Executive Summary ES-1 

## Executive Summary

An emissions inventory that identifies and quantifies a country's primary anthropogenic 1 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 th at enables Parties to the United Nations Framework Convention on Climate Change (UNFCCC) to compare the relative contribution of differe nt 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 woul d prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved with in 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
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 this report as an opportunity to fulfill these commitments. This chapter summarizes the latest information on U.S. anthropogenic greenhouse gas emission trends from 1990 through 2008. To ensure that the U.S. emissions invent ory is comparable to those of other UNFCCC Parties, the estimates presented here were calculated using methodologies consistent with those recommended in the Revised 1996 IPCC Guidelines for National Greenhouse Gas In ventories (IPCC/UNEP/OECD/IEA 1997), the IPCC Good Practice Guidance and Uncertainty Management in Nation al Greenhouse Gas Inventories (IPCC 2000), and the IPCC Good Practice Guidance for Land Use, Land-Use Ch ange, and Forestry (IPCC 2003). Additionally, the U.S. emission inventory has begun to incorporate new methodologies and data from the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (IPC C 2006). The structure of this repo rt is consistent with the UNFCCC guidelines for inventory reporting. 4 For most source categorie s, the Intergovernmental Panel on Climate Change (IPCC) methodologies were expanded, resulting in a more comprehensive and detailed estimate of emissions.

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Box ES- 1: 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 themselv es, through the use of better methods or data, and the overall usefulness of the report. In this effort, the United States follows the IPCC Good Practice Guidance (IPCC 2000), wh ich states, regarding recalculations of th e time series, "It is good practice to recalculate historic emissions when me thods are changed or refined, when new source categories are included in the national inventory, or when errors in the estimates are iden tified and corrected." 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.

1 The term “anthropogenic”, in this context, refers to greenhouse gas emissions and rem ovals 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). 2 Article 2 of the Framework Conventio n on Climate Change published by the UN EP/WMO Informati on Unit on Climate Change. See <http://unfccc.int>. 3 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 <http://unfccc.int>. 4 See <http://unfccc.int/res ource/docs/cop8/08.pdf>.ES-2 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 In each Inventory report, the results of all methodology changes and historical data updates are presented in the "Recalculations and Improvements" chapter; detailed descri ptions 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 2007) has been recalculated to reflect the change, per IPCC Good Practice Guidance. Changes in historical data are generally the result of changes in statistical data supplied by other agenci es. References for the data are provided for additional information.

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### Background Information
Naturally occurring greenhouse gases include water vapor, carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), and ozone (O 3 ). 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. 5 Some other fluorine-containing halogenated substances—hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF 6 )—do not deplete stratospheric ozone but are potent greenhouse gases. These latter substances are addressed by the UNFCCC and accounted for in national gr eenhouse gas emission inventories. There are also several gases that do not have a direct globa l 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 (NO x ), and non-CH 4 volatile organic compounds (NMVOCs). Aerosols, which are extremely small particles or liquid droplets, such as those produced by sulfur dioxide (SO 2 ) or elemental carbon emissions, can also affect the absorp tive characteristics of the atmosphere. Although the direct greenhouse gases CO 2 , CH 4 , and N 2 O occur naturally in the atmosphere, human activities have changed their atmospheric concentrations. From the pr e-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). 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 inte rnational 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). 6 The IPCC developed the Global Warming Potentia l (GWP) concept to compare the ability of each

5 Emissions estimates of CFCs, HCFCs, ha lons and other ozone-depleting substanc es are included in the annexes of the Inventory report for informational purposes. 6 Albedo is a measure of the Earth’s reflec tivity, and is defined as the fraction of the total solar radiation incident on a bod y that is reflected by it.Executive Summary ES-3 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 CO 2 , and therefore GWPweighted emissions are measured in teragrams (or million metric tons) of CO 2 equivalent (Tg CO 2 Eq.) 7 , 8 All gases in this Executive Summary are presented in units of Tg CO 2 Eq.
The UNFCCC reporting guidelines for nati onal inventories were updated in 2006, 9 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 2008 are consistent with estimates developed prior to the publication of the IPCC Third Assessment Report (T AR) and the IPCC Fourth Assessment Report (AR4). Therefore, to comply with international reporting stan dards under the UNFCCC, official emission estimates are reported by the United States using SAR GWP values. All estimates are provided throughout the report in both CO 2 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 this report. The GWP values used in this report are listed below in Table ES-1. Table ES-1: Global Warming Potentials (100-Year Time Horizon) Used in this Report

Gas GWP CO 2 1 CH 4 * 21 N 2 O 310 HFC-23 11,700 HFC-32 650 HFC-125 2,800 HFC-134a 1,300 HFC-143a 3,800 HFC-152a 140 HFC-227ea 2,900 HFC-236fa 6,300 HFC-4310mee 1,300 CF 4 6,500 C 2 F 6 9,200 C 4 F 10 7,000 C 6 F 14 7,400 SF 6 23,900 Source: IPCC (1996) * The CH 4 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 CO 2 is not included.

Global warming potentials are not provided for CO, NO x , NMVOCs, SO 2 , and aerosols because there is no agreedupon 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).



### Recent Trends in U.S. Greenhouse Gas Emissions and Sinks
In 2008, total U.S. greenhouse gas emissions were 6,956.8 Tg CO 2 Eq. Overall, total U.S. emissions have risen by approximately 14 percent from 1990 to 2008. Emissions declined from 2007 to 2008, decreasing by 2.9 percent (211.3 Tg CO 2 Eq.). This decrease is primarily a result of a de crease in demand for transp ortation fuels associated with the record high costs of these fuels that occurred in 2008. Additionally, electricity demand declined in 2008 in part due to a significant increase in the cost of fuels used to generate electricity. In 2 008, temperatures were cooler

7 Carbon comprises 12/44 ths of carbon dioxide by weight. 8 One teragram is equal to 10 12 grams or one million metric tons. 9 See <http://unfccc. int/resource/docs/2006/sbsta/eng/09.pdf>.ES-4 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 in the United States than in 2007, both in the summer and the winter. This lead to an increase in heating related energy demand in the winter, however, much of this increa se was offset by a decrease in cooling related electricity demand in the summer. 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 2008.

Figure ES-1: U.S. Greenhouse Gas Emissions by Gas

Figure ES-2: Annual Percent Change in U.S. Greenhouse Gas Emissions

Figure ES-3: Cumulative Change in Annual U.S. Greenhouse Gas Emissions Relative to 1990

Table ES-2: Recent Trends in U.S. Gr eenhouse Gas Emissions and Sinks (Tg CO 2 Eq. or million metric tons CO 2 Eq.) Gas/Source 1990 1995 2000 2005 2006 2007 2008 CO 2 5,100.8 5,427.3 5,977.2 6,108.4 6,017.2 6,120.2 5,921.2

Fossil Fuel Combustion 4,735.7 5,029.5 5,593.4 5,753.3 5,652.8 5,757.0 5,572.8

Electricity Generation 1,820.8 1,947.9 2,296.9 2,402.1 2,346.4 2,412.8 2,363.5 Transportation 1,485.8 1,608.0 1,809.5 1,895.3 1,876.7 1,893.7 1,785.3 Industrial 845.4 862.6 852.2 825.6 850.7 842.2 819.3 Residential 339.1 353.3 371.2 358.4 322.1 341.7 342.7 Commercial 216.7 223.2 227.7 221.3 206.0 217.4 219.5 U.S. Territories 27.9 34.5 35.9 50.6 50.9 49.1 42.5 Non-Energy Use of Fuels 119.6 142.9 146.1 136.5 141.4 135.3 134.2 Iron and Steel Production &

Metallurgical Coke Production 102.6 95.7 88.1 67.7 70.5 72.8 69.0 Cement Production 33.3 36.8 41.2 45.9 46.6 45.2 41.1 Natural Gas Systems 37.3 42.2 29.4 29.5 29.5 30.8 30.0 Lime Production 11.5 13.3 14.1 14.4 15.1 14.6 14.3 Incineration of Waste 8.0 11.5 11.3 12.6 12.7 13.3 13.1 Ammonia Production and Urea

