Maybe I'm strange, but I will crumble up the shells and give them back to the chickens. I haven't researched this to see if it's a bad thing to do or a good thing to do, but the chickens love it, so it's not going to waste at least! Otherwise, just compost it!
I cant say for unhatched eggs. but eggshells in general are very good for dogs, but Ive only given them to mine in powder form. So maybe if you had a way to grind them pretty fine? When I had my wolf/husky hybrid I could give her a whole cracked egg but she could devour anything