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Comment by agumonkey | Hacker News Reader

is it ? I thought it was mostly digested by fungi / bacteria / insects without re-emitting it

Digestion breaks things down for energy which means producing CO2. You can simplify organic chemistry on these scales as spending energy to store carbon or gaining energy to release it.

In some situations you can get net carbon storage which is how we got fossil fuels in the first place, but this is really slow. On the order of 1 Billionth the total fossil fuels stored per year.

I asked below but maybe you'll know the answer. Basically insects/bacteria cellular respiration produces CO2 just like us ?

update: found some answer https://www.amentsoc.org/insects/fact-files/respiration.html

I never considered that.

Also, how unlikely that this CO2 is reabsorbed by the plants (granted that can only occur after winter when leaves are back) ?

Yeah, of course. Bacteria, insects, fungi, and any animal break down plant matter (fruits, salads, wood), releasing CO2 in the process. Fire does the same, only the energy is emitted as heat and light, not movement and wasting time on HN.

CO2 + sunlight is again converted into organic material by plants (and some bacteria). It really doesn’t matter if it’s the „same“.

This is the basic carbon cycle.

You'll get a residue of organic materials that don't immediately return to the atmosphere, and eventually accumulate into fossil fuels, but that's a very slow accumulation, a fraction of the carbon that is initially captured when a unit of forest grows from scratch.

Carbon is an element. Most organisms to a lot of chemical rearrangement of the element, but the element is not created or destroyed in biological processes. Any carbon kept during life is released at death.

But not necessarily released as CO2, which is what "re-emitted" means to me. If it goes atmosphere -> tree -> fungus -> bits of fungus buried in the ground for millions of years, that's effective sequestration.

It may well be, but that's not what happens to most of the wood in trees— most of it rots (CO2 released slowly by the organisms consuming the wood) or burns (CO2 released by combustion).

As said below, it's not C, but CO2 we were worried about. Also I admit that I don't know if humus organism produce CO2 from wood remains.

This is true only in part.

We have found shells, made of Calcium carbonate, still relatively intact more than 3000 years after the death of the animal. Some shells had last for 500000 years (See Nature 2014-dec-03)

Under the sea there are entire ecosystems based in dead shells.

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