Concrete that sucks — CO2, that is
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.