And scale is really the issue. All the world's forests combined currently absorb about 20% of CO2 humans currently emit. To go neutral, you're looking at planting around 12 trillion trees. Worse still, about 30% of Earth's land surface area are already covered by forests, so you can't simply expand the forests to get the required carbon capture.
The only realistic way to achieve 100% carbon capture by biological means would be to seed algae blooms in the ocean, which for short term carbon uptake would work pretty well, but when that algae dies it is way harder to prevent it from decomposing, meaning you don't get long term sequestration. Further, you are talking about terraforming-level changes to marine environments all over the world. Beyond the catastrophic effects that can have on other species, the full effects of what that might do to us are impossible to fully predict.
Artificial carbon capture might have higher capital costs since the equipment is not self replicating, but it can be orders of magnitude more efficient in terms of energy, CO2 capture rate, and land use requirement.
Again, this doesn't really matter since this wouldn't physically fit on the planet.
Other organisms can be used as well, but again you need to sequester the carbon.
https://psci.princeton.edu/tips/2020/11/3/cement-and-concret...
We would need to consume timber at about 1000 times the current rate for timber demand to equal the necessary tree planting rate for carbon capture.
I’m thinking about salt as an example. It is a by-product of many industries and cost have gone down a lot since the industrial revolution. I’m imagining that today’s salt demand is heftily induced as a result. I mean, it is cheap enough to spray on highways to melt the ice.
Trees tend to stop growing after about 150 years, so trees left standing longer than that will delay releasing the CO2 they've already captured, but will not continue to capture carbon. Indeed you probably want to cull trees before their growth rates start to decline around the 100 year mark to maximize your carbon capture rate.
Eg https://carbonfarmersofaustralia.com.au/carbon-farming/soil-...
Of course this is a crude estimate, not all trees are equal and planting trees in such large numbers would undoubtedly have other effects, but no matter what you are talking about an absurdly large number.
Haber-Bosch traditionally has relied on large fossil fuel inputs, but it's possible to get the hydrogen from the process via hydrolysis of water, powered by renewable energy (or nuclear), and use electricity instead of fossil fuels to run the high-temperature, high-pressure catalytic reaction (H2 + N2 -> NH3).
The same arguments apply to carbon capture and fixation: you can do it in an industrial setting, for example the North African desert (which doesn't support much plant growth), you could use seawater as the hydrogen source and plentiful sunlight and PV/concentrated thermal for electricity to drive the carbon capture (fans etc.) and the analogous version of Haber-Bosch (Fischer-Tropsch) for CO2 - CO + H2 -> hydrocarbons.
Even restoring all the forests that have existed pre the industrialization will not help much, because it only resets a small part of the emissions. All fossil fuel burned is still in the atmosphere, likewise increasingly more methane.
Additionally, it's easily used for green washing.
Plant trees -> Yai carbon is offset, can emit like before; then trees are cut down, burn or don't even grow, and the next company can plant trees at the same land
Would be interesting to try it IRL, as you'd potentially have lots of different approaches being tried vs some kind of top down solutions
> Specifically, a coordinated global round of unconventional quantitative easing through the issuance of a complementary currency, called the carbon coin, to be issued in proportion to the mass of carbon that is mitigated.
That is just nuts.
The result would be like every other time money is printed: Wealth flows to those that know how to game the system while inflation erodes the wealth and income of normal people.
Beyond trees, we should also be growing algae and other plant mater to sequester more carbon and produce oils, sugars and other useful ingredients for our lives. This can be done at sea or in areas where water is scarce and normal vegetation grows poorly.
Or a jet is more efficient than a blackpoll warbler at migrating across the Atlantic.
Or a knife is more effective than a claw at cutting through things.
In a world full of examples, why should carbon capture be any different?
Trees weren't designed to capture carbon, so there's every reason to think something which is can do a better job.
They weren't, but just like jets and knives require a lot of human labor to manufacture in mass quantities, any artificial solutions are likely to be the same for a while. Trees, on the other hand, are fully automatic, self-replicating machines that require almost no human labor (perhaps for initial plantings in a place where they don't already grow, or don't grow in sufficient quantities with their natural self-replication). Basically, if you plant a bunch of tree saplings somewhere suitable, you can leave it alone for 300 years and come back and find a forest.
Once we are on renewable energy, the efficiency argument will make it undeniably efficient.
This drought is teaching us that "just grow a tree" is not always viable, and the resulting water crisis is also begging the question "with who's water?"
Irrigation is about 95%.