NATIONWIDE INVENTORY
OF AIR POLLUTANT EMISSIONS
1968
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
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NATIONWIDE INVENTORY
OF AIR POLLUTANT EMISSIONS
1968
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
National Air Pollution Control Administration
Raleigh, N. C.
August 1970
For sale by the Superintendent of Documents, U.S. Government Printing Office,
'Washington, D.C., 20402 - Price 30 cents
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This report was prepared by the Division of Air Quality and Emission
Data, Bureau of Criteria and Standards, NAPCA, under the super-
vision of Alan J. Hoffman.
The AP series of reports is issued by the National Air Pollution
Control Administration to report the results of scientific and engineer-
ing studies, and information of general interest in the field of air
pollution. Information reported in this series includes coverage of
NAPCA intramural activities and of cooperative studies conducted in
conjunction with state and local agencies, research institutes, and
industrial organizations. Copies of AP reports may be obtained upon
request, as supplies permit, from the Office of Technical Information
and Publications, National Air Pollution Control Administration, U. S.
Department of Health, Education, and Welfare, 1033 Wade Avenue,
Raleigh, North Carolina 27605.
National Air Pollution Control Administration Publication No. AP-73
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PREFACE
The National Air Pollution Control Administration (NAPCA) has
gathered comprehensive data, summarized in this report, on the emis-
sion of air pollutants in the United States. The data presented are the
estimates of the 1968 nationwide emissions of the five primary air pol-
lutants: carbon monoxide (CO), sulfur oxides (SOx), particulates, hy-
drocarbons (HC), and nitrogen oxides (NOX) • Emission trends from
1966 through 1968 are included as well as motor vehicle emissions pro-
jected to 1990.
Because of the increasing availability of more comprehensive data
and emission factors, revisions will be made in emission quantities in
the future. Consequently, the numbers given in this document are sub-
ject to change.
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LIST OF TABLES
Table Page
1 Estimated Nationwide Emissions, 1968 3
2 Nationwide Carbon Monoxide Emissions, 1968. ... 4
3 Nationwide Emissions of Carbon Monoxide by Year 6
4 Nationwide Emissions of Particulates, 1968 .... 7
5 Participate Emissions from Industrial Processes,
1968 7
6 Nationwide Emissions of Particulates by Year .... 9
7 Nationwide Sulfur Oxides Emissions, 1968 10
8 Nationwide Emissions of Sulfur Oxides by Year . . 11
9 Nationwide Hydrocarbon Emissions, 1968 13
10 Nationwide Emissions of Hydrocarbons by Year ... 14
11 Nationwide Nitrogen Oxides Emissions, 1968 ... 15
12 Nationwide Emissions of Nitrogen Oxides by Year . 16
13 Emissions from Fuel Combustion by Stationary
Sources, 1966 through 1968 17
14 Vehicle Travel in United States, 1968 24
15 Fuel Consumption by Stationary Sources, 1968 ... 27
16 Fuel Consumption by Stationary Sources, 1966 . . 28
17 Industrial Process Production, 1968 30
18 Solid Waste Disposal, 1966 and 1968 31
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LIST OF FIGURES
Figure
1 Carbon Monoxide Emission Estimates Based on
Present Legislative Standards 20
2 Hydrocarbon Emission Estimates Based on Present
Legislative Standards . 20
3 Nitrogen Oxides Emission Estimates Based on Pre-
sent Legislative Standards 20
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CONTENTS
Page
INTRODUCTION 1
NATIONWIDE EMISSIONS 3
Carbon Monoxide 3
Participates 5
Sulfur Oxides 9
Hydrocarbons 12
Nitrogen Oxide.s 14
FUEL EMISSIONS FROM STATIONARY SOURCES 17
PROJECTIONS OF MOTOR VEHICLE EMISSIONS 19
METHODOLOGY 23
Motor Vehicles 23
Aircraft 24
Railroads 24
Vessels 25
Non-Highway Use of Motor Fuels 25
FUEL COMBUSTION IN STATIONARY SOURCES 27
Coal 27
Fuel Oil 27
Natural Gas 28
Wood 28
INDUSTRIAL PROCESSES 29
SOLID WASTE DISPOSAL 31
MISCELLANEOUS SOURCES 33
Forest Fires 33
Structural Fires 33
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Coal Refuse Burning. ... .... . 33
Organic Solvent Evaporation . 33
Gasoline Marketing . . . 34
Agricultural Burning 34
REFERENCES. . ... 35
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NATIONWIDE INVENTORY OF AIR
POLLUTANT EMISSIONS, 1968
INTRODUCTION
This report summarizes the estimates for 1968 of nationwide
emissions of the five primary air pollutants, with information on nation-
wide emissions given by source category and location (urban and non-
urban). Information on emission trends from 1966 to 1968 is included
as •well as projections of motor vehicle emissions to the year 1990 for
HC, CO, and NOX- Presented also are the methodology and basic data
used to make the emission estimates, such as fuel usage, vehicle miles
of travel, and solid waste disposal methods. A more detailed presen-
tation of nationwide emission estimates, together with a description of
estimating techniques, is included in the data file that serves as NAPCA's
reference source with respect to nationwide emission estimates.
The nationwide estimates in this document are for the year 1968.
More recent estimates are difficult to develop since many of the basic
data are not available for a more current year. Data for 1968 should,
however, provide the basis for an adequate estimate of present condi-
tions .
The accuracy of the estimates given for the pollutants varies. De-
tailed studies have been completed for three of the five primary pollu-
tants: CO, SOX, and NOX. Estimates for these pollutants should be
accurate. For the others, estimates maybe inaccurate because of the
lack of emission factors and basic source information. In addition, in-
formation on the extent and degree of control exercised over particulate
emissions in several categories is not yet adequate.
For the purposes of presenting and comparing nationwide emis-
sions, 1966 was picked as the base year so that deviations in emissions
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from one year to another are compared to those occurring in 1966.
