EPA-600/2-74-002
March 1974
Environmental Protection Technology Series
Control of Environmental Impacts
from Advanced Energy Sources
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Office of Research and Development
U.S. Environmental Protection Agency
Washington, O.C. 20460
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RESEARCH REPORTING SERIES
Rcaearch reports of the Office of Research and Development,
Environmental Protection Agency, have been grouped into five
scrion. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximuia interface
in related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVI RONWEWTAL PROTECTION
TECHNOLOGY series. This series describee research performed
to develop and demonstrate instrumentation, equipment and
methodology to repair or prevent environmental degradation
from point and non-point sources of pollution. This work
provides the new or improved technology required for the
control and treatment of pollution sources to meet environmental
quality standards.
This report has been reviewed by the Office of Research and
Development. Approval does not signify that the contents
necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
For»l»bytb«ggp«fai««p4«m»fP<*mn«pti, O-«. OoytmaMot Prtotfa* Offlc*
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EPA-600/2-7^-002
March 1971*
CONTROL OF ENVIRONMENTAL IMPACTS
FROM ADVANCED EHERGY SOURCES
By
Evan E. Hughes
Edvard M. Dickson
Richard A. Schmidt
Contract Ho. 68-01-OU83
Program Element 1AB013
Roap/Task PEMP 22
Project Officer
James C. Johnson
Air Technology Branch
U.S. Environmental Protection Agency
Washington, DC 20U60
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, DC 20U60
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ABSTRACT
The technology and the environmental effects associated with the
production of energy from some new or advanced sources are reviewed.
These include solar, geothermal, oil shale, solid wastes, underground
coal gasification, and hydrogen energy sources. Projections to the
year 2000 of the levels of energy production from the first four of these
sources are presented. Environmental impacts on air quality, water
quality, and land uses are derived per unit of energy produced. Levels
of pollutant emissions and other environmental effects of the development
of these advanced energy sources are projected. Impacts likely to require
control measures are identified. Subjects for research and development
directed toward control of environmental impacts are recommended. These
recommendations are incorporated into a research and development plan.
Approximate priority assignments derived from consideration of the timing
of development and the importance and degree of definition of the identified
environmental effects are given.
This report was submitted in fulfillment of Contract 68-01-0483
by Stanford Research Institute under sponsorship of the Environmental
Protection Agency. Work was completed as of March 1974.
ii
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CONTENTS
ABSTRACT . . ii
LIST OF FIGURES vii
LIST OF TABLES viii
UNITS OF MEASURE x
ACKNOWLEDGMENTS xiii
I CONCLUSIONS 1
II RECOMMENDATIONS 3
III INTRODUCTION: FRAMEWORK FOR ANALYSIS 4
A. Background 4
B. Selection of Energy Sources 7
C. Analysis of Each Energy System 8
1. State of the Art 8
2. Resulting Environmental Impacts 9
3. Relative Significance of the Impacts 9
4. General Implications for EPA 10
5. Specific Research and Development Needs 10
D. Formulation of a Research and Development Plan .... 10
1. Identification of Research and Development
Needs 11
2.- Priorities 11
3. Approach to Research and Development Planning . . 12
IV SUMMARIES OF ADVANCED ENERGY SOURCES 13
A. Overview of the Advanced Energy Sources 13
B. Solar Energy Summary 15
iii
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IV SUMMARIES OF ADVANCED ENERGY SOURCES (Continued)
c.
D.
E.
F.
G.
H.
1. Environmental Consequences
2. Recommendations
Geothermal Energy
Energy from Oil Shale
1. State of the Art
3. Recommendations
1. State of the Art
Application of Control Technology
1. Nature of the Problem
2. Preliminary Assessment of Existing Emission
Control Technology
3. Elements of a Research Program for Assessment
of Control Technology
16
20
20
29
29
32
40
40
46
47
47
48
49
50
53
62
GENERAL RECOMMENDATIONS FOR CONTROLLING ENVIRONMENTAL
IMPACTS FROM ADVANCED ENERGY SOURCES
A.
B.
C.
D.
E.
F.
Support for Improved Technology
Support for Demonstration of Economic Viability ....
Use of Standards at Various Stages of New Technology. .
2. Early Commercial Operation
3. Significant Scale Operation
Strategy for Dealing with Indirect Impacts
Energy Efficacy as an Indicator of Environmental
Impact
1. The Concept
2. Environmental Implications
3. Implications for EPA Activities
69
69
70
71
72
73
73
74
75
76
76
84
85
iv
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VI RECOMMENDATIONS FOR ADVANCED RESEARCH
AND DEVELOPMENT PLANNING 86
A. A Listing of Control Requirements 86
1. Solar Energy 86
2. Geotherraal Energy 87
3. Oil Shale 87
4. Energy from Solid Wastes 88
5. Underground Coal Gasification 88
6. Hydrogen as an Energy Carrier 89
B. Subjects for Research and Development 89
1. Solar Energy: Continuous Review of Solar
Energy Development 89
2. Geothermal Energy 90
3. Oil Shale 91
4. Energy from Solid Wastes 92
5. Underground Coal Gasification 93
6. Hydrogen as an Energy Carrier: Periodic Review
of the Technology 94
C. Classification of the Recommendations 94
1. Formulation of Performance Standards
or Guidelines 95
2. Development of the Technology to Control
Certain Emissions and Effluents 96
3. Development of New Energy Technology Having
Apparent Environmental Advantages 96
4. Further Analysis of Effects on Air
and Water Quality 97
5. Further Analysis of General Environmental Effects
of Advanced Energy Technologies 98
6. Matrix Summary of the Ordering by Type and Media . 98
D. Assignment of Priorities 100
REFERENCES 104
APPENDICES
A SOLAR ENERGY 107
B GEOTHERMAL ENERGY 167
C ENERGY FROM OIL SHALE 213
D ENERGY FROM SOLID WASTES 245
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APPENDICES (Continued)
E. UNDERGROUND COAL GASIFICATION 289
F. HYDROGEN AS AN ENERGY CARRIER 313
BIBLIOGRAPHIC DATA SHEET
vi
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FIGURES
1 Projected Growth of Geothermal Electricity 21
2 Oil Shale Utilization—Processes, Environmental
Effects, and State of Knowledge 31
3 Energy System 77
vii
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TABLES
1 Advanced Energy Sources Studied 8
2 Summary of Total Projected Annual Energy Production
Levels from Advanced Sources .' 14
3 Solar Energy: Estimated Annual Energy Production 17
4 Air Pollutant Emissions: Materials for Production
of Thermal Solar Energy Collectors for Buildings*
Materials, and Activities Displaced, 1985 19
5 Projected Environmental Impacts of Geothermal Energy 24
6 Emission Factors for Geothermal Plants Compared
with Emission Standards for Fossil Fuel Power Plants 27
7 Projected Annual Fuel Production from Oil Shale Development . . 30
8 Projected Annual Water Requirements - Oil Shale 34
9 Projected Annual Land Requirements - Oil Shale 35
10 Projected Annual Water Quality Effects from Surface
Disposal of Processed Oil Shale 36
11 Projected Annual Gaseous Emissions - Oil Shale 38
12 Projected Annual Particulate Emissions - Oil Shale 39
13 Projected Environmental Impacts of Energy
from Solid Wastes 43
14 Emission Factors for Energy from Solid Waste Compared
with Fossil Fuel Emission Standards 45
15 Emission and Control of Hydrogen Sulfide in Geothermal
Energy Production 56
16 Emissions and Controls for Air Pollutants from Oil
Shale Production 58
17 Emissions and Controls for Air Pollutants from Processes
Producing Energy from Solid Wastes 63
18 Energy Input/Output Submatrix of the U.S. Economy 80
viii
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19 Energy Efficacy Coefficient for Conventional
Technological Systems 80
20 Abbreviated List of Important Uses of Energy and Energy
Intensive Materials in Conventional Energy Technology
Systems 82
21 Estimated Upper Limits to the Energy Efficacy Coefficient
for Solar Energy Technologies 83
22 Classification Matrix for Research and Development
Recommendations 99
23 Priorities of Research and Development Recommendations . . . 103
ix
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UNITS OF MEASURE
Conversion of U.S. units of measure to the metric system is now
proceeding rapidly. Several agencies of state and federal governments
now call for the use of metric units (e.g., the geothermal group of the
California Division of Oil and Gas). The Environmental Protection Agency
has required the use of metric units in this report.
SRI has, therefore, employed the International System of Units (SI),
which is based upon the meter, kilogram, and second as the basic measures
of length, mass, and time. Within this system, energy units are derived
combinations of the basic units. The preferred unit for energy is the
joule. However, the kilowatt hour, a hybrid unit, is more widely under-
stood at this time and has been used frequently in this report, sometimes
outside the context of electric power. (Among those seeking to institute
global uniformity in the use of units, the kilowatt hour is considered to
be less acceptable than the joule, and the use of the kilowatt hour may
ultimately be discarded).
During the period of changeover to metric units, a certain amount of
confusion must be expected—especially since energy is measured in such
various units as kilocalories, barrels of oil equivalent, kilowatt hours,
therms, and so on. To minimize this confusion, SRI has expressed energies
in joules or multiples of the watt hour and made sparing use of hybrid
units, such as metric ton and the engineering units of the English system.
The prefixes kilo, mega, and tera are sometimes used in accordance with
standard SI practice. The following listing summarizes the most common
conversion factors that readers may want to have available while reading
this report.
-------
Further information on the International System of Units can be
found in Special Publication 330, National Bureau of Standards, Depart-
ment of Commerce.
Energy
1 Btu = 1.055 X 10 joule (J)
-4
1 Btu = 2.929 X 10 kilowatt hour (kWh)
6
1 kWh = 3.600 X 10 joule (J)
1 kcal = 4.186 X 103 joule (J)
Length
-2
1 inch = 2.540 X 10 meter (m)
1 inch = 2.54 centimeter (cm)
1 foot = 0.3048 meter (m)
1 yard = 0.9144 meter (m)
1 mile = 1.609 kilometer (km)
Mass
1 pound = 0.4536 kilogram
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Volume
-2
1 cubic foot = 2.832 X 10 cubic meter (m )
—3 3
1 gallon = 3.785 X 10 cubic meter (m )
3
1 barrel (oil) = 0.1590 cubic meter (m )
Pressure
1 pound per square inch = 6.895 X 10 Pascal (Pa)
1 bar = 10 Pascal (Pa)
5
1 atmosphere = 1.013 X 10 Pascal (Pa)
2
1 Pascal = 1.0 newton/m
Equivalents
Factor
10
-3
10
-2
10
10
10
10
-1
6
10
10
10
12
Prefix
milli
centi
dec!
deka
hecto
kilo
mega
giga
tera
Symbol
m
c
d
da
h
k
M
G
T
xii
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ACKNOWLEDGMENTS
The following members of the professional staff of SRI contributed
directly to this study:
Staff Member Title Area of Contribution
*
Seymour B. Alpert Senior Industrial Energy from solid wastes
Economist
Edward M. Dickson Senior Physicist Solar energy and hydrogen
as an energy carrier
John P. Henry, Jr. Director, Energy Project supervision
Technology Department
Evan E. Hughes, Jr. Operations Analyst Geothermal energy and energy
from solid wastes
Edwin M. Kinderman Staff Scientist Energy from solid wastes
Albert J. Moll Senior Engineer- Underground coal gasification
Economist
Robert G. Murray Senior Chemical Energy from oil shale
Engineer
Robert M. Rodden Director, Operations Project supervision
Evaluation Department
Richard A. Schmidt* Senior Geologist Energy from oil shale and
geothermal energy
*
Now with Electric Power Research Institute,
xili
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I CONCLUSIONS
Six emerging energy technologies have been examined: solar energy,
geothermal energy, oil shale development, energy from solid wastes, under-
ground coal gasification, and hydrogen as an energy carrier.
Three of these six new energy sources require immediate attention
from EPA because they are expected to be deployed soon and have been
found to have significant direct environmental effects. These three
are: geothermal energy, oil shale, and energy from solid waste.
Major problem areas associated with geothermal energy technology
are: hydrogen sulfide emissions, disposal of saline waters, land sub-
sidence, and land use guidelines.
Major problem areas in oil shale development are: emissions from
retorts, disposal of waste waters, disposal of processed waste shale,
rehabilitation of lands, and consumptive use of scarce water.
Major problems in obtaining energy from solid wastes are: emissions
of exotic pollutants, ash disposal, and treatment of process water.
None of these three technologies is expected to produce a major
share of U.S. energy in either the near or long term, but their environ-
mental effects could become acute in local areas.
Solar thermal energy for heating and cooling may be deployed soon,
but, in general, this energy source has environmental effects that are
indirect, less severe, and more easily controlled by existing technologies
and statutes.
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The environmental effects of using hydrogen as an energy carrier
are similar to those of solar energy In that they are primarily indirect,
associated with materials processing.
The environmental effects of in-situ gasification of coal are dif-
ficult to foresee because no practical technological system has been
developed.
Such conclusions have led to the assignment of priorities and the
formulation of recommendations as summarized in the next section of this
report.
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II RECOMMENDATIONS
For the three new energy technologies assigned highest priority--
geothermal, oil shale, and solid wastes—EPA should initiate at once
programmed research directed toward the demonstration of control strate-
gies and technologies, and the enunciation of operating standards and
guidelines in the areas of air quality, water quality, and land use
practices.
The following types of research and development are needed for one
or more of the new energy sources:
• Background studies leading to enunciation of standards
or guidelines.
• Development of control technologies.
• Stimulation of new technologies.
• Further research to better define some potential problems.
Priorities within the EPA program of research and development for
control of environmental impacts from new energy sources should be
assigned on the basis of the nearness of deployment of the various
technologies, with consideration given to the expected magnitudes of
the energy production and environmental effects, and to the degree of
definition of the problem.
Specific recommendations for elements of a research and development
program are given in Section VI of this report; priorities are assigned
on the basis recommended above.
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Ill INTRODUCTION: FRAMEWORK FOR ANALYSIS
A. Background
In March 1973, Stanford Research Institute (SRI) began a series of
discussions with representatives of the U.S. Environmental Protection
Agency (EPA) that resulted in this report in support of EPA's energy-
related program planning activities. The purpose of the report is to
provide the technical background and data necessary for EPA to evaluate
alternative research and development programs to achieve control of pollu-
tants associated with development of nonconvent'ional energy sources. The
effort was intended to provide partial source material to assist EPA in
formulating its research program strategy and recommendations for prospec-
tive research projects addressed to priority topics. A draft final report
was submitted to EPA late in 1973. Some revisions were incorporated into
the report early in 1974.
The main text of the report summarizes information on advanced sources
of energy and serves as a concise introduction to the principal conclusions
and recommendations. The first part, therefore, is convenient for those
who need to be familiar with essential factors of advanced energy sources
and associated environmental effects, but who do not require extensive,
detailed data.
The appendices present more detailed descriptions of individual
advanced energy sources and their environmental effects. This material,
which was the major data leading to the study team's conclusions and
recommendations, is intended to serve as a convenient reference for those
who are more directly concerned with advanced energy sources and control
of their environmental effects.
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Abundant domestic supplies of conventional, low-cost energy to meet
projected demands are no longer taken for granted in the United States.
The range of choice of conventional energy sources is narrowing, and
attention to new energy sources is required. Increased demand for energy,
in many respects, is incompatible with public concern over the environ-
mental impact from the operations of energy production and consumption.
Yet, it is apparent that the conflict between energy need and environ-
mental quality must be reconciled if the nation is to achieve progress
in and maintain a style of living that offers each individual opportuni-
ties to realize his or her potential and participate fully in a dynamic
society.
It is apparent that the present energy crisis faced by the United
States features severely restricted options. The ability of domestic
supplies to meet demands while we conserve environmental quality is the
difficulty. Unless a coordinated and comprehensive effort is initiated
to provide new options for meeting the nation's energy needs and environ-
mental goals, the possibility of one or more of the severe energy and
environmental crisis scenarios looms greater.
The importance and visibility of the energy situation make it imper-
ative that government agencies charged with responsibility in energy
development have access to accurate and complete information addressed
to their special requirements. Often, however, such information is lack-
ing, or at best is incomplete; information is especially lacking on the
environmental impacts of energy production and utilization. Past ac-
tivities were frequently undertaken to emphasize efficient and economical
energy development, and minimum consideration was given to resulting
environmental effects. Previous activities did not necessarily require
-------
data on environmental effects because they were external to market cal-
culations. With respect to advanced energy sources, John Kenneth
i*
Galbraith has observed that it is especially important to avoid "...
substitutlion] of new forms of pollution to which people are not accus-
tomed for those to which they have become reconciled." Galbraith goes
on to note that "instead of eliminating [pollution], one natural recourse
is to urge the public that it is imaginary or benign or is being elimi-
nated by actions that are imaginary."
Positive actions to deal with pollution control of advanced energy
sources require detailed information, but in many respects the requisite
data are incomplete. As the environmental effects from energy production
processes have become matters of intense national concern. Considerable
efforts have been expended to quantify the levels of emissions, effluents,
and solid wastes produced by existing or planned energy production facili-
ties employing fossil or nuclear fuels. Further, strenuous efforts to
formulate pollution control strategies and upgrade control technologies
have been undertaken by public and private organizations. Although there
are certain exceptions, most pollution control technology is being
applied to existing energy generation facilities. This is natural because
the energy production technology originated first, but it represents a sub-
stantial investment that can be modified only with considerable difficulty
and great cost. However, the impetus for pollution control is beginning
to show positive results in improved air and water quality at many places
around the nation. That even small environmental quality improvements
are being realized in the face of rather formidable odds is a rather re-
markable achievement.
Clearly, it would have been more efficient and economical if pollution
control technology had been incorporated in facilities at the time of their
References are listed at the end of the report, before the appendices.
-------
design and construction, or in the case of some processes, if production of
pollutants had been suppressed from the beginning. This important lesson
learned from experience with conventional energy systems can be applied
both to new developments using fossil fuels and to advanced energy sources.
An increasing body of data is being developed for potential improvement
in conventional energy systems. But it is the purpose of this report to
provide information important to the research and development stages of
advanced energy systems, to support the planning activities of the
Environmental Protection Agency.
B. Selection of Energy Sources
As used in this work, the term "advanced energy sources" refers to
those resources or technologies that produce energy or fuel through
systems that are different in concept and in operation from those in
common use at present. This definition is intentionally broad to en-
compass a variety of advanced energy sources. However, in order to con-
centrate on those advanced energy sources of greatest development and
environmental impact potential, only those that may become operational
in the period from 1980 to 2000 were included in this analysis. These
advanced energy sources may be categorized broadly into (1) resource-
based sources and (2) technology-based sources. Resource-based sources
are those in which some naturally occurring resource material not presently
employed for energy production would be developed and processed in some
way to extract its energy or fuel. Technology-based sources are those
that feature the application of new technological methods or systems
that concentrate the energy content of diffuse or disaggregated sources.
Table 1 lists, for these categories, the advanced energy sources included
in the present study.
Many of these advanced energy sources may be further subdivided into
several subtypes. These are dealt with in Section IV and in the several
appendices to this report.
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Table 1
ADVANCED ENERGY SOURCES STUDIED
Category
Resource-based
Technology-based
Advanced
Energy Source
Geothermal energy
Oil shale
Solid wastes
Underground coal gasification
Solar energy
Hydrogen
C. Analysis of Each Energy System
Advanced energy sources include an array of diverse technologies and
systems. Such systems are commonly developed to deal with special problems
posed by the advanced sources and often lack counterparts in other, more
conventional systems. Hence, attempts at analysis based on technical
factors alone are infeasible. Accordingly, the present study was struc*-
tured around the development stage of each advanced energy source, and
its resulting environmental impact. The study included investigation of
the relative significance of the impact, its general implications for EPA,
and specific research and development needs. The approach used in analyz-
ing each of these factors is described separately below.
1. State of the Art
A concise account of the present state of development of tech-
nology for energy production from advanced sources was prepared from avail-
able information. This account included, where appropriate, discussion
of subtypes of advanced sources (e.g., dry steam and hot water subtypes of
geothermal resources). The discussion also included examination of the
8
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several stages of operations required for the development of advanced
energy sources (e.g., mining, crushing, transportation, retorting, and
upgrading of oil shale). Although drawn from the technical literature,
these data were compiled to serve as a basis for further analysis as well
as a ready reference for those nontechnical readers who require informa-
tion about advanced energy sources and the manner in which they may be
utilized.
2. Resulting Environmental Impacts
The environmental impact resulting from advanced energy source
development was quantified to the extent possible from available data
compiled during the preparation of the description above. The impact
on air and water quality was expressed in units of pollutant per unit
of energy produced (e.g., weight of SO per megawatt). Also, units of
£
solid wastes and land requirements were similarly quantified. Although
the estimated environmental impact from advanced energy sources derived
from such work may be somewhat uncertain because of the generally imperfect
state of knowledge about such systems, such quantification, nevertheless,
serves a useful purpose in providing some idea of the dimensions of the
impact likely to be experienced.
3. Relative Significance of the Impacts
Quantification of environmental impact on a unit energy basis
permits calculation of the total pollution load associated with develop-
ment of various energy capacities. This will enable planners to calculate,
in advance of development, the apparent uncontrolled environmental impact
from developments of varying size. When compared against measurements
of ambient environmental quality in the vicinity of projected develop-
ments or environmental quality standards established by cognizant
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regulatory agencies, the resulting data can yield an assessment of the
relative significance of the impacts. Such information is needed in
determining the degree to which available control technology can contain
the pollutants emitted.
4. General Implications for EPA
As the nation's need for energy increases, it will become
necessary to employ advanced energy sources to a great degree. Should
these sources approach becoming important contributors to regional or
local energy supply, it will be essential for the EPA to be prepared to
implement appropriate measures to safeguard environmental quality from
the outset of development. Knowledge of the characteristics of advanced
energy technologies and the resulting environmental impact is of clear
importance in the definition of future environmental quality standards
and pollution control requirements.
5. Specific Research and Development Needs
The analysis of each advanced energy system included an identi-
fication of specific research and development areas where further work
appears necessary. This information is essential in formulating the
requisite program plans for accomplishing improvements in energy production
with less pollution as well as in attaining more effective control tech-
nology for present systems.
D. Formulation of a Research and Development Plan
The detailed information resulting from the analysis of each advanced
energy system was used in formulating a broad plan for advanced energy
research and development, a plan addressed to improved control of environ-
mental impact. This plan was based on a common framework for identifying
10
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research and development needs and an approach to setting priorities. Each
of these factors is detailed separately below and followed by a description
of its use in formulation of the overall research plan presented in Section
VI of this report.
1. Identification of Research and Development Needs
The individual analyses of advanced energy sources resulted in
identification of cases where potentially important environmental impacts
may occur. In these cases, regardless of the information available from
previous research, additional work is needed either to define the environ-
mental effects more precisely or to determine the means to secure their
control. In short, therefore, the analysis of research needs and assess-
ment of their significance varies according to the state of knowledge
about the advanced energy sources themselves.
2. Priorities
The research and development needed to control environmental
impact is broad in scope. So much needs to be done, that it will be
impossible to undertake all the necessary work concurrently. It is apparent
that research and development priorities will have to be established by
EPA as it formulates its programs and that the priorities will depend on
many determinants. This study is only one input to the planning process.
In order to make the results of this study most useful to EPA
decision makers, the following guidelines for establishing research
priorities were employed in compiling detailed recommendations given
in Section VI of this report:
• The estimated times of development of advanced energy sources
form primary guidelines for establishing research priorities.
It is apparent that, when preliminary analyses suggest en-
vironmental impacts of some importance from advanced energy
11
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sources, the scope of research for control technology will
need to be greatest for those sources that are projected to
reach operational status at the earliest date.
• Where two advanced energy sources are estimated to reach
operational status at about the same time and the apparent
environmental impacts are identified with comparable precision,
then research and development should be directed toward con-
trol of the most severe environmental impact.
• Where two advanced energy sources are estimated to become
operational at about the same time and their impacts are
of equal severity, then research and development should
be directed toward the best defined problems.
3. Approach to Research and Development Planning
The approach to research and development planning in this work
was to employ tables that relate estimated energy development from
advanced sources to projected environmental effects. The estimated energy
production levels from these sources, at five-year intervals until the year
2000, were compiled from available sources and supplemented by original
SRI projections as necessary. Using the scaling factors relating unit
impact to unit of energy produced, derived from the detailed analyses
of individual sources, the project team calculated the expected impact
in particular years. The relationship of uncontrolled environmental
impacts to present levels of control standards was analyzed where applic-
able. These data are contained in Section IV of the report. These data
were then employed to recognize classes of problems requiring research
efforts. A matrix classifying the efforts by type of research and medium
of impact was constructed and used to formulate the plan for research and
development presented in Section VI.
With the foregoing description of the framework for analysis
employed in this study as background, it is now appropriate to turn to
examination in the next section of the projected environmental impact
from advanced energy sources.
12
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IV SUMMARIES OF ADVANCED ENERGY SOURCES
This section presents summary information on each advanced energy
source analyzed in this study. Tables that present projected energy
production and environmental impact are also included in this section.
Further information on each source is given, for those who desire greater
detail, in several appendices at the end of the report.
A. Overview of the Advanced Energy Sources
A summary of total amounts of energy projected to be derived from
advanced sources during the remaining years of the present century is
presented in Table 2. The table shows that advanced sources begin to
reach appreciable levels of energy production only in the middle or late
1980s. These estimates are conservative in that no crash programs to de-
velop new technologies are taken into account. Some conservation is
warranted by the long lead times inherent in design, construction, test-
ing and de-bugging•of facilities before they can be relied upon to sup-
port routine operations at high output levels. These lead times would
be long regardless of the environmental effects and controls that are of
primary concern to this study. Although it may be argued by some that
requirements for environmental control would cause serious delays in re-
alizing energy production from advanced sources, detailed data reviewed
in the course of this work led to the general conclusions that such delays
(if any) would be small in comparison with the time required to resolve
more fundamental technical, institutional, or economic problems. There
would, in short, be sufficient opportunity to deal with environmental con-
trol considerations while dealing with energy production technology re-
search and development. No significant time constraint is foreseen.
13
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Table 2
SUMMARY OF TOTAL PROJECTED ANNUAL ENERGY PRODUCTION LEVELS
FROM ADVANCED SOURCES
(10* joules per year)
Source
1970
1975
1980
1985
1990
1995
Percent of U.S.
demand filled
by above
sources
3 X 10
-3
3 X 10
-2
0.8
6
2000
Solar*
Geothermalt
Oil Shale*
Solid -Wastes*
Total*
U.S. demand *
0
1.8
0
0
1.8
70,000
0
14
0
10
24
83,000
0
72
610
55
740
98 , 000
400
180
2,000
300
2,900
120,000
2,500
360
2,700
950
6,500
140,000
4,000
720
3,400
3,000
11,000
170 , 000
12,000
1,400
4,000
10,000
27,000
200,000
13
Data from Table 3.
Data from Table 5.
§
Data from Table 13.
Totals may not check because figures are rounded.
Data from Table 7.
Assuming continued exponential growth, 20-year doubling time,
-------
A key question about advanced energy sources relates to their potential
contribution to overall energy supply. The projections in Table 2 sug-
gest that even the greatly increased amounts of energy from these sources
by 1990 will be only about 5 percent of the total demand estimated for
that year. Clearly, although not a major fraction of the national energy
consumption, advanced energy sources could be quite significant factors
in regional or local energy supplies. Similarly, environmental impact
from advanced energy source development, although likely to be small in
terms of the national pollution load, may well be severe on local levels.
Analysis of the problems posed by such situations requires a detailed ex-
amination of the environmental baselines of regions where advanced energy
sources may be developed. Such examination is beyond the scope of the
present study.
B. Solar Energy Summary
There are many technologies for using solar energy. For direct
collection of solar radiation, photovoltaic solid-state materials may be
used to generate electric power directly, thermal systems can be used to
generate electric power or to provide space conditioning, and crops can
be grown and harvested to fuel boilers or provide a feedstock for biological
production of gaseous fuels. There are many situations where joint use of
photovoltaic and thermal collection systems offer special benefits; these
range from building rooftop collectors to large installations comparable
in output to modern nuclear fission power plants. In addition, an earth-
orbitting satellite-borne photovoltaic collector transmitting power to
earth by a microwave beam is conceptually feasible. Moreover, solar
energy can be extracted from natural geophysical reservoirs by tapping
the winds or taking advantage of temperature differences in the ocean to
drive turbines.
X
15
-------
Because solar energy is such a dilute resource, large collection
areas are required, which implies the need for a large investment in
collector hardware. As a consequence, scientific and engineering fea-
sibility is far ahead of economic feasibility for all solar energy tech-
nologies. Currently, small-scale thermal collection and special-use
photovoltaic collection are economically feasible. The National Science
Foundation is launching a major effort to achieve commercial realization
(within the next decade) of small-scale thermal collection for the heating
and cooling of buildings. Since the use of crops grown specifically for
their fuel value represents an extension of well-developed agricultural
and forestry practice, this approach could probably be commercialized
within a decade also, but it is not receiving similar priority. Table 3
shows the annual energy production estimated by the NSF/NASA solar energy
panel if their research and development schedule is followed. It is
rather likely that the funding priorities administered by the NSF will
be the dominant factor influencing the rate of solar energy development.
1. Environmental Consequences
Although solar energy is widely reported to be pollution free,
this represents an oversimplification of the situation. For all solar
energy technologies, vast collection areas are required, and enormous
quantities of materials would be consumed to produce the necessary hard-
ware. Although most solar energy installations would be nearly benign
to the environment at the site, traditional environmental consequences
would be caused where the materials were mined, refined, and formed into
\
solar energy collectors. The neglect of these indirect, but nevertheless
cumulatively important, environmental consequences of solar energy utiliza-
tion should not continue.
Although design considerations are tentative, it is possible
to compile data on the emissions that are likely to result directly from
16
-------
Table 3
18
SOLAR ENERGY: ESTIMATED ANNUAL ENERGY PRODUCTION (in units of 10 joule)*
Thermal collection
Buildings1"
Central electric
Photovoltaic
Central electric
Satellite borne
Buildings
Ocean thermal gradients
Wind power
Energy plantations
Combustion
Conversion to
chemical fuel
e
(mainly methane)*
1970
0*
0
0
0
1975
0
0
1980 1985 1990 1995 2000
0
0
0
0
0
0
0.1
0
0
0.3
0.5
0
0
2.0
1.0
0
0
3.0
2.0
0.8
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
0.8
0.8
0.8
0.8
0.8
5.0
These estimates are based largely upon Table 3 in "An Assessment of Solar Energy as
a National Resource," NSF/NASA Solar Energy Panel, December 1972, and reflect cur-
rent national R&D spending priorities for development of solar energy collection.
The comparatively early emergence of this technology reflects the vigorous govern-
mental R&D support currently being supplied by the National Science Foundation.
Entries of zero indicate that this technology will achieve less than 1% penetration
of this market it is intended to serve. However, demonstration experiments and
pilot plants of significant size can be expected, often with considerable publicity.
§
The comparatively early emergence of this technology reflects the present state of
the art, the great national demand for methane, and the rapidly declining availa-
bility of methane from natural gas.
17
-------
the fabrication of rooftop thermal energy collectors of the type
envisioned by the NSF/NASA Solar Energy Panel. These data are displayed
in Table 4 and compared with emissions related to materials production or
emissions from activities that the installation of this solar energy tech-
nology may displace. Clearly some tradeoffs in the quantities and species
of pollutants are involved in reaching a judgment of whether this solar
energy technology will improve overall air quality. However, if the
control technologies now available are rigorously applied to the industries
producing materials required for rooftop thermal solar energy collectors,
this technology could achieve a significant reduction of energy resource
consumption and air pollution in urban areas.
Unfortunately, as Table 3 illustrates, the lead time for other
solar energy technologies is so long and the technology (design, materials
requirements, future materials production methods) is so uncertain that
a compilation of air pollutants similar to that in Table 4 for other
solar energy technologies cannot be justified at this time.
There are some special environmental problems related to solar
energy collection. For example, substantial quantities of biocides would
probably be necessary to prevent fouling of the flow-through passages
in the boilers of installations designed to tap ocean thermal gradients;
local climate modifications might result from altered heat balances caused
by large-scale insolation collection installations; aesthetic problems
would arise from new architectural design constraints for buildings
equipped with solar energy collectors; the legal problem of "sun rights"
would emerge; and questions of land use in arid, but sunny parts of the
United States would become important. Additionally, there would be a
subtle pressure for population redistribution towards locations where
solar energy could provide power at low cost.
18
-------
Table 4
AIR POLLUTANT EMISSIONS: MATERIALS FOR PRODUCTION OF THERMAL SOLAR
ENERGY COLLECTORS FOR BUILDINGS, MATERIALS, AND ACTIVITIES DISPLACED, 1985*
(104 kg)
5
Materials consumed
Glass (soda lime)
Alternative metals
Aluminum (best controls,
most common process)*
Copper (controlled)
Material displaced
Asphalt roofing
Activity displaced per year
Natural gas combustion
for domestic space
conditioning (uncon-
trolled)
Total
Participates
30
48§
5.6
0.88
15
Fluorides
SOF*
1.0
—
—
— •-
Sulfur Oxides
—
0.091§
1800
—
0.49
Carbon Monoxide
—
2.6§
—
1.2
16
Hydrocarbons
—
0.15§
—
2.0
6.5
Nitrogen Oxides
—
91§
—
—
65
This information is abstracted from Table 4 in Appendix A.
The variable "F" represents the weight percentage of fluoride input to the furnace.
Existing installations generally do not achieve this degree of control, although the control technologies are currently
available.
Includes emissions arising from the production of electric power (from natural gas) for the electrolysis process.
-------
2. Recommendations
The Environmental Protection Agency should establish a modest
program to maintain awareness of evolving solar energy technology and
liaison with those who work on solar energy and major interest groups.
By continually refining the forecast of both the direct and indirect
environmental consequences, EPA would be able to keep developers informed
and influence the development of hardware and systems design. Thereby,
EPA can seek to lessen any detrimental environmental consequences and
achieve full exploitation of environmental benefits. This suggested
program is described more completely in Appendix A.
C. Geothermal Energy
Geothermal energy already is a source of commercial electric power
in the United States. Power production at The Geysers in California should
produce over 3 billion kWh from about 500 MW of installed capacity in 1975.
While the ultimate level of production of electricity from geothermal
energy is extremely uncertain, it is clear that the present level of
production is a small fraction of what is possible. The steam reservoir
now being tapped at The Geysers is representative of only one type of
geothermal resource, the vapor-dominated hydrothermal convection source,
which is the least abundant type but the type most easily tapped for
electric power production. Most of the uncertainty as to the ultimate
energy production from geothermal resources derives from the fact that
the technology and the costs required for the exploitation of other types
of geothermal energy reservoirs are so undetermined.
Projections of the annual electric energy production from geothermal
energy sources are presented in Figure 1. The figure shows two projections
from a National Petroleum Council (NPC) study3 and two projections by SRI,
one for California alones and the other adopted for this report. Also
20
-------
1000
n^ i | r i r \ i
5 PERCENT OF USA ELECTRICAL ENERGY
AT PRESENT GROWTH RATE_
I
100
CO
0
tr.
ut
us
HI
til
Z
Z
X
1 PERCENT
OF USA
SRI CALIFORNIA
ONLY
USDI
BuMines
• White (Present Technology. World Limit)
• NPC (Permanent Hydrothermal Potential of USA, High)
I White (USA Limit with 1/3 Price Increase)
SRI (California Limit)
I NPC (Permanent Hydrothermal Potential of USA, Low)
SOURCES OF GEOTHERMAL ESTIMATES:
NPC National Petroleum Council, U.S. Energy Outlook: An Initial ~
Appraisal by the New Energy Forms Task Group, 1972.
SRI This report. ~
SRI Calif. Stanford Research Institute Report, "Meeting California's Energy ~
Requirements, 1975-2000," 1973.
USD! U.S. Department of Interior Report, "Assessment of Geothermal
Energy Resources," 1972. _
BuMines U.S. Bureau of Mines analysis cited In USDI, Final Environmental
Statement for the Geothermal Leasing Program. Vol. I, 1973, p. 11-18.
White D. E. White In Kruger and Otte
-------
shown are various estimates of levels of ultimate or year 2000 production.
The relative significance of the projected levels of geothermal energy
production is indicated by the straight lines showing 5 percent and 1 per-
cent of total U.S. electricity production based on projecting the 1970
level with a 10-year doubling time (i.e., a 7 percent annual growth rate).
The production level adopted as the definition of "significant" in Appen-
dix B is 33 billion kWh and occurs near the intersection of the SRI pro-
jection and the one percent line.
The kWh, the usual unit of electrical energy, has been chosen to
measure the level of geothermal energy development. This choice reflects
the judgment that virtually all exploitation of geothermal energy will
be for the production of electricity. Significant use of geothermal
energy for space heating is ruled out by the fact that the heat can1t be
transported to structures beyond the field itself. Use of geothermal
energy for process heat is unlikely because of the relatively low tempera-
tures of geothermal reservoirs, as indicated in Table B-5 in Appendix B on
geothermal energy.
Another judgment reflected in the projections of geothermal energy
production shown in Figure 1 concerns the time scales for development of
different types of geothermal energy. Neither the SRI nor the NPC projec-
tions anticipate the use of geothermal resources other than the hydro-
thermal convective type prior to 1985. A hydrothermal convective reservoir
exists where water and an abnormally high rate of heat flow coincide
naturally. A well drilled into the reservoir yields both hot water and
steam (a wet geothermal field), or, rarely, as at The Geysers, steam
alone (a dry geothermal field). The technology for producing electricity
from such geothermal fields exists. This technology is at the commercial
stage for dry fields (The Geysers) and at the demonstration (Cerro Prieto)
or pilot (Nlland) stages for wet fields. The technologies for exploiting
the other types of geothermal resources mentioned in Appendix B
22
-------
(stimulated dry hot rock, geopressured, and magmatic) are largely con-
ceptual at present. The first attempts to demonstrate the extraction of
energy from dry hot rock are planned to take place after 1975.
The projection adopted in this report does assume that some energy will
be derived from geothermal sources other than the hydrothermal convective
ones before the end of the century. Table 5 contains an estimate of 50
billion kWh from such sources in the year 2000, but this value is only a
fraction of the range of estimates given for that year in Figure 1. The
more than usually speculative nature of projections of the development of
these new forms of geothermal energy can be emphasized by quoting D. E.
White, a geothermal specialist of the U.S. Geological Survey: "l am
reluctant to offer estimates of geothermal resources that are now sub-
marginal but that may be utilized with appropriate technological break-
114
through; adequate cost data are completely lacking.
A final point to be made regarding the timing and the magnitude of
geothermal resource exploitation is that both are tied directly to the
research and development effort mounted by government and industry. It
is generally agreed that the potential of geothermal energy is vastly in-
creased if technical breakthroughs allow the exploitation of geopressured,
magmatlc, and dry rock sources. As White goes on to say, "However, major
geothermal contributions [greater than 10 percent of our energy needs]
could result from such breakthroughs."4 The development now underway is
projected in Figure 1 to make geothermal energy a resource of local im-
portance, but it is not likely to make it a source for more than 5 percent
of the national consumption of electrical energy.
A number of the quantifiable environmental effects of generating
electricity from geothermal energy are summarized in Table 5. The pro-
jected levels of geothermal energy development and the factors for scaling
23
-------
Table 5
PROJECTED ENVIRONMENTAL IMPACTS OF GEOTHERMAL ENERGY
Item
Unit
1975 1985
2000
Scaling Factor
Geothermal electricity
Energy from dry hydrothermal
Energy from wet hydrothermal
Energy from other reservoirs
Total geothermal energy
Total geothermal power
capacity
Waste heat
Heat rejected at plant sites
Air pollutants
Hydrogen sulfide
Ammonia
Methane
109 kWh/yr
109 kWh/yr
109 kWh/yr
109 kWh/yr
GW
1015 J/yr
106 kg/yr
106 kg/yr
106 kg/yr
4
0
0
4
0.5
72
18
24
18
30
20
0
50
7
900
220
300
220
50
300
50
400
60
7,200 18 MJ/kWh (16 percent efficiency)
1,800 4.5 g/kWh
2,400 6.0 g/kWh
1,800 4.5 g/kWh
Land requirement
Area of geothermal fields
Water
Liquid brought to surface
Total dissolved solids brought
to surface
Solid waste
Volume of TDS brought to surface
after evaporation of the water
sq km
15 200 1,800 30 sq km/GW
109 kg/yr 8 900 14,000 40 kg/kWh (wet), 2 kg/kWh (dry)
109 kg/yr
106 m3/yr
10
150 0.5 kg/kWh (wet), zero (dry)
90 0.5 mVlOOO kg
-------
environmental effects to those levels are given explicitly in the table.
The scaling factors are taken from the discussion of environmental effects
in Section II of Appendix B and are derived explicitly from properties
of two hydrothermal convective fields: The Geysers (dry) and Cerro Prieto
(wet). They should be as applicable to geothermal sites in general as
single factors can be from single geothermal sites. The thermal efficiency,
which determines the waste heat load, is typical of the best hydrothermal
convective fields. The factors for emissions to the air are from average
values at The Geysers. The hydrogen sulfide level in some wet geothermal
wells is appreciably higher6 (by a factor of 5), so further experience
with wet geothermal resources may suggest a larger scaling factor for these
uncontrolled emissions. The land use factor was also derived from ex-
perience at The Geysers, in this case, experience with steam production
rates, transport distances, and depletion effects. The scaling factors
for water, total dissolved solids, and solid waste are characteristic of
the Cerro Prieto geothermal water, which has a salinity somewhat below
2 percent.
One method to estimate the degree of control needed to bring the effects
quantified in Table 5 to within some acceptable limits is to determine the
effect on ambient environmental quality of the projected level of emissions
or other impact and to compare the resulting indicator of ambient quality
with an appropriate environmental quality standard. This method is used
in Appendix B to estimate that something like 98 percent control may be
in order for hydrogen sulfide emissions at The Geysers and that more than
90 percent control of total dissolved solids would be needed for a geo-
thermal field like Cerro Prieto producing energy on a significant scale
and discharging geothermal fluid into a fresh water stream that has one-
tenth the mean annual flow of the Colorado River. This method requires
the use of a model for calculating ambient quality, given a production
level and a scaling factor.
25
-------
Another method for estimating the need for control of an environ-
mental effect is to compare the directly expressed emission or effluent
or the land-use factor with a comparable standard associated with a
similar industry or process (rather than with an ambient quality standard).
This method would result in a control requirement independent of the
production level, because the standard is applied directly to quantities
like the scaling factors in Table 5. The need for control of hydrogen
sulfide emissions is estimated according to this method, by comparing
them to the standards for sulfur dioxide emissions from the fossil fuel
alternatives to geothermal power plants. The fact that hydrogen sulfide
is oxidized to sulfur dioxide in the atmosphere within 2 to 48 hours
suggests that the comparison is appropriate.6 Table 6 presents the
quantitative comparison. The conclusion suggested by Table 6 is that,
on a per kWh basis, where the geothermal plant suffers from its 16 percent
efficiency (as compared to the 40 percent efficiency of the best fossil
fuel plants), the emission of sulfur as hydrogen sulfide at the Geysers
plant is comparable to the emission of sulfur as sulfur dioxide from a
i
coal-fired plant meeting the EPA standards for a new source. Both are
within 50 percent of the value of 3 grams of sulfur per kWh. By way of
further comparison, the burning of 1 percent sulfur coal to produce elec-
tricity at 40 percent thermal efficiency also results in an emission
factor of 3 grams of sulfur per kWh if the coal has a heating value of
30 MJ/kg (13,000 Btu/lb). The control requirement estimated on the basis
of this comparison can be anywhere from zero to nearly 90 percent, the
high requirement resulting from a situation where the hydrogen sulfide
content of the geothermal fluid is about five times the average at The
Geysers.
The control requirements for materials dissolved in the geothermal
fluids are being met at The Geysers and at Niland by reinjection of the
fluids into the subsurface geothermal reservoir after the heat energy
26
-------
Table 6
EMISSION FACTORS FOR GEOTHERMAL PLANTS COMPARED
WITH EMISSION STANDARDS FOR FOSSIL FUEL POWER PLANTS
to
Description
Geothermal
Typical case at The Geysers
Bad case in Imperial Valley
Fossil fuel*
Coal-fired plant
Oil-fired plant
Form
of the
Emission
V
V
S°2
S00
Emission in Grams
of Sulfur per
Mega joule of Heat
Factor
0.2
1.0
*
Standard
—
—
0.26
0.17
Thermal
Efficiency
(percent)
16
16
40
40
Emission in Grams
of Sulfur per
Kilowatthour
of Electricity
Factor Standard
4
20
—
—
—
2.3
1.5
EPA standards from The Federal Register, 23 December 1971.
-------
has been extracted at the power plant. This procedure has the additional
environmental virtue of decreasing the probability and the magnitude of
subsidence caused by depletion of the reservoir. Reinjection introduces
another possibility that geothermal brine will contaminate a fresh water
aquifer by leakage through a well casing, but this threat must be dealt
with anyway in the wells bringing the brine to the surface. In the semi-
arid western United States, where most of the hydrothermal convective
resources are to be found, the only environmentally sound alternative to
reinjection of spent geothermal fluids is extensive treatment and mineral
recovery. This alternative is being investigated to determine its tech-
nical and economic feasibility.
Other environmental effects of generating electricity from geothermal
energy are identified in Appendix B. The most important ones have been
presented in Table 5. and in this summary. The recommendations for re-
search and development to control the adverse effects and to realize the
advantages of geothermal energy are presented in Section VI of this
report.
28
-------
D. Energy from Oil Shale
1. State of the Art
Oil shale is not shale, and it does not contain oil; it is in-
stead, a fine-grained, compact, laminated sedimentary rock that contains
kerogen, an organic, high molecular weight mineraloid of indefinite com-
position. Kerogen can be extracted from oil shale by retorting that
results in a hydrocarbon liquid akin to natural crude oil that in turn
can be processed and refined much as petroleum. Attention is directed to
oil shale as an advanced energy source because certain deposits (especially
in Colorado, Utah, and Wyoming) are relatively rich in kerogen that, if
recoverable, could represent an important source of supplementary refinery
feedstocks or substitute for natural gas.
Only those portions of oil shale deposits containing the richest
kerogen content and occurring in thick beds can be considered as reserves
for prospective developments. Still, these reserves are approximately
9 3
equivalent to a giant oil field, estimated at about 5.2 x 10 m (33 billion
barrels) of oil. More than ten times as much shale oil is estimated to
occur in lower grade and thinner beds, but it is improbable that these
resources will experience development in this country.
Table 7, based largely on the work of the U.S. Department of
the Interior, shows the amounts of shale oil projected to be developed
6 *3
by the year 2000. Rapid development is projected, reaching 16 x 10 m
(100 million barrels) per year by 1980 and increasing more than sixfold
by the end of the century. Most of the shale for processing is estimated
to be derived from mining, with small amounts from in-situ development
in later years.
The alternate approaches to oil shale utilization are shown in
Figure 2. According to projections, most future oil shale development
will start with mining followed by crushing, retorting, refining, and
29
-------
Table 7
PROJECTED ANNUAL FUEL PRODUCTION FROM OIL SHALE DEVELOPMENT
Total estimated oil
production
Underground mining
Surface mining
In-Situ
CioV)
1970 1975 1980 1985 1990 1995
0 0 16 52 70 87
00 8 24 32 40
00 8 24 32 40
00 0467
200
•MBMMMI
105
48
40
17
Source: Stanford Research Institute, using data from U.S. Department of the
Interior, "Final Environmental Impact Statement for the Prototype
Oil Shale Leasing Program** in four volumes, 1973, Volume I, "Regional
Impacts of Oil Shale Development". Data presented here calculated
on the assumption of 330 days of plant operation per year.
-------
IN SUV
QAI NATURAL
(K) HYDRAULIC
(K) ELECTRO-
(JC) CHEM, EXPLOSIVE |
(SB) NUCLEAR
FRACTURING
«A) IN-FORMATION \
(3C1 NUCLEAR CHIMNEY/
OIL SHALE DEPOSIT
CONVENTIONAL (It
MINING
COMBINATION
MINING AND
IN SITU
RETORTING
J
ENVIRONMENTAL
PROBLEMS
fCOMBUSTION WC)
I HOT GASES (»AI
STEAM (3A)
I SOLVENT LEACHING ISA)
V.BACTERIAL ACTION WA)
PRODUCT
RECOVERY
(SA)
COMBUSTION GASES AND
NUCLEAR CONTAMIN-
ATION TO AIR
SOLVENT LOSS TO AQUIFERS
NUCLEAR CONTAMINATION
OF AQUIFERS
LAND SUBSIDENCE
{GAS DRIVE (SCI
ARTIFICIAL LIFT (X)
{UNDERGROUND -VCvt «nd Fm (SB)
OPEN PIT OBI I Block C*rtn| OB)
(1A)
•)
-i
ENVIRONMENTAL
PROBLEMS
CRUSHING
HYOROGASIFICATION
(1C) THERMAL AND CHEM. TREATING
(1C) HYDROQBNAT1ON
Hv4roarMklm
REFINING
CODE -
i el
Oil
V
2. Somt
ln( from:
C, Bo*
no
EXPOSING SALT BEDS
OPENING SALINE GROUND
WATER TRAPS
LOWERING GROUND WATER
LEVEL
RETORTING
1
-H
SNG
fiHNMl OAI
'GAS COMBUSTION 4 PMTWlii (»AI
UNION (1AI I P«f*o (9B)
TOSCO (»AI V
HYDROGEN ATMOSPHERE ISA)
LURGI-RUHRGAS «A)
SPENT SHALE
UTILIZE WAI
.DISPOSE Mhw IIH (SB)
"VWOjpKvvB Y9^l
Oun»(»A)
LIQUID FUELS
BY-PRODUCTS
ENVIRONMENTAL
PROBLEMS
SOURCI-
«n »tl|ln»l »t»»f» In N
AMMONIA (1C)
SULFUR PC)
AROMATICS WAI
SPECIALTIES (SAI
COKE IK)
PITCH net
ASPHALT OC)
WAX OAI
. "Prowwcn It* Oil S»»t» O«v»lttpm»M," U.S. Oiptrtnwnt o«
GASOLINE
DIESEL FUEL
JET FUEL
DISTILLATE FUEL OIL
RESIDUAL FUEL OIL
LIQUEFIED PETROLEUM GAS
PARTICULATE EMISSIONS (1C)
SULFUR OXIDES UCI
NITROGEN OXIDES (K)
TRACE ELEMENTS (1C)
LEACHING OF SOLUBLE
SALTS (JA)
FIGURE 2 OIL SHALE UTILIZATION — PROCESSES. ENVIRONMENTAL EFFECTS, AND STATE OF KNOWLEDGE
-------
disposal of processed shale. Mining of oil shale has been performed on
a pilot basis, but never at the scale anticipated for full-size operations,
3 3
For example, one 8 x 10 m (50,000 barrel) per day plant would require
7
approximately 5.7 x 10 kg (62,500 tons) of mined oil shale per day. Many
plants of this size are projected. Clearly, there are a number of oper-
ational problems to be addressed in undertakings of such magnitude.
Mined shale is crushed and transported to a plant where it is
retorted. Several retorting processes have been developed at various
times. The processes differ in their method of heat transfer to the shale
for kerogen recovery. The two retorting approaches most likely to be
developed are those that employ heat transfer either by (1) burning com-
bustion gases generated in the retort or (2) introduction of hot solids
into the retorting bed. Each of these methods results in environmental
impacts that will need to be controlled.
2. Environmental Consequences
Oil shale development may result in a number of adverse environ-
mental consequences unless proper steps are taken to achieve pollution
control. Environmental impact will include dust, sulfur dioxide in flue
gases, nitrogen oxide in combustion products formed by burning crude shale
oil, and sour water decanted from the product oil. Retorting shale pro-
duces a strong odor characteristic of organic nitrogen compounds, and it
may be dispersed widely. Additionally, shale processing required signif-
icant amounts of water consumption and also results in large amounts of
processed shale that will need disposal and management to avoid creation
of long-standing sources of significant pollutant amounts.
32
-------
The analysis in the present study, based on work done by the
U.S. Department of the Interior and other sources, quantified the following
environmental consequences and projected impacts from oil shale develop-
ment to the year 2000:
• Water Use. Availability of water is recognized as a
principal constraint upon oil shale development be-
cause the deposits are located in arid regions.
Table 8, in which the overall industry size is limited
to 3.2 x 10^ m3 (2 million barrels) per day because
of the availability of water, shows the total annual
consumptive water requirements for each type of mining.
This amount of water consumption would preempt other
potential uses and thereby contribute indirectly to
environmental impacts associated with oil shale de-
velopment .
• Land Requirements. Land is required for oil shale
production facilities, but by far the largest land
disturbance in oil shale development is related to
surface disposal of processed shale. Table 9 shows
the projected annual land requirements for oil shale
production until the year 2000.
• Water Quality. Oil shale development could lead to
degradation of water quality in the vicinity of de-
velopments. Although effluents from processing plants
will require obvious controls, a major source of water
pollution will be from surface disposal of processed
oil shale. Table 10 shows estimated leachate, salinity,
sediment, and heavy metals produced from weathering
and erosion of processed shale disposed of at the
surface near oil shale developments in the Piceance
Basin region of Colorado.
Control of these potential pollutants will require
treatment of processed shale disposal areas. Materials
that may be leached from disposal piles must be con-
tained and prevented from leaving the disposal site.
Ideally, research to find alternative uses for pro-
cessed shale, which would obviate the need for its
surface disposal, would be perhaps the most effective
means of realizing control over the potential water
quality effects of oil shale development.
33
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Table 8
PROJECTED ANNUAL WATER REQUIREMENTS - OIL SHALE
Total estimated oil
production, 106m3
1970 1975
1980
16
1985
52
1990
70
1995
87
105
Recurring annual
water consumption
(a) Underground mine
production, 106m3 0
Water consumption
(@ 4.1 m3/m3 oil) 0
(b) Surface mine
production, 10 m 0
Water consumption
(@ 4.0 m3/m3 oil) 0
(c) In-situ production,
106m3 0
0
8
33
32
24
98
24
96
32
130
32
130
6
40
160
40
160
48
40
17
Water consumption
(@ 2.1 m3/m3 oil) 0
TOTAL ANNUAL WATER
CONSUMPTION, 106m3
65
8.4
200
13
270
15
340
4<
(Totals may not check
because of rounding.)
