SEPA CENTER FOR CORPORATE
CLIMATE
LEADERSHIP
U.S. Environmental Protection Agency
Supporting organizations in GHG measurement and management • www.epa.gov/climateleadership
Greenhouse Gas Inventory Guidance
Direct Emissions from Mobile
Combustion Source
SEPA
United States
Environmental Protection
Agency
December 2020
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The U.S. EPA Center for Corporate Climate Leadership's (The Center) GHG guidance is based on The Greenhouse Gas
Protocol: A Corporate Accounting and Reporting Standard (GHG Protocol) developed by the World Resources Institute
(WRI) and the World Business Council for Sustainable Development (WBCSD). The Center's GHG guidance is meant to
extend upon the GHG Protocol to align more closely with EPA-specific GHG calculation methodologies and emission
factors, and to support the Center's GHG management tools.
For more information regarding the Center for Corporate Climate Leadership, visit www.epa.gov/climateleadership.
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Table of Contents
Table of Contents
Section 1: Introduction 1
1.1 Scope 1 versus Scope 3 Mobile Source Emissions 2
1.2 Greenhouse Gases Included 2
1.3 Biofuels 3
Section 2: Calculating C02 Emissions 4
Section 3: Calculating CH4 and N20 Emissions 6
Section 4: Choice of Activity Data and Emission Factors 7
4.1 Activity Data 7
4.2 Fuel Carbon Content and Heat Content 9
4.3 Emission Factors 10
Section 5: Completeness 11
Section 6: Uncertainty Assessment 12
Section 7: Documentation 13
Section 8: Inventory Quality Assurance and Quality Control (QA/QC) 14
Appendix A: Default C02 Emission Factors 15
Appendix B: Default CH4 and N20 Emission Factors 17
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Direct Emissions from Mobile Sources
Section 1: Introduction
Section 1: Introduction
Greenhouse gas (GHG) emissions are produced by mobile sources as fuels are burned. Carbon dioxide (C02), methane
(CH4), and nitrous oxide (N20) are emitted directly through the combustion of fuels in different types of mobile equipment.
A list of mobile sources that could potentially be included in an organization's GHG inventory is provided in Table 1. GHG
emissions from mobile sources also include hydrofluorocarbon (HFC) and perfluorocarbon (PFC) emissions from mobile air
conditioning and transport refrigeration leaks. The calculation of fugitive HFC and PFC emissions from mobile sources is
described in the Center's guidance for Direct FuRitive Emissions from RefriReration, Air Conditioning Fire Suppression, and
Industrial Gases.
Table 1: Categories of Mobile Sources
Category
Onroad Vehicles
—Passenger Cars
—Vans, Pickup Trucks & SUVs
—Heavy-Duty Vehicles
—Combination Trucks
—Buses
Nonroad Vehicles
—Construction Equipment
—Agricultural Equipment
—Forklifts
—Other Nonroad Equipment
Waterborne
—Ships
—Boats
Rail
—Freight Trains
—Commuter Rail
—Amtrak
Air
—Commercial Aircraft
—Executive Jets
Primary Fuels Used
Gasoline
Diesel Fuel
Diesel Fuel
Diesel Fuel
Residual Fuel Oil
Gasoline
Diesel Fuel
Electric
Kerosene Jet Fuel
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Section 1: Introduction
1.1 Scope 1 versus Scope 3 Mobile Source Emissions
This document presents the guidance for calculating scope 1 direct GHG emissions resulting from the operation of owned
or leased mobile sources that are within an organization's inventory boundary. This guidance applies to all sectors whose
operations include owned or leased mobile sources.
All other organization-related mobile source emissions, including employee commuting, employee travel, and upstream/
downstream third-party transportation emissions, such as those associated with transporting material inputs or product
distribution, are considered scope 3 indirect emissions. This guidance document focuses on scope 1 emissions. While
some of the approaches in this document can also apply to scope 3 sources, organizations should refer to the separate
scope 3 guidance document for specific approaches to calculate scope 3 mobile source emissions.
Furthermore, this guidance focuses on accounting for emissions resulting directly from an organization's activities, not on
the full life cycle greenhouse gas emissions associated with those activities. For example, a fleet owner would use this
guidance to account for emissions resulting from fleet fuel usage, but not for the emissions associated with producing the
fuel.
Users of this guidance should be aware, however, that the choice of transportation modes and fuels can greatly influence
GHG emissions from a life cycle perspective. A transportation mode may have relatively few GHG emissions from the
vehicle itself, but emissions could be higher from the production of the fuel.
1.2 Greenhouse Gases Included
The greenhouse gases C02, CH4, and N20 are emitted during the combustion of fuels in mobile sources. For most
transportation modes, CH4and N20 emissions comprise a relatively small proportion of overall transportation-related GHG
emissions (approximately one percent combined)1. For onroad vehicles less than 15 years old, CH4, and N20 emissions
typically account for one percent of emissions or less. However, for older gasoline fueled onroad vehicles, CH4, and N20
could be a more significant (approximately five percent) portion of total GHG emissions. CH4and N20 emissions are
typically an even higher percentage of total GHG emissions from nonroad or alternative fuel vehicles.
Organizations should account for all C02, CH4, and N20 emissions associated with mobile combustion. Given the relative
emissions contributions of each gas, CH4 and N20 emissions are sometimes excluded by assuming that they are not
material. However, as outlined in Chapter 1 of the GHG Protocol, the materiality of a source can only be established after
it has been assessed. This assessment does not necessarily require a rigorous quantification of all sources, but at a
minimum, an estimate based on available data should be developed for all sources and categories of GHGs, and included
in an organization's GHG inventory.
Information on methods used to calculate C02 emissions is found in Section 2. Information on an approach for
determining CH4 and N20 emissions is found in Section 3. The approach to calculating C02 emissions from mobile
combustion sources varies significantly from the approach to calculating CH4 and N20 emissions. While C02 can be
reasonably calculated by applying emission factors based on the fuel quantity consumed, CH4 and N20 emissions depend
largely on the emissions control equipment used (e.g., type of catalytic converter) and vehicle miles traveled. Emissions of
these gases also vary with the efficiency and vintage of the combustion technology, as well as maintenance and
1 See Table 3-7 of U.S. EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2018, EPA430-R-20-002, April 2020.
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Section 1: Introduction
operational practices. Due to this complexity, a much higher level of uncertainty exists in the calculation of CH4 and N20
emissions from mobile combustion sources, compared to the calculation of C02 emissions.
1.3 Biofuels
Not all mobile combustion sources burn fossil fuels. Biomass (non-fossil) fuels (e.g., ethanol, biodiesel) may be combusted
in mobile sources independently or co-fired with fossil fuels. The emission calculation methods discussed in this document
can be used to calculate C02, CH4, and N20 emissions from combustion of these fuels. The GHG Protocol requires that C02
emissions from biomass combustion for mobile sources are reported as biomass C02emissions (in terms of total amount
of biogenic C02) and are tracked separately from fossil C02 emissions. Biomass C02 emissions are not included in the
overall C02-equivalent emissions inventory for organizations following this guidance. CH4 and N20 emissions from biofuels
are included in the overall C02-equivalent emissions inventory.
