Perfluorocarbon Emissions Research Articles

Process Optimization to Avoid Perfluorocarbon Emission During Neodymium Rare Earth Electrolysis in Molten LiF-NdF3-Nd2O3

Influence of Nd2O3 in LiF-NdF3-Nd2O3 melt on carbon anode oxidation was investigated by infra-red spectroscopy and electrochemical techniques to prevent CFX(g) formation during Nd metal production. A gas extractor device was developed to provide fast analysis of the electrochemically produced gas: the carbon anode was only oxidized into CO2(g) until a critical current density was reached. For higher values, CF4(g) and C2F6(g) were also produced. It was associated to diffusion limited current density of NdOF5 4−. To avoid CFX(g) production during the process, the influence of Nd2O3 and temperature on this limiting current density was determined by steady-state voltammetry.

Plasma Etching of SiO2 Contact Holes Using Hexafluoroisopropanol and C4F8

This study presents the feasibility of the use of hexafluoroisopropanol (HFIP) as a substitute to perfluorocarbon (PFC) for the plasma etching of SiO2 to confront the continuous increase in demand for PFC emission reduction. SiO2 etching is conducted in HFIP/Ar and C4F8/Ar plasmas, respectively, and its characteristics are compared. The SiO2 etch rates in the HFIP/Ar plasma are higher compared with those in the C4F8/Ar plasma. The thickness of the steady-state fluorocarbon films formed on the surface of SiO2 are lower in the HFIP/Ar plasma compared with in the C4F8/Ar plasma. Higher SiO2 etch rates and thinner fluorocarbon films in the HFIP/Ar plasma are attributed to the oxygen atoms in HFIP, which generate oxygen radicals that react with the fluorocarbon films to turn into volatile products. Due to the higher dissociation of C-F bonds in CF4 compared with in HFIP, the etch rates of SiO2 in the C4F8/Ar plasma increase more rapidly with the magnitude of the bias voltage compared with those in the HFIP/Ar plasma. The etch profiles of the 200 nm diameter SiO2 contact holes with an aspect ratio of 12 show that fairly anisotropic SiO2 contact hole etching was achieved successfully using the HFIP/Ar plasma.

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

The perfluorocarbons (PFCs), tetrafluoromethane (CF4) and hexafluoroethane (C2F6), 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 CF4 and C2F6 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 2008–2019. We also compile and analyze the available bottom‐up CF4 and C2F6 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.

Global trends and European emissions of tetrafluoromethane (CF<sub>4</sub>), hexafluoroethane (C<sub>2</sub>F<sub>6</sub>) and octafluoropropane (C<sub>3</sub>F<sub>8</sub>)

Abstract. Perfluorocarbons (PFCs) are amongst the most potent greenhouse gases listed under the United Nations Framework Convention on Climate Change (UNFCCC). With atmospheric lifetimes on the order of thousands to tens of thousands of years, PFC emissions represent a permanent alteration to the global atmosphere on human timescales. While the industries responsible for the vast majority of these emissions – aluminium smelting and semi-conductor manufacturing – have made efficiency improvements and introduced abatement measures, the global mean mole fractions of three PFCs, namely tetrafluoromethane (CF4, PFC-14), hexafluoroethane (C2F6, PFC-116) and octafluoropropane (C3F8, PFC-218), continue to grow. In this study, we update baseline growth rates using in situ high-frequency measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) and, using data from four European stations, estimate PFC emissions for northwest Europe. The global growth rate of CF4 decreased from 1.3 ppt yr−1 in 1979 to 0.6 ppt yr−1 around 2010 followed by a renewed steady increase to 0.9 ppt yr−1 in 2019. For C2F6, the growth rate grew to a maximum of 0.125 ppt yr−1 around 1999, followed by a decline to a minimum of 0.075 ppt yr−1 in 2009, followed by weak growth thereafter. The C3F8 growth rate was around 0.007 ppt yr−1 until the early 1990s and then quickly grew to a maximum of 0.03 ppt yr−1 in 2003–2004. Following a period of decline until 2012 to 0.015 ppt yr−1, the growth rate slowly increased again to ∼ 0.017 ppt yr−1 in 2019. We used an inverse modelling framework to infer PFC emissions for northwest Europe. No statistically significant trend in regional emissions was observed for any of the PFCs assessed. For CF4, European emissions in early years were linked predominantly to the aluminium industry. However, we link large emissions in recent years to a chemical manufacturer in northwest Italy. Emissions of C2F6 are linked to a range of sources, including a semi-conductor manufacturer in Ireland and a cluster of smelters in Germany's Ruhr valley. In contrast, northwest European emissions of C3F8 are dominated by a single source in northwest England, raising the possibility of using emissions from this site for a tracer release experiment.

