4 ms·

CO2 makes up roughly 0.04% of the atmosphere. Handwaving, that means for every ton of carbon you remove you'd need to process at least 250 tons of air. To captu

by kec 4y ago

CO2 makes up roughly 0.04% of the atmosphere. Handwaving, that means for every ton of carbon you remove you'd need to process at least 250 tons of air. To capture humanities current yearly output, you'd need to process over 7 Trillion tons of air per year... the scales just don't make sense.

tito 4y ago
Yes the scales are hard to fathom. And we've been doing that for about 100 years. It's not pretty, but there's a trillion tons of excess carbon dioxide in the atmosphere. We need to stop emitting as fast as possible and remove the rest. Every gallon of gasoline burned adds 20 pounds of carbon dioxide to the atmosphere.
dane-pgp 4y ago
> 7 Trillion tons of air per year Thanks for running these numbers. I have a few more calculations to add which support what you're saying. Let's consider a fairly standard industrial air compressor[0] which has a rating of "CFM at 90 PSI: 18.1". This means 18.1 cubic feet of air per minute. A cubic foot of air "weighs approximately 0.0807 lbs" according to an expert answer on PhysLink[1]. Using `units`, then: You have: 18.1 * 0.0807 lbs / minute You want: tonnes / year * 348.46671 So 7 trillion tonnes would require about 20 billion times more air movement than one of these compressors. [0] https://ingersollrandcompressedair.com/ss5l5-single-stage-air-compressor.html https://ingersollrandcompressedair.com/ss5l5-single-stage-ai... [1] https://www.physlink.com/education/askexperts/ae650.cfm https://www.physlink.com/education/askexperts/ae650.cfm
- chmod775 4y ago
  Can you explain how the comparison to air compressors is at all relevant here? Those move a tiny amount of air. Your typical tiny PC fan can move 70 CFM, so about 3.5 times the amount of your industrial air compressor. A typical 30 inch fan can easily move 10000 CFM. Here's what I could find on how the technology works: > While a few different techniques have been developed, the most common involves industrial-scale fans that transmit ambient air through a filter. This latter component then uses a chemical adsorbent (which holds molecules in the form of a thin film on its surface) to produce a pure, storable stream of carbon dioxide. https://singularityhub.com/2019/08/23/the-promise-of-direct-air-capture-making-stuff-out-of-thin-air/ https://singularityhub.com/2019/08/23/the-promise-of-direct-...
  - dane-pgp 4y ago
    I wasn't sure that an air compressor is a good comparison, but I thought that a typical fan was also not a good comparison because the air it moves doesn't have much resistance to it. Presumably if you're trying to force air through a process that separates out CO2, there will be more back pressure than just blowing into the open air. Assuming, though, that the process could keep up with the air flow that 100 of those 30 inch fans could produce (if we imagine a shipping container being about 10 feet wide by 10 feet tall) then that's 1 million CFM, which is 50,000 times my original comparison, so only 400,000 units would be needed. To pick some more arbitrary numbers, if 100 factories were built, each producing one unit per week, that would take 4000 weeks or roughly 80 years. Feel free to consider more realistic numbers, which may lead to different conclusions.
    - chmod775 4y ago
      They give the following numbers: 80 containers, 36000 tons of CO2/year, 90% efficiency. We also know that there's roughly 0.75g of CO2 in a m^3 of air. So we do some math, converting to a proper system of measurement and back to lalaland units using 907.2 kg in a US ton and 35.315 cubic feet in a m^3: 36000 [tons of CO2/year/80 containers] / 80 [containers] * 907.2 [kg/ton] * 1000 [grams/kg] / 0.75 [g/m^3] / 90% [efficiency] / (365 * 24 * 60) [minutes/year] * 35.315 [cubic feet/m^3] = 40636.4383562 [cubic feet / minute / container] So one of their containers filters about 40000 CFM at 90% efficiency. Was any of this helpful? Not at all. Just looking at tons of CO2 produced vs. captured would have given us the same picture, and that's the numbers we started with. > if 100 factories were built, each producing one unit per week That's a tiny amount at planet scale and also incredibly slow. Humanity builds around 150,000 cars every single day. Some factories crank out a thousand a day. And I'm going to go out on a limb and claim that a car is probably a more complex product.