Consumption 16.8 17.8 16.4 12.8 12.3 14.0 11.8 Cropland Remaining Cropland 7.1 7.0 7.5 7.9 7.9 8.3 7.6 Limestone and Dolomite Use 5.1 6.7 5.1 6.8 8.0 7.7 6.6 Aluminum Production 6.8 5.7 6.1 4.1 3.8 4.3 4.5 Soda Ash Production and

Consumption 4.1 4.3 4.2 4.2 4.2 4.1 4.1 Petrochemical Production 3.3 4.1 4.5 4.2 3.8 3.9 3.4 Titanium Dioxide Production 1.2 1.5 1.8 1.8 1.8 1.9 1.8 Carbon Dioxide Consumption 1.4 1.4 1.4 1.3 1.7 1.9 1.8 Ferroalloy Production 2.2 2.0 1.9 1.4 1.5 1.6 1.6 Phosphoric Acid Production 1.5 1.5 1.4 1.4 1.2 1.2 1.2 Wetlands Remaining Wetlands 1.0 1.0 1.2 1.1 0.9 1.0 0.9 Petroleum Systems 0.6 0.5 0.5 0.5 0.5 0.5 0.5 Zinc Production 0.9 1.0 1.1 0.5 0.5 0.4 0.4 Lead Production 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Silicon Carbide Production and

Consumption 0.4 0.3 0.2 0.2 0.2 0.2 0.2 Land Use, Land-Use Change, (909.4) (842.9) (664.2) (950.4) (959.2) (955.4) (940.3)Executive Summary ES-5 and Forestry (Sink) a Biomass - Wood 215.2 229.1 218.1 206.9 207.9 207.4 198.4 International Bunker Fuels b 111.8 99.8 98.5 110.5 129.1 127.1 135.2 Biomass - Ethanol 4.2 7. 7 9.2 22. 6 30.5 38.3 53.3 CH 4 613.4 613.2 586.0 553.2 568.2 569.2 567.6

Enteric Fermentation 132.4 143.7 136.8 136.7 139.0 141.2 140.8 Landfills 149.3 144.1 120.7 125.6 127.1 126.5 126.3 Natural Gas Systems 129.5 132.6 130.7 103.6 103.1 99.5 96.4 Coal Mining 84.1 67.1 60.4 56.9 58.3 58.1 67.6 Manure Management 29.3 33.9 38.6 42.2 42.3 45.9 45.0 Petroleum Systems 33.9 32.0 30.2 28.2 28.2 28.8 29.1 Wastewater Treatment 23.5 24.8 25.2 24.3 24.5 24.4 24.3 Forest Land Remaining Forest

Land 3.2 4.3 14.3 9.8 21.6 20.0 11.9 Rice Cultivation 7.1 7.6 7.5 6.8 5.9 6.2 7.2 Stationary Combustion 7.4 7.1 6.6 6.6 6.2 6.5 6.7 Abandoned Underground Coal

Mines 6.0 8.2 7.4 5.6 5.5 5.7 5.9 Mobile Combustion 4.7 4.3 3.4 2.5 2.3 2.2 2.0 Composting 0.3 0.7 1.3 1.6 1.6 1.7 1.7 Field Burning of Agricultural

Residues 0.8 0.7 0.9 0.9 0.9 1.0 1.0 Petrochemical Production 0.9 1.1 1.2 1.1 1.0 1.0 0.9 Iron and Steel Production &

Metallurgical Coke Production 1.0 1.0 0.9 0.7 0.7 0.7 0.6 Ferroalloy Production + + + + + + + Silicon Carbide Production and

Consumption + + + + + + + Incineration of Waste + + + + + + + International Bunker Fuels b 0.2 0.1 0.1 0.1 0.2 0.2 0.2 N 2 O 322.3 342.5 345.5 328.3 329.5 327.7 318.2

Agricultural Soil Management 203.5 205.9 210.1 215.8 211.2 211.0 215.9 Mobile Combustion 43.9 54.0 53.2 36.9 33.6 30.3 26.1 Nitric Acid Production 18.9 21.0 20.7 17.6 17.2 20.5 19.0 Manure Management 14.4 15.5 16.7 16.6 17.3 17.3 17.1 Stationary Combustion 12.8 13.3 14.5 14.7 14.5 14.6 14.2 Forest Land Remaining Forest

Land 2.7 3.7 12.1 8.4 18.0 16.7 10.1 Wastewater Treatment 3.7 4.0 4.5 4.7 4.8 4.9 4.9 N 2 O from Product Uses 4.4 4.6 4.9 4.4 4.4 4.4 4.4 Adipic Acid Production 15.8 17.6 5.5 5.0 4.3 3.7 2.0 Composting 0.4 0.8 1.4 1.7 1.8 1.8 1.8 Settlements Remaining

Settlements 1.0 1.2 1.1 1.5 1.5 1.6 1.6 Field Burning of Agricultural

Residues 0.4 0.4 0.5 0.5 0.5 0.5 0.5 Incineration of Waste 0.5 0.5 0.4 0.4 0.4 0.4 0.4 Wetlands Remaining Wetlands + + + + + + + International Bunker Fuels b 1.1 0.9 0.9 1.0 1.2 1.2 1.2 HFCs 36.9 62.2 103.2 119.3 121.8 127.4 126.9

Substitution of Ozone

Depleting Substances c 0.3 29.0 74.3 103.2 107.7 110.1 113.0 HCFC-22 Production 36.4 33.0 28.6 15.8 13.8 17.0 13.6 Semiconductor Manufacture 0.2 0.3 0.3 0.2 0.3 0.3 0.3 PFCs 20.8 15.6 13.5 6.2 6.0 7.5 6.7ES-6 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 Aluminum Production 18.5 11.8 8.6 3.0 2.5 3.8 2.7 Semiconductor Manufacture 2.2 3.8 4.9 3.2 3.5 3.6 4.0 SF 6 32.6 27.9 19.1 17.8 17.0 16.1 16.1

Electrical Transmission and

Distribution 26.6 21.4 15.0 14.0 13.2 12.7 13.1 Magnesium Production and

Processing 5.4 5.6 3.0 2.9 2.9 2.6 2.0 Semiconductor Manufacture 0.5 0.9 1.1 1.0 1.0 0.8 1.1 Total 6,126.8 6,488.8 7,044.5 7,133.2 7,059.9 7,168.1 6,956.8 Net Emissions (Sources and

Sinks) 5,217.3 5,646.0 6,380.2 6,182.8 6,100.7 6,212.7 6,016.4 + Does not exceed 0.05 Tg CO 2 Eq.

a Parentheses indicate negative valu es or sequestration. The net CO 2 flux total includes both emissi ons and sequestration, and constitutes a sink in the United States. Sinks are only included in net emissions total.
b Emissions from International Bunker Fuels and Biomass Combustion are not included in totals.

c Small amounts of PFC emissions also result from this source. Note: Totals may not sum due to independent rounding. Note: One teragram (Tg) equals one million metric tons.

Figure ES-4 illustrates the relative contribution of the direct greenhouse gases to total U.S. emissions in 2008. The primary greenhouse gas emitted by human activities in the United States was CO 2 , representing approximately 85.1 percent of total greenhouse gas emissions. The largest source of CO 2 , and of overall greenhouse gas emissions, was fossil fuel combustion. CH 4 emissions, which have declined by 5.5 percent since 1990, resulted primarily from enteric fermentation associated with domestic livestock , decomposition of wastes in landfills, and natural gas systems. Agricultural soil management and mobile source fuel combustion were the major sources of N 2 O emissions. Ozone depleting substance substitute emissi ons and emissions of HFC-23 during the production of HCFC-22 were the primary contributors to aggregate HFC emissions. PFC emissions resulted as a by-product of primary aluminum production and from semiconductor manufacturing, while electrical transmission and distribution systems accounted for most SF 6 emissions.

Figure ES-4: 2008 Greenhouse Gas Emissions by Gas (percents based on Tg CO 2 Eq.)

