Corn cobs: what matters here is how hard it is, not how big, because the plate works by impact against the ring, much like a pestle. Only the top-range models get particles this fine: with the basic ones the residue stops earlier. It is the hard centre of the cob: break it into rounds before feeding it in. The husks, however, go in the food waste bin, whatever the model. With that one precaution it becomes an ordinary scrap. If you produce a lot of it, it is worth checking your water utility’s rules.