Source: SRI calculations based on U.S. Department of the Interior, Final Environmental
Statement for the Prototype Oil Shale Leasing Program," Vol. I, 1973,
pp. 111-9,34.
34
-------
Table 9
PROJECTED ANNUAL LAND REQUIREMENTS - OIL SHALE
1970 1975 1980
1985
1990
1995
2000
Total estimated oil
production,
Recovery annual land
requirements, ha
Underground mine
production, 106m3
Disturbance, ha
(@ 11 ha/106m3 oil)1"
Surface mine production,
16
52
70
24
32
88
260
350
106m3
24
32
Disturbance, ha
87
40
440
40
105
48
530
40
(
-------
Table 10
PROJECTED ANNUAL WATER QUALITY EFFECTS FROM SURFACE DISPOSAL OF PROCESSED OIL SHALE
1970 1975 1980 1985 1990 1995 2000
Total estimated oil
productlon, 10®m3
16
52
70
87
105
Surface disposal of pro-
ceaeed ahale, 10 kg
(® 40% of total proceaaed
•bale, 3.4xl03kg/m3)
54
180
240
300
360
Area required for diapoaal,
ha (« 1.3 ha/109kg pro-
ceaaed ahale)* 0
72 230
310
385
465
Leachate produced, 10*kg
<« 17x10®kg/ha)t
120 390
530 650
790
Dissolved aollda produced,
103kg (O 150 kg/ha) 0
12
39
54
66
81
Sediment produced,
(0 4.8 m3/ba)
0.3
1.1 1.5
1.8
2.2
Heavy metals, 106kg
(O 0.086 kg/m3oll)
1.4 4.5
6.0 7.5
9.0
Aaaumea 76m (250 ft) average depth of spent shale disposal.
Assumes the top 10cm (4 in) of spent shale is leached.
Source: SRI calculation based on U.S. Department of the Interior, "Final Environmental
Statement for the Prototype Oil Shale Leasing Program," Vol. I, 1973,
pp. 111-14, 88, 90, 99.
36
-------
• Air Quality. Development of the western oil shale de-
posits will result in a decline of general air quality
through emissions of chemical compounds and particulate
matter to the atmosphere. Table 11 shows estimated
sulfur oxide and nitrogen oxide emissions associated
with projected levels of oil shale development. The
data indicate that uncontrolled SOX emissions will
greatly exceed maximum EPA standards unless control
measures are employed. Uncontrolled NOX emissions,
on the other hand, will be less than the maximum
standard level, and unless the standard is altered,
they would not appear to require special control
procedures at this time. It must be remembered, how-
ever, that this initial analysis does not consider
the possible adverse environmental impact resulting
from the cumulative effects of such emissions from
many sources in an air basin. This potentiality,
which needs to be examined by further research and
analytical work, could lead to the need for NO
control.
In addition to chemical emissions, oil shale development promises
to be inherently dusty, and significant amounts of particulates could be
produced as indicated in Table 12. The table shows that uncontrolled dust
levels associated with oil shale development are in excess of the EPA
standard. This will require some measure of dust control to bring these
emissions within the limits established by present standards. Dust con-
trol will be required at several stages of oil shale development, especially
in mining, crushing, transportation, and disposal. It is clear that the
degree to which dust control can be realized will vary greatly in the
different stages. A key question is whether each stage must be within
established standards, or whether the standard applies only to the overall
operation.
37
-------
Table II
I'ltUJMUTNU ANNUAL UAHWUUH KMJWB1QNK « Oil, MtlAl.H
ltv*i RI
BPA
(e) Tut Hi wo
00% I'lintroi level Cm (a),
10flUg 0 0 0,1 30 40 BO
Annum! ng I he tiuliur iu emitted MM 00*
IftZft IfiM ilBA i»JP ij9j>
Total intimated nil
product I mi, iQ*ma 0 o 10 QB 70 07 100
Hill fur UN hkiH
(a) 00 amlaaiona, 10aHg
(o 8,7 kg/m8 oti)* oo ei 3QQ 400 ooo 000
(I.) HQ^ ,,ml"«lun. , 10flhg
(O H hn/ma nil) (i 0 W UBO 740 B«0 HQO
10flUg (00, 'A Ug.'mS oil) 0 0 8, « 10 14 17 81
(d) BiteaM 10
"v«r itindird m mini-
mum •miMHion fit** («),
toflHg o o HH aao aeo 4so uao
Nil rug w»
(a) NO •miHHiana, 10flUg
(0*0, 4fl kg/m3 .,il) 00 7,4 84 38 40 48
00 NO amiuiani, 10flHg
(«*0,fl» Hg/ffla <•(!) 00 II 96 48 RO 71
NON •miNHlon V8V«1 it
minimum HPA aundard,
10flhg (A <>,R7 h«/mft "il) 0 0 0,1 SO 40 80 00
(d) (Usftoii) NON •mlMHtana
«omp«r*d to nt«nd«rd m
minimum «ml««lon nt« (a),
0 0 (1,7) (0,0) (8,0) (10.) (18)
SlU oNlnulMi 1'inM baited on U,8. Department of the Interior "final Bnvirnnmental
gutement for the Prototype on Hhale Leaalng Program, 1078, Volumes I and III,
-------
PHOJBOTMI) ANW1A1, PARTI6UIAT8 BMJDfllONB - OU, iHALB
ifijfi ItTJ. ifiifi ifiift ifilfl jjfift •*.'.'«».'
Total ainmatad all
product tun, 10flm8 Q o Id Alt 7ti H7 iOft
Unoontfollid
iOflU§ (» 0,084 hg/m*) 0 Q 0,9 8,H 3,rt 4,7 !>,/
"Tvpioul" Uum Itvfl,
106U| (0 84 i/m3) o o o.ftft I,M a. i a,o :i,n
Pun •minion i«vil§ it
10fl Mg/m8
g/m»(,oaa m/bbi)] o o i,a 4.^ n.a 7,0 H,I
BNOIII
eompirid ta •t'lndard ni
unoontwllid tmiiiinn
nt«i, lQflUg 0 Q 0,(j
lowrotii BH! oalouUtioni butd on U,M, Dipurtmtni or (h» Int«rtoi>, 'Vtnui flnvtronmanUl
HUtamBnl' fur thu Pi-Qtotyp« Oil 8hnU Uftf4ni Progrwn," Vol. I,
p, m-iaa.
-------
3. Recommendations
The magnitude of potential oil shale developments, their location
in virtually undeveloped, arid regions of the American West where sub-
stantial amounts of public lands occur, and the apparent Impacts on air
and water quality and land use are strong points in the argument that
the Environmental Protection Agency undertake a program of research and
development. The suggested program is described in Section VI of this
report and in Appendix C.
E. Energy from Solid Wastes
The energy equivalent of 2 million barrels of oil per day (the national
energy consumption equivalent is 35 million barrels of oil per day) is
the estimate given in Appendix D for the energy potential of both urban
and agricultural wastes in the United States. The assumptions made to
arrive at this estimate are (1) that total wastes are 30 kg per person
per day, (2) that population is 2OO million people, (3) that energy
content of wastes is 8 MJ/kg (4000 Btu/lb), (4) that efficiency of
collection and conversion to energy is 25 percent, and (5) that energy
equivalent of a barrel of oil is 6 GJ. According to this estimate, solid
wastes could supplement the national energy supply by six percent. The
greatest uncertainty in this energy supply assessment is in the choice of
the fraction of the total wastes that are assumed to be converted to
energy. A 25 percent recovery rate is optimistic under present circum-
stances, where only about a sixth (5 kg per person per day) of the total
solid waste is urban refuse (the most easily collected component). Other
estimates of the energy potential of solid waste, based on present waste
collection patterns, are closer to 1.5 percent of national energy con-
siaption.8;9
40
-------
With even the most advanced of the solid waste conversion processes
only now moving from the demonstration toward the commercial stage, an
initial growth rate tor the new technology is not established and a pattern
of growth toward some ultimate limit cannot be extrapolated. For the sake
of projecting the Increasing emission levels from a growing use of this
energy resource, this report assumes that energy from solid waste will
amount to five percent of total U.S. energy in the year 2OOO and will reach
that level at a growth rate characterized by a doubling time of two years
during the 1975 to 1985 decade and of three years during the remainder of
the century. This assumption leads to the energy production levels pre-
sented in Table 2 and Table 13.
Energy recovery can be achieved by incineration of urban or "dry"
agricultural wastes. Process heat or power produced in steam or gas
turbines are the usable products. Energy can also be recovered from
gases produced through pyrolysis. The gases can be burned at the facility
to produce power, or they can be transmitted elsewhere tor use* If used
as synthesis gas, the pyrolysis gas substitutes for gas made from other
fossil resources. Anerobic digestion can be used for urban refuse dis-
posal if these urban wastes are mixed with "wet" materials such as sewage.
The digestion process produces a methane containing gas suitable for com-
bustion or purification for transport. Anerobic digestion is the most
likely method for disposal of agricultural wastes, especially in those
locations and situations that produce large quantities of readily col-
lectable manure and food processing wastes.
All the processes of energy recovery from waste disposal have an
advantage over sanitary landfill through minimization of land requirements,
elimination of putrescible materials, and simplification of disease and
vector control. However, extensive energy recovery operations increase
the potential for air pollution. In tests at the Chicago incinerator, a
41
-------
particulate emission rate of approximately 0.4 kilogram per tonne of urban
refuse processed has been achieved. These emissions met the requirements
of no more than 0.183 grams per cubic meter (0.08 grains per SCF). An ur-
ban population of 175 million (estimated for the mid-1980s) will produce
approximately 262 million tonnes of refuse. If 75 percent of this refuse
were incinerated under proper controls, the pollution resulting would be
about 100,000 tonnes of particulates per year. This should be compared
with the 1.4 million tonnes of particulates from uncontrolled combustion
of solid wastes or the 25 million tonnes of particulates that comprise
the estimated annual air burden of the United States. Pyrolysis process
will produce similar or smaller particulate loads ranging downward from
100, 000 to perhaps 10,000 tonnes. Anerobic digestion should produce
relatively little particulate contamination.
The experience at the Combustion Power Inc. pilot plant in Menlo Park,
California, provides the data for determining emission factors applicable
to gaseous, as well as particulate, air pollutants. This plant incinerates
solid waste in a fluidized bed combustor and generates electricity by
passing the combustion products through a gas turbine. The emission
factors are shown in Table 13. The emission factor for particulates at
the Chicago incinerator, used in the estimate of the previous paragraph,
is somewhat more than half of the one adopted in Table 13, an indication
of the accuracy of the emission factors used. It should be noted that the
factor of five as the emission level advantage of pyrolysis over incinera-
tion referred to in Appendix D may be decreased substantially when the
subsequent burning of the fuel produced by pyrolysis is included as part
of the energy production system. The emission factors given in Table 13,
therefore, are useful as upper limits for estimates of emission levels from
both incineration and pyrolysis. The time scale for development of energy-
producing solid waste facilities presented in Table 13 is not quite
42
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Table 13
PROJECTED ENVIRONMENTAL IMPACTS OF ENERGY FROM SOLID WASTES
Item
Unit
1975
1985
2000
Emission Factor
CO
Energy
Annual production
Fraction of U.S. total
Air Pollutants
Particulates
S02
N02
CO
HC1
IO15 J/yr
percent
IO6 kg/yr
IO6 kg/yr
IO6 kg/yr
iO6 kg/yr
IO6 kg/yr
10
0.01
1
1
2
0.4
1
300
0.2
30
30
60
12
30
10,000
5
1,000
1,000
2,000
400
1,000
0.1 kg/GJ
0.1 kg/GJ
0.2 kg/GJ
0.04 kg/GJ
0.1 kg/GJ
Note: The present annual national emission levels are approximately
• Particulates,, 20,000 X IO6 kg/yr
• S02, 30,000 X IO6 kg/yr
• N02, 20,000 X IO6 kg/yr.
-------
as short as the one for the projection just cited. The result is that the
particulate emission level of hundreds of thousands of tonnes is projected
for about the year 1990 rather than the mid-1980s.
The small fraction of total emissions likely to be attributable to
these solid waste processes is due to the extremely small amount of energy
now being produced from solid wastes. Even at the rapid growth rate pro-
jected, a doubling every two years until 1985 and every third year there-
after, the start from a mere 5,000 tonnes per day in a few demonstration
i
plants in 1975 does not lead to even a tenth of a percent of the national
energy consumption until after 1982. Under these conditions, the small
fraction of national pollutant levels accounted for by solid waste energy
processes has no implication regarding the quality of the emission con-
trol technology. An indication of the need, if any, for lower emission
levels from solid-waste energy plants must be sought by considering the
maximum production to be reached sometime after the year 2000 or by com-'
paring the emission factors given in Table 13 with those from similar pro-
cesses for which standards exist.
The maximum possible production of energy from solid waste, if
virtually all the waste is converted to energy, is 25 percent of total
national energy consumption. With total collection being uneconomical
and unlikely, the six percent value cited at the start of this section
is a better estimate of the ultimate level of energy production from
solid wastes. This suggests that emission levels quite comparable
to those given in Table 13 for the year 2000 are likely to constitute
the ultimate level of emissions if current technology for producing energy
from solid waste is fully used.
Table 14 presents another approach for estimating a control require-
ment. The emission factors adopted here on the basis of experience with
pilot and demonstration plants are compared with emission standards for
44
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Table 14
EMISSION FACTORS FOR ENERGY FROM SOLID WASTE
COMPARED WITH FOSSIL FUEL EMISSION STANDARDS'
Emissions
Pollutant
Particulates
SO.
NO
Type of Plant
Solid waste*
Coal
Oil
Solid waste*
Coal
Oil
f
Solid waste1
Coal
Oil
Gas
Factors
(kg/GJ)
0.1
0.1
0.2
Standards
(kg/GJ)
0.1*
0.04
0.04
0.52
0.34
0.30
0.13
0.09
All standards are taken from The Federal Register of
23 December 1971.
The emission factors for energy from solid wastes are
based on measurements made on the CPU-400 system of
Combustion Power, Inc.
The emission standard for particulates from a solid
waste energy plant is derived from the published stan-
dard for incinerators (0.18 g per standard cubic meter
at 12 percent 0)2) by assuming that the combustible
fraction of the solid waste is 55 percent of the total
and has a composition given by C30H48Oi9. The heat value
assumed is 15 MJ per kg for the combustible fraction, i.e.,
8 MJ/kg for the total.
45
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fossil-fuel fired, steam generating plants. The implication of Table 14
is that little additional control is needed. More information on the
status of control technology and the degree of control required is pre-
sented below in Section IV-H.
Hazardous chemicals can be emitted from any of the disposal processes.
Most heavy metal and carcinogens will be associated with particulates and,
as a first approximation, hazards from these special sources can be taken
as being in proportion to the total particulate emissions from the various
processes. Volatile chemicals, such as mercury and many organic compounds,
will also be emitted. The organic chemical substances are not expected in
quantities large enough to be of environmental concern.
Residues from the energy producing processes, such as ash and waste
waters, can produce undesirable effects. Ash deposits must be handled
in a way that prevents unacceptable levels of leaching by underground
streams and rain water, which would transfer acid, alkali, or heavy metal
residues and pollute natural waters. Quench and scrub waters must be
treated to control similar effects, but the treatment is standard, and
present controls appear to be adequate to prevent adverse effects.
Anerobic digestion may pose special problems in disposal of treated
residues. Urban wastes may still have substantial volume after anerobic
digestion and, therefore, continue to require considerable land for dis-
posal. In addition, if the bacterial processes are poisoned, the "stuck"
digester will be filled with a vile, smelly, difficult-to-handle product.
F. Underground Coal Gasification
The underground gasification of coal is as yet a commercially unproven
concept. Decades of development in the USSR, England, the United
States, and other countries have failed to produce a viable process. The
46
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two current underground gasification programs under development in the
United States face immense technical problems. There is a substantial
risk that the current programs will likewise fail to demonstrate a viable
process. However, the economic impact of successful development of the
concept as a substitute for gasifying strip-mined coal is potentially
large. The environmental impact of large-scale commercial development of
underground coal gasification, vis-k-vis strip-mined coal gasification,
may also be large, depending upon:
• Failure of current efforts to devise acceptable means of
reclaiming stripped arid land.
• Demonstration that there are no unacceptable environmental
effects of underground coal gasification.
No support by the EPA of the current development programs is recommended
at this time. However, the EPA should follow the progress of the current
programs and retain the option of reconsidering this decision at a later
date.
G. Hydrogen as an Energy Carrier
1. State of the Art
Currently, hydrogen is produced mainly from methane or by steam
reforming processes driven by fossil fuels. In the long term, when fossil
fuels become scarce, hydrogen is a likely energy carrier for use in mobile
applications. Such hydrogen could be produced by electrolysis using
electric power from any basic energy resource or, perhaps, by closed cycle
thermochemical decomposition of water using high temperature heat from a
nuclear reactor. As petroleum and gas become less available, hydrogen
will be needed in large quantities if coal is to be gasified to methane
and liquefied to other hydrocarbons. However, hydrogen also might be
utilized as a fuel directly. Hydrogen is also seen as an important option
47
-------
for energy storage somewhat analogous to pumped hydrostorage. It has been
determined that, in some circumstances, transmission of energy in the form
of hydrogen conveyed by pipeline can be more effective than overhead
electric transmission. Moreover, because of the variability in Insolation
many solar energy technologies may not be viable without an energy storage
mechanism such as hydrogen.
Experience with gaseous hydrogen in Europe and liquid hydrogen
in the U.S. space program has contributed greatly to the understanding of
handling and storage techniques. Considerable information has been gained
about the embrittlement of metals in a high-purity hydrogen environment.
The safety record with hydrogen has been impressive; it suggests that the
widespread belief that hydrogen is intrinsically less safe than more
familiar fuels is probably not warranted.
Except for thermochemical decomposition of hydrogen, nearly
every aspect of the prophesied hydrogen energy economy has shown scientific
and engineering feasibility. In many applications, economic feasibility
is near. Furthermore, engineering improvements, together with the expected
rise in price of competing fossil fuel energy carriers, are almost certain
to increase the economically attractive uses of hydrogen.
2. Environmental Consequences
Research has demonstrated that internal and external combustion
engines can be operated easily and more cleanly on hydrogen. Hydrocarbon
and carbon monoxide emissions are reduced to those stemming from lubricating
oils, and nitrogen oxides are also greatly reduced. Consequently, hydrogen
used as a fuel in transportation systems offers the potential of cleaner
urban air. (However, many logistic and engineering hurdles impede such
application.)
48
-------
Used for energy storage and energy transmission by electric
utilities, hydrogen could lessen many of the aesthetic impacts and
emotional reactions associated with overhead electric transmission lines
and pumped hydro storage. If provided from independent sources, the use
of hydrogen in coal gasification or liquefaction would greatly improve
the utilization of coal resources and thereby reduce the annual amount
of land disspoilment or disruption.
Today's hydrogen energy technologies are not without their own
environmental problems, however. The electrolyzers now in operation emit
asbestos particulates and employ nickel catalysts. Since asbestos is a
known carcinogen and nickel is in short supply, health hazards and re-
source limitations will probably require new technical approaches to
electrolysis. The addition of a hydrogen production step in the energy
economy suggests that a lower overall system efficiency is to be expected.
An increased thermal discharge to the environment would, therefore, follow.
To make up for the net decrease in efficiency, more basic energy resources
would be needed.
H. Application of Control Technology
Identification of the environmental impacts associated with advanced
energy sources is of primary importance to formulation of strategies for
research and development leading to control over adverse effects. It is
also useful to consider the degree to which existing types of control
technology might be applied to pollutants released from advanced sources.
Although, as the preceding discussion in this section (further documented
in greater detail in the Appendices) shows, the advanced energy sources
differ significantly from conventional sources, they do produce pollutants
that are generally similar to those released by more ordinary energy
sources. As a result, it is natural to inquire about the adequacy or
49
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Inadequacy of existing control technology applied to the tie advanced energy
sources. Full examination of Huch technology would be a major undertaking
clearly beyond the scope of thin Initial planning study, Nevertheless, an
initial appraisal of the nature of the problem in direct application of
existing control technology to advanced energy sources and a preliminary
assessment of emission control technology from these sources it presented
below as an aid to program planning, It is followed by specific recom-
mendations for further work in this regard.
1. Nature of the Problem
The application of existing pollution control technology to
reduce environmental impacts from advanced energy sources is a multlfac-
eted problem. Clearly, an important consideration is the degree to which
technologies developed'for some other application can be employed directly
or modified for use with advanced energy sources. In some cases, even if
existing control technologies might be adapted to advanced energy sources,
it is not apparent that their efficiencies would be comparable to those
achieved in more common uses,
Critical as they may be, however, technological considerations
in application of pollution control technology cannot be separated from
economic factors, In other words, even the most attractive adaptation of
existing pollution control technology to advanced energy sources will fail
if it leads to unacceptable costs for installation and operation. The
record of the recent past Illustrates that there exist technologies to
control a wide variety of combinations of pollutants and sources. [See,
for example, "Compilation of Air Pollutant Emission Control Factors," U.S.
Environmental Protection Agency Report No. AP-42, Second Edition (April
1073)]. The degree to which the most efficient technology has been de-
ployed, however, is determined by economic factors, and such deployment Is
-------
certainly not universal, Further limitation* on technology applications
are exlitIng rules and regulations specifying equipment and procedures.
These institutional constraints also influence both economic and technical
activities. Difficult to define for conventional energy sources, these
are even more a deterrent to ready application to advanced energy sources.
The nature of the problem in assessment of existing control technology,
therefore, is that the utility of thin technology is determined by many
complexly Interrelated technical, economic, and institutional factors.
Consequently, a definitive account of the adequacy of existing control
technology for application to advanced energy sources 10 beyond the scope
of this report. Such an account would require that the control efficiency
be expressed as a function of cost. This report can, however, provide an
example of the needed research and a preliminary assessment of emission
control technology for advanced energy sources. This Is given below,
followed by recommendations for a comprehensive examination of the topic
as a part of planning for RfcD undertakings.
The approach to assessment of existing emission control technology
as applied to advanced energy sources may be formalized and systemized
through reference to a simple equation:
E •
-------
C = average efficiency of control equipment used in the
industry for the specific source
C = amount of application of control in the industry (on
a production capacity basis) for the specific source
For the present application to advanced energy sources, the following gen-
eral comments and qualifications are in order:
(a) P will be locally significant, but will be small in
relation to overall national energy production out to
the end of the century.
(b) P times ef, the national uncontrolled emission of the
pollutant, could become locally important, even though
small in comparison with other sources nationwide.
(c) C is obtained from some advanced energy pilot plant
c
experience and from some industrial processes that
are similar to the advanced energy processes.
(d) C is zero in cases where pilot plants for new energy
t
technologies have not applied any controls. However,
the concern of this report is the level of emissions
accompanying operation on a significant scale. Since
the installations for significant scale operations have
yet to be built, it is assumed that all of them will
include controls and C is taken to be unity in the
t
projections presented here.
It is clear that early goals of future R&D on advanced energy
sources should be (a) to reduce uncertainty on emission controls (and
other pollution suppression), and (b) to demonstrate the economical in-
stallation and operation of these controls from the outset in energy source
development. In this way, those who contemplate ventures for production
of energy from these sources will have technical guidance and encouragement
52
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in incorporating optimum control technology into their plans. Coupled
with economic incentives, this could lead to widespread application of
effective pollution control technology from the outset of developments.
2. Preliminary Assessment of Existing
Emission Control Technology
In illustration of the nature of the problem discussed above,
a preliminary assessment of the application of existing emission control
technology to advanced energy sources was performed. This assessment is
limited to consideration of the technology of the problem, and does not
attempt to provide coverage of the vital economic and institutional fac-
tors that will largely determine the deployment and operation of the tech-
nology. The foregoing indicates that such work needs to be carried out,
but it is incorporated here only to the extent that the present use of a
control system implies that its cost is not prohibitive in its present
application. It is expected that the costs of installing control tech-
nology as a part of new plants would be a smaller proportion of total
plant cost than is their present application. However, as indicated above,
the technical effectiveness of the control when applied to a new energy
technology is an important unknown.
The illustration presented below is based on emission control
technology because (a) many advanced energy sources yield pollutants to
the atmosphere, often in substantial quantities, (b) these pollutants
could, if uncontrolled and concentrated in sufficient magnitude in a
restricted area, result in adverse effects or hazards, and (c) there are
several standard reference works available to guide such an assessment.
Still, it must be recognized that the assessment suffers from several
serious weaknesses:
53
-------
(a) The actual control technology for advanced energy
sources is not established and that used in the
assessment often is drawn from more conventional
processes judged to be similar. This assumption
may not be valid upon deeper examination.
(b) The efficiencies of existing technologies may be
degraded when applied to advanced energy sources
owing to different operating conditions (e.g.,
saline waters of geothermal reservoirs and high
metal content of solid waste fuel). This needs
to be investigated in detail.
(c) Ambient environmental conditions in the vicinity
of advanced energy sources may be different in
degree or in character from those present at more
conventional sites, requiring more stringent con-
trols to safeguard or maintain environmental quality
(e.g., salinity in Colorado River Basin from oil
shale development).
(d) Standards for emission control for advanced energy
sources may not be identical to those employed for
other analogous conventional sources and therefore
the estimated control requirements may be misleading.
As pointed out in Section V, however, it is likely
that new technologies can be brought into compliance
with standards too strict for achievement by existing
technologies.
Despite these inherent limitations in analysis, it is useful to
have some idea of the capabilities and the applications of existing control
technology to advanced energy sources as a guide to program planning.
54
-------
Therefore, a preliminary assessment has been carried out. Three tables
present the results of this initial assessment for energy from geothermal,
oil shale, and solid waste sources. These advanced energy sources are in-
cluded because their direct emissions could become locally important in
coming years; solar energy is omitted because its effects are largely in-
direct. The tables illustrate the following points:
(1) Geothermal Energy—No need for control of NH or CH
* o 4
emissions has been established, so the focus is on
H S control. Table 15 presents some data relevant to
the control of hydrogen sulfide from geothermal energy
sources. Because refinery techniques to control H S
are not applicable to a gas flow that is mostly steam,
the operators of The Geysers power plant have had to
try alternative means to remove the H S from the gas
streams vented to the atmosphere. The 90 percent con-
trol indicated in the table has been achieved in tests
at The Geysers but has not yet been applied to routine
operations. Thus, the method of H S removal by catalyzed
precipitation of sulfur is one developed explicitly for
geothermal energy, but is not yet a completely demon-
strated method. There is also reason to believe that
the degree of control obtainable by this method may
not be adequate to achieve the strict California stan-
dard for ambient concentrations of H S. While there
2
are solid grounds for optimism regarding the eventual
success of this control at The Geysers, there is no
guarantee that it can be transferred to the more abun-
dant, but less developed, wet geothermal resources.
55
-------
Table 15
EMISSION AMD CONTROL OF HYDROGEN SULFIDB IN GEOTHERHAL ENERGY PRODUCTION*
0>
Emission^
Factor
' Cue kg/GJ
Percent
Control
Projected*
Annual
Emissions
10* kg
Control Technology
1. Comparison standard— 0.17
one-half the mass of
SO permitted from an
oil-fired steam gener-
ator1
2. Uncontrolled emission of 0.2
H 8 at The Geyseras(dry)
3. Emission of ELS with 0.02
control being developed
at The Geysers4
4. Uncontrolled H S from 1.0
high sulfur wells in
Imperial Valley8(wet
field)
S. H 8 from high sulfur 0.1
well with some control8
NA
1500
NA
Problems with the
Control Technology
NA
t/RaD Implication
90
90
1800
180
9000
900
None
Scrubbing in cooling tower
using iron or nickel to '
catalyze precipitation of
sulfate as sulfur
None
Scrubbing similar to that
developed for dry steam
at The Geysers
NA
May not meet ambient
standard for H S9
2
NA
Transferability of
control technology
not assured
Coal fired comparison standard is 0.26
kg/GJ;1 Meeting California ambient
H S standard may require emissions as
low as 0.004 kg/GJ3
Final teats early in 1974; Commercial
operation on new unit late in 1974;
Solid product must be sold or sent
to landfill
Serious effort on sulfur control awaits
demonstration of power plant feasibility;
Over 90 percent control could be
required3
NA - Not applicable
'Sources and notes are referred to by the superscripted numbers and are listed below.
Emission factors are in kilograms per 10* Joules of thermal energy brought to power plant. Multiplication by 2.3 gives the factor in Ib per 10* Btu. Conver-
sion from kilowatthours of electricity to gigajoules of thermal energy assumes a heat rate of 22 MJ/kwh (21,000 Btu/kWh or 16 percent thermal efficiency) for a
geotherul plant. Table 6 shows how geothermal emission factors compare to fossil fuel emission factors on both a per unit heat and per unit electricity basis.
Total emissions of 838 are projected on the basis of 4 x 1011 kWh of electricity produced at about 16 percent efficiency from 9 x 10* GJ of geothermal energy
delivered to generating plants. This level of production is predicted for the year 2000 in Figure 1 and Table S.
SOURCES AND NOTES:
1. Emission standards set by EPA for SO from fossil fuel steam generators. Published in The Federal Register, 23 December 1971.
2. Appendix B of this report estimates a control requirement of 98 percent baaed on a comparison of a box model calculation of the ambient concentration of H S
emitted by a 4500 MW geothermal generating capacity and the California ambient air quality standard for H S.
S, Calculated in Appendix B from data, given by J. P. Finney, "Design and Operation of The Geysers Power Plant,' in P. Xruger and C. Otte (ed.), Geothermal
Energy: Resources, Production, Stimulation, p. 148 (Stanford University Press, Stanford, California 1973).
4. G. V. Allen and B. K. McCluer of Pacific Gas and Electric Company in "Fifth Progress Report to the Public Utilities Commission of the State of California:
Geysers Hydrogen Sulflde Emissions Abatement Program" (28 December 1973).
5. M. Goldsmith, "Geothermal Resources in California—Potentials and Problems" EQL Report No. S, p. 32, California Institute of Technology, Environmental
Quality Laboratory (December 1971).
6. Assumes successful application of The Geysers control system to wet geothermal field.
-------
(2) Oil Shale—As indicated in Table 16, emission of SO , NO ,
; T- - ~~ X X
and particulates are expected from oil shale operations.
All retorting methods result in the formation of H S, and
&
it is conceivable that sulfur will be emitted in this
reduced form when it occurs in a gas of low heating value,
as is the case in all but the indirectly heated (Class IV)
retorts. Similarities between oil shale production and
other industrial processes suggest the possible applica-
tion of either desulfurizatlon plants used in refineries
or stack gas sulfur dioxide scrubbing plants envisioned
for boilers. In either case, 90 percent control can be
anticipated and may be adequate. However, both the per-
formance and the adequacy problems regarding sulfur emis-
sions from oil shale require further study.
Adequacy of the control depends on the comparison standard
adopted. While the Interior Department environmental
statement referenced in Tables 11 and 16 suggests some
difficulty in meeting the relevant Colorado emission
standards for sulfur, the EPA standards for fossil fuel
boilers cited for comparison in Table 16 are not far
from the uncontrolled emission factors. However, Table 16
should not be taken as an indication that there is no
serious problem. In addition to the Colorado standards,
there are two other criteria that suggest a substantial
control need: (1) The calculation of ambient air quality
cited as Source 10 in Table 16 implies that both sub-
stantial emission control and a very tall stack may be
needed to meet the EPA primary ambient air quality
57
-------
Table 16
EMISSIONS AND CONTROLS FOR AIR POLLUTANTS FROM OIL SHALE PRODUCTION*
Case'*'
Emission
Factor*
kg/BJ
Percent
Control
Projected^
Annual
Emissions
10 kg Control Technology
Problems with the
Control Technology
Comment/RU) Implication
Hydrogen Sulflde
-------
Table 16 (Continued)
Case'
Sulfur Oxides as 80,
(Continued):
2
15. Colony Oil Co, design
for desulfurlzatlon of
Class IV retort off
Projected^
Emission Annual
Factor* Percent Emissions
kg/GJ Control
160
12. Proposed control of 0.04 90
preceding in-situ
retort?
•
13. Uncontrolled Class IV 0.6 0 2400
retort, indirectly
. heated3
14. Moderate desulfuriza- 0.06 90 240
tlon of Class IV
retort off gas9
Control Technology
Stack gas scrubbing after
burning B S to SO
Ho desulfurlzatlon, only
combustion converting
V *° B02
Removal of H S prior to
combustion to 80
0.006 99 24 Low-pressure MKA (mono-
ethanolomine) process to
remove H S prior to com-
bustion to SO.
Problems with the
Control Technology
Cement/Rid) Implication
Reliability and cost
problems with stack
gas SO scrubbers"
NA
None identified
Not yet demonstrated
Assumes adaptability of one of the
80 scrubbing systems currently
being developed or demonstrated6
High (S percent) B S content of off
gas should make this level of control
readily attainable;8 This case, with
tall (250 m) stack, is calculated to
meet ambient SO standards10
Potentially an environmental advantage
of Class IV retorts
01
CO
Nitrogen Oxides as NO^
16. Comparison standard—
gas-flred steam gen-
erator1
0.09
.NA
360
NA
NA
Oil-fired comparison is 0.13 kg/OJ;
Coal-fired is 0.30 kg/GJ1
17. Hurl mum uncontrolled
emission level18
18. Maximum emissions,
low control13
19. Minimum uncontrolled
emission level19
20. Minimum emissions,
high control18
Particulatea:
21. Comparison standard--
fossil fuel steam
generator1
22. Uncontrolled16
23. Minimum emission from
anticipated processes
other then TOSCO II
0.020
0.016
0.013
0.003
0.04
0.1
0.003
20
NA
9717
80
64
50
12
160
240
12
retort
.16
None
Lime-slurry scrubbing
None
Combustion modification,
especially two-stage
combustion1*
NA
None
Wet scrubbing, bag filters,
dust suppression with water,
separators integral to the
oil production18
NA
Insignificant degree
of control
NA
Potential for causing
incomplete combustion
NA
NA
None identified
Not yet applied to oil shale
Bureau of Mines tests on coal
furnaces;14 not yet applied to oil
shale
Hypothetical case
-------
Table 16 (Continued)
Case'
Emission
Factor^
kg/GJ
Pe.rticula.tes (Continued):
24. Maximum emission from
anticipated processes
other than TOSCO II
retort18
25. Maximum emission from
anticipated processes
including use of the
Clas's IV TOSCO II
retort with fluid-bed
Projected^
Annual
Percent Emissions
Control 10skg
0.015
0.03
85l
70lfl
60
120
Control Technology
Wet scrubbing, bag filters,
dust suppression with water,
separators integral to the
oil production1
Wet scrubbing, bag filters,
dust suppression with water,
separators integral to the
oil production
Problems with the
Control Technology
None identified
Likely to be inade-
quate degree of
control
Comment/R&D Implication
preheater10
NA
*
Not applicable
Sources and notes are indicated by the superscripted numbers and are listed below.
"'The classes of retorts are those described in Appendix C.
^Emission factors are in kilograms per 109 joules. Multiplication by 2.3 converts the factor to lb/108Btu. The energy unit in the denominator of the
emission factor re ers to the heating value of the oil produced, which is taken to be 40 GJ/m3 or 6 million Btu/bbl. The commercial plant size assumed
throughout the Interior Department's environmental Impact statement Is 50,000 bbl/day, which amounts to an energy output in the form of oil equivalent
to 13,000 GJ/hr. It should be noted that the comparison emission standards are expressed as mass per unit of energy input to a steam generator. A
possible air pollution guideline for the oil shale industry would be to limit emissions at the production stage to a small fraction of those permitted
at the combustion of the fuel.
'Projected annual emissions are based on the production level of 105 X 10em3/yr (about 2 million bbl/day) given in Table 7 as an estimate for the
year 2000. This is 4 X 1018 Joules/yr as given in Table 2.
SOURCES AND NOTES: I
1. EPA new source standards given in The Federal Register, 23 December 1971.
2. S. Williamson, Fundamentals of Air Pollution, p> 390 (Addison-Wesley Publishing Co., Reading, Mass., (1973) gives California ambient standard for
one hour averaging time as 0.5 ppm for SO and 0.03 ppm for H S.
2 2
3. U.S. Department of the Interior, "Final Environmental Statement for the Prototype Oil Shale Leasing Program," Volume I, p. 1-18 (1973).
4. ibid., p. 1-40.
5. ibid., p. 1-19.
6. ibid., p. Ill-134.
7. Refinery experience indicates that 90 percent control cannot be achieved unless the tall gas from the desulfurization or sulfur recovery plant is Itself
cleaned by a separate process, probably SOg scrubbing. Reference: C. S. Russell, Residuals Management in Industry: A Case Study of Petroleum Refining.
p. 165 (Resources for the Future, Johns Hopkins University Press, Baltimore, Maryland, 1973).
-------
OJ
Table 16 (Concluded)
8. R. S. Greeley, "status of Stack Gas Sulfur Dioxide Control," Tbe MITRE Corporation (January 1973).
9. U.S. Dept. of Interior, op. cit., p. Ill-136.
10. ibid., p. III-146.
11. ibid., p. Ill-126.
12. ibid., p. Ill-129.
13. ibid., p. Ill-128.
14. G. A. Mills and H. Perry, "Fossil Fuel: Power and Pollution," Chemtech,•January 1973, pp. 53-63.
IS. Estimated to be over 30 times the controlled emission cited as Case 23. The reference of Case 23 gives no estimate of an uncontrolled emission factor.
16. U.S. Dept. of Interior, op_._ cit., p. III-133.
17. Reference 16 gives the emission factor, not the percent control. The percent control given here is an estimate based on expected performance of the
controls described in Reference 16. This assumption is the basis for the uncontrolled emission factor given as Case 22.
18. U.S. Dept. of Interior, op^clt., pp. 122-123, 132.
19. Derived from ratio of this emission factor to that adopted in Case 22 as the uncontrolled emission factor.
-------
standard for SO ; (2) It is reasonable to expect that emis-
sions from the production of a fuel can be reduced to only
a fraction (perhaps a tenth) of the sulfur emitted by the
burning of the fuel.
Table 16 indicates that the control needs for emission of
NO and particulates are not as critical as those for
sulfur emissions. By any'emission criterion, even the
requirement that emissions at the production stage be
less than a tenth those at the combustion stage, the con-
trol technology indicated for NO in Table 16 will be
adequate, if it is transferable to oil shale production
processes. In the case of particulates, there appears
to be a need for some reduction of the emission factor
from the TOSCO II retorting process.
(3) Energy from Solid Wastes—The emission factors given
above in Tables 13 and 14 were based on experience at the
Combustion Power Inc: .pilot plant and include the effects
of the controls in use there. Table 17 presents a more
general survey of both controlled and uncontrolled emissions
from other methods of processing solid wastes. As far as
air pollution is concerned, the Union Carbide pyrolysis
process looks very promising. Also, the transferability
of some incinerator control technology would be an asset.
Appropriate demonstrations and tests of these technologies
and their transferability merit immediate consideration.
3. Elements of a Research Program for Assessment
of Control Technology
Based on the work performed during this study, the elements of a
recommended research program for assessment of pollution control technol-
ogy for advanced energy sources can be identified. These include the
following:
(1) Refining the estimates of control requirements for
emissions, effluents, solid wastes, and land use
by taking into account the characteristics of the
regions where advanced energy sources will be
developed.
62
-------
Table 17
EMISSIONS ADD CONTROLS FOR AIR POLLUTANTS FROM PROCESSES PRODUCING ENERGY FROM SOLID WASTES*
Emission'
Projected*
Annual
Case
Factor Percent* Emissions,
kg/OJ Control 10ekg
Sulfur Oxides as SO :
1. Comparison standard-- 0.35
oil fired steam
generator1
HA
1400
Control Technology
NA
Problems with the
Control Technology
NA
CommentXRU) Implication
Coal fired comparison would be O.S kg/CJ1
2. Uncontrolled municipal 0.15
incinerator9
600
None
NA
Usually no SO control employed
3. Combustion Power Inc.
gas turbine8
0.1
33
4. Garrett pyrolysls pro- 0.35
ductlon of fuel oil4
400 Fluldized bed combustor
1400 None
None
NA
Easily meets standard because municipal
refuse Is a low-sulfur fuel
Emission factor, 0.1 kg/GJ at pyrolysls
plant and 0.2S kg/GJ at combustion of oil;
assumes no control at the combustion of the
oil; product oil is 0.3 percent sulfur by
weight.6
0
W
5. Union Carbine pyrolysls 0.007 95
production of fuel gas6
6. New York City, tests^t 0.04 75
73rd St. incinerator
28 Scrubber with basic aqueous
solution
ISO Medium energy wet
venturi scrubber
None identified
None identified
Plant waste writer requires treatment
Demonstration experiment, preliminary
results
7. British Incinerator
experience6
0.06
Nitrogen Oxides as NO :
2'
8. Comparison standard— 0.09
gas-fired steam
generator1
60
NA
240
360
Wet collectors
NA
Corrosion can be
caused by HC1 In
the gas stream
NA
Other possible comparisons1: oil-fired,
0.13 kg/OJ; coal-fired, 0.30 kg/GJ
9. Uncontrolled municipal 0.15
incinerator3
600
None
NA
Usually no NO control attempted
10. Combustion Power Inc.
gas turbine3
0.2
800
Fluidized bed combustor
Inadequate control Model tests had indicated better NO
control than demonstrated here
11. Garrett pyrolysis
production of fuel
oil*
0.2
800 Liquid scrubber integral to
the pyrolysls system; None
at combustion of the oil
Inadequate control Emission factor at pyrolysis plant is only
at combustion stage a tenth of total (0.02 kg/GJ)
12. New York City, tests 0.003 98
at 73rd St. incinera-
tor
13. British incinerator 0.05 67
experience8
12 Medium energy wet venturi
scrubber
200 Not indicated
None identified Emission factor for N increased by factor
of ten if emissions In reduced form as
NH are included; preliminary results
3
Not indicated Worst case has twice this emission factor
-------
Table 17 (Continued)
Case
Projected
Emission Annual
Factor, Percent Emissions,
kg/OJ Control Ip'kg
Hydrocarbons as CH .
14. Companion standard—
none exists
IS. Uncontrolled municipal 0.08
incinerator8
NA
Control Technology
NA
320 None
Problems wlth the
Control Technology
NA
NA
Comment/RtD Implication
Generally combustion is so complete that
emissions from stationary sources are
negligible
16. Combustion Power Inc. 0.015
gas turbine3
80
60 Fluldlzed bed combustor
None
Carbon Monoxide:
17. Comparison standard-
none exists
NA
NA
NA
Generally combustion is so complete that
emissions from stationary sources are
negligible
OS
18. Uncontrolled municipal 2
incinerator8
19. Combustion Power Inc. <0.04
gas turbine3
>98
8,000 None NA
<160 Fluidized bed combustor None
Chloride as HC1:
SO. Comparison standard— 0.2
a British recommenda-
tion6
NA
800
NA
Maximum HC1 content In flue gases recommended
by The Alkali Inspector in Britain
21. Uncontrolled munlci- 0.4
incinerator9
1600 "one
NA
RC1 emissions depend primarily on polyvinyl
chloride content of the refuse
22. Combustion Power Inc. 0.1
gas turbine3
75
400 Fluldlzed bed combustor
None
Alkaline content in waste is presumed to
absorb some HC1 during the combustion
23. New York City, tests 0.01
at 73rd St. Incinera-
tor7
97
40
Medium energy wet
venturi scrubber
None identified
Preliminary results
24. British incinerator 0.05
experience8
87
200
Wet collectors
Corrosion unless
alkaline solu-
tion used
-------
Table 17 (Continued)
CM*
BmlBaion
Factor, Percent
kg/GJ Control
Paxtlculates:
8B. Comparison »tandard~ 0.04
fossil fuel steam
generator1
26. Uncontrolled munioi- 2
pal incinerator8
NA
27. Combustion Power Inc.
gas turbine3
0.08
96
Projected
Annual
Emissions,
10° kg
160
8000
320
Control Technology
NA
None
Baffled aettllng chanter
followed by two stages of
cyclone separation, 6-lnoh
and 3.6-inch
Problems with the
Control Technology
NA
NA
Clogging by molten
ash deposits;
Inadequate control
of fine partlcu-
lates; this is beat,
not typical, con-
trol
it/RtiD Implication
Incinerator standard of 0.18 g/m3 at 12
percent CO would mean a comparison
standard of 0.08 kg/OJ1
Most incinerators control 60 percent of
this through settling chamber and water
spray*
Clogging alleviated by water injection;
control of fine particulars in a high
temperature (>700°C) gaa stream is a
significant problem in this and other
processes
28.
cn
Oarrett pyrolysls
production of fuel
oil4
29.
Union Carbide pyrol-
ysls production of
fuel gas6
30. Chicago Northwest
Incinerator'
.10
0.06 97 240 Cyclone separator followed
by liquid scrubber are
integral td pyrolysis
system; bag filter used
on cooled gas emitted at
pyrolysls plsnt; control
at oil combustion not
specified
0.012 99.4 48 Electrostatic precipltator
followed by scrubbing with
basic aqueous solution
0.04 98 leo Electrostatic preolpltator
of 96.8 percent design
efficiency
None identified
None identified
Somewhat lower flue
gas temperature
could result in
corrosion of pre-
oipitator by con-
densed acids11
Emission factor at pyrolysls plant is 0.02
kg/GJ (99 percent control); oil combustion
assumed to meet 0.04 kg/GJ steam generator
standard
Pyrolysls furnace itself credited with 96
percent control; leaks at pyrolysis plant
assumed negligible; emission only when
cleaned product gas is burned
Electrostatic preolpltator has potential
for adequate control when temperature and
content of flue gas permits its use
31. New York City, tests
at 73rd St. Inciner-
ator7
0.07 96.8 280 Settling chamber and
medium energy wet
venturi scrubber
None Identified
Preliminary results
32. Coventry, England,
incineratorla
0.2 90 800 Electrostatic preolpi-
tator said to be 96.S
percent efficient
Inadequate control
33. British incinerator
experience*
0.1 95 400 Usually electrostatic
preoipltators of 97
percent efficiency; A
few cases of cyclone
separators
Inadequate control
Mechanical collectors said to be 80 percent
efficient and wet collectors 92 percent
-------
Table 17 (Continued)
Case
Fine Particulates (<5|im):
34. Comparison atandard—
none exlata
35. Uncontrolled Inciner-
ator with a typical
high fraction of fine
parti dilates
36. CoBbustlon Power Inc.
gaa turbine3
37. SRI calculation
Projected
Emission Annual
Factor, Percent Emissions,
kg/OJ Control 10°kg
NA
O.S
0.08
0.07
84
86
2000
320
280
Control Technology
HA
Hone
Baffled settling chamber;
6-inch cyclone; 3.5-lnch
cyclone
Two stages of 6-lnch
nulticyclone
Problems with the
Control Technology
NA
HA
Clogged by nolten
ash unless water
injected
HA
Comment/RiD Implication
Assumes 25 percent of mass consists of
participates < Sum; consistent with British
experience6 and BAHCO analysis13
Represents best performance, typical may
be only 60 percent control
Based on size distribution of caae 35 and
collection efficiencies oited by EPA14
OS
0>
HA • Hot applicable
*
Sources are referred to by the superscripted numbers and are listed below.
Emission factors are in kilograms per 109 joules. Multiplication by 2.3 gives the factor In Ib per 10* Btu. The factors given have been calculated
from values given in the references cited by assuming that each kg of solid waste is one-fourth carbon by weight and has a heat value of 9 HI (4000
Btu/lb). It happens that the common incinerator emission unit of 1 gr/scf at 12 percent CO converts to almost exactly 1 kg/OJ.
^Percent control is calculated here by comparison to the uncontrolled emission given as the second case under each pollutant category. Actual measure-
Bents preceding and following the control devices used in the various cases cited would generally give a different value for control efficiency due to
differences between each source and the average uncontrolled emission adopted.
»The total energy value of the solid wastes processed to recover energy Is taken here to be 4 x 1018 J/yr. This is about 5 percent of present annual
energy consumption in the United States and about 2 percent of that projected for the year 2000. Table 13 gives the energy value of solid waste
expected to be processed for energy In 1975 as only 0.01 x 10*8 J/yr.
SOURCES:
1. EPA emission standards for fossil fuel fired steam generators published 23 December 1971 In The Federal Register.
2. EPA, Office of Air Quality Planning and Standards, Compilation of Air Pollutant Emission Factors, Second Edition, p. 2.1-3 (April 1973).
3. R. H. VandexVolen, "Energy from Municipal Refuse through Fluldized Combustion: The CPU-400 Pilot Plant," paper presented at 66th Annual Meeting
of AIChE, November 1973.
4. SRI study of the Carrett process.
' 5. R. W. Borlo, "combustion and Handling Properties of Oarrett's Pyrolyttc Oil," Final Report of Combustion Engineering, Inc., Project 900127,
December 1972. •
-------
Table 17 (Concluded)
6. Private coonnmlcatlon from R. S. Paul of Union Carbide Corporation.
7. E. F. Gilardi and B. F. ScU.lt, "Comparative Result* of Sampling Procedures Used During Testing of Prototype Air Pollution Control Devices at
Hew York City Municipal Incinerators," Proc. 1972 Rational Incinerator Conference. ASMS, pp. 102-110 <1972).
8, R. B, Watson and J. H. Burnett, "Recent Developments and Operating Experience with British Incinerator Plant," ibid., pp. 155-165.
9. E. R, Kaiser and A, A. Carottl, 'Municipal Incineration of Refuse with 2% and 4% Addition of Four Plastics," Department of Chemical Engineering,
New York University, New fork (June 1971),
10. G. Stabenow, "Performance.of the New Chicago Northwest Incinerator," ibid., pp. 178-194
11. F. R. Rehn, discussion of Stabenow paper, Discussions 1972 National Incinerator Conference, ASHB, pp. 25-26 (1972).
12. N. Rayaan and P, J. Scott, "Design of a Refuse Incineration Plant for the City of Coventry, England," Proc. 1972 N.I.C., op.cit., pp. 186-17.7.
13. Midwest Research Institute, "Participate Pollutant System Study, Volume Ill-Handbook of Emission Properties," p. 523 (May 1971).
14. EPA, Office of Air'Quality Planning and Standards, op.cit., p. A-3.
O>
•4
-------
(2) Surveying the existing control technologies that
may be appropriate to the environmental impacts
identified for the advanced sources.
(3) Specifying the technical problems and limitations
associated with these existing control technologies
in new applications.
(4) Analyzing the economics of the transferability of
those control technologies from their present uses
to advanced sources and the impact upon overall
energy production costs.
(5) Preparing detailed research and development program
plans for control of pollutants from advanced energy
sources.
68
-------
V GENERAL RECOMMENDATIONS FOR CONTROLLING ENVIRONMENTAL IMPACTS
FROM ADVANCED ENERGY SOURCES
A. Introduction
EPA is involved in research and development related to new energy
technology in order to ensure that the goal of an adequate national energy
supply is achieved with acceptable impact on the environment. From its
extensive experience in observing, regulating, and ameliorating the adverse
impacts of the several energy technologies currently dominant, EPA recog-
nizes the considerable advantages of incorporating environmental protection
measures into developing technologies rather than taking remedial steps
after a technology is in use on a large scale. This consideration is
especially important in the context of energy technology, because huge
investments in long-life capital equipment are required. Although EPA
is not in a position to develop the clean energy sources desired, it can
ensure that those responsible for development give adequate consideration
to environmental protection measures so that an environmentally acceptable
product results.
The standard-setting authority of EPA has been essential to control
the pollution from existing facilities and technologies. This authority,
however, should not be reserved only for present pollution problems; it
is perhaps even more useful in guiding the development of future technology.
Experience with regulations concerning use of a retrofit device or an
add-on process has shown that this approach is extremely expensive and
usually achieves rather limited pollution abatement. Given appropriate
and timely advance standards set by EPA, the producer of an energy technol-
ogy can utilize his expertise to find the optimum way to meet the standards,
69
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Provided that the standards reflect a proper balance between techno-
logical feaHibility and environmental quality, the virtues of the early
setting of a standard are apparent, Through monitoring, modeling, and
studies of health effects, EPA is improving its knowledge of environmental
quality requirements. Knowledge of the frontiers of relevant technology
Is required lor the proper weighing of technical feasibility. One purpose
of this report by SRI is to help meet the EPA need for such knowledge.
The contribution of EPA toward the goal of an adequate supply of clean
energy goes beyond the setting of standards. Through projects concerned
with the technology of the future, EPA has seized the opportunity to in-
fluence technological feasibility In the realm of pollution control. While
standards are necessary to guide the design of energy technology, they can
be expected to change with developing technology. One factor bringing
about such change is EPA support for projects that may demonstrate the
technical and economic feasibility of significantly higher standards.
B. Support for Improved Technology
It Is within the mission of the Environmental Protection Agency to
support research and development efforts to improve technology for the
control of pollutants emitted by advanced energy sources. The subjects
recommended in the next section (see Section VI-C-2) for inclusion in a
research and development program involve such support, particularly where
the present study has identified environmental Impacts that are likely to
be unacceptable if no more than current control measures are employed.
Support for the improvement of technology not designed primarily as
control technology can also be Justified as part of the mission of EPA
when the new technology has the potential for improving environmental
quality by supplanting a more polluting technology. Therefore, some of
our recommendations call for supporting the development of certain element!
of energy production technology that offer environmental advantages; thoie
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in Section VI-C-3 pertaining to geothermal energy development fall in this
category. Because the development of geothermal technology is also within
the mission of other federal agencies (such as the Atomic Energy Commission
and the National Science Foundation), further investigation by EPA may
reveal that environmental goals are already being adequately served without
the need for direct EPA involvement at the present time.
Recommendations given in Section VI-B pertaining to solar energy,
underground coal gasification, and hydrogen as an energy carrier, have
implications for eventual EPA support of new energy production technologies.
C. Support for Demonstration of Economic Viability
Although the technical work on advanced energy sources and control
of associated environmental Impacts is important, it is equally important
to demonstrate conclusively the economic viability of technical accomplish-
ments. It would be of little use to prove that some technique, apparatus,
or material would result in complete pollution control if the related costs
are so great that they preclude deployment.
To overcome the uncertainties of the costs of a particular pollution
control scheme, a demonstration in an operational situation is often nec-
essary. While no economic demonstration activity is explicitly recommended
In Section VI, such demonstrations would logically follow the technical
work suggested. Of course, the government or its contractors should not
replace the private sector in determining the economic viability of a new
process. However, It seems apparent that EPA can and should bring some
technologies to the stage where the private sector has a clear incentive
to pursue the demonstration of economic feasibility. An incentive could
be supplied through enunciation of standards, but in many cases, legal or
practical considerations may, Instead, lead EPA to support some demonstrations
of economic viability prior to the setting of standards.
