United States Environmental Protection Agency Office of Air Quality Planning and Standards Research Triangle Park NC 27711 March 1981 Air National Air Pollutant Emission Estimates, 1970—1979 ------- EPA-450/4-81-010 National Air Pollutant Emission Estimates, 1970 — 1979 Monitoring and Data Analysis Division U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Air. Noise, and Radiation Office of Air Quality Planning and Standards Research Triangle Park, North Carolina 27711 March 1981 ------- This report is published by the U.S. Environmental Protection Agency to report information of general interest in the field of air pollution . Copies are available free of charge to Federal employees, current contractors and grantees, and nonprofit organizations - as supplies permit - from the Library Services Office (MD-35), U.S. Environmental Protection Agency. Research Triangle Park, North Carolina 27711; or, for a fee, from the National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161. ------- ABSTRACT This report presents estimates of trends in nationwide air pollutant emissions for the five major pollutants: particulates, sulfur oxides, nitrogen oxides, volatile organic compounds, and carbon monoxide. Estimates are presented for each year from 1970 through 1979. Emission estimates are broken down according to major classifications of air pollution sources. A short analysis of trends is given, along with a discussion of methods used to develop the data. ------- CONTENTS Section Page LIST OF TABLES . . . • vii LIST OF FIGURES viii 1.SUMMARY 1 2.NATIONWIDE EMISSION TRENDS, 1970-1979 3 2.1 Particulates 3 2.2 Sulfur Oxides 3 2.3 Nitrogen Oxides 3 2.4 Volatile Organic Compounds 3 2.5 Carbon Monoxide . 4 3.METHODS 21 3.1 Transportation 22 3.1.1 Motor Vehicles 22 3.1.2 Aircraft 22 3.1.3 Railroads 23 3.1.4 Vessels 23 3.1.5 Nonhighway Use of Motor Fuels 23 3.2 Fuel Combustion in Stationary Sources 23 3.2.1 Coal 23 3.2.2 Fuel Oil 24 3.2.3 Natural Gas 24 3.2.4 Other Fuels 24 3.3 Industrial Processes 24 3.4 Solid Waste Disposal 25 3.5 Miscellaneous Sources 25 3.5.1 Forest Fires 25 3.5.2 Agricultural Burning 25 3.5.3 Coal Refuse Burning. .... 26 3.5.4 Structural Fires 26 3.5.5 Nonindustrial Organic Solvent Use 26 ------- CONTENTS (continued) Page 4.ANALYSIS OF TRENDS 27 4.1 Participates 29 4.2 Sulfur Oxides 30 4.3 Nitrogen Oxides 31 4.4 Volatile Organic Compounds 31 4.5 Carbon Monoxide 31 5.REFERENCES 36 TECHNICAL REPORT DATA AND ABSTRACT 37 ------- LIST OF TABLES Table Page 1. Summary of National Emission Estimates 2 2. National Estimates of Participate Emissions 5 3. National Estimates of Sulfur Oxide Emissions 6 4. National Estimates of Nitrogen Oxide Emissions 7 5. National Estimates of Volatile Organic Compound Emissions 8 6. National Estimates of Carbon Monoxide Emissions 9 7. Nitrogen Oxide Emissions from Highway Vehicles 10 8. Volatile Organic Compound Emissions from Highway Vehicles 11 9. Carbon Monoxide Emissions from Highway Vehicles 12 10. Particulate Emissions from Fuel Combustion 13 11. Sulfur Oxide Emissions from Fuel Combustion 14 12. Nitrogen Oxide Emissions from Fuel Combustion 15 13. Particulate Emissions from Industrial Processes 16 14. Sulfur Oxide Emissions from Industrial Processes 17 15. Nitrogen Oxide Emissions from Industrial Processes 18 16. Volatile Organic Compound Emissions from Industrial Processes. . . .19 17. Carbon Monoxide Emissions from Industrial Processes 20 18. Theoretical 1979 National Emission Estimates with 1970 Level of Control 28 VII ------- LIST OF FIGURES Figure Page 1. Highway Vehicle NOx Emissions Estimates 33 2. Highway Vehicle VOC Emissions Estimates 34 3. Highway Vehicle CO Emission Estimates 35 viii ------- NATIONAL AIR POLLUTANT EMISSION ESTIMATES 1970-1979 1. SUMMARY Table 1 summarizes estimated national emissions for each year. As shown in the table, estimated participate emissions (TSP) have decreased substantially, emissions of sulfur oxides (SOx), volatile organic compounds (VOC), and carbon monoxide (CO) have declined slightly, while nitrogen oxide emissions (NOx) have increased. These data entirely replace those published earlier for 1970-1976 in EPA report National Air Pollutant Emissions Estimates 1940-1976 (EPA-450/1-78-003), for 1970-1977 in the National Air Quality Monitoring, and Emissions Trends Report, 1977 (EPA-450/2-78-052) and for 1970-1978 in National Air Pollutant Emission Estimates, 1970-1978 (EPA-450/480-002).Because of modifications in methodology and use of more refined emission factors, data from this report should not be compared with data in these earlier reports. Reporting of emissions on a nationwide basis, while useful as a general indicator of pollutant levels, has definite limitations. National totals or averages are not the best guide for estimating trends for particular localities. Yet, it is important that some criteria be established for measurement of national progress in the control of air pollutant emissions. The emission estimates presented herein represent calculated estimates based on standard emission inventory procedures. Since these data are estimates only and do not represent the results of any program for the measurement of actual emissions, their accuracy is somewhat limited. Similarly, it would' not necessarily be expected that these emission estimates would be in agreement with emission estimates derived through a different emission inventory procedure. The principal objective of compiling these data is to identify probable overall changes in emissions on a national scale. It should be recognized that these estimated national trends in emissions may not be representative of local trends in emissions or air quality. ------- TABLE 1 SUMMARY OF NATIONAL EMISSION ESTIMATES Year 1970 1971 1972 1973 1274 1975 1976 1977 1978 1979 Change 1970- 1979 TSP 21.0 19.2 17.0 15.8 14.0 11.6 10.6 9.9 9.7 9.5 -54.8% TERAGRAMS/YEAR SOX NOX 28.3 26.9 27.4 28.5 26.7 25.2 25.9 25.4 24.3 24.5 -13.4% 19.1 19.6 20.7 21.2 20.8 20.2 21.8 22.4 22.7 22.6 418.3% VOC 27.7 27.0 27.4 26.8 25.5 23.4 24, 24, 25, 24.6 -11.2% CO 112.9 112.6 110. 108. 102. .7 ,1 .4 98.0 99.4 96.4 94.9 91.4 -19.0% Note: One teragram equals 1012 grams (106 metric tons) or approximately 1.1 x 10° short tons. ------- 2. NATIONWIDE EMISSION TRENDS, 1970-1979 Tables 2 through 6 show trends in the emissions of each pollutant according to major source categories. More detailed breakdowns of the emissions from highway vehicles are given in Tables 7 through 9, for stationary source fuel combustion in Tables 10 through 12, and for industrial processes in Tables 13 through 17. In the industrial process tables the Standard Industrial Classification (SIC) in which the process is included is shown. These designations are not intended to represent the complete emissions for all SIC categories and serve only to identify and classify the industrial processes shown. In all tables data are reported in metric units, either as teragrams (lp!2 grams) or gigagrams (10" grams) per year. One teragram equals approximately 1.1 x 10^ short tons and one gigagram equals approximately 1.1 x 10^ short tons. 2.1 Particulates Particulates emissions result primarily from fuel combustion in stationary sources and from industrial processes. From 1970 through 1979, total particulate emissions have decreased by 55 percent. This substantial decrease is due primarily to installation of control equipment on in- dustrial processes and coal-fired stationary fuel combustion sources. In addition, particulate emissions have decreased because of less burning of solid waste. 