The largest issue with concrete is that we misuse it. As a building material it has great thermal mass ( aiding temperature stability ) and longevity. But all too often buildings are poorly designed for renovation, and hence end up being torn down after a couple of decades. A small fraction of the useful lifetime of the structure. Any building using concrete for a structure should be aiming to last at least 100 years.
For those who didn't read the article: the chemistry of Portland cement works against it. Production requires heating the calcium carbonate to a high temperature to extract carbon dioxide from it. Which obviously produces large amounts of CO2 proportional to concrete production. However, concrete also absorbs carbon dioxide from the air over its lifetime. So the measured emissions aren't the entire story.
Perhaps in future we will consider this an excellent source of carbon dioxide for the production of various hydrocarbons. I've heard of several efforts to create octane using carbon dioxide from the air, but you need a large amount of energy to extract a useful amount of CO2. Well this would be a good source of high concentration CO2. Perhaps not for octane ( we should really be moving away from combustion engines ) but perhaps plastics and other products that are currently derived from crude oil.
> Any building using concrete for a structure should be aiming to last at least 100 years.
I don't know which country you have in mind but in Europe the construction industry by law is obligated to design concrete structures for residential buildings that ensures a useful life of at least 50 years, and by definition that means that the building structure shall not require maintenance for at least 50 years.
Moreover, concrete as a widespread structural material is relatively new, and city centers are still packed with contrete buildings that were built when the technology started popping up.
In fact, in general a building with concrete structure is only demolished when it's not possible to retrofit or renovate it effectively, due to unrelated reasons such as increasing occupation density that would not be cost-effective by reinforcing the concrete structure.
My point is that concrete structures are not demolished with enough frequency to be of any concern. The main reason is that concrete structures are simply too expensive to be demolished, moreso in urban centers. Thus your concern simply isn't relevant in the real world because economics already impose the same restrictions that are expressed in your environmental concerns.
>carbon-cured concrete: in carbon curing, concrete is cured with gaseous carbon dioxide, from the plastic phase forward. The curing of concrete with pressurized carbon dioxide generates not only the ordinary reaction products of cement but also carbonate-based reaction products. Consequently, the process binds carbon dioxide, and it is even possible to make the final product carbon negative if ordinary cement is replaced with alternative binders with a low carbon footprint.
Do we want 100 year old buildings? I don't think we can predict the needs of building even 20 years into the future. City layout could change drastically. Monumental buildings should last a long time, but not every structure.
The alternative is to build from wood whenever possible, and capture extra cabon in building material. This increases market need for wood and therefore forestation.
I don't think we want 100yr old buildings (except for history like a famous temple etc.). Certainly in my country old buildings are not designed in any environmentally conscious way. They aren't energy saving. They aren't in any way designed to be naturally cooler in the summer or hotter in the winter. They aren't designed for the changing needs of society which went from walking and horses 100 years ago whatever it is today. Why would I think a building made today is going to be a good building for the needs of people 100yrs from now?
Statistics on how much CO2 something emits can vary wildly. For instance, meat consumption has high CO2 emissions when you include the CO2 emitted by transporting grain to feed animals. But most typical studies would include that under emissions due to transportation. Hence why you can have some studies claiming meat accounts for a double-digit percentage of emissions while others claim that all agriculture contributes to ~3% of emissions.
The citation for this claim doesn't seem very robust. It links to the Ellen MacArthur foundation website, but just to the front page. After some of my own Googling it looks like it's coming from this publication [1]. This study drew up some estimates on the amount of textiles produced and discarded as well as a simple conversion of 4.7 Kg of CO2 for every Kg of textiles produced. The source for this ratio of CO2 to kilogram of textiles simply says "McKinsey Analysis"/
That was my biggest take away from the Biosphere documentary, as it was the concrete used in it's construction that eventually led to the abundance of CO2 and lack of O2 in that closed system.
We'll clearly have to use something else for building moon bases.
Doesn't matter. The rags companies get clothing and Africa imports tons of clothing for free. The clothes aren't all just made and discarded, they often have a second life.
Using CLT (and passive house principles) can reduce the total CO2 emmissions of a house by 90% in its total life span. The wood in CLT stores carbon and the passive house principles reduces energy needs.
Yes. And better than that using this at scale is going to require massively scaling up wood production (i.e. forestry). This too will help with capturing a lot of co2 in the soil. A lot of countries would end up restoring farm land to production forests and probably end up using sustainable practices for this.
