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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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      CommentAuthorfostertom
    • CommentTimeMay 21st 2018 edited
     
    https://www.theguardian.com/environment/2018/may/21/drax-power-station-to-lead-fresh-carbon-capture-trial

    "In theory, BECCS can reduce greenhouse gases in the atmosphere, as the trees for the [bio-mass] power station absorb carbon dioxide as they grow, while the carbon dioxide released from generating electricity does not enter the atmosphere."

    But

    "The carbon will be stored in a compressed form on the site, which the firm hopes to sell to an as-yet-unidentified partner for industrial processes."

    Carbon is harmless, it's carbon dioxide (or methane) that is the greenhouse gas. So far so good. But what's going to happen to the carbon after it's sold to industry? If it gets re-oxidised, maybe way down its future life-cycle, we'll be right back where we started. How can anyone be sure that the carbon will be turned into unoxidsable form - perhaps carbon fibre (does that ever burn?) or nano-tubes or whatever?
  1.  
    Posted By: fostertom"The carbon will be stored in a compressed form on the site, which the firm hopes to sell to an as-yet-unidentified partner for industrial processes."

    Posted By: fostertomIf it gets re-oxidised, maybe way down its future life-cycle

    Re oxidised it to CO2 - and then sell it to the fizzy drinks industry........

    I get nervous when I hear of schemes that have a solution with no end game. " we can store it on site".......until we can think of something to do with it........ Isn't that what they do with nuclear waste?
    • CommentAuthormark_s
    • CommentTimeMay 21st 2018
     
    Their chief exec was on the Today programme this morning.
    Very unimpressive. Sounded like he didn't have a clue.
    • CommentAuthortony
    • CommentTimeMay 21st 2018
     
    you cant compress carbon, only gasses
    •  
      CommentAuthorfostertom
    • CommentTimeMay 21st 2018
     
    Oh yes - so that must mean they're capturing the CO2 but not splitting the C from the O2 (which requires input of the same huge amount of energy as was released when the C was burnt).

    So selling CO2 to industry - does anyone know what industry might usefully do, that locks CO2 up permanently, never to escape? The only thing I can think of is feeding the CO2 to growing plants (making sure none leaks out of the greenhouse ha ha), which use solar energy input via photosynthesis to split the C from the O2, combining the C with H (from water) to make woody cellulose.

    But then the plant dies, is burnt, rots or is composted, the C recombines with atmospheric O2 and we're back where we started.

    If the plant was burnt to charcoal (with v restricted O2 supply) i.e. only the H of the cellulose is burnt, leaving the C as solid charcoal, then that could perhaps be buried so deep that it never sees oxygen ... but then any anaerobic bacteria would have a field day turning it to methane ...
    •  
      CommentAuthorSteamyTea
    • CommentTimeMay 21st 2018
     
    Most of the CCS systems I have seen only capture a small percentage of CO2 from the exhaust. Then store is as a liquid. I doubt if this scheme is any different, probably just a case of getting funding from somewhere. £400,000 will probably just about cover the scaffolding costs on a chimney I would have thought.
    I have seen estimate of between 250-300g/kWhe for biomass, so they would have to capture at least that to make the system 'negative' to clean up atmosphere. That figure of 250-300g/kWhe includes regrowth.
  2.  
    Posted By: tonyyou cant compress carbon, only gasses


    Posted By: fostertomOh yes - so that must mean they're capturing the CO2 but not splitting the C from the O2 (which requires input of the same huge amount of energy as was released when the C was burnt).

    A typical product of combustion is CO (carbon monoxide) which is colourless odourless and deadly. It is also a compressible gas. So......add another O and then you can make your fizzy drinks:shocked::shocked::bigsmile:
    • CommentAuthortony
    • CommentTimeMay 21st 2018
     
    Nice carbon capture system is growing trees out tomatoes etc

    Better plan is not to burn them in the first place which is also cheaper and better.
    • CommentAuthorbhommels
    • CommentTimeMay 21st 2018
     
    As far as I have read about CCS, it looks like the better it works, the lower the overall efficiency of the coal plant, which sounds right, intuitively.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 21st 2018 edited
     
    Trees and tomatoes aren't carbon capture in the sense of permanently (hopefully) removing from atmosphere. The even bigger natural carbon process - formation of sea shells - *is* more permanent carbon capture eventually into limestone - though ocean acidification is slowing the formation and increasing the re-dissolving of CaCO3.
    •  
      CommentAuthorSteamyTea
    • CommentTimeMay 21st 2018
     
    And you can compress carbon, which has a density of about 2g/cm^3, to diamond, which has a density of about 3.5g/cm^3
    • CommentAuthorgyrogear
    • CommentTimeMay 23rd 2018 edited
     
    Posted By: fostertomdoes anyone know what industry might usefully do, that locks CO2 up permanently, never to escape?


