June 28, 2001 Shredded foam insulation from junked refrigerators is releasing substantial amounts of ozone-depleting chlorofluorocarbons, or CFCs, into the earth's atmosphere — and the more finely shredded the foam, the faster the release, a Danish researcher reports.
The first study looking at how and how fast CFC gas releases from foam insulation used in older refrigerators is reported in the July 15 issue of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.
More than eight million refrigerators and freezers in the United States reach the end of their useful lives and are thrown away annually, generally ending up at a landfill where they are shredded to recover scrap metal. Shredding one discarded refrigerator can quickly release more than 100 grams of CFC-11 into the environment, reports Peter Kjeldsen, Ph.D., an associate professor at the Technical University of Denmark. All 500 grams of CFC gas in the insulation of each refrigerator — a total of nearly 4,000 tons of CFC emissions — can eventually seep from the appliances over the next 300 years, he said.
"The future atmospheric concentrations of CFC-11, and their effect on the ozone layer, will mainly depend on the continued release from insulation foams," Kjeldsen said.
Comparing their laboratory CFC-release rates to computer models, the researchers found that all CFC gas embedded in the energy-saving insulation is slowly, but surely, released after the foam is ripped apart. The smaller the size of the shredded foam, the faster the release, he noted. Some other countries, including Denmark, dispose of the foam before scrapping the refrigerator, which eliminates most CFC emissions, Kjeldsen said.
Although CFCs were developed in the 1930s, the majority of the CFC emissions are coming from refrigerators made during the 1980s, when a new type of insulating foam featuring the material was used. The appliances normally last for around 20 years, Kjeldsen said.
"Use of these results may help evaluate changes in the atmospheric concentrations of CFC-11 in the future," he said. "They add to the understanding of a very important source of CFCs."
Chlorine contained in CFCs damages the earth's ozone layer, a thin shield of oxygen that protects the planet from ultraviolet radiation. A single chlorine atom — contained in CFCs and also found naturally — can destroy more than 100,000 ozone molecules, although ozone can be reformed over time by a chemical reaction stimulated by sunlight. The upper part of the atmosphere known as the stratosphere contains approximately 3 billion kilograms of ozone — enough to create a layer about an eighth of an inch thick that circles the globe.
Depletion of the ozone layer leads to higher levels of a certain type of ultraviolet (UV) radiation reaching the earth's surface. Previous testing has shown that higher UV-B levels increase the risk of skin cancer, harm plant life, reduce the population of sea life and contribute to the increase of carbon dioxide and other greenhouse gases believed to be responsible for atmospheric warming, according to the U.S. Environmental Protection Agency.
Because of the dangers of exhausting the ozone layer, more than 120 countries signed the 1987 "Montreal Protocol" to control CFC emissions. After 1995, when production of most CFCs stopped, they ceased being used in aerosol cans and in the coolant known as Freon™. New products, including refrigerators, use substitutes with similar properties. Additional amounts of CFC-11 can be found in air conditioners, insulation and some industrial appliances. A different type of CFC is used in the product marketed as Styrofoam™.
The research cited above was partially funded by the Danish Technical Research Council.
Peter Kjeldsen, Ph.D., is an associate professor in the department of environment and resources unit at the Technical University of Denmark in Lyngby, Denmark.
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