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Seriously, everyone suggestions a crackpot idea for sequestering carbon should do the basic arithmetic for how much annual human emissions are (40 billion metri

Seriously, everyone suggestions a crackpot idea for sequestering carbon should do the basic arithmetic for how much annual human emissions are (40 billion metric tons). I like https://blogs.scientificamerican.com/life-unbounded/the-crazy-scale-of-human-carbon-emission/ https://blogs.scientificamerican.com/life-unbounded/the-craz... for the perspective it offers: current human CO2 emissions are equivalent to the entire continent of Africa being covered in coniferous forest and burning to the ground in forest fires, every year. If there is any way we save ourselves from this, it's from reduced emissions.

OscarCunningham 8y ago
How is that possible? Surely the volume of fossil fuels being burnt isn't remotely comprable to the volume of that forest.
- ksdale 8y ago
  I don't know if the math is correct, but oil and coal are far more energy dense than wood which may account for the discrepancy.
  - atomic77 8y ago
    This would have been my explanation too, but to my surprise, wood is only about 1/3 of the energy density of diesel fuel. I'm not sure why i expected it to be an order of magnitude difference. https://en.wikipedia.org/wiki/Energy_density#Energy_densities_of_common_energy_storage_materials https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...
    - ksdale 8y ago
      Interesting! I too, would have expected a much larger difference.
  - teraflop 8y ago
    I think the math is somewhat wrong. The original source link for that "4.81 metric tons per acre" number is broken, but it appears to be talking about tons of carbon, not CO2 (which is roughly 27% carbon by mass). The article underestimates the amount of CO2 released by forest fires by roughly a factor of 4, and therefore overestimates the required land area by the same factor. It's still a pretty staggeringly huge amount of land, though.
  - LeifCarrotson 8y ago
    > oil and coal are far more energy dense than wood In addition, a block of wood is a lot more dense than an acre of forest, which is a lot more dense than the difference in carbon content between an acre of forest and an acre of charred burned forest. While reading the article, I mentally substituted "a forest the area of Africa" with "an oil tank the size of Africa and as deep as a forest is tall", which is clearly unreasonable. And they mention "4.81 tons" in passing - a ton is a lot, and surely 4.81 tons is a huge volume of gas, but how much? We need to run the numbers. Crude petroleum has a density of about 0.8 g/cc = 0.8 ton/m^3 and a carbon composition of 85%. 4.81 tons of carbon x (1 kg crude / 0.85 kg carbon) x (1 m^3 / 0.8 ton crude) = 7 m^3 of crude. Looking it up, a typical tractor-trailer tanker truck might carry 40 m^3 of crude...so this can be stated as mankind burning a yearly volume of one truckload of fuel for every 6 acres in Africa, which is a lot more believable. Going back to the oil-per-acre analogy, an acre is a little more than 4000 square meters, so (assuming it's all oil - ignoring coal, natural gas, and other CO2 producers like, I don't know, human-initiated forest fires) this is a film of oil over the continent of Africa 1.7mm deep. That's a lot more believable than imagining a towering petroleum forest.
