The carbon stored in a tree is proportional to its weight, about half its dry weight is carbon [https://scied.ucar.edu/sites/default/files/images/long-conte...].

Also in all those discussions of processes(!) I find people even here seem to be looking at points in time only, and usually at the start of the process. That also includes the issue of looking at just one tree instead of a forest. When you look at the whole system individual tree life cycle doesn't matter any more. Some trees grow old and die or are harvested (what happens?), others grow in their place, overall the forest remains at a pretty stable and fixed weight. Unless you find trees that keep growing for miles and miles higher for thousands of years.

Look at total biomass, not at tree life cycles! The equations at that point of a mature forest are balanced. The whole forest stores a fixed amount and that's it. As long as we keep bringing carbon from very ancient forests back out of the earth, it does not matter how many forests there are. You will only get a temporary dip.

This whole thing is ridiculous: Even if we decided to bury grown trees deep underground to remove their carbon from the surface forever - why not save the huge effort (and the energy that process needs which again has to be fed somehow - with even more fossil fuels for quite some time to come) and simply leave the ancient forests where they are (deep underground)?

You can plant trees as much as you like, as long as we continue to bring up carbon from underground it is useless - apart from a temporary (small) dip. The above-ground forests will never be big enough to compensate for the below-ground forests being brought back up.

A quick search shows links and links of opinion and "studies" all about "we can store carbon underground!" Well, wait, what?? I don't get it. - it's already (down) there!! Earth did just that a long time ago! Just stop bringing it up, then you don't need to find ways to get it back down, which according to the laws of physics is a net-negative process. For the same amount somehow stored underground we need far more for the energy to do so, as long as we rely on carbon for energy (which won't change any time soon at scale across the world). And if we don't need the carbon for energy we won't bring it up any more (about three quarters of oil is used for energy or heating, an even higher share of natural gas and coal).

I really don't understand the discussion at all. It seems like a great distraction, all those studies and headlines and discussions about storing CO2 underground? For the reason mentioned. After you get it out and burn it (i.e. turned it into CO2), you will need even more of it to get the energy to get it back down where it already was to begin with. Even if we would have 100% solar/wind, the whole scenario does not sound very useful to me at the imagined scale. Even using it as temporary energy store/source for energy demand when wind/solar are not available should be done with what already is above ground, or if it involves a blow-ground cycle it should be one far smaller than the current extraction and the imagined reburying.

Having more forests is wonderful for many reasons (even though at this point vast areas are removed - https://www.livescience.com/27692-deforestation.html). However, the attention it gets as some sort of "solution" for global CO2 levels amazes me (in combination with the fact I just linked even more - stopping what we are doing would be soooo much more impactful, both destruction of current and previous forests above as well as underground).