Imagine if Concrete Could Help Reverse
Low-embodied carbon concrete is a highly viable, if not well-known, emission-reducing technology. It may not be sexy, but it’s high impact, proven, and market ready. Here’s how it works, and how you can advocate for sustainable construction policy in your community.
What is concrete?
Concrete is the second most used material in the world after water. The Romans used concrete in the majority of their construction over two thousand years ago, and in the 1800s, the invention of Portland cement revolutionized concrete production and the modern concrete industry began to take shape.
Cement is the key ingredient used to bind fine and coarse rocks to produce concrete. Today, global production of Portland cement – used in 98% of modern concrete – is about 4 billion metric tons per year, and is projected to rise to 5 billion metric tons per year by 2030. Our current cement production would create enough concrete to build 1,000 Hoover Dams every year. Hailed for its relatively low cost, strength, and durability, the use of concrete building materials is showing no signs of letting up, especially as emerging economies continue to urbanize. In fact, China used more cement between 2011 and 2013 than the United States did in the entire 20th century.
Why is concrete important for climate change?
Despite the ubiquity of concrete in our built environment, little has been done to address the material’s climate impact. Cement makes up 12% of concrete mix, but its production leads to the majority of concrete’s greenhouse gas (GHG) emissions. Every kilogram of cement produced releases more than 0.5kg of carbon dioxide into the atmosphere. Altogether, that accounts for as much as 8% of global CO2 emissions – more than double that of the aviation industry. If the cement industry were a country, it would be the third largest GHG emitter in the world.
Without a doubt, the carbon intensity of cement production (the emissions per ton of cement produced) needs to be reduced. The good news is, through efficiency improvements and alternative fuel use, carbon intensity has already fallen by more than 18% over the past few decades. But, much more progress needs to be made. Fortunately, there are entrepreneurs and policy makers bringing new technologies to market so that one day the world’s cities and infrastructure can be built with carbon-neutral (and even carbon-negative) concrete.
How is low-carbon concrete made?
It starts with cement. Changing the material proportions of cement itself (reducing carbon-intensive “clinker”), and reducing cement content in concrete mixes is a low-cost, well-established pathway to squeezing carbon out of concrete.
But a new category of solutions actually utilize post-industrial CO2 in the manufacture and processing of concrete, locking greenhouse gases safely away from the atmosphere forever. Early innovators in this carbon capture and utilization space are at the vanguard of low-carbon concrete, each approaching the challenge differently.
New Jersey-based Solidia is replacing limestone-based Portland cement with wollastonite-derived cement, resulting in 70% lower emissions over the lifecycle of their product compared to Portland cement.
Montreal-based Carbicrete is using waste slag from the steel industry as its binding material instead of cement.
Halifax-based CarbonCure is outfitting existing concrete-production plants with their technology to create stronger concrete blocks that capture carbon dioxide.
Each of these innovators, and others like them, have demonstrated that their products yield concrete that exceeds building standards, cures faster, and generates positive financial returns, all while reducing carbon dioxide emissions by hundreds of millions of tons every year at scale.
But that’s not all. Each of these approaches involves the injection of carbon dioxide during the concrete production process. That means carbon dioxide captured from any industrial source (e.g., fossil fuel burning power plants, coke and steel mills, even cement producing facilities themselves) or pulled directly from the air is injected as a gas and mineralizes into calcium carbonate rock as the concrete cures. The mineralized carbon dioxide is stored in the concrete for good, even when the building it was constructed with is eventually demolished.
That’s right – the most abundant building material in the world can not only be produced with lower carbon emissions, it can actually sequester carbon dioxide. Over time, as the carbon footprint of concrete production goes down and carbon sequestration potential goes up, concrete could become a carbon sink and, in turn, create exciting new markets for negative emissions technologies like direct air capture.
What can we do now?
Governments at every level are some of the largest purchasers of concrete. Cities like Austin and Honolulu have adopted resolutions to begin procuring low-carbon concrete for city construction projects. The Canadian government is planning to ensure that all concrete used in federal projects use lower emitting cement. Marin County in the Bay Area has gone a step further, fully incorporating low-carbon concrete into its building code for both public and private construction.
But governments won’t get there on their own. Advocates for policy changes are desperately needed. The OpenAir Collective – a global network of volunteers advancing negative emissions-based climate solutions – has answered that call. They helped shape New York State’s Low Embodied Carbon Concrete Leadership Act (LECCLA), which is currently under consideration and would make low-carbon concrete more competitive in the state’s procurement process (short explainer video here). Following this experience, OpenAir is launching a new network so that lessons, resources, and advocacy tools can be shared with citizen groups and climate organizers across the country to promote low-carbon concrete in their communities.
You and your community can make a significant impact on global GHG emissions by organizing and advocating for reductions in the carbon emissions of concrete, and the removal of existing carbon dioxide from the atmosphere. If this mission sounds interesting to you, click here to sign up and join our network for access to the first iteration of tools and resources as they become available to help you get started right away.