Emissions of Tetrafluoromethane (CF₄) and Hexafluoroethane (C₂F₆) From East Asia: 2008 to 2019

Abstract

The perfluorocarbons (PFCs), tetrafluoromethane (CF 4 ) and hexafluoroethane (C 2 F 6 ), are potent greenhouse gases with very long atmospheric lifetimes. They are emitted almost entirely from industrial sources, including the aluminum and rare earth metal smelting industries that emit them as by-products, and the semiconductor and flat panel display manufacturing industries that use them and vent unutilized amounts to the atmosphere. Despite extensive industrial efforts to quantify and curb these emissions, "top-down" PFC emission estimates derived from atmospheric measurements continue to rise and are significantly greater than reported process-and inventory-based "bottom-up" emissions. In this study, we estimate emissions of CF 4 and C 2 F 6 from East Asia, where PFC emitting industries are heavily concentrated, using a top-down approach (a Bayesian inversion) with high-frequency atmospheric measurements at Gosan (Jeju Island, South Korea) for [2008][2009][2010][2011][2012][2013][2014][2015][2016][2017][2018][2019]. We also compile and analyze the available bottom-up CF 4 and C 2 F 6 emissions in East Asia from industrial and government reports. Our results suggest that the observed increases in global PFC emissions since 2015 are driven primarily by China's aluminum industry, with significant contributions from Japan's and Korea's semiconductor industry. Our analysis suggests that Chinese emissions occur predominantly from the aluminum industry, although their emissions per production ratio may be improving. Our results for Japan and Korea find significant discrepancies between top-down and bottom-up emissions estimates, suggesting that the effectiveness of emission reduction systems (abatement) used in their semiconductor industries may be overestimated. Overall, our top-down results for East Asia contribute significantly to reducing the gap in the global PFC emission budgets.Plain Language Summary CF 4 and C 2 F 6 , emitted mainly from the aluminum and semiconductor industries, are some of the longest-lived greenhouse gases known, and among the compounds included under the United Nations Framework Convention on Climate Change in the global effort to reduce greenhouse gas emissions and mitigate climate change. Despite significant progress from both industries in understanding and reducing their emissions over the last 3 decades, the global emissions of CF 4 and C 2 F 6 modeled using atmospheric measurements continue to rise, and are significantly larger than those currently reported by industry and government. In this study, we estimate CF 4 and C 2 F 6 emissions over 2008-2019 in East Asia, where the aluminum and semiconductor industries are heavily concentrated, using a regional inverse model framework combined with measurements at a site in East Asia (Gosan, Jeju Island, South Korea). Our results confirm the dominant role of East Asian emissions in the global budgets of CF 4 and C 2 F 6 , led by emissions from China's aluminum industry. Our regional emission estimates are significantly larger than those r...

In Situ Observations of Halogenated Gases at the Shangdianzi Background Station and Emission Estimates for Northern China

“…Between 2008 and 2015, the CF 4 emissions from China stabilized at 2–6 Gg year –1 , which was more than twice the range of 1–3 Gg year –1 reported by the Emission Database for Global Atmospheric Research (EDGAR) v6.0 . The values reported in 2017–2019 increased by 29% over those reported in 2012–2014 . Here, the CF 4 emissions from northern China during 2020–2021 were estimated as 1.6 ± 0.4 Gg year –1 .…”

“…Emissions of CF 4 , NF 3 , and SF 6 derived using the tracer ratio method in this study compared with the reported estimates for northern China. ,− ,,− …”

“…Moreover, the accuracy of emissions obtained via inverse modeling is limited by the a priori emission distribution, representativeness of the observations, and measurement accuracy. Therefore, few studies have estimated CF 4 and NF 3 emissions from China, with large gaps present in the reported emissions, ,,, and no studies focused on the emissions of CF 4 and NF 3 from northern China. An inverse modeling result showed that China had the largest CF 4 emissions among East Asian countries during 2008–2015 .…”

“…50 The values reported in 2017−2019 increased by 29% over those reported in 2012−2014. 49 Here, the CF 4 emissions from northern China during 2020−2021 were estimated as 1.6 ± 0.4 Gg year −1 . The NF 3 emission from China derived via inverse modeling (0.36−1.08 Gg year −1 ) 9 during 2014−2015 was also considerably higher than the bottom-up estimate of 0.03 Gg year −1 .…”

Atmospheric Observation of Fluorinated Greenhouse Gases around Four Chemical Plants in China

“…The impact of climate change and biological toxicity was studied to evaluate the environmental impacts of F-gases [26][27][28][29][30][31]. The emissions of F-gases have been calculated based on bottomup and top-down methods [24,32,33], and atmospheric observation was the important support for emission estimation. The atmospheric observations of F-gases have been mostly carried out at background and urban sites.…”