[GSBN] Fwd: Embodied energy comparisons: SB vs Stick-built

Derek Roff derek at unm.edu
Mon Feb 16 00:51:10 CST 2009


Thank you, Andrew, for replying to my concerns and questions.  I'd 
like to investigate two points a little further, if you are willing. 
The first is getting the 2x4 to the job site.  I see that I wasn't 
sufficiently explicit in my use of that phrase.  I was not thinking 
simply of transportation.  I was thinking of all the fuel burning, 
carbon releasing things that are required to produce and deliver that 
2x4.

My mental model begins when the tree is harvested with chain saws and 
perhaps larger scale motorized harvesting.  It is brought out of the 
forest with large diesel vehicles, then loaded on trucks for 
transport to a sawmill.  Road building is involved, whether this is a 
forest or a plantation.  Road maintenance is involved.  Tires are 
replaced, vehicle parts are replaced.  At the sawmill, we run the 
saws, and light/heat the buildings.  Sawdust and scrap are burned, 
more or less efficiently, which releases some of the carbon which had 
been stored in the tree.

At some stage, the lumber is sent to the drying kiln, which also uses 
fossil fuel.  All of the office workers, sitting in their 
heated/cooled offices, are releasing carbon in order to help produce 
that 2x4.  Almost all the direct and indirect workers arrive and 
leave their workplaces by fossil fuel vehicle.

The 2x4 goes to the planer.  It is graded.  It may be moved a few 
times in storage and warehousing.  It is transported in various 
steps, with repeated loading and unloading, until it finally gets to 
the job site.  Meanwhile, the harvest site is being cleaned up and 
prepared for replanting.  Slash may be burned, which has a greenhouse 
gas impact far worse than the simple CO2 contained.  The new trees 
are planted.  Some level of care is expended until the next harvest.

Each of the items in this chain had to be built, maintained, and at 
some time will be dismantled.  A little bit of carbon from each of 
these steps must be counted against the carbon stored in the 2x4.  At 
the point when we are ready to harvest again, we reach the beginning 
of the cycle, as I have delineated it.  Only then can we stop the 
meter on the carbon used to produce and deliver a 2x4.

There are probably other factors that I have overlooked.  These were 
the kinds of things that I was thinking of when I said that I would 
be surprised if you could get a 2x4 to the job site with a negative 
(good) carbon balance.  I am prepared to be surprised again, but I 
wonder if all of these kinds of things included in your calculations, 
Andrew.  I would love to see the estimates on these factors.  Perhaps 
they will be in your upcoming thesis.

I'd like to better understand this statement that you made:

"The numbers in my report are net, to the factory gate. So, a negative
number for timber indicates the overall CO2 that has been removed from
the atmosphere."

Please tell me more about what goes into the "net" numbers.  And is 
this "factory gate" the last milestone before the 2x4 heads to the 
job site, or is it earlier in the process?


The other thing I would like to hear a little more about is Bill's 
question about building size and energy usage.  In the US, for the 
last 100 years, carbon released due to heating/cooling energy use 
during the building's life cycle has been many times the embodied 
energy of construction.  A larger house will waste more energy, and 
therefore release more carbon, using the fossil fuel energy sources 
that supply the overwhelming majority of homes.

How can this be factored into the carbon sequestering discussion? 
How much difference would there be between an average new house, and 
a highly energy efficient one, in terms of the relative importance of 
size and carbon sequestering?

Thanks again for sharing your time and information.

Derek



--On Monday, February 16, 2009 12:12 PM +1300 Graeme North 
<graeme at ecodesign.co.nz> wrote:

