Scientists figure out how to turn toxic red mud into steel: 'Now it's up to the industry to decide'
They may not be squeezing water from stone, but scientists in Germany have achieved a near-equally impressive feat.
They have created steel from mud, or more specifically, from a toxic red slurry left after aluminum production that can leach into the ecosystem.
It's the result of research from Max-Planck-Institut für Eisenforschung into cutting steel industry pollution, which is reported to account for about 8% of the world's atmospheric carbon pollution, according to the institute.
"Our process could simultaneously solve the waste problem of aluminum production and improve the steel industry's carbon footprint," Matic Jovičevič-Klug, who played a key role in the research, said in a lab summary.
Waste from making aluminum —198 million tons of this mud is generated each year, per Max-Planck — contains up to 60% iron oxide. The slurry is melted with an electric arc furnace, and hydrogen is used to separate iron in a 10-minute process called plasma reduction. At this point, the iron is ready to be turned into steel.
By using green hydrogen in the process, the Max-Planck technique improves on past methods because it leaves recyclable byproducts and no air pollution, according to the lab.
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"If green hydrogen would be used to produce iron from the [4.4 billion tons] of red mud that have been generated in global aluminum production to date, the steel industry could save almost [1.6 billion tons] of CO2," Max-Planck research group leader Isnaldi Souza Filho said in the report.
The aluminum industry is massive. Data collector Statista reports that the market size hit $150 billion in 2020. It's expected to reach $210 billion by 2027, mostly for packaging and construction materials.
Max-Planck's summary notes that the high-alkaline mud, containing heavy metals, is often buried in landfills. The waste sometimes leaches out of the pits when it rains. It can even dry out and blow around afterward.
Astoundingly, the German process has the potential to manufacture more than 771 million tons of cleaner steel from the billions of tons of red waste already made.
It's not the only effort to avoid pollution from the construction sector. Some builders are turning back to timber as a steel alternative. Better methods are now allowing sturdy wooden structures to reach new heights. By using wood in builds, the material continues to store some of the carbon dioxide the tree had cleaned from the air when it was alive. That air pollution is typically released when the wood is burned or when it decomposes, per the U.S. Forest Service.
These efforts can have a direct impact on our health, as well. Air pollution is associated with an increased risk of heart disease, cancer, and even dementia.
For Max-Planck's part, the mud recycling process has cleared economic analysis. The team said the technique can be easily added to existing aluminum production sites since facilities already have much of the equipment needed. Now the experts are looking at ways to better use some of the other heavy, and in some cases precious, metals being collected from the mud.
"It was important for us to also consider economic aspects in our study," lab director Dierk Raabe said in the report. "Now it's up to the industry to decide whether it will utilize the plasma reduction of red mud to iron."
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