F-Gases: Man-made Fluorinated Greenhouse Gases

What are F-gases? Where do they come from? What are they used for? How do fluorinated gases affect climate change? What is their atmospheric lifetime, global warming potential (GWP) and concentration in the atmosphere? Why are HFCs being phased out by the Montreal Protocol? We answer all these questions and more.
Noctilucent clouds
F-gases are a rapidly growing contributor to the greenhouse effect. Image: NASA.gov. Courtesy of John Boardman.

What Are Fluorinated Gases?

Fluorinated gases (“F-gases” – the F stands for fluorine, the chemical element common to all) are a family of synthetic chemicals used in a wide range of industrial applications. There are four types: HFCs, PFCs, SF6 and NF3.

F-gases are highly potent greenhouse gases (GHGs), that trap heat in the troposphere and redirect it back down to Earth’s surface. This positive radiative forcing constitutes the ‘greenhouse effect‘ – the key mechanism behind global warming.

F-gases were developed in the early 1990s for use in the manufacture of aerosol sprays, and as refrigerants. They were created as replacements for other groups of laboratory-made gases, such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which were found to damage the stratospheric ozone layer and were duly banned by the Montreal Protocol.

Unfortunately, according to a 2015 NASA study, HFCs also contribute to ozone depletion by a small but measurable amount, countering a decades-old assumption. 1 HFC emissions cause warming in the stratosphere, which accelerates the chemical reactions that damage ozone molecules. In addition, they reduce ozone levels in the tropics by boosting the upward movement of ozone-poor air.

However, the contribution of HFCs to ozone depletion is small compared to earlier gases. For instance, trichlorofluoromethane, or CFC-11, which is no longer used, used to cause about 400 times more ozone depletion than HFCs.

HFCs are now being phased out by mid-century, under the Kigali Amendment to the Montreal Protocol.

For more about these ozone depleting substances and the ozone hole, as well as the pioneering work of Nobel Prize-winning scientists Frank Sherwood Rowland and Mario Molina, see: The Montreal Protocol on Substances That Deplete the Ozone Layer (1987).

Graph of F-Gases in Atmosphere
Graph shows a decline in atmospheric concentrations of CFCs in response to global controls placed on CFC manufacture and trade by the Montreal Protocol (1987). Note the corresponding rise in levels of HCFCs and HFCs. Image source: NOAA Annual Greenhouse Gas Index (AGGI) 2020.

Why Are F-gases a Climate Concern?

They are extremely powerful greenhouse gases (GHGs) that can remain active in the atmosphere for centuries. They can have a global warming potential (GWP) up to 23,000 times greater than carbon dioxide (CO2) – see below. Thus, despite being emitted in relatively small quantities their contribution to climate change is disproportionately large and growing.

What Are the Main Types of Fluorinated Gases?

There are four main types of F-gases:

Hydrofluorocarbons (HFCs) containing hydrogen, fluorine, and carbon);

Perfluorocarbons (PFCs) containing fluorine and carbon);

Sulfur Hexafluoride (SF6); and

Nitrogen Trifluoride (NF3).

As far as Earth’s climate crisis is concerned, HFCs are by far the most important.

These four types replaced the now-banned Chlorofluorocarbons (CFCs) and Bromofluorocarbons (Halons), as well as Hydrochlorofluorocarbons (HCFCs), which are being phased-out by 2030.

What’s the Difference Between CFCs, HCFCs and HFCs?

CFCs are the first generation of fluorine-based gases. They are classified as having high ozone depleting potential (ODP) and high global warming potential (GWP).

HCFCs are second generation of fluorine based gases, the original replacements for CFCs. HCFCs are classified as having medium ODP and medium-high GWP. They are slightly more environmentally friendly than CFCs.

HFCs are third generation fluorine-based gases. HFCs are classified as having zero ODP and medium to high GWP and are more environmentally friendly alternative to CFCs and HCFCs. However, as we saw, studies now indicate that HFCs do deplete the ozone layer.

All these compounds belong to the family of fluorine-containing gases, yet only HFCs are categorized as “F-gases”. There seems to be no obvious reason for this, and it makes the whole subject slightly confusing. But there you are.

