dry wood is mostly CO2
FWIW, you appear to be confusing two claims:
“Most mass in trees was previously part of the surrounding air”
“dry wood is mostly CO2”
From a US Forest Service website:
Wood is best defined as a three-dimensional biopolymer composite composed of an interconnected network of cellulose, hemicelluloses and lignin with minor amounts of extractives, and inorganics. The major chemical component of a living tree is water, but on a dry weight basis, all wood cell walls consist mainly of sugar-based polymers (carbohydrates, 65-75%) that are combined with lignin (18-35%).
https://research.fs.usda.gov/treesearch/42245
“Trees are mostly made of air” (direct quote from post title) is more clickbait headline than scientific fact.
How about posting on local subreddits, Facebook groups, etc.? Reddit posts can easily get tens of thousands of views. The leverage seems far higher than canvassing.