From a New York Times science section article by Henry Fountain:
Concrete may seem an unlikely material for scientific advances. At its most basic, a block of concrete is something like a fruitcake, but even more leaden and often just as unloved. The fruit in the mix is coarse aggregate, usually crushed rock. Fine aggregate, usually sand, is a major component as well. Add water and something to help bind it all together — eggs in a fruitcake, Portland cement in concrete — mix well, pour into a form and let sit for decades.
Let a lot of it sit. Every year, about a cubic yard of concrete is produced for each of the six-billion-plus people on the planet.
It’s the Portland cement that’s at the heart of one of the environmental problems caused by concrete:
About a ton of CO2 is emitted for every ton of cement produced. The basic manufacturing process involves burning limestone and other minerals at about 2,700 degrees Fahrenheit to create an intermediate product called clinker.
And to design for “less bad” concrete:
The cement industry, particularly in the United States and Europe, has reduced CO2 emissions through the use of more efficient kilns and processes, and is now allowed to add some ground unburned limestone to the clinker, reducing the actual cement in the mix. But about half of the CO2 from cement cannot be eliminated — it is produced in the reaction, called calcination, that occurs as the limestone (which consists of calcium carbonate) is being burned.
But a much more inspired approach is one that turns the whole process on its head and asks whether, instead of trying to do less harm, concrete manufacture can do more good:
At a site adjacent to a gas-fired electricity generation plant in Moss Landing, Calif., the Calera Corporation is developing a process to bubble power plant flue gases through seawater or other brackish water, using the CO2 in the gases to precipitate carbonate minerals for use as cement or aggregates in concrete. The process mimics, to some extent, what corals and other calcifying marine organisms do.
Calera calculates that producing a ton of these minerals consumes half a ton of CO2, so the resulting concrete could potentially be carbon negative — sequestering carbon dioxide permanently.
This is the thinking of green 2.0, which rejects the do less harm paradigm and replaces it with do more good. It’s the way to go.
Think manufacturing processes that improve the location from which the resources are taken. Waste processes that
leaves the disposal sites better off. Not less resource negative or resource neutral but resource positive.
Besides, from a commercial perspective, less bad is not a positive selling point. It’s just a reason for people to feel less guilty about a product until they finally find a way to avoid it. Figure out how to honestly make them feel good about the product–so it does more good instead of less harm–and they won’t need to avoid it.