May 2009
User's Manual
China Landfill Gas Model
Version 1.1
Prepared on behalf of:
Rachel Goldstein
Landfill Methane Outreach Program
U.S. Environmental Protection Agency
Washington, D.C.
Prepared by:
Clint Burklin, P.E.
Eastern Research Group, Inc.
Morrisville, NC 27560 and
Bryce Lloyd
Organic Waste Technologies (Hong Kong) Limited
Hong Kong SAR, China
EPA Contract EP-W-06-022
Task Order 28
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DISCLAIMER
This user's manual has been prepared specifically for China on behalf of the U.S. EPA's
Landfill Methane Outreach Program, U.S. Environmental Protection Agency. The methods
contained within are based on engineering judgment and represent the standard of care that
would be exercised by a professional experienced in the field of landfill gas projections. The
U.S. EPA and its contractors ERG and OWT do not guarantee the quantity of available landfill
gas, and no other warranty is expressed or implied. No other party is intended as a beneficiary of
this work product, its content, or information embedded therein. Third parties use this report at
their own risk. The U.S. EPA and its contractors ERG and OWT assume no responsibility for the
accuracy of information obtained from, compiled, or provided by other parties.
ABSTRACT
This document is a user's manual for a computer model, Version 1.1 of a landfill gas
(LFG) generation model for estimating LFG generation and recovery from existing or future
municipal solid waste (MSW) landfills in China (China Landfill Gas Model v 1.1; referred to as
China LFG Model hereafter). The model was developed by ERG and OWT under contract to the
U.S. EPA's Landfill Methane Outreach Program (LMOP). The China LFG Model can be used to
estimate LFG generation rates from landfills, and potential LFG recovery rates for landfills that
have, or plan to have, gas collection and control systems in China.
The China LFG Model is an Excelฎ spreadsheet model based on a first order decay
equation. The model requires the user to input site-specific data for landfill opening and closing
years, refuse disposal rates, landfill location (in terms of climate zones), approximate coal ash
content of the waste, history of landfill fires, and a number of landfill characteristics that
determine LFG collection efficiency. Based on the site-specific data supplied by the user, the
model selects recommended values for input variables, including methane generation rate
constant (k), potential methane generation capacity (L0), collection efficiency, and fire discount
factor and estimates generation and recovery rates. Users can also specify their own values for
these input variables, provided the information is reliable. The recommended values for input
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variables were developed using data on climate, waste characteristics, and disposal practices in
China, and the estimated effect of these conditions on the amounts and rates of LFG generation.
Actual LFG recovery rates from four landfills in China were evaluated, but insufficient data were
available to accurately calibrate the model results to actual recovery rates. Default values are
recommended when site specific data are not available or are insufficient.
The China LFG Model was developed with the goal of providing general estimation of
LFG generation and recovery potential. Other models evaluated during the model development
process included the U.S. EPA Central America Landfill Gas Model Version 1 (SCS, 2007), and
the Intergovernmental Panel on Climate Change (TPCC) 2006 Waste Model. The China LFG
Model incorporates components of each of these models that help it to reflect conditions at
disposal sites in China.
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TABLE OF CONTENTS
Section Page
DISCLAIMER ii
ABSTRACT ii
LIST OF FIGURES v
LIST OF TABLES v
GLOSSARY OF TERMS vi
1.0 INTRODUCTION 1-1
1.1 Landfill Gas Generation 1-3
1.1.1 Methane Generation Rate Constant (k) 1-4
1.1.2 Ultimate Methane Generation Potential (LO) 1-6
1.1.3 Landfill Fires 1-8
1.2 Landfill Gas Recovery 1-8
1.2.1 Estimating Collection Efficiency 1-9
1.3 The Model 1-13
2.0 ESTIMATING LANDFILL GAS GENERATION AND RECOVERY 2-1
2.1 Model Inputs 2-1
2.2 Model Output - Table 2-7
2.3 Model Output-Graph 2-9
3.0 REFERENCES 3-1
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LIST OF FIGURES
Figure 1- Model Inputs
Figure 2 - Climatic Zones in China
Figure 3 - Model Inputs (Continued)
Figure 4 - Sample Model Output Table
Figure 5 - Sample Model Output Graph
LIST OF TABLES
Table 1 - Methane Generation Rate (k)
Table 2 - Ultimate Methane Generation Potential (L0)
Table 3 - Landfill Collection Efficiency
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GLOSSARY OF TERMS
TERM
DEFINITION
Climate Zone
One of three zones in China (1 - Cold and Dry; 2 - Cold
and Wet; and 3 - Hot and Wet) characterized by the mean
annual temperature (MAT), mean annual precipitation
(MAP), and the ratio of MAP to potential
evapotranspiration (PET).
Closure Year
The year in which the landfill ceased, or is expected to
cease, accepting waste.
Coal-based Landfill
Coal-based landfill means the area served by the
landfill uses predominantly coal for heating and
cooking, and the coal ash is disposed of in the
landfill.
Collection Efficiency
The estimated percentage of generated landfill gas that is
or can be collected by a gas collection system.
The percentage of the landfilled area that has (or will
have) a comprehensive and operating landfill gas
collection system.
Collection System Area Coverage
Landfill Fire
Uncontrolled combustion of waste placed in a
landfill. Landfill fires can be above ground or
underground (subsurface). Signs of landfill fires
include smoke (especially from cracks and fissures
in the waste mass), elevated gas temperature and
carbon monoxide levels, smoke-stained gas vents,
smoldering wastes, excessive settlement, etc.
Landfill Gas
Landfill gas is a product of biodegradation of refuse
in landfills and consists of primarily methane and
carbon dioxide, with trace amounts of non-methane
organic compounds and air pollutants.
