United States
Environmental Protection
Age ncy
April 2011
Inventory of U.S. Greenhouse Gas Emissions and Sinks.
1990-2009
Executive
Summary
An emissions inventory that identifies and quantifies a country's primary anthropogenic1 sources and sinks of
greenhouse gases is essential for addressing climate change. This inventory adheres to both (1) a comprehensive
and detailed set of methodologies for estimating sources and sinks of anthropogenic greenhouse gases, and (2) a
common and consistent mechanism that enables Parties to the United Nations Framework Convention on Climate Change
(UNFCCC) to compare the relative contribution of different emission sources and greenhouse gases to climate change.
In 1992, the United States signed and ratified the UNFCCC. As stated in Article 2 of the UNFCCC, "The ultimate
objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in
accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere
at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved
within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not
threatened and to enable economic development to proceed in a sustainable manner."2
All material taken from the Inventory
of U.S. Greenhouse Gas Emissions
and Sinks: 1990-2009, U.S.
Environmental Protection Agency,
Office of Atmospheric Programs,
EPA 430-R-11-005, April 2011. You
may electronically download the full
inventory report from U.S. EPA's
Global Climate Change web page at:
www.epa.gov/climatechange/
emissions/usinventory.html.
Parties to the Convention, by ratifying, "shall develop, periodically
update, publish and make available...national inventories of anthropogenic
emissions by sources and removals by sinks of all greenhouse gases not
controlled by the Montreal Protocol, using comparable methodologies..."3
The United States views the Inventory as an opportunity to fulfill these
commitments.
This chapter summarizes the latest information on U.S. anthropogenic
greenhouse gas emission trends from 1990 through 2009. To ensure that the
U.S. emission inventory is comparable to those of other UNFCCC Parties, the
estimates presented here were calculated using methodologies consistent with
those recommended in the Revised 1996 Intergovernmental Panel on Climate
Change (IPCC) Guidelines for National Greenhouse Gas Inventories
(IPCC/UNEP/OECD/IEA 1997), the IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse
Gas Inventories (IPCC 2000), and the IPCC Good Practice Guidance for Land Use, Land-Use Change, and Forestry (IPCC
2003). Additionally, the U.S. emission inventory has continued to incorporate new methodologies and data from the 2006
IPCC Guidelines for National Greenhouse Gas Inventories (IPCC 2006). The structure of the inventory report is consistent
The term "anthropogenic", in this context, refers to greenhouse gas emissions and removals that are a direct result of human activities or are the result of
natural processes that have been affected by human activities (IPCC/UNEP/OECD/IEA 1997).
r\ ^
Article 2 of the Framework Convention on Climate Change published by the UNEP/WMO Information Unit on Climate Change. See .
Article 4(1 )(a) of the United Nations Framework Convention on Climate Change (also identified in Article 12). Subsequent decisions by the Conference
of the Parties elaborated the role of Annex I Parties in preparing national inventories. See .
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 1
-------
with the UNFCCC guidelines for inventory reporting.4 For most source categories, the IPCC methodologies were expanded.
resulting in a more comprehensive and detailed estimate of emissions.
Box ES-1: Methodological approach for estimating and reporting U.S. emissions and sinks
In following the UNFCCC requirement under Article 4.1 to develop and submit national greenhouse gas emissions inventories, the emissions
and sinks presented in the inventory report are organized by source and sink categories and calculated using internationally-accepted
methods provided by the IPCC.5 Additionally, the calculated emissions and sinks in a given year for the U.S. are presented in a common
manner in line with the UNFCCC reporting guidelines for the reporting of inventories under this international agreement.6 The use of
consistent methods to calculate emissions and sinks by all nations providing their inventories to the UNFCCC ensures that these reports are
comparable. In this regard, U.S. emissions and sinks reported in this inventory report are comparable to emissions and sinks reported by
other countries. Emissions and sinks provided in this inventory do not preclude alternative examinations, but rather this inventory report
presents emissions and sinks in a common format consistent with how countries are to report inventories under the UNFCCC. The inventory
report itself follows this standardized format, and provides an explanation of the IPCC methods used to calculate emissions and sinks, and
the manner in which those calculations are conducted.
ES.1. Background Information
Naturally occurring greenhouse gases include water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O).
and ozone (O3). Several classes of halogenated substances that contain fluorine, chlorine, or bromine are also greenhouse
gases, but they are, for the most part, solely a product of industrial activities. Chlorofluorocarbons (CFCs) and
hydrochlorofluorocarbons (HCFCs) are halocarbons that contain chlorine, while halocarbons that contain bromine are
referred to as bromofluorocarbons (i.e., halons). As stratospheric ozone depleting substances, CFCs, HCFCs, and halons are
covered under the Montreal Protocol on Substances that Deplete the Ozone Layer. The UNFCCC defers to this earlier
international treaty. Consequently, Parties to the UNFCCC are not required to include these gases in their national
greenhouse gas emission inventories.7 Some other fluorine-containing halogenated substances—hydrofluorocarbons (HFCs).
perfluorocarbons (PFCs), and sulfur hexafluoride (SF6)—do not deplete stratospheric ozone but are potent greenhouse gases.
These latter substances are addressed by the UNFCCC and accounted for in national greenhouse gas emission inventories.
There are also several gases that do not have a direct global warming effect but indirectly affect terrestrial and/or solar
radiation absorption by influencing the formation or destruction of greenhouse gases, including tropospheric and
stratospheric ozone. These gases include carbon monoxide (CO), oxides of nitrogen (NOX), and non-CH4 volatile organic
compounds (NMVOCs). Aerosols, which are extremely small particles or liquid droplets, such as those produced by sulfur
dioxide (SO2) or elemental carbon emissions, can also affect the absorptive characteristics of the atmosphere.
Although the direct greenhouse gases CO2, CH4, and N2O occur naturally in the atmosphere, human activities have
changed their atmospheric concentrations. From the pre-industrial era (i.e., ending about 1750) to 2005, concentrations of
these greenhouse gases have increased globally by 36, 148, and 18 percent, respectively (IPCC 2007).
See < http://unfccc.int/resource/docs/2006/sbsta/eng/09.pdf>.
See < http://www.ipcc-nggip.iges.or.jp/public/index.html>.
See < http://unfccc.int/national_reports/annex_i_ghg_inventories/national_inventories_submissions/items/5270.php>.
Emissions estimates of CFCs, HCFCs, halons and other ozone-depleting substances are included in the annexes of the inventory
purposes.
2 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Beginning in the 1950s, the use of CFCs and other stratospheric ozone depleting substances (ODS) increased by nearly
10 percent per year until the mid-1980s, when international concern about ozone depletion led to the entry into force of the
Montreal Protocol. Since then, the production of ODS is being phased out. In recent years, use of ODS substitutes such as
HFCs and PFCs has grown as they begin to be phased in as replacements for CFCs and HCFCs. Accordingly, atmospheric
concentrations of these substitutes have been growing (IPCC 2007).
Global Warming Potentials
Gases in the atmosphere can contribute to the greenhouse effect both directly and indirectly. Direct effects occur when
the gas itself absorbs radiation. Indirect radiative forcing occurs when chemical transformations of the substance produce
other greenhouse gases, when a gas influences the atmospheric lifetimes of other gases, and/or when a gas affects
atmospheric processes that alter the radiative balance of the earth (e.g., affect cloud formation or albedo).8 The IPCC
developed the global warming potential (GWP) concept to compare the ability of each greenhouse gas to trap heat in the
atmosphere relative to another gas.
The GWP of a greenhouse gas is defined as the ratio of the
time-integrated radiative forcing from the instantaneous release of
1 kilogram (kg) of a trace substance relative to that of 1 kg of a
reference gas (IPCC 2001). Direct radiative effects occur when
the gas itself is a greenhouse gas. The reference gas used is CO2,
and therefore GWP-weighted emissions are measured in teragrams
(or million metric tons) of CO2 equivalent (Tg CO2 Eq.).9' 10 All
gases in this Executive Summary are presented in units of Tg CO2
Eq.
The UNFCCC reporting guidelines for national inventories
were updated in 2006, * * but continue to require the use of GWPs
from the IPCC Second Assessment Report (SAR) (IPCC 1996).
This requirement ensures that current estimates of aggregate
greenhouse gas emissions for 1990 to 2009 are consistent with
estimates developed prior to the publication of the IPCC Third
Assessment Report (TAR) (IPCC 2001) and the IPCC Fourth
Assessment Report (AR4) (IPCC 2007). Therefore, to comply
with international reporting standards under the UNFCCC, official
emission estimates are reported by the United States using SAR
GWP values. All estimates are provided throughout the inventory
report in both CO2 equivalents and unweighted units. A
comparison of emission values using the SAR GWPs versus the
TAR and AR4 GWPs can be found in Chapter 1 and, in more
detail, in Annex 6.1 of the inventory report. The GWP values
used in the inventory report are listed below in Table ES-1.
Table ES-1: Global Warming Potentials (100-Year
Time Horizon) Used in the Inventory Report
Gas
C02
CH;
N20
HFC-23
HFC-32
HFC-125
HFC-134a
HFC-143a
HFC-152a
HFC-227ea
HFC-236fa
HFC-4310mee
CF4
C2F6
C^FIO
C6F14
SF6
GWP
1
21
310
11,700
650
2,800
1,300
3,800
140
2,900
6,300
1,300
6,500
9,200
7,000
7,400
23,900
Source: IPCC (1996)
* The CH4 GWP includes the direct effects and those indirect
effects due to the production of tropospheric ozone and
stratospheric water vapor. The indirect effect due to the
production of C02 is not included.
