They are polymer but it doesn't say which polymer, if they are PLA then they are biodegradable and safe to burn but I think that making them from PLA might not make them so robust? They are probably made from some petrolium-based plastic, so they probably aren't very burnable and thinking on it you don't want them flammable.

Looking at the structure it looks like it wouldn't take much to link them together and I think the materials look easy to reuse.