From The BBC.
It's the most powerful greenhouse gas known to humanity, and emissions have risen rapidly in recent years, the BBC has learned.
Sulphur hexafluoride, or SF6, is widely used in the electrical industry to prevent short circuits and accidents.
But leaks of the little-known gas in the UK and the rest of the EU in 2017 were the equivalent of putting an extra 1.3 million cars on the road. Levels are rising as an unintended consequence of the green energy boom.
Cheap and non-flammable, SF6 is a colourless, odourless, synthetic gas. It makes a hugely effective insulating material for medium and high-voltage electrical installations. It is widely used across the industry, from large power stations to wind turbines to electrical sub-stations in towns and cities. It prevents electrical accidents and fires.
However, the significant downside to using the gas is that it has the highest global warming potential of any known substance. It is 23,500 times more warming than carbon dioxide (CO2). It also persists in the atmosphere for a long time, warming the Earth for at least 1,000 years.
"As renewable projects are getting bigger and bigger, we have had to use it within wind turbines specifically," said Costa Pirgousis, an engineer with Scottish Power Renewables on its new East Anglia wind farm, which doesn't use SF6 in turbines. "As we are putting in more and more turbines, we need more and more switchgear and, as a result, more SF6 is being introduced into big turbines off shore. It's been proven for years and we know how it works, and as a result it is very reliable and very low maintenance for us offshore."
Across the entire UK network of power lines and substations, there are around one million kilograms of SF6 installed. A study from the University of Cardiff found that across all transmission and distribution networks, the amount used was increasing by 30-40 tonnes per year. This rise was also reflected across Europe with total emissions from the 28 member states in 2017 equivalent to 6.73 million tonnes of CO2. That's the same as the emissions from 1.3 million extra cars on the road for a year.
Just one kilogram of SF6 warms the Earth to the same extent as 24 people flying London to New York return.
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| Source: The BBC |
The most important means by which SF6 gets into the atmosphere is from leaks in the electricity industry.
Electrical company Eaton, which manufactures switchgear without SF6, says its research indicates that for the full life-cycle of the product, leaks could be as high as 15% - much higher than many other estimates.
Louis Shaffer, electrical business manager at Eaton, said: "The newer gear has very low leak rates but the key question is do you have newer gear? We looked at all equipment and looked at the average of all those leak rates, and we didn't see people taking into account the filling of the gas. Plus, we looked at how you recycle it and return it and also included the catastrophic leaks."
Developed countries are expected to report every year to the UN on how much SF6 they use, but developing countries do not face any restrictions on use. Right now, scientists are detecting concentrations in the atmosphere that are 10 times the amount declared by countries in their reports. Scientists say this is not all coming from countries like India, China and South Korea.
The question of alternatives to SF6 has been contentious over recent years.
For high-voltage applications, experts say there are very few solutions that have been rigorously tested.
"There is no real alternative that is proven," said Prof Manu Haddad from the school of engineering at Cardiff University. "There are some that are being proposed now but to prove their operation over a long period of time is a risk that many companies don't want to take."
However, for medium voltage operations there are several tried-and-tested materials. Some in the industry say that the conservative nature of the electrical industry is the key reason that few want to change to a less harmful alternative. "I will tell you, everyone in this industry knows you can do this; there is not a technical reason not to do it," said Louis Shaffer from Eaton.
"It's not really economic; it's more a question that change takes effort and if you don't have to, you won't do it." One study found that the methods used to calculate emissions in richer countries "severely under-reported" emissions over the past two decades.
It's obvious, isn't it? We're going to have to stop using it. It's going to have to be replaced. Ironically, it will be perfect for terraforming Mars, because of its potency and 1000-year life. CFCs (also fluorine compounds and potent greenhouse gases) will degrade too quickly on Mars because of the UV-flux. But seriously, do we want to raise Earth's temperature by 10 degrees C?
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