Air pollution from ships: Recent developments

All developments on air pollution by ships are fairly recent. Annex VI of the international Marpol-convention, regulating the emissions of CFCs, Halons, Volatile Organic Compounds (VOCs) from cargoes, emissions from incinerators and exhaust gas emissions from engines (NOx and SOx) entered into force in May 2005. The International Maritime Organization is currently discussing an upgrade of the air pollution issues covered by Annex VI and some that are not in Annex VI, such as greenhouse gas emissions. CO2 is the most important greenhouse gas emitted by ship. Fuel consumption by the world merchant fleet is expected to grow to between 250–300 million tons per year with corresponding CO2 emissions of 800–960 million tons per year. In Western Europe land based measures have reduced sulphur emissions substantially, leaving shipping as an important remaining source of these emissions. Average sulphur content of heavy fuel oils is 3%, with a limit of 4.5% imposed by Annex VI. Both the Baltic- and the North Sea have the status of SOx emission control area, limiting sulphur content to 1.5%.A significant reduction of the emissions of sulphur oxides from ships is technically possible. One way is to reduce the sulphur content in heavy fuels, but there are several drawbacks. The first is that many refineries do not have the facility to produce low sulphur fuels in large quantities. They may have to invest in new installations, which takes time. The second is that desulphurization costs a lot of energy. There is a penalty in the form of additional CO2 emissions from the refineries. The third is that investing in desulphurization may be less attractive than in investing to produce more light products. Other ways to reduce SOx emissions are the use of low sulphur distillates or exhaust gas cleaning.As to NOx emissions it is believed that new technologies allow a further stepwise reduction of these emissions. Regulations may follow what is feasible. For VOCs, so far Annex VI provides for the possibility to address these emissions (cargo vapours) from ships. There is a tendency to use the possibility and actually reduce these emissions. New elements may enter Annex VI in due course. Addressing particulate matter and PAH’s may be among these.Local air quality in some ports provokes looking at all kinds of possibilities to reduce local air pollution. Again ships’ emissions are becoming relatively more important as land based emissions are diminishing. In growing economies, more shipping also means more ship based pollution in absolute figures. “Cold ironing”, i.e. electric power from shore based plants to ships (instead of power supply by the ships’ diesel generators) is among the possibilities that have been discussed during the last 10 years. It remains to be seen if this issue will at the stage of practical application on a large scale.


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  • Accession Number: 01609323
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 16 2016 9:19AM