From the “settled science” department and the University or California Irvine, comes this inconvenient fact. For years we’ve been told by academics that cement is another nasty global warming contributor, because of CO2 released during production.
“Cement manufacturing is responsible for 5 to 8 percent of global CO2 emissions,” notes Del Gado, a theoretical physicist who is part of Georgetown’s Institute for Soft Matter Synthesis and Metrology. “Although there have been calls for creating so-called ‘green cement,’ the sustainability and science communities have yet to find a way to reduce CO2 emissions while retaining the efficiency, durability and cost efficiency of cement. Our study could help change that.”
Now, not so much.
Concrete jungle functions as carbon sink, UCI and other researchers find
Cement-based materials eventually reabsorb much of the CO2 released during creation
Steven Davis / UCI
Irvine, Calif. – Cement manufacturing is among the most carbon-intensive industrial processes, but an international team of researchers has found that over time, the widely used building material reabsorbs much of the CO2 emitted when it was made.
“It sounds counterintuitive, but it’s true,” said Steven Davis, associate professor of Earth system science at the University of California, Irvine. “The cement poured around the world since 1930 has taken up a substantial portion of the CO2 released when it was initially produced.”
For a study published today in Nature Geoscience, Davis and colleagues from China, Europe and other U.S. institutions tallied the emissions from cement manufacturing and compared them to the amount of CO2 reabsorbed by the material over its complete life cycle, which includes normal use, disposal and recycling. They found that “cement is a large, overlooked and growing net sink” around the world – “sink” meaning a feature such as a forest or ocean that takes carbon dioxide out of the atmosphere and permanently tucks it away so that it can no longer contribute to climate change.
Cement manufacturing is considered doubly carbon-intensive because emissions come from two sources. CO2 molecules are released into the air when limestone (calcium carbonate) is converted to lime (calcium oxide), the key ingredient in cement. And to generate the heat necessary to break up limestone, factories also burn large quantities of natural gas, coal and other fossil fuels.
Davis and his fellow researchers looked at the problem from a different angle. They investigated how much of the gas is removed from the environment over time by buildings, roads and other kinds of infrastructure. Through a process called carbonation, CO2 is drawn into the pores of cement-based materials, such as concrete and mortar. This starts at the surface and moves progressively inward, pulling in more and more carbon dioxide as years pass.
More than 76 billion tons of cement was produced around the world between 1930 and 2013, according to the study; 4 billion tons were manufactured in 2013 alone, mostly in China. It’s estimated that, as a result, a total of 38.2 gigatons of CO2 was released over that period. The scientists concluded, however, that 4.5 gigatons – or 43 percent of emissions from limestone conversion – were gradually reabsorbed during that time frame.
“Cement has gotten a lot of attention for its sizable contribution to global climate change, but this research reinforces that the leading culprit continues to be fossil fuel burning,” Davis said.
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These are the goofballs that want to run the global economy. God help us.
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2873672
They just now noticed this?
This article is at least a year and a half old:
http://www.cement.org/for-concrete-books-learning/concrete-technology/concrete-design-production/concrete-as-a-carbon-sink
Sheesh, I’ve known that for at least 20 years. And I’ve never bothered to actually study this subject.
Everyone except the Carbon Moonies charged with finding new things to worry about knew that.
Well, I didn’t know that. But then I never really thought about it, either. Learned something today.
About the only useful observation that came out of the Biosphere debacle was that concrete absorbs CO2 in around 1993 https://en.wikipedia.org/wiki/Biosphere_2#Challenges
We are going to have to pave the world over n order to save it.
I wonder if that’s one reason why the US is a carbon sink according to that CO2 observing satellite.
It doesn’t hurt, but forest growth and soil absorption are likely more significant. If only because there’s a lot more soil and forested land.
Now only if CO2 made a difference wrt warming…wait a minute – now only if the planet was warming…All CO2 talk is irrelevant (unless you’re a plant that is)
Precisely. And OTOH Patrick Moore points out that activities like cement making actually contribute to the depleted bank of CO2 that plants are starved of and whose increase is (beneficially) greening up the planet.
Per IPCC AR5 Figure 6.1 the biospheric carbon balance contains 46,713 Gt of C.
38.2 Gt of CO2 = 10.4 Gt of C or 218 ppm of the total biospheric carbon.
Doesn’t look so big now, does it?
A 57%/43% sequester/retained split means a difference of 2 ppmv in the atmosphere.
