I have always put them in my compost and when i turn the compost over everything is all nice and earthy excepte egg shells. Last year I put shovels of mostly broken down compost in to the bottom of planters then in the fall dumped them in to a pile in my garden. They are still recognizable egg shells that are going on 1.5 years i'd say?
And why is it egg shells are ok to compost anyway seeing as they aren't plant based?
I just dried out a bunch from brunch on sunday and crushed them up before I put them in the compost but that seemed like more work than I feel like doing regularly. I am wondering if they are even worth it anymore.
Re: do egg shells EVER break down?
I also do the microwave/smash thing and the shells disappear in the compost pile.
Egg shells add calcium, a required micronutrient, to your compost.