There are several transportation fuels that are actually blends of fossil and non-fossil fuels. For example, E85 is an ethanol
(biomass fuel) and gasoline (fossil fuel) blend containing 51 percent to 83 percent ethanol, and B20 is a blend of 20
percent biodiesel (biomass fuel) and 80 percent diesel fuel (fossil fuel). The majority of motor gasoline used in the United
States is made up of a blend of gasoline and ethanol. Typically, the blend is E10 (10 percent ethanol and 90 percent
gasoline), but the content of ethanol in gasoline varies by location and by year. Combustion of these blended fuels results
in emissions of both fossil C02 and biomass C02. Organizations should report both types of C02 emissions if blended fuels
are used.
The blend percentage can be used to estimate the quantity of fossil fuel and biofuel. For example, if the organization
consumes 1,000 gallons of E10, that can be treated as 100 gallons of ethanol and 900 gallons of gasoline. Separate fossil
and biomass emission factors can then be applied to this mix of fuels. If an organization lacks specific biofuel content data,
the organization may assume 10 percent ethanol for gasoline and may use the national average ethanol content for
E85.This is reported in the U.S. ElA's Annual Energy Outlook, and is currently 74 percent2.
An organization may operate "flex-fuel" vehicles, which can use either fossil fuels or a biofuel blend. If the organization is
uncertain which fuel is used in these vehicles, fossil fuel should be assumed.
Recently, there has been increased scientific inquiry into accounting for biomass in energy production. The EPA's Science
Advisory Board recently found that "there are circumstances in which biomass is grown, harvested and combusted in a
carbon neutral fashion but carbon neutrality is not an appropriate a prior assumption; it is a conclusion that should be
reached only after considering a particular feedstock's production and consumption cycle. There is considerable
heterogeneity in feedstock types, sources and production methods and thus net biogenic carbon emissions will vary
considerably."3 According to the GHG Protocol Corporate Standard, "consensus methods have yet to be developed under
the GHG Protocol Corporate Standard for accounting of sequestered atmospheric carbon as it moves through the value
chain of biomass based industries," though some general considerations for accounting for sequestered atmospheric
carbon are discussed in Chapter 9 and Appendix B of the GHG Protocol Corporate Standard.
2 U.S. Energy Information Administration, Annual Energy Outlook 2020, Table A2: Energy Consumption by Sector and Source. Available 11/24/2020
here: https://www.eia.gov/outlooks/aeo/.
5 EPA Science Advisory Board Review of the 2011 Draft Accounting Framework for C02 Emissions for Biogenic Sources Study. 2012.
https://vosemite.epa.gOv/sab/sabproduct.nsf/0/2F9B572C712AC52E8525783100704886PQpenDocument.
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Section 2: Calculating C02 Emissions
Section 2: Calculating C02 Emissions
The C02 emissions associated with fuel combustion are a function of the
volume of fuel combusted, the density of the fuel, the carbon content of
the fuel, and the fraction of carbon that is oxidized to C02. One of three
equations can be used to calculate C02 emissions for each type of fuel
combusted. The appropriate equation to use depends on what is known
about the characteristics of the fuel being consumed.
Equation 1 is recommended when fuel consumption is known only in
mass or volume units, and no information is available about the fuel heat
content or carbon content. This equation is the least preferred.
It has the most uncertainty because its emission factors are based on default fuel heat content, rather than actual heat
content.
Equation 2 is recommended when the actual fuel heat content is
provided by the fuel supplier or is otherwise known. In such cases, the
fuel use in energy units can be multiplied directly by the emission
factor (EF2). Equation 2 is a preferable approach over Equation 1
because it uses emission factors that are based on energy units as
opposed to mass or volume units. Emission factors based on energy
units are less variable than factors per mass or volume units because
the carbon content of a fuel is more closely related to the heat
content of the fuel than to the total physical quantity of fuel.
Equation 3 is recommended to calculate Commissions when the
actual carbon content of the fuel is known. Carbon content is
typically expressed as a percentage by mass, which requires fuel
use data in mass units. This equation is most preferred for C02
calculations because C02 emissions are directly related to the
fuel's carbon content. Follow the steps below to calculate
emissions.
Step 1: Select the appropriate equation.
Based on the information available on the characteristics of the
fuel being consumed, select the appropriate equation to use in
calculating emissions. See the discussion above on the three
possible equations.
Step 2: Determine the amount of fuel combusted.
Each fuel type should be quantified separately. This can be based on fuel receipts or purchase records. Methods for
determining fuel use are discussed in Section 4.1.
Equation 1:
Emissions = Fuel x EF,
Where:
Emissions = Mass of C02 emitted Fuel =
Mass or volume of fuel combusted
EF, = C02 emission factor per mass or
volume unit
Equation 2:
Emissions = Fuel x HHV x EF2
Where:
Emissions = Mass of C02 emitted
Fuel = Mass or volume of fuel combusted
HHV = Fuel heat content (higher heating
value), in units of energy per mass or
volume of fuel
EF2 = C02 emission factor per energy unit
Equation 3:
Emissions = Fuel x CC x 44/12
Where:
Emissions = Mass of C02 emitted
Fuel = Mass or volume of fuel combusted
CC = Fuel carbon content, in units of mass of
carbon per mass or volume of fuel
44/12 = ratio of molecular weights of C02 and
carbon
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Section 2: Calculating C02 Emissions
Step 3: Determine equation inputs.
The selected equation specifies which inputs are needed to calculate emissions. As appropriate, determine the fuel carbon
content, fuel heat content, and/or emission factors associated with each fuel consumed. Further guidance is given in
Section 4, and emission factors are provided in Appendix A.
Step 4: Calculate emissions.
Use the appropriate equation with the fuel consumption and other equation inputs to calculate the emissions of C02. The
EPA SmartWay Transport Partnership (SmartWay) has various tools on its website that allow an organization to calculate
C02 emissions for their mobile source fleet. If the organization has more detailed information on the vehicle models and
fuel type, it may elect to use the tools available on the SmartWay website (https://www.epa.Rov/smartway) instead of
using the default values for C02 emission factors in this document. Organizations that choose to use EPA's SmartWay tools
should include the specific data and factors used in their Inventory Management Plan (IMP).
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Section 3: Calculating CH4 and N20 Emissions
Section 3: Calculating CH4 and N20 Emissions
One of two equations can be used to calculate CH4 and N20 emissions for each type of fuel combusted. Equation 4 is
applicable to onroad vehicles such as cars, trucks, and buses. Equation 5 is applicable to nonroad vehicles such as
construction or agricultural equipment, forklifts, ships, boats, rail vehicles, or aircraft.