Albedo is a measure of the earth's reflectivity, and is defined as the fraction of the total solar radiation incident on a body that is reflected by it.
Carbon comprises 12/44*" of carbon dioxide by weight.
One teragram is equal to 1012 grams or one million metric tons.
11
See .
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 3
-------
Global warming potentials are not provided for CO, NOX, NMVOCs, SO2, and aerosols because there is no agreed-upon
method to estimate the contribution of gases that are short-lived in the atmosphere, spatially variable, or have only indirect
effects on radiative forcing (IPCC 1996).
ES.2. Recent Trends in U.S. Greenhouse Gas Emissions and Sinks
In 2009, total U.S. greenhouse gas emissions were 6,633.2
Tg or million metric tons CC>2 Eq. While total U.S. emissions
have increased by 7.3 percent from 1990 to 2009, emissions
decreased from 2008 to 2009 by 6.1 percent (427.9 Tg CO2
Eq.). This decrease was primarily due to (1) a decrease in
economic output resulting in a decrease in energy consumption
across all sectors; and (2) a decrease in the carbon intensity of
fuels used to generate electricity due to fuel switching as the
price of coal increased, and the price of natural gas decreased
significantly. Since 1990, U.S. emissions have increased at an
average annual rate of 0.4 percent.
Figure ES-1 through Figure ES-3 illustrate the overall
trends in total U.S. emissions by gas, annual changes, and
absolute change since 1990.
Table ES-2 provides a detailed summary of U.S.
greenhouse gas emissions and sinks for 1990 through 2009.
Figure ES-1
U.S. Greenhouse Gas Emissions by Gas
8.000 -
7.0DO -
6,000 -
uf 5,000 -
0
% 4,000 -
3,000 -
2,000
1,000
0
I MFCs, PFCs, & SF.
Nitrous Oxide
Methane
I Carbon Dioxide
Bills.
Figure ES-2
Annual Percent Change in U.S. Greenhouse Gas
Emissions
4%-,
o%
-2%
3.3%
12.8%
M%M%1j|| j|%M%lj|W •
•0.6%
T-cxico^-mtnr- _
oioioiCTiaiaiaioioi -
Figure ES-3
Cumulative Change in Annual U.S. Greenhouse Gas
Emissions Relative to 1990
1,100
1,000
900
800
S 700
o~ 600
° 500
400
300
200
100
-100J
1.082
CNJ co ^- m to r*- eo
gggggggg
4 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Table ES-2: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks (Tg or million metric tons C02 Eq.)
Gas/Source
C02
Fossil Fuel Combustion
Electricity Generation
Transportation
Industrial
Residential
Commercial
U.S. Territories
Non-Energy Use of Fuels
Iron and Steel Production &
Metallurgical Coke Production
Natural Gas Systems
Cement Production
Incineration of Waste
Ammonia Production and Urea
Consumption
Lime Production
Cropland Remaining Cropland
Limestone and Dolomite Use
Soda Ash Production and
Consumption
Aluminum Production
Petrochemical Production
Carbon Dioxide Consumption
Titanium Dioxide Production
Ferroalloy Production
Wetlands Remaining Wetlands
Phosphoric Acid Production
Zinc Production
Lead Production
Petroleum Systems
Silicon Carbide Production and
Consumption
Land Use, Land-Use Change, and
Forestry (Sink) "
Biomass- Wood"
International Bunker Fuels °
Biomass - Ethanol "
CH4
Natural Gas Systems
Enteric Fermentation
Landfills
Coal Mining
Manure Management
Petroleum Systems
Wastewater Treatment
Forest Land Remaining Forest Land
Rice Cultivation
Stationary Combustion
Abandoned Underground Coal Mines
Mobile Combustion
Composting
Petrochemical Production
Iron and Steel Production &
Metallurgical Coke Production
Field Burning of Agricultural Residues
Ferroalloy Production
1990
5,099.7
4,738.4
1,820.8
1,485.9
846.5
338.3
219.0
27.9
118.6
99.5
37.6
33.3
8.0|
16.sl
11.5
7.1
5.1
4.1
6.8
3.3
1.4
1.2
2.2
1.0
1.5
0.7
0.5
0.6
0.4
(861.5)
215.2
111.8
4.2\
674.9
2000
5,975.0
5,594.8
2,296.9
1,809.5
851.1
370.7
230.8
35.9
144.9
85.9
29.9
40.4
1 11.1
1 16.4
14.1
7.5
5.1
4.2
6.1
4.5
1.4
1.8
1.9
1.2
1.4
1.0
0.6
0.5
0.2
(576.6)
218.1
98.5
9.4\
659.9
189.8 209.3
132.1 136.5
147.41
84.1
31.7
35.4
23.5
3.2|
7.1|
7.4l
6.0|
4.7l
0.3|
0.9l
1.0!
o.sl
+|
111.7
60.4
42.4
31.5
25.2
1 14.3
1 7.5
6.6l
1 7.4
3.4l
1 1.3
1.2l
1 0.9
1 0.3
+
2005
6,113.8
5,753.2
2,402.1
1,896.6
1823.1
357.9
223.5
50.0
143.4
65.9
29.9
45.2
1 12.5
1 12.8
14.4
7.9
6.8
4.2
4.1
4.2
1.3
1.8
1.4
1.1
1.4
1.1
0.6
0.5
0.2
(1,056.5)
206.9
109.7
23.0
631.4
190.4
136.5
112.5
56.9
46.6
29.4
24.3
9.8
6.8
6.6
1 5.5
2.5
1 1.6
1.1
1 0.7
1 0.2
| +
2006
6,021.1
5,653.1
2,346.4
1,878.1
848.2
321.5
208.6
50.3
145.6
68.8
30.8
45.8
12.5
12.3
15.1
7.9
8.0
4.2
3.8
3.8
1.7
1.8
1.5
0.9
1.2
1.1
0.6
0.5
0.2
(1,064.3)
203.8
128.4
31.0
672.1
217.7
138.8
111.7
58.2
46.7
29.4
24.5
21.6
5.9
6.2
5.5
2.3
1.6
1.0
0.7
0.2
+
2007
6,120.0
5,756.7
2,412.8
1,894.0
842.0
342.4
219.4
46.1
137.2
71.0
31.1
44.5
12.7
14.0
14.6
8.2
7.7
4.1
4.3
3.9
1.9
1.9
1.6
1.0
1.2
1.1
0.6
0.5
0.2
(1,060.9)
203.3
127.6
38.9
664.6
205.2
141.0
111.3
57.9
50.7
30.0
24.4
20.0
6.2
6.5
5.6
2.2
1.7
1.0
0.7
0.2
+
2008
5,921.4
5,565.9
2,360.9
1,789.9
802.9
348.2
224.2
39.8
141.0
66.0
32.8
40.5
12.2
11.9
14.3
8.7
6.3
4.1
4.5
3.4
1.8
1.8
1.6
1.0
1.2
1.2
0.6
0.5
0.2
(1,040.5)
198.4
133.7
54.8
676.7
211.8
140.6
115.9
67.1
49.4
30.2
24.5
11.9
7.2
6.5
5.9
2.0
1.7
0.9
0.6
0.3
+
2009
5,505.2
5,209.0
2,154.0
1,719.7
730.4
339.2
224.0
41.7
123.4
41.9
32.2
29.0
12.3
11.8
11.2
7.8
7.6
4.3
3.0
2.7
1.8
1.5
1.5
1.1
1.0
1.0
0.5
0.5
0.1
(1,015.1)
183.8
123.1
61.2
686.3
221.2
139.8
117.5
71.0
49.5
30.9
24.5
7.8
7.3
6.2
5.5
2.0
1.7
0.8
0.4
0.2
+
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 5
-------
Table ES-2: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks (Tg or million metric tons C02 Eq.) (continued)
Gas/Source
Silicon Carbide Production and
Consumption
Incineration of Waste
International Bunker Fuels0
N20
Agricultural Soil Management
Mobile Combustion
Manure Management
Nitric Acid Production
Stationary Combustion
Forest Land Remaining Forest Land
Wastewater Treatment
N20 from Product Uses
Adipic Acid Production
Composting
Settlements Remaining Settlements
Incineration of Waste
Field Burning of Agricultural Residues
Wetlands Remaining Wetlands
International Bunker Fuels °
MFCs
Substitution of Ozone Depleting
Substances d
HCFC-22 Production
Semiconductor Manufacture
PFCs
Semiconductor Manufacture
Aluminum Production
SF6
Electrical Transmission and
Distribution
Magnesium Production and
Processing
Semiconductor Manufacture
Total
Net Emissions (Sources and Sinks)
1990
:
0.2l
315.2
197.8
43.9
14.5
JD.^t
0.2l
20.8
2.2l
18.51
34.4
28.41
u.og
6,181.8
5,320.3
2000
+
o./|
341.0
206.8
53.2
17.1
19.41
14.6
12.1
4.5l
4.9l
5.5
1.4l
1.ll
0.4l
0.1!