And this is all spread out over 83 years.
I’m not sure I follow this. There seems to be some confusion between C and CO2.
Yeah, me too, Nicholas Schroeder. Can you explain this, or is it explained on the AR5 figure that I haven’t looked up yet (but I will).
NOAA has a formula for converting carbon into co2. Without looking it up its 3.67 or 3.62. I think that it to further confuse the issue. Further they have to account for a substantial amount of co2 that is vanishing over and above the stated 50% that is acknowledged to be sinking. . There is no indication of why or how so much co2 is not making its way into the atmosphere. NOAA has also recently changed one of its metrics, disallowing one of their estimates to lower co2 production.
I see it as a desperate attempt to shore up their failing analysis. It’s like the tropical hotspot or the heat hiding somewhere.
It’s based on the atomic weights of carbon and oxygen and the molecular weight of CO2. the atomic weights of C and O are (with rounding for simplicity) 12 and 16, respectively. Therefore, the molecular weight of CO2 is 44 (rounded).
So carbon makes up approximately 27% (27.3) of CO2 and oxygen makes up 72.7% of CO2. To convert weight (mass) of CO2 to either C or O, multiply the mass CO2 by the respective %. For example, 38.2 Gt CO2 * 27.3% (for C) = 10.4 GT C.
Thank you, rishrac and Phil R. Very much appreciated.
Metal carbonates (CO3-2) would actually be a net sink because they can fractionally absorb some extra CO2 to form bicarbonates (HCO3-), this being part and parcel of the oceanic pH buffering system. But it’s not important on the grand scale of things, because of the practical difficulties of digging up all the worlds limestone and spreading around to absorb a little bit more atmospheric CO2.
Why this guy describes his findings as “counterintuitive” baffles me. Perhaps he never actually studied chemistry before.
“Why this guy describes his findings as “counterintuitive” baffles me. Perhaps he never actually studied chemistry before.”
————————
I think the statement speaks to the audience at large. ChemEs, etc. are a tiny fraction of the population.
Consider the near universal human frailty whereby any true and valid information which contradicts what an individual believes about a subject becomes difficult- to- impossible for the individual to accept.
This is a bit of a double-edged sword. As much as I dislike massively subsidized, ineffective, and downright destructive wind power installations, we can’t use the “carbon footprint” of concrete as an argument against them. I’ve seen that argument made here before.
There are two aspects to the CO2 footprint of concrete. The first is the CO2 released from the materials being processed. The second is all the energy that goes into processing all those materials.
Concrete for windmills is mostly buried, isn’t it? It’s primarily used as a below ground mass to secure and counter-balance the massive, vibrating towers.
If so, it would be largely shielded from atmospheric CO2 by its surrounding earth.
That would presumably greatly reduce its total CO2 reabsorption, wouldn’t it?
I suspect that soluble carbonates like sodium carbonate and sodium bicarbonates, that abound in moist or wet soils along with carbonic acid deliver plenty of CO2 to the buried concrete footings.
Whoa—you mean maybe they were wrong about concrete? I had always been told it is contributing to global warming.
“More than 76 billion tons of cement was produced around the world between 1930 and 2013, according to the study; 4 billion tons were manufactured in 2013 alone, mostly in China. It’s estimated that, as a result, a total of 38.2 gigatons of CO2 was released over that period. The scientists concluded, however, that 4.5 gigatons – or 43 percent of emissions from limestone conversion – were gradually reabsorbed during that time frame.”
Please note:
38.2gt emitted
4.5gt reabsorbed
Not a net sink, just 12% less bad than was assumed.
I noticed that as well and wondered if maybe it was a typo: 4.5 instead of 14.5. So I tried 14.5/38.2 which is 38%. In the right ball park but not really close enough. Somebody needs to take another look at those numbers.
“or 43 percent of emissions from LIMESTONE conversion – were gradually reabsorbed during that time frame.”
@ur momisugly Marcus
Yes, you’re right. I was reading it wrong. But it was the juxtaposition of the numbers and the fact that emissions from limestone conversion weren’t separated out that confused me.
@sagalout…I agree, it was confusing at first glance…
They pulled a switch to make it look like a smaller amount absorbed by the 43% being calculated on the 10.4Gt of C and not on the CO2.
