Greenhouse Gases: Synthetic Chemicals

   Manufacturing processes use or generate many synthetic chemicals that are powerful greenhouse gases. Although these gases are produced in relatively small quantities, they trap hundreds to thousands of times more heat in the atmosphere than an equal amount of carbon dioxide does. In addition, their chemical bonds make them exceptionally long-lived in the environment.

     Human-made greenhouse gases include chlorofluorocarbons (CFCs), a family of chlorine-containing gases that were widely used in the 20th century as refrigerants, aerosol spray propellants, and cleaning agents. Scientific studies showed that the chlorine released by CFCs into the upper atmosphere destroys the ozone layer. As a result, CFCs are being phased out of production under a 1987 international treaty, the Montréal Protocol on Substances that Deplete the Ozone Layer. CFCs were mostly banned in industrialized nations beginning in 1996 and will be phased out in developing countries after 2010. New chemicals have been developed to replace CFCs, but they are also potent greenhouse gases. The substitutes include hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).

      Although HCFCs are less damaging to the ozone layer than CFCs, they also contain chlorine and are scheduled to be completely phased out by 2030 under amendments made in 2007 to the Montréal Protocol. Developed countries must end their use of HCFCs by 2020 under the amended protocol.

   Although HFCs and PFCs do not destroy the ozone layer, they are powerful greenhouse gases. In addition, they last longer in the atmosphere than CFCs, which have an average lifespan of 120 years. PFCs are exceptionally long-lived chemicals—they can persist in the atmosphere between 2,600 and 50,000 years, depending on the specific compound. Their accumulation in the atmosphere is therefore essentially irreversible. PFCs are used in the production of aluminum, in the manufacture of semiconductors, and as refrigerants.

     Another human-made chemical, sulfur hexafluoride, is one of the most potentially destructive greenhouse gases ever produced. This synthetic gas compound has nearly 24,000 times the warming effect of an equal amount of carbon dioxide over a period of 100 years. It is an exceptionally stable gas with an estimated lifespan of 3,200 years once it is released in the atmosphere. Sulfur hexafluoride is used as insulation for high-voltage electrical equipment and in the production and casting of magnesium.