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TERM
DEFINITION
Methane Generation Rate Constant (k)
k is a model constant that determines the estimated rate of
landfill methane generation. The first-order
decomposition model assumes that k values before and
after peak landfill gas generation are the same, k is a
function of moisture content in the landfill refuse,
availability of nutrients for methanogens, pH, and
temperature. (Units = I/year)
Opening Year
The year in which the landfill begins, or is expected to
begin, accepting waste.
Ultimate Methane Generation Potential
(Lo)
L0 is a model constant that represents the potential
capacity of a landfill to generate methane (a primary
constituent of landfill gas). L0 depends on the amount of
degradable organic carbon in the refuse. (Units = cubic
meters per megagram (m3/Mg))
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1.0 INTRODUCTION
The China Landfill Gas Model (China LFG Model) provides an automated estimation
tool for quantifying landfill gas (LFG) generation and recovery from existing or future municipal
solid waste (MSW) landfills across China. This manual provides an introduction to the model
and step-by-step instructions for using the model.
The main purpose of the China LFG Model is to provide landfill owners, operators, and
potential developers with a tool to evaluate the feasibility and potential benefits of collecting and
using the generated LFG for energy recovery or other uses. To accomplish this purpose, this
computer model provides estimates of potential LFG recovery rates and available emission
reductions. This is accomplished using the LFG generation rates estimated by the model and
estimates of the efficiency of the collection system in capturing generated gas, known as the
collection efficiency. The model provides LFG recovery estimates by multiplying the LFG
generation by the estimated collection efficiency; potentially available emission reductions
estimates are obtained by multiplying the LFG recovery estimates by the methane content, the
density of methane, and the global warming potential of methane (21). The model also estimates
energy output from either a direct use project or an electricity generation project.
Landfill gas is generated by the decomposition of refuse in the landfill, and can be
recovered through the operation of gas collection facilities installed at the landfill. The following
information is needed to estimate LFG generation and recovery from a landfill (see the Glossary
of Terms):
The annual refuse disposal rate for the landfill;
The methane generation rate (k) constant;
The ultimate methane generation potential (L0);
The collection efficiency of the gas collection system;
Whether there are (and/or have been) landfill fires at the site; and
The opening and closure years of the landfill.
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The model employs a first-order exponential decay function that assumes that LFG
generation is at its peak following a time lag representing the period prior to methane generation.
The model assumes a six month time lag between placement of waste and LFG generation. For
each unit of waste, after six months the model assumes that LFG generation decreases
exponentially as the organic fraction of waste is consumed.
For sites with known (or estimated) year-to-year solid waste disposal rates, the model
estimates the LFG generation rate in a given year using the following equation, which is used by
the U.S. EPA's Landfill Gas Emissions Model (LandGEM) version 3.02 (EPA, 2005).
1 n
QM=y
^
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accordance with the methodology presented in the IPCC 2006 guidelines (IPCC, 2006). The
recommended k and L0 values vary depending on the climate zone and waste composition, and
can be used to produce typical LFG generation estimates for landfills located in each of the three
climate zones in China. Users can also specify their own values for k and L0 provided that the
information is reliable.
The China LFG Model also requires the user to provide information, either actual or
anticipated/planned, on certain landfill construction and operation characteristics that determine
the collection efficiency of the existing or potential future gas collection system. Based on the
information provided by the user, the model would recommend a value for the collection
efficiency. The recommended collection efficiency would then be used in combination with the
LFG generation estimates to arrive at LFG recovery estimates. The user also has the option to
input an alternative collection efficiency assumption or a site-specific collection efficiency.
EPA recognizes that modeling LFG generation and recovery accurately is difficult due to
limitations in available information for inputs to the model. However, as new landfills are
constructed and operated, and better information is collected, the present modeling approach can
be improved. In addition, as more landfills in China develop gas collection and control systems,
additional data on LFG generation and recovery will become available for model calibration and
the development of improved model recommended values.
Questions and comments concerning the LFG model should be directed to Rachel
Goldstein of EPA's LMOP at (202) 343 9291, or e-mail to Goldstein.Rachel@epamail.epa.gov.
1.1 Landfill Gas Generation
The China LFG Model estimates LFG generation resulting from the biodegradation of
refuse in landfills. The anaerobic decomposition of refuse in solid waste landfills generates LFG.
The composition of MSW LFG is assumed by the model to be approximately 50 percent
methane (CH4) and 50 percent other gases, primarily carbon dioxide (CC^) with trace amounts of
other compounds.
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This computer model uses a first-order decomposition rate equation and estimates
volumes of LFG generation in cubic meters per minute (m3/min) and cubic meters per hour
(mVhr). Methane generation is estimated using two parameters: (1) L0 is the ultimate methane
generation potential of the refuse, and (2) k is the methane generation rate constant. For a unit of
waste, LFG generation is assumed to be at its peak the first year following placement in the
landfill. The model provides recommended values of L0 and k based on input provided by the
user; however, the model also allows the user to enter L0 and k values derived using site-specific
data collected at the landfill.l
1.1.1 Methane Generation Rate Constant (k)
The methane generation rate constant, k, determines the rate of generation of methane
from refuse in the landfill. Its unit is I/year, and describes the rate at which refuse placed in a
landfill decays and produces biogas. The higher the value of k, the faster total methane
generation at a landfill increases (as long as the landfill is still receiving waste) and then declines
(after the landfill closes) over time. The value of k is a function of the following factors:
(1) refuse moisture content, (2) availability of nutrients for methane-generating bacteria, (3) pH,
and (4) temperature.
