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Annex 7 285<br />
are also highly paraffinic, waxy crude oils that would be unsuitable for heavy fuel oil production for marine<br />
bunkers owing to their high pour points (TransBaltic, 2012). But even if only LSHFO with a 0.5% sulphur<br />
content was produced for use in maritime shipping, an investment of refineries in further desulphurization of<br />
high sulphur residues would be inevitable since the low sulphur vacuum gas oil (heavy oil leftover that can<br />
be further refined in a catalytic cracking unit) is currently used as feedstock for other purposes and since next<br />
to the maritime shipping sector there are hardly any other users of the high sulphur residues (Purvin & Gertz,<br />
2009).<br />
Since the SECA limit is lower than the global sulphur limit, ships which operate both outside and inside the<br />
SECA have the compliance option of switching fuel when entering the SECA if their fuel oil combustion<br />
equipment and devices allow this.<br />
Next to using fuel with the required sulphur content, scrubbers for exhaust gas cleaning can be used as a<br />
secondary compliance method. When a scrubber is used, the ship does not have to use a fuel other than HFO,<br />
but the use of a scrubber will raise energy demand slightly.<br />
Regulation 13 of MARPOL Annex VI sets NO x emission limits for installed marine diesel engines of over<br />
130 kW output power. The requirements limit the total weighted cycle emissions in terms of g/kWh and<br />
depend on the date of the construction of a ship and on the engine’s rated speed. Currently, no specific<br />
stringency levels hold for NO x emission control areas (NECAs), but ships constructed on or after 1 January<br />
2016 will have to comply with NO x Tier III standards when operating in the North American ECA or the<br />
United States Caribbean Sea ECA, which are already designated NECAs. In addition, Tier III requirements will<br />
apply to installed marine diesel engines when operated in other NECAs which might be designated in the<br />
future. However, Tier III will then apply to ships constructed on or after the date of adoption by MEPC of such<br />
an ECA, or a later date as may be specified in the amendment designating the NO x Tier III ECA (IMO, 2014, c)).<br />
Table 56 – IMO NO x limits<br />
Tier Geographical scope Ship construction date<br />
(on or after)<br />
Total weighted cycle emission limit (g/kWh)<br />
n = engine’s rated speed (rpm)<br />
n < 130 n = 130–1,999 n ≥ 2,000<br />
I Global 1 January 2000 17.0 45 * n -0.2 9.8<br />
II Global 1 January 2011 14.4 44 * n -0.23 7.7<br />
III In North American and United<br />
States Caribbean Sea ECAs<br />
1 January 2016 3.4 9 * n -0.2 2.0<br />
Source: IMO (2014, d))<br />
Whereas the global Tier I and Tier II requirements can be met by adjustments in engine design and calibration,<br />
this is not the case for the Tier III requirements, which are 80% stricter than Tier I limits.<br />
In its final report (MEPC 65/4/7), the Correspondence Group on Assessment of Technological Developments<br />
to Implement the Tier III NO x Emission Standards under MARPOL Annex VI identified that the following<br />
technologies have the potential to achieve NO x Tier III limits, either alone or in some combination with each<br />
other:<br />
1 Selective catalytic reduction (SCR);<br />
2 Exhaust gas recirculation (EGR);<br />
3 The use of LNG, either dual-fuel (diesel pilot injection with gaseous LNG as main fuel) or alternative<br />
fuel arrangements; and<br />
4 Other technologies: direct water injection, humid air motor, scrubbers, treated water scrubber, variable<br />
valve timing and lift, and dimethyl ether as an alternative fuel.<br />
Fuel mix scenarios used in emissions projection model<br />
The fuel mix is an exogenous variable in the CO 2 emissions projection model. It has two effects on the<br />
estimated emissions. On the one hand, there is the direct effect on the CO 2 emissions due to the different CO 2<br />
emissions factors of the fuels, and on the other, there is an indirect effect via the cost-efficiency of the CO 2<br />
abatement measures. If ships decide to comply with the air pollution regulation by switching from HFO to