+1
0.9
103.2
74.31
28.6
o.sl
13.5
4.9l
8. el
20.1
16.0
3.0
j j ^1
7,112.7
6,536.1
2005
*
0.1
322.9
211.3
36.9
17.3
16.5
14.7
8.4
4.8
4.4
5.0
1.7
1.5
0.4
0.1
+
1.0
120.2
104.2
15.8
0.2
6.2
3.2
3.0
19.0
15.1
2.9
1.0
7,213.5
6,157.1
2006
*
0.2
326.4
208.9
33.6
18.0
16.2
14.4
18.0
4.8
4.4
4.3
1.8
1.5
0.4
0.1
+
1.2
123.5
109.4
13.8
0.3
6.0
3.5
2.5
17.9
14.1
2.9
1.0
7,166.9
6,102.6
2007
*
0.2
325.1
209.4
30.3
18.1
19.2
14.6
16.7
4.9
4.4
3.7
1.8
1.6
0.4
0.1
+
1.2
129.5
112.3
17.0
0.3
7.5
3.7
3.8
16.7
13.2
2.6
0.8
7,263.4
6,202.5
2008
*
0.2
310.8
210.7
26.1
17.9
16.4
14.2
10.1
5.0
4.4
2.0
1.9
1.5
0.4
0.1
+
1.2
129.4
115.5
13.6
0.3
6.6
4.0
2.7
16.1
13.3
1.9
0.9
7,061.1
6,020.7
2009
*
0.1
295.6
204.6
23.9
17.9
14.6
12.8
6.7
5.0
4.4
1.9
1.8
1.5
0.4
0.1
+
1.1
125.7
120.0
5.4
0.3
5.6
4.0
1.6
14.8
12.8
1.1
1.0
6,633.2
5,618.2
+ Does not exceed 0.05 Tg C02 Eq.
a Parentheses indicate negative values or sequestration. The net C02 flux total includes both emissions and sequestration, and constitutes a net sink in the
United States. Sinks are only included in net emissions total.
b Emissions from Wood Biomass and Ethanol Consumption are not included specifically in summing energy sector totals. Net carbon fluxes from changes in
biogenic carbon reservoirs are accounted for in the estimates for Land Use, Land-Use Change, and Forestry.
c Emissions from International Bunker Fuels are not included in totals.
d Small amounts of RFC emissions also result from this source.
Note: Totals may not sum due to independent rounding.
Figure ES-4 illustrates the relative contribution of the direct greenhouse gases to total U.S. emissions in 2009. The
primary greenhouse gas emitted by human activities in the United States was CO2, representing approximately 83.0 percent
of total greenhouse gas emissions. The largest source of CO2, and of overall greenhouse gas emissions, was fossil fuel
combustion. Methane emissions, which have increased by 1.7 percent since 1990, resulted primarily from natural gas
systems, enteric fermentation associated with domestic livestock, and decomposition of wastes in landfills. Agricultural soil
management and mobile source fuel combustion were the major sources of N2O emissions. Ozone depleting substance
substitute emissions and emissions of HFC-23 during the production of HCFC-22 were the primary contributors to aggregate
HFC emissions. PFC emissions resulted as a byproduct of primary aluminum production and from semiconductor
manufacturing, while electrical transmission and distribution systems accounted for most SF6 emissions.
6 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Figure ES-4
2009 Greenhouse Gas Emissions by Gas
(percents based on Tg C02 Eq.)
Overall, from 1990 to 2009, total emissions of CO2 and
CH4 increased by 405.5 Tg CO2 Eq. (8.0 percent) and 11.4 Tg
CO2 Eq. (1.7 percent), respectively. Conversely, N2O emissions
decreased by 19.6 Tg CO2 Eq. (6.2 percent). During the same
period, aggregate weighted emissions of HFCs, PFCs, and SF6
rose by 54.1 Tg CO2 Eq. (58.8 percent). From 1990 to 2009,
HFCs increased by 88.8 Tg CO2 Eq. (240.41 percent), PFCs
decreased by 15.1 Tg CO2 Eq. (73.0 percent), and SF6 decreased
by 19.5 Tg CO2 Eq. (56.8 percent). Despite being emitted in
smaller quantities relative to the other principal greenhouse
gases, emissions of HFCs, PFCs, and SF6 are significant because
many of these gases have extremely high global warming
potentials and, in the cases of PFCs and SF6, long atmospheric
lifetimes. Conversely, U.S. greenhouse gas emissions were
partly offset by carbon sequestration in forests, trees in urban
areas, agricultural soils, and landfilled yard trimmings and food
scraps, which, in aggregate, offset 15.3 percent of total
emissions in 2009. The following sections describe each gas:
contribution to total U.S. greenhouse gas emissions in more detail.
Carbon Dioxide Emissions
The global carbon cycle is made up of large carbon flows and reservoirs. Billions of tons of carbon in the form of CO2
are absorbed by oceans and living biomass (i.e., sinks) and are emitted to the atmosphere annually through natural processes
(i.e., sources). When in equilibrium, carbon fluxes among these various reservoirs are roughly balanced. Since the Industrial
Revolution (i.e., about 1750), global atmospheric concentrations of CO2 have risen about 36 percent (IPCC 2007), principally
due to the combustion of fossil fuels. Within the United States, fossil fuel combustion accounted for 94.6 percent of CO2
emissions in 2009. Globally, approximately 30,313 Tg of CO2 were added to the atmosphere through the combustion of
fossil fuels in 2009, of which the United States accounted for about 18 percent.12 Changes in land use and forestry practices
can also emit CO2 (e.g., through conversion of forest land to agricultural or urban use) or can act as a sink for CO2 (e.g.,
through net additions to forest biomass). In addition to fossil-fuel combustion, several other sources emit significant
quantities of CO2. These sources include, but are not limited to non-energy use of fuels, iron and steel production and cement
production (Figure ES-5).
As the largest source of U.S. greenhouse gas emissions, CO2 from fossil fuel combustion has accounted for
approximately 78 percent of GWP-weighted emissions since 1990, growing slowly from 77 percent of total GWP-weighted
emissions in 1990 to 79 percent in 2009. Emissions of CO2 from fossil fuel combustion increased at an average annual rate
of 0.4 percent from 1990 to 2009. The fundamental factors influencing this trend include: (1) a generally growing domestic
economy over the last 20 years, and (2) overall growth in emissions from electricity generation and transportation activities.
Between 1990 and 2009, CO2 emissions from fossil fuel combustion increased from 4,738.4 Tg CO2 Eq. to 5,209.0 Tg CO2
Eq.—a 9.9 percent total increase over the twenty-year period. From 2008 to 2009, these emissions decreased by 356.9 Tg
CO2 Eq. (6.4 percent), the largest decrease in any year over the twenty-year period.
Global CO2 emissions from fossil fuel combustion were taken from Energy Information Administration International Energy Statistics 2010
El A (201 Oa).
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 1
-------
Figure ES-5
2009 Sources of CO, Emissions
Fossil Fuel Combustion
Non-Energy Jseof Fuels
Iron and Steel Production
& Metallurgical Coke Production
Natural Gas Systems
Cement Production
Incineration of Waste •
Ammonia Production and _
Urea Consomption •
Lime Production |
Cropland Remaining Cropland •
Limestone and Dolomite Use •
Soda Ash Production and Consomption I
Aluminum Production I
Petrochemical Production
Carbon Dioiide Consomption
Titanium Dioiide Production
Ferroalloy Production
Wetlands Remaining Wetlands
Phosphoric Acid Production
Zinc Production
Lead Production |
Petroleum Systems
Silicon Carbide Production and
Consumption
5,209
CO; as a Portion
of all Emissions
Historically, changes in emissions from fossil fuel
combustion have been the dominant factor affecting U.S.
emission trends. Changes in CC>2 emissions from fossil
fuel combustion are influenced by many long-term and
short-term factors, including population and economic
growth, energy price fluctuations, technological changes.
and seasonal temperatures. In the short term, the overall
consumption of fossil fuels in the United States fluctuates
primarily in response to changes in general economic
conditions, energy prices, weather, and the availability of
non-fossil alternatives. For example, in a year with
increased consumption of goods and services, low fuel
prices, severe summer and winter weather conditions.
nuclear plant closures, and lower precipitation feeding
hydroelectric dams, there would likely be proportionally
greater fossil fuel consumption than a year with poor
economic performance, high fuel prices, mild
temperatures, and increased output from nuclear and
hydroelectric plants. In the long term, energy
consumption patterns respond to changes that affect the
scale of consumption (e.g., population, number of cars.
and size of houses), the efficiency with which energy is
used in equipment (e.g., cars, power plants, steel mills.
and light bulbs) and behavioral choices (e.g., walking.
bicycling, or telecommuting to work instead of driving).
The five major fuel consuming sectors contributing
to CO2 emissions from fossil fuel combustion are electricity generation, transportation, industrial, residential, and
commercial. Carbon dioxide emissions are produced by the electricity generation sector as they consume fossil fuel to
provide electricity to one of the other four sectors, or "end-use" sectors. For the discussion below, electricity generation
emissions have been distributed to each end-use sector on the basis of each sector's share of aggregate electricity
consumption. This method of distributing emissions assumes that each end-use sector consumes electricity that is generated
from the national average mix of fuels according to their carbon intensity. Emissions from electricity generation are also
addressed separately after the end-use sectors have been discussed.
Note that emissions from U.S. territories are calculated separately due to a lack of specific consumption data for the
individual end-use sectors.
