NTE
PB95-177002 Information it our business.
ESTIMATE OF GLOBAL METHANE EMISSIONS FROM
LANDFILLS AND OPEN DUMPS
PECHAN (E.H.> AND ASSOCIATES, INC., DURHAM, NC
FEB 95
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
-------
EPA-600/R-95-019
February 1995
ESTIMATE OF GLOBAL METHANE
EMISSIONS FROM LANDFILLS
AND OPEN DUMPS
by
Michiel R.J. Doom
E.H. Pechan & Associates, Inc.
3500 Westgate Drive, Suite 103
Durham, NC 27707
Morton A. Barlaz
North Carolina State University
Raleigh, NC 27695
Contract No. 68-D1-0146
Work Assignment No. 1/015, 1/022, 2/031, and 2/034
Project Officer
Fnsan A. Thorneloe
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
Prepared for:
U.S. Environmental Protection Agency
Office of Research and Development
Washington, D.C. 20460
-------
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
reflect the views Bnd policy of the Agency, nor does mention 01 trade names or
commercial products constitute endorsement or recommendation for use.
This documenl is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22761.
11
-------
ABSTRACT
Methane (CH4) produced via the anaerobic decomposition of waste buried in landfills
and open dumps is a significant contributor to global methane emissions, with estimates
ranging from 10 to 70 teragrams (Tg or 1012 grams) per year. Global anthropogenic
sources emit 360 Tg/yr (IPCC, 1992), which sugmsts that landfills may account for 3 to 19
percent. Methods of managing solid waste vary pidely, ranging from open dumps and
open burning to sanitary landfills with leachate collection systems and landfill gas (LFG)
control. This report presents an empirical model to estimate global CH4 emissions from
landfills and open dumps, based on data from LFG recovery projects, developed by the U.S.
Environmental Protection Agency's Air and Energy Engineering Research Laboratory
(AEERL). The AEERL CH4 estimates for 1990 range between 19 and 40 Tg/yr with a mid-
point of 30 Tg/yr. The United States is the biggest contributor to global CH4 emissions
from this source with estimates ranging from 8 to 17 Tg/yr with a mid-point of 13 Tg/yr.
Many developed countries are encouraging incentive programs or regulatory
requirements for municipal solid waste landfills that could result in a reduction of CH4
from landfills, Several countries are adopting source reduction and recycling programs
reducing the paper fraction in landfills and consequently the CH4 potential. The
Netherlands has adopted a stringent composting program that segregates vegetable and
garden waste from the remaining waste stream. Also, more stringent controls for LFG
emissions are being considered by many Tuntries. The United Kingdom, as do several '
other countries, has an incentive program that encourages CH4 utilization. The United*
States has proposed federal regulations for municipal solid waste landfills that, if
implemented, are estimated to result in a CH4 emissions reduction of 5 to 7 Tg/yr by the
year 2000. As different programs are implemented over the next several years wc will
have a better understanding of their effect on CH4 emissions from landfills.
The potential CH4 reduction that may result from these incentives and/or regulatory
controls may not be realized if economic development and overall population growth
(especially in developing or newly industrialized countries) result in more absolute waste
generation. Also, in developing countries, there is a distinct intent to improve solid waste
management methods for sanitation reasons. Better solid waste management methods in
these countries may increase the amount of waste that will be landfilled and thus increase
CH4 emissions.
Substantial uncertainty in the global estimates from this source results from a lack of
data characterizing: (1) country-specific waste generation; (2) waste management
practices; (3) CH4 potential of the waste in place; (4) CH4 that is emitted from waste piles
and open dumps; and (5) the use of U.S. LFG rccovci^ data as a surrogate for CH4
emissions.
111
-------
CONTENTS Page
ABSTRACT iii
FIBRES v
TABLES v
ACRONYMS AND DEFINITION OF MUNICIPA^, SOLID WASTE vi
ACKNOWLEDGEMENTS vii
INTRODUCTION 1
METHANE PRODUCTION FROM THE ANAEROBIC DECOMPOSITION OF
SOLID WASTE 4
METHANE POTENTIAL OF MUNICIPAL SOLID WASTE IN LANDFILLS .... 6
METHODOLOGY 9
U.S. REGRESSION MODEL 9
LANDFILL GAS RECOVERY AND FLARING 10
ESTIMATION OF COUNTRY-SPECIFIC WASTE QUANTITIES 10
Rural MSW Generation Rates 11
Commercial, Market, and Institutional Waste Generation Rates 12
Total MSW Generation Rates 12
ADAPTATION OF U.S. MODEL FOR OTHER COUNTRIES *16
Country-specific Waste Management Practices 16
Degree of Anaerobic Decomposition in Landfills and Open Dumps 17
Waste Composition Expressed in Methane Potential 18
ESTIMATE OF GLOBAL METHANE EMISSIONS FROM LANDFILLS
AND OPEN DUMPS 21
TRENDS 25
DEVELOPING COUNTRIES 25
DEVELOPED COUNTRIES 28
UNCERTAINTIES 30
UNCERTAINTIES ASSOCIATED WITH THE U.S. REGRESSION MODEL 30
Generation Time 30
Mass of waste in plar- 30
Methane o vation 30
Recover' e. ency oC I »projects 31
UNCERTAINTIES IN W . j! TENERA'IION ESTIMATES 31
UNCERTAINTIES I " \S1'E DISPOSAL, ESTIMATES 32
UNCERTAINTIES E :THk 7E GENFrVTION ESTIMATES 33
REFERENCES 35
1 v
-------
FIGURES
Number Eflgfi
1. Least squares regression analysis of LFG flow rates versus welled waste for 105
LFG recovery sites in the United States 3
2. Global methane emissions from landfills and ODen dumps by continent 23
TABLES
Number Page
1. GLOBAL ESTIMATES OF METHANE EMISSIONS FROM LANDFILLS
AND OPEN DUMPS 1
2. DEFAULT MSW GENERATION RATES 13
3. WORLD MSW GENERATION RATES AND REFERENCES 14
4. DEFAULT FRACTIONS LANDFILLED OR DUMPED 17
5. MEASURED CH< POTENTIALS FOR DRY AND WET WASTES 19
6. WORLD METHANE EMISSIONS FROM LANDFILLS AND OPEN DUMPS 22
7. COMPARISON OF DIFFERENT COUNTRY-SPECIFIC METHANE EMISSIONS
FROM LANDFILLS AND OPEN DUMPS 24
8. EFFECT OF TRENDS ON GLOBAL METHANE EMISSIONS FROM LANDFILLS *
AND OPEN DUMPS 26
9. SENSITIVITY ANALYSIS OF GLOBAL METHANE EMISSIONS 33
10. COUNTRY-SPECIFIC WASTE DATA AND METHANE EMISSIONS 44
v
-------
ACRONYMS AND DEFINITION OF MUNICIPAL SOLID WASTE
AEERL Air and Energy Engineering Research Laboratory
BMP Biochemical Methane Potential
EPA United States Environmental Protection Agency
IPCC International Panel on Climate Cqange
LFG Landfill Gas
MSW Municipal Solid Waste
OECD Organization of Economic Cooperation and Development
ORD Office of Research and Development
OSW Office of Solid Waste
g
gram
H
kilogram (e 1,000 grams)
Tg
teragram (=10" grams)
lb
pound (=0.454 kg)
ft3
cubic feet (=0.0283 cubic meters)
1
liter
_3
m
cubic meter
min
minute
hr
hour
yr
year
cap
capita
ch4
methane
C02
carbon dioxide
Definition of MSW:
Municipal solid waste includes wastes from residential, commercial, and certain
industrial sources, and excludes construction and demolition wastes, sludges, power
plant ashes, hazardous wastes and industrial procees wastes. (Industrial sources
producing MSW include workshops and other small industries that are typically
mingled with shops and which produce waBte that is comparable to commercial or
residential waste in composition, as well as in management method.)
vl
-------
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the advice and assistance of the persons
identified below.
Susan Thorneloe, EPA Work Assignment Manager, Air and Energy Engineering
Research Laboratory, U.S. EPA, Research Triangle Park, NC. Susan provided
oversight and coordinated the review of the report. Her long term vision made it
possible to produce this report as part of an extended research program that started
with the study of landfill gas from six U.S. landfill sites and now encompasses
greenhouse gases from global solid waste. Through her many internationol contacts
she was able to ensure the input of several key international waste/global warming
experts.
Kathleen Hogan, Office of Atmospheric Programs, Office of Air and Radiation,
U.S. EPA, Washington, DC , helped to review the report and provided valuable
comments.
Luis Diaz and George Savage of CalRecovery, Hercules, CA, helped to review the
report and contributed significantly with practical information and country-specific
data.
David Campbell of AEA Technology, Abingdon, United Kingdom, offered his imposing
expertise and insight to assess logic and accuracy of the report.
Simon Aumflnier of ETSU, Department of Trade and Industry, Harwell, United
Kingdom, helped to review the report and provided useful comments.
Darcy Campbell, Ann Leininger, and Peter Self of Radian Corporation, Research
Triangle Park, NC, assisted in researching the literature and developing the initial
methodology and emission estimates.
Randy Strait, Bill Barnard, Dorothy Titus, and Kathy Manwaring, E.H. Pechan &
Associates, Durham, NC, provided editorial comments and general assistance.
v 11
-------
INTRODUCTION
Methane (CH4) produced via the anaerobic decomposition of waste buried in landfills
and open dumps is a significant contributor to global methane emissions, with estimates
ranging from 10 to 70 Tg/yr (Table 1). Global anthropogenic sources emit 360 Tg/yr
(IPCC, 1992), which supgests that landfills may account for 3 to 19 percent of the total.
TABLE 1. GLOBAL ESTIMATES OF METHANE EMISSIONS FROM LANDFILLS
AND OPEN DUMPS
AVERAGE
RANGE
REFERENCE
(Tg/yr)
(Tg/yr)
50
30 - 70
Blngemer & Crutzen, 1987'
62
-
OECD, 1991'
15
10 - 20
Rlchard9, 1089'
30
19 • 40
This Report
Potential emissions, not corrected lor the amount that Is flared or utilized.
Uses IPCC/OECD (1987) methodology with updated country-specific data on
municipal solid waste generation rates.
Existing emission estimation methodologies for this souice tend to assume that
optimal conditions for anaerobic decomposition exist within a landfill. However, this is
rarely the case as the information in the following section and an article by Ratt\je (1991)
indicate. To address this concern, AEERL haB used landfill gas (LFG) recovery data to
develop an empirical model relating LFG flows to waste in place. This model, described
in Doom, et al. (1994), was the result of an extensive research program initiated in 1990.
The AEERL research program started with a review of available models and data and
identified several theoretical models and laboratory experiments used to estimate CH4
from individual landfills. However, adapting these methodologies for global estimates
posed several problems, the foremost being that these methodologies rely on site-specific
data that are not available for many countries. Some emission estimation methodologies
were found to be reasonable, but the estimates were based on assumed values for certain
parameters, such as refuse generation rates and {waste composition data. TheBe data are
not available or are unreliable for many countritw. To develop a new and better model,
AEERL initiated a second phase in the program aimed at the identification of key
variables that affect CH4 generation and at the development of an empirical model based
on those variables.
1
-------
One important postulate of the AEERL program was that landfills with gas recovery
systems, where LFG is collected and measured py personnel on site, offer a unique
opportunity for studying CH4 emissions. LFG recovery rates can be used to estimate CH4
generation which in turn can be related to CH4 emissions. However, in order to use this
approach, the accuracy of such LFG data needed to be verified. Furthermore, the
availability of additional information on the landfills from which LFG data were collected,
including the amount and nature of the waste present, needed to be examined.
The first step in developing this second phase program was a field study of six United
States (U.S.) landfills with LFG recovery systems. This pilot Btudj was aimed at
verifying the existence and accuracy of the waste in place and gas flow data. The results
of this pilot study were sufficiently encouraging such that n large-scale field study was
conducted at 30 U.S. landfills. The objective of this study was to develop a statistical
model of annual landfill CH4 emissions as a function of climate, refuse mass, age, waste
acceptance rate, composition, and compaction, as well as obtaining an emission factor,
which could be used to estimate both U.S. and global CH4 emissions from landfills. Sites
were chosen to represent a wide range of climatic conditions as they occur in the United
States. The research concluded that the mass of waste in place showed a significant ^
correlation with CH4 flow rates. None of the climate variables — annual rainfall, average
temperature, and dewpoint — had significant correlations with CH4 flow rate. The effect
of refuse age on gas production was also analyzed. Gas flow rates correlated most
strongly with refuse age for 10 to 20 year old refuse. Although these results were not
conclusive, they suggest that the generation time for gas production is 20 to 30 years with
an average of 25 years (Campbell et al., 1991; Peer et al., 1992).
Two assumptions needed to be made to relate CH4 flow rates from recovery projects to
CH4 generation rates. It was assumed that the average recovery efficiency of a gas
collection system is 75 percent (adapted from Augenstein and Pacey, 1990). Furthermore,
it was assumed that 10 percent of unrecovered CH4 is oxidized (adapted from Whalen et
al., 1990). Both assumptions are based on very limited data and represent engineering
judgement.
Because a large amount of the variability remained unexplained in the field study
described above, a decision was made to refine the correlation between LFG flow and
waste mass. A larger LFG recovery data base was produced, which included data from
105 U.S. LFG recovery projects. Two regression functions were generated using the
expanded and verified data-set. The first one is a nonlinear regression function,
dependent on size-specific information for landfills, applicable to countries that have size-
specific landfill data (i.e., the United States). The second function is linear and is
essentially an emission factor (Figure 1). Both models are detailed in Doom et al., (1994).
