Why Concrete is the Sustainable Building Material of the Future

Ryan Duncombe, Beam Project

Photo by Joel Filipe on Unsplash

So far we’ve discussed ways that emissions from electricity, transportation, and agriculture can be reduced through new technologies. The fourth of the five Grand Challenges of emissions reduction is manufacturing, so now we’re going to dive into one the largest sources of CO2 emissions worldwide — concrete.

Concrete is an ancient and fascinating material with a long history of human use — concrete ruins have been discovered from ancient cultures on multiple continents, including from the Mayans, Syrians, and Romans. Today, concrete is the most widely used man-made material in the world. Three tons of it are produced every year for each person alive. Globally, only water is a more consumed resource.

Yet, many people (including some of us at Beam Project!) were surprised by our Instagram post that explained how the production of concrete, and especially the cement that holds it together, releases at least twice as much CO2 per year as the airline industry worldwide, and up to 8% of total global emissions.

So, why does concrete production result in more emissions than airplanes, which burn thousands of gallons of jet fuel all day every day? Well, the answer hinges on understanding the difference between cement and concrete. Concrete is, in essence, rocks pasted together with cement. Standard concrete today is made by mixing, roughly, 70% aggregates (everything from fine sand to coarse rock), 15% cement, and 15% water. It is the addition of water to cement that hardens and binds the rest of the sand and aggregate together, forming concrete.

It’s that 15% cement that makes concrete enormously costly emissions-wise to create. Cement accounts for 70% of the total emissions footprint of concrete. That’s because it’s made by heating limestone to more than 2500 degrees Fahrenheit, requiring immense amounts of fossil fuel-derived energy. And it gets worse! That only accounts for about half of the emissions of cement, as the heating process triggers a chemical release of vast quantities of CO2 from the limestone itself. Overall, producing 100 tons of cement emits 90 tons of CO2 into the atmosphere. Combine this with the fact that concrete is the most widely-used building material in the world and you have your explanation of how it’s responsible for so much carbon in our atmosphere.

Why We Should (and Will) Continue to Use Concrete

All that being said, concrete does have many sustainability advantages over other materials, and it’s also ripe for the kind of technological innovation we here at Beam Project do our best to support. The two-thirds of concrete that is aggregate, both the fine sand and coarser rock, can be (and often is already) sourced from waste materials or byproducts from power plants, steel mills, and other manufacturing facilities. Concrete is also extremely durable, and long-lasting structures are sustainable structures. It has robust insulation properties and leads to minimal waste because the exact quantities are easy to produce for any given project. Concrete can even reabsorb some carbon from the atmosphere over time. However, these strategies only reduce overall carbon emissions by a marginal degree, and it’s clear that widespread development of new technologies is crucial to supply truly clean concrete for the future. And doing so now is all the more important because annual cement production is predicted to increase between 12 and 23% by 2050 as cities continue to expand. If CO2 emissions can be dramatically reduced, or even negated, concrete will be one of our most valuable resources in producing a sustainably low-carbon future.

The Future of Concrete

So, can we make concrete sustainably without increasing cost? The good news is there are plenty of startups producing clean concrete right now. And furthermore, compared to many sustainable tech fields, a lot of these technologies are fairly mature and already being implemented economically on large scales.

CO2Concrete is a group out of UCLA that has developed a method of diverting CO2 emitted from power plants, chemical plants, and cement plants and using it to create precast concrete products. Precast concrete is assembled off-site in pre-made bricks, as opposed to ready-mix concrete that is produced in custom molds on-site (precast concrete makes up 20% of the global market share in concrete to ready-mix’s 80% — so both are significant). This process is possible because of “CO2 mineralization” — the conversion of gaseous CO2 into solid minerals like calcium carbonate upon reaction with calcium ions in concrete. Amazingly, this results in a stronger concrete and removes the need for using any ordinary, CO2-emitting cement. CO2Concrete estimates that this process releases 75% less CO2 than traditional methods, and the final concrete product will continue to absorb CO2 from the atmosphere over time. The team at CO2Concrete has already produced over 100 tons of this stuff for projects in the U.S. and is rapidly expanding operations.

Carbon Cure, a Canadian startup, has developed a similar method of CO2 mineralization in calcium carbonate in concrete, though in a ready-mix formula. Although Carbon Cure’s concrete still requires some traditional cement, their ready-mix product can be shipped in standard cement trucks, offering greater flexibility and access to 80% of the market precast products don’t have. They’ve already achieved widespread use in North America, delivering over 600,000 truckloads of their concrete for projects — meaning they’ve reduced CO2 emissions by over 130 million pounds already!

CarbiCrete is another Canadian company, with a fully carbon-negative precast concrete product. They’ve entirely replaced cement by combining steel slag — a readily available waste product from steel production — and CO2. They’re a younger company, but they’ve been rapidly gaining attention, and their business model of supplying traditional concrete producers with the process and support to produce CarbiCrete’s concrete product can be implemented in any traditional concrete manufacturing plant.

For a different approach entirely, there’s bioMASON. Remember that concrete is essentially any combination of paste and aggregates that hardens over time? Well, bioMASON is taking that to the extreme — they’re using microorganisms to grow cement. Or rather, biocement®, which is stronger, solidifies faster, and can be produced more sustainably than traditional cement. It also looks pretty awesome. biocement® is made by mixing sand with a ­­­species of bacteria that, upon being fed water and calcium, hardens to form concrete bricks with the same composition as natural stone. These bricks are enormously versatile, and they’re developing a powder version that can be shipped around the world.

Finally, for this op-ed at least, Solidia has a cement-free concrete product also formed by calcium carbonate, but with the addition of silica for added strength. Solidia concrete costs less than traditional concrete to produce, and cures, or hardens, within 24 hours as opposed to 28 days for traditional concrete. Sadly, this means paw prints and bird tracks in sidewalks might soon be a thing of the past.

If the concrete production methods these startups employ replaced traditional methods, they would eliminate more than 1.5 gigatons of CO2 every year. And this isn’t pie-in-the-sky daydreaming, this is achievable. A report from the International Energy Agency and the Cement Sustainability Initiative estimates that new technologies can help reduce emissions from the cement industry by 24% by 2050. But that report also calls for accelerating action, because both the difficulty and the tight timeline of these goals means they won’t be achieved without a concerted effort from industry, government, and citizens.

In Conclusion

All of the startups we’ve discussed here demonstrate the tremendous potential for rapid adoption of cleaner concrete. They also show the need for this problem to be approached from every angle possible to support change in the many ways concrete is currently used, as a diverse problem requires diverse solutions. The key thing they all have in common, though, is that each of these approaches is creating economic value for CO2, creating financial incentives for reducing global carbon emissions. Finding and creating value for CO2 has historically been very difficult, so the importance of this cannot be overstated.

Concrete is here to stay: it’s versatile, cheap, and durable. It’s also a ready industry for innovation, in all of its many markets, and many technologies needed to provide the world with a carbon-negative building material are here now. Even the currently existing infrastructure for producing concrete is ready in its current state to produce cleaner concrete products, given the right knowledge and the right starting materials.

These startups are in a prime position to transform how we make concrete while maintaining its economic output. Put another way, these startups are ready to “disrupt” without being disruptive. With a little help and continued innovation, they can have an outsized impact in fighting global warming.

Learn more about how we’re trying to help at www.beamproject.co/.

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