EPA/6G0/A-94/0S9
Chapter 17
Industrial Sources
L. Lee Beck,1 Stephen D. J'iccot,2 and David A. Kirchgessner1
'United Slates Emironmental Prelection Agency, Air end Energy Engineering Research
Laboratory, Research Triangle Park, North Carolina 27711
' Southern Research institute. Research Triangle Perl'-, North Carcluui 27709
1. Introduction
This chapter identifies and describes major industrial sources of methane
(CH4) emissions. For each source type examined, CH4 release points are
identified and a detailed discussion of the factors affecting emissions is provided.
A summary and discussion of available global and country-specific CH4 emissions
estimates are also presented.
The major emission sources examined include coal mining operations and
natural gas production and distribution systems. However, a variety of minor
industrial sources are also examined because their collective contributions to the
global CH4 budget may be significant. Although the treatment of these minor
sources may not be comprehensive, the limited available data are presented for
several different sources. Among the minor industrial sources examined here are:
coke production facilities, chemical manufacturing operations, peat mining
operations, light water nuclear reactors, fossil fuel combustion equipment (boilers
and automobiles), geothennal electricity generation facilities, salt mining
operations, residential refuse burning, and shale oil mining operations.
2. Coal mining operations
Historically, coal use in the United States suffered a nearly catastrophic
decline after World War II. It was not until the mid 1970s that bituminous coal
production once again equalled the levels seen in the mid 1940s. Production in
1970 was about 545 million tonnes and had grown more or less consistently to 830
million tonnes by 1987. This growth \vfll undoubtedly be mirrored in countries
that have significant coal reserves and are undergoing industrialization. The
NATO ASI Scr.ci. Vol. I ! 3
Atmospheric Mc'-hsnc: Screes. Sinks, and Rcic
in Glrhal Cftanj«
by M A K Khali!
C Sj-ri(iger-Vci|j(» B.-riir: Hcj<1c!tx:T£ IW3
-------
400
trend is perhaps epitomized in China where coal production rose from 620 to
1050 million tonnes between 1980 and 1989.
The global environmental effects of coal production and use will increase
as coal production increases. The underground mining of coal is accompanied
by the emission of CII4 and the production of large quantities of waste water and
coal wastes. The use of iongwall milling often results in subsidence at the
surface, which can produce significant property damage and can be costly to
prevent Surface mining can produce significant scarring of the land, but, if
proper land reclamation techniques are applied, surface mine sites can be
restored to near original conditions. Because of the high cost of these
techniques, this restoration may not be done in all countries. Combustion of coal
results in the release of large quantities of "conventional" pollutants including
sulfur dioxide, nitrogen oxides, and particulate matter. It is also one of the
largest sources of anthropogenic carbon dioxide emissions. Although several of
these pollutants can be controlled with today's pollution control technologies, the
large capital investments required may not always be available in developing
countries.
21 Sources of methane emissions in the coal mining industry. Three
categories of mines within the coal mining industry are known to emit CH4 to the
atmosphere: underground mines, surface mines, and abandoned or inactive
mines. Much more is known about the emissions from underground mines than
from any other mining category. Based on currently available data, underground
mines are generally believed to be the most significant source of CH4 within the
coal mining industry.
In general, CH4 can be released into a coal mine from all of the seams
disturbed during the mining process. Seams other than the one being mined may
be disturbed by the mechanical or blasting operations which occur at
underground and surface coal mines. In an underground Iongwall mine, some
studies suggest that this zone of disturbance may extend up to 200 meters (m)
into the roof rock and 100 m below the worked seam (Creedy, 1983). For safety
reasons, underground mines use various methods to remove CH4 from the mine;
however, CH4 is not a safety concern in surface mines. In some countries, a
portion of the CI14 removed from underground mine workings is burned for
energy, but in most cases the CH,( is released to the atmosphere.
-------
401
Methane from underground mines can be released from three sources:
ventilation shafts; gas drainage systems; and coal crushing and handling
operations (Boyer et a!., 1990; Piccot et at., 1990). Figure 1 illustrates these
sources. Ventilation air, although generally containing 1 percent or less CH,., is
known to contribute the majority of underground mine emissions because of the
enormous volume of air used to ventilate mines. Gas drainage wells are drilled
into the area immediately above the seam being mined. They provide conduits
for venting CH4, which accumulates in the rubble-filled areas formed when the
mine roof subsides following longwall mining. Other types of drainage systems
are used that extract CH4 from coal seams well in advance of mining operations.
The purpose of all gas drainage systems is to remove CH4 that would otherwise
have to be removed by larger and more costly shaft ventilation systems.
Currently, few published data exist for the release of CH4 from gas drainage
systems. However, unpublished data obtained from industry representatives
indicate that drainage well CH4 emissions may account for a significant fraction
of the total emissions associated with longwall mines (Boyer et al., 1990;
Kirchgessncr ct al., 1993a). In some parts of the world, such as western and
eastern Europe, CH4 from gas drainage systems is utilized and is not released to
the atmosphere.
Very few measurements have been taken at surface mines. Data from six
surface mines in the United States suggest that the primary sources of emissions
are exposed coal surfaces, in particular the areas fractured by coal blasting
(Piccot et al., 1991; Kirchgessncr et al., 1993b). In general, the strata overlying
the coal do not appear to be a significant source of emissions, but, as in
underground mines, emissions may be contributed by underlying seams or faults.
Emissions from abandoned mines may come from unsealed mine shafts or
from vents installed to prevent the buildup of CH4 in the mir.es. There has been
little research to characterize this potential source. However, in a continuing
study by the U.S. Environmental Protection Agency (USEPA), CH4 emissions
have been measured as they escape from vents installed at abandoned under-
ground mines. Although only a small number of mines have been examined,
preliminary results indicate that emissions vary significantly and that the rate of
emissions from an abandoned mine may be strongly influenced by barometric
pressure changes. For several mines, emission rates were negligible while at one
mine emissions were almost half of those produced when the mine was active.
-------
402
UNDERGROUND MIKE
CM«
,ch,
CH.
CH,
-Shsft/Venfllnion System
Cca',
^ Car Durrp
- BggagS
Coal Sean
SURFACE MIME
Spoi Levelirg
Ovwfcurdon
ftervova'.
_D*gI/ie DnTmg and E.^hg
r^T-r-^ Overburden
1
t gc-J&qy*?!
'<3K^A
Coal Loading
figure 1. Sources of methane emissions at underground and surface coal mines.
-------
403
The rate of release of CH4 from mined coal varies depending on coal type,
local geology, geologic history, and other factors. Methane can be released
quickly, in a matter of hours., or slowly, over a period of several months. Since
mined coal is typically removed within a day, there is a potential for emissions to
occur in the post-mining operations. Post-mining operations can include coal
breaking, crushing, drying, storage, and transportation. Although measurement
data are very limited, Boyer et al. (1990) estimate that on average 25 percent of
the CH a contained in the mined coal could be emitted after the coal has left the
underground mine. Researchers at British Coal suggest that coal handling and
transport operations in Great Britain may produce about 2 m3/tonne of coal when
a coal with a CH4 content of 5 m3/tonnc is mined (i.e., 40 percent of the CH4
contained in the mined coal is released after it leaves the mine; Watt Committee
on Energy, 1991; Creedy, 1993).
3. Factors affecting methane emissions from coal mines.
Numerous studies have examined the physical factors which control the
production ana release of Ctl4 by coal. These studies have been conducted to
evaluate the potential of coalbed CH4 resources, enhance the safety of
underground mines, or estimate global CH4 emissions. Generally, the studies
address one of two topics: controlling the CH4 content of coals, or controlling
the concentration of CH4 in the mine atmosphere and mine ventilation air. Most
of these studies have focused on underground mining operations.
