A Concrete Route to Net Zero
Concrete and cement's role in the climate crisis and the emergence of promising sustainable alternatives
Greta Jarvis, MS, MPH Candidate
Concrete vs. Cement: What's the Difference?
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While often used interchangeably, the words concrete and cement actually refer to two distinct building materials. Concrete is made from a mix of several ingredients, most often gravel, sand, water, and – surprise! – cement (Logan, 2020). Making cement is a bit more complicated...read on to learn more!
Cement & Greenhouse Gases
When thinking about major contributors to greenhouse gases, concrete and cement may not be the first things that come to mind. And yet, the production of these building materials accounts for eight to ten percent of global carbon dioxide emissions (Suhendro, 2014).
How can this be? Making concrete involves mixing gravel, sand, water, and cement – the final ingredient being the main carbon dioxide culprit (Gates, 2021). Cement starts by isolating calcium carbonate from limestone, a rock that consists of calcium, carbon, and oxygen (Gates, 2021). While burning limestone at high temperatures successfully separates the calcium carbonate from the carbon dioxide, there is a cost (Gates, 2021). Not only does the process of burning release carbon dioxide into the atmosphere, so too does the chemical breakdown of the limestone itself (MinuteEarth, 2019).
The resultant calcium carbonate is then mixed with the other ingredients listed above to create what we recognize as the concrete all around us – roads, sidewalks, driveways, bridges, fences, buildings, floors, and more.
When all is said and done, every one ton of cement emits 0.9 tons of carbon dioxide (MinuteEarth, 2019). Check out The Problem With Concrete, a 3-minute video by MinuteEarth highlighted in the following section, for a helpful illustration of this process.
Why does this matter? The emission of greenhouse gases like carbon dioxide contributes to climate change, one of the greatest threats to global public health that we face today. We are already seeing the devastating impacts of climate change, with “intense droughts, water scarcity, severe fires, rising sea levels, flooding, melting polar ice, catastrophic storms, and declining biodiversity” naming just a few (United Nations, 2021).
Creating a healthier future for our earth, our communities, our children, and ourselves means tackling the climate crisis head-on, which must include new ways of manufacturing cement that do not depend upon greenhouse gases. Fortunately, we are beginning to see heightened attention to this issue as well as exciting innovations confirming that net-zero cement is indeed possible!
Photo by Scott Webb from Unsplash
Cement Fast Facts
Concrete is the second most highly used material on the planet after water (Feldman, 2021).
The base of the Statue of Liberty consists of 27,000 tons of concrete (Gates, 2020)!
The United States manufactures about 96 million tons of cement yearly, or about 600 pounds per person (Gates, 2020).
China is the world's largest producer of cement, with about 1.6 billion tons annually (Gates, 2020).
Cement & Environmental Justice
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The United States is home to many cement plants, of which we have already explored the noxious dark side. Though producing raw materials for the bedrock of our nation’s built environment, these large industrial sites are unsightly hubs of noise, blue collar employment, and carbon monoxide emissions.
Unsurprisingly, they are often also located in communities stamped with the highest of the Center for Disease Control’s (CDC) Social Vulnerability Index ratings, with scores of 1 representing the greatest level of vulnerability and 0 the least. These numbers are the CDC’s way of quantifying “a community’s ability to prevent human suffering and financial loss in a disaster” and synthesize factors such as “poverty, lack of access to transportation, and crowded housing” (Centers for Disease Control and Prevention, 2021). Let's explore a few examples.
Riverside, California (1500 Rubidoux Blvd):
CDC Vulnerability Index 0.8219
Ada, Oklahoma (14500 County Road):
CDC Vulnerability Index 0.8985
There are several ways to approach reducing and, ultimately, eliminating the carbon footprint of cement. Aiming to use less concrete and cement is an obvious first step – but we need much more than that. Fortunately, we are starting to see the emergence of brilliant innovations and technologies that are paving the way toward net-zero cement.
This is a cutting-edge area of science, research, and development. You'll notice that many of the references for the following sections highlight rays of light shining especially bright during these last few years. This should give us reason for hopeful anticipation of the many incredible advancements to come. Let’s take a tour of some of the most promising!
Biocement®
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Biomason is a female-owned company in North Carolina that has been working to create sustainable, high-quality cement since 2012. The key ingredient to their success? Bacteria!
Co-founder, president, and CEO Ginger Krieg Dosier came up with this idea while thinking about how one natural cement-like material, coral, is formed (Biomason, 2021). Recall that the production of cement requires heating limestone to very high temperatures to extract calcium carbonate, which is then mixed with sand, gravel, and water. Coral, by contrast, is built when microscopic organisms called coral polyps “secrete layers of calcium carbonate beneath their bodies,” essentially weaving together water, calcium, and sand (How reefs are made, 2021).
Biomason replicates this process by using a non-pathogenic and naturally occurring strain of bacteria, in which the “chemical reaction needed to make calcium carbonate is powered by the microbe’s metabolism” (PBS NewsHour, 2017). In other words, the need for fossil fuels and high heat is entirely eliminated.
This allows Biomason to create a biocement® that “has the lowest carbon footprint on the market”; “exceed[s] the physical properties of standard materials for compressive strength, absorption, freeze-thaw, adhesion, and dimensional tolerance[;] and [is] safer for humans and the planet” (Biomason, 2021). Another plus? Biocement® takes much less time to cure: “While traditional concrete can take up to 28-days, Biomason biocement® reaches its final strength in less than 72 hours of growth.” (Biomason, 2021).
