The term “green steel” has gained some prominence in metallurgical and financial reporting, tying investors’ ambitions to efforts by researchers and steelmakers to address the perceived liabilities of their industry. The claim that steelmaking is responsible for 10% of all global carbon emissions has become a convenient peg for numerous pitches and projects. “Green steel” broadly describes operations that use renewable energy sources and have reduced CO2 emissions and minimal waste byproducts.
But it remains a very loose term, with more assurances than clear definitions about what is “green steel.” One exception may be developing at a workshop in Massachusetts. “With this milestone, we are taking a major step forward in making green steel a reality and we’re doing it right here in the U.S., demonstrating the critical innovation that can enhance domestic manufacturing,” according to Boston Metal CEO Tadeu Carneiro.
From an idea spawned in a Massachusetts Institute of Technology lab, in 2022 the tech start-up business began scaling up a production cell for its Molten Oxide Electrolysis (MOE) process, to produce iron for steelmaking. The unit (described as “reactor”) started in January this year, and delivered roughly one ton of molten iron by mid-February.
Like electrolytic production of primary aluminum, MOE uses electricity to separate primary metals from their oxides. The molten iron produced is ready to be converted into steel.
In more detail, an inert anode is placed in the reactor vessel containing an electrolyte solution of ferrous metal oxides. As the solution’s temperature rises to about 1600°C, an electrolytic reaction takes place that separates the oxides and leaves liquid iron.
Conceptually, this process is an alternative to blast furnace ironmaking – which relies on coal and coke to separate iron from oxides, but that results in the carbon emissions that are the bane of regulators and investors. Blast furnaces produce iron, not steel, but they are the particular culprit in steelmakers being held responsible for 10% of the world’s carbon emissions.
According to the Boston Metal vision, the molten metal iron tapped from an MOE cell can be processed directly into steel using ladle metallurgy. They intend to license their process to operators who may establish production for thousands or millions of tons of annual output.
“We are the only company with a direct and scalable approach to more efficient and clean steelmaking, and I can now say that tonnage steel is flowing from our multi-inert anode MOE cell,” Carneiro stated.
The developers emphasize that MOE is able to convert any grade of iron ore into liquid metal, without emitting any carbon. A subsidiary business, Boston Metal do Brasil, is profitably recovering metal from mining waste, and the industrial-scale demonstration in Massachusetts proves that the inert anode is able to withstand the heat and corrosive conditions of electrolysis, they report.
Boston Metal’s next step will be to build a larger production cell, according to senior vice president Adam Rauwerdink, PhD. The current reactor proves MOE’s industrial viability, but is not production-scale to deliver a ton or more of molten iron each day. Such demonstration plant should be operational by 2027, though further details are unavailable.
“The power of MOE technology has been unlocked to deliver the most direct and scalable approach to efficient steel decarbonization,” stated Adam Rauwerdink, PhD, Boston Metals SVP business development. “We have defined a path forward for meeting the challenges of this hard-to-abate industry while creating economic growth throughout the steel value chain.”