The Humanure Handbook, by Joseph Jenkins. At the time this was written, the book is in it’s 4th edition. The work was available as a free pdf download, so you may still find it somewhere on the internet. Regardless, it is worth the purchase price to have a paper copy. The author delves deeply into humans and our waste from a historical perspective, and a practical perspective. Of course, there is plenty of potty humor, but the work represents a thorough examination of science, culture and practicality of human waste. This book is a must have and an excellent read!