Two basic differences can occur in emission rates from year to
year. The first is an actual change based on increases (or decreases)
in fuel usage, industrial production, population, vehicular travel, or
refuse disposal rates. The second type, an apparent change, consists
of actual changes combined •with changes in emission factors or the in-
clusion of new sources. Thus a source category may appear to show a
decrease in emissions when actually the emissions are the same and
only the emission factor used to convert the basic data into emission
data was revised. Or, a category's emission rate can jump drastically
because of the inclusion of a source that was not previously considered.
Refinements in estimating techniques, development of new emis-
sion factors, actual changes in pollutant emissions, and the introduction
and improvement of controls will necessitate frequent revisions of pol-
lutant estimates. Present plans call for updating the reference data
annually.
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NATIONWIDE EMISSIONS
Nationwide emission estimates for the year 1968 are presented
in Table 1. The totals are for the most part higher than previous NAPCA
estimates, primarily because of the inclusion of sources not previously
considered. For example, emission estimates have been included for
forest fires, burning of coal refuse banks, and an increased number of
industrial process sources. The numbers presented here should be re-
presentative of current emissions.
Table 1. ESTIMATED NATIONWIDE EMISSIONS, 1968
(Ifl6 tons/year)
Source
Transportation
Fuel combustion in
stationary sources
Industrial processes
Solid waste disposal
Miscellaneous
Total
CO
63.8
1.9
9.7
7.8
16.9
100.1
Particulates
1.2
8.9
7.5
1.1
9.6
28.3
S0xa
0.8
24.4
7.3
0.1
0.6
33.2
HC
16.6
0.7
4.6
1.6
8.5
32.0
N0xb
8.1
10.0
0.2
0.6
1.7
20.6
aSOx expressed as SOg throughout this summary.
bNOx expressed as NOg throughout this summary.
CARBON MONOXIDE
In 1968, approximately 100 million tons of carbon monoxide (Table
2) was emitted in the United States. The amount will be lower in 1970,
largely because the use of controls on vehicle exhausts will counteract
any increases in emissions of CO from other sources.
Gasoline-powered motor vehicles are the largest single emitters
of CO and account for 59 million tons per year, or 59 percent of the
total. The next largest source category includes forest fires, structural
fires, agricultural burning, and the burning of coal refuse banks, which
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collectively emit about 17 million tons per year. (This is an extremely
rough approximation.) Industrial sources emit almost 10 million tons
of CO, a large majority of it from foundries, petroleum refineries,
sintering, and kraft paper mills. Solid waste disposal, stationary fuel
combustion, and transportation sources other than automobiles account
for the remaining 14 million tons.
Table 2. NATIONWIDE CARBON MONOXIDE EMISSIONS, 1968
Source
Transportation
Motor vehicles
Gasoline
Diesel
Aircraft
Railroads
Vessels
Non-highway use of motor fuels
Fuel combustion in stationary
sources
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Forest fires
Structural fires
Coal refuse burning
Agricultural burning
Total
Emissions,
106 tons/yr
63.8
59. 2
59.0
0.2
2.4
0.1
0.3
1.8
1.9
0.8
0.1
Na
1.0
9.7
7.8
16.9
7.2
0.2
1.2
8.3
100.1
Percent
of total
63.8
59.2
59.0
0.2
2.4
0.1
0.3
1.8
1.9
0.8
0.1
N
1.0
9.6
7.8
16.9
7.2
0.2
1.2
8.3
100.0
aN = Negligible.
The estimated 60 million tons (60 percent of the national total)
emitted iri urban areas is largely from motor vehicle exhaust. Even
though vehicular travel is evenly divided between urban and rural areas,
traffic in urban areas, where slower driving speeds prevail, accounts for
70 percent of total motor vehicle emissions of CO. In addition, essen-
tially all of the aircraft emissions (at altitudes below 3, 000 feet), indus-
trial emissions, and the majority of emissions from fuel combustion
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and refuse disposal occur in urban areas.
In 1966, 101. 6 million tons of carbon monoxide was emitted in the
United States. Emissions decreased to 100. 1 million tons in 1968 as a
result of the following changes in source categories:
1. A 1. 4-million-ton actual decrease in motor vehicle
emissions due to Federal emission exhaust standards.
2. A 1. 0-million-ton overall decrease in industrial process
emissions. This was due to changes in emission factors
for pulp and paper and increases from other industries
such as grey-iron foundries and oil refineries. This is
an apparent decrease only, since emissions from this
category actually increased. If the new emission factors
are applied to the 1966 data, the actual change from 1966
to 1968 was an increase of 0. 9 million tons.
3. A 0. 2-million-ton actual increase in emissions from
solid waste disposal.
4. A 0. 7-million-ton actual increase from uncontrolled
transportation sources such as aircraft, diesel-powered
motor vehicles, and the off-highway use of motor fuels.
Table 3 shows changes in CO emission rates by source category
for the years 1966 through 1968. An apparent decrease in emissions oc-
curred in the industrial process category, as shown in the table, al-
though the actual rate increased. This was due to changes made in
emission factors used for the 1967 estimates.
PARTICULATES
The accurate estimation of nationwide particulate pollution is
extremely difficult because many particulate emissions, unlike gaseous
emissions, are under some sort of control. The extent and efficiency
of these controls have not been evaluated nationally. In addition,
emissions from many activities have not been quantified. The follow-
ing estimates should be viewed with these limitations in mind.
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Table 3. NATIONWIDE EMISSIONS OF CARBON MONOXIDE BY YEAR
(106 tons)
Source
Transportation
Motor vehicles
Other
Fuel combustion
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Man-made
Forest fires
Total
1966
64.5
60-6
3.9
1.9
0.9
N
N
1.0
10.7
7.6
16.9
9.7
7.2
101.6
1967
65.0
61.2
3.8
1.9
0.9
N
N
1.0
9.5
7.8
16.9
9.7
7.2
101.1
1968
63.8
59.2
4.6
1.9
0.8
0.1
N
1.0
9.7
7.8
16.9
9.7
7.2
100.1
Change from
1966 to 1968
-0.7
-1.4
+0.7
Na
-0.1
+0.1
N
N
-1.0b
+0.2
N
N
N
-1.5
aN = Negligible.