For those unfamiliar with CLT, this is a high tech building material suitable for making e.g. sky scrapers or other types of buildings. It's much lighter and stronger than concrete. Because it is lighter, you save a lot of fuel transporting it. It's fire resistant and rot resistant because it is chemically treated. It's also much easier to work with as you can drill, glue, saw, etc. it. Additionally, you can do this off site meaning actual onsite construction activities are a lot more straight forward, less noisy, and much less wasteful. Think Ikea for buildings.
To sketch you a picture of how awesome this stuff is, the Japanese are planning to build a 1100 feet skyscraper made of wood, steel, and clt in Tokyo, which is of course a city that regularly sees earthquakes and tropical storms. https://www.archdaily.com/889142/japan-plans-for-supertall-w....
The biggest challenge is going to be simply scaling the production of this material and transitioning the construction industry to mostly using this instead of concrete. Right now it's kind of a novelty / niche thing and it is going to take a while to reach efficiencies and economies of scale we have with concrete today. It's not exactly cheap (yet) but it could become cheaper long term; especially if you consider all the benefits (technical and environmental).
While CLT has been certified for 60 years, I don't know how the adhesives they are using are certified for that long. The working life of common industrial adhesives is remarkably short [1]. The key is not just moisture control, but also temperature regulation.
With rigorous humidity and temperature regulation, some adhesives have an as-yet undetermined lifespan. I'm still looking for transportable passive designs without active mechanical assistance that keep humidity at or below 40% and temperature variation to within ±10° C in temperate zones.
Using actual timbers in a place like Canada should be the norm. Many of the biggest trees are left after a clearcut because they're just too big. When everything around them is cut they tend to die quicker (due to exposure). If they do get cut and milled, they often get processed into dimensional lumber (2x4s) instead of being used as timber.
Also the power needed to grind clinker down to powder is huge, overall comminution (grinding) industrial processes are among the biggest electricity consumer in the world.
I don't have the answer, but I can imagine this is hard to compile because so many things emit CO2 all over their supply chain. So the question becomes, when do you consider something the 'final' product in the line.
If it's cement, you presumably can't count 'construction' as it would be double-counted. Do you count an iPhone just during production? Or do you include shipping? If you include shipping, you can't have 'cargo ships' as it's own category.
I'm not quite understanding why the article should present alternatives. That's not what the article is really about. However, the article does present alternatives concerning the company BioMason.
Setting aside CO₂ concerns for a moment, I was explaining cement to a young child today and was suddenly struck by how marvelous cement is: It’s poured as a liquid yet solidifies into rock, and has been known since ancient times [1].
One question I've had about cement being a major source of CO2 emissions that I haven't seen addressed anywhere is that my understanding is as cement cures it does so by absorbing CO2 which is what turns it into rock.
Does this not cancel out the effect of making the cement in the first place? And if not, why not?
Would love to know if anyone has a good understanding.
While concrete does absorb CO2 there is a large misconception that it can absorb as much as is output during production. In reality any concrete worth its cost can only absorb a very small fraction of the production output.
A largely overlooked issue with the idea of concrete absorbing CO2 is exposed surface area. Imagine a hydro dam, one side is saturated with water, the other side is air. The dam is also usually quite thick, several meters to hundreds of meters. That really limits the available absorption surface especially considering the ratio of surface area to volume. Concrete foundations, epoxy coated parkades, even painted surfaces start to drastically reduce the possibility of CO2 being absorbed.
Think of concrete like a membrane or a sponge. The thicker the membrane you want to pass a fluid through, the higher the pressure you would require. So using our pressure as atmospheric, getting a high depth of CO2 absorption requires a well connected pore structure, and a long time frame.
Add to this membrane metaphor the issue of size. We design concrete structures to prevent fluid transfer, especially hydro dams! H2O is a smaller molecule than CO2, and the static pressure on the ‘wet’ side of a hydro dam increases 1 atmosphere every 10m.
As concrete sets and gains strength, its porosity decreases. This process happens rapidly in the first few days, and only ever stops when the cement runs out of free water to absorb. CO2 absorption depth is a pretty common test when evaluating a structure for rehabilitation purposes (carbonation dept testing) as CO2 will mess with the concrete PH and corrode reinforcing steel which (depending on many factors) can be as shallow as 5cm from the concrete surface. I’ve seen structures with up to 5cm of depth, but that is outside of the norm. 1-2cm of CO2 absorption depth for a structure from the 50’s is pretty common in my area.
