Global warming: there is a greenhouse gas worse than CO₂

Sulphur hexafluoride (SF₆) is a synthetic gas that has been used in electrical equipment since the 1960s. In medium- and high-voltage switchgear and circuit-breakers, it is used to insulate live parts and to extinguish the electric arc that forms when the current is interrupted. Its technical properties have contributed to its widespread use in power networks: the majority of sulphur hexafluoride used worldwide is destined for the electricity sector.

The flip side of the coin is climate-related. The global warming potential of SF₆ gas over a hundred years is approximately 23,500 times that of CO₂: one kilogramme released is equivalent, over this timeframe, to approximately 23.5 tonnes of CO₂. Once released, the gas remains in the atmosphere for around a thousand years. Emissions stem mainly from leaks in equipment installed in transmission and distribution networks. Even small quantities therefore have a significant and very long-lasting impact.

As electrification grows, the problem becomes more pressing: to connect new renewable generation and power transport, buildings and industrial activities, we need more extensive grids and new switching equipment. The equipment installed today may remain in service for decades. If they continue to use SF₆, the technological choices made at this stage risk locking a source of emissions into the system for a very long time. The problem does not only concern new installations: it is necessary to minimise leaks from equipment already in operation and to recover the gas properly when it is decommissioned.

SF₆-free alternatives are already available for many applications. In the medium-voltage sector, equipment has been in use for years that employs air as an insulator and a vacuum to interrupt the current; for high voltage, availability is more limited and uptake has yet to increase. The European Regulation on fluorinated gases has set out a phased approach: from 1 January 2026, no new medium-voltage switchgear up to 24 kV using fluorinated gases for insulation or current interruption may be put into service; further deadlines follow in 2028, 2030 and 2032 for other classes of equipment. From 2035, only regenerated or recycled SF₆ gas will be permitted for maintenance and servicing, subject to the exceptions provided for in the regulation.

It is in this context that the Global SF₆ Pledge, promoted by Germany, comes into play. The initiative, which will be launched on 19 November during COP31, aims to coordinate governments, improve emissions inventories and measurement, and support national reduction plans, including through the roll-out of SF₆-free solutions. The challenge is to take action on both fronts: reducing leaks from equipment already in operation and ensuring that new electricity grids do not continue to rely on this gas.