Researchers at UCLA have developed a method that could remove almost all the carbon dioxide emitted during the process of creating cement, according to a UCLA news release.
Currently, cement production involves heating limestone in a kiln powered by planet-warming dirty energy such as petroleum or coal. This produces a kilogram of carbon dioxide for every kilogram of cement created, per the release. In fact, cement production accounts for about 8% of the atmospheric carbon pollution in the world. Of those emissions, 60% comes from the limestone itself being heated and broken down into lime, while 40% comes from the fuels used to power the kilns. On top of that, creating one metric ton of lime (more than 2,200 pounds) requires enough energy to more than power an average American home for a month, all according to UCLA.
Instead, researchers proposed using calcium hydroxide, which produces just water when heated, to create lime. They placed limestone in a water-based solution containing a common industrial acid and used membrane nanofiltration to separate the calcium from limestone. They then used an electrochemical process to create calcium hydroxide.
This process generates hydrochloric acid, baking soda, oxygen, and hydrogen. The researchers proposed that the hydrogen could be used to power the kilns to create cement. This all combines to eliminate an estimated 98% of carbon pollution from the lime-creation part of the process.
"The ZeroCAL approach offers an elegant solution to eliminate carbon dioxide emissions associated with the process of cement production," said Gaurav Sant, director of the Institute for Carbon Management and UCLA's Pritzker Professor of Sustainability.
While the process does require more energy than traditional cement production, researchers are hopeful that further research will lessen that load.
Cement producers have been looking to transition to greener processes for some time now. Some of the largest in the world have invested $75 million in greener production practices. Meanwhile, scientists have discovered a means of creating a type of cement that reportedly absorbs carbon from the atmosphere.
For their part, the UCLA researchers believe their nearly carbon-free procedure shows real promise.
"It has become crystal clear that mitigating climate change demands urgent, paradigm-shifting actions across many areas to decarbonize our society," said study co-author Fabian Rosner, an assistant professor of civil and environmental engineering at UCLA. "We believe the ZeroCAL process offers a unique pathway to enable accessible and rapidly scalable decarbonization of cement production in a way we have not previously considered."
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