Biomason’s multidisciplinary team of biologists, architects, engineers, material scientists, and production associates has made great strides since their founding in 2012. Current partners, investors, and customers include H&M, DropBox, National Science Foundation, United States Marine Corps, United States Coast Guard, and Gensler (Biomason, 2021).
How does Ginger describe her company's status in 2021? “This is a big commercialization year for us… This is the breakout year.” (Feldman, 2021). The future of biocement® – and its contribution to a healthier and greener planet – is looking bright.
This PBS News Hour special introduces us to Ginger Krieg Dosier, her team, and the star of the show that makes Biomason's biocement® possible: bacteria!
Hope on the Horizon
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Researchers are continually exploring alternatives for replacing limestone in conventional cement recipes. One recent study identified that using residual materials from the production of kaolin (a clay mineral) and aluminum in lieu of limestone-derived calcium carbonate yields high-performing, cost-effective, more environmentally friendly cement (Galluccio, 2019). Other potential limestone substitutes include volcanic ash and ground glass (Alternative cement, 2021).
Members of the Global Cement and Concrete Association came together in 2020 to create a Net Zero Roadmap that "sets out in detail how collectively, in collaboration with built environment stakeholders and policymakers, [they] will fully decarbonise the cement and concrete industry and provide net zero concrete for the world" (Concrete Future, 2021).
In September 2021, California Governor Gavin Newsom “signed landmark legislation by Senator Josh Becker that will make California the first state to directly target greenhouse gas emissions from cement” (CA governor signs…, 2021). Senate Bill 596 mandates that the state create a strategic plan for fully transitioning to net-zero cement as quickly as possible, with the year 2045 as a hard deadline.
Brimstone Energy, a research and development company based in the Bay Area, has developed "a process capable of producing carbon-neutral...cement and supplementary cementitious materials" (Brimstone Energy, 2021). To support the expansion of this method to a scale that can meet global demand, investors DCVC and Breakthrough Energy Ventures financed Brimstone Energy with $5.1 million seed money in November of 2021 (Brimstone Energy announces..., 2021).
References
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Alternative cement @projectdrawdown #climatesolutions. Project Drawdown. (2021, September 29). Retrieved November 15, 2021, from https://www.drawdown.org/solutions/alternative-cement.
Biomason. (n.d.). Retrieved November 12, 2021, from https://www.biomason.com/.
Brimstone Energy. (n.d.). Retrieved November 22, 2021, from https://www.brimstone.energy/.
Brimstone Energy announces financing to accelerate development of the first-ever zero-carbon portland cement. Business Wire. (2021, November 16). Retrieved November 22, 2021, from https://www.businesswire.com/news/home/20211116005372/en/Brimstone-Energy-Announces-Financing-to-Accelerate-Development-of-the-First-Ever-Zero-Carbon-Portland-Cement.
CA governor signs state senator Josh Becker's landmark bill to decarbonize cement. Senator Josh Becker. (2021, November 24). Retrieved November 30, 2021, from https://sd13.senate.ca.gov/news/press-release/september-23-2021/ca-governor-signs-state-senator-josh-beckers-landmark-bill-to.
Centers for Disease Control and Prevention. (n.d.). CDC's Social Vulnerability index (SVI). Centers for Disease Control and Prevention. Retrieved November 22, 2021, from https://svi.cdc.gov/map.html.
Concrete - the world's most widely used material - targets carbon neutral future. GCCA. (2020, August 31). Retrieved November 10, 2021, from https://gccassociation.org/news/concrete-the-worlds-most-widely-used-material-targets-carbon-neutral-future/.
Concrete Future. Global Cement and Concrete Association. (n.d.). Retrieved November 15, 2021, from https://gccassociation.org/concretefuture/.
Galluccio, S., Beirau, T., & Pöllmann, H. (2019). Maximization of the reuse of industrial residues for the production of eco-friendly CSA-belite clinker. Construction and Building Materials, 208, 250–257. https://doi.org/10.1016/j.conbuildmat.2019.02.148
Gates, B. (2021). How to Avoid a Climate Disaster: The Solutions We Have and the Breakthroughs We Need. Alfred A. Knopf.
Feldman, A. (2021, June 14). Startup biomason makes biocement tiles, retailer H&M Group plans to outfit its stores' floors with them. Forbes. Retrieved November 12, 2021, from https://www.forbes.com/sites/amyfeldman/2021/06/14/startup-biomason-makes-bio-cement-tiles-retailer-hm-group-plans-to-outfit-its-stores-floors-with-them/?sh=ce11b8257c9e.
How reefs are made. Coral Reef Alliance. (2021, September 9). Retrieved November 12, 2021, from https://coral.org/en/coral-reefs-101/how-reefs-are-made/.
Logan, A. (2020, April 3). Explained: Cement vs. concrete - their differences, and opportunities for Sustainability. MIT News | Massachusetts Institute of Technology. Retrieved November 9, 2021, from https://news.mit.edu/2020/explained-cement-vs-concrete-understanding-differences-and-sustainability-opportunities-0403.
MinuteEarth. (2019, March 1). The Problem with Concrete [Video]. YouTube. https://www.youtube.com/watch?v=GSc9hu917OU
PBS NewsHour. (2017, March 7). These cement-making bacteria could build the cities of the future [Video]. YouTube. https://www.youtube.com/watch?v=lIS0gtCbadU&t=186s
Suhendro, B. (2014). Toward green concrete for better sustainable environment. Procedia Engineering, 95, 305–320. https://doi.org/10.1016/j.proeng.2014.12.190
United Nations. (n.d.). What is climate change? United Nations. Retrieved November 30, 2021, from https://www.un.org/en/climatechange/what-is-climate-change.