Molten oxide could cut steelmaking emissions

A process developed by the Massachusetts Institute of Technology (MIT) claims to reduce the carbon footprint of steelmaking- one of the world’s leading industrial sources of greenhouse gases.

The idea for the method arose when Donald Sadoway, a professor of Materials Chemistry at MIT, received a grant from NASA to look for ways of producing oxygen on the moon.

Sadoway found that a process called molten oxide electrolysis could use iron oxide from the lunar soil to make oxygen. He tested the process using lunar-like soil from Meteor Crater in Arizona finding that it produced steel as a byproduct.

In addition to producing no emissions, the process lends itself to smaller-scale factories

Sadoway’s method used an iridium anode, but since iridium is expensive and supplies are limited, he found this was not a viable approach for bulk steel production on Earth.

Instead, the MIT team identified an inexpensive metal alloy that can replace the iridium anode in molten oxide electrolysis.

Antoine Allanore, who also worked on the research, said: “There are only two classes of materials that can sustain these high temperatures — metals or ceramics.”

Allanore, who worked in the steel industry before joining MIT, said progress has been slow both because experiments are difficult at these high temperatures, and also because the relevant expertise tends to be scattered across disciplines.

“Electrochemistry is a multidisciplinary problem, involving chemical, electrical and materials engineering,” he said.

The answer turned out to be an alloy of chromium and iron — constituents that are “abundant and cheap.”

In addition to producing no emissions other than pure oxygen, the process lends itself to smaller-scale factories.

Apart from eliminating the emissions, the process yields metal of exceptional purity, Sadoway added. It could also be adapted to carbon-free production of metals and alloys including nickel, titanium and ferromanganese, with similar advantages.

Ken Mills, a visiting professor of materials at Imperial College, London, said the approach outlined in this paper “seems very sound,” but he warned that unless legislation requires the industry to account for its greenhouse-gas production, it’s unclear whether the new technique would be cost-competitive.

Nevertheless, he said, it “should be followed up, as the authors suggest, with experiments using a more industrial configuration.”

Sadoway, Allanore and a former student have formed a company to develop the concept, which is still at the laboratory scale, to a commercially viable prototype electrolysis cell.

They expect it could take about three years to design, build and test such a reactor.