''Apparent change.
A rough estimate places the national emissions of participates at
about 28. 3 million tons for 1968 (Table 4). Besides the 6. 7 million tons
attributed to forest fires, Zl. 6 million tons was emitted by combustion,
transportation, and industrial process sources.
Total emissions from fuel combustion in stationary sources are
estimated to have been over 8. 9 million tons for 1968. Power plants
and industries emitted 5. 6 million tons and Z. 6 million tons, respective-
ly. The burning of coal accounted for 9Z percent, or 8. Z million tons,
of fuel combustion emissions.
Although complete data are not available, industrial process
sources are estimated to have accounted for the emission of 7.5 million
tons of particulates. (Table 5 presents a detailed breakdown of particulate
emissions from industrial processes. ) Iron and steel mill complexes
comprised the largest source in this category, collectively generating
some 1. 9 million tons of particulate matter annually. The sand, stone,
and rock industries and cement plants, the next largest sources, each
emitted 870 thousand tons.
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Table 4. NATIONWIDE EMISSIONS OF PARTICULATES, 1968
Source
Transportation
Motor vehicles
Gasoline
Diesel
Aircraft
Railroads
Vessels
Non-highway use of motor fuels
Fuel combustion in stationary
sources
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Forest fires
Structural fires
Coal refuse burning
Agricultural burning
Total
Emissions, 106 tons/yr
1.2
0.8
0.5
0.3
Na
0.2
0.1
0.1
8.9
8.2
0.3
0.2
0.2
7.5
1.1
9.6
6.7
0.1
0.4
2.4
28.3
Percent of total
4.3
2.8
1.8
1.0
N
0.7
0.4
0.4
31.4
29.0
1.0
0.7
0.7
26.5
3.9
33.9
23.7
0.4
1.4
8.4
100.0
aN = Negligible.
Table 5. PARTICULATE EMISSIONS FROM
INDUSTRIAL PROCESSES, 1968
(tons/year)
Industry
Iron and steel
Other primary metals
Grey-iron foundries
Other secondary metals
Cement
Stone, sand, rock, etc.
Coal cleaning
Phosphate rock
Lime
Asphalt batching
Other mineral products
Oil refineries
Other chemical industries
Grain handling and storage
Pulp and paper
.Flour and feed milling
Other
Emissions
1,910,000
40,000
170,000
50,000
870,000
870,000
185,000
205,000
450,000
540,000
180,000
100,000
90,000
800,000
720,000
320,000
30.000
Transportation and solid waste disposal accounted for the remain-
ing 2. 3 million tons.
Estimates of particulate emissions in highly industrialized urban
areas range from 200, 000 to 600, 000 tons per year.
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Among these areas are Chicago (600, 000 tons), Pittsburgh (400, 000
tons), and Philadelphia (200, 000 tons). On the other hand, several
heavily populated metropolitan areas, such as Los Angeles (177, 000
tons), Washington (35, 000 tons), and Denver (33, 000 tons), have lower
particulate emission rates due to the absence of heavy industry and the
lack of coal combustion.
In cities with high particulate emissions, coal combustion and
industrial processes are the primary sources. In Pittsburgh, for
example, 73 percent of particulate emissions was attributable to coal
combustion and 24 percent to industrial processes. In Chicago, 47 per-
cent came from coal combustion and 46 percent from industrial pro-
cesses.
In cities "where emission surveys were recently conducted, near-
ly every coal-fired power plant was equipped with some sort of control
device. This is essentially true also of the larger industrial process
sources, such as cement plants and iron and steel mills. In contrast,
the multitude of smaller sources, such as foundries, concrete batching
plants, and grain storage and handling facilities, are for the most part
uncontrolled.
From 1966 to 1968, the nationwide emission of particulate pol-
lutants dropped about 300,000 tons, from 28.6 to 28.3 million
tons. The changes, summarized in Table 6, that affected these rates
are:
1. An increase in power plant use of coal but a counteract-
ing increase in collection efficiency of control equipment.
(New control equipment and phasing out of old boilers. )
2. A decrease in amount of coal burned by industry and other
sources (residential, commercial, and institutional) for
heat and power.
3. A decrease in emissions from transportation sources
other than motor vehicles, especially railroads and ves-
sels.
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4. An increase in emissions from solid waste disposal
practices.
5. A decrease in industrial process emissions. This is an
apparent decrease only, since the differences are due to
changes in emission factors and basic data.
Table 6. NATIONWIDE EMISSIONS OF PARTICULATES BY YEAR
(106 tons)
Source
Transportation
Motor vehicles
Other
Fuel combustion
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Man-made
Forest fires
Total
1966
1.2
0-7
0.5
9.2
8.5
0-3
0-1
0.3
7.6
1.0
9.6
2.9
6.7
28.6
1967
1.1
0.7
0.4
8.9
8.2
0.3
0.2
0.2
7.3
1.1
9.6
2.9
6.7
28.0
1968
1.2
0.8
0.4
8.9
8.2
0.3
0.2
0.2
7.5
1.1
9.6
2.9
6.7
28.3
Change from
1966 to 1968
Na
+0.1
-0.1
-0.3
-0.3
N
+0.1
-0.1
-O.lb
+0.1
N
N
N
-0.3
aN = Negligible.
^Apparent change.
SULFUR OXIDES
In 1968, approximately 33.2 million tons of sulfur oxides, pri-
marily SO2) was emitted in the United States (Table 7). More than 24
million tons, or 74 percent of the national total, was produced by the
burning of fuels. Coal combustion accounted for 20. 1 million tons and
fuel oil combustion for about 4. 3 million tons. Power plants, of which
there are approximately 940 in the country, emitted 16. 8 million tons
of sulfur oxides, and industrial plants emitted 5. 1 million tons. The
remaining 2. 5 million tons was discharged by the space heating of
homes and businesses.
