I've thought about it myself and the best answer that comes to mind is clear-cutting entire forests, tossing that biomass down a mineshaft, and replanting to start the process over again. All this talk of planting trees removes atmospheric carbon, but until it's out of the system entirely we're one forest fire away from wiping out decades of carbon removal.
You might be interested to learn of Climeworks if you're looking for a more reliable way to remove emissions than planting trees (which is, indeed, mostly not really working as well as too slow).
This looks a lot like what I was thinking of. They don't provide much information about their extracting filter, but after the CO2 is extracted it is compressed into water creating carbonic acid, then injected it into a suitable basalt formation with an impermeable cap so that carbonate salts could form[1]. They claim all the injected CO2 could become carbonates in under 10 years[2].
If this works like they say, then it's cause for hope.
I've seen those designs but never looked too deep into them. Maybe I've seen too many of the 'collect water from thin air' devices and become cynical. If their 90% efficiency is counting manufacturing and power costs then it could be worthwhile in cities and other areas with high atmospheric carbon levels. Same problem as the trees though, if we leave them out or use them for something they'll break down and be back in the carbon cycle. However we collect the carbon we need to lock it in place.
I would guess that 90% does not include R&D and is only about the general production costs like from manufacturing and building. So with scaling up (if they don't do R&D but just add a plant) it should be 90%.
It's a good question though, perhaps worth asking them.
10 Gigatonnes a year at a stable rate with an initial large bonus amount for the first decade or so. More if you bury more than the core logs. Burial isn't as bad as needing old mineshafts either, a small, deep pit something like 25m square is enough to bury 1km square of logged materials.
There are still issues with this proposal such as the potential for land degradation and biodiversity loss but good potential for mitigating these things as well. The main sells to me are that a) all the tech to get started today exist and are widely deployed and b) it results in carbon being re-interred in a fairly direct reversal of what we've been doing to dig it out.
Do not clear-cut forests. You will obliterate the biome that is the understory. It's like giving yourself a haircut and removing your scalp down to the skull.
Okay, good point. Maybe turning the entire Amazon into a reverse coal mine would do more harm than good. I still think we need long-term carbon storage and using pre-existing timber seems like a good first step. If there's a better capture solution in terms of tonnes/KWH/year go with that, but tossing trees down a hole is a good example.