Figure ES-6, Figure ES-7, and Table ES-3 summarize CO2 emissions from fossil fuel combustion by end-use sector.
<0.5
25
To 100 125 15D
8 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Figure ES-6
Figure ES-7
2009 C02 Emissions from Fossil Fuel Combustion by
Sector and Fuel Type
2009 End-Use Sector Emissions of C02, CH4, and N20
from Fossil Fuel Combustion
2,500 -
2,000 -
Sj.500 -
o"
O
i?
1,000 -
500 -
Relative Contribution
by Fuel Type
Petroleum
I Coal
Natural Gas
2,154
1,720
730
224
42
339
•
I
I
Note: Electricity generation also includes emissions of less than 0.5 Tg C02
Eq. from geothermal-based electricity generation.
2,000 -,
1,500 -
1,000 -
500 -
I From Direct Fossil
Fuel Combustion
From Electricity
Consumption
990
1,750
1,132
42
Table ES-3: C02 Emissions from Fossil Fuel Combustion by Fuel Consuming End-Use Sector (Tg or million metric tons C02 Eq.)
End-Use Sector
Transportation
Combustion
Electricity
Industrial
Combustion
Electricity
Residential
Combustion
Electricity
Commercial
Combustion
Electricity
U.S. Territories a
Total
Electricity Generation
1990
1,489.0
1,485.9 1
3.0
1,533.2
846.5 1
686.7 1
931.4 1
338.3 1
593.0 1
757.0
219.0 1
538.0
27.9
4,738.4
1,820.8
2000
1,813.0
1,809.5
3.4
1,640.8
851.1
789.8
1,133.1
370.7
762.4
972.1
230.8
741.3
35.9
5,594.8
2,296.9
2005
1,901.3
1,896.6
4.7
1,560.0
823.1
737.0
1,214.7
357.9
856.7
1,027.2
223.5
803.7
50.0
5,753.2
2,402.1
2006
1,882.6
1,878.1
4.5
1,560.2
848.2
712.0
1,152.4
321.5
830.8
1,007.6
208.6
799.0
50.3
5,653.1
2,346.4
2007
1,899.0
1,894.0
5.0
1,572.0
842.0
730.0
1,198.5
342.4
856.1
1,041.1
219.4
821.7
46.1
5,756.7
2,412.8
2008
1,794.6
1,789.9
4.7
1,517.7
802.9
714.8
1,182.2
348.2
834.0
1,031.6
224.2
807.4
39.8
5,565.9
2,360.9
2009
1,724.1
1,719.7
4.4
1,333.7
730.4
603.3
1,123.8
339.2
784.6
985.7
224.0
761.7
41.7
5,209.0
2,154.0
a Fuel consumption by U.S. territories (i.e., American Samoa, Guam, Puerto Rico, U.S. Virgin Islands, Wake Island, and other U.S. Pacific
Islands) is included in the inventory report.
Note: Totals may not sum due to independent rounding. Combustion-related emissions from electricity generation are allocated based
on aggregate national electricity consumption by each end-use sector.
Transportation End-Use Sector. Transportation activities (excluding international bunker fuels) accounted for 33
percent of CO2 emissions from fossil fuel combustion in 2009.13 Virtually all of the energy consumed in this end-use sector
came from petroleum products. Nearly 65 percent of the emissions resulted from gasoline consumption for personal vehicle
use. The remaining emissions came from other transportation activities, including the combustion of diesel fuel in heavy-
If emissions from international bunker fuels are included, the transportation end-use sector accounted for 35 percent of U.S. emissions from fossil fuel
combustion in 2009.
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 9
-------
duty vehicles and jet fuel in aircraft. From 1990 to 2009, transportation emissions rose by 16 percent due, in large part, to
increased demand for travel and the stagnation of fuel efficiency across the U.S. vehicle fleet. The number of vehicle miles
traveled by light-duty motor vehicles (passenger cars and light-duty trucks) increased 39 percent from 1990 to 2009, as a
result of a confluence of factors including population growth, economic growth, urban sprawl, and low fuel prices over much
of this period.
Industrial End-Use Sector. Industrial CO2 emissions, resulting both directly from the combustion of fossil fuels and
indirectly from the generation of electricity that is consumed by industry, accounted for 26 percent of CO2 from fossil fuel
combustion in 2009. Approximately 55 percent of these emissions resulted from direct fossil fuel combustion to produce
steam and/or heat for industrial processes. The remaining emissions resulted from consuming electricity for motors, electric
furnaces, ovens, lighting, and other applications. In contrast to the other end-use sectors, emissions from industry have
steadily declined since 1990. This decline is due to structural changes in the U.S. economy (i.e., shifts from a manufacturing-
based to a service-based economy), fuel switching, and efficiency improvements.
Residential and Commercial End-Use Sectors. The residential and commercial end-use sectors accounted for 22 and 19
percent, respectively, of CO2 emissions from fossil fuel combustion in 2009. Both sectors relied heavily on electricity for
meeting energy demands, with 70 and 77 percent, respectively, of their emissions attributable to electricity consumption for
lighting, heating, cooling, and operating appliances. The remaining emissions were due to the consumption of natural gas
and petroleum for heating and cooking. Emissions from these end-use sectors have increased 25 percent since 1990, due to
increasing electricity consumption for lighting, heating, air conditioning, and operating appliances.
Electricity Generation. The United States relies on electricity to meet a significant portion of its energy demands.
Electricity generators consumed 36 percent of U.S. energy from fossil fuels and emitted 41 percent of the CO2 from fossil
fuel combustion in 2009. The type of fuel combusted by electricity generators has a significant effect on their emissions. For
example, some electricity is generated with low CO2 emitting energy technologies, particularly non-fossil options such as
nuclear, hydroelectric, or geothermal energy. However, electricity generators rely on coal for over half of their total energy
requirements and accounted for 95 percent of all coal consumed for energy in the United States in 2009. Consequently.
changes in electricity demand have a significant impact on coal consumption and associated CO2 emissions.
Other significant CO2 trends included the following:
• Carbon dioxide emissions from non-energy use of fossil fuels have increased 4.7 Tg CO2 Eq. (4.0 percent) from
1990 through 2009. Emissions from non-energy uses of fossil fuels were 123.4 Tg CO2 Eq. in 2009, which
constituted 2.2 percent of total national CO2 emissions, approximately the same proportion as in 1990.
• Carbon dioxide emissions from iron and steel production and metallurgical coke production decreased by 24.1 Tg
CO2 Eq. (36.6 percent) from 2008 to 2009, continuing a trend of decreasing emissions from 1990 through 2009 of
57.9 percent (57.7 Tg CO2 Eq.). This decline is due to the restructuring of the industry, technological
improvements, and increased scrap utilization.
• In 2009, CO2 emissions from cement production decreased by 11.5 Tg CO2 Eq. (28.4 percent) from 2008. After
decreasing in 1991 by two percent from 1990 levels, cement production emissions grew every year through 2006;
emissions decreased in the last three years. Overall, from 1990 to 2009, emissions from cement production
decreased by 12.8 percent, a decrease of 4.3 Tg CO2 Eq.
• Net CO2 uptake from Land Use, Land-Use Change, and Forestry increased by 153.5 Tg CO2 Eq. (17.8 percent) from
1990 through 2009. This increase was primarily due to an increase in the rate of net carbon accumulation in forest
carbon stocks, particularly in aboveground and belowground tree biomass, and harvested wood pools. Annual
10 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
carbon accumulation in landfilled yard trimmings and food scraps slowed over this period, while the rate of carbon
accumulation in urban trees increased.
Methane Emissions
Methane (CH4) is more than 20 times as effective as CO2 at
trapping heat in the atmosphere (IPCC 1996). Over the last two
hundred and fifty years, the concentration of CH4 in the
atmosphere increased by 148 percent (IPCC 2007).
Anthropogenic sources of CH4 include natural gas and
petroleum systems, agricultural activities, landfills, coal mining.
wastewater treatment, stationary and mobile combustion, and
certain industrial processes (see Figure ES-8).
Some significant trends in U.S. emissions of CH4 include
the following:
• In 2009, CH4 emissions from coal mining were 71.0 Tg
CO2 Eq., a 3.9 Tg CO2 Eq. (5.8 percent) increase over
2008 emission levels. The overall decline of 13.0 Tg
CO2 Eq. (15.5 percent) from 1990 results from the
mining of less gassy coal from underground mines and
the increased use of CH4 collected from degasification
systems.
• Natural gas systems were the largest anthropogenic
source category of CH4 emissions in the United States
in 2009 with 221.2 Tg CO2 Eq. of CH4 emitted into the
Figure ES-8
2009 Sources of CH, Emissions
Natural Gas Systems
Enteric Fermentation
Landfills
Coal Mining
Manure Management
Petroleum Systems ^^|
Waslewater Treatment ^H
Foresl Land Remaining Forest Land |
Rice Cultivation |
Stationary Combustion |
Abandoned Underground Coal Mines |
Mobile Combustion [
Composting |
Petrochemical Production |
Iron and Steel Production i-««
S Metallurgical Coke Production I
-------
emissions is the result of increases in the amount of landfill gas collected and combusted,14 which has more than
offset the additional CH4 emissions resulting from an increase in the amount of municipal solid waste landfilled.
