How efficient at sinking carbon are trees? As in, once the tree decomposes, the carbon gets largely released back into the air.
But yeah, "shitload of trees" + "some way of storing them at end of life that doesn't result in carbon back into the atmosphere" seems like a pretty solid plan.
Trees are some of the best carbon sinks there are. Far greater than any artificial ones we have so far. Trees last a long time, and when they die you can just plant more.
The real issue is that trees take a long time to get to their maximum sink potential, and require a LOT of water, nutrients, and excellent soil to get there.