In the midst of the era of decarbonizationthe first thing that comes to mind when we think about ways to emit less CO₂ into the atmosphere is the transition to renewable energy or electric vehicles. However, we can often overlook something that sends as many CO₂ emissions into the atmosphere each year as all the cars in the world: the cement. This material is essential and, although We have been looking for a replacement for yearsa team from the University of California believes they have found the key to creating greener cement.
A cement without limestone that relies on silicates.
Portland cement. It is the basic material that ‘links’ our reality. This paste resulting from the mixture of water, sand and stones is very resistant and, as we say, although we have been looking for a substitute for some time, the truth is that we have not found the key. It is still a structural part of buildings, bridges, dams or tunnels and the problem is that the cement industry is estimated to represent around 4.4% of global greenhouse gas emissions.
And one of the problems with this cement is limestone. It is a simple rock to refine, but it requires a lot of energy. It is not that limestone pollutes by itself, but because of the process that must be followed to process it and make it a good ingredient in cement. This limestone must be heated to more than 1,500 degrees Celsius to produce the calcium oxide necessary for the mixture and it is estimated that half of all CO₂ emissions linked to cement production are related solely to that process with limestone.
Focus shift. With that in mind, Jeff Prancevic (a geologist at the University of California, Santa Barbara) and Cody Finke (of Brimstone Energy) set out to replace the elephant in the room. If Portland cement is the most used and the limestone refining process is what pollutes the most in the process, the rock had to be removed from the equation. The key? Find other rocks rich in calcium, but that are easier to refine.
Basalt to the rescue. And in the study published in Nature They detail how basalt is that rock that meets what they are looking for. After carrying out different analyses, they came to the conclusion that, in theory, manufacturing cement from these calcium-rich silicates can require less than 60% of the energy needed by limestone, reducing CO₂ emissions by 80% in the process.
In numbers. It is estimated that, in the refining of limestone, 600 kg per metric ton of cement of CO₂ are sent into the atmosphere, but if we use other silicates, the authors calculate that these emissions could be around 50 kg per ton. In the least conservative calculations, the proposed solution would still cut more than 25% CO₂ compared to the standard process with limestone.
Another interesting point is that the processing of these other rocks has the potential to give us valuable byproducts with high iron and aluminum content that could benefit other industries. That is, the material would be used more while contaminating less.
The pasta question. The problem is… the same as always. When we talk about a new lbrick from recycled plasticsof sugar bricks or of others in the shape of a ‘staple’ that do not need cement to join together, the bottom line is that the construction industry should make a radical change in its processes. It is a huge liner that cannot be swerved overnight, no matter how many benefits these new materials have.
And the same thing happens here. Although it is not about creating an alternative to cement, but rather using other rocks to extract the calcium that the mixture needs, the money comes into play in two ways. The first for the basalt deposits. If the cement industry has been organized around enormous limestone deposits to optimize processes, switching to basalt would imply relocating plants or creating new supply chains that would increase both time and costs.
If something works… On the other hand, the margins of the cement industry, which has been shown to be extremely conservative throughout history. There is a product that works and changing something in the chain would involve carrying out a reorganization that they may not want to undertake. There is also the fact that yes, basalt has iron and aluminum as a byproduct, but the plants would have to be conditioned to be able to treat it properly, which would mean a huge initial investment.
The authors of the study themselves indicate that it is difficult for an industry that for a century has been organized around Portland cement changed its way of acting one bit, but they also point out that, precisely for this reason, they have focused on finding materials such as basalt that are abundant, with reserves to maintain the current pace of construction for thousands of years and that emit less into the atmosphere.
It is obtaining calcium from a different rock and its authors call on the industry, and other researchers, to experiment with new technologies that help accelerate the decarbonization of cement. The problem is that, as we say, there are too many drawbacks that the industry itself probably does not want to take on.
Image | Cemco
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