UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 ANN ARBOR, MI 48105

September 12, 2007

 OFFICE OF 

 AIR AND RADIATION

MEMORANDUM

SUBJECT: Estimation of Particulate Matter Emission Factors for Diesel Engines on OceanGoing Vessels

FROM: Mike Samulski

Assessment and Standards Division

TO: Docket EPA-HQ-OAR-2007-0121

This memorandum describes an analysis of exhaust particulate matter emission rates for 

propulsion and auxiliary diesel engines on ocean-going vessels. Basic emission rates were 

determined from in-use test data collected on a number of ships. In addition, this memorandum 

describes adjustments to the emission rates for fuel sulfur content.

I. Background

As part of its ongoing efforts to reduce emissions from mobile sources, EPA is 

considering new exhaust emission standards for Category 3 marine engines. Category 3 engines 

refer to the large engines (>30 liters/cylinder) typically used on ocean-going vessels. Currently, 

these engines are subject to Tier 1 emission standards for oxides of nitrogen (NOx). These Tier 

1 standards, which went into effect in 2004, essentially adopt the NOx standards established 

through the International Maritime Organization (IMO).

Earlier this year, the U.S. government submitted a paper to IMO recommending more 

stringent NOx standards for ocean-going vessels as well as new standards for particulate matter 

(PM) and sulfur oxides (SOx). EPA is also developing an Advanced Notice of Proposed 

Rulemaking which describes potential new national emission standards for Category 3 marine 

engines.

An important part of this rulemaking effort is to calculate the emissions contribution from 

Category 3 marine engines. Since the Tier 1 rulemaking, EPA and others have made significant 

efforts to better quantify exhaust emissions from ocean-going vessels. One area of this work has 

been the development of exhaust emission factors for PM. We are updating our estimates of PM 

emission factors for engines on ocean-going vessels using an expanded set of emission test data.
2

II. Methodology

Through a literature search, we were able to collect PM test data on several marine 

engines operating both on distillate fuel and on residual fuel. These data and the associated

reference sources are included in Appendices A and B to this memo.

All of the PM test data were collected under steady-state operation. However, the engine 

operation (load and speed) varied from test to test. For several of the engines, emission test data 

were collected at multiple load points. In this analysis, we averaged the modal test data to 

determine a single PM emission rate for each engine. We then averaged the emission rates for

the engines to develop PM emission factors.

In some cases, engines were tested at very low power operation. A characteristic of 

reporting emissions on a brake-specific basis is that the value approaches infinity as power 

approaches zero. For this reason, test modes at very low loads were excluded from this analysis. 

A total of four test modes were excluded for this reason. Fuel sulfur concentration has a 

significant effect on PM emissions. Therefore, test data were excluded where the fuel sulfur was 

not reported or was reported as abnormally low for a residual fuel. A total of five engines were 

excluded for this reason.

For two of the test reports, PM emissions were reported in fuel-specific terms rather than 

brake-specific terms. In these cases, we used an assumed brake-specific fuel consumption rate of 

200 g/kW-hr to convert the emission factors to units of g/kW-hr. This is the same fuel 

consumption rate that was used by the IMO in developing a brake-specific SO2 limit equivalent 

to the 1.5% fuel sulfur requirement in Sulfur Emission Control Areas. Where appropriate, the 

appendix presents the emission data both in terms of g/tonne of fuel consumed and g/kW-hr.

The test data is divided between tests on distillate fuel and tests on residual fuel. Higher 

PM emission rates were expected for residual fuel compared to distillate fuel for two reasons. 

First, residual fuel tends to have much higher fuel sulfur than distillate fuel. A portion of the fuel 

sulfur forms sulfate PM in the exhaust. This is discussed in more detail below. The second 

reason is related to general fuel quality. Residual fuel has a higher density, poorer ignition 

quality, and contaminants such as ash and heavy metals that can increase PM emissions. One 

study measured PM on a marine engine operating on low sulfur residual and distillate fuel.1 This 

study showed much higher non-sulfate PM on the residual fuel than the distillate fuel.

