United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/3-90-011a
March 1991
Air
<&EPA Air Emissions from
Municipal Solid Waste
Landfills - Background
Information for Proposed
Standards and Guidelines
This document printed on recycled paper
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EPA-450/3-90-011a
Air Emissions from Municipal
Solid Waste Landfills -
Background Information for'
Proposed Standards and Guidelines
Emission Standards Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
March 1991
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DISCLAIMER
This report is issued by the Emission Standards Division of the
Office of Air Quality Planning and Standards of the Environmental
Protection Agency. It presents technical data of interest to a
limited number of readers. Copies are available free of charge
to Federal employees, current contractors and grantees, and non-
profit organizations - as supplies permit - from the Library
Services Office (MD-35), U. S. Environmental Protection Agency,
Research Triangle Park, NC 27711, phone 919-541-2777 (FTS 629-
2777), or may be obtained for a fee from the National Technical
Information Service, 5285 Port Royal Road, Springfield, VA 22161,
phone 703-487-4650 (FTS 737-4650).
Publication No. EPA-450/3-90-011a
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ENVIRONMENTAL PROTECTION AGENCY
Background Information Document
for Air Emissions from Municipal Solid Waste Landfills
Prepared by:
^
James B. WeigoM/ (Date)
Acting Directo
Emission Standards Division
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
1. The standards of performance and emission guidelines limit emissions
from new and existing municipal solid waste landfills to 150 Mg/year of
non-methane organic compounds (NMOC's). Section 111 of the Clean Air
Act (42 U.S.C. 7411), as amended, directs the Administrator to establish
standards of performance and emission guidelines for any category of
source of air pollution that "... causes or contribute significantly to
air pollution which may reasonably by anticipated to endanger public
health or welfare."
2. Copies of this document have been sent to the following Federal
Departments: Office of Management and Budget, Commerce, Interior, and
Energy; the National Science Foundation; and the Council on
Environmental Quality. Copies have also been sent to members of the
State and Territorial Air Pollution Program Administrators; the
Association of Local Air Pollution Control Officials; EPA Regional
Administrators; and other interested parties.
3. For additional information contact:
Ms. Alice H. Chow
Standards Development Branch (MD-13)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Telephone: (919) 541-5626
4. Copies of this document may be obtained from:
U.S. EPA Library (MD-35)
Research Triangle Park, NC 27711
Telephone: (919) 541-2777
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: (703) 487-4600
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CONTENTS
Figures . . ........... iv
Tables vi
1. Introduction 1-1
2. Health and Welfare Effects of Air Emissions from Municipal
Solid Waste Landfills ........ 2-1
2.1 Introduction .2-1
2.2 Effects on Human Health and Vegetation Caused by Ambient
Ozone Formed from Nonmethane Organic Emissions 2-3
2.3 Cancer and Noncancer Health Effects 2-5
2.4 Methane Emissions Contributing to Global Warming .... 2-15
2.5 Explosion Hazards. ......... 2-15
2.6 Odor Nuisance 2-22
2.7 Adverse Effects on Soils and Vegetation from MSW
Landfill Air Emissions 2-23
2.8 References 2-27
3. Municipal Landfill Air Emissions. .............. 3-1
3.1 General Landfill Information 3-1
3.2 Emissions from Municipal Landfills 3-8
3.3 Baseline Emission Estimates 3-24
3.4 Explosion Hazards and Odor Nuisance 3-44
3.5 References 3-48
4. Landfill Gas Collection and Control Techniques 4-1
4.1 Landfill Gas Collection Techniques 4-1
4.2 Landfill Gas Emission Control/Treatment Techniques . . . 4-15
4.3 Secondary Air Emissions from MSW Landfill Control
Techniques 4-47
4.4 References 4-60
5. Regulatory Alternatives 5-1
5.1 Derivation of Regulatory Alternatives. .... 5-1
5.2 Existing Municipal Solid Waste Landfills 5-2
5.3 New Municipal Solid Waste Landfills 5-5
5.4 References 5-8
6. Environmental and Energy Impacts of Potential Controls. . . .6-1
6.1 Air Pollution Impacts 6-1
6.2 Water Pollution Impacts 6-6
6.3 Energy Impacts 6-6
6.4 References 6-8
7. Cost of Regulatory Alternatives 7-1
7.1 Development of the Collection System Costs 7-1
7.2 Development of Control System Costs. . . 7-24
7.3 Control Costs for Model Landfills 7-40
7.4 National Cost Impacts 7-49
7.5 References . 7-53
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CONTENTS, Continued
8. Economic Impacts. ......... ....... 8-1
8.1 Overview of Municipal Solid Waste Management ...... 8-1
8.2 Landfill Disposal of Municipal Solid Waste ....... 8-13
8.3 Regulatory Alternatives and Control Options. ...... 8-43
8.4 Analysis of Economic Impacts ....... • • 8-50
8.5 Analysis of Emissions Reductions and
Cost-effectiveness .......... 8-92
8.6 Analysis of Distributional Impacts . 8-102
8.7 Discount Rate Sensitivity Analysis 8-117
8.8 Summary and Conclusions. ...... 8-125
8.9 References . • 8-127
9. Guidance for Implementing the Emission Guidelines and
Compliance Schedule . ..... 9-1
9.1 Determination of Control Requirement 9-4
9.2 Design Guidelines for Gas Collection Systems 9-15
9.3 Collection Systems Operating Guidelines 9-32
9.4 Design and Operating Guidelines for Control Systems. . . 9-33
9.5 Compliance Schedule. .................. 9-34
9.6 References . 9-37
Appendices
A. Evolution of the Background Information Document. A-l
B. Index to Environmental Considerations .... B-l
C. Landfill Gas Composition Data C-l
D. Gas Generation Rate Modeling. ......... D-l
E. Test Methods and Procedures E-l
F. Tables on the Economic Impacts of the Energy Recovery
Option F-l
G. Theoretical Collection System Design G-l
11 i
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FIGURES
Page
3-1 Landfill cell design 3-7
3-2 Two stages of anaerobic decomposition of complex organic
wastes 3-16
3-3 Evolution of typical landfill gas composition . 3-19
3-4 Time-dependent contribution to national baseline emissions. . . . 3-35
4-1 Active collection system 4-4
4-2 Extraction well 4-5
4-3 Vertical trench for an active collection system 4-7
4-4 Horizontal trench collection system ....... 4-8
4-5 Zones of influence for gas extraction wells 4-11
4-6 Technique for sitting wells 4-13
4-7 Enclosed flare 4-18
4-8 Discrete burner, thermal incinerator 4-23
4-9 Distributed burner, thermal incinerator 4-24
4-10 Simplified schematic of gas turbine 4-27
4-11 The four-stroke, spark ignition cycle 4-30
4-12 Pretreatment adsorption system 4-36
4-13 Pressure swing adsorption process .... 4-38
4-14 Packed tower adsorption process . 4-41
4-15 Selexol absorption process 4-43
4-16 Membrane process. 4-45
7-1 Theoretical header pipe system. 7-13
7-2 Graphical representation of the system pressure drop 7-15
7-3 Blowers purchase price (1979 dollars) 7-21
7-4 Motor purchase cost (1979 dollars). 7-22
7-5 Flare equation for capital and annual operating costs 7-28
7-6 Turbine capital cost 7-36
8-1 Flow of municipal solid waste from generation to disposal .... 8-2
8-2 Sources of municipal solid waste 8-5
8-3 Service arrangements for MSW collection 8-7
8-4 Share of MSW managed in disposal alternatives 8-10
8-5 Municipal waste combustion technologies: Distribution of
design capacity 8-12
8-6 Distribution of annual quantity of MSW received at landfills. . . 8-15
8-7 Landfill technologies 8-16
8-8 Ownership of municipal landfills 8-21
8-9 Ownership of landfills by size 8-22
8-10 Jurisdiction limitations of municipal landfills 8-24
8-11 Methods of financing municipal solid waste landfilling 8-29
8-12 Revenue sources for landfill operations by size 8-30
8-13 Revenue sources for landfill operations by ownership 8-31
9-1 Overall three-tiered approach for determination of control
requirements 9-7
9-2 Example of Tier 1 using NMOC emission rate cutoff as the
regulatory option 9-8
9-3 Example of Tier 2 using NMOC emission rate cutoff as the
regulatory option 9-10
iv
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FIGURES, Continued
Number Page
9-4 Example of Tier 3 using NMOC emission rate cutoff as the
regulatory option ..... . 9-11
9-5 Technique for siting wells. ...... 9-21
9-6 Maximum blower vacuum as a function of landfill depth for
three cover types . „ . 9-22
9-7 Estimated radius of influence as a function of blower vacuum. . . 9-24
9-8 Gas extraction well and well head assembly 9-26
9-9 Horizontal trench collection system 9-29
9-10 Estimated radius of influence for a passive system well as a
function of the collection/control system pressure drop 9-31
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TABLES
Number Page
2-1 Summary of the Health and Welfare Effects Associated with MSW
Landfill Emissions and Components 2-2
2-2 Summary of the Health Effects Associated with Toxic MSW
Landfill Emissions Component ... 2-7
2-3 Classification of Evidence Based on Animal and Human Data. ... 2-9
2-4 Acute Injury and Deaths Associated with Municipal Landfill Air
Emissions Explosion and Fires. ....... 2-17
2-5 Documented Cases of Landfill Gas Migration and Associated Fires
and Explosions 2-18
2-6 Response Components of Annoyance Factors Derived from a Survey
of 704 Residents of Dusseldof 2-24
3-1 Active Municipal Landfill Size Distribution 3-2
3-2 Average Composition of Waste in Active Municipal Waste
Landfills 3-4
3-3 Factors Affecting Production Mechanisms 3-12
3-4 Factors Affecting Transport Mechanisms 3-14
3-5 NMOC Concentrations 3-23
3-6 Summary of Nonmethane Organic Compounds Found in Landfill Gas. . 3-25
3-7 1997 National Baseline Emission Estimates 3-30
3-8 Values for k and L 3-32
3-9 Summary of State Regulations Controlling Air Emissions from MSW
Landfills 3-39
3-10 Highly Odorous Components of Landfill Gas 3-46
4-1 Comparison of Various Collection Systems 4-3
4-2 Enclosed Ground Flare Combustion Efficiency Data 4-21
4-3 Nonmethane Organic Air Emission Destruction Efficiency - Results
of Field Tests of the Combustion of Landfill Gas Using Internal
Combustion Engines 4-32
4-4 Net Air Impact for Landfill Air Emission Control Techniques. . . 4-48
4-5 Secondary Air Emissions - Results of Field Tests of the
Combustion of Landfill Gas Using Flares 4-50
4-6 Secondary Air Emissions - Results of Field Tests of the
Combustion of Landfill Gas Using Turbines 4-53
4-7 Secondary Air Emissions - Results of Field Tests of the
Combustion of Landfill Gas Using Internal Combustion Engines . . 4-55
4-8 Derivation of Net Secondary Air Impacts for Gas Turbines and
1C Engines 4-59
5-1 Regulatory Alternatives for Existing Landfills 5-3
5-2 Distribution of Existing Landfills Affected by the Regulatory
Alternatives 5-4
5-3 Regulatory Alternatives for New Landfills 5-6
5-4 Distribution of New Landfills Affected by the Regulatory
Alternatives 5-7
6-1 Net Present Value of Air Impacts of Regulatory Alternatives for
Existing Landfills 6-3
6-2 Net Present Valu.e of Air Impacts of Regulatory Alternatives for
New Landfills 6-4
VI
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TABLES, Continued
Number
6-3 Net Present Value of the Net Energy Impacts of Each Regulatory
Alternative. . . . ...... ...... ........... 6-7
7-1 Major Components of the Gas Extraction System .......... 7-2
7-2 Assumptions Used in Designing the Gas Extraction System ..... 7-3
7-3 Design Equations for the Gas Extraction System ......... 7-5
7-4 Capital Cost Bases and Equations for the Gas Collection
Systems ............................. 7-16
7-5 Direct and Indirect Capital Cost Factors for the Collection
System ............................. 7-18
7-6 Cost Index ........................... 7-20
7-7 Annual ized Cost Bases for the Gas Extraction System ....... 7-25
7-8 Flare System Components ..................... 7-26
7-9 Flare-Bases for Total Capital and Annual Operating Cost ..... 7-29
7-10 Installed Capital Costs for Turbine Plants ........... 7-32
7-11 Equations Used to Cost Analyze the Gas Turbine ......... 7-33
7-12 Data on Operating Personnel Requirements . ........... 7-39
7-13 Model Landfills. ................... ..... 7-41
7-14 Estimated Control Costs for the Existing Model Landfill at a
Stringency Level of 250 Mg NMOC/yr ............... 7-42
7-15 Estimated Control Costs for the Existing Model Landfill at a
Stringency Level of 100 Mg NMOC/yr .......... ..... 7-43
7-16 Estimated Control Costs for the Existing Model Landfill at a
Stringency Level of 25 Mg NMOC/yr. ........ ....... 7-44
7-17 Estimated Control Costs for the New Model Landfill at a
Stringency Level of 250 Mg NMOC/yr ........ ....... 7-45
7-18 Estimated Control Costs for the New Model Landfill at a
Stringency Level of 100 Mg NMOC/yr ............... 7-46
7-19 Estimated Control Costs for the New Model Landfill at a
Stringency Level of 25 Mg NMOC/yr ....... . ........ 7-47
7-20 National Cost Impacts of Controlling Existing Landfills at
Three Stringency Levels ........ . ...... . ..... 7-50
7-21 National Cost Impacts of Controlling New Landfills at
Three Stringency Levels ..................... 7-51
8-1 Materials in the Municipal Waste Stream, 1986. ..!!!..!! 8-4
8-2 Disposal Costs per Mg MSW at Landfills of Various Sizes. . 8-27
8-3 Estimated RCRA Subtitle D Costs to Landfills ...... . . . . 8-36
8-4 Estimated Number and Annual Acceptance Rate of Existing
Municipal Landfills, 1988 to 2013 ........... ..... 8-37
8-5 Historical and Projected Shares of Municipal Solid Waste
Managed in Municipal Waste Combustors .............. 8-42
8-6 Summary Information for Affected Closed and Existing
Landfills ................ ..... ....... 8-52
8-7 Length of Control Period for Affected Closed and Existing
Landfills. .................... ...... .8-54
8-8 Length of Control Period Prior to Closure for Affected
Existing Landfills ....................... 8-55
8-9 Length of Control Period Prior to Closure for Affected
Existing Landfills: Private Landfills Only ........... 8-56
VII
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TABLES, Continued
Number Page
8-10 Net Present Value of Enterprise Costs for Affected Closed and
Existing Landfills 8-58
8-11 Annualized Enterprise Control Cost per Mg of MSW for Affected
Existing Landfills 8-60
8-12 Annualized Enterprise Control Cost per Mg of MSW for Affected
Existing Landfills with Date of Closure Before 1998: Private
Landfills Only 8-62
8-13 Annualized Enterprise Control Cost per Mg of MSW for Affected
Existing Landfills with Date of Closure Between 1998 and 2002:
Private Landfills Only 8-63
8-14 Annualized Enterprise Control Cost per Household for Affected
Existing Landfills 8-65
8-15 Net Present Value of Social Costs for Affected Closed and
Existing Landfills 8-67
8-16 Summary Information for Affected New Landfills 8-75
8-17 Length of Control Period for Affected New Landfills. ...... 8-76
8-18 Length of Control Period Prior to Closure for Affected New
Landfills . . . . 8-77
8-19 Net Present Value of Enterprise Costs for Affected New
Landfills 8-79
8-20 Annualized Enterprise Control Cost per Mg of MSW for Affected
New Landfills 8-81
8-21 Annualized Enterprise Control Cost per Household for Affected
New Landfills 8-83
8-22 Net Present Value of Social Costs for Affected New Landfills . . 8-84
8-23 MSW Tonnage Shares of Municipal Waste Combustors (MWCs) and
Landfills Without and With Various EPA Regulations 8-87
8-24 Net Present Value of Emissions Reductions for Affected Closed
and Existing Landfills 8-94
8-25 Cost Effectiveness for Affected Closed and Existing
Landfills 8-95
8-26 Net Present Value of Emissions Reductions for Affected New
Landfills 8-98
8-27 Cost Effectiveness for Affected New Landfills 8-101
8-28 Service Area Population for a Subset of the Affected Closed
and Existing Landfills 8-106
8-29 Annualized Enterprise Control Cost per Household for a Subset
of the Affected Closed and Existing Landfills. . 8-107
8-30 Annualized Enterprise Control Cost as a Percentage of Local
Taxes Paid by Households in the Service Area for a Subset of
the Affected Closed and Existing Landfills 8-108
8-31 Net Present Value of Capital Costs as a Percentage of Net
Municipal Debt for a Subset of Affected Publicly Owned Closed
and Existing Landfills 8-110
8-32 Service Area Population for A Subset of the Affected New
Landfills 8-112
8-33 Annualized Enterprise Control Cost per Household for a Subset
of the Affected New Landfills 8-114
vm
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TABLES, Continued
Number Page
8-34 Annualized Enterprise Control Cost as a Percentage of Local
Taxes Paid by Households in the Service Area for a Subset
of the Affected New Landfills. ....... . . . . 8-115
8-35 Net Present Value of Capital Cost as a Percentage of Net
Municipal Debt for a Subset of Affected Publicly Owned New
Landfills . 8-116
8-36 Net Present Value of Social Costs for Affected Closed and
Existing Landfills Using a Three Percent Discount Rate ..... 8-118
8-37 Net Present Value of Social Costs for Affected Closed and
Existing Landfills Using a 10 Percent Discount Rate 8-119
8-38 Total Annualized Social Costs for Affected Closed Existing
Landfills Using Various Discount Rates . . 8-121
8-39 Net Present Value of Social Costs for Affected New Landfills
Using a Three Percent Discount Rate. .... ..... 8-122
8-40 Net Present Value of Social Costs for Affected New Landfills
Using a 10 Percent Discount Rate ................ 8-123
8-41 Total Annualized Social Costs for Affected New Landfills Using
Various Discount Rates . . ...... 8-124
9-1 Comparison of Various Collection Systems ... 9-17
ix
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1. INTRODUCTION
This document supports legislative action taken by the
U.S. Environmental Protection Agency (EPA) under Sections lll(b) and lll(d)
of the Clean Air Act (CAA) (42 U.S.C. 1857 et seq), as amended, to control
air emissions from municipal solid waste landfills (hereafter referred to as
municipal landfills) as defined in Subtitle D of the Resource Conservation
and Recovery Act. Section 111 directs the Administrator to establish
standards of performance for any category of new stationary source which"...
causes, or contributes significantly to air pollution which may reasonably
be anticipated to endanger public health or welfare." Municipal landfill
air emissions are being regulated because of the adverse health and welfare
impacts caused by the following characteristics of landfill gas:
(1) presence of volatile organic compounds; (2) presence of toxic and
potentially hazardous compounds; (3) explosion potential; and (4) odor
nuisance.
Standards of performance for stationary sources are required to
reflect"... the degree of emission reduction achievable which (taking into
account the cost of achieving such an emission reduction, and any nonair
quality health and environmental impacts and energy requirements) the
Administrator determines has been adequately demonstrated for that category of
sources." The standards developed under Section lll(b) apply only to new
stationary sources that have been constructed or modified after regulations
are proposed by publication in the Federal Register.
Under Section lll(d), EPA has established procedures whereby States
submit plans to control existing sources of "designated pollutants."
Designated pollutants are those which are not included on a list published
under Section 108(a) or 112(b)(l)(a), but to which a standard of performance
applies under Section lll(b). Section lll(d) requires emission standards to
be adopted by the States and submitted to EPA for approval. The standards
would limit emissions of designated pollutants from existing facilities,
which would be subject to the standards of performance for new stationary
sources if they were new sources.
1-1
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Subpart B of 40 CFR 60 contains the procedures under which States
submit these plans to control existing sources of designated pollutants.
Subpart B requires the States to develop plans for the control of designated
pollutants within Federal guidelines. As indicated in Subpart B, EPA will
publish guidelines for development of State emissions standards for a
designated pollutant. These guidelines will apply to designated facilities
which emit those designated pollutants and will include useful information
for States, such as discussion of the pollutant's effects, description of
control techniques and their effectiveness, costs, and potential impacts.
Finally, as guidance for the States, recommended emission guidelines and
times for compliance are identified.
The chapters of this document present the technical information on
which the legislative actions under Sections lll(b) and lll(d) are based.
They also present the necessary information discussed above for States to
consider in establishing standards for existing municipal landfills.
Chapter 2 provides background information on the health and welfare
impacts of municipal landfill air emissions. This includes the cancer and
noncancer health effects of components in landfill gas; documented cases where
explosions and fires have occurred; and studies listing identified problems
with odors emanating from landfills.
Chapter 3 provides an overview of municipal landfill characteristics
and discusses their emission potential. It describes the mechanisms by
which emissions occur; quantifies baseline VOC emissions from new and
existing landfills; quantifies the typical concentration of hazardous
compounds; and details the ways in which explosion hazards and odor nuisance
problems can occur.
Chapter 4 presents the techniques for controlling municipal landfill
air emissions. This includes details on achieving the efficient collection
of landfill gas; applicability and efficiency of available control systems;
and potential byproduct emissions.
Chapter 5 presents the alternatives for regulating new and existing
landfills. This section includes a discussion of the derivation of the
regulatory alternatives and the corresponding impacts on existing and new
municipal solid waste landfills.
1-2
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Chapter 6 quantifies the health, welfare, environmental (air and water
pollution) and energy impacts for each regulatory alternative.
Chapter 7 presents the estimated costs of controlling municipal
landfill air emissions. This includes the design features of the collection
and control system as well as the basis for capital and annual operating
costs. The approach for estimating nationwide cost impacts is also discussed
Chapter 8 presents the economic impacts ... [complete after the chapter
is finished].
Chapter 9 provides a description of the emission guidelines and
compliance schedule for States to follow.
1-3
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EPA-4SO/3-90-011a
Air Emissions from Municipal
Solid Waste Landfills -
Background Information for
Proposed Standards and Guidelines
Emiuion Standard* Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Offio* of Air and Radiation
Ofltoa of Air Quality Pluming and Standard*
R»M«fch Triangto Pa*. North Carolina 27711
July 1900
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I. HEALTH AND WELFARE EFFECTS OF AIR EMISSIONS
FROM MUNICIPAL SOLID WASTE LANDFILLS
2.1 INTRODUCTION
This chapter presents a summary of the potential adverse health and
welfare effects of air emissions from municipal solid waste (MSW) landfills.
The five major effects of MSW landfill air emissions are (1) human health
and vegetation effects caused by ozone formed from nonmethane organic
compound (NMOC) emissions, (2) carcinogenicity and other possible noncancer
health effects associated with specific MSW landfill emission constituents,
(3) global warming effects from methane emissions, (4) explosion hazards,
and (5) odor nuisance. In addition, soils and vegetation on or near the
landfills are adversely affected by MSW landfill emissions migrating through
the soil. The above effects are briefly summarized below and in Table 2-1.
A variety of different NMOCs have been detected in air emissions from
MSW landfills. In the atmosphere, NMOCs can contribute to formation of
ozone through a series of photochemical reactions. The ozone formed through
these reactions can exert adverse effects on human health and on vegetation.
The effects ozone exerts on both human health and vegetation are discussed
in greater detail in Section 2.2.
There are potential acute and chronic health hazards associated with
several chemical species in MSW landfill emissions. The potential cancer
risks associated with exposure to MSW landfill emissions have been
considered by EPA (see Section 2.3). There are also other chronic noncancer
health effects associated with some of the individual chemicals found in MSW
landfill air emissions. Qualitative descriptions of both the cancer and
noncancer health effects are also included in Section 2.3.
The landfill gas that is generated from the decomposition of municipal
solid waste in a landfill consists of approximately 50 percent methane and
50 percent carbon dioxide, and less than 1 percent NMOCs. The methane
emissions are of concern for two reasons: 1) methane, one of the
"greenhouse gases", contributes to the phenomenon of global warming
2-1
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TABLE 2-1. SUMMARY OF THE HEALTH AND WELFARE EFFECTS ASSOCIATED WITH
MSW LANDFILL EMISSIONS AND COMPONENTS
Component
Health and welfare effects
Ozone
Toxics
Methane
Odor
Alterations in pulmonary function,
aggravation of pre-existing
respiratory disease, damage to lung
structure; foliar injury, such as
stippling or flecking, reduced growth,
decreased yield
Leukemia, aplastic anemia, multiple
myeloma, cytogenic changes, damage to
liver, lung, kidney, central nervous
system, possible embryotoxicity,
brain, liver and lung cancer, possible
teratogenicity
Death, burns, dismemberment due to
explosions and fires; property damage;
contribution to phenomenon of global
warming; MSW landfill emissions
migrating through the soil on or near
the landfill inhibits revegetation,
causing deep root death
Odor nuisance, leading to annoyance,
irritability, tension, reduction in
outdoor activities, reduction in
property values, decreased commercial
investment leading to decreased sales,
tax revenue
2-2
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(Section 2.4); and 2) the accumulation of methane gas in structures both
within and beyond the landfill boundary has resulted in explosions, fires,
and subsequent loss of property (Section 2.5).
Pollutants that exert effects on human welfare are pollutants that
affect the quality of life, cause damage to structures, or result in a loss
of vegetation. The welfare effects of concern associated with MSW landfill
air emissions include, in addition to destruction of property by explosions,
emanation of odors and effects on soil and vegetation. Although odor
perception is extremely variable and subjective, sociological studies have
shown extreme annoyance and emotional disturbances in individuals residing
in areas where objectionable odors are present. Property values may
decrease and economic disadvantages may result in communities in or near a
source of perceived malodorous emissions such as those from MSW landfills.
Section 2.6 discusses odor generation by MSW landfills and some of the
studies and surveys that have been done about the problem of odor nuisance.
Also, revegetation of uncontrolled landfills after closure is often
unsuccessful because the landfill gases affect plant root structure. This
effect is discussed in Section 2.7.
2.2 EFFECTS ON HUMAN HEALTH AND VEGETATION CAUSED BY AMBIENT OZONE FORMED
FROM NONMETHANE ORGANIC EMISSIONS
2.2.1 Health Effects Associated with Exposure to Ozone
Ozone and other oxidants found in ambient air are formed as the result
of atmospheric physical and chemical processes involving two classes of
precursor pollutants, NMOCs and nitrogen oxides (NO ). NMOCs are
constituents of the air emissions from MSW landfills. Therefore, emissions
of NMOCs from landfills also contribute to ozone formation. The effects of
ozone on human health are well documented. There are several .different
mechanisms through which ozone can exert adverse effects on human health.
Ozone can penetrate into different regions of the respiratory tract and be
absorbed through the respiratory system. Indirect effects of ozone are
those such as adverse effects on the pulmonary system resulting from
chemical interactions of ozone as it progresses through the system. Finally
there may be adverse effects on other body organs and tissues caused
indirectly by reactions of ozone in the lungs.
2-3
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Specific adverse human health effects associated with exposure to ozone
2
include:
• changes in pulmonary function;
0 symptomatic effects;
• aggravation of pre-existing respiratory disease;
• damage to the lung structure;
t increases in susceptibility to respiratory infections; and
• adverse effects on blood enzymes, central nervous system, liver
and endocrine system.
Pulmonary function decreases have been reported in healthy adult subjects
after one to three hours of exposure to ozone. Subjects at rest (not
exercising) have shown decreases in lung function at concentrations of about
nc
4"
0.5 ppm ozone. Persons that are heavily exercising have experienced
decreases in lung function at about 0.1 ppm ozone.
Symptomatic effects, such as cough, shortness of breath, general
trouble in breathing and pain when breathing have been reported in
controlled human exposure studies. These effects reportedly occurred when
exposure levels exceeded an ozone concentration of 0.12 ppm.
There is some indication from a group of epidemiological studies that
persons with existing respiratory diseases may experience aggravation of
their conditions when exposed to ozone. Definitive data correlating
increased rates of asthma attacks to ozone exposure do not exist, however.6
Another possible effect of ozone exposure is damage to the lung
structure. Laboratory studies of rats and monkeys have shown inflammation
and damage to lung cells following exposure to ozone. Studies on rats,
mice, and rabbits have shown increased susceptibility of the animals to
bacterial respiratory infections following ozone exposure.7 Considering the
differences in human and animal physiology and immune defenses, it is still
reasonable to hypothesize that humans exposed to ozone could experience
increased susceptibility to respiratory infections,,8
Finally, some animal studies have indicated that exposure to ozone
exerts adverse effects on the cardiovascular, liver and endocrine systems.
2-4
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Definitive data on humans to substantiate these occurrences are not
available. However, the body of evidence from the animal studies suggests
g
that ozone can cause effects in tissues and organs other than the lung.
2.2.2 Adverse Effects of Ozone on Vegetation
Foliar injury on vegetation is one of the earliest and most obvious
manifestations of ozone impacts. The specific effects can range from
reduced plant growth and decreased yield, to changes in crop quality and
alterations in susceptibility to abiotic and biotic stresses. The plant
foliage is the primary site of ozone effects, although significant secondary
effects, including reduced growth and yield, can occur. Ozone injury to
foliage is identified as a stippling or flecking. Such injury has occurred
experimentally in various plant species after exposure to 60 ug/m
(0.03 ppm) ozone for 8 hours. Studies with tobacco and other crops
confirmed that ozone injures vegetation at sites near urban centers. It
is now recognized that vegetation at rural sites may be injured by ozone
12
that has been transported long distances from urban centers. Studies of
the effect of ozone on plant growth and crop yield indicate occurrences of
detrimental effects. For example, field studies in the San Bernadino Forest
during the last 30 years show that ambient ozone has reduced the height
growth of Ponderosa pine by 25 percent and has reduced the total volume of
wood produced by 84 percent.
2.3 CANCER AND NONCANCER HEALTH EFFECTS
The adverse human health effects associated with MSW landfill emissions
have not been directly determined by human or animal studies. In the
absence of such data, EPA has evaluated some of the individual chemical
constituents of MSW landfill emissions. Over 100 chemical constituents have
been detected in MSW landfill emissions, as shown in Table C-l of
Appendix C. Exposure to the several of the landfill constituents has been
associated with cancer and noncancer health effects. Both cancer and
noncancer health effects have not been quantified in a national study, due
to limitations in the emissions data. However, these adverse effects can be
discussed qualitatively. Adverse effects on target organ systems such as
the kidney, liver, pulmonary, and central nervous systems have been
2-5
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associated with various components of air emissions from MSW landfills. A
detailed summary of the health effects is given in in Section 2.3.1.2.
2.3.1 Hazard Identification
Hazard identification is a qualitative step for determining whether or
not exposure to a given substance is associated with any adverse health
effect. Because epidemiological and animal studies of the health effects of
MSW landfill emissions, which are mixtures of many chemicals, have not been
found, the hazard identification process was based on a review of the
health data of the MSW components. This review focused on nine carcinogenic
constituents known to be present in MSW landfill air emissions (benzene,
carbon tetrachloride, chloroform, ethylene dichloride, methylene chloride,
perchloroethylene, trichloroethylene, vinyl chloride, and vinylidene
chloride—Table 2-2). There were other carcinogenic compounds emitted, but
these nine pollutants have been repeatedly measured in the air emissions
• i
from various MSW landfills.
One of the initial steps that EPA takes in addressing the potential for
health effects is to consider the quality of the available data for each MSW
landfill gas constituent. The EPA has developed a classification scheme for
characterizing the weight-of-evidence for human carcinogenicity. Evidence
of possible carcinogenicity in humans comes primarily from two sources:
long-term animals tests and epidemiologic investigations. Results from
these studies are supplemented with available information from other
relevant toxicologic studies. The question of how likely an agent is to be
a human carcinogen is answered in the framework of a weight-of-evidence
judgment. Judgments about the weight of evidence involve considerations of
the quality and adequacy of the data and the kinds and consistency of
responses induced by a suspect carcinogen. There are three major steps to
characterizing the weight-of-evidence for carcinogenicity in humans:
(1) characterization of the evidence from human studies and from animal
studies individually, (2) combination of the characterizations of these two
types of data into an indication of the overall weight-of-evidence for human
carcinogenicity, and (3) evaluation of all supporting information to
determine if the overall weight-of-evidence should be modified.
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TABLE 2-2. SUMMARY OF THE HEALTH EFFECTS ASSOCIATED WITH
TOXIC MSW LANDFILL EMISSIONS COMPONENTS
Component
Health and welfare effects
Benzene
Carbon tetrachloride
Chloroform
Ethylene dichloride
Methylene chloride
Perchloroethylene
Trichloroethylene
Vinyl chloride
Vinylidene chloride
Leukemia, aplastic anemia, multiple
myeloma, cytogenic changes — human
carcinogen
Damage to liver, lung, kidney, central
nervous system. Possible
embryotoxicity--probable human
carcinogen
Damage to liver, kidney, central
nervous system—probable human
carcinogen
Damage to central nervous
system—probable human carcinogen
Probable human carcinogen
Probable human carcinogen
Probable human carcinogen
Central nervous system effects; brain,
liver and lung cancer; possible
teratogen--human carcinogen
Damage to liver, kidney—possible
human carcinogen
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The EPA has developed a system for stratifying the weight-of-evidence.
This classification is not meant to be applied rigidly or mechanically. At
various points in the above discussion, there is the need for an overall,
balanced judgment of the totality of the available evidence. Particularly
for well-studied substances, the scientific data base will have a complexity
that cannot be captured by any classification scheme. The EPA's
weight-of-evidence system is summarized in Table 2-3 and the specific weight
of evidence classifications for the nine carcinogens of concern are provided
in Section 2.3.2.14
2.3.2 Health Effects of Individual Compounds
A discussion of the adverse health effects and the weight evidence
classification for the nine carcinogens is presented below.
2.3.2.1. Benzene. Benzene administered orally to rats has resulted in
increased incidences of Zymbal gland carcinomas. In mice, inhalation
exposures have shown subsequent anemia and other disorders of the blood
imm
17
forming tissues. Other studies with mammalian cells have shown cytogenic
abnormalities following benzene exposure.
In humans, chronic exposure to benzene has resulted in abnormalities of
the blood such as anemia, leucopenia, thromobocytopenia (pancytopenia).
Epidemiological studies have shown highly statistically significant causal
associations between leukemia and.occupational exposure to benzene and
benzene-containing solvents.
Other studies of human populations exposed to benzene have shown
significant increases in chromosomal aberrations. In some instances, the
aberrations have persisted for years after the cessation of exposure.18
According to IARC, there is sufficient evidence that benzene is a human
carcinogen and limited evidence that it is carcinogenic in experimental
animals. EPA classifies benzene as a Group A carcinogen, a human
carcinogen. The Group A classification is used only when there is
sufficient evidence from human studies to support a causal association
between exposure to a given substance and induction of cartcer.
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TABLE 2-3. CLASSIFICATION OF EVIDENCE BASED ON ANIMAL AND HUMAN DATA
a,b
Animal Evidence
Human evidence
Sufficient
Limited
Inadequate
No data
No evidence
Sufficient
A
Bl
B2
B2
B2
Limited
A
Bl
C
C
C
Inadequate
A
Bl
D
D
D
No
data
A
Bl
D
D
D
No
evidence
A
Bl
D
E
E
The above assignments are presented for illustrative purposes. There may
be nuances in the classification of both animal and human data indicating
that different classifications than those given in the table should be
assigned. Supporting data (e.g., structure-activity relationships,
short-term test findings, etc.) should also be considered in the
weight-of-evidence classification.
3 A = human carcinogen
B2 = probable human carcinogen
C = possible human carcinogen
D = not classifiable as to human carcinogenicity
E = evidence of noncarcinogenicity for humans
2-9
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2.3.2.2 Carbon tetrachloride. Carbon tetrachloride causes damage to
20
the liver, lungs, kidneys and central nervous system in humans. The
potential for embryotoxicity exists, especially for males. The
carcinogenicity of carbon tetrachloride has been observed in tests with
three animal species. Primarily, the tumors found in the animals were liver
tumors.21 The human data on carcinogenicity of carbon tetrachloride are
centered on case reports and one epidemiological study. Using the EPA
weight of evidence criteria for carcinogenicity, carbon tetrachloride is
classified as a probable human carcinogen, Group B2.
2.3.2.3 Chloroform. Exposure to chloroform has been associated with
adverse effects on the liver, kidneys, and central nervous system of
humans.22 Additional effects on the human cardiac system have also been
23
reported, including cardiac arrhythmias and cardiac arrest. There is also
some evidence that chloroform has carcinogenic potential in several animal
species, including mice (eight strains), rats (two strains) and one strain
of dogs. In these studies, chloroform was administered orally. The
evidence for carcinogenicity of chloroform in animals includes statistically
significant increases in kidney tumors in rats and mice, and liver tumors in
mice.
No epidemiological studies have been found evaluating chloroform by
itself. But several studies have indicated small, but statistically
significant increases in rectal, bladder and colon cancer in humans
consuming drinking water that contained chloroform as well as other
trihalomethanes. Because chloroform was not thought to be the only possible
carcinogen in the drinking water, the studies cannot be used to define
chloroform's carcinogenic potential in humans. At this time, the
epidemiologic evidence for the carcinogenicity of chloroform is
inadequate. The overall weight of evidence classification for chloroform
is B2--probable human carcinogen,26 based on existing sufficient animal
evidence and inadequate epidemiological evidence.
2.3.2.4 Ethvlene dichloride. The adverse effects of, ethylene
dichloride (EDC) that have been reported in the literature are largely
associated with the gastrointestinal and nervous systems in humans. Subtle
neurological effects (e.g., fatigue, irritability, sleeplessness) may be
2-10
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more prevalent than overt symptoms of central nervous system toxicity at
lower concentrations.
EDC was shown to be carcinogenic in a National Cancer Institute
lifetime bioassay. Several types of tumors were observed in both rats and
mice. In rats, carcinogens of the forestomach and circulatory system
hemangiosarcomas were found. Hepatocellular carcinomas,
alveolar/bronchiolar adenomas, and mammary carcinomas were seen in mice
27
exposed to EDC. The route of exposure for this bioassay was gavage
(oral). No statistically significant increases in tumors occurred in rats
28
or mice following lifetime inhalation exposure. No case reports on
studies in humans concerning carcinogenicity of EDC were found in the
29
literature.
The weight of evidence classification for EDC is B2, meaning it is a
probable carcinogen in humans. The classification is based on sufficient
animal evidence from the lifetime oral exposure bioassay along with an
absence of epidemiologic data.
2.3.2.5 Methvlene chloride. Bioassays conducted by the National
Toxicology Program (NTP) demonstrated that methylene chloride is oncogenic
(tumor-causing) in both rats and mice when exposed via inhalation. In the
mouse bioassay, statistically significant increases in liver and lung tumors
ir
32
.were observed. Statistically significant increases in benign mammary
gland tumors were seen in the rat bioassay.'
Data on humans exposed to methylene chloride, primarily in the
workplace, are judged to be inadequate for evaluating the carcinogenic
potential of methylene chloride. Therefore, methylene chloride is
classified as a Group 82 carcinogen--probable human carcinogen—because
there is sufficient animal evidence and inadequate epidemiological evidence.
There has been some difference of opinion on the carcinogenic potential
of methylene chloride as related to species differences in metabolic
pathways. The EPA has evaluated the latest data related to the risk of
cancer and exposure to methylene chloride. The EPA has concluded that the
evidence of the carcinogenic mechanism of methylene chloride qnd species
differences in use of the metabolic pathways are not sufficient to support
an estimate of zero cancer risk to humans.
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2.3.2.6 Perchloroethvlene
In humans, transient liver damage has been linked to short-term
exposures to perchloroethylene at relatively high levels. Some slight
effects on the central nervous system have been reported in humans exposed
to relatively high perchloroethylene concentrations. Excluding
carcinogenicity, toxicity testing in experimental animals, along with
limited human data, suggest that long-term exposure to low concentrations of
perchloroethylene is not likely to present a health concern.
However, inhalation bioassays conducted by the National Toxicology
Program on rats and mice of both sexes showed evidence of carcinogenicity
for perchloroethylene.36 In the National Toxicology Program studies,
increases in mononuclear cell leukemia, and rare kidney tumors were observed
in rats. Liver tumors were observed in mice. Using the EPA weight of
evidence classifications, perchloroethylene is considered a probable human
carcinogen, Group 82.
2.3.2.7 Trichloroethvlene. The evidence for carcinogenicity of
trichloroethylene is shown by tumor induction in male rats and both sexes of
38
mice by oral and inhalation exposure. Statistically significant increases
in renal adenocarcinomas and adenomas were observed in bioassays of male
rats by either inhalation or oral exposures. Either exposure route produced
39
elevated incidences of leukemia in one strain of male rats. Inhalation
exposure produced hepatomas and hepatocellular carcinoma (liver tumors) in
two mouse strains. Inhalation exposure also produced malignant lymphomas in
40
one strain of female mice. Leydig cell tumors have also been reported in
two studies.
Epidemiological evidence for carcinogenic potential of
trichloroethylene is inadequate. EPA reviewed seven epidemiologic studies
or surveys and concluded all were inadequate to allow characterization of
42
carcinogenic potential.
EPA has classified trichloroethylene as a Group B2--probable human
carcinogen. This classification is based on the existence of sufficient
animal evidence and inadequate epidemiological evidence.
2.3.2.8 Vinvlidene chloride. Metabolism of vinylidene chloride
produces substances (metabolites) that exert adverse effects on the liver
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and kidneys. Eighteen animal studies were identified by EPA in the
literature that provided information on the carcinogenic potential of
vinylidene chloride. None of the studies that were conducted using the
inhalation exposure pathway was conducted over the lifetime of the study
45
animals. In the single study that was judged to be adequate for assessing
carcinogenic potential, statistically significant increases in kidney tumors
were observed in one strain of male mice.
There is no adequate epidemiologic evidence to assess the
47
carcinogenicity of vinylidene chloride in humans. Because there is
limited animal evidence for carcinogenicity and inadequate evidence from
epidemiological studies, EPA has classified vinylidene chloride as a
Group C--possible human carcinogen.
2.3.2.9 Vinvl chloride. In'mice, exposure to vinyl chloride via
inhalation has produced lung tumors, mammary carcinomas and angiosarcomas of
the liver (malignant tumors). Cancer of the liver and other organs was also
49
observed in rats exposed to vinyl chloride.
In occupational exposures of humans, vinyl chloride disease is the name
given to the total clinical syndrome associated with vinyl chloride
exposure. The disease includes circulatory disturbances in the extremities
(hands and feet), Raynaud syndrome, skin changes and changes in liver
function.
Other studies have shown chromosomal aberrations in the lymphocytes of
humans occupationally exposed to vinyl chloride. In addition, increased
incidences of fetal loss have been associated with occupational exposure to
52
vinyl chloride.
Studies of humans exposed to vinyl chloride in the workplace have shown
a causal relationship between the vinyl chloride exposure and development of
cancer of the liver, brain and lung. Angiosarcomas are rare tumors.
Finding seven cases of these tumors in a single group of workers at one
vinyl chloride plant is strong evidence of the carcinogenicity of vinyl
chloride. Vinyl chloride is classified as a Group A carcinogen; a human
carcinogen.
2-13
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2.3.3 Cancer Risk Assessment
Based on the available information, EPA attempted to quantify the
potential carcinogenic risks to the people exposed to MSW landfill
emissions. However, unlike other source categories that have been regulated
previously, the EPA was not able to quantify for this source category as one
of the critical risk assessment parameters—toxics emissions rates. This
was because the MSW landfill data base was generated by collecting available
information from numerous sources which were not specifically designed to
quantify toxics emissions rates. Although the data base of 931 facilities
contained some data for the toxic constituent concentrations and the
landfill gas emissions rates, there was no facility for which both values
were known. Both the toxic constituent concentration and the landfill gas
emission rate are required to compute the toxic emission rate. In addition,
the EPA had no reliable technique to replace a missing value for either
toxics emissions parameter from the other reported parameters in the
database. Thus, the EPA could not reliably calculate a toxics mass emission
rate and, in turn, could not reliably calculate a risk estimate for even one
facility.
Other attempts, such as random assignment of known (measured) values to
those facilities with missing values, were made to extrapolate nationwide
54
risk estimates from the limited toxics data. In doing so, this
extrapolation (the estimation of the toxic landfill gas mass emission rates)
was creating an additional level of uncertainty above and beyond a more
typical risk assessment. After considering this additional uncertainty in
conjunction with the other known uncertainties associated with risk
assessment, the EPA concluded that MSW landfill risk estimates would not be
credible. Furthermore, because these regulations are being proposed under
Sections lll(b) and (d) of the Clean Air Act and are technology-based, risk
estimates were not required in selecting among the regulatory options (see
Chapter 5). However, even though the risk associated with exposure to
landfill emissions could not be reliably quantified, the available
information indicates that toxic emissions do emanate from MSW landfills and
suggests a need to regulate this source category's emissions.
2-14
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2.4 METHANE EMISSIONS CONTRIBUTING TO GLOBAL WARMING
Greenhouse gases serve to trap heat from the sun and maintain the
earth's climate. Methane and other greenhouse gases such as carbon dioxide
and nitrous oxide occur naturally in the atmosphere. They serve as a
thermal blanket allowing solar radiation to pass through the atmosphere
while absorbing some of the infrared radiation emitted back from the earth's
surface. The absorption of radiation warms the atmosphere and provides the
present climate. The earth would be approximately 30 degrees colder without
the presence of greenhouse gases. The atmospheric temperature will increase
if the concentrations of greenhouse gases are increased.
Anaerobic decomposition of municipal solid waste in landfills results
in the decomposition of municipal solid waste in landfills results in the
generation of methane and carbon dioxide. An estimate of the amount of
methane and carbon dioxide from MSW landfills is provided in Chapter 3.
Methane is more potent than C02 due to its radiative characteristics and
other effects methane has on atmosphere chemistry. Molecule-for-molecule
methane traps 20-30 times more infrared energy in the atmosphere. Therefore
even a small increase in the methane concentration in the atmosphere is a
concern to scientists trying to predict the warming of the climate.
There is considerable uncertainty with regard not only to the timing
but also to the ultimate magnitude of any global warming. However, there is
currently strong scientific agreement that the increasing emissions of
greenhouse gases such as methane will lead to temperature increases. Within
EPA and the international scientific community efforts are underway to
reduce these uncertainties, estimate the cost of mitigation, and identify
possible control options. Reduction of methane emissions from MSW landfills
is one of many options available to reduce possible global warming.
2.5 EXPLOSION HAZARDS
2.5.1 Health Effects Associated with the Explosivitv Of Municipal Solid
Waste Landfill Air Emissions
Decomposition of the waste in MSW landfill air emissions produces the
explosive methane gas. If the methane accumulates in structures on or
off-site, explosions or fires can result. MSW landfill air emissions have
2-15
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resulted in documented explosions and fires both within and beyond the
landfill boundaries. Section 2.5.2 of this chapter describes the welfare
effects such as the explosion hazards and associated property damage. This
section briefly presents information on the health effects associated with
the explosions resulting from MSW landfill gas emissions.
MSW landfill gas can migrate off-site and emissions can escape into
confined spaces such as basements, crawl-spaces, utility closets and false
ceilings. Explosions of the gas have caused severe personal injury and
death. Table 2-4 lists documented cases of acute injury and death caused by
explosions and fires related to MSW landfill gas emissions.
2.5.2 Explosivitv of MSW Landfill Air Emissions
MSW landfill gas is composed largely of methane and carbon dioxide.
Methane gas is odorless and is highly explosive when mixed with air at a
volume between 5 and 15 percent (the lower and upper explosive limits of
methane). Methane can migrate off-site from the landfill and possibly
collect in basements or crawl spaces of nearby structures. For example,
methane has migrated from the Port Washington landfill in New York into
homes near the landfill. Within two years, four explosions occurred in
homes very near the landfill. Subsequent testing by the Nassau County Fire
Marshall discovered explosive levels of methane in or around twelve homes in
the vicinity of the landfill.
Table 2-5 lists documented examples of explosions or fires
associated with MSW landfill gas. These examples show clearly that
structural damage and the loss of facility use are real possibilities
related to these gas explosions. Instances of facility abandonment are also
documented as shown in the table.
There is also documentation that the presence and migration of MSW
landfill emissions adversely affects property value of surrounding land
parcels. For example, at the Midway landfill in the Seattle, Washington,
area, MSW landfill gas migrated under a major interstate highway and
percolated up in residential areas. There was immediate concern in the
neighborhood; 11 families were evacuated. A program to subsidize the sale
of houses in the area was started by the City. Information collected
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TABLE 2-4. ACUTE INJURY AND DEATHS ASSOCIATED WITH MUNICIPAL
LANDFILL AIR EMISSIONS EXPLOSIONS AND FIRESd
Location, date
Incident, injury
Comack, NJ. 1984
Manchester, NJ. 1983
Cleveland, OH. 1980
Commerce City, CO. 1977
Sheridan, CO. 1975
Sheridan, CO. 1975
Richmond, VA. 1975
Winston-Salem, NC. 1969
Atlanta, GA. 1967
Madison, WI (no date given)
Gas migrated to landfill weigh-station
on-site. Explosion killed one, injured one
Spark from landfill pump probably ignited
gas. One person burned.
Explosion at foundry adjacent to landfill.
One killed.
Explosion in tunnel being built under a
railroad right-of-way. Two workmen killed,
four fireman injured.
Gas migrated into drainage pipe under
construction. Welding truck led to fire.
Two injured.
Gas accumulated in drain pipe running
through landfill. Children playing with
candle caused explosion. Several children
injured.
Gas migrated from nearby landfill into
apartment. Two injured.
Gas migrated from adjacent landfill into
basement of armory. Lighted cigarette led
to explosion. Three killed, five seriously
injured.
Gas migrated from adjacent landfill into
sealed basement of single story recreation
center building. Lighted cigarette led to
explosion. Two workmen killed, six injured.
Explosion destroyed sidewall of a townhouse,
Two people seriously injured.
Reference 62.
These incidences highlight explosions and health effects. Other incidences
of explosions related to methane migration from MSW landfills and
property destruction are given in Table 2-6.
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TABLE 2-5. DOCUMENTED CASES OF LANDFILL GAS MIGRATION AND
ASSOCIATED FIRES AND EXPLOSIONS3
Landfill name/1ocation/date
Damages and other comments
Pittsburgh, PA
September 1987
Bakersfield Landfill
Fresno, California
April 1984
BKK Landfill
West Covina, California
August-October 1984
Babylon Landfill
Comack, New Jersey
May 1984
Hardy Road Landfill
Akron, Ohio
1984
1-95 Landfill
Lorton, Virginia
1984
Landfill near Lake Township
Canton, Ohio
1984
PJP Landfill
Jersey City, New Jersey
1984
Smithtown Landfill
Smithtown, New York 1984
Offsite gas migration is suspected to
have caused house to explode.
Incident is under investigation.
Toxics are being monitored in homes
near the landfill.
Fresno police bomb squad used site for
practice. A bomb was buried and was
detonated causing LFG explosion.
Explosive levels of methane were also
migrating off-site.
Twenty residences temporarily
evacuated due to explosive methane
levels in adjoining soils.
Methane migrated to a house on-site
and exploded.
One house destroyed. Ten houses
evacuated temporarily.
Explosion and fire occurred.
Two homes and a day care center
temporarily evacuated.
Landfill fires causing air pollution
have been a continual problem.
Explosion damaged room in transfer
station.
(continued)
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TABLE 2-5. (Continued)
Landfill name/location/date
Damages and other comments
Wallingford Landfill
Wallingford, Connecticut
June 1984
Anderson Township Landfill
Cincinnati, Ohio
1983
Monument Street Landfill
Baltimore, Maryland
April 1983
Ocean County Landfill
Manchester, New Jersey
December 1983-
Operating Industries Landfill
Monterey Park, California
August 1983
Shawnee County Landfill
Topeka, Kansas
August 1983
Fells Street Landfill
Richmond, Virginia
1975
Tyler, Texas
May 1982
Explosive levels of methane detected
in dog pound. Dog pound temporarily
closed, ventilation system to be
installed.
Explosion destroyed residence across
the street from the landfill. Minor
injuries reported.
Vent pipes were not maintained causing
vents to become nonfunctional. Street
light fire was believed related to
methane migration. Ongoing lawsuit
concerns presence of priority
pollutants.
Spark from landfill pump probably
ignited methane gas, causing explosion
and fire. Office building destroyed.
Vinyl chloride detection caused SCAQMD
to order 30-day shutdown of landfill.
It reopened, subject to closure in
6 months.
Home abandoned due to high methane
levels.
In 1975, explosion occurred in nearby
apartment building. The city decided
to buy and demolish it. Two schools
sited on the landfill were closed
until a control system was installed.
TOPS office building sited on closed
landfill. Methane has caused
problems since early 1970's. Failure
of ventilation exhaust fan resulted in
"significantly high" levels of methane
in the building.
(continued)
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TABLE 2-5. (Continued)
Landfill name/location/date
Damages and other comments
Mission Avenue
Oceanside, California
1981
Port Washington Landfill
North Hempstead, New York
1981
Beantown Dump
Rockville, Maryland
1980
Warner Hill Landfill
Cleveland, Ohio
1980
Reilly Construction Company
Springfield, Illinois
1979
Allegheny County Landfill
Frostburg, Maryland
1978
Campground Landfill
Louisville, Kentucky
1978
Lees Lane Landfill
Louisville, Kentucky
1978
Unnamed Landfill
Adams County, Colorado
Schools surrounding the landfill were
evacuated and classes were suspended
for 4-5 months.
Explosions in furnace rooms of several
homes. Minor damage occurred.
Furnaces were replaced.
Small explosion occurred in enclosed
back room of auto body shop. Shop
closed for 1 month until control
system was installed.
Explosion killed foundry worker on
site adjacent to landfill.
Methane migrated into construction
company offices adjacent to the
landfill. Limited fires occurred.
No explosion. Building evacuated and
use restricted for 4 weeks.
Limited fire in off-site equipment
maintenance building. No explosion.
Building use restricted for 2 months.
Building was highly ventilated until
gas control system installation.
No physical damages occurred.
Buildings evacuated for short period
of time.
Small fires and explosions. Several
houses evacuated and condemned.
Benzene (29.5 ppm) and vinyl chloride
(17.9-122.6 ppm) detected off-site.
Explosion at a construction project
adjacent to the landfill.
(continued)
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TABLE 2-5. (Continued)
Landfill name/location/date
Damages and other comments
Fells Street Landfill
Richmond, Virginia
1982
Winston-Salem, North Carolina
1969
Greentree Hills Landfill
Madison, Wisconsin
The 1982 incident occurred when
children trespassed onto the landfill
site, entered a control system
manhole, and lit a match, resulting in
an explosion.
Methane migrated into National Guard
Armory.
Explosion blew out one sidewall of a
townhouse. Three adjacent apartment
buildings and several homes evacuated
for 20-30 days. Claims filed against
the city total $5.2 million dollars.
References 63,64.
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on property values recorded during the operation of the program indicated a
decrease of 5 to 10 percent in residential property value.
2.6 ODOR NUISANCE
Odors are frequently associated with air emissions from MSW landfills.
Odors escape along with MSW landfill gas from surface cracks in the
landfill. As waste is added to the landfill, disturbances of soil layers
can also provide a means of escape for odors. Individuals vary in their
ability to detect odors and in the degree of pleasantness or unpleasantness
they experience with various odors.65 However, the types of odors generally
associated with the decomposition of organic material that occurs at
landfills are most likely to be unpleasant or objectionable. This section
describes the occurrence of odors at MSW landfills, and lists examples of
the types of odorous compounds likely to emanate from landfills. The
section also describes how odors affect human welfare by the unpleasantness
of the odors themselves, by possibly lowering the property value of real
estate near a MSW landfill, and by the potential for odors to cause
properties to be abandoned and therefore leading to loss of facility and
property use,
2.6.1 Odor Generation
Municipal landfill gas is generated largely by bacterial decomposition
of organic materials in the municipal solid waste. As the decomposition
proceeds, odiferous compounds can escape from the landfill through cracks in
the landfill surface cover.
Other possible sources of odors associated with air emissions from MSW
landfills are the actual wastes themselves. Household wastes that are often
disposed in MSW landfills include chemicals in cleaners, paints, pesticides
and adhesives. These consumer products often contain solvents or other
compounds with distinctive odors. As these household products are added to
a landfill, the odors associated with some of these chemicals may be
noticeable to nearby residents or passersby. These odors may also emanate
on a continuing basis from cracks in the landfill surface cover.
2.6.2 Adverse Effects of Odors on Human Welfare
The influence of odors on the comfort and welfare of individuals is
difficult to prove. Odors can result in social and behavioral changes in an
2-22
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exposed population. However, odor perception and impact is subjective.
Different individuals may react differently to the same type and intensity
of odor. Therefore, it is difficult to quantify a degree of unpleasantness
associated with different odors. The descriptions in this section on the
adverse effects of odors on human welfare are necessarily qualitative.
A few studies in the United States and the Federal Republic of Germany
have investigated the social and behavioral effects of odors on the
population. These studies have indicated that annoyance is a common
reaction of residents in communities where unpleasant odors are encountered.
Examples of responses from a survey of 704 residents of Dusseldorf are shown
in Table 2-6. In the U.S., studies have indicated that odors have
interfered with daily activities. U.S. studies are generally older and not
quite as specific as other studies in the literature.
It seems likely that the presence of odors would also exert the same
type of detrimental effect on property value. At this time, the effect
cannot be quantified. As was discussed earlier in relation to explosivity,
property values around the Midway landfill in the Seattle area decreased
from 5 to 10 percent with increased awareness of the presence of MSW
landfill gas. The decreases could not be directly correlated to odors
associated with the landfill.
Odors can also cause temporary or perhaps permanent loss of facility
use. Although specific studies were not found that documented any loss of
property use because of the odors from MSW landfills, it is possible that
such adverse effects would occur. The responses shown in Table 2-7 indicate
that odors can interfere in outdoor activities and interfere with the
comfort of living. If a population perceives an odor as offensive and has
questions about other possible effects beyond an annoying odor, the use of
recreational or social facilities near the odor source may be greatly
reduced or eliminated.
2.7 ADVERSE EFFECTS ON SOILS AND VEGETATION FROM MSW LANDFILL AIR EMISSIONS
The inability to grow vegetation or trees at MSW landfills is believed
to be caused by one or more of the following factors: (1) lack of oxygen in
the root zone; (2) toxicity of carbon dioxide to the roots; or (3) anaerobic
2-23
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TABLE 2-6. RESPONSE COMPONENTS OF
ANNOYANCE FACTORS DERIVED FROM A
SURVEY OF 704 RESIDENTS OF
DUSSELDORF*
Survey responses
Reduced social contacts
No pleasure in coming home
Odor leads to tensions within the family
Odor interferes with or disturbs communication
Odor spoils appetite
Odor interferes with comfort of living
Odor interferes with outdoor activities
Odor induces anger
Reference 67.
2-24
-------
conditions of the soil permitting the accumulation of reduced metals, such
as iron (Fe), manganese (Mn) and zinc (In), in concentrations toxic to the
6ft
vegetation. Generally when landfill gases are present in the surface
soil, the concentration increases at deeper soil layers. Thus, although the
deeper rooted trees die, the shallow rooted ground vegetation continues to
live. Diffusion of ambient air into the soil and diffusion of landfill
gases out of the soil frequently result in the soils nearest the surface
(top several inches) remaining in an aerobic condition, whereas the levels
69
where the deepest roots are present can be anaerobic.
According to the literature, there is a good deal of variability in
tolerance to low oxygen in the root zone. The growth of red and black
raspberries was inhibited by exposure to 10 percent oxygen, whereas apple
trees required 10 percent oxygen in the soil in order to sustain growth.
Tomato plants grown in solution culture exhibited marked reduction in growth
and ability to take up potassium (K) when exposed to three percent oxygen in
the root zone. Leone et al. reported that red maple, which is
flood-tolerant, was also more tolerant of soil contaminated by simulated
72
landfill gas than sugar maple, which is not tolerant of flooding.
Greenhouse and field studies, and other research reported in the
literature all confirm that the presence of landfill gases in the root zones
of vegetation can be injurious to the extent of causing the death of
vegetation. The major characteristics of landfill gas deleterious to plants
when found in the root zone were the high carbon dioxide and methane and low
oxygen concentrations resulting from anaerobic refuse decomposition.
Further studies indicate the extent of effects of landfill air emissions on
vegetation. Various investigators have experienced difficulties in growing
vegetation at completed or closed landfill sites. Stunting of corn and
sweet potatoes became evident in areas adjacent to a New Jersey site where
gases had migrated away from the landfill into the root zone of corn and
74 75
sweet potato plants. ' Death and poor growth of loblolly and other pines
planted on such sites in southern Alabama have also been attributed to the
presence of fermentation gases in the soil environment. Poor tree growth
in these areas has also been associated with lack of soil moisture and
2-25
-------
increasing amounts of ammonia, nitrogen, iron, manganese, zinc, and
copper.
Closed refuse and fill sites at 15 locations in New Jersey, New York
State, metropolitan New York City, New England, Washington, Oregon, and
Alabama were sampled both where vegetation was dead or dying and where the
same species were growing normally. Inspection of the contents of a soil
sampling tube inserted to a depth of 20 cm in soil at sites where vegetation
was dead or dying commonly revealed an anaerobic situation (dark, foul
smelling soil). Soil at sites where plant species were growing were
commonly found to be in aerobic conditions. Instrument readings of methane
(CH.) and carbon dioxide (CO,) were as high as 50 percent and 43 percent
78
respectively, at the anaerobic sites.
Soil tests at a closed landfill in central New Jersey showed that,
4 years after closure, the deepest 15 cm of a 60 cm soil cover was still
distinctly anaerobic. The upper 45 cm of soil showed evidence of aerobic
conditions; however attempts to establish herbaceous vegetation at the site
demonstrated that only a few grass species ["reliant" hard fescue (Festuca
longifolia Thuil.), redtop (Agrostis alba L.) and sheep's fescue (F. ovina
I.)] could survive under the undesirable soil conditions created by the
landfill gases. Attempts to establish woody species also failed, even where
grasses had been established.
Experimental work and site investigations have demonstrated an
inability of the landfill cover to support and maintain vegetation, which
also leads to increased erosion potential. If the cover is eroded, there is
a chance that refuse will be exposed. Opening the landfill cover could lead
to contaminated runoff from the site, increased odor nuisance, and increases
in rodent or vermin populations. According to CFR Part 60, this may be
defined as an effect on public welfare.
2-26
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2.8 REFERENCES
1. U.S. Environmental Protection Agency. 1987. Review of the National
Ambient Air Quality Standard for Ozone. Preliminary Assessment of
Scientific and Technical Information. OAQPS. Draft Staff Paper.
Research Triangle Park, NC.
2. Reference 1.
3. Reference 1.
4. Reference 1.
5. Reference 1.
6. Reference 1.
7. Reference 1.
8. Reference 1.
9. Reference 1.
10. Hang, W.L.T. and S. Rogers. 1982. Environmental and Public Health
Implications of the Port Washington Landfill. A study by the Toxics
Project of the New York Public Interest Research Center, Inc. (NYPIRC).
p. 5.
11. Reference 10.
12. Reference 10.
13. Reference 10.
14. Reference 1.
15. International Agency for Research On Cancer. 1982. IARC Monographs on
the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Some
Industrial Chemicals and Dyestuffs. Volume 29. World Health
Organization. Lyon, France, pp. 93-127.
16. Reference 15.
17. Reference 15.
18. Reference 15.
19. Reference 15.
2-27
-------
20. U.S. Environmental Protection Agency. 1984. Health Assessment
Document for Carbon Tetrachloride. Final Report. OHEA, Cincinnati,
OH. EPA 600/8-82-OOlf. pp. 2-7 to 2-8.
21. Reference 20.
22. U.S. Environmental Protection Agency. 1985. Health Assessment
Document for Chloroform. Final Report. OHEA, Washington, DC.
EPA 600/8-84-004f. pp. 1-5 to 1-14.
23. Reference 22.
24. Reference 22.
25. Reference 22.
26. Reference 22.
27. U.S. Environmental Protection Agency. 1985. Health Assessment
Document for 1,2-Dichloroethane (Ethylene dichloride). Final Report.
OHEA, Cincinnati, OH. EPA 600/8-84-006f. pp. 1-5 to 1-6.
28. Reference 27.
29. Reference 27, p. 9-204.
30. Reference 27.
31. U.S. Environmental Protection Agency. 1987. Update to the Health
Assessment Document and Addendum for Dichloromethane, Review draft.
OHEA, Washington, DC. EPA 600/8-87-030a. pp. 5-9, 108-111.
32. Reference 31.
33. Reference 31.
34. U.S. Environmental Protection Agency. 1985. Health Assessment
Document for Tetrachloroethylene (perchloroethylene). Final Report.
OHEA, Washington, DC. EPA 600/8-82-005f. pp. 1-1 to 1-5.
35. Reference 34.
36. U.S. Environmental Protection Agency. 1986. Addendum to the Health
Assessment Document for Tetrachloroethylene (Perchloroethylene).
Review Draft. OHEA, Cincinnati, OH. EPA 600/8082-005 fa.
37. Reference 36.
2-28
-------
38. U.S. Environmental Protection Agency. 1987. Addendum to the Health
Assessment Document for Trichloroethylene. Review Draft. OHEA,
Washington, DC. EPA 600/8-82-006. pp. 6-1 to 6-10.
39. Reference 38.
40. Reference 38.
41. Reference 38.
42. Reference 38.
43. Reference 38.
44. U.S. Environmental Protection Agency. 1985. Health Assessment
Document for Vinylidene Chloride. Final Report. OHEA, Washington, DC.
EPA 600/8-83-031f. pp. 1-1 to 1-8.
45. Reference 44. pp. 10-161 to 10-167.
46! Reference 44. pp. 10-161 to 10-167.
47. Reference 44. pp. 10-161 to 10-167.
48. Reference 44. pp. 10-161 to 10-167.
49. International Agency for Research on Cancer. 1974. IARC Monographs
on the Evaluation of Carcinogenic Risk of Animals to Man. Some
Antithyroid and Related Substances, Nitrofurans and Industrial
Chemicals. Vol. 7. World Health Organization. Lyon, France.
pp. 298-305.
50. Agency for Toxic Substances and Disease Registry. 1988. lexicological
Profile for Vinyl Chloride. Draft. Prepared by Technical Resources,
Inc., Revised by Syracuse Research Corporation, pp. 39-60.
51. Reference 50.
52. Reference 50.
53. Reference 49.
54. U.S. Environmental Protection Agency. 1990. Memorandum from Peters,
W., PAB, to Kellam, R., SDB. March 1990. Risk Assessment for
Municiapl Solid Waste Landfills. Draft.
2-29
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55. Fisher, Linda J., Assistant Administrator for Policy, Planning and
Evaluation, U.S. Environmental Protection Agency, Testimony before the
Subcommittee on Water and Power Resources of the Committee on Interior
and Insular Affairs, U.S. House of Representatives.
December 1, 1988.
56. Wubbles, D.J., J. Edmonds. March 1988. A Primer on Greenhouse Gases.
Lawrence Livermore National Laboratory, Department of Energy.
57. Bishop, J.E. October 24, 1988. "Global Threat". The Wall Street
Journal.
58. Wilkey, M.L., R.E. Simmerman, H.R. Isaacon. 1982. Methane from
Landfills: Preliminary Assessment Workbook. Argonne National
Laboratory, Department of Energy.
59. Reference 56.
60. Reference 55.
61. Personal communication, Joe Pestinger, City of Seattle Good Neighbor
Program, with P. Cruse, Radian Corporation, January 7, 1988.
62. U.S. Environmental Protection Agency. 1988. Draft Report to Congress
on Solid Waste Disposal in the United States. Vol. 11. pp. 4-81 -
4-89. Washington, DC.
63. Reference 38. pp. 8-10 - 8-14.
64. Personal communication, Susan Thorneloe, U.S. Environmental Protection
Agency with Jerry Barron, Allegheny County Bureau of Air Pollution
Control, February, 1988.
65. Fogiel, M. ed. 1978. Odorous Compounds. In: Modern Pollution
Control Technology. Vol. 1. Research and Education Association.
New York, NY. pp. 15-1 - 15-11.
66. National Research Council. 1979. Odors from Stationary and Mobile
Sources. National Academy of Sciences, Washington, DC. pp. 3-12 -
3-32.
67. Reference 66.
68. Flower, F.B., Gilman, E.F., and Leone, LA. 1981. Landfill Gas, What
It Does To Trees And How Its Injurious Effects May Be Prevented.
J. Arboriculture. Vol. 7. No. 2. pp. 43-51.
69. Reference 68.
2-30
-------
70. Rajappan, J., and Boyton, C.E. 1956. Responses of Red and Black
Raspberry Root Systems to Differences in 0?, C0?, Pressures and
Temperatures. Proc. of the Am. Soc. Hort. Sci. Vol. 75. pp. 402-500.
71. Valmis, J., and Davis, A.R. 1944. Effects of Oxygen Tension on
Certain Physiological Responses of Rice, Barley, and Tomato. Plant
Physiol. Vol. 18. pp. 51-65.
72. Leone, I.A., Flower, F.B., Gilman, E.F., and Arthur, J.J. 1979.
Adapting Woody Species and Planting Techniques to Landfill Conditions:
Field and Laboratory Investigations. U.S. Environmental Protection
Agency Report 600/2-79-128. p. 134.
73. Reference 72.
74. Leone, I.A., Flower, F.B., Arthur, J.J., and Gilman, E.F. 1977.
Damage to New Jersey Crops by Landfill Gases. Plant Dis. Rep. Vol.
61. pp. 295-299.
75. Flower, F.B., Leone, I.A., Gilman, E.F., and Arthur, J.J. 1978. A
Study of Vegetation Problems Associated with Refuse Landfills. U.S.
Environmental Protection Agency Report 600/2-78-094. p. 94-95.
76. Gilman, E.F., Leone, I.A., and Flower, F.B. 1981. The Adaptability of
19 Woody Species in Vegetating a Former Sanitary landfill. Forest Sci.
Vol. 27. No. 1. pp. 13-18.
77. Reference 75.
78. Reference 75.
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3. MUNICIPAL LANDFILL AIR EMISSIONS
This chapter presents a description of municipal solid waste landfills
and a characterization of landfill air emissions. Section 3.1 provides an
overview of municipal landfills. Section 3.2 describes the sources of
emissions from municipal landfills, while Section 3.3 presents estimates of
municipal landfill air emissions in 1992 (expected year of regulation) and
projected emissions from new municipal landfills established between 1992
and 1997. Finally, Section 3.4 describes the explosion hazards and odor
nuisance associated with municipal solid waste landfill air emissions.
3.1 GENERAL LANDFILL INFORMATION
The term "municipal solid waste landfill" in this document refers to
landfills regulated under a subsection of Subtitle D of the Resource
Conservation and Recovery Act (RCRA) that receive primarily household and/or
commercial waste. RCRA Subtitle D landfills receive only nonhazardous waste
(with the exception of small quantity generator and household hazardous
waste) and are categorized according to the primary type of waste received.
Municipal landfills may receive small quantities of waste types other than
household and commercial wastes (as discussed in Section 3.1.1).
Based on the 1986 EPA survey of municipal solid waste landfills, there
are presently an estimated 6,034 active municipal landfills in the United
States receiving about 209 million megagrams (Mg) of waste annually. Of the
209 million Mg of waste received, approximately 150 million Mg (72 percent)
is household waste and 58 million Mg (28 percent) is commercial waste. The
total estimated design capacity of these active municipal landfills is
11,100 million Mg and the total estimated quantity of refuse in place is
4,330 million Mg. Thus, the overall proportion of total design capacity
1 2
currently filled is about 39 percent. '
The distribution of landfill sizes based on design capacity and
corresponding average refuse acceptance rates is shown in.Table 3-1. Most
of the active municipal landfills (about 93 percent) have a design capacity
of 5 million Mg or less. The overall proportion of design capacity
currently filled ranges from 29 percent for landfills having a design
3-1
-------
TABLE 3-1. ACTIVE MUNICIPAL LANDFILL SIZE DISTRIBUTION3
Design capacity
(million Mg)
<1
1-5
5-10
10-20
>20
TOTAL
Median
Average
Number of
landfills
4,284
1,327
241
91
91
6,034
Percent
of total
landfill
population
71
22
4
1.5
1.5
100
Percent
filled0
45
44
40
37
29
-
-
39
Average
acceptance
rate
(Mg/day)
50
470
1,370
2,000
3,910
-
11.5
282
Reference 2
Amount of refuse in place relative to the total design capacity of the
landfill.
3-2
-------
capacity greater than 20 million Mg to 45 percent for landfills having a
design capacity less than 1 million Mg. The average acceptance rates range
from 50 Mg/day for the smaller landfills (<1 million Mg design capacity) to
about 4,000 Mg/day for the larger landfills (>20 million Mg design
capacity).
There is a large difference between the average and median refuse
acceptance rates for the total landfill population. This is due to the
relatively small number of large municipal landfills which account for a
disproportionately large share of the total waste received. The median
value of annual refuse acceptance rate for the total landfill population is
3,000 Mg/yr (11.5 Mg/day), whereas the average value is 73,000 Mg/yr
(282 Mg/day).3
3.1.1 Municipal Waste Composition
The types of waste potentially accepted by municipal landfills can be
categorized into 12 waste types: (1) municipal solid waste, (2) household
hazardous waste, (3) municipal sludge, (4) municipal waste combustion ash,
(5) infectious waste, 6) waste tires, (7) industrial nonhazardous waste,
(8) small quantity generator hazardous waste, (9) construction and
demolition waste, (10) agricultural waste, (11) oil and gas waste; and
(12) mining waste. The average composition of these waste found in
municipal landfills is presented in Table 3-2. Below is a brief description
of each waste type.
3.1.1.1 Municipal Solid Waste. Most of municipal solid waste (MSW) is
comprised of paper and yardwastes. It is also comprised to a lesser extent
4
of glass, metals, plastics, food wastes, rubber, textiles, and wood.
3.1.1.2 Household Hazardous Waste. Household hazardous waste consists
mostly of household cleaners, automotive products, home maintenance
products, and lawn and garden products.
3.1.1.3 Municipal Sludge. Municipal sludge is generated from drinking
water and waste water treatment plants. Sewage sludge is predominantly
organic matter, while drinking water sludge is a mixture of organic and
inorganic components.
3.1.1.4 Municipal Waste Combustion Ash. This waste is derived from
the incineration of municipal solid waste. About 90 percent of municipal
3-3
-------
TABLE 3-2. AVERAGE COMPOSITION OF WASTE
IN ACTIVE MUNICIPAL WASTE LANDFILLS
Mean waste
Waste type composition (wt %)
Household wastes 71.97
Commercial nonhazardous wastes 17.19
SQG Hazardous wastes 0.08
Asbestos-containing waste materials 0.16
Construction/Demolition wastes 5.83
Industrial process wastes 2.73
Infectious wastes 0.05
Municipal incinerator ash 0.08
Other incinerator ash 0.22
Sewage sludges 0.51
Other commercial wastes 1.19
3-4
-------
waste combustion ash is currently disposed of in landfills. However, this
practice may be prohibited in the future by EPA because of the concern that
heavy metals present in combustion ash can be readily mobilized and
transported in municipal landfill leachate. The EPA is currently conducting
a study to determine the appropriate controls necessary for the management
of municipal waste combustion ash.
3.1.1.5 Infectious Waste. Infectious waste is by and large originated
at hospitals and research testing labs. The types of infectious wastes
include isolation wastes; cultures of infectious agents; human blood
products; pathological wastes; contaminated injection needles; contaminated
animal carcasses; and body parts and bedding.
3.1.1.6 Waste Tires. This waste includes discarded vehicle tires
which eventually are deposited in a municipal landfill. It has been
estimated that about 70 percent of discarded tires are disposed of in
landfills.7
3.1.1.7 Industrial Non-Hazardous Waste. This category includes any
refuse from industrial facilities that are not defined as hazardous waste
under RCRA. Approximately 80 percent of this waste is generated by the
p
following industries : Industrial Organic Chemicals; Iron and Steel
Manufacturing; Fertilizer and Agricultural Chemicals; Electric Power
Generation; and Plastics and Resins Manufacturing.
3.1.1.8 Small Quantity Generator Hazardous Waste. Small quantity
generators are defined in RCRA as those producing less than 100 kg per month
of hazardous wastes. The dominant SQG waste type is used lead-acid
batteries, comprising about 60 percent of SQG waste. The next most abundant
g
SQG waste is spent solvents, comprising about 18 percent of SQG waste.
3.1.1.9 Construction and Demolition Waste. Construction and
demolition wastes consist mostly of concrete, asphalt, brick, stone,
plaster, wall board, glass, and piping. Paint and solvent waste associated
with construction is considered a SQG waste.
3.1.1.10 Agricultural Wastes. Agricultural waste consist primarily of
animal, crop, and irrigation wastes.
3.1.1.11 Oil and Gas Wastes. Oil and gas wastes are chiefly liquid
brines and drilling muds.
3-5
-------
3.1.1.12 Mining Wastes. Mining wastes are mostly debris from
crushing, cleaning, and floatation processes used in the mineral extraction
industry.
3.1.2 Landfill Design and Operation
The two major approaches to the design and operation of a municipal
landfill are: 1) the trench method; and 2) the area method. The trench
method involves excavating daily trenches designed to receive one day's
waste. Daily trenches are typically 100 to 400 ft long, 3 to 6 ft deep, and
15 to 25 ft wide. The waste is spread in layers, 1.5 to 2 ft thick, and
then compacted before the next layer is applied. The trench method is most
suitable on flat or gently rolling land with a low ground water table.
The area method involves the application of waste over the natural
ground surface. Waste is generally applied in layers of less than 2 ft and
is then compacted before successive layers are applied. The area method is
often used in areas such as California, where natural depressions (e.g.
canyons) are abundant. If the landfill site has a high water table, the
excavation method may not be feasible and the area method must be used.
Common to both landfill ing methods is the basic landfill cell. A
schematic of the cell design is provided in Figure 3-1. A cell is usually
designed to receive one day's waste and is closed at the end of the day.
The height of the cell is usually less than 8 ft. The working face of a
cell can extend to the facility boundaries. The waste is compacted into the
cell at compaction densities range from 500 to 1500 Ib/per cubic yard.
After compaction, daily cover material is applied. Most states require that
at least a 6-inch cover be applied at the end of the day. A 2-ft final
cover of material capable of supporting vegetation is required for a
completed landfill. Interim cover requirements (for areas unattended for a
period of time) vary from State to State but are usually about 1 ft. After
compaction and cell closure, settlement occurs. Ninety percent of the
settlement occurs within the first five years.
Liners can be used to prevent water entry to control leachate
production. They are also used to control landfill gas migration. There
are two basic types of landfill liners: soil and synthetic. Soil liners
consist of compacted clay. These liners can achieve reduced permeabilities
3-6
-------
2 ft Find Earth Cover
••Required
21 or 3:1 Typical Stop*
6 In. Intermediate
Eerth Cover
Defy Cover
Sector* View or eSenteryLendrl
Figure 3-1. Landfill cell design.
3-7
-------
of 10"7 cm per second. Types of synthetic liners include asphalt, cement,
soil sealants, sprayed liquid rubbers, and synthetic polymeric membranes.
Reduced permeabilities of 10"10 cm per second can be achieved with these
liners.12 Less than 16 percent of municipal landfills use liners. Clay
liners are used more often than synthetic liners in Subtitle D landfills.
Due to the Federal and State restrictions on acceptance of liquids in
landfills, solidification or fixation of liquid waste is often required
before it can be disposed. Liquid received in drums is decanted into pits
or directly into the landfill. The liquid may be mixed with other waste,
absorbents, or cement. Sometimes "trenching" or "lagooning" methods are
used. These involve pouring liquids into excavated areas within a waste
layer.14 The liquid is then allowed to infiltrate downward and laterally to
be absorbed by the waste. As reported in the summary of the 1986 EPA survey
of MSW landfills, only 1.2 percent accept free liquid solvents, 5.4 percent
accept bulk liquids, and 3 percent accept drummed liquids. These
percentage may vary in some parts of the U.S. However, prior to the
Hazardous and Solid Waste Amendments of 1984, hazardous wastes (solids and
liquids) were codisposed with municipal wastes at some landfills.
3.2 EMISSIONS FROM MUNICIPAL LANDFILLS
This section is divided into five subsections. The source of municipal
landfill air emissions is identified in Section 3.2.1. The mechanisms
responsible for these emissions are discussed in Section 3.2.2. The factors
impacting the emissions mechanisms, and thus emission rate, are discussed in
Section 3.2.3. Reported emission rates and a technique for estimating
emissions from municipal landfills are presented in Section 3.2.4. Finally,
Section 3.2.5 discusses landfill gas composition.
3.2.1 Landfill Cells
Landfill cells represent the major source of volatile constituents from
municipal landfills. As the waste is received, it is initially placed in an
open cell. At this time, the waste is in direct contact with the ambient
air and some loss of volatile constituents to the atmosphere is likely.
This newly received waste is likely to remain in contact with the ambient
air for a period of several hours as the waste is covered and possibly
3-8
-------
compacted with other newly received wastes. In good practice, a 6-inch soil
cover is placed over the newly received wastes at the end of the day.
However, emissions of volatile constituents continue (through the soil
cover) as the landfill cell is completed and after the landfill cell is
closed. In addition to emissions of nonmethane organic compounds (NMOC)
contained in the waste placed in the landfill cell, volatile organics may
also be produced by biological processes or chemical reactions in the
landfill as well.
Many municipal landfills are equipped with landfill gas collection
systems. The purpose of these collection systems is to vent or collect
landfill gas generated from the biological degradation of municipal type
wastes. The two basic types of collection systems employed are: passive
and active. Passive collection systems are generally installed to vent
landfill gases to the atmosphere for the purpose of preventing lateral
migration or to reduce the potential for explosion. Although the vented gas
composition is primarily methane and C09, of NMOC are also present in the
17
vented landfill gas.
Active collection systems include blowers or compressors and are
generally vented to a flare or energy recovery equipment (e.g., boiler, gas
turbine, internal combustions engines). However, active collection systems
may also be vented directly to the atmosphere. Even at landfills with
flares or energy recovery equipment, these systems may be a significant
emission source. During periods of equipment malfunction, the collected
landfill gas is often discharged directly to the atmosphere. In addition,
the objective of energy recovery systems is to recover methane from the
landfill gas stream. As part of the recovery scheme, nonmethane
constituents may be removed and discharged to the atmosphere.
3.2.2 Landfill Emission Mechanisms
Mechanisms governing the rate of organic emissions from landfill cells
can be separated into two types: production and transport. For emissions
to occur, the volatile organic must first be present in gaseous form. The
gaseous organic compound must then be transported to the atmosphere above
the landfill. Either mechanism can limit the emission rate. However,
transport appears to be the limiting emission mechanism.
3-9
-------
3.2.2.1 Production Mechanisms. The first step governing municipal
landfill air emissions is the production of the pollutant in its vapor
phase. This may be accomplished through one of three production mechanisms:
vaporization, biological decomposition, or chemical reaction.
3.2.2.2 Vaporization. Vaporization is the change of state from liquid
or solid to vapor. The change of state occurs due to the chemical phase
equilibrium that exists within the landfill. Organic compounds in the
landfill cell will vaporize until the equilibrium vapor concentration is
reached.
3.2.2.3 Biological Decomposition. A second mechanism by which a
volatile constituent may be produced in its vapor phase is biological
decomposition. Higher molecular weight organic constituents in the landfill
wastes may be decomposed by naturally occurring bacteria. The product of
this decomposition can be a lower molecular weight constituent with a higher
vapor pressure or volatility. For example, vinyl chloride is formed as a
18
result of degradation of trichloroethene and dichloroethene in the refuse.
It has also been suggested that lignin in municipal waste forms substituted
aromatics and eventually forms benzene, toluene, phenols, alcohols, ketones,
19
and esters.
The production of volatile organics (other than methane) is dependent
on the availability of nutrients for bacteria, refuse composition, moisture
content of the waste, oxygen availability, age of landfill, the presence of
biological inhibitors, temperature, and pH.
3.2.2.4 Chemical Reaction. The chemical reaction of materials present
in landfills is another possible mechanism for the production of volatile
constituents. These reactions may occur as the result of contact between
reactive wastes placed in the landfill or reactive gases generated in the
landfill.
3.2.2.5 Transport Mechanisms. When a volatile constituent is
present in its vapor phase, it can be transported to the surface of the
landfill, through the air boundary layer above the landfill, and into the
atmosphere. This transport may occur all or in part by one of three major
transport mechanisms: diffusion, convection, and displacement. Diffusion
can be further broken down into molecular diffusion through pores in the
3-10
-------
landfill and diffusion through the air boundary layer above the landfill.
