For that we can turn to the results of a long-term study called the Garbage Project.

Starting in 1987, researchers at the University of Arizona have excavated, hand-sorted, and measured contents of 15 landfills across the country. One of their goals has been to analyze what we really throw away and how wastereduction strategies affect our habits.

Among their most interesting findings was that three items notorious for filling up landfills — fast-food packaging, disposable diapers, and plastic grocery bags — really accounted for an almost negligible amount of dump space. In fact, researchers figured that landfill managers wouldn’t notice any difference if these items were completely out of the waste stream.

They also found that we pitch out less product packaging today than in decades past, but not because of recycling programs. In the early 1950s, packaging made up more than half of all landfill waste by volume. Today it accounts for less than a third, despite the fact that four-fifths of the estimated 2.7 million tons of plastic PET bottles made annually wind up in landfills.

Packaging discarded per-person has actually dropped in the last 20 years. The trend, say garbologists, arises from innovations by manufacturers. They’ve figured out ways to both make packages lighter and more crushable, and to market products in the form of concentrates or refillables.

If you really want to have a positive impact on landfills, forget about remodeling your kitchen. It turns out one of the biggest culprits for taking up landfill space is construction and demolition debris. It occupies 20% or more of the volume. But even worse is ordinary paper. Nearly half the refuse researchers excavated was newspapers, magazines, packaging paper, computer printouts, and phone books.

Paper is bad news for landfills partly because it biodegrades quite slowly. That’s why researchers could read papers deposited some 40 years prior. Also problematic is that ink on old newspapers has been the main contributor of lead, a worse source even than discarded batteries, light bulbs, and lead-solder-seamed cans. The issue isn’t as urgent today, though, because newsprint ink made after the mid-1980s contains much less of the heavy metal.

Another trend worth noting during these days of spiraling agricultural prices is how people waste food. Households overall throw away more than you’d guess. About 15% of perishable goods go in the garbage. That’s true even during times when food is expensive.

What s eems to happen as prices rise, say researchers, is that people start buying cheaper food in larger quantities. They tend not to store the extra stuff properly or they don’t know how to prepare it. So there are a few more dinner disasters that even the dog won’t eat. And, later on, more decomposing organic matter that produces landfill methane.

Here’s a final tip from the Garbage Project: You’ll waste less food if you stick to a steady diet of the same basic ingredients. And you can tell your kids they’ll be responsible for less methane if they finish their vegetables.

— Leland Teschler, Editor