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D. Use of Standards at Various Stages of New Technology
The use of standards that set the limits of allowable pollutants re-
sulting from industrial activities is widespread and enforcement of these
standards provides the major incentive for industry to undertake environ-
mental protection measures. Thus, through the use of standards, EPA is in-
directly bringing the expertise of industries to bear on solution of their
own pollution problems. This approach, therefore, multiplies the effort
going into the development of environmental protection technology.
Some specific areas where new or revised standards could be useful
in reducing adverse effects of energy production are listed in Section
VI-C-1. To stimulate successful environmental protection measures effec-
tively, the standards must be formulated sufficiently early that improve-
ments can be incorporated efficiently into the design of technologies.
The standards must also be strict enough to prevent undesirable effects
when a small industry scales up to become a mature industry fully ex-
ploiting the available resources. There is, of course, no guarantee that
technologies compatible with existing technologies will also be adequate
to prevent undesirable effects from eventually occurring. However, the
chance of achieving both goals is greater for a completely new technology
than for one already frozen in a particular pattern. The earlier the in-
teraction between the requirements of environmental quality and the technical
constraints, the more likely that a successful resolution will occur. Rec-
ommendations in Section VI-C-1 call for the initiation of the studies
needed to set adequate environmental protection standards. As the advanced
energy technologies proceed through the anticipated stages of their de-
velopment towards deployment, somewhat different considerations (indicated
in the sections that follow) will prevail.
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1. Development
During the development stage of the technology to obtain energy
from advanced sources, it is appropriate to use existing standards applicable
to related industries as guidelines. This procedure will avoid both the
premature constriction of a new technology and the waste of EPA resources
on insignificant sources of pollution. Such comparisons to formal standards
for related processes are made at various points in this report.
A key purpose of development operations should be to determine
the species and quantity of pollutants released so that approaches to
their control can be devised. Some of the recommendations for further
research, listed primarily in Section VI-C-4, are directed toward this
goal.
Formal guidelines or standards are desirable to facilitate the
incorporation of environmental protection into the design and cost assess-
ment of developing energy technologies. But the need for an early enun-
ciation of the standard sometimes conflicts with the need to avoid the
establishment of a misleading guideline. Erroneous standards, if too
strict, can unduly discourage promising techniques or, if too lenient,
unduly encourage an environmentally unsound technology. Until the data
can give confidence that the right balance between environmental, ec-
onomic, and technical considerations can be struck, extrapolations from
existing standards provide the best guidelines.
2. Early Commercial Operation
The term "commercial" implies that a technology has developed
to the point that an operator has decided to deploy the technology in
the belief that it will prove economically feasible. Whenever deployment
results in undesirable environmental consequences that cannot be mitigated
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without the imposition of an economic penalty that destroys the feasibility
of the project, it can be concluded that there has been a failure in the
environmental management at the technological development stage. In rec-
ognition of its responsibility to help prevent this kind of failure, EPA
is pursuing studies such as this one.
Reaching the early commercial stage implies that technical and
economic uncertainties have been overcome sufficiently to attract some
investment capital. Uncertainties regarding environmental impact also
should have been reduced substantially by experiments performed during the
development stage. These experiments can provide a basis for further re-
ducing environmental and economic uncertainties and for the setting of
specific standards to be met by the new technology. However, the fact
that the deployment of the new technology is still very limited at this
stage makes it possible to allow the first commercial plants to temporarily
exceed the standards that will eventually be needed to accommodate a mature
industry based on the new technology. To minimize uncertainty at this
stage, promulgation of a standard based on present feasibility for the
early commercial installations is needed together with some formal in-
dication of the standard that is expected to be met by the eventual full
sized industry. Subjects recommended for standard setting activities are
listed in Section VI-C-1.
3. Significant Scale Operation
The advanced energy sources considered in this report will not
be major contributors to the national energy production before the end
of this century (see Section IV). However, local or regional environ-
mental effects of the new energy technologies will be appreciable during
the 1980's. During the decade of the 1980s, EPA will most probably be
concerned with setting standards applicable to new energy technologies
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operating at significant scales of production. As a result of anticpating
attention to the development of these new technologies, EPA may find that
the requirements of environmental protection are consistent with technical
and economic feasibility.
E. Strategy for Dealing with Indirect Impacts
Besides direct impacts, there can be many indirect environmental
consequences. Most recommendations in Section VI are in response to
identified direct environmental impacts. However, as emphasized in the
summary of solar energy (Section IV-A), most of the environmental impacts
of that technology are indirect. The distinction can be put as follows:
• Direct impacts result from activities comprising the
sequence of operations leading to energy production
(e.g., mining, crushing, retorting, and disposing of
oil shale).
• Indirect impacts have their environmental effect at the
site of other activities required to support the advanced
energy development (e.g., emissions from the smelting of
copper to be used in the construction of rooftop collectors
of solar energy).
Recommendations for research and development related to the control
of indirect impacts appear primarily in Sections IV-A and VI-B-1. These
recommendations include a suggestion for the establishment of communications
links with the developers of solar energy technology and for viewing ex-
isting new source standards as controls on the indirect impacts of solar
energy.
Through communication with the developers of solar energy, EPA can
work to minimize the indirect impacts of the eventual technology by di-
recting attention to the environmental effects of activities such as the
production of materials and shifts in population. The existing liaison
between EPA and NSF, the federal agency with principal responsibility for
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solar energy development, has already been used to initiate such communi-
cations. Recommendations in Section VI include calls for communication
with developers of technology for the use of hydrogen and underground
coal gasification, but these activities have a lower priority than solar
energy.
Through the formulation and enforcement of standards for new sources
of emissions and effluents, EPA has a means of controlling indirect, as
well as direct, impacts of new energy technology. To cite again the solar
energy example, the deployment of solar energy collectors on a significant
scale will appreciably increase the demand for certain materials and will
therefore necessitate the expansion of the industries producing these
materials. Appreciable expansions are subject to the standards for new
sources of pollution, once EPA has promulgated them for a particular
industry or process.
A third recommendation for dealing with the indirect impacts of
advanced energy technologies is presented in the separate section below.
This is the recommendation regarding the use of the energy efficacy
concept.
F. Energy Efficacy as an Indicator of Environmental Impact
1. The Concept
Except for acts of philanthropy, the economic system is based
on the concept of profit; only those endeavors that generate monetary
return in excess of investment are pursued. This principle has an analog
in energy economics; in order to remain viable, energy systems must generate
more net energy than they themselves consume in all the steps of their
operations. The use of energy by an energy resource system is illustrated
in Figure 3. As long as mankind is capable of locating and extracting
76
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ENERGY SYSTEM
EXPLORATION
PRODUCTION
DISTRIBUTION
EXPENDABLE
MATERIALS
MATERIALS
PRODUCTION
RECOVERABLE
MATERIALS
UNRELATED
END-USE
CONSUMPTION
SA-2714-7
FIGURE 3 ENERGY SYSTEM
fossil fuels, it is not difficult to maintain an apparent status of net
energy gain in return for exploration, development, extraction, and re-
fining activities. This situation, however, is somewhat analogous to
withdrawing money from the bank and pretending it is wages. Nature has
stored energy resources upon which mankind is now drawing.
In anticipation of the future, when mankind may be forced
to draw upon an "income" energy resource (such as solar), it is important
to develop an index that reveals whether an energy collection technology
is generally worthy of development, an index that takes into account all
direct and indirect impacts.
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Energy efficacy, defined here as the ratio between the net
usable energy output and the sum of all required energy inputs, can be
used to evaluate the value of a given technology. The greater the energy
efficacy coefficient, the greater the profitability of the technology
(measured in energy terms). The energy efficacy equation is
Energy efficacy = Energy available for unrelated use
Energy consumption related to energy system
Technological options should obviously be pursued among only those technol-
ogies with an energy efficacy index greater than 1.0 (the break-even point).
If it were found, for example, that a certain solar energy technology
system were to require an expenditure of more energy in its production and
operation than it could collect and make available during its lifetime,
then it could be concluded, justifiably, that the technology must be im-
proved or abandoned.
In the computation of the energy efficacy coefficient, it is
essential to draw the system boundaries realistically enough to include all
the truly important energy inputs. A complete vertical analysis is re-
quired. For example, if an energy technology consumes steel, then it is
important to include not only the energy required for steel making and
metal forming, but also the energy expended in mining and transporting the
necessary iron ore, coking coal, and limestone. Vertical analyses generally
reveal that the indirect energy consumption greatly exceeds the obvious
direct energy consumption.10'11 For instance, although Alcoa reports 2
that present day aluminum production requires about 22 kWh/kg, a vertical
analysis h
80 kWh/kg.
analysis has shown that the total energy input into aluminum is about
10
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It may seem that evaluation in energy units would be redundant
to an evaluation in monetary terms and that to determine the energy ef-
ficacy of a given technology would require only the application of a con-
version factor. Unfortunately, there are at least two reasons why no
simple conversion is possible. First, the amount of labor required for
different technological systems varies widely. For example, a petroleum
refinery exhibits a high degree of automation, while silicon solar cells
currently require manual assembly. Second, there are major differences
throughout the economy in the price of energy; 3 these depend upon the
type of energy, the volume of purchase, corporate arrangements, and
regulatory factors. Consequently, the apparent redundancy between monetary
and energy measure is, in fact, largely illusory. In fact, the lack of
proportionality between monetary and energy measurement scales can obscure
the potential of some energy technologies that appear too expensive in
monetary terms, but which actually yield a good return on energy invest-
ment.
It has, nevertheless, recently been possible to convert the
monetary input/output matrix of the U.S. economy (for 1963) into an energy
input/output matrix by giving attention to the complicating factors men-
T *^
tioned. The energy input/output matrix currently available can be used
to trace the flow of energy between energy sectors of the economy. An
energy sector submatrix of the U.S. economy is shown in Table 18. From
13
these numbers and ancillary information, it is possible to determine
roughly the energy efficacy of three of the most important contemporary
basic energy resource technological systems—coal, petroleum, and gas
(see Table 19). The efficacies for these contemporary technologies are
surprisingly low, especially for petroleum and gas. The reasons behind
these low efficacy figures are difficult to itemize fully. However,
much of the energy consumed by these energy systems goes to functions that
are easily overlooked, such as the function of providing ventilation in
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Table 18
ENERGY INPUT/OUTPUT SUBMATRIX OF THE U.S. ECONOMY"
(1963)
^""^-^x^Seller
Buyer *>x>^
Coal raining
Petroleum
refining
Electric
utilities
Gas utilities
Coal
Mining
9.7
41
90
6.8
Petroleum
Refining
2.7
250
35
15
Electric
Utilities
1.4
14
47
1.9
Gas
Utilities
2.0
200
49
150
* 12
All energy is expressed in units of TWh (10 Wh) to two
significant figures.
Source: Herendeen
13
Table 19
ENERGY EFFICACY COEFFICIENT FOR CONVENTIONAL
TECHNOLOGICAL SYSTEMS
System
Coal mining
Petroleum
refining
Gas utilities
Nuclear fission
reactors (LWR)
Efficacy
42
4.8
5.9
<32
Comment
Excludes energy re-
quired for delivery
to final demand.
Excludes energy re-
quired for delivery
to final demand.
Based entirely upon
energy consumed by
gaseous diffusion
isotopic enrichment
of fuel.
Source
Reference 13
Reference 13
Reference 13
References 14,
15
80
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underground coal mines. The situation is likely to be similar for under-
ground oil shale mines.
The energy input into materials expended in resource recovery
is even more easily overlooked. For example, steel casings routinely used
by the petroleum industry to line oil wells or geothermal wells represent
a sizable investment in an energy intensive material that is often un-
retrievably expended. An analogous situation can be found in underground
coal mining where steel bolts designed to prevent roof collapse are fre-
quently left behind after the deposit has been mined out. A representative,
but incomplete listing of important energy inputs to conventional energy
industries is given in Table 20. Of course, an important distinction must
be made between materials that are consumed by the energy system in a
fashion that does not allow their ultimate recovery for recycling or reuse
(such as the steel casings in an oil well) and materials that are re-
coverable in the future (such as the steel in an oil refinery). It is
therefore significant, for example, that in terrestrial solar energy in-
stallations, there will be only a negligible amount of material expended
irretrievably. In a sense, therefore, the vast materials demands of solar
energy collectors are "deposits in a materials bank" that could possibly
be withdrawn later for reuse.
Data sufficient to determine the energy efficacy coefficient for
nuclear fission is apparently uncollected, but an upper limit is readily
obtained by consideration of only the isotopic enrichment of uranium in
the nuclear fuel cycle. This limit is shown in Table 19.
One of the most important uses of the energy efficacy coeffi-
cients for conventional energy resources will be as a conceptual design
guideline for the development of new energy technologies. The American
economy can clearly function using energy efficacy indexes as low as
about five (see Table 19). Thus, new energy technologies should ultimately
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Table 20
ABBREVIATED LIST OF IMPORTANT USES OF ENERGY
AND ENERGY INTENSIVE MATERIALS IN CONVENTIONAL
ENERGY TECHNOLOGY SYSTEMS
System
Energy Use
Materials
Coal (underground)
Elevators
Ventilators
Conveyors
Crushers
Boring machines
Hauling
Steel for roof control
Steel for rails
Petroleum
Drilling (includes
dry holes)
Crude oil pumping
Pipeline pumping
Hauling
Refinery process
heat
Steel for well casings
Drilling clays
Tetraethyl lead
Nuclear fission
reactors (LWR)
Uranium mining
Isotopic enrichment
Pumping of heat-
transfer fluid
Pumping of power-
plant coolant
Fuel rod cladding
Isotopic separation
membranes
Radioactivated materials
used in processing and
structures
be viable and the general economy should be sustainable if they can meet
or exceed the indexes of petroleum and gas. As an example, upper limits
to the energy efficacy index for the various forms of solar energy have
been estimated, based upon the considerations given elsewhere in this
report. These are given in Table 21. Although it must be emphasized that
the true efficacy will be lower than these estimates because many factors
have been neglected, it can be concluded that a satisfactory performance
for certain solar energy technologies is probably attainable.
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Table 21
ESTIMATED UPPER LIMITS TO THE ENERGY EFFICACY
COEFFICIENT FOR SOLAR ENERGY TECHNOLOGIES*
System
Energy Efficacy
Coefficient'''
Comment "f
Energy plantations
<3
Ocean thermal
gradients
Photovoltaic system
(large satellite)
Photovoltaic system
(large terrestrial)
Thermal system
(large plant)
<6
<27
<55
Thermal system
(small plant, on
buildings)
<56
Electric output. American
Southwest. Assumes three crops
per year, field drying, and
combustion to generate elec-
tricity. Energy costs of pro-
viding inter basin water trans-
fer for irrigation are included.
Electric output. Considers only
energy input into material (alu-
minum) for boiler, condenser,
and cool water intake conduit.
Electric output. Published pro-
jections revised to account for
indirect energy inputs into ma-
terials.
Electric output. Considers only
total energy input to aluminum
support structure for solar cell
array.
Electric output. Considers only
total energy input to aluminum
support structure (which may
form part of collector) and
double glazed glass cover.
Heat output. Considers only
total energy input to copper
rooftop collector and double
glazed glass cover.
Thirty-year installation lifetimes are assumed.
Consideration of additional energy inputs necessarily reduces
the energy efficacy coefficient.
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2. Environmental Implications
It is now clearly discernable that energy extraction, trans-
portation, processing, storage, distribution, and consumption activities
are the most significant sources of environmental degradation in the
United States. This fact, unfortunately, is not widely appreciated;
disemination of the recent document entitled "Energy and the Environment—
Electric Power" by the Council on Environmental Quality 6 is intended to
convey this message to the public.
Besides its obvious utility as a measure of the value of new
energy technologies, the energy efficacy coefficient should prove to be
an important indicator of environmental impact. The evidence is abundant
(but disorganized and dispersed) that the path of least energy consumption
is also the path of least disruption and insult to the environment. Cog-
nizance of this principle is implicit in an Oak Ridge National Laboratory
analysis of the resource recovery issue in waste management that pointed
out the many concomitant opportunities for energy conservation and en-
vironmental quality preservation raised by well designed recycling pro-
1?
grams. The principle should be no less true for energy technologies
themselves.
By use of the energy efficacy coefficient, for example, one
could infer that solar energy technologies will create significant, although
indirect, environmental impacts irrespective of the often-cited claims to
the contrary articulated by solar energy advocates. Besides its use as
a macroscopic indicator that could be used to rank the desirability—in
environmental terms—of new energy technologies, the very same vertical
analysis categorizing the energy inputs necessary for the derivation of
*
the energy efficacy coefficient would provide a firm base for the compila-
tion of indirect environmental consequences. Considerable further work
is required, however, in order to perfect the concept and permit it to be
employed as an analytical tool to guide decision making.
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3. Implications for EPA Activities
As part of its evolution to an agency that anticipates events
and influences developments important in the environmental arena, EPA
might find it worthwhile to sponsor further research to determine the
energy efficacy coefficient for present and future energy technologies.
In addition, EPA could detail the relationship between impairment of
environmental quality and energy utilization, and thereby document the
usefulness and significance of the energy efficacy concept as an indicator
of environmental impacts. EPA could develop a methodology to incorporate
the energy efficacy concept into the planning process. Success in this
endeavor would logically be followed by development of an analogous "energy
utilization" coefficient that would be applicable to any existing or pro-
posed technological system. Use of this latter coefficient could be
expected to yield results important for the ordering of EPA priorities
and environmental quality control.
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VI RECOMMENDATIONS FOR ADVANCED ENERGY
RESEARCH AND DEVELOPMENT PLANNING
The analyses of advanced energy sources (summarized in Section IV
and detailed in the Appendices) resulted in a number of specific recom-
mendations for further research and development. These recommendations
are compiled in this section and classified by type and priority. They can
be used to define the elements of a future research and development
program.
A. A Listing of Control Requirements
This study of advanced energy technology has led to the identifica-
tion of some areas where controls should be required to prevent unaccept-
able effects on the environment. These areas are listed below under the
energy sources in the order in which the sources appeared in Section IV.
1. Solar Energy
Because solar energy technologies appropriate for large-scale
use are currently less clearly defined than others under consideration,
and, moreover, because their environmental impacts are generally indirect,
the following items are not strictly analogous to the entries in other
categories. Control requirements should include:
• Development of design guidelines concerning materials
likely to be used in solar energy collections to ensure
- Minimum consumption.
- Avoidance of materials that may release toxic sub-
stances when eroded by long exposure to the natural
environment.
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- Selection of materials that require the least energy
in their production.
- Avoidance of the use of scarce elements (e.g., Ga).
- Choice of materials that can be recycled easily upon
normal retirement or breakdown.
Development of operations guidelines and initiation of
legislation or precedent-setting case law in areas con-
cerning
- Land use.
- Solar energy collection in international waters.
- Releases of hazardous materials in accidents (espe-
cially for ocean thermal gradient installations).
- "Sun rights" (analogous to mineral rights).
2. Geothermal Energy
Control requirements for geothermal energy should include :
• Substantial reduction of hydrogen sulfide emissions from
dry steam field at The Geysers.
• Isolation of geothermal brine by means of closed-cycle
generating systems.
• Prevention of ground-water contamination during reinjec-
tion of geothermal fluids.
• Treatment or reclamation of saline geothermal waters.
• Reduction of need for fresh cooling water in dry regions.
• Land use consistent with noise, subsidence, construction,
and depletion associated with development of a geother-
mal energy field.
3. Oil Shale
Control requirements for energy production from oil shale should
include:
• Rehabilitation of spent shale disposal sites to a state
consistent with land-use plan and by means consistent
with water supply.
87
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•
Isolation of process water from fresh- water system
(realizing "zero-discharge").
Sulfur dioxide control: emission of the gas itself and
possible leaching if it is absorbed in shale residue in
Union A or Lurgi-Ruhrgas retorts.
Reduction of oxides of nitrogen emissions according to
need determined by final forms of both air quality
standard and retort technology.
• Reduction of effluents and emissions that are also
produced in conventional refineries to levels consis-
tent with standards for refineries.
• Minimization of consumptive use of water.
4. Energy from Solid Wastes
Control requirements for energy production from solid wastes
should include:
• Monitoring oi1 treatment to control pH and other content
of leachate from ash residue.
• Removal of gaseous sulfur compounds to meet emission
standards comparable to requirements that sulfur content
of coal be significantly below one percent.
• Monitoring and possibly reducing emission of vapors
and volatiles such as hydrogen chloride, mercury, and
partially oxidized organic compounds.
• Removal of particulates from exhaust stream
as required to meet standards.
• Reduction of particulate surface area available to
adsorb carcinogens and other toxic substances.
• Removal of hydrogen sulfide produced in anaerobic diges-
tion processes.
• Disposal of sour digester residue.
• Conventional control of dust, noise, and odor.
• Treatment or dilution of quench water.
5. Underground Coal Gasification
Control requirements for energy production from solid wastes
should include
88
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• Prevention of water pollution similar to acid mine
drainage caused by entrance of ground water into coal
seam depleted by gasification.
• Assurance that land use and structures are consistent
with possible subsidence of surface above depleted seams.
• Removal of hydrogen sulfide from gas stream at surface.
• Protection of adjacent mineral resources from explosive
fracturing proposed in some concepts.
• Location of deep seams unquestionably isolated from
air and ground water.
6. Hydrogen as an Energy Carrier
Before use of hydrogen as a fuel increases substantially,
significant changes in production and consumption technologies are likely.
Control requirements should include:
• Establishment of emissions and effluent standards cover-
ing the materials suggested for use in high efficiency
electrolyzers, high temperature thermal decomposition
of water, and fuel cells.
• Establishment of design guidelines to steer development
away from selection of materials that require large
amounts of energy or that have large known detrimental
environmental impacts during their production processes.
B. Subjects for Research and Development
The control requirements imply the need for various types of research
and development. SRI has identified a number of such needs as a result
of this study. They are listed below, again organized under the energy
technologies presented in this report.
1. Solar Energy: Continuous Review of Solar Energy Development
A continuing effort should be made to influence the course of
development of solar energy technologies so that they conform to EPA
guidelines (suggested above in the list of control requirements) estab-
lished to minimize the need for remedial measures.
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2. Geothermal Energy
Subjects for research and development should include:
(a) Emission standard for hydrogen sulfide. Environmental
impact analysis (including modeling and comparisons)
should be continued in order to set and justify an
emission standard for hydrogen sulfide from geothermal
power plants.
(b) Hydrogen sulfide emission control technology. Experiments
on hydrogen sulfide control at The Geysers should be con-
tinued. Problems encountered in two attempted processes—
catalyzed solution as sulfate and catalyzed precipitation
as elemental sulfur—should be identified and new tech-
niques should be devised.
(c) Closed-cycle geothermal plants. A binary cycle generating
plant employing heat exchange from the geothermal brine
should be developed because of its potential for using
high salinity sources without producing effluents and
emissibns.
(d) Turbogenerators driven by liquid geothermal brine. The
exploitation of hot water and geopressured resources
would be facilitated by the existence of a turbine using
both the pressure and heat energies of both the liquid
and steam supplied by hot water dominated geothermal
reservoirs.
(e) Geological site survey techniques. The methods now used
to determine the geological structure and resources of a
site should be studied to assess their adequacy for en-
vironmental protection and to identify ways to decrease
the cost of adequate surveys.
(f) Reinjection of geothermal brine. The potential for con-
tamination of ground or surface waters during reinjection
operations should be assessed. Ways to improve this vi-
tal technology should be identified.
(g) Treatment and reclamation of saline water. Nearly all
geothermal fluids will contain too heavy a burden of dis-
solved solids to be injected into a local water stream.
Because it represents an alternative to reinjection and
a potential source of water and minerals, the technology
for treating saline geothermal water should be investi-
gated.
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(h) Cooling systems for semi-arid regions. The low thermal
efficiency of geothermal power plants, the relatively
low condenser discharge temperature, the high salinity
of most geothermal liquids, and the limited fresh water
supply at most western geothermal sites combine to com-
plicate the disposal of waste heat from a geothermal
power plant. Existing technology and new concepts should
be studied, both as an aid in the development of the
energy resource and as an important step in the control
of adverse environmental impacts.
(i) Standards (guidelines) for land use. Environmental
effects due to the noise, land subsidence, construction,
and eventual retirement of facilities associated with
geothermal power production can best be controlled through
wise land use planning. The criteria for such planning
should be formulated.
3. Oil Shale
Subjects for research and development should include:
(a) Rehabilitation ofdisposal areas. The land used for dis-
posal of spent shale wastes should be rehabilitated in a
way consistent with water supply limits and land use
criteria. Additional study is recommended.
(b) Water pollution from shale wastes. Monitoring and model-
ing work is needed to quantify the effects of various
shale disposal techniques on water quality.
(c) Treatment and reclamation of saline water. Both runoff
water from shale disposal areas and process water from
oil production may be subjects for treatment. The avail-
able techniques should be evaluated.
(d) Evaluation of the zero-discharge criterion. It is said
that oil shale will be produced by methods that prevent
process water from reentering the fresh water system.
Before development proceeds much further, the practicality
and the necessity of this zero-discharge assumption should
be tested.
(e) Emissions from in-situ retorting. Some in-situ methods
may prove viable. These methods should be identified,
their emission factors determined, and the control need
and potential studied.
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(f) Sulfur dioxide control. Methods of controlling sulfur
dioxide emissions from oil shale retorts must be demon-
strated. An intermedia effect that needs study is the
possible leaching of sulfur dioxide absorbed in the shale
residue in some retorts.
(g) Refinement of estimates of emission factors for retorts.
To determine control requirements, more accurate knowl-
edge of emission factors for the most promising retorts
is needed.
(h) Application of refinery pollution control techniques.
The transferability and the adequacy of applying con-
ventional refinery emission and effluent control tech-
niques to the upgrading of crude oil from shale should
be investigated.
(i) Application of control techniques from coal processing.
The potential for applying methods used to control wastes
and emissions in coal processes, especially coking and
gasification, should be assessed.
(j) Alternatives to consumptive use of water. There will be
economic incentives for the oil shale industry to avoid
a production limit set by water availability. Therefore,
EPA should be aware of the alternatives to consumptive use
of water and evaluate the environmental assets and liabil-
ities of these alternatives.
(k) Geological site survey techniques. Knowledge of the geol-
ogy of the site is a crucial element in protecting the
environment from potential adverse impacts from any in-
situ process.
4. Energy from Solid Wastes
Subjects for research and development should include:
(a) Data on exotic pollutants. An assessment should be made
of the possibility that incineration and pyrolysis of
man-made materials can result in unacceptable emissions
of exotic pollutants—metals, hydrogen chloride, car-
cinogenic compounds—for which no emission standards
exist. Upper limits of the emission factors for such
pollutants should be determined by measurements of the
quantity and composition of emissions from existing
demonstration plants.
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(b) Determination of emission factors. The adequacy of the
data on emissions now being obtained at demonstration
plants for converting solid waste to energy should be
assessed. If monitoring of the emissions at these plants
is inadequate to lead to the setting of standards and
control requirements, monitoring programs should be revised.
(c) Emission standard for fine particles. The facts that
(1) smaller particulates have greater surface area per
unit of mass, (2) most heavy molecules of low volatility
(the metals and carcinogens) pass into the atmosphere
adsorbed to the surface of particulate matter, and
(3) the smaller particles are more effective per unit
mass in decreasing visibility, suggest the need to con-
sider a standard tied to the surface area of particulate
emissions.
(d) Water pollution from ash disposal. The local .conditions
determining the water pollution potential of leaching
from incinerator ash residue should be identified and
quantified.
(e) Treatment of process water. The assumption that standard
water treatment (secondary) should be adequate to control
pollution from quench and scrub water should be verified.
The implications for choosing sites for solid-waste energy
facilities should be made explicit.
(f) Cleaning the pyrolysis gas. The economic and environmental
consequences of scrubbing pyrolysis gas before it is mixed
with air for combustion should be determined. The emis-
sion factors for combustion of pyrolysis gas, at or away
from the site of the pyrolysis, should be measured and
correlated with the scrubbing process used.
5. Underground Coal Gasification
Subjects for research and development should include:
(a) Geological site survey techniques. The prevention of
pollution from an in-situ process requires knowledge of the
geology of the site. The methods now used to determine the
geological structures and resources of a site should be
studied to assess their adequacy for environmental protec-
tion and to identify ways to decrease the cost of adequate
surveys.
93
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(b) Eventual monitoring of tests. After initial tests on
site have confirmed the promise of an in-situ gasification
technique, monitoring of emissions at the surface and
effects on water quality underground should be carried
out in order to set standards and determine control
requirements. Some baseline data at the site will be
required for a proper monitoring program.
(c) Periodic review of the technology. To ensure that
adequate environmental protection measures are incorpo-
rated in the development of underground coal gasifica-
tion, a periodic review of this development should be
carried out. Should environmental or economic attractive-
ness imply a more rapid move toward deployment of some
in-situ technology, a continuing review would be desir-
able.
6. Hydrogen as an Energy Carrier: Periodic Review of the Technology
To ensure that adequate environmental protection measures are
incorporated in the development of hydrogen for energy storage and trans-
portation, a periodic review of this development should be carried out.
Should environmental or economic attractiveness imply a more rapid move
toward deployment of hydrogen technology, a continuing review would be
desirable.
C. Classification of the Recommendations
The subjects just listed call for several types of research in
support of several different methods of improving environmental quality.
It follows that actions related to the research needs listed here will
not be the responsibility of any one division within EPA. In order to
facilitate the channeling of these recommendations within EPA and to make
explicit the different categories of these recommendations as envisioned
by SRI, the subjects for research and development are listed below accord-
ing to the nature of the recommendation and the media (air, water, or
land) most directly involved. It should be noted that some environmental
effects defy the air-water-land categorization and that virtually all
94
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environmental problems have intermedia aspects. In this listing by type,
each title is followed by an indication of the primary medium involved
and the subsection designation [l, 2(a), 2(b)"] from Section VI-B.
The recommended subjects for research and development are classified
below according to the type and goal of the research.
1. Formulation of Performance Standards or Guidelines
This work involves the derivation of quantitative standards for
emissions, effluents, or land use on the basis of (1) considerations of
environmental quality, and (2) anticipated levels of development of the
sources of environmental impacts. Such standards would be based solely
on environmental impact analysis and, therefore, as pointed out in
Section V-A, would be subject eventually to considerations of technical
and economic feasibility.
The following is a list of the titles and section numbers of
the recommendations that call for information and analysis leading to the
formulation of standards or guidelines :
• An emission standard for hydrogen sulfide from geothermal
power plants [AIR, 2(a)3*
• Standards (guidelines) for land use in geothermal fields
[LAND, 2(1)].
• Rehabilitation of disposal areas for spent oil shale
[LAND, 3(a)].
• Evaluation of the zero-discharge criterion for oil shale
processing [WATER, 3(d)].
• Sulfur dioxide control in oil shale retorting [AIR, 3 (f)].
• Emission standards for fine particles from solid waste
energy producing processes [AIR, 4(c)].
• Continuous review of solar energy development [ALL MEDIA,!].
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2. Development of the Technology to Control Certain
Emissions and Effluents
The preliminary analysis carried out as part of the present
study has identified certain environmental impacts of advanced energy
sources as likely to be unacceptable and, therefore, as requiring a
higher degree of control than now being employed. These are areas where
promising control technologies should be identified and their development
supported.
The following recommendations by SRI are directed toward the
realization of adequate control technology:
• Develop hydrogen sulfide emission control technology
for geothermal power plants [AIR, 2(b)].
• Develop treatment and reclamation of saline water asso-
ciated with both geothermal and shale-oil energy produc-
tion [WATER, 2(g) and 3(c)].
• Develop sulfur dioxide control in oil-shale retorting
[AIR, 3(f)].
3. Development of New Energy Technology Having Apparent
Environmental Advantages.
The technologies listed under this heading are not simply for
the control of emissions or effluents but are essential parts of energy
production systems. They are presented as candidates for EPA support on
the grounds that they have potential for becoming part of new energy
systems that are particularly attractive on environmental grounds. The
recommended technologies are :
• Closed-cycle geothermal power plants [WATER, 2(c)].
• Turbogenerators driven by liquid geothermal brine
[WATER, 2(d)].
• Cooling systems for geothermal power plants in semi-
arid regions [WATER, 2(h)].
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4. Further Analysis of Effects on Air and Water Quality
Most of the recommended subjects for research and development
fall into this category. These are areas where environmental effects of
advanced energy technology have been identified as being important but
have not been analyzed to the point of recognizing definite needs for
controls or standards.
Further study of the effects of advanced energy technology
on air and water quality is needed in the following areas:
• Reinjection of geothermal brine [WATER, 2(f)].
• Water pollution from shale wastes [WATER, 3(b)].
• Emissions from in-situ retorting of oil shale [AIR, 3(e)].
• Refinement of estimates of emission factors for retorts
used in oil shale processing [AIR, 3(g)].
• Application of refinery pollution control techniques to
oil shale processing [MULTIMEDIA, 3(h)].
• Alternatives to consumptive use of water in oil shale
processing [WATER, 3(j)].
• Data on exotic pollutants from energy producing solid
waste disposal [MULTIMEDIA, 4(a)].
• Determination of emission factors for solid-waste energy
processes [AIR, 4(b)].
• Water pollution from ash disposal from solid-waste energy
processes [WATER, 4(d)].
• Treatment of process water from energy-producing solid-
waste disposal [WATER, 4(e)].
• Cleaning the pyrolysis gas in solid-waste energy processes
[AIR, 4(f)].
• Eventual monitoring of tests of underground coal gasifica-
tion processes [MULTIMEDIA, 5(b)].
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5. Further Analysis of General Environmental Effects of
Advanced Energy Technologies
The recommendations not adequately described in the above
categories are listed here. What they have in common is an applicability
to the full range of media and to intermedia effects. The recommendation
for study of geological site survey techniques is of special significance
because, in addition to its multimedia implications, it has applications
in three of the advanced technologies studied. The solar energy recom-
mendation is repeated in this category because of its implications beyond
standards or guidelines.
The following further studies of the environmental effects of
advanced energy technology are recommended by SRI:
• Geological site survey techniques for use in establishing
environmental control requirements at the sites of geother-
mal energy production, in-situ oil shale retorting, and
underground coal gasification [MULTIMEDIA, 2(e), 3(k), and
• Continuous review of solar energy development [MULTIMEDIA, l]
• Periodic review of the technology for underground coal
gasification [MULTIMEDIA, 51 (c)].
• Periodic review of the technology for using hydrogen as
an energy carrier [MULTIMEDIA, 6].
6. Matrix Summary of the Ordering by Type and Media
The classification just presented can be summarized in matrix
form, as shown in Table 22. This matrix indicates the classifications
by type of recommendation and by type of environmental impact.
Although there are several key recommendations relating to
standards and technology development, most of the recommendations per-
tain to the need for further research to better define the nature of
advanced energy systems and their resulting environmental impacts. These
impacts are estimated to have principal effect on air and water quality
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Table 22
CLASSIFICATION MATRIX FOR RESEARCH
AND DEVELOPMENT RECOMMENDATIONS
Classification by
Type of
Recommendat ion
Develop a standard
Develop control
technology
Support promising
energy technology
Conduct further
research
Classification by Type of Impact
Air Quality
2(a)*
3(f)
4(c)
2(b)
3(f)
3(e)
3(g)
3(h)
3(i)
4(a)
4(b)
4(f)
5(b)
Water Quality
3(d)
2(g) and 3(c)
2(c)
2(d)
2(h)
2(f)
3(b)
3(h)
3(i)
3(j)
4(a)
4(d)
4(e)
5(b)
Land Use
3(a)
2(i)
Other
1
2(e), 3(k), and 5(a)
1
5(c)
6
Recommendations appear here according to their subsection numbers in
Section VI-B.
99
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unless research and development is successful in suppressing release of
pollutants or in achieving control over them.
The structure of Table 22 reflects a judgment regarding the nature
of recommendations and character of environmental impacts. Perhaps
the best known systems and impacts are those for which research and
development is concerned with development of standards and control
technology. Lesser known systems need research and development for
quantification of the environmental impacts and discovery of the nature
of pollutants produced from these sources. With respect to type of impact,
Table 22 reflects the view that the environmental media that may disperse
pollutants most widely or may be the means of transmitting such pollutants
to other media require-most intensive work. This classification is
valuable in establishing priorities for conducting the necessary research
and development work.
D. Assignment of Priorities
The scope and complexity of the research and development programs
identified to control environmental impacts from advanced energy sources
are such that all the desirable work cannot be performed concurrently;
priorities must be employed. In the final analysis, the EPA bears the
responsibility for determination of the priorities and ranking criteria
for the research and development programs that it administers or conducts.
This study, while it can offer support to the EPA's process of program
planning, is no substitute for these activities.
There are many factors involved in setting priorities. These in-
clude (1) estimated costs, (2) work to be done, (3) anticipated classes
of results, (4) interactions with other activities, and (5) the time
results are required to guide further actions. Identification of work
to be done has already been covered in earlier sections.
100
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If limited to the projected time scale for development of advanced
research sources, the ranking of research and development priorities for
advanced energy could be listed as follows:
Priority
Ranking Advanced Energy Source Main Determinations Needed
1 Geothermal dry steam Air quality impacts
2 Oil shale Air and water quality impacts
3 Solid wastes Air and water quality impacts
4 Solar thermal Indirect impacts
5 Geothermal hot water Water quality impacts
6 Solar energy plantation Land use and wastes impacts
7 Underground coal gasification Water quality impacts
8 Solar photovoltaic Indirect impacts
9 Other geothermal Water quality impacts
10 Hydrogen Indirect impacts
This listing reflects the principle that "research and development should
be done first on those advanced energy sources expected to be deployed
at the earliest dates. Such priorities enhance the prospect that control
approaches will be available at times when sizable energy production from
these sources is expected.
However, it is incomplete to base priorities solely on the expected
timing of development. As indicated in the classification approach
described in the previous section, the several research and development
recommendations for individual advanced energy sources can be categorized
according to type of work and expected impact. Accordingly, it would be
worthwhile to assign higher priority to those research and development
efforts expected to contribute to more than one advanced energy source
(e.g., saline water treatment for geothermal and oil shale developments)
and to those expected to contribute to the solution of problems beyond
the advanced technologies dealt with in this report (e.g., control of
fine particulate emissions). Additionally, it is clearly more important
101
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to address the control of identified environmental impacts from soon-to-
be-developed advanced energy sources than it is to pursue further research,
although such further research is recognized as both desirable and
essential.
With these additional factors in mind, another ranking of priorities
for research and development is given in Table 23. This table ranks the
specific research topics by affected environmental media. Items listed
at the top of the table are those with the highest priority. The ranking,
somewhat subjective, still reflects considerations of timing, magnitude
of impact, and degree of definition of the problem. The table suggests
that research and development is required at an early date to address
environmental impacts associated with development of geothermal resources,
oil shale developments, and energy production from solid wastes. This
research and development is required to demonstrate practical pollution
control strategies and technologies to achieve applicable operating
standards for air quality, water quality, and land-use practices. Solar
thermal energy warrants attention soon, but attention of a different
nature because of the indirect effects involved. Research and development
for control of environmental effects from other forms of solar energy
production, underground coal gasification, and hydrogen as an energy
carrier is also desirable, but the need for research and development is
not as urgent because these sources are estimated to require more time
to develop.
Priority ranking of the types of research and development required
for control of environmental impacts from advanced energy sources repre-
sents an important part of the overall planning process. Clearly, how-
ever, essential cost factors and overall agency requirements also will
need to be considered by EPA in arriving at a final plan for efforts in
the energy sector.
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Table 23
PRIORITIES OF RESEARCH AND DEVELOPMENT RECOMMENDATIONS*
Ranking
Highest
Lowest
Air
2(b)
2(a)
3(f)
4(c)
3(e)
3(g)
3(h)
4(a)
4(b)
4(f)
5(b)
Water
2(g), 3(c)
3(d)
3(b)
2(c)
2(d)
2(h)
2(f)
3(h)
4(a)
4(d)
4(e)
5(b)
Land
3(a)
2(i)
Other
1
2(e), 3(k), 5(a)
5(c)
6
Recommendations appear here according to the subsection
numbers of Section VI-B.
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REFERENCES
1. J. K. Galbraith, Economics and the Public Purpose, p. 208 (Houghton
Mifflin Company, New York, 1973).
2. "U.S. Energy Outlook: An Interim Report, an Initial Appraisal
by the New Energy Forms Task Group," National Petroleum Council,
Washington, D.C. (1972).
3. "Meeting California's Energy Requirements, 1975-2000," SRI Project
ECC-2355, Stanford Research Institute, Menlo Park, California
(May 1973).
4. D. E. White, "Characteristics of Geothermal Resources," p. 91, in
Geothermal Energy; Resources, Production, Stimulation, P. Kruger
and C. Otte, editors (Stanford University Press, Stanford,
California, 1973).
5. M. Goldsmith, "Geothermal Resources in California—Potentials and
Problems," p. 32, EQL Report No. 5, California Institute of
Technology, Environmental Quality Laboratory (December 1971).
6. E. Robinson and R. C. Robbins, "Sources, Abundances, and Fate of
Gaseous Atmospheric Pollutants," Final Report, SRI Project PR-6755,
Stanford Research Institute, Menlo Park, California (February 1968).
7. A.D.K. Laird, "Water from Geothermal Resources," in Geothermal
Energy; Resources, Production, Stimulation, P. Kruger and C. Otte,
editors (Stanford University Press, Stanford, California, 1973).
8. L. L. Anderson, report prepared for the U.S. Bureau of Mines, cited
in Energy and the Future, p. 73, A. L. Hammond, W. D. Metz, and
T. H. Maugh, editors (American Association for the Advancement of
Science, Washington, D. C., 1973).
9. A. Darnay, Deputy Assistant Administrator for Solid Waste Manage-
ment Programs, U.S. Environmental Projection Agency, in testimony
before Senate Interior Subcommittee (30 October 1973).
104
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10. R. S. Berry and M. F. Fels, "The Production and Consumption of
Automobiles: An Energy Analysis of the Manufacture, Discard,
and Reuse of the Automobile and Its Component Materials," Report
to the Illinois Institute for Environmental Quality (July 1972).
11. P. Chapman, "No Overdrafts in the Energy Economy," New Scientist,
pp. 408-410 (17 May 1973).
12. E. A. Walker, Vice President for Science and Technology Aluminum
Company of America, in testimony before the Joint Hearings on
Conservation and Efficient Use of Energy, U.S. Congress (12 July
1973) .
13. R. A. Herendeen, "An Energy Input-Output Matrix for the United
States, 1963: User's Guide," Document No. 69, Center for Advanced
Computation, University of Illinois at Urbana-Champaign (March
1973).
14. "Uranium Enrichment," report of the Ad Hoc Forum Policy Committee,
Atomic Industrial Forum, New York (1972).
15. "AEC Gaseous Diffusion Plant Operations," U.S. Atomic Energy Com-
mission (February 1968).
16. "Energy and the Environment—Electric Power," Council on Environ-
mental Quality, U.S. Government Printing Office (1973).
17. D. J. Rose, J. H. Gibbons, and W. Fulkerson, "Physics Looks at
Waste Management," Physics Today, pp. 32-41 (February 1972).
105
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Appendix A
SOLAR ENERGY
by
Edward M. Dickson
107
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CONTENTS
LIST OF ILLUSTRATIONS 1Q9
LIST OF TABLES 109
I SOLAR ENERGY: STATE OF THE ART HO
A. Introduction HO
B. The Technological Systems 113
1. Thermal Energy Collection from Insolation .... 113
2. Electrical Energy 115
a. Photovoltaic Conversion 115
b. Wind Power 118
c. Hydropower ng
d. Thermal Differences in the Sea 12Q
3. Renewable Fuels 121
II SOLAR ENERGY: ENVIRONMENTAL IMPACTS 123
A. Introduction 123
B. Specific Solar Energy Technologies 125
1. Thermal Collection of Insolation 125
a. Electric Energy Generation from Large-Scale
Solar Energy Collection 125
b. Thermal Installation for Local Heating and
Cooling of Buildings 131
2. Photovoltaic Collection of Solar Energy I39
a. Large-Scale Centralized Terrestrial
Collection 139
b. Satellite-Borne Solar Energy Collectors . . . 143
c. Small-Scale Installations on Buildinps . . . 146
3. Thermal Energy from the Sea 147
4. Wind Power I52
5. Energy Plantations ^53
III SOLAR ENERGY: IMPLICATIONS AND RECOMMENDATIONS FOR
FOR EPA ACTION 157
REFERENCES 162
108
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LIST OF ILLUSTRATIONS
1 Power Balance for the Earth Ill
2 Thermal Energy Balance 132
LIST OF TABLES
1 Estimated Minimum Materials Requirement for 1-GW
Electrical Output Thermal Solar Energy Plant 129
2 Energy Investment in Finished Metal 130
3 Selected Materials Requirements for Residential
Solar Energy Systems, 1985 134
4 Air Pollutant Emissions Associated with Materials
Production for Thermal Solar Energy Collectors for
Buildings, 1985 137
5 Present Status of Solar Utilization Techniques 158
109
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I SOLAR ENERGY: STATE OF THE ART
A. Introduction
Energy received from the sun represents by far the most significant
component of the thermal balance of the earth. As indicated in Figure 1,
solar energy not only warms the earth but also drives the winds, the
ocean currents, the hydrologic cycle, and is responsible for photo-
synthesis in plant materials.1 Historically, mankind has used all these
aspects of solar energy, although in the industrialized nations, the last
century has seen almost total reliance on hydropower and the photosyn-
thetic energy stored over geologic time in the form of coal and oil.
Recently, however, attention has been drawn to the possibility, and
impending need, to utilize solar energy more directly. Although the
energy density of solar radiation reaching the surface of the earth is
o
rather low (about 0.8 kW/m during the brightest six to eight hours of
the day in the relatively cloudless deserts of the U.S. Southwest),2
solar radiation has the advantage of being available everywhere—at least
during certain parts of the year. Opportunities for increased solar
energy utilization can be classified in three broad categories:
• Thermal energy
• Electrical energy
• Synthesis of renewable chemical fuels.
Naturally, these categories are not mutually exclusive, and all include
four basic system elements: collection or extraction, conversion, storage,
Numbered references are listed on page 1 at the end of Appendix A.
110
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Solar Input
(173.000)
Heat Output
(122,000)
Tidal Energy
from Moon and Sun
Direct Reflection (52.000)
Winds. Waves, Convections, and Ocean Currants (370)
Evaporation and Precipitation
(41.000)
STORAGE
(WATER)
Direct Warming of Surface and Atmosphere (81.000)
Tides and Tidal Currents (3)
Conduction in Rocks (32)
Convection in Volcanoes and Hot Springs
(0.2)
Photosynthesis (40)
STORAGE
(FOSSIL FUELS)
NUCLEAR
ENERGY
GEOTHERMAL
ENERGY
NOTE: Number* in parenthesis ere terawattt (1012 watts).
SOURCES: M. King Hubbert. "Energy Rwourcw of tti* Earth" Scientific American.
September 1971, pp. 61-70.
John Holdren and Philip Herrera, Energy (Sierra Club, Sen Francisco). 1071.
CHEMICAL
ENERGY
FIGURE 1 POWER BALANCE FOR THE EARTH
-------
and distribution. Among the various solar energy systems possible,
different combinations of these elements assume dominant importance.
These basic elements are defined briefly below as a prelude to discussion
of various systems.
Collection and Extraction—Solar energy can be exploited by extract-
ing momentum from winds, falling water, and ocean currents; by oxidation
of organic materials; by utilization of thermal differences in the oceans
to drive heat engines; by thermal capture of solar radiation; and by
generation of electricity from photovoltaic cells exposed to incident
radiation. Since the density of energy available in many of these sources
is rather low, facilities for collection or extraction generally require
large areas of exposure or contact.
Conversion—The form of energy obtained from the collection or ex-
traction process is frequently inappropriate for direct use, distribu-
tion, or convenient storage. Consequently, conversion of energy between
thermal, electrical, and chemical forms is usually a prerequisite for a
solar energy system.
Storage—Geographical, diurnal, seasonal, and meteorological varia-
tions in insolation provide a major constraint in the application of
solar energy because human activity patterns and, consequently, demand
for energy do not coincide with the availability of sunshine. Since
storage of large quantities of energy in electrical form is difficult,
storage in a large thermal reservoir or in chemical compounds is usually
considered the most attractive.
Distribution—Once collected or extracted, it is necessary to
transfer the energy to its point of use. Over short distances, heat
112
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exchange fluids can be effective, but over large distances electrical or
chemical distribution is more efficient. Electrical distribution can be
accomplished by fairly conventional methods. Chemical distribution is
especially convenient if the energy has been stored in liquid or gaseous
chemical compounds because this facilitates transmission by pipeline or
bulk carriers.
B. The Technological Systems
1. Thermal Energy Collection from Insolation
In the simplest solar energy systems, suitable for heating or
cooling a small building, the collection of solar energy results directly
in a temperature rise in a heat exchange fluid, which in turn is used to
warm space, heat water, or cool space by use of an absorption refrigera-
tion cycle.3'4 In these systems, collection and storage considerations
dominate, since no conversion is required and transmission is minimal.
Numerous tests have demonstrated the engineering feasibility of heating
and cooling buildings in the appropriate climate.3'6 Because about
22 percent of all energy currently consumed in the United States is used
for space conditioning and water heating,5 thermal solar energy systems
for use in buildings are especially beguiling. Indeed, a recent NSF/NASA
report suggests that 50 years from now such systems could provide about
35 percent of the country's space conditioning energy requirements.6
Studies of insolation have shown that large areas of the United States,
especially the Southwest, are well suited for this application.5
Present systems usually use flat plate collectors and often use
water as the heat transfer and storage fluid. Although engineering
feasibility has been demonstrated,3'5'6 economic feasibility remains
elusive, and experience has revealed several remaining engineering
challenges:
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• Ensured durability, and long, low maintenance life-
times for low cost collectors and plumbing
• Increased thermal exchange and storage efficiency
• Integration with the existing energy utility network
to provide supplemental energy as needed
Large scale centralized thermal solar energy installations have
been envisioned to provide the thermal energy required for the generation
of electricity using conventional Rankine cycles. For these large in-
stallations, efficient distribution of thermal energy within the array of
collectors presents a formidable problem, requiring the pumping of
enormous quantities of heat exchange fluids or the use of advanced-concept
"heat pipes." To store enough heat to keep the generators in operation
during periods of low collection and throughout the night, enormous*
thermal storage reservoirs are necessary.3'7'8 To provide energy storage
adequate to buffer seasonal variations, the thermal storage must be sup-
plemented with chemical or mechanical storage (such as pumped storage
of water). Hydrogen obtained from the electrolysis of water during
periods of peak power is frequently regarded as the logical choice for
chemical storage.9'10'11
Vast quantities of hydrogen are required to buffer the energy
output of a large solar energy installation. Storage as a cryogenic
liquid at 20.4°K is technically feasible,13 although the liquification
process consumes energy and thereby lowers the overall system efficiency.
Metal hydrides, such as MgH2, offer an alternative hydrogen storage
capability since they exhibit very high atomic densities of hydrogen,
and the diffusion of hydrogen through the magnesium is relatively rapid
at convenient temperatures.13 Procedures to process the vast amounts of
About 300 metric tons of eutectic salts are required per day of reserve
energy for an electric power output of 1 MW.
114
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metal hydride that would be required have not been detailed. When needed,
electricity could be regenerated either by combustion of the hydrogen in
conventional power plants or by fuel cells. It is believed to be likely,
moreover, that reversible fuel cells suitable for both electrolysis and
recombination can be devised.
Other storage mechanisms widely considered to be feasible in-
volve exploitation of the heat of fusion of eutectic mixtures of salts,7
although there has not been agreement on the most appropriate substances.
A cycle employing Al burned to Al O which is then recycled to Al by
2 3
using peak period electrical power has been mentioned.7
Unlike thermal approaches to the heating and cooling of build-
ings with solar energy, the system feasibility of a large scale thermal
process solar energy installation has not been demonstrated. Relevant
research and development has been concentrated on the following topics
to improve overall system efficiency:
• Suitable energy storage mechanisms, especially eutectic
salt mixtures.
• Selective optical coatings that are highly absorptive
in the visible portion of the spectrum, but that have
low emissivity in the infrared portion. The coatings
must be durable at elevated temperatures and must have
long lifetimes.
• Inexpensive and durable focusing devices, such as
plastic cylindrical Fresnel lenses to concentrate the
incident radiation on thermal transfer fluid piping.
• Efficient heat transfer fluids and materials with
acceptably low corrosion potential.
2. Electrical Energy
a. Photovoltaic Conversion
Many semiconductor materials have been found that absorb
photons from the solar flux and thereby generate an electrical current.
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The materials most exploited for photovoltaic "solar cells" have been
cadmium sulfide, CdS, and high purity single crystal silicon.14 Recent
developments have suggested that Schottky diodes16 and gallium arsenide
(GaAs)16 may also possess substantial potential for application. In
addition, recent research has shown that chlorophyll can be used as an
electron donor to semiconductors, thus opening the possibility of a
symbiotic chlorophyll-semiconductor solar cell.17 At the present time,
CdS solar cells are relatively easy to make, but silicon cells are expen-
sive and almost entirely handmade by cottage industry methods,14 and
almost entirely consumed in the U.S. Space program. Degradation of
performance after environmental exposure is one of the lingering diffi-
culties with all solar cells. Ironically, since most of the applications
to date have been in space probes, more is known about damage caused by
environmental exposure in space than on earth. Except for meteorite
damage, the space environment is more benign for solar cells than the
terrestrial environment. Efficiencies with which the various cells con-
vert incident solar energy to electricity are summarized below. (For
comparison, fossil fuel electrical power generation plants typically
operate at 30 percent efficiency.)