2.2 Sulfur Oxides Sulfur oxide emissions occur mostly from stationary source fuel combustion. In addition, sulfur oxide emissions from industrial processes are significant. From 1970 to 1979, emissions of sulfur oxides decreased by 13 percent. This decrease relates primarily to decreased emissions from primary nonferrous smelters and sulfuric acid manufacturing plants. Emissions from stationary source fuel combustion have decreased slightly due to expanded use of fuels with low sulfur contents and installations of flue gas desulfurization systems by electric utilities. 2.3 Nitrogen Oxides Emissions of nitrogen oxides are produced almost entirely by fuel combustion by stationary sources and transportation sources, Nitro- gen oxide emissions increased about 18 percent from 1970 to 1979. This increase is due to increased motor vehicle travel and increased fuel use by electric utilities. The nationl recession in 1975 resulted in significantly less industrial activity and corresponding NOX emissions. ------- 2.4 Volatile Organic Compounds Volatile organic compound emissions decreased slightly, by about 11 percent. As a result of the Federal motor vehicle control program, emissions from highway vehicles decreased by 30 percent. In addition, emissions from miscellaneous organic solvent use decreased, mainly due to the substitution of water-based emulsified asphalts for those liquified with petroleum distillates. However, emissions from industrial processes increased. This increase partially offsets the decreases in emissions for other source categories, resulting in an overall minor change in total emissions. 2.5 Carbon Monoxide Carbon monoxide emissions occur largely from transportation sources. As a result of the Federal motor vehicle control program, emissions from highway vehicles decreased by 16 percent from 1970 to 1979. Industrial process emissions decreased mainly in the carbon black (obsolescence of the channel process) and petrole.um refining industries (increased use of CO boilers on catalytic cracking unit catalyst regenerations). Emissions from the burning of solid waste and agricultural materials also declined substantially. ------- TABLE 2 NATIONAL ESTIMATES OF PARTICIPATE EMISSIONS SOURCE CATEGORY Transportation Highway vehicles Aircraft Railroads Vessels Other off-highway vehicles Transportation Total Stationary Source Fuel Combustion Electric Utilities Industrial Commercial-Institutional Residential Fuel Combustion Total Industrial processes Solid waste disposal Incineration Open burning Solid Waste Total Miscellaneous Forest fires Other Burning Misc. Organic Solvent Miscellaneous Total 1970 0.9 0.1 0.1 1.3 10.2 0.4 0.7 1.1 TERAGRAMS/YEAR 1971 1972 9.6 0.4 0.5 0.9 9.4 0.3 0.4 0.7 1973 1974 1975 1976 1977 1978 1979 1.0 0.1 0.1 0.1 0.1 1.4 1.0 0.1 0.1 0.1 0.1 1.4 1.1 0.1 0.1 0.1 0.1 1.5 1.1 0.1 0.1 0.1 0.1 1.5 1.0 0.1 0.1 0.0 0.1 1.3 1.1 0.1 0.1 0.0 0.1 1.4 1.1 0.1 0.1 0.0 0.1 1.4 1.1 0.1 0.1 0.0 0.1 1.4 1.1 0.1 0.1 0.0 0.1 1.4 4.1 2.8 0.2 0.2 7.3 3.6 2.1 0.2 0.2 6.1 2.9 1.4 0.2 0.1 4.6 2.9 1.1 0.2 0.1 4.3 8.5 0.3 0.3 0.6 2.6 1.0 0.2 0.1 3.9 7.0 0.3 0.3 0.6 2.4 0.8 0.2 0.1 3.5 1.9 0.7 0.2 0.1 2.9 1.8 0.7 0.2 0.2 2.9 1.7 0.6 0.2 0.2 2.7 1.5 0.6 0.2 0.2 2.5 5.5 0.3 0.3 0.6 0.7 0.4 0.0 1.1 0.9 0.3 0.0 1.2 0.7 0.2 0.0 0.9 0.7 0.2 0.0 0.9 0.8 0.2 0.0 1.0 0.6 0.1 0.0 0.7 4.9 4.4 0.2 0.2 0.4 0.9 0.1 0.0 1.0 0.2 0.2 0.4 0.7 0.1 0.0 0.8 4.4 0.2 0.2 0.4 0.7 0.1 0.0 0.8 4.3 0.2 0.2 0.4 0.8 0.1 0.0 0.9 Total 21.0 19.0 17.0 15.8 14.0 11.6 10.6 9.9 9.7 9.5 ------- TABLE 3 NATIONAL ESTIMATES OF SULFUR OXIDE EMISSIONS SOURCE CATEGORY Transportation Highway Vehicles Aircraft Railroads Vessels Other Off-highway Vehicles Transportation Total Stationary Source Fuel Combustion Electric Utilities Industrial Commercial-Institutional Residential Fuel Combustion Total Industrial Processes Solid Waste Disposal Incineration Open Burning Solid Waste Total Miscellaneous Forest Fires Other Burning Miscellaneous Organic Solvent Miscellaneous Total TERAGRAMS/YEAR 1970 1971 1972 1973 1974 1975 6.4 0.0 0.0 0.0 5.9 0.0 0.0 0.0 1976 1977 1978 1979 0.3 0.0 0.1 0.2 0.1 0.7 0.3 0.0 Q.i q.i 0.1 .0.6 0.3 0.0 0.1 0.1 0.1 0.6 0.3 0.0 0.1 0.1 0.1 0.6 0.3 0.0 0.1 0.1 0.1 0.6 0.3 0.0 0.1 0.1 0.1 0.6 0.4 0.0 0.1 0.2 0.1 0.8 0.4 0.0 0.1 0.2 0.1 0.8 0.4 0.0 0.1 0.2 0.1 0.8 0.4 0.0 0.1 0.2 0.1 0.8 15.6 3.6 1.3 0.6 21.1 15.4 3.0 1.3 0.6 20.3 15.6 2.9 1.3 0.4 20.2 17.0 2.6 1.3 0.4 21.3 16.5 2.3 1.2 0.4 20.4 16.5 2.2 1.0 0.3 20.0 17.1 2.1 1.2 0.3 20.7 16.9 2.0 1.1 0.3 20.3 16.0 2.0 1.1 0.3 19.4 16.0 2.3 1.0 0.3 19.6 6.5 0.0 0.0 0.0 6.5 0.0 0.0 0.0 5.7 0.0 0.0 0.0 4.6 0.0 0.0 0.0 0.0 0.1 0.0 0.1 0.0 0.1 0.0 0.1 0.0 0.1 0.0 0.1 0.0 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.0 0.1 0.2 0.1 0.8 17.1 2.1 1.2 0.3 20.7 4.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.0 0.1 0.2 0.1 0.8 16.9 2.0 1.1 0.3 20.3 4.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.1 0.0 0.0 0.0 4.1 0.0 0.0 0.0 Total 28.3 26.9 27.4 28.5 26.7 25.2 25.9 25.4 24.3 24.5 ------- TABLE 4 NATIONAL ESTIMATES OF NITROGEN OXIDE EMISSIONS SOURCE CATEGORY Transportation Highway Vehicles Aircraft Railroads Vessels Other Off-highway Vehicles Transportation Total Stationary Source Fuel Combustion Electric Utilities Industrial Commercial-Insitutional Residential Fuel Combustion Total Industrial Processes ^ Solid Waste Disposal Incineration Open Burning Solid Waste Total Miscellaneous Forest Fires . Other Burning > Misc. Organic Solvent Miscellaneous Total TERAGRAMS/YEAR 1970 : 1971 1972 .1973 1974 1975 0.8 0.1 0.3 0.4 0.8 0.1 0.2 0.3 1976 1977 1978 1979 5.2 o.i - 0.6 0.1 1.2 7.2 5.7 0.1 0.6 0.1 1.2 7.7 6.3 0.1 0.7 0.1 1.2 8.4 6.6 0.1 0.7 0.1 1.2 8.7 6.4 0.1 0.7 0.1 1.3 8.6 6.4 0.1 0.7 0.1 1.3 8.6 6.7 0.1 0.7 0.1 1.4 9.0 6.8 . 0.1 0.7 • 0.1 1.4 9.1 6.9 0.1 0.7 0.2 1.5 9.4 6.7 0.1 0.7 0.2 1.5 9.2 0.8 0.1 0.1 0.2 6.6 0.1 0.7 0.1 1.2 8.7 6.2 4.4 0.5 0.4 11.5 0.8 0.0 0.1 0.1 0.1 0.0 0.0 0.1 6.4 0.1 0.7 0.1 1.3 8.6 6.1 4.2 0.5 0.3 11.1 0.8 0.0 0.1 0.1 0.2 0.0 0.0 0.2 5.1 4.4 0.5 0.4 10.4 5.3 4.3 0.5 0.4 10.5 5.7 4.4 0.5 0.4 11.0 6.2 4.4 0.5 0.4 11.5 6.1 4.2 0.5 0.3 11.1 6.1 3.9 0.4 , 0.3 10.7 6.6 4.2 0.5 0.4 11.7 7.1 , 4.2 0.5 0.4 12.2 7.1 4.2 0.5 0.4 12.2 7.5 4.1 0.4 0.3 12.3 0.7 0.0 0.1 0.1 0.8 0.0 0.1 0.1 0.8 0.0 0.1 0.1 0.8 0.0 0.1 0.1 0.8 0.0 0.1 0.1 0.2 0.1 0.0 0.3 0.2 0.1 0.0 0.3 0.2 0.1 0.0 0.3 0.1 0.0 0.0 0.1 0.2 0.0 0.0 0.2 0.1 0.0 0.0 0.1 0.2 o.o • 0.0 0.2 0.2 0.0 0.0 0.2 0.2 0.0 0.0 0.2 0.2 0.0 0.0 0.2 Total 19.1 19.6 20.7 21.2 20.8 20.2 21.8 22.4 22.7 22.6 ------- TABLE 5 NATIONAL ESTIMATES OF VOLATILE ORGANIC COMPOUND EMISSIONS SOURCE CATEGORY Transportation Highway Vehicles Aircraft Railroads Vessels Other Off-highway Vehicles Transportation Total Stationary Source Fuel Combustion Electric Utilities Industrial Commercial-Institutional Residential Fuel Combustion Total Industrial Processes Solid Waste Disposal Incineration Open Burning Solid Waste Total Miscellaneous Forest Fires Other Burning Misc. Organic Solvent Miscellaneous Total 1970 0.5 1.3 1.8 0.7 0.3 2.2 3.2 TERAGRAMS/YEAR 1971 1972 1973 0.5 1.0 1.5 0.9 0.3 2.0 3.2 1974 1975 1976 1977 1978 1979 10.6 0.3 0.2 0.4 0.6 12.1 10.5 0.3 Q.2 Q.4 Q.6 12.0 10.5 0.3 0.2 0.4 0.6 12.0 10.0 0.2 0.2 0.4 0.6 11.4 9.2 0.2 0.2 0.4 0.6 10.6 8.8 0.2 0.2 0.4 0.6 10.2 8.6 0.2 0.2 0.5 0.6 10.1 8.3 0.2 0.2 0.5 0.6 9.8 8.0 0.2 0.2 0.5 0.6 9.5 7.2 0.2 0.2 0.5 0.7 8.8 0.1 0.1 0.0 0.1 0.3 0.1 0.1 0.0 0.1 0.3 0.1 0.1 0.0 0.1 0.3 0.1 0.1 0.0 0.1 0.3 0.1 0.1 0.0 0.1 0.3 0.1 0.1 0.0 0.0 0.2 0.1 0.1 0.0 0.0 0.2 0.1 0.1 0.0 0.0 0.2 0.1 0.1 0.0 0.0 0.2 0.1 0.1 0.0 0.0 0.2 10.3 10.0 11.0 11.3 0.4 0.7 1.1 0.4 0.6 1.0 10.9 0.4 0.5 0.9 9.8 10.7 0.4 0.5 0.9 0.4 0.4 0.8 11.2 0.4 0.4 0.8 12.3 0.4 0.4 0.8 12.4 0.4 0.4 0.8 0.7 0.2 2.1 3.0 0.6 0.2 2.0 2.8 0.7 0.2 1.9 