1

 METHODOLOGY FOR ESTIMATING NONROAD EMISSIONS

I. INTRODUCTION

This following methodology provides a description of the procedures used to generate 2002 and 

2009 county-level pollutant emission estimates for nonroad mobile engines included in the 

United States Environmental Protection Agency’s (EPA’s) NONROAD2005 Model, as well as 

locomotive engines and aircraft operations. For the NONROAD2005 Model engines, emission 

estimates were calculated for volatile organic compounds (VOCs), oxides of nitrogen (NOx), and 

carbon monoxide (CO), particulate matter (PM10), fine particulate matter (PM2.5), and sulfur 

dioxide (SO2). Revised geographic allocation files for NONROAD2005 Model option files and 

revised housing unit data used for the model runs are also included. The National Mobile 

Inventory Model (NMIM) was used to develop emissions of ammonia (NH3) for 2002 and 2009 

since the NONROAD2005 Model does not have that capability.

II. 2002 NONROAD MODEL SOURCE CATEGORY 

EMISSIONS

The Department used EPA’s Final NONROAD2005 Model to generate 2002 and 2009 annual emissions 

for the Philadelphia area, which includes Bucks, Chester, Delaware, Montgomery, and Philadelphia 

Counties in Pennsylvania. The Department prepared NONROAD2005 model option files that account 

for temperatures and gasoline Reid vapor pressure (RVP) values representative of the Philadelphia 5-

county area for summer weekdays. The Philadelphia 5-county area was treated as its own climactic 

zone. The average RVP value used for the 5-county area was 6.7. Minimum, maximum, and average 

temperatures for July for each region were obtained from the Pennsylvania State Climatologist website, 

Pennsylvania State Climatologist, Penn State University, 2002 Temperature Data by Weather Station

which is available at http://pasc.met.psu.edu/PA_Climatologist/cityform.html. The RVP and 

temperature inputs were applied to all equipment categories to obtain both summer day and annual 

emissions. 

Table 1 lists the counties included in the Philadelphia area and the weather station where the temperature 

data were obtained for each of the regions. Table 2a and 2b presents the RVP and temperature data used 

in the model runs for each region of Pennsylvania. The Department used EPA’s Final NONROAD2005 

Model and NMIM to generate 2002 and 2009 annual emissions for the 5-county Philadelphia area. The 

Department prepared NONROAD2005 Model option files that account for average temperatures and 

gasoline Reid vapor pressure (RVP) values representative of the entire year. 
2

Table 1. Regions of Pennsylvania and Associated Maintenance Areas

Region Weather Station Counties in Region FIPSST FIPSCNTY

Southeast Philadelphia Bucks County 42 017

Chester County 42 029

Delaware County 42 045

Montgomery County 42 091

Philadelphia County 42 101

Table 2a. Summer Day NONROAD Model Temperature 

and RVP Inputs

Temperature*

Region Season Maximum Minimum Average RVP**

Southeast Summer 87 69 78 6.7

* Temperature in degrees Fahrenheit

** RVP in pounds per square inch (psi)

Table 2b. Annual Average Day NONROAD Model 

Temperature and RVP Inputs

Temperature*

Region Maximum Minimum Average RVP**

Southeast 66 49 57 6.7

* Temperature in degrees Fahrenheit

EPA-recommended diesel fuel sulfur levels for marine and land equipment for all years were 

used as inputs to the model, as outlined in Diesel Fuel Sulfur Inputs for the Draft 

NONROAD2004 Model used in the 2004 Nonroad Diesel Engine Fuel Rule, April 27, 2004. 

In past versions of the NONROAD Model, state recreational marine vessels populations were 

underestimated when compared to boat registrations tracked by the Pennsylvania Fish and Boat 

Commission (PFBC). EPA’s population of recreational marine vessels in the model now seem 

more representative of the number of boat registrations that the Pennsylvania Fish and Boat 

Commission tracks. We used EPA’s default values in the model runs. We also examined 

geographic allocation factors for residential lawn and garden equipment. These improvements 

are discussed further in the next section. All other categories rely on default data included in the 

model for population and activity estimates.

