Here in Indonesia we eat eggs a lot and still have no idea of what should we do with the shells. I got one alternative. a liquid fertilizer made from it.
We knew from the lab project in schools that acid (in vinegar) can softened the egg shell and produce bubbles that are carbon dioxide. The reaction between acid and egg shells is just another acid-alkaline reactions: the calcium meet the acetic acid form a salt that is more soluble. But from what i read this reaction isn’t stable if it’s react with carbon dioxide again it will hardened. Maybe, but there’s also another reaction that is the small quantity of protein left on the shell will hydrolyzed if react with acid. It will break down and release the nitrogen, which is beneficial for the plants.
Based on my experience using this fertilizer, specially to orchids, they love it, they grew lot’s of more new roots just in few days! and then new stem grows! (isn’t it signs of sufficient supply of calcium? then there is soluble calcium left!) if i combine it with fish emulsion fertilizer they grow amazing! roots, leafs and flower altogether! can you imagine that???
Here’s how i make it:
I got 10 liter bucket full of egg shells i got for free from a bakery (you know they think it’s a waste). I grind them into small cracks, I added 1 bottle (200 ml) of vinegar and filled with water until it covers all the egg shell and stir it in order to even the reaction. I put the bucket lid and leave it for at least 2 weeks. i strained it and use the liquid. The remain shell I dried and grind it finely and applied it to the soil.
Yea, it stinks but you only need small amount of it, i used 1 tablespoon of this liquid fertilizer to 500 ml of water and sprayed it to my orchid as root and foliage feed. I also used the rest of it for my father’s 30 acres rice field, and my tomato garden. They love it, you can see the improvement few days after applying it! but remember to always check the pH level before applying it, if it too acid you can add lime to it, but i used to add little bit of wood ash to it.
Right now i still don’t know yet about the effect of the ground shells, it’s not as easy as liquid fertilizer that you can apply directly to orchid and see their reactions. Let’s see in few months! i’ll let you know!