means in a China-Dominated REE Processing World

For Rare Earth Exchanges readers, the central strategic point is not that coal ash instantly solves US rare earth dependence. It’s that:

• The US may possess a significant secondary resource base of rare earths already mined and stockpiled as waste.
• This resource is spread across 40+ states, often near existing industrial infrastructure and grid connections.
• Yet processing and separation capacity for rare earths remains concentrated in China, with only limited capacity elsewhere.

In other words, coal ash could reduce US vulnerability at the resource level, but does nothing by itself to break China’s grip on separation, refining, and magnet manufacturing. Any serious move to tap this coal-ash resource would require:

• Domestic leaching and separation plants capable of handling low-grade, heterogeneous feedstock
• Long-term offtake contracts, likely with magnet and alloy manufacturers, to justify capital investment
• Tight integration with environmental remediation plans for legacy coal-ash ponds and landfills, including groundwater protection and community engagement

Done well, coal-ash REE recovery could become a two-for-one proposition: a modest but real new REE supply plus funding to clean up some of the dirtiest industrial sites in the United States.

Limitations, Uncertainties, and Controversial Questions

Reedy et al. are explicit that this is a reconnaissance-level assessment, not a bankable feasibility study:

• No detailed process economics: there is no full cost curve for recovering REEs from specific ash deposits under real-world regulatory and financing conditions.
• Data gaps: coal-ash production and disposition data are incomplete in some years; older ash sites may be poorly mapped, partially reclaimed, or subject to changing environmental rules.
• Grade vs ore: REE concentrations in ash are well below conventional hard-rock ore grades, so project economics will hinge on co-benefits (such as environmental remediation and avoided disposal costs) and future technology improvements.
• Regulatory and social license: many coal-ash sites sit in environmentally vulnerable or disadvantaged communities. Reframing waste as feedstock raises environmental justice questions: who benefits, who carries residual risks, and how are communities included in decision-making?

The study’s large theoretical value figures (US$165 billion / US$97 billion) are highly sensitive to price assumptions and optimistic recovery factors. Until transparent pilot results and real project financings emerge, investors should treat these numbers as order-of-magnitude indicators, not forward revenue guidance.

How ScienceAlert Told the Story—and What REEx Would Add

A recent ScienceAlert article (opens in a new tab) by Michelle Starr does an effective job translating the paper into a vivid “trash to treasure” narrative, emphasizing:

• The idea that coal ash is a latent REE resource
• The approximate value brackets (US$56B → US$8.4B → US$97B with Y + Sc)
• The environmental upside of cleaning up coal-ash ponds while recovering critical minerals

From a Rare Earth Exchanges vantage point, however:

• The piece naturally leans into headline-friendly figures (“almost $100 billion buried in the US”) without fully stressing how much depends on technology maturation, regulatory clarity, and industrial-policy design.
• The China processing bottleneck is mostly implied rather than dissected; casual readers might conclude the US is one decision away from independence, when in reality the midstream—separation, refining, metals, and magnets—remains the real chokepoint.
• The article notes that coal-ash grades trail conventional ore, but does not detail how this affects project economics, risk profile, and the likely need for federal subsidies, loan guarantees, or price-floor mechanisms.

In short, ScienceAlert captures the excitement; Reedy et al.’s paper—and REEx’s analysis—restore the constraints. Coal ash is a promising secondary REE resource, but without a parallel build-out of non-Chinese processing and magnet capacity, it will not, on its own, loosen Beijing’s strategic grip on the rare earth value chain.

Citations

Reedy RC, Scanlon BR, Bagdonas DA, Hower JC, James D, Kyle JR, Uhlman K. “Coal ash resources and potential for rare earth element production in the United States.” International Journal of Coal Science & Technology 11, 74 (2024). https://doi.org/10.1007/s40789-024-00710-z (opens in a new tab)

Starr M. “Almost $100 Billion Worth of Rare Earth Elements May Be Buried in The US.” ScienceAlert, 30 November 2025.

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