[Strawbale] re: Embodied Energy, Carbon research of Big Bales...
Mark BP / Low Energy Design Ltd
mark at lowenergydesign...
Mon Nov 5 03:59:03 CET 2007
Max, I look forward to the results of your work.
I did a very simple analysis of comparative embodied energy as part of
my thesis 2 years ago - strawbale construction came out considerably
better than any of the construction methods which are "mainstream" in
Britain. I'm glad that someone is committing to a more detailed
analysis regime - a tool by which we can compare lifecycle energy costs
of different options at the design stage would be most welcome.
Re what you actually include when calculating embodied energy: it
depends on local practice. Would the straw stems normally be cut
anyway? (as opposed to just chopping off the grain heads) - if yes, then
you don't need to include that energy cost. Would they normally be
baled anyway? - if yes, then you don't need to include that one either,
or maybe a differential between the energy costs for a baling strategy
convenient to the farmer and a baling strategy that yields good building
bales. For nearly all bales in Britain (where I used to live), and for
a high proportion (maybe even a majority) in the Canadian prairies
(where I live now), the only energy costs appropriate to include for the
bales themselves are for transport to site and for any use of power
tools in construction of the bale walls (e.g. in precompression, or for
spraying of plaster).
But it is also important to do this on a whole-building basis - thicker
walls result in larger roof and floor assemblies and hence in higher
embodied energy figures for those parts of the building.
And I think I can predict pretty confidently that in a bale building the
embodied energy from the strawbales will be dwarfed by that from other
materials, especially cement. So to my mind a really useful tool would
pay more attention to concrete and stucco than to bales.
The other issue that complicates this when you get to carbon intensity -
at least here in the prairies - is just how much carbon is sequestrated
by digging straw into the ground. Our provincial government has made
rather large and grandiose claims for this practice as part of their
climate change strategy, and I am - to say the least - sceptical (not
least because it enables them to evade the responsibility of developing
a truly sustainable energy policy, which would involve them having to
sometimes say no to the coal industry and to those in the provincial
power company who don't like thinking in new ways). If there are any
agronomists on this list who can shed light on this issue, I at least
would be grateful.
I wasn't able to find OPTIMIZE via CMHC's labyrinthine website.
However, I did find this:
which makes reference to this:
Not having had a proper look at either the former document or the latter
site (and LCA model), I can't comment on their quality, but they're
worth knowing about at the very least.
Borden, Saskatchewan, Canada
Robert Tom wrote:
> On Sun, 04 Nov 2007 13:14:03 -0500, Max Vittrup Jensen
> <max at permalot...> wrote:
>> It so happen to be that Canadian François Gonthier-Gignac and I are
>> in process of developing a tool to promote cleaner ways of building
>> through optimizing Embodied energy, energy efficiency and costs in
>> residential housing.
> Some time ago (10 years ?) through the auspices of Canada Mortgage &
> Housing Corp.
> there was a LCA software program developed called "OPTIMIZE" that
> enabled one to model the embodied energy of a proposed design, as
> well as the life cycle costs and other things like replacement costs
> at the end of the life cycle, water consumption, waste generation,
> ease of re-use/recycling of the deconstructed building materials and
> if I recall correctly, potential for off-gassing of VOCs and actual
> dollar costs.
> I've gone through a number of hard drives since then so I can't pull
> up the actual printout results (about 10 pages per run I think) at
> the moment but if you contact CMHC, they should be able to provide
> you with documentation.
>> put to the task of coming up with an amount of kilo joule whichgoes
>> into 1 single big bale, my approach would be to find out how many
>> big balesan average (European) baling machine make per hectare, and
>> find out the liters ofdiesel consumed. These figures should give the
>> individual answer.The LCA (Life Cycle Analysis) tool then also need
>> some figures for transport to storageand to site,
> Typically, the figure for embodied energy would include the energy
> consumed for transport to storage and to the site, as well as the
> "production energy" for harvesting and baling operations and any
> other energy consumed during the process of construction to get the
> bales in place in the walls. You will this defined in:
> Cole, Raymond J. and Rousseau, David. 1992.
> Environmental auditing for building construction: energy and air
> pollution indices for building materials. Building and Environment
> 27, #1 (January)
> Obviously, since big bales require the use of heavy machinery at each
> and every stage of their handling, the embodied energy per kilogram
> of straw will be greater than that for "regular"-sized two and three
> string bales so the figures provided for the EE of straw in the
> references provided earlier in this thread, will not apply.
> Also, I'm pretty sure that the EE numbers in the sources mentioned
> were compilied by looking at Canadian and Australian
> farming/transportation/building practises which I suspect, would be
> noticeably different than those for most European locations, mostly
> due to scale.
> Even here in Canada, one will see quite a difference in scale between
> 2 different provinces within the same country (ie Prairies vs
> Central provinces.)
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