Heat pumps may cause dangerous water pollution, report warns

Heat pumps are widely regarded as a silver bullet to the problem of decarbonising heating systems, but a new report from the German government suggests the refrigerants used in many units may have serious environmental impacts, particularly on water.

The findings do not spell doom for the heat pump revolution many climate activists want to see, but they would require a significant overhaul in the way many air conditioner and heat pump manufacturers build their systems.

The report, the result of a two year study by the German Environment Agency, concerns the use of halogenated refrigerants – known in the English speaking world as hydrofluoroolefins (HFOs) – in air conditioners and heat pumps.

It concludes that their use is already adding significant amounts trifluoroacetate acid (TFA) to the atmosphere, contaminating rain and water supplies, and potentially causing health problems such as liver and kidney damage.

HFOs have increasingly been used as an alternative refrigerant to chlorofluorocarbons (CFCs), which are responsible for damaging the ozone layer; and hydrofluorocarbons (HFCs), which have a high global warming potential. The use of both CFCs and HFCs has been banned or limited under the Montreal Protocol.

HFOs have low global warming potential and do not damage the ozone layer, making them a seemingly convenient alternative. But the new research warns growing use of HFOs in heat pumps and air conditioners would “add a large additional share to the amounts of TFA or trifluoroacetate in the atmosphere”. It finds TGA levels in Germany are already several times higher than they were 25 years ago.

“TFA or trifluoroacetate inputs into groundwater and drinking water can only be removed with considerable effort. Therefore, fluorinated refrigerants, foam blowing agents and aerosol propellants should be replaced by more sustainable solutions with halogen–free substances,” the report says. 

The answer, the report argues, is to shift to  “natural refrigerants” such as ammonia, carbon dioxide, and hydrocarbons such as propane or isobutane.

This is entirely doable, they say. Household refrigerators, for example, almost exclusively use isobutane. However, the use of HFOs is favoured by AC manufacturers.

Derek Harbison, energy efficiency consultant with Negawatt Projects, said the report had come as a “shock to the refrigeration world”, and should serve as a wake up call for manufacturers to start building systems with natural refrigerants.

He said refrigeration and heating made up around 25 per cent of Australia’s energy use. “There are more air conditioning systems in Australia than there are people by around 2 to 1.Then you add in fridges, car air conditioning, hot water heat pumps,” he said.

“As we migrate over to these systems, we need to be making a choice as to what sort of systems we are using and the effect that they have on the environment.”

Studies have found high levels of RTA in water caused liver and kidney disease in rats.