Figure ES-9
Nitrous Oxide Emissions
Nitrous oxide is produced by biological processes that
occur in soil and water and by a variety of anthropogenic
activities in the agricultural, energy-related, industrial, and
waste management fields. While total N2O emissions are much
lower than CO2 emissions, N2O is approximately 300 times
more powerful than CO2 at trapping heat in the atmosphere
(IPCC 1996). Since 1750, the global atmospheric concentration
of N2O has risen by approximately 18 percent (IPCC 2007).
The main anthropogenic activities producing N2O in the United
States are agricultural soil management, fuel combustion in
motor vehicles, manure management, nitric acid production and
stationary fuel combustion, (see Figure ES-9).
Some significant trends in U.S. emissions of N2O include
the following:
• In 2009, N2O emissions from mobile combustion were
23.9 Tg CO2 Eq. (approximately 8.1 percent of U.S.
N2O emissions). From 1990 to 2009, N2O emissions
from mobile combustion decreased by 45.6 percent. However, from 1990 to 1998 emissions increased by 25.6
percent, due to control technologies that reduced NOX emissions while increasing N2O emissions. Since 1998.
newer control technologies have led to an overall decline in N2O from this source.
• Nitrous oxide emissions from adipic acid production were 1.9 Tg CO2 Eq. in 2009, and have decreased significantly
since 1996 from the widespread installation of pollution control measures. Emissions from adipic acid production
have decreased by 87.7 percent since 1990, and emissions from adipic acid production have remained consistently
lower than pre-1996 levels since 1998.
• Agricultural soils accounted for approximately 69.2 percent of N2O emissions in the United States in 2009.
Estimated emissions from this source in 2009 were 204.6 Tg CO2 Eq. Annual N2O emissions from agricultural soils
fluctuated between 1990 and 2009, although overall emissions were 3.4 percent higher in 2009 than in 1990.
2009 Sources of N20 Emissions
Nitric Acid Production ^^^^H
Stationary Combustion ^^^^H
N,0 as a Portion
Forest Land Remaining Forest Land ^^| of all Emissions
Wastewater Treatment ^| /" »^\
N.O from Product Uses ^| / \
Adipic Acid Production | 1 4'5* j
Composting | \ /
Settlements Remaining Settlements |
Incineration of Waste
Field Burning of Agricultural Residues
Wetlands Remaining Wetlands
I I I I
0 10 20 30 40
Tg C0; Eq.
205
50
The CO2 produced from combusted landfill CH4 at landfills is not counted in national inventories as it is considered part of the natural C cycle of
decomposition.
12 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Figure ES-10
2009 Sources of MFCs, PFCs, and SF6 Emissions
Substitution of Ozone
Depleting Substances
Electrical Transmission
and Distribution
HCFC-22 Production
Semiconductor
Manufacture
Aluminum Production I
and Processing
Magnesium Production I
MFCs, PFCs, and
SF, as a Portion of
all Emissions
0
10
20 30
TgCO,Eq.
40
50
HFC, PFC, and SF6 Emissions
HFCs and PFCs are families of synthetic chemicals that are
used as alternatives to ODS, which are being phased out under
the Montreal Protocol and Clean Air Act Amendments of 1990.
HFCs and PFCs do not deplete the stratospheric ozone layer.
and are therefore acceptable alternatives under the Montreal
Protocol.
These compounds, however, along with SF6, are potent
greenhouse gases. In addition to having high global warming
potentials, SF6 and PFCs have extremely long atmospheric
lifetimes, resulting in their essentially irreversible accumulation
in the atmosphere once emitted. Sulfur hexafluoride is the most
potent greenhouse gas the IPCC has evaluated (IPCC 1996).
Other emissive sources of these gases include electrical
transmission and distribution systems, HCFC-22 production.
semiconductor manufacturing, aluminum production, and
magnesium production and processing (see Figure ES-10).
Some significant trends in U.S. HFC, PFC, and SF6 emissions include the following:
• Emissions resulting from the substitution of ODS (e.g., CFCs) have been consistently increasing, from small
amounts in 1990 to 120.0 Tg CO2 Eq. in 2009. Emissions from ODS substitutes are both the largest and the fastest
growing source of HFC, PFC, and SF6 emissions. These emissions have been increasing as phase-outs required
under the Montreal Protocol come into effect, especially after 1994, when full market penetration was made for the
first generation of new technologies featuring ODS substitutes.
• HFC emissions from the production of HCFC-22 decreased by 85.2 percent (31.0 Tg CO2 Eq.) from 1990 through
2009, due to a steady decline in the emission rate of HFC-23 (i.e., the amount of HFC-23 emitted per kilogram of
HCFC-22 manufactured) and the use of thermal oxidation at some plants to reduce HFC-23 emissions.
• Sulfur hexafluoride emissions from electric power transmission and distribution systems decreased by 54.8 percent
(15.6 Tg CO2 Eq.) from 1990 to 2009, primarily because of higher purchase prices for SF6 and efforts by industry to
reduce emissions.
• PFC emissions from aluminum production decreased by 91.5 percent (17.0 Tg CO2 Eq.) from 1990 to 2009, due to
both industry emission reduction efforts and lower domestic aluminum production.
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 13
-------
ES.3. Overview of Sector Emissions and Trends
In accordance with the Revised 1996IPCC Guidelines for
National Greenhouse Gas Inventories (IPCC/UNEP/OECD/IEA
1997), and the 2003 UNFCCC Guidelines on Reporting and
Review (UNFCCC 2003), Figure ES-11 and Table ES-4
aggregate emissions and sinks by these chapters. Emissions of
all gases can be summed from each source category from IPCC
guidance. Over the twenty-year period of 1990 to 2009, total
emissions in the Energy and Agriculture sectors grew by 463.3
Tg CO2 Eq. (9 percent), and 35.7 Tg CO2 Eq. (9 percent),
respectively. Emissions decreased in the Industrial Processes,
Waste, and Solvent and Other Product Use sectors by 32.9 Tg
CO2 Eq. (10 percent), 24.7 Tg CO2 Eq. (14 percent) and less
than 0.1 Tg CO2 Eq. (0.4 percent), respectively. Over the same
period, estimates of net C sequestration in the Land Use, Land-
Use Change, and Forestry sector (magnitude of emissions plus
CO2 flux from all LULUCF source categories) increased by
143.5 Tg CO2 Eq. (17 percent).
Figure ES-11
U.S. Greenhouse Gas Emissions and Sinks by
Chapter/IPCC Sector
Industrial Processes
Waste
LULUCF (sources)
7,500
7,000
6.500
6.000
5,500
5,000
. 4,500
4,000
' 3,500
, 3,000
2,500
2,000
1,500
1,000
500 -
0
(500) -
(1,000)
(1,500) J
Land Use. Land-Use Change and Forestry (sinks)
S
oioioi
SSSS
s
Note: Relatively smaller amounts of GWP-weighted emissions are also
emitted from the Solvent and Other Product Use Sectors.
Table ES-4: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks by Chapter/IPCC Sector (Tg or million metric tons C02
Eq.)
Chapter/IPCC Sector
Energy
Industrial Processes
Solvent and Other Product Use
Agriculture
Land Use, Land-Use Change, and Forestry (Emissions)
Waste
Total Emissions
Net C02 Flux from Land Use, Land-Use Change, and
Forestry (Sinks)3
Net Emissions (Sources and Sinks)
5,
6,
(5
5,
1990
287.8
315.8
44
383.6
15.0
175.2
181.8
161.5)
320.3
6
7
(
6
2000
,168.0
348.8
4.9
410.6
36.3
143.9
,112.7
576.6)
,536.1
2005
6,282.8
334.1
4.4
418.8
28.6
144.9
7,213.5
(1,056.5)
6,157.1
2006
6,210.2
339.4
4.4
418.8
49.8
144.4
7,166.9
(1,064.3)
6,102.6
2007
6,290.7
350.9
4.4
425.8
47.5
144.1
7,263.4
(1,060.9)
6,202.5
2008
6,116.6
331.7
4.4
426.3
33.2
149.0
7,061.1
(1,040.5)
6,020.7
2009
5,751.1
282.9
4.4
419.3
25.0
150.5
6,633.2
(1,015.1)
5,618.2
a The net C02 flux total includes both emissions and sequestration, and constitutes a sink in the United States. Sinks are only included in net
emissions total.
Note: Totals may not sum due to independent rounding. Parentheses indicate negative values or sequestration.
14 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Figure ES-12
2009 U.S. Energy Consumption by Energy Source
Nuclear Electric
Energy
The Energy chapter contains emissions of all greenhouse
gases resulting from stationary and mobile energy activities
including fuel combustion and fugitive fuel emissions. Energy-
related activities, primarily fossil fuel combustion, accounted for
the vast majority of U.S. CO2 emissions for the period of 1990
through 2009. In 2009, approximately 83 percent of the energy
consumed in the United States (on a Btu basis) was produced
through the combustion of fossil fuels. The remaining 17
percent came from other energy sources such as hydropower.
biomass, nuclear, wind, and solar energy (see Figure ES-12).
Energy-related activities are also responsible for CH4 and N2O
emissions (49 percent and 13 percent of total U.S. emissions of
each gas, respectively). Overall, emission sources in the Energy
chapter account for a combined 87 percent of total U.S.
greenhouse gas emissions in 2009.
