Just a thought, but for your volunteer baking, could you reduce the number of eggshells overall by partially or fully substituting the eggs with flax eggs, egg replacer, or fruit mash such as applesauce or banana? That way, you only have your home eggshells to worry about. I do a lot of vegan baking, so if this is a path you’re curious about I’m more than happy to help if you give me an idea of what you’re making :D