2
-------
300
250
c" 200-
E
| 150
*
o
= 100
50
8ol
o
I
o%°
5 10 15 20 25
Welled Waste , miHion metric tons
Notes: VaJues for three very large sites are not shown, but are taken into account tn analyses.
Dashed fries indicate 95% confidence interval (plus or minus two standard deviations).
30
Figure 1. Least squares regression analysis of LFG flow rales versus welled waste for 105 LFG
recovery sites in the United States
-------
Since no correlation was found between climate variables and CH« flow rates, the
maximum amount of CH< that may be generated by a certain batch of waste (CH<
potential) will only depend on the chemical composition of the waste in j.1ace. The
fraction of this amount that will be actually generated or emitted will depend on physical
characteristics of the landfill or dump; for instance, how much of the refuse exists under
anaerobic conditions. Hence, the linear model may be adapted to develop emission
estimates for countries other than the United States.
METHANE PRODUCTION FROM THE ANAEROBIC DECOMPOSITION OF
SOLID WASTE
The anaerobic decomposition of organic matter, aa it occurs in a landfill, is a complex
process that requires that several groups of microorganisms act in a synergistic manner
under favorable environmental conditions. Anaerobic refuse decomposition has been
reviewed in detail by Barlaz et al. (1990), and more detail on the microbiology of
municipal waste decomposition has been reported by Barlaz. et al. (1989a).
Three trophic groups of anaerobic bacteria must be present to produce CH4 from
biological polymers such as cellulose, hemicellulose, and protein: (1) hydrolytic and
fermentative microorganisms, (2) obligate proton-reducing acetogens, and (3) methanogens
(Wolfe, 1979; Zehnder, 1982). The hydrolytic and fermentative group is responsible for
the hydrolysis of biological polymers. The initial products of polymer hydrolysis are
soluble sugars, amino acids, long-chain carboxylic acids, and glycerol. Following polymer
hydrolysis, the hydrolytic and fermentative microorganisms ferment the initial products of
decomposition into short-chain carboxylic acids, alcohols, carbon dioxide (COa), and
hydrogen. Acetate, a direct precursor of CH4, is also formed.
The second group of bacteria, 'obligate proton-reducing acetogens,' convert the
fermentation products of the hydrolytic and fermentative microorganisms to C02,
hydrogen, and acetic acid. The conversion of fermentation intermediates, such as
butyrate, propionate, and ethanol is thermodynamically favorable only at very low
hydrogen concentrations. Thus, these substrates are utilized only when the obligate
proton-reducing acetogenic bacteria can function in syntrophic association with hydrogen
scavengers, such as CH^-producing or sulfate-reducing organisms. The third group of
bacteria necessary for the production of CH< are the methanogens. M^jor substrates
utilized by methanogens for the production of CH4 are acetate, formate, methanol,
methylamines, and hydrogen plus C02 (Wolin and Miller, 1985).
While CH< and C02 are the terminal producls of anaerobic decomposition, C02 and
water are the terminal products of aerobic decomposition. Aerobic decomposition occurs
in management facilities where waste is exposed to air, such as when compost is turned
for aerating, and in uncontrolled dumps, such aB when refuse iB spread in thin layers or
exposed jo oxygen by scavenging. Also, air may enter a dump or landfill if the
atmospheric pressure is higher than the pressure inside the dump or landfill. This
situation may occur when there is a sudden rise in atmospheric pressure and at landfills
with gas collection systems that are being overpumped. When refuse is buried in large
4
-------
piles, whether at an open dump or in a sanitary landfill, the oxygen entrained at burial is
consumed rapidly, and substantial quantities of CH4 may be produced (Bhide et al., 1990).
Landfilled waste contains numerous constituents that have the potential to
biodegrade under anaerobic conditions. The traditional method of classifying municipal
solid waste (MSW) according to sortable categories [e.g., paper, plastic, food waste, yard
waste, glass, metals, rubber, wood, textiles, dirt, and miscellaneous (U.S. EPA, 1990)) is
appropriate for recycling studies anu overall solid waste management planning. However,
data specific to the chemical composition of refuse are more applicable to analysis of
refuse decomposition. Refuse representative of typical MSW from Madison, Wisconsin, in
1987 was reported to contain 51.2 percent cellulose, 11.9 percent hemicellulose, no more
than 4.2 percent protein, and 15.2 percent lignin (Barlaz, 1988). Measurements of the -
cellulose concentration of Madison refuse taken from the period of 1984 through 1986
showed values of 40 to 48 percent (Barlaz, 1985). Cellulose plus hemicellulose accountfid
for 91 percent of the CH< potential of refuse (Barlaz et al., 1989b).
The components of MSW that contain significant biodegradable fractions are food
waste, yard waste, and paper. Paper has a combined cellulose and hemicellulose content
of 50 to 100 percent. Lignin is the other megor organic component of refuse; however,
lignin does not decompose significantly under anaerobic conditions (Young and Frazer,
1987).
Methane formation d es not occur immediately after refuse is placed in a landfill or
dump. It can take months or years for the proper environmental conditions and the
required microbiological populations to become established. Numerous factors control
decomposition, including moisture content, nutrient concentrations, presence and
distribution of microorganisms, particle size, water flux, pH level, and temperature.
Reviews of the effect of each of these factors on CH4 production are provided in Barlaz et
al., (1990); Pohland and Harper (1986) and Halvadakis (1983).
The two factors that appear to have the most impact on CH4 production are moisture
content and pH. The effect of refuse moisture content has been summarized by
Halvadakis (1983), although some of the data in the summary relate to manure and not
municipal waste. The broadest data sets are those constructed by Emberton (1986) and
Jenkins and Petus (1985). Emberton measured CH4 production rates in excavated landfill
samples under laboratory conditions. Jenkins and Petus sampled refuse from landfills
and tested how CH< production was affected by the moisture content of refuse. In both
studies, the CH4 pioduction rate exhibited an upward trend with increasing moisture
content, despite differences in refuse density, age, and composition. It is difficult to
translate the results of these laboratory studies to actual landfills. An attempt by AEERL
to identify a statistically significant correlation between LFG recovery and annual
precipitation found no such correlation, (Peer et al., 1992).
A second key factor influencing the rate and onset of CH< production is pH. The
optimum pH level for activity by methanogenic bacteria is between 6.8 and 7.4. Methane
production rates decrease sharply with pH values below about 6.5 (Zehnder, 1982). When
refuse is buried in landfills, there is often a rapid accumulation of carboxylic acids; this
5
-------
results in a temporary pH decrease and a long time-lapse between refuse burial and the
onset of CH« production that can range from months to years.
Neutralizing leachate and recycling it back through refuse has been shown to enhance
the onset and rate of CH4 production in laboratory studies (Pohland, 1975; Buivid, 1981;
Barlaz et al., 1987, 1989a). Given that moisture and pH have been reported as the two
most significant factors limiting CH4 production, the stimulatory effect of leachate
neutralization and recycling is logical. Neutralization of leachate provides a means of
externally raising the pH of the refuse ecosystem. Recycling neutralized leachate back
through a landfill increases and stabilizes refuse moisture content and substrate
availability. It also enhances mixing in what would otherwise be an immobilized batch
reactor. Field experience with loachate recycling systems is limited and more information
is needed to fully document its value. It is expected that new information will becomfc
available in the next few years.
The lapsed time preceding the onse' of CH4 production in landfills is important when
considering the management of individual landfills for biogas recovery or emissions
mitigation. When evaluating global CH4 emissions from MSW management systems, the
age at which landfills and uncontrolled dumps begin to produce CH4 is of lesser
importance. For estimating global emissions, it is the total CH4 production potential that
is more critical.
METHANE POTENTIAL OF MUNICIPAL SOLID WASTE IN LANDFILLS
The CH4 potential of landfilled refuse can be determined in three ways. The
theoretical CH4 potential of the main chemical constituents may be calculated or
laboratory tests may be conducted; also field tests may be performed. All methods have in
common the question whether the data are representative or not because, even in field
tests, waste composition and other parameters that affect CH4 generation may show
unpredictable variability between locations.
Knowledge of the chemical composition of refuse buried in a landfill makes it possible
to estimate the maximum volume of CH4 that may be produced. The mass of CH4 that
would be produced if all of a given constituent were converted to CH4, C02, and ammonia
may be calculated from Equation (1) (Parkin ^nd Owen, 1986).
CnH,ObNQ * (n - (a/4) - (f>/2)+3(c/4)JWao - m
|(n/2) -(fl/8)+(6/4) +3(c/8)JC^+[(n/2) +(a/8) -(6/4)-Z{cfS)\CHA*cNH9
Using this stoichiometry, potential CH4 production volume from cellulose (CeH,0Os)
and hemicellulose (C6Hfl04) is 415 and 424 liters per dry kilogram (1/kg) at standard
temperature and pressure, respectively. These methane potentials represent maximum
CH4 production if 100 percent of the cellulose and hemicellulose were converted to CH4.
However, decomposition of these constituents in landfills is well below 100 percent for
several reasons, but mainly because (1) some cellulose and hemicellulose is surrounded by
6
-------
lignin or other recalcitrant materials (such as plastic) and, therefore, is not biologically
available; and (2) without active intervention, buried refuse is not evenly exposed to
moisture, microorganisms, and nutrients. Barlaz et al. (1989b) applied mass balances to
shredded refuse incubated in laboratory-scale lysimeters with leachate recycle. Cai bon
recoveries of 87 to 111 percent were obtained, where a perfect mass balance would give a
carbon recovery of 100 percent. Greater than 100 percent recoveries were obtained in
some cases due to sampling and analytical error. Mineralization of 71 percent of the
cellulose and 77 percent of the hemicellulose was measured in a container sampled after
111 days. Mass balances were useful for documenting the decomposition of specific
chemical constituents and demonstrating the relationship between cellulose and
hemicellulose decomposition and CH4 production.
Stoichiometry may also be used to estimate the CH4 potential remaining in a landfill
by sampling the refuse, performing the appropriate chemical analyses, and calculating the
CH4 potential. Ideally, the initial chemical composition and CH4 potential of the refuse
would be known, in which case comparing that initial CH4 potential with the potential at
the time of sampling would provide information on the fraction of the refuse that has been
degraded. Representative sampling of a full-scale sanitary landfill is not realistic.
Sampling size is limited to volumes that can be reasonably handled and reduced by
proven techniques. However, it is possible to obtain multiple samples at presumably
representative locations within a landfill to get an estimate of the range and extent of
decomposition.
Another technique for assessing the CH4 potential of refuse is the biochemical
methane potential (BMP) test (Shelton and Tiedje, 1984; Bogner, 1990). In the BMP test,
the anaerobic biodegradability of a small sample of refuse (6 to 10 g) is measured in a
small batch reactor [100 to 200 milliliter (ml)]. While the BMP represents an upper
bound of CH4 potential from refuse, it will be lower than the stoichiometric estimate
described above. BMP's also require representative sampling in landfills. A recent
application of the BMP test was presented by Wang et al. (1994).
Comparison of CH4 production data between field-scale landfills and laboratory
experiments is difficult because there are essentially no data in the open literature on
CH4 production rates in field-scale facilities. Interpretation of data from field-scale
landfills is complicated by questions regarding the mass of refuse responsible for
production of a measured volume of gas and the efficiency of gas collection. While
laboratory data are of higher quality due to the more closely controlled conditions, they
are not completely representative of the field. Also, data are not perfectly comparable in
that experimental conditions (e.g., moisture, particle size, temperature, etc.) are not
uniform between studies. In addition, most laboratory experiments were conducted to
explore techniques for enhancing CH4 production. The enhanced CH4 production rates
would not be expected at field-scale landfills unless certain enhancement techniques are
employed.
Total CH4 yields of 42 to 144 1/kg dry refuse have been repurled in laboratory tests
conducted with leachate recycling and neutralization (Barlaz et al., 1987; Barlaz, 1988;
Kinman, 1987; Ehew and Barlaz, 1994; and Buivid, 1981). These Btudies show significant
variation in CH4 production rate and CH4 yield. Some of the differences can be explained
7
-------
by differences in experimental design. For example, the data reported bv Barlaz et nl.
(1987) and Barlaz (1988) differ in reactor volume (100 vs. 2 1), temperature (25°C vs.
41°C), and the rate of leachate recycling. Also, Buivid (1981) used refuse with an
abnormally high paper content.
CH4 yields were measured in field-scale test cells as part of the Controlled Landfill
Project in Mountain View, California (Pacey, 1989). Total yields of 38.6 to 92.2 1 CH4 /dry
kg of refuse were measured after 1,597 days. However, mass balance data suggested that
significant volumes of CH4 were not measured in certain test cells. A number often used
by the LFG industry as an estimate of CH< production in field-scale landfills is 0.1 cufcic
feet CH4 per wet pound per year (ft3/wet lb-yr). Assuming refuBe buried at 20 percent
moisture and a 15-year period for gas production, this converts to an annual yield of 7.8 1
CFtydry kg-yr, a number comparable to some of the lower values reported in the
literature.
Even in landfills with venting systems, some of the CH4 is likely to escape from the
landfill through the final cover. The fraction released through the final cover will be a
function of the type of gas venting system in place and the type of cover. Probably not all
the CH4 that escapes from landfills is released to the atmosphere. Some may be
converted to C02 as it passes through the cover soil by aerobic methanotrophic bacteria.
