PLAINFIELD, N.H. — The world of plastics is in a mess these days because it has made a mess. Polyethylene, polystyrene, polyvinyl chloride and all the other polys pile up--on roadsides, in the ocean and in landfills. They are likely to last several hundred years, after serving us sometimes only for a few hours or weeks--if indeed they could be said to serve at all. The primary role of many plastics is to catch attention in a store, where they are garishly shaped and colored with, among other things, toxic heavy metals. Environmentalists say the dumps fill up not with packaging, but with marketing.
Until we noticed dumps filling, most of us never thought about streams of plastics flowing through our lives--18 million tons each year, including 6.5 million tons of packaging and more than $3 billion dollars' worth of plastic garbage bags in which to throw the other plastics out. Now we approach panic. Pending in state legislatures are 66 proposed bans on non-biodegradable packaging; 12 packaging taxes; 74 source separation and recycling mandates, and 19 requirements that state governments purchase recycled materials.
It's not fair to blame plastics for our trash problem, says the industry. Plastics make up only 4% to 7% of municipal solid waste (by weight; by volume it's more like 20% to 30%). But plastics are the focus of most legislation, perhaps because they are the fastest growing constituent of trash, or because they are used for so many trivial purposes, or because they are so nearly immortal.
Immortality is one quality that makes plastics useful, of course. They are impervious to bacteria, acid, salt, rust, breakage, almost any agent except heat--and some of them can even stand up to heat. If they didn't junk up our lives so, we would regard them as miracle substances--long, long hydrocarbon chains, crafted to take on almost any properties we want. Plastics can be transparent or opaque, hard as steel or pliant as silk, squeezable or rigid, moldable into any conceivable shape.
And, environmentalists would say, they are made from depleting supplies of oil and gas, wrested from the ends of the earth, synthesized in energy-consuming, hazardous-waste-generating processes and disposed of carelessly. Messy, from beginning to end. If we were properly charged for the full human and environmental costs of plastics, we would not eliminate them--they are far too useful for that--but we would treat those specialized molecules with the respect they deserve. We would not use them for a few days or hours and throw them out.
The standard environmentalist formula for dealing with precious but polluting materials is simple: Reduce, reuse, recycle, in that order, and then, as a last resort, dispose with care. Of course the plastics industry makes money in inverse order. It is looking for a way to keep us buying millions of tons of plastics each year--and to have them miraculously disappear when we throw them away.
Therefore industry's favorite answers to the plastics problem are two: incineration and degradation.
As a descendant of petroleum, plastic burns beautifully. Like all hydrocarbons, it combusts into carbon dioxide, a greenhouse gas, plus a host of other pollutants. Some of them derive from additives such as heavy metals (which end up either in air emissions or incinerator ash). Others, like toxic dioxins and furans, come from high-temperature reactions between hydrocarbons and chlorine. Polyvinyl chloride (PVC) releases so much hydrochloric acid as it burns that it corrodes the incinerator. For that reason one incinerator manufacturer recommends keeping PVC out of incinerated trash.
Incineration can recapture a small fraction of the energy and effort put into making plastics. Degradation doesn't even do that.
Degradable plastics come in two forms: biodegradable and photodegradable. The biodegradable kind mixes the long plastic molecules, which nothing in nature can digest, with starch; microorganisms will happily munch away on starch.
On the side of the road a bottle or bag made of biodegradable plastic slowly falls apart--into tiny shards of undegradable plastic. The bottle or bag disintegrates, but the plastic is still there. Presumably it is inert and harmless, but no one really knows the implications of a world filled with plastic sand.
In a landfill, biodegradation happens very slowly, if at all. Nothing degrades well in a landfill. William Rathje, a University of Arizona anthropologist, drills core samples from old landfills and finds intact food, paper, cloth--20 years old. He can date the layers exactly, because he can read the newspapers. Landfills are not compost heaps. They haven't the proper air circulation, moisture content, mixture of nutrients or communities of microorganisms to encourage natural breakdown.