Hydrofluorocarbons (HFCs) are powerful greenhouse gases. The most powerful of these compounds is trifluoromethane, also known as HFC-23. One kilogram of HFC-23 in the atmosphere contributes as much to the greenhouse effect as 12,000 kilograms of CO₂. It takes around 200 years for the gas to decay in the atmosphere. For this reason, more than 150 countries have committed to significantly reducing their HFC-23 emissions as part of the Kigali Amendment to the Montreal Protocol.
The main source of HFC-23 is the industrial production of certain coolants and polytetrafluoroethylene (PTFE), better known as Teflon. HFC-23 is a byproduct of the synthesis of a precursor to Teflon. Since 2020, all Teflon manufacturers have been required to destroy the climate-damaging gas. According to reports from individual countries, this is also happening: on paper, global emissions of HFC-23 for 2020 were only 2,000 tons. The actual global emissions, which have been determined in numerous studies, paint a different picture: in 2020 alone, around 16,000 tons of the greenhouse gas entered the atmosphere.
Precise measurements thanks to tracer gas
Why this discrepancy? To answer this question, researchers from Empa, the University of Bristol and the Netherlands Organisation for Applied Scientific Research (TNO) took a close look at the HFC-23 emissions from a Teflon factory in the Netherlands. They have just published their latest findings in the scientific journal Nature.
In order to record the factory’s emissions as comprehensively and accurately as possible, the researchers used a new method. They released a tracer gas in the immediate vicinity of the factory: a non-toxic gas that does not occur in the atmosphere and decomposes within a few weeks. At a distance of around 25 kilometers, they measured the concentrations of HFC-23 and other byproducts of Teflon production – as well as the concentration of the tracer. “Because we knew exactly how much tracer we had released and how much of it reached the measuring point, we were able to calculate the emissions of HFC-23 and other gases,” says lead author Dominique Rust, who worked on the project as part of her doctorate at Empa.
To reduce HFC-23 emissions, the factory uses reduction measures; the gas is burned before it can escape. But the new study shows: “The emissions we measured were higher than those reported by the factory,” explains Empa researcher Martin Vollmer. “However, the amount emitted is still low, which shows that the reduction measures are working well.” Co-author Kieran Stanley from the University of Bristol agrees: “These results are really encouraging. They show that reduction measures for factories that produce fluoropolymers such as Teflon can significantly reduce emissions of this highly potent greenhouse gas.” And Empa researcher Stefan Reimann adds: “If all factories had similar emissions to those we measured, we could prevent global emissions of HFC-23, which correspond to almost 20% of the CO₂ emissions from global aviation.”
Verification and compliance
So if the mitigation measures are effective, how can the high levels in the atmosphere be explained? “We have to assume that the measures reported by countries do not always reflect reality,” says Martin Vollmer. The authors of the study are calling on countries to have their Teflon factories independently audited. “Such an independent review of greenhouse gas emissions from the production of fluoropolymers and coolants is necessary to fill the gaps in our understanding of the sources of emissions and to check whether countries are fully complying with the various international climate and environmental agreements,” adds Stanley. “The collaboration with the Teflon manufacturer and the Dutch authorities was key to the success of our study,” says Rust, who is now a research fellow at the University of Bristol.
The tracer method developed by the researchers would be suitable for independent audits of factories and industrial areas – also for other gases, the scientists are convinced. Empa researchers are already planning another study in South Korea in October, in which they want to use the tracer method to determine emissions of halogenated substances in the South Korean capital Seoul. “At the Cabauw measuring station, TNO will expand the monitoring of greenhouse gases as part of the European ICOS infrastructure to include continuous monitoring of halogenated substances. This will enable us to track the location of the sources of halogenated substances and determine their emissions that passed by the station during this experiment,” adds TNO researcher Arnoud Frumau.