What Are F-Gases Used For?

Fluorinated gases have a wide variety of industrial uses. This versatility has made them the fastest growing greenhouse gases in the world.

HFCs (up to 90 percent in some countries) are employed in refrigeration and automobile air conditioning units. But they are also found in insulating foams, fire extinguishers and aerosol propellants. PFCs are used in the electronics industry (for etching of silicon wafers) and in the aerospace industry, as well as in the cosmetic and pharmaceutical industry. One PFC (Carbon tetrafluoride PFC-14) is also produced as a by-product during aluminium smelting.

Sulphur hexafluoride is employed mainly as an insulating gas, in high voltage switchgear and in the manufacture of aluminum and magnesium.

Nitrogen trifluoride is primarily used in the microelectronics fabrication industry in the etching of wafers.

Most HFCs are contained within equipment and other appliances. Emissions derive from seepage during manufacturing and maintenance, as well as during regular usage. And if the equipment (like a refrigerator or car) is improperly disposed of, HFCs will continue to escape into the air until all used up. See also: Air Pollution: Types, Causes & Effects.

As you can see, F-gases are used in a number of applications (refrigerators, air conditioners) that help people to stay cool as rising temperatures continue to break records. This will lead to further positive climate feedbacks and still higher temperatures. More heat causes more demand for air conditioning, leads to more emissions of F-gases, leads to more heat, and so on.

US Emissions of F-Gases
U.S. Emissions of Fluorinated Gases (1990-2018) Image: U.S. Environmental Protection Agency 2020.

F-Gas Emissions

F-gas emissions continue to rise as a whole, despite declines in the emissions of certain types within certain areas. Within the EU, for example, they almost doubled from 1990 to 2014 – unlike emissions of greenhouse gases like carbon dioxide or methane, both of which fell over the same period.

Since 2015, however, due to EU legislation, F-gas emissions have been declining (Source: EEA data).

In the United States, F-gas emissions rose by roughly 83 percent from 1990 to 2018. This increase was driven by a 268 percent rise in HFC emissions since 1990, due to the fact that HFCs were widely introduced as a replacement for ozone-depleting substances, like CFCs and HCFCs.

At the same time, emissions of PFCs and sulfur hexafluoride have declined during this period due to the implementation of emission reduction procedures in the aluminum manufacturing sector (PFCs) and the electricity transmission industry (SF6). 2

It’s worth remembering that the replacement of CFCs by HFCs during the 1990s led to a natural drop in overall fluorine-related GHG emissions due to the fact that CFCs had a significantly higher GWP than HFCs. Previously, CFCs accounted for 12-15 percent of total greenhouse gas (GHG) emissions.

By 2004, the new F-gases like HFCs accounted for roughly 1.3 percent of greenhouse gas emissions. 3 4

At present, according to the UN Emissions Gap Report 2020, F-gas emissions account for about 3.3 percent of all global GHG emissions – a 65 percent rise over the 2005 figure. And they are expected to continue rising due to increasing demand for refrigeration and air-conditioning, especially in developing countries.

According to the United Nations, HFC emissions are rising by 8 percent per year and annual emissions are forecast to reach between 7 and 19 percent of global CO2 emissions by 2050. 5

Graph of halogenated gases in atmosphere
Global atmospheric levels of selected ozone depleting substances and F-gases (1978–2015). Graph shows growing concentrations of greenhouse gases that contain fluorine, chlorine, or bromine, measured in parts per trillion (ppt). Image: US EPA. Data sources: Halocarbons and Other Atmospheric Trace Species group, NOAA. Advanced Global Atmospheric Gases Experiment (AGAGE) (2016).

F-Gas Emissions Statistics

Obtaining precise, up to date statistics on emissions of fluorinated gases is not easy. First, data on F-gases is commonly subsumed under a general category of “non-CO2 greenhouse gases”, which also includes significantly larger outputs of methane (CH4) and nitrous oxide (N2O).

Second, some F-gases have short lifetimes and are therefore not easy to track.

Third, most HFCs are used in the refrigerant and automobile air conditioning industries, a major slice of which is located in China, where accurate statistics are even scarcer. For instance, China produces US$10.4 billion worth (22.8 percent) of exported refrigeration appliances.