Studies of coalbed CH4 contents have identified pressure, coal rank, and
moisture content as important determinants of coalbed CH4 content. Kim (1977)
related gas content to coal temperature and pressure, and in turn to coal depth.
After including coal analysis data to represent rank, Kim produced a diagram
relating gas content to coal depth and rank. Although the validity of the rank
relationship has been questioned, it generally appears to have been accepted by
recent authors (Schwarzer and Bvrer, 1983; Lambert et al., 1980; Murray, 1980;
Aineri et al., 1981). Independently of Kim's work, Basic and Vukic (1989)
established the relationship of CH4 content with depth in brown coals and lignite.
Several studies have recognized the decrease in CH4 adsorption on coal as
moisture content increases in the lowest moisture regimes (Anderson and Hofer,
1965; Jolly et al., 1968; Joubert et al., 1974). Moisture content appears to reach
a critical value above which further increases produce no significant change in
-------
404
CHr, content- Coals studied by Joubert et al. (1974) showed critical values
ranging from 1 to 3 percent.
In a recent study by Kirchgessuer et al. (1993a), a set procedure was
developed which integrates the influences of several factors known to affect CH4
content in coalbeds. Two equations were produced for estimating coalbed CH4
contents in cubic meters per tonne at the basin or seam level: one for coals with
heating values less than 34,860 joules/gram (J/g) (Eqn. (1) below), and one for
coals with heating values equal to or greater than 34,860 J/g (Eqn. (2) below).
The equations for estimating coal bed CH4 content (IS) were developed by
performing multivariate regression analyses on a database of 137 U.S. coal
samples. The R2 for Eqn. (1) is 0.56, and the R2 for Eqn. (2) is 0.71. Coal
properties in the equations have sound geological bases for inclusion and the
parameters included follow patterns predicted in the literature. Coal depth (D)
in meters appears in both equations. Moisture content (M) in percent and
parameters closely tied to coal rank such as heating value (HV) in joules/gram,
and the ratio of carbon content to volatile matter (FR) are also included. As a
final step iii the procedure, the IS values obtained from the equations are
multiplied by a factor to yield an estimate of total CH4 content (i.e., anthracite
1.11; low volatile bituminous 1.10; medium volatile bituminous 1.20; high volatile
B and C bituminous 1.12).
Although more difficult to quantify, the amount of CH4 contained in a
given quantity of coal may be influenced by the burial and erosional history of
a coal seam (Watt Committee on Energy, 1991). In some geological
configurations, the CH4 content of coal increases with coal rank but decreases on
approach to the Permo-carboniferous erosion surface.
Early investigations in the United States which attempt to identify
correlates of CH4 emissions from coal mine ventilation air include those by Irani
et al. (1972) and Kissel et al. (1973). Irani et al. developed a linear relationship
between CH4 emissions and coal seam depth for mines located in five seams.
IS = 0.0159D
0)
IS = 0.0136D + 0.0015 HV + 2.6809FR - 56.490
(2)
-------
405
Kissel et al. demonstrated a linear relationship between CH. emissions and
coalbed CH4 content for six mines. Although both studies suffer from a paucity
of mines and seams in their analyses, Kissel et al. made the important observation
that mine emissions greatly exceed the amount of CH4 associated with the mined
coal seam alone. Emissions are produced not only by the mined coal, but also
by tiie coal left behind, overlying and underlying seams, arid nearby gas deposits.
For the six mines studied, emissions per tonne mined exceeded coalbed Cfi4 per
tonne mined by factors of six to nine.
In studies conducted by Boyer et al. (1990) and Kirchgessner, et al.
(1993a), regression equations were developed relating coal production rate and
coalbed CK4 content to the emissions from underground mines. These equations
were developed to estimate global emissions from underground mines, using
similar data and techniques. To develop these equations, multivariate regression
analyses were performed using mine-specific data for the United States. In the
analysis performed by Kirchgessner et al., a database of 269 mine-specific
emission measurements was used to produce an equation with an R2 value of
0.59. This means that about 60 percent of the variation in CH4 emissions from
the mines in the database can be explained by the independent variables included
in the equation. In the analyses performed by Boyer ct a!., a database of about
60 mine-specific observations was used to produce an equation with an R2 value
of 0.35. Although not fully understood, one likely reason for the difference in R2
values between the two studies is that the equation developed by Kirchgessner
et al. was estimated using a database which contained over 4 times more
individual mine measurements than the Boyer equation.
3.1 Summary of global emissions estimates. Over the past 30 years there
have been several attempts to estimate the global emissions of CIL from coal
mining operations. Although we do not address them all, the estimates presented
represent the approximate range of published emission rates. This section
summarizes these estimates, describes and compares the basic assumptions used
in their development, and identifies key relationships that exist among their..
Table 1 presents a summary of global CH4 emissions estimates developed
by various researchers for coal raining operations. Estimates range from 7.9 to
64 teragrams fig) per year. The lower estimate of 7.9 Tg/yr is unrealistic.
Although the specific assumptions used in developing this estimate arc not clear,
it appears to be based on the implicit assumption that emissions from coal mines
-------
Table 1. Summary of estimates of global methane emissions from coal mining operations.
Source
Year for
Estimate
CH^ Emissions
O'g/yr)
Comments
Koyama (1963, 1964)
1960
20
Includes hard coal only (lignite not included).
Hitchcock and Wcchsler
(1972)
1967
7.9 to 27.7
Includes the emissions from hard coals (6.3 to 22
Tg/year) and lignite (1.6 to 5.7 Tg/year). Based on Bates
and Witherspoon, and Koyama.
Ehhalt and Schmidt
(1978)
1967
7.9 to 27.7
Estimates taken from Hitchcock and Wcchsler.
Seiler (1984)
1975
30
Results based on an extrapolation of Koyama's results
using updated coal production. Analysis by Boycr el al.,
suggests this study includes only hard coal.
Tolkachev and Zimakov
(1983)"
1979
20 lo 25
Basis unknown.
Criilzcn (1987)
not specified
(assume middle
1980s)
34
Docs not include emissions from the mining of lignite
coals. Based on work by Crutzen, and Ehhalt and
Schmidt.
Cicerone and Orcmland
(1988)
not specified
(assume middle
1980s)
25 lo 45
(average 35)
Results based on analyses conducted by Koyama, Ehhall,
and Seiler. Analysis by Boyer et al., suggest this study
includes only hard coal.
Boycr et al. (1990)
1987
33 to 64
(average 47.4)
Includes all coal types and emissions from mining and
post-mining operations.
Fung et al. (1991)
not specified
(assume middle
1980s)
35
Estimate developed by comparing model concentrations
derived from published budgets with atmospheric
methane measurements.
Kirchgessner et al.
(1993a)
1989
45.6
Includes all coal types & emissions from mining & post-
mining.
a. Results arc as cilcd in Okken and Kram (1989).
-------
407
are equal to the amount of CH4 trapped in the coal removed from the mine
(Hitchcock and Wechsler, 1972; Bates and Witherspoon, 1952). Although this
trapped CH4 is released when coal is fractured and removed from the mine, this
assumption fails to account for other CH4 release mechanisms that occur. These
release mechanisms, which were described earlier, can significantly contribute to
the total emissions from mining operations. A second iow estimate of 23.1
Tg/year reported by Darmstadter et al. (1984) for 1980 appears to be based on
an unrealistically low emission factor.
