Green steel startup Boston Metal is doubling down on critical metals

Green steel startup Boston Metal is doubling down on critical metals The company is focusing on metals like niobium, tantalum, and nickel rather than steel. The startup Boston Metal has raised a $75 million funding round to produce critical metals, MIT Technology Review can exclusively report. The company has been known largely for its efforts to clean up steel production, an industry that's responsible for about 8% of global greenhouse emissions today. With the additional money, the new focus could help it survive at a time when support for industrial decarbonization has been waning in the US. In addition to steel, Boston Metal has also worked to use its technology with other metals, and a subsidiary (Boston Metal do Brasil) is setting up a commercial facility in Brazil to produce niobium, tantalum, and tin. The funding will help support that facility’s operation as well as future efforts to produce critical metals like vanadium, nickel, and chromium, says CEO Tadeu Carneiro. The funding comes after the company faced cash-flow problems following an industrial accident at the Brazil facility earlier this year. Boston Metal’s core technology is called molten oxide electrolysis (MOE). It involves running electric current through a reactor filled with ore dissolved in a molten electrolyte. The electricity heats everything up to about 1,600 °C (3,000 °F) and drives chemical reactions that separate the desired metal (or metals) from the ore. The metal gathers at the bottom of the reactor, where it can be siphoned off. In early 2025, Boston Metal completed the largest run of its pilot industrial cell in Woburn, Massachusetts, producing about a ton of steel. But the focus is currently on making other metals, which are more valuable and can command a higher price. The company’s Brazilian subsidiary is working to test and start up an industrial-scale plant that takes in a low-grade material and makes a mixture of critical metals. Niobium, for example, is used in some steel alloys, as well as in alloys used to make jet engines and the superconducting magnets of MRI scanners. Tantalum is used in aerospace applications like rocket nozzles and turbine blades, as well as medical devices and electronics. Construction on the Brazil plant kicked off in 2024 and took about 18 months, but the company ran into some challenges that delayed official startup. In January there was an issue with the plant’s refractory system, the equipment that insulates the reactor and prevents corrosion. That caused electrolyte to leak. Operators shut down the system and removed the metal, and there weren’t any injuries or environmental issues, Carneiro says. But the leak did interfere with the timeline for the plant’s opening, which meant the company missed a milestone and lost out on funding that had been committed. It restructured and laid off 71 employees in April. This new funding will help support the plant moving forward. “Because of this delay, we had a big stress in our cash flow, so the investors came very strong to support us,” Carneiro says.…