Third IMO Greenhouse Gas Study 2014

Inventories of emissions of GHGs and other relevant substances 107
The approach taken in this study is compatible with the Second IMO GHG Study 2009, which defined PM as
substances including sulphate, water associated with sulphate ash and organic carbons, measured by dilution
method. Therefore, the model can accommodate changes in fuel sulphur content. This reflects the changes in
PM emissions factors arising from ECAs as defined in MARPOL Annex VI.
For further information on specific emissions factors, FCFs and references, see Annex 6.
CO baseline
Emissions of carbon monoxide (CO) were determined by methods originally described in Sarvi et al. (2008),
Kristensen (2012) and IVL (2004). From these sources, the CO EF baseline factors presented in Table 45 were
used.
Table 45 – CO baseline emissions factors
Eng speed/type Fuel type ME EF baseline (kg/tonne fuel) Aux eng EF baseline (kg/tonne fuel) Reference
SSD
MSD
HSD
HFO
HFO
HFO
2.77
2.51
na
na
2.38
2.38
EPA, 2007
EPA, 2007
EPA, 2007
Otto LNG 7.83 7.83 Kristensen, 2012
GT HFO 0.33 na IVL, 2004
STM HFO 0.66 na IVL, 2004
It should be noted that CO emissions are also unaffected by the sulphur content of the fuel burned and are
the same for HFO and distillates. For further information on specific emissions factors and references, see
Annex 6.
CH 4 baseline
Emissions of methane (CH 4 ) were determined by analysis of test results reported in IVL (2004) and MARINTEK
(2010). Methane emissions factors for diesel-fuelled engines, steam boilers and gas turbines are taken from IVL
(2004), which states that CH 4 emissions are approximately 2% magnitude of VOC. Therefore, the EF baseline is
derived by multiplying the NMVOC EF baseline by 2%. The emissions factor for LNG Otto-cycle engines is 8.5g/
kWh, which is on a par with the data for LNG engines (MARINTEK, 2010 and 2014). However, this value may
be slightly low for older gas-fuelled engines, especially if run on low engine loads, and slightly high for the
latest generation of LNG engines (Wärtsilä, 2011). This emissions factor was used in the bottom-up approach
to determine the amount of methane released to the atmosphere from each of the vessels powered by LNG.
The majority of LNG-powered engines operating during the 2007–2012 time frame are assumed to be Ottocycle;
all LNG engines have been modelled as low-pressure, spark injection Otto-cycle engines, which have
low NO x emissions. From these sources, the CH 4 EF baseline factors presented in Table 46 were used.
Table 46 – CH 4 baseline emissions factors
Eng speed/type Fuel type ME EF baseline (kg/tonne fuel) Aux eng EF baseline (kg/tonne fuel) Reference
SSD
MSD
HSD
HFO
HFO
HFO
0.06
0.05
na
na
0.04
0.04
IVL, 2004
IVL, 2004
IVL, 2004
Otto LNG 51.2 51.2 MARINTEK, 2010
GT HFO 0.01 na IVL, 2004
STM HFO 0.01 na IVL, 2004
It should be noted that CH 4 emissions are also unaffected by the sulphur content of the fuel burned and are
the same for HFO and distillates. For further information on specific emissions factors and references, see
Annex 6.