[permaculture] Trees and CO2
toby at patternliteracy.com
Thu Oct 20 14:49:12 EDT 2005
Okay, this has got numbers dancing in my head and they won't stop. Forests
hold 3 tonnes (metric tonne is 1000 kg) of carbon per hectare. CO2 is
roughly 27% carbon by weight (atomic mass of C=12, O=16), and a typical car
puts out 550 kg of CO2/year (Energy Star figures), which would be 150 kg of
carbon. So 3000kg/Ha divided by 150 kg/car equals 20, thus a Ha of crankin'
young forest makes up for 20 cars. That seems pretty good. Some forestry
websites say that you can up sequestration to 5-10 tonnes//Ha/yr by managing
for sequestratation by species choice and clever thinning.
Next: Ward's Motor Vehicle Facts & Figures, 1999, says there were
671,000,000 cars and trucks in the world. So figure at least 700 million by
now (thank you, China), which means we need 35 million hectares of forest
(700M cars/20 cars per Ha) to hold all that carbon. 88 million acres. That's
only 137,000 square miles, or a forest 370 miles (600 km) on a side. That
seems pretty doable--the western US probably has that much, for sure if we
add in some of Canada. (Canada won't mind, right? They're used to it.)
I'm going to get in my car now and drive real fast, with less guilt than
Okay, I'm back. Also, those figures are only looking at carbon stored in
wood. But aren't there all those metabolic products, those evanescent sugars
being pumped out, sunnily, in the leaves (are they counting leaf weight? I
suspect not) and transformed into food for the tree (and where does
unmetabolized tree food go--what does tree poop look like, anyway?), exuded
by roots and eaten by soil critters, sloughed off as bark and dead cells,
puffed away as pollen, slurped up by bugs and birds. I'll bet that's a lot
of carbon, maybe more than turns into wood if tree metabolism is like most.
Typical of a reductionist to think, trees are wood, so wood is all the
carbon there is in a tree--and ignore metabolism. I wonder what all the
bio-process carbon adds up to?
Not seeing the forest for the wood?
3 tonnes of carbon per year ain't so bad.
I hope this isn't too alarming a picture of how my mind works when I free
On 10/20/05 9:52 AM, "robscott at freeshell.org" <robscott at freeshell.org>
> Genest, I think we need more specifics. A "hectare of trees" -- seedlings?
> old growth? species? a hectare of photosynthetic leaf area? or what?
> Toby's calculations are a step in the direction of specificity.
> But: tree species have different carbon sequestration rates, and trees
> have different sequestration rates at different times in their life cycle.
> A system which is *designed* to sequester carbon will do so more
> efficiently than, say, an old growth forest where the trees aren't
> actively growing new tissue so much as performing maintenance respiration.
> Rob Scott
> Urbana, IL
>> On Oct 19, 2005 William Genest <genest at pivot.net> wrote:
>> Just attended a lecture on Global warming and heard some dismaying
>> figures about trees' ability to sequester carbon. Apparently a
>> hectare of trees only sequesters about 3 tons of carbon per year ?!?!
>> Is that true ? Anyone have any other info on this ?
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