> Hi Derek
>
>
> Undoubtedly, building smaller uses fewer resources than building
> large, if you are buildng with the same materials AND there is a net
> carbon emission from those materials. But there are buts. The way to
> get your head around this is to think from a global level down to
> your
> own building level. (Think globally, act locally.)
>
>
> THE major (far and away) threat to the planet is climate change.
> Yes,
> OK, population (P), consumption levels (C), and the particular
> impact
> of the particular technology of consumption (T) are big issues
> (I=PCT:
> Ehrlich and Holdren). But the biggest way they are, in aggregate,
> currently impacting on the planet is via climate change. Sure,
> reducing P, C, and T reduces overall impact (I), and getting each of
> them down seems a sensible aim. But while doing that, climate is the
> pressing issue. The problem for the planet (which is not quite the
> same as the problem for the humans) is that too much many GHGs are
> being dumped in the atmosphere. So, if overall fewer GHGs can be
> dumped into the atmosphere, and more GHGs can be removed from the
> atmosphere, the better.
>
>
> On that basis, if Jane and Joe Bloggs are going to build a house,
> there is the potential for them to build it in such a way that it,
> overall, removes CO2 from the atmosphere. They can do that by
> reducing
> the CO2 emitting materials and technologies, And by increasing the
> ones that have a net absorption. They will have to work pretty hard
> at
> this, but it can be done. IF they build it bigger, and the extra
> size
> comes from timber, straw and other carbon-storing materials,
> (shingle
> roof, timber floor, timber window frames) then the net effect will
> be
> that their house has removed more CO2 from the atmosphere than it
> has
> emitted. This will include things like having their own solar hot
> water system, probably their own on site electricity generation,
> and a
> few other things.  If the extra size also requires more aluminium
> window frames (bad), more steel roof, more concrete floor, lots more
> copper wiring and plumbing, then they may find they are emitting
> more
> CO2 overall. So, yes, bigger CAN be better.
>
>
> One caveat here: my analysis has been done on NZ materials and
> houses.
> The Nth American situation will be different. But probably not that
> different. Someone will just have to run the numbers. Perhaps later
> in
> the year I will be able to make an on-line calculator available that
> will help in this regard, although getting the Nth American numbers
> for materials is one challenge. Thermal analyses for different
> cliamtes woud be needed too. (As a complete aside, does anyone have
> a
> guess if/how much people would be prepared to pay for such a gadget
> -
> that calculated the CO2 impact of a particular house design?)
>
>
> OK Derek, be surprised: the CO2 released in getting a 4x2 out of a
> tree, to the site, and into a house IS less (a lot less) than the
> CO2
> removed from the atmosphere and stored in that 4x2. Again, my
> numbers
> are from NZ, but Nth America will be pretty similar. The idea that
> transport releases lots of CO2 is only true when you think about all
> the cars and trucks running around. It is a fallacy that transport
> CO2
> emissions are a big part of the emissions for materials and
> products.
> Transport is almost always less than 5%, and frequently less than 2%
> of the total. Basically it's a big red herring in this debate. Sure,
> local is better, but other things are more important - like
> aluminium
> uses heaps of electricity to make, and timber doesn't. The distance
> that aluminium has to be transported, even if it's twice around the
> globe, is insignificant (like, right off the radar) compared to the
> manufacturing energy and CO2.
>
>
> The numbers in my report are net, to the factory gate. So, a
> negative
> number for timber indicates the overall CO2 that has been removed
> from
> the atmosphere.
>
>
> Yes, indeed Derek. Your question "What would have happened to this
> material if I hadn't used it in my house?" is an excellent one. The
> best question in this regard is, I think, "What is the effect of
> doing
> abc or xyz?" If the effect of using a 4x2 to build your house is to
> bring down a virgin forest, that ain't a good idea. Go forth and
> protect virgin forests! But, in NZ, and I expect there too, timber
> for
> houses comes from plantation forests. When you cut them, they get
> replaced. They're an on-going carbon removal system - as long as the
> carbon in the timber gets sequestered, and not returned to the
> atmosphere. That's how our atmosphere got to have the high
> oxygen/low
> CO2 levels it did - by forests turning atmospheric carbon into
> below-ground carbon, as coal, oil and gas.
>
>
> So, turn that tree carbon into houses and things. Then make sure the
> houses last a long time and don't rot. And, make sure that at the
> end
> of the life of the house, the demolition timber either gets re-used,
> or gets buried in well managed landfills that stop the timber from
> rotting. (Then it's on its way to becoming coal, which, hopefully
> won't get dug up and burnt in a few million years.) There is
> evidence
> that between 1 and about 25% of the carbon remains intact in the
> timber after burial. (Depends on things like the moisture and oxygen
> levels in the landfill - which can be controlled.)
>
>
> Straw is basically the same story. If burnt or allowed to rot in the
> paddock it returns its carbon to the atmosphere. If put into (dry)
> houses, its carbon stays there. The by-product question is a bit of
> a
> red herring here. Whichever way you allocate the energy and
> emissions
> for the grain/straw, there's a net global carbon benefit from
> sequestering the carbon in the straw into a house (or whatever).
>
>
> And finally, absolutely agree about the large perspective.
>
>
> Cheers
> Andrew Alcorn
>



Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu




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