When people talk about fighting climate change, they usually focus on electric cars, renewable energy, or cutting fossil fuel use.
But one major source of greenhouse gas emissions often receives far less attention: cement.
Cement is the key ingredient in concrete, one of the most widely used building materials in the world. It is essential for roads, bridges, buildings, and other infrastructure.
Yet cement production creates enormous amounts of carbon dioxide.
In fact, researchers say the cement industry produces greenhouse gas emissions comparable to all the world’s passenger cars combined.
Now, scientists believe a common volcanic rock called basalt could offer a cleaner way to make cement.
The research, led by scientists including Jeff Prancevic from University of California Santa Barbara and researchers from Brimstone Energy, was published in Communications Sustainability.
Most modern cement is a type called Portland cement. To make it, companies heat limestone to extremely high temperatures above 1,500°C. This process creates quicklime, a crucial ingredient in cement.
The problem is that limestone naturally contains large amounts of carbon. When heated, it releases carbon dioxide directly into the atmosphere. Producing one ton of cement can release hundreds of kilograms of carbon dioxide, even before accounting for the fuel used to heat the kilns.
The researchers explored whether calcium-rich silicate rocks such as basalt or gabbro could replace limestone in cement production. Unlike limestone, these rocks contain very little carbon.
The team found that using basalt could dramatically lower emissions and energy use. According to their estimates, producing cement from silicate rocks might require less than 60% of the energy needed for limestone-based cement production.
Carbon dioxide emissions could also fall by more than 80% under ideal conditions.
The researchers also discovered that Earth has enormous supplies of basalt. Existing geological data suggest there is enough accessible basalt to support cement production for hundreds of thousands of years at current demand levels.
Another advantage is that basalt contains useful metals such as iron and aluminum. These materials could potentially be recovered during cement production and used in industries like steelmaking and aluminum manufacturing.
The scientists noted that basalt naturally contains calcium and iron in ratios similar to what society already uses for cement and steel production. This means a single raw material could help produce multiple important industrial products while reducing waste and energy use.
Despite the promise, the researchers acknowledge that changing the cement industry will not be easy. Cement is relatively cheap, and the current limestone-based process has been refined for more than a century. The construction industry is also cautious about changing materials and standards.
Still, the researchers believe their approach has an important advantage: it produces the same Portland cement already widely used around the world. This means it could potentially fit into existing supply chains and construction systems more easily than entirely new cement alternatives.
The team hopes the study encourages more scientists and companies to explore cleaner cement technologies that could help reduce one of the world’s biggest industrial sources of carbon emissions.
