We organic garden and use egg shells in our compost. We have chickens and they are organic too. In our compost pile we add potatoe peelings, grass clippings, vegtables that have no meat, news paper. Just about anything that has no meat or chemicals. We also have the biggest worms I have ever seen in our compost.
I also feed my chickens the egg shells and potatoe peelings to help them out too. And the goats love potatoes if they are lucky enough to get them.