EPA/600/R-13/3 04
September 2012
Materials Management:
State of the Practice 2012
White Paper
U.S. Environmental Protection Agency
Office of Research and Development
US Environmental Protection Agency
Office of Research and Development
Land Remediation and Pollution Control Division
National Risk Management Research Laboratory
Cincinnati, Ohio, 45268
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Notice
The U.S. Environmental Protection Agency (U.S. EPA) through the Office of Research and Development
funded and managed the research described here under contract order number: EP-W-09-004 to RTI
International and its subcontractor Innovative Waste Consulting Services (IWCS). The report has been
subject to the Agency's review and has been approved for publication as a U.S. EPA document. Use of
the methods or data presented in this manual does not constitute endorsement or recommendation for use.
Mention of trade names or commercial products does not constitute endorsement or recommendation.
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Table of Contents
Abbreviations and Acronyms v
Executive Summary 1
1. Introduction 1
1.1 Background 1
1.2 White Paper Objectives, Scope, and Organization 2
2. MSW Management Background and Decision Making Fundamentals 3
2.1 Transition from Waste to Materials Management 3
2.2 Integrated Waste Management System Elements 4
2.2.1 Segregation, Collection, and Transport 4
2.2.2 Processing and Materials Recovery 5
2.2.3 Energy Recovery 5
2.2.4 Disposal 7
2.3 MSW Management Decision Making 7
3. MSW Management Technologies 11
3.1 Overview 11
3.2 Landfilling 11
3.2.1 Technology Description 11
3.2.2 Commercialization Status 14
3.2.3 Materials and Energy Recovery 14
3.2.4 Environmental Concerns 15
3.2.5 Economic Considerations 16
3.3 Anaerobic Digestion 17
3.3.1 Technology Description 17
3.3.2 Commercialization Status 18
3.3.3 Materials and Energy Recovery 22
3.3.4 Environmental Concerns 22
3.3.5 Economic Considerations 23
3.4 Aerobic Composting 24
3.4.1 Technology Description 24
3.4.2 Commercialization Status 26
3.4.3 Materials and Energy Recovery 28
3.4.4 Environmental Concerns 28
3.4.5 Economic Considerations 29
3.5 Combustion 29
3.5.1 Technology Description 29
3.5.2 Commercialization Status 31
3.5.3 Materials and Energy Recovery 32
3.5.4 Environmental Considerations 33
3.5.5 Economic Considerations 34
3.6 Gasification 35
3.6.1 Technology Description 35
3.6.2 Commercialization Status 38
3.6.3 Materials and Energy Recovery 39
3.6.4 Environmental Concerns 39
3.6.5 Economic Considerations 40
3.7 Pyrolysis 41
3.7.1 Technology Description 41
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3.7.2 Commercialization Status 43
3.7.3 Materials and Energy Recovery 44
3.7.4 Environmental Concerns 45
3.7.5 Economic Considerations 46
4. Impact Assessment Methodology 47
4.1 Systems-Based Impact Assessment 47
4.2 Environmental Impacts 47
4.3 Economic Impacts 49
4.4 Social Impacts 51
4.4.1 SIA in the U.S 52
4.4.2 International Practice of SIA 54
4.5 Summary of Data Gaps for Developing Impact Tools 54
5. Summary 56
6. References 58
Appendix A—Examples of Existing Solid Waste Management Decision Support Tools 1
in
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List of Figures
Figure 2-1. Typical Energy Content of Various MSW Constituents, Mixed MSW, and Other
Energy or Fuel Sources (Tchbanoglous et al., 1993; U.S. EIA 2012) 6
Figure 2-2. MSW Constituents and Their Treatability by Technology 7
Figure 2-3. Simplified MSW Decision-Making Process Flow Diagram 10
Figure 3-1. A Generalized Process Flow Diagram for MSW Landfilling 13
Figure 3-2. Distribution of Landfill Gas Beneficial Use Project Types in the U.S. as of 2012
(U.S. EPA, 2012b) 15
Figure 3-3. A Generalized Process Flow Diagram for Anaerobic Digestion 20
Figure 3-4. Geographical Distribution of MSW AD Plants from 5 Most Prominent Vendors
(BTA, Valorga, DRANCO, Biostab, and Kompogas) 20
Figure 3-5. Distribution of Capacities of AD Plants Supplied by 5 Most Prominent Vendors 21
Figure 3-6. Estimated Capital Costs as a Function of OFMSW AD Facilities Capacity
(Tsilemou et al., 2006) 24
Figure 3-7. A Generalized Process Flow Diagram for Composting 25
Figure 3-8. Geographical Distribution of Food Scrap Composting Facilities in the U.S.
(Olivares and Goldstein, 2008) 27
Figure 3-9. Distribution of Food-Scrap Annual Tonnage Acceptance Rates of U.S. Food Scrap
Composting Facilities (Olivares and Goldstein, 2008) 27
Figure 3-10. A Generalized Process-Flow Diagram for MSW Combustion 30
Figure 3-11. Distribution of Different MSW Combustor Types in the U.S. (Berenyi, 2012) 31
Figure 3-12. Annual Total Mass of Air Pollutants Emitted by MSW combustors in the U.S.in
2005 (Stevenson, 2007) 33
Figure 3-13. Average Initial and Additional Capital Cost for MSW Combustion Plants in the
U.S 35
Figure 3-14. A Generalized Process Flow Diagram for MSW Gasification 36
Figure 3-15. Distribution of MSW Gasification Reference Plant Capacities for Six Most
Prominent Technology Providers 38
Figure 3-16. A Generalized Process Flow Diagram for Pyrolysis 42
Figure 3-17. Distribution of Capacities of MSW Pyrolysis Plants Located Worldwide 44
Figure 4-1. Generalized Contaminant Transport and Exposure Pathways 48
Figure 4-2. Assessing an MSW Management Facility's Economic Impact 50
List of Tables
Table 2-1. Common Economic, Environmental, and Social Considerations Currently Used in the
MSW Management Decision-making Process 8
Table 3-1. Ranges of Air Pollutant Emission Concentrations for 12 Existent MSW
Gasification Facilities 40
Table 4-1. Economic Impact Modeling Approaches 49
Table 4-2. U.S. Principles and Guidelines for Social Impact Assessment 53
Table 4-3. Suggested Process for Implementing and SIA (ICPGSIA, 2003) 53
Table 4-4. Qualitative Data Availability Rating for Key Assessment Inputs for Different MSW
Technologies 54
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Abbreviations and Acronyms
AD Anaerobic Digestion
AFB Air Force Base
APCD Air Pollution Control Device
BTU British Thermal Unit
C:N Carbon to Nitrogen ratio
CAA Clean Air Act
CH4 Methane
cm Centimeter
CO Carbon Monoxide
CO2 Carbon Dioxide
CPI Consumer Price Index
DOE Department Of Energy
EBMUD East Bay Municipal Utility District
EPA Environmental Protection Agency
FDEP Florida Department of Environmental Protection
ft Feet
GCCS Gas Collection and Control System
GHG Greenhouse Has
H2 Hydrogen
H2O Water
H2S Hydrogen Sulfide
HC1 Hydrogen Chloride
HDPE High-Density Polyethylene
HF Hydrogen Flouride
Hg Mercury
ICPGSIA Interorganizational Committee on Principles and Guidelines for Social Impact
Assessment
IES International Environmental Solutions
1-0 Input-Output
IWCS Innovative Waste Consulting Services, LLC
kg Kilogram
kW Kilowatt
kWh Kilowatt-hour
LFG Landfill Gas
m Meter
MACT Maximum Achievable Control Technology
MBTU Mega-BTU
Mg Mega-gram
MJ Mega-Joule
MRF Material Recovery Facility
MSW Municipal Solid Waste
MW Megawatt
N Newton
N2 Nitrogen
N2O Nitrous Oxide
NAICS North American Industry Classification System
NMOC Non-Methane Organic Compound
NOx Mono-Nitrogen Oxide
NSPS New Source Performance Standards
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AD
Anaerobic Digestion
NY
New York
O&M
Operation and Maintenance
02
Oxygen
OE
Organic Energy
OFMSW
Organic Fraction of Municipal Solid Waste
ORD
Office of Research and Development
PAH
Polycyclic Aromatic Hydrocarbon
PAYT
Pay-As-Y ou-Throw
PC
Personal Computer
PCB
Polychlorinated Biphenyl
PM
Particulate Matter
RCC
Resource Conservation Challenge
RCRA
Resource Conservation and Recovery Act
RDF
Refuse-Derived Fuel
RRA
Resource Recovery Act
RTI
Research Triangle Institute International
SCAQMD
South Coast Air Quality Management District
sec
Second
SHC
Sustainable and Healthy Communities
SIA
Social Impact Assessment
S02
Sulfur Dioxide
sox
Sulfur Oxide
SSL
Soil Screening Level
SSO
Source-Separated Organics
SWANA
Solid Waste Association of North America
TCLP
Toxicity Characteristic Leaching Procedure
TPD
Tons Per Day
TPY
Tons Per Year
TRIO
Total Resource Impacts and Outcomes
US
United States
VOA
Volatile Organic Acid
VOC
Volatile Organic Compound
WTE
Waste-To-Energy
yr
Year
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Executive Summary
Community leaders and planners face the challenge of providing safe, responsible, and profitable methods
for managing the municipal solid wastes (MSW) produced by their residents, businesses and visitors.
Desired objectives include not only minimizing impacts on the community and the environment but also
maximizing opportunities to recover resources and energy from a municipality's discarded materials. The
U.S. EPA, in support of the paradigm shift from MSW management to materials management, has
developed a new research thrust to promote the concept of sustainable materials management, broadly
defined as an approach to the sustainable use materials, integrating actions intended to reduce adverse
environmental impacts, and preserving natural capital throughout the life cycle of materials while
accounting for economic efficiency and social equity.
Through a new initiative of the sustainable materials management effort, a research program designated
as Sustainable and Healthy Communities (SHC), the U.S. EPA strives to inform and empower decision
makers in local communities, as well as in federal, state, and tribal community-driven programs, to
efficiently and equitably weigh and integrate human health, socio-economic, environmental, and
ecological factors into their decisions in a manner that fosters community sustainability. The SHC
Strategic Research Action Plan strives to develop a Total Resource Impacts and Outcomes (TRIO)
accounting method to account more comprehensively for the full costs and benefits of community
decisions with respect to the three pillars of sustainability (the environment, the economy, and society).
As a first step in the SHC TRIO initiative, this whitepaper was developed for the Office of Research and
Development (ORD) to summarize the current state of the practice with respect to MSW (materials)
management, to outline the various factors that contribute to a community's decision-making process, and
to discuss existing and needed information and tools for empowering community decision making.
Six materials management technologies were assessed with respect to each technology's process, material
and energy pathways, commercialization status, and associated economics. The inclusion and
implementation of a materials recycling program were treated as a standard component of any integrated
MSW management system, regardless of the particular technology employed. Some of the technologies
evaluated—landfilling and combustion—represent common practice today in the U.S., and information
regarding these technologies is readily abundant. Other technologies - composting and anaerobic
digestion - may be typical for particular material streams (e.g., biosolids, yard trash, food scrap), but for
mixed MSW treatment, experience in the U.S. is limited (though internationally these processes are more
widely utilized). The last group of technologies—gasification and pyrolysis—are the subject of growing
interest because of their potential for materials and energy recovery, but experience with full-scale
implementation on mixed municipal remains very limited, even internationally. All technologies offer
some opportunities for energy and materials recovery.
Factors commonly considered by communities when assessing the environmental, social, and economic
impacts of various materials management technologies are summarized, as are existing tools utilized to
evaluate sustainable MSW management decisions; existing tools are limited in their ability to address all
three pillars of sustainability concurrently. Opportunities do exist to develop, or improve upon existing,
tools for communities to make critical decisions regarding MSW. Such tools would empower policy
makers to assess a full complement of available technologies (including emerging technologies) while
acknowledging commercialization status and each pillar of sustainability. Steps forward to support
community decisions to efficiently and equitably weigh and integrate health, social, economic and
environmental considerations into sustainable community decision making, such as quantifying
environmental and economic factors in a comprehensive and uniform manner, and gathering new
information to better quantifying social trade-offs, were identified.
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1. Introduction
1.1 Background
The consumption of materials in the United States (U.S.) and throughout the world has increased
tremendously in recent decades. As reported by the U.S. Environmental Protection Agency (U.S. EPA),
during the past 50 years, people have consumed more resources than in all previous history. In addition,
of all the materials consumed in the U.S., over the past 100 years, more than 50% were depleted in the
past 25 years. This increased the rate of materials consumption—much of it consisting of non-renewable
materials—"has led to serious environmental effects such as habitat destruction, biodiversity loss, overly
stressed fisheries, and desertification." (U.S. EPA, 2009)
The substantial increase in materials consumption in the U.S. has translated into a significant increase in
the generation of industrial and municipal solid waste (MSW); the reported 100% increase in material
consumption from 1970 to 1995 resulted in an increase in MSW generation rate of more than 70% during
the same period (USGS, 1998; U.S. EPA, 201 la). MSW is the primary waste stream that communities
(through their local governments) are responsible for managing. Historically, the spectrum of
management options and services selected by communities has ranged from systems where MSW is
collected and transported elsewhere for further management, to development and operation of regional
solid waste management facilities for the management of MSW from various surrounding communities.
Given the amount of MSW that needs to managed—approximately 250 million tons of MSW was
generated in the U.S. in 2010 (U.S. EPA, 2011a)—communities' decisions on materials and methods used
for MSW management have significant economic, social, and environmental implications.
The idea of sustainability—broadly defined as the ability to meet current societal needs while not
compromising the anticipated needs of future generations—has not historically been integrated with
community decision making regarding MSW management. Primary reason for this is that the
conventional decision-making processes and tools communities use to make environmental, economic,
and social trade-offs are often not well-characterized in terms of the implications for and interactions
among human health, ecosystem services, economic vitality, and social equity (U.S. EPA, 2012a). The
need for a holistic decision-making approach for MSW management is widely recognized as an essential
component for transitioning to a sustainable society (USGS, 1998; U.S. EPA, 2009; Pereira, 2012).
In its new research initiative, the Sustainable and Healthy Communities Research Program (SHC), the
U.S. EPA strives to inform and empower decision makers in local communities, as well as in federal,
state, and tribal community-driven programs, to efficiently and equitably weigh and integrate human
health, socio-economic, environmental, and ecological factors into their decisions in a way that fosters
community sustainability. The SHC Strategic Research Action Plan strives to develop a Total Resource
Impacts and Outcomes (TRIO) accounting method to account more comprehensively for the full costs and
benefits of community decisions with respect to the three pillars of sustainability (the environment, the
economy, and society). The broader objectives of the research initiative—structured into four interrelated
themes—are the following (U.S. EPA, 2012a):
¦ Develop dynamic data and tools (e.g., national atlas for sustainability; metrics to characterize
and communicate linkages among human health, well-being, and environmental changes) to
assist communities in framing sustainability goals and decisions, and measuring and
communicating the progress towards these aims.
¦ Develop information and methods to quantify ecosystem goods (e.g., timber) and services
(e.g., decomposition of organic matter in the soil) and their impact on human health and well-
being, and the ways alternative decisions can affect ecosystem goods and services, and
human health and well-being.
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¦ Identify technologies and approaches to enhance energy and materials recovery from existing
waste streams to improve the effectiveness and efficiency of methods and guidance to address
existing land and groundwater contamination sources, and to encourage the use of innovative
approaches to reduce new sources of pollution.
¦ Integrate linkages among resources and assets managed by communities and develop a
systems approach for evaluating various options as a whole. The high-priority resources and
assets (sectors) that community decision makers commonly manage are: providing solid
waste collection and disposal; maintaining and diversifying transportation options;
developing building codes and zoning for land-use planning; and implementing shared
public/private responsibilities for meeting infrastructure (e.g., distribution of water and power
needs).
Because of the complexity of the decision-making process and long-term implications of these decisions
on the three pillars of sustainability, materials management was recognized as one of the four priority
sectors for developing dynamic decision-making tools that account for TRIO. Technological
advancement, increasing resource constraints, regulatory intervention, and communities' desire to make
MSW management more sustainable are some of the key factors that have led to a significant shift in the
MSW management philosophy from waste to materials management.
1.2 White Paper Objectives, Scope, and Organization
This white paper is an initial step in a process that will result in the development of TRIO-based materials
management tools for communities. The objectives of this document are as follows:
i. Describe the current state of the practice and science of MSW management. This includes a
basic technological description of the overall process, materials, and energy pathways involved
with the implementation of each and the commercialization status of each technology in the U.S.
ii. Identify factors that can be used to assess the environmental, social, and economic impacts
of the various solid waste management operations. Each control technology was evaluated in
terms of environmental releases (e.g., emissions, wastewater, solid residuals). A general
discussion of factors as well as approaches that can be used to assess social and economic
impacts is provided as these are highly site-specific. Financial considerations examined include
the direct cost and benefit of the different MSW management technologies.
iii. Identify opportunities and information gaps. The transition from waste to materials
management represents a fundamental change in dealing with MSW management and the state of
MSW management technologies discussed in this white paper represents the initial step towards
the development of a comprehensive tool that acknowledges the three pillars of sustainability.