    - OscarCunningham 8y ago
      Thanks for doing the maths! That gives an intuition more in line with what I would have suspected. Equivalently it's the anount of oil needed to cover Costa Rica to a depth of 1m. Still quite a lot!
- dexen 8y ago
  Living trees are only about 15...18% carbon by weight. [1] Other greenery is probably even less, given that significant proportion of trees' mass is in the trunk as cellulose (some 50% of it)[2], which is about 44% carbon. On the other hand, CO2 is only about 27% carbon (also by weight). [3] [1] https://web.extension.illinois.edu/askextension/thisQuestion.cfm?ThreadID=19549&catID=192&AskSiteID=87 https://web.extension.illinois.edu/askextension/thisQuestion... [2] https://www.britannica.com/science/cellulose https://www.britannica.com/science/cellulose, https://en.wikipedia.org/wiki/Cellulose https://en.wikipedia.org/wiki/Cellulose [3] mostly O16, mostly C12, 12 / (12+16+16)
zamalek 8y ago
> should do the basic arithmetic North America is sitting at around 6.5Gt p/a, three [experimental] plants sequester 0.55Mt p/a. You'd need 35000 plants in just North America. 216000 plants world-wide.
daveFNbuck 8y ago
Concrete production accounts for about 5% of CO2 emissions, so this does reduce emissions.
- hinkley 8y ago
  And turning a source into a sink is better than stopping. Assuming that this process takes more energy than the current process, you could still be looking at a target of, say, 8% reduction of anthropogenic carbon.
logfromblammo 8y ago
How about this? Create an Africa-sized algae bloom with iron and urea fertilization, in the middle of the waste-plastic zone in the north Pacific gyre. Krill eat the algae. Baleen whales eat the krill and the plastic. Then we train/drug the older whales, so they swim far away from the continental shelf, dive deep, and commit suicide on the bottom. We solve two problems with one stroke. (Then the gorillas just freeze to death when winter comes.) ~ I think the only workable schemes for active carbon sequestration involve artificially weathering calcium and magnesium containing oxide rocks to expose more surface area, and turn them into carbonates. That has to be done on a scale that far exceeds the entire global demand for concrete. Like building a 1:1 scale replica of the white cliffs of Dover, every year, for no economically exploitable reason. Grind up olivines, pyroxenes, calcium-rich plagioclases, periclases, perovskites, spinels, etc. into sand, eventually get chalk.
- Reason077 8y ago
  Algae/phytoplankton tend to sink to the bottom of the ocean and become a long-term carbon store when they die anyway. That's how much of the oil and gas we're burning today was formed in the first place. No need for elaborate training of whales :)
roryisok 8y ago
Reduced emissions are not enough. Even if we got to zero emissions worldwide in the next 20 years (impossible), the excess carbon in the atmosphere already needs to be dealt with. There are greenhouses gases coming from the permafrost. The forest carbon sinks we depend on are being reduced every year by logging and wildfires. The ocean is heating up and probably becoming less effective as a carbon sink. Basically, not only are we putting out more carbon per year, we're also removing less of it. We need more crackpot schemes, and we need them yesterday. Not instead of emission reduction but in conjunction with it

