Atmosphere-based US emission estimates of SF6 for 2007 - 2018

<p>Sulfur hexafluoride (SF₆) is a potent greenhouse gas (GHG) that is primarily emitted from electrical circuit breakers and heavy-duty gas-insulated switchgears in electric transmission and distribution equipment, magnesium production and processing, and electronics production. It has a 100-year global warming potential of 23500 and an atmospheric lifetime of 850 (580 - 1400) years. Because of its extremely large global warming potential and long atmospheric lifetime, its emissions, while currently small, have an outsized influence on changing climate over the long term.&#160; However, current US emissions of SF₆ are uncertain. The US SF₆ consumption that was used to estimate SF₆ emissions in the US EPA national GHG reporting to the UNFCCC has an uncertainty of 30 &#8211; 60%, depending on whether to use the US SF₆ supplier reports or user reports. With different inventory methodologies, the national emissions estimates of SF₆ from the EDGAR and US EPA&#8217;s GHG inventories differ by more than a factor of 4. Here, we will present the first detailed U.S. national and regional emissions of SF₆ that were derived from an inverse analysis of an extensive flask-air sampling network from the US NOAA&#8217;s Global Greenhouse Gas Reference Network and high-resolution atmospheric transport simulations for 2007 - 2018. We will discuss our atmosphere-based top-down emission estimates in comparison with the existing bottom-up emission inventories, our derived seasonal variation of SF₆ emissions, and associated implications regarding each industry&#8217;s contribution to emissions and optimal emissions mitigation strategies. Because atmospheric SF₆ measurements are also used to assess atmospheric transport errors assuming no biases in SF₆ emissions reported by the EDGAR inventory, our analysis also has important implications on limitations in such applications.</p>