Something to consider is that it only takes a matter of hours to release the CO2 when calcining limestone, but it takes years to decades for the carbonation to take place. They said that they took the entire life cycle into account, but many of the projects, like Hoover Dam and the Aswan Dam have yet to be demolished when the useful life is over. It will take considerable energy (and probably release of CO2) to crush and transport the old concrete to whatever its final resting place will be. So, I doubt if the full life-cycle has been fully accounted for. Fundamentally, the full accounting has been delayed and their optimistic figures only represent the situation at an intermediate point in time.
Aww! Only 43% off? Some of the variables in the IPCC GCM computer models are several hundred percent undetermined, like the effect of doubling CO2 levels. So what is the big deal about a petty 43%?/sarc
Best I can figure, the only contribution to “global warming” that cement makes is the fact that it retains heat into the night, thus raising the overnight lows. As far as I can tell, that is also the ONLY warming that we are experiencing, meaning that day time highs haven’t gone up, just night time lows giving us a higher “average daily temperature.” Maybe I can’t figure though.
Does this mean that Climate Scientists should live in concrete towers rather than ivory towers?
Think of all the elephants that woul be saved.
So we would be at “normal” or below normal temps today if LBJ had paved over Vietnam?
The numbers do not add up.
CO2; MW = 44
CaO; MW = 56
Ratio = 44/56 = 0.79
CaCO3; MW = 100
Ratio CaCO3/CaO = 100/56 = 1.79
So 76 tons cement produced gives 60 tons CO2 from 136 tons CaCO3!
This is the conversion from calcium carbonate to calcium oxide. No account for the fuel is made here, just the chemical conversion.
(the ratios are all the same so use grams, kg, tons, gt, etc.)
They throw out 38.2 gt. as a working number. Then they say 4.5 gt absorbed, well OK.
Then they say 4.5 gt = 43% of 38.2! Well, it mostly is not.
And the number for CO2 from CaCO3 conversion is 60 gt, not 38.2 gt.
This does not make sense.
Are we talking concrete or cement? The figure of 4 billion metric tons for 2013 agrees with what I read elsewhere for concrete, which is about 10-15% cement. The rest is water and aggregate (sand, gravel or recycled concrete). It’s the manufacture of cement which releases C02.
So I think the figures here need to be scaled back to arrive at cement production.
Good point. Just a quick look at mixing and matching concrete or cement numbers (using your 10-15%) in the data above, and they still do not make any sense.
Lets try this:
76 gt concrete * 0.15 (your handy number) = 11.4 gt cement, and 9 gt CO2
They say 4.5 gt absorbed so
4.5/9.0 = 50%, more or less close to the claimed 43%.
At this point I feel like I am just playing with numbers and making stuff up. As astrologer could do as much.
But then again, they say cement, and give numbers.
AW, you’re correct, they have confused cement and concrete. For example Assoc. Prof. Davis reportedly said “The cement poured around the world since 1930….” Concrete gets poured, not cement. So we can’t be sure if they are always talking about concrete, or are sometimes talking about cement. They also mention units of both billion tons and gigatons. These are equivalent.
The rule of thumb is around 1 tonne of cement produces 1 tonne of CO2. This has come down in recent years with increased efficiency of cement plants, and also substitution of carbonate raw materials. However, as noted previously their numbers just don’t add up anyway.
The carbonation of concrete is well known, but for high strength, dense concretes it is a very slow process – maybe a few millimetres penetration into the concrete over several decades. The concrete has to be reduced to rubble and left exposed to the air for appreciable carbonation to occur.
Yes, I think this basically BS. I have known for a long time that lime white wash absorbs CO2 into its suface and basically reverts to being limestone. However, I had presumed that concrete was too dense for this happen at anything more than a trivial thickness.
Most construction involving poured concrete also uses vibrators to help the air bubbles rise out. This results in a dense compacted finish against the shuttering.
Even when buildings get pulled down they are pulverised, they remain fairly massive lumps of concrete.
But concrete remains permeable to water, and the water which enters the concrete contains some CO2, so it can get all into the concrete, not just at the surface.
In fact, it is well known that concrete continues to strengthen indefinitely under most conditions because the hydration process never stops. Needles shaped crystals grow ever longer over time, interlocking and making the concrete stronger as they grow.
As CO2 concentration in the atmosphere goes up, it stands to reason that there will be more of it dissolved in the water which infiltrates the concrete and is incorporated into the crystalline matrix.
So even buried concrete likely absorbs CO2 over time.
Concrete and cement are two different things …?