Residential Lawn and Garden Equipment

The EPA’s NONROAD2005 model uses 2003 U.S. Census data of all housing units in 

Pennsylvania to allocate residential lawn and garden equipment, even though EPA guidance 

states that emissions should be based only on the number of single detached, single attached, and 

double housing units. EPA’s method in the NONROAD2005 Model alters the allocation of lawn 

and garden emissions in some Pennsylvania counties significantly. The Department will use data 
3

obtained by E.H. Pechan from the 2000 Census, updated to 2002, and used in the state’s 2002 

inventory on the number of single detached, single attached, and double housing units for both 

the state and all counties in the state. Table 3 presents the Census data (Bureau of the Census, 

2003), which can be found in 2000 County and State Housing Units by Unit Type, Census 2000, 

http://factfinder.census.gov/servlet/. The total number of housing units was incorporated into the 

NONROAD2005 Model geographic allocation factor file, PA HOUSE.ALO, for use in 

allocating state-level lawn and garden equipment populations to all Pennsylvania counties for 

2002.

Table 3. Number of Single and Double-Family Housing Units from 2002 Census

County # 1-Unit Detached

Housing Units

# 1-Unit Attached 

Housing Units

# 2-Unit 

Housing Units

Total # of 

Housing Units

Adams 24,549 2,206 1,490 28,245

Allegheny 345,479 46,899 29,002 421,380

Armstrong 22,268 824 1,014 24,106

Beaver 54,418 2,312 2,863 59,593

Bedford 14,684 248 501 15,433

Berks 78,946 32,377 5,803 117,126

Blair 36,919 1,844 2,668 41,431

Bradford 16,861 232 1,224 18,317

Bucks 141,951 30,506 5,425 177,882

Butler 46,271 2,523 2,215 51,009

Cambria 44,453 3,795 2,882 51,130

Cameron 1,749 35 176 1,960

Carbon 14,431 5,104 990 20,525

Centre 27,786 2,691 1,749 32,226

Chester 99,549 25,911 3,155 128,615

Clarion 11,635 118 471 12,224

Clearfield 24,829 412 1,064 26,305

Clinton 10,141 662 711 11,514

Columbia 16,856 1,328 1,388 19,572

Crawford 24,430 397 1,933 26,760

Cumberland 51,934 10,450 2,792 65,176

Dauphin 52,961 20,195 3,848 77,004

Delaware 93,642 64,529 9,361 167,532

Elk 11,355 79 807 12,241

Erie 70,504 2,955 9,504 82,963

Fayette 41,679 3,094 2,473 47,246

Forest 1,660 8 18 1,686

Franklin 34,720 4,292 2,073 41,085

Fulton 4,084 56 133 4,273

Greene 10,387 481 416 11,284

Huntingdon 12,463 331 686 13,480

Indiana 23,215 825 1,232 25,272

Jefferson 14,276 237 729 15,242

Juniata 6,455 355 166 6,976

Lackawanna 53,357 3,328 12,626 69,311

Lancaster 98,364 32,122 7,370 137,856

Lawrence 28,316 799 1,489 30,604

Lebanon 27,272 8,647 2,225 38,144

Lehigh 59,753 29,474 5,118 94,345
4

Table 3. Number of Single and Double-Family Housing Units from 2002 Census

County # 1-Unit Detached

Housing Units

# 1-Unit Attached 

Housing Units

# 2-Unit 

Housing Units

Total # of 

Housing Units

Luzerne 82,363 15,404 9,435 107,202

Lycoming 31,568 2,812 2,998 37,378

McKean 13,794 158 972 14,924

Mercer 34,859 735 1,817 37,411

Mifflin 12,327 1,788 966 15,081

Monroe 40,696 1,726 1,457 43,879

Montgomery 163,211 53,370 9,599 226,180

Montour 4,769 645 346 5,760

Northampton 60,344 19,729 4,755 84,828

Northumberland 21,955 9,280 1,657 32,892

Perry 12,209 733 398 13,340

Philadelphia 48,724 359,877 46,425 455,026

Pike 15,501 395 299 16,195

Potter 5,263 62 281 5,606

Schuylkill 32,695 17,989 2,092 52,776