by kec 4y ago

tito 4y ago

Yes the scales are hard to fathom. And we've been doing that for about 100 years. It's not pretty, but there's a trillion tons of excess carbon dioxide in the atmosphere. We need to stop emitting as fast as possible and remove the rest. Every gallon of gasoline burned adds 20 pounds of carbon dioxide to the atmosphere.

dane-pgp 4y ago

> 7 Trillion tons of air per year Thanks for running these numbers. I have a few more calculations to add which support what you're saying. Let's consider a fairly standard industrial air compressor[0] which has a rating of "CFM at 90 PSI: 18.1". This means 18.1 cubic feet of air per minute. A cubic foot of air "weighs approximately 0.0807 lbs" according to an expert answer on PhysLink[1]. Using `units`, then: You have: 18.1 * 0.0807 lbs / minute You want: tonnes / year * 348.46671 So 7 trillion tonnes would require about 20 billion times more air movement than one of these compressors. [0] https://ingersollrandcompressedair.com/ss5l5-single-stage-air-compressor.html https://ingersollrandcompressedair.com/ss5l5-single-stage-ai... [1] https://www.physlink.com/education/askexperts/ae650.cfm https://www.physlink.com/education/askexperts/ae650.cfm

chmod775 4y ago
Can you explain how the comparison to air compressors is at all relevant here? Those move a tiny amount of air. Your typical tiny PC fan can move 70 CFM, so about 3.5 times the amount of your industrial air compressor. A typical 30 inch fan can easily move 10000 CFM. Here's what I could find on how the technology works: > While a few different techniques have been developed, the most common involves industrial-scale fans that transmit ambient air through a filter. This latter component then uses a chemical adsorbent (which holds molecules in the form of a thin film on its surface) to produce a pure, storable stream of carbon dioxide. https://singularityhub.com/2019/08/23/the-promise-of-direct-air-capture-making-stuff-out-of-thin-air/ https://singularityhub.com/2019/08/23/the-promise-of-direct-...
- dane-pgp 4y ago
  I wasn't sure that an air compressor is a good comparison, but I thought that a typical fan was also not a good comparison because the air it moves doesn't have much resistance to it. Presumably if you're trying to force air through a process that separates out CO2, there will be more back pressure than just blowing into the open air. Assuming, though, that the process could keep up with the air flow that 100 of those 30 inch fans could produce (if we imagine a shipping container being about 10 feet wide by 10 feet tall) then that's 1 million CFM, which is 50,000 times my original comparison, so only 400,000 units would be needed. To pick some more arbitrary numbers, if 100 factories were built, each producing one unit per week, that would take 4000 weeks or roughly 80 years. Feel free to consider more realistic numbers, which may lead to different conclusions.
  - chmod775 4y ago
    They give the following numbers: 80 containers, 36000 tons of CO2/year, 90% efficiency. We also know that there's roughly 0.75g of CO2 in a m^3 of air. So we do some math, converting to a proper system of measurement and back to lalaland units using 907.2 kg in a US ton and 35.315 cubic feet in a m^3: 36000 [tons of CO2/year/80 containers] / 80 [containers] * 907.2 [kg/ton] * 1000 [grams/kg] / 0.75 [g/m^3] / 90% [efficiency] / (365 * 24 * 60) [minutes/year] * 35.315 [cubic feet/m^3] = 40636.4383562 [cubic feet / minute / container] So one of their containers filters about 40000 CFM at 90% efficiency. Was any of this helpful? Not at all. Just looking at tons of CO2 produced vs. captured would have given us the same picture, and that's the numbers we started with. > if 100 factories were built, each producing one unit per week That's a tiny amount at planet scale and also incredibly slow. Humanity builds around 150,000 cars every single day. Some factories crank out a thousand a day. And I'm going to go out on a limb and claim that a car is probably a more complex product.