All bamboo batting is not equal. Are you talking about 100% bamboo, the 50/50 rayon-bamboo, the 50-50 cotton-bamboo, the 50-50 silk-bamboo?
I have used 100% bamboo and loved it.
As to the environmental effects: cotton is heavily sprayed with chemicals/pesticides. Bamboo grows well without pesticides but there are other environmental concerns about deforestation, etc. Poly is entirely petro-chemicals (oil-based). Rayon is a 50/50(or so) blend of natural products and chemicals used in manufacturing it. And there's probably something wrong with using silk also! Pick your poison!
Whew - pretty heavy for a quilting board!