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Rare earth elements: Hidden in plain sight
As global demand for rare earth elements surges, researchers are turning to unconventional methods-including fungi and industrial waste-to extract these critical materials without traditional mining.
Fungi as miners: A lab experiment in Austria
At the University of Vienna, scientists Alexander Bismarck and Mitchell Jones are cultivating fungi in petri dishes and plastic bags filled with clay laced with rare earth elements. Their goal? To determine whether fungi can absorb these valuable metals, which are essential for batteries, magnets, and renewable energy technologies.
"You might actually be able to recover resources," says Bismarck, who leads the university's polymer and composite engineering group. The process, dubbed "mycomining," involves growing fungi on contaminated industrial sites, where their mycelia-microscopic, root-like networks-could extract rare earths over large areas.
"We really could do this over large areas and quite easily collect that biomass using existing agricultural machinery."
Mitchell Jones, materials scientist at the University of Vienna
However, Jones acknowledges the concept is still speculative. While fungi grow quickly and thrive in harsh conditions, scaling up the process presents challenges, including potential environmental risks like altering natural ecosystems.
The rare earth dilemma: Scarcity amid abundance
Despite their name, rare earth elements-17 chemically similar metals like dysprosium, yttrium, and scandium-are not actually rare. They are scattered across the Earth's crust in low concentrations, making extraction difficult and costly. China currently dominates the industry, controlling roughly 70% of global mining and 90% of processing.
Geopolitical tensions have intensified competition for these resources. The U.S., for example, has allocated $12 billion to build a strategic reserve of rare earths and sought access to deposits in Ukraine and Greenland. Yet, experts argue that domestic alternatives exist-if nations look closely enough.
Waste not: Industrial byproducts as a resource
Julie Klinger, an environmental studies professor at the University of Wisconsin-Madison, highlights a 2025 study showing that critical minerals, including rare earths, are already present in vast quantities of industrial waste across the U.S. "If we look at waste with fresh eyes, we see a different picture in terms of scarcity and abundance," she says.
Examples abound:
- Coal ash: Left over from burning coal, these piles contain rare earths at concentrations higher than natural deposits. A 2023 study estimated their value in the U.S. alone at $8.4 billion.
- Red mud: A byproduct of aluminum production, red mud contains rare earths at 10 to 20 times the concentrations found in the Earth's crust. Texas-based ElementUSA plans to extract gallium and scandium from these waste piles, with a prototype plant set to launch in 2028.
- Mine tailings: Leftover materials from mining, such as those at California's Mountain Pass Rare Earth Mine, often contain residual rare earths that could be recovered.
Innovative extraction methods
Researchers are developing novel techniques to recover rare earths from waste:
- Flash joule heating: Developed by Rice University's James Tour, this process uses electric currents to heat waste materials to extreme temperatures, causing rare earths to bond with chlorine and vaporize for capture. The method is energy-efficient and portable, though separating individual rare earths remains a challenge.
- Solvent extraction: ElementUSA plans to use acids and solvents to extract rare earths from red mud, targeting scandium for use in lightweight aircraft alloys that could reduce fuel consumption by up to 15%.
Oona Snoeyenbos-West of the University of Arizona is also exploring fungal-based extraction, focusing on strains already adapted to contaminated sites. She aims to launch a start-up to commercialize the approach.
Economic and environmental hurdles
Despite the promise of these methods, economic viability remains a challenge. Rare earths are not as valuable as metals like gold or platinum, making traditional mining more cost-effective-at least for now. "The real devil in the detail here is that rare earths are fundamentally different when it comes to the price point," Klinger notes.
To offset costs, projects are targeting multiple materials. For example, coal ash carbon could be sold for water filters, while biogas from fungi could serve as fuel. ElementUSA plans to extract iron alongside gallium and scandium from red mud.
A symbiotic future?
If successful, these innovations could transform waste management. Instead of costly cleanup efforts, industries might recover valuable materials while remediating contaminated sites. Klinger describes this as a "kind of symbiosis," where economic and environmental goals align.
"Gigantic heaps of coal ash, mine tailings, and red mud are traditionally expensive and difficult to deal with," she says. "But if new processes allow rare earth harvesters to engage in remediation while hoovering up rare earths, industry and environmentalists might no longer be at odds."
The shift could reduce reliance on imports, bolster domestic supply chains, and turn waste into a resource-proving that sometimes, the solution is hiding in plain sight.
