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Also not a chemist, but here's my basic understanding. The tree absorbs CO2 from the atmosphere and combines it with water (H2O) from the soil to produce more complex chemical compounds (such as carbohydrates). This process uses sunlight as the source of energy, and is better known as photosynthesis. The chemical compounds thus produced are used by the tree as structural material (the wood), or as stored energy (basically, reverting the photosynthesis reaction, aka "burning", releases the energy). If the tree matter gets consumed by animals, those animals are going to use the stored energy, and ultimately re-release the stored carbon as CO2. If the tree just dies and is allowed to decompose, bacteria and other microorganisms will do the same: they'll eat the carbohydrates that the tree produced, and they'll breathe out the resulting CO2. If the tree is burned as fuel, the CO2 gets re-emitted directly. So, to truly remove that CO2 from the atmosphere, the tree needs to be felled once it's stopped growing, and the resulting wood stored someplace where it can't be decomposed by microorganisms. Burying it is one solution to this (and this is what happened during the carboniferous era, when much of our coal and oil got created: dead trees fell in shallow swamps and were quickly buried under a layer of silt which prevented the decomposition). Again, I'm no expert, so I'm happy to stand corrected if I've made any mistakes above. |
There are some active land management techniques which do something similar with shrubs/plants/grasses which generate an enormous amount of soil and therefore trap a lot of carbon.