Overall, from 1990 to 2008 total emissions of CO 2 increased by 820.4 Tg CO 2 Eq. (16.1 percent), while CH 4 and N 2 O emissions decreased by 45.8 Tg CO 2 Eq. (7.5 percent) and 4.1 Tg CO 2 Eq. (1.3 percent), respectively. During the same period, aggregate weighted emissions of HFCs, PFCs, and SF 6 rose by 59.4 Tg CO 2 Eq. (65.9 percent). From 1990 to 2008, HFCs increased by 90.0 Tg CO 2 Eq. (243.7 percent), PFCs decreased by 14.1 Tg CO 2 Eq. (67.8 percent), and SF 6 decreased by 16.5 Tg CO 2 Eq. (50.5 percent). Despite being emitted in smaller quantities relative to the other principal greenhouse gases, emissions of HFCs, PFCs, and SF 6 are significant because many of these gases have extremely high global warming potentials and, in the cases of PFCs and SF 6 , 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 13.5 percent of total emissions in 2008. 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 an d reservoirs. Billions of tons of carbon in the form of CO 2 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 CO 2 have risen about 36 percent (IPCC 2007), principally due to the combustion of fossil fuels. Within the United States, fossil fuel combustion accounted for 94.1 percent of CO 2 emissions in 2008. Globally, approximately 30,377 Tg of CO 2 wereExecutive Summary ES-7 added to the atmosphere through the combustion of fossil fuels in 2008, of which the United States accounted for about 19 percent. 10 Changes in land use and forestry practices can also emit CO 2 (e.g., through conversion of forest land to agricultural or urban use) or can act as a sink for CO 2 (e.g., through net additions to forest biomass). In addition to fossil-fuel combustion, several other sources emit significant quantities of CO 2 . These sources include, but are not limited to non-energy use of fuels, iron and steel production and cement production (Figure ES-5).

Figure ES- 5: 2008 Sources of CO 2 Emissions

As the largest source of U.S. greenhouse gas emissions, CO 2 from fossil fuel combustion has accounted forapproximately 79 percent of GWP-weighted emissions since 1990, growing slowly from 77 percent of total GWPweighted emissions in 1990 to 80 percent in 2008. Emissions of CO 2 from fossil fuel combustion increased at an average annual rate of 1 percent from 1990 to 2008. The fundamental factors influencing this trend include (1) a generally growing domestic economy over the last 19 years, and (2) significant overall growth in emissions from electricity generation and transportation activities. Between 1990 and 2008, CO 2 emissions from fossil fuel combustion increased from 4,735.7 Tg CO 2 Eq. to 5,572.8 Tg CO 2 Eq.—an 18 percent total increase over the nineteen-year period. From 2007 to 2008, these emissions decreased by 184.2 Tg CO 2 Eq. (3.2 percent). Historically, changes in emissions from fossil fuel combustion have been the dominant factor affecting U.S. emission trends. Changes in CO 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. On an annual basis, the overall consumption of fossil fuels in the United States generallyfluctuates in response to changes in general economic conditions, energy prices, weather, and the availability of nonfossil alternatives. For exampl e, in a year with increased consumption of goods and services, low fuel prices, severe summer and winter weather conditions, nuclear plant clos ures, 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 increas ed output from nuclear and hydroelectric plants.

Figure ES- 6: 2008 CO 2 Emissions from Fossil Fuel Combustion by Sector and Fuel Type

Figure ES- 7: 2008 End-Use Sector Emissions of CO 2 , CH 4 , and N 2 O from Fossil Fuel Combustion

The five major fuel consuming sectors contributing to CO 2 emissions from fossil fuel combustion are electricity generation, transportation, industrial, residential, and commercial. CO 2 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 elect ricity that is generated from the na tional average mix of fuels according to their carbon intensity. Emissions from electricity generatio n are also addressed separately after the end-use sectors have been discussed. Note that emissions from U.S. territories are calculated sepa rately 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 CO 2 emissions from fossil fuel combustion by end-use
sector.

Table ES-3: CO 2 Emissions from Fossil Fuel Combustion by Fuel Consuming End-Use Sector (Tg CO 2 Eq.) End-Use Sector 1990 1995 2000 2005 2006 2007 2008

10 Global CO 2 emissions from fossil fuel combustion were taken from Energy Information Administration International Energy Statistics 2009 < http://tonto.eia.doe.gov/cfapps/i pdbproject/IEDIndex3.cfm> EIA (2009).ES-8 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 Transportation 1,488.8 1,611.0 1,813.0 1,900.1 1,881.2 1,898.8 1,789.9

Combustion 1,485.8 1,608.0 1,809.5 1,895.3 1,876.7 1,893.7 1,785.3 Electricity 3.0 3.1 3.4 4.7 4.5 5.0 4.7 Industrial 1,532.2 1,578.8 1,642.0 1,562.5 1,562.8 1,572.2 1,510.9

Combustion 845.4 862.6 852.2 825.6 850.7 842.2 819.3 Electricity 686.8 716.2 789.8 737.0 712.0 730.0 691.6 Residential 932.2 995.1 1,133.6 1,215.1 1,152.9 1,197.9 1,184.5

Combustion 339.1 353.3 371.2 358.4 322.1 341.7 342.7 Electricity 593.0 641.8 762.4 856.7 830.8 856.1 841.8 Commercial 754.6 810.0 968.9 1,025.0 1,005.0 1,039.1 1,044.9

Combustion 216.7 223.2 227.7 221.3 206.0 217.4 219.5 Electricity 538.0 586.8 741.3 803.7 799.0 821.7 825.4 U.S. Territories a 27.9 34.5 35.9 50.6 50.9 49.1 42.5 Total 4,735.7 5,029.5 5,593.4 5,753.3 5,652.8 5,757.0 5,572.8 Electricity Gen eration 1,820.8 1,947.9 2,296.9 2,402.1 2,346.4 2,412.8 2,363.5 Note: Totals may not sum due to independent rounding. Com bustion-related emissions from electricity generation are allocated based on aggregate national electricity consumption by each end-use sector.

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 this report.

Transportation End-Use Sector. Transportation activities (excluding inte rnational bunker fuels) accounted for 32 percent of CO 2 emissions from fossil fuel combustion in 2008. 11 Virtually all of the energy consumed in this enduse sector came from petroleum products. Nearly 53 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-dut y vehicles and jet fuel in aircraft.

Industrial End-Use Sector. Industrial CO 2 emissions, resulting both directly from the combustion of fossil fuels and indirectly from the generation of el ectricity that is consumed by indu stry, accounted for 27 percent of CO 2 from fossil fuel combustion in 2008. Approximately 54 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 furn aces, ovens, lighting, and other applications.

Residential and Commercial End-Use Sectors. The residential and commercial end-use sectors accounted for 21 and 19 percent, re spectively, of CO 2 emissions from fossil fuel combustion in 2008. Both sectors relied heavily on electricity for meeting energy demands, with 71 and 79 per cent, respectively, of their emissions attributable to electricity consumption for lighting, heating, cooling, an d operating appliances. The remaining emissions were due to the consumption of natural gas and petroleum for heating and cooking.
Electricity Generation. The United States relies on electricity to meet a significant portion of its energy demands, especially for lighting, electric motors, heating, and air c onditioning. Electricity generators consumed 37 percent of U.S. energy from fossil fuels an d emitted 42 percent of the CO 2 from fossil fuel combustion in 2008. The type of fuel combusted by electricity generators has a significant effect on their emissi ons. For example, some electricity is generated with low CO 2 emitting energy technologies, particularly no n-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 ener gy in the United States in 2008. Consequently, changes in electricity demand have a significant impact on coal consumption and associated CO 2 emissions. Other significant CO 2 trends included the following:

• CO 2 emissions from non-energy use of fossil fuels have increased 14.6 Tg CO 2 Eq. (12.2 percent) from 1990 through 2008. Emissions from non-energy uses of fossil fuels were 134.2 Tg CO 2 Eq. in 2008, which constituted 2.3 percent of total national CO 2 emissions, approximately the same proportion as in 1990.

• CO 2 emissions from iron and steel production and metallurgical coke production decreased from 2007 to

11 If emissions from international bunker fuels are included, the tr ansportation end-use sector accounted for 35 percent of U.S. emissions from fossil fu el combustion in 2008.Executive Summary ES-9 2008 (3.8 Tg CO 2 Eq.), continuing a trend of decreasing emissions from 1990 through 2008 of 33 percent. This decline is due to the restructuring of the industry, technological improvements, and increased scrap utilization.

