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We pull almost all of the CO2 we burn from coal and oil, which were basically underground carbon reserves. To replace all of that CO2 with plant matter would ta

We pull almost all of the CO2 we burn from coal and oil, which were basically underground carbon reserves. To replace all of that CO2 with plant matter would take an immense amount of nutrients, which have to come from somewhere. Then there's the chance that the plant matter will turn to coal or oil again, meaning it may be used again. By turning the CO2 directly into carbonate, you both remove the need for nutrients and turn the CO2 into a form that is both incredibly stable and not useful for any energy purposes, lessening the chance that it will make its way back into the atmosphere.

lend000 10y ago
Exactly. We have pulled an unnatural amount of "usable carbon" to the surface, which, even if it becomes a part of a natural, stable, cycle, will leave us with a higher net amount of CO2 in the atmosphere. We can only go back to "natural" CO2 levels through unnatural means, unless we are willing to measure time on a geological time scale (the millions of years it will take to replace oil reserves from the swamps of today). So until then, we would still be dealing with an acidic ocean and a greenhouse atmosphere.
- schiffern 10y ago
  >We can only go back to "natural" CO2 levels through unnatural means Ok, but let's be careful not to exclude the middle here. "We got here by mining (an industrial activity), therefore we can't use plants in any part of a carbon sequestration chain (even one that also involves industrial activity)." Trying to use this argument as a blanket ban on plants becomes little more than an appeal to sympathetic magic. The only thing that matters is how much CO2 a technique can buffer (annual production x time constant), not whether or not it uses plants at any stage. Plants already have enormous annual production, but for economic/thermodynamic reasons it's hard for purely factory-based techniques to achieve sufficient scale. It becomes a money sink both up-front and operationally, respectively because A) factories are expensive, and B) hard thermodynamic constraints mean that it's at a fundamental competitive disadvantage compared to any typical [reminder: energy consuming] factory.
  - lend000 10y ago
    > therefore we can't use plants in any part of a carbon sequestration chain (even one that also involves industrial activity) Not sure where your logic is coming from here. I am not saying we shouldn't use plants, but I am saying that even if we let forests retake "all the land," the stable CO2 level would be a bit higher than pre-industrialization, and it would stay that way for a long time until dead plant matter returned significant amounts of carbon to the deeper parts of the crust. Therefore, using other methods like the one in the article are necessary if we want to reduce CO2 levels.
    - schiffern 10y ago
      >let forests retake "all the land," I agree, a hands-off approach is insufficient. We would need to actively manage those forests (which is just as unnatural an activity btw), using intelligent design to improve upon the carbon density possible solely from blind natural processes. Big industrial thermodynamic sinks don't scale (and imo never will), simply because they can't economically compete with conventional energy consuming factories. An approach is needed that sequesters carbon while also producing sufficiently valuable goods to society (ie probably not rocks). Food is one possibility, and can avoid carbon futility since in perennial systems the annual food yield is a small percentage of the total carbon stored in the biome.
jrapdx3 10y ago
Plant nutrients are minerals, primarily nitrogen, potassium and phosphorus, in the base form of inorganic compounds or salts. When a plant dies it decomposes and the minerals are released and "recycled". Certainly that's how fossil carbon got to be stored in the first place (by growth of plants) so obviously the availability of nutrients in soils was naturally adequate to support the deposition of carbon. Carbonates are among the most common minerals on earth, particularly as calcium carbonate in its many forms. Calcium carbonate is slightly soluble in water and subject to degradation in acidic environments. While hardly an impervious carbon dioxide store, that's a benefit in that its easy degradation makes it an extremely useful mineral supporting essential infrastructure industries. IOW sequestering carbon as carbonates doesn't imply the CO2 is inaccessible but simply not reduced to an elemental or hydrocarbon form readily usable as an energy source. It's a trade-off between storage in an easier/quicker non-energy form or a protracted/difficult-to-implement energy-source form. Worth considering that in geological time the carbonate vs. carbon storage pools will probably "even out" since both are clearly mutable.

lend000 10y ago

Exactly. We have pulled an unnatural amount of "usable carbon" to the surface, which, even if it becomes a part of a natural, stable, cycle, will leave us with a higher net amount of CO2 in the atmosphere. We can only go back to "natural" CO2 levels through unnatural means, unless we are willing to measure time on a geological time scale (the millions of years it will take to replace oil reserves from the swamps of today). So until then, we would still be dealing with an acidic ocean and a greenhouse atmosphere.

schiffern 10y ago
>We can only go back to "natural" CO2 levels through unnatural means Ok, but let's be careful not to exclude the middle here. "We got here by mining (an industrial activity), therefore we can't use plants in any part of a carbon sequestration chain (even one that also involves industrial activity)." Trying to use this argument as a blanket ban on plants becomes little more than an appeal to sympathetic magic. The only thing that matters is how much CO2 a technique can buffer (annual production x time constant), not whether or not it uses plants at any stage. Plants already have enormous annual production, but for economic/thermodynamic reasons it's hard for purely factory-based techniques to achieve sufficient scale. It becomes a money sink both up-front and operationally, respectively because A) factories are expensive, and B) hard thermodynamic constraints mean that it's at a fundamental competitive disadvantage compared to any typical [reminder: energy consuming] factory.
- lend000 10y ago
  > therefore we can't use plants in any part of a carbon sequestration chain (even one that also involves industrial activity) Not sure where your logic is coming from here. I am not saying we shouldn't use plants, but I am saying that even if we let forests retake "all the land," the stable CO2 level would be a bit higher than pre-industrialization, and it would stay that way for a long time until dead plant matter returned significant amounts of carbon to the deeper parts of the crust. Therefore, using other methods like the one in the article are necessary if we want to reduce CO2 levels.
  - schiffern 10y ago
    >let forests retake "all the land," I agree, a hands-off approach is insufficient. We would need to actively manage those forests (which is just as unnatural an activity btw), using intelligent design to improve upon the carbon density possible solely from blind natural processes. Big industrial thermodynamic sinks don't scale (and imo never will), simply because they can't economically compete with conventional energy consuming factories. An approach is needed that sequesters carbon while also producing sufficiently valuable goods to society (ie probably not rocks). Food is one possibility, and can avoid carbon futility since in perennial systems the annual food yield is a small percentage of the total carbon stored in the biome.

jrapdx3 10y ago

Plant nutrients are minerals, primarily nitrogen, potassium and phosphorus, in the base form of inorganic compounds or salts. When a plant dies it decomposes and the minerals are released and "recycled". Certainly that's how fossil carbon got to be stored in the first place (by growth of plants) so obviously the availability of nutrients in soils was naturally adequate to support the deposition of carbon. Carbonates are among the most common minerals on earth, particularly as calcium carbonate in its many forms. Calcium carbonate is slightly soluble in water and subject to degradation in acidic environments. While hardly an impervious carbon dioxide store, that's a benefit in that its easy degradation makes it an extremely useful mineral supporting essential infrastructure industries. IOW sequestering carbon as carbonates doesn't imply the CO2 is inaccessible but simply not reduced to an elemental or hydrocarbon form readily usable as an energy source. It's a trade-off between storage in an easier/quicker non-energy form or a protracted/difficult-to-implement energy-source form. Worth considering that in geological time the carbonate vs. carbon storage pools will probably "even out" since both are clearly mutable.