Third IMO Greenhouse Gas Study 2014

Inventories of emissions of GHGs and other relevant substances 97
Other refrigerants, SF 6
Sulphur hexafluoride (SF 6 ) is a colourless, odourless, non-toxic, non-flammable gas that has a high dielectric
strength. It has been used as a dielectric in microwave frequencies, as an insulating medium for the power
supplies of high-voltage machines and in some military applications, for example as a torpedo propellant.
Sulphur hexafluoride is also gaining use in non-electrical applications, including blanketing of molten
magnesium (molten magnesium will oxidize violently in air), leak detection and plasma etching in the semiconductor
industry. Sulphur hexafluoride also has some limited medical applications. SF 6 is extensively used
as a gaseous dielectric in various kinds of electrical power equipment, such as switchgear, transformers,
condensers and medium- to high-voltage (>1 kV) circuit breakers (Compressed Gas Association, 1990). In
circuit breakers, SF 6 is typically used in a sealed pressurized chamber to prevent electrical arcing between
conductors.
According to World Bank data (2010), global SF 6 emissions were 22,800 thousand tonnes CO 2 e, which
corresponds to 463 tons (i.e. short tons, as per key definition of “ton”) of SF 6 emitted from all sectors. (According
to UNFCCC, SF 6 has a GWP of 23,900.) The use of SF 6 in electrical switchgear in general (all land, air and sea
installations) is primarily (90%) concentrated on the high-voltage segment (>36 kV) and the remaining 10% for
the medium (1 kV–36 kV) voltage segment (Schneider 2003). Ships rarely use electrical systems over 11 kV and
typical nominal voltages are in the 1 kV–11 kV range (Ackermann and Planitz, 2009). The leaks from sealed
systems are small: EPA (2006) estimates a range of 0.2%–2.5% per year. However, the mass of SF 6 on board
the global fleet is unknown, which prohibits detailed analysis of SF 6 emissions from shipping.
If this 90%/10% division is assumed, which represents SF 6 use in high/medium voltage systems, and also
applies to emissions, medium-voltage systems would be responsible for 46.3 tons of SF 6 emitted annually. If all
medium-voltage systems were installed in ships (i.e. no medium-voltage installations on land), the maximum
contribution to total GHG emissions from shipping would be 1.1 million tons (46.3 tons × 22,800 CO 2 e/ton)
of CO 2 e (IPCC, 2007), which is less than 0.1% of the total CO 2 emissions from shipping in 2010. The actual
emissions of SF 6 are likely to be less than this, because alternative solutions (vacuum, CO 2 ) are also available in
arc quenching. Because SF 6 emissions from ships are negligible, they are not considered further in this report.
Other refrigerants, PFCs
Several binary and ternary blends of various HFC, HCFC, PFC and hydrocarbon refrigerants have been
developed to address continuing service demand for CFC-12. These blends are tailored to have physical and
thermodynamic properties comparable to the requirements of the original CFC-12 refrigerant charge.
HFCs were used to replace halon-based systems in the mid 1990s. A small quantity of PFC (mainly C 4 F 10 ) was
imported by a US company into the EU to be used as an alternative fluid in firefighting fixed systems. The
main application of these PFC-based fixed systems is for fire protection by flooding closed rooms (e.g. control
rooms) with halon to replace oxygen. Imports for new systems stopped in 1999, as this application of PFCs
was not regarded as an essential use (AEA, 2010). The electronics and metal industry is a large consumer of
PFC compounds, which are used as etching agents during manufacturing (IPCC/TEAP, 2005). The main PFC
used as a refrigerant is octafluoropropane (C 3 F 8 ), which is a component of the R-413a refrigerant (Danish EPA,
2003). The composition of R-413a is 88% R134a, 9% C 3 F 8 and 3% isobutane and it is used in automotive air
conditioning (Danish EPA, 2003). Another refrigerant with C 3 F 8 is Isceon 89, a mixture of 86% HFC-125, 9%
C 3 F 8 and 5% propane. Isceon 89 is used for deep-freezing purposes (-40°C to -70°C), like freeze-dryers,
medical freezers and environmental chambers (DuPont, 2005).
The annual leakage of all refrigerants from cooling equipment of reefer and fishing vessels is estimated at
2,200 tons. The extreme worst-case estimate assumes that all this is Isceon 89, which contains 9% of C 3 F 8 .
This would total 201 tons of C 3 F 8 and correspond to (8,830 CO 2 e/ton × 201 tons) 1.8 million tons of CO 2 e,
which is about 0.2% of the total CO 2 emitted from ships in 2010. The emissions of C 3 F 8 from ships are likely
to be smaller than this value because the need for extreme cooling is limited; only some reefer cargo ships and
fishing vessels may need this temperature range. Because PFC emissions from ships are likely to be negligible,
they are not considered further in this report.