Equation 5:
Emissions = Fuel x EF,
Where:
Emissions = Mass of CH4 or N20 emitted
Fuel = Volume of fuel combusted
EF, = CH4 or N20 emission factor per volume
unit
Follow the steps below to calculate emissions.
Step 1: Select appropriate equation.
As discussed further above, Equation 4 is applicable to onroad vehicles and Equation 5 is applicable to nonroad vehicles.
Step 2: Determine the distance traveled or the amount of fuel combusted.
For road vehicles, gather data on the distance traveled, which is typically obtained from odometer readings. For nonroad
vehicles, gather data on the volume of fuel combusted, which is typically obtained from fuel purchase records. Methods
for determining distance and fuel use are discussed in Section 4.1.
Step 3: Determine emission factors.
The selected equation specifies the appropriate emission factors to be used. Further guidance is given in Section 4.3, and
emission factors are provided in Appendix B.
Step 4: Calculate emissions.
Use the appropriate equation with the distance or fuel consumption and the appropriate emission factors to calculate the
emissions of CH4 and N20. Multiply the emissions of CH4 and N20 by the respective global warming potential (GWP) to
calculate C02-equivalent emissions. The GWPs are 25 for CH4 and 298 for N20, from the Intergovernmental Panel on
Climate Change (IPCC), Fourth Assessment Report (AR4), 2007. Sum the C02 equivalent emissions from CH4 and N20 with
the emissions of C02 to calculate the total C02-equivalent (C02e) emissions.
Equation 4:
Emissions = Distance x EF4
Where:
Emissions = Mass of CH4 or N20 emitted
Distance = Vehicle distance traveled
EF, = CH4 or N20 emission factor per distance
unit
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Section 4: Choice of Activity Data and Emission Factors
Section 4: Choice of Activity Data and Emission Factors
4.1 Activity Data
To maximize the accuracy of emissions calculations, it is useful to have as much information as possible about the
organization's vehicles. Ideally, a list of vehicles would be created with the following information provided for each vehicle:
• Fuel type
• Fuel use
• Distance traveled (for onroad vehicles)
• Fuel economy (if either fuel use or distance traveled is unavailable)
• Vehicle type
• Emissions control technology and/or model year
If vehicle-specific information is not available, the calculation methods can be applied to subtotaled fuel use data by fuel
type, and to subtotaled distance data by vehicle type and model year.
This section provides guidance on fuel use data, distance data, and fuel economy. When calculating C02 emissions, and
when calculating CH4 and N20 emissions from nonroad vehicles, the activity data that need to be gathered is the quantity
of fuel combusted for each fuel type. When calculating CH4 and N20 emissions from onroad vehicles, the activity data
needed is the distance traveled. These emissions also depend on vehicle type and control technology or model year, which
are discussed in Appendix B.
The most accurate method of determining the amount of fuel combusted, and therefore the preferred method, is to
gather data from fuel receipts or purchase records. If fuel is purchased at commercial fueling stations, fuel receipts can
typically be obtained from the vehicle operators, or through records from centralized fuel card services. If fuel is delivered
to the organization's facilities either to fill on-site fuel storage or to fill vehicles directly, fuel use can be determined
through delivery records or fuel invoices. If natural gas vehicles are fueled on-site, fuel purchase data can be obtained
from monthly natural gas bills. If a particular fuel type is used for both stationary and mobile sources, care should be taken
to avoid double counting the fuel use.
If purchase records are used, several factors could lead to
differences between the amount of fuel purchased and the
amount of fuel actually combusted during a reporting period.
These factors can include changes in fuel storage inventory,
fugitive releases, or fuel spills.
For changes in fuel storage inventory, Equation 6 can be used to
calculate actual fuel use.
Fuel purchase data are usually reported as the amount of fuel
provided by a supplier as it crosses the gate of the facility. However, once fuel enters the facility there could be some
losses before it actually is combusted. Before calculating emissions, organizations should subtract the amount of fuel lost
Equation 6: Accounting for Changes in
Fuel Inventory
Fuel B = Fuel P + (Fuel ST- Fuel SE)
Where:
Fuel B = Fuel burned in reporting period
Fuel P = Fuel purchased in reporting period Fuel
ST = Fuel stock at start of reporting period Fuel SE
= Fuel stock at end of reporting period
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Section 4: Choice of Activity Data and Emission Factors
in fugitive releases or spills from the amount of fuel purchased. These losses are particularly important for natural gas,
which could be lost due to fugitive releases from facility valves and piping, as these fugitive emissions could be significant.
These fugitive natural gas releases (essentially methane emissions) should be accounted for separately from combustion
emissions.
It is possible that organizations may only know the dollar amount spent on a type of fuel. This is the least accurate method
of determining fuel use and is not recommended for GHG reporting. If the amount spent on fuel is the only information
initially available, it is recommended that organizations contact their fuel supplier to request data in physical or energy
units. If absolutely no other information is available, organizations should use fuel prices to convert the amount spent to
physical or energy units, and should document the prices used. Price varies widely for specific fuels, especially over the
geographic area and timeframe typically established for reporting GHG emissions.
For onroad vehicles, distance traveled data are also required in addition to fuel use. This distance should be tracked in
units of vehicle-miles or vehicle-kilometers, as opposed to passenger-miles or passenger-kilometers, which are often used
for scope 3 mobile source emissions. Distance data are best obtained from vehicle odometer readings. These could be
provided from the vehicle operators or from vehicle maintenance records. If a centralized fuel card service is used,
odometer readings may be required to be entered when fuel is purchased, in which case the odometer readings are
typically available from fuel card records. In the absence of distance data for a specific year, a reasonable approximation of
annual distance traveled can be made by dividing a vehicle's current odometer reading by the number of years it has been
operating.
C02 emissions, and CH4, and N20 emissions for nonroad vehicles should be calculated using actual fuel use data. CH4 and
N20 emissions for onroad vehicles should be calculated using actual distance traveled data. These approaches are
especially recommended if emissions from mobile sources are a significant component of an organization's total GHG
inventory. If accurate records of either fuel use or distance traveled are not available, the missing data can be estimated
using fuel economy factors. For example, if fuel use in gallons is known, this can be multiplied by fuel economy in miles per
gallon to obtain miles traveled. If distance traveled in miles is known, this can be divided by fuel economy in miles per
gallon to obtain gallons of fuel use. Estimating fuel use with fuel economy factors is not as preferable as directly obtaining
fuel use data, with the exception of fuel data based on the dollar amount spent on fuel. If accurate data are known on
distance traveled and fuel economy for specific vehicle types, this method is preferred overusing fuel price data.
The preferred method for determining fuel economy for onroad vehicles is to use organization records by specific vehicle.
This includes the miles per gallon (mpg) values listed on the sticker when the vehicle was purchased, or other organization
fleet records. If sticker fuel economy values are not available, the recommended approach is to use fuel economy factors
from the website www.fueleconomy.gov. This website, operated by the U.S. Department of Energy and the U.S.
