|Paper/plastic: Sara Stinchcomb carries groceries to her car in Annapolis, Md. The town had proposed a ban on plastic bags; it failed. |
|Disposable bottles by NatureWorks are designed to biodegrade. |
Biodegradable plastics have gotten cheaper and more reliable, but some still object to their ecological 'footprint.'By Tony Azios | Correspondent of The Christian Science Monitor
from the December 19, 2007 edition
Paper, plastic ... or biodegradable? Yes, get ready to add a third option at the grocery store checkout line as biodegradable plastics enter the mainstream consumer market.
It is hard to imagine that the plastic grocery bag made its debut only 30 years ago. But now, even in Antarctica, scientists regularly find them blowing about.
The problem is that, unlike many other overnight sensations, plastics stick around. It can take roughly 1,000 years for some petroleum-based plastics to disintegrate. And when they do disintegrate, traditional plastics leave behind a messy legacy of fragments and chemical residues that get absorbed into streams and soil. In the meantime, they clog landfills and rivers, or kill whales and sea turtles that mistake them for food. With up to 1 trillion plastic bags manufactured annually and 2.7 million tons of plastic used just to bottle water each year, concern is rising worldwide.
Enter bioplastics, designed to degrade into an ecofriendly mix of water, carbon dioxide, and biomass. While biodegradable plastics have been introduced before in the past 20 years, they have failed to achieve widespread use due to their inferior strength and higher cost. But this is changing, says Steve Mojo, executive director of the Biodegradable Products Institute (BPI) in New York City.
"In the last decade, we've seen that through improved production technology … these materials have become comparatively durable and affordable, without leaving behind the remnants that petroplastics do," says Mr. Mojo.
While the cost of producing bioplastics ranges from as little as 10 percent more to many times that of traditional plastics, bioplastics companies have seen an increased demand due to rising environmental concerns among consumers and changing environmental regulations. The improved strength, meanwhile, is great news to any trash collector or conscientious pet owner who knows the hazards of an inferior plastic bag.
But when it comes to disposal, not all bioplastics are created equal, leading to confusion for consumers and waste-management groups alike. Bioplastics are not uniform in their ability to decompose under different conditions. While some brands can biodegrade within a few months in backyard compost piles, others require several months at industrial composting facilities.
NatureWorks, the largest producer of bioplastics (they make about 300 million pounds per year), distributes beverage bottles made from polylactic acid (PLA), a hydrobiodegradable polymer. Its bottles are touted as biodegradable within 100 days – but only if it reaches an industrial composting plant with high humidity and temperatures.
According to the Container Recycling Institute, such bottles are unlikely to end up at such plants; of the estimated 25 billion single-serving, plastic water bottles Americans will buy this year, 8 out of 10 (22 billion) end up in landfills. Many stores do not accept returned PLA plastic for recycling or composting. And given that scarcely more than 100 industrial composting facilities exist nationwide, some question the benefits of bioplastics largely destined to end up as litter or in dumps.
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."