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Yes, but bacteria action continues in that soil and continues releasing CO2 for a long time to come. Some of it will feed new plants (anything taken from the so

Yes, but bacteria action continues in that soil and continues releasing CO2 for a long time to come. Some of it will feed new plants (anything taken from the soil is not being taken from the air). The question is how much of that soil carbon truly becomes permanently sequestered? Some of it may be there for a long time, but the humus layer will not become infinitely thick. Once we are talking about an old growth forest, the forest will have reached a somewhat steady state. I am not saying it cannot continue to act as a carbon sink, just that I suspect it to become less effective over time, and that it will not work in all conditions. A number of research papers have pretty much shown this lately, not just this one.

jvanderbot 6y ago
Assuming rich soil accumulates over time in a long-running forest, what happens to the lower layers? Do they release carbon more quickly as they "die" or do they store it? If they store it, then that's sequestration, right?
- vkou 6y ago
  It is sequestration, but it can take thousands of years for an inch of rich soil to accumulate in a 'steady state' system. Most fossil fuel carbon was originally sequestered in a world where very few things could break down dead trees. That world is millions of years gone, current natural carbon sinks are 99% temporary.
  - saalweachter 6y ago
    There's a certain argument to be made for timber farming as a way to extend our temporary carbon sinks -- trees that fall over rot, releasing their carbon, trees that are cut down and turned into houses may be protected from decay for tens or hundreds of years. You could really go whole-hog into attempting to maximize the amount of timber you can stuff into a house -- start building double-stud walls with 12 inch on-center spacing just to triple the number of 2x6's used, fall in love with giant cross-laminated timber panels, etc etc.
    - vkou 6y ago
      That is incredibly labour and energy-inefficient. You're better off burying raw timber, as opposed to processing it, cutting it up, transporting it to a worksite, and paying professionals to hammer it into place.
      - saalweachter 6y ago
        How do you feel about baking the timber in solar ovens first, before burying the charcoal, to go full terra preta?
    - elihu 6y ago
      It seems to me that the low-hanging fruit is to sequester the sawdust and scraps that result from sawing logs into boards. I assume that much of that ordinarily finds its way into other products (paper, particle board, etc...), but that it's economically less valuable than usable boards and thus burying it the ground has lower cost. There does seem to be increasing interest though in making large structures out of wood, so maybe that's a pretty good route for carbon storage.
    - henearkr 6y ago
      Just to precise, "tree-roting" is incredibly slow, and the tree mainly turns into other living forms (thus, also sequestered carbon) rather than in carbon dioxide (one part does, but far from 100%). It's like when you eat, you do not turn your food in pure gas, do you? And then the excreted/remaining mass will be buried etc (and will partly be turned into earthworms, nematodes, bacteria, moss, fungi, etc).
      - saalweachter 6y ago
        Hmmm, that's an interesting question. A person breaths out about 2.3 lbs of CO2 each day, which amounts to 0.6 lbs of carbon, all of which must have come from your food. Meanwhile, a person defecates about 1 lb per day, about 75% of which is water. Of the residue, about 25-50% of it is bacteria, and the remainder the undigested portion of your food. Bacteria is typically accounted 53% carbon; the undigested fats, carbohydrates and proteins will vary a lot in percentage, but is 40% carbon for carbohydrates, 50% for proteins, and "more" for fats. Which leaves a lot of variance, but something like 0.15 lbs of carbon exiting at as a solid seems like a reasonable estimate. So the answer would be: you turn about 80% of the carbon in your food into CO2 gas.
  - User23 6y ago
    > It is sequestration, but it can take thousands of years for an inch of rich soil to accumulate in a 'steady state' system. And as anyone that's been to western England knows, it takes a single generation for it to all blow away and leave you with nothing but a barren heath that's good only for grazing sheep.
- goodcanadian 6y ago
  Some will be sequestered in this way, but how much and under what conditions? Tropical rain forests, for example, are known to have very poor soils despite the massive amount of biomass growing in them. Almost everything is recycled back into the forest very quickly. Clearly, no significant accumulation of sequestered carbon is occurring there. On the other hand, peat bogs occur because dead plant matter falls into a low oxygen environment and doesn't really decay, so there can be a build up of sequestered carbon there, but that is rather specific conditions.
  - craigbaker 6y ago
    Some of the biomass is also washed away and becomes marine sediments, which can store a significant amount of carbon. https://cbmjournal.biomedcentral.com/articles/10.1186/s13021-017-0077-x https://cbmjournal.biomedcentral.com/articles/10.1186/s13021...

