Dinitrogen monoxide
The production of hexanedioic acid (adipic acid), used to manufacture PA 6,6, uses large quantities of nitric acid in the final stage, with consequent release of the gas dinitrogen monoxide (nitrous oxide), N2O. Although modern plants produce much lower quantities of this gas than was previously the case, it is not easy to treat, and many thousands of tonnes are released into the atmosphere annually.
There are concerns over increases in atmospheric concentration, for two main reasons:

  • N2O has a "greenhouse" effect in the atmosphere, which is over 200 times as strong as carbon dioxide, and so may contribute to climate change
  • N2O is involved in reactions responsible for the thinning of the ozone layer

Production of hexanedioic acid for PA 6,6 is estimated to account for 10% of dinitrogen monoxide emission, and so alternative production methods are being developed that either recycle the gas, or use reagents other than nitric acid. Find out more about these developments.

Waste and Recycling
Over 60% of all polyamide produced is used to manufacture carpets, other furnishing products and clothing items. Until recently the only option when these materials reached the end of their useful life was to dispose of them along with all other household waste - in many countries this means burying in landfill sites, or incineration.

Recycling is always a better option where it is feasible, and this is increasingly being used with nylon carpets. As the technology becomes established, several countries are bringing in legislation that will eventually prohibit disposal of carpet in landfill, forcing suppliers and consumers to recycle old carpet. Click here to find out more about carpet recycling.

Recycling to produce new carpet material is now possible, paving the way to closed loop recycling, link to recycling section when written in which little further input of raw material is needed.

photo: carpet waste often ends up in landfill

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