May 5, 2008

Carbon Sense Solutions trumpets ability to capture carbon during curing

Halifax firm’s technology captures attention of concrete industry, too

PETER KENTER

correspondent

The concrete industry has been actively looking for ways to reduce its carbon footprint. A Canadian company says that new technology available to concrete manufacturers can not only make some concrete operations carbon-neutral, but actually make them carbon-negative.

Halifax-based Carbon Sense Solutions Inc. has developed a proprietary technology known as the CO2 Accelerated Concrete Curing process that captures carbon inside precast concrete at the same time as it virtually eliminates the burning of fuel used in current heat-curing processes.

“The process essentially removes the requirement for heat or steam-accelerated curing, substituting a chemical reaction between carbon and calcium-containing components of concrete, including alite, belite and portlandite,” says Robert Niven, president of the company.

“This process doesn’t just store the carbon emissions temporarily, it locks carbon into the concrete permanently.”

Niven says that the precast concrete produced using the process is almost identical to traditional precast. “Our product is less permeable and has less water retention and demonstrates earlier strength development,” says Niven. “Testing also shows that the final product eliminates cracking as a result of shrinkage.”

So where does the carbon go?

“If you think of concrete as a sponge, this process fills all of the pores with calcium carbonate — essentially limestone,” he says. “About half the weight of the cement that goes into concrete will be carbon, so this amounts to about five per cent of the final product by weight.” The by-products of the process: heat and water.

The process also incorporates traditional waste materials that are often added to concrete, including steel slag. “Some slags contain calcium and magnesium and the carbonation process will incorporate those materials,” says Niven.

Concrete companies can virtually eliminate the use of heat generated by fossil fuels in the curing process, saving 30 to 50 per cent of plant energy and eliminating the CO2 created in generating the heat.

But producing the limestone-saturated concrete provides an interesting conundrum — companies producing the material may actually find themselves with a carbon-deficit, consuming all of the CO2 they produce and looking for more.

“Initially, you would ideally take it from on site,” says Niven. “Under the current situation, that’s a mixed blessing, because the process is so effective at capturing CO2 you would need to get it from somewhere else.”

Under a carbon-trading scheme, however, companies that are carbon efficient can sell carbon credits to companies that are less efficient, allowing a precast concrete company to make a tidy income on sales of carbon credits alone. “People would pay you to get rid of their carbon,” says Niven.

To some degree, delivering the carbon efficiently would depend on the creation of a carbon capture and storage network that would see CO2 liquefied and carried through a series of underground conduits.

A surprise $5 million grant from the federal government contained in its latest budget is earmarked for further research on the concept in Nova Scotia.

Niven’s company hopes to provide consulting services to the province to help determine where carbon-dioxide emissions from large, fossil-fueled power plants and industries can be stored.

“In the short term, you could capture carbon from a neighbouring industry or have it delivered as carbon dioxide in compressed form in metal cylinders,” says Niven.

Much of Niven’s initial testing has involved the manufacturing of precast concrete pavers, but two larger-scale pilot projects in Nova Scotia and British Columbia are currently under negotiation.

The project has gained support from such organizations as the Cement Association of Canada (CAC) and the Canadian Precast/Prestressed Concrete Institute. “In our discussions with Mr. Niven we were impressed with the way his research was presented,” says Bill Dooley, vice president, Atlantic Region with the CAC.

“Given that all industries and governments are looking for solutions to climate change and emissions, this is a process that I believe we should try to commercialize.”

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