SOx and Particulate Matter Emissions
Sulphur contained in fuel causes emissions of sulphur dioxide (SO2) and also contributes to the formation of secondary particulate matter (PM) that is particularly harmful both to humans and the environment.
These emissions have a major health impact, with shipping air pollution estimated to cause around 50,000 premature deaths per year in Europe.
SOX emissions also cause environmental problems such as the acidification of soil and water and damage to biodiversity. It is necessary to control SOX emissions from the shipping sector. International shipping uses heavy fuel oil (residual fuels) with a very high sulphur content. The marine fuel currently in use is on average 2,700 times dirtier than the fuel used in the road sector where strict limits have applied for many years.
IMO is an agency of the United Nations which has been formed to promote maritime safety. It was formally established by an international conference in Geneva in 1948, and became active in 1958 when the IMO Convention entered into force (the original name was the Inter-Governmental Maritime Consultative Organization, or IMCO, but the name was changed in 1982 to IMO). IMO currently groups 167 Member States and 3 Associate Members.
IMO ship pollution rules are contained in the “International Convention on the Prevention of Pollution from Ships”, known as MARPOL 73/78. On 27 September 1997, the MARPOL Convention has been amended by the “1997 Protocol”;, which includes Annex VI titled “Regulations for the Prevention of Air Pollution from Ships”. MARPOL Annex VI sets limits on NOx and SOx emissions from ship exhausts, and prohibits deliberate emissions of ozone depleting substances.
Heavy fuel oil (HFO) is allowed provided it meets the applicable sulfur limit (i.e., there is no mandate to use distillate fuels).
Alternative measures are also allowed (in the SOx ECAs and globally) to reduce sulfur emissions, such as through the use of scrubbers. For example, in lieu of using the 1.5% S fuel in SOx ECAs, ships can fit an exhaust gas cleaning system or use any other technological method to limit SOx emissions to ≤ 6 g/kWh (as SO2).