Making the 2bn tonnes of cement used globally every year, for concrete and other things, pumps out 5% of the world's CO2 emissions - more than the entire aviation industry.
A new cement has been developed, which consumes rather than produces CO2.
http://www.guardian.co.uk/environment/2008/dec/31/cement-carbon-emissions
**11/19/10 Update
"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."
http://www.cleanbreak.ca/2008/07/24/concrete-that-sucks-co2-that-is/
And...
Call him cement man.
Back when Stanford Professor Brent Constantz was 27, he created a high-tech cement that revolutionized bone fracture repair in hospitals worldwide. People who might have died from the complications of breaking their hips lived. Fractured wrists became good as new.
Now, 22 years later, he wants to repair the world.
Constantz says he has invented a green cement that could eliminate the huge amounts of carbon dioxide spewed into the atmosphere by manufacturers of the everyday cement used in concrete for buildings, roadways and bridges.
His vision of eliminating a large source of the world's greenhouse CO2 has gained traction with both investors and environmentalists.
Already, venture capitalist Vinod Khosla is backing Constantz's company, the Calera Corp., which has a pilot factory in Moss Landing (Monterey County) churning out cement in small batches.
http://www.truth-out.org/article/green-cement-may-set-co2-fate-concrete
