Studies in the past prove that air pollutants from emissions have a lot of negative effects on the environment and the public. Many states and local governments all over the world have done their part in taking action to this environmental problem. There arise different bodies that regulate the release of harmful substances such as particulate matter, carbon monoxide, sulfur dioxide, lead and nitrogen oxides in the atmosphere or at the sea. Significant contributors to air pollutions are emissions from diesel engines of automobiles and large ships. The arising number of container ships, tankers, bulk carriers and cruise ships make the shipping fleets responsible for 18-30% of the world’s nitrogen oxide and 9% of global sulfur oxide. Thus in the year 1973, an specialized agency from United Nation namely IMO (International Maritime Organization) brought forth the International Convention for the Prevention of Pollution from Ships or MARPOL.
MARPOL (shortened Marine Pollution) is one of IMO’s conventions that focus on preventing different forms of marine pollution including oil, noxious liquid substances, harmful substances, waste water, garbage and emissions of sulfur oxide and nitrogen oxide at sea. MARPOL convention includes six technical Annexes that list regulations on the mentioned marine pollutants. Annex I and II were entered into force in the year 1983 containing the regulations for oil and noxious liquid substances. Annex III entered into force on 1992 containing general requirements on packaging of harmful substances. In September 2003, set of regulations regarding the discharge of waste water were entered into force under Annex IV followed by ban imposed on dumping any form of plastic in the sea in the year 1988 under Annex V. The current MARPOL convention includes Annex VI which contains regulations on sulfur oxide, nitrogen oxide and ozone depleting substances.
According to MARPOL Annex VI Regulation 13, emissions of NOx from diesel engine with more than 130 kW power output installed on ships constructed on or after January 1, 2000, or which undergo major conversion, must not exceed the limits below, where n = rated engine speed:
TIER I (on or before January 1, 2000)
17.0 g/kWh when n is less than 130 rpm;
45.0*n(-0.2)g/kWh when n is 130 or more but less than 2,000 rpm;
9.8 g/kWh when n is 2,000 rpm or more.
TIER II (on or after January 2011)
14.4 g/kWh when n is less that 130 rpm;
44.n(0.23) g/kWh when n is 130 or more but less than 2,000 rpm;
7.7 g/kWh when n is 2,000 rpm or more.
TIER III (on or after January 1, 2016)
3.4 g/kWh when n is less than 130 rpm;
9.n(-0.2) g/kWh when n is 130 or more but less than 2,000 rpm;
2.0 g/kWh when n is 2,000 rpm or more.
Before these standards were implemented IMO has to have them ratified by 50% of the world’s gross tonnage and for the six Annexes they always meet the requisite number of nations. Signatory states are required to comply to MARPOL as well as owners of ships that will be operating in the waters of member states.