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On a hot July morning, in a test facility outside of Paris, a group of scientists, engineers, and architects wearing hard hats and goggles watched through protective glass as the machine molded a gray viscous mixture into The size of the batch of bricks. Along the production line, forklift operators carefully load the building blocks into the curing chamber, just like bread in a bakery.

What they witnessed was the trial run of a new concrete manufacturing process developed by Solidia Technologies, which the New Jersey-based company hopes will greatly change the way this building material is manufactured. The company said that by adjusting the chemical composition of one of the basic components of concrete—cement—and changing its curing process, the company said it can make concrete cheaper than traditional processes while significantly reducing carbon emissions associated with cement production. .

Cement is one of the most serious carbon pollution industries in the global economy. In 2015, it accounted for about 8% of global carbon dioxide (CO2) emissions. If ranked by a single country, the cement industry will become the world's third-largest greenhouse gas emitter after China and the United States. With the continued economic development and rapid urbanization in Southeast Asia and Sub-Saharan Africa, this already large footprint is only expected to continue to grow in the next few decades. According to the International Energy Agency and the Cement Sustainable Development Initiative, cement production may increase by 23% by 2050.

This corresponds to a major challenge to climate change. A 2018 study estimated that by 2030, cement-related emissions must be reduced by at least 16%. If countries are to achieve the 2015 Paris climate agreement target, that is, to limit the temperature rise below 2 degrees Celsius in this century, then After that, the decline was even greater.

According to industry experts, reducing emissions on this scale will require widespread adoption of less carbon-intensive cement alternatives being developed by laboratories around the world. But in a market where a few major manufacturers are cautious about changing existing business models, lack of strong policies to encourage green technology, and the construction industry is reasonably cautious about new building materials, the prospect of such a radical transformation is still far away. . From some.

The amazing carbon footprint of the concrete industry is mainly due to the large scale of material use. This ordinary combination of sand and gravel bonded together by cement, this artificial stone is ubiquitous, and is almost a part of every structure in our modern architectural environment.

"There can be no society today without concrete," said Robert Courland, author of the book "Concrete Planet." It is the most abundant synthetic material in existence. According to the Australian Trade Organization Cement Industry Federation, if you separate all the concrete used in the world every year, then everyone on the planet will get three tons of concrete, making it second only to Water is the second largest resource consuming in the world.

Because of its abundance, concrete has caused huge losses to the environment. For example, the process of making Portland cement is the most common form used to produce concrete, and it is one of the most carbon-intensive manufacturing processes available; just making one ton can produce more than 1,000 pounds of carbon dioxide.

The process starts with crushed limestone, mixing the limestone with other raw materials, and then feeding it into a large rotating cylindrical kiln heated to above 2,600 degrees Fahrenheit. The kiln body is inclined at a small angle, and the material is poured into the raised end. When they move toward the roaring flame at the lower end of the kiln, some of the components will burn off in the form of gas, while the rest will combine to form a gray ball called clinker. The block of material—about the size of marble—is cooled and then ground into a fine powder to form a key binding element that hardens the concrete when it is cured with water.

This process has hardly changed since it was invented nearly two centuries ago, and it generates carbon emissions in two ways. First, fossil fuels are usually burned to heat the kiln to the high temperatures required to decompose materials, and carbon is emitted in the process. In addition, the thermal decomposition process itself causes emissions because the carbon captured in the limestone combines with oxygen in the air to produce carbon dioxide as a by-product.

Gaurav Sant, a professor of civil and environmental engineering at the University of California, Los Angeles, said that up to two-thirds of cement-related carbon emissions come from this reaction, which is why cement manufacturing is considered a particularly difficult process to decarbonize. Los Angeles (University of California, Los Angeles). He said that because carbon dioxide emissions are part of the chemical process itself, even if you completely switch to low-carbon or zero-carbon energy to heat the kiln, only part of the problem can be solved.

Cement manufacturers have taken measures to reduce emissions. Due to improvements in energy efficiency and adjustments to concrete mixes, the average carbon dioxide intensity of global cement production has fallen by 18% in the past 20 years. Some companies have also installed technologies to prevent carbon dioxide emissions from entering the atmosphere, although these systems can only capture so much and may not be able to prove feasible on the scale required to produce a significant impact.

Although industry leaders have recently pledged to further reduce carbon dioxide emissions, Sant warned that existing technologies can only achieve some of the carbon dioxide emissions required to achieve the Paris target. "What the industry really needs to do is to invest money and energy to produce new or alternative types of cement, which require less or no clinker," he said. "This is the only way they can solve the problem of carbon dioxide emissions upstream of cement production."

