TimmyH
Global Warming: A Concrete Solution
July 24th 2008 05:05
A Canadian concrete maker has developed a way of storing carbon-dioxide emissions from its factories and industrial facilities inside its precast concrete products. During the curing process, the concrete is exposed to carbon-dioxide rich flue gases. Although as yet unproven, Industry experts say that the technology holds enormous potential.
The active ingredient in concrete, Cement, is made by baking limestone and clay powders, usually with heat from fossil fuels. As such, concrete products account for more than 5 percent of human carbon-dioxide emissions. Additional emissions are created when heat and steam are used to accelerate the curing process.
But Carbon Sense Solutions, based in Halifax, believes that their process could actually allow precast concrete to store these carbon emissions. The technology makes use of the natural process whereby concrete absorbs CO2 from the atmosphere in a natural chemical reaction.
As Caron Sense Solutions founder, Robert Niven, explains:
The freshly mixed concrete is exposed to carbon-dioxide-rich flue gases. This rapidly speeds up the reactions between the calcium-containing minerals in the cement and the gas itself. The change almost entirely eliminates the need for heat and steam in the system, which saves energy and hence reduces emissions.
A pilot program is beginning next month in Nova Scotia and preliminary results should be available by the end of the year. If successful, Niven expects that it could be used to reduce more than 20 percent of all carbon-dioxide emissions by the concrete industry.
“If the technology is commercialized as planned, it will revolutionize concrete manufacturing and mitigate hundreds of megatons of carbon dioxide each year, while providing manufacturers with a cheaper, greener, and superior product,” he says.
Almost 60 tonnes of carbon-dioxide could be stored within 1,000 tonnes of concrete as solid limestone. Another advantage is that the new concrete product is more resistant to cracking and shrinking, as well as being more permeable to water.
Concrete carbonation has been around for decades, but there has never been an economically viable way to strengthen or improve the finished product. Rick Bohan, director of construction technologies at the Portland Cement Association says “It’s almost too good to be true.”
“Considering concrete is the most abundant man-made material on earth, and that the precast market is growing, the estimated carbon dioxide storage potential of this is 500 megatons a year,” Niven says. “That is on par with other global carbon dioxide mitigation solutions, such as carbon capture and geological storage.”
Concrete does absorb carbon-dioxide over time, but only up to a point. Research professor Tarun Naik, director of the University of Wisconsin-Milwaukee's Center for By-Products Utilization says that the first two or three millimetres of the surface form a crust which eventually stops absorption. But Naik says that using less sand in the mixture can increase the porous nature of the concrete and allow for more CO2 to be absorbed. This is a simpler process than the one Carbon Sense Solutions has been championing and can be applied more broadly.
Other processes are also being explored as alternatives including Montreal’s CO2 Solution which uses an enzymatic approach whereby CO2 is captured from cement-factory flue stacks and converts it back into limestone which can be re-used in the cement-making process. Some experts have said that this could reduce carbon emissions by one tonne for every tonne of concrete produced.
The active ingredient in concrete, Cement, is made by baking limestone and clay powders, usually with heat from fossil fuels. As such, concrete products account for more than 5 percent of human carbon-dioxide emissions. Additional emissions are created when heat and steam are used to accelerate the curing process.
But Carbon Sense Solutions, based in Halifax, believes that their process could actually allow precast concrete to store these carbon emissions. The technology makes use of the natural process whereby concrete absorbs CO2 from the atmosphere in a natural chemical reaction.
As Caron Sense Solutions founder, Robert Niven, explains:
The freshly mixed concrete is exposed to carbon-dioxide-rich flue gases. This rapidly speeds up the reactions between the calcium-containing minerals in the cement and the gas itself. The change almost entirely eliminates the need for heat and steam in the system, which saves energy and hence reduces emissions.
A pilot program is beginning next month in Nova Scotia and preliminary results should be available by the end of the year. If successful, Niven expects that it could be used to reduce more than 20 percent of all carbon-dioxide emissions by the concrete industry.
“If the technology is commercialized as planned, it will revolutionize concrete manufacturing and mitigate hundreds of megatons of carbon dioxide each year, while providing manufacturers with a cheaper, greener, and superior product,” he says.
Almost 60 tonnes of carbon-dioxide could be stored within 1,000 tonnes of concrete as solid limestone. Another advantage is that the new concrete product is more resistant to cracking and shrinking, as well as being more permeable to water.
Concrete carbonation has been around for decades, but there has never been an economically viable way to strengthen or improve the finished product. Rick Bohan, director of construction technologies at the Portland Cement Association says “It’s almost too good to be true.”
“Considering concrete is the most abundant man-made material on earth, and that the precast market is growing, the estimated carbon dioxide storage potential of this is 500 megatons a year,” Niven says. “That is on par with other global carbon dioxide mitigation solutions, such as carbon capture and geological storage.”
Concrete does absorb carbon-dioxide over time, but only up to a point. Research professor Tarun Naik, director of the University of Wisconsin-Milwaukee's Center for By-Products Utilization says that the first two or three millimetres of the surface form a crust which eventually stops absorption. But Naik says that using less sand in the mixture can increase the porous nature of the concrete and allow for more CO2 to be absorbed. This is a simpler process than the one Carbon Sense Solutions has been championing and can be applied more broadly.
Other processes are also being explored as alternatives including Montreal’s CO2 Solution which uses an enzymatic approach whereby CO2 is captured from cement-factory flue stacks and converts it back into limestone which can be re-used in the cement-making process. Some experts have said that this could reduce carbon emissions by one tonne for every tonne of concrete produced.
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Things like this will make all the difference.