Cement is one of the most-used manmade materials in the world. And the kilns that produce this in-demand building material belch about 8 percent of the global carbon dioxide emissions.
But a team from ETH Zurich and the US company Heirloom Carbon Technologies now propose a way to dramatically cut emissions from future cement factories. By employing established technologies, cement factories could not only capture their own emissions, the researchers write in the journal Chem Circularity, but also remove additional carbon dioxide from the atmosphere
The world produces about 4 billion tons of cement every year. Manufacturing cement, which is the key ingredient of concrete, is notoriously difficult to decarbonize. That’s because it requires heating limestone at high temperatures in large fossil fuel-burning kilns. And the chemical reaction itself releases carbon dioxide.
The ETH team proposes powering kilns with clean electricity rather than fossil fuels. That would cut the carbon emissions from heat production. Heirloom Carbon’s direct air capture technology would then capture the carbon dioxide released during limestone conversion. The gas would be compressed and permanently stored underground.
The company’s DAC technology, called calcium looping, is “uniquely positioned for such integration,” the team writes in the paper. That’s because the process cycles calcium between two compounds: calcium carbonate and calcium hydroxide. These are the same materials and chemical conversion steps used in cement manufacturing.
Limestone, or calcium carbonate, is the starting point. When heated, the limestone breaks down into calcium oxide, also known as quicklime, and carbon dioxide. In the proposed system, adding water to the quicklime would make it absorb more carbon dioxide from the atmosphere and turn back into limestone, and the loop would continue.
According to the researchers’ calculations, electrifying the kiln and using calcium-looping DAC could reduce the climate impact of cement production by 78% by 2050.
Heirloom has been running a plant in California since 2023. The plant can capture 1,000 tonnes of carbon dioxide a year. “Heirloom was an ideal partner for us because the company is already operating the first calcium looping DAC systems on a commercial scale,” said Vittoria Bolongaro, a graduate student and lead author of the paper, in a press release.
The team analyzed various energy scenarios. These included operating the plant using the current US electricity mix; using a clean electricity mix consisting of wind and solar energy; and a fully autonomous clean-energy system with photovoltaics and battery storage.
“We were able to show that the technology has a net-negative carbon footprint,” Bolongaro said. “In other words, commercial calcium looping DAC plants with carbon dioxide storage remove more carbon dioxide than they generate over their entire lifecycle.”
Source: Vittoria Bolongaro et al. Life cycle assessment of solid calcium-looping direct air capture and its synergistic dual use for net-negative cement. Chem Circularity, 2026
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