CH4 oxidation has been documented in landfill cover soil studied under laboratory
conditions (Whalen et al., 1990). However, there are no data on the quantitative
significance of CH4 oxidation above field-scale landfills. Methane escaping through cracks
in a landfill cover most likely will not reside in the cover for a period sufficient to undergo
significant oxidation.
6
-------
METHODOLOGY
U.S. REGRESSION MODEL
The methodology used to estimate global CH4 emissions from waste in landfills and
open dumps is based on a simple regression model described under "Ratio Method," in ,
Appendix A of Doorn et al. (1994). As depicted in Figure 1, the model relates waste in
place to LFG flow data from 105 U.S. LFG utilization projects. To convert the LFG *
recovery flow rate [in cubic meter per minute (m3/min)j to a CH4 emission rate (in g/min)
a conversion factor (CF) was used [Equation (2)]:
CF* c* p • * 525,600 » 213*10® (2)
r y m3
where: p = LFG density (677 g/m3),
c = relative CH4 concentration in LFG (0.50 1/1),
r = average efficiency of the gas recovery systems (75 percent). Based
on expert judgement (Augenstein and Pacey, 1990),
o = oxidation factor (0.1); accounts for the CH4 fraction that does not
reach the atmosphere because it is oxidized while seeping out of the
landfill (Mancinelli and McKay, 1985), and
525,600 = a factor to convert from minutes to yoars.
CH4 emissions (Tg/yr) Y are then calculated using Equation (3).
Y «> CF*R*X, (3)
where: X = estimate of waste in plac^(Tg/yr), decomposing under anaerobic
conditions.
For sanitary landfills, which are considered to be completely anaerobic, X is equal to total
waste in place. Total U.S. CH4 emissions arc decreased to account for CH4 which is
currently recovered or flared YR. Landfill gas recovery and flaring is discussed in the
following sub-section. With R = 8.76*10 " m3/g min and CF = 213*108 Equation (3) may
be rewritten as:
Y - 1.07" 10"3Af- YB W
9
-------
LANDFILL GAS RECOVERY AND FLARING
Richards (1989) and Thorneloe (1992) estimate that worldwide there are about
270 sites in 20 countries where LFG is recovered. According to Thorneloe (1992),
approximately 1.2 Tg/yr CH4 was utilized in the United States and 0.5 Tg/yr was flared.
Gendebien et al. (1991) mentions a number of 174 European sites, producing
approximately 0.3 Tg/yr of CHV Germany and the United Kingdom are the biggest
contributors, with 98 and 61 recovery sites respectively. Outside of Europe, LFG is
utilized in Canada, Brazil, Chile, South Africa, Australia, India and a few other countries
(El Rayes and Edwards, 1991; Kessler, 1991; Lcci, 1988; Bateman, 1988; Hughan, 1991;
Bhide and Sundaresan, 1990; and Gendebien et al., 1991).
In regard to the CH< quantities burned in flares, very little information has been
retrieved. Most OECD countries have regulations that require installation of LFG
recovery systems, although, in Japan, it is only compulsory to provide vent pipes (Cossu,
1990a). Biogas collection is mandatory in Italy for MSW landfills (Cossu and Urbini,
1990). In how far these and other regulations pertaining to waste management are
obeyed is another topic. According to De Poli and Pasqualini (1991), there are 2,000
operating landfills in Italy of which only 480 have permits. Of these 480 landfills, 73
have LFG provisions: 12 utilization schemes and 61 flares. For Northern European
countries, observance of regulations may be better. In these countries landfills are
considered sanitary landfills and are equipped with liners, covers, and LFG recovery
installations. Depending on the efficiency of the gas collection systems, a significant part
of the LFG may be prevented from escaping to the atmosphere. For North European
Countries without specific LFG recovery data, it is assumed that 20 percent of the CH4
from landfills is either recovered or flared.
ESTIMATION OF COUNTRY-SPECIFIC WASTE QUANTITIES
For most countries, data on total waste in place decomposing under anaerobic
conditions (X in Equations 3 and 4) are not available and have to be developed from
annual waste generation rates. As the temporal variability of country-specific waste
generation rates is unknown, it is assumed that waste generation is steady state. (In the
section on uncertainties the validity of this assumption is discussed and the impact of this
assumption on total CH4 emissions is illustrated in a sensitivity analysis.) To obtain
waste mass X the annual waste generation rate M (Tg/yr) is multiplied by the CH<
generation time G (yr) which gives:
V- 1.87 »10-3 OM - Y„ (5)
G is the "life time" of a batch of waste during which it continues to produce CH<. G is
dopendent on climate and on waste composition (i.e. increases in temperature, moisture,
and food fraction will increase G), TVP»caHyi a G of 20 to 30 years (average 25) is
assumed to be reasonable for U.S. waste (Augenstein and Pacey, 1990; EMCON
Associates, 1982). For countries with a warmer climate, G might be considerably shorter,
10
-------
yet this will not affect the ultimate emission calculations since, in this methodology, G is
eliminated from consideration. This important consequence may be illustrated as follows.
If in a certain country, where waste decays rather rapidly, G were to be 12.5 instead of 25
years, then the emissions per waste mass (which is the emission factor CFR) will have to
be twice as high, hence the product stays unaltered. Assuming a G of 25 Equation (5)
may be written as:
Country-specific MSW generation data are available in the literature for most
industrialized and some developing countries. Information on MSW generation in
developing and Eastern European countries is more difficult to obtain and often anecdotal.
Most of the available data for developing countries are provided on a per capita basis for
only the larger cities. Therefore, the methodology to estimate total MSW for countries
with no national data distinguishes between urban and rural MSW. When national MSW
generation data were not available, urban MSW generation rates were combined with
population (United Nations, 1990} and urbanization data (Population Reference Bureau,
Inc., 1989) to determine the amount of MSW generated in urban centers of countries.
MSW in rural areas was estimated separately.
Rural MSW Generation Rates
For most OECD countries, the assumption was made that urban and rural per capita
MSW generation rates are equal. In these countries consumption habits, spending, and
availability of goods do not appear to differ between rural and urban locations. The same
assumption was made for (former communist) Eastern European countries because per
capita income and consumption supposedly did not vary for rural and urban citizens.
In general, few data on rural waste generation and management were found. United
Republic of Tanzania (1989) gives a number of 0.36 kg/cap/day for two distinctly rural
areas of the municipality of Dar es Salaam. One area is characterized as low income and
the other as low-to-medium income. El-Halwagi et al. (1988) and Mwiraria et al. (1991)
mention that in rural communities in Egypt and Uganda, most refuse is reused (fed to
animals) and the remaining waste is burned in open pits. Based on these papers, one
might assume that rural waste generation in theBe countries is minimal. On thei other
hand, Oluwande (1984) mentions that traditions in rural Nigeria dictate that refuse is
disposed of at distinct sites near the village.
Due to lack of data on other countries, the number from United Republic of Tanzania
(1989) is used for all other African countries, with the exception of Egypt and Uganda and
their immediate neighbors. The information from Oluwande (1984) on waste disposal %
traditions in rural Nigeria implies that refinement of rural waste numbers cannot only be
47*10"3Af - Y„,
(6)
where: Y
M
CH4 emissions (Tg/yr),
annual waste generation rate (Tg/yr),
CH4 emissions (Tg/yr),
11
-------
based on economical data, such as per capita disposable income, but must include
cultural data as well.
Erdin (1986) presents a waste generation rate of 0.47 kg/cap/day for rural Turkev,
which was also used for Iraq, Syria, Iran, Jordan, Portugal, and Greece. A refuse
generation rate of 0.2 kg/cap/day for "small cities with limited income," (Kessler, 1991)
was used for all Latin American countries and remaining Asian countries.
Commercial. Market, and Institutional Waste Generation Rates
Commercial and institutional waste includes waste from markets, parka, shops,
restaurants, hotels, offices, government buildings, military bases, and universities.
Because their composition is similar to that of residential waste (Maniatis and Vanhille,
1987; and Cointreau, 1984), commercial and institutional waste are usually classified as
MSW. Literature on developed countries is usually detained enough to assess which types
of waste are being discussed. For developing countries, the literature does not always
specify if commercial, institutional, or market waste is included in MSW or "refuse." It is,
therefore, necessary to have an understanding of nonresidential MSW generation rates in
developing countries.
For developing countries, Cointreau (1982) gives the following waste generation rates:
0,1 to 0.2 kg/cap/day for commercial refuse, and 0.05 to 0.2 kg/cap/day for street
sweepings, as well as for institutional refuse. Mwiraria et al. (1991) give generation rates
for market waste (0.3 kg/cap/day), commercial and industrial waste (0.1 kg/cap/day), and
street sweepings (0.1 kg/cap/day), for Kampala, Uganda. Mwiraria gives a household
generation rate of 0.15 to 0.6 kg/cap/day, depending on income. Adding the above
numbers by Mwiraria et al. give a total MSW generation rate for Kampala of 0.7 to
1.1 kg/cap/day. The lower number is comparable to many MSW generation rates for cities
in developing countries found in the literature wee Table 10 at the end of the report).
Therefore, it may be concluded that MSW or "refuse" generation rates in the literature
generally include commercial, market, and institutional waste.
It is important to note that the numbers in the paragraph above are for urban
populations only. No information is available on commercial, market, and institutional
waste in rural areas. Consequently, no attempt has been made to adjust for generation
rates for these types of waste for rural regions of developing countries. This is justified by
assuming that rural nonresidential waste generation rates are significantly lower than for
urban regions, because commercial establishments, universities, hotels, and governmental
departments are typically found in cities.
Total MSW Generation Rates
In Table 2, default, daily, per capita MSW generation rateB for urban and rural areas
are presented. Table 3 lists wapte generation rates in Tg/yr for larger countries, as well
as the references that were used. (Data for all countries are included in Table 10 at the
end of the report.)
12
-------
Total MSW generation ranged from 1.7 to 1.9 kg/cap/day for the United States and
Canada (U.S. EPA, 1992; El Rayes and Edwards, 1991). The MSW generation rates in
other OECD countries are approximately 1.2 kg/cap/day. For most of these countries, total
national yearly MSW generation was available. Generation rates were not used for the
United States, Canada and Australia because estimates of total waste-in-place in landfills
were available for these countries (U.S. EPA, 1988; Doom et al., 1994; El Rayes and
Edwards, 1991; Hughan, 1991). Information on the amount of MSW generated and
landfilled in the European countries that are not OECD members and the former Soviet
Union is very limited. Generation and urbanization data from the former Soviet Union
were allocated over the Commonwealth of Independent States by using population data.
(See Table 3 for references.)
For most Asian countries, estimates of MSW generation were at best identified for one
or two major cities, but not for the entire country. Urban waste generation estimates
ranged from 0.4 kg/cap/day for the Philippines to 1.0 kg/cap/day for Singapore, with an
average of 0.7 kg/cap/day. It is assumed that urban MSW generation rates for some
Arabian, oil exporting countries are considerably higher (2.0 kg/cap/day). A national MSW
generation estimate was available only for Japan. (See Table 3 for references.)
Few data were retrieved on MSW generation and management in Latin America and
the Caribbean Islands. Again, most of the available information is only for the larger cities.
The average per capita MSW generation rate for cities in Costa Rica, Mexico, Brazil,
Colombia, Chile, Paraguay, Peru, and Venezuela is estimated to be 0.7 kg/day. (See Table 3
for references.)
For African countries, several useful papers on MSW generation and disposal exist.
Average urban African MSW generation is approximately 0.7 kg/cap/day. For countries
with insufficient information, waste generation rjtes from neighboring countries were
extrapolated. (See Table 3 for references.)
TABLE 2. DEFAULT MSW GENERATION RATES
MSW GENERATION RATE
(kg/cap/day)
URBAN
RURAL
Latin America
0.6 • o.e
0.2
Africa
0.6 • 0.B
0.30
Asia (low Income)
0.3 ¦ 0.4
0.2
Asia (middle Income)
0.6 • 0.8
0.2
Asia (high income)
2.0
0.2
Most OECD countries
detB available same as urban
Spain, Portugal, Italy, Greece
0.6 * 0.85
0.3 • 0.S
Former communist countries
0.4 - 0.6
same as urban
13
-------
TABLE 3. WORLD MSW GENERATION RATES AND REFERENCES
1
MSW
COUNTRY
GENERATED
REFERENCES USED
(Tg/yr)
AFRICA
Algeria
5
Based on datB from neighboring countries
Cameroon
2
Cointreau, 1991
Egypt
4
El-Halwagl et al, 1988; El-Halwagl el al., 1986
Ethiopia
2
Based on data from neighboring countries
Ghana
2
HolmeB. 1984
Mall
1
Kaltwaeser, 1986
Morocco
4
Baeed on data Irom neighboring countries
Nigeria
16
Cointreau, 1982; Oluwande, 1984
Senegal
1
Cointreau, 1991
South Alrica
11
Carra and Cossu, 1990; Verrler, 1990
Sudan
3
Based on data Irom neighboring countries
Tanzania
2
United Republic of Tanzania, 1989
Tunisia
1
Cointreau, 1982
Uganda
1
Mwlraria, el al, 1991
Zaire
3
Based on data Irom neighboring countries
Other Alrica
23
Based on data from neighboring countries
Total Alrica
82 |
ASIA
Bangladesh
7
Ahmed, 1986; lohanl and Tanh, 1980
China
316
Oluwande, 1984; Xlanwenand Yanhua, 1991
Hong Kong
2
Cointreau, 1082
|
India
SB
Bhlde and Sundaresan, (990; Bhlde et al., 1990; Lohanl and Tanh, 1B80, United
Nations, 1989 '
Indonesia
22
Cointreau, 1S82; Sutanto ol al., 1986; Manlatls and Vanhllle, 1987
Iran
12
Based on data Irom neighboring countries
Japan
41
Bartone, 1990; Carra and Cossu, 1990; Cossu, 1990a
Malaysia
4
Holmes, 1984; United Nations, 1389
Nepal
1
Lohanl and Tanh, 1980
North Korea
5
Based on data from neighboring countries
Pakistan
9
Cointreau, 1982
Philippines
5
Cointreau, 1982; Diaz and Golueke, 1987; Holmes, 1984; United Nations, 1BB9
Saudi Arabia
0
Based on data from neighboring countries
Singapore
1
Cointreau, 19B2; United Nations, 19B9
South Korea
33
United Nations, 1989
Sri Lanka
2
Holmes, 1984; United Nations, 1989
Syria
3
Holmes, 1984
Taiwan
3
Mel-Chan, 1B88
Thailand
5
United Nations, 1980
Uzbekistan
4
Based on data Irom neighboring countries
Yemen
2
Diaz and Golueke, 19B7; Holmes, 19B4
Vietnam
14
Based on data from neighboring countries
Other Asia
25
Jased on data from neighboring countries
Total Asia
9B1
Note: Totals may nol squat sum of Individual numbers due to rounding.
