August 10, 2012

MEMORANDUM

To: EPA

- HQ

- OAR

- 2010

- 0799 Subject: Mobile Source Contribution to U.S. GHGs in 2010

A. Overview On an annual basis, the U.S. Environmental Protection Agency develops a national inventory of the U.S. primary anthropogenic sour ces and sinks of GHG emissions. The

report is submitted to the United Nations per the U.S. commitment to develop a comprehensive inventory of GHG emissions under the United Nations Framework Convention on Climate Change (UNFCCC). T he report estimates GHG e missions for all sectors of the U.S. economy, with the major sectors represented being i ndustrial,

t ransportation, r esidential, c ommercia l, and a griculture.

This memo will focus on the emissions estimated in the GHG Inventory report published by EPA on A pril 15, 2012

, “Inventory of U.S. Greenhouse Gas Emissions and Sinks:

1990

- 2010”

. 1 Of particular interest are the values estimated in the report for the

t rans portation sector as well as mobile source emissions that are attributed to other

economic sectors

. This memo will attempt to answer the following questions:

1) Has t ransportation been the fastest

- growing sector in terms of U.S. GHG

emissions since 1990? 2) What percentage of transportation and mobile source GHG totals did light

- duty

vehicles comprise ? 3) What percentage of U.S. national GHG totals did transportation sources and

mobile sources comprise ? 4) What percentage of Clean Air Act Section 202(a) GHG totals did light

- duty

vehicles comprise ? 5) What percentage of U.S. national GHG totals did Clean Air Act Sec tion 202(a)

sources comprise ? 6) For light

- duty vehicles, what percentage of overall GHG emissions did CO 2 comprise ?

B. Definitions The GHG Inventory contains specific definitions for the terms “ t ransportation” and “ n on

t ransportation m obile”. Transportation includes all onroad vehicles, aviation, marine, and rail, along with other small er sources of emissions

. Non

- transportation mobile sources include any vehicle or equipment not used on the traditional road system, but excluding aircraft, rail and watercraft

. 2 This category includes snowmobiles, golf carts, riding lawn mowers, agricultural equipment, and trucks used for off

- road purposes, among others.The reason for the distinction is that , in standard Inventory convention, n on

transportation mobile source s are not part of the official national estimates for the

t ransportation sector. Non

- transportation mobile source e missions are instead included in

the totals for their respective sectors ; e.g
., a gricultural e quipment is part of a griculture

sector emission s, c onstruction e quipment is part of i ndustrial sector emissions, etc. Table

1 below indicates Inventory convention for which modes are considered to be in the

t ransportation sector and which are n on

- transportation mobile.

For regulatory purposes, it is often of interest for EPA to represent mobile source

emissions . For the purposes of this memo, mobile source emissions as a whole refers to

the aggregate of transportation emissions and non

- transportation mobile emissions.

Table 1 : Modes contained in Transportation and Non

- transportation mobile sectors

Mobile Source Emissions Transportation Non

- Transportation Mobile Passenger Cars Agricultural Equipment Light

- Duty Trucks Construction and Mining Equipment

Medium

- and Heavy

- Duty T rucks Lawn and Garden Equipment

Buses Logging Equipment Motorcycles Recreational Equipment

Aviation

Marine

Rail Pipelines and Lubricants a

C. Key Questions to be Addressed

1) Has the Transportation sector been the fastest

- growing sector in terms of GHG

emissions since 1990?

Emissions by economic sector are presented in two ways in the GHG Inventory : by distributing electricity

- related emissions over the economic sectors or by disaggregating the electricity

- related emissions and presenting electricit y as an economic sector of its

own. Commonly, EPA presents transportation sector emissions with the electricity

related emissions included, In order to be consistent, this memo will present the sectors with electricity

- related emissions distributed.

While the t ransportation sector has experienced the largest absolute increase in GHG emissions since 1990, it has not the sector with the largest increase on a percentage basis. As a result, it is not correct to state that the t ransportation sector is the fast est

- growing sector in terms of GHG emissions since 1990. Rather, it is more appropriate to state that

the t ransportation sector is the source of the largest absolute increa se in GHG emissions

since 1990.

a Only CO 2 emissions from pipelines and lubricants are estimated as part of t ransportation sector totals

.Table 2 : U.S. Greenhouse G as Emission s Allocated to Economic Sector with Electricity

Related Emissions Distributed (Tg CO 2e ) 3

Economic Sector 1990 2010 Absolute Change Percentage

Change Industry 2237.7 2019.0

- 218.7

- 9.8% Transportation 1548.3 1838.6 290.3 18.7%

Residential 953. 2 1226.6 273.4 28.7%

Commercial 939.4 1171.0 231.6 24.7% Agriculture 462.9 521.1 58.2 12.6%

U.S. Territories 33.7 45.4 11.7 34.7%

Total Emissions 6175.2 6821.8 646.6 10.5%

2) What percentage of transportation and mobile source GHG totals did light

- duty

vehicles comprise ? 3) What percentage of U.S. national GHG totals did transportation sources and mobile

sources comprise ?