Study of Perfluorocarbon Release During Aluminum Production in Vertical-Stud Electrolytic Cells with Self-Baking Anode in Between Anode Effects

Emissions of perfluorocarbons (PFCs) from the vertical-stud Soderberg cells during aluminum production outside of anode effects were studied. PFC emissions were monitored at the flue gas pipe coming from 22 cells provided with automated alumina feeding system. In the process of measurements, no significant PFC emissions were detected. Based on the results of the analysis, it was concluded that only PFC emissions from the Soderberg cells produced during anode effects should be monitored without accounting for PFC emissions formed outside of anode effects.

An Ex-ante LCA Study of Rare Earth Extraction from NdFeB Magnet Scrap Using Molten Salt Electrolysis

A new recycling process for the extraction of rare earths from neodymium–iron–boron (NdFeB) magnet scrap is being developed, based on the direct extraction of rare earths from end-of-life magnet material in a molten fluoride electrolysis bath. Rare earths are required in their metallic form for the production of new NdFeB magnets, and the suggested process achieves this through a single step. The process is being developed on a laboratory scale and has been proven to work in principle. It is expected to be environmentally beneficial when compared to longer processing routes. Conducting life cycle assessment at R&D stage can provide valuable information to help steer process development into an environmentally favorable direction. We conducted a life cycle assessment study to provide a quantitative estimate of the impacts associated with the process being developed and to compare the prospective impacts against those of the current state-of-the-art technology. The comparison of this recycling route with primary production shows that the recycling process has the potential for much lower process-specific impacts when compared against the current rare earth primary production route. The study also highlights that perfluorocarbon emissions, which occur during primary rare earth production, warrant further investigation.

Estimating perfluorocarbon emission factors for industrial rare earth metal electrolysis

Rare earth (RE) metals have been widely applied in new materials, leading to their drastic production increase in the last three decades. In the production process featured by the molten-fluoride electrolysis technology, perfluorocarbon (PFC) emissions are significant and therefore deserve full accounting in greenhouse gas (GHG) emission inventories. Yet, in the ‘2006 IPCC Guidelines for National Greenhouse Gas Inventories’, no method currently exists to account for PFC emissions from rare earth metal production. This research aims to determine emission factors for industrial rare earth metals production through on-site monitoring and lab analysis of PFC concentrations in the exhaust gases from rare earth metal electrolysis. Continuous FTIR measurements and time-integrated samples (analysed off-site by high-precision Medusa GC–MS) were conducted over 24–60 h periods from three rare earth companies in China, covering production of multiple rare earth metals/alloys including Pr-Nd, La and Dy-Fe. The study confirmed that PFC emissions are generated during electrolysis, typically in the form of CF4 (∼90% wt of detected PFCs), C2F6 (∼10%) and C3F8 (<1%); trace levels of c-C4F8 and C4F10 were also detected. In general, PFC emission factors vary with rare earth metal produced and from one facility to another, ranging from 26.66 to 109.43 g/t-RE for CF4 emissions, 0.26 to 10.95 g/t-RE for C2F6, and 0.03 to 0.27 g/t-RE for C3F8. Converted to 211.60 to 847.41 kg CO2-e/t-RE for total PFCs, this emissions intensity for rare earths electrolysis is of lower (for most RE production) or similar (Dy-Fe production) level of magnitude to industrial aluminium electrolysis.

Universal Approach to Estimate Perfluorocarbons Emissions During Individual High-Voltage Anode Effect for Prebaked Cell Technologies

Recent investigations on aluminum electrolysis cell demonstrated limitations to the commonly used tier-3 slope methodology to estimate perfluorocarbon (PFC) emissions from high-voltage anode effects (HVAEs). These limitations are greater for smelters with a reduced HVAE frequency. A novel approach is proposed to estimate the specific emissions using a tier 2 model resulting from individual HVAE instead of estimating monthly emissions for pot lines with the slope methodology. This approach considers the nonlinear behavior of PFC emissions as a function of the polarized anode effect duration but also integrates the change in behavior attributed to cell productivity. Validation was performed by comparing the new approach and the slope methodology with measurement campaigns from different smelters. The results demonstrate a good agreement between measured and estimated emissions as well as more accurately reflect individual HVAE dynamics occurring over time. Finally, the possible impact of this approach for the aluminum industry is discussed.