Data gaps and opportunities that may be explored as next steps in the U.S. EPA's SHC research
program were identified in the process of developing this white paper.
This white paper is organized into five sections. Section 1 presents the background of the SHC research
initiative, the white paper objectives, and organization. Section 2 gives a brief description of the MSW
management transition to material management; a broad overview of the fundamentals of various MSW
management technologies; and the factors generally considered in the decision-making process. Section 3
presents a detailed description of individual MSW management technologies. Part 4 shows potential
methodologies that can be used to assess the economic, environmental, and social impacts of the various
technologies and the associated inputs. It also presents data gaps, and future research needs for
developing TRIO accounting methods for MSW decision making. Section 5 summarizes the current
practice of MSW management and next steps for moving forward with respect to enhanced decision-
making.
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2. MSW Management Background and Decision Making
Fundamentals
2.1 Transition from Waste to Materials Management
Solid waste disposal was first regulated under the Solid Waste Disposal Act of 1965. This rule did not
provide prescriptive requirements for landfills or incinerators, but instead primarily focused on training,
planning, and demonstration projects. Congress intended that states and tribes would be primarily
responsible for regulating solid waste disposal. Under the Resource Recovery Act (RRA) of 1970, the
federal government became more involved with solid waste management, creating national disposal
criteria for hazardous waste and encouraging waste reduction and recovery. Also in 1970, the Clean Air
Act (CAA) banned the uncontrolled burning of MSW and required controls to treat and reduce the
particulate emissions associated with the combustion of waste materials.
The Solid Waste Disposal Act was amended in 1976 and became what is known today as the Resource
Conservation and Recovery Act (RCRA). However, the original and subsequent amendments made to the
Act in the 1980s focused on hazardous waste management instead of non-hazardous solid waste disposal
practices. For the first time, RCRA also provided a detailed solid waste definition but did not include
guidance on non-hazardous MSW management. In 1991, the Federal Subtitle D landfill regulations for
MSW landfills provided location restrictions as well as design, operation, monitoring, and financial
assurance requirements. In 1991, the U.S. EPA also proposed regulations under the CAA concerning
landfill gas control under the New Source Performance Standards (NSPS). These rules were promulgated
in 1996 and had been periodically updated. As waste combustion became commonplace, additional rules
were passed to address the emissions of dioxin and mercury. These rules are known as the Maximum
Achievable Control Technology (MACT) regulations of the 1990s. Apart from federal and state
regulations that establish a variety of exclusionary criteria (mostly environmental-related) for siting
certain types of MSW management facilities, local and land-use considerations must also be addressed as
part of the siting and planning process for new MSW management facilities.
Past resource conservation efforts in the U.S. have primarily focused on making decisions to best recycle
and manage materials that typically were thought of as wastes—for example, the U.S. EPA published the
decision maker's guide to MSW management, which provided guidance specific to technical and
economic considerations for planning and operation of MSW management facilities and programs (U.S.
EPA, 1995). These efforts reduced and prevented environmental impacts but have not broadly considered
sustainability with respect to overall materials management and flow across the entire life cycle. As a
result, in late 2002, the U.S. EPA created the Resource Conservation Challenge (RCC) to promote
conservation of natural resources on a national level. Specific MSW-related goals of the RCC included
increasing the national recycling rate to 35% by 2008 and maintaining the national average MSW
generation rate at less than 4.5 pounds per person per day. The RCC targeted four areas: MSW recycling,
beneficial use of secondary materials, priority and toxic chemical reactions, and green initiatives
(electronics). The RCC marked a substantial transition of addressing waste management from safe
disposal (cradle-to-grave approach) to a cradle-to-cradle approach. This method emphasizes recovery and
reuse in manufacturing to offset a number of virgin materials used, and consequently, reduce the
environmental impact of overall materials management based on the fundamentals of life-cycle
assessment.
A variety of technology options (recycling, thermal treatment, biological treatment) exists to optimize
recovery of energy and various MSW constituents and use for remanufacturing and to manage the
residual waste. Each of these technology options has unique inputs and outcomes. An understanding of
the current state of the practice of MSW management technology options; the factors that impact
communities' sustainability; and the current decision-making process is needed before the development of
a TRIO-based tool is undertaken.
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2,2 Integrated Waste Management System Elements
While this white paper present approaches for MSW management, modern MSW management systems
do not consist of a single system, but rather are comprised of multiple components, commonly referred to
as an integrated MSW management system. Prior to the detailed discussion of MSW treatment
technologies, the roles of integrated MSW management systems elements with respect to the three pillars
of sustainability are discussed. Community's MSW management system begins with the upfront material
separation or set-out by households and businesses, followed by the manner in which the materials are
collected and transported to their destination(s). Processing of MSW to recover targeted recyclables from
segregated materials, is an integral part of nearly all systems. Although "zero" waste may be a goal of
some MSW management systems, in almost all cases, some part of a community's MSW will still require
disposal through landfilling.
2,2,1 Segregation, Collection, and Transport
The type of segregation and collection scheme is integrally related to the overall MSW management
system. Historically, MSW collection commonly involved the single pickup of mixed MSW. However,
more recent collection practices include multiple groups of different portions of the MSW stream.
Examples of different targeted MSW component group include recyclables; source-separated organics
(SSO) such as yard trimmings and food scraps; and residual materials that do not fit either of these two
categories.
Recyclables diversion is typically accomplished in two ways: drop-off recycling centers and curbside
recycling. The U.S. EPA (201 la) reported that more than 9,000 curbside recycling programs exist in the
U.S. The two main approaches currently used for curbside recycling are a single-stream and dual-stream
collection. In single-stream recycling, recyclables are commingled in a single container. In the dual-
stream system, the generator separates the targeted materials into two broad categories: fibers (e.g., paper
and paperboard) and containers (e.g., plastic, glass, metal). In addition to single- and dual-stream
recycling, some communities implement wet-dry collection systems where residents are required to
separate their MSW into wet (e.g., organics such as food and yard waste, food wrappers, used tissues, and
paper towels) and dry (e.g., recyclables such as bottles, cans and cardboard) categories. Colored bags
allow waste collection personnel to distinguish between the two materials.
More than 7,000 communities across the U.S. have implemented Pay-As-You-Throw (PAYT) programs,
where MSW generators are charged by the quantity of non-recyclable MSW they produce rather than a
flat rate, to encourage participation in curbside recycling (Skumatz and Rogoff, 2010). Approaches such
as using different-sized containers with service fees correlating to holding capacity, selling specially
colored bags provided exclusively by local municipalities for MSW collection, or selling unique tags to
attach/stick to refuse bags have been used to implement PAYT.
The type of collection vehicle and the collection frequency is contingent on a number of factors such as
the kind of curbside recycling program and collection source (e.g., residential, commercial). Typical
trucks used for residential collection are automated/semi-automated, where workers may control a
mechanical arm to pick up and load MSW, as well as rear-loading trucks, where MSW is loaded manually
in the back (EDP, 2004). Commercial collection vehicles are generally front-loading trucks where large
containers are lifted via mechanical arms in the front of the truck and deposited into the back of the
vehicle. Depending on the location of the MSW management facility, the collection vehicles may be
routed to a transfer station, where MSW is packed in larger semi-trailer/trailers for transport to another
MSW management service, which could be transported to a processing facility, disposal facility, or a
combustion facility, typically by truck or by rail.
Although MSW collection and transportation has a significant economic, environmental, and social
impact, this sector is not a focus of this white paper. The collection and transportation activity links the
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materials management industry to the transportation sector, which is another priority area for the U.S.
EPA Office of Research and Development's SHC Strategic Research Action Plan.
2.2.2 Processing and Materials Recovery
There are three main types of MSW MRFs, which are used to recover recyclables: single-stream, dual-
stream, and mixed-waste (or "dirty") MRFs. Berenyi (2007) reported a total of nearly 560 MRFs in
operation in the U.S.; approximately 52% and 33% of all MRFs were dual-stream and single-stream,
respectively, as of 2006. While single- and dual-stream MRFs depend on a degree of generator
segregation, where MSW has been separated into recyclables and non-recyclables, dirty MRFs are
capable of processing the entire as-collected MSW stream and are therefore not reliant on generator
participation.
The material recovery process at MRFs can be broken down into three separate phases: pretreatment,
primary separation, and secondary separation (Griffiths et al., 2009). Pre-treatment typically involves
processes such as MSW de-containerization (e.g., bag breaking, de-baling) and removal of bulky
materials. Primary separation may include categorization between flat and 3-dimensional objects for
single- and dual-stream MRFs, and a much more complicated process for recovering recyclables for dirty
MRFs. Secondary separation includes final processing into individual marketable recyclable categories.
MRFs can have varying degrees of automation, from picking lines to optical sorters; more than 80% of
those that process both containers and fibers have conveyors, balers, and magnetic separators, while more
than 25% of the facilities also have eddy current separators, air classifiers, and trommels (Berenyi, 2007).
MRFs may have multiple input lines and may have the ability to process both single- and dual-stream
feeds.
Dirty MRFs are estimated to represent less than 5% of all MRFs in the U.S. (KCI, 2009). These facilities
generally sort MSW into two or three output streams that consist of recyclables (which may be further
classified on or off site), non-recyclables (residuals), and possibly biodegradables, which can potentially
be used for aerobic/anaerobic digestion. As expected, dirty MRFs are associated with a much higher
residual production rates. In an R.W. Beck and Cascadia Consulting Group (2006) survey of California
MRFs, the average residual rate from 21 dirty MRFs was approximately 81%.
Although material recovery processes are important in the overall scope of managing the MSW generated
in the U.S., the processes in place already view these components of the MSW stream as "materials",
thus, the analysis presented in this white paper did not examine traditional material recovery processes.
2.2.3 Energy Recovery
Energy recovery can be realized through thermal or biological treatment, or some combination of the two,
with the exception of aerobic composting. Thermal treatment is defined as the chemical transformation of
MSW to heat, solid residue, and a gaseous fraction that may be combustible, depending on the process
used for treatment. Approximately 11.7%ofMSW generated in the U.S. is managed via thermal
treatment (U.S. EPA, 201 la). Combustion is the most commonly used thermal treatment method
worldwide for MSW. Almost all of the currently operating waste-to-energy (WTE) plants in the U.S.
operate on the complete combustion process.
Biological treatment relies upon microbes to decompose biodegradable organics into simpler organic and
inorganic compounds under controlled conditions. While energy can be recovered from all organic
constituents of MSW (including plastics, textiles, woody biomass) via thermal treatment, only the
biodegradable fraction (e.g., food scraps, paper) of MSW can be used to generate energy from biological
processes.
The energy form and yield depend on the properties of the incoming MSW and process. For example,
only steam and/or electricity can be generated from MSW combustion, whereas syngas from the other
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thermal treatment options (pyrolysis and gasification) can be used to produce electricity and liquid vehicle
fuel. MSW properties such as composition, calorific value, and moisture content dictate the energy yield.
Figure 2-1 presents the energy content of mixed MSW and its constituents as compared to the typical
energy content of coal, which is used to produce more than 50% of the electricity generated in the U.S.
The average energy content of mixed MSW is approximately 5,000 British Thermal Units (BTU) per lb
(11.6 MJ kg1) (Tchobanoglous et al., 1993).
Figure 2-1 also presents the energy contents of ethanol and methanol, which can be produced as the end
product(s) of gasification or pyrolysis. Inert MSW constituents, such as glass and ferrous and non-ferrous
metals, are thermally stable at temperatures associated with most of the thermal treatment options. Water,
which typically constitutes approximately 20% of MSW (by weight), vaporizes and becomes a part of the
exhaust gas (referred to as flue gas).
Wood Plastic Paper
Food
Waste
- 14000
- 12000
10000
- 8000
6000
- 4000
- 2000
Mixed
MSW
Coal Ethanol Methanol
Fuel
Figure 2-1. Typical Energy Content of Various MSW Constituents, Mixed MSW, and Other Energy
or Fuel Sources (Tchbanoglous et al., 1993; U.S. EIA 2012)
The gross energy released from 1 lb of MSW with an energy content of 5,000 BTUs/lb is equivalent to
1.47 kWh of electricity assuming a 100% process efficiency, irrespective of the technology used. Based
on the amount of MSW generated in the U.S. annually, the gross energy content is approximately 735,000
million kWh; accounting for the typical net efficiency of MSW combustion facilities with energy
recovery (15%), the approximate net energy recovery potential if all MSW (250 million ton per year) was
combusted is 110,250 million kWh—enough to meet approximately 7.7% residential electricity demand
in the U.S.. From a biological conversion standpoint, if all MSW generated in the U.S. was landfilled,
and the collected landfill gas/biogas was converted to electricity, the net energy yield at steady state,
which can take decades to occur, would be approximately 62,700 million kWh (assuming 3,200 standard
ft3 methane generation potential per ton, 75% collection efficiency and 35% efficiency of internal
combustion engines)- enough to meet approximately 4.4% residential electricity demand in the U.S.; the
U.S. residential sector used about 1,430 billion kWh is 2011 (U.S. EIA 2012).
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It should be noted that these numbers assume that no energy loss occurs (i.e., the energy efficiency of the
system is 100%). The actual net output would be lower than these estimates because none of the
treatment options are 100% efficient, and many of the options require energy input.
2.2.4 Disposal
Despite the variety of technologies that process or recover components of the MSW stream, disposal of
unprocessed MSW as well as residuals from MSW treatment or recovery operations is still heavily relied
upon. Even though many technologies to handle MSW exist, none of the techniques are equipped to
address the whole MSW stream without generating some residual that requires disposal. For example, the
ash produced from MSW combustion generally requires landfilling because of limitations to the
beneficial use of the material because of concerns over potential environmental risks or lack of
sustainable, beneficial use end markets.
2.3 MSW Management Decision Making
A variety of pathways exists to manage MSW and recover various MSW constituents for use in
remanufacturing and energy recovery. A significant technical factor in MSW management technology
selection is the feedstock, i.e., the portion of the MSW waste stream that can be treated or managed using
a given technology. Figure 2-2 presents a series of charts to illustrate the part of the overall MSW stream
that can be processed or otherwise managed through the major technologies examined in this paper. As
shown, landfill disposal may manage up to 100% of the MSW stream, while other technologies, because
of process constraints, have the ability to handle a smaller fraction of the MSW relative to landfilling.
Note that the figure does not represent any particular order in terms of most or least sustainable
technologies, it merely illustrates the concept that an important factor in MSW management decision
making includes the selection of a combination of technologies that has the practical ability to handle the
entire MSW stream. This consideration is in addition to the review of all three pillars of sustainability.
Landfilling Thermal Biological
(100%) Treatment Treatment
(83%) (62%)
Non-Combustibles
Figure 2-2. MSW Constituents and Their Treatability by Technology
Various factors that communities currently consider when selecting MSW management options were
compiled based on a review of recently-published MSW conversion technologies reports and request-for-
proposals published by diverse communities (SBC, 2003; URS, 2005; SWANA, 2011; ECDSWM, 2012).
Table 2-1 broadly presents the key factors that are typically considered in the decision-making process, as
well as key questions for each decision parameter. In general, the three pillars of sustainability are
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usually assessed to a degree and generally are evaluated independently rather than in an integrated
manner. As expected, the economic component is often weighted more heavily in community decision
making because finances are frequently of most immediate concern and are more easily quantified than
social considerations, and environmental regulations must be complied with during the design and
operation of facilities regardless of technology.
Table 2-1. Common Economic, Environmental, and Social Considerations Currently Used in the
MSW Management Decision-making Process
Sustainability
Pillar
Decision Parameters
Key Questions
Economic and
Facility Cost
Considerations
Capital Investment
What will be the cost of design, siting, permitting,
procurement, and construction?
Revenues
What are the anticipated sources of income for the
technology or management system? Examples may
include tipping fees and sale of end products.
Financial risk
Who will operate the facility and what are their capabilities?
Does the operator have the financial capacity and requisite
experience? How will the facility integrate with existing
components of the MSW management system?
Resource requirements
What resources (e.g., workforce, utilities) will be required
for the facility or system?
Feedstock
What components) of the MSW stream will the technology
or system handle?
Products and end-
uses/Landfill diversion
What type of end products will remain from the facility or
system? How can those products be managed, and are
there data to support the potential management methods?
Is the technology or system compatible with established
diversion or zero waste goals?
Scaling flexibility
What is the throughput of the system or technology, and
how scalable is the technology?
Land use and location
considerations
What are the property requirements and potential
locational constraints?
Job creation, economic
impacts
What will be the regional economic impact of the new
facility?
Impacts on nearby
property values
How will property values in the area surrounding the facility
be affected, if at all?
Environmental
Water emission
Land/soil
Air Emissions
Odor
Noise
How do pollutant releases vary among materials
management technologies?
The emissions (e.g., water, air, land/soil, noise, odor) must
be within the applicable regulations.
Social
Public safety/risks
Is there health or safety risks associated with the facility or
its emissions?
Transportation
congestion
Is there adequate road capacity to handle increased truck
traffic?
(continued)
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Table 2-1. Common Economic, Environmental, and Social Considerations Currently Used in the
MSW Management Decision-making Process (continued)
Sustainability
Pillar
Decision Parameters
Description
Social
(continued)
Environmental justice
What are the demographic characteristics of residents who
will be most affected by the facility? Are there
disproportionate, adverse impacts on minorities or the
poor?
