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The idea is to replace limestone, which is almost half carbon dioxide, with volcanic rocks like basalt, which release little carbon when heated. In theory, the gain is enormous: less energy and up to 80% fewer emissions. In practice, however, turning a century-old industry upside down is the big obstacle.
After decades of searching for a substitute for the dirtiest ingredient in cement, scientists at the University of California claim to have found a promising alternative in basalt, an almost inexhaustible volcanic rock. The discovery, according to the researchers, could help decarbonize one of the world’s most polluting sectors and even lower production costs, tackling a climate problem as big as that of all the cars on the planet combined.
The study was led by geologist Jeff Prancevic from the University of California, Santa Barbara, in partnership with Cody Finke from Brimstone Energy, and published in a scientific journal of the Nature group. It’s worth adjusting expectations right from the start: although the press has used the expression “Holy Grail,” it is a theoretical proposal and a call to the industry, with enormous practical barriers that the authors themselves acknowledge, and not a ready-to-use solution.
Why cement is so polluting
The cement industry accounts for about 4.4% of global greenhouse gas emissions, a volume comparable to that of all passenger cars in the world combined, even though almost no one associates the material with climate change.
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After nearly twenty years of halted and resumed construction, the Transnordestina has reached 79% completion and finally promises to connect the hinterland to two ports on the Northeast coast.
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Madrid wants to build the world’s largest Ferris wheel at 260 meters and €300 million, surpass Dubai, transform Spain’s landscape, and create its own ‘Eiffel Tower’ in a project that still faces resistance and depends on approval.
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Saudi Arabia and Qatar signed the agreement to connect Riyadh to Doha with a high-speed train traveling at 300 kilometers per hour, covering 785 kilometers of desert in about two hours.
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What is the ideal distance between one pillar and another? The measurement used in houses with up to 2 floors can avoid huge beams, low ceilings, and extra construction costs.
The major problem lies in limestone, the rock from which calcium is extracted to manufacture Portland cement, the most used type on the planet. To transform limestone into quicklime, the key ingredient of the mixture, it must be heated to more than 1,500 degrees Celsius. The crucial detail is that limestone is, chemically, almost half carbon dioxide, which is released directly into the atmosphere during this process, adding about 500 kilograms of CO₂ per ton of cement, not counting the energy spent to heat the kilns.
The proposed solution: change the rock
Instead of looking for a substitute for the cement itself, they propose changing the rock from which calcium is extracted, using calcium-rich silicate rocks, such as basalt and gabbro, instead of limestone. The advantage is chemical: in these volcanic rocks, calcium comes from silicates, not carbonates, meaning they have little carbon trapped in their structure.
In practice, this means that heating basalt to extract calcium does not release that enormous amount of CO₂ that limestone does. And there is an important advantage: the final result would be the same Portland cement that the construction industry already knows and uses, without requiring changes in construction methods. This differentiates the proposal from other alternative cements that never took off because they required adapting the entire chain.
The numbers that excite
The gains calculated by the study are significant, even if theoretical. According to the researchers, manufacturing cement from these silicates could require less than 60% of the energy needed to process limestone and reduce CO₂ emissions associated with this production stage by more than 80%. Even in more conservative calculations, the reduction would exceed 25%.
There is also an interesting bonus: the processing of these rocks can generate valuable by-products rich in iron and aluminum, which could supply other industries, such as steelmaking. In theory, more material would be utilized, reducing waste and improving the overall efficiency of industrial production. All this, according to the authors, would be possible with technologies that already exist today, without relying on future inventions.
The major obstacle: turning a transatlantic
Here is the point that prevents euphoria and needs to be said frankly. The cement industry has been organized for over a century around massive limestone deposits, and switching to basalt would require relocating factories or creating new supply chains, which would increase time and costs, in an effort comparable to making an ocean liner change course overnight.
Moreover, the sector’s profit margins are historically conservative, and adapting factories to process basalt and its byproducts would require a huge initial investment. The study’s authors themselves admit that it is unlikely that an industry structured around traditional Portland cement will easily change its practices. Therefore, they themselves classify the work as a call for researchers and companies to experiment with new technologies, rather than a guaranteed turnaround.
An abundant rock and the Brazilian case
One of the strongest arguments in favor of the proposal is the availability of the raw material. Basalt is one of the most abundant rocks in the Earth’s crust, with reserves capable of sustaining the current pace of construction for thousands of years, which eliminates the risk of scarcity that could render the idea unfeasible in the long term.
This point is especially relevant for Brazil, which has enormous basalt reserves, particularly in the South and Midwest regions, associated with the volcanic formations of the Paraná Basin. In a country that is a major consumer of cement and has strong construction activity, the possibility of producing a lower carbon footprint cement from such a common rock in the national territory is a topic that deserves attention, within the broader debate on decarbonizing the heavy industry.
The research on basalt as a substitute for limestone in cement is encouraging and targets one of the world’s biggest and most ignored climate problems. The promise of drastically cutting emissions using an abundant rock while maintaining the same cement as always is powerful. But, as the scientists themselves emphasize, the path from theory to factory is long and full of economic and logistical obstacles. More than a ready-made Holy Grail, the study is an invitation for industry and science to take seriously the urgency of decarbonizing cement.
And you, did you know that cement pollutes as much as all the cars in the world combined? Do you believe the industry will agree to switch limestone for basalt in the name of the climate, or will cost speak louder? Leave your comment, share your opinion on the decarbonization of construction, and share the article with those interested in science, environment, and innovation.
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