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Table 7. NATIONWIDE SULFUR OXIDES EMISSIONS, 1968
Source
Transportation
Motor vehicles
Gasoline
Diesel
Aircraft
Railroads
Vessels
Non-highway use of motor fuels
Fuel combustion in stationary
sources
Coal
Distillate fuel oil
Residual fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Forest fires
Coal refuse
Total
Emissions, 106 tons/yr
0.8
0.3
0.2
0.1
Na
0.1
0.3
0.1
24.4
20.1
0.4
3.9
N
N
7.3
0.1
0.6
N
0.6
33.2
Percent of total
2.4
0.9
0.6
0.3
N
0.3
0.9
0.3
73.5
60.5
1.2
11.8
N
N
22.0
0.3
1.8
N
1.8
100.0
&N = Negligible.
Industrial processes added an additional 7. 3 million tons annually
to the nationwide emissions. Four industries collectively contributed
most of this total: petroleum refineries (2. 1 million tons), smelters
(3. 9 million tons), sulfuric acid manufacturing plants (0. 6 million tons),
and coking operations (0. 6 million tons).
The remaining 1. 5 million tons of sulfur oxides "was emitted by
the combustion of coal refuse banks (0.6 million tons), the combustion
of fuels for transportation (0. 8 million tons), and the disposal of solid
wastes (0. 1 million tons).
The majority of sulfur oxides emissions are concentrated in
specific regions of the country. The seven industrial northeastern
states, in which coal and residual fuel oil are important sources of
heat and power, accounted for 16 million tons, or almost 50 percent
of the national total. The only other states with estimated emissions
of more than 1 million tons per year were Arizona and Texas. In these
1C
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two states, the primary sources are smelters and refineries, which
collectively contributed in excess of 80 percent of each state's total.
From 1966 to 1968, emissions of sulfur oxides increased 2.3
million tons, an actual increase resulting from the following changes
(shown in Tables 8 and 13):
1. A 2. 4-million-ton increase from steam electric power
plants due to increased coal and oil consumption.
2. A 0. 5-million-ton decrease from industrial and resi-
dential fuel sources due mainly to decreased coal usage.
3. A 0. 2-million-ton increase in industrial processes, such
as petroleum refining, smelting, and sulfuric acid pro-
duction.
4. A 0. 2-million-ton actual increase in emissions from
automobile and other transportation sources.
5. Increased sulfur content of coal due to exhaustion of
sources of low-sulfur coal.
Table 8. NATIONWIDE EMISSIONS OF SULFUR OXIDES BY YEAR
(106 tons)
Source
Transportation
Motor vehicles
Other
Fuel combustion
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Man-made
Forest fires
Total
1966
0.6
0-2
0.4
22.5
18.7
3.8
Na
N
7.1
0.1
0.6
0.6
N
30-9
1967
0.7
0-3
0.4
23.1
19.1
4.0
N
N
7.2
0.1
0.6
0.6
N
31.7
1968
0.8
0.3
0.5
24.4
20.1
4.3
N
N
7.3
0.1
0.6
0.6
N
33.2
Change from
1966 to 1968
+0.2
+0.1
+0.1
+1.9
+1.4
+0.5
N
N
+0.2
N
N
N
N
+2.3
aN = Negligible.
11
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All changes that occurred in sulfur oxides emissions are actual
changes. The differences in emission rates, then, are due to natural
increases or decreases in fuel consumption, motor vehicle travel,
solid waste disposal, or industrial production.
About two-thirds of the nationwide emission of sulfur oxides oc-
curs within urban areas . Power plants, industries, businesses, and
homes all contribute to emissions in urban areas. Much of the pollution
in rural areas is emitted by a relatively small number of large individ-
ual sources. Individual smelters, many of which are located away from
metropolitan areas, may emit over 100, 000 tons per year. In addition,
almost half of the nation's 940 power plants, including seven of the
eight largest SO2 emitters, are located in rural areas. Annual emis-
sions from these seven range from ZOO, 000 to 300, 000 tons per year.
HYDROCARBONS
In 1968, approximately 32 million tons of hydrocarbons (Table 9)
•was emitted in the United States. Of the sources surveyed, motor
vehicles were the largest single emitters of HC, accounting for 15.6
million tons per year, or 5Z percent of the total. Industrial process
losses were the next largest source, accounting for 4. 6 million tons.
Other sources, such as forest fires, organic solvent evaporation,
fuel combustion in stationary sources, and disposal of solid wastes ac-
counted for the majority of the remaining 11.8 million tons.
An estimated 19 million tons, or 60 percent of the national total,
was emitted in urban areas. Motor vehicles accounted for 7 million
tons of this total. Although vehicular travel will increase rapidly in
the next few years, proposed control measures will significantly re-
duce the HC emissions (see Motor Vehicle Projections). The percent-
age reduction of HC emissions, however, will be greatest in rural
areas because travel speeds, which are in inverse relation to HC
emissions, are higher in rural areas.
12
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Table 9. NATIONWIDE HYDROCARBON EMISSIONS, 1968
Source
Transportation
Motor vehicles
Gasoline
Diesel
Aircraft
Railroads
Vessels
Non-highway use of motor fuels
Fuel combustion in stationary
sources
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Forest fires
Structural fires
Coal refuse burning
Agricultural burning
Organic solvent evaporation
Gasoline marketing
Total
Emissions, 10^ tons/yr
16-6
15.6
15.2
0.4
0.3
0.3
0.1
0.3
0.7
0.2
0.1
Na
0.4
4.6
1.6
8.5
2.2
0.1
0.2
1.7
3.1
1.2
32.0
Percent of total
51.9
48.8
47.5
1.3
0.9
0.9
0.3
1.0
2.2
0.6
0.3
N
1.3
14.4
5.0
26.5
6.9
0.3
0.6
5.3
9.7
3.7
100.0
aN = Negligible.
From 1966 to 1968, there was an increased emission of 0. 5 mil-
lion tons of HC (Table 10). This was due to the following:
1. A 1-million-ton decrease in emissions from transporta-
tion sources. This is an actual decrease effected as the
result of Federal exhaust emissions standards.
