Ask HN: Is burning trees for energy a sustainable source of energy?

This week Michael Moore promoted a just released documentary "Planet of the Humans" which is free on YouTube.

At 55m40[1] seconds the following unsubstantiated claim is made by a spokesperson from the Energy Justice Network, "If we cut every tree in the US (sic and used it for energy) it would only power the US for a year". The implication is that tree-based biomass power is delusional and the film spends a lot of time showcasing the spread and support of this delusion.

Below is an analysis of the claim above and using data from high ranking Google search results:

Trees in the US: 300Billion, average tree diameter: 14 inches, weight of a 14inch diameter tree: 1 US ton, percent of tree that is water: 50%. Average energy use per capita US per year: 11MWh.

That leaves ~1000lbs of carbohydrates (cellulose) for fuel which is ~450,000 grams. At 4kcal per gram = ~17kJoules per gram ~=> 7.6GJ per tree => 2.1MWh per tree.

So that's six trees per person per year. Not the ~900 claimed by the film. Given that it takes ~60 years to regrow a tree to 14inch diameter, we can grow trees much faster (3x?) than we cut them assuming energy use in the US stays flat which it has for the last 10 years.

Cutting down trees at mass scale is an unsettling thought, but that is not a reason to reject a mostly carbon neutral fuel source if it is a plausible intermediary solution and arguably preferable alternate fuel source.

Can anyone comment on why biomass/tree burning is such a bad idea given the discussion above ?

[1]https://youtu.be/Zk11vI-7czE?t=3332