It has been acknowledged that high marine traffic areas and beyond are vulnerable to the build-up of high levels of Sulphur Dioxide - SO emissions from commercial shipping. The subsequent significant cost implications to Public Health and the Environment from SO emissions have been the catalyst for change.


In 1997, following mounting pressure on the marine industry to reduce the sulphur footprint of commercial vessels, the International Maritime Organisation (IMO) amended Regulation 13 of the International Convention for the Prevention of Pollution from Ships (MARPOL) with Annex VI, which entered into force on May 17, 2005, focusing on the prevention of air pollution from ships.


Since 2009, it was known that shipping contributed about 9% of global SO pollution levels. The High Sulphur Fuel Oil [HSFO] that commercial vessels use and its resultant exhaust emissions have a sulphur content originating from the sulphur that naturally occurs in crude oil, which the refining process cannot completely remove.


Annex VI was to be the vehicle through which reducing maximum limits on SO emissions was to be phased in between 2005 and 2020, and was initially set globally at 4.5%. At that time, this did not pose insurmountable problems for the ship operating community, as a 4.5% cap could be complied with by means of diligent operation of ships’ engines using traditional  HFSO.


It has been recognized that high marine traffic areas (such as the North Sea in Europe) were particularly vulnerable to the build-up of high levels of SO emissions from commercial ships. Endorsed by the IMO, a North European Emissions Control Area (ECA) was set up in 2008, limiting the permitted sulphur emissions from ships to 1.5%. This limit was subsequently reduced to 1% in 2010.



These new levels would be difficult to achieve with HFSO. The introduction of low-sulphur fuel oils [LSFO] in marketable quantities by oil companies in recent years has meant that existing engines could be “switched over” from using HSFO in most global areas to LSFO as vessels approached and entered the North European ECA. In 2010, the European ECA maximum cap for permitted SOx emissions was reduced to 1.0%.


Similar concerns over levels of SOx emissions were evident in the US and Canada. Consequently, the IMO endorsed the setting up of a North American ECA (see Figure 2). In 2012, under a revised and considerably strengthened Annex VI to MARPOL, the North American ECA limit was, like its North European equivalent, set at 1%.4 At the same time, the global cap (outside of the two ECAs) was reduced from 4.5% to 3.5%. 



At the start of 2015, the maximum permitted caps on sulphur emissions in both the North American and North European ECAs was reduced from 1% to 0.1%.5 To demonstrate that these new rules were going to be rigorously enforced, there were reports as early as January 2, 2015 that samples of the exhaust fumes from vessels operating inside the US-administered waters of the North American ECA were being collected by the US Coastguard to check on compliance. However, outside the two ECAs, vessels could continue to legally burn fuels that emitted up to 3.5% sulphur. Under Annex VI to MARPOL, the IMO announced that, on January 1, 2020, the global cap on sulphur emissions will be reduced to 0.5% from the current 3.5%.


It is not possible to achieve these low levels of sulphur emissions using traditional HSFO that has not been treated before the exhaust gases are released. At the time of the announcement of the regulatory changes, many in the industry doubted the 2020 timeline for SOx reductions would be adhered to. January 2020 is now a reality; following a short grace period, compliance with the new sulphur cap of 0.5% will be mandatory. Ship operators and refiners are now faced with some stark choices if they are to remain compliant with Annex VI of the MARPOL convention.

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