Emissions of HFOs and HCFOs from Europe and comparison with forecasts
A pre-print [1] reports annual emissions for NW Europe (Belgium, Germany, France, UK, Ireland, Luxembourg and the Netherlands) by 2023 for widely used HFO-1234yf, HFO-1234ze(E), and HCFO-1233zd(E) and extrapolates these to the EU27+. Atmospheric observations (mole fraction concentrations) reported from the Advanced Global Atmospheric Gases Experiment (AGAGE) network for European observations are used to determine emission trends and regional distribution. For Northwest Europe, emissions of HFO-1234yf increased from <100 tonnes/year in 2014 to 1500 tonnes/year in 2023, presumably due to its introduction in the mobile air conditioning and refrigeration sectors. Over the same time period, HFC-134a emissions have not increased supporting this interpretation. HFO-1234ze(E) emissions were low during 2014–2017, followed by a rapid increase in 2018/2019, potentially due its introduction as an aerosol propellant, after which they increased more slowly to 960 tonnes/year in 2023. HCFO-1233zd(E) emissions are derived from 2017 onwards, showing a steady increase from 200 tonnes/year to 1000 tonnes/year in 2023. HFO and HCFO observations from most AGAGE sites globally are also reported to the end of 2024 and the dense European station network is used in a detailed modelling study to estimate 10 years (2014–2023) of emissions from Northwest (NW) Europe.
The pre-print states that in 2023 for the European Union (EU) and the UK, HFO-1234yf is mainly used in mobile air-conditioning (77%) and also other RACHP applications, HFO-1234ze(E) is used in RACHP, foam blowing and as aerosol propellant, and HCFO-1233zd(E), originally marketed as a solvent but is now mainly used as a foam blowing agent and in minor quantities in RACHP, with the former currently assumed to be the major emission source in the EU. The emissions data is indicative of a faster transition from HFC-134a to HFO-1234yf and HFO-1234ze(E) for Europe compared to the footprint regions of Gosan (Asia), in line with the stringent HFC phase-out regulations in Europe.
Extrapolation to the EU27+ (27 EU countries plus the UK, Switzerland, and Norway)
For HFO-1234yf, the authors use a population-based extrapolation from the NW Europe countries (254 million people in 2023) to the EU27+ (27 EU countries plus the UK, Switzerland, and Norway, 530 million people in 2023), resulting in 3100 tonnes for 2023 for EU27+. Alternatively, the authors derive almost identical emissions (3200 tonnes) by upscaling emissions based on the number of passenger cars (in 2023, NW Europe 139 million vs 296 million in the EU27+). For HFO-1234ze(E) a population-based extrapolation to EU27+ results in 2000 tonnes in 2023. For HCFO-1233zd(E) a population-based extrapolation to EU27+ results in 2170 tonnes in 2023.
Comparison of estimated emissions with forecasts
In 2021, a UBA report [2] described the current status and the development of the use and emissions of halogenated refrigerants, foam blowing agents and aerosol propellants in Germany and in the EU. The AnaFgas model was used to estimate emissions and uses a scenario of maximum future use and emissions of halogenated substitutes. It is a "bottom-up" inventory model that determines demand and emission scenarios for F-gases in relevant sectors and sub-sectors for the EU-27. Compared to emissions derived from atmospheric observation, the UBA estimated significantly higher emissions for 2020 for HFO-1234yf and HFO-1234ze(E), although it underestimates emissions of HCFO-1233zd(E). In total for the three substances, the UBA estimated 2.4 times higher emissions. The UBA estimated emissions for 2020 are 1.5 times higher than 2023 emissions from atmospheric observations. This would suggest that the UBA forecast model may have significantly overestimated emissions for 2030, even under the previous F-gas Regulation. The table below provides a comparison of emissions from atmospheric observations with forecast emissions.
Table. Comparison of emissions from atmospheric observations with forecast emissions
| Emissions in tonnes | Extrapolated to EU27+ and for 2020 from Figure 6 [1] based on atmospheric observations | UBA AnaFgas model [2] for EU 28 Estimated in 2021 report |
||
| 2023 | 2020 | 2020 | 2030 | |
| HFO-1234yf | 3200 | 1700 | 6903 | 37,439 |
| HFO-1234ze(E) | 2000 | 1700 | 4289 | 5,491 |
| HCFO-1233zd(E) | 2170 | 1300 | 113 | 732 |
| Total | 7370 | 4700 | 11305 | 43,662 |
The 2023 REACH Dossier Chemical Safety Report (CSR) [3] estimated projected total emissions of HFO-1234yf in Europe in 2030 at 7,090 tonnes, assuming HFO-1234yf would be fully implemented in the European vehicle fleet by that time. Some emissions of HFO-1234yf from other RACHP applications would also occur. If these were in the same ratio as the pre-print’s estimated use in MAC (77%) then total emissions would be about 9200 tonnes. Assuming a continued linear increase in HFO-1234yf emissions, based on the observed trend for 2022 to 2023, reported in the pre-print, would also result in about 9200 tonnes of emissions for EU27+ in 2030 (see explanatory note). The UBA report estimated emissions of 37,439 tonnes of HFO-1234yf in 2030 (see table).
A key study for HFO-1234yf emissions from MAC in Europe EU is the Henne et al. [4] study. This simulation assumed that all car air conditioning systems are operated with the refrigerant HFO-1234yf. The study included low and high emissions scenarios, which used different annual leakage rates and end-of-life losses. The model assumed complete replacement of HFC-134a by HFO-1234yf and used predicted vehicle numbers for the year 2020 to calculate emissions. In reality, the complete conversion to HFO-1234yf did not occur by 2020 but does not invalidate the simulation. Future changes in vehicle numbers or for example changes in leakage rates would affect the derived emissions to some extent. The authors arrived at a total emission level of HFO-1234yf for Europe (EU+ Croatia, Norway, Switzerland and Turkey) for 2020 of 11,000 to 19,200 tonnes/year.
The emissions reported in the pre-print suggest that HFO-1234yf emissions in 2030 could be at or below the Henne et al. low emission scenario, even taking into account emissions from other RACHP applications.
Explanatory note: From Figure 6b in the pre-print, the increase in HFO-1234yf emissions from 2022 to 2023 is about 400 tonnes. This is also the steepest increase for the available years. Assuming an annual increase of 400 tonnes until 2030 results in 4300 tonnes emissions for NW Europe. An approximate extrapolation to the EU27+ using the 2023 vehicle data results in about 9200 tonnes of emissions.
References
[1] M. K. Vollmer, J. R. Pitt, D. Young, S. Henne, B. Mitrevski, J. Mühle et al., Global Observations and European emissions of the halogenated olefins HFO-1234yf, HFO-1234ze(E), and HCFO-1233zd(E) from the AGAGE (Advanced Global Atmospheric Gases Experiment) network. Preprint egusphere-2025-4824, https://doi.org/10.5194/egusphere-2025-4824
[3] Solstice Advanced Materials 2023. REACH Dossier. Chemical Safety Report 2,3,3,3-tetrafluoropropene (HFO-1234yf). January.
[4] Henne, S.; Shallcross, D. E.; Reimann, S.; Xiao, P.; Brunner, D.; O’Doherty, S.; Buchmann, B., Future emissions and atmospheric fate of HFC-1234yf from mobile air conditioners in Europe, Environmental Science and Technology, 2012, 46, 1650−1658. DOI: 10.1021/es2034608.