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Carbon Dioxide Emissions Energy Consumption Carbon Dioxide Emissions
and Economic Growth
Total emissions of carbon dioxide in the United States and its territories in 1999 are estimated at 1,526.8 million metric tons carbon equivalent—19.4 million metric tons carbon equivalent (1.3 percent) more than in 1998 (Table 4). The growth in emissions in 1999 is more typical of the average annual growth rate during the 1990s (1.4 percent) than was the 0.1-percent growth in 1998 (Figure 1). Table 4. U.S. Carbon Dioxide Emissions from Energy and Industry, 1990-1999 In the United States, most carbon dioxide (98 percent) is emitted as the result of the combustion of fossil fuels; consequently, carbon dioxide emissions and energy use are highly correlated. Historically, economic growth, the weather, the carbon intensity and energy intensity of the economy, and movements in energy prices have caused year-to-year fluctuations in energy consumption and resulting carbon dioxide emissions. A preliminary analysis, detailed later in this chapter, indicates that total carbon dioxide emissions in 1999 could have been higher— by as much as 29 million metric tons carbon equivalent—if weather patterns had been normal and if electricity generation from non-fossil fuels had not been unusually high (see discussion on "U.S. Carbon Dioxide Emissions in 1999: Effects of Weather and High Levels of Nuclear and Hydroelectric Power Generation"). On a sectoral level, residential and commercial energy consumption is dominated by electricity use for air conditioning and fuel use for winter heating. The United States, as in 1998, again experienced warmer-than-normal winter and summer weather in 1999, with heating degree-days 6.4 percent below normal and cooling degree-days 3.5 percent above normal. Below-normal heating degree-days reduce the demand for fuel used for space heating, and above-normal cooling degree-days increase the demand for air conditioning. In terms of energy demand, however, heating degree-days outweigh cooling degree-days. Thus, the warmer winter more than offset the warmer summer. In part due to these deviations from normal weather, residential emissions of carbon dioxide rose by only 0.4 percent (from 288.8 million metric tons carbon equivalent in 1998 to 290.1 million metric tons carbon equivalent in 1999), while commercial sector emissions fell by 0.4 percent (from 244.5 million metric tons carbon equivalent in 1998 to 243.5 million metric tons carbon equivalent in 1999). Industrial energy consumption, particularly in the manufacturing sector, is much less affected by the weather and more strongly affected by economic fluctuations than is energy consumption in the residential and commercial sectors. In 1999, carbon dioxide emissions from industrial energy use increased by only 0.2 percent, from 480.2 million metric tons carbon equivalent in 1998 to 481.2 million metric tons carbon equivalent in 1999. The underlying cause of the relatively small growth in industrial carbon dioxide emissions is not entirely clear, particularly in view of the 3.6-percent increase in industrial production in 1999. The six most energy-intensive industries—paper; chemicals; stone, clay and glass; primary metals; petroleum products; and food— together account for approximately two-thirds of total industrial energy-related carbon dioxide emissions. In 1999, two of those six industries grew by less than 1 percent (food by 0.7 percent and primary metals by 0.8 percent); two grew by slightly more than 1 percent (paper by 1.1 percent and petroleum by 1.3 percent); and only two grew by more than 2 percent (chemicals by 2.1 percent and stone, clay and glass by 2.9 percent). Output from the less energy-intensive industries grew rapidly (e.g., computer equipment by 57.2 percent and semiconductors and related components by 47.4 percent). Because the less energy-intensive industries use relatively little energy to produce goods, even large increases in their output are associated with only minor increases in energy consumption and related carbon dioxide emissions. Transportation sector energy demand is largely driven by income growth, fuel prices, and fuel economy trends. Propelled by gross domestic product (GDP) growth of 4.1 percent in 1999 and real disposable income growth of 3.2 percent, transportation energy-related carbon dioxide emissions increased by 2.9 percent, from 481.9 million metric tons carbon equivalent in 1998 to 496.1 million metric