Using Building Materials for Carbon Capture

Global temperatures will keep rising until we achieve net-zero carbon dioxide (CO2) emissions—when the CO2 we add to the atmosphere equals the amount we remove. To meet the 2015 Paris Agreement goal of limiting global warming to below 2°C (ideally 1.5°C) above preindustrial levels, we may need to remove 2 to 15 billion tons of CO2 annually. However, we currently lack sustainable methods to capture and permanently store such large amounts of CO2.

A report in ScienceAdvisor suggests that replacing traditional building materials with CO2-storing alternatives could help sequester carbon on a massive scale. Given the global demand for infrastructure and the long lifespan of buildings, this approach could be a practical way to achieve long-term CO2 removal. Building materials like concrete, asphalt, steel, and bricks are widely used, with predictable demand—around 30 billion tons of concrete, for example, are used annually. Unfortunately, some materials, particularly cement, are major sources of CO2 emissions. Cement, which makes up about 15% of concrete, requires heating to 1450°C during production, releasing large amounts of CO2 through the calcination of limestone. Cement production contributes 7.8% of global CO2 emissions and 5.1% of total greenhouse gases.

What if materials like concrete, asphalt, and bricks could be made to capture and store CO2 from the atmosphere?

Carbonatable concrete aggregates, such as calcium oxide (CaO), magnesium oxide (MgO), and silica (SiO2), can react with atmospheric CO2 to form stable carbonate compounds. These materials are extracted from natural resources through heating or acid leaching. This process offers a way to remove significant amounts of CO2 from the air and store it permanently.

Among the materials studied, asphalt aggregates, bricks, cement, and concrete aggregates showed the highest CO2 storage potential due to their large-scale use. Researchers found that replacing traditional cement and concrete aggregates with CO2-storing alternatives alone could remove 13.1 Gt of atmospheric CO2 annually.