Environmental Protection Agency, lists city, highway, and combined fuel economies by make, model, model year, and
specific engine type. Current year and historic model year data are both available.
Organizations should consider the following notes on the use of the fueleconomy.gov website to determine fuel economy
values and fuel use:
• The default recommended approach is to use the combined city and highway mpg value for organization specific
vehicle or closest representative vehicle type.
• The fuel economy values listed for older vehicles were calculated when the vehicle was new. The fuel economy
could decline over time, but the decline is not considered to be significant given other uncertainties around use of
the data.
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Section 4: Choice of Activity Data and Emission Factors
• The website also lists estimated GHG emissions, but these are projected emissions based on an average vehicle
miles traveled per year. These are not likely to be accurate estimates for fleet vehicles, and are not recommended
for use in GHG inventories.
For heavy-duty, onroad vehicles, and nonroad vehicles, activity data could come in different forms. For some types of
vehicles, activity data could be represented in terms of hours or horsepower-hours of operation, or, for some, it could be
by ton-miles shipped. This activity data should be available from organization records. Specific information on fuel
consumed per unit of activity data may be available from vehicle suppliers, manufacturers, or in organization records.
For freight transport, organizations should be particularly aware of any long duration idling. Idling can generate significant
carbon emissions, and anti-idling strategies can be a cost-effective strategy to reduce emissions. If fuel use is tracked
directly, the fuel related to idling is accounted for in the calculation. If fuel use is estimated based on distance data,
organizations should be aware of and document the time spent (i.e., hours) idling and make sure it is included in their
calculations of GHG emissions.
4.2 Fuel Carbon Content and Heat Content
Emissions of C02 from fuel combustion are dependent on the amount of carbon in the fuel, which is specific to the fuel
type and grade of the fuel. It is recommended that organizations determine the actual carbon content of the fuels
consumed, if possible. The most accurate method to determine a fuel's carbon content data is through chemical analysis
of the fuel. This data may be obtained directly from the fuel supplier.
Carbon content can also be determined by fuel sampling and analysis. Fuel sampling and analysis should be performed
periodically with the frequency dependent on the type of fuel. The sampling and analysis methodologies used should be
detailed in the organization's IMP. Refer to 40 CFR Part 75, Appendix G or 40 CFR Part 98, Subpart C for recommended
sampling rates and methods.
If actual fuel carbon content is available, either from the supplier or from sampling and analysis, Equation 3 in Section 2
may be used to calculate C02 emissions. It is also good practice to track the carbon content values used and to indicate if
they vary over time.
If carbon content is not available, it is recommended that organizations determine the actual heat content of the fuel, if
possible. The heat content of purchased fuel is often known and provided by the fuel supplier because it is directly related
to the useful output or value of the fuel. Heat content can also be determined by fuel sampling and analysis, using
methods discussed above. It is recommended that organizations use heat contents determined by one of these methods
rather than default heat content, as these should better represent the characteristics of the specific fuel consumed. If
actual fuel heat content is available, either from the supplier or from sampling and analysis, then Equation 2 in Section 2
may be used to calculate C02 emissions. It is also good practice to track the heat content values used and to indicate if
they vary over time.
When determining fuel heat content or tracking fuel use data in energy units, it is important to distinguish between lower
heating values (LHV) and higher heating values (HHV), also called net calorific value and gross calorific value, respectively.
Heating values describe the amount of energy released when a fuel is burned completely, and LHV and HHV are different
methods to measure the amount of energy released. A given fuel, therefore, always has both a LHV and a HHV. The LHV
assumes that the steam released during combustion remains as a gas. The HHV assumes that the steam is condensed to a
liquid, thus releasing more energy. HHV is typically used in the U.S. and in Canada, while other countries typically use LHV.
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Section 4: Choice of Activity Data and Emission Factors
All emission factors and default heat content values in this guidance are based on HHV. Therefore, if fuel consumption is
measured in LHV units, it must be converted to HHV before calculating emissions. To convert from LHV to HHV, a simplified
convention used by the International Energy Agency can be used. For coal and petroleum, divide energy in LHV by 0.95.
For natural gas, divide by 0.90.
4.3 Emission Factors
If actual fuel carbon content is not available, calculating C02 emissions relies on default emission factors. These factors
approximate the carbon content of fuel to quantify the amount of C02 that will be released when the fuel is combusted.
Appendix A provides two main types of default emission factors: factors defined per unit of fuel mass or volume (Table A-l
and A-2), and factors defined by per unit of fuel energy content (Table A-3 and A-4). As discussed in Section 2, using the
emission factors per energy unit, along with Equation 2, is preferable to using emission factors per mass or volume. CH4
and N20 emissions depend not only on the fuel characteristics but also on the combustion technology type and control
technologies. N20 is influenced by catalytic converter design, while CH4 is a byproduct of combustion, but can also be
affected by catalytic converter design. CH4 and N20 emissions are often calculated as a function of vehicle miles traveled.
Table B-l in Appendix B provides emission factors by vehicle type and control technology. Information on the control
technology type of each vehicle is posted on an under-the-hood label. To calculate emissions, organizations can multiply
the appropriate emission factor by the distance traveled for each vehicle type.
Determining the specific control technologies of vehicles in your fleet gives the most accurate calculation of CH4 and N20
emissions. Organizations should be aware that in order to account for reductions obtained from certain emission savings
strategies, it is necessary to use this approach and determine the particular emission control technologies for the vehicles
in question.
If determining the specific technologies of the vehicle in a fleet is not possible, or is too labor intensive for a particular
fleet, organizations can calculate CH4 and N20 emissions using emission factors by vehicle type and model year,
provided in Table B-2. These emission factors are based on a weighted average of available control technologies for
each model year.
Emission factors for alternative fuel onroad vehicles and for nonroad vehicles are given in Tables B-7 and B-8 of
Appendix B.
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Section 5: Completeness
Section 5: Completeness
in order for an organization's GHG inventory to be complete, it must include all emission sources within the organization's
chosen inventory boundaries. See Chapter 3 of the GHG Protocol for detailed guidance on setting organizational
boundaries and Chapter 4 of the GHG Protocol for detailed guidance on setting operational boundaries of the inventory.
On an organizational level, the inventory should include emissions from all applicable facilities and fleets of vehicles.
Completeness of organization-wide emissions can be checked by comparing the list of sources included in the GHG
emissions inventory with those included in other emissions inventories/environmental reporting, financial reporting, etc.
At the operational level, an organization should include all GHG emissions from the sources included in their inventory.
Possible GHG emission sources are stationary fuel combustion, combustion of fuels from mobile sources, purchases of
electricity, emissions from air conditioning equipment, and process or fugitive emissions. Organizations may refer to this
guidance document for calculating emissions from mobile source fuel combustion, and to The Center's GHG Guidance
documents for calculating emissions from other sources. For example, the calculation of HFC and PFC emissions from
mobile source air conditioning equipment is described in the Center's guidance "Direct Fugitive Emissions from
Refrigeration, Air Conditioning, Fire Suppression, and Industrial Gases."
