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In the Sixties, plastics stood for everything divorced from nature, but these days the material is literally coming down to earth. New containers and packaging made from a corn-based polymer known as polylactide (PLA) can be composted—though at very high temperatures, not in your kitchen bin. Still, it's a hopeful alternative to the 100 billion plastic bags tossed out each year and the 1.5 million tons of petroleum-based plastic used in bottles annually worldwide.

PLA requires 25 to 55 percent less fossil fuels to produce than does plastic derived from petroleum, and it decomposes in 47 to 90 days, so long as it's composted in commercial facilities that operate at high temperatures. However, the conventional corn from which they're made isn't entirely green, since it's grown with pesticides.

Currently, several U.S. cities and counties—including San Francisco, Oakland and Seattle—are trying municipal composting with curbside collection, and at least one company, Nat-Ur, is specifically marketing its compostable plastic bags to these markets. If your city doesn't pick up compostables, you'll have to drop off your kitchen scraps and biodegradable plastics at the composting facility yourself.

PLA is also used in food containers at Dartmouth and Cornell colleges, at Oakland Coliseum sports events, at some supermarkets and in Newman's Own line of organic salad greens. "We had record growth in 2005 over 2004, exceeding more than 100 percent," says Mary Rosenthal, global communications leader at NatureWorks. "In addition, our growth is global: 40 percent of our volume is in Asia, 30 percent is in Europe and 30 percent is in North America." Steve Mojo, executive director of the Biodegradable Products Institute (BPI), which certifies compostable plastics, notes that "Part of this growth is because there's more interest in food-waste diversion than ever before, and part is because product quality has improved and the price differential is closing with the price of oil on the rise."

But don't expect to find them replacing grocery bags anytime soon. "Our shopping bags range from four to eight times the price of a polyethylene bag, so we have a problem breaking into that market," says Terry Phillips, a partner at BioBagUSA, a manufacturer of the biodegradable bags.