Perfluorocarbon emissions from electrolytic reduction of rare earth metals in fluoride/oxide system

Perfluorocarbons (PFC) are important greenhouse gas. In the aluminum electrolysis industry, PFC emission had been valued. The electrolytic reduction of rare earth metals in fluoride/oxide system with carbon anode and tungsten cathode also has PFC emission. But the PFC emission in rare earth metals industry received less attention. The PFC emissions during the electrolysis were studied by tracking the change of CF4 concentration in the flue gas of neodymium electrolysis and dysprosium-iron alloy electrolysis. The results showed that there were continuous CF4 overflows in the electrolysis process. The CF4 was outburst when anode effect occurred. The anode effect was always accompanied with the low electrolysis temperature. In addition, because of the electrolytic dysprosium-iron alloy requires higher cell voltage, the PFC emissions are higher than rare earth electrolysis. In general, PFC emissions from rare earth metal electrolysis are quite same as the aluminum electrolysis industry.

Quantification of perfluorocarbons emissions during high voltage anode effects using non-linear approach

Significant amounts of greenhouses gases are produced annually by aluminium smelters around the globe. Most of these emissions are carbon dioxide but perfluorocarbons are nonetheless an essential part of GHG inventories for aluminium smelters. The total mass of perfluorocarbons declared is estimated using a linear relationship between some process parameters and a specific emission coefficient. However, this linear method does not accurately represent the observed behaviour of PFC emissions.Continuous gas measurements were performed using a Fourier-transformed infrared spectrometer connected to the gas treatment centre for several days. With the data collected from individual high voltage anode effects, four new models are proposed to estimate the emissions of tetrafluoromethane, along with three new models to estimate hexafluoroethane emissions.These non-linear models are compared to the existing methods and the overall accuracy of each model is calculated in comparison to in-situ measurements. The accuracy of each model to predict emissions associated to individual anode effects have been investigated as well and the results indicate that tetrafluoromethane emissions can be more accurately predicted by the proposed non-linear models. Models proposed to predict hexafluoroethane emissions are optimistic, but further refinements are necessary to optimise the accuracy of individual predictions.

Reducing Greenhouse Gas Emission from the Neodymium Oxide Electrolysis. Part II: Basics of a Process Control Avoiding PFC Emission

The neodymium electrolysis produces unnecessary high emission of CF4 and C2F6. These perfluorocarbons (PFCs) are potent greenhouse gases and are not filtered or destroyed in the off-gas. A process control in analogy to the aluminum electrolysis can reduce the PFC emission to a great extend and keep the process in a green process window. Therefore, a theoretical analysis is done of the cell voltage of the industrial neodymium electrolysis in dependence on the neodymium oxide concentration in the electrolyte. The analysis shows the different contributions to the cell voltage focusing on the impact of the anodic overvoltage on the cell voltage, by which the electrolysis process can be controlled. The model of the cell voltage is evaluated by laboratory neodymium electrolysis with a similar setup as the industrial cell. The relation of the oxide concentration, the anodic current density and the cell voltage with the cell resistance are measured. The continuous off-gas measurements show the gas concentration and PFC emissions. The effect of Nd2O3 feeding on the galvanostatic electrolysis is analyzed as well. Based on the results a process control strategy is proposed similar to the aluminum electrolysis strategy. The green process window is in a narrow oxide concentration range, making a continuous and precise oxide feeding essential.

Incorporating Pollution Taxes and/or Subsidies into Master Planning in Semiconductor Foundry Plants

The continued development of manufacturing industries along with increasing greenhouse gas emissions has become a critical concern that forces mankind to reduce global warming. Given the long atmospheric lifetimes of Perfluorocarbons (PFCs), it is especially important to reduce the emissions of PFCs which are commonly found in the semiconductor industry. In this study, we propose four master planning models that incorporate pollution taxes, subsidies, and/or progressive pollution taxes into capacity allocation to examine the problem of anthropogenic PFC emissions. The results show that master planning with subsidies and/or progressive taxes provides more flexibility to a foundry plant than that with flat taxes only. Setting emission limits and considering taxation for master planning is the first step toward the success of an environmental policy.

