Updates to the Greenhouse Gas and
Energy Consumption Rates in
MOVESZOlOa
&EPA
United States
Environmental Protection
Agency
-------
Updates to the Greenhouse Gas and
Energy Consumption Rates in
MOVES2010a
Assessment and Standards Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
NOTICE
This technical report does not necessarily represent final EPA decisions or
positions. It is intended to present technical analysis of issues using data
that are currently available. The purpose in the release of such reports is to
facilitate the exchange of technical information and to inform the public of
technical developments.
&EPA
United States
Environmental Protection
Agency
EPA-420-R-12-025
August 2012
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Contents
1 Updates to Energy Rates and Sourcebin Distribution for MOVES201 Oa 2
1.1 Introduction 2
1.2 Background: Energy Rates in the MOVES model 3
1.3 Structural Changes: 6
1.3.1 Updating the Database Sourcebinid Structure for Energy Rates 6
1.3.2 Converting MOVES2010 rates to the MOVES2010a structure 6
1.3.3 Changes to Engine Technologies 8
1.4 Updating Energy Rates 8
1.5 Inventory Impacts of Changes relative toMOVES2010 13
2 Methane and N2O in MOVES2010 16
Differences Between MOVES and "Sources and Sinks" 16
2.1 Nitrous Oxide Emission Rates: 18
2.2 Methane Emission Rates: 22
2.3 Alternative Fuels 26
3 Updates to the Methane Rates for MOVES 20 lOa 28
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1 Updates to Energy Rates and Sourcebin Distribution for MOVES2010a
1.1 Introduction
MOVES is the U.S. Environmental Protection Agency's (EPA) Motor Vehicle Emission
Simulator. It helps to answer "what if questions, such as "How would particulate matter
emissions decrease in my state on a typical weekday if truck travel was reduced during rush
hour?" or "How does the total hydrocarbon emission rate change if my fleet switches to gasoline
from diesel fuel?" The purpose of the tool is to provide an accurate estimate of emissions from
mobile sources under a wide range of user-defined conditions. It is a state-of-the-art upgrade to
EPA's modeling tools for estimating emissions from highway vehicles, based on analysis of
millions of actual emission test results and considerable advances in the Agency's understanding
of vehicle emissions.
MOVES2010 was released in December of 2009. MOVES2010a was released in the
summer of 2010 and updated MOVES2010. MOVES2010a incorporates new car and light truck
greenhouse gas emissions standards affecting model years 2012 and later (published May 7,
2010) and updates to the Corporate Average Fuel Economy (CAFE) standards affecting model
years 2008 through 2011.1 MOVES2010a includes reductions in greenhouse gas emission rates
associated with those standards in future calendar years, and small reductions in refueling and
sulfur-related emissions associated with the reductions in vehicle fuel consumption. This
document details some of the updates for the MOVES2010a release. Specifically, the updates
described in this document include:
• Updates to the MOVES database to reflect new data and projections for 2008 and
newer light duty energy rates
o Model year 2008-2010 vehicle data
o Model year 2011 Fuel Economy (FE) final rule projections
o Model year 2012-2016 FE/GHG final rule projections
o Corrections to model year 2000+ light duty diesel energy start rates
• Modifications to the organization of energy rates in MOVES database (DB)
o Improved consistency between energy rates and remainder of MOVES
o Redefined energy rate structure
o Removed unused engine technologies from the MOVES DB
o Removed unused emission rates from MOVES DB
This report also documents the methane and nitrous oxide rates, and includes discussion
of the changes made in MOVES2010a in the way that methane emissions are determined for all
vehicle types and model years.
This report assumes that the user is familiar with the MOVES model and its database
design. A detailed knowledge of the emission rate structure may prove helpful to the reader.
1 MOVES2010a, which only contains regulations that were final as of its release, does not reflect the impacts of
Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and
Vehicles (finalized in 2011) or the Proposed Rulemaking to Establish 2017 and Later Model Year Light-Duty
Vehicle Greenhouse Gas Emissions and CAFE Standards (published in 2011).
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Additional detail on MOVES is available on the MOVES technical background website
(http://www.epa.gov/otaq/models/moves/movesback.htm).
1.2 Background: Energy Rates in the MOVES model
The energy rates in MOVES2010 were originally developed for MOVES2004, and are
documented in "MOVES2004 Energy and Emission Inputs Draft Report" (EPA420-P-05-003).
As documented in that report, EPA created the MOVES 2004 energy rates by analyzing second
by second (1 Hz) resolution data from 16 EPA test programs covering approximately 500
vehicles and 26 non-EPA test programs covering approximately 10,760 vehicles. "Holes" in the
data were filled using either the Physical Emission Rate Estimator (PERE) 2 or interpolation.
A partial timeline of the energy rates in MOVES is presented below.
• MOVES2004
o Released with a full suite of energy rates to allow estimation of fuel
consumption and GHG emissions.
o Energy rates developed for fine detail of vehicle attribute and advanced
technology, anticipating need for policy modeling (ex. "How does reducing
vehicle weight affect energy consumption?")
o Documentation: MOVES2004 Energy and Emission Rate Inputs (Report:
EPA420-P-05-003, February 2005)
• MOVES2010
o Relatively minor updates from MOVES2004
o Heavy Duty energy rates updated based on new scaled tractive power (STP)
methodology
o LD rates updated to include 2008-2011 model year 2011 Corporate Average
Fuel Economy (CAFE) Standards for light trucks
• MOVES2010a
o Light Duty energy rates updated substantively to account for CAFE model
year 2011, LD GHG model year 2012-2016 standards
o All energy rates updated structurally to greatly simplify MOVES' energy
approach with focus on inventory development, rather than policy modeling
As seen above, between MOVES 2004 and MOVES2010a, MOVES shifted being from a
technology modeling tool to primarily serving as an inventory model. This shift was partially
driven by the emergence of the EPA OMEGA (Optimization Model for reducing Emissions of
Greenhouse gases from Automobiles) model.3 OMEGA, which EPA used in recent mobile
source greenhouse gas (GHG) rulemakings, 4 estimates the technology cost and emission impacts
of vehicle GHG standards. Many light duty energy policy questions no longer are estimated by
2 Report: Fuel Consumption Modeling of Conventional and Advanced Technology Vehicles in the Physical
Emission Rate Estimator (PERE) EPA420-P-05-001, February 2005
3 OMEGA web address: http://www.epa.gov/otaq/climate/models.htm
OMEGA Version 1.3 documentation: EPA-420-B-10-042
4 Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards; Final
Rule: EPA-HQ-OAR-2009-0472-11424
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EPA with the MOVES model, but rather with the more narrowly focused OMEGA model. At
the same time, the MOVES model has become the official EPA model for estimating mobile
source emissions in State Implementation Plans and conformity modeling.5
Due to this change in scope, EPA reevaluated the structure of the energy rates for
MOVES2010a. In MOVES, emission rates6 are defined by vehicle emission category
(sourcebin) discriminators which describe combinations of vehicle attributes. MOVES allows
different emission rates to be defined by different sourcebin discriminators; a given combination
of pollutant and process can require any combination of the discriminators listed in Table 1-1.
