from Hacker News

Cement is the source of 8% of the world's CO2 emissions (2018)

by fn1 on 9/27/20, 4:58 AM with 149 comments

  • by shortercode on 9/27/20, 8:53 AM

    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.

  • by aero-glide on 9/27/20, 5:52 AM

    Very interesting, didn't expect it to be that high. Another thing I came across recently : The fashion industry is responsible for 10 % of annual global carbon emissions. Source : https://www.worldbank.org/en/news/feature/2019/09/23/costo-m...

  • by ehou on 9/27/20, 6:29 AM

    The article doesn't mention one alternative: CLT (cross laminated timber) as a building material for houses and flats. See https://www.bbc.com/future/article/20190717-climate-change-w... for example.

    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.

  • by immmmmm on 9/27/20, 3:55 PM

    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.

    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...

  • by iTokio on 9/27/20, 6:02 AM

    Is there a serious source ranking all global CO2 emissions? Where percentages add up to 100%?

  • by straw11 on 9/27/20, 6:35 AM

  • by dehrmann on 9/27/20, 5:58 AM

    Meanwhile, there's a sand shortage: https://www.bbc.com/future/article/20191108-why-the-world-is...

    Concrete might look very different in 25-50 years.

  • by mehrdadn on 9/27/20, 5:49 AM

    Bill Gates also mentioned he's now most worried about steel & cement in one of Mark Rober's videos: https://www.youtube.com/watch?v=-k-V3ESHcfA

  • by ferros on 9/27/20, 5:59 AM

    That’s an attention grabbing headline number, but what it doesn’t tell you is what would alternatives mean in terms of co2 emissions?

    Let’s say we take cement out or drastically reduce it. Where does co2 sit in increased consumption of viable alternatives.

  • by divbzero on 9/27/20, 6:41 AM

    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].

    [1]: https://en.wikipedia.org/wiki/Cement#History

  • by loourr on 9/27/20, 2:06 PM

    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.

  • by _nalply on 9/27/20, 7:56 AM

    By the way, the bridge is part of the Brennerautobahn between South Tyrol in Italy and Innsbruck in Austria. The exact bridge is located in Italy.

    http://www.constructionphotography.com/Details.aspx?ID=14133...

    Opentopomap: https://opentopomap.org/#map=13/46.93620/11.45582

  • by hinkley on 9/27/20, 6:51 AM

    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.

  • by pengaru on 9/27/20, 6:34 AM

    It's also 11% of global anthropogenic mercury emissions.

    https://www.epa.gov/international-cooperation/mercury-emissi...

  • by nlh on 9/27/20, 4:41 PM

    TIL concrete and cement are not the same thing. The words are often used interchangeably, but that's apparently incorrect:

    https://www.cement.org/cement-concrete-applications/cement-a...

  • by nix23 on 9/27/20, 10:37 AM

  • by kinase on 9/27/20, 7:51 AM

    Crazy that quarrying and transport is less than 10% of the CO2 from Concrete.

  • by swiley on 9/27/20, 6:26 AM

    Would living in tents reduce CO2 emissions? Is that preferable?

  • by gogopuppygogo on 9/27/20, 6:04 AM

    I’ve been touting this fact for years.

    90% of landfill debris is from demolition.

    We need more renovation instead of new construction.

  • by URfejk on 9/27/20, 9:11 AM

    "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...