What to do with egg shells

[SammynDqtz]

When I make a makeral mix for my cats, it uses 3 eggs, so I take the shells and bake them in the oven at 350 degrees for 10 minutes... then I roll them into a few paper towels and get out the rolling pin, a few roll overs, with a good amount of pressing, and they are close to dust.

 

[BoxerMumma]

A electric coffee bean grinder works great! I use mine all the time with grinding egg shells, it comes out a nice powder. even put larger pieces in homemade doggie treats