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

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.