Does burning wood release all of the carbon a tree has captured in its lifetime? Does a dead decomposing tree do the same?

Question

Anytime carbon capture comes up, the conversation devolves into commenters saying the entire idea is dumb and trees already exist. I’d like to know more about the full life cycle of a tree and if the carbon it captures is permanent.

In: 199

Answer 1

So a tree you burn almost entirely gets converted into CO2. A tree that decomposes gets converted into co2 and methane, but a very small quantity will get trapped in layers of soil as long-chain carbon molecules (essentially a precursor to crude oil), and will slowly get burried deep within the earth. This can take millions of years to fully take hold though.

So in the balance of things a decaying tree (taken on its own) is better for climate change in the long term (because it sequesters some carbon), but may actually be worse short term (because methane is a more potent, but short lives greenhouse gas). Burning the tree does release all the net carbon a tree has captured however, but it’s usually pretty pure CO2, especially in industrial applications.

That being said it’s easier to think of trees in terms of average forrested area, and forrest density as opposed to individual trees. This is because forrests generally replace fallen trees at the rate that they are removed (if we don’t interfere with the process).

So if you cut down a tree for fuel and replant it continually you can generally consider it approximately carbon neutral (some carbon is sequestered if you plant a lumber forrest in a grassland, some is released if you convert an old growth forrest into a lumbering forrest). If you plant a forrest and legally protect it and let it grow, it will squester a lump sum of carbon once the forrest is fully grown (think 20-80 years) and very very slowly (think millions of years) build up permanent oil reserves and trapped carbon in layers of soil (think centuries). If you cut down a forrest it will release a lump sum of carbon and cause errosion of the soil, and expose any oil it may have deposited.

Results may varry based on specific contexts: for instance lumbering for building materials sequesters a much larger lump sum of carbon than a lumbering forrest that burns the wood. The carbon will end back up in the atmosphere but if there’s a whole forrest worth of wooden products out there that came from that forrest, that forrest is essentially sequestering twice as much wood. Also some woods are denser than others or grow faster