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Acidification

The transition from use of HFCs to HFOs will lead to more TFA and less HF formation.

Both are substances considered potential contributors to acidification, also known as acid rain. Lindley et al.[1]compared the acidification potential of HFCs, HFOs and HCFOs emissions in the EU and concluded that the relative acidification potential of these compounds is very similar and that these compounds contribute less than 0.5% of the main acidification air pollutants—sulphur dioxide (SO2), nitrogen oxides (NOx) and ammonia (NH3)—resulting in an insignificant contribution to acidification both presently and up to at least 2030.[2]

While hydrogen fluoride (HF) and hydrogen chloride (HCl) are not considered main air-pollutants in the EU, they have the potential to contribute to acidification. Hydrofluorocarbons (HFCs), hydrofluoro-olefins (HFOs) and hydrochlorofluoro-olefins (HCFOs) are used as refrigerants and for other applications. They break down in the atmosphere to produce HF and HCl (for HCFOs) and some of these fluorocarbons also break down to produce trifluoroacetic acid (TFA).

For the emissions of these fluorocarbons in the EU, a worst-case scenario estimates their theoretical potential contribution to acidification and compares it to the acidification potential for the main air pollutants contributing to acidification, which are nitrous oxides (NOx), sulphur oxides (mainly SO2), and ammonia (NH3). The Acidification Potential from these fluorocarbons in 2016 is estimated at <0.5% of the total due to SO2, NOx, NH3, and it can be concluded that this is insignificant in the context of the main acidification air-pollutants. Assuming that the EU targets for emissions of SO2, NOx and NH3 by 2030 are achieved, the Acidification Potential from HFCs, HFOs and HCFOs in 2030 is also estimated at <0.5% of the total due to SO2, NOx, NH3 and will remain insignificant [3]

  • Lindley, A., McCulloch, A. and Vink, T. Contribution of Hydrofluorocarbons (HFCs) and Hydrofluoro-Olefins (HFOs) Atmospheric Breakdown Products to Acidification (“Acid Rain”) in the EU at Present and in the Future. Open Journal of Air Pollution,2019,  8, 81-95. https://doi.org/10.4236/ojap.2019.84004 ↩
  • World Meteorological Organization (WMO). Scientific Assessment of Ozone Depletion: 2022, GAW Report No. 278, Chapter 2 Hydrofluorocarbons (HFCs). Available at https://ozone.unep.org/science/assessment/sap ↩
  • Lindley, A., McCulloch, A. and Vink, T. Contribution of Hydrofluorocarbons (HFCs) and Hydrofluoro-Olefins (HFOs) Atmospheric Breakdown Products to Acidification (“Acid Rain”) in the EU at Present and in the Future. Open Journal of Air Pollution,2019,  8, 81-95. https://doi.org/10.4236/ojap.2019.84004 ↩