Approximate Efficiencies
Usual Observed Theoretical
Cadmium sulfide 6% 8% --%
Silicon single crystal 13 16 22
GaAs — 18 26
Schottky diodes — 6 22
The intermittent nature of sunlight on earth poses a
special problem to all schemes to utilize photovoltaic collection of
solar energy. At present, it is awkward and costly to store large
quantities of energy in electrical form, thus making it difficult to
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envision a large solar energy plant with electrical storage sufficient
to buffer variations in supply and demand.3'7 Consequently, one of the
key issues in the development of solar electrical power is the identifi-
cation and evaluation of an efficient and economical energy storage
capability. Since the energy is made available in electrical form,
again electrolysis of water to make hydrogen for storage and later com-
bustion is widely believed to be a suitable strategy.9•10»1x
Although photovoltaic collection of solar energy is not
usually associated with the heating and cooling of buildings, the elec-
trical output can be used to operate a heat pump (these usually have an
"effective" efficiency of 200 to 300 percent) to accomplish the necessary
heat transfer. One analysis18 has indicated that in Phoenix, Arizona,
a home using solar cells, hydrogen generation for energy storage, and
fuel cells for dark period electrical generation could be energetically
self-sufficient. Indeed, an annual excess hydrogen generation was
projected. Research and development related to terrestrial photovoltaic
solar energy is currently concentrated on
• Discovery of new materials exhibiting photo-
voltaic properties at suitable energy conversion
efficiencies.
*^
• Improved solar cell efficiency, fabrication
techniques, durability, and lifetime, all at
lower cost.
• Electrolysis and fuel cells with improved effi-
ciencies and greater durability (including the
possibility of a dual-purpose reversible cell).
Because the earth's atmosphere reflects and absorbs much
of the incident solar energy, serious suggestions have been made to con-
struct an extensive satellite borne array of solar cells in synchronous
earth orbit.6'19>3OfS6's7f28 A satellite station would receive about
ten times as much incident energy as is available on earth and would be
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able to operate around the clock. The electrical energy generated by
the satellite could be beamed to earth as microwave radiation and there-
after converted to electricity in conventional form for distribution.
In spite of the obvious difficulties of construction in space, problems
associated with the variability of insolation on earth would be consider-
ably alleviated.
A satellite solar power station, SSPS, capable of providing
about 10 GW on earth would require placing about 25 million kilograms of
material into orbit.6 This would require an estimated 300 to 1,000
flights of a second generation space shuttle.6 The SSPS would presumably
be assembled in orbit from prefabricated modular elements. The SSPS is
envisioned to consist of two large arrays of photovoltaic solar cells,
each with an area of about 16 square kilometers feeding a 1-km diameter
phased array of microwave generators acting as a transmitter. On the
earth, a special antenna about 7 km in diameter would intercept the micro-
wave beam, rectify the current, and enter the received energy into a
fairly conventional electrical distribution network.6 Although such an
SSPS might generate 10 GW of electrical energy, this amount would be
only about 3 percent of the 1970 installed U.S. electrical generating
capacity and less than 1 percent of the capacity believed necessary by
1990.29
Many problems remain to be solved before an SSPS could
become a reality, and most of the current research is devoted to estab-
lishing the feasibility of the concept.
b. Wind Power
Extraction of mechanical energy from winds was prevalent
many years ago (as evidenced by picturesque windmills in much of Europe);
however, interest in wind power had almost completely waned 60 years
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ago.6 Since then, applications have been mainly in rural areas, and
even these have decreased with rural electrification. However, some
operational experience was gained in the United States during World
War II from the operation of a wind power generator at Grandpa's Knob,
Vermont; the 1.3-MW generator operated sporadically between 1941 and
1945.30 Since wind power is variable in most locations, energy storage
mechanisms, similar to those discussed above, are necessary to make wind
power significantly more convenient to use. Research and development in
the area of wind power has been almost nonexistent, although the recent
NSF/NASA solar energy assessment6 is rekindling interest and there is
now some slight governmental funding (NSF/NASA).31 Work is especially
needed in the areas of:
• Materials development for lightweight high
strength turbine blades.
• Windmill structures using contemporary
materials.
c. Hydropower
The extraction of energy from falling water is, like wind
power, a very old technology. In the United States very little unex-
ploited potential remains for hydropower development—especially without
arousing substantial controversy on environmental, recreational, and
aesthetic grounds. Consequently, hydropower is seldom regarded as a
beckoning opportunity to extract stored solar energy. Nevertheless,
several technological research and development activities currently in
progress may improve the effectiveness of hydropower including:
• Pumped storage for peak shaving of electrical
generation
• Superconducting electricity generators
• Weather modification to increase flows in
appropriate rivers.
119
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Although, strictly speaking, hydropower is a stored form of solar energy,1
the nearly complete exploitation of its potential suggests that it should
receive no further attention in this study.
d. Thermal Differences in the Sea
A vast quantity of solar energy is stored in the heat
capacity of the oceans. Year-round absorption of incident radiation
warms surface waters in the tropics. Solar energy driving the winds and
the precipitation cycle annually builds up polar snowpacks that melt in
the spring, giving rise to cold subsurface currents.6 Because of con-
vection on a global scale, the warm surface waters move poleward and the
cool subsurface waters move toward the tropics. In some areas, warm
surface waters override (by a few thousand feet) significantly colder
waters. In the temperate zones, this creates a significant opportunity
to operate a heat engine between the effectively infinite warm and cool
heat reservoirs that exist in the sea.6'21'S2'23'32'33
Enormous quantities of warm and cool sea water circulated
past efficient heat exchangers could drive a conceptually simple heat
engine at relatively low thermodynamic efficiency. However, by process-
ing very large quantities of water, this engine nevertheless could yield
significant quantities of energy in electrical form. For plants of this
nature, efficient heat transfer and energy transmission to the shore and
to distant inland locations become the dominant considerations. Because
these plants extract energy from essentially continuous sources, the
problem of energy storage can be neglected.
Although this concept is not new, few attempts have been
made to demonstrate engineering feasibility. Two successful demonstra-
tions succumbed to mechanical failure after only short periods of opera-
tion.6 Interest in this concept of solar energy extraction is increasing,
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and several serious engineering studies are now in progress. Some of
the major explorations yet to be accomplished include:
• Consideration of mechanical design and construc-
tion strategies
• Refined identification of optimal sites
• Evaluation of alternative energy transmission
technologies suited for land-sea links.
3. Renewable Fuels
Once collected or extracted, solar energy can be stored chemi-
cally in synthetic fuels, such as hydrogen obtained from electrolysis.
Processes have been suggested to go a step further and to collect C02
from the atmosphere for combination with the electrolytic H to synthesize
A
organic molecules such as methane, methanol, and gasoline suitable for
use as fuel.24 Since virtually the sole products of combustion of the
*
fuels are water and CO , the process would be a closed cycle with nature
2
supplying the return path. The chief advantages of the synthetic fuels
approach to solar energy utilization are that mismatches in solar energy
and supply can be buffered more easily, the fuel can be stockpiled or
distributed by conventional means to areas remote from the solar energy
installation, and the fuels can be used in mobile applications such as
in aircraft. Inorganic chemical cycles in which the depleted chemicals
are returned to the solar energy installation for recharging are also
possible, including A1-A1 O or Mg-MgH cycles.8'13
23 a
Quite another approach to generation of renewable fuels is to
use natural photosynthesis to generate organic molecules in a plantation
devoted to growing plants solely for the purpose of energy production.25
*
Some nitrogen oxides may be formed if combustion occurs in air at high
temperatures.
121
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Under optimal conditions, some plants are able to fix about two percent
of the incident sunlight. Grown and harvested completely, without the
usual agricultural regard for segregation into product and waste, the
total plant can be used either to fire conventional electric generators
or to be chemically converted, refined, and concentrated into organic
molecules suitable for use as fuels.6 Some of this reduction process
may be accomplished organically by fermentation processes. These con-
version processes can also intercept and utilize organic materials from
the urban, agricultural, and livestock waste streams.6 Although photo-
synthetic utilization of solar energy has long been a major feature of
human culture, the following issues are being studied as a prelude to
the possible application of the concept of an energy plantation.
• Determination of the known plants that not only fix
sunlight efficiently but also are easily harvested
and processed.
• Identification of necessary processes to maintain a
closed system, such as returning nutrients to the
soil.
• Analysis of the energetics of the complete system to
ascertain the net energy gain.
• Genetic alteration of plants to maximize their photo-
synthetic efficiency to yield maximum biomass per
unit area cultivated.
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II SOLAR ENERGY: ENVIRONMENTAL IMPACTS
A. Introduction
In the popular literature (and most of the professional literature
as well), solar energy is depicted as a "pollution free" source of energy,
ideally suited to a culture in which environmental quality is held in
high regard. It is true that solar energy installations will not be
sources of air pollution, and because they will consume energy cleanly
delivered in the form of electromagnetic radiation from the sun, they
will not be directly responsible for creating a demand for strip-mined
coal or oil from offshore wells. Nor, in many cases, will solar energy
installations be responsible for thermal pollution of streams or other
bodies of water used to provide cooling water for stream driven electric
generating plants. However, it is not true, and it is extremely naive
and shortsighted to maintain, that no adverse environmental effects would
result from the harnessing of solar energy.
It is extremely important to appreciate that not all the pollution
associated with any given energy source occurs at the site of energy con-
version or final utilization. For example, it has long been recognized
that environmental damage resulting from coal mining is a consequence and
one of the societal costs of the generation of electrical energy by con-
ventional coal-fired generating plants. The environmental disruption
associated with the mining and with production of the steel that is used
to fabricate the actual generation plant, with the railroads or barges
that deliver the coal, and with the machinery at the mines is likewise
a consequence of this form of energy utilization. However, relatively
few people have extended their thinking far enough to include consideration
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of these ancillary parts of the system that delivers energy from its
basic source to the final user. In its evaluation of environmental ef-
fects associated with various energy technologies, it is essential that
EPA take the larger view and consider the entire energy system along with
the various component technologies.
Seen in this way, it is clear that utilization of solar energy
simply cannot be pollution free—that is only a cliche. Indeed, it is
inherent in the nature of solar energy as a widespread, but dilute source
of energy that utilization invariably requires collection devices that
cover a large area and therefore consume vast quantities of materials.
It is in the extraction, production, and processing of these materials
that many of the environmental impacts of solar energy utilization lie.
Certainly, deployment of alternative forms of energy production facilities
also consume materials with attendant environmental disruptions. A major
problem facing policy-makers in the energy resource and environmental
quality arenas is the comparative evaluation of alternative energy systems.
One general and pervasive aspect of solar energy utilization that
also indirectly affects environmental quality results from the uneven
geographic availability of insolation suitable for capture of solar
energy. Should solar energy become an economically viable resource, all
accounts indicate that the arid areas of the Southwest will be the most
attractive geographical location to utilize this resource by direct cap-
ture of sunshine. Depending on the development of other energy resources
elsewhere in the nation, it is possible that in the future energy may be
available in the Southwest at lower prices than in other regions. This,
together with a climate many people regard as attractive, would lead to
an inexorable, although slow, migration of the industry, employment oppor-
tunities, and population to the Southwest much as has been occurring in
the last two decades toward the southeastern states.3 Inasmuch as most
of the Southwest is arid and, as experience in Arizona has shown, prone
124
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to air pollution problems, exploitation of solar energy could result in
a significant increase in urban-related environmental problems in the
southwestern states.
The following sections consider the magnitude of the major, most
obvious materials demands created by the various forms of solar energy
outlined in the previous sections. Other environmental effects are also
considered, such as possible adverse effects on local or regional climates,
biota, land use, and water or air resources.
B. Specific Solar Energy Technologies
1. Thermal Collection of Insolation
a. Electric Energy Generation from Large-Scale
Solar Energy Collection
Installations envisioned for the large-scale collection
of insolation by thermal means are discussed in two basic forms. The
first entails a system of simple reflectors or inexpensive, low preci-
sion optical lenses to focus direct sunlight on a conduit through which
a. heat transfer fluid is pumped. The incident energy heats the fluid,
and this captured energy is continually removed as the pumped fluid passes
by a heat exchange element that forms the high temperature reservoir for
a boiler (water need not be the working fluid) driving a conventional
thermodynamic electric generation plant. To enhance the buildup of heat,
the conduit is generally colored black and is enclosed in a glass or
plastic greenhouse-like environment; to inhibit the loss of energy by
convection, the enclosure can be evacuated.
Conceptually, this scheme is very old; however, modern
thinking has added, either on the collecting conduit or on the protec-
tive cover, a thin film selective coating that is transparent to electro-
magnetic radiation in the visible part of the spectrum (in which most of
125
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the solar radiation lies) but is opaque in the infrared part of the
spectrum (in which most of the reradiation from the hot conduit lies).
An important limitation of this form of collector is the inability of a
mirror or lens concentrator to focus the indirect or diffuse solar radiation
that results from radiation scattered from molecules of the gases composing
the air, particulates, the earth's surface, clouds, and so forth. Moreover,
focused collectors need continued reorientation to follow the sun, at least
in its seasonal excursions to be effective. Since diffuse radiation is a
substantial fraction of the sunshine normally received (often about 20
percent), an inability to utilize the energy in the diffuse radiation is
a serious limitation of focus-collector systems.35 It is now quite evi-
dent, even to some of the recent advocates of focused collectors, that
even in Arizona there are too many days with thin cloud cover or haze for
focused collectors to be attractive.36
The second basic collector type is a "flat plate collector
consisting of a conduit containing a heat absorbing fluid that snakes
around a "blackened" planar collecting surface. Again, the use of selec-
tive coatings and evacuation enhances the performance of the collector.
A variation in this concept has recently been designed that behaves like
a flat plate collector but has a configuration that is more easily
evacuated.36 The power generation steps would be essentially identical
to those described above.
The intermittent nature of sunlight and the thermal time-
lag inherent in the system of circulating fluid make it necessary to
accompany the collectors and power generation facilities with an energy
storage mechanism. Storage can either be in thermal form such as in the
mixture of eutectic salts (which, like a bath oi ice and water, maintains
a constant temperature over a wide range of stored energy) or in chemical
form, such as hydrogen, derived from electrical energy produced during
peak periods.
126
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It is extremely informative to estimate the quantities of
materials required for installations following the basic concepts outlined
above. All the estimates will be optimistic in the sense that any real
installation will require more materials than derived from these simpli-
fied assumptions. Assuming a reasonable value of 30 percent for the
efficiency of conversion of insolation to thermal energy, a thermal
solar energy plant with 1 GW of electric output would require about
7
1.5 X 10 square meters of collector surface.* In any design, it will
be essential to support the collector, and presumably the support could
be made to form the collector's back surface. If this support material
is a metal and is rather optimistically assumed to have an average thick-
ness of 1 mm, then the volume of this substrate material required would
4
be about 1.5 X 10 cubic meters. Presumably the collector would be covered
7
with glass as a protective cover; consequently, about 1.5 X 10 square
meters of glass would be required. (If the collector is not evacuated,
a double-glazed glass cover would be advantageous to reduce convective
losses of energy from the collector. This would double the glass require-
ment.) If the energy storage is accomplished in a salt mixture that is
basically Na SO (anhydrous sodium sulfate), then a 1-GW plant would re-
8
quire about 3.2 X 10 kg of this salt for each day of storage capacity.
The selective coatings that are used to improve the performance of the
collector generally include a refractory metal; molybdenum,8 hafnium,8
and gold8 have been mentioned. If these materials were used in a layer
about 0.07 micrometers thick, about 1.1 cubic meters of the material
would be required.
*
New water cooled nuclear power reactors typically have a rated elec-
trical output of about 1 GW; comparisons are made for 1 GW installations
to facilitate comparisons.
127
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The significance of these resource requirements can best
be grasped by comparison with recent U.S. annual production figures as
summarized in Table 1. Clearly, materials requirements are a significant
consideration for contemplated solar energy developments, especially
when it is realized that many installations of 1 GW output would be
necessary. One of the most prominent advocates of a thermal collector
solar energy installation speaks in terms of building ten plants of 1-GW
capacity per year. Clearly, there will be environmental impacts asso-
ciated with these resource demands, although they will not occur at the
solar energy collection site itself.
It is also instructive to evaluate the quantity of energy
that would be required to extract, refine, process, and fabricate a few
of the key materials required in the plant. Recent work on the energy
requirements for the production and consumption of automobiles has pro-
vided a detailed vertical analysis of the energy invested in several
3 8
materials. These are shown in Table 2 and form the basis for the last
column of Table 1. The annual electrical energy output of a 1-GW plant
running constantly at full capacity (possible only if adequate energy
storage is provided) is 8.76 TWh. From this it can be seen that it
would take about 0.36 years' operation to recover the energy invested
on aluminum substrate material alone. Therefore, the expected productive
lifetime of the installation becomes an important parameter, because the
plant must reap more energy than is committed in the fabrication and
operation of the installation.
As already indicated, a 1-GW thermal solar energy installa-
tion would require on the order of 1.5 X 107 m2 of collector surface.
This is equivalent to a square nearly 4 kilometers on a side. An actual
installation would be expected to require more land area, because the
collector is unlikely to form a single continuous sheet and there are
128
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Table 1
ESTIMATED MINIMUM MATERIALS REQUIREMENT FOR 1-GW
ELECTRICAL OUTPUT THERMAL SOLAR ENERGY PLANT*
Alternative sub-
strate materials
Aluminum
Steel
Copper
Cover material
Flat glass
Thermal storage for
one day's output
Na2S04
Thin film selective
coating
Hafnium
Quantity
Volume
1.5 x 104 m3
1.5 x 104 m3
1.5 x 10* m3
1.5 x 107 m2
1.1 X 105 m3
1 m3
Mass
4 x 107 kg
1 x 108 kg
1.3 x 108 kg
depends on
thickness
3 x 108 kg
1.5 x 104 kg
U.S. Annual Production
(year)
3.6 x 109 kg (1970)
1.2 x 1011 kg (1970)
1.4 x 109 kg (1970)
2.7 X 107 m2t (1970)
6 X 1011 kg (1969)
3.2 X 104 kg (1970)
Requirements as
Fraction of U.S.
Annual Output
(percent and
year)
1 % (1970)
0.1 (1970)
9 (1969)
56 (1970)
0.05 (1969)
46 (1970)*
Energy Devoted
to Materials
Production for
Solar Plant Twh
(1012 Wh)
3.2
1.7
5.3
__
—
—
to
(£>
j . O9
Installed electrical generating capacity in 1970 in the United States was 340 GW.
+
Plate or float glass between 1/8-in. and 1/4-in. thickness. A lower quality material such as sheet glass
would probably be adequate.
* 37
Current production of hafnium is apparently demand-limited rather than resource-limited.
-------
Table 2
ENERGY INVESTMENT IN FINISHED METAL
(Rolled)
Metal
Aluminum
Carbon steel
Copper
Energy (kWh/kg)
80
17
40
ancillary structures such as the generators and energy storage facilities.
This raises a significant land-use question even in the arid land of the
Southwest where this type of plant is most likely to be located. How-
ever, it is important to realize that much of the land in the Southwest
is under direct control of the federal government and is used occasionally
for various military tests that have rendered the land unsafe for public
access, although probably safe enough for a solar energy plant. Addi-
tionally, other large tracts of land are controlled by native Americans;
to them solar energy installations may represent a very attractive income-
producing use of their land. It has been publicly noted that the "Four
Corners" powerplant operated by Arizona Public Service Company already has
under lease more land for the strip mining of coal to fire the plant than
would be needed to construct a thermal solar energy installation of the
same capacity.
A significant environmental constraint on the deployment
of large thermal solar energy installations in the Southwest is the acute
shortage of water suitable for use as a cooling agent to recondense the
working fluids of the boiler. The cooling water needed for each 1-GW
electrical generator would be similar to that of a modern water cooled
nuclear reactor of the same capacity, namely about 50 cubic meters per
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second. Even if a nearly closed cycle cooling system using wet cooling
towers were used, the amount of water needed to make up for evaporative
losses is sufficiently large that cooling water will present an important
issue in resource management in the Southwest.
The possibility of inadvertent climatic modification is
one issue raised by large-scale energy collection. Figure 2 shows that
collection of solar energy alters the flux of energy surrounding an in-
stallation. There has been considerable speculation, but no actual inves-
tigation, of the local climatic modification such collection would induce.
Certainly some effects can be expected, since temperature gradients in
the air are an important determinant of the winds and cloud cover. Since
solar energy collection is sensitive to the degree of cloud cover or haze,
investigation of this aspect will ultimately be necessary before an opti-
mized plant design can be reached, because water vapor added by cooling
towers or an alteration in cloud cover induced by the plant itself could
degrade the plant's performance.
b. Thermal Installation for Local Heating
and Cooling of Buildings
The most widely discussed concept for the heating and cool-
ing of buildings concerns the use of flat-plate collectors essentially the
same as those described above. However, rather than use the collected and
stored thermal energy to generate electricity, the energy is used directly
to heat the interior of the building and provide the hot water supply;
with the use of an absorption refrigeration device, thermal energy also
g
can be used to drive an air conditioner for cooling a building. Several
designs, however, have used a combination of thermal collection and photo-
voltaic collection to raise the overall collector efficiency.4'3 In thes<
systems, electrical and thermal energy are available, and the electricity
131
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NORMAL
CO
SOLAR ENERGY COLLECTION
REFLECTED
35%
30% USED
TO CITY
30%
' .v: - " -^ m
V/^//////7/////7^ \ I J
'•W'*; ftV.:i'v'-'.;'•f''^^'' •>:?:^:r:^-l:\"'0.•'';"' -IV;X>*-*S
95% \^ -•i.f.-r
ro, , CPTFO .".'°'«- •.'!'•'• •
COLLECTED -.- v;-V ? .
• •••
:'.-;-;oV-.-v;'.f -. - ..;. ^>
.•:f^\«-;-N?y.;-.-V^- v^-° ••:••• •••••••••°.: :•.•/••- ^ ••••»••• •b-:.-
:-6Vo-^Vi ;•-.:.•;•''•:•? -::^. •;••••' .ov-'.^-..-- '••<>':•. es% => ••
v^^-::->:;^.;;-,^-::Vr^:-Vi^v^ RETURNED ,V
.0- •.••»••••••?••..•••••»••. 1 « . '•.*
•' .•.'•.-•".• '.''.*.*•«.> • '.•*•' •••'.-* •.*.•.•.•«.•.-/ i •'.:*: •'••• -.''"?•
.*• f-.'..-. .a.'.=,.:..i»-.; -i-1- :».»•'.-. :«-;.i-o-; ?.•».:?•.-.';,.« :.-
V^^/-oxv//..-;-:'---.>--.-v.V.?-ri.'W
:X.v;Af;
.•• -o.t .«. o
''"--0'-" *
SA-2714-1
FIGURE 2 THERMAL ENERGY BALANCE (ADAPTED FROM REFERENCE 8)
-------
can either be used for building appliances or to drive a heat pump* that
adds to the heating and cooling ability of the solar energy collected
in the thermal form.
To become a viable concept, residential thermal solar
energy systems require storage facilities to provide useful energy into
the evening, in the early morning, and on days with little insolation.
Most studies have concluded that it is impractical to provide enough
storage capacity to enable a building to rely completely on solar energy.
It has been stated that about one-half day's store is the optimum amount.
Consequently, systems of this type must be backed up with a nearly full-
sized conventional heating and cooling system.
Although some redundancy can be removed by integrating
the solar energy and conventional systems at the time the building is
built, it is apparent that a solar energy system for the heating and
cooling of buildings alters the resource demands created by building
construction. The desirability of having a conventional system for back-
up also has rendered it most likely that this application of solar energy
will find use only in new buildings. The NSF/NASA solar energy study
projects 10 percent market penetration in new construction by the follow-
ing time periods:
*
A heat pump is a device that essentially acts as a reversible refriger-
ator. When used to cool the interior of a building, it exhausts the ex-
tracted heat to the outdoors much as an air conditioner. However, when
set to the impossible task of refrigerating the outdoors, it exhausts the
extracted heat to the interior of a building, and thereby provides warmth
to the occupants. In moderate climates, this last application can be use-
ful even during the winter and usually delivers two or three units of heat
energy to the building interior for each unit expended in operation. Thus
these devices have an effective efficiency, or efficacy, of 200-300 percent.
133
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• Water heating—in 1980
• Space heating—in 1985
• Space cooling—in 1985.
It is instructive to examine the implications of these projections on the
demand for materials that would lead to off-site environmental impacts
during their production.
In recent experience, approximately 1.5 million housing
starts per year have been reported. If it is assumed that a 60-square
meter thermal solar collector could provide about 75 percent of the heat-
ing and cooling requirements for a house, then in 1985 a national produc-
7
tion of about 1.8 X 10 square meters of residential-type collector would
be required. These collectors would probably consist of a glass cover
surface and metal thermal backing and thermal exchange network probably
of aluminum or copper. Table 3 shows materials requirements that can be
contrasted with the annual production shown in Table 1. Once again, it
is evident that applications of solar energy would create substantial de-
mands for basic materials. It is important to note that the above esti-
mates apply only to the collector portion of the system, and other mate-
rials would be required to provide the needed thermal storage capability.
Table 3
SELECTED MATERIALS REQUIREMENTS FOR
RESIDENTIAL SOLAR ENERGY SYSTEMS,
1985
Material
Amount
Double glazed flat glass
Backing and heat exchange
material if copper
if aluminum
3.6 X 107 m2
7.2 X lo7 kg
2.2 X 107 kg
134
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Some may argue that the Introduction of residential solar energy collectors
may result in offsetting reductions in materials demands elsewhere in the
economy, such as a reduction in the average size of wire needed to supply
electricity to a home. No doubt some of this offset will occur, but it
is not a straightforward task to identify the sources or magnitudes of
possible offsets in materials demands.
Thermal collectors for use on buildings provide a good ex-
ample of indirect environmental impact. Air pollutant emissions factors
have been compiled by the Environmental Protection Agency for the aluminum,
copper and glass industries.45 Even though it is too early to judge
whether copper or aluminum will be the material used in commercial pro-
duction of rooftop thermal solar energy collectors, it is instructive to
itemize emissions of some relevant air pollutants for the materials listed
in Table 3. This is done in Table 4 which also shows the emissions asso-
ciated with roofing materials that the solar energy collectors might
render unnecessary and the emissions from the same amount of domestic
space heating achieved by the combustion of natural gas. For aluminum,
the emissions factors given refer to the best available control technol-
ogy for the most commonly used series of processes. Many installations
do not achieve this degree of control today. It should be noted, morever,
that the technology of aluminum production may change dramatically in the
future. The Aluminum Company of America has recently announced a new
method of production that reportedly reduces the electricity required by
about 30% and is based upon a chloride process rather than a fluoride
* £J
process. Consequently, the nature of the emissions and the control
requirements and strategies are very likely to change in the next few
decades (see Table 4).
135
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The use of solar energy collectors on buildings, either
thermal or photovoltaic, will lead to other environmental effects. One
effect is related to the aesthetics of building design. It will be a
challenge to architects and engineers to integrate solar energy collectors
into the structure to make the buildings aesthetically pleasing (although
it is natural to expect an evolution in the aesthetic tastes of the public),
Another challenge will be the extent that solar energy collectors can be
made to substitute for existing roofing or siding materials. Because of
the constraints placed on architects by the availability of solar energy,
enhanced consciousness of the ability to use fenestration and insolation
to control the interior climate can be expected. In addition, land use
in developing neighborhoods using solar energy will show increased atten-
tion to orientation and spacing of structures and thoroughfares to minimize
energy needs and maximize solar energy capture. These aesthetic aspects
of solar energy will play a significant role in its public acceptance.
Much as mineral rights have become an important aspect of
land ownership, so sun rights may become an important determination of a
homeowner's desire or ability to plant trees—especially those casting a
shadow on a neighbor's collector. Ironically, in many parts of the country
where trees play an important role in moderating the climate in residential
areas, the evolution of solar energy utilization could lead to a relatively
treeless cityscape—thereby enhancing the desire for artificial climate
control.
It is now well known that cities and other conglomerations
of human habitation create "heat islands," partly as a result of energy
released by human activity but more by the texture and "roughness" of the
cityscape itself. Although the effect of a large array of rooftop solar
collectors on the urban heat island has not been investigated, it is
apparent that some alteration would be expected. Since the urban heat
136
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AIR POLLUTANT EMISSIONS ASSOCIATED WITH MATERIALS PRODUCTION FOR THERMAL SOLAR ENERGY COLLECTORS FOR BUILDINGS, 1985
(Kmlailona factor! given per unit final material product) Compiled from Reference 45
Material
Glaaa <«oda-
llme)
Aluminum (beat
control*, moat
Copper (con-
trolled)*
Aaphalt roofing
Natural gaa for
domaatlc apace
conditioning
Amount Required
3.2 x 108 kg
2.2 x 107 kg
7.2 X 107 kg
(Amount
potentially
aaved)
1.8 x 107 «2
(Amount
potentially
aaved)
5.1 x 108
m3/year
Total Partlculatea
gmlaalona Total
Factor Emlaalona
1.0 x 10"s 3.0 x 10s kg
kgAg
2.2 X 10*2 4.8 x 105 kg
k«Ag*
8.1 X 10"* 5.8 x 10* kg
kgAg
4.9 X 10-* 8.8 X 103 kg
3.0 x 10"* 1.5 x 10s
kg/.3 kg/year
Fluorldea
Caaeoua _ Partlculate _, .
Emiaaiona Emlaatona Emlaalona Emlaalona
Factor Factor
2F x 10"3 kgAg* 6F x 10* kg*
2.7 X 10"4 5.9 X 103 kg >2.0 X 10"* >4.S X
kgAg kgAg 1O3 kg
--
_
Sulfur Oxide*
Bmlaalou Total
Factor Emlaalona
-
4.1 X 10"S 9.1 x 10* kg
kgAgf
0.25 kgAg l.g x 107 kg
9.6 x 10"8 -1.9 x 103
kg/m3 kg/year
Caibon Monoxide
Emlealone Total
Factor Emiaalona
-
1.2 x ID"3 2.6 X 10* kg
kgAg}
--
6.6 x 10-* 1.2 x 10* kg
kg/.2
3.2 x 10"4 1.6 X 10s
kg/m3 kg/year
Hydrocarbona
Emiaaiona Total
Factor Emlaalona
..
6.8 x 10"5 1.5 x 103 kg
kgAgi
-
1.1 x 10-3 2.0 x 10* kg
kg/.2
1.28 xlO"4 6.5 x 104
kg/m3 kg/year
Nitrogen Oxides
Emlaaiona Total
Factor Emlaalona
-
4.1 x 10"Z 9.1 x 10* >t
kg/leg}
--
- -
1.28 x 10~3 6.5 x 10*
kg/at3 ki/yo.vr
'publlahed Information doea not epeelfy whether tbele aeUaalona are gaieoua or partlculate. The variable F In tho atated ealaalona atanda for the weight percentage of fluoride Input to the furnace. For exuple. If the fluoride
input ie 5% the total niaalona would be 30 x 10* kg.
fBxlatlng inatallatlona do not generally achieve this degree of control. However, theae data refer to actual Inatallatlona where controll have been evaluated.
Includes pollutant enlaelone froei a power plant burning natural gaa to produce electricity for the electrolyala procaaa.
'AriaIng froai the production of electric power (from natural gaa) for the electrolyala proceaa.
-------
island is believed to influence the extent of urban cloud cover, precipi-
tation, and even atmospheric mixing, an alteration of the urban heat is-
land could conceivably affect urban air quality. This is expected to
entail a series of subtle effects, and it is premature to predict its
importance.
2. Photovoltaic Collection of Solar Energy
a. Large-Scale Centralized Terrestrial Collection
The most favorable location for large scale terrestrial
collection using photovoltaic technologies is in the Southwest. In the
area around Phoenix, Arizona, the integrated annual insolation is about
o
2 Mffh/m .18 If an installation is to deliver energy at a rate equivalent
to a steady 1 GW, then solar cells operating with a 10 percent photovoltaic
* 4
efficiency would require about 4.4 X 107 square meters of collector area
(optimistically assuming a lossless energy storage technique). This is
equivalent to a square about 6.6 kilometers on a side.*
Because of the lower efficiency of photovoltaic collection
compared with thermal collection, a 1-GW photovoltaic installation would
require about three times as much collector area. However, there are
advantages of photovoltaic over thermal collection:
• Photovoltaic collection results directly in
an electrical output whereas thermal collec-
tion requires an electrical generation stage.
• There is no need to pump a heat exchange fluid
through the collector system because the energy
is collected electrically.
It is worth noting that units 2 and 3 of the San Onofre, California,
nuclear power station, will each produce 1.1 GW, and occupy about 10
square meters.
139
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• There is no need to utilize double glazed glass
enclosures or thin film selective coatings;
however, the photo cells do require encapsulation
for protection to prevent environmental degrada-
tion.
• Energy storage in the chemical form can be more
efficiently accomplished by using peak hour
electrical energy to electrolyze water to yield
hydrogen for later combustion or electrical
generation in a fuel cell.
• No cooling water is necessary, since there is
no thermal generation of electricity that
requires cooling a boiler working fluid.
The quantities of materials required are, again, quite
large. A substrate would be needed to support the cells, and if this
4 3
were metal 1-mm thick, then 4.4 X 10 m of metal would be required.
This is nearly three times the quantity given in Table 1 for the thermal
collection system. In addition, if silicon solar cells with a typical
thickness of 0.25 mm (0.01 inch) ° were used, the demand for high purity
silicon would be 2.6 X 107 kg. The electronics semiconductor industry
and the manufacturers of silicon for solar cells used in spacecraft both
consume material of this quality. However, production in 1970 was only
about 5 X 10^ kg. 4o Thus an increase in production of about a factor
of 50 would be needed to establish even a single l^GW solar energy in-
stallation based on silicon solar cells. The estimated 1970 production
of low purity metallurgical grade silicon was 6.6 X 1Q7 kg.40 However,
no shortage of silicon exists in the United States or the world, since it
is one of the most abundant elements in the earth's crust; common sand
is SiO2. Great quantities of silica sand are consumed annually for
glass and refractory products.
A major drawback of silicon solar cells is the need to
use slices of what is known as "single crystal," which means that the
140
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material is a large, essentially perfect' crystal. While it is easy
to obtain small samples of perfect crystals for most materials, it is
difficult to obtain large perfect crystals because they must be care-
fully drawn from a melt of material of very high purity. Because of the
high melting point of silicon and the extreme chemical reactivity of
molten silicon, maintenance of the purity required for making single
crystals of silicon is difficult. The need to use single crystals in
silicon solar cells contributes to the very high costs of these solar
cells. Furthermore, the high degree of purity required necessitates the
expenditure of considerable amounts of energy during the multiple refining
steps of the material production.
To overcome the drawbacks of silicon solar cells, several
other semiconductor materials have been found with promising photovoltaic
properties. Among these are CdS and CuS, which do not require single
crystals to construct an effective solar cell, although they do have a
low efficiency. The most promising material, from an observed and theo-
retical efficiency point of view, is a solar cell composed of the semi-
conductor GaAs. These cells can be made by vacuum deposition of thin
films in the manner now common in the fabrication of integrated circuit
solid state electronics. In a typical GaAs solar cell, the layers of
—6
Ga and As are only about 10 meter thick.
The quantity of Ga required for the 1 GW solar energy in-
stallation under consideration is about 44 cubic meters or 2.6 X 105 kg.
This greatly exceeds the 1968 production of Ga of about 300 kg and the
1968 world production of 1000 kg. It also is about a factor of 10 greater
than the expected cumulative total of 2.7 X 104 kg that the U.S. Geological
3 7
Survey predicts will be recoverable by the year 2000. At the present, Ga
production is limited by demand. Although solid state electronics are
now using many semiconductors based on Ga compounds, the quantity of Ga
consumed is actually quite small. Recovery of Ga is principally as a
141
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very minor constituent from bauxite and zinc ores, and there is little
prospect of finding ores rich enough to exploit solely for their Ga con-
o +t
tent. However, Ga is recoverable from the fly ash that results from
3 *y
the combustion of coal. Because of the shortage of Ga that could
develop once a good GaAs solar cell is routinely producible, it can be
expected that on retirement of these solar cells the Ga content would be
recycled. Thus, one would not expect a widespread problem of Ga residuals
entering the environment. The Geological Survey reports that the toxicity
of Ga in vegetation has not been established.37 There exist supplies of
As much more than adequate to match the available Ga.
Since even a single 1 GW photovoltaic solar energy instal-
lation based on GaAs solar cells would exhaust resources of Ga, it must
be concluded that a large scale photovoltaic system cannot depend on
GaAs solar cells.
Degradation from environmental exposure is one of the per-
sistent technical difficulties impeding the terrestrial use of photo-
voltaic solar cells. In normal use, exposure to the sunlight results in
a temperature rise, which not only lowers the efficiency of the cells
but also speeds internal diffusion processes which ultimately leads to
the cell becoming ineffective. Unless a photovoltaic solar energy col-
lector can be made to last long enough to recover all the energy invested
in its production and maintenance, it would be folly to deploy such systems.
At the present, no information is available to indicate the total energy
inverted in the solar cells themselves, but it is straightforward to
determine that, if the support substrate were made of Al, 1 mm thick, it
would require about 1.1 years of operation merely to recover the energy
invested in the aluminum substrate. Consequently for photovoltaic solar
energy collection, the lifetime of the collector system is a very impor-
tant parameter.
142
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As in the case of large installations using thermal collec-
tion, alteration of the local climate is an important concern. The effects
would tend to be somewhat different, since a photovoltaic system absorbs
a smaller fraction of the incident solar energy, but as a compensation
the collectors would be spread over a large area of land.
b. Satellite-Borne Solar Energy Collectors
Studies have shown that the SSPS of optimum size would
deliver about 10 GW of power to the earth. 7»3S AS noted previously,
this would require placing 2.5 X 10^ kgs of material into orbit and would
require between 300 and 1000 flights of a second generation space shuttle.
In addition, about 1.4 X 104 kg of propellant would be expended by the
SSPS in altitude or orientation control. Like all solar energy projects,
much of the environmental impact comes from the vast materials demands
created.
For most solar energy systems, the environmental impact is
limited to the terrestrial or lower atmosphere regimes. However, the
many flights of the space shuttle required to deploy the SSPS will result in
injection into the upper atmosphere of significant quantities of water
vapor arising from the combustion of liquid hydrogen and liquid oxygen
fuel. Therefore, this raises the same questions about potential altera-
tion of the upper atmosphere as were raised by the operation of a fleet
of supersonic transports. Scientific debate has not completely settled
the question of the impact of water vapor injection into the stratosphere.
Proponents of the SSPS (notably Peter Glaser of Arthur D.
Little, Inc.) have stated that the energy expended to construct the SSPS
could be recovered by SSPS operation according to the following schedule:
143
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Materials Months Operation
• Propellants 6
• Solar cells 3
• Ground support equipment 3
This list is clearly incomplete and, moreover, fails to
account for indirect energy inputs which could be expected to increase
this payback time by about a factor of five. It has also been claimed
that as the SSPS would not place undue demands on resource supplies
including Ga. However, a single SSPS of dimensions usually cited38
that used GaAs solar cells would appear to require about 1()5 kg of Ga;
this quantity 4 times as large as the cumulative total the Geological
Survey expects to have become available by the year 2000.
The solar energy collected by the SSPS would be sent to
earth over a beam of microwave radiation at about 3.3 GHz.2 »38 The
cross section of this beam must be made large enough that the energy
density in the microwave flux is below levels that could cause damage
to the health of humans and other organisms. To achieve an acceptably
low energy density at the edges of the beam,* the receiving antenna
would need to be about 7 km in diameter and would intercept about 90 per-
2 7 2 ft
cent of the transmitted energy. ' The hazards to passengers flying
through the beam in an aircraft are theoretically negligible, although
experimental confirmation would be warranted; the hazards to birds flying
3 8
through the beam are not known.
The present U.S. standards based on human health impairment from thermal
(heating) effects is 10 mW/cm2. However, the Russians believe that dan-
gers of a nonthermal nature exist and have set their standard a factor
of 1000 more stringent. Scientific debate has not clarified this dis-
crepancy.4
144
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Some climatic change could be induced by an SSPS for
several reasons. The first, and probably the most important reason
arises from the additional energy added to the heat load of the planet.
Unlike terrestrial collection, which intercepts only radiation that would
reach the earth anyhow, an SSPS intercepts and beams to earth radiation
that would not otherwise have reached the surface of the earth. In this
manner, an SSPS contributes to an alteration of the thermal radiation
balance between the earth and outer space. The detailed effects that
would result from an alteration of the heat balance are debatable, but
it is generally held that climatic change would result.
An SSPS could also potentially affect the climate through
the heating of the atmosphere by the microwave beam. However, the attenu-
ation of the beam by the molecules constituting the atmosphere as well as
by suspended matter (including rain) is sufficiently small that no problems
are expected.28 The energy loss rejected to the environment by the re-
ceiving antenna and electrical rectification circuits has been calculated
3 8
to be less than 10 percent. This percentage is far lower than the re-
jected heat from conventional or nuclear power generation (between 60 and
70 percent). It is believed that this amount of waste heat can be con-
3 8
vected directly into the atmosphere, and therefore no cooling water
would be needed, thereby removing at least one important environmental
constraint on the siting of a receiving antenna.
Even though terrestrial solar energy collection schemes do
not require a continuous expanse of level land, details of the terrain
pose even less of a constraint on the SSPS receiving antenna. It could
be sited on otherwise derelict land such as unrestored strip mines.38
Moreover, the receiving antenna can be sited near the ultimate energy
consumption, such as the Northeast, thereby eliminating the cost and
environmental disruption of electrical distribution.
145
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c. Small-Scale Installations on Buildings
Because photovoltaic collectors capture a smaller percentage
than thermal collectors, the surface area required for the photovoltaic
systems is larger. In thermal systems, the collected energy would be used
directly to heat or cool a building, but in a photovoltaic system, the
electrical output would be required to drive an electrical resistance
heater, a heat pump, or air conditioners. Moreover, with present battery
technology it is awkward, as well as expensive, to provide much energy
storage capability. Photovoltaic systems, however, do offer the advantage
of having an electrical output that is more easily controlled and dis-
tributed throughout the structure. Therefore, this increases the likeli-
hood that existing structures would be retrofitted to make use of solar
energy.
The space program has had need for ensembles of solar cells
arrayed on flexible sheets that could be transported into space in a small
package and then unfurled. Industrialists believe that eventually solar
cells can be fabricated and interconnected in a single process that would
result in a thin, flexible, durable sheet of solar collector material that
could be used as the "skin" of new or existing structures. If this were
achieved at low enough cost, many orientation and spacing design con-
straints could be relaxed for buildings using solar energy. The building
could simply be "papered" with solar cells (some of which would operate
inefficiently because of poor orientation or exposure). Such a solar cell
skin material would also make viable the collection of solar energy on
buildings in northern climates.
As can be expected from the delicate nature of the solar
energy resource, any photovoltaic system designed for buildings will
require a substantial commitment of special materials resources.
146
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The aesthetic and local climatic consequences of photo-
voltaic systems on buildings would be quite similar to thermal collection
of solar energy on buildings as discussed above.
3. Thermal Energy from the Sea
Some preliminary conceptual designs for sea solar plants have
9 3 3 2 O
been published. ' Warm surface waters at about 25 C are drawn past
heat exchange surface where energy is transferred to a working fluid that
vaporizes; the warm water is exhausted, slightly cooled to about 23 C.
The vaporized working fluid drives a turbine to generate electricity and
then the working fluid is reliquified as it passes another heat transfer
surface that is cooled by water about 5 C that has been pumped up from
the depths; the cooling water is warmed slightly and is exhausted at
about 7 C. The thermodynamic efficiency of a turbine working between
such a slight temperature difference is only a few percent at best. For
this reason, the extraction of solar energy stored in the heat capacity
of sea water requires a thermal exchange surface with a very large area.
23 *55l
From published discussions of conceptual designs, ' it is
possible to estimate the materials requirements for a 1-GW plant. The
heat transfer surfaces for the boiler and condenser need to have an area
7 2
of about 1.4 X 10 m . This surface area is essentially the same as that
estimated for the 1-GW large scale thermal plant discussed earlier.
Consequently, if the heat exchange surfaces can be made rather thin, say
1 mm, the materials requirements are nearly the same as the large scale
terrestrial thermal plant. A highly efficient heat transfer surface made
of an aluminum alloy has been mentioned as an appropriate choice.32
Unlike the terrestrial collection of solar energy, the heat
transfer surface need not be arrayed in a single large surface. Instead,
it can consist of a network of parallel tubes or passages through which
147
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the water can pass. Experience with structures in the marine environment
has given clear evidence that it will prove very difficult to prevent the
fouling of the relatively small heat transfer tubes by marine organisms.43
It will be essential, however, to inhibit colonization of the small
passages by organisms because their presence will both lower the efficiency
of the heat transfer surfaces and will impede the flow of the water. The
energy required to pump the vast quantities of water involved already
pose a significant design constraint, even without accounting for these
additional losses. Consequently it can be forecast with reasonable cer-
tainty that chemical inhibitors would be injected into the flowing water
to suppress the unwanted growth of organisms within the heat transfer
apparatus. Since the concept calls for a once-through passage of vast
quantities of water, the amount of biological inhibitors released to the
marine environment would be very large. It will require careful analyses
by experienced marine biologists to ascertain whether the amount of in-
hibitor employed can be chosen to prevent colonization of the power plant
on one hand, yet not harm the natural ecology downstream from the plant
on the other hand. There is another source of contamination besides the
inhibitor. The metallic surfaces of the passages and conduits may corrode
and erode at about a rate of 0.025 mm (1 mil) per year. Besides imposing
an engineering design constraint to ensure that the thin walls of the in-
stallation (1 mm or 40 mils) have an adequate lifetime, this erosion
could become a non-trivial environmental contaminant.
To collect the water from the depths, a long, vertically
suspended conduit is needed; designs routinely mention lengths of more
than 600 meters, and the conduit would need to be about 38 meters in
diameter for a 1-GW plant. Presumably this conduit can be designed to
flex with the currents and need not be particularly thick. If the conduit
is 1 cm in thickness, it would require about 5 X 103 m3 of material; if
aluminum were used, the requirement would be about 1.4 X 10? kg. This is
148
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about 15 percent more aluminum than would be required for the heat
transfer surfaces.
Since the entire plant would be submerged and parts would extend
vertically for long distances under water, very considerable marine con-
struction problems are implied. However, there has been experience with
FLIP, a research oceanographic platform that is sailed into position like
a ship and then partially flooded and thereby flipped on end to become a
long, submerged vertical research platform. However, use of such a tech-
nique undoubtedly implies more structural integrity and therefore more
materials.
Although a submerged structure poses considerable questions of
construction technique, submersion eliminates some of the problems normally
associated with boilers and turbines in conventional electric generation
32
plants. In particular, conventional boilers are operated at high tem-
peratures and experience a large pressure differential between the two
sides of the boiler wall. As a result of the pressure differential,
compounded by the weakening of most materials at elevated temperatures,
the boiler walls need to be rather thick. For a submerged boiler, the
depth of submersion can be selected so that the pressure of the sea water
O O «> o
exactly matches the pressure of the vaporized working fluid. ' More-
over, the low temperature of the sea water driving the boiler very sub-
stantially reduces the thickness needed to provide the requisite structural
integrity. The low temperature of the sea water also implies that a
working fluid with a low boiling point, such as ammonia or propane, is
needed. Some workers,43 however, are wary of relying upon submersion to
establish a pressure balance. They point out that prior to startup of
the facility and in the event of a rupture, the pressure of the water might
crush the closed system containing the heat transfer fluid, thereby re-
sulting in a massive spill. Since ammonia (which is very toxic) is believed
to be one of the most suitable heat transfer fluids for this
technology,3a»33»43 a spill could have a catastrophic effect upon marine life.
149
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Clearly, a great deal of water must be moved past the heat ex-
change surfaces to extract sufficient energy to make the concept viable.
In fact, it has been cited that about one-third of the gross power output
Q Q
must be consumed to drive the pumps. Other information, however, leads
to a somewhat lower estimate: about one-eighth the power needs to be
O O
consumed to drive the pumps. In any event, the movement of this much
water requires some careful thought in engineering design to prevent the
warm and cool effluents from mixing in such a way that an eddy current is
established, drawing cool water to the warm water intake and thereby
stagnating the very thermal differences required to run the plant. Pro-
ponents of this concept of tapping solar energy maintain that it will be
possible to make use of natural currents to sweep away the water once it
it used and to replenish both the warm and cool thermal reservoirs.
Assuring this cleansing effect places a constraint on the choice of loca-
tions suitable for these plants.
Even though careful design may prevent thermal stagnation, the
movement of these vast quantities of water will lead to a change in the
ecology of the ocean. Whether this change is for the better or the worse
will be partly a matter of plant design and human desires. It is well
known that the richest fishing grounds are found in areas where there is
a natural upwelling to the surface of nutrient-rich cool waters from the
depths.42 A plant to extract solar energy stored in sea water will arti-
ficially create much the same effect by raising nutrient rich cool waters
near the surface. This "plowing" of the ocean can be expected to increase
the population size of living forms as well as alter the species composi-
tion of the population, since the ecological niche will have been altered
by the change in temperature. Since this could be managed to lead to a
larger harvest of marine life, this could be regarded as a beneficial
side effect.
150
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An important aspect of the solar sea power concept is the loca-
tion of the plants. Many countries, especially the less developed ones,
border warm tropical waters. However, the combination of water conditions
necessary to operate a plant are seldom found very near the shore; many
locations are more than 40 kilometers offshore. Countries in the Caribbean
area are important exceptions. A suitable site has been identified about
6 km off the Florida coast (east of Miami) and about 2 km off Puerto Rico.
The distant locations of these large plants from the nearest shores may
raise important questions of international law regarding exploitation
rights in international waters, environmental change, and the establish-
ment of installations that could interfere with navigation.
The long distance from shore of most possible installations
poses problems of delivering the energy generated to the point of appli-
cations. Underwater electric transmission lines have been considered,
but some people working in the area feel that production of hydrogen at
the plant site for later distribution for use as a fuel represents the
most desirable solution to the problem of energy delivery. Production of
hydrogen at the site clearly requires additional structures, perhaps on
floating platforms. Hydrogen could be sent to shore by underwater pipe-
lines or in liquid form in special tank ships. It is clear that either
an underwater electrical transmission line or a hydrogen pipeline would
result in some environmental disruption during construction.
One of the chief advantages of the use of solar energy stored
in the sea lies in the continuous availability of the energy. There
would be no important diurnal changes and only slight seasonal changes
in the power output of the station. This uniformity of output effectively
eliminates the need to store energy that is typical of terrestrial collec-
tion of insolation. This fact allows the plant output to be designed to
closely match actual demand and thereby eliminate the need to commit
materials resources for spare plant capacity that is used only occasionally.
151
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4. Wind Power
The extraction of energy from the winds, although a very old
technology, has fallen into such disfavor that few serious attempts have
been made to evaluate its potential for energy production in light of
modern aerodynamic concepts and lightweight, high strength materials.
Winds are generally not continuous, although they are usually predictable
and are remarkably regular in their occurrence. Consequently, like almost
all other solar energy concepts, utilization of wind power requires an
energy storage mechanism to buffer the timing discrepancy between supply
and demand for energy. Since all wind power concepts envision the use of
a turbine of various designs to extract the kinetic energy of the winds
and convert It into rotational energy of a shaft, generation of elec-
tricity is the most obvious form of energy output. Once again, the awk-
wardness of storing energy in electrical form suggests that the electrolysis
of water to obtain hydrogen or some other chemical form of energy storage
would be appropriate.
Not all regions of the country have winds of sufficient regu-
larity or strength to make wind power an attractive proposition—especially
since idle time greatly Increases the already high capital investment in
/
wind power generators. A brief inventory of appropriate sites on U.S.
soil or near the shoreline have indicated that in the year 2000 it might
be possible to generate about 175 GW.a
Large-scale application of wind power will require very large-
sized windmills. The recent NSF/NASA solar energy report6 suggests that
a turbine about 60 meters In diameter would be required to generate 2MW.
Thus 500 of these 60-meter turbines would have to be deployed to generate
1 OW of power—when the wind blows at the design level of the turbine.
Although too few conceptual designs of large windmills have been
published to make estimates of materials needs for windmills a productive
152
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exercise at this time, it is clear that, like all solar energy collection
processes, the materials needs of the collection mechanisms are enormous.
Thus, although wind power may itself be pollution free, substantial off-
site pollution associated with the materials production would occur.
Wind power cannot be considered separately from climate or
weather modification. For one reason, it is still unknown whether the
erection of lines or clusters of windmills that extract from 10 to 20
percent of the kinetic energy from the area swept by the turbine would
alter the local or regional climate. Just as a windbreak of trees offers
sufficient impedance to the flow of wind to result in a local shift in
air flow, and hence microclimate at the ground, so an array of windmills
would probably offer sufficient Impedance to somewhat deflect the winds.
Another reason is that the deployment of windpower Installations might be
materially affected (either beneficially or detrimentally) by weather
modification programs undertaken for other purposes. Enhancement of
wind power potential might Itself become a motive of weather modification
projects.
5. Energy Plantations
Growing plants to be used as fuel for an electricity generating
plant or as feedstock for a process such as fermentation that yields a
chemical fuel can be appropriately termed an "energy plantation." This
concept IB being studied (at SRI among other places) to determine its
feasibility. In the past, rather lavish claims based upon unreallstlcally
optimistic assumptions of photosynthetic efficiency have been advanced
about the effectiveness of this concept.8B
An energy plantation would borrow heavily from both modern in-
tensive agricultural and forestry techniques. Plants would be selected
to optimize the following variables:
153
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• Photosynthetic efficiency through the growing cycle
(including periods when the canopy of foliage is not
closed).
• Amount of dry plant material produced per unit energy
input into husbandry activities (e.g., cultivation,
harvesting, irrigation).
• Resistance to disease and climatic variations.
• Convertibility of plant material into a usable form
(such as by chipping).
• Ease of harvesting and handling.
Rather large areas are required for an energy plantation.
Sugar cane is one of the most suitable plants identified to date. With a
typical 20-month growing period, about 650 square kilometers of sugar
cane plantation would be required to sustain a 1-GW electric power plant.
Therefore, it is clear that a highly efficient, highly mechanized opera-
tion is essential to the viability of the energy plantation concept.
Many environmental problems associated with an energy plantation
transfer from experience with intensive agricultural production:
• Displacement of natural plant and animal populations.
• Erosion control.
• Irrigation practice including concern for induced
chemical change in the soil.
• Pest control (plant and animal).
• Maintenance of fertility.
• Run-off polluting waterways (fertilizer, pesticides).
• Dust and erosion control during tilling and harvesting.
• Simplifications of ecosystems.
• Introduction of exotic species (and their potential for
escape and infestation elsewhere).
• Major land and water development projects.