Modern concrete, through many different means, has a highly disconnected pore structure (compared to the concrete of the 50’s). New concrete, is designed to reduce any type of fluid transfer especially after the first few days of curing. This will reduce the depth of CO2 absorption further.
So bringing this all back together, consider the absorption depth of 2cm, a structure with minimal exposed surface area, and some sort of coating or cladding… and you very quickly realize that you are not going to be off setting CO2 production outputs by any significant margin, and its not in your best interests either.
I was looking for brick pavers recently and was having quite a time locating actual bricks instead of cement pavers colored badly and textured worse to look vaguely like bricks to nobody sober during daylight hours. I can only assume their target audience is a drunken man, at night, in a rainstorm.
I have to wonder why we are still looking for new ways to employ Portland cement at this point, over alternatives. You can, I’m told, reduce the footprint of clinker a bit with fly ash, but you get that mostly from coal, so it’s splitting the “savings” with an equally problematic cousin, and at any rate that supply should be in steady decline now, although I guess we discovered the Tennessee Valley Authority has stockpiles of the stuff when they lost one of them a decade or two ago.
> I was looking for brick pavers recently and was having quite a time locating actual bricks
I am not an American but I am not sure I have even seen a paver made from brick now that I think about it. I suspect the larger a brick is, the more chance of cracking.
So if it makes you feel any better, you probably would not find one in New Zealand either.
I remember a while back reading about work on increasing the recycled content of concrete (using old concrete as aggregate in new concrete, I think?) but I did not bookmark it and none of my last set of searches seemed to be in the right direction.
There’s a Wikipedia page on the subject but little of it sounds familiar, and those bits have no citations.
"Eliminate carbon dioxide, and plants would shrivel and die. So would lake and ocean phytoplankton, grasses, kelp and other water plants. After that, animal and human life would disappear. Even reducing CO2 levels too much – sending them back to pre-industrial levels, for example – would have terrible consequences for crops, other plants, animals and humans.":
https://www.masterresource.org/carbon-dioxide/co2-gas-of-lif...
The minimum necessary CO2 level for plant life is about 100 ppm. That is a quarter of current levels. No plant life, no animal life, no life on the continents. Only a few chemeotroph bacteria survive.
The long term geobiological trend is for C02 to decrease through absorption by weathering rocks and burial of biogenic limestone in subduction zones. C02 was thought to be as much 50% early Earth. Then a percent or two in early Phanerozoic 400 million years ago. And natural about .025% in the current ice age.
shortercode|5 years ago
For those who didn't read the article: the chemistry of Portland cement works against it. Production requires heating the calcium carbonate to a high temperature to extract carbon dioxide from it. Which obviously produces large amounts of CO2 proportional to concrete production. However, concrete also absorbs carbon dioxide from the air over its lifetime. So the measured emissions aren't the entire story.
Perhaps in future we will consider this an excellent source of carbon dioxide for the production of various hydrocarbons. I've heard of several efforts to create octane using carbon dioxide from the air, but you need a large amount of energy to extract a useful amount of CO2. Well this would be a good source of high concentration CO2. Perhaps not for octane ( we should really be moving away from combustion engines ) but perhaps plastics and other products that are currently derived from crude oil.
barumi|5 years ago
I don't know which country you have in mind but in Europe the construction industry by law is obligated to design concrete structures for residential buildings that ensures a useful life of at least 50 years, and by definition that means that the building structure shall not require maintenance for at least 50 years.
Moreover, concrete as a widespread structural material is relatively new, and city centers are still packed with contrete buildings that were built when the technology started popping up.
In fact, in general a building with concrete structure is only demolished when it's not possible to retrofit or renovate it effectively, due to unrelated reasons such as increasing occupation density that would not be cost-effective by reinforcing the concrete structure.
My point is that concrete structures are not demolished with enough frequency to be of any concern. The main reason is that concrete structures are simply too expensive to be demolished, moreso in urban centers. Thus your concern simply isn't relevant in the real world because economics already impose the same restrictions that are expressed in your environmental concerns.
nabla9|5 years ago
Turning the cons of concrete into pros (carbon-cured concrete) https://www.vttresearch.com/en/news-and-ideas/turning-cons-c...