Industrial Processes
The Industrial Processes chapter contains byproduct or fugitive emissions of greenhouse gases from industrial processes
not directly related to energy activities such as fossil fuel combustion. For example, industrial processes can chemically
transform raw materials, which often release waste gases such as CO2, CH4, and N2O. These processes include iron and steel
production and metallurgical coke production, cement production, ammonia production and urea consumption, lime
production, limestone and dolomite use (e.g., flux stone, flue gas desulfurization, and glass manufacturing), soda ash
production and consumption, titanium dioxide production, phosphoric acid production, ferroalloy production, CO2
consumption, silicon carbide production and consumption, aluminum production, petrochemical production, nitric acid
production, adipic acid production, lead production, and zinc production. Additionally, emissions from industrial processes
release HFCs, PFCs, and SF6. Overall, emission sources in the Industrial Process chapter account for 4 percent of U.S.
greenhouse gas emissions in 2009.
Solvent and Other Product Use
The Solvent and Other Product Use chapter contains greenhouse gas emissions that are produced as a byproduct of
various solvent and other product uses. In the United States, emissions from N2O from product uses, the only source of
greenhouse gas emissions from this sector, accounted for about 0.1 percent of total U.S. anthropogenic greenhouse gas
emissions on a carbon equivalent basis in 2009.
Agriculture
The Agriculture chapter contains anthropogenic emissions from agricultural activities (except fuel combustion, which is
addressed in the Energy chapter, and agricultural CO2 fluxes, which are addressed in the Land Use, Land-Use Change, and
Forestry Chapter). Agricultural activities contribute directly to emissions of greenhouse gases through a variety of processes.
including the following source categories: enteric fermentation in domestic livestock, livestock manure management, rice
cultivation, agricultural soil management, and field burning of agricultural residues. CH4 and N2O were the primary
greenhouse gases emitted by agricultural activities. Methane emissions from enteric fermentation and manure management
represented 20 percent and 7 percent of total CH4 emissions from anthropogenic activities, respectively, in 2009.
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 15
-------
Agricultural soil management activities such as fertilizer application and other cropping practices were the largest source of
U.S. N2O emissions in 2009, accounting for 69 percent. In 2009, emission sources accounted for in the Agriculture chapter
were responsible for 6.3 percent of total U.S. greenhouse gas emissions.
Land Use, Land-Use Change, and Forestry
The Land Use, Land-Use Change, and Forestry chapter contains emissions of CH4 and N2O, and emissions and removals
of CO2 from forest management, other land-use activities, and land-use change. Forest management practices, tree planting
in urban areas, the management of agricultural soils, and the landfilling of yard trimmings and food scraps resulted in a net
uptake (sequestration) of C in the United States. Forests (including vegetation, soils, and harvested wood) accounted for 85
percent of total 2009 net CO2 flux, urban trees accounted for 9 percent, mineral and organic soil carbon stock changes
accounted for 4 percent, and landfilled yard trimmings and food scraps accounted for 1 percent of the total net flux in 2009.
The net forest sequestration is a result of net forest growth and increasing forest area, as well as a net accumulation of carbon
stocks in harvested wood pools. The net sequestration in urban forests is a result of net tree growth in these areas. In
agricultural soils, mineral and organic soils sequester approximately 5.5 times as much C as is emitted from these soils
through liming and urea fertilization. The mineral soil C sequestration is largely due to the conversion of cropland to
permanent pastures and hay production, a reduction in summer fallow areas in semi-arid areas, an increase in the adoption of
conservation tillage practices, and an increase in the amounts of organic fertilizers (i.e., manure and sewage sludge) applied
to agriculture lands. The landfilled yard trimmings and food scraps net sequestration is due to the long-term accumulation of
yard trimming carbon and food scraps in landfills.
Land use, land-use change, and forestry activities in 2009 resulted in a net C sequestration of 1,015.1 Tg CO2 Eq. (Table
ES-5). This represents an offset of 18 percent of total U.S. CO2 emissions, or 15 percent of total greenhouse gas emissions in
2009. Between 1990 and 2009, total land use, land-use change, and forestry net C flux resulted in a 17.8 percent increase in
CO2 sequestration, primarily due to an increase in the rate of net C accumulation in forest C stocks, particularly in
aboveground and belowground tree biomass, and harvested wood pools. Annual C accumulation in landfilled yard trimmings
and food scraps slowed over this period, while the rate of annual C accumulation increased in urban trees.
Table ES-5: Net C02 Flux from Land Use, Land-Use Change, and Forestry (Tg or million metric tons C02 Eq.)
Sink Category
Forest Land Remaining Forest Land
Cropland Remaining Cropland
Land Converted to Cropland
Grassland Remaining Grassland
Land Converted to Grassland
Settlements Remaining Settlements
Other (Landfilled Yard Trimmings and Food
Scraps)
Total
1990
(681.1)
(29.4)
2.2
(52.2)
(19.8)
(57.1)
(24.2)
(861.5)
2000
(378.3)
(30.2)
2.4
(52.6)
(27.2)
(77.5)
(13.2)
(576.6)
2005
(911.5)
(18.3)
5.9
(8.9)
(24.4)
(87.8)
(11.5)
(1,056.5)
2006
(917.5)
(19.1)
5.9
(8.8)
(24.2)
(89.8)
(11.0)
(1,064.3)
2007
(911.9)
(19.7)
5.9
(8.6)
(24.0)
(91.9)
(10.9)
(1,060.9)
2008
(891.0)
(18.1)
5.9
(8.5)
(23.8)
(93.9)
(11.2)
(1,040.5)
2009
(863.1)
(17.4)
5.9
(8.3)
(23.6)
(95.9)
(12.6)
(1,015.1)
Note: Totals may not sum due to independent rounding. Parentheses indicate net sequestration.
Emissions from Land Use, Land-Use Change, and Forestry are shown in Table ES-6. The application of crushed
limestone and dolomite to managed land (i.e., liming of agricultural soils) and urea fertilization resulted in CO2 emissions of
7.8 Tg CO2 Eq. in 2009, an increase of 11 percent relative to 1990. The application of synthetic fertilizers to forest and
settlement soils in 2009 resulted in direct N2O emissions of 1.9 Tg CO2 Eq. Direct N2O emissions from fertilizer application
to forest soils have increased by 455 percent since 1990, but still account for a relatively small portion of overall emissions.
Additionally, direct N2O emissions from fertilizer application to settlement soils increased by 55 percent since 1990. Forest
16 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
fires resulted in CH4 emissions of 7.8 Tg CO2 Eq., and in N2O emissions of 6.4 Tg CO2 Eq. in 2009. Carbon dioxide and
N2O emissions from peatlands totaled 1.1 Tg CO2 Eq. and less than 0.01 Tg CO2 Eq. in 2009, respectively.
Table ES-6: Emissions from Land Use, Land-Use Change, and Forestry (Tg or million metric tons C02 Eq.)
Source Category 1990 2000 2005 2006 2007 2008 2009
C02 8.1 8.8 8.9 8.8 9.2 9.6 8.9
Cropland Remaining Cropland: Liming of Agricultural Soils 4./B 4.3B 4.3 4.2 4.5 5.0 4.2
Cropland Remaining Cropland: Urea Fertilization 2AM 3.2U 3.5 3.7 3.7 3.6 3.6
Wetlands Remaining Wetlands: Peatlands Remaining Peatlands 1.ol 1.2l 1.1 0.9 1.0 1.0 1.1
CH4 3.2 14.3 9.8 21.6 20.0 11.9 7.8
Forest Land Remaining Forest Land: Forest Fires 3.2l 14.sB 9.8 21.6 20.0 11.9 7.8
N20 3.?l 13.2 9.8 19.5 18.3 11.6 8.3
Forest Land Remaining Forest Land: Forest Fires 2.6l 11.7M 8.0 17.6 16.3 9.8 6.4
Forest Land Remaining Forest Land: Forest Soils 0.11 0.4l 0.4 0.4 0.4 0.4 0.4
Settlements Remaining Settlements: Settlement Soils 1.ol 1.11 1.5 1.5 1.6 1.5 1.5
Wetlands Remaining Wetlands: Peatlands Remaining Peatlands + + + + + + +_
Total 15.0 36.3 28.6 49.8 47.5 33.2 25.0
+ Less than 0.05 Tg C02 Eq.
Note: Totals may not sum due to independent rounding.
Waste
The Waste chapter contains emissions from waste management activities (except incineration of waste, which is
addressed in the Energy chapter). Landfills were the largest source of anthropogenic greenhouse gas emissions in the Waste
chapter, accounting for just over 78 percent of this chapter's emissions, and 17 percent of total U.S. CH4 emissions.15
Additionally, wastewater treatment accounts for 20 percent of Waste emissions, 4 percent of U.S. CH4 emissions, and 2
percent of U.S. N2O emissions. Emissions of CH4 and N2O from composting are also accounted for in this chapter;
generating emissions of 1.7 Tg CO2 Eq. and 1.8 Tg CO2 Eq., respectively. Overall, emission sources accounted for in the
Waste chapter generated 2.3 percent of total U.S. greenhouse gas emissions in 2009.
ES.4. Other Information
Emissions by Economic Sector
Throughout the Inventory of U.S. Greenhouse Gas Emissions and Sinks report, emission estimates are grouped into six
sectors (i.e., chapters) defined by the IPCC: Energy; Industrial Processes; Solvent Use; Agriculture; Land Use, Land-Use
Change, and Forestry; and Waste. While it is important to use this characterization for consistency with UNFCCC reporting
guidelines, it is also useful to allocate emissions into more commonly used sectoral categories. This section reports
emissions by the following economic sectors: Residential, Commercial, Industry, Transportation, Electricity Generation.
