Appendix D

Emissions Estimation Methodology for Ocean-Going Vessels
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Emissions Estimation Methodology for 

Ocean-Going Vessels 

May 2011

California Air Resources Board

Planning and Technical Support Division
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Table of Contents

I. Executive Summary ..........................................................................................1

A. Background...................................................................................................2

B. Purpose and Overview..................................................................................3

C. Public Process..............................................................................................4

II. EMISSION ESTIMATION METHODOLOGY ....................................................5

A. Emission Inventory Inputs.............................................................................5

1. Base Year Vessel Population ....................................................................5

2. Operating Mode Specific Activity Hours....................................................6

a. Transit Mode ..........................................................................................6

Distance Traveled: Vessel Traffic Lanes...............................................................6

Vessel Speed......................................................................................................10

b. Maneuvering ........................................................................................10

c. Hotelling ...............................................................................................11

d. Anchorage............................................................................................11

3. Main engine, auxiliary engine, & auxiliary boiler power ..........................12

4. Load Factor.............................................................................................13

a. Main Engines .......................................................................................13

b. Auxiliary Engines..................................................................................13

5. Emission Factors ....................................................................................14

 6. Fuel Consumption....................................................................................16

7. Growth rate..............................................................................................17

8. Control Measures ...................................................................................19

B. Methodology.............................................................................................21

III. RESULTS ......................................................................................................22

A. Emissions in the 100 nautical mile CEIDARS zone ....................................22

IV. REFERENCES.............................................................................................24
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Tables

Figures

Figure 1 Vessel Traffic Lanes ..............................................................................8

Figure 2 Vessel Traffic Lanes – Northern California ............................................9

Figure 3 Vessel Traffic Lanes – Southern California............................................9
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Ocean-Going Vessel Emission Estimation Methodology

I. Executive Summary

Air Resources Board (ARB) staff have revised the methodology to calculate 

emissions from ocean-going vessels in California. This revised inventory will be 

used to support regulatory analysis of statewide regulations to reduce emissions 

from ocean-going vessels. 

The inventory presented here is an update to those developed by staff in May, 

2008 in support of a number of programs, including the Fuel Regulation for 

Ocean-Going Vessels and the 2007 Shore Power Regulation. 

The update includes a number of minor revisions and corrections that include: 

recoding the model to increase calculation speed, updated auxiliary engine 

information, updated ship routing, revised vessel speed reduction compliance 

rates, an adjustment factor to estimate the effects of the recession and 

improvements in the user interface of the model. 

Emissions are calculated by estimating ship emissions on a ship by ship and a 

port call by port call basis, using actual ship engine power estimates, speeds,

and actual ship hoteling times where possible. Base year emissions were 

forecasted using a set of growth factors specific to each port and each ship type. 

Emissions were calculated for the 100 nautical mile zone that is used for ARB’s 

emissions inventory system. They include the benefits of the 2007 Shore Power 

Regulation, the benefits of the San Pedro Bay Ports voluntary vessel speed 

reduction program, the proposed benefits of the current proposal, the fuel-related 

benefits of the North American Environmental Control Area (ECA), but not the 

NOx benefits of IMO Tier 3 engine standards. 

Using the proposed methodology, we estimate 2005 statewide emissions from 

ocean going vessels in the 100 nautical mile regulatory zone were over 14 tons 

per day of diesel PM, over 155 tons per day of oxides of nitrogen (NOx), and 

over 7,400 tons per day of carbon dioxide (CO2). Detailed emission estimates 

are presented in Table ES-1.

The emissions model that produced these estimates is publicly available in 

accordance with AB 1085 and is available at 

http://www.arb.ca.gov/ports/marinevess/ogv/ogv1085.htm. 

Table ES-1 summarizes the emissions by district for the 100 nautical mile SIP 

zone. In 2005, emissions were almost evenly split between Southern and 

Northern California.
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Table ES-1 2005 Ship Emissions by District (tons/day) in the 100 nm Zone

District NOx PM2.5 SOx CO2

mmtCO2

Bay Area AQMD 44.3 4.0 32.3 0.7

Mendocino County AQMD 9.3 0.8 5.7 0.1

Monterey Bay Unified APCD 17.8 1.5 10.9 0.2

North Coast Unified APCD 14.0 1.2 8.6 0.2

Northern Sonoma County APCD 4.2 0.3 2.5 0.0

San Diego County APCD 5.1 0.5 3.8 0.1

San Joaquin Valley Unified APCD 0.1 0.0 0.1 0.0

San Luis Obispo County APCD 11.4 1.0 6.9 0.1

Santa Barbara County APCD 53.1 4.5 32.1 0.6

South Coast AQMD 44.8 4.6 42.8 0.9

Ventura County APCD 16.1 1.4 10.1 0.2

Yolo/Solano AQMD 0.2 0.0 0.2 0.0

Total 220.2 19.6 155.8 3.2

2005 Total Emissions in 100 nm Zone

tons/day

The following section provides background on the ship emissions inventory, the 

purpose and goals in preparing this emissions inventory, and a general overview 

of the methodology used to estimate emissions. 

A. Background

For the purposes of this inventory, an ocean-going vessel (OGV) is a commercial 

vessel greater than or equal to 400 feet in length or 10,000 gross tons; or 

propelled by a marine compression ignition engine with a displacement of greater 

than or equal to 30 liters per cylinder. 

The ARB California Emissions Inventory Data and Reporting System (CEIDARS) 

includes all OGV emissions occurring within 100 nautical miles of the California 

coastline. This zone is also used for State Implementation Plan (SIP) purposes. 

Figure 1 shows this zone, as well as the 24 nm regulatory zone used for the 2008 

low sulfur fuel rule and the amended regulatory zone used in the current 

regulation. 

OGV emissions occur during three distinct operating modes: transit (emissions 

from vessel operations between ports), maneuvering (slow speed vessel 

operations while in-port areas), and hoteling (also known as berthing; in-port 

emissions while moored to a dock). 