    Yes of course, agriculture, namely, growing hemp (man's best plant).

    This absorbs the CO2, then you mix the hemp with lime and turn it into limecrete, build houses with it, when the house is eventually demolished, the crushed-up limecrete goes into new, so it is perpetually recyclable.

    gg
    • CommentAuthorfinnian
    • CommentTimeMay 23rd 2018
     
    There's a lot of potential for locking up CO2 by using the right kind of minerals in concrete/cement/brick production: various oxide rocks will (slowly) take up CO2 as they age. Mostly this is thought of as mitigating the CO2 emissions of making portland cement, though, rather than a net 'win'.

    You can also deliberately inject CO2 into building materials.
    https://www.theguardian.com/environment/2017/aug/25/green-building-materials-carbon-capture-technology-ready-by-2020-says-manufacturer
    • CommentAuthorgyrogear
    • CommentTimeMay 23rd 2018
     
    Posted By: finnianYou can also deliberately inject CO2 into building materials.


    yes, as well as vehicle air-conditioning systems !

    gg
    •  
      CommentAuthorfostertom
    • CommentTimeMay 23rd 2018 edited
     
    Are these lock-ups permanent? or at least releasable only on geological-cycle timescales? Does hemp embedded in lime remain biologically inert when wetted e.g. sodden after being crushed at cycle-end?
    • CommentAuthorfinnian
    • CommentTimeMay 24th 2018
     
    At least turning oxide rocks into carbonate rocks, which is what the schemes I was talking about involve, is one of the major geological-timescale processes that keeps CO2 levels in check. This just speeds up the silicate weathering cycle.

    The building material eventually ends up as rubble under the next round of construction.
    • CommentAuthorTimSmall
    • CommentTimeMay 24th 2018 edited
     
    •  
      CommentAuthorfostertom
    • CommentTimeMay 24th 2018
     
    There's major resistance to plans for disposal of power station (incl waste burning) bottom ash etc for blockmaking, as that material is usually toxic, containing everything that wasn't vapourised. So objections to transit, spillage, dust etc as well as to the finished toxic product for indoor use.
    • CommentAuthorfinnian
    • CommentTimeMay 25th 2018
     
    Using fly ash (or incinerator bottom ash) to partially replace portland cement is a different thing to what I wrote about upthread, and TimSmall's links.

    Most building products, whether they are 'natural' or not are toxic in the sense that you shouldn't eat them and breathing in dust is best avoided. Things that come out of the ground all tend to have various metal elements in them. I'm more worried about stuff than can be vaporised (VOCs) rather than stuff that can't.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 25th 2018
     
    Posted By: finnianUsing fly ash (or incinerator bottom ash) to partially replace portland cement is a different thing to what I wrote about upthread, and TimSmall's links.
    Yes, true - I thought someone else mentioned power station ash, maybe on another thread. The thing about bottom ash is that it's a rich concentration of everything that won't vapourise from a huge quantity of fuel. Especially if the fuel is municipal waste, masses of low-level toxins get quite highly concentrated. I realise this has nothing to do with CCS.
    • CommentAuthorTimSmall
    • CommentTimeMay 25th 2018
     
    I presume they'll also have quite a large supply of wood ash too, which shouldn't be too bad...
    • CommentAuthorgyrogear
    • CommentTimeMay 25th 2018
     
    Posted By: fostertomDoes hemp embedded in lime remain biologically inert when wetted e.g. sodden after being crushed at cycle-end?


    per: http://hempcretehouse.coffeecup.com/

    "Hempcrete is recyclable. When the house is demolished the material can be ground up and spread on farmers' fields. Concrete cannot do that. Landfill costs are a significant part of demolition costs. Eventually, landfills will become closed to construction debris. When that happens, construction must be recyclable. This is starting to happen in Europe. Old hempcrete can be used to make new hempcrete. You can recycle up to 10% of old material into your batch of new material. Cement cannot do that."

    gg
    • CommentAuthorfinnian
    • CommentTimeMay 25th 2018
     
    I guess the question is what happens to the carbon in the 90% of your crushed up hempcrete that you dump in the farmer's field. At that point you are hoping the carbon stays locked up in the soil, which is a big unknown.

    A big issue with biofuels and bulk bio-materials (including wood) is that there is only so much arable land and forest around, and it would be nice if some of it were left alone, rather than converted into human dwellings and used to power jets.

    Cement-based products can actually be recycled in various ways, although this tends to be downcycling (crush, use as aggregate, fill etc). Perhaps people should be thinking about how to design block or brickwork so you can reuse the blocks at end of life (like choice of mortar or using mechanical fixings instead).
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