Different waste types can have significantly different k values as a result of differences in
decay rates. Food waste, for example decays faster than paper or wood. The k value also varies
with climate, especially temperature, precipitation, and evapotranspiration. In the current model,
a location in China is categorized as "cold or hot" and "dry or wet" based on the following two
criteria in accordance with Table 3.4 in the IPCC 2006 Guidelines:
Cold vs. Hot:
A location is "cold" if the mean annual temperature (MAT) is 20ฐC or lower
A location is "hot" if the MAT is higher than 20ฐC
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Dry vs. Wet:
For "hot" locations,
It is dry if the mean annual precipitation (MAP) is less than 1000 millimeters (mm)
It is wet if the MAP is 1000 mm or more
For "cold" locations,
It is dry if the ratio of mean annual precipitation (MAP) to potential
evapotranspiration (PET) is less than 1
It is wet if the ratio of MAP to PET is greater than 1
Using the above two criteria, each location in China can be classified as belonging to one
of the following three climatic zones (or regions):
Region 1: Cold and Dry
Region 2: Cold and Wet
Region 3: Hot and Wet
It should be noted that there are no hot and dry locations in China. To facilitate
identification of the climatic zone in which a landfill is located, a map of China with the climatic
zones delineated has been developed (see Figure 2 in Section 2.1); the user only needs to locate
the landfill on the map to identify the corresponding climatic zone.
Unless a user-specified k value is entered into the China LFG Model, the model uses a
recommended value of k selected based on the climatic zone in which the landfill is located. The
recommended values of k were developed based on values calculated using IPCC methodology
and waste composition data from landfills in different locations of China, adjusted through
comparison with actual LFG recovery data from several landfills in China. The recommended k
values for the three climatic zones are shown in Table 1 below.
1 Site-specific L0 and k values may be developed for landfills with operating gas collection and control systems by
calibrating the China LFG Model using known landfill gas recovery data; alternatively, L0 and k values can be
estimated based on climate and waste composition using IPCC methodologies (IPCC, 2006).
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TABLE 1: METHANE GENERATION RATE (k)
Climatic Zone
Cold and Dry
Cold and Wet
Hot and Wet
k (per year)
0.04
0.11
0.18
It should be noted that the value of k for the "Cold and Wet" climate zone in Table 1 was
based on typical national waste composition because no typical waste composition for that
climate zone was available during model development; the value of k for this climate zone was
also not adjusted through comparison with actual LFG recovery data because such data were not
available.
1.1.2 Ultimate Methane Generation Potential (L0)
Except in dry climates where a lack of moisture limits methane generation, the value for
the ultimate methane generation potential of refuse (Lo) depends almost exclusively on the type
of refuse present in the landfill. The higher the biodegradable organic carbon content of the
refuse, the higher the value of L0. The units of L0 are in cubic meters of methane per metric tonne
of refuse, which means that the L0 value describes the total amount of methane gas potentially
produced by a metric tonne of refuse as it decays over its lifetime. The values of theoretical and
obtainable L0 range from 6.2 to 270 m3/Mg refuse (EPA, 1991).
Unless a user-specified L0 value is entered into the China LFG Model, the model uses a
recommended value of L0 selected based on the climatic zone in which the landfill is located.
The recommended values of L0 are based on values calculated using IPCC methodology and
waste composition data from landfills in different locations of China, adjusted through
comparison with actual LFG recovery data from several landfills in China.
In addition to the landfill location, it has been reported that a major factor affecting waste
composition (and thus L0) in China is whether residents and businesses in the area served by a
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landfill predominantly use coal for heating and cooking purposes (such an area can be referred to
as "coal-based"). The reason is that the wastes in coal-based areas, if coal ash is disposed of in
the landfill, tend to have a much higher inert/ash content (typically more than 30%). In the
absence of detailed data, it is assumed for the development of the current model that the value of
L0for wastes in a coal-based landfill is half of the value of L0 for wastes in a non-coal-based
landfill in the cold regions of China. In the hot region of China, the value of L0for wastes in a
coal-based landfill is assumed to be 3/4 of the value of L0 for wastes in a non-coal-based landfill.
Alternatively, if information on waste composition is available, whether coal ash makes
up a significant fraction of the waste could be used to infer whether a landfill is in a coal-based
area. Specifically, if the data indicate that coal ash makes up more than 30% of the waste, the
waste's coal ash content can be described as significant and the landfill can be assumed to be in a
coal-based area.
The recommended L0 values for the three climatic zones are shown in Table 2 below.
TABLE 2: ULTIMATE METHANE GENERATION POTENTIAL (L0)
Climatic Zone
Cold and Dry
Cold and Wet
Hot and Wet
Lo (m3/Mg)
Coal Ash Content
<30% (Non-Coal-
Based Landfill)
70
56
56
Coal Ash Content
>30% (Coal-Based
Landfill)
35
28
42
It should be noted that the value of L0 for the "Cold and Wet" climate zone in Table 2
was based on typical national waste composition because no typical waste composition for that
climate zone was not available during model development; the value of L0 for this climate zone
was also not adjusted through comparison with actual LFG recovery data because such data were
not available.
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1.1.3 Landfill Fires
Landfill fires have been reported or observed at a number of landfills in China. Landfill
fires can be above ground or underground (subsurface). Once fires are started, especially
subsurface landfill fires, they are very difficult to extinguish or control. Signs of landfill fires
include smoke (especially from cracks and fissures in the waste mass), elevated LFG
temperatures or carbon monoxide levels, smoke-stained gas vents, smoldering wastes, and
accelerated settlement.