Z. A 1. 1-million-ton increase in industrial process
emissions. This large increase was due in part to the
inclusion of new industrial sources since the 1966 emis-
sion estimates were made and in part to natural in-
creases in emissions from existing sources.
3. Natural increases in solid waste disposal emissions,
gasoline marketing and handling, and solvent evaporation.
13
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Table 10. NATIONWIDE EMISSIONS OF HYDROCARBONS BY YEAR
(106 tons)
Source
Transportation
Motor vehicles
Other
Fuel combustion
Coal
Fuel oil
Natural gas
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Man-made
Forest fires
Total
1966
17.6
16.5
1.1
0.7
0.2
0.1
N
0.4
3.5
1.5
8.2
6.0
2.2
31.5
1967
17.3
16.3
1.0
0.7
0.2
0.1
N
0.4
4.3
1.6
8.3
6.1
2.2
32.2
1968
16.6
15.6
1.0
0.7
0.2
0.1
N
0.4
4.6
1.6
8.5
6.3
2.2
32.0
Change from
1966 to 1968
-1.0
-0.9
-0.1
Na
N
N
N
N
+l.lb
+0.1
+0.3
+0-3
N
+0.5
aN = Negligible.
^Apparent change.
NITROGEN OXIDES
In 1963, about 21 million tons of NOX was emitted in the United
States (Table 11). Although basic data are not complete for 1970,
emissions are thought to have increased to 23 million tons, a change
primarily due to an increase of about 4 percent per year in emissions
from motor vehicle exhausts and a slightly lower rate of increase for
stationary combustion source emissions.
Motor vehicles and the burning of coal, oil, and natural gas are
the principal sources of NOX. In 1968, these sources accounted for
over 18 million tons or almost 88 percent of the national total. Of the
10.0 million tons generated by the combustion of fuels, power plants
emitted 4. 0 million tons; industries, 4. 8 million tons; and home and
office heating, the remaining 1.2 million tons. Natural gas, the pri-
mary source, accounted for over 4.4 million tons. An estimated 8
million tons of NOX was emitted by transportation sources, with 7 mil-
lion tons of that coming from motor vehicles. Industrial processes,
solid waste disposal, and other miscellaneous sources accounted for
14
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Table 11. NATIONWIDE NITROGEN OXIDES EMISSIONS, 1968
Source
Transportation
Motor vehicles
Gasoline
Diesel
Aircraft
Railroads
Vessels
Non-highway use of motor fuels
Fuel combustion in stationary
sources
Coal
Fuel oil
Natural gas0
Wood
Industrial processes
Solid waste disposal
Miscellaneous
Forest fires
Structural fires
Coal refuse burning
Agricultural burning
Total
Emissions, 106 tons/yr
8.1
7.2
6.6
0.6
Na
0.4
0.2
0.3
10.0
4.0
1.0
4.8
0.2
0.2
0.6
1.7
1.2
N
0.2
0.3
20.6
Percent of total
39.3
34.9
32.0
2.9
N
1.9
1.0
1.5
48.5
19.4
4.8
23.3
1.0
1.0
2.9
8.3
5.8
N
1.0
1.5
100.0
aN = Negligible.
Includes LPG and kerosene.
Nitrogen oxides and CO, probably more than other pollutants, are
closely related to the distribution of population in the country since
motor vehicles and all fuels-coal, fuel oil, natural gas, kerosene,
and liquefied petroleum gas (LPG)—contribute significantly to total
emissions. It is not surprising, therefore, that over 60 percent of NOX
emissions in the country occur in urban areas. In terms of sources,
45 percent of the NOX emissions from motor vehicles are in urban
areas because, unlike those of CO and HC, they are unaffected by
travel speed. The percentage of vehicular emissions of NOX in urban
areas is relatively low.
Nitrogen oxides increased 3. 9 million tons from 1966 to 1968
(Table 12), largely because of the following changes:
1. A 2. 7-million-ton apparent increase from the burning
15
-------
of natural gas. Most of this increase was due to the in-
clusion in the estimates of new sources such as gas
transmission and gas pipelines.
2. A 0. 5-million-ton actual increase in emissions from
utilities, mainly from increased coal combustion.
3. A 0. 5-million-ton increase in emissions from motor
vehicles resulting from increased vehicular activity and
an increased emission factor because of exhaust emis-
sion controls. This is an actual increase.
Table 12. NATIONWIDE EMISSIONS OF NITROGEN OXIDES BY YEAR
(106 tons)
Source
Transportation
Motor vehicles
Other
Fuel combustion
Coal
Fuel oil
Natural gas
Wood
LPG and kerosene
Industrial processes
Solid waste disposal
Miscellaneous
Man-made
Forest fires
Total
1966
7.6
6.6
1.0
6.7
4.0
0.9
1.6
0.2
0.2
0.5
1.7
0.5
1.2
16.7
1967
7.6
6.7
0.9
9.5
3.8
1-0
4.2
0.2
0.3
0.2
0.6
1.7
0-5
1.2
19.6
1968
8.1
7.2
0.9
10.0
4.0
1.0
4.5
0.2
0.3
0.2
0.6
1.7
0-5
1.2
20.6
Change from 1966 to 1968
+0.5
+0.5
Na
+3.3
N
+0.1
+2.9b
N
+0.3b
N
+0.1
N
N
N
+3.9
aN = Negligible.
bApparent change.
16
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FUEL EMISSIONS FROM STATIONARY SOURCES
Table 13 presents nationwide emissions from fuel combustion in
stationary sources from 1966 through 1968.
