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Green Cement Absorbs Carbon
Peace Corps Online writes "Concrete accounts for more than 5 percent of human-caused carbon dioxide emissions annually, mostly because cement, the active ingredient in concrete, is made by baking limestone and clay powders under intense heat that is generally produced by the burning of fossil fuels. Now Scientific American reports that British start-up company Novacem has developed a 'carbon-negative' cement that absorbs more carbon dioxide than it emits over its life cycle. The trick is to make cement from magnesium silicates rather than calcium carbonate, or limestone, since this material does not emit CO2 in manufacture and absorbs the greenhouse gas as it ages. 'The building and construction industry knows it has got to do radical things to reduce its carbon footprint and cement companies understand there is not a lot they can do without a technology breakthrough,' says Novacem Chairman Stuart Evans. Novacem estimates that for every ton of Portland cement replaced by its product, around three-quarters of a ton of CO2 is saved, turning the cement industry from a big emitter to a big absorber of carbon. Major cement makers have been working hard to reduce CO2 emissions by investing in modern kilns and using as little carbon-heavy fuel as possible, but reductions to date have been limited. Novacem has raised $1.7M to start a pilot plant that should be up and running in northern England in 2011."
Even if it is negligible, "going green" is the trendy thing to do nowadays, so as long as it seems like they're making an effort, that's far more important than if it actually helps.
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It's the composition of quite a few minerals, including asbestos, but also talc and soapstone. The issue with asbestos isn't the chemical composition per se, but rather its inclination to break into micron-sized fibers that can be deposited in the lungs. Compare fine silica, which is nearly chemically inert, but poses a serious danger if inhaled.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
You're right in that we want strong and durable concrete. As another poster pointed out we are constantly changing the concrete mix proportions and admixtures. Admixes themselves are relatively new (~50 years) in the grand scheme of making concrete. It gets introduced slowly...and the universities then test it beyond belief for different properties. Maybe you'd like to be a grad student in civil engineering and make hundreds, or perhaps thousands of ever so slightly different mixes to determine the properties of your variable. I'm all for making concrete more "green" and I figure the universities and companies will test it before they use it in important projects.
One of my dorm friends, Jakob Husum, wrote his dissertation on ways of optimizing cement productions.
One of the rather impressive/scary things about that, is that it is responsible for about 2% of the world's energy consumption. That's an insane amount of energy for something that isn't even an end product.
The first paragraph of the paper actually grabs you by the balls and twists firmly:
Can't quite remember how much of the energy if spent on the last bit, but I think it was something like 25%. That's 0.5% of the world's energy usage spent on a 1% efficient process. Now imagine you could up the efficiency to 10% or even 5%. That'd be a reduction of the world's energy usage of 0.45 or 0.4% respectively, simply by improving a single process.
Now, there are a lot of arguments for saving energy. Saving the environment, less pollution etc., but it's hard to overlook the economic incentive of cutting back energy costs of a production, where a large part of the process is 1% efficient.
weight of air, approximately 28 grams per mole /., priceless. Also weightless.
weight of carbon dioxide, 44 grams per mole
Being a tard on
Global warming may or may not be happening.
That's a tautology much like "water may or may not be wet," so by definition it's logically true. "Global warming is happening." That's a statement of scientific fact, it's empirically true.
We don't know exactly, however it has been established beyond any reasonable doubt that human activity is a major contributor.
Up to that point this was such a beautiful example of agnatology relying on nothing but formally True statements. Why did you have to ruin it? How very disappointing!
Better to be despised for too anxious apprehensions, than ruined by too confident a security. --Edmund Burke
No need to worry about the availability of Magnesium Silicates, they just found the mother-lode in the South American rain forest.
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