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Wednesday, Feb. 21, 2007 01:24 pm

Alternative to plastic

Manufacturers are introducing biodegradable substitutes

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Food containers such as these may soon be made mostly from corn and other plant-based materials.
PHOTO COURTESY OF GETTY IMAGES
Untitled Document Dairy products such as yogurt always seem to come in packages that aren’t easily recycled. Aren’t there more eco-friendly containers these companies could use?
It is technically possible to recycle polypropylene, the material used in many food containers. The challenge lies in separating it from other plastics, including its own many variations, once it arrives at the waste station. Because of the difficulty and expense of sorting, collecting, cleaning, and reprocessing plastics of all kinds, in many places it is only economically viable to recycle a few select types. These usually include polyethylene terephthalate (PETE, designated No. 1 in a code established by the Society of the Plastics Industry), high-density polyethylene (HDPE, No. 2), and sometimes polyvinyl chloride (PVC, No. 3). Polypropylene — classified as No. 5 by SPI — is a thermoplastic polymer, meaning that its density and resins give it a high melting point, enabling it to tolerate hot liquid without breaking down. For this reason, it is used in a wide range of food-packaging applications in which the product initially goes into the container hot or is later microwave-heated in the container. It is also used to make bottle caps, computer disks, straws, and film packaging. Its toughness, strength, ability to serve a barrier to moisture, and resistance to grease, oil, and chemicals also make it an attractive material for many uses. Environmentally friendly alternatives to polypropylene and other plastics are beginning to be developed, however. NatureWorks, a division of Cargill, has developed a corn-based plastic called polylactic acid. Although it looks and functions like other plastics, PLA is fully biodegradable because it is derived from plant-based materials. Whether it is composted or sent to a landfill, it will biodegrade into its constituent organic parts, though how long that process takes is a matter of debate. Another pioneering company is Massachusetts-based Metabolix, which has partnered with corporate giant Archer Daniels Midland to make corn plastics that the company claims will “biodegrade benignly in a wide range of environments, including marine and wetlands.”
A handful of natural-foods companies and retailers, including Newman’s Own Organics, Del Monte Fresh Produce, and Wild Oats Markets, are already using corn plastic for some of their packaging, though not yet to replace heat-resistant polypropylene. Analysts expect such plant-based alternatives to come on stronger and stronger in the days ahead as petroleum becomes more expensive and more politically unstable. Even Coca-Cola has started experimenting with replacing its traditional plastic soda bottles with a corn-based alternative. And last October, as part of its “green” overhaul, Wal-Mart announced that it would replace 114 million plastic produce containers a year with PLA varieties, sparing about 800,000 barrels of oil annually.
 
For more information: NatureWorks, www.natureworksllc.com; Metabolix, www.metabolix.com; the Society of the Plastics Industry, www.plasticsindustry.org.
 

 Send questions to Earth Talk, care of E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881 or e-mail earthtalk@emagazine.com
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