I don't think it's necessarily unreasonable. As I understand it, the lumber industry has optimized the ability to grow massive amounts of fast growing pine as quickly as possible. So this isn't suggesting that we start clearcutting forests, it's suggesting that we start growing massive amounts of lumber with the explicit purpose of converting it to charcoal and burrying it.
it actually is a bad idea if you look into the details
trees aren't just carbon, they are bio mass/nutrition
and if you constantly remove bio mass you sooner or later run into issues
(Which we already do in some places, e.g. when over using fields (see US dust storms), or with some managed Forrest getting increasingly more unstable not just because of warmed climate but also because of removing dead treas leading to an interruption of the natural nutrient recycling (and insect habitats) leading to Nutrition deficiency in the long run.)
but we do have working carbon removal technologies, they are just not cheap
hence why you want companies to pay for them, it gives them a huge reason to reduce emissions instead
It is such an unreasonable idea! Ignoring the loss of biomass (and the fact that there would be no way to implement this scheme without providing a very unwelcome financial incentive to cut down trees wherever they are found), you'd use as much CO2 in the machinery required to cut the trees down and dig a big hole! Unless you're suggesting we do it all by hand? In which case, the picture of a crazed, doomsday cult is complete. I suppose at least it involves less murder than the Aztecs and their sacrifices.