At a foundry in Germany, workers pour molten iron into a mold. Carbon dioxide from blast furnaces accounts for a significant portion of greenhouse gas emissions.Steelmaking, the fiery process that undergirds modern life, comes with a huge cost to the climate. Greenhouse gases gush from the burning fossil fuels that drive 1600°C blast furnaces and melt raw iron ore. Purifying the molten ore by mixing it with refined coal, or coke, releases a second, bigger surge of carbon dioxide.
One idea is to swap the coke for hydrogen. DOE is spending nearly $1 billion on two commercial-scale iron smelters, one in Mississippi and another in Ohio, that can bathe heated pellets of iron ore in hydrogen. It strips away the oxygen, forming water as a byproduct instead of carbon dioxide, and at lower temperatures of about 1100°C.
Michael Street and Angela Jaurez inspect a plate of iron made at the experimental Boulder, Colorado, facility of the low-carbon iron-manufacturing startup Electra.Electra expects to open a new pilot plant in 2025. The company says its technology can accommodate low-quality ore left behind by mines, and because it operates at low temperatures and can be turned on and off quickly, it can use fluctuating renewable energy.
On the still more speculative end are efforts to build a 21st century iron furnace. At DOE’s Argonne National Laboratory, scientists are using microwaves to heat hydrogen to 600°C, until it forms a plasma. At these temperatures, the ionized hydrogen can strip oxygen even from solid ore. “It’s going to take quite a while to scale,” says John Kopasz, a chemist leading the research. So far, it has worked in a laboratory, producing just a few grams of iron at a time.