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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."
No mention in the article of the strength of the new material. How would this compare to regular concrete?
I see one of the early tags is 'negligible.'
Maybe it is in terms of global CO2 levels, but under a cap and trade system, this will turn an industry that might have to buy CO2-emission rights into one that could make money selling them!
This sounds like a concrete nightmare:
If a material absorbs so much CO2 over it's lifespan, it significantly alters the chemical composition and therefore strength.
I doubt any builder will use this material unless it's been proven that the new material is sufficiently stable.
Example: as a geology student, I ran into an area in central spain with lots of Gypsum sediments (Ca|MG.SO4). Putting limestone and concrete buildings on this sediment wasn't done until the 20th century, but all the buildings built in that area are long gone, even though in nearby towns they still stand tall. Reason? The Gypsym in the soil chemically eats the mortar and limestone (CaCO3) out of the structure on top of it, making it crumble within a few decades. The Gypsum areas are largely a wasteland where only very few buildings remain.
Now, Mg.Ca-CO3 (dolomite limestone) is largely as stable or more stable than pure limestone, and certainly harder, but any new formula for the glue in concrete will have to pass the test of time before it will be widely adopted, especially in e.g. bridges and skyscrapers...
Perhaps we can start with the interstates, nobody would notice if they started to crumble early ;)
"The building and construction industry knows it has got to do radical things to reduce its carbon footprint and cement companies"
Seriously? At least here in the Midwest (USA), construction bids still go to the lowest bidder and there are huge piles of construction waste that go straight to the landfill. They won't change until someone makes them change.
:wq
Fly ash, which is the ash waste from burning coal is also being used in concrete to lessen the amount of C02 concrete creates as well as improve strength. My question is since this fly ash has a high amount of toxins(heavy metals) in it, would the toxins be locked in the concrete or would they seep out if exposed to water or other stresses over time.
I am curious to know this because apparently fly ash can make concrete easier to work with in insulated concrete form construction and because other types of materials that compete with concrete seem to be using it. Gigacrete.com ( supposedly 10,000 psi strength) though not for structural use is an example. I can't tell if they are using weasel words though because they claim there binder is nontoxic, I can't tell if they are purposely talking about the binder being non toxic and not the fly ash.
I hope someday to build a house out of ICF's (insulated concrete forms), I guess I must have taken to heart that story of the three little pigs when I was young.
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."
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.
and by that phrase, I mean its popular bullshit. Most of the "green" things that have been devised over the past few years do NOTHING other than hold the carbon and make it the next generations problem instead. I thought the entire idea here was to NOT do that, but then again we live in an excessively hypocritical society that makes things up so they can make money, and this may just have been the latest and greatest. I'm not saying environmentalism is bad, but the majority of it so far isn't actually doing any good for the environment, its just helping the stock holders behind the products involved.
"They confiscated everything, even the stuff we didn't steal!"
A similar product was presented on Australian TV) in 2005.
It's not a bug, it's a lepidopter!
On top of that, Farmer's Almanac, long a very trusted and reliable predictor of future events, has predicted a cooling ...
It's good to see the Slashdot audience moving back to reliance on such scholarly peer-reviewed journals. That's science, that is, science by the quart.
Do not mock my vision of impractical footwear
Frankly, the mention of the term "carbon footprint" puts this squarely in the "hype" category.
Why did that get modded 5 insightful? Carbon Footprint is a valid and useful term.
The only reason I can see why some might like the above comment is if they are so conservative on climate change, they reject even the terms used in discussing it.
It would almost qualify as an example of the logical fallacy known as the "Appeal to Ridicule" but it wasn't quite intelligent enough.
http://en.wikipedia.org/wiki/Appeal_to_ridicule
-- the only thing we have to fear is really scary things
The summary doesn't explain things very well. Just to set things straight, most of the CO2 emissions from portland cement production is not from the fuel burned in the kilns but from the gas released by the limestone itself during the calcination process. The only real incentive for the use of energy efficient kilns is to reduce fuel costs and not to reduce emissions. The upside is that cement will reabsorb much of the released CO2 as it cures over the course of time.
I am becoming gerund, destroyer of verbs.
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
It's not impossible but remember that (IIRC) theoretical optimum thermal efficiency is (THigh-Tlow)/THigh.
In practice that means that waste heat is generally too cold for this process. If it were hot enough to make cement it would be hot enough to extract power from.
Waste heat from Combustion Turbines (CTs) is already being used to generate steam in cogen plants.
'Pure' CTs are typically super-peaker plants. Lousy efficiency but they start and ramp fast. Which in practice means their heat is too unpredictable to run that kind of process in any case.
Typical applications of CoLo heating are greenhouses, malls and other large buildings. Market forces are making this (space heating) happen quite nicely where ever economically practical.
My university was/is entirely heated by the waste heat of the coal fired plant on campus (50+ year old setup). Good fun in the steam tunnels. Access to boiler rooms.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
Why not just plant more trees around buildings made of concrete? That seems to me to be a more useful, long-term "incentive" program than some we've seen lately.
The house I live in is a mere 150 years old, but most of the street it is in was built between 1690 and 1695. In fact, our foundations go back to then. The composition and structure of Bath stone has been extensively studied, and I would imagine the results are just a small part of the data the technologists will take into account.
And your point was, again?
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."