Two types of engines are found on OGVs, main engines and auxiliary engines. 

The main engine is a very large diesel engine used primarily to propel the vessel 

at sea. Main engines are used during the transit and maneuvering modes. 

Auxiliary engines on OGVs provide power for uses other than propulsion (except 
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for diesel-electric vessels). Typically, an OGV will have a single, large main 

engine used for propulsion, and several smaller auxiliary “generator-set” engines. 

Auxiliary engines are used during all three operating modes. An exception to this 

configuration is diesel-electric vessels where diesel engine generator sets 

provide power for both propulsion and auxiliary power needs. 

In addition to the engines, most ships have auxiliary boilers to provide steam 

heat for a variety of uses, including fuel heating and hot water. Some crude oil 

tankers also use boilers for moving crude oil product on and off the ship. Boilers 

are used during slow speed vessel operations or in port; at cruise speed, most 

vessels are equipped with an “economizer” at cruise speeds which uses exhaust 

gas to provide heat. Below certain engine loads, however, there is not sufficient 

waste heat available from the exhaust, and boilers are activated. For the 

purposes of this inventory, it is assumed that boilers are operated during 

maneuvering, hoteling, and during anchorage. 

There are a number of types of ocean-going vessels including: auto carriers, bulk 

cargo carriers, container vessels, general cargo carriers and other miscellaneous 

vessels, passenger vessels, reefers (refrigerated vessels), roll-on-roll-off vessels 

(also known as a Ro-Ro: vessels in which vehicles can be driven on or off the 

vessel). A list of the different types of ocean-going vessels and a brief 

description of the goods transported by them presented in Table I-1. 

Table I-1: Categories of Ocean-Going Vessels Included in the

Emissions Inventory

Vessel Type Description

Auto Vessels designed to carry autos and trucks 

Bulk Cargo Bulk carriers are vessels used to transport bulk items such as 

mineral ore, fertilizer, wood chips, or grain.

Container Container vessels are cargo vessels that carry standardized 

truck-sized containers.

General Cargo Vessels designed to carry non-contaminated cargo such as 

steel, palletized goods, and heavy machinery. 

Passenger Passenger cruise vessels are passenger vessels used for 

pleasure voyages. 

Reefers

Vessels used to transport perishable commodities which 

require temperature-controlled transportation, mostly fruits, 

meat, fish, vegetables, dairy products, and other foods.

Ro-Ro

A vessel designed to carry large wheeled cargo such as large 

off-road equipment, trailers or railway carriages. RORO is an 

acronym for “roll on/roll off”.

Tankers Vessels designed to transport liquids in bulk. 

B. Purpose and Overview

The ARB is revising the emission inventory for ocean-going vessels to reflect 

new information and improved methodologies. The new information includes 
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updated activity data, additional sources of ship hoteling and anchorage 

information and ship-specific engine and speed data. Additionally, the growth 

assumptions were updated with additional years of trend data, the effects of the 

recession, and the benefits of recent regulations. This document describes the 

inventory methodology and data inputs that were developed in support of the 

shore power regulation and the proposed main engine regulation.

2005 was chosen as the base year; this year was chosen to be consistent with 

the modeling performed for the current regulation. Because gridded emissions 

are required for modeling, a gridded inventory developed for this document; grid 

cells were mapped to the appropriate zone to summarize the data. Base year 

emissions were forecasted by assessing trends in the growth of vessel net 

registered tonnage for the years 1994-2010. Net registered tonnage (NRT) is a 

measure of the volume of a ship’s cargo capacity; the growth in NRT is directly 

proportional to the growth in installed power of a vessel’s main propulsion 

engine. Controlled future year emissions for 2010 and 2015 were forecasted with 

the benefits of the 2007 shore power regulation, the expanded San Pedro Bay 

ports voluntary 40 nautical mile vessel speed reduction zone, and the benefits of 

the North American Environmental Control Area.

C. Public Process

Allowing stakeholders and the general public to review and comment on a 

product associated with a rulemaking process is a critical element of that 

rulemaking process. The following steps were taken to ensure interested parties 

could provide input.

Multiple public workshops or workgroups were held beginning in 2007 and 

continuing through 2010 that provided the stakeholders and the general public 

the opportunity to review and comment on the inventory. A number of 

teleconferences were conducted with port representatives and port consultants 

as well. We provided local air districts the opportunity to review, comment on the 

methodology and the inventory by conducting meetings and teleconferences. 

Comments obtained through these meetings, teleconferences and workshops 

were used to assess and modify the inventory.
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II. EMISSION ESTIMATION METHODOLOGY

Ship emissions were calculated, to the extent possible, on a vessel and port call 

specific basis. Where possible, vessel specific power data was used, and port 

call specific hoteling times were used to calculate emissions. 

A. Emission Inventory Inputs

Data needed for estimating ship emissions include:

• Base year vessel population

• Operating Mode specific activity hours

• Main engine, auxiliary engine, & auxiliary boiler power 

• Vessel type and mode specific engine load

• Emission factors

• Vessel type and port growth rate

• Control measures

1. Base Year Vessel Population 

There were several sources of activity data that were used for the inventory. 

First, vessel port calls were obtained from a database maintained by the 

California Lands Commission (SLC, 2007). This database includes vessel 

identification, port of arrival, previous port, next port, and date and time of arrival. 

The Lands Commission compiles this database from marine exchanges and port 

authorities statewide. 2005 was chosen as the base year for this inventory for 

consistency with the air quality modeling done for this regulation. Second, vessel 

specific hoteling times and berth locations were obtained from port officials 

responsible for ship docking, or Wharfingers, in Los Angeles, Long Beach, 

Oakland, San Diego, San Francisco and Hueneme. Data was obtained for 2004 

through 2006, but only 2005 data was used for this inventory. These data were 

reconciled to the extent possible with the port call data from the Lands 

Commission (SLC, 2007); for all ports, approximately 94-98% of the port calls 

were reconciled between the two databases. The remaining port calls in the 

Lands Commission database which could not be reconciled were assigned the 

port average hoteling times by vessel type. 