Landfill fires can consume a significant amount of the organic matter and thus drastically
reduce the LFG generation rate. Landfill fires can also damage the LFG collection system,
poison the methanogenic bacteria, and reduce the collection efficiency. For landfills where
current or past landfill fires have been observed or are likely present, a reduction of 20 to 40% in
the methane estimate might occur as the combined result of loss of organics and damaged
collection system. If the user indicates that signs of current or past landfill fires were observed,
the model applies a default fire discount factor (30% percent reduction) to the methane estimate.
1.2 Landfill Gas Recovery
Landfill gas generated in landfills can be captured by gas collection and control systems
that typically burn the gas in flares or, alternatively, the collected gas can be used beneficially.
Beneficial uses of LFG include use as fuel in energy recovery facilities, such as internal
combustion engines, gas turbines, microturbines, steam boilers, furnaces, kilns, or other
equipment that uses the gas as fuel to generate electricity or useable heat.
In addition to the energy benefits from the use of LFG, collection and control of
generated LFG helps to reduce emissions that are harmful to the environment. Control of LFG
destroys methane, which is a greenhouse gas that contributes to global climate change. Control
of LFG also destroys organic compounds that could adversely affect human health. The
collection and control of LFG also reduces the potential for methane migration, both on-site and
off-site, thus mitigating the risks of explosions or fires.
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1.2.1 Estimating Collection Efficiency
Collection efficiency is a measure of the ability of the gas collection system to capture
generated LFG. It is a percentage value that is applied to the LFG generation projection
produced by the model to estimate the amount of LFG that is or can be captured for flaring or
beneficial use. Although rates of LFG capture can be measured, rates of generation in a landfill
cannot be measured (hence the need for a model to estimate generation); therefore there is
considerable uncertainty regarding actual collection efficiencies achieved at landfills.
In response to the uncertainty regarding collection efficiencies, the U.S. EPA (EPA,
1998) has published what it believes are reasonable collection efficiencies for landfills in the
United States (U.S.) that meet U.S. design standards and have "comprehensive" gas collection
systems. According to the U.S. EPA, collection efficiencies at such landfills typically range from
60% to 85%, with an average of 75%. A comprehensive LFG collection system is defined as a
system of vertical wells and/or horizontal collectors providing 100%collection system coverage
of all areas with waste within one year after the waste is deposited. Most landfills, particularly
those that are still receiving wastes, have less than 100%collection system coverage, and require
a "coverage factor" adjustment to the estimated collection efficiency. Sites with security issues
or large numbers of uncontrolled waste pickers will not be able to install equipment in unsecured
areas and cannot achieve comprehensive collection system coverage.
Table 3, "Landfill Collection Efficiency," shows an example of how to estimate the
collection efficiency using responses to several questions related to landfill construction and
operation to determine discounts to the collection efficiency. For example, if the responses are
"Yes" to questions 1 to 2 and 4 to 7 and "No" to question 3, then there is no discount beyond the
collection efficiency value of 85% related to questions 1 to 7. Furthermore, if the LFG System
Area Coverage Percentage falls in bracket I, then the final estimated collection efficiency is 85%
times the Area Coverage Factor (ACF) (0.95 in this case), or approximately 81%.
TABLE 3: LANDFILL COLLECTION EFFICIENCY
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No.
1
2
3
4
5
6
7
8
Question
Is the waste placed in the landfill properly
compacted on an ongoing basis?
Does the landfill have a focused tipping area?
Are there leachate seeps appearing along the
landfill side slopes? Or is there ponding of
water/leachate on the landfill surface?
Is the average depth of waste 10 m or greater?
Is any daily or weekly cover material applied to
newly deposited waste?
Is any intermediate/final cover applied to areas of
the landfill that have reached interim or final
grade?
Does the landfill have a geosynthetic or clay
liner?
In which bracket (I to V) does the LFG System
Area Coverage Percentage fall?
Collection Efficiency Discount
(below 85%)
Yes
0%
0%
10%
0%
0%
0%
0%
No
3%
5%
0%
10%
10%
5%
5%
Multiply by Area Coverage
Factor (see below)
The LFG System Area Coverage Percentage is defined as the percentage of the landfilled
area that has a comprehensive and operating LFG collection system; brackets I to V are defined
in the table below. The collection efficiency would be reduced by the ACF, which is estimated in
accordance with the following table:
LFG System Area
Coverage Percentage
80-100%
60 - 80%
40 - 60%
20 - 40%
< 20%
Bracket
I
II
III
IV
V
Area Coverage Factor
(ACF)
95%
75%
55%
35%
15%
Note that the recommended method for estimating collection efficiency assumes that
some portion (at least 15%) of generated LFG will escape collection, no matter how well
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designed the landfill or how comprehensive the gas collection system is. The following steps are
recommended to adjust the efficiency below 85%:
To evaluate collection efficiency, start at 85%, and then apply a discount based on the
responses to each of seven questions, as described in Table 3 and below.
We suggest a 3% discount for "No" to Question 1, a 5% discount for "No" to
Question 2, a 10% discount for "Yes" to Question 3, a 10% discount each for "No" to
Questions 4 and 5, and a 5% discount each for "No" to Questions 6 and 7 (i.e., a
maximum of 48% discount to the collection efficiency) for the seven questions.
Question 1 asks whether the waste placed in the landfill is properly compacted on an
ongoing basis. The response should be "Yes" only if the incoming waste is
compacted thoroughly as the waste is placed (or if the waste arrives at the landfill
already compacted and baled). Thorough and timely compaction of the waste placed
in the landfill reduces the amount of air (thus oxygen) in the waste mass, promoting
anaerobic decomposition that generates LFG. Proper compaction of the waste would
also minimize differential settlement (thus reducing potential problems with the
collection piping), and decrease the amount of surface water infiltration (thus
lowering the amount of leachate).
