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Capturing carbon with concrete
March 6, 2008 - Exclusive
By David Ehrlich, cleantech.com
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A new process from Nova Scotia's Carbon Sense Solutions could pack away 500 megatons of carbon dioxide annually.
The race to develop integrated carbon capture and storage solutions could have some fresh competition in the form of concrete made with sequestered carbon dioxide.
Halifax, Nova Scotia-based Carbon Sense Solutions, an environmental consulting firm, has developed a method for storing carbon dioxide in pre-cast concrete which it said has the potential to put away 500 megatons of CO2 annually.
Carbonation of concrete has been around for awhile, but the process from Carbon Sense could lead the pack.
"What's different about this application is that it operates under atmospheric conditions, using as-captured flue gas," Robert Niven, president of Carbon Sense, told Cleantech.com.
"It's cheap, it's profitable. The others aren't."
He said it uses bolt-on technology with existing equipment.
Niven spoke about the process, called CO2 Accelerated Concrete Curing, at the Atlantic Climate Change conference in Halifax.
Pre-cast concrete uses a reusable mold to form walls, panels, beams and columns that are cured in a plant and then shipped to a construction site, offering faster production over pouring and curing on-site.
Niven said his company's process could use the existing carbon dioxide emissions from a pre-cast concrete plant, funneling the emissions into a separate green product line.
The resulting concrete has a higher compressive strength, is less permeable and has a faster curing time than regular pre-cast concrete, according to Niven.
Regular pre-cast concrete can take 12 to 24 hours to cure using steam, while the CO2 carbonated concrete only takes an hour, and doesn't use any steam. Plants could see 30 percent to 40 percent in energy savings with the new process.
Other companies are also trying to come up with cleantech solutions for the construction industry.
Sunnyvale, Calif.-based Serious Materials pulled in $50 million in financing last year for a green drywall product (see How green is your drywall?).
The company's EcoRock drywall uses almost no energy in its core production, resulting in zero emissions. Serious Materials expects to go into production with EcoRock this year.
Sage Electrochromics, based in Faribault, Minn., is also in the green construction game, producing a dynamically tinting window that can keep the view, but still block the heat and sunlight when needed (see Windows get smart in green building).
The carbon storing concrete from Carbon Sense can store 60 tons of carbon dioxide for every 1,000 tons of concrete, according to Niven.
"Right now, most pre-cast plants do have enough extra CO2 that they could redirect into this process," he said.
A plant could have a product line that isn't suitable for carbonation, and will still require steaming and curing, which releases carbon dioxide. That carbon dioxide can be dropped into the CO2 sequestering concrete.
But Niven said there's an interesting problem that could arise.
"In the end, you have this challenge, because you become a net-negative CO2 emitter," he said. "It's a wonderful story. You're able to suck in more CO2 than you can produce. That's a great challenge to have."
He said the ideal solution would be to have the pre-cast factories next to large stationary sources of carbon dioxide, such as power plants.
Carbonation first entered the pre-cast concrete industry in the 1950s.
"They introduced it to solve the problem of shrinkage cracking. That was a big issue, you have a lot of defects," he said. "And by carbonating the product, you completely shrink it, so that you don't have the shrinkage cracks."
But he said the system was very crude.
"It didn't actually accept much of the CO2, you had a thin crust of CO2 penetration on the outside, but you wouldn't get most of the mass carbonated on the interior," said Niven. "Since then, people have looked at very high technology, but expensive, applications."
He said his company would be able to work with the existing equipment in a plant.
"That's why we're able to run this pilot plant so soon and be able to commercialize it, across the globe, as soon as possible."
Niven holds a master's in environmental engineering from McGill University in Montreal, where testing on the concrete took place.
"A lot of the work was done through academia, and right now it's supported by my own company, and after this we're going into partnerships with industry and government," he said.
Carbon Sense is in negotiations with a pre-cast concrete company in the province and could have a pilot project up later this year, with the concrete potentially hitting the market in 2009.
"After the pilot studies are successfully completed, we're probably looking at licensing agreements for pre-cast concrete manufacturing plants, here in Nova Scotia and certainly abroad," said Niven.
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