Table 1-1 - Sourcebin Discriminators
Sourcebin Discriminators
Fuel type
Engine Technology
Regulatory Class
Model Year Group
Engine Size
Weight Class
Ultimately, these discriminators are strung together in a rigidly defined format and are
used as unique database keys in the "emissionrate" or "emissionratebyage" tables in MOVES.
Not all source type/pollutant/process combinations require data for all sourcebinid components,
and unused components of the sourcebinid can be left as zeros.7 Previous versions of MOVES,
including MOVES2010, require that energy rates discriminate by all sourcebinid components
other than regulatory class (Table 1-2).
5 Policy Guidance on the Use of MOVES2010 and Subsequent Minor Revisions for State Implementation Plan
Development, Transportation Conformity, and Other Purposes, April 2012,
http://www.epa.gov/otaq/models/moves/documents/420b 12010.pdf
6 The MOVES design treats energy consumption as an emission rate. Therefore, in this document, the term
emissions is interchangeably used to refer to energy.
7 The table "sourcetypepolprocess" in the MOVES DB controls which components of the sourcebinid are required
for each sourcetype, pollutant, and process combination.
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Table 1-2 - MOVES 2004 Energy Sourcebin Discriminators
Fuel Type
Diesel
CXG
LPG
EthanoI(ES5l
MeihanoI(ES5)
OK H,
Liquid H,
Electric
Engine Techuologv
Model Year
Group
Loaded
Weight
Eugiiie Size
This contrasts to the emission rates used for criteria pollutants, which use a broader set of
criteria (Table 1-3).
Table 1-3 - Contrasting Criteria Pollutants and Energy in MOVES2010
Criteria Pollutants
Fuel type
Engine Technology
Regulatory Class
Model Year Group
Engine Size
Weight Class
Age Group
Energy
Fuel type
Engine Technology
Regulatory Class
Model Year Group
Engine Size
Weight Class
Age Group
Note: discriminators in bold, italic are used to classify that set of emissions in MOVES.
In MOVES2010, heavy duty vehicle running energy consumption was restructured
without engine size and weight class sourcebin discriminators.8 MOVES2010a extends this
format to all combinations of sourcetypes and energy-related processes (start, running, extended
idle). Removing two sourcebin discriminators significantly reduces the size of the database
table, and pre-aggregating by engine size and vehicle weight shifts the size/weight calculations
from MOVES onto external sources. A summary table of the changes to the energy sourcebin
structure is presented below (Table 1-4).
Table 1-4 - Changes to Energy Sourcebin Discriminators between MOVES2010 and 2010
Descriptors used in MOVES2010
Fuel type
Model year group (decadal)
Engine size
Vehicle Weight
Size and weight distribution by sourcetype
Engine Technology
Descriptors used
in Moves2010a
Fuel type
Model year group
(single year)
Regulatory class
Report: Development of Emission Rates for Heavy-Duty Vehicles in the Motor Vehicle Emissions Simulator
MOVES2010 (EPA-420-B-12-049)
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1.3 Structural Changes:
1.3.1 Updating the Database Sourcebinid Structure for Energy Rates
Seven database tables were changed to alter the sourcebin discriminators used for energy
rates (Table 1-5). These changes aggregated the database so that size and weight were no longer
distinguishing characteristics. The database was then re-disaggregated according to regulatory
class.
As part of this process, the number of engine technologies in the MOVES database was
reduced. This change altered four additional database tables (Table 1-5). The MOVES2010
engine technologies included hybrid varieties, fuel cell vehicles, and "advanced internal
combustion" vehicles. These technologies were removed from the model, and the associated
emission rates were removed from the emissionratebyage table.
Table 1-5 - Summary of Database Changes required
1
2
3
4
5
6
7
8
9
10
11
Table Name
datasource
emissionrate
emissionratebyage
fuelengfraction
enginetech
fuelengtechassoc
pollutantprocessmodelyear
regclassfraction
sampl evehi cl epopul ati on
sizeweightfraction
sourcetypepolprocess
Change Summary
Added a new datasourceid that refers to this document.
Updated energy rates with new values and sourcebinids
Removed emission rates for enginetypeids other than
conventional internal combustion (1) & electric (30)
Updated fuel and engine type combinations to remove
enginetypes other than 1 & 30
Removed engine technologies other than 1 & 30
Removed engine technologies other than 1 & 30
Changed the energy polprocessids (9101,9102, 9190) to
have single year modelyeargroupids (increase resolution of
rates).
Removed engine technologies other than 1 & 30.
Reflects removal of sizeweightid and engine technologies
(engtechid)
Truncated
Stopped requiring sizeweightid, and began requiring
regclassid for energy polprocessids (9101, 9102, 9190) for
all sourcetypes.
1.3.2 Converting MOVES2010 rates to the MOVES2010a structure
EPA created energy rates for the new sourcebin structure by aggregating the MOVES
2010 energy rates by regulatory class. For those regulatory classes that were mapped to a single
source type, the conversion between the MOVES2010 structure and the MOVES2010a structure
was a 1:1 correspondence. For those sourcetypeids that mapped to several regulatory classes
(Table 1-6), the methodology is described below.