A review of the global estimates presented in Table 1 reveals that many are
closely related; that is, the basis of several estimates can be traced back to key
assumptions made by some of the earliest researchers. Figure 2 illustrates the
relationships which exist between various global estimates of CH4 emissions from
coal mines. As the figure shows, many published estimates have been based
primarily on methodologies developed by Koyama (1963, 1964) and Bates and
Witherspoon (1952). In general, estimates developed by Seiler (1984), Hitchcock
and Wechsler (1972), Ehhalt (1974), Ehhalt and Schmidt (1978), Crutzen (1987),
and Cicerone and Oremland (1988) were developed based in large part on CK4
emission factors developed by Bates and Witherspoon (1952) and Koyama (1963,
1964). Koyama's emission factors have been used by Hitchcock and Wechsler,
and Ehhalt and Schmidt to estimate an upper end of the range of coal mine
emissions.
Estimates by Dover et al. (1990) and Kirchgessner et al. (1993a) are on a
country-specific basis and were not developed based on other researchers'
emission factors. Instead, new emissions relationships were developed based on
measurement data contained in databases on coal properties and mine emissions
rates.
The coal mine estimate of Fung et al. (1991) presented in Table 1 was
developed differently from the other estimates discussed here. Fung et al. used
a combination of global CI 14 mass balances and atmospheric modeling techniques
to infer a budget for all CH4 sources including coal mines. In general, several
CH< budget scenarios were constructed and tested to determine which was best
able to reproduce the meridional gradient and seasonal variations of CII4
concentrations observed in the atmosphere. One budget scenario for all CH4
sources, including coal mines, was selected by Fung et ai. because it was judged
to reproduce the atmospheric record best. The coal mine estimate associated
-------
408
I DATA Qt« COAL PROPERTIES, ETC.
KOYAMA
RATKS AMD
WITHERSPOON
SEiLER
HITCHCOCK
EHHALT.
EHHALT AND
SCHMIDT
CRUTZEN
CICERONE AND
OREMLAND
BOYER et al.
IKIRCHGESSKER. ee al
-.b
Figure 2. Relationships among various global estimates of
methane emissions from coal mines.
with this budget scenario is shown in Table 1. There are methodological and
other differences among the estimates that contribute to the variations observed
in the results in Table 1. First, the estimates are developed for different years:
estimates from 1960 through 1989 are presented- Since coal production increased
significantly during this period, an increase in emissions is expected and a direct
comparison of these estimates cannot be made. Second, Tabic 1 shows that
several estimates fail to account for all the coal produced globally. Estimates
developed by Koyama (1963,1954), Crutzen (1987), and Cicerone and Oremland
(1988) are known to account for the emissions associated with hard coal
production only and do not include the emissions associated with brown or lignite
-------
409
coals. Although these types of coals typically do not contain much CH4, their
contribution to global emissions cannot be neglected. Estimates developed by
Hitchcock and Wechsler (1972), Hhhalt and Schmidt (1978), Boyer et al. (1990),
and Kircligessner et al. (1993a) include emissions associated with all coal types.
Another difference among these estimates is that many do not appear to include
the global emissions associated with post-mining operations (i.e., crushing,
grinding, handling, and transport). The estimates developed by Boyer et al. and
Kircfcgessner et al. are the only ones that specifically include an estimate of the
emissions from post-mining operations. None of the estimates includes the
emissions associated with abandoned mines.
A simple evaluation of the global estimates presented in Table 1 could lead
to the potentially erroneous conclusion that the two-fold increase in CH4
emissions since 1960 can be explained primarily by the two-fold increase in global
coal production thai occurred during the same period. However, the actual
change in global coal mine emissions cannot be determined from the estimates
in Table 1 because significant differences exist in the emissions rates used to
develop those estimates, and many estimates do not include the emissions from
lignite coals. Table 2 compares CH, emission rates associated with a variety of
studies. These data indicate that the emission rates used to estimate emissions
in the most recent studies tend to be lower than those used in early studies.
Table 2. Summary of methane emission rates associated with various global emissions
estimates.
Source
Year
Emission rate (m3
methane/tonne coal
mined)
Koyama (1963, 1964)
1960
19.5
Hitchcock and Wechsler
(1972)
1967
5.0 to 17.5
Seiler (1984)
1975
19.5
Crutzcn (1987
not specified; assume
middle 1980s
18 to 193
Bqyer et al. (19S0)
1987
14.2
Kirchgessncr et al. (1993a)
1989
13.8
" As cited in iiovcr et al. (1V9U)
-------
410
In two recent studies, emissions from con I mines were estimated on a
country-specific, basis (Bover et al., 1990; Kirchgessner et al., 1993a). Both
studies represent relatively comprehensive attempts to characterize key countiy-
spccific factors which may significantly influence emissions by (i) estimating
country-level or basin-level coalbed CIL contents, (2) estimating the emissions
associated with different mining techniques (i.e., surface mining and underground
mining), and (3) subtracting CI14 recovered and used at coal mines from the
global estimate. Summaries of the country-specific estimates from both studies
are presented in 'lable 3. A comparison of the two studies shows that total
emissions are relatively similar but significant differences exist in the emission
estimates for key countries and regions. For China, the United States, South
Africa, and India, Boycr et al. produce estimates that are about two times higher
than Kirchgessner et al. Conversely, estimates for the "Rest of the World" and
"Surface Mining" are higher in Kirchgessner et al. by a factor of about two. The
reasons for these differences have not been determined.
Other researchers have also estimated emissions for individual countries.
Although these estimates are not global in nature, they are reported here because
they generally represent the results of a focused and detailed assessment of
country-specific coal and mine emission characteristics. As a result, they can be
used to independently examine the representativeness of the country-specific
estimates presented in Table 3. The results are summarized in Table 4. The
reader should be cautioned that Table 4 is not intended to be a comprehensive
summary of individual country estimates. Although the tabic includes mainly
those results obtained from participants in the NATO Advanced Research
Workshop on the Global Methane Cycle (this volume and in Khalil and Shearer,
1993), other independent assessments are also included.
The country-specific estimates in Table 4 generally agree with the estimates
in 'lable 3. The estimates of Kirchgessner et al. and Hoyer et al. generally agree
with estimates developed for Poland and the former Soviet Union by Pilcher et
al. (1991) and Andronova and Karol (1993). However, estimates for Australia
and the United Kingdom developed by Kirchgessner et al. and Boycr et al. are
about two times higher than the estimates presented in Table 4. Estimates for
the United Kingdom developed by Kirchgessner et al. are based on coalbed CH4
content measurements for seams mined in the United Kingdom, and on mine
emissions relationships developed from 260 U.S. coal mine emissions
-------
411
Tabic 3. Country-specific emission estimates developed by Buyer et al (1990) and
Kirchgessner et ai. (1993a).
Boyer et al. (1990) Kirchgessner et al. (1993a)
Country 1987 Coal 1937 CH4 1989 Coal 19S9 CH,
Production Emissions Production Emissions
(106 tonnes) (teragrams) (10,: tonnes) (teragrams)
Underground Mining
China
891
16.0
1,053
93
Former Soviet
Union
429
7.7
418
7.9
United States
337
6.1
356
3.5
Poland
193
33
181
3.6
South Africa
111
2.0
115
0.7
India
85
1.5
95
0.7
United Kingdom
86
1.5
71
1.3
West Germany
79
1.4
73
1.1
Australia
47
0.9
59
1.1
Czechoslovakia
26
0.4
-
-
Rest of the World
Not Reported
2.9
567
6.S
Subtotal
-
43.7a
2,983
36.0
Surface Mining
Subtotal
Not Reported
3.7*
2,154
6.9
Post-Mining
Emissions
-
Included
above
-
2-7
Total Mining
4,630°
47.4
5,142
45.6
3 A range of emissions from 30.3 to 59.1 million tonnes was established in this study for
underground mines.
b A range of emissions from 2.6 to 5.0 million tonnes was established in this study for
surface mines.
c This value cannot be obtained by summing the production rates listed above because
values for Surface Mining and the Rest of the World were not reported by Boyer et a!.;
however, total production was reported.
