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Refrigerants: What Are They?

May 2023

Note: This is cross-posted to the Recoolit blog.

At Recoolit, our mission is to reduce climate impact by collecting and destroying waste refrigerants. This mission is often unclear to people who aren't familiar with the refrigeration industry. We often hear questions like, "What are refrigerants?" or "Why are refrigerants a problem?" We've skipped over such questions on our explainer page because they're quite technical, and we don't want to overwhelm our customers. This post is for those special nerdy few who want to know all the gory details!

Heat pumps -- How do they work?

Refrigerators and air conditioners are all a type of heat pump -- a device that moves heat from one location to another. They do this by means of a fluid that is pumped through a closed loop.

First, the fluid is compressed, which causes it to heat up, turn into a gas, and become much warmer than the surrounding air. Next, the gas is pumped through a heat exchanger -- like a radiator on a car -- which results in the gas becoming cooler while the surrounding air becomes warmer. In a heat pump on "warming" mode, this heat exchanger is located inside a building or room, and this warming is the desired effect.

The gas is then pumped to a second heat exchanger, where it is allowed to expand, turning it back into a liquid. The expansion cools the fluid. It's then pumped through a second heat exchanger, where it becomes warmer, while the air around it becomes cooler. In a heat pump on "cooling" mode, this second heat exchanger is inside the refrigerator, freezer, or too-warm room or building.

The fluid is then pumped back to the compressor, and the cycle begins again. Mechanically, all heat pumps rely on just these few components -- a compressor, pumps, heat exchangers, and the fluid -- sometimes a gas, sometimes a liquid -- that runs between them. Physically, this process relies on just a few basic principles of nature -- the ideal gas law, plus the laws of thermodynamics.

What are refrigerants?

Refrigerants are the fluid used inside heat pumps to move heat from one place to another. There are many considerations when picking a substance to use as a refrigerant. For instance, a common early refrigerant was ammonia (R-717). Ammonia boils at a low temperature, which makes it easy to turn into a gas. It does not freeze until a very low temperature, so there's no risk of it freezing inside the heat pump during the expansion phase. And it has a fairly high specific heat, which means that it can absorb and release a lot of heat.

Unfortunately, ammonia is highly toxic and corrosive. Other early refrigerants, such as sulfur dioxide (R-764) and methyl chloride (R-40), were also toxic. To avoid the safety issues associated with early refrigerants, scientists began experimenting with other substances. In 1928, Thomas Midgley, Jr. invented the first chlorofluorocarbon (CFC) refrigerant, which was marketed by DuPont as Freon-12 (R-12). R-12 was cheap to produce, non-toxic, non-flammable, non-corrosive, and it had a low boiling point and a high specific heat. These properties led to R-12 becoming the most popular refrigerant in the world, with production peaking at over 1 billion tons per year in the 1980s.

The Montreal Protocol

When searching for safer replacements to early refrigerants, scientists looked for substances which were highly stable, since stable substances pose less of a health risk to humans. This made R-12 an attractive choice, since it was highly stable and non-toxic. However, this stability also proved to be a problem. In the 1970s, scientists studying the ultimate fate of CFCs like R-12 discovered that these gasses could make their way up to the stratosphere. There, they could be broken down by ultraviolet radiation, releasing chlorine atoms (the first C in CFC and HCFC). The chlorine would then react with, and destroy, atmospheric ozone.

In response to these findings, in 1987 the international community adopted the Montreal Protocol on Substances that Deplete the Ozone Layer. The agreement was initially signed by 46 countries, and has since been ratified by 198 parties, including all member states of the United Nations. It sets out a schedule for the phase-out of the production and consumption of ozone-depleting substances (ODSs), including CFCs like R-12 and HCFCs like R-22.

The phase-out schedule differed for different substances and in different places. For instance, R-12 was phased out in developed countries in 1996, and in developing countries in 2010. Meanwhile, R-22, an HCFC common in home and commercial heat pumps, was phased out in developed countries in 2010, but it continues to be in-use in developing countries until 2030.

GWP and the Kigali Amendment

If you recall, one of the properties of a good refrigerant is its ability to absorb and release heat. Refrigerants continue to play this role even after they've been released into the atmosphere. In particular, they absorb and release heat in the form of infrared radiation, which is the same type of radiation that is absorbed and released by greenhouse gasses like carbon dioxide and methane.

The heat-trapping ability of a greenhouse gas is measured by its global warming potential (GWP). The standard basis of comparison is the most common greenhouse gas, carbon dioxide (CO2), which has a GWP of 1. The GWP of Freon, or R-12, is 10,900. This means that, released into the atmosphere, R-12 traps 10,900 times as much heat as an equivalent amount of CO2.

CFCs and HCFCs phased out under the Montreal protocol were often replaced by hydrofluorocarbons, which have many of the desirable properties of a refrigerant, but without the ozone-destroying chlorine. For example, an HFC called R-134a is a common replacement for R-12 in automotive air conditioners. However, R-134a has a GWP of 1,430 -- much less than R-12, but still substantially heat-trapping.

When the Montreal protocol was adopted in 1987, the focus was on the ozone-depleting properties of CFCs and HCFCs. However, as the world began to phase-out these substances, it became clear that their global warming potential was also a problem. In response, in 2016 the international community adopted the Kigali Amendment to the Montreal Protocol. The Kigali amendment is meant to prevent additional global warming from refrigeration by phasing-out the production and consumption of hydrofluorocarbons (HFCs), which are the most common replacements for CFCs and HCFCs. The amendment has, so far, been ratified by 148 parties.

Like the Montreal Protocol, the Kigali Amendment sets out a schedule for the phase-out of HFCs, but this schedule differs from place to place. For instance, for R-3 In the developed world, the phase-out began in 2019, and is scheduled to complete by 2036. In the developing world, however, the phase-out is not scheduled to end until 2045, with some countries receiving additional extensions to 2047 or later.

How Recoolit Fits In

Refrigerant pollution is a major global problem, and the world is working hard to solve it. However, as you can see, even the phase-out of ozone-depleting substances like R-22 will not be complete until 2030. With high-GWP HFCs like R-134a, the process has barely begun, and will last for decades.

What do we do in the meantime? This is where Recoolit comes in. While the world works to phase out harmful refrigerants, we can work to reduce the amount of refrigerant pollution that is released into the atmosphere.

Certainly, some of this release is accidental or the result of equipment malfunction. However, a significant portion of refrigerant pollution is the result of intentional venting. This is because, without Recoolit, technicians simply have no other way to dispose of refrigerant properly. Even well-intentioned technicians, who are concerned about pollution and environmental impacts, have no other choice when a system must be drained for maintenance or repair. We've seen technicians vent refrigerant through a hose inserted into a bucket of water, in the (mistaken) belief that this will somehow "scrub" the refrigerant.

Additionally, the process of recovering refrigerant is time-consuming and expensive. The international protocols do not provide any funding for the transition to cleaner refrigerants, or to mitigate the damage from refrigerant pollution. This is where you come in. Now that you know about the problem, you can help us solve it. Fund our work by buying our carbon credits. Tell your friends and colleagues about the problem, and about our solution.

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