As described in Chapter 1 of the GHG Protocol, there is no materiality threshold set for reporting emissions. The
materiality of a source can only be established after it has been assessed. This does not necessarily require a rigorous
quantification of all sources, but at a minimum, an estimate based on available data should be developed for all sources.
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Section 6: Uncertainty Assessment
Section 6: Uncertainty Assessment
There is uncertainty associated with all methods of calculating emissions from mobile combustion sources. EPA does not
recommend that organizations quantify uncertainty as +/- percentage of emissions or in terms of data quality indicators.
It is recommended that organizations attempt to identify the areas of uncertainty in their emissions and make an effort to
use the most accurate data possible. The accuracy of calculating emissions from fuel combustion in mobile sources is
partially determined by the availability of data on the amount of fuel consumed or purchased. If the amount of fuel
combusted is directly measured or metered, then the resulting uncertainty should be fairly low. Data on the quantity of
fuel purchased should also be a fairly accurate representation of fuel combusted, given that any necessary adjustments
are made for changes in fuel inventory, fuel used as feedstock, etc. However, uncertainty may arise if only dollar value of
fuels purchased is used to estimate fuel consumption. If fuel economy factors are used to estimate fuel use, uncertainty
may arise if distance traveled and/or fuel economy is roughly estimated.
The accuracy of calculating emissions from mobile combustion sources is also determined by the factors used to convert
fuel use into emissions. Uncertainty in the factors is primarily due to the variability in which they are measured, and the
variability of the supply source.
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Section 7; Documentation
Section 7: Documentation
Organizations should report data for the appropriate types of mobile sources listed in Table 2. In order to ensure that
emissions calculations are transparent and verifiable, the documentation sources listed should be maintained. These
documentation sources should be collected to ensure the accuracy and transparency of the data, and should also be
included in the organization's IMP.
Table 2: Documentation Sources for Mobile Combustion
Data
Fuel consumption data
Distance traveled data
Fuel economy data
Heat contents and carbon contents used other than
defaults provided
Prices used to convert dollars of purchased to amount or
energy content of fuel consumed
All assumptions made in calculating fuel consumption,
heat contents, and emission factors
Documentation Source
Purchase receipts or utility bills; delivery receipts; contract
purchase or firm purchase records; stock inventory
documentation; metered fuel documentation
Official odometer logs or other records of vehicle distance
traveled
Company fleet records, showing data on fuel economy;
vehicle manufacturer documentation showing fuel economy
Purchase receipts or utility bills; delivery receipts; contract
purchase or firm purchase records; other documentation
from suppliers; EIA, EPA, or industry reports
Purchase receipts; delivery receipts; contract purchase or
fuel firm purchase records; EIA, EPA, or industry reports
All applicable sources
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Direct Emissions from Mobile Sources
Section 8: Inventory Quality Assurance and Quality Control (QA/QC)
Section 8: Inventory Quality Assurance and Quality
Control (QA/QC)
Chapter 7 of the GHG Protocol provides general guidelines for implementing a QA/QC process for all emissions
calculations. For mobile combustion sources, activity data and emission factors can be verified using a variety of
approaches:
• Fuel energy use data can be compared with data provided to Department of Energy or other EPA reports or
surveys.
• If any emission factors were calculated or obtained from the fuel supplier, these factors can be compared to U.S.
average emission factors.
• If actual data are available for both fuel use and distance traveled, distance can be divided by fuel use to calculate
fuel economy. This can be compared to expected fuel economy for that vehicle type as a way to check the
accuracy of the actual data.
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Direct Emissions from Mobile Sources
Appendix A: Default C02 Emission Factors
Appendix A: Default CO2 Emission Factors
This appendix contains default factors for use in calculating C02 emissions for different types of transportation fuels, using
the method described in Section 2.
The emission factors in Table A-l and A-2 can be used in Equation 1 from Section 2 to calculate GHG emissions if fuel use is
known only in mass or volume units, and no information is available about the fuel heat content or carbon content. These
emission factors are developed by multiplying the emission factors in Table A-3 and A-4 by the default heat content of the
fuels, which is also shown in Table A-l and A-2.
The emission factors in Table A-3 and A-4 can be used in Equation 2 from Section 2 to calculate GHG emissions when the
actual fuel heat content is known or when the fuel use is provided in energy units.
All C02 emission factors assume that 100 percent of the carbon content of the fuel is oxidized to C02, as is recommended
by the Intergovernmental Panel on Climate Change (IPCC).
Table A-l: Emission Factors for Equation 1 (EF ) - Emissions per Mass or
Volume Unit for Fossil Fuel Combustion
Heat Content
Emission
Fuel
(HHV)
Factors
Liquid Fuels
(mmBtu/gal)
(kg CO,/gal)
Aviation Gasoline
0.120
8.31
Diesel Fuel
0.138
10.21
Kerosene-type Jet Fuel
0.135
9.75
Liquefied Natural Gas (LNG)
0.085
4.50
Liquefied Petroleum Gases (LPG)
0.092
5.68
Motor Gasoline
0.125
8.78
Residual Fuel Oil
0.150
11.27
Gaseous Fuels
(mmBtu/scf)
(kg CO,/scf)
Compressed Natural gas
0.001026
0.05444
Table A-2: Emission Factors for Equation 1 (EF ) - Emissions per Mass or
Volume Unit for Biomass Fuel Combustion
Heat Content
Emission
Fuel
(HHV)
Factors
Liquid Fuels
(mmBtu/gal)
(kg CO,/gal)
Biodiesel (100%)
0.128
9.45
Ethanol (100%)
0.084
5.75
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Direct Emissions from Mobile Sources
Appendix A: Default C02 Emission Factors
Table A-3: Emission Factors for Equation 2 (EF ) - Emissions per
Energy Unit for Fossil Fuel Combustion
Emission
Fuel Factors
Liquid Fuels (kg C02/gal)
Aviation Gasoline 69.25
Diesel Fuel 73.96
Kerosene-type Jet Fuel 72.22
Liquefied Natural Gas (LNG) 53.06
Liquefied Petroleum Gases (LPG) 61.71
Motor Gasoline 70.22
Residual Fuel Oil 75.10
Gaseous Fuels
Compressed Natural Gas 53.06
Table A-4: Emission Factors for Equation 2 (EF ) - Emissions per Energy
Unit for Biomass Fuel Combustion
Emission
Fuel Factors
Liquid Fuels (kg C02/mmBtul)
Biodiesel (100%) 73.84
Ethanol (100%) 68.44
Source for the emission factors in this appendix: Federal Register (2017) EPA; 40 CFR Part 98; June 13, 2017. Table C-l,
Table C-2, Table AA-1: https://www.ecfr.gov/cgi-bin/text-
idx?SID=ae265d7d6f98ec86fcd8640b9793a3f6&mc=true&node=pt40.23.98&rRn=div5#ap40.23.98 19.1.
