While all plants do have tannins in their makeup nothing I have on plant nutrition says they take up tannins from soil. Using that tannin rich water in the compost will be okay and using it to water trees and shrubs is okay.

kimmq is kimmsr

I poured some pure tannin water around the perimeter of a new weed-compost pile, hoping it would kill weed seeds... The liquid smells, but more like drowned-worm smell than anaerobic. I suppose there's overlap there.... Airstones sound great. I take it they run on electricity though, which I can't see running outdoors where it's needed. And are they easily clogged by detritus? Would I have to filter the tannin water before using one?
I was hoping you'd weigh in, with your paper experience, kimm.

Any tannins that might have been in the wood would have been removed during the pulping process along with the lignin. All the paper industry wants from the material used to make paper is the cellulose fibers. I don't recall that tannins were of much interest in class discussions and the textbooks are long gone.

kimmq is kimmsr

kimmq, I meant that I was hoping you'd weigh in and you did.

people who grow orchids soak tea bags for the tannins to water their plants with. I use some drifted in my fish tank to balance the hard water among other benefits. . I boil and soak it first leaving just a little bit of diluted so the tank water doesn’t brown. Then take the boiled water and dilute for my plants. If orchid roots can absorb and benefit I would bet any plant that roots attack to a tree also would