Demographic impacts
How will the facility change the characteristics of the
community's population?
Aesthetics /seen
quality
Is the facility's appearance compatible with nearby land
uses? How will the facility modify the way nearby residents
feel about their community?
Control
Options that offer community decision-makers better
control over MSW flow and associated economics are
preferred over options with less control.
Need for additional
public services
What other public services may be demanded in the
community? Will emergency responders require additional
specialized training?
A flow diagram depicting the generalized steps in the decision-making process that communities may use
to make MSW management decisions is presented in Figure 2-3. The first phase of the process is for a
community to characterize fully and understand their waste management needs—how much waste they
generate, its composition, and sources. Next, they can assess the management alternatives and their
impacts. As part of this assessment, a few examples of the decisions and trade-offs that the communities
may face with regard to MSW management include the following:
¦ Is source segregation and processing of organics more sustainable compared to landfilling
with gas collection and energy recovery?
¦ Is the combustion of individual components of MSW for energy recovery more sustainable
than segregation and remanufacturing of these elements into new products?
¦ Which landfill gas-to-energy conversion technology provides the most viable solution for the
facility and community?
Another factor that complicates the decision-making process is that communities have little or no control
over changing their waste management decisions once contracts are signed and systems implemented.
For example, if a city signs a 30-year contract for landfill gas rights to a project developer, the city loses
its control over landfill gas for 30 years and would not be able to dictate the way its use should change
with time, even if such a change is subsequently determined to be more sustainable. Because of the
complexity of the decision-making process and the long-term implications of the decisions made on the
three pillars of sustainability, MSW management was recognized as one of the four priority sectors for
developing a dynamic decision-making tool(s) that accounts for TRIO.
A variety of PC-based tools exists to evaluate the cost and environmental emissions associated with
different MSW management processes, many of which are based on the principles of life cycle analysis.
A summary of these tools is provided in Appendix A. While several tools offer valuable comparative
information such as energy use or greenhouse gas emissions, the available tools analyze economic and
environmental aspects individually and mostly neglect to consider social issues or impacts.
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Define Issue to be Addressed
or
Decision to be Made
Assess Alternatives
Waste Management Hierarchy
T
J
J
Produce Less
Waste (P2)
Promote
Materials Reuse
Increase
Recycling
T
Management
Options for
Remaining
Waste
L
1
1
r
Biological Conversion/
Anaerobic Treatment
Biological Conversion/
Aerobic Treatment
Thermal Treatment
1
r
For Each Option:
1. Evaluate technology requirements, feasibility and costs
2. Evaluate potential environmental releases and impacts
3. Evaluate the local and regional economic impacts
4. Evaluate the site-specific and regional social impacts
r
Using Outputs for Each, Community Makes a Decision Based
on Factors or Impacts Most Important to Them
Figure 2-3. Simplified MSW Decision-Making Process Flow Diagram
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3. MSW Management Technologies
3.1 Overview
A variety of technologies exists to manage the MSW fraction that is not captured for recycling. The state
of the practice of the MSW management technologies presented in this white paper was developed by
using a broad domain of information, including peer-reviewed journal articles, scientific textbooks,
guidance documents, manufacturer or vendor literature/websites, an assortment of database information,
facility operating records, facility permitting documents, white papers, and miscellaneous technical
reports. These sources of information were reviewed to:
¦ Identify technologies and the associated processes currently used to manage MSW
worldwide;
¦ Assess process inputs (e.g., SSO, unprocessed MSW, and outputs);
¦ Gather commercialization status of the identified technologies;
¦ Collect capital and operating and maintenance costs of the designated facilities
¦ Conduct a broader assessment of data available pertaining to environmental emissions (e.g.,
greenhouse gas [GHG] emissions, air pollutants, leachate).
Technologies that are fundamentally similar have a broad range of configurations that are unique to a
subset of MSW components or have different pre- and post-processing operations. Based on a review of
published literature, vendor information, and available databases, six fundamentally unique technologies
were identified for MSW management: landfilling, anaerobic digestion, aerobic composting, combustion,
gasification, and pyrolysis. Other MSW management techniques in the early developmental phases or
technologies that are integrated with other industry types (e.g., producing refuse-derived fuel (RDF) for
combustion in boilers in the cement industry or food waste co-digestion in anaerobic digesters at
wastewater treatment facilities) were not explored as separate and distinct technologies in this paper.
The following subsections include descriptions of the technologies and their commercialization status as
well as discussions of the waste management technology characteristics that are needed to conduct
community economic, social, and environmental impact assessments. For example, for each technology,
information is presented about the capital and operating cost, expected employment, and possible releases
of pollutants to various environmental media. Because social impact assessment (SIA) is entirely site-
specific, it is not possible to discern how social impacts differ among the technologies presented here
outside of the site-specific context. For this reason, the overall SIA process that could be used after site-
specific data were available is discussed separately in Section 4.4.
3.2 Landfilling
3.2.1 Technology Description
Landfilling remains the dominant method for managing MSW in the U.S. and many other parts of the
world. Operators of modern landfills rely on the construction and operation of engineering controls to
minimize deleterious impacts to human health and the environment. Landfills are understandably
acknowledged as a less preferred method of managing MSW in the materials management hierarchy.
Landfills consume land and can produce environmental emissions, but they remain a technique of
standard practice largely because of their relatively small capital and operations cost and flexibility to
accept a range of incoming waste amounts and waste types.
Fundamental to the MSW landfilling approach is the construction and operation of containment systems
to protect land resources from biological, chemical, and ecological impacts. Containment liner systems
are typically constructed from combinations of compacted earth with low permeability and geosynthetic
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products such as plastic membranes. The liner systems allow the capture of leachate (liquid that contacts
or emerges from solid waste), which is removed from the landfill using natural and synthetic drainage
layers and mechanical pumping systems. The exact configuration of the containment system depends on
applicable regulatory requirements and site-specific design considerations. U.S. Subtitle D landfill
regulations require a bottom liner system to contain at least two feet of compacted soil with a
permeability of less than 10~7 cm sec-1 overlain by a plastic geomembrane (typically 60-mil HDPE) and a
leachate collection and removal system capable of maintaining the depth of ponded leachate on the liner
to less than 30 cm (1 ft).
Waste is deposited on top of the containment system after a suitable protective layer has been placed, with
the waste placed in designated cells, and lifts over time as part of a waste filling plan. Operators control
possible adverse outcomes of waste landfilling—such as odor, litter, fires, and runoff of rainfall that has
contacted the waste—using best operating practices such as placement of cover soil or equivalent
alternative materials and proper waste compaction and grading. Throughout the operation, the operator
must monitor the groundwater and soil vapor surrounding the containment areas, and if needed, institute
appropriate remedial measures.
The biodegradable organic fraction of MSW undergoes decomposition in an anaerobic environment to
produce landfill gas and stabilized residues. Figure 3-1 presents a generalized process flow diagram for
landfilling. Landfill gas is primarily composed of approximately 50 to 55% methane (CH4), 40 to 45%
carbon dioxide (CO2), and trace amounts of other gasses (U.S. EPA, 2005). After a sufficient volume or
mass of waste has been placed, infrastructure for the capture and control of landfill gas produced from the
MSW in the landfill are installed. The operator's decision to install gas collection infrastructure may
depend on economics, local conditions, regulatory requirements, or a combination of these factors. A
landfill's gas collection and control system (GCCS) frequently includes wells or trenches constructed in
the waste to provide a conduit for gas removal, well-head controls at individual or clustered extraction
points, a piping system to route gas removed from the landfill to a central collection location, and a gas
treatment or energy system. Under the CAA, MSW landfills larger than a certain size must assess
whether a threshold mass of non-methane organic compounds (NMOCs) are produced per year (50 Mg
yr"1) and if so, the gas must be collected and controlled. The CAA regulations require monitoring and
maintenance of the GCCS, which includes evaluating gas quality, landfill gas temperature, and extraction
pressure on a routine basis from expected collection points. For GCCS operated without a stringent
regulatory framework, similar monitoring and maintenance measures may be employed to reduce
environmental emissions and to optimize gas recovery when an energy conversion system is present.
The anaerobic decomposition process in landfills proceeds at a very slow rate and continues for decades
because landfills are designed primarily as waste containment systems rather than waste treatment
systems. At some facilities, the landfill operator takes deliberate steps to encourage the waste
decomposition process by operating the landfill as a bioreactor landfill. The bioreactor operation of
landfills most commonly entails introduction of liquids (e.g., leachate, wastewater) to the buried waste to
promote an environment favorable for anaerobic decomposition—bioreactor operation requires a series of
operational benefits (e.g., enhanced gas production, accelerated waste stabilization) and challenges (e.g.,
increased management of liquids, additional operations monitoring) that are unique to this type of
activity. Some operators have explored landfill mining or reclamation to reduce the site's disposal
footprint; increase the efficiency of landfill's airspace use; mitigate potential future environmental
impacts from old, unlined landfill units; and increase materials recovery (Jain et al., 2012).
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Figure 3-1. A Generalized Process Flow Diagram for MSW Landfilling
At the end of a landfill's operating life, the facility must be appropriately closed, monitored and
maintained for a defined period. Landfill closure involves the construction of a capping system to
minimize infiltration of rainfall into the waste mass and gas escape to the atmosphere. The U.S. Subtitle
D regulations also require certification that closure of the facility was completed, as well as
documentation on the site's property deed that the facility was operated as a landfill. The aftercare period
of an MSW landfill, referred to as post-closure care, consists of facility maintenance to ensure the
integrity of the containment and capping systems, removal and treatment of leachate, operation of the
GCCS (if present), and continued monitoring of the environment outside the landfill (groundwater, soil
vapor). Current U.S. regulations require post-closure care for 30 years, though there are current research
and discussion on the correct steps to identify the appropriate time for ending or scaling back post-closure
care requirements.
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3.2.2 Commercialization Status
Based on a nationwide survey, van Haaren et al. (2010) estimated approximately 1,900 landfills were
active in the U.S. as of 2008, and estimates by the U.S. EPA in 2010 indicate about 54% of the 250
million tons of MSW generated were landfilled. GHG reporting data for landfills for the year 2010 show
that the largest landfills (1,202 sites that emit more than 25,000 metric tons of CO2 equivalents) account
for the emission of 117 million metric tons of CO2 equivalents or approximately 3.6% of all GHG
emissions in the U.S.
Currently, there are approximately 2,400 operating or recently closed MSW landfills in the U.S., and
about a quarter of these landfills (562) have an operational LFG energy system (U.S. EPA, 2012b). There
are also several landfills that actively collect LFG, but do not beneficially use the gas, but the U.S. EPA
estimates that about 540 additional MSW landfills could turn their gas into energy in the future. Thus, the
number of landfills that actively collect and control gas could potentially represent half of the total
number of operating landfills.
As for landfills operated as bioreactors, SWANA estimated that approximately 80 landfills in the U.S.
were operated as bioreactors (SWANA 2004). An estimated 32 landfill mining projects have been
executed in the U.S., the majority of which are older facilities that were built before bottom liner
requirements (Jain et al., 2012).
3.2.3 Materials and Energy Recovery
Materials and energy recovery at landfills can be achieved in a variety of ways, but a collection of landfill
gas and conversion into energy is the most common. Material recovery from landfill reclamation has
been practiced on a limited basis as described previously, with the main recovered materials consisting of
soil, stabilized organics, and recyclables such as metals and plastics.
Energy recovery from landfill gas may include electricity generation, direct use of LFG as a fuel source in
industries or specialized applications, and processing the gas to pipeline quality natural gas (U.S. EPA,
2012b). More than 80% of approximately 600 landfills that beneficially use LFG in the U.S. generate
electricity using technologies such as internal combustion engines, gas turbines, and micro-turbines
(Figure 3-2). Direct-use applications include use in steam boilers, industrial kilns, and applications where
heat is desired, such as leachate evaporation or heating greenhouses. Twenty-nine landfill gas projects
involve processing to a pipeline or fuel-quality (i.e., compressed or liquefied) natural gas (U.S. EPA,
2012b). This technology requires much more gas clean up than conventional electricity generation or
direct use—a variety of vendors provide remediation technologies such as membranes, pressure swing
adsorption, and molecular sieves.
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Electricity
Generation
80%
^Leachate
Evaporation
2%
Pipeline
Quality
Natural Gas
5%
Figure 3-2. Distribution of Landfill Gas Beneficial Use Project Types in the U.S. as of 2012
(U.S. EPA, 2012b)
The waste stabilization process that produces LFG is largely the same as that occurring in a waste
anaerobic digester, only with a larger quantity of waste and with less overall process control. Since the
residual solids product of anaerobic digestion is often recovered as a resource similar to compost from an
aerobic composting operation, the recovery of stabilized residual has been proposed as a step in enhanced
landfill operations, including older landfills as well as bioreactor landfills, which are landfills designed
and operated to more rapidly decompose organic matter by encouraging anaerobic decomposition. The
idea of operating a landfill as a bioreactor carries with it the concept of reclaiming the airspace in a
shorter timeframe relative to a conventionally managed landfill. The percentage gain in landfill space
through the operation of a bioreactor landfill can be as high as 15-30%, due to an increase in the density
of waste mass and volume loss due to mineralization of solid waste components to the gas phase.
A landfill mining effort may be conducted on bioreactor landfills, and other stabilized landfills to recover
materials, reduce groundwater impacts from unlined areas, or more efficiently use landfill airspace (Jain
et al., 2012). In this process, stabilized landfill material is excavated and processed to recover one or
more size fractions for recovery and reuse, and another fraction that must be landfilled again. Screens are
used to separate the combined portion of degraded organic materials and cover soils from larger waste
components. Other targeted materials for recovery may include ferrous metal, which can be removed
using a magnet and possibly refuse derived fuel in the form of plastics and similar materials with a high
calorific value.
3.2.4 Environmental Concerns
Environmental concerns associated with landfilling as a waste management technology include those
directly related to landfill operations (e.g., impacts to groundwater, surface water, and air, development of
nuisance conditions) and those related to inefficient use of land and material resources. The operational,
control, and containment strategies, as required under the regulations, are intended to minimize the
environmental and human health risks associated with MSW landfills. Landfill operators following best
management practices will substantially reduce off-site issues with odors, dust, litter, and vectors (e.g.,
birds), though it may be impossible to eliminate all problems completely for homes and businesses in
close proximity to the facility.
Well-designed, constructed, and operated liner and leachate collection systems reduce the number of
contaminants migrating from a landfill to the underlying soil and groundwater compared to unlined or
poorly constructed facilities. Groundwater issues observed at landfills commonly result from problems in
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construction and operation. For example, improper quality assurance and quality controls during liner
system construction could cause defects (breaks, tears, or holes) that may lead to a release of leachate and
thus potentially impacting groundwater. Another example of a source of groundwater impacts may be the
migration of LFG because of the absence of gas controls or improper operation of in-place gas checks. In
some instances (e.g., Florida), elevated chemical constituents have been measured in groundwater
monitoring wells downgradient from newly-constructed lined landfill cells, which has been attributed to
the onset of reducing conditions which release naturally-occurring chemicals. Regardless of whether
construction and operational defects exist at a given landfill, the presence of the groundwater monitoring
system allows for relatively rapid detection of potential problems, and Subtitle D rules require the
evaluation and remediation of confirmed groundwater impacts.
The emission of LFG occurs throughout the life of a landfill. In the early stages of landfill development,
regulations often do not require active gas controls, and the quantity of LFG produced is typically too
small to justify the implementation of collection infrastructure to recover the gas to produce energy; thus,
LFG is actively released into the atmosphere during this time. Once a GCCS is in place, LFG fugitive
emissions still occur in areas that are not covered by the GCCS (which occurs most commonly at sites
that are still actively putting new waste), although CAA regulations require the progressive installation of
GCCS components at regular intervals. The net emission of LFG into the environment is thus dependent
on the active life of the landfill and the acceptance rate of waste at the landfill. Other gasses that may be
present in LFG can also pose issues to site workers and the landfill's vicinity (e.g., H2S). The degree of
problems associated with other gasses such as H2S often depends on the efficiency that LFG is collected,
the characteristics of the waste placed in the landfill, and the area of the landfill that is covered by the
GCCS.
Landfills also pose an environmental concern because they represent a generally inefficient use of
resources. The disposal of waste into landfills in most cases renders those resources no longer usable
(unless recovered in the future through mining). Furthermore, materials placed in a landfill represent
wasted resources, thus likely causing additional virgin materials use and extraction since these materials
were not captured in the recycling or reuse management pathway. Last, even though the implementation
of energy recovery projects from LFG represent a positive step (compared to landfilling with no energy
recovery), this process is still inefficient and does not fully capture the energy potential of the resources
that are present within the landfill.
3.2.5 Economic Considerations
Costs associated with landfilling include site investigation, hydrogeological studies, engineering design,
permitting, site infrastructure construction (such as roads, scale house, shops, administration building),
cell construction, waste placement and compaction operations, leachate collection and management,
GCCS construction and operation (if required), closure cap construction, a groundwater monitoring
system, gas control system, and post-closure care. Cost information presented in this section consists of a
combination of landfill construction rules of thumb as well as cost ranges presented in the literature. As
with any construction effort, site-specific considerations can have a considerable impact on overall costs,
as well as materials and construction experience availability.