Snyder 10,263 644 526 11,433

Somerset 22,159 1,236 1,312 24,707

Sullivan 2,165 18 84 2,267

Susquehanna 12,139 180 711 13,030

Tioga 11,076 150 753 11,979

Union 9,341 652 527 10,520

Venango 17,197 227 1,080 18,504

Warren 13,031 239 930 14,200

Washington 60,711 3,891 3,187 67,789

Wayne 14,311 249 750 15,310

Westmoreland 113,694 4,839 5,997 124,530

Wyoming 7,858 159 412 8,429

York 95,921 20,218 6,102 122,241

Total 2,724,746 860,086 235,658 3,820,490

After the model runs, model outputs were processed to develop annual emissions inventories for 

VOC, NOx, CO, PM10, PM2.5, SO2, and NH3. Nonroad equipment refueling, either by portable 

container or at the gasoline pump, is being accounted for under Pennsylvania’s area source 

inventory. As such, spillage and vapor displacement VOC emission estimates were subtracted 

from the total VOC emission estimates for all NONROAD2005 Model emissions. Therefore, 

only exhaust, crankcase, and evaporative diurnal components are included in these VOC 

estimates. Emissions from nonroad equipment were tabulated in both source classification code 

format. 

III. 2002 LOCOMOTIVE EMISSIONS

Much of the locomotive emissions were captured from a 1999 survey conducted by the 

Department included hydrocarbon (HC) and NOx for the following locomotive source categories:

2285002006 : Railroad Equipment, Diesel, Line Haul Locomotives: Class I Operations

2285002007: Railroad Equipment, Diesel, Line Haul Locomotives: Class II/III Operations

2285002008: Railroad Equipment, Diesel, Line Haul Locomotives: Passenger Trains (Amtrak)
5

2285002010: Railroad Equipment, Diesel, Yard Locomotives

All line haul locomotive emissions were grouped into one SCC category in the appendix, 

2285002005.

Norfolk Southern and CSX Corporations purchased Conrail. The takeover of Conrail’s assets 

occurred in June 1999. For that reason, it was a very bad time to develop a representative 

emission inventory for these railroads. Both Conrail and Norfolk Southern suffered major 

gridlock in Pennsylvania and beyond during 1999. Consequently, fuel consumption and air 

emissions for these two railroads were greatly reduced in 1999. The Department requested and 

received 2002 fuel usage from these railroad companies and developed a 2002 emissions 

inventory for them. Fuel consumption increased 60 percent from 1999 to 2002. Clearly, this 

was not due to normal economic growth. All other emissions from railroad companies operating 

in Pennsylvania in 1999 were grown with a growth factor to obtain 2002 emissions.

To estimate 2009 locomotive emissions, the Department projected the 2002 inventory to 2009 

using national fuel consumption information supplied to the Department by the Association of 

American Railroads in combination with emissions factors developed by EPA and presented on 

the EPA website in the Emissions Factors for Locomotives, EPA420-F-97-051, December 1997, 

Table 9, Fleet Average Emission Factors For All Locomotives. According to the Association of 

American Railroads, national railroad annual fuel consumption has grown consistently at about 

1.6 percent over the last 15 years. We used the following normalized emission growth factors 

for locomotive emissions. These numbers compare well with the EPA Economic Growth 

Analysis System (EGAS) 5.0 in the near-term i.e. 2009. EGAS 5.0 may be downloaded from 

http://www.epa.gov/ttn/ecas/egas5.htm.