The company is trying different methods to reduce or eliminate the amount of clinker required to make concrete. For example, bioMASON, located in North Carolina, uses natural bacteria as a binder to make concrete bricks, while the UCLA spin-off company CO2Concrete has developed a technology that can directly extract carbon dioxide from the flue of a power plant to produce solids The minerals can then be used to replace the carbonates of traditional Portland cement. Other companies, such as banah in the UK and Zeobond in Australia, focus on using by-products from other industrial processes to make so-called "geopolymers" to replace clinker in cement production.

Experts say that Solidia, a New Jersey company that completed operations in France this summer, is one of the most promising companies. The process was first developed at Rutgers University in 2008 and involves manipulating cement chemistry to significantly reduce the kiln temperature required to produce clinker, and then using waste carbon dioxide instead of water to solidify concrete made of cement.

"Compared with ordinary Portland cement-based concrete, the combination of these technologies reduces the carbon footprint by up to 70% at a lower cost," said Tom Schuler, President and CEO of Solidia, which has received well-known venture capital investment The funding supports companies Kleiner Perkins and Bright Capital, oil giant BP, and Switzerland-based LafargeHolcim (the world’s largest cement producer).

Another company dedicated to alternative cement solutions is CarbonCure, which is headquartered in Halifax, Nova Scotia. CarbonCure is the brainchild of Rob Niven, a civil engineer, who developed a system to pump liquefied carbon dioxide into the wet concrete during mixing. As the concrete hardens, the carbon in carbon dioxide reacts with the concrete to become a mineral, effectively reducing the demand for cement without affecting the strength or price of the concrete.

"In any given building or infrastructure project, this carbon dioxide mineralization process can reduce the carbon absorbed by hundreds or even thousands of acres of trees in a year," said Christie Gamble, CarbonCure's Director of Sustainability. She said that global deployment can reduce about 550 million tons of carbon dioxide each year, which is equivalent to reducing 150 million cars on the road.

At present, CarbonCure's technology requires minor modifications, including computer systems, tanks for storing carbon dioxide, and pipes for pumping carbon dioxide into the concrete mixture. It has been installed in nearly 150 concrete plants in North America. The company said it is also expanding into Southeast Asia and Europe.

In one of the most fashionable neighborhoods in Atlanta, Georgia, a multi-storey commercial office building under construction, a real-world demonstration of their products is taking shape. The building will be completed by the end of this year and will be the first large-scale development project to use CarbonCure concrete in the entire structure. According to Gamble, this project alone can prevent more than 750 tons of carbon dioxide from being released into the atmosphere, which is equivalent to 800 acres of forest land that can store carbon dioxide a year.

Although companies like Solidia and CarbonCure have begun to make progress, they still have a long way to go to capture a small portion of the market. Schuler said the main obstacle is the general conservatism in the construction industry. "The general attitude in the industry is seeing is believing," Schuler said. The company has spent approximately US$100 million on research and development and trials, such as trials conducted in France to convince commercial customers.

The reluctance to adopt new technologies is understandable. "When it comes to ensuring the safety of life in the structure, you have to make sure that everything you do will work," Santer said. But he also believes that today's safety regulations cannot assess the new concrete production processes required to significantly reduce the industry's carbon emissions.

"The problem is that we have relied on normative norms and standards that tell us to be specific in a certain way for too long, instead of using performance-based standards to stimulate departmental innovation," he said.

Another major issue is cost. "While novel solutions are not always more costly than traditional solutions, in some cases the willingness to pay additional costs is limited," Jeremy Gregor, executive director of the MIT Center for Concrete Sustainability Li said that the center is a research group focused on the production and use of sustainable concrete. For example, a 2015 study found that the cost of geopolymer-based cement is three times that of traditional cement.

Gamble said that there is also a lack of policies to offset these higher costs and encourage investment in climate-friendly cement, and implied that “technical progress alone cannot reduce cement emissions.” She said, “Measures such as emission caps and fines need to be adopted to pass on. The market signals and encourages the widespread adoption of more environmentally friendly technologies."

Finally, she admitted that low-carbon cement is still a long way from mass adoption. But she remains optimistic: "It may take 20 years, 30 years, or even more. But we are beginning to see the first light on this path."

Given the huge scale of its carbon footprint, cement alone can accomplish or undermine efforts to slow global warming. For Gregory, the only way out is to continue to accelerate the efforts of the entire industry.

"Postponing or avoiding this challenge," he said, "is not a real choice."

Marcello Rossi is a freelance science and environmental journalist based in Milan, Italy. His works have been published by Al Jazeera, Smithsonian Institution, Reuters, Wired, and external media.

This article was originally published in Undark. Read the original text.

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