Table II-1 summarizes the number of port calls by ship type and by port. 
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Table II-1 2005 Port Calls in California

Arrival Port Auto Bulk Container Cruise General & 

Miscellaneous Reefer Ro-ro Tanker Total

Avalon/Catalina 134 8 142

Carquinez 49 74 2 5 330 460

El Segundo 223 223

Humboldt 13 13

Long Beach 168 291 1385 148 181 38 82 532 2825

Los Angeles 61 152 1525 274 91 48 2 314 2467

Monterey 9 3 12

Oakland 16 1793 94 17 1920

Pacific Lightering Zone 132 132

Port Hueneme 211 1 3 9 155 11 13 403

Redwood 56 1 1 58

Richmond 55 42 9 4 9 333 452

Sacramento 19 38 1 5 63

San Diego 129 43 2 230 57 80 22 2 565

San Francisco 54 2 77 58 1 100 292

Stockton 94 23 50 167

Total 673 842 4716 877 577 321 145 2043 10194

2. Operating Mode Specific Activity Hours

Three operating modes are used to characterize OGV activity: transit (emissions 

from vessel operations between ports), maneuvering (slow speed vessel 

operations while in-ports), and hoteling (also known as berthing; in-port 

emissions while moored to a dock or at anchor). For regulatory purposes, 

hoteling emissions in this inventory will be termed “hoteling” for ships moored at 

dock, and “anchorage” for ship activity at anchor at or near a port, but not 

moored to a dock. Main engine emissions occur during transit and maneuvering 

modes. Auxiliary engine emissions occur during all modes. Auxiliary boilers are 

operated during maneuvering, hoteling, and anchorage. Separate emission 

factors have been developed for main engines in the transit and maneuvering 

modes. Main engines do not operate during hoteling except for the generator 

sets on diesel-electric vessels. For the purposes of this emissions inventory, all 

diesel-electric vessel emissions are reported as auxiliary engine emissions. 

a. Transit Mode

Operating hours in transit mode is calculated as distance traveled divided by 

vessel speed. Distance traveled is determined by evaluating the route taken 

between ports by the vessel; speed is a function of both the speed of which a 

vessel is capable of and of any speed limitations in effect. 

Distance Traveled: Vessel Traffic Lanes

The lanes used to estimate ship activity at sea were a composite of three 

sources. First, near-port vessel lanes were extracted from the Army Corps of 

Engineers (ACE) National Waterway Network (USACE, 2007). The portions of

this network that reflect the vessel traffic patterns defined in navigational charts

were used; other parts of the ACE network that did not reflect actual ship traffic 

patterns were not used. The vessel traffic separation scheme used in the Santa 

Barbara Channel, in which vessels traveling south travel further west than those 

going north, is an example of the ACE data that was used for the model. For 

vessel traffic further out at sea, the Ship Traffic, Energy and Environment Model 
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(STEEM) developed by Dr. Chengfeng Wang and Dr. James Corbett (Wang, 

2007) was used to define traffic lanes. Third, automated instrumentation system 

(AIS) telemetry data collected during 2007 was used to define the traffic lanes 

that connect these two networks. 

Figure 1 shows the vessel traffic lane network used for the inventory. Figures 2

and 3 show a close-up of the Northern California and Southern California 

portions of the network. 

Vessel routing between ports for the 2008 and updated inventory was defined by 

the assumption that ships will take the shortest route between origin and 

destination on the vessel traffic network. The shortest path was calculated using 

Arc GIS Network Analyst.

Since the 2008 inventory, minor adjustments to the shipping lane network have 

been made to ensure that vessel routes conform to known transit routes, such as 

in the Santa Barbara Channel. Vessel routes were verified with automated 

instrumentation system (AIS) ship data to the extent possible. Additionally, the 

current inventory routes tankers travelling to and from Northern and Southern 

California further away from shore, to conform with existing practice. 

Vessel traffic lane locations with respect to the main coastline of California were 

identified and cataloged to identify how far off the coastline ship activity occurred. 
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Figure 1

Vessel Traffic Lanes
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Figure 2

Vessel Traffic Lanes – Northern California

Figure 3

Vessel Traffic Lanes – Southern California
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Vessel Speed

The maximum vessel speed was obtained from the 2007 version of LloydsFairplay PC Register (Lloyds-Fairplay, 2007). The cruise speed was estimated 

to be 0.937 times the maximum speed, which results in a load factor of 0.823 

during cruise mode. These figures were obtained from a survey performed for 

the Port of Los Angeles emission inventory (Starcrest, 2005 and 2007). It was 

assumed that vessels traveled at cruise speed in areas without specific speed 

restrictions. 

Vessel speed restrictions for traffic lanes in various areas were determined from 

nautical charts. One such example is the precautionary zone in Los Angeles and 

Long Beach harbor, in which speed is restricted to either 11 or 9 knots depending 

on the type of ship. Vessel speeds within the Southern California voluntary 

vessel speed reduction zone were obtained from the Southern California Marine 

Exchange (MXSOCAL, 2007). 

b. Maneuvering

Maneuvering time was calculated as the distance traveled during maneuvering 

divided by speed, plus 15 minutes for docking or undocking. For coastal ports, 

maneuvering was assumed to begin at the point where the pilot boarded the 

vessel and ended at the berth. For ports within the San Francisco Bay Area, 

maneuvering distances were estimated based on the Environ (Environ, 2007) 

Port of Oakland inventory, AIS data, or discussions with port officials. It was 

assumed that fast ships (container ships, cruise ships, reefers) maneuvered 

inbound at 7 knots and slow ships (all other types) at 5 knots; all outbound ships 

were assumed to maneuver at 8 knots. 
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c. Hoteling

Hoteling time can be defined as beginning when a ship ties up at a berth, and 

ends when it leaves that berth. Likewise, anchorage is defined as beginning 

when a ship drops anchor and ends when the anchor is raised and the ship 

begins moving again. During hoteling and anchorage, vessels use at least one 

of their auxiliary engines to generate electric power for the ship. Auxiliary boilers 

are also used. Some ships will shift berths during a given port call for various 

reasons; for the purpose of this inventory, the hoteling time used for calculations 

combines the total hoteling time for all berths visited during a given port call. 

