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Despite this year’s abrupt U-turn in federal energy policy, US innovators are still front and center in the global decarbonization race. That includes the somewhat unglamorous but carbon-heavy field of concrete, where a research team at Worcester Polytechnic Institute in Massachusetts has introduced a bio-inspired concrete alternative that sequesters carbon during the production process, achieving true carbon-negative status.
Concrete Has A Carbon Problem, Bigly
The research team calculates that their new alternative building material sequesters 6.1 kilograms of carbon per cubic meter du…
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Despite this year’s abrupt U-turn in federal energy policy, US innovators are still front and center in the global decarbonization race. That includes the somewhat unglamorous but carbon-heavy field of concrete, where a research team at Worcester Polytechnic Institute in Massachusetts has introduced a bio-inspired concrete alternative that sequesters carbon during the production process, achieving true carbon-negative status.
Concrete Has A Carbon Problem, Bigly
The research team calculates that their new alternative building material sequesters 6.1 kilograms of carbon per cubic meter during the production process. In contrast, conventional concrete emits roughly 330 kilograms of carbon during production.
Getting to -6 from +330 is quite an achievement, considering the carbon intensity of conventional concrete. Part of the challenge involves reducing the high heat required to transform limestone into the “clinker” that forms the basis of traditional cement, which is the glue that holds gravel and other concrete aggregates together.
Another significant challenge is to replace the limestone itself. A sedimentary rock composed mainly of calcium carbonate fossils, limestone releases a copious amount of carbon dioxide when heated. The US Geological Survey estimates that limestone accounts for almost 66% of the carbon emissions attributed to cement production.
“While most people realize that cars, planes, and power plants contribute to climate change, there’s another major source of greenhouse gases that’s often overlooked. It’s all around us –perhaps even right where you are as you read this. It’s concrete, and the cement used to make it,” USGS elaborated in a think piece last year (see lots more concrete background here).
The Long Road To The Superbricks Of The Future
The roster of solutions to concrete’s carbon problem has been growing into the bio-based space. In a new study published in the journal Matter, the WPI research team notes that one area of focus involves deploying microbes to precipitate calcium carbonate, with bamboo, mycelium, fungi, and bacteria-based materials also among the other alternatives. However, the researchers also note that cost, complexity, engineering issues, and the potential for negative environmental impacts are limiting factors for bio-inspired cement alternatives.
The WPI team itself encountered a significant roadblock in an earlier work, in which they described a bio-inspired process for growing minerals on a polymer scaffold. They introduced trace amounts of the enzyme carbonic anhydrase, which catalyzed water and carbon dioxide to form carbonic acid. The carbonic acid then interacted with calcium to produce calcite, which attached itself to the scaffold.
“The material exhibits a compressive strength of 12 MPa and a degree of self-healing capability,” the researchers reported, with MPa being shorthand for megapascal, a valuation of the compressive strength of a concrete mix. By that measure, 12 MPa is pretty good for a first effort. It comes within shouting distance of the minimum MPa for some uses, though the American Cement Association notes that high-strength concrete typically has a strength of at least 55 MPa.
The WPI team also took note of a more substantial issue, noting that the strength of their new material “decreases significantly under humid conditions,” which they describe as a “universal problem for biologically inspired construction materials that use hydrophilic polymers as scaffolds.”
“Although incorporating biomaterials reduces carbon emissions, these products are not water resistant and require a protective layer,” they emphasize.
The Hydrophobic Solution
If you caught that thing about hydrophilic, so did the WPI team. In the new work, they took a different tack. Under the title, “Durable, high-strength carbon-negative enzymatic structural materials via a capillary suspension technique,” they describe how they deployed sand to form a hydrophobic scaffold upon which calcium carbonate crystals can grow.
“We present a strong, cost-effective, carbon-negative building material, named enzymatic structural material (ESM), that integrates enzymatically formed CaCO3 crystals into a hydrochar scaffold via capillary suspension,” they explain.
“This enables versatile fabrication, rapid molding into various structures within hours, and scalability for mass production, bypassing the 28-day curing required for conventional concrete,” the researchers add. In addition to the carbon sequestration benefit, they also cite recyling and repairability as an additional plus in the sustainability column, helping to reduce construction waste and extend the lifespan of a project.
While not hitting the high-strength mark for conventional concrete, the research team achieved a respectable compressive strength of 25.8 MPa, making ESM suitable for roof decks and wall bricks among other applications.
WPI also emphasizes that ESM takes only hours to cure, compared to the four-week timetable typical of most concrete mixtures, helping to accelerate housing construction and post-disaster rebuilding efforts.
“Because ESM is produced with low energy and renewable biological inputs, it also aligns with global goals for carbon-neutral infrastructure and circular manufacturing,” ESM points out.
US Innovators Keep On Innovating
Don’t get too excited just yet. The road from the laboratory to the shelves of your local hardware store is a long one. The WPI team plans to focus their next steps on parsing out the ecological efficiency of their ESM formula, while improving its performance and laying the groundwork for scaled-up production.
In the meantime, various near-term carbon cutting solutions are emerging on the market. One example from the CleanTechnica archive is the Massachusetts startup Sublime Systems. The company’s low carbon “Sublime Cement” is beginning to catch on among construction industry stakeholders in the US, with Microsoft being one high profile example.
When last heard from, the American Cement Association (a rebrand of the Portland Cement Association earlier this year) also continues to hold the torch for global leadership in the decarbonization movement. “The association has a once-in-a-generation opportunity to set a global standard for innovation and create a sustainable future,” ACA says of its “Roadmap to Carbon Neutrality.” Released in May of 2024, the Roadmap provides space for carbon capture and sequestration but the overall emphasis is on next-generation solutions that deploy low carbon feedstocks and renewable energy at the production end. ACA also counts energy efficiency improvements and renewable energy at the building design and construction end towards its 2050 carbon neutral goal.
So much for last year’s effort. This year has been a different story. In May the US Department of Energy clawed back carbon capture grants for cement producers among other industries, leading ACA President and CEO Mike Ireland to call the action “a missed opportunity for both America’s cement manufacturers and this administration.”
Nevertheless, the ACA moved forward with a decarbonization agenda for its third annual Sustainability Summit in August. “While 2025 has brought landmark changes in Washington that directly affect cement companies, the industry’s top goal of decarbonization remains the same,” Ireland declared in a preview of the event. The Summit also highlighted alternative kiln fuels and low carbon cement blends along with a commitment to continue investing in carbon capture systems despite the federal funding cuts.
Photo: A new, bio-inspired carbon negative replacement for concrete is working its way through the laboratory at Worcester Polytechnic University in Massachusetts (courtesy of WPI).
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