Behind the EPA’s new rule to clean up coolants such as HFCs
The U.S. Environmental Protection Agency is moving to eliminate a class of chemicals widely used as coolants in refrigerators, air conditioners and heat pumps.
If that feels like déjà vu, it should.
These chemicals, called hydrofluorocarbons, or HFCs, were commercialized in the 1990s as a replacement for earlier refrigerants that were based on chlorofluorocarbons, or CFCs. CFCs were destroying the ozone layer high in the Earth’s atmosphere, which is essential for protecting life from the sun’s harmful ultraviolet radiation.
HFCs are much less harmful than CFCs, but they create another problem — they have a strong heat-trapping effect that is contributing to global warming.
Several states have announced plans over the past few years for phasing out HFCs. Now the EPA, following a vote in Congress, is proposing federal regulations to cut HFC production and imports starting in 2022, and aims to reduce their production and use by 85 percent within 15 years.
Let’s take a closer look at what HFCs are and what might replace them next.
How HFCs keep rooms and food cool
Refrigerators and air conditioning use a technology known as a heat pump. It sounds almost miraculous — heat pumps use energy to take heat out of a cold place and dump it in a warm place.
Here’s how a refrigerator works: A fluid — CFCs back in the old days, and now HFCs — circulates in the walls of the refrigerator, absorbing the ambient heat to keep the fridge cooled down. As that liquid absorbs the heat, it evaporates. The resulting vapor is pumped to the coils on the back of the refrigerator, where it is condensed back to a liquid under pressure. In the process, the heat absorbed from inside the fridge is released into the surrounding room. Air conditioners and home heat pumps do precisely the same thing: They use electric-powered compressors and evaporators to move heat into or out of a house.
Choosing the right fluid for a refrigerator means finding a substance that can be evaporated and condensed at the right temperatures by changing the pressure on the fluid.
CFCs seemed to fit the bill perfectly. They didn’t react with the tubing or compressors to corrode the equipment, and they weren’t toxic or flammable.
Unfortunately, the chemical stability of CFCs turned out to be a problem that threatened the whole world, as scientists discovered in the 1980s. Leaking CFCs, mostly from discarded equipment, remain in the atmosphere for a long time. Eventually they make their way to the stratosphere, where they are finally destroyed by UV radiation from the sun. But when they break down, they create chlorine that reacts with the protective ozone, letting dangerous radiation through to the Earth’s surface.
When production of CFCs was eliminated in the 1990s to protect the ozone layer, new refrigerants were developed and the industry shifted to HFCs.
Why HFCs are a climate problem
HFCs are like CFCs but much more reactive in air, so they never reach the stratosphere where they could harm Earth’s protective radiation shield. They largely saved the world from impending ozone disaster, and they are found in refrigerators and heat pumps everywhere.
But while HFCs’ chemical reactivity prevents them from depleting the ozone layer, their molecular structure allows them to absorb a lot of thermal radiation, making them a greenhouse gas. Like carbon dioxide on steroids, HFCs are extremely good at capturing infrared photons emitted by the Earth. Some of this radiant energy warms the climate.
Unlike CO2, reactive HFCs are consumed by chemistry in the air, so they only warm the climate for a decade or two. But a little bit goes a long way — each HFC molecule absorbs thousands of times as much heat as a CO2 molecule, making them powerful climate pollutants.
HFCs leaking from discarded cooling equipment are estimated to contribute about 4 percent of global greenhouse gas emissions —…