Also, anecdotal evidence suggests that the global regulation of HFCs and other F-gases does not always encourage full disclosure by producers.

For more on GHG stats, see: Greenhouse Gas Statistics.

How Long Do F-Gases Stay in the Atmosphere?

Atmospheric lifetimes of F-gases vary widely. Compared to CFCs – which endure on average for a century or more – and HCFCs – which typically stay active for a decade or less – HFCs are quite short-lived. A considerable number have a lifetime of between 15 and 29 years.

In comparison, perfluorocarbons (PFCs) and sulphur hexafluoride (SF6), can remain in the atmosphere for thousands of years. PFC-14, for instance, has a lifespan of 50,000 years.

Once released into the lower atmosphere, F-gases disperse around the globe, before (eventually) being removed by sunlight. HFCs typically break down relatively quickly: the atmospheric lifespan of HFC-134a, for example, is about 13.5 years. Breakdown takes place in the troposphere (the lowest layer of the atmosphere), where they are split by reactions with hydroxyl radicals (OH).

Lifetimes of F-Gases Compared to CO2

GasLifetime in Atmosphere
CO2 (reference)30-35,000 years
CFCs (reference)45-1,000 years
HCFCs (reference)1-18 years
HFCs – Hydrofluorocarbons66 days-250 years
PFCs – PerfluorocarbonsUp to 50,000 years
NF3 – Nitrogen Trifluoride550 years
SF6 – Sulphur Hexafluoride3,200 years
Source: Intergovernmental Panel on Climate Change. AR5 (2013)

Effects of F-Gases on Climate Change

Like all GHGs, fluorinated gases exert a harmful effect on our climate system because they absorb heat trying to escape into space and re-radiate it down to the surface of the planet. But F-gases are worse than other GHGs because they trap more heat.

The heat-trapping power of a GHG is reflected in its “global warming potential” (GWP) over a specific period – usually 100 years. GWP indicates how the heat-trapping power of the gas in question compares to carbon dioxide. Methane, for example, has a GWP of 28. Which means that one unit of methane traps the same amount of heat as 28 units of carbon dioxide.

As the following table shows, F-gases typically have a much higher GWP rating than other GHGs such as carbon dioxide (GWP of 1), methane (28) or nitrous oxide (265).

One ton of sulphur hexafluoride, for instance, traps the same amount of heat as 23,500 tons of CO2. This compound is the most powerful greenhouse gas evaluated, to date. Meantime, HFC-23, one of the most abundant HFCs, is 12,400 times more damaging to the climate than carbon dioxide.

Global Warming Potential of F-Gases

GasGWP (20yrs)GWP (100yrs)
Carbon Dioxide (reference)11
HFC-23 Hydrofluorocarbon10,80012,400
CF4 Perfluorocarbon48806630
Nitrogen Trifluoride NF312,80016,100
Sulphur Hexafluoride SF67,50023,500
Source: Intergovernmental Panel on Climate Change. AR5 (2013)

Regulation of Gases Under the Montreal Protocol

The Montreal Protocol (1987) and its subsequent amendments regulate the use of all first- and second-generation fluorine-based gases due to their ozone-depleting properties, and also due to their disastrous effect on global warming. Gases banned or being phased out under the Montreal treaty include: CFCs, HBFCs, carbon tetrachloride, and methyl chloroform (in 1996); methyl bromide and bromochloromethane (in 2005); HCFCs (by 2030).

Under the Kigali Amendment (2019) to the Montreal treaty, countries have also agreed to phase out the production and consumption of HFCs (a third generation fluorine-based gas) by more than 80 percent by mid-century to avoid more than 70 billion tonnes of CO2-eq emissions by 2050, and global warming of up to 0.5°C by 2100. 6

50 Global Warming FAQs
50 Climate Change FAQs

Data on Global Warming Potential of F-Gases

The following tables on the GWP of fluorinated gases are based on data from the Intergovernmental Panel on Climate Change, as listed in its Fifth Assessment Report (AR5) (2013) 7