-------
412
measurements. The C'reedy estimate is based on relationships developed from
United Kingdom measurements data supplied by British Coal for both ccalbed
CH4 content and mine emissions rates. The discrepancy between the two
estimates lies in the assumptions that relate coalbed CH4 content by depth to
mine production to calculate total emissions from underground mines.
Table 4. Summary of other country-specific mine emission estimates.
Co untiy
Emissions
Cg/y1")
Source
Comments
Australia
0.45
DJ. Williams,
CSIRO, Minerals
Research
Laboratories,
Australia
Preliminary 1989 estimate for
underground mines only.
Former
Soviet
Union
3.5 to 11.2
(average
7.4)
Andronova and Karol
(1993)
Estimate is for 1938. The
maximum potential emissions
are 17.3 Tg.
Poland
3.3
Pilcher et al. (1991)
Estimate is for 198S.
Turkey-
0.22
Personal communi-
cation with H. Kose
and T. Onargan3
Estimate is for 1990.
United
Kingdom
0.75 ± 0.1
Creedy (1993)
This measurements-based
estimate includes emissions from
all coal types and coal handing
and transport losses
(1990/1991).
United
States
3.0
Piccot and Saeger
(1990)
Estimate includes emissions for
under- ground coal mines only
(estimate for 1985)
11 Both are from the University of The 9 Eylul, Izmir, Turkey.
4. Natural gas production and distribution
Natural gas has long been recognized as the environmentally preferred
fossil fuel. It produces virtually no sulfur dioxide or particulate emissions, and
far fewer nitrogen oxide and carbon monoxide emissions than other fossil fiiels.
For this reason, and because it is widely available, relatively easily recovered, and
readily usable, the global consumption of natural gas has approximately doubled
-------
413
since 19"!). Among the industrialized nations, the United States is an exception
to this pattern in that it consumes about 10 percent less natural gas today than
in 1970. This has variously been attributed to an excessively restrictive regulatory
structure (DOE, 1991) and to a misconception of the future natural gas price
structure stemming from an underestimate of available U.S. reserves in the 1970s
(Hay et a!., 1988). The U.S. National Energy Strategy produced in 1991 has
recommended removing or revising excessive regulation inhibiting natural gas
transactions (DOE, 1991), and the Gas Research Institute has stated that
domestic natural gas reserves are sufficient for the next several decades (Hay ct
al., 1988). Both of these factors should accelerate the slow rate of increase in
U.S. domestic natural gas utilization which is already occurring.
Natural gas emits about half as much carbon dioxide per unit of energy
output as coal, and about two-thirds as much as oil. Recognizing this, the
Intergovernmental Panel on Climate Change has formalized the recommendation
to switch to natural gas as fuel where possible to achieve short term mitigation
of the global climate change problem (Environment Agency of Japan, 1990). It
must first be demonstrated, however, that CH4 leakage from the increased
production and utilization of natural gas would not nullify the benefit of
decreased carbon dioxide production.
4.1 Sources of methane emissions in the natural gas industry. The natural gas
industry can be broadly divided into the production, transmission, and
distribution sectors diagramed in Figure 3. Each of these sectors can contribute
steady or fugitive CtL emissions and intermittent emissions. Fugitive emissions
result from normal operations and result primarily from leaking components such
as valves, flanges, and seals. Intermittent emissions result from routine
maintenance procedures, system upsets, and occasional large scale accidents.
Methane emissions from the production sector usually include those from
well drilling, gas extraction, and field separation facilities. In this discussion gas
processing plants are also included. Emissions from well drilling result primarily
from occasional venting and flaring employed to prevent blowouts. During
extraction, CH4 may be emitted by natural-gas-fired engines used for power
generation, various wellhead components collectively referred to as the
"Christmas tree," and occasional venting and flaring when gas volumes do not
warrant recovery. Field separation may involve gas heating, gas or liquid
separation, and gas dehydration. Principal sources of emissions are fugitive leaks,
-------
414
PRODUCING
WELLS
G«!hsr!r>g Un«s
TRANSMISSION'
LINES
Ci'.y Gsli
Hduslrisf Ccncvmsr
CISTTHB JTTON
SYSTEM
Figure 3. Natural gas pipeline system.
-------
415
venting and flaring, natural-gns-powered pneumatic devices, and combustion
losses from heaters and dehvdrators. Gas processing plants arc usually located
close to the production area and may be regarded as part of the production
process. Gas plants are used to separate natural gas liquids from Hie gas stream
and to fractionate the liquids into their components. The processes which are
currently most commonly used in these plants are cryogenic expansion,
refrigeration, and refrigerated absorption. Primary emissions sources from gas
processing plants are fugitive losses, compressor exhaust, and venting and flaring.
Methane emissions associated with the transmission sector are produced
by the pipelines, compressor stations, and metering and pressure regulation,
stations. Leaks from the pipelines are caused by corrosion, material and
construction defects, miscellaneous leaks at valves, flanges, and fittings, and earth
movement which can cause strains and cracks. Venting can occur at points in the
pipeline where residual liquids collect and must be drained. Pneumatic devices
powered by natural gas are found throughout the transmission sector and are
typically vented to the atmosphere. Maintenance procedures such as pipe
scraping result in emissions during launching and retrieving of the scraper.
Dehydrators must receive periodic blowdowns and purges which are vented, and
pipelines must occasionally be purged during installations, abandonments,
replacement5:, repairs, and emergency shutdowns. Compressor stations produce
fugitive emissions from the usual sources (e.g., flanges, seals), occasional unflarec
venting from system overpressure, and gas turbine start-up and operating
emissions.
The primary sources of emissions from the distribution system, which
delivers natural gas to the end users, are pipeline leaks. These leaks result, in
varying degrees, from all of the same causes as leaks in transmission pipelines.
Gas is intentionally vented after isolating segments of lines for repair, and is used
to purge air from the pipeline after repair. Blow and purge operations on meters
and regulators are typically vented to the atmosphere. The distribution system,
because of its size, is generally regarded as the most significant source of CH4
emissions in the natural gas network.
Injection facilities can be located at various points in the system, depending
upon the facilities' function. Gas is frequently reinjected at the production site
to maintain oil or gas reservoir pressure. Gas is also injected into underground
reservoirs for storage. Normal operations at these facilities produce the usual
-------
416
fugitive emissions, releases during routine maintenance, and venting for
overpressure protection of compressors, scrubber vessels, and wellhead injection
stations.
The final category of emission sources (not discussed under the three-part
industry breakdown above) is liquefied natural gas (LNG) facilities. Functions
performed at an LNG facility include receiving, storage, and regasifi cation.
Equipment consists of unloading piping, pumps, insulated storage tanks for LNG,
and heaters and compressors for regasification. During norms! operation,
fugitive releases occur but, because of the nature of these facilities, maintenance
can be scheduled well in advance and the necessary controlled venting can be
directed to the flare system. Pressure relief system releases are typically flared
as well.
4.2 Summary of emission estimates. Numerous estimates of emissions for
the natural gas industry are available. Global emissions estimates from as long
as 20 years ago have been produced, primarily for the purpose of determining
global balances of atmospheric trace gases, but more recently for assessing global
climate change issues. In the past few years, as a result of the awareness of
methane's role in global climate change, country-specific and sector-specific
estimates of emissions have also become available. Estimates of global emissions
from the natural gas industry are summarized in Table 5. Estimates produced
during the 1980s typically range from 25 to 50 Tg/yr and assume leakage rates of
from 1 to 4 percent Ehhalt and Schmidt's (1978) estimate of 7 to 21 Tg/yr is a
notable exception but is explained by their acceptance of Hitchcock and
Wechsler's (1972) estimate. This estimate would correspond with the others if
expanded to 1985 gas production values. Seller's (1984) estimate of 19 to 29
Tg/yr is also low but is explained by his use of 1975 gas production data.
