At the heart of the energy transition is a metal transition. Wind farms, solar panels, and electric cars require many times more copper, zinc, and nickel than their gas-powered alternatives. They also require more exotic metals with unique properties, known as rare earth elements, which are essential for the magnets that go into things like wind turbines and EV motors.

Today, China dominates the processing of rare earth elements, refining about 60% of those materials for the world. With demand for such materials forecasted to skyrocket, the Biden administration has said the situation poses national and economic security threats. 

'Being able to make your own materials domestically means that you're not at the behest of a foreign monopoly,' says co-founder Tomás Villalón ’14, pictured. Image: Courtesy of Phoenix Tailings.

Substantial quantities of rare earth metals are sitting unused in the United States and many other parts of the world today. The catch is they are mixed with vast quantities of toxic mining waste.

Phoenix Tailings is scaling up a process for harvesting materials, including rare earth metals and nickel, from mining waste. The company uses water and recyclable solvents to collect oxidised metal, then puts the metal into a heated molten salt mixture and applies electricity.

The company, co-founded by MIT alumni, says its pilot production facility in Woburn, Massachusetts, is the only site in the world producing rare earth metals without toxic byproducts or carbon emissions. The process does use electricity, but Phoenix Tailings currently offsets that with renewable energy contracts.

The company expects to produce more than 3,000 tonnes of the metals by 2026, which would have represented about 7% of total US production last year.

Now, with support from the Department of Energy, Phoenix Tailings is expanding the list of metals it can produce and accelerating plans to build a second production facility.

For the founding team, including MIT graduates Tomás Villalón ’14 and Michelle Chao ’14 along with Nick Myers and Anthony Balladon, the work has implications for geopolitics and the planet.

“Being able to make your own materials domestically means that you’re not at the behest of a foreign monopoly,” says Villalón. “We’re focused on creating critical materials for the next generation of technologies. More broadly, we want to get these materials in ways that are sustainable in the long term.”

Tackling a global problem

Villalón got interested in chemistry and materials science after taking Course 3.091 (Introduction to Solid-State Chemistry) during his first year at MIT. In his senior year, he got a chance to work at Boston Metal, another MIT spin-off that uses an electrochemical process to decarbonise steelmaking at scale. The experience got Villalón, who majored in materials science and engineering, thinking about creating more sustainable metallurgical processes.

But it took a chance meeting with Myers at a 2018 Bible study for Villalón to act on the idea.

“We were discussing some of the major problems in the world when we came to the topic of electrification,” says Villalón. “It became a discussion about how the US gets its materials and how we should think about electrifying their production. I was finally like, ‘I’ve been working in the space for a decade, let’s go do something about it.’ Nick agreed, but I thought he just wanted to feel good about himself. Then in July, he randomly called me and said, ‘I’ve got [$7,000]. When do we start?’”

Villalón brought in Chao, his former MIT classmate and fellow materials science and engineering major, and Myers brought Balladon, a former co-worker, and the founders started experimenting with new processes for producing rare earth metals.

“We went back to the base principles, the thermodynamics I learnt with MIT professors Antoine Allanore and Donald Sadoway, and understanding the kinetics of reactions,” says Villalón. “Classes like Course 3.022 (Microstructural Evolution in Materials) and 3.07 (Introduction to Ceramics) were also really useful. I touched on every aspect I studied at MIT.”

The founders also received guidance from MIT’s Venture Mentoring Service (VMS) and went through the US National Science Foundation’s I-Corps programme. Sadoway served as an adviser for the company.

After drafting one version of their system design, the founders bought an experimental quantity of mining waste, known as red sludge, and set up a prototype reactor in Villalón’s backyard. The founders ended up with a small amount of product, but they had to scramble to borrow the scientific equipment needed to determine what exactly it was. It turned out to be a small amount of rare earth concentrate along with pure iron.

Today, at the company’s refinery in Woburn, Phoenix Tailings puts mining waste rich in rare earth metals into its mixture and heats it to about 1,300 degrees Fahrenheit. When it applies an electric current to the mixture, pure metal collects on an electrode. The process leaves minimal waste behind.

“The key for all of this isn’t just the chemistry, but how everything is linked together, because with rare earths, you have to hit really high purities compared to a conventionally produced metal,” says Villalón. “As a result, you have to be thinking about the purity of your material the entire way through.”

From rare earths to nickel, magnesium, and more

Villalón says the process is economical compared to conventional production methods, produces no toxic byproducts, and is completely carbon free when renewable energy sources are used for electricity.

The Woburn facility is currently producing several rare earth elements for customers, including neodymium and dysprosium, which are important in magnets. Customers are using the materials for things like wind turbines, electric cars, and defence applications.

The company has also received two grants with the US Department of Energy's ARPA-E program totalling more than $2m. Its 2023 grant supports the development of a system to extract nickel and magnesium from mining waste through a process that uses carbonisation and recycled carbon dioxide. Both nickel and magnesium are critical materials for clean energy applications like batteries.

The most recent grant will help the company adapt its process to produce iron from mining waste without emissions or toxic byproducts. Phoenix Tailings says its process is compatible with a wide array of ore types and waste materials, and the company has plenty of material to work with: mining and processing mineral ores generates about 1.8 billion tons of waste in the US each year.

“We want to take our knowledge from processing the rare earth metals and slowly move it into other segments,” says Villalón. “We simply have to refine some of these materials here. There’s no way we can’t. So, what does that look like from a regulatory perspective? How do we create approaches that are economical and environmentally compliant not just now, but 30 years from now?”