Jeeze, next thing you’ll be telling me is temperature and heat are two different things as well.
And please please please don’t tell me my models have to be accurate as well as precise, ’cause then somebody would ask what the difference is (and I don’t (care to) know).
And isn’t that the same as using carbon and carbon dioxide interchangably
Since CO2 is not harmful but beneficial, and it likely has very tiny influence on the temperature of the Earth, it is all just an exercise in tedious analysis of a complicated equation that ultimately is inconsequential anyway.
IWO, big deal…so what?
Just think of it this way. Cement is to concrete what flour is to bread. A component.
This made me think of an old Gallagher joke.
“They say that cities are destroying the environment. They’re wrong. It’s the farmers. Farmers plant crops that leach the nutrients from the soil. They rotate the crops, they rotate the nutrients they leach from the soil. Where in the cities they lay down the parking lots and asphalt. Seal in the nutrients.”
Reminds me of George Carlin ” The planet is going to be fine”!
The Earth will eventually get around to going what is was going to do anyway, and shake us off like a case of the fleas.
The only stuff lost to the planet is anything we launch into space which does not come back.
Everything else is just reshuffling atoms and molecules that the Earth has been shuffling around for billions of years.
So, 38.2G tons of CO2 was released making cement, then 4.5G tons (11.8%) of that was more or less slowly incorporated into 76G tons of concrete. What did I misunderstand?
You’d think that concrete in standing structures, with their surface area, would grab up even more than buried limestone. Who has a CRC HandBook and a P-chem text with the figures for the industrial process?
Over 2.2*10^11 pounds of calcium carbonate are produced, 4.4*10^10 pounds of sodium carbonate…. no… water softeners… magnesium carbonates…dolomite… naaaah, I’ve got nothing useful here. Help.
Nothing useful here?
You might consider a career in government financed money wasting I mean climate science.
This is bad news. Plants need all the CO2 they can get. And CO2 is a weak warmer. We need more warmth.
What about all the pure traditional lime mortar and plaster that has been used around the world prior to the invention of portland cement also? This is still reabsorbing CO2 and will do so for hundreds if not thousands of years. The book Plastering Plain and Decorative by William Millar published in 1897 mentions this stonemasons proverb “When a hundred years are past and gane then gude mortar will turn into stane”, Not that it matters as its great plant food!
The list of solutions for solving nonexistent problems is virtually endless. The money to fund such nonsensical research is not. Just think of the progress forfeited in lieu of studies such as this. Not that it’s worthless, only that it’s not worthy of priority .
Down is the new up. Does this mean we can stop promoting hay bale construction techniques for buildings?
Straw Bales….
(and sorry to continue with this ….)
You’re excused, but only this time.
What it does is turns “The Donald’s” wall into a “green” project.
You see! Those large cement foundations required for wind farms aren’t so bad after all! And when the wind generator eventually dies, we can leave the skeleton there to keep absorbing evil CO2 because it would require a non-carbon sink machine to fix it. (end sarcasm)
What will now become of all those collegiate researchers who have devoted years towards development of a green cement?
Now, I like this term (‘Green cement’). I can abuse the ignorant by saying 100% of rigid paving structures on project ‘X’ will indeed be green (concrete), and that while green concrete is on the site the specifications for working on and around are modified to protect such.
In my book Green concrete is defined as per:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwjt9KeCwrrQAhUEsFQKHUUXD5kQFgg0MAQ&url=http%3A%2F%2Fwww.concreteconstruction.net%2Fhow-to%2Fwhat-is-green-concrete_o&usg=AFQjCNGbRW5nHakysQA4FZlDvLZsfRYLDw
CO2 in the atmosphere only matters to plants.
Thermalization and the complete dominance of water vapor in reverse-thermalization explain why CO2 has no significant effect on climate. Terrestrial EMR absorbed by CO2 is effectively rerouted to space via water vapor.
CO2 is not merely harmless, it is profoundly helpful. It is helpful in that it is plant food and, perhaps more importantly, it reduces plant’s need for water.
Carbonation makes the concrete less alkaline and reduces the corrosion protection of the steel reinforcement. The depth of concrete over the reinforcement is increased to allow for this. So it’s worse than we thought, increased CO2 is making concrete acidic and destroying buildings! The Romans must be cross that they missed out on Carbon Credits for the Pantheon.
(I’m sure someone will discover that the Pantheon is, in fact, part of some Carbon Credit boondoggle.)