In the Regulatory Support Document for locomotive emission standards, national emissions 

account for future, phased-in controls that will reduce NOx, PM, and HC emissions as well 

(EPA, 1997). Relevant emission factors SOx and NH3 for locomotives do not exist. Emissions 

of SOx and NH3 by locomotives were not included in the inventory. Emission reductions, which 

include rule effectiveness and rule penetration, are estimated based on the percent change in 

emissions from the base year to a given projection year. Normalized fuel use and emission 

factors for locomotives are given in Table 4. The Department changed the 2002 locomotive 

emissions for NOx, PM, SOx and VOC by the normalized percentages shown in Table 5 which 

account for changes in emissions.

Table 4. Normalized Growth for Fuel Use and Emission Factors for Locomotives

Year Normalized 

Fuel Use 

Growth

Normalized 

NOx 

Emission 

Factor

Normalized 

VOC 

Emission

Factor

Normalized 

CO 

Emission 

Factor

Normalized 

PM

Emission 

Factor

2002 1.0000 1.0000 1.0000 1.0000 1.0000

2009 1.1175 0.6765 0.8785 1.0000 0.8676
6

Table 5. Normalized Emissions Growth Factors for Locomotive

Year NOx 

Emission 

Growth 

(Fuel use 

growth * 

emission 

factor)

HC/VOC 

Emission 

Growth 

(Fuel use 

growth * 

emission 

factor)

CO Emission 

Growth (Fuel 

use growth * 

emission 

factor)

PM Emission 

Growth (Fuel 

use growth * 

emission 

factor)

2002 1.0000 1.0000 1.0000 1.0000

2009 0.7560 0.9817 1.1175 0.9696

To estimate VOC emissions from HC, the Department applied a VOC/HC conversion factor of 

1.005 to the HC emissions. This conversion factor was obtained from EPA’s Documentation for 

Aircraft, Commercial Marine Vessel, Locomotive, and Other Nonroad Components of the 

National Emission Inventory, Volume I: Methodology (EPA, 2002).

Estimated annual emissions were divided by 365 to obtain a daily emission estimate which was 

assumed to be a good estimate for emissions during an average summer day.

IV. AIRCRAFT EMISSIONS

Aircraft emissions at Philadelphia International Airport (PHL), the largest airport in the state, 

were estimated using the most up-to-date information available, which was supplied by the City

of Philadelphia. Aircraft related emissions were also estimated for Northeast Philadelphia 

Airport (PNE) using up-to-date information. The methodology for estimating emissions at PHL 

and PNE is explained in greater detail in Appendix F2. 

Small airport emission estimation methodology. Small aircraft emissions occurring at airports 

in Bucks, Chester, and Montgomery Counties were calculated by using small airport operation 

statistics, which can be found at www.airnav.com and the Federal Aviation Administration’s 

(FAA) APO Terminal Area Forecast Detailed Report. Emission factors for a typical general 

aviation single engine, multi-engine, and jet engine aircraft were derived by averaging the 

emissions factors from a basket of emission factors for common aircraft of each of the three 

types of aircraft. Emission factors and operational characteristics contained in EDMS were used 

for this calculation. The proportion of operations between the three groups of aircraft was 

determined by examining the number of each aircraft type based at each airport. For military

operations at small airports, the type of aircraft and its emission factors are sometimes 

identifiable. If not, emission factors calculated to represent an “average” military aircraft are 

used. 

Growth at small airports was estimated using estimates of future operations contained in the 

FAA APO Terminal Area Forecast Detailed Report. The normalized growth in operations was 

applied directly to 2002 emissions to obtain growth in emissions. Changes in technology, such 

as a new engine design, which may result in more or less emissions was not taken into account. 
7

Fleet mix may be slightly different in the future and this may also change emissions. This 

unpredictable effect was not taken into account.

Military aircraft. Willow Grove Naval Air Station (NAS) is located in Bucks County. Willow 

Grove is the source of significant air traffic and air emissions. It was estimated that NOx 

emissions were emitted at a rate of over one ton per day in 1990. Since the terrorist event at the 

World Trade Center in 2001, it has become difficult to obtain operations data from the military. 