LNG sourced from: GREET™ Software, GREET1_2019 Model, Argonne National Laboratory. The GREET model provides
carbon content and fuel density, which are used to develop the C02 emission factor.
U.S. EPA Center for Corporate Climate Leadership - GFIG Inventory Guidance
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Appendix B: Default CH4 and N20 Emission Factors
The U.S. EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks ("EPA Inventory") provides a summary of tests that
have been performed to determine CH4 and N,0 emissions from mobile sources4. Annex 3, Table A-lll of the EPA
Inventory lists CH4 and N,0 emission factors by different types of onroad vehicles and control technologies (see Table B-l).
Also listed is the percent of the different control technologies installed by model year of vehicle (see Tables B-3 through B-
6). These two sources can be combined to determine CH4 and N,0 emission factors by model year of vehicle as shown in
Table B-2. The methodologies and sources used to derive the factors in these tables are documented in the EPA Inventory.
Table B-l: CH4and N20 Emission Factors for Onroad Vehicles
Emission Factor
Vehicle Type/Control Technology
(gCH/mile)
(g N20/mile)
Gasoline Passenger Cars
EPA Tier 2
0.0072
0.0048
Low Emission Vehicles
0.0100
0.0205
EPA Tier 1
0.0271
0.0429
EPA Tier 0
0.0704
0.0647
Oxidation Catalyst
0.1355
0.0504
Non-Catalyst
0.1696
0.0197
Uncontrolled
0.1780
0.0197
Gasoline Light-Duty Trucks
EPA Tier 2
0.0100
0.0025
Low Emission Vehicles
0.0148
0.0223
EPA Tier 1
0.0452
0.0871
EPA Tier 0
0.0776
0.1056
Oxidation Catalyst
0.1516
0.0639
Non-Catalyst
0.1908
0.0218
Uncontrolled
0.2024
0.0220
Gasoline Heavy-Duty Vehicles
EPA Tier 2
0.0297
0.0015
Low Emission Vehicles
0.0300
0.0466
EPA Tier 1
0.0655
0.1750
EPA Tier 0
0.2630
0.2135
Oxidation Catalyst
0.2356
0.1317
Non-Catalyst
0.4181
0.0473
Uncontrolled
0.4604
0.0497
Diesel Passenger Cars
Aftertreatment
0.0302
0.0192
Advanced
0.0005
0.0010
Moderate
0.0005
0.0010
Uncontrolled
0.0006
0.0012
Diesel Light Trucks
Aftertreatment
0.0290
0.2140
Advanced
0.0010
0.0015
4 U.S. EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2018, EPA430-R-20-002, April 2020.
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Table B-l: CH4and N20 Emission Factors for Onroad Vehicles
Vehicle Type/Control Technology
Moderate
Uncontrolled
Diesel Medium-and Heavy-Duty Trucks and Buses
Aftertreatment
Advanced
Moderate
Uncontrolled
Motorcycles
Non-catalyst Control
Uncontrolled
Emission Factor
(g CH4/mile) (g N20/mile)
0.0009
0.0011
0.0095
0.0051
0.0051
0.0051
0.0672
0.0899
0.0014
0.0017
0.0431
0.0048
0.0048
0.0048
0.0069
0.0087
Table B-2: Weighted Average Model Year CH4and N20 Emission Factors for Onroad Vehicles
Emission Factor
Emission Factor
Vehicle Type/Model Year
(g CH4/mile)
(g N20/mile)
Vehicle Type/Model Year
(gCH/mile)
(g N20/mile)
Gasoline Fueled Vehicles
Gasoline Fueled Vehicles
Passenger Cars
Vans, Pickup Trucks, & SUVs
1973-1974
0.1696
0.0197
1973-1974
0.1908
0.0218
1975
0.1423
0.0443
1975
0.1634
0.0513
1976-1977
0.1406
0.0458
1976-1977
0.1594
0.0555
1978-1979
0.1389
0.0473
1978-1979
0.1614
0.0534
1980
0.1326
0.0499
1980
0.1594
0.0555
1981
0.0802
0.0626
1981
0.1479
0.0660
1982
0.0795
0.0627
1982
0.1442
0.0681
1983
0.0782
0.0630
1983
0.1368
0.0722
1984-1993
0.0704
0.0647
1984-1993
0.1294
0.0764
1994
0.0617
0.0603
1994
0.1220
0.0806
1995
0.0531
0.0560
1995
0.1146
0.0848
1996
0.0434
0.0503
1996
0.0813
0.1035
1997
0.0337
0.0446
1997
0.0646
0.0982
1998
0.0240
0.0389
1998
0.0517
0.0908
1999
0.0215
0.0355
1999
0.0452
0.0871
2000
0.0175
0.0304
2000
0.0452
0.0871
2001
0.0105
0.0212
2001
0.0412
0.0787
2002
0.0102
0.0207
2002
0.0333
0.0618
2003
0.0095
0.0181
2003
0.0340
0.0631
2004
0.0078
0.0085
2004
0.0221
0.0379
2005
0.0075
0.0067
2005
0.0242
0.0424
2006
0.0076
0.0075
2006
0.0221
0.0373
2007
0.0072
0.0052
2007
0.0115
0.0088
2008
0.0072
0.0049
2008
0.0105
0.0064
2009
0.0071
0.0046
2009
0.0108
0.0080
2010
0.0071
0.0046
2010
0.0103
0.0061
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Table B-2: Weighted Average Model Year CH4and N20 Emission Factors for Onroad Vehicles
Emission Factor
Emission Factor
Vehicle Type/Model Year
(g CH4/mile)
(g N20/mile)
Vehicle Type/Model Year
(gCH/mile)
(g N20/mile)
Gasoline Fueled Vehicles
Gasoline Fueled Vehicles
2011
0.0071
0.0046
2011
0.0095
0.0036
2012
0.0071
0.0046
2012
0.0095
0.0036
2013
0.0071
0.0046
2013
0.0095
0.0035
2014
0.0071
0.0046
2014
0.0096
0.0034
2015
0.0068
0.0042
2015
0.0096
0.0033
2016
0.0065
0.0038
2016
0.0095
0.0035
2017
0.0054
0.0018
2017
0.0095
0.0033
2018
0.0052
0.0016
2018
0.0094
0.0031
<1980
0.4604
0.0497
1996-2018
0.0672
00069
1981-1984
0.4492
0.0538
1960-1995
0.0899
0.0087
1985-1986
0.4090
0.0515
1987
0.3675
0.0849
1988-1989
0.3492
0.0933
1990-1995
0.3246
0.1142
Diesel Fueled Vehicles
1996
0.1278
0.1680
Passenger Cars
1997
0.0924
0.1726
2007-2018
0.0302
0.0192
1998
0.0655
0.1750
1996-2006
0.0005