Under the current modeling, different PM emission factors are used for medium-speed 

and slow-speed engines. Therefore, we considered that medium-speed and slow-speed engines 

may have significantly different PM emission factors. However, based on the data in Appendix 

A, no significant difference was observed. Consistent with the existing analysis, we use the 

same emission factors for auxiliary and propulsion engines. Therefore, the test data were 

 

1 Kasper, A., Aufdenblatten, S., Forss, A., Mohr, M., Burtscher, H., “Particulate Emissions from a Low-Speed 

Marine Diesel Engine,” Aerosol Science and Technology, 41:24–32, 2007.
3

combined to calculate a single emission factor for each fuel type. Table 1 presents the average 

PM emission rate and fuel sulfur level. Descriptive statistics are presented in Appendix C.

Table 1: 95 Percent Confidence Range

for CI Marine Fuel Sulfur and PM Data

Distillate Residual

Sulfur % 0.24 +/- 0.20 2.46 +/- 0.27

PM g/kW-hr 0.23 +/- 0.08 1.35 +/- 0.24

III. Fuel Sulfur Adjustments

As mentioned above, the sulfur content of the fuel affects PM emissions through the 

formation of sulfate PM in the exhaust. To estimate the relationship between PM emissions from 

marine vessels, we developed an equation that corrects PM emissions for changes in fuel sulfur 

level. We use the nominal PM emission rates and fuel sulfur levels in Table 1 and correct these 

values for different fuel sulfur levels using the following equation:

PMEF = PMNom + [(SAct – SNom) × BSFC × FSC × MWR × 0.0001]

where:

PMEF = PM emission factor adjusted for fuel sulfur

PMNom = PM emission rate at nominal fuel sulfur level

= 0.23 g/kW-hr for distillate fuel, 1.35 g/kW-hr for residual fuel

SAct = Actual fuel sulfur level (weight percent)

SNom = nominal fuel sulfur level (weight percent)

= 0.24 for distillate fuel, 2.46 for residual fuel

BSFC = fuel consumption in g/kW-hr

= 200 g/kW-hr used for this analysis

FSC = percentage of sulfur in fuel that is converted to direct sulfate PM

= 2.247% used for this analysis

MWR = molecular weight ratio of sulfate PM to sulfur

= 224/32 = 7 used for this analysis

Rates of sulfur oxides and sulfate PM emitted from marine engines are directly related to 

the amount of sulfur in the fuel. Although the majority of the sulfur in the fuel forms sulfur 

oxides in the exhaust (primarily SO2), a small but significant fraction forms direct sulfate PM. In 

the NONROAD model, EPA uses a factor of 2.247 percent to represent the fraction of fuel sulfur 

that forms direct sulfate PM in the exhaust of diesel engines. This factor was developed 

empirically based on test data from several nonroad engines operating on distillate fuel with 

varied sulfur levels.2 One study showed similar fractions of sulfur from the fuel found on 

 

2 Environmental Protection Agency, “Exhaust and Crankcase Emission Factors for Nonroad Engine Modeling--

Compression-Ignition,” EPA420-P-04-009, NR-009c, April 2004.
4

particles in the exhaust for marine engines operating on high sulfur residual fuel.3 Therefore, we 

use the established sulfur to sulfate conversion factor for this analysis.

In engine exhaust, sulfate is bound with water to form sulfuric acid (H2SO4). Other than 

in a chemical laboratory, sulfuric acid does not exist without a further bond with water. The 

usually accepted amount of water binding to sulfuric acid in diesel exhaust is seven water 

molecules per molecule of sulfuric acid.

4,5,6

 The actual ratio can vary depending on what else is 

present with the PM and also depending on humidity. H2SO4 has a molecular weight of 98 and 

water has a molecular weight of 18. Using a ratio of seven water molecules per molecule of 

sulfuric acid, we calculate that the molecular weight ratio of direct sulfate PM to sulfur from the 

fuel is (98 + 7 × 18)/32 = 224/32 = 7.