Agriculture, and U.S. Territories.
Table ES-7 summarizes emissions from each of these sectors, and Figure ES-13 shows the trend in emissions by sector
from 1990 to 2009.
Landfills also store carbon, due to incomplete degradation of organic materials such as wood products and yard trimmings, as described in the Land-Use.
Land-Use Change, and Forestry chapter of the inventory report.
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 17
-------
Table ES-7: U.S. Greenhouse Gas Emissions Allocated to Economic Sectors (Tg or million metric tons C02 Eq.)
Implied Sectors
Electric Power Industry
Transportation
Industry
Agriculture
Commercial
Residential
U.S. Territories
Total Emissions
Land Use, Land-Use Change, and Forestry
(Sinks)
Net Emissions (Sources and Sinks)
1990
1,868.9
1,545.2
1,564.4
429.0
395.5
345.1
33.7
6,181.8
(861.5)
5,320.3
2000
2,337.6
1,932.3
1,544.0
485.1
381.4
386.2
46.0
7,112.7
(576.6)
6,536.1
2005
2,444.6
2,017.4
1,441.9
493.2
387.2
371.0
1 58.2
7,213.5
(1,056.5)
6,157.1
2006
2,388.2
1,994.4
1,497.3
516.7
375.2
335.8
59.3
7,166.9
(1,064.3)
6,102.6
2007
2,454.0
2,003.8
1,483.0
520.7
389.6
358.9
53.5
7,263.4
(1,060.9)
6,202.5
2008
2,400.7
1,890.7
1,446.9
503.9
403.5
367.1
48.4
7,061.1
(1,040.5)
6,020.7
2009
2,193.0
1,812.4
1,322.7
490.0
409.5
360.1
45.5
6,633.2
(1,015.1)
5,618.2
Note: Totals may not sum due to independent rounding. Emissions include C02, CH4, N20, MFCs, PFCs, and SF6.
See Table 2-12 of the inventory report for more detailed data.
Emissions Allocated to Economic Sectors
2,500 -,
2,000
1,500-
1,000
500
Electric Power Industry
^^^ ^^"^^
Transportation
—\
Industry
Agriculture
Commercial
—~*_-~—•
Residential
Figure ES-13 Using this categorization, emissions from electricity
generation accounted for the largest portion (33 percent) of
U.S. greenhouse gas emissions in 2009. Transportation
activities, in aggregate, accounted for the second largest
portion (27 percent), while emissions from industry accounted
for the third largest portion (20 percent) of U.S. greenhouse
gas emissions in 2009. In contrast to electricity generation and
transportation, emissions from industry have in general
declined over the past decade. The long-term decline in these
emissions has been due to structural changes in the U.S.
economy (i.e., shifts from a manufacturing-based to a service-
based economy), fuel switching, and energy efficiency
improvements. The remaining 20 percent of U.S. greenhouse
gas emissions were contributed by, in order of importance, the
agriculture, commercial, and residential sectors, plus emissions
from U.S. territories. Activities related to agriculture
accounted for 7 percent of U.S. emissions; unlike other
economic sectors, agricultural sector emissions were dominated by N2O emissions from agricultural soil management and
CH4 emissions from enteric fermentation. The commercial sector accounted for 6 percent of emissions while the residential
sector accounted for 5 percent of emissions and U.S. territories accounted for 1 percent of emissions; emissions from these
sectors primarily consisted of CO2 emissions from fossil fuel combustion.
Carbon dioxide was also emitted and sequestered by a variety of activities related to forest management practices, free
planting in urban areas, the management of agricultural soils, and landfilling of yard trimmings.
Electricity is ultimately consumed in the economic sectors described above. Table ES-8 presents greenhouse gas
emissions from economic sectors with emissions related to electricity generation distributed into end-use categories (i.e..
emissions from electricity generation are allocated to the economic sectors in which the electricity is consumed). To
distribute electricity emissions among end-use sectors, emissions from the source categories assigned to electricity generation
were allocated to the residential, commercial, industry, transportation, and agriculture economic sectors according to retail
Note: Does not include U.S. Territories.
18 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
sales of electricity.16 These source categories include CO2 from fossil fuel combustion and the use of limestone and dolomite
for flue gas desulfurization, CO2 and N2O from incineration of waste, CH4 and N2O from stationary sources, and SF6 from
electrical transmission and distribution systems.
Table ES-8: U.S. Greenhouse Gas Emissions by Economic Sector with Electricity-Related Emissions Distributed (Tg or million
metric tons C02 Eq.)
Implied Sectors 1990 2000 2005
Industry 2,238.3 2,314.4 2,162.5
Transportation 1,548.3 1,935.8 2,022.2
Commercial 947.7( 1,135.8 1,205.1
Residential 953.8 1,162.2 1,242.9
Agriculture 460.0 518.4 522.7
U.S. Territories 33.7 46.0 I 58.2
Total Emissions 6,181.8 7,112.7 7,213.5
Land Use, Land-Use Change,
and Forestry (Sinks) (861.5) (576.6) (1,056.5)
Net Emissions (Sources
and Sinks) 5,320.3 6,536.1 6,157.1
See Table 2-14 of the inventory report for more detailed data.
2006 2007
2,194.6 2,192.9
1,999.0 2,008.9
1,188.5 1,225.3
1,181.5 1,229.6
544.1 553.2
59.3 53.5
7,166.9 7,263.4
(1,064.3) (1,060.9)
6,102.6 6,202.5
2008 2009
2,146.5 1,910.9
1,895.5 1,816.9
1,224.5 1,184.9
1,215.1 1,158.9
531.1 516.0
48.4 45.5
7,061.1 6,633.2
(1,040.5) (1,015.1)
6,020.7 5,618.2
When emissions from electricity are distributed among Figure ES-14
these sectors, industrial activities account for the largest share
of U.S. greenhouse gas emissions (29 percent) in 2009.
T +U J1 +'t, +1TTC
transportation is tne second largest contributor to total u.o.
emissions (28 percent). The commercial and residential sectors
contributed the next largest shares of total U.S. greenhouse gas
emissions in 2009. Emissions from these sectors increase
substantially when emissions from electricity are included, due
to their relatively large share of electricity consumption (e.g.,
lighting, appliances, etc.). In all sectors except agriculture, CO2
accounts for more than 80 percent of greenhouse gas emissions,
primarily from the combustion of fossil fuels. Figure ES-14
shows the trend in these emissions by sector from 1990 to 2009.
2,500 -
2,000 -
5^ 1,500-
o'
ES
(21
1,000-
cfin
3UU
o-
Economic Sectors
^ " —
^^^
-^--*^
^>*^
^_^-^
---
^ ^-^
_ — -— — •*" ^
isiiillslli
^^ Industry
• r — TT^O
Transportation \»
^^--Residential
-~^-* «x.
- Commercial
Agriculture
iiiliiiis
Note: Does not include U.S. Territories.
Emissions were not distributed to U.S. territories, since the electricity generation sector only includes emissions related to the generation of electricity in
the 50 states and the District of Columbia.
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 19
-------
Box ES-2: Recent Trends in Various U.S. Greenhouse Gas Emissions-Related Data
Total emissions can be compared to other economic and social indices to highlight changes over time. These comparisons include: (1)
emissions per unit of aggregate energy consumption, because energy-related activities are the largest sources of emissions; (2) emissions per
unit of fossil fuel consumption, because almost all energy-related emissions involve the combustion of fossil fuels; (3) emissions per unit of
electricity consumption, because the electric power industry—utilities and nonutilities combined—was the largest source of U.S. greenhouse
gas emissions in 2009; (4) emissions per unit of total gross domestic product as a measure of national economic activity; and (5) emissions
per capita.
Table ES-9 provides data on various statistics related to U.S. greenhouse gas emissions normalized to 1990 as a baseline year. Greenhouse
gas emissions in the United States have grown at an average annual rate of 0.4 percent since 1990. This rate is slightly slower than that for
total energy and for fossil fuel consumption, and much slower than that for electricity consumption, overall gross domestic product and
national population (see Figure ES-15).
Table ES-9: Recent Trends in Various U.S. Data (Index 1990 = 100)
Variable
GDPb
Electricity Consumption c
Fossil Fuel Consumption c
Energy Consumption c
Population d
Greenhouse Gas Emissions e
1990
100
100
100
100
100
100
2000
140
127
117
116
113
115
2005
157
134
119
118
118
117
2006
162
135
117
118
120
116
2007
165
138
119
120
121
117
2008
165
138
116
118
122
114
2009
160
132
108
112
123
107
Growth
Rate3
2.5%
1.5%
0.5%
0.6%
1.1%
0.4%
a Average annual growth rate
b Gross Domestic Product in chained 2005 dollars (BEA 2010)
c Energy content-weighted values (EIA 201 Ob)
d U.S. Census Bureau (2010)
e GWP-weighted values
Figure ES-15
U.S. Greenhouse Gas Emissions Per Capita and Per Dollar of Gross
Domestic Product
1701
160
150-
_ 140
§ 130-
£ 100-
•o
- 90-
80-
70-
60
Real GDP
Emissions
per $GDP
o T— cMco^-mtof-cocj)
i— CM CO
CM CM CM
CM CM CM CM CM
Source: BEA (2010), U.S. Census Bureau (2010), and emission estimates in the inventory report.