Approximate up-front (pre-construction) costs for a landfill may range from $0.75 million to more than
$1 million (Duffy 2005a, KDEP 2012). Lined landfill cell(s) construction entails earthwork for sub-grade
preparation, compacted clay liner or geosynthetic clay liner construction, geomembrane liner installation,
and leachate collection system construction—the total cost for these components may range from
$150,000 to $450,000 per constructed acre—this does not include earthwork needed to prepare the grades
for the assembled components, which may vary significantly from site to site. Note that construction
costs are frequently incurred, particularly at large sites as lined cells are usually built to provide several
years of capacity while not being so large as to be cost prohibitive. Operation and maintenance costs of
landfills consist of waste handling, cover use, litter control, training, utilities, permitting, financial
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assurance, sampling and compliance monitoring, leachate treatment, and transportation make up a
substantial portion of a landfill's overall cost, normally comprising more than 50% of a landfill's overall
value.
The capital costs associated with a GCCS include installation of extraction wells/trenches, piping
network, a blower/flare system, and a condensate management system. GCCS construction cost may
range from $24,000 to $35,000 per acre (Duffy 2005b, U.S. EPA 201 lb), while atypical O&M cost for a
GCCS is approximately $4,100 per acre per year (U.S. EPA 201 lb), though this figure may be more
(perhaps substantially) depending on the number of gas collection wells and the system's configuration.
Approximate closure cap construction cost (excluding GCCS) ranges from $150,000 to more than
$300,000 per acre (Duffy, 2005b, KDEP, 2012; MDE, no date), while annual post-closure care costs
(which includes site security, cap maintenance, environmental monitoring) ranges from $2,000 to $3,000
per acre U.S..
Various factors, such as LFG collection rates, vicinity to industrial plants and their energy usage,
prevailing electricity, and natural gas prices, dictate landfill gas beneficial use project economics. The
landfill gas-to-electricity construction cost ranges from $1,400 per kW (for a project size larger than 3
MW) to $5,500 per kW (for projects smaller than 1 MW) (U.S. EPA, 201 lb). The O&M cost ranges
from $130 per kWh (for project size larger than 3 MW) to $380 per kWh (for projects smaller than 1
MW). Because of the relatively smaller number of pipeline-quality natural gas and vehicle fuel
production projects, the cost of these projects is not as readily available as for electricity generation
projects.
Economic motivations for landfill reclamation may vary, but reclaiming airspace, recovering the
landfilled materials, and reducing future environmental liability are shared objectives. Net costs and
benefits for mining depend on factors such as the cost of land acquisition, actual or potential future
remediation costs, and value and demand of excavated materials (either recyclables or reclaimed soil and
decomposed organics). IWCS (2009) reported landfill reclamation costs of approximately $4.50 per m3
without further waste processing and $7.0 per m3 with waste processing.
Tipping fees and the sale of electricity or processed landfill gas are the primary sources of revenue for
landfill operators. Van Haaren et al. (2010), based on a nationwide survey, reported that the statewide
average tipping fee in the U.S. ranged from $15 to $96 per ton. The electricity or processed landfill gas
sale prices are highly contingent upon the electricity and natural gas prices (www.eia.gov) and federal
incentives for renewable power.
U.S. Census Bureau data for the classification code of municipal landfills shows that approximately
19,000 full-time personnel are employed at landfills or an average of about 10 per facility. The number of
people employed at a landfill will depend on the size of the site as well as ancillary functions or activities
(e.g., active GCCS, energy conversion system, leachate recirculation).
3.3 Anaerobic Digestion
3,3,1 Technology Description
Anaerobic digestion (AD) involves controlled biodegradation of organic matter by microbes in the
absence of oxygen to produce both CHrrich biogas and a stabilized solid residual. The captured CH4 can
be used for power generation or utilized in a direct thermal application (e.g., space heating, boiler fuel)
while the solids portion of the digester effluent can be land applied or used after composting. The
primary benefit of the digestion of readily decomposable MSW constituents, such as food waste, is the
recovery of biogas and the associated control of the release of GHG. Though landfills with an active
GCCS must progressively install new components to collect gas from newly-placed waste, the lag time
required in CAA rules is 2 years for areas at final grade and 5 years after waste is placed, thus, newly-
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placed food waste in a landfill is expected to decompose primarily before an active GCCS is expanded to
control the decomposition gases. .
A variety of organic scrap materials, such as manure, biosolids, SSO, and the organic fraction of MSW
(OFMSW) recovered through a mixed-waste material recovery facility, separately or as part of the AD
pretreatment process, can be individually or co-digested. The amount of pre-processing necessary
depends on the particular feedstock involved. The primary pre-processing needs for AD systems include
the removal of non-biodegradable constituents, particle-size reduction, and adjusting the moisture content
and feedstock carbon-to-nitrogen ratio (CIWMB, 2008; Verma, 2002; Heo et al., 2004).
Most commercial AD systems in the U.S. are designed to accept manures and sludge; around 3,500
wastewater treatment plants and 190 commercial livestock farms currently utilize AD systems (U.S.
DOE, 2004; U.S. EPA, 2012c). However, the presence of non-biodegradable components (e.g., plastics
and bones) and variably sized organic matter in OFMSW/SSO requires additional pretreatment steps
typically not employed for the more common AD systems. Equipment such as trommel screens,
hydrocyclones, pulpers/grinders, metal separators, and flotation tanks can be used for size reduction and
the removal of contaminants.
The anaerobic decomposition of organics to biogas occurs in four distinct and sequential phases:
hydrolysis, acidogenesis, acetogenesis, and methanogenesis (Gerardi, 2003; CIWMB, 2008; Li et al.,
2011; Gavala et al., 2003). Hydrolysis involves the conversion of complex molecules and compounds,
such as carbohydrates, lipids, and proteins found in organic matter into simple sugars, long chain fatty
acids, and amino acids, respectively. During acidogenesis, acidogens convert hydrolysis products through
fermentation into volatile organic acids (VOAs), acetic acid, CO2, and hydrogen (H2) gas. In
acetogenesis, acetogens convert the VOAs into more acetic acid, CO2, and H2 gas. During
methanogenesis, methanogens produce CH4 using the acetic acid or CO2 and H2 gas produced from the
acetogenic and acidogenic phases. The progression of the stages depends on feed characteristics,
moisture content, temperature, pH, and availability of nutrients and microbes.
A variety of AD system configurations is currently offered by vendors primarily located in Europe. The
five most AD system vendors in Europe are BTA, Valorga, DRANCO, Biostab, and Kompogas. The
processes of all the vendors, with the exception of Biostab, are continuous-feed, single-stage systems;
Biostab offers batch and continuous feed, as well as single- and two-stage AD systems. Batch and multi-
stage AD provide the ability to exercise greater process control than continuous single-stage operations.
The solids content and operating temperature are other aspects that differentiate the AD systems offered
by these vendors. Valorga, DRANCO, and Kompogas systems are high solids (solid content >20%)
systems. These high-solid content processes are thermophilic (45-70 °C) processes, whereas BTA is a
low-solid (solid content <20%) process. The low solid content digesters are generally mesophilic (20-45
°C) means. Biostab offers both high-solids and low-solids AD systems. The advantages of high-solids
processes include a higher loading and biogas production rate for the same reactor volume, a less
intensive dewatering process for the stabilized residues, and a lower wastewater discharge. By contrast,
the low-solid systems are generally less sensitive to the introduction of toxins due to the high dilution of
the feedstock (Tchobanoglous et al., 1993).
The choice of digester operation temperature will impact the magnitude of pathogen and weed seed
destruction, the concentration of CH4 within the biogas, and the rate at which digestion occurs; all of
these increase with increasing operation temperature. While AD is an exothermic process, there is
usually a required heat input in order to achieve thermophilic temperatures. Figure 3-3 presents a
generalized process flow for the system.
3.3.2 Commercialization Status
More than 200 AD facilities are reported to treat OFMSW/SSOs worldwide (De Baere and Mattheeuws,
2010). The process plants for approximately 130 of these facilities were supplied by five vendors (BTA,
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Valorga, DRANCO, Biostab, and Kompogas). The European AD plant size installed during the period
from 2005-2010 was approximately 30,000 tons per year (TPY). Figure 3-4 presents the geographical
distribution of these plants. More than 90% of these plants are located in Europe, with Germany and
Switzerland accounting for nearly 50% of European MSW AD plants.
There are currently two operating commercial-scale, food-scrap AD facilities in Canada: Toronto's
Dufferin Organic Processing Facility (capacity of 60 tons per day [TPD]) and the Newmarket Organic
Processing Facility (capacity of approximately 450 TPD). As of 2008, due to the quantity of SSO
collected in Toronto, Dufferin was processing 128 TPD. However, because of odors and a resulting court
order, the Newmarket facility was only handling about 51 TPD (Arsova, 2010). According to BTA
International's reference plant list, both of these facilities were designed to accept biowaste and the
organics from commercial waste as primary feedstock. As identified at the Digesting Urban Residuals
Forum (CalRecycle, 2012), construction is underway for an additional food-scrap AD site in Toronto: the
New Disco Road Organic Processing Facility, with a base capacity of about 170 TPD. All three of these
sites are designed to utilize the BTA AD process. Both the Dufferin and Disco Road sites have plans to
refine biogas for natural gas pipeline injection and production of vehicle fuel. Another AD site in North
America is located on the French island of Martinique in the Lesser Antilles. According to Axpo-
Kompogas, this AD system has a capacity of about 60 TPD.
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Materials Management: State of the Practice 2012
lil'A 600 R-13:304
Yard
Trimmings
MSW
Material
Recovery
in-biodegradabl
Organics I
Inorganics
Wastewater
De-watering I
Composting
Process
Control
•Agitation
Digestate
Compost
Biogas
Clean
Biogas
Treatment
Residues
Boiler /
Steam
Turbine
Electricity
Vehicle Fuel
Pipeline Quality
Natural Gas
1
Biogas
Conditoning/Use
Gas
Cleaning
Gas Turbine
I Internal
Combustion
Engine
Feedstock
Conditioning
•Size Reduction
•Moisture Adjustment
•C:N Adjustment
\•Contaminant Removal
Heat
(Thermophilic)
Steam
Direct Use (e.g.
Boiler Fuel)
Advanced Gas
•Pressure Swing
Adsorption
\*Molecular Sieves/
Cleaning
•Membranes
Figure 3-3. A Generalized Process Flow Diagram for Anaerobic Digestion
Switzerland
20% (23)
Asia
6% (7)
France
10% (12)
Others'
30% (35)
Spain
9% (11)
North
America
2% (3)
Germany
31% (36)
Figure 3-4. Geographical Distribution of MSW AD Plants from 5 Most Prominent Vendors
(BTA, Valorga, DRANCO, Biostab, and Kompogas)
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The two primary feedstocks that are used for the reference plants of the top five MSW AD vendors are
biowaste (i.e., yard trimmings and SSO) and OFMSW. Based on the reference plant lists published by
four of the five MSW AD technology providers (excluding Kompogas, due to uncertainty in feedstock), it
appears that approximately half of the reference sites are designed to process strictly SSO and yard
trimmings (which would require significantly reduced pre-treatment), and half are intended to handle the
OFMSW.
Out of the total 130 referenced plants by the top five MSW AD technology vendors, more than 80% have
a capacity less than 300 TPD (Figure 3-5). Out of the 24 plants with a capacity of more than 300 TPD, 14
were manufactured by Valorga, which creates AD systems that commonly accept mixed-MSW or a
combination of mixed-MSW with additional feedstock for processing at an up-front material recovery
facility. These higher reported capacities may be a result of the fact that AD plants that process and
separate out the OFMSW typically only utilize 30 to 70% of the MSW stream for actual digestion (De
Baere and Mattheeuws, 2010); therefore, reported capacities may substantially exceed the organics input
rate into the digester units.
(/)
£
re
Q.
d>
o
£
d>
a
a>
£
a>
E
3
BTA International
V////A Valorga International
Kompogas
Organic Waste Systems
Ros Roca
°o uO
Plant Capacity (TPD)
Figure 3-5. Distribution of Capacities1 of AD Plants Supplied by 5 Most Prominent Vendors
There is only one commercial-scale food-scrap AD facility (owned and operated by Clean World
Partners, LLC) in the U.S. (American River Packaging, Sacramento, California). It is a high-solids (up to
50%) system that currently accepts about 7.5 TPD of food scraps from area food producers and 0.5 TPD
1 Capacities as reported by vendor information - these numbers do not necessarily represent input into the
digester(s), but may represent total tonnage acceptance prior to organic separation. Capacities listed as TPY were
converted to TPD by dividing by 365.
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of unrecyclable paper residuals from the packaging company. This facility has operated since March
2012, and the biogas produced powers two microturbines that together generate about 1,300 kWh of
electricity each day, which totals to about 37% of the packaging company's needs (Zhang, 2012;
Biocycle, 2012).
Two pilot-scale food-scrap AD studies were conducted, in California, to assess MSW organics co-
digestion at existing wastewater treatment plant AD sites, or individually as the primary feedstock. One
study evaluated the potential of co-digesting food scraps with wastewater treatment plant biosolids at the
East Bay Municipal Utility District (EBMUD) wastewater treatment plant (EBMUD, 2008). After pre-
processing onsite, post-consumer food scraps were found to produce three times as much CH4, require
two-thirds the retention time, produce half the residual biosolids, and could be processed at five times the
solids concentration as a comparable mass of wastewater solids (U.S. EPA, 2012d). The additional pilot-
scale food scrap AD study was jointly performed by the University of California, Davis, and Onsite
Power Systems as reported by Zhang et al. (2010).
Several entities in the U.S. have considered the use of AD as an MSW management technology in New
York, California, Washington, Minnesota, Iowa, and Florida. In March 2012, New York City released a
Request for Proposals for the development and application of WTE conversion technologies, including
anaerobic digestion. Several commercial MSW, organic AD facilities, are planned for
construction/operation in the near future.
3.3.3 Materials and Energy Recovery
Two primary products result from AD that may require further processing: biogas and digestate. Biogas
is typically comprised of 40-75% CH4 (CIWMB, 2008). In a survey of 16 European AD facilities that
processed OFMSW, industrial organic waste, or one of these feedstocks co-digested with some other
organic waste, the average biogas production per ton of input was approximately 2,900 ft3 (R. W. Beck,
2004). Biogas can be utilized in a direct-use application, such as boiler or process heating, refined for
injection into a natural gas pipeline, processed and converted into a vehicle fuel, or combusted or utilized
in a fuel cell for conversion into electricity. Biogas may need to be treated for removal of contaminants
such as H2S prior to its beneficial use.
If the entire food scraps stream generated in the U.S. (34.75 million tons per year) was anaerobically
digested, and biogas was used for electricity generation, approximately 10 billion kWh of electricity can
be generated assuming 3,200 standard ft3 methane production potential per ton and 35% efficiency of
internal combustion engines— enough to meet approximately 0.7% residential electricity demand in the
U.S.
Because digestate contains organic material that is not fully stabilized, it is generally treated aerobically
prior to use as compost (Trzcinski and Stuckey, 2011; Tambone et al., 2010; Levis et al., 2010; Zhang et
al., 2010). The quality of the feedstock and the efficiency of pre- and post-processing will influence
whether or not the digestate can be composted or provided to a composting operation in order to be
realized as a source of revenue. Arsova (2010) observes that while some AD facilities can readily market
their digestate as feedstock for vicinity composters, others have a hard time giving away their compost for
free. Based on the particular AD technology employed and whether or not an end-market for the
digestate is found (which could require drying), there may be a highly variable amount of wastewater
discharge.
3.3.4 Environmental Concerns
The majority of the nutrients present in the original AD feedstock (including nitrogen, phosphorous, and
potassium) remain in the digestate in a mineralized form that is more available for plant utilization.
However, depending upon the original feedstock stream, there may be concentrations of other
constituents of concern, such as salts, heavy metals, and persistent organic contaminants (e.g., PCBs,
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PAHs) (Monnet, 2003; Tchobanoglous, 1993). These are generally less of concern for "clean" feedstock
materials, such as yard trimmings or food scraps, but are a much greater concern following the use of the
OFMSW that may have a variety of materials that can contribute to overall contamination of the digestate
product.
Depending upon the required moisture content of the input feedstock, there can be a variable amount of
wastewater (filtrate) available at the end of the digestion process. Scarce data are available regarding
estimated filtrate discharge quantities, though one study described that anaerobic processes can be
expected to produce approximately 24-41 gallons of liquid per ton (Fricke et al., 2005). Some AD
technologies, including DRANCO and BTA, take a portion of the filtrate and introduce it into the
feedstock in order to assist in moisture control and microbial "seeding."
Because the AD process is enclosed, the gasses that are produced during the decay process (GHGs such
as CH4 and odor-causing gasses such as H2S or VOCs), can be actively controlled. The ability to collect
CH4 in the process represents additional GHG reduction relative to the decomposition and CH4 collection
at landfills since GCCS at landfills is not typically installed early enough to capture the CH4 generated
from highly decomposable organics that are the target of AD systems. Similarly, AD systems can be
outfitted with engineering controls such as biofilters and negative air space facilities to reduce odor
emissions; however, instances of odor emissions have been reported at OFMSW facilities and in the
surrounding vicinity, especially during the pre-treatment and post-treatment stages (SWANA, 2011;
SVSWA, 2008; Arsova, 2010).