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able 1-6 - Mapping between Sourceusetypes and Regulatory Classe
SourcetypelD
11
21
31,32
41,43,51,52,53,54,61,62
42
Possible
Regulatory Classes
10
20
30,41,42
46,47
46,48
Information from the 1997 and 2002 Vehicle Inventory and Use Survey (VIUS) as
aggregated in the MOVES2010 database table samplevehiclepopulation (SVP) was used as a
mapping tool between regulatory class and source type. The SVP table specifies the distribution
of each source type and model year combination across fuel type, engine technology,
SCCVtypelD,9 engine size, vehicle weight, and regulatory class, with each row specifying a
unique set of attributes. The SVP table was joined to the emissionrate table so that an additional
column was added to the SVP with the corresponding MOVES2010 energy emission rate. This
process was repeated for start rates, running rates, and extended idle rates. This produced a set
of SVP tables, each with an additional emission rate column for the relevant process.
In order to create emission rates by regulatory class, we weighted each emission rate
attached to the SVP table using year 0 populations from the sourcetypeagepopulation table of the
MOVES execution database. The sales for each source type model year combination were
distributed to the appropriate row of the SVP using the SVP stmyfraction column. Using the
sales-based weighting, the emission rates were aggregated by regulatory class, fuel type, and
model year. For start rates, this process was executed for operating mode 108, which is a cold
start. The other seven start operating modes are modifications of a cold start with different soak
times. As in previous version of MOVES, soak time effects derived from a California Air
Resources Board report on uncatalyzed hydrocarbon emissions10 were applied to develop the
other seven operating modes (101,102, 103,104,105,106,107).
For running rates, the process outlined above was necessary only for motorcycles,
passenger cars, passenger trucks, and light commercial trucks. The running rates for other
sourcetypes already had been set to be a single set of rates in MOVES2010.11 This process was
repeated for each operating mode.
In MOVES, only sourcetypeid 62 (long-haul combination truck) has extended idle
operation. Therefore, both regulatory class 46 (Medium Heavy Duty (19.5K Ibs < GVWR <
33K Ibs)) and regulatory class 47 (Heavy Heavy Duty (GVWR > 33K Ibs)) were set to have the
same extended idle rate as MOVES2010 sourcetypeid 62 vehicles.
9 An SCCvtype, or source classification code vehicle type, is an alternative vehicle identification scheme which is
used in the MOVES model.
10 Methodology For Calculating And Redefining Cold And Hot Start Emissions, S. Sabate, March 1996
11 These changes to the heavy duty energy rates are described in the heavy duty vehicles emission rate report. All
heavy duty vehicles uses the same energy rates, but are differentiated by drive cycle and weight. Therefore, the
vehicle specific power (VSP) distribution of these vehicles differs.
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1.3.3 Changes to Engine Technologies
Engine technologies other than conventional internal combustion are not used
substantially in the MOVES2010 default database. While these engine technologies each have
different energy rates (Table 1-7), emission rates for pollutants other than energy are either set
equivalent to the rate for conventional internal combustion vehicles or to zero.12'13 Therefore,
"conventional internal combustion" in the MOVES2010 database is effectively a description of
all engine types other than electric for non-energy emissions. In recognition of this convention,
we removed all engine technologies other than conventional and electric from the MOVES2010a
database.
Table 1-7 - Engine Technologies in MOVES2010
engTechID
1
2
11
12
20
21
22
30
40
50
Engine Technology Name
Conventional Internal Combustion
Advanced Internal Combustion
Moderate Hybrid - Conventional Internal
Combustion
Full Hybrid - Conventional Internal Combustion
Hybrid - Advanced Internal Combustion
Moderate Hybrid - Advanced Internal Combustion
Full Hybrid - Advanced Internal Combustion
Electric
Fuel Cell
Hybrid - Fuel Cell
InMOVES2010a
YES
YES
As reflected in Table 1-7, the database tables were altered to reflect these changes.
Additionally, the emission rates supporting these engine technologies (2.8 million rows) were
removed from the 4 million row MOVES2010 emissionratebyage table. Approximately 8,600
rows were removed from the emissionrate table.
1.4 Updating Energy Rates
After modifying the database structure and populating it with transformed energy rates,
several additional changes were made. The 2008 and newer model year light duty vehicles
(regulatory classes 20 and 30) were updated based on new data (model year 2008-2009) and
rulemaking projections (model year 2010+). We also updated the energy emission rates to
reflect the 2011 CAPE rulemaking and the 2012-2016 Light Duty Greenhouse Gas (LD GHG)
and CAFE rulemakings. A number of other minor changes were also made.14'15
12 As an example, advanced internal combustion engines have criteria emission rates equivalent to conventional
internal combustion engines, but electric engines have criteria emission rates equaling zero.
13 In Draft MOVES2009 and MOVES2010, sourcerypeid 31 and 32 have non-zero penetrations of engtechid 2 in
model years 2008 and newer. In earlier model versions, engine tech 2 was used as a means of reaching the fuel
economy targets set in the 2008-2011 CAFE light truck rule. The changes described in this document negate the
need for the penetration of advanced engine technology.
14 An error was corrected in light duty diesel energy starts. To fix the problem, start-emission rates for model year
2000 and newer light and medium duty diesel vehicles (reg class 20, 30, 41, &42) were set to the MY 1999 rate.
This is an approximately 55% reduction from the corresponding rates in the MOVES2010 database. While a large
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The new energy consumption rates were based on a top-down analysis whereby CO2
emission rates output from MOVES were calibrated to projected CC>2 emission rates. CC>2
emissions were used due to their direct proportionality to energy consumption rates. We assume
that the rulemakings affected the quantity of energy consumed, but not the distribution between
operating modes, nor the ratio between start and running.16 As a result, we adjusted the energy
rates using simple ratios between the old emission rates and the new emission rates (Table 1-8).
Baseline values were derived by running MOVES2010 at the national/annual level using an
input database that produced emission output only for regulatory classes 20 and 30. Emission
quantity was divided by vehicle miles traveled to determine emission rates.