154
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The problem of vegetable wastes typical of foodstuff agriculture would be
avoided in an energy plantation because the crop would be completely
utilized. However, after combustion or chemical processing, there would
be an ash or sludge residual that would require disposal. Unlike coal
ash, however, these residuals can be returned to the soil (in a controlled
manner) without harm. This return of residuals to the soil is, in fact,
desirable to lessen the need to add chemical fertilizers. Maintenance
of the humus content of the soil could become a problem because no organic
matter would be returned to the soil to decompose.
Compared with other solar energy collection techniques, an
energy plantation requires relatively little commitment of physical
materials. Instead, a significant commitment of land and water that might
have major usefulness for foodstuff production is required. Although
lands considered marginal for conventional agriculture might be selected,
hilly terrain or low productivity of the soil compromise the energy
efficiency of the system.
An aquatic plantation, either fresh or marine, may also prove
feasible. Water hyacinth, for example, has attributes that are especially
attractive for the rapid production of biomass. A land-based aquatic
plantation would require the establishment of a large number of ponds to
produce an adequate quantity of aquatic plant matter. These ponds, of
course, would require continued surveillance to control incidental pest
species—e.g., mosquitos. Although natural waterways»could act not only
as a growth substrate but also as a means for waterborne plants to deliver
themselves to a downstream processing plant, it is not very likely that
sufficient surface area could be made available for this purpose. One
significant problem with water hyacinth and some algae species is that they
spread easily and are difficult to control. Their reputations as "weeds"
would probably lead to public resistance to their deliberate and large-
scale cultivation and encouragement—especially if natural waterways were
contemplated.
155
-------
As in all energy processes, it is important to consider the
energy balance to ensure that more energy is actually produced than is
consumed in the various processes. Drying the crop turns out to be the
major energy requirement in the energy plantation system. Sun drying
appears to be the most efficient way to eliminate the water from the
plant tissues preparatory to combustion or digestion. The cut plants can
be crushed and rended during harvesting to open the plant tissues to
accelerate drying. Left in the field for only a matter of days or weeks,
nearly all the water can be eliminated from plants so conditioned. Should
additional drying prove necessary, careful attention to design could
make waste heat available from the energy conversion installation for final
drying. Because field drying occupies land that could otherwise be
supporting plant growth, this second form of solar energy utilization
increases the amount of land needed for the plantation by about 10 percent.
Several ideas have been advanced to improve the photosynthetic
efficiency of the plants cultivated:
• Use the warmed power plant cooling water to irrigate
the plantation.
• Recycle the CO2 from the combustion process by erecting
canopy-like enclosures for the crop.
These measures must be evaluated in terms of the investment and operating
energies required by the hardware of the irrigation system and the en-
closing canopies to determine whether the measures result in an actual
net increase in system effectiveness.
156
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Ill SOIAR ENERGY: IMPLICATIONS AND
RECOMMENDATIONS FOR EPA ACTION
Although it is not accurate to maintain that the use of solar energy
is "pollution free," most of its environmental impacts would arise in-
directly rather than directly. The prevailing theme of solar energy
utilization is the deployment of collectors with a large surface area,
and most of the environmental effects would result from the mobilization
of sufficient natural resources to construct these collectors. Conse-
quently, many of the environmental impacts of the use of solar energy
can be classified as a continuation or intensification of the impacts
resulting from present resource development activities. However, a few
unique impacts such as certain land use questions, the evolution of sun
rights, and the plowing of the sea, would result from the various solar
energy systems already discussed.
The present status of solar energy utilization technology is sum-
marized in Table 5 (adapted from Ref. 6). Thermal collection for use
in buildings is currently receiving emphasis from the National Science
Foundation, the agency of the federal government assigned to oversee
solar energy research. Contracts to be awarded by NSF in late 1973 will
lead to hardware that can be marketed in about 1978. The use of solar
energy for biological conversion of organic matter to fuels, such as
methane, may become a minor activity by 1985, although in that time
frame this effort is expected to remain largely confined to solid waste
conversion. No other class of solar energy technology is expected to
6
be ready for meaningful deployment until the 1985-2000 time frame.
Because of the present major uncertainties in the configuration of
solar energy utilization technologies, it seems premature for EPA to
initiate the development of technologies intended to control potential
157
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Table 5
PRESENT STATUS OF SOLAR UTILIZATION TECHNIQUES
CM
00
Application
Thermal energy for buildings
Water heating
Building heating
Building cooling
Combined system
Renewable clean fuel sources
Combustion of organic matter
Bioconversion of organic materials to methane
Pyrolysis of organic materials to gas. liquid, and solid fuels
Chemical reduction of organic materials to oil
Electric power generation
Thermal conversion
Photovoltaic
Res ident ial/commercia 1
Ground central station
Space central station
Wind energy conversion
Ocean thermal difference
Status
^
y
&4
a
1
X
X
X
X
X
X
X
X
X
\
X
X
X
X
^J
c
ft
o
§
Q
X
X
X
X
X
X
X
X
X
X
1^
n
a
H
*
E
a
X
33
X
X
X
X
X
X
X
X
c
o
c +>
a ea
i-« l*
O, +»
*
« §
'-t E
£2
X
X
X
X
c
-------
adverse environmental impact. Indeed, because 00 much of the environ-
mental Impact of solar energy would be associated with the production of
materials on a vast scale for collectors, most of this control function
Is already being accomplished by the present EPA air, water, solid waste,
and land use programs that address the environmental problems associated
with minerals recovery and materials production.
EPA is, however, in a favorable position to Initiate a program to
influence the course of development of solar energy technologies in
directions that will minimize or avoid future environmental control
activities. This program could begin modestly but increase in importance
and effort as solar energy technologies become more clearly defined in
terms of configurations, processes, and the materials employed. Either
an office within EPA or a contractor could be assigned a continuing re-
sponsibility for Interactive liaison with the solar energy research and
development activities sponsored by government and Industry, By keeping
abreast of the state of the art and analyzing potential environmental
Impacts on the one hand, and by conveying to the technologists the en-
vironmental implications of the devices being developed on the other
hand, a continuing and constructive cooperative dialogue could be estab-
lished. In this manner EPA would be taking positive advantage of the
available opportunity to anticipate and Influence technology as It emerges,
rather than become obligated to take remedial action to correct environ-
mental insult.
A set of guideline objectives common to all solar utilization tech-
nologies might take the following form:
• Technologies should employ the minimum amount of materials
possible, especially those whose production is known to
have significant environmental impacts.
150
-------
• Technologies should avoid use of materials for which
there are few domestic resources, so that recovery of
lean resources will not disrupt the environment and re-
quire large quantities of processing energy.
• Devices should be designed to facilitate their dis-
mantling and recycling upon retirement.
• The materials employed should not be toxic, to avoid
contamination of the environment during the erosion or
*
weathering resulting from prolonged exposure.
• Designs should be secure against the release of hazard-
ous or toxic materials during a device failure or natural
disaster event.
• Designs and concepts should take early cognizance of
potential legal or institutional barriers, such as the
emergence of the concept of "sun rights" analogous to
mineral or water rights.
In addition to these general guideline objectives, EPA could impart its
t
concern for potential environmental problems associated with specific
technologies, such as
• Release of chemicals to suppress growth of marine organ-
isms in ocean thermal difference installations.
This category includes some subtle but significant concerns. For ex-
ample, it has been reported that sheep grazing under overhead high-
voltage electric transmission lines have been killed from copper^poison-
ing. The soil directly under the wires contained concentrations of
copper higher than those of nearby soil, although neither concentra-
tions were high on an absolute scale. Since this enrichment of copper
in the soil under the wires was not found in rural areas, it has been
suggested that erosion of copper cables may result from the action of
sulfur dioxide in the polluted air of urban areas.44
160
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• Special pesticide requirements of energy plantations.
• Climate modification induced by large terrestrial ar-
rays of solar energy collectors.
161
-------
REFERENCES
1. M. King Hubbert, "The Energy Resources of the Earth," Scientific
American, Sept. 1971, pp. 241-339.
2. Allen L. Hammond, "Solar Energy: A Feasible Source of Power?"
Science, May 14, 1971, p. 660.
3. Allen L. Hammond, "Solar Energy: The Largest Resource," Science,
Sept. 22, 1972, pp. 1088-1090.
4. "Solar Energy May Achieve Wide Use by 1980's," Chemical & Engineer-
ing News, January 29, 1973, pp. 12-13.
5. "Solar Energy Research," Staff Report of the Committee on Science
and Astronautics, U.S. House of Representatives, 92nd Congress,
December 1972.
6. "An Assessment of Solar Energy as a National Energy Resource,"
NSF/NASA Solar Energy Panel, December 1972.
7. Aden B. Meinel and Majorie P. Meinel, "Physics Looks at Solar
Energy," Physics Today, February 1972, pp. 44-50.
8. Aden B. Meinel and Majorie P. Meinel, "Solar Energy—Is It a Feasible
Option?" Presented at the Symposium of the Forum on Physics and
Society, American Physical Society, June 5, 1972.
9. Gregory M. Haas, "Large-Scale Utilization of Solar Energy" (MITRE
Corporation, Report M72-168), September 1972.
10. Gregory M. Haas, "Solar Energy," Symposium on Energy Resources
and the Environment," February 1972 (MITRE Corporation, Report
M72-50), pp. 61-70.
11. W. Hausz, G. Leeth, and C. Meyer, "Eco Energy," Intersociety Energy
Conversion Engineering Conference, September 1972.
162
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12. D. P. Gregory and J. Wurm, Production and Distribution of Hydrogen
as a Universal Fuel," Intersociety Energy Conversion Engineering
Conference, September 1972.
13. R. H. Wiswall and J. J. Reilly, "Metal Hydrides for Energy Storage,"
Intersociety Energy Conversion Engineering Conference, September 1972,
14. Allen L. Hammond, "Photovoltaic Cells: Direct Conversion of Solar
Energy," Science, November 17, 1972, pp. 732-733.
15. W. A. Anderson and A. E. Delahoy, "Schottky Barriers for Terrestrial
Solar Energy," Presented at Energy: Demand, Conservation, and In-
stitutional Problems Conference, February 1973.
16. "Getting More from the Sun" Industrial Research, July 1972, p. 72.
•
17. "Power to the People from Leaves of Grass," New Scientist, August 3,
1972, p. 228.
18. C. E. Backus, "A Solar Electric Residential Power System," Inter-
society Energy Conversion Engineering Conference, September 1972.
19. "Solar Power Satellites Could Ease Energy Crisis," Chemical &
Engineering News, January 1, 1973, p. 17.
20. Peter E. Glaser, "Satellite Solar Power Station: An Option of
Power Generation," Intersociety Energy Conversion Engineering
Conference, September 1972.
t ,M
21. J. H. Anderson, "The Sea Plant—A Source of Power, Water, and Food
Without Pollution," Presented at the International Solar Energy
Conference, May 1971, Reprinted in the Congressional Record
October 27, 1971.
22. Clarence Zener, "Solar Sea Power," Physics Today, January 1973,
pp. 48-53.
23. J. Hilbert Anderson and James H. Anderson, "Thermal Power from
Seawater," Mechanical Engineering, April 1966, pp. 41-46.
24. K. R. Williams and N.V.L. Campagne, "Synthetic Fuels from Atmo-
spheric Carbon Dioxide," Presented at the Meeting of the American
Chemical Society (Boston), April 1972.
163
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25. G. C. Szego, J. A. Fox, D. R. Eaton, "The Energy Plantation," Inter-
society Energy Conversion Engineering Conference, September 1972.
26. P. Glaser, "Potential of Power from Space" Eascon '72 Record,
1972, pp. 34-41.
27. W. C. Brown, "Satellite Power Stations: A New Source of Energy?"
Spectrum, March 1973, pp. 38-47.
28. P. Glaser, "Power from the Sun Via Satellite" Briefing before the
Subcommittee on Space Science and Applications and the Subcommittee
on Science and Astronautics, House of Representatives, May 24, 1973.
29. Federal Power Commission, "The 1970 National Power Survey, Part l"
(U.S. Government Printing Office) December 1971.
30. J. McCaull, "Windmills," Environment, January/February 1973,
pp. 6-17.
31. "Federal Windpower Program," Science Trends, June 18, 1973,
pp. 61-62.
32. A. Lavi,and C. Zener, "Solar Sea Power," Spectrum, to be published
1973.
33. W. D. Metz, "Ocean Temperature Gradients: Solar Power from the
Sea," Science, June 22, 1973, pp. 1266-1267.
34. "The Industrial Shift that Never Stops," Business Week, July 14,
1973, pp. 62c-62e.
35. H. C. Hottel and J. B. Howard, New Energy Technology: Some Facts
and Assessments (MIT Press, Cambridge, Mass.) 1971.
36. A. B. Meinel, M. P. Meinel, B. 0. Seraphin, D. B. McKenny,
"Progress in Solar Photothermal Power Conversion," A Report Presented
to the Subcommittee on Environment, Committee for Interior and
Insular Affairs, U.S. House of Representatives, July 13, 1973.
37. D. A. Brobst and W. P. Pratt (Eds.), United States Mineral Resources,
Geological Survey Professional Paper 820. (U.S. Government Printing
Office, Washington), 1973.
164
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38. R. S. Berry and M. F. Fels, "The Production and Consumption of
Automobiles: An Energy Analysis of the Manufacture, Discard, and
Reuse of the Automobile and its Component Materials," (Report to
the Illinois Institute for Environmental Quality), July 1972.
39. "The Sun Breaks Through as an Energy Source," Business Week.
May 19, 1973, pp. 68d-68k.
40. E. L. Ralph, "Large Scale Solar Electric Power Generation," Solar
Energy. Vol. 14, December 1972, pp. 11-20.
41. R. Bowers and J. Frey, "Technology Assessment and Microwave Diodes,"
Scientific American, February 1972, pp. 13-31.
X
42. J. D. Isaacs, "The Nature of Oceanic Life," Scientific American.
September 1969, pp. 147-162.
43. J. G. McGowan, J. W. Connell, L. L. Arabs, W. P. Goss, "Conceptual
Design of a Rankine Cycle Powered by the Ocean Thermal Difference,"
Proceedings of the 8th Intersociety Energy Conversion'Engineering
Conference (Philadelphia, Pennsylvania), August 13-16, 1973,
pp. 420-427.
44. T. H. Maugh, "Trace Elements: A Growing Appreciation of Their
Effects on Man," Science. July 20, 1973, pp. 253-254.
45. "Compilation of Air Pollutant Emission Factors (Second Edition)",
U.S. Environmental Protection Agency, April 1973.
46. "Chloride Route to Cheaper Aluminum" New Scientist. March 1, 1973,
pp. 487.
165
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Appendix B
GEOTHERMAL ENERGY
by
Evan E. Hughes
167
-------
CONTENTS
I GEOTHERMAL ENERGY: STATE OF THE ART 170
A. Introduction 170
B. Use of Natural Geothermal Steam 171
1. Contrasts: Fossil Fuel Versus Geothermal 171
2. Constraints on Plant Size 176
3. Impurities in Natural Steam 178
4. Other Consequences of Using Natural Steam I84
5. Hot Water Versus Vapor-Dominated
Geothermal Systems 185
6. Power Plants for Hot Water Resources I86
C. Use of Stimulated Geothermal Resources 190
D. Use of Geopressured and Magmatic Resources 192
II GEOTHERMAL ENERGY: ENVIRONMENTAL IMPACTS 193
A. Introduction 193
B. Survey of Properties and Impacts of
Geothermal Resources 193
C. Scaling Factors for Environmental Impacts 199
1. Scaling Factor for Land Use 199
2. Emission and Effluent Factors 200
D. Environmental Impacts of Large-Scale Use of
Geothermal Energy 201
1. Land-Related Impacts 202
2. Impact on Air Quality 203
3. Impact on Water Quality 204
III GEOTHERMAL ENERGY: IMPLICATIONS FOR EPA 206
REFERENCES 210
168
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ILLUSTRATIONS
1 Geotherraal Power Plant—Dry Steam Wells,
Single Cycle 176
2 Geothermal Power Plant- Generation—Hot Water Wells,
Binary Cycle 189
TABLES
1 Comparison of Fossil Fuel and Geothermal
Power Plants 174
2 Land Use and Depletion Considerations for
Three Possible Well Spacings 179
3 Noncondensable Gases in the Geothermal Steam
at the Geysers . 181
4 Composition of Geothermal Fluids 182
5 Characteristics of Selected Geothermal Fields ....... 194
169
-------
I GEOTHERMAL ENERGY: STATE OF THE ART
A. Introduction
The production of electric power from energy contained in steam and
hot water beneath the earth's surface is currently being accomplished.
In fact, such production has been going on since 1904 in Italy and since
1960 in the United States. Therefore, this discussion of the environ-
mental impacts of the production of energy from geothermal sources can be
based in part on actual experience. The main reason for treating geo-
thermal energy as a new energy technology is that any use of this resource
on a scale at all comparable with that of this country's use of energy
would indeed be new and could become visible as a new set of environmental
impacts. This working paper examines the present use of geothermal energy
and draws conclusions regarding the environmental impacts of the projected
use of this resource to meet a significant fraction of future energy needs
in the United States.
First we survey the present technology for converting geothermal
energy into electrical energy. The experience with this technology forms
the basis for our recognition of some environmental impacts and for our
projections of changes in the nature and scale of geothermal energy use.
We do not necessarily view the present state of the art as the technology
that will actually be deployed to tap most of the geothermal energy
resource, but it should provide a more accurate projection of future geo-
thermal technology than projections we now have for other energy sources
not currently in commercial operation.
170
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B. Use of Natural Geothermal Steam
In a geotfaermal power plant, the steam used to drive the generators
of electrical power is obtained from wells drilled into reservoirs of
steam or hot water hundreds of meters below the earth's surface. The
crucial -contrast to a conventional fossil fuel power plant is the fact
that the steam is obtained without the combustion of fuel to fire a boiler.
This contrast provides the basis for the expectation that geothermal
energy will alleviate the environmental problems so clearly associated
with our usual steam-electric plants. No combustion means no emission
of the familiar air pollutants: oxides of nitrogen, oxides of sulfur,
carbon monoxide, unburned hydrocarbons, and particulates. This constitutes
a significant environmental advantage.
The steam that is obtained from below the earth's surface is not
t
identical to the steam obtained from the boiler of a fossil fuel plant.
The differences between the steams necessitate differences in the turbine-
generators used to convert the steam energy into electrical energy. The
differences between the steams also give rise to additional contrasts
between the environmental impacts of fossil fuel and geothermal power
plants. These contrasts, occurring both before and after the boiler stage,
do not accumulate to the environmental advantage of the geothermal plant.
We now turn to an examination of these technical and environmental differ-
ences as they appear in state-of-the-art power plants of the two types.
1. Contrasts; Fossil Fuel Versus Geothermal
The turbine is the classical heat engine stage of a steam power
plant. It receives energy in the form of the heat of the high temperature,
high pressure steam and converts some of that heat into the mechanical
energy of the rotating shaft common to both the turbine and the generator.
The heat energy not converted into mechanical energy emerges from the
171
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turbine as the heat of the low temperature, low pressure steam bound for
the condenser unit of the power plant. The laws of thermodynamics limit
the fraction of the input heat energy that can be converted into mechanical
energy (work) to a value that depends on the temperatures of the steam
at input and output. To maximize this ratio of work to input energy the
input temperature must be as high as possible and the output temperature
as low as possible. Modern fossil fuel plants obtain therraodynamic effi-
ciencies of over 40 percent by superheating the steam that goes into the
turbine from the boiler. But a geothermal steam plant must take the steam
provided by the subsurface reservoir and such geothermal steam, although
sometimes superheated, has never been found at temperatures comparable
with those obtainable in boilers. The consequence of these physical facts
is that a geothermal plant must take in and exhaust out considerably more
heat than a fossil fuel plant producing the same amount of electrical
energy.
Here are the figures for a quantitative comparison of the sort
just described: A modern fossil fuel powered plant (Pacific Gas and
Electric's new units numbered 7 and 8 at Moss Landing, California) has
o
turbines accepting superheated steam at a temperature of 540 C and a
o
pressure of 25 MPa and exhausting this steam to the condensers at 29 C
and 4.1 kPa (1.2 inches of mercury). The theoretical efficiency of an
ideal heat engine operating between these two temperatures is 63 percent.
The actual operating experience at the plant is that 8.71 MJ of heat
content of fuel produce 1 kWh of electricity. This implie~ an actual
boiler and conversion efficiency of 41 percent, which also implies that,
if the unit were scaled up to generate electrical power at the rate of
1.0 gigawatt (GW), then waste heat would be exhausted into the plant's
environment at the rate of 5.2 TJ per hour (2.4 GW). These figures are
to be compared with a recent (1971) addition to this country's geothermal
generating capacity. The turbines of a modern geothermal plant (PG&E's
-------
units 5 and 6 at The Geysers, California) accept the steam provided at a
temperature of 180°C and a pressure of 0.784 MPa and exhaust this steam
to the condensers at 52° C and 14 kPa (4" Hg). The theoretical efficiency
of an ideal heat engine operating between these two temperatures is 28
percent. The actual operating experience at the plant is that 22.8 MJ
of heat content of steam (8.2 kg of steam at the entering temperature and
pressure) produce 1 kWh of electricity. This ratio of electricity to heat
implies a conversion efficiency of 16 percent. It also implies that to
generate electrical power at the rate of 1000 MW this type of geothermal
plant would exhaust heat into the environment at the rate of 19.3 TJ per
hour (5.2 GW). The numbers used in developing this comparison are summa-
rized in Table 1.
The low thermal efficiency revealed by the figures just given
is inherent in geothermal energy development. The input steam cannot
be at a temperature higher than that provided by the natural reservoir.
Increased efficiency obtained by lowering the temperature at the discharge
end of the turbine is limited by the ambient temperature of the local
environment. Because the heat energy in geothermal steam is supplied
without fuel costs, geothermal plants are economically competitive with
fossil fuel plants despite their lower thermal efficiency. Given that
known geological steam reservoirs have temperatures in the range 200 to
350°C {400 to 650°F), marked improvement in thermal efficiency cannot be
expected, and the relatively larger injection of heat into the plant's
environment must be accepted as a necessary consequence of geothermal
power production.
Increases in the economic efficiency of power plants are indi-
cated by decreases in the cost of generating a given amount of electrical
energy. Such increases in efficiency have been realized through the
economics of scale in the case of fossil fuel and nuclear plants. The
173
-------
Table 1
COMPARISON OF FOSSIL FUEL AND GEOTHERMAL POWER PLANTS
Fossil Fuel Geothermal
Moss Landing Units 7 and 8 The Geysers Units 5 and 6
Rated capacity of unit 750 MW 55 MW
Steam temperature entering turbine 540°C (1000°F) 180°C (355°F)
Steam pressure entering turbine 25 MPa (3675 psia) 784 kPa (114 psia)
Steam temperature leaving turbine 29°C (84°F) 52°C (126°F)
Steam pressure leaving turbine 4.1 kPa (1.2" Hg) 14 kPa (4.0" Hg)
Ideal thermal efficiency 63 percent 28 percent
Actual heat rate 8.7 MJ/kWh (8,296 Btu/kWh) 23 MJ/kWh (21,690 Btu/kWh
Actual efficiency 41 percent 16 percent
9 9
Heat rejected at plant site per GW electric power 1.4 GW (5x10 Btu/hr) 5.2 GW (18x10 Btu/hr)
Source: SRI, 1973.
-------
trend toward larger plants would have to be included in an assessment of
the state of the art in the technology of such plants. In the geothermal
case, however, the peculiarities of reliance on a natural source of steam
enter the analysis and suggest that the limit on unit size is already
within sight and is appreciably below the thousand megawatt sizes now
common for new fossil fuel and nuclear generating plants. Generating
units at The Geysers have been scaled up by successive factors of two
since the early 1960s, but are now seen as leveling off not much above
the 106-MW capacity of the unit scheduled to go on line in 1974.x* In
that particular case, the limit is said to be based on considerations of
transportation of the unit over the access roads and of the length of
steam supply lines. This latter consideration concerns an issue of
importance to any geothermal plant, namely, the power generating capacity
per unit of land area.
The geothermal power plant does away with the boiler required
in fossil fuel and nuclear plants, but in its place it must substitute a
network of wells and pipelines to tap and transport the energy contained
in the geothermal steam. (A schematic diagram of the system used at The
Geysers is shown in Figure 1.) In terms of environmental impact, it is
more useful to view the steam gathering facilities as replacements for the
raining, oil drilling, fuel processing, and other such facilities associ-
ated with fossil fuel or nuclear plants. However viewed, the particular
kind of energy collection used in a geothermal plant determines many of
the technological constraints and environmental impacts of this means of
producing electrical energy. Unit size and waste heat production have
already been named in this connection. Other consequences of using
naturally occurring geothermal steam are discussed in succeeding sections.
-------
STEAM WELLS
D
TURBINE
GAS
*
t
! BAROMETRIC
! CONDENSER
n-»n ,*«
INDUCED-DRAFT COOLING TOWER
OVERFLOW
] HOT WELL
\ N, SECOND STAGE EJECTOR AND
\ AFTERCONDENSER
— Steam
•— Water
... Gas
FIRST STAGE EJECTOR AND INTERCONDENSER
SOURCE: Kaufman, 1964. (Reference 2)
FIGURE 1 GEOTHERMAL POWER GENERATION—DRY STEAM WELLS, SINGLE CYCLE
2.
Constraints on Plant Size
We have stressed the fact that the steam temperature is determined
by the geophysical conditions of the natural reservoir, and to this extent
it is beyond the control of the plant designer. However, the designer
does have control over details of how the natural reservoir is to be tapped.
Decisions must be made as to the size and spacing of the wells drilled
into the reservoir. These decisions tend to be based on experience Qb-
tained in operating geothermal steam fields and power plants. An important
design decision, related to the eventual decision on generating unit size
already mentioned, concerns the spacing of the wells. To minimize the
energy lost in transporting the steam to the turbine, the wells should
be placed as close as possible to the power plant, and hence close to
each other. But two other features call for a large separation of steam
wells, namely, (1) the interference effect whereby the addition of a nearby
well decreases the steam production rate of an existing well and (2) the
depletion rate effect whereby the spacing of wells closer together causes
176
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the total production rate to decline in a shorter length of time.3 Once
the depletion characteristics of the field are known, this information
combined with the desired lifetime for the generating plant determines
the rate of production of steam that can be maintained for the lifetime of
the plant from a given surface area of land. Because there is a limit to
the distance the steam can be usefully transported over the surface, there
is a limit to the land area that can be tapped for a single generating
unit. There follows then a limit to the capacity of the generating unit.
Again, some numbers taken from the operating experience at The
Geysers can illustrate the design considerations we have just discussed.
The closest well spacing is about one well per five acres of land. To
place wells much closer together would result in unacceptably large inter-
ference effects and short depletion time. Adopting 2 hectares (5 acres)
per well for the spacing and combining it with the observed production rate
per well of 68,000 kg/hr (150,000 Ibs/hr) gives a figure of 34,000 kg of
steam per hour per hectare at The Geysers. Given that experience dictates
a limit of less than a mile for the distance over which steam can be
4
economically transferred by pipe, we arrive at the expectation of obtain-
ing about 9 million kg of steam per hour from the 250 hectares in the
square mile of land one could tap for a single plant.
The quality of this steam and the efficiency of the generators are
6
such that it requires about 900,000 kg of steam per hour (2x10 Ibs/hr)
to generate 100 MW of electrical power.6 This suggests that a plant of
1,000 MW could be powered by the steam within transportable distance
of the plant. However, depletion considerations reduce this maximum
plant size still by a considerable factor. Measurements of production
rates of steam wells over the past six years at The Geysers show
an average exponential decay with a five year half-life for wells spaced
at two hectares. This implies that over the 20-year lifetime of a generat-
ing unit the production of wells at this spacing would fall to one-sixteenth
177
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of their initial production rate, thus necessitating the drilling of 16
times the number of wells needed initially. Because land sufficient for
drilling a large number of replacement wells must be set aside, the actual
capacity of a generating unit supportable on a square mile of land is on
the order of 100 MW rather than 1000 MW. Thus the peculiarities of the
geothermal resource limit the possibilities for economies of scale in
the building of the turbine-generator units.
Estimates of the land area needed to support a given geothermal
generating capacity can be derived from the same specific facts used here
to explain the relatively small unit sizes contemplated for geothermal
electrical power generation. Because the subsequent discussions of
environmental impact in this report make use of this estimate of the land
area involved, the figures just presented are summarized in Table 2.
Table 2 also shows that the larger spacings such as 8 or 18 hectares per
well lead to substantially the same generating capacity per square mile
because the decreased number of wells is compensated for by the increase
in well lifetime. Thus, as one might expect, the power capacity per unit
area is determined by the nature of the steam resource rather than by the
way it is tapped.
3. Impurities in Natural Steam
The effects discussed so far are based on the energy content of
natural geothermal steam. A number of other technical and environmental
effects have their basis in the material content of naturally occurring
geothermal steams. These steams vary in content from one geothermal
deposit to another, but the natural deposits invariably contain impurities
that would not be allowed in water for the boiler of a fossil fuel or
178
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Table 2
LAND USE AND DEPLETION CONSIDERATIONS
FOR THREE POSSIBLE WELL SPACINGS
-j
to
Number of wells possible on one
square kilometer
Time for production rate to drop
by half
Number of wells to support 30 MW
plant at initial production rate
of 60,000 kg steam/hr per well
Number of wells needed per initial
well to make up for depletion over
20-year period
Total number of wells drilled to
support 30 MW plant for 20 years'
operation
Area required to support 30 MW
plant for 20 years of operation
2 hectares
(5 acres)
per well
50
5 years
16
80
1.6 sq km
8 hectares
(20 acres)
per well
12
12 years
15
1.2 sq km
18 hectares
(45 acres)
per well
19 years
10
1.8 sq km
Source: SRI, 1973.
-------
nuclear plant. The presence of impurities has technical consequences for
the construction and operation of a geothermal power plant and has en-
vironmental consequences for both the air and water media.
The technical complications that arise from the use of natural
steam are the special steps needed to avoid impact damage and corrosion.
Traps and separators to capture sand particles are built into the steam
pipe system and the dust content of the steam is monitored to minimize
damage caused by the impact of small particles on the turbine blades. At
The Geysers, the operating time between overhauls of the turbines should
soon be extended to about two years, a figure to be compared with the five
to six year interval that is routine with PG&E's fossil fuel units.'
Molecular impurities present in the steam at The Geysers include a variety
of metals and ions, as well as a variety of noncondensable gases. These
constituents are detailed in Tables 3 and 4. The presence of these
materials can adversely affect the operating equipment as well as the sur-
rounding environment. This threat of corrosion is met by the use of
special alloys and protective coatings in the construction of the power
plant. Tests lasting for several years are being performed at The Geysers
to determine which materials are most resistant to the particular cor-
rosive influences present. Austenitic stainless steel, 13-percent chromium
steel, and aluminum appear to have key roles in the construction of a geo-
thermal power plant resistant to corrosion and impact erosion.10
Because a geothermal reservoir discharges gases other than
steam when tapped, there is the potential for air pollution. The non-
condensable gases found in the geothermal steam at The Geysers were listed
in Table 3. The most abundant such impurity is carbon dioxide, which is
not regarded as an air pollutant. (It can be argued that manmade C00 has
£
the potential to affect global climate, but that is not a regional air
pollution issue and, in any case, is not an adverse effect peculiar to
geothermal power plants. In fact, the C02 emissions from a fossil fuel
180
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Table 3
NONCONDENSABLE GASES IN THE
GEOTHERMAL STEAM AT THE GEYSERS
Percent by weight
Gas
Carbon dioxide
Hydrogen sulf ide
Methane
Ammonia
Nitrogen
Hydrogen
Ethane
TOTAL
Low
0.0884
0.0005
0.0056
0.0056
0.0016
0.0018
0.0003
0.120
High
1.90
0.160
0.132
0.106
0.064
0.019
0.002
2.19
Design
0.79
0.05
0.05
0.07
0.03
0.01
-
1.00
Source: Finney, 1973 (Reference 1, Table 1),
181
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Table 4
COMPOSITION OF OEOTHERMAL FLUIDS
Parta per million by weight
Component
Sodium
Potaaalum
Calcium
Lithium
Magneaium
Strontium
Barium
Rubidium
Ceaium
Iron
Manganeae
Lead
Zinc
Silver
Copper
Silicon dioxide
Chlorine
Boron
Fluorine
Sulfur
Total Dlaaolved
Solid*
Ammonium
Bicarbonate
The Geyaera,
California
.12
.10
,20
,002
.06
,10
—
_•
—
—
—
—
—
__
—
.50
20,00
,10
.10
7.10 (eulfate)
Cerro Prleto,
Mexico
5,610
1,040
321
14
Negative
28
57
—
--
—
--
_-
__
Trace
Trace
--
0,604
12
Trace
10
Niland,
California
53,000
16 , 500
27,800
210
10
440
250
70
20
2,000
1,370
80
500
--
__
400
155,000
300
__
30
28,38
236.0
775.0
17,000
250,000
Source: Rex, 1070 (Reference 8) and Koenlg, 1070 (Reference 0),
1§2
-------
plant are about 20 times those from an equivalent geothermal plant.)11
The moat critical air pollutant liated in Table 3 IB hydrogen suiflde.
Since no emission controls are yet in use at The Geysers, the
gases listed escape freely to the air. This emission occurs sporadically
as a result of the venting of steam and continuously as a result of the
release of steam from the turbine to the condenser and cooling tower. The
environmental impact of such emissions is discussed later in this report.
The amount of sulfur put into the air by a 1000-MW geothermal plant at The
Geysers would be comparable with that emitted by a 1000-MW fossil fuel
plant burning coal with a 1 percent sulfur content. The sulfur is emitted
as H 8 from a geothermal plant and as SO from a fossil fuel plant. PGfcE
IB investigating the possibility of controlling H 8 emissions by the con-
2
densing of the sulfur as sulfate in the condenser. Apparently about 30
percent of the sulfur already goes out of the steam via this route,13
Catalyzed precipitation of the sulfur is also under Investigation.
The impurities in the steam that have their primary effect as
dissolved matter in the condensate were listed in Table 4. In addition
to the equipment corrosion problems posed by these materials in solution,
a potential water pollution problem arises from the ejection of condensate
Into the local water supply. The high content of boron and ammonium in
the condensate led to the decision not to continue disposal into local
streams at The Geysers after unit number 4 was added in 1008. The alter-
native to ejecting the condensed steam and its contents into the water
supply is the reinjection of this material into the subsurface geothermal
reservoir. This has been successfully carried out at The Geysers for the
past several years. The alternative of chemical treatment of the power
plant's waste water was found to be prohibitively expensive.13
183
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4. Other Consequences of Using Natural Steam
In addition to the effects on equipment, air, and water dis-
cussed so far, the reliance on a natural source of steam has other environ-
mental effects that differ from those associated with other types of
steam generating plants. Foremost among such effects are those arising
from the exploration and drilling that necessarily accompany the tapping
of a geothermal energy source. Exploration and drilling also accompany
the production of energy from oil and gas. This means that both the tech-
nology and the environmental impact of these aspects of geothermal energy
development are similar to the oil and gas case.
Two significant contrasts should be pointed out. First, in the
geothermal case the exploration and drilling take place at the site of the
generating plant. This fact implies the concentration of the impacts
associated with fuel collection, fuel processing and transport, and elec-
tricity generation to a single site. It also implies the lack of the
freedom to place the electrical generator close to the site of electricity
consumption. The second contrast to oil and gas drilling operations is
the particular noise problem associated with geothermal steam production.
The inadvertent blowout of a geothermal steam well produces a loud noise
as the steam rushes into the air. Some deliberate ventings of geotherraal
steam into the atmosphere must occur as a part of normal operations when
a well is being put on line to feed its steam into a generating unit being
started up. At The Geysers, although mufflers are installed to reduce
such noises once a well is completed, a noise problem remains. Some noise
is inevitable and cannot be muffled, as when the steam reservoir is first
tapped during the drilling. It is also a fact that the noise is hard to
muffle because of its intensity and the low frequency of its spectrum.
184
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5. Hot Water Versus Vapor-Dominated Geothermal Systems
The description up to this point has been based on the one case
where geothermal energy has been put to use in the United States, namely,
The Geysers power plant in California. This particular geothermal reser-
voir is an example of the type that is most easily tapped for electric
power generation. It is a vapor-dominated geothermal system as opposed
to a hot water-dominated system. The present discussion of the state of
the art of geothermal energy must go on now to include aspects peculiar
to the hot-water systems. The inclusion of this material is made all the
more necessary by the fact that most of the known geothermal energy
resources of this country are systems dominated by hot water.
The distinction between hot water-dominated geothermal systems
and vapor-dominated geothermal systems is made on the basis of which of
the two relevant phases of water, the vapor or the liquid phase, is the
continuous fluid that controls the pressure within the subsurface geo-
thermal reservoir.1* The significant contrast as far as the production
of electrical energy is concerned is that to tap the energy of a hot
water-dominated system large quantities of liquid water containing dis-
solved minerals must be brought to the surface. The vapor required by the
turbine-generator is obtained either by using the hot water to vaporize
some other fluid, such as isobutane, which then becomes the working fluid
for the turbine, or by allowing the hot water to turn into steam by virtue
of its being subject to lower pressure than it experienced in the reser-
voir. This latter process, allowing the water to flash to steam, has the
disadvantage of using only the fraction of the water that becomes steam
as an energy input to the turbine. This fraction is only about 15 to
25 percent.9
185
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6. Power Plants for Hot Water Resources
Flashed steam from hot water wells is being used to produce
electricity in New Zealand and Mexico. The New Zealand geothermal power
plant at Wairakei (160 MW) has not been an unqualified success. The first
experimental plant was abandoned in 1964 after only a year of operation
because of an insufficient steam supply from the wells.15 The plant was
constructed again on a more centralized plan using extensive pipelines to
bring the steam to a site where a river could be used for cooling water.
Recent discoveries of natural gas in New Zealand have resulted in a deci-
sion to postpone the expansion of geothermal power which had been planned
for this decade.
The experience with geothermal power from hot water wells in
Mexico is more likely to be useful for applications envisioned for the
United States. At Cerro Prieto, near the north end of the Gulf of
California, a 75-MW geothermal power plant is just beginning operation.
The reservoir is water at temperature somewhat over 300° C and of high
salinity, about 15,000 parts per million. The Cerro Prieto plant is on
the southern extremity of a geothermal field extending into the Imperial
Valley of California, and warrants special attention because of the great
similarity of the resource to significant geothermal resources in the
United States. The conversion of steam to electricity will be comparable
in efficiency and method with that at The Geysers. But because Cerro
Prieto is a hot water field, the 9 kg of steam needed to produce 1 kWh
of electricity will be accompanied to the surface by at least 30 kg
of water of high salinity.ls> 17 No attempt is being made at Cerro Prieto
to reinject this waste brine into the geothermal reservoir, but plans for
similar installations in California's Imperial Valley envision either
reinjection or desalination of the brine.18
186
-------
One method of estimating the economic costs or the environmental
impacts of geothermal power from a hot water source such as the Imperial
Valley is to assume similarity to the actual experience at The Geysers
and then to add on the additional costs or impacts associated with the
brine. This method has been used by Goldsmith.19 As experience accumu-
lates at the Cerro Prieto plant, another basis for such estimates will be
established.
As was mentioned above, reinjection is being carried out at The
Geysers. Because the reinjection there is easier than it would be in a
hot water field, two important contrasts should be noted. First, the
amount of waste water brine to be disposed of is much greater in the case
of a hot water system. At The Geysers, the condensed geothermal steam
becomes the cooling fluid for the condenser by virtue of its passage
through the evaporative process in the cooling tower. Since this evapo-
rative cooling is accomplished by the evaporation of about 80 percent of
the condensed steam, the amount of condensate remaining to be disposed of
by reinjection is only 20 percent of the mass of steam brought to the
surface in the first place. Given the additional fact that a typical hot
water generating system produces at least 3 pounds of water for every
pound of steam, it follows that about 15 times as much waste water is to
be reinjected (or otherwise treated and disposed of) than is being rein-
jected for a comparable generating system at The Geysers. The second con-
trast in the reinjection processes derives from the lower pressure required
for reinjection in the case of a vapor-dominated system like The Geysers.
Because the steam pressure in a vapor-dominated reservoir is less than the
hydrostatic pressure at the same depth,30 the natural gravitational pres-
sure of the column of water in the reinjection well is sufficient to force
the waste water back into the reservoir. On the other hand, reinjection
into a hot water reservoir may require pumping to increase the pressure
above hydrostatic and, therefore, may require energy from the power plant.
It is more like the reinjection practiced in many oil fields.
187
-------
There is an alternative technology for the exploitation of hot-water-
dominated geothermal energy resources, a technology that is further removed
from our present base of experience in that it is not simply a system like
The Geysers with provision for handling of hot water wastes added on. This
alternative power generation scheme is referred to in various ways, the
most common being combined cycle, binary cycle, or vapor-turbine cycle.
The method entails bringing the hot water to the surface under enough
pressure to keep it in the liquid phase, extracting its thermal energy by
heat exchange to another fluid, expanding this working fluid through a
turbine to power the electrical generator, and reinjecting the hot water,
now somewhat cooled by the heat exchange, back into the geothermal reser-
voir. A schematic of a generating plant using this technology is shown
in Figure 2. This schematic is for a 10-MW binary cycle power plant built
as a test facility by San Diego Gas and Electric Company (SDGE) near
Niland on the Buttes anomaly in the Imperial Valley. This particular
example of a binary cycle plant includes the possibility of flashing some
of the hot water (brine) to steam before the passage through the heat
exchanges.
The design of an electrical generating system using a hot water
geothermal source contains a number of trade-off decisions based on a
knowledge of economic costs and environmental impacts, as well as of tech-
nical principles. Thus, the complications of the binary cycle must be
weighed against those of sending steam flashed from saline water directly
into the turbine and condenser. The benefits of getting input heat from
water or steam at the highest possible temperature and pressure must be
weighed against the costs in dollars and energy of using pumps rather
than natural percolation action to get that heat to the surface. The air
quality advantages of the binary cycle, which derive from keeping both
the geothermal brine and the working fluid in closed cycles and away from
exposure to the atmosphere, must be weighed against its added water
188
-------
00
(O
NONCONDENSIBLE
GASES
STEAM-ISOBUTANE
HEAT EXCHANGERS
BRINE
FLASH
DRUM
I
BRINE-ISOBUTANE
HEAT EXCHANGER
r
FUTURE
I I
TURBINE
GENERATOR
ISOBUTANE
CONDENSER
•*—
TO AND FROM
COOLING TOWER
ISOBUTANE
ACCUMULATOR
ISOBUTANE
CIRCULATING PUMP
BRINE REINJECTION
PUMP
GEOTHERMAL RESERVOIRS;
SOURCE: San Diego Gas and Electric Company Geothermal Tost Facility.
FIGURE 2 GEOTHERMAL POWER GENERATION—HOT WATER WELLS, BINARY CYCLE
-------
resource costs, which derive from not having condensed steam available
for use as cooling water. Work has been done to establish systematic
procedures for optimizing the performance of a binary cycle generating
plant given the characteristics of a particular geothermal site.21 The
combination of such engineering work and the operating experience begin-
ning to emerge from small scale projects around the world will soon put
the assessment of hot water sources on an empirical basis more like that
for dry steam sources such as The Geysers.
The description so far has dealt with the tapping of naturally
occurring geothermal reservoirs. These reservoirs consist of hot water
or steam heated by thermal energy from within the earth and contained
within some large, continuous volume under the earth's surface. These
energy resources are tapped by using the naturally occurring water or
steam to carry the heat to the surface via wells drilled for that purpose.
Therefore, such natural reservoirs constitute hydrothermal-convection
systems whether they are dry or wet in nature. In addition to the tech-
niques discussed so far, there are ways to obtain geothermal energy with-
out depending solely on natural occurrences of the combination of (1) a
geothermal heat source, (2) a large volume capable of holding water or
steam, and (3) the presence of water in the heated volume. Energy ob-
tained by intervention designed to create this combination where it does
not occur naturally is referred to as stimulated geothermal energy.
C. Use of Stimulated Geothermal Resources
Like the hydrothermal-convective systems we have been describing,
geothermal energy systems that result from stimulation must rely on some
natural mechanism to bring heat from the earth's interior, and, as in the
case of hydrothermal-convective systems, the greater the rate of natural
heat flow the greater the potential of the energy resource. Stimulation,
then, does not entail the generation of the heat source but rather entails
190
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the creation of one or both of the other two ingredients of the combina-
tion required for a geothermal reservoir, namely, the large, continuous
volume and the water present in that volume. The large, continuous volume
of a useful geothermal reservoir usually consists of the spaces within
interconnected cracks in fractured crystalline rocks. This suggests
that the creation of a geothermal reservoir can be stimulated by inter-
vening to fracture rock that is near a strong heat source but is not suf-
ficiently fractured to constitute the chamber needed to store and transport
water or steam. Various means of fracturing the hot, dry rock have been
suggested and some have been studied in detail. Hydrofracturing, high
explosives, acid treatments, thermal fracturing, and nuclear explosives
have all been mentioned in this context. Considerable analysis has been
done on nuclear stimulation as a part of the AEC's Plowshare program.
Because the development of stimulated geothermal energy is appreciably
behind that of hydrothermal convective and because extensive use of stimu-
lated sources will have to follow the demonstrated success of significant
exploitation of the natural hydroconvective sources, this report does not
pursue the technology and environmental impact of stimulated geothermal
energy. To the extent that the guarantee that geothermal energy can assume
a major share of the production of electricity in the United States becomes
a determining factor in the decisions of utilities to go ahead with use
of this source at all, the possibilities for stimulating geothermal energy
«
could become crucial because of the vast increase in potential sites that
would accompany a stimulation capability. However, at the present tine,
utilities are going ahead with development of hydrothermal convective
sources, and concentration on these environmental impacts is warranted
for the near term. The tests of stimulation techniques should be carried
out with environmental protection in mind, both in the physical execution
and in the data collection stages. This appears to be the case.
191
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D. Use of Geopressured and Magmatic Resources
Two other categories of geothermal energy exploitation are currently
under discussion but are not yet in the testing stages. These are the
use of geopressured resources and the use of magmatic resources. Geo-
pressured reservoirs consist of hot water and methane gas stored in the
interstices of porous, as opposed to fractured, rock in sedimentary
basins. Such aquifers are detected by their abnormally high fluid pres-
sures and can be tapped for energy in three ways: (1) the chemical energy
of the contained methane gas, (2) the mechanical energy of the water
released from its high pressure containment, and (3) the thermal energy
(heat) of the water. The relatively low quality (i.e., low temperature)
of the thermal energy in these reservoirs prevents their exploitation by
the techniques now used for hydrothermal convective sources and, thus,
puts their possible use further into the future.
The second category, magmatic geothermal reservoirs, consists of the
locations where hot, molten rock from the earth's interior has penetrated
close enough to the surface to become accessible via drilling. At
present, neither the extent of such resourcss nor the technology for
tapping them are clear. In short, geopressured and magmatic resources
exist as potential sources of geothermal energy production but are so far
behind hydrothermal convective resources in terms of their utilization
that they lack priority for present environmental impact research.
192
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II GEOTHERMAL ENERGY: ENVIRONMENTAL IMPACTS
A. Introduction
The description of geothermal energy technology presented in the
first part of this working paper emphasized that the major environmental
liabilities of geothermal energy are direct consequences of the fact
that we must accept the hot water or steam as nature provides it. The
major environmental advantages are consequences of the same fact, viewed
in a different light, namely, the fact that nature has provided us with
thermal energy capable of producing electricity without the necessity
of combustion in a boiler or fission in .the core Of a nuclear reactor.
Hence, we should focus on the properties of geothermal steam or water
as providing the best introduction to some details of the environmental
impact associated with the use of the most accessible geothermal energy
resource, namely the hydrothermal convection system. Table 5 summarizes
several properties of such geothermal reservoirs, selected from fields
being studied or tapped throughout the world. A brief description of
the contents of Table 5 can serve to introduce this discussion of environ-
mental impacts of geothermal energy.
B. Survey of Properties and Impacts of Geothermal Resources
The temperatures in column 2 are low in comparison with the 500°C
(or higher) temperatures of the steam generated in the boiler of a
modern fossil fuel plant. The consequence of this was stressed by the
comparison of PG&E's latest fossil fuel and geothermal generating units
given in the first part of the paper. The low thermal efficiency which
characterizes geothermal plants is the inevitable consequence of the
193
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Table 5
CHARACTERISTICS OF SELECTED GEOTHERMAL FIELDS
(1)
Field
Larderello, Italy
The Geysers, U.S.A.
Matsukawa , Japan
Otake , Japan
Wairakei, New Zealand
Broadlands, New Zealand
Pauzhetsk, U.S.S.R.
Cerro Prieto, Mexico
Niland, U.S.A.
Ahuachap£n, El Salvador
Hveragerdi, Iceland
Reykjanes , Iceland
Namafjall, Iceland
(2)
Reservoir
temperature, °C
245
245
230
200+
270
280
200
300+
300+
230
260
280
280
(3)
Reservoir
fluid
Steam
Steam
Mostly steam
Water
Water
Water
Water
Water
Brine
Water
Water
Brine
Water
(4)
Enthalpy,
cal/g
690
670
550
~ 400
280
400+
195
265
240
235
220
275
260
(5)
Average
well depth,
meters
1,000
2,500
1,100
500
1,000
1,300
600
1,500
1,300
1,000
800
1,750
900
(6)
Fluid
salinity,
ppm
< 1,000
< 1,000
< 1,000
~ 4,000
12,000
—
3,000
~ 15,000
260,000
10,000
~ 1,000
~ 40,000
~ 4,000
(7)
Mass flow
per well,
kg/hr
23,000
70,000
50 , 000
100,000
—
150,000
60,000
230,000
~ 200,000
320,000
250,000
~ 400,000
400,000
(8)
Non-
condensable
gases, %
5
1
< 1
< 1
< 1
~ 6
—
~ 1
< 1
~ 1
*"*"' 1
~ 1
6
Source: Koenig, 1973 (Reference 22).
-------
Second Law of Thermodynamics given the temperature difference available
when the steam in the reservoir is no hotter than 300°C. The temperature
relevant to the calculation of the maximum possible thermal efficiency
is the temperature of steam entering the turbine and this must be con-
siderably lower than the reservoir temperature. A typical value for
existing geothermal plants is 180°C for the entering steam. The cor-
responding value for the steam produced in the light water reactors now
in use for nuclear power plants is about 300°C. In actual operation,
efficiencies are typically 40 percent for a modern fossil fuel plant,
30 percent for a current nuclear plant, and 15 percent for a geothermal
plant. These operating efficiencies correspond to the following rates
of heat rejection into the environment at the plant site: fossil fuel,
5.4 MJ/kWh; nuclear, 8.4 MJ/kWh; and geothermal, 20.3 MJ/kWh.
When finally translated into environmental impact, the relatively
low temperatures of the geothermal reservoirs imply that for every
kilowatt-hour of electricity generated at a typical inland geothermal
site about 6 kwh of heat will be put into the atmosphere in the form
of water vapor emerging from an evaporative cooling structure. Most
photographs of The Geysers show condensed steam rising into the air
from a row of short, wide cylinders on the top of an induced-draft
horizontal cooling tower. This is the visible form of the disposal of
waste heat from a 106 MW generating plant.
The implications of column 2 of Table 5 for heat disposal are similar
to the implications of columns 3 and 4 for fluid disposal. The specific
enthalpy given in column 4 is a measure of the heat energy per unit mass
of the geothermal fluid and, therefore, is directly related to the rate
at which mass must be processed through the system to produce a particular
amount of electric power. The Geysers1 specific enthalpy of 670 cal/g (2.8
MJ/kg) is 1200 Btu/lb in old engineering units, which was the basis for
195
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the 9 kg (20 Ibs) of steam per kWh figure used in the first part of this
paper. Even more important than the lower values of specific enthalpy
characteristic of the reservoirs that are water rather than steam is
the fact that most of the liquid is not flashed to vapor. Thus, the
distinction in column 3 is crucial in considering the amount of matter
that must be handled to produce the desired electrical energy. The
next stage in the expansion of geothermal energy use will be the ex-
ploitation of hot-water-dominated reservoirs, and the typical operation
will result in about three pounds of water for every pound of steam.
The next column in Table 5 gives some indication of how deep the
wells must be to tap these hydrothermal convective reservoirs. The
depth of the wells is a major factor in the cost of developing a geo-
23 24
thermal field, ' although the relationship between costs of drilling
and the final cost of the electricity is not yet established and used
25
in the pricing of the electricity. A typical 2 km (7000 ft) well at
The Geysers now costs about $400,000. In terms of environmental impacts,
the figures on well depth in the table call attention to the fact that
many impacts of geothermal energy production are similar to those of
oil production. The depths indicated in column 5 are not atypical of
the depths of oil wells, although the average oil well now drilled in
the United States is probably more comparable with experience at The
Geysers than with the lesser depths of the other fields included in
Table 5. The early stages of development of a geothermal field produce
environmental impacts quite similar to the exploration, road building,
drilling, and testing stages of oil field development. One difference
in drilling procedure is that air is used as the circulating fluid to
remove drill cuttings once a geothermal drilling operation enters a
steam bearing zone. This results in a so-called "controlled blow-out"
which is noisy compared with oil drilling, where mud is the circulating
196
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fluid. Muffling of the sound is helpful, but not completely effective.
This noisy stage of the drilling is said to amount to only a few days
26
out of the total drilling time.
The salinity of the steam or water obtained from the various geo-
thermal fields is indicated in column 6 of the table. For comparison
we note that the salinity of sea water at a typical mid-ocean point is
27
3.48 percent by weight. This is the basis for the change in designation
from "water" to "brine" in column 3 as the transition is made from 15,000
to 40,000 ppm salinity levels. The environmental implication of the
salinity figures in Table 5 is that geothermal fluids cannot be discharged
into fresh surface waters as a matter of course. In the first part of
this paper it was pointed out that at The Geysers the unevaporated con-
densate (which constitutes 20 to 25 percent of the mass of the steam
originally brought to the surface) is disposed of by reinjection into
the geothermal reservoir rather than by discharge into Big Sulphur
Creek. Yet, the much more saline geothermal waters at Cerro Prieto
and Wairakei are discharged without treatment into surface waters. Local
considerations account for the different practices, and it is a safe bet
that the local considerations in the semi-arid regions of the western
United States will call for either reinjection or treatment of the waters
from geothermal systems.
