Wednesday, December 31, 2008

Carbon Sequestration

Please allow me to get up in your grill and debunk one of the favored shibboleths of the environmentalist or "Green" movement. In a recent editorial in the "Oregonian" on the subject of sustainability and City government the author stated "As we all learned in kindergarten, planting trees creates oxygen, captures carbon, and eases global warming".

Let me state at the outset that even if the above statement were true it is highly unlikely that I would have learned it in kindergarten (1952-1953). I am quite sure that I did not learn that trees produce oxygen and store carbon at the knee of Mrs. Gross my kindergarten teacher in Reno, Nevada. More importantly it must be noted that the simple rules of biology, chemistry, and mathematics render the whole idea of "carbon sequestration" to the to the arena of "not so much". Here's why:

Carbon: The subject here is biomass, not just trees. We are talking about all green plants. It is true that the process of photosynthesis results in the intake of carbon dioxide from the atmosphere and it's subsequent conversion to carbon based cells making up leaves, stems, twigs, reproductive bits, etc.

Oxygen: It is also true that the above mentioned photosynthetic process results in the release of oxygen as the CO2 is converted in the process. OK, carbon in, oxygen out... So far so good.

Death: If no biomass ever died our atmosphere would quickly become so oxygen rich that the first spark would ignite all organic material on the planet in a really big firestorm. Fortunately plants (also unfortunately, humans) die. In fact plants are constantly shedding vast amounts of dead material in the form of leaves, needles stems, and of course overall death of the organism. So lets, look again at the flow of oxygen and carbon.

When plant material dies, or is burned the result is the same - Oxidization. That is when a leaf falls to the earth it is gradually consumed by microorganisms which consume the plant material. In the digestive process the process of metabolic respiration takes place converting the food to energy. This results in the consumption of atmospheric oxygen, and the release of our old friend carbon dioxide. In other words, all the carbon sequestered by living plants is eventually returned to the atmosphere either by respiration or fire. All of the oxygen originally released is consumed either by metabolic respiration or fire.

Ah, but what about wood, the alert reader may ask. It is true that wood in service (lumber in your house, furniture, etc.) sequesters carbon for the duration of its existence as wood. Two factors limit the importance of wood as a reservoir of carbon. Firstly if you look at the life cycle of a tree, you will observe that the total production of disposable biomass (leaves, fruit, twigs, etc.) dwarfs the volume of wood in the bole (trunk) of the tree. Hence most of the biomass of trees returns its carbon to the atmosphere on an annual basis. Secondly, when said wood rots, is eaten by termites, or burns, our old friend oxidization returns its carbon back to the atmosphere as CO2. This brings up an interesting question. If all the Oxygen delivered up to the atmosphere is eventually traded for CO2 upon the metabolism or burning of biomass, what then accounts for the free Oxygen in the atmosphere? I believe I have an answer for this question but will leave it up to you to posit your own answers in the comments section to follow.

Please do not assume from my clinical dissection of carbon sequestration that I do not value the "green" world. Deforestation of large tracts of land via slash and burn agriculture, reckless harvesting, wildfire etc. certainly has detrimental environmental consequences. In addition to the production of oxygen via photosynthesis, trees are prodigious movers of water. The process of transpiration of water provides the majority of water feeding the tropical storms of the mid latitudes. This is one of the reasons that massive deforestation leads to desertification. Forests and grasslands protect, even create, watersheds. But, please do not buy into the carbon sequestration, carbon offset, carbon management politics being heaped upon us by the biologically illiterate activists. If your goal is to put carbon "in jail" via planting of trees, please consider that the net effect of these efforts will be at best negligible. There are a lot better reasons to plant trees than this.

In conclusion. I am haunted by the fact that I must be wrong about all this. How else could our local Land Rover dealer in good faith make the following offer. Upon purchase of a gas swilling carbon emitting Land Rover automobile the dealer will donate sufficient funds to an environmental activist group who will in turn plant sufficient trees to offset the production of carbon by your car for 50 years! Please fair reader tell me how this is not pure balderdash, hokum, or at least a bonehead error on the part of the Land Rover company. Surely, we can just plant a few trees and save the climate, the planet, and relieve us of this unrelenting guilt...

1 comment:

  1. I ran across an article in Scientific American this morning regarding the use of rangeland for carbon sequestration. It is located at Give it a read. Dg


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