2.8 0.5 0.1 1.7 2.3 0.9 0.1 1.6 2.6 0.7 0.1 1.6 2.4 0.7 0.1 1.8 2.6 0.7 0.1 1.6 2.4 Total 27.7 27.0 27.4 26.8 25.5 23.4 24.4 24.4 25.4 24.6 ------- TABLE 6 NATIONAL ESTIMATES OF CARBON MONOXIDE EMISSIONS SOURCE CATEGORY Transportation Highway Vehicles Aircraft Railroads Vessels Other Off-highway Vehicles Transporation Total Stationary Source Fuel Combustion Electric Utilities Industrial Commercial-Institutional Residential Fuel Combustion Total Industrial Processes Solid Waste Disposal Incineration Open Burning Solid Waste Total Miscellaneous Forest Fires Other Burning Misc. Organic Solvent Miscellaneous Total 1970 79.0 0.9 0.3 1.2 7.3 88.7 0.2 0.5 0.1 TERAGRAMS/YEAR 1971 1972 1973 9.0 2.7 3.7 6.4 5.1 1.9 0.0 7.0 1974 1975 1976 1977 1978 71.4 0.8 0.3 1.5 5.7 79.7 1979 79.4 0.9 0.2 1.3 7.0 88.8 0.2 0.5 0.1 0.9 1.7 8.8 2.3 2.7 5.0 6.7 1.6 0.0 8.3 80.9 0.8 0.3 1.3 6.8 90.1 0.3 0.5 0.1 0.7 1.6 8.4 2.2 2.1 4.3 5.2 1.1 0.0 6.3 79.7 0.8 0.3 1.4 6.6 88.8 0.3 0.5 0.1 0.6 1.5 8.6 2.1 1.7 3.8 4.5 0.9 0.0 5.4 74.6 0.8 0.3 1.4 5.8 82.9 0.3 0.5 0.1 0.6 1.5 8.1 1.9 1.5 3.4 5.6 0.9 0.0 6.5 73.5 0.8 0.2 1.4 5.7 81.6 0.3 0.5 0.1 0.7 1.6 6.9 1.8 1.3 3.1 4.0 0.8 0.0 4.8 73.0 0.8 0.3 1.5 5.8 81.4 0.3 0.5 0.1 0.7 1.6 6.6 1.5 1.2 2.7 6.4 0.7 0.0 7.1 0.8 1.7 6.6 1.5 1.1 2.6 5.1 0.7 0.0 5.8 70.3 0.9 0.3 1.6 5.5 78.6 0.3 0.5 0.1 0.9 1.8 6.3 1.4 1.1 2.5 5.0 0.7 0.0 5.7 65.9 0.9 0.3 1.5 5.9 74.5 0.3 0.5 0.1 1.0 1.9 6.3 1.4 1.1 2.5 5.5 0.7 0.0 6.2 Total 112.9 112.6 110.7 108.1 102.4 98.0 99.4 96.4 94.9 91.4 ------- TABLE 7 NITROGEN OXIDE EMISSIONS FROM HIGHWAY VEHICLES SOURCE CATEGORY Gasoline-powered Vehicles Passenger cars Light Duty Trucks-1 Light Duty Trucks-2 Heavy Duty Trucks Motorcycles Diesel-powered Vehicles Passenger Cars Heavy Duty Trucks Total 1970 (GIGAGRAMS/YEAR) 1971 1972 1973 1974 1975 1976 1977 1978 1979 3,240 380 160 490 0 3,490 420 180 52Q P 3,760 500 220 540 0 3,940 510 240 560 0 3,730 490 250 550 0 3,750 460 260 550 0 3,820 510 330 560 0 3,810 510 380 560 0 3,710 490 440 540 0 3,390 460 450 520 10 000000000 10 960 1,040 1,250 1,300 1,340 1,410 1,470 1,590 1,740 1,900 5,230 5,650 6,270 6,550 6,360 6,430 6,690 6,850 6,920 6,740 10 ------- TABLE 8 VOLATILE ORGANIC COMPOUND EMISSIONS FROM HIGHWAY VEHICLES SOURCE CATEGORY Gasoline-powered Vehicles Passenger Cars Light Duty Trucks-1 Light Duty Trucks-2 Heavy Duty Trucks Motorcycles Diesel-powered Vehicles Passenger Cars Heavy Duty Trucks Total GIGAGRAMS/YEAR 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 8,320 920 310 900 90 0 110 8,230 920 300 820 130 0 120 8,030 1,000 330 810 150 0 140 7,650 930 330 770 180 0 150 6,920 880 340 690 200 0 140 6,640 790 360 690 200 0 150 6,260 810 470 700 200 0 160 5,890 770 540 680 200 0 170 5,610 700 630 640 210 0 180 4,930 620 630 640 170 0 200 10,650 10,520 10,460 10,010 9,170 8,830 8,600 8,250 7,970 7,190 11 ------- TABLE 9 CARBON MONOXIDE EMISSIONS ROM HIGHWAY VEHICLES (GIGAGRAMS/YEAR) SOURCE CATEGORY 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 Gasoline-powered Vehicles Passenger cars 61,050 61,640 61,740 60,560 56,100 54,950 52,780 50,800 49,620 45,330 Light Duty Trucks-1 6,150 6,180 6,950 6,680 6,490 5,920 6,340 6,090 5,750 5,310 Light Duty Trucks-2 2,050 1,940 2,160 2,160 2,230 2,460 3,280 3,800 4,480 4,580 Heavy Duty Trucks 9,100 8,820 9,130 9,240 8,700 9,050 9,480 9,530 9,270 9,460 Motorcycles 290 440 500 570 650 660 660 660 680 570 Diesel-powered Vehicles Passenger Cars 000000000 10 Heavy Duty Trucks 330 360 430 450 420 440 470 500 550 610 Total 78,970 79,380 80,910 79,660 74,590 73,480 73,010 71,380 70,350 65,870 12 ------- TABLE 10 PARTICIPATE EMISSIONS FROM FUEL COMBUSTION IN STATIONARY SOURCES SOURCE CATEGORY Coal Electric Utilities Industrial Resi denti al/Commerci al Coal Total Fuel Oil Electric Utilities Industrial Resi denti al/Commerical Fuel Oil Total Natural Gas Electric Utilities Industrial Resi dent i al/Commerci al Natural Gas Total Wood Industrial Residential Wood Total Other Fuels Industrial Residential Other Fuels Total Fuel Combustion Total (GIGAGRAMS/YEAR) 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 3,960 2,360 210 6,530 no 50 100 260 20 40 30 90 310 50 360 40 10 50 3,470 1,640 200 5,310 110 40 100 250 20 40 30 90 290 50 340 40 10 50 2,780 980 160 3,920 110 50 110 270 20 40 30 90 270 40 310 40 10 50 2,750 750 160 3,660 130 50 100 280 20 40 30 90 250 40 290 40 10 50 2,490 580 160 3,230 130 50 90 270 20 40 30 90 250 40 290 40 10 50 2,290 490 130 2,910 110 30 80 220 10 30 30 70 200 60 260 40 10 50 1,740 420 110 2,270 120 50 90 260 10 30 40 80 190 60 250 40 10 50 1,600 350 110 2,060 140 60 90 290 10 30 30 70 190 80 270 30 10 40 1,570 350 110 2,030 140 50 80 270 10 30 30 70 180 100 280 30 10 40 1,400 360 100 1,860 120 50 80 250 20 30 30 80 170 120 290 30 10 40 7,290 6,040 4,640 4,370 3,930 3,510 2,910 2,730 2,690 2,520 13 ------- TABLE 11 SULFUR OXIDE EMISSIONS FROM FUEL COMBUSTION IN STATIONARY SOURCES (GIGARAMS/YEAR) SOURCE CATEGORY 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 Coal Electric Utilities Industrial Resi denti al/Commerci al Coal Total Fuel Oil Electric Utilities Industrial Resi denti al/Conmerci al Fuel Oil Total Natural Gas Electric Utilities Industrial Resi denti al/Commerci al Natural Gas Total Wood Industrial Residential Wood Total Other Fuel Industrial Residential Other Fuels Total Fuel Combustion Total 14,150 2,790 510 17,450 1,440 620 1,400 3,460 0 0 0 0 30 0 30 110 20 130 21 ,070 13,910 2,280 480 16,67,0 1,450 590 1,340 3,380 0 0 0 0 30 0 30 90 20 no 20,190 14,260 2,150 340 16,750 1,370 640 1,390 3,400 0 0 0 0 30 0 30 100 10 no 20', 290 15,490 1,870 300 17,660 1,560 660 1,310 3,530 0 0 0 0 20 0 20 90 10 100 21,310 14 15,010 1,560 300 16,870 1,520 650 1,320 3,490 0 0 0 0 30 0 30 100 10 no 20,500 15,120 1,590 220 16,930 1,360 460 1,070 2,890 0 0 0 0 30 0 30 90 10 100 19,950 15,690 1,330 220 17,240 1,430 620 1,230 3,280 0 0 0 0 30 0 30 120 10 130 20,680 15,270 1,140 250 16,660 1,620 750 1,210 3,580 0 0 0 0 30 0 30 120 10 130 20,400 14,330 1,190 250 15,770 1,660 660 1,110 3,430 0 0 0 0 30 0 30 no 10 120 19,350 14,520 1.540 230 16,290 1,440 620 1,020 3,080 0 0 0 0 30 0 30 120 10 130 19,530 ------- TABLE 12 NITROGEN OXIDE EMISSIONS FROM FUEL COMBUSTION IN STATIONARY SOURCES SOURCE CATEGORY Coal Electric Utilities Industrial Resi denti al/Commerci al Coal Total Fuel Oil Electric Utilities Industrial Resi denti al/Commerci al Fuel Oil Total Natural Gas Electric Utilities Industrial Resi denti al/Commerci al Natural Gas Total Mood Industrial Residential Wood Total Other Fuels Industrial Residential Other Fuels Total Fuel Combustion Total 1970 (GIGAGRAMS/YEAR) 1971 1972 1973 1974 1975 1976 1977 1978 1979 3,380 680 40 4,100 650 160 440 1,250 1,070 3,290 310 4,670 180 0 180 60 50 110 3,460 550 40 4,050 780 160 440 1 ,380 1,090 3,380 320 4,790 170 0 170 50 50 100 3,690 530 40 4,260 950 170 450 1,570 1,090 3,440 330 4,860 170 0 170 60 50 110 4,090 470 40 4,600 1,110 190 450 1,750 990 3,510 320 4,820 160 0 160 50 50 100 4,130 440 50 4,620 1,050 180 410 1,640 940 3,360 310 4,610 170 0 170 60 40 100 4,270 470 40 4,780 980 140 380 1,500 860 3,040 320 4,220 190 0 190 60 40 100 4,710 430 40 5,180 1,050 200 430 1,680 840 3,270 330 4,440 200 0 200 70 40 110 5,030 410 40 5,480 1,220 230 420 1,870 870 3,270 310 4,450 190 0 190 70 40 110 5,070 420 50 5,540 1,150 220 410 1,780 870 3,250 320 4,440 200 0 200 60 40 100 5,560 460 50 6,070 980 210 380 1,570 960 3,180 330 4,470 210 0 210 70 30 100 10,310 10,490 10,970 11,430 11,140 10,790 11,610 12,100 12,060 12,420 15 ------- TABLE 13 PARTICULATE EMISSIONS FROM INDUSTRIAL PROCESSES SOURCE CATEGORY (SIC) Cattle Feed lots (0211) Cotton Ginning (0724) Metallic Ore Mining (10) Coal Mining (1211) Crushed Stone (142) Sand and Gravel (144) Clays (145) Potash/Phosphate Rock (1474,1475) Feed and Grain Milling (204) Lumber and Plywood (24) Pulp Mills (261,262) Chemicals (28) Petroleum Refining (2911) Asphalt Paving and Roofing (295) Glass (321,322) Cement (3241) Brick and Tile (3251) Concrete, Lime, Gypsum (327) Clay Sintering (3295) Iron and Steel (3312) Ferroalloys (3313) Iron and Steel Foundries(332) Primary Nonferrous Smelters(333) Secondary Nonferrous Smelters(334,336) Grain Elevators(4421,5153) Total 1970 (GIGAGRAMS/YEAR) 1971 1972 1973 1974 1975 1976 1977 1978 1979 20 20 580 350 1,220 50 500 40 80 80 520 250 70 570 50 1,390 1,080 540 90 1,250 160 200 320 50 670 20 20 530 300 1,140 50 420 40 80 80 460 210 70 560 50 1,360 1,170 440 90 1,040 140 200 300 60 790 20 30 530 300 1,090 50 360 40 . 