A new study by the German Environment Agency (GEA) has identified long term environmental and health risks associated with the use of hydrofluoroolefins (HFOs).
The report questions whether HFOs are a suitable replacement for hydrofluorocarbons (HFCs) and presents natural refrigerants as the only viable option going forward.
However, refrigerant producers claim HFOs are climate friendly and safe for the environment.
HFOs have proven to be an excellent replacement for HFCs but the report claims using HFOs could create new problems in the future as these products degrade.
This is because, when released into the atmosphere by leaks or improper end-of-life disposal of a unit, HFOs break down into trifluoroacetic acid (TFA).
Because TFA is widely used in organic chemistry its lifecycle is well known by German scientists.
They identify TFA as a highly persistent (long-lived) substance which represents a danger to the environment and humans, as it has so far unknown consequences for ecosystems and health.
Atmospheric TFA descends to earth in rainfall, and the report notes that higher levels of TFA have been found in rainwater. It is not readily biodegradable and may be toxic to aquatic life at certain concentrations.
TFA cannot be removed by current water treatment technology. It accumulates in local lakes, freshwater and soils, and therefore drinking water of humans and animals, the report said.
This is why the use of HFOs as a substitute for HFCs “must be regarded as problematic.”
“While the environmental effects of TFA are considered to be negligible over the next few decades, potential longer-term impacts require further evaluations due to the environmental persistence of TFA, and to the uncertainty in growth due to future uses of HFOs,” the report stated.
“Releasing chemicals that can last for generations in the environment, especially when there is an uncertainty about the environmental and health impacts, must be avoided when alternatives are available.”
The report said refrigerants known to yield TFA include HFC-227a, HFC-236fa, HFC-245fa, HFC365mfc, HFO-1234ze(E), HFO-1336mzz(E) and the mixtures R449A, R452C, R454C.
It went on to outline the benefits of natural refrigerants.
“Systems with water as refrigerant are very promising for temperatures above 0 °C. These systems are already used for server cooling and other industrial applications,” the report said.
“The use of propane for chillers is well established. The state-of-the-art propane chillers use multi-cycle hydraulic system to minimize the refrigerant charge and are a perfect solution for cold water production in any size with high efficiency.
“Every refrigeration application can be realised with natural refrigerants and hence reduce the risk of negative, long-term environmental effects such as climate warming, or pollution caused by chemicals.”
The report said HFC-134a and HFC-32 are used in HFC/HFO blends and therefore will not only yield TFA but also cause ozone depletion due to the emissions of their by-products during production.
“The problem with risk assessments of TFA is the considerations of known thresholds only and neglecting the persistence of the chemicals since some negative effects might not be discovered yet,” the report said.
“Therefore, phasing out HFOs (and consequently TFA), or emission reduction strategies along with best practise measures that help ensure efficient capturing of HFO/TFA during recycling operations, will help reduce the risk to human and environmental health.
“There is no technical need for these substances, since HFOs are totally unnecessary in new refrigerant systems.”