Substantial increase in perfluorocarbons CF4 (PFC-14) and C2F6 (PFC-116) emissions in China

Abstract: The perfluorocarbons tetrafluoromethane (CF4, PFC-14) and hexafluoroethane (C2F6, PFC-116) are potent greenhouse gases with near-permanent atmospheric lifetimes relative to human timescales, and global warming potentials thousands of times that of  CO2.

Using long-term atmospheric observations from a Chinese network and an inverse modelling approach (top-down method), we determined that CF4 emissions in China increased from 4.7 (4.2-5.0, 68% uncertainty interval) Gg yr-1 in 2012 to 8.3 (7.7-8.9) Gg yr-1 in 2021, and C2F6 emissions in China increased from 0.74 (0.66-0.80) Gg yr-1 in 2011 to 1.32 (1.24-1.40) Gg yr-1 in 2021, both increasing by approximately 78%. Combined emissions of CF4 and C2F6 in China reached 78 Mt CO2-eq in 2021. The absolute increase in emissions of each substance in China between 2011-2012 and 2017-2020 was similar to (for CF4), or greater than (for C2F6), the respective absolute increase in global emissions over the same period.  Substantial CF4 and C2F6 emissions were identified in the less populated western regions of China, probably due to emissions from the expanding aluminum industry in these resource-intensive regions. It is likely that the aluminum industry dominates CF4 emissions in China, while the aluminum and semiconductor industries both contribute to C2F6 emissions.

Based on atmospheric observations, this study validates the emission magnitudes reported in national bottom-up inventories and provides insights into detailed spatial distributions and emission sources beyond what is reported in national bottom-up inventories.

Significance: We investigate the emissions of two potent greenhouse gases, tetrafluoromethane (CF4, PFC-14) and hexafluoroethane (C2F6, PFC-116), in China.

Based on atmospheric observations within China, we report substantial increases in CF4 and C2F6 emissions in China over the last decade. These increases in national emissions are sufficient to explain the entire increases in global emissions over the same period. We suggest that substantial CF4 and C2F6 emissions could be due to by-product emissions from the aluminum industry in the less populated and less economically developed western regions in China.

The findings highlight the importance of mitigating CF4 and C2F6 emissions in China and provide guidance for directing mitigation strategies towards specific regions and/or industries.