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:
http://www.cmhc-schl.gc.ca/en/inpr/bude/himu/coedar/upload/Sustainable-Building-A-Materials-Perspective.pdf
,
which makes reference to this:
http://www.athenasmi.ca/about/lcaModel.html .
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.
Mark Bigland-Pritchard
Borden, Saskatchewan, Canada
Robert Tom wrote:
On Sun, 04 Nov 2007 13:14:03 -0500, Max Vittrup Jensen
<max@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.
http://www.cmhc-schl.gc.ca
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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