The king of confusion in food-waste sorting. Which of these is NOT food waste?

Clam and conch shells are excluded from food waste because Korea's food-waste system is built to convert scraps into animal feed or compost, and hard shells, along with bones, eggshells, and tough seeds, can't be broken down that way and would damage or contaminate the processing equipment. So despite coming from food, they are sorted into general waste instead.

Watermelon rind and leftover rice, by contrast, are genuinely soft organic matter that composts or converts to feed easily, which is exactly why they belong in food waste even though people sometimes assume tough rinds should be treated like shells.

This shell-versus-soft-scrap distinction trips up even long-term residents, and many apartment complexes post illustrated guides near the waste-disposal area specifically because the food-waste category is the one locals get wrong most often too.