Eggshells – Decomposition After One Year

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Robert Pavlis

A year ago I started a study to see if eggshells decompose in soil; Eggshells – Decomposition Study. It is now one year later and time to have a look at the buried eggshells.

eggshell decomposition study - year 1
Eggshell decomposition study – year 1

Decomposition After One Year

I dug up one of the baskets holding the eggshell and slowly removed the soil from around the egg. I then put the eggshell in water to rinse out the soil inside the egg, as shown in the picture above. In the process two pieces broke off the egg.

I scraped the inside of the egg to see if the inner membrane was still there, but it was gone. It had completely decomposed. This is not surprising since this membrane contains a lot of protein which easily decomposes.

The remaining shell was intact and showed no visual signs of decomposition.

Archaeological Eggshells

One of the commenters in the post Eggshells – Decomposition Study, suggested I look at some research on eggshells found at archeological digs.

Plant Science for Gardeners by Robert Pavlis

I found a report entitled “An Analysis of the Avian Fauna and Eggshell Assemblage From a 19th Century Enslaved African American Subfloor Pit, Poplar Forest, Virginia“. This is quite an interesting read from a historical perspective. The study looked at a property in Virginia that was at one time owned by Thomas Jefferson. It was a tobacco plantation that contained a small community of slaves from 1840 to 1860. Excavation of the site found thousands of eggshell fragments from both chickens and ducks, which had been raised by the community.

The key point for us is the fact that over the last 165 years, the eggshells in the soil did not decompose very much. In fact the researchers could still distinguish chicken eggshells from duck eggshells.

Do you still think eggshells decompose in the garden in a year or two?

As reported in my last post, they do decompose if they are crushed to a very fine powder in something like a mortar and pestle.


To learn more about eggshells, have a look at these posts:

Eggshells – Do They Decompose in the Garden

Eggshells – How Not to Use Them in the Garden

Eggshells Control Slugs – Do They Really Work?

Eggshells – Decomposition After Three Years


  1. Thesis for Kathryn Elizabeth Lamzik;


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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

26 thoughts on “Eggshells – Decomposition After One Year”

  1. Okay, so… Forgive me if this sounds dumb, but… There are tons of birds flying around any given neighborhood. All those birds nest and lay eggs every year. So if eggshells don’t decompose for hundreds of years, why aren’t we seeing accumulations of wild bird egg shells?

    • They easily break into smaller pieces. I have some chicken egg shells in the garden that have been sitting in a protected area for at least 5 years – still there. Just because you can’t see something does not mean it is decomposed.

    • I am 61, and have lived by a woods and/or wooded property all of my
      life. I have, of course, seen countless birds shells that have been pushed out of nests after the peeps emerged from them. These fragile
      bird shells get stepped on and crushed, (sometimes into a fine powder-like substance), and walked into the ground. Okay, so…Forgive me if this sounds ‘logical’ to you, but try letting your
      common sense ‘kick-in’, and just think about how obtuse your question really is.


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