Table 13. EMISSIONS FROM FUEL COMBUSTION BY STATIONARY
SOURCES, 1966 THROUGH 1968
(1()6 tons/year)
Source
1966
Utilities
Industrial
Residential-commercial
Total
1967
Utilities
Industrial
Residential-commercial
Total
1968
Utilities
Industrial
Residential-commercial
Total
Particulates
5.6
3.0
0.6
9.2
5.6
2.7
0.6
8.9
5.6
2.7
0.6
8.9
SOX
14.4
5.5
2.6
22.5
15.4
5.1
2-6
23.1
16.8
5.1
2.5
24.4
NOX
3.5
2.4
0.8
6.7
3.6
5.0
0.9
9.5
4.0
5.1
0.9
10.0
Particulate emissions from, steam-electric utilities have remained
about constant during this time period. This is due to the increased
efficiency of control equipment and the phasing out of older boilers.
Emissions from industrial sources have declined because of a decrease
in coal usage.
On the other hand, SOX emissions from utilities have increased
over 16 percent because of increased coal consumption compounded by
higher coal sulfur content.
Nitrogen oxides emissions show a large jump from 1966 to 1968.
This is due, however, to the inclusion of new sources such as natural
gas transmission and natural gas pipelines, as well as the inclusion of
other fuels, such as LPG and kerosene, and is, then, an apparent
increase.
17
-------
PROJECTIONS OF MOTOR VEHICLE EMISSIONS
The graphs given here present the automotive emissions of CO,
HC, and NOX projected to the year 1990 and are based on emission
regulations presently in force and those forthcoming in 1970 and 1971.
Only gasoline-powered vehicles are included in the projections since
they account for more than 95 percent of the vehicular emissions of
these pollutants.
The vehicular travel data used were extracted from projections,
presented in Landsberg's Resources in America's Future, * that were
made by Resources for the Future, a nonprofit research foundation
affiliated with Johns Hopkins University. These projections have been
widely accepted and are frequently used in studies concerned with
natural resources and environmental pollution. Completed in 1963, the
projections are of three separate levels (high, medium, and low) of
expected motor vehicle travel in the United States. Actual data for the
past 5 years reflect a rate of increase in travel close to the medium
projections. Computations, therefore, are based on the expectation
that future increases will continue along these lines. The. projected
emission levels are presented in Figures 1 through 3.
Carbon monoxide emissions are estimated to have reached a peak
during the calendar year 1967. The 1968 enactment of Federal stand-
ards should produce a steady decrease in emissions that will persist
until about 1980, when increases in motor vehicle travel will counter-
act the effects of the controls and an upward trend can again be antici-
pated. It is anticipated that emissions in urban areas, although expected
to follow the same general trend, will increase at a somewhat faster
rate than total nationwide emissions.
Hydrocarbon emissions display a trend similar to that shown by
CO. The 1963 crankcase control device decelerated the rate of increase
19
-------
60
50
S, 40
20
1960
yJOTAL
......URBAN
Figure 1. Carbon monoxide
emission estimates based on
present legislative standards.
1965
1970
1975
YEAR
1985 1990
Figure 2. Hydrocarbon emis-
sion estimates based on pre-
sent legislative standards.
1960
vTOTAL
......URBAN
1965
1970
1975
YEAR
1980
1985
1990
24
22
20
18
5, 16
1 14
g, 12
1 10
= 8
6,
4
2
0
1960
TOTAU
URBAN...
Figure 3. Nitrogen oxides
emission estimates based on
present legislative standards.
1965
1970
1975 1980
YEAR
1985
1990
20
-------
of emissions even though the magnitude of emissions increased. Peak
emissions occurred in 1967. Subsequent exhaust and evaporation con-
trols will reduce emissions to a minimum in 1983 (5.24 million tons)
before they begin to increase once again.
Because of lack of controls, NOX emissions are estimated to
increase at the same rate as motor vehicular travel. Figure 3 presents
NOX emissions based on no controls. There is an obvious change in
the slope of the curve for the year 1968 because of exhaust emission
controls that increased the NOX emission rate.
21
-------
METHODOLOGY
Basically, the emission estimates for any given year were derived
by multiplying the projected annual vehicle miles of travel (by type and
age of vehicle and driving conditions) by the appropriate emission
factor (grams per vehicle-mile).
Separate travel data were developed for urban and rural driving
for automobiles and light- and heavy-duty trucks. Data on the distri-
bution by age of the vehicles were also developed. By using the above
categories of data, factors such as driving speeds, amount of exhaust,
and the deterioration of control devices—all of which affect the
emission rate from individual vehicles—could also be considered.
Emission factors were developed from cycle data. Conversion
factors developed from road data were used to relate cycle-based
emissions to on-the-road vehicle estimates. Emission factors used in
making these projections reflect the variations that result from type
and age of vehicles, vehicle speed, type of transmission, and control
devices.
MOTOR VEHICLES
Emission estimates from gasoline-powered motor vehicles were
obtained by two basic approaches, both of which were necessary since
complete lists of emission factors were not available for SOX and
particulates as they were for CO, HC, and NOX.
Estimates of CO, HC, and NOX were based upon vehicle-mile
tabulations and emission factors developed from both road and cycle
data. 2 The distribution of vehicle miles by vehicle type and location
is presented in Table 14. The emission factors used account for
variations in emissions due to type, speed, age, transmission, size of
engine, and size of vehicle.
Estimates of SOX and particulate emissions were based on the con-
sumption of 75, 500 million gallons of gasoline. 3 An average particulate
23
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Table 14. VEHICLE TRAVEL IN UNITED STATES, 1968
(109 miles)
Vehicle
Passenger cars
Light-duty trucks
Heavy-duty trucks
Class II
Class III
Class IVa
Gasoline
Diesel
Total
Urban
409.02
32.42
9.06
6.03
11.36
7.80
475.69
Rural
374.56
48.63
13.58
9.06
27.81
19.50
493.14
Total
1968
783.58
81.05
22.64
15.09
39.17
27.30
968.83
1966
744.80
80.63
22.52
14.01
38.97
21.63
922.56
alncludes buses.
emission factor and an average sulfur content of gasoline of 0. 035
percent were applied to the gallonage. The average emission factors
used to obtain estimates in this report are taken from Duprey.
Emissions from diesel-powered motor vehicles were also based
on fuel consumption data because of a lack of road-emission data.