A sample calculation is presented below for adjusting the nominal PM emission rate for 

changes in fuel sulfur. In this example, PM is calculated for an engine operating on residual fuel 

with a fuel sulfur content of 2.7 percent:

PMEF = PMNom + [(SAct – SNom) × BSFC × FSC × MWR × 0.0001]

= 1.35 g/kW-hr + [(2.7% - 2.46%) × 200 g/kW-hr × 2.247% × 7 × 0.0001]

= 1.35 g/kW-hr + 0.08 g/kW-hr

= 1.43 g/kW-hr

IV. PM Emission Rates

As described above, nominal PM emission rates were determined separately for distillate 

and residual fuel based on average measured PM from several engines. The nominal fuel sulfur 

rates associated with the PM data were determined using averages from the same data set. 

Because the sulfate portion of the PM is directly related to the fuel sulfur content, an equation 

was developed to adjust the nominal PM emission rates based on fuel sulfur. These PM 

emission rates are presented in Figure 1, for distillate and residual fuel as a function of fuel sulfur 

content. In addition, this figure presents the actual PM test data used to develop the nominal PM 

emission rates.

 

3 Lyyränen, J., Jokiniemi, J., Kauppinen, E., Joutsensaari, J., “Aerosol Characterisation in Medium-Speed Diesel 

Engines Operating with Heavy Fuel Oils,” Journal of Aerosol Science, Vol. 30, No. 6, pp. 771-784, 1999.

4

Fujii, T., Ikezawa, H., Kotani, Y., “A Study of the Analysis of PM Components with CR-DPF,” Society of 

Automotive Engineers Paper 2002-01-1686, 2002.

5 Environmental Protection Agency, “Size Specific Total Particulate Emission Factors for Mobile Sources,” EPA 

Report 460/3-85-005, August 1985.

6 Environmental Protection Agency, “Emission of Sulfur-Bearing Compounds from Motor Vehicle and Aircraft 

Engines, A Report to Congress,” EPA Report 600/9-78-028, August 1978.
5

Figure 1: Marine Engine PM Data versus Fuel Sulfur Concentration

0

0.5

1

1.5

2

2.5

3

0 0.5 1 1.5 2 2.5 3 3.5

Fue l Sulfur %

P M [g/kW-hr]

Dis tillate

HFO

Fuel S corr dist

Fuel S corr HFO
6

per engine % Fuel PM PM % Fuel PM

Data Source Vessel Year Engine rpm kW Fuel % Load Sulfur g/kW-hr g/tonne Sulfur g/kW-hr

Cooper (2003) F3_Tanker_3 - Caterpillar 3508 n/a Auxiliary 1800 720 Dist 63 0.06 0.14 0.06 0.15

Cooper (2003) F3_Tanker_3 - Caterpillar 3508 n/a Auxiliary 1800 720 Dist 63 0.06 0.16

Cooper (2003) A1_Ferry_5 - Sulzer 6ASL n/a Auxiliary 750 960 Dist 45-63 0.08 0.21 0.08 0.33

Cooper (2003) A1_Ferry_5 - Sulzer 6ASL n/a Auxiliary 750 960 Dist 45-63 0.08 0.45

Cooper (2001) A_High Speed Passenger Ferry unk Auxiliary n/a 455 Dist 46 0.09 0.28 0.09 0.31

Cooper (2001) A_High Speed Passenger Ferry unk Auxiliary n/a 455 Dist 53 0.09 0.29

Cooper (2001) A_High Speed Passenger Ferry unk Auxiliary n/a 455 Dist 26 0.09 0.36

Cooper (2001) A_High Speed Passenger Ferry unk Main_SS n/a 6,875 Dist 90 0.09 0.10 0.09 0.10

Cooper (2003) B2_Ferry_1 - Sulzer 8ASL n/a Auxiliary 750 1,270 Dist 59 0.09 0.31 0.09 0.31

Miller et al. (2007) Dist 0.16 0.27 1.3 0.16 0.27

Wright (1997) E5_Tanker 1990 Main_MS 1,492 Dist 75 0.16 0.30 1.4 0.16 0.40

Wright (1997) E5_Tanker 1990 Main_MS 1,492 Dist 62 0.16 0.40 1.8

Wright (1997) E5_Tanker 1990 Main_MS 1,492 Dist 21 0.16 0.40 1.6

Wright (1997) E5_Tanker 1990 Main_MS 1,492 Dist 42 0.16 0.50 2.1

Wright (1997) E4_Naval Unit* n/a Auxiliary n/a 3,933 Dist 80 0.18 0.20 1.0 0.18 0.28

