Are egg shells safe to compost?

Composting at home can be a great way to recycle your food and yard waste into free nutrients for your landscaping or garden. But certain kitchen scraps, like egg shells, can pose a bit of a challenge.

While egg shells are an excellent source of calcium and other nutrients for a garden, they don’t always break down as readily as other composted items, and some people may worry about whether salmonella will end up in their compost if they toss egg shells in.

According to a post by Michigan State University Extension, the safety steps that commercial egg producers must follow, such as washing eggs before packaging them, already reduce the risk of salmonella contamination. And, in the same way that properly cooking eggs can kill potential bacteria, the hot composting method — where a compost pile’s temperature rises above 140-160 degrees Fahrenheit — can also kill a variety of pathogens (as well as weed seeds).

“Egg shells are often such a small percentage of the whole, that rarely are they able to overwhelm a batch of compost,” Extension expert Beth Clawson writes. “Overall, after the composting process is finished and cured, most pathogens will be brought to a similar level as the surrounding soil thus reducing the amount of salmonella bacteria in your compost.”

If you want the egg shells’ nutrients without finding big pieces of egg shell in your finished compost, Clawson advises letting the shells dry for a few days, or placing them in a warm oven to speed the drying process. Once they’re dry they can be crushed more completely before you add them to your compost.

Read more about composting here, and find other soil and composting resources at MSU Extension.