Hoteling times used for the inventory obtained were specific to individual port 

calls and were obtained from port Wharfingers. Port calls that could not be 

identified in Wharfinger data were assigned average hotelling times by port and 

by vessel type from the Wharfinger data that was available. Table II-2 

summarizes the average hoteling times by vessel type for 2006. 

Table II-2 2005 Hoteling Time Averages (hours per visit)

Arrival Port Auto Bulk Container Cruise General & 

Miscellaneous Reefer Ro-ro Tanker

Avalon/Catalina 13 34

Carquinez 18 65 13 43 34

El Segundo 34

Humboldt 61

Long Beach 16 64 54 13 39 33 30 34

Los Angeles 21 73 50 12 53 42 36 36

Monterey 13 45

Oakland 15 21 15 43

Pacific Lightering Zone 34

Port Hueneme 16 12 7 61 71 11 21

Redwood 62 54 34

Richmond 19 64 32 61 32 34

Sacramento 57 49 32 34

San Diego 18 82 44 11 58 57 29 34

San Francisco 66 32 11 62 30 34

Stockton 61 42 34

Although the number of port calls by container ships to Oakland is roughly 

equivalent to the number of port calls at either Los Angeles or Long Beach, the 

hotelling time of these ships in Oakland is much shorter. Often, container ships 

will call on both Oakland and either Los Angeles or Long Beach; presumably, 

fewer containers are loaded or unloaded in Oakland than in southern California. 

d. Anchorage

Ship and visit-specific anchorage data (ship identification, hours anchored, and 

anchorage location) was obtained from MXSOCAL in Southern California

(MXSOCAL, 2007) and the US Coast Guard Vessel Traffic Service (USCG, 
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2007) in the San Francisco Bay Area. Table II-3 summarizes average anchorage 

times for ships that anchored. It was assumed that ship operations during 

anchorage were the same as during hoteling; that is, auxiliary engines and 

boilers operated at hoteling loads, and the main engine was not in operation. 

Table II-3 2006 Average Anchorage Times (hours per visit)

Arrival Port Auto Bulk Container Cruise General & 

Miscellaneous Reefer Ro-ro Tanker

Carquinez 5 27 20 19

Long Beach 14 41 12 35 11 17 73

Los Angeles 9 30 12 2 31 16 5 32

Oakland 35 9 21

Redwood 25 7

Richmond 15 51 5 20

Sacramento 23 15 46

San Francisco 11 193 2 12 23

Stockton 52 38 29

3. Main engine, auxiliary engine, & auxiliary boiler power 

The main source of engine power was the PC-Register commercial ship 

database obtained from Lloyds-Fairplay (Lloyds-Fairplay 2007). Information from 

this database that was used in the inventory included main engine power, 

auxiliary engine generation capacity, main engine speed, vessel type, date of 

build, cruise speed, and flag of vessel. This data was supplemented with data 

collected by Starcrest and the Ports of Los Angeles and Long Beach as part of 

their Vessel Boarding Program (Starcrest 2005, 2007a and 2007b). Current and 

former vessel names were also used to identify vessels in activity records that 

were lacking IMO (International Maritime Organization) ID numbers. Vessel 

averages by vessel type were used if data were missing; if main engine speed 

data were missing it was assumed that they were slow speed engines. Ship 

auxiliary boiler power ratings were assigned averages developed by Starcrest

(Starcrest 2007a and 2007b) from the vessel boarding program. 

The 2008 inventory used average auxiliary engine power from the 2005 ARB 

Ocean Going Vessel Survey. In the current inventory, approximately 60% of ship 

auxiliary engine power ratings are based on auxiliary power generation capacity 

from the Lloyds-Fairplay PC Register database (Lloyds-Fairplay, 2007). Another 

15% of ships have auxiliary engine power ratings from the Port of Los 

Angeles/Port of Long Beach vessel boarding program, and the remaining ships 

utilize the average power ratings from the 2005 survey. 
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Table II-4 Average Vessel Characteristics

Table II-4 summarizes the average vessel speed and main engine, auxiliary 

engine, and boiler power by vessel type. For boilers, fuel use rates were 

converted to equivalent kilowatts.

4. Load Factor

a. Main Engines

At cruise speed, the main engine load is 82.5%; as has been previously 

described, this estimate was based on a vessel boarding program and survey 

done by Starcrest as part of the POLA and POLB inventories (Starcrest 2005, 

2007a and 2007b). At higher loads, fuel consumption and engine maintenance 

costs go up dramatically, so vessel operators tend to operate at this level. At 

slower speeds, main engine load was calculated using the propeller law, which 

states that propulsion load varies by the cube of the vessel speed. Main engine 

load was calculated by dividing the actual vessel speed by the maximum vessel 

speed and cubing the result. 

At main engine loads of less than 20%, engine emissions are multiplied by an 

adjustment factor which accounts for higher emission rates at low loads. The 

adjustment factor is calculated using an exponential equation developed by 

Sierra Research for the U.S. Environmental Protection Agency (USEPA, 2000).

b. Auxiliary Engines

The auxiliary engine load factor represents the actual engine power used divided 

by the total installed auxiliary engine power. Table II-5 shows the load factors, in 

percent, by vessel type.

The primary source of data on auxiliary engine load was the 2005 and 2007 ARB 

OGV surveys and the vessel boarding program done by Starcrest for the Port of 

Los Angeles and the Port of Long Beach emission inventories (Starcrest 2005, 

2007a and 2007b). 

