This photo didn’t load in the first reply. Sorry!
I had thought of getting information from the waste, but I can’t really figure out how to differentiate different dishes in the menu by it. (even liquid, solid, and then trying to figure out which dish is bad seems a little intangible). And it seems very messy and very high maintenance in the usual circumstances in which waste do get collected.
I was thinking more of a prime time customer feedback system.