0.0010
1999
0.0648
0.1724
1983-1995
0.0005
0.0010
2000
0.0630
0.1660
1960-1982
0.0006
0.0012
2001
0.0577
0.1468
2002
0.0634
0.1673
2003
0.0602
0.1553
2004
0.0298
0.0164
Light Trucks
2005
0.0297
0.0083
2007-2018
0.0290
0.0214
2006
0.0299
0.0241
1996-2006
0.0010
0.0015
2007
0.0322
0.0015
1983-1995
0.0009
0.0014
2008
0.0340
0.0015
1960-1982
0.0011
0.0017
2009
0.0339
0.0015
2010
0.0320
0.0015
2011
0.0304
0.0015
2012
0.0313
0.0015
2013
0.0313
0.0015
Medium- and Heavy-Duty Vehicles
2014
0.0315
0.0015
2007-2018
0.0095
0.0431
2015
0.0332
0.0021
1996-2006
0.0051
0.0048
2016
0.0321
0.0061
1983-1995
0.0051
0.0048
2017
0.0329
0.0084
1960-1982
0.0051
0.0048
2018
0.0326
0.0082
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance 19
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Table B-3: Control Technology Assignments for Gasoline Passenger Cars
Non-
EPA Tier
EPA Tier
CARB
CARB LEV
EPA Tier
CARB LEV EPA Tier
Model Years
catalyst
Oxidation
0
1
LEV
2
2
3 3
1973-1974
100%
-
-
-
-
-
-
-
1975
20%
80%
-
-
-
-
-
-
1976-1977
15%
85%
-
-
-
-
-
-
1978-1979
10%
90%
-
-
-
-
-
-
1980
5%
88%
7%
-
-
-
-
-
1981
-
15%
85%
-
-
-
-
-
1982
-
14%
86%
-
-
-
-
-
1983
-
12%
88%
-
-
-
-
-
1984-1993
-
-
100%
-
-
-
-
-
1994
-
-
80%
20%
-
-
-
-
1995
-
-
60%
40%
-
-
-
-
1996
-
-
40%
54%
6%
-
-
-
1997
-
-
20%
68%
12%
-
-
-
1998
-
-
<1%
82%
18%
-
-
-
1999
-
-
<1%
67%
33%
-
-
-
2000
-
-
-
44%
56%
-
-
-
2001
-
-
-
3%
97%
-
-
-
2002
-
-
-
1%
99%
-
-
-
2003
-
-
-
<1%
85%
2%
12%
-
2004
-
-
-
<1%
24%
16%
60%
-
2005
-
-
-
-
13%
27%
60%
-
2006
-
-
-
-
18%
35%
47%
-
2007
-
-
-
-
4%
43%
53%
-
2008
-
-
-
-
2%
42%
56%
-
2009
-
-
-
-
<1%
43%
57%
-
2010
-
-
-
-
-
44%
56%
-
2011
-
-
-
-
-
42%
58%
-
2012
-
-
-
-
-
41%
59%
-
2013
-
-
-
-
-
40%
60%
-
2014
-
-
-
-
-
37%
62%
1%
2015
-
-
-
-
-
33%
56%
11% <1%
2016
-
-
-
-
-
25%
50%
18% 6%
2017
-
-
-
-
-
14%
1%
29% 56%
2018
-
-
-
-
-
7%
-
42% 52%
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Table B-4: Control Technology Assignments for Gasoline Light-Duty Trucks
Model
Non-
EPA Tier
EPA Tier
CARB
CARB
EPA Tier
CARB
Years
catalyst
Oxidation
0
1
LEV
LEV 2
2
LEV 3
EPA Tier 3
1973-1974
100%
-
-
-
-
-
-
-
-
1975
30%
70%
-
-
-
-
-
-
-
1976
20%
80%
-
-
-
-
-
-
-
1977-1978
25%
75%
-
-
-
-
-
-
-
1979-1980
20%
80%
-
-
-
-
-
-
-
1981
-
95%
5%
-
-
-
-
-
-
1982
-
90%
10%
-
-
-
-
-
-
1983
-
80%
20%
-
-
-
-
-
-
1984
-
70%
30%
-
-
-
-
-
-
1985
-
60%
40%
-
-
-
-
-
-
1986
-
50%
50%
-
-
-
-
-
-
1987-1993
-
5%
95%
-
-
-
-
-
-
1994
-
-
60%
40%
-
-
-
-
-
1995
-
-
20%
80%
-
-
-
-
-
1996
-
-
-
100%
-
-
-
-
-
1997
-
-
-
100%
-
-
-
-
-
1998
-
-
-
87%
13%
-
-
-
-
1999
-
-
-
61%
39%
-
-
-
-
2000
-
-
-
63%
37%
-
-
-
-
2001
-
-
-
24%
76%
-
-
-
-
2002
-
-
-
31%
69%
-
-
-
-
2003
-
-
-
25%
69%
-
6%
-
-
2004
-
-
-
1%
26%
8%
65%
-
-
2005
-
-
-
-
17%
17%
66%
-
-
2006
-
-
-
-
24%
22%
54%
-
-
2007
-
-
-
-
14%
25%
61%
-
-
2008
-
-
-
-
<1%
34%
66%
-
-
2009
-
-
-
-
-
34%
66%
-
-
2010
-
-
-
-
-
30%
70%
-
-
2011
-
-
-
-
-
27%
73%
-
-
2012
-
-
-
-
-
24%
76%
-
-
2013
-
-
-
-
-
31%
69%
-
-
2014
-
-
-
-
-
26%
73%
1%
-
2015
-
-
-
-
-
22%
72%
6%
-
2016
-
-
-
-
-
20%
62%
16%
2%
2017
-
-
-
-
-
9%
14%
28%
48%
2018
-
-
-
-
-
7%
-
38%
55%
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Appendix B: Default CH4 and N20 Emission Factors
Table B-5: Control Technology Assignments for Gasoline Heavy-Duty Vehicles
Model
Non-
EPA Tier
EPA Tier
CARB
CARB LEV
EPA Tier
CARB LEV EPA Tier
Years
Uncontrolled
catalyst
Oxidation
0
1
LEV
2
2
3 3
<1980
100%
-
-
-
-
-
-
-
-
1981-1984
95%
-
5%
-
-
-
-
-
-
1985-1986
-
95%
5%
-
-
-
-
-
-
1987
-
70%
15%
15%
-
-
-
-
-
1988-1989
-
60%
25%
15%
-
-
-
-
-
1990-1995
-
45%
30%
25%
-
-
-
-
-
1996
-
-
25%
10%
65%
-
-
-
-
1997
-
-
10%
5%
85%
-
-
-
-
1998
-
-
-
-
100%
-
-
-
-
1999
-
-
-
-
98%
2%
-
-
-
2000
-
-
-
-
93%
7%
-
-
-
2001
-
-
-
-
78%
22%
-
-
-
2002
-
-
-
-
94%
6%
-
-
-
2003
-
-
-
-
85%
14%
-
1%
-
2004
-
-
-
-
-
33%
-
67%
-
2005
-
-
-
-
-
15%
-
85%
-
2006
-
-
-
-
-
50%
-
50%
-
2007
-
-
-
-
-
-
27%
73%
-
2008
-
-
-
-
-
-
46%
54%
-
2009
-
-
-
-
-
45%
55%
-
2010
-
-
-
-
-
-
24%
76%
-
2011
-
-
-
-
-
-
7%
93%
-
2012
-
-
-
-
-
-
17%
83%
-
2013
-
-
-
-
-
-
17%
83%
-
2014
-
-
-
-
-
-
19%
81%
-
2015
-
-
-
-
-
-
31%
64%
5%
2016
-
-
-
-
-
-
24%
10%
21% 44%
2017
-
-
-
-
-
-
8%
8%
39% 45%
2018
-
-
-
-
-
-
13%
-
35% 52%
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Table B-6: Control Technology Assignments for Diesel Onroad Vehicles and
Motorcycles
Vehicle Type/Control Technology
Years Diesel Passenger Cars and Light-Duty Trucks
Uncontrolled
Moderate control
Advanced control
Aftertreatment
Diesel Medium- and Heavy-Duty Trucks and Buses
Uncontrolled
Moderate control
Advanced control
Aftertreatment
Motorcycles
Uncontrolled
Non-catalyst controls
Model
1960-82
1983-95
1996-2006
2007-2018
1960-90
1991-2003
2004-2006
2007-2018
1960-95
1996-2018
Table B-7 shows the default CH4 and N,0 emission factors for alternative fuel vehicles by vehicle and fuel type.