tons carbon equivalent in 1999. The increase in emissions accompanied large percentage increases in consumption of distillate fuel, aviation fuel, and motor gasoline. Although net generation of electricity increased by 2.0 percent in 1999, total carbon dioxide emissions from the electric power sector increased by only 1.0 percent, from 608.5 million metric tons carbon equivalent in 1998 to 614.3 million metric tons carbon equivalent in 1999. The growth rate in emissions was less than the growth rate in net generation in part because 54.5 billion kilowatthours of the net increase (73.2 billion kilowatthours) came from nuclear power plants, which produce essentially no carbon dioxide emissions. Nuclear electricity generation was 8.1 percent higher in 1999 than in 1998. Nonfuel uses of fossil fuels, principally petroleum, sequestered 89.8 million metric tons carbon equivalent in 1999—4.8 million metric tons carbon equivalent (5.7 percent) more than in 1998. The major fossil fuel products that sequester carbon include liquefied petroleum gas (LPG), feedstocks for plastics and other petrochemicals, and asphalt and road oils. It is estimated that, of the amount of carbon sequestered in the form of plastic, about 3.5 million metric tons carbon equivalent was emitted as carbon dioxide from the burning of plastic components in municipal solid waste. Emissions of carbon dioxide from non-energy-consuming industrial processes contributed 0.6 million metric tons carbon equivalent to the 1999 increase in emissions (Table 4). Emissions from cement production processes (excluding the energy portion) rose from 10.7 to 10.9 million metric tons carbon equivalent, while emissions from natural gas flaring rose from 3.9 to 4.2 million metric tons carbon equivalent. The consumption of energy in the form of fossil fuel combustion is the largest single contributor to greenhouse gas emissions in the United States and the world. Of total 1999 U.S. carbon dioxide emissions, 98 percent, or 1,510.8 million metric tons carbon equivalent, resulted from the combustion of fossil fuels. This figure represents an increase of 1 percentage point over 1998 levels. In the short term, year-to-year changes in energy consumption and carbon dioxide emissions tend to be dominated by weather, economic fluctuations, and movements in energy prices. Over longer time spans, changes in energy consumption and emissions are influenced by other factors such as population shifts and energy consumers’ choice of fuels, appliances, and capital equipment (e.g., vehicles, aircraft, and industrial plant and equipment). The energy-consuming capital stock of the United States—cars and trucks, airplanes, heating and cooling plants in homes and businesses, steel mills, aluminum smelters, cement plants, and petroleum refineries—change slowly from one year to the next, because capital stock is retired only as it begins to break down or becomes obsolete. The Energy Information Administration (EIA) divides energy consumption into four general sectoral categories: residential, commercial, industrial, and transportation.20 Emissions from electric utilities, which provide electricity to the end-use sectors, are allocated in proportion to the electricity consumed in each sector (Table 5). Emissions from independent power producers and industrial cogenerators are included in the industrial sector estimates. EIA is in the process of moving the data on electricity generated in the industrial sector into a combined electric power sector that includes electric utilities, nonutility generators, and industrial cogenerators. When that process is completed, this report will follow the same protocol. In the interim, this report provides, below, a separate preliminary estimate of emissions from the entire electric power sector for the 1990 to 1999 time period.21 Table 5. U.S. Carbon Dioxide Emissions from Energy Consumption by End-Use Sector, 1990-1999 At 290.1 million metric tons carbon equivalent, residential carbon dioxide emissions represented 19 percent of U.S. energy-related carbon dioxide emissions in 1999. The residential sector’s pro-rated share of electric utility emissions accounted for about two-thirds of that amount (193.4 million metric tons carbon equivalent).22 Since 1990, residential electricity-related emissions have grown by 1.9 percent annually. In contrast, emissions from the direct combustion of fuels (primarily natural gas) have increased by 0.7 percent per year, to 96.7 million metric tons carbon equivalent.
