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Efficient method to capture carbon dioxide from the atmosphere

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Re: Efficient method to capture carbon dioxide from the atmosphere

#31

Post by cogman10 »

roflmaostc wrote: post #4
cyphertruck wrote: post #2

Economics rules everything. How much does this cost vs simply planting trees, when the value of harvesting the trees is included? Since tree farms are generally profitable, and wood is expensive, it seems this method is likely to be economically less efficient.

The problem is you cannot plant enough trees around the globe to offset our CO2 emissions. Also, a forest only absorbs CO2 while alive. Once it dies, it emits CO2 too. You would need to permanently store the wood somewhere (submerging in water, etc). Recent article: https://www.theguardian.com/environment/2025/nov/28/africa-f...

It's possible to permanently capture the carbon if you turn the wood into charcoal and ultimately bury or store that.

But left out to rot and yeah, the fungus and bacteria will ultimately consume the wood and release CO2 as a byproduct.

Re: Efficient method to capture carbon dioxide from the atmosphere

#32

Post by dheera »

gus_massa wrote: post #6
cyphertruck wrote: post #2

Economics rules everything. How much does this cost vs simply planting trees, when the value of harvesting the trees is included? Since tree farms are generally profitable, and wood is expensive, it seems this method is likely to be economically less efficient.

I agree. Plants are not very efficient (1% or 2%) but they include packaging the CO2 in a stable form. You can store the grain or wood for long periods of times. In this case, it looks like they get CO2 as a gas. It's cheaper because you don't have to use energy to undo the burning, but it's difficult to store for a long time. (I'm not sure if someone tried to make a fake underground bog in abandoned mine. Just fill…

> stable form

Not really, forest fires happen and then a few hundred of years of sequestered CO2 gets released back in an instant.

Organic material with oxygen gas floating around is not stable.

Sequestering carbon into the ocean might be a better strategy. Not flammable and not subject to stupid capitalism effects around land prices.

Re: Efficient method to capture carbon dioxide from the atmosphere

#33

Post by adammarples »

S3verin wrote: post #9
cyphertruck wrote: post #2

Economics rules everything. How much does this cost vs simply planting trees, when the value of harvesting the trees is included? Since tree farms are generally profitable, and wood is expensive, it seems this method is likely to be economically less efficient.

Planting trees is not effective since it takes decades to capture the carbon, but the next years are crucial for determining long term climate developments.

There is no carbon capture technology on earth that can be rolled out at a scale over the next few years that can compete with planting trees. Especially not one that has just been invented in one university. Ash grows 90cm per year, that's all carbon. Scale that to millions and billions.

Re: Efficient method to capture carbon dioxide from the atmosphere

#35

Post by OsrsNeedsf2P »

adregan wrote: post #26
roflmaostc wrote: post #4

Earlier quoted context omitted.

The problem is you cannot plant enough trees around the globe to offset our CO2 emissions. Also, a forest only absorbs CO2 while alive. Once it dies, it emits CO2 too. You would need to permanently store the wood somewhere (submerging in water, etc). Recent article: https://www.theguardian.com/environment/2025/nov/28/africa-f...

One little appreciated fact is that trees also respirate CO2 when they are cracking their stored sugars produced via photosynthesis. So they don’t sequester all of the CO2 that they consume.

It's little appreciated since tree growth still consumes CO2

Re: Efficient method to capture carbon dioxide from the atmosphere

#36

Post by HPsquared »

elil17 wrote: post #14

A better title would be "More efficient method to capture CO2 from the atmosphere." The method is not objectively efficient, but may be more efficient than other methods (solvents/sorbents) used for DAC.

Yes it's important to distinguish "efficiency getting closer to theoretical maximum" from "actually cheap and economically feasible".

Re: Efficient method to capture carbon dioxide from the atmosphere

#37

Post by yodon »

cyphertruck wrote: post #2

Economics rules everything. How much does this cost vs simply planting trees, when the value of harvesting the trees is included? Since tree farms are generally profitable, and wood is expensive, it seems this method is likely to be economically less efficient.

>Economics rules everything

Physics rules everything, once you start trying to run at scale.

The density of carbon per unit volume in solid materials of interest doesn't vary that much, whether you sink it in trees or in exotic materials like diamonds. That means you can calculate the volume of material required so sink a desired amount of atmospheric carbon.

If you want to have a measurable impact on the atmosphere, say dialing it back to 1980 CO2 levels, you're talking not about making a pile of stuff but about making a mountain range that's a mile high and hundreds of miles long.

Now figure out how many trucks you're going to need to move that much material from where your sequestering machine is to where your pile of stuff is.

Or if you want to dump that material in the ocean (which someone else will certainly object to), extend your calculation to figure out how many container trucks worth of material you need to dump into the ocean every hour to accomplish your atmospheric cleanup in whatever amount of time you choose (a decade? If it takes a century, that's not fast enough).

And finally think about surface to volume ratios. You're trying to sink it into a volume, but you can only get the gas into the volume through its surface, so the speed of your process is limited by surface area.

If you want to do it with trees, my personal spitball estimates are that you probably need to plant somewhere between the entire state of Connecticut and the entire state of Colorado to have the kind of impact one would want (there's more subtlety to tree calculations than one generally likes to admit, so feel free to come in with way higher numbers than I did).

Which brings us back to economics. If you have a well-managed forest of that size and scale, someone is eventually going to come along, maybe in 100 years, maybe in 500 years, and say "hey if we cut this down, we could burn the wood to heat our homes" and all that carbon goes back into the atmosphere, so you actually need to sink it into something that is energetically unfavorable for recovery, which means you also need to expand a huge amount of energy to sink the carbon into that energetically unfavorable state.

Re: Efficient method to capture carbon dioxide from the atmosphere

#39

Post by HPsquared »

cjbenedikt wrote: post #21
net01 wrote: post #7

What are the use cases of CO2 appart for making my Coke fizz?

You can combine it with H2 to produce synthetic fuels. Not ideal but could reduce fossil fuel use and hence new CO2 released.

Third ingredient missed out: lots of energy.

Re: Efficient method to capture carbon dioxide from the atmosphere

#40

Post by HPsquared »

jnsaff2 wrote: post #25
Detrytus wrote: post #3

This solves only part of the problem: it captures CO2 and can release it later. But you still need to figure out what to do with this CO2, how to turn it into something useful.

Stable storage would be limestone. To bring it down to pre-industrial levels it would mean that each person on earth would get a cube of 5 meters a side. IDK, build houses out of limestone like we have been doing for ages.

Roads maybe?
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