There are so many things you can do with them, including eating them! Save your eggshells in the fridge till you have enough, dry them in your oven, then crush them in a vitamix or use a mortar and pestle to grind a fine powder. One eggshell will make around a teaspoon of powder. You can then use eggshell powder as a calcium supplement with yourself, your pets or put it into your garden. If you are planning to ingest - yourself or your pets, it would be very useful to know where your eggs have come from and their age. With a slightly less fine grind, if you have hens, supplement their grit. Or, use the eggshell halves as little seed starters. The beauty of eggshell seed starters is the they plant straight into the garden. Egg shells can be readily disposed in your Bokashi Bin, compost or Council Benchtop Bin if you live in Adelaide. The egg shells will break down faster if crushed up a little.