There is more than one way to make green steel: Why electricity may be better than hydrogen (The Economist – May 31, 2023)

Steelmakers around the world hope to decarbonise by changing the way they pluck oxygen from iron-oxide ores. This is done using either carbon monoxide (CO) derived indirectly from coke in a blast furnace, or by “direct reduction” with syngas, a mixture of CO and hydrogen.

Both create carbon dioxide, a greenhouse gas. As a consequence, steelmaking is reckoned responsible for about 9% of man-made greenhouse-gas emissions. A widespread aspiration is thus to introduce direct reduction by hydrogen alone. The only by-product of such a reaction would be water (or rather, steam).

Clever. But, thinks Tadeu Carneiro, not clever enough. Mr Carneiro runs Boston Metal, a firm based not in Boston, but rather in Woburn, 17km to the north-west. Employing the insights of Donald Sadoway of the Massachusetts Institute of Technology, Boston Metal has created a way of separating iron from its ore by electrolysis. Instead of releasing CO2 or steam, its approach produces pure oxygen—which is not merely harmless, but actually valuable.

Electrolytic separation of metals from their oxides is not new. Aluminium is made this way. But the process uses carbon electrodes, and the oxygen liberated at the anode reacts with this carbon to generate CO2.

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