51–60 of 267 posts
1. Plant trees 2. Cut down trees 3. Sink trees to the bottom of a great lake
If you do the math, this essentially doesn't work out. :( Trees are far too slow, even if you have a good way to lock up the carbon once the trees capture it. For an intuitive understanding, consider: Our surplus of CO2 comes (mostly) from burning fossil fuel that took millions of years for the original plant life to accumulate.
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There is a non-negotiable entropy cost associated with removing CO2 from the atmosphere: you need to either pump it, so P0 = 0.0004 atm; if P1 = 5 atm (liquid CO2) then E = M R T ln(5 / 0.0004) / 44 => E/M = about 500 J/kg, or you need to absorb it chemically, which requires a chemical with a vapor pressure of CO2 I expect that we will eventually develop technology for CO2 extraction, but it's not going to be easy or…
How did you calculate 500 J/kg? If you spend energy to pressurize gas, you can get it back when restoring the original pressure, right?
Also, you can't restore the initial pressure because at the initial pressure the CO2 takes up a whole atmosphere of space!
I empathize with people who are trying to help by reducing their footprint. Though I fear it'll all be in vain when a machine is invented that can suck a lifetime's worth of frugality out of the air in a fraction of a second.
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Yes, but forests capture carbon quickly until the average age of the trees starts increasing. So zero to 50 years is good, but after that things really slow down. The amount of wood becomes relatively constant. So slowly, very slowly leaves fall/get eaten by bugs, break down, and get absorbed by new trees. But there is a net gain, just a very slow one. Then things like continents collide, mountain ranges come and go,…
Consider the scale of what you're describing now: cutting down and burying all trees on earth every 30 years. We could certainly _burn_ all of them every 30 years, but that wouldn't help. The figure you need is the marginal capture after the emissions from the process. Wikipedia says our current emissions from fossil fules and cement production is estimated at 10GtC (not absurd compared to your numbers, since you cou…
Certainly it wouldn't likely be 100% every 30 years, but 3.3% every year. As far as geo-engineering significant climate change this looks like one of the easier approaches actually.
Of course it's much more feasible with the continued migration towards solar, wind, hydro, and related.
Sadly I think Nuclear got the short end of the stick for mostly political reasons. Things like putting a nuke plant in a known tsunami zone, without protection, because of political lobbying.
So all in all, agreed.
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> There is no magic powder we can mix that'll cause CO2 to precipitate out of the atmosphere and fall to the ground like snow; it's a grueling energy intensive process to filter that out of the air around us. Why not to cool down air so that CO2 would fall off? Cooled air can be used for pre-cooling incoming "dirty" air stream?
I had the same thought as well. It's an option, but the energy required to cool air to the precipitation point of CO2 (-79C) is pretty large, and the cooling process itself will produce greenhouse gas, so you end up with a pretty small return.
You would use cooled separated products to pre-cool incoming stream of "dirty" air. CO2, having low concentration, won't fall off at -79C (or we'd have that effect in Antarctica today), but if you go to ~-140C, you'll have some results.
Why cooling process will produce greenhouse gas? You'd use energy from "green" sources to compensate for required expenses.
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(I wrote the post) This is good feedback that this is buried in the appendix -- I pulled that section up and made it inline with the flow of the post. Does that help?
Section "How to take CO2 out of the sky" > Briefly: there are plant-based, mineral-based, and chemical options. Where are cryocooling-based options?
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How did you calculate 500 J/kg? If you spend energy to pressurize gas, you can get it back when restoring the original pressure, right?
I integrated the PV curve at constant temperature, so P = nRT/V and dW = P dV = nRT dV/V. Then we can write W = nRT log(V0 / V1) = nRT log(P1 / P0), and n = M / 44, the molar mass of CO2. Also, you can't restore the initial pressure because at the initial pressure the CO2 takes up a whole atmosphere of space!
I didn't get your last line though. I assume you compress "dirty" air.
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Section "How to take CO2 out of the sky" > Briefly: there are plant-based, mineral-based, and chemical options. Where are cryocooling-based options?
I'm not sure what this is? You might be thinking of solar radiation management or other "geoengineering" techniques to try to make the earth shiner and reflect more sunlight, making us cooler at a constant CO2 concentration. Theres a ton of interesting topics within that to write about, I mention it briefly as "things I didn't include"
In terms of geoengineering, it seems like these two are our best bets:
https://en.wikipedia.org/wiki/Stratospheric_aerosol_injectio... to prevent runaway warming. As a side effect, the dispersed sunlight helps plant growth. Solar power generation is negatively impacted though.
https://en.wikipedia.org/wiki/Iron_fertilization to sequester CO2. As a side effect, marine life and fish stocks would be boosted by the greater plankton food supply.
In any case it seems absolutely bonkers that we are still selling fossil-fueled-vehicles and building coal power plants when we clearly have the technology and capability to replace both of them.