Is it true that nothing really “biodegrades” in a landfill?

Dear EarthTalk: Is it true that nothing really “biodegrades” in a landfill?

—Laura, via e-mail

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 the mail. But the likelihood that such items will be exposed to sunlight while buried dozens of feet deep in a landfill is little to none. And if they do biodegrade at all, it is only likely to be into smaller pieces of plastic.

Some landfills are now being designed to promote biodegradation through the injection of water, oxygen, and even microbes. But these kinds of facilities are costly to create and as a result have not caught on. Another recent development involves landfills that have separate sections for compostable materials, such as food scraps and yard waste. Some analysts believe that as much as 65 percent of the waste currently sent to landfills in North America consists of such “biomass” that biodegrades rapidly and could generate a new income stream for landfills, marketable soil.

But getting people to sort their trash accordingly is another matter entirely. Indeed, paying heed to the importance of the environment’s “Three Rs” (Reduce, Reuse, Recycle!) is likely the best approach to solving the problems caused by our ever-growing piles of trash. With landfills around the world reaching capacity, technological fixes are not likely to make our waste disposal problems go away.

CONTACTS: U.S. Environmental Protection Agency (EPA) Reduce-Reuse-Recycle page;