Atmospheric abundance and global emissions of perfluorocarbons CF&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, C&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;F&amp;lt;sub&amp;gt;6&amp;lt;/sub&amp;gt; and C&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;F&amp;lt;sub&amp;gt;8&amp;lt;/sub&amp;gt; since 1800 inferred from ice core, firn, air archive and in situ measurements

Abstract. Perfluorocarbons (PFCs) are very potent and long-lived greenhouse gases in the atmosphere, released predominantly during aluminium production and semiconductor manufacture. They have been targeted for emission controls under the United Nations Framework Convention on Climate Change. Here we present the first continuous records of the atmospheric abundance of CF4 (PFC-14), C2F6 (PFC-116) and C3F8 (PFC-218) from 1800 to 2014. The records are derived from high-precision measurements of PFCs in air extracted from polar firn or ice at six sites (DE08, DE08-2, DSSW20K, EDML, NEEM and South Pole) and air archive tanks and atmospheric air sampled from both hemispheres. We take account of the age characteristics of the firn and ice core air samples and demonstrate excellent consistency between the ice core, firn and atmospheric measurements. We present an inversion for global emissions from 1900 to 2014. We also formulate the inversion to directly infer emission factors for PFC emissions due to aluminium production prior to the 1980s. We show that 19th century atmospheric levels, before significant anthropogenic influence, were stable at 34.1 ± 0.3 ppt for CF4 and below detection limits of 0.002 and 0.01 ppt for C2F6 and C3F8, respectively. We find a significant peak in CF4 and C2F6 emissions around 1940, most likely due to the high demand for aluminium during World War II, for example for construction of aircraft, but these emissions were nevertheless much lower than in recent years. The PFC emission factors for aluminium production in the early 20th century were significantly higher than today but have decreased since then due to improvements and better control of the smelting process. Mitigation efforts have led to decreases in emissions from peaks in 1980 (CF4) or early-to-mid-2000s (C2F6 and C3F8) despite the continued increase in global aluminium production; however, these decreases in emissions appear to have recently halted. We see a temporary reduction of around 15 % in CF4 emissions in 2009, presumably associated with the impact of the global financial crisis on aluminium and semiconductor production.

Prediction of Low-Voltage Tetrafluoromethane Emissions Based on the Operating Conditions of an Aluminium Electrolysis Cell

Greenhouse gas (GHG) generation is inherent in the production of aluminium by a technology that uses carbon anodes. Most of those GHG are composed of CO2 produced by redox reaction that occurs in the cell. However, a significant fraction of the annual GHG production is composed of perfluorocarbons (PFC) resulting from anode effects (AE). Multiple investigations have shown that tetrafluoromethane (CF4) can be generated under low-voltage conditions in the electrolysis cells, without global anode effect. The aim of this paper is to find a quantitative relationship between monitored cell parameters and the emissions of CF4. To achieve this goal, a predictive algorithm has been developed using seven cell indicators. These indicators are based on the cell voltage, the noise level and other parameters calculated from individual anode current monitoring. The predictive algorithm is structured into three different steps. The first two steps give qualitative information while the third one quantitatively describes the expected CF4 concentration at the duct end of the electrolysis cells. Validations after each step are presented and discussed. Finally, a sensitivity analysis was performed to understand the effect of each indicator on the onset of low-voltage PFC emissions. The standard deviation of individual anode currents was found to be the dominant variable. Cell voltage, noise level, and maximum individual anode current also showed a significant correlation with the presence of CF4 in the output gas of an electrolysis cell.

Quantifying aluminum and semiconductor industry perfluorocarbon emissions from atmospheric measurements

AbstractThe potent anthropogenic perfluorocarbon greenhouse gases tetrafluoromethane (CF4) and hexafluoroethane (C2F6) are emitted to the atmosphere mainly by the aluminum and semiconductor industries. Global emissions of these perfluorocarbons (PFCs) calculated from atmospheric measurements are significantly greater than expected from reported national and industry‐based emission inventories. In this study, in situ measurements of the two PFCs in the Advanced Global Atmospheric Gases Experiment network are used to show that their emission ratio varies according to the relative regional presence of these two industries, providing an industry‐specific emission “signature” to apportion the observed emissions. Our results suggest that underestimated emissions from the global semiconductor industry during 1990–2010, as well as from China's aluminum industry after 2002, account for the observed differences between emissions based on atmospheric measurements and on inventories. These differences are significant despite the large uncertainties in emissions based on the methodologies used by these industries.