80 90 440 210 70 560 50 1,340 1,180 410 90 1,050 150 180 280 50 730 20 20 550 280 1,060 50 300 40 70 90 310 180 80 600 50 990 1,070 390 90 960 160 160 250 50 720 20 20 530 250 880 50 170 40 60 80 330 160 80 520 50 850 500 340 70 840 150 130 200 50 570 20 20 470 250 690 40 90 30 60 70 180 130 70 330 40 690 400 280 40 630 90 80 170 50 590 20 20 440 260 590 40 70 30 50 80 150 140 60 250 50 700 260 230 20 550 80 80 140 50 550 20 30 350 260 510 50 50 30 50 90 150 130 60 160 50 650 270 180 20 490 70 70 100 40 500 20 20 390 250 550 50 60 30 50 90 90 130 50 170 50 660 300 180 10 500 60 60 100 40 500 20 30 390 280 570 50 50 30 50 80 100 120 50 170 40 620 240 150 10 470 40 60 90 50 540 10,190 9,620 9,380 8,540 6,940 5,510 4,910 4,380 4,410 4,300 16 ------- TABLE 14 SULFUR OXIDE EMISSIONS FROM INDUSTRIAL PROCESSES SOURCE CATEGORY Natural Gas Production (1311) Pulp Mills (261,262) Sulfuric Acid (2819) Carbon Black(2895) Petroluem Refining (2911) Glass(321,322) Cement(3241) Lime(3274) Iron and Steel (3312) Primary Copper (3331) Primary Lead and Zinc (3332, 3333) Primary Aluminum(3334) Secondary Lead (3341) Total 1970 (GIGAGRAMS/YEAR) 1971 1972 1973 1974 1975 1976 1977 1978 1979 100 70 540 0 620 20 580 30 300 3,650 410 70 20 100 70 530 0 660 20 580 30 230 3,220 360 70 20 120 70 570 10 690 20 600 30 270 3,740 310 70 20 150 70 570 10 760 30 610 30 290 3,690 190 80 20 160 70 440 10 750 30 580 30 280 3,080 160 80 20 160 70 330 10 730 30 490 30 240 2,290 110 60 20 130 80 250 10 700 30 530 30 250 2,220 110 70 30 120 80 260 10 720 30 580 30 230 2,070 90 80 30 130 80 260 10 720 30 630 30 220 1,930 0 80 30 120 80 250 10 680 30 680 30 230 1,870 0 80 30 6,420 5,890 6,520 6,500 5,690 4,570 4,440 4,330 4,150 4,090 17 ------- TABLE 15 NITROGEN OXIDE EMISSIONS FROM INDUSTRIAL PROCESSES (GIGAGRAMS/YEAR) SOURCE CATEGORY 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 Pulp Mi 11s(261,262) 20 20 30 30 30 20 30 30 30 30 Organic Chemicals(286) 60 60 60 70 60 60 50 50 50 60 Ammonia(2873) 40 40 40 40 40 40 40 50 40 50 Nitric Acid(2873) 180 170 170 170 160 140 140 130 120 120 Petroleum Refining (2911) 310 310 320 330 330 320 330 350 350 340 Glass(321,322) 40 40 50 50 50 50 50 60 60 60 Cement (3241) 90 90 100 100 100 80 90 90 100 100 Iron and Steel(3312) 50 40 50 50 50 40 40 40 40 40 Total 790 770 820 840 820 750 770 800 790 800 18 ------- TABLE 16 VOLATILE ORGANIC COMPOUND EMISSIONS FROM INDUSTRIAL PROCESSES SOURCE CATEGORY Crude Oil Production, Storage, and Transfer(l311,4463) Food and Beverages(20) Text lies(22) Graphic Arts(27) Plastics(2821,3079) Organic Chemicals(286) Other Chemicals(28) Petroleum Refining(2911) Rubber Tires(3011) Glass(321,322) Iron and Steel(3312) Petroleum Product Storage and Transfer(5171,5541) Dry Cleaning(721) Adhesives1 Degreasing1 Solvent Extraction Processes1 Surface Coating1 Other Organic Solvent Use1 Total 1970 (GIGAGRAMS/YEAR) 1971 1972 1973 1974 1975 1976 1977 1978 1979 590 120 180 280 400 890 570 720 100 50 110 1,670 280 460 560 230 1,730 1,370 590 120 180 260 390 950 500 760 110 50 80 1,740 270 430 510 220 1,610 1,270 600 120 180 300 450 1,060 480 790 110 50 100 1,830 300 490 500 240 1,880 1,480 600 120 180 310 470 1,150 490 820 110 50 110 1,890 300 500 520 240 1,930 1,540 580 130 180 280 460 1,210 460 850 110 50 100 1,830 280 460 470 220 1,780 1,470 570 130 170 240 390 1,070 370 880 90 50 90 1,840 250 400 400 190 1,470 1,210 580 130 170 270 450 1,280 430 880 90 60 100 1,890 260 440 420 200 1,650 1,380 600 140 150 280 480 1,390 450 . 940 120 60 90 1,900 270 460 420 220 1,810 1,460 610 140 180 330 560 1,500 450 960 110 70 90 1,940 320 550 460 260 2,200 1,530 610 150 190 340 590 1,580 460 960 100 60 90 1,810 330 560 460 260 2,230 1,640 10,310 10,040 10,960 11,330 10,920 9,810 10,680 11,240 12,260 12,420 ^This is a general category which includes process emissions from organic solvent use in a wide variety of industries. Thus no specific SIC is given. 19 ------- TABLE 17 CARBON MONOXIDE EMISSIONS FROM INDUSTRIAL PROCESSES SOURCE CATEGORY Pulp Mills (261,262) Inorganic Pigments(2816) Charcoal(2861) Organic Chemicals(286) Ammonia(2873) Carbon Black(2895) Petroleum Refining(2911) Asphalt Roofing(2952) Iron and Steel(3312) Iron Foundries(3321) Primary Aluminum(3334) Total 1970 (GIGAGRAMS/YEAR) 1971 1972 1973 1974 1975 1976 1977 1978 1979 550 20 60 340 100 2,600 1,990 10 1,620 1,090 590 550 20 60 360 110 2,380 2,050 10 1,470 1,160 580 590 20 60 420 110 1,780 2,080 10 1,560 1,180 610 610 20 60 440 110 1,890 2,120 10 1,580 1,060 670 610 30 50 460 110 1,680 2,040 10 1,460 920 730 550 20 30 470 120 1,410 2,030 10 1,100 590 580 620 30 30 450 120 1,550 1,340 10 1,180 590 630 630 30 30 500 130 1,760 1,180 10 1,160 470 680 650 30 30 540 120 1,630 880 10 1,210 440 720 700 30 30 560 130 1,610 850 10 1,200 400 750 8,970 8,750 8,420 8,570 8,100 6,910 6,550 6,580 6,260 6,270 20 ------- 3. METHODS The generation of an emission inventory involves many steps to achieve the desired result, which is to estimate the amount of emissions for selected pollutants in a defined geographical area. Ideally, nationwide emission estimates should result from a sum- mation of county, state, and regional data in which each component is reported separately. The National Emissions Data System (NEDS) uses this procedure. The methods used to prepare data for this publication are as similar as possible to those used for NEDS data preparation. Since NEDS uses a more detailed procedure involving calculation of emissions for individual sources and summation of these individual emission totals to produce national totals, there is a much greater chance for errors or omissions to occur in the NEDS data. Because of the basic similarity of techniques, dis- crepancies between national totals reported herein and those given in NEDS reports are due largely to incomplete data reporting and errors in the NEDS data. The quality of NEDS data over time has improved so that the differences between NEDS emission reports for 1977 and later years and national emission totals determined by the procedure used for this publication are not as great as in earlier NEDS reports. Moreover, historical NEDS data are not revised to account for updated emission factors, errors or omissions in the data. As a result annual NEDS publications do not necessarily represent a consistent trend in estimated emissions. Because it is impossible to test every pollutant source indivi- dually, particularly area sources, an estimating procedure must be used. In order to do this, however, one must either estimate the emissions directly or estimate the magnitude of other variables that can then be related to emissions. These indicators include fuel consumption, vehicle miles, population, sales, tons of refuse burned, raw materials'processed, etc., which are then multiplied by appropriate emission factors to obtain emission estimates. The limitations and applicability of emission factors must be understood. In general, emission factors are not precise indi- cators of emissions from a single source; rather, they are quan- titative estimates of the average rate of pollutant released as a result of some activity. They are most valid when applied to a large number of sources and processes. If their limitations are recognized, emission factors are extremely useful in determining emission levels. A detailed discussion of emission factors and related information is contained in Reference 2. The emission factor thus relates quantity of pollutants emitted to indicators such as those noted above, and is a practical approach for determining estimates of emissions from various source categories. 