The Navy refused to give the Department any operations data that would allow us to determine 

emissions produced from operations at Willow Grove. Therefore, emissions from Willow Grove 

are not included in our inventory. 

V. COMMERCIAL MARINE VESSELS

Emissions from ship traffic in the Port of Philadelphia were estimated by using primarily the 

methodology outlined in the Commercial Marine Activity for Deep Sea Ports in the United 

States, Final Report1. A section in the report details the characteristics of ports on the Delaware 

River. Maritime Exchange for the Delaware River and Bay supplied ship arrival information. 

Ship arrivals for each pier, terminal, and facility were tabulated for the year in the report titled 

Ship Arrivals for the Delaware River Ports 20032, which included arrivals for years 1995-2003. 

Arrivals for 2002 were used for the 2002 inventory.

By mutual agreement between Pennsylvania and New Jersey, downbound traffic north of the 

Pennsylvania-Delaware border is included in the Pennsylvania emissions inventory while New 

Jersey captures all the upbound traffic north of the border. Most commercial marine vessel 

(CMV) emissions in the port are produced by hotelling emissions and tugboat trips. Ship shifts 

and large vessel movements do not contribute significantly to emissions. The pollutants that are 

produced in the largest quantity by ships are NOx. 

Large Vessel Emissions

Large oceangoing vessels use Category 3 marine engines and use primarily bunker fuel.

The distance from the Delaware border for each shipping terminal was estimated using 

information on the U.S. Army Corps of Engineers website, at www.wrsc.usace.army.mil3. EPA 

guidance was followed for estimating the time required for a ship to travel the Delaware River 

from its berth to the Delaware border. All commercial ship traffic must slow to approximately

60-70 percent power around the time that they enter into Pennsylvania. This translates into 8 

Table 5. Normalized Growth in Aircraft Operations

County (Airport) 2002 2009

Bucks County (Doylestown) 1.0000 1.0377

Chester County (Chester County) 1.0000 1.0377

Montgomery County (Perkiomen) 1.0000 1.0377
8

knots for tankers and 14 knots for container ships. An average speed of 11 knots was used for all 

ships. Once the vessel is within 3 to 4 miles of its intended berth or anchorage, it will continue at 

slow or dead-slow speed that ranges from 2 to 6 knots. We applied this methodology in reverse 

for a ship traveling out of its berth. An average speed of 4 knots was used for all vessels that are 

within 4 miles of their intended berth to calculate time for maneuvering. EPA guidance suggests 

that ships traveling with the current would travel three miles per hour faster than an upbound 

ship. Along the Delaware River near Philadelphia, speed limits are established in many areas 

that ships cannot exceed without causing damaging wakes. We assume river currents effect to be 

zero, because pilots will travel at 11 knots regardless since the speed limit is about 11 knots in 

many places

Equation for estimating time-in-mode: 

TRSZ + MAN = (DDB – 4) / (S60-70% +SRC) + 4/4 4

Where:

TRSZ + MAN = Time-in-mode for reduced speed zone and for maneuvering.

DDB – 4 = Distance to the Delaware border minus four miles needed for 

maneuvering speed (in nautical miles).

(S60-70% + SRC) = Reduced speed plus the speed of the river current. 

4/4 = Four miles for maneuvering divided by four knots

The length of time that each ship spent maneuvering in each county was calculated by finding 

the length of the river that runs by each county. Total maneuvering emissions were then 

apportioned to each county in the Philadelphia port. Emission factors used for maneuvering 

large ships for NOx, hydrocarbons, carbon monoxide, sulfur compounds, and particulate matter 

were 550 lb, 24lb, 60lb, 27 lb, and 33 lb, respectively, per 1000 gallons of fuel. Emission factors 

for class I CMV ships was obtained from Procedures For Emission Inventory Preparation 

Volume IV: Mobile Sources4. 

