WMO, UNEP and NASA put question marks to HFOs 

By R744.com team, Oct 05, 2009, 12:39 3 minute reading

The world’s leading experts have put serious question marks to the safe use of olefins, mentioning the formation of TFA, ozone depletion, ground-level ozone, and HFCs with higher GWP as issues pending for evaluation. Their update of the Scientific Assessment of Ozone Depletion 2006 was presented at the Montreal Protocol Geneva meeting in July. 

The world’s leading scientists investigating ozone depletion have raised several issues that require “still some work to ensure safe substitutes for high GWP HFCs”. In a presentation at the Montreal Protocol meeting in Geneva in July, their presentation contained a slide about the possible consequences of CF3CF=CH2 or CF3CF=CHF substitutes for R134a. While complying with the requirement of a low Global Warming Potential (GWP), the olefins would need to be more thoroughly tested for the formation of trifluoroacetic acid (TFA), the production of ozone pollution, the formation of ozone depleting substances (ODS), and the possible formation of HFCs with a higher GWP.

The presentation was based on the “Scientific Assessment of Ozone Depletion 2006” report worked on by world leading experts from the World Meteorological Organization (WMO), United Nations Environment Programme (UNEP), North American Space Agency (NASA), and National Ozeanic and Atmospheric Organization (NOAA). Their recommendation to investigate the atmospheric impacts of HFOs in more detail comes at a time when carmakers consider the use of HFC-1234yf as a substitute for R134a in Mobile Air Conditioning.

Issues raised

More specifically the scientists put question marks to the following issues:
  • Formation of TFA: The experts raise an issue that has been confirmed by others before. HFC-1234yf is a Volatile Organic Compound (VOC), decomposing close to the earth surface into trifluoroacetic acid (TFA). TFA will be leached out from the atmosphere by the rain, developing a herbicide effect. The effects on the earth’s ecosystem are still unknown as the eco-toxicological potential of TFA has only been evaluated to a small extent. The strong organic acid TFA will remain stable in the nature over a long period due to its low decomposition potential.
  • Ozone production: Ozone (O3) has the same chemical structure whether it occurs miles above the earth in the stratosphere – where it protects the earth from ultraviolet light -, or at ground-level in the troposphere where it is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight to become a primary constituent of smog. Olefins are now suspected to accelerate the formation of this “bad” ground-level ozone responsible for respiratory diseases, including bronchitis and asthma. Ground-level ozone can also reduce lung function with repeated exposure leading to permanently scaring lung tissue. It damages vegetation and ecosystems.
  • Ozone depleting substances (ODS): The potential formation of ODS needs to be investigated further for the probability that unsaturated HFCs – the latest generation of HFCs - might again lead to ozone depletion, and hence to a problem thought to be tackled with the bans on CFCs and HCFCs.
  • HFCs with higher GWP: The environmental, meteorological, and space agencies are putting doubts to the claims that olefins might at least solve the problem of high global warming impacts, and hence the effect of an accelerating greenhouse effect. Moreover, a first analysis of a slide (page 17) showing possible reaction processes suggests that given the high chemical reactivity of unsaturated HFCs the toxic impact of aldehydes would be higher than that of carbonic acids. Some might harm the human nervous system, while others might “only” be pollutants. All aldehydes formed as end products are water-soluble and will be leached from the atmosphere.  


By R744.com team (@r744)

Oct 05, 2009, 12:39

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