Displacement can be further broken down into displacement due to compaction
and settlement of the waste, displacement due to barometric pressure
changes, and displacement due to ground water table fluctuations.
For municipal landfills, landfill gas convection is by far the
predominant transport mechanism. Landfill gas, mainly consisting of methane
and carbon dioxide produced by the biodegradation of refuse, sweeps vapors
present in the landfill to the landfill surface as it flows through the
refuse. The generation of landfill gas is discussed in detail in
Section 3.2.3.
3.2.3 Factors Affecting Municipal Landfill Air Emissions
As discussed in the previous section, municipal landfill emission rates
are a function of production and transport mechanisms. Either mechanism can
be the rate determining mechanism. However, transport appears to be the
limiting one.
3.2.3.1 Factors Affecting Production Mechanism. As discussed in the
previous section, there are three types of production mechanisms active in
landfills: vaporization, chemical reaction, and biological decomposition.
The factors affecting each of these production mechanisms are summarized in
Table 3-3.
As shown in Table 3-3, the major factors affecting vaporization are the
concentration of individual compounds in the landfill, physical properties
of the individual organic constituent, and the landfill conditions. The
emission rate of a specific organic constituent is expected to be a direct
function of its concentration in the landfill. Assuming that vaporization
is controlled by equilibrium rather than kinetics, the physical properties
important to the rate of vaporization are the pollutant vapor pressure,
solubility in water, and partition coefficient between the adsorbed and free
phases. Compounds with higher vapor pressure to solubility ratios (pseudo
Henry's Law Constant) vaporize faster. Also, adsorption of the organic
constituent onto solids present in the landfill can play a key role in
determining the equilibrium concentration of the organic constituent. The
octanol-water coefficient of the organic compound is an indicator of the
partitioning between the adsorbed and free phases. Compounds with lower
3-11
-------
TABLE 3-3. FACTORS AFFECTING PRODUCTION MECHANISMS
Mechanism
Factors affecting mechanism
Vaporization
Chemical reaction
Biological decomposition of
liquid and solid compounds
into other chemical species
- Partial pressure of the constituent
- Constituent concentration at the
liquid-air interface
- Temperature
- Confining pressure
- Composition of waste
- Temperature
- Moisture content
- Practice of separate disposal areas for
different waste types
- Nutrient availability for bacteria
- Refuse composition
- Age of landfill
- Moisture content
- Oxygen availability
- Industrial waste acting as biological
inhibitors (toxic to bacteria)
- Temperature
- pH
3-12
-------
octanol-water coefficient are adsorbed onto organic solids less readily and
tend to vaporize more quickly. Other factors*that can affect the rate of
vaporization are the landfill temperature and pressure. Higher temperatures
and lower pressure yield higher vaporization rates.
The extent to which chemical reactions lead to municipal landfill air
emissions is not well understood. Obviously two incompatible (reactive)
compounds must be present in the same location of the landfill in order for
a chemical reaction to take place. The primary factor affecting the rate of
production due to chemical reaction is the composition of the refuse placed
in landfill cells. Possible chemical reactions are also affected by the
landfill temperature, but only if the reactive compounds are present.
Higher temperature can result in either increased or decreased reaction
rates.
Biological decomposition of one organic compound into another is
affected by the composition of the landfill refuse and the landfill
conditions supporting biological activity. In order for a compound to be
produced, a predecessor compound must first be present in the landfill. In
addition, conditions in the landfill must be supportive of the particular
bacteria responsible for the decomposition. Bacteria present in landfills
are in general sensitive to nutrient availability, age of the refuse,
moisture content, temperature, oxygen availability, biological inhibitors,
and pH. The best overall indicator of biological activity is the rate of
landfill gas generation, since landfill gas is the product of refuse
decomposition.
3.2.3.2 Factors Affecting Transport Mechanism. As discussed
previously, there are a number of transport mechanisms active in landfills.
These include molecular diffusion, landfill gas convection, displacement due
to compaction and settling, displacement due to barometric pressure changes,
and displacement due to water table fluctuations. The factors affecting
each of these identified transport mechanisms are summarized in Table 3-4.
Although landfill gas convection is by far the major factor affecting the
emission rate from landfills, factors affecting the other identified
transport mechanisms are also discussed below.
3-13
-------
TABLE 3-4. FACTORS AFFECTING TRANSPORT MECHANISMS
Mechanism
Factors affecting mechanism
Molecular diffusion through
soil cover
Molecular diffusion through
boundary layer
Biogas convection
Displacement due to compaction
and settlement
Displacement due to barometric
pressure changes
Displacement due to
water table fluctuations
- Soil porosity
- Concentration gradient
- Diffusivity of constituent
- Soil thickness
- Wind speed
- Concentration gradient
- Diffusivity of constituent
- Nutrient availability for bacteria
- Refuse composition
- Moisture content
- Age of landfill
- Oxygen availability
- Industrial waste acting as biological
inhibitors
- Temperature
- pH
- Presence of gas collection system
- Amount of compaction practiced
- Compatibility of waste
- Overburden weight (settlement)
- Changes in atmospheric pressure
Rate of precipitation
Rate of evaporation
Horizontal versus vertical permeability
Presence of a liner
3-14
-------
Molecular diffusion is the transport of a volatile organic due to the
concentration gradient existing between a point in the landfill and the
ambient air above. Factors affecting the rate of molecular diffusion
include the concentration gradient, the diffusivity of the organic compound,
the porosity of the soil cover, the cover thickness, and the wind speed
above the landfill. The most important factor affecting the rate of
diffusion is the concentration of organics in the landfill vapor, since the
concentration of organics in the ambient air is relatively low (compared to
landfill concentrations). In addition, the rate of diffusion is directly
affected by the diffusivity of the organic compound, the soil cover
thickness, and the soil cover porosity. The gas phase transport above the
landfill is also affected by wind speed. Higher wind speeds reduce the
width of the concentration gradient and thus increase the rate of diffusion.
The emission rate due to displacement mechanisms is directly affected
by the volume of gas displaced. Higher compaction densities result in
higher emission rates due to compaction. Highly variable barometric
pressures result in higher emission rates due to barometric pumping, and
highly variable water table levels result in higher emission rates due to
water table fluctuations.
Among the different types of transport mechanisms, landfill gas
convection is the predominant transport mechanism. In addition, landfill
gas generation is also an indicator of biological activity in the landfill,
and should indicate the production rate of organics due to biological
decomposition.
3.2.4 Landfill Air Emissions Rate
Landfill gas, consisting primarily of methane and carbon dioxide, is
produced by microorganisms in the landfill under anaerobic conditions.
Anaerobic decomposition of complex organic material is normally a two-state
20
process as shown in Figure 3-2. In the first stage, there is no methane
production. The complex organics are altered in form by a group of
facilitative and anaerobic bacteria commonly called "acid formers". Complex
materials such as cellulose, fats, proteins, and carbohydrates are
hydrolyzed, fermented, and biologically converted to simple organic
materials. Usually, the end products of the first stage are organic fatty
3-15
-------
Acid- Methane-
forming | | forming
COMPLEX 1 bacteria .J ORGAN 1C I bacteria ^ • CH4
ORGANICS r P| ACIDS _J **! C02
FIRST STAGE SECOND STAGE
Figure 3-2. Two stages of anaerobic decomposition of complex organic
wastes.20
3-16
-------
acids. During the second stage of methane fermentation, the organic acids
are consumed by methanogenic bacteria and converted into methane and carbon
dioxide. The methanogenic bacteria are strictly anaerobic, and even small
21
quantities of oxygen are toxic to them.
3.2.4.1 Factors Affecting Landfill Gas Generation Rate
Landfill gas generation rate is a function of the following factors:
• Composition of refuse,
t moisture content of refuse,
• age of refuse,
• temperature of the landfill,
t pH and alkalinity of the landfill, and
• quantity and quality of nutrients.
3.2.4.2 Composition of Refuse. Refuse composition directly affects
the rate of landfill gas generation. The higher the percentage of
biodegradable materials (e.g., food and garden wastes, paper, textiles, and
wood), the higher the landfill gas generation rate. Refuse composition can
change with seasons and geographical locations. For example, there is
higher percentage of garden wastes in tropical or fast-growing geographic
areas. Certain compounds potentially present in the waste may be toxic to
any bacteria active in the landfill and can upset the activity of
methanogenic bacteria, resulting in a decreased gas generation rate.
Examples of such substances are toxic organic solvents like carbon
tetrachloride, chloroform and common salts of sodium, potassium, magnesium,
22
calcium, ammonium, and sulfide at high concentrations.
3.2.4.3 Moisture Content of Refuse. A high refuse moisture content
(60 to 90 percent, wet weight basis) can increase the landfill gas
generation rate. However, a typical refuse moisture content at the time of
placement is about 25 percent. Since landfill design and .operation usually
focus on preventing water entry to control leachate production, landfill
moisture content usually remains low.
3-17
-------
3.2.4.4 Aae of Refuse. Landfill gas generation rate and composition
go through different phases throughout the lifetime of a landfill. The
changes in gas composition can be characterized by four distinct phases
(Figure 3-3).23 In the first phase (several days to weeks), oxygen is
present from the time of waste placement and carbon dioxide is the principal
gas produced. In the second phase, an anaerobic condition exists once
oxygen has been depleted. During this period, significant amounts of carbon
dioxide and some hydrogen are produced. During the anaerobic third phase,
methane production is initiated and the amount of carbon dioxide produced
decreases. The fourth phase is also anaerobic in which gas production rate
approaches pseudo-steady state. The duration of each phase is a function of
the specific conditions within the landfill. Once methane production
begins, it continues for a number of years (reportedly 17 to 57 years). The
total time of gas generation depends on landfill conditions. For moderately
decomposable wastes in a typical landfill, the gas generation rate peaks
within six years after initial waste placement and declines steadily
24
afterwards.
3.2.4.5 Temperature of the Landfill. The methane production rate is
sensitive to the landfill temperature. The optimum temperature for
anaerobic digestion of refuse is 29°C to 38°C for mesophilic operation and
49°C to 57°C for "thermophilic operation. At temperatures below 10°C,
there is a dramatic drop in generation rate.
3.2.4.6 pH of the Landfill. The optimal pH for methane fermentation
is in neutral to slightly alkaline range (7.0 - 7.2). Initially, most
landfills have an acidic environment for the first several years but the pH
rises towards neutrality after those years.
3.2.4.7 Landfill Gas Generation Rate Model. Landfill gas generated
by the methanogens acts as a stripping (or transport) gas for the nonmethane
organic compounds (NMOCs) present in municipal landfills. Based on
available data, the landfill gas production rate appears to range from
?fi ?R
0.75 to 34 liters of landfill gas per kilogram of wet refuse per year.
As discussed in Section 3.2.4.1, there are several site-specific factors
that affect the landfill gas generation rate. These factors cause the
generation rate to be highly variable from landfill to landfill and
3-18
-------
TIME AFTER PLACEMENT
(N*f. 14)
I. Aerobic
II. Anaerobic, Non-Methanogenic
III. Anaerobic, Methanogenic, UnrUady
IV. Anaerobic, Methanogenic, Steady
Figure 3-3. Evolution of typical landfill gas composition.
23
3-19
-------
difficult to predict. In an attempt to account for the site-specific
conditions, a theoretical model and be used to predict the gas generation
rate.
Several models are available for estimating the gas generation rate
from a landfill using site-specific input parameters. Three relatively
simplistic (first-order kinetic) models are the Palos Verdes,
Sheldon-Arleta, and Scholl Canyon models. There are other models such as
GTLEACH-I which treats the landfill as a fixed-film microbial treatment
process operating in a batch-wise configuration with a continuous dilution
and wash out. However, GTLEACH-I requires extensive input data which
includes numerous initial concentrations, moisture content, and leachate
29
flowrate.
The basic approach in landfill gas generation modeling is to use the
most simplified model available that is consistent with fundamental
principals. The model is then empirically adjusted for the kinetic rate
constant(s) to account for variations in refuse moisture content and other
landfill conditions. The Scholl Canyon model which is a first order, single
stage model was chosen to estimate the landfill gas generation rate for
analyses presented in this document. It is the most simplistic model with
only two parameters and yields comparable results to other models, if
comparable input values are used.
The Scholl Canyon model assumes that the gas production rate is at its
peak upon initial waste placement, after a negligible lag time during which
anaerobic conditions are established in the landfill. The gas production
rate is then assumed to decrease exponentially (i.e., first order decay) as
the organic fraction of the landfill refuse decreases. The Scholl Canyon
model can be refined further by dividing the landfill into smaller submasses
to account for different ages of the refuse accumulated over time. A
convenient submass for computational purposes is the amount of refuse
accumulated in one year. The total methane generation from the entire
landfill (sum of each submass' contribution) is at its peak upon the
landfill closure if a constant annual acceptance rate is assumed.
3-20
-------
Assuming that the refuse has been accepted at the same annual rate over
time (i.e. all submasses are of the same size), the model equation is as
follow:
QCH4 = Lo R (exp(-kc) - exp(-kt)}
where,
QPU. = methane generation rate at time t, m /yr
LQ = potential methane generation capacity of the refuse, m /Mg
R = average annual refuse acceptance rate during active life, Mg/yr
k = methane generation rate constant, 1/yr
c = time since landfill closure, year
t = time since the initial refuse placement, year
Lag time during which anaerobic conditions are established can be
incorporated into the Scholl Canyon model by substituting c and t by
(c + lag time) and (t + lag time), respectively. The typical lag time
ranges from 200 days to several years depending on the landfill
conditions.
The theoretical value for potential methane generation capacity of
refuse, L , depends on the type of refuse only. The higher the cellulose
content of the refuse, the higher the value of the theoretical methane
generation capacity. The theoretical methane generation capacity is
determined by a stoichiometric method which is based on a gross empirical
formula representing the chemical composition of composite refuse or
individual refuse type. Some researchers have reported "obtainable L "
which accounts for the nutrient availability, pH, and moisture content
within the landfill. The researchers point out that "obtainable L " is less
than the theoretical L . Even though refuse may have a high cellulose
content, if the landfill conditions are not hospitable to the methanogens,
the potential methane generation capacity of the refuse may never be
reached. The "obtainable L " is approximated from overall biodegradability
of "typical" composite refuse or individual waste components, assuming a
conversion efficiency based on landfill conditions. The reported values of
3-21
-------
theoretical and obtainable L (along with the estimation method) range from
220 to 9540 ft3 (6.2 to 270.1 m3) CH4 per Mg of refuse.32"43
The methane generation rate constant, k, determines how quickly the
methane generation rate decreases, once it reaches the peak rate upon
placement. The higher the value of k, the faster the methane generation
rate from each submass decreases over time. The value of k is a function of
the following major factors: (1) refuse moisture content, (2) availability
of the nutrients for methanogens, (3) pH, and (4) temperature. In general,
increasing moisture content increases the rate of methane generation rate
up to a moisture level of 60 percent, above which the generation rate does
not increase.44 The pH of 6.6 to 7.4 is thought to be optimal for
methanogens. Some studies suggest buffering to moderate the effects of
volatile acids and other acid products which tend to depress the pH below
the optimal pH. ' Temperature affects microbial activity within the
landfill, which in turn affects the temperature of the landfill. Warm
landfill temperatures favor methane production and methane production may
also reflect seasonal temperature fluctuation in cold climates where the
landfill is shallow and sensitive to ambient temperatures. Values of k
obtained from available literature, laboratory simulator results, industry
experts, and South Coast Air Quality Management District (SCAQMD) test
reports, and back-calculated from measured gas generations rates and
Section 114 letter responses, and industry experts range from .003 to
0.21 1/yr.47"51
Other methods for estimating the nationwide NMOC emissions were
evaluated. A comparison of these methods is provided in Appendix D. The
alternative methods include the NMOC emission factor method, the South Coast
Air Quality Management District method, and the municipal waste generation
rate method.
3.2.5 Landfill Gas Composition
Landfill gas consists of approximately 50 percent by volume carbon
dioxide, 50 percent methane, and trace amounts of nonmethane organic
compounds (NMOC). The concentration 'of NMOC can range from 237 ppm to
14,294 ppm as shown in Table 3-5. The sources for the data provided in
3-22
-------
TABLE 3-5. NMOC CONCENTRATIONS
Landfill ID
A
B
C
D
E
F
G
H
I
J
K
L
M
N
0
P
Q
R
S
T
U
V
w
Co-disposal site
No
No
No
No
No
No
Yes
No
No
Yes
No
No
No
No
No
No
Yes
Yes
No
No
No
Yes
Yes
NMOC concentration
(ppm)
237
244
364
487
514
528
595
639
704
710
947
1,060
1,066
1,135
1,356
1,372
1,519
1,560
6,381
6,555
7,857
11,793
14,294
Reference
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67,68
69
70
71
72
73
74
75
3-23
-------
Table 3-5 are Waste Management of North America, South Coast Air Quality
Management test reports, and responses to Section 114 questionnaires " .
Concentrations of individual nonmethane organic compounds found in
landfill gas are summarized in Table 3-6. After carbon dioxide and methane,
ethane, toluene, and methylene chloride are the next major constituents in
landfill gas with average concentrations of up to 143, 52, and 20 ppm,
respectively. The most frequently detected compounds are trichloroethene,
benzene, and vinyl chloride. These results are based on responses to
Section 114 letters for 46 landfills.76"81 Details for the 46 landfills are
provided in Appendix C.
The organic air emissions from municipal landfills may include some
toxic compounds and hazardous compounds with carcinogenic and other
noncancer health effects. The carcinogenic and noncancer health effects
resulting from exposure to these compounds are summarized in Chapter 2.
3.3 BASELINE EMISSION ESTIMATES
Baseline emission estimates are presented in this section for three
categories of municipal solid waste landfills: existing active landfills,
existing closed landfills, and new landfills. In this document, existing
active landfills are defined as those landfills which receive municipal
refuse prior to March 1, 1992 (the estimated promulgation date) and continue
to receive municipal refuse. Landfill gas emissions are expected from the
refuse already placed in these landfills as well as future refuse
placements. The second category of landfills, existing closed landfills,
are defined as those landfills which received municipal waste after
November 7, 1987, but reached capacity and closed before March 1, 1992.
Although no new refuse has been placed in these landfills since 1987,
emissions will continue to evolve from these landfills until the refuse
completely decays. The universe of closed landfills is much larger than
defined here, but has been limited to this small subset due to the lack of
information on the numerous landfills closed prior to 1987. The third
category of municipal landfills, new landfills, is defined as those
landfills which first receive municipal waste on or after March 1, 1992.
The contribution of nationwide MSW landfill air emissions from these new
3-24
-------
TABLE 3-6. SUMMARY OF NONMETHANE ORGANIC COMPOUNDS FOUND IN LANDFILL GAS
a
CHEMICAL NAME
ETHANE
TOLUENE
METHYLENE CHLORIDE
HYDROGEN SULFIDE
ETHYL8ENZENE
XYLENE
1,2 - DIMETHYL BENZENE
LIMONENE
TOTAL XYLENE ISOMERS
a-PlNENE
DICHLORODI FLUOROMETHANE
ETHYLESTER BUTANOIC ACID
PROPANE
TETRACHLOROETHENE
VINYL CHLORIDE
METHYLESTER BUTANOIC ACID
ETHYLESTER ACETIC ACID
PROPYLESTER BUTANOIC ACID
1,2 - DICHLOROETHENE
METHYL ETHYL KETONE
THIOBISMETHANE
METHLYCYCLOHEXANE
TRICHLOROETHENE
NONANE
BENZENE
ETHANOL
ACETONE
2 - BUTANOL
OCTANE
No. of
Times
Quantified
26
40
37
3
31
2
1
1
27
1
31
1
26
39
42
1
1
1
37
27
1
2
44
1
45
1
26
1
1
Average
Cone.
ppm
142.79
51.60
19.70
16.50
14.64
14.52
12.78
10.22
10.04
9.70
8.83
8.65
7.68
7.15
7.04
6.63
6.13
5.50
5.09
4.80
4.57
4.33
3.80
3.63
3.52
3.41
3.36
3.30
3.30
Average
Cone. Detected
ppm
252.63
59.34
24.5
252.97
21.73
333.85
588
470
17.11
446
13.1
398
13.59
8.43
7.71
305
282
253
6.33
8.17
210
99.7
3.98
167
3.6
157
5.94
152
152
Highest
Cone.
ppm
1780
758
174
700
428
664
588
470
70.9
446
43.99
398
86.5
77
48.1
305
282
253
84.7
57.5
210
197
34
167
52.2
157
32
152
152
Lowest
Cone.
ppm
0
0.2
0
11
0.15
3.7
588
470
0
446
0
398
0
0
0
305
282
253
0
0
210
2.4
0.01
167
0
157
0
152
152
(continued)
-------
TABLE 3-6. (Continued)
CHEMICAL NAME
PENTANE
HEXANE
HETHYLESTER ACETIC ACID
1 - METHOXY - 2 - METHYL PROPANE
2 - BUTANONE
1,1 - DICHLOROETHANE
1 - BUTANOL
BUTANE
4 - METHYL - 2 - PENTANONE
2 • METHYL PROPANE
1 - METHYLETHYLESTER BUTANOIC ACID
<*> 2 - METHYL. METHYLESTER PROPANOIC ACID
ro CARBON TETRACHLORIDE
CHLOROETHANE
1,1,3,TRIMETHYL CYCLOHEXANE
2 - METHYL - 1 - PROPANOL
1,2 - DICHLOROETHANE
TR I CHLOROFLUOROMETHANE
CHLOROMETHANE
2,5 DIMETHYL FURAN
2 - METHYL FURAN
CHLORODI FLUOROMETHANE
PROPENE
METHYL ISOBUTYL KETONE
ETHYL MERCAPTAN
01 CHLOROFLUOROMETHANE
1,1,1 - TR I CHLOROETHANE
TETRAHYDROFURAN
ETHYLESTER PROPANOIC ACID
No. Of
Times
Quant i f i ed
26
26
1
1
1
33
1
26
1
1
1
1
37
29
1
1
37
46
30
1
1
27
1
26
3
28
38
1
1
Average
Cone.
ppm
3.19
3.01
2.96
2.96
2.80
2.52
2.17
2.08
1.93
1.83
1.50
1.50
1.49
1.28
1.24
1.11
1.05
0.99
0.90
0.89
0.87
0.79
0.78
0.78
0.78
0.73
0.69
0.65
0.57
Average
Cone. Detected
ppm
5.64
5.33
136
136
129
3.51
100
3.68
89
84
69
69
1.85
2.03
57
51
1.3
0.99
1.38
41
40
1.35
36
1.38
11.93
1.2
0.84
30
26
Highest
Cone.
ppm
46.53
25
136
136
129
19.5
100
32
89
84
69
69
68.3
9.2
57
51
30.1
11.9
10.22
41
40
12.58
36
11.5
23.8
26.11
9
30
26
Lowest
Cone.
ppm
0
0
136
136
129
0
100
0
89
84
69
69
0
0
57
51
0
0
0
41
40
0
36
0
1
0
0
30
26
(continued)
-------
TABLE 3-6. (Continued)
CHEMICAL NAME
BROMOD I CHLOROMETHANE
ETHYL ACETATE
3 - METHYLHEXANE
C10H16 UNSATURATED HYDROCARBON
METHYLPROPANE
CHLOROBENZENE
ACRYLONITRILE
METHYLETHYLPROPANOATE
1,1 - DICHLOROETHENE
METHYL MERCAPTAN ,
1,2 - DICHLOROPROPANE
U> i - PROPYL MERCAPTAN
rv> CHLOROFORM
""* 1,1,2,2 - TETRACHLOROETHANE
1,1,2,2 - TETRACHLOROETHENE
2 - CHLOROETHYLVINYL ETHER
t - BUTYL MERCAPTAN
DIMETHYL SULFIDE
DICHLOROTETRAFLUOROETHANE
DIMETHYL DISULFIDE
CARBONYL SULFIDE
1,1,2-TRICHLORO 1 ,2,2-TRI FLUOROETHANE
METHYL ETHYL SULFIDE
1,1,2 - TRICHLOROETHANE
1,3 - BROMOCHLOROPROPANE
1,2 - DIBROMOETHANE
C-1,3 - DICHLOROPROPENE
t-1,3 - DICHLOROPROPENE
ACROLEIN
No. of
Times
Quantified
29
1
1
1
1
29
26
1
32
3
28
2
36
28
2
28
2
2
1
2
1
1
1
28
1
2
2
2
26
Average
Cone.
ppm
0.45
0.43
0.43
0.33
0.26
0.24
0.18
0.16
0.16
0.12
0.07
0.07
0.06
0.06
0.06
0.05
0.03
0.02
0.02
0.02
0.02
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.00
Average
Cone. Detected
ppm
0.71
20
20
15
12
0.38
0.32
7.3
0.23
1.87
0.12
1.55
0.08
0.1
1.33
0.08
0.64
0.55
1.1
0.55
1
0.5
0.32
0
0.01
0
0
0
0
Highest
Cone.
ppm
7.85
20
20
15
12
10
7.4
7.3
3.1
3.3
1.8
2.1
1.56
2.35
2.6
2.25
1
1
1.1
1
1
0.5
0.32
0.1
0.01
0
0
0
0
Lowest
Cone.
ppm
0
20
20
15
12
0
0
7.3
0
1
0
1
0
0
0.05
0
0.28
0.1
1.1
0.1
1
0.5
0
0
0.01
0
0
0
0
(continued)
-------
TABLE 3-6. (Continued)
CHEMICAL NAME
1,4 -DICHLOROBENZENE
BROHOFORM
1,3 - DICHLOROPROPANE
1,2 - DICHLOROBENZENE
1,3 - DICHLORBENZENE
D I BROMOCHLOROMETHANE
BROHOMETHANE
No. of
Times
Quantified
28
28
26
29
29
f 2B
28
Average
Cone.
ppm
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Average
Cone. Detected
ppm
0
0
0
0
0
0
0
Highest
Cone.
ppm
0
0
0
0
0
0
0
Lowest
Cone.
ppm
0
0
0
0
0
0
0
References 75-81.
t*>
CO
-------
landfills will be small initially, but with time, these landfills will
become the major contributor to nationwide MSW landfill air emissions.
A summary of the estimated 1997 baseline emissions from each category
of MSW landfills is presented in Table 3-7. As shown in this table, total
NMOC emissions from MSW landfills are estimated to be 530,000 Mg per year in
1997. Of this total, existing landfills are expected to account for
510,000 Mg per year (98 percent of the total) and new landfills are expected
to account for 9,300 Mg per year (2 percent of the total). Assuming that
waste disposal volumes will remain about the same, the nationwide emissions
from MSW landfills are expected to remain roughly constant. However, the
contribution from each of the three landfill categories defined above is
expected to change. The expected contribution of each MSW landfill category
with respect to time is illustrated in Figure 3-4.
The baseline emission estimates presented in Table 3-7 were developed
using three sources of information in combination with the Scholl Canyon gas
generation model discussed in 3.2.4.7- These are: (1) results of the 1987
EPA MSW landfill survey, (2) the available data on gas generation rates, and
(3) the available data on NMOC concentrations in landfill gas.
In 1986, EPA sent municipal landfill survey questionnaires to 1,250 of
the estimated 6,034 active MSW landfills in the United States. From this
survey, EPA received responses for a total of 1,174 active MSW landfills.
Of these 1,174 landfills, the information provided on location (latitude and
longitude), annual waste acceptance rate, refuse in place, age, depth, and
design capacity were complete for 931 landfills. The landfill
characteristics reported for these 931 landfills formed the basis for all
national impacts presented in this document.
The EPA survey was designed to provide a stratified sample of both
large and small municipal landfills and the design of the survey was
considered in extrapolating from the 931 responses used up to the national
total. Of the 931 landfill responses used, 151 were for large landfills and
780 were for small landfills. In comparison, EPA estimated that 362 of the
6,034 active municipal landfills were large and 5,672 were small when
3-29
-------
TABLE 3-7. 1997 NATIONAL BASELINE EMISSION ESTIMATES
Number of Methane emissions NMOC emissions
Landfill category landfills (Mg/year) (Mg/year)
Existing MSW Landfills 7,480 1.8 x 107 510,000
(Active and Closed)
New MSW Landfills 928 5.3 x 105 10,000
ALL AFFECTED LANDFILLS 8,408 1.8 x 107 520,000
3-30
-------
designing the survey. Therefore, the following scale factors were developed
for large and small landfill responses:
Large landfill scaling factor = 362/151 = 2.40
Small landfill scaling factor = 5,672/780 =7.27
These scale factors were used to extrapolate the estimated baseline
emissions from each of the 931 landfills up to the nationwide total.
The second source of information used to develop national baseline
emission estimates was gas generation rate data. As discussed in
Section 3.2.4.7, the gas generation rate is a function of time and the time
dependent behavior can be predicted using models such as the Scholl Canyon
model. The use of this model does, however, require two landfill specific
constants (k and L ), as well as the landfill characteristics. If
sufficient gas generation data were available for a given landfill, the
values of k and L could be determined by regressing the measured gas
generation rate versus time. Such data were not available for any
landfills, but one time gas generation rate determinations were available
82
for 54 landfills. In the absence of time dependent data, values of k were
back-calculated from the measured flow for a low, medium, and high value of
L using the Scholl Canyon model equation. Ultimate gas generation rate
(LQ) values of 2,100, 6,350, and 8,120 ft3/Mg (59.5, 179.8 and 230 m3/Mg) of
refuse were selected as high, medium, and low values, (or 80th, 50th and
20th percentile values) respectively, based on available information
82
sources. Using this approach, a total of 139 sets of k and L were
developed from the available gas generation data. In approximately
20 cases, a value for k could not be calculated for a given L due to the
lack of convergence on a single value. These sets of k and L , presented in
Table 3-8, were randomly assigned to each of the 931 landfills.
The third source of information used in developing national baseline
emission estimates was the available NMOC concentration data for landfill
gas. Such data were available for landfill gas collected at 23 landfills.
If there was more than one test result, the most recent data was used. If
82
multiple results were provided, the arithmetic average was used. These
3-31
-------
TABLE 3-8. VALUES FOR k AND LQ
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
k
(i/yr)
0.011
0.008
0.050
0.010
0.008
0.006
0.002
0.002
0.006
0.002
0.001
0.029
0.006
0.006
0.028
0.019
0.024
0.006
0.004
0.038
0.021
0.015
0.047
0.010
0.008
0.026
0.007
0.007
0.022
0.015
0.026
0.017
0.025
0.006
0.004
0.014
0.011
0.024
0.017
0.028
0.019
0.060
0.012
0.009
0.048
0.030
(frW
6,350
8,120
2, A 00
6.350
8,120
2*100
6,350
8,120
2,100
6,350
8,120
2,100
6,350
8.120
6,350
8,120
2,100
6,350
8,120
8,120
6,350
8,120
2,100
6.350
8,120
2,100
6,350
8,120
6.350
8.120
6.3SO
8.120
2.100
6.350
8,120
6.350
8.120
6,350
8.120
6.350
8.120
2.100
6.350
8,120
6,350
8,120
3-32
-------
TABLE 3-8. (Continued)
47
48
49
SO
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
k
(i/yr)
0.020
0.015
0.049
0.033
0.031
0.024
0.140
0.080
0.041
0.006
0.005
0.009
0.002
0.002
0.016
0.011
0.015
0.012
0.075
0.012
0.009
0.150
0.017
0.012
0.085
0.015
0.011
0.046
0.011
0.008
0.030
0.022
0.070
0.015
0.011
0.026
0.019
0.130
0.019
0.014
0.011
0.003
0.003
0.021
0.006
0,005
(ft3/0g)a
6.350
8.120
6,350
8,120
6.350
8,120
6.350
8,120
2,100
6,350
8.120
2.100
6,350
8.120
6,350
8,120
6.350
8.120
2,100
6.350
8.120
2,100
6,350
8,120
2.100
6.350
8,120
2,100
6,350
8,120
6.350
8.120
2.100
6.350
8.120
6,350
8,120
2,100
6.350
8.120
2.100
6,350
8.120
2*100
6.350
8,120
3-33
-------
TABLE 3-8. (Continued)
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
k
U/yr)
0.026
0.019
0.029
0.021
0.030
0.022
0.041
0.029
0.034
0.024
0.140
0.021
0.016
0.060
0.014
0.011
0.025
0.007
0.006
0.120
0.021
0.016
0.210
0.027
0.020
0.035
0.026
0.036
0.026
0.023
0.007
0.006
0.041
0.012
0.009
0.010
0.003
0.003
0.040
0.012
0.009
0.065
0.018
0.014
0.065
0.019
0.015
(fttftg)3
6,350
8,120
6.350
8.120
6,350
8.120
6.350
8.120
6.350
8.120
2.100
6.350
8.120
2.100
6.350
8.120
2.100
6.350
8.120
2.100
6.350
8.120
2.100
6.350
8.120
6.350
8.120
6.350
8.120
2.100
6.350
8.120
2.100
6,350
8.120
2.100
6.350
8.120
2.100
6.350
8.120
2.100
6.350
8.120
2.100
6.350
8.120
a
'To convert to m /Mg use the following
conversion:
Ift3/Mg = .028 m3/Mg
3-34
-------
1
CA»
cn
o
a.
o
o
5
en
c
o
n
OC
UJ
o
o
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1 H
0
1992
Existing Landfills
1997
2002
TIME
2007
2012
Figure 3-4. Time-dependent contribution to national baseline emissions.
-------
23 NMOC concentrations, provided in Table 3-8, were randomly assigned to
each landfill in the database.
The three information sources described above were used in combination
with the Scholl Canyon model to develop baseline emission estimates for each
category of municipal landfills. However, as indicated in the following
subsections the approach varied slightly for each landfill category.
3.3.1 Baseline Emissions From Existing Active Landfills
As mentioned above, the EPA survey of MSW landfills was completed in
1987. Between the time the survey was conducted and the effective date of
regulations being considered (expected to be 1992), many of the landfills
included in the survey are expected to reach design capacity and close. In
addition, it is expected that a number of landfills will be constructed and
will begin to accept municipal refuse between 1987 and 1992. The location
and size of these additional landfills is not know, but one would expect
these newly opened landfills to be located near the landfills projected to
close. It was also assumed that the newly opened landfills would closely
resemble the landfills they replace in terms of physical and operating
characteristics. This assumption was made for the sake of a qualitative
analysis. In actuality, the newly opened landfills may be bigger and fewer
in numbers. Based on this premise, EPA has projected the general location
and characteristics of active landfills in 1992 using the 1987 survey data.
For each of the 931 landfills active in 1987, the refuse in place has been
projected in the year 1992 using information reported in the 1987 survey.
If the landfill was projected to reach capacity before 1992, then a landfill
with the same physical and operating characteristics has been projected to
replace the closed landfill. Therefore, the overall number of landfills and
national acceptance rate have been assumed to remain constant.
The baseline methane generation rate was estimated for each of the
931 landfills using the Scholl Canyon model discussed in Section 3.2.4.7,
the projected landfill characteristics in 1992, and the assigned set of k
and LQ. The methane generation rate was then multiplied by 2 to estimate
the total gas generation rate (since methane accounts for only half of the
landfill gas composition). This estimate of total landfill gas generation
rate was then multiplied by the assigned NMOC concentration to estimate the
3-36
-------
baseline NMOC emission rate. After estimating the baseline emission rate
for each of the 931 landfills, the national baseline emission rate was
estimated. The emission rate estimated for each landfill was multiplied by
the appropriate scale factor and the scaled emission estimates were summed
for all 931 landfills.
3.3.2 Baseline Emissions From Existing Closed Landfills
The baseline emissions from existing closed landfills were estimated
very much the same as for existing active landfills. The only difference
was the set of landfills and their characteristics. As mentioned above,
existing closed landfills in this document are defined as those landfills
which received municipal refuse prior to November 7, 1987, but reached
capacity and closed prior to March 1, 1992. The location and
characteristics of landfills in this category were determined from the 1987
EPA survey of active municipal landfills. The reported refuse in place,
annual acceptance rates, and design capacities were used to project the
landfills closing between 1987 and 1992. Based on the EPA municipal
landfill survey 231 of the 931 landfills included in the impact analyses are
expected to reach capacity and close by 1992. Applying the scaling factors
presented above, these 231 landfills represent a total of 1,446 landfill
nationwide.
The nationwide emission estimates for closed landfills were developed
using the Scholl Canyon model presented in Section 3.2.4.7, assigned sets of
k and L , assigned NMOC concentrations, and the appropriate scale factors.
Emission estimates for methane and NMOC were developed for each landfill,
then scaled and summed to estimate total nationwide emissions.
3.3.3. Baseline Emissions From New Landfills
The physical and operating characteristics of new landfills were
projected based on the EPA survey of active landfills in 1987 and the
premise that new landfills will have characteristics similar to the
landfills they replace. Information on refuse in place, annual acceptance
rates, and design capacities provided in the EPA survey were used to project
landfills reaching capacity and closing between 1992 and 1997. For each
landfill projected to close during this time period, a new landfill with
identical physical and operating characteristics was assumed to open, with
3-37
-------
a few exceptions. If the landfill that closes is a co-disposal site (i.e.,
had been assigned an NMOC concentration obtained from a co-disposal
landfill), the new landfill was randomly re-assigned a non-codisposal NMOC
concentration. As a result of RCRA regulations, co-disposal practices are
not expected to new landfills. If the new landfill was projected to close
in less than 20 years, the design capacity was modified so that the landfill
would be active for at least 20 years at the same rate of waste acceptance.
If the new land fill was projected to stay active in excess of 200 years,
the design capacity was modified to yield a maximum active life of 200 years
at the same acceptance rate. Using this approach, a total 143 new landfills
were projected to open, from the set of 931 landfills. Applying the
appropriate scale factors, these 143 landfills represent 928 landfills
nationwide.
Emissions from the projected 928 new landfills were also estimated
using the Scholl Canyon model, assigned values of k and LQ, assigned values
of NMOC concentration, and the appropriate scale factors. However, one
difference should be noted. Emission estimates for methane and NMOC were
developed for each projected landfill, then scaled and summed to estimate
total nationwide emissions.
3.3.4 State Regulations
In the past, the regulation of emissions from MSW landfills has mostly
been associated with controlling methane migration/explosion potential and
odor nuisance under RCRA. Within the last several years, however, a small
number of state and local jurisdictions have commissioned special studies to
assess the potential human health and environmental impacts associated with
landfill air emissions. Table 3-9 summarizes the state regulations that
address the control of air emissions from municipal solid waste landfills.
As summarized in Table 3-9, 27 states have implemented laws regulating
air emissions from municipal solid waste landfills. California is the only
state, at the present time, that has implemented air emissions regulations
for landfills under the state's air pollution control authority. The other
states have implemented landfill air emissions regulations under solid waste
laws.
3-38
-------
TABLE 3-9. SUMMARY OF STATE REGULATIONS CONTROLLING AIR EMISSIONS FROM HSU LANDFILLS
State
Alaska
Control criteria
cone, of gases >LEL*
Collection/control
system requirements
some form of venting.
Test ing/ report ing
requirements
None
Exemption criteria
None
Reference
number
83
or other controls
California
levels of tested air
contaminants pose •
health risk
avg. max. cone, of
total organ!es over
a certain area
>500 ppm
max. eonc. of
organic compounds
as methane at any
>500 ppm
flaring, internal
combustion engine,
or gas treatment and
sale
chemical
characterization of
gas on and off-site
monitoring probes at
landfills perimeter
to detect gas
migration
periodic sampling and
testing of methane
and toxics, and
testing of the
efficiency of
of controls
in-place (RIP)
tonnage
<1,000,000 tons
84, 85
Delaware
cone, of gases
>LEL*
vent i ng
if monitoring
required, then it
must remain in place
at least 5 years,
quarterly gas
composition data
must be taken, and
quarterly gas
generation rate
data may be required
None
86
Florida to prevent explosion
and fires, damage to
vegetation, and
objections I odors
off-site
site specific design
requirements, and
must prevent lateral
movement of gases by
collection
None
None
87
Illinois
prevention of air
pollution
None
None
None
88
Indiana methane cone. >25X
of the LEL* within
facility structures
or >LEL at the
facility boundary
None
a methane monitoring
program approved by
the commissioner
must implemented
None
89
Kansas
methane eonc. >25X
of the LEL* within
facility structures
or at the facility
boundary
None
None
None
90
(continued)
3-39
-------
TABLE 3-9. (Continued)
State
Control criteria
Collection/control
system requirements
Testing/reporting
requirements
Exemption criteria
Reference
number
Kentucky methane cone. >25X
of the LELa within
facility structures
or >LEL* at the
facility boundary
sites within 500 ft
of a residential,
farm, coMiercial or
industrial building
submit a Methane gas
contingency control
plan
None
Hone
None
91
Louisiana cells containing
material and meeting
criteria of
LAC 33:VI1.
1305.0.7.a.1i must be
connected to a gas
control system
venting or gas
dispersal into
the air
monthly surveys must
be conducted, upon
request of the
department, for the
presence of strong
odors
None
92
Maine
methane cone. »25X
LEI* within facility
structures or >LEL
at the facility
boundary
None
None
None
93
Maryland methane cone. >25X of
LEL* within facility
structures or >LEL
at the facility
boundary
None
None
None
Michigan if gases present a
a hazard to those
operating the fill
or living and
working nearby
a means of assuring
that gases cannot
travel laterally or
accumulate in
structures must be
designed and
employed
None
None
95
Minnesota
if gases are found
to migrate
laterally, or
explosive cone.
reached
venting, or other
means approved by
the commissioner
None
None
96
(continued)
3-40
-------
TABLE 3-9. (Continued)
State
Control criteria
Collection/control
system requirements
Test i ng/report ing
requirements
Exemption criteria
Reference
number
Mississippi
if the future use of
a landfill involves
a recreational park
None
control installation
delayed until
significant gas
releases have been
detected or until
closure procedures
are initiated
None
97
Missouri
methane cone. >25X
of LEL within
facility structures
or »5X of the LEL
at the facility
boundary
venting or flaring
those facilities
required to monitor
gases Mist submit
the results to the
department
None
98
New Hampshire
methane cone. >2SX
LEL* within facility
structures or >50X
of the LEL at the
facility boundary
None
None
None
99
New Jersey
if methane is found
to accumulate in any
structure, causing a
potential hazard
if potential damage
to vegetation beyond
the perimeter is
present
methane cone. >25X
of the LEL within
facility structures
or at the facility
boundary
venting, collection,
or combustion
gas samples must be
taken before, and
after combustion,
and methane gas
sensors must be
installed to
trigger an alarm
when methane gas
is detected
None
100
New York methane cone. >25X
of the LEL* within
facility structures
or >LEL at the
facility boundary
None
None
None
101
North Dakota
if lateral migration
occurs, creating a
potentially
hazardous condition
venting, or other
means approved by
department
None
None
102
(continued)
3-41
-------
TABLE 3-9. (Continued)
State
Oregon
Control
methane c<
criteria
jne. >25X
Collection/control
system requirement*
Hone
Testing/reporting
requirement!
the department may
Exemption criteria
None
• i --rm_
Reference
number
103
of the LEL within
facility ttructurea
>LEL at the
facility boundary
odor become* a
becomea a public
nuisanee
require gas samples
to be taken at a
specified interval
and submit the
reaulta of an
analyaia within a
specified time frame
Pennsylvania
all site* muat
install control*
vent < ng
gas monitoring
must be installed
None
104
Rhode Island
if lateral movement
gases or
accumulation of
gases in confined
structures occurs
venting
None
Nene
105
South Dakota
if department
considers necessary
None
None
None
106
Texas
control of air
pollution
venting
None
None
107
Virginia
gases must be
controlled
None
a ga* management
plan and gas
monitoring
procedures muct be
implemented
None
108
Washington
methane cone. >25X
of the LEL within
facility structures
or >LEL at the
facility boundary
cone, of gases
>100 ppmv of
hydrocarbons in
off-site structures
collection and sale
flaring utilized for
energy value
None
acceptance rate
<10,000 cubic
yards/year or
little or no gases
will be produced
1 109
(continued)
3-42
-------
TABLE 3-9. (Continued)
State
Wisconsin
Control
methane ci
criteria
>nc. >25X
Col lection/control
system requirements
vent i ng
Testing/reporting
requirements
gas monitoring
Exemption criteria
None
Reference
number
110
of the LEL" within
facility structures
or > the louer
detection limit at
the facility
boundary
probes must be
installed outside
the limits of the
landfill
must collect
combust all
hazardous air
contaminants
and
Wyoming violation of Air
Qua Ii ty
Regulations
None
None
None
111
(tower explosive limit) means the lowest percent by volume of • mixture of gas which will propagate a flame in
at 25 C atmospheric pressure.
"LEL
.air
atmospheric pressure.
New Jersey's Solid and Hazardous Waste Management Regulations provide extensive design and sampling specifications
for a landfill gas collection system.
3-43
-------
Twelve of the 28 states regulate air emissions from landfills based on
the methane concentration in or near the landfill. Five states base control
criteria on the potential for lateral migration of the landfill gas, which
could result in off-site hazards (such as explosions and fires) and/or
odor nuisances. Four states have regulations that simply state that
landfills must control air pollution. California and Washington base
control criteria on the levels of tested air contaminants, while Louisiana
bases control on the properties of the material in the landfill.
Pennsylvania is the only state that requires all landfills to install
controls, regardless of gas concentration or the type of waste deposited.
Uncontrolled venting was found to be a generally accepted method for
controlling the emissions from landfills, while several states also
encourage flaring, internal combustion, and treatment and sale of the gas.
Twelve states mention no specific requirement for the type of controls that
must be installed.
3.4 EXPLOSION HAZARDS AND ODOR NUISANCE
3.4.1 Explosion Hazards
Methane, a major component of landfill gas, is highly explosive when it
is present in air at a concentration between 5.5 and 15 volume percent. The
concentration of methane produced during the bacterial decomposition of
municipal wastes typically exceeds the upper explosion limit. However, as
methane migrates outside of the landfill perimeter, it can be diluted by air
to explosive concentrations.
Landfill gas migration occurs because of the pressure gradient
developed by landfill gas generation through the biodegradation of refuse.
The landfill gas moves toward low pressure areas through pathways of least
resistance. The extent to which landfill gas migrates laterally instead of
vertically depends on where the pathways of least resistance are located.
If the landfill surface layers are relatively impermeable, there will be a
greater tendency for gas to migrate laterally out of the landfill. Natural
and man-made barriers can reduce the permeability of the landfill surface
layers. Such barriers include clay deposits, a high water table, compacted
subgrade, and wet or frozen surface soil. Lateral gas migration can also be
3-44
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enhanced if adjacent soils are relatively permeable or corridors for gas
movement exist. Some examples of gas corridors include storm sewer
culverts, and buried utility lines. Landfill gases have reportedly migrated
as far as 300 meters into structures located on or near the landfill. In
addition to the danger of explosion, migrating landfill gas can also
displace air in enclosed areas and cause asphyxiation of individuals in
112
these areas.
The U. S. Environmental Protection Agency has promulgated regulations
for controlling explosive gases from sanitary landfills based on the methane
concentrations in structures built on the landfill and in the soil at the
property boundary. The rule states that the concentration of explosive
gases generated by a facility should not exceed 1.25 volume percent methane
(25 percent of lower explosion limit) in facility structures and 5.5 volume
percent methane at the property boundary. The revised Subtitle D Criteria,
proposed 8/88, requires monitoring of the LEL facility structures and the
property boundary.
3.4.2 Odor Nuisance
Landfill gas has a distinctive odor due to trace vapors which are
present at low concentrations in the gas. This odor is generally regarded
as unpleasant, and it can cause a considerable environmental nuisance in the
vicinity of the site. A transport of odors from the landfill to neighboring
sites is affected by such factors as the rate of gas production, operating
practices (refuse coverage depth and materials used), and the local
topography.
Odorous compounds in landfill gas are formed during the refuse
decomposition process. The presence of significant quantities of industrial
wastes or household solvents can increase the number of compounds released.
The major contribution to odor comes from two groups of compounds. The
first group is dominated by esters and organosulfurs, but also includes
butan-2-ol and certain solvents which may have been deposited with the
waste. These compounds are not widespread and are variable in their
concentrations. The second group is widespread and includes alkyl benzenes
and limonene. Together, with other hydrocarbons, these are probably
responsible for the background smell associated with a landfill. Typical
3-45
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TABLE 3-10. HIGHLY ODOROUS COMPONENTS
OF LANDFILL GAS
Odor threshold
Compound (mg/m )
Group A
Limonene 0.06
Xylenes 0.4
Ethyl benzene 0.2
Propyl benzenes 0.04
Butyl benzenes 0.1
Group B
Methanethiol 4 x 10"5
Dimethyl sulfide 0.01
Butan-2-ol 0.1
Methyl butanoate 0.005
Ethyl propionate 0.1
Ethyl butanoate 0.003
Propyl propionate 0.1
Butyl acetate 0.03
Propyl butanoate 0.1
Dipropyl ethers 0.07
Reference 114.
3-46
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odorous compounds which may be present in the landfill gas are listed in
Table 3-10. Included in this table are the odor thresholds for each
114
compound.
The majority of malodorous compounds are formed during the anaerobic
nonmethanogenic and anaerobic stages of decomposition. During the early
stages of decomposition, alcohols are particularly noticeable. Initial
ethanol concentrations may exceed 1 g/m . The sweet, putrid smells of these
compounds lead to the most penetrating pulmes which become less potent with
time. The orhanosulfurs are also well represented in the early stages of
decomposition. These usually overpower the hdyrogen sulfude which is
typically present at concentrations between 0.1 and 20 mg/m . ' No
major odor problems should be associated with the final stage of
decomposition the anaerobic methanogenic as the gases formed are not
themselves odorous. However, the presence of methane has been reported to
enhance perception of other malodorants.
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3.5 REFERENCES
1. Westat, Inc. Survey of State and Territorial Subtitle D Municipal
Landfill Facilities. Draft Final Report. Submitted to U.S. EPA/OSW.
October 13, 1987.
2. OSW Survey of Municipal Landfills. Data base supplied by DPRA, Inc.
September 1987.
3. Reference 2.
4. Franklin Associates, Ltd. Characterization of Municipal Solid Waste in
the United States, 1960 to 2000. Final Report. July 11, 1986.
5. U.S. Environmental Protection Agency, Office of Solid Waste.
Preliminary Results of the Municipal Solid Waste Landfill Survey
(unpublished). April, 1987.
6. U.S. Environmental Protection Agency, Office of Solid Waste. Solid
Waste Disposal in the United States. Report to Congress (draft).
1987.
7. U.S. Department of Energy, Idaho Operations Office. Scrap Tires: A
Resource and Technology Evaluation of Tire Pyrolysis and Other Selected
Alternate Technologies. EGG-2241, EG&G Idaho, Inc., Idaho Falls, ID.
1983. p iii.
8. Reference 6.
9. Abt Associates, Inc. National Small Quantity Hazardous Waste Generator
Survey. Prepared for U.S. Environmental Protection Agency.
Cambridge, MA. 1985.
10. Brunner, D.R. et al. Sanitary Landfill Design and Operation.
U.S. Environmental Protection Agency, Rockville, MD. 1972.
pp. 26-27.
11. Tchobanoglous, G., Theisen, H., Eliassen, R. Solid Wastes, Engineering
Principles and Management Issues. McGraw-Hill, New York. 1977.
p. 333.
12. GCA Corporation. Subtitle D Phase I Document: Revised Draft Report.
Prepared for U.S. Environmental Protection Agency. Bedford, MA.
August 1986. pp. 6-12 and 6-13.
13. Reference 1.
14. Crawford, J.F. and Smith, P.G. Landfill Technology. Butterworths.
London. 1985. p. 54-56.
3-48
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15. DPRA. Municipal Landfill Survey Summary. Compiled 1986 responses for
U.S. Environmental Protection Agency. Manhattan, KS. September, 1987.
16. Reference 15.
17. South Coast Air Quality Management District. Landfill Gas Emissions.
Report of the Task Force. July 1982.
18. Vogel, T.M., Criddle, C.S., and McCarty, P.L. Transformation of
Halogenated Aliphatic Compounds. Environ. Sci. Technol. Vol 21, No. 8.
1987. p. 734.
19. UNOCAL. Municipal Solid Waste Landfills: Toxic Chemical Releases and
the Role of Industrial Wastes in Those Releases. 1987. p. 3-6.
20. Emcon Associates. Methane Generation and Recovery From Landfills. Ann
Arbor, Ann Arbor Science, 1982. p. 38.
21. Reference 20, p. 7.
22. McCarty, P. L. Anaerobic Waste Treatment Fundamentals. Public Works,
No. 9-12, 1964. p. 95.
23. Reference 20, p. 38.
24. Reference 20, p. 40.
25. Reference 22, p. 123.
26. Reference 20, p. 42.
27. SCS Engineers. Gas Emission Rates from Solid Waste Landfills. Memo
to Allen Geswein, EPA-OSW. November 17, 1986.
28. EPA Project Summary. Critical Review and Summary of Leachate and Gas
Production from Landfills. EPA/600/S2-86/073. March 1987.
29. Williams, N.D. et al. Simulation of Leachate Generation from Municipal
Solid Waste.
30. Reference 20.
31. Pohland, F.G. Critical Review and Summary of Leachate and Gas
Production from Landfills. EPA/600/2-86/073. August 1986.
32. Reference 20.
33. Reference 20.
34. Reference 20.
3-49
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35. Reference 20=
36. Reference 20.
37. Blanchet, M.J. and Staff of the Pacific Gas and Electric Company -
Treatment and Utilization of Landfill Gas. Mountain View Project
Feasibility Study. EPA-530/SW-583, 1977.
38. Reference 31.
39. Reference 20.
40. Reference 31.
41. Reference 31.
42. Reference 31.
43. Reference 31.
44. Reference 31.
45. Reference 31.
46. Reference 31.
47. Bogner, J.E. The U.S. Landfill Gas Resource: Low-cost Biogas from
Municipal Solid Waste. Argonne National Laboratory, Argonne, IL.
Prepared by U.S. Department of Energy. January 11, 1988.
48. Telecon. Y.C. McGuinn, Radian Corporation with Peter Soriano, GSF
Energy Inc. May 4, 1988.
49. Reference 48.
50. Pohland, F.G. and et al. Leachate Generation and Control at Landfill
Disposal sites. Water Poll. Res. J. CANADA: Volume 20, No. 3, 1985.
51. DeWalle, F.B., Chian, E.S.K., and E. Hammerberg, 1978, Gas Production
from Solid Waste in Landfills, J. Environmental Engineering Division
ASCE, 104(EE3):415-432.
52. South Coast Air Quality Management District. Source Test Report.
85-592. El Monte, CA. December 1985.
53. South Coast Air Quality Management District. Source Test Report.
84-496. El Monte, CA. October 1984.
54. South Coast Air Quality Management District. Source Test Report.
85-511. El Monte, CA. November 1985.
3-50
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55. Letter from Douglas, J., Waste Management of North America, to
McGuinn, Y.C., Radian Corporation. Subject: Landfill Air Emissions,
June 15, 1988.
56. Reference 17.
57. Reference 54.
58. Reference 55.
59. South Coast Air Quality Management District. Source Test Report.
86-0342. El Monte, CA. July 1986.
60. South Coast Air Quality Management District. Source Test Report.
85-102. El Monte, CA. February 1985.
61. Reference 55.
62. Reference 60.
63. Reference 55.
64. Reference 55.
65. Reference 55.
66. South Coast Air Quality Management District. Source Test Report.
87-0391. El Monte, CA. December 1987.
67. South Coast Air Quality Management District. Source Test Report.
86-0220. El Monte, CA. May 1986.
68. Reference 54.
69. Reference 55.
70. Reference 55.
^
71. South Coast Air Quality Management District. Source Test Report.
87-0110. El Monte, CA. April 1987.
72. South Coast Air Quality Management District. Source Test Report.
87-0318. El Monte, CA. October 1987.
73. South Coast Air Quality Management District. Source Test Report.
87-0329. El Monte, CA. October 1987.
74. South Coast Air Quality Management District. Source Test Report.
87-0376. El Monte, CA. November 1987.
3-51
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75. South Coast Air Quality Management District. Source Test Report.
85-461. El Monte, CA. September 1985.
76. Letter from R.W. Van Blanderan, BioGas Technology, Inc., to Farmer, J.
U.S. Environmental Protection Agency. Response to Section 114
Questionnaire. December 2, 1987.
77. Letter from D.A. Stringham and W.H. Wolfe, Waste Management of
North America, to Farmer, J. U.S. Environmental Protection Agency.
Response to Section 114 Questionnaire. January 29, 1988.
78. Letter from D. Antignano, Energy Tactics, Inc., to Farmer, J.
U.S. Environmental Protection Agency. Response to Section 114
Questionnaire. November 25, 1987
79. Letter from G. Rodriguez, Pacific Light and Energy Systems, to
Farmer, J. U.S. Environmental Protection Agency. Response to
Section 114 Questionnaire. December 1, 1987.
80. Letter from D.L. Kolar, Browning-Ferris Industries, to Farmer, J.
U.S. Environmental Protection Agency. Response to Section 114
Questionnaire. February 4, 1988.
81. Letter from M. Nourot, Laidlaw Gas Recovery Systems, to Farmer, J.
U.S. Environmental Protection Agency. Response to Section 114
Questionnaire. December 8, 1987.
82. Memorandum from McGuinn, Y.C., Radian Corporation, to S. Thorneloe,
U.S. Environmental Protection Agency. Subject: Use of a Landfill Gas
Generation Model to Estimate VOC Emissions from Landfills.
Jurie 21, 1988.
83. Alaska Solid Waste Management Regulations, Revised September 20, 1987.
84. State of California Air Resources Board. Hazardous Waste Disposal Site
Testing Guidelines. Janaury 1987.
•i
85. South Cost Air Quality Managment District. Guidelines for
Implementation of Rule 1150.1. May 1987.
86. Delaware Solid Waste Disposal Regulations, Amended effective
September 1, 1987.
87. Florida Solid Waste Disposal Facilities Regulations, January 25, 1989.
88. Illinois Solid and Special Waste Management Regulations, Recodified
September 30, 1983.
89. Indiana Solid Waste Management Permit Regulations, May 1, 1989.
3-52
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90. Kansas Solid Waste Management Regulations, May 1, 1984.
91. Kentucky Waste Management Regulations, October 26, 1988.
92. Louisiana Solid Waste Regulations, March 1, 1988.
93. Maine Solid Waste Management Regulations, February 24, 1987.
94. Maryland Solid Waste Management Regulations, Adopted effective
March 7, 1988.
95. Michigan Solid Waste Management Regulations, Effective
December 2, 1981.
96. Minnesota Solid Waste Disposal Regulation, November 7, 1988.
97. Mississippi Solid Waste Management Regulations, June 1, 1987.
98. Missouri Solid Waste Rules, December 29, 1988'.
99. New Hampshire Solid Waste Management Rules, August 19, 1988.
100. New Jersey Solid and Hazardous Waste Management Regulations,
August 1, 1988.
101. New York Solid Waste Management Facilities Rules, April 1, 1987
102. North Dakota Solid Waste Management Regulations, Recodified
July 1, 1980.
103. Oregon Solid Waste Regulations, August 8, 1984.
104. Pennsylvania Solid Waste Regulations, April 9, 1988.
105. Rhode Island Rules for Solid Waste Management Facilities,
December 1, 1982.
106. South Dakota Solid Waste Regulations, April 30, 1989.
107. Texas Solid Waste Management Regulations, July 1, 1989.
108. Virginia Solid Waste Regulations, January 1, 1989.
109. Washington Solid Waste Regulations, November 3, 1988.
110. Wisconsin Solid Waste Regulations.
111. Wyoming Solid Waste Management Rules, December 22, 1975.
3-53
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112. U.S. Army Corps of Engineers. Landfill Gas Control at Military
Installations. Technical Report N-173. January 1984.
113. Federal Register. Vol 44. No. 179. September 13, 1978. p. 53438.
114. Young, P.J. and A. Parker. Origin and Control of Landfill Odors.
Chemistry and Industry. November 1984.
115. Young, P.J. and A. Parker. Origin and Control of Landfill Odors.
Chemistry and Industry. November 1984.
116. Baker, J.M., C.J. Peters, R. Perry, and C. Knight. Odor Control in
Solid Waste Management. Effluent and Water Treatment Journal.
April 1983.
117. Reference 54.
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4. LANDFILL GAS COLLECTION AND CONTROL TECHNIQUES
Control of municipal landfill air emissions requires both effective
collection of the generated landfill gases and effective recovery or
destruction of organics in the collected gas. This chapter describes the
gas collection and control technologies that can be used to control methane
and nonmethane organic compound (NMOC) emissions from municipal landfills.
The effective design of gas collection systems is discussed in Section 4.1,
and applicable control devices are discussed in Section 4.2. The advantages
and disadvantages of the various control techniques, in terms of
environmental impacts, are compared in Section 4.3.
4.1 LANDFILL GAS COLLECTION TECHNIQUES
Landfill collection systems can be categorized into two basic types:
active collection systems and passive collection systems. Active collection
systems employ mechanical blowers or compressors to provide a pressure
gradient in order to extract the landfill gas. Passive collection systems
rely on the natural pressure gradient (i.e., internal landfill pressure
created due to landfill gas generation) or concentration gradient to convey
the landfill gas to the atmosphere or a control system.
Based on theoretical evaluations, well-designed active collection
systems are considered the most effective means of gas collection.
Generally, passive collection systems have much lower collection efficiency
since they rely on natural pressure or concentration gradient as a driving
force for gas flow rather than a stronger, mechanically-induced pressure
gradient. A passive system, however, can be nearly equivalent in collection
efficiency to an active system if the landfill design includes synthetic
liners on the top, bottom, and sides of the landfill.
Active collection systems can be further categorized into two types:
vertical well systems and horizontal trench systems. Vertical well systems
are discussed in Section 4.1.1. Passive systems are discussed in
Section 4.1.2. The type of collection system employed often depends on the
landfill characteristics and landfill operating practices. For example, if
a landfill employs a layer-by-layer landfill ing method (as compared to
4-1
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cell-by-cell methods), an active horizontal trench collection system may be
preferred over an active vertical well collection system due to the ease of
collection system installation. However, if the water table extends into
the refuse, a horizontal trench system has a tendency to flood, thus
decreasing the collecting efficiency. Applications, advantages, and
disadvantages of different collection systems are summarized in Table 4-1.
4.1.1 Active Collection Systems
Active collection systems employ mechanical blowers or compressors to
create a pressure gradient and extract the landfill gas. A typical active
collection system with extraction wells is shown in Figure 4-1. Active
collection systems consist of two major components:
t Gas extraction wells and/or trenches, and
• Gas moving equipment (e.g., piping and blowers)
4.1.1.1 Gas Extraction Wells/Trenches. Gas extraction wells may be
installed in the landfill refuse or along the perimeter of the landfill.
For a landfill that is actively accepting waste, wells are generally
installed in the capped sections. Additional wells are installed as more
refuse is accumulated.
The wells consist of a drilled excavation 12 to 36 inches in diameter.
A 2 to 6 inch diameter pipe (PVC, HOPE, or galvanized iron) is placed in the
well, and the well is filled with 1-inch diameter or larger, crushed stone.
The pipe is perforated in the area where gas is to be collected but solid
near the surface to prevent air infiltration. A typical extraction well is
shown in Figure 4-2.
In unlined landfills, gas extraction wells are usually drilled to the
depth of the ground water table or to the base of the landfill, whichever is
less. In lined landfills, wells are typically drilled to only 75 percent of
the landfill depth to avoid damaging the liner system. Typical well depths
range from 20 to 50 feet but may exceed 100 feet. The spacing between gas
extraction wells depends on the landfill characteristics (e.g., type of
waste, degree of waste compaction, landfill gas generation rate, etc.) and
the magnitude of pressure gradient applied by the blower or compressor.
Typical welT spacing ranges from 50 to 300 feet.
4-2
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TABLE 4-1. COMPARISON OF VARIOUS COLLECTION SYSTEMS
Collection system type
Preferred applications
Advantages
Disadvantages
Active vertical well
collection systems
Landfills employing
cell-by-cell
landfi11 ing methods
Cheaper or equivalent
in costs when compared
to horizontal trench
systems
Difficult to install and
operate on the active
face of the landfi11
(may have to replace
welIs destroyed by
heavy operative
equipment)
Horizontal trench
collection systems
Landfills employing
layer-by-layer
landfi11 ing methods
LandfiI Is with
natural depressions
such as canyon
Easy to install since
drilling is not required
Convenient to install
and operate on the
active face of the
landfill
The bottom trench layer
has higher tendency to
collapse and difficult
to repair once it
col lapses
Has tendency to flood
easily if water table is
high
Difficult to maintain
uniform vacuum along the
length (or width) of the
landfiII
Passive col lection
systems
Landfills with good
containment (side
liners and cap)
Cheaper to install and
maintain if only a few
wells are required
Collection efficiency
is generally much lower
than active collection
systems
Costs is generally
higher than active
systems when designed
for the same collection
efficiency
4-3
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Landfill
PLANVEW
QM Extraction W«M
Monitoring Prob*
Figure 4-1. Active collection system.
4-4
-------
VALVf BOX AND COVtfl
GAS
COLLECTION
HEADER
' 3VC MOMTQWING
POflT VV/CAP
sou*c«: scs. mo
Figure 4-2. Extraction well.
4-5
-------
Trenches may be installed instead of or in combination with wells to
collect the landfill gas. The trenches can be vertical or horizontal at or
near the base of the landfill. A vertical trench is illustrated in
Figure 4-3. A vertical trench is constructed in much the same manner as a
vertical well is constructed, except that it extends to the surface along
one dimension of the landfill. Horizontal trenches are installed within a
landfill cell as each layer of waste is applied. This allows for gas
collection as soon as possible after gas generation begins and avoids the
need for above-ground piping which can interfere with landfill maintenance
equipment. A horizontal trench is illustrated in Figure 4-4.
4.1.1.2. Gas Moving Equipment. A gas collection header system conveys
the flow of collected landfill gas from the well or trench to the
blower/compressor facility. A typical header pipe is made of PVC or
polyethylene and is 6 to 24 inches in diameter.
The collected landfill gas is conveyed through the header system by a
blower or compressor. The size and type of compressor or blower depend on
total gas flow rate, total system pressure drop, and vacuum requirements.
For systems requiring only a small vacuum (up to 40 inches of water),
centrifugal blowers are often used. Centrifugal blowers offer the advantage
of easy throttling throughout their operation range. These blowers can
accommodate total system pressure drops of up to 50 inches of water and can
transport high flow rates (100 to 100,000 cfm). For lower flow rates and
higher pressures, regenerative (combination of axial and centrifugal)
blowers are often used.
Rotary lobe or screw-and-piston type compressors are used when the
system vacuum requirement is greater than 2 to 3 psi (55 to 85 inches of
water) and high discharge pressures (>100 psig) are required for pipeline
transport or processing. Systems with compressors have limited
flow-throttling capability. Compressors are positive displacement type
devices and excessive throttling of flow can damage the compressor.
4-6
-------
aoeviEW
3**
-------
QM Collection Rp*
QasColtoctlon
Existing Ground
Figure 4-4. Horizontal trench collection system.
4-8
-------
4.1.2 Passive Collection Systems
As indicated above, passive collection systems rely solely on natural
pressure or concentration gradient in the landfill to capture the landfill
gas. Like active collection systems, passive collection systems use
extraction wells to collect landfill gas. The construction of passive
collection wells is similar to that of active wells which is illustrated in
Figure 4-2.
The well construction for passive systems is much less critical than
active systems. This is primarily because the collection well is under
positive pressure and air infiltration is not a concern. Additionally,
elaborate well head assemblies are not required since monitoring and
adjustment is not necessary. However, it is important that a good seal be
provided around the passive well when synthetic cover liners are used.
Either a boot type seal, flange type seal, concrete mooring or other sealing
technique is typically used at each well location to maintain the integrity
of the synthetic liner.
4.1.3 Effectiveness of Landfill Gas Collection
The purpose of this section is to provide some general criteria for
evaluating the effectiveness of landfill gas collection systems. The
collection efficiency has not been determined at any landfill. However, one
landfill facility operator estimated that a well-designed system can
typically collect about 50 to 60 percent of the gas generated within a
landfill.3'4
The effectiveness of an active landfill gas collection system depends
greatly on the design and operation of the system. From the perspective of
air emission control, an effective active collection system design would
include the following attributes:
0 Gas moving equipment capable of handling the maximum landfill gas
generation rate.
• Collection wells and trenches configured such that landfill gas is
effectively collected from all areas of the landfill.
• Design provisions for monitoring and adjusting the operation of
individual extraction wells and trenches.
4-9
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An effective passive landfill gas collection system would also include
a collection well or trench configuration that effectively collects landfill
gas from all areas of the landfill. The efficiency of a passive collection
system would also greatly depend on good containment of the landfill gas.
An example of good containment would be synthetic liners on the top, sides
and bottom of the landfill.
The first criteria that should be satisfied for an active system is gas
moving equipment capable of handling the maximum landfill gas generation
rate. Blowers or compressors and header pipes need to be sized to handle
the maximum landfill gas generation rate. In addition, collection header
pipes should also be sized to minimize pressure drop. The maximum landfill
gas generation rate is highly variable but may be estimated using the range
reported in one EPA study (0.001-0.0008 m landfill gas/kg of dry
refuse/yr).
Each extraction well or trench has a zone of influence within which
landfill gas can be effectively collected. The zone of influence of an
extraction well or trench is defined as the distance from the well center to
a point in the landfill where the pressure gradient applied by the blower or
compressor approaches zero. The zone of influence determines the spacing
between extraction wells or location of trenches since an effective
collection system covers the entire area of the landfill. The zones (or
radii) of influence for gas extraction wells are illustrated in Figure 4-5.
The spacing between extraction wells depends on the depth of the
landfill, the magnitude of the pressure gradient applied by the blower or
compressor, type of waste, degree of compaction of waste, and moisture
content of gas. For perimeter extraction wells, additional variables such
as the outside soil type, permeability of the soil, moisture content of the
soil, and stratigraphy should be considered. One EPA study reports a
typical well spacing to be 260 feet with a radius of influence of 150 feet.6
These distances are based on a well extraction rate of 50 ft3/minute and a
well vacuum of 3 inches of water.
The desired method for determining effective well spacing at a specific
landfill is the use of field measurement data. The EPA Method 2E can be
used to determine the average stabilized radius of influence for both
4-10
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* Extraction wells
R » Radius of Influence
s = Optima! well spacing * 1.732 R
Figure 4-5. Zones of influence for gas extraction wells.
4-11
-------
perimeter wells and interior wells. This measured radius of influence can
then be used to site wells. A good practice is to place wells along the
perimeter of the landfill (but still in the refuse) no more than the
perimeter radius of influence from the perimeter and no more than two times
the perimeter radius of influence apart. As illustrated in Figure 4-6, a
helpful technique is to site the location of each well and draw a circle
with radius equal to the radius of influence (perimeter radius of influence
for perimeter wells and interior radius of influence for interior wells).
Once the perimeter wells are sited on the landfill plot plan, the interior
wells are sited at no more than two times the interior radius of influence
in an orientation such that essentially all areas of the landfill are
covered by the radii of influence.
In situations where field testing is not performed, the well spacing
can be determined based on theoretical concepts. Understanding the
behavior of landfill gas through the municipal landfill refuse and cover
(final or daily cover) material is important in order to design the landfill
gas collection system properly. The flow of landfill gas can be described
by Darcy's Law. Darcy's Law correlates the flow of gas through a porous
media as a function of the gas properties (e.g., density and viscosity), the
properties of the porous media (e.g., permeabilities of refuse and cover),
and pressure gradient.
When active collection systems (both vertical and horizontal) are
designed, it is also important to understand the relationship between the
magnitude of vacuum applied and the degree of air infiltration into the
landfill. Excessive air infiltration into the landfill can kill the
methanogens, which produce landfill gas from the municipal refuse. If
excessive air infiltration continues, decomposition becomes aerobic and the
internal landfill temperature can increase and possibly lead to a landfill
fire. If the landfill conditions are such that air infiltration into the
landfill is significant (e.g. highly permeable cover and/or shallow
landfill), the magnitude of vacuum applied may need to be reduced to
minimize the amount of air infiltration. Direct consequence of the reduced
vacuum is an increased number of wells or trenches required to achieve the
same collection efficiency. Therefore, consideration of air infiltration is
4-12
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Emisiion Control Alttm«tiv«t
Landfill Art*
Q«t Ixtraetion
W«4I Art*
of lnflu«nct
Figure 4-6. Technique for siting wells.
4-13
-------
required in designing the active collection systems for shallow landfills.
The problem of air infiltration does not exist for passive systems since
passive systems rely on the natural pressure gradient (i.e., difference
between atmospheric pressure and internal landfill pressure) rather than
applying vacuum.
The theoretical approach, which can be used to design different types
of landfill gas collection systems (active well systems, active horizontal
trench systems, and passive systems), is based on specific landfill
information. Information on the following landfill characteristics are used
in the design equations:
- Landfill design capacity
- Average annual refuse acceptance rate
Age of landfill upon closure
Landfill depth
- Refuse methane generation potential, L
- Landfill gas generation rate constant, k
- Refuse permeability, krefu$e
- Cover permeability, kcover
The first four parameters are usually readily available for a given
landfill. The refuse methane generation potential (L ) and the landfill gas
generation rate constant (k) are the required inputs to the first order
landfill gas generation rate model which is described in detail in Chapter 3
and they vary depending on the landfill characteristics such as the refuse
composition, refuse moisture content, pH, and temperature. The values of LQ
and k must be assumed unless landfill specific test data are available. The
values of krefu$e and kCQver also vary from landfill to landfill but can be
estimated from the available literature values. Available literature values
and actual data for LQ and k may be found in a memorandum titled "Use of a
Landfill Gas Generation Model to Estimate VOC Emissions from Landfills".7 A
detailed discussion of the theorectical approach for designing active
vertical, active horizontal, and passive vertical collection systems is
provided in Appendix H.
4-14
-------
In a good design each extraction well or trench is equipped with a
throttling valve and pressure gauge in order to adjust and monitor the
collection system. In addition, the gas collection header system is
designed so that water condensate can be separated from the collected gas
(e.g., via sloping of the pipings or water traps at low points. Wells are
also equipped with at least one sample port that can be used to monitor
pressure and to collect gas samples periodically.
4.2 LANDFILL GAS EMISSION CONTROL/TREATMENT TECHNIQUES
There are two basic types of landfill gas control/treatment options
available: (1) combustion of the landfill gas, and (2) purification of the
landfill gas. The combustion techniques can further be categorized into two
types: (1) combustion techniques which destroy organics without energy
recovery, and (2) combustion techniques which recover energy from the
destruction of organics.
The combustion techniques which do not recover energy are flares and
afterburners. The energy recovery techniques include gas turbines, internal
combustion engines, and boiler-to-steam turbine systems, all of which
generate electricity from the combustion of landfill gas. Boilers may also
be used at the landfill site or off-site to recover energy from landfill gas
in the form of steam.
Purification techniques (adsorption, absorption, membranes) process raw
landfill gas to pipeline quality natural gas. All purification techniques
involve removal of water before removing carbon dioxide. The water is
removed by either absorption with glycols or adsorption with silica gel,
alumina, or molecular sieve. The removal method of nonmethane hydrocarbons
depends on the different CO^ removal techniques chosen and the composition
of the landfill gas. Usually the same techniques used for CCL removal are
also used to remove nonmethane hydrocarbons by simply adding an extra
absorption, adsorption, or condensation step. Removal of nonmethane
hydrocarbons is often an important part of the purification scheme.
Standard natural gas pipelines generally do not accept halogenated compounds
and sulfur derivatives. Consequently the removal of these compounds is also
a significant part of process design.
4-15
-------
The selection of a recovery technique versus a control technique is
highly dependent on such factors as the landfill gas generation rate, the
availability of a market for the recovered energy, and environmental
impacts. If the landfill characteristics are such that the landfill does
not produce enough gas to economically support combustion techniques with
energy recovery (i.e., gas turbines, internal combustion engines,
boiler/steam turbines) or purification techniques, flaring may be best
suited for the'specific landfill. Developers of landfill gas recovery
systems cite the following factors as necessary for economically feasible
landfill gas recovery projects: (1) refuse in place of greater than
2 million tons (1.8 million Mg), (2) depth of refuse greater than 35 feet,
(3) landfill area of greater than 35 acres, (4) refuse type which can
generate large quantities of landfill gas (e.g., vegetation), (5) continued
landfill operation (several years) for an active landfill, and (6) short
P
time elapsed after closing for a closed landfill.
If there are no customers for the electricity produced or medium/high
Btu gas, energy recovery techniques are not feasible. Also, the local value
of electricity and natural gas (high Btu gas) is important in choosing the
energy recovery techniques. Finally, the environmental impacts of the
control/treatment techniques also need to be considered. In general,
internal combustion engines have the greatest secondary air impaced (e.g.,
NOX, CO, and S0x emissions) when compared to the other combustion
techniques. The environmental impacts of purification techniques are a
function of the specific technique used and the add-on control techniques
employed.
4.2.1 Flares
4.2.1.1 Flare Process Description. Flaring is an open combustion
process in which the oxygen required for combustion is provided by either
ambient air or forced air. Good combustion in a flare is governed by flame
temperature, residence time of components in the combustion zone, turbulent
mixing of the combustion zone, and the amount of oxygen available for
combustion.
4.2.1.1.1 Open flares. Flares as described in this section can be
located at ground level or can be elevated. Although some of these flares
4-16
-------
operate without external assist (to prevent smoking), most use steam or air,
or the velocity of the gas itself, to mix the gas and air. Flares located
at ground level can be shielded with a fence. These flares, whether or not
at ground level, are described in 40 CFR 60.18. Because they cannot be
easily sampled the conditions necessary to achieve 98 percent reduction are
described in 40 CFR 60.18.
Landfill gas is conveyed to the flare through the collection header and
transfer lines by one or more blowers. A knock-out drum is normally used to
remove gas condensate. The landfill gas is usually passed through a water
seal before going to the flare. This prevents possible flame flashbacks,
caused when the gas flow rate to the flare is too low and the flame front
pulls down into the stack.
Purge gas (H*, CCL, or natural gas) also helps to prevent flashback in
the flare stack caused by low gas flow rate. The total volumetric flow rate
to the flame must be carefully controlled to prevent low flow flashback
problems and to'avoid flame instability. A gas barrier or a stack seal is
sometimes used just below the flare head to impede the flow of air into the
flare gas network.
4.2.1.1.2 Enclosed flares. Flares described in this section are at
ground level and are closely enclosed with fire resistant walls (shell)
which extend above the top of the flame. Air is admitted in a controlled
manner to the bottom of the shell. The temperature above the flame can be
monitored and the off gas sampled. This type of flare is in use at several
landfills in California and in other states. Many of these flares have been
sampled and have consistently shown combustion efficiencies of greater than
98 percent for the NMOC contained in landfill gas.
The basic elements of an enclosed ground flare system are shown in
q
Figure 4-7. The landfill gas is conveyed to the flare station through the
collection header and transfer lines by one or more blowers. Purge gas is
usually needed only for initial purging of the system upon start-up.
Landfill gas condensate is removed by a knockout drum. A water seal or
flame barrier is located between the knockout drum and the flare to prevent
flashbacks. The number of burner heads and their arrangement into groups
for staged operation depends on the landfill gas flow rate and composition.
4-17
-------
Purg*
OM
oo
UndnQw
OM Coteclton I to>d
-------
To ensure reliable ignition, pilot burners with igniters are provided.
The burner heads are enclosed in a shell that is internally insulated. The
shell can be of several shapes, such as cylindrical, hexagonal, or
rectangular. The height of the flare must be adequate for creating enough
draft to supply sufficient air for smokeless combustion and for dispersion
of the thermal plume. Some enclosed ground flares are equipped with
automatic damper controls. The damper adjusts the intake of the air by
opening and closing the damper near the base of the stack, depending on the
combustion temperature. A thermocouple located about 3 ft below the stack
outlet is typically used to monitor combustion temperature. Stable
combustion and efficient operation can be obtained with landfill gases that
have heat content as low as 100 to 120 Btu/scf (or 10 to 12 percent CH4).
4.2.1.2 Flare Combustion Efficiency. Flare combustion efficiency is a
function of many factors: (1) heating value of the gas, (2) density of the
gas, (3) flammability limits of the gas, (4) auto-ignition temperature of
the gas, and (5) mixing at the flare tip. Combustion efficiency test data
for industrial elevated flares are not readily available because of the
difficulty in obtaining representative samples at the stack outlet.
However, results are available from testing pilot-scale flares.
The EPA has established open flare combustion efficiency criteria
(40 CFR 60.18) which specify that 98 percent combustion efficiency can be
achieved provided that certain operating conditions are met: (1) the flare
must be operated with no visible emissions and with a flame present, (2) the
net heating value of the flared stream must be greater than 11.2 MJ/scm
(300 Btu/scf) for steam-assisted flares, and 7.45 MJ/scm (200 Btu/scf) for a
flare without assist, and (3) steam assisted and nonassisted flares must
have an exit velocity less than 18.3 m/sec (60 ft/sec). Steam assisted and
nonassisted flares having an exit velocity greater than 18.3 m/sec
(60 ft/sec) but less than 122 m/sec (400 ft/sec) can achieve 98 percent
control if the net heating value of the gas stream is greater than
37.3 MJ/scm (1,000 Btu/scf). Air-assisted flares, as well as steam-assisted
and nonassisted flares with an exit velocity less than 122 m/sec
4-19
-------
(400 ft/sec) and a net heating value less than 37.3 MJ/scm (1000 Btu/scf),
can determine the allowable exit velocity by using an equation in
40 CFR 60.18.
Unlike open flares that are not easily sampled, enclosed flares can be
measured to obtain reliable test data. The effect of the surrounding
environment (e.g., wind velocity) is minimized because the flare is
enclosed. An enclosed ground flare burns with multiple small diffusion
flames from burner heads that can be stage-operated depending on the gas
flow rate. The design of enclosed ground flares allows for a wide range of
combustion air flow rates and temperature control.
The SCAQMD of California requires that the flares in use at municipal
solid waste landfills be the enclosed ground type flares with automatic air
damper control. The SCAQMD also requires that the flare have a residence
time and combustion temperature of at least 0.3 second and 1400°F,
respectively. The combustion temperature is measured at 3 ft below the flare
stack outlet. SCAQMD source tests for flares at municipal solid waste
landfills indicate that 98 percent combustion efficiency is observed at
methane concentration as low as 10 to 12 percent.
Flare NMOC emission data and combustion efficiencies for several
11-21
landfills are presented in Table 4-2.
4.2.1.3 Applicability of Flares. Flares in use at landfills for air
emission control include those sites using flares as the main method of
control and others using flares as a back-up to an energy recovery system.
As stated earlier, the SCAQMD requires that flares in use to control air
emissions at municipal solid waste landfills be the type that are enclosed
with an automatic air damper control. Periodic sampling of these flares is
conducted to ensure that an emission reduction of 98 percent is being
achieved.
4.2.2 Thermal Incineration
4.2.2.1 Thermal Incineration Process Description. Any organic
chemical heated to a high enough temperature in the presence of sufficient
oxygen will be oxidized to carbon dioxide and water. This is the basic
operating principle of a thermal incinerator. The theoretical temperature
4-20
-------
TABLE 4-2. ENCLOSED GROUND FLARE COMBUSTION EFFICIENCY DATA
ro
Landfill6
Scholl Canyon
Palos Verdes
(Flare Station 2)
Palos Verdes
(Flare Station 3)
Calabasas
Puente Hills
Puente Hills
(Flare HMD
BKK
Date
of test
08/01/86
10/15/87
11/16/87
11/16/87
10/09/87
07/31/86
12/01/87
02/20/86
02/21/86
03/04/86
03/05/86
03/06/86
NHOC
Concentration (ppm)
Inlet Outlet
3,063
20,618
51,627
76.56
20,041
198
7.065
6,426
5,332
19,235
8,717
9,663
.048
<.016
<.747
.67
<49.7
.74
.30
40.6
53.9
22.8
82.63
48.3
Mass Flow
Inlet
33.4
239
2,893
3.8
237
2.2
130
8.9
9.83
61.5
79.4
26.3
NMOC
Rate (Ib/yr)
Outlet
.005
<.0012
<.1159
.09
<3.7
.005
.05
.92
1.51
.31
1.147
.69
Combustion
Temperature
N/Ad
1,400-1,500
1,556
1,356
N/A
N/A
1,710
1,468
1,599
1,400
1,343
1,360
Efficiency
(X)
>99.99
>99.99
>99.99
98
>98.44
99.79
99.96
89.6
84.6
99.4
98.5
97.4
Reference
11
12
13
14
15
16
17
18
19
20
21
21
Combustion Efficiency (%) = 100 (Inlet flowrate-outlet flowrate)/(inlet flowrate)
Landfill information obtained from South Coast Air Quality Management Test Reports.
