Saturday, October 9, 2010

More on Carbon Sequestration

Brother Dave followed up on comments regarding carbon sequestration in forests in my previous post with the following erudite comments:


Per your request I looked at your latest posting. I have always been
of the view (without data of course) that a mature forest (read "old
growth") is probably not sequestering much or any carbon on an
incremental basis. Admittedly there is a huge amount of carbon locked
up in those big trees, but that is not really the policy issue. The
analysis should always be at the margin. How much annual incremental
carbon is sequestered (through tree growth) or released (through tree
death or harvest and resulting decomposition) is the question the
analysis should be focused on. I think the greenies tend to confuse
the debate by focusing on a static analysis rather than a dynamic one.

It sounds like the site you were visiting had slow growth rates
resulting from 100 year old logging practices and resulting site index
damage. OK, not much incremental sequestration and if there are some
really old trees around which are falling down it could be negative.
As an alternative think back to the trip we took to Mt. St. Helens a
few years back. Remember the Weyco noble fir forest that had been
planted up there. Those trees looked like they were growing so fast
that you could hear them grow if you were quiet enough at night. The
incremental carbon sequestration on that site had to be quite large
compared to the site you were looking at and even bigger than the
adjoining federal lands where no replacement timber had been planted.

This tends to lead to an argument that we should liquidate old growth
and plant new trees which we pick for rapid growth and then apply a
variety of growth generating silvicultural practices. Makes sense in
the abstract, but I am not sure it is quite that simple. First you
have to consider what happens to the old growth forest you liquidate.
About the best you can do with that is convert it to building products
and put it into structures which will defer the carbon release for
another 100 years or so. As to the slash and residuals fro the
manufacturing process the preferred prescription seems to be to use it
for energy generation. Those of us in my industry and the biofuels
industry like to argue that any carbon released in that process is
irrelevant because of the replacement sequestration occurring in the
tree farm. Fair enough, so long as you don't count the tree farm
twice that way, once for the benefit of the guy who owns it and once
for benefit of the guy who is burning the slash and residuals.

A better solution is to maximize the recovery from the log/tree into
building materials and other useful products which do not release the
carbon for an extended period. Is there a process to turn slash into
a solid object such as a plastic? If so how much energy does that
process consume. This gets really complicated. Another question that
occurs to me is the rate at which growing trees sequester carbon. I
can just about guarantee that if you plotted annual sequestration
versus tree age, it would not be a straight line. It would start out
very low (because the tree is very small) and end very low (because
the tree is not growing). Again, however, no data. However, all this
means is that the replacement of old growth with a new tree farm does
not give you a year one payback. It will take time before the
incremental sequestration of the tree farm catches up and "covers" the
carbon released as a result of the harvest. All nice in theory but
pretty much worthless speculation without real data. This is the kind
of question where the assumptions swallow the answer and site
differences will yield significant variances in outcome.

Oh well. Way to complicated for this mere finance lawyer. I have to
go and prepare to teach a class to a bunch of third year law students
on deal making.


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