Vessel Type Speed Main Power Auxiliary Power Boiler Power

(knots)

Auto 19 11593 2999 278

Bulk 15 7803 2459 82

Container 23 37265 8156 380

Cruise 21 0 44042 750

General 15 7580 1799 99

Reefer 20 11091 3605 348

Ro-ro 18 12181 2605 82

Tanker 15 13034 2339 1593

(kilowatts)
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Table II-5: OGV Auxiliary Engine Load Characteristics (percent load)

Vessel Type Load Factor (%)

Hoteling Maneuvering Transit

Auto Carrier/Ro-Ro 26% 45% 15%

Bulk Carrier/General 

Cargo

10% 45% 17%

Container Ship 18% 50% 13%

Passenger 16% 64% 80%

Reefer 32% 45% 15%

Tanker 26% 33% 24%

5. Emission Factors

Emission factors for OGVs vary by pollutant, operating mode (transit, 

maneuvering, or hoteling), engine type (main engine/slow speed, main 

engine/medium speed, or auxiliary/medium speed), and fuel type (heavy fuel oilHFO or marine distillate). Emission factors for diesel particulate matter (PM), 

oxides of nitrogen (NOx), sulfur dioxide (SO2), hydrocarbons (HC), carbon 

monoxide (CO), and carbon dioxide (CO2) were compiled. Emission factors for 

main and auxiliary engines of ocean-going vessels are expressed as grams of 

pollutant emitted per kilowatt-hour of energy (g/kW-h). Although emission 

factors for auxiliary boilers are usually expressed in terms of grams of pollutant 

emitted by metric tonne of fuel burned, they were converted to g/kW-h using a

methodology defined by Starcrest (Starcrest, 2007a). 

Tables II-6, II-7, and II-8 below present the emission factors used in the 

development of the ocean-going vessel emissions inventory. Table II-6 presents 

the emission factors for main engines during transit or high load operation while 

at sea. If data on main engine speed for a given vessel was not known, it was 

assumed the engine was slow speed. 
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Table II-6: Main Engine Emission Factors – Transit Mode (g/kW-hr)

Table II-7 presents the emission factors for main engines during maneuvering or 

low load operation near ports. 

Table II-7: Main Engine Emission Factors –Maneuvering (g/kW-hr)

Table II-8 presents the emission factors for auxiliary engines, including dieselelectric vessels. As shown in the table, the emission factors for auxiliary engine 

vary depending on the type of fuel used.

Table II-9 presents the emission factors for auxiliary boilers, which use heavy fuel 

oil. These emission factors were converted to grams per kilowatt hour from 

grams per tonne of fuel using methodology developed by Starcrest

(Starcrest, 2007a). 

Engine Speed Fuel CH4 CO CO2 NOx PM10 PM2.5 ROG SOx

Slow Marine Distillate (0.1% S) 0.07 1.10 588 17.0 0.25 0.23 0.78 0.36

Slow Marine Distillate (0.5% S) 0.07 1.10 588 17.0 0.38 0.35 0.78 1.90

Slow Heavy Fuel Oil 0.08 1.38 620 18.1 1.50 1.46 0.69 10.50

Medium Marine Distillate (0.1% S) 0.08 1.10 645 13.2 0.25 0.23 0.65 0.40

Medium Marine Distillate (0.5% S) 0.08 1.10 645 13.2 0.38 0.35 0.65 2.08

Medium Heavy Fuel Oil 0.09 1.10 677 14.0 1.50 1.46 0.57 11.50

High Marine Distillate (0.1% S) 0.08 1.10 645 12.1 0.25 0.23 0.65 0.40

High Marine Distillate (0.5% S) 0.08 1.10 645 12.1 0.38 0.35 0.65 2.08

High Heavy Fuel Oil 0.09 1.10 645 12.7 1.50 1.46 0.23 11.50

Engine Speed Fuel CH4 CO CO2 NOx PM10 PM2.5 ROG SOx

Slow Marine Distillate (0.1% S) 0.07 1.10 588 17.0 0.25 0.23 0.78 0.36

Slow Marine Distillate (0.5% S) 0.07 1.10 588 17.0 0.38 0.35 0.78 1.90

Slow Heavy Fuel Oil 0.08 1.38 620 18.1 1.50 1.46 0.69 10.50

Medium Marine Distillate (0.1% S) 0.08 1.10 645 13.2 0.25 0.23 0.65 0.40

Medium Marine Distillate (0.5% S) 0.08 1.10 645 13.2 0.38 0.35 0.65 2.08

Medium Heavy Fuel Oil 0.09 1.10 677 14.0 1.50 1.46 0.57 11.50

High Marine Distillate (0.1% S) 0.08 1.10 645 12.1 0.25 0.23 0.65 0.40

High Marine Distillate (0.5% S) 0.08 1.10 645 12.1 0.38 0.35 0.65 2.08

High Heavy Fuel Oil 0.09 1.10 645 12.7 1.50 1.46 0.23 11.50
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Table II-8: Auxiliary Engine Emission Factors – Transit, Maneuvering, and

Hotelling (g/kW-hr)

Table II-9: Auxiliary Boiler Emission Factors (g/kW-hr)

The emission factors for main engines, auxiliary engines and auxiliary boilers 

used by ARB staff are generally consistent with the emission factors used by 

Starcrest in developing the 2005 Port of Los Angeles emissions inventory and 

the updates done in 2007. The Starcrest emission factors were based on work 

done by Entec (Entec, 2002). The Entec emission factors were developed using 

Lloyd’s of London and IVL Swedish Environmental Institute data that related 

emissions to engine speed and the type of fuel used. 