Total carbon dioxide emissions from the residential sector increased by 0.4 percent in 1999 (Table 6). Year-to-year, residential sector emissions are heavily influenced by weather. For example, in 1996, a relatively cold year, carbon dioxide emissions from the residential sector grew by 5.9 percent over 1995. In 1997, they declined by 0.4 percent due to warmer weather. Table 6. U.S. Carbon Dioxide Emissions from Residential Sector Energy Consumption, 1990-1999 Since 1990, growth in carbon dioxide emissions attributable to the residential sector has averaged 1.5 percent per year. As a result, residential sector emissions in 1999 were 35.9 million metric tons carbon equivalent higher than in 1990, representing 22 percent of the total increase in U.S. energy-related carbon dioxide emissions since 1990. Long-term trends in residential carbon dioxide emissions are heavily influenced by demographic factors, living space attributes, and building shell and appliance efficiency choices. For example, the movement of populations into the Sunbelt tends to increase summer air conditioning consumption and promote the use of electric heat pumps, which increases indirect emissions from electricity use. Growth in the number of households, resulting from increasing population and immigration, contributes to more residential energy consumption. Commercial sector carbon dioxide emissions, at 243.5 million metric tons carbon equivalent, account for about 16 percent of total energy-related carbon dioxide emissions, of which almost three-quarters (182.6 million metric tons carbon equivalent) is the sector’s pro-rated share of electric utility emissions. Although commercial sector emissions largely have their origin in the space heating and cooling requirements of structures such as office buildings, lighting is a more important component of commercial energy demand than it is in the residential sector. Thus, although commercial sector emissions are strongly affected by the weather, they are affected less than residential sector emissions. In the longer run, because commercial activity is a factor of the larger economy, emissions from the commercial sector are more affected by economic trends and less affected by population growth than are emissions from the residential sector. Emissions attributable to the commercial sector’s pro-rated share of electricity consumption declined by 1.4 percent in 1999, while emissions from the direct combustion of fuels (dominated by natural gas, as in the residential sector) increased by 2.6 percent. Overall, carbon dioxide emissions related to commercial sector activity declined by 0.4 percent—from 244.5 to 243.5 million metric tons carbon equivalent—between 1998 and 1999 (Table 7), as the reduction in electricity-related emissions outweighed the increase in emissions form the direct combustion of fuels. Since 1990, commercial emissions growth has averaged 1.8 percent per year—the largest growth of any energy-use sector—and commercial sector carbon dioxide emissions have risen by a total of 35.8 million metric tons carbon equivalent, or 22 percent of the total increase in U.S. energy-related carbon dioxide emissions. Table 7. U.S. Carbon Dioxide Emissions from Commercial Sector Energy Consumption, 1990-1999 Transportation sector emissions, at 496.1 million metric tons carbon equivalent, accounted for one-third of total energy-related carbon dioxide emissions in 1999. Almost all (98 percent) of transportation sector emissions result from the consumption of petroleum products, particularly, motor gasoline (60 percent of transportation sector emissions), diesel fuel or “middle distillates” (20 percent), jet fuel (13 percent), and residual oil or heavy fuel oil, largely for maritime use (4 percent). Motor gasoline is used primarily in automobiles and light trucks, and middle distillates are used in heavy trucks, locomotives, and ships. Emissions attributable to the transportation sector grew by 2.9 percent, from 481.9 million metric tons carbon equivalent in 1998 to 496.1 million metric tons carbon equivalent in 1999 (Table 8). Fuel-use patterns and related emissions sources in the transportation sector are different from those in the other energy-use sectors. By far the largest single source of emissions, motor gasoline, at 299.1 million metric tons carbon equivalent, grew by 2.1 percent. The highest rates of growth were for jet fuel emissions (which grew by 3.1 percent, from 64.2 to 66.3 million metric tons carbon equivalent) and distillate fuel emissions (which grew by 3.8 percent, from 96.4 to 100.1 million metric tons carbon equivalent). Of the total growth in U.S. energy-related carbon dioxide emissions in 1999, 91.9 percent (14.2 million metric tons carbon equivalent) was accounted for by the transportation sector. Since 1990, carbon dioxide emissions attributable to energy use in the transportation sector have grown annually at a rate of 1.6 percent, increasing by a total of 64.3 million metric tons carbon equivalent and representing 39.6 percent of the growth in energy-related carbon dioxide emissions from all sectors. Table 8. U.S. Carbon Dioxide Emissions from Transportation Sector Energy Consumption, 1990-1999 Industrial sector emissions, at 481.2 million metric tons carbon equivalent, accounted for about 32 percent of total U.S. energy-related carbon dioxide