Estimates at the higher end of the typical range by Sheppard et al. (1982), Blake
(1984), and Cicerone and Orcmland (1988) are derived by adding assumed values
for vented gas to the calculated values for gas leakage. Keeling (1973) assumed
a leakage rate of 6-10 percent and estimated emissions of 40-70 Tg/yr.
Sheppard et al. (1982) and subsequently Blake (1984) estimate emissions
from venting and flaring at wellheads to be about 30 Tg/yr. Cicerone and
Oremland (1988) provide a later, independent estimate of 14 Tg/yr. It can be
inferred from the discussions that these estimates are for both gas and oil fields
and it is assumed that oil fields produce the majority of emissions. The estimates
-------
417
are not separated by industry, however, and such matters as flaring efficiencies
and venting versus flaring practices by individual countries are not discussed.
There are currently no reliable data oil global venting and flaring emissions from
oil and gas fields.
Table 5. Estimates of global emissions for the natural gas Industry.
Source
Reported
Year
Estimate
(Tg/yr)
Assumed Loss Rates
%
Hitchcock and
Wechsler (1972)
1968
7-21
1-3
Keeling (1973)
1968
40-70
6-10
Ehhalt and Schmidt
(1978)
1968
7-21
1-3
Sheppard et al. (1982)
1975
50
2 (leakage) + 25% for
vented and flared
Blake (1984)
1975
50-60
2-3 (leakage) + 30 Tg
for vented
Seller (1984)
1075
19-29
2-3
Bolle et al. (1986)
Not specified
35
3-4
Crutzen (1987)
Not specified
33
4
Danustadtcr et
-------
418
companies' accounting systems rather than actual gas losses, it is generally
recognized that emissions estimates should not be based on these statistics.
Table ft. Summary of studies showing gas losses by industry sector.
Source
Location &
Year
Summiiry
of Findings
Description
Emissions
Tilkicioglu and
Winters^ 19S9)
USA-1983
Gas field and field
separation facilities
Gas transmission
Gas distribution
Gas process plants
Total
1.12 Tg/yr
0.97 Tg/yr
0.43 Tg/yr
0.31 Tg/yr
2.8-1 Tg/yr
Cotterigham et
al. (1989)
PG&Ea
Distribution
Transmission
Dig-ins
Total
198,000 Mcf/vr"
42,000 Mcf/yr
106.000 Mcf/vr
646,000 Mcf/yr or
0.08% of adjusted
operating receipts
Chem Systems
International
Ltd.
(1989)
US A-1988
Production
Transmission
Distribution
Over?.!!
% UAGC ; % Loss
0.13
0.54 0.13
2-2
0.5-1.0
W. Germany
1989
Production
Transmission
Overall
0.16
0.01
<1.0
Netherlands
1989
Overall
Negative11
UK 1989
Overall
<1.0
Former USSR
1989 . . .
Transmission
Distribution
-2.0
>2.0
11 Pacific Gas and Electric (PG&E) is a cas distributor in the United States.
b 1 ft; = 2S.3L (0.0283 m3).
c Unaccounted for gas.
6 Ar. apparent gain was indicated.
-------
•119
Table 7. 1985 transmission/distribution system losses reported by IEA in Piccot
et aL (1990).
Estimated Transmission % Loss
Pipeline and or
Country Throughput2 Distribution Emission
(1,000 TOE)b Losses Factor
(1,000 TOE)
Low Reported I x>sses
Tunisiac 637 1.6 0.2
West Germany 43.4 0.16 0.4
Japan 35.6 0.21 0.6
Italy 28.1 0.22 0.8
Brazil 2,054 24 1.2
France 25.7 0.32 1.2
Moderate Reported I./jsses
Austria 4.7 0.08 1.7
Czechoslovakia 7,748 136 1.8
Spain 2.2 0.05 2.3
Former Soviet 1,530,148 34,428 2.3
Union
Hungary 8,327 198 2.4
Poland 9,060 236 2.6
Pakistan 6,820 176 2.6
High Reported Losses
Chile 189 6.1 3.2
United Kingdom 48 1.7 3.6
East Germany 7,820 365 4.7
Argentina . . 15,355 851 5.5
a.
b.
c.
Hie sum of indigenous production and imports.
TOE = tonnes of oil equivalents (1 TOE = 107 kcai).
Based on 1984 data since 1985 data appear to be atypical.
-------
'lable 6 summarizes those studies that break down gas losses by industry
sector. Although the number of countries covered is limited, the estimates in
these studies suggest that, except for the former Soviet Union, gas actually leaked
to tlie atmosphere consists of less than 1 percent of throughput. The most
detailed study is specific to the Pacific Gas and Electric Company in the United
States which suggests that actual leakage represents only 0.08 percent of gas
received. These estimates could vary considerably if a larger sample of countries
is considered.
Table 7 is reproduced from a report by Piccot et al. (1990) and is derived
from International Energy Agency energy balances for selected countries. The
average loss weighted by each country's throughput is estimated to be 23
percent. This table reports a percentage loss for the United Kingdom of 3.6
percent which is considerably higher than the value reported in Table 6.
Unfortunately, the source of this discrepancy cannot be determined from
available information. It is possible that for some of countries included in Table
7 the estimates may suffer from the same shortcoming as UAG statistics in that
they may not provide sufficient detail to allow differentiation of actual leakage
from other accounting losses. In those cases, the estimates could be high.
Table 8. Country-specific gas emission estimates.
Source
Year
Estimates
Mitchell et al. (1990)
Not specified
United Kingdom
Low: 1.9% of supply
Medium: 5.3% of supply
High: 10.8% of supply
(nreferred estimate is medium to
high)
Selzer (1990)
Not specified
West German)'; 0.3 Tg/yr
Tilkicioglu (1990)
19SS
U.S.A.: 3.1 Tg/vr
Dixon (1990)
19S7-19SS
Australia: 2% of production
Table 8 contains country-specific emission estimates from various other
sources. Again, a relatively high estimate of 5.3 to 10.8 percent of supply for the
United Kingdom emerges, as does another low estimate of 0.3 Tg/yr for West
Germany.
-------
Clearly, the wide range of sometimes conflicting estimates reflects the high
degree of uncertainty associated with current global estimates of Cil4 emissions
from natural gas extraction, processing, transmission, and distribution systems.
Despite the plethora of emissions estimates available for the gas industry, it is
clear that they are based on very little hard data. It is likely that the loss rates
for natural gas systems will vary significantly among countries because the types
of systems, system operating characteristics, and system ages likely vary
significantly from country to country.
5. Minor industrial sources
Industrial sources of CH, that have been given the greatest attention in the
literature include coal mining operations and the production and distribution of
natural gas. Logically, attention has been focused here because both sources are
responsible for producing significant quantities of CH4. However, other
industrial sources also release CH4 into the atmosphere. Individually these
sources emit minor quantities of CH4 but collectively their contribution to the
global budget may be significant. Very little research has been done to
characterize the CH4 emissions from these minor industrial sources, and they are
rarely included in assessments of the global CFL cycle. Although current
estimates of CH, emissions for minor industrial sources require more study to
reduce uncertainties, estimates developed so far suggest that the combined
emissions from all sources may be as significant as the more traditional sources
(i.e., coal mines, natural gas production and distribution systems, and solid waste
disposal landfills). These estimates are briefly discussed here.
An early attempt to estimate CH4 emissions from industrial and other
sources located in urban areas was conducted by Blake (1984). In Blake's
analysis, a limited number of ambient air samples were collected in several cities,
and it was observed that these samples routinely exhibited elevated Levels of CTf4.
