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Cement carbon dioxide emissions quietly double in 20 years

Cement carbon dioxide emissions are quietly doubling in 20 years

Sheep graze on a pasture near a cement factory on the outskirts of Beijing, China, October 17, 2015. New global data released in May 2022 shows that emissions of heat-trapping gases from cement making in the past 20 years is doubled year. It’s all powered by China, which is responsible for more than half of the global carbon emissions from cement. Credit: AP Photo/Ng Han Guan, File

Carbon dioxide emissions from cement making, a less-discussed but significant source of carbon pollution, have doubled in the past 20 years, new global data shows.

By 2021, global emissions from making cement for buildings, roads and other infrastructure reached nearly 2.9 billion tons (2.6 billion metric tons) of carbon dioxide, which is more than 7% of global carbon emissions, according to emissions scientist Robbie Andrew of Norway. CICERO Center for International Climate Research and the Global Carbon Project. Twenty years ago, in 2002, cement emissions amounted to about 1.4 billion tons (1.2 billion tons) of carbon dioxide.

Driven by China, global cement emissions have more than tripled since 1992, most recently at 2.6% per year. Not only is more cement being made and used. At a time when all industries are supposed to clean up their processes, cement has actually gone in the opposite direction. According to the International Energy Agency, cement’s carbon intensity — how much pollution is emitted per ton — has increased by 9.3% between 2015 and 2020, mainly due to China.

“Cement emissions have grown faster than most other carbon sources,” said climate scientist Rob Jackson of Stanford University, who leads the Global Carbon Project, a group of scientists that monitor global climate pollution and publish their work in peer-reviewed journals. “Cement emissions were also unusual because they never fell during COVID. They didn’t grow as much, but they never fell like oil, gas and coal did. Frankly, I think it’s because the Chinese economy has never really come to a complete standstill.”

Cement is unusual compared to other major materials, such as steel, because not only does it require a lot of heat to make, which causes emissions, but the chemical process of making cement itself produces a lot of carbon dioxide, the main man-made heat-trapping gas. long-term.

The cement recipe calls for a lot of a key ingredient called clinker, the crumbly binder in the whole mixture. Clinker is made when limestone, calcium carbonate, is taken from the ground and heated to 2700 to 2800 degrees (1480 to 1540 degrees Celsius) to make calcium oxide. But that process removes carbon dioxide from the limestone and goes into the air, Andrew said.

Rick Bohan, senior vice president for sustainability at the Portland Cement Association industry group, said, “In the US, 60% of our CO2 is a chemical fact of life… The reality is that concrete is a universal building material. There is no construction project that does not use a certain amount of concrete.”

Cement, the main ingredient of concrete, is found in buildings, roads and bridges.

“Every person on the planet consumes, on average, more than a kilogram (2.2 pounds) of cement per day,” said systems scientist Steve Davis of the University of California Earth. “Of course you don’t go, you know, Home Depot and buy a bag of cement every day. But on your behalf, the roads, buildings and bridges out there consume more than a kilo. And that’s kind of baffling to me.”

Even though there are greener ways to make cement, drastically reducing its emissions is so difficult and requires such a huge change in infrastructure and the way of doing business, the International Energy Agency does not foresee that the cement industry will emit CO2 by 2050. Instead, there will still be emissions from cement, steel and aviation that must be offset against negative emissions elsewhere, said IEA researchers Tiffany Voss and Peter Levi.

“These are hard, hard to cut,” Andrew said.

But industry’s Bohan said his group is confident they can achieve net-zero carbon emissions by 2050, if it gets the help of governments and especially cement users to properly accept and use green cement. One of several ways to make greener cement is by mixing fly ash, a waste product from burning coal, in place of some of the clinker and he said there is more than enough fly ash available even if using coal is reduced.

IEA’s Voss said the move to green cement “isn’t there yet” due to technology, infrastructure and other concerns. But many inside and outside the industry are working on the problem.

China is critical as it produced more than half of the world’s cement emissions by 2021, with India a distant second at around 9%, Andrew’s data shows. The United States spewed out 2.5% of cement emissions, ranking fifth behind Vietnam and Turkey.

“China is a huge country and its development has accelerated,” Andrew said. “It has driven everything.”

Not only is China making and using more cement, but carbon intensity has skyrocketed recently, IEA’s Voss said. That’s because earlier in its development China used cheaper, weaker, low-clinker cement and collapsed buildings and bridges, so now the Chinese government requires stronger cement, Norway’s Andrew said.

That’s reasonable conservatism that slows efforts to make greener cement, Davis said. People aren’t eager to try untested cement recipes because “these are the structural materials of our society,” he said.

Portland limestone cement, for example, has 10% fewer emissions, but customers are so concerned about its strength that they often say they’ll only want to use it if they use 10% more, said industry’s Bohan.

Different uses of cement have specific needs, such as strength versus longevity, but users often just want the strongest and most durable when they don’t need it, and this creates unnecessary emissions, Bohan said.

And while people are talking about curtailing flying, global emissions from aviation are less than half those from concrete, according to Global Carbon Project. There is “flight shaming” among scientists and activists, but no building shaming, Davis said.

Cement as it ages, sucks some carbon dioxide out of the air, just like trees do, in small measurable, significant amounts, Jackson said.

“Our primary focus should be on fossil fuel use, because that’s where most of the emissions come from,” Stanford’s Jackson said. “I don’t think cement is on most policymakers’ radar.”

Maybe not for most, but for some. California, Colorado, New Jersey and New York have all passed legislation on cleaner concrete and the trend is growing.


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Quote: Cement carbon dioxide emissions quietly double in 20 years (2022, June 22) retrieved June 23, 2022 from https://phys.org/news/2022-06-cement-carbon-dioxide-emissions-quietly.html

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