A foamy threat to ozone

U.S. residents junk some 8 million refrigerators annually. The unrecyclable components, including polyurethane foam insulation, often go into community landfills. Through the early 1990s, this foam usually incorporated chlorofluorocarbon-11 (CFC-11), a gas that destroys stratospheric ozone. Environmental scientists have now found that the speed with which this now-banned chlorofluorocarbon escapes into air depends on the way waste managers handle the discarded foam.

Results from earlier studies of large, intact pieces of foam suggested it might take more than 500 years for just half of the CFC-11 to diffuse out. However, when environmental engineer Peter Kjeldsen of the Technical University of Denmark in Lyngby actually measured gas emissions at landfills, he found much CFC-11. He traced it to the interred foam.

Kjeldsen’s data showed that 60 percent of the CFC resides in gas pockets in the foam instead of within the plastic itself. He therefore suspected that shredding–as occurs when a refrigerator is dismantled for scrap–releases the CFC. To test his hunch, Kjeldsen cut up foam from old refrigerators into cubes 1 or 2 centimeters on a side and monitored CFC-11 releases.

In the July 15 Environmental Science & Technology, his group reports results from a raft of different tests. They indicate that releases of CFC from the cubes were, per unit volume, 100 to 10,000 times as great as those reported for relatively large, intact foam pieces. These new data suggest that once shredded, foam could lose perhaps 25 percent of its CFC-11 within a single year, Kjeldsen says.

Unlike the United States, he notes, Denmark and a few other nations now chemically treat such foam to destroy its CFC-11 content before the gas can enter the environment.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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