21 ------- A discussion of trends is meaningful only when there is a common basis for evaluation. It was necessary, therefore, to quantify emissions using the same criteria for each year. This meant using the same estimation techniques, using equal or equivalent data sources, covering the same pollutant sources, and using compatible estimates of pollutant control levels from year to year. Estimates for previous years were updated using current emission factors and including the most recent information .available. The criteria used in calculating emissions was the same for all years. The methodology used in generation of emission estimates for individual source categories follows. 3.1 Transportation 3.1.1 Motor Vehicles Emission estimates from gasoline-and diesel-powered motor vehicles were based upon vehicle-mile tabulations and emission factors. Seven vehicle categories are considered; light duty gasoline (mostly passenger cars), light duty diesel passenger cars, light duty trucks (trucks less than 6000 pounds in weight), light duty trucks 6000 to 8500 pounds in weight, heavy duty gasoline trucks and buses, and heavy duty diesel trucks and buses, and motorcycles. The emission factors used are based on the latest available data from Reference 3. The MOBILE 2 model, developed by the EPA Office of Mobile Source Air Pollution Control was used to calculate emission factors. The factors are based on national average conditions and do not include corrections for specific geographical areas to account for local model year distributions, altitude, temperature, or hot/cold vehicle operation differences. For each of these variables, only national averages were considered in the emission factors. Average speed is taken into account on a nationwide basis according to the published distribution of vehicle-miles travelled (VMT) for urban and rural fractions. These data are published in Reference 4. For rural VMT, the average speed is considered to be 45 miles per hour, and for urban VMT, 19.6 miles per hour. 3.1.2 Aircraft Aircraft emissions are based on emission factors and air- craft activity statistics reported by the Federal Aviation Administration.5 Emissions are based on the number of landing-takeoff (LTD) cycles. Any emissions in cruise mode, 22 ------- which is defined to be above 3000 feet (1000 meters) are ignored. Average emission factors, which take into account the national mix of aircraft types for general aviation, military, and commercial aircraft, are used to compute the emissions. 3.1.3 Railroads The Department of Energy reports consumption of diesel fuel and residual fuel oil by railroads.^ Average emission factors applicable to diesel fuel consumption were used to calculate emissions. The average sulfur content of each fuel was used to estimate SOX emissions. 3.1.4. Vessels Vessel use of diesel fuel, residual oil, and coal is reported by the Department of Energy.6,/ Gasoline use is based on national boat and motor registrations, coupled with a use factor (gallons/ motor/year) from Reference 8. Emission factors from AP-42^ are used to compute emissions. Since AP-42 does not contain an emission factor for coal use by vessels, an average emission factor for coal combustion in boilers was used. 3.1.5 Nonhighway Use of Motor Fuels Gasoline and diesel fuel are consumed by off-highway vehicles. The fuel use is divided into seven categories; farm tractors, other farm machinery, construction equipment, industrial machinery, small general utility engines such as lawnmowers and snowthrowers, snow- mobiles, and motorcycles. Fuel use is estimated for each category from estimated equipment population and an annual use factor of gallons per unit per year.° 3.2 Fuel Combustion in Stationary Sources 3.2.1 Coal Bituminous coal, lignite, and anthracite coal use are reported by the Department of Energy.7 Most coal is consumed by electric utilities. Average emission factors and the sulfur content of each type of coal were used to estimate emissions. Degree of particu- late control was based on a report by Midwest Research Institute^ together with data from NEDS10. Sulfur content data for electric utilities are available from the Department of Energyll. Sulfur contents for other categories are based on NEDS data. 23 ------- 3.2.2 Fuel Oil Distillate oil, residual oil, and kerosene are consumed by stationary sources nationwide. Consumption by user category is reported by the Department of Energy.6 Average emission fac- tors and the sulfur content of each fuel were used to estimate emissions. 3.2.3 Natural Gas Natural gas consumption data are also reported by the Department of Energy.12 Liquefied petroleum gas (LPG) use is also in- cluded with natural gas for the purpose of estimating emissions. Average emission factors from AP-42^ were used to calculate the emission estimates. 3.2.4 Other Fuels Consumption of wood, coke, coke-oven gas, and bagasse is based on data reported in NEDS.10 Average emission factors were used to calculate emissions, which are relatively minor on a national basis. 3.3 Industrial Processes In addition to fuel combustion, certain other industrial pro- cesses generate and emit varying quantities of pollutants into the air. The lack of published national data on production, type of equipment, and controls, as well as an absence of emission factors, makes it impossible to include estimates of emissions from all industrial process sources. Production data for industries that are known to produce the great majority of emissions were derived from literature data. Generally, the Minerals Yearbook,13 published by the Bureau of Mines, and Current Industrial Reports,14 published by the Bureau of the Census, provide adequate data for most industries. Average emission factors were applied to production data to obtain emissions. Control efficiencies applicable to various processes were estimated on the basis of published reports^ and from NEDS data.l° For the purposes of this report, petroleum product storage and marketing operations (gasoline, crude oil, and distillate fuel oil storage and transfer, gasoline bulk terminals and bulk plants, re- tail gasoline service stations) are included as industrial processes. Also included as industrial processes are industrial surface coating and degreasing operations, graphic arts (printing and publishing), and dry cleaning operations. All of these proces- ses involve the use of organic solvents. Emissions from the con- sumption of organic solvents are estimated based on data reported in reference 15. It is assumed that all solvents consumed are eventually released as air pollution. 