• In 2008, CO 2 emissions from cement production decreased by 4.1 Tg CO 2 Eq. (9.0 percent) from 2007. After decreasing in 1991 by two percent from 1990 levels, cement production emissions grew every year through 2006; emissions decreased in the last two ye ars. Overall, from 1990 to 2008, emissions from cement production increased by 24 percent, an increase of 7.9 Tg CO 2 Eq.

• Net CO 2 flux from Land Use, Land-Use Change, and Forestry increased by 30.9 Tg CO 2 Eq. (3 percent) from 1990 through 2008. This increase was primarily due to an increase in the rate of net carbon accumulation in forest carbon stocks, particularly in aboveground and belowg round tree biomass, and harvested wood pools. Annual 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
According to the IPCC, CH 4 is more than 20 times as effective as CO 2 at trapping heat in the atmosphere. Over the last two hundred and fifty years, the concentration of CH 4 in the atmosphere increased by 148 percent (IPCC 2007). Anthropogenic sources of CH 4 include landfills, natural gas and petroleum systems, agricultural activities, coal mining, wastewater treatment, stationary and mobile combustion, and certain industrial processes (see Figure ES- 8).

Figure ES- 8: 2008 Sources of CH 4 Emissions

Some significant trends in U.S. emissions of CH 4 include the following:

• Enteric Fermentation is the larg est anthropogenic source of CH 4 emissions in the United States. In 2008, enteric fermentation CH 4 emissions were 140.8 Tg CO 2 Eq. (25 percent of total CH 4 emissions), which represents an increase of 8.5 Tg CO 2 Eq. (6.4 percent) since 1990.

• Landfills are the second larges t anthropogenic source of CH 4 emissions in the Unite d States, accounting for 22 percent of total CH 4 emissions (126.3 Tg CO 2 Eq.) in 2008. From 1990 to 2008, net CH 4 emissions from landfills decreased by 23.0 Tg CO 2 Eq. (15 percent), with small increases occurring in some interim years. This downward trend in overall emissions is the result of increases in the amount of landfill gas collected and combusted, 12 which has more than offset the additional CH 4 emissions resulting from an increase in the amount of municipal solid waste landfilled.

• CH 4 emissions from natural gas systems were 96.4 Tg CO 2 Eq. in 2008; emissions have declined by 33.1 Tg CO 2 Eq. (26 percent) since 1990. This decline is due to improvements in technology and management practices, as well as some replacement of old equipment.

• In 2008, CH 4 emissions from coal mining were 67.6 Tg CO 2 Eq., a 9.6 Tg CO 2 Eq. (16 percent) increase over 2007 emission levels. The overall decline of 16.4 Tg CO 2 Eq. (20 percent) from 1990 results from the mining of less gassy coal from underground mines and the increased use of CH 4 collected from degasification systems.

• CH 4 emissions from manure management increased by 54 percent since 1990, from 29.3 Tg CO 2 Eq. in 1990 to 45.0 Tg CO 2 Eq. in 2008. The majority of this in crease was from swine and dairy cow manure, since the general trend in manure management is one of increasing use of liquid systems, which tends to produce greater CH 4 emissions. The increase in liquid systems is the combined result of a shift to larger facilities, and to facilities in the West and Southwest, all of which tend to use liquid systems. Also, new regulations limiting the application of manure nutrients have shifted manure management practices at smaller dairies from daily spread to manure managed and stored on site.

12 The CO 2 produced from combusted landfill CH 4 at landfills is not counted in national i nventories as it is considered part of the natural C cycle of decomposition.ES-10 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 

### Nitrous Oxide Emissions

N 2 O 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 N 2 O emissions are much lower than CO 2 emissions, N 2 O is approximately 300 times more powerful than CO 2 at trapping heat in the atmosphere. Since 1750, the global atmospheric concentration of N 2 O has risen by approximately 18 percent (IPCC 2007). The main anthropogenic activities producing N 2 O in the United States are agricultural soil management, fuel combustion in motor vehicles, nitric acid production, stationary fuel combustion, manure management, and adipic acid production (see Figure ES-9).

Figure ES-9: 2008 Sources of N 2 O Emissions

Some significant trends in U.S. emissions of N 2 O include the following:

• Agricultural soils accounted for approximately 68 percent of N 2 O emissions in the United States in 2008. Estimated emissions from this source in 2008 were 215.9 Tg CO 2 Eq. Annual N 2 O emissions from agricultural soils fluctuated between 1990 and 2008, although overall emissions were 6.1 percent higher in 2008 than in 1990. N 2 O emissions from this source have not shown any significant long-term trend, as they are highly sensitive to the amount of N applied to soils (which has not cha nged significantly over the time-period), and to weather patterns and crop type.

• In 2008, N 2 O emissions from mobile combustion were 26.1 Tg CO 2 Eq. (approximately 8 percent of U.S. N 2 O emissions). From 1990 to 2008, N 2 O emissions from mobile combustion decreased by 40 percent. However, from 1990 to 1998 emissions increased by 26 percent, due to control technologies that reduced NO x emissions while increasing N 2 O emissions. Since 1998, newer control technologies have led to a steady decline in N 2 O from this source.

• N 2 O emissions from adipic acid production were 2.0 Tg CO 2 Eq. in 2008, and have decreased significantly since 1996 from the widespread installation of pollution control measures. Emissions from adipic acid production have decreased by 87 percent since 1990, and emissions from adipic acid production have remained consistently lower than pre-1996 levels since 1998.


### HFC, PFC, and SF 6 

### Emissions
HFCs and PFCs are families of synthetic chemicals that ar e 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 accep table alternatives under the Montreal Protocol. These compounds, however, along with SF 6 , are potent greenhouse gases. In addition to having high global warming potentials, SF 6 and PFCs have extremely long atmospheri c lifetimes, resulting in their essentially irreversible accumulation in the atmosphere once emitted. Sulfur hexafluoride is the most potent greenhouse gas the IPCC has evaluated. Other emissive sources of these gases include HCFC-22 production, electrical transmission and distribution systems, semiconductor manufacturing, aluminum production, and magnesium production and processing (see Figure ES-10).

Figure ES-10: 2008 Sources of HFCs, PFCs, and SF 6 Emissions

Some significant trends in U.S. HFC, PFC, and SF 6 emissions include the following:

• Emissions resulting from the substitu tion of ODS (e.g., CFCs) have been consistently increasing, from small amounts in 1990 to 113.0 Tg CO 2 Eq. in 2008. Emissions from ODS substitutes are both the largest and the fastest growing source of HFC, PFC, and SF 6 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.Executive Summary ES-11 • HFC emissions from the production of HCFC-22 decreased by 63 percent (22.8 Tg CO 2 Eq.) from 1990 through 2008, 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.

• SF 6 emissions from electric power transmission and distribution systems decreased by 51 percent (13.6 Tg CO 2 Eq.) from 1990 to 2008, primarily b ecause of higher purchase prices for SF 6 and efforts by industry to reduce emissions.

• PFC emissions from aluminum production decreased by 85 percent (15.8 Tg CO 2 Eq.) from 1990 to 2008, due to both industry emission reduction efforts and lower domestic aluminum production.



### Overview of Sector Emissions and Trends

In accordance with the Revised 1996 IPCC Guidelines for Nati onal Greenhouse Gas Inventories (IPCC/UNEP/OECD/IEA 1997), and the 2003 UNFCCC Guid elines 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 In tergovernmental Panel on Climate Ch ange (IPCC) guidance. Over the nineteen-year period of 1990 to 2008, total emissions in the Energy, Industrial Processes, and Agriculture sectors climbed by 775.0 Tg CO 2 Eq. (15 percent), 16.2 Tg CO 2 Eq. (5 percent), and 39.7 Tg CO 2 Eq. (10 percent), respectively. Emissions decreased in the Waste and Solvent and Other Product Use sectors by 18.1 Tg CO 2 Eq. (10 percent) and less than 0.1 Tg CO 2 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 CO 2 flux from all LULUCF source categories) increased by 13.7 Tg CO 2 Eq. (1.5 percent).

