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Dear EarthTalk: Is it true that nothing really “biodegrades” in a landfill?
— Laurie via email
Organic substances “biodegrade” when they are broken down by other living organisms (such as enzymes and microbes) into their constituent parts, and in turn recycled by nature as the building blocks for new life. The process can occur aerobically (with the aid of oxygen) or anaerobically (without oxygen). Substances break down much faster under aerobic conditions, as oxygen helps break the molecules apart.
Most landfills are fundamentally anaerobic because they are compacted so tightly and thus do not let much air in. As such, any biodegradation that does take place does so very slowly. “Typically in landfills, there’s not much dirt, very little oxygen, and few if any microorganisms,” says green consumer advocate and author Debra Lynn Dadd. She cites a landfill study conducted by University of Arizona researchers that uncovered still-recognizable 25-year-old hot dogs, corncobs and grapes in landfills, as well as 50-year-old newspapers that were still readable.
Biodegradable items also may not break down in landfills if the industrial processing they went through prior to their useful days converted them into forms unrecognizable by the microbes and enzymes that facilitate biodegradation. A typical example is petroleum, which biodegrades easily and quickly in its original form, crude oil. But when petroleum is processed into plastic, it is no longer biodegradable, and as such can clog up landfills indefinitely.
Some manufacturers make claims that their products are photodegradable, which means that they will biodegrade when exposed to sunlight. A popular example is the plastic “polybag” in which many magazines now arrive protected in
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