Life-Cycle Studies: Nylon
Nylon cannot be melted down and used again, and recycling nylon requires it to be broken down into its constituent chemicals. But the process offers an alternative to sending billons of kilograms of nylon carpets to landfills each year in the United States alone. DuPont, Evergreen, and BASF Corporation have built nylon-carpet recycling facilities in North America and Europe. While the purification and remanufacturing processes do create some waste, this system (which recycles 25 million kilograms of carpet annually) is nearly a closed loop.
For the 1 billion tires discarded worldwide each year, numerous alternative uses are possible. Half of U.S. tire scrap is burned as fuel in cement kilns, waste-to-energy plants, and industrial boilers. Burning a tire yields about one-sixth the energy required to produce it, and doing so releases the carbon that constitutes 85 percent of a tire. More than half the tires discarded in California are patched up for further driving or shredded to become products such as insulation, playground cushioning, and mulch. A Connecticut public health study, however, warned in 2007 that tire crumbs could release carcinogenic chemicals into the air and ground water.
The leading alternative to nylon, at least for clothing, is polyester, but it also consumes significant oil during production. Although the manufacture of cotton foregoes fossil fuels, in the world’s leading cotton-producing country, the United States, cotton accounts for a quarter of the country’s energy-intensive, polluting pesticides. Despite recent increases, organic cotton production still amounts to a mere 0.03 percent of the worldwide total. Moreover, a Cambridge University study found that polyester materials consume less lifecycle energy than organic apparel, which require frequent washings at high temperatures, tumble-drying, and ironing. Perhaps a Nobel Prize in chemistry awaits the green chemist who invents a sustainable alternative.