The latest milestone means that Boston Metal just got one step closer to commercializing its technology. The company’s process uses electricity to make steel, and depending on the source of that electricity, it could mean cleaning up production of one of the most polluting materials on the planet. The world produces about 2 billion metric tons of steel each year, emitting over 3 billion metric tons of carbon dioxide in the process.

While there are still a lot of milestones left before reaching the scale needed to make a dent in the steel industry, the latest run shows that the company can scale up its process.

Boston Metal started up its industrial reactor for steelmaking in January, and after it had run for several weeks, the company siphoned out roughly a ton of material on February 17. (You can see a video of the molten metal here. It’s really cool.)

Work on this reactor has been underway for a while. I got to visit the facility in Woburn, Massachusetts, in 2022, when construction was nearly done. In the years since, the company has been working on testing it out to make other metals before retrofitting it for steel production. 

Boston Metal’s approach is very different from that of a conventional steel plant. Steelmaking typically involves a blast furnace, which uses a coal-based fuel called coke to drive the reactions needed to turn iron ore into iron (the key ingredient in steel). The carbon in coke combines with oxygen pulled out of the iron ore, which gets released as carbon dioxide.

Instead, Boston Metal uses electricity in a process called molten oxide electrolysis (MOE). Iron ore gets loaded into a reactor, mixed with other ingredients, and then electricity is run through it, heating the mixture to around 1,600 °C (2,900 °F) and driving the reactions needed to make iron. That iron can then be turned into steel. 

Crucially for the climate, this process emits oxygen rather than carbon dioxide (that infamous greenhouse gas). If renewables like wind and solar or nuclear power are used as the source of electricity, then this approach can virtually cut out the climate impact from steel production. 

MOE was developed at MIT, and Boston Metal was founded in 2013 to commercialize the technology. Since then, the company has worked to take it from lab scale, with reactors roughly the size of a coffee cup, to much larger ones that can produce tons of metal at a time. That’s crucial for an industry that operates on the scale of billions of tons per year.