OscarCunningham 8y ago

How is that possible? Surely the volume of fossil fuels being burnt isn't remotely comprable to the volume of that forest.

ksdale 8y ago
I don't know if the math is correct, but oil and coal are far more energy dense than wood which may account for the discrepancy.
- atomic77 8y ago
  This would have been my explanation too, but to my surprise, wood is only about 1/3 of the energy density of diesel fuel. I'm not sure why i expected it to be an order of magnitude difference. https://en.wikipedia.org/wiki/Energy_density#Energy_densities_of_common_energy_storage_materials https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...
  - ksdale 8y ago
    Interesting! I too, would have expected a much larger difference.
- teraflop 8y ago
  I think the math is somewhat wrong. The original source link for that "4.81 metric tons per acre" number is broken, but it appears to be talking about tons of carbon, not CO2 (which is roughly 27% carbon by mass). The article underestimates the amount of CO2 released by forest fires by roughly a factor of 4, and therefore overestimates the required land area by the same factor. It's still a pretty staggeringly huge amount of land, though.
- LeifCarrotson 8y ago
  > oil and coal are far more energy dense than wood In addition, a block of wood is a lot more dense than an acre of forest, which is a lot more dense than the difference in carbon content between an acre of forest and an acre of charred burned forest. While reading the article, I mentally substituted "a forest the area of Africa" with "an oil tank the size of Africa and as deep as a forest is tall", which is clearly unreasonable. And they mention "4.81 tons" in passing - a ton is a lot, and surely 4.81 tons is a huge volume of gas, but how much? We need to run the numbers. Crude petroleum has a density of about 0.8 g/cc = 0.8 ton/m^3 and a carbon composition of 85%. 4.81 tons of carbon x (1 kg crude / 0.85 kg carbon) x (1 m^3 / 0.8 ton crude) = 7 m^3 of crude. Looking it up, a typical tractor-trailer tanker truck might carry 40 m^3 of crude...so this can be stated as mankind burning a yearly volume of one truckload of fuel for every 6 acres in Africa, which is a lot more believable. Going back to the oil-per-acre analogy, an acre is a little more than 4000 square meters, so (assuming it's all oil - ignoring coal, natural gas, and other CO2 producers like, I don't know, human-initiated forest fires) this is a film of oil over the continent of Africa 1.7mm deep. That's a lot more believable than imagining a towering petroleum forest.
  - OscarCunningham 8y ago
    Thanks for doing the maths! That gives an intuition more in line with what I would have suspected. Equivalently it's the anount of oil needed to cover Costa Rica to a depth of 1m. Still quite a lot!
dexen 8y ago
Living trees are only about 15...18% carbon by weight. [1] Other greenery is probably even less, given that significant proportion of trees' mass is in the trunk as cellulose (some 50% of it)[2], which is about 44% carbon. On the other hand, CO2 is only about 27% carbon (also by weight). [3] [1] https://web.extension.illinois.edu/askextension/thisQuestion.cfm?ThreadID=19549&catID=192&AskSiteID=87 https://web.extension.illinois.edu/askextension/thisQuestion... [2] https://www.britannica.com/science/cellulose https://www.britannica.com/science/cellulose, https://en.wikipedia.org/wiki/Cellulose https://en.wikipedia.org/wiki/Cellulose [3] mostly O16, mostly C12, 12 / (12+16+16)

zamalek 8y ago

> should do the basic arithmetic North America is sitting at around 6.5Gt p/a, three [experimental] plants sequester 0.55Mt p/a. You'd need 35000 plants in just North America. 216000 plants world-wide.

daveFNbuck 8y ago

Concrete production accounts for about 5% of CO2 emissions, so this does reduce emissions.

hinkley 8y ago
And turning a source into a sink is better than stopping. Assuming that this process takes more energy than the current process, you could still be looking at a target of, say, 8% reduction of anthropogenic carbon.

logfromblammo 8y ago

How about this? Create an Africa-sized algae bloom with iron and urea fertilization, in the middle of the waste-plastic zone in the north Pacific gyre. Krill eat the algae. Baleen whales eat the krill and the plastic. Then we train/drug the older whales, so they swim far away from the continental shelf, dive deep, and commit suicide on the bottom. We solve two problems with one stroke. (Then the gorillas just freeze to death when winter comes.) ~ I think the only workable schemes for active carbon sequestration involve artificially weathering calcium and magnesium containing oxide rocks to expose more surface area, and turn them into carbonates. That has to be done on a scale that far exceeds the entire global demand for concrete. Like building a 1:1 scale replica of the white cliffs of Dover, every year, for no economically exploitable reason. Grind up olivines, pyroxenes, calcium-rich plagioclases, periclases, perovskites, spinels, etc. into sand, eventually get chalk.

Reason077 8y ago
Algae/phytoplankton tend to sink to the bottom of the ocean and become a long-term carbon store when they die anyway. That's how much of the oil and gas we're burning today was formed in the first place. No need for elaborate training of whales :)

roryisok 8y ago

Reduced emissions are not enough. Even if we got to zero emissions worldwide in the next 20 years (impossible), the excess carbon in the atmosphere already needs to be dealt with. There are greenhouses gases coming from the permafrost. The forest carbon sinks we depend on are being reduced every year by logging and wildfires. The ocean is heating up and probably becoming less effective as a carbon sink. Basically, not only are we putting out more carbon per year, we're also removing less of it. We need more crackpot schemes, and we need them yesterday. Not instead of emission reduction but in conjunction with it