3.3.5 Economic Considerations
Due to the absence of commercially operating OFMSW facilities within the U.S., limited information is
available to project facility capital and operational costs. Tsilemou et al. (2006), Clarke (2000), and R.W.
Beck (2004) compiled capital cost of European AD facilities (Figure 3-6). As expected, the capacity-
dependent capital investment required for these plants decreases as the plant size increases due to
economies of scale, with a median capital cost of $240,000, $180,000, and $70,000 for <50 TPD, 50-
100 TPD, and >100 TPD facilities, respectively.
Based on the data reported by Tsilemou et al. (2006) and Clarke (2000)2 the 25th and 75th percentile of
operating cost were found to be $37 and $69 per ton3, respectively, with an average cost of approximately
$53 per ton. There are also several additional general economic considerations for the implementation of
AD for organics in MSW. Tipping fees and revenue from beneficial biogas use are primary sources of
income for AD. Additionally, federal and local grants/tax credits may be available, which may make the
development of an energy recovery project more viable. AD projects may be able to obtain and sell
carbon credits based on avoided GHG emissions. Finally, the marketability of the digestate—depending
on its quality and demand—represents a potential economic benefit or cost, depending on whether the
digestate is able to be beneficially used.
2 The operating cost of the Studsgard Biogas Plant was not included because it mostly processes manure.
3 Operation costs from Tsilemou et al. (2006) that were noted as partial were not included in this range. All
operations costs were converted to 2011 dollars as noted above.
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< 50
50-100
Capacity (TPD)
> 100
Figure 3-6. Estimated Capital Costs4 as a Function of OFMSW AD Facilities Capacity5
(Tsilemou et al., 2006)
3.4 Aerobic Composting
3.4.1 Technology Description
Composting is the controlled biological decomposition of organic constituents (e.g., yard trimmings, food
waste, and paper) by microbes (e.g., bacteria, protozoa, fungi) and micro invertebrates (e.g., worms,
larvae) in the presence of oxygen to a biologically stable, soil-like end product, CO2, water vapor, and
heat (Rynk, 1992; Tchobanoglous and Kreith, 2002). In addition to diverting a portion of the waste
stream away from landfilling, compost has additional potential benefits, including the ability to rebuild
the structure of organically depleted soils, enhance moisture retention of existent soils, reintroduce
nutrients previously removed as a result of vegetation removal/maintenance, kill pathogens and weed
seeds, and remediate/treat contaminated soils (Haug, 1993; U.S. EPA, 1989). It is common to refer to the
compost process name based on the characteristics of the material stream composted (i.e., feedstock). For
example, "MSW composting" refers to composting any portion of the MSW stream (e.g., food and soiled
paper, yard trimmings), while "mixed-MSW composting" refers to composting materials removed from
the mixed MSW stream through variable amounts of pre-processing. Figure 3-7 presents a generalized
process flow diagram for composting.
4 Costs by Tsilemou et al. (2006) were converted from 2003 euros to dollars and the Consumer Price Index was
used to translate all historic amounts to 2011 dollars.
5 Where applicable, tons per year was converted to tons per day.
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Yard
Trimmings
MSW
Material
Recvery
Non-biodegradable
Organics I Inorganics
Water
Feedstock
Conditioning
•Size Reduction
~Moisture Adjustment
*C:N Adjustment
•Contaminant Removal
•Bulking Agent
(possible)
Figure 3-7. A Generalized Process Flow Diagram for Composting
The temperature of the decomposing material correlates with the rate of decomposition and sequentially
transitions through three major phases known respectively as the lag, active, and curing stages. The
fluctuation in temperature as a result of the microbial activity is a commonly-used indicator to track the
progress of the composting process. The lag phase includes the period of time immediately following
material placement as the microbe population increases and means the more readily decomposable
nutrients (e.g., sugars, cellulose); this phase may take up to several days but can be much shorter. During
the active phase, the temperature of the degrading material plateaus; the microbe population releases heat
as quickly as it dissipates out of the system. The curing step occurs as degradable compounds become
less available, and the temperature slowly declines and eventually achieves ambient levels and may last
1-2 months or longer (Tchobanoglous and Kreith, 2002; Rynk, 1992).
There are two main temperature ranges over which the active phase of different composting systems are
operated: mesophilic (5-45 °C), or thermophilic (45-75 °C), where sustained thermophilic temperatures
are used to destroy pathogens, weed seeds, and larvae. If temperatures rise above about 70 °C, the
microbes within the material begin to die or become dormant, reducing the compost maturation rate
(USCC, 2009; Rynk, 1992).
There are a variety of composting methods used, but the primary systems in use are windrow and in-
vessel systems, with windrow systems being the most common in the U.S. Windrow composting is
accomplished by arranging feedstock into long triangular or trapezoidal rows which may be covered or
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uncovered, have a forced/passive aeration system or periodically turned to supply oxygen to the pile.
Turned windrows are usually operated in an approximately 1-2-month active phase and roughly 1-month
curing stage. The curing step usually requires less maintenance due to the declining activity of microbes
and therefore requires less frequent windrow turning. The major benefits of windrow composting include
operational simplicity, ease of operation, and relatively low up-front capital costs in comparison to equal-
sized in-vessel systems (Dougherty, 1998). Windrow composting can have issues such as the limited
ability of odor control, the land area needed, increased process duration, and limited control of
temperature associated with seasonal climatic variation.
In-vessel composting systems are often used in situations where there is a need for stricter environmental
controls (odor emissions and/or leachate discharges) and when space is limited. In-vessel systems are
often employed for composting food or other high-nitrogen feedstock, and therefore, often require the
addition of a high-carbon material such as leaves, sawdust, or wood chips to achieve more thorough
decomposition and to prevent the ammonia and VOC odors associated with a low carbon to nitrogen
(C:N) ratio (Bonhotal et al., 2011). These systems typically employ forced aeration and/or mechanical
turning and provide better process control. Generally, the entire composting process does not occur
within the composting vessel; the compost curing stage is usually accomplished outside the vessel and
thus will have an additional space requirement.
The various in-vessel systems have been examined in previous research and are described herein
(Dougherty, 1998; CCWI, 2010). Bin systems often have the dimensions of shipping containers or
construction and demolition debris roll-off boxes. They may be opened or closed, and are typically
aerated from the bottom. To improve decomposition rate, bins may be opened and mixed a few times per
batch. The typical in-vessel bin composting time can take from 2-3 weeks. Silo systems may have the
smallest footprint of all the in-vessel systems and are configured similarly to agricultural silos. The
feedstock is introduced into the unit from the top, and an auger is commonly used to remove the material
from the bottom. Like bins, these systems often are aerated from the bottom; adequate aeration can be a
problem if the silo/feedstock material is too tall and the weight of the material causes some degree of self-
compaction. The C:N ratio and moisture content of the material should be optimized prior to insertion
due to the difficulty of later adjustment of these parameters. Silo systems may have a holding time of 1-2
weeks.
Agitated bed composting systems are arranged in long, narrow channels. The feedstock is periodically
turned and incrementally moved across the length of the canal by overhead machines that are able to
move down the length of each channel. These systems can be arranged to sense automatically when
turning is necessary based on temperature sensor data, or set to activate at intervals. These systems are
also generally aerated from the bottom. Standard channel dimensions are approximately 1-2.5 meters, a
width of 2-4 meters, and a length of 60-90 meters. Typical throughput times may last 1.5-3 weeks. Of
the different in-vessel systems, rotating drums usually have the shortest residence time. The systems are
particularly well adapted for material mixing and aeration, with the air flow commonly moving against
the feedstock flow. Holding times in the drums may last around 5-10 days.
Post-processing of the compost is dependent upon the original composition of the feedstock and the needs
of the end user. For example, compost feedstock that used a low-biodegradable bulking agent contained
larger-sized pieces of organic matter (e.g., yard trimmings), or included non-biodegradable residuals (e.g.,
mixed-MSW composting) may require screening prior to final use. Other potential post-processing
operations may include drying and/or bagging, depending upon the particular end-use market.
3.4.2 Commercialization Status
As of 2010, there was approximately 3,000-yard trimming compost facilities in the U.S. However,
composting food scraps and food-soiled paper segregated at the source of generation (i.e., SSO) is
becoming more common; according to a 2010 national survey, 68 communities in the U.S. had an SSO
collections program (CCWI, 2010). The majority of the nearly 3,000-yard trimmings composting
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facilities are located in the Midwest and Northeast (U.S. EPA, 201 la). Approximately 270 composting
facilities accepted food scraps, and about 70% of these facilities received other organics such as yard
trimmings U.S. (Olivares and Goldstein, 2008). As of 2009, Europe had nearly 2,000 composting
facilities that treated discarded household organics (Boldrin et al., 2009). Figure 3-8 presents the
geographical distribution of food-scrap composting facilities in the U.S. As can be seen, approximately
half of all the food scrap composting facilities in the U.S. are located in seven states (California,
Pennsylvania, Washington, Massachusetts, Maine, New York, and North Carolina).
California 13%
(34)
Pennsylvania
7.9% (21)
.Washington
7.1% (19)
Massachusett
s 6.4% (17)
North
Carolina 5.2%
(14)
New York
5.2% (14)
Maine 5.2%
(14)
Figure 3-8. Geographical Distribution of Food Scrap Composting Facilities in the U.S.
(Olivares and Goldstein, 2008)
Below is Figure 3-9, which shows the distribution of scrap food capacities of approximately 170
composting facilities that accept this material.
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Even with extensive preprocessing, mixed-MSW composting has achieved limited success in the U.S. due
to the potential for odors and unfavorable economics (especially in comparison to landfill disposal costs)
(Haug, 1993). About half of the mixed-MSW composting facilities started in the past 25 years have shut
down or converted to another type of MRF (Yepsen, 2009). In a recent survey of existing facilities,
Sullivan (2011) found 11 facilities that accept up to 575 TPD of mixed MSW. Market demand for
compost derived from mixed MSW is often weak; Renkow and Rubin (1998) found that the majority of
mixed MSW composting facilities gave the compost end product away free of charge.
3.4.3 Materials and Energy Recovery
Due to the aeration and pre-treatment requirements of compost, and because the heat released from the
microbial population over the course of decomposition is not recovered, this process is an energy sink
(i.e., an overall net energy input is required) during composting. Provided that sufficient pre-treatment
took place to remove all non-degradable portions of the original feedstock material, the only end-product
from the aerobic treatment of MSW organics is the stabilized compost product.
3.4.4 Environmental Concerns
The most commonly acknowledged environmental benefit of composting is the promotion of organic
matter and nutrient cycling for agriculture that would otherwise have utilized synthetic fertilizers (U.S.
EPA, 201 lc; Stutz et al., 2003; Haug, 1993). As mentioned previously, soil structure is improved as
organic matter is introduced back into the soil, which allows increased moisture retention and thereby
allows the compost to be used in erosion control measures (Tejada and Gonzalez, 2007). Various studies
have also documented the use of composting in the remediation and degradation of soils contaminated
with petroleum products and solvents, as well as to assist in binding heavy metals, reducing their
leachability (U.S. EPA, 1989; Coker, 2006; Faucette, 2010; USCC, 2008). Compost end use is dictated
by available markets, the quality of the material, and the regulatory framework for reuse.
The quality issue that would most likely limit compost use would be the presence of heavy metals and
organic chemicals. The U.S. EPA has published generic ingestion exposure-based soil screening levels
(SSL) as part of their soil screening guidance for cleanup of contaminated sites (U.S. EPA, 1996). Many
states use a similar risk assessment methodology to develop their thresholds for clean soils and land-
applied composts. Many researchers have published the concentrations of heavy metals found within
compost; in general, yard trimmings and SSO composting contain heavy metal concentrations below SSL
values, while mixed-MSW compost has been reported to contain lead, arsenic, zinc, and chromium above
the respective SSL (Farrell and Jones, 2009; Ciavatta et al., 1993; Deportes et al., 1995; Fricke and
Vogtmann, 1994; Greenway and Song, 2002; Hargreaves et al., 2008; Pinamonti et al., 1997; Tandy et al.,
2009). There are growing concerns regarding the presence of organic compounds (e.g., commonly used
herbicides) in the yard trimming compost (e.g., Michel et al. 2012).
Quantitative data on GHG emissions from the composting process are lacking. Anaerobic pockets that
result from an inadequate air supply (e.g., little windrow turning) may contribute to the release of CFL
and nitrous oxide, both of which are potent GHGs (Boldrin et al., 2009). However, the GHG emissions
from the aerobic composting process, specifically as it relates to the decomposition of food and food-
soiled paper discards, are expected to be lower than those associated with anaerobic degradation of the
same material in a landfill site, especially facilities without landfill gas recovery (Lou and Nair, 2009;
CAR, 2010).
Measures may be necessary to capture and collect compost leachate, particularly in an open windrow
operation. The particular contaminants found within composting leachate will depend on the specific
composting feedstock used, but potential compounds may include nitrates, ammonia, and various organic
compounds. Little published data regarding leachate characteristics at open (e.g., windrow-type) SSO
composting facilities are available, and the requirement to collect and control leachate varies depending
on the jurisdiction. In-vessel systems will typically have a means of capturing leachate produced, and this
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leachate can potentially be recirculated back into the system, used as a fertilizer, or (in accordance with
local regulations) discharged to a wastewater treatment plant (Aslam, 2007).
Odor control/mitigation is one of the most significant operating concerns to minimize the impact on the
surrounding population. Carbon-, sulfur-, and nitrogen-based compounds may be produced, which can
cause odors; the degree of the release of odorous compounds depend on microbial metabolic rates,
availability of nutrients, moisture content, oxygen content, and temperature of the feedstock (Coker,
2012). According to one study (Epstein and Wu, 2000), approximately 90% of the odors generated
during the composting process originated from the active and curing phases (collectively representing the
vast majority of the composting process).
For enclosed facilities, in-vessel systems, and negative pressure aerated windrows, odors are typically
controlled through the use of a biofilter, which may consist of wood chips, peat, or cured compost (TSH,
2006; Boldrin et al., 2009). Unless properly maintained, the biofilter may also prove to be a source of
odors (Aslam, 2007). Gasses produced during the composting process have been shown to cause issues—
for example, a build-up of H2S at a facility in a confined space resulted in a worker fatality (Garrison,
2012).
3.4.5 Economic Considerations
The operation, maintenance, and capital costs of composting vary significantly, which may be attributable
to differences in climate, technology, operational skill, and demography. For instance, a report by U.S.
EPA (1989) reviewed eight-yard trimmings composting facilities and found that the per ton cost ranged
from less than $20 to nearly $102 ($33 to $168 when converted to 2011 dollars using CEN Index, 2012)
for acceptance rates ranging from 116 to 15,600 tons per year, with little correlation between the cost and
production rate of the facility. In a previous survey of 19 U.S. mixed-MSW composting facilities, it was
estimated that the operations cost for mixed-MSW composting is about $50 perton (1995 dollars or $77
per ton in 2011 dollars using CEN Index, 2012) (Renkow and Rubin, 1998).
The economic feasibility of composting depends on the market demand and possible revenue sources
(e.g., tipping fees, compost sale, carbon credits) or other incentives (e.g., grants or tax breaks). Finding a
market for compost appears to be mostly dependent on the success of removing the non-biodegradable
material from the feedstock as well as proximity to potential end users. While there are a variety of
compost end uses, including agriculture, silviculture, sod production, home gardening, soil remediation,
erosion control, and roadside vegetation establishment, there appears to be limited data on compost
market distribution. Cedar Grove of Seattle and Jepson Prairie Organics of San Francisco—two of the
largest food scrap composting operations in the U.S.—provide compost to agriculture and landscaping
services in addition to selling bagged compost for individual consumer use (JPO, 2012; Cedar Grove,
2012).
Based on a review of workforce requirements for 26 yard trimmings composting sites located across 10
different states, an estimated average of one worker is needed per 2,500 TPY accepted for an acceptance
rate of 10,000 TPY or greater, and one person for every 710 TPY accepted for those that received less
than 10,000 TPY (ILSF, 1993). The Toxics Action Center (2010) provided a labor summary for three
different composting facilities in Vermont, where an average of one worker was employed for
approximately every 960 TPY of compost production, which is equivalent to one worker for every 1,920
TPY of feedstock accepted, assuming 50% mass loss during the composting process (Dougherty, 1998;
Aldrich and Bonhotal, 2006).
3.5 Combustion
3.5.1 Technology Description
In the combustion process, MSW is burned to generate heat, which can be harnessed to produce steam
that ultimately can be converted to electricity via a turbine. The combustion process completely oxidizes
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the organic fraction of MSW (biodegradable as well as non-biodegradable) in the presence of excess air
and results in a gaseous end product (flue gas) and solid residue (bottom ash and fly ash). Overall, the
entire process typically reduces the waste volume by 90% (Carim et al.. 2007). Figure 3-10 presents a
generalized process flow diagram for combustion.
