Eggshell Powder

Eggshell powder can be a great source of calcium to add to your homemade pet food, a great alternative to using calcium carbonate supplements, and a good way to make use your typically discard eggshells.

In order to make sure eggshell powder is safe and the most bio-available when added to pet food, you do have to make sure it’s cleaned and ground properly.

What Is In Eggshell?

Eggshell is about 95% natural calcium carbonate, which is why it’s such a great substitute for calcium carbonate supplements. In addition to calcium, it does contain trace amounts of other essential minerals, including magnesium. This extra boost in magnesium can make eggshell a better fit for homemade dog foods in particular.

Store Bought vs Farm Fresh Eggs

You can use any type of chicken eggshell – whether it’s from the grocery store or from your own backyard chickens!

Brown vs White Eggs – Bleached Eggs?

You can safely use any colored eggshells for eggshell powder. Color variations in eggs are due to genetic variations in shell pigment, and don’t denote any difference in quality due to the color itself. Despite the fact that most organic eggs are brown, and brown eggs are marketed as “healthier” or more “natural”, there is no difference in quality simply due to shell color. White eggs are not mechanically processed for their white color – they are laid white by the chicken!

So that being said, it’s also important to note that all grocery store eggs are cleaned to remove the bloom (the natural protein coating on the shell) and any other residue during processing. This has led to the widespread belief that eggs are “bleached” but this is a myth (or at the very least, a very large exaggeration). Eggs are cleaned using commercial solutions to sanitize eggshells and make them safe for handling, This process does not make eggs, including their shells, unsafe for consumption.

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You will need:

  • eggshells
  • coffee grinder, mortar and pestle, or freezer ziploc bag and blunt instrument (rubber mallet, rolling pin or jar)
  • sieve or fine mesh strainer*
  • Container to hold your powder
  • optional: fork/spoon and funnel

* the strainer should be very fine – such as those used for straining tea leaves or rinsing quinoa

1. Clean and dry your eggshells.

Boil shells for 20 minutes. If your eggshells are from hard boiled eggs, you can skip this step. Rinse.

Bake shells in the oven for 15-20 minutes at 225F or air dry in the sun.

You can save your eggshells over time to grind in a big batch. If storing eggshells for later grinding, make sure to clean and dry them prior, and store in and airtight container.

2. Gently crumble your eggshells using your hands into large pieces.

Place these eggshells in your coffee grinder, mortar, or in the ziploc bag and close.

3. Crush your eggshells to a powder.

If using the grinder, grind until you can no longer hear any large fragments. Let powder settle before opening the grinder.

If using mortar and pestle, grind until it is a powder. You may need to work slowly to allow the powder to settle.

If using a ziploc bag and blunt instrument, make sure your ziploc bag is firmed closed. I recommend using a freezer bag for the thicker plastic. Roll over and crush the eggshells with your blunt instrument until it is a powder.

4. Place your mesh strainer over the container you want to store the eggshell powder in. Transfer the ground eggshells to the mesh strainer. If you want, you can use a funnel between the strainer and container.

5. Gently sieve the eggshell powder through the strainer by tapping on the side of the strainer, gently moving it back and forth, or using a fork or spoon to tap and scrape the powder inside the strainer.

Be gentle – focus on keeping the powder moving around the sieve (rather than through) so that the large pieces don’t settle to the bottom and block the finer powder on top from going through. You don’t want to “push” any large pieces through the strainer.

It’s important to strain out larger pieces because it’s less likely they can be digested and absorbed. I do also recommend removing the eggshell membrane because it has a very different nutritional profile than the shell.

6. As you sieve the powder, you should be left with large shell fragments and eggshell membrane pieces left in the strainer. These should be discarded.

7. The powder remaining in the powder should be extremely fine, with no shell fragments or membrane pieces! This is your eggshell powder that can be used as a supplement.

References:

Concepts of Eggshell Quality (https://edis.ifas.ufl.edu/vm013)

Use of chicken eggshell to improve dietary calcium intake in rural sub‐Saharan Africa (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6221107/)

Mineral, Amino Acid, and Hormonal Composition of Chicken Eggshell Powder and the Evaluation of its Use in Human Nutrition (https://pubmed.ncbi.nlm.nih.gov/11194049/)