Last week I saw a few headlines surface about R-1234yf that caught my attention. The premise of these articles was that the very popular HFO R-1234yf was toxic. Now, if true, this is a huge deal. There was already a significant battle in the European Union when R-1234yf was first being rolled out about the flammability risk and now… we may have a potential toxicity risk as well?
Let me back up for a moment here folks. First a brief history lesson, as many of you know the HFO R-1234yf was brought into the market as a replacement for the HFC R-134a. This was done due to R-134a very high Global Warming Potential number of one-thousand four-hundred and thirty. Every time R-134a was released into the atmosphere either by leak, accident, or on purpose it actively impacted Global Warming and Climate Change.
To prevent further damage to the climate automotive manufacturers begin transitioning away from 134a over to this new HFO. 1234yf only had a GWP of four. A remarkable difference when compared to 134a. The problem with 1234yf is that it is flammable. This flammability rating caused a lot of hesitation from automotive manufacturers. In fact one of them, Daimler, fought the change tooth and nail. Eventually, they came up with their own automotive air conditioning system using R-744 Carbon Dioxide.
Eventually the fight on the flammability risk was nullified and we began to see more and more vehicles switch over to R-1234yf. As I write this article today ninety percent of new vehicles are using this HFO refrigerant. Each year that passes we are seeing more and more manufacturers switch over. The flammable risk was accepted as a necessary risk for helping the environment.
The Study
Last week there was a study done by the Advancing Earth and Space Science association (AGU). AGU is a scientific research firm that works in growing the exchange of scientific knowledge through publishing studies and holding meetings. They are based out of Washington District of Columbia. One of their most recent studies found that R-1234yf is toxic. Now when I use the word toxic it is not like how other refrigerants are toxic. For example, if there is an ammonia leak then it can be extremely deadly. That is why that refrigerant is rated as a B2L from ASHRAE.
R-1234yf is still rated as an A2L refrigerant from ASHRAE. Class A rating on toxicity signifies refrigerants for which toxicity has not been identified at concentrations of less than or equal to four-hundred parts per million. The difference here is that this study focused instead on what the refrigerant does when released into the atmosphere, specifically on Trifluoroacetic acid. I wasn’t familiar with this type of acid so I had to do a bit of research.
“Trifluoroacetic acid (TFA) is a breakdown product of several hydrochlorofluorocarbons (HCFC), regulated under the Montreal Protocol (MP), and hydrofluorocarbons (HFC) used mainly as refrigerants. Trifluoroacetic acid is (1) produced naturally and synthetically, (2) used in the chemical industry, and (3) a potential environmental breakdown product of a large number (>1 million) chemicals, including pharmaceuticals, pesticides, and polymers. The contribution of these chemicals to global amounts of TFA is uncertain, in contrast to that from HCFC and HFC regulated under the MP.” – Source
As you can see from the above quote these Trifluoroacetic acids are found in all of the man made refrigerants such as HCFCs, HFCs, and HFOs. The difference though is the amount that is found in each classification of refrigerant. You see folks, it turns out that HFOs are significantly worse when it comes to TFAs. The below quote is from the study that AGU completed:
“Replacement of HFC‐134a with the short‐lived hydrofluoroolefin (HFO) HFO‐1234yf as the coolant in mobile air conditioners will lead to an increase in TFA deposition. The yield of TFA from HFC‐134a is <0.2, while the yield from HFO‐1234yf is 1. One model estimates replacement of HFC‐134a with HFO‐1234yf will result in annual TFA wet deposition of 160–240 μg m−2 in continental North America (Luecken et al., 2010), which is higher than the cumulative deposition during the last decade of record for each ice core (Devon Ice Cap, 110 μg m−2 (2005–2014); Mt. Oxford icefield, 127 μg m−2 (2007–2016)). Another model predicts annual TFA deposition of 42.3 μg m−2 to the area including the Devon Ice Cap (Wang et al., 2018). This represents an increase compared to our observed annual TFA fluxes from 2001 to 2014, which ranged from 3.9 to 21.5 μg m−2 a−1. Both models suggest a large future increase in TFA deposition in the Arctic compared to our measurements from 1970 to 2015.” – Source
That definitely paints a picture of the difference between HFCs and HFOs. The HFOs contribute five times as much TFA when broken down into the environment. The question now though is what impact will this have on the environment? Does everything need to change? The below quotes I found from National Library of Medicine. They go into the impacts that TFAs have and will have on the environment:
“Total contribution to existing amounts of TFA in the oceans as a result of the continued use of HCFCs, HFCs, and hydrofluoroolefines (HFOs) up to 2050 is estimated to be a small fraction (<7.5%) of the approximately 0.2 μg acid equivalents/L estimated to be present at the start of the millennium” – Source
“As an acid or as a salt TFA is low to moderately toxic to a range of organisms. Based on current projections of future use of HCFCs and HFCs, the amount of TFA formed in the troposphere from substances regulated under the MP is too small to be a risk to the health of humans and environment. However, the formation of TFA derived from degradation of HCFC and HFC warrants continued attention, in part because of a long environmental lifetime and due many other potential but highly uncertain sources.” – Source
Conclusion
So the question now is what will happen next? Will this be enough to warrant another phase down in the next five, ten, or twenty years? If so, then what will be the next logical step for automotive applications? Also, it is not just automotive applications. Could this TFA problem found in 1234yf carry over to other up and coming HFO refrigerants?
Should we continue to pursue the HFO route, or should we begin looking at natural refrigerants such as CO2, Ammonia, and Hydrocarbons more seriously? Time will tell I guess…