Average factors were applied to the 5, 350 million gallons of diesel fuel
consumed by motor vehicles.
AIRCRAFT
The emissions in this category were determined from the results
of an extensive study just completed for NAPCA. ? Estimates of all
pollutants, except sulfur oxides, •were presented for emissions at
altitudes below 3, 000 feet based on the number of flights made by
different types of aircraft. Sulfur oxides emissions were calculated
on the basis that aircraft fuels contain an average of 0. 055 percent
sulfur and that about 20 percent of the total fuel is consumed at a
altitudes below 3, 000 feet.
RAILROADS
The 1968 fuel consumption by railroads was 3, 530 million gallons
of diesel fuel, ISO million gallons of residual fuel oil, and 100 million
gallons of distillate fuel oil. The average emission factors, except
those for SOX, applicable to diesel fuel combustion were assumed to be
24
-------
applicable also to residual and distillate fuel oils. The average sulfur
content of each fuel was used in estimating SOX emissions.
VESSELS
Ships and vessels consumed 766 million gallons of diesel fuels,
3, 690 million gallons of residual fuel oil, 200 million gallons of gaso-
Q Q
line, and 400 thousand tons of coal. ' ' These figures represent
quantities sold in this country rather than quantities consumed, so that
the fuels actually consumed within the country should be considerably
less. Although emission factors are not available for this category,
average emission factors applicable to other types of combustion were
applied in order to obtain a gross estimate.
NON-HIGHWAY USE OF MOTOR FUELS
The non-highway consumption of motor fuels was 2. 3 billion
gallons of gasoline and 2. 08 billion gallons of diesel fuel. Average
emission factors for gasoline and diesel fuel combustion were used.
Fuel consumption in the aviation and marine categories was excluded
from this section since these sources were included in previous
sections.
-------
FUEL COMBUSTION IN STATIONARY SOURCES
COAL
Approximately 498 million tons of bituminous coal and lignite and
11 million tons of anthracite coal were consumed in the United States
(excluding that consumed by railroads, ships, and vessels).' Con-
sumption by user category is summarized in Table 15. Average
emission factors and the sulfur content of fuels for each category were
used to estimate emissions. It was assumed that 79 percent of the
particulate emissions from electric generating plants and 62 percent
from industrial sources were collected.
Table 15. FUKL CONSUMPTION BY STATIONARY SOURCES, 1968
Source
Electric utilities
Coke plants
Steel and rolling mills
Cement mills
Oil companies, gas
pipelines, and gas
transmission
Other manufacturing
Military
Residential, com-
mercial, institutional,
and light industrial
Total
Coal,
106 tons/yr
297.1
91.3
5.7
9.4
-
82.6
22.9
509.0
Fuel oil, 106 bbl/yr
Residual
185.0
39.3
135.7
35.0
182.7
577.7
Distillate
3.0
9.4
45.8
12.6
523.3
594.1
Total gas,
109 ft3/yr
3,144
-
3,720
7,030
6,525a
20,419
aDoes not include light industrial sources.
FUEL OIL
Approximately 594 million barrels of distillate fuel oil and 577
million barrels of residual fuel oil were consumed by stationary fuel
Q
combustion sources in 1968. Consumption by user category is sum-
27
-------
marized in Table 15. Average emission factors and the sulfur content
of fuels for each category were used to estimate emissions. It was
assumed that there are no SOX controls on fuel oil combustion sources.
NATURAL GAS
Total gas consumption, 99 percent of which consists of natural
gas, exceeded 20.0 trillion cubic feet as shown in Table 15. Average
emission factors and the sulfur content of fuels were used to estimate
emissions.
WOOD
Total wood consumption by user category was not available;
however, the total energy produced by wood combustion was approxi-
mately 780 x 1012 Btu for 1968. u Assuming 9, 000 Btu per pound
of wood, nearly 4. 4 x 10^ tons of wood was consumed. Average
emission factors were used to estimate total emissions.
Table 16 provides the basic data used to calculate the 1966
emission estimates. It is presented here mainly for purposes of com-
parison.
Table 16. FUEL CONSUMPTION BY STATIONARY SOURCES, 1966
Source
Electric utilities
Coke plants
Steel and rolling mills
Cement mills
Oil companies
Other manufacturing
Military
Residential, com-
mercial, institutional,
and light industrial
Total
Coal,
106 tons/yr
266.4
96.4
8.0
9.3
91.0
25.6
497.0
Fuel oil, 106 bbl/yr
Residual
140.7
35.2
141.1
41.9
177.8
536.7
Distillate
3.6
10.5
47.1
16.3
490.7
568.2
Total gas.
109 ft3/yr
2,610
6,630
5,760a
15,000
aDoes not include light industrial sources.
23
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INDUSTRIAL PROCESSES
Certain industrial processes generate and emit varying quantities
of pollutants into the air in addition to those produced by fuel combus-
tion. The lack of published national data on production, type of equip-
ment, and controls, as well as emission factors, makes it impossible
to include estimates of emissions from all industrial process sources.
This type of data is especially lacking with respect to hydrocarbons
because the multitude of emission sources and the lack of data combine
to prohibit the estimation of emissions from all but a few sources.
Table 17 summarizes the annual production of the various indus-
trial processes surveyed. Also indicated are the sources for which
emission-estimates were made and those sources that are probably
significant but for which no quantitative estimates could be made. In
all cases, average emission factors were applied to total production
numbers, when they were available, to obtain emissions. Various
degrees of control were assumed.
