There`s a story in Technology Review about a Halifax, Nova Scotia-based company called Carbon Sense Solutions that has found a way to make precast concrete products CO2-sucking vacuums. The interesting thing about concrete is that over hundreds of years they absorb CO2, a natural process called carbonation. The amount of absorption partially offsets the CO2 emissions that result from the calcination of limestone during the manufacture of cement, which is a key active ingredient of concrete. One problem, however, is that during the earlier stages of carbonation the outer two or three millimetres of the concrete forms a hardened crust that significantly slows down CO2 absorption. What Carbon Sense claims to have done is packed hundreds of years of carbonation into as little as one hour, using a curing process that consumes dramatically less energy than conventional heat/steam curing {see presentation here}. In fact, compared to steam curing, company CEO Robert Niven says his approach - building on 40 years of research at McGill University - uses up to 44 per cent less energy and 39 per cent less water.

Now, it only works with precast concrete products - i.e. prefab tunnels, manholes, septic tanks, walls, blocks and beams. Even concrete wind-turbine towers are precast. This represents between 10 to 15 per cent of the North American concrete market, which is predominantly ready-mix {i.e. construction folks mix it and mould it on site}. In some European countries, however, precast is closer to 40 per cent of the market. Given we`re talking about a $125-billion global market annually, even 10 per cent is a market worth pursuing.

Frankly, it sounds too good to be true, given the cement and concrete industry represent more than 5 per cent of global CO2 emissions and something has to be done about it. If all precast operations used Carbon Sense`s process, it would sequester as much as 20 per cent of those emissions in concrete, says Niven. How could this be? Because a precast plant alone wouldn`t have enough emissions to feed the process. To maximize CO2 absortion, a precast plant would have to get more CO2 from the flue stacks of neighbouring industrial facilities - assuming ideal logistics. Niven also says the process could take advantage of a plan, originating from Alberta, to build a CO2 pipeline across Canada that would feed enhanced oil recovery projects and other industrial uses {yeah, when donkeys fly}.

There`s no shortage of innovative companies tackling the concrete problem. CalStar, Calera, CO2 Solution - they all have their own interesting twist to greening up concrete`s dirty image. Hopefully one of them, 10 or 20 years from now, will prove that they have the secret sauce that matters. Niven says a pilot plant at a precast concrete facility in Nova Scotia should be announced shortly, and there are plans for a second pilot plant with a precast manufacturer in British Columbia.

Niven wouldn`t go into too much detail about the process, citing proprietary concerns, so let`s just hope the preliminary results from his first two pilot projects go far toward supporting his claims.
tyler.blogware.com/blog/_archives/2008/7/24/3808814.html