Column 7 giving the rate of mass flow typical of single wells at
the various geothermal sites illustrates again the point that much larger
amounts of fluid must be handled at the surface when the geothermal re-
source is a hot-water-dominated system. Another point already made is
that this mass ultimately will be removed from the plant site by evap-
oration, reinjection, or surface dischage (with treatment presumably
preceding the discharge).
197
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Two other aspects of the environmental impacts of geothermal energy
follow from the mass flow rates. First, the mass flow rate can be com-
bined with specific enthalpy in column 5 and the observed operating
efficiency (ultimately limited by the reservoir temperature given in
column 2) to obtain the electrical power producible by a single well.
In the first part of the paper, this sort of calculation was combined
with some facts of depletion experience to arrive at the estimate of
100 Mw per square mile for the land surface density of electric power
production at The Geysers. Second, the high rate of removal of material
accompanying appreciable generation of electricity from a geothermal
field could cause local geophysical effects, namely, subsidence of the
land surface or stimulation of earth tremors. Subsidence has long been
observed in some oil fields, and has been treated by injection of water
to replace oil removed from the reservoir. Earth tremors have been
associated with the injection of liquid wastes into subsurface reservoirs
in Colorado. Such'experiences indicate the possibility of these geo-
physical impacts also arising from geothermal energy production practices,
but whether they would occur and whether their occurrence would con-
stitute an adverse environmental impact depend on properties of the par-
ticular site as well as on factors not adequately understood.
Column 8, the final column of Table 5, directs attention to the
air pollution problem that can be associated with geothermal energy.
Gases or volatiles come to the surface as a part of the geothermal
fluid, and the fraction of this material that does not condense out to
be handled as a liquid can escape into the air. To date, the escape of
such gases has not been viewed as air pollution on a scale requiring
control measures, but the need for control is likely to arise. This
possibility is pointed out by the facts that the odor of hydrogen sulfide
is detectable at The Geysers and that some corrosion of electrical
198
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circuit elements at the power plants can be attributed to the concentra-
28
tion of this gas found in the atmosphere near the plants. Control of
hydrogen sulfide is under active investigation at The Geysers. The
nature and quantity of the noncondensable gases in The Geysers' steam
were presented in the first part of this paper as Table 3. Hydrogen
sulfide's role as the most important of these prospective pollutants
was indicated there. Ammonia probably ranks second.
C. Scaling Factors for Environmental Impacts
Those prepared to be critical of the alleged cleanliness of geo-
thermal energy suspect that this new energy technology is simply enjoying
the benefits of the invisibility that goes along with being small. The
preliminary environmental analysis presented so far contains enough in-
formation to make some tests of this suspicion. What is required is
knowledge of the nature of the environmental impacts and an estimate of
how the sizes of the various impacts are related to the amount of elec-
tricity produced. That estimate is the scaling factor needed to project
the impacts of use on a larger scale.
1. Scaling Factor for Land Use
For the impacts that are related more or less directly to the
amount of land needed for the production of geothermal energy the re-
quired scaling factor has been estimated in Section I of this chapter. A
factor of about 33 MW per sq km was derived by considering the production
and depletion rates of wells spaced about 2 hectares apart at The Geysers.
In the discussion that followed, it was pointed out that Table 2 presents
figures indicating that a similar value is obtained by considering wells
spaced with areas of 8 or 18 hectares per well. Therefore, for the
scaling of land use impact we adopt the factor 33 MW per square kilometer.
199
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As a rough indicator of accuracy, we submit that a factor smaller than
15 MW per sq km is very unlikely, as is a factor larger than 50 MW per
square kilometer. The factor was obtained from a consideration of
hydrothermal convective reservoirs and should be considered applicable
only to this type of geothermal field.
2. Emission and Effluent Factors
Similar scaling factors can be obtained for estimating environ-
mental impacts on air and water quality. Given information on the
fractions of various potential pollutants in the geothermal fluids, in-
formation such as contained in Tables 3 and 4, and empirical rules for
steam-to-electricity conversion, such as the 9 kg of steam per kWh
rule applicable to The Geysers and Cerro Prieto, the appropriate emission
factors (for air) or effluent factors (for water) are easily obtained.
The results for the two most critical emissions to the air at The Geysers
are factors of 4.5 kg per hour per megawatt (MW) for hydrogen sulfide
and 6.3 kg per hour per MW for ammonia. To obtain the effluent factors
for the Imperial Valley fields (Niland and Cerro Prieto), it is nec-
essary to know the water-to-steam ratio for the flashing procedure used
in the operation. Assuming 18 percent of the water flashes to steam17
(a 9-to-2 ratio) and using the 9 kg steam per kwh factor previously intro-
duced, the figures in Table 4 lead to the following effluent factors
for Cerro Prieto:
• Salinity—17, 000 ppm and 40 kg/hr per kW give an
effluent factor of 700 kg/hr per MW.
• Boron—12 ppm and 40 kg/hr per kW give an effluent
factor of 0.5 kg/hr per MW.
200
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For The Geysers some effluent factors so derived are:
• Salinity—28.4 ppm and 9 kg/hr per kW give an
effluent factor of .25 kg/hr per MW.
• Boron—.10 ppm and 9 kg/hr per kW give an effluent
factor of .001 kg/hr per MW.
• Ammonium—236 ppm (the rest goes to the air as gaseous
ammonia) and 9 kg/hr per kW give an effluent factor
of 2 kg/hr per MW.
These emission factors can be used, together with a knowledge of the air
or water flow through the region of the geothermal field, to estimate
the air or water quality that would result from uncontrolled emissions
from a given level of electricity generation. When the resulting estimate
of quality is compared with an air or water quality standard, we have an
indication of the presence or absence of a significant environmental
impact.
D. Environmental Impacts of Large-Scale Use of Geothermal Energy
Before applying this test of environmental impact to a few cases,
it would be worthwhile to cite the actual experience at The Geysers.
We have noted that hydrogen sulfide emissions at The Geysers
has been sufficient to cause odor and some corrosion of electrical
equipment. The experience with water pollution there is that Big
Sulphur Creek, the channel for natural surface water flow at The Geysers,
has an inadequate volume of flow at its low season to dilute the power
plant condensate. Ammonia and boron were the primary water pollution
concerns. As has been mentioned, the result of this concern was a
decision to reinject the condensate into the geothermal reservoir.
To test the proposition that geothermal energy would not appear
to be clean if it were used on a significant scale, we must adopt some
quantitative definition of the term "significant scale." To do this
201
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we will look at California's projected electrical energy consumption
and see what happens if we assume that geothermal resources account for
one-fourth of that projected growth. During the past year, SRI has de-
veloped projections of energy supply and demand in California. Here we
will take some figures from that work for the period 1975 to 1985. The
analysis by SRI projects the electric energy consumption in California
to be 168 billion kWh during the year 1975 and 300 billion kWh during
the year 1985. The increase in annual electrical consumption is then
projected to be 132 billion kWh during that 10-year period. Defining
geothermal energy use on a significant scale to be one quarter of this
increase calls for an estimate of the environmental impact of building and
operating enough geothermal generating capacity to produce 33 billion
kWh of electricity during a year.
1. Land-Related Impacts
The land area needed to produce this electricity by geothermal
means can be estimated as follows: Facilities capable of generating
3.8 million kW would produce 33 billion kWh of electricity if they oper-
ated all the time at full capacity for a year, i.e., operating with a
100 percent load factor. Since an 80 percent load factor is more likely
for a geothermal plant supplying base line power, we will proceed on
the assumption that 4,500 MW (4.5 million kW) of geothermal generating
capacity would supply one-fourth of the increase in electricity con-
sumption in California over the decade 1975 to 1985. The land area
needed for this would be 135 sq km, according to the 33 MW per square
kilometer land-use factor we have adopted. This area is 52 square
miles or 33,300 acres. For comparison, it may be noted that power
production at The Geysers now occupies about 30 sq km of a reservoir
that is known to extend for about 50 sq km and probably extends to a
202
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considerably larger area. The Imperial Valley covers over 3,000 square
kildmeters, with about half the land now devoted to agriculture. It
appears that there is enough land for significant use of geothermal
energy in California. However, because the land requirements of geo-
thermal energy are appreciable and because the use of land as near as
possible to the consumption of electricity is desirable, the possibilities
for multiple use of geothermal lands should be investigated.
2. Impact on Air Quality
What would be the impacts on air and water from the generation
of 33 billion kWh per year by geothermal plants with a total generating
capacity of 4,500 MW located on over 100 sq km of California land? This
question will be answered subject to the scaling factors already estimated
and to assumptions concerning the volume of air and water available for
dilution of the pollutants. For air, we will assume a box model of an
air basin with wind and inversion height parameters characteristic of
29
inland mountain and valley terrain. For water, there are no character-
istic parameters of flow that would be useful, because the variation
from one geothermal site to another can be very large. However, to have
some number for sensing the scale of the problem, the Colorado River will
be used as a reference in what follows.
The box into which the hydrogen sulfide and ammonia are assumed
to be emitted has a square base 10 km on a side (on the order of the 135 sq
km) and is 0.3 km high. (A characteristic adverse inversion height is
29
a few hundred meters. ) Light winds, 5 km/hr, move air in one direction
through the box for 14 hours a day, thus providing a volume of 0.3 km
x 10 km x 70 km to contain a day's emissions from the power plants.
These emissions from plants totaling 4,500 MW are at the rate of 20,000
kg/hr for hydrogen sulfide and 28,000 kg/hr for ammonia, giving a daily
203
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total of 500,000 kg of hydrogen sulfide and 700,000 kg of ammonia. These
totals diluted in the daily volume of 200 cubic km result in a pollutant
3 3
concentration of 2500 |ig/m for hydrogen sulfide and 3500 |J.g/m for
ammonia. The California state standard to prevent odor from hydrogen
i-
30
3
sulfide is 0.03 ppm, which is 45 |ig/m , less than 2 percent of the con-
centration just estimated. The odor threshold for ammonia is 46.8 ppm,
3
which is about 35,000 |ig/m , a factor of 10 greater than the concentra-
tion just estimated. The conclusion is that in the case of hydrogen
sulfide, at least, there is a potential air pollution problem from the
production of geothermal energy on a significant scale.
3. Impact on Water Quality
We have used air pollutant emission factors based on experience
at The Geysers. In turning now to water pollution considerations, we
have effluent factors for both The Geysers and Cerro Prieto, and, as
Table 4 indicates, we could obtain yet another set of effluent factors
based on the geothermal brine at Niland. This further emphasizes the
fact that water pollution considerations are likely to differ signifi-
cantly from one site to another. Proceeding to make some gross estimate
of the environmental impact from discharging geothermal waters into
surface waters, we take the Colorado River to establish a sense of the
amount of water available in the arid Southwest where hot water geothermal
resources exist. The mean annual flow of water in the Colorado River is
? / 31
about 480 m°/sec. Making the generous assumption that 10 percent
of this water is available to dilute the Cerro Prieto type of geothermal
waters from our envisioned 4,500-MW geothermal generating capacity, we
find that a flow of 170 million liters per hour is available to handle
the 2000 kg per hour effluent of boron and the 3 million kg per hour
effluent of total dissolved solids. Including the 40 kilograms per hour
204
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of geothermal water associated with each kilowatt of electricity, we
have another 180 million liters per hour, making a total of about 350
million liters of water per hour. The resultant concentration of dis-
solved boron is then 2000 kg in 350 million liters, or 6 mg/£. For total
dissolved solids (salinity), we have 3 million kg in 350 million liters
or 8400 mg/t. The permissible concentration of these materials given
32
in the 1968 Report of the Committee on Water Quality Criteria are
1.0 mg/t, for boron and 500 mg/{, for the total dissolved solids. Thus,
it would take the whole (rather than one-tenth) of the Colorado flowing
with pure water to provide enough dilution for the surface discharge
of waters from geothermal power plants making a significant contribution
to California's 1985 electrical energy production. This estimate tends
to confirm the necessity of the plans being made for reinjection or
treatment of the discharge from hot water geothermal wells.
205
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Ill GEOTHERMAL ENERGY: IMPLICATIONS FOR EPA
Considerations of what is possible within the well established
technologies of fossil fuel and nuclear power plants have entered into
the setting of the particular environmental protection standards now
applied to these plants. To the extent that what may be necessary for
adequate environmental protection was compromised in favor of what ap-
peared technically possible with fossil fuel and nuclear fission plants,
it would be desirable to set higher standards for future technology.
Thus, the apparent air quality advantages arising from the lack of com-
bustion at a geothermal plant suggest that tighter atmospheric emission
standards be set for geothermal plants.
EPA should be in a position to follow the development of geothermal
energy technology and to use its knowledge of the state of the art, to-
gether with its standard-setting authority to stimulate the technology
of minimum adverse environmental impact. It is important that the mech-
anisms designed to stimulate such technology do not create barriers and
disincentives that prevent a technology with overall environmental ad-
vantages from capturing the market it deserves. The activities of EPA
related to geothermal energy should be directed toward acquiring the
knowledge needed to strike the right balance between constructive stim-
ulation and unwarranted restrictions. In the matter of air quality,
for instance, a policy is needed that ensures that the geothermal ad-
vantages, i.e., no emissions of oxides of nitrogen, reactive hydro-
carbons, carbon monoxide, particulates, and radioactive fission products,
can be realized at the same time that the unacceptable current emission
level of hydrogen sulfide is brought under control. The most obvious
206
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implication is a policy allowing a lenient hydrogen sulfide standard
during the early development of geothermal energy technology while
indicating that strict controls are envisioned for the technology that
eventually operates on a significant scale.
In the case of hydrogen sulfide emissions, the implementation of
such a policy requires that the preliminary estimate given in this paper
for the potential impact of emissions be refined to obtain a clear idea
of the degree of hydrogen sulfide control likely to be necessary for
environmental protection. This estimate would be the basis for a goal
to guide both EPA and geothermal energy producers as this method of
generating electricity continues to develop. The preliminary estimate
we have given suggests that something on the order of 98 percent con-
trol may be required, and implies the need for EPA to direct its at-
tention to the hydrogen sulfide problem associated with geothermal
energy. That the problem has intermedia aspects is indicated by some
current ideas for control of hydrogen sulfide emission to the air by
oxidizing the sulfur to sulfate in solution in the water or by precipi-
tating it as a solid.
Although other federal agencies share the responsibility for sup-
porting promising technological development while EPA alone has the
primary responsibility for environmental protection, the Agency does have
opportunities for encouraging technical advances deemed promising on
environmental grounds. Thus, the results of a study of hydrogen sulfide
emission control could be the basis for both the setting of emission
goals and the provision of support for some specific technical experi-
ments.
The findings presented in this working paper indicate that the
development of the binary cycle turbogenerator could lead to geothermal
plants free of air pollution by enabling the heat energy to be extracted
207
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without exposing the geothermal fluid to the air. This particular tech-
nology appears worthy of support on other environmental grounds as well.
It appears the most promising means for exploiting the energy contained
in extremely saline geothermal brines like those found in the Imperial
Valley. This binary cycle technology also provides a means for tapping
low quality (i.e., low temperature), but potentially nonpolluting energy
sources such as geopressured reservoirs or regions of high temperature
gradients in the oceans.
Three other technologies emerge as candidates for further study and
possible support as a result of the findings presented here: (1) methods
for reinjection of geothermal brines, (2) processes for the treatment
and reclamation of saline waters, and (3) condenser cooling systems.
The need to study condenser cooling systems arises from two facts: (1)
The hot-water-dominated geothermal fields of the western United States
are areas where cooling water is not abundant. (2) Because these are
hot water sources the use of geothermal waters for cooling will have more
severe environmental consequences than are apparent from the experience
with the vapor-dominated field at The Geysers. In particular, the pos-
sibility of using dry cooling towers, now estimated to cost about three
33
times as much as their wet counterparts, should be investigated.
Further environmental analysis of geothermal energy should stress
the contrasts between the environmental impacts of geothermal energy
production and those of its fossil fuel and nuclear alternatives. Such
an emphasis would lay the groundwork for the day when EPA may wish to
simultaneously weigh the advantages and disadvantages of a whole array
of present and future energy technologies with an eye toward applying
pressure for or against particular energy options for the United States.
That day has not arrived. In the meantime, the comparative analysis is
needed not only for the possible tightening of standards suggested above
208
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but also for pointing out areas where geothermal energy has impacts more
adverse than its alternatives. In these areas there is a need for EPA
to apply pressure toward the incorporation of appropriate changes in the
developing technology. The Investigation leading to this paper has re-
vealed some areas meriting this sort of attention from EPA. There is
the possibility that the reinjection of geothermal brines may contaminate
the ground water supply through leaks in the well casings. There is an
array of intermedia problems associated with geothermal brines: the
air pollution and lowered enthalpy of flashing to steam, versus the
reinjection and cooling problems of liquid processing, versus the solid
waste potentials of treatment. Specifically, the Bureau of Reclamation's
plan for obtaining useful water from the geothermal brines in the Imperial
Valley bears looking into, as does a study of the potentials for the re-
covery of materials from geothermal brines, contracted for by the Bureau
of Mines. The land use problems arising from both the sizable area re-
quirements and the specific nature of geothermal activities indicate that
a study featuring a comparison with oil field experience and an assessment
of the possibilities for multiple use of the land would be useful.
These implications for EPA are put forward on the basis of our per-
ception of the role currently required of EPA in matters of new energy
technology. According to this perception, the need now is to follow
and to influence the emerging technologies so that necessary environmental
protection measures are incorporated in their technical development and
in the projections of costs. The influence is to be exerted by requiring
certain standards of performance and by supporting particular lines of
research and development.
209
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REFERENCES
1. J. P. Finney, "Design and Operation of The Geysers Power Plant,"
in P. Kruger and C. Otte (ed.), Geothermal Energy; Resources,
Production, Stimulation (Stanford University Press, Stanford,
California) 1973, p. 149. .
2. A. Kaufman, "Geothermal Power: An Economic Evaluation," U.S. Bureau
of Mines, Information Circular 8230, 1964, p. 9.
3. C. F. Budd, "Steam Production at The Geysers Geothermal Field," in
Kruger and Otte (reference 1), 1973, p. 138.
4. M. Goldsmith, "Geothermal Resources in California—Potentials and
Problems, " California Institute of Technology, Environmental Quality
Laboratory, EQL Report No. 5, December 1971, p. 29.
5. C. F. Budd (reference 3), 1973, p. 130.
6. C. F. Budd (reference $), 1973, p. 136.
7. J. P. Finney (reference 1), 1973, p. 160.
8. R. W. Rex, "investigation of Geothermal Resources in the Imperial
Valley and Their Potential Value for Desalination of Water and
Electricity Production, " University of California (Riverside),
Manuscript, 14 pp., 1 June 1970.
9. J. B. Koenig, "Geothermal Exploration in the Western United States,"
Geo thermic s, Special Issue No. 2, p. 1, 1970.
10. J. P. Finney (reference 1), 1973, pp. 153-158.
11. R. G. Bowen, "Environmental Impact of Geothermal Development," in
Kruger and Otte (reference 1), 1973 p. 209.
12. R. G. Bowen (reference 11), 1973, p. 208.
13. J. P. Finney (reference 1), 1973, p. 159.
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14. D. E. White, L.J.P. Muffler, and A. H. Truesdell, "Vapor-Dominated
Hydrothermal Systems Compared with Hot-Water Systems, " Economic
Geology, Vol. 66, No. 1, p. 75, January - February, 1971.
15. J. B. Koenig, "Worldwide Status of Geothermal Resources Development,"
in Kruger and Otte (reference 1), 1973, p. 30.
16. M. Goldsmith (reference 4), 1971, p. 20.
17. J. B. Koenig (reference 15), 1973, p. 45.
18. United States Department of the Interior, Bureau of Reclamation,
"Geothermal Resource Investigations, Imperial Valley, California:
Developmental Concepts," January 1972.
19. M. Goldsmith (reference 4), 1971, pp. 18-34.
20. D. E. White, "Characteristics of Geothermal Resources, " in Kruger
and Otte (reference 1), 1973, p. 84.
21. J. H. Anderson, "The Vapor-Turbine Cycle for Geothermal Power Gen-
eration," in Kruger and Otte (reference 1), 1973, pp. 167-169.
22. J. B. Koenig (reference 15), 1973, Table 2, p. 24.
23. C. F. Budd (reference 3), 1973, p. 132.
24. J. H. Anderson (reference 21), 1973, pp. 163-164.
25. D. H. Hebb, "Some Economic Factors of Geothermal Energy," The Mines
Magazine, July 1972, pp. 15-19.
26. R. G. Bowen (reference 11), 1973, p. 201.
27. J. Harte and R. H. Socolow, Patient Earth (Holt, Rinehart and
Winston, Inc., New York, N.Y.), 1971, p. 338.
28. J. P. Finney (reference 1), 1973, p. 158.
29. S. J. Williamson, Fundamentals of Air Pollution (Addison-Wesley
Publishing Company, Reading, Massachusetts), 1973, pp. 171-172.
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30. G. Leonardardos, D. Kendall, and N. Barnard, Journal of the Air
Pollution Control Association, Vol. 19, 91 (1969), cited by S. J.
Williamson, reference 26, p. 15.
31. M. Morisawa, Streams; Their Dynamics and Morphology (McGraw Hill,
New York, N.Y.), 1968, p. 14.
32. Federal Water Pollution Control Administration, "Water Quality
Criteria: Report of the National Technical Advisory Committee to
the Secretary of the Interior, " April 1968, p. 20.
33. R. D. Woodson, "Cooling Towers," Scientific American, Vol. 224,
No. 5, May 1971, p. 77.
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Appendix C
ENERGY FROM OIL SHALE
by
Robert G. Murray
213
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CONTENTS
LIST OF ILLUSTRATIONS , 215
LIST OF TABLES 215
I INTRODUCTION 216
II STATE OF THE ART OF OIL SHALE TECHNOLOGY 220
A. Mining _. . 220
B. Crushing 222
C. Transporting Shale . 223
D. Retorting 223
1. Classes of Retorts 223
2. SNG Producing Retort 226
3. In-Situ Retorting 226
E. Upgrading Crude Shale Oil 229
F. Disposal of Waste Materials 230
III ENVIRONMENTAL IMPLICATIONS OF OIL SHALE DEVELOPMENT 232
A. Water Use 233
B. Land Disturbance 238
C. Air Degradation 238
D. Treatment of Processed Oil Shale and Reclamation
of Mined Lands 241
E. Aesthetic Impact of an Oil Shale Industry ....... 242
REFERENCES 244
214
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ILLUSTRATIONS
1 Oil Shale Areas in Colorado, Utah, and Wyoming 217
2 Oil Shale Utilization—Processes, Environmental Effects,
and State of Knowledge 221
TABLES
Possible Environmental Problems from In-Situ Production
of Shale Oil 228
Estimated Land Requirement for 2 Million Barrels per Day
Shale Oil Production Using Different Processes (20-Year
Project Life) 239
215
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I INTRODUCTION
Oil shale is considered as a solid fuel because it contains organic
matter (kerogen) that can be recovered by heating and converted into a
crude shale oil, gas, and residue. Oil shale deposits occur in at least
30 states, but the largest domestic deposits are in the Green River
formation underlying roughly 40,000 square kilometers (16,000 sq mi) in
Colorado, Utah, and Wyoming (Figure 1).
The Green River formation is a series of lake sediments with minor
river deposits. Although the Green River formation covers a broad area
in Colorado, Wyoming, and Utah, the largest accumulation of organic
material occurs in the Piceance Basin. The general stratigraphic rela-
tionships of sedimentary formations have been investigated by previous
workers, and the thickness of several major units has been determined.
The most important rock units for purposes of this study are the
oil shale formation itself and the material between the oil shale and
the surface. The richest and thickest oil shale beds are contained in
the Parachute Creek member of the Green River formation. This member
is exposed in precipitous cliffs at the southern part of the basin. The
Parachute Creek member, which ranges from about 150 to 500 meters thick,
is subdivided into three zones.' Richest oil shales occur near the base
of the upper zone, in the Mahogany zone. The thickness of the Mahogany
zone and its oil content are subject to considerable variations. Repre-
sentative averages of oil recovery for thicknesses up to 30 meters of the
o
Mahogany zone range from about 100 to 180 m per million kg (25 to 42
gallons per ton). A decrease in thickness and oil yield is indicated
near the margins of the basin.
216
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IDAHO
UTAH
WASHAKIE
BASIN::;:
WYOMING:;^;! ;;
UTAH
COLORADO
i.SAND:
;WASH;
•; BASIN
PICEANCE CREEK
BASIN
Area of Oil Shale Deposits
BATTLEMENT
MESA
Area of Nahcolite or Trona Deposits
Area of 0.1 m /tonne or Richer Oil
Shale 3m or More Thick
50
100
200
SCALE — km
FIGURE 1 OIL SHALE AREAS IN COLORADO, UTAH, AND WYOMING
SA-2714-8
217
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It is useful to classify shale reserves in terms of quality so that
some perspective may be gained on the probable timing of commercial
i*
development. Reserves of high-grade shale, defined as those deposits
o
containing at least 0.15 m° oil per tonne shale (35 gal/ton) in beds at
least 9 meters thick, are present that can yield 5.2 x 10 m3 (33 billion
barrels) of oil. Reserves of intermediate grade of shale, at least
O Q Q
0.1 m /tonne (25 gal/ton) and 9 meters thick, can yield 64 x 10 m
(400 billion barrels) of oil. There are larger reserves of lower grade
shale, but is improbable that these will be recovered in this century.
Since approximately 30 percent of the high-grade shale exists in
privately owned reserves, commercial development can be expected soon even
if the federal leasing program should be delayed. The U.S. Department
of the Interior plans to lease the shale reserves in each of the three
states and has recently issued an environmental impact statement on this
program. This leasing program will enhance the probability of commercial
shale processing within the next five years.*
A production level of 8,000 m3 (50,000 barrels) of oil per day is
generally believed to be the smallest quantity that can be produced
profitably at present oil prices. The tracts to be leased are about
20 X 10^ m^ (5,000 acres) each, which will allow production of between
8,000 to 16,000 m3 per day for a period of at least twenty years.
The quantity of oil recovered per unit area will depend upon the
method of mining and retorting used, as well as on the shale assay and
bed thickness. Demonstrated room and pillar mining has achieved shale
*
Numbered references are listed on page 244 at the end of Appendix C.
The final environmental statement was published in October 1973 and
the first leases put up for bids in January 1974.
218
-------
recovery on the order of 60 percent of the in-place reserves. Other
methods of mining that recover a higher percentage of the reserves have
been conceived, but as yet there is no demonstrated method for deeply
buried shale.
The growth rate of a shale-processing industry depends upon technology
and the availability of shale reserves, water, and capital. Technical
success of mining retorting and disposal methods will reduce risks and
provide the investment climate for a faster buildup of the industry. A
low level of effluent emissions from all processing steps will allow the
necessary social acceptability required for industrial growth. The
ultimate limit on the size of the shale industry will be set by the
availability of water in the shale region. This limit is probably in
the range of 2.4 X 105 to 4.0 X 105 m3 (1.5 to 2.5 million barrels) per
day with demonstrated methods of mining and retorting. It is reasonable
to assume that methods of shale oil recovery will be developed that reduce
this water requirement and will thus allow a higher limit on the ultimate
size of the industry.
SUMMARY OF OIL SHALE RESOURCES
Piceance Basin, Colorado
1. Total estimated resources ~2 X 10^^ m
(~1,200 billion barrels)
2. Total resources in beds more than ~2 X 1010 m
9 m (30 feet) thick, averaging (~120 billion barrels)
O
more than 0.125 m /tonne (30 gal-
lons per ton), Fischer Assays
Q 1
3. Estimated recoverable reserves ~8 X 10 m
(50 billion barrels)
Source: National Petroleum Council, December 1972
219
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II STATE OF THE ART OF OIL SHALE TECHNOLOGY
This section describes the present state of development of the proces-
sing steps required to recover liquid or gaseous products from oil shale.
A graphic representation of the state of knowledge applicable to the various
operations is presented in Figure 2.3 The probable direction and incentives
of future research are also discussed.
A. Mining
Because most of the good oil shale occurs below an overburden of other
rock or shale containing little or no oil, it will be necessary to use under-
ground mining methods. There are a few areas where the shale lies close to
the surface so that strip mining would be possible, but these are an excep-
tion to the general geology of the deposit. Surface mining has been used
to supply small amounts of shale for tests. Room-and-pillar mining has been
demonstrated at production rates equivalent to those reached in commercial
practice from a single working face.
The generally accepted method of room-and-pillar mining is to create
a room with a roof span of about 18 m (60 feet) leaving 25 percent of the
shale in place as pillars. If the mined area is to be abandoned as soon
as it has been mined out, the installation of roof bolts is usually
unnecessary. Bolting is required in haulageways and rooms used for long
periods of time. If a bench-and-header type of mining is used, it is
possible to mine to a height of 18 m. Under these conditions very large
mining and transporting equipment can be used underground.
If room-and-pillar mining is to be used in thick shale deposits, it
would be necessary to develop more than one level and to leave a fairly
220
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IN SITU (2-3)
(3A) NATURAL
(2C) HYDRAULIC
<2C) ELECTRO-
(2C) CHEM. EXPLOSIVE
(3B) NUCLEAR
FRACTURING
(2A) IN-FORMATION V
(3C) NUCLEAR CHIMNEY/
OIL SHALE DEPOSIT
CONVENTIONAL (2)
MINING
COMBINATION
MINING AND
IN SITU
RETORTING
ENVIRONMENTAL
PROBLEMS
f COMBUSTION (2C>
HOT GASES (2A)
STEAM (3A)
SOLVENT LEACHING (3A)
BACTERIAL ACTION (3A)
PRODUCT
RECOVERY
to
to
(3A)
COMBUSTION GASES AND
NUCLEAR CONTAMIN-
ATION TO AIR
SOLVENT LOSS TO AQUIFERS
NUCLEAR CONTAMINATION
OF AQUIFERS
LAND SUBSIDENCE
/GAS DRIVE (2C)
\ARTIFICIAL LIFT (2C>
["Room and Pillar (1A)
/ UNDERGROUND 4 Cut and Fill (3B)
\OPEN PIT I3B) I Block Caving (3B)
L_.
ENVIRONMENTAL
PROBLEMS
CRUSHING
HYDROGASIFICATION
(1C) THERMAL AND CHEM. TREATING "1
<2C) HYDROGENATION /Mild-Cat. Crack. L
IHydrocracking I
REFINING
CODE -
State of knowledge applicable to oil shale
1. Reasonably mall demonstrated
2. Some experimental knowledge
3. Little known
4. Conceptual
-with knowledge stemming from:
A. Shale experience
B. Petroleum or other Industry
experience
C. Both
(1C)
(2C)
EXPOSING SALT BEDS
OPENING SALINE GROUND
WATER TRAPS
LOWERING GROUND WATER
LEVEL
RETORTING
GAS COMBUSTION
UNION (1A)
TOSCO (1A)
HYDROGEN ATMOSPHERE (3A)
LURGI-RUHRGAS (2A)
I
Bureau (1A)
Patrosix (2A)
Paraho (2B)
SNG
'1
tu
SPENT SHALE
I/UTILIZE (2A)
V.DISPOSE Mine fill I3B)
Revegetate (2A)
Dump (2A)
LIQUID FUELS
U
BY-PRODUCTS
ENVIRONMENTAL
PROBLEMS
(1CH
AMMONIA (1C)
SULFUR (1C)
AROMATICS (2A)
SPECIALTIES (3AI
COKE (1C)
PITCH (1C)
ASPHALT (1C)
WAX (2A)
SOURCE: BaMd on original figure In H. Perry. "Protp*ct« for Oil Shall Development," U.S. Department of Interior, 1968.
GASOLINE
DIESEL FUEL
JET FUEL
DISTILLATE FUEL OIL
RESIDUAL FUEL OIL
LIQUEFIED PETROLEUM GAS
PARTICULATE EMISSIONS (1C)
SULFUR OXIDES (1C)
NITROGEN OXIDES <2C)
TRACE ELEMENTS (2C)
LEACHING OF SOLUBLE
SALTS (2A)
FIGURE 2 OIL SHALE UTILIZATION — PROCESSES. ENVIRONMENTAL EFFECTS, AND STATE OF KNOWLEDGE
-------
thick layer of shale between levels. Under these conditions the total
shale recovery could be as low as 40 percent.
Entry to a room-and-pillar mine may be by horizontal adit or by shaft.
Early work was done on adit entry because this is the less expensive method.
It will be necessary to use shaft entry on most of the high quality shale
reserves.
Some research is being done on block caving, long wall retreat caving,
and pillar retreat caving in an effort to reduce the quantity of good shale
left in the mine. The objection to these caving methods is that the land
surface is lowered, usually in an uneven manner, as the mining progresses.
Subsidence may not be objectionable if the land is ultimately reclaimed and
revegetated. One problem with caving schemes that result in subsidence is
that some areas have aquifers above the high quality shale. Caving in these
areas would destroy the integrity of the aquifer and could lead to serious
problems of leaching soluble minerals from lower shale formations.
Research in the direction of reducing the quantity of explosives re-
quired for blasting or of nonblasting methods of rock busting would be
desirable. Blasting creates both fine particulates and combustion products
that must be vented from the mine.
B. Crushing
Retorts require shale to be of smaller particle size than that resulting
from mining operations. The required size varies from a 5.1 cm (2-inch)
maximum for the gas combustion retort to less than 1.3 cm (1/2 inch) lor
the Lurgi-Ruhrgas retort. The gas combustion retort cannot process shale
finer than 0.95 cm (3/8 inch) and consequently these fines must be re-
moved and either discarded or agglomerated. Two or three stages or crush-
ing and screening are required to reduce run-of-the-mine shale to re-
torting size.
222
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The primary environmental problems associated with crushing are the
creation of dust and noise, but both problems can be controlled by current
technology.
C. Transporting Shale
Mined shale must be transported to the crushing and screening plant,
and crushed shale must be transported to the retort. Spent shale or shale
ash must be transported to the disposal area. All methods of transport
projected for oil shale have been used repeatedly in commercial mining
operations so that no new problems are expected. The major problems are
the creation of dust and noise.
D. Retorting
1. Classes of Retorts
Retorting processes have been grouped into four classes according
to the method of heat transfer to the shale.4
Class I—Heat is transferred to the shale through a wall.
The simplest form of this retort is a Fischer assay de-
vice for measuring the amount of oil that may be recovered
from a sample of shale. The shale is placed in a closed
container and heated by means of a fire outside of the re-
tort. The retorted gas and liquids are uncontaminated by
air and the sulfur compounds are in a reduced state, such
as HgS. Because the heat source is external to the retort,
any fuel may be used. The emissions from the heat source
will depend upon the fuel used. This type of retort is
expensive in terms of capital and operating costs per unit
of produced oil. It is not likely to be competitive with
other types of retorts.
Class II—Heat is transferred to the shale from hot gases
generated in the retort by the combustion of some of the
carbon and hydrogen present in the shale. Examples are
the gas combustion retort, the Union Oil Company retort
and the Laramie simulated in-situ retort. A controlled
223
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amount of air and recycle gas is introduced into the retort
and mixture of product oil and low Btu gas is recovered.
The advantages of this system are low capital and operating
costs per unit of shale input. Disadvantages are low re-
covery of the total energy in the shale and the production
of a large quantity of flue gas containing about 3 MJ/m^
(80 Btu/SCF) energy content. For example a typical gas
combustion retort plant producing 16,000 m (100,000 bar-
rels) per day of shale oil would also produce about 23
million cubic meters per day of low Btu gas. Sulfur con-
tained in this gas would be on the order of 200 tonnes per day.
Class III—Heat is transferred to the shale by passing
previously heated gases or liquids through the shale bed.
Two examples are the Petrosix retort and the Union B retort.
By recirculating high Btu product gas through the retort,
the problems of the Class II retort are eliminated. The
gas has much more value and sulfur compounds can be removed
by amine scrubbing. However, the capital cost of the equip-
ment required to heat the recirculating gas makes this a
very expensive type of retort. Additional problems are
caused by the tendency of the external gas heater to accumu-
late carbon deposits caused by oil mist in the gas. It is
not likely that this class of retort will become commercial.
Class IV—Heat is transferred by the introduction of hot
solids into the retorting bed. The two best known examples
of this class are the TOSCO II retort in which heat is
transferred by ceramic balls and the Lurgi-Ruhrgas retort
in which heat is transferred by recirculating hot shale ash.
The principal of retorting is to combine raw shale with
enough hot recycle solids to produce retorting temperatures
in the mixture. This class of retort is fairly expensive
but does recover a high percent of the energy in the shale.
The gas from the retort is high Btu and sulfur compounds
are in the reduced state. Both TOSCO II and Lurgi-Ruhrgas
retorts have the potential to become commercial.
In the TOSCO II retort the ceramic balls are heated in a
separate furnace which may be fired with any acceptable fuel.
The Lurgi-Ruhrgas retort employs a lift burner to burn the
residual carbon from the educted shale so that no additional
fuel is required to supply retorting heat. The Lurgi Company
claims that very little S02 is found in the flue gas from
the lift burner because it is absorbed on the fine shale
particles.
224
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This method of classifying retorts is useful to this study in
that the waste products from the retort are quite different in the
different classes. However, there is no known Class I retort under
development, and it is unlikely that Class III retorts will be competitive
with either Classes II or IV.
Class II retorts produce a large quantity of low heating value
(3.7 MJ/nr* or 100 Btu/SCF) gas as a byproduct, and most of the sulfur
in this gas is in the form of SO_. The residual shale has had most of
the organic carbon removed.
Class IV retorts produce gaseous products that are not diluted
with air so that the gas has a high heating value and the sulfur is in the
reduced state. The residual organic carbon may remain on the spent shale
(TOSCO II) or it may be burned off in a subsequent process step (Lurgi-
Ruhrgas). Generally, the residual shale is in the form of small particles.
All classes of retorts will require some emission control
devices. General environmental problems will be the production of
dust from shale handling, sulfur dioxide in stack gases from retorts
and furnaces, nitrogen oxides in combustion products formed by burning
crude shale oil, and sour water decanted from the product oil. Retorting
shale produces a strong odor that is characteristic of organic nitrogen
compounds and that may be carried several miles in a steady wind.
R&D in retorting processes is most likely to be directed
toward increasing the mechanical reliability and reducing the capital
and operating costs. The developers of retorting processes realize
that they will be required to meet certain environmental regulations in
order to operate. They are confident that when regulations are promul-
gated they will be consistent with those already set for similar processes
in related industries, e.g., stack gas emissions from power plants, and
that they have the ability to devise methods to meet the requirements.
225
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Because most of the retort developers are negotiating process royalty
plans or other financial arrangements with potential custowers, they do
not readily give out technical details of their processes,
*
2. SHG Producing Retort
The Institute of Gas Technology is developing a retort to produce
high Btu gas directly from oil shale.5 Retorting heat is supplied in part
by hot hydrogen containing gas and also by the exothermic heat of the •eth-
anation reaction in the retort. The retort operates at about 20,000
Pascal pressure (several hundred pounds per square inch) and is relatively
expensive. However, it does recover More of the total organic material
on the shale than the other types of retorts. The environmental problems
are expected to be similar to the liquid-producing retorts,
3- In-6itu Retorting
In-situ methods tor removing hydrocarbon* from oil shale have a
great many advantagest and much thought has been put into their development,
most in-situ concepts contemplate the use of beat to retort the oil shale
without removing it from the ground. Research has recently been conducted
into methods of extracting the hydrocarbons by solvent action or the use of
bacteria.
The type of in-situ retort receiving »ost attention Is one In
which a chamber of solid shale tilled with shale particle* is created
underground. The shale in this chamber is heated and the oil is educted,
collected, and pimped to the surface.
226
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Proposed heat sources include underground combustion, steam, not
gas, hot solvents, and combinations of these beat sources. Methods of
providing a flow path for the retorting fluid include the use of wells,
tunnels, natural porosity, a variety of fracturing techniques, and combin-
ations of these methods.
Laboratory investigations on the use of tbiobacillus, a sulfur
oxidizing bacterium, to release kerogen from the mineral matter in shale
are now in progress,6 The bacteria used do not require a hydrocarbon food
but use sulfur and other nutrients from the shale. Mo assessment of the
probability of technological or economic success can be made at this time.
To date, the field tests on in-situ methods of shale oil produc-
tion have not indicated that a commercial venture would be economically
successful. However, there are both economic and environmental incentives
to develop in-situ oil recoveryt and it is reasonable to expect much re-
search to/ward this end. As would be expected in this early stage of in-
situ development, most of the effort has been directed toward devising
retort technology and very little work has been done on solving the environ-
mental problems associated with any specific process.
The different methods of in-situ extraction will produce different
impacts on the environment. The most prominent problems associated with the
different in-situ processes are listed in Table I.
It should be noted that in cases where the research is being
conducted by private companiest very little information on the technical
details is published. Information on simulated in-situ retorting is
available from the Bureau of Mines at Laramie, Wyoming, based on experi-
ments in a ISO ton capacity, above ground vessel. Laramie has also
conducted experimental shale fracturing tests. This information is
available to the public and could be used to derive quantitative estimates
of combustion products. However, it is characteristic of in-situ
227
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Table 1
POSSIBLE ENVIRONMENTAL PROBLEMS
FROM IN-SITU PRODUCTION OF SHALE OIL
In-Situ Process
Environmental Problems
Circulation of hot fluids
Circulation of solutions or
solvents
Circulation of biologically
active solutions
Underground combustion
Nuclear chimney retorting
Loss of fluid to atmosphere
Loss of fluid through fractures
S02, NOX, and particulates in flue gas
Displacement of saline groundwater
Odorous off-gases
Loss of volatiles to atmosphere
Loss of solution to adjacent areas
Contamination of aquifers
Loss of solution to adjacent areas
Contamination of groundwater
S02 in off-gases
Fine particulate matter from shale matrix
carried to surface in circulating fluid
NO
X,
and particulates in off -gas
Odors in off-gas
Loss of fluids to adjacent areas
Contamination of aquifers
All problems common to underground com-
bustion
Blasting Shockwaves detrimental to con-
ventional mines and other installations
Nuclear contamination of aquifers, air,
and products.
processes that the location will determine the magnitude of many of the
problems having to do with loss of fluids to adjacent areas.
Real data on the environmental problems of in-situ retorting
will be expensive. Some large-scale tests in locations where the in-situ
project is to be located will be required. Methods of monitoring fluid
losses deep underground must be devised and be dependable over a range of
geologic conditions.
228
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E. Upgrading Crude Shale Oil
Shale oil produced in retorts or by most in-situ methods is not suit-
able for direct use. It is a heavy, viscous oil that contains about
0.7 wt % sulfur, about 1.8 wt % nitrogen, and oxygen compounds and usually
has a pour point of about 27° C (80°F). Most plans for recovering oil
from shale include a refining step to produce low sulfur fuel oil or a
high quality synthetic crude oil. This refining unit is usually planned
to be placed close to the retorts so that only a short distance of heated
pipeline will be required.
Upgrading processing steps may include coking to remove asphaltenes
and shale ash from the lighter fractions and hydrogenation to remove the
sulfur, nitrogen, and oxygen compounds. Upgrading research may provide
methods of eliminating the coking step to obtain higher yields of liquid
products.
The environmental problems of upgrading are quite similar to those
found in conventional petroleum refining. Possible contaminants are:
H S, NH , HCN, phenols, benzene, dissolved oil, SO , and particulates.
& «3 ^
Likely by-products are elemental sulfur and liquid ammonia. Sulfur may
have to be stockpiled or disposed of.
SNG may be made by direct hydrogasification in a retort, as previously
noted, or by gasification of crude shale oil. The most economic path is
still uncertain. Each method will present a different proportion of the
effluent products found in the other upgrading processes.
The impact on the shale-producing area would be considerably reduced
if an economic method of transporting crude shale oil can be developed that
would allow upgrading units to be spread out among the several marketing
areas. The result would be a reduction in water use and in population per
unit of produced shale oil in the oil shale region.
229
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F. Disposal of Waste Materials
From the standpoint of volume of waste materials, by far the largest
will be shale residue. Other waste materials will be similar to those
produced in coal gasification or liquification processes that are now
being studied. It will be useful to divide waste materials into (1)
shale-related wastes and (2) process-related wastes.
Shale-related wastes will be mostly mineral matter. Some of the com-
ponents will be soluble, requiring great care and considerable expense to
handle properly. Approximately 85 percent of all material mined for use in
conventional retorts will be waste. Shale rock not subjected to retorting
temperature remains insoluble except for included soluble salts that may be
exposed to rock surfaces by size reduction. Once shale has been retorted,
the organic binding is destroyed and the rock loses its strength and is
easily crushed. Under these conditions soluble minerals may be exposed to
the surface and easily leached out.
The amount of shale mining and retorting in the past was so small that
no special precautions were taken to prevent runoff from spent shale dumps
from entering natural water supplies. Methods for preventing shale wastes
from contaminating water supplies have been devised. The most comprehensive
include the placing of impermeable membranes under the shale dump, collec-
tion of all water entering the spent shale, evaporation of this water, and
disposal of the precipitated salts.
Because future regulations will probably include rehabilitation of dis-
posal areas so that they will support plant growth, soluble salts may have
to be removed from the final surface and plant nutrients may have to be
added. The initial revegetation effort is expected to require more water
than that supplied by normal precipitation.
230
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Some R&D work on spent shale disposal has been conducted by government
agencies, educational research groups, and private companies. The reports
are not entirely consistent. Reports of privately financed rehabilitation
tests stress the fact that ground cover crops can be grown on shale dump
areas. The work done at Colorado State University indicates that soluble
salts are leached out of spent shale by a variety of mechanisms over a
long period of time.7'8 It may be concluded that much more work should be
done in this area.
Process-related wastes will be quite similar in nature and magnitude
to those generated by other hydrocarbon refining industries. Advances in
disposal methods in coke processing, refineries, and coal gasification
plants will be of use in shale oil plants. To a large extent the future
shale processing industry will benefit from research in related process
industries.
231
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Ill ENVIRONMENTAL IMPLICATIONS OF OIL SHALE DEVELOPMENT
Environmental Aspects; Overview
Oil shale operations could cause significant environmental impacts.
Large amounts of material would need to be handled. As the organic
material represents only a small part of the total rock, the processed
shale remains for disposal. The increase in bulk resulting from crushing
and processing will prevent disposal by backfilling the shale mine, and
surface disposal of at least one-third of the material will be required;
actually, the amount of processed shale disposed of at the surface could
be closer to two-thirds the total material processed. This processed
shale will be finely divided, and will contain water soluble salts that
could contaminate streams or ground water unless steps are taken to seal
the disposal area for prevention of escape of deleterious materials.
Revegetation of disposal areas is under study, and it remains to be deter-
mined whether encouraging experiments can be successfully extended to
large-scale operations that would be necessary in connection with com-
mercial oil shale development. A major environmental aspect is the
possibility of encountering large volumes of saline water in mining opera-
tions. Management of this water would pose significant problems in mining
operations, and could have adverse effects on ground water conditions in
the area of the deposits.
The major environmental problems that will occur with the growth of
an oil shale industry may be grouped into four categories: water use,
land disturbance, air degradation, and aesthetic changes. The first three
categories may be measured by physical methods; the aesthetic changes
are not easily measured, are generally subjective, but nevertheless are
real.
232
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Oil shale is an energy source of national importance. The probability
that oil shale will be developed is very high because the alternative to
nonuse of shale leads to unattractive national consequences. The national
problem with the production of shale oil, as with any other resource, is
to ensure that true production, environmental, and social costs are re-
flected in the price of the product. In the case of oil shale the en-
vironmental and social costs will probably be lowest if the following
parameters are minimized:
• Land disturbance
• Water use
• Population increase in area
• Construction activity
• Total SO emitted to air
2
• Total dissolved solids discharged into river and ground waters.
The above items are "per unit of usable product." Resource recovery
should be maximized.
A word of caution about the dangers of oversimplifying this complex
subject is in order. It is not possible to predict with accuracy how the
shale-processing industry will develop, what retorting or mining methods
will be used, or how fast it will grow. The best that can be done at pres-
ent is to indicate ranges of resource use under certain assumed conditions.
The numbers derived will be no better than the underlying assumptions.
A. Water Use
It is generally believed that available water will limit the ultimate
size of an oil shale industry. All good western shale is in the upper
Colorado River drainage system, the only replenishable source of water.
There is ground water in the shale area, some fresh and some containing
233
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up to 60,000 ppm dissolved minerals. At present it is estimated that
2.2 X 108 m3 (180,000 acre feet) per year of Colorado River water could
be made available for shale development. This quantity of river water,
plus the use of ground water local to the mine sites, would allow an
overall industry size ranging from 2.4 X 105 to 4 X 10$ m3 (1.5 to
2.5 million barrels) per day of shale oil.
The water used per unit of net product will depend upon the type of
mining, retorting, and upgrading used. In-situ methods are expected to re-
quire less water than conventional mining and retorting.
The largest single environmental problem will be the prevention of a
salinity increase in the Colorado River water. Removal of 2.2 X 108 m3
(180,000 acre feet) per year of water from the upper rivers of the system
is expected to increase the salinity at Hoover Dam by 6 to 10 milligrams
per litre or about 1.4 percent.
It is generally conceded by those planning shale projects that no pro-
cess water will be allowed to flow back into the river system. Plans usually
include methods of using blowdown streams and other highly mineralized
water to wet down spent shale and mining operations. So far these concep-
tual schemes have not been tested in a pilot program.
Water quality. Oil shale development could lead to impacts on
water quality in the mining area, mainly from processed shale. Most present
plans call for processed shale to be disposed of by transport as a slurry
and depositing it in nearby canyons in engineered fills that take account
of the characteristics of soil foundations and local geological factors.
Although processed shale can be compacted to become virtually impermeable
to rainfall so that there is no loss in strength in the mass of the de-
posit, snowfall eliminates the compaction in the top foot or so, and at
least the top 2 feet of the deposit becomes permeable to water. This
234
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enables soluble salts to be leached directly from the processed shale.
Moreover,
". ... drying of the processed shale surface causes movement
of water from the interior of the deposit to the surface by
capillary action. On reaching the surface, the water evapo-
rates leaving behind a white deposit that is clearly visi-
ble on the black surface. This deposit is dissolved during
(subsequent) rainfall with the result that both concentration
and composition of dissolved solids in the runoff water vary
with time and depend on the amount of drying prior to the
rain."*
Furthermore,
". . . it would appear that compaction increases the con-
centration of dissolved solids in the runoff because compac-
tion increases (density) and decreases (permeability). The
rate at which the deposit (of soluble salts on the surface) is
formed is clearly dependent on the rate at which capillary
action can carry the very concentrated solution from the pores
within the shale residue to the surface, because the material
can be evaporated more rapidly than it can be transported to the
surface by capillary action."
Use of slurry transport of processed shale to the disposal site
will lead to entrapment of significant amounts of moisture in the dis1-
posal piles, no matter how well-engineered the fill may be. Clearly,
this provides the mechanism for the capillary action and related surface
concentration and dissolved solids at the surface of the deposit.
". . . it would appear that maximum concentrations in the
runoff will be found when compaction is greatest, slopes
are steep, drying has been extensive, runoff has just begun,
the shale residue has a low permeability, runoff water tem-
perature is high, rainfall intensity is low, and length of
overload flow is short."
*
Ward, J. C., et al, "Water Pollution Potential of Spent Oil Shale
Residues," EPA Report 14030, December 1971.
235
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SUMMARY OF WATER POLLUTION POTENTIAL OF SPENT
OIL SHALE RESIDUES
1. Leaching tests show that there is a definite potential for high
concentrations of Na+, Ca"1"*", Mg++, and SO^ in the runoff from
spent oil shale residues. However, with proper compaction, the
piles become essentially impermeable to rainfall. On the other
hand, snowfall eliminates the compaction in the top 20 to 40 cm
and at least the top half meter of the residue becomes permeable
to water.
2. Soluble salts are leached readily from spent shale columns.
3. Chemical concentrations of the effluent from spent shale columns
may be predicted by using the relationships developed between
soluble and exchangeable ions in soils which are in equilibrium
with a water solution.
4. Sediment contained in runoff water from spent oil shale residue
will be detrimental to water quality unless removed by settling.
5. Sediment in the runoff water from spent oil shale residue may
be efficiently settled by the addition of small amounts of
aluminum sulfate and/or by long periods of quiescent detention.
6. The chemical quality of surface runoff water from oil shale
residue may be estimated by procedures developed within this
report.
7. The dissolved solids concentration in snowmelt water is in-
creased significantly by contact with oil shale residue, but
not as much as in runoff from rainfall.
8. The chemical quality of surface runoff water from melting snow
on oil shale residue may be estimated by procedures developed
in this report.
9. The long contact period associated with snowmelt results in
water percolation into a bed of oil shale residue and subse-
quent saturation.
10. Saturation eliminates compaction of oil shale residue.
11. Weathering of oil shale residue increases the tendency for per-
colation to occur.
236
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12. Percolation caused by snowmelt may result in creep and slides.
13. Water which percolates through a bed of oil shale residue is
very high in total dissolved solids.
14. Both the composition and concentration of dissolved solids in
snowmelt runoff water from oil shale residue change with the
cumulative volume of runoff.
15. Precipitation in the form of snow will not all appear an run-
off.
16. The overland flow water quality model developed in this report
is applicable to runoff from both rainfall and snowfall on oil
shale residue.
17. Natural snow has a negligible dissolved solids concentration.
18. Compaction reduces the quality of runoff from rainfall and tends
to be reduced by snowfall in at least the top few feet of depth.
19. The oil shale retorting residue need not be saturated for per-
colation from snowmelt to occur.
Sources:
Items 1 to 6: Ward, J. C., et al, "Water Pollution Potential of
Spent Oil Shale Residues," EPA Report 14030,
December 1971.
Items 7 to 19: Ward, J. C., and S..E. Reinecke, "Water Pollution
Potential of Snowfall on Spent Oil Shale Residues,"
Colorado State University, June 1972.
To control the potential water pollution problem from processed shale,
the following actions might be considered:
• Sealing the base of the shale disposal area by an impermeable
layer so as to prevent losses of soluble materials by per-
colation downward through the deposits.
• Control of the amount of water used in shale deposit so as
to minimize the rate of solution and transport of soluble
salts to the surface of the deposit through capillary ac-
tion.
237
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• Protection of the surface of the deposit against weathering,
erosion, and snowmelt effects by a layer of soil that, ideally,
will be suitable for revegetation. The topsoil removed from
the base of the disposal area might well be stockpiled and
used for this purpose.