Model year 2008 and model year 2009 data were drawn from EPA's "Light-Duty
Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends: 1975 through
2009" (EPA420-R-09-014). The "Lab" average CO2 values for each model year were adjusted
upward by 25% to reflect real world fuel consumption.17 The gasoline vehicles were set to this
value. As the CAFE rules regulate fuel consumption in miles per gallon and treat gasoline and
diesel vehicles equally, diesel energy consumption rates were multiplied by approximately 1.15
in order to compensate for the greater energy density of diesel fuel.18
For model year 2011 through 2016, rates were derived from the model year 2012-2016
Light Duty Greenhouse Gas (LD GHG) rulemaking analysis. The projections used in
MOVES2010a are based upon the same assumptions as used the emission modeling conducted
for the LD GHG rule. Model year 2010 was interpolated as a midpoint between model year
2009 and 2011. Note that the regulatory standards for model year 2011 and newer are in a
classification schema that differs from that used in MOVES2010a.19 Using vehicle level data
from the rulemaking, we reanalyzed the vehicles to match the MOVES2010a vehicle
classification scheme. As a result of this difference in classification scheme, the average CC>2
emission rate shown in this document is not expected to match those in the regulatory
documents.
fraction of this particular process, light duty diesel energy consumption is approximately 3% of total light and
medium duty energy consumption, and start emissions are approximately 3% of light and medium duty diesel
energy consumption. The impact of this change on total light and medium duty energy consumption is
approximately 0.05%.
15 The 2008-2011 CAFE light truck rule was reflected inMOVES2010 through the use of advanced internal
combustion vehicles. For MOVES20 lOa, we removed this engine technology and directly modified the energy rates
for regclassid 30 to reflect the CAFE rules.
16 Maintaining the same ratio between running and start energy consumption rates likely overstates the reductions to
the start process, and may be revisited in future MOVES model versions. While some technologies that reduce
energy consumption (ie, engine downsizing) reduce start energy consumption, many others (such as aerodynamic
improvements) do not. As starts are a very small portion of total energy consumption, the choice of approach has
little impact.
17 Final Rulemaking: Light-Duty Vehicle Greenhouse Gas Emissions Standards and Corporate Average Fuel
Economy Standards (published May 7, 2010). In miles per gallon, there is approximately a 25% gap between
laboratory measured and real world achieved fuel economies.
18 The relative energy densities of diesel and gasoline fuel are approximately 129,000 btu/gallon and 115,000
btu/gallon respectively.
19 In MYs 2011 and later, small SUVs are considered cars, rather than light trucks under the CAFE and GHG
regulations.
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Projected improvements in air conditioning system efficiency were included in the
energy rates themselves rather than in a modification of the MOVES2010a air conditioning
function. However, because the MOVES A/C adjustments are multiplicative, this change will
also reduce the energy consumption from air conditioning.
For the model year 2011 CAFE standards, a 1.15x adjustment was made for diesel
vehicles. For 2012 and beyond, the diesel vehicles were presumed to meet the same CC>2
standard as the gasoline vehicles.
Rates for model years after 2016 were set equivalent to model year 2016. The following
tables (Table l-9,Table l-10,Table 1-11, & Table 1-12) show the g/mile rate for the laboratory
combined Federal Test Procedure (FTP)THighway Fuel Economy Test (FIFET) driving schedules
and on-road value equivalents. The tables showing on-road values are what were used to modify
the model. Note that no source type is composed solely of regulatory class 30, and that these
tables were produced using a set of user input files that isolate the output of this regulatory class.
Table 1-8 - Ratios used to develop new rates in MOVES2010a
20
2008
2009
2010
2011
2012
2013
2014
2015
2016
Ratios Used
From MOVES2010 to MOVES2010a
Trucks
Gas
0.904
0.896
0.898
0.831
0.790
0.769
0.747
0.716
0.677
Diesel
0.723
0.716
0.717
0.663
0.550
0.535
0.519
0.497
0.470
Cars
Gas
0.981
0.969
0.985
1.002
0.919
0.893
0.868
0.830
0.782
Diesel
1.007
0.995
1.011
1.028
0.823
0.800
0.777
0.743
0.700
20 Note that these ratios were applied against the emissionrate table, and that the model year 2008-2011 light duty
truck rule was reflected in MOVES2010 through an engine technology mix. Thus, the CC>2 output from
MOVES2010 was actually quite a bit lower than these ratios would indicate.
10
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Table 1-9 - Test Cycle MPG
2008
2009
2010
2011
2012
2013
2014
2015
2016
MPG - Test Cycle
MOVES2010
Trucks
Gas
20.5
20.5
20.6
20.6
20.7
20.7
20.7
20.7
20.8
Diesel
16.4
16.4
16.4
16.4
16.5
16.5
16.5
16.5
16.5
Cars
Gas
29.7
29.7
29.8
29.8
29.9
29.9
30.0
30.0
30.0
Diesel
26.7
26.7
26.7
26.8
26.8
26.8
26.8
26.9
26.9
MOVES2010a
Trucks
Gas
22.7
22.9
22.9
24.8
26.1
26.9
27.7
29.0
30.7
Diesel
22.7
22.9
22.9
24.8
29.9
30.8
31.7
33.2
35.1
Cars
Gas
30.5
30.9
30.4
29.9
32.7
33.7
34.7
36.3
38.5
Diesel
30.5
30.9
30.4
29.9
37.4
38.5
39.7
41.5
44.1
Table 1-10 - On-road MPG
2008
2009
2010
2011
2012
2013
2014
2015
2016
MPG - On Road
MOVES2010
Trucks
Gas
16.4
16.4
16.5
16.5
16.5
16.5
16.6
16.6
16.6
Diesel
13.1
13.1
13.1
13.1
13.2
13.2
13.2
13.2
13.2
Cars
Gas
23.8
23.8
23.8
23.9
23.9
23.9
24.0
24.0
24.0
Diesel
21.3
21.4
21.4
21.4
21.4
21.5
21.5
21.5
21.5
MOVES2010a
Trucks
Gas
18.1
18.3
18.3
19.9
20.9
21.5
22.2
23.2
24.5
Diesel
18.1
18.3
18.3
19.8
23.9
24.6
25.4
26.5
28.1
Cars
Gas
24.4
24.7
24.3
24.0
26.2
26.9
27.7
29.0
30.8
Diesel
24.4
24.7
24.3
24.0
30.0
30.8
31.8
33.2
35.3
11
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Table 1-11 - Test-Cycle CO2
2008
2009
2010
