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Composting Egg Shells


March 1, 2017

Question from Master Composter WR:  Hi everyone.  I throw eggshells into my compost and don’t bother to rinse them first.  I just read this article on which talks about composting in item #8, and then I read the user comments because I was curious to know what readers said about composting.  Someone said this: "Egg shells are fine if rinsed clean or cooked dry. The idea is to remove all food value so they don't attract wild animals. If left moist they may breed dangerous bacteria in compost systems that generate inadequate heat."I actually don’t believe the last sentence above is accurate (about “dangerous bacteria”).  But would like to know your take on this. Someone else said this: "I've always composted egg shells; they help add calcium to the soil! Never milk products or meat, though - they attract the wrong kinds of microbes!" Again, I don’t think this is accurate.  I don’t think the problem with those is “the wrong kinds of microbes”, I think it is just that they might attract the wrong type of higher animals (like mice and raccoons and dogs).  But, am I wrong? Again, any thoughts?


Answer by JZ:  My thoughts: The only organic aspect of an egg shell would be the albumin lining of the shell - presumably that’s the reference to the “ food value “ attracting vermin?  If shells are dried then crushed, then distributed ( mixed in ) a composting operation, then I doubt that there would be a scent that vermin could identify.

There may possibly be some Salmonella on egg shells. But you would have to ingest or get the compost into a lesion in order for the organism to be have an impact in your body.   Don’t eat your compost.

How does one ID “dangerous bacteria “ in a compost operation ?   Any microorganism might cause a problem in humans by getting into the right place at right time and/or if a person has a compromised immune system. Common sense would be to always sprinkle a pile before turning, avoid getting compost on mucous membranes, hand scrubbing & washing garden produce.

The quoted statements, in my opinion, are not science-based, but anecdotes.  In trying to be safe (?) some people come up with unique statements that may be difficult to prove and / or dispute.

When egg shell questions come up in a basic class, my response is to dry & crush the shells, then add.  If a home composter is wary of that approach, then I suggest that a person further research the topic to satisfy their need and / or If some organic is bothersome to you, just leave it out of your composting operation.

These unique / anecdotal questions come up in a composting class - some people do accept an answer that is science based.

Answer by JH: I can only provide anecdotal information because I don't know the science, but I routinely toss unrinsed eggshells in my compost and don't notice any problems. My chickens help turn the compost and consume the bugs, and the finished compost often goes into the chicken run - chickens are fine.

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