24 ------- 3.4 Solid Waste Disposal A study conducted in 1968 on solid waste collection and disposal practices^ was the basis for estimating emissions from solid waste disposal. Results of this study indicate that the average collection rate of solid waste is about 5.5 pounds per capita per day in the United States. It has been stated that a conservative estimate of the total generation rate is 10 pounds per capita per day. The results of this survey were updated based on data re- ported in NEDS and used to estimate, by disposal method, the quantities of solid waste generated. Average emission factors were applied to these totals to obtain estimates of total emissions from the disposal of solid wastes. 3.5 Miscellaneous Sources 3.5.1 Forest Fires The Forest Service of the Department of Agriculture publishes information on the number of forest fires and the acreage burned.17 Estimates of the amount of material burned per acre are made to estimate the total amount of material burned. Similiar estimates are made to account for managed burning of forest areas. Average emission factors were applied to the quantities of materials burned to calculate emissions. 3.5.2 Agricultural Burning A studylS was conducted by EPA to obtain from local agri- cultural and pollution control agencies estimates of the number of acres and estimated quantity of material burned per acre in agricultural burning operations. These data have been updated and used to estimate agricultural burning emissions, based on average emission factors. 25 ------- 3.5.3 Coal Refuse Estimates of the number of burning coal-refuse piles existing in the United States are made in reports by the Bureau of Mines.1" Their publication presents a detailed discussion of the nature, origin, and extent of this source of pollution. Rough estimates of the quantity of emissions were obtained using this information by applying average emission factors for coal combustion. It was assumed that the number of burning refuse piles decreased to a negligible amount by 1975. 3.5.4 Structural Fires The United States Department of Commerce publishes, in their statistical abstracts, information on the number and types of structures damaged by fire^O. Emissions were estimated by applying average emission factors for wood combustion to these totals. 3.5.5 Nonindustrial Organic Solvent Use This category includes nonindustrial sales of surface coatings (primarily for architectural coating) solvent evaporation from consumer products (aerosols, space deodorants, polishes, toiletries, etc.), use of volatile organic compounds as general cleaning solvents, paint removers, and liquefaction of asphalt paving compounds, and other undefined end uses. Total national organic solvent use is estimated from chemical production reports of the U.S. Tariff Commission^ together with estimates of the portion of total production for use as solvent for each chemical.15 jt is assumed that all solvent production is equal to the amount necessary to make up for solvent lost through evaporation. Estimated- emissions from organic solvent use by industrial processes and selected nonindustrial solvent use categories were obtained from Reference 15. Solvent use not accounted for by industrial processes is reported as nonindustrial organic solvent use, with annual estimates adjusted according to solvent production levels. 26 ------- 4. Analysis of Trends National trends in air pollutant emissions are a function of a number of factors. Air pollution control measures and economic conditions have the strongest impact on total emissions. National emission trends do not provide any insight into the distribution or concentration of air pollution sources within the United States. Therefore, local emission trends do not necessarily coincide with national emission trends. Based on the national implementation of control measures for some classes of sources, such as highway motor vehicles, it is reasonable to infer that for most localities, the national trend in emissions reasonably approximates local trends in emissions for the same class of sources. In addition to the fact that national emission trends do not measure local changes in emission densities, national emission trends may not be consistent with air quality trends because of the impact of meteorological factors on air quality data. Also, the estimates for TSP, SOx, and NOx emissions include more substances than are routinely measured by ambient air monitoring equipment. For example, high-volume air samplers collect only suspended particulates approximately 0.3 to 100 micro-meters in diameter, but TSP emission inventories include both suspended and settled particulates generated by man's activities. Likewise sulfur dioxide (SO?) and nitrogen dioxide (NO?) ambient air monitors measure only those two compounds while oxides of sulfur (SOx) and nitrogen (NOx) are included in the emission estimates. In each case, the substance measured by the ambient air monitor is the most prevalent constitutent of its pollutant class or is acknowledged to be its most representative indicator. Estimates of oxidant emissions are not provided because most oxidant species are secondary pollutants generated by photochemical reactions in the atmosphere. Emission estimates of VOC, a major ingredient in oxidant-producing reactions, were developed from current emission factors.2.3 Generally, excluded from VOC estimates were emissions of methane, ethane, methyl chloroform, and other compounds which are considered to be of negligible photochemical reactivity. Organic species were identified based on Reference 22. If no data were available for a source category, the total hydrocarbon emission factor from Reference 2 was used. Highway vehicle emissions were estimated as nonmethane VOC's.3 The following sections discuss the most important factors influencing the emission trends for each pollutant. 27 ------- TABLE 18 THEORETICAL 1979 NATIONAL EMISSION ESTIMATES BASED ON 1970 LEVEL OF CONTROL (TERA6RAMS/YEAR) Source Category TSP SOX NOX VOC CO Transportation Highway Vehicles Non-Highway Transportation Total Stationary Source Fuel Combustion Electric Utlities Industrial Resi denti al /Commerci al Fuel Combustion Total Industrial Processes(SIC) Mining Operations (10,12,13,14) Food and Agricultural (02,07,20) Wood Products(24,26) Chemical s(28) Petroleum Refining(29) Metal s(33) Mineral Products(32) Miscellaneous Industrial Processes Total Solid Waste Miscellaneous Total 1979 Actual Emissions (Table 1) Theoretical 1979 Emissions As A Percentage of 1970 Actual Emissions 1970 Actual Emissions (Table 1) Theoretical 1979 Emissions As A Percentage of 1970 Actual Emissions 1.3 0.3 1.6 6.7 2.1 0.5 9.3 3.1 1.3 0.7 0.3 0.1 1.8 4.2 0.0 11.5 1.1 1.2 24.7 9.5 260% 21.0 118% 0.4 0.4 0.8 25.5 2.8 1.5 29.8 0.3 0.0 0.1 0.8 0.9 3.7 0.8 0.0 6.6 0.0 0.1 37.3 24.5 152% 28.3 132% 28 7.6 2.5 10.1 7.5 4.1 0.7 12.3 0.0 0.0 0.0 0.3 0.3 0.1 0.2 0.0 0.9 0.4 0.3 24.0 22.6 106% 19.1 126% 14.6 1.6 16.2 0.1 0.1 0.0 0.2 0.6 0.1 0.0 2.8 1.0 0.1 0.1 8.3 13.0 1.9 3.3 34.6 24.4 142% 27.7 125% 107.9 8.7 116.6 0.3 0.5 1.1 1.9 0.0 0.0 0.7 3.0 2.3 3.5 0.0 0.0 9.5 6.9 7.4 142.3 91.4 156% 112.9 126% ------- 4.1 Particulates Particulate emissions result primarily from fuel combustion in stationary sources and from industrial processes. Substantial reductions in particulate emissions have occurred because of the installation of control equipment on these sources. The extent of the reduction is most evident from the data in Table 18 which shows theoretical 1979 national emission estimates, assuming that pol- lutant control levels did not change since 1970. Overall, particulate emissions would have increased by about 18 percent if the extent of particulate control had not increased. In reality, as shown in Table 1, particulate emissions decreased about 55 percent. Thus, 1979 actual particulate emissions were less than half of