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General: Embodied CO2 in timber

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    • CommentAuthorondrejg
    • CommentTimeAug 23rd 2012
     
    I found this embodied energy and CO2 database of building materials from University of Bath: http://www.greenspec.co.uk/embodied-energy.php
    I believe these figures are used for CsH and BREEAM. One thing that seems very strange to me is a very high CO2 for timber (0.72 kgCO2/kg). According to several other sources which I have seen the embodied CO2 of timber is negative, so timber buildings can be negative in terms of embodied CO2. Can someone explain where this big difference comes from? Negative CO2 makes sense as the CO2 is "captured" in timber as it grows. What is the rationale behind timber embodied CO2 of 0.72 being higher than brick (0.24) or concrete (0.159)
    Thanks
    • CommentAuthorbarney
    • CommentTimeAug 24th 2012
     
    Well i guess you need to cut it down, machine it, transport it, account for the fact that it is no longer there to absorb CO2 etc. The metric of kgCo2/kg is also skewed by the density - look at the relative density of brick and timber per m3 - and then deduce what the installed effects are - ie a m3 of timber will "do" more than a m3 of brickwork for practical construction units.

    Regards

    Barney
    •  
      CommentAuthorfostertom
    • CommentTimeAug 24th 2012
     
    Posted By: barneyaccount for the fact that it is no longer there to absorb CO2
    If the Bath index doesn't assume that equal or more timber is re-planted, then it will indeed give a higher CO2 figure - but surely replanting is assumed? If so, then "the fact that it is no longer there to absorb CO2" drops out of the picture.
    • CommentAuthorbarney
    • CommentTimeAug 24th 2012
     
    "excludes sequestration" would be the other aspect I guess Tom ?

    Regards

    Barney
    •  
      CommentAuthorfostertom
    • CommentTimeAug 24th 2012
     
    Also maybe "excludes end-of-life"?

    What exactly does the Bath index include? On the face of it, 'embodied energy' is just what's embodied up to and incl the point of installation, with the proviso that in the case of renewable materials, hopefully the actual renewing (already or shortly) is assumed and included in the 'embodied' calc.

    With e.g. green timber, it may have been cut, sawn and installed before replanting has happened - but the replanting can be assumed.
    • CommentAuthorTimSmall
    • CommentTimeAug 24th 2012
     
    Posted By: fostertom "but the replanting can be assumed."


    It might (or might not) be safe to assume this for FSC certified timber. Definitely not for others tho'. It's very easy to buy "far eastern" ply from a number of sources around here (and this area has both a green council and MP!) which is probably made from virgin rain forest... I'm also bit doubtful about the Chinese Oak flooring which is locally available too.

    http://www.greenpeace.org/international/en/news/Blogs/makingwaves/green-forestry-labels-pefc-sfi-called-into-qu/blog/37371/

    http://www.fsc-watch.org/

    etc. etc.
    • CommentAuthorTimber
    • CommentTimeAug 24th 2012
     
    Yeah, the bath numbers are a bit squewed (depending on your view point) and make timber look a bit worse than it is (that is european softwood from well managed sources). Agree on rain forest destruction.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 24th 2012
     
    Surely, as FSC or not makes a great difference, there should be separate ratings. Can't believe they're assuming the worst, when FSC is available and widely used.
    • CommentAuthorTimber
    • CommentTimeAug 24th 2012
     
    Yeah, funny isn't it!

    It also makes me chuckle that many of the Concrete guys burn biomass in their plants to reduce CO2 emissions of the cement manufacturing process!

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