ARB staff developed an alternate particulate matter emission factor for engines 

burning heavy fuel oil based upon an extensive review of emission tests 

described in scientific literature. This emission factor, set at 1.5 grams/kilowatthour, is based upon the use of HFO fuel with 2.5% sulfur content. The basis of 

this emission factor is fully described in a white paper written by ARB staff in 

2007, which is available on the ARB web site (CARB, 2008). 

For CO emissions from the main engines during transit, staff elected to use a 

U.S. EPA emission factor published in the Environ report (Environ, 2007). This 

emission factor is consistent with the CO emission factors used by Starcrest for 

the Port of Los Angeles emission inventory (Starcrest, 2005). 

6. Fuel Consumption

It was assumed that all main engines and auxiliary boilers burned heavy fuel oil. 

The main engine assumption was based on the 2005 ARB OGV survey; the 

auxiliary boiler assumption was based on communications with boiler 

manufacturers. For auxiliary engines, it was assumed that 92% of cruise ships 

burned heavy fuel oil and 8% distillate. For all other ships, it was assumed that 

71% use heavy fuel oil and 29% use distillate in their auxiliary engines. These 

data were obtained from the 2005 ARB OGV survey. 

Engine Speed Fuel CH4 CO CO2 NOx PM10 PM2.5 ROG SOx

Medium Marine Distillate (0.1% S) 0.09 1.10 690 13.9 0.25 0.23 0.52 0.40

Medium Marine Distillate (0.5% S) 0.09 1.10 690 13.9 0.38 0.35 0.52 2.10

Medium Heavy Fuel Oil 0.09 1.10 722 14.7 1.50 1.46 0.46 11.10

Fuel CH4 CO CO2 NOx PM10 PM2.5 ROG SOx

Heavy Fuel Oil 0.03 0.20 970 2.1 0.80 0.78 0.11 16.50
D - 17

Table II-10 Fuel Consumption Rates (g/kW-hr)

Engine Engine Speed Mode Fuel Fuel Use Rate

All All Marine Distillate 217

All All Residual 227

Boiler N. A. All Residual 305

High Transit Residual 213

Medium Transit Marine Distillate 203

Slow Transit Marine Distillate 185

Medium Transit Residual 213

Slow Transit Residual 195

High Maneuvering Residual 213

Medium Maneuvering Marine Distillate 203

Slow Maneuvering Marine Distillate 185

Medium Maneuvering Residual 213

Slow Maneuvering Residual 195

Auxiliary

Main

Fuel consumption rates were obtained from Entec (Entec, 2002) and vary by 

engine, engine speed, and mode of operation. Fuel use rates are expressed in 

the same units as emission factors; in grams per kilowatt hour. Table II-10 

summarizes the fuel consumption rates used. 

7. Growth rate

Growth rates were estimated by vessel type and by port. These growth rates 

were based upon an analysis of US Army Corps of Engineers vessel call data 

(USACE, 2006) between the years 1994-2005. The total net registered tonnage 

(NRT), a measure of the volume of cargo a ship can carry, was determined by 

vessel type and by port. Previous ARB OGV growth rates were based on total 

installed main engine power determined from vessel call data between the years 

1997 and 2003. Growth in NRT is directly proportional to growth in installed 

power. NRT was used to estimate growth because it was not possible to 

determine main engine power for many of the records; in contrast, NRT data was 

available for almost 99% of the records analyzed. The growth rates selected are 

the midpoint between the best fit compounded annual growth rate in NRT 

between 1994 through 2005 and the best fit linear (arithmetic) growth rate in NRT 

for the same time period. The sum of growth of all California ports was set to 

equal to the statewide growth with the assumption that the ports will grow 

proportionally to their historical NRT growth between the years 1994-2005. 

Growth rates developed using this methodology were checked and verified 

against other studies, including the Port of Los Angeles and Port of Long Beach 

emission inventory updates done in 2007 (Starcrest, 2007a and 2007b), the Port 

of San Diego emission inventory (Starcrest, 2007c), and the Port of Oakland 

emission inventory (Environ, 2007). 
D - 18

Table II-11 Growth Rates by Port and Vessel Type

Table II-11 summarizes the growth rates by port and by vessel type. Growth 

rates are stated in this table as annual compound growth rates.

The economic recession that officially started in December of 2007 and ended in 

June 2009 was the most severe since the Great Depression, and had a severe 

impact on industries throughout California. In addition to the methodological 

improvements staff incorporated the impacts of the recession on OGV emissions. 

To forecast activity following the recession, staff developed three recovery 

scenarios to encompass the possible rate of growth (“fast”, “slow”, and 

“average”). The fast recovery scenario assumed that total activity would return to 

projected historically average levels in 2017 and then grow at the historical 

average rate. A return to trend by 2017 was based on the Congressional Budget 

Office forecast which indicated that real gross domestic product at a nationwide 

level will converge with potential gross domestic product trends no later than 

2015. This forecast was modified with the assumption that California’s recovery 

will lag the nation by several years, yielding the 2017 recovery date assumed for 

the fast recovery scenario. For the slow recovery scenario, staff assumed that 

activity would be permanently depressed relative to historical levels, but continue 

to grow at the growth rate in the 2009 San Pedro Bay Ports Forecast Update 

beginning in 2011(Tioga, 2009). The average scenario is the average of the fast 

and slow scenarios. 

The impact of the recession on net registered tonnage in 2009 was estimated 

from port call and TEU data spanning January 1, 2009 through July 31, 2009 and 

scaling the results to the entire year. These totals were then checked at the 

beginning of 2011 with the final totals from 2009 and 2010. 

