Establishment and verification of HFC-134a-gridded emission inventory in China

Hydrofluorocarbon-134a (HFC-134a) has been experiencing an annual increase in global emissions and atmospheric concentration in recent years, as a major substitute for ozone-depleting substances (ODSs). It has attracted considerable global attention owing to its double environmental effects, including high global warming potential and degradation to form trifluoroacetic acid (TFA). There are discrepancies in the results of existing top-down and bottom-up studies, and existing studies have only estimated the total HFC-134a emissions at national or regional scales. The lack of methods for building and verifying high-spatial-resolution emissions inventories makes it difficult to analyze the spatial distribution of emissions and regional contributions, as well as to identify emission hotspot grids. This study utilized emission factors and an atmospheric dispersion model to establish a methodology for calculating and validating a gridded emission inventory of HFC-134a, and evaluated its dual environmental impacts. This study focused on China and calculated a gridded emission inventory of HFC-134a for the period from 1995 to 2020. The results showed that the banks and emissions of HFC-134a increased from 0.9 kt and 0.1 kt yr^-1 in 1995 to 301 kt (273-332 kt) and 48 kt yr^-1 (39-56 kt yr-1) in 2020, respectively. Guangdong, Jiangsu, and Shandong provinces in eastern China had the largest cumulative emissions, with a total cumulative emission amount of 98 kt, accounting for 28% of the national emissions, and were also the provinces where the hotspot grids were mainly distributed. The high spatial resolution emission inventories can provide important input data for atmospheric models to simulate transport and transformation processes and assess environmental impacts, thus improving the accuracy of modelling and prediction. In addition, prediction results showed that if HFC-134a was phased out solely in accordance with the emission reduction requirements of the Kigali Amendment, there would still be HFC-134a banks and emissions in China by the year 2060. If emissions were reduced according to the carbon-neutral emission reduction path proposed in this study to meet a high consumption demand for HFC-134a, it was feasible to achieve nearly zero emissions in 2060. Nevertheless, if HFO-1234yf and R-513A were selected as substitutes for HFC-134a, it could result in the production of more TFA through atmospheric degradation, which could have an adverse impact on the aquatic ecosystem and plants. Therefore, it is necessary to actively explore more environmentally friendly alternatives in the future.