Wright (1997) E4_Naval Unit* n/a Auxiliary n/a 3,933 Dist 60 0.18 0.20 1.0

Wright (1997) E4_Naval Unit* n/a Auxiliary n/a 3,933 Dist 40 0.18 0.30 1.2

Wright (1997) E4_Naval Unit* n/a Auxiliary n/a 3,933 Dist 25 0.18 0.40 1.6

Cooper (2003) D1_Ro-ro Ferry_2 - Watersila4R32 n/a Auxiliary 720 1,480 Dist 43-48 0.23 0.17 0.23 0.18

Cooper (2003) D1_Ro-ro Ferry_2 - Watersila4R32 n/a Auxiliary 720 1,480 Dist 43-48 0.23 0.19

Environment Canada (1997) Tugboat_2 Detroit Diesel Series 149T 1986 Main_HS 1900 1,200 Dist low cruise 0.24 0.01 1.8 0.24 0.02

Environment Canada (1997) Tugboat_2 Detroit Diesel Series 149T 1986 Main_HS 1900 1,200 Dist normal cruise 0.24 0.02 3.9

Environment Canada (1997) Ferry_12 MAK 12M551AK 1976 Main_MS 425 5,850 Dist normal cruise 0.35 0.03 6.6 0.35 0.03

Cooper (2003) C1_Ferry_6 - Wartsila 824 n/a Auxiliary 720 940 Dist 36-50 1.20 0.30 1.20 0.37

Cooper (2003) C1_Ferry_6 - Wartsila 824 n/a Auxiliary 720 940 Dist 36-50 1.20 0.44

average 0.24 0.26 0.24 0.23

std deviation 0.30 0.14 0.31 0.13

per mode per engine

APPENDIX A: PM Emission Test Data

Table A-1: PM Emission Data for CI Marine Engines Operating on Distillate Fuel
7

per engine % Fuel PM PM % Fuel PM

Data Source Vessel Year Engine rpm kW Fuel % Load Sulfur g/kW-hr g/tonne Sulfur g/kW-hr

Environment Canada (1997) UNK_Sulzer V12 12ZAAV40 n/a Auxiliary 514 11,737 HFO 66 1.29 1.00 5.0* 1.29 1.00

Environment Canada (1997) MKD Container_Kawasaki MAN B&W 10L90MC 1997 Main_SS 82 58,600 HFO Low Cruise 1.46 1.90 9.3 1.46 2.60

Environment Canada (1997) MKD Container_Kawasaki MAN B&W 10L90MC 1997 Main_SS 82 58,600 HFO Normal Cruise 1.46 3.30 16.3

Fleischer (1998) HFO 1.50 0.44 1.50 0.44

Environment Canada (1997) UNK_Sulzer V12 12ZAAV40 n/a Auxiliary 514 11,737 HFO 66 1.74 1.10 5.5 1.74 1.10

Environment Canada (1997) Cargo_Sulzer RND90 1980 Main_SS 122 27,135 HFO Normal Cruise 1.82 1.20 6.2 1.82 1.35

Environment Canada (1997) Cargo_Sulzer RND90 1980 Main_SS 122 27,135 HFO Low Cruise 1.82 1.50 7.5

Environment Canada (1997) Cargo_B&W Missui 7K67GF 1978 Main_SS 145 13,100 HFO Normal Cruise 1.86 1.00 4.9 1.86 1.20

Environment Canada (1997) Cargo_B&W Missui 7K67GF 1978 Main_SS 145 13,100 HFO Low Cruise 1.86 1.40 6.8

Cooper (2003) E1_Container/Ro-ro_1 - Wartsila 8R32 n/a Auxiliary 720 2,675 HFO 41 2.20 0.67 2.20 0.67

Cooper (2003) E2__1 - Wartsila 6R32 n/a Auxiliary 720 2,005 HFO 39 2.20 0.54 2.20 0.54