Given the uncertainty in forecasting emissions after such a deep recession, staff 

relied on the average recovery scenario. This scenario, for the years of interest 

Port Auto Bulk Container Cruise General Reefer Roro Tanker

Avalon/Catalina 3.9% 1.0%

Carquinez -4.0% -0.7% -4.0% 0.3% -4.0% -0.9%

El Segundo 5.4%

Hueneme 5.9% -27.0% 8.3% 7.3% 8.3% 1.4% 5.9% 5.0%

Humboldt -13.4% 0.0% -0.7%

Los Angeles-Long Beach 1.4% -2.3% 6.8% 3.9% 1.0% -8.0% 1.4% 1.0%

Monterey 0.0% 0.0%

Oakland -3.8% 4.4% 4.4% 4.4%

Pacific Lightering Zone 5.4%

Redwood 5.2% 5.2%

Richmond -1.4% -3.8% -5.4% -5.4% -1.4% 0.0%

Sacramento -5.4% -1.9% -1.9% -2.1%

San Diego 4.0% 1.5% 6.8% 8.7% 2.7% 7.0% 4.0% 5.0%

San Francisco -0.9% 3.4% -0.9% 5.3% -0.9% 0.0% 0.0% 0.0%

Stockton 3.4% 1.9% 1.9% 5.3%
D - 19

for these regulatory amendments, is also supported by the most recent San 

Pedro Bay forecasts.

8. Control Measures

There are several control measures built into the ship inventory:

• 1997 MARPOL Annex VI Emission Standards (IMO Tier 1)

• 2004 Los Angeles/Long Beach 20 nm Voluntary Speed Reduction Zone

• 2005 US EPA Category 3 Engine Standards (MARPOL Annex VI)

• 2005 Auxiliary Engine Regulation (not currently enforced)

• 2007 Shore Power Regulation

• 2009 Los Angeles/Long Beach 40 nm Voluntary Speed Reduction Zone

• 2012 North American Environmental Control Area

The 1997 MARPOL standards were established by the International Maritime 

Organization (IMO) at the International Convention on the Prevention of Pollution 

from Ships”, known as MARPOL. It provides for limits on NOx emissions from 

ships, depending on engine speed. For slow speed engines, NOx is limited for 

ships built after 1999 to 17 gms/kw-hr, which is a six percent reduction. 

The Los Angeles/Long Beach Voluntary Speed Reduction (VSR) Zone was 

established by the Southern California Marine Exchange (MXSOCAL) in 2004. 

This is a voluntary control measure which requests that ships not exceed a 

speed of 12 knots within 20 nautical miles of Point Fermin. In 2009, this zone 

was expanded to 40 nautical miles from Point Fermin. This inventory calculates 

the benefits of this control by the inclusion of ship and port call specific speed 

data obtained from the Southern California Marine Exchange. The approximate 

compliance rate for the 2006 base year was 65%. For forecasted years, it was 

assumed that full compliance would be attained by 2014.

%Compliance

Year 0-20nm 20-40nm

2005 48% 0

2006 65% 0%

2007 72% 0%

2008 81% 0%

2009 91% 48%

2010 100% 63%

2011 100% 70%

2012 100% 80%

2013 100% 90%

2014 100% 100%
D - 20

The 2005 US EPA category 3 standards are an implementation of the 

International Maritime Organization (IMO) Tier 1 standards agreed to by 136 

countries; the agreement is commonly known as MARPOL Annex VI (MARPOL 

stands for Marine Pollution). Ships built on or after 2000 are required to emit 

approximately 6-12% less NOx, depending on engine speed. In 2008, the IMO 

expanded the tier 1 standard to apply retroactively to ships built before 2000, and 

also added a Tier 2 standard which applies to ships built after 2010, and a Tier 3 

standard which applies to post-2015 ships in environmental control areas 

(ECAs). IMO Tier 2 and Tier 3 standards are not included in this inventory in this 

document for consistency with the inventory used for modeling.

In 2005, the ARB approved a regulation which requires ship auxiliary engines to 

use 0.5% sulfur fuel on or after 2007, and 0.1% sulfur after 2010. The final rule 

was approved by the Office of Administrative Law in October, 2007. Enforcement 

of the regulation was suspended in 2008 due to a legal challenge. The regulation 

was enforced for 7 months in 2007, and for 116 days in 2008.

In 2007, the ARB approved a regulation which requires container ships, cruise 

ships, and reefer ships visiting five California ports to use shore power. Fleets 

with less than 25 visits per year are exempt; ships are permitted 3 hours of 

auxiliary engine use per visit after the regulation goes into effect. By 2014, fleets 

are required to use shore power for 50% of visits; by 2020, they are required to 

use shore power for 80% of visits. 

In 2010, the International Maritime Organization officially accepted the North 

American Environmental Control Area (ECA), beginning in August, 2012. At that 

date, the sulfur content of fuel will be limited to 1% sulfur within 200 nautical 

miles of the coastline; in 2015, this limit will drop to 0.1% sulfur. Also, Tier III 

NOx emission standards, requiring advanced emission controls such as SCR 

systems, will have to be met in the ECA for ships built on or after 2016. 

For standards based on age of the ship, it was assumed for forecasting purposes

that the age profile by ship type will be the same as the average age profile for 

ships observed for the years 2004-2006. This assumption will be revisited as 

new data is received; the recession has delayed new ship orders and it is likely 

that compliance rates for the IMO NOx standards will be less since ship fleets will 

tend to be older.
D - 21

B. Methodology

The basic equation used for estimating emissions from ocean-going vessels is:

E y, t, om, e = Σ Pop t ∗ EF e, om, f ∗ Hrs om, t ∗ VP om, t ∗ %Load om, t

where

E = pollutant specific emissions (tons per year of NOx, HC, CO2, SO2, and 

diesel PM)

Pop = population of ocean-going vessels by vessel type

EF = emission factor by engine type, operating mode, and fuel (units of glkwhr) 

Hrs = average annual use in hours by operating mode and vessel type

VP = average power by operating mode and vessel type

% Load = average engine load by operating mode and vessel type

y = inventory year

om = operating mode (transit, maneuvering, hoteling)

t = vessel type (auto, container, bulk cargo, etc.)

f = fuel (HFO or MGO/MDO)

e = engine type

Each of these elements, and how they were incorporated into the ocean-going 

vessel emission estimates, are discussed below. 
D - 22

III. Results

A. Emissions in the 100 nautical mile CEIDARS zone

Ship emissions presented here include all emissions within the 100 nautical mile 

zone used for the CEIDARS database system and for State Implementation Plan 

(SIP) purposes. They include the benefits of the 2007 Shore Power Regulation, 

the benefits of the San Pedro Bay Ports voluntary vessel speed reduction 

program, the proposed benefits of the current proposal, the fuel-related benefits 

of the North American Environmental Control Area (ECA), but not the NOx 

benefits of IMO Tier 3 engine standards. 