Figure ES-11: U.S. Greenhouse Gas Emissions and Sinks by Chapter/IPCC Sector

Table ES-4: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks by Chapter/IPCC Sector (Tg CO 2 Eq.) Chapter/IPCC Sector 1990 1995 2000 2005 2006 2007 2008 Energy 5,224.1 5,545.8 6,087.5 6,187.9 6,089.1 6,182.9 5,999.0 Industrial Processes 318.3 339.1 351.9 334.7 339.7 350.9 334.5 Solvent and Other Product Use 4.4 4.6 4.9 4.4 4.4 4.4 4.4 Agriculture 387.8 407.7 410.9 419.7 417.2 423.0 427.5 Land Use, Land-Use Change, and

Forestry (Emissions) 15.0 17.2 36.3 28.6 49.8 47.6 32.2 Waste 177.2 174.5 153.0 158.0 159.7 159.3 159.1 Total Emissions 6,126.8 6,488.8 7,044.5 7,133.2 7,059.9 7,168.1 6,956.8 Net CO 2 Flux from Land Use, LandUse Change, and Forestry (Sinks)* (909.4) (842.9) (664.2) (950.4) (959.2) (955.4) (940.3) Net Emissions (Sources and Sinks) 5,217.3 5,646.0 6,380.2 6,182.8 6,100.7 6,212.7 6,016.4 * The net CO 2 flux total includes both emissions and sequestration, and c onstitutes 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 negativ e values or sequestration.



### 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. CO 2 emissions for the period of 1990 through 2008. In 2008, approximately 84 percent of the energy consumed in the United States (on a Btu basis) was produced through the combustion of fossil fuels. The remaining 16 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 CH 4 and N 2 O emissions (37 percent and 13 percent of total U.S. emissions of each gas, respectively). Overall, emission sources in the Energy chapter account for a combined 86 percen t of total U.S. greenhouse gas emissions in 2008.ES-12 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 Figure ES-12: 2008 U.S. Energy Consumption by Energy Source



### Industrial Processes
The Industrial Processes chapter contains by-product or fugitive emissions of greenhouse gases from industrial processes not directly related to energy activities such as fossil fuel combustion. For ex ample, industrial processes can chemically transform raw materials, wh ich often release waste gases such as CO 2 , CH 4 , and N 2 O. 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 pr oduction and consumption, titanium dioxide production, phosphoric acid production, ferroalloy production, CO 2 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 SF 6 . Overall, emission sources in the Industrial Process ch apter account for 5 percent of U.S. greenhouse gas emissions in 2008.



### Solvent and Other Product Use
The Solvent and Other Product Use chapter contains greenhouse gas emissions that are produced as a by-product of various solvent and other product uses. In the United States, emissions from N 2 O 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 2008.


### Agriculture
The Agricultural chapter contains anthropogenic emissi ons from agricultural activities (except fuel combustion, which is addressed in the Energy chapter, and agricultural CO 2 fluxes, which are addressed in the Land Use, LandUse Change, and Forestry Chapter). Agricultural activities contribute directly to em issions 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. CH 4 and N 2 O were the primary greenhouse gases emitted by agricultural activities. CH 4 emissions from enteric fermentation and manure management represented 25 percent and 8 percent of total CH 4 emissions from anthropogenic activities, respectively, in 2008. Agricultura l soil management activities such as fertilizer application and other cropping practices were the largest source of U.S. N 2 O emissions in 2008, accountin g for 68 percent. In 2008, emission sources accounted for in the Agricultural chapters were responsible for 6.1 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 CH 4 and N 2 O, and emissions and removals of CO 2 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 have resulted in a net uptake (sequestration) of C in the United States. Forests (including vegetation, soils, and harvested wood) accounted for 84 percent of total 2008 net CO 2 flux, urban trees accounted for 10 percent, mineral and organic soil carbon stock change s accounted for 5 percent, an d landfilled yard trimmings and food scraps accounted for 1 percent of the total net flux in 2008. The net forest sequestration is a result of net forest growth and increasing forest area, as well as a ne t 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 5.9 times as much C as is emitted from these soils through liming and urea fertilization. The mineral soil C sequestration is largely du e to the conversion of cropland to permanent pastures and hay production, a reduction in summer fallow areas in se mi-arid areas, an increase in the adoption of conservation tillage practices, and an increase in the amounts of organi c fertilizers (i.e., manure and sewage sludge) applied to agriculture lands. The landfilled yard trimmings and f ood scraps net sequestration is due to the long-term accumulation of yard trimming carbon and food scraps in landfills.Executive Summary ES-13 Land use, land-use change, and forestry activities in 2008 resulted in a net C sequestration of 940.3 Tg CO 2 Eq. (Table ES- 5). This represents an offset of 16 percent of total U.S. CO 2 emissions, or 14 percent of total greenhouse gas emissions in 2008. Between 1990 and 2008, total land use, land-use change, and forestry net C flux resulted in a 3.4 percent increase in CO 2 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 pe riod, while the rate of annual C accumulation increased in urban trees.

Table ES- 5: Net CO 2 Flux from Land Use, Land-Use Change, and Forestry (Tg CO 2 Eq.) Sink Category 1990 1995 2000 2005 2006 2007 2008 Forest Land Remaining Forest

Land 1 (729.8) (692.6) (467.7) (806.6) (812.5) (806.9) (791.9) Cropland Remaining Cropland (29.4) (22.9) (30.2) (18.3) (19.1) (19.7) (18.1) Land Converted to Cropland 2.2 2.9 2.4 5.9 5.9 5.9 5.9 Grassland Remaining

Grassland (52.0) (26.7) (52.6) (9.0) (8.9) (8.8) (8.7) Land Converted to Grassland (19.8) (22.3) (27.3) (24.6) (24.5) (24.3) (24.2) Settlements Remaining

Settlements 2 (57.1) (67.3) (77.5) (87.8) (89.8) (91.9) (93.9) Other (Landfilled Yard

Trimmings and Food Scraps) (23.5) (13.9) (11.3) (10.1) (10.3) (9.8) (9.5) Total (909.4) (842.9) (664.2) (950.4) (959.2) (955.4) (940.3) Note: Totals may not sum due to independent rou nding. Parentheses indica te 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 CO 2 emissions of 7.6 Tg CO 2 Eq. in 2008, an increase of 8 percent relative to 1990. The application of synthetic fertilizers to forest and settlement soils in 2008 resulted in direct N 2 O emissions of 1.9 Tg CO 2 Eq. Direct N 2 O emissions from fertilizer application to forest soils have increased by 422 percent sin ce 1990, but still account for a relatively small portion of overall emissions. Additionally, direct N 2 O emissions from fertilizer application to settlement soils increased of 62 percent since 1990. Non-CO 2 emissions from forest fires in 2008 resulted in CH 4 emissions of 11.9 Tg CO 2 Eq., and in N 2 O emissions of 9.7 Tg CO 2 Eq. CO 2 and N 2 O emissions from peatlands totaled 0.9 Tg CO 2 Eq. and less than 0.01 Tg CO 2 Eq. in 2008, respectively. Table ES-6. Emissions from Land Use, Land-Use Change, and Forestry (Tg CO 2 Eq.) Source Category 1990 1995 2000 2005 2006 2007 2008 CO 2 8.1 8.1 8.8 8.9 8.8 9.3 8.6 Cropland Remaining Cropland:

Liming of Agricultural Soils 4.7 4.4 4.3 4.3 4.2 4.5 3.8 Urea Fertilization 2.4 2.7 3.2 3.5 3.7 3.8 3.8 Wetlands Remaining Wetlands:

Peatlands Remaining Peatlands 1.0 1.0 1.2 1.1 0.9 1.0 0.9 CH 4 3.2 4.3 14.3 9.8 21.6 20.0 11.9 Forest Land Remaining Forest

Land: Forest Fires 3.2 4.3 14.3 9.8 21.6 20.0 11.9 N 2 O 3.7 4.9 13.2 9.8 19.5 18.3 11.7 Forest Land Remaining Forest

Land: Forest Fires 2.6 3.5 11.7 8.0 17.6 16.3 9.7 Forest Land Remaining Forest

Land: Forest Soils 0.1 0.2 0.4 0.4 0.4 0.4 0.4 Settlements Remaining

Settlements: Settlement Soils 1.0 1.2 1.1 1.5 1.5 1.6 1.6 Wetlands Remaining Wetlands:

Peatlands Remaining Peatlands + + + + + + + Total 15.0 17.2 36.3 28.6 49.8 47.6 32.2 + Less than 0.05 Tg CO 2 Eq.ES-14 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 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 la rgest source of anthropogenic greenhouse gas emissions in the Waste chapter, accounting for just over 79 percent of this chapter’s emissions, and 22 percent of total U.S. CH 4 emissions. 13 Additionally, wastewater treatment accounts for 18 percent of Waste emissions, 4 percent of U.S. CH 4 emissions, and 2 percent of U.S. N 2 O emissions. Emissions of CH 4 and N 2 O from composting are also accounted for in this chapter; generating emissions of 1.7 Tg CO 2 Eq. and 1.8 Tg CO 2 Eq., respectively. Overall, emission sources accounted for in the Waste chapter generated 2.3 percent of total U.S. greenhouse gas emissions in 2008.