Table B-7: CH4and N20 Emission Factors for Alternative Fuel Onroad Vehicles
Vehicle Type/Fuel Type
Emission Factor
(gChU/mile) (g N20/mile)
Light Duty Cars
Methanol (Flex Fuel ICE) 0.008 0.006
Ethanol (Flex Fuel ICE) 0.008 0.006
CNG (ICE) 0.082 0.006
CNG (Bi-Fuels) 0.082 0.006
LPG (ICE) 0.008 0.006
LPG (Bi-Fuels) 0.008 0.006
Biodiesel (BD100) 0.03 0.019
Light Duty Trucks
Ethanol (Flex Fuel ICE) 0.012 0.011
CNG (ICE) 0.123 0.011
CNG (Bi-Fuels) 0.123 0.011
LPG (ICE) 0.012 0.013
LPG (Bi-Fuels) 0.012 0.013
LNG 0.123 0.011
Biodiesel (BD100) 0.029 0.021
Medium Duty Trucks
CNG (ICE) 4.2 0.001
CNG (Bi-Fuels) 4.2 0.034
LPG (ICE) 0.014 0.034
LPG (Bi-Fuels) 0.014 0.001
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Table B-7: CH4and N20 Emission Factors for Alternative FuelOnroad Vehicles
Vehicle Type/Fuel Type
Emission Factor
LNG
Biodiesel (BD100)
Heavy Duty Trucks
Neat Methanol (ICE)
Neat Ethanol (ICE)
CNG (ICE)
LPG (ICE)
LPG (Bi-Fuels)
LNG
Biodiesel (BD100)
Buses
Neat Methanol (ICE)
Neat Ethanol (ICE)
CNG (ICE)
LPG (ICE)
LNG
Biodiesel (BD100)
(g ChU/mile)
4.2
0.009
(g N20/mile)
0.043
0.001
0.075
0.075
0.028
0.028
0.001
0.026
0.026
0.001
0.043
3.7
0.013
0.013
3.7
0.009
0.022
0.022
0.032
0.032
0.001
0.017
0.001
10
0.034
10
0.009
0.043
Table B-8 shows the default CH4 and N,0 emission factors for nonroad vehicles by vehicle and fuel type. These emission
factors are based on emission factors in Table A-114 and A-115 of the EPA Inventory which are given in terms of mass of
emissions per mass of fuel combusted. The emission factors are converted to emissions per gallon of fuel using the fuel
density conversions in Annex 6.5 of the EPA Inventory. Emission factors for LPG and biodiesel vehicles are assumed to be
equal to gasoline and diesel vehicles, respectively.
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance 24
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Direct Emissions from Mobile Sources
Appendix B: Default CH4 and N20 Emission Factors
Table B-8: CH4 and N20 Emission Factors for Nonroad Vehicles
Vehicle Type/Fuel Type
Emission Factor
(g CH4/gal fuel) (g N20/gal fuel)
Residual Fuel Oil
0.55
0.55
Ships and Boats
Gasoline (2 stroke)
Gasoline (4 stroke)
9.54
4.88
0.06
0.23
Diesel
0.31
0.50
Locomotives
Diesel
0.80
0.26
Aircraft
Jet Fuel
Aviation Gasoline
7.06
0.30
0.11
Gasoline (2 stroke)
12.96
0.06
Agricultural Equipment
Gasoline (4 stroke)
Diesel
7.24
0.28
0.21
0.49
LPG
2.19
0.39
Agricultural Offroad Trucks
Gasoline
Diesel
7.24
0.13
0.21
0.49
Gasoline (2 stroke)
12.42
0.07
Construction/Mining
Gasoline (4 stroke)
5.58
0.20
Equipment
Diesel
0.20
0.47
LPG
1.05
0.41
Construction/Mining Offroad
Gasoline
5.58
0.20
Trucks
Diesel
0.13
0.49
Gasoline (2 stroke)
15.57
0.06
Lawn and Garden Equipment
Gasoline (4 stroke)
Diesel
5.84
0.33
0.18
0.47
LPG
0.35
0.41
Gasoline
2.58
0.25
Airport Equip.
Diesel
0.17
0.49
LPG
0.33
0.41
Gasoline (2 stroke)
15.14
0.06
Industrial/Commercial
Gasoline (4 stroke)
5.48
0.20
Equipment
Diesel
0.23
0.47
LPG
0.44
0.41
Gasoline (2 stroke)
12.03
0.08
Logging Equipment
Gasoline (4 stroke)
6.71
0.18
Diesel
0.10
0.49
Gasoline
5.78
0.19
Railroad Equipment
Diesel
0.44
0.42
LPG
1.20
0.41
Gasoline (2 stroke)
7.81
0.03
Recreational Equipment
Gasoline (4 stroke)
Diesel
8.45
0.41
0.19
0.41
LPG
2.98
0.38
Source for the emission factors in Appendix B: U.S. EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990- 2018,
EPA 430-R-15-003, April 2020, Tables A-107 through A-115.
U.S. EPA Center for Corporate Climate Leadership - GHG Inventory Guidance
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