Based on these measurements, an emission flux rate for the world's cities was
first calculated (0.06/m2/day) and then multiplied by an estimate of the land
surface area covered by the world's cities. Based on these rather crude
calculations, Blake estimated that non-automobile-related emissions from the
world's urban areas are about 10 Tg/yr. Urban CH4 sources can include a variety
of industrial and other activities.
-------
422
At a recent international workshop on methane and nitrous oxide emission
sources, new emissions estimates for minor sources were reported by Piccot and
Beck (1993) and by Berdowski et al. (1993). Sources examined in both studies
included industrial activities such as coke production facilities, petroleum
refineries, printing operations, gasoline storage and marketing facilities, fossil fuel
combustion, organic chemical manufacturing operations, and others. Non-
industrial sources such as the combustion of solid waste in the residential sector
were also examined.
The approach used to estimate global emissions in both studies was based
on the use of source-specific emission factors (i.e., CH4 emissions per unit of
source-specific activity). For example, emissions from petroleum refineries were
estimated by Piccot and Beck by multiplying an individual country's refinery
crude oil throughput by an emission factor that quantifies the amount of CH4
emitted from all refinery processes per tonne of crude oil throughput. In both
studies many of the CI I4 emissions factors were based on the emissions
characteristics of industrial and other operations in the United States. In some
cases an attempt was made to represent specific factors influencing emission rates
in individual countries (e.g., Piccot and Beck estimated the emissions reductions
due to the use of 3-way catalytic emission controls on light duty motor vehicles
in different countries). Although differences in the types of industrial processes
and pollution control equipment used among countries may affect the magnitude
of the emission factors used, most studies have not attempted to rigorously
characterize these differences. At this point there can only be speculation about
how these differences may affect the emission estimates.
Estimates of the CI L emissions from selected minor sources examined by
Piccot and Beck and Berdowski et al. are compared in 'iable 9. The base year
for both sets of estimates is 1990. The most significant source categories
identified include residential on-site waste burning (estimated by Piccot and Beck
only), mobile sources, fossil fuel combustion, coke production and iron and steel
processes, and petroleum refining. Although emission estimates for these sources
differ somewhat between the two studies, it appears that their overall
contribution to the global budget is close to 10 Tg/yr. Emissions from coke
production facilities were also estimated by Darmstadtcr et al. (1984) to be 4 Tg
for 1980—higher than that estimated by both Piccot and Beck and Berdowski et
al.
-------
Table 9. Emissions estimated by Piccot and Beck (1993) and Berdowski et al. (1993) for
minor industrial and other sources of methane.
Source Description
Residential on-site waste burning
Mobile sources
Fossil fuel combustion
Petroleum refining
Selected industrial sources
Berdowski et al. ¦ ¦ Piccot and Beck
(Tg/yr) (Tg/yr)
Not estimated 33
3.0 (± 2) 1.8
4.5 (± 1.5) 1.6
0.5 0.6
0.1
0.3
1.4
9.1
Organic chemical manufacturing 0.2
Coke production and iron and
steel processes. < 2.0
Other miscellaneous sources -
(industrial waste, forest fires and
managed burning, sewage treatment
plants, kraft paper manufacturing,
printing and publishing, petroleum
storage and distribution).
TOTAL
Table 10. Emissions estimated by Lacroix (1993) for various industrial sources of
methane.
Source Description Emissions (Tg/yr)
Combustion of Fossil Fuels 4.6 ± 0.4
Petroleum Refining 3.5 ± 0.5
Petrochemicals 2.0 ± 1.0
Peat Mining 2.0 ±1.0
Geothermal Electricity Production 1.2 ± 0.7
Total Emissions 133 ± 3.6
Global estimates of CH4 emissions from several minor industrial sources
have also been estimated by Lacroix (1993). Table 10 summarizes the emissions
estimated by Lacroix for five industrial sources of CH4. Total emissions from the
five sources are 13.3 Tg/yr. The approach used by Lacroix is based on emission
-------
-124
factors (JKA-KPA, 1990) and commercial fuel use for 19K7 in compilations of the
International Energy Agency adjusted for a world average energy growth rate of
2 percent per year to the present.
The estimates of Lacroix include several sources addressed by Piccot and
Beck and by Berdowski et al. For most sources examined, agreement in the
emissions estimates among the three studies is variable. For example, the
combined average emissions from both petrochemical plants and refining
operations estimated by Lacroix range from 4.0 to 7.0 Tg/yr. Both Piccot and
Beck and Berdowski et al. estimate that emissions from these two sources arc less
than 1 Tg/yr. Agreement on the emissions from fossil fuel combustion-related
activities is only moderate among all of the studies. Piccot and Beck estimate
that emissions from all fossil fuel combustion-related activities (i.e., stationary and
mobile sources) are 3J) Tg/yr while Berdowski et si. estimate the value to be
much higher — 7.5 Tg/yr. Lacroix estimates combustion-related emissions to be
4.6 Tg/yr, closer to the value reported by I'iccot and Beck. However, there is
significant disagreement in the distribution of combustion-related emissions
between stationary and mobile sources emissions of 3.0 to 43 Tg/yr, much higher
than estimates developed by Hitchcock and Weclisler (1972) (0.5 Tg/yr) and by
Piccot and Beck (1.8 Tg/yr).
Lacroix includes estimates for other industrial sources not addressed in
most studies, including peat mining and geothermal electricity production. The
total emissions from these two sources are 3.2 Tg/yr.
There is some evidence that mining oil shale and salt may release CH4 into
the atmosphere. Although we arc not aware of attempts to estimate the global
emissions from these mining operations, measurements collected by the U.S.
Bureau of Mines (USBOM) suggest that some salt and oil shale deposits contain
CH4 that can be released during mining. Data provided by the USBOM show
that normal production-grade salt adjacent to anomalous salt zones (Le., zones
with brine seeps, gas seeps, and other factors that differ from normal salt) can
contain CH4 in quantities of .0.1 m3 of CH4 per tonne of salt mined. Salt within
the anomalous zones can contain between 0.4 and 1.8 ni3 of CH4 per tonne
mined. With oil shale, USBOM data show that oil shale samples at two mines
in the United States have CH4 contents of from 0.195 to 1.3 rn3 per tonne mined.
In general, these CH4 contents are much lower than the CH4 contents typically
encountered in coal produced at underground mines.
-------
425
6. Radiocarbon emissions estimates for industrial sources.
In a recent, Cicerone and Oremland (1988) recognized that emissions from
sources of radiocarbon-free CII4 may be understated. Radiocarbon-free CFT,
sources include C(I4 hydrate deposits and many of the industrial sources included
here (i.e., coal mines, natural gas processing and transmission systems, and a few
of the minor industrial sources). Cicerone and Oremland cite studies suggesting
that sources of radiocarbon-free CH4 may release twice the emissions than earlier
studies by Koyams (1963), Ehhalt (1974), Sheppard et al. (1982), Seiler (1984),
Crutzen (1987) and others have estimated. Tt was suggested that collectively
these sources contribute up to 50 Tg/yr more than has previously been estimated
(i.e., total emissions from fossil fuel sources, CH4 hydrates, and others are 135
Tg/vr).
Several other studies also suggest that the CEL budgets for sources of
radiocarbon-free CH4 may have been underestimated in the early studies cited
above. In a recent study conducted by the National Aeronautics and Space
Administration, model calculations based on carbon-14 data, atmospheric CH4
concentrations, and other information indicate that 12"! Tg/yr of atmospheric CIL
was emitted from fossil carbon sources during 1987 (Whalen ct aL, 1989). Tnis
is about 50 percent higher than Cicerone and Orcmland's estimate for coal mines
and natural gas drilling, venting, and transmission systems. If the more recent
coal mine estimates by Boyer et al. (1990) are considered, and if the emissions
from minor industrial sources are taken into account, the gap begins to close
between Whalcn's estimate of 123 Tg/yr and the "bottom-up" estimates for
sources of radiocarbon-frce CII4.
