It's all about the worms.

There is one creature that nearly every system or garden should not be without and that is the worm. Worms will consume a variety of things from leftovers such as kitchen scraps, cardboard, and egg shells. Once processed, these leftovers become rich plant food in the form of castings, also called vermicompost, one of the essential ingredients to healthy plant growth. This is packed with some of the best nutrients your plants will need to grow. They are also good for making your soil more granular (more crumbly), which helps improve your soil’s structure allowing air and water to move more freely. As worms move around your soil, they also create tunnels. These tunnels help aerate the soil underneath.