Ground egg shells are extremely high in calcium and contain virtually no phosphorus. They are approximately 95% calcium carbonate. Eggshells present healthy, balanced calcium due to trace amounts of other minerals contained in it, and eggshell calcium is probably the best natural source of calcium, and it is easier for your body to digest and absorb.
One whole medium sized eggshell makes about one teaspoon of powder, which yields about 750 - 800 mgs of elemental* calcium plus other microelements, i.e. magnesium, boron, copper, iron, manganese, molybdenum, sulphur, silicon, zinc, etc. There are 27 elements in total. The composition of an eggshell is very similar to that of our bones and teeth.
(Elemental amounts are the amounts absorbable.)
You can use any kind of egg (chicken, goose, duck), but it is best to use organic or certified organic eggs from free-range birds. If the bird does not get proper nutrients the eggshells won’t contain the nutrients we need.
How To Make Ground Egg Shell Powder
If you have access to enough egg shells, you can make your own finely ground egg shell powder. If you don't have enough egg shells, you can always ask friends, neighbors, relatives and others to save their egg shells for you.
Simply collect egg shells. For ease, wash egg shells before you crack the eggs and then also rinse them off after. Dont bother removing the membrane as that contains useful nutrients.
Let them dry out on the counter and then collect them in a container in the freezer over time until you are ready to finish a batch.
Once you have a good collection of egg shells, you can dump the container onto a cookie pan, smash up some of the larger chunks if you want, then bake them at 300° F for twenty or thirty minutes. Turn off the oven and let the shells cool off in the oven. This helps to sterilize and dry the shells and makes them more brittle for easier grinding.
Grind handfuls of eggshell to a very fine powder using a coffee grinder. If you desire, you can use a sifter or strainer to remove any remaining larger pieces, but most grinders should be able to do the job right.
Store powdered eggshell in a sealed container and keep in a dry place.
Use eggshell powder as you would any calcium supplement.