emissions in 1999. In terms of fuel shares, electricity purchased from electric utilities was responsible for 37.3 percent of total industrial sector emissions (179.5 million metric tons carbon equivalent), natural gas for 29.4 percent (141.6 million metric tons carbon equivalent), petroleum for 21.7 percent (104.2 million metric tons carbon equivalent), and coal for 11.3 percent (54.5 million metric tons carbon equivalent). Generally, industrial sector emissions are strongly affected by the growth of the economy. Estimated carbon dioxide emissions related to energy consumption in the industrial sector increased by only 0.2 percent in 1999—from 480.2 to 481.2 million metric tons carbon equivalent (Table 9)—despite GDP growth of 4.1 percent. Since 1990, growth in carbon dioxide emissions attributable to industrial sector energy consumption has averaged 0.6 percent per year. As a result, total energy-related industrial emissions in 1999 were 5.8 percent (26.3 million metric tons carbon equivalent) higher than they were in 1990, despite a much larger economy. The increase in industrial sector emissions from 1990 to 1999 represents 16.2 percent of the total growth in U.S. energy-related carbon dioxide emissions. Table 9. U.S. Carbon Dioxide Emissions from Industrial Sector Energy Consumption, 1990-1999 In 1999 the six most energy-intensive industry groups, which together account for approximately two-thirds of total industrial energy-related carbon dioxide emissions, grew less rapidly than the overall economy (4.1 percent) or the manufacturing component of industrial production (4.3 percent). The 1999 growth rates for the six energy-intensive industries (Figure 2) were 0.8 percent (primary metals), 2.1 percent (chemicals), 1.1 percent (paper), 2.9 percent (stone, clay and glass), 1.3 percent (petroleum), and 0.7 percent (food).23 Thus, all the energy-intensive industries grew less rapidly than the economy as a whole. The topic on "Energy-Related Carbon Dioxide Emissions in Manufacturing" discusses the importance of the energy-intensive industries to overall emissions, using data from EIA’s 1994 Manufacturing Energy Consumption Survey (MECS). A new survey of manufacturers was conducted by EIA in 1998, but the results are not yet available. Figure 2. Energy-Intensive Industrial Production Annual Growth Rates, 1997-1999 (Percent per Year) What makes the low growth in industrial sector emissions even more remarkable is that this sector includes emissions from independent (nonutility) power producers and industrial cogenerators, which provide electrical energy to the grid that is consumed in other sectors of the economy. Thus, the inclusion of carbon dioxide emissions resulting from the generation of electricity by independent power producers tends to overstate the amount of carbon dioxide attributable to the industrial sector, implying that actual emissions growth related to electrical and thermal energy use in the industrial sector may be lower than estimated here. A contributing factor to the low growth in industrial sector carbon dioxide emissions is the erosion of the older energy-intensive (and specifically coal-intensive) industrial base. For example, coke plants consumed 38.9 million short tons of coal in 1990 but only 27.9 million short tons in 1999. Additionally, other industrial coal consumption has declined from 76.3 million short tons in 1990 to 68.0 million short tons in 1999. As a result, carbon dioxide emissions attributable to industrial coal use have declined by 13.9 million metric tons carbon equivalent or about 20 percent since 1990, helping to offset an increase of 23.3 million metric tons carbon equivalent in natural-gas-related carbon dioxide emissions (also about 20 percent) over the same time period. Because natural gas is more than 40 percent less carbon-intensive than coal, the substitution of natural-gas-fired output for coal-fired output has further contributed to the modest growth in industrial emissions. Declines in residual and distillate fuel use have resulted in an additional decrease in emissions of 5 million metric tons carbon equivalent between 1990 and 1999. In the data presented by sector above, carbon dioxide emissions from electric utility fuel use are assigned to the energy-consuming sectors. However, because the electric power industry is changing and the “electric utility” designation is becoming less relevant, this section and the data in Table 10 present an estimate of carbon dioxide emissions for the entire electric power industry. By this accounting, emissions from the electric power industry as a whole made up 41 percent of total U.S. energy-related carbon dioxide emissions in 1999. Table 10. U.S. Carbon Dioxide Emissions from Electricity Generation, 1990-1999 Carbon dioxide emissions from the electric power industry, despite a strong economy, increased by only 1.0 percent, from 608.5 million metric tons carbon equivalent in 1998 to 614.3 million metric tons carbon equivalent in 1999 (Table 10).24 Although 1999 was warmer than average, the summer of 1998 was even warmer than the summer of 1999, thus, demand for electric power was dampened by the decline in cooling degree-days from 1998 to 1999. Since 1990, electric power industry carbon dioxide emissions have grown by 20.5 percent, while total carbon dioxide emissions have grown by 12.0 percent.
