Quebec company offers breath of carbon-neutral air with cement alternative

Quebec company Patio Drummond has relied on cement powder to produce concrete for five decades, but now it's offering an environmentally friendly alternative aimed at reducing greenhouse gas emissions.

Patio Drummond is offering a cement-free, carbon-negative concrete option to consumers who want to reduce their impact on the environment.

That option is CarbiCrete blocks which are bound together using a byproduct from steel production. In the curing chamber, carbon dioxide (CO2) is captured within the blocks themselves.

"As we inject the CO2, the calcium carbonate forms, and that's what binds the concrete and makes it hard," said Philippe Girardin, co-owner of Patio Drummond, which is based in Drummondville, Que.

CarbiCrete is based in the Montreal borough of Lachine. 

"With cement-based concrete, the first step involves mixing cement with aggregate and water," the company says on its website.  

"With CarbiCrete, cement is replaced with steel slag, which is mixed with the other materials using standard equipment."

An independent analysis confirms that CarbiCrete blocks are carbon-negative over their lifecycle. The unique feature of trapping CO2 within the blocks offsets the emissions produced during their making, presenting a greener alternative to conventional cement-based concrete blocks.

Tonne of CO2 per tonne of cement

Chris Stern, CEO of CarbiCrete, said every tonne of regular cement produced is a tonne of CO2 produced. 

"If you look at the entire worldwide production, you're looking at eight per cent of GHG or four gigatonnes of carbon dioxide," he said.

Concrete is expected to contribute 12 per cent of global greenhouse gas emissions by 2060, thanks in large part to one of its main ingredients, cement.

There are two reasons why manufacturing cement releases a lot of carbon: the combustion of fossil fuels typically used to heat the necessary kilns and the chemical reaction that releases carbon stored in limestone, one of the main ingredients. 

The Global Cement and Concrete Association has promised carbon-neutral concrete by 2050, a goal Canada wants to help the industry achieve.

"We live in a world that's still going to need cement and concrete," said Keith Brooks, programs director with the research and education group Environmental Defence, citing the physical infrastructure necessary to create denser, more energy-efficient cities. 

"The industry's going to have to do its part to get there. But it is possible." 

Other ways of reducing the environmental impact of cement production include using materials such as fly ash, a waste product of coal combustion. Then there's volcanic ash, a cement alternative so old that the ancient Greeks and Romans used it. 

There's also a way to recycle existing concrete.

Challenge lies in making concrete truly sustainable

The challenge is making sure concrete is truly sustainable, said Shahria Alam, professor of civil engineering at the University of British Columbia. His team is researching how to make this possible. 

In order to call it "green concrete," Alam said, we should ask "whether it's giving us long-term sustainability, not only in the first generation but multiple generations." 

Last week, Patio Drummond introduced CarbiCrete blocks to the market after years of rigorous testing and millions of dollars' worth of investment in equipment. These blocks account for a tenth of the cinder blocks produced by the company.

Despite a 30 per cent higher price tag, there is already demand for this environmentally conscious choice, Girardin said.

"The tests we've done show that the longevity or durability of the product is even better than a standard block," he said.

CarbiCrete blocks represent a significant step forward in reducing CO2 emissions in the construction industry, said Sidney Omelon, an associate professor of material science at McGill University.

"In my opinion there's no one single solution to solving our CO2 emission problem," she said. "So I really welcome any and all new technologies.

Patio Drummond currently has two curing chambers that manufacture 2,400 CarbiCrete cinder blocks a day. The company hopes to double that production within a year.