"Single-use disposable diapers are responsible for about 4 percent of the refuse in North American landfills. They represent the third-largest single consumer item in landfills (after newspapers and beverage containers) and comprise a staggering one-third of the nonbiodegradable waste. The word disposable is a misnomer: these diapers do not go away! The average baby will contribute 2.75 tons of disposable diaper garbage to this heap by the time he is toilet trained. Once there, these diapers pose a nonbiodegradable health hazard and an ecological nightmare, potentially contaminating surrounding area and water supplies with chemical toxins as well as natural biological pollutants...Even supposedly biodegradable disposables contribute to these environmental problems, since they require light and air, and are usually too compacted, to decompose. They may take generations to break down, if ever, and still leave bits of plastic behind."
Staying Conscientious About the Reality of Disposable Diapers
From Diaper Free: The Gentle Wisdom of Natural Infant Hygiene by Ingrid Bauer.