Today’s Solutions: June 18, 2024

University of Cambridge scientists identified a new way for recycling cement from demolished concrete buildings, which might reduce emissions from one of the world’s most polluting industries. Cement, the cornerstone of contemporary construction, accounts for a considerable share of worldwide CO2 emissions due to its energy-intensive manufacturing process.

What’s the environmental impact of cement?

Cement manufacture is a major cause of climate change. It accounts for 7.5 percent of human-caused CO2 emissions, making it the third highest source of emissions if it were a country, following China and the United States. The principal culprit is the chemical reaction that occurs when limestone is heated to high temperatures, which is typically accomplished by burning fossil fuels.

The production method entails heating limestone to around 1600 degrees Celsius in massive kilns, which not only consumes a considerable amount of energy but also emits large amounts of CO2. For every tonne of cement produced, approximately one tonne of CO2 is released.

The breakthrough: electric cement

The Cambridge researchers devised a method to revive spent cement by subjecting it to high temperatures again. This procedure, which was previously performed in cement kilns, can now be powered by electric arc furnaces used in steel recycling. These furnaces, fueled by renewable energy sources such as wind and solar, have the potential to eliminate the CO2 emissions connected with cement manufacture.

Cyrille Dunant, the lead scientist, stated, “We have shown the high temperatures in the furnace reactivate the old cement and because electric arc furnaces use electricity they can be powered by renewable power, so the entire cement-making process is decarbonized.”

Combining cement and steel recycling

The novel approach takes advantage of the chemical similarities between used cement and steel recycling slag. Slag, a byproduct of steel manufacture, occurs when chemicals are introduced to molten metal to avoid impurities. The Cambridge team realized that spent cement may serve a similar purpose in electric arc furnaces.

Mark Miodownik, Professor of Materials and Society at University College London, applauded the concept, calling it “genius.” He stressed the possibility of considerable emission savings if the technology can be developed profitably. “Can it compete against the existing infrastructure that is very unsustainably going to keep pumping cement into our lives?” He asked. “Cement is already a billion-dollar industry. It’s David and Goliath we are talking about here.”

The researchers successfully tested the method on a small-scale electric arc furnace at the Materials Processing Institute in Middlesbrough. The first high-quality Portland cement manufactured using this process was nicknamed “electric cement.” Celsa, a Spanish business, plans to reproduce the process in a full-scale electric arc furnace in Cardiff, to demonstrate its industrial viability.

Dunant highlighted the dual environmental benefits: “It also makes steel recycling less polluting because making the chemicals currently used as slag has a high carbon cost too.”

A vision for global impact

This innovation has a tremendous potential impact. Given current steel recycling rates, the Cambridge team believes that their low-carbon cement may cover up to a fourth of the UK’s needs. As the usage of electric arc furnaces expands globally, the manufacturing of electric cement may increase, resulting in a significant reduction in cement-related emissions worldwide.

The expectation is that electric cement will be not only more ecologically friendly but also less expensive to make by utilizing waste heat from steel recycling processes. If properly expanded, this technology has the potential to revolutionize the cement industry by drastically decreasing its carbon footprint and contributing to global efforts to battle climate change.

 

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