Making steel with electricity

MIT spinout Boston Metal is commercialising a new method for making steel and other metals, to help clean up the emissions-intensive industry.

Steel is one of the most useful materials on the planet. A backbone of modern life, it’s used in skyscrapers, cars, airplanes, bridges, and more. Unfortunately, steelmaking is an extremely dirty process.

The most common way it’s produced involves mining iron ore, reducing it in a blast furnace through the addition of coal, and then using an oxygen furnace to burn off excess carbon and other impurities. That’s why steel production accounts for around 7 to 9 per cent of humanity’s greenhouse gas emissions worldwide, making it one of the dirtiest industries on the planet.

Now Boston Metal is seeking to clean up the steelmaking industry using an electrochemical process called molten oxide electrolysis (MOE), which eliminates many steps in steelmaking and releases oxygen as its sole by-product.

The company, which was founded by MIT Professor Emeritus Donald Sadoway, Professor Antoine Allanore, and James Yurko PhD ’01, is already using MOE to recover high-value metals from mining waste at its Brazilian subsidiary, Boston Metal do Brasil. That work is helping Boston Metal’s team deploy its technology at commercial scale and establish key partnerships with mining operators. It has also built a prototype MOE reactor to produce green steel at its headquarters in Woburn, Massachusetts.

And despite its name, Boston Metal has global ambitions. The company has raised more than $370 million to date from organisations across Europe, Asia, the Americas, and the Middle East, and its leaders expect to scale up rapidly to transform steel production in every corner of the world.

“There’s a worldwide recognition that we need to act rapidly, and that’s going to happen through technology solutions like this that can help us move away from incumbent technologies,” Boston Metal Chief Scientist and former MIT postdoc Guillaume Lambotte says. “More and more, climate change is a part of our lives, so the pressure is on everyone to act fast.”

A decades-long search
Since the 1980s, Sadoway had conducted research on the electrochemical process by which aluminium is produced. The focus of the research was to find a replacement for the consumable anode used in that process, which makes carbon dioxide as a by-product. During that work, he began to conceptualise a similar electrochemical process to make iron, the precursor to steel.

But it wasn’t until around 2012 that Sadoway and Allanore, then a postdoc at MIT, discovered an iron-chromium alloy that could serve as a cheap enough anode material to make the process commercially viable and produce oxygen as a by-product. That’s when the pair partnered with James Yurko, a former student, to found Boston Metal.

Boston Metal’s molten oxide electrolysis process takes place in modular MOE cells, each the size of a school bus. Iron ore rock is fed into the cell, which contains the cathode (the negative terminal of the MOE cell) and an anode immersed in a liquid electrolyte. The anode is inert, meaning it doesn’t dissolve in the electrolyte or take part in the reaction other than serving as the positive terminal. When electricity runs between the anode and cathode and the cell reaches around 1 600 degrees Celsius, the iron oxide bonds in the ore are split, producing pure liquid metal at the bottom that can be tapped. The by-product of the reaction is oxygen, and the process doesn’t require water, hazardous chemicals, or precious-metal catalysts.

The production of each cell depends on the size of its current. Lambotte says with about 600 000 amps, each cell could produce up to 10 tons of metal every day. Steelmakers would license Boston Metal’s technology and deploy as many cells as needed to reach their production targets.