At a concrete plant in San Francisco, the concrete loaded into ready-mix trucks now includes captured CO2. The plant, owned by Central Concrete, a northern California business unit of U.S. Concrete, recently adopted technology from CarbonCure, one of a handful of startups trying to address one of the world’s biggest sources of emissions. The process of making cement, which is used like glue to hold concrete together, is the source of around 8% of the CO2 pumped into the atmosphere globally. If the industry were a country, it would be the third-largest emitter after China and the United States–and as countries like China rapidly build, the problem is also growing.
Central Concrete, which has 12 plants in the Bay Area, had already been working to tackle its carbon footprint before partnering with CarbonCure. “Everything we do, we develop around low carbon mix designs,” says Herb Burton, regional vice president and general manager of U.S. Concrete. By using materials like fly ash in its mixes, for example, the company can cut the amount of cement it needs in half. But the new technology from the startup, which the concrete company now uses at seven of its locations, can help it push the carbon footprint down further.
The process uses liquefied CO2 captured from industrial sites and injects it into a concrete mixer, where the CO2 chemically reacts with calcium to convert it into a mineral. Emissions from another factory that would have otherwise gone into the atmosphere become permanently embedded in the concrete. “We get rid of it forever,” says Christie Gamble, director of sustainability at the Canada-based CarbonCure.
The CO2 makes the concrete stronger, so it’s also possible to use less cement, reducing the carbon footprint further and making the whole process affordable. “Cement is also the most expensive ingredient that goes into concrete,” says Gamble. “So by using less of it, it offsets the costs that are involved in the technology in the process.”
The result, she says, is concrete delivered to construction sites that meets performance and quality standards and has the same cost as standard concrete, but a lower footprint. Right now, the carbon reduction is relatively small, at 5%. But the startup, which got new funding from the Bill Gates-led Breakthrough Energy Ventures in September 2018, believes that it can double or triple that reduction. Ultimately, it aims to make concrete carbon neutral.
Another startup, Solidia, says that its system can cut the carbon footprint of concrete by as much as 70%. One of the company’s technologies tweaks the chemistry of making cement to save energy and cut the emissions of that manufacturing process by 30-40%. The other technology uses captured CO2 to help concrete set–a process that usually takes vast quantities of water. For precast concrete, that has a second advantage of making the concrete ready to use in 24 hours, rather than the weeks that it usually takes to harden. (In a separate process, the company also makes use of CO2 in ready-mix concrete on roads and other on-site uses.)
After around a decade of development and tests, the tech is now scaling up commercially. LafargeHolcim, a massive cement and concrete company, is selling to customers in the U.S. and North America. EP Henry, a company that makes paving stones, is launching the technology to thousands of its contractors over the next few weeks. For cement companies, the new process is a comparable cost or less expensive than the conventional process. For concrete companies, it’s lower-cost; companies can save because of the quicker curing time and other factors, such as the fact that the product is a lighter color and requires less pigment. “If you don’t make these guys more money from the beginning, they’re just not going to adopt it, whether it’s sustainable or not,” says Tom Schuler, CEO of Solidia Technologies.
It’s challenging, the companies say, to change an industry that has used essentially the same process for the last 200 years. “The biggest challenge and hurdle that we face is that this is something new and innovative in an industry that has been slow to adopt new innovations,” says Gamble. Companies like Central Concrete are outliers; CarbonCure is now in 125 plants in Canada and the U.S., but there are more than 6,500 concrete plants in those countries alone. But change is likely coming.
“They recognize as an industry that they really need to make a change in order to make sure that they’re competitive going forward,” says Schuler. “That’s the key point that we make to our customers, that sustainability is really a question of competitiveness more than anything else. Being resource efficient going forward is going to be critical for companies all over the world.”
A few other startups are developing new technologies that also use captured CO2. Researchers at UCLA, for example, recently launched a startup called CO2Concrete with a new technology that the researchers say has a better uptake of CO2 than others on the market. Carbicrete, a startup based in Montreal, replaces cement with steel slag and then cures it with CO2, producing a final product that is carbon-negative.
The building industry is ready for alternatives. “I think other people in the industry are starting to look at sustainability because the market’s always going to drive need, and right now you have an appetite in the market, by progressive owners and progressive architects, to really impact the carbon footprint of the built environment,” says Burton.