14
-------
TABLE 3. WORLD MSW GENERATION RATES AND REFERENCES (continued)
MSW
COUNTRY
GENERATED
(T0/yr)
REFERENCES UJ ED
EUROPE
Austria
2
Lechner, 1990; Bartone & Haley, 1990; Bartone, 1990; Carra & Cossu, 1990
Bulgaria
2
Bartone and Haley, 1990
Denmark
4
Christensen, 1990; Bartone, 1990; Carra and Cosau, 1990
Finland
3
Ettala, 1f"C Carra and Cossu, 1990
France
50
Bartone, 1990; Carre and Cossu, 1990
Germany
60
Stegmann, 1990; Bartone, 1990; Carre end Cossu, 1990
Greece
2
Bartone, 1990
Hungary
3
Bartone and Haley, 1990
Ireland
1
Bartone, 1990
Italy
17
Cossu and Urblni, 1990; Bartone, 1990; Carra and Cossu, 1990
Netherlands
9
Belter, 1990; Bartone, 1990; Carra and Cossu, 1990; Scheepers, 1991
Norway
2
Bartone, 1990
Poland
S
Bartone and Haley, 1990
Portugal
3
Bartone and Haley, 1990
Romania
5
Bartone and Haley, 1990
Spain
9
Bartone, 1990
Sweden
2
Bartone, 1990; CBrra and Cossu, 1990; Nllason, 1990
Swllzerland
3
Gandolla, 1990. Bartone, 1990; Carra and Cossu, 1990
Turkey
12
Erdln, 1986; Bartone and Haley, 1990
United Kingdom
37
Cossu, 1990b, Bartone, i1990; Carra and Cosau, 1990
Russia
32
Peterson and Perimullej, 1989
Other Europe
17
Based on data from neighboring countries
Total Europe j
293
NORTH and LATIN AMERICA and the CARIBBEAN
Canada
21
El Reyes and Edwards, 1991; Bartone, 1990; Carra and Cossu, 1990
Argentina
8
Based on data Irom neighboring countries
Brazil
31
Kessler, 1991; Bartone el al., 1991
Colombia
5
Cointreau, 1982
Mexico
?0
Based on data Irom neighboring countries
Paraguay
1
Diaz and Golueke, 1987
Peru
4
Based on data Irom neighboring countries
Venezuela
4
Bartone et al., 1991
Other America
16
Based on data from neighboring countries
Total ex United States
110
United States (1990)
263
Doom et al, 1994, U.S. EPA, 1992
AUSTRALIA and OCEANIA
Australia
12
Bateman, 1988; Hughan, 1991
New Zealand
4
Lassey et al., 1992
Total Oceania
16
TOTAL GLOBAL
1,346
Note: Totals may not equal sum of Individual numbers due to rounding.
16
-------
ADAPTATION OF U.S. MODEL FOR OTHER COUNTRIES
To adapt Equation (6) for other countries, three modifications must be made. The
first modification concerns the fact that waste management practices in countries may
differ considerably from the U.S. practice of sanitary landfilling. The second modification
addresses the degree of anaerobic decomposition versus aerobic decomposition of the
landfilled/dumped waste. The third adjustment addresses the relationship between
composition and CH4 potential of waste in place.
Country-specific Waste Management Practices
Data in the literature are limited to MSW in general, or specific types of MSW, such
as commercial or institutional waste. Fo» some countries, data on other types of waste
were found. In these countries, significant amounts of industrial waste, demolition and
construction debris, and other wastes are also being landfilled. The quantities of these
wastes that also may be landfilled, appear to be considerable. Nevertheless, most of these
wastes have a low CH4 potential compared to MSW. In this report, estimated waste
quantities do not include industrial waste and construction and demolition debris.
In developed countries, not all waste that is generated will actually be landfilled.
Parts may be incinerated, composted, or recycled. For most OECD countries, ample data
are available to determine the fraction of MSW, L, which is disposed of in landfills or
dumps. According to Bartone and Haley (1990)JEastern European countries practice
little or no recycling or incineration. Only in PcUand a considerable amount of MSW is
recycled (17 percent). In Bulgaria, Hungary, and Romania more than 95 percent is
landfilled or dumped. It is assumed that Eastern European, (former) communist
countries have reasonably effective collection services. Wealthy Middle Eastern oil
producing countries may be expected to have relatively well functioning collection
systems. Also, countries that are popular tourist resorts may have reasonably well
organized waste collection systems.
Many papers describe studies conducted to develop more adequate waste management
methods in certain urban areas. These studies are concerned with quantifying the waste
that should be disposed. This quantity may be lesB than the waste that is generated
because part of the waste may be reused (fed to animals) or burned within the household.
Exclusion of this fraction might seem justified for the purpose of this report (i.e.,
developing methane estimates from dumped or landfilled waste). However, due to
inadequate municipal collection services, people may also be forced to dispose of the
remaining waste themselves (e.g., in dumps on vacant city lots or in smaller pits).
Therefore, waste that is not collected was not excluded from the estimate of MSW
generated.
Most developing countries have inadequate collection services. Also, much of the
garbage is scavenged before it is collected, especially paper, textiles, and metal products.
Refuse may also be burned for heating or cooking purposes, fed to domestic animals,
dumped in rivers or other bodies of water, swept out onto the street, or buried. In
addition, garbage is often burned at the dump to reduce the volume. This practice
16
-------
decreases the amount of material available for anaerobic decomposition. Finally, the open
dumps are often scavenged again by humans and animals.
In Table 4, default values for L are given for each region of the world. L values are
based on expert judgement. The uncertainty created by the lack of data to determine L
for developing countries is relatively small since most CH4 from solid waste ia produced in
OECD countries.
TABLE 4. DEFAULT FRACTIONS lANDFILLED OR DUMPED
DEFAULT FRACTIONS
LANDFILLED OR DUMPED
(«.)'
Latin America
O
O
^1
Africa
0.4
Asia (high Income)'
CO
o
o
Asia (lower Income)
0.3-06
OECD countries
data available
Other Europe
I 0,8-1
Former USSR
' 0.B - 1
Notes: All values are bf.sed on engineering judgement.
1 L = MSW generated that Is not being Incinerated, composted,
recycled, scavenged, ted to animals, or otherwise deferred
from dumping or landtllllng.
2 Hong Kong, Singapore, Israel, Saudi Arabia, Oman,
United Arab Emirates.
Degree of Anaerobic Decomposition in Landfills and Open Dumps
As discussed in the Introduction, earlier studies by AEERL were aimed at
establishing correlations between LFG flow rates, waste in place, and certain other
variables. Taking into account that no correlation has been found between climate and
gas flow, the CH4 emission per waste mass will only depend on the parameters used in CF
[Equation 2)1 and on qualitative waste data.
For U.S. landfills, which are considered to be completely anaerobic, X is equal to total
waste in place. In open dumpB, a significant portion of the waBte may be decomposing
aerobically, due to infiltration of air into the dump. Not only may the dumps be small,
they may also be shallow, resulting in an increased area/volume ratio.
17
-------
To account for the influence of air within a dump, a country-specific factor F is
introduced to express the average degree to which anaerobic decomposition takes place
within dumps (Equation (7)].
F=0.3 + y (7)
F varies between 0.3 for small open dumps and 0.8 for large dumps; for sanitary landfills
F is set at 1.' U is the fraction of the population considered urban for the country in
question The underlying assumption is that for highly urbnnized countries, collected
waste would go to a limited number of large dumps which would likely be largely (e.g.,
80 percent) anaerobic due to their size. In countries with little urbanization and, hence,
many small rural communities, waste that is collected would be disposed of in small
dumps or piles which are assumed to be only partially anaerobic (e.g., 40 percent).
Part of the waste in open dumps is likely to be submerged in water (Pacey, 1994),
because open dumps do not have liners, lenchnte drainage systems, and top covers. This
type of water is different from moisture or watqb contained within the refuse, as it will
impede aerobic as well as anaerobic decomposition. The degree in which waste in place in
dumps will be submerged in water will depend on the amount of precipitation,
evaporation, and local morphology and topography (ground water infiltration and seepage
out of the dump).
Expansion of the methodology to account for all these factors, many of which are site-
specific, is beyond the scope of this study. Nevertheless, with the possible exception of
highly arid countries, no "dump countries" (i.e., countries that do not practice sanitary
landfills) may be excluded beforehand from having submerging water in their dumps.
Consequently, it appears reasonable to adjust for the loss of waste that is submerged in
dumps by using a constant that is not country-specific. As such, Equation (7) (which
applies only to "dump countries") may be used to account for the described phenomenon.
The constant in Equation (7) has been adjusted downward to account for water that has
submerged waste in open dumps.
Waste Composition Expressed in Methane Potential
For many countries, some data on MSW composition are available in the literature.
(Most references listed in Table 3 also have composition data.) However, these data
usually apply to one or two cities only. Due to lack of rural waste composition data,
urban composition data were adopted for the entire country. For countries without waste
composition data, data from neighboring or otherwise comparable countries were used. In
Table 5, waste composition is expressed in CH4 p* ontial P by making use of data from
1 In Japan approximately 53 percent or actual landfill sitoB, although Banitary, may bo considered
somi-aerobic. Those landfills are equipped .with large scale von ting systems that also serve as leachato
collectors. Therefore, F a 0.75 Tor Japan. (Leo et at., 1694.)
18
-------
waste decomposition tests (Barlaz, 1994). Table 10 at the back of the report includes
country-specific waste composition data which were used in the calculations for P.
'ilie determination of P for U.S. waste is illustrated in the following example:
Averaged over 25 years, U.S. MSW diseased In landfills contains 10 percent food waste, 20
percent yard trimmings, 32 percent paper and paperboard, and 38 percent inerls (U.S. EPA,
1992). Therefore, P = 10% x 69 + 20% x 38 + 32% x 128 o 57 ml CH^/wet g burled waste.
TABLE 5. MEASURED CH4 POTENTIALS FOR DRY AND WET WASTES
MEASURED CH4
WATER
CH,
COMPONENT
POTENTIAL
CONTENT
POTENTIAL
(ml/dry g)
(%)
(ml/wet g)
food
297
70
89
assumed average yard waste
f6
50
38
grass
144.4 I
leaves
30.8
branches
61.3
assumed average pa per waste
126
0
126
newspaper
75.2
boxes
151.1
office paper
182.8
coaled paper
84.4
other waste
0
As mentioned in the introduction, the emission factor used in this report is based on
field measurements of CH4 from U.S. waste. Compared to U.S. waste, waste in other
countries will probably have a different composition and CH< potential. In the
methodology, this difference is accounted for hy relating the country-specific CH4 potential
to the U.S. potential. By adjusting for L, F, and the relative CH< potential, the equati-£-* 47*10-**M - Y„
(8)
us
19
-------
where: Y = CH« emissions (Tg/yr),
L = fraction of MSW disposed of in landfills or dumps (0.4£L£l),
F = degree to which landfills or dumps may be considered anaerobic
(OZFZl),
P = CH4 potential (ml/g),
Pus = U.S. CH, potential = 57 ml/g,
M = waste generation rate (Tg/yr),
Yr = CH< recovered or flared (Tg/yr).
Equation (8) may be rewritten as:
y- 0.62 - Yr
Global estimates are obtained by summing coiintry-specific emissions.
20
-------
ESTIMATE OF GLOBAL METHANE EMISSIONS FROM LANDFILLS
AND OPEN DUMPS
Table 6 gives country-specific CH4 emission estimates from landfills and open dumps.
Estimates per continent are presented in Figure 2. For the United States and large
European contributors, estimates are based on 1990 data. For other countries, estimates
are based on literature that was published after 1980. Estimates of global landfill CH<
emissions range from 19 to 40 Tg/yr, with a midpoint of 30 Tg/yr. The United States is
the biggest contributor, currently accounting for over 40 percent of world emissions.2
High waste generation rates, population, limited recycling and incineration, and the
practice of sanitary landfilling account for the high U.S. estimates.
