Drinking method #3
Wash 8 shells and crush them. Pour the juice of 2 lemons over them and let it stay in the fridge for couple of days. When the shell softens, strain the liquid and then mix it with 1 liter of water and 1 tablespoon of honey. Let it marinate for 7 days and then consume 1 teaspoon 2-4 times per day.
Boiling eggshells in your coffee helps to clarify the grounds and reduce bitterness. This is actually a really old method. Learn how to do it here.
Sprinkle them in your garden
Critters like slugs and snails have soft bodies and don’t like climbing over sharp eggshells.