It sounds like a perfect eco-solution: plastic from plants, not petroleum. And indeed, plastics made from cornstarch and other crops, such as potato starch, castor oil and soy protein, are popping up everywhere. Sony uses them in its Walkmans; they comprise parts of Toyota's Prius; Wal-Mart packages fresh fruits and vegetables in them.
There's just one catch: Bioplastics aren't quite as green as they might seem, for many of the same reasons that biofuels are an environmental Catch-22. For one, using crops to produce plastic diverts those plants from the food supply. The recent rise in global food prices demonstrates the danger of this; also, much new cropland is cleared at the expense of carbon-absorbing forests. Crop production requires carbon-dioxide-emitting energy, and unless the plants are organically grown (unlikely for bioplastic sources), pesticide and fertilizer runoff is an issue.
Some critics point out that many consumer bioplastics are used for items such as utensils and plates that tend to get thrown away, which isn't sustainable behavior. "People who wouldn't buy paper plates because they didn't want to generate more trash might now buy compostable plates thinking they'll biodegrade easily," says Diane MacEachern, author of "Big Green Purse: Use Your Spending Power to Create a Cleaner, Greener World" (Avery, 2008).
Plant plastics don't always compost easily at home, and many people don't compost anyway. They're unlikely to disintegrate in a landfill because of the high temperatures required. And any degradation releases methane, a potent greenhouse gas. (However, when incinerated, as some garbage is, bioplastics burn cleanly.) Bioplastics degrade most successfully in commercial composting facilities, which is why bioplastic bags for leaf collections make sense.
So what's better: plastics or "plantics," as they're sometimes called? It depends. Bioplastic production requires less fossil fuel energy, and it's not made from fossil fuels as regular plastic is. Places to recycle bioplastics are hard to find, but if capabilities improve, bioplastics could be a more sustainable option. And as with biofuels, the future for bioplastics appears to be in crops that are more energy-efficient to produce. "There could be uses [in bioplastics] for algae and cellulosic materials like switch grass," says PK Melethil, a technical services associate for Zero Waste Alliance, a Portland, Ore.-based nonprofit organization. "But it's not going to happen in the next five or 10 years."
MacEachern says she'd "much rather see the plastics industry increase the amount of plastic that's recycled." She cites Preserve ( http:/
In other words, bioplastics are promising but complicated. Even if your sandwich comes in a corn-based takeout container, there is no such thing as a free lunch.
-- Eviana Hartman