- UK scientists found a way to clean up blast furnaces, the most carbon-intensive part of steelmaking.
- Steel accounts for up to 9% of global emissions and is one of the most difficult climate challenges.
Steel built much of our modern world, but it also racked up a massive carbon footprint along the way.
Now, researchers at the University of Birmingham have developed a process to clean up the most carbon-intensive part of the steelmaking process: blast furnaces.
Currently, coking coal and iron ore are fed into furnaces and heated to sky-high temperatures to create liquid iron, which is then refined into steel. About 70% of steel used around the world for buildings, cars, and household appliances is made this way.
For every metric ton of steel produced, nearly two metric tons of carbon dioxide is released into the atmosphere, according to the World Steel Organization. The industry accounts for up to 9% of global emissions, meaning that if it were a country, it'd be the third-largest emitter behind China and the US.
Harriet Kildahl, a co-author of the research by University of Birmingham, told Insider that her team found a way to make steel with 90% less coking coal, which could reduce carbon emissions by a similar percentage.
Kildahl described it as a "closed-loop" system that captures and recycles carbon dioxide to trigger the chemical reactions that convert iron ore into steel. A mineral known as perovskite is used to react with carbon dioxide at lower temperatures, she said. The system could be retrofitted onto furnaces.
"Some coking coal is used to start up this thermochemical cycle, but from that point on, you would never need to add any more," Kildahl said.
The system could be easier and cheaper to adopt than other strategies to decarbonize steel because it repurposes blast furnaces rather than replacing them, Yulong Ding, a co-author of the research, told Insider. His team is searching for industrial partners to build a plant and test the process on a pilot scale.
Technologies that don't use fossil fuels for steel production are emerging, though they haven't been proven to work on a commercial scale.
The Swedish steelmaker SSAB built a plant that uses green hydrogen from renewable energy and delivered a small amount of fossil-free steel to Volvo last year. SSAB aims to reach commercial scale by 2026. Startups like Boston Metal and Electra, which are backed by Bill Gates' venture-capital firm and heavy industry, are in the early stages of testing two ways to use electricity to convert iron ore to steel.
Yet every strategy has its drawbacks, including the one out of the UK.
"I found this very innovative and promising," said Jihye Kim, an assistant professor at the Colorado School of Mines who researches critical mineral extraction from the wasted byproducts from steel production. "But there are a few disadvantages."
Kim said the researchers' approach doesn't replace 100% of coke, so other materials like biomass, charcoal, or recycled plastic must be added. Using mostly gas instead of solid coke in the blast furnace also raises questions about its stability at an industrial-sized plant. Extra heat and power might be required, although ideally that could be met with renewables.
In the end, different strategies are needed to decarbonize steel, Kim said. "We can use multiple techniques at the same time."