Never (Ever) Put Eggshells Back in the Carton
Sure, it's a convenient way to keep things tidy when you're baking up a storm, but it turns out that putting eggshells back in the carton with the rest of your uncracked eggs is a big food safety no-no. The reason? Cross-contamination.
Unfortunately, bacteria like salmonella can be lurking on the outside, as well as the inside of your eggs. And, according to Egg Safety Center, storing fresh eggs and eggshells together "greatly increases the risk of bacteria transfer by hands, utensils, air, etc." The organization goes on to warn against reusing egg cartons at all, as they can become a "reservoir for bacteria."
And if we're being honest, it's also just an all-around bad habit to fall into. Empty eggshells have no business in your clean fridge. Sorry.
So, instead of holding onto potentially harmful waste, err on the safe side throw away empty cartons and cracked shells immediately. Or, better yet, toss them all in a compost bin.