So at various places on the web :
A single mature tree can absorb carbon dioxide at a rate of 48 lbs./year. cite
A tree can absorb as much as 48 pounds of carbon dioxide per year. cite
I cannot find the original publication or published research this number was taken from. So my question is:
1> Is there a link to a published study in a scientific journal quantifying the NET CO2 an average tree absorbs per year ? (Net is important because a tree makes CO2 too)
Here’s a citethat looked at amount of carbon sequestered in two types of forests and estimates the amount of CO2 absorbed per tree.
Enilno, thank you for the effort. The cite you gave has very different Co2 capture rates from other cites.
Anyways, your cite is in turn taken from a book - "Forests and Global Change, Vol. 2, Forest Management Opportunities for Mitigation of Carbon Emissions. Neil Sampson and Dwight Hair, Washington, 1996." I cannot find that book in any library of the US. cite
So I repeat my original question, is there a peer reviewed, scientific publication that looks at amount of CO2 absorbed by an average tree or something similar ?
The problem is, there is no such thing as an “average tree.” Some tree species grow much more rapidly than others. And trees may grow much faster under optimum conditions of rainfall and temperature than they do on average. It sounds as if the figure in your OP is a maximum figure, since it says “as much as.”
Is it safe to assume that CO2 sequestration is roughly equal to the weight of the wood that’s grown?
So you could probably figure out roughly how much wood a tree grows in a year and multiply it by something like 2.59 (the # of pounds of CO2 given off by burning a pound of wood).
What this means is that faster growing trees will generally sequester CO2 faster.
Excluding the weight of the moisture in the wood.
Technically true, but some of that water’s been split into hydrogen and oxygen and incorporated into the lignin.
Lignin is really a family of organic polymers with varying structure but one composition by weight is 63.4% carbon, 5.9% hydrogen, 0.7% ash, and 30% oxygen.
But a molecule of CO2 is actually only 27% carbon. To remove a pound of CO2 from the atmosphere, 27% of that pound is incorporated into the tree’s structure. This 0.27 pounds of pure carbon makes up 65% of a pound of dry wood. A pound of CO2, thus, becomes 0.42 pounds of wood. Trees are about 30% water, so a pound of CO2 becomes about 0.6 pounds of tree.
Okay - I agree there is no such thing as an average tree. What I am requesting is a published (peer reviewed) scientific study of a typical or specific tree species. So far I have not found any and hence the request.
Something along the lines - we studies 159 trees of species X in the rain forest of Brazil over 5 years and the median CO2 absorbed by each tree was XX with a standard deviation of ZZ.
Failing that type of study, I’d be okay with any measurements scientifically taken and published in a peer reviewed journal of repute.
Bear in mind that an old growth forest is very nearly carbon-neutral; the only carbon that is permanently sequestered in a forest more than about 800 years old is carbon that is permanently deposited into the soil (as peat, for example), or removed in the form of wood products that are stored elsewhere. All the rest of the carbon that is sequestered is in the form of biomass that will eventually decay and return to the atmosphere.
Not quite right. The tree has a net carbon intake, which comes from the air. You could collect all the wood PLUS all the leaves, fruit, nuts, and other yearly stuff, and you’d have it. But this pile will also contain water and ash (ash being the residual stuff that would be left after burning). So you could thoroughly dry this huge pile, then weigh it, then burn it, then weigh the ashes. The difference would be the lifetime carbon sequestration. Cipher the oxygen weight based on molecular weights, and you’d have the total lifetime CO2 sequestration.
Well, at least I think so.
Except all of the non-wood biomass would be very quickly released back to the atmosphere. And bump is already using a figure for pounds of CO[sub]2[/sub] released per pound of wood burned (which will surely vary somewhat from species to species, but which is probably mostly consistent).
Oh, yeah – what I describe would be a weird artificial situation where you never let the non-wood biomass recycle itself. So, leave the extras out of the pile.
You also can’t look at an average by tree species because a young, far growing individual will sequester more carbon than an old one that is dropping as much wood as it grows. A small baby tree will sequester less than a big tree. And so forth.
How can you get 2.59lbs of something from burning 1lb of something else. A pound of feathers weighs the same as a pound of bricks right?
Because carbon dioxide isn’t just carbon. Most of the mass of carbon dioxide comes from the oxygen, which (mostly) comes from the air, not from the wood. It’s like how one pound of sugar makes five pounds of pound cake.
Ah! Makes perfect sense, thanks!
From the basic chemical equation for combustion: CH[sub]4[/sub] + 2 O[sub]2[/sub] = CO[sub]2[/sub] + 2 H[sub]2[/sub]O.
For 16 pounds methane combined with 64 pounds oxygen we get 44 pounds carbon dioxide and 36 pounds water, 80 pounds on one side of the equation and 80 pounds on the other … and I use pounds[sub]mass[/sub] here, so substituting kilograms is correct.
So that’s 2.75 times the mass under perfect conditions.
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One point here is that not all the biomass is returned to the atmosphere, some of it actually stays in the biology as bacteria, fungus, animals and other plants.
Well, if you’re burning methane, at least. I don’t know what the elemental proportions are of wood, but I would expect sugar to be a better approximation.
EDIT: Call it roughly C[sub]6[/sub]H[sub]10[/sub]O[sub]5[/sub], for a long chain of glucoses.
The USDA Forest Service has done or collected research. It’s easier to see the conclusions they’ve drawn than the research. But here’s alist of papers related to “urban forests.” They may be internal rather than peer reviewed.
There are several online or downloadable calculators meant to calculate carbon sequestration. The calculator that you have to use if you’re trying to get an urban greening type grant is the CUFR Tree Carbon Calculator (CTCC). Inputs include the type of tree and the climate zone - trees grow faster in warmer weather.
Like the Hitchhiker’s Guide to the Galaxy, if it is wrong, it is definitively wrong. For some grant programs, your application will live or die according to its CTCC results vs. cost. According to the linked page “Updated versions of the underlying growth equations used in the model are becoming available.” I have no idea whether the equations became available or where they would be.
Would it also depend upon the CO2 levels in the area? For example a tree in a forest out in a pristine area might be lower but a high planted next to a highway could pick up more.