2011
2012
2013
2014
2015
2016
CO2 - Test Cycle
MOVES2010
Trucks
Gas
433.9
432.9
431.9
431.1
430.3
429.6
429.0
428.4
427.8
Diesel
621.8
621.0
620.1
619.4
618.7
618.1
617.5
617.0
616.5
Cars
Gas
299.2
298.7
298.3
297.8
297.4
297.0
296.7
296.4
296.1
Diesel
381.9
381.3
380.8
380.4
380.0
379.6
379.2
378.9
378.6
MOVES2010a
Trucks
Gas
392.0
388.0
388.0
358.1
339.9
330.6
320.5
306.6
289.6
Diesel
449.4
444.8
444.8
410.5
340.2
330.9
320.8
306.9
289.9
Cars
Gas
291.4
287.6
292.0
296.8
271.9
264.1
256.4
245.0
230.6
Diesel
333.7
329.4
334.5
339.9
271.9
264.1
256.4
245.0
230.6
Table 1-12 - On-road CO2
2008
2009
2010
2011
2012
2013
2014
2015
2016
CO2 - On Road
MOVES2010
Trucks
Gas
542.3
541.1
539.9
538.9
537.9
537.0
536.2
535.5
534.8
Diesel
777.3
776.2
775.2
774.2
773.4
772.6
771.9
771.2
770.6
Cars
Gas
374.1
373.4
372.8
372.3
371.7
371.3
370.8
370.4
370.1
Diesel
477.3
476.7
476.1
475.5
475.0
474.5
474.0
473.6
473.2
MOVES2010a
Trucks
Gas
490.0
485.0
485.0
447.6
424.9
413.2
400.6
383.2
362.0
Diesel
561.7
556.0
556.0
513.1
425.3
413.6
401.0
383.6
362.3
Cars
Gas
364.2
359.5
365.0
370.9
339.8
330.1
320.5
306.3
288.2
Diesel
417.2
411.8
418.1
424.9
339.8
330.1
320.5
306.3
288.2
12
-------
Following the conventions in MOVES2010, for all years, electricity, E85 (85%
ethanol/gasoline blends), and compressed natural gas (CNG) energy consumption rates were set
equal to gasoline. Based on MOVES2010, CNG start energy rates were set equal to the gasoline
rates for starts multiplied by 1.05
1.5 Inventory Impacts of Changes relative to MOVES2010
The structural changes described in this document had little impact on model results. For
any pollutant, national annual scale runs conducted for calendar year 2001 with the new database
differ by less than 0.1% as compared to MOVES2010. A few specific processes related to
energy differ by greater amounts (<10%), but have insignificant impact on total inventories.
With one exception, there are no changes in processes unrelated to energy.21
The data changes, which reflect new data and the model year 2012-2016 LD GHG
rulemaking, impact the results to a greater extent than the structural changes. As described
above, we conducted national annual runs in order to estimate the impact of the database
changes. The structural changes were evaluated with a national annual run in calendar year
2001. Calendar year 2001 was chosen because it predates any of the new data in the database. A
second run was conducted in calendar year 2021 to assess the impact of the new data and
projections for model year 2008 and newer. The MOVES runs were conducted with all vehicle
types and all fuel types.
21 Ammonia (NH3) emissions also increase with the new database. The MOVES2010 database did not have NH3
emission rates for engine technologies other than conventional internal combustion. Therefore the advanced internal
combustion light trucks in MOVES2010 erroneously did not produce NH3 emissions. MOVES2010a fixes this
issue.
13
-------
Table 1-13 - Fuel/Pollutant/Process affected in Calendar Year 2001
Fuel
Affected
CNG
CNG
CNG
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
CNG
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Pollutant
Affected
90
91
93
115
105
31
90
105
115
91
92
93
31
98
98
105
115
115
105
92
31
90
93
91
31
Pollutant (Text)
CO2
Energy
Energy
PM2.5 - Sulfate
PM10 - Sulfate
SO2
CO2
PM10
PM2.5
Energy
Energy
Energy
SO2
CO2
CO2
PM10- Sulfate
PM2.5- Sulfate
PM2.5- Sulfate
PM10- Sulfate
CO2
SO2
Energy
Energy
Energy
SO2
Processes
Affected
2
2
2
2
2
16
2
16
16
2
2
2
2
2
2
16
16
2
2
2
2
2
2
2
16
Process (Text)
Starts
Starts
Starts
Starts
Starts
Crankcase - Starts
Starts
Crankcase - Starts
Crankcase - Starts
Starts
Starts
Starts
Starts
Starts
Starts
Crankcase - Starts
Crankcase - Starts
Starts
Starts
Starts
Starts
Starts
Starts
Starts
Crankcase - Starts
% Change
807
/O
807
/O
-8%
-4%
-4%
-4%
-4%
-4%
-4%
-4%
-4%
-4%
-4%
-4%
-2%
-1%
-1%
-1%
-1%
-1%
-1%
-1%
-1%
-1%
-1%
The calendar year 2001 results shown in Table 1-13 are driven by the modification of the
energy rate sourcebins from a size/weight basis to a regulatory class basis. These effects are
minimal on most pollutants and processes. Specifically, the organizational changes to the
database had no effect on heavy duty running rates, which had already been aggregated in this
manner. It also had minimal effect on those source types (passenger cars and motorcycles),
which have a 1:1 to relationship with regulatory class. All the processes listed above are related
to starts, which have a relatively small impact on total energy consumption.
Passenger truck and light commercial trucks are the only source types that were
composed of similar regulatory classes in MOVES 2010 but different size/weight distributions.
As a result, post-aggregation, the revised energy rates for each of these vehicles converged into a
population weighted average of the two sets of energy rates. In regulatory class 30, the diesel
fuel type is dominated by light commercial trucks, while the gasoline fuel type is dominated by
passenger trucks. For further detail, a narrower light truck inventory comparison between
MOVES2010 and MOVES2010a is shown below for calendar year 2007 (Table 1-14):
14
-------
Table 1-14 - Comparison of National CO2 Inventories in Calendar Year 2007 (Million Metric Tons)
Gasoline Passenger Truck
Gasoline Light Commercial Truck
Diesel Passenger Truck
Diesel Light Commercial Truck
Total
MOVES2010
400.6
132.2
10.2
22.6
565.6
MOVES2010a
415.0
122.7
9.8
23.0
570.4
Difference Percentage
3.6%
-7.2%
-4.7%
1.9%
0.9%
In the second MOVES test run (calendar year 2021), we evaluated the impact of the
energy rate updates (Table 1-15). As the scope of the impacts is larger, the table below is
aggregated by emission process in order to show impacts by fuel and pollutant. Decreases are
seen in energy related pollutants such as PM sulfate, energy and CC>2, 862. Smaller reductions
are seen in ethanol emissions, as well as those emissions related to refueling and spillage.