Uncertainties in this global estimate are expressed by giving lower- and upper-bound
values. The standard deviation in the emission/actor, developed from the LFG flow data
is 9 percent (Doom et a!., 1994). Approximate fp percent confidence intervals are
obtained by adding plus/minus two standard deviations to the estimate. Because of the
limited data upon which parameters were based to estimate the variables (p, o, r, c, G,
M, Yff, L,F,Pt and Pvs ) the errors associated with the assumptions were not quantified.
For this analysis, it was assumed that the cumulative error associated with the
parameters would be at least as high as that associated with the emission factor
developed from the LFG flow data (i.e. plus/minus 18 percent). Therefore, ranges are
expressed by adding plus/minus 36 percent to the emissions estimate, although this error
estimate is based on engineering judgement rather than rigorous statistics.
I
The now rule for tho control of nonmothono LFG, proposed under the Clean Air Act Amondmonts or
1990, in expoctod to have a mqjor impact on reducing landfill CH, emission!) from both now and
existing MSW landfills in the United States and Is estimated to reduce CH4 omissionB by 6 to 7 Tg
(Federal Register, 1991; and U.S. EPA, 1991).
-------
TABLE 6. WORLD METHANE EMISSIONS FROM LANDFILLS AND OPEN DUMPS
POPULATION
TOTAL EMISSIONS
Lower Bound
Midpoint
Upper Bound
(million)
(Tfl/yr)
(Tg/yr)
(Tg/yr)
Africa
South Africa
26
0.2
0.3
0.4
Nigeria
102
0.1
0.2
0.2
Egypt
51
0.0
0.1
0.1
Other Africa
391
0.3
0.5
07
Total Africa
570
0.7
1.0
1.4
Aala
f
China
1,032
f 1.8
2.6
3.8
India
685
0.3
0.4
0.6
South Korea
43
0.3
0.4
06
Japan
117
0.3
0.4
0.5
Indonesia
170
0.2
0.3
0.5
Other Asia
678
1.0
1.5
2.1
Tola) Asia
2,725
3.6
5.B
8.0
Europe
1.8
Germany
76
0.8
1.3
United Kingdom
56
0.6
1.2
1.7
France
53
0.6
1.0
1.4
RusbIb
145
0.9
0.8
1.1
Italy
58
0.3
0.5
0.7
Ukraine
51
0.2
0.3
0.4
Turkey
51
0.2
0.3
04
Poland
38
0.1
0.2
0.3
Other Europe
228
1.0
1.5
2.1
Total Europe
749
4.6
7.1
9.7
North and Latin America
and the Caribbean
17
United States
227
8
13
Canada
24
o.e
o.e
1.3
Brazil
119
0.4
0.6
0.8
Mexico
81
0.2
0.3
0.4
Other America
187
0.4
0.6
0.8
Total America ex. United
410
1.5
2.4
3.2
States
Oceania
1.0
Auatralla
15
0.5
0.7
New Zealand
3
0.1
0.1
0.1
Total Oeear*1.'
16
0.5
0.0
1.1
4,669
19
30
40
22
-------
OCEANIA (2%)
EUROPE
\ (23%)
AFRICA W
(3%) 1
AMERICA EX. U.S.
(8%)
UNITED STATES (42%)
Figure 2. Global methane emissions from landfills and open dumps by
continent.
Several countries, including New Zealand, Australia, Canada, and the United
Kingdom, have produced their own estimates for CH4 emissions from MSW landfills.
Although these estimates may be more accurate than the ones developed under this
study, they have not been included in Table 6 as this would impede comparison of the
different methodologies that were used. Instead, Table 7 compares AEERL's country-
specific estimates for CH4 emissions from this source category with estimates from other
studies.
The Canadian estimate in Table 7 is based on the Scholl Canyon model, which is a
waste decomposition differential equation. Comparison of this method with the AEERL
method is of particular interest, since Canada and the United States are economically and
culturally similar. In Canada 90 percent of generated MSW is landfilled, whereas, in the
United States 70 percent is landfilled. Also, the MSW generation rate is slightly higher
in the United States then in Canada (2.0 vs 1.8 kg/cap/day). The United States has
9.5 times the population of Canada (227 million versus 24 million). Upscaling the
Canadian CH4 emission estimate and adjusting for the aforementioned differences gives a
number of 11 Tg/yr with lower and upper bound values of 7 and 16 Tg/yr. This number is
analogous to the U.S. AEERL estimate of 13 Tg/yr with lower and upper bound values of
8 and 17 Tg/yr.
23
-------
For the United Kingdom a similar comparison may be made. The United Kingdom
landfills 90 percent of its generated MSW. The United Kingdom MSW generation rate is
1.6 kg/cap/day and the population is 56 million. Upscaling the United Kingdom estimate
and acUusting for the differences gives a CH4 emission estimate of 8 Tg/yr. This number
is the same as the lower bound of the AEERL estimate. It should be pointed out that
differences in the generation and disposal of commercial and other nonresidential MSW
between the two countries are not accounted for.
TABLE 7. COMPARISON OF DIFFERENT COUNTRY-SPECIFIC METHANE EMISSIONS
FROM LANDFILLS AND OPEN DUMPS
COUNTRY
AEERL STUDY
OTHER STUDY
(all units In
Tg/yO
Lower
Bound
Mid-
point
Upper
Bound
Lower
Bound
Mid-
point
Upper
Bound
Model
Reference
Australia
0.5
0.7
1.0
0.43
0.6|
0.91
Blngemer &
Crutzen
(1988)
Hughan, 1991
New Zealand
0.1
0.1
0.1
0.19
0.27
0.49
Royds Garden
(1969)
Lassey et al., 1992
0.11
not
given
0.19
HolHnger & Hunt
(1987)
0.19
0.29
0.49
Blngemer &
Crutzen
(1990)
United
Kingdom
0.8
1.2
1.7
1.3
2
2.7
Aumftnler el al.,
1993
Canada
0.6
0.9
1.3
0.9
1.4
1.9
Scholl Canyon
(1991)
Et Rayes and
Edwards, 1991
United States
6
13
17
15
23
31
Blngemer &
Crutzen
(1987)
IPCC, 1992
3
6
e
Scholl Canyon
(1990)
Augensteln,
1990
8
10
12
LFG Recovery
Regression
(1990)
U.S. EPA, 1993
Notes: If not given by the authors, 'Other Study* lower and upper bound estimate values are * 36%.
24
-------
TRENDS
The potential control of CH4 emissions from MSW landfills has been targeted by the
United States and other countries as part of greenhouse gas reduction programs designed
to meet the goals of treaties signed at the United Nations Conference on Environment and
Development (UNCED) held in 1992. For example, the United States is scheduled to
promulgate Clean Air Act regulations for municipal solid waste landfills by the spring of
1995. This rule is estimated to result in a CH< emissions reduction of 5 to 7 Tg/yr by
2000.
In general, the waste generated by developing countries has been projected to
increase over the next several decades. This trend can be attributed to projections of
higher population increases in developing countries and not to increased per-capita waste
generation. Recently, declining economic conditions have resulted in reduced waste
generation rates in Caracas, Venezuela; Mexico City, Mexico; and Buenos Aires,
Argentina (Bartone et al. 1991). Despite efforts toward source reduction and recycling,
per-capita waste generation is expected to increase in the United States (U.S. EPA, 1992)
and to a lesser degree in other industrialized countries.
As anaerobic decomposition of waste is a process that may take up to 25 years or
longer, changes in activity data, such as waste disposal rates, will have a delayed effect
on CH, emissions from this source category. Trends in global waste management and
their impacts on CH< release are discussed below. Table S presents a quantitative
summary of the effect of a number of trends on global CH4 emissions.
DEVELOPING COUNTRIES
For developing countries throughout the world several general trends and factors can
be outlined that will influence solid waste generation, disposal, and thus CH4 emissions.
These trends and factors are:
• Populations in many developing countries continue to increase rapidly;
• There is a major migration toward cities, resulting in rapid urban growth;
• Most of the uTban centers have a poor infrastructure;
• Economical growth has dwindled for a number of countries;
• Often, there is a bustling, unofficial recycling industry (Diaz and Golueke, 1987);
• In many cities the solid waste problem has reached unacceptable and intolerable
proportions (Oluwande, 1984; Diaz and Golueke, 1987); and
• In the last few years, people have become more aware of the need to implement
solid waste management programs (United Republic of Tanzania, 1989; El-
Halwagi et al., 1988).
25
-------
TABLE 8. EFFECT OF TRENOS ON GLOBAL METHANE EMISSIONS FROM LANDFILLS
AND OPEN DUMPS
% CHANGE IN
% CHANGE IN
TREND
RESULTING IN:
ACTIVITY
GLOBAL CH,
PARAMETER
EMISSIONS (V)
DEVELOPING COUNTRIES
Declining economic conditions
Declining waste generallo
%
M: 10
Rapid population growlh'
Increasing waste generation
Population: >2.5
(per year over
previous 10 years)
+5
Urbanization
More city waste
U: +10
+2
Improving waste management
More waste to open dumps or
landfills
L: +10
+3
DEVELOPED COUNTRIES
European countries upgrade
all dumps to sanitary landlills
Increased methane emissions
F = 1
+6
Active recycling, Incineration,
and composting programs
Decreasing waste disposal at
landfills
L: -10
P: -10
(L,P combined)
Active LFG recovery'
Decreased methane emissions
+10
-2
Active LFG recovery'
Decreased methane emissions
+20
Active LFG recovery4
Decreased methane emissions
+50
-4
Active LFG recovery"
Decreased methane emissions
+50
-25
Legend: M » annual waste generation rate.
U d degree ol urbanization.
L » MSW fraction that Is dumped/landllllod.
P » CH, potential.
Notes: 1 Assume 2.5 percent annual Increase over 10 years ¦ 28%. Peoples Republic of China excluded.
2 Assume 10% Increase In LFG recovery activity for countries that already recover LFG. Assume 10% of CH4
emitted will be recovered in other countries. Numbers do not Include anticipated reductions resulting Irom new
U.S. landfill rule.
3 Same as Note 3, with 20% recovery activity.
4 Assume 50 percent reduction in CH, emissions In countries with sanitary landlills (Northern Europe, Canada,
United States, Japan, Australia, and New Zealand). This Is equal lo the estimated level of reduction that is
anticipated under the new landlill rule. Numbers do not Include anticipated reductions resulting from new U.S.
landfill rule.
5 Same as Note 4, Including anticipated reductions Irom new U.S. landlill rule.
Since the per-capita waste generation rate in developing countries is relatively low
and a large part of the food and paper waste is scavenged, population growth in these
countries will have a subdued eiTect on the global landfill CH4 budget: a 2.5 percent
population increase over 10 yearB (total of 28 percent) would, over time, result in an CH4
emissions increase of 5 percent. In the same manner, a 10 percent increase in
-------
urbanization in developing countries would result in an CH4 emissions increase of
2 percent (Table 8).
While absorbing considerable fractions of city budgets, waste management systems
are often inefficient (Cointreau, 1984). The faulty infrastructure in many cities makes
efficient waste collection very difficult. Often streets are too narrow for vehicles larger
than a donkey or handcart. Waste transportation must (in part) rely on mechanized
equipment. However, for many areas, waste collection has been stalled due to inadequate
equipment maintenance, resulting from a lack of know-how and spare parts. Sometimes
consulting firms and other Western organizations have tried to implement waste
management techniques suitable to Western cities in developing countries (Betts, 1984).
Nowadays, there appears to be a trend toward solutions that are tailored more toward the
specific needs of these cities and their inhabitants. Given the urgency of the situation,
and options for efficiency improvement, more practical solutions are likely to be
implemented, which would increase the amount of collected waste. Since, landfilling is
the most practical and usually the cheapest solution (Betts, 1984), the potential for CH4
generation would increase. This increase, expressed in CH4 emissions would be relatively
small: 10 percent more waste to dumps or landfills, would eventually increase global CH4
emissions from landfills and open dumps by 3 percent (Table 8).
Some Asian countries are upgrading their collection methods by introducing
compactor trucks and covered containers. These changes could serve to decrease the
amount of scavenging and increase the amount of MSW that is dumped. Economic
constraints, in tandem with a history of slow MSW management development, indicate
that the use of sanitary landfills will not increase markedly in the near future for most of
Asia. In China, the largest Asian LFG producer, the annual amount of refuse that is
discharged has increased by 10 percent between 1987 and 1989. This extraordinarily high
growth rate was in part due to the switch from coal to natural gas heating in homes. Gas
furnaces do not allow for the addition of domestic waste. Instead, this waste now has to
be discarded as MSW resulting in an increase in carbon content. Most likely, the focus of
China's waste management will be on landfilling. With the increasing carbon contents,
LFG utilization will become more attractive and may be encouraged (Xianwen and
Yanhua, 1991).
In Africa's foreseeable future, the only MSW management methods reported to hold
promise for expanded and successful application are recycling, composting, or possibly
biogas recovery if markets and appropriate technologies can be developed to support these
systems (Cointreau, 1982; Betts, 1984; Oluwande, 1984; Vogler, 1984; and El-Halwagi et
al.f 1988). Furthermore, El-Halwagi et al. (1988) report that Egypt is constructing its
first sanitary landfill with a capacity of 1,000 tonnes per day. Much of the recyclable
material in the MSW stream ia currently being recovered, at least when comparing the
amount of material recycled in low-income countries with that of middle-income and
developed nations. However, because the recycling efficiency is low, recyclable materials
are still available in the waste streams, and because wages are low in the developing
countries, further recycling may be a viable option (Wright et al., 1988).
