A New Furnace Design Could Make Steelmaking Cheaper and Cleaner

Steelmaking today relies heavily on coal-fired furnaces and produces roughly 7% of the carbon emissions that drive climate change — about as much as the fashion industry. Decarbonizing the process has proved difficult because profit margins are thin and existing furnaces have long service lives, making new investment hard to justify.

Hertha Metals, founded by mechanical engineer Laureen Meroueh, has built a new furnace that simplifies the chemistry of steelmaking. In a single step, it turns iron ore into refined liquid steel, and it swaps coal for natural gas as the furnace's fuel. Meroueh says the combined changes cut emissions by at least half and lower production costs by 25% compared with standard steelmaking.

Other approaches to “green steel” use hydrogen to free oxygen from iron ore, a method that could eventually cut or eliminate emissions. Meroueh says Hertha is, for now, sticking with a fossil fuel — natural gas — mainly to keep costs down, but she says the current furnace could switch to a fully decarbonized system later without drastically changing the hardware, if hydrogen becomes more affordable.

Iryna Zenyuk, director of the National Fuel Cell Research Center at the University of California, Irvine, said, “There's huge value in reducing the size of this production system,” adding that conventional steel plants are massive, inefficient and energy-hungry, so even energy savings alone would be a big step forward.

Hertha's pilot plant in Conroe, Texas, near Houston, currently produces one metric ton of steel per day. The company is building a new plant next to it, expected to produce 10,000 metric tons of high-purity steel a year once it reaches full capacity by the end of 2027. Meroueh believes a third site could push Hertha's output to 500,000 metric tons a year by 2030 — still a fraction of the roughly 80 million metric tons of steel the US produces annually.