Sooner or later, any effort to reduce carbon emissions from buildings hits a wall—a concrete wall.
Concrete poses a considerable environmental challenge due largely to the carbon emissions tied to cement, one of its key ingredients. For every tonne of cement produced, about 800 kilograms of CO2 are released into the atmosphere. Estimates have attributed as much as five per cent of total global CO2 emissions to cement production, and it’s not hard to see why. No other construction material can quite compare with concrete for sheer ubiquity.
“There’s so much production of concrete in the world—it’s the most abundant man-made material out there—that it seemed like a wasted opportunity to keep making concrete without trapping carbon dioxide within it,” says Christie Gamble, director of sales and marketing at CarbonCure Technologies.
To tackle this challenge, the Nova Scotia company devised a technology that injects CO2 captured from industrial projects into concrete as it is being mixed. The CO2 reacts with calcium in the mix and turns into calcium carbonate. This is not exactly a sequestration technology, but rather one that uses calcification to vanish the CO2 entirely. Even if the concrete crumbles or the building is demolished, the CO2 can’t be released because it no longer exists.
Gamble says that the CO2-enriched concrete appears like any other blend. The colour, texture and workability all remain unaffected. The only significant difference is that the calcium carbonate contributes to the compressive strength of the concrete—as much as a 10 per cent improvement at 28 days on average. The concrete can actually maintain its strength while using less cement. And that is where the CO2 savings can be found.
For every cubic metre of concrete, CarbonCure generally injects about half a kilogram of CO2 , Gamble estimates. That also allows producers to reduce cement content by five per cent, which equates to avoiding about 12 to 15 kilograms of CO2 production, depending on the mix.
Those numbers may actually be a bit conservative, according to Norm Kuntz, Calgary district manager of BURNCO. His company began using the technology at its Calgary location in 2016, making it just the second concrete supplier in Canada and the first in Alberta to install CarbonCure. He believes the potential for cement reduction is closer to 10 per cent, which would equal a 30-kilogram reduction of CO2 emissions for each cubic metre of concrete.
BURNCO plans to begin its commercial push for the technology later in 2017. For now, the company is demoing various mixes and gathering data as it works out a marketing model for the technology. Kuntz expects there to be little impact on cost for what the company hopes to promote as greener concrete.
“There is a saving from cement reduction, and then there’s what it’s costing to get the system installed and put the carbon dioxide in,” he says. “It’s fairly balanced. It will either be no price increase or just a modest price increase on this system.”
CarbonCure wants to be more than a green add-on for concrete production, however. The company’s goal is to become a new standard for the industry. It is already capturing some wider attention as one of 27 semi-finalists in the $20-million Carbon XPRIZE competition sponsored by NRG Energy and Canada’s Oil Sands Innovation Alliance, which is looking for novel ways to convert CO2 emissions into products of value.
“We’re feeling pretty good about our chances right now because of the fact that we’ve already gotten to the point where we’re demonstrating it’s a viable technology,” Gamble says. “A lot of the other applications are in the conceptual design phase, while we’re in the expand and roll-out phase.”
Finalists will be announced in December 2017, and the overall winner will be unveiled in 2020.