Wright (1997) E3_Tanker 1990 Main_SS 8,130 HFO 81 2.26 0.80 4.1 2.26 1.18

Wright (1997) E3_Tanker 1990 Main_SS 8,130 HFO 63 2.26 1.10 5.3

Wright (1997) E3_Tanker 1990 Main_SS 8,130 HFO 19 2.26 1.30 5.9

Wright (1997) E3_Tanker 1990 Main_SS 8,130 HFO 40 2.26 1.50 7.4

Maeda (2004) HFO 2.36 1.06 2.36 1.06

MAN B&W (2004) Container_7L32/40 1998 Auxiliary 720 3,125 HFO 33 2.40 1.64 2.40 1.72

MAN B&W (2004) Container_7L32/40 1998 Auxiliary 720 3,125 HFO 53 2.40 1.68

MAN B&W (2004) Container_7L32/40 1998 Auxiliary 720 3,125 HFO 22 2.40 1.74

MAN B&W (2004) Container_7L32/40 1998 Auxiliary 720 3,125 HFO 73 2.40 1.83

MAN B&W (2004) Container_Hitachi 12K90MC mk6 1998 Main_SS 94 54,860 HFO 25 2.40 1.36 2.40 1.67

MAN B&W (2004) Container_Hitachi 12K90MC mk6 1998 Main_SS 94 54,860 HFO 53 2.40 1.55

MAN B&W (2004) Container_Hitachi_12K90MC mk6 1998 Main_SS 94 54,860 HFO 78 2.40 1.80

MAN B&W (2004) Container_Hitachi_12K90MC_mk6 1998 Main_SS 94 54,860 HFO 86 2.40 1.97

Cooper (2002-Entec) 5L28/32 High Speed Passenger Ferry__Man B&W 1990 Auxiliary NA NA HFO NA 2.50 0.94 2.50 0.94

Environment Canada (1997) MKD Container_Kawasaki MAN B&W 10L90MC 1997 Main_SS 82 58,600 HFO "Normal Cruise" 2.78 2.40 11.8 2.78 2.45

Environment Canada (1997) MKD Container_Kawasaki MAN B&W 10L90MC 1997 Main_SS 82 58,600 HFO "Low Cruise" 2.78 2.50 12.4

Wright (1997) E2_Ro-ro Ferry 1982 Main_MS 3,160 HFO 85 2.86 1.40 6.8 2.86 1.45

Wright (1997) E2_Ro-ro Ferry 1982 Main_MS 3,160 HFO 59 2.86 1.40 6.4

Wright (1997) E2_Ro-ro Ferry 1982 Main_MS 3,160 HFO 41 2.86 1.50 6.6

Wright (1997) E2_Ro-ro Ferry 1982 Main_MS 3,160 HFO 31 2.86 1.50 6.5

Environment Canada (1997) Cargo_Sulzer_RND90 1980 Main_SS 122 27,135 HFO Low Cruise 2.93 1.80 9.1 2.93 1.95

Environment Canada (1997) Cargo_Sulzer_RND90 1980 Main_SS 122 27,135 HFO Normal Cruise 2.93 2.10 10.5

Wright (1997) E6_Tanker 1982 Main_SS 12,505 HFO 61 2.97 1.30 6.5 2.97 1.55

Wright (1997) E6_Tanker 1982 Main_SS 12,505 HFO 78 2.97 1.50 7.6

Wright (1997) E6_Tanker 1982 Main_SS 12,505 HFO 40 2.97 1.50 7.3

Wright (1997) E6_Tanker 1982 Main_SS 12,505 HFO 18 2.97 1.90 8.7

Environment Canada (1997) Container_Sulzer_9RTA_84C 1991 Main_SS 97 45,000 HFO Low Cruise 3.00 0.40 1.8 3.00 1.00

Environment Canada (1997) Container_Sulzer_9RTA_84C 1991 Main_SS 97 45,000 HFO Normal Cruise 3.00 1.60 8.0

Environment Canada (1997) Cargo_Mitsui_Man_B&W_5S60MC 1992 Main_SS 102 12,750 HFO Normal Cruise 3.11 1.50 7.4 3.11 1.50