>carbon-cured concrete: in carbon curing, concrete is cured with gaseous carbon dioxide, from the plastic phase forward. The curing of concrete with pressurized carbon dioxide generates not only the ordinary reaction products of cement but also carbonate-based reaction products. Consequently, the process binds carbon dioxide, and it is even possible to make the final product carbon negative if ordinary cement is replaced with alternative binders with a low carbon footprint.
The Carbon Reuse Economy: Transforming CO2 from a pollutant into a resource https://cris.vtt.fi/en/publications/the-carbon-reuse-economy...
jmiskovic|5 years ago
The alternative is to build from wood whenever possible, and capture extra cabon in building material. This increases market need for wood and therefore forestation.
asiachick|5 years ago
aero-glide|5 years ago
manfredo|5 years ago
The citation for this claim doesn't seem very robust. It links to the Ellen MacArthur foundation website, but just to the front page. After some of my own Googling it looks like it's coming from this publication [1]. This study drew up some estimates on the amount of textiles produced and discarded as well as a simple conversion of 4.7 Kg of CO2 for every Kg of textiles produced. The source for this ratio of CO2 to kilogram of textiles simply says "McKinsey Analysis"/
1. https://www.ellenmacarthurfoundation.org/assets/downloads/pu...
akira2501|5 years ago
We'll clearly have to use something else for building moon bases.
thinkloop|5 years ago
Waterfall|5 years ago
ECA_stax|5 years ago
ehou|5 years ago
Using CLT (and passive house principles) can reduce the total CO2 emmissions of a house by 90% in its total life span. The wood in CLT stores carbon and the passive house principles reduces energy needs.
jillesvangurp|5 years ago
For those unfamiliar with CLT, this is a high tech building material suitable for making e.g. sky scrapers or other types of buildings. It's much lighter and stronger than concrete. Because it is lighter, you save a lot of fuel transporting it. It's fire resistant and rot resistant because it is chemically treated. It's also much easier to work with as you can drill, glue, saw, etc. it. Additionally, you can do this off site meaning actual onsite construction activities are a lot more straight forward, less noisy, and much less wasteful. Think Ikea for buildings.
To sketch you a picture of how awesome this stuff is, the Japanese are planning to build a 1100 feet skyscraper made of wood, steel, and clt in Tokyo, which is of course a city that regularly sees earthquakes and tropical storms. https://www.archdaily.com/889142/japan-plans-for-supertall-w....
The biggest challenge is going to be simply scaling the production of this material and transitioning the construction industry to mostly using this instead of concrete. Right now it's kind of a novelty / niche thing and it is going to take a while to reach efficiencies and economies of scale we have with concrete today. It's not exactly cheap (yet) but it could become cheaper long term; especially if you consider all the benefits (technical and environmental).
yourapostasy|5 years ago
With rigorous humidity and temperature regulation, some adhesives have an as-yet undetermined lifespan. I'm still looking for transportable passive designs without active mechanical assistance that keep humidity at or below 40% and temperature variation to within ±10° C in temperate zones.
[1] https://www.bhhomeinspections.com/building-materials-life-ex...
[2] http://www.woodcentral.com/woodworking/forum/archives.pl/bid...
decasteve|5 years ago
immmmmm|5 years ago
Cement ball mills are less than 1% efficiency.
https://en.wikipedia.org/wiki/Cement_mill
Having done two postdocs in the field i can tell its not progressing very fast...
toomuchtodo|5 years ago
nom|5 years ago
iTokio|5 years ago
treve|5 years ago
If it's cement, you presumably can't count 'construction' as it would be double-counted. Do you count an iPhone just during production? Or do you include shipping? If you include shipping, you can't have 'cargo ships' as it's own category.
jekdoce|5 years ago
discordance|5 years ago
https://ourworldindata.org/emissions-by-sector
straw11|5 years ago
dehrmann|5 years ago
Concrete might look very different in 25-50 years.
nix23|5 years ago
True more like it looked in 150 BC:
https://en.wikipedia.org/wiki/Roman_concrete
mehrdadn|5 years ago
ferros|5 years ago
Let’s say we take cement out or drastically reduce it. Where does co2 sit in increased consumption of viable alternatives.
x86_64Ubuntu|5 years ago
divbzero|5 years ago
[1]: https://en.wikipedia.org/wiki/Cement#History
loourr|5 years ago
Does this not cancel out the effect of making the cement in the first place? And if not, why not?
