AN UPDATE ON FLUOROCARBONS

Dear subscribers,

In this EFCTC January 2025 newsletter, we report in detail on the latest findings about HFC-23 production during the degradation of some HFOs and some HCFOs in the atmosphere. Most significant is that different research groups are now reaching similar conclusions about very low HFC-23 yields from some HFOs and some HCFOs. In 2021 one research group created a lot of debate in the scientific community with the claim that very high yields of HFC-23 were formed from degradation of some HFOs. These results received widespread attention. EFCTC explained that “The experiments were performed under collision-less conditions (zero pressure), which are not representative of atmospheric conditions.”  In contrast, the same research group now states that the yields of HFC-23 are very low. These results are consistent with those recently published by another research group.

We discuss another publication about the reaction of HCFO-1233zd(E) with ozone. Very small yields of HFC-23 can be produced from some HFOs and some HCFOs by reaction with ozone in the atmosphere.  The results reported for HCFO-1233zd(E) are complementary to those reported in the EFCTC 2024 January newsletter, for the other used HFOs/HCFOs.  For all these refrigerants CF3H formed in the reaction with ozone does not change the conclusion that they will not make any significant contribution to radiative forcing of climate change.

The EFCTC 2024 October newsletter reported on a published an upper limit estimate for photo-chemical production of HFC-23 in the atmosphere, from the photolysis of CF3CHO (an intermediate breakdown product of some HFCs, HFOs and HCFOs) and ozonolysis of some HFOs. An estimate is now provided by EFCTC based on new information for HFC-23 yield and a review of HFO emissions. Compared to the upper limit estimate of 340 tonnes/year in 2022, EFCTC estimate emissions at less than 17 tonnes HFC-23.  Globally, emissions of HFC-23 were 14,000 ± 900 tonnes/year in 2023.

In addition, we report on the installation of nine air-source heat pumps using R-454C (GWP 146, A2L) refrigerant have replaced gas boilers at a university campus in the UK.  The units were selected as they can deliver domestic hot water up to 70°C, to be used for both heating and hot water.

Finally, the annual European Union greenhouse gas inventory 1990–2022, in its inventory document 2024, submitted to the UNFCCC, reports that HFC emissions as CO2e have again been reduced in 2022 and have reported significant CO2e reductions in past years. HFCs emissions in 2022 have been reduced by 28% compared to 2015 and have also been reduced as a share of total emissions greenhouse gas emissions accounting for 1.9% of total GHG emissions in 2022.

Do you want to learn more about EFCTC and fluorocarbons? More information is on the fluorocarbons.org website!

Thank you for your continued interest in EFCTC!

Different research groups now reaching similar conclusions about very low HFC-23 yields from some HFOs and some HCFOs

Most HFOs and HCFOs (excluding HFO-1234yf) decompose in the atmosphere via the intermediate CF3CHO (trifluoroacetaldehyde). The intermediate CF3CHO, produced in 100% yield, breaks down further by photolysis or reaction with hydroxyl radical.  Photolysis produces low yields of CHF3 (HFC-23).
One research group has now reported [1] an extremely low yield of HFC-23 (0.064%) from CF3CHO, in contrast to their previous published results [2], which reported a very high yield of HFC-23 (11%). These new results by Thomson et al. are consistent with a paper by Sulbaek Andersen et al. [3] who found that HFC-23 formation from CF3CHO was of ‘no significant importance.’ 

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Reaction of Ozone with HCFO-1233zd(E)

A recently published paper by Nielsen et al. [1] measured a very low yield of HFC-23 (CHF3) from HCFO-1233zd(E). The presence of an olefinic bond (C=C bond) in HFOs and HCFOs results in their relatively rapid reaction with hydroxyl radicals (·OH) present in the atmosphere, leading to short atmospheric lifetimes measured in days or weeks, and small direct global warming potentials.

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Estimate of HFC-23 production from HFO and HCFO emissions

The Scientific Assessment Panel (SAP) published estimates of photo-chemical production of HFC-23 in the atmosphere, from the photolysis of CF3CHO (an intermediate breakdown product of some HFCs, HFOs and HCFOs) and ozonolysis of some HFOs [1].
An estimate is now provided by EFCTC based on new information for HFC-23 yield and a review of HFO emissions. The objective of the SAP report [1] was to define an upper limit for this source in 2022 as part of the evaluation of the HFC-23 emissions gap [2] and not an estimate of emissions.

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R-454C air-source heat pumps used to replace gas boilers at university campus

Nine air-source heat pumps using R-454C (GWP 146, A2L) refrigerant have replaced gas boilers at a university campus in the UK. Do you to know more?

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