In the future, Brazil hopes to build recycling and composting plants, and sanitary
landfills. Mexico also hopes to increase its number of sanitary landfills (Kessler, 1991 and
27
-------
Richards, 1988). Few LFG recovery sites are currently operating in Brazil, Chile, and
Mexico, although there seems to be some interest in increasing the number of such sites
in Brazil (Kessler, 1991; and Richards, 1988).
DEVELOPED COUNTRIES
In densely populated countries, siting of new landfills is becoming increasingly
difficult. Yet, waste generation per capita is still on the rise. To resolve this dilemma,
some countries, including the Netherlands, Germany, and Denmark, have started
vigorous programs to increase the share of MSW handled by recycling, composting,
incineration and other methods. These programs have been successful in diverting
certain waste streams away from landfills. However, alternative MSW management
technologies arc not always advanced enough to recycle many types of waste. Also,
markets for the newly created, secondary raw materials need to be developed. Therefore,
in these countries Iandfilling will remain necessary, at least in the near future
(Stegmann, 1990). In addition, landfills will continue to be necessary to dispose of
incinerator ash and other nonrecyclable products. Of course the CH4 potential of
incinerator ash is essentially zero.
Landfilling is the predominant MSW management method in both the United States
and Canada. Although, there is a trend in both countries toward more recycling, more
incineration, and less Iandfilling, absolute MSW generation is projected to continue to
grow (U.S. EPA, 1992; U.S. EPA, 19ft8; El Rayes and Edwards, 1991; and Alter, 1991),
Until the end of the century, it is not expected that the carbon content in MSW will differ
considerably from current levels, (U.S. EPA, 1992). Based on this information and U.S.
EPA (1992) and Willumsen (1990), it can be assumed that the current rate of LFG
generation will continue for several more decades and reductions in emissions may be
expected only from increased LFG recovery, as discussed below.
If recycling, incineration, and composting efforts in developed countries are
increased by 10 percent, this would eventually result in a reduction of annual global CH4
emissions from landfills and open dumps of 7 percent (Table 8). This relatively large
reduction is due to three reasons: (1) developed countries account for 70 percent of all CH<
emitted; (2) paper recycling and composting reduce the waste quantity that has to be
landfilled; and (3) paper recycling and especially composting reduce the overall CH<
potential of the remaining waste.
Sanitary landfills or open dumps are used almost exclusively for MSW management
in Greece, Hungary, Portugal, Poland, Romania, Bulgaria, former Yugoslavia, and the
former Soviet Union (Bartone and Haley, 1990; ind Curi, 1988). The Polish Government
issued guidelines for landfill design and operation in January 1993 along Western
European lines. There has been little progress towards their general adoption however.
Russia hopes to establish an effective recycling program and has begun construction of a
sanitary landfill near Moscow. At the present time, no LFG recover sites were identified
in the aforementioned countries. A U.S. company, Natural Power is negotiating a gas
recovery contract with a landfill in Kiev in the Ukraine. This site has 9 million tons of
28
-------
waste. The gas is to be used to generate electricity for Kiev (Thorneloe, 1992), If this
project proves successful, additional projects may be initiated.
Table 8 includes a sensitivity analysis to illustrate the long term effect that would
take place if all European countries (including Russia, Latvia, Lithuania, Estonia, and
Bylorussia) would be using sanitary landfills, instead of in open dumps for waste disposal.
In this scenario, leaving all other parameters unaltered, and assuming no LFG recovery,
global CH4 emissions from this source category would increase by 6 percent.
Table 8 illustrates the effect of increased LFG recovery on global CH4 emissions from
landfills, The amounts of CH< emitted to the atmosphere will decrease as more is
controlled through flaring or utilization (Thorneloe, 1994; and Bonomo and Higginson,
1988). Several countries are tightening regulations to control LFG emissions and are *
actively encouraging LFG utilization. The Netherlands may triple its number of LFG
utilization schemes over the next few years (Scheepers, 1993). Landfills in the United
States are currently recovering or flaring about 1.7 Tg of CH4. The new rule for the
control of nonmethane LFG, proposed under the Clean Air Act Amendments of 1990, is
expected to have a major impact on reducing landfill CH4 emissions from both new and
existing MSW landfills in the United States and is estimated to reduce CH4 emissions by
5 to 7 Tg (Federal Register, 1991; and U.S. EPA, 1991). A doubling of landfill gas
recovery efforts in developed countries, combined with the impact of the new landfill rule
in the United States will lead to a reduction of global CH4 emissions from landfills and
open dumps by 25 percent.
29
-------
UNCERTAINTIES
UNCERTAINTIES ASSOCIATED WITH THE U.S. REGRESSION MODEL
Generation Time
The generation time G is the "life time' of a batch of waste during which it produces
CH4. The U S methodology does not explicitly consider G, because the regression model is
developed from data from LFG recovery projects at landfills which are assumed to have
waste of different ages. Therefore, the regression model implicitly accounts for G and
differences in waste age. However, this is true only if the age distribution of waste in all
U.S. landfills is the same as the age distribution of the U.S. landfill population used to
develop the regression model.
Because G is eliminated from the equation used to estimate CH4 emissions from
landfills and open dumps for countries other than the United States the uncertainty in
the emissions estimates is not affected by uncertainties in G. (See the discussion on page
10 and 11 in the Methodology section.)
Mass of waste in place
The mass of waste in place in a landfill is a critical parameter for estimation of the
emission factor. In the United States refuse mass data are gathered by site operators and
are not always properly documented. If site-specific data are available, refuse mass can
be calculated by several different methods. At a few sites, the trucks are weighed at the
gates. In most cases, however, the operators keep count of the number of trucks and
estimate the load, which is essentially a volumetric determination, requiring the use of a
density value. The density of landfilled refuse in the United States has been estimated to
range from 500 to 1,300 lbs/yard'1 depending on characteristics such as compaction and
moisture content.
IMtethgne oxidation
Not all CH< produced in a landfill would be emitted to the air. CH< oxidation has
been documented in landfill cover soil studied under laboratory conditions (Whalen et al.,
1990). However, there are no data on the quantitative significance of CH4 oxidation for
landfills. CH4 escaping through cracks in a landfill cover most likely will not reside in the
cover for a period sufficient to undergo significant oxidation. On the other hand CH4
oxidation in undisturbed soil under summer temperatures (daily maximum of 100'F
(38°C)1 may be significant. A study in the United Kingdom reported an upper-bound of
value for landfill CH4 oxidation of 40 to 50 percent (Kashinkunti, et al., 1993; Aumdnier,
et al., 1993). For this report, assessment cf the amount of CH< that may be oxidized on
its way out of the landfill (i.e., 10 percent) is based on expert judgement. Open dumps, %
which have no soil cover, may release CH< without oxidation. In this report, no attempt
has been made to adjust for the absence of this layer.
30
-------
As Equations (2) and (3) on page 9 indicate, there is a linear function between "1- o"
(i.e. the amount of CH« that is not oxidized) and global CH< emissions estimates from
landfills and open dumps Y. For instance, if oxidation were 20 percent, instead of 10
percent, global CH< emissions from this source category would be 29 Tg/yr, with lower-
and upper-bound values of 19 aod 41 Tg/yr.
Recovery efficiency of LFG projects
The recovery efficiency of LFG projects is thought to be highest when the projects are
undertaken to comply with regulatory programs; however, this cannot be assumed in all
cases. The overall recovery efficiency is typically affected by well spacing and the
permeability of the cover layer. The only published estimate of pas recovery efficiency is
based on expert judgements and gives a most probable value of 75 percent with lower and
upper bounds of 50 to 90 percent (Augenstein and Pacey, 1990).
To adjust for the recovery efficiency r of LFG collection systems, the gus flow is
multiplied by the reciprocal value of r (Equation 2). Since rSl, variations in r will be
magnified; for instance, if r were 0.675 (10 percent smaller than 0.75), this would result in
an increase in CF and thus, in total global CH4 emissions from this source category of
15 percent. Therefore, uncertainty in r may contribute significantly to uncertainties in
global CH4 emissions from this source category.
UNCERTAINTIES IN WASTE GENERATION ESTIMATES
Reliable waste in place estimates exist for only a few countries. For other countries
waste generation rates combined with waste management information were used. Local
waste generation data are usually readily available, however, they typically apply only to
the year the study was conducted and to a certain city or region. Extrapolation of these
data to national levels may be a source of considerable uncertainty. Fortunately, the
countries that are expected to produce the moat waste also have the most extensive waste
generation, composition and disposal data. j
As mentioned in the Trends section, yearly waste generated by developing, as well as
developed, countries has been projected to increase over the next several decades. For
developing countries thia trend can be attributed to projections of higher population
increases and not to increased per-capita waste generation, which has, in fact, declined for
some countries. For some developed countries increasing waste generation rates are
offset partially or completely by increased recycling, incineration, and composting efforts.
Unfortunately, for most countries, except the United States, no information exists on
historical variations in national waste generation rates. Therefore, in this report waste
generation is assumed to be steady state. Waste generation rateB that were different in
the past from current rates will affect country-specific CH4 emissions estimates.
To assess the sensitivity of global CH< emissions from this source category to an
overestimation of waste generation rateB, changes in waste disposal rates (i.e., generation
minus recycling, incineration, composting, and scavenging) have to be projected
backwards over a period that represents the time in which most CH< would have taken
31
-------
place. Although CH4 generation time G may be as long as 30 years for temperate
climates, most CH4 may be generated within a shorter time frame, especially in countries
with a (sub-)tropical climate. For the purpose of this sensitivity analysis, it is assumed
that all CH4 is generated within a 15-year time frame. Also, it is assumed here that the
CH4 generation rate over this period is steady state (i.e., all waste that is less than
16 years old generates CH4 at the same rate).
For the purpose of conducting this sensitivity analysis, it is assumed that waste
generation rates in developed and developing countries are growing by 2.5 percent per
year, except for the United States In the United States the amount of waste that has
been landfilled over the last decade has not changed significantly (U.S. EPA, 1992),
therefore, U.S. rates are considered steady state. Table 9 presents the results of this
sensitivity analysis. A 2.5 percent (United States = 0 percent) increase in annual national
waste generates over the preceding 15 years will result in an overestimation of CH4
emissions by 9 percent.
For developing countries, the literature does not always specify the type of MSW that
is discussed. Table 9 presents the results of a sensitivity analysis to assess the effect of
different assumptions on global CH4 emissions from landfills and open dumps. For
<-.xomple, a 10 percent increase (decrease) in MSW generation {e.g., due to over-(under)
estimation of commercial and institutional waste] in developing countries would result in
a 3 percent increase (decrease) of global CH< emissions from landfills and open dumps.
From Table 9 it may be concluded that over or undfr estimation of commercial and
institutional waste does not contribute significantly to the uncertainty of the total CH4
emissions estimate.
UNCERTAINTIES IN WASTE DISPOSAL ESTIMATES
For many countries, it is hard to assess how much of the waste generated will
eventually be landfilled or dumped. In developing countries, much of the wasio may be
scavenged and recycled. The methodology corrects for this reduction of waste by applying
a factor L (Table 4). However, recycling or reusing waste components, such as food and
paper or cardboard will also have an effect on the waste CH4 potential. If the CH4
potential of the waste dumped in these countries is 50 percent less than previously
assumed, the total global CH4 emissions would be reduced by 2 percent (See Table 9).
In certain rural areas of the world it may be that practically all generated MSW is
recycled, burned, or otherwise used. The assumption that no waBte in rural parts of
developing countries is dumped or landfilled would result in a reduction of total global
CH4 emissions from landfills and open dumps by 11 percent.
32
-------
TABLE 9. SENSITIVITY ANALYSIS OF GLOBAL METHANE EMISSIONS
ISSUE
RESULTING IN.
f
% CHANGE IN
ACTIVITY
PARAMETER
% CHANGE IN
GLOBAL CH4
EMISSIONS (Y)
ALL COUNTRIES,
EXCLUDING United States
Reassessment of steady
state waste generation rate
assumption
Overestimate of annual national
waste generation rate
^TOTAV +2.5
(previous 10 years)
-9
DEVELOPING COUNTRIES
Reassessment rural waste
No methane from rural waste
MrubaL1 *100
-11
Open dumps in tropical
countries turn acidic'
Less melhane from open dumps
Ydumm: "SO
•8
More scavenging and
recycling than previously
assumed
Less food and paper waste to
dumps
P: -50
-2
Over estimation MSW
M: +10
+3
COUNTRIES MAKING USE OF DUMPS (Developing Countries plus Eastern and Southern Europe)
Dumps are more aerobic
than assumed
Less methane emitted
F: -10
4
*
legend. M a annual waste generation rate
Y a CH, emissions
P = CH, potential
F a degree In which dumps are anaerobic
Note t All developing countries, excluding Peoples Republic ol China and North Korea.
UNCERTAINTIES IN METHANE GENERATION ESTIMATES
The CH4 generation and actual emissions from waste in open dumps is prone to
considerable uncertainty. CH4 generation and emissions from open dumps will depend on
the size and configuration of the dump, and on temperature, moisture, and compaction of
the waste in place. A small, uncompacted heap of garbage is likely to decompose
aerobically, whereas a large dump may be expected to be largely anaerobic. Bhide et al.
(1990) reported biogas recovery from two shallow, uncontrolled dumps in India suggesting
that open dumps are a source of CH4. Therefore, open dumps have been included in the
emission estimates. The fraction of waste in open dumps and waste piles that is decaying
anaerobically may have been overestimated. A reduction of 10 percent of this fraction for
all countries that make use of open dumps, results in a reduction of global CH4 emissions
from landfills and open dumps of 4 percent (Table 9).
