Adding eggshells to compost

Overcoming the concern about salmonella bacteria from the eggs in your compost is less challenging when armed with knowledge.

For decorative purposes.
Photo by Beth Clawson, MSU Extension.

Let’s just start out by saying: putting eggshells in your compost is okay; they are a rich source of calcium and other essential nutrients that plants need. Michigan State University Extension encourages composting as a way to reduce organic yard and kitchen waste and enrich your garden soil, however eggshells are often clearly identifiable after the compost product is finished. This is not a problem, but seems unsightly to some people. To avoid this, let them dry out for a few days or place them in a warm oven to dry more quickly. Drying your shells allows them to crush more completely before you add them to your compost bin. Many people are concerned about news of contaminated foods and the risk of salmonella from improperly cooked eggs. This concern is then transferred to their compost and garden if they add eggshells to their compost.

The bacterium Salmonella has several genus and subgroups. Not all of them are transferable to humans but all of them exist in the environment all the time. We are always exposed to this bacterium, which is why hand washing is consistently advertised as a public health measure. The U.S. Department of Agriculture (USDA) requires the egg industry to take many steps to ensure the safety of the food that comes from farms to the consumer. Farmers are required to wash eggs before packaging to reduce salmonella contamination. This infographic illustrates lessons learned from foodborne bacteria outbreaks.   

The type of salmonella that lives in the chicken often gets transferred to the shell and then to the egg if the shell is cracked. Cooking your eggs kills salmonella bacteria, so does the hot composting process when the temperature rises above 140-160 degrees Fahrenheit. Hot composting can kill a variety of pathogens and weed seeds. Eggshells are often such a small percentage of the whole, that rarely are they able to overwhelm a batch of compost. 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.

MSU Extension educators working across Michigan provide community food systems and gardening educational programming and assistance. For more information, you can contact an educator through MSU Extension’s “Find an Expert” search tool using the keywords “community food systems.”

For additional information on composting:

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