[akvadrako]

If you think CO₂ is something we should reduce, the tree planting idea that's been talked about recently looks pretty good. Even if their costs are off by a factor of 10 it's still affordable; trees are an almost ideal carbon capture tool.

[john_moscow]

Planting trees will trap some atmospheric carbon in the lumber. However, once the lifespan of the tree is over and it starts rotting away, most of the carbon will get released back into the atmosphere, as it has been happening for millions of years.

In my opinion, it's not about planting the trees, it's about finding a way to turn the carbon trapped by them into something logistically and economically comparable to fossil fuels.

[akvadrako]

That's not a problem because new trees will grow in their place. Those trees can capture all the carbon humans have put into the atmosphere so far.

[john_moscow]

But that means that planting a tree binds a finite "tree lifetime" amount of carbon. So, in order to neutralize the worldwide carbon emissions using trees, we would need to keep planting them as long as we keep releasing CO2. So we would need to consume X square miles of agriculturally suitable land per year to simply keep the net emission at zero.

Now, IIRC, the energy density of oil is much higher than the one of lumber. I haven't done the calculation, but we might simply run out of suitable area way before any reasonable effect is reached. Don't forget that the logistics of tree planting will spend some CO2 as well, and given the finite CO2-per-planted-tree amount, it could be considerable.

Also if the trees have not spread naturally in the past millions of years in the area where you would want to plant them, there might be some ecological reasons to it. Hence, they may not survive long-term, or may get wiped by forest fires, or may require irrigation, fertilizers or other support that also produces CO2.

[akvadrako]

I agree it isn’t a complete answer to the question of how to return co2 levels to some level forever, but it has a good cost benefit ratio and could buy 50 years.

The study showed that the available land at a low cost, much less than alarmist propaganda, is enough to reverse all the co2 emissions so far.

[john_moscow]

That sounds interesting. As a numbers person, I would appreciate a link to the study and some basic TDLR napkin math.

[akvadrako]

This article contains a link to the paper: https://www.theguardian.com/environment/2019/jul/04/planting...