It is odorless, colorless and non-toxic, but is currently the climate’s number one enemy. We are talking about sulfur hexafluoride gas (SF6), used throughout the world mainly as an insulating and protective gas in medium and high voltage electrical panels. In the past, it was also used as a filling gas for sports shoes and as an insulating gas in soundproof windows, until this use was banned in 2006. Today, however, a new German study brings it back to attention, confirming that SF6 is currently the most potent greenhouse gas known, with a climate impact around 24,000 times greater than CO₂.
Using advanced measurements and computer models, the international team led by researchers from Goethe-Universität Frankfurt has identified an emission source of the sulfur hexafluoride gas in southern Germany that had not yet been taken into account in Germany’s climate balance sheet until now.
Sulfur hexafluoride is a gas that is little talked about, yet it represents one of the most extreme climate threats on the planet. A single kilogram of SF₆ has a global warming impact equal to approximately 24 tonnes of carbon dioxide, making it approximately 24,000 times more harmful to the climate.
Due to its chemical stability and extreme climate impact, the United Nations requires all member states to regularly report their SF₆ emissions.
Where is sulfur hexafluoride used?
Despite its very high global warming potential, SF₆ is fundamental to key sectors of modern technology: it is a backbone of electricity grids. The main and most widespread use of SF₆ is as an insulating and protective gas in electrical equipment. It is the most effective insulating gas known for high voltage systems.
Furthermore, SF₆ has a very high dielectric power, i.e. it excellently resists the passage of electric current even at high voltages, as occurs in the switches used by transmission network operators, in power plants or in high-power industrial plants. These systems guarantee high reliability and require very little maintenance.
The German study
SF₆ is today considered the most potent greenhouse gas of all. A study by the Goethe-Universität Frankfurt am Main reports that just one kilo of this gas has the same effect on global warming as approximately 24 tons of CO₂. This is huge, and it comes down to the fact that SF₆ retains heat extremely effectively and remains in the atmosphere for thousands of years without degrading.
For many years, in Germany it was believed that the majority of SF₆ emissions came from a very particular source: old sound-absorbing windows. In fact, in the 1970s and until the early 1990s, this gas was used as an acoustic insulator inside German double glazing. When these windows were dismantled or disposed of, the gas trapped inside them slowly released into the atmosphere.
The German national emissions inventory has long based its calculations on this assumption. However, the study highlighting the southern German region as particularly problematic from the point of view of this greenhouse gas, cast doubt on this view, suggesting that there could be other more important sources of emissions, such as some industrial applications. The historical belief, however, was that the disposal of old windows was the predominant factor.
This type of regional distribution of emissions is not in line with previous hypotheses according to which emissions mainly arise from the disposal of old soundproof windows,” explains Katharina Meixner, lead author of the study published in the journal ACS Environmental Science & Technology – Air. “What is striking, however, is that this region is home to the only SF6 production and recycling plant in Europe that we are aware of.” Meixner emphasizes that “only by understanding where emissions come from in Germany can they be accounted for correctly and addressed effectively to reduce greenhouse gas emissions.”
Andreas Engel explains:
Previous scientific studies have already shown that emissions during the production, use and recycling of highly volatile substances are often more difficult to avoid and therefore higher than previously assumed.
The climate paradox
The case of SF₆ highlights a critical paradox: the substances used to make our technology more efficient, compact and safe, such as highly reliable electrical equipment, are often the same ones that are most difficult to manage in terms of environmental losses. The German study shows in fact that the emissions generated during the production, use and recycling of highly volatile substances are often greater than expected.
Precisely understanding and quantifying these emissions, as done by the Frankfurt researchers, is essential, since the impact of this very long-lived greenhouse gas, even in small quantities, is catastrophic. It’s like trying to put out a forest fire with a glass of water, only that water, in the case of SF₆, is extremely concentrated and infinitely more potent.
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