Environment Canada (1997) Cargo_Mitsui_Man_B&W_5S60MC 1992 Main_SS 102 12,750 HFO Low Cruise 3.11 1.50 7.7

Environment Canada (1997) Cargo_Kawasaki_MAN_K7SZ70/125 1978 Main_SS 145 13,300 HFO Normal Cruise 3.19 1.30 6.4 3.19 1.40

Environment Canada (1997) Cargo_Kawasaki_MAN_K7SZ70/125 1978 Main_SS 145 13,300 HFO Low Cruise 3.19 1.50 7.5

Wright (1997) E1_Ro-ro Ferry 1986 Main_MS 4,840 HFO 35 3.21 1.80 7.7 3.21 1.95

Wright (1997) E1_Ro-ro Ferry 1986 Main_MS 4,840 HFO 70 3.21 2.10 10.5

Environment Canada (1997) Cargo_Sulzer_7RTA52U 1996 Main_SS 135 14,840 HFO Low Cruise 3.24 0.40 2.1 3.24 0.80

Environment Canada (1997) Cargo_Sulzer_7RTA52U 1996 Main_SS 135 14,840 HFO Normal Cruise 3.24 1.20 6.2

Miller et al. (2007) HFO 3.30 1.45 3.30 1.45

average 2.54 1.46 2.46 1.35

* corrected EF from 0.65 to 5.04 kg/tonne based on conversion between ARB and Env. Canada std deviation 0.55 0.55 0.63 0.55

per mode per engine

Table A-2: PM Emission Data for CI Marine Engines Operating on Residual Fuel
8

APPENDIX B: PM Emission Data Sources

Cooper, D., “Exhaust Emissions from High Speed Passenger Ferries,” Atmospheric Environment 

35 (2001) 3817-3830, March 8, 2001.

Cooper, D., “Exhaust Emissions from Ships at Berth,” Atmospheric Environment 37 (2003) 

3817-3830, May 12, 2003.

Entec UK Limited, “Quantification of Emissions from Ships Associated with Ship Movements

between Ports in the European Community,” July 2002.

Environment Canada, “Port of Vancouver Marine Emissions Test Project,” ERMD Report #97-

04, 1997.

Fleischer, F., Ulrich, E., Krapp, R., Grundmann, W., “Comments on Particulate Emissions from 

Diesel Engines when Burning Heavy Fuels,” International Council on Combustion Engines 

Congress, 1998.

Maeda, K., Takasaki, K., Masuda, K., Tsuda, M., Yasunari, M., Measurement of PM Emission 

from Marine Diesel Engines,” CIMAC Paper 107, International Council on Combustion Engines 

Congress, 2004.

MAN B&W, “Emission Measurement Results; A.P. Moeller – Sine Maersk,” February, 2004.

Miller, et. al., “Measurements of NOx and Particulate Matter from the Large Propulsion Engines 

on Ocean-going Vessels,” presentation for Clean Ships: Advanced Technology for Clean Air, 

February 7-9, 2007.

Wright, A., “Marine Diesel Engine Particulate Emissions,” Trans IMarE, Vol. 109, Part 4, pp. 

345-366, May 20, 1997.
9

APPENDIX C: Descriptive Statistics

Table C-1: Descriptive Statistics for Data Collected on Distillate and Residual Fuel

Sulfur % PM g/kW-hr Sulfur % PM g/kW-hr

Mean 0.24 0.23 2.46 1.35

Standard Error 0.09 0.04 0.13 0.11

Median 0.16 0.27 2.40 1.35

Mode 0.09 0.31 2.20 1.00

Standard Deviation 0.31 0.13 0.63 0.55

Sample Variance 0.10 0.02 0.39 0.30

Kurtosis 9.76 -1.08 -1.06 0.25

Skewness 3.03 -0.49 -0.35 0.57

Range 1.14 0.39 2.01 2.16

Minimum 0.06 0.02 1.29 0.44

Maximum 1.20 0.40 3.30 2.60

Sum 2.93 2.74 56.6 31.0

Count 12 12 23 23

Confidence Level (95.0%) 0.20 0.08 0.27 0.24

Distillate Residual