Table 1-15 - Impacts of Changes in Calendar Year 2021
Fuel Affected
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Gasoline
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Diesel
Gasoline
Diesel
Gasoline
Pollutant
Affected
115
105
92
91
93
90
31
98
21
87
80
79
86
1
92
93
91
90
98
105
115
31
5
30
30
Pollutant (Text)
PM2.5 - Sulfate
PM10 - Sulfate
Energy
Energy
Energy
CO2
SO2
CO2
Ethanol
voc
NMOG
NMHC
TOG
THC
Energy
Energy
Energy
CO2
CO2
PM10
PM2.5
SO2
Methane
NH322
NH3
%
Change
-14%
-14%
-14%
-14%
-14%
-14%
-14%
-14%
-5%
-2%
-2%
-2%
-2%
-2%
-1%
-1%
-1%
-1%
-1%
-1%
-1%
-1%
1%
7%
25%
: As noted in 21 above, this increase in ammonia emissions is due to a related fix.
15
-------
2 Methane and N2O in MOVES2010
In MOVES2004, EPA based its estimates of emissions of methane (CH4) and nitrous
oxide (N2O) on test results of the Federal Test Procedure (FTP) and the then current
version of EPA's "Inventory of U.S. Greenhouse Gas Emissions and Sinks." For Draft
MOVES2009, EPA used both an enlarged database of test results plus a newer version of
EPA's "Sources and Sinks" report23 (primarily Table A-88 of its Annex 3).
EPA used the estimates from its "Sources and Sinks" report to fill holes its test data
(i.e., when either no or limited results from Federal Test Procedure (FTP) were
available).
Emission rates for N2O and for CH4 in Draft MOVES2009 were estimated for engine
starts and for running operation and were not calculated for individual operating modes.
This is in contrast to rates for other pollutants (e.g., HC, CO, NOx) for which running
emissions are calculated for each of 23 operating modes (based on vehicle speed and
power) and for which start emissions are calculated for each of 8 operating modes (based
on vehicle soak time prior to engine start).
Differences Between MOVES and "Sources and Sinks"
EPA publishes an annual report of emissions of greenhouse gases ("Inventory of U.S.
Greenhouse Gas Emissions and Sinks"). Although the basic emission rates in EPA's
"Sources and Sinks" report are based on technology groups, the basic emission rates in
MOVES are based on (among other parameters) model year groups. Therefore , the
initial analysis was to estimate emission rates by technology groups and then to convert
those to model year groups. The conversion from technology groups to individual model
years was based on the distribution of the individual technologies in each model year as
detailed in the "Sources and Sinks" report (Tables A-84 through A-87 of the 2008
publication).
A second difference between those sets of rates is that the rates in EPA's "Sources and
Sinks" report are estimates of emissions over the entire FTP driving cycle (in grams per
mile) including the engine start while those in MOVES are given separately for starts
(grams per start) and running operation (grams per hour).
To estimate running emission rates of N2O and CFLi in the draft MOVES2009 model,
EPA used the same approach that it used in the analysis for the MOVES2004 model.
That is, EPA assumed that the hourly emissions rate for the Bag-2 portion of the FTP is
representative of the overall running rate (in grams per hour). To calculate this rate, EPA
multiplied the Bag-2 emissions (in grams per mile) by the average speed of Bag-2 (i.e.,
16.023 miles per hour), which produces the requisite emission rate (in units of grams per
hour).
23 "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 - 2006," EPA Report No. EPA 430-R-08-005,
April 2008. Available at: http://www.epa.gov/climatechange/emissions/usinventoryreport.html
16
-------
Multiplying that hourly rate by the duration of the full LA-4 driving cycle (i.e., 1,372
seconds or 0.381111 hours) yields the total estimated running emissions of the LA-4 (or
FTP) in grams. Then, multiplying the composite FTP emissions (in grams per mile) by
the length of the LA-4 driving cycle (7.45 miles) yields the estimated total emissions (in
grams) produced during the FTP. Subtracting those two quantities (total grams emitted
during the FTP minus the total grams from the running emissions) yields an estimate of
the emissions (in grams) from a generic start (57 percent hot-start and 43 percent cold-
start).
It is these two rates (running emissions in grams per hour and generic start emissions
in grams per start) that EPA used in the MOVES2004 model and updated in the Draft
MOVES2009 model.
17
-------
2.1 Nitrous Oxide Emission Rates:
Table 3-1 compares the nitrous oxide FTP emission rates (by technology group) from
EPA's "Sources and Sinks" report, the comparable rates from MOVES2004, and the
means of test data obtained from a study by Environment Canada.24
Table 2-1: Comparison of FTP Nitrous Oxide Emissions (grams / mile)
Vehicle Type /
Control Technology
Gasoline Passenger Cars
EPA Tier 2
LEVs
EPA Tier!
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Light-Duty Trucks
EPA Tier 2
LEVs
^ATierl
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Heavy-Duty Vehicles
EPA Tier 2
LEVs
gp^"^7i
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
"Sources &
Sinks" Rnt
0.0036
0.0150
676429
0.0647
o76504
0.0197
0.0197
0.0066
0.0157
0.0871
0.1056
676639
0.0218
0.0220
0.0134
0.0320
O7i75(j
0.2135
O7i3i7
0.0473
0.0497
MOVES2004
0.012
0.012
61)30
0.054
67642
0.017
0.017
0.009
0.009
67667
0.090
67654
0.019
0.019
0.019
0.019
67i"38
0.183
67113
0.041
0.043
FTP Data
0.0050
0.0101
676283
0.0538
—
—
—
—
0.0148
676674
0.0370
676906
—
—
—
—
—
0.0814
—
—
—
"Greenhouse Gas Emissions from 1997-2005 Model Year Light Duty Vehicles," Environment Canada Report No.
ERMD Report #04-44.