Implications of non-anode effect-related PFC emissions from primary aluminium

Smelter exhaust measurements for perfluorocarbon (PFC) emissions were carried out at 13 facilities in China from 2008 to 2010. The work has resulted in better global inventory of PFC emissions from primary aluminium production by having a measurement database of emission factors from Chinese aluminium producers. The measurements made in China revealed that PFC emissions could be produced during primary aluminium production that do not relate directly to anode effects. Although these emissions are much lower than during anode effects, they are generally always present and, therefore, are potentially substantial. Evaluations of two possible causes were completed, however, both were inconclusive. First, whether the non-anode effect (NAE)-related emissions are related to imbalances in anode current. Second, whether emissions were related to imbalances in cell voltage. Further investigations are needed to identify the root cause and to identify options to reduce these emissions. Although these NAE-related emissions were discovered in Chinese smelters, industry should investigate to see whether similar emissions might be occurring in smelters outside China at lower levels. In addition, the discovery of the NAE emissions necessitates the reexamination of the Intergovernmental Panel on Climate Change (IPCC) methodology for calculating PFC emissions. The current methodology is based on the presumption that anode effects are responsible for all PFC emissions and, therefore, PFC emissions can be calculated from anode effect process data alone.

Global emission estimates and radiative impact of C&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;F&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt;, C&amp;lt;sub&amp;gt;5&amp;lt;/sub&amp;gt;F&amp;lt;sub&amp;gt;12&amp;lt;/sub&amp;gt;, C&amp;lt;sub&amp;gt;6&amp;lt;/sub&amp;gt;F&amp;lt;sub&amp;gt;14&amp;lt;/sub&amp;gt;, C&amp;lt;sub&amp;gt;7&amp;lt;/sub&amp;gt;F&amp;lt;sub&amp;gt;16&amp;lt;/sub&amp;gt; and C&amp;lt;sub&amp;gt;8&amp;lt;/sub&amp;gt;F&amp;lt;sub&amp;gt;18&amp;lt;/sub&amp;gt;

Abstract. Global emission estimates based on new atmospheric observations are presented for the acylic high molecular weight perfluorocarbons (PFCs): decafluorobutane (C4F10), dodecafluoropentane (C5F12), tetradecafluorohexane (C6F14), hexadecafluoroheptane (C7F16) and octadecafluorooctane (C8F18). Emissions are estimated using a 3-dimensional chemical transport model and an inverse method that includes a growth constraint on emissions. The observations used in the inversion are based on newly measured archived air samples that cover a 39-yr period, from 1973 to 2011, and include 36 Northern Hemispheric and 46 Southern Hemispheric samples. The derived emission estimates show that global emission rates were largest in the 1980s and 1990s for C4F10 and C5F12, and in the 1990s for C6F14, C7F16 and C8F18. After a subsequent decline, emissions have remained relatively stable, within 20%, for the last 5 yr. Bottom-up emission estimates are available from the Emission Database for Global Atmospheric Research version 4.2 (EDGARv4.2) for C4F10, C5F12, C6F14 and C7F16, and inventories of C4F10, C5F12 and C6F14 are reported to the United Nations' Framework Convention on Climate Change (UNFCCC) by Annex 1 countries that have ratified the Kyoto Protocol. The atmospheric measurement-based emission estimates are 20 times larger than EDGARv4.2 for C4F10 and over three orders of magnitude larger for C5F12 (with 2008 EDGARv4.2 estimates for C5F12 at 9.6 kg yr−1, as compared to 67±53 t yr−1 as derived in this study). The derived emission estimates for C6F14 largely agree with the bottom-up estimates from EDGARv4.2. Moreover, the C7F16 emission estimates are comparable to those of EDGARv4.2 at their peak in the 1990s, albeit significant underestimation for the other time periods. There are no bottom-up emission estimates for C8F18, thus the emission rates reported here are the first for C8F18. The reported inventories for C4F10, C5F12 and C6F14 to UNFCCC are five to ten times lower than those estimated in this study. In addition, we present measured infrared absorption spectra for C7F16 and C8F18, and estimate their radiative efficiencies and global warming potentials (GWPs). We find that C8F18's radiative efficiency is similar to trifluoromethyl sulfur pentafluoride's (SF5F3) at 0.57 W m−2 ppb−1, which is the highest radiative efficiency of any measured atmospheric species. Using the 100-yr time horizon GWPs, the total radiative impact of the high molecular weight perfluorocarbons emissions are also estimated; we find the high molecular weight PFCs peak contribution was in 1997 at 24 000 Gg of carbon dioxide (CO2) equivalents and has decreased by a factor of three to 7300 Gg of CO2 equivalents in 2010. This 2010 cumulative emission rate for the high molecular weight PFCs is comparable to: 0.02% of the total CO2 emissions, 0.81% of the total hydrofluorocarbon emissions, or 1.07% of the total chlorofluorocarbon emissions projected for 2010 (Velders et al., 2009). In terms of the total PFC emission budget, including the lower molecular weight PFCs, the high molecular weight PFCs peak contribution was also in 1997 at 15.4% and was 6% of the total PFC emissions in CO2 equivalents in 2009.

