ATMOSPHERIC SF6 - TRENDS, SOURCES, AND PROSPECTS

Sulfur hexafluoride (SF6) is the most potent greenhouse gas known. Its atmospheric concentration has increased by 2 orders of magnitude sinc e industrial production started in 1953. Once released into the atmosp here, SF6 will only be removed exceedingly slowly due to its atmospher ic lifetime of about 3200 yr. These features have brought SF6 into the climatic impact discussion aimed at reduction of emissions. The domin ant uses of SF6 are in gas insulated switchgear (GIS) and in blanketin g or degassing molten aluminum and magnesium. From 1978 onward, the ra pidly growing global SF6 burden is well-documented by atmospheric obse rvations. Concerning the SF6 applications responsible for that, a vast range of speculations is circulating. The underlying information gap- which preempts the design of any reduction program-will be bridged for the first time. Recently reported global sales of SF6 for end-use app lications form the basis of this investigation but need Various revisi ons. The good agreement between emissions modeled out of revised sales data and atmospheric observations since the 1970s allows the extrapol ation of the atmospheric SF6 record further back to the 1950s. Our ana lysis also shows that the natural background of SF6 is lower than 0.04 ppt. A geographical analysis of SF6 uses suggests that the North Amer ican market needs to be better specified. With certain technological e fforts, a global reduction of SF6 releases of up to 90% seems feasible , equivalent to 5500 t for the year 1995, and climatically equivalent to 132 million ton of CO2.