Scientists at ETH Zurich have discovered a way to combine cement production with carbon removal via direct air capture (DAC) technology. This could significantly reduce harmful emissions and even make cement production carbon-negative.
Cement is produced on a massive scale (4 billion tons annually) making it a major source of CO2, as carbon dioxide is released when limestone is heated. The new method utilizes the same chemical processes to capture CO2 from the atmosphere, thereby reducing the cement industry’s climate impact.
The team from ETH Zurich, led by André Bardow, and the US company Heirloom Carbon Technologies have examined how cement production can both capture its own emissions and remove additional CO2 from the air.
In this process, limestone and related calcium compounds circulate through a chemical cycle. According to the researchers, combining cement production with DAC technology could reduce its climate impact by up to 78% by 2050.
The proposed system uses an electric furnace instead of coal, gas and other fossil fuels, in consequence eliminating combustion emissions.
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The carbon dioxide released during the heating and decomposition of limestone is captured before it enters the atmosphere, after which it is compressed and permanently stored underground to prevent its release back into the atmosphere.
The system can also capture CO2 directly from the air by adding water to quicklime, which produces slaked lime that reacts with atmospheric carbon dioxide and reverts to limestone.
The technology’s potential
Combining DAC technology with cement production offers the unusual advantage that both utilize similar materials and high-temperature processes. This means there is no need to create an entirely new industry, because the technology can be integrated into existing cement production chains.
Researchers have assessed the environmental impact of this technology on an industrial scale. They examined the entire process from raw material extraction and equipment construction to energy consumption, facility operations and the storage of captured CO2.
Projections for 2050 suggest that calcium-looping systems could remove more CO2 than they emit over their entire lifecycle, with efficiency expected to range between 85% and 96%.
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