C0utlet concentrations corrected to 3 percent oxygen.
Exit flare temperature was not available.
-------
required for thermal oxidation to occur depends on the structure of the
chemical involved. Some chemicals are oxidized at temperatures much lower
than others.
A thermal incinerator is usually a refractory-lined chamber containing
a burner at one end. As shown in Figure 4-8, discrete dual fuel burners,
inlets for the offgas, and combustion air are arranged in a premixing
chamber to thoroughly mix the hot products from the burners with the offgas
air streams. The mixture of hot reacting gases then passes into the main
combustion chamber. This section is sized to allow the mixture enough time
at the elevated temperature for the oxidation reaction to reach completion
(residence times of 0.3 to 1 second are common).
Where thermal incinerators are used to control vent streams from
methane recovery systems, auxiliary fuel is typically required. Thermal
incinerators designed with natural gas as the auxiliary fuel may also use a
grid-type (distributed) gas burner as shown in Figure 4-9. The tiny gas
flame jets on the grid surface ignite the vapors as they pass through the
grid. The grid acts as a baffle for mixing the gases entering the chamber.
This arrangement ensures burning of all vapors at lower chamber temperature
and uses less fuel. This system makes possible a shorter reaction chamber
yet maintains high efficiency.
Other parameters affecting incinerator performance are the offgas
heating value, the water content in the stream and the amount of excess
combustion air (the amount of air above the stoichiometric air needed for
reaction). The offgas heating value is a measure of the heat available from
the combustion of the VOC in the offgas. Combustion of offgas with a
heating value less than 1.86 MJ/Nm (50 Btu/scf) usually requires burning
auxiliary fuel to maintain the desired combustion temperature. Auxiliary
fuel requirements can be lessened or eliminated by the use of recuperative
heat exchangers to preheat combustion air. Offgas with a heating value
above 1.86 MJ/Nm (50 Btu/scf) may support combustion but may need auxiliary
fuel for flame stability.
Combustion devices are always operated with some quantity of excess air
to ensure a sufficient supply of oxygen. The amount of excess air used
varies with the fuel and burner type but should be kept as low as possible.
4-22
-------
Stack
Wi
Audttwy
FtMiBunw
(DtaerMt)
Air/ Mbdng
Optional HM<
Raoovwy
Combmtton Sactton
Figure 4-8. Discrete burner, thermal incinerator.
4-23
-------
Bumar Plato
(NaturaiOaa)
AudBaiyFual
Figure 4-9. Distributed burner, thermal incinerator.
Stack
Fan
Optional Haat
Racovary
4-24
-------
Using too much excess air wastes fuel because the additional air must be
heated to the combustion chamber temperature. Large amounts of excess air
also increase flue gas volume and may increase the size and cost of the
system. Packaged, single unit thermal incinerators can be built to control
3
streams with flow rates in the range of 0.1 Nm /sec (200 hundred scfm) to
about 24 Nm3/sec (50,000 scfm).
4.2.2.2 Thermal Incinerator Combustion Efficiency. The NMOC
destruction efficiency of a thermal oxidizer can be affected by variations
in chamber temperature, residence time, inlet VOC concentration, compound
type, and flow regime (mixing). Test results show that thermal oxidizers
can achieve 98 percent destruction efficiency for most NMOC at combustion
chamber temperatures ranging from 700 to 1300°C (1300 to 2370°F) and
22
residence times of 0.5 to 1.5 seconds. These data indicate that
significant variations in destruction efficiency occurred for C, to C,-
alkanes and olefins, aromatics (benzene, toluene and xylene), oxygenated
compounds (methylethylketone and isopropanol), chlorinated organics (vinyl
chloride) and nitrogen containing species (acrylonitrile and ethylamines) at
chamber temperatures below 760°C (1400°F). This information used in
conjunction with kinetics calculations indicates the combustion chamber
parameters for at least a 98 percent VOC destruction efficiency are a
combustion temperature of 870°C (1600°F) and a residence time of
0.75 seconds (based upon residence in the chamber volume at combustion
23
temperature). A thermal oxidizer designed to produce these conditions in
the combustion chamber should be capable of high destruction efficiency for
almost all NMOC even at low inlet concentrations.
4.2.2.3 Applicability of Thermal Incinerators. In terms of technical
feasibility, thermal incinerators are applicable as a control device for any
vent stream containing NMOC. In the case of landfill gas emission, however,
their use is primarily limited to control of vent streams from methane
recovery systems. Other NMOC destruction techniques are generally more
economical for the control of landfill gas.
Incinerators can be designed to handle minor fluctuations in flows.
However, excessive fluctuations in flow (upsets) might not allow the use of
4-25
-------
incinerators and would require the use of a flare. Presence of compounds
such as halogens or sulfur might require some additional equipment such as
scrubbers.
4.2.3 Gas Turbines
4.2.3.1 Gas Turbine Process Description. Gas turbines take large
amounts of air from the atmosphere, compress it, burn fuel to heat it, then
expand it in the power turbine to develop shaft horsepower. Figure 4-10 is
04
a simplified schematic of a gas turbine. Ambient air is compressed and
combined with fuel in the combustor. The combustor exhaust stream flows to
the power turbine which converts some of the stream's fuel energy to rotary
shaft power. This shaft power drives the inlet compressor and an electrical
generator (or some other load).
Two basic types of gas turbines have been used in landfill
applications: simple cycle and regenerative cycle. A simple cycle gas
turbine has been described above. The gas temperatures from the power
turbine range from 430 to 600°C (800 to 1,100°F). The regenerative cycle
gas turbine is essentially a simple cycle gas turbine with an added heat
exchanger. Thermal energy is recovered from the hot exhaust gases and used
to preheat the compressed air. Since less fuel is required to heat the
compressed air to the turbine inlet temperature, the regenerative cycle
improves the overall efficiency of the gas turbine.
4.2.3.2 Gas Turbine Combustion Efficiency. The most prevalent type of
gas turbine found in landfill energy recovery applications is the Solar
Model Centaur. Based on a field test and information provided by the
manufacturer, these turbines are capable of achieving greater than
98 percent destruction of NMOC or a 20 ppm NMOC outlet concentration at
26 27
3 percent oxygen. '" Results from the only test of a Solar Model Centaur
turbine showed a 6.2 ppm NMOC outlet. The NMOC destruction efficiency
during this test could not be determined because the inlet NMOC
concentration was not measured.
Achievement of high combustion efficiency requires the controlled
mixing of fuel and air and the simultaneous satisfaction of several
conditions:
• Air velocities in the combustor below flame speed.
4-26
-------
Cornprwaor
Expander
Turbine
Hot Exhaust Gasm
Rotary Shaft Poww
4— (to driv« pump,
compr»t»or, or
•(•ctrtcal generator)
Figure 4-10. Simplified schematic of gas turbine.
4-27
-------
t Air/fuel ratio within flammability limits.
• Sufficient residence time to complete reactions.
• Turbulent mixing of fuel/air throughout the combustion zone.
• Ignition source to start the reaction.
The heart of the gas turbine is its combustion system. Since the
overall fuel/air ratio of the gas turbine is usually outside the flammable
range, the combustor is divided into three zones to achieve efficient
burning of the fuel. Air from the gas turbine compressor is divided and
supplied to the primary combustion zone to initiate the main reaction. The
reaction is mostly completed in the secondary zone. The dilution zone is
used to direct the hot gases into the turbine section and reduce the
temperature to meet turbine design requirements for long component life and
time between inspections. Dilution is accomplished by using the correct
combustor hole pattern to achieve the proper temperature profile.
4.2.3.3 Applicability of Gas Turbines. There are about 20 landfills
28
in the U.S. which employ gas-fired turbines. The applicability of a gas
turbine depends on the quantity of landfill gas generated, the availability
of customers, the price of electricity, and environmental issues. Gas
turbines tend to have lower emissions of NO , CO and PM than
A
comparably-sized internal combustion engines.
4.2.4. Internal Combustion (1C) Engines
4.2.4.1 1C Engine Process Description. Reciprocating internal
combustion engines produce shaft power by confining a combustible mixture in
a small volume between the head of a piston and its surrounding cylinder,
causing this mixture to burn,, and allowing the resulting high pressure
products of combustion gas to push the piston. Power is converted from
29
linear to rotary form by means of a crankshaft.
There are two methods of igniting the fuel and air mixture:
spontaneous compression ignition and spark ignition. Since spark ignition
engines are typically used for in landfill energy recovery applications,
only spark ignition internal combustion engines are discussed in this
section. These internal combustion engines may be described by the number
4-28
-------
of strokes per cycle (two or four) and the method of introducing air and
fuel into the cylinder. In the four-stroke cycle, the sequence of events
may be summarized as follows and illustrated in Figure 4-11:
• Intake Stroke—Suction of the air or air and fuel mixture into the
cylinder by the downward motion of the piston.
• Compression Stroke—Compression of the air or air and fuel
mixture, thereby raising its temperature.
t Ignition and Power (Expansion) Stroke—Combustion and consequent
downward movement of the piston with energy transfer to the
crankshaft.
0 Exhaust Stroke—Expulsion of the exhaust gases from the cylinder
by the upward movement of the piston.
This description applies to a naturally aspirated engine which utilizes the
vacuum created by the moving piston to suck in the fresh air charge.
However, many engines blow air into the cylinder with either a turbocharger
or a supercharger. The turbocharger is powered by a turbine that is driven
by the energy from the relatively hot exhaust gases while a supercharger is
driven off the engine crankshaft. Air pressurization is used to increase
the power density, or power output per unit weight (or volume) of the
engine. Since the density of air increases with pressure, the mass of air
that can be introduced into the cylinder increases with pressure.
Furthermore, since the air-to-fuel ratio at maximum power is fixed by
combustion requirements, more fuel can be introduced into the cylinder with
high pressure air than with atmospheric pressure air. Therefore, more power
can be obtained from a given cylinder configuration. As the air pressure is
increased, its temperature is also raised. For this reason the pressurized
air is often cooled before it enters the cylinder to further increase power.
This process is called intercooling or aftercooling. All high power
turbocharged natural gas-fueled engines are intercooled to prevent premature
auto-ignition of the fuel and air mixture.
4.2.4.2 1C Engine Combustion Efficiency. The combustion or fuel
efficiency of 1C engines under full load is a function primarily of the
air-to-fuel ratio although many other factors (such as charge homogeneity)
can have an effect. As fuel efficiency decreases, emissions of nonmethane
4-29
-------
INTAKf STROKf
!»»••« .«*»« •»•*•.
»OWW O* V/OUK STKOKt
FU«|-«I> mutyi* baxx.
Figure 4-11.
The four-stroke, spark ignition cycle. Four strokes of 180
if crankshaft rotation each or 720 of crankshaft rotation per
cycle.
4-30
-------
organic compounds (NMOC) and carbon monoxide (CO), the products of
incomplete combustion, increase. Minimum NMOC and CO emissions occur
usually at some air-to-fuel ratio slightly leaner than stoichiometric.
Below this optimum ratio, CO and NMOC emissions increase because of low
temperature and insufficient oxygen for combustion. Above this ratio NMOC's
increase because of low temperature.
The Environmental Protection Agency (EPA) has made a survey of the
combustion efficiencies of 1C engines burning various gaseous fuels
including landfill gas. For most of these engines only data on methane
combustion efficiency is available. For these engines it is assumed that
NMOC combustion efficiency will be equal to methane combustion efficiency.
For a few engines NMOC combustion efficiency is known. The conclusion
reached from all the information available is that 1C engines can and do
achieve 98 percent NMOC emission reduction at most locations. There are two
situations where combustion efficiency may be less. First, if the engine is
operated at reduced load, efficiencies can drop to about 95 percent. Most
of these engines are operated at full load all the time. However, some
engines are operated at less than full load to extend their operating life.
The second factor effecting NMOC emission reduction is the fact that, in
general, the State and local agencies that presently regulate internal
combustion engines burning landfill gas tend to require the lowest possible
NO , even at cost of lower engine efficiencies and higher emissions of NMOC.
Some areas now require NO levels that result in combustion efficiencies
very close to 98 percent. Internal combustion engine efficiency data for
landfill gas are presented in Table 4-3.
4.2.4.3 Applicability of 1C Engines. 1C engines are being used at
about 40 landfills because of their short "construction tima, ease of
installation, and operating capability over a wide range of speeds and
loads. 1C engines fueled by landfill gas are available in capacities
ranging from approximately 500 KW up to well over 3,000 KW. A rule of thumb
is that 1 million cubic feet of landfill gas per day at 450 Btu/scf will
generate 1,250 to 1,600 KW/hr of electricity.32
4-31
-------
TABLE 4-3. NONMETHANE ORGANIC AIR EMISSION DESTRUCTION EFFICIENCY - RESULTS OF FIELD
TESTS OF THE COMBUSTION OF LANDFILL GAS USING INTERNAL COMBUSTION ENGINES
Landf i I I
name/ location
American Canyon
CA
Guadelupe Landfill
Los Gatos, CA
Marsh Road
Menlo Park, CA
OJ
ro
Neuby Island
San Jose, CA
Shoreline Park
Mountain View, CA
City of Glendale
Scholl Canyon
Information About Turbine/Generator
Number
and size Power output
Type (kilowatts) (megawatts)
Rich two - 820 1.6
burn
Rich three - 525 1.6
burn
Rich four - 525 2.1
burn
Rich four - 500 2.0
burn
Lean two - 1,875 3.8
burn
Rich one - 1,600 0.6
burn
Field
Date
of
test
12/85
12/85
11/86
11/86
11/86
09/86
09/86
09/86
09/86
01/87
01/87
01/87
01/87
12/85
12/85
01/86
Test Data
Engine
number
1
2
1
2
3
1
2
3
4
1
2
3
4
1
2
2
Results
Outlet
flow rate
(dscfm)
2,640
2,400
987
744
1,090
1,420
.370
,460
,490
.410
,760
,260
,160
4,960
5,210
1,424
Outlet
concentration
of NMHC*
at 3%
Oy, dry
(ppmv)
<2
<2
0.19
3.8
1.5
<0.97
<0.98
10.1
8.7
<1.6
<1.5
<1.5
<1.5
<1.5
<1.6
11
References
33
33
33
33
33
33
33
33
33
33
33
33
33
33
33
34
"Concentration of nonmethane organic compounds is expressed as hexane.
-------
4.2.5 Boilers
Boilers can be categorized into three types depending on the heat input
to the furnace. Utility boilers are defined as boilers with heat input
greater than 100 x 10 Btu/hr; industrial boilers are the boilers with heat
input of 10 -100 x 10 Btu/hr; and domestic/commercial boilers are the
boilers with less than 10 x 10 Btu/hr of heat input. The majority of the
landfill gas-fired boilers are industrial boilers with corresponding heat
inputs of approximately 10.5 x 10 Btu/hr (350 scfm at 50 percent CH.) to
c "
90 x 10 Btu/hr (3000 scfm at 50 percent CH.). Therefore, the discussion of
the boilers is focused on industrial boilers.
4.2.5.1 Boiler Process Description. The majority of industrial
boilers are of water tube design. In a watertube boiler, hot combustion
gases contact the outside of heat transfer tubes which contain hot water and
steam. These tubes are interconnected by a set of drums that collect and
store the heated water and steam. The water tubes are of relatively small
diameter, 5 cm (2.0 inches), providing rapid heat transfer, rapid response
to steam demands, and relatively high thermal efficiency. Energy transfer
can be above 85 percent efficient. Additional energy can be recovered from
the flue gas by preheating combustion air in an air preheater or by
preheating incoming boiler feedwater in an economizer unit.
When firing natural gas, forced or natural draft burners are used to
thoroughly mix the incoming fuel and combustion air. In general, burner
design depends on the characteristics of the fuel stream. A particular
burner design, commonly known as a high intensity or vortex burner, is
normally selected for gas streams with low heating values (i.e., streams
where a conventional burner may not be applicable). These burners
effectively combust low heating value streams by passing the combustion air
through a series of spin vanes to generate a strong vortex.
4.2.5.2 Combustion Efficiency. Furnace residence time and temperature
profiles vary for industrial boilers depending on the furnace and burner
configuration, fuel type, heat input, and excess air level. A mathematical
model has been developed that estimates the furnace residence time and
temperature profiles for a variety of industrial boilers. The model
predicts mean furnace residence times between 0.25 to 0.83 seconds for
4-33
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natural gas-fired watertube boilers in the size range from 4.4 to 44 MW
(15 to 150 x 106 Btu/hr). Boilers at or above the 44 MW size have
residence times and temperatures that ensure a 98 percent NMOC destruction
efficiency. Furnace exit templates for this range of boiler sizes are at or
above 12,000°C (2,200°F) with peak furnace temperature occurring in excess
of 1,540°C (2,810°F). Although test data for landfill gas are not
available, boilers are considered high destruction efficiency devices for
NMOC present in landfill gas.
4.2.5.3 Applicability of Boilers. Landfill gas-fired boilers may be
utilized in two ways. The landfill gas may be routed to an on-site boilers
or piped and sold to an off-site boiler to supply heat on hot water. The
landfill gas may also be routed to an on-site boiler to generate steam which
in turn is fed to a steam turbine to generate electricity. The majority of
landfill gas-fired boilers are utilized as a simple heat or hot water
source. There is only one operating landfill gas-fired boiler to steam
turbine facility in the U.S. Another facility is under construction. The
landfill gas-fired boiler/steam turbine system produces very little
by-product emissions. However, it requires high initial capital investment
and a minimum gas flow rate of 6,000 to 8,000 scfm.
4.2.6 Adsorption
4.2.6.1 Adsorption Process Description. Adsorption is a mass-transfer
operation involving interaction between gaseous and solid phase components.
The gas (adsorbate) is captured on the solid phase (adsorbent) surface by
physical or chemical adsorption mechanisms. Physical adsorption is a
mechanism that takes place when intermolecular (van der Waals) forces
attract and hold the gas molecules to the solid surface. Chemisorption
occurs when a chemical bond forms between the gas and solid phase molecules.
A physically adsorbed molecule can be readily removed form the adsorbent
(under suitable temperature and pressure conditions) while the removal of a
38
chemisorbed component is much more difficult.
The most commonly encountered industrial adsorption systems use
activated carbon as the adsorbent. Activated carbon is effective in
capturing certain organic vapors by the physical adsorption mechanism. In
addition, adsorbate may be desorbed for recovery by regeneration of the
4-34
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adsorption bed with steam. Oxygenated adsorbents such as silica gels,
diatomaceous earth, alumina, molecular sieves or synthetic zeolites exhibit
a greater selectivity than activated carbon for capturing some compounds.
However, these adsorbents have a strong preferential affinity for water
vapor over organic gases and are of little use for high moisture gas streams
such as those from landfills. The landfill gas adsorption process for high
Btu gas recovery consists of two major steps: (1) pretreatment removal of
nonmethane hydrocarbons and water, and (2) removal of CO^.
4.2.6.1.1 Removal of nonmethane hydrocarbons. The removal of
nonmethane hydrocarbon contaminants generally requires the use of activated
carbon beds. The carbon can either be replaced or thermally regenerated.
Thermal regeneration of the carbon bed requires the heating of the bed with
a gas stream as high as 600°F. This regeneration vent stream containing
nonmethane hydrocarbons is usually incinerated in a thermal combustion
chamber. An example of a pretreatment carbon bed system is shown in
Figure 4-12 and the detailed pretreatment process description is given
below.39
The landfill gas enters the adsorbent bed, and as the gas passes
through the bed, the remaining water and chemical impurities are adsorbed.
The resulting pre-treated mixture of methane and carbon dioxide exits the
bed and is sent to the main adsorption process for further processing.
After the bed becomes saturated, and before breakthrough of any
contaminants, the adsorption step is halted and feed is switched to a bed
which has just completed regeneration. The breakthrough of the bed is then
regenerated with hot gas to remove the.chemical impurities from the
adsorbent. The by-product carbon dioxide which is produced in the CCL
removal step may be used as the hot gas. The regeneration vent stream
exiting this vessel contains heavy hydrocarbons and other impurities removed
from the landfill gas during the adsorption step. This effluent stream can
be sent to a thermal combustor to destroy heavy hydrocarbons and other
impurities.
Following regeneration of the adsorbent bed, the adsorbent must be
cooled to ambient temperature prior to being placed back on adsorption.
This is accomplished by passing a cool gas stream through the bed. The
4-35
-------
Ctoan Feed to Pressure
Swing Adsorption
Regeneration Gas
B
Vent
GornpraMor
Ft*
Thermal Combustor
PROCESS CYXXE
A Adeorpbon
9 n^QWMTVIG
C Cooldown
Figure 4-12. Pretreatment adsorption system.
4-36
-------
effluent from the cool-down step is heated with the thermal combustor flue
gas (if a thermal combustor is used) and then used to heat another bed. By
utilizing the waste heat from the thermal combustor, the amount of fuel can
be minimized.
4.2.6.1.2 Removal of CO... To upgrade the Btu content of the landfill
gas to pipeline specifications, a minimum of -970 Btu/scf is typically
required. To meet this heat content requirement, essentially all of the C02
must be removed. The gas will also contain some nitrogen and oxygen which
can reduce the Btu content. However, the removal of nitrogen requires
40
extremely low temperatures that are uneconomical and impractical. As a
result, only the carbon dioxide is removed in upgrading the Btu content of
the landfill gas. Typically, molecular sieves have been used for the
removal of CCL. The adsorption process commonly used for CCL removal is a
pressure swing process which uses vacuum to regenerate the molecular sieve
beds rather than heat. A diagram of a pressure swing adsorption process is
shown in Figure 4-13 and the detailed description of a 5-step pressure swing
41
adsorption process is given below.
The pretreated landfill gas stream at feed gas pressure, combined with
a methane recycle stream, enters the bottom of a bed on the adsorption step.
The carbon dioxide in the feed gas is selectively adsorbed on the molecular
sieve producing an exit stream of high-purity methane (99 percent) at
slightly less than feed gas pressure. The adsorption step is continued
until the bed becomes saturated with carbon dioxide and the mass transfer
zone is just short of column breakthrough.
After the adsorption step, the values are switched and the bed is
concurrently purged at feed gas pressure with a stream of high-purity carbon
dioxide from the carbon dioxide surge vessel. The purpose of the
high-pressure rinse step is to remove any methane which is present in the
void gas or co-adsorbed on the molecular sieve following the adsorption
step. The high pressure rinse step is an important feature of the process
and results in greatly increased methane recovery. The purge gas which
exits the bed is recycled as feed to a bed undergoing the adsorption step.
Following the high-pressure rinse step, the valves are switched and the
bed which is saturated with high-purity carbon dioxide is depressurized to
4-37
-------
Product CH«
Feed
From
Pretreatment
Step
A - Adsorption
B - High Press flinse
C - Depressunzation
0 - Evacuation
E - Repressunzation
Vacuum
Pump
By-Product
CO2
Figure 4-13. Pressure swing adsorption process,
4-38
-------
atmospheric pressure. The desorbed carbon dioxide is recompressed to
slightly above feed pressure and used as rinse for a bed undergoing the high
pressure rinse step.
After the bed reaches atmospheric pressure, the valves are switched and
the bed is connected to the suction of the vacuum system which reduces the
bed pressure to a subatmospheric pressure. The desorbed carbon dioxide and
any remaining methane are discharged at a slight positive pressure.
Following the evacuation step, the bed is repressurized to feed gas
pressure with a portion of the high-purity methane produced.
Repressurization is done countercurrent to the adsorption step to drive any
residual carbon dioxide from the exit end of the bed. Once the feed
pressure is reached, the bed is ready to repeat the cycle.
Following separation in the pressure swing adsorption process, the
product methane stream may require additional compression depending on the
pipeline pressure requirements. If the pipeline pressure exceeds the
80-150 psig operating range of the pressure swing adsorption process,
additional product compression will be necessary.
4.2.6.2 Adsorption Control Efficiency. Control of NMOC emissions,
when using methane recovery systems, is typically accomplished by routing
all vent streams to a thermal incinerator. As discussed in Section 4.2.2.2,
thermal incinerators are capable of achieving greater than 98 percent
destruction efficiency. Therefore, routing all vent streams from the
methane recovery system to an efficient thermal incinerator provides greater
than 98 percent reduction of NMOC emissions.
4.2.6.3 Applicability of Adsorption Process. The feasibility of using
adsorption versus other control/recovery techniques is determined by the
landfill gas composition, flow rate, natural gas price, and the distance to
the local gas company pipeline. Currently there are very few (two or three
in the U.S.) landfill facilities which employ adsorption to recover landfill
gas due to high capital investment required and low natural gas prices.
4.2.7 Absorption
4.2.7.1 Absorption Process Description. The mechanism of absorption
consists of the selective transfer of one or more components of a gas
mixture into a solvent liquid. The transfer consists of solute diffusion
4-39
-------
and dissolution into a solvent. For any given solvent, solute, and set of
operating conditions, there exists an equilibrium between solute
concentration in the gas mixture and solute concentration in the solvent.
The driving force for mass transfer at a given point in an operating
absorption tower is related to the difference between the actual
concentration ratio and the equilibrium ratio. Absorption may only entail
the dissolution of the gas component into the solvent or may also involve
chemical reaction of the solute with constituents of the solution. The
absorbing liquids (solvents) used are chosen for high solute (VOC or C02)
solubility and include liquids such as water, mineral oils, nonvolatile
hydrocarbon oils, and aqueous solutions of oxidizing agents such as sodium
43
carbonate and sodium hydroxide.
Devices based on absorption principles include spray towers, venturi
scrubbers, packed towers, and plate columns. The control of NMOC and toxics
or removal of C02 by gas absorption is generally accomplished in packed
towers or plate columns. Packed towers are mostly used for handling
corrosive materials, for liquids with foaming or plugging tendencies, or
where excessive pressure drops would result form the use of plate columns.
They are less expensive than plate columns for small-scale operations where
the column diameter is less than 0.6 m (2 ft). Plate columns are preferred
for large-scale operations, where internal cooling is desired or where low
44
liquid flow rates would inadequately wet the packing.
A schematic of a packed tower is shown in Figure 4-14. The gas to be
absorbed is introduced at the bottom of the tower and allowed to rise
through the packing material. Solvent flows from the top of the column,
countercurrent to the vapor, absorbing the solute from the gas phase and
carrying the dissolved solute out of the tower. Cleaned gas exits at the
top for release to the atmosphere or for further treatment as necessary.
The saturated liquid is generally sent to a stripping unit where the
absorbed VOC or C02 is recovered. Following the stripping operation the
absorbing solution is either recycled back to the absorber or sent to a
treatment facility for disposal.
The solvents that can be used for the removal of water in absorption
process include ethylene glycol, diethylene glycol, and triethylene glycol.
4-40
-------
Cleaned Qas Out
To Final Control Device
VCCUdwi
Q«ln
AbtofbtngUquJd
wUhVOCOut
To OtapOMl or VOC/SoJv«nt
Figure 4-14. Packed tower absorption process.
4-41
-------
For landfill gas applications, ethylene glycol is most commonly used since
diethylene glycol and triethylene glycol require high regeneration
temperature. The solvents used for the removal of heavy hydrocarbons vary
depending on the type of solvent selected for the removal of C02- Some
solvents used for the removal of C02 also absorb heavy hydrocarbons.
The solvents used for the removal of C02 can be classified into the
following groups; 1) organic solvents, 2) alkaline salt solutions, and
3) alkanolamines. Organic solvents include Sulfinol, Selexol, Fluor,
Purisolj and Rectisol. Organic solvents have an advantage over other
absorption solvents because of their high acid gas loading and reduced
circulation. However, organic solvents have a tendency to absorb heavy
hydrocarbons thus causing faster degradation of the solvent. For a high
concentration of hLS, the Fluor and Selexol processes have been used. In
the Selexol process, C02 is absorbed at low temperatures and high pressure.
When the pressure is reduced, carbon dioxide is released. It is critical to
remove as much water and heavy hydrocarbons as possible before C02
absorption since water and heavy hydrocarbons will reduce the affinity of
Selexol for COp. The typical Selexol process diagram is shown in
Figure 4-15. The Rectisol (Methanol) process is very similar to the
Selexol process except that it operates at lower temperatures.
Alkaline salt solution processes (potassium carbonate base) are
applicable for treating gas with high C02 content, usually at pressures
greater than 200 psig. Alkaline salt solution processes are not usually
recommended for landfill gas treatment since most of the solvents cannot
reduce C02 content to pipeline specifications.
The alknolamine solvents include MEA (monoathanolamine), DEA
(diethanolamine), and TEA (triethanolamine). An 18 percent ME'A is the most
commonly used solvent to remove C02. DEA is also used since it is
noncorrosive up to 35 percent where as MEA is corrosive above 18 percent.
The disadvantage of DEA is a relatively large energy requirement for
regeneration.
4.2.7.2 Absorption Control Efficiency. Similar to adsorption
techniques, reductions in NMOC emissions are achieved by routing all vent
streams to a destruction device such as a thermal incinerator. Greater than
4-42
-------
-p.
I
OJ
LaonSotvanl
SwnMMn Soh^rt
Figure 4-15. Selexol absorption process.
-------
98 percent NMOC reduction efficiency can be achieved by routing all vent
streams from the methane recovery system to a well-designed thermal
incinerator.
4.2.7.3 Applicability of Absorption Process. There are few landfills
in the U.S. which employ absorption (notably the Selexol process) to treat
landfill gas. The applicability of an absorption process is determined by
the landfill gas composition, flow rate, natural gas price, and distance to
the local gas company pipeline. The absorption process also requires high
initial capital investment.
4.2.8 Membranes
4.2.8.1 Membrane Process Description. Separation of gases by membrane
permeation operates on the principle of selective permeability of one gas
over another. The separation of carbon dioxide from a mixture of carbon
dioxide and methane is accomplished by the fact that carbon dioxide
permeates through the membrane much more rapidly than methane does. The
result is an increase in the concentration of carbon dioxide on the low
pressure side of the membrane. The methane is then concentrated on the high
pressure side as the carbon dioxide is removed.
There are basically three types of membranes used commercially;
1) spiral-wound, 2) tubular, and 3) hollow fiber. The most common type of
membranes used is spiral-wound, composed of cellulose acetate-based polymer.
The spiral-wound membrane elements are packaged in pressure tubes. The feed
gas enters the pressure tube under high pressure (500 psig), flows through
the spiral-wound element and separates the gas mixture into two components;
1) low pressure permeate which contains the more permeable gas (carbon
dioxide) of the mixture, and 2) high pressure residual gas which contains
the less permeable component of the mixture (methane). The pressure tubes
can be mounted on a skid in either a parallel or series array depending on
the recovery required and flow rate of the feed gas.
A typical membrane process is shown in Figure 4-16.50 The feed gas is
compressed to 500 psig, the condensed water and hydrocarbons are knocked out
and/or pretreated in a carbon bed, heated to approximately 120°F, and fed to
the first stage membranes which consist of three parallel pressure tubes.
The feed gas is heated to 120°F for the optimal separation since membrane
4-44
-------
LandfflQaa
CCkvarrtt©
atmbaphafe or
to flare
Dahydrator
60-70 *F
Carbon Towar
140-160*
Carbon Towar
2nd Staga Mambranaa
1st Staga Mambranaa
Haatar
tt
120T
Saiaa Qaa (900 •(• Btu/eu. ft)
| M| IndteataaQMFIowMatarLocatkxi
Figure 4-16. Membranes process.
4-45
-------
pore size and gas permeability are a function of temperature. The high
pressure residual gas is then reheated to 140 - 160°F and fed to the second
stage membranes. The permeate gas is vented to the atmosphere or flared.
The second stage membranes consist of three pressure tubes in series. The
high pressure residual gas is the product stream and the permeate gas is
recycled back to the feed stream. The product gas is approximately
90 percent methane. About 25 percent of the product is used as compressor
fuel.
A thorough filtration is required to prevent scaling or fouling,
especially for the hollow fiber membranes. These membranes are easily
damaged by foreign particles and water can affect their performance. The
temperature is also very critical in a membrane system. The membranes can
be damaged above 160°F, and the capacity of the membranes is highly
temperature sensitive.
4.2.8.2 Membrane Control Efficiency. The NMOC control efficiency is
dependent on the disposition of the waste gas streams (nonmethane).
Depending on the heat content of the vent streams, they may be controlled by
flaring or incineration. As discussed earlier, these combustion devices are
capable of achieving greater than 98 percent destruction efficiency.
Therefore, greater than 98 percent NMOC reduction can be achieved, if all
vent streams are routed to a flare or incinerator.
4.2.8.3 Applicability of Membranes. The advantages of the membrane
process are its small size, simple operation, low capital cost, and
flexibility. It can handle a wide range of operating pressures, and the
system can be easily modified by adding or removing the pressure tubes (in
series or parallel) to adjust for the changing flow rates. However, as the
methane recovery percent increases, the corresponding recovery cost also
increases exponentially.
There are two landfill facilities in the U.S. which employ a membrane
52
process. The desirability of the membrane process versus other control or
recovery techniques will depend on the landfill gas flow rate, the price of
natural gas, the distance to the nearest gas company's pipeline, and the
ratio of product gas flow rate to the pipeline flow rate. One advantage of
the membrane process is its flexibility since the membrane elements can
4-46
-------
either be added or removed to adjust for the wide range of flow rates. If
the ratio of the pipeline flow rate to the product flow rate is very high,
the product Btu content requirement may not be as strict due to the dilution
effect.
4.3 SECONDARY AIR EMISSIONS FROM MSW LANDFILL CONTROL TECHNIQUES
This section provides a discussion of the secondary air emissions
associated with MSW landfill control devices such as flares, boilers, gas
turbines, and 1C engines, which were discussed in Section 4.2. These
control techniques themselves generate emissions in the process of
controlling air emissions from MSW landfills. Consequently, EPA is
concerned about the impact of these secondary emissions in evaluating the
overall benefits of applying landfill air emission controls .
A summary of both the reduction and secondary air impacts associated
with each of the applicable landfill air emission control devices is
presented in Table 4-4. These air impacts are presented for two
perspectives. The first is a very narrow perspective which considers only
the air impacts at the landfill site. Emissions of particulate matter (PM),
sulfur dioxide (S02), nitrogen oxides (NO ), carbon monoxide (CO), carbon
dioxide (CO^), and hydrogen chloride (HC1) may be increased at the lanfill
site due to operation of the control device. The second perspective is much
broader and takes into account the reduction in utility power requirements
and the air emission associated with electric power generation. In the case
of landfill energy recovery devices such as gas turbines and 1C engines,
energy recovered is expected to reduce local or regional electric utility
power generation. For the purpose of this analysis, electricity generated
from landfill energy recovery techniques is assumed to displace an equal
amount of electricity that would otherwise be generated from coal-fired
utility boilers. Based on current utility fuel costs, this is a reasonable
assumption. Therefore, the net secondary air impacts presented in Table 4-4
represent the difference between air emissions generated by the control
equipment and air emissions that would be generated from producing an
equivalent amount of electricity with a coal-fired boiler/steam turbine.
4-47
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TABLE 4-4. NET AIR IMPACT FOR LANDFILL AIR EMISSION CONTROL TECHNIQUES
Control technique
Enclosed flare
Incinerator
Boi ler
(net impact)
Gas turbine
(net impact)
1C engine
(net impact)
Emission Reductions
(Ib/MM scf LFG)
NMOC3 CH4b N0xc
56-3,395 21,840 4.9
56-3,395 21,840 4.9
56-3,395 21,840 70
0
56-3,395 21,840 26.4
-224
56-3.395 21,840 111
-139
Secondary Air Emissions (Ib/MM
cod
58
58
17
0
12.5
0
259
0
HCle
12
12
12
12
12
12
12
12
coz
60,000
60,000
50,000
0
60,000
0
60,000
0
scf LFG)
PM
Meg.
Neg.
Neg.
Neg.
37
-15
Neg.
-15
S02f
3.0
3.0
3.0
2.3
3.0
-597
3.0
-597
Estimated from NMOC concentrations found in Chapter 3 which range from 237 ppm to 14,294 ppm. Assumed
a molecular weight af NHOC equal to hexane.
Estimated assuming that landfill gas is 50 percent methane.
Secondary NO air emissions for flares and incinerators are average values from the data in Tables 4-5
and 4-7, respectively. The NO air emissions for boilers was obtained from AP-42 for natural gas
fired boilers and converted to Ib/MM scf LFG assuming 500 Btu/scf. The NO air emissions for turbines
and 1C engines are average values from Table 4-8.
Secondary CO air emissions for flares and incinerators are average values from the data in Tables 4-5
and 4-7, respectively. The CO air emissions for boilers was obtained from AP-42 for natural gas fired
boilers and converted to Ib/MM scf LFG assuming a heat value of 500 Btu/scf. The CO air emissions
for turbines and 1C engines are average values from Table 4-8.
Secondary HCl air emissions were calculated from the NMOC compositions provided in Table 3-9 assuming
all the chlorine converted to HCl.
Secondary SO- air emissions were calculated from the NMOC compositions provided in Table 3-9 assuming
all the sulfur converted to SO,.
4-48
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4.3.1 Secondary Air Emissions from MSW Landfill Control Systems
The following sections discuss the source and average amounts of
secondary emissions from the control techniques discussed in Section 4.2.
Factors which may impact the level of emissions of a given pollutant are
also discussed. Although hydrocarbon emissions are presented, it is
important to remember that the concentration of nonmethane organic
compounds in the MSW landfill gas can range from 237 to 14,300 ppm, as shown
in Chapter 3. The impact of secondary emissions must be considered in light
of the NMOC emission reductions achieved from controlling landfill air
emissions.
One factor that may impact secondary emission rates, but has not been
addressed directly in calculating the emission factors presented in
Table 4-4, are existing and proposed Federal and State regulations. The
size of the turbines currently in use at MSW landfills is below the cutoff
of the Federal regulation. However, 48 States have rules that would cover
the use of gas turbines at MSW landfills. Regarding 1C engines, the South
Coast Air Quality Management District (SCAQMD) has regulations limiting
emissions from these devices. In addition, NSPS for 1C engines and small
boilers have been proposed. If promulgated, these regulations would affect
such devices used to control air emissions from MSW landfills. Other State
and local regulations may exist. Generally, such regulations would decrease
the emission levels of the criteria pollutants.
4.3.1.1 Secondary Air Emissions from Flares. As part of an EPA study,
emission measurements of NO and hydrocarbons from a pilot-scale open pipe
53
type (or elevated) flare were conducted. The study concluded that the NO
A
concentration (on an air-free basis, zero percent 02) generally increases
witfi increasing combustion efficiency for most flare heads and gas mixtures.
The Los Angeles County Sanitation Districts measured the NOV and CO
r j X
from enclosed flares at two of its MSW landfills. As shown in Table 4-5,
the NO emissions range from 1.4 to 10.0 Ib/MM scf of landfill gas. The CO
A
emissions range from 13.7 to 87.4 Ib/MM scf of landfill gas.
4.3.1.2 Secondary Air Emissions from Thermal Incinerators. The
secondary air emissions generated from thermal oxidation of landfill gas are
the same ones generated from flaring landfill gas. These are NOX, CO, and
4-49
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TABLE 4-5. SECONDARY AIR EMISSIONS - RESULTS OF FIELD TESTS OF THE COMBUSTION OF LANDFILL GAS USING FLARES
Date
Landfill of Nitrogen Oxides Carbon Monoxide
name/ location test (ppmv) (Ibs/hr) (Ib/MM scf LFG) (ppmv) (Ibs/hr) (Ib/MM scf LFG)
Puente Hills 02/86 18.8 1.3 10.0 42.0 1.8 13.7
CA 02/86 16.0 1.4 8.1 254.0 13.3 74.9
BKK Corp. 03/86 7.5 2.1 2.1 172.0 5.9 28.7
West Covina, CA 03/86 5.0 0.3 1.4 527.0 21.2 87.4
03/86 10.0 0.6 2.7 522.0 18.6 87.4
Reference
55
56
57
58
59
Concentration data are expressed at 15 percent oxygen on a dry basis.
^k
i
en
o
-------
C02. Additionally, small quantities of PM may be generated. Also, small
quantities of HC1 may be generated depending on the presence of chlorinated
compounds in the landfill gas. At typical thermal oxidizer combustion
temperatures, essentailly all chlorine present exists in the form of
hydrogen chloride (HC1).60
Although no data are available for thermal oxidation of landfill gas,
the secondary air emissions from thermal oxidizers can be reasonably
estimated from thermal oxidizer data collected from other applications.
Test results from the two thermal oxidizers applied in the chemical
manufacturing industry indicate that outlet NOV concentrations, the
61
secondary pollutant of greatest concern range from 8 to 30 ppmv. This
range is consistent with the NO emissions measured from enclosed ground
A
flares (a very similar combustion device) burning landfill gas. Therefore,
due to the lack of thermal oxidizer data and the similarity to enclosed
ground flares, secondary emissions from thermal oxidizers are assumed to be
the same as enclosed ground flares.
4.3.1.3 Secondary Air Emissions from Gas Turbines. The emissions
generated by gas turbines burning landfill gas are those common to all
combustion processes: NO , CO, and particulate (PM). The NO formation is
A A
directly related to the pressure and temperature during the combustion
process. The other pollutants are primarily the result of incomplete
combustion.
The most important factor that affects NMOC destruction efficiency is
the peak flame temperature in the primary combustion zone. Emissions of
NMOC and CO increase as this peak flame temperature decreases. Also, for
simple cycle gas turbines, lower pressure ratio designs tend to have higher
CO and NMOC emissions than high pressure ratio designs.
Nitric oxides (NO ) produced by combustion of fuels in gas turbines are
formed (mostly) by the combination of nitrogen and oxygen in the combustion
air (thermal NO ). The NO emissions increase with increasing peak flame
" /\
temperature and increasing pressure ratios. There is, therefore, a trade
off between low NOX operation with a low peak flame temperature or a low
pressure ratio and low NMOC and CO operation with high peak flame
temperature or a high pressure ratio.
4-51
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Small gas turbines of the size used for landfill applications are
designed to meet the EPA NOX emission limits of 150 ppmvd at 15 percent
oxygen (40 CFR Part 60, Subpart 6G). When landfill gas is burned in a gas
turbine the resulting peak flame temperature is significantly lower than
that from burning natural gas. Landfill gas turbines can be operated with
NO levels that meet the EPA standard and in addition have combustion
efficiencies greater than 99 percent. Although the landfill gas turbines in
the EPA survey were below the EPA size cutoff, six of the seven turbines met
the NOX standard.64
A survey was conducted by EPA of the by-product emissions of gas
turbines burning various gaseous fuels including landfill gas. Test data
for seven turbines burning landfill gas is presented in Table 4-6 and is
summarized below:
t NO Emissions—The range in the concentration of NO was 11 to
174 ppmvd at 15 percent oxygen or 0.4 to 6.2 g/hp-h?. The average
concentration was 44 ppmvd at 15 percent oxygen or 1.9 g/hp-hr.
• CO Emissions—The range in concentration of CO was 15 to
1,300 ppmvd at 15 percent oxygen or 0.2 to 26 g/hp-hr. The
average concentration was 466 ppmvd at 15 percent oxygen or
10.4 g/hp-hr.
4.3.1.4 Secondary Air Emissions from 1C Engines. The primary
pollutants from landfill gas fueled 1C engines are NO , NMOC, CO, and
particulates. The NO formation is directly related to high pressures and
A
temperatures during the combustion process. The other pollutants are
primarily the result of incomplete combustion.
For 1C engines burning most fuels, NOX, CO, and NMOC emissions can be
reduced by the use of a catalytic converter. For 1C engines burning
landfill gas, however, this is not possible. Various compounds from the
landfill poison the catalyst resulting in loss of conversion efficiency in a
few days. To change emissions for these engines it is therefore necessary
to adjust the air-to-fuel ratio. Unfortunately, there is a trade-off
between N0x and NMOC emissions. Engine adjustments intended to lower NMOC
4-52
-------
TABLE 4-6. SECONDARY AIR EMISSIONS - RESULTS OF FIELD TESTS OF THE COMBUSTION OF LANDFILL GAS USING TURBINES*
Landfill
name/ location
Metro Landfill
Franklin, WI
Omega Landfill
Germantown, WI
Palos Verdes
Rolling Hills, CA
Puente Hills
Los Angeles, CA
Puente Hills
Los Angeles, CA
Date
of
test
04/86
04/86
04/86
03/84
07/84
08/84
02/86
Unit
tested
(#)
1
1
2
1
1
2
1
Secondary Air Emissions
Nitrogen Oxides
(ppmv)
34
24
30
174**
23
11
11
(g/hp-hr)
a
a
a
6.2
0.5
0.5
0.4
(Ib/MM scf)
a
a
a
29.5
30.0
25.0
21.2
(ppmv)
NM
NH
NM
255
15
294
1,300
Carbon Monoxide
(g/hp-hr)
NM
NM
NM
7.2
0.2
8.1
26
(Ib/MM scf)
a
a
a
346
12.5
400
1,630
Reference
66
66
66
67
68
68
69
•Concentration data are expressed at 15 percent oxygen on a dry basis.
w "This represents an average of 3 runs (243, 145, 133 ppmvd at 15 percent oxygen).
NM = Not Measured
a = This value was not provided and could not be calculated because insufficient information Mas provided.
-------
emissions result in increased NOX emissions and vice versa. Although the
relationship between NMOC and NO is complex and depends on many factors,
A
the general relationship is illustrated below:
NO (g/hp-hr) % Destruction Efficiency
A
2=0 98.3
5.0 98.7
10.0 99.1
The technical problem involved in reducing NOX by increasing
air-to-fuel ratio is that the extra lean mixtures are difficult to ignite
and engines misfire or will not start. Engine designs overcome this problem
by one or more of the following techniques.
• The use of fuel injection rather than carburetors so that all
cylinders get the same mix.
• The use of indirect injection where combustion begins in a fuel
rich mix in a small antechamber and travels from there to the
excess air region of the main chamber.
t The use of a homogenous mix with a cratered piston to provide
swirl (mixing) and a short flame path, with high voltage spark
plugs.
• The use of techniques of fuel injection which result in a layer of
fuel rich mix around the spark plug in the main chamber while the
rest of the main chamber has excess air.
The EPA has made a survey of the secondary air emissions of 1C engines
burning various gaseous fuels including landfill gas. Test data for
15 internal combustion engines burning landfill gas is presented in
Table 4-7 and summarized below:-
• NO Emissions—The range is the concentration of NO was 50 to
225 ppmvd at 15 percent oxygen or 0.6 to 3.6 g/hp-hP. The average
concentration was 136 ppmvd at 15 percent oxygen or 2.4 g/hp-hr.
t CO emissions—The range in concentration of CO was 30 to 550 ppmvd
at 15 percent oxygen or 0.4 to 7.2 g/hp-hr. The average
concentration was 220 ppmvd at 15 percent oxygen or 2.4 g/hp-hr.
4.3.1.5 Secondary Air Emissions from Boilers. Emissions from boilers
include particulate matter (PM), sulfur oxides (SO ), nitrogen oxides (NO ),
A X
4-54
-------
TABLE 4-7. SECONDARY AIR EMISSIONS - RESULTS OF FIELD TESTS OF THE COMBUSTION OF LANDFILL GAS USING INTERNAL COMBUSTION ENGINES*
cn
en
Landfill
name/location
American Canyon
CA
Guadelupe Landfill
Los Gatos, CA
Marsh Road
Menlo Park, CA
Newby Island
San Jose, CA
Shoreline Park
Mountain View, CA
City of Glendale**
Scholl Canyon
Date
of
test
12/85
12/85
11/86
11/86
11/86
09/86
09/86
09/86
09/86
01/87
01/87
01/87
01/87
12/85
12/85
01/86
Unit
tested
(#>
1
2
1
2
3
1
2
3
4
1
2
3
4
1
2
1
Secondary Air Emissions
Nitrogen Oxides
( ppmv )
59
50
68
210
225
141
156
192
178
159
103
192
178
54
73
442
(g/hp-hr)
0.8
0.6
1.4
2.4
3.3
3.0
3.2
3.0
3.2
3.6
2.8
3.2
3.5
0.7
0.9
8.5
(Ib/MM scf)
126
94.3
a
a
a
a
a
a
a
a
a
a
a
95.2
129
a
(ppmv)
218
268
271
379
180
43
89
223
54
30
276
550
312
211
192
216
Carbon Monoxide
(g/hp-hr)
1.8
2.0
3.5
2.6
1.6
0.6
1.2
2.8
0.6
0.4
4.6
7.2
3.8
1.6
1.5
2.4
(Ib/MM scf)
283
314
a
a
a
a
a
a
a
a
a
a
a
222
215
a
Reference
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
•Concentration data are expressed at 15 percent oxygen on a dry basis.
"The outlet is ducted to a catalytic converter for reducing NO emissions.
is 90 ppmvd at 15 percent oxygen.
NM = Not Measured
a = This value was not provided and could not be calculated due to insufficient information.
The local regulatory allowable emission limit for this unit
-------
and lesser amounts of carbon monoxides (CO), hydrocarbons (HC), and trace
elements. Nitrogen oxides are the major pollutants of concern for natural
gas-fired boilers. The PM emissions factors for boilers firing natural gas
or MSW landfill gas are very low because natural gas or MSW landfill gas has
little or no ash content and combustion is more complete than with other
fuels.72
The SO emissions from boilers are predominantly in the form of S0? and
A ™
depend directly on the sulfur content of the fuel. The sulfur oxide
emissions from boilers fired with MSW landfill gas will be negligible due to
its low sulfur content. Nearly all NOX emissions from natural gas or MSW
landfill gas fired boilers are thermal NOX- An increase in flame
temperature, oxygen availability, and/or residence time at high temperatures
leads to an increase in NO production. The rate of CO emissions from
A
boilers depends on the combustion efficiency. For example, operation at
very low excess air levels (less than two or three percent) can decrease
combustion efficiency and subsequently increase CO emissions
significantly.
The emission factors for natural gas-fired boilers were used to
estimate emissions from MSW landfill gas-fired boilers since the landfill
gas mainly consists of methane and CO^. The emission factors for natural
gas-fired industrial boilers are 0.14 Ib NOX/106 Btu, 0.35 Ib CO/105 Btu,
and 1 x 10'3 - 5 x 10"3 lbPM/106 Btu.74
Nitrogen oxide emissions can be reduced through several operating
modification such as staged combustion, low excess air firing, and flue gas
recirculation. Flue gas recirculation was proven to be an effective method
of reducing NO emissions from a MSW landfill gas-fired boiler yielding a
NOY emission factor of 0.04 lb/106 Btu (or 18 lb/106 ft).75
^
4.3.1.6 Secondary Emissions from Adsorption. The possible sources of
secondary emissions in an adsorption system are thermal combustor flue gas
(or carbon bed regeneration vent if thermal combustor is not used) and
secondary COg stream which may contain trace amounts of nonmethane
hydrocarbons and methane. Emissions from the thermal combustor will include
NO SO , CO, and PM. The emission rates of these pollutants are a function
A A
of the design and operating parameters of the thermal combustor.
4-56
-------
4.3.1.7 Secondary Emissions from Absorption. The possible sources of
secondary emissions in an absorption process are the contaminated solvent
stream and the regeneration vent. The emission rates will depend on the
type of the solvent selected, design/operating parameters, and the method of
treating contaminated solvent.
4.3.1.8 Secondary Emissions from Membranes. Aromatics, chlorinated
hydrocarbons, and alcohols permeate with the carbon dioxide while the heavy
hydrocarbons remain with the high pressure methane stream. If a
pretreatment system is employed to remove water and other hydrocarbon
contaminants, the CO- vent stream will mainly be composed of CCL and trace
amounts of methane (2 - 18 percent CH. depending on the number of membrane
elements and configuration). Therefore, the major sources of secondary
emissions are the C02 vent stream and pretreatment condensate stream. If
the compressor (which compresses the feed gas before it enters the
membranes) is fueled by the product gas or natural gas, the compressor
exhaust also is a source of secondary emissions such as NOV7 SOV, CO, and
77 xx
PM/7
4.3.3 The Potential for Energy Recovery Control Techniques to Reduce
Demand at Utilities
In evaluating the options for control of air emissions at MSW
landfills, it is important to consider the overall impact of the controls.
The emission controls involving energy recovery generally yield electricity
or steam. The electricity or steam produced by these controls would
otherwise be produced by some other means. In the case of electricity, the
net electricity generated by the MSW landfill control technique reduces the
need for utility power generation. This reduction in utility requirements
is likely to result in the reduction of secondary emissions from coal-fired
power plants.
Under the current market conditions, demand for electricity exceeds
supply. Typically, the less expensive hydro-electric and nuclear powered
plants are run at maximum capacity, with the additional demand being met
first by natural-gas fired plants, and then by oil and coal-fired boilers.
Because the coal-fired boiler is more expensive per kilowatt, any reduction
4-57
-------
in demand associated with generation at MSW landfills will likely replace
coal-fired generation (within the constraints of grid accessibility and
pre-existing contractual arrangements).
EPA judged that an analysis of secondary emissions from control
techniques at MSW landfills should consider the differential between
emissions from an 1C engine or a gas turbine and the emissions they might
"displace" at a coal-fired utility plant. The emission limits under the
NSPS for coal-fired utility boilers (40 CFR 60, Subparts D and Da) are
0.03 Ib PM/106 Btu, 1.2 Ib S02/106 Btu, and 0.5 Ib NOX/106 Btu. These
emission limits for coal-fired utility boilers were used along with the
secondary emissions presented in Tables 4-6 and 4-7 for 1C engines and gas
turbines to estimate the net impact of control techniques involving energy
recovery. These net impacts and the derivation of these net impacts is
presented in Table 4-8. The emission factors for the energy recovery
techniques were simply compared to the emission factors for the utility
boiler to estimate relative impacts.
4-58
-------
TABLE 4-8. DERIVATION OF NET SECONDARY AIR
IMPACTS FOR GAS TURBINES AND 1C ENGINES
PM S02 NOX HC1 CO
Coal-fired utility boiler 0.03 1.2 0.5 Neg. ND
co2
120
controlled to meet the
NSPS (Ib/MMBtu)
Reduction in coal-fired3 15 600 250 Neg. ND ND
utility boiler emissions
per unit of landfill gas
burned in a turbine or
1C engine (Ib/MM scf LFG)
Secondary air emissions Neg. 3.0 26.4 12 12.5 60,000
from a gas turbine
burning landfill gas
(Ib/MM scf LFG)
Net secondary air -15 -597 -224 12 Ob 0
emissions from a gas
turbine burning landfill
gas (Ib/MM scf LFG)
Secondary air emissions Neg. 3.0 111 12 259 60,000
from an 1C engine
burning landfill gas
(Ib/MM scf LFG)
Net secondary air -15 -597 -139 12 0 0
emissions from an 1C
engine burning landfill
gas (Ib/MM scf LFG)
aAssumed that the relative fuel-to-electricity conversion efficiencies are
the same for boilers, turbines, and 1C engines.
Assumed the CO emissions from the combustion of coal to be negligible.
4-59
-------
4.4 REFERENCES
1. EPA Handbook. Remedial Action at Waste Disposal Sites (Revised).
Publication No. EPA/625/6-85/006. October 1985.
2. Van Heuit, R.E., Extraction, Metering and Monitoring Equipment for
Landfill Gas Control Systems. In: Proceedings from the GRCDA 6th
International Landfill Gas Symposium, Industry Hills, California,
March 14-18, 1983. 226 p.
3. Telecon. McGuinn, Y.C., Radian Corporation with L. Crosby, GSF Energy,
Inc. February 15, 1987. Efficiency of gas collection systems.
4. Meeting Report. Comments Received at the NAPCTAC meeting.
May 18, 1989.
5. EPA Project Summary. Critical Review and Summary of Leachate and Gas
Production from Landfills. EPA/600/52-86-073, March 1987.
6. U.S. Environmental Protection Agency. Recovery of Landfill Gas at
Mountainview: Engineering Site Study. Publication
No. EPA/530/SW-587d.
7. Memorandum from McGuinn, Y.C., Radian Corporation to Susan A.
Thorneloe, U. S. Environmental Protection Agency. June 21, 1988. Use
of a Landfill Gas Generation Model to Estimate VOC Emissions from
Landfills.
8. Jansen, G.R. The Economics of Landfill Gas Projects. In: Proceedings
of the 6th GRCDA Internal Landfill Gas Symposium, Industry Hills,
California. March 14-18, 1983. 138 p.
9. Kalcevic, V. (I.T. Enviroscience.) Control Device Elevation. Flares
and the Use of Emissions as Fuels. In: U. S. Environmental Protection
Agency. Organic Chemical Manufacturing Volume 4: Combustion Control
Devices. Research Triangle Park, N.C. Publication
No. EPA-450/3-80-026. December 1980. Report 4.
10. U.S. Environmental Protection Agency. Evaluation of the Efficiency of
Industrial Flares - Flare Head Design and Gas Composition. Air and
Energy Engineering Research Laboratory. EPA-600/2-85-106. Research
Triangle Park, N.C. September 1985.
11. South Coast Air Quality Management District. Source Test
Report 86-0375. October 29, 1986.
12. South Coast Air Quality Management District. Source Test
Report 87-0329.
4-60
-------
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
South Coast Air Quality Management District,, Source Test
Report 87-0376.
24.
25.
26.
South Coast Air Quality Management District.
Report 87-0376.
Source Test
South Coast Air Quality Management District, Source Test
Report 87-0318.
South Coast Air Quality Management District. Source Test
Report 85-369.
South Coast Air Quality Management District. Source Test
Report 87-0391.
South Coast Air Quality Management District,, Source Test
Report 86-0087.
South Coast Air Quality Management District. Source Test
Report 86-0088.
South Coast Air Quality Management District.
Report 86-0122.
Source Test
South Coast Air Quality Management District. Source Test
Report 86-0123 and 86-0124. October 29, 1986.
U.S. Environmental Protection Agency. Reactor Processes in synthetic
Organic Chemical Manufacturing Industry - Background Information for
Proposed Standards. Preliminary Draft. March 1985.
U.S. Environmental Protection Agency. Control of Volatile Organic
Compound Emissions from Air Oxidation Processes in Synthetic Organic
Chemical Manufacturing Industry - Background Information for Proposed
Standards, EPA Publication No. 450/3-82-OOla. October 1983. pp. 7-5.
U.S. Environmental Protection Agency. Guidance for Lowest Achievable
Emission Rates from 18 Major Stationary Sources of Particulates,
Nitrogen Oxides, Sulfur Dioxide, or Volatile Organic Compounds.
EPA-450/3-79-024. April 1979.
Scott Research Laboratories, Inc. Turbine Exhaust Emissions Measured
at Facilities of New York Power Pool, report No. SRL 1378-01-0374.
March 1974. Referenced by Reference 18.
Letter from Wilfred S.Y. Hung, Chief, Product Emissions, Solar Turbines
Incorporated, to S. Wyatt, U.S. Environmental Protection Agency.
March 9, 1989. Response to request for information on gas turbines
used to burn landfill gas.
4-61
-------
27. Report of Stack Testing at County Sanitation District of Los Angeles,
Puente Hills Landfill. August 15, 1984. (Test Conducted on July 31
and August 3, 1984). Prepared by Engineering-Science.
28. Stambler, Irwin. Solar Carving Out Landfill Market for Saturn and
Centaur Gas Turbines. In: Gas Turbine World. October 1988.
pp. 30-35.
29. U.S. Environmental Protection Agency. Stationary Internal Combustion
Engines. Standards Support and Environmental Impact Statement,
Volume I: Proposed Standard of Performance. Draft EIS.
EPA-450/2-78-125a.
30. Thorneloe, Susan and Les Evans. The Use of an Internal Combustion
Engine or a Gas Turbine as a Control for Air Emissions from Municipal
Solid Waste Landfills. Revised Draft Memorandum. U.S. Environmental
Protection Agency. May 31, 1989.
31. Landfill Gas Survey Update. In: Waste Age. March 1989.
pp. 171-174.
32. Reference 7. 144 p.
33. Letter from Matt Nourot, Laidlaw Gas Recovery Systems to Jack R.
Farmer, U.S. EPA. December 8, 1987. Response to Section 114
Questionnaire.
34. Evaluation Test on a Landfill Gas-Fired Internal Combustion Engine
System at the City of Glendale No. 1 Scholl Canyon Power Plant.
ARB/SS-87-08. California Air Resources Board. July 1986.
35. U.S. Environmental Protection Agency. Fossil Fuel Fired Industrial
Boilers - Background Information Document, Volume 1: Chapter 1-9.
Research Triangle Park, N.C. Publication No. EPA-450/3-82-066a.
March 1982. 3-27 p.
36'. U.S. Environmental Protection Agency. A Technical Overview of the
Concept of Disposing of Hazardous Wastes in Industrial Boilers (DRAFT).
Cincinnati, OH. EPA Contract No. 68-03-2567. October 1981. 44 p.
37. Trip Report. McGuinn, Y.C., Radian Corporation to Thorneloe, S.A.,
U.S. Environmental Protection Agency. January 20, 1988. Report of
November 18, 1988 vist to Palos Verdes Landfill in Los Angeles, CA.
38. See Reference 22.
39. Potochnik, K.E., and Van Sloun, J.K. Landfill Gas Treatment Experience
with the Gemini-5 System. Air Products and Chemicals, Incorporated.
1987. Brochure provided by Air Products, Inc.
4-62
-------
40. Love, D.L. Overview of Process Option and Relative Economics. In:
Proceedings of the 6th GRCDA International Landfill Gas Symposium.
March 14-18, 1983. Industry Hills, CA. 132 p.
41. Reference 23.
42. Standifer, R.L. (I.T. Enviroscience.) Control Device Evaluation Gas
Adsorption. In: U.S. Environmental Protection Agency. Organic
Chemical Manufacturing, Volume 5: Adsorption, Condensation, and
Adsorption Devices. Research Triangle Park, N.C. Publication
No. EPA-450/3-80-027. December 1980. Report 3.
43. Reference 40. 76 p.
44. Perry, R.H., Chilton, Ch.H. Eds. Chemical Engineers Handbook. 5th
Edison McGraw-Hill, New York. 1973. 14-2 p.
45. Reference 40. 136 p.
46. Ashare et al. Evaluation of Systems for Purification of Fuel Gas From
Anaerobic Digestion. COO-2991-44. Dynatech R/D Company. Cambridge,
MA. 1978. Referenced by Baron et al. Landfill Methane Utilization
Technology Workbook. CPE-8101. Johns Hopkins University. Laurel, MD.
Prepared for U.S. Department of Energy. February 1981.
47. Reference 40. 137 p.
48. Reference 40. 137 p.
49. Schell, W.J., and Houston, C.D. Membrane Systems for Landfall Gas
Recover Separax Corporation. Proceedings of the 6th GRCDA
International Landfill Gas Symposium. March 1978, 1983. Industry
Hills, CA. 170 p.
50. Trip Report. McGuinn, Y.C., Radian Corporation to Thorneloe, S.A.,
Environmental Protection Agency. February, 1988. Report of
November 19, 1987 visit to Rossman Landfill in Oregon City, OR.
51. Reference 40.
52. Trip Report. McGuinn, Y.C. Radian Corporation to Thorneloe, S.A.,
U.S. Environmental Protection Agency. June 1, 1988. Report of
November 17, 1987. Visit to Rossman Landfill in Oregon City, OR.
53. U.S. Environmental Protection Agency. Evaluation of the Efficiency of
Industrial Flares - Flare Head Design and Gas Composition. Air and
Energy Engineering Research Laboratory. EPA-600/2-85-106. Research
Triangle Park, N.C. September 1985.
4-63
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54. Consulich, J. and Eppich, J. Puente Hills Energy Recovery from Gas
Facility. Los Angeles County Sanitation Districts. In: Proceedings
of ASME Industrial Power Conference. Atlanta, Georgia. October 1987.
55 p.
55. Reference 18.
56. Reference 19.
57. Reference 20.
58. Reference 21.
59. Reference 21.
60. Reference 22. 7-5 p.
61. Reference 22. 7-5 p.
62. McGee, R.E. and D.W. Esbeck. Caterpillar Capital Company, Inc.
Development, Application, and Experience of Industrial Gas Turbine
Systems for Landfill Gas to Energy Projects. Proceedings of GRCDA's
llth Annual International Landfill Gas Symposium. March 21-24, 1988.
63. Reference 26.
64. Reference 30.
65. Reference 30.
66. Letter from Sue Briggum, Waste Management, to Susan Thornelow,
U.S. Environmental Protection Agency. September 28, 1988. Response to
request for field test data on turbine used to burn landfill gas.
67. Source Test Report (C-84-33) Conducted at L.A. Sanitation District,
Emissions from a Landfill Gas-Fired Turbine/Generator Set, Tested
March 6, 1984. Issued June 28, 1989.
68. Reference 27.
69. Evaluation Test on a Landfill Gas-Fired Turbine at the Los Angeles
County Sanitation District's Puente Hills Landfill Electric.
70. Reference 30.
71. Reference 33.
4-64
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72. Radian Corporation. State-of-the-Art Emission Control Technology
Guidelines for Selected Sources of Air Pollution. Prepared for the
New Jersey Department of Environmental Protection Bureau of Air
Pollution Control. DCN No. 88-245-048-13. December 30, 1987.
8-4 p.
73. Reference 35. pp. 8-5.
74. U.S. Environmental Protection Agency. Compilation of Air Pollutant
Emission Factors. Volume 1. AP-42. Fourth Edition. September 1985.
75. Reference 34.
76. Reference 47.
77. Telecon. McGuinn, Y.C., Radian Corporation with Hichman, L., GRCDA.
January 12, 1988.
4-65
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5. REGULATORY ALTERNATIVES
This chapter describes the regulatory alternatives considered for
controlling air emissions from municipal solid waste landfills. Regulatory
alternatives are considered for two groups of landfills: new landfills and
existing landfills. New landfills will be regulated under Section lll(b) of
the Clean Air Act (CAA), while existing landfills will be controlled under
the guidelines of Section lll(d). The derivation of regulatory alternatives
is discussed in Section 5.1. The impact of these alternatives with respect
to the number of landfills affected and the achievable emission reductions
are discussed in Sections 5.2 and 5.3 for existing and new landfills,
respectively.
5.1 DERIVATION OF REGULATORY ALTERNATIVES
In establishing the regulatory alternatives, the approach was taken to
require air emission controls only for a subset of landfills which provides
the greatest emission reduction at a reasonable costs. Controlling only a
portion of the landfill population would involve establishing a cutoff
(based on a site-specific characteristic) below which landfills are not
required to install controls. After consideration of several regulatory
formats for the cutoff, the EPA chose the annual nonmethane organic compound
(NMOC) mass emission rate. Three stringency levels of this format are
evaluated in this chapter: 25, 100, and 250 Mg NMOC/yr. The cutoff level
of 25 Mg NMOC/yr is the most stringent, while 250 Mg NMOC/yr is the least
stringent.
If a landfill's NMOC mass emission rate exceeds the cutoff before
closure then gas collection and control systems must be installed. The
landfill must continue to be controlled until the landfill has closed, the
collection and control system has been in place for at least 15 years, and
the NMOC mass emission rate falls below the same cutoff value. A cutoff is
to be selected that provides the greatest emission reduction at a reasonable
cost. The NMOC emission reduction for each of the stringency levels
considered are discussed in Sections 5.2 and 5.3 for existing and new
5-1
-------
landfills, respectively. The control costs for each of these stringency
levels is discussed in Chapter 7.
5.2 EXISTING MUNICIPAL SOLID WASTE LANDFILLS
The OSW survey of municipal solid waste landfills described in detail in
Chapter 3 was used to generate the database of existing landfills. The
category of existing landfills includes two types of landfills: those
projected to be actively collecting waste in 1992 and those projected to
have reached their design capacity and closed between 1987 and 1992. The
landfills actively collecting waste in 1992 includes those landfills that
would hypothetically open to replace the those closing between 1987 and
1992.
The number of existing landfills affected by the three stringency
levels and the corresponding emission reduction were determined from a model
which estimates the NMOC mass emission rate for each landfill in the
database each year until the landfill closes, determines if controls are
required and determines when controls can be removed.
Since the landfills may be affected by the cutoff at different points
in time and for varying lengths of time, the series of emission reductions
are the net present value in 1992 at a rate of 3 percent. The number of
landfills affected by each stringency level and corresponding net present
value of the emission reduction were scaled to the national level and summed
to provide the total nationwide impact.
As shown in Table 5-1, approximately 1,900 landfills nationwide out of
the total population of 7,480 landfills (6,034 active and 1,446 closed)
would have to install controls with a cutoff of 25 Mg NMOC/yr, the most
stringent option. The corresponding NMOC and methane emission reduction is
about 13 million Mg NMOC and 411 million Mg CH4 (net present value in 1992).
At the least stringent cutoff of 250 Mg NMOC/yr, approximately 386 landfills
nationwide (5 percent) would be affected. This stringency level would yield
a nationwide NMOC emission reduction of 10 million Mg and a methane
reduction of 200 million Mg (net present value in 1992).
The distribution of existing landfills affected by the stringency
levels with respect to design capacity is shown in Table 5-2. At the
5-2
-------
TABLE 5-1. REGULATORY ALTERNATIVES FOR EXISTING LANDFILLS
Total Percentage of NPV of
Stringency number of total landfill NPV of NMOC methane
level landfills population reduction reduction
(Mg NMOC/yr) affected (%) (million Mg) (million Mg)
25 1,884 25.2 12.6 411
100 853 11.4 11.2 307
250 386 5.2 9.6 200
5-3
-------
TABLE 5-2. DISTRIBUTION OF EXISTING LANDFILLS
AFFECTED BY THE REGULATORY ALTERNATIVES
Stringency
level
(Mg NMOC/yr)
25
100
250
<1
514
134
22
Distributed byfiDesign
Capacity (10° Ma)
Between
1 and 5
837
348
181
Between
5 and 10
295
176
48
238
195
135
Total
1,884
853
386
5-4
-------
stringency level of 25 Mg NMOC/yr, approximately 72 percent of the total
number of landfills affected are small, or less than 5 million Mg in size,
while 13 percent are large, or greater than 10 million Mg in size. In
comparison, approximately 35 percent of the landfill affected by the 100 mg
NMOC/yr level are greater than 10 million Mg in size, while 53 percent are
less than 5 million Mg in size.
5.3 NEW MUNICIPAL SOLID WASTE LANDFILLS
The number of new landfills affected by the three stringency levels and
the corresponding emission reduction were estimated as described in
Section 5.2 for existing landfills. [Refer to Chapter 3 for further
discussion on the database of landfills and the manipulation of the
information.]
Table 5-3 provides the total number of landfills affected by each'
stringency level and the corresponding NMOC and methane emission reduction.
At the most stringent level, approximately 247 landfills are affected
nationwide which is 27 percent of the new landfill population projected to
be built between 1992 and 1997. The corresponding net present values of
NMOC and methane emission reductions are 991,000 Mg and 51 million Mg,
respectively. At 250 Mg NMOC/yr, 41 landfills would have to install
controls, which would result in nationwide net present values of NMOC and
methane emission reductions of 630,000 Mg and 27 million Mg, respectively.
A distribution of the new landfills affected by the stringency levels
is presented in Table 5-4 with respect to landfill design capacity.
Approximately 179 out of the 247 landfills affected by a stringency level of
25 Mg NMOC/yr are less than 5 million Mg, while 16 percent are greater than
10 million Mg in size. Out of the 41 landfills affected by the least
stringent level, 250 Mg NMOC/yr, 24 percent are less than 5 million Mg and
42 percent are greater than 10 million Mg.
5-5
-------
TABLE 5-3. REGULATORY ALTERNATIVES FOR NEW LANDFILLS
Total Percentage of NPV of
Stringency number of total landfill NPV of NMOC methane
level landfills population reduction reduction
(Mg NMOC/yr) affected (%) (million Mg) (million Mg)
25 247 26.7 0.99 51
100 104 11.2 0.83 41
250 41 4.4 0.63 27
5-6
-------
TABLE 5-4. DISTRIBUTION OF NEW LANDFILLS
AFFECTED BY THE REGULATORY ALTERNATIVES
Stringency
level
(Mg NMOC/yr)
Distributed byfiDesign
Caoacitv (10° Ma)
Between Between
<1 1 and 5 5 and 10 >10
Total
25 58 121 29 39 247
100 0 46 22 36 104
250 0 10 14 17 41
5-7
-------
5.4 REFERENCES
1. U.S. Environmental Protection Agency, Office of Solid Waste Survey of
Municipal Landfills. Data base supplied by DPRA, Inc.
September 1987.
5-8
-------
6. ENVIRONMENTAL AND ENERGY IMPACTS OF POTENTIAL CONTROLS
The environmental and energy impacts of each regulatory alternative
being considered for controlling emissions from landfills have been assessed
relative to baseline conditions and are presented in this chapter. Baseline
conditions represent the level of control and emissions in the absence of
New Source Performance Standards (NSPS) or Section lll(d) guidelines.
The impacts presented in this chapter were estimated using results of
the 1987 EPA MSW landfill survey and emission estimation procedures
described in Chapter 3. Impacts were calculated for each landfill in the
database and the aggregated results were scaled up to yield nationwide
estimates. Section 6.1 presents the estimated air impacts; Sections 6.2
addresses the potential water impacts; and Section 6.3 presents the energy
impacts.
Under each of the selected regulatory options, individual landfills
would be required to control landfill air emissions at different points in
time and for varying lengths of time. As a result of this variability, it
is difficult to assess and compare the relative impacts of each regulatory
alternative without normalizing the values to some consistent basis.
Therefore, all impacts quantified in this chapter are presented as net
present values (NPVs) with 1992 as the base year. Future emissions are
discounted using a rate of three percent. For example, 1 Mg of emissions in
1993 is counted the same as 0.97 Mg of emissions in 1992 and the same as
1.03 Mg of emissions in 1994.
6.1 AIR POLLUTION IMPACTS
The implementation of any option being considered is expected to
result in significant NMOC and methane emission reductions. However,
emissions of other pollutants such as NO , and CO (due to combustion) may be
A
increased. Estimates of both the emission reductions and emission increase
for all air pollutants of concern are presented in the following sections.
6.1.1 NMOC Emission Reductions
Under each of the regulatory options, a subset of landfills would be
required to control NMOC emissions by installing and operating: (1) a
6-1
-------
landfill gas collection system and (2) a control device which provides
98 percent destruction (and/or a 20 ppmvd outlet at 3 percent oxygen for
enclosed combustion devices) for NMOC. Tables 6-1 and 6-2 present estimates
of the nationwide NMOC emission reductions (expressed as NPVs) at existing
and new landfills, respectively, for each regulatory alternative. The
approach used to calculate NMOC emissions from MSW landfills is explained in
Chapter 3. The 1992 NPV NMOC emission reductions was computed using a
discount rate of 3 percent. The 1992 NPV of emission was then scaled to the
national level, summed for all landfills expected to require control, and
multiplied by 0.98 to reflect a 98 percent reduction.
For existing landfills, the NPV of achievable emission reductions is
estimated to be 9.6 million Mg of NMOC under the least stringent nonbaseline
regulatory alternative (Option 3, 250 Mg/yr cutoff). In comparison, the NPV
of achievable NMOC emission reductions under the most stringent regulatory
alternative (Option 1, 25 Mg/yr) is estimated to be 12.6 million Mg.
For new landfills, (i.e., those estimated to open between 1988 and
1993), the NPV of NMOC emission reductions is estimated to be 630,000 Mg
under Option 3, the least stringent nonbaseline regulatory alternative.
Under Option 1, the most stringent alternative, the NPV of estimated NMOC
emission reductions is estimated to be 990,000 Mg.
6.1.2 Methane Emission Reductions
Landfill gas is comprised of approximately 50 percent methane,
50 percent carbon dioxide, and up to 1.4 percent NMOC, by volume. The
control techniques used by regulated landfills for NMOC emissions control
will also reduce emissions of methane. The NPV of potential reductions in
methane are included in Tables 6-1 and 6-2 for existing and new landfills,
respectively.
As shown in Table 6-1, the NPV of methane reductions are estimated to
be 200 million Mg for existing landfills and 27 million Mg for new landfills
under Option 3, the least stringent option. In comparison, the NPV of
methane reductions are estimated to be 411 million Mg for existing landfills
and 51 million Mg for new landfills, under regulatory Option 1, the most
stringent option.
6-2
-------
TABLE 6-1. NET PRESENT VALUE OF AIR IMPACTS OF REGULATORY ALTERNATIVES FOR EXISTING LANDFILLS3
Stringency
Regulatory level
alternative (Mg NMOC/yr)
1 25
2 100
3 250
Emission Reductions
NHOC Methane
(10° Mg) (10° Mg) PM
12.6 411 .29
to 0
11.2 307 .21
to 0
9.6 200 -0.13
to 0
A »
Secondary Air Emissions (10" Mg)"
so2
-11.6
to .06
-8.2
to .04
-5.4
to .03
N0x CO
-4.4 0
to 1.4 to 1.1
-3.1 0
to .97 to .80
-2.0 0
to .63 to .52
co2
0 to
1,200
0 to
830
0 to
540
HCL
.23
.17
.11
aAir impacts are discounted at 3 percent and represented in terms of the net present value of the
impacts in 1992.
Stringency level reflects level above which control must be installed and below which controls may
be discontinued.
Ranges of secondary air emissions represent the lower and upper factors,from Table 4-4. For
example, the factors for N0x range from -224 lb/10 scf LFG to 70 lb/10 scf LFG.
6-3
-------
TABLE 6-2. NET PRESENT VALUE OF AIR IMPACTS OF REGULATORY ALTERNATIVES FOR NEW LANDFILLS8
Stringency
Regulatory level
alternative (Hg NMOC/yr)
1 25
2 100
3 250
Emission Reductions
NMOC Methane
<106 Mg) (10° Mg) PM
.99 51 -.03
to 0
.83 41 -0.3
to 0
.63 27 -.02
to 0
t. -
Secondary Air Emissions (10W Mq)*"
so2
-1.4
to .007
-1.1
to .006
-.72
to .004
N0x
-.51
to .16
-.41
to .13
-.27
to .08
CO
0
to .13
0
to .11
0
to .07
co2
0
to 140
0
to 110
0
to 73
HCL
.03
.02
.02
3Air impacts are discounted at 3 percent and represented in terms of the net present value of the impacts
in 1992.
Stringency level reflects level above which control must be installed and below which controls may be
discontinued.
Ranges of secondary air emissions represent the lower and upper factors from Table 4-4. For example,
the factors for N0x range from -224 lb/10 scf LFG to 70 lb/10 scf LFG.
6-4
-------
6.1.3 Secondary Air Emissions
The control devices used to reduce landfill air emissions are expected
to generate secondary air emissions of nitrogen oxides (NO ), sulfur dioxide
A
(SCL), carbon monoxide (CO), Table 6-1. Table 6-2. particulate matter (PM),
and carbon dioxide (C02). The estimated range of secondary air emissions
for new and existing landfills is included in Tables 6-1 and 6-2 for
existing and new landfills, respectively. Since the mix of control devices
that would be installed under each of the regulatory options could not be
accurately predicted, the secondary air emissions are presented as ranges
rather than as single values. The upper end of the range represents
installation of the control device with highest net secondary air emissions
of that pollutant. The lower end of the range represents the net secondary
air emissions of a pollutant, if all landfill owners installed the control
device with the lowest secondary air emissions of that pollutant.
Consistent with emission reductions, these impacts are presented as NPVs.
As shown in Tables 6-1 and 6-2, control of landfill gas emissions could
actually result in decreased emissions of NO , PM, and SO-. These potential
reductions are based on the assumption that electricity produced from energy
recovery devices will equally offset the demand for electricity at utility
coal-fired generating plants. Since the emissions from combusting landfill
gas are less than combustion of coal at utility generating plants per unit
of energy, landfill energy recovery systems could actually reduce emissions
of NOX, PM, and SO^
The secondary impacts were estimated using the net emission factors
from Table 4-4. A detailed discussion of these factors is provided in
Chapter 4. Since landfill gas consists of approximately 50 percent methane,
the NPV of methane emission reduction, in Mg, was simply converted to a
volumetric gas rate using the Ideal Gas Law and then doubled to determine
the NPV of landfill gas controlled. This landfill gas volume was then
multiplied by the factors presented in Table 4-4 to estimate the NPV of
secondary air emissions.
6-5
-------
6.2 WATER POLLUTION IMPACTS
The main water pollution impact associated with regulating municipal
landfills is the condensate formed in gas collection systems. Limited data
are available on condensate formation rates. However, estimates from
3 industry sources indicate a range of about 0.01 to 0.6 gallons of
condensate per scfm of landfill gas. " The condensate formed will contain
a small amount of organics which may need to be treated.
6.3 ENERGY IMPACTS
Regulated landfills would be required to install a gas collection
system and a gas control device. The gas collection system would require a
relatively small amount of energy to run the blowers and the pumps. The gas
control device would not be expected to require additional energy because
the blower for the collection system is expected to maintain the air flow
required by the control device. Furthermore, certain gas control devices
recover energy and would contribute to a net energy savings on a nationwide
basis. The NPV of energy impacts is presented in Table 6-3.
6-6
-------
TABLE 6-3. NET PRESENT VALUE OF THE NET ENERGY IMPACTS
OF EACH REGULATORY ALTERNATIVE3
Regulatory
alternative
1
2
3
Stringency
level
(Mg NMOC/yr)
25
100
250
Net Energy Imoacts (10 Btu)
Fl
New
150,000
120,000
77,000
ares
Existing
1,200,000
880,000
570,000
Enerqy
New
7.6 x 108
6.1 x 108
4.0 x 108
Recovery1"
Existing
6.4 x 109
4.6 x 109
3.0 x 109
Impacts are presented in terms of the net present value in 1992.
Stringency level reflects level above which controls are required and below
which controls may be removed.
Based on gas turbines at 30 percent efficiency.
6-7
-------
6.4 REFERENCES
1. McGuinn, Y.C. Trip Report. Radian Corporation to Municipal Landfill
File. January 20, 1988. Summary of November 16, 1987 visit to the
Puente Hills Landfill.
2. McGuinn, Y.C. Trip Report. Radian Corporation to Municipal Landfill
File. January 20, 1988. Summary of November 17, 1987 visit to the
Toyon Canyon Landfill.
3. Letter and attachments from R. Echols, BFI to S. Thorneloe, EPA.
October 14, 1988
6-8
-------
1, COST OF REGULATORY ALTERNATIVES
This chapter presents the approach taken to estimate the cost of
collecting and controlling air emissions from existing and new municipal
landfills. There are several different control or recovery techniques that
can be used to reduce air emissions from landfills. The analysis presented
in this chapter evaluates an active collection system and two control
techniques: one without energy recovery (i.e., flare) and one with energy
recovery (i.e., gas turbine).
Section 7.1 presents the design characteristics and costs of the gas
collection system. The capital and annual operating costs associated with
the flare and gas turbines are presented in Section 7.2. Example costs
associated with installing and operating collection and control/recovery
systems can be found in Section 7.3. Section 7.4 describes the national
cost impacts under the gas collection and control/recovery options.
7.1 DEVELOPMENT OF THE COLLECTION SYSTEM COSTS
This section presents the method used to develop design criteria for
collecting the landfill gas. Details regarding costs for installing and
operating a collection system are presented and discussed in Sections 7.1.2
and 7.1.3, respectively. Major components of a gas collection system are
listed in Table 7-1 and are discussed in the following sections.
7.1.1 Collection System Sizing
Active gas collection systems consist of a multitude of extraction
wells, well connectors, a gas header pipe system, a gas mover system, and a
condensate collection system. Table 7-2 and 7-3 list the assumptions and
equations used to conceptually design a gas collection system for cost
estimating purposes.
Design of the gas collection system is based primarily on the landfill
dimensions and the landfill gas generation rate. The landfills analyzed in
this chapter are assumed to have equal dimensions (i.e., the length is equal
to the width). This assumption is not expected to affect the cost of
installing and operating collection and control equipment. The landfill gas
generation rate is estimated by the Scholl Canyon Model of first order
7-1
-------
TABLE 7-1. MAJOR COMPONENTS OF THE GAS EXTRACTION SYSTEM
a
Item
Materials
Gas Extraction Wells
Lateral Well Connections
Gas Collection Header
Gas Mover System
Condensate Collecting System
2 to 6" perforated piping, schedule
40 to 80,
1" crushed stone or river gravel
10 ft PVC piping
valve
fittings
3" or greater PVC piping (depending on
flow/pressure requirements)
fittings
Heavy duty, industrial type turbo
blower
Variable-speed motor
valves
piping
2 to 6" PVC piping
fittings
knockout tank
pH adjustment
Reference 1.