Question 2 asks whether the landfill has a focused tipping area. The response should
be "Yes" only if the tipping area is smaller than approximately 30 m by 30 m. A
focused tipping area minimizes the area through which air and surface water can
infiltrate into the waste mass. It is also a good landfill practice as there would be less
exposed waste, thereby minimizing odor and pest nuisances.
Question 3 asks whether there are leachate seeps appearing along the landfill side
slopes, and whether there are ponds of water/1 eachate on the landfill surface. The
response should be "No" only if there are neither leachate seeps nor ponds of
water/1 eachate. The absence of leachate seeps and surficial ponds of water/1 eachate is
indicative of a relatively well-drained waste mass with low leachate levels, which is
beneficial to LFG collection.
Question 4 asks whether the average depth of waste is 10 m or greater. The response
should be "Yes" only if the depth of waste averaged over the entire landfill exceeds
10m. Since the waste close to the top of the landfill tends to decompose aerobically
and does not contribute to LFG generation, a shallower landfill would have a lower
apparent collection efficiency since it has a larger proportion of such waste.
Question 5 asks whether any daily or weekly cover material is applied to newly
deposited waste. The response should be "Yes" only if newly deposited waste is
covered with an appropriate material (such as soil, plastic tarp, or geosynthetics) on a
regular basis, preferably daily but at least weekly; material with large voids such as
gravels, construction and demolition debris or leaves and branches are not considered
appropriate cover material. The timely application of appropriate cover material to
newly deposited waste is essential to minimize the amount of rapidly decomposing
waste (such as food waste) that undergoes aerobic decomposition; it is also necessary
for the reduction of air and surface water infiltration and thus promote anaerobic
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decomposition. Furthermore, it allows the collection system to operate under the
necessary vacuum without drawing excessive air/oxygen into the system.
Question 6 asks whether any intermediate/final cover is applied to areas of the
landfill that have reached interim or final grade. The response should be "Yes" only if
areas of the landfill that have reached interim or final grade receive an intermediate or
final cover in a timely manner; i.e., preferably within one year of reaching such
grades. Similar to daily or weekly cover, it is also necessary for the reduction of air
and surface water infiltration, and allows the collection system to operate under the
necessary vacuum.
Question 7 asks whether the landfill has a geosynthetic or clay liner. The response
should be "Yes" only if most, if not all, of the landfill has a properly designed bottom
liner made of geosynthetics, clay or other appropriate material.
Question 8 is related to the LFG System Area Coverage Percentage, namely in which
bracket (I to V) does it fall. The LFG System Area Coverage Percentage is defined as
the percentage of the landfill area that has a comprehensive and operating LFG
collection system. The response to Question 8 should be selected based on the value
of the LFG System Area Coverage Percentage according to the following table:
LFG System Area
Coverage Percentage
80-100%
60 - 80%
40 - 60%
20 - 40%
< 20%
Bracket
I
II
III
IV
V
The estimation of collection efficiency has been partly automated in the model; the
adjustment of the collection efficiency below 85% will be performed automatically, if a "Yes" or
"No" response is provided to each of the seven questions. The model will also select the
appropriate ACF, if the bracket (I to V) in which the LFG System Coverage Percentage falls is
identified. The model will then reduce the adjusted collection efficiency by the ACF to calculate
the final collection efficiency. Users can also specify their own value for the collection
efficiency, if the information is reliable.
1.3 The Model
The China LFG Model can be operated in a Windows 2000ฎ, Windows XPฎ, or Vista
ฎ
environment. The program is a Microsoft Excel spreadsheet. Open the model file ("LMOP
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China Model vl-l.xls") by choosing "file," "open," and then "open" when the correct file is
highlighted. To enable the model to run correctly, the user will need to "enable macros" when
prompted; since high security settings may automatically disable macros, it may be necessary to
change the computer's security settings to enable macros.
The model has three worksheets as follows:
A model inputs worksheet;
A model output worksheet in a table format; and
A model output worksheet in a graph format.
Only the inputs worksheet is accessible initially. The output table and output graph
worksheets will become accessible, once all necessary information has been entered, by clicking
on the "View Output Table" and "View Output Graph" buttons.
When using the model, all of the editing by the user should take place in the model inputs
worksheet.
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2.0 ESTIMATING LANDFILL GAS GENERATION AND RECOVERY
2.1 Model Inputs
All model inputs are entered into the model inputs worksheet. Cells highlighted in yellow
require user inputs. See Figure 1 for model inputs. The following inputs are required to run the
model properly and produce acceptable outputs (tables and graphs). If the landfill is an existing
landfill, the inputs should be based on recorded data and actual conditions (where available),
although inputs based on anticipated (or planned) conditions can be entered in some steps to
obtain hypothetical estimates for evaluation purposes. For future landfills, by definition, inputs
can only be based on anticipated (or planned) conditions.
Step 1. Enter the landfill name and title of the case study/project (Cell E10). The information
entered here will automatically appear in the first heading of the output table and the
output graph.
Step 2. Enter the location (city and province) of the landfill (Cell El 1). The information
entered here will automatically appear in the second heading of the output table and
the output graph.
Step 3. Enter the year the landfill opened and began receiving waste (Cell El2). This value
will feed into the annual landfill activity data table below and into the output table.
Step 4. Enter the year the landfill closed (or is projected to close) (Cell El3). This value will
feed into the annual landfill activity data table below and into the output table.
