In concrete plants around the world, mixing trucks receive a contaminated mix of sand, gravel and water and cement, but a facility outside Washington D.C. is adding a new ingredient to clean up the process: carbon dioxide. This hybrid mix - known as “green” concrete - reduces the carbon footprint of one of the world's most polluting industrial sectors and is emerging as an alternative to carbon storage options, such as underground wells and pipelines, that require regulatory approval and local support.
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Green Concrete cannot sequester the billions of tons of carbon needed to meet global climate goals, but it offers an immediate and partial solution to concrete emissions until other options emerge, and thanks to government incentives and investments by companies like Amazon and Microsoft, it seems to be working.
<The Inflation Reduction Act of 2022 offered billions of dollars in tax breaks to companies that capture carbon, in factories or from the atmosphere, and then sequester it underground or in products like concrete.
Amazon used green concrete for its Arlington headquarters and invested directly in Carbon Cure Technologies, a startup that manages the injection of carbon trapped in concrete during manufacturing. Amazon has also invested directly in Carbon Cure Technologies, a startup that manages the injection of carbon trapped in concrete during manufacturing.
Microsoft has also invested in Carbon Cure, one of several companies and academic researchers experimenting with new ways to produce this concrete." Microsoft has also invested in Carbon Cure, one of several companies and academic researchers experimenting with new ways to produce this concrete.
<Scott Schell, an architect and industry director at ClimateWorks, an environmental charity organization, said: "It's like we're on the cusp of a second industrial revolution."
Concrete manufacturers produce nearly 30 billion tons annually to construct the world's buildings, roads and bridges, emitting several billion tons of carbon dioxide in the process, or roughly 7% of the global total. Most of the emission comes from concrete.
Most of the emissions come from heating limestone and clay up to 2,700 degrees Fahrenheit to make cement, the material that binds the other ingredients together. Most of the emissions come from heating limestone and clay up to 2,700 degrees Fahrenheit to make cement, the material that binds the other components together.
$7 billion in sales last yearSolutions for concrete emissions
A Second Industrial Revolution
30 billion tons per year
Vulcan uses carbon injection at more than 20 of its 140 concrete facilities in the U.S. and produced more than 1 million cubic yards of green concrete last year, or roughly 10% of its total concrete shipments. The company has several hundred plants that produce crushed stone, sand and gravel, and had total sales of more than $7 billion last year. The concrete typically takes no more than 90 minutes of mixing to properly set, and its plants are spread across the globe, thus providing a network that can alleviate carbon storage bottlenecks, without the need for pipelines.
Microcrete has hundreds of plants that produce crushed stone, sand, and gravel, with sales of $1 billion last year. Microsoft is also testing microalgae-derived limestone concrete at one of its data centers in Quincy, Washington.
Microsoft is also testing concrete made from limestone derived from microalgae.
Stages of making green concrete
To make green concrete, liquid carbon dioxide is sprayed into the mixing drums of concrete trucks, where it reacts with calcium ions in the cement to form solid calcium carbonate, the element found in building materials. The rock-like calcium carbonate reduces the amount of cement required, reducing concrete emissions by about 5% and preventing carbon that would otherwise be released into the atmosphere.
"Anytime we can reduce the amount of cement required, we can reduce the amount of carbon that would otherwise be emitted into the atmosphere," says Teck Chua, technical services manager for Vulcan Materials, the building materials company that operates the 83-year-old Arlington plant that produces the green concrete: "Anytime we can reduce the amount of cement, we can reduce the amount of carbon dioxide."
Any time we can reduce the amount of cement, we can reduce the amount of carbon dioxide. <Other companies are working on new concrete mixes using everything from fly ash from coal plants, or slag from steel mills, to further reduce cement and its emissions, while a research team at MIT found that the carbon footprint of concrete could be reduced by 15% by 2020, "just by adding baking soda to the cement before mixing it."
As he put it.
