The Unmentionable World of Human Waste and Why It Matters. - By Rose George - Slate Magazine

http://www.slate.com/id/2201466/entry/0/ --- Of all the peoples of the world, the Chinese are probably the most at home with their excrement. They know its value. For 4,000 years they have used raw human feces to fertilize fields. China's use of "night soil," as the Chinese rightly call a manure that is collected after dark, is probably the reason that its soils are still healthy after four millennia of intensive agriculture, while other great civilizations—the Maya, for one—floundered when their soils turned to dust.