7-2
-------
TABLE 7-2. ASSUMPTIONS USED IN DESIGNING THE GAS EXTRACTION SYSTEM
A. Gas Production
Methane generation rate: Estimated by the Scholl Canyon model
Landfill gas generation rate: Twice the methane generation rate
B. Landfill Characteristics
In-place refuse density: 650 kg/m
Operating hours: 8760 hr/yrc
The landfill has equal dimensions
C. Gas Characteristics
Methane concentration of the landfill gas: 50 percent
Landfill gas temperature: 550°R (90°F)e
Gas velocity through the piping: 610 m/min (2,000 ft/min)
Specific gravity of the landfill gas relative to air: 1.05
D. Extraction Well Design
Extraction flowrate/well: 0.04 m /min-m (0.4 cfm/ft) of landfill
depth9
Default vacuum pressure at each extraction well:
1.01 x 105 N/m2 (.9928 atm)h
The depth of the extraction wells is 75 percent that of the landfill
depth.
(continued)
7-3
-------
TABLE 7-2. (Continued)
E. Blower System
280 m3/min (10,000
Requires 30 man-hours to install the blower and motor system
1
The maximum flowrate 1 turbo blower can accommodate:
k
wer an moor
Retail electrical cost: 10.0511/KW.hr.
F. Condensate System
Landfill gas enters collection system at 90°F and 100 percent
saturation. Cools to 495°R.m
Reference 2.
Typical municipal refuse density reported in Reference 3.
cThe extraction and control systems are assumed to operate continuously.
Typical methane concentration for landfill gas reported in References 4, 5,
6, and 7.
eAverage landfill gas temperature reported in Reference 8.
Reference 9 reports that 2000 ft/min (610 m/min) is a typical gas velocity
in ductwork for exhausts containing volatile organic compounds and other
gaseous pollutants.
Reference 10. Average extraction per well provided in References
11,12,13,and 14 divided by the average landfill depth.
Typical pressure drop of extraction wells for sites visited.
References 15, 16, and 17.
Reference 18. Typical extraction well depth based on References 11, 12,
13, and 14.
JThe maximum landfill gas flowrate for a turbo blower in Figure 7-5 is
10,000 cfm (280 nT/min).
kReference 19.
Reference 20.
Vference 21.
7-4
-------
TABLE 7-3. DESIGN EQUATIONS FOR THE GAS EXTRACTION SYSTEM
A. Estimation of Landfill Gas Generation Ratea
«lfg ' 2 Lo R
-------
TABLE 7-3. (Continued)
Radius of Influence, ROI
ROI = (QwDesign Capacity/art. PrefuseQgen)1/2 (4)
where,
R = radius of influence, m
Q = landfill gas flowrate per well, m /yr
Design Capacity = design capacity of the landfill, kg
TT= 3.14
Refuse = refuse - - 3 b
Q = peak landfill gas generation rate, m /yr
Landfill Pressure, PL°
4-7
K
L
in (ROI/r) P]fg Prefuse Qqen * 3.15 x 10
Design Capacity krefu$e (WD/L)
where,
2
P. = internal landfill pressure, Newton/m
2
P = vacuum pressure, Newton/m
ROI = radius of influence, m
r = radius of outer well (or gravel casing), m
'refuse = refuse density, 650 kg/m
2
^refuse = intrinsic refuse permeability, m
Ahfq = landfill gas viscosity, Newton-sec/m
Design Capacity « design capacity of landfill, kg
WD = well depth (i.e., 0.75L), m
L = landfill depth, m
Q = peak landfill gas generation rate, m /yr
3.15 x 10" = conversion factor
(continued)
7-6
-------
TABLE 7-3. (Continued)
Optimal Number of Extraction Wells, WellSjQ-,.
WellsTOT = (Landfill surface area)/(7rR2) (6)
where,
WellSjQj = Total number of-wells required
TT= 3.14
2 2
landfill surface area = (length) , m
ROI = radius of influence
F. Total Length Feet of Straight Header Pipe, Hh
Hh = A
n 2 * ROI + L (6)
where,
H. = length of straight header pipe, m
2
A = area of the landfill, m
L = length of the landfill, m
ROI = radius of influence, m
G. Diameter of Header Piping, d, for the Row of Extraction Wells
[QR*4 "I
(914.4 m/minfrj
1/2
(8)
where,
d = diameter, meters
TT = 3.14
QR = flowrate due to a row of extraction wells, m /min
914.4 m/min = maximum gas velocity through the piping
(see Table 7-2)
(continued)
7-7
-------
TABLE 7-3. (Continued)
H. "Equivalent Length" due to standard 90° elbows
EQe1bQW = [2.78 (d * 39.37) - 1.02] * .3048 (9)
where,
EQ = equivalent length, m, due to elbow
d = diameter of the pipe, m
I. "Equivalent Length" due to standard tees
EQTee = [5.82 (d * 39.37) - 2.73] * .3048 (10)
where,
EQ = equivalent length, m, due to tee
d = diameter of the pipe, m
J. Pressure drop across each row of header system piping^
2
P2 = [(Pv * -000145) - A * B1 * 6896.43 (11)
where,
QR * 2118.87
28.0 (d * 39. 37)2'667
B = So (H * 6.214 x 10~4) T
289
where,
2
P, = exiting pressure, N/m
3
QR = flowrate, m/min
d = diameter of piping, m
Sg = specific gravity of the landfill gas
H = length of piping, m
T = landfill gas temperature, °K
2
Py = vacuum pressure, N/m
(continued)
7-8
-------
TABLE 7-3. (Continued)
NOTE: The length of piping, H, includes the "Equivalent Lengths"
associated with 1 elbow and (wellsTOj/(L/2ROI) number of
tees.
K. Pressure drop across the final leg of header pipe.
P3 = [i
where,
- [(P2 * .000145)2 - C2 * D]1/? * 6896'43
QR * 2118.87
28.0 (d * 39. 37)2-667
D = So (H * 6.214 x 10'4) T
289
where,
2
P, = final system pressure prior to the gas mover systems, N/m
3
Q. = 1/2 the total extraction flowrate, m /min
d = diameter of piping, m
H = length of piping, m
Sg = specific gravity of the landfill gas
T = landfill gas temperature, °K
2
P- = exiting pressure of each row of header or pipe, N/m
NOTE: The length of piping, H, includes the "Equivalent Lengths"
associated with 2 elbows and (L/4 * ROI) number of tees.
L. Total system pressure drop,AP-r0-r
APTQT - (PL - P3) (13)
= total system pressure drop, N/m
p
M. Motor horsepower requirement
H QTOT (14)
SM ~ 7
™ 3.1536 x 1Q/ (.65)
~~~~~~~ (continued)
7-9
-------
TABLE 7-3. (Continued)
where,
WCM = watt
5n o
QT = flowrate per blower m /yr
l U I 2
PTQT = total system pressure drop, N/m
.65 = motor efficiency
N. Number of Blowers required
# Blowers = QTOT/(283.2 m3/min) (15)
where,
total gas production rate, m /min
283.2 m /min = maximum flowrate 1 turbo blower can accomodate
(see Table 7-2)
0. Condensate Flowrate, Qcon(j9
.0203 QTQT (lg)
gcond " 760 - 1.87APTOT
where,
Q . = flowrate of condensate, m /min
Q-J.QJ = total gas production rate, m /min
= total system pressure drop, N/m
Reference 22, p. 8.
The peak landfill gas generation rate can be estimated using equation (1)
with t equal to the landfill age at closure.
Reference 23, p. 202.
dReference 24, p. 3-3.
Reference 25.
Assumed that one blower can process up to 10,000 cfm (283.2 m /min) of
landfill gas.
^Reference 26.
7-10
-------
27
decay. Equation 1 in Table 7-3 gives the form of the model used to
estimate the landfill gas generation rate. A detailed discussion of this
model can be found in Chapter 3.
7.1.1.1. Gas Extraction Well. The gas extraction wells are assumed to
be installed within the interior, or refuse fill, of the landfill. Vertical
extraction wells (12 to 36 inch diameter) are excavated and back filled with
1 inch or larger crushed stone and 5 to 15 centimeters (2 to 6 inches) in
28
diameter perforated PVC piping. In this cost analyses, the depth of the
extraction wells are assumed to be 75 percent of the landfill depth to
insure that the well will not puncture the landfill lining or interfere with
a leachate collection system when installed.
A design parameter referred to as the "radius of influence" is
estimated to determine the number of extraction wells required to cover the
entire landfill area. The radius of influence is the maximum distance that
a well can extract a gas molecule by means of a pressure differential. The
radius of influence, R, can be estimated using Equation 2 found in
Table 7-3.
The number of extraction wells can be estimated by dividing the
landfill area at capacity by the area that one extraction well can
2
influence. This "area of influence" is simply R . This approach estimates
the maximum number of wells required to extract all of the landfill gas that
is expected to be generated. The gas extraction rate for each extraction
•3 OQ
well is assumed to be 0.04 m /min-ft (0.4 cfm/ft) of landfill depth.
7.1.1.2 Lateral Well Connections. The number of lateral well
connections is equal to the number of extraction wells. Included in the
well connection is a control valve, 3 meters (10 feet) of PVC piping, and a
monitoring port with cap.
7.1.1.3 Header System. Each extraction well is connected to a 15 to
70 centimeter (6 to 27 inch) diameter PVC header pipe system. The header
pipe system is laid out to convey a vacuum from a gas mover system to the
wells and in turn transport the landfill gas to an emission control device.
The configuration of the header system realistically depends on the landfill
perimeter configuration.
7-11
-------
The total length of PVC header pipe required to conduct the vacuum and
transport the landfill gas can be estimated by using Equation 5 presented in
Table 7-3, The gas extraction wells in this cost analysis are placed in
straight rows, spaced at a distance of two times the radius of influence.
Each row of extraction wells is connected to an adjacent header pipe which
converges to a final, larger diameter pipe. This final header pipe is
referred to as the "final leg". All of the adjacent header pipes converge
upon this final leg. The header pipe system is assumed to be installed on
the surface of the landfill. Figure 7-1 illustrates the header pipe system
layout used in this cost analysis.
7.1.1.4 Gas Mover System. The blowers and motors used to transport
the exhaust gas to the emission control device are sized for the maximum
volume of landfill gas that is expected to be produced during the functional
life of the gas mover system (15 years). The pressure drop due to piping
across the entire collection system and the total gas production rate of the
landfill are functional parameters required to determine the size of gas
moving equipment. The components of a gas moving system include a
heavy-duty, industrial type, turbo blower(s) and variable-speed motor(s).
It is assumed that the blower(s) can be idled down to accommodate the
landfill gas production rate as it changes through the years of operation.
Equations 9 and 10 in Table 7-3 are used to estimate the pressure drop
across the header pipe system (excluding the extraction wells). A number of
assumptions and calculations are made in order to use Equations 9 and 10.
Such calculations include the header pipe diameters and "equivalent length"
estimations for standard elbows and tees. It is assumed that the landfill
gas temperature is 550°R (90°F) with a gas molecular weight of 30. The
5 ?
pressure is assumed to be 1.01 x 10 Newton/m (0.9926 atm) exiting each
extraction well. The total system pressure drop is the sum of the total
pressure drop across the header system and extraction wells. Refer to
Figure 7-2 for a graphical interpretation of the system pressure drop.
A flow rate of 280 m /min (10,000 cfm) of landfill gas is assumed to be
the maximum volumetric flow rate that a single blower can accommodate.
Therefore, the number of blowers, and the number of motors, can be estimated
by applying Equation 13 in Table 7-3. Once the system pressure drop and
7-12
-------
Emission Control Alternatives
Gas Colltctlon Piping
Landfill Arta
Oaa
Extraction
Walls
Gaa Extraction
Wall Araa
of Influanea
Figure 7-1. Theoretical header pipe system.
7-13
-------
peak landfill gas flow rate during the motor(s)' functional life are
determined, Equation 12 in Table 7-3, is used to determine the horsepower
requirement of the motor(s).
7.1.1.5 Condensate System. Condensation of the landfill gas usually
occurs on the inside of the header pipe system due to the cooler
temperatures at the surface of the landfill. The condensing landfill gas
vapor consists mainly of water; however, it also contains trace amounts of
nonmethane organic compounds. A typical condensate disposal procedure used
is to collect the condensate in a knock-out tank, adjust the condensate's pH
by adding caustic at the landfill facility prior to discharge to a public
water treatment facility.
In this design analysis, the knock-out pot and the pH adjustment
facility are sized based on the maximum expected landfill gas flow rate.
The amount of condensate PVC piping, usually 5 to 10 centimeters (2 to
4 inches) in diameter, is estimated to be 4 percent of the header pipe
requirement. Two equations were derived to express the installed capital
and the annual operating cost of the condensate system as a function of the
landfill gas flowrate. These equations are based on documented equipment
purchase costs and information regarding leachate disposal from
32 33
landfills. ' These equations are presented in Section 7.1.2.5.
7.1.2 Capital Cost Bases
The equations and bases for the capital costs of the equipment required
to collect landfill gas are presented in Table 7-4. The capital cost
represents the total financial resources required to plan, engineer,
install, and test run the collection system. These costs are segregated
into direct and indirect costs. The direct capital cost Includes the
investment required to purchase and install the extraction wells, well
connections, header system, gas mover system, and condensate system. The
indirect costs include engineering, contractor's fee, construction fee,
start-up, performance test, model study, and contingencies. Typically,
direct and indirect costs for fixed-capital investments are percentages of
the purchased equipment cost, ranging from 15 to 40 percent. The cost
factors presented in Table 7-5 are similarly applied to the purchase cost.
The purchase cost is assumed to be 60 percent of the direct capital cost.
7-14
-------
en
-j
ro
cr>
-j
o
o>
n>
-o
fl>
o>
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o
3
O
-h
r*-
3"
O>
T3
(D
(D
Q.
O
-O
P, = 0 9026 aim
Parlor alad PVC PJ(
j
j
•
*
1
i
•
5
>
i
a n
1
ting j
V
.
Monitoring Valve
] ^ O CO
Olamalar
1
t
,-fc, c
I
«
i
i
P. = 1 aim
yy//
Ps = aim
-------
TABLE 7-4. CAPITAL COST BASES AND EQUATIONS FOR THE GAS COLLECTION SYSTEM
Item
Unit
Cost per unit/bases
A. Gas Extraction Well
a,b
B. Lateral Well Connections'
C. Gas Collection Header3
D. Gas Mover System0
E. Condensate Collection System
Pipingd
Knockout pot6
pH adjustment
Vertical meter
(greater than
24.4m)
Each
Linear meter
Each
a) Blower (see
Figure 7-4)
b) Motor (see
Figure 7-5)
$205.00 (1985)
$410.00/meter over
24.4m
$1,250.00 (1985)
$65.60
.04 ($ Header)
$3,000
$22,500 ( ?cond)
V2.79 /
0.6
Equations Used to Estimate the Total Item Costs
Extraction Wells
$ Wells =-Total number of wells (well depth, m) ($205.00/m) (1)
Lateral Well Connections
$ Connections = Total number of wells ($l,250.00/well) (2)
Gas Collection Header
$ Header = Total length (m) ($65.60/m) (3)
(continued)
7-16
-------
TABLE 7-4. (Continued)
Item
Unit
Cost per unit/bases
Gas Mover System
- Blower = Figure 7-4
- Motor = Figure 7-5
Condensate Collection System
$ Condensate = 0.04 ($ Header) + 3,000 + 22,500 (Qcond\
\ 0.6
2.79y/
(4)
Reference 34, p. 6-25.
Reference 35.
Reference 36, p. 562.
Reference 37.
Reference 38.
Reference 39, p. 7-9.
Price quoted at $62.50/ft.
7-17
-------
TABLE 7-5. DIRECT AND INDIRECT CAPITAL COST FACTORS FOR THE COLLECTION SYSTEM
a
Direct Cost Factors
Purchase
Taxes
Freight
Instal I at ion
Foundation
Erection
Electrical
Piping
Bui Iding
Indirect Cost Factors
Engineering and supervisors
Construction and field expenses
Construction fee
Start-up
Performance test
Model study
Contingencies
Extraction
wells
b
*
*
c
*
*
*
*
*
.10
.10
.10
.01
.01
.02
.03
Well
connection
b
*
*
c
*
•
*
*
*
.10
.10
.10
.01
.01
.02
.03
Header
system
b
*
*
c
*
«
*
*
*
.10
.10
.10
.01
.01
.02
.03
Gas
mover
blower
d
.03
.05
352.00
.12
.40
.01
.02
.40
.10
.10
.10
.01
.01
.02
.03
System
motor
e
.03
.05
*
.12
.40
.01
.02
.40
.10
.10
.10
.01
.01
.02
.03
Condensate
system
f
.03
.05
*
.12
.40
.01
.02
.40
.10
.10
.10
.01
.01
.02
.03
•Included in installed costs
**Included in blower installation costs
Reference 43, p. 3-11; Reference 44
b
60X of the estimated installed cost
C40X of the estimated installed cost
Obtained from Figure 7-4
eObtained from Figure 7-5
Obtained from Equation 4 in Table 7-4
NOTE: All cost factors applied to the purchase price.
7-18
-------
7.1.2.1 Gas Extraction Well. The direct capital cost of one gas
extraction well in 1985 dollars is estimated to be $205.00 per vertical
meter up to 24 meters ($62.50 per vertical foot up to 80 feet). For wells
greater than 24 meters, the rate converts to approximately $410 per
vertical meter beyond 24 meters. The direct capital cost is escalated to
1987 dollars using the piping cost indices reported in
40
Chemical Engineering and presented in Table 7-6. Typical percentages of
fixed-capital investment values for direct and indirect costs range from
41
15 to 40 percent of the purchased equipment cost. Therefore, all the
indirect cost factors presented in Table 7-5 are applied to the purchase
price which is assumed to be 60 percent of the direct capital cost. The
total installed capital cost of gas extraction wells is simply the product
of the total number of wells required, the extraction well depth, and the
total installed capital cost (including direct and indirect capital).
7.1.2.2 Lateral Well Connection. The 1985 direct capital cost of a
lateral well connection is estimated to be $1,250.00 each. This value is
the median value reported for lateral well connections in Reference 1. The
1985 direct capital cost is escalated to 1987 dollars using the indices
presented in Table 7-6. The total installed cost of lateral well
connections is merely the product of the total number of extraction wells
and total installed capital cost per connection.
7.1.2.3 Header System. The direct capital cost per linear foot of PVC
piping, including all appropriate fittings, for landfills less than or equal
to 5 million tons of refuse at capacity is estimated to be $66.00 per linear
42
meter in 1985. This figure is the lower end value reported in the
Reference 2 for gas collection headers. Equation 3 in Table 7-4 is used to
estimate the direct capital cost per linear foot for* those landfills.with a
refuse capacity greater than 5 million tons. The 1985 direct capital cost
is escalated to 1987 dollars using the factors in Table 7-6. The total
installed capital cost of the header system is the product of the length of
header required and the total installed capital cost per linear foot.
7.1.2.4 Gas Mover System. Figures 7-3 and 7-4, obtained from
Reference 43, are used to estimate the 1979 purchase price for the heavy
duty blower(s) and variable-speed motor(s), respectively. The purchase
7-19
-------
TABLE 7-6. COST INDEX
Equipment item
Extraction Well
Well Connection
Header Pipe
Bl ower
Motor
Condensate System
Turbine System
CE index
Pipe
Pipe
Pipe
Pumps
Pumps
Pipe
Equipment
Base year
August 1985
August 1985
August 1985
August 1979
August 1979
August 1985
August 1983
index August 1987 index
- 384.3
- 384.3
- 384.3
- 284.5
- 284.5
- 384.3
- 335.9
388.8
388.8
388.8
431.0
431.0
388.8
344.9
Source: Reference 45.
7-20
-------
10* <
(0
5
1
i
I
10-.
Turbo Blowfft
*
•10*
. -10»
o
3
o
5"
C0
-10*
10
Capacity, ft 3/mln
(Ift3/min = .028m3/nrin)
Figure 7-3. Blowers purchase price (1979 dollars).
48
7-21
-------
10*-
(0
5
1
2
a
3
I
3/1 SpMd Variation
12 18 24 30
Horstpowtr
(1 horsepower = 745 watts)
42
Figure 7-4. Motor purchase costs (1979 dollars)
49
7-22
-------
price of each is escalated to 1987 dollars using the pump cost index
reported in Reference 47. The total capital cost for the initial gas mover
system is estimated based on the maximum landfill gas flow rate expected
during the functional life of the system. The gas mover system is assumed
to require 30 man-hours of labor to install each blower and motor
combination. The appropriate tax and freight charges are applied to the
purchase price of the blower(s) and motor(s) in addition to the remaining
direct installation factors presented in Table 7-5.
7.1.2.5 Condensate System. Equation 4 in Table 7-4 is used to
estimate the capital cost of the condensate system. The condensate
collection system includes a knockout pot, a pH adjustment system, and
piping. Costs for the individual components are also provided on Table 7-4.
Factors in Table 7-5 are used to estimate the appropriate tax and freight
charges, installation costs, and the indirect costs associated with the
condensate system.
7.1.2.6 Yearly Incremental Capital Cost Bases. For those landfills
that are not closed and still accepting refuse, an additional capital
investment will be required each year to collect the gas produced by the new
refuse. The incremental amount of capital required to install additional
extraction wells, well connectors, header pipe, and condensate pipe is equal
to the ratio of the refuse acceptance rate to the refuse capacity. Once the
direct capital cost has been determined for each item, the appropriate
indirect cost factors are applied to the purchase price and subsequently
added to the direct capital cost to estimate the incremental capital cost.
This incremental cost will be incurred each year-until the landfill reaches
design capacity. All prices are updated to August, 1987 values using the
47
Chemical Engineering indices.
7.1.2.7 Replacement Costs. At the end of the first gas mover system's
functional life, a new system will be sized for the maximum landfill ga's
flow rate expected in the next 15 years (the estimated system functional
life). Replacement equipment will be sized every 15 years over the control
period. Wells, well connections, header piping, and condensate system are
not replaced.
7-23
-------
7.1.3 Operating Cost Bases
The bases for the annual operating cost of the gas collection system
are presented in Table 7-7 (1987 dollars). The operating costs are the
yearly expenditures necessary to operate and maintain the gas collection
system. These costs include operating and maintenance labor, operating
materials, replacement parts, utility for the blower system only, and waste
disposal. The indirect operating expenses include plant overhead, property,
insurance, taxes, administration, and other costs associated with owning the
equipment. It is assumed that it requires one full time operator to operate
and maintain the gas collection system during the day. An automatic
control system is assumed to operate and control the gas collection system
at night. It is also assumed that the computer maintaining the control
system will shutdown the collection system and notify the facility's
off-duty operator via a dial-up system in case of a malfunction. The
condensate is adjusted for pH and disposed to a POTW.
7.2 DEVELOPMENT OF CONTROL SYSTEM COSTS
This section presents the capital and annual operating costs associated
with the flare system and gas turbine system. The costs for both control
options are based on systems designed to handle the maximum landfill gas
production expected during the functional life of the equipment.
7.2.1 Bases For Flare System
As discussed in Chapter 4, the domestic municipal solid waste landfills
that flare landfill gas use an enclosed ground flare. The primary
components of the landfill flare system costed for this analysis are
itemized in Table 7-8. The flare system consists of an enclosed flare with
an automatic air damper for emission control to ensure the flare exhaust is
smokeless. It is resumed that the landfill flare system can achieve a
98 percent volatile organic destruction efficiency without requiring
additional combustion fuel such as natural gas. As mentioned in
Section 4.2.1.2, combustion efficiencies greater than 98 percent are
observed when methane concentrations are greater than 10 percent. A typical
methane concentration in landfill gas is 50 percent. The flare is also
assumed to operate 8760 hours per year.
7-24
-------
TABLE 7-7. ANNUALIZED COST BASES FOR THE GAS EXTRACTION SYSTEM
Direct operating cost
Cost factor
1) Operating Labor
a) Operator
b) Supervisor
8 man-hours/day, 365 day/year @ 7.42/hr*
15% of lab
2) Operating Material
3) Maintenance
a) Labor
b) Material
Nominal
0.5 hr/shift, 1 shift/day, 365 day/year
? 8.16/hrb
100% of 3a
4) Replacement Parts0
5) Utilities
a) Electricity,
blower only
$0.0511/kwhc
6) Condensate Disposal
$.033/gallon condensate
Indirect Operating Costs
7) Overhead
8) Property, Insurance,
Taxes, Administration
80% of la + Ib + 3au
40% of Capital Costs1
aUSDL, mill worker rate of 6.18 plus fringes of 20 percent; 1983,
Reference 51, p. 3-12.
Reference 52, p. 6-24.
Reference 53.
Reference 54.
7-25
-------
TABLE 7-8. FLARE SYSTEM COMPONENTS
Flare Tip
Flare Pilots with Flame Safeguard
Flare Stack
Ignition Panel
Pipe Racks
Flare Guy Wires Support
Knockout Drums with Seals
Platforms
Manual or Automatic Dampers
Temperature Sensor
Temperature Controller
Flame Arrestor and Motor Operated Shut Off Valve
NOTE: References indicate that flare service (i.e., steam and
air assistance) is not required for typical landfill flare systems.
Source: References 55, 56, 57, and 58.
7-26
-------
Two empirically derived equations were used to calculate the installed
capital and annual operating cost of the flare system. These equations were
developed based on flare purchase costs provided by flare vendors and direct
and indirect cost escalation factors from available literature. " This
approach was taken in lieu of estimating the cost individual flare system
components. The equations are presented in Figure 7-5, with supporting data
in Table 7-9.
7.2.1.1 Flare System Capital Cost. Equation 1 in Figure 7-5 is used
to estimate the total installed capital cost of the flare system as a
function of the input gas flow rate. The capital cost for the entire flare
control system includes the purchase and installation of all equipment, pipe
or duct, and pipe supports. The exhaust from the gas moving system (part of
the gas extraction system is assumed to transport the landfill gas to the
flare system. Therefore, a gas moving system is not included in the flare
system.
7.2.1.2 Flare System Operating Costs. Equation 2 in Figure 7-5 is
used to estimate the direct annual operating cost of the flare system. It
is assumed in the derivation of Equation 2 that the direct annual operating
cost equals 6 percent of the total installed capital costs. An indirect
operating cost equal to four percent of the total capital investment is
added to the direct annual cost.
7.2.1.3 Flare System Replacement Costs. At the end of the functional
life of the flare system, a new system is designed to handle the maximum
landfill gas flow rate expected in the next 15 year equipment life.
Replacement equipment will be sized and costed every 15 years during the
control period.
7.2.2 Bases For Gas Turbine System
The gas turbine system cost is based on a simple-cycle, heat engine
that converts the landfill ga's, containing 50 percent methane, to electrical
energy. More than 20 turbines are in use at 18 municipal solid waste
landfills to recover energy from landfill gas. It is assumed that the
electrical energy produced by the turbine system is sold to a local utility.
A recovery credit is incorporated in the annual cost of the turbine system
to reflect electricity sold. Table 8-5 in Chapter 8 lists the electricity
7-27
-------
ro
00
-$
n>
en
o>
-5
as
o>
200,000
20.000
o
-J
o
ft)
•o
tu
3
ex.
o
•o
(D
-I
(O
O
O
(/I
1 Total Installed = 28.3 x (Total FBowrala) + 56,296 7
* Total Annual Operations = 1.687 x (Total Flowrata) + 3497
100,000
1 1
1.000 1.500
1 1 1
2.000 2.500 3,000 3,500
Total Flowrate, Q, ftVi»,n
(Ift3/min = .028 m3/min)
4.000 4.500 5.000
SL
O
-------
TABLE 7-9. FLARE-BASES FOR TOTAL CAPITAL AND ANNUAL OPERATIONS COST
Capital Costs
I. Direct Capital Costs:
• Purchase Price, A
Flowrate. Q. ft3/mina
450 ft?/min
1000 ftf/mln
4500 ftvmin
• Installation
Purchase Price, $
$25,000
35,000
70,000
- Foundation
- Structure
- Equipment Erection
- Electrical
Total Base Cost, B, = A + .51A
- Sales Tax
- Freight
- Contractors Fees
II. Indirect Capital Cost:
• Total Contract, C,
- Engineering
- Contingencies
Cost Factor
6% of A
15% of A
15% of A
15% of A
25% of A + 25% of B
16% of A
30% of (B A)
B + Sales Tax, Freight, Fees
10% of C
15% of C
Total Capital Cost = C + Engineering + Contingency
I. Direct Operating Costs:
Flowrate. 0. ft /min
450
1000
4500
Purchase Price, $
$ 3,960
5,544
11,088
(continued)
7-29
-------
TABLE 7-9. (Continued)
II. Indirect Operating Costs:
Total Indirect Costs = 4% that of the total capital costs
alft3 min - .028 m3/mi
References 65 and 66.
References 67.
The annual operating cost is assumed to equal 6 percent that of the total
installed capital costs. Organic Chemical Manufacturing. Volume 4:
"Combustion Control Devices."
7-30
-------
rates used by state. Section 7.2.2.1 presents the approach used to size the
gas turbine system. Land requirements and an electrical switch gear station
are included in the cost. The bases and method used to develop the total
capital and annual cost are presented in Sections 7.2.2.2 and 7.2.2.3,
respectively.
7.2.2.1 Gas Turbine Sizing. The size of the gas turbine system is
based on the potential electrical output generated by using the landfill gas
as fuel. The heat content of the landfill gas, based on a gas composition
of 50 percent methane, is assumed to be 500 Btu/ft . The gas turbine system
is considered to be 30 percent efficient in converting the landfill gas to
electrical energy. It is recognized that a gas turbine with a power output
of 2.93 to 29.3 MW will be subject to NO emission limits of 150 ppmvd at 15
6ft
percent oxygen. However, it is assumed that this limit will be achievable
with dry control technologies (i.e., combustion modifications). Therefore,
the gas turbine system does not require wet controls to meet the NO
^
emission limit. As with the gas collection system, the gas turbine is
assumed to operate 8760 hours per year obtaining all electrical service from
its own electrical generation.
7.2.2.2 Bases For Gas Turbine System Capital Cost. An empirically
derived equation was used to calculate the installed capital cost of a
simple-cycle, gas turbine and related equipment. This equation is based on
reported costs for actual gas turbine installations. The capital cost for
the gas turbine is shown in Table 7-10. The data are used to directly
derive the net installed capital cost for gas turbines rather than to
calculate and sum the capital cost of each individual component. Table 7-11
shows the equations used to estimate the capital cost associated with land
requirements, an electrical switch gear system, and working capital.
Since most of the installed plant capital cost data are for
cogeneration plants, this data is plotted against gas turbine output and is
fitted to these points as shown in Figure 7-6. However, it is difficult to
perform regression with only a few points for simple-cycle plants. Since
the gas turbine is the major component of the plant cost for both types of
plants, it is assumed that the line for simple-cycle turbines should have a
slope similar to that of a cogeneration plant. Therefore, the line for
7-31
-------
TABLE 7-10. INSTALLED CAPITAL COSTS FOR TURBINE PLANTS'
Type plant
Cogeneration
Simple -cycle
Simple-cycle
Cogeneration
Cogeneration
Cogeneration
Cogeneration
Simple-cycle
Simple-cycle
Cogeneration
Cogeneration
Cogeneration
Cogeneration
Cogeneration
Size
(MM)
3.8
3.1
0.8
20
19.6
45
75
50
63
2.8
20
0.8
1.1
0.65
Cost
(106 $)
1983
3.7
1.25
0.86
11
6.7
30
25
25
17
1.8
16
2.2
2.5
1.5
Cost
(io6 $)
1987
4.04
1.36
.94
12
7.3
32.7
27.3
27.3
18.6
1.9
17.5
2.4
2.7
1.6
Source
Turbomachinery, Ap. 83
Turbomachinery, Ap. 83
Turbomachinery International
Utility Costs Study, 1982
Cogen. World, Summer 83
GTW, Jan 83
GTW, March-Apr 83
GTW, Sept-Oct 83
GTW, Handbook, 79-80
Trip Report to El Paso
Electric Company
Amer. McG - 114 Response
Cogen. World, Summer 83
GTW Sept-Oct 83
Cogen. World, Summer 83
Cogen. World, Summer 83
Data shown are from References 69 through 77.
3A11 costs corrected to 1987 dollars using the CE plant cost index 344.9.
7-32
-------
TABLE 7-11. EQUATIONS USED TO COST ANALYZE THE GAS TURBINE
A. Simple-cycle plant capital costs3
(106 $) = 0.84 (TMW)0-7 (1)
where,
TMW = total electrical output, MW
B. Land costs
(103 $) = AA (21,961)/1000 (2)
where,
AA = acres required
C. Switch Gearc
5 - 85,000
where,
MW = electrical output
D. Working Capital
$ = 25% of (direct operating costs) (4)
E. Operating Labor
(103 $/year) = (DLC x HRS)/1000 (5)
where,
DLC = $18.64/hr
MRS = hours per year worked
(continued)
7-33
-------
TABLE 7-11. (Continued)
F. Supervisory Labor
103 $/year) = SLC x .15 x HRS)/1000 (6)
where,
SLC = annual supervisory labor hourly charge rate equal to
$24.24/hr
MRS = hours per year an operator works
G. Maintenance Costs6
(103 $) = .00275 (TMW) (MRS) for < 10 MW (7)
or
(103 $) = .00125 (TMW) (MRS) for < 10 MW (8)
TMW = total electrical output, MW
MRS = hours per year of operation
H. Payroll Overhead
$/year = 30% of (operating labor + .5 [maintenance cost] + (9)
supervisory labor)
I. Plant Overhead
$/year = 26% of (operating labor + supervisory labor) (10)
J. G & A, Taxes, Insurance
$/year = 4% of (replacement capital cost of turbine system) (11)
K. Interest on Working Capital
$/year = 10% of (working capital + land) . (12)
(continued)
7-34
-------
TABLE 7-11. (Continued)
Cost item
Operating labor
Supervision9
Land costs
Fuel electricity
Cost Bases
Unit
$/hr
$/hr
$/acre
$/kw-hr
Cost factor
$18.64
$24.24
$21,961
0
Simple-cycle plant capital costs are based on plant cost data obtained from
gas turbine user and literature sources. References 78, 79, and 80
through 86.
A price of $21, 961 per acre is an assumed in this cost analyses.
References 87.
The working capital is assumed to be 25 percent of the direct
operating cost.
elncludes both maintenance labor, and materials. References 88 and 89.
Industrial boiler cost report, August 31, 1982, Table 2-11 escalated to
1987 dollars using CE index.
"A 30 percent premium above operating labor.
7-35
-------
<*>
a*
0>
I
cr>
c
cr
a>
o
o>
•o
n
o
I
I
1.0
100
so
10
1.0
Size (MW)
o Coflanefallon
• Simple Cycle
-------
simple-cycle turbines is based on the available data, but drawn to the line
for cogeneration. These lines and their respective equations are shown in
Figure 7-6 and represent 1983 dollars.
Based on several plant visits, the average amount of land needed for a
simple-cycle gas turbine is between 1 and 1.5 acres. The amount of land is
broken down into turbines under 10 MW in size and turbines over 10 MM in
size. Equation 2 in Table 7-11 is used to estimate the capital cost for
land based on the acreage required.
Land prices will be a very small percentage of the total capital costs.
In some cases, there would not be any land costs associated with the gas
turbine. This would be the case if the gas turbine and equipment are to be
located in an area already owned by the landfill facility. Therefore, land
capital costs are conservatively included in the total turbine capital cost.
Equation 3 in Table 7-11 was used to estimate the capital cost
associated with the electrical switch gear. Equation 3 is derived from
electrical switch gear cost information reported in a Section 114 response
90
and by applying the "six-tenths-factor" rule. It is assumed with the use
of this equation that the capital cost of the switch gear is a direct
function of the gas turbine output.
The final item included in the initial capital investment of the turbine
system is the working capital. This is assumed to be 25 percent of the
direct operating cost.
7.2.2.3 Operating Costs For the Gas Turbine System. The components
and operating cost bases are presented in Table 7-11. This section provides
the bases for estimating direct operating costs. Included in the direct
operating costs are operating and supervising labor, maintenance labor, and
maintenance materials. The bases for estimating indirect operating costs
are not discussed because these costs are simply estimated with the factors
shown in Table 7-11.
7-37
-------
91-95
• Direct Operating Costs
Operating and supervising labor. Data on the operating labor
requirements for the gas turbines are shown in
Table 7-12. Based on these data, gas turbines require one
operator whenever the turbine is operating. However, this
assumption is probably conservative. For example,
simple-cycle turbines (less than 20 MW) would likely not
require a full-time operator. Therefore, in this cost
analysis, it is assumed that only one operator will be
required during the day time hours. The gas turbines will be
operated by an automatic controller during the night time
hours.
The capital cost associated with supervising labor is assumed
to be equal to 15 percent of the operating labor plus an
additional 30 percent salary premium.
96 97
• Maintenance Labor and Materials '
Comments received from Solar Gas Turbines, Inc., and Dow Chemical
regarding typical maintenance labor and material costSgare used in
the development of Equations 7 and 8 in Table 7-11. ' Dow's
comments indicated that total maintenance costs are $.002/KWH for
aircraft derived gas turbines. Solar estimated that total
maintenance costs for small turbines range from $.002/KWH to
.0035/KWH. The hours of operation is assumed to be 8760 per year.
7.2.2.3 Gas Turbine Replacement. At the end of the first gas
turbine's equipment life, a new system will be sized and costed to
accommodate the maximum expected during the next 15 year equipment life.
Replacement costs will be estimated for every 15 year interval in the
control period.
7.2.3 Cost Effectiveness
The cost effectiveness of the flare and gas turbine options is
estimated using two different economic approaches: single stage discounting
and two-stage discounting. Single stage discounting is used to reflect the
impact to industry, while two stage discounting is used to reflect the
impact to society.
With single stage discounting, the cost effectiveness is calculated by
dividing the net present value of the costs by the net present value of the
emission reduction. This method is equivalent to the conventional method of
dividing the annual cost by the annual emission reduction since both the
7-38
-------
TABLE 7-12. DATA ON OPERATING PERSONNEL REQUIREMENTS'
Approxi-
mate Number Number of Operators
turbine of gas operators per
size MW turbines per shift turbine
Application
Houston Lighting
and Power
Wharton Station
El Paso Electric
Crown Zellerbach
Southern California
Edison, Long Beach
Southern California
50
60
30
50
70
8
2
1
7
4
7
2b
lc
5
4
.9
1
1
0.7
1
Combined-cycle
Combined-cycle
Combined-cycle
Combined -cycle
Combined-cycle
^References 98, 99, and 101.
One operator plus a legman.
cThere is one additional person in the control room to assist the gas
turbine operator if necessary. However, this additional person mainly
takes care of plant systems not connected with the gas turbine cogeneration
system.
7-39
-------
costs and the emission reductions occur over the same time period. In
the single stage discounting of costs and emission reduction, interest rates
of four and eight percent were used for publicly and privately owned
landfills, respectively.
Two stage discounting is used in situations where the capital costs
imposed by regulations are likely to be passed on directly through to
I Q2
consumers. In this approach, the estimated capital costs of a regulation
are first annualized from the year the cost is incurred to the year the
equipment is removed using the marginal rate of return on capital. In this
cost analysis, a 10 percent marginal rate of return is used. Both benefits
and costs are then discounted at the social rate of time preference. In
other words, the annualized capital costs, actual operating costs, and
actual emission reductions are brought back to some reference year using a
three percent social rate and then are annual ized over the total control
period using the same social rate of time preference. The cost
effectiveness can then be calculated by dividing the net present value of
the costs by the net present value of the emission reduction or by dividing
the annualized cost by the annual ized emission reduction.
7.3 CONTROL COSTS FOR MODEL LANDFILLS
This section provides a comparison of the costs associated with the
control of landfill gas at three stringency levels: 25 Mg NMOC/yr, 100 Mg
NMOC/yr and 250 Mg NMOC/yr. Two model landfills were selected from the OSW
database of landfills to represent the typical cost of controlling landfill
air emissions for new and existing landfills. The landfills were selected
based on their size, age, and gas generation factors which are typical of
the landfills in the database. The physical characteristics of these model
landfills are provided in Table 7-13.
7.3.1 Capital and Operating Costs
Tables 7-14, 7-15, and 7-16 show the year-to-year control costs for a
typical existing landfill at stringency levels of 250 Mg NMOC/yr, 100 Mg
NMOC/yr, and 25 Mg NMOC/yr, respectively. Tables 7-17, 7-18, and 7-19 show
the control costs for a new landfill at stringency levels of 250 Mg NMOC/yr,
100 Mg NMOC/yr, and 25 Mg NMOC/yr, respectively. Only the first 20 years of
the control period are shown in these tables for simplicity. In many cases,
7-40
-------
TABLE 7-13. MODEL LANDFILLS3
Landfill characteristic
Design capacity (Mg refuse)
Age in 1992 (years)
Depth (feet)
Average acceptance rate (Mg refuse/yr)
NMOC concentration (ppmv)
Methane generation rate constant (1/yr)
Methane generation potential (ft /Mg refuse)
Type of owner
Existing model
6,986,160
20
250
253,405
6,381
.028
6,350
Public
New model
5,949,500
(open
1994)
25
297,475
6,381
.008
8,120
Public
Information extracted from the EPA Survey of Municipal Solid Waste
Landfills (Reference 103).
These values were randomly assigned to the landfills in the EPA database.
See Chapter 3 for further discussion of these variables.
7-41
-------
TABU 7-14. 1STIHATID CdTNL COSTS M Til UISTII6 HONL UIDFILL IT 1STIIKDCT UVIL OF 250 H| HOC/rr
run AID inucTiN STSTIII COST IIUUOM
'i
1 2 3 4 5 .6 7 8 9 10 11 12 13 14 15 16 17 IB 19 20
902 936 968 999 1030 1059 1088 1116 1144 1170 1138 1106 1076 1046 1017 989 962 935 910 684
5068096 5321501 5574906 5828311 6081716 6335121 6518526 6841931 6986160 6986160 6986160 6986160 6986160 6986160 6986160 6986160 6986160 6986160 6986160 6986160
23.8923 1.1946 1.1946 1.1946 1.1946 1.1946 1.1946 1.1946 0.6799 00000000000
153306 00000000000000 138613 0000
768062 35588 35573 35558 3554.4 35532 35520 35508 20205 0 0 0 0 0 0 35671 0000
e
921368 35588 35573 35558 35544 35532 35520 35508 20205 0 0 0 0 0 0 174284 0000
0 14184 14341 14494 14643 14T8T 14928 15064 15197 15326 15169 15016 14867 14723 14582 14445 13725 13595 13470 13347
0 83381 84882 86380 87876 S9370 90861 92349 93223 93287 93210 93135 93062 92991 92923 94283 94218 94155 94093 94033
0 97565 99223 100875 102519 104157 105788 107414 108421 108613 108379 108151 107929 107714 107505 108728 107942 107750 107563 107381
0 917 949 979 1009 1038 1067 1094 1121 1147 1115 1084 1054 1025 997 969 943 917 891 867
mi or comoL <•)
WC niSSIN (Hf/p)
unsi ii PUCI (HI)
KILLS IISTALUD
rUII CAPITAL COST (t)
OTUCTIOI CAPTIAL COST ($)
TOTAL CAPITAL COST
rUII OPUATIIG COST (t)
iniACTIOl OPIUTIK COST (t)
TOTAL OPIIATIK COST ($)
me nissim IIDOCTIOI du/?r)
IP? Or CAPT1AL COST ($) (b):
IP* Or ONIATIK COST (*)=
IPI or me nissim IIWCTIOI
COST irncTimiss mi)--
3,363,800
2,982,444
22,228
286
(i) Older tkii itriijeicj letel, tkii ludfill m coitrolled for 64 jeut. •
(b) IPV : let premt value. Coita and eiiiiiott icre broujit back to tie bate fear, 1992, at a rate of 3 1.
-------
mil 7-15. ISTIIUTID COITIOL COSTS KM THIIIISTIK BODIL LAIDFILL IT 4 STIIKIKT UIIL OF 100 H| HOC/jr
to
FUJI AID UTUCTIH SISIH COST BIUIDOM
t
t 2 3 4 5 6 7 t 9 10 11 12 13 14 15 16 17 18 19 20
902 936 968 999 1030 1059 10U 1116 1144 1170 113S 1106 1076 1046 1017 989 962 935 910 884
5068096 5321601 5574906 5128311 6081716 6335121 658152$ 6841931 6986160 6986160 6986160 8986160 6986160 6986160 6986160 6986160 6986160 6986160 6986160 6986160
23.8923 1.1946 1.1946 1.1946 1.1946 1.1946 1.1946 1.1946 0.6799 00000000000
153306 00000000000000 138613 0000
768062 35588 35573 35558 35544 35532 35520 35508 20205 0 0 0 0 0 0 35671 0 0 0 0
921368 35588 35573 35558 35544 35532 35520 35508 20205 0 0 0 0 0 0 174284 0000
0 14184 14341 14494 14643 14787 14926 15064 15197 15326 15169 15016 14867 14723 14582 14445 13725 13595 13470 13347
0 83381 84882 86380 87876 89370 90861 92349 93223 93287 93210 93135 93062 92991 92923 94283 94218 94155 94093 94033
0 97565 99223 100875 102519 104157 105788 107414 198421 108613 108379 108151 107929 107714 107505 108728 107942 101750 107563 107381
0 917 949 979 1009 1038 1067 1094 1121 1147 1115 1084 1054 !025 997 969 943 917 891 867
nu or comoi ui
HOC niSSIH (If/jr)
UFDSI II PUCI (l|)
HILLS IISTALUD
run ciPiTti COST ID
nTUCTiOl CIPTIAl COST (t)
TOTAL CAPITAL COST
FLU! OPIiATIIG COST (t)
UTUCTIOI OPIUTIK COST (t)
I
TOTAL OPIUTIK COST (t)
HOC DISSIOIUNCTIM (Wit)
IPV Of CiRIlL COST It) (b):
IP? OF OPIUTIK COST (I)--
in or me nissid HDOCTIM
COST imCTIfDISS (I/If)-
3,677,897
3,298,747
22,755
307
(«) Older this itriiincy 1ml, tiia Iwdfill MI coat rolled for 96 jtut
(b) IPV - let preieit talne. Coils aid Million wre brogfkt back to tbe bate year, 1992, at a rate of 3 I.
-------
TABLI 1-16. ISTIIUTID COITtOL COSTS 101 THI HISTIIG HODIL LAID!ILL AT * STIIICIICI LHIL OF 25 Bj IBOC/jr
Till Or COmOL (a)
HOC BISSIM (Bc/ir)
liniSI II PLACI (If)
KILLS IISTALLID
FLAII CAPITAL COST (t)
IITIACTIOI CAPTIAL COST ($)
TOTAL CAPITAL COST
rLAII OPIUTIK COST (t)
UTIACTIOI OPIUTIK COST (t)
TOTAL OPIIATIK COST (t)
HOC BISSIOI IIDUCTIM (H|/r)
in or CAPTIAL COST it)
-------
TABLI7-17. ISTIHATID COITtOL COSTS POI TSIIN HOHL LAIDPILL AT 4 STIIKIICT U?IL Of 250 H| WOC/n
FLAII UD iniACTioi STSTM COST NUIDOW
1 2 3 4 5 6 7 8 9 10 11 12 13 H 15 16 17 IB 19 20
265 292 315 338 361 383 406 428 450 472 493 490 486 482 478 474 470 467 463 459
3272225 3569700 3867175 4164650 4462125 4759600 5057075 5354550 5652025 5949500 5949500 5949500 5949500 5949500 5949500 5949500 5949500 5949500 5949500 5949500
99.6804 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 0000000000
98364 00000000000000 96793 0000
981445 85342 85217 85106 85008 84919 84838 84764 84C9t 84634 0 0 0 0 0 23855 0000
1079809 85342 85217 85106 85008 84919 84838 84764 64696 84634 0 0 0 0 0 120648 0000
0 8854 8966 9078 9188 9298 9407 9515 9622 9729 9634 9815 9796 9777 9758 9740 9659 9640 9622 9604
0 92486 95959 99428 102893 106354 109811 113265 116716 120164 120224 120214 120203 120192 120181 121125 121115 121104 121094 121084
0 101339 104925 108506 112081 115652 119218 122780 126339 129893 130059 130028 129999 129969 129940 130865 130773 130145 130716 130688
0 286 309 331 354 376 398 419 441 462 484 480 476 472 468 465 461 457 454 450
TIAI OF C0mOL It)
HOC IMISSIOI (Hf/r)
IIFOSI II PLACI (Of)
HILLS IISTALLID
FLAII CAPITAL COST (I)
^ HTUCTIOI CAPTIAL COST (I)
£ TOTAL CAPITAL COST
FLAU OPIUTIK COST (J)
QTUCTIOI OPIUTIK COST |$)
TOTAL OPIUTIK COST ($)
HOC niSSIM UNCTIOI (H|/?r)
IP* OF CAPTIAL COST (I) (b)= 3,770,993
IP? Of OPHATIK COST ($)= 2,707,316
IPI OF noc nissin HDOCTIOI (HO= 8,351
COST IFFICTIIIIISS (I/Mi)- 776
(a) Under tilt etrinjencj luel, thu landfill HI controlled for 95 yeart.
(b) Id ; get preieot nine. Coats and eiiitioat nere brought back to the base rear, 1992, it a rate of 3 1.
-------
T48LI 7-18 ISTIDATID CflWIOL COSTS N)i TNI (IK HODIL UIDFILL *T 4 STIIICIICT LlfiL Of 100 t){ IBOC/yr
CT>
rut or comoL ui
HOC OIISSIOI (H|/;r)
nrusi ii PUCI (Hf)
KILLS IISTiUID
run CAPITAL COST ft)
UTUCTIOi CAPTIAl COST (t)
TOTiL CAPITAL COST
run OPIUTIIG COST w
mucTioi OPIUTIK COST m
TOTIL OPIUTIK COST (t)
HOC HHSSIM IINCTIOI (Ifc/Fr)
IP? 01 CAPTIAL COST (t) (b)=
IP? Or OPIUTIK COST II):
IP? or HOC mssioi IINICTIOI in
COST irricri?niss (mr-
•
I 2
101 125
1189900 1487375
36.2474 9.0619
94832 0
390378 87173
485210 87173
0 7899
0 68454
0 76353
0 123
4,278,308
3,240,861
t}- 9.453
795
3
150
1784850
9.0619
0
86705
86705
8018
71988
80007
147
4
174
2082325
9.0619
0
86350
66350
8136
75509
83645
170
run AID
5
198
2379800
9.0619
0
86069
86069
8253
79018
87272
194
mUCTIOl SISTDt COST BIUIDOM
6
222
2677275
9.0619
0
85840
85840
8370
82518
90887
217
7
245
2974750
9.0619
0
85641
85648
8465
86010
94494
240
8
269
3272225
9.0619
0
85484
85484
1599
89495
98094
263
9
292
3569700
9.0619
0
85342
85342
8712
92974
101686
286
10
315
3867175
9.0619
0
85217
85217
8825
96447
105272
309
11
338
4164650
9.0619
0
85106
85106
8936
99916
108853
331
12
361
4462125
9.0619
0
85008
85008
9047
103381
112428
354
13
383
4759600
9.0619
0
84919
84919
9157
106842
115999
376
14
406
5057075
9.0619
0
84838
84838
9266
110299
119565
398
15
428
5354550
9.0619
0
84764
84764
9374
113753
123127
419
16
450
5652025
9.0619
98364
109077
207441
9481
118180
127661
441
17
472
5949500
9.0619
0
.84634
84634
9729
121628
131356
462
18
493
5949500
0
0
0
0
9834
121688
131522
484
19
490
5949500
0
0
0
0
9815
121677
131492
480
20
486
5949500
0
0
0
0
9796
121666
131462
476
(<) Under this atriigencj leiel, Ibis landfill MI coitrolled for 116 fears.
(b) IP? ; let preaent nine. Coats and eiisiiou sere broujbt back to the baae rear, 1992, it a rite of 3 I.
-------
TtBLI 1-19. ISTIHATID COTiOL COSTS FOi THIIH HOUL UIDFILL AT ft STflKUCT LIIIL OP 25 H| BOC/jr
FLAIIIID UTUCTIH S1STI8 COST UUIDOM
I 2 3 4 5 6 7 8 9 10 1! 12 13 14 15 16 17 18 19 20
25 51 76 101 125 150 114 191 222 245 269 292 315 338 361 383 406 428 450 472
2)7475 594950 892425 1189900 1487375 1784850 2082325 2379800 2677215 2974750 3272225 3569700 3867175 4164650 4462125 4759600 5057015 5354550 5652025 5949500
9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619 9.0619
89426 00000000000000 98364 0000
126940 90857 88864 87832 87173 86705 86350 86069 85840 85648 65484 65342 85217 85106 85008 109282 84838 84764 84696 84634
216366 90857 88864 87832 81173 86705 86350 86069 85840 85648 85484 85342 85211 85106 85008 207646 84838 84764 84696 84634
0 7321 7442 7563 1683 1802 7920 8037 6153 8268 8383 8496 8609 6720 8831 8941 9407 9515 9622 9729
0 57863 61484 65064 68618 72153 15614 79183 82682 66174 89659 93138 96612 100081 103546 107981 111438 114892 118343 121792
0 65183 68927 72628 16301 79955 83594 17220 90836 94443 9(042 101634 105221 10(801 112371 116922 120845 124408 121966 131520
0 50 74 98 123 147 170 194 217 240 2(3 2(6 309 331 354 376 398 419 441 462
Tlil OF CORIOL (a)
WOC niSSlM (Di/rr)
IIFVSI ii PUCI (Be)
MILLS IISTALLID
FLAII CAPITAL COST ($)
UTUCTIOI CAPT1AL COST (|)
TOTAL CAPITAL COST
riAII OPIUTIIG COST (I)
UTUCTIOI OPUATIIC COST (I)
TOTAL OPIUTIIG COST ())
me nissioi IINCTIOI
IF* Of UPTIU, COST |U (b)=
in 01 OPIUTIK COST (t)=
in OF noc nissioi IIMICTIOI
COST irFicminss H/HII--
4.371,648
3.426,269
9,644
809
(i) Older tkii itrineicj leiel, this ludfill RM control ltd for 119 yean.
(b) IPV - ut present ulue. Coats and eiiasioii lere brought back to the bite jtu, 1992, it * rite of 3 I.
-------
the control period will exceed 20 years. The control period for the model
existing landfill at a stringency level of 250 Mg NMOC/yr is 64 years. At a
stringency level of 25 Mg NMOC/yr, the control period is 108 years. For the
new landfill, the control periods range from 95 to 119 years in going from
the least stringent to the most stringent cutoffs.
As shown in the tables, a collection system and control device are
installed when the emission rate exceeds the specified cutoff. The control
device (in this case the control device is a flare) and some components of
the collection system (such as the blower) are sized for the maximum
expected landfill gas generation rate and installed in the first year of
control. Extraction wells and required collection headers are also
installed in the first year of control based on the existing refuse in
place. As additional refuse is placed in the landfill, more extraction
wells and headers are installed. As a result, capital costs are incurred
when the landfills emissions reaches the cutoff and each year thereafter,
until the landfill has reached capacity. After the landfill has reached its
refuse capacity, capital costs are only incurred every 15 years to replace
equipment.
It is assumed that the first year of control is spent installing the
equipment and that operating costs are not incurred until the second year of
control, as exemplified in Tables 7-14 through 7-19. The operating cost
increases each year as refuse is accepted, until the landfill reaches
capacity. Once the landfill reaches capacity, the operating cost becomes
relatively constant until equipment must be replaced. Capital and operating
cost estimates were developed using the methodologies and costs presented in
Sections 7.1 and 7.2.
7.3.2 Cost Effectiveness
The two stage cost effectiveness of controlling NMOC emissions at the
three stringency levels are also presented in Tables 7-14 through 7-16 for
the existing landfill and Tables 7-17 through 7-19 for new landfills. The
cost effectiveness for the existing landfill at a stringency level of
250 Mg NMOC/yr is approximately $290/Mg NMOC reduced. At the most stringent
level, 25 Mg NMOC/yr, the cost effectiveness increases to $311/Mg NMOC. The
7-48
-------
cost effectiveness for the new landfill ranges from $776/Mg NMOC to $809/Mg
NMOC in going from the least stringent to the most stringent cutoffs.
The cost effectiveness values presented in Tables 7-14 through 7-19 are
calculated from the capital and operating costs and the emission reduction
incurred over the entire control period. The costs and emission reductions
in each year are brought back to the net present value in 1992 at a rate of
3 percent as described in Section 7.2.3. The cost effectiveness is the
total net present value of the control costs (capital plus operating)
divided by the net present value of the emission reduction.
7.4 NATIONAL COST IMPACTS
This section presents the national cost impacts for both existing and
new landfills for the stringency levels of 250 Mg NMOC/yr, 100 Mg NMOC/yr,
and 25 Mg NMOC/yr. These national cost impacts were developed using the EPA
survey of municipal solid waste landfills discussed in Chapter 3 and the
cost estimation methods provided in Sections 7.1 and 7.2 The control costs
were computed for each landfill in the survey datafile as shown in the model
cases in Section 7.3. The costs were then scaled to the national level and
summed to provide the national cost impact.
7.4.1 Existing Landfill Cost Impacts
The national cost impacts of controlling existing landfill air
emissions at three stringency levels are presented in Table 7-20. At the
least stringent cutoff, 250 Mg NMOC/yr, approximately 9.6 x 106 Mg NMOC (net
present value) is reduced by controlling 386 landfills yielding an overall
cost effectiveness of $407/Mg NMOC. At the most stringent level, 25 Mg
NMOC/yr, the overall cost effectiveness is $927/Mg which results from
reducing 1.3 x 10 Mg NMOC (net present value) from approximately
1,900 landfills.
7.4.2 New Landfill Cost Impacts
Table 7-21 presents the national cost impacts for new landfills, at
three stringency levels. At an overall cost effectiveness of $897/Mg NMOC,
approximately 630,000 Mg NMOC (net present value) can be reduced from
41 landfills under the- stringency level of 250 Mg NMOC/yr. At the
stringency level of 25 Mg NMOC/yr, 247 landfills would be reducing
7-49
-------
TABLE 7-20. NATIONAL COST IMPACTS OF CONTROLLING EXISTING LANDFILLS
AT THREE STRINGENCY LEVELS
Stringency Level (Mg NMQC/vr)
25 100 250
Total number of landfills affected 1,884 853 386
NPV capital cost (106$) 6,440 4,830 2,400
NPV operating cost (106$) 5,120 2,830 1,510
NPV NMOC emission reduction (106Mg NMOC) 12.6 11.2 9.6
Overall cost effectiveness ($/Mg NMOC) 927 640 407
7-50
-------
TABLE 7-21. NATIONAL COST IMPACTS OF CONTROLLING NEW LANDFILLS
AT THREE STRINGENCY LEVELS
Total number of landfills affected
NPV capital cost (106$)
NPV operating cost (106$)
NPV NMOC emission reduction (106Mg NMOC)
Overall cost effectiveness ($/Mg NMOC)
Stringency
25
247
788
614
.99
1,416
Level (Ma
100
104
548
348
.83
1,081
NMOC/vr)
250
41
362
200
.63
897
7-51
-------
approximately 990,000 Mg NMOC (net present value) at a cost effectiveness of
$l,416/Mg NMOC. The overall nationwide cost effectiveness for the new
landfills is slightly higher than the existing landfills because the NMOC
emissions from the new landfills would not include NMOC's from co-disposal
of hazardous waste as some of the existing landfills might.
7-52
-------
7.5 REFERENCES
1. The U.S. Environmental Protection Agency. Office of Research and
Development. Handbook: Remedial Action at Waste Disposal Sites.
Cincinnati, OH. Publication No. EPA/625/6-85/006. October 1985.
2. Emcon Associates. Methane Generation and Recovery from Landfills.
Ann Arbor, Ann Arbor Science, 1982.
3. South Coast Air Quality Management District. Landfill Gas Emission
Report of the Task Force. July 1982.
4. Reference 1
5. Trip Report. McGuinn, Y.C., Radian Corporation to Thorneloe, S.A.,
Environmental Protection Agency. February 1988. Report of November
19, 1987 visit to Rossman Landfill in Oregon City, Oregon.
6. Trip Report. McGuinn, Y.C., Radian Corporation to Thorneloe, S.A.,
Environmental Protection Agency. February, 1988. Report of
November 16, 1987 visit to Puente Hills Landfill in Los Angeles,
California.
7. Reference 3.
8. Reference 7.
9. Vatairik, W.M. and R.B. Neveril. Part IV. Estimating the size and
cost of Ductwork. Chemical Engineering, Volume 87, No. 26,
December 29, 1980. pg. 71.
10. Memorandum from Kuo, I.R., Average Landfill Gas Flow per Well and Well
Depth to Municipal Landfill Project File. September 29, 1989.
11. Reference 5.
12. Trip Report. McGuinn, Y.C., Radian Corporation to Thorneloe, S.A.,
Environmental Protection Agency. February, 1988. Report of
November 17, 1987 visit to Toyon Canyon, Los Angeles, California.
13. Trip Report. McGuinn, Y.C., Radian Corporation to Municipal Landfill
File. January 20, 1988. Report of November 18, 1987 visit to Palos
Verdes Landfill in WJiittier, California.
14. Trip Report. McGuinn, Y.C., Radian Corporation to Municipal Landfill
File. June 1, 1988. Report of November 18, 1987 visit to City of
Greensboro Landfill, Greensboro, North Carolina.
15. Reference 5.
7-53
-------
16. Reference 6.
17. Reference 12.
18. Reference 10.
19. Richardson Engineering Services, Inc., Process Plant Construction
Estimating Standards, Volume 4, 1982-1984. pg. 100-111.
20. Reference 2.
21. Letter from Echols, R.L., Browning-Ferris Industries, to
Thorneloe, S.A., Environmental Protection Agency. October 14, 1988.
22. Memorandum from McGuinn, Y.C., Design of Municipal Solid Waste
Landfill Gas Collection Systems and Their Relative Installation Costs,
to Thorneloe, S., EPA. February 22, 1989.
23. Bennett, C.O., J.E. Meyers. Momentum, Heat, and Mass Transfer.
McGraw-Hill. 1982.
24. Crane Engineering Division. Flow of Fluids Through Valves, Fittings,
and Pipe. Technical Paper No. 410. 1982. Chapter 3.
25. McQuiston, F.C., J.D. Parker. Heating, Ventilating, and Air
Conditioning. John Wiley & Sons, Inc. 1982. p. 368.
26. Reference 24.
27. Reference 2.
28. Reference 1.
29. Reference 10.
30. Reference 25.
31. Letter from Lalka, R.A., County Sanitation Districs of Los Angeles
County to All Bidders for the Construction of the Puente Hills
Landfill - Phase III Gas Collection Trenches, County Sanitation
District No. 2 of Los Angeles County. July 23, 1987.
32. Reference 21.
33. Science Applications International Corporation. Draft Decision
Document for Hazardous Waste Treatment Industry Effluent Guidelines
Development. August 17, 1987.
34. Reference 1.
7-54
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35. Telecon. Kuo, I.R. Radian Corporation with Kellett, D., Kelletts
Well Boring. December 2, 1988.
36. Peters, M., K. Timmerhaus. Plant Design and Economics for Chemical
Engineers. McGraw-Hill, 1980.
37. Reference 31.
38. Reference 21.
39. Reference 33.
40. Economic Indicators. Chemical Engineering, Volume 94, No. 17.
November 23, 1987. pg. 7.
41. Reference 35.
42. Reference 1.
43. The U.S. Environmental Protection Agency. Office of Air Quality
Planning and Standards. Capital and Operating Costs of Selected Air
Pollution Control Systems. Publication No. 450/5-80-002.
December 1978.
44. The U.S. Environmental Protection Agency. Office of Air Quality
Planning and Standards. Capital Costs Manual, 3rd Edition,
EPA 450/5-87-001A. February 1987.
45. Reference 39.
46. Reference 19.
47. Reference 39.
48. Reference 35, p. 562.
49. Reference 35, p. 563.
50. Reference 35.
51. Reference 42.
52. Reference 1.
53. Department of Energy, Energy Information Administration. Monthly
Energy Review. DOE/EIA-0035(87/07). July 1987. p. 101.
54. R. Burke, EPA: Office of Solid Waste and Emergency Response, to
Docket No. F-88-CMPL-FFFFF, September 19, 1988, Unit Costs used in
draft municipal solid waste landfill regulatory impact analysis.
7-55
-------
55. Letter from McGuinn, Y.C., Radian Corporation to Nourot, M., Laidlaw
Gas Recovery. March 7, 1989. Municipal landfill flares.
56. Letter from Johnson, M.C., Sur-Lite Corporation to McGuinn, Y.C.,
Radian Corporation. Standard sur-Lite Cylindrical Flaring System.
December 23, 1987.
57. Letter from McGuinn, Y.C., Radian Corporation to Ziles, D., McGill
Environmental Systems. March 7, 1989. Municipal landfill flares.
58. Letter from McGuinn, Y.C., Radian Corporation to Alfred, J., John Zink
Company. March 7, 1989. Municipal landfill flares.
59. Reference 19.
60. Reference 39.
61. Reference 54.
62. Reference 55.
63. Reference 56.
64. Stambler, I. Carving out landfill market for Saturn and Centaur. Gas
Turbine World. 18:30-35. October, 1988.
65. Reference 54.
66. Reference 55.
67. Reference 56.
68. Thorneloe, S. and L. Evans. The Use of an Internal Combustion Engine
or a Gas Turbine as a Control for Air Emissions from Municipal Solid
Waste Landfills. Revised Draft Memorandum. U.S. Environmental
Protection Agency. May 31, 1989.
69. Turbomachinery International, April, 1983.
70. Gas Turbine World and Cogeneration 11:5, November 1982.
71. Turbomachinery International Utility Cost Study, 1982.
72. Gas Turbine World, Summer 1983.
73. Gas Turbine World, January 1983.
74. Gas Turbine World, March-April 1983.
75. Gas Turbine World, September-October 1983.
7-56
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76. Gas Turbine World Handbook, 1979-1980.
77. Letter and Attachments from Knight, D., American McGaw, to
Dalrymple, D., Radian Corporation. Response to request for
information on stationary gas turbines.
78. Resnick, W. Process Analysis and Design for Chemical Engineers.
McGraw-Hill. 1981.
79. Reference 68.
80. Reference 69.
81. Reference 70.
82. Reference 71.
83. Reference 72.
84. Reference 73.
85. Reference 74.
86. Reference 75.
87. The U.S. Environmental Protection Agency, Office of Planning and
Standards. Organic Chemical Manufacturing Volume 4: Combustion
Control Devices. Research Triangle Park, NC. Publication No. EPA
450/3-80/026. December 1980.
88. Letter from Tucker, M., Dow Chemical, to Cuffe, S., USEPA. November
11, 1983.
89. Letter from Solt, C., Solar Turbine, Inc., to Noble, E., USEPA.
October 19, 1984.
90. Reference 86.
91. Reference 85.
92. Trip Report. Dalrymple, D., Radian Corporation, to Noble, E., EPA,
October 4, 1983. Report of June 27, 1983 visit to El Paso Electric
Company in Newman, Texas.
93. Trip Report. Dalrymple, D., Radian Corporation, to Noble, E., EPA,
March 28, 1984. Report of June 17, 1983 visit to Crown Zellerbach in
Antioch, California.
7-57
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94. Trip Report. Dalrymple, D., Radian Corporation, to Noble, E., EPA.
December 15, 1983. Report of June 22-23 visit to Southern California
Edison's Long Beach and Coolwater generation station.
95. Reference 13.
96. Reference 87.
97. Reference 88.
98. Reference 77.
99. Reference 102.
100. Reference 103.
101. Reference 104.
102. Kolb, J.A., and J.D. Scherga. A Suggested Approach for Discounting
the Benefits and Costs of Environmental Regulations. April 1988.
103. OSW Survey of Municipal Landfills. Data base supplied by DPRA, Inc.,
September 1987.
7-58
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8. ECONOMIC IMPACTS
This chapter evaluates the economic impacts of the §lll(d) Guidelines
and §111 (b) Standards under the Clean Air Act that EPA will propose for
closed/existing and new landfills, respectively. Section 8.1 presents an
overview of the management of municipal solid waste, including recycling,
incineration, and landfilling alternatives. Section 8.2 provides a
detailed profile of landfills. Section 8.3 briefly describes the
regulatory alternatives and control options under consideration. It also
discusses the implications of the assumptions underlying the economic
analysis. Section 8.4 examines the main economic impacts of the relevant
regulatory alternatives. Section 8.5 discusses emissions reductions and
the cost-effectiveness of the regulatory alternatives. Section 8.6
analyzes some distributional impacts of the regulatory alternatives.
Finally, Section 8.7 examines the sensitivity of the social costs of the
regulatory alternatives to changes in the discount rate.
8.1 OVERVIEW OF MUNICIPAL SOLID WASTE MANAGEMENT
Figure 8-1 shows the flow of municipal solid waste (MSW) from genera-
tion to disposal. MSW is generated as a by-product of consumption and
production. After collection, sorted and unsorted MSW is either directly
landfilled, incinerated in a municipal waste combustor, or sent to a cen-
tralized recycling facility. Most residues from recycling and combustion
are sent to sanitary landfills. The main exception is hazardous ash from
combustors, which is sent to a hazardous-waste landfill.
Section 8.1.1 describes the sources and composition of MSW and dis-
cusses trends in waste generation. Section 8.1.2 discusses the collection
transfer, and transportation of MSW. Section 8.1.3 discusses materials
recovery through centralized recycling and source reduction. Finally,
Section 8.1.4 examines the combustion and landfilling of MSW.
8-1
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Centralized
Recycling
Marketable
Materials
Disposing
Combustion
Processing
Nonhazardous
Ash
I
Sanitary
Landfilling
Hazardous
Ash
t
Hazardous
Waste
Landfilling
Figure 8-1. Flow of municipal solid waste from generation to disposal.1
8-2
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8.1.1 Generation
Municipal solid waste includes all nonhazardous wastes from household,
institutional, commercial, municipal and industrial sources.2 Approxi-
mately 143 million Mg of MSW were generated in the United States in 1986.3
This represents an average annual per capita generation of 0.60 Mg (about
3.6 pounds per day).4 Table 8-1 presents the estimated quantities and
shares of these discarded materials. Paper and paperboard comprise over
40% of gross discards. Yard wastes (e.g., grass clippings, tree trimmings,
and leaves) represent the second largest portion - about 20%. Glass,
metals, plastics, and food waste each comprise an additional 6 to 9% of the
total.
As shown in Figure 8-2, generators of MSW can be classified into four
broad groups:
• Residential,
• Commercial (e.g., offices, restaurants, and retail stores),
• Industrial (e.g., plants and factories), and
• Others.
The residential group generates approximately one-half of all municipal
solid waste. The second largest group, commercial, generates about one-
fourth of MSW. Most industrial by-products are either recycled, reused, or
managed as hazardous wastes, leaving only a small portion to enter the
municipal waste stream. Consequently, industrial sources are responsible
for less than 5% of municipal solid waste. Other miscellaneous wastes such
as sewage sludges and incinerator ash comprise about one-sixth of the muni-
cipal solid waste.
Various underlying factors influence the trends in the quantity of MSW
generated over time. These factors include changes in population, individ-
ual purchasing power and disposal patterns, trends in product packaging,
and technological changes that affect disposal habits and the nature of
materials disposed.7 Franklin Associates projects that MSW generation will
increase at an annual rate of 1.43; over the period 1986 to 2000, and that
about 175 million Mg of MSW will be generated in 2000.8 This growth rate
slightly exceeds estimates of population growth, reflecting an increase in
annual per-capita generation from 0.60 to 0.73 Mg.9
8-3
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TABLE 8-1. MATERIALS IN THE MUNICIPAL WASTE STREAM, 1986*
Materials
Paper and paperboard
Glass
Metals
Plastics
Rubber and leather
Textiles
Wood
Food wastes
Yard wastes
Miscellaneous waste
Quantity
(106Mg)
58.7
11.7
12.4
9.3
3.6
2.5
5.3
11.3
25.7
2.4
Share of
gross discards
(%)
41.0
8.2
8.7
6.5
2.5
1.7
3.7
7.9
18.0
1.7
Total wastes 143.0 100.0
These estimates exclude waste flows from demolition and construction, sludges, automobile bodies, nonhazardous
industrial sources, incinerator residues, nonfood products discarded in containers, and packaging of imported goods.
Details may not add to totals due to rounding.
8-4
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Other (13%)
Industrial (4%)
Commercial (28%)
Residential (55%)
Figurt 8-2. Sources of municipal solid waste.6
8-5
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8.1.2 Collection and Transportation
Collection and transportation are necessary components of all MSW
management systems regardless of the specific disposal options. MSW must
be collected from generators and transported to a combustor, a recycling
facility, a transfer station, or directly to a landfill. When recycling
occurs, the residue must subsequently be transported to a combustor or
landfill. Likewise, ash from municipal waste combustion must be trans-
ported to a landfill for disposal.
Collection of MSW varies by service arrangement between local govern-
ments and collectors and by level of service provided to households. The
following five service arrangements account for over 99% of arrangements
found in a 1978 National Science Foundation survey of municipalities:^
• Private - A private firm collects waste from households for a
fee, but does not have exclusive territorial rights,
• Municipal - municipal employees collect waste,
• Contract - local government contracts with a private firm for the
exclusive right to collect waste in a specified area. The pri-
vate firm is paid by the local government,
« Self-service - households deliver waste directly to disposal
sites or transfer stations, and
• Franchise - local government awards a private firm the exclusive
right to collect waste in a specified area. The private firm
collects fees directly from households.
The private and municipal service arrangements are the most popular with
each used in about 30% of municipalities (see Figure 8-3). Contracts with
private firms are found in 17% of municipalities, while 6% grant fran-
chises. About 15% of municipalities collect waste under a self-service
arrangement. Several different service areas may exist within a single
municipality. For example, industrial and residential waste may be col-
lected through different arrangements, or waste in different parts of a
municipality may be collected by different contractors.
The level of service provided to households is usually linked to the
frequency and location of pickup. With respect to collection frequency,
about 60% of the cities collect waste once per week and 30% collect more
8-6
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Franchise (6%)
Unknown (1%)
Self-Service (15%)
Contract (17%)
Private (31%)
Municipal (30%)
Figure 8-3. Service arrangements for MSW collection.11
8-7
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frequently. The remaining 10% collect less frequently than weekly. The
most common locations of pickup are backyard, curbside, and alley.12
Solid waste transfer is the process in which collection vehicles un-
load their wastes at centrally located transfer stations. Thus, smaller
loads are consolidated into larger vehicles better suited for long-distance
hauls. The larger vehicles then deliver the waste to the disposal site.13
The larger vehicles are usually tractor-trailer trucks; however, trains and
barges are becoming more popular for waste transfer.14,15,16
Transfer stations can decrease disposal costs in four basic ways:
(1) hauling costs are decreased by decreasing the number of drivers and
vehicles hauling waste to disposal sites, (2) turn-around time of collec-
tion vehicles is decreased when they do not have to haul waste to disposal
sites, (3) larger vehicles can haul waste more efficiently allowing dis-
posal at inexpensive distant disposal sites, and (4) some new transfer
stations can recover marketable materials.17,18,19
As public opposition to MSW disposal facilities increases and the
costs of disposal at locations near generators rise, long-distance hauls to
disposal sites are becoming necessary.20,21,22 where very long haul dis-
tances are required, trains or barges are often used rather than tractor-
trailers. Many waste planners prefer hauling waste by train or barge,
because these modes of transportation are the safest and most invisible way
to transport waste. They can also carry more weight legally and can be
less expensive over very long hauls.23
8.1.3 Materials Recovery
As explained in EPA's Agenda for Action, the growing shortage of land-
fill space and the high cost of managing MSW make the recovery of materials
from waste an attractive alternative to direct landfill ing. Materials
recovery increases the life of existing landfills by diverting potentially
large quantities of waste from landfills.24 Materials recovery also
reduces the depletion of natural resources and removes toxic materials from
the waste stream prior to disposal, enhancing the safety of landfilling and
combust ion.25
Materials are recovered from the municipal waste stream using two
methods: source separation and centralized recycling. In the United
8-8
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States, most materials are recovered through source separation, whereby
waste generators manually separate materials for reuse or recycling before
disposal. Disadvantages associated with source separation include both
economic and perception problems. Existing waste collection vehicles are
often ill-equipped and inefficient for curbside collection of separated
materials. In addition, most people currently view discarded materials as
"waste" rather than reusable materials. Thus, source separation programs
often are not regarded as viable waste management options by decision-
makers. 26
Centralized recycling facilities separate marketable materials from
the waste stream after collection. Transfer stations are often used in
centralized recycling for sorting the waste for reusable materials during
transfer.27 The primary disadvantage of centralized waste processing is
its high cost. Recycling activities are often not financially feasible
when only the sale of recovered materials is considered. However, cen-
tralized recycling may be advantageous in communities where landfill dis-
posal costs are high and there are substantial cost savings associated with
reducing the size of the waste stream.28
8.1.4 Disposal Alternatives
After materials recovery, there are two options available for the
management of collected MSW: landfilling and municipal waste combustion.
Figure 8-4 presents a breakdown of 1986 gross MSW discards into landfill-
ing, combustion, and materials recovery. As indicated, landfilling is the
predominant MSW management option. In 1986, about 83% of gross MSW dis-
cards was landfilled and only 6% was incinerated. About 11% of gross
discards was recycled.30
8.1.4.1 Landfilling. A landfill is an area of land or an excavation
where waste is placed for permanent disposal. Municipal solid waste
management uses two types of landfills: hazardous waste landfills and
sanitary landfills. The primary purpose of hazardous waste landfills in
the management of MSW is the disposal of hazardous ash residue from
combustors. Sanitary landfills receive nonhazardous waste from residen-
tial, commercial and industrial sources and a small amount of small -
quantity-generator hazardous waste.
8-9
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Combustion (6%)
Materials Recovery (11%)
Landfilling (83%)
Figure 8-4. Share of MSW managed In disposal alternatives.29
0-10
-------
Although landfill ing is the predominant disposal alternative, it is
becoming less attractive as an MSW management option. The public is becom-
ing aware of the potential health, safety, and environmental impacts of
landfilling (e.g., groundwater contamination, air emission of pollutants,
and danger of explosion). As a result, public opposition toward landfill-
ing has increased and a NIMBY (not-in-my-backyard) attitude toward land-
fills has become prevalent. Likewise, the regulatory environment surround-
ing landfilling is becoming increasingly stringent, making landfilling more
expensive.31 Increasing costs, public opposition, and land scarcity have
closed many lajidfills and have made the siting of new landfills in-
creasingly difficult.
The Office of Solid Waste in the U.S. Environmental Protection Agency
projects that over 70% of existing landfills in 1986 will close by the year
2003, representing nearly three-fourths of the 1986 MSW landfill capacity.
By 2013, only 10% of existing-capacity in 1986 will remain. If current
trends in landfill siting and development continue, only about one-third of
lost capacity will be replaced.32
8.1.4.2 Municipal Waste Combustion. Municipal waste combustion (MWC)
is the process of reducing the volume of MSW through incineration. MWC
facilities range in design capacity from less than 25 Mg per day to more
than 2000 Mg per day.33 Combustion of MSW reduces waste volume by as much
as 90%. Therefore, many municipal planners view MWC as an important method
of reducing the need for additional landfill capacity.
Four broad categories of technologies are available for MWC: mass
burn, modular, refuse-derived fuel (RDF), and other. In 1987, 161 MWC
facilities with approximately 63,000 Mg per day of design capacity were in
operation. Of existing capacity, approximately 55% was mass burn, 27%
modular, 9% RDF, and 9% other.34 See Figure 8-5.
Mass burn combustion requires no preprocessing of MSW other than the
removal of very large items (e.g., tree trunks) and some mixing to produce
a more homogeneous fuel.36 Rams and/or grates move the waste through the
combustor. Mass burn combustors can operate using either waterwall tech-
nology, which usually incorporates energy recovery, or refractory technol-
ogy, which is an older, less efficient, design without energy recovery.37
8-11
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Other (9%)
Modular (27%)
Refuse-Derived
Fuel (9%)
Mass Bum (55%)
Figure 8-5. Municipal waste combustion technologies:
Distribution of design capacity.35
8-12
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Modular combustors consist of one or more factory prefabricated com-
bustor units. Like mass burn facilities, modular combustors require mini-
mal preprocessing of MSW and move waste through the combustor using either
rams or grates. Modular combustor plants range in capacity from 25 to 500
Mg of MSW per day. Modular combustors incinerate waste using either a
"starved air" design where the amount of oxygen is controlled to achieve
pyrolysis or an "excess air" design where the amount of oxygen is not con-
trolled.38
RDF combustors incinerate sorted and preprocessed MSW referred to as
"refuse-derived fuel" (RDF). The sorting and preprocessing of MSW into RDF
may or may not be performed at the same location as the combustor. Sorting
is typically performed using a system of shredders, magnets, screens, air
classifiers, and conveyers. Preprocessing of MSW ranges from simply remov-
ing noncombustibles and shredding to the production of high-quality fuel
pellets. RDF yields a higher heat value, lower ash volume and more com-
plete combustion than nonprocessed waste.39
Other MWC technologies include fluidized-bed gasification and
fluidized-bed combustion. Combustors using fluidized-bed technologies
incinerate MSW more efficiently than mass burn, modular, or RDF units by
making the waste behave as a liquid or gas. However, fluidized-bed tech-
nologies are relatively new and still undergoing refinement.^
8.2 LANDFILL DISPOSAL OF MUNICIPAL SOLID WASTE
This section presents a profile of municipal solid waste (MSW)
landfills. Section 8.2.1 describes some characteristics of municipal
landfills. Section 8.2.2 discusses the costs of landfilling and methods of
paying for landfill operations. Section 8.2.3 examines the changing
regulatory environment in which landfills operate. Finally, Section 8.2.4
describes trends in landfilling MSW.
8.2.1 Characteristics of Municipal Solid Waste Landfills
Landfilling is defined as the disposal of waste through a three-step
process that includes:*!
• Spreading collected waste into thin layers in the landfill,
• Compacting the layers into the smallest practical volume, and
• Covering the compacted waste with soil on a daily basis.
8-13
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EPA's National Survey of Solid Waste (Municipal) Landfill Facilities docu-
mented 6,034 landfills operating in 1986.4^ An estimated 535 landfills
closed in 1987, leaving 5,499 landfills in operation in 1988.4^
Landfills vary widely in the annual quantity of waste received, as
Figure 8-6 shows. Most landfills receive small quantities of waste and
relatively few receive very large quantities. The average annual quantity
of waste received by landfills is 31,400 Mg, but an estimated 84% of
landfills receive less than the average amount. The median amount of waste
received, 2,570 Mg per year, better represents the typical landfill.4^
Although landfills accepting over 100,000 Mg of MSW per year comprise
only 8% of the landfill population, they manage an estimated 74% of
landfilled waste. It is estimated that the largest 21 landfills (0.3%)
receive over 23% of landfilled waste.4& Landfills in the size category
with the largest number of facilities, those accepting 907 to 9,070 Mg of
MSW per year, receive less than 5% of landfilled waste.47
8.2.2 Technologies
Landfills generally use either the "trench" or "area fill" methods of
landfill ing, but combinations of the two methods are also used. Figure 8-7
presents the percentage of landfills using the trench or area fill methods
of landfill ing or a combination. About one-half of all landfills use the
trench method exclusively, while about 30% of landfills use only the area
fill method. Approximately 15% of landfills incorporate a combination of
the trench and area fill methods. Only 5% of landfills use some other
method.49,50
The trench method involves spreading and compacting the waste on the
sloped end of an excavated trench. Cover material is obtained from the
original trench excavation.51 Trench landfilling has the following
advantages:
• makes cover material readily available,
• exposes a minimum-size working face,
• gives optimum drainage during filling operations, and
• is easily adapted to wide variation in size of operation.
However, landfills using this method of landfilling must pay close
attention to soil depth and groundwater conditions.