Electric utility carbon dioxide emissions have increased by 12 percent, from 479.5 million metric tons carbon equivalent in 1990 to 532.7 million metric tons carbon equivalent in 1999. Increases in the shares of generation from nuclear and hydroelectric power plants have kept the growth in emissions lower than would have been the case had more of the growth been in fossil-fuel-powered generation (see discussion on "U.S. Carbon Dioxide Emissions in 1999: Effects of Weather and High Levels of Nuclear and Hydroelectric Power Generation"). Carbon dioxide emissions attributable to nonutility power producers have risen by 171 percent, from 30.1 million metric tons carbon equivalent in 1990 to 81.6 million metric tons carbon equivalent in 1999. Over that time period the nonutility power sector has grown by 139 percent, from 216.7 billion kilowatthours of generation in 1990 to 517.4 billion kilowatthours in 1999. One of the factors that has increased the carbon intensity of nonutility power producers is their increased reliance on coal. In 1990, only 14 percent of nonutility generation was coal-powered. By 1999, coal’s share had risen to 22 percent.25 As the industry has been deregulated, some of the coal-fired generation facilities formerly operated by electric utilities have been divested and are now being operated by nonutility power producers. In 1999, 89.8 million metric tons carbon equivalent was sequestered through nonfuel uses of fossil fuels (Table 11). A small amount of this was coal-based (less than 0.5 million metric tons carbon equivalent), about 5.3 million metric tons carbon equivalent was natural-gas-based, and the remainder (84.1 million metric tons carbon equivalent) was petroleum-based. The products that sequester carbon include feedstocks for plastics and other petrochemicals, asphalt and road oil, liquefied petroleum gas, lubricants, and waxes. The amount sequestered in 1999 was 5.7 percent higher than in 1998, when 85.0 million metric tons carbon equivalent was sequestered. Since 1990 sequestration of carbon in this manner has increased by 21.1 million metric tons carbon equivalent or 30.7 percent, translating to an annual average growth rate of 3 percent, or more than twice the rate of growth in carbon dioxide emissions. Table 11. U.S. Carbon Sequestered by Nonfuel Use of Energy Fuels, 1990-1999 Carbon Dioxide Emissions and Economic Growth The relationship between economic growth and growth in energy-related carbon dioxide emissions is important in understanding both past emissions growth and what may be the trend in future emissions. Figure 3 shows U.S. carbon dioxide and GDP growth during the 1990s indexed to 1990. The United States experienced a period of prosperity during the 1990s, with economic growth averaging 3.1 percent per year. Carbon dioxide emissions, however, grew by an average of only 1.4 percent annually. As a result, the carbon dioxide intensity of U.S. GDP (carbon dioxide emissions divided by GDP) actually declined by 1.7 percent per year, and in 1999 was 14.3 percent lower than it was in 1990. In order to analyze trends in the carbon dioxide intensity of GDP, it is important to evaluate both the energy intensity of GDP (energy consumed per dollar of GDP) and the carbon dioxide intensity of energy use (carbon-equivalent emissions per unit of energy consumed). When the economy grows faster than carbon dioxide emissions, as in the 1990s, it means that either the energy/GDP intensity, the carbon/energy intensity, or both have declined, causing a divergence between the growth rates for GDP and carbon dioxide emissions. In examining 1990 to 1999 growth rates, it is clear that the primary cause of the divergence between the growth rates for GDP and carbon dioxide emissions is a decline in the energy intensity of the economy, which has fallen by an average of 1.5 percent per year since 1990. In comparison, the carbon intensity of U.S. energy use has declined by an average of only 0.2 percent per year during the 1990s. Thus, it is primarily the use of less energy per unit of economic output, not the use of low-carbon fuels, that has kept the rate of carbon dioxide emissions growth below the GDP growth rate. The decrease in the energy intensity of the U.S. economy has resulted, in part, from an increase in the non-energy-intensive sectors of the economy relative to the traditional energy-intensive manufacturing industries, as well as energy efficiency improvements. For example, the robust economic growth in 1999 occurred for the most part in industries that are less energy-intensive than the traditional basic industries: for example, computer equipment manufacturing grew by 51 percent, and the manufacture of semiconductors and related components grew by 44 percent in 1999. Such growth in the so-called “new economy” means that less energy is used and less carbon dioxide is emitted per