Emissions of Halogenated Compounds in East Asia Determined from Measurements at Jeju Island, Korea

High-frequency in situ measurements at Gosan (Jeju Island, Korea) during November 2007 to December 2008 have been combined with interspecies correlation analysis to estimate national emissions of halogenated compounds (HCs) in East Asia, including the chlorofluorocarbons (CFCs), halons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF(6)), and other chlorinated and brominated compounds. Our results suggest that overall China is the dominant emitter of HCs in East Asia, however significant emissions are also found in South Korea, Japan and Taiwan for HFC-134a, HFC-143a, C(2)F(6), SF(6), CH(3)CCl(3), and HFC-365mfc. The combined emissions of CFCs, halon-1211, HCFCs, HFCs, PFCs, and SF(6) from all four countries in 2008 are 25.3, 1.6, 135, 42.6, 3.6, and 2.0 kt/a, respectively. They account for approximately 15%, 26%, 29%, 16%, 32%, and 26.5% of global emissions, respectively. Our results show signs that Japan has successfully phased out CFCs and HCFCs in compliance with the Montreal Protocol (MP), Korea has started transitioning from HCFCs to HFCs, while China still significantly consumes HCFCs. Taiwan, while not directly regulated under the MP, is shown to have adapted the use of HFCs. Combined analysis of emission rates and the interspecies correlation matrix presented in this study proves to be a powerful tool for monitoring and diagnosing changes in consumption of HCs in East Asia.

High increase of global F-gas emissions until 2050

Emissions of fluorinated greenhouse gases (GHGs) (hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphurhexafluoride (SF6)) have increased significantly in recent years and are estimated to rise further. Banks and emissions of HFCs, PFCs and SF6 in the year 2050 are projected per sector in a business-as-usual scenario. The total global emissions of fluorinated GHGs will amount to 4 GT CO2 eq. by 2050 if no mitigation measures are taken. The contribution of F-gases to global warming will increase from approx. 1.3% (2004) to 7.9% of projected total anthropogenic CO2 emissions in this business-as-usual scenario in 2050. For significant reductions in future emissions of Kyoto F-gases, additional efforts from both developed and developing countries are needed.

Large Emissions of Perfluorocarbons in East Asia Deduced from Continuous Atmospheric Measurements

The atmospheric mixing ratios of perfluorocarbons (PFCs), extremely potent greenhouse gases, have been continuously measured at two Japanese stations (Cape Ochiishi and Hateruma Island) since 2006, to infer their global and regional emissions. The baseline mixing ratios of the measured C(2)-C(4) PFCs [PFC-116 (C(2)F(6)), PFC-218 (C(3)F(8)), and PFC-318 (c-C(4)F(8))] showed slight annual increases of 1%-3%. Enhanced mixing ratios above baseline were occasionally observed at both sites in air masses that had passed over metropolitan regions in East Asia, suggesting high PFC emissions from those regions. We applied transport models to these pollution events and an inversion technique to estimate national emissions. The results suggest that, among the studied regions (China, Japan, North Korea, South Korea, and Taiwan), China was the largest PFC emitter, accounting for more than half of the regional emissions, followed by Japan. The estimated total emissions of each PFC from East Asia were 0.86 Gg yr(-1) for PFC-116, 0.31 Gg yr(-1) for PFC-218, and 0.56 Gg yr(-1) for PFC-318. They contributed greatly to global emissions as derived from the annual increases in the baseline mixing ratios, accounting for more than 75% of global PFC-218 and PFC-318 emissions and for approximately 40% of global PFC-116 emissions.