I'm not clear what the starch is - I presume some kind of complex amyloid, but there are also biodegradable polymers based on acetic and other short-chain simple acids. They might not degrade quickly, but there's a difference between a couple of years and tens of thousands if not longer, plus the results are unlikely to be toxic. I don't think you're supposed to eat them, but I'd imagine it's less of a chore than baked pitta chips.