Construction materials can be non-environment-friendly. Well, what if it can be more eco-friendly, even more so that it can sequester carbon?
Apparently, we have that now. Carbicrete is a Montreal company which has made an innovation. Its concrete captures more carbon than it emits.
The technology behind it doesn’t need calcium-based cement. For those of you who are not familiar with the construction industry, it’s a key ingredient in traditional concrete. It’s responsible for around 8% of all global CO2 emissions.
Carbicrete CEO Chris Stern said, “It’s negative emissions. We’re taking CO2 out of the system every time we make a block.”
Concrete that keeps being carbon negative
Carbicrete is one of the many startups or companies racing to find low-carbon or carbon-free alternatives to traditional concrete. But this one claims to be one of the only ones having achieved negative carbon.
This company doesn’t use cement. Instead, it combines waste slag from the steel industry plus carbon captured from industrial plants that would otherwise have gone into the atmosphere.
Stern said, “We’re taking it from there and then injecting it into concrete and getting rid of it forever.”
According to the CEO, the company captures more carbon during the production process than is emitted during the manufacture of the concrete. That makes the resulting concrete carbon-negative.
Additionally, the process relies on emissions produced by other industries. So, Carbicrete is also helping to reduce the amount of additional CO2 going into the atmosphere rather than actively removing it from the atmosphere.
And since CO2 captured from the sky via direct air capture (DAC) companies becomes more affordable, we may have easier access to carbon negative concrete.
“We’d love to get it from a direct air capture unit. We’re not there yet just because the industry is not there yet but it’s certainly well-positioned for us,” said Stern.
Eliminating emissions through collaboration
Founded in 2016, Carbicrete licenses its technology to concrete manufacturers who can integrate it into their existing production processes for concrete masonry units (CMUs) and precast panels.
Collaborating with Quebec manufacturer Patio Drummond, the company is building up its production capabilities to 25,000 CMUs per day. The first building using material is set to be built in Canada at the start of next year.
Stern believes the technology can help to reduce the 2.2 billion tonnes of carbon emissions that are generated by the cement industry every year.
“We can take care of megatons on a yearly basis, [capturing] anywhere between 100 and 300 [million tonnes of CO2]. So it’s definitely going to make a dent,” he said.
No cement involved
As mentioned, Carbicrete technology doesn’t require cement. It’s the binding agent that makes up around 12% of traditional concrete but is responsible for half of the material’s carbon footprint.
To make cement, calcium carbonate (usually in the form of limestone) is heated to around 1,480C to extract calcium oxide.
The process emits CO2, which accounts for 40% of limestone’s mass, into the atmosphere. Moreover, this energy-intensive process is usually powered by fossil fuels, creating additional emissions.
Carbicrete, on the otherhand, can cut about two kilograms of CO2 for every concrete masonry unit. Now, the company gets its calcium oxide from a waste byproduct from the steel-making process called slag.
In Carbicrete’s system, they inject calcium oxide with CO2 captured from industrial sites. This curing process creates calcium carbonate, which helps to fortify the concrete.
This is different from traditional concrete production, where cement is cured with water, essentially turning it back into strengthened calcium carbonate.
Stern explained, “It’s effectively doing the same job as hydration in a regular concrete product.
“The chemical composition of a concrete block that we make is exactly the same as a regular concrete block but we take a different road to get there.”
As a result, the carbonated concrete can have up to a 30% higher compressive strength than conventional concrete. According to Stern, its energy consumption is “literally not comparable” to that of traditional cement.
Steel slag dependence and other needs
We can say that Carbicrete still has limited potential for now. Meaning that they’ve still got challenges to overcome.
That’s because the current carbon curing process requires a controlled environment of a factory. Therefore, the company has to cast CMUs and concrete panels in advance before having them delivered to a construction site.
This precludes its use in liquid ready-mix concrete, which is cast and cured on-site to create a building’s foundations and floors. And so, the company’s currently developing a new technology. Unfortunately, we won’t see it in an industrial scale for another 5 to 10 years.
“It all comes down to how we can make a mobile, flexible curing system and have that on-site,” said Stern.
Then there’s also steel slag dependence. Only around 250 million tonnes of the industrial byproduct are produced every year compared to four billion tons of cement.
According to Stern, “There’snot enough steel slag to make enough concrete to serve the world’s needs on a yearly basis.
“It’s possible to replace 10 to 20% of the current concrete production. But concrete is the second most-consumed resource on the planet outside of water. So if we make a billion tonnes of concrete, that’s a massive amount.”
Other companies with similar efforts
Carbicrete isn’t the only company that strives to make environmentally friendly construction materials. Now, the ones mentioned here are not carbon neutral, but they’re now available at a much larger scale.
Canadian company CarbonCure uses captured CO2 emissions to cure regular cement. They mean to reduce the amount of cement needed to create a batch of ready-mix concrete and cut emissions by 5%.
CarbonCure has made more than eight million cubic metres of concrete with its technology.
Its senior director of sustainability Christie Gamble said, “Carboncure is on a mission to reduce 500 megatons of carbon emissions annually by the year 2030.
“To date, we’ve been able to reduce over 100,000 tons of CO2. We’re proud of that reduction so far [but] we still have a long way to go.”
In New Jersey, a company called Solidia uses carbon instead of water to cure a special cement that is low in lime, reducing CO2 emissions by up to 70%.
When we use these types of concrete, that could deliver 61% of the carbon savings of the concrete. And, the concrete and cement industry claims it needs to make net carbon negative by 2050.