dollar of GDP. The production of computer software requires very little energy consumption in comparison with industrial processes such as steelmaking. As long as U.S. economic growth continues to be led by industries that use relatively little energy per unit of output, it will have little direct effect on energy consumption and related carbon dioxide emissions. Economic growth of this kind does, however, have an indirect effect on emissions as people with more disposable income use more energy services (such as travel) and tend to live in larger houses. On the other hand, such income effects can be offset somewhat by more energy-efficient vehicles, building shells, appliances, and heating and cooling equipment. Adjustments to Energy Consumption Total energy consumption and the carbon emissions upon which they are based correspond to EIA’s coverage of energy consumption, which includes the geographic area of the United States defined as the 50 States and the District of Columbia. Under international protocol, however, the United States is also responsible for emissions emanating from its territories, and their emissions are added to the U.S. total. Conversely, because the Intergovernmental Panel on Climate Change (IPCC) definition of energy consumption excludes international bunker fuels from the statistics of all countries, emissions from international bunker fuels are subtracted from the U.S. total. Additionally, beginning with this year’s report, military bunker fuels have been subtracted because they are also excluded by the IPCC from the national total. These sources and subtractions are enumerated and described as “adjustments to energy.” U.S. Territories Energy-related carbon dioxide emissions for the U.S. territories are added as an adjustment in keeping with IPCC guidelines for national emissions inventories. The territories included are Puerto Rico, the U.S. Virgin Islands, American Samoa, Guam, the U.S. Pacific Islands, and Wake Island. Most of these emissions are from petroleum products; however, Puerto Rico and the Virgin Islands consume coal in addition to petroleum products. For 1999, total carbon dioxide emissions from the U.S. Territories are estimated at 13.5 million metric tons carbon equivalent (Table 4). International Bunker Fuels In keeping with the IPCC guidelines for estimating national greenhouse gas emissions, carbon dioxide emissions from international bunker fuels are subtracted from the estimate of total U.S. energy-related emissions of carbon dioxide. The estimate for bunker fuels is based on purchases of distillate and residual fuels by foreign-bound ships at U.S. seaports, as well as jet fuel purchases by international air carriers at U.S. airports. Additionally, U.S. military operations that consume fuel originally purchased in the United States are subtracted from the total, because they are also considered international bunker fuels under this definition. For 1998, the most recent year for which data are available, the emissions estimate for bunker fuels is 2.7 million metric tons carbon equivalent.26 In 1999, it is estimated that a combined total of approximately 29.3 million metric tons carbon equivalent was emitted from international bunker fuels (26.6 million metric tons carbon equivalent) and military bunker fuels (assuming the latter was close to the 1998 estimate). This amount is subtracted from the U.S. total in Table 4. Just over half of the carbon dioxide emissions associated with international bunker fuels are attributed to the combustion of jet fuels. Emissions from marine bunker fuels, largely attributable to oil burned by ocean-going merchant ships, account for the balance of emissions from civilian bunker fuels. Other Carbon Dioxide Emissions Energy Production In addition to emissions resulting from fossil energy consumed, oil and gas production leads to emissions of carbon dioxide from sources other than the combustion of those marketed fossil fuels. The two energy production sources estimated for this report are:
Because many States require flaring of natural gas, EIA assumes that all gas reported under the category “Vented and Flared” is actually flared and therefore is a carbon dioxide emission rather than a methane emission. In 1999, about 4.2 million metric tons carbon equivalent was emitted in this way (Table 4). By computing the difference between the estimated carbon dioxide content of raw gas and the carbon dioxide content of pipeline gas, the amount of carbon dioxide that has been removed (scrubbed) in order to improve the heat content and quality of natural gas can be calculated. This amount was about 4.9 million metric tons carbon equivalent in 1999 (Table 4). Appendix D describes additional energy production sources that are excluded from this report.27 Industrial Process Emissions Industrial emissions not caused by the combustion of fossil fuels