Cement CO2 emissions quietly double in 20 years

Heat retention Carbon dioxide emissions from the cement industry, a source less talked about but a major source of carbon pollutiondoubled in the past 20 years, new global data show.

In 2021, global emissions from the cement industry for buildings, roads and other infrastructure amounted to 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 Global Carbon Project. Twenty years ago, in 2002, cement emissions were about 1.4 billion tons (1.2 billion metric tons) of carbon dioxide.

Driven by China, global cement emissions have more than tripled since 1992, and have recently grown at an annual rate of 2.6%. It’s not just about making and using more cement. At a time when all industries were supposed to clean up their operations, cement was actually going in the opposite direction. The carbon intensity of cement — the amount of pollution emitted per ton — increased 9.3% from 2015 to 2020, mainly due to China, according to the International Energy Agency.

Cement emissions have grown faster than most other carbon sourcesStanford University climate scientist Rob Jackson, who leads the Global Carbon Project, a group of scientists that tracks climate pollution around the world and publishes their work in peer-reviewed journals, said. Cement emissions were also unusual because they never decreased during COVID. They did not grow as much, but they never rejected the way oil, gas and coal grew. Frankly, I think it’s because the Chinese economy has never completely shut down.”

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

The cement recipe requires a lot of the main ingredient called clinker, which is the crumbly binding agent in the entire mixture. Clinker is made when limestone and calcium carbonate are extracted from the ground and heated to 2,700 to 2,800 degrees (1,480 to 1,540 degrees Celsius) to convert it to calcium oxide. This process removes carbon dioxide from the limestone, Andrew said, and it goes into the air.

Rick Bohan, Senior Vice President of Sustainability at Portland Cement Industrial Group, said, “In the United States, 60% of our carbon dioxide is a chemical fact of life…The truth is concrete is a global building material. Not a single construction project isn’t used in it. A pot of concrete.”

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

“Every person on the planet, on average, consumes more than a kilogram (2.2 pounds) of cement per day,” said Steve Davis, an Earth systems scientist at the University of California. “Obviously you wouldn’t go, you know, to Home Depot and buy a bag of cement every day. But on your behalf, roads, buildings and bridges use more than a kilogram. And that kind of mind boggles me.”

Although there are greener ways to make cement, drastically reducing its emissions is very difficult and requires such a massive change in infrastructure and the way business is done, the IEA does not envision that the cement industry will reach zero carbon emissions by 2050 and instead From that, there will still be emissions from cement, steel and aviation that need to be weighed against negative emissions elsewhere, said IEA researchers Tiffany Voss and Peter Levy.

These are tough and hard to cut,” Andrew said.

But Bohan of the industry said his group is sure they can reach net zero carbon emissions by 2050, if they get help from governments and especially cement users to properly accept and use green cement. One of the many ways to make cement greener is to mix fly ash, a waste from burning coal, in place of some clinker, and he said there is enough fly ash available even with less coal use.

The IEA’s Voss said the switch to green cement “has not yet been achieved” due to technology, infrastructure and other concerns. But many inside and outside the industry are working to solve the problem.

Andrew’s data shows that China is key as it produced more than half of the world’s cement emissions in 2021, followed by India in second place at around 9%. The United States released 2.5% of emissions from cement, ranking fifth after Vietnam and Turkey.

“China is a huge country and its development is increasing,” Andrew said. “He drives everything.”

Not only is China making and using more cement, said Voss of the International Energy Agency, but its carbon intensity has been rising a lot lately. This is because earlier in its development, China used cheaper and weaker low-clinker cement, and buildings and bridges were collapsing, so the Chinese government is now mandating stronger cement, Andrew of Norway said.

This is a reasonable conservatism slowing efforts to make greener cement, Davis said. He said people are not excited about trying untested cement recipes because “these are the structural materials for our community.”

For example, Portland limestone cement has 10% lower emissions, but customers are so concerned about its strength that they often say they only want to use it if they use 10% more, Bohan of the industry said.

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

And while people talk about limiting flyingGlobal aviation emissions are less than half of those emissions coming from concrete, according to the Global Carbon Project. Davis said there is “shame on escape” among scientists and activists, but no shame in construction.

Just like trees, cement with age absorbs some of the carbon dioxide from the air, in measurable small and large amounts, Jackson said.

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

Maybe not on most, but on some. The states of California, Colorado, New Jersey, and New York have passed legislation on cleaner concrete and this trend is increasing.


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