Emissions are presented for the years 2005, 2010, and 2015. Table III-1 

summarizes ship emissions by district. It is important to note here that the 

assignment of emissions to districts is for comparison purposes only. The ARB 

California Emissions Inventory Data and Reporting System (CEIDARS) emission 

inventory database requires emissions occurring in the Outer Continental Shelf 

(OCS) Air Basin to be assigned to specific counties and specific air pollution 

control districts. It is important to note that meteorology defines how OCS 

emissions impact land; assignment of specific OCS areas to counties and 

districts is done for database reasons and for comparison, and not to indicate 

that a specific county or district is either responsible or impacted by a specific 

OCS area. There exists no official federal or state governmental assignment of 

OCS waters to specific counties, districts or air basins. 
D - 23

Table III-1

Total Emissions by District in 100 nm Regulatory Zone

District NOx PM2.5 SOx CO2

mmtCO2

Bay Area AQMD 44.3 4.0 32.3 0.7

Mendocino County AQMD 9.3 0.8 5.7 0.1

Monterey Bay Unified APCD 17.8 1.5 10.9 0.2

North Coast Unified APCD 14.0 1.2 8.6 0.2

Northern Sonoma County APCD 4.2 0.3 2.5 0.0

San Diego County APCD 5.1 0.5 3.8 0.1

San Joaquin Valley Unified APCD 0.1 0.0 0.1 0.0

San Luis Obispo County APCD 11.4 1.0 6.9 0.1

Santa Barbara County APCD 53.1 4.5 32.1 0.6

South Coast AQMD 44.8 4.6 42.8 0.9

Ventura County APCD 16.1 1.4 10.1 0.2

Yolo/Solano AQMD 0.2 0.0 0.2 0.0

Total 220.2 19.6 155.8 3.2

District NOx PM2.5 SOx CO2

mmtCO2

Bay Area AQMD 39.2 1.6 10.3 0.6

Mendocino County AQMD 8.2 0.3 1.8 0.1

Monterey Bay Unified APCD 16.7 1.2 8.1 0.2

North Coast Unified APCD 12.5 0.6 3.8 0.2

Northern Sonoma County APCD 3.8 0.1 0.5 0.0

San Diego County APCD 4.7 0.1 0.7 0.1

San Joaquin Valley Unified APCD 0.1 0.0 0.0 0.0

San Luis Obispo County APCD 10.8 0.8 5.9 0.1

Santa Barbara County APCD 51.5 2.2 14.4 0.6

South Coast AQMD 37.8 1.1 7.3 0.8

Ventura County APCD 15.1 0.3 1.8 0.2

Yolo/Solano AQMD 0.1 0.0 0.1 0.0

Total 200.5 8.3 54.8 2.9

District NOx PM2.5 SOx CO2

mmtCO2

Bay Area AQMD 50.0 0.8 1.6 0.7

Mendocino County AQMD 10.9 0.2 0.2 0.1

Monterey Bay Unified APCD 21.9 0.3 0.5 0.3

North Coast Unified APCD 16.2 0.2 0.4 0.2

Northern Sonoma County APCD 4.9 0.1 0.1 0.1

San Diego County APCD 6.1 0.1 0.2 0.1

San Joaquin Valley Unified APCD 0.1 0.0 0.0 0.0

San Luis Obispo County APCD 14.1 0.2 0.3 0.2

Santa Barbara County APCD 72.8 1.1 1.6 0.9

South Coast AQMD 43.8 0.9 2.7 0.9

Ventura County APCD 21.2 0.3 0.5 0.3

Yolo/Solano AQMD 0.1 0.0 0.0 0.0

Total 262.3 4.2 8.1 3.7

tons/day

2005 Total Emissions in 100 nm Zone

tons/day

2010 Total Emissions in 100 nm Zone

tons/day

2015 Total Emissions in 100 nm Zone
D - 24

IV. REFERENCES

1. CARB, 2005a. California Air Resources Board, Emissions Estimation 

Methodology for Ocean-Going Vessels, October 2005. Available at 

http://www.arb.ca.gov/regact/marine2005/appd.pdf.

2. CARB, 2005b. California Air Resources Board, 2005 Oceangoing Vessel 

Survey of Results, 2005. Available at 

http://www.arb.ca.gov/regact/marine2005/appc.pdf.

3. CARB, 2006. California Air Resources Board, Final Statement of 

Reasons for Rulemaking Including Summary of Comments and Agency 

Responses - Public Hearing To Consider The Adoption Of Regulations To 

Reduce Emissions From Auxiliary Diesel Engines And Diesel-Electric 

Engines Operated On Ocean-Going Vessels Within California Waters And 

24 Nautical Miles Of The California Baseline, October, 2006, available at

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Estimation Methodology for Ship Auxiliary Engines in California, October, 

2007. Available at 

http://www.arb.ca.gov/regact/2007/shorepwr07/appb.pdf

5. CARB, 2007b. California Air Resources Board, Ocean-Going Vessel PM 

Emission Factors for Heavy Fuel Oil White Paper, March, 2007. Available 

at

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.pdf 

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Reduce Emissions From Diesel Auxiliary Engines On Ocean-Going 

Vessels While At-Berth At A California Port, October, 2007, available at

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.pdf

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D - 25

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http://www.ndc.iwr.usace.army.mil//data/dataclen.htm

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