18
-------
Comparison of FTP Nitrous Oxide Emissions (grams / mile) Con't
Vehicle Type /
Control Technology
Diesel Passenger Cars
Advanced
Moderate
Uncontrolled
Diesel Light-Duty Trucks
Advanced
Moderate
Uncontrolled
Diesel Heavy-Duty Vehicles
Advanced
Moderate
Uncontrolled
Motorcycles
Non-Catalyst Control
Uncontrolled
"Sources &
Sinks" Rpt
0.0010
0.0010
0.0012
0.0015
0.0014
0.0017
0.0048
0.0048
0.0048
0.0069
0.0087
MOVES2004
0.001
0.001
0.001
0.002
0.002
0.002
0.005
0.005
0.005
0.007
0.009
FTP Data
—
—
—
—
0.0049
—
—
—
Twenty-two of the thirty-two technology groups contain no FTP N2O test data. For those
rates, we use the "Sources and Sinks" data.
19
-------
In the following table, we take those 32 composite FTP N2O rates (22 based on the "Sources
and Sinks" rates and the remaining 10 based on newer FTP test data) and disaggregate them into
running rates (in grams per hour) and start rates (in grams per generic start).
Table 2-2: Separating Composite FTP N2O Emissions into Running and Start
Vehicle Type /
Control Technology
Gasoline Passenger Cars
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Light-Duty Trucks
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Heavy-Duty Vehicles
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
FTP Comp
(g / mile)
0.0050
0.0101
OXJ283
0.0538
670504''
0.0197
0.0197
0.0066
0.0148
070674
0.0370
076906
0.0218
0.0220
0.0134
0.0320
671750
0.0814
67i'3i7
0.0473
0.0497
Running
(g / hour)
0.0399
0.0148
6;23i6
0.6650
a<5235
0.2437
0.2437
0.0436
0.0975
0.6500
0.2323
0.8492
0.2044
0.2062
0.1345
0.3213
L7569
0.8172
L"3222
0.4749
0.4990
Start
(g / start)
0.0221
0.0697
671228"
0.1470
61379
0.0539
0.0539
0.0325
0.0728
'672546
0.1869
63513
0.0845
0.0853
0.0486
0.1160
6^6342
0.2950
0';4773
0.1714
0.1801
20
-------
Separating Composite FTP N2O Emissions into Running and Start Con't
Vehicle Type /
Control Technology
Diesel Passenger Cars
Advanced
Moderate
Uncontrolled
Diesel Light-Duty Trucks
Advanced
Moderate
Uncontrolled
Diesel Heavy-Duty Vehicles
Advanced
Moderate
Uncontrolled
Motorcycles
Non-Catalyst Control
Uncontrolled
FTP Comp
(g / mile)
0.0010
0.0010
0.0012
0.0015
0.0014
0.0017
0.0049
0.0048
0.0048
0.0069
0.0087
Running
(g / hour)
0.0168
0.0168
0.0202
0.0253
0.0236
0.0286
0.0828
0.0809
0.0809
0.0854
0.1076
Start
(g / start)
0.0010
0.0010
0.0012
0.0015
0.0014
0.0018
0.0051
0.0049
0.0049
0.0189
0.0238
21
-------
2.2 Methane Emission Rates:
The following table (table 3-3) compares the methane FTP emission rates (by technology
groups) from the EPA's "Sources and Sinks" report, the rates from MOVES2004, and the means
of the Environment Canada test data.
Table 2-3: Comparison of FTP Methane Emissions (grams / mile)
Vehicle Type /
Control Technology
Gasoline Passenger Cars
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Light-Duty Trucks
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Heavy-Duty Vehicles
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
"Sources &
Sinks" Rpt
0.0173
0.0105
0.0271
0.0704
0.1355
0.1696
0.1780
0.0163
0.0148
0.0452
0.0776
0.1516
0.1908
0.2024
0.0333
0.0303
0.0655
0.2630
0.2356
0.4181
0.4604
MOVES2004
0.013
0.013
0.020
0.066
0.133
0.162
0.171
0.017
0.017
0.034
0.071
0.143
0.184
0.195
0.034
0.034
0.047
0.218
0.208
0.403
0.445
FTP Data
0.0110
0.0083
0.0242
0.0665
0.1351
0.1568
—
—
0.0117
0.0357
0.0708
0.1413
0.0390*
—
—
—
0.0515
0.2487
0.2135
—
—
* Possible outlier (single test vehicle).
22
-------
Comparison of FTP Methane Emissions (grams / mile) Con't
Vehicle Type /
Control Technology
Diesel Passenger Cars
Advanced
Moderate
Uncontrolled
Diesel Light-Duty Trucks
Advanced
Moderate
Uncontrolled
Diesel Heavy-Duty Vehicles
Advanced
Moderate
Uncontrolled
Motorcycles
Non-Catalyst Control
Uncontrolled
"Sources &
Sinks" Rot
0.0005
0.0005
0.0006
0.0010
0.0009
0.0011
0.0051
0.0051
0.0051
0.0672
0.0899
MOVES2004
0.001
0.001
0.001
0.001
0.001
0.002
0.004
0.004
0.004
0.067
0.090
FTP Data
—
—
—
—
0.0039
—
—
—
Note that 17 of the 32 technology groups have no FTP CFLt test data. For those rates, the
"Sources and Sinks" data for the FTP rates were used. Also, for non-catalyst light-duty gasoline
trucks, there was only one FTP result, and that single FTP methane result appears to be an outlier
(i.e., too low). Therefore, for that technology group we also used the "Sources and Sinks" rate.
In the following table (Table 3-4), those 32 composite FTP CFLt rates (18 based on the
"Sources and Sinks" rates and the remaining 14 based on newer FTP test data) were
disaggregated into running rates (in grams per hour) and start rates (in grams per generic start).