Would love to know if anyone has a good understanding.
concguy|5 years ago
A largely overlooked issue with the idea of concrete absorbing CO2 is exposed surface area. Imagine a hydro dam, one side is saturated with water, the other side is air. The dam is also usually quite thick, several meters to hundreds of meters. That really limits the available absorption surface especially considering the ratio of surface area to volume. Concrete foundations, epoxy coated parkades, even painted surfaces start to drastically reduce the possibility of CO2 being absorbed.
Think of concrete like a membrane or a sponge. The thicker the membrane you want to pass a fluid through, the higher the pressure you would require. So using our pressure as atmospheric, getting a high depth of CO2 absorption requires a well connected pore structure, and a long time frame.
Add to this membrane metaphor the issue of size. We design concrete structures to prevent fluid transfer, especially hydro dams! H2O is a smaller molecule than CO2, and the static pressure on the ‘wet’ side of a hydro dam increases 1 atmosphere every 10m.
As concrete sets and gains strength, its porosity decreases. This process happens rapidly in the first few days, and only ever stops when the cement runs out of free water to absorb. CO2 absorption depth is a pretty common test when evaluating a structure for rehabilitation purposes (carbonation dept testing) as CO2 will mess with the concrete PH and corrode reinforcing steel which (depending on many factors) can be as shallow as 5cm from the concrete surface. I’ve seen structures with up to 5cm of depth, but that is outside of the norm. 1-2cm of CO2 absorption depth for a structure from the 50’s is pretty common in my area.
Modern concrete, through many different means, has a highly disconnected pore structure (compared to the concrete of the 50’s). New concrete, is designed to reduce any type of fluid transfer especially after the first few days of curing. This will reduce the depth of CO2 absorption further.
So bringing this all back together, consider the absorption depth of 2cm, a structure with minimal exposed surface area, and some sort of coating or cladding… and you very quickly realize that you are not going to be off setting CO2 production outputs by any significant margin, and its not in your best interests either.
_nalply|5 years ago
http://www.constructionphotography.com/Details.aspx?ID=14133...
Opentopomap: https://opentopomap.org/#map=13/46.93620/11.45582
hinkley|5 years ago
I have to wonder why we are still looking for new ways to employ Portland cement at this point, over alternatives. You can, I’m told, reduce the footprint of clinker a bit with fly ash, but you get that mostly from coal, so it’s splitting the “savings” with an equally problematic cousin, and at any rate that supply should be in steady decline now, although I guess we discovered the Tennessee Valley Authority has stockpiles of the stuff when they lost one of them a decade or two ago.
teruakohatu|5 years ago
I am not an American but I am not sure I have even seen a paver made from brick now that I think about it. I suspect the larger a brick is, the more chance of cracking.
So if it makes you feel any better, you probably would not find one in New Zealand either.
s0rce|5 years ago
Waterfall|5 years ago
pengaru|5 years ago
https://www.epa.gov/international-cooperation/mercury-emissi...
nlh|5 years ago
https://www.cement.org/cement-concrete-applications/cement-a...
unknown|5 years ago
[deleted]
nix23|5 years ago
https://constructionclimatechallenge.com/2016/11/18/co2-abso...
kinase|5 years ago
Oricle|5 years ago
[deleted]
Anka33|5 years ago
[deleted]
hobby-coder-guy|5 years ago
[deleted]
swiley|5 years ago
hannob|5 years ago
straw11|5 years ago
vaccinator|5 years ago
gogopuppygogo|5 years ago
90% of landfill debris is from demolition.
We need more renovation instead of new construction.
wcoenen|5 years ago
From page 128 of https://dnr.mo.gov/env/swmp/docs/wcs98constructionwaste.pdf
hinkley|5 years ago
There’s a Wikipedia page on the subject but little of it sounds familiar, and those bits have no citations.
cranekam|5 years ago
URfejk|5 years ago
peter303|5 years ago
The long term geobiological trend is for C02 to decrease through absorption by weathering rocks and burial of biogenic limestone in subduction zones. C02 was thought to be as much 50% early Earth. Then a percent or two in early Phanerozoic 400 million years ago. And natural about .025% in the current ice age.