National Geographic interviewed David about his book. Here's a selection:
Question: Explain what you mean by “Unless we change how we think about [poop], we are doomed to forever live in it.”
Until very recently, people thought of poop like just a big pile of manure [that needs to be disposed of]. So it ends up in waterways, creating pollution that leads to people getting sick. We need to think about ways to use the energy in that poop in various ways. For example, people are using poop to produce electricity and heat with biodigesters. Countries like Rwanda have mandated that public institutions have to take waste and put it through biodigesters—this creates methane that in turn produces heat or electricity. So it’s not just waste.
Q. Can you describe some more unsung benefits of poop?
The thing about excrement in general is that it’s part of life. Part of the argument I make in the book is that as soon as you have life, you have essentially poop. As life developed, the waste for one animal became food for another animal. We depend on a web of recycling of nutrients, and poop is an important part of that. People get sqeaumish but they shouldn’t be. If you don’t think of it as poop, but instead think of it as recycling nutrients, this is a really interesting and sustainable way to produce food.