Cement production – the largest building material in the world – is known to be a major source of greenhouse gas emissions, accounting for about 8 percent of all emissions.
If cement production were a country, it would be the third largest emitter in the world.
A team of researchers from the Massachusetts Institute of Technology has come up with a new way to manufacture materials that can eliminate these emissions altogether, while creating some other useful products.
The results are reported today in a paper by Yat-Ming Chiang in PNAS, along with a professor of science and engineering at Kyocera at MIT, and postdoctoral Leah Ellis, graduate student Andres Badell, et al.
“For every kilogram of cement made today, about one kilogram of carbon dioxide is produced,” says Chiang.
This increases the 3 to 4 gigabytes (billions of tons) of cement and carbon dioxide emissions produced annually today, and this amount is expected to increase.
He says the number of buildings worldwide is expected to double by 2060, which is equivalent to “building a new New York City every 30 days.”
The commodity is now very inexpensive to produce: it costs about 13 cents per kilogram, which it says is cheaper than bottled water.
Therefore, it is very difficult to find ways to reduce carbon emissions without making materials expensive.
Chiang and his team spent the past year exploring alternative routes and attacked the idea of using an electrochemical process to replace the current system of fossil fuels.
Ordinary portland cement, the most widely used standard variety, is manufactured by grinding limestone and then baked at high temperatures with sand and clay, which is made from burning coal.
The process produces carbon dioxide in two different ways: from burning coal, and from gases from limestone during heating.
Each of these is approximately equal to total emissions
Xiang states that the new process will significantly remove or reduce both sources. Although it showed basic electrochemical processes in the laboratory, more work is needed to make this process work on an industrial scale.
First, the new approach can eliminate the use of fossil fuels in the heating process, replacing electricity generated from clean and renewable sources.
“Renewable electricity is the least expensive electricity in many geographic areas, and its costs are still declining,” Qiang says.
The team felt that trying to gain acceptance for a new type of cement – something that many research groups have done in different ways – would be a tough battle, given that all over the world the newly used and relatively unused materials of how materials are used are officially used and how construction companies can experience Reluctant.
The new process focuses on the use of electrolysis, something many people have faced as part of chemistry classes in high schools, where the battery is connected to two pieces of electricity in a glass of water, from one electrode to oxygen.
The resulting bubbles and one bubble cause electric molecules to split into their constituent atoms, causing hydrogen from the other.
More importantly, the oxygen electrode in the electrophoresis produces acid, while the hydrogen electrode produces a base.
In the new process, a large amount of limestone is dissolved in acid in one electrode and high purity carbon dioxide is released, while calcium hydroxide, known as lime, hardens in the other. as it turned out.
Calcium hydroxide can then be treated in the second stage of cement formation, which is mostly calcium silicate.
Carbon dioxide can then be easily sequenced, as a pure and concentrated stream, ready to produce value-added products such as liquid fuels to replace gasoline or to extract oil or carbonated beverages. Also used. Dry ice.
The result is that carbon dioxide is not released into the environment through the whole process, Qiang says.
The calculations show that the hydrogen and oxygen emitted from the process can be reunited, for example in the fuel cell, or burned to produce enough energy to feed the entire process, Ellis says. She, nothing but water vapor.
In the laboratory demonstration, the team took the necessary electrochemical steps, where lime is produced from calcium carbonate, but on a smaller scale.
This process seems to vibrate the globe, producing a group of white particles suspended inside the glass container while lime escapes from the solution.
While the technology is simple and can, in theory, be easily scaled up, the typical cement plant today produces about 700,000 tons of material per year.
“How do you enter an industry like this and put your foot in the door?” Asks the main author of the paper Ellis.
One method, she says, is to try to change the entire system, adding other parts “in a gradual way” rather than completing one part of the process at a time.
Chiang said the team’s initial proposed system was “not because we necessarily think we have a precise strategy” for the best approach possible, but people in the electricity sector are thinking more about this to get started, “and come up with new ideas.”
This is an important first step, but it’s not a solution. Fully developed. “