8-14
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60%
50%
40%
30%
20% •
10% -
D
B
Percentage of
Landfills
x.
s
/
Share of MSW
Accepted
< 9 9 to 91 91 to 907 907 to 9.070 9.070 to 90.700 to > 907,000
90,700 907,000
Annual Quantity of MSW Received (Mg)
Figure 8-6. Distribution of annual quantity of MSW received at landfills.44
8-15
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Other (5%)
Combination (21%)
Area Fill
Method (28%)
Trench
Method (46%)
Rgura 8-7. Landfill technologies.4*
8-16
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The area fill method involves spreading and compacting waste uniformly
on the surface of the ground and covering with soil-52 The cover material
may be imported or may be excess material from trench landfill ing. The
area fill method is generally used when the land is gently sloping or land
depressions are present.* Area fill landfill ing accommodates large
operations and is advantageous where groundwater conditions or soil depth
do not allow excavation.54 However, cover material is not always readily
available, and drainage problems may require expensive liners.55
Landfilling methods combining the trench and area fill methods provide
the flexibility to adapt site construction to the particular needs of a
community. The "progressive slope" or "progressive ramp" method is one
system where soil is excavated directly adjacent to the working face and
spread over one day's waste. The remaining depression is then filled with
the next day's waste, which is covered with soil from another adjacent
excavation, and so on. The progressive slope method eliminates the need to
import cover material, while allowing a portion of the discarded waste to
be deposited below the original surface.
8.2.2.1 Environmental effects of landfills. The principal
environmental concern when constructing and operating a landfill is the
formation of highly contaminated leachate that can be discharged into
surface water or groundwater. This leachate forms when precipitation or
groundwater passes through the landfill or when water drains from discarded
solid waste. EPA tests of leachate from municipal landfills have detected
high concentrations of contamination by volatile organic chemicals (VOCs),
acid organics, and base-neutral organics. Contamination by polychlorinated
biphenyls (PCBs) and chlorinated pesticides was also found, but with less
frequency.56 The EPA estimated in«-1987 that only 36% of landfills monitor
groundwater near landfills and only 15% monitor for surface water contami-
nation. However, only 2% of active landfills have ever been found to be a
source of groundwater contamination.57
*A variation of the area fill method is the "ramp" method. With the ramp
method solid waste is spread and compacted on a slope. Cover material is
obtained from directly in front of the working face and compacted on the
waste.53
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The most effective way to limit the harmful effect of leachate is to
prevent its formation. Leachate generation can be limited by controlling
the movement of water through the landfill cover and into the waste.
Promoting runoff of precipitation and evaporation of water from cover
material reduces the generation of leachate. This is usually accomplished
by using soil with low permeabilities as cover material and increasing the
slope of the landfill surface. Membrane or other nonsoil covers are used
in areas where appropriate soil materials are unavailable or extraordinary
environmental conditions exist.58
If hydrogeologic conditions indicate that leachate generation will
cause harm to surrounding water resources, it becomes necessary to install
a liner and possibly a leachate collection system. A properly designed
liner will effectively limit the movement of leachate contaminants through
the base of the landfill and into the underlying geologic formations.
Liners may either physically prevent leachate movement or chemically remove
contaminants from water that travels through the liner. At the same time
the liner must withstand chemical and physical attacks from the decaying
waste.
Liner composition may be of natural or synthetic materials. Common
liner materials include:
compacted soils and clays,
admixes such as asphalt concrete or soil cement,
polymeric membranes such as rubber and plastic sheetings,
sprayed on linings,
soil sealants, and
chemisorptive liners.59
The EPA estimates that 60% of active landfills employ liners in leachate
management. Approximately 87% of landfills with liners use a clay or soil
material.60
Leachate usually accumulates in the bottom of lined landfills. If the
leachate is not removed, pressure will build at low points in the liner
possibly resulting in a discharge around the liner onto the ground surface.
If the pressure builds to a very high level, the liner may become damaged
and allow leachate to pass. To prevent such discharges, leachate collec-
tion systems hydraulically pipe leachate to the surface for treatment and
8-18
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disposal. Treatment of leachate may include: recirculation back into the
landfill, physical or chemical treatment, land disposal, or discharge to a
sewer or surface water.61 The EPA estimates that only 12% of active
landfill units have leachate collection and treatment systems.62
A second environmental concern posed by landfills is the formation and
release of methane gas. Decomposition of MSW begins immediately upon
placement in a landfill. Initially, aerobic decomposition occurs and
carbon dioxide gas is generated. This decomposition by bacteria begins
after the supply of oxygen is depleted. This decomposition generates
methane gas, which can continue for many years after landfill closure. The
generation of methane gas at landfills is potentially dangerous because
methane gas
• Is explosive in high concentrations,
• Can asphyxiate people and animals, and
• Kills vegetation as it passes through soil.63
Methane gas is recovered either with the use of gas recovery wells or
passive venting systems. Methane gas may be burned off in flares
immediately after collection, or the considerable energy content may be
recovered. As discussed in Chapter 4, energy may be recovered from
landfill gas in several ways, including:
• Upgrading gas to pipeline quality for delivery through natural
gas distribution systems,
• Using gas as a boiler fuel to generate steam, and
• Generating electricity from the combustion of gas.64
The Public Utilities Regulatory Policies Act of 1978 (PURPA) provides
significant incentives to recover energy from methane gas by requiring
electric utilities to purchase electricity from small power producers such
as landfills.65 However, the EPA estimated in 1986 that only 7% of
landfills monitored for methane gas and only 2% operated a gas recovery
system.66
Proper closure of landfills is necessary once they are filled. Land-
fill closure typically involves installation of a final landfill cover or
cap limiting the entry of water in order to control leachate generation.67
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After closure, landfill sites have many potential uses ranging from golf
courses to sites for commercial buildings. For example, Denver, Colorado's
Mile High Stadium is constructed on a former landfill site.68 However,
long-term care of landfill sites may continue for an additional 20 to 30
years after closure under current conditions. Gas or leachate may migrate
from the landfill if control mechanisms fail or were not installed.
Monitoring for contamination and remedial action may be necessary. Simi-
larly, inspections of the landfill cover and possible regrading to prevent
ponding may be required.69
8.2.2.2 Ownership and Jurisdictions Served. Waste disposal sites,
especially landfills, are likely to be owned and operated by public
entities. Government institutions also play a large role in regulating the
disposal of MSW. Local communities, in particular, often take the lead in
MSW management. Many factors justify their interest, including concerns
that: MSW may pose a threat to the public health, improperly disposed
waste may result in adverse environmental impacts, and problems such as
noise, traffic, and odor may result from the disposal of MSW. Municipal
officials often believe that owning and operating landfills provide them
with the necessary control over these factors.70
Figure 8-8 shows that over 85% of municipal landfills are publicly
owned. The most common owners of landfill facilities are county and city
governments, who together own nearly 60% of all landfills. The federal
government owns 3% of existing landfills, which are mainly facilities on
military installations. State governments own less than one percent of
landfills. Less than 15% of landfills are owned by private entities.
Economies of scale exist in landfill ing MSW, making the unit costs of
operating small landfills relatively high compared to larger landfills.
Consequently, it is usually not profitable for private waste disposal firms
to operate small landfills. Figure 8-9 shows the ownership of landfills by
size. Not surprisingly, large landfills are more likely to be privately
owned than small landfills. About 32% of landfills receiving more than 180
thousand Mg of MSW per year are privately owned while nearly 90% of land-
fills receiving less than 900 Mg of waste per year are publicly owned.7^
Similarly, the median annual quantity of waste received is approximately
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Federal Government (3%) State Government (<1%)
Private (14%)
Other Local
Governments (25%)
County Governments
(29%)
City Governments
(28%)
Figure 8-8. Ownership of municipal landfills.71
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1,596
Number
of 800
Landfills
Publicly Owned
Privately Owned
Unknown
<0.9 0.9 to 9 9 to 45 45 to 90 90 to 180
Annual Quantity of MSW Received (103 Mg)
35
>180
Figure 8-9. Ownership of landfills by size.72
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7,000 Mg for publicly owned landfills and approximately 41,000 Mg for
privately owned landfills.74
Landfills typically serve specific jurisdictions (see Figure 8-10).
According to the EPA survey of municipal landfills about 77% of landfills
serve specific jurisdictions. However, landfills may serve multiple
jurisdictions. The actual number of jurisdictions served by landfills
varies widely. While the average landfill serves only three jurisdictions,
one landfill facility reported receiving waste from 53 specific
jurisdictions.76
8.2.3 Costs of Municipal Solid Waste Landfill ing
Landfill costs are frequently divided into five major categories:77
pre-development,
construction,
operating,
closure, and
long-term care.
Pre-development costs include the costs associated with investigating
available landfill sites and assessing their suitability. Pre-development
costs generally represent less than 10% of total landfill site development
costs and include expenditures associated with
• land acquisition,
• preliminary site engineering,
• preliminary legal services, and
• licensing and permit review.
Pre-development costs vary widely because of differences in land
costs, state regulations, and the level of MSW management services desired.
Land costs depend on the local real estate markets, the amount of land
required, and the land's proximity to urban areas. As NIMBY attitudes
toward landfills have increased, less expensive land farther from cities
has been purchased. However, increasing transportation costs associated
with higher fuel prices place limits on the distance that waste may reason-
ably be hauled. Similarly, engineering and legal costs have increased as
state permitting processes have become increasingly complex.7^
Landfill site construction costs include the major up-front expendi-
tures and all construction costs throughout the life of the facility.
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Serve Any Jurisdictions
(23%)
Serve Specific Jurisdictions
(77%)
Figure 8-10. Jurisdiction limitations of municipal landfills.75
8-24
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Landfill construction costs typically represent 25% to 35% of total
landfill costs and include the costs of
excavation and soil placement,
1iner construction,
leachate collection system,
surface water drainage controls,
gas venting and/or collection system,
facilities (.buildings, etc.), and
site-access (roads, etc.).79
Typically, costs associated with liner construction account for about 60%
of construction costs. Therefore, a major factor in determining landfill
construction costs is the type of liner design used. Other factors
influencing construction costs include local economic conditions, haul
distances for construction materials, and time of year.80
Operating costs represent the greatest portion of landfill costs.
Operating costs typically represent 40% to 50% of total landfill costs and
include expenditures associated with
• environmental monitoring (leachate, groundwater, surface water,
landfill gas, and air emissions),
maintenance,
labor,
utilities,
administrative costs, and
fuel for machinery.
Operating costs vary widely between landfills because of large differences
in environmental monitoring. Landfills using "state-of-the-art" monitoring
and collection systems are significantly more costly to operate than
landfills incorporating older technologies.81
Closure costs typically represent the smallest share of total landfill
costs. Depending upon the complexity of closure operations, costs usually
range from 1% to 5% of total landfill costs. Closure costs include the
costs of
• placing the final cover or cap on the landfill site,
• installing gas venting or collection systems, and
• documenting that the site has been properly closed.
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Long-term care includes actions required by federal and state
regulations to ensure that closed landfills present no danger to public
health and safety. The costs of long-term landfill care can range from 10
to 15% of total landfill costs and include the costs of
• environmental monitoring,
» leachate treatment, and
• land surface care to ensure proper drainage of surface water.82
Landfill costs vary widely depending on the amount of waste disposed.
Table 8-2 presents the unit costs of municipal solid waste landfills.
These costs combine capital and operating costs into a single unit cost
value. The costs suggest that significant economies of scale (unit costs
decrease with increasing production) exist in landfill ing MSW, as noted
above. For example, MSW disposal costs $92.20/Mg of waste in a 10 Mg/day
private landfill while disposal costs are only $10.60/Mg at a private
landfill when waste input is 1,360 Mg/day.*
Ultimately, the costs of developing and operating municipal solid
waste landfills are covered by user ("tipping") fees, general tax revenues,
or a combination of the two.f The use of taxes as a revenue source rather
than tipping fees has implications on waste disposal services. First, when
disposal costs are included in taxes, most people are not aware of the
actual costs involved.84 without an effective mechanism for transmitting
cost information, waste generators have no incentive to reduce their
generation rates. Second, tax-supported facilities are typically
underfunded relative to actual disposal costs, resulting in poorer
operation than fully funded landfills supported by tipping fees.85
*Differences in the disposal costs at public and private landfills of the
same size are attributable to differences in the interest rates available
to public and private entities for financing capital expenditures. This is
discussed in more detail in Section 8.3.3.
flnitial development costs are usually financed by borrowing money
(either through selling bonds or loans). Eventually, the borrowed money
is repaid with revenues from tipping fees, general tax revenues, or a
combination of the two.
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TABLE 8-2. DISPOSAL COSTS PER Mg MSW AT LANDFILLS OF VARIOUS
SIZES"
Disposal costs for Disposal costs for
MSW accepted public owners private owners
(Mg/day) (Mg/yr) ($/Mg) ($/Mg)
10
25
70
160
340
680
1,360
2,360
5,900
17,700
41,300
88,400
177,000
354,000
71.90
43.80
31.00
16.70
10.80
7.97
7.83
92.20
58.20
40.90
22.20
14.50
10.70
10.60
Docs not include Subtitle D costs.
8-27
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Figure 8-11 shows the methods of generating revenues for municipal
landfills. Approximately 30% of landfills receive all their revenues from
tipping fees, and approximately 35% of landfills receive all their revenues
from taxes. The remaining 35% of landfills cover the costs of waste
disposal through a combination of tipping fees and taxes.8?
Factors that influence the choice of revenue sources include landfill
size and ownership. Figure 8-12 illustrates the percentage of landfills
receiving 80% or more of their revenues from taxes and tipping-fees
relative to quantity of waste received. Landfills receiving small
quantities of waste are likely to rely heavily on taxes for their revenue
while larger landfills rely on both taxes and tipping fees.89
Not surprisingly, private owners of landfills rely heavily on tipping-
fees relative to other owners of landfills (see Figure 8-13). However,
private owners also tend to own larger landfills. It remains unclear
whether private landfills rely on tipping fees because they are larger, or
larger landfills rely heavily on tipping fees because they are private.91
According to the National Solid Waste Management Association, the
average tipping fee charged by landfills in 1988 was $29.69 per Mg.92 This
fee is more than twice the average fee charged in 1986.* Although the
increase is a reflection of increasing land disposal costs, a distinction
must be drawn between tipping fees and the actual costs of landfilling.
Communities often set tipping fees to cover current operating costs without
regard to amortization of capital expenditures (capital equipment, land,
closure, and long-term care costs). Similarly, the cost of disposal for
the 35% of landfills supplementing tipping-fee revenues with taxes is
usually much higher than the fee charged.93
Inefficient landfill pricing may be a major cause of current MSW
disposal capacity problems. Dunbar and Berkman94 and Crew and
Kleindorfer95 claim that tipping fees set below the full marginal cost to
society of waste disposal have resulted in waste generation rates greater
than if tipping fees equalled marginal cost, because recycling and
conservation are rejected in favor of artificially low cost landfilling.
*Much of the large increase is a result of the addition of sites in the
Northeast with high tipping fees.
8-28
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Tipping Fees
Exclusively (30%)
Tipping Fees and
Taxes (35%)
Taxes Exclusively
(35%)
Figure 8*11. Methods of financing municipal solid waste landflll|ng{86
8-29
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over 80% of Revenue
Tipping Fees over 80% of Revenues
75 175 375
Quantity of Waste Received per Day (Mg;
750
Figure 8-12. Revenua sourcos for landfill operations by size.88
1500
8-30
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Landfills Receiving
Over 80% of
Revenues from
Tipping Fees
Privatt City Federal State County Other Local
Government Government Government Government Government
Figure 8-13. Revenue sources for landfill operations by ownership.90
8-31
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Tipping fees lower than marginal social cost have also discouraged private
efforts to expand disposal capacity, because of competition from subsidized
public landfills.
In addition to tax subsidies, tipping fees do not cover the actual
costs to society of disposal because landfill costs usually do no include
three important social costs:
• Depletion costs of existing landfills (discounted present value
of the difference in landfill costs today and the future costs of
a replacement landfill),
• Opportunity costs of land used in landfills, and
• Environmental costs (risk of environmental damage from land-?
fills).
Dunbar and Berkman argue that excluding such costs has contributed to the
current crisis in MSW management in major Northeast metropolitan areas.96
8.2.4 Changing Regulatory Environment
As the public has become aware of the potential health, safety, and
environmental impacts of solid waste management, opposition toward.land-
fill ing has increased and a NIMBY attitude toward landfills has become
prevalent. Public awareness and concern about the potential impacts of
landfilling have placed significant new pressures on state and federal
legislators to strengthen regulations on solid waste disposal. As a
result, the regulatory environment surrounding landfilling is becoming
increasingly stringent, making it a less attractive waste disposal option.
8.2.4.1 Recent and Proposed State Regulations. The pressures of
increasing population density, decreasing landfill capacity, and NIMBY
attitudes toward MSW management most strongly influence state and local
officials. Hence, the cnanging regulatory environment is most evident at
the state level. In 1988 alone, 24 states enacted legislation substan-
tially changing the manner in wh.ich MSW is managed.97
In recent years, recycling has dominated municipal solid waste legis-
lation. Ten states had mandatory source separation laws by January 1989
with more states expected to follow.98 one of the most comprehensive
source separation program was enacted in New Jersey in 1980. The program's
goal was to extend the life of existing landfills by recycling 25% of the
municipal solid waste stream by 1986.99
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Many other states have enacted similar laws encouraging materials
recovery. The most common laws establish goal-oriented source reduction
programs. Other laws encourage recycling by imposing surcharges on all
waste entering landfills or by offering low-interest loans to institutions
establishing recycling programs.100
States are also moving quickly to establish stringent requirements on
landfill construction and operation. Conditions in some states have become
regulated to the point that siting new landfills is characterized by some
officials as "looking for a needle in a haystack."101 Examples of state
landfill regulatory conditions include:
Connecticut - Stringency of landfill regulations has prevented new
municipal solid waste landfill sitings since 1978.102
Florida - New landfill laws require trained operators, liners,
leachate collection systems, groundwater monitoring, and
closure plans.103
New York - Landfill design regulations require double composite
liners, groundwater monitoring, and leachate collection
systems. The rules are considered much more stringent
than proposed federal regulations.104
Pennsylvania - New regulations require mini-wastewater treatment plants
for leachate management, double liners, and liability
insurance. The National Solid Waste Management
Association expects the new requirements to force
closure of many facilities.105
Virginia - New landfill regulations require double-synthetic
liners, groundwater monitoring, and leachate
col lection.106
8.2.4.2 Forthcoming Federal Regulations. Pressures for more
stringent landfill regulations have also been felt at the federal level. *
EPA is currently developing a regulatory program for municipal solid waste
landfills under both the Resource Conservation and Recovery Act and the
Clean Air Act.
Clean Air Act Regulations and Standards
As explained in this document, EPA's Office of Air Quality Planning
and Standards is developing air emissions for closed/existing and new
municipal landfills under §lll(d) and §lll(b) of the Clean Air Act (CAA).
8-33
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EPA has scheduled proposal of these regulations for 1990. The CAA regula-
tions will limit air emissions of nonmethane organic compounds, air toxics,
odors, carbon dioxide, methane, and other explosive gases from landfills.
The regulations will require the active collection and disposal of air
emissions.
Resource Conservation and Recovery Act Regulations
Subtitle D of the Resource Conservation and Recovery Act (RCRA) regu-
lates municipal solid waste landfills. EPA initially issued criteria for
landfills in 1979 that prohibit
operating a landfill in a floodplain,
harming endangered species,
discharging wastewater without permits,
contaminating groundwater,
open burning of waste, and
failing to control disease vectors (i.e., rats).
The 1984 Hazardous and So-lid Waste Amendments to RCRA directed EPA to
revise these initial landfill criteria to further protect the public health
and the environment. The EPA is currently considering new rules regulating
the siting, operation, closure, and post-closure of landfill facilities. 107
The rules under consideration restrict the location of new and existing
landfills near airports, floodplains, wetlands, fault areas, seismic impact
zones, and other unstable areas.
The Subtitle D rules under consideration also impose numerous design
and operating criteria on landfills. In many cases, they would signifi-
cantly change the manner in which landfills operate. They would require:
daily cover of waste,
control of disease-vector populations,
monitoring for explosive gasses in facility structures, *
limiting public access to landfill sites,
eliminating surface water discharge,
run-on/run-off water controls,
extensive record keeping, and
eliminating leachate recirculation.
Furthermore, the Subtitle D rules under consideration would require a
program to detect and prevent the disposal of the following wastes:
• regulated hazardous wastes
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• polychlorinated biphenyls (PCBs), and
• bulk and noncontainerized liquids, and containers holding free
liquids (unless the liquids are household or septic wastes).
The Subtitle D rules under consideration would also impose extensive
new post-closure requirements on landfill owners. Particularly, they would
require landfill owners to develop a long-term care plan with a minimum
scope of 30 years requiring maintenance and operation of:
• leachate collection systems,
• groundwater monitoring systems,
• final covers, and
• gas monitoring systems.
In addition to more stringent siting, operating, and closure criteria,
the rules under consideration would include new groundwater monitoring and
corrective action requirements. Furthermore, owners and operators would
need to demonstrate the ability to finance closure, long-term care, and any
potential corrective action of known contamination.108
In conclusion, the new Subtitle D rules under consideration would
impose significant new costs on landfill operations. Table 8-3 shows esti-
mates of the costs of the rules on landfills of different sizes. Increases
in landfill costs will range from 20 to 40 percent due to the Subtitle D
requirements. Not surprisingly, many landfill facilities are expected to
close after promulgation of the new rules.
8.2.5 Future Prospects for Municipal Solid Haste Landfill ing
Rising costs and increasingly stringent regulations have resulted in
many landfill closures. Between 1978 and 1988, an estimated 14,000 land-
fills, or 70% of landfills operating in 1978 closed. In addition, EPA
estimates that one-half of all ^municipalities will run out of landfill
space in 10 years and that one-third will run out within 5 years.HO Table
8-4 presents the projected closures of existing landfills and the corres-
ponding change in MSW acceptance rate. In 1988, 5,499 landfills handled
187 million Mg of waste. EPA projects that existing landfills still oper-
ating in 2013 will only accept 19 million Mg of MSW.1^
While many landfills have closed in recent years, the number of new
facilities opening has experienced a rapid decline. Specifically, the
number of facilities opening each year has declined from between 300 and
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TABLE 8-3. ESTIMATED RCRA SUBTITLE D COSTS TO LANDFILLS109
Subtitle D Subtitle D
criteria Cost increase criteria Cost increase
MSW accepted costs-public public owners costs-private private owners
(Mg/day) (Mg/yr) ($/Mg) (%) ($/Mg) (%)
10
25
70
160
340
680
1,360
2,360
5,900
17,700
41,300
88,400
177,000
354,000
18.50
12.90
7.89
5.98
4.33
2.85
2.82
25.7
23.3
25.5
35.8
40.1
35.8
36.0
23.80
17.70
10.40
7.96
5.84
3.83
3.82
25.8
29.6
25.4
35.9
40.3
35.8
36.0
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TABLE 8-4. ESTIMATED NUMBER AND ANNUAL ACCEPTANCE RATE OF
EXISTING MUNICIPAL LANDFILLS, 1988 TO 2013111
Number Annual quantity
of of waste received
Year landfills (106 Mg)
1988 5,499 170
1993 3,332 119
1998 2,720 85
2003 1,594 54
2008 1,234 32
2013 1,003 17
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400 per year in the early 1970s to between 50 and 200 in the late 1980s,
without any accompanying increase in landfill size. If current trends in
landfill development continue, only one-third of disappearing capacity will
be replaced.H3
Siting Difficulties
In most states, siting problems have been the major cause of
decreasing landfill capacity.114 Public opposition and a NIMBY attitude
are the major obstacles to successful siting of landfills and other waste
management facilities. Psychologists suggest that three main factors
contribute to the NIMBY syndrome:115
• public perceptions of landfills conflict with the "cleanliness
ethic" of most individuals,
• landfills may negatively influence the self-image of both the
individuals living nearby and their neighborhoods collectively,
and
• rural communities that manage their own wastes resent having MSW
forced onto them by urban communities who are used to others
managing their waste.
Economics also play an important role in landfill siting. A common
objection to landfill siting is the impact on the value of nearby
properties. Although a 1972 study conducted for the EPA concluded that
solid waste disposal sites have no apparent negative effect on property
values, other studies have suggested that neighboring properties may
experience as much as a 25% reduction in value. 11(>
Landfill siting and development problems are most acute in the
%
Northeast. Landfill problems in specific states include:
Connecticut - No new landfills have been sited since 1978,
New Jersey - Landfill shortages have transformed the state into a net
exporter of municipal solid waste (MSW exported exceeds
MSW disposed inside the state),
Pennsylvania - Cannot find a replacement site for 4,500 Mg/day
(approximately 0.6 percent of total national capacity)
landfill in Scranton that closed in 1987, ^7 and
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New York - Unable to site a replacement facility for 24,500 Mg/day
(over 3% of total national capacity) landfill in Staten
Island that is expected to close within 5 years.
Proposals to replace this capacity with combustors are
facing public opposition.! 18
However, the landfill capacity problems are not isolated to the Northeast.
For example, population growth in Florida indicates a need for an
additional 2,700 acres of landfill area annually through 1995. A recent
survey of state solid waste management offices by the Association of State
and Territorial Solid Waste Management Officials found only four states
reporting no capacity problems: Kansas, Nevada, North Dakota, and South
Dakota.H9
Although public opposition in many areas has prevented development of
new landfills, several states have experienced success at landfill siting.
A survey by the NSWMA identified successful state landfill siting programs
in Wisconsin and Delaware.120
Wisconsin's landfill siting program is perhaps the most successful.
Under the program landfills are being sited at a rate of 10 to 20 per year,
making most capacity problems short-term.121 Wisconsin's program divides
the siting process into two steps:
(1) The landfill application is reviewed by the state's Department of
Natural Resources for feasibility, necessity, and regulatory
compliance, and
(2) After DNR approval and determination of need, other matters
(including compensation) are negotiated between the landfill
developer and "affected local community".122
Wisconsin's siting program is successful for two reasons: (1) the program
limits the number of points in the process where a siting can be stopped
and the number of reasons why a siting can be stopped; and (2) the program
allows for negotiation of almost any characteristic of the landfill short
of blocking its development.123
Delaware has created the Delaware Solid Waste Authority (DSWA), a
government entity charged with siting new landfills. Although the program
is criticized for limiting private participation, the program has success-
fully overcome political pressures and NIMBY attitudes. In the past five
years, the DSWA has sited three new landfills (one for each county in the
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state) and a combustor. Landfill capacity for each county is now
sufficient for an estimated 30 to 40 years.124
Decreasing landfill capacity has made importing and exporting trash
between states and counties commonplace. For example, over one million
tons of MSW is imported and disposed in Ohio landfills. The quantity of
MSW exported from New Jersey actually exceeds the quantity of MSW managed
inside the state. In the face of landfill siting problems, states and
counties with diminishing landfill capacities are taking steps to keep
waste generated in other jurisdictions from crossing borders and being
disposed in their landfills. At least ten states have enacted legislation
limiting or prohibiting waste imports between states or counties:125
Arkansas
Georgia
Maryland
New York
Pennsylvania
Delaware
Kentucky
New Jersey
Ohio
Rhode Island
Various legislation has also been introduced in the U.S. Congress that
would ban the transport of waste across state lines or outside the United
States. The frequency of waste import bans have led some to observe that a
"garbage war exists between the states." Although the constitutionality of
waste import bans is questionable, they present serious interim problems
for states and counties with diminishing landfill capacity.126
Increasing Role of Transportation
Long-distance hauling of MSW has been a primary response to rising
landfill disposal costs and increasing public opposition to disposal
sites.127 Examples of municipalities that are required to transport waste
very long distances include:128,129(130
New York City - MSW is hauled 400 to 500 miles to Ohio and to upstate
New York,
Philadelphia - Hauls MSW hundreds of miles to upstate New York and
Ohio. Has $9 million contract to ship MWC ash to
Panama,
Newark, NJ - Faced with a 400% increase in disposal costs, MSW is
hauled to Pennsylvania and upstate New York,
Portland, OR - Preparing to haul MSW by truck, rail, and barge to a
landfill 140 miles away in eastern Oregon,
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Boston - Hauls MSW over 100 miles to upstate New York.
Hauling MSW long distances can substantially increase MSW disposal
costs. For example, Waste Management Inc. estimates that the cost of
transporting MSW from New York or Philadelphia to an upstate New York
landfill could be as high as $880 ($44/Mg) for a tractor trailer carrying
20 Mg of MSW.131 This value for transportation costs alone is substan-
tially more than the national average for tipping fees charged at land-
fills. As less expensive landfills near generators continue to close,
expensive long-distance hauls of MSW are likely to become commonplace,
resulting in tremendous increases in waste disposal expenditures.
Trend Toward Municipal Waste Combustion
The growing shortage of landfill space and rising landfill costs have
forced municipal planners to consider alternative waste management options.
Materials recovery is usually viewed as an attractive option because it
increases the life of existing landfills by diverting potentially large
quantities of spent materials into reuse.132 Materials recovery also slows
the depletion of natural resources and removes toxic materials from the
waste stream prior to disposal, enhancing the safety of landfill ing and
combustion.133
However, most attention toward alternatives to landfilling has been
given to municipal waste combustion (MWC). As noted earlier, municipal
waste combustion is the process of reducing the volume of MSW through
incineration. Combustion of MSW is attractive because it reduces waste
^
volume by as much as 90%. Therefore, many municipal planners view MWC as
an important means of extending the lives of existing landfills and
reducing the need for additional landfill capacity.
Table 8-5 presents the historical and projected shares of MSW managed
in MWCs from 1960 to 2000. In 1960 the entire municipal solid waste stream
was either landfilled or recycled; no waste was incinerated. By 1986, the
quantity of MSW incinerated in municipal waste combustors had risen to six
percent of the total waste stream. Franklin Associates projects that by
the year 2000 about 17% of the MSW stream will be incinerated.
However, municipal waste combustion has many problems similar to
landfilling. MWC siting problems have been significant and have prevented
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TABLE 8-5. HISTORICAL AND PROJECTED SHARES OF MUNICIPAL SOLID
WASTE MANAGED IN MUNICIPAL WASTE COMBUSTORS134
Year
1960
1965
1970
1975
1980
1981
1982
1983
1984
1985
1986
1990*
1995a
2000a
Gross discards
of MSW
(106Mg)
79.4
92.8
109.3
113.6
129.4
. 131.3
128.8
134.6
139.3
138.3
143.0
151.8
163.4
174.8
Combustion
of MSW
(10<»Mg)
0.0
0.2
0.4
0.6
2.4
2.1
3.2
4.5
5.9
6.9
8.7
12.1
20.4
29.0
Share of
gross discards
(%)
0.0
0.2
0.4
0.5
1.9
1.6
2.5
3.3
4.2
5.0
6.1
8.0
12.5
16.6
aPrqjection.
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siting in several locations. 135 Additionally, the EPA is considering new
air emission regulations that would significantly increase the capital and
operating costs of municipal waste combustion.136 Similarly, legislation
has been introduced in the U.S. Congress that would require ash from MWCs
to be treated as hazardous waste and disposed in hazardous waste
landfilIs.13/ According to a Kidder Peabody report, more MWC capacity was
canceled than was ordered in 1987, resulting in a 10% decline in projected
capacity.138
8.3 REGULATORY ALTERNATIVES AND CONTROL OPTIONS
8.3.1 Regulatory Alternatives
As explained in detail in Chapter 5, EPA is considering regulatory
alternatives for controlling air emissions from two types of municipal
solid waste landfills: closed/existing landfills and new landfills. EPA
will control emissions from closed/existing landfills under the guidelines
of §lll(d) of the Clean Air Act (CAA) and will regulate emissions from new
landfills under CAA §lll(b).
EPA will require closed/existing and new landfills to install and
operate emissions controls as long as their annual nonmethane organic
compound (NMOC) emission rates exceed a specified cutoff level. In other
words, landfills must install emission controls once NMOC emissions reach a
specified cutoff level, and they must continue controlling NMOC emissions
until they drop below the specified cutoff, which may be many years after
closure. EPA is evaluating three possible cutoff levels for NMOC emissions
from closed/existing and new landfills: 25, 100, and 250 Mg of NMOC per
year. The 25 Mg NMOC/yr cutoff level is the most stringent, while the 250
Mg NMOC/yr is the least stringent, because the former requires emissions
controls for lower levels of emissions than the latter.
8.3.2 Emissions Control Options
Chapter 4 describes the two basic emissions control approaches for
landfills: combustion without energy recovery (i.e., flares) and energy
recovery (mainly involving the combustion of the landfill gas to produce
steam or electricity). For simplicity, we refer to these two control
approaches as the flare option and the energy recovery option. So
landfills exceeding specified NMOC emission rates will have a choice
8-43
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between the flare option or the energy recovery option for controlling
emissions. The remainder of this chapter emphasizes the economic impacts
of the various NMOC stringency levels assuming that all affected landfills
choose the flare option. However, we also discuss some of the economic
impacts of the energy recovery option. Appendix F contains the tables
evaluating the energy recovery option.
The assumption that all affected landfills choose the flare option
results in overestimates of the actual costs of the regulatory alternatives
for two reasons. First, the affected landfills that would have installed
energy recovery equipment in the absence of EPA emissions regulations
should be excluded from cost estimates for such regulations. Second, it
will be cheaper for some of the other affected landfills to install energy
recovery equipment rather than flares, because the revenues from energy
recovery will exceed the extra cost of the energy recovery equipment. So
the costs of the flare option will overestimate the costs actually incurred
at these landfills. These two reasons are discussed in more detail below.
As indicated in Section 8.2, some landfills in recent years have
installed energy recovery equipment in the absence of EPA emissions
regulations, because they expect the revenues from the sale of electricity
(or steam or medium/high Btu gas) to exceed the cost of the energy
recovery. In other words, these landfills expect their energy recovery
efforts to make a profit. Presumably, some landfills in the future would
have also installed energy recovery equipment in the absence of EPA
regulations. Theoretically, these landfills would be excluded from the
group of landfills affected by EPA's emissions control regulations, because
they would be controlling their emissions in the absence of such-
regulations. So neither the flare costs nor the NMOC emission reductions
at these landfills should be attributed to the EPA emissions regulations.
There is no way to precisely determine which landfills would have
installed energy recovery equipment in the absence of EPA emissions
regulations. First, the acceptance of new technologies (such as energy
recovery from landfill gas) often spreads slowly. Consequently, some
landfills that would profit from energy recovery may not choose this option
as a result of a general aversion to new technologies. Second, energy
8-44
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recovery requires more capital equipment than flaring landfill gases.
Since revenues from energy recovery involve some uncertainty, some landfill
owners may have difficulty getting the additional capital required for
energy recovery, or they may not want to risk the additional capital on
this option. Finally, landfill gas generation rates depend on factors such
as the amount and composition of MSW going into landfills over time and
rainfall. The model in Chapter 7 assumes values for many of these factors.
To the extent that the actual values for these factors differ from the
assumed values, the model may overestimate or underestimate the profit-
ability of energy recovery at particular landfills. In these cases, the
model's predictions of which landfills will choose an energy recovery
option in the absence of EPA emissions regulations may not be accurate.
An EPA emissions regulation will probably stimulate the adoption of
energy recovery at some landfills, because such a regulation will lower the
cost of this option. In particular, evaluating the feasibility of energy
recovery requires costly information on the characteristics and flow of
landfill gases. The EPA regulatory alternatives under consideration will
require many landfills to test their landfill gases in order to determine
the need for controlling NMOC emissions. Thus, many landfills will have to
collect the landfill gas information that is needed to evaluate the energy
recovery option. Furthermore, the flare and energy recovery options can
use the same wells and collection system. Therefore, landfills that must
control their NMOC emissions will need to install wells and a collection
system that they could also use for energy recovery. Having already
incurred the costs of getting information on landfills gases and installing
wells and a collection system, the additional costs of the energy recovery
option are relatively small. Thus, some (possibly many) landfills will
choose an energy recovery option that would not have chosen this option in
the absence of the EPA regulation.
For our analysis of the energy recovery option, we assume that
landfills showing a profit from energy recovery (based on the model
described in Chapter 7) would have installed energy recovery equipment in
the absence of EPA emissions regulations. Furthermore, we also assume that
the landfills that will not make a profit from energy recovery will select
8-45
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the least-cost emissions control option/ In some cases the flare option
will have the lowest cost, while in other cases the revenues from energy
recovery will result in the energy recovery option having a lower net cost
than the flare option. In summary, our energy recovery option reports the
cost-minimizing control option (either flares or energy recovery) only for
landfills with energy recovery costs that exceed energy recovery revenues
(i.e., landfills with positive energy recovery costs).
In conclusion, the flare option overestimates the actual cost of the
regulatory alternatives, because some landfills will install cheaper
emissions controls voluntarily. On the other hand, the energy recovery
option will underestimate compliance costs when:
• landfills that would have implemented an energy recovery option
in the absence of EPA emissions regulations are required to
control their emissions longer than they would voluntarily (i.e.,
when the required emissions control period is longer than the
profit maximizing energy recovery period), and
• landfills that the model predicts would profit from energy
recovery decide to install flares (for reasons discussed above)
in order to comply with the EPA emissions regulation.
However, the energy recovery option will overestimate compliance costs at
landfills that select an energy recovery option as a result of the EPA
emissions regulation and make a profit, but would not have installed energy
recovery in the absence of EPA emissions regulations (because they did not
realize that they would profit from energy recovery, for example). The
aggregate result of these opposing tendencies is unknown.
8.3.3 Additional Assumptions and Their Implications
The model described in Chapter 7 has two features that lead to over-
estimates of the number of landfills affected by the §lll(d) and lll(b)
regulatory alternatives under consideration and the compliance costs and
emissions reductions at the affected landfills for each of the
alternatives. These features are:
• the model assumes that every landfill that closes after 1986 is
replaced by a landfill having identical characteristics, and
• the model uses data on individual landfills that overestimate the
total amount of MSW going to landfills each year.
We discuss each of these features below.
8-46
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As indicated in Section 8.2, over half of the 6,034 active landfills
in 1986 are expected to close by the year 1998. At the same time very few
new landfills are being developed (for reasons discussed previously).
Consequently, the total number of landfills in the United States is
declining. On the average, new landfills are not larger than the closing
landfills, so landfill capacity is also declining as the number of
landfills falls.
At the current time there is no method for predicting which landfills
that close will be replaced by new landfills. Furthermore, there is no
method for determining the characteristics of the replacement landfills
(such as their design capacity). Since the number and characteristics of
replacement (i.e., new) landfills are needed for the costing model in
Chapter 7, it is assumed that every landfill that closes between 1987 and
1997 is replaced by a landfill having identical characteristics to the
landfill that closed.* Since there will probably be fewer landfills, this
assumption tends to overestimate the number of landfills affected by the
regulatory alternatives under consideration. This leads to overestimating
the total cost of the regulatory alternatives.
In 1986 EPA's Office of Solid Waste (OSW) conducted a survey of
municipal landfills in the United States (as discussed above). This survey
obtained extensive information on the characteristics of landfills, such as
their design capacity, year of opening, anticipated year of closing, refuse
in place at the end of 1986, and the amount of MSW received in 1986. The
cost model in Chapter 7 uses data from the OSW landfills survey in deter-
mining which landfills are affected by the regulatory alternatives under
consideration and the compliance costs and emissions reductions for each
affected landfill for these alternatives. In particular, the amount of MSW
received in 1986 is an important variable in determining compliance costs
and emissions reductions.
*Landfills that close between 1987 and 1992 are categorized as "closed"
landfills. "Existing" landfills include landfills that will close some-
time after 1992 and landfills that replace landfills that close between
1987 and 1992. "New" landfills are landfills that replace landfills that
close between 1992 and 1997- See Chapter 3 for additional details on
these designations.
8-47
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The OSW landfills data were collected to evaluate regulatory alterna-
tives under Subtitle D of RCRA. There were two difficulties in using the
OSW landfills data to analyze control costs and emissions reductions for
CAA §lll(d) and lll(b) regulatory alternatives. One difficulty was the
conversion of cubic yards of MSW into tons. The other difficulty involved
differences in historical MSW acceptance rates and the 1986 acceptance
rate. The resolution of these difficulties resulted in MSW acceptance
rates that are useful on an individual landfill basis but substantially
overestimate national MSW generation.
In conclusion, the two factors just discussed lead to overestimates of
the number of landfills affected by the §lll(d) and lll(b) regulatory
alternatives under consideration and overestimates of the national costs
and emissions reductions of controls at these affected landfills. So the
actual economic impacts of these regulatory alternatives will probably be
less than the economic impacts described in the remainder of this chapter.
Two other assumptions underlying the economic analysis of the regula-
tory alternatives under consideration are noteworthy. First, we assume
that different discount rates are appropriate for publicly owned landfills
and privately owned landfills when evaluating the costs of emissions con-
trols from the perspective of landfill owners, which we designate as enter-
prise costs. As explained in detail in Appendix A of Morris et al., expen-
ditures by public entities have a lower opportunity cost than expenditures
by private entities.139 jn particular, we use a 4% discount rate for the
capital and operating costs of compliance for publicly owned landfills and
a 8% discount rate for compliance costs at privately owned landfills. This
results in publicly owned landfills having a higher net present value of
enterprise costs than privately owned landfills for the same stream of com-
pliance costs over the same time period.
Following recent EPA guidelines, we use a 2-stage discounting approach
for calculating compliance costs from a social perspective. Under this
approach capital costs are annualized over the years that controls are
operated (i.e., the control period) using a 10% rate for all landfills (re-
gardless of ownership). Then the resulting annualized capital costs and
the annual operating costs for all landfills are discounted using a 3%
8-48
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rate. Kolb and Scheraga explain the rationale for calculating the social
costs of compliance using this 2-stage discounting approach.140
A second important assumption in the economic analysis is that pub-
licly owned landfills have more flexibility in generating the revenues to
pay for the capital and operating costs of emissions controls than pri-
vately owned landfills. Specifically, public entities can generate the
revenues for compliance costs by increasing taxes of various types or by
increasing user fees at the landfi-11 while it is still accepting MSW.
Alternatively, private landfills can only cover compliance costs by
increas-ing user fees during the landfill's operating life.*
The difference in public and private landfills regarding their ability
to generate the revenues for covering the costs of emissions controls has
important implications for the annualization period for such costs. In
particular, we annualize the enterprise costs for publicly owned landfills
over the control period. Even though the landfill will be closed during
some of the control period, the public entity that owns the landfill will
still be able to tax former users of the landfill (and possibly others) in
order to cover the compliance costs. Alternatively, we annualize enter-
prise costs for privately owned existing landfills over the period from
1992 (the anticipated promulgation date of the regulatory alternative
selected) to the landfill's closure date.f We assume that these landfills
must sufficiently increase user fees during this time period to cover
compliance costs over the entire control period (including the years after
closure). Thus, the necessary increase in user fees may be quite large
whenever compliance costs are relatively high and the number of years until
closure is relatively small.
*The difference in the ability of public versus private landfills to
generate revenues for compliance costs is particularly significant for
affected landfills that are closed before the regulations are promulgated.
Public entities that own a closed landfill can increase taxes on house-
holds and businesses that were previously served by the closed landfill in
order to pay for emissions controls. Owners of private landfills that are
closed have no way to generate revenues to cover the costs of emissions
controls.
fWe annualize enterprise costs for privately owned new landfills over the
entire operating life of these landfills.
8-49
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8.4 ANALYSIS OF ECONOMIC IMPACTS
As described in Section 8.3, the EPA is considering regulatory alter-
natives for controlling air emissions from both closed/existing landfills
and new landfills. Section 8.4 first discusses the economic impacts of the
three possible nonmethane organic compound (NMOC) emissions level cutoffs
under the Guidelines of §lll(d) of the Clean Air Act (CAAj. Then, this
section discusses the economic impacts of proposed regulations under the
Standards of CAA §111(b) for the same three possible NMOC emissions level
cutoffs. In evaluating the impacts of controls under each section of the
CAA, we consider two basic control options: combustion without energy
recovery (the flare option), and energy recovery (the energy recovery
option).
As described above, increasing NMOC emissions cutoffs (i.e., 25 Mg
NMOC/yr, 100 Mg NMOC/yr, and 250 Mg NMOC/yr) represent decreasing levels of
stringency for the controls. Thus, for example, more landfills are
affected by each control option at the 25 Mg level than at the 100 Mg
level. Landfills will be required to operate controls in every year for
which their emissions level exceeds the chosen cutoff level. So some
landfills may need to operate controls for many years after closure, until
the NMOC emissions fall below the chosen cutoff level.
8.4.1 Section lll(d) Guidelines
Guidelines under §lll(d) of the CAA address existing sources of
emissions. In the case of landfills, these guidelines will apply to both
closed and existing landfills, since the level of NMOC emissions builds
throughout the active life of a landfill and continues after closure. As
indicated in Section 8.3, the model used to estimate emissions assumes that
each landfill that closes is replaced by another identical landfill serving
the same area.
We first characterize the landfills affected under each stringency
level for the flare option, then we address the economic impacts of the
stringency levels on affected landfills. Next, we examine the energy
recovery option, characterizing the affected landfills under each strin-
gency level and estimating the economic impacts of that option.
8.4.1.1 Flare Option. Under the flare option, landfills are assumed
to control their NMOC emissions by collecting the NMOCs and then burning
8-50
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them, with no provision for energy recovery. We assume that all landfills
generating NMOC emissions above a given stringency level are affected by
the §lll(d) Guideline. As mentioned above, three possible stringency
levels are being evaluated: 25 Mg NMOC/yr, 100 Mg NMOC/yr, and 250 Mg
NMOC/yr.
Of 7124 landfills (6034 existing landfills and 1090 closed landfills)
eligible for coverage under the §lll(d) Guidelines, between 5% and 26% of
the landfills would be affected, depending on the stringency level
selected. As indicated in Table 8-6, if the most stringent 25 Mg NMOC/yr
cutoff were selected, 1884 landfills would be affected. If the 100 Mg
NMOC/yr stringency level were selected, 853 landfills would be affected,
while only 386 landfills would be affected if the 250 Mg NMOC/yr stringency
level were selected.
In addition to the total number of affected landfills, Table 8-6 shows
a distribution of affected landfills by design capacity under each of the
possible stringency levels. Under the most stringent 25 Mg stringency
level, a larger proportion of the total number of affected landfills is
small (27% have less than 1 million Mg design capacity, 71% have less than
5 million Mg design capacity) than under the less stringent cutoff levels.
Only 16% of the affected landfills would have a design capacity below
1 million Mg under the 100 Mg stringency level, while only 6% would fall
into this smallest size category under the least stringent 250 Mg cutoff
level.
As mentioned above, some landfills will be required to operate emis-
sions controls for many years after they close. This is of particular
concern for private landfills, since increased user fees while they are
still active and accepting MSW are their only means of paying for the^e
controls. The bottom part of Table 8-6 shows the number of affected
privately owned landfills under each stringency level. The landfills
expected to have the greatest difficulty paying for the NMOC controls are
those which are privately owned and already closed. For these landfills,
there exists no possibility of recovering the costs of compliance through
increased user fees. As shown by the last line, 4% of the affected land-
fills under the most stringent 25 Mg level are privately owned closed
landfills. Under the 100 Mg stringency level, 6% of the affected landfills
8-51
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TABLE 8-6. SUMMARY INFORMATION FOR AFFECTED CLOSED AND EXISTING LANDFILLS
CO
on
ro
Number of affected landfills
(Percent of total closed and existing landfills)
Distribution of affected landfills
by design capacity
(K^Mg)
ItoS
5 to 10
>10
Total
Privately owned affected landfills
(Percent of affected landfills) v
Existing
Closed
25
1,884
(26)
514
(27)
837
(44)
295
(16)
238
(13)
1,884
(100)
406
(22)
334
72
Stringency Levels
(Mg NMOC/yr)
100
853
(12)
133
(16)
349
(41)
176
(21)
195
(23)
853
(100)
210
(25)
162
48
250
386
(5)
22
(6)
181
(47)
48
(12)
135
(35)
386
(100)
121
(31)
82
39
Note: The numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
are privately owned closed landfills, while under the 250 Mg level, 10% are
privately owned and closed.
As noted earlier, landfills will be required to operate emissions
controls as long as their NMOC emissions exceed the selected cutoff level.
In general, different landfills will reach a given emissions cutoff level
in different years. Similarly, the number of years that emissions will
exceed the cutoff level will vary from landfill to landfill, and therefore
the year that controls may be removed will vary from landfill to landfill.
Thus, the possible economic impacts of the emissions controls will be
incurred by various landfills during different time periods.
Table 8-7 depicts the distribution of the length of the control period
for affected closed and existing landfills under each of the three strin-
gency levels. In general, the control periods range from one to more than
277 years, with the maximum length of control period being slightly longer
as the stringency of control increases. The average length of control
period ranges from 66 years for the 100 Mg stringency level to 79 years for
the 25 Mg stringency level.
As mentioned above, the ease with which landfills will be able to
recapture the costs of installing and operating the controls will decrease
after the landfill closes. Until that time, the landfill may increase its
user fees to offset some of its increased costs. After closure, the public
owners of the landfill will have to find some other means of raising reve-
nues (such as taxes), while the private owners will not be able to raise
revenues at all. Private landfills must therefore increase user fees
sufficiently to offset all their control costs while the landfill is still
accepting MSW. Thus, the shorter the length of time between the start of
controls and landfill closure, the greater the financial burden of a given
control cost on a landfill, especially if it is privately owned.
Table 8-8 provides information about the length of control period
prior to closure for all affected closed and existing landfills, and 8-9
provides such information for privately owned affected landfills. The 22%
to 23% of affected landfills that are privately owned under the 25 Mg and
100 Mg stringency levels, respectively, have slightly longer control
periods prior to closure than the publicly owned affected landfills, while
the 27% of affected landfills which are privately owned under the 250 Mg
8-53
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TABLE 8-7. LENGTH OF CONTROL PERIOD FOR AFFECTED CLOSED AND EXISTING LANDFILLS
CD
tn
Average length of control period (years)
Distribution of affected landfills by
length of control period
(years)
*25
26 to 50
51 to 100
101 to 150
>150
Total
25
79.2
298
(16)
305
(16)
607
(32)
582
(31)
92
(5)
1,884
(100)
Stringency Levels
(Mg NMOC/yr)
100
66.3
244
(29)
165
(19)
229
(27)
157
(»8)
58
(7)
853
(100)
250
67.8
94
(24)
46
(12)
150
(39)
80
(21)
16
(4)
386
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding.
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TABLE 8-8. LENGTH OF CONTROL PERIOD PRIOR TO CLOSURE FOR AFFECTED EXISTING LANDFILLS
00
en
01
'
Average length of control period
prior to closure (years)
Distribution of affected landfills by
length of control period prior to closure
(years)
•y
£5
6 to 10
11 to 20
r
21 to 50
>50
Total
25
20.4
370
(24)
244
(16)
513
(34)
261
(17)
133
(9)
1,521
(100)
Stringency Levels
(Mg NMOC/yr)
100
17.7
239
(34)
99
(14)
227
(33)
63
(9)
70
(10)
698
(100)
250
19.7
94
(31)
29
(10)
106
(35)
41
(13)
32
(11)
302
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding. Excludes closed landfills.
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CD
tn
TABLE 8-9. LENGTH OF CONTROL PERIOD PRIOR TO CLOSURE FOR AFFECTED EXISTING
LANDFILLS: PRIVATE LANDFILLS ONLY
Stringency Levels
(Mg NMOC/yr)
25 100 250
Average length of control period 23.0 20.1 17.0
prior to closure (years)
Distribution of affected landfills by
length of control period prior to closure
(years)
*5 73
(22)
6 to 10 39
(ID
11 to 20 130
(39)
21 to 50 46
(14)
> 50 .46
(14)
Total 334
(100)
56
(35)
17
(10)
53
(33)
19
(12)
17
(10)
162
(100)
22
(27)
10
(12)
29
(35)
19
(23)
2
(3)
82
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding. Excludes closed landfills.
-------
stringency level have a slightly shorter control period prior to closure.
Of particular concern may be the privately owned landfills with ten years
or less between the imposition of controls and closure. These comprise 112
of the privately owned affected landfills under the 25 Mg stringency level,
73 under the 100 Mg stringency level, and 32 under the 250 Mg stringency
level.
One measure of the cost of complying with the regulatory alternatives
under consideration is the net present value of enterprise costs. This
measure, shown in Table 8-10, is computed by discounting the flow of
capital and operating costs to arrive at a measure of the current value of
the costs that will be incurred throughout the control periods for the
various landfills. Since most landfills will begin and end controls at
different times, using a net present value measure of costs is the appro-
priate way to compare costs between landfills.
As explained in Section 8.3, the interest rates faced by public owners
of landfills differ from those faced by private owners, so we discount the
stream of capital and operating costs using a different discount rate for
each ownership group. We discount the capital and operating costs incurred
by public landfill owners as a result of complying with the regulatory
alternatives under consideration using a 4% discount rate, while we
discount costs incurred by private landfill owners to their present value
using an 8% discount rate. Table 8-10 presents these costs, along with a
distribution of the number of affected landfills in several enterprise cost
categories for each of the three stringency levels.
The maximum net present value (NPV) of enterprise costs incurred by
any landfill is $61 million under the 25 Mg stringency level, $54 million
under the 100 Mg stringency level, and $51 million under the 250 Mg strin-
gency level. When summed across all landfills affected by controls under
each stringency level, the national total NPV of enterprise costs ranges
from $1.93 billion under the 250 Mg stringency level to $5.86 billion under
the 25 Mg stringency level (see Table 8-10). A larger proportion of
affected landfills incurs a relatively low NPV of enterprise costs ($3
million or less) under the 25 Mg level than under the 100 Mg level or the
250 Mg level. The mean NPV of enterprise costs per affected landfill under
the 250 Mg stringency level, $5.00 million, exceeds that for the other two
stringency levels.
8-57
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TABLE 8-10. NET PRESENT VALUE OF ENTERPRISE COSTS FOR AFFECTED CLOSED AND EXISTING
LANDFILLS
00
en
oc
Net Present Value
National enterprise costs ($10*0
Capital
Operating
Total
Average total enterprise cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of enterprise costs ($10^)
^OJ
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0
>10.0
Total
25
2,233
3,625
5^58
3.11
119
(6)
165
(9)
1,060
(56)
331
(18)
161
(8)
48
(3)
1,884
(100)
Stringency Levels
(Mg NMOC/yr)
100
1,618
2,015
3,634
4.26
60
(7)
90
(11)
341
(40)
205
(24)
111
(13)
46
(5)
853
(100)
250
871
1,058
1,929
5.00
15
(4)
19
(5)
169
(44)
101
(26)
53
(14)
29
(7)
386
(100)
Note: Numbers in parentheses are percentages. Net present value 01 enterprise cost is calculated using a 4 percent discount
rate for publicly owned landfills and an 8 percent discount rate for privately owned landfills. Details may not add to
totals due to rounding.
-------
Table 8-11 shows another measure of enterprise costs. The annualized
enterprise control cost per Mg of MSW for affected existing landfills is
computed based on each landfill's NPV of enterprise costs. These costs are
annualized using the following formula:
NPV enterprise costs
(1 - (l+r-rVr
where r is the interest rate and t is time.
The interest rate and the length of time over which costs are annual-
ized depend on the ownership of the landfill. As explained previously,
publicly owned landfills are annualized using a 4% interest rate over the
time period during which controls will be in place. Privately owned land-
fills, on the other hand, will not be able to recapture their compliance
costs after they stop accepting MSW. The enterprise costs for privately
owned landfills, therefore, are annualized over the period from 1992 until
the landfill closes, using an 8% interest rate.
To compute the annualized enterprise cost per Mg of MSW for affected
existing landfills, the annualized cost is divided by the quantity of waste
accepted by the landfill in 1986.* One measure of the average annualized
cost per Mg of waste accepted is the national annualized cost per Mg of
MSW, which is computed for each stringency level by summing the annualized
enterprise costs for all the affected landfills at that level, and then
dividing by the summed quantities of waste accepted by all the affected
landfills in 1986. The national average annualized costs per Mg of MSW at
each stringency level is less than $1 per Mg. These national annualized
costs per Mg of MSW range from $0.72/Mg at the 250 Mg stringency level to
$0.89/Mg at the 25 Mg level.
Table 8-11 also contains a frequency distribution of affected land-
fills by annualized cost per Mg of MSW accepted in 1986. The frequency
distribution indicates that the proportion of affected landfills incurring
annualized costs of $1.25 per Mg of MSW or less increases as the level of
stringency decreases. At the 25 Mg stringency level, about 45% of
*As noted in Section 8.3, the historical annual average amount of MSW
accepted by the landfill is substituted for the quantity of MSW received in
1986 for some landfills.
8-59
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TABLE 8-11. ANNUALIZED ENTERPRISE CONTROL COST PER Mg OF MSW FOR AFFECTED
EXISTING LANDFILLS
25
Stringency Level
(Mg NMOC/yr)
100
250
CO
en
o
National annualized cost per Mg MSW
($/MgMSW)
Distribution of affected landfills by
annualized cost per Mg MSW
($/MgMSW)
£ 0.50
0.50 to 1.25
1.25 to 3.00
3.00 to 10.00
> 10.00
0.89
0.84
0.72
207
(14)
474
(31)
426
(28)
320
(21)
94
(6)
135
220
(32)
206
(30)
123
(18)
14
(2)
77
(25)
106
(35)
92
(30)
27
(9)
0
(0)
Total
1,521
(100)
698
(100)
302
(100)
Note: Numbers in parentheses are percentages. Costs tor publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent from 1992 to the year of closure. Details may not
add to totals due to rounding. Exchul s closed landfills.
-------
landfills experience annualized costs of $1.25 per Mg or less; the maximum
annualized cost at this level of stringency, however, is $57 per Mg. At
the 100 Mg stringency level the maximum annualized cost falls to S25 per Mg
of MSW, and the proportion experiencing costs of $1.25 per Mg or less
increases to 51%. Finally, at the 250 Mg stringency level, 60% of affected
landfills experience annualized costs per Mg of MSW of $1.25 or less, and
the maximum annualized cost experienced is only $8 per Mg.
As noted above, the enterprise costs for privately owned landfills are
annualized over a period beginning when the regulation takes effect in 1992
and ending when the landfill closes. Privately owned landfills can only
recapture their costs through increased user fees while they are still
accepting MSW. The shorter the period of time between 1992 and the year
the landfill closes, therefore, the greater the potential burden of a
particular amount of control costs on the landfill's owners. Tables 8-12
and 8-13 give the same information as Table 8-11, but for privately owned
landfills which have five or fewer years until closure or 5 to 10 years
until closure, respectively. Table 8-12 shows that the national annualized
enterprise cost per Mg of MSW accepted for private landfills with five
years or less until closure is more than five times the national annualized
costs for all affected landfills at each stringency level. Specifically,
at the 250 Mg stringency level, the national annualized enterprise cost is
$5.33 per Mg of MSW, it is $4.37 per Mg of MSW at the 100 Mg level, and it
is $5.24 per Mg at the 25 Mg stringency level. At the 100 Mg stringency
level, 90% of the 41 affected landfills that are expected to close by 1997
experience annualized costs between $3.00 and $10.00 per Mg of MSW.
For private landfills closing between 1998 and 2002, unit control
costs are not nearly as high as the unit control costs of private landfills
closing before 1988 (see Table 8-13). The national average measure is
$1.17/Mg of MSW at the 25 Mg stringency level, $0.95/Mg of MSW at the
100 Mg stringency level, and only $0.48/Mg at the 250 Mg stringency level.
At the 250 Mg stringency level, only two landfills affected are expected to
close between 5 and 10 years after 1992, and they incur costs less than
$0.50 per Mg of MSW. At the 100 Mg stringency level, only 7 affected land-
fills are expected to close between 1998 and 2002, and they experience
annualized enterprise costs between $0.50/Mg and $1.25/Mg. At the 25 Mg
8-61
-------
TABLE 8-12. ANNUALIZED ENTERPRISE CONTROL COST PER Mg OF MSW FOR AFFECTED EXISTING
LANDFILLS WITH DATE OF CLOSURE BEFORE 1998: PRIVATE LANDFILLS ONLY
CO
en
(SS
National annualized cost per Mg MSW
($/Mg MSW)
Distribution of affected landfills by
annualized cost per Mg MSW
($/Mg MSW)
<0,50
o
0.50 to 1.25
1.25 to 3.00
3.00 to 10.00
> 10.00
s
Total
25
5.24
0
(0)
2
(4)
2
(4)
39
(67)
15
(26)
58
(100)
Stringency Level
(Mg NMOC/yr)
100
4.37
0
(0)
2
(5)
2
(5)
37
(90)
0
(0)
41
(100)
250
5.33
0
(0)
0
(0)
2
(14)
12
(86)
0
(0)
14
(100)
Note: Numbers in parentheses are percentages. Costs tor privately owned landfills are annualized at 8 percent from 1992 to
the year of closure. Details may not add to totals due to rounding. Excludes closed landfills.
-------
TABLE 8-13. ANNUALIZED ENTERPRISE CONTROL COST PER Mg OF MSW FOR AFFECTED EXISTING
LANDFILLS DATE OF CLOSURE BETWEEN 1998 AND 2002: PRIVATE LANDFILLS ONLY
CD
GJ
National annualized cost per Mg MSW
($/Mg MSW)
Distribution of affected landfills by
annualized cost per Mg MSW
($/Mg MSW)
£0.50
0.50 to 1.25
1.25 to 3.00
(
3-00 to 10.00
> 10.00
Total
25
1.17
0
(0)
10
(59)
0
(0)
7
(41)
0
(0)
17
(100)
Stringency Level
(Mg NMOC/yr)
100
0.95
0
(0)
7
(100)
0
0
0
(0)
0
(0)
7
(100)
250
0.48
2
(100)
0
(0)
0
(0)
0
(0)
0
(0)
2
(100)
Note: Numbers in parentheses are percentages. Costs for privately owned landfills are annualized at 8 percent from 1992 to
the year of closure. Details may not add to totals due to rounding. Excludes closed landfills.
-------
level, 17 landfills are expected to close between 1998 and 2002, with
annualized costs between $0.50/Mg and SlO.OO/Mg.
Table 8-14 presents the annualized enterprise cost per household for
affected existing landfills. This attempts to assess the annualized cost
that will be borne by households served by affected landfills. To compute
this measure, the annualized enterprise costs are divided by an estimated
number of households served by the affected landfills.* The national
annualized enterprise cost per household for each stringency level is
computed by summing the annualized enterprise costs incurred by all
affected landfills at that stringency level, and then dividing by an
estimate of the total number of households served by those landfills in
1986. The national annualized enterprise cost ranges from $4.16 per
household at the 250 Mg stringency level to $5.18 per household at the
25 Mg stringency level. At the intermediate 100 Mg stringency level, the
national annualized enterprise cost is S4.90 per household.
The frequency distribution of affected landfills by annualized enter-
prise cost per household, also shown in Table 8-14, indicates that one-
fifth of affected landfills at the 25 Mg stringency level will incur
annualized enterprise costs of $3.50 per household or less, and 43% will
incur annualized enterprise costs of $7.00 per household or less, although
the maximum annualized cost at this stringency level is $332 per household.
At the 100 Mg stringency level, the maximum annualized cost incurred is
S148 per household; however, one-quarter of the affected landfills will
incur annualized costs of $3.50 per household or less and one-half will
incur costs of $7.00 per household or less. Only 10% of affected landfills
will incur annualized costs of $30.00 per household or more under the
100 Mg stringency level. At the 250 Mg stringency level, over one-third of
*We estimated the number of households served by affected landfills
using the amount of MSW received by these landfills and an average amount
of MSW generated by households. We calculated the latter by dividing the
total amount of MSW going to all landfills based on the OSW data by the
estimated number of households served by landfills in the United States.
This resulted in a much higher MSW generation rate per household than other
estimates, but this MSW generation rate is consistent with the MSW accept-
ance rates used in the cost model. Nevertheless, these MSW generation
rates per household probably result in overestimates of annualized enter-
prise costs per household served by affected landfills.
8-64
-------
TABLE 8-14. ANNUALIZED ENTERPRISE CONTROL COST PER HOUSEHOLD FOR AFFECTED EXISTING
LANDFILLS
Stringency Level
(Mg NMOC/yr)
25 100 250 __
National annualized cost per household 5.18 4.90 4.16
($/Household)
Distribution of affected landfills by
annualized cost per household
($/Household)
00
en
en
£3.50
3.50 to 7.00
7.00 to 15.00
15.00 to 30.00
> 30.00
Total
313
(21)
336
(22)
407
(27)
216
(14)
249
(16)
1,521
(100)
190
(27)
164
(23)
184
(26)
87
(12)
73
(10)
698
(100)
108
(36)
75
(25)
85
(28)
15
(5)
19
(6)
302
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent from 1992 to the year of closure. Details may
not add to totals due to rounding. Excludes closed landfills.
-------
the affected landfills experience annualized costs per household of S3.50
or less and 61% incur costs of $7.00 per household or less.
A .measure of the potential cost to society of complying with the regu-
latory alternatives is the net present value of social costs. This meas-
ure, shown in Table 8-15, is computed by first annualizing capital costs
and then discounting the flow of capital and operating costs to arrive at a
measure of the present value of the costs that will be incurred throughout
the control periods for the various landfills. A net present value measure
of costs is the appropriate way to compare costs between landfills since
most landfills will begin and end controls at different times.
As noted in Section 8.3, computing the net present value of social
costs involves a two-stage process. First, the capital costs, which are
incurred in discrete "lumps" periodically throughout the control period,
are annualized over the control period using a 10% rate. Then the result-
ing stream of annualized capital costs and. the stream of annual operating
costs are discounted using a 3% discount rate. These costs are combined to
yield the total net present value (NPV) of social costs incurred by each
affected landfill. The maximum NPV of social costs incurred by any land-
fill is $140 million under the 25 Mg stringency level, $112 million under
the 100 Mg stringency level, and $75 million under the 250 stringency
level.
When summed across all affected landfills under each stringency level,
the national total NPV of social costs ranges from $3.92 billion under the
250 Mg stringency level to $11.65 billion under the 25 Mg stringency level
(see Table 8-15). While more landfills are affected under the more strin-
gent 25 Mg level than under the other two stringency levels, a larger
proportion of affected landfills incurs relatively lower NPV of social
costs ($3 million or less) under the 25 Mg level than under the 100 Mg
level or the 250 Mg level. The mean NPV of social costs per affected
landfill under the 250 Mg stringency, $10.1 million, exceeds the mean NPV
of social costs for the other two stringency levels.
Annualizing the net present value of social costs provides another
measure of the cost to society of the regulatory alternatives under
consideration. In this situation we annualized the net present value of
the social cost ot each affected landfill over the years from 1992 to the'
8-66
-------
TABLE 8-15. NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED CLOSED AND EXISTING
LANDFILLS
00
0»
Net Present Value
National social costs ($106)
Capital
Operating
Total
Average total social cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of social costs ($10^)
£0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0
>10.0
Total
25
6,438
5,213
11,651
6.18
31
(2)
97
(5)
654
(35)
421
(22)
464
(25)
217
(»)
1,884
(100)
Stringency Levels,
(Mg NMOC/yr)
100
4,326
2,831
7,157
8.39
29
(3)
24
(3)
206
(24)
189
(22)
261
(3D
144
(17)
853
(100)
250
2,403
1,514
3,917
10.1
7
(2)
7
(2)
61
(16)
92
(24)
137
(35)
82
(21)
386
(100)
Note: Numbers in parentheses are percentages. Net present value of social cost is computed using a two-step discounting
procedure. First, capital costs are annualized at 10 percent over the control period. Then, present values are computed by
discounting annual operating costs and annualized capital costs at 3 percent. Details may not add to totals due to rounding.
-------
end of the landfill's control period using a 3% discount rate, and then we
summed these individual annualized values to get the total annualized
social cost. The resulting total annualized social cost for affected
closed and existing landfills for each stringency level is:
• $416 million for the 25 Mg stringency level
• $297 million for the 100 Mg stringency level
• $150 million for the 250 Mg stringency level.
Thus, the annualized social cost of the 100 Mg stringency level is almost
twice the annualized social cost of the 250 Mg stringency level. The
annualized social cost of the 25 Mg stringency level is 40% higher than the
annualized social cost for the 100 Mg stringency level.
8.4.1.2 Energy Recovery Option. As discussed in Section 8.3, it will
be more economical for some landfills to reduce emissions by using flares,
while for others it will be more economical to use an energy recovery
technique. While energy recovery is more costly, especially in terms of
initial capital investment, it also will bring in some revenue from the
sale of the purified landfill gas or the energy produced from various uses
of this gas. In considering the energy recovery options, we omit the
landfills that would actually profit from energy recovery according to the
model in Chapter 7, because we assume these landfills would initiate the
use of energy recovery even in the absence of EPA emissions control
regulations. We therefore conclude that neither the emissions reductions
nor the costs of emissions control with energy recovery at these landfills
should be attributed to the regulatory alternatives under consideration.
So assessing the impacts of these regulatory alternatives involves studying
only those landfills that would experience positive costs using the least
costly control option.
When we omit all landfills that would find energy recovery profitable
(that is, landfills where the revenue from energy recovery exceeds the
energy recovery costs)„ the number of affected landfills at each potential
level of stringency is considerably smaller. As Table F-l in Appendix F
shows, the number of affected landfills falls from 1884 to 1024, a decrease
of 46% under the most stringent regulatory alternative (i.e., 25 Mg of
NMOC/yr). At the 100 Mg stringency level, the number of affected landfills
8-68
-------
falls by 62%, from 853 to 325. Finally, at the least stringent 250 Mg
level, the number of affected landfills falls by 80%, from 386 to only 77.
Table F-l also shows the number of privately owned affected landfills
under the energy recovery option. As described above, privately owned
landfills may have the greatest difficulty paying for the emissions
controls, because all their costs must be recaptured through increased user
fees during the period when the landfill is still actively accepting MSW.
The number of privately owned affected landfills varies from 27 under the
least stringent 250 Mg cutoff to 68 under the 100 Mg stringency level, and
215 under the 25 Mg stringency level. From 10 to 29 of the privately owned
landfills will close by 1992 and therefore are expected to have no way of
recapturing the costs of compliance.
As described above, landfills must use emissions controls during a
control period that will vary in length from landfill to landfill, extend-
ing beyond the closure of the landfill. Table F-2 depicts the length of
control period, while F-3 shows the length of control period prior to
closure. Although the control period may be as long as 130 years under the
250 Mg stringency level, 235 years under the 100 Mg stringency level, and
277 years under the 25 Mg stringency level, the average length of the
control period is much shorter. The average control period for affected
landfills under the 250 Mg stringency level is 36 years, while it is 51
years under the 100 Mg stringency level, and it is 70 years under the 25 Mg
stringency level. Also, as shown in the frequency distribution of affected
landfills by length of control period, the proportion of affected landfills
with control periods less than, for example, 50 years, is roughly two-
thirds under the 250 Mg and 100 Mg stringency levels, but is only 43% under
the 25 Mg stringency level.
f-
The shorter the time between the imposition" of controls and a land-
fill's closure, the more difficult it will be for the landfill to recover a
given amount of compliance costs by increasing user fees at the landfill.
This problem, of course, is particularly serious for landfills which are
already closed, but it may also affect landfills with a fairly short period
of time (for example, only 5 or 10 years) between the start of the controls
and the landfill's closure. Table F-3 shows the length of the control
period prior to closure for existing landfills under the energy recovery
8-69
-------
option. While some landfills have as much as 177 years of operating life
under the 25 Mg stringency level, the average length of control period
prior to closure for that stringency level is about 21 years. For the less
stringent levels, the average operating lives are even shorter—14.5 years
for the 100 Mg stringency level and less than 9 years for the 250 Mg strin-
gency level. A larger share of the affected landfills will have shorter
control periods before closure at the less stringent 250 Mg and 100 Mg
levels of control than at the most stringent 25 Mg level. At the 250 Mg
stringency level, 81% have 10 years or less of controls prior to closure,
while 63% have ten years or less prior to closure at the 100 Mg stringency
level, and 41% have 10 years or less prior to closure at the 25 Mg strin-
gency level.
To measure the impacts of the regulatory alternatives under considera-
tion on the owners of landfills, we use the net present value (NPV) of
enterprise costs. These costs include both capital investments and operat-
ing costs, less revenues from energy recovery for those landfills that
choose the energy recovery option. Table F-4 shows these costs, along with
a frequency distribution of landfills by NPV of enterprise costs. We
assume that the landfill will choose the control option that minimizes its
costs of control. To determine which option a particular landfill will
select, we discount the capital and operating costs incurred ovsr time to
compute a NPV of each. For publicly owned landfills, we use a 4% discount
rate, while for privately owned landfills we use an 8% discount rate. The
NPV of enterprise costs for the flare control option for each landfill is
compared with the NPV of enterprise costs for the energy recovery option
minus the revenue from the energy recovery activity.
Allowing landfills £o employ an energy recovery control option has two
overall effects on the impacts of the regulation. First, fewer landfills
are affected, because we assume that any landfill for which the energy
recovery option is profitable would have instituted such a system in the
absence of any EPA emissions regulation. Thus, we can attribute neither
the emissions reductions nor the costs of installing and operating energy
recovery equipment to the regulatory alternatives under consideration.
Second, the remaining landfills incur lower enterprise costs, both in the
aggregate and on average. As just noted, the number of landfills affected
8-70
-------
by the regulation falls for each stringency level. As a result, we would
expect aggregate NPV of enterprise costs to be lower, even if the average
NPV of enterprise costs per landfill did not decrease. In fact, however,
the average NPV of enterprise costs per landfill does decrease, falling 54%
to 68% when we allow landfills to choose the least costly control option
(see Table F-4). At the 100 Mg stringency level, for example, the average
NPV of enterprise costs per landfill under the flare option is $4.26
million. When the landfills are allowed to choose their least costly
control option, the average landfill now only incurs an NPV of enterprise
costs of $1.39 million. As a result of these combined trends, the aggre-
gate NPV of enterprise cost falls by 75% and 93%, depending on the strin-
gency level. The frequency distribution of affected landfills by NPV of
enterprise costs is even more skewed toward the lower cost categories under
the energy recovery option than under the flare option. At the 25 Mg
stringency level, for example, 71% of landfills incur NPV of enterprise
costs less than $3 million under the flare option, while 93% of landfills
incur NPV of enterprise costs less than $3 million under the energy
recovery option.
Annualized enterprise cost is another measure of the impacts of enter-
prise costs on landfill owners. This is computed for publicly owned
landfills by annualizing the NPV of enterprise costs for each landfill
using a 4% interest rate over the period during which controls are in place
for that landfill. Costs for privately owned landfills are computed by
annualizing the NPV of enterprise costs for each landfill using an 8%
interest rate over the period from 1992 through the year when the landfill
closes.
Table F-5 displays the annualized enterprise costs per Mg of MSW for
landfills having positive energy recovery costs. This is computed by
dividing the NPV of enterprise costs by the reported quantity of waste
accepted in 1986. The national annualized cost per Mg of MSW accepted is
computed by summing annualized enterprise cost for all the affected land-
fills under each stringency level, and then dividing by the sum of the
reported quantities of waste accepted by all affected landfills in 1986.
These quantities range from $1.43/Mg of MSW accepted at the 250 Mg strin-
gency level to $2.66/Mg of MSW at the 100 Mg stringency level. The
8-71
-------
national annualized cost per Mg of MSW for the 25 Mg stringency level falls
between those values, at $1.64/Mg of MSW accepted. Although these costs
are low, they are about two to three times higher than the national
annualized enterprise costs per Mg of MSW under the flare option (see Table
8-11). This occurs because many of the affected landfills with low
enterprise costs per Mg of MSW under the flare option will make a profit
from energy recovery. So these low unit cost landfills are omitted from
the group of affected landfills under the energy recovery option.
Table F-5 also shows a frequency distribution of affected landfills by
annualized cost per Mg of MSW. The proportion of affected landfills
experiencing annualized costs exceeding $3.00 per Mg is 43% under both the
25 Mg stringency level and the 100 Mg stringency level; the maximum annual-
ized cost incurred at the 25 Mg level is $57.15 per Mg, while the maximum
is $25.42 per Mg at the 100 Mg level. At the 250 Mg stringency level, the
proportion of landfills with annualized costs of $3.00 per Mg or more falls
to 24%, and the maximum annualized cost is $8.39.
We measure the impacts of the §lll(d) regulatory alternatives under
consideration on the users of affected landfills with the annualized
enterprise cost per household. This is computed by dividing the annualized
enterprise cost by the estimated number of households (based on an average
waste generation rate per household) served by the landfill. The national
annualized cost per household, shown at the top of Table F-6, is computed
by summing the annualized enterprise costs for each affected landfill at
each stringency level, and then dividing by the sum of the estimated number
of households served by all the affected landfills at that stringency
level. The national annualized cost per household varies from $8.33 per
household at the 250 Mg stringency level, to $9.50 at the 25 Mg stringency
level, to $15.47 at the 100 Mg stringency level. As was the case for
annualized costs per Mg of MSW, national annualized household costs under
the energy recovery option are much higher than the annualized household
costs under the flare option, because many of the low household cost
landfills are not affected by tht regulatory alternatives under the
assumptions of the energy recovery option.
The frequency distribution of affected landfills by annualized cost
per household suggests that the 821 affected landfills at the 25 Mg
8-72
-------
stringency level incur annualized costs per household that are more
concentrated at the lower values ($7.00 per household or less) than the
costs incurred by the 252 affected landfills at the 100 Mg level. The
national average cost per household at the 100 Mg stringency level is about
S15, but one-quarter of affected landfills at this level incur annualized
costs of $30 per household or more.
The net present value of social costs in Table F-7 measures the
potential impacts of the stringency levels under consideration on society.
The capital costs of compliance are annualized at a 10% rate, then the
resulting stream of annualized capital costs plus operating costs are
discounted at a 3% rate to determine the net present value of these costs.
The NPV of revenues from energy recovery then are subtracted from total
costs for those landfills that use the energy recovery option. As indi-
cated in Table F-7, the national social cost of the regulatory alternatives
ranges from $253 million for the least stringent 250 Mg level of control to
$2.96 billion for the most stringent 25 Mg level of control. While aggre-
gate costs are higher at the more stringent levels of control, average
social cost per landfill is lower, because more landfills with lower costs
are affected. Specifically, the average total social cost per affected
landfill is $2.89 million at the 25 Mg stringency level, $2.55 million at
the 100 Mg stringency level, and $3.27 million at the 250 Mg level.
To provide another perspective on the social cost of the regulatory
alternatives under consideration, we calculated the annualized social cost
for the three stringency levels for the energy recovery option. Specifi-
cally, we annualized the net present value of social cost for each landfill
over the years from 1992 to the end of its control period using a 3%
discount rate, and then we summed the individual annualized values to
estimate the total annualized social cost. These costs are:
• $124 million for the 25 Mg stringency level
• $68 million for the 100 Mg stringency level
• $19 million for the 250 Mg stringency level.
Note that annualized social cost exceeds $100 million only for the most
stringent regulatory alternative under the energy recovery option.
Furthermore, these annualized social costs are much lower than the
8-73
-------
annualized social cost of the three stringency levels under the flare
option. Specifically, the annualized social cost of the 100 Mg stringency
level under the energy recovery option ($68 million) is just one-fourth of
the annualized social cost of this same stringency level under the flare
option (S297 million).
8.4.2 Section lll(b) Standards
The §lll(b) Standards apply to landfills constructed and opened after
1992 when the regulation takes effect. In our case, we assume these new
landfills are replacing other landfills that closed. Specifically, we
assume that every landfill that closes after 1992 is replaced by an identi-
cal landfill serving the same area.
8.4.2.1 Flare Option. Of 944 new landfills nationwide, there are 41
affected by the flare option at the 250 Mg stringency level, 104 affected
by the flare option at the 100 Mg stringency level, and 247 affected by the
flare option at the 25 Mg stringency level. Tables 8-16 through 8-18
provide information on these affected landfills.
Table 8-16 shows the number of affected new landfills, along with the
number of such landfills which are privately owned. As with the closed/
existing landfills, privately owned new landfills will need to recapture
the costs of compliance with the regulation while they are still accepting
MSW. At the 25 Mg level of stringency. 51 of the affected landfills are
privately owned, 24 are privately owned at the 100 Mg stringency level,
while 14 are privately owned at the 250 Mg stringency level. Table 8-16
also shows a frequency distribution of affected new landfills by design
capacity. At the most stringent 25 Mg cutoff level the majority of
affected landfills have less than 5 million Mg of capacity, while at the
less stringent levels of control the majority are larger.
Table 8-17 depicts the length of control periods for affected new
landfills. Again, the landfills must operate the emissions controls for as
long as their emissions exceed the selected cutoff level. The year when
controls must begin varies from landfill to landfill; the length of time
during which controls must be operated also varies from landfill to
landfill, and so, therefore, does the date when controls may be removed.
While some landfills must keep controls in place for as long as 124 years,
8-74
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TABLE 8-16. SUMMARY INFORMATION FOR AFFECTED NEW LANDFILLS
CD
I
in
Number of affected landfills
(Percent of total new landfills)
Distribution of affected landfills
by design capacity
(lO^Mg)
<. 1
1 to 5
5 to 10
> 10
Total
Privately owned affected landfills
(Percent of affected landfills)
25
247
(26)
58
(23)
121
(49)
29
(12)
39
(16)
247
(100)
51
(21)
$||ringepcy Levels
(Mg NMOC/yr)
100
104
(ID
0
(0)
46
(44)
22
(21)
36
(35)
104
(100)
24
(23)
250
41
(4)
0
(0)
10
(24)
14
(34)
17
(41)
41
(100)
14
(35)
Note: The numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
TABLE 8-17. LENGTH OF CONTROL PERIOD FOR AFFECTED NEW LANDFILLS
25
Stringency Levels
(Mg NMOC/yr)
100
250
CO
Average length of control period (years) 74.4
Distribution of affected landfills by
length of control period
(years)
59.6
59.1
$ 25
26 to 50
51 to 100
101 to 150
Total
31
(13)
63
(26)
61
(25)
92
(37)
247
(100.0)
17
(16)
41
(39)
22
(21)
24
(23)
104
(100.0)
9
(22)
10
(24)
17
(41)
5
(12)
41
(100.0)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
TABLE 8-18. LENGTH OF CONTROL PERIOD PRIOR TO CLOSURE FOR AFFECTED NEW LANDFILLS
f
Average length of control period
prior to closure (years)
Distribution of affected landfills by
length of control period prior to closure
(years)
*5
6 to 10
11 to 20
21 to 50
Total
25
14.3
36
(14)
32
(13)
152
(62)
27
(11)
247
(100)
Stringency Levels
(Mg NMOC/yr)
100
13.3
17
(16)
5
(5)
75
(72)
7
(7)
104
(100)
250
13.3
7
(17)
10
(24)
17
(42)
7
(17)
41
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
the average length of control period is about 60 years for the 250 Mg and
100 Mg stringency levels, and 74 years for the 25 Mg stringency level.
Table 8-17 also shows that the more stringent the level of control, the
higher the proportion of landfills that will incur long periods of control.
Table 8-18 shows the average length of control period prior to closure
for affected new landfills, and a frequency distribution of affected land-
fills by length of control prior to closure. In general, most affected new
landfills need not begin controlling emissions until fairly close to their
closure date. The average length of time between beginning controls and
closure is 13 or 14 years. At the 25 Mg stringency level, 14% of affected
landfills will have only 5 years or less of controls before closure, while
16% will have 5 years or less at the 100 Mg stringency level. Finally, 17%
will have 5 years or less at the 250 Mg level.
Table 8-19 provides another measure of the severity of impacts on
landfill owners from the regulatory alternatives under consideration. It
describes the net present value of enterprise costs for affected new
landfills. As discussed above, the streams of capital and operating costs
incurred by the landfill owners over time are discounted to their present
value in order to compare one landfill's costs to another's. To reflect
the differences in the cost of capital for private and public landfill
owners, different discount rates are used in the discounting process:
costs for publicly owned landfills are discounted using a 4% rate, while
the costs for privately owned landfills are discounted using an 8% rate.
The net present value of capital costs and the net present value of oper-
ating costs are summed for each landfill, which yields the total net pres-
ent value of enterprise costs. These costs are summed across landfills to
estimate the aggregate (nationwide) net present valut of enterprise costs.
Table 8-19 shows that the 247 new landfills affected by the 25 Mg
level of control have total enterprise costs of $641 million, while the 104
new landfills affected by the 100 Mg level of stringency have an aggregate
net present value of enterprise costs of $407 million, and the 41 new land-
fills affected by the 250 Mg stringency level have aggregate net present
value of enterprise costs of $249 million. Although some landfills have a.