jvanderbot 6y ago

Assuming rich soil accumulates over time in a long-running forest, what happens to the lower layers? Do they release carbon more quickly as they "die" or do they store it? If they store it, then that's sequestration, right?

vkou 6y ago
It is sequestration, but it can take thousands of years for an inch of rich soil to accumulate in a 'steady state' system. Most fossil fuel carbon was originally sequestered in a world where very few things could break down dead trees. That world is millions of years gone, current natural carbon sinks are 99% temporary.
- saalweachter 6y ago
  There's a certain argument to be made for timber farming as a way to extend our temporary carbon sinks -- trees that fall over rot, releasing their carbon, trees that are cut down and turned into houses may be protected from decay for tens or hundreds of years. You could really go whole-hog into attempting to maximize the amount of timber you can stuff into a house -- start building double-stud walls with 12 inch on-center spacing just to triple the number of 2x6's used, fall in love with giant cross-laminated timber panels, etc etc.
  - vkou 6y ago
    That is incredibly labour and energy-inefficient. You're better off burying raw timber, as opposed to processing it, cutting it up, transporting it to a worksite, and paying professionals to hammer it into place.
    - saalweachter 6y ago
      How do you feel about baking the timber in solar ovens first, before burying the charcoal, to go full terra preta?
  - elihu 6y ago
    It seems to me that the low-hanging fruit is to sequester the sawdust and scraps that result from sawing logs into boards. I assume that much of that ordinarily finds its way into other products (paper, particle board, etc...), but that it's economically less valuable than usable boards and thus burying it the ground has lower cost. There does seem to be increasing interest though in making large structures out of wood, so maybe that's a pretty good route for carbon storage.
  - henearkr 6y ago
    Just to precise, "tree-roting" is incredibly slow, and the tree mainly turns into other living forms (thus, also sequestered carbon) rather than in carbon dioxide (one part does, but far from 100%). It's like when you eat, you do not turn your food in pure gas, do you? And then the excreted/remaining mass will be buried etc (and will partly be turned into earthworms, nematodes, bacteria, moss, fungi, etc).
    - saalweachter 6y ago
      Hmmm, that's an interesting question. A person breaths out about 2.3 lbs of CO2 each day, which amounts to 0.6 lbs of carbon, all of which must have come from your food. Meanwhile, a person defecates about 1 lb per day, about 75% of which is water. Of the residue, about 25-50% of it is bacteria, and the remainder the undigested portion of your food. Bacteria is typically accounted 53% carbon; the undigested fats, carbohydrates and proteins will vary a lot in percentage, but is 40% carbon for carbohydrates, 50% for proteins, and "more" for fats. Which leaves a lot of variance, but something like 0.15 lbs of carbon exiting at as a solid seems like a reasonable estimate. So the answer would be: you turn about 80% of the carbon in your food into CO2 gas.
- User23 6y ago
  > It is sequestration, but it can take thousands of years for an inch of rich soil to accumulate in a 'steady state' system. And as anyone that's been to western England knows, it takes a single generation for it to all blow away and leave you with nothing but a barren heath that's good only for grazing sheep.
goodcanadian 6y ago
Some will be sequestered in this way, but how much and under what conditions? Tropical rain forests, for example, are known to have very poor soils despite the massive amount of biomass growing in them. Almost everything is recycled back into the forest very quickly. Clearly, no significant accumulation of sequestered carbon is occurring there. On the other hand, peat bogs occur because dead plant matter falls into a low oxygen environment and doesn't really decay, so there can be a build up of sequestered carbon there, but that is rather specific conditions.
- craigbaker 6y ago
  Some of the biomass is also washed away and becomes marine sediments, which can store a significant amount of carbon. https://cbmjournal.biomedcentral.com/articles/10.1186/s13021-017-0077-x https://cbmjournal.biomedcentral.com/articles/10.1186/s13021...