Apr 1st 2026|Boulder, Colorado|5 min read
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It is a wonderful idea. Eliminate the carbon-dioxide emissions from steelmaking (which amount to about 8% of anthropogenic greenhouse-gas emissions, more than three times the amount released by civil aviation) by liberating iron from its ore using electricity instead of chemicals. It works for non-ferrous metals like aluminium, so why not ferrous ones? Two firms are trying, with varying degrees of success, while a third is adapting chemical liberation to make it greener.
In conventional steelmaking, iron ore reacts with substances called reducing agents that pluck away the oxygen, leaving behind metallic iron. The reducing agents in question are either carbon monoxide (CO) produced by the partial combustion of coke or a mixture of hydrogen and CO created by reacting methane from natural gas with steam. The reaction with carbon monoxide produces CO2; the reaction with hydrogen produces water.
That is not the end of the matter, though. The resulting iron is full of impurities retained from the ore, especially silica, alumina and phosphorus. It has to be processed further, to remove these and also to lower the amount of carbon it has picked up while being reduced. A simpler, cleaner one-step process would thus be welcome.
Electra, a firm based in Boulder, Colorado, has developed a version of the “electrowinning” approach usually employed to process copper ores. As Kevin Galloway, the firm’s vice-president of product, explains, the electrowinning of iron involves dissolving the ore in sulphuric acid, which leaves behind the silica, alumina and phosphorus, and then running a current through the solution, a process known as electrolysis, to plate the iron itself onto an electrode. Do this carefully and the result is a sheet of pure iron.
The company has proved its process works, and it is now trying to scale up from a laboratory prototype to industrial production. Construction has thus begun of a demonstration facility intended to turn out 500 tonnes of iron a year. That is, admittedly, peanuts compared with the 2m-4m tonnes a year a modern blast furnace would yield, but the plan is then to build modules which will produce 200,000 tonnes a year each.
That modularity will reduce initial capital expenditure. This, plus the high value of the pure iron Electra’s process yields (it could, for example, be used to make specialist magnets) compared with the output of conventional ironmaking, and the fact that it can cope with low-grade ores which steelmakers now eschew will, Mr Galloway hopes, give the firm the edge it needs to cross the “Valley of Death” that claims so many startup firms as they attempt to scale to commercial production.
Boston Metals, a firm in Woburn, Massachusetts, is indeed currently struggling in that valley. Its process also employs electrolysis, albeit at temperatures above the 1,538°C required to melt iron, rather than the far more manageable 60°C required by Electra. It relies on dissolving the ore in a molten mixture of other metal oxides and running an electric current through the mix. Pure, liquid iron sinks to the bottom of the reaction vessel. The impurities, collectively called slag, remain dissolved in the molten oxides.
This had worked in a laboratory, and the firm’s boss, Tadeu Carneiro, had hoped to scale up in collaboration with a steel company. But that idea is now on ice after what the firm described in February as “a critical equipment failure” at its facility in Brazil, which was applying the idea to a high-value metal called niobium. Boston says it is thus shutting up shop in Woburn.
Hertha, the third of the green-steel trio, is also the most recent and arguably the brashest. Its founder, Laureen Meroueh, has devised a chemical-reduction process that heats up pure methane so that it breaks apart into hydrogen and carbon, a process called pyrolysis. This hydrogen and a proportion of the carbon are then injected into a molten mixture of ore in order to reduce the oxide to iron and also to adjust the carbon content of the resulting liquid metal. Silica, alumina and phosphorus are meanwhile removed as slag by reaction with chemicals such as calcium and magnesium oxides. Then, as in Boston Metal’s approach, the iron sinks beneath the slag, for easy tapping.
Hertha’s reaction vessel is an electric-arc furnace—a standard piece of equipment normally used to melt scrap steel for recycling. Dr Meroueh’s laboratory prototype is therefore already turning out several hundred tonnes of iron a year. Her plan is to scale this up to 10,000 tonnes by the end of 2027, and to have full-size modules that will produce between 300,000 and 500,000 tonnes by 2030.
As the fate of Boston Metals shows, the path to product for any startup is paved with potholes. But both Electra’s and Hertha’s approaches look like more promising paths to green steelmaking than the one chosen by established firms, such as ArcelorMittal and Thyssenkrupp, of employing expensive electrolytically generated hydrogen as the reducing agent.
Electra cuts out the middle man by using electricity directly, rather than for generating hydrogen, while Hertha’s hydrogen-generation process is cheaper than electrolysis. Dr Meroueh is, though, keen to point out that her method could be adapted to use electrolytic hydrogen, and thus become completely green, if the price of that gas were to fall sufficiently.
Whether these firms can cross the Valley of Death remains to be seen. But although greener steel may not be as exciting as making electric vehicles, or as breast-beatingly performative as flying less, it would be no less important. ■
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This article appeared in the Science & technology section of the print edition under the headline “Blast off”
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