7. Summary
Over the past 30 years there have been several attempts to estimate the
global emissions of CH4 from coal mining operations. The estimates presented
in this section arc representative of the range of emission estimates published.
Emissions estimates range from 7.9 to 47.2 Tg/yr for various years between 1960
and 1989. The estimates vary because of differences in assumptions made for
emission factors (i.e., emissions/tonne of coal mined) and coal production rates.
Although it is not possible to identify the most "correct" estimate, it is likely that
for the late 1980s emission estimates which are less than 25 to 30 Tg/yr are
unrealisticallv low. We believe a more realistic range for this period would be
-------
426
35 to Tg/yr. Several recent studies have attempted to characterize country-
specific emissions and have included mine emission souices not previously
addressed (i.e., coal handling operations); Emission estimates from these studies,
which are at tlie upper end of the range cited above, may be the most
representative available in spite of the significant uncertainties which still remain.
None of the estimates presented here include emissions from abandoned
underground coal mines, so the range of 35 to 48 Tg/yr may still be low.
Numerous estimates of emissions for the natural gas industry are available.
Global emissions estimates from as long as 20 years ago have been produced,
primarily for the purpose of determining emission inventories and global balances
of atmospheric trace gases. Methane emissions estimates produced during the
1980s typically range from 25 to 50 Tg/yr and assume leakage rates of from 1 to
4 percent Clearly, the wide range of sometimes conflicting estimates reflects the
high degree of uncertainty associated with current global estimates of CH4
emissions from natural gas extraction, processing, transmission, and distribution
systems. Despite the plethora of emissions estimates available for the gas
industry, it is clear that they are based on very little hard data. More detailed
country-specific assessments will be needed before a "best estimate" or a narrow
range of emissions can be established. It is likely that the loss rates for natural
gas systems will vary significantly among countries because the types of systems,
system operating characteristics, and system ages likely vary significantly from
country to country.
Several minor industrial sources also release CK4 into the atmosphere.
Individually these sources emit small quantities of CH4 but collectively their
contribution to the global budget may be significant Although current estimates
of CH, emissions for minor industrial sources are limited and highly uncertain,
estimates suggest that the combined emissions from all minor industrial sources
identified so far may be between 10 and 15 Tg/yr, nearly as significant as some
of the more traditional CH4 sources. It is likely that emissions from these sources
account for some of the difference observed between the total fossil fuel
contribution estimated by carbon-14 analysis, and the bottom-up estimates of
major industrial sources. Based on the literature cited here the most significant
minor sources include residential on-site waste burning, peat mining and
geothermal power production, mobile sources, stationary source fossil fuel
combustion, coke production and iron and steel processes, and petroleum
-------
refining. Estimates of emissions from specific minor sources vary widely between
different studies indicating that further work is needed to develop more
representative estimates.
References
Ameri, S., F.T. Al-Saiidoon, C.W. Byrer. 1981. Coalbed methane resource
estimate of the Piceance Basin {Report No. DOE/ME1CITPRJS2-6). U.S.
Department oF Energy, Morgantown, West Virginia, 44 p.
American Gas Association. 1986. Lost and unaccounted for gas. In: Issue Brief
1986-28. American Gas Association, Arlington, Virginia, 4 p.
Anderson, R.B., T_J.F.. Hofer. 1965. Activation energy of diffusion of gases into
poro-js solids. Fuel, 44:303.
Aadronova, GA, I.L. Karol. 1993. The contribution of USSR sources to global
methane emission. Chemosphere, 26 (1-4):111-126.
Basic, A., M. Vukic. 1989. Dependence of methane contents in brown coal and
lignite seams on depth of occurrence and natural conditions. In:
Proceedings nf the 23rd International Conference of Safety in Mines Research
Institutes- U.S. Department of the Interior, Bureau of Mines, Washington.
D.C.
Bates, D.R., A1E. Witherspoon. 1952. The photo-chemistry of some minor
constituents of the Earth's atmosphere (C02, CO, CH4, N2O). Roy.
Astronom. Soc. Monthly Nol, 112.
Berdowski, JJ.M., J.GJ. Olivier, C Veldt- 1993. Methane emissions from fuel
combustion and industrial processes. In: Proceedings of the International
Workshop on Methane and Nitrons Oxide: Methods in National Inventories
and Options for Control, February 1993, Amersfoort, The Netherlands.
Blake, D.R. 1984. Increasing Concentrations of Atmospheric Methane, 1979-
1983 (Ph.D. Dissertation). University of California, Irvine, California.
Bolie, H.J., W. Seiler, B. Bolin. 1986. Other greenhouse gases and aerosols. In:
Tne Greenhouse Effect, Climatic Change, and Ecosystems (B. Bolin, ed.),
John Wiley and Sons, New York, 157-203.
Boyer, C.M., J.R. Kelafant, V.A. Kuuskraa, K.C. Manger, D. Kruger. 1990.
Methane emissions from coal mining: issues and opportunities for
reduction (EPA Report No. EPA-40019-901008). U.S. Environmental
Protection Agency, Office of Air and Radiation, Washington, D.C.
Cnem Systems International. Ltd. 1989. Me'Jiane Losses from Natural Gas
Utilization, prepared by Chem Systems International, 1 ,td„ for the National
Energy Admin., Sweden, 42 p.
Cicerone, R_J., R_ Oremland. 1988. Biogeochemical aspects of atmospheric
methane. Global Biogeochem. Cycles, 2:299-327.
-------
428
Cotteughasn, XL, R.M. Cowgill, J.B. Godkin, J.R. Grmstead, 1XJ. LuttreU, F.A.
Nelson, R.H. Noistering. J.D. Peterson. R. Quintanilla. J.L Robertson,
E.R. Walucu, R.L. Waller, R-E. Wlasenko, R.M. Wong. 1989.
Unaccounted-for Gas Project, Pacific Gas and Electric Company, San
Francisco, California.
Crcedy, D.P. 1983. Scam gas-content data-base aids in firedamp prediction.
Ihe Mining Engineer, August 1933:79-82.
Greedy, D.P. 1993. Methane emissions from coal-related sources in Britain:
Development of a methodology. Chemosphere, 26 (I-4):419-44Q.
Crutzen, P.I. 1987. Role of the tropics in atmospheric chemistry. In:
Geophysiology of Amazonia (R. Dickinson, ed.), John Wiley and Sons, New
York.
Darmstadtcr, J., L. Ayrcs, R.U. Avres, W.C. Clark, P. Crosson, P. Crutzen, TE.
Graedel, R. Mc.Gill, R-E Richards, J.A. Tarr. 1984. Impacts of world
development on selected characteristics of the atmosphere: an integrative
approach, volume 2-appendices (Report No.ORNL/Sub/86-22033/i/V2).
Oak Ridge National Laboratory, Oak Ridge, Xennessee.
Department of Energy. 1991. National energy strategy (Report No. DOE/S-
0082P). U.S. Department of Energy, Washington, D.C., 217 p.
Dixon, D.E 1990. Methane losses from theAustralian natural gas industry. In:
Internationa/ Workshop on Methane Emissions from Natural Gas Systems,
Coal Mining, and Waste Management Systems. Environment Agency of
Japan, U.S. Agency for International Development,, and U.S.
Environmental Protection Agency, Washington, D.C, 709 p.
Ehhalt, D.H. 1974. The atmospheric cycle of methane. Tellus, 26:58-70.
Ehhalt, D.H., U. Schmidt 1978. Sources and sinks of atmospheric methane.
