The struggle to curb HFC-23 emissions

Posted: October 21, 2024

“How much HFC-23 can be easily destroyed by existing technology at a factory-wide scale?” That’s one of the questions a group of researchers with funding from the Swiss National Science foundation were trying to answer with their research, which was published in August in the journal Nature.  

The reason they wanted to know the answer to this question is simple: Hydrofluorocarbons, or HFCs, are potent greenhouse gases. Of the different kinds of HFCs, trifluoromethane, often known as HFC-23, is the longest-living and most potent. One kilogram of HFC-23 in the atmosphere equals 12,000 kilogram of CO₂ in terms of greenhouse gas emissions, and it takes over 200 years for the gas to degrade in the atmosphere.

FC-23 is primarily produced as an incidental byproduct in the production of certain coolants and polytetrafluoroethylene (PTFE), a key ingredient in most non-stick cookware, better known as Teflon. The production process involves the reaction of chloroform with hydrogen fluoride, which yields HFC-23 and hydrochloric acid as a by-product.

Because HFC-23 is such a powerful and long-lasting greenhouse gas, The US Environmental Protection Agency requires that facilities producing HFC-23 emit no more than 0.1 per cent of the HFC-23 produced on a line. And in 2016, more than 150 nations agreed to reduce their HFC-23 emissions as part of the Kigali Amendment to the Montreal Protocol.

But while the EPA predicts that HFC-23 emission control regulations could help reduce cumulative HFC-23 emissions by more than 7,000 metric tonnes (or more than 3.7 million metric tonnes of carbon dioxide equivalent yearly), evidence suggests that compliance with these regulations has been spotty. For example, on paper, worldwide HFC-23 emissions were barely 2,000 tonnes in 2020. But the real worldwide emissions estimated from atmospheric measurements amounted to 16,000 tonnes.

The good news is that existing technologies can help destroy a significant amount of these HFC-23s before they’re released into the atmosphere.

How effective is current technology at cutting HFC-23 emissions?

In a recent study published in Nature, researchers from Switzerland, the UK and The Netherlands measured HFC-23 emissions from a Teflon factory in The Netherlands. The factory uses destruction technologies to curb its HFC-23 emissions; in other words, the gas is burned off before it can escape. To measure how much HFC-23 was still being released after it was burned off, researchers released a tracer gas (a non-toxic gas that does not occur in the atmosphere and decomposes within a few weeks) right next to the factory. Then, they measured the concentrations of HFC-23 and other by-products of Teflon manufacturing and the concentration of the tracer at a distance of around 25 kilometers.

"Since we knew exactly how much tracer we had released and how much of it arrived at the measuring point, we were able to calculate the emissions of HFC-23 and other gases," said Dominique Rust, a research associate at the University of Bristol and one of the authors of the study in a press release. The researchers found that although the measured emissions were higher than the ones the factory reported, the amount emitted was low, showing that the abatement measures are effective.

The researcher’s conclusion to this study should inspire confidence in chemicals companies looking for ways to mitigate their HFC-23 emissions. The authors concluded that if all industries worldwide managed emissions in the same way as the Dutch site, HFC-23 emissions could be reduced by at least 85%, equivalent to 170 million metric tonnes of carbon dioxide per year or nearly one-fifth of the carbon dioxide emissions produced by total airline traffic.

How can chemical companies effectively cut HFC-23 emissions?

Chemical companies can effectively reduce their HFC-23 emissions by implementing a few simple strategies:

• Optimizing the production processes of HCFC-22 can minimize the generation of HFC-23 as a by-product. Adjusting operational parameters can slash the HFC-23/HCFC-22 ratio from 4% to 1.5%.
• Adopting current destruction technology, such as thermal oxidation. Thermal oxidation systems designed for HFC-23 incinerate the greenhouse gas at high temperatures (about 2000°F) in a controlled environment. This process converts HFC-23 into carbon dioxide and water vapor along with hydrogen fluoride and hydrogen chloride. HFC-23 incineration can reduce the HFC-23/HCFC-22 ratio below 1%. The emission factor for HFC-23 during production processes can be as low as 0.19% when thermal oxidation systems are in place. This aligns with the goal of maintaining emissions below the 0.1% threshold set by regulations
• Implementing real-time monitoring systems can help track emissions and destruction efficiency, allowing immediate corrective actions if needed.

^{Global emissions of HFC-23 derived based on the present study (red diamond); based on this study, applied to earlier years (red line); expected emissions with reported destruction measures (blue line); actual emissions (black line). Image: Adapted from Rust, D., Vollmer, M.K., Henne, S. et al. Effective realization of abatement measures can reduce HFC-23 emissions. Nature 633, 96–100 (2024).}