Beyond CO2
We are addressing other greenhouse gases like hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), nitrous oxide (N2O) and sulfur hexafluoride (SF6). Low N2O emission is a requirement for exhaust treatment systems. We have prohibited SF6 in tires and PFCs in open systems since 1999. We restrict the use of HFCs in vehicle air conditioning and prohibit the use of HFCs in other on-board vehicle applications (e.g., as used in some spare tire kits). We prohibited the use of SF6 in magnesium casting as of January 2004 through our Restricted Substance Management Standard. We are working with our suppliers to optimize air conditioning efficiency, reduce leakage rates and investigate alternatives.
We have measured the rates of emission of N2O, CH4 and HFCs associated with the use of our products. In 1999 and 2000, we published reports on N2O emissions (Environmental Science and Technology, 33, 4134, 1999; Chemosphere: Global Change Sci., 2, 387, 2000). In 2002, we published a report on HFC-134a emissions (Environmental Science and Technology, 36, 561, 2002). In 2004, we published a report on CH4 emissions (Environmental Science and Technology, 38, 2005, 2004).
These studies show that N2O and CH4 emissions from vehicles have a global warming impact, which are approximately 1 to 3 percent and 0.3 to 0.4 percent, respectively, of that of CO2 emissions from vehicles. The global warming impact of R-134a leakage from an air-conditioning-equipped vehicle is approximately 4 to 5 percent of that of the CO2 emitted by the vehicle.