Co-mingled
MSW
Inorganics
Combustible
MSW (RDF)
Co-mingled
MSW I RDF
Atmospheric
Air
Bottom Ash
Metals
Landfill
Boiler I
Steam
Turbine
Air
Pollution
Control
Clean Flue
Gas
Steam
Electricity
Mechanical
Processing
•Size Reduction
'Screening
•Density
\Separation
Figure 3-10. A Generalized Process-Flow Diagram for MSW Combustion
The extent of MSW pre-processing prior to combustion is dictated primarily by the combustion system.
Little to no pre-processing is performed for mass-fired or mass-burn systems or modular mass-burn
systems, which are designed to combust comingled MSW, whereas MSW is extensively pre-processed
(e.g., size reduction, screening, and/or density separation to segregate non-combustibles such as metal and
glass) for combustion in a refuse derived fuel (RDF)-fired combustor. Based on a recent nationwide
survey of MSW combustion facilities, Berenyi (2012) reported 63 mass-burn, 15 RDF, and 7 modular
facilities operating in the U.S. (Figure 3-11).
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Modularf71
8
Figure 3-11. Distribution of Different MSW Combustor Types in the U.S. (Berenyi, 2012)
The combustion process entails continuous feeding of co-mingled MSW or RDF into a combustion
chamber through a feed chute using a loading crane. MSW is positioned on a grate system, which is one
of the most critical components of the MSW combustors. Various grate designs can be used for MSW
combustors. The primary function of the grate is to provide a platform on which the MSW or RDF can
burn and move through the combustor from the feed chute outlet to the bottom ash system inlet. The
shifting grates allow for mixing of the waste as a way to ensure optimized combustion (Carim et al.,
2007).
Oxygen, the primary oxidizing agent in combustion, is supplied by injecting atmospheric air into the
combustion chamber. Air can be introduced from under the grates (otherwise known as under-fire air or
primary air) or above the grates (known as over -fire air or secondary air). Excess air is typically added
to ensure complete combustion of the MSW. Apart from providing an essential reactant for the process,
air also provides turbulence and mixing for uniform combustion, cools the grates, and controls the
combustion temperature. In general, the greater the air introduction rate, the lower the combustion
temperature. The
combustion temperature impacts the corrosion of grates, chamber walls, and boiler tubes, and the
emission of odorous compounds (Tchobanoglous and Kreith, 2002). Insufficient air flow can result in
excessive combustion temperatures, which can lead to fluidized ash that can be exceedingly corrosive to
the grate. Air needed for combustion can be drawn from MSW storage/processing area to minimize
fugitive odor emissions from these sectors.
3.5.2 Commercialization Status
Combustion is the most common type of MSW thermal treatment used worldwide; there are more than
600 MSW combustion plants in operation around the world (Themelis, 2003). Growth in the number of
WTE facilities has been observed in Europe and Asia in the past 20 years, with positive correlations
between areas of population density and the percentage of the MSW fraction that is combusted (Dijkgraaf
and Vollebergh, 2004). By contrast, MSW combustion in the U.S. increased steadily from 1982 to 1993
(with 136 facilities in operation in 1993) but has since declined, with 85 operating facilities in 2011
(Berenyi, 2012). In 2010, approximately 11.7% of MSW generated in the U.S. was combusted for energy
recovery. Almost half (38) of the 85 U.S. facilities are located in four states (Florida, New York,
Minnesota, and Massachusetts).
The decline of operating and planned combustion facilities in the U.S. over the past 30 years could be
based on a variety of factors, but major factors include more stringent air emission standards established
by U.S. EPA, a Supreme Court decision regarding waste flow control, as well as siting difficulties. In
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1990, the CAA was amended to reduce the pollutants emitted from MSW combustors based on the best-
performing waste combustion plants that had multiple air pollution technologies and the results that could
be achieved by these systems. In order to meet these new regulatory standards, facilities across the U.S.
were required to retrofit and purchase better air pollution control devices (APCD) and monitoring systems
to control hazardous and priority pollutants. Thus, the capital cost to retrofit older facilities with new
APCD became a hurdle, resulting in the closure of some facilities.
In the past, most MSW combustion facilities were guaranteed a certain tonnage of the waste stream
(referred to as flow control) during the facility's operating period. However, in May 1994, the U.S.
Supreme Court identified this guarantee of delivery of waste to a privately-owned facility as a violation of
the dormant commerce clause. Since many facilities were built with the idea that waste flows to the
facility were guaranteed, this court decision impeded the development of future MSW combustion
facilities in the U.S. Note that in 2007, a Supreme Court ruling regarding the constitutionality of flow
control to a facility operated as a public benefit corporation was made and ruled that MSW flow control to
a public facility (which reflects treatment of private entities such as haulers equally) is not in violation of
the commerce clause. This decision is expected to encourage publicly-owned solid waste management
authorities to pursue or at least more closely consider MSW combustion as a potential management
option.
Siting difficulties have also likely contributed to the lack of new MSW combustion facilities in recent
years. High facility capital costs, concerns/opposition by affected populations, a lengthy regulatory
approvals process, and the potential for other impediments such as political debate, can all dramatically
impact the ability to site a new facility. As an example, a WTE analysis report for the Oneida-Herkimer
Solid Waste Authority (NY) suggested that the site selection and permitting process for a new WTE
facility would take at least 10 years and cost at least $10 million (OHSWA 2007).
3.5.3 Materials and Energy Recovery
The primary byproducts of the combustion process are flue gas, solid residues (including bottom ash and
fly ash), and energy in the form of heat. Flue gasses produced from MSW combustion primarily consist
of CO2 and water vapor. Excess O2 and N2 contained in atmospheric air are not used during the
combustion process, so they are also components of the flue gas.
Currently, 72 out of all of the combustion facilities in the U.S. generate electricity, and the rest produce
steam as the end-product. The high-temperature flue gas is passed through a boiler to recover heat via
generation of steam, which in turn can be used to generate electricity using a steam turbine. The
temperature of the flue gas subsequently decreases due to the transfer of heat from flue gas to water in
boiler tubes. Based on a survey conducted by Berenyi (2012), a net of approximately 500 kilowatt-hours
(kWh) and 700 kWh of electricity is generated by the combustion of 1 ton of MSW from a mass-fired and
an RDF-fired combustor, respectively. Assuming MSW energy content of 5,000 BTU per lb, a 500 kWh
per ton electricity generation is equivalent to a net system efficiency of approximately 16%. The low
efficiency of the system is attributed to a 70% heat loss due to the relatively low efficiency of steam
turbines. Other significant heat losses include heat lost due to evaporation of the MSW combusted, heat
trapped by the discharging ash and flue gas.
The solid waste residue that remains on the grates after combustion is bottom ash and ash that is
transported with the flue gas as particulate matter after combustion is fly ash. The amount of ash that is
produced from the combustion process depends on the incoming MSW stream and has been reported to
range from 15-34% by weight of the MSW processed (Tchobanoglous et al., 1993; ABCs, 2007; U.S.
EPA, 2012e; Berenyi, 2012). Of the ash that is produced, approximately 80% is bottom ash; the
remaining 20% is fly ash (Carim et al., 2007; Gines et al., 2009; U.S. EPA, 2012e). Fly ash is usually
mixed with bottom ash after collection. In the U.S., the solid residues from combusted MSW are
dewatered, if needed, and ultimately deposited in a lined, Subtitle D landfill.
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Recently, many owners and operators invested in metal separators to recover metals prior to ash disposal
or recycling due to the rising demand and price of scrap metals. All of the mass-burn facilities in the U.S.
process bottom ash to recover ferrous metal; facilities that handle bottom ash to recover non-ferrous metal
(namely aluminum) have more than doubled, from 12 in 2004 to 27 in 2010 (Berenyi, 2012).
3.5.4 Environmental Considerations
The major air pollutants that are formed or emitted during the combustion process include particulate
matter; heavy metals such as lead, mercury, and cadmium; gases such as CO and NOx; acidic gases such
as SOx, HC1, and HF; and trace organic compounds such as polychlorinated dioxins and furans (Hasselriis
et al., 1996; Churchill, 1997; Ruth, 1998; World Bank, 1999; McKay, 2002; Albina and Themelis, 2003).
CAA regulations require MSW combustion facilities in the U.S. to treat flue gas before releasing it to the
atmosphere. The volume of flue gas that needs to be addressed is related to the amount of excess air
added to the process; therefore, air pollution control costs increase with increasing amounts of excess air
added. A variety of APCD is used to treat flue gas. These include wet scrubbers for acidic gasses,
electrostatic precipitators and baghouses for particulate matter, and selective non-catalytic reactors for
NOx.
Since the passing of the Maximum Achievable Control Technology regulations, emissions from
combustion facilities have declined substantially in the U.S. between 1990 and 2005; SOx and NOx have
been reduced by 88% and 24%, respectively (Stevenson, 2007; Stantec, 2011). The declines are based on
advancements in thermal treatment technology and operational control; improvements in waste diversion
and source separation prior to thermal treatment; and enhancements in the design and operation of APCD.
Figure 3-12 presents cumulative amounts of air pollutants emitted by MSW combustors in 2005
(Stevenson, 2007). Based on the amount of MSW combusted in 2005, the amount of pollutants emitted
per ton of MSW burned was estimated; approximately 33.7 million tons of MSW was combusted in 2005.
These estimates are presented in Figure 3-12 as well. The amount of CO2 emitted was not tracked until
required by GHG regulations in 2010 (40 CFR 98). These rules specify estimation of CO2, CFU, and N2O
emissions based on the amount of steam produced, the boiler rating, and specified emission factors.
106
105
104
_ 103
S 102
CD
Cl
C
o
c
o
101
10°
101
10"2
10"3
10"4
10"5
10"6
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h 101
h 10"2
h 10"3
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13
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£
o
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PM
HCI
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NOy
Cd
Pb
Hg
Figure 3-12. Annual Total Mass of Air Pollutants Emitted by MSW combustors in the U.S.in 2005
(Stevenson, 2007)
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Liquid emissions are associated with wastewater from dewatering of quenched bottom ash, effluent from
wet scrubbers, and wastewater from treatment systems used to produce boiler water (Tchobanoglous et
al., 1993).
Fly ash, resulting from flue gas treatment, usually has high concentrations of heavy metals (lead, mercury,
and cadmium), dioxins, and complex organics. A primary concern in the utilization/disposal of ash is
whether or not the ash will leach chemical constituents at levels greater than risk-based thresholds or
toxicity characteristic hazardous levels. One of the reasons bottom ash and fly ash are mixed the
following generation is to reduce the likelihood of leaching chemical constituents at levels above the U.S.
EPA's hazardous thresholds.
Beneficial uses of MSW combustor ash (both bottom and fly ash) as granular fill, agricultural soil
amendment, road base, cement production for buildings, and aggregate or mono disposal have been
reported internationally (Kosson et al., 1996; Deschamps, 1998; Okoli and Balafoutas, 1999; Kamon et
al., 2000; Marschner and Noble, 2000; Zhang et al., 2002; Lo and Liao, 2007). Concern over the
utilization of bottom ash in concrete production is its impact on mechanical properties such as durability
and strength. The quenching of bottom ash after it is removed from the grate could result in swelling to
occur in the concrete, which can reduce its overall strength (Gines et al., 2009). However, some research
has shown that replacement of bottom ash for cement and for gravel as aggregate did not affect the overall
durability of the concrete (Pera et al., 1997; Juric et al., 2006). Various studies have conducted chemical
characterization of MSW combustors ash in the U.S. to assess its beneficial use (e.g., NREL, 1999;
Forteza et al., 2004).
Another environmental consideration of MSW combustion is the reduction in the volume of MSW. As
discussed, beneficial use of ash from MSW combustion facilities is relatively limited, so standard practice
involves disposing of ash into Subtitle D-equivalent landfills along with un-combusted MSW or into ash
monofils. So while the volume reduction and subsequent energy production (at combustion facilities
which recover energy) represent benefits, in most cases the solid residue remaining still necessitates a
lined landfill for disposal.
3.5.5 Economic Considerations
Figure 3-13 presents the average initial and additional capital investment for each of the combustion
technology types based on data reported by Berenyi (2012) (in 2010 dollars)—the "additional capital
cost" represents required air pollution control retrofits and upgrades. The average O&M cost was
reported to range from approximately $24 to $210 per ton. The tipping fee, electricity sale, and recovered
materials sale were reported to constitute on average 57%, 38%, and 5% of the total revenue, respectively.
In countries with limited land availability (e.g., Japan), the high cost of land makes MSW combustion a
preferred option because of its smaller footprint. However, Dijkgraaf and Vollebergh (2004) found that
the cost of incineration is much higher than that of landfilling, even in densely populated countries where
land acquisition and landfill siting can be cost intensive. Given the substantial initial capital cost, as well
as additional capital cost and relatively high O&M cost, a sufficient incoming material throughput and the
sale of recovered energy is necessary for the economic viability of MSW combustion facilities.
U.S. Census Bureau data for solid waste combustors indicates a total of approximately 4,500 people are
employed full-time at combustion plants, or an average of about 53 personnel per plant.
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>¦
03
"O
S—
00
< §
250-
200-
150-
100-
50-
0 ¦
$52
$176
$46
$186
H Additional Capital Cost
1 Initial Capital Cost
$84
$57
$151
$142
All Plants Mass Burn RDF Modular
Figure 3-13. Average Initial and Additional Capital Cost for MSW Combustion Plants in the U.S.
3.6 Gasification
3.6.1 Technology Description
Gasification involves the thermochemical conversion of carbon-based materials (e.g., the biodegradable
and non-biodegradable organic portion of MSW) through reactions with free or bound O2 under elevated
temperatures (usually above 600 °C) into a synthetic fuel gas (i.e., syngas) (Ciferno and Marano, 2002;
Arena, 2012a; Gupta and Cichonski, 2007). Syngas is mainly comprised of CO and H2, but may have
substantial quantities of N2 if air is used for the oxidizing gas (Arena, 2012a; Jenkins and Willams, 2006).
Syngas may be directly combusted for steam-cycle power generation, or after varying degrees of cleaning
and refining, may also be fired in internal combustion engines and gas turbines, and can potentially be
converted into chemicals, liquid fuels, or even fertilizer products (Ciferno and Marano, 2002; GTC,
2012). Figure 3-14 presents a generalized process flow diagram for gasification.
While gasification reactions are differentiated from strict pyrolysis by the addition of a limited amount of
an oxidant, gasification always utilizes a pyrolysis step where carbonaceous material is volatilized and
reduced into lower weight compounds (char)—this char is then subsequently gasified through partial
oxidation (Klein, 2002; Gupta and Cichonski, 2007; Periera et al., 2012).
There are a variety of commercially-available technologies which may be used for MSW gasification, and
these can be organized by whether they are fixed bed, fluidized bed, or plasma arc processes. However,
each of these may be further categorized according to particular gasifier chamber arrangement (e.g.
updraft vs. downdraft air introduction methods for fixed-bed arrangements and bubbling vs. circulating
beds for fluidized-bed arrangements) and by heating mechanism (whether direct or indirect).
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Figure 3-14. A Generalized Process Flow Diagram for MSW Gasification
Arena (2012b) presented general information including technology type, equipment manufacturer and
feedstock material for approximately 100 commercial gasification plants which are capable of processing
MSW and/or other waste materials (e.g. automotive shredder waste, sludge). Of these facilities,
approximately 75% use either shaft-furnace (a particular type of fixed-bed system) or fluidized-bed
processes. These gasification technology types are further detailed below.
Shaft furnace systems include a primary vertical gasification chamber in which the bottom portion,
through the combustion of the coke and waste material, achieves temperatures of up to 1,800 °C which
gasify or liquefy all solid materials; heavy metals are carried away with the syngas and captured through
air pollution control devices downstream of gasification (Arena, 2012b). Nippon Steel, a leading provider
of shaft furnace systems, manufacturers gasification systems which may accept untreated MSW along
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with coke and limestone. The coke provides a reducing agent while the lime helps regulate the viscosity
of the molten material periodically discharged from the bottom of the gasification/direct melt chamber
(Tanigaki et al., 2012). Oxygen-enriched air is used as the oxidation agent to achieve controlled
combustion. At Nippon Steel facilities, syngas is typically routed to a combustion chamber, where the
recovered heat is used for power production (Tanigaki et al., 2012; UC Riverside, 2009). Combustion fly
ash may be introduced in the initial gasification chamber in order to displace the coke requirement and as
a means of material management.
Fluidized bed systems commonly introduce air through a bed of inert material (such as silica sand)
located at the bottom of the gasification chamber; the mixing of this bed promotes efficient heat transfer,
mixing and reactions (Klein, 2002). Ebara is a prominent MSW gasification equipment manufacturer
which provides fluidized bed systems. Because of the relatively low operating temperatures of some
fluidized bed gasification chambers, (Ebara gasification chambers run around 600 °C), metals can be
recovered from the bottom of the gasification reactor along with other ash materials. These systems are
typically coupled with an ash-melting furnace stage immediately following the gasification stage, where
syngas is combusted in order to fuse fly ash and recover the resulting slag material. Like Nippon Steel,
the heat produced from syngas combustion in Ebara gasifiers is generally used for power generation (UC
Riverside, 2009). Ebara fluidized bed gasifiers require shredding and drying of waste prior to input (ARI,
2006). Some degree of pre-treatment before gasification may be needed to create a more homogenous
feedstock material, free of bulky items. This treatment may range from minimal mechanical processing
(e.g., size-reduction by shredding or segregation of metals and glass) to more elaborate preparation (e.g.,
drying, compaction, or pyrolysis) (E4Tech, 2009; URS, 2005). Recovered materials may either be
recycled or landfilled depending on markets, particular materials present, and efficacy of the material
recovery process.