Pageoph, i.76:452-463.
Environment Agency of Japan. 1990. International workshop on methane
emissions from natural gas systems, coal mining, and waste management
systems. Environment Agency of Japan, U.S. Agency for International
Development, and U.S. Environmental Protection Agency, Washington,
D.C., 709 p.
Fung, I., J. John, J. Lerner, E. Matthews, M. Prather, J..P Steele, P.J. Eraser.
1991. Three-dimensional model synthesis of the global methane cycle. J.
Geophys. Res., 9(5:13,033-13,055.
Hay, N.E., P.L. Wilkinson, W.M. James. 1988. Global climate change and
emerging energy technologies far electric utilities: the role of natural gas.
American Gas Association, Arlington, Virginia, 30 p.
Hitchcock, D.R., A.E. Wechsler. 1972. Biological cycling of atmospheric trace
gases (Report No. NASV/-2I2S). National Aeronautic and Space
Administration, Washington, D.C., 415 p.
-------
429
Irani, M.C., F_D. Thimons, T.G. Bobick. 1972. Methane emission from U.S. coal
mines, a survey (Report No. IC 8558). U.S. Department of the Interior,
Bureau of Mines, Pittsburgh, Pennsylvania.
JEA-EPA 1990. Methane emissions and opportunities for control: workshop
results of intergovernmental panel on climate change, response strategies
working group. Japan Environment Agency/United States Environmental
Protection Agency, Washington, D.C. ...
jolly, D.C., IJH. Morris, F.B. Htnsely. 1968. An investigation into the
relationship between the methane sorption capacity of coal and gas
pressure. The Mi:iung Engineer 127:539.
Joubert, J.I., C.T Grein, B. Bienstock. 1974. Effect of moisture on the methane
capacity of American coals. Fuel, 53:186.
Keeling, CD. 1973. Industrial production of carbon dioxide from fossil fuels
and limestone. Tellus, 25:174-198.
Khalil, MA.K., M.J. Shearer, Eds. 1993. Chemosphere, 26 (1-4).
Kim, A.G. 1977. Estimating methane content of bituminous coalbcds from
adsorption data (Report AJo. RJ 8245). U.S. Department of the Interior,
Bureau of Mines. Pittsburgh, Pennsylvania.
Kirchgessner, D-A, S.D. Picco:, J.D. Winkler. 1993a. Estimate of global
methane emissions from coal mines. Chemosphere, 26 (l-4):453-472.
Kirchgessner, DA, S.D. Piccot, A. Chadha, T. Minnich. 1993b. Estimation of
methane emissions from a surface coal mine using open-path FITR
spectroscopy and modeling techniques. Chemosphere, 26 (l-4):23-44.
Kissel, RN_, CM. McCulloch, CH. Elder. 1973. The direct method of
determining methane content of coal beds for ventilation design (Report No.
RI 7767). U.S. Department of the Interior, Bureau of Mines, Pittsburgh,
Pennsylvania.
Koyaina, X 1963. Gaseous metabolism in lake sediments and paddy soils and
the production of atmospheric methane and hydrogen. J. Geophys. Res.,
68:3,971-3,973.
Koyarna, T 1964. Biogeocheinical studies on lake sediments and paddy soils and
the production of hydrogen and methane. Recent Researches in the Fields
of Hydrosphere, Atmosphere, and Geochemistry, 143-177.
Lacroix, AV. 1993. Unaccounted-for sources of fossil fuel and isotopically-
enriched methane and their contribution to the emissions inventory: A
review and synthesis. Chemosphere, 26 (l-4):507-558.
Lambert, S.W., M.A Trevits, PF. Steidl. 1980. Vertical borehole design and
completion practices to remove methane gas from minable coalbeds (Report
No. boE/CMTCITR-80/2). U.S. Department of Energy, Washington, D.C,
163 p.
Mitchell, C., J. Sweet, T. Jackson. 1990. A study of leakage from the UK natural
gas distribution system. Energy Policy, November 1990:809-818.
-------
430
Murray, DX). 1930. Methane from coalbeds - A significant undeveloped source of
natural gas. Colorado School of Mines Research Institute, Golden,
Colorado. 37 p.
Okkcn, PA., T Kram. 1989. CTIjCOi-cmission from fossil fuels global warming
potenti?.!. In: Proceedings of the International Energy Agency Workshop on
Greenhouse Gases, June 1989, Paris.
Ficcot, S.D., M. Sneger. 1990. National- ana state-level emissions estimates of
radiatively important trace gases (RTTG) from anthropogenic sources
{Report No. EPA-600/8-90-073; NITS PB91-103572). U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina.
Piccot, S.D., I_ Beck. 1993. Estimation of methane emissions from minor
anthropogenic sources. In: Proceedings of the International Workshop on
Methane and Nitrous Oxide: Methods in National Inventories and Options for
Control, February 1993, Amersfoort The Netherlands.
Piccot, S.D., A. Chadha, J. DeWaters, X Lynch, P. Marsosudiro, W. Tax, S.
Walata, J. D. Wiiikler. 1990. Evaluation of significant anthropogenic
sources of radiatively important trace gases (Report No. EPA-60Q/8-90-079;
NTIS PB91-127753). U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina.
Piccot, S.D., A. Chadha, D.A. Kirchgessner, R. Kagenn, M.J. CzerrJawski, T
Minnich. 1991. Measurement of methane emissions in the plume of a
large surface coal mine using open-path FUR spectroscopy. In:
Proceedings of 84th Annual Meeting of the Air and Waste Management
Association, June 1991, Vancouver, British Columbia, Canada.
Pilcher, R.C., C. Bibler, R_ Glickert, L. Machesky, J. Williams. 1991. Assessment
of the potential for economic development and utilization of coalbed
methane in Poland {Report No. EPA-400/1-91-032). U.S. Environmental
Protection Agency, Office of Air and Radiation, Washington, D.C.
Schwarzer, R.R., C.W. Eyrer. 1983. Variation in the quantity of methane
adsorbed by selected coals as a function of coal petrology and coal
chemistry {Report No. DE-AC21-80MCI4219). U.S. Department of Energy,
Morgantown. West Virginia.
Seiler, W. 1984. Contribution of biological processes to the global budget cf
CH4 in the atmosphere. In: Current Perspectives in Microbial Ecology (M.J.
Klug and C.A. Reddy, eds.), American Society for Microbiology,
Washington, D.C.
Selzer, H. 1990. ArithropogCn methane emission. In: International Workshop an
Methane Emissions from Natural Gas Systems, Coal Mining, and Waste
Management Systems, Environment Agency of Japan, U.S. Agency for
International Development, and U.S. Environmental Protection Agency,
Washington, D.C., 709 p.
-------
Sheppard, J.C. H. Westberg, J.E Hopper, JC Ganesan. 1982. inventor}' of
global methane sources and their production rates. / Geopiivs. Res.,
57:1305-1312.
Tilkicioglu. B.H., and D.R. Winters. 1989. Annual Methane Emission Estimate of
the'Natural Gas and Petroleum Systems in the United States, draft report
prepared for the U.S. Environmental Protection Agency Office of Air and
Radiation by Pipeline Systems Incorporated, Walnut Creek, CA, 101 pages.
Watt Committee on Energy. 1991. Quantification of methane emissions from
British coal mine sources (Draft Report).
Wlialen. M., N. Tanaka, R. Henry, B. Deck, J. Zeglen, J.S. Vogel, J. Southon, A.
Shemesh, R. Fairbanks, W. Broecker. 1989. Carbon-14 in methane
sources and in atmospheric methane: the contribution from fossil carbon.
Science, 245:286-290.
-------
TECHNICAL REPORT DATA 1
A
-------
|