Table 3 : 2010 Transportation and Mobile Source Emissions

Transportation Sources GHG

Emissions (Tg CO2e) % of

Domestic Transport % of

Domestic

Mobile % of

Domestic

Total Light

- Duty Vehicles 1134.3 61.7% 55.5% 16.6% Passenger Cars 787.9 42.9% 38.6% 11.5% Light

- Duty Trucks 346.4 18.8% 17.0% 5.1% Motorcycles 3.8 0.2% 0.2% 0.1%

Buses 16.5 0.9% 0.8% 0.2%

Medium

- and Heavy

- Duty Trucks 402.3 21.9% 19.7% 5.9%

Aviation Total 143.9 7.8% 7.0% 2.1%

Commercial Aviation 115.2 6.3% 5.6% 1.7%

General Aviation 16.1 0.9% 0.8% 0.2% Military Aircraft 12.6 0.7% 0.6% 0.2%

Marine Total 43.3 2.4% 2.1% 0.6%

Recreational Boats 16.8 0.9% 0.8% 0.2% Ships 26.5 1.4% 1.3% 0.4%

Rail 46.3 2.5% 2.3% 0.7% Pipelines 38.8 2.1% 1.9% 0.6%

Lubricants 9.5 0.5% 0.5% 0.1% Transportation Total 1838.6 100.0% 90.0% 27.0%
Agricultural Equipment 48.2 2.4% 0.7% Construction and Mining Equipm ent 73.6 3.6% 1.1%

Other Non

- T ransportation Mobile 82.5 4.0% 1.2%Non

- Transportation Mobile Total 204.3 10.0% 3.0%

Mobile Total 2042.9 100.0% 29.9%

Total GHG emissions 6821.8 100.0%4) What percentage of Clean Air Act Section 202(a) GHG totals d id light

- duty vehicles

comprise ? 5) What percentage of U.S. national GHG totals did Clean Air Act Section 202(a)

sources comprise ?

The sources covered under Section 202(a) of the Clean Air Act are onroad sources, as listed in Table 4 below: cars; light tru cks; motorcycles; buses; and heavy

- duty trucks.

H o wever, the Section 202(a) total differs slightly from the onroad total from the GHG Inventory because hydrofluorocarbon (HFC) emissions asso ciated with refrigerated transport are not considered a 202(a) so urce

. The specific difference between the onroad and 202(a) totals is attributed to medium

- and heavy

- duty trucks, where 11.6 Tg CO 2 e are associated with refrigerated transport.

Table 4 : 2010 Section 202(a) Emissions

Transportation Sources GHG

Emissions (Tg CO 2 e) % of

Section

202a % of Total

GHG

Emissions Light

- Duty Vehicles 1090.2 70.6% 16.0% Passenger Cars 769.3 49.8% 11.3% Light

- Duty Trucks 320.9 20.8% 4.7% Motorcycles 3.8 0.2% 0.1%

Buses 16.1 1.0% 0.2%

Medium

- and Heavy

- Du ty Trucks 390.6 25.3% 5.7% Cooling from Sec. 202a sources 44.5 2.9% 0.7%

Section 202a Totals 1545.2 100.0% 22.7% GHG Inventory On

- Road Totals 1556.8 22.8%

Total domestic GHG emissions 6821.8 100.0%6) W hat percentage of GHG emissions did CO 2 comprise for light

- duty vehicles ?

Table 5 : CO2 as a percentage of GHG emissions by mode

Transportation Sources CO2

Emissions (Tg) GHG

Emissions (Tg CO 2 e) CO 2 as

percentage of

GHG emissions
Light

- Duty Vehicles 1073.5 1134.3 94.6%
Passeng er Cars 757.5 787.9 96.1% Light

- Duty Trucks 316.0 346.4 91.2% Motorcycles 3.7 3.8 98.3%

Buses 16.0 16.5 97.3% Medium & Heavy

- Duty

Trucks 389.3 402.3 96.8%

Aviation Total 142.4 143.9 99.0%

Commercial Aviation 114.0 115.2 99.0%

General Aviation 15.9 1 6.1 98.9% Military Aircraft 12.5 12.6 99.0%

Marine Total 42.6 43.3 98.4%

Recreational Boats 16.6 16.8 99.2% Ships 26.0 26.5 98.0%

Rail 43.5 46.3 94.1% Pipelines 38.8 38.8 100.0%

Lubricants 9.5 9.5 100.0%
Transportation Total 1759.5 1838.6 95.7%

1 U.S. Environmental Protection Agency. 2012. Inventory of U.S. Greenhouse Gas Emissions and Sinks:

1990

– 2010. EPA 430

- R

- 12

- 001. Availa ble at http://www.epa.gov/climatechange/Downloads/ghgemissions/US

- GHG

- Inventory

- 2012

- Main

- Text.pdf

2 U.S. Environmental Protection Agency. 2012. Inventory of U.S. Greenhouse Gas Emissions and Sinks:

1990

– 2010. Annex 3. p. A

- 32. EPA 430

- R

- 12

- 001. http://www .epa.gov/climatechange/Downloads/ghgemissions/US

- GHG

- Inventory

- 2012

- Annex

- 3

- Additional

- Source

- or

- Sink

- Categories.pdf

3 U.S. Environmental Protection Agency. 2012. Inventory of U.S. Greenhouse Gas Emissions and Sinks:

1990

– 2010. pp. 2

- 19

– 2

- 20

. EPA 430

- R

- 1 2

- 001. Available at http://www.epa.gov/climatechange/Downloads/ghgemissions/US

- GHG

- Inventory

- 2012

- Main

- Text.pdf