what they would have been without control efforts. More specifically, with no change in the level of control, emissions from fuel combustion in stationary sources would have increased from 7.3 teragrams to 9.3 teragrams, a 27 percent increase. In fact, particulate emissions decreased to 2.5 teragrams, a 66 per- cent decrease. The electric utility sector has the largest potential for particulate emissions. This is due to the extensive use of coal- fired boilers to generate electricity. In 1970, electric utilities consumed approximately 321 million tons of coal. By 1979, this total had increased to about 527 million tons. Despite this extensive increase in coal consumption, particulate emissions from electric utilities decreased 63 percent. Improvement or installation of control equipment on existing sources and New Source Performance Standards (NSPS) requirements for new facilities can be credited with the achievement of this emission reduction. Particulate emissions from other stationary fuel combustion sectors have also decreased. Additional control equipment has been installed on industrial and commercial coal-fired boilers. In addition, the actual consumption of coal by these and the residential sector declined from 1970 to 1979. Particulate emissions from industrial processes also decreased because of installation of additional controls. As noted in the tables, with no change in the level of control, increases in in- dustrial production would have caused a slight increase in emis- sions from 10.2 to 11.5 teragrams. In fact, industrial process particulate emissions decreased 58 percent to 4.3 teragrams. Substantial reductions were achieved in mineral products (cement, crushed stone, brick, lime, etc.) and primary metal industries, most notably in iron and steel production. 29 ------- A caveat that should be noted with respect to these participate emission estimates is that fugitive particulate (emissions from unconfined sources such as storage piles, material loading, etc.) emissions are incompletely accounted for in the emission totals. Rough estimates of industrial process fugitive emissions are included for some industries. Area source fugitive dust emissions (unpaved roads, construction activities, etc.) are not included at all. Similarly, natural sources of particulates, such as wind erosion or dust, are not included. (An exception is forest fires, some of which result from natural causes). In total, these fugitive emissions may amount to a considerable portion of total particulate emissions. The controls applied to these sources have so far been minimal. Due to the lack of adequate emission factors and emission inventory techniques for these sources, fugitive particulate emissions have not been included in most emission inventories. As additional data become available, it is expected that estimates of fugitive particulate emissions will be included in future reports. 4.2 Sulfur oxides Fuel combustion by stationary sources produces most sulfur oxide emissions. In addition, certain industrial processes, such as smelting of copper, lead, and zinc ores, sulfuric acid manu- facturing, and other industries also produce sulfur oxide emis- sions. Significant emission reductions from industrial processes have occurred, mostly from non-ferrous smelters and sulfuric acid plants. By-product recovery of sulfuric acid at smelters has in- creased since 1970. As a result sulfur oxide emissions that previ- ously would have been released to the atmosphere are recovered as sulfuric acid. Since 1972 new sulfuric acid manufacturing plants have been subject to New Source Performance Standards requirements. These rules have contributed to decreased emissions as new plants built to meet new product demands or replace old facilities must meet more stringent emission limitations than old facilities. As shown in the tables, sulfur oxide emissions from electric utilities account for more than half of total emissions. Combustion of sulfur-bearing fuels, chiefly coal and residual fuel oil, is responsible. Between 1970 and 1979 utility use of coal increased about 64 percent and residual oil use increased about 50 percent. Emissions from utilities have increased only slightly, because fuels with lower sulfur content have been used to the extent that they were available. Flue gas desulfurization systems have seen only limited use to date, but by the late 1970's enough units were in service to prevent additional increases in electric utlity emissions. 1979 electric utility emissions would have been approximately 5 percent higher without the operation of flue gas desulfurization controls. The theoretical 1979 National emission estimates given in Table 18 for stationary fuel combustion sources are based on 1979 fuel amounts but 1970 average sulfur contents. On this basis, electric utility emissions would have increased 64 percent. In fact, emissions increased only 3 percent. Sulfur oxide emissions from other fuel combustion sectors decreased, primarily due to less coal burning by these consumers. 30 ------- 4.3 Nitrogen oxides Nitrogen oxide emissions result almost entirely from transportation.and stationary fuel combustion sources. Only limited controls have been applied to sources of NOx emissions. Table 18 shows that with the 1970 control level, national NOx emissions would have been only 6 percent higher than actual 1979 emissions. The emissions from stationary fuel combustion sources reflect the actual growth in fuel consumption. For mobile sources, NOx emissions were controlled as a result of the Federal Motor Vehicle Control Program (FMVCP). Nitrogen oxide emissions from highway vehicles would have increased 46 percent, had there been no change in control level since 1970. The estimates of actual NOx emissions show a 29 percent increase. 4.4 Volatile organic compounds Emissions of VOC decreased primarily due to motor vehicle controls and less burning of solid waste. Had controls not been implemented, a substantial increase in emissions from highway vehicles would have occurred. From 1970 to 1979 vehicle-miles of travel in the U.S. increased by about 37 percent.4 A comparable increase in emissions would have occurred had 1970 control levels remained unchanged. As a result of the controls put in place, VOC emissions from highway vehicles actually decreased 32 percent. VOC emissions also decreased due to the substitution of water-based emulsified asphalts (used for road paving) for asphalts liquefied with petroluem distillates (cutback asphalts). This is reflected in the decreased emissions reported for miscellaneous organic solvent use. These decreases were offset by increases in industrial process emissions so that overall, total VOC emissions were reduced only slightly. Emissions from petroleum refining and chemical pro- duction increased due to expanded production of organic chemicals and petroleum products. Emissions from petroleum product storage and marketing also increased due to increase demand for gasoline and other petroleum products. 4.5 Carbon monoxide Carbon monoxide emissions occur mainly from highway vehicles. From 1970 through 1972, emissions from highway vehicles increased. In 1973, CO emissions decreased and subsequently have decreased further through 1979. Overall, from 1970 to 1979, highway vehicle emissions decreased 6 percent. This trend is the result of the competing forces of growth in motor vehicle-miles travelled (VMT) and controls to limit CO emissions from motor vehicles. From 1970 through 1972, controls had a limited effect in reducing emissions. 