I began saving shells when we first got our chicks. It has been a couple of months now and we have a good supply. I rinse them of any egg goo after cooking, then toss them in a bowl I keep on top of the fridge. When the bowl gets full I crush them down. When it gets full of crushed shells I set it out on the porch for a day or two to let the sun kill the ick. Then I put the crushed shell into a storage container. So far we have two half gallon ice cream containers of egg shells. A little bit of work, but I am not working, so I don't mind.