B. Land Disturbance
Although Figure 1 shows large areas of shale reserves underlying
41,000 square kilometers (16,000 square miles) of land, the area of in-
terest in this century will be much smaller in extent. The area most
likely to be developed in the next 25 years will be about 2,100 square
kilometers (800 square miles) in Colorado in the Piceance Basin and up
to 1,000 square kilometers (400 square miles) on the east side of the
Uinta Basin, in Utah.
Land will be required for access roads and utility lines, mine and
plant facilities, mine development spoil disposal, and shale residue
disposal. The amount of land required will be dependent on the type of
mining and disposal employed and will vary with geographic factors. Table
2 provides an estimate of the total- land that will be altered as a result
of producing 320,000 m3 (2,000,000 barrels) per day of oil for a 20-year
period. This will range from 2 to 8 percent of the 3,000 square kilome-
ters of good shale reserve land, depending on the mining and retorting
process used.
C. Air Degradation
Industrialization of the western shale regions will result in a decline
of the general air quality. The main sources of air pollutants will be
vehicular emissions from mining, construction, and transporting equipment;
dust from shale-handling operations; and gases from retorting and refining
units. Minor sources of air degradation will be from the increased vehicular
238
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Table 2
ESTIMATED LAND REQUIREMENT FOR 2 MILLION BARRELS PER DAY*
SHALE OIL PRODUCTION USING DIFFERENT PROCESSES
(20-Year Project Life)
Land Use
Mine development
Overburden disposal
Temporary storage of
lowgrade ore
Active well area
Surface facilities
Off sites
Shale residue disposal
Total disturbed area
Maximum disturbed area
during project life*
Square Kilometers of Land Disturbed
Surface Mine Underground Mine In-Situ Mine
42 —
82
12
80
8
16
104
64
16
16
240
370
16
16
240
2741"
114*
250
152'
74*
* 3
320,000 m per day.
Assumes above-ground disposal of shale residue.
§
Assumes two-thirds of shale residue returned to mine.
Allowing 10 years for restoration of shale disposal sites (or well sites)
traffic and residential heating caused by an increase in population in the
area and emissions from the mine-blasting procedures.
Conventional dust control technology is available to limit particulate
emission from mine ventilation systems to 0.023 g/m^ (0.01 grain per
cubic foot.) Crushing and screening operations can be held to a similar
emission rate by properly designed enclosures and the use of wet scrubbing,
bag filters, and dust suppression with water sprays. One problem that
239
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has been observed in past retorting operations is that dust is carried
off shale residue areas after the initial dust control water has evaporated.
The problem is to achieve adequate dust control with minimum use of
water.
Emissions from stack gases will be different for the different
retorting processes. As previously discussed, the class of retort will
determine whether the sulfur is in the oxidized or reduced form. Sulfur
in the reduced form can be scrubbed from the retort gas using any of
several methods, such as hot carbonate or amines. Oxidized sulfur in flue
gas from the Union A or Lurgi-Ruhrgas retorts appears to be absorbed on
the shale residue to a great extent. This point should be checked by
pilot plant tests. SO in the low heating value from gas combustion retorts
may be more of a problem. The concentration of SO2 will be fairly low,
i
but the large quantity of gas produced could result in thousands of kilo-
grams per day of S02 emissions. Presumably any stack gas scrubbing method
developed for coal-fired power plants could be used on this low heating
value gas.
Very little information is available on potential problems with NO
H
in off-gases from shale oil retorts. Most retorting processes control the
temperature of combustion in a range lower than that needed to fix nitrogen
in the air. However, there is a high level of nitrogen in the shale oil
that can increase NOX emissions if the oil is burned in conventional
steam-raising boilers.
Particulates in flue gases from retorts can be removed using existing
electrostatic precipitators and wet scrubbers. Very little information is
available on the existence of hazardous trace elements in shale ash.
The odor produced by retorting oil shale is distinctive and long last-
ing. On a subjective scale of odor preference, it is not so pleasant as
an onion-dehydrating plant but much pleasanter than a kraft paper mill.
There is no published work on the control or elimination of odors from shale
retorting.
240
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To control adverse air quality effects from oil shale development,
it seems likely that the following methods would be practiced.
• Process design to reduce the concentrations of undesirable
or harmful emissions as an integral part of the operation.
• Control of emissions to the extent necessary to remove
compounds that remain in the released gases so as to comply
with established standards of air quality.
• Control of particulates and dust resulting from the several
stages of oil shale operations through a variety of collection
and suppression methods that are appropriate to the indivi-
dual stages.
D. Treatment of Processed Oil Shale and Reclamation
of Mined Lands
Oil shale mining and processing removes only a small portion of
the total rock (less than 1 percent by weight). It is not a simple task
to dispose of the remainder. The acts of mining, crushing, and processing
reduce the size of oil shale fragments and increase its volume by about
one-third; even if the mine openings could be completely refilled, con-
siderable amounts of processed oil shale would have to be disposed at
the surface—closer to two-thirds of the total material handled. Pro-
cessed shale will be finely divided (especially when mined by rapid ex-
cavation techniques) and will contain water soluble salts that could
contaminate streams or ground water unless steps are taken to protect
the disposal area. Control of erosion of disposal areas through revege-
tation also remains to be demonstrated, and species of plants and fertil-
izer/nutrient requirements to support vegetative growth on processed
shale need to be determined.
One means of finding the solution to treatment of processed oil
shale and reclamation of mined lands or disposal sites is to examine
factors such as those briefly described above in connection with opera-
tions conducted or in progress at the vicinity of the Naval oil shale
241
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reserves in Colorado. Previous work in that area produced quantities of
oil shale for testing; the demonstration projects should provide a basis
for conducting carefully structured experiments to examine the potential
environmental effects of oil shale development through rapid excavation
so as to determine prospective solutions to be incorporated into the
design of excavation operations.
E. Aesthetic Impact of an Oil Shale Industry
The spectrum of changes caused by the development of a new industry
ranges from those that are easily quantified, such as size of mine tailing
area, to effects that are purely subjective, such as increased monotony of
landscape. For convenience, all environmental changes that contain a high
proportion of subjective evaluation are placed in the aesthetic category.
This category includes changes in land use, plant growth, wildlife, recre-
ational facilities, and cultural and scenic values.
The shale areas have a low population density, on the order of 1
person per square kilometer (three per square mile) less than half of
whom live in towns. The population doubles during the few weeks of the
deer-hunting season. Advanced planning of mine and process facility lo-
cations would allow the preservation of the few historic Indian culture
ruins in the area. The quantity of shale residue accumulating in surface
disposal areas will eventually create large plateau areas in a region
that consists of rounded hills and deeply cut canyons.
Mining, transportation, and processing operations will produce noises
similar to those now being experienced in other related industries. In
addition to the usual human discomfort and loss of working efficiency,
industrial noises will adversely affect the wildlife in the immediate area.
For the most part, noise control methods developed for other industrial
242
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and transportation equipment will be satisfactory for the shale industry.
There may be instances where long conveyor systems used between proces-
sing units create enough noise to prevent normal wildlife migration paths
from being used, even though there is no physical barrier.
243
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REFERENCES
1. "An initial Appraisal by the Oil Shale Task Group—1971-1985,"
National Petroleum Council, Washington, D.C. (1972).
2. "Draft Environmental Statement for the Proposed Prototype Oil-Shale
Leasing Program," U.S. Department of Interior, Washington, D.C. (1972).
3. H. Perry, "Prospects for Oil Shale Development," U.S. Department of
the Interior, Washington, D.C. (1968).
4. R. A. Cattell, B. Guthrie, and L. W. Schramm, "Retorting Colorado Oil
Shale—A Review of the Work of the Bureau of Mines, U.S. Department
of the Interior," in Oil Shale and Cannel Coal, Vol. 2 (The Institute
of Petroleum, London, 1951).
5. S. A. Weil et al., "Hydrogasification of Oil Shale," Annual Report for
1972, Project 1U-4-7 for the American Gas Association, Institute of Gas
Technology, Chicago, Illinois (1972).
6. T. F. Yen, private communication. Also see Oil and Gas Journal, p. 108
(November 13, 1972).
7. J. C. Ward et al., "Water Pollution Potential of Spent Shale Residues,"
Colorado State University, Fort Collins, Colorado (1971).
8. J. C. Ward et al., "Water Pollution Potential of Snowfall on Spent Oil
Shale Residues," Colorado State University, Fort Collins, Colorado
(1972) .
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Appendix D
ENERGY FROM SOLID WASTES
by
Edwin M. Kinder-man
-------
CONTENTS
LIST OF ILLUSTRATIONS 247
LIST OF TABLES 247
I INTRODUCTION—SOME FACTS ABOUT SOLID WASTE DISPOSAL . . 248
II THE TECHNOLOGY AND STATUS OF ENERGY RECOVERY
FROM WASTE 253
A. Energy Recovery Through Incineration 253
B. Direct Energy Recovery and Energy Materials
Production—Pyrolysis 255
C. Energy Products Made by Other Processes 263
1. Hydrogasification 263
2. Catalytic Gasification 264
D. Digestion Processes ..... 264
1. Anaerobic Digestion 264
2. Enzymatic Digestion 268
III ENVIRONMENTAL IMPACTS OF SPECIFIC ENERGY-PRODUCING
WASTE-DISPOSAL PROCESSES 269
A. Introduction 269
B. Miscellaneous Effects 276
C. Specific Environmental Impacts of Solid
Waste Disposal Plants 277
D. Some Research Needs and Opportunities 283
REFERENCES 285
246
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ILLUSTRATIONS
1 Monsanto Landgard Process Block Flow Diagram 257
2 Union Carbide Oxygen Refuse Converter Block
Flow Diagram . 259
3 Block Flow Diagram of West Virginia University Process . . . 261
TABLES
1 Composition and Heating Value of Union Carbide
Oxygen Process Product Gas . 259
2 Composition of Product Gas—West Virginia
University Pyrolysis Process ... 262
3 Collector Efficiencies for Municipal Incineration
Particulate-Control Systems 270
4 Concentration of Some Trace Materials
in Incinerator Fly Ash 271
5 Estimated Environmental Impact of Solid-Waste Disposal Methods
for Urban Wastes, Relative to Ordinary Incineration . . . •-. 281
6 Potentially Carcinogenic Chemicals 283
247
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I INTRODUCTION—SOME FACTS ABOUT SOLID WASTE DISPOSAL
Steadily increasing quantities and concentrations of solid waste
require processing. The quantity increases because of increasing
population and because social and technological trends give rise
to greater quantities of solid waste per capita. Concentrations of
waste grow larger as metropolitan areas grow in population, as factories
grow larger, and as agricultural and fuel processing operations become
more intensive. Processing of these wastes is required primarily
because great concentrations of waste give rise to increasingly
undesirable effects. These range from the purely aesthetic ones of
unsightliness and odor to the physical impairment of health, necessitating
vector control and disease prevention. The general move of our society
towards a clean environment demands a general cleanup of refuse of
>
all kinds and under all conditions. Large concentrations of refuse,
while posing special problems, also offer the best prospect for applying
economic solutions to the disposal problem.
The simplest and most used method for waste processing is sanitary
landfill. In proper applications of this method, control is maintained
over hazardous materials, pollution of ground waters, disease vectors,
and air pollution arising from open burning. However, control over all
these factors is difficult to maintain indefinitely, and a proper site
is not always available within a reasonable distance of the principal
sources of the waste. The sanitary landfill method, moreover, is a
large consumer of land, although the filled land can often be put to
another use at a later date.
248
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Not all data measuring the quantity of solid waste are consistent.
For example, data from one 1968 survey indicates that U.S. per capita
solid waste production was 2.41 kg (5.32 pounds) per day, with urban
refuse at 2.59 kg (5.72 pounds) per day.1** On the other hand, data from
the 1968 National Survey of Community Solid Waste Practices shows average
quantities of 3.59 and 3.71 kg (7.92 and 8.19 pounds) per day, respectively,
for national and urban refuse.2* The last figures include park and sewage
treatment solids in the totals, but neither included agricultural and
food industry wastes.
The quantities of all wastes to be handled in the future are expected
to increase. The annual consumption of all materials involved in packaging
has steadily increased in the last decade. More municipal sewage treatment
plants will contribute to the load to be handled. Many agricultural oper-
ations are being modified and concentrated to the point that the wastes
are a substantial nuisance, but available in concentrations that make
possible economic recovery of energy values. Total agricultural wastes
are estimated to be 22.5 kg (50 pounds) or more per capita per day.
With urban refuse amounting to approximately 3.6 kg (8 pounds) per
day per capita, about 1.5 x 103 kg of refuse is generated annually per
individual. When such refuse is compacted to approximately 450 kilograms
per cubic meter (750 pounds per cubic yard) and 135 kilograms (300 pounds)
of soil are used as cover there results an annual disposal requirement of
3.17 cubic meters (4.15 cubic yards) per capita. Fills often range from 3
to 30 meters in depth. With a 3 meter deep fill, about one square meter
(10.6 square feet) of surface is required per person annually. An urban
population of one million will require approximately 21 hectares (50 acres)
*
References are listed at the end of this report.
Data in the References expressed in English units have been converted to
metric units and often rounded to reflect the precision of the original
values.
249
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filled to a depth of 15 meters (45.8 feet) each year.41 One source sets
a rule of thumb of 0.864 cubic meters (1.13 cubic yards) of landfill per
person per year.3 This requirement is presumably based on generation
rates of less than 4.5 kilograms (10 pounds) per capita per day.
The costs and bulk of landfill can be reduced by shredding, milling,
crushing, pulverizing, or otherwise reducing the size of bulky refuse
before it is compacted and covered. The treated refuse can be segre-
gated into fractions having material value. Classification into ferrous
(magnetic) metals, nonferrous metals, glass and ceramics, and paper
components is possible. Simple separation of magnetic materials from
mixed refuse is more common than any other separation scheme. The
separated material value pays for the additional cost of the size
reduction operation.
Incineration of wastes reduces their weight and volume substantially,
70 to 80 percent on a weight basis, and by a factor of 10 or more on a
volume basis. Ordinary incineration normally requires additional fuel
and is an energy consumer. Incineration is compatible with pretreatment
operations such as size reduction and separation of valuable materials.
Some recovery of valuable materials is possible after the Incineration
proper.
Incineration reduces problems with disease vector control, as it
destroys putrescible material and most pathogenic organisms. It also
destroys flammable materials and reduces the hazards of fire (and of the
consequent air pollution). The absence of edible material (after incin-
erator treatment) reduces or eliminates the population of rodents and
*
Ocean dumping is used by New York City and some other large communities.
The wisdom and safety of this practice is debatable.
250
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other scavengers at the refuse disposal area. This also improves
vector control.
Incinerators have potential for detrimental effects. Combustion
creates fly-ash that must be captured; and improper combustion conditions,
frequently encountered when hetrogeneous materials are burned, cause
imcomplete combustion and soot and smoke that might contain carcinogens.
The heat of incineration will release volatile metals, acids and other
substances that might also pollute the air. The incinerator must
include equipment that will control such emissions within socially
desirable and legally mandated limits.
Capital and operating costs of many incinerators are high. The
average amortized cost of incinerator operation is probably in excess
of $7 per tonne of solid waste treated; and much higher costs have
been reported ($14 per tonne in Washington, D.C., and New Jersey;
$22 per tonne in New York City). This is a high price to pay for an
inherently wasteful operation; landfill costs (exclusive of land) range
4
from less than $0.50 to less than $3.50 per tonne of solid waste handled.
As incineration Implies, much of the usual solid waste is combustible,
and heating values of the combustible fractions average around 4500-
5500 kilogram calories per kilogram (18-22 MJ/kg or 8000-10,000 Btu/lb
dry). The heating values of as-received (wet) refuse have a wide range
from 1650 to 3300 kilogram calories per kilogram (7-14 MJ/kg or 3000
to 6000 Btu per pound). Usual values range from 2200 to 2800 kilogram
calories per kilogram (9-11 MJ/kg or 4000 to 5000 Btu per pound),
This is a substantial heat value to waste through landfill or
incineration at a time when fuels are in short supply. Additionally,
with low sulfur coals currently priced at $1.60 to $2.40 per million
kilogram calories ($0.40 to $0.60 per million Btu), delivered price,
and projected costs of low sulfur oil at $4.00 per million kilogram
calories ($1.00 per million Btu) in the mid 70s, a tonne of refuse
i
251
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contains as much as $10 in potential energy value. Properly used waste
can help reduce our dependence on outside energy resources. At 25 percent
overall efficiency for collection and conversion to energy a total waste
load (including agricultural) of more than 27 kilograms (60 pounds) per
day per capita would lead to an energy recovery equivalent to about 2
million barrels per day of oil, compared to a current total energy demand
of about 35 million barrels of oil equivalent.5 The U.S. is now importing
approximately twice that quantity. The economic value is likely to justify
the investments necessary for energy conversion.
Energy recovery from refuse can be achieved from:
(1) Incineration with heat recovery
(2) Pyrolysis with heat recovery
*
(3) Pyrolysis with energy product recovery
(4) Hydrogasification with energy product recovery
(5) Bacterial digestion with energy product recovery
(6) Enzymatic digestion with energy product recovery.
It is the intent of this paper to describe briefly the basic
technology and status of the six general methods of energy recovery
listed above. Following this, the potential environmental impacts
will be presented and recommendations for future Environmental Protection
Agency action outlined.
The phrase "energy product" is used to mean a clean, readily combustible
fuel.
252
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*
II THE TECHNOLOGY AND STATUS OF ENERGY RECOVERY FROM WASTE
A. Energy Recovery Through Incineration
Incineration can be used to produce steam for space heating, process
industry use, or for power generation. It can also be used to produce
hot gases suitable for power generation in gas turbines. European in-
stallations to produce steam for power and heating have produced 1.1 to
1.6 kilograms of steam per kilogram of refuse burned, and 75 to 180 kilo-
watt hours of electricity per tonne of refuse burned.6 Installations in
Montreal and Chicago are based upon European technology. The Montreal
plant is designed to produce 45,350 kilograms (100,000 pounds) of steam
at 260°C (500°F) and 16 kg per sq cm (1.5 MPa or 225 psia) pressure from
12.5 tonnes of refuse. The Chicago plant has a similar capacity.
Incineration in any such plant is a straightforward process. How-
ever, difficulties arise in the erosion and corrosion of furnace linings
caused by the heterogeneous nature and variable composition of the fuel.
Also, the flow of refuse through the system may be impeded by slagging
and clinker formation. Particulate deposition on boiler tubes and heat
exchange surfaces may reduce steam-raising efficiency. Slag character-
istics can be controlled by controlling the temperatures in the combus-
tion chamber, and excess airflow and auxiliary fuel can be used to this
end.
*
Much of the material reported in this section is drawn from a series of
studies performed by Stanford Research Institute for itself and for
various industrial and governmental clients. This body of work will
not be referenced further.
253
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Refractory problems can be minimized through use of waterwall com-
bustion chambers, or by use of a large air excess. The latter creates
problems with particulate controls on the stack gas; the former seems to
have operational difficulty.
Despite the apparent simplicity of the process, incinerators are not
yet generally accepted for refuse recovery even when steam and electric
power production is an adjunct. The matching of refuse disposal to steam
demand is difficult because of seasonal variations in demand. Also, steam
conditions do not permit efficient generation of electricity, so product
values, and prices, are low. The potential for environmental pollution
(to be discussed later) adds to the capital costs. It is not likely that
direct incineration for steam production will be much used in the future.
Such problems as slagging, caused by variability of input and by the
heterogeneous nature of refuse, can be controlled if the refuse is only
a small part of the total feed to a furnace. Mixtures of refuse and coal
are being fed to furnaces of the Meramec Power Station, Union Electric Co.,
St. Louis, Missouri, in an experimental program. Prepared waste (approxi-
mately 90 percent of input waste from which magnetic material has been
removed) is fed with coal at an approximate rate of 1 kilogram of waste
to 8 kilograms of coal. The combustion takes place in a chamber modified
to accept dual feed (coal and refuse); steam is produced in a conventional
boiler with reheat; and steam at the super-heater outlet will be at
standard conditions of 98 kilograms per sq cm (9.6 MPa or 1400 pounds
per square inch gage) and 510°C (950°F). The maximum continuous steam
production is 420,000 kilograms (925,000 pounds) per hour. The reheat
steam temperature is 490°C (925°F). This high quality steam has more
value than that produced in refuse-only incineration. The experiments
in progress will establish the technical and economic feasibility of
this type of incineration operation. At an estimated future cost of
254
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$1.60 to $2.40 per million kilogram calories ($0.40 to $0.60 per million
Btu) for low sulfur coal, the additional capital requirement, amortiza-
tion, maintenance, labor, and downtime costs must be less than $4.90 to
$7.20 per tonne of refuse burned in order for the process to be economi-
cally viable. Note that these costs are comparable to those of the more
economic direct incineration units. The process will be limited to regions
where coal of the proper quality (sulfur content and slagging character-
istics) is available.
Incineration to produce hot gases that drive a gas turbine has been
tested on a pilot scale. The Combustion Power Company Inc., Menlo Park,
California, has designed a plant that will handle 400 tonnes of refuse
per day with a maximum capacity of 8000 kilowatt electric power. Com-
bustion of prepared refuse (sized, and with ferrous metals removed) in a
fluidized bed is followed by extensive cleanup of particulates from the
hot combustion gases. The hot clean gases at approximately 810-820°C
(1500°F) are fed to the turbine. The fluidized bed minimizes slagging
and complete combustion at low temperatures and minimizes pollution from
unburned hydrocarbons, oxides of nitrogen, and acid gases. Tests on a
100 tonne per day plant will be completed in 1974.
B. Direct Energy Recovery and Energy Materials Production—Pyrolysis
Pyrolysis, or thermal degradation, can be used to produce various
gaseous or liquid products suitable for energy production or equivalent
chemicals production, for use at a later date; or it can be used to
generate steam for immediate use. The basic technology of refuse pyroly-
sis has been demonstrated in many fields. For example, Shell Oil and
Texaco Development Companies offer partial oxidation-pyrolysis processes
for manufacture of clean synthesis gas and/or hydrogen. Between 150 and
200 of these plants have been in commercial operation. Lurgi GmbH also
licenses coal gasification processes based on combustion and pyrolysis.
255
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In the United States, several pyrolysis processes have been investi-
gated and some are now reaching demonstration stage under EPA grants.
The steam-generating pyrolysis processes include Landgard, developed by
Monsanto Chemical Co. A 1000 tonne per day demonstration plant to be
used by the City of Baltimore is expected to produce the following
products:
6 6
Steam 2.18 x 10 kilograms/day (4.8 X 10 Ib/day)
Ferrous metal 70 tonnes/day
Aggregated glass 170 tonnes/day
Char 80 tonnes/day
The char has some residual heating value, but it will go to a landfill
TI
operation. Instead of low-pressure steam, the process can produce a low-
heating value, 1000 kilogram calories per cubic meter (111 Btu per SCF)
gas, at the rate of 1.3 X 106 kilogram calories (5.3 X 106 Btu) per'tonne
of refuse (about 4 MJ/m3 gas at the rate of 5.5 GJ/tonne).
In the process, presized refuse is fed to a rotary kiln that is
heated partially by combustion of oil or gas feed. (See process diagram
in Figure 1.) This extra fuel amounts to 10 to 12 percent of the input
energy. The refuse is pyrolyzed, producing a gas and an inert mixture
that is quenched and sorted to recover mineral values. The pyrolysis
gas is burned with air to produce low pressure steam. The combustion
gases are scrubbed and released to the atmosphere.
A similar process developed by Devco Management Inc., with engineering
by Tellepsen Engineering Company, is in the pilot stage. A 120 tonne per
day plant is reported to be operating in New York City. These processes,
like the direct incineration ones, produce low-quality steam and also
suffer the difficulties of load matching.
256
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RECEIVING
AND
STORAGE
1
SHREDDER
STORAGE
Off-Gas
I
KILN
_£
J L
AFTER-BURNER
Water
I
Air
WASTE HEAT
BOILER
Water
I
I
Steam
GAS
SCRUBBER
PUMP
FAN
1
PLUME
SUPPRESSION
T
Solids
1
QUENCHER
I
MAGNETIC
SEPARATOR
To
Wet fr Separation
Char and Recovery
WASHER
Iron
FIGURE 1 MONSANTO LANDGARD PROCESS BLOCK FLOW DIAGRAM
257
-------
Another process designed to produce combustion gases for steam or
power has been demonstrated by Torrax Systems Inc. in a 75 tonne per day
pilot operation. This process, too, uses extra fuel to preheat input air
to 1200°C (2200°F). The bulk, untreated refuse is fed to a tubular fur-
nace where oil or gas is burned to produce pyrolysis heat. The high design
temperatures of the vertical shaft gasifier produce fluid slags that drop
to the bottom of the furnace. There the slag is continuously drawn off
and quenched. The dry product, pyrolysis gas, has a heat content of about
1250 kcal/m3 (5.2 MJ/m3 or 140 Btu/SCF). The gas yield is about 1.5
million kcal (6.3 GJ or 6 million Btu) per tonne of refuse fuel, after
allowance is made for the extra fuel used. This low-Btu gas can be burned
to raise steam or drive a gas turbine. The slag can be sorted and valuable
materials recovered.
Higher-heating value gases that can be economically transported
short distances, used as synthesis gas, or converted into high-Btu substi-
tute natural gas product, as well as used directly for steam and electric
power production, can be produced by the Union Carbide oxygen converter
process and the West Virginia University process, which uses a modifica-
tion suggested by Stanford Research Institute. In the Union Carbide
process, refuse, as collected, is charged directly to a vertical shaft
furnace through lock hoppers as illustrated in the flow diagram (Figure 2).
The refuse is pyrolyzed as it falls through hot combustion gases rising
from the combustion zone where residual char and nonvolatile organics
are burned in an oxygen atmosphere. The inorganic materials appear as
a molten slag, which is drawn off and quenched. The produce gas has a
o
heating value of approximately 2600 kcal per cubic meter (11 MJ/m or 300
Btu/SCF). It is cleaned of particulates and oil droplets in an electro-
static precipitator. The gases are scrubbed to remove HC1, HgS, and
organic acids. The salts from the scrubber are fed to the furnace and
eliminated with the slag. Approximately 75 percent is recovered of the
258
-------
Refuse
Feed Off Gas
1 Fuel Gas
V n;i
Oxygen '»
Water
Quench
SHAFT Water V
FURNACE
t
1
Molten
Metal
and Glass
\ '
SLAG .
COLLECTOR
rapor ELECTROSTATIC Off <
PRECIPITATOR
Oil | Nei
FUEL GAS Clean 1
USE
i
Granulated
Metal and Glass
Neutralizing
Agent
jas ACID
ABSORBER
jtralized Organic I
Salts in Solution!
i
-uel Gas
Off
Gas
1
>ER
Waste
Water
SA-2714-3
FIGURE 2 UNION CARBIDE OXYGEN REFUSE CONVERTER BLOCK FLOW DIAGRAM
heating value in the fuel. The product gas with the composition indicated
in Table 1 could be chemically altered to produce methane, a substitute
natural gas.
Table 1
COMPOSITION AND HEATING VALUE OF UNION CARBIDE
OXYGEN PROCESS PRODUCT GAS
Component
CO
H2
C°2
CH4
C (hydrocarbons)
2
Inert
Gross heating value kilogram
calories per cubic meter
CMJ/m3)
Refuse Product Gas
(Percent)
49
29
15
4
1
2
2570
(286)
(11)
259
Methanated
(Percent)
0.1
7
3
78
4
8
7900
(877)
(32)
-------
Data on process performance and pollutants will be available shortly
as the Company is constructing and will operate soon a 200 tonne per day
pilot plant in Charleston, West Virginia.
A process similar to the Torrax and Union Carbide ones has been the
subject of small-scale pilot plant investigations. Combustion with air
provides the heat to a shaft furnace. Combustion in a lower zone is
followed by pyrolysis in an atmosphere of combustion gas and steam. The
temperatures are lower and the wastes are clinkered rather than slagged.
The product gas contains more than 50 percent nitrogen, and the product
3
gas has a low 1000 kilogram calories per cubic meter (4 MJ/m or 110
Btu/SCF) energy content.
The West Virginia University, or Bailie process, illustrated in
Figure 3, uses air instead of oxygen to burn and pyrolyze the refuse,
but, through use of a two-chamber fluidized bed system suggested by
Stanford Research Institute, produces a medium heat content gas, 3900
3
kcal per cubic meter (16 MJ/m or 430 Btu/SCF). This gas is not diluted
significantly with nitrogen from the air. Prepared refuse, size-reduced,
classified, and dried, is fed to a pyrolysis reactor containing a fluid-
ized bed of heated sand. Rapid pyrolysis follows. The product gas is
first cleaned of char fines and oil and then of acid gases. The char
and oil are transferred to a second chamber, a combustion reactor, where
they are burned in air. This combustion heats a fluidized sand bed. The
heated sand flows to the pyrolysis reactor, and cooled sand and bulk char
return to the combustion reactor. Combustion gases are used to dry the
incoming refuse. The process recovers over 75 percent of the heating
value of the refuse, and minerals are recovered in the prepyrolysis,
classification step. The product gas is useful as an energy source, a
synthesis gas, and as a starting material for production of a high heating
value fuel. Its estimated composition, given in Table 2, is similar to
the raw Union Carbide pyrolysis gas but has a higher energy content.
260
-------
Water
179 tons/day
Solid Waste
679 tons/day
at 30% H2O
(600 tons/day at 5ft
FEED
PREPARATION
» H20
i
Noncom
154 t
Prepared Waste
346 tons/day "~
FLUIDIZED
SOLIDS
PYROLYSIS
> i
Hjstible* Ash an
ons/day 67 to
Pyrolysis Gas
PYROLYSIS GAS
QUENCH,
COMPRESSION
AND SCRUBBING
Fuel Gas
at 50 psig
9.2 million
SCF/day
at 417 Btu/SCF
I
d Sand
ns/day
HEATING VALUE OF
SOLID WASTE
4.95 billion Btu/day
HEATING VALUE OF
FUEL GAS
3.82 billion Btu/day
(77% RECOVERY OF
FEED HEATING VALUE)
SA-1886-6R
FIGURE 3 BLOCK FLOW DIAGRAM OF WEST VIRGINIA UNIVERSITY PROCESS
-------
Table 2
COMPOSITION OF PRODUCT GAS—WEST VIRGINIA
UNIVERSITY PYROLYSIS PROCESS
Composition
Component ^ (Percent)
CO
C°2
H2
CH4
C2H6
C3H8
Gross heating value kilogram calories per cubic 'meter
(Btu per standard cubic foot)
(MJ per normal cubic meter)
27.1
14.7
41.7
7.7
7.8
1.0
3900
(430)
(16)
This gas, too, could be methanated, if local conditions demanded. Con-
ceptual plant designs for 500 and 1300 tonne per day plants have been
prepared, but no development work is in progress.
Another process primarily designed for the production of storable
and transportable liquid product is to be demonstrated in a 200 tonne
per day plant at San Diego, California. The Garrett Research and Develop-
ment Company process involves size reduction, classification, drying,
secondary shredding, flash pyrolysis in a proprietary process, and product
recovery. The low-temperature process being demonstrated at San Diego
will produce oils more suitable for combustion than for refining. Yields
of approximately 0.16 cubic meter (one barrel) of oil per tonne of refuse
are expected. Higher temperatures in the pyrolysis unit could produce a
3 3
gas with substantial heating value—6900 kcal/m (29 MJ/m or 770 Btu/SCF)-
g
at yields estimated as 1.9 X 10 kilogram calories (8 GJ or 8.0 GJ or 7.6
million Btu) per tonne of refuse fed to the process.
262
-------
A pyrolysis process which does handle sewage sludge mixed with urban
solid wastes is under demonstration in the State of Delaware. This pro-
cess, developed by Hercules, Inc., does not produce or consume an energy
product. It will not be considered further. However, it is important to
note that the other incineration and pyrolysis processes discussed above
are not well adapted to handling the high water contents of animal manures
and sewage sludges, while the Hercules process will.
The Union Carbide, Bailie, and Garrett processes create products with
substantial heating value and chemicals content. They can be transported
economically or converted to a transportable product. For these reasons,
these processes may become more generally used than the other processes
described in this section.
C. Energy Products Made by Other Processes
1. Hydrogasification
Another gas-producing process is under development by the Bureau
of Mines. It uses technology similar to that developed by the Institute
of Gas Technology for gasifying coal. Only limited, small-scale work has
been done in batch equipment to define process conditions. Basically,
hydrogen, or mixtures of carbon monoxide and steam, contact solid refuse
*
under pressure to produce a product gas containing methane, carbon
monoxide, hydrogen, carbon dioxide and water vapor. Heating values of
3 3
2900-5100 kcal/m (12-21 MJ/m or 330-570 Btu/SCF) and energy yields of
6
0.93-2.3 X 10 kilogram calories per tonne are projected. The gas could
be readily converted to higher energy content by consecutive water shift
and methanation reactions. However, the high pressures required will re-
quire inefficient batch operation or new developments in high-pressure
feeding systems for heterogeneous materials.
A typical experiment involved hydrogen at (550°C or 1022 °F) and 91 kilo-
grams per square centimeter of pressure (8.9 MPa or 1300 psig).
263
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2. Catalytic Gasification
Batch experiments at the University of Wyoming have shown that
steam can react with solid refuse at moderate pressures, 2.1 to 18.3
kilograms per square centimeter (30 to 260 psig), and temperatures of
650 to 760°C (1200 to 1400°F), to produce a product that is half methane
and half carbon dioxide. One pound of catalyst and relatively large
quantities of potassium carbonate are required for each pound of waste.
The product gas can be easily treated to remove carbon dioxide
leaving a high-heating value material, and for this reason the process
is of interest. However, at this time the experiments have been on a very
small scale, and the stability and longevity of the large quantities of
catalyst required have not been established. The process is so far from
demonstration that its true potential cannot be assessed and we will not
consider it further in this report.
D. Digestion Processes
1. Anaerobic Digestion
Fermentation or digestion processes play a part in all naturally
occurring waste disposal processes. They have been used to stabilize
concentrated organic sludges or wastes in water. (Mixtures of sludge
and urban refuse are used as starting material for the Hercules, Inc.,
process.) In the past, the generation of gas (methane) product has been
incidental to the economic and sanitary disposal of unwanted organic
wastes. The need for energy product and the advantages of large-scale
processes now made possible by growth and concentration of urban refuse
loads offer new incentive to develop and enhance gas recovery.
264
-------
Aerobic and anaerobic environments have been used for digestion
of solid wastes; however, only the latter process produces methane. The
digestion process is usually conducted in an aqueous environment, so
normal urban wastes are mixed with water or with watery wastes such as
sewage sludge. Small particles speed the reaction, so the wastes must
be pulverized as much as practicable. Mixing is required, if high
processing rates are to be achieved.
Anaerobic digestion requires nitrates, nitrites, sulfates,
carbon dioxide, or similar oxygenated compounds. These supply the oxygen
needed for bacterial action. Typical reactions are
Organic matter + Nitrates + living cells _
and
more living cells +N + CO +HO+NH
2223
Organic matter + CO + living cells -
2
more living cells + CH + H 0 + NH + CH COOH
423 3
The direct energy yield of anaerobic digestion is much smaller than for
aerobic digestion. However the energy difference is stored chemically in
the methane and other products. Not all organic material is biodegradable,
The biodegradable material undergoes three steps.
(1) Solubilization (or pulping). (This may or may not be
assisted by bacteria.)
(2) Acid forming in which the complex soluble material is
reduced to simple organic acids.
(3) Transformation of acids, primarily to methane and carbon
dioxide.
265
-------
In the continuous operations necessary for large-scale conversion,
the three steps are occurring simultaneously. Temperature and pH control
are important. The temperature range for the bacteria of interest lies
between 5 and 65 C (40 and 150 F). Three different categories have peak
metabolic rates within the indicated temperature ranges.
Temperature
Bacteria (Degrees Centigrade)
Psychrophilic 10-25
Mesophyllic 30-37
Thermophilic 55-60
Generally, the rate of bacterial action for a particular strain doubles
for each 10°C increase in temperature. These bacteria are sensitive to
poisons such as oxygen, chlorinated hydrocarbons, and heavy metals. While
most anaerobic bacteria grow well over a wide range of acidity, the
methane-forming bacteria are extremely sensitive, growing best in the pH
range of 6.5 to 7.0.
In a system with all processes occurring simultaneously, and
with the nutrient medium and poison species and concentration constantly
changing as new materials are introduced, full control of bacterial growth
is difficult to achieve. If the acid-forming bacteria grow too rapidly,
the pH may drop below 6.5 or 6. The methane-forming bacteria will then
cease to grow, and the process stops halfway. This "stuck," or sour,
digestor is full of organic acids that make disposal unpleasant and
difficult.
266
-------
Another reaction of environmental interest is the bacterial
action of the particular bacteria known as desulfovibria.
Organic matter 4- sulfates + desulfovibria cells ~»
living cells + H^S + CQ^ + N^ + NHg
Since this reaction can occur in any anaerobic digestor, the H S-
Z
containing effluent must be controlled or treated to prevent unpleasant
odors.
A system arranged for methane production would perform the
following operations:
• Size reduction.
• Segregation of heavy metals (and chlorinated hydrocarbon
films, if possible).
• Slurrying of sewage solids and solid refuse (3 percent total
solids).
• Digestion in heated tanks 60°C (140°F) with thermo-
philic bacteria. (Note that heat is required.)
• Gas collection and purification (removal of carbon dioxide,
hydrogen sulfide, phosphene).
• Separation of undigested solids.
• Disposal (landfill) of inert solids.
Available experience indicates that gaseous fuel could be pro-
i 4
duced at the rate of 1.0 x 10' joule (10 Btu) per person per day from
a mixture of sewage and urban solid wastes. Only 2 percent of the
total will come from sewage sludge, although it is a necessary ingredient
in the digestion process. Inert materials remaining after digestion may
amount to as much as 50 percent of the volume of compacted dry refuse.
Incineration of this undigested material to reduce its volume is possible,
but the incineration will be difficult without additional drying steps
267
-------
and there are problems such as the odor of gaseous by products. By con-
trast about 90 percent of animal wastes can be converted to gaseous form,
and treatment of other agricultural wastes will leave from 10 to 50 percent
solids for ultimate disposal.
No large-scale digestions that recover gaseous fuel from wastes
are in operation in the United States; however, the art of sewage treat-
ment that would form the basis of any gas production and recovery opera-
tion has been practiced for many years.
2. Enzymatic Digestion
Enzyme-based photosynthetic processes have been reported to
produce hydrogen from water. These might be adapted to produce hydrogen
from wastes, directly or indirectly. The technology is so little ad-
vanced that we are unable to offer any prognosis for the process or to
predict its environmental impact. We will not discuss it further.
Landfill, and to a lesser extent, incineration, is the primary
method for refuse disposal today. Future developments are expected to
emphasize the importance of incineration with energy recovery, pyrolysis
to produce energy products, and anaerobic digestion to produce methane.
In fact, these latter two methods are expected to be the basis of most
large-scale disposal facilities of the future. We will discuss the
environmental effects of incineration, pyrolysis and anaerobic digestion
in the following section.
268
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Ill ENVIRONMENTAL IMPACTS OF SPECIFIC
ENERGY-PRODUCING WASTE-DISPOSAL PROCESSES
A. Introduction
In assessing the potential effect of solid-waste recovery and its
conversion to energy or energy materials, we will first consider the
known or estimated effluents of typical energy-producing incineration,
pyrolysis, and digestion processes. We will then make range estimates
of the extent to which each general process will be adopted to establish
total pollution impacts.
The literature dealing with energy-producing waste disposal processes
is deficient in definitive data on quantity and quality of a given effluent
from a given process. As a result, the following paragraphs will contain
a few numbers that are based on quantitative data directly related to
the process discussed and some that are based on inference from similar
processes having quantitative data. Most will be inferred or assumed
from qualitative estimates. Air pollution data from incinerator-type
operations is directly available. Water pollution data for incinerators
and all pollution data for other processes will be inferred with different
degrees of extrapolation or interpolation.
Pollution data from disposal-only incineration processes can be
applied directly to incineration processes that generate steam. Un-
treated stack gas from municipal refuse is reported to contain 15 kilo-
grams of particulates per tonne of refuse (30 Ibs/ton).7 This is typical
of single chamber incinerators.8 This particulate effluent rate can be
substantially reduced by systems to control particulates.9 (See Table 3.)
269
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Table 3
COLLECTOR EFFICIENCIES FOR MUNICIPAL
INCINERATION PARTICULATE-CONTROL SYSTEMS
Efficiency
Type (percent)
Settling chamber 0-30
Settling chamber and water spray 30-60
Wetted baffles 60
Mechanical collector 30-80
Scrubber 80-95
Electrostatic precipitator 90-96
Fibric filter 97-99
At 90 percent removal, the particulate emissions reaching the atmo-
sphere will be 1.5 kg/tonne (3 pounds per ton), and at 99 percent removal
they will be 0.15 kg/tonne (0.3 pound per ton). Combustion of one tonne
of refuse with 270 percent excess air will produce approximately 7,800
cubic meters (275,000 cubic feet) of gas at standard conditions.10 This
gas has a CO content of 6 percent. At 12 percent CO (the standard
2 2
basis for comparison), the concentration of particulates would be 0.366
and 0.0366 grams per cubic meter (0.16 and 0.016 grains per SCF) for
90 and 99 percent removal. A recovery of particulates of at least 95
percent is required, if the required upper limit for particulate pollution
of 0.183 grams per cubic meter (0.08 grains per SCF) is to be met, under
the assumed conditions.
Practical data from the Chicago steam-raising incinerator indicate
that precipitator efficiencies of 96 to 97 percent were achieved and
original particulate loads before the precipitator of about 10 kilograms
270
-------
(22 pounds) of particulate per tonne of refuse burned were reduced to
about 0.42 kilogram (0.93 pound) at the stack exit.11 Direct incinera-
tion will also add approximately 0.4 kilogram (1 pound) sulfur dioxide
and 1.3 kilograms (3 pounds) nitrogen oxides to the air per tonne of
refuse burned.
The usual particulates will contain inorganic materials, including
detectable amounts of free mercury and beryllium, lead and zinc.12
(See Table 4.)
Table 4
CONCENTRATION OF SOME TRACE MATERIALS
IN INCINERATOR FLY ASH
Be
Hg
Pb
Zn
Study 1
(amount)
Small or trace
Small or trace
Small or trace
Small or trace
Study 2
(percent)
0.001-0.01
0.01-0.1
1-10
These heavy metals and others, such as cadmium and selenium, are potential
health hazards whose overall effect is poorly known at present. Lead
particulate inhalation may cause chronic intoxication; soluble lead
components are cumulative poisons. Particulate beryllium produces
pulmonary fibrosis. Cadmium oxide dust or fumes may cause pulmonary
edema or hemorrhage. Zinc inhalation may lead tp '.'metal fume fever", and
damage to the respiratory tract.13 Total potentially hazardous inorganic
effluent from a properly controlled stack is likely to be much lower
than 0.05 kilogram per tonne (0.1 pound per ton) of refuse incinerated.
271
-------
Handling of the collected incinerator fly ash also poses potential hazard
to the refuse disposal worker.
While the ash is primarily inorganic in character, some organic
material remains unburned. Chlorinated hydrocarbons and polynuclear
hydrocarbons (resulting from pyrolysis as well as incomplete combustion)
both pose potential health hazards. The former can cause damage to the
central nervous system; the latter are known carcinogens. Quantities of
these materials are low; total organic carbon in fly ash ranges from 10
to 20 percent, and the fraction of toxic or hazardous materials is much
lower (although undetermined). Total potential hazardous organic material
emitted from controlled stacks is certainly below 50 grams (0.1 pound)
per tonne of urban solid waste burned.
Other volatile materials may escape combustion at low excess air
values. These may cause problems with eye irritation and odor, but are
not fundamentally hazardous. Formic, acetic, palmetic, stearic, and
oleic acids; methyl and ethyl acetate and ethyl stearate; formaldehyde
and acetaldehyde, hydrocarbons, and phenols have been found in incinerator
stack gases. Potentially hazardous materials such as phosgene and hydro-
gen cyanide can be formed, but we expect these would be found in very low
concentration. Hydrogen chloride can be an undesirable product when
chlorinated hydrocarbons (such as those contained in plastic films) are
burned. Proper incineration practice, including afterburning with addi-
tional fuel, should reduce all of these to unnoticeable or negligible
levels.
The extent of use of quench water in incinerator practice is not
recorded in the literature. In many instances air cooling is used.
However, we will assume that all incineration for energy production
utilizes water quench on the ash. We estimate 5 to 50 kilograms (10
to 100 pounds) of quench water will be discharged per tonne of refuse
272
-------
treated. This material will have high pH (6 to 11.8) and contain suspended
and dissolved solids in varying amounts [as much as 6 grams and 10 grams
of solids per kilogram (0.006 and 0.01 pounds per pound) of water, re-
spectively]. Secondary treatments incorporated in the solid waste dis-
posal facility should provide adequate control.
The 180 to 225 kilograms (400 to 600 pounds) of residue after in-
cineration of a tonne of refuse may have valuable materials extracted,
but we will assume that all 225 kilograms is placed in landfill. This
material is principally silicon, aluminum, calcium, and iron oxides.
Leachates from it may percolate to ground waters, streams, and so forth.
These leachates will have high hardness, but the composition and quantity
are too dependent upon local conditions for any judgment of their ultimate
environmental effect to be made without extensive field work and analysis.
The environmental impact analysis for the individual location must define
the potential effects.
Fluidized bed incineration will probably produce no more airborne
particulates than will normal incineration if both facilities are prop-
erly managed. In fact, the Combustion Power Company process in which
combustion gases are fed to a turbine to generate electricity requires
extreme cleanliness. Particles and metal vapors can cause erosion and
other problems with turbine blades; thus the process includes three
stages of cyclone separation for particle removal.
Fluidized bed processes can usually be adjusted so as to absorb
sulfur dioxide into the bed. The low combustion temperatures in the
bed are expected to reduce nitrogen oxide formation. This better thermal
contact should also reduce the quantities of unburned organic material,
including chlorinated and polynuclear hydrocarbons.
Combustion (incineration) processes in which refuse makes up a
small fraction of the total material fired will operate under the same
273
-------
general conditions and produce the same general environmental effects
as coal-fired boilers. The uncontrolled fly and bottom ash loads may
be as much as 3 to 7 percent higher per pound of steam produced in the
boiler when mixed refuse and coal is burned instead of coal only, but
the emissions per tonne of refuse burned should be less than those listed
above. The quantity of air required is expected to drop from 200 percent
or more to 20 to 25 percent excess air. The reduced volume flow will
cause less carryover to the cleanup system, and the more compact systems
may be generally more efficient.
Pyrolysis processes such as Landgard, that produce steam as a prin-
cipal product, will have air effluent problems similar to those of the
combustion systems. Exit gas flows will lie between those found in
normal incineration and those in combined burning with coal. Particulate
loads will be no higher, and perhaps lower, than those from direct in-
cineration processes. The secondary combustion of the pyrolysis gas
will consume some of the hydrocarbons and other combustibles that escape
from direct incineration. The gas burned in this step has a low calorific
value, and thus flame temperatures will be lower than in incineration.
Therefore, nitrogen oxide levels should be lower. Whether particulate,
hydrocarbon, and nitrogen oxide emission levels are lower for pyrolysis
for energy production plants than for incineration plants is probably
more dependent upon individual differences in design and methods of
operation than upon process fundamentals. Ash or slag characteristics,
leaching of ash to ground water, and quench water discharge factors are
expected to be about the same for incinerator and pyrolysis plants.
The emissions from pyrolysis processes directed to the production
of energy product should be small. The product gases from each will be
contained and can be scrubbed to remove acid gases and particulates.
The entire gas output of the Torrax and Union Carbide processes will
be so treated. The Bailie process produces separate streams of product
274
-------
and combustion gas. The latter will be quite small in volume when com-
pared to that from direct incineration processes. Only 10 to 15 percent
of the combustibles will be directly burned. The burning, in a fluldized
bed, should require little excess air, produce only small quantities of
nitrogen oxides, and have low unburned hydrocarbon loads. Ash loads
from several of these processes will approximate those from direct in-
cineration. The fluidized beds of the Bailie process will produce about
50 percent more ash than the other processes. Thus, the landfill is
larger and leachate loads may be slightly higher for it than from the
other processes. Quench water discharge will be slightly larger, but
treatment will reduce the effect to negligible proportions.
The proprietary nature of the Garrett process precludes direct com-
parison of expected effects; however, we expect it will produce stack
gas, water, and solid waste effluents in amounts similar to those of the
other energy product processes.
We cannot comment in detail on potential emissions from hydrogas-
ification and catalytic methanation processes, as those are apparently
far from demonstration, and serviceable data are lacking. However, it
is likely that if developed, they will behave like the other energy-
product-producing processes and have relatively low emission effect.
Anaerobic digestion, properly conducted, will collect product gases.
The principle undesirable product, hydrogen sulfide, can be removed.
However, removal of small quantities of hydrogen sulfide from carbon-
dioxide-containing mixtures may prove to be difficult and uneconomical.
More difficult to handle may be the problems encountered during off-
specification operations. These will probably be caused by poisoning
of the bacteria either by metals or acid. The "sour," partially treated
mess is vile-smelling. Its disposal by landfill or incineration would
not be well received by people for several miles downwind of a large plant.
275
-------
Substantial quantities of organic material remain untouched by
anaerobic digestion. The wastes could be further reduced in volume by
incineration, if they can be dried sufficiently. If they are not so
treated, the volume of waste placed in landfill could be as much as
50 percent of that from the original shredded and compacted waste.
B. Miscellaneous Effects
Several of the processes may require drying of the as-received
solid waste on an occasional or regular basis. (As-received refuse may
have from 20 to 50 percent water; 30 percent is very common.) This
drying and the combustion of the refuse will release moisture to the
environs of the plant. A 10,000 tonne per day plant will release
2500 to 4000 tonnes of moisture per day. Drying can produce noxious
odors in the drying gas stream. Most of this can be removed by passing
the exit gas through a high-temperature flame, one at 700 to 820°C (1300-
1500°F). This requirement for an extra combustion step and necessity for
extra fuel could reduce the economic attractiveness qf the process that
requires it.
Handling, size reduction, and classification activities create dusts,
especially if the solid waste has been dried. The operator and designer
must take potential dusting into account so as to minimize its effects.
Vents or hoods over the equipment can lead the dusty air to a separate
filter system or to the main stack. Total particulate discharge will
not be measurably affected, and this impact can be credited to the general
particulate discharge.
In any discussion of environmental effects, it should be noted that
any waste-disposal process will require refuse collection, with the
attendant noise and environmental effects of large truck transportation.
At the collection station the noise of refuse transfer operations and
the odors coming from untreated refuse in storage will create local
276
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problems. Size reduction, which is essential for some processes and
desirable for any materials recovery operation, is very noisy. Relatively
small shredders capable of handling 5 tonnes per hour will produce noise
levels of 80 to 85 decibels at 50 feet from the machine.14 This is
equivalent to the noise arising from diesel trucks, compactors, and other
equipment to be encountered at disposal sites. The noise impact will be
restricted to a relatively small area in the immediate vicinity of the
plant.
C. Specific Environmental Impacts of Solid Waste Disposal Plants
Most high solids (urban) wastes will be treated by energy-producing
*
incineration or pyrolysis processes. Fewer will be treated by direct
incineration, with qualitatively similar environmental effects, and some
by anaerobic digestion. If 75 percent of urban wastes are treated by
some form of incineration or pyrolysis process, an urban population of
175 million in 1985 will produce from 50,000 to 250,000 tonnes of
t
particulate contamination. The lower figures are associated with
pyrolysis plants producing energy product. In most cases these plants
will use less combustion air and/or release smaller volumes of combustion
products to the atmosphere. If the effluent gases are held to the same
volumetric standard, then the total effluent from pyrolysis gases will
be smaller. For comparison, we note that solid waste disposal (primarily
direct incineration) now contributes 1.4 million tonnes of particulates
annually to an atmospheric pollution that totals 25 million tonnes of
particulates.16 The energy recovered from this urban waste could be as
We include energy materials in this category.
t
Assuming particulate emission for each plant meets the current national
standard of 0.183 grams per cubic meter(0.08 gram per SCF).
277
-------
much as 2.5 percent of the total anticipated energy demand in 1985, at
the same time the particulate burden in the atmosphere will be reduced
to below 1 percent of the current total.
The quantities of lead and zinc placed annually in the atmosphere
can range from a few tonnes to perhaps a thousand tonnes. The current
release of a comparable metal, cadmium, is estimated at 86,000 kilograms
(190,000 pounds) through (uncontrolled) incineration.15 Rubber
tire wear contributes 5150 kilograms (11,400 pounds), and super-
phosphate dispersal contributes 22,500 to 225,000 kilograms (50,000 to
500,000 pounds). (The superphosphate is not emitted directly into the
atmosphere.)
Potential carcinogens and other hazardous organic materials may be
discharged as particulates in tens to hundreds of tonne quantities.
These quantity estimates are a reasonable maximum based on complete use
of well-controlled, energy-producing incinerators, or production of
energy products from pyrolysis.
We estimate that pyrolysis processes producing energy product will
produce perhaps one-tenth to one-fifth as much particulate pollution as
incineration processes. The larger factor has been used in the estimates
of metals emission above. However, the exact ranges of quantities and
concentrations to be expected from large economical plant operation need
to be established by adequate experimentation at demonstration plants.
We now turn to the local effects of particulate emission. A 10,000
tonne per day solid-waste disposal-by-incineration plant serving some 2
million persons will discharge 15,000 kilograms (33,000 pounds) of partic-
ulates per day (assuming 90 percent control). Typical large cities with
populations over one million have areas of 2500-5000 square kilometers.
If we assume these particulates are discharged into a box with a base
60 kilometers square (3600 sq km) and a height of 0.3 kilometer, and that
278
-------
the box is swept with light winds (5 kilometers per hour) for 14 hours
a day, a volume of 1260 cubic kilometers is provided in which this effluent
is dispersed. The concentration of particulate would then be 12 micrograms
per cubic meter. Because the box model assumes quite unfavorable inversion
3
conditions, the 12 |_ig/m concentration level would seldom be reached.
For reference, we note that former urban air particulate concentrations of
3*
over 100 per |Jg/m are now being reduced by good air pollution control
3
practices to meet secondary standards of 60 |ig/m .
