Is there a fundamental reason you can't treat the wood to make it non flammable and non digestible, and just stack them in big piles somewhere?
Edit: Hope yall realize this was sarcasm and none of these options would sequester the carbon long term.
Then sink them in the ocean.
Aside from weighing it down enough to stop floating, of course.
Edit: Hope yall realize this was sarcasm and none of these options would sequester the carbon long term.