I read on Pinstrest, (I don't know which one) that you should save the water you boil your eggs in. Let the water cool and then use it on you plants.
This idea is great for potted plants, because it give extra calcium to the plant. I though about this for a couple days, and it make a lot of sense because the tell you to break up egg shells and give it to dog to boosted their calcium.
Have you ever tried this? I'm going to have to try next I make boiled eggs.