Why You Should Never Put Eggshells Back in the Carton

published Oct 21, 2019
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Credit: Emma Christensen/Kitchn

Cracking eggs is a daily occurrence in our house. Someone is always scrambling a few for a quick breakfast taco or a lunch of folded eggs, or we’re throwing an egg into some weekday blondie batter for baking.

For much of my life, empty cracked eggshells went right into the trash. But then we moved to a city with a robust curbside compost program and I got lazy—returning the cracked eggshells back to the carton so I could toss the whole thing in our compost bin at the end of the week.

Turns out I’ve been making a horrible food safety blunder with my empty eggshell storage, because I was *today* years old when I learned you should not store empty eggshells alongside your fresh eggs. Here’s what you need to know about discarded eggshells, and why setting them next to your fresh eggs is such a bad idea.

Credit: Joe Lingeman

Is it safe to keep used eggshells in the carton?

It can feel weirdly satisfying to crack the day’s eggs for breakfast and return their discarded shells to the cardboard carton for later composting. It feels tidy and efficient—and even cleaner, as you aren’t dripping egg whites across the kitchen or your work surface to toss them in the trash or compost bin.

And it worked for me, personally, as I could just put the whole carton — empty eggshells and all—in our curbside compost bin for the city to pick up each week. I literally never considered whether it was safe to place empty eggshells and fresh eggs in the same carton. And given how quickly my family goes through a dozen eggs, it seemed they didn’t have time to go bad, anyway. Then I started doing a little research.

Cross-contamination is the enemy when it comes to fighting bacteria in the kitchen — you probably know you shouldn’t wash raw chicken, as it just spreads bacteria around. And you are also aware that it’s dangerous to eat too much raw cookie dough, because even the freshest raw eggs can be contaminated. (Flour is also a problem in cookie dough.) It turns out that cross-contamination is a giant concern when it comes to mixing eggshells with fresh eggs.

According to Egg Safety Center, storing fresh eggs and eggshells together “greatly increases the risk of bacteria transfer by hands, utensils, air, etc.” This is especially important if you do want to sneak a little brownie batter from the bowl with as little bacterial risk as possible.

Furthermore, it’s not a good idea to reuse old cartons for storing fresh eggs either (sorry to my neighborhood chicken coop, we’ve got to find an alternative), as they aren’t exactly cleanable, and the reservoirs can hold bacteria that cross contaminates old bacteria with fresh eggs. Instead, discard empty cartons straightway (to the outside compost bin if you have one) and immediately discard cracked shells to the trash or compost after emptying them.

This pose originally ran on Kitchn. See it there: Why You Should Never Put Eggshells Back in the Carton