31 ------- From 1973 on, the control measures have been successful in reducing emissions despite growth in VMT. For 1974 and 1979 sharp re- ductions in emissions from the previous years occur because of decline in VMT for these years. Overall, 1979 VMT is still 37 percent higher than in 1970. If no controls other than those in place in 1970 had been implemented, highway vehicle emissions would have increased in proportion to the growth in VMT. Figures 1,2, and 3 show the trend in estimated actual emissions from highway vehicles along with estimated emissions for two other theoretical scenarios. The estimated emissions with constant 1970 emission factors show the expected emissions if there were no Federal Motor Vehicle Control Program. In this case substantial increases in emissions occur as a result of growth in VMT. The estimated emissions with constant 1970 VMT show the predicted effects of FMVCP if no growth in VMT occur. The substantial emission reductions that occur in this case may apply to areas with congested traffic volumes where VMT had reached a practical growth limit by 1970, so that no future growth in VMT was possible. This situation may exist in central business districts or other loca- tions in major metropolitan areas. CO emissions from other sources either decreased or remained about the same from 1970 to 1979. The most sizeable reductions resulted from decreased burning of solid waste and agricultural materials. 32 ------- Highway Vehicle NO Emissions (10b MT/yr) " 7.5 7.0 6.5 6.C 5.5 5.0 4.5 4.0 0.0 Emissions with Constant 1970 Emission Factors Estimated Actual Emissions Emissions with Constant 1970 VMT .'1970 1971 1972 T973 1974 1975 1976 1977 1978 1979 Figure 1. Highway Vehicle NOX Emissions Estimates 33 ------- Highway? Vehicle VCfC' Emissions (TO-6 MT/yr) 15 14 13 12 11 10 5 8 ssions with Constant 1970 Emission Factors Estimated Actual Emissions Emissions with Constant 1970 VMT 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 Figure 2. Highway Vehicle VOC Emissions Estimates 34 ------- Highway Vehicle CO - 110 Emissions (106 MT/yi 100 90 80 70 60 50 Emissions with Constant 1970 Emission Factors Estimated Actual Emissions Emissions with Constant 1S70 VMT 40 30 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 Figure 3. Highway Vehicle CO Emissions estimates 35 ------- 5. References *1.National Emissions Report, National Emissions Data System (NEDS).NADB, OAQPS.US Environmental Protection Agency,Research Triangle Park.NC. Publication No.EPA-450/4-80-005.March 1980. 2.Compilation of Air Pollutant Emission Factors,Third Edition (Inclu- ding Supplements 1-10).US Environmental Protection Agency,Research Triangle Park,NC.Publication No.AP-42. 3.Mobile 2 Users's Guide and Supporting Background Documentation (Draft) US Environmental Protection Agency, Office of Mobile Source Air Pollution Control, Ann Arbor, Michigan.1979 *4.Highway Statistics.Federal Highway Administration,US Department of Transportation,Washington,DC.1979. *5.FAA Air Traffic Activity.Federal Aviation Administration,US Department of Transportation,Washington,DC.1979. *6.Energy Data Reports,Sales of Fuel Oil and Kerosine,Energy Infor- mation Administration,US Department of Energy,Washington,DC 1979. *7.Energy Data Reports,Bituminous Coal and Lignite Distribution, Energy Information Administration,US Department of Energy, Washington,DC 1979. 8.Exhaust Emissions from Uncontrolled Vehicles and Related Equipment Using Internal Combustion Engines.Southwest Research Institute, San Antonio,TX.Prepared for US Environmental Protection Agency, Research Triangle Park,NC.EPA Contract No.EHS 70-108.Oct 1973. 9.Particulate Pollutant Systems Study.Midwest Research Institute,Kansas City,MO.Prepared for US Environmental Protection Agency,Research Triangle Park,NC.Natural Air Pollution Control Administration Contract No.CPA 22-69-104.May 1971. 10.Standard Computer Retrievals from the National Emissions Data System (NEDS).Unpublished computer report available from NADB,OAQPS,US Environmental Protection Agency, Research Triangle Park.NC. *11.Energy Data Reports, Cost and Quality of Fuels for Electric Utility Plants-1979, Energy Information Administration, US Department of Energy, Washington, D.C. Publication No. DOE/EIA-0191(79).June 1980. *12.Energy Data Reports.Natural Gas Production and Consumption,Energy Information Administration,U.S. Department of Energy,Washington,D.C. 1979. *13.Minerals Yearbook.Bureau of Mines, US Department of the Interior, Washington,DC. *14.Current Industrial Reports.Bureau of the Census,US Department of Com- merce, Washington,DC. 15.Ends Use of Solvents Containing Volatile Organic Compounds, The Research Corporation of New England, Wethersfield, CT.EPA Publication EPA-450/3-79-032, May 1979. 16.1968 National Survey of Community Solid Waste Practices.Public Health Service,US Department of Health,Education,and Wei fare,Cincinnati, OH.PHS Publication No.1867.1968. *These publications are issued periodically. The most recent publication available when this document was prepared is cited. 36 ------- *17.Wildfire Statistics.Forest Service,US Department of Agriculture, Washington,DC 1977. 18.Emissions Inventory from Forest Wildfires,Forest Managed Burns, and Agricultural Burns.US Environmental Protection Agency, Research Triangle Park,NC 27711.Publication No.EPA-450/3-74-062. November 1974. 19.Coal Refuse Fires,An Environmental Hazard.Bureau of Mines,US Department of the Interior,Washington,DC.Information Circular 8515.1971. *20.Statistical Abstract of the United States.Bureau of the Census, US Department of Commerce,Washington,DC. 1977 (98th ed.) *21.Synthetic Organic Chemicals,US Production and Sales.US Tariff Commission,Washington,DC. 22.Volatile Organic Compound (VOC) Species Data Manual Second Edition,US Environmental Protection Agency,Research Triangle Park,NC.Publication No.EPA-450/4-80-015.July 1980. 23.Standard Industrial Classification Manual 1972, Executive Office of the President, Office of Management and Budget, Washington, D.C. *These publications are issued periodically. The most recent publication available when this document was prepared is cited. 37 ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) 1. REPORT NO. EPA-450/4-81-010 3. RECIPIENT'S ACCESSIONiNO. 4. TITLE AND SUBTITLE National Air Pollutant Emission Estimates, 1970-1979 5. REPORT DATE March 1981 6. PERFORMING ORGANIZATION CODE 7. AUTHOR(S) Monitoring and Data Analysis Division 8. PERFORMING ORGANIZATION REPORT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS U.S. Environmental Protection Agency Office of Air, Noise and Radiation Office of Air Quality Planning and Standards Research Triangle Park, North Carolina 27711 10. PROGRAM ELEMENT NO. 11. CONTRACT/GRANT NO. 12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED Final - 1970-1979 14. SPONSORING AGENCY CODE 15. SUPPLEMENTARY NOTES 16. ABSTRACT This report presents estimates of trends in nationwide air pollutant emissions for the five major pollutants: sulfur oxides, particulates, carbon monoxide, hydrocarbons, and nitrogen oxides. Estimates are broken down according to major types of air pollutant sources. A short analysis of emission trends is given, along with a discussion of methods used to develop the data. 7. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS b.IDENTIFIERS/OPEN ENDEDTERMS c. COSATI Field/Group trends, emissions, inventory, air pollutants, nationwide, sulfur oxides, carbon monoxide, particulates, hydrocarbons, nitrogen oxides, controllable emissions, miscellaneous sources 3. DISTRIBUTION STATEMENT Release unlimited 19. SECURITY CLASS (ThisReport) Unclassified 21. NO. OF PAGES 44 20. SECURITY CLASS (Thispage) Unclassified 22. PRICE EPA Form 2220-1 (9-73) ------- |