Hotelling Emissions

Hotelling emissions from large CMV were calculated by determining the number and types of 

vessels that visited Pennsylvania ports. The average number of hours that each type of ship 

spends hotelling during a typical port visit was obtained from Commercial Marine Activity for 

Deep Sea Ports in the United States, Final Report5. Tugboats do not contribute to hotelling 

emissions. Fuel usage for hotelling was obtained from Procedures for Emission Inventory 

Preparation Volume IV: Mobile Sources4. Emission factors were the same factors used for 

locomotives and class II CMV engines as stated below. Emissions were distributed to the county

level on the basis of the percentage of commercial vessel visits to each of the three Pennsylvania 

counties.

Tugboat Emissions

Tugboats use Category 2 marine engines and use primarily distillate fuel. Emissions from 

tugboat operations in the Port of Philadelphia were derived by using the total number of tugboat 
9

trips supplied by the Waterborne Commerce of the United States6report for calendar year 2002, 

found on the U.S. Army Corps of Engineers website. Average trip distances were estimated 

from this report. The report gives the approximate origin of the tugs. Many tugs are involved in 

lightering operations that are south of the Pennsylvania/Delaware border. Average trip times 

were estimated by using information obtained in telephone calls to tugboat operators in Port of 

Philadelphia and the equations provided in Commercial Marine Activity for Deep Sea Ports in 

the United States, Final Report.7 

Tugboats were separated into six horsepower bins. Fuel usage was estimated by using 

information found in Shipboard Marine Engines Emission Testing for the United States Coast 

Guard.

8

 

Table 6. Tugboat Fuel Use Characterization

Horsepower Bin Number of Tugs 

in the Port

Fuel Usage 

(gal/hr)

0-750 7 25

750-1500 7 44

1500-3000 19 105

3000-5000 13 200

5000-8000 3 250

Total Tugs 49

Emission factors from tugboats and pushboats are nearly nonexistent. Tugboat engines also 

known as type II marine engines are engineered and perform similarly to locomotive engines. 

Since some locomotive engines are the same size and operate under similar load and activities as 

tugboat engines, emission factors of locomotive engines were used at the suggestion of Greg 

Janssen of EPA9. Emission factors of locomotives from the U.S. EPA website, www.epa.gov 12

show NOx, hydrocarbon, carbon monoxide, sulfur, and particulate matter emissions at 609 lb, 

50.6, 80.3, 20.3, and 20.6 lb, respectively, per 1000 gallons of fuel. Since these tugs are under 

load like locomotives, the emission factors of locomotives seem more appropriate than other 

emission factors available.

Distributing Tugboat Emissions to the County Level

The method outlined in allocating to the county level in Commercial Marine Activity for Deep 

Sea Ports in the United States 11 was not followed due to the geographic shape of the port. 

Delaware and Philadelphia counties get most of the emissions from commercial vessels since 

that is where most of the trips are recorded. The approximate number of tug trips to each county 

was estimated from trip statistics in Waterborne Commerce of the United States report12. 

Emissions were allocated to the county level as described by the equation below. Delaware and 

Philadelphia County had roughly the same amount of traffic while Bucks County had 

significantly less tug traffic.
10

Equation for Allocating Tugboat Emissions to the County Level

TDC = (TTPH + TTCH + TTSR) / 2 + TTTH / 3

Giving the example

TDC = Hours tugboats spend traveling in Delaware County

TTPH = Hours spent traveling from Philly Harbor to border

TTCH = Hours spent traveling from Camden Harbor to border

TTSR = Hours spent traveling from Schuylkill River to border

2 = Number of counties ships pass

TTTH = Hours spent traveling from Trenton Harbor to border

3 = Number of counties ships pass

TDC = (6584 + 19737 + 4794)/2 + 1820/3 = 16,164 hours

It was estimated that tugboats spend about 45% of their time in Philadelphia and 

Delaware Counties and 10% of their time in Bucks County. This estimate seems reasonable. 