29
-------
U)
o
Table 17. INDUSTRIAL PROCESS PRODUCTION, 1968
Source
Iron and steel mills
Coke manufacture
Grey-iron foundries
Aluminum primary
Copper primary
Lead primary
Zinc primary
Miscellaneous secondary metals
Petroleum refineries
Cement
Acid manufacture
Phosphoric
Nitric
Sulfuric
Hydrochloric
Mineral industries
Explosives
Petrochemicals
Cotton
Pulp mills, Kraft and neutral
sulfite semichemieal (NSSC)
Grain handling
Grain milling
Production,
10^ tons (except as noted)12
134,000
65,000
22,000
3,255
1,440
467
1,100
2,300
3,700 x 106 bbl
403,000 x 103 bbl
4,500
6,100
28,400
1,700
2,650,000
-
-
11 x 106 bales
28,100
530,000
160,000
CO
ua
e
e
u
e
e
Particulates
eb
e
e
e
e
e
e
e
e
e
e
e
a
e
u
e
e
e
e
SOX
e
e
e
e
e
e
HC
e
e
e
NOX
e
e
e
u
_
au = Emissions probably large but not estimated.
be = Emissions estimated.
-------
SOLID WASTE DISPOSAL
A study on solid waste collection and disposal practices has
recently been completed by the Bureau of Solid Waste Management of
the U.S. Department of Health, Education, and Welfare. 13 Results
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 estimated
that a conservative estimate of the total generation rate is 10 pounds
per capita per day.
The results of this survey and the various assumptions necessary
have been compiled to show the estimated distribution of solid waste
disposal practices in Table 18. Average emission factors were applied
to these totals to obtain estimates of total emissions from the disposal
of solid wastes.
Table 18. SOLID WASTE DISPOSAL, 1966 AND 1968
Disposal method
Municipal incineration
On-site incineration
Sanitary landfills
Open dumps
Burned
Non-burned
Wigwam burners
Hog feeding
Composting, treatment plants, etc.
Total
Waste, 10^ tons/yr
1966
16
57
10
227
77
151
27
1
19
358
1968
19
55
29
218
82
136
27
1
18
367
31
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MISCELLANEOUS SOURCES
FOREST FIRES
The United States Forest Service has provided information on the
number of wild fires and the amount of controlled burning that occur
in the United States. These data indicate that about 4. 57 million
acres (representing 145. 6 million tons of combustible materials) of
uncontrolled fires and 3. 52 million acres (representing 76. 4 million
tons of combustible materials) of controlled fires occurred in 1966.
Average emission factors were applied to these totals.
STRUCTURAL FIRES
Approximately one million buildings were attacked by fires in the
United States. By using various assumptions, the amount of combusti-
bles and average emission factors were estimated and a rough approx-
imation of emissions was obtained.
COAL REFUSE BURNING
It is estimated that 19 billion cubic feet of burning coal refuse
piles existed in the United States in 1964. By using assumed densities
and average lives for coal piles, a rough estimate of emissions was
obtained.
ORGANIC SOLVENT EVAPORATION
Insufficient national data were available to permit the estimation
of hydrocarbon emissions from organic solvent evaporation. A rough
estimate of nationwide emissions was made from the extrapolation, on
a national scale, of data gathered in four metropolitan areas: Los
Angeles, San Francisco, St. Louis, and Washington, D. C. Due to the
nature of these urban areas, the nationwide totals arrived at may be
high One-third of the total HC emissions is attributed to evaporation
from the solvents handled by the paint and varnish industry, for which
estimates of gallonage and resultant emissions were available.
33
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GASOLINE MARKETING
The evaporation of motor fuels during the filling of tank trucks,
service station tanks, and automobile tanks is included in this section.
Other sources are the evaporation of gasoline from storage tanks at
refineries and bulk terminals and evaporation during the operation of
motor vehicles. These emissions were included in the petroleum
refinery and motor vehicle sections. Average evaporation factors
•were applied to the amount of gasoline and diesel fuel consumed in
order to estimate HC emissions from gasoline marketing.
AGRICULTURAL BURNING
Nearly 280 million tons of agricultural refuse is burned annually
in the United States. This includes crop residues, scrub, brush,
weeds, grass, and other vegetation.
34
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REFERENCES
1. Landsberg, H. , L. L. Fischman, and J. L. Fisher. Resources
in America's Future. Baltimore, Johns Hopkins Univ. Press,
1963. 1017 p.
2. Goodman, K. , J. Kurtzweg, and N. Cernansky. Determination
of Air Pollutant Emissions from Gasoline-Powered Motor Vehicles,
U.S. DHEW, PHS, EHS, National Air Pollution Control Adminis-
tration. Raleigh, N. C. (In Press).
3. Automobile Facts and Figures/1968. Automobile Manufacturers
Association. Washington, D. C. 1969.
4. Motor Gasolines, Winter 1968-69. Petroleum Products Survey
No. 60. U.S. Dept. of Interior, Bureau of Mines. Washington,
D. C. July 1969.
5. Duprey, R. L. Compilation of Air Pollutant Emission Factors.
U.S. DHEW, PHS, EHS, National Air Pollution Control Adminis-
tration. Raleigh, N. C. PHS Publication No. 999-AP-42. 1968.
67 p.
6. Motor Truck Facts/1968. Automobile Manufacturers Association.
Washington, D. C. 1969.
7. Nature and Control of Aircraft Engine Exhaust Emissions. NAPCA
Contract No. PH22-68-27. Northern Research and Engineering
Corp. , Cambridge, Mass. 1969.
8. Shipments of Fuel Oil. Mineral Industry Surveys. U.S. Dept. of
Interior, Bureau of Mines. Washington, D. C. September 1969.
9. Coal: Bituminous and Lignite — 1968. Mineral Industry Surveys.
U.S. Dept. of Interior, Bureau of Mines. Washington, D. C.
February 1970.
35
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10. Natural Gas Production and Consumption— 1968. Mineral Industry
Surveys. U.S. Dept. of Interior, Bureau of Mines. Washington,
D. C. August 1969.
11. Schurr, S. and B. C. Netschert. Energy in the American Econo-
my 1850-1975. Baltimore, Johns Hopkins Univ. Press, 1960.
pp. 36-42.
12. 1969 Minerals Yearbook. U.S. Dept. of Interior, Bureau of
Mines. Washington, D. C. 1969.
13. 1968 National Survey of Community Solid Waste Practices. Air
Interim Report. U.S. DHEW, Public Health Service. Cincinnati,
Ohio. PHS Publication No. 1867. 1968.
36
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