### 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 im portant 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 sect ors, and Figure ES-13 shows the trend in emissions by sector from 1990 to 2008.

Figure ES-13: Emissions Allocated to Economic Sectors

Table ES-7: U.S. Greenhouse Gas Emissions Allocated to Economic Sectors (Tg CO 2 Eq.) Implied Sectors 1990 1995 2000 2005 2006 2007 2008 Electric Power Industry 1,867.2 1,993.7 2,336.8 2,443.5 2,387.5 2,454.0 2,404.2 Transportation 1,545.0 1,695.2 1,932.3 2,016.1 1,993.0 2,003.5 1,886.1 Industry 1,506.6 1,531.3 1,469.1 1,350.9 1,380.2 1,374.2 1,342.4 Agriculture 433.2 460.8 485.3 494.1 515.1 518.0 504.1 Commercial 395.1 399.6 387.3 399.0 389.2 404.4 410.9 Residential 345.9 367.6 386.7 370.7 334.9 356.2 359.3 U.S. Territories 33.7 40.7 46.9 58.9 60.0 57.8 49.9 Total Emissions 6,126.8 6,488.8 7,044.5 7,133.2 7,059.9 7,168.1 6,956.8 Land Use, Land-Use Change, and

Forestry (Sinks) (909.4) (842.9) (664.2) (950.4) (959.2) (955.4) (940.3) Net Emissions (Sources and

Sinks) 5,217.3 5,646.0 6,380.2 6,182.8 6,100.7 6,212.7 6,016.4 Note: Totals may not sum due to inde pendent rounding. Emissions include CO 2 , CH 4 , N 2 O, HFCs, PFCs, and SF 6 . See Table 2-12 for more detailed data.

Using this categorization, emissions from electricity generation accounted for the largest portion (35 percent) of U.S. greenhouse gas emissions in 2008 . Transportation activities, in aggregat e, accounted for the second largest portion (27 percent), while emissions from industry accounted for the third largest portion (19 percent) of U.S. greenhouse gas emissions in 2008. 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

13 Landfills also store carbon, due to incomp lete degradation of organic materials such as wood products and yard trimmings, as described in the Land-Use, Land-Use Change, an d Forestry chapter of the Inventory report.Executive Summary ES-15 changes in the U.S. economy (i.e., shifts from a manufact uring-based to a service-based economy), fuel switching, and energy efficiency improvements. The remaining 19 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 N 2 O emissions from agricultural soil management and CH 4 emissions from enteric fermentation. The commercial sector accounted for 6 percent of emissions while the residential sector accounted for 5 percent of emissions an d U.S. territories accounted for 1 percent of emissions; emissions from these sectors primarily consisted of CO 2 emissions from fossil fuel combustion.

CO 2 was also emitted and sequestered by a variety of activitie s related to forest management practices, tree planting in urban areas, the management of agricultura l soils, and landfilling of yard trimmings. Electricity is ultimately consumed in the economic sect ors 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 electri city generation are allocated to the econom ic 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 accordin g to retail sales of electricity. 14 These source categories include CO 2 from fossil fuel combustion and the use of limestone and dolomite for flue gas desulfurization, CO 2 and N 2 O from incineration of waste, CH 4 and N 2 O from stationary sources, and SF 6 from electrical transmission and distribution systems. When emissions from electricity are dist ributed among these sectors, industry accounts for the largest share of U.S. greenhouse gas emissions (29 percent) in 2008. Emissions from the residential and commercial sectors also increase substantially when emissions from el ectricity are included, due to their relatively large share of electricity consumption (e.g., lighting, appliances, etc.). Transporta tion activities remain the second largest contributor to total U.S. emissions (27 percent) despite the considerable decline in emissions from this sector during the past year. In all sectors except agriculture, CO 2 accounts for more than 80 percent of greenhouse gas emissions, primarily from the combustion of fossil fuels. Figure ES-14 shows the tr end in these emissions by sector from 1990 to 2008. Table ES-8: U.S Greenhouse Gas Emissions by Economic Sector with Electricity-Rel ated Emissions Distributed (Tg CO 2 Eq.) Implied Sectors 1990 1995 2000 2005 2006 2007 2008 Industry 2,179.8 2,228.0 2,239.2 2,071.1 2,077.3 2,084.2 2,018.4 Transportation 1,548.2 1,698.3 1,935.8 2,020.9 1,997.6 2,008.6 1,890.8 Commercial 946.8 1,000.2 1,141.5 1,216.5 1,202.2 1,240.1 1,250.6 Residential 954.0 1,024.5 1,162.4 1,242.2 1,180.3 1,226.9 1,215.6 Agriculture 464.2 497.1 518.7 523.5 542.5 550.5 531.6 U.S. Territories 33.7 40.7 46.9 58.9 60.0 57.8 49.9 Total Emissions 6,126.8 6,488.8 7,044.5 7,133.2 7,059.9 7,168.1 6,956.8 Land Use, Land-Use Change,

and Forestry (Sinks) (909.4) (842.9) (664.2) (950.4) (959.2) (955.4) (940.3) Net Emissions (Sources and

Sinks) 5,217.3 5,646.0 6,380.2 6,182.8 6,100.7 6,212.7 6,016.4 See Table 2-14 for more detailed data.

Figure ES-14: Emissions with Electricity Distributed to Economic Sectors

[BEGIN BOX]

14 Emissions were not distributed to U.S. territories, since the electricity gene ration sector only includes emissions related to the generation of electricity in the 50 states and the District of Columbia.ES-16 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 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 fo ssil fuel consumption, becaus e 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 2008; (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 0.7 percent since 1990. This rate is slightly slower than that for total energy, approximately the same as for fossil fuel consumption, and much slower than that for either electricity consumption or overall gross domestic product. TotalU.S. greenhouse gas emissions have also grown slightly slower than national population since 1990 (see Figure ES15).

Table ES-9: Recent Trends in Vari ous U.S. Data (Index 1990 = 100)

Variable 1990 1995 2000 2005 2006 2007 2008 Growth Rate a GDP b 100 113 140 157 162 165 166 2.9% Electricity Consumption c 100 112 127 134 135 138 136 1.8% Fossil Fuel Consumption c 100 107 117 119 117 119 115 0.8% Energy Consumption c 100 107 116 119 118 120 118 0.9% Population d 100 107 113 118 119 120 121 1.1% Greenhouse Gas Emissions e 100 106 115 116 115 117 114 0.7%

a Average annual growth rate
b Gross Domestic Product in chained 2000 dollars (BEA 2008)

c Energy content-weighted values (EIA 2008a)
d U.S. Census Bureau (2008)

e GWP-weighted values

Figure ES-15: U.S. Greenhouse Gas Emissions Per Capita and Per Dollar of Gross Domestic Product Source: BEA (2008), U.S. Census Bureau (2008 ), and emission estimat es in this report.

[END BOX]



### Indirect Greenhouse Gases (CO, NO x 

### , NMVOCs, and SO 2 

### )

The reporting requirements of the UNFCCC 15 request that information be provided on indirect greenhouse gases, which include CO, NO x , NMVOCs, and SO 2 . 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 SO 2 , by affecting the absorptive characteristics of the atmosphere. Additionally, some of these gases may react with other chem ical compounds in the atmosphere to form compounds that are greenhouse
gases. Since 1970, the United States has published estimates of annual emissions of CO, NO x , NMVOCs, and SO 2 (EPA

15 See <http://unfccc.int/res ource/docs/cop8/08.pdf>.Executive Summary ES-17 2008), 16 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 ga ses. Industrial processes—such as the manufacture of chemical and allied products, metals processing, and industri al uses of solvents—are also significant sources of CO, NO x , and NMVOCs.

