The Trail Companion

Geoffrey Skinner

Go to your closet or your boxes of camping gear-and count how many items are made of nylon. In my own closet, I can spot two raincoats, rain pants, wind pants, shorts, pack covers, several backpacks, various stuff sacks, three sleeping bags...and that's just for starters. I own a lot of nylon and appreciate its lightness and versatility. I consider myself to be environmentally aware, yet the nylon that is used in most of my outdoor gear is one of the more environmentally damaging textiles to manufacture.
      I hadn't thought much about the environmental impact of nylon until I read an article in the National Outdoor Leadership School's The Leader: the voice of the National Outdoor Leadership which described the nylon manufacturing process and examined a new, "greener" method. The particular nylon used in my outdoor gear is nylon-6,6, a condensation polymer of hexamethlylenediamine and adipic acid. The first chemical is a pertroleum derivative, with the usual environmental consequences of petroleum processing. Adipic acid, however, is an even more serious matter. A paper by researchers from Nagoya University in Japan, "A green route to adipic acid: direct oxidation of cyclohexanes with 30 percent hydrogen peroxide," which appeared in the Sept. 11, 1998 issue of Science, noted that we produce over two million tons of nylon annually, which is also used in carpets, tires, auto parts and many other products. The nylon manufacture requires over 2.2 million metric tons of adipic acid, which in turn requires the oxidation of cyclohexanol or cyclohexanone by nitric acid, a process that produces nitrous oxide (N₂O), an ozone-depleting greenhouse gas. Efforts are made to minimize the release of nitrous oxide, yet adipic acid production is responsible for an estimated 5-8% of all the nitrous oxide produced worldwide annually. Since nylon was first synthesized in the 1930s, production has resulted in millions of tons of nitrous oxide being released into the atmosphere.
      All of that nitrous oxide means that my beloved nylon has serious environmental impacts. Both precursors to nylon require petroleum processing, in addition to adipic acid's nitrous oxide release that may contribute to global climate change (not to mention disposal of worn out nylon goods). The good news is that at least the adipic acid portion of the process can be accomplished without releasing nitrous oxide. The Nagoya University researchers developed a means of oxidizing cyclohexane with crystalline adepic acid using hydrogen peroxide (H₂O2) instead of nitric acid. That still leaves the problem of petroleum derivatives, but fossil fuel use is currently so pervasive that the impact from nylon manufacture comprises only a small fraction of the overall impact.
      Hydrogen peroxide is more expensive than nitric acid, but the researchers saw no technical barrier to a greener route to nylon manufacture. If hydrogen peroxide costs can be reduced (a goal of the chemical industry for a variety of manufacturing processes) and-this is where, as consumers, you and I come in-market pressures are brought to bear on the manufactures of nylon products, including outdoor gear manufacturers, "greener" nylon will become available. Currently, none of the gear manufacturers are producing products made with this type of nylon. Calls to North Face and REI were unfortunately met with little success-the employees with whom I spoke were unfamiliar with the term; the outdoor clothing representative at REI suggested that I should call Patagonia, since they have often been leaders in technical innovations. When I spoke to Eric Wilmann, who deals with product questions at Patagonia, he told me that they would likely be the first to use it if it were available. He said that Patagonia has looked into a number of more environmentally friendly synthetic fibers over the years, but the main barrier to creating products using "green" nylon is that the outdoor gear industry uses such a small percentage of the total nylon produced each year that they simply lack the ability to even obtain the amount needed for a pilot project. Unlike organic cotton, where the fibers are produced in small enough quantities it isn't difficult to halt the mill and clean it to run a batch of organic cotton, the chemical plants producing nylon run such huge batches that the equivalent run of "green" nylon would be about 45 seconds long! The key to being able to get a small enough batch will be teaming up with a really large consumer of nylon, such as a major carpet manufacturer.
     In the meantime, Patagonia is looking into other synthetics, including a polyester recycling program that repolymerizes PET plastics (such as pop bottles) and essentially recreates virgin polyester (current practice is limited to grinding up the plastic, which limits the use of the resulting fibers). Down the road, they may also be able to use biopolymers.
      If "green" nylon products do come available, we can choose and request these products to purchase when we shop for new gear. Initially, we will pay more for the privilege of more environmentally friendly gear, but as the outdoor community becomes aware of this option and manufactures see the demand, prices will fall. While shopping for a better world may have serious limitations as a path to improving the environment, I will probably continue to buy and use nylon in my outdoor activities, as well as in many other realms of my life. Choosing "green" nylon outdoor products is the one realm in which I could most easily make a small step toward reducing my contribution to nitrous oxide damage to the atmosphere.

K. Sato, M. Aoki, R. Noyori, Science, 1998 September 11; 281: 1646-1647.

L. Pagliaro, "'Greener' nylon: something we should demand," The leader: the voice of the National Outdoor Leadership School, spring 1999; v. 22, no. 2: 9.

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