OF the 180 million tons of solid waste Americans throw into landfills each year, about 20 percent, by volume, is plastics. About 8 percent of the total volume of garbage is plastic packaging, everything from soda pop bottles to hamburger containers.
That 8 percent holds the greatest hope for recycling, and the collection and reuse of many plastics have significantly increased in recent years. But there's still a huge amount of room for improvement. About 6 percent of the total plastics used in packaging was recycled in 1993, according to the Plastics Institute of America.
A reason more plastics have not been recycled is economics: Making new plastic from recycled bottles and cartons has usually been more expensive than making it from the basic raw material, petroleum and natural gas. So the stuff has gone into landfills instead.
Thorny technical problems, such as separating the various kinds of plastics that get into the waste stream, pose another hurdle. A key problem, says Howard Herzog, a senior research engineer at Massachusetts Institute of Technology (MIT) in Cambridge, Mass., is the need for ``very pure feed stock'' to meet the specifications for many plastic products. Mr. Herzog served as an adviser to student researchers who recently wrote a ``working paper'' on the problems of plastics recycling.
Unlike glass bottles, plastic containers are not washed and reused, but melted down. The federal government sets very high standards for the ingredients that go into food containers, and much of the melted-down waste plastic can't meet those standards.
Only a relatively small percentage of used soft-drink containers, for instance, is recycled into new bottles, says Bill Sacks, executive director of the Plastics Institute of America. Most such containers, which carry the recycling code ``1'' and are made of polyethylene terephthalate (PET), get melted down and turned into carpet fiber, fill for insulated apparel, and various other nonfood-related items, Mr. Sacks says.
Plastic recycling rises
A relatively high 35 to 40 percent of the PET containers sold are recycled. The heavier plastic ``base cups'' that encase the bottom of large soda bottles are also recycled at a relatively high rate, around 15 percent. They're made of high density polyethylene (HDPE), as are many other common containers, such as milk bottles, and carry the recycling number ``2.'' They can be recycled into such products as irrigation drainage tiles or sheet plastic. But these categories are the exceptions, according to the working paper produced by MIT researchers. The amount of plastic recycled each year is rising, it notes, but so is the amount produced and pumped into the waste stream, so the level of reuse stays low.
That conclusion is challenged by the plastics industry itself, which emphasizes that the recycling of plastic packaging is growing rapidly. More than 1 billion pounds of plastics were recycled last year, representing a 12 percent increase over 1992, says James Hendricks, spokesman for the American Plastics Council, an industry group. The numbers of companies getting into recycling is growing too, he says, as are the numbers of firms using recycled plastics to manufacture goods - and often highlighting that fact as a point of environmental good citizenship.
In some parts of the country, plastics recyclers are running short of raw materials, Mr. Hendricks says. As communities become more aware of the market for recyclable plastic they'll do more to separate it out from other waste, he says.
One option for some used plastic might be to burn it for fuel, the MIT report notes. The heat-producing capacity of plastics - measured in British thermal units per pound - exceeds that of bituminous coal and nearly equals that of fuel oil.
Some new waste-to-energy facilities can burn plastics right along with other trash, but other types of burning would require the separation of plastics from other municipal waste to arrive at a purer fuel. Burning also raises environmental concerns about toxic fumes, although that problem can be addressed by current clean-air technologies.
More promising, according to the MIT researchers, would be steps to alter the economic equation. A tax could be added to landfill charges; recycling could be made easier and more convenient by providing better collection services for plastic containers; returnable deposits could be put on a wider range of plastic products; the market for products made from recycled plastic could be expanded by informing the public of their benefits, and perhaps even by government-procurement preferences.
Sacks suggests that market forces are already at work alleviating the problem. In recent months, the cost of ``virgin materials'' - newly produced plastic resins - has jumped, he says, probably because of shortages and rapid increases in consumption. Recycled plastics are thus more likely to become economically competitive.
In fact, Sacks says, plastic resins produced from recycled PET and HDPE bottles are currently significantly cheaper than the virgin products.