From: Ramez Naam (mez@apexnano.com)
Date: Sun Dec 01 2002 - 19:56:26 MST
From: spike66 [mailto:spike66@attbi.com]
> We both got the same answer with regard to the mass of
> carbon to be scrubbed, you said 5E13 kg, I said 1E14 kg,
> within a factor of 2 is close enough. Also my conservative
> swag takes into account the other mass in wood besides
> carbon, so lets just say 1E14 kg of wood, thats 1E10 big
> trees, and yes I do think we could put something like that
> into place with nothing technologically more tricky than
> pipes and canals.
Just out of curiosity, how does this handle future carbon emissions?
Do we have to keep planting another billion trees a year? Does the
number of trees we plant increase each year as our carbon emissions
increase?
FYI, some random data about forests worldwide.
The US has about 10% of the world's forest land. As of 97, US forests
contained roughly 2 x 10^10 cubic meters of wood. The dry weight of a
cubic meter of wood is roughly 500 kg. So the US contains roughly
10^13 kg of wood (dry weight) and we can estimate the dry weight of
all the world's forests at 10^14 kg.
So your proposal involves roughly doubling the size of worldwide
forests. This will undoubtedly take time, since the mean age of trees
worldwide is almost certainly in the tens of years, and trees grow
larger with age. This would also take the US to roughly 1.5 x the
amount of forest land here when the first European settlers arrived.
That sounds quite challenging but not completely impossible.
In the US our 10^13kg of forest are spread across ~300 million
hectares of land. Total US land area is ~9 billion hectares, so
forests currently constitute around 3% of US land area. If we estimate
the price of a hectare of extremely rural land as $1000 (about what it
costs in rural Washington state, where I live), then we're talking
about $300 Billion just to buy enough land in the US to plant these
forests on (assuming that there's sufficient rural non-forested land
available), plus presumably additional funds to plant and maintain the
trees. So let's say a $500B initial investment plus some rather small
amount per year. $500B is only about $50B more than the combined
annual military and homeland defense budgets in the US. I'd be fine
with cutting say a third off those budgets for each of three years and
doing the purchasing and planting over that time.
Fascinating.
I do wonder about where the nitrogen and phosphorous to do this come
from, though. Mining phosphorous from the ocean bed doesn't sounds
like a good idea, as it may disturb clathrate beds down there and
release a huge amount of carbon into the atmosphere.
*shrug* Overall it sounds almost viable, modulo the questions about
whether we have to keep planting more and more forests each year to
deal with even increasing carbon emissions. At some point we really
do have to stabilize the carbon content of the atmosphere, and
emissions reductions are a powerful tool in that.
mez
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