`THE issue is more complex than we'd initially supposed,'' says Craig Weatherby, ready to pull the grocery bags labeled BIODEGRADABLE from the shelves of the Bread & Circus organic supermarkets around Boston. ``It sounded better than it is.'' In a few months, the biodegradable totes will be replaced with ordinary plastic or heavy paper. ``We don't want to foster the misapprehension that this is the way to deal with plastics,'' says Mr. Weatherby.
But the concept of making plastics degradable is catching on in the United States. Laws banning regular plastics are being passed; scientists are scrambling to find new ways to make degradables; shoppers are finding more products with the degradable label.
Not everyone is convinced that making plastics degradable will solve the the solid-waste problem.
``We have lots of questions about degradables ... which must be answered before we can determine appropriate roles for their use right now,'' says Susan Mooney, a scientist at the Environmental Protection Agency (EPA) in Washington.
``People like the concept [of degradability] because it's passive ... as opposed to recycling,'' says Jean Statler, vice-president of communications at the Council for Solid Waste Solutions, a plastics-industry group created to address disposal and reuse issues.
The popular notion that degradables go back to nature ``harmlessly and without anybody having to spend money is ... totally out of whack with reality,'' says Ms. Statler.
On one issue all agree: Degradable products are helpful in certain situations, such as when they end up as litter on land and in marine environments, where they are offensive to humans and dangerous to wildlife.
But the remaining questions must be addressed, say some, before a commitment is made to degradable plastics, especially at the expense of other options.
Three main questions about degradable plastics still need to be answered:
1.What is left after the degradation process? At present there are no standards dictating what residuals are safe in size and chemical content. ``Are we breaking plastics down into harmful pieces, which make people feel better because they disappear visibly, but leaving the environment to pay the price for out of sight, out of mind?'' asks Amy Perry, solid-waste program director at the Massachusetts Public Interest Research Group, a nonprofit environmental and consumer organization based in Boston.
``Our concern about plastics is mostly related to their metal and chlorine content,'' says Allen Hershkowitz, senior staff scientist at the Natural Resources Defense Council in New York. ``Twenty-eight percent of all the cadmium in the waste stream is found in plastics, as pigments, stabilizers, or coloring agents,'' he says, and 2 percent of the lead.
2.What happens to degradables in closed landfills? In the US, 80 percent of all municipal solid waste still goes into landfills; of this, 70 percent is naturally degradable.
Research by Arizona archaeologist William Rathje shows that degradation in landfills is slow, if it happens at all. He has unearthed several naturally degradable items now mummified: a newspaper from 1964 still readable, a steak from the '70s still edible.
But current standards for landfills do not say air- or watertight, says Paul Cassidy, EPA engineer. ``No matter how well designed, it's not going to be watertight. There's always going to be some precipitation that gets in.'' Which means there will be some degradation; only in arid, anaerobic conditions will we find intact trash. Mr. Cassidy notes that it's up to the states to decide on proper management of landfills.
The trash is staying put and piling up; in five years one-third of the nation's municipal landfills will reach capacity and be forced to close for lack of space.
3.What is the impact of degradability on plastics recycling? Some recyclers of plastics have found that degradable additives interfere with the process, gum up equipment, and result in a less-stable product.
Barry Appelget of Greensboro, N.C., had to stop using degradable bags in his recycling plant because they were weakening the final products - construction panels and agricultural ground covers. ``The [recycling] equipment didn't notice it, and we didn't notice it until the customer complained that the sheets were falling apart in a few months' time,'' he says.
The solution, says Ramani Narayan, a polymer engineer at Purdue University, is to immerse all plastics in an acid wash, which will rinse out the starches and purify the resins.
But Mr. Appelget says this isn't cost-effective. ``We're a for-profit business. We can't afford to sort out degradables or add an extra step.... [Plastics recycling] is a marginally profitable situation.''
Indeed, recycling is in its infancy: Collection is sporadic; separating plastics is time-consuming; end-use markets are limited and unreliable. Today only 1 percent of all plastics are recycled, says Ed Stanna of the Council on Plastics Packaging in the Environment in Washington. (By comparison, glass bootles and jars are made from 25 to 30 percent recycled materials, and aluminum containers from more than 50 percent.)
Plastics are often cited as proportionately the most rapidly growing component of the waste stream. In landfills, they account for 7 percent of total weight and about 20 percent by volume, estimates Ms. Statler of the Council for Solid Waste Solutions, stressing that this is far behind yard and paper wastes.
But plastics are under public fire, she says, ``because they're pervasive and viewed as unnatural,... [P]eople think the only thing you can do with plastics is throw them away.''
Meanwhile, as the plastics industry is trying to expand recycling - opening plants, funding research, looking for end-markets - it fears that the public rush to degradables will make recycling less profitable. ``This is a market-driven industry,'' says Statler. ``If there's an outcry for degradable products, the industry will respond. But we realize that it's not the panacea to the solid-waste crisis.''
Michael Levy, manager of legislative and regulatory affairs for Mobil Chemical Company, says that because the starch used in degradable bags makes them weaker, more polyethylene resin is needed to make them as strong as regular bags. ``When the consumers find out that this extra cost isn't going to do what they expect [shrinking landfills],'' says Mr. Levy, ``we don't want to be behind it.'' Adding plastic is retrogressive after years of developing thinner bags, he says.
While environmentalists and members of the plastics industry fear a premature rush to degradables, scientists and makers of degradables fear a rush to the wrong type of degradables.
Today there are three types: biodegradable (an organic substance such as cornstarch or cellulose is added to make the plastic edible for microbes in the soil); chemical (a natural catalyst like metal salt is added); and photodegradable (a light-sensitive chemical is added to or sprayed on the plastic to make it disintegrate in ultraviolet light).
Degradable bags are about 25 percent more expensive than nondegradables because the technology is limited to small-scale production and raw materials are costly, says Jill Beresford of Beresford Packaging in Taunton, Mass., a manufacturer of degradable and regular plastic shopping bags. In addition, she says, the cornstarch additive is ``inherently abrasive and hard on machinery,'' causing more downtime and broken machinery.
The degradable bags made by Beresford (and other companies in the US and Canada) will break down anywhere - without needing air, water, or light. They contain 15 percent pro-oxidant/starch additive, called ``Polyclean,'' a proprietary material from Archer Daniels Midland (ADM), an agricultural products company in Decatur, Ill. (see story in box).
ADM says their additive is ideal for all types of plastics and applications: single-use packaging, compost bags, grocery sacks, milk jugs, and hamburger holders.
The US Food and Drug Administration has not approved the use of degradable plastics in food packaging, although a photodegradable application is in the approval process, says Ken Falci, an FDA consumer safety officer in Washington. (Plastic food packaging falls under FDA jurisdiction, because polymers can migrate into foods and are considered additives.) One concern about degradable packages is that they could have a shorter shelf life than the food inside.
``In the long run, there is no simple solution - you need a combination ... recycling, degradability, composting, incineration,'' says Purdue's Dr. Narayam. ``We need materials that can be put back into some process, without harming the environment. That's the bottom line.''