Step 5. Enter the expected methane content of the LFG (Cell E14). This value will be used to
calculate the net flow of the recovered gas. It is recommended that this value be left
at 50% unless specific information is available from the site that warrants a different
value.
Steps 6 through 16 are required if you want the model to recommend values for k, LO, collection
efficiency, and fire discount factor. You can skip to Step 17 if you have reliable information on
these parameters and would like to enter site-specific values for these parameters (except the fire
discount factor) instead.
Step 6. Select the climatic zone (region) of China where the landfill is located. This will
impact the k and LO values. To see a map of China with the three climatic zones
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delineated (Figure 2), click the 'Show Map of Regions of China' button; click the
'Hide Map of Regions of China' button afterwards to continue entering inputs.
Step 7. Select the appropriate answer to the question "Does coal ash make up a significant
fraction (more than 30%) of the waste placed in the landfill?". This will impact the
LO value, which is lower if a significant fraction of the waste is coal ash.
Step 8. Indicate whether there are signs of current or past subsurface fires at the landfill.
This will impact the L0 value.
The following eight steps require the user to provide information on the construction and
operation of the landfill that determines the collection efficiency of the gas collection system.
For Steps 9 through 15, select "Yes" or "No" as appropriate in response to each question; for
Step 16, select the appropriate bracket (I to V) based on the value of the LFG System Area
Coverage Percentage. Detailed discussions on how to select the appropriate responses to these
eight questions were presented in Section 1.2.1.
Step 9. Is the waste placed in the landfill properly compacted on an ongoing basis?
Step 10. Does the landfill have a focused tipping area?
Step 11. Are there leachate seeps appearing along the landfill side slopes? Or are there ponds
of water/leachate on the landfill surface?
Step 12. Is the average depth of waste 10 m or greater?
Step 13. Is any daily or weekly cover material applied to newly deposited waste?
Step 14. Is any intermediate/final cover applied to areas of the landfill that have reached
interim or final grade?
Step 15. Does the landfill have a geosynthetic or clay liner?
Step 16. Which bracket (I to V) applies to the LFG System Area Coverage? The LFG
System Area Coverage Percentage is defined as the percentage of the landfill area
that has a comprehensive and operating LFG collection system.
LFG System Area
Coverage Percentage
80-100%
60 - 80%
40 - 60%
Bracket
I
II
III
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20 - 40%
< 20%
IV
V
If you do not have sufficient information to answer all of the questions in Steps 9 through
16, the model will not provide a recommended value for the collection efficiency. In such case,
you can skip to Step 17 to enter an assumed/nominal value for collection efficiency. For a typical
landfill constructed and operated in accordance with the state of practice in China, it is
reasonable to use 25 to 40% as the collection efficiency before landfill closure /completion of the
gas collection system and 50 to 65% subsequently.
FIGURE 1 - MODEL INPUTS
China Landfill Gas Model (v1.1)
Instructions
Please complete the information in the yellow highlighted cells, This
information is the minimum input required for proper model operation.
General Information
Namemtle:
Location:
Year Opened:
Year ClQjcdJProjcctcd to Close:
Expected Methane Content of LFG:
Landfill Name
Citj. Province
1333
2013
BOX
Edit title at left which feeds into the
output table and graph.
Input |ear landfill began receiving vaste.
Input closure jear (i.e.. the final |ear in vhich landfill vill receive vaste).
Please enter the expected methane content of the landfill gas. A value of 50^; is recommended unless specific
information is available from the site that warrants a different value. This yalue will be used to calculate the net
Flow of recovered gas.
Landfill Characteristics:
Region of China where the landfill is located (Identify from the map):
Does coal ash make up a significant fraction [greater than 30v;) of the waste
placed in the landfill?
Are there signs of current or past subsurface fires at the landfill?
Reg on 2 (CoU and Wet} jj
No jj
No jj
Snw, Mac of
Regions of China
Criteria Determining Collection Efficiency
Is the waste placed in the landfill properly compacted on an ongoing basis?
Does the landfill have a focused tipping area?
Are there leachate seeps appearing along the landfill sideslopes? Or is there ponding of
water/leachate on the landfill surface?
Is the average depth of waste 10rn or greater?
Is any daily or weekly cover material applied to newly deposited waste?
Is any intermediate^inal cover applied to areas of the landfill that have reached interim or final
grade?
Does the landfill have a geosynthetic or clay liner?
In which bracket (I to V) does the LFG System Area Coverage Percentage fall?
Yes
Yes J
No jj
^ jd
Yes _*j
Yes jj
Yes jj
iid
See user's manual for assistance in answering the above questions or for instructions on how to enter a user-specified or default collection efficiency below.
FIGURE 2 - CLIMATIC ZONES IN CHINA
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CLIMATE ZONE
1 COLD AND DRY
2 COLD AND WET
3 HOT AND WET
Step 17. Review the values of k, L0, collection efficiency, and fire discount factor
recommended by the model based on his inputs in Steps 6 through 16. These appear
under "Model Recommended Value." If you wish to change one or more of these
values, or if you did not complete Steps 6 through 16 and want to enter site-specific
value(s) for one or more of these parameters (except for the fire discount factor),
enter the preferred value(s) under "User Recommended Value." Specifically, enter
single values for k, LO, and collection efficiency into Cells H43 through H45,
respectively. This should be done only if you have reliable site-specific information
on these parameters, or if you do not have sufficient information to answer the
questions in Steps 9 through 16 and would like to enter an assumed/nominal value
for the collection efficiency. If you enter a value for collection efficiency into cell
H45, then the model will feed it into the annual landfill activity data table below and
use it to estimate the LFG recovery rates.