Table ES- 10: Emissions of NO x , CO, NMVOCs, and SO 2 (Gg) Gas/Activity 1990 1995 2000 2005 2006 2007 2008 NO x 21,728 21,227 19,145 15,933 15,071 14,410 13,578

Mobile Fossil Fuel Combustion 10,862 10,536 10,199 9,012 8,488 7,965 7,441 Stationary Fossil Fuel Combustion 10,023 9,862 8,053 5,858 5,545 5,432 5,148 Industrial Processes 591 607 626 569 553 537 520 Oil and Gas Activities 139 100 111 321 319 318 318 Incineration of Waste 82 88 114 129 121 114 106 Agricultural Burning 30 30 37 40 40 38 40 Solvent Use 1 3 3 3 4 4 4 Waste 0 1 2 2 2 2 2 CO 130,536 109,114 92,872 71,555 67,909 64,348 60,739

Mobile Fossil Fuel Combustion 119,360 97,630 83,559 62,692 58,972 55,253 51,533 Stationary Fossil Fuel Combustion 5,000 5,383 4,340 4,649 4,695 4,744 4,792 Industrial Processes 4,125 3,959 2,216 1,555 1,597 1,640 1,682 Incineration of Waste 978 1,073 1,670 1,403 1,412 1,421 1,430 Agricultural Burning 766 745 888 930 905 960 970 Oil and Gas Activities 302 316 146 318 319 320 322 Waste 1 2 8 7 7 7 7 Solvent Use 5 5 45 2 2 2 2 NMVOCs 20,930 19,520 15,227 13,761 13,594 13,423 13,254

Mobile Fossil Fuel Combustion 10,932 8,745 7,229 6,330 6,037 5,742 5,447 Solvent Use 5,216 5,609 4,384 3,851 3,846 3,839 3,834 Industrial Processes 2,422 2,642 1,773 1,997 1,933 1,869 1,804 Stationary Fossil Fuel Combustion 912 973 1,077 716 918 1,120 1,321 Oil and Gas Activities 554 582 388 510 510 509 509 Incineration of Waste 222 237 257 241 238 234 230 Waste 673 731 119 114 113 111 109 Agricultural Burning NA NA NA NA NA NA NA SO 2 20,935 16,891 14,830 13,466 12,388 11,799 10,368

Stationary Fossil Fuel Combustion 18,407 14,724 12,849 11,541 10,612 10,172 8,891 Industrial Processes 1,307 1,117 1,031 831 818 807 795 Mobile Fossil Fuel Combustion 793 672 632 889 750 611 472 Oil and Gas Activities 390 335 287 181 182 184 187 Incineration of Waste 38 42 29 24 24 24 23 Waste 0 1 1 1 1 1 1 Solvent Use 0 1 1 0 0 0 0 Agricultural Burning NA NA NA NA NA NA NA Source: (EPA 2009, disaggregated based on EPA 2003) except for estimates from field burni ng of agricultural residues. NA (Not Available) Note: Totals may not sum due to independent rounding.



### Key Categories

The IPCC’s Good Practice Guidance (IPCC 2000) defines a key category as a “[source or sink category] that is prioritized within the national inventory system because its estimate has a signi ficant influence on a country’s total

16 NO x and CO emission estimates from field bur ning of agricultural residues were estimat ed separately, and therefore not taken from EPA (2008).ES-18 Inventory of U.S. Greenhous e Gas Emissions and Sinks: 1990–2008 inventory of direct greenhouse gases in terms of the abso lute level of emissions, the trend in emissions, or both.” 17 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 inve stigation 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 presents 2008 emission estimates for the key categories as defined by a level analysis (i.e., the contribution of each source or sink cat egory 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 of the inventory report.

Figure ES-16: 2008 Key Categories



### Quality Assurance and Q uality 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 th ese 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 a ssociated with the emission estimates. Some of the current estimates, such as those for CO 2 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 asso ciated with the estimates presented. Acquiring a better understanding of the uncertain ty associated with inventory estimates is an important step in helping to prioritize future work and improve the ov erall quality of the Inventory. Recognizing the benefit of conducting an uncertainty analysis, the UNFCCC repor ting 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 presen ted for all source and sink categories. Within the discussion of each emission source, specific factors affecting the uncert ainty surrounding the estimates are discussed. Most sources also contai n a quantitative uncertainty assessment, in accordance with UNFCCC reporting guidelines.

17 See Chapter 7 “Methodological Choice and Re calculation” in IPCC (2000). <http://www.ipccnggip.iges.or.jp/pub lic/gp/gpgaum.htm>Fi g ure ES-1: U.S. Greenhouse Gas Emissions b y Gas 6,127 6,089 6,192 6,312 6,413 6,489 6,704 6,753 6,795 6,856 7,044 6,924 6,967 6,994 7,095 7,133 7,060 7,168 6,957

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008Tg CO2Eq. HFCs, PFCs, & SF Nitrous Oxide

Methane Carbon Dioxide 6

1.7% 1.9% 1.6% 1.2% 3.3%

0.7% 0.6% 0.9% 2.8%

0.6% 0.4% 1.5%

0.5% 1.5%

0% 1% 2% 3% 4%

Fi g ure ES-2: Annual Percent Chan g e in U.S. Greenhouse Gas Emissions

Fi g ure ES-3: Cumulative Chan g e in Annual U.S. Greenhouse Gas Emissions Relative to 1990 6,127 6,089 6,192 6,312 6,413 6,489 6,704 6,753 6,795 6,856 7,044 6,924 6,967 6,994 7,095 7,133 7,060 7,168 6,957

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008Tg CO2Eq. HFCs, PFCs, & SF Nitrous Oxide

Methane Carbon Dioxide 6

-0.6% 1.7% 1.9% 1.6% 1.2% 3.3%

0.7% 0.6% 0.9% 2.8%

-1.7% 0.6% 0.4% 1.5%

0.5%

-1.0% 1.5%

-2.9% -4% -3% -2% -1% 0% 1% 2% 3% 4%

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

-38 65 185 286 362 577 626 669 729 918
797 840 867 969 1,006 933 1,041

830

-100

0 100 200 300 400 500 600 700 800 900 1,000 1,100

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008Tg CO2Eq.Figure ES-4: 2008 Greenhouse Gas Emissions by Gas (percents based on Tg CO 2 Eq.) CO 2 85.1% CH 4 8.2% N 2 O 4.6% HFCs, PFCs, & SF 6 2.2%

5,637.9

Cropland Remaining Cropland Ammonia Production and Urea Consumption Incineration of Waste Lime Production Natural Gas Systems

Cement Production Iron and Steel Production & Metallurgical Coke Production Non-Energy Use of Fuels

Fossil Fuel Combustion

CO 2 as a Portion of all Emissions 5

, 573

Figure ES-5: 2008 Sources of CO 2 Emissions CO 2 85.1% CH 4 8.2% N 2 O 4.6% HFCs, PFCs, & SF 6 2.2%

5,637.9

0 25 50 75 100 125 150 Silicon Carbide Production and Consumption Lead Production Zinc Production Petroleum Systems Wetlands Remaining Wetlands Phosphoric Acid Production Ferroalloy Production Carbon Dioxide Consumption Titanium Dioxide Production

Petrochemical Production Soda Ash Production and Consumption Aluminum Production Limestone and Dolomite Use Cropland Remaining Cropland Ammonia Production and Urea Consumption Incineration of Waste Lime Production Natural Gas Systems

Cement Production Iron and Steel Production & Metallurgical Coke Production Non-Energy Use of Fuels

Fossil Fuel Combustion

Tg CO 2 Eq. 85.1% CO 2 as a Portion of all Emissions 5

, 573

< 0.5

< 0.5

< 0.5 < 0.5Natural Gas
Petroleum Coal

Figure ES-6: 2008 CO 2 Emissions from Fossil Fuel Combustion by Sector and Fuel Type Note: Electricity generation also includes emissions of less than 0.5 Tg CO 2 Eq. from geothermal-based electricity generation.

