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MARPOL Annex VI regulations include caps on sulfur content of fuel oil as a measure to control SOx emissions and, indirectly, Particulate Matter(PM) emissions (there are no explicit PM emission limits). 

Special fuel quality provisions exist for SOx Emission Control Areas (ECA). The applicable sulfur limits set forth by Annex VI for ships operating globally as well as in ECA area's along with implementation dates are listed 

Outside Special Area
Before 1st Jan 2012=4.5% sulphur m/m
After 1st Jan 2012=3.5% sulphur m/m
After 1st Jan 2020=0.5% sulphur m/m

Inside Special Area
Before 1st July 2010=1.5% sulphur m/m
After 1st July 2010=1.0% sulphur m/m
After 1st Jan 2015=0.10% sulphur m/m

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 ECAs and globally) to reduce sulphur emissions, such as using scrubbers. For example, in lieu of using the 1.5% Sulphur fuel in 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)].

Under the revised MARPOL Annex VI, the term Sulphur Emission Control Area, or SECA, is being replaced with Emission Control Area, or ECA. This will allow for ECAs to specify limits not just for sulphur oxides (SOx), but also for particulate matter (PM), and (NOx).


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