Not really a home improvement question per se but somewhat related: Can main trunks of used Xmas trees be recycled into particle board if all the branches were cut off? I mean if you had 100s or 1000s of them?
Not on topic, and no, too much bark. Debark them and there's nothing left. Feel free to invent a debarker that will work on tiny trees, and then find out that tiny trees are still an insignificant fiber source, with excessive handling costs associated. Grinding them up for mulch is about the best thing you can do with them, other than not getting a disposable tree in the first place.