Figure 2. Lifetime & Global Warming Potential of Chlorofluorocarbons (CFCs)

Greenhouse GasLifetime (yrs)GWP (20yrs)GWP (100 yrs)
CFC-11 45.069004660
CFC-12 100.010,80010,200
CFC-13 640.010,90013,900
CFC-113 85.064905820
CFC-114 190.077108590
CFC-115 1,020.058607670
Source: IPCC Fifth Assessment Report (2013)

Figure 3. Lifetime & Global Warming Potential of Hydrochlorofluorocarbons (HCFCs)

Greenhouse GasLifetime (yrs)GWP (20yrs)GWP (100 yrs)
HCFC-21 1.7543148
HCFC-22 11.952801760
HCFC-122 1.021859
HCFC-122a 3.4945258
HCFC-123 1.329279
HCFC-123a 4.01350370
HCFC-124 5.91870527
HCFC-132c 4.31230338
HCFC-141b 9.22550782
HCFC-142b 17.250201980
HCFC-225ca 1.9469127
HCFC-225cb 5.91860525
Source: IPCC Fifth Assessment Report (2013)

Figure 4. Lifetime & Global Warming Potential of Hydrofluorocarbons (HFCs)

Greenhouse Gas Lifetime (yrs)GWP (20yrs)GWP (100yrs)
HFC-23 222.010,80012,400
HFC-32 5.22430677
HFC-41 2.8427116
HFC-125 28.260903170
HFC-134 9.735801120
HFC-134a 13.437101300
HFC-143 3.51200328
HFC-143a 47.169404800
HFC-152 0.46016
HFC-152a 1.5506138
HFC-161 66 days134
HFC-227ca 28.250802640
HFC-227ea 38.953603350
HFC-236cb 13.134801210
HFC-236ea 11.041101330
HFC-236fa 242.069408060
HFC-245ca 6.52510716
HFC-245cb 47.166804620
HFC-245ea 3.2863235
HFC-245eb 3.11070290
HFC-245fa 7.72920858
HFC-263fb 1.227876
HFC-272ca 2.6530144
HFC-329p 28.445102360
HFC-365mfc 8.72660804
HFC-43-10mee 16.143101650
Source: IPCC AR5 (2013)

Figure 5. Lifetime & Global Warming Potential of Perfluorocarbon (PFCs)

Greenhouse GasLifetime (yrs)GWP (20yrs)GWP (100 yrs)
PFC-14 50,000.048806690
PFC-116 10,000.0821011,100
PFC-c216 3,000.068509200
PFC-218 2,600.066408900
PFC-318 3,200.071109540
Perfluorodecalin (cis) 2,000.054307240
Perfluorodecalin 2,000.047206290
Source: IPCC AR5 (2013)

Figure 6. Lifetime & Global Warming Potential of Bromocarbons and Halons

Greenhouse GasLifetime (yrs)GWP (20yrs)GWP (100 yrs)
Methyl bromide 0.892
Methylene bromide0.341
Halon-1201 5.21350376
Halon-1202 2.9848231
Halon-1211 16.045901750
Halon-1301 65.078006290
Halon-2301 3.4635173
Halon-2311/Halothane 1.015141
Halon-2401 2.9674184
Halon-2402 20.034401470
Source: IPCC AR5 (2013)

References

  1. “Ozone depletion by hydrofluorocarbons.” Margaret M. Hurwitz, et al. Geophysical Research Letters. Volume 42, Issue 20. Pages 8686-8692. []
  2. Greenhouse Gases. US EPA. []
  3. “Fluorinated greenhouse gases and fully halogenated CFCs.” []
  4. “Evolution of uses and emissions of fluorinated gases, in particular those of hydro-fluorocarbon type (HFC)”. Greenfacts.org []
  5. “About Montreal Protocol.” UN Environment. []
  6. “Evolution of uses and emissions of fluorinated gases, in particular those of hydro-fluorocarbon type (HFC)”. Greenfacts.org []
  7. “Anthropogenic and Natural Radiative Forcing.” Page 731. Myhre, G. et al. 2013: In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the IPCC Fifth Assessment Report. Cambridge University Press. PDF: www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter08_FINAL.pdf []
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