33
-------
Waste in place that is submerged in watei will not produce significant amounts of
CH4. Such water may easily be found in open dumps because these do not possess liners,
drainage systems, and/or top covers. There is some anecdotal evidence that such
impediment of CH4 generation may also occur in unsubmerged waste when the dump is
particularly moist. This has been observed in tropical countries with a hot and moist
climate (Pacey, 1994).
As was described in the subsection entitled: "Methane Production from the Anaerobic
Decomposition of Solid Waste," initial products of decomposition of organic matter are
sugars, amino acids, carboxylic acids, and glycerol. The formation of acids will result in a
drop in pH which is unfavorable for other types of organisms necessary for CH4
production. It is believed that the high temperature and moisture in dumps in these
tropical countries create a condition in which the aforementioned pH drop is particularly
pronounced. Table 9 illustrates that a 50 percent reduction of CH., emissions from open
dumps in tropical countries would imply an 8 percent reduction of global CH4 emissions
from this source category.
The CH< production of other types of landfills such as those containing industrial and
hazardous wastes is not well understood Definitions of "industrial waste" may vary.
Some authors include construction and demolition debris, thus reporting vast amounts of
industrial waste with practically no CH4 potential. Industrial waste can also consist of
waste streams that decompose under anaerobic conditions. Certain industrial waste
streams, such as that of the food industry, have a high organic content and are potentially
significant sources of CH4. In the United States, landfills containing hazardous waste will
have low CH4 production because of the low moisture content and the requirement that
only solid materials be accepted. In addition, chemicals in the waste stream may be toxic
to the microbes. The disposal of industrial and hazardous waste with MSW was common
in the United States through 1975 and is still common in many other countries. Waste
streams in developing countries are virtually uncontrolled and codisposal of MSW,
industrial wastes, and night soil residues in landfills is common (Cointreau, 1982).
34
-------
REFERENCES
Ahmed, M.F. 1986. Recycling of Solid Wastes in Dhaka. In: Waste Management in
Developing Countries, 1. KJ. Thome-Kozmiensky, ed. EF-Verlag fur Energie und
Umwelttechnik GmbH, Berlin, Germany, pp. 169-173.
Alter, H. 1991. The Future Course of Solid Waste Management in the U.S. Waste
Management & Research, pp. 9, 3-20.
Augenstein, D. 1990. Greenhouse Effect Contributions of United States Landfill
Methane. GRCDA 13th Annual Landfill Gas Symposium, Lincolnshire, IL.
Augenstein, D., and J. Pacey. 1990. Modeling Landfill CH, Generation. International
Conference on Landfill Gas: Energy and Environment, Bournemouth, United Kingdom.
October 17, 1990.
Aumfinier, S., P.S. Lawson, and A.Shepherd. 1993. A Preliminary Assessment of
Methane Emissions from U.K. Landfills. Department of the Environment Report
No. CWM 063/93
Barlaz, M.A. 1985. Factors Affecting Refuse Decomposition in Sanitary Landfills. M.S.
Thesis, Department of Civil and Environmental Engineering, University of Wisconsin,
Madison, WI.
Barlaz, M.A., M.W. Milke, and R.K. Ham. 1987. Gas Production Parameters in Snnitnrv
Landfill Simulators. Waste Management and Research, 5, p. 27.
Barlaz, M.A. 1988. Microbiological and Chemical Dynamics During Refuse
Decomposition in a Simulated Sanitary Landfill. Ph.D. Dissertation, Department of Civil
and Environmental Engineering, University of Wisconsin, Madison, WI.
Barlaz, M.A., D.M. Schaefer, and R.K. Ham. 1989a. Bacterial Population Development
and Chemical Characteristics of Refuse Decomposition in a Simulated Sanitary Landfill.
Appl. Env. Microbiol., 55, 1, p. 55-65. j
Barlaz, M.A., R.K. Ham and D.M. Schaefer,. 1989b. Mass Balance Analysis of
Decomposed Refuse in Laboratory Scale Lvaimeters, Journal of Environmental
Engineering, ASCE, 115, 6, pp. 1088 - 1102.
Barlaz, M.A, R.K Ham, and D.M. Schaefer. 1990. CH« Production from Municipal
Refuse: A Review of Enhancement Techniques and Microbial Dynamics. CRC Critical
Reviews in Environmental Control, Volume 19, Issue 6.
Barlaz, M.A. 1994. Department of Civil Engineering, North Carolina State University.
Unpublished data.
36
-------
Bartone, C.R. 1990. Economic and Policy Issues in Resource Recovery from Municipal
Solid Wastes. Resources Conservation Recycling., 4, pp. 7-23.
Bartone, C.R., and C. Haley. 1990. The Bled Symposium: Introduction. Resources
Conservation Recycling, 4, pp. 1-6.
Bartone, C.R., L. Leite, T. Triche, and R. Schertenleib. 1991. Private Sector Participation
in Municipal Solid Waste Service: Experiences in Lntin America. Waste Management
and Research, 9, pp. 495-509.
Bateman, C.S. 1988. Landfill Gas Development in Australia. In: Proceedings of the
International Conference on Landfill Gas and Anaerobic Digestion of Solid Waste.
Y.R. Alston and G.E. Richards, eds. Harwell Laboratory, Oxfordshire, U.K. pp. 156-161.
October 4-7, 1988.
Beker, D. 1990. Snnitnrv Landfilling in the Netherlands. In: International Perspectives
on Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and R. Cossu, eds.
Academic Press, New York, NY. pp. 139-155,
Betls, M.P. 1984. Trend in Solid Waste Management in Developing Countries. In:
Managing Solid Wastes in Developing Countries. J.R. Holmes, ed. John Wiley & Sons,
Ltd., Chichester, United Kingdom, pp. 291-302.
Bhide, A.D., and B.B. Sundaresan. 1990. Solid Waste Management in Developing
Countries. Indian National Scientific Documentation Centre, Nagpur, India, pp.14-21.
Bhide, A.D., S.A. Gaikwad, and B.Z. Alone. 1990. CH, from Land Disposal Sites in India.
In: Proceedings of the International Workshop on CH, Emissions from Natural Gas
Systems, Coal Mining and Waste Management Systems. Environment Agency of Japan,
the U.S. Agency for International Development, and the U.S. EPA, Washington, DC.
April 9-13, 1990. f
Bingemer, H.G., and P.J. Crutzen. 1987. The Production of CH1 from Solid Wastes.
Journal of Geophysical Research, Vol. 92, No. D2, pp. 2181-2187. February 20, 1987.
Bogner, J.E. 1990. Controlled Study of Landfill Biodegradation Rates Using Modified
Biochemical Methane Potential Assays. Waste Management and Research, 8, pp. 329-
352.
Bonomo, L , and Higginson, A.E. 1988. International Overview on Solid Waste
Management. Harcourt Brace Jovanovich, New York, NY. p. 268.
Buivid, M.G. 1981. Fuel Gas Enhancement hv Controlled Landfilling of Municipal Solid
Waste. Resource Recovery and Conservation, 6, p. 3.
Carra, J.S., and R. Cossu. 1990. International Perspectives on Municipal Solid Wastes
and Sanitnrv Lnndfilling. J.S. Carra and R. Cossu, eds. Academic Press, New York, NY.
pp. 1-4.
36
-------
Campbell, D., D. Epperson, L. Davis, R. Peer, and W. Gray. Radian Corporation. 1991.
Analysis of Factors Affecting Methane Gas Recovery from Six Landfills. Prepared for U.S.
EPA, Air and Energy Engineering Research Laboratory. Research Triangle Park, NC.
EPA-600/2-91-055 (NTIS PB92-101351).
Christensen, T.H. 1990. Sanitiarv Landfilling in Denmark. In: International
Perspectives on Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and
R.. Cossu, eds. Academic Press, New York, NY. pp. 37-50.
Cointreau, S.J. 1982. Environmental Management of Urban Solid Wastes in Developing
Countries. A Project Guide, Urban Development Technical Paper No. 5, World Bank,
Washington, DC. pp. 1-17.
Cointreau, S.J. 1984. Solid Waste Collection Practice and Planning in Developing
Countries. Johr Whiley and Sons Ltd., Chichester, United Kingdom, pp. 151-182.
Cointreau, S.J. 1991. Personal communication between S.J. Cointreau, Solid Waste
Management Consulting Services, Roxbury, CT, and L.C. Huff, Radian Corporation,
Research Triangle Park, NC. September 27, 1991.
Cossu, R., and G. Urbini. 1990. Sanitary Landfilling in Italy. In: International
Perspectives on Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and
R. Cossu, eds. Academic Press, New York, NY. pp 94-109.
Cossu, R. 1990a. Sanitary Landfilling in Japan. In: International Perspectives on
Municipal Solid Wastes and Sanitary Landfilling, J.S. Carra and R. Cossu, eds.
Academic Press, New York, NY. pp. 110-138.
Cossu, R. 1990b. Sanitary Landfilling in the United Kingdom- In: international
Perspectives on Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and
R. Cossu, eds. Acaden.ic Press, New York, NY. pp. 199-220.
Curi, K. 1988. Comparison of Solid Waste Management in Tourisitic Arena of Developed
and Developing Areas. In: Proceedings of the 5th International Solid Waste Conference,
Internal Solid Waste and Public Cleansing Association, Copenhagen, Denmark.
September 1988.
De Poli, F., and S. Pasqualini. 1991. Landfill Qas: The Italian Perspective. In:
Proceedings of Third International Landfill Symposium, Cagliari, Italy. October 1991.
Diaz, L.F., and C.G. Golueke. 1967. Solid Waste Management in Developing Countries.
BioCycle, 28(6), pp. 50-55.
Doom, M.R.J., L.A. Stefanski, and M.A. Barlaz. 1994. Estimate of Methane Emissions
from U.S. Landfills. Prepared for U.S. EPA/AEERL, Research Triangle Park, NC. EPA-
600/R-94-166 (NTIS PB94-213519).
37
-------
El-Halwagi, M.M., S.R. Tewfik, M.H. Sorour, and A.G. Abulnour. 1986. Municipal Solid
Waste Management in Egypt: Practices and Trends. In: Waste Management in
Developing Countries, 1. K.J. Thome-Kozmiensky, ed. EF-Verlag fur Energie und
Umwelttechnik GmbH, Berlin, pp. 283-288.
El-Halwagi, M.M., S.R. Tewfik, M.H. Sorour, and A.G. Abulnour. 1988. Municipal Solid
Waste Management in Egypt, Proceedings of the 5th International Solid Waste
Conference, International Solid Waste and Public Cleansing Association, Copenhagen,
Denmark, pp. 415-424. September 1988.
El Rayes, H.t and W.C. Edwards. 1991. Inventory of CH^ Emissions from Landfills in
Canada. B.H. Levelton & Associates, Ltd. Prepared for Environment Canada, Hull,
Quebec, pp. 25-69.
Emberton, J.R. 1986. The Biological and Chemical Characterization of Landfills. In:
Proceedings of Energy from Landfill Gas, Solihull, West Midlands, UK. October 30-31,
1986.
EMCON Associates. 1982. CH, Generation and Rpnoverv from Landfills. Ann Arbor
Science Publishers, Inc., Ann Arbor, MI.
Erdin, E. 1986. Solid Waste Management and Disposal in Turkey Today. Waste
Management in Developing Countries, 1. K.J. Thome-Kozmiensky, ed. EF-Verlag fur
Energie und Umwelt Technik, GmbH, Berlin.
Ettala, M.O. 1990. Sanitiarv Landfilling in Finland. In: International Perspectives on
Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and R. Cossu, eds.
Academic Press, New York, NY. pp. 67-77.
Federal Register, Vol. 56, No. 104, pp. 24468 - 24528. May 30, 1991
Gandolla, M. 1990. Sanitary Landfilling in Switzerland. In: International Perspectives
on Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and R. Cossu, eds.
Academic Press, New York, NY. pp. 190-198.
Gendebien, A., M. Pauwels, M. Constant, H.C Willumsen, J. Butson, R. Fabry,
G.L. Ferrero, and E.J. Nyns. 1991. Landfill i .is: From Environment to Energy. State-
of-the-Art in the European Community Contact. In: Proceedings of Third International
Landfill Symposium, Cagliari, Italy. October 14-18, 1991.
Halvadakis, C.P. 1983. Landfill Methanogenesis: Literature Review and Critique.
Technical Report No. 271, Department of Civil Engineering, Stanford University.
Holmes, J.R. 1984. Solid Waste Management Decisions in Developing Countries. In:
Managing Solid Wastes in Developing Countries. John Wiley and Sons Ltd., Chichester,
United Kingdom, pp. 1-17.
38
-------
Hughan, R. 1991. Generation of Methane from Landfills. Section from internal report.
Climite Change Support Section. Department of the Arts, Sport, the Environment,
Tourism & Territories, Canberra, Australia.
IPCC. 1992. Climate Change 1992. The Supplementary Report to the IPCC Scientific
Assessment. Published for The Intergovernmental Panel on Climate Change (IPCC),
World Meteorological Organization/United Nations Environment Programme.
J.T. Houghton, G.J. Jenkins, and J.J. Ephraums, eds., Cambridge University Press,
United Kingdom.
Jenkins, R.L., and J.A. Petus. 1985. In: Biotechnological Advances in Processing
Municipal Wastes for Fuels and Chemicals. A.A. Antonopoulos, ed. Argonne National
Laboratories. Report ANL/CNSV - TM -167, p. 419.
