The weirdest ways scientists are mining for critical minerals, from water to weeds

Since ancient history, mining has been a dirty business. While we’ve developed new tools, chemicals, machines, and techniques, most of today’s mining still boils down to digging in the dirt. As the world ramps up production of the technologies it needs to move away from fossil fuels, this widespread disturbance of Earth and ecosystems will continue in the accelerating search for critical minerals like lithium, cobalt, nickel, and rare-earth elements.

But what if there were another way? Or, better yet, many other ways. After all, the minerals we need aren’t just buried underground. As the basic building blocks of much of the world’s matter, these elements have accumulated everywhere: in plant life, in the ocean, in our industrial waste, and even in rocks hurtling through outer space. While the ability to pull enough minerals from these sources to power the energy transition is still a long way off, scientists and entrepreneurs are hard at work trying to find out if each of these sources can compete with traditional mining methods. In the process, they’re also raising challenging questions about how far we’ll need to stretch human ingenuity to meet the challenge of the energy transition — and just how clean even the most advanced type of “mining” can ever be.

a textured illustration of a piece of seaweed growing in a body of water

Mining our water

For more than a century, eccentric scientists have dreamed of wringing precious metals from the Earth’s most vast resource: its oceans. The seas contain millions to trillions of metric tons of gold, cobalt, and other elements, including 17,000 times more lithium than the world’s terrestrial reserves. Unlike more controversial forms of deep-sea mining that require dredging the ocean floor, these dissolved minerals can be extracted directly from the ocean water itself.

In the 1920s, German chemist Fritz Haber hatched a plan to extract gold from seawater in order to pay back Germany’s debt from World War I. But unlike Haber’s other groundbreaking science — he invented synthetic processes that more or less led the way to both modern agriculture and chemical warfare — this effort yielded no real fruit, even after years of research in secret labs on German ships. In the decades since, the United States, United Kingdom, and Japan have all studied seawater as a potential source of uranium, but none of these efforts yielded widespread success, either. The basic problem has always been that the ocean’s elements are dispersed so broadly that extracting them often costs more than the market value of the minerals.

Today, in the face of a looming critical mineral shortage, scientists are renewing their efforts to overcome this hurdle. They’ve turned to an unassuming source: algae. Scientists at the Pacific Northwest National Laboratory in Sequim, Washington, are exploring the potential of a type of seaweed that can naturally concentrate minerals at levels thousands of times higher than the surrounding seawater.

For years, the lab had been studying algae — the broad class of photosynthetic organisms that include phytoplankton, seaweed, and kelp — for a completely different reason: as a potential source for renewable biofuels. The lab would grow algae in tanks, then extract all its organic compounds to use for fuel. This process left behind a concentrated powdery waste product, chock-full of all the remaining minerals that weren’t needed for the fuel. At first, researchers didn’t realize the potential of this overlooked byproduct. Scott Edmundson, a research scientist at the lab, recalls when he realized, “Oh, there’s a lot of minerals here that we really are undervaluing.”

As part of an Department of Energy experimental research program, they developed a system to pump seawater into onshore grow tanks full of a type of mineral-loving seaweed called Ulva. From there, they harvested and dried the seaweed, then processed it into the mineral-rich powder, which they dubbed “bio-ore.” This powder contains precious elements like nickel, cobalt, and rare earths at levels thousands of times higher than seawater. For example, concentrations of the rare earth element neodymium — an essential component in wind turbines — can be up to 479,000 times higher than the original seawater.

The dream of pulling gold or cobalt or many other critical minerals out of seawater is still far from being commercially feasible. But scientists like Edmundson — and others like Cornell University scientist Maha Haji, who has designed mineral filters that could be hung from abandoned oil rigs to pull cobalt from the Gulf of Mexico — think seawater mining has the potential to fundamentally reshape how the world sources its minerals.

“If you can make that work, and you can do it in a way that’s environmentally responsible, that has such high potential for providing the minerals we need in a sustainable, egalitarian way,” Edmundson said. “If you have access to the ocean, you have access to the minerals.”

— Jesse Nichols

an illustration of a yellow plant growing from a half circle of earth

Mining our weeds

Each spring, Albania’s mountainous roads are suddenly lined by striking yellow weeds with oblong leaves and tiny blossoms. A relative of broccoli, cabbage, and wild mustard, Odontarrhena chalcidica is expertly adapted to the rocky soils of this Balkan country, which are unsuitable for most other kinds of vegetation because of their high nickel content. O. chalcidica has developed the ability to not just survive in this environment, but to use its toxicity to its advantage: The plant draws nickel up from the soil and stores it in its leaves and stems, which botanists believe serves as a defense against predators and diseases.

But this defensive maneuver could also make this unremarkable-looking weed a critical tool for the clean energy transition. For years, scientists have known that plants like O. chalcidica, known as hyperaccumulators, can be harvested and burned to extract the nickel contained within their cells. This is called phytomining. Now, companies are starting to catch on, working to apply phytomining on a scale that could actually put a dent in global demand for nickel, which is used in solar panels, wind turbines, and the lithium-ion batteries that power electric vehicles.

One of these is Metalplant, a startup founded four years ago by three American and Albanian entrepreneurs. Metalplant worked with researchers at Albania’s Agricultural University of Tirana to transform O. chalcidica from a simple weed into a valuable crop. The company estimates that the plant can produce between 440 and 880 pounds of nickel per hectare in one growing season. Theoretically, that means the entire global nickel demand in 2020 could be met by growing O. chalcidica on around 23,000 square miles, an area slightly smaller than West Virginia. Though Metalplant hasn’t yet revealed its buyers, the company harvested its second batch of O. chalcidica last June, containing a few hundred pounds of precious nickel.

Eric Matzner, one of Metalplant’s three co-founders, doesn’t believe supplanting the entire global nickel supply chain is a realistic near-term goal. But he imagines that his company can provide a cleaner source of nickel — one that doesn’t cause the kind of deforestation, air and water pollution, and seizure of Indigenous lands seen in Indonesia, the world’s largest producer of the metal. Though traditional nickel mines currently have a cost advantage due to their sheer scale, Metalplant aims to become competitive by providing an additional service: carbon dioxide removal. The company is using a technique known as enhanced rock weathering, which involves spreading crushed rocks containing silicate minerals on O. chalcidica fields as they grow. This rock debris not only boosts yields by replenishing nickel in the soil, but it also reacts with carbon dioxide in the air to lock away the greenhouse gas as a solid, which later gets washed away by rain and ultimately deposited in the ocean.

The result, which the company calls “carbon negative” nickel, can be purchased by carmakers that aim to offset their own carbon emissions. In theory this could enable an electric vehicle to claim carbon neutrality for its entire life cycle. And it’s not just carmakers who are interested: Researchers at the University of Lorraine in Nancy, France, recently formed a partnership with steelmaker Aperam to use phytomined nickel in stainless steel production. In March of last year, the U.S. Department of Energy announced that it would fund research into phytomining, seeking to make the process more efficient and increase its scale — with the ultimate goal of boosting the domestic supply chain for nickel and reducing imports. (ARPA-E, the program that distributes the funding, has been targeted by the Trump administration, and its future role in supporting phytomining research is unclear.)

Companies like Metalplant have a long way to go before they can draw buyers away from established nickel producers in Indonesia. But Albania has a few other advantages: Its mountains are rich in olivine, a rock that’s ideal for ERW, and its numerous hydropower dams provide ample renewable energy needed to crush those rocks so they can be spread and sequester carbon dioxide. Albanian farmers are struggling with poor harvests and an exodus of young people to cities and abroad, which means they welcome the chance to explore new economic opportunities, according to Matzner. The way he sees it, “We’re literally growing money on trees.”

— Diana Kruzman

an illustration of an excavator sitting atop a half circle of rubble

Mining our waste

Centuries of mining, drilling, and burning fossil fuels has left large swathes of Appalachia covered in a big, toxic mess. Billions of tons of coal ash — the hard residue left over from coal burnt by power plants — are buried or piled in the open air across the region, slowly poisoning the soil and water around them. Heavy metals leak from old mines into nearby creeks, turning the water bright orange as they oxidize. And much of the mineral-rich radioactive liquid that’s used to drill miles underground for fracked natural gas gets deposited into storage wells that can leak into the water tables around them.

These waste streams are so toxic in part because they contain metals and minerals from the coal seams and shale formations from which we draw our fossil fuels. In other words, in one of the many ironies of the climate crisis, fossil fuel extraction has unearthed large quantities of the very materials that could wean us off of carbon-intensive energy: minerals like lithium, cobalt, manganese, and nickel, which are essential for green infrastructure such as the batteries that store renewable energy.

Scientists have been researching the mineral mining potential of coal waste for decades. Newer research is now also exploring the possibility of pulling lithium from the wastewater produced by oil and gas extraction: A study from the National Energy Technology Laboratory this past May suggests that up to 40 percent of current domestic lithium demand could be sourced from fracking wastewater in the Marcellus Shale. (That quantity is still “strikingly small” relative to anticipated future demand for lithium, according to Sean O’Leary with the Ohio River Valley Institute.)

What’s unknown, however, is whether these minerals can ever be gathered cheaply enough to compete with mining them in more conventional ways. Extracting critical minerals from solid waste like coal ash is a pretty resource- and energy-intensive process: The burnt residue has to be crushed into powder and processed multiple times with acids and sodium hydroxide, and then dissolved into a liquid form to extract the desirable elements. (Processing acid mine drainage is less involved, and therefore less expensive, because it’s already a liquid.)

While a few private companies have partnered with universities to conduct pilot projects — such as Rare Earth Salts, Aqua Metals, and General Electric with Pennsylvania State University; Montana Resources with West Virginia University; and Element USA with the University of Texas, Austin — there are still major questions to answer about the technology’s market viability. In addition to uncertainty about cost competitiveness, is there enough supply to warrant investment in processing plants?

Sarma Pisupati, director of the Center for Critical Minerals at Pennsylvania State University, points out that every coal seam contains a distinct mix of minerals, and it’s difficult to determine the location and volume of a significant store of rare-earth minerals without direct sampling from a given site. “We need detailed analysis and estimates of reserves that we have in the ground before we can sink in millions and millions of dollars to build a plant,” he said.

We have some early ideas of what those reserves might look like. A 2024 study from the University of Texas estimates that there are 11 million tons of rare-earth elements in coal ash reserves around the country, but there’s huge variation in the types and concentration of those elements between, say, waste sites in Wyoming and Pennsylvania. Another report from the Department of Energy’s Office of Fossil Energy and Carbon Management notes that processing such a relatively small mass of these elements from thousands of tons of coal ash means that any commercial mineral extraction plant would have to find some other economic purpose — like turning the leftover, post-processing coal waste into fertilizer or concrete additives.

Alternatively, fossil fuel companies themselves could be incentivized to extract the in-demand minerals from their own waste. This is one reason why environmental groups are ambivalent on the promise of mineral extraction from fossil fuel waste, according to Rob Altenburg, senior director of climate and energy for the organization PennFuture, an environmental advocacy nonprofit in Pennsylvania. On one hand, an economic motivation to clean up and utilize fossil fuel waste could be a boon for ecosystems and communities dealing with legacy pollution.

“But when you are essentially giving [fossil fuel] companies another revenue stream, are you creating a net benefit for the environment by addressing this waste, or are you subsidizing something … that is then going to outcompete a cleaner alternative?” he said.

— Eve Andrews

an illustration of an asteroid streaking past an orange and red striped planet represented as a half circle

Mining outer space

A big problem with finding the metals needed to power the energy transition is that the purest ores available in Earth’s crust have long been used up. The more we mine, the more we’re chasing lower-quality, harder-to-access reserves.

To bypass the increasing environmental cost associated with churning up our world to access the riches stored within, starry-eyed entrepreneurs and engineers have turned their gazes to the heavens. They’re hoping that primordial rocks left over from the formation of the solar system, drifting between the planets untouched for eons, could provide all the metals that humanity might need for centuries to come.

“Asteroid mining as a whole is the only solution that anybody has devised that is a holistic approach to cleaning up mining,” said Matt Gialich, founder and CEO of the California-based company AstroForge.

AstroForge and a small handful of competitors are proposing different ways to one day extract materials from an asteroid and return them to Earth. But the nascent industry has a long path ahead: To date, only three missions — none of which was undertaken by the private sector — have successfully visited asteroids near Earth and returned home with samples.

But in late February, AstroForge’s Odin spacecraft hitched a ride on a SpaceX Falcon 9 alongside other vehicles destined for the moon. If successful, Odin would be the first commercial deep-space mission in history, likely traversing hundreds of millions of miles before darting by its target asteroid to photograph it and confirm its metallic composition. (After launch, however, Odin appeared to be in a slow, uncontrolled tumble on its way to deep space, and Gialich and his team struggled to communicate with the spacecraft. As it drifts further into deep space, their chances of success diminish.)

Metallic asteroids are prime targets for off-world mining because of the high concentrations of valuable elements — particularly nickel, cobalt, iron, and platinum-group metals — they may contain. (Until a spacecraft successfully visits one of these bodies, we really only have estimates based on meteorites believed to have originated from similar asteroids.) At first, the space miners would focus on platinum and related metals because they are some of the most valuable on Earth: A ton of platinum costs over $30 million, whereas a ton of nickel sells for around $20,000. Gialich estimates that Astroforge’s future mining missions could return one ton of platinum each.

Eventually, once they have established their profitability and can shift to collecting the abundant iron, nickel, and cobalt that asteroids also contain, Gialich and others hope that a thriving asteroid mining industry could lead to a mining moratorium on Earth.

“I think if we are successful,” Gialich said, “this makes precious metal mining on the planet illegal.”

Before that happens, there are a lot of kinks to be worked out. Right now, under the 1967 Outer Space Treaty, no country can lay territorial claims to land on another world, whether that be the moon, an asteroid, or Mars. But emerging national laws have given companies and countries the license to extract materials and have a legal claim to anything they can physically take for themselves.

More importantly, perhaps, no one yet knows the best way to extract these metals. Some have suggested using special chemicals to dissolve the materials and filter out the desirable metals. Others have talked about using magnetic rakes to comb through the pulverized dust coating the asteroids to pull out the rocks and granules that contain platinum group metals. One recent paper even proposed using nuclear thermal rockets to melt the asteroids, then collecting the molten materials in crucibles and allowing evaporation to separate the metals.

Even if a workable method is devised and the raw cost-revenue calculations work out to make it a profitable industry, space mining raises deeper questions. The launches required to hurtle mining vessels into deep space would take tremendous amounts of fuel and further contribute to the space industry’s growing problems of polluting the upper atmosphere and damaging biodiversity. The mining itself, without proper regulations, may even create new streams of meteors that could endanger satellites providing crucial services to the people of Earth.

Despite its challenges, many in and around the field argue that their efforts will not only make the energy transition more sustainable, but that they will also be a necessary step for humanity to evolve beyond our earthly cradle. But is it worth expanding into the final frontier if we haven’t yet learned to tread lightly?

— Syris Valentine

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