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.
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Soil microbial ecologist here who researches decomposition in soil!
Yeah if you burn wood, you are rapidly releasing most/all of the carbon still in the tree immediately back into the atmosphere. Decomposing wood also loses all of its carbon over time. But here’s why trees are still great for carbon capture:
1. They tend to live for a really long time, trapping all that carbon long-term
2. Some of their carbon while the tree is alive gets buried in the soil as roots or as root exudates (sugars that the roots release into the soil). So even when the tree dies, some of the carbon it captured over its lifetime has already gone onto another stage in the ecosystem and remains “sequestered” or trapped. Like the next point, for example:
3. While the trees are alive, they share a lot of their carbon with microbes in the soil which also help to keep the carbon in the soil as microbial biomass (bacteria and fungi especially)
4. When the tree dies and conditions aren’t great for decomposition (e.g. very cold and/or dry) then the tree decomposes extremely slowly so it’s still helping to store that carbon. Also a lot of the carbon in trees is trapped in long fibrous chains that are difficult to decompose, slowing down the process and helping the carbon stick around for a while.
5. When the tree dies and decomposes, the microbes are doing the bulk of that decomposition. The carbon turns into microbial biomass. Some of this still ends up back in the atmosphere when the microbes themselves still die and decompose. But sometimes the dead microbes don’t decompose very well and their carbon gets buried long-term deep in the soil
IN FACT – related to point 5, we’re working on engineering microbes that don’t readily decompose when they die. So they trap carbon from whatever they eat, die, and stay somewhat preserved in the soil so that the carbon gets trapped in the soil. Very cool stuff! But this process still relies on a thriving plant community to capture that carbon in the first place, so we need forests and other healthy plant-based ecosystems.
Why can’t we just take all this extra carbon and split it in a nuclear reactor to break it down into something we need, like Helium? Get 3 Heliums and some energy, right?
Most plants release sugars into the soils to feed beneficial microorganisms. That sugar comes from atmospheric carbon. A ton of carbon gets sequestered in the soil until you till it up.
So not all of the captured carbon is released when the tree burns and even less does when it decomposes for reasons other comments have mentioned.
Yep, trees are taken solar energy and loose carbon dioxide and turning into the complex tight or carbons that do eventually become oil and coal is left underground long enough, call Nestor as such, left on the surface and exposed to the right conditions, they are basically a battery of solar energy and can be turned into fire music. That does release all the carbon products they’ve stored and sequestered, but we absorb some of the oxygen they let out, over their lives.
In short they are a battery. They accumulate energy their entire lives.
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
Matter is not created or destroyed in chemical reactions.
If you take a tree, harvest it, use it for lumber to build a house, that wood captures the carbon until the house is destroyed.
Carbon that was CO2 that then becomes a tree (various organic molecules) will decompose to CO2 and other molecules if it rots.
If you burn the tree is mostly becomes CO2.
Plants use carbon to build their bodies. So one way to capture carbon is to grow a forest, which captures a bunch of carbon, and when it has reached maturity you cut it down and use the wood as building material. Then you plant more trees. That way, the carbon is stored in buildings instead of being released right back due to the trees burning or decomposing.
It seems the answer is to shoot old trees into the sun and plant new ones in their place to eliminate the stored carbon.
So the carbon capture is not permanent, but you have to think about how natural decomposition processes work – they aren’t a solitary process. Decomposition is the process of a ton of smaller organisms from microorganisms to bird-sized animals consuming/carrying away pieces of the plant. Some natural offgassing will happen but most of it is being absorbed by other lifeforms in order to continue their own lifecycles. And those lifeforms, in turn, become food that ultimately feeds new plants, including trees.
The bigger problem is how much of the Earth we would need to reforest to actually achieve carbon capture storage on the scales we need to offset even a fractional portion of the cO2 reductions we need to achieve. Reforestation isn’t just effective carbon capture – it’s a massively good idea in general – but it can’t be the single answer to the amount of cO2 capture that humanity needs to achieve.
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