Kaltwasser, B.J. 1986. Solid Waste Management in Medium Sized Towns in the Sahel
Area. In: Waste Management in Developing Countries, 1. K.J. Thome-Kozmiensky, ed.
EF-Verlag fur Energie und Umwelttechnik GmbH, Berlin, pp. 299-307.
Kessler, T. 1991. Brazilian Trends in Landfill Gas Exploitation. ETATEC Consultores
s/c Ltda, Silo Paulo, Brazil.
Kashinkunti, R.D., H.H. Westberg, and B.K. Lamb. 1993. Soil Oxidation of Methane
Influenced by Natural Gas Leaks. Air & Waste Management Association. In Proceedings
from the 86th Annual Meeting & Exhibition, Denver, Colorado. June 13-18,1993.
Kinman, R.N. 1987. Gas Enhancement Techniques in Landfill Simulators. Waste
Management and Research, 5, p. 13-25.
Lassey, K.R., D.C. Lowe, M.R. Manning, and G.C. Waghorn. 1992, A Source Inventory
for Atmospheric Methane in New Zealand and Its Global Perspective. Journal of
Geophysical Research. March 1992, vol. 97-4, p. 3751.
Lechner, P. 1990. Sanitary Landfilling in Austria. In: International Perspectives on
Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and R. Cossu, eds.
Academic Press, New York, NY. pp. 16-2o.
Leci, C.L. 1988. Landfill Gas as a Town's Gas Extender, the Santiago. Chile Experience.
In: Proceedings of the International Conference on Landfill Gas and Anaerobic Digestion
of Solid Waste. Harwell Laboratory, Oxfordshire, UK October 4-7, 1988.
Lee, N., T. Kusuda, T. Shimaoka, Y. Matsufuji, and M. Hanashima. 1994. Pollutant
Transformations in Landfill Layers. Waste Management & Research 12, 33-48, 1994.
Lohani, B.N., and N.C. Tanh. 1980. Problems and Practices of Solid Waste Management
in Asia. Journal of Environmental Science, pp 29-33. May/June 1980.
39
-------
Mancinelli, R.L., and C.P. McKay. 1985. Methane Oxidizing Bacteria in Sanitary
Landfills. In: Proceedings of First Symposium on Biotechnical Advances in Processing
Municipal Wastes for Fuels and Chemicals, A.A. Antonopoulos ed. Argonne National
Laboratories.
Maniatis, K., and S. Vanhille. 1987. Solid Waste Management in Indonesia. Status and
Potential Resources Conservation Recycle, 15(87), pp. 277-290.
Mei-Chan, L. 1986. Waste Management in the Taiwan Area. In: Waste Management in
Developing Countries, 1. K.J. Thome-Kozmiensky, ed, EF-Verlag fur Energie und
Umwelttechnik GmbH, Berlin, pp. 299-307.
Mwiraria, M., J. Broome, R. Semb, and W.P. Meyer. 1991. Municipal Solid Waste
Management in Uganda and Zimbabwe. UNDP and the World Bank, Water and
Sanitation Program, Washington, D.C. (Draft Report) May 18, 1991.
Nilsson, P. 1990. Sanitary Landfilling in Sweden. In: International Perspectives on
Municipal Solid Wastes and Sanitary Landfilling. J.S. Carra and R. Cossu, eds.
Academic Press, New York, NY. pp. 1-14.
OECD (Organization for Economic Cooperation and Development). 1991. Estimation of
Greenhouse Gas Emissions and Sinks. Final Report from OECD Experts Meeting, 18-21
February 1991, Paris, France. Prepared for Intergovernmental Panel on Climate Change.
OECD, Paris, France.
Oluwande, P.A. 1984. Assessment of Solid Waste Management Problems in China and
Africa. In: Managing Solid Wastes in Developing Countries. J.R. Holmes, ed. John
Wiley & Sons, Ltd., Chichester, United Kingdom, pp. 71-89.
Pacey, J. 1989. Enhancement of Degradation: Large-Scale Experiments. In: Saniteiy
Landfilling: Process Technology and Environmental Impact, T. Christensen, R. Cossu and
R. Stegmann, eds. Academic Press, London, pp. 103-119.
Pacey, J. 1994. Personal communication between J. Pacey, FHC, Inc., Pebble Beach, CA,
with M.R.J. Doom, E.H. Pechan & Associates, Inc., Durham, NC.
Parkin, G.F., and W.F. Owen. 1986. Journal of the Environmental Engineering Division,
ASCE, 112, 5, p. 867.
Peer, R.L., D.L. Epperson, D.L. Campbell, and P. von Brook. Radian Corporation. 1992.
Development of an Empirical Model of Methane Emissions from Landfills. Prepared for
U.S. EPA, Air and Energy Engineering Research Laboratory, Research Triangle Park, NC.
EPA-600/R-92-037 (NTIS PB92-152876).
Peer, R.L., S.A. Thorneloe, and D.L. Epperson. 1993. A Comparison of Methods for
Estimating Global Methane Emissions from Landfills. Chemosphere, 26(1-4) pp. 387-400.
40
-------
Peterson, C., and A. Perlmutter. 1989. Compostinp in the Soviet Union. BioCycle,
pp. 74-75- July 1989.
Pohland, F.G. 1975. Sanitary Landfill Stabilization with Leachate Recycle and Residual
Treatment. Prepared for U.S. EPA, Municipal Environmental Research Laboratory,
Cincinnati, OH. EPA-600/2-75-043 (NTIS PB248-524).
Pohland, F.G. and S.R. Harper. 1986. Critical Review and Summary of Leachate and
Gas Production from Landfills. Prepared for U.S. EPA, Hazardous Waito Engineering*
Research Laboratory, Cincinnati, OH. EPA/600/2-86/073 (PB86-240181).
Population Reference Bureau, Inc. 1989. World Population Data Sheet. Population
Reference Bureau, Inc., Washington, DC. Demographic data and estimates for the
countries and regions of the world.
Rattye, W.L. 1991. Once and Future Landfills. National Geographic, pp. 117-134.
May 1991.
Rhew, R., and M. A. Barlaz. 1994. Effect of Lime Stabilized Sludge as Landfill Cover on
Refuse Decomposition. Journal of Environmental Engineering, American Society of
Chemical Engineers (accepted for publication).
Richards, K.M. 1988. Landfill Gas — A Global Review. In: Biodeterioration 7,
D.R, Houghton, R.N. Smith, and H.O.W. Eggins, eds. Elsevier Applied Science, London,
pp. 774-790.
Richards, KM. 1989. Landfill Gas: Working with Gaia. Biodeterioration Abstracts,
3(4), pp. 317-331. and C.A.B. International, Vol. 3, No. 4. December 1989.
Scheepers, M.J.J. 1991. Landfill Gas in the Dutch Perspective. In Proceedings of the
Third International Landfill Symposium. S. Margherita di Pula, Cagliari, Italy. 14-18
October 1991. pp. 481-490. j
Scheepers, M.J.J. 1993. Personal communication between M.J.J. Scheepers, Landfill Gas
Advisory Center, Apeldoorn, the Netherlands.and M.R.J. Doom, E.H. Pechan &
Associates, Inc., Durham, NC.
Shelton, D.R., and J.M. Tiedje, 1984. General Method for Determining Anaerobic
Biodegradation Potential. Applied Environmental Microbiology, 47, 4, pp. 850-857.
Stegmann, R. 1990. Sanitnrv Landfilling in the Federal Republic of Germany. 'In:
International Perspectives on Municipal Solid Wastes and Sanitary Landfilling,
J.S. Carra and R. Cossu, eds. Academic Press, New York, NY. pp. 51-66.
Sutanto, H., J. Peters, P. Gopfert, and J. Jager. 1986. The State of. and Possibilities for.
Material Recycling in Jakarta. In: Waste Management in Developing Countries, 1.
K.J. Thome-Kozmiensky, ed. EF-Verlag fur Energie und Umwelt Technik GmbH, Berlin.
41
-------
Thorneloe, S. 1992. Landfill Gas Recovery/Utilization - Options and Economics. In:
Proceedings for the 16th Annual Conference by the Institute of Gas Technology on Energy
from Biomass and Wastes, Orlando, FL. March 1992.
Thorneloe, S. 1994. Emissions and Mitigation at Landfills and Other Waste
Management Facilities. In Proceedings: The 1992 Greenhouse Gas Emissions and
Mitigation Research Symposium. EPA/600/R-94-008 (NTIS PB94-132180). January 1994.
pp. 4-46 through 4-57. %
U.S. Environmental Protection Agency. 1988. Solid Waste Disposal in the United States.
Report to Congress. Volume I. EPA/530-SW-88-011 (NTIS PB89-110381). October 1988.
U.S. Environmental Protection Agency. 1990. Characterization of Municipal Solid Waste
in the United States: 1990 Update. U.S. EPA, Office of Solid Waste and Emergency
Response, Washington, DC. EPA-530/SW-90-042 (NTIS PB90-215112).
U.S. Environmental Protection Agency. 1991. Air Emissions from Municipal Solid Wnstc
Landfills—Background Information for Proposed Standards and Guidelines. U.S. EPA,
Office of Air Quality Planning and Standards, Research Triangle Park, NC. EPA-450/3-
90-011a (NTIS PB91-197061).
U.S. Environmental Protection Agency. 1992. Characterization of Municipal Solid Waste
in the United States. 1992 Update. U.S. EPA, Office of Solid Waste and Emergency
Response, Washington, DC. EPA/530-R-92-019 (NTIS PB92-207166).
U.S. Environmental Protection Agency. 1993. Anthropogenic Methane Emissions in the
United States. Estimates for 1990. Report to Congress. Prepared by U.S. EPA, Office of
Air and Radiation, Washington, DC. EPA/430-R-93-003.
United Nations. 1989. Citv Profiles. Prepared by the United Nations Centre for
Regional Development and the Kitakyushu CityfGovernment, Kitakyushu, Japan. 64 pp.
United Nations. 1990. 1988 Demographic Yearbook. Fortieth Issue. Department of
International Economic and Social Affairs, Statistical Office. New York, NY.
United Republic of Tanzania. 1989. Masterplan of Solid Waste Management for Par es
Salaam. Volume II: Annexes. Ministry of Water, Department of Sewerage and
Sanitation. Prepared by HASKONING, Royal Dutch Consulting Engineers and
Architects, Nymegen, The Netherlands, and M-Konsult Ltd., Consulting Engineers,
Dar es Salaam, Tanzania, pp. 1-39, 47-49, 74-94, 109-124,142-145,
Verrier, S.J. 1990. Urban Waste Generation. Composition and Disposal in South Africa.
In: International Perspectives on Municipal Solid Wastes and Sanitary Landfilling.
J.S. Carra, and R. Cossu, eds. Academic Press, Harcourt Brace Jovanovich, London,
United Kingdom, pp. 161-176.
42
-------
Vogler, J.A. 1984. Waste Recycling in Developing Countries: A Review of the Social.
Technological, and Market Forces. In: Managing Solid Wastes in Developing Countries,
J.R. Holmes, ed. John Wiley & Sons, Ltd., Chichester, England, pp. 241-266.
Wang, Y., C.S. Byrd, and M.A. Barlaz. 1994. Anaerobic Biodegradabilitv of Cellulose and
Hemicellulose in Excavated Refuse Samples Using a Biochemical Methane Potential
Assay. Journal of Industrial Microbiology, 13 (1994) 147-153.
Whalen, S.C., W.S. Reeburgh, and K.A. Sandbeck. 1990. Rapid CHf Oxidation in a
Landfill Cover Soil. Applied Environmental Microbiology, 56, 11, pp. 3405 - 11.
Willumsen, H. 1990. Landfill Gas. Resources Conservation Recycling, 4(90), pp. 121-133.
Wolfe, R.S. 1979. Methanogenesia. In: Microbial Biochemistry, International Review of
Biochemistry. J.R. Quayle, ed. University Park Press, Baltimore, MD. Vol. 21,
Wolin, M.J., and T.L. Miller. 1985. In: Biology of Industrial Microorganisms.
A.L. Dernsin and N.A. Solomon, eds. Bei\jamin/Cumings Publishing Co. Inc., Menlo Park,
CA. pp. 189-221.
Wright, F., Bartone, C., and ArlosorofT, S. 1988. Integrated Resource Recovery-
Optimizing Waste Management. In: Proceedings of the 5th International Solid Wastes
Conference, International Solid Wastes and Public Cleansing Association, Copenhagen,
Denmark, pp. 619-624, 09/88.
Xianwen, C., and Z. Yanhua. 1991. Landfill Gas Utilization in China. In: Proceedings
of the Third International Landfill Symposium, Sardinia, Italy, pp. 1747-1753. October
1991.
Young, L.Y., and A.C. Frazer. 1987. Geomicrob^>logy Journal. 5, p 261.
Zehnder, A.J.B. 1982. Microbiology of CH. Bacteria. In: Anaerobic Digestion.
D.E. Hughes, ed. Elsevier Biomedical Press B.V., Amsterdam, p. 45.
43
-------
TABLE 10. COUNTRY-SPECIFIC WASTE DATA AND METHANE EMISSIONS
wa;
5TECC
IMPOSITION
TOTAL EMISSIONS
i.
*
JC.
c
a>
O
I.
a.
e
3
S3
"3
1
£
1
o
•D
a
UL_
c*
|
1.
1
c
------- |