Ferry Emissions

Two ferries travel between Philadelphia and Camden seven times per day for eight months of the 

year. The vessels are idling and not emitting too much in the way of NOx for a large portion of 

their duty-cycle. Emissions standards for boats operating at low load and of comparable size 

were obtained from the Shipboard Marine Engines Emission Testing for the United States Coast 

Guard-Final Report13. 

Other Emissions

There is good reason to believe that significant emissions occur as a result of lightering 

emissions in the port. However, according to the Army Corps of Engineers and their consultant 

on the Delaware River Main Channel Deepening Project, Moffatt and Nichols, lightering 

operations occur south of the Pennsylvania border in Delaware.

The Coast Guard operates at least four vessels in the port, but it was impossible to obtain 

information on their operations.

The U.S. Army Corps of Engineers operates a dredging vessel in the Port of Philadelphia. The 

vessel, named Dredge McFarland, produced 197 tons of NOx and 60 tons of CO in 2002 

according to the Delaware River Main Channel Deepening Project: General Conformity and 

Mitigation Analysis14. No other pollutants were given. It was impossible to ascertain exactly

what percentage of time this ship exactly spent in Pennsylvania. It was roughly estimated from 

the conformity analysis that about 20 percent of the operations that occurred in the PhiladelphiaCamden-Wilmington air basin occurred north of the Pennsylvania/Delaware border. Therefore, 

it is assumed that 10 percent of all dredging emissions occurred in Pennsylvania and 10 percent 

in New Jersey.
11

Emissions Growth

Emissions growth is based on two factors: future fuel consumption and future emissions 

standards. Emissions standards or programs that take place in the future will greatly lower 

emissions produced by CMV engines. Fuel use growth and future emission reductions used to 

calculate total future emissions were based upon information contained in the Final Regulatory 

Impact Analysis: Control of Emissions from Marine Diesel Engines.

15

 

Fuel use growth for CMV was obtained from Table 5.8 for Category 2 engines, “Baseline 

Emissions from Category 2 CI Marine Engines Operated in U.S. Waters,”16 and from Table 5-11 

for Category 3 engines in the regulatory impact analysis. An average annual fuel use growth of 

0.9 percent was estimated in the table for Category 2 engines. Fuel use for Category 3 engines is 

growing about 1.0% per year. The methodology does not rely on fuel use to estimate growth for 

Category 3 marine engines. It uses total emissions from Category 3 engines in port settings. 

These emission estimates can be found in the Final Regulatory Support Document: Control of 

Emissions from New Marine Compression Ignition Engines at or Above 30 Liters per Cylinder. 

Corresponding baseline emission increases (absent controls) in carbon monoxide NOx, HC, CO, 

SOx, and PM are given. 

Category 2 Marine Engine Emissions

Emission reductions for NOx for Category 2 engines were obtained from Table 5-9, “Projected 

NOx Emission Reductions from Category 2 CI Marine Engines Operated in U.S. Waters.” 17 

Table 5-9 was used for NOx because it shows emission reductions of Category 2 CI marine

engines exclusively. Table 5-15, Emission Reductions from Engines Subject to Tier 2 

Standards18, was used to estimate emission reductions of PM and hydrocarbons for Category 2 

vessels. The tables gave reductions for 2010. The reduction estimates were interpolated linearly 

between 2000 and 2010 to obtain reductions and emissions for the year 2009. 

Table 7 shows the growth rates in emissions used to estimate emissions in the inventory.

Table 7. Normalized Growth in Emissions produced by Category 2 

CMV in the U.S. (distillate fuel)

Normalized Future Emission 

Factors

Normalized Growth in Emissions 

(CMV Growth * Normalized 

Future Emission Factors)

Year CMV 

Fuel Use 

Growth

CO

& 

SOx

NOx VOC PM CO

& 

SOx

NOx VOC PM

2002 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000

2009 1.065 1.000 0.960 0.980 0.924 1.065 1.022 1.043 0.985
12

Category 3 Marine Engine Emissions

The best estimates for emissions growth for Category 3 marine diesel engines were found in the 

United States Environmental Protection Agency document Final Regulatory Support Document: 

Control of Emissions from New Marine Compression Ignition Engines at or Above 30 Liters per 

Cylinder, Table 7.2-1, Projected Emission Inventories from Category 3 Marine Diesel Engines in 

Port Areas.19 The growth in emissions from 2002 to 2009 was estimated by interpolating 

between the years given in Table 7.2-1 for the years 1996 and 2010. Emissions growth in 

Category 3 marine engines is much higher than Category 2 marine engines. 

