Live lightly on the earth

Jan. 9, 2003
If environmental visionaries are right, biodegradable plastics may one day turn landfills into giant compost heaps.

Consumers will soon find produce and other grocery goods packaged in biodegradable materials. Products targeting the packaging market include Eastman Chemical Co.'s Eastar BIO GP copolymer which can be thrown in the compost heap to safely degrade away.
U.S. consumers generate more than 30 billion lb of plastic waste annually. But someday the landfills holding all this debris may turn into giant compost heaps, or so says environmental designer William McDonough, a former dean at the University of Virginia's agricultural school and his partner Michael Broungart, a European chemist and founder of Germany's Green Party. The two are authors of Cradle to Cradle (Remaking the way we make things).

CEOs at companies including Ford, Herman Miller, Volvo, DuPont, and BASF are listening. They are joining forces with the duo that envision a world in which factory wastewater is clean enough to drink and where buildings generate more energy than they consume. Also visible in their crystal ball: eco-friendly products that easily reenter the water and soil without depositing synthetic materials or toxins. The result: No more waste, recycling, or complicated government regulations.

One precept the pair describes is a "world of two metabolisms." The first focus, biological metabolism, is to design products that become biological nutrients. These products would literally be consumed by microorganisms in the soil. Packaging makes up about 50% of municipal solid waste by volume. Most of it can be designed as biological nutrients or "products of consumption," the authors argue. The goal, they say, is to design packaging from materials that can be tossed on the ground or on a compost heap to safely biodegrade.

The second mechanism is technical metabolism -- basically where parts and materials can be reprocessed and reused. The authors advocate what they call "upcycling." Here parts and components (i.e., "technical nutrients") continually circulate in new products. This vision differs from conventional recycling in that materials stay pure and viable within a closed-loop cycle, rather than being "recycled or down cycled" into lower grade materials. Contrast this with current recycling efforts in the automobile sector where, for example, processors crush, press, and process high-ductile steel from car bodies. The steel eventually gets smelted with a variety of other materials which compromises its high ductility and drastically restricts its future use.

While technical metabolism may be years off, its biological counterpart could well be on its way to fruition. According to researchers at New York's Polytechnic University, advances in practical processing of materials such as starch, cellulose, and lactic acid have already boosted worldwide consumption of biodegradable polymers from 14 million kg in 1996 to an estimated 68 million in 2001. "But," says Polytechnic researcher Richard Gross, "consumers have thus far attached little or no added value to the property of biodegradability." This forces industry to compete head-to-head on cost performance with existing familiar products.

"Conventional polymers such as polyethylene and polypropylene persist for many years after disposal. Built for the long haul, these polymers seem inappropriate for applications in which plastics are used for a short time and then disposed," says Gross. Biodegradable polymers such as polyethylene terephthalate adipate and polylactic acid now serve in an expanding range of applications. These include yard and food waste/compost bags, food packaging, fast-food serviceware, short-life containers, engineered fabrics and nonwovens, medical disposables, coated paper packaging, and agricultural films.

Researchers at Cornell University are also developing plant-based green composites. Made from soybean protein and plant-based fibers, these composites may someday replace more robust, mass-produced plastic parts for disposable and other short-lived products. The researchers are developing composites reinforced with fibers from kenaf and banana stems, pineapple, and henequen leaves. The focus is on improving composite strength and stiffness as well as reducing water absorption to prevent premature degradation.

Martyn Poliakoff, professor of chemistry at the University of Nottingham in the U.K., sums up the situation. "Worldwide research aimed at cleaner processing has increased sharply," he says. "Academic interest is reinforced by funding agencies that increasingly insist academic research address quality-of-life issues and be more commercially exploitable."

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