Correlation between air quality and emission rate is dependent
upon the stack height and stack gas velocity of the individual plant and
the daily and annual weather conditions at the site. Thus the influence
on local and regional air quality of a single solid-waste disposal process
must be established on an individual basis. Regional air quality as a
function of regional emission varies, too, as a function of meteorology.
However, some selected metropolitan regions, e.g., Chicago, New Jersey,
New York, Connecticut, Los Angeles, and the San Francisco Bay Area, have
/ 3
estimated median annual air qualities of 0.065, 0.14, 0.16, and 0.38 (j,g/m
particulates per daily tonne of particulate emission.17 Air qualities
3
(pollution ) of 0.10, 0.22, 0.30, and 0.58 Ug/m per tonne will be ex-
ceeded 20 percent of the time in these same cities.
Using these data, we deduce that the 10,000 tonne per day plant
discharging 15 tonnes of particulate effluent would have median pollution
effect over the entire area of roughly 1 to 6 (Jig particulate per cubic
meter. The pyrolysis plant producing energy product would contribute
3
1 Ug/m or less of particulate to the air burden. These data lead us
to conclude that the urban areas would have ultimate particulate loads
*
See Figure 1, Estimated Emissions of Air Pollutants by Weights, Nationwide,
1970, Preliminary D.ata, EPA. This is taken in turn by Mitre Corp. Report
MTR 6013.
279
-------
from energy producing waste disposal amounting to 1 to 10 percent of the
established secondary air quality standards. While improved stack dis-
bursal and further improvement in collection efficiency may be required
under special circumstances, the concentrations of heavy metals introduced
to the atmosphere (as particulate ash) from a 10,000 tonne per day plant
are expected to fall well below values commonly encountered in urban
atmospheres.
The quantities of sulfur and nitrogen oxides emitted also will be
relatively small in all processes. Direct energy production processes
(without fluidized bed combustion), e.g., Landgard, will emit sulfur
dioxide (SO ) in weight quantities equivalent to particulate emissions.
£
Nitrogen oxide emissions will be about three times larger. If these
processes were used to dispose all urban wastes, they would add 200,000 to
250,000 tonnes and 600,000 to 750,000 tonnes, respectively, to the national
air pollution load. Currently, national sulfur oxides (SO ) emissions are
Ji
1 fi
estimated to be 34 and nitrogen oxides (NO ) emissions, 23 million tonnes.
X
Fluidized bed combustion will reduce expected emissions from waste disposal
by substantial amounts. The same general prediction can be made regarding e
energy product processes which utilize pyrolysis. Thus, as simple un-
controlled incineration is replaced by fluidized bed incineration and energy
product recovery pyrolysis, the effluent loads L(particulate, SO and
£t
nitrogen dioxide (NO )] from waste disposal will be reduced from 250,000
2
and 750,000 tonnes to perhaps 50,000 and 150,000 tonnes. The air con-
centrations will be similarly reduced. Relative or comparison data on the
various emissions are shown in Table 5.
Table 5 compares the quantities of each effluent emitted by other
waste-disposal processes to the quantity of effluent emitted by the in-
cineration for energy process. Particulates are assumed to be limited
to 0.183 gram per cubic meter (0.08 grains per SCF) of stack gas emitted.
280
-------
Table 5
ESTIMATED ENVIRONMENTAL IMPACT OF SOLID-WASTE DISPOSAL METHODS
FOR URBAN WASTES, RELATIVE TO ORDINARY INCINERATION
to
00
Incineration for energy
Pyrolysis for energy
Pyrolysis with energy product
Anaerobic digestion
Particulates
1
< 1
1/10-1/3
nil
SO
X
1
< 1
« 1
nil
NO
X
1
< 1
« 1
nil
H S
2
nil
nil
nil
possible
trace
Organics
1
1
« 1
unknown
Solids,
Leachates
1
1
1
1-3
Special disposal problems from stuck or sour digestor.
-------
Incineration processes will release small quantities of unburned
hydrocarbons and partial combustion products. We are unable to estimate
either the quantities emitted from incinerators or the effects to be
expected from exposure of humans, animals or plants to these small con-
centrations of such materials. It can be pointed out that incineration
and combustion in stationary sources are not now judged to be significant
contributors to total hydrocarbon emissions.19 Furthermore, man-made
emissions of partial combustion products, principally carbon monoxide,
are now attributable almost entirely to vehicles and petroleum refineries.
Established limits for exposure deal with occupational exposures
of 8-hour days and 40-hour weeks or a total exposure of 2000 hours per
year. The effects of and limits for continual exposure have not been
determined. If we apply the practice for limiting exposure to radio-
active materials for nonoccupational (general population) groups to one-
third that set as a limit for occupational exposure to the case of airborne
/ 3
chemicals, then clinical exposure limits are generally above 100 |j.g/m .
We do not expect concentrations of any single chemical in particulate form
/ 3
to be above 10 |ig/m in the undiluted stack gas.
It must be noted that fourteen potentially carcinogenic chemicals
are on a "prohibited" list, shown below in Table 6. These, or mixtures
of these down to 1 percent carcinogen, are to be handled as toxic materials,
and exposure to them poses a grave danger to employees.20 By regulation,
occupational exposure is controlled, to eliminate all contact (including
inhalation) with these chemicals.
Even fewer data are available on effluent from scale anaerobic
digestion. We expect particulate quantities to be low, and hydrogen
sulfide emissions to be controllable. Incineration and pyrolysis effluents
such as SO and NO will not be present in quantity. As the process will
2 2
be applied primarily to agricultural and food processing wastes, which
282
-------
Table 6
POTENTIALLY CARCINOGENIC CHEMICALS
Compound
No.
Chemicals
Chemical
Abstracts
Registry No.
1
2
3
5
6
7
8
9
10
11
12
13
14
2-Acetylaminofluorene
4-Aminodiphenyl
Benzidine (and its
salts)
3,3 '-Dichlorobenzidine
(and its salts)
4-Dimethylaminoazobenzene
alpha-Naphthylamine
beta-Naphthylamine
4-Nitrobiphenyl
N-Nitrosodimethylamine
beta-Propiolactone
bis-Chloromethyl ether
Methyl Chloromethyl ether
4,4'-Methylene(bis)-2-
chloroaniline
Ethyleneimine
53963
92671
92875
91941
60117
134327
91598
92933
62759
57578
542881
107302
101144
151564
are digested almost completely, solid residues will not be an important
consideration. However, when it is applied to urban wastes, the solid
waste problem could be appreciable.
D. Some Research Needs and Opportunities
It is apparent from the discussion above that definitive knowledge
of the kinds and quantities of materials generated by and released from
energy-producing solid waste disposal processes is lacking. Mercury
and other heavy metals, chlorinated hydrocarbons, and polynuclear
(carcinogenic) materials are among those for which information would
be especially significant. Operation of demonstration plants of newly
283
-------
developed processes offer opportunities for generating this information.
Demonstration plant operation offers opportunities for correlating the
character of plant input to effluents and establishing the feasibility
and effectiveness of waste segregation on environmental control. The
demonstration plant operations should also develop ways to minimize all
pollution effects, such as direct water wastes, leachates, and so on.
More measurements on effluents from existing incinerators would also
be helpful in establishing baseline information. Volatile organic species
and their concentrations are a potential concern. Our ability to detect
or measure quantitatively will be tested in many instances.
Basic information on the mechanisms by which leaching transports
metals, acid, alkali, and other contaminants from landfill to streams and
water supplies should be established. Testing of the effects of existing
ash-dominated landfill on the surroundings is needed.
The relative contribution of solid waste disposal processes to the
overall environmental result can only be established after data of these
kinds is gathered. It is apparent that several otherwise desirable pro-
cesses will be discharging very small quantities of potentially harmful
inorganic and organic materials into the atmosphere, and perhaps into
ground waters. Final evaluation of the processes must depend on the de-
velopment of sound information on the hazard (if any) from these materials
at the very low concentrations expected. From these data on hazard and
effluent concentration, one could establish possible needs for further
effluent control, and direct the development of control methods. One
could also evaluate the needs for control in terms of the relative hazard
from solid waste disposal and other processes.
284
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REFERENCES
1. "The National Solid Wastes Survey," U.S. Department of Health,
Education, and Welfare, Public Health Service, p. 13 (1968), as
quoted in R. G. Bond and P. Straub, Handbook of Environmental
Control, Vol II, Solid Waste, p. 49 (CRC Press, Cleveland, Ohio,
1973).
2. "1968 Survey of Community Solid Waste Practices," in Bond and
Straub, p. 51.
3. T. J. Sorg and H. L. Hickman, "Sanitary Landfill Facts," Solid
Wastes Program, National Center for Urban and Industrial Health,
Public Health Service, U.S. Department of Health, Education, and
Welfare, Cincinnati, Ohio, 1968.
4. Public Works, 100 (3); 79 (March 1969), in Bond and Straub,
Figure 3.2-233, p. 367.
5. S. Field, "The U.S. Energy Puzzle," paper presented at the Thirty-
Eighth Midyear Meeting, Division of Refining, American Petroleum
Institute, Philadelphia, Pa., 17 May 1973.
6. C. Rogers', Public Works, Vol 93, No. 7, p. 75 (June 1962), in Bond
and Straub, p. 483.
7. Table 2.1.1, "Compilation of Air Pollutant Emission Factors,"
Publication AP-42, 2nd ed., U.S. Environmental Protection Agency,
Office of Air and Water Quality Programs, (April 1973).
8. Air Pollution Engineering Manual, J. A. Davidson, ed., Publication
No. 999-AP-40, U.S. Department of Health, Education, and Welfare,
Cincinnati, Ohio (1967).
9. Table 2.1.2, in Publication AP-42, Reference 7.
10. Table 3.2-310 and Table 3.2-311, in Bond and Straub, Reference 4.
11. G. Stabenow, J. of Engineering for Power, Vol 95, Series A, Number
3, p. 137 (July 1973).
285
-------
12. Table 3.2-334, p. 470, in Bond and Straub.
13. C. G. Golucke and P. N. McGauhey, "Comprehensive Studies of Solid
Wastes Management," pp. 89-ff, Sanitary Engineering Research
Laboratory, University of California (1969), reported in Table
2-6, pp. 138-175, Bond and Straub.
14. F. Walton, Combustion Power Co., Inc. (private communication).
15. "Environmental Quality," The Third Annual Report of the Council on
Environmental Quality (August 1972), p. 6.
x
16. "Cadmium, The Dissipated Element," ORNL Report NSL-EP-21, reported
in "Estimated Emissions of Air Pollutants, Nationwide, 1970, Pre-
liminary Data," Environmental Protection Agency (1970).
17. "Air Quality Data for 1968 from the National Air Surveillance
Network and Contributing State and Local Networks," Office of Air
Programs Environmental Protection Agency, Research Triangle Park,
North Carolina. Also, "Report for Consultation on the Air Quality
Control Region," Consumer Protection and Health Service, Public
Health;Service, U.S. Department of Health, Education, and Welfare.
18. J. H. Cavender, D.S. Kircher, and A. J. Hoffman, "Nationwide Air
Pollutant Emission Trends 1940-1970," Environmental Protection
Agency (January 1973), p. 4.
19. "Profile of Air Pollution Control," Air Pollution Control District,
County of Los Angeles, 1971.
20. Code of Federal Regulations, Title 29, Part 1910, published in
The Federal Register, VoJ 38, No. 85, p. 10929 (May 3, 1973).
286
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Appendix E
UNDERGROUND COAL GASIFICATION
by
Albert J. Moll
287
-------
CONTENTS
LIST OF ILLUSTRATIONS 289
LIST OF TABLES 289
I INTRODUCTION 290
II STATE OF THE ART OF UNDERGROUND COAL GASIFICATION 291
A. Past Development Work 291
1. Mechanisms and Methods of Operation 291
2. Electrolinking 292
• 3. Hydraulic Linking . 295
4. Pneumatic Fracturing 296
5. Gasification 296
B. Current Program of the Bureau of Mines: Gasification
in Horizontal Direction 297
C. Current Program of the Atomic Energy Commission
and Lawrence Livermore: Explosive Fracturing with
Downward Gasification 298
D. Evaluation of the Current Programs 302
III ENVIRONMENTAL EFFECTS OF UNDERGROUND COAL GASIFICATION . . 305
A. Comparison with Surface Gasification:
Effects upon Land Surface 305
B. Direct Water and Air Pollution 306
C. Resource Recovery and Earth Tremors 306
D. Summary of Environmental Effects 307
IV IMPLICATIONS FOR THE ENVIRONMENTAL PROTECTION AGENCY . . . 309
References 31°
288
-------
ILLUSTRATIONS
1 In-Situ Coal Gasification by the Percolation Method 293
2 Plan View of Reaction Paths Initiated 294
by Electrolinking at Gorgas
3 Livermore Underground Coal Gasification Concept 299
4 Proposed Arrangement of Explosives 299
5 Coal Gasification by the Livermore Underground Method-
Block Flow Diagram » 30Q
TABLES
1 Effects of Underground Coal Gasification Compared
with Strip Mining plus Surface Gasification 308
289
-------
I INTRODUCTION
Underground (in-situ) coal gasification is a concept whereby fuel
gas is made from underground coal deposits by reaction with oxygen and
steam. The product gas may be in the form of substitute natural gas (SNG) .
or a low heating value gas (low Btu gas) that may be burned at the site
to generate electricity. Gasification with oxygen is necessary to make
SNG, while air may be used to make low heating value gas. Underground
coal gasification is distinct from surface coal gasification. In surface
coal gasification the coal is first mined and then gasified in process
vessels on the surface. Underground gasification serves to replace the
combined functions of mining and surface gasification—as well as coal
crushing, coal storage, and ash disposal. Once formed, the raw gas must
be reacted and purified much like the raw gas made by surface gasification.
There are at least two commercial processes for surface coal gasi-
fication, Lurgi and Koppers-Totzek, and several other processes are being
developed in the United States. At the present time, underground coal
gasification is largely undeveloped in spite of decades of research in
the United States, Britain, the USSR, and other countries. There are
two active governmental development programs underway in the United
States on underground coal gasification. One program is being carried
out by the Bureau of Mines and the other by the Atomic Energy Commission.
However, formidable technical problems must be overcome before under-
ground gasification can be commercialized.
290
-------
II STATE OF THE ART OF UNDERGROUND COAL GASIFICATION
A. Past Development Work
1. Mechanisms and Methods of Operation
The following reactions take place simultaneously during coal
gasification:
Combustion Coal + 0 •* HO + CO
22 2
Hydrolysis Coal + HO -» CH + CO
"Carbonization Coal -» C + CH + HO
f± £
Bouduard (undesirable
side reaction) 2CO -» C H- CO
2
Water gas C + HO -» H + CO
2 2
Shift CO + HO -* H + CO
222
Methanation 3H + CO -> CH -f- HO
£ 4 £t
In underground coal gasification, the most important of these reactions
are combustion, carbonization, and water gas. Combustion provides the
heat for carbonization and the water gas reaction. If there is poor gas
contact with the coal, or poor permeability through the coal, little of
the carbon product of the carbonization reaction is gasified by the water
gas reaction. Thus, if carbonization predominates, there is low air (or
oxygen) acceptance and a low yield of gas from the coal. The desired
type of operation occurs when gasification follows carbonization. This
type of operation is marked by high air acceptance and high gas yield.
291
-------
Previous studies, including both shaft and shaftless methods
of underground coal gasification, are extensively reviewed in a report
prepared for the Bureau of Mines.* The shaft methods require underground
mines to prepare the coal for gasification. Most of the work in the USSR
and England was devoted to shaft methods; however, there is no current
interest in shaft methods because most of the effort spent mining coal
would still be required.
With shaftless methods, no underground labor is used, and all
access to the coal is through boreholes drilled from the surface into
the coal seam. The approach used in the shaftless methods has been to
inject air into an inlet borehole, ignite the coal, and attempt to pro-
duce gas from one or more outlet boreholes. The most simple shaftless
•
method is the percolation method shown in Figure 1. Usually some means
must be used to make the coal bed more permeable; methods of achieving
permeability that have been tried or suggested include electrolinking,
pneumatic fracturing, hydraulic fracturing, and explosives.
2. Electrolinking
The process of electrolinking, the electrocarbonization of
coal, was first tried in the United States in 1947 in the laboratory of
the University of Missouri. Field tests were undertaken subsequently
under a cooperative contract between the University of Missouri and the
Sinclair Coal Company of Kansas City. In 1951 at Gorgas, Alabama, the
Bureau of Mines (in cooperation with the Alabama Power Company) further
investigated the electrolinking-carbonization of coal underground. In
England (about 1952) study and investigation were also directed to the
References are listed at the end of this appendix,
292
-------
BLAST INLET
A
GAS OFFTAKE
(a) SECTION THROUGH BOREHOLES
19 7
4 13
-65
18 14
00
17 >^ 15
16
(b) PLAN OF BOREHOLES
SA-2714-4
SOURCE: Bureau of Mines.
FIGURE 1 IN-SITU COAL GASIFICATION BY THE PERCOLATION METHOD
application of a technique to underground gasification processes. In
the Russian work, which began prior to World War II, electrolinking-
carbonization was successfully applied in large installations.
In the process of electrolinking, electrodes are installed
within the coal bed at a given spacing. Passing an electric current
between the electrodes carbonizes the coal by resistance heating to form
a path of increased permeability; gasification can then proceed along
this path. The Bureau of Mines performed experiments with an electrode
spacing of approximately 45 meters with some success.
293
-------
Figure 2 shows a pattern of electrolinked carbonization paths
among a number of boreholes and illustrates one difficulty, viz., the
lack of control when using this technique. The path of the current be-
tween two electrodes may be markedly affected by coal bed changes re-
sulting from prior experimental work on the undisturbed coal seam. There-
fore, the resultant unpredictability of electrolinking in the establishment
of single gasification paths appears to offer a major difficulty. But,
if multiple paths are to be established simultaneously, which is possible
in a commercial application of area gasification, the precise path be-
tween two individual electrodes may be inconsequential.
BH 14
BH 16
BH 12
BH 11
BH 13
BH 10
BH 8
0 10 20
SCALE, METERS
SOURCE: Bureau of Mine*.
SA-2714-5
FIGURE 2 PLAN VIEW OF REACTION PATHS INITIATED BY
ELECTROLINKING AT GORGAS
294
-------
Estimates made during the tests indicated that about 80 percent
of the electrical energy had passed through the coal bed during the
electrolinking phase, and this proportion rose to about 97 percent toward
the end of the electrolinking-carbonization phase. Whether or not
electrolinking-carbonization should have proceeded further to prepare a
bed of greater permeability for the gasification operations was not well
established. The results of British and Russian work were similar to
those reported above.
3. Hydraulic Linking
The process of hydraulic linking involves injecting fluids
under high pressure into a previously undisturbed coal seam to cause
fracturing and consequently an increase in permeability. Hydraulic
fracturing techniques have been used in oil field work for many years,
and the method has been tried in the United States and Russia in connec-
tion with underground coal gasification.
In the United States, several tests were carried out at Gorgas
by the Bureau of Mines. In the second and final test in 1957, the coal
bed was fractured by injecting fluids at a rate of 750 to 2300 liters
per minute at 63 to 70 kilograms per square centimeter (900 to 1000 psi)
pressure. A total of 5000 kilograms (11,000 pounds) of sand were sus-
pended in 128,100 liters (33,580 gallons) of water containing a gelling
agent for stabilization. The fluid fractured the coal, and the sand
served as a propping agent to hold the cracks and crevices open after
release of the pressure; fracturing continued for about three hours.
The injection took place in a centrally located drill hole. In these
tests, there were 50- to 100-fold increases in permeability at the in-
jection borehole, and air acceptance to other boreholes was increased
about fivefold. Such effects should last at least several years. Sub-
sequently, the hydraulically fractured areas were successfully gasified.
295
-------
The Bureau of Mines has also done considerable work with in-
corporating liquid explosives in the fluids, and this technique shows
some promise for further increasing the permeability in coal seams. For
example, it may be possible to electrolink or to fracture hydraulically,
then fill the fractures with liquid explosives, and explode them to pro-
duce larger volumes of fractured structures.
4. Pneumatic Fracturing
Work has been conducted in the United States and England on
the use of high-pressure air to fracture coal formations pneumatically.
Generally, it is possible to achieve initial success this way, but upon
release of the pressure the new fractures tend to close, eliminating the
temporarily increased permeability. This closing tendency also occurs
in hydraulic fracturing if there is no sand to prop the fractures open
after the pressure is released.
5. Gasification
After permeability is attained, gasification of the coal pro-
ceeds along the seam in essentially a horizontal direction. The small
scale gasification tests made by the Bureau of Mines in the 1950s at
Gorgas, Alabama, were carried out in a relatively thin (about 1 meter)
seam of coal. Although a considerable amount of data was obtained, the
results of the tests were discouraging:: the energy content of the gas
formed was low and variable, oxygen usage was high, and coal recovery
was poor. There were several reasons for the relatively poor performance.
One reason for poor performance was that poor gas contact with the
burning face allowed oxygen bypassing; another reason was that the
burning front tended to be unstable with preferential reaction of the
coal along the top of the seam. The Gorgas tests were ended in 1958
with these problems still unsolved.
296
-------
B. Current Program of the Bureau of Mines:
Gasification in Horizontal Direction
As indicated above, the approach of the Bureau of Mines in the past
has involved gasification in a horizontal direction after one of a
variety of methods has been used to achieve permeability. Their current
underground coal gasification program applies the same approach, although
the emphasis is on thick-seamed western coal.
A review of previous work1 included a recommendation that the Bureau
of Mines reactivate the underground gasification program on a limited
scale. A modest two-phase program was suggested; neither phase included
gasification experiments in the field.
The Bureau of Mines appears to have decided to forego the studies
recommended in favor of field gasification tests. Their present program
is aimed at establishing feasibility and showing that the problems en-
countered in previous programs can be solved. If the current program
is successful, the Bureau would like to launch a more ambitious series
of field tests to develop a commercial scale gasification process.
In fiscal 1973, about $600,000 was spent making underground gasifi-
cation tests on a site near Hanna, Wyoming. The coal seam used is 9
meters (29 feet) thick with a 120 meter (400 foot) overburden and dips
at a 7 degree angle. Initial air acceptance tests gave unacceptably
low rates by the percolation method. A hydrofracturing operation in
March 1973 gave a fivefold increase in air utilization rates, however,
the primary reaction occurring was still carbonization. In June 1973,
after new drilling took place to take advantage of the hydrofracturing,
air acceptance suddenly increased dramatically with a simultaneous
violent blowout at a production hole. This obviously marked the estab-
lishment of a gasification path along one of the hydraulic fractures.
The product gas was high in carbon monoxide indicating that gasification,
297
-------
as well as carbonization was occurring. It has not yet been determined
if the product gas rate and quality are such that the test will be con-
sidered successful. Preliminary reports indicate that the test results are
encouraging for air blown gasification to make low heating value gas for
on-site power generation, however, some oxygen-blown tests are also planned.
C. Current Program of the Atomic Energy Commission and Lawrence Livermore:
Explosive Fracturing with Downward Gasification
Lawrence Livermore Laboratory issued Atomic Energy Commission (AEC)
sponsored reports in 1972 and 1973 outlining a new underground coal gasi-
fication process.2>3 The process is based on using underground explosives
to fracture deep coal beds followed by gasification in the downward
direction; about $200,000 was spent on this work in fiscal 1973. At the
present time, the Livermore process is merely conceptual, since only a
limited amount of laboratory work has been performed.
Figure 3 illustrates the Livermore process in operation. The coal
seam is first fractured by simultaneous detonation of a pattern of
chemical explosive charges (Figure 4). Next, injection and production
wells are drilled as shown in Figure 3. The coal at the top of the
\
fractured zone is ignited; oxygen and brackish water are then injected
into the top of the fractured coal bed through injection wells to main-
tain gasification. The product gas is removed from the bottom of the
coal bed through directionally drilled production wells. Gasification
in the downward direction in this manner is believed to be inherently
stable because rapid reacting hot spots are slowed by the bouyancy of
the hot gases. The production gas is treated in surface facilities to
make pipeline specification gas, as shown in the block flow diagram
(Figure 5). When the coal in one fractured zone has all been gasified,
a new explosive pattern (Figure 4) must be detonated. Presumably, a
certain amount of coal must be left ungasified between fractured zones.
298
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PIPELINE GAS
GAS PURIFICATION PLANT
CO
,GAS PRODUCTION WELLS
OXYGEN PLANT
WATER PLANT
SHALE
SALINE
WATER WELLS
COAL AND SHALE
/< ^Wfeii^n^vx
SHALE ' \, ^HHH^^^^^^X^7 INJECTION WELLS
REACTION ZONE
TA-6990-57R
FIGURE 3 LIVERMORE UNDERGROUND COAL GASIFICATION CONCEPT
TOP VIEW
0)
£
1
ui
Q
EXPLOSIVES
EMPLACEMENT
PLAN
500
1000
WATER TABLE
SANDSTONE
AND SHALE
COAL
AND SHALE
SIDE VIEW ^•:-:S.^x(&&*^f:-&*™ ••••::-tt'-'~ ••-'•'• ••••*"••••••< .-. -••:•
600 m
TA-699O-5RR
FIGURE 4 PROPOSED ARRANGEMENT OF EXPLOSIVES
299
-------
Recovered Water
BRACKISH
WATER
WELLS
Water 4000 MTPD
OXYGEN
PLANT
CO.
GAS
PURIFI-
CATION
7.8 x 106 NCM/D (274 x 106 SCF/D)
CH4 90 mol%
Inerts 10 mol%
Oxygen 4267 MTPD
TA-6990-59R
FIGURE 5 COAL GASIFICATION BY THE LIVERMORE UNDERGROUND
METHOD-BLOCK FLOW DIAGRAM
The production gas is predicted to be primarily a mixture of methane
and carbon dioxide,2 with a negligible concentration of carbon monoxide
and hydrogen sulfide. Achieving a high methane yield underground would
be important economically, not only in eliminating surface methanation
facilities but also in minimizing consumption of expensive oxygen. Also,
underground removal of sulfur compounds would avoid surface facilities
for sulfur removal and recovery. The high methane content in this
concept results from gasification reactions followed by the methanation
reaction, rather than from the carbonization reaction. Methanation is
the key reaction in achieving high methane content under ground. At
high temperatures (above about 800°C), methanation is limited by equili-
brium. At lower temperatures, methanation proceeds slowly without the
presence of highly active nickel catalysts. Livermore personnel believe
that methanation will go nearly to completion because of the high pres-
sure and the long gas residence times (about an hour in the high tempera-
ture zone) combined with catalytic action of the ash and shale. The
30O
-------
limited number of small scale laboratory experiments performed are said
to support this belief.
An important objection to the feasibility of underground methanation
is the virtual impossibility of maintaining close temperature control of
the underground reactions. The Livermore report assumes that the tempera-
ture may be controlled by controlling the rate of water injection. How-
ever, the water and the oxygen cannot be intimately mixed. Furthermore,
it is possible that above a certain level of water injection the gasifi-
cation reactions will be extinguished. Consequently, a substantial
amount of underground methanation must be regarded as unlikely.
It is also claimed that enough sulfur will be removed from the gas
underground by the chemical constituents of the shale such that additional
sulfur removal facilities on the surface will be unnecessary. This as-
sumption also appears to be overly optimistic. Assuming that the coal
gasified contains 1 weight percent sulfur, the carbon dioxide-rich gas
purged from the acid gas removal section would contain over 11,000 ppm
sulfur dioxide after incineration. This sulfur dioxide level is about
40 times the emission levels likely to be allowed for new facilities.
Therefore, at least 97 percent removal of underground sulfur would be
required to avoid surface sulfur removal facilities. Such a high under-
ground sulfur removal is regarded as unlikely.
Livermore personnel have laid out an ambitious development program
for the process. They propose a nine year period on laboratory, bench
scale, and modeling programs followed by site selection and large scale
prototype operation. The funding for such a program lias not yet been
approved.
301
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D. Evaluation of the Current Programs
Problems common to the Bureau of Mines and the AEC-Livermore concepts
include the following:
• Possible extreme variations in gasification characteristics from
site to site.
• Variable product gas composition with time.
• Roof collapse with resulting decrease in permeability and surface
subsidence.
• Possible plugging and reduced permeability because of the presence
of slag or tars.
The problem of site-related variations is common to most mineral ex-
traction methods. The problem is more serious in underground gasification
since there are chemical and thermal aspects—as well as the mechanical
aspects—of the extractive process that are affected by the configuration
of the resource. Consequently, a steeply pitched coal seam may have a
gasification rate and gas yield that differs from those encountered with
a flat coal seam. Site-to-site variations with the AEC-Livermore concept
is expected to be greater than with the Bureau of Mines method because
of the additional effect of interlaying rock layers on the effectiveness
of the underground explosives.
Time variation in product gas composition would probably be in the
form of a decline in heating value of the gas because of partial gas
combustion by unconsumed oxygen that has by-passed the coal. This problem
is especially severe when gasifying in the horizontal direction as pro-
posed by the Bureau of Mines. The tendency for preferential reaction at
the top of the coal seam results in a cavity there through which oxygen
can by-pass the coal and burn some of the product gas. A possible solu-
tion is to continuously fill the cavity with material that would fuse and
expand to prevent oxygen by-passing. A large development program would
be needed to develop the required methods and materials. The problem is
302
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less likely to occur with the AEC-Livennore concept because of the probable
stability of the downward reaction front. However, some less serious
problems of temporary decreases in crude gas composition may be en-
countered with the AEC-Livermore concept when the reaction front crosses
barren rock zones.
Roof collapse could affect gasification severely in some cases; but,
in most cases it is not believed to seriously reduce permeability.
Furthermore, roof collapse is not likely to help significantly in re-
ducing oxygen bypassing. Another possible problem, surface subsidence—
considered to be unavoidable—is discussed separately in the discussion
of environmental effects in Section III of this appendix.
Plugging of the pores and cracks in the formation could reduce per-
meability of the formation and slow the gas production rate. Little is
known concerning whether or not such plugging would actually occur,
•
especially when gasifying western coals. Plugging by tars would occur
downstream of the reaction front during the cooling of the crude product
gas, and plugging by slag upstream of the reaction zone would be a po-
tential problem, especially with the Livermore concept if the temperature
of the reaction zone gets out of control. Only extensive field testing
would determine if plugging is an important problem area.
There are two special potential problems specifically involving the
AEC-Livermore concept:
• Oxygen loss by ground water intrusion
• Ignition loss in crossing barren shale zones.
The problem of oxygen loss is potentially severe because of doubling of
oxygen usage would add at least 19£/GJ (20£ per million Btu) to the SNG
cost. Moreover, if excessive ground water intruded into the reaction
zone, loss of ignition could occur. The mechanism for potential oxygen
loss and ground water intrusion is as follows: As the reaction proceeds
303
-------
a cavity is formed above the reaction zone, which will eventually lead to
collapse of the rock roof. If there is an overlying aquifer, the ground
water would flow downward displacing the oxygen and causing the oxygen to
flow upward into the space formerly occupied by the ground water. It is
not known how near the aquifer would need to be to the reaction zone to
cause this undesirable effect; it would depend upon the permeability of
the collapsed rock. This problem could potentially limit the choice of
attractive underground gasification sites severely.
The problem of loss of ignition as the reaction front crosses barren
rock partings is also mainly site related. However, it is not know how
thick the partings need to be to cause loss of ignition. The maximum
parting thickness may range from one to one hundred meters, based on the
present inadequate estimates. Livermore personnel believe that many of
these so-called barren rock zones may contain enough coal inclusions to
maintain ignition.
Considering these problems and the undeveloped state of the tech-
nology, underground gasification must be regarded as a potentially at-
tractive—but very risky—long term prospect for gasifying otherwise
uneconomical coal deposits. However, even after an extensive development
program, large scale underground gasification may not prove to be feasible.
304
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Ill ENVIRONMENTAL EFFECTS OF UNDERGROUND COAL GASIFICATION
A. Comparison with Surface Gasification: Effects
upon Land Surface
The environmental effects of underground coal gasification would be
quite different from those resulting from mining and surface gasification.
Underground coal gasification, if it is developed commercially, would
probably be used to gasify coal which is not presently strippable and
for which even deep mining technology is not well understood. Therefore,
a comparison of environmental effects with strip mining and surface gasi-
fication is a study of the alternate use of two different resources, as
well as two different technologies. Plans for surface gasification
facilities are underway in several locations in the western United States.
In all areas the coal to be gasified will be strip-mined, resulting in
massive problems of land reclamation.4 The arid climate of the region
complicates reclamation efforts by retarding revegetation.
The effect of underground gasification upon the surface is in the
form of mild subsidence, which leaves surface soil and vegetation intact.
Moreover, less land space is required for surface facilities because
space is not needed for coal storage, coal preparation, gasification,
and ash disposal facilities. Of course, the ash residue from underground
gasification stays underground.
Surface subsidence probably precludes the use of underground gasifi-
cation under sites where permanent structures exist. In addition, it may
305
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limit future building on these sites. The amount of surface subsidence
to be expected is not well understood, but it is known that it will vary
with the seam thickness of the coal gasified, the depth of the coal, and
the nature of the rock strata overlaying the coal. For deep underground
gasification, surface subsidence is expected to be a small fraction of
the seam-thickness. A study of potential surface subsidence effects
will be a requirement of any program for commercializing underground
gasification.
B. Direct Water and Air Pollution
Some aspects of underground coal gasification are potential causes
of environmental concern. Potential problems of ground water pollution
and leakage of toxic carbon monoxide containing gas are not well defined.
Toxic gas leakage is regarded as extremely unlikely for deep coal de-
posits if there are no nearby outcrops of the coal seams. There is little
evidence regarding potential ground water pollution resulting from com-
pleted underground gasification projects; a possible analogy is the water
pollution resulting from abandoned deep mines. The Livermore concept of
using explosives to prepare coal for underground gasifications avoids—
or minimizes—direct water and air pollution effects by gasifying only
deep coal more than 150 meters (500 feet) below the surface.
C. Resource Recovery and Earth Tremors
The technology of underground coal gasification may be used only on
otherwise unrecoverable coal. It should be noted that the Livermore
method would involve repeated patterns of explosives (for example,
Figure 4). It is probable that unfractured "walls" would need to be
left between successive fractured zones. Therefore, the coal in the
interstices between fractured zones may not be recoverable.
306
-------
The Livermore concept could interfere with mining of other minerals
at the same site more than would conventional strip or deep mining. This
issue of resource recoverability must be decided on a site-by-site basis.
In addition, there is a small possibility of earth tremors—as has
been feared—as a result of underground nuclear explosions; however,
there is little evidence concerning this possibility.
D. Summary of Environmental Effects
Overall, it is clear that underground gasification would have less
severe effects on the environment than a combination of strip mining and
surface gasification. Typical resource requirements and effluent amounts
are compared in Table 1.
The usefulness of the analysis of environmental effects depends upon
the successful development of a commercial process for underground gasi-
fication. At the present time, success is not assured and companies
interested in coal gasification are concentrating on surface gasification
plants. Only large scale demonstration of underground gasification will
change the situation.
307
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Table 1
EFFECTS OF UNDERGROUND COAL GASIFICATION COMPARED WITH
STRIP MINING PLUS SURFACE GASIFICATION
Underground Strip Mining Plus
Coal Gasification Surface Gasification
Land area for plant facilities,
square meters 81,000 490,000
Stripped land per year, square meters 0 1,000,000
Total land subjected to subsidence
w per year, square meters 510,000 0
o
00
Water required, cubic meters per year 11,000,000 11,000,000
Sulfur recovered, kg per day (needs
to be disposed of if it cannot be
sold) 180,000 180,000
Ash to be disposed, kg per day 0 1,800,000
Basis: One plant producing 7 million normal cubic meters (250 million standard
cubic feet) of SNG per day; coal containing one percent sulfur and 10
percent ash; 50 percent recovery of coal for Scheme A with a seam thick-
ness of 15.2 meters (50 feet); 50 percent recovery of coal stripped for
Scheme B with a seam thickness of 7.6 meters (25 feet).
-------
IV IMPLICATIONS FOR THE ENVIRONMENTAL PROTECTION AGENCY
Underground coal gasification need not be a subject of near term
concern on the part of the EPA, because of the undeveloped state of the
technology. However, there are potential environmental advantages of
underground gasification over surface gasification of stripped western
coal. These advantages will be minimized if techniques for reclamation
of stripped arid land are improved and if such reclamation is required
by law.
At present it would be premature for EPA to commit substantial re-
sources to either the prevention of undesirable environmental effects of
underground coal gasification or to the development of this technology
as an environmentally attractive alternative to coal mining followed by
surface gasification. Reasons for this conclusion include the following:
• Other federal agencies are supporting the development of
underground coal gasification.
• There is great risk that large-scale underground coal gasifi-
cation is not technically feasible
• The potential environmental advantages of underground gasifi-
cation are not compelling.
• Undesirable environmental effects (discussed herein) which
are particular to underground gasification are possible.
Instead, SRI recommends that the EPA expend a small effort in fol-
lowing the progress of the development programs sponsored by the Bureau
of Mines and the AEC. If at a future date both technical feasibility
and environmental superiority of underground coal gasification is demon-
strated, the EPA should at that time support commercialization. A some-
what more immediate role of EPA may be to monitor any large-scale under-
ground gasification tests for undesirable environmental effects, such as
those discussed herein.
309
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REFERENCES
1. "A Current Appraisal of Underground Coal Gasification," U.S. Bureau of
Mines, PB-209274 , prepared by Arthur D. Little, Inc. (17 April 1972).
2. G. H. Higgins, "A New Concept for In-Situ Coal Gasification," prepared
for U.S. Atomic Energy Commision by Lawrence Livermore Laboratory
(27 September 1972) .
"
3. D. R. Stephens, "Economic Estimates of Lawrence Livermore Laboratory
Concept of In-Situ Coal Gasification," prepared for U.S. Atomic Energy
Commission by Lawrence Livermore Laboratory (7 February 1973) .
4. "Rehabilitation Potential of Western Coal Lands," study by the National
Academy of Sciences and the National Academy of Engineering for the
Ford Foundation Energy Policy Project (1973).
310
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Appendix F
HYDROGEN AS AN ENERGY CARRIER
by
Edward M. Dickson
311
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CONTENTS
I INTRODUCTION 313
II STATE OF THE ART OF HYDROGEN TECHNOLOGY 315
A. Production 315
B. Storage and Distribution 316
C. Use 317
D. Safety 319
III ENVIRONMENTAL IMPACTS OF HYDROGEN USE 320
IV IMPLICATIONS FOR EPA 322
REFERENCES 324
312
-------
I INTRODUCTION
It is becoming increasingly apparent that during the years remaining
in this century hydrogen will emerge as an important additional component
of diversity in the energy economy.1'3 An energy economy completely
dependent on hydrogen used as a fuel, however, is unlikely ever to occur.
Hydrogen is not a basic energy resource because it is not found in
molecular form in nature. Consequently, energy must be supplied from some
other basic energy resource to generate hydrogen from water or other
hydrogen-containing chemical compounds. As seen in this light, hydrogen
obviously cannot "solve" the developing problem of a basic energy shortage.
Rather, hydrogen can become important only as an "energy carrier" used to
store and transmit energy in chemical form. The potential for use of
hydrogen is particularly large in the transportation area because the
traditional fuels (oil and gas) are becoming increasingly precious.
In addition to its use as a fuel, consumption of hydrogen will gain
in importance in chemical processing. At the present time the two major
uses of hydrogen are: The production of ammonia, a chemical that is very
important to the agriculture industry; and as a vital reactant in petro-
chemical reforming.3 Currently, this hydrogen is produced by the chemical
decomposition of methane (CH4) and by the so-called steam reforming of
water with fossil fuels providing the necessary heat input.1 Clearly,
as these sources of fuel become increasingly costly with the depletion
of resources, production of hydrogen by these means will become less and
less attractive. Hydrogen is also currently used to chemically reduce
some mineral uses.
*
References are listed on page 324 at the end of this appendix.
313 .
-------
' By far the largest potential use of hydrogen in the near future will
occur in the gasification of coal. Because coal contains approximately
one hydrogen atom for each carbon atom, the hydrogen deficit must be made
up to manufacture CH from coal. Many coal gasification plans call for
the combustion of some of the coal resource to provide heat for steam
reforming of water to gain the necessary extra hydrogen. Obviously, the
lifetime of any given coal resource could be extended if an independent
source of hydrogen were available.
Hydrogen is frequently mentioned as a prime possibility for storage
and delivery of energy collected by various solar energy technologies.
Indeed, many of these technologies may not become operational without a
parallel development of hydrogen storage, distribution, and utilization
technology.
314
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II STATE OF THE ART OF HYDROGEN TECHNOLOGY
A. Production
Hydrogen can be produced by electrolysis of either water or a hydro-
gen halide without consuming fossil fuel resources.5 Because water is an
abundant resource, it is the most favored feedstock. Electrolysis requires
a source of electricity, but other energy technologies such as geothermal,
solar, nuclear fission reactors, or possibly a nuclear fusion reactor can
supply this. Obviously, the net efficiency of hydrogen production is
dependent on the independent energy efficiencies of electric generation
and electrolysis. In the past, water electrolysis has been used only in
special situations, and energy efficiency has been a less important design
consideration than cost and reliability. Currently available electrolysis
units operate at efficiencies of about 65 percent, but areas of research
have been identified that offer the possibility of increasing this figure
to perhaps 90 percent.3 Such an improvement in electrolysis efficiency
is an essential prelude to combining hydrogen generation with low effi-
ciency electric generation such as solar or geothermal.
Research is underway to develop closed cycle thermochemical processes
that could side-step electrical generation and use directly the high
temperature heat that a gas-cooled nuclear reactor could provide.*>5
None of these cycles has been demonstrated to complete satisfaction and
probably a decade or more of R&D effort is needed before commercial
realization. This approach to hydrogen production is likely to have
important environmental consequences because of the very reactive chem-
icals and very high temperatures that are anticipated. Indeed, the con-
ditions of operation are so severe that many materials problems are
315
-------
foreseen for containment vessels.5 In addition, no cycle of chemical
reactions is ever truly closed. One need only recall how ostensibly
closed systems engaged in chlor-alkali production resulted in release of
large amounts of mercury into the environment,6 because a need always
exists to periodically cleanse the system of accumulated contaminants—
some of which arise from erosion of containment vessels.
B. Storage and Distribution
The vast quantities of hydrogen that may require storage could
hardly be managed in gaseous form, especially since large high pressure
vessels are extremely costly and the dangers of rupture are great. The
liquid state, at about 20°K, has been considered a more practical form
for storage.
Experience in the U.S. space program has demonstrated that trained
personnel in suitable environments can handle liquid hydrogen (used as
rocket fuel) in vast quantities.7 Consequently, cryogenic storage is
considered to be feasible in many of the potential applications of hydro-
gen. At the present time liquid hydrogen is routinely shipped by railroad
tank car and in large trucks over the public highways.8 Cryogenic tech-
nology is well-developed, and advances relevant to liquid hydrogen con-
tainment and handling are being made constantly.
Numerous metals and alloys form metal hydrides.9 Some of these
hydrides actually exhibit a packing density of hydrogen atoms that exceeds
that found in liquid hydrogen.9 Research has demonstrated that a suitably
packaged powder or metal sponge can serve as a convenient and rather safe
form of hydrogen storage. Research in the metal hydride field is con-
tinuing in an attempt to make large-scale storage of hydrogen via metal
hydrides fully practical.
316
-------
Pipelines have been used for many years in Germany for the long
distance movement of hydrogen.6,10 Chemical and petroleum process indus-
tries in the United States also have experience in hydrogen pipelines.10
In certain circumstances, the transmission of energy could be accomplished
more economically today by a hydrogen pipeline than by electric trans-
mission line.2^11 Moreover, operations of natural gas pipelines have
shown that by varying the pipeline pressure the pipeline system itself
can serve as a reservoir for vast quantities of gas.
C. Use
Experiments, some sponsored by EPA, have shown that an internal
combustion engine can be easily modified to run on hydrogen. 12,13 Because
no hydrocarbons are in the fuel, there are no carbon monoxide (CO) or
hydrocarbon (HC) emissions (aside from a trivial amount arising from the
lubricating oils). Moreover, nitrogen oxide (NO ) emissions are lower
X
when the engine is run on hydrogen than on gasoline.12 This strongly
suggests that automobiles designed to operate on hydrogen fuel would
greatly alleviate urban air pollution. Before a hydrogen-fueled auto-
mobile could become a practical reality, however, numerous difficulties
associated with fuel distribution and on-board storage require solution.
Conceptual design studies have determined that jet aircraft could
be run easily on hydrogen.i*>T-B Indeed, because of its higher energy
density (on a weight basis), hydrogen offers the potential for reoptimiz-
ing the design of aircraft. It is now clear that the gross take-off
weight could be reduced without impairing the payload or range.15 Again,
however, logistical difficulties suggest that a transition to hydrogen-
fueled aircraft may be slow to occur.
Fuel cell technology is the inverse of electrolysis technology in
many respects.18 A fuel cell combines hydrogen and oxygen to generate
317
-------
an electric current with water and heat being the only effluents. Most
fuel cells run on hydrogen and oxygen; those that consume other fuels
*
first chemically "reform" the input fuel into hydrogen and waste by-
products before actual consumption in the fuel cell.!? Most applications
of fuel cells have been in the space program, federal support of fuel
cell R&D has waned in recent years. Most contemporary fuel cell effort
is done by industry and is proprietary. Pratt and Whitney Aircraft Cor-
poration, considered the leader in the field, is developing fuel cell
technology for electric utilities, and Public Service Gas and Electric
of New Jersey has placed orders for the technology. Much of the basic
electrochemistry research is applicable to both electrolysis and fuel
cells.
Electric utilities currently envision three major applications of
hydrogen in their operations:
. Electric generation by fuel cells in small installations
that are quiet, nearly pollution free, and lack major
requirements for cooling water, and can be located near
the final demand in urban areas.is
. Underground pipeline transmission of energy from remote
nuclear power stations to urban areas along heavily
developed corridors that make deployment of additional
overhead electric transmission difficult because of
land use and aesthetic constraints.n>i8
. The use of hydrogen as a chemical means to store large
amounts of energy to buffer mismatches in energy supply
and demand.18 This application stems from a recognition
that pumped hydrostorage is not well-suited for many
geographical locations.i9
Various combinations of these three applications are obviously conceptually
attractive. A few energy utilities are now taking these possibilities
very seriously.
318
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D. Safety
In any discussion of hydrogen use, the question of safety arises.
The public has seemingly concluded that hydrogen is unsafe—apparently
solely on the basis of the publicity that is constantly renewed about
the destruction of the Hindenburg in 1937 with the loss of 36 lives.20
Many people who have considered the safety of hydrogen in comparison to
existing fuels believe that the fear of hydrogen is overdrawn.3jii>2o
Hydrogen is undeniably dangerous, but so are gasoline and methane, yet
the public treats these two fuels with nonchalance in spite of regular
and often spectacular accidents.21
A special hazard derives from the embrittlement of some metals
immediately upon exposure to a high-purity hydrogen environment.22 This
phenomenon is most pronounced around room temperature and high strength
steels are especially affected.22 As a result of the greatly decreased
flexibility of the metal, the design of devices intended to convey, store,
or use hydrogen must reflect knowledge of embrittlement to avoid unexpected
component failure and the consequent safety hazards this creates. Some
knowledgeable people feel, however, that with proper attention to design,
embrittlement will affect the economics more severely than the safety of
hydrogen usage.
The physical properties of hydrogen make it less hazardous than
conventional fuels in some situations but more hazardous in others. A
blanket dismissal of hydrogen use on the basis of unsophisticated con-
sideration of its safety is unwarranted.
319
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Ill ENVIRONMENTAL IMPACTS OF HYDROGEN USE
Hydrogen consumed as a fuel will certainly result in less noxious
emissions of the common air pollutants at the point of combustion.
Against this, however, the knowledge must be weighed that at some other
location, where the hydrogen is generated, environmental impacts may
exist such as thermal pollution from a nuclear reactor generating elec-
tricity for electrolysis, radioactive wastes from the nuclear fuel cycle,
and similar effects associated with all the candidate prime mover energy
technologies. Moreover, because the generation of hydrogen adds another
step in the chain of energy distribution from basic resource to final
demand, it will inevitably reduce the net energy efficiency of the system
and thus release more energy into the environment as waste heat. Improve-
ments in hydrogen generation technology, however, may greatly lessen this
effect.
The extension of some of these current hydrogen technologies to a
large scale may create environmental problems of its own. For example,
present water electrolysis cells use an asbestos membrane to separate
the hydrogen and oxygen coproducts.33 Since the oxygen may often be
merely released to the atmosphere as a nominally harmless effluent rather
than be retained for use, small asbestos particles can be released to the
air. It is now fairly well-established that small asbestos particles
are a dangerous carcinogen, and EPA has formulated air quality standards
specifically covering asbestos.S4,SB jn the small electrolysis instal-
lations currently in operation, the oxygen is filtered to remove these
asbestos particles. While such treatment is probably quite adequate to
maintain an acceptable level of asbestos particles in small plants,
320
-------
expansion of the process to the very large scale envisioned would most
likely result in an unacceptable airborne concentration of these particles.
Another air quality implication arises from the possible use of
powdered metal hydrides for hydrogen storage. One of the most likely
candidates is an alloy of magnesium and nickel.9 Evidence is mounting
that uptake of small .amounts of many nickel compounds can be responsible
for dysfunction in humans and many other biological systems.26
Some resource availability limitations arise in the use of hydrogen.
For example, to provide the storage sufficient to power an automobile
conforming to typical American standards would require about 200 kg of a
magnesium-based metal hydride.s? To supply 100 million automobiles (about
10
the current number) would therefore require about 2.0 x 10 kg of mag-
nesium and this is about 200 times the 1971 U.S. magnesium metal produc-
o
tion of about 10 kg.28 Currently available electrolysis technology uses
nickel catalysts. It is far from clear whether electrolysis technology
could continue to be dependent on nickel since this metal is in short
supply (almost all the U.S. consumption is imported) and is vital to the
steel industry for productuction of quality steels.ss
321
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IV IMPLICATIONS FOR EPA
At first glance, it may seem that the subject of hydrogen could be
neglected by EPA for a decade or so. Such neglect would almost certainly
prove unwise because the emergence of hydrogen in the U.S. energy economy
is made all the more likely by the other transitions in energy technology
and usage patterns that are believed to be necessary. In many respects,
hydrogen is the common denominator of many of the emerging new energy
technologies. It is the most obvious chemical means of energy storage
and is the chemical element most needed to facilitate synthesis or pro-
cessing of other fuel. Thus, although hydrogen may never come into the
hands of the general public, it will, nevertheless, play a key role behind
the scenes of the energy economy.
Stanford Research Institute is currently engaged in a Technology
Assessment of a Hydrogen Energy Economy under National Science Foundation
sponsorship. The exploration of the societal and environmental impacts
now being performed as part of that study can be expected to provide use-
ful input into EPA planning activities. After information from the tech-
nology assessment is received, EPA could profitably establish a modest
program to follow the development of hydrogen technologies and seek to
influence its development in a manner that has environmental benefits.
The program should be analogous to that outlined in Appendix A of this
report.
In the interim, EPA could beneficially sponsor research in the
following areas.
. Further quantification of the emissions characteristics
of engines (both internal and external combustion)
operated on hydrogen.
322
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. Environmental side effects of fuel cell technology.
• Environmental pollutants associated with water
electrolysis technology.
. Effluents and emissions that might be associated with
thermochemical decomposition of water by the use of
high temperature heat from nuclear reactors.
This research would ensure that the potential environmental benefits of
hydrogen used as a fuel are not overlooked.
323
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REFERENCES
I. Synthetic Fuels Panel, Hydrogen and Other Synthetic Fuela (Federal
Council on Science and Technology RfeD Ooale, U.S. Government
Printing Office, Washington, D.C., September 1972).
2. D, P. Gregory, et al; A Hydrogen Energy System (American Gaa
Asaoclatlon, Alexandria, Virginia, August 1072).
3. T. H. Maugh, "Hydrogen: Synthetic Fuel of the Future," Science,
pp. 840-852 (November 24, 1072).
4. "Hydrogen Sought via Thermochemlcal Method*," Chemical and Engineer-
ing Newa. pp. 32-33 (September 3, 1973).
8. C. Marcetti, "Hydrogen: Maater Key to the Energy Market/' Euro-
Spectra, pp. 117-120 (December 1071).
6. L. Dunlop, "Mercury: Anatomy of a Pollution Problem," Chemical it
Engineering Newa, pp. 22-34 (July S, 1071).
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BIBLIOGRAPHIC DATA
SHEET
1. Report No.
EPA-600/2-74-002
3. Recipient's Accession No.
4. Title and Subtitle
Control of Environmental Impacts from Advanced Energy Sources
5. Report Date March 1974
6.
7. Author(s)
Evan E. Hughes. Edward M. Dickson. Richard A. Schmidt
8. Performing Organization Kept.
°' Project 2714
9. Performing Organization Name and Address
Stanford Research Institute, Menlo Park, California 94025
10. Project/Task/Work Unit No.
11. Contract /Grant No.
68-01-0483
12. Sponsoring Organization Name and Address
Office of Research and Development, U.S. Environmental
Protection Agency, Washington, B.C., 20460
13. Type of Report & Period
Covered
Final
14.
15. Supplementary Notes
16. Abstracts T1;ie technology and environmental effects associated with production of energy
from new or advanced sources are reviewed. These include solar, geothermal, oil shale,
solid wastes, underground coal gasification, and hydrogen energy sources. Projections
to the year 2000 of levels of energy production from the first four of these sources are
presented. Environmental impacts on air and water quality, and land use are derived pex
unit of energy. Levels of pollutant emissions and other environmental effects of the
development of these advanced energysources are projected. Impacts likely to require
control measures are identified. Subjects for research and development directed toward
control of environmental impacts are recommended. These recommendations are incorporate^
into a research and development plan. Approximate priority assignments derived from
consideration of the timing of development and the importance and degree of definition
of the identified environmental effects are given.
17. Key Words and Document Analysis. 17o. Descriptors
environmental impacts
energy technology
air pollutants
solar energy
geothermal energy
oil shale
solid wastes
in-situ coal gasification
hydrogen
17b. Identifiers/Open-Ended Terms
17c. COSATI Field/Group
18. Availability Statement
Unlimited
19.. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (Thi
is
UNCLASSIFIED
21. No. of Pages
326
22. Price
FORM NTIS-39 (REV. S-72)
USCOMM-OC M8S2-P72
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