Table 8 shows the emissions increases of Category 3 CMV in port areas.

Growth in Emissions from Category 3 Marine Diesel Engines in Port Areas in the U.S. 

Year CO SOx NOx VOC PM

2002 1.000 1.000 1.000 1.000 1.000

2009 1.249 1.046 1.187 1.247 1.215

 

1 United States Environmental Protection Agency, Office of Mobile Sources, Assessment and 

Modeling Division, Commercial Marine Activity for Deep Sea Ports in the United States, Final 

Report, Ann Arbor, Michigan, June 30, 1999.

2

Ship Arrivals for the Delaware River Ports 2002, Maritime Exchange for the Delaware River 

and Bay, 240-242 Cherry Street, Philadelphia PA 19106-1906

3 U.S, Army Corps of Engineers, Navigation Data website, 

http://www.iwr.usace.army.mil/ndc/index.htm, July 19, 2001.

4 U.S. Environmental Protection Agency, Office of Mobile Sources, Procedures for Emission 

Inventory Preparation, Volume IV: Mobile Sources, EPA-450/4-81-026d (Revised), Ann Arbor 

Michigan, 1992, Chapter 7.

5 United States Environmental Protection Agency, Office of Mobile Sources, Assessment and 

Modeling Division Commercial Marine Activity for Deep Sea Ports in the United States, Final 

Report, Table 8-5.

6 Website of the Waterborne Commerce Statistics Center of the United States, United States 

Army Corps of Engineers, July 19, 2001.

7 United States Environmental Protection Agency, Office of Mobile Sources, Assessment and 

Modeling Division, Commercial Marine Activity for Deep Sea Ports in the United States, Final 

Report, p. 8-5.
13

 

8 Volpe National Transportation Systems Center and United States Coast Guard Headquarters 

Naval Engineering Division, prepared by Environmental Transportation Consultants, Shipboard 

Marine Engines Emission Testing for the United States Coast Guard Final Report, 1995.

9 Email exchange with Greg Janssen of U.S. EPA, Office of Transportation and Air Quality, 

Assessment and Standards Division, Ann Arbor Michigan, January 24, 2001.

11 United States Environmental Protection Agency, Office of Mobile Sources, Assessment and 

Modeling Division, Commercial Marine Activity for Deep Sea Ports in the United States, Final 

Report, p. 4-13.

12 Website of the Waterborne Commerce Statistics Center of the United States, United States 

Army Corps of Engineers, July 19, 2001.

13 Volpe National Transportation Systems Center and United States Coast Guard Headquarters 

Naval Engineering Division, prepared by Environmental Transportation Consultants, Shipboard 

Marine Engines Emission Testing for the United states Coast Guard Final Report, 1995

14 Moffatt & Nichol, Walnut Creek, CA, General Conformity Analysis and Mitigation Report, 

Final Draft, February 2004.

15 United States Environmental Protection Agency, Office of Mobile Sources, Engines and

Compliance Division, Final Regulatory Analysis: Control of Emissions from Marine Diesel 

Engines, November 1999.

16 Ibid., p. 109

17 Ibid., p. 110

18

 Ibid., p. 115

19

 United States Environmental Protection Agency, Office of Transportation and Air Quality, 

Final Regulatory Support Document: Control of Emissions from New Marine Compression 

Ignition Engines at or Above 30 Liters per Cylinder, p. 7-6, EPA420-R-09-004, January 2003.