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Inside the Effort to Turn Pollution into Sustainable Concrete


Gaurav N. Sant has a refreshing attitude about climate change. 

He’s optimistic. 

As UCLA Professor of Civil and Environmental Engineering and Materials Science and Engineering, Sant understands the scale of this challenge as well as anyone. “Don’t get me wrong: Climate change is an enormous problem of global dimensions,” Sant says. “But we’re not going to do ourselves any favors by saying that this is a problem that we cannot solve.” 

Sant has reason for optimism. He and his UCLA colleagues have found a solution at the source of the problem itself: carbon dioxide (CO2). Billowing from power plant smokestacks and other sources around the world, CO2 is the main greenhouse gas driving climate change. According to the U.N., global CO2 emissions must reach net zero by 2050, or many effects of climate change will be irreversible. 

In the face of this challenge, Sant and his colleagues asked a question: Instead of sending all of this CO2 pollution into the atmosphere, what if we transformed it into a useful product? The result is called CO2Concrete, a win-win technology that captures emissions and recycles them into a lighter, stronger and sustainable alternative to traditional concrete. 

Taking inspiration from seashells

The technology behind CO2Concrete is based on a concept called “CO2 mineralization,” or the conversion of CO2 gas into solid minerals. To put this into simpler terms, Sant points to a similar process found in nature. 

“We live in Los Angeles,” he says. “Take a walk on the beach and pick up a seashell. You see what a seashell is: It’s made of white stuff, it’s pretty strong and it looks kind of cute. CO2Concrete is based around the same material that bonds a seashell: calcium carbonate, or limestone. Exactly how sea creatures produce their own home, i.e., a seashell, we can use carbon dioxide that comes out of the flue gas of a power plant, apply very simple, acid-based neutralization chemistry, and produce a cemented construction component.” To create this concrete rapidly, and on a large scale, the CO2Concrete team is developing a system of 3D printing that further revolutionizes the material. 

Thinking about concrete in terms of Legos

Mathieu Bauchy, UCLA Assistant Professor of Civil and Environmental Engineering, is a collaborator on CO2Concrete. Bauchy envisions a future without a need for concrete trucks that mix and pour concrete at construction sites. This traditional process is slow, Bauchy explains, and not well-controlled. Traditional concrete is also one of the weakest materials relative to its weight. To address these shortcomings, the team has designed a 3D printing system that embeds CO2 efficiently while creating a stronger product. 

“The idea is to create precast concrete building blocks that can be assembled Lego-style,” he says. “3D printing allows us to create a porous structure, where CO2 can be embedded very efficiently into CO2Concrete. So it’s a two-step process. You 3D print an optimized concrete structure that offers higher performance in terms of strength, and you use 3D printing to enhance the absorption of CO2 into these materials.” 

For a building process that hasn’t changed much in decades, 3D printing has the potential to usher in a new era of precision manufacturing and rapid assembly.

Visual diagram of CO2Concrete manufacturing process

From the lab to real power plants

Despite competitors pursuing similar goals, Sant and Bauchy are confident in their technology. “We’re able to absorb CO2 from dilute flue gases into CO2Concrete without any need for purification or enrichment — avoiding a need for what’s known as carbon capture,” Sant says. “We’ve essentially removed the Achilles heel that has prevented the utilization of waste carbon dioxide in a cost-effective manner. This is maybe the single most significant outcome that we’ve been able to access that others have not.”

Sant and Bauchy aren’t content with prototypes. Their goal is to develop a solution that makes economic sense in an industry driven by profit. “The construction sector likes a couple of things,” Sant says. “It likes materials that are cheap, because this is an industry that’s based on what’s known as the lowest bid. It likes materials that are functionally equivalent to regular concrete. And perhaps most importantly, it does not want to change how it operates. CO2Concrete offers all of these attributes, along with a greatly reduced carbon impact.” 

In the spring of 2020, CO2Concrete will be put to the test at a real power plant in Wyoming. The team are one of several finalists for the $20 million NRG COSIA Carbon XPRIZE, a global competition to develop technologies that convert CO2 emissions from power plants.

“We’re going to run a live demonstration,” Sant says. “We’ve been funded by the Department of Energy and the Anthony and Jeanne Pritzker Family Foundation via multi-million dollar grants to actually build the first-of-its-kind industrial scale system that will demonstrate the CO2Concrete process at scale at a real power plant. We’re going to do that in Wyoming, and then we’re going to do it again at the National Carbon Capture Center in Alabama.”

Putting his work in the larger context of climate change, Sant acknowledges that the problem cannot be solved with technology alone. Large cultural, societal and regulatory shifts are required as well. To accomplish these things, he believes positive thinking is essential.

“The reality is that [climate change] is not going to be solved in your generation and mine,” Sant says. “It’s going to be solved by this generation and others as we go down the road. So if you don’t set the perception as positive, you’re going to disincentivize people from wanting to participate. We need to be thoughtful about how and why people choose to take on the careers that they do ... I think it’s a question around human behavior and psychology, and how you get people to work on things that are really important, while knowing they can actually make a difference.” 

At a time when the news around climate change is increasingly dire, projects like CO2Concrete are a ray of hope. And with live demonstrations of this breakthrough technology, it is proof that with knowledge — and positive thinking — we can make our world a better place.