Three standard oxidation media for gasification include air, oxygen-enriched air, and pure oxygen. The
properties of the resultant syngas depend on the type of oxidant used (Arena, 2012a). Partial oxidation
with air produces a syngas with high-nitrogen content (up to 60%) and a low heating value
(approximately 110 - 190 Btu ft"3). Syngas with higher energy content is produced as the nitrogen content
of the input air is reduced. Partial oxidation with pure oxygen produces a syngas with a medium heating
value (approximately 270 - 540 Btu ft"3) (Ciferno and Marano, 2002).
The heat needed to maintain the elevated temperature for sustaining the gasification reactions is provided
either by direct heating, where heat is produced by partial combustion of a portion of the carbon
feedstock, or by indirect heating where an external source of heat such as steam or plasma arc is used to
achieve the gasification temperatures. Steam-heated processes are especially useful for the production of
high-hydrogen syngas, where the oxygen in the water molecules oxidizes carbon during the formation of
CO and CO2 (Gupta and Cichonski, 2007). However, after reviewing numerous gasification equipment
manufacturers, none was identified which have reference gasification plants using steam for indirect
MSW heating.
Plasma torches can also be used to supply heat for gasification reactions and to vitrify ash, or may be
utilized for syngas conditioning to remove entrained tars, thereby enhancing the syngas conversion
efficiency (Arena, 2012a). Plasma arc torches take a minimal quantity of gas and change it into a plasma
flame using electricity. For cost reasons, the most common gas used with plasma arc is air, but O2,
helium, argon, H2, and other gasses can also be used. While there are instances of plasma torches being
utilized for the gasification process in order to provide the necessary heat for waste gasification and/or ash
vitrification, plasma gasification is not standard among commercial facilities; only 4 were noted by Arena
(2012b) from two different manufacturers, and two of these facilities accepted less than 10 TPD. This
technology may not be proven commercially in part due to the substantial maintenance requirements
involved with equipment upkeep resulting from the very high temperatures associated with its use.
Stantec (2011) reported that Japanese facilities which use plasma arc treatment technology had to replace
the plasma chamber lining every 3 months and therefore utilize redundant systems.
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3.6.2 Commercialization Status
Gasification technology vendor information was used from Arena (2012b), the University of California,
Riverside (2009), and equipment manufacturer data to identify those gasification equipment
manufacturers with the most MSW-processing reference plants. There are at least 104 MSW gasification
technology reference plants known to be operating worldwide (Arena, 2012b). Approximately 60% of
these facilities use processes/technology from six different manufacturers. Figure 3-15 shows the
capacity distribution of reference plants from these six manufacturers. Besides Organic Energy (OE)
Gasification and Ener-G systems, which are located primarily in South Korea and Norway, respectively,
the majority of (the 69) MSW gasification plants represented below are located in Japan. Of the
commercial MSW gasification facilities analyzed, approximately 85% have a capacity less than 300 TPD.
20
Plant Capacity (TPD)
Figure 3-15. Distribution of MSW Gasification Reference Plant Capacities for Six Most Prominent
Technology Providers
In the 1970s, gasification of solid waste for the production of electricity received increased attention in
the U.S. and several processes were proposed and tested (e.g., the Andco-Torrax and Union Carbide
Purox). The wide-scale application of the technology at the time was unsuccessful due to limited
experience using unprocessed MSW for gasification, challenges related to the variable nature of the MSW
stream, difficulty in technology scale-up, and gas cleaning needs (Rensfelt and Ostman, 1996).
There currently appears to be no commercially-sized, mixed-MSW gasification plant in the U.S., though
three pilot-scale/demonstration projects were identified: an InEnTec facility in Arlington (Oregon), the
Pyrogenesis Plant at Hurlburt Field Air Force Base (AFB) (Florida) and Covanta's Gasification Plant
(Oklahoma). The 25-TPD capacity InEnTec G100P plasma gasification facility is located at the
Columbia Ridge Landfill in Arlington, Oregon, and the site has been in operation since November 2011
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(Wolman 2012). According to InEnTec's system description, the process is comprised of three primary
components including a pre-gasifier (where the majority of organic materials are gasified), a plasma
processing vessel (which liquefies/gasifies any remaining solids), and a thermal residence chamber which
subsequently provides additional treatment for remaining organic materials in the syngas.
The Hurlburt Plant consisted of a 10.5-tpd transportable waste gasification system designed to treat
MSW, hospital, and other solid waste generated at Hurlburt and Eglin AFBs. The plant began operation in
January 2010. A site inspection report in April 2012 suggested issues with slag handling, water
consumption, and wastewater generation rates. The plant ceased processing solid waste in September
2011, and the project was verified as closed by FDEP in July 2012 (Novy, 2012; FDEP, 2012).
Based on a personal communication, an official from Covanta indicated that an MSW-fired boiler was
retrofitted to demonstrate syngas production from MSW gasification at an MSW combustion plant in
Tulsa, Oklahoma. The gasifier was operated for a ten-month period to demonstrate the commercial
viability of the Covanta gasification technology and accepted approximately 350 TPD of post-recycled,
unprocessed MSW. However, while the demonstration reportedly was successful, the company indicated
that commercial-scale implementation was years away (Orlando, 2012).
One proposed gasification/syngas-to-ethanol facility, which is currently being commissioned in Florida is
projected to produce 8 million gallons per year of ethanol and have a gross electricity output of 6 MW
using 300 Tdp of yard trimmings and MSW as a feedstock (U.S. DOE, 2011; Ineos, 2012). Several
proposed MSW gasification projects have been terminated due to reasons such as siting, permitting,
financing, and securing waste (or a combination of these factors). For example, the contract to construct a
600-TPD plasma gasification facility (St. Lucie County, Florida) was terminated because Geoplasma, the
company, contracted for building and operating the plant, was unable to secure necessary funding while
St. Lucie County was unable to secure and provide waste from the city of Fort Pierce (Blandford, 2012).
Approximately 15 WTE facilities in various stages of planning include a form of gasification (plasma
gasification or gasification/bioconversion) (Berenyi, 2012).
3.6.3 Materials and Energy Recovery
The primary end-products of the gasification process are syngas, ash and/or slag, and syngas or flue gas
treatment residues. Syngas is mostly comprised of CO and H2 with lower quantities of CO2, CH4, H2O
and light hydrocarbons (Tchobanoglous et al., 1993; Filippis et al., 2004; Consonni and Vigano, 2012).
The amount of CO2 and H2O produced can vary depending on the oxidizing agent used. Use of a more
oxygen-rich agent can lead to a higher CO2 and H2O content (Pinto et al., 2011). Syngas can also contain
impurities such as sulfur, mercury, particulates, alkali metals, and chloride in addition to nitrogen (N2),
depending on the process used and the feedstock quality (Arena, 2012a; SWANA, 2011).
Syngas, because of its calorific value, can be beneficially used. Before syngas can be utilized in an
energy recovery process, it may need to be cleaned to reduce the quantity of tars, particulates, and alkali
metals where the particular syngas end use dictates the level of gas cleanup that is required.
URS (2005) estimated that the net energy production potential from gasification could be as high as 900
kWh per ton of input material. However, SWANA (2011) estimates that the net energy produced as a
result of gasification is similar to or less than that achieved through the use of a combustion process (500
to 700 kWh per ton). However, as described previously, syngas has the potential to be further refined into
purer gaseous (e.g., H2) or liquid fuels. The requirements for converting syngas into fuel or chemicals are
usually very stringent in terms of syngas refining/cleaning due to the complexity of fuel synthesis.
Potential fuels that can be produced from syngas include methanol and ethanol.
3.6.4 Environmental Concerns
Depending upon the particular gasification technology employed for MSW treatment, there may be
varying degrees of air pollutants, ash, and wastewater discharge. Air pollutants of concern generally fall
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into the same categories as those released from complete or controlled-air combustion WTE facilities,
including particulate matter (PM), acidic gasses (e.g., HC1), nitrous and sulfur oxides (NOX and SOX,
respectively), mercury (Hg) and dioxins and furans. The University of California, Riverside (2009)
evaluated the emissions from 12 gasification facilities which processed MSW. The range of pollutant
concentrations noted at these facilities is presented in Table 3-1. Pytlar (2010) describes that these air
emission results are similar to those from the mass burn and controlled air WTE facilities, with the
exception of lower-end values corresponding to NOx, Hg and dioxins/furans.
Table 3-1. Ranges of Air Pollutant Emission Concentrations for 12 Existent MSW
Gasification Facilities
Pollutant
Units
Min
Max
PM
mg N-M"3
1
18.2
HCL
mg N-M-3
2.8
55.8
NOX
mg N-M"3
10
150
SOX
mg N-M"3
4
41.1
Hg
mg N-M"3
0.0001
0.0002
Dioxins/Furans
ng N-M"3
0.000072
0.0983
There are generally two types of ash which may be recovered from the gasification reactor of gasification
facilities, dependent on the process temperature and MSW feedstock: bottom ash or vitrified ash (slag).
Ash/slag generation rates will depend on the particular characteristics of the MSW input (and the degree
of pretreatment it has received), but reported total ash (including fly ash) generation estimates range from
0.15-0.35 tons per ton of MSW input (Tanigaki, 2012; FCE, 2004). Whether this ash would need to be
disposed of at a Subtitle C or D facility would be mainly dependent upon the leachability of the final ash
material, though slag's resistance to leaching is improved by the rapidity with which the molten material
is quenched (Moustakas et al., 2005). The limited data on slag leachability appears to indicate that it may
meet toxicity characteristic leaching procedure (TCLP) limits for consideration as a non-hazardous
material (Arena, 2012a; Moustakas et al., 2005), however, further research is needed in order to
substantiate this claim. Finding beneficial use options for fly ash and non-slag bottom ash material is
challenging due to its heavy metal content (Belgiorno et al., 2003), though due to similarity to ash
produced from combustion WTE facilities, it may find use in cement and concrete manufacturing
(Gomez-Barea et al., 2009).
The quantity of wastewater discharge will also be dependent upon the particular gasification process, but
it is likely that wastewater amounts will be directly related to the syngas/ash quenching process used and
whether quenching is direct (comes in contact with the hot material) or indirect (an intermediate medium
is used for cooling, such as through the utilization of a heat exchanger). Reported wastewater discharges
among three different MSW gasification technology vendors ranged from 1-19 gallons per ton of MSW
throughput (FCE, 2004). However, wastewater discharge rates can clearly vary over a significant
spectrum: according to its permit application, the plasma arc gasification facility which was located at
Hurlburt AFB in Florida appears to have been anticipated to produce 370 gallons of wastewater per ton
throughput (Pyrogenesis, 2009). Literature was not found which reported wastewater pollutant
concentrations for MSW gasification facilities.
3.6.5 Economic Considerations
There are no commercially operating MSW gasification facilities in North America. The Salinas Valley
Solid Waste Authority and HDR (SVSWA, 2008) estimated that tipping fees for Thermoselect MSW
gasification plants in Japan are in the range of $200-$300 per ton of waste processed.
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Alternative Resources, Inc. (ARI, 2008) provided gasification equipment manufacturer estimates for
capital and operational costs of potential facilities constructed and operated in New York City. Ebara
provided an estimated a capital cost for a 2,959 TPD facility of nearly $258,000 per TPD throughput with
an approximate operations cost of $29 per ton processed. Interstate Waste Technologies, which uses the
Thermoselect gasification technology, proposed a facility which would process 2,612 TPD with a capital
cost of about $155,000 per TPD throughput with an operations cost of $53.55 per ton processed.
A gasification plant's own economic viability is likely to depend on the success of thermal/electric
generation and sales. Based on a review of prominent MSW gasification facility technologies, the
gasification process is often coupled with syngas combustion for steam cycle power generation.
Laboratory and full-scale evaluations have shown that full combustion (single-stage incineration) of
biomass combined with a steam cycle power generation (19-27% efficient) is generally more efficient
than a gasification process combined with the same (9-20% efficient). However, gasification combined
with combustion engines or combined-cycle gas turbines (after appropriate syngas cleaning) may result in
electrical efficiencies approaching those attained through direct combustion steam cycles, as 13-24 % and
23-26%, respectively (Panepinto and Genon, 2011; FCE 2004).
3.7 Pyrolysis
3.7.1 Technology Description
Pyrolysis is the thermal decomposition of materials in the absence of oxygen to a combustible gaseous
stream (commonly referred to as syngas), a liquid fuel, and a solid residue (referred to as char or slag)
(Reaven, 1994; Tchobanoglous et al., 1993; Velghe et al., 2011). Pyrolysis has been used for the
production of charcoal from wood in ancient Egypt and ancient Greece (Stoller and Niessen, 2009;
Tiilikkala et al., 2010). Pyrolysis has also been used to treat tires thermally since the mid-1990s
(Zabaniotou and Stavropoulos, 2003). A generalized process flow diagram is presented in Figure 3-16.
Size reduction, removal of inorganics, and drying of waste are the primary pre-processes that are used in
MSW pyrolysis plants and are commonly recommended/required by the current technology providers
(Helmstetter and Sussman, 1977; Igarashi et al., 1984; Tchobanoglous and Kreith, 2002; Malkow, 2004).
The pre-processed MSW is fed into a pyrolysis reactor and maintained at elevated temperatures ranging
from 400 to 800 °C using an external heat source to decompose it thermally into syngas, liquid fuel, and
char (Malkow, 2004; Buah et al., 2007; Baggio et al., 2008). The threshold temperature (or range) at
which significant thermal degradation occurs is reported to be dependent on chemical characteristics and
particle size (Buah et al., 2007). As the process takes place in the absence of air, mechanisms such as
airlock, slide gates, and screw feed can be used to supply MSW continuously to the reactor while
minimizing air intrusion (LASDPW, 2004; Stoller and Niessen, 2009).
The significant differences among the pyrolysis processes are the heating mechanism, a heat source(s)
used to maintain the desired temperature in the pyrolysis reactor, reactor design, and MSW residence
time. Pyrolysis, being an endothermic reaction, requires an external energy source to create and maintain
temperatures needed to decompose the target materials thermally. A majority of the processes use heat
generated from gasification of the char (produced from MSW pyrolysis) at a much higher temperature,
along with the heat from syngas combustion to achieve the desired reactor temperature. In the
Thermoselect process, the MSW in the pyrolysis reactor is directly exposed to the heat from the gasifier,
and the solid residue from pyrolysis is gasified using pure oxygen (Thermoselect, 2003; LASDPW,
2004). The reactor in some processes such as EDDITh and Mitsui R21 is externally heated solely using
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lil'A 600 R-13:304
Organics
(Biodegradable and
non-Biodegradable)
Beneficial
Use I
, Landfill ,
Gas
Cleaning
Clean
Syngas
Treatment
Residues
Mechanical
Processing
•Size Reduction
•Drying
•Removal of
Inorganics
Inorganics
Heat
Syngas
Conditoning/Use
Boiler I
Steam
Turbine
Gas Turbine
I Internal
Combustion
Engine
Refinement
Electricity
Vehicle Fuel
Petrochemicals
Steam
Direct Use (e.g.
Boiler Fuel)
Figure 3-16. A Generalized Process Flow Diagram for Pyrolysis
the flue gasses from syngas combustion and gasification is not utilized in the process. Air heated with
flue gas (from the combustion of syngas and pyrolytic char) is used to heat the pyrolysis reactor to
maintain the temperature needed to sustain the pyrolysis reaction in the Mitsui R21 process (Harada,
2003). Auxiliary fuel sources such as natural gas are used to start the process until the heat produced
from the process is adequate to sustain the desired reactor temperature. Information on the Entech
process is scarce.
Regarding the reactor design, a majority of the processes use a rotary kiln. Some processes use fluidized
bed reactors or a static dram (Igarashi et al., 1984; Sumio et al.? 2004). The provision of recovering
ferrous and non-ferrous metal at the end of the process is a common element in most of the processes
described by Malkow (2004). Metals recovery occurs at the end of the pyrolysis char gasification process
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in the Thermoselect process, and it occurs before the char combustion process in the Mitsui R21 process
(Thermoselect, 2003; Harada, 2003).
The longer pyrolysis process is known as "slow pyrolysis" and is characterized by lengthy residence
times (hours) with an increasing temperature rate until a final temperature is achieved. Shorter residence
times of the waste are usually known as "flash pyrolysis," where the waste is subject to instant high
temperatures instead of steady temperature increases (Baggio et al., 2008; CH2M HILL, 2009). Based on
the limited information available, all the operating MSW pyrolysis plants appear to use the slow pyrolysis
process, where MSW is subjected to pyrolysis for approximately 60 minutes (GEC, 2002; Malkow, 2004;
LASDPW, 2004).