Step 18. For collection efficiency, if you want to enter different values for different years,
enter them into the corresponding cells in Column 4 of the Annual Landfill Activity
Data table, see Figure 3. If not, skip to Step 19. The model defaults to assume that
each year's collection efficiency is the same as the previous year; therefore, values
for collection efficiency need to be entered only in the years it changes. For example,
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if the landfill improves (or plans to improve) the gas collection system or puts a final
cap in place during a given year, you might want to enter a higher collection
efficiency in Column 4 for that year. The model will automatically apply that
collection efficiency to the subsequent years.
Step 19. Enter the average or actual annual waste disposal rate for the landfill in the opening
year in Column 2 of the Annual Landfill Activity Data table (Cell E56). The model
defaults to assume that the annual disposal rate for the years between the opening
year and the closure year (inclusive) remains constant. If you want to enter different
disposal rates for different years, continue to Step 20; otherwise, skip to Step 21.
Step 20. Enter the amount of waste disposed (in metric tonnes) for each year the site is open
in Column 2, see Figure 3. The model accommodates up to 100 years of waste
disposal history or projection. The model defaults to assume that each year's waste
disposal amount is the same as that of the previous year; therefore, values for amount
of waste disposed needs to be entered only in the years it changes. The disposal
estimates should be based on available records of actual disposal rates and be
consistent with site-specific data on amount of waste in place, total site capacity, and
projected closure year. For years without historical data, adjust the disposal amounts
until the calculated total tonnes in place matches estimated actual tonnes in place (as
of the most recent year with waste-in-place data).
Step 21. Enter the actual LFG recovery rates in cubic meters per hour (for sites with active
gas collection systems) in Column 5 of the Annual Landfill Activity Data table (see
Figure 3). This should be the average annual total LFG flow at the flare station
and/or energy recovery plant (NOT the sum of flows at individual wells) and is
usually based on gas flow measurements. If the measured methane content was not
entered in Step 5, adjust all flow rates to 50% methane equivalent by multiplying the
measured flow by the measured methane content of the LFG and then dividing the
result by 50% as indicated in the table below. (This is not necessary if the measured
methane content was entered in Step 5.) The numbers placed in these cells will be
displayed as data points in the graph output sheet, so do not input zeros for years
with no flow data (leave blank instead). The actual measured values entered will not
change the gas generation and recovery curves. Comparing the gas recovery
projected by the model to actual data points provides an indication of how well the
model is predicting gas recovery at the landfill.
Equation for adjusting methane content to 50%:
Measured
Measured methane %
= Flow rate
Flow Rate
China Landfill Gas Model vl.l User's Manual
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50 % methane
2-5
at 50% methane
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FIGURE 3 - MODEL INPUTS
Modeling
Based on y
different ua
Annual Li
Input into c<
You may ch
these data r
Parameters
Dur inputs, the model will use the "model recommended" values below to estimate the gas potential of the landfill. If you have reliable data that suggest a
ue should be used, you may enter it uder the user recommended value and it will be used to generate the gas estimates.
Model User
Recommended Recommended
Value Value
k (Hyr) 0.11
Li(m\metric tonne)
Collection Efficiency
Fire Discount Factor
56
64X
None
Cannot Be Changed
ndfill Activitg Data
jlumn 2 the landfill's annual waste acceptance rate. The model recommended or user recommended collection efficiencies have been entered into column 4.
ange these if you have better data for any given year. If the landfill has a gas collection system in place and has measured actual gas recovery for given years.
nay be entered into column 5 (do not enter zeros).
1
Year
1993
1994
1995
1996
1997
199S
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2
Disposal Rate
(metric tonnesfgr)
20.671
637.340
710.128
683.853
736.020
839.742
831.353
581.686
657.314
734.154
1.176.472
1.212.000
1.343.320
1.477.016
1.681.515
1.788.500
1.860.040
1.334.442
1.354.813
1.435.232
1.227.323
0
3
Vaste-in-Place
(metric tonnes)
20,671
65S.611
1.368.739
2.052,592
2,848,612
3.688,354
4.580,307
5,161,993
5,819,907
6.614,061
7.790,533
9.002,533
10,345,853
11,822.869
13.504.384
15.282.384
17.152,924
19.087.366
20.442,185
21,877,477
23,104,800
23.104.800
4
LFG Collection
Sf s tซB Efficiency
64K
64%
64X
64X
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
5
Actual Measured
Recoverj (m9lhr)
2.468
3.347
-j Via* Output Ta*>
: ri^ View O irtp ut G raph
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2.2 Model Output - Table
Model results are displayed in a table located in the model "Output Table" worksheet
(see Figure 4 for a sample table layout). The model output - table worksheet (and the model
output - graph worksheet) is accessible only after all required information has been entered in the
model input worksheet. The titles of the table have been set by user inputs in the model inputs
worksheet. The table provides the following information, which was either copied from the
model inputs worksheet or calculated by the model:
Projection years starting with the landfill opening year and continues for 100 years in
total.
Annual disposal rates.
Cumulative amount of waste in place at the end of each projection year.
LFG generation rates for each projection year in cubic meters per minute and cubic
meters per hour.
Collection system efficiency for each projection year.
LFG recovery rates for each projection year in cubic meters per minute and cubic
meters per hour.
Carbon dioxide equivalent of recoverable methane gas in metric tonnes per year
(MTCO2e/year).
Potentially available energy output from a direct use project in megajoules per hour
(MJ/hr) (assuming the gas is combusted in a boiler with 85% efficiency to produce
steam).
Potentially available energy output from a electric generation project in megawatts
(MW) (assuming the gas is combusted in an engine with 30% efficiency to produce
electricity).
