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Thursday, July 26, 2007

Robert Samuelson wrote a very very bad op-ed which contained a claim which interested Matthew Yglesias

eliminate tax subsidies (mainly the mortgage interest rate deduction) for housing, which push Americans toward ever-bigger homes. (Note: If you move to a home 25 percent larger and then increase energy efficiency 25 percent, you don't save energy.)

Yglesias notes that 0.75*1.25<1 and suggests a remedial arithmetic course. I am willing to go further and make a personal sacrifice. I have a mustache. I am willing to support an unconstitutional law that no person who had a mustache on July 26 2007 can ever write an op-ed ever again (damn that would ban Matt too. Cut it off before it's too late).

The argument about houses and global warming interested me. This is one of my obsessions. I think that an important part of the world carbon budget is being ignored. The use of wood in construction causes carbon sequestration.

Greens might hate me for saying this but cutting down trees and building houses reduces global warming. Consider 2 possibilities. 1) We stop building more and more huge houses and let the forests reach equilibrium or 2) we repeatedly clear cut forests and use the wood for houses. In case 1, no carbon is fixed in the forests (in equilibrium photosynthesis and rotting cancel out). A tree farm or repeatedly clear cut forest fixes tons of C02 (humans remove the wood before it has a chance to rot and plant new saplings which grow real fast). If we build more and more houses and don't tear down the old ones (think Northern Virginia) a lot of carbon ends up in houses.

So if I assume that wood used in construction never rots or burns I calculate that carbon sequestration from the lumber business is going on at a rate of about 500,000,000 tons of wood a year. Residential emissions of C02 are about twice that. I have the weight per mole of carbon of wood and C02 at my blog. The point is that carbon sequestration by turning forests into tree farms is a huge huge deal in the USA (and aren't we net importers of lumber buying more from Canada than we sell ?).

So far I have used

residential emissions of C02 about 1,2 million tons per year (metric) (this is mostly via demand for electricity not direct emissions from heating and cooking and stuff).
Ruthless theft from nature of lumber by board foot (falsely called production)
48,773 million board feet.
a board foot is 2.36 liters and wood floats so I will say a board foot weighs about 2kg

The old wood to C02 equivalence wood is about one third water. The rest is mostly cellulose weighing (about) 38 grams per mole of carbon so pulp wood would weigh about 57 grams per mole of carbon. CO2 weighs 48 grams per mole of carbon, that is, 48 tons per million moles.

So one thousand board feet contain as much carbon as 2*48/57 = 1.68 tons of C02.

If the wood used as lumber never rots or is burned (very big if) the timber industry sequesters carbon at a rate equivalent to 82 million tons of carbon a year. That is not tiny compared to residential C02 emissions.

Of course much of lumber is used for non residential construction and some C02 emission due to huge houses are not direct but come from increased fuel for commuting from absurd exurbs.

Still the construction corresponds to one year's increase in housing not the stock of housing. The annual increase in residential C02 emission was about 1.4% per year from 1990 to 2006 so roughly times roughly 18 million English tons about a quarter of gross sequestration due to the timber industry of 82 million tons of C02 equivalent.

I'd guess that the increase in housing would reduce global warming if people would just commute in Priuses.


Neil Bates said...

Er, actually if you increased energy efficiency 25% you would use 0.8 instead of 0.75 of the old energy to do the same things, which works out OK when multiplying 1.25 * 0.8! For example, if energy efficiency was 60% before, then rose 25%, the new efficiency is 75%. (NOT to be confused with "percentage points" which would raise it to 85%. You'd be surprised how much that gets gamed ...) That should mean, use of 1000J gets you 750J of real energy instead of 600J. That is the same as 0.8 of the old 1250J you would have needed before, to get 750J (1250 * 0.6 = 750.) Then if energy use is per square foot, that works out to break even. OTOH, that maybe isn't the best way to define "efficiency" in this context. But I think Samuelson meant something was non-linear anyway; not that he does a good job in general.

PS, just to show you how intuition can mess up your thoughts: You might think, half of the population must be below average, right? But that's true only with a symmetrical distribution like the standard distribution. If for example there are lots of high values at the top, skewing the average, then plenty more than half of the sample can be less than average (as with income in the USA!) Don't confuse average and median.

(Fun commenter fact: I'm #1, 2, 3 and 4 in Google search for "quantum measurement paradox"! Check it out, I may be on to something ...

Link #1)


Anonymous said...

You might want to run these numbers by a forestry expert.

Most of the carbon in a forest is not in the timber: much is in the leaves and branches and much is underground.

Harvesting the wood tends to release CO2 from the branches and leaves. Not sure about the soil.

Here's one link:

And a quote from the link:
The carbon pool at the Montmorency Forest site contains 17.3 kg of carbon/m² (or 173 t of carbon/ha), distributed as follows:

* 7.3 kg in the vegetation
o 4.5 kg in the wood
o 1.5 kg in the branches and leaves
o 1.3 kg in the roots
* 10 kg on and within the soil
o 3 kg in humus
o 7 kg in mineral soil
I have the sense that some of these calculations have been done, though there are nontrivial error bounds. Carbon sequestration isn't exactly a new idea.

Robert said...

Neil' I happen to have a rather strong personal interest in matters arising from the difference between the median and the mean (see The Journal of Econometric Volume 106 pp 297-324 2002.

I know that Yglesias' critique depends on a matter of definition. Still it was funny.

I will so google. I am interested in quantum measurement paradoxes (assuming it has something to do with the EPR experiment)

On the leaves and junk, I had a plan for what to do with that (click the link on the wood vs Coal grams per mole of carbon). I want to bury it in the desert. However, like the wood, the other tree material is in steady state in nature. unlike the wood it is also in steady state with repeated clear cutting. Thus it is irrelevant to my calculation in this post.

Robert said...

Very interesting Neil' (except I don't understand your idea at all). Oddly, I have thought about the EPR experiment too. I blogged about it here