23
-------
Table 2-4: Separating Composite FTP CH4 Emissions into Running and Start
Vehicle Type /
Control Technology
Gasoline Passenger Cars
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Light-Duty Trucks
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
Gasoline Heavy-Duty Vehicles
EPA Tier 2
LEVs
EPA Tier 1
EPA Tier 0
Oxidation Catalyst
Non-Catalyst Control
Uncontrolled
FTP Comp
(g / mile)
0.0110
0.0083
0.0242
0.0665
0.1351
0.1568
0.1780
0.0163
0.0117
0.0357
0.0708
0.1413
0.1908
0.2024
0.0333
0.0303
0.0515
0.2487
0.2135
0.4181
0.4604
Running
(g / hour)
0.1131
0.0632
'673164
0.9952
271613
2.3654
2.6855
0.1114
0.0801
03775
0.9788
2.0255
0.4807
2.4970
0.3111
0.2831
0.48J6
3.6353
2.8555
5.5908
6.1565
Start
(g / start)
0.0386
0.0379
'676596
0.1165
671831
0.2666
0.3026
0.0790
0.0568
O7i223
0.1544
072808
0.1071
0.5563
0.1295
0.1179
072005
0.4674
'675026
0.9841
1.0837
24
-------
Separating Composite FTP CH4 Emissions into Running and Start Con't
Vehicle Type /
Control Technology
Diesel Passenger Cars
Advanced
Moderate
Uncontrolled
Diesel Light-Duty Trucks
Advanced
Moderate
Uncontrolled
Diesel Heavy-Duty Vehicles
Advanced
Moderate
Uncontrolled
Motorcycles
Non-Catalyst Control
Uncontrolled
FTP Comp
(g / mile)
0.0005
0.0005
0.0006
0.0010
0.0009
0.0011
0.0039
0.0051
0.0051
0.0672
0.0899
Running
(g / hour)
0.0098
0.0098
0.0117
0.0195
0.0176
0.0215
0.0765
0.0997
0.0997
1.0138
1.3563
Start
(g / start)
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.1143
0.1528
25
-------
2.3 Alternative Fuels
Since no additional FTP data were available, the emission rates of N2O and CFLt in the draft
MOVES2009 model are based entirely on EPA's "Inventory of U.S. Greenhouse Gas Emissions
and Sinks: 1990 - 2006" (Table A-89 of its Annex 3). Those FTP rates from that report are
reproduced in the following table (Table 3-5):
Table 2-5 Composite FTP Emissions from Alternative Fuels
Vehicle Type /
Fuel Type
Light-Duty Vehicles
Methanol
CNG
LPG
Ethanol
Biodiesel (BD20)
Heavy-Duty Vehicles
Methanol
CNG
LNG
LPG
Ethanol
Buses
Methanol
CNG
Ethanol
N20
(g / mile)
0.067
0.050
0.067
0.067
0.001
0.175
0.175
0.175
0.175
0.175
0.175
0.175
0.175
CH4
(g / mile)
0.018
0.737
0.037
0.055
0.000
0.066
1.966
1.966
0.066
0.197
0.066
1.966
0.197
26
-------
Disaggregating those composite FTP rates into start and running rates yields the following
results:
Table 2-6: Methane Emission Rates from Alternative Fuels
Vehicle Type /
Fuel Tvne
Light-Duty Vehicles
Methanol
CNG
LPG
Ethanol
Heavy-Duty Vehicles & Buses
Methanol
CNG
LNG
LPG
Ethanol
Running
(g / hour)
0.2192
8.9755
0.4506
0.6698
0.8038
23.9429
23.9429
0.8038
2.3992
Starts
(g / start)
0.0506
2.0700
0.1039
0.1545
0.1854
5.5218
5.5218
0.1854
0.5533
Table 2-7: Nitrous Oxide Emission Rates from Alternative Fuels
Vehicle Type /
Fuel Tvne
Light-Duty Vehicles
Methanol
CNG
LPG
Ethanol
Heavy-Duty Vehicles & Buses
Methanol
CNG
LNG
LPG
Ethanol
Running
(g / hour)
0.6431
0.4799
0.6431
0.6431
1.6797
1.6797
1.6797
1.6797
1.6797
Starts
(g / start)
0.2541
0.1896
0.2541
0.2541
0.6636
0.6636
0.6636
0.6636
0.6636
27
-------
3 Updates to the Methane Rates for MOVES 2010a
For MOVES2010a, the MOVES calculations to derive methane (CH4 ) from total
hydrocarbons (THC) values were updated, rather than as a separate emission rate as in earlier
versions of the model. This change more closely aligns the methane calculations with the
calculation of other hydrocarbon compounds in MOVES. As an example, volatile organic
compounds (VOCs) are calculated in a chained (multiplicative) manner rather than as
independent emission rate. Similarly, the chained calculation of methane is based upon the
assumption of a direct relationship between CH4 and THC by age, vehicle type, and fuel. As
seen earlier in this report, those vehicles that tend to have higher THC (such as heavy duty
vehicles) also tend to have higher methane emissions.
In the MOVES calculations, methane must be removed from the THC inventory in order
to calculate values for other hydrocarbon species needed in air quality analysis. However, as the
standalone methane emission rates were neither age nor temperature sensitive, there were some
disconnects between THC and methane (where THC varied with age and temperature, but
methane did not). "Chaining" the calculation of methane emissions to THC values allows EPA
to make these improvements to the methane inventory, as well.
Additionally, connecting THC and methane removes a potential issue where methane
emissions could have exceeded THC emissions. Where THC and CH4 are both calculated
independently in MOVES2010 and earlier MOVES versions, MOVES could calculate a negative
amount for these other compounds, which is physically not possible.
In MOVES2010a, CH4 is calculated by applying a multiplicative factor (CH4THCRAtio
in the MethaneTHCRatio table) to the calculated THC value after all adjustments to THC have
been made for all fuel types. Once the CH4 value has been determined, CH4 is used in MOVES
as it was before in all further calculations.
To create the new rates for pre-model year 2003 vehicles, methane and THC Emission
rates for all gasoline and diesel vehicles were read from the movesoutput file and the ratio is
computed. Light duty vehicle, light duty truck, and heavy duty gasoline vehicles were the only
source types which were run. All of the other source types were filled with these data.
Motorcycles were filled with light duty vehicle rates.
To create the new ratios for 2004 and newer vehicles, the MOVES 2010a rates were
transferred from the MOVES2010 data using a process similar to that described above. The
LDV rates are again used for the motorcycles.
The methane ratios for 2007 and newer model year diesel trucks were not taken from the
MOVES2010 estimates. The constant value of 0.5846 was derived from new technology diesel
vehicle emission testing done for the Health Effects Institute (HEI) Advanced Collaborative
Emissions Study (ACES)25.
25 HEI ACES: Khalek, I., Rougher, T., and Merritt, P. M. 2009. Phase 1 of the Advanced Collaborative Emissions
Study. Prepared by Southwest Research Institute for the Coordinating Research Council and the Health Effects
Institute, June 2009. Available at www.crcao.org.
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Methane ratios for ethanol are a constant value of 0.37 for the running and engine start
processes and zero for all other processes. All raw gasoline evaporative methane ratios can be
assumed to be zero since gasoline formulations typically contains negligible amounts of
methane.
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