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Beneath the table, the following information is provided:
The methane content assumed for the model projection (50%, unless changed by the
user in the Inputs worksheet).
The k value used for the model run.
The LQ value used for the model run.
To print the table, select "File", "Print", "OK".
FIGURE 4 - SAMPLE MODEL OUTPUT TABLE
-
Return to Inputs Page
Year
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
Disposal
Rale
metric tonnesfgr
20,671
637,940
710,128
683,853
796,020
839,742
891,953
581,686
657,914
794,154
1.176,472
1.212,000
1,343,320
1.477,016
1.681,515
1,788,500
1,860,040
1,934,442
1.354,819
1,435,292
1,227,323
0
0
0
0
0
0
0
0
0
0
0
Landfill Name
City, Province
Waste
In-Place
metric tonnes
20,671
653.611
1,368,739
2,052,592
2,848,612
3,688,354
4,580,307
5.161,993
5,819,907
6.614,061
7,790,533
9,002,533
10,345,853
11,822,869
13,504,384
15,292,884
17,152,924
19,087,366
20,442,185
21,877,477
23,104,800
23,104,800
23,104,800
23,104,300
23,104,800
23,104,800
23,104,800
23,104,800
23,104,800
23,104.800
23,104.800
23,104.800
LFG
Generation Rate
(m'fmin) | (m'lhr)
0
0
15
29
41
55
68
81
85
91
89
115
130
147
164
185
205
225
245
250
256
256
230
206
184
165
148
133
119
106
95
85
0
28
879
1,737
2,472
3,280
4,062
4,832
5,108
5,456
5,951
6,905
7,808
8,792
8,853
11,077
12,317
13,523
14,704
14,985
15,345
15,389
13,786
12,350
11,064
9.911
8,879
7,954
7,125
6,383
5,718
5,123
Collection
Sgstem
Efficiencg
{*)
My.
64%
64%
MY.
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
64%
LFG Recoverg from
Existing and
Planned Sgstem
(mVmin)|| (m'fhr) || MTCO.e
0
0
9
18
26
35
43
51
54
58
63
73
83
83
105
118
131
144
156
158
163
164
146
131
118
105
94
85
76
68
61
54
0
18
560
1,108
1,576
2,091
2,589
3,081
3,256
3,478
3,793
4,402
4,978
5,605
6,281
7,062
7,852
8,621
9,374
9,553
8,783
9,811
8,788
7,873
7,053
6,318
5,660
5,071
4,542
4,069
3,645
3,266
0
1.163
36.937
73.046
103.916
137.881
170.769
203.168
214.735
229.386
250.176
290.313
328.268
369.658
414.261
465.723
517.844
568.562
618,183
630,021
645,154
647,008
578,613
519.237
465,150
416.698
373.292
334.408
299.574
268.368
240.414
215.371
Energg Output
From Direct
(MJJhr)
0
298
9.452
18.692
26.591
35.282
43.688
51.888
54.848
58.687
64.017
74.287
84.000
94.591
106.004
118.173
132.510
145,488
158,185
161,214
165,087
165,561
148,316
132.866
119.026
106.628
95.521
85.571
76.657
68.672
61.519
55,111
Energg Output
From Electric
(MV)
0.000
0.028
0.902
1.783
2.537
3.366
4.169
4.960
5.242
5.600
6.107
7.087
8.014
9.024
10.113
11.369
12.641
13.880
15.081
15.380
15.749
15.795
14.148
12.675
11.355
10.172
9.113
8.163
7.313
6.551
5.869
5.258
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2.3 Model Output - Graph
Model results are also displayed in graphical form in the model "Output Graph" worksheet. See
Figure 5 for a sample graph layout. Data displayed in the graph includes the following:
A curve of LFG generation rates during the projection years in cubic meters per hour.
A curve of LFG recovery rates during the projection years in cubic meters per hour
Actual (historical) LFG recovery rates in cubic meters per hour, shown as individual
data points.
The titles of the graph have been set by user inputs in the model inputs worksheet.
To print the graph, click anywhere on the graph and select "File", "Print", "OK".
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FIGURE 5 - SAMPLE MODEL OUTPUT GRAPH
Return to Inputs Page
18.000 B
16.000
W.OOO
12.000
ซ 10.000
8.000
6.000
4.000
2.000
Landfill Name
City. Province
m
1893 1888 2003 2008 2013 2018 2023 2028 2033 2038 2043 2048 2053 2058 2063 2068 2073 2078 2083 2088
Estimated Recovery
LFG Generation
+ Actual Recovery
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3.0 REFERENCES
EPA, 1991. Regulatory Package for New Source Performance Standards and III(d) Guidelines
for Municipal Solid Waste Air Emissions. Public Docket No. A-88-09 (proposed May 1991).
Research Triangle Park, NC. U.S. Environmental Protection Agency.
EPA, 1998. Compilation of Air Pollutant Emission Factors, AP-42, Volume 1: Stationary Point
and Area Sources, 5th ed., Chapter 2.4. Office of Air Quality Planning and Standards. Research
Triangle Park, NC. U.S. Environmental Protection Agency.
EPA, 2005. Landfill Gas Emissions Model (LandGEM) Version 3.02 User's Guide. EPA-600/R-
05/047 (May 2005), Research Triangle Park, NC. U.S. Environmental Protection Agency.
IPCC, 2006. 2006IPCC Guidelines for National Greenhouse Gas Inventories.
Intergovernmental Panel on Climate Change (IPCC), Volume 5 (Waste), Chapter 3 (Solid Waste
Disposal).
EPA, 2007. Central America Landfill Gas Model (Version 1.0) User's Manual (March 2007).
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