Third IMO Greenhouse Gas Study 2014

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