Research published in the Proceedings of the National Academy of Sciences (PNAS) has found that three HFOs produce the extremely powerful greenhouse gas trifluoromethane (R23) when they react with ozone.
The multinational team of researchers tested five HFOs in reaction with ozone, finding that the commonly used HFO-1234ze(E) – as well as HFO-1336mzz(Z) and HFO-1243zf – produced R23, which has a global warming potential (GWP) of 14,800 over 100 years.
HFO-1234ze(E) – which is used as a refrigerant, propellant, and foam-blowing agent – was the worst offender, producing eight times as much R23 as HFO-1336mzz(Z) and HFO-1243zf. According to the study, factoring these new findings in would increase the 100-year GWP of HFO-1234ze(E) from under 1 to around 14.
Despite these alarming figures, the real-world climate impact of the three HFOs remains unclear, as a very small percentage of each HFO interacts with ozone; upwards of 97 per cent of each HFO breaks down on contact with OH in the lower atmosphere.