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  7. Composting with Eggshells

It always makes for a funny moment when a guest at my home has a need to open my bottom oven and is greeted by a big bowl of eggshells.  I am invariably asked, “Uh, why are there eggshells in your oven?”  Then I have to try to give them the abbreviated version of my composting and organic gardening trials, tribulations and adventures.  At the end of the discussion, I usually get an “Oh…” (which in their mind is followed by ‘that's more than I really needed to know' or ‘wow, she's way crunchier than I realized').

We have been avid composters for many years and used to throw our eggshells into the compost heap with the rest of our compostables.  But, as we used the compost, we began to see that the eggshells remained relatively intact, thereby not contributing as much to my garden as they might.

Benefits of Eggs in the Garden:

  • Eggshells are primarily comprised (95%) of calcium carbonate (the same brittle white stuff that chalk, limestone, cave stalactites, sea shells, coral, and pearls are made of).  The remaining 5% includes calcium phosphate and magnesium carbonate and soluble and insoluble proteins.  Calcium is needed for cell wall development and growth.  A common symptom of calcium deficiency is blossom end rot in tomatoes, peppers, melons, and eggplants.
  • Crushed eggshells on the surface of your soil act similarly to diatomaceous earth in your garden.  Diatomaceous earth is a natural product made of ground-up fossilized water plants.   When sprinkled on the soil, it will lacerate the bodies of destructive slugs and similar pests, thereby stopping them in their tracks before they chomp on your plants.

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So, in order to help the eggshells help my garden, I needed them to break down quicker.  I started collecting them in my BIG aluminum bowl.  I keep the bowl in my oven to keep them out of sight and to help them dry out.  They do smell when they get too hot, but I'll let them stay in for a bit when warming oven up or when it's cooling down.

crushed egg shells

 Once the bowl in filled to capacity, I run them through my food processor until they resemble sand.  In case you are wondering…yes, the eggshells will scratch the bowl of your food processor so that it looks a little dull.  But the effectiveness of the food processor is not diminished in any way.  I wonder if the eggshells actually help sharpen the blades?

food processor bowl


Once I have this eggshell sand I sprinkle it on top of my soil.  It will still take a little time to dissolve/decompose so that turns into usable calcium, but in the mean time, it's being useful as a slug barrier.  I do this several times a year, so I'm constantly adding calcium, in addition to my other compost.  The “Lasagna” image for soil building is helpful here.  As a note, it's always a good idea to get your soil tested to make sure you don't get one of the elements out of whack.  Most extension agencies offer this service for free.

 After I distributed my most recent batch of shell sand, I read that adding a small amount of vinegar will speed the decomposition, but will not add significant acidity as it is neutralized by the calcium carbonate in the eggs.  I plan to try this the next time my egg bowl is full.

What are some organic/natural soil amendments you have found to be useful?

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Until next time,  






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  1. Gail Bi

    April 16, 2015 at 10:25 am

    You can also use eggshells as a deterrent to cabbage moths in your garden. An old wives tale that I’ve tried with success

  2. lynn

    April 16, 2015 at 1:11 pm

    Gail, do you just sprinkle them around the cabbages? I’m not familiar with that use, but will surely employ it in my battle against destructive critters. Thanks for sharing.

  3. Bongs

    April 18, 2015 at 10:29 am

    Hi, I do believe this is an exxellent blog. I stumbledupon it 😉 I will return once again since I saved as a favorite it.

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