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| Paper/plastic: Sara Stinchcomb carries groceries to her car in Annapolis, Md. The town had proposed a ban on plastic bags;
it failed. Kathleen Lange/AP |
'Bioplastic' may become third option to paper or plastic
Biodegradable plastics have gotten cheaper and more reliable, but some still object to their ecological 'footprint.'
from the December 19, 2007 edition
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In contrast to NatureWorks, Mirel, a product line of Metabolix Inc., says its products – including bags, gift cards, and razor-blade handles – will decompose in a backyard composter within two months, and within four months in soil, fresh water, or salt water.
Currently, both companies' products are primarily made of modified corn feedstock, as opposed to petroleum byproducts. Ultimately, the natural polymers biodegrade as microorganisms consume them. While this source of plastic seems earth friendly, some environmentalists say the footprint of corn cultivation should be considered.
"Corn, overall, is very energy intensive, requiring a considerable amount of fertilizer and gasoline to produce and transport each bushel," says Janet Larsen, research director of the Earth Policy Institute in Washington. "The nitrogen-rich fertilizer then often becomes runoff in streams, rivers, and oceans, creating algal blooms that kill marine life."
Using feedstock for plastic further exacerbates record high corn prices, says Ms. Larsen, adding that corn supplies are already stretched thin by demands for food and ethanol. "This should make society ask, 'Do we really want to be turning food into plastic?' "
The definition of bioplastics has been further clouded by Symphony Environmental, a British bioplastics company that claims to have developed a petroleum-based plastic that biodegrades into a benign mix of water, CO2, and biomass. By adding a small amount of degradant in the manufacturing process, the plastic begins the decomposition process after a preset time that varies from product to product. Because no fragments of petropolymers remain, these products can safely be composted, says the manufacturer.
"There is a widespread confusion that all [bioplastics] are made from renewable resources and that all of them are biodegradable," says BPI's Mojo. "Not all plastics made from renewable resources are biodegradable, and not all that are biodegradable are based on natural resources."
Mojo, who works closely with the American Society for Testing and Materials International to develop specifications for products that biodegrade in various environments, says that "the industry is in its infancy" and work is being done to develop more uniformity in composting and recyclability. "We will see more bioplastics in the next five to 10 years as technology advances, and we will see visible improvements in strength, cost, and degradability," he adds.
In the meantime, Larsen of the Earth Policy Institute suggests the environmentally conscious choose a fourth option at the checkout line: "We would do better to bring our own canvas bags shopping or buy reusable water bottles and move away from the throwaway mentality that one-time use products afford us."
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