NPV of enterprise costs as high as $22 million at each stringency level,
the average NPV enterprise costs per landfill are much lower. While the
8-78
-------
TABLE 8-19. NET PRESENT VALUE OF ENTERPRISE COSTS FOR AFFECTED NEW LANDFILLS
oo
i
Net Present Value
National enterprise costs (S106)
Capital
Operating
Total
Average total enterprise cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of enterprise costs ($10^)
£0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
>5.0
Total
25
245
396
641
2.60
39
(16)
41
(17)
111
(45)
36
(14)
20
(8)
247
(100)
Stringency Levels
(Mg NMOC/yr)
100
177
230
407
3.92
7
(7)
10
(10)
53
(51)
14
(13)
20
(19)
104
(100)
250
117
132
249
6.07
2
(5)
2
(5)
23
(56)
2
(5)
12
(29)
41
(100)
Note: Numbers in parentheses are percentages. Net present value of enterprise costs is calculated using a 4 percent discount
rate for publicly owned landfills and an 8 percent discount rate for privately owned landfills. Details may not add to
totals due to rounding.
-------
aggregate NPV enterprise costs are highest at the 25 Mg stringency level,
the average NPV enterprise cost per facility for this level, $2.60 million,
is lower than for the other two stringency levels, because so many more
landfills with lower costs are affected by the 25 Mg stringency level. At
the 100 Mg stringency level, the average NPV enterprise cost per facility
is $3.92 million, while the average NPV enterprise cost per facility is
$6.07 million at the 250 Mg stringency level.
The frequency distribution of affected new landfills by NPV of enter-
prise costs in Table 8-19 indicates that a higher proportion of affected
landfills under the more stringent control alternatives experience-a rela-
tively low NPV of enterprise costs. For example, under the 25 Mg strin-
gency level, one-third of affected facilities have a NPV of enterprise
costs of $1 million or less. Under the 100 Mg stringency level, one-sixth
have a NPV of enterprise costs of $1 million or less, and only 10% have a
NPV of enterprise costs of $1 million or less under the 250 Mg stringency
level.
Annualizing enterprise costs is another way of using these costs to
assess impacts on landfill owners. The NPVs of enterprise costs for
publicly owned landfills are annualized using a 4% rate of interest over
the period of time during which the controls will be in place. For
privately owned landfills, we annualize enterprise costs using an 8% rate
of interest during the active operating life of the landfill, since
privately owned landfills will not be able to recapture the costs of
compliance after they close. We then divide these annualized enterprise
costs by the reported quantity of waste that the landfills accepted in
1986.
The first line in Table 8-20 shows the national annualized enterprise
cost per Mg of MSW accepted by affected new landfills for each stringency
level. This is computed by summing the annualized enterprise cost for all
affected landfills at a stringency level, and then dividing by the total
MSW accepted by all those landfills. The national annualized cost per Mg
of MSW accepted is less than $1.00 per Mg for all stringency levels. At
the 250 Mg stringency level, the national cost is $0.46 per Mg. As the
stringency increases to the 100 Mg level, the national annualized cost
increases to $0.48 per Mg of MSW. At the most stringent 25 Mg cutoff
level, the national annualized cost rises to $0.60 per Mg of MSW accepted.
8-80
-------
TABLE 8-20. ANNUALIZED ENTERPRISE CONTROL COST PER Mg OF MSW FOR AFFECTED NEW
LANDFILLS
Stringency Level
(Mg NMOC/yr)
25 100 250
National annualized cost per Mg MSW 0.60 0.48 0.46
($/Mg MSW)
Distribution of affected landfills by
annualized cost per Mg MSW
($/Mg MSW)
00
ca
S0.25
0.25 to 0.50
0.50 to 1.00
1.00 to 3.00
>3.00
Total
10
(4)
41
(17)
77
(31)
75
(30)
44
(18)
247
(100)
12
02)
31
(30)
24
(23)
37
(36)
0
(0)
104
(100)
5
(12)
14
(34)
12
(29)
10
(24)
0
(0)
41
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent over the life of the landfill. Details may not add
to totals due to rounding.
-------
Table 8-20 also has a frequency distribution of affected landfills by
the annualized enterprise cost per Mg of MSW accepted. This distribution
reveals that, the higher the stringency level, the higher the proportion of
affected landfills incurring annualized costs greater than $1.00 per Mg of
MSW accepted. At the least stringent 250 Mg cutoff level, only one-quarter
of the 41 affected landfills have costs of $1.00 per Mg or higher, and no
affected landfill experiences annualized costs exceeding $1.15 per Mg. At
the 100 Mg stringency level, however, over one-third of the 104 affected
landfills have annualized costs at least as high as $1.00 per Mg; at this
stringency level, the maximum annualized cost- is $1.89 per Mg of MSW.
Finally, at the most stringent 25 Mg level, almost half of the 247 affected
landfills have annualized costs of $1.00 per Mg or higher, and at least two
landfills have annualized costs of $5.88 per Mg.
Table 8-21 assesses the potential impact of the regulatory alterna-
tives on the households that will be served by these new landfills based on
the annualized enterprise cost per household. We compute the overall
annualized enterprise cost per household by summing the annualized enter-
prise costs for each affected landfill under each stringency level, and
then we divide the summed annualized enterprise costs by the estimated
number of households served by the affected landfills. The national cost
per household varies from $2.69 at the 250 Mg stringency level to $2.78 at
the 100 Mg stringency level to $3.48 at the 25 Mg stringency level.
As we found for closed/existing landfills, the 25 Mg stringency level
has the highest proportion of affected new landfills incurring relatively
high costs per household. At that stringency level, over three-fourths of
the 247 affected landfills incur costs of $3.00 per household or more. At
the 250 Mg stringency level, the proportion of landfills incurring costs of
more than $3.00 per household falls to about one-half. At the 100 Mg
stringency level, the proportion of affected landfills incurring costs per
household as high as $3.00 is lowest of all—only 7% of the 104 affected
landfills have costs that high.
Another way of assessing the possible impact of the regulatory alter-
'natives under consideration is to examine the net present value (NPV) of
social costs resulting from each possible stringency level (see Table
8-22). As with the NPV of enterprise costs, the aggregate total NPV of
8-82
-------
TABLE 8-21. ANNDALIZED ENTERPRISE CONTROL COST PER HOUSEHOLD FOR AFFECTED NEW
LANDFILLS
Stringency Level
(Mg NMOC/yr)
25 100 250
National annualized cost per household 3.48 2.78 2.69
($/Household)
Distribution of affected landfills by
annualized cost per household
($/Household)
CD
I
CXJ
GJ
£0.75
0.75 to 1.50
1.50 to 3.00
3.00 to 10.00
> 10.00
Total
2
(1)
7
(3)
44
(18)
121
(49)
73
(30)
247
(100)
15
(14)
29
(28)
53
(51)
7
(7)
0
(0)
104
(100)
0
(0)
7
(17)
12
(29)
22
(54)
0
(0)
41
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent over the life of the landfill. Details may not add
to totals due to rounding.
-------
TABLE 8-22. NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED NEW LANDFILLS
00
I
00
Net Present Value
National social costs C$106)
Capital
Operating
Total
Average total social cost
per affected landfill (S106)
Distribution of affected landfills by
net present value of social costs ($106)
£0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0
>10.0
Total
25
788
614
1,403
5.68
7
(3)
17
(7)
92
(37)
44
(18)
65
(26)
22
(9)
247
(100.0)
Stringency Level??
(Mg NMOC/yr)
100
548
348
8%
8.63
0
(0)
0
(0)
39
(37)
7
(7)
36
(35)
22
(21)
104
(100)
250
362
200
562
13.7
0
(0)
0
(0)
7
(17)
7
(17)
15
(37)
12
(29)
41
(100)
Note: Numbers in parentheses are percentages. Net present value or social cost is computed using a two-step discounting
procedure. First, capital costs are annualized at 10 percent over the control period. Then, present values are computed
by discounting annual operating costs and annualized capital costs at 3 percent. Details may not add to totals due to
rounding
-------
social costs increases as the level of stringency increases. At the most
stringent 25 Mg cutoff level, the aggregate total NPV of social costs, $1.4
billion, is more than twice the aggregate total NPV of social costs at the
250 Mg level, $562 million. The aggregate total NPV of social costs at the
100 Mg level, $896 million, lies between the cost of the other stringency
levels. Also following the pattern demonstrated by the enterprise costs,
the number of affected landfills increases substantially as the stringency
level increases, and the average NPV of social costs per landfill decreases
as the level of stringency increases. While some landfills have NPV of
social costs as high as $51 million, the average NPV of social costs per
affected landfill ranges from $13.7 million at the 250 Mg stringency level,
to $8.63 million at the 100 Mg stringency level, to $5.68 million at the 25
Mg stringency level. Finally, the frequency distribution in Table 8-22
shows, in a different manner than the averages, that the smaller number of
affected landfills at the lower stringency levels have a higher NPV of
social costs per landfill.
Our last measure of the cost to society of the §111 (b) regulatory
alternatives under consideration is the annualized net present value of
social costs. As explained above, we annualized the net present value of
the social cost for each affected landfill over the years from 1992 to the
end of the landfill's control period using a 3% discount rate, and then we
summed these individual annualized values to get the total annualized
social cost. The resulting total annualized social cost for affected new
landfills for each stringency level is:
• $45 million for the 25 Mg stringency level
• $30 million for the 100 Mg stringency level
• $19 million for the 250 Mg stringency level.
As expected, the least stringent regulatory alternative (the 250 Mg
stringency level) has the lowest annualized social cost, while the most
stringent regulatory alternative (the 25 Mg stringency level) has the
highest annualized social cost.
Up to this point, we have assumed that the §lll(b) regulatory alterna-
tives under consideration will not affect the quantity of MSW going to new
landfills. Actually, landfill emissions controls will increase the cost of
landfilling relative to other MSW disposal options (i.e., incineration),
8-85
-------
which will provide an incentive for some substitution among disposal
technologies. In other words, increases in landfill costs attributable to
§lll(b) controls will cause a shift in MSW flows away from landfills and
towards MWCs. However, EPA is also considering other regulations affecting
both landfills and MWCs, as explained in Section 8.2. The net effect of
all these regulations on MSW flows is not clear.
To help determine the possible effects on MSW flows of various EPA
regulations under consideration, developed an econometric model of the
actual choices made by communities between 1980 and 1986 with respect to
building either a new landfill or a new MWC.141 This model estimates the
share of MSW going to landfills and MWCs based on disposal costs and the
socioeconomic characteristics of communities. By adding the estimated
control costs associated with various landfill and MWC regulations to
landfill and MWC disposal costs, respectively, the model predicts changes
in MSW flows attributable to the regulations.
Table 8-23 presents the results of applying the Bentley/Spitz model
incrementally to three EPA regulations: the Subtitle D controls under the
Resource Conservation and Recovery Act, the CAA §lll(b) controls applying
to.MWCs, and the CAA §lll(b) controls applying to landfills. Under
baseline conditions, about 72% of MSW goes to landfills. In other words,
the choices that communities make regarding building new MWCs and landfills
result in 72% of their MSW going to landfills and 28% going to MWCs in the
absence of any new EPA regulations. The Subtitle D controls will increase
the cost of landfilling, which will cause more communities to choose the
MWC disposal technology. However, the CAA §111(b) controls under
consideration for MWCs will substantially increase the costs of this
disposal technology, which will result in a large shift in MSW flows
towards landfills according to the Bentley/Spitz model. Finally, the CAA
§lll(b) controls under consideration for landfills will increase land-
filling disposal costs slightly, so these controls will only result in a
very small shift in MSW flows towards MWCs.*
*As indicated in Table 8-20, the annualized enterprise control cost
per Mg of MSW for affected new landfills is $0.48 under the 100 Mg strin-
gency, level. In contrast, the annualized enterprise control cost per Mg of
MSW for affected new MWCs is $9.65 for Regulatory Alternative IV under
Scenario III.142 This supports the conclusion that the impact of the
landfill emissions controls on MSW flows will be much smaller than the
impact of the MWC emissions controls.
8-86
-------
TABLE 8-23. MSW TONNAGE SHARES OF MUNICIPAL WASTE COMBUSTORS (MWCS) AND LANDFILLS
WITHOUT AND WITH VARIOUS EPA REGULATIONS
oo
t
00
Baseline
Baseline Plus Subtitle D Control Costs*
Baseline Plus Subtitle D
and MWC Emissions Control Costs**
Baseline Plus Subtitle D, MWC
and Landfills Emissions Control Costs***
MSW Tonnage Shares
MWCs Landfills
27.75% 72.25%
30.66% 69.34%
21.24% 78.55%
21.61% 78.39%
Total
100%
100%
100%
100%
*Estimates of Subtitle D Control costs taken from the RIA143.
"Estimates of MWC emissions control costs are based on Regulatory Alternative IV under Scenario
***Landfills emissions control costs are based on the 100 Mg stringency level.
-------
Overall, the three regulations will increase MSW flows to landfills
about 6 percentage points (i.e., from 72% to 78%). These results suggest
that some increase in MSW acceptance rates at new landfills is appropriate
for estimating the costs of the §lll(b) regulatory alternatives under
consideration for landfills. However, the three assumptions (discussed in
Section 8.3) producing high MSW acceptance rates in the costing model in
Chapter 7 probably still lead to overestimates of the costs of these
regulatory alternatives.
8.4.2.2 Energy Recovery Option. Under the energy recovery option,
the landfill owners are allowed to either combust their emissions or
control them as part of energy recovery, depending upon which approach is
least costly for them. Undoubtedly, some landfills will find energy
recovery not only less costly than flares, but actually profitable. We
assume that the owners of such landfills would install energy recovery
systems even in the absence of the emissions control regulation. There-
fore, we do not attribute either the emissions reductions or the costs of
these energy recovery systems to the regulatory alternatives under consid-
eration. We limit our analysis, therefore, to those landfills for which
the costs of installing and operating emissions controls of either type
will be positive. Appendix F has the tables on the affected new landfills
having positive energy recovery costs.
By eliminating landfills that profit from energy recovery, the §lll(b)
regulatory alternatives affect far fewer new landfills. Table F-8 shows
that the number of affected new landfills varies from 10 under the least
stringent 250 Mg level of control, to 39 under the 100 Mg stringency level,
and 140 under the 25 Mg stringency level. Additionally, the frequency
distribution of affected new landfills by design capacity reveals that no
small landfills (1 million Mg or less) are affected by the 100 Mg and 250
Mg stringency levels under the energy control option. As discussed above,
privately owned landfills may have less flexibility in paying for emissions
controls, because they must recapture the costs of these controls through
increased user fees while the landfill is still accepting MSW. Under the
250 Mg and 100 Mg stringency levels, none of the affected landfills are
privately owned. Under the 25 Mg stringency level, however, there are 34
privately owned landfills, which is almost one-quarter of the affected new
landfills.
8-88
-------
Table F-9 shows the length of the control period for affected new
landfills with positive energy recovery costs. The average length of the
control period ranges from 56 years for the 100 Mg stringency level to 75
years for the 250 Mg stringency level. The average length of the control
period for the 25 Mg and 100 Mg stringency levels is slightly below the
average length of the control period for these stringency levels under the
flare option (see Table 8-17). However, the average length of the control
period under the 250 Mg stringency level increases under the energy
recovery option, despite no affected landfills having a control period in
excess of 100 years at this stringency level.
Another measure of the potential impacts from the regulatory alterna-
tives is the length of time after controls begin and before closure of the
landfill. If the landfill is still accepting MSW, its owners can attempt
to increase user fees to recapture some of the costs of compliance. Table
F-10 shows the length of control period prior to closure. While there are
many fewer affected landfills when landfills that profit from energy
recovery are eliminated, the length of control period prior to closure is
slightly shorter for the landfills with positive energy recovery costs.
Comparing Table F-10 with Table 8-18 reveals that the landfills with posi-
tive energy recovery costs have shorter periods of time prior to closure
when compared with all affected new landfills under the flare option. Both
the average length of control period prior to closure and the distribution
of affected landfills by length of control period prior to closure at all
three stringency levels demonstrate the difference. Under the flare
option, between 14% and 17% of affected new landfills close within five
years of implementing emissions controls; alternatively, between 18% and
30% of affected new landfills with positive energy recovery costs close
within five years of implementing emissions controls.
To assess the impact of the regulatory alternatives on the owners of
affected new landfills under the energy recovery option, we compute the net
present value (NPV) of enterprise costs under the flare option and the
energy recovery option, omitting landfills that would profit from energy
recovery. Then, we assume that the landfill owner will choose the least
costly of the control options. To compute the national values at the top
of Table F-ll, we aggregate the NPV of capital and operating costs for
8-89
-------
affected landfills for each stringency level. Then we sum the energy
recovery revenues for the landfills that select the energy recovery option
for each stringency level. Finally, we calculate the total aggregate NPV
of enterprise costs by adding the capital and operating sums and subtract-
ing the revenue sum. At the 250 Mg stringency level, this total equals
about $18 million, or an average of $1.83 million for each of the affected
new landfills. At the 100 Mg stringency level, the total aggregate NPV of
enterprise costs is $63 million, or an average of $1.61 million for each of
the affected landfills at that level. Finally, at the 25 Mg stringency
level, the total NPV of enterprise costs is $150 million, which averages
$1.07 million for each of the affected landfills.
Table F-ll has a frequency distribution of affected new landfills by
NPV of enterprise costs. At the 250 Mg stringency level, all the affected
landfills experience NPV of enterprise costs between $500,000 and $2.2
million. At the 100 Mg stringency level, all the affected landfills have
NPV of enterprise costs between $500,000 and $3.5 million. Finally, NPV of
enterprise costs range from below $500,000 to $3.8 million at the 25 Mg
stringency level.
Another measure of the impacts of the regulatory alternatives on land-
fills is the annualized enterprise control cost per Mg of MSW accepted by
the landfill. Table F-12 shows the annualized enterprise costs for land-
fills with positive energy recovery costs when owners are allowed to select
the least costly means of achieving emission reductions, either using
flares or using energy recovery. At each stringency level, the annualized
cost per Mg of MSW is less than $1.00. At the 250 Mg stringency level the
overall annualized cost is only $0.59 per Mg. It is $0.92 per Mg at the
100 Mg stringency level, and it is $0.95 per Mg at the 25 Mg stringency
level. These national annualized costs per Mg of MSW are between 28% and
92% higher than the national annualized costs per Mg of MSW under the flare
option, because many of the low cost per Mg landfills under the flare
option are omitted from the affected landfills under the assumptions of the
energy recovery option.
The frequency distribution of affected new landfills by annualized
enterprise control costs per Mg of MSW in Table F-12 shows that all the
affected landfills have annualized costs between $0.50 and $3.00 per Mg for
8-90
-------
the 100 Mg and 250 Mg stringency levels. The maximum annualized cost at
the 250 Mg stringency level is $1.08 per Mg, and the maximum at the 100 Mg
stringency level is $1.42 per Mg. At the 25 Mg stringency level, on the
other hand, affected landfills have unit costs ranging from below $0.25 per
Mg to $5.30 per Mg. Over one-quarter of the affected landfills under this
stringency level have annualized costs per Mg of $3.00 or higher.
To assess the possible impacts of the emissions control alternatives
on the households served by affected landfills, we computed the annualized
enterprise control costs per household. Table F-13 has these costs for
affected landfills with positive energy recovery costs when landfill owners
may choose either the flare option or the energy recovery option. At the
250 Mg stringency level, the national annualized cost is $3.41 per house-
hold. The annualized cost per household increases to $5.36 at the 100 Mg
stringency level, and the annualized cost per household is $5.53 at the 25
Mg stringency level. As was the case for annualized costs per Mg of MSW,
national annualized household costs under the energy recovery option are
higher than annualized household costs under the flare option for reasons
discussed above.
Table F-13 also contains a frequency distribution of affected new
landfills by the annualized cost per household. At the 250 Mg stringency
level, the 10 affected landfills have annualized costs between $1.50 and
$10.00 per household. At the 100 Mg stringency level, the 39 affected
landfills have annualized enterprise costs between $3.00 and $10.00 per
household. Finally, the 140 affected landfills at the 25 Mg stringency
level have annualized enterprise costs ranging from less than $0.75 per
household to more than $10.00 per household.
Table F-14 shows another means of measuring the cost of complying with
the emissions control .regulations under the energy recovery option—the NPV
of social costs. The aggregate NPV of social costs falls almost 78% at the
25 Mg stringency level under"the energy recovery control option. At the
100 Mg stringency level, the aggregate NPV of social costs falls by 84%
under this option, and the aggregate NPV of social costs falls by about 90%
at the 250 Mg stringency level compared to the costs under the flare
option. This decrease in the aggregate NPV of social costs is largely the
result of a reduction in the number of affected landfills. However, the
8-91
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average total social cost per affected landfill under the energy recovery
option is less than half the average total social cost per affected
landfill under the flare option for all three stringency levels.
To provide another perspective on the social cost of the §lll(b)
regulatory alternatives under consideration, we calculated the annualized
social cost for the three stringency levels under the energy recovery
option. These costs for the affected new landfills under the energy
recovery option are:
• $10.5 million for the 25 Mg stringency level
• $4.3 million for the 100 Mg stringency level
• $1.6 million for the 250 Mg stringency level.
These annualized social costs are substantially lower than the annualized
social costs under the flare option. For example, the $4.3 million annual-
ized social cost for the 100 Mg stringency level under the energy recovery
option is just one-seventh of the $30.2 million annualized social cost for
the same stringency level under the flare option.
8.5 ANALYSIS OF EMISSIONS REDUCTIONS AND COST-EFFECTIVENESS
At the same time that we are considering the costs of complying with
the §lll(d) and lll(b) regulatory alternatives under consideration, we must
also consider the cost-effectiveness of these alternatives. In this case
cost-effectiveness is measured as the annualized compliance cost per Mg of
reduction in the emission of nonmethane organic compounds (NMOCs). We
discuss compliance costs for each stringency level and each option in the
previous section. In this section, we examine both the emissions reduc-
tions and cost-effectiveness of the regulatory alternatives under consid-
eration for both closed/existing and new landfills under jeach of two
control options. We will first examine the emissions reductions and the
cost-effectiveness of the flare control option for closed and existing
landfills. Then we present the same two measures for these landfills under
the energy recovery option. Finally, we examine the emissions reductions
and cost-effectiveness of both control options for new landfills.,
8.5.1 Section lll(d) Guidelines
As shown in Table 8-6 in Section 8.4, the number of closed and exist-
ing landfills affected by the §lll(d) Guidelines under the flare control
8-92
-------
option ranges from 386 at the 250 Mg' stringency level to 853 at the 100 Mg
level to 1884 at the 25 Mg stringency level. As explained above, we omit
landfills that make a profit from energy recovery when analyzing the
impacts of the energy recovery option. So the number of closed and exist-
ing landfills affected by the guidelines under the energy recovery option
is lower: 77 under the 250 Mg stringency level, 325 under the 100 Mg
level, and 1024 under the 25 Mg level.
8.5.1.1 Flare Option. Table 8-24 shows the emissions reductions
resulting from the three regulatory alternatives under the flare option.
Total undiscounted NMOC emissions reductions range from 24.1 million Mg at
the 250 Mg stringency level, to 28.6 million Mg at the 100 Mg stringency
level, to 33.2 million Mg at the 25 Mg stringency level. These emissions
reductions are spread over the period of time during which the affected
landfills are using the flare emission controls. In order to compare
emissions reductions with the costs from Section 8.4, we discount the NMOC
emissions reductions using a 3% rate of discount. The discounted NMOC
emissions reductions range from 9.6 million Mg at the 250 Mg stringency
level to 11.2 million Mg at the 100 Mg stringency level to 12.6 million Mg
at the 25 Mg stringency level. The average discounted NMOC emission reduc-
tion decreases as the stringency level increases, because the number of
affected landfills increases faster than the NMOC emissions reductions.
Thus, the average NMOC emission reduction per affected landfill is 24,966
Mg at the 250 Mg stringency level, 13,110 Mg at the 100 Mg stringency
level, and 6,674 Mg at the 25 Mg stringency level.
We combined these measures of NMOC emissions reductions with the dis-
counted NPV of social costs presented in Table 8-15 to estimate the cost-
effectiveness of the flare option for closed and existing landfills (see
Table 8-25). At the top of the table is the national cost-effectiveness of
each stringency level, computed by dividing the aggregate NPV of total
social cost by the total discounted NMOC emissions reduction. The national
cost-effectiveness of the flare option at the 250 Mg stringency level is
$407 per Mg of NMOC reduced. At the 100 Mg stringency level, the national
cost-effectiveness is $640 per Mg of NMOC reduced, and the national cost-
effectiveness is $927 per Mg of NMOC reduced at the most stringent 25 Mg
level.
8-93
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TABLE 8-24.
NET PRESENT VALUE OF EMISSIONS REDUCTIONS FOR AFFECTED CLOSED AND
EXISTING LANDFILLS
Net Present Value
Stringency Levels
(Mg NMOC/yr)
25 100 250
Undiscounted NMOC emission reduction 33.2
(10* Mg)
Discounted NMOC emission reduction 12.6
28.6 24.1
11.2 9.64
Average discounted NMOC emission
reduction per affected landfill
(Mg)
co Distribution of affected landfills by
i> discounted NMOC emission reduction
•*" per affected landfill
(Mg)
6,674
13,110
24,966
* 1,000
, 1,000 to 2,000
2,000 to 5,000
5,000 to 10,000
> 10,000
Total
593
(31)
453
(24)
425
(23)
162
(9)
251
(13)
1,884
(100)
104
(12)
138
(16)
228
(27)
135
(16)
248
(29)
853
(100)
22
(6)
17
(4)
43
(11)
63
(16)
241
(63)
386
(100)
Note: Numbers in parentheses are percentages. Net present value of emission reductions is calculated using a 3 percent
discount rate. Details may not add to totals due to rounding.
-------
TABLE 8-25. COST EFFECTIVENESS FOR AFFECTED CLOSED AND EXISTING LANDFILLS
CO
VO
en
National cost effectiveness
($/Mg NMOC)
Distribution of affected landfills by
cost effectiveness
($/Mg NMOC)
s 1,000
1,000 to 2,000
2,000 to 5,000
5,000 to iO,000
> 10,000
Total
Incremental cost effectiveness
25
927
382
(20)
447
(24)
721
(38)
269
(14)
65
(4)
1,884
(100)
3,225
Stringency Level
(Mg NMOC/yr)
100
640
433
(51)
251
(30)
123
(14)
24
(3)
22
(2)
853
(100)
2,097
250
407
295
(76)
70
(18)
19
(5)
2
(1)
0
(0)
386
(100)
—
Note: Numbers in parentheses are percentages. Cost effectiveness is calculated by dividing the net present value of social
cost by the discounted NMOC emission reduction (see Tables 8-15 and 8-24). Details may not add to totals due to
rounding.
-------
The frequency distribution of affected landfills by cost-effectiveness
demonstrates that as the stringency level decreases, an increasing propor-
tion of landfills has a cost-effectiveness under $1,000 per Mg of NMOC
reduced. At the 25 Mg stringency level, only 20% of affected landfills
have cost-effectiveness measures that low, while more than half of the
affected landfills fall below $1,000 per Mg of NMOC at the 100 Mg strin-
gency level. Finally, three-fourths of the affected landfills have a cost-
effectiveness less than $1,000 per Mg of NMOC at the 250 Mg stringency
level. At the bottom of the table, incremental cost-effectiveness measures
the change in national cost-effectiveness experienced as the stringency
level increases first from 250 Mg to 100 Mg, and then from 100 Mg to 25 Mg.
As the stringency level increases from 250 Mg to 100 Mg, the incremental
cost-effectiveness is $2,097 per Mg of NMOC reduced. Moving from 100 Mg to
25 Mg results in an incremental cost effectiveness of $3,225 per Mg of NMOC
reduced.
8.5.1.2 Energy Recovery Option. Table F-15 presents the emissions
reductions resulting from the three regulatory alternatives under the
energy recovery option. Because so many landfills would find energy recov-
ery profitable, there are far fewer affected landfills under the energy
recovery option. Consequently, the total undiscounted NMOC emissions
reductions under this option are much less than under the flare option.
Specifically, total undiscounted NMOC emissions reductions range from 1.26
million Mg at the 250 Mg stringency level, to 3.06 million Mg at the 100 Mg
stringency level, to 5.81 million at the 25 Mg stringency level. These
emissions reductions are spread over the period of time during which land-
fills are operating the emission controls. In order to compare emissions
reductions with^the costs from Section 8.4, we discount the NMOC emissions
reductions using a 3% rate of discount. The discounted NMOC emissions
reductions range from Oc59 million Mg at the 250 Mg stringency level to
1.15 million Mg at the 100 Mg stringency level to 2.04 million Mg at the 25
Mg stringency level. The average discounted NMOC emission reduction
decreases as the stringency level increases, because the number of affected
landfills increases faster than the NMOC emissions reductions. Thus, the
average NMOC emission reduction per affected landfill is 7,560 Mg at the
250 Mg stringency level, 3,546 Mg at the 100 Mg stringency level, and 1,993
8-96
-------
Mg at the 25 Mg stringency level. The averages are less than one-third of
the average NMOC emission reductions under the flare option.
Table F-16 shows the social cost-effectiveness of the energy recovery
option. The national cost-effectiveness measures are higher at each level
of stringency than the cost-effectiveness of the stringency levels under
the flare option, with the greatest increase occurring at the 25 Mg strin-
gency level. The frequency distribution of affected landfills by cost-
effectiveness under the energy recovery option shows that the affected
landfills are concentrated in the lower cost-effectiveness categories at
the less stringent levels of control. As under the flare option, the
degree of concentration increases as the level of stringency decreases. At
the 25 Mg stringency level, only 15% of affected landfills have a cost-
effectiveness under $1,000 per Mg of NMOC reduced. At the 100 Mg level,
58% fall below $1,000 per Mg of NMOC, and 88% fall below $1,000 per Mg of
NMOC at the 250 Mg level. Also displaying a similar pattern to the flare
option, the incremental cost-effectiveness increases as the level of
stringency increases, although the measures of incremental cost-
effectiveness are much lower at each level of stringency than under the
flare option.
8.5.2 Section lll(b) Standards
New landfills will be regulated under the §lll(b) Standards. We
present measures of emissions reductions and cost-effectiveness for
affected new landfills under each control option in this section.
8.5.2.1 Flare Option. Under the flare control option, the number of
affected new landfills ranges from 41 at the 250 Mg stringency level, to
104 at the 100 Mg stringency level, to 247 at the 25 Mg stringency level.
Table 8-26 shows the emissions reductions for new landfills under this
control option. The first line shows the total undiscounted NMOC emissions
reductions at each stringency level. These measures, showing the total
emissions reductions achieved throughout the control period for all
affected new landfills, ranges from 1.74 million Mg at the 250 Mg strin-
gency level, to 2.33 million Mg at the 100 Mg stringency level, to 2.93
million Mg at the 25 Mg stringency level.
In order to compare emissions reductions between landfills when the
emissions reductions occur at different times at different landfills, we
8-97
-------
TABLE 8-26. NET PRESENT VALUE OF EMISSIONS REDUCTIONS FOR AFFECTED NEW LANDFILLS
09
UD
03
Net Present Value
25
Stringency Levels
(Mg NMOC/yr)
100
Average discounted NMOC emission
reduction per affected landfill
(Mg)
Distribution of affected landfills by
discounted NMOC emission reduction
per affected landfill
(Mg)
4,015
7,983
250
Undiscounted NMOC emission reduction
(10<>Mg)
Discounted NMOC emission reduction
2.93
0.99
2.33
0.83
1.74
0.63
15,278
$ 1,000
1,000 to 2,000
2,000 to 5,000
5,000 to 10,000
> 10,000
Total
106
(43)
39
(16)
68
(27)
10
(4)
24
(10)
247
(100)
2
(2)
15
(14)
53
(51)
10
(10)
24
(23)
104
(100)
5
(12)
2
(5)
2
(5)
8
(19)
24
(59)
41
(100)
Note: Numbers in parentheses are percentages. Net present value of emission reductions is calculated using a 3 percent
discount rate. Details may not add to totals due to rounding.
-------
discount the NMOC emissions reductions using a 3% rate of discount. This
discounted NMOC emission reduction, when summed across all affected land-
fills, ranges from 0.63 million Mg at the 250 Mg stringency level to 0.83
million Mg at the 100 Mg stringency level and 0.99 million Mg at the 25 Mg
stringency level.
The average discounted NMOC emission reduction per affected landfill
is much higher at the 250 Mg stringency level than at the 25 Mg stringency
level because the number of affected landfills falls faster than discounted
NMOC reduction as the stringency level decreases. At the 250 Mg stringency
level, the average discounted NMOC emission reduction is 15,278 Mg of NMOC,
more than three times the average discounted NMOC emission reduction per
landfill at the 25 Mg stringency level (4,015 Mg of NMOC). At the 100 Mg
stringency level, the average discounted NMOC emission reduction, 7,983 Mg
of NMOC per affected landfill, falls between the average emission reduction
values of the other two stringency levels. The frequency distribution of
affected new landfills by discounted NMOC emission reduction shows that the
proportion of landfills achieving relatively greater NMOC emissions
reductions increases as the stringency level decreases.
We can construct cost-effectiveness measures for affected new land-
fills by combining information about emission reduction with information
about the NPV of social costs in Table 8-22. Specifically, we estimate
national cost-effectiveness by dividing the total social cost by the total
discounted emission reduction for each stringency stringency level. As
shown in Table 8-27 this value ranges from $897 per Mg of NMOC reduced at
the 250 Mg stringency level, to $1,081 per Mg of NMOC at the 100 Mg level,
to $1,416 per Mg of NMOC at the 25 Mg stringency level. The frequency
distribution demonstrates that, as with closed/existing landfills, the
''proportion of affected new landfills having cost-effectiveness measures
less than $1000 per Mg of NMOC increases as the degree of stringency
decreases. At the 25 Mg stringency level, only 13% of landfills have a
cost-effectiveness under $1,000 per Mg of NMOC, while at the 100 Mg
stringency level, 44% have a cost-effectiveness of $1,000 per Mg or less.
At the 250 Mg stringency level, 59% of affected landfills have a cost-
effectiveness under $1,000 per Mg.
8-99
-------
The last line of Table 8-27 shows incremental cost-effectiveness--
i.e., the change in cost-effectiveness experienced as one moves from the
250 Mg stringency level to the 100 Mg level, and then from the 100 Mg
stringency level to the 25 Mg stringency level. As the stringency level
increases from 250 Mg to 100 Mg, the incremental cost-effectiveness is
$1,648 per Mg of NMOC reduced. The incremental cost-effectiveness of
moving from the 100 Mg stringency level to the 25 Mg stringency level is
$3,136 per Mg of NMOC reduced.
8.5.2.2 Energy Recovery Option. Table F-17 presents the emissions
reductions for affected new landfills with positive energy recovery costs.
The undiscounted NMOC emission reduction for each stringency level ranges
from 0.25 million Mg of NMOC reduced at the 250 Mg stringency level, to
0.49 million Mg of NMOC reduced at the 100 Mg stringency level, to 0.83
million Mg at the 25 Mg stringency level. The discounted NMOC emissions
reductions range from 0.06 million Mg at the 250 Mg stringency level to
0.25 million Mg at the 25 Mg stringency level. As the level of stringency
decreases, the average discounted NMOC emission reduction per affected new
landfill increases, because the number of affected landfills falls more
rapidly than the discounted NMOC emissions reductions. At the 25 Mg strin-
gency level, the average discounted NMOC emission reduction per affected
landfill is 1,765 Mg. At the 100 Mg stringency level, the average dis-
counted emission reduction is 3,818 Mg per affected landfill, while the
average discounted NMOC emission reduction per affected landfill rises to
6,680 Mg per affected landfill at the 250 Mg stringency level. Again, the
smaller number of landfills affected at the 250 Mg stringency level experi-
ence greater emissions reductions on average. The frequency distribution
of affected landfills by discounted NMOC emission reduction per affected
landfill (at the bottom of Table F-17) supports this consideration.
Table F-18 shows the cost-effectiveness of the three stringency levels
for the energy recovery control option for affected new landfills. The
national cost-effectiveness of each stringency level varies from $891 per
Mg of NMOC reduced at the 250 Mg stringency level to $963 per Mg of NMOC
reduced at the 100 Mg level, to $1,244 per Mg of NMOC reduced at the 25 Mg
stringency level. These national cost-effectiveness measures are lower
than the cost-effectiveness of the stringency levels under the flare
option.
8-100
-------
TABLE 8-27. COST EFFECTIVENESS FOR AFFECTED NEW LANDFILLS
CO
i
National cost effectiveness
($/MgNMOC)
Distribution of affected landfills by
cost effectiveness ($/Mg NMOC)
£1,000
1,000 to 2,000
2,000 to 5,000
5,000 to 10,000
> 10,000
Total
Incremental cost effectiveness
25
1,416
31
(13)
68
(27)
102
(41)
39
(16)
7
(3)
X
247
(100)
3,136
Stringency Level
(Mg NMOC/yr)
100
1,081
46
(44)
39
(38)
19
(18)
0
(0)
0
(0)
104
(100)
1,648
250
897
24
(59)
7
(17)
10
(24)
0
(0)
0
(0)
41
(100)
—
Note: Numbers in parentheses are percentages. Cost effectiveness is calculated by dividing the net present value of social
cost by the discounted NMOC emission reduction (see Tables 8-22 and 8-26). Details may not add to totals due to
rounding.
-------
The frequency distribution in Table F-18 demonstrates that the propor-
tion of affected landfills experiencing a cost-effectiveness of $1,000 per
Mg of NMOC reduced or less, increases substantially as the level of strin-
gency decreases. At the 25 Mg stringency level, only one-sixth of affected
new landfills have a cost-effectiveness of $1,000 per Mg of NMOC or less,
while 38% are below that level of cost-effectiveness at the 100 Mg strin-
gency level. At the 250 Mg stringency level, 70% of the affected new land-
fills have a cost-effectiveness under $1,000 per Mg of NMOC reduced.
Finally, at the bottom of Table F-18, incremental cost-effectiveness
is $870 per Mg of NMOC reduced as the stringency level increases from 250
Mg to 100 Mg. Moving from the 100 Mg stringency level to the 25 Mg
stringency level results in an incremental cost-effectiveness of $1,661 per
Mg of NMOC reduced. These incremental cost-effectiveness values are about
one-half of the corresponding incremental cost-effectiveness values under
the flare option.
8.6 ANALYSIS OF DISTRIBUTIONAL IMPACTS
The Regulatory Flexibility Act of 1980 requires federal agencies to
determine if regulations will have a "significant economic, impact on a
substantial number of small entitities." According to EPA guidelines,^
regulatory impacts are significant if:
• compliance costs are greater than five percent of production
costs,
• compliance costs, as a percent of sales, are at least 10
percent higher for small entities than for other entities,
• capital costs of compliance are a significant portion of
available capital, or
• the regulation is likely to result in closures of small
entities.
The guidelines indicate that a "substantial number" of small entities is
"more than 20 percent of these (small entities)." Finally, the EPA
generally relies upon Small Business Administration guidelines for
identifying "small entities."146 However, the Regulatory Flexibility Act
defines small government jurisdictions as those having fewer than 50,000
people. Since over three-fourths of U.S. landfills are owned by government
8-102
-------
agencies, the potential impacts of the regulatory alternatives on small
governmental entities are very relevant.
As explained below, the §lll(d) Guidelines and lll(b) Standards under
consideration will not affect a substantial number of small entities under
EPA guidelines. Consequently, regulatory flexibility analyses are not
required for these two rulemakings. Nevertheless, this section presents
some distributional impacts on households and government jurisdictions of
the flare option for the three stringency levels under consideration for
the §lll(d) Guidelines and lll(b) Standards. These distributional impacts
re>y on household and governmental data developed by EPA's Office of Solid
Waste (OSW) for a landfills rulemaking under Subtitle 0 of the Resource
Conservation and Recovery Act (RCRA).
8.6.1 Section lll(d) Guidelines
As indicated earlier in Table 8-6, the 25, 100, and 250 Mg stringency
levels for the §lll(d) Guidelines affect only 26%, 12%, and 5%, respec-
tively, of all the closed and existing landfills in the United States in
1992. Since most landfills are small (i.e., 1 million Mg of design
capacity or less), while the regulatory alternatives under consideration
affect mainly large landfills (i.e., landfills with a design capacity over
1 million Mg), it is very unlikely that any of the stringency levels will
affect more than 20 percent of the small landfills.*
To further investigate the impacts of the 25, 100, and 250 Mg
stringency levels on small landfills, we analyzed the distribution of
affected closed and existing landfills by design capacity relative to the
total number of closed and existing landfills in the same size categories.
All three stringency levels affect less than 10 percent of the closed and
* Lacking information on the size of governmental jurisdictions served
by most landfills, we assume that small landfills serve small municipal-
ities. This assumption is reasonable for two reasons. First, it is very
unlikely that small municipalities will have large landfills, given the
high cost of developing and operating large landfills. Second, large
municipalities generate large amounts of solid waste, which requires a
large amount of disposal capacity. Because of economies of scale in
landfill operations and the difficulty of siting landfills, large munici-
palities will probably not be served by several small landfills. However,
some large municipalities may be served by a municipal waste incinerator
and a small landfill. In such cases, impacts on small landfills will not
necessarily imply impacts on small municipalities.
8-103
-------
existing landfills having a design capacity of 1 million Mg or less. While
the 100 Mg stringency level affects 12% of the closed and existing land-
fills in total, it affects less than 4% of the closed and existing small
landfills (i.e., landfills with 1 million Mg of design capacity or less).
In conclusion, the §lll(d) Guidelines do not require a Regulatory
Flexibility Analysis, because they do not affect a significant number of
small entities.
Although a Regulatory Flexibility Analysis is not required by the
§lll(d) Guidelines, we examine some distributional impacts of the various
stringency levels under consideration. As indicated previously, these
distributional impacts rely on household and governmental data developed by
EPA's OSW for a landfills rulemaking under Subtitle D of RCRA. These data
were available for only a subset of the affected closed and existing
landfills for the three stringency levels under consideration for the
§111(d) Guidelines.* The specific distributional impacts examined for the
subset of affected landfills are:
• population of the service area
• annualized control costs per household
• annualized control costs as a percentage of annual local
taxes paid by households
• net present value of capital costs as a percentage of net
municipal debt (for publicly owned landfills).
The first measure (i.e., population of the service area) shows the number
of people served by the affected landfills. This provides information on
the size of the communities affected by the regulatory alternatives under
consideration. The second measure reflects the potential annual cost of
the controls to the households served by the affected landfills. The third
*The affected closed and existing landfills for which OSW data are
available are generally smaller (in terms of design capacity, refuse in
place in 1987, and the amount of MSW received in 1986) than the other
affected landfills. In fact, the size difference is statistically signifi-
cant for the affected landfills under the 25 Mg stringency level according
to Student-t tests on design capacity and refuse in place. The size
differences between the affected closed and existing landfills for which
OSW data are available and the other affected landfills are not statis-
tically significant under the 100 Mg and 250 Mg stringency levels.
8=104
-------
measure examines the relative impact of the controls on households, by
comparing annual control costs to households' annual local tax "burden."
Finally, the fourth measure provides some information on the relative size
of the capital costs of the regulatory alternatives under consideration for
the affected municipalities.
Table 8-28 shows the population of the service area for the subset of
affected closed and existing landfills. Approximately half of the affected
landfills serve between 10,000 and 50,000 people under all three stringency
levels. In general, as the stringency level increases, more landfills
serving smaller communities are affected, as indicated by the changes in
the distribution of affected landfills by the service area population.
About one-fifth of the affected landfills at the 100 Mg stringency level
serve 10,000 people or less, while another one-fifth serve 10,000 to 25,000
people.
The households served by more than two-thirds of the subset of
affected closed and existing landfills incur less than $25 per year in
control costs under all three stringency levels (see Table 8-29). The
households served by 18% of the affected landfills incur more than $50 per
year in control costs under the 100 Mg stringency level.* Nevertheless,
the national average control cost per household is just $13 for the 100 Mg
stringency level.
To further investigate the potential household impacts of the emis-
sions controls under consideration, Table 8-30 shows annualized control
costs as a percentage of local taxes paid by households in the service area
of the subset of affected closed and existing landfills. The national
average control cost as a percentage of local taxes paid by households is
under 1.3% for all three stringency levels. Control costs as a percentage
of local taxes paid are less than or equal to 1% for households served by
40% of the affected landfills at the 100 Mg stringency level. At the other
*The number of households in the service areas of these landfills is
low compared to the amount of MSW going into the landfills. In other
words, the amount of waste going into the landfills in these areas implies
a greater number of households based on the typical amount of MSW generated
by households. So the relatively high household costs for these affected
landfills are a result of overestimated control costs stemming from over-
estimated MSW acceptance rates and/or underestimated numbers of households
served by these landfills.
8-105
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TABLE 8-28. SERVICE AREA POPULATION FOR A SUBSET OF THE AFFECTED CLOSED AND
EXISTING LANDFILLS
00
t—•
o
National average service area population
(103 people)
Distribution of affected landfills
by service area population
(103 people)
< 10
10 to 25
25 to 50
50 to 150
150 to 500
> 500
Total
25
79.5
315
(28)
278
(25)
254
(23)
169
(15)
65
(6)
27
(2)
1,108
(100)
Stringency Levels
(MgNMOC/yr)
100
138.9
95
(21)
89
(19)
133
(28)
82
(17)
48
(10)
24
(5)
471
(100)
250
107.2
15
(8)
41
(23)
48
(27)
34
(19)
38
(21)
5
(3)
181
(100)
Note: The numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
, -A"'-
^ *
TABLE 8-29. ANNUALIZED ENTERPRISE^COSTS PER HOUSEHOLD FOR A SUBSET OF THE AFFECTED
CLOSED AND EXISTING LANDFILLS
25
Stringency Levels
(Mg NMOC/yr)
100
250
National average annuitized cost per
household
($/Household)
Distribution of affected landfills by
annualized cost per household
($/Household)
9.49
12.91
9.46
£5
5 to 10
10to25
25 to 50
>50
Total
217
(20)
239
(22)
303
(27)
170
(15)
179
(16)
1,108
000)
89
(19)
131
(28)
94
(20)
72
(15)
85
(18)
471
(100)
56
(31)
46
(26)
41
(23)
19
(10)
19
(10)
181
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned closed and existing landfills are annualized at 4
percent over the control period. Costs for privately owned existing landfills are annualized at 8 percent from 1992 to
the year of closure. Costs for privately owned closed landfills are annualized at 8 percent over the the control period.
Costs for Details may not add to totals due to rounding.
-------
TABLE 8-30. ANNUALIZED ENTERPRISE COST AS A PERCENTAGE OF LOCAL TAXES PAID BY
HOUSEHOLDS IN THE SERVICE AREA FOR A SUBSET OF THE AFFECTED CLOSED AND
U-'X&TI AEFECTED LANDFILLS
Stringency Leveig
(Mg NMOC/yr)
25 100 250
National average annualized enterprise cost 0.9 1.2 1.0
as a percent of taxes paid by households
Distribution of affected landfills by average
annualized cost as a percent of taxes
paid by households
CD
O
CO
Si 452
(41)
lto2J 341
(31)
2.5 to 10 208
(19)
> 10 107
(10)
Total 1,108
(100)
189
(40)
142
(30)
89
(19)
51
(11)
471
(100)
77
(43)
68
(38)
29
(16)
7
(4)
181
(100)
Note: Numbers in parentheses are percentages. Costs tor publicly owned closed and existing landfills are annualized at 4
percent over the control period. Costs for privately owned existing landfills are annualized at 8 percent from 1992 to
* the year of closure. Costs for privately owned closed landfills are annualized at 8 percent over the the control period.
Details may not add to totals due to rounding.
-------
extreme, control costs exceed 10% of local taxes paid for households served
by one-ninth of the affected landfills under this same stringency level.*
As a final measure of the distributional impact of the §lll(d)
regulatory alternatives under consideration, Table 8-31 examines the net
present value of capital costs as a percentage of net municipal debt for a
subset of affected publicly owned closed and existing landfills. Overall,
the capital costs of the three stringency levels under consideration repre-
sent less than 2.5% of the net debt of municipalities served by publicly
owned closed and existing landfills. Capital costs are less than or equal
to 5% of municipal debt for the municipalities served by over six-tenths of
affected landfills under the 100 Mg stringency level. However, capital
costs are more than double the net municipal debt for the municipalities
served by about 2% of the affected landfills at this stringency level.t
In conclusion, the distributional impacts of the §lll(d) regulatory
alternatives are very low overall for the subset of affected closed and
existing landfills. Costs per household in absolute and relative terms are
low for the households served by most affected landfills. Similarly, the
capital costs of the alternatives under consideration are also low relative
to net municipal debt.
8.6.2 Section lll(b) Standards
Table 8-16 in Sec. 8.4.2 indicates that the 25, 100, and 250 Mg
stringency levels for the §lll(b) Standards affect only 26%, 11%, and 4%,
respectively, of all the new landfills in the United States between 1992
*The landfills having control costs in excess of 10% of local taxes
paid by households are the same landfills having relatively high control
costs per household. As explained above, the relatively high annualized
costs as a percentage of local taxes are attributable to overestimated
control costs resulting from overestimated MSW acceptance rates and/or
underestimated local taxes as a result of underestimated numbers of
households served by these landfills.
*The seven landfills in this category at the 100 Mg stringency level
are the result of scaling the estimated capital costs of emissions controls
as a percentage of net municipal debt at one landfill in the database.
This landfill has an extremely high MSW acceptance rate relative to the
number of households it serves. Thus, its high capital costs as a
percentage of net municipal debt is probably attributable to overestimated
capital costs as a result of an overestimated MSW acceptance rate and/or an
underestimate of net municipal debt as a result of an underestimate of the
number of municipalities served by this landfill.
8-109
-------
TABLE 8-31.
NET PRESENT VALUE OF CAPITAL COSTS AS A PERCENTAGE OF NET MUNICIPAL DEliT
FOR A SUBSET OF AFFECTED PUBLICLY OWNED CLOSED AND EXISTING LANDFILLS
25
Stringency Levels
(Mg NMOC/yr)
100
250
National average capital cost as a
percent of net municipal debt
1.9
2.4
1.6
Distribution of affected landfills by
capital cost as a percent of net
municipal debt
I
(-•
»—»
o
100
Total
150
(18)
334
(40)
257
(31)
60
(7)
36
(4)
837
(100)
29
(9)
169
(52)
82
(25)
39
(12)
7
(2)
326
(100)
14
(16)
41
(47)
15
(17)
17
(20)
0
(0)
87
(100)
Note: Numbers in parentheses are percentages. Net present value ot capital cost tor publicly owned landfills is calculated
using a 4 percent discount rate. Details may not add to totals due to rounding.
-------
and 1997. Since the total number of affected new landfills is relatively
small, it is very unlikely that any of the stringency levels will affect
more than 20% of the small landfills for the reasons described in Section
8.6.1. We confirmed this tentative conclusion with an analysis of the
distribution of affected new landfills by their design capacity relative to
the total number of new landfills in the same size categories. Thus, the
§lll(b) Standards under consideration do not require a Regulatory Flexi-
bility Analysis, because they do not affect a significant number of small
entities.
Although a Regulatory Flexibility Analysis is not required for the
§lll(b) Standards under consideration, we examine the distributional
impacts of the various stringency levels for a subset of the affected new
landfills (i.e., those landfills for which OSW developed household and
governmental data for a landfills rulemaking under Subtitle 0 of RCRA).*
These distributional impacts are:
• population of the service area
• annualized control costs per household
• annualized control costs as a percentage of annual local
taxes paid by households
• net present value of capital costs as a percentage of net
municipal debt (for publicly owned landfills).
We examined these same distributional impacts for the §lll(d) regulatory
alternatives in Section 8.6.1.
Table 8-32 presents the population of the service area for the subset
of affected new landfills. While a third of the affected new landfills for
the 25 Mg stringency level serve 10,000 people or less, none of the
affected landfills under the other stringency levels serve such small
communities. In general, the 25 Mg stringency level affects smaller
communities than the 100 and 250 Mg alternatives. More than two-thirds of
*As observed for the closed/existing landfills, the affected new
landfills for which OSW data are available are generally smaller than the
other affected landfills. However, Student-t tests revealed no significant
size differences for any of the stringency levels under consideration.
8-111
-------
TABLE 8-32. SERVICE AREA POPULATION FOR A SUBSET OF THE AFFECTED NEW LANDFILLS
National average service area population
(103 people)
Distribution of affected landfills
by service area population
* (103 people)
£10
10 to 25
25 to 50
50 to 150
150 to 500
>500
Total
25
53.7
43
(34)
17
(13)
46
(36)
2
(2)
10
(8)
10
(8)
128
(100)
Stringency Levels
(Mg NMOC/yr)
100
93.5
0
(0)
10
(16)
33
(52)
0
(0)
10
(16)
10
(16)
63
(100)
250
92.5
0
(0)
10
(42)
2
(8)
0
(0)
10
(42)
2
(8)
24
(100)
Note: The numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
the affected landfills under the 100 Mg stringency level serve communities
with 10,000 to 50,000 people.
The national average annualized cost per household for the subset of
affected new landfills is below $11 for all three stringency levels (see
Table 8-33). As the stringency level decreases, the national average
annualized household cost also decreases. Over half the affected landfills
under the 100 Mg stringency level have annualized costs per household of
$25 or less. However, annualized household costs exceed $50 for 16% of the
affected new landfills, ranging as high as $76 per household per year.*
Table 8-34 shows that the national average annualized enterprise cost
as a percent "of local taxes paid by households is below 1% for the subset
of affected new landfills under all three stringency levels. Control costs
as a percent of local taxes are under 1% for the households served by
almost three-fourths of the affected landfills for the 100 Mg stringency
level. Only one-ninth of the affected landfills have control costs as a
percent of local taxes paid by households above 10%, with 15% being the
maximum.T
The final measure of the distributional impact of the §lll(b)
Standards under consideration is the net present value of capital costs as
a percentage of net municipal debt for a subset of affected, publicly
owned, new landfills. Table 8-35 shows that these capital costs are about
2% of net municipal debt as a national average for the affected new land-
fills. While over four-tenths of the affected new landfills have capital
costs under 1% of net municipal debt under the 100 Mg stringency level, the
*The number of households served by landfills having annual household
costs above $25 at the 100 Mg stringency level is very low compared to the
amount of MSW going into these landfills. So the relatively high costs for
these landfills are a result of overestimated control costs caused by
overestimated MSW acceptance rates and/or underestimated numbers of house-
holds served by these landfills.
tThe seven landfills in this category at the 100 Mg stringency.level
are the result of scaling the annualized costs as a percentage of local
taxes per household at one landfill in the database. This landfill has a
very low amount of local taxes per household (i.e., $105). Consequently,
its costs-compared-to-taxes percentage is relatively high.
8-113
-------
TABLE 8-33. ANNUALIZED ENTERPRISE COSTS PER HOUSEHOLD FOR A SUBSET OF THE AFFECTED
NEW LANDFILLS
25
Stringency Levels
(Mg NMOC/yr)
100
250
National average annualized costs
per household
($/Household)
Distribution of affected landfills by
annualized cost per household
($/Household)
00
I
10.56
8.55
8.37
*5
5 to 10
10 to 25
25 to 50
>50
TotaB
29
(23)
22
(17)
24
(19)
22
(17)
31
(24)
128
(100)
17
(27)
22
(35)
7
01)
7
(11)
10
(16)
63
(100)
10
(42)
3
(13)
2
(8)
7
(29)
2
(8)
24
(100)
Note: Numbers in parentheses are percentages. Losts tor publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent over the life of the landfill. Details may not add
to totals due to rounding.
-------
TABLE 8-34. ANNUALIZED ENTERPRISE COST AS A PERCENTAGE OF LOCAL TAXES PAID BY
HOUSEHOLDS IN THE SERVICE AREA FOR A SUBSET OF THE AFFECTED NEW
LANDFILLS
Stringency Levels
(Mg NMOC/yr)
_ _ 25 _ 100 _ 250
National average annualized enterprise cost 0.8 0.7 0.5
as a percent of taxes paid by households
Distribution of affected landfills by average
annualized cost as a percent of taxes
paid by households
00
I
si
V
1 to 2.5
2.5 to 10
>10
Total
70
(55)
34
(27)
10
(8)
14
(11)
128
(100)
46
(73)
7
(H)
3
(5)
7
(11)
63
(100)
15
(63)
7
(29)
2
(8)
0
(0)
24
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent over the active life of the landfill. Details may
not add to totals due to rounding.
-------
TABLE 8-35. NET PRESENT VALUE OF CAPITAL COST^AS A PERCENTAGE OF NET MUNICIPAL DEBT
FOR A SUBSET OF AFFECTED PUBLICLY OWNED NEW LANDFILLS
25
Stringency Levels
(Mg NMOC/yr)
100
250
National average capital cost as a
percent of net municipal debt
2.1
2.2
1.4
Distribution of affected landfills by
capital cost as a percent of net
municipal debt v
CD
I
O>
£l 20
(22)
1 to 2.5 31
(34)
2.5 to 10 22
(24)
>10 17
(19)
Total 90
(100)
17
(41)
7
(17)
7
(17)
10
(24)
41
(100)
3
(25)
0
(0)
7
(58)
2
(17)
12
(100)
Note: Numbers in parentheses are percentages. Met present value of capital cost for publicly owned landfills is calculated
using a 4 percent discount rate. Details may not add to totals due to rounding.
-------
capital costs for almost one-quarter of the affected new landfills under
this stringency level are more than 10% of net municipal debt.*
In summary, the distributional impacts of the §lll(b) regulatory
alternatives are very low overall for the subset of affected new landfills.
Costs per household in absolute and relative terms are low for the house-
holds served by almost all the affected new landfills. Similarly, the
capital costs of the regulatory alternatives under consideration are also
low relative to net municipal~debt.
8.7 DISCOUNT RATE SENSITIVITY ANALYSIS
Section 8.4 analyzes the net present value of social costs for
affected landfills calculated using a two-stage discounting procedure.
First, we annualized capital costs over the control period using a 10%
discount rate. Then, we discounted the sum of annualized capital costs and
annual operating costs at 3% to obtain the net present value of social
costs. To investigate the sensitivity of capital costs, operating costs,
and total costs to changes in the discount rate, we recalculated social
costs using a single discount rate applied to both capital and operating
costs.
8.7.1 Section lll(d) Guidelines
Table 8-36 contains the net present value of social costs using a 3%
discount rate for affected closed and existing landfills for each §lll(d)
regulatory alternative under consideration. The costs in this table show a
significant decrease in capital costs compared to the costs in Table 8-15
(net present value of social costs using two-stage discounting). Operating
costs are discounted using 3% in both cases, so there is no difference
between the operating costs presented in these tables. Table 8-37 shows
the effect of a 10% discount rate on the net present value of social cost.
This table shows a further reduction in capital costs as well as a
*The 10 landfills in this category at the 100 Mg stringency level are
the result of scaling the capital costs of two landfills in the database.
Both these landfills have extremely high MSW acceptance rates relative to
the number of households they serve. So their relatively high capital
costs compared to net municipal debt are probably attributable to
overestimated capital costs as a result of overestimated MSW acceptance
rates and/or an underestimate of net municipal debt as a result of an
underestimate of the number of municipalities served by these landfills.
8-117
-------
TABLE 8-36. NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED CLOSED AND EXISTING
LANDFILLS USING A THREE PERCENT DISCOUNT RATE
I
(-«
»-•
CO
Net Present Value
National social costs tflO6)
Capital
Operating
Total
Average total social cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of social costs C$106)
<0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0
>10.0
Total
25
2,473
5,213
7,686
4.08
53
(3)
131
(7)
850
(45)
508
(27)
265
(M)
77
(4)
1,884
000)
Stringency Levels
(Mg NMOC/yr)
100
1,764
2,831
4,595
5.39
29
(3)
46
(5)
283
(33)
242
(28)
185
(22)
68
(8)
853
(100)
250
963
1,514
2,477
6.42
7
(2)
7
(2)
119
(31)
135
(35)
79
(20)
39
(JO)
386
(100)
Note: Numbers in parentheses are percentages. Net present value of social costs are computed using a 3 percent discount rate.
Details may not add to totals due to rounding.
-------
TABLE 8-37. NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED CLOSED AND EXISTING
LANDFILLS USING A TEN PERCENT DISCOUNT RATE
CO
I
t—•
>—'
10
Net Present Value
National social costs (S106)
Capital
Operating
Total
Average total social cost
per affected landfill (S106)
Distribution of affected landfills by
net present value of social costs ($10**)
£0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0
.
>10.0
Total
25
1312
1,569
3^81
1.79
286
(15)
683
(32)
783
(42)
132
(7)
53
(3)
27
(1)
1384
(100)
Stringency Levely
(Mg NMOC/yr)
100
1,318
906
2,224
2.61
111
(13)
140
(16)
433
(51)
104
(12)
38
(4)
27
(3)
853
(100)
250
719
470
1,189
3.08
32
(8)
41
(11)
232
(60)
43
(11)
19
(5)
19
(5)
386
(100)
Note: Numbers in parentheses are percentages. Net present value of social costs are computed using a 10 percent discount
rate. Details may not add lo totals due So rounding.
-------
significant reduction in operating costs when compared with the two-stage
results. For the 100 Mg stringency level in particular, going from two-
stage to single-stage discounting using a 3% discount rate reduces the
average cost by 36%; using a 10% discount rate reduces the average cost by
69%.
We estimated annualized social costs by applying an annualization
factor to the net present value of total social costs. In all cases we
annualized social costs from 1992 to the end of each landfill's control
period. Table 8-38 compares costs calculated using two-stage discounting,
single-stage discounting at 3%, and single-stage discounting at 10% for
affected closed and existing landfills. As expected, two-stage discounting
results in higher costs than either of the single-stage calculations.
However, annualized costs calculated using a 3% discount rate are lower
than annualized costs calculated using a 10% discount rate because of the
variable annualization period across affected landfills.
8.7.2 Section lll(b) Standards
Tables 8-39 and 8-40 contain the results of calculating the net
present value of social costs for affected new landfills using a 3% and 10%
discount rate, respectively. Comparing costs in Table 8-39 with those in
Table 8-22 (net present value of social costs using two-stage discounting)
shows a decrease in capital-costs, but no change in operating costs. Table
8-40 shows a further reduction in capital costs as well as a significant
reduction in operating costs when compared with the two-stage results. For
the 100 Mg stringency level in particular, going from two-stage to single-
stage discounting using 3% reduces the average cost by 37%; using a 10%
discount rate reduces the average cost by 83%.
Table 8-41 compares annualized social costs for affected new landfills
using different discount rates. As expected, two-stage discounting results
in higher costs than the single-stage discounting.. Unlike the results for
affected closed/existing landfills, the single-stage annualized costs for
affected new landfills follow the same pattern as the net present value of
costs. That is, annualized costs calculated using a 3% discount rate are
higher than those calculated using a 10% discount rate.
8-120
-------
CO
I
TABLE 8-38. TOTAL ANNUALIZED SOCIAL COSloR AFFECTED CLOSED AND EXISTING LANDFILLS
USING VARIOUS DISCOUNT RATES ($10*)
Stringency Level
(Mg NMOC/yr)
25 100 250
2-Stage Discounting* 416 297 150
3% Discount Rale** 281 202 99
10% Discount Rate** 358 257 129
ro • • ~-~~ •
i—«
* Two-stage discounting involves annualizing each landfill's capital costs at 10% over its control period. Then net present
values are computed by discounting annual operating costs and annualized capital costs at 3%. Finally, the net present
values are annualized at 3% from 1992 to the end of each landfill's control period and then summed.
** Net present values are annualizd from 1992 to the end of each landfill's control period and then summed.
-------
TABLE 8-39= NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED NEW LANDFILLS USING A THREE
PERCENT DISCOUNT RATE
CO
I
ro
ro
Net Present Value
National social costs C$106)
Capital
Operating
Total
Average total social cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of social costs ($106)
£0.5 v
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0 ,
>10.0
Total
25
299
614
913
3.7
14
(6)
10
(4)
131
(53)
60
(24)
22
(9)
10
(4)
247
(100)
Stringency Levels
(Mg NMOC/yr)
100
215
348
564
5.4
0
(0)
0
(0)
46
(44)
34
(33)
14
(13)
10
(10)
104
(100)
250
143
200
343
8.4
0
(0)
0
(0)
7
(17)
22
(54)
2
(5)
10
(24)
41
(100)
Note: Numbers in parentheses are percentages. iNet present value ot social cost is calculated using a 3 percent discount rate.
Details may not add to totals due to rounding.
-------
TABLE 8-40. NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED NEW LANDFILLS USING A TEN
PERCENT DISCOUNT RATE
co
i
ro
UJ
Net Present Value
National social costs ($1(X>)
Capital
Operating
Total
Average total social cost
per affected landfill (S106)
Distribution of affected landfills by
net present value of social costs ($10*>)
£0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0
>10.0
Total
25
127
112
239
1.0
109
(44)
68
(28)
53
(21)
10
(4)
7
(3)
0
(0)
247
(100)
Stringency Levels
(Mg NMOC/yr)
100
90
63
154
1.5
41
(39)
17
(16)
36
(35)
3
(3)
7
(7)
0
(0)
104
(100)
250
58
35
93
2.3
7
(17)
7
(17)
17
(41)
3
(7)
7
(17)
0
(0)
41
(100)
Note: Numbers in parentheses are percentages. Net present value of social cost is computed using a 10 percent discount rate.
Details may not add to totals due to rounding
-------
00
t
f\J
-p.
TABLE 8-41. TOTAL ANNUALIZED SOCIAL COST^FOR AFFECTED NEW LANDFILLS USING VARIOUS
DISCOUNT RATES ($10*)
Stringency Level
(Mg NMOC/yr)
25 100 250
2-Stage Discounting* 45.2 30.2 19.0
3% Discount Rate** 29.6 19.2 11.8
10% Discount Rate** 23.9 15.5 9.3
* Two-stage discounting involves annualizing each landfill's capital costs at 10% over its control period. Then net present
values are computed by discounting annual operating costs and annualized capital costs at 3%. Finally, the net present
values are annualized at 3% from 1992 to the end of each landfill's control period and then summed.
** Net present values are annualizd from 1992 to the end of each landfill's control period and then summed.
-------
8.8 SUMMARY AND CONCLUSIONS
We focused our economic analysis on the flare option for controlling
NMOC emissions from closed/existing and new landfills, although we also
presented results for a cost-minimizing energy recovery option for the
subset of affected landfills having positive energy recovery costs. The
flare option assumes that all affected landfills will control NMOC emis-
sions using flares, which overestimates the actual cost of the regulatory
alternatives because some landfills will choose a cheaper energy recovery
option. As explained in Section 8.3, our energy recovery option under-
estimates the costs of the regulatory alternatives at some landfills and
overestimates compliance costs at other landfills, with the aggregate
effect being unknown. Although EPA emissions controls will increase the
likelihood that landfills will select an energy recovery option, there is
no way to accurately predict which affected closed/existing and new
landfills will actually select this option.
As discussed in Section 8.3, two features of the costing model
presented in Chapter 7 are noteworthy for the economic analysis. First,
the model assumes that landfills that close between 1987 and 1997 are
replaced by an identical landfill serving the same area, while recent
evidence indicates that the number of U.S. landfills is actually declining.
The model also uses relatively high MSW acceptance rates, which is an
important parameter in determining NMOC emissions rates and the cost of
emissions controls. These features lead to overestimates of the number of
affected landfills, compliance costs, and emissions reductions.
In summary, the actual economic impacts of the §111(d) and lll(b)
regulatory alternatives under consideration are probably less than the
economic impacts presented in this chapter. Nevertheless, our analysis of
these regulatory alternatives leads to several specific conclusions:
• the regulatory alternatives will affect only a small fraction of
the closed/existing and new landfills (generally less than 15%),
and most of the affected landfills are relatively large.
• The number of affected closed, private landfills, which have no
way of generating revenues to cover compliance costs, is small
under the flare option and even smaller under the energy recovery
option.
8-125
-------
• Most control periods are relatively long under the various
stringency levels and control options, with most of the control
period coming after the closure of affected landfills.
• The national net present value of enterprise costs decreases
substantially as the stringency level decreases under both
control options for affected closed/existing and new landfills,
but the average enterprise cost rises as the stringency level
decreases.
• The national annualized enterprise control cost per Mg of MSW is
below $1 per Mg for stringency levels under the flare option for
affected existing and new landfills and for stringency levels
under the energy recovery option for affected new landfills.
National annualized enterprise control costs per Mg of MSW range
between $1.43/Mg and $2.66/Mg for affected existing landfills
under the energy recovery option.
• The costs of the regulatory alternatives are very low for most
households—the majority of affected existing landfills have
compliance costs under $15 per household per year and the
majority of affected new landfills have compliance costs under
$10 per household per year.
• While the national cost-effectiveness of almost all the
stringency levels under both the flare and energy recovery
options is less than $1000 per Mg of NMOC emissions reduction,
cost effectiveness varies greatly among affected landfills—much
more than is typical for EPA stationary-source regulations.
• The regulatory alternatives under consideration for closed/
existing and new landfills wil-1 not affect a substantial number
of small entities, so a Regulatory Flexibility Analysis is not
required for either the §lll(d) or lll(b) rulemakings.
• The social costs of the regulatory alternatives for affected
closed/existing and new landfills are very sensitive to the
discount rate, because of the long control periods under
stringency levels for both the flare and energy recovery control
options.
In general, the economic impacts of the §111(d) and lll(b) regulatory
alternatives on households and municipalities are too small to signifi-
cantly influence the choice among these alternatives. Privately owned
landfills that are already closed and must install emissions controls may
be significantly impacted by the regulatory alternatives, because they have
no way of recovering their compliance costs. However, there are very few
closed, privately owned landfills that are affected under any of the
8-126
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regulatory alternatives. The control costs of the regulatory alternatives
at affected landfills will probably not lead to a significant shift in MSW
flows from landfills to municipal waste combustors. Finally, all of the
regulatory alternatives will stimulate the adoption of energy recovery
technologies at affected landfills.
8.9 REFERENCES
1. Morris, Glenn, E., Brenda L. Jellicorse, (Catherine B. Heller,
0. Timothy Neely, and Tayler H. Bingham. Economic Impact of Air
Pollutant Emission Standards for New Municipal Waste Combustors.
Research Triangle Institute. Final report prepared for Office of Air
Quality Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, August 1989. p. 3-1.
2. U.S. Environmental Protection Agency. Background Document for The
Solid Waste Dilemma: An Agenda for Action. Draft Report of the
Municipal Solid Waste Task Force, Office of Solid Waste, U.S.
Environmental Protection Agency. September 1988.
3. Franklin Associates, Ltd. Characterization of Municipal Solid Waste
in the United States 1960 to 2000 (Update 1988). Prepared for Office
of Solid Waste and Emergency Response. U.S. Environmental Protection
Agency. EPA 68-01-7310WA65, March 1988. p. 18.
4. Reference 3, pp. 18-19.
5. Reference 3, p. 21.
6. U.S. Environmental Protection Agency. National Survey of Solid Waste
(Municipal) Landfill Facilities. Prepared by Westat, Inc. EPA/68-01-
7359, September 1988. p. 7-3.
7. Reference 3.
8. Reference 3, p. 18.
9. Reference 3, p. 18.
10. Columbia University Graduate School of Business, International City
Management Association, and Public Technology, Inc. Evaluating
Residential Refuse Collection Costs: A Workbook for Local Government,
Prepared for National Science Foundation, Division of Applied
Research, NSF APR-74-02061. 1978. p. 6-7-
11. Reference,10, p. 8.
12. Reference 10.
8-127
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13. Peluso, Richard A., and Ernest H. Ruckert, III. Waste Transfer: The
Basics. Waste Age, 19(12):88-92. December 1988.
14. Reference 10.
15. Adler, Cy A. Moving Wastes on Rail May Help Contain the Crisis.
World Wastes. 30(12) :20-21. December 1987.
16. Trains: 'Invisible' Movers of Refuse? Waste Age. 19(12):102-110.
December 1988.
17. Gordon, I. Keith. How to Think About Waste Transfer. Waste Age.
19(2):89-92, 123. February 1988.
18. Peluso, Richard A., and Ernest H. Ruckert. A New Look at Waste
Transfer Waste Age. .18(6) :99-104o June 1987.
19. Peluso, Richard A., and Ernest H. Ruckert, III. Waste Transfer: The
Basics. Waste Age. 19(12):147-152. December 1988.
20. Reference 2.
21. Reference 15.
22. Voell, Paula, and Anthony Voell. Shrinking Northeast Fills Force
Long-distance Hauls. World Wastes, 3J[(12):33-34. March 1988.
23. Reference 16.
24. Letcher, Robert Cowles, and Mary T. Sheil. Source Separation and
Citizen Recycling. In: The Solid Waste Handbook, a Practical Guide,
Robinson, William D. (ed.). New York, Wiley-Interscience. 1986.
p. 215-258.
25. Reference 2.
26. Reference 1.
27. Reference 18.
28. Reference 18.
29. Reference 3, p. 18.
30. Reference 3, p. 18.
31. Glebs, Robert T., and Ed C. Scaro. Yes, Costs Are Rising. Waste Age,
17(l):42-46. January 1986.
32. Reference 2, p. 2.E-4.
33. Reference 1.
8-128
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34. Radian Corporation. Municipal Waste Combustion Industry Profile--
Facilities Subject to Section lll(d) Guidelines. Final report.
Prepared for U.S. Environmental Protection Agency. September 1988.
p. 3-8.
35. Reference 34.
36. Radian Corporation. Municipal Waste Combustion Study: Report to
Congress. Prepared for the U.S. Environmental Protection Agency.
NTIS. Washington, DC. June 1987.
37. Reference 1.
38. Reference 1.
39. Reference 1.
40. Reference 1.
41. O'Leary, Phillip R., Larry Canter, and William D. Robinson. Land
Disposal. In: The Solid Waste Handbook, A Practical Guide.
Robinson, William D. (ed.). New York, Wiley-Interscience, p. 259-376.
42. Reference , p. 7-2.
43. Reference 2, p. 2.E-4.
44. Reference 6, p. 7-2.
45. Reference 6, p. 7-1.
46. Reference 6, p. 7-1.
47. Reference 6, p. 7-2.
48. Reference 6, p. A-4.
49. Reference 6, p. A-4.
50. Temple, Barker & Sloan, Inc., ICF, Inc., Pope-Reid Associates, and
/ American Management Systems, Inc. Draft Regulatory Impact Analysis of
Proposed Revisions to Subtitle D Criteria for Municipal Solid Waste
Landfills. Prepared for U.S. Environmental Protection Agency, Office
of Solid Waste. Washington, DC. August 5, 1988.
51. Reference 41. (
52. Reference 41.
53. O'Leary, Phil, and Berrin Tansel. Land Disposal of Solid Wastes:
Protecting Health and Environment. Waste Age. L7(3):68-78. March
1986.
8-129
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54. Reference 41.
55. Reference 41.
56. U.S. Environmental Protection Agency. 1988 Report to Congress: Solid
Waste Disposal in the United States, Volume II. EPA/530-SW-88-011B.
October. 1988.
57. Reference 6, p. A-17.
58. Reference 41.
59. Reference 41.
60. Reference 6, p. 9-2.
61. Reference 41.
62. Reference 6, p. 9-5.
63. Reference 41.
64. O'Leary, Phil, and Berrin Tansel. Landfill Gas Movement, Control and
Uses Waste Age. 17(4):104-116. April 1986.
65. Boykin, Rigdan H., Bernays Thomas Berclays, and Calvin Lieberman.
Marketing Resource Recovery Products. In: The Solid Waste Handbook,
A Practical Guide. Robinson, William D. (ed.). New York, Wiley-
Interscience, p. 621-652.
66. Reference 6, p. A-16.
67. O'Leary, Phil, and Berrin Tansel. Landfill Closure and Long-term
Care. Waste Age. J7(10):53-64. October 1986.
68. Naber, Thomas. Today's Landfill is Tomorrow's Playground. Waste Age.
18(9):46-58. September 1987.
69. Reference 67.
70. Reference 1.
71. Reference 6, p. A-2.
72. U.S. Environmental Protection Agency, Office of Solid Waste. Database
from National Survey of Solid Waste (Municipal) Landfill Facilities.
Washington, DC. 1988.
73. Reference 1.
74. Reference 72.
8-130
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75. Reference 72.
76. Reference 72.
77. Reference 31.
78. Glebs, Robert T. Landfill Costs Continue to Rise. Waste Age.
19(3):84-93. March 1988.
79. Reference 78.
80. Reference 78.
81. Reference 78.
82. Reference 78.
83. Reference 1, p. 3-21.
84. Reference 2.
85. Reference 2.
86. Reference 2, p. 2.E-13.
87. Reference 2.
88. Reference 2, p. 2.E-15.
89. Reference 2.
90. Reference 2, p. 2.E-16.
91. Reference 2.
92. Pettit, C. L. Tip Fees Up More Than 30% in Annual NSWMA Survey.
Waste Age. 20(3):101-106. March 1989.
93. Reference 2.
94. Dunbar, Frederick C., and Mark P- Berkman. Sanitary Landfills Are Too
Cheap! Waste Age. 18(5):91-99. May 1987-
95. Crew, Michael A., and Paul R. Kleindorfer. Landfill Tipping Fees
Should be Much Higher. Waste Age. ^9(2):131-34. February 1988.
96. Reference 94.
97. Solid Waste Report. Slants and Trends. 19(42):325. October 17,
1988.
8-131
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98. Waste Age Magazine Launches Bi-weekly Recycling Times. Recycling
Times. Preview Sample Issue. January 1989. p. 1.
99. Reference 24.
100. Reference 97.
101. Solid Waste News. Slants and Trends. 19(47):365. November 21, 1988
102. Disposal Crisis Coming: State-by-State Answers. Waste Age.
18(0:57-64. January 1987-
103. Reference 2.
104. Solid Waste News. New York Issues New Solid and Infectious Waste
Rules. i£(37):286-287- September 12, 1988.
105. Solid Waste Report. Pennsylvania Landfill Rules will Close Down Many
Sites. 19(25):194. June 20, 1988.
106. Solid Waste Report. Double Liners Now Required at Virginia Landfills.
19(44):342. October 30, 1988.
107. Reference 50.
108. Fleming, William. Subtitle D: A Summary of the Proposed Rules.
World Wastes, 3J.( 12):40-42. December 1988.
109. Reference 1, p. 3-21.
110. Reference 2, p. 2.E-3.
111. Reference 2, p. 2E-4.
112. Reference 2.
113. Reference 2, p. 2E-4.
114. Reference 102.
115. Michaels, Mark. How Landfills Look to the Public Mind. World Wastes.
3J.:34-37. May 1988.
116. Pettit, C. L., and Charles Johnson. The Impact on Property Values of
Solid Waste Facilities. Waste Age. 18(4):97-102. April 1987.
117. Reference 22, p. 33.
118. Reference 22, p. 34.
119. Reference 102.
8-132
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120. Johnson, Charles. Successful State Siting Practices. Waste Age.
17(3):57, 150-151. March 1986.
121. Reference 102, p. 64.
122. Shuff, Richard G. 'Bribes' Work in Wisconsin. Waste Age.
19(3):51-55. March 1988.
123. Reference 120.
124. Reference 120, p. 150.
125. Parker, Bruce J. Waste Import Ban Efforts are Growing. Waste Age.
18(10):46-61. October 1987.
126. Reference 125.
127. Reference 18.
128. Reference 22.
129. Johnson, Bruce. Portland: First in the West to Send Waste Long
Distance. World Wastes. 31(10):21-26,32. October 1988.
130. Reference 15.
131. Reference 22.
132. Reference 24.
133. Reference 2.
134. Reference 3, p. 18.
135. McCoy, R. W., Jr., and R. J. Sweetnam, Jr. A Status Report on
Resource Recovery. Kidder, Peabody Report. April 29, 1988.
136. Reference 1.
137. Solid Waste Report. Ash Disposal Focus of Incineration Debate.
19(48) :374.~ November 28, 1988.
138. Reference 135, p. 3.
139. Reference 1.
140. Kolb, Jeffrey A., and Joel D. Scheraga. A Suggested Approach for
Discounting the Benefits and Costs of Environmental Regulations. U.S.
Environmental Protection Agency. Washington, DC, April 1988.
141. Bentley, Jerome T., and William Spitz. A Model of the MSW Choice
Decision, Prepared for the U.S. EPA. Princeton, NJ: Mathtech
Incorporated. 1989.
8-133
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142. Reference 1.
143. Reference 50.
144. Reference 1.
145. U.S. Environmental Protection Agency. Memoranda to Administrator and
Office Directors on EPA Implementation of the Regulatory Flexibility
Act. February 9, 1982.
146. U.S. Small Business Administration. The Regulatory Flexibility Act.
Washington DC: Office of the Chief Council for Advocacy. October
1982.
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9. GUIDANCE FOR IMPLEMENTING THE EMISSION GUIDELINES
AND COMPLIANCE SCHEDULE
This chapter, in concert with the entire background information
document, has been prepared in accordance with regulations established
under Section lll(d) of the Clean Air Act. Under the regulations contained
in Subpart B of 40 CFR 60, EPA has established procedures whereby States
submit plans to control existing sources of "designated pollutants".
Designated pollutants are pollutants which are not included on a list
published under Section 108(a) (National Ambient Air Quality Standards) or
112(b)(l)(A) (Hazardous Air Pollutants), but to which a standard of
performance for new sources applies under Section lll(b). Under
Section lll(d), emission standards are to be adopted by the States and
submitted to EPA for approval. The standards would limit the emissions of
designated pollutants from existing facilities which, if new, would be
subject to the standards of performance for new stationary sources. Such
facilities are called designated facilities. The purpose of this chapter is
to provide guidance in implementing the emission guidelines and compliance
schedules for existing municipal solid waste landfills, and to provide
information upon which States may base their plans. The guidance provided
in this chapter also applies to new municipal solid waste landfills.
After public review and comment on the draft emission guidelines, a
final guideline will be published, and the emission guideline and compliance
schedule will be promulgated under Subpart C of 40 CFR 60. The States will
then have nine months to develop and submit plans for control of the
designated pollutant (municipal landfill gas emissions) from designated
facilities. Within four months after the date for submission of such plans,
the Administrator will approve or disapprove each plan (or portions
thereof). If a State plan (or portion thereof) is disapproved, the
Administrator will promulgate a plan (or portion thereof) within six months
after the date for plan submission. These and related provisions of
Subpart B are basically patterned after Section 110 of the Act and 40 CFR 51
(concerning the adoption and submittal of State implementation plans under
Section 110).
9-1
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As discussed in the preamble to Subpart B (40 FR 5340,
November 17, 1975), a distinction is drawn between designated pollutants
which may cause or contribute to endangerment of public health (referred to
as "health-related pollutants") and those for which adverse effects on
public health have not been demonstrated (referred to as "welfare-related
pollutants"). For health-related pollutants, emission standards and
compliance times in State plans must be at least as stringent as the
corresponding emission guidelines and compliance times in EPA's guideline
document, but 40 CFR 24.(g) does allow States to adopt and enforce emissions
standards and compliance times which are more stringent than those provided
in the published guidelines. In addition, as provided in Subpart B, States
may apply less stringent requirements for particular designated facilities
or classes of facilities, on a case-by-case basis, when economic factors or
physical limitations make such less stringent control more reasonable. Such
justification may include unreasonable control costs resulting from plant
age, location, process design, or the physical impossibility of installing-
the specified control system. States may also relax compliance time if
sufficient justification is provided. Justification for such a relaxation
may include unusual time delays caused by unavailability of labor,
climatological factors, scarcity of strategic materials, and large work
backlogs for vendors or contractors.
For reasons discussed at length in Chapter 2 of this background
information document, the Administrator has determined that air emissions
from municipal solid waste landfills are health-related pollutants.
Briefly, this determination is based on four specific health and welfare
effects attributable to these emissions: (1) the adverse health and welfare
effects resulting from nonmethane organic emissions, (2) the contribution to
global warming of methane emissions, (3) explosion hazard, and (4) odor
nuisance. Therefore, the States must develop regulations to control these
emissions that are at least as stringent as the final guidelines.
