Dumping wet wood--even very, very wet wood in a lake and sinking it to the bottom does not "remove a massive amount of fresh water from the ecosystem". It does not remove any fresh water from the ecosystem.
Sinking wood into a lake won't remove the carbon unless you have a very deep lake, and you'd need many, many of them to have any impact on the CO2 levels whatsoever. The scale of wood that would need to be harvested is far beyond dropping some logs in a lake.
They need to go into a deep enough pit where the methane produced from anerobic breakdown won't reach the atmosphere.
The conditions that created the lignite coal and peat simply aren't that easily reproducible, especially with large volume of wood (rather than ferns over thousands and millions of years).
Sinking wood into a lake won't remove the carbon unless you have a very deep lake, and you'd need many, many of them to have any impact on the CO2 levels whatsoever. The scale of wood that would need to be harvested is far beyond dropping some logs in a lake.
They need to go into a deep enough pit where the methane produced from anerobic breakdown won't reach the atmosphere.
The conditions that created the lignite coal and peat simply aren't that easily reproducible, especially with large volume of wood (rather than ferns over thousands and millions of years).