Dung, manure, feces, waste; call it what you want, it's part of every animal life form. What goes in must come out, and fortunately there are many positives on the receiving end. Animal waste is a great supply of vitamins and nutrients, and acts as a food supply for many smaller animals. It is also a great fertilizer when properly decomposed. Take a trip along the digestive track of a human being, and follow the digestive track of our world, the sewage system.