Biodegradable Plastics

How Safe Are the New Green Plastics?

There has been a good deal of recent innovation in biodegradable plastics. Some manufacturers have turned to starch, from sources like potatoes and corn, for their packaging, others to sophisticated bio-tech.

Corn plastics (polylactides or PLA) have been in the news of late-it fully biodegrades in47 days, requires up to 50 percent less fossil fuel than regular plastic, and is not toxic to incinerate. The West Coast's Wild Oats Markets is projecting a nationwide shift to food containers made of corn plastic in all 90 stores within the next year and will provide onsite recycling bins for customers, with the resulting compost being resold for gardening. 500,000 corn cups were used by Coca Cola at the 2002 Salt Lake City Olympics. On the other hand, it's much more expensive than conventional plastic and can't withstand the temperatures of hot food (it breaks down at 140 degrees Fahrenheit). Jointly, Dow Chemical and Cargill expect "to be making 1 billion pounds of corn-derived plastics each year." 10 percent of the nation's annual corn supply!

Since corn plastics decompose at higher temperature than most kitchen or garden bin (which usually are 120 degrees F.), you will likely need to deposit them with municipal composters which do function at higher temperatures . For composters in your area, see www.cargilldow.com/corporate/pdf/compost_facilities.pdf.

Look for the Biodegradable Products Institute's "Compostable" label on certified products-it means the plastic you have breaks down as fast as, say, yard trimmings, breaks into small fragments, and can support plant growth after breaking down when taken to a professional composting facility.

Are starch-based plastics safe?

Well, since they don't use petroleum, you're OK against the usual candidates for leaching. Oddly enough, in fact, if starch-based plastics become popular, we may start asking another familiar question: "Are they organic?" They've become somewhat cost-effective partly because industrial agriculture manufactures so much excess product-which means they're made with pesticides. On the whole, starch-based plastics are better for you and the earth, but many questions remain.


There's a more cost-effective, versatile alternative to starch plastics, though it isn't as quickly compostable and thus doesn't qualify for the official label. ECM BioFilms makes an additive for polyethylene and polypropylene that "structures" soil microorganisms on the plastic's surface, allowing them to efficiently break down the plastic to inert organic materials (carbon dioxide or methane, and water) within 5 years. The process works with or without oxygen and with or without light, which means it can work in landfills and backyards. Further, since these microorganisms live only in the soil, the plastic with additive has, like normal plastic, an infinite shelf-life and isn't vulnerable to liquids, heat, or light. It's recyclable, too. Bob Sinclair, ECM's CEO, told us that, unlike with starch-based plastics, plastic companies "don't have to go reinventing the wheel"-they can add 1 to 5 percent additive to their normal mix and manufacture as normal with little added expense. Thus, he thinks, it's more viable for use on a large scale than starch plastics. Not too many U.S. companies are using the additive, he says, but that's only because the demand isn't being voiced-it's popular abroad, and would be easy to introduce into U.S. plants as they're presently designed. One American company that does use the additive is Planet Friendly Plastics, which makes garbage, kitchen, and grocery bags, among others. There's still the problem of extracting the petroleum used in this plastic's manufacture, as it is still plastic in the first years of its life, and it isn't incinerator safe.

Source: http://www.thegreenguide.com/doc/100/plasticsja

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