20 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Indirect Greenhouse Gases (CO, NOX, NMVOCs, and S02)
The reporting requirements of the UNFCCC request that information be provided on indirect greenhouse gases, which
include CO, NOX, NMVOCs, and SO2. These gases do not have a direct global warming effect, but indirectly affect
terrestrial radiation absorption by influencing the formation and destruction of tropospheric and stratospheric ozone, or, in the
case of SO2, by affecting the absorptive characteristics of the atmosphere. Additionally, some of these gases may react with
other chemical compounds in the atmosphere to form compounds that are greenhouse gases.
Since 1970, the United States has published estimates of annual emissions of CO, NOX, NMVOCs, and SO2 (EPA 2010,
EPA 2009),18 which are regulated under the Clean Air Act. Table ES-10 shows that fuel combustion accounts for the
majority of emissions of these indirect greenhouse gases. Industrial processes—such as the manufacture of chemical and
allied products, metals processing, and industrial uses of solvents—are also significant sources of CO, NOX, and NMVOCs.
Table ES-10: Emissions of NOX, CO, NMVOCs, and S02 (Gg)
Gas/Activity
1990
2000
2005
2006
2007
2008
2009
NOX
Mobile Fossil Fuel Combustion
Stationary Fossil Fuel Combustion
Industrial Processes
Oil and Gas Activities
Incineration of Waste
Agricultural Burning
Solvent Use
Waste
CO
Mobile Fossil Fuel Combustion
Stationary Fossil Fuel Combustion
Industrial Processes
Incineration of Waste
Agricultural Burning
Oil and Gas Activities
Waste
Solvent Use
NMVOCs
Mobile Fossil Fuel Combustion
Solvent Use
Industrial Processes
Stationary Fossil Fuel Combustion
Oil and Gas Activities
Incineration of Waste
Waste
Agricultural Burning
S02
Stationary Fossil Fuel Combustion
Industrial Processes
Mobile Fossil Fuel Combustion
Oil and Gas Activities
Incineration of Waste
Waste
Solvent Use
Agricultural Burning
NA (Not Available)
Note: Totals may not sum due to independent rounding.
Source: (EPA 2010, EPA 2009) except for estimates from field burning of agricultural residues.
14,380
7,965
5,432
537
318
114
13,547
7,441
5,148
520
318
106
See .
11,468
6,206
4,159
568
393
128
18
NOX and CO emission estimates from field burning of agricultural residues were estimated separately, and therefore not taken from EPA (2008).
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 21
-------
Key Categories
The 2006IPCC Guidelines for National Greenhouse Gas Inventories (IPCC 2006) defines a key category as a "[source
or sink category] that is prioritized within the national inventory system because its estimate has a significant influence on a
country's total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, or
both."19 By definition, key categories are sources or sinks that have the greatest contribution to the absolute overall level of
national emissions in any of the years covered by the time series. In addition, when an entire time series of emission
estimates is prepared, a thorough investigation of key categories must also account for the influence of trends of individual
source and sink categories. Finally, a qualitative evaluation of key categories should be performed, in order to capture any
key categories that were not identified in either of the quantitative analyses.
Figure ES-16
2009 Key Categories
CO; Emissions Irom Stationary Combustion - Coal
C0? Emissions from Mobile Combustion - Road
CO, Emissions from Stationary Combustion - Gas
CO, Emissions from Stationary Combustion - Oil
Fugitive CH4 Emissions from Natural Gas Systems
Direct N,0 Emissions from Agricultural Soil Management |
CO; Emissions from Mobile Combustion - Aviation |
CH, Emissions from Enteric Fermentation |
C0;, Emissions from Non-Energy Use of Fuels |
Emissions from Substitutes for Ozone Depleting Substances |
CH, Emissions from Landfills |
C02 Emissions from Mobile Combustion: Other |
Fugitive CH, Emissions from Coal Mining |
CH, Emissions from Manure Management |
Indirect N,0 Emissions from Applied Nitrogen |
C0? Emissions from Iron and Steel Production & Metallurgical Coke Production |
CO, Emissions from Natural Gas Systems |
Fugitive CH, Emissions from Petroleum Systems
CH, Emissions from Wastewater Treatment
Non-CD, Emissions from Stationary Combustion
CH, Emissions from Rice Cultivation
Key Categories as a
Portion of all Emissions
i
200
I
T
T
400 600 800 1,000 1,200 1,400 1,600 1,800 2,000
Tg CO, Eq.
Note: For a complete discussion of the key category analysis, see Annex 1 of the inventory report. Darker bars indicate a Tier 1 level assessment key category.
Lighter bars indicate a Tier 2 level assessment key category.
Figure ES-16 presents 2009 emission estimates for the key categories as defined by a level analysis (i.e., the contribution
of each source or sink category to the total inventory level). The UNFCCC reporting guidelines request that key category
analyses be reported at an appropriate level of disaggregation, which may lead to source and sink category names which
differ from those used elsewhere in the inventory report. For more information regarding key categories, see section 1.5 and
Annex 1.
19
See Chapter 7 "Methodological Choice and Recalculation" in IPCC (2000). .
22 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
-------
Quality Assurance and Quality Control (QA/QC)
The United States seeks to continually improve the quality, transparency, and credibility of the Inventory of U.S.
Greenhouse Gas Emissions and Sinks. To assist in these efforts, the United States implemented a systematic approach to
QA/QC. While QA/QC has always been an integral part of the U.S. national system for inventory development, the
procedures followed for the current inventory have been formalized in accordance with the QA/QC plan and the UNFCCC
reporting guidelines.
Uncertainty Analysis of Emission Estimates
While the current U.S. emissions inventory provides a solid foundation for the development of a more detailed and
comprehensive national inventory, there are uncertainties associated with the emission estimates. Some of the current
estimates, such as those for CO2 emissions from energy-related activities and cement processing, are considered to have low
uncertainties. For some other categories of emissions, however, a lack of data or an incomplete understanding of how
emissions are generated increases the uncertainty associated with the estimates presented. Acquiring a better understanding
of the uncertainty associated with inventory estimates is an important step in helping to prioritize future work and improve
the overall quality of the inventory report. Recognizing the benefit of conducting an uncertainty analysis, the UNFCCC
reporting guidelines follow the recommendations of the IPCC Good Practice Guidance (IPCC 2000) and require that
countries provide single estimates of uncertainty for source and sink categories.
Currently, a qualitative discussion of uncertainty is presented for all source and sink categories. Within the discussion of
each emission source, specific factors affecting the uncertainty surrounding the estimates are discussed. Most sources also
contain a quantitative uncertainty assessment, in accordance with UNFCCC reporting guidelines.
Box ES-3: Recalculations of Inventory Estimates
Each year, emission and sink estimates are recalculated and revised for all years in the Inventory of U.S. Greenhouse Gas Emissions and
Sinks, as attempts are made to improve both the analyses themselves, through the use of better methods or data, and the overall usefulness
of the inventory report. In this effort, the United States follows the 2006 IPCC Guidelines (IPCC 2006), which states, "Both methodological
changes and refinements overtime are an essential part of improving inventory quality. It is good practice to change or refine methods"
when: available data have changed; the previously used method is not consistent with the IPCC guidelines for that category; a category has
become key; the previously used method is insufficient to reflect mitigation activities in a transparent manner; the capacity for inventory
preparation has increased; new inventory methods become available; and for correction of errors." In general, recalculations are made to the
U.S. greenhouse gas emission estimates either to incorporate new methodologies or, most commonly, to update recent historical data.
In each inventory report, the results of all methodology changes and historical data updates are presented in the "Recalculations and
Improvements" chapter; detailed descriptions of each recalculation are contained within each source's description contained in the report, if
applicable. In general, when methodological changes have been implemented, the entire time series (in the case of the most recent inventory
report, 1990 through 2009) has been recalculated to reflect the change, per the 2006 IPCC Guidelines (IPCC 2006). Changes in historical
data are generally the result of changes in statistical data supplied by other agencies. References for the data are provided for additional
information.
Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009 23
-------
References
BEA (2010) 2009 Comprehensive Revision of the National Income and Product Accounts: Current-dollar and "real" GDP,
1929-2009. Bureau of Economic Analysis (BEA), U.S. Department of Commerce, Washington, DC. July 29, 2010.
Available online at < http://www.bea.gov/national/index.htnrfgdp >.
EIA (2010) Supplemental Tables on Petroleum Product detail. Monthly Energy Review, September 2010, Energy
Information Administration, U.S. Department of Energy, Washington, DC. DOE/EIA-0035(2009/09).
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EPA (2010) "2009 Average annual emissions, all criteria pollutants in MS Excel." National Emissions Inventory (NEI) Air
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Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattenberg, and K. Maskell. (eds.). Cambridge University Press.
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IPCC/UNEP/OECD/IEA (1997) Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories.
Intergovernmental Panel on Climate Change, United Nations Environment Programme, Organization for Economic Co-
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24 Executive Summary of the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009
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United States
Environmental Protection Agency
EPA 430-S-11-001
April 2011
Office of Atmospheric Programs (6207J)
Washington, DC 20460
Official Business
Penalty for Private Use
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