The guidance document mandated under Subpart B must provide
specific information to assist States in the development of a plan under
Section lll(d). Much of this information is nearly identical for both
9-2
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new and existing landfills, and has already been provided in this
background information document as listed below:
BID
Chapter(s)
Health and welfare effects of air emissions of Chapter 2
MSW Landfills
Landfill gas collection and control techniques Chapter 4
i
Control technology efficiency and environmental Chapter 6
effects
National emission reduction potential of guideline Chapter 6
Rather than duplicate the information which is already provided in this BID,
this chapter will focus on the following:
o Time necessary for normal design, installation, and start-up of
identified collection and control systems.
o An emission guideline reflective of Best Demonstrated Technology
(BDT), and a compliance guideline.
The guidance presented in this section applies to all existing
municipal solid waste (MSW) landfills that accepted refuse at any time
between November 8, 1987 and the date of proposal of the New Source
Performance Standards (NSPS) for MSW landfills. Existing landfills that
have capacity available and are not closing prior to accepting any
additional refuse are also affected. Landfills which commence construction,
or in the absence of construction received refuse, on or after the date of
proposal (the NSPS) are defined as new landfills and are subject to the
NSPS. The requirements for new landfills are identical to those for
existing landfills.
Only a portion of the existing landfills subject to the emission
guidelines are required to install air emission control systems. This is
the subset of existing municipal solid waste landfills with the greatest
potential for adversely impacting public health and welfare. However, many
of the landfills included under this definition of designated facility may
not pose a significant threat to public health and welfare. The public
9-3
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health and welfare threat posed by individual municipal solid waste
landfills varies widely and more specific guidance on if and when air
emission control systems are required at a specific landfill is provided in
Section 9.1=
For those facilities required to install landfill gas collection and
control systems, specific guidelines for the design and operation of these
systems are provided in Sections 9.2, 9.3, and 9.4. The guidelines are
separated into two distinctive components: guidelines for effective
collection of the municipal landfill gas; and control of the collected
landfill gas. Section 9.2 provides guidelines on the design of an effective
gas collection system. Section 9.3 provides guidelines on effective
operation of the gas collection system. Section 9.4 provides design and
operating guidelines for the air emission control device.
Finally, the schedule for compliance with these emission guidelines is
presented in Section 9.5. A schedule for compliance is provided for both
initial installation of the collection/control system and continued
expansion of the collection/control system, as new refuse is placed in
active portions of the landfill.
9.1 DETERMINATION OF CONTROL REQUIREMENT
The owner or operator of a designated MSW landfill with a maximum
design capacity less than 100,000 Mg refuse must submit a report to the
State agency documenting the landfill size. Documentation should include a
map or plot of the landfill which provides the size and location of the
landfill and identifies all areas where refuse may be landfilled as
permitted by the state or county. Documentation should also include the
maximum design capacity as specified in the State or county or RCRA permit.
If the design capacity has not been specified, then the capacity should be
estimated and a copy of the estimation method submitted for review. Upon
the State's verification that the maximum design capacity of the landfill is
less than 100,000 Mg, the landfill owner/operator is not required to perform
further testing reporting, or to install controls. If the design capacity
is increased by the addition of new areas, by an increase in the depth of
9-4
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refuse deposition, by greater compaction, or any other means, an amended
design capacity report must be submitted. If the revised capacity exceeds
100,000 Mg, the landfill would then be subject to the additional provision
of the guideline.
The owner or operator of a designated MSW landfill with a maximum
design capacity greater than 100,000 Mg refuse is required to periodically
determine the nonmethane organic compound (NMOC) emission rate from his/her
landfill each year, from the effective date of an approved State plan for
implementing the emission and compliance guidelines until closure of the
landfill. This includes landfills with an existing collection/control
system in place. A procedure for determining periodic NMOC emission rate is
provided in Section 9.1.1 below. The determined NMOC emission rate is to be
reported to the State each year along with supporting data and calculations.
If the NMOC emission rate is determined to be greater than or equal to
150 Mg of NMOC per year, then the landfill owner is required to install a
collection system which effectively captures the generated gas and conveys
this collected gas to a control system capable of achieving at least a
98 percent reduction in NMOC or a 20 ppmv outlet concentration (dry basis)
at 3 percent oxygen. A recovery system can be used to process the landfill
gas for subsequent sale, but all atmospheric vents from the recovery system
are required to be routed to a control system capable of achieving an
overall 98 percent reduction in NMOC or 20 ppmv outlet at 3 percent oxygen.
Specific design and operating requirements for the collection and control
systems are provided in Section 9.2, 9.3, and 9.4.
At landfills with active collection systems in place, the existing
collection system can be used to determine the NMOC mass emission rate only
if the system is operating according to the guidelines provided in this
chapter. Landfills with passive collection systems in place must have
synthetic liners on the bottom, sides, and top of the landfill, as well as,
meet the operating guidelines in Section 9.3. Use of existing collection
equipment to determine the NMOC mass emission rate is discussed separately
in Section 9.1.2.
9-5
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The owner of a regulated landfill is required to operate the collection
and control system, in accordance with the operating guidelines, for a
minimum of 15 years, until the landfill is no longer accepting waste and
until emissions from the landfill are determined to be less than
150 Mg/year. The procedure for determining when control is no longer
required is outlined in Section 9ol.3.
9.1.1 NMOC Emission Rate Determination
The NMOC emission rate is to be determined using the tiered approach as
illustrated in Figure 9-1. In the first tier (illustrated in Figure 9-2),
the landfill owner or operator is to estimate the NMOC emission rate using
the following equation, assuming the acceptance rate is constant from year
to year:
MNMOC = 2Lo R <3-595 X 10~9>
where,
MNMQC = mass emission rate of NMOC, Mg/yr
L - refuse methane generation potential, m /Mg refuse
R = average annual acceptance rate, Mg/yr
k = methane generation rate constant, 1/yr
c = years since closure (c = 0 for active and/or new
landfills)
t = age of landfill, yrs
^NMOC = concentration °f NMOC, ppmv as hexane
-9
3.595 x 10 = conversion factor
The average acceptance rate, R, can be determined by dividing the
refuse in place by the age of the landfill. This method for determining the
emission rate should only be used for landfills with little or no knowledge
of the actual year-by-year refuse acceptance rate. If refuse acceptance
rate information is available, the landfill owner should determine the
methane generation rate for each yearly submass of refuse and total the
results to obtain an accurate overall landfill emission rate. The following
equation can be used for the submass approach:
Q. = 2 k LQMi (e'kti) (CNMQC) (3.595 x 10'9)
9-6
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No
Landfill
does not -
require control
Yes
Tied
Using landfill characteristics and default
values for k,L. and concentration of
nonmethane organic compounds (NMOC),
determine If the landfill Is exempt from
control requirements.
Is landfill closed?
Repeat Tier 1 each year.
No
Landfill
does not —
require control
Exempt from control?
Install Controls
Or
Tier 2
Determine the landfill NMOC concentration
using EPA test procedures. Redetermlne
If the landfill Is exempt from control
requirements using site-specific NMOC
concentration.
Yes
Is landfill closed?
Repeat Tier 2, updating the NMOC
concentration data at me specified Intervals.
Exempt from control?
Yes
Or
Landfill
does not
require control
No
Install Controls
Tier3
jas generation rate
using EPA test procedures. From the
site-specific k and NMOC concentration
data, redetermine If control Is required.
Is landfill closed?
Repeat Tier 3, updating the NMOC
concentration data at trie specific
Intervals. Updating the rate constant
value Is not required.
Exempt from control?
Yes
No
Install Controls
Figure 9-1. .Overall Three-Tiered Approach for Determination of
Control Requirements
9-7
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_ TieM _ ___
Compare the NMOC mass emission rate using landfill characteristics
and k=.02, Lo=230, and a NMOC concentration of 8,000.
2 L8 R (f. e *) (0^2.883 x 10'")
Where:
Mass emission rate of NMOC [=] Mg/yr
,^,, ^
L a- refuse methane generation potential [=] m'/Mg refuse
R = Average annual acceptance rate of refuse [=] Mg/yr
k = methane generation rate constant [=] 1/yr
c = years since closure (c = 0 for active landfills)
t = age of landfill [=] yrs
CMMOO= concentration of NMOC [=] ppmv
2. 883 x to" = conversion factor
Compare the computed NMOC emission-rate to the
regulatory level of 150 Mg/yr.
Yes
Exempt from controls?
Install
Controls
or
Tier 2
Figure 9-2. Example of Tier 1 Using NMOC Emission Rate Cutoff
as the Regulatory Option
9-8
-------
where:
Qi = NMOC emission rate from the i section, Mg/yr
k = landfill gas generation constant, 1/yr
L = methane generation potential, m /Mg
th
M. = mass of the i section, Mg
th
ti = age of the i section, yrs
CNMOC = concentratlon °f NMOC, ppmv
.9
3.595 x 10 = conversion factor
Regardless of which method is chosen, the nondegradable refuse, such as
demolition refuse, should be subtracted from the mass or acceptance rate to
avoid overestimating the landfill emission rate. A combination of the two
methods may be used if acceptance rate information, such as gate receipts,
is only available for a limited time period.
Landfill gas flowrate and/or composition data obtained within 5 years
prior to the initial Tier 1 evaluation may be used to determine
site-specific values for k and CNMO- provided that the methods used to
obtain the data are comparable to EPA Method 2E for flowrate determination
and Method 25C for NMOC concentration analysis. The value for k must be
computed as outlined in Section 5 of Method 2E regardless of the method used
to obtain the raw data. Sufficient documentation of the methods used to
obtain these data must be submitted for the State to review. Documentation
should include detailed test procedures, test log or data sheets, and any
accompanying calculations. In the absence of site-specific data, the values
to be used for k, L , and NMOC concentration are .02/yr, 230 m /Mg, and
8,000 ppmv, respectively. If the calculated NMOC emission rate is greater
than 150 Mg/yr, then the landfill owner must either install controls or
determine a site-specific NMOC concentration to use in the equation above.
If the landfill owner chooses to determine the NMOC concentration, then the
steps of Tier 2, illustrated in Figure 9-3, are to be followed. If the NMOC
emission rate determined from Tier 2 is greater than 150 Mg/yr, then the
landfill owner must either install controls or determine a site-specific gas
generation rate constant, k. If the owner chooses to determine k, then the
steps of the third tier, illustrated in Figure 9-4, are to be followed. If
9-9
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Tier 2
Install a minimum of 5 sample probes.
Collect and analyze samples using EPA
Method 25C.
Compute the NMOC mass emission rate using the
the average site-specific NMOC concentration.
Compare to tha regulatory level of 150 Mg/yr.
3'595 X10< >
Where:
CNMOC" the average NMOC concentration [»] ppmv
Exempt from Controls?
No
Yes
Install Controls
Tiers
Determine the number of samples required to demonstrate that the average NMOC
emission rate is less than the threshold with 80% confidence. Use procedure in
Ch. 9 of EPA document SW-846. , _ ,
Where: A
n=number of samples required to demonstrate 80% confidence
t ^student-t value for a two-tailed confidence interval and a probability
of 0.20 and for a degrees of freedom equal to the initial numberof samples
less one. (for a minimum of 5 initial samples, the degrees of freedom is
4, and the corresponding t value is 1.S33)
3 -standard deviation of the initial set of samples (ppm)
A-NMOC mass emission rate cutoff - M NMOC
A2L, H(e*5e*) (3.595x10*)
Install the required no. of probes
or 50 probes, whichever is less,
within 12 months.
Analyze sample using Method 25C
Compare average NMOC mass
emission rate to the regulatory
level of 150 Mg/yr.
Exempt from Controls?
No
Install Controls
Tiers
Compare average NMOC mass emission
rate plus 2 standard deviations to the
regulatory level of 150 Mg/yr.
Repeat each year until closure
using the site specific NMOC
concentration redetermine the
NMOC concentration every 10 years.
No
Repeat each year until closure
using the site specific NMOC
concentration. Redetermine the
NMOC concentration every 5 years.
Figure 9-3. Example of Tier 2 Using NMOC Emission Rate Cutoff
as the Regulatory Option
9-10
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Tier 3
Is the history of the landfill known?
Yes
No
Site a cluster of at least 3 wells
In a landfill area of at least 600 feet
by 600 feet containing refuse
placed 2 to 10 years prior
Site 5 equal volume wells In a landfill
area of at least 8,361 m'/well.
Upon approval, install test wells. Wells should be constructed in
accordance with the specifications provided by Method 2E
Wells must be drilled 75% of the landfill depth.
Install 3 radial arms of pressure probes. Probes are to be placed at radial
distances of 3.05, 15.2, 30.5, and 45.7 meters out from the well center.
The probes placed 3.05 meters from the well should be placed half as deep
as the nonperforated section of the test well. The remaining probes are to be
placed even with the start of the perforated section of the well.
Perform static testing according to Method 2E Measure the static
landfill gas flow using Method 2E Measure the concentration of
0,, N,, CO* and CH,, using Method 25C.
Perform short term testing according to Method 2E
Start extracting gas at 2 times the static flow. Increase the vacuum
by 3.74 mm Hg and measure the flow, the pressure probe readings,
and analyze the gas for O,, Nf CHU and CO,.
Figure 9-4. Example of Tier 3 Using NMOC Emission Rate Cutoff
as the Regulatory Option
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When 1% air is detected in the landfill gas or the Inner,
shallow pressure probe readings show a negative pressure
decrease the blower vacuum by 3.74 mm Hg.
Measure the flow, gas composition, and pressure probes dally.
Adjust vacuum to malntlan steady state conditions.
After achieving steady state for 24 hours
determine the radius of influence. The radius of Influence is
the distance of the deep pressure probe that shows zero
differential (i.e. P = P Landfill - P vacuum = 0)
Perform long term multiple-well extraction testing according
to Method 2E extracting the gas at the steady state rate
Identified In the short term test Collect and analyze the
landfill gas.
History Known
History Not Known
Calculate CH.
generation rate
constant, k, by trial and error.
ke« =Q
2L.M,,.,
Where:
k = CH. generation rate constant, 1/yr
Q. = Flowrate for volume tested, rrf /yr
M_ - Mass refuse in volume tested, Mg
t = age of volume tested, years
L = refuse methane generation potential [=] m'/Mg
Calculate total landfill gas flowrate
Total 0^=21 R(#-e-)
Where:
Q = total flowrate of LFG, rrf /yr
t = age of total landfill yrs
Calculate total landfill flowrate.
Q^*Volume of landfill
Volume of Test
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the NMOC emission rate determined in Tier 3 is greater than 150 Mg/yr, then
controls must be installed in accordance with the compliance schedule
provided in Section 9.5.
In determining the NMOC emission rate, the entire municipal solid waste
landfill is considered rather than any subdivision of the landfill, such as
an individual cell. The entire landfill is defined as the contiguous
landfill property designated for solid waste disposal irrespective of
subdividing access roads. This includes closed portions of the landfill (no
longer accepting refuse), as well as active portions. Additionally,
multiple ownership does not affect the definition of a municipal solid waste
landfill.
9.1.2 Landfills with a Collection/Control System In Place Prior to
Regulation
An owner of a landfill with an existing collection/control system in
place has the option of using the tiered approach or using the existing
equipment to determine the NMOC mass emission rate for comparison against
the standard. The landfill owner may use existing landfill gas collection
equipment to determine the NMOC mass emission rate, only if the collection
system meets the operating guidelines in Section 9.3. That is, the
landfill owner must be able to show that there is not excessive air
infiltration and that there is not a positive pressure at each well head.
An excessive influx of air may result in an overestimation of the landfill
gas flowrate. A positive pressure reading at the well head with a fully
open valve means additional wells are required. The landfill owner must
also be able to document that the collection system is effectively
collecting landfill gas from all gas producing areas of the landfill.
The NMOC mass emission rate can be determined by measuring the total
landfill gas flowrate and by determining the NMOC concentration of the gas.
The flowrate measurement should be taken at the common header pipe that
leads to the control device using an orifice meter as described in
Method 2E. The NMOC concentration can be determined by collecting and
analyzing a landfill gas sample from the common header pipe using
Method 25C. The average NMOC concentration of at least three gas samples
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should be used. The following equation can be used to determine the annual
NMOC mass emission rate:
where:
MNMOC = l'*9 X 10" QLFG CNMOC
= mass emission rate of NMOC, Mg/yr
3
9as» m /min
= NMOC concentration, ppmv
If the resulting NMOC mass emission rate is greater than 150 Mg NMOC/yr,
then the landfill should continue to operate the collection/control system
according to the guidelines outlined in Section 9.3. It is not mandatory
that existing collection system meet all of the design specifications
included in 9.2, if the collection system meets the operating guidelines
provided in Section 9.3. If the NMOC emission rate is less than
150 Mg/yr, then the landfill is exempt from control for that year only. The
NMOC mass emission rate should be determined periodically until the landfill
closes, and if the NMOC emission rate exceeds 150 Mg/yr at any time,
controls should be operated until the requirements of 9.1.3 are met.
9.1.3 Guidelines for Discontinuing Control
Control of landfill air emissions is no longer required when it meets
all of the following criteria:
o Controls have been in place and operated for at least 15 years;
o The landfill is no longer accepting waste; and
o Emissions from the landfill are less than 150 Mg/yr.
The annual NMOC mass emission rate must be less than 150 Mg/yr for
three consecutive testing periods, between 90 and 180 days apart, in order
to meet the emission criteria above.
The emission rate is to be determined by measuring the total landfill
gas flowrate and by determining the NMOC concentration of the gas. The
flowrate measurement should be taken at the common header pipe that leads to
the control device using an orifice meter as described in Method 2E. The
NMOC concentration should be determined by collecting and analyzing a gas
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sample from the common header pipe using Method 25c. The following equation
should be used to determine the annual NMOC mass emission rate for each set
of flow and NMOC concentration measurements.
MNMOC= 1'89x 10~3 QLFG CNMOC
where:
mass emission rate of NMOC, Mg/yr
^^owra^e °f landfill gas, m /min
NMOC concentration, ppmv
Again, the determined NMOC mass emission rate should be less than
150 Mg/yr for three consecutive quarters before operation of the control
system is discontinued.
9.2 DESIGN GUIDELINES FOR GAS COLLECTION SYSTEMS
Landfill gas collection systems can be categorized into two basic
types: active collection systems and passive collection systems. Active
collection systems employ mechanical blowers or compressors to provide a
pressure gradient in order to extract the landfill gas. The systems can be
further categorized into two types: vertical well systems and horizontal
trench systems. Passive systems rely on the natural pressure gradient
(i.e., internal landfill pressure created due to landfill gas generation) or
concentration gradient to convey the landfill gas to the atmosphere or to a
control system.
The Agency has evaluated the effectiveness of both active and passive
collection systems and has concluded that well designed active collection
systems are the most effective means of collecting landfill gas. The
Agency also found that well designed passive collection systems can
approximate the efficiency of an active system when used in conjunction with
synthetic liners and caps. Generally, passive collection systems have much
lower collection efficiency than active collection systems since they rely
on natural pressure gradient (i.e., internal landfill pressure created due
to landfill gas generation) or concentration gradient rather than the
pressure gradient induced by a blower or compressor. However, the Agency's
study revealed that passive collection systems can be nearly equivalent, if
the landfill design includes synthetic liners on the top, bottom, and sides
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of the landfill. Landfills with highly impermeable containment such as
canyons or quarries may also be well-suited for passive systems, however,
these should be evaluated on a case-by-case basis taking into account
fissures and cracks that may exist in the containment.
Selection of a collection system type often depends on the landfill
characteristics and landfill operating practices. For example, if a
landfill employs a layer-by-layer landfill ing method (as compared to
cell-by-cell methods), an active horizontal trench collection system may be
preferred over an active vertical well collection system due to the ease of
collection system installation. However, if the water table extends into
the refuse, horizontal trench systems have a tendency to flood, thus
decreasing the collection efficiency. Applications, advantages, and
disadvantages of different collection systems are summarized in Table 9-1.
For landfills required to install collection and control systems, the
owner of the landfill is first required to develop the collection system
design. The design must be based on the specifications for an active
vertical collection system provided in Section 60.758 of the NSPS.
Alternatively, an owner or operator who wishes to use a collection system
not based on those specifications must submit a plan to the State Agency for
review. Alternative designs would still need to satisfy the four criteria
of an effective collection system provided below, and the plans submitted
for review must address each of the four criteria. Provisions for expanding
the system as waste accumulates must be indicated in the plan. This plan
should include the type of collection system (active or passive), an
estimate of^the maximum expected gas collection rate, a plot plan of the
entire landfill with proposed well placements and estimated radii of
influence, and specifications for gas moving equipment. If a passive system
is proposed, containment specifications and the estimated collection/control
system pressure drop should also be provided. This plan is to be reviewed
by the State and, upon approval of the plan, the collection system is to be
installed in accordance with the compliance schedule provided in
Section 9.5.
i
The landfill gas collection system must be designed to provide
effective collection of the landfill gas. In order for the landfill gas
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TABLE 9-1 COMPARISON OF VARIOUS COLLECTION SYSTEMS
Collection system type
Preferred applications
Advantages
Disadvantages
tetive Collection Systems
Vertical Wells
Landfills employing
cell-by-cell
tandfilling methods
Cheaper or equivalent
in costs when compared
to horizontal trench
systems
Difficult to install and
operate on the active
face of the landfiII
(may have to replace
wells destroyed by
heavy operative
equipment)
Horizontal Trench
Landfills employing
layer-by-layer
landfi11 ing methods
Landfills with
natural depressions
such as canyon
Easy to install since
drilling is not required
Convenient to install
and operate on the
active face of the
landfill
The bottom trench layer
has higher tendency to
collapse and difficult
to repair once it
col lapses
Has tendency to flood
easily if water table is
high
Difficult to maintain
uniform vacuum along the
length (or width) of the
landfill
Passive Collection Systems
LandfiI Is with good
containment (side
liners and cap)
LandfiI Is with only
gas migration
problems
Cheaper to install and
maintain if only a few
wells are required
Collection efficiency
is generally much lower
than active collection
systems
Costs is generally
higher than active
systems when designed
for the same collection
efficiency
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collection system to be considered effective, it must: (1) provide
collection of landfill gas from all gas generating areas within the
landfill; (2) provide well spacing adequate to collect landfill gas from all
areas of the landfill without overdraw of air into the landfill; (3) provide
a gas moving system capable of handling the maximum expected gas flow; and
(4) include monitoring and adjustment provisions to facilitate effective
operation. Additionally, the gas collection wells are to be constructed in
conformance with certain specifications.
The first requirement, collection of landfill gas from all gas
producing areas, is common to all collection system types. The gas
collection system must be designed to provide gas collection from all gas
producing areas of the landfill which contain refuse that is at least two
years old. Areas known to contain asbestos should not be included in the
collection system design. The collection system should also be designed to
extend into each new area of the landfill within two years of the initial
placement of refuse in that area. For shallow areas, extraction wells can
be installed and vertically extended as more refuse is added. Since this
type of installation may make filling that portion of the landfill
difficult, it is recommended that the landfill owner/operator manage the
filling pattern to avoid shallow sections that meet the age criteria.
Certain landfills will contain sections of refuse that do not produce a
significant amount of landfill gas, either due to the age of the refuse or
the type of refuse. These "nondegradable" sections may be excluded from
control if the landfill owner or operator can show that emissions from the
all such sections contribute less than one percent to the total amount of
emissions from the landfill. Emissions from a given section may be computed
using the following equation:
Q. = 2 k LQ Mi (e'kti) (CNMQC) (3.595 x 10'9)
where:
Qi = NMOC emission rate from the ith section, Mg/yr
k * landfill gas generation constant, 1/yr
L = methane generation potential, m /Mg
= mass of the degradable refuse in the i section, Mg
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= age of the refuse in the i section, yrs
= concentration of NMOC, ppmv
_g
3.595 x 10 = conversion factor
The values for k, LQ, and CNMQC used in the tiered procedure should be used
if a specific k and CNMQC for the given section has not been determined
through field testing. The mass of the nondegradable refuse contained
within the given section may be subtracted from the total mass of the
section when estimating emissions. The landfill owner or operator should
provide records showing the amount and type of refuse claimed as
nondegradable and the location of such refuse within the landfill. If more
than one section is proposed for exclusion from control, an emissions
estimate should be made for each section. The sum of the emissions from all
the potentially excluded sections must be less than one percent of the total
landfill emissions to qualify for exemption.
The remaining requirements of an effective collection system, adequate
well spacing, flow capacity, and well construction are somewhat specific to
the type of collection system selected. These requirements are addressed in
the following sections specific to each collection system type.
9.2.1 Design Guidelines for Active Vertical Collection Systems
Four design features of the proposed vertical collection system must be
evaluated by the owner or operator and by the State reviewer when a
collection system design plan is submitted for review to ensure that an
effective collection system is installed. These are the proposed well
spacing, the proposed well construction, provisions for well monitoring and
adjustment, and capacity of the gas mover system. Each of these design
features are addressed below.
9.2.1.1 Vertical Well Spacing. The desired method for determining
effective well spacing at a specific landfill is the use of field
measurement data. EPA Method 2E, prescribed in Tier 3 of the NMOC emission
rate determination, can be used to determine the average stabilized radius
of influence for both perimeter wells and interior wells. If such a
determination has been made using EPA Method 2E, the determined radii of
influence are to be used in setting the well spacing. Wells placed along
the perimeter of the landfill (but, still in the refuse) are to be placed no
9-19
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more than the perimeter radius of influence from the perimeter and no more
than two times the perimeter radius of influence apart. As illustrated in
Figure 9-5, a helpful technique is to site the location of each well and
draw a circle with radius equal to the radius of influence (perimeter radius
of influence for perimeter wells and interior radius of influence for
interior wells). Once the perimeter wells are sited on the landfill plot
plan, the interior wells are to be sited at no more than two times the
interior radius of influence in an orientation such that essentially all
areas of the landfill are covered by the radii of influence. Figure 9-5
provides an illustrative demonstration of this concept.
In situations where the landfill owner chooses not to perform EPA
Method 2E, the well spacing must be determined based on theoretical
concepts. In order to evaluate the proposed well spacing for these
situations, it is important to understand the relationship between applied
vacuum (well vacuum) and air infiltration. It is advantageous to apply
higher vacuum in order to maximize the radius influence and minimize the
number of wells required. But, higher vacuum leads to increased air
infiltration. Consequently, excessive air infiltration (greater than one to
two percent air) kills the methanogens which produce the landfill gas,
supports aerobic decomposition of the refuse, and can potentially lead to a
landfill fire.
In the absence of field measurement data, reasonableness of the
proposed well vacuum must first be reviewed. The maximum vacuum that can be
applied at the well, without excessive air infiltration, is restricted
primarily by three landfill characteristics: the landfill depth, gas
permeability of the cover or cap material, and the cover thickness.
Assuming a 2 ft final cover as required under RCRA, the theoretical vacuum
that can be applied without excessive air infiltration is presented in
Figure 9-6 for three cover materials. As illustrated in the figure, the
maximum vacuum is greatly a function of landfill depth. The maximum vacuum
that can be applied is also dependent on the landfill gas generation rate.
However, since this can only be .determined for a specific site through field
measurement, the figure is based on the Scholl-Canyon model with a rate
constant (k) of .02 years and an ultimate gas generation constant (L ) of
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Designated Asbestos Area
Perimeter
Non-biodegradable
y//////
I /, of the Total Emissions
* =Well
R = Radius of Influence
^p = Perimeter Radius of Infuence
Top View
Figure 9-5. Technique for siting wells.
9-21
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vo
I
rv>
r\>
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Landfill Depth (m)
Figure 9-6. Maximum Blower Vacuum as a Function of Landfill Depth for
Three Cover Types
-------
230 m /Mg. The theoretical basis for Figure 9-6 is further described in
Appendix G.
In cases where field measurement is not performed, the proposed well
vacuum should be compared to the predicted maximum from Figure 9-6. If the
proposed vacuum is less than or equal to that indicated in Figure 9-6, then
the proposed value can be used to determine the radius of influence from
Figure 9-7. If the proposed well vacuum is greater than the maximum
indicated in Figure 9-6, then the value obtained from Figure 9-6 should be
used to determine the radius of influence from Figure 9-7. Consistent with
the theoretical correlation presented for maximum well vacuum, the
correlation presented in Figure 9-7 for radius of influence is based on the
1 3
Scholl-Canyon model with a k of .02 years and L of 230 m /Mg. The
theoretical basis and calculations are detailed in Appendix G.
Once the radius of influence is determined, the proposed well placement
can be evaluated. Identical to the criteria outlined above when using a
field measured radius of influence, the wells are to be sited along the
perimeter of the landfill no more than the radius of influence from the
landfill perimeter and two times the radius of influence apart. Once the
perimeter wells are sited, then wells are to be sited throughout the
interior of the landfill, at a distance of no more than two times the radius
of influence. The only difference in this technique and the one described
above is that a single radius of influence is used in siting both perimeter
and interior wells.
9.2.1.2 Well Construction. The landfill gas extraction well is to be
constructed of polyvinyl chloride (PVC), high density polyethylene (HOPE)
pipe, fiberglass, stainless steel, or other suitable nonporous material, at
least 3 inches in diameter. The well should extend from the landfill
surface to at least 75 percent of the landfill depth. It is recommended
that the bottom two thirds of the pipe be perforated with 1/2 inch diameter
holes spaced at 90 degrees every 6 inches. Slotted pipe having equivalent
perforations is also suitable. The pipe should be placed in the center of a
2 ft diameter bore and backfilled with gravel to a level 1 ft above the
perforated section. A 4 ft layer of backfill material should be placed on
top of the gravel followed by at least 3 ft of bentonite. The remainder of
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VO
I
ro
1
8
i
•5
TJ
£
36
34 -
32 -
30 -
28 -
26 -
24 -
22 -
20 -
18 -
16 -
14 -
12 -
10 -
8 -
6 -
4 -
2
I
30
10 20
Maximum Vacuum (in water)
40
I
50
60
Figure 9-7. Estimated Radius of Influence as a Function of blower Vacuum
-------
the bore can be backfilled with cover material or a material of equal or
lower permeability.
9.2.1.3 Monitoring and Adjustment Design Provisions. To facilitate
periodic well monitoring and adjustment, the well head should be equipped
with a valve, flanges, gaskets, connectors and access couplings. The well
assembly should also include at least one sample port that can be used to
monitor pressure or collect gas samples periodically. The extraction well
assembly and well head assembly are illustrated in Figure 9-8.
The well head may be connected to the collection header pipes below or
above the landfill surface. The advantage of installing header pipes above
ground is the ease of maintenance and operation. The disadvantage is the
higher probability of damaging header pipes with landfill operating
equipment and the possibility of blockage in the pipeline due to the
condensate freezing in areas with severe winters.
9.2.1.4 Gas Mover Sizing. The gas mover (fan, blower or compressor)
system should be designed to handle the peak landfill gas flowrate over the
life of the gas moving equipment. This attribute can be evaluated by first
projecting the peak landfill gas flowrate and comparing this flow to the
proposed equipment specifications. The peak gas flow rate can be projected
using the following expression:
where,
Peak Flow [m3/yr] = 2LQ R (1 - e"kt)
L = refuse methane generation potential, m /Mg refuse
R = average annual acceptance rate, Mg/yr
k = methane generation rate constant, 1/yr
t = age of the landfill plus the gas mover equipment life or active
life of the landfill, which ever is less, in years
A value of 230 m /Mg is recommended for L . If Method 2E has been
performed, the value of k determined from the test should be used; if not, a
value of .02 years" is recommended.
9.2.2 Design Guidelines for Active Horizontal Collection Systems
Four design features of the proposed horizontal collection system
should be evaluated by the State reviewer to ensure that an effective
9-25
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Sample Port Valve Box and Cover Compacted
\ Soil or Refuse
Gas
Collection
Header to Blower
4" PVC
Perforated Pipe
24".
Diameter
Figure 9-8. Gas extraction well and well head assembly.
9-26
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collection system is installed. These are the proposed well spacing, the
proposed trench construction, provisions for trench monitoring and
adjustment, and capacity of the gas mover system. Each of these design
features are addressed below.
9.2.2.1 Horizontal Trench Spacing. The preferred method for
determining effective trench spacing at a specific landfill is the use of
field measurement data. Although EPA Method 2E is based on a vertical well
test, results of this method can be used to determine radius of influence in
the horizontal direction. If such a determination has been made using EPA
Method 2E, the determined radius of influence is to be used in setting the
horizontal spacing. The trenches should be spaced at a distance of no more
than two times the measured radius of influence (measured radius of
influence for internal vertical wells) apart. The vertical spacing of
trenches, however should be closer. Since compaction of the refuse causes
refuse permeability to be lower in the vertical direction, influence of the
trench is less in the vertical direction than in the horizontal direction.
A vertical spacing of one forth the horizontal spacing is recommended to
account for lower permeability in the vertical direction.
In situations where the landfill owner chooses not to perform EPA
Method 2E, the well spacing is to be determined based on the same
theoretical concepts presented in Section 9.2.1.1 for vertical well spacing.
Using the proposed trench vacuum, the theoretical radius of influence in the
horizontal direction can be obtained from Figure 9-7. This radius of
influence is to be used identically to the interior radius of influence
determined discussed above. The trenches are to be spaced no more than two
times the theoretical radius of influence apart horizontally, and vertically
no more than one-half the theoretical radius of influence.
9.2.2.2 Trench Construction. The horizontal trenches may be
constructed of PVC, HOPE, corrugated steel, or other suitable nonporous
material. In order to minimize the collapse of the trenches due to the
refuse accumulation and/or landfill operation equipment, some employ
alternating pipe connections which typically consist of pipes with adjacent
diameters (e.g., 8" and 10", 10" and 12", etc.) loosely fitted together.
Loose fitting pipes of different diameters allow landfill gas to freely flow
9-27
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through yet also handles the stress due to the refuse weight and/or
equipment better than straight pipe connections. Some landfill owners
prefer using corrugated steel pipes since the heat of the landfill tends to
reduce the stress strength of PVC or HOPE pipes. Typical construction of
the horizontal trench collection system is illustrated in Figure 9-9.
9.2.2.3 Monitoring and Adjustment Design Provisions. To facilitate
periodic trench monitoring and adjustment, each layer of trenches should be
connected to a common header leg that extends to the surface and is
equipped with a valve, flanges, gaskets, connectors and access couplings.
The header leg assembly should also include at least one sample port that
can be used to monitor pressure or collect gas samples periodically. The
trench header assembly should allow for controlling individual layers of
trenches.
9.2.1.4 Gas Mover Sizing. The gas mover (fan, blower or compressor)
system should be designed to handle the peak landfill gas flowrate over the
life of the gas moving equipment. Identical to vertical well collection
systems, this attribute can be evaluated by first projecting the peak
landfill gas flowrate and comparing this flow to the proposed equipment
specifications. The peak gas flow rate can be projected using the following
expression:
Peak Flow [m3/yr] = 2LQ R (1 - e"kt)
where,
L = refuse methane generation potential, m /Mg refuse
R = average annual acceptance rate, Mg/yr
k = methane generation rate constant, 1/yr
t = age of the landfill plus the gas mover equip, life or active
life of the landfill, which ever is less, in years
A value of 230 m is recommended for L . If Method 2E has been performed,
the value of k determined from the test should be used; if not, a value of
.02 years" is recommended.
9.2.3 Design of Passive Collection Systems
As indicated above, passive systems are accepted as BDT only when
combined with a synthetic liner on the top, bottom, and sides of the
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Ran
Qas Coltoctton
TrwxshM
Existing Ground
QM Collection Pipe
Figure 9-9. Horizontal trench collection system.
9-29
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landfill. If such a collection system is proposed, two design features will
need to be evaluated, the proposed well spacing and the proposed well
construction. Each of these design features are addressed below.
9.2.3.1 Passive Well Spacing. The preferred methodology for
determining the well spacing for passive collection systems is to use the
average static landfill pressure determined from field testing. If EPA
Method 2E has been performed, first determine the average static landfill
pressure using all of the deep probe static pressure measurements. Second,
the pressure drop across the control system should be established, based on
control equipment specifications. The pressure drop across the flare (or
other control device), flame arrester, and collection header piping should
be considered. The expected pressure drop across the control system
(usually provided in vendor specifications) should be subtracted from the
landfill pressure to determine the differential pressure driving force.
Using this differential pressure (between the landfill gauge pressure and
the control system pressure drop), the theoretical radius of influence can
be determined using Figure 9-10. Based on this theoretical radius of
influence, wells should be placed throughout the landfill such that all
areas of the landfill are covered and the distance between wells is no more
than two times the radius of influence.
If EPA Method 2E has not been performed at the landfill, then the
static landfill pressure should be determined by field measurement. The
landfill should be divided into 5 equal volumes of refuse and a pressure
probe should be installed near the center of each equal volume, following
the probe installation procedures outlined in Section 3.3.1 of EPA
Method 2E. A differential pressure gauge should be used to measure the
gauge pressure at each pressure probe every 8 hours for 3 days. All 120 of
these pressure measurements should be averaged to determine the static
landfill pressure. This static landfill pressure should be used the same as
Method 2E results (discussed above). The expected control system pressure
drop (including the flare tip, flame arrester, collection header) is to be
subtracted from the static landfill pressure to determine the differential
pressure driving force. This differential pressure can then be used in
conjunction with Figure 9-10 to determine the theoretical radius of
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CO
10
9 -
8 -
7 -
cu
o
c
-------
influence. Wells should be placed throughout the landfill such that all
areas of the landfill are covered and the distance between wells is no more
than two times the radius of influence.
9.2.3.2 Passive Well Construction. The passive extraction well is to
be constructed of polyvinyl chloride (PVC) or high density polyethylene
(HOPE) pipe, at least 4 inches in diameter. The well should extend from the
landfill surface to at least 75 percent of the landfill depth. It is
recommended that the bottom two thirds of the pipe be perforated with
1/2 inch diameter holes spaced at 90 degrees every 6 inches. The pipe
should be placed in the center of a 2 ft diameter bore and backfilled with
gravel to a level 1 ft above the perforated section. The remainder of the
hole should be backfilled with a cover or backfilling material.
The well construction for passive systems is much less critical than
active systems. This is primarily because the collection well is under
positive pressure and air infiltration is not a concern. Additionally,
elaborate well head assemblies are not required since monitoring and
adjustment is not necessary. However, it is important that a good seal be
provided around the passive well in order to maintain the integrity of the
synthetic liner and maximize containment. Therefore, it is recommended that
a boot type seal, flange type seal, concrete mooring or other sealing
technique be used at each well location to maintain integrity of the
landfill cap.
9.3 COLLECTION SYSTEM OPERATING GUIDELINES
Active landfill gas collection systems should be periodically monitored
and adjusted to: (1) maximize landfill gas collection, and (2) ensure that
air infiltration into the system does not exceed safe levels. Additionally,
due to the inconsistency typically found within landfills, it may be
necessary to install additional wells in certain areas of high gas
generation.
To insure effective collection of landfill gas, the pressure and air
content should be measured at each well head (vertical collection systems)
or common header leg (horizontal collection systems) at least once every
month. If the measured pressure at the well head is positive, then the flow
from that well or set of trenches should be increased by opening the valve.
9-32
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Infiltration of too much air into a landfill may cause a fire or
explosion hazard. Therefore, EPA has determined that the N« concentration
(as a surrogate for air concentration) in the collected gas should be
maintained under 1 percent by volume. If the N2 concentration exceeds
1 percent, the valve at the well head assembly should be adjusted to
decrease the flow from that well, thus decreasing the level of air
infiltration. In cases where the well or leg pressure is positive and the
flow cannot be increased due to the exceedance of the N2 concentration
limit, additional extraction wells should be installed and added to the
collection system.
In all types of collection systems with header piping, condensation of
water and organics is expected to occur as a result of cooler temperatures
above the surface of the landfill. This condensate is generally collected,
treated for pH, and routed to a water treatment facility or discharged under
NPDES permit or otherwise handled according to RCRA Subtitle D and/or
Subtitle C requirements.
9.4 DESIGN AND OPERATING GUIDELINES FOR CONTROL SYSTEMS
All collected landfill gas must be routed to a control device capable
of achieving 98 percent reduction of the NMOC emissions by weight. The
Agency has identified a number of control devices that can achieve the
specified reduction. These include: open flares, enclosed ground flares,
gas turbines, internal combustion (1C) engines, boilers, incinerators, and
purification systems. Open flares that are in conformance with the
design and operating requirements of 40 CFR 60.18 are assumed to yield
98 percent destruction of NMOC emissions. Enclosed combustors, however,
such as enclosed ground flares, turbines, 1C engines, boilers, and
incinerators, require a performance test to demonstrate 98 percent
destruction efficiency or an outlet NMOC concentration of 20 ppmvd at
3 percent oxygen using EPA Method 25. Purification systems, such as
adsorption and absorption, do not require performance testing if all vent
streams from the system are routed to an open flare or enclosed combustor
that meet the specifications listed above. Control of only some portion of
the vent streams would be allowed if overall 98 percent destruction in NMOC
emissions is achieved.
9-33
-------
Alternatively, the landfill owner may select any NMOC destruction
device, or design and operate one of the listed devices outside the range of
the parameters specified if the device can be demonstrated to achieve
98 percent destruction of NMOC emissions. EPA Method 25 should be used to
determine the performance of alternative control devices.
9.5 COMPLIANCE SCHEDULE
Landfill owners/operators of all designated existing MSW landfills are
required to submit a design capacity report and an initial NMOC mass
emission rate estimate (Tier 1) within 90 days of the effective data of
their respective approved State plan for implementing the emission and
compliance guidelines. Owners and/or operators of new landfills must submit
a design capacity report and an initial NMOC mass emission rate estimate
(Tier 1) within 90 days of start-up (i.e., refuse acceptance). Suggested
contents of the report are discussed in Section 9.1.
Landfills with design capacities less than 100,000 Mg are not required
to perform further testing or reporting, unless the design capacity is
changed due to the addition of new areas, increase in depth, etc. If such a
change occurs, the landfill owner/operator is required to submit an amended
design capacity report within 90 days of the change.
Landfills with design capacities greater than 100,000 Mg, must file an
annual or periodic report of the NMOC mass emission rate (Tier 1) until the
landfill closes or the rate exceeds the regulatory cutoff.
When the NMOC emission rate, calculated in Tier 1, reaches
150 Mg/yr, the owner/operator must submit either a notification of intent to
install a collection system based on the specifications in Section 60.758 or
a collection system design plan for review within 1 year. If the landfill
owner/operator elects to perform the Tier 2 sampling in order to generate a
site-specific NMOC concentration or gas generation rate to use for the
calculation of the more precise NMOC emission rate, he/she must report these
calculations within one year of the initial Tier 1 calculation as well.
If the NMOC emission rate calculated in Tier 2 equals or exceeds
150 Mg/yr, then either controls must be installed or the owner/operator can
choose to perform Tier 3 testing; either must be done within 1 year after
9-34
-------
agency approval of a design which has been submitted for review, which takes
approximately 6 months, or within 18 months after the submittal of a
notification of intent. Should the NMOC emission rate calculated in Tier 2
be below 150 Mg/yr, then the Tier 2 calculation must be repeated annually,
while updating the NMOC concentration data at the specified intervals, as
described in Section 9.1. If the value for the NMOC emission rate from the
Tier 3 testing still equals or exceeds 150 Mg/yr then controls must be
installed within one year of the Tier 3 results. If the Tier 3 emission
rate calculation is below 150 Mg/yr then the Tier 3 calculation must be
repeated annually, while updating the NMOC concentration data at the
specified intervals, as described in Section 9.1.
The Tier 3 test will be valuable for those landfills that need to
install collection systems, because, as discussed in Section 9.2, flow rates
obtained may be used in designing the collection system. Additionally, the
test wells can serve as collection wells, if they meet the operating
criteria.
After the collection and control systems have been installed, the
owner/operator has 90 days to complete and submit the initial performance
test results. Also, semiannual compliance reports must be submitted in
which the following would be included: (1) any period in which the value of
any of the monitored operating parameters falls outside the ranges
identified in the initial performance test; (2) results of all annual
performance tests; (3) identification of any periods for which data were
excluded from these calculations; (4) any period when air pollution control
equipment malfunction occurred.
Upon closure of the landfill, a closure report must be filed. If,
after closure, the landfill meets the criteria outlined in Section 9.1 for
discontinuing control, the landfill owner/operator must submit a report.
The report should include documentation verifying that the collection and
control system has been operating according to the specifications for a
minimum of 15 years and that the NMOC mass emission rate has been below
150 Mg/yr for three consecutive 90 day-periods.
The landfill owner/operator may discontinue control upon the State's
verification that the above requirements have been met.
9-35
-------
The proposed regulation would also require that certain types of
records be maintained. Records of the accumulated refuse in place,
collection system design (including proposed and subsequent well or trench
spacing), control device vendor specifications, the initial performance test
results, and monitoring parameter established during the initial performance
test, must be maintained on site as long as the collection system and
control devices are required to be operated.
9-36
-------
9.6 REFERENCES
1. Y.C. McGuinn, Radian Corporation, to S.A. Thorneloe, EPA:CPB,
February 22, 1989, Design of municipal solid waste landfill gas
collection systems and their relative installation costs.
9-37
-------
APPENDIX A
EVOLUTION OF THE BACKGROUND INFORMATION DOCUMENT
-------
APPENDIX A
EVOLUTION OF THE BACKGROUND INFORMATION DOCUMENT
A.I INTRODUCTION
The purpose of this study was to develop background information to
support New Source Performance Standards (NSPS) for Municipal Solid Waste
Landfills (MSW landfills). Work on this study was performed by the Radian
Corporation from August 1987 to 1990 under contract with the
U. S. Environmental Protection Agency, Office of Air Quality Planning and
Standards.
The following chronology lists the major events which have occurred
during the development of background information for the MSW landfills NSPS
Major events are divided into three categories: (1) site visits,
(2) meetings and briefings, (3) reports and mailings.
G.2 SITE VISITS
November 16, 1987 Site visit to Puente Hills Landfill,
Whittier, CA
November 17, 1987 Site visit to Toyon Canyon Landfill Power Station,
Los Angeles, CA
November 18, 1987 Site visit to Palos Verdes Landfill,
Whittier, CA
November 18, 1987 Site visit to Rossman Landfill,
Oregon City, OR
December 15, 1987 Site visit to Rumpke Landfill,
Greensboro, NC
September 13, 1989 Site visit to Wilder's Grove Landfill,
Raleigh, NC
G.2 MEETINGS AND BRIEFINGS
November 16, 1987 Meeting with representatives of the Los Angeles
County Sanitation District
November 17, 1987 Meeting with representatives of the South Coast
Air Quality Management District
A-l
-------
March 21-24, 1988
May 17, 1988
May 18-19, 1988
June 8, 1988
August 24, 1988
October 5, 1988
January 19, 1989
March 16, 1989
March 20-24, 1989
May 4, 1989
June 7, 1989
September 6, 1989
Presentation at Governmental Refuse Collection and
Disposal Association symposium, Houston, TX
Meeting with representatives of the Governmental
Refuse Collection and Disposal Association to
discuss comments on draft background information
document
Presentation at the National Air Pollution Control
Techniques Advisory Committee (NAPCTAC)
Meeting with representatives of Waste Management,
Inc., to discuss comments on draft background
information document
Meeting with Waste Management of North America,
Inc. and the landfill Gas Committee of the
Governmental Refuse Collection and Disposal
Association, to discuss comments on draft
background information document
Meeting with representatives of Browning-Ferris
Industries to discuss status of project
Meeting with Browning-Ferris Industries to discuss
responses to Section 114 letters
Meeting with Waste Management, Inc. to discuss
status of project and Section 114 responses
Presentation of status of project at Governmental
Refuse Collection and Disposal Association
symposium, Monterey, CA
Presentation of status of project at National Solid
Waste Management Association (NSWMA) in Chicago, IL
Presentation at the National Air Pollution Control
Techniques Advisory Committee (NAPCTAC)
Meeting with representatives of Combustion
Engineering to discuss comments on field test
procedures
G.3 REPORTS AND MAILINGS
April 5, 1988 Mailing for NAPCTAC meeting on May 18, 1988
A-2
-------
March 15, 1989 Mailing for public comment on the preliminary
analysis of the design and costing for collection
systems ,
July 14, 1989 Mailing for public comment on draft field test
procedures and test methods
A-3
-------
APPENDIX B
INDEX TO ENVIRONMENTAL CONSIDERATIONS
-------
APPENDIX B
INDEX TO ENVIRONMENTAL CONSIDERATIONS
A.I INTRODUCTION
This appendix consists of a reference system which is cross indexed
with the October 21, 1974, Federal Register (30 FR 37419) containing EPA
guidelines for the preparation of Environmental Impact Statements. This
index can be used to identify sections of the document which contain data
and information germane to any portion of the Federal Register guidelines.
The are, however, other documents and docket entries which also contain
data and information, of both a policy and a technical nature, used in
developing the proposed standards. This appendix specifies only the
portions of this document that are relevant to the indexed items.
B-l
-------
TABLE B-l. INDEX TO ENVIRONMENTAL CONSIDERATIONS
Agency guideline for preparing
regulatory action environmental
impact statements (39 FR 37419)
Location within
the background information document
• Background and Summary of
Regulatory Alternatives
Regulatory alternatives
Statutory basis for
proposing standards
Source category and
affected industries
Emission control
technologies
Environmental, Energy, and
Economic Impacts of
Regulatory Alternatives
Regulatory alternatives
Environmental impacts
Energy impacts
Cost impacts
Economic impacts
The regulatory alternatives are
summarized in Chapter 5.
The statutory basis for the proposed
standards is summarized in Chapter 1.
A discussion of the source category
is in Chapter 3; details of the
"business/economic" nature of the
industries affected are presented in
Chapter 8. Affected are presented
in Chapter 8.
A discussion of emission control
technologies is presented in
Chapter 4.
Various regulatory alternatives are
discussed in Chapter 5.
The environmental impacts of various
regulatory alternatives are presented
in Chapter 6, Section 6.1, and 6.2.
The energy impacts of various
regulatory alternatives are
presented in Chapter 6, Section 6.3.
Cost impacts of various regulatory
alternatives are presented in
Chapter 7.
The economic impacts of various
regulatory alternatives are
presented in Chapter 8.
B-2
-------
APPENDIX C
LANDFILL GAS COMPOSITION DATA
-------
APPENDIX C
LANDFILL GAS COMPOSITION DATA
The speciated landfill gas composition data for 46 municipal solid
waste landfills are presented in Table C-l. This data was obtained from
Section 114 responses and South Coast Air Quality Management District Test
Reports. The identity of the landfills evaluated have been withheld due to
the presence of confidential business information. All of the data is
reported in ppmv unless otherwise noted.
C-l
-------
TABLE C-1. SPECIATEO NHOC COMPOSITION
LANDFILL ID
CHEMICAL NAME
ETHANE
TOLUENE
METHYLENE CHLORIDE
HYDROGEN SULFIDE
ETHYLBENZENE
XYLENE
1,2 - DIMETHYL BENZENE
LIMONENE
TOTAL XYLENE ISOMERS
rt-PINENE
D ICHLOROO 1 FLUOROHETHANE
ETHYLESTER BUTANOIC ACID
PROPANE
TETRACHLOROETHENE
VINYL CHLORIDE
METHYLESTER BUTANOIC ACID
ETHYLESTER ACETIC ACID
PROPYLESTER BUTANOIC ACID
1,2 - DICHLOROETHENE
METHYL ETHYL KETONE
THIOBISMETHANE
METHLYCYCLOHEXANE
TRICHLOROETHENE
NONANE
BENZENE
ETHANOL
A
929.5
35.53
0.18
36.95
64.98
0
9.76
0.74
9.98
0.13
0
0.22
1.53
B
758
428
664
588
470
446
19
398
77
305
282
253
34
210
197
34
167
23
157
C D E
17
49.3 244.5 60.
174 38.
4
2.
43.
48
28.5 14.
0.05 48.1 6.
84.7 8.
1.
20.4 6.
0.95 52.2 2.
F
80
91 0.251
82
.2
47
99
.8
93 0.177
11 1
58
48
96 0.069
76 0.299
G
0
19.38
44
0.25
0.5
32.95
0
7.1
15
2.78
0
1.38
1.05
H
0
77.17
14
7
15.26
11.92
4.67
5.63
10.92
7.82
7.67
5.23
1.53
1 J
0
3
1.8 8
0.15
0.45
23.3
7
0.1 0.9
11.35
1.65
0
0.8 0.4
0.4 0.1
K
0
17.2
0.7
1.3
2.9
0
5.2
0.3
1
0
0
0.3
0.3
I
0
1.45
0.2
0.23
9.78
11.85
0
0.23
2.7
0.83
3.75
0.18
0.35
H
0
12.7
35
0.65
1.55
34.5
6.5
1
7.7
1.2
3.65
1.55
0.7
N
0
28.22
3.25
4.06
8.55
1.3
0
2.4
8.43
5.27
12
1.54
2.6
-------
TABLE C-1. SPECIATED NHOC COHPOSITION
LANDFILL ID
CHEMICAL NAME
ETHANE
TOLUENE
METHYLENE CHLORIDE
HYDROGEN SULFIDE
ETHYLBENZENE
XYLENE
1,2 - DIMETHYL BENZENE
LIMONENE
TOTAL XYLENE ISOMERS
<>C -PINENE
DICHLORODIFLUOROHETHANE
ETHYLESTER BUTANOIC ACID
PROPANE
TETRACHLOROETHENE
VINYL CHLORIDE
HETHYLESTER BUTANOIC ACID
ETHYLESTER ACETIC ACID
PROPYLESTER BUTANOIC ACID
1,2 - DICHLOROETHENE
METHYL ETHYL KETONE
THIOBISMETHANE
METHLYCYCLOHEXANE
TRICHLOROETHENE
NONANE
BENZENE
ETHANOL
0 F
0
40
127.5 0.00536
5
12.5
7.45
86.5
11.95
19 2
18.5
4.95
21.5 0.00615
1.95 0.00436
0
268.75
125.28
29.91
35.35
70.75
16
4.26
12.63
16.92
4.55
18.75
12.98
5.53
R
0
37
14
4
12
0
0
11
13
13
5.5
3.1
1.2
S T
1420
13 221
0.5 24.5
700
3.4 48.1
0
0 0
18.2
8.2
0.84 15.2
6.5 0
NM
0.2 7.85
0.57 2.42
U
0
13.9
24.67
3.73
4.63
24.47
1.4
2.63
12.43
3.93
5
1.67
0.77
V U X
0
5.85 0.197 34.2
2 0.146666
0.7
1.5
11.45
11
0.4 0.0035 5.4
5.2 0.7 3.42
0.5 0.016
6
0.2 0.0158 4.86
0.15 0.186666 1.48
Y
0
68.5
3.45
22
67.5
16.5
0
7.75
3
1.35
57.5
4.7
1.5
Z
0
30
50
3.8
12
30
68
9.3
5.3
0.9
15
3.4
1
AA
0
2.5
2
0.55
1.3
0.5
0
0.4
0.4
0.25
NM
0.2
0
BB
18.39
12.13
2.65
1.14
1.04
-------
TABLE C-1. SPECIATEO MHOC COMPOSITION
LANDFILL ID
CHEMICAL NAME
ETHANE
TOLUENE
METHYLENE CHLORIDE
HYDROGEN SULFIDE
ETHYLBENZENE
XYLENE
1.2 - DIMETHYL BENZENE
LIHONENE
TOTAL XYLENE ISOMERS
<* -PINENE
DICHLORODI FLUOROMETHANE
ETHYLESTER BUTANOIC ACID
O
1 PROPANE
** TETRACHLOROETHENE
VINYL CHLORIDE
HETHYLESTER BUTANOIC ACID
ETHYLESTER ACETIC ACID
PROPYLESTER BUTANOIC ACID
1,2 - DICHLOROETHENE
METHYL ETHYL KETONE
THIOBISMETHANE
METHLYCYCLOHEXANE
TRICHLOROETHENE
NONANE
BENZENE
ETHANOL
CC DD
0
47.5
82 9.25
10.9
37.5
8.85
0
12.25
6.7 7.6
5.45
11
3.75
4 0.65
EE
0
2.1
3
0.2
0.45
14.25
6.5
0.25
1.95
0.3
NM
0.15
0
FF GG
0
27.2 31.5
0 20
2.73 5.7
5.57 10
8.9 11.75
0.63
1.53 4.6
14.4 2.05
2.87 6.2
6.33 5
0.5 3.25
0.83 1
HH
0
23.33
0.33
5.27
13.33
13.27
0
3.7
4.93
6.23
31.33
1.63
0.57
II JJ KK LL MM NN
0
8.63 53 64 4.73
0 54.9 18.4
11 47.9
4.6 1.7
12
19 0 7.3
0
3.8 7.5 0.012
18.73 0 4.5 7.7 3.43
8.8 3.8 0 0.097
21
0.76 9.47 1.8 1.2 3.9 0.025
0.916 32.3 0.6 0.77 2.84
00 PP
0
15 10.05
32 17
2.2 0.3
3.7
0.75
37.5
36.5
1 0.95
3.25
1.2 0.9
4.7
2.4
2.4 0.45
1.2 0.2
-------
TABLE C-1. SPECIATEO HHOC COMPOSITION
LANDFILL ID
00
RR
SS
TT
CHEMICAL NAME
ETHANE
TOLUENE
HETHYLENE CHLORIDE
HYDROGEN SULF1DE
ETHYLBENZENE
XYLENE
1,2 - DIMETHYL BENZENE
LIMONENE
TOTAL XYLENE ISOHERS
of -PINENE
D 1 CHLORODI FLUOROME THANE
ETHYLESTER BUTANOIC ACID
7* PROPANE
01 TETRACHLOROETHENE
VINYL CHLORIDE
METHYLESTER BUTANOIC ACID
ETHYLESTER ACETIC ACID
PROPYLESTER BUTANOIC ACID
1,2 - DICHLOROETHENE
METHYL ETHYL KETONE
THIOBISMETHANE
METHLYCYCLOHEXANE
TRICHLOROETHENE
NONANE
BENZENE
ET HANOI
930
8.65 4.91 123
1.48
23.4
70.9
0
13.1
0.3017 0.441 6.82
14.28 2.57 5.61
0.1638 0.28 0.11
0.309 0.748 2.02
0.595 2.57 2.65
1240
51
50.95
7.22
22.8
0.19
25.3
64.95
3.83
1.3
7.8
4.55
-------
TABLE C-1. SPECIATED NHOC COMPOSITION
o>
LANDFILL ID
CHEMICAL NAME
ACETONE
2 - BUTANOL
OCTANE
PENTANE
HEXANE
HETHYLESTER ACETIC ACID
1 - HETHOXY - 2 - METHYL PROPANE
2 - BUTANONE
1,1 - DICHLOROETHANE
1 - BUTANOL
BUTANE
4 - METHYL - 2 - PENTANONE
2 - METHYL PROPANE
1 - HETHYLETHYLESTER BUTANOIC ACID
2 - METHYL. METHYLESTER PROPANOIC ACID
CARBON TETRACHLORIDE
CHLOROETHANE
1,1,3 TRIMETHYL CYCLOHEXANE
2 - METHYL - 1 - PROPANOL
1,2 - DICHLOROETHANE
TR 1 CHLOROFLUOROHETHANE
CHLOROMETHANE
2,5 DIMETHYL FURAN
2 - METHYL FURAN
CHLORODI FLUOROMETHANE
PROPENE
ABCDEFGH
0 1.84 2.25 4.5
152
152
0.58 11.1 0 3.83
2.49 20.82 0 4.17
136
136
129
0.3 11.85 11.18 5.63
100
0 18.76 0 0.83
89
84
69
69
0 0.065 0 0.0026 0 0
0.43 3.25 9.2 2.33
57
51
0.02 30.1 0.02 0.447 0.78 0
0.66 000 1.35 0 1.08 1.3
1.12 0.9 0.28 0.18
41
40
0.97 12.58 0 0.77
36
1 J K I M N
0 0 0 2.5 2.25
0.5 1.2 0 9 0
3 2.4 0 10 0
1.75 0.6 0.05 0 0.85
11050
0 0 0.05 0 0
1.6 0 0.5 8.25 0.2
0.05 0000 0.55
0 2.35 0.7 0.73 7.9 0.48
1.25 0 0 6.1 0.1
3.85 0030
-------
TABLE C-1. SPECIATED NMOC COMPOSITION
LANDFILL ID
AA
BB
CHEMICAL NAME
ACETONE
2 - BUTANOL
OCTANE
PENTANE
HEXANE
METHYLESTER ACETIC ACID
1 - METHOXY - 2 - METHYL PROPANE
2 - BUTANONE
1,1 - D1CHLOROETHANE
1 - BUTANOL
BUTANE
4 - METHYL - 2 - PENTANONE
2 - METHYL PROPANE
1 - HETHYLETHYLESTER BUTANOIC ACID
2 - METHYL, HETHYLESTER PROPANOIC ACID
CARBON TETRACHLORIDE
CHLOROETHANE
1.1,3 TRIMETHYL CYCLOHEXANE
2 - METHYL - 1 - PROPANOL
1,2 - DICHLOROETHANE
TRICHLOROFLUOROMETHANE
CHLOROHE THANE
2,5 DIMETHYL FURAN
2 - METHYL FURAN
CHLORODI FLUOROMETHANE
PROPENE
12
3.25
6.5
19.5
16.5
0 0.0134
1.35
0.45
2.85 0
0.6
0
20
0.39
6.34
11.87
0
0
2
0
0.06
0.7
0
1
0
0
2.6 0.053
0
0 0
4.9 0.026
0 0
2.1 0
1.4 0.21
0
0
0
13.4
1.21
0
0
0.76
0
0.77
7.19
0
5.33
46.53
7.13
6.33
6.07
0
7.33
0
0.5
1.33
0
8.5
0.5
0
0.45 10
1.5
0 0.0001 0.009
0
0 10 0.176
0.45 0 0
1.2
1.9
32
0
0
0
0
0
0.5
0
0.2
0
0
14
45
25
7.9
32
0
3.7
0.1
1.1
3.6
0
NM
0
0
0.1
0
0
0
0
0 0
0
0.1
-------
TABLE C-1. SPECUTEO NHOC COHPOSITION
LANDFILL ID
CHEMICAL NAME
.........
ACETONE
2 - BUTANOL
OCTANE
PENTANE
HEXANE
METHYLESTER ACETIC ACID
1 - METHOXY - 2 - METHYL PROPANE
2 - BUTANONE
1,1 - DICHLOROETHANE
1 - BUTANOL
BUTANE
4 - METHYL - 2 - PENTANONE
2 - METHYL PROPANE
-------
TABLE C-1. SPECIATED NHOC COMPOSITION
LANDFILL ID
RR
SS
TT
CHEMICAL NAME
ACETONE
2 - BUTANOL
OCTANE
PENTANE
HEXANE
HETHYLESTER ACETIC ACID
1 - METHOXY - 2 - METHYL PROPANE
2 - BUTANONE
1,1 - DICHLOROETHANE
1 - BUTANOL
BUTANE
4 - METHYL - 2 - PENTANONE
2 • METHYL PROPANE
1 - METHYLETHYLESTER BUTANOIC ACID
2 - METHYL, METHYLESTER PROPANOIC ACID
CARBON TETRACHLORIDE
CHLOROE THANE
1.1,3 TRIMETHYL CYCLOHEXANE
2 - METHYL - 1 - PROPANOL
1,2 - DICHLOROETHANE
TRICHLOROFLUOROME THANE
CHLOROMETHANE
2,5 DIMETHYL FURAN
2 - METHYL FURAN
CHLOROD 1 F LUOROME T HANE
PROPENE
0
3.96
6.06
0.71
0
0.00063 0.0007 0
0.11
0.056 0.1635 0
0 0 0.47
1.34
1.33
0
0.67
17.96
8.95
0
0
0.95
0.18
0.63
10.22
4.79
-------
TABLE C-1. SPECIATEO NHOC COMPOSITION
LANDFILL ID
CHEMICAL NAME
METHYL ISOBUTYL KETONE
ETHYL MERCAPTAN
D 1 CHLOROFLUOROMETHANE
1,1.1 - TRICHLOROETHANE
TETRAHYDROFURAN
ETHYLESTER PROPAN01C ACID
BROMODICHLOROMETHANE
ETHYL ACETATE
3 - METHYLHEXANE
C10H16 UNSATURATED HYDROCARBON
METHYLPROPANE
0 CHLOROBENZENE
1
I— ACRYLONITRILE
o
METHYLETHYLPROPANOATE
1.1 - DICHLOROETHENE
METHYL MERCAPTAH
1.2 - DICHLOROPROPANE
j - PROPYL MERCAPTAN
CHLOROFORM
1,1,2,2 - TETRACHLOROETHANE
1,1,2,2 - TETRACHLOROETHENE
2 - CHLOROETHYLVINYL ETHER
t - BUTYL MERCAPTAN
DIMETHYL SULFIDE
ABCDEFGHIJKLMN
'
0 0 0 2.5 00 0.45 0 0.5
0.36 5.01 MM 0 0 0 NM NM NM
0.03 5.5 0.48 0.193 0.6 0.37 0.2 0.6 0.03 1.35 0
30
26
0.22 0.12 00 00000
20
0.15 0 00 00 0.05 0 0.2
0 0.8 00 00000
0.08 0.23 0.43 0.18 3.1 0.15 0 0 0.1 0.05
0.06 0.02 00 00000
1.56 0.94 0 0.049 00 00000
0 00000 0.01 0 0
0 00000 2.25 0 0
-------
TABLE C-1. SPECIATED NHOC COMPOSITION
LANDFILL ID
CHEMICAL NAME
METHYL ISOBUTYL KETONE
ETHYL HERCAPTAN
DICHLOROFLUOROHETHANE
1,1,1 - TRICHLOROETHANE
TETRAHYOROFURAN
ETHYLESTER PROPANOIC ACID
BROHOD 1 CHLOROMETHANE
ETHYL ACETATE
3 - HETHYLHEXANE
C10H16 UNSATURATED HYDROCARBON
HETHYLPROPANE
CHLOROBENZENE
ACRYLONITRILE
METHYLETHYLPROPANOATE
1.1 - DICHLOROETHENE
METHYL MERCAPTAN
1,2 - DICHLOROPROPANE
j • PROPYL MERCAPTAN
CHLOROFORM
1,1,2,2 - TETRACHLOROETHANE
1,1,2,2 - TETRACHLOROETHENE
2 - CHLOROETHYLVINYL ETHER
t - BUTYL MERCAPTAN
DIMETHYL SULFIDE
0 f Q R
1.15 5 1
NM 0 NM
4.2 0.5 1.3
0 2.48 0
0 10 0
0 00
0.65 0.75 0
1.8 0.5 0
0 00
0 00
0 00
STUVUXYZAABB
NM 1 0 11.5 1.2 NM
11
UU UU UU UM UM UU
nn nn nn nn nn nn
0 1.24 0.47 0 0.00024 9 0 1.9 0
0 7.85 0 0 0.001 000
0000 000
7.4 0 0 000
0.04 0 0.13 0 0 0.2 0 0.07
3.3
0 0 0.27 0 000
2.1
0000 0.001 0.234 000
0000 2.35 0.2 0
0.05
0000 000
0.28
0.1
-------
TABLE C-1. SPEC1ATEO NHOC COMPOSITION
LANDFILL 10
CHEMICAL NAME
METHTL ISOBUTYL KETONE
ETHYL MERCAPTAN
DICHLOROFLUOROHETHANE
1,1.1 - TRICHLOROETHANE
TETRAHYDROFURAN
ETHYLESTER PROPANOIC ACID
BROMOD 1 CHLOROMETHANE
ETHYL ACETATE
3 - METHYLHEXANE
C10H16 UMSATURATED HYDROCARBON
METHYLPROPANE
CHLOROBEMZENE
1 ACRYLONITRILE
^**
ro METHYLETHYLPROPANOATE
1.1 - DICHLOROETHENE
METHYL MERCAPTAN
1.2 - OICHLOROPROPANE
i - PROPYL MERCAPTAN
CHLOROFORM
1.1,2.2 - TETRACHLOROETHANE
1,1,2,2 - TETRACHLOROETHENE
2 - CHLOROETHYLVINYL ETHER
t - BUTYL HERCAPTAN
DIMETHYL SULFIDE
DICHLOROTETRAFLUOROETHANE
DIMETHYL DISULFIDE
CC DD EE FF GG HH II JJ
A NH 3.33 3.33
NM 0 NM NM NM
0.4 0 0 0.25 0 0.016
000 0
000 0.1
000 0
0.2 0 0 0.1 0
0.35 00 0
000 0
000 0
000 0
KK LL HM NN
1
1 23.8
NM 1.7
0 0.37 0.019
0 0
0 0 0.1
0
0 0.064 0
1 1.3
0 0.03
1
000 0.0016
0 0
2.6
0 0
1
1
1.1
1
00 PP
0
NM
0.7 1.15
0
20
15
12
0
0
7.3
0.2
0
0
0
0
-------
TABLE C-1. SPECIATED NHQC CONPOSITION
LANDFILL ID
00
RR
SS
TT
CHEMICAL NAME
METHYL ISOBUTYL KETONE
ETHYL MERCAPTAN
DICHLOROFLUOROMETHANE
1,1,1 - TRICHLOROETHANE
TETRAHYDROFURAN
ETHYLESTER PROPANOIC ACID
BROHOO 1 CHLOROME THANE
ETHYL ACETATE
3 • HETHYLHEXANE
C10H16 UNSATURATED HYDROCARBON
O METHYLPROPANE
ti. CHLOROBENZENE
Co
ACRYLONITR1LE
METHYLETHYLPROPANOATE
1,1 - DICHLOROETHENE
METHYL MERCAPTAN
1,2 - DICHLOROPROPANE
j - PROPYL MERCAPTAN
CHLOROFORM
1,1,2,2 - TETRACHLOROETHANE
1,1,2,2 - TETRACHLOROETHENE
2 - CHLOROETHYLVINYL ETHER
t - BUTYL MERCAPTAN
DIMETHYL SULFIOE
'
0.48
0.0152 0.023 0.16
2.02
0.43
0
0
0.22
0.00278 0.0058 0
0.11
0
26.11
0.77
7.8
0
0
0.49
0.12
0
0
0
-------
TABLE C-1. SPECIATED NHOC COMPOSITION
LANDFILL ID
CHEMICAL NAME
o
1— >
•fe
D 1 CHLOROTETRAFLUOROETHANE
DIMETHYL DISULFIDE
CARBONYL SULFIDE
1,1,2-TRICHLORO 1.2,2-TRIFLUOROETHANE
METHYL ETHYL SULFIDE
1,1,2 - TRICHLOROETHANE
1,3 - BROMOCHLOROPROPANE
1.2 - DIBROMOETHANE
C-1, 3 - OICHLOROPROPENE
t-1,3 - OICHLOROPROPENE
ACROLEIN
1,4 -DICHLOROBEN2ENE
BROHOFORM
1,3 - DICHLOROPROPANE
1,2 - DICHLOROBENZENE
1.3 - DICHLORBENZENE
DIBROMOCHLOROMETHANE
BROMOMETHANE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
NM
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-------
TABLE C-1. SPECIATED NHOC COMPOSITION
LANDFILL 10
AA
CHEMICAL NAME
o
1
01
0 1 CHLOROTETRAFLUOROETHANE
DIMETHYL DISULFIDE
CARBONYL SULFIOE
1.1,2-TRICHLORO 1.2,2-TRIFLUOROETHANE
METHYL ETHYL SULFIDE
1,1.2 - TRICHLOROETHANE
1,3 - BROMOCHLOROPROPANE
1,2 - DIBROMOETHANE
C-1, 3 - DICHLOROPROPENE
t-1,3 - DICHLOROPROPENE
ACROLEIN
1,4 -DICHLOROBENZENE
BROMOFORM
1,3 - DICHLOROPROPANE
1.2 - DICHLOROBENZENE
1,3 - DICHLORBENZENE
D 1 BROHOCHLOROMETHANE
BROMOMETHANE
0
0
0
0
0
0
0
0
0
0.1
0
0
0
0
0
0
0
0
0
NM
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.1
0.32
0
0
0
0
0
0
0
0
0
0
NM
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.005
0.0005
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
NM
0
0
0
0
0
0
0
-------
TABLE C-1. SPECIATEO NNOC COMPOSITION
LANDFILL 10
BB
CC
DD
EE
ff
GG
HH
II
JJ
KK
LL
MM
NH
00
CHEMICAL NAME
o
1
<£
----------
D 1 CHLOROTETRAFLUOROETHANE
DIMETHYL DISULFIDE
CARBONYL SULFIDE
1.1,2-TRICHLORO 1.2,2-TRIFLUOROETHANE
METHYL ETHYL SULFIDE
1.1,2 - TRICHLOROETHANE
1,3 - BROMOCHLOROPROPANE
1,2 - DIBROMOETHANE
C-1, 3 - DICHLOROPROPENE
t-1,3 - DICHLOROPROPENE
ACROLEIN
1,4 -DICHLOROBENZENE
BROHOFORH
1,3 - DICHLOROPROPANE
1,2 - DICHLOROBENZENE
1,3 - DICHLORBENZENE
D 1 BROMOCHLOROMETHANE
BROHOMETHANE
0
0
0
0
0
0
0
0
0
0
NH
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
0
0
1.1
0.5
0
0
-------
TABLE C-1. SPECIATEO NNOC COMPOSITION
LANDFILL ID
00
RR
SS
TT
CHEMICAL NAME
I
!-•
«»J
DICHLOROTETRAFLUOROE THANE
DIMETHYL DISULF1DE
CARBONYL SULFIDE
1,1,2-TRICHLORO 1.2,2-TRIFLUOROETHANE
METHYL ETHYL SULFIDE
1,1,2 - TRICHLOROETHANE
1,3 - BROHOCHLOROPROPANE
1,2 - DIBROMOETHANE
C-1,3 - DICHLOROPROPENE
t-1,3 - DICHLOROPROPENE
ACROLEIN
1,4 -OICHLOROBENZENE
BROMOFORM
1,3 - DICHLOROPROPANE
1,2 - DICHLOROBENZENE
1,3 - DICHLORBENZENE
DIBROMOCHLOROMETHANE
BROMOMETHANE
NM
0
0
0
0
0
0
0
-------
APPENDIX D: GAS GENERATION RATE MODELING
This appendix provides samples calculations for estimating the landfill
air emission rate using the Scholl Canyon model, as well as, a brief
discussion of alternative methods. Section D.I contains a short description
of the Scholl Canyon model and sample calculations for 4 model cases.
Section D.2 discusses the emission factor method, the SCAQMD method and the
Municipal Waste Generation Rate method as alternative techniques for
estimating nationwide landfill air emissions.
D.I Scholl Canvon Model.
The Scholl Canyon model is a single stage, first order kinetic model.
It assumes that after a negligible lag time during which anaerobic
conditions are established, the gas production rate is at its peak. After
the lag time, the gas production rate is assumed to decrease exponentially
as the organic fraction of the landfill refuse decreases. The model
equation is as follows:
_ k, _ k,
dt ~ 0
where,
8r = methane production rate, ft /lb of refuse-yr.
k = rate constant, I/year
t = time, year
LO = total volume of methane ultimately to be produced,
ft3/"lb of refuse
D-l
-------
If the refuse mass is broken down into the submasses which are placed during
each year of the landfill's operation, the model equation is:
dG "
— = kL = kLQ L r. exp (-k.t.)
dt i=l
where,
r. = fraction of total refuse mass contained in submass i
t. = time from placement of submass i to point in time at which
composite production rate is desired, yr
k. = gas production rate constant for submass i, I/year
The rate constant , k, can be calculated if the time and quantity of each
refuse submass placement, and the gas flowrate at a given time are known.
Once k is calculated from the equation, the methane generation rate at any
time can be estimated. Figure D-l depicts the Scholl Canyon model
2
simulation for two different values of LQ.
D.I.I Sample Calculations Using Scholl Canyon Model
This section discusses how to use the Scholl Canyon Model to estimate
gas generation for several hypothetical landfills (Case 1 through 4 below).
In case 1, information on how to estimate the VOC emission rate and toxic
compound emission rate is also presented. To use the model, it is necessary
for the landfill owner or operator to obtain representative values of gas
generation rate, nonmethane organic compound concentration, and toxic
compound concentration via field testing (as discussed in Chapter 9.0).
D-2
-------
TIHC
emcon
flssociotes
Figure D-l. Estimated methane production (Scholl Canyon Kinetic Model)
D-3
-------
D.I.1.1 Case 1
Given: Landfill A was in operation for 15 years accepting refuse at
an average rate of 133,300 Mg/yr. It closed after 15 years
of operation with 2 x 10 Mg of refuse in place (RIP).
Test well data conducted one year after closure (16 years
after initial placement of refuse), indicated that Landfill A
is capable of producing 0.0715 ft /lb-yr of methane gas.
Test well data also showed that the average concentration of
nonmethane organic compounds is 1500 ppm and the
concentration of toxic compounds is as follows: benzene
(120 ppm), methylene chloride (50 ppm), vinyl chloride
(100 ppm).
Calculate: Kinetic constant (k), methane generation rate as a function
of time, emission rate of VOC, and emission rate of toxic
compounds.
1. First, reduce test well data to the actual recoverable methane
production rate.
Total recoverable methane gas rate = (test well flowrate)(refuse in
place)
Total recoverable methane gas rate = (0.0715) (2 x 10 g) 1b
454 g
315 x 106 ft3 methane/yr.
D-4
-------
2. Calculate the fraction of submass i, r ^ , by treating yearly
accumulation as the mass of submass i.
0.0667
2 x 106
3. Calculate the kinetic constant, k, using the recoverable methane gas
rate calculated in Step 1 and t of 16 years.
t. = 15
^ - k Lo Mt
J4. — U U
dt t = 16
where, t = time after closure (= 1 year)
Mt = amount of refuse accumulated at time t
t.. + t = age of submass i
[Note that the actual age of the submass i is corrected by adding the time
after closure.]
Assuming LQ of 100 liter CH4/Kg refuse or 3.53 x 103 ft3 CH4/Mg refuse,
315 x 106 ft3 CH. - ft3 CH, ,
k (3'53 x 10 Mg refuse > <2 x 10 ^ refuse>
i = 15
X (0.0667) exp [-k (t + 1)]
i = 1
i = 15
0.669 = k £ exp [-k (t. + 1)]
= k {exp (-2k) + exp (-3k) + ... exp (-16k)}
D-5
-------
Solving for k by trial and error procedures, k = 0.1 1/yr.
4. Express the model equation with calculated k.
i = 15
dG = k LQ Mt £ ri exp [-k (t. + tc)]
dt
i , t. = 15
= (0.1) (3.53 x 1(T) (2 x 10°) (0.0667) n £ exp [-0.1 (t. + tc)]
t. = 1
7 *1 A 15 3 CH4
= 4.707 x 10' ] 7 exp [-0.1 (t. + t)] in fr — 2— (1)
t . - 1 ] c yr
5. The future methane gas generation rate now can be calculated by
changing tc> For example, the methane gas generation 5 years after
closure may be calculated by setting t = 5 in Equation (1).
6. The methane gas generation rate before closure can be calculated by
modifying the equation (1).
dG
n
exp (-k t.)
.
— (before closure) = (k L M ) J_ _ _ ]_ (2)
dt ° n t. = 1 (n)
where, Mn = amount of refuse accumulated over n years.
n = number of years since the initial placement of refuse
but before closure
dG t. = n
— (before closure) = (
-------
Figure D-2 shows the methane generation rate as a function of time for
Landfill A.
7. The VOC emission rate can be calculated by inputting the nonmethane
organic compound (i.e. VOC) concentration measured during field
testing. The example below represents VOC emissions in year 16 of the
landfill.
The methane generation rate (315 x 10 ft /yr) should be
multiplied by 2 to calculate total gas generation. This step
assumes that landfill gas is 50 percent methane.
o 315 x 106 ft3/yr x 2 = 630 x 106 ft3/yr
Using the calculated nonmethane organic compound concentration of
1500 ppm and assuming an average VOC molecular weight of 80:
630 x
106 ft3
yr
0.0015 VOC
Ib mol
359 ft3
80 Ib
Ib mol
= 210,000 Ib VOC per year
= 95 Mg VOC per year
The toxic compound emission rate can be calculated by inputting the
concentration of each toxic compound measured during field testing.
The example below represents toxic compound concentration in year 16 of
the landfill.
630 x 106 ft3
yr
0.00012 benzene
Ib mol
359 ft3
78 Ib
Ib mol
= 16.400 Ib benzene = 7,400 k§ benzene
yr yr
D-7
-------
700
Methane Gas Generation Rate vs. Time
RIP - 2X10*6 Uq. 13 Yr Activ* Ufe
u
i/i
o
X.
a
o
o
£
600 -
500 -
400 -
300 -
200 -
100 -
!2
Year Sine* th« nitial S»fus« Placsment
D k - 0.1 1/yr
:a
Figure D-2. Methane gas generation rate as a function of time,
D-8
-------
630 x 106 ft3
yr
0.00005 MC
Ib mol
359 ft3
85 Ib
Ib mol
= 7,450 Ib MC = 3,380 kg. MC
yr yr
630 x 106 ft3
y**
0.00015 VC
Ib mol
359 ft3
62 Ib
Ib mol
= 16,300 Ib Vinyl Chloride = 7,400 kg VC
yr yr
0.4.2 Case 2
Given:
Landfill B was in operation for 15-years accepting refuse at
an average rate of 133,300 Mg/yr. It clsoed after 15 years
of operation with 2 x 10 Mg of refuse in place (RIP). Test
well data conducted two years after closure (17 years after
initial placement of refuse), indicated that Landfill B is
capable of producting 0.061 ft /lb-yr of methane gas.
Calculate: Kinetic constant (k) and methane generation rate as a
function of time.
1. First, reduce test well data to the actual recoverable methane
production rate.
Total recoverable methane gas rate = (test well flowrate)(refuse in
place)
D-9
-------
Total recoverable methane gas rate = (0.061) (2 x 1012 g) 1b
454 g
= 269 x 106 ft3 methane/yr.
2. Calculate the fraction of submass i, ri , by treating yearly
accumulation as the mass of submass i.
r. m 133,300 m 0 Q667
2 x 106
3. Calculate the kinetic constant, k, using the recoverable methane gas
rate calculated in Step 1 and t of 17 years.
t. = 15
dG
dt t - 17
k LQ Mt I exp [-k (t. + tc)]
where, t = time after closure (= 2 years)
M^ = amount of refuse accumulated at time t
t^ + tc = age of submass i
Assuming LQ of 100 liter CH4/Kg refuse or 3.53 x 103 ft3 CH4/Mg refuse,
269 x 106 ft3 CH, . ft3 CH. ,
—^ = k (3.53 x 10J Mg ) (2 x 105 Mg refuse)
1^ 15
X J] (0.0667) exp [-k (t + 2)]
i = 1
D-10
-------
i = 15
0.571 = k £ exp [-k (t. + 2)]
= k {exp (-3k) + exp (-4k) + ... exp (-17k)}
Solving for k by trial and error procedures, k = 0.2 1/yr.
4. Express the model equation with calculated k.
i = 15
^= k Lo Mt .£ ri exp £'k ^i + V]
dt
, , t. = 15
= (0.2) (3.53 x 10J) (2 x 10b) (0.0667) nT exp [-0.1 (t. + t )]
t. = 1 ic
7 t. = 15 - CH.
= 9.414 x 10' ^ exp [-0.2 (t. + t )] in ff3 — 5
t.=-l 1 c yr
5. The methane gas generation rate before closure can be calculated by:
AC* t. = n
— (before closure) = (k L MJ L exp (-k t.) (2)
dt ° n t. = 1 - L-
1 (n)
where, M = amount of refuse accumulated over n years.
n = number of years since the initial placement of refuse
but before closure
dG
— (before closure) = (0.2)(3.53 x 10J) Mn t . exp (-0.2t.)
dt - n t. - i i
n
D-ll
-------
Figure D»3 shows the methane generation rate as a function of time for
Landfill B.
D.4.3 Case 3
Given: Landfill C was in operation for 15 years accepting refuse at
an average rate of 333,300 Mg/yr. It closed after 15 years
of operiaton with 5 x 10 Mg of refuse in place (RIP). Test
well data conducted one year after closure (16 years after
initial placement of refuse), indicated that Landfill C is
capable of producing 0.0715 ft /lb-yr of methane gas.
Calculate: Kinetic constant (k) and methane generation rate as a
function of time.
1. First, reduce test well data to the actual recoverable methane
production rate.
Total recoverable methane gas rate = (test well flowrate)(refuse in
place)
Total recoverable methane gas rate = (0.0715) (5 x 1012 g) 1b
454 g
= 790 x 106 ft3 methane/yr.
