Latest SAP and TEAP reports on HFC-23 emissions and sources

The Scientific Assessment Panel (SAP) [1] and the Technical and Economic Assessment Panel (TEAP) [2] to Montreal Protocol have published reports in September 2024 about the sources and emissions of HFC-23. This is in response to a request by parties to the Montreal Protocol (Decision XXXV/7: Emissions of HFC-23). Important conclusions relating to HFC-23 emissions and sources are:

SAP: The HFC-23 emissions gap

Global emissions of HFC-23 estimated from measured atmospheric abundances can be contrasted with values derived from reporting to the United Nations Framework Convention on Climate Change (UNFCCC), the Multilateral Fund for the Implementation of the Montreal Protocol (MLF), and the Ozone Secretariat. From 1995 to 2014, good consistency was observed between estimated and reporting-based global emissions of HFC-23. This was the case even from 2005 to 2014 when reported HFC-23 destruction, mostly in China and supported by the UNFCC’s Clean Development Mechanism (CDM), peaked near 9 kt yr-1. After 2014, differences (or gaps) emerged between estimated and reporting-based global emissions of HFC-23. The gaps grew to reach a peak of 15 kt in 2019 and have decreased in the three years since 2019 to reach approximately 10.5 - 12.5 kt in 2022.

The increasing emission gaps between 2015 and 2018 are similar in magnitude and coincident in time with the destroyed amounts of HFC-23 reported by China to the MLF, amounts that are consistent with the country’s Hydrochlorofluorocarbon Production Phase-out Management Plan (HPPMP) agreement with the MLF Executive Committee.

The emission gaps after 2015 are substantially larger than can be explained by emissions from all known sources and reported abatements. An assessment by the Technology and Economic Assessment Panel (TEAP) estimates HFC-23 emissions from all known sources and reported abatements after 2020 to be in the range of 1.47 - 3.54 kt yr-1, which is substantially smaller than the atmospherically-derived mean of 15 kt yr-1 during 2020 to 2022.

The decrease in the gaps after 2020 is concurrent with a declining ratio of global atmospherically derived HFC-23 emissions relative to reported total HCFC-22 production (E23/P22), suggesting an increase in the inferred overall abatement of HFC-23 emissions.

From 2015 to 2019, regional HFC-23 emission estimates were derived for eastern China from atmospheric abundances measured at the Gosan, Korea, station. The emissions from eastern China increased during these years from 5.7 +/- 0.3 to 9.5 +/- 1 kt yr-1 despite reporting provided to the MLF showing that by 2018 more than 95% of the HFC-23 generated in China had been destroyed, stored, or used as feedstock.

TEAP: Reported and estimated emissions of HFC-23

Total production of HCFC-22 reported under Article 7 was 1,196,999.4 tonnes in 2022 (sub-totals in tonnes: A5 parties, 989,637.7; non-A5 parties, 207,361.7). Estimated HFC-23 by-product generation from HCFC-22 production is expected to be in the range of about 18,000 to 36,000 tonnes in 2022. The total amount of HFC-23 emissions from HCFC-22 production reported under Article 7 and the UNFCCC (for the United States) was about 836 tonnes in 2022.

The combined reported and best available annual estimate of HFC-23 emissions from known emissions sources is about 1,470–3,540 tonnes. These estimates exclude the potential additional source of HFC-23 from atmospheric oxidation of less than 430 tonnes per year in recent years, as reported by SAP.  Under the UNFCCC’s Category 2 Industrial Processes and Product Use for net HFC-23 emissions and removals, total HFC-23 emissions were reported to be 1,431 tonnes for 2021 for Annex I parties only.

Data reported under Article 7 and the UNFCCC for HFC-23 emissions predominantly from HCFC-22 production contribute a major portion of TEAP’s estimates of total HFC-23 emissions from known sources, noting also that around 95% of the estimated total global HFC-23 by-product generation is from HCFC-22 production.

TEAP has identified all the major sources that are likely to contribute most of the HFC-23 emissions and these are outlined in the report. Any smaller unknown sources are unlikely to bridge the large difference with SAP estimates.

References

[1] Report of the Scientific Assessment Panel in response to Decision XXXV/7: Emissions of HFC-23, 15 September 2024, Lead Authors: S. A. Montzka, NOAA Global Monitoring Laboratory, USA; J. B. Burkholder, NOAA Chemical Sciences Laboratory, USA, available here, or from or from  Scientific Assessment Panel (SAP) | Ozone Secretariat (unep.org).

[2] Report of the Technology and Economic Assessment Panel September 2024, Volume 5: Response to Decision XXXV/7: Emissions of HFC-23, available at https://ozone.unep.org/science/assessment/teap