This is achieved with electrolysis and has the added benefit of releasing oxygen as a byproduct, a team from the Massachusetts Institute of Technology reported in the journal Nature.
The new method, molten oxide electrolysis (MOE), "offers both a substantial simplification of the process and a significant reduction in energy consumption," the researchers wrote.
"MOE is also considered a promising route for mitigation of CO2 emissions in steelmaking."
Iron, the key ingredient of steel, is extracted from ore mined from the Earth's crust in a process known as smelting, which today requires the addition of carbon at extremely high heat — releasing CO2.
For their electrolysis method, the team developed special new chromium-based anodes that can handle the high temperature and corrosion of the electrical current flowing through them.
Previous attempts at electrolysis iron extraction had used expensive iridium-based anodes, said a Nature press statement that described the new anodes as "affordable and durable".
In a commentary on the study, Derek Fray of the University of Cambridge's metallurgy department said the findings should stimulate further work to design a large pilot reactor, though "considerable technical development will be required for the authors' discovery to be used commercially".
About a billion tonnes of iron was produced worldwide in 2011, Fray wrote in Nature — contributing about five per cent of that year's global increase in atmospheric CO2.