accounted for only about 1.3 percent (19.2 million metric tons carbon equivalent) of total U.S. carbon dioxide emissions in 1999 (Table 12). Process-related emissions from industrial sources depend largely on the level of activity in the construction industries and on production at oil and gas wells. These sources include limestone and dolomite calcination, soda ash manufacture and consumption, carbon dioxide manufacture, cement manufacture, and aluminum production. Table 12. U.S. Carbon Dioxide Emissions from Industrial Processes, 1990-1999 Estimated industrial process emissions of carbon dioxide in 1999 were 2.8 million metric tons carbon equivalent (17.1 percent) higher than in 1990 and 0.3 million metric tons carbon equivalent (1.7 percent) higher than in 1998. Of the total carbon dioxide emissions from industrial processes, 57 percent are from cement manufacture. When calcium carbonate is heated (calcined) in a kiln, it is converted to lime and carbon dioxide. The lime is combined with other materials to produce clinker (an intermediate product from which cement is made), and the carbon dioxide is released to the atmosphere. In 1999, the United States manufactured an estimated 86.0 million metric tons of cement, resulting in the direct release of carbon dioxide containing 10.9 million metric tons carbon equivalent into the atmosphere. This calculation is independent of the carbon released by the energy consumed in making cement. This represents an increase in carbon dioxide emissions of 1.9 million metric tons carbon equivalent (20.4 percent) compared with 1990 and an increase of about 0.2 million metric tons carbon equivalent (2.1 percent) compared with 1998. There are numerous other industrial processes in which carbonate minerals are used in ways that release carbon dioxide into the atmosphere, including the use of limestone in the production of lime and in flue gas desulfurization and the manufacture and some uses of soda ash. Carbon dioxide is also released during aluminum smelting, when carbon anodes (with the carbon derived from nonfuel use of fossil fuels) are vaporized in the presence of aluminum oxide. Approximately 8.2 million metric tons carbon equivalent was released in emissions from these other industrial process sources in 1999. Municipal solid waste that is combusted contains, on average, a portion that is composed of plastics. The carbon in these plastics has normally been accounted for as sequestered carbon, as reported in Table 11. However, according to the IPCC, to properly account for that carbon, emissions from the plastics portion of the municipal solid waste must be counted in total national emissions inventories. These emissions produce about 3.5 million metric tons carbon equivalent. Under international agreement, the emissions are counted under the category of waste management, although most of the municipal solid waste is burned in the production of electricity. These emissions are calculated by the U.S. EPA, with the most recent estimate being for 1998. The 1998 value has been used as an estimate for 1999.28 This year, in keeping with EIA’s Strategic Plan for electronic dissemination of EIA data, the appendixes for this report are not included in the print version of the report but instead are being made available for viewing and/or download at web site www.eia.doe.gov/oiaf/1605/ggrpt/index.html. Appendix B describes the derivation of the carbon emissions coefficients used for this report. For the convenience of readers, the carbon coefficients that appear in Appendix B are repeated in Table 13. Table 13. Carbon Emissions Coefficients at Full Combustion, 1990-1999 Because motor gasoline consumption accounts for nearly 20 percent of all U.S. anthropogenic carbon dioxide emissions, small changes in the emissions coefficient can yield relatively large changes in the overall emissions estimate. Thus, EIA revises the emissions coefficient for motor gasoline annually. As is the case for all petroleum products, the emissions coefficient for motor gasoline is a function of its density and carbon content. This relationship is particularly clear for motor gasoline, which is largely free of impurities due to the narrow range of operating conditions in modern automobile engines. All other emissions coefficients for fossil fuels remain unchanged from previous editions of this report, with the exception of crude oil. The crude oil coefficient is not used directly in EIA estimation methods but is provided for those analysts wishing to perform a top-down calculation for comparative purposes.29 More detailed discussion of variations in emissions coefficients is provided in Appendix B. If you would like to receive any information relating to any of our greenhouse gas reports via e-mail, click here and subscribe by entering your e-mail address.
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