Egg shells should be placed in your general waste bin.
Egg shells can also be used to make a wonderful (and nontoxic!) abrasive for those tough-to-clean pots, pans, and thermoses. Mix them with a little soapy water for a powerful cleaner.
Eggshells are rich in calcium and other minerals that help your garden thrive. Crush eggshells into tiny pieces and use them as compost.
Fill an egg carton with empty, rinsed eggshell halves and poke a hole in each one for drainage. Then add potting soil and one or two seeds to each shell. When the seedlings are big enough for transplanting outside, just crack the shell at the bottom and plant them, shell and all. It’s biodegradable!