3.7.2 Commercialization Status
Pyrolysis has been commercially used to thermally treat homogenous waste streams such as sawdust, rice
hulls, and wood chips for more than 50 years. Attempts were made to treat MSW in the U.S. and Japan
via pyrolysis from the late 1960s through the late 1970s (Helmstetter and Sussman, 1977; Igarashi et al.,
1984; Stoller and Niessen, 2009). Two of the MSW pyrolysis plants were built in the U.S. in the 1970s: a
1,000-TPD plant in Baltimore, Maryland (by Monsanto based on its patented Landgard process), and a
200-TPD plant in El Cajon, California (by Occidental Research Corporation). Between the late 1970s
and early 1980s, both the plants shut down and were demolished for a variety of reasons, including
significant operational issues (e.g., the failure of refractory lining, operational issue from char slagging for
the Baltimore plant), the inability to achieve the projected throughputs, and the inability to produce
outputs of projected quality (e.g., the calorific value of the liquid fuel from El Cajon plant was
significantly lower than initially expected) (Helmstetter and Sussman, n.d.; Tchobanoglous et al., 1993;
Stoller and Niessen, 2009). A majority of these problems were attributed to heterogeneity of the MSW,
relatively larger particle size of MSW even after shredding, and the abrasive nature of shredded MSW.
Similarly, an 110-TPD demonstration facility in Fondotoce, Italy (which became operational in 1992) and
a plant in Karlsruhe, Germany (which began operating in 1999), both of which used the Thermoselect
process, were closed in 1999 and 2004, respectively (Thermoselect, 2003; IWT, 2007). IWT (2007)
reported that the Fontodoce plant was decommissioned as the project had met its technology development
and optimization goal. GHEJ and GAIA (2006) reported the decommissioning reasons to include
environmental violations such as contamination of nearby lakes with compounds such as chlorine,
cyanide, and nitrogen. Themoselect (2003) indicated that the Karlsruhe plant was closed by the owners
because of business strategy decisions. However, according to GHEJ and GAIA (2006), the plant in
Germany was closed because of failures to meet air emission and wastewater emission standards, an
inability to produce power as projected, an inability to process MSW at its design capacity, and a variety
of operational issues.
A small-scale plant owned by International Environmental Solutions (IES) also began its demonstration
period in Romoland, California. This facility consisted of a waste pre-processing system (to size reduce
waste to less than 2 inches and dry waste to moisture content less than 20%), a pyrolytic gasifier, a
thermal oxidizer for combustion of the syngas, a waste heat recovery unit, a steam turbine, and associated
air pollution control equipment (SWANA, 2011). The U.S. DOE (2011) reported that IES was fined by
South Coast Air Quality Management District (SCAQMD) in 2009 for operating the facility without an
air permit. The facility was recently dismantled and relocated to Mecca (California) for processing tires
on a commercial scale (U.S. DOE, 2011).
Based on a review of the literature and other available resources, 29 operating pyrolysis plants that use
MSW as a feedstock were identified worldwide. The majority of these facilities are located in Europe and
Japan (LCC, 2005; CH2M HILL, 2009). More than 70% of the plants are located in Asia, with 13 out of
21 Asian plants located in Japan. Of the 29 plants, 6 plants are located in Europe with the remaining 2
located in Oceania. No facility is currently operational in the U.S. The U.S. DOE (2011) recently
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completed an environmental assessment of a proposed MSW pyrolysis plant in Wisconsin, and there are a
few more MSW pyrolysis plants under consideration in the U.S. (SWANA, 2011).
Figure 3-17 shows the distribution of different pyrolysis technologies as a function of capacity. The plant
sizes range from 15 metric tons per day (Australia) to 550 tons per day (Kurashiki City, Japan). As
shown, the Entech technology seems to be dominant in facilities with lower throughput (<100 tpd). In
general, Mitsui R-21 and Thermoselect process have been used for a wider range of throughput than
another pyrolysis process. Nineteen out of 29 operating plants became operational since 2000; only 10 of
the current plants were operational before 2000. It should be noted that detailed information on most of
these plants lacks, so the current status of these plants is not reliably known.
w
c
TO
CL
<1)
.Q
E
3
P77Z7A Mitsui R-21
I I Entech
Thermoselect
Other Technologies1
¦
Hf
W\
¦
g
i
A.CP A
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fuel (e.g., alkanes, methanol, Dimethyl Ether), petrochemicals, or electricity (Reaven, 1994;
Thermoselect, 2003; UCR, 2009; Grammelis, 2011). In general, the syngas from operating MSW
pyrolysis plants is exclusively used for electricity generation (URC, 2009). Power generation is
accomplished either by combusting syngas in an internal combustion engine or via combustion of syngas
in a boiler to produce steam, which in turn is used to generate electricity using steam turbines (Harada,
2003; Sumio et al., 2004).
Syngas cleaning, while essential for combusting in an internal combustion engine, is generally not needed
for oxidation or co-firing in boilers (Pytlar, 2010). For example, syngas from the Thermoselect process is
treated to remove chlorinated hydrocarbon, acid gasses, and sulfur compounds before combustion in an
internal combustion engine for electricity generation (Thermoselect, 2003; Sumio et al., 2004; LASDPW,
2004). However, the syngas in the Mitsui R21 process is combusted with pyrolytic char in a boiler
without any pre-treatment. The flue gas from the boiler, in this case, is treated to remove air pollutants
using bag filters, dechlorination bag filters, and catalytic reactors before it is released into the atmosphere;
the solid residues from air pollution control devices are landfilled (Harada, 2003). LASDPW (2004)
reported that the Karlsruhe plant (Germany), which processed 289,000 tons of MSW per year, produced
12.7 MW of power, of which 10 MW was used to meet the plant's electricity needs. Assuming there are
365 operating days per year, the net electricity generation is estimated to be less than 100 kWh per ton of
waste; the facility may not be operating a peak MSW throughput, so the estimate may be lower than the
actual net power output. GHEJ and GAIA (2006) reported that this plant did not produce a net power
output in 2002. The power generation capacities reported by UCR (2009) for different MSW pyrolysis
plants were not analyzed because it is not clear whether the reported numbers correspond to the net or
gross power output.
The quality of solid residue, which in turn is contingent on the process, dictates its end use. For example,
the EDDITh pyrolysis process is reported to produce a char with an energy content of 6878 MBtu per lb
(16 MJ kg1) and therefore can be used as refuse derived fuel (Malkow, 2004). The slag from the Mitsui
R21 process has been reported to be used for the production of asphalt pavement (Harada, 2003). The
slag from the Chiba Recycling Center demonstration project was reported to contain elevated levels of
copper and therefore was used for copper smelting (Sumio et al., 2004). LASDPW (2004b) indicated that
char/slag from a plant in Burgau, Germany, was being landfilled.
3.7.4 Environmental Concerns
Lower emissions and the associated cost compared to combustion are some of the most common potential
benefits cited for pyrolysis, attributed to lower temperatures and significantly reduced flue gas rates due
to no or substantially reduced oxygen/air addition (Li et al., 1998; CH2M HILL, 2009). Air emission data
from MSW pyrolysis operation are scarce because of a limited number of pyrolysis plant operations. The
emission data reported by Chen (2006) from an MSW pyrolysis demonstration plant in California
suggested that the emissions (pounds per ton of MSW feed) for VOCs, particulate matter, and
dioxin/furan from MSW pyrolysis potentially can be greater than the average emissions from MSW
combustion plants; the more significant emissions may be due to inadequate treatment by the air pollution
control devices used for the demonstration plant. UCR (2009) compiled independent compliance air
emission test data from a pyrolysis plant in Nagasaki, Japan (the plant uses the Thermoselect process), a
plant in Toyohashi, Japan (the plant uses Mitsui R21 process), and from a Romoland, California plant for
particulate matter, NOx, SOx, HC1, mercury, and dioxin/furans. The concentrations were reported per unit
volume of flue gas rather than per unit ton of feed MSW. Some data on trace gas constituents of syngas
and their emission factors from laboratory experiments have been published (Garcia et al., 2003).
Similarly, data on the quality and quantity of wastewater and solid residues are scarce.
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3.7.5 Economic Considerations
Information on capital and operating and maintenance costs are lacking due to the small number of
pyrolysis plants. As most of the plants are owned and operated by the technology vendors, cost data are
generally not released, although some estimates of capital and O&M cost have been reported (LCC,
2005). The cost of four MSW pyrolysis facilities, processing a combined sum of 1,500 TPD, was
estimated as $55 million in 1975, or $140 million in 2009 dollars due to inflation at the CPI (Stoller,
2009). The applicability of these numbers is questionable as these facilities, which were constructed 30-
40 years ago, were unsuccessful and shut down.
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4. Impact Assessment Methodology
4.1 Systems-Based Impact Assessment
One of the primary objectives of SHC is the development of a system-based tool(s) that would support
communities in making sustainable decisions pertaining to MSW management options based on a
systematic, comprehensive, coordinated assessment of environmental, economic, and social impacts and
the linkages among these pillars of sustainability. This section discusses, in general, terms, the inputs
needed and methods that could be used to identify and characterize impacts of MSW management
projects. Actual types of impacts and assessment methods associated with particular projects would be
site-specific; tailoring of these methods would be required to fit the technology and region concerned.
The fundamental principle remains: to help communities identify sustainable, materials management
solutions requires the concurrent consideration of the environmental, social, and economic consequences
of each option. The choice of a waste management measure results in a series of linked impacts. It is
necessary to understand the linked impact pathways through which change in one domain (i.e.,
environmental, economic, or social) triggers impacts across other areas, as well as any iterative
consequences within each area that may result in second- or higher-order impacts or cumulative impacts
(Vanclay, 2003).
4.2 Environmental Impacts
Assessment of environmental impacts begins with understanding the MSW management technology to
identify possible pollutants released to each environmental media. After identifying the pollutants
released by each technology and the environmental media to which they are released, conducting an
environmental impact assessment requires understanding the baseline environmental conditions in the
community so that changes in those conditions can be quantified. Questions to be considered include:
What is the existing air quality? What is the prevailing wind direction and wind speed? What are the
nearby bodies of water, and where do they flow? What are the existing land uses and soil conditions near
the facility site? What is the groundwater quality in aquifers underlying the proposed facility? How is
the groundwater used? What are the future resource demands? Next, the estimated pollutant releases
from each technology option can be traced through the environment. Figure 4-1 shows a simplified
diagram of potential pathways through which these pollutants may reach either human or ecological
receptors.
As shown in Figure 4-1, pollutants may potentially be released by MSW management operations to air,
soil, groundwater, or surface water. Pollutants may fall out of the air and be deposited on the ground or
on plants. People or animals may touch the soil or plants, and the pollutants may be absorbed through
their skin. Alternatively, animals or humans may eat the plants (or plants that take up the pollutants from
the soil), and thereby be exposed. If surface water or groundwater is contaminated, people or animals
may drink it. Aquatic animals and plants may absorb the chemicals, and then other animals or people
may eat them. By understanding the amount and toxicity of various chemicals potentially released by a
technology, as well as the different environmental routes by which individuals or animals may be
exposed, and at what levels, potential impacts to human health, ecosystems, and ecosystem goods and
services could be identified, and in turn, the economic and social implications could be determined.
The science and tools for modeling contaminant transport in the environment and assessment of risk to
the environment and human health are moderately developed; the SHC program strives to improve these
further. The key inputs that are needed for risk assessment are environmental emissions (e.g., leachate,
air pollutants) and site-specific hydrogeological and climatic conditions. Apart from environmental
emissions, site, and region-specific hydrogeological meteorological conditions have a significant impact
on the transport of various contaminants and eventual exposure. The TRIO tool should allow estimation
of risk to human health for each technology option based on population density and demographics,
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Surface or
Underground Mine
Milling
Overburden and
Tailings Waste
Management
Air
>
r
Soil
,
Surface Water
i
k
r
Groundwater
Ecological
Receptors
Ingestion and
Direct Contact
Plant
Uptake
Human
Receptors
Ingestion
Figure 4-1. Generalized Contaminant Transport and Exposure Pathways
aggregate chemical exposure, and hydrogeological and meteorological conditions using an accepted
human-health risk assessment methodology. The program should also estimate the impact on ecosystems
goods and services based on current land use and potential effects of various media. For example,
groundwater impact may compromise agricultural land use surrounding the facility.
As discussed in the previous section, environmental emission data for anaerobic digestion, gasification,
and pyrolysis are scarce as these technologies are not yet used on a commercial scale for managing MSW
in the U.S. As the emissions data from facilities using some of these technologies outside the U.S. (e.g.,
anaerobic digestion facilities in Europe, gasification, and pyrolysis plants in Japan) are not readily
available in the existing literature, compilation of these data would require an extensive survey of these
facilities. Although the emissions data from international applications may not be actually applicable to
the U.S., these data would serve as valuable inputs for environmental impact assessment of these
technologies until they are implemented in the U.S. and data from U.S. facilities are available.
A large volume of emissions data is collected and reported for landfills and MSW combustors to
regulatory authorities for compliance purposes. For example, extensive leachate and groundwater quality
data, and surface emission monitoring data from MSW landfills in the U.S. are routinely collected and
submitted to regulatory authorities for compliance purposes. However, these data need to be compiled in
fashion (e.g., as a function of geographic location, liner type, climatic conditions such as rainfall, cells
area) that allows the use of these data in environmental impact assessment of these facilities. Because
emissions (leachate and air pollutants) from composting facilities are not rigorously monitored like MSW
landfills and incinirators, the quantity and quality of emissions data for MSW composting facilities are
limited. An extensive data collection effort would be needed to gather these data.
As missing or lacking data become available for the emerging technologies, this data, and the extensive
data from commonly practiced technologies can be extrapolated conservatively to estimate the emissions
for the emerging technologies based on a thorough understanding of the fundamental processes and sound
engineering judgment. For example, leachate from SSO's anaerobic digestion, which is fundamentally
similar to anaerobic decomposition, is expected to have lower heavy metals concentrations than those of
landfill leachate as the feedstock is source segregated and, therefore, contact with household hazardous
waste is minimized. Use of metal concentrations that is typical of landfill leachate for leachate from
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anaerobic digestion would provide a conservative environmental impact assessment. The uncertainty and
reliability associated with the inputs and outputs should also be factored into the models.
The methodologies (such as life cycle assessment) used for the existing models (Appendix A) can be
utilized as building blocks for the proposed models. The proposed model should have built-in region- and
technology-specific emissions for ease of use as well as the option for a well-informed user to enter user-
specified emissions. The proposed models should be designed to update frequently the default emission
values as more data become available. The environmental impact model would need to be integrated with
the tools to assess the outcomes for environmental, economic, and social aspects based on a common
denominator.
4.3 Economic Impacts
Economic impacts are defined as changes in an economy, relative to baseline conditions, that result from
a new project, policy, or program. The objective of an economic impact analysis is to quantify the
changes in employment, income, and output as a result of an initial change in spending and hiring at the
project. Depending on the dollar value and geographic scale of the project, economic impacts may be
examined for individual industry sectors, local or regional areas, or for the national or international
economy. Different analytical approaches may be appropriate, depending on the size and geographic
scope of the project and the questions the analyst wants to answer.
Incremental expenditures within the region as a result of the purchase, installation, and operation of the
MSW management operation are the exogenous shock that initiates the regional economic impact. The
incremental expenditures may not equate to the engineering costs of the project (described for each
technology option in the previous sections) because only the share of the expenses that occurs within the
region will initiate an increase in the region's level of economic activity. For example, some capital
equipment needed to implement an MSW management measure may be manufactured and purchased
outside the area. Thus, for each MSW management measure under consideration, information about
requirements for resources, labor, and supplies should be captured and used as inputs in the economic
impact assessment.
There are several standard modeling approaches used to analyze regional economic impacts resulting
from a project, policy, or program. Their characteristics, advantages, and disadvantages are listed in
Table 4-1.
Table 4-1. Economic Impact Modeling Approaches
Model Type
Description
Strengths
Weaknesses
Input-Output
Detailed static model of
demand and supply linkages
between all sectors of a
regional economy
Easy to understand; models
and data are commercially
available
Detailed disaggregated
relationships
Provides only a snapshot of
the economy at a point in
time, does not deal well
with big changes to the
economy's structure
Econometric
Statistical relationship
between economic variables
More customizable
Less standardized, data-
intensive
General Equilibrium
Models supply and demand
responses throughout the
economy, through changes in
prices, wages, and taxes
Dynamic, behavioral, can
be non-linear
Complex to build
Relatively aggregated, so
there is less detail
To illustrate the overall approach that can be used to quantify these regional impacts, use of an input-
output analysis is presented as follows. A regional input-output (I-O) model provides a detailed
description of the seasonal pattern of supply and demand linkages between different sectors of the
region's economy, including industry, government, and households. Regional 1-0 models are
commercially available for user-specified areas (see the U.S. Bureau of Economic Analysis' RIMS II
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model [BEA, 2012], or MIG's IMPLAN model [MIG, 2012] as examples), making them relatively easy
to understand and economical to use. If a project has multiple phases (such as construction, operation,
and decommissioning), the economic impacts of each phase should be examined separately. Spending
and hiring at the MSW management facility lead to a feedback loop, as employees spend some of their
incomes within the region, and firms that provide materials and supplies to the facