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A single lithium-ion electric vehicle battery pack can contain more than 100 pounds of nickel, along with many other metals. Those raw materials often come from mines that drive deforestation and produce pollution and huge carbon emissions in places like Indonesia; the emissions from nickel are the fourth largest in the world of mining. Multiply those numbers by the millions of metals needed for batteries, turbines, and other parts of a renewable energy transition, and the quantities are staggering.

But a French company, Genomines, is trying to paint a different image of what a mine can be. Instead of open pits and mounds of rubble, it envisions waving fields of yellow daisies in South Africa. Genomines is engineering plants in the family Asteraceae to soak up metals like nickel from soils. It’s one of several companies working on phytomining, the practice of using plants to extract heavy metals from soil.

Mining has been one of humanity’s most destructive cuts into the planet, causing water degradation, geopolitical havoc, and even a race to the bottom of the ocean in search of the next place to dig up precious minerals. But while mines leave giant scars in the environment, plants can be quietly put to work to suck up metals in the soils, especially in places where industrial processes or previous mines have left damage. Of the 320,000 plant species in the world, around 700 have evolved a cool trick: hyperaccumulating different metals from the ground. Doing so helped protect the plants from predators that can’t eat the metallic leaves, and it also let them live in environments where others couldn’t—like toxic, metal-laden soils.

Phytomining itself isn’t new: scientists started to use plants to clean up cesium in the soil near Chernobyl after the nuclear disaster in 1986. The US Department of Agriculture also started to use plants in the late 1980s to gather metals from soils, but the agency had to halt its own project when one of its test plants became so prevalent that it tipped into being an invasive species at the testing region in Oregon. At the time, mining many of these metals was inexpensive, so the idea of mobilizing plants didn’t make much sense.

Now, market forces and better science have brought about a new era of phytomining. As demand for metals to create electric batteries grows, and finding those metals becomes increasingly difficult, phytomining offers not only an alternative mining future but also an opportunity to flip the script on waste. “Supply chain issues and the need for nickel in batteries has brought around a renewed interest,” says Rupali Datta, a biochemist at Michigan Technical University who is working on a phytomining project funded by the US Department of Energy (DOE).

Most of the world’s nickel currently comes from mines in Indonesia, and by some estimates, the reserves of high-grade nickel could run out before the end of the decade. Even the lower-grade ore that goes into batteries could be depleted by 2050. Getting new mines and refineries online is a long, slow, and expensive process, even when projects are well designed and environmentally responsible.

Alicja Babst-Kostecka, an environmental scientist at the University of Arizona who is researching phytomining, sees the practice as a particularly promising nature-based solution. It’s not just about cleaning up contaminated lands, she says, but also potentially recovering valuable metals while restoring ecosystems. “That dual benefit—remediation plus resource generation—is what gives phytomining its momentum right now.”

To make mining through plants into a workable reality, though, takes advances in plant biology, ecology, analytical chemistry, and biotechnology—as well as the right environments where soils may have limited alternative uses. And so the race is on.

As cheap as a farm,
with the income of a mine

Several startups have already started making phytomining into a reality. Researchers at Genomines are bioengineering daisies (they won’t say exactly which species, but it’s a plant native to South Africa) to make them taller with larger leaves, so the plants can store more metal. They have also created a soil microbiome to make the metal more available for the plants to pull up, and they say they’ve been successful in increasing the amount of metal stored within the plants from about 2% to nearly 8% of body mass. To extract the metal, the plants must be mashed up and heated—releasing a “bio-ore” that can be purified for many uses.

Fabien Koutchekian, a former mining engineer who cofounded Genomines, says he’s excited about the ways that phytomining could open up paths for mines to become smaller, more environmentally friendly, and more versatile—fitting in alongside a farm or a town instead of lying in an industrial region at the edge of a city. “The promise is that we could have a very small mine, a mine that would be way more modular,” he says. That also means that the economics would be easier to scale—a small footprint, but with a large potential stream of valuable products. “It could still have the same economics of a farm, but with the revenues of a mine.”

Genomines’s process is still lengthy: the company starts growing its plants in France, to ensure they are stable enough for field trials and to control the technology. Once they’re healthy enough for travel, at eight weeks old, the seedlings are moved to South Africa. After six months, the plants are harvested and the company recovers the metal from the biomass through a combination of techniques, including bioleaching and heating the plant material. Scientists transform the plants into a nickel-rich bioconcentrate (like charcoal with a very high nickel content) through a process called pyrolysis—essentially heating the plants in the absence of oxygen to ensure they purify out some of the organic content while capturing carbon dioxide in an offgas for renewable energy generation. The company says it anticipates 2.5 tons of nickel per hectare, equivalent to a field of 40,000 plants. That means creating battery-grade nickel at about 40% of the cost of traditional metals.

The benefits keep multiplying: not only does the process create valuable metal, but it also remediates degraded land. And because the plants are perennials, they can last up to 15 years without needing to be replanted. The company has raised $45 million to scale up its efforts. By 2030, Genomines aims to produce 150,000 tons of bio-nickel per year, which could supply batteries for up to three million electric cars.

About 80 countries have nickel-rich deposits, meaning many places around the world are potential micro-spots for metal extraction. Naturally metal-rich soils are good places to look, but former mines that are now dump sites can also work.

Genomines isn’t alone. Another startup, Metalplant, has launched a phytomining farm using the shrub Odontarrhena chalcidica in Albania, in an area where the soil is so rich in nickel that it’s difficult to grow traditional crops. A third company, Botanickel, is working in Malaysia and Greece to create plant-generated stainless steel. (Two-thirds of the world’s nickel is used to make stainless steel, which is an alloy containing many metals.) 

The New Plants
of Research

The resurgence of phytomining is bolstered by new research. Last year, The US Department of Energy’s ARPA-E (Advanced Research Projects Agency-Energy) announced $9.9 million for seven projects in phytomining. The agency hopes to foster domestic supply of the metal from the more than 15,000 square miles of nickel-rich soils along the border of California and Oregon, and along the Pennsylvania-Maryland border.

Rupali Datta’s team in Michigan is taking a holistic view of phytomining, using soil chemistry, microbial manipulations, and specific plants to increase the uptake of nickel. They are also working on a biosensor that could measure the amount of nickel in the plants—currently a laborious process, but important information. In general, when a hyperaccumulator’s biomass is burned, the ash can contain up to 20% metal, which is often very pure and doesn’t require much refining.

Datta’s greenhouse studies will use vetiver grass—a plant used to remediate lead contamination—and test its ability to accumulate nickel. The initial results show that it can accumulate a lot of the metal, but it does so in the roots. Part of the project’s goal is to coax the plant to move the metal into the leaves and stem, where it’s easier to harvest. Datta has studied the grass for years and is now testing it against other hyperaccumulators; it also has the advantage of being native to the US “Ours are going to be plants that are not genetically modified,” she adds. “So if our method works, then deployment will be a little bit easier compared to some of the other projects.”

Babst-Kostecka, who is also funded by the Energy Department grant, is working to figure out which plant species will thrive under which conditions and soil chemistries. Many hyperaccumulators grow slowly and have very particular needs. Her team is researching how exactly plants suck up metal, store it, and move it around their bodies, especially in metal-rich environments like the sites of former mines. But plants are only part of the story, she says. “Soil microbiomes, root-microbe associations, and broader soil biota influence both plant performance and metal availability.”

Metalplant is another DOE grantee. The company plans to take its plants from Albania and genetically modify them for success in North America—while also introducing sterility to prevent the invasive behavior that shut down the first experiments in phytomining.

Phytomining may have the most impact where conventional mines just won’t work and where extracting is technically difficult, environmentally damaging, or socially unacceptable. “It may never replace large-scale ore mining for bulk metals,” Babst-Kostecka says, “but it can fill in meaningful gaps.”

Future Farm
to Batteries

Nickel is the low-hanging fruit of the phytomining world, but some researchers are thinking bigger. The technology also shows promise for collecting other minerals, especially cobalt, thallium, and selenium, which are controlled almost entirely by China and deeply needed for technologies like semiconductors and batteries. Scientists could also harness the potential of synthetic biology to engineer artificial hyperaccumulators that are customized for metal choice, geographical location, and environmental conditions.

The damage of mines looms large on the surface of the Earth. Phytomining can be part of the process of healing damaged landscapes, restoring soil health, and mitigating past and future mining legacies, Babst-Kostecka says. “The fact that we can use biological processes to recycle metals and rehabilitate land makes phytomining deeply aligned with sustainability and environmental justice.”

Phytomining won’t solve all resource-supply or environmental challenges. But the researchers point out it offers a unique set of benefits, especially for legacy mine sites and contaminated lands that are otherwise neglected or difficult to restore. And importantly, phytomining asks people to rethink what they consider waste. Many landscapes labeled as damaged or valueless may, with the right biological systems, become productive again, both ecologically and economically. And most potently, it can bring humans a new view of the unseen powers of humble plants in damaged regions.

Katharine Gammon is a freelance science writer based in Santa Monica, California. She writes for a wide range of magazines covering technology, society, and animal science.

Top image: ©Anthropocene Magazine