2. Calculate the fraction of submass i, r., by treating yearly
accumulation as the mass of submass i.
r. = 331,300 =
5 x 106
D-12
-------
L)
in
a
z
t
2
aoo
Methane Gas Generation Rate vs. Time
RtP - 2X10~6 Mq. 15 Yr Acllv* Uf«
700 -
600 -
500 -
400 -
300 -
200 -
100 -
iii r
8 12
16
20
'ear Sine* :h« nitiai ?«fU3« 3!ac«m«nt
a * - 0.2 1/yr
24
2B
Figure D-3. Methane gas generation rate as a function of time,
D-13
-------
3. Calculate the kinetic constant, k, using the recoverable methane gas
rate calculated in Step 1 and t of 16 years.
t. = 15
dG _ k L Mt £ exp [-k (t. + t )]
11 — U L j. i I \*
dt t = 16 *1 = 1
where, t = time after closure (= 1 year)
M^ = amount of refuse accumulated at time t
t- + t = age of submass i
Assuming LQ of 100 liter CH4/Kg refuse or 3.53 x 103 ft3 CH4/Mg refuse,
790 x 106 ft3 CH. , ft3 CH. ,
-^r-1 = k (3.53 x ID"3 Mg refu*e ) (5 x 10b Mg refuse)
i = 15
X Y, (0-0667) exp [-k (t + 1)]
i = 1
i = 15
0.669 = k £ exp [-k (t. + 1)]
= k {exp (-3k) + exp (-4k) + ... exp (-17k)}
Solving for k by trial and error procedures, k = 0.1 1/yr.
4. Express the model equation with calculated k.
i = 15
^ = k Lo Mt
dt
= k Lo Mt ri
3 fi *i " 15
= (0.1) (3.53 x 10J) (5 x 10°) (0.0667) ^ exp [-0.1 (t. + tc)]
D-14
-------
= 15
3CH4
= 11.77 x 10' ') exp [-0.1 (t. + t)] in ft
t. -1 c yr
5. The methane gas generation rate before closure can be calculated by:
dG
t. -n
— (before closure) = (k Lrt M_) L exp (-k t.)
dt ° n t. = 1 3-
1 (n)
(2)
where, Mn = amount of refuse accumulated over n years.
n = number of years since the initial placement of refuse
but before closure
dG ,
— (before closure) = (0.1)(3.53 x 10"3) Mr
dt n
t. = n
exp (-0.lt.)
Figure D-4 shows the methane generation rate as a function of time.
D.4.4 Case 4
Given:
Landfill D was in operation for 15 years accepting refuse at
an average rate of 333,300 Mg/yr. It closed after 15 years
of operation with 5 x 10 Mg of refuse in place (RIP). Test
well data conducted two years after closure (17 years after
initial placement of refuse), indicated that Landfill D is
capable of producing 0.061 ft /lb-yr of methane gas.
Calculate: Kinetic constant (k) and methane generation rate as a
function of time.
D-15
-------
Methane Gas Generation Rate vs. Time
u
V)
o
z
o -o
5 C
H
ii
0
(3
I
C
a
£
RIP - 3X10"6 Mq. 15 Yr Activ* Life
16
20
Yeor Sine* th« Initial Refuse Placement
a k - 0.1 l/yr
Figure D-4. Methane gas generation rate as a function of time.
D-16
-------
1. First, reduce test well data to the actual recoverable methane
production rate.
Total recoverable methane gas rate = (test well flowrate)(refuse in
place)
12
Total recoverable methane gas rate = (0.061) (5 x 10 g) 1b
454 g
= 680 x 106 ft3 methane/yr.
2. Calculate the fraction of submass i, r., by treating yearly
accumulation as the mass of submass i.
r1 = 33-L3QO = Q Q667
5 x 106
3. Calculate the kinetic constant, k, using the recoverable methane gas
rate calculated in Step 1 and t of 17 years.
ti = 15
dG _ k L Mt £ exp [-k (t. + t )]
ji = 0 L 4. i It
dt t = 17 li = l
where, t = time after closure (= 2 years)
M. = amount of refuse accumulated at time t
t. + t = age of submass i
Assuming LQ of 100 liter CH4/Kg refuse or 3.53 x 103 ft3 CH4/Mg refuse,
680 x 106 ft3 CH. o ft3 CH. ,
-J^ = k ^3'53 x 10 Mg refuse > (5 x 10 ^ refuse^
D-17
-------
i = 15
X £ (0.0667) exp [-k (t + 2)]
i = 1
i = 15
0.571 = k £ exp [-k (t. + 2)]
i = 1
= k {exp (-3k) + exp (-4k) + ... exp (-17k)}
Solving for k by trial and error procedures, k = 0.2 1/yr.
4. Express the model equation with calculated k.
i = 15
dG = k LQ Mt r. exp [-k (ti + tc)]
— i = 1
dt
•* fi ^A15
= (0.2) (3.53 x 10*) (5 x 10°) (0.0667) 1 £ exp [-0.2 (t. + tj]
t. = 1 T c
, t. = 15 3 CH4
= 23.54 x 10' ^ exp [-0.2 (t. + t)] in fr —
t. =1 ' c yr
5. The methane gas generation rate before closure can be calculated by:
*r t. = n
dG i _
— (before closure) = (k ln Mn) L exp (-k t.)
dt ° n t. = 1 ]-
1 (n)
where, M = amount of refuse accumulated over n years.
n = number of years since the initial placement of refuse
but before closure
D-18
-------
j~ t. = n
dG _ i ^
— (before closure) = (0.2)(3.53 x 1
-------
u,
u
I/I
§
3 c
0 O
0
o
o
£
Methane Gas Generation Rate vs. Time
RIP - 5X10-6 Mq. 15 Yr Activ* Life
:2
!6
24
Year Sine* th« Initial Ratusa Plac«m«nt
D k - 0.2 1/yr
Figure D-5. Methane generation rate as a function of time.
D-20
-------
TABLE D-l. NATIONWIDE NMOC EMISSION RATE FROM
EXISTING LANDFILLS IN 1987.
Source
Landfill air Thousand
emission Mg NMOC/yr
estimation
method
Comments
EPA LF Survey
EPA LF Survey
SCAQMD 1984
Scholl Canyon
Emission Factor
200
335
Based on refuse
in place in Southern
California generated
by 10 million people.
243
Potential NMOC
emissions from all
existing landfills.
Reference year 1992.
Potential NMOC
emissions from all
existing landfills.
"Current" NMOC
emissions from
all existing
active and closed
landfills.
1986 EPA-sponsored Based on the yearly 74.8
Study estimates of municipal
generated from
1960 to 2000.
"Current" NMOC
emissions from
all existing
active and closed
landfills.
D-21
-------
Eligible OSW Survey Responses
Calculate Scale Factors
for Small & Large LFs
For Each LF
Scaled Des.Cap. - Scale Factor X Design Capacity
LFs in Dry States
LFs in Wet States
Pottntl«l VOC Emissions «
(13.6 «j VOC/yr-10* Nf tafuMH Scale* OM.Cw.)
Potential VOC Emissions •
(13.( N| VOC/yr-10* * tefuM)(Sc*l
M OM.Cu.)(2.6)
TOTAL POTENTIAL NATIONWIDE VOC EMISSION RATE
FROM ALL EXISTING ACTIVE MUNICIPAL LANDFILLS
Figure D-6. Calculation schematics for emission factor method,
D-22
-------
The in-place refuse for the South Coast in 1983 was estimated using the
refuse generation rate per capita and population estimates:
The major assumptions made in the South Coast study were:
o The average refuse generation rate of 7.9 Ibs refuse/capita-day
was assumed to be constant over the 26 year period.
o Refuse has been accumulated since 1957. (Prior to 1957, most of
refuse was incinerated).
o All municipal waste generated is disposed in landfills.
The nationwide landfill air emission rate can be estimated by scaling
the SCAQMD refuse in place to the national level. The following additional
assumptions were made to scale to the national level:
o 15 percent of the U.S. population lives in "dry" states and 85%
lives in "wet" states.
o The U.S. population in 1987 is 277 million.
o The SCAQMD emission factor of 13.6 Mg VOC/million Mg of refuse-yr is
used.
o The emission rate from landfills in "wet" states (>21" of annual
precipitation) is 2.6 times greater on a per Mg of refuse basis.
Calculation of the Nationwide landfill air emission rate using this approach
is shown below:
o Current Nationwide VOC Emission Rate from Wet States,
= 300 x 106 Mg refuse x 2JJ x 1Q6 people x Q 85 x
10 x 10 people
13-6 Mg VOC x 2 6 _ 249,800 Mg VOC/yr
yr -10 Mg refuse
o Current Nationwide VOC Emission Rate from Dry States,
= 300 x 106 Mq refuse x 2JJ x 1Q6 people x Q 15 x
10 x 10 people
13'I "fl VOC = 16,950 Mg VOC/yr
yr -10 Mg refuse
D-23
-------
o Total Current Nationwide VOC Emission Rate = 267,000 Mg VOC/yr
D.2.3 Municipal Waste Generation Rate Method. The municipal solid
waste generation rate from 1960 to 2000 was integrated over the period of
1960 to 1987 (see Figure D-7) to yield the total amount of municipal waste
generated over the past 27 years. By assuming that 85 percent of the
municipal waste generated is disposed by landfill methods and 85 percent of
the U.S.A. population lives in "wet" states, the nationwide landfill air
emission rate based on the municipal waste generation rate can be
calculated. The assumption that 85 percent of the nationwide municipal
waste is based on the estimate provided in an EPA study. The remaining 15
percent is reportedly combusted.
The nationwide landfill air emission rates from new landfills were then
calculated using the same calculation scheme shown in Figure D-6. The
national potential landfill air emission rate in 1993 and actual landfill
air emissionrate expected in 1993 from new landfills are estimated to be
52,000 megagrams/yr and 16,000 megagrams/yr, respectively. The results are
also shown in Table D-l.
D-24
-------
I960
1966
1970
1975
I960
1988
1990
2000
Figure D-7, Gross discards, materials recovery, energy recovery,
and discards of municipal solid waste 1960 to 2000.
D-25
-------
D.3 REFERENCES
1. Emcon Associates. Methane Generation and Recovery from Landfills.
Ann Arbor, Ann Arbor Science. 1982.
2. Reference 1.
3. Franklin Associates, Ltd. Characterization of Municipal Solid Waste in
the United States, 1960 to 2000. Final Report. July 11, 1986.
4. The U.S. Environmental Protection Agency. Municpal Waste Combustion
Study - Characterization of the Municipal Waste Combustion Industry.
EPA/530-SW-87-021h. June 1987-
D-26
-------
APPENDIX E
TEST METHODS AND PROCEDURES
-------
APPENDIX E
TEST METHODS AND PROCEDURES
Appendix E contains the three test methods developed by EPA for
proposal as part of this rulemaking. These include proposed
Method 23 - Determination of Landfill Gas Production Flow Rate, which begins
on the following page, proposed Method 3C - Determination of Carbon Dioxide,
Methane, Nitrogen, and Oxygen from Stationary Sources, which begins on
page E-21, and proposed Method 25C - Determination of Nonmethane Organic
Compounds (NMOC) in Landfill Gas, which begins on page E-27.
E-l
-------
APPENDIX E - REFERENCE METHODS
METHOD 2E - DETERMINATION OF LANDFILL GAS
GAS PRODUCTION FLOW RATE
1. Applicability and Principle
1.1 Applicability. This method applies to the measurement of
landfill gas (LFG) production flow rate from municipal solid waste
landfills and is used to calculate the flow rate of nonmethane organic
compounds (NMOC) from landfills.
1.2 Principle. Extraction wells are installed either in a
cluster of three or at five dispersed locations in the landfill. A
blower is used to extract LFG from the landfill. LFG composition,
landfill pressures, and orifice pressure differentials from the wells
are measured and the landfill gas production flow rate is calculated.
1.3 Safety. Since this method is complex, experienced personnel
only should perform the test. Explosion-proof equipment shall be used
for testing because of the potential explosion hazard of the landfill
gas. No smoking shall be allowed on the landfill site during testing.
Breathing protection is recommended.
2. Apparatus
2.1 Well Drilling Rig. Capable of boring a 24-in. diameter hole
into the landfill to a minimum of 75 percent of the landfill depth.
The depth of the well shall not exceed the bottom of the landfill or
the liquid level.
E-2
-------
2.2 Gravel. No fines, 1 to 3 in. in diameter.
2.3 Bentonite.
2.4 Backfill Material. Clay, soil, and sandy loam have been
found to be acceptable.
2.5 Extraction Well Pipe. Polyvinyl chloride (PVC), high density
polyethylene (HOPE), fiberglass, or stainless steel, with a minimum
diameter of 4 in.
2.6 Well Assembly. PVC ball or butterfly valve, sampling ports
at the well head and outlet, and an in-line orifice meter. A schematic
of the well assembly is shown in Figure 1.
2.7 Cap. PVC or HOPE.
2.8 Header Piping. PVC or HOPE.
2.9 Auger. Capable of boring a 6- to 9-in. diameter hole to a
depth equal to the top of the perforated section of the extraction
well, for pressure probe installation.
2.10 Pressure Probe. PVC or stainless steel (316), 1-in.
Schedule 40 pipe. Perforate the bottom two thirds. A minimum
requirement for perforations is with four 1/4-in. diameter holes spaced
90 apart every 6 in.
2.11 Blower and Flare Assembly. Explosion-proof blower, capable
of pulling a vacuum of 25 in. H20 and of extracting LFG at a flow rate
of 300 ft3/min> a water knockout, and flare or incinerator.
2.12 Standard Pitot Tube and Differential Pressure Gauge for Flow
Rate Calibration with Standard Pitot. Same as Method 2, Sections 2.7
and 2.8.
2.13 Orifice Meter. Orifice plate, pressure tabs, and pressure
measuring device to measure the LFG flow rate.
2.14 Barometer. Same as Method 4, Section 2.1.5.
E-3
-------
BLOWER
OUTLET SAMPLE
PORT
WATER
KNOCKOUT
ORIFICE
METER
WELL HEAD
CONTROL VALVE
WELL HEAD
SAMPLE PORT
Figure 1. Schematic of above ground assembly.
E-4
-------
2.15 Differential Pressure Gauge. Water-filled U-tube manometer
or equivalent, capable of measuring within 0.01 in. H20, for measuring
the pressure of the pressure probes.
3. Procedure
3.1 Placement of Extraction Wells. The landfill owner or
operator may install a single cluster of three extraction wells in a
test area or space five wells over the landfill. The cluster wells are
recommended but may be used only if the composition, age of the refuse,
and the landfill depth of the test area can be determined.
3.1.1 Cluster Wells. Consult landfill site records for the age
of the refuse, depth, and composition of various sections of the
landfill. Select an area near the perimeter of the landfill with a
depth equal to or greater than the average depth of the landfill and
with the average age of the refuse between 2 and 10 years old. Avoid
areas known to contain nondecomposable materials, such as concrete and
asbestos. Locate wells as shown in Figure 2.
3.1.1.1 The age of the refuse in a test area will not be uniform,
so calculate a weighted average to determine the average age of the
refuse as follows.
Aavg
where,
A = Average age of the refuse tested, yr.
f. = Fraction of the refuse in the i section.
Ai = Age of the ith fraction, yr.
E-5
-------
PERIMETER
INTERIOR
LANDFILL
O = WELL
Figure 2. Cluster well placement.
E-6
-------
3.1.2 Equal Volume Wells. Divide the sections of the landfill
that are at least 2 years old into five areas representing equal
volumes. Locate an extraction well near the center of each area.
3.2 Installation of Extraction Wells. Use a well drilling rig to
dig a 24-in. diameter hole in the landfill to a minimum of 75 percent
of the landfill depth, not to exceed the bottom of the landfill or the
liquid level. Perforate the bottom two thirds of the extraction well
pipe. A minimum requirement for perforations is with four 1/2-in.
diameter holes spaced 90° apart every 4 to 8 in. Place the extraction
well in the center of the hole and backfill with gravel to a level 1 ft
above the perforated section. Add a layer of backfill material 4 ft
thick. Add a layer of bentonite 3 ft thick, and backfill the remainder
of the hole with cover material or material equal in permeability to
the existing cover material. The specifications for extraction well
installation are shown in Figure 3.
3.3 Pressure Probes. Locate pressure probes along three radial
arms approximately 120° apart at distances of 10, 50, 100, and 150 ft
from the extraction well. The tester has the option of locating
additional pressure probes at distances every 50 feet beyond 150 ft.
Example placements of probes are shown in Figure 4. The probes 50,
100, and 150 ft (and any additional probes located along the three
radial arms) from each well (deep probes) shall extend to a depth equal
to the top of the perforated section of the extraction wells. All
other probes (shallow probes) shall extend to a depth equal to half the
depth of the deep probes.
3.3.1 Use an auger to dig a hole, 6- to 9-in. in diameter, for
each pressure probe. Perforate the bottom two thirds of the pressure
probe. A minimum requirement for perforations is four 1/4-in. diameter
E-7
-------
PVC OR HOPE CAP,
4" (mini DIA.
1
75% OF THE
LANDFILL DEPTH
f
:'
1 n
3'
i.
PERFORATE
V) OF PIPE
LENGTH
—
i
^•» *^^
• •« * <
^ »*«
e * o ,
••** ^.(
» « *
* 0. ,%
*-*>^'
*'***•*
«••--• 4
•0 »^*
• • * *
» %%*
»-«* *
*a*.V
"*ea%.1
?f*f.
•vt
'*'*•;•
>{\««
*•* *•*«
••«.*•••«
'^•tfA 4
**»*« *
• •• •*<
O
o
0
o
0
o
o
-
o
o
o
o
o
o
PVC OR HOPE PIPE,
^^-— - 4* (min) OIA.
GROUND SURFACE
^
Z£K
Hi
— .
I
« 0 '
» o »
''.'•<
'I \
:%
«*^JL
— • 1
«• .«
'.•**
0*A
' ***•*'
*'•• *
^*\.
4 V >«
V^O*
'.*•*,'
'**,
la'%°i
' »
'.:•.
• * • «
« • «
;%VrW?^
24' DIA.
WELL8ORE
I^^% EXISTING COVER
^4 MATERIAL
BENTONITE SEAL
"""""' /%%&/})
COHESIONLESS
BACKFILL MATERIAL
GRAVEL, NO FINES
—• " 1 to 3* DIA.
PVC OR HOPE
PIPE
PVC OR HOPE
CAP, 4' (min) DIA.
^"^"•"*
Figure 3. Gas extraction well.
E-8
-------
600'
100'
™
!<
ii
600'
! o \
X ° /'
v »;
» »'
\
; Qfs ' j
x x'
H *--'
I /
( ' '
;
! I »
\ » v
\ \
\ \
A = W«ll
O = Shallow Probe
X = D««p Prob«
Figure 4. Cluster well configuration.
E-9
-------
holes spaced 90° apart every 6 in. Place the pressure probe in the
center of the hole and backfill with gravel to a level 1 ft above the
perforated section. Add a layer of backfill material at least 4 ft
thick. Add a layer of bentonite at least 1 ft thick, and backfill the
remainder of the hole with cover material or material equal in
permeability to the existing cover material. The specifications for
pressure probe installation are shown in Figure 5.
3.4 LFG Flow Rate Measurement. Locate an orifice meter as shown
in Figure 1. Attach the wells to the blower and flare assembly. The
individual wells may be ducted to a common header so that a single
blower and flare assembly and orifice meter may be used. Use the
procedures in Section 4.1 to calibrate the orifice meter.
3.5 Leak Check. A leak check of the above ground system is
required for accurate flow rate measurements and for safety. Sample
LFG at the well head sample port and at the outlet sample port. Use
Method 3C to determine nitrogen (N2) concentrations. Determine the
difference by using the formula below.
Difference » CQ
where,
C = Concentration of N0 at the wellhead, ppm.
w c
CQ = Concentration of Ng at the outlet, ppm.
The system passes the leak check if the difference is .less than 10,000.
3.6 Static Testing. Close the control valves on the wells during
static testing. Measure the gauge pressure (P ) at each deep pressure
probe and the barometric pressure (Pbar) every 8 hr for 3 days.
E-10
-------
4' (mini
QUICK CONNECT
CAP
1' PtPi
COVER MATERIAL,
OH EQUIVALENT
BENTONITE
SANDY LOAM OR
APPROPRIATE
COVER
GRAVEL
OF PROM
LENGTH
8- ro 9- 30R6 HOLE
Figure 5. Pressure probe.
E-ll
-------
Convert the gauge pressure (in. hLO) of each deep pressure probe to
absolute pressure (in. H^O) by using the following equation. Record as
pr
P. (in. H20) = (0.5353) Pfaar (mm Hg) + Pg (in. H20)
3.6.1 For each probe, average all of the 8-hr deep pressure probe
readings and record as P.,. P. is used in Section 3.7.6 to determine
la la
the maximum radius of influence.
3.6.2 Measure the static flow rate of each well once during
static testing.
3.7 Short Term Testing. The purpose of short term testing is to
determine the maximum vacuum that can be applied to the wells without
infiltration of air into the landfill. The short term testing is done
on one well at a time. Burn all LFG with a flare or incinerator.
3.7.1 Use the blower to extract LFG from a single well at twice
the static flow rate of the respective well measured in Section 3.6.2.
If using a single blower and flare assembly and a common header system,
close the control valve on the wells not being measured. Allow 24 hr
for the system to stabilize at this flow rate.
3.7.2 Test for infiltration of air into the landfill by measuring
the gauge pressures of the shallow pressure probes and using Method 3C
to determine the LFG N2 concentration. If the LFG N- concentration is
less than 1 percent and all of the shallow probes have a positive gauge
pressure, increase the blower vacuum by 2 in. H-0, wait 24 hr, and
repeat the tests for infiltration. Continue the above steps of
increasing blower vacuum by 2 in. H20, waiting 24 hr, and testing for
infiltration until the concentration of N2 exceeds 1 percent or any of
E-12
-------
the shallow probes have a negative gauge pressure, at which time reduce
the blower vacuum so that the N2 concentration is less than 1 percent
and the gauge pressures of the shallow probes are positive.
3.7.3 At this blower vacuum, measure P. every 8 hr for 24 hr
and record the LFG flow rate as Q and the probe gauge pressures for
all of the probes as P^. Convert the gauge pressures of the deep
probes to absolute pressures for each 8 hr reading at Q as follows.
Pf (in. H20) = (0.5353) Pfaar (mm Hg) + Pf (in. H20)
3.7.4 For each probe, average the 8-hr deep pressure probe
readings and record as P^,.
3.7.5 For each probe, compare the initial average pressure (P.,)
1 cl
from Section 3.6.1 to the final average pressure (Pfa)- Determine the
furthermost point from the well head along each radial arm where
Pfa - ''ia' ^is distance is tne maximum radius of influence, which is
the distance from the well affected by the vacuum. Average these
values to determine the average maximum radius of influence (R_J.
iTlQ
3.7.7 Calculate the depth (D) affected by the extraction well as
follows.
°st = WD + Rma
where,
WD = Well depth, ft.
E-13
-------
3.7.8 Calculate the void volume for the extraction well (V) as
follows.
°-40
3.7.9 Repeat the procedures in Section 3.7 for each well.
3.8 Calculate the total void volume of the test wells (Vy) by
summing the void volumes (V) of each well.
3.9 Long Term Testing. The purpose of long term testing is to
extract two void volumes of LFG from the extraction wells. Use the
blower to extract LFG from the wells. If a single blower and flare
assembly and common header system are used, open all control valves and
set the blower vacuum equal to the highest stabilized blower vacuum
demonstrated by any individual well in Section 3.7. Every 8 hr, sample
the LFG from the well head sample port, measure the gauge pressures of
the shallow pressure probes, the blower vacuum, the LFG flow rate, and
use the criteria for infiltration in Section 3.7.2 and Method 3C to
test for infiltration. If Infiltration is detected, do not reduce the
blower vacuum, but reduce the LFG flow rate from the well by adjusting
the control valve on the well head. Continue until the equivalent of
two total void volumes (V ) have been extracted, or until Vt = 2 V .
V u V
3.9.1 Calculate Vt, the total volume of LFG extracted from the
wells, as follows.
vt - 60
E-14
-------
where,
= Total volume of LFG extracted from wells, ft .
Q.J = LFG flow rate measured at orifice meter at the ith interval,
ft3/min.
tyi = Time of the ith interval (usually 8), hr.
3.9.2 Record the final stabilized flow rate as Qf. If, during
the long term testing, the flow rate does not stabilize, calculate Q^
by averaging the last 10 recorded flow rates.
3.9.3 For each deep probe, convert each gauge pressure to absolute
pressure as in Section 3.7.4. Average these values and record as P .
S a
For each probe, compare P. to PC3. Determine the furthermost point
1 a 5 a
from the well head along each radial arm where P < P. . This
Sd 1 a
distance is the stabilized radius of influence. Average these values
to determine the average stabilized radius of influence (R.,).
S a
3.10 Determine the NMOC mass emission rate using the procedures
in Section 5.
4. Calibrations
4.1 Orifice Calibration Procedure. Locate a standard pitot tube
in line with an orifice meter. Use the procedures in Section 3 of
Method 2 to determine the average dry gas volumetric flow rate for at
least five flow rates that bracket the expected LFG flow rates, except
in Section 3.1, use a standard pitot tube rather than a Type S pitot
tube. Method 3C may be used to determine the dry molecular weight. It
may be necessary to calibrate more than one orifice meter in order to
bracket the LFG flow rates. Construct a calibration curve by plotting
the pressure drops across the orifice meter for each flow rate versus
the average dry gas volumetric flow rate in ft /min of the gas.
E-15
-------
5. Calculations
5.1 Nomenclature.
A = Average age of the refuse tested, yr.
A. = Age of refuse in the i fraction, yr.
A = Age of landfill, yr.
A = Acceptance rate, Mg/yr.
C = NMOC concentration, ppm.
D = Depth affected by the test wells, ft.
D t = Depth affected by the test wells in the short term test,
ft.
f = Fraction of decomposable refuse in the landfill.
f. = Fraction of the refuse in the i section.
k = Landfill gas generation constant, yr° .
L = Methane generation potential, ft /Mg.
L ' = Revised methane generation potential to account for the
amount of nondecomposable material in the landfill, ft /Mg.
Mi = Mass of refuse of the ith section> M9-
Mr = Mass of decomposable refuse affected by the test well, Mg.
Pbar = AtmosPneric pressure, mm Hg.
P = Gauge pressure of the deep pressure probes, in. HLO.
Pi = Initial absolute pressure of the deep pressure probes
during static testing, in. FLO.
P. = Average initial absolute pressure of the deep pressure
I a
probes during static testing, in. H20.
Pf = Final absolute pressure of the deep pressure probes during
short term testing, in. H-O.
Pfa = Average final absolute pressure of the deep pressure probes
during short term testing, in. H20.
E-16
-------
PS = Final absolute pressure of the deep pressure probes during
long term testing, in. H20.
P$a = Average final absolute pressure of the deep pressure probes
during long term testing, in. H20.
Qf = Final stabilized flow rate, ft /min.
Qi = LFG flow rate measured at orifice meter during the i
interval, ft /min.
Q = Maximum LFG flow rate at each well determined by short term
test, ft /min.
Qt = NMOC mass emission rate, ft /min.
Rm = Maximum radius of influence, ft.
R™, = Average maximum radius of influence, ft.
[Ha
R = Stabilized radius of influence for an individual well, ft.
R = Average stabilized radius of influence, ft.
S a
t. = Age of section i, yr.
tt = Total time of long term testing, yr.
V = Void volume of test well, ft .
V = Volume of refuse affected by the test well, ft .
Vt = Total volume of refuse affected by the long term testing,
a3.
V = Total void volume affected by test wells, ft .
WD = Well depth, ft.
P= refuse density, Mg/ft3 (Assume 0.018 Mg/ft3 if data are
unavailable).
E-17
-------
5.2 Use the following equation to calculate the depth affected by
the test well. If using cluster wells, use the average depth of the
wells for WD.
D = WD + R a
Sa
5.3 Use the following equation to calculate the volume of refuse
affected by the test well.
Vr-Rsa7TD
5.4 Use the following equation to calculate the mass affected by
the test well .
Mr
5.5 Modify L to account for the nondecomposable refuse in the
landfill.
Lo' - f Lo
5.6 In the following equation, solve for k by iteration. A
suggested procedure is to select a value for k, calculate the left side
E-18
-------
of the equation, and if not equal to zero, select another value for k.
Continue this process until the left hand side of the equation equals
zero, +0.001.
k -k A
avg H
Lo'
5.7 Use the following equation to determine landfill NMOC mass
emission rate if the yearly acceptance rate of refuse has been
consistent (+10 percent) over the life of the landfill.
2 LQ' Ar (1 - e"k A) C (1.018 x 10"10)
5.8 Use the following equation to determine landfill NMOC mass
emission rate if the acceptance rate has not been consistent over the
life of the landfill.
Qf = 2 k L ' C (1.018 x 10"10) £ M. e-kti
to i=1 i
6. Bibliograohv
1. Same as Method 2, Appendix A, 40 CFR Part 60.
2. Emcon Associates, Methane Generation and Recovery from Landfills,
Ann Arbor Science, 1982.
3. The Johns Hopkins University, Brown Station Road Landfill Gas
Resource Assessment, Volume 1: Field Testing and Gas Recovery
Projections. Laurel, Maryland: October 1982.
4. Mandeville and Associates, Procedure Manual for Landfill Gases
Emission Testing.
E-19
-------
5. Letter and attachments from Briggum, S., Waste Management of
North America, to Thorneloe, S., EPA. Response to July 28, 1988
request for additional information. August 18,1988.
6. Letter and attachments from Briggum, S., Waste Management of
North America, to Wyatt, S., EPA. Response to December 7, 1988
request for additional information. January 16, 1989.
E-20
-------
******
METHOD 3C - DETERMINATION OF CARBON DIOXIDE, METHANE, NITROGEN,
AND OXYGEN FROM STATIONARY SOURCES
1. Applicability and Principle
1.1 Applicability. This method applies to the analysis of carbon
dioxide (C02), methane (CH4), nitrogen (N2), and oxygen (02) in samples
from municipal landfills and other sources when specified in an
applicable subpart of the regulations.
1.2 Principle. A portion of the sample is injected into a gas
chromatograph (GC) and the C02, CH4, N2, and 02 concentrations are
determined by using a thermal conductivity detector (TCD) and
integrator.
2. Range and Sensitivity
2.1 Range. The range of this method depends upon the
concentration of samples. The analytical range of TCD's is generally
between approximately 10 ppm and the upper percent range.
2.2 Sensitivity. The sensitivity limit for a compound is defined
as the minimum detectable concentration of that compound, or the
concentration that produces a signal-to-noise ratio of three to one.
For C02, CH., N2, and 02, the sensitivity limit is in the low ppm
range.
3. Interferences
Since the TCD exhibits universal response and detects all gas
components except the carrier, interferences may occur. Choosing the
appropriate GC or shifting the retention times by changing the column
flow rate may help to eliminate resolution interferences.
E-21
-------
To assure consistent detector response, helium is used to prepare
calibration gases. Frequent exposure to samples or carrier gas
containing oxygen may gradually destroy filaments.
4. Apparatus
4.1 Gas Chromatograph. GC having at least the following
components:
4.1.1 Separation Column. Appropriate column(s) to resolve C02,
CH., N2, 02, and other gas components that may be present in the
sample. One column that has been advertised to work in this case is
column CTR I available from All tech Associates Inc., 2051 Waukegan
Road, Deerfield, Illinois 60015. NOTE: Mention of trade names or
specific products does not constitute endorsement or recommendation by
the U. S. Environmental Protection Agency.
4.1.2 Sample Loop. Teflon or stainless steel tubing of the
appropriate diameter. NOTE: Mention of trade names or
specific products does not constitute endorsement or recommendation by
the U. S. Environmental Protection Agency.
4.1.3 Conditioning System. To maintain the column and sample
loop at constant temperature.
4.1.4 Thermal Conductivity Detector.
4.2 Recorder. Recorder with linear strip chart. Electronic
integrator (optional) is recommended.
4.3 Teflon Tubing. Diameter and length determined by connection
requirements of cylinder regulators and the GC.
4.4 Regulators. To control gas cylinder pressures and flow
rates.
4.5 Adsorption Tubes. Applicable traps to remove any 02 from the
carrier gas.
E-22
-------
5. Reagents
5.1 Calibration and Linearity Gases. Standard cylinder gas
mixtures for each compound of interest with at least three
concentration levels spanning the range of suspected sample
concentrations. The calibration gases shall be prepared in helium.
5.2 Carrier Gas. Helium, high-purity.
6. Analysis
6.1 Sample Collection. Use the sample collection procedures
described in Methods 3 or 25C to collect a sample of landfill gas
(LFG).
6.2 Preparation of GC. Before putting the GC analyzer into
routine operation, optimize the operational conditions according to the
manufacturer's specifications to provide good resolution and minimum
analysis time. Establish the appropriate carrier gas flow and set the
detector sample and reference cell flow rates at exactly the same
levels. Adjust the column and detector temperatures to the recommended
levels. Allow sufficient time for temperature stabilization. This may
typically require 1 hour for each change in temperature.
6.3 Analyzer Linearity Check and Calibration. Perform this test
before sample analysis. Using the gas mixtures in Section 5.1, verify
the detector linearity over the range of suspected sample
concentrations with at least three points per compound of interest.
This initial check may also serve as the initial instrument
calibration. All subsequent calibrations may be performed using a
single-point standard gas provided the calibration point is within
20 percent of the sample component concentration. For each instrument
calibration, record the carrier and detector flow rates, detector
filament and block temperatures, attenuation factor, injection time,
E-23
-------
chart speed, sample loop volume, and component concentrations. Plot a
linear regression of the standard concentrations versus area values to
obtain the response factor of each compound. Alternatively, response
factors of uncorrected component concentrations (wet basis) may be
generated using instrumental integration. NOTE: Peak height may be
used instead of peak area throughout this method.
6.4 Sample Analysis. Purge the sample loop with sample, and
allow to come to atmospheric pressure before each injection. Analyze
each sample in duplicate, and calculate the average sample area (A).
The results are acceptable when the peak areas for two consecutive
injections agree within five percent of their average. If they do not
agree, run additional samples until consistent area data are obtained.
Determine the tank sample concentrations according to Section 7.2.
7. Calculations
Carry out calculations retaining at least one extra decimal figure
beyond that of the acquired data. Round off results only after the
final calculation.
7.1 Nomenclature.
A = Average sample area.
BW = Moisture content in the sample, fraction.
C = Component concentration in the sample, dry basis, ppm.
C^ = Calculated NMOC concentration, ppm C equivalent.
Ctm = Measured NMOC concentration, ppm C equivalent.
Pbar = Barometric pressure, mm Hg.
Pti = Gas sample tank pressure after evacuation, mm Hg absolute.
Pt = Gas sample tank pressure after sampling, but before
pressurizing, mm Hg absolute.
E-24
-------
P. r = Final gas sample tank pressure after pressurizing, mm Hg
absolute.
PW = Vapor pressure of H20 (from Table 3C-1), mm Hg.
Tti = Sample tank temperature before sampling, °K.
Tt = Sample tank temperature at completion of sampling, °K.
Txr = Sample tank temperature after pressurizing, °K.
r - Total number of analyzer injections of sample tank during
analysis (where j = injection number, l...r).
R = Mean calibration response factor for specific sample
component, area/ppm.
7.2 Concentration of Sample Components. Calculate C for each
compound using Equations 3C-1 and 3C-2. Use the temperature and
barometric pressure at the sampling site to calculate BW- If the
sample was diluted with helium using the procedures in Method 25C, use
Equation 3C-3 to calculate the concentration.
B.. =
W
bar
A
3C-1
3C-2
R(1-BU
C =
If
ftf
Pti
Tti
3C-3
R(1-BW)
8. Bibl iographv
1. McNair, H.M., and E.J. Bonnelli. Basic Gas Chromatography.
Consolidated Printers, Berkeley, CA. 1969.
E-25
-------
TABLE 3C-1. MOISTURE CORRECTION
Vapor pressure Vapor pressure
Temperature, C of H20, mm Hg Temperature, C of hLO, mm Hg
4
6
8
10
12
14
16
6.1
7.0
8.0
9.2
10.5
12.0
13.6
18
20
22
24
26
28
30
15.5
17.5
19.8
22.4
25.2
28.3
31.8
E-26
-------
*****
METHOD 25C^ DETERMINATION OF NONMETHANE ORGANIC
COMPOUNDS (NMOC) IN LANDFILL GASES
1. Applicability and Principle
1.1 Applicability. This method is applicable to the sampling and
measurement of nonmethane organic compounds (NMOC) as carbon in
landfill gases.
1.2 Principle. A sample probe that has been perforated at one
end is driven or augered to a depth of 3 feet (ft) below the bottom of
the landfill cover. A sample of the landfill gas is extracted with an
evacuated cylinder. The NMOC content of the gas is determined by
injecting a portion of the gas into a gas chromatographic column to
separate the NMOC from carbon monoxide (CO), carbon dioxide (CO^), and
methane (CH^); the NMOC are oxidized to C02, reduced to CH4, and
measured by a flame ionization detector (FID). In this manner, the
variable response of the FID associated with different types of
organics is eliminated.
2. Apparatus
2.1 Sample Probe. Stainless steel, with the bottom third
perforated. The sample probe shall be capped at the bottom and shall
have a threaded cap with a sampling attachment at the top. The sample
probe shall be long enough to go through and extend no less than 3 ft
below the landfill cover. If the sample probe is to be driven into the
landfill, the bottom cap should be designed to facilitate driving the
probe into the landfill.
E-27
-------
2.2 Sampling Train.
2.2.1 Rotameter with Flow Control Valve. Capable of measuring a
sample flow rate of 100 + 10 ml/min. The control valve shall be made
of stainless steel.
2.2.2 Sampling Valve. Stainless steel.
2.2.3 Pressure Gauge. U-tube mercury manometer, or equivalent,
capable of measuring pressure to within 1 mm Hg in the range of 0 to
1,100 mm Hg.
2.2.4 Sample Tank. Stainless steel or aluminum cylinder, with a
minimum volume of 4 liters and equipped with a stainless steel sample
tank valve.
2.3 Vacuum Pump. Capable of evacuating to an absolute pressure
of 10 mm Hg.
2.4 Purging Pump. Portable, explosion proof, and suitable for
sampling NMOC.
2o5 Pilot Probe Procedure. The following are needed only if the
tester chooses to use the procedure described in Section 4.2.1.
2.5.1 Pilot Probe. Tubing of sufficient strength to withstand
being driven into the landfill by a post driver and an outside diameter
of at least 0.25 in. smaller than the sample probe. The pilot probe
shall be capped on both ends and long enough to go through the landfill
cover and extend no less than 3 ft into the landfill.
2.5.2 Post Driver and Compressor. Capable of driving the pilot
probe and the sampling probe into the landfill. The Kitty Hawk
portable post driver has been found to be acceptable. NOTE: Mention
of trade names or specific products does not constitute endorsement by
the Environmental Protection Agency.
E-28
-------
2.6 Auger Procedure. The following are needed only if the tester
chooses to use the procedure described in Section 4.2.2.
2.6.1 Auger. Capable of drilling through the landfill cover and
to a depth of no less than 3 ft into the landfill.
2.6.2 Pea Gravel.
2.6.3 Bentonite.
2.7 NMOC Analyzer, Barometer, Thermometer, and Syringes. Same as
in Sections 2.3, 2.4.1, 2.4.2, 2.4.4, respectively, of Method 25.
3. Reagents
3.1 NMOC Analysis. Same as in Method 25, Section 3.2.
3.2 Calibration. Same as in Method 25, Section 3.4, except omit
Section 3.4.3.
4. Procedure
4.1 Sample Tank Evacuation and Leak Check. Conduct the sample
tank evacuation and leak check either in the laboratory or the field.
Connect the pressure gauge and sampling valve to the sample tank.
Evacuate the sample tank to 10 mm Hg absolute pressure or less. Close
the sampling valve, and allow the tank to sit for 60 minutes. The tank
is acceptable if no change is noted. Include the results of the leak
check in the test report.
4.2 Sample Probe Installation. The tester may use the procedure
in Sections 4.2.1 or 4.2.2. CAUTION: LFG contains methane and
therefore explosive mixtures may exist on or near the landfill. It is
advisable to take appropriate safety precautions when testing
landfills, such as refraining from smoking.
4.2.1 Pilot Probe Procedure. Use the post driver to drive the
pilot probe at least 3 ft below the landfill cover. Alternative
E-29
-------
procedures to drive the probe into the landfill may be used subject to
the approval of the Administrator.
4.2.1.1 Remove the pilot probe and drive the sample probe into
the hole left by the pilot probe. The sample probe shall extend at
least 3 ft below the landfill cover and shall protrude about 1 ft above
the landfill cover. Seal around the sampling probe with bentonite and
cap the sampling probe with the sampling probe cap.
4.2.2 Auger Procedure. Use an auger to drill a hole through the
landfill cover and to at least 3 ft below the landfill cover. Place
the sample probe in the hole and backfill with pea gravel to a level
2 ft from the surface. The sample probe shall protrude at least 1 ft
above the landfill cover. Seal the remaining area around the probe
with bentonite. Allow 24 hr for the landfill gases to equilibrate
inside the augered probe before sampling.
4.3 Sample Train Assembly. Just before assembly, measure the
tank vacuum using the pressure gauge. Record the vacuum, the ambient
temperature, and the barometric pressure at this time. Assemble the
sampling probe purging system as shown in Figure 1.
4.4 Sampling Procedure. Open the sampling valve and use the
purge pump and the flow control valve to evacuate at least two sample
probe volumes from the system at a flow rate of 100 + 10 ml/min. Close
the sampling valve and replace the purge pump with the sample tank
apparatus as shown in Figure 2. Open the sampling valve and the sample
tank valves and, using the flow control valve, sample at a flow rate of
100 + 10 ml/min until the sample tank gauge pressure is zero.
Disconnect the sampling tank apparatus and use the carrier gas bypass
valve to pressurize the sample cylinder to approximately 1,060 mm Hg
absolute pressure with helium and record the final pressure.
E-30
-------
SAMPLING
VALVE
VENT
FLOW CONTROL
VALVE
JT
PURGE PUMP
SAMPLING
PROBE
SAMPLE PROBE
CAP
ROTAMETER
LANDFILL COVER SURFACE
Figure 1. Schematic of sampling probe purging system.
E-31
-------
FLOW CONTROL
VALVE
SAMPUNG
PflOBE
SAMPLE PROBE
CAP
SAMPUNG
VALVE
ROTAMETER
LANDFILL COVER SURFACE
VACUUM GAUGE
QUICK DISCONNECT
SAMPLE TANK VALVE
SAMPLE TANK
Figure 2, Schematic of sampling train.
E-32
-------
Alternatively, the sample tank may be pressurized in the lab. If not
analyzing for N2, the sample cylinder may be pressurized with zero air.
4.4.1 Use Method 3C to determine the percent N2 in the sample.
Presence of N2 indicates infiltration of ambient air into the gas
sample. The landfill sample is acceptable if the concentration of N2
is less than one percent.
4.5 Analysis. The oxidation, reduction, and measurement of
NMOC's is similar to Method 25. Before putting the NMOC analyzer into
routine operation, conduct an initial performance test. Start the
analyzer, and perform all the necessary functions in order to put the
analyzer into proper working order. Conduct the performance test
according to the procedures established in Section 5.1. Once the
performance test has been successfully completed and the NMOC
calibration response factor has been determined, proceed with sample
analysis as follows:
4.5.1 Daily Operations and Calibration Checks. Before and
immediately after the analysis of each set of samples or on a daily
basis (whichever occurs first), conduct a calibration test according to
the procedures established in Section 5.2. If the criteria of the
daily calibration test cannot be met, repeat the NMOC analyzer
performance test (Section 5.1) before proceeding.
4.5.2 Operating Conditions. Same as in Method 25, Section 4.4.2.
4.5.3 Analysis of Sample Tank. Purge the sample loop with sample, and
then inject the sample. Under the specified operating conditions, the
C02 in the sample will elute in approximately 100 seconds. As soon as
the detector response returns to baseline following the C02 peak,
switch the carrier gas flow to backflush, and raise the column oven
temperature to 195°C as rapidly as possible. A rate of 30°C/min has
E-33
-------
been shown to be adequate. Record the value obtained for any measured
NMOC. Return the column oven temperature to 85°C in preparation for the
next analysis. Analyze each sample in triplicate, and report the
average as Ctn].
4.6 Audit Samples. Same as in Method 25, Section 4.5.
5, Calibration and Operational Checks
Maintain a record of performance of each item.
5.1 Initial NMOC Analyzer Performance Test. Same as in
Method 25, Section 5.2, except omit the linearity checks for C02
standards.
5.2 NMOC Analyzer Daily Calibration.
5.2.1 NMOC Response Factors. Same as in Method 25,
Section 5.3.2.
5.3 Sample Tank Volume. The volume of the gas sampling tanks
must be determined. Determine the tank volumes by weighing them empty
and then filled with deionized water; weigh to the nearest 5 g, and
record the results. Alternatively, measure, to the nearest 5 ml, the
volume of water used to fill them.
6. Calculations
All equations are written using absolute pressure; absolute
pressures are determined by adding the measured barometric pressure to
the measured gauge of manometer pressure.
6.1 Nomenclature.
BW = Moisture content in the sample, fraction.
Ct = Calculated NMOC concentration, ppm C equivalent.
Ctm - Measured NMOC concentration, ppm C equivalent.
Pjj - Barometric pressure, mm Hg.
Pti » Gas sample tank pressure after evacuation, mm Hg absolute.
E-34
-------
Pt = Gas sample tank pressure after sampling, but before
pressurizing, mm Hg absolute.
Ptf = Final gas sample tank pressure after pressurizing, mm Hg
absolute.
PW = Vapor pressure of H20 (from Table 1), mm Hg.
Tti = Sample tank temperature before sampling, °K.
"L = Sample tank temperature at completion of sampling, °K.
"Lr = Sample tank temperature after pressurizing, °K.
r = Total number of analyzer injections of sample tank during
analysis (where j * injection number, l...r).
6.2 Water Correction. Use Table 1, the LFG temperature, and
barometric pressure at the sampling site to calculate Bw.
B -'-*
B" Pb
6.3 NMOC Concentration. Use the following equation to calculate
the concentration of NMOC for each sample tank.
!M
pt pti
Tt Tn
r '
L(1-v r
>i Ctni
E-35
-------
TABLE 25C-1. MOISTURE CORRECTION
Vapor pressure 0 Vapor pressure
Temperature,°C of H20, mm Hg Temperature, °C of H20, mm Hg
4
6
8
10
12
14
16
6.1
7.0
8.0
9.2
10.5
12.0
13.6
18
20
22
24
26
28
30
15.5
17.5
19.8
22.4
25.2
28.3
31.8
E-36
-------
7. Bibliography
1. Salo, Albert E., Samuel Witz, and Robert D. MacPhee.
Determination of Solvent Vapor Concentrations by Total Combustion
Analysis: A Comparison of Infrared with Flame lonization Detectors.
Paper No. 75-33.2. (Presented at the 68th Annual Meeting of the Air
Pollution Control Association. Boston, Massachusetts.
June 15-20, 1975.) 14 p.
2. Salo, Albert E., William L. Oaks, and Robert D. MacPhee.
Measuring the Organic Carbon Content of Source Emissions for Air
Pollution Control. Paper No. 74-190. (Presented at the 67th Annual
Meeting of the Air Pollution Control Association. Denver, Colorado.
June 9-13, 1974.) 25 p.
E-37
-------
APPENDIX F
TABLES ON THE ECONOMIC IMPACTS OF THE ENERGY RECOVERY OPTION
F-i
-------
TABLE F-l. SUMMARY INFORMATION FOR AFFECTED CLOSED AND EXISTING LANDFILLS WITH
POSITIVE ENERGY RECOVERY COSTS
Number of affected landfills
(Percent of total closed and existing landfills)
Distribution of affected landfills
by design capacity
(106Mg)
<1
no 5
5 to 10
>10
Total
Privately owned affected landfills
(Percent of affected landfills)
Existing
Closed
25
1,024
(14)
470
(46)
475
(46)
62
(6)
17
(2)
1,024
(100)
215
(21)
186
29
Stringency Levels
(Mg NMOC/yr)
100
325
(5)
126
(39)
170
(52)
24
(7)
5
(2)
325
(100)
68
(21)
56
12
250
77
(1)
14
(18)
56
(73)
2
(3)
5
(6)
77
(100)
27
(35)
17
10
Note: The numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
TABLE F-2. LENGTH OF CONTROL PERIOD FOR AFFECTED CLOSED AND EXISTING LANDFILLS WITH
POSITIVE ENERGY RECOVERY COSTS
Average length of control period (years)
Distribution of affected landfills by
length of control period
(years)
^25
26 to 50
51 to 100
101 to 150
>150
Total
25
69.6
213
(21)
230
(22)
310
(30)
235
(23)
36
(4)
1024
(100)
Stringency Levels
(Mg NMOC/yr)
100
50.8
167
(51)
49
(15)
36
(ll)
51
(16)
22
(7)
325
(100)
250
36.0
39
(51)
10
(13)
27
(35)
2
(3)
0
(0.0)
77
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
TABLE F-3. LENGTH OF CONTROL PERIOD PRIOR TO CLOSURE FOR AFFECTED EXISTING LANDFILLS
WITH POSITIVE ENERGY RECOVERY COSTS
Average length of control period
prior to closure (years)
Distribution of affected landfills by
length of control period prior to closure
(years)
<5
6 to 10
11 to 20
21 to 50
>50
Total
25
20.9
228
(28)
109
(13)
247
(30)
172
(21)
65
(8)
821
(100)
Stringency Levels
(Mg NMOC/yr)
100
14.5
124
(49)
36
(14)
53
(21)
10
(4)
29
(12)
252
(100)
250
8.6
36
(57)
15
(24)
2
(3)
10
(16)
0
(0)
63
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding. Excludes closed landfills.
-------
TABLE F-4. NET PRESENT VALUE OF ENTERPRISE COSTS FOR AFFECTED CLOSED AND EXISTING
LANDFILLS: COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
-ri
cn
Net Present Value
National enterprise costs ($10^)
Capital
Operating
Energy Recovery Revenue
Total
Average total enterprise cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of enterprise costs ($10^)
<0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
>5.0
Total
25
1,052
2,024
1,625
1,450
1.42
155
(15)
179
(18)
627
(61)
63
(6)
0
(0)
1,024
(100)
Stringency Levels
(Mg NMOC/yr)
100
324
424
299
450
1.39
61
(19)
70
(22)
162
(50)
32
(10)
0
(0)
325
(100)
250
121
155
154
123
1.59
17
(22)
17
(22)
33
(43)
10
(13)
0
(0)
77
(100)
Note: Numbers in parentheses are percentages. Net present value of enterprise costs is calculated using a 4 percent discount
rate for publicly owned landfills and an 8 percent discount rate for privately owned landfills. Details may not add to
totals due to rounding.
-------
TABLE F-5. ANNUALIZED ENTERPRISE CONTROL COST PER Mg OF MSW FOR AFFECTED EXISTING
LANDFILLS: COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
25
Stringency Levef
(Mg NMOC/yr)
100
250
National annualized cost per Mg MSW
($/Mg MSW)
Distribution of affected landfills by
annualized cost per Mg MSW
($/MgMSW)
0>
1.64
2.66
1.43
<0.50
0.50 to 1.25
1.25 to 3.00
3.00 to 10.00
> 10.00
Total
104
(13)
153
(19)
211
(26)
259
(32)
94
(H)
821
(100)
29
(12)
24
00)
90
(36)
94
(37)
15
(6)
252
(100)
17
(27)
0
(0)
31
(49)
15
(24)
0
(0)
63
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent from 1992 to the year of closure. Details may
not add to totals due to rounding. Excludes closed landfills.
-------
TABLE F-6. ANNUALIZED ENTERPRISE CONTROL COST PER HOUSEHOLD FOR AFFECTED EXISTING
LANDFILLS: COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
Stringency Level
(Mg NMOC/yr)
25 100 250
National annualized cost per household 9.50 15.47 8.33
($/Household)
Distribution of affected landfills by
annualized cost per household
($/Household)
<3.50 138 29 17
(17) (12) (27)
3.50 to 7.00 111 24 0
(14) (10) (0)
7.00 to 15.00 182 83 32
(22) (33) (51)
15.00 to 30.00 162 58 7
(20) (23) (11)
> 30.00 228 58 7
(28) (23) (11)
Total 821 252 63
(100) (100) (100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent from 1992 to the year of closure. Details may
not add to totals due to rounding. Excludes closed landfills.
-------
TABLE F-7. NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED CLOSED AND EXISTING
LANDFILLS: COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
00
Net Present Value
National social costs ($106)
Capital
Operating
Energy Recovery Revenue
Total
Average total social cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of social costs ($10^)
<0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
5.0 to 10.0
>10.0
Total
25
2,351
2,846
2,238
2,958
2.89
31
(3)
95
(9)
530
(52)
269
(26)
89
(9)
10
(1)
1,024
(100)
Stringency Levels
(Mg NMOC/yr)
100
622
580
374
828
2.55
29
(9)
29
(9)
170
(52)
53
(16)
44
(14)
0
(0)
325
(100)
250
239
213
198
253
3.27
7
(9)
10
(13)
22
(29)
14
(18)
24
(31)
0
(0)
77
(100)
Note: Numbers in parentheses are percentages. Net present value or social cost is computed using a two-step discounting
procedure. First, capital costs are annualized at 10 percent over the control period. Then, present values are computed by
discounting annual operating costs and annualized capital costs at 3 percent. Details may not add to totals due to rounding.
-------
TABLE F-8. SUMMARY INFORMATION FOR AFFECTED NEW LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
Number of affected landfills
(Percent of total new landfills)
Distribution of affected landfills
by design capacity
(106Mg)
^1
8 io 5
5 to 10
>10
Total
Privately owned affected landfills
(Percent of affected landfills)
25
140
(15)
58
(41)
73
(52)
7
(5)
2
(l)
140
(100)
34
(24)
Stringency Levels
(Mg NMOC/yr)
100
39
(4)
0
(0)
32
(82)
7
(18)
0
(0)
39
(100)
0
(0)
250
10
(1)
0
(0)
3
(30)
7
(70)
0
(0)
10
(100)
0
(0)
Note: The numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
I
I—»
o
TABLE F-9 LENGTH OF CONTROL PERIOD FOR AFFECTED NEW LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
Stringency Levels
(Mg NMOC/yr)
25 100 250
Average length of control period (years) 65.0 56.2 75.2
Distribution of affected landfills by
length of control period
(years)
<25
26 to 50
51 to 100
101 to 150
Total
24
(17)
46
(33)
36
(26)
34
(24)
140
(100)
7
(18)
15
(38)
7
(18)
10
(26)
39
(100)
3
(30)
0
(0)
7
(70)
0
(0)
10
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
TABLE F-10.
LENGTH OF CONTROL PERIOD PRIOR TO CLOSURE FOR AFFECTED NEW LANDFILLS
WITH POSITIVE ENERGY RECOVERY COSTS
25
Stringency Levels
(Mg NMOC/yr)
100
250
Average length of control period
prior to closure (years)
13.0
12.1
7.3
Distribution of affected landfills by
length of control period prior to closure
(years)
*5 29
(21)
6 to 10 24
(17)
11 to 20 73
(52)
21 to 50 14
(10)
Total 140
(100)
7
(18)
0
(0)
32
(82)
0
(0)
39
(100)
3
(30)
7
(70)
0
(0)
0
(0)
10
(100)
Note: Numbers in parentheses are percentages. Details may not add to totals due to rounding.
-------
TABLE F-ll. NET PRESENT VALUE OF ENTERPRISE COSTS FOR AFFECTED NEW LANDFILLS: COST-
MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY RECOVERY COSTS
Net Present Value
National enterprise costs ($10^)
Capital
Operating
Energy Recovery Revenue
Total
Average total enterprise cost
per affected landfill ($106)
^ Distribution of affected landfills by
,L net present value of enterprise costs ($10^)
ro
<0.5
0.5 to 1.0
1.0 to 3.0
3.0 to 5.0
>5.0
Total
25
86
181
116
150
1.07
53
(38)
27
(19)
53
(38)
7
(5)
0
(0)
140
(100)
Stringency Levels
(Mg NMOC/yr)
100
64
110
112
63
1.61
0
(0)
7
(18)
25
(64)
7
(18)
0
(0)
39
(100)
250
32
48
62
18
1.83
0
(0)
2
(20)
8
(80)
0
(0)
0
(0)
10
(100)
Note: Numbers in parentheses are percentages. Net present value of enterprise costs is calculated using a 4 percent discount
rate for publicly owned landfills and an 8 percent discount rate for privately owned landfills. Details may not add to
totals due to rounding.
-------
TABLE F-12. ANNUALIZED ENTERPRISE CONTROL COST PER Mg OF MSW FOR AFFECTED NEW
LANDFILLS: COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
Stringency Level
(Mg NMOC/yr)
25 100 250
National annualized cost per Mg MSW 0.95 0.92 0.59
($/Mg MSW)
Distribution of affected landfills by
annualized cost per Mg MSW
($/MgMSW)
co
<0.25
0.25 to 0.50
0.50 to 1.00
1.00 to 3.00
>3.00
Total
17
(12)
10
(7)
34
(24)
43
(3D
36
(26)
140
(100)
0
(0)
0
(0)
10
(26)
29
(74)
0
(0)
39
(100)
0
(0)
0
(0)
8
(80)
2
(20)
0
(0)
10
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent over the life of the landfill. Details may not add
to totals due to rounding.
-------
TABLE F-13. ANNUALIZED ENTERPRISE CONTROL COST PER HOUSEHOLD FOR AFFECTED NEW
LANDFILLS: COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY
RECOVERY COSTS
Stringency Level
(Mg NMOC/yr)
a
25 100 250
National annualized cost per household 5.53 5.36 3.41
(S/Household)
Distribution of affected landfills by
annualized cost per household
($/Household)
<0.75
0.75 to 1.50
1.50 to 3.00
3.00 to 10.00
> 10.00
Total
10
(7)
7
(5)
10
(7)
48
(34)
65
(46)
140
(100)
0
(0)
0
(0)
0
(0)
39
(100)
0
(0)
39
(100)
0
(0)
0
(0)
8
(80)
2
(20)
0
(0)
10
(100)
Note: Numbers in parentheses are percentages. Costs for publicly owned landfills are annualized at 4 percent over the control
period. Costs for privately owned landfills are annualized at 8 percent over the life of the landfill. Details may not add
to totals due to rounding.
-------
TABLE F-14.
NET PRESENT VALUE OF SOCIAL COSTS FOR AFFECTED NEW LANDFILLS: COST-
MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY RECOVERY COSTS
Net Present Value
National social costs ($10^)
Capital
Operating
Energy Recovery Revenue
Total
25
261
326
278
309
Stringency Levels
(Mg NMOC/yr)
100
146
151
155
142
250
77
69
88
58
Average total social cost
per affected landfill ($106)
Distribution of affected landfills by
net present value of social costs ($10^)
2.20
3.68
5.95
5.0
Total
0
(0)
24
(17)
82
(59)
27
(19)
7
(5)
140
(100)
0
(0)
0
(0)
22
(56)
10
(26)
7
(18)
39
(100)
0
(0)
0
(0)
2
(20)
0
(0)
8
(80)
10
(100)
Note: Numbers in parentheses are percentages. Net present value or social cost is computed using a two-step discounting
procedure. First, capital costs are annualized at 10 percent over the control period. Then, present values are computed
by discounting annual operating costs and annualized capital costs at 3 percent. Details may not add to totals due to
rounding
-------
TABLE F-15.
01
NET PRESENT VALUE OF EMISSIONS REDUCTIONS FOR AFFECTED CLOSED AND
EXISTING LANDFILLS: COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE
ENERGY RECOVERY COSTS
Net Present Value
Undiscounted NMOC emission reduction
Discounted NMOC emission reduction
Average discounted NMOC emission
reduction per affected landfill
(Mg)
Distribution of affected landfills by discounted
NMOC emission reduction per affected landfill
(Mg)
< 1,000
1,000 to 2,000
2,000 to 5,000
5,000 to 10,000
> 10,000
Total
25
5.81
2.04
1,993
429
(42)
305
(30)
208
(20)
58
(6)
24
(2)
1,024
(100)
Stringency Levels
(Mg NMOC/yr)
100
3.06
L15
3,546
82
(25)
94
(29)
94
(29)
29
(9)
24
(8)
324
(100)
250
1.26
0.59
7,560
17
(22)
0
(0)
22
(29)
14
(18)
24
(31)
77
(100)
Note: Numbers in parentheses are percentages. Net present value of emission reductions is calculated using a 3 percent
discount rate. Details may not add to totals due to rounding.
-------
TABLE F-16.
COST EFFECTIVENESS FOR AFFECTED CLOSED AND EXISTING LANDFILLS:
COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY RECOVERY COSTS
National cost effectiveness
($/Mg NMOC)
Distribution of affected landfills by
cost effectiveness
($/Mg NMOC)
^ 1,000
1,000 to 2,000
2,000 to 5,000
5,000 to 10,000
> 10,000
Total
Incremental cost effectiveness
25
1,449
157
(15)
269
(26)
414
(41)
143
(14)
41
(4)
1,024
(100)
2,287
Stringency Level
(Mg NMOC/yr)
100
719
189
(58)
102
(31)
7
(2)
12
(4)
15
(5)
325
(100)
989
250
433
68
(88)
7
(9)
0
(0)
2
(3)
0
(0)
77
(100)
—
Note: Numbers in parentheses are percentages. Cost effectiveness is calculated by dividing the net present value of social
cost by the discounted NMOC emission reduction (see Tables F-7 and F-15). Details may not add to totals due to
rounding.
-------
TABLE F-17.
CO
NET PRESENT VALUE OF EMISSIONS REDUCTIONS FOR AFFECTED NEW LANDFILLS:
COST-MINIMIZING OPTION AT LANDFILLS WITH POSITIVE ENERGY RECOVERY COSTS
Net Present Value
Undiscounted NMOC emission reduction
(!06Mg)
Discounted NMOC emission reduction
Average discounted NMOC emission
reduction per affected landfill
(Mg)
Distribution of affected landfills by discounted
NMOC emission reduction per affected landfill
s 1,000
1,000 to 2,000
2,000 to 5,000
> 5,000
Total
25
0.83
0.25
1,765
77
(55)
17
(12)
39
(28)
7
(5)
140
(100)
Stringency Levels
(Mg NMOC/yr)
100
0.49
0.15
3,818
0
(0)
7
(18)
25
(64)
7
(18)
39
(100)
250
0.25
0.06
6,680
0
(0)
2
(20)
0
(0)
8
(80)
10
(100)
Note: Numbers in parentheses are percentages. Net present value of emission reductions is calculated using a 3 percent
discount rate. Details may not add to totals due to rounding.
-------
TABLE F-18.
COST EFFECTIVENESS FOR AFFECTED NEW LANDFILLS: COST-MINIMIZING OPTION AT
LANDFILLS WITH POSITIVE ENERGY RECOVERY COSTS
I
(—»
10
National cost effectiveness
($/Mg NMOC)
Distribution of affected landfills by
cost effectiveness ($/Mg NMOC)
< 1,000
1,000 to 2,000
2,000 to 5,000
5,000 to 10,000
> 10,000
Total
Incremental cost effectiveness
25
1.244
24
(17)
53
(38)
39
(28)
17
(12)
7
(5)
140
(100)
1,661
Stringency Level
(Mg NMOC/yr)
100
963
15
(38)
24
(64)
0
(0)
0
(0)
0
(0)
39
(100)
870
250
891
7
(70)
3
(30)
0
(0)
0
(0)
0
(0)
10
(100)
—
Note: Numbers in parentheses are percentages. Cost effectiveness is calculated by dividing the net present value of social
cost by the discounted NMOC emission reduction (see Tables F-14 and F-17). Details may not add to totals due to
rounding.
-------
APPENDIX G
THEORETICAL COLLECTION SYSTEM DESIGN
-------
APPENDIX G
THEORETICAL COLLECTION SYSTEM DESIGN
G.I INTRODUCTION
This appendix provides the theoretical approach for designing landfill
gas collection systems. Design equations for active vertical wells, active
horizontal trenches, and passive vertical wells are detailed in
Sections G.3, G.4, and G.5, respectively. These equations were used in
Chapters 5, 6, and 7 to quantify the nationwide impact of controlling
landfills and as the foundation for the collection system design procedure
outlined in Chapter 9. The design procedure in Chapter 9 is a graphical
interpretation of the theoretical design equation. The derivation of this
procedure, is provided in Section G.6.
G.2 ASSUMPTIONS
The following assumptions have been made in developing the design
equations for landfill gas collection systems:
o The design of the active vertical and passive collection systems is
based on the peak landfill gas generation rate which is calculated
using: (1) an equation that describes the radius of influence of
extraction wells and (2) site-specific information for each
landfill (e.g., amount of refuse in place, landfill depth, landfill
age, acceptance rate, etc.).
o Scholl Canyon Model, a first order decay model described in
Chapter 3, is used to estimate the landfill gas generation rate.
o The lag time (typically less than one to two years) for the
landfill gas generation is negligible when compared to the total
life of landfill gas generation. Thus, the peak landfill gas
generation rate is assumed to occur at the time of closure.
G.3 THEORETICAL APPROACH FOR ACTIVE VERTICAL WELL COLLECTION SYSTEM DESIGN
The geometry of an active well system is illustrated in Figure G-l.
The radius of influence for a vertical well can be obtained by the following
mass balance equation:
Ra - (Qw>a Design Capacity/irl Prefuse Qgen E^1/2 (1)
G-l
-------
Refuse
t
To header system
-P.v
P-I
WD
SIDE VIEW
R 3 radius of Influence
a
0 » cover thickness
WO - well depth
I * landfill depth
P * vacuum pressure
P. * Internal landfill pressure
r » radius of well
Figure G-l. Model active vertical well collection system geometry.
G-2
-------
where,
R = radius of influence for active collection systems, m
3
Q = landfill gas flowrate per well, m /sec
w, a
Design Capacity = design capacity of the landfill, kg
TT = 3.14
refuse = refuse density, kg/m3
L = landfill depth, m
Q = peak landfill gas generation rate, m /sec
E = fractional collection efficiency of active well
systems
Equation (1) calculates the radius of influence based on the maximum
landfill gas generation rate (QQen) and the collection efficiency of the
active vertical well system (EJ. If the lag time for landfill gas
a
generation is neglected, Q is assumed to occur at the time of landfill
closure and can be determined using the Scholl Canyon model:
Qgen =2 LQ R (1 - exp(-kt)) (2)
where,
Q««« = Peak landfill gas generation rate, m /yr
gen ,
L = refuse methane generation potential, m methane/Mg refuse
R = average refuse acceptance rate, Mg/yr
k = landfill gas generation rate constant, 1/yr
t = landfill age upon closure
To calculate Q using Equation (2), it is necessary to know values for
L and k. As discussed above, LQ and k vary from landfill to
landfill depending on the composition, moisture content, pH, and internal
landfill temperature. Values of L and k have been determined empirically
for a total of 54 landfills based on test well data and/or data from
existing landfill gas collecting systems. For these landfills, the
estimated L and k correspond to the collected landfill gas flowrate
6-3
-------
(Q x E ) rather than the total landfill gas generation rate. Using the
gen a
values of ln and k derived in this way, the product of Qn and E, may be
0 y"n a
calculated using the following equation:
Qgen Ea = 2 Lo R [1 ' exp
where,
L' = refuse methane generation potential estimated from test well data
and/or existing landfill gas collection system, m methane/Mg
refuse.
k' = landfill gas generation rate constant estimated from test well data
and/or existing landfill gas collection system, 1/yr
Once the radius of influence is calculated, the number of wells
necessary can be calculated from the landfill area.
n = A/(TTRa2) (4)
where,
n = number of wells 2
A = area of landfill, m
= design capacity/(refuse density X depth)
R = radius of influence, m
TT= 3.14
From Darcy's Law, the landfill pressure corresponding to the calculated
radius of influence, refuse permeability, the magnitude of vacuum applied,
and the collectable landfill gas flowrate (i.e. Q X Ea) can be
calculated.
(Qqen Ea)
Pv - Design Capacity krefu$e (WD/L)
where,
2
P-, = internal landfill pressure, Newton/m
1 2
P = vacuum pressure, Newton/m
G-4
-------
R = radius of influence, m
a
r = radius of outer well (or gravel casing), m
refuse = refuse density, 650 kg/m3
^refuse = intrinsic Defuse permeability, m
= landfill gas viscosity, Newton-sec/m
Design Capacity = design capacity of landfill, kg
WD = well depth (i.e., 0.75L), m
L = landfill depth, m
Q = peak landfill gas generation rate, ft /yr
E, = fractional collection efficiency of active well system
a
Once the radius of influence and the number of wells are calculated, it
is necessary to check if significant air infiltration exists under the given
refuse permeability, cover permeability, and vacuum applied.
The flow of air through the cover material is illustrated in
Figure G-2. At steady state, the flowrate through the interface of
atmosphere and the cover material, and the flowrate through the interface of
cover material and the refuse are the same. Thus, the following equation is
obtained at steady state:
v . = k (P . - P.)/(u . D )
air cover v atm i//v^air cover'
where,
' krefuse,v
vo-v. = air velocity through cover and refuse, m/sec
d I l ty
k = intrinsic cover permeability, m
P . = atmospheric pressure, Newton/m
P. = interface pressure, Newton/m
2
M . = air viscosity, Newton-sec/m
D = cover thickness, m
^refuse v = intrinsic vertical refuse permeability, Newton-sec/m
2
P = vacuum pressure, Newton/m
X = length of solid pipe, m
G-5
-------
Air flow
Coven -
Refuse
SIDE VIEW
Racos0
Y
Ra • radius of influence
X * length of solid pipe
1
internal landfill pressure
interface pressure
Py » vacuum pressure
Figure G-2. Air flow through landfill cover.
G-6
-------
It should be noted that the vertical refuse permeability is used for air
infiltration equations rather than the horizontal permeability (or simply
permeability). According to industry experts, the horizontal permeability
is approximately 10 times greater than the vertical permeability due to the
layering effect of the refuse accumulation.
The flowrate of air can be calculated using the following equation:
"air ' («
'"air Ra <
If the maximum allowable percent of oxygen in the total collected
landfill gas is assumed to be 0.5 percent, the corresponding allowable
4
percent of air in landfill gas is 2.44 percent. Therefore, the minimum
solid pipe length required (X) can be calculated by the following equation:
= kcover A/^ D>
refuse,v
Note that Equation (8) only accounts for the air infiltration from the
surface of a landfill (i.e, the air infiltration from the sides of landfill
is negligible compared to the air infiltration from the surface of landfill)
Equation (8) can be simplified to:
cover <"atm ' "v> ^a1r <°-0244>
-------
well needs to be solid. For shallow landfills, the magnitude of vacuum
required can be calculated using Equation (9) by setting X to be the
available solid pipe length.
The radius of influence is then recalculated based on the new vacuum
and the landfill pressure calculated using Equation (5). The radius of
influence for shallow landfills is expected to be smaller since the pressure
driving force (or pressure gradient) would be less. Thus, to achieve the
same collection efficiency in a shallow landfill as in a deeper landfill,
the number of wells required in a shallow landfill will be larger.
The design calculation steps for active vertical well collections
systems are illustrated in Figure G-3.
G.4 THEORETICAL APPROACH FOR HORIZONTAL TRENCH COLLECTION SYSTEMS DESIGN
The geometry of a model horizontal trench system is illustrated in
Figure G-4. The governing equations for horizontal trench systems are also
based on a mass balance equation and Darcy's Law. The basic approach for
designing horizontal trench collection systems is to use the radius of
influence calculated for active vertical wells (using Equation (1)) to
determine the horizontal spacing between trenches, since the radius of
influence is a function of the refuse permeability and the landfill
pressure. The landfill pressure, in turn, is a function of the
landfill gas generation rate and degree of containment (i.e., type of liner,
etc.). The vertical spacing between the trench layers can be calculated by
the following equations using vertical refuse permeability.
RU ln(R,,/r) = [(Pi " P» ) Design Capacity k,.... _ „ (WD/L)]/
v v iv reruse,v
rp ii tn f \-\
1 v n.FG refuse vygen a'J
Sv - 2 Ry
where,
2
P-| = internal landfill pressure, Newton/m
P = average vacuum pressure along the trench length,
Newton/m
6-8
-------
Calculate the product of peak landfill gas generation rate and active
vertical well collection system efficiency using equation (3)
Calculate radius of influence using equation (1)
Calculate the landfill pressure using equation (5)
Calculate the minimum solid pipe length, X using equation (9)
Compare X to the available solid pipe length (0.75 L X 0.333)
Is X greater than the available solid pipe length?
\
Yes
Calculate the vacuum pressure necessary to make
X = available length by using equation (9)
Recalculate radius of influence under the new
vacuum pressure using equation (5)
Calculate the number of wells necessary using equation (4)
Figure G-3. Active vertical well collection system design calculation steps,
G-9
-------
jk
/ j
To header
SIDE VIEW
cover
v, average
cover thickness
average vacuum pressure
spacing between trench layers
Figure G-4. Model horizontal trench system geometry.
G-10
-------
S = vertical spacing between trench layers (i.e., radius
v of influence for vertical direction), m
R = vertical radius of influence, m
r = radius of gravel casing, m
refuse = refuse density, 650 kg/m3
^Ifa = Infill 9as viscosity, Newton-sec/m
^refuse v = intrinsic vertical refuse permeability, m
Design Capacity = design capacity of landfill, kg
WD = well depth, m (typically 0.75 L)
L = landfill depth, m
Q = peak landfill gas generation rate, m /yr
E = fractional collection efficiency of active well system
a
Note that the vacuum pressure used in Equation (11) is an average vacuum
pressure along the length of a trench. If the vacuum is pulled only at one
end of a trench, there may be a significant pressure drop along the length of
the trench unless the collected gas flowrate is too small to yield a
significant pressure drop. The pressure drop can be minimized if vacuum is
pulled evenly using a manifold system.
The number of trench layers can be calculated by:
HT - L/SV (12)
where,
n-, = number of trench layers
L = landfill depth, m
S = vertical spacing between trenches, m
6-11
-------
Once the vertical spacing between the trench layers is calculated, the
horizontal spacing between trenches can be calculated by the following
equations:
Rh2 ln(Rh/r) = [(P^ - Py2) Design Capacity krefuse>h (WD/L)]/ (13)
Refuse (Qger,
Sh - 2 Rh
where,
2
P, = internal landfill pressure, Newton/m
P = average uacuum pressure along the trench length,
Newton/m
R. = horizontal radius of influence, m
S. = horizontal spacing between trench layers, m
r = radius of gravel casing, m
2
^Ifa = landfill gas viscosity, Newton-sec/m
Refuse = refuse density, 650 kg/m3
^refuse h = intrinsic horizontal refuse permeability, m
Design Capacity = design capacity of landfill, kg
WD = well depth, m (typically 0.75 L)
L = landfill depth, m
Q = peak landfill gas generation rate, m /yr
E, = fractional collection efficiency of active well system
Q,
Assuming that the landfill is square, the number of trenches per trench
layer can be calculated by:
nt = A1/2 /Sh (14)
where,
n. = number of trenches per trench layer
2
A = landfill area, m
S = horizontal spacing between trenches, m
G-12
-------
Therefore, the total required trench length for a square landfill is:
L, - nt n. A1/2
where,
Lt = total length of trench, m
2
A = landfill area, m
The air infiltration equations for the active vertical collection
systems also apply to the horizontal trench collection systems. If the
landfill is shallow, the radii of influence for vertical and horizontal
directions are calculated (for active vertical well systems) using the
reduced magnitude of vacuum and they are applied to horizontal trench
systems as the vertical and horizontal spacings.
The design calculation steps for horizontal trench collection systems
are presented in Figure G-5.
G.5 THEORETICAL APPROACH FOR PASSIVE COLLECTION SYSTEMS DESIGN
The geometry of the model passive well system is illustrated in
Figure G-6. The governing equations for active systems also apply to
passive systems except that the pressure gradient in Equation (5) is based
on the difference in landfill pressure and atmospheric pressure as follows:
Prefuse
Patm - Design Capacity krefu$e (WD/L) <16>
where,
2
PT = internal landfill pressure, Newton/m
2
P . = atmospheric pressure, Newton/m
R = radius of influence for passive system, m
r = radius of outer well (or gravel casing), m
refuse = refuse density> 65°
k .. = intrinsic refuse permeability, m
^ = landfill gas viscosity, Newton-sec/m
G-13
-------
Calculate the product of peak landfill gas generation rate and active
vertical well collection system efficiency using equation (3)
Calculate radius of influence for active vertical
well collection system using equation (1)
Calculate the landfill pressure using equation (5)
Adjust the vacuum pressure to minimize air
infiltration using equation (9)
Calculate vertical radius of influence and vertical spacing for
horizontal trench collection system with same efficiency as
active vertical well system using equation (11)
Calculate number of trench layers using equation (12)
Calculate horizontal radius of influence and horizontal
spacing for horizontal trench collection system using
using equation (13)
Calculate number of trenches per layer using equation (14)
Calculate total trench length required using equation (15)
Figure G-5. Horizontal trench system design calculation steps.
G-14
-------
t
To passive control
equipment or header
J" S.
atm i
1
1
1
1
1
1
8
RP
p
a
>1
0,
cover
radius of Influence
of passive well
* atmospheric pressure
Internal landfill pressure
cover thickness
SIDE VIEW
Figure G-6. Model passive collection system geometry.
G-15
-------
Q = peak landfill gas generation rate, m /yr
E = fractional collection efficiency of passive well
system
Design Capacity = design capacity of landfill, kg
WD = well depth, m (typically 0.75 L)
L = landfill depth, m
The ratio of the radius of influence of passive systems to the radius
of influence of active systems can be expressed by the following equation:
~ n n (il)
V ln(Ra/r) [(P1 ' Pv )/PvJ Ep
By setting the ratio of collection efficiencies on passive systems and
active systems to one, the passive system design needed to achieve the same
collection efficiency as an active system can be determined. Based on the
radius of influence of the passive wells obtained from Equation (17) the
number of passive wells necessary can be calculated as follows:
n = A/(7TRp2) (18)
where,
n = number of wells
o
A = landfill area, m
R = radius of influence for passive system, m
As discussed earlier, the problem of air infiltration does not exist for
passive systems since the passive systems rely on the natural pressure
gradient. The design calculation steps for passive collection systems are
illustrated in Figure G-7.
G-16
-------
Calculate the product of peak landfill gas
generation rate and active vertical well
collection system efficiency using Equation (3)
Calculate radius of influence for active
vertical well collection system using
Equation (1)
Calculate the landfill pressure
using Equation (5)
Calculate radius of influence for passive
collection system with same efficiency as
active vertical well system using
Equation (17)
Calculate number of passive wells
necessary using Equation (18)
Figure G-7. Passive collection system design calculation steps
G-17
-------
G.6 GRAPHICAL INTERPRETATION OF THE THEORETICAL APPROACH
A graphical interpretation of the design equations provided in the
previous sections was performed to simplify the approach landfill owners
would have to take to design collection systems in the absence of
site-specific data. Sections G.6.1 and G.6.2 describe the derivation of the
simplified design approach for active collection systems and passive
collection systems, respectively.
G.6.1 Simplified Approach for Active Collection System Design
The approach outlined in Chapter 9 for active collection systems is a
two step process. The first step is to determine the maximum blower vacuum
allowed for a given landfill depth. From Equation 9 in Section G.3, a
relationship between the blower vacuum (P ) and the landfill depth (L) was
obtained.
o Derivation of P as a function of L
Given:
x = (k
Equation
\ /(/
refuse, v'v
/*air .
9
cover
0244
> + ]
Mqgen/A)(.0244/kcover)(^/krefuse)
But A can be expressed in terms of L
A = DC
^refuse
G-18
-------
where,
L - Landfill depth, m
DC = Design Capacity, Mg -
refuse = refuse density, kg/m
P - P - \( 7RI Wk ^ j- l]e WD M
° ' rv ratm u'/:3LMK'cover; lKrefusenucover;j
* (Qgen/DC)( refuseL)('0244/kcover)( air/krefuse)
Using the following values for refuse density, refuse
permeability, and air viscosity:
refuse = 65° 13 2
3.743 x 10"13 m2 ,
l- 8x 10 N-sec/m2
and assuming atmospheric pressure is equal to 1 atm, the equation
becomes:
Py = 1 - [(.25L)(kcover) + (Dcover)(3.743 x 10'13)]
* (WDC)(L/kcoverH-004>
The ratio of Q to DC will vary from landfill to landfill due to
differences inactive life and refuse composition. For the sake
of simplicity, however, a single conservative value of this ratio
was developed and used to generate a relationship between P and L
that would apply to a wide variety of landfills. The OSW database
of municipal landfills served as the source for values of Qaen/DC.
The Scholl Canyon model for landfill gas generation (Equation 2)
was used to determine the maximum expected landfill gas flowrate
for each landfill in the database. In order to obtain consistency
in the landfill gas generation rate between landfills, a value of
0.02 1/yr was used for k, the gas generation rate constant, and a
value of 230 m methane/Mg refuse was used for L , the gas
generation potential. These values represent the 80th percentile
of the k's and L 's that were randomly assigned to the landfills
in the database to obtain national and economic impacts. More
information on k and L is provided in Chapter 3.
The resulting values of Qaen/DC ranged from .000025 cfm/Mg to
.0007 cfm/Mg. The average Was assumed to provide a reasonable,
yet conservative value for Qaen/DC that could apply to a wide
range of landfills. Using tnfs value of Qaen/DC, the relationship
between P and L was obtained for three types of caps: synthetic,
clay, and soil. Using cover permeabilities and thicknesses
provided in Table G-l, the following equations were developed for
the three cover types:
Synthetic: PV = 1 - (4.2 x 10"7 L2 + 4.7 x 10"4 L)
G-19
-------
TABLE 6-1. COVER PERMEABILITIES AND THICKNESSES
Cover type Permeability (m) Thickness (m) Reference
Synthetic 1.0 x 10"18 7.6 x 10"4 6
Clay 5.0 x 10°15 .61 7
Soil 1 x 10"14 .61 8
G-20
-------
Clay: Py = 1 - (4.2 x 10"7 L2 + 7.6 x 10"5 L)
Soil: Py = 1 - (4.2 x 10"7 L2 + 3.8 x 10"5 L)
These equations are illustrated in Figure 9-6 in Chapter 9.
The second step in designing an active landfill gas collection system
is to determine the radius of influence that corresponds to the maximum
blower vacuum determined in the first step. From Equation 5 in Section G.3,
a relationship between radius of influence for an active system (R,) and
a
blower vacuum (P ) can be obtained.
* Cation of Ra as a function of PV
Given Equation 5
p,2 - >>v2 - «a2 0" LFG refuse
Pv DC krefuse
Solving for R
a
R2 ln ' P2 - P2 k
refuse
p Q
v ygen LFG refuse
Using the following values:
r = .3048 m ,, ,
krefuse ' 3'743 * 10 »
WD/L = 0.75 , ,
. „ - 1.15 x 10"5 N-sec/nr
refuse ' 65° ^
the expression becomes
R 2 ln(R/.3048) = P 2 - P 2 DC 8.06
^-^^^^—
P Q
v xgen
Using the average value of Qaen/DC provided in the derivation of
P as a function L and assumtn^ a landfill gas pressure of
1101 atm, the expression becomes
R} ln(R /.3048) - (1.02 - PU2/PU)(1.7 x 104)
0 d V V
This equation is illustrated in Figure 9-7 in Chapter 9.
G-21
-------
As mentioned in Chapter 9 using this approach to collection system
design may result in an excessive number of wells when compared to the
recommended empirical approach.
G.6.2 Simplified Approach for Passive Collection System Design
The approach outlined in Chapter 9 for passive collection systems is to
determine the appropriate radius of influence for a given pressure drop
across the collection and control device. The initial step in formulating
this correlation was to develop a relationship between the radius of
influence for a passive system (R ) and the landfill gas pressure (P-,).
• Derivation of R as a function of P-j
From Equation 17
RP2 1n(RP/r) - [(P/ - Patn,2)/Patm] Ep
Ra2 ln(Ra/r) [(P,2 - Pv2)/Py] Ea
Assume the collection efficiencies of an active collection system
and a passive collection system are equal (i-e., Ep/Ea = 1) and
solve for Rp.
From Equation 5
= (DC/Qgen) Krefuse
[(P1 • Pv )/Pv] LFG refuse
•'• RP2 ln |