1

, 050 1,193 1,518 1,818

1,500 2,000Eq. From Direct Fossil Fuel Combustion

From Electricity Consumption 43 219 343 819 1,785 2,363

0 500 1,000 1,500 2,000 2,500U.S. TerritoriesCommercialResidentialIndustrialTransportationElectricityGenerationTg CO2Eq. Petroleum

Coal

Natural Gas Relative Contribution by Fuel Type

Figure ES-7: 2008 End-Use Sector Emissions of CO 2 , CH 4 , and N 2 O from Fossil Fuel Combustion 43 1,050 1,193 1,518 1,818

0 500 1,000 1,500 2,000U.S. TerritoriesCommercialResidentialIndustrialTransportationTg CO2Eq. From Direct Fossil Fuel Combustion

From Electricity Consumption 43 219 343 819 1,785 2,363

0 500 1,000 1,500 2,000 2,500U.S. TerritoriesCommercialResidentialIndustrialTransportationElectricityGenerationTg CO2Eq. Petroleum

Coal

Natural Gas Relative Contribution by Fuel TypeFi ES 8 2008 S f CH Ei i 0 50 100 150 Incineration of Waste Silicon Carbide Production and Consumption Ferroalloy Production Iron and Steel Production & Metallurgical Coke Production Petrochemical Production Field Burning of Agricultural Residues Composting Mobile Combustion Abandoned Undergro und Coal Mines Stationary Combustion Rice Cultivation Forest Land Remaining Forest Land Wastewater Treatment Petroleum Systems Manure Management Coal Mining Natural Gas Systems Landfills Enteric Fermentation

Tg CO 2 Eq. 8.2% CH 4 as a Portion of all Emissions

< 0.5 < 0.5 < 0.5

Figure ES-8: 2008 Sources of CH 4 Emissions

Figure ES-9: 2008 Sources of N 2 O Emissions 0 10 20 30 40 Wetlands Remaining Wetlands Incineration of Waste Field Burning of Agricultural Residues

Settlements Remaining Settlements Composting A dipic Acid Production N2O from Product Uses Wastewater Treatment Forest Land Remaining Forest Land Stationary Combustion

Manure Management Nitric Acid Production

Mobile Combustion A gricultural Soil Management

Tg CO 2 Eq. 216 0 50 100 150 Incineration of Waste Silicon Carbide Production and Consumption Ferroalloy Production Iron and Steel Production & Metallurgical Coke Production Petrochemical Production Field Burning of Agricultural Residues Composting Mobile Combustion Abandoned Undergro und Coal Mines Stationary Combustion Rice Cultivation Forest Land Remaining Forest Land Wastewater Treatment Petroleum Systems Manure Management Coal Mining Natural Gas Systems Landfills Enteric Fermentation

Tg CO 2 Eq. 8.2% CH 4 as a Portion of all Emissions

< 0.5 < 0.5 < 0.5 < 0.5 < 0.5

4.6% N 2 O as a Portion of all EmissionsFigure ES-10: 2008 Sources of HFCs, PFCs, and SF 6 Emissions 86.6%

5 000 5,500 6,000 6,500 7,000 7,500

Agriculture Waste Industrial Processes LULUCF (sources) 0 10 20 30 40 50 Magnesium Production and Processing Aluminum Production Semiconductor Manufacture Electrical Transmission

and Distribution HCFC-22 Production Substitution of Ozone Depleting Substances

Tg CO 2 Eq. 113

2.2% HFCs, PFCs, and SF 6 as a Portion of all Emissions

Fi g ure ES-11: U.S. Greenhouse Gas Emissions and Sinks b y Chapter/IPCC Secto r 86.6%

(1,000)

(500) 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,5001990199119921993199419951996199719981999200020012002200320042005200620072008Tg CO2Eq.

Energy

Land Use, Land-Use Change and Forestry (sinks) Agriculture Waste Industrial Processes LULUCF (sources)

Note: Relatively smaller amounts of GWP-weighted emission s are also emitted from the Solvent and Other Product Use sectors 0 10 20 30 40 50 Magnesium Production and Processing Aluminum Production Semiconductor Manufacture Electrical Transmission

and Distribution HCFC-22 Production Substitution of Ozone Depleting Substances

Tg CO 2 Eq. 113

2.2% HFCs, PFCs, and SF 6 as a Portion of all EmissionsFi g ure ES-12: 2008 U.S. Ener gy Consumption b y Ener gy Sourc e Petroleum

37.4%

Natural Gas

24.0% Coal 22.6% Nuclear Electric Power 8.5% Renewable Energy 7.4%

1,500 2,000 2,500O2Eq. Electric Power Industry

Transportation

Industr y

Note: Does not include U.S. Territories. Figure ES-13: Emissions Allocated to Economic Sectors Petroleum

37.4%

Natural Gas

24.0% Coal 22.6% Nuclear Electric Power 8.5% Renewable Energy 7.4%

0 500 1,000 1,500 2,000 2,5001990199119921993199419951996199719981999200020012002200320042005200620072008Tg CO2Eq.

Residential Electric Power Industry

Transportation

Industry

Agriculture CommercialNote: Does not include U.S. Territories. Figure ES-14: Emissions with Electricity Distributed to Economic Sector s 0 500 1,000 1,500 2,000 2,5001990199119921993199419951996199719981999200020012002200320042005200620072008Tg CO2Eq. Transportation Industry

Residential (black)

Agriculture Commercial (gray)

Real GDP 160 170

Fi g ure ES-15: U.S. Greenhouse Gas Emissions Per Capita and Per Dollar of Gross Domestic Produc t 0 500 1,000 1,500 2,000 2,5001990199119921993199419951996199719981999200020012002200320042005200620072008Tg CO2Eq. Transportation Industry

Residential (black)

Agriculture Commercial (gray)

Emissions per $GDP Emissions per capita Population Real GDP

60 70 80 90 100 110 120 130 140 150 160 1701990199119921993199419951996199719981999200020012002200320042005200620072008Index (1990 = 100)CH4 Emissions from Manure Mana g ement Indirect N2O Emissions from A pp lied Nitro g en Fu g itive Emissions from Coal Minin g CO2 Emissions from Iron and Steel Production & Metallurgical Coke Production Fu g itive Emissions from Natural Gas S y stems Emissions from Substitutes for Ozone De p letin g Substances CH4 Emissions from Landfills CO2 Emissions from Non-Ener gy

Use of Fuels CH4 Emissions from Enteric Fermentation Mobile Combustion: Aviation Direct N2O Emissions from A g ricultural Soil Mana g ement CO2 Emissions from Stationar y Combustion - Oil CO2 Emissions from Stationar y Combustion - Gas Mobile Combustion: Road & Other CO2 Emissions from Stationar y Combustion - Coal

96% Key Categories as a Portion of all Emissions

Fi g ure ES-16: 2008 Ke y Cate g ories Notes: For a complete discussion of the key category analysis, see Annex 1. Black bars indicate a Tier 1 level assessment key category. Gray bars indicate a Tier 2 level assessment key category. 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000 2,200 Non-CO2 Emissions from Stationar y Combustion N2O Emissions from Manure Mana g ement Fu g itive Emissions from Petroleum S y stems

CO2 Emissions from Cement Production CH4 Emissions from Manure Mana g ement Indirect N2O Emissions from A pp lied Nitro g en Fu g itive Emissions from Coal Minin g CO2 Emissions from Iron and Steel Production & Metallurgical Coke Production Fu g itive Emissions from Natural Gas S y stems Emissions from Substitutes for Ozone De p letin g Substances CH4 Emissions from Landfills CO2 Emissions from Non-Ener gy

Use of Fuels CH4 Emissions from Enteric Fermentation Mobile Combustion: Aviation Direct N2O Emissions from A g ricultural Soil Mana g ement CO2 Emissions from Stationar y Combustion - Oil CO2 Emissions from Stationar y Combustion - Gas Mobile Combustion: Road & Other CO2 Emissions from Stationar y Combustion - Coal

Tg CO 2 Eq. 96% Key Categories as a Portion of all Emissions