I love eggs. I eat them almost everyday for breakfast, but I treasure the eggshells just as much. I keep a container by the stove and every time I crack an egg the shell gets tossed inside. My son is not too keen on on my container. Last time he left to go back to school he exclaimed how happy he would be not to have to put shells into the container. The container was mostly full. OK it was overflowing. He would try to put a shell in and it and several others would topple out onto the counter.
I like to cook my eggshells before they go out into the garden. It makes me think I won't be contaminating my garden with salmonella. It also dries them out and makes them easier to work with. But I won't heat up my oven just for eggshells and I have a tenancy to forget to put them in the oven when I'm in the middle of cooking something. So the eggshell containers would overflow.
After the umpteenth time the mountain of eggshells toppled over, I decided I had to change my ways. Now when the container is full, another glass container comes out and the shells are put in that and stuck in the cold oven. They sit there until the oven is used. This way I never forget to cook them up. This morning I was making a squash casserole and cooked my shells. BTW never cook eggshells for very long. Ten minutes seems fine. Longer can make your kitchen really stinky.
When I cooled down my eggshells I prepared to put them in their next container for storage - a double ziplock bag. I double it because the eggshells go in fairly whole and I can crush them through the plastic. Once layer means bits of eggshell on the floor, but two seem to keep them contained while crushing. Today this container was full. This only happens a couple of times a year. It was time to deal with them.
Years ago I put them in the garden or compost just roughly crushed like this, but I really hate the look of half crushed shells. They look really ugly in the soil. So I started to powder them in my food processor (warning do this will cloud your hopper, the eggshells are harder than plastic). I not only liked the aesthetics of this but found they worked better.
I use eggshells mostly to fertilize my tomatoes. I put at least a cup of powdered shells in each planting hole. Tomatoes love calcium and eggshells have a lot. It helps the tomatoes grow and helps prevent blossom end rot. In addition if I'm still having trouble with BER, I make eggshell tea. I put a cup of eggshells into a quart of water and let them steep for 2-3 days. Warning: this smells vile so keep it outside. Then I dilute it and use it to water the tomatoes. It works really well.