If you have chickens you probably dispose of a lot of eggshells. I know I was throwing out dozens and dozens a week until I started looking for ways to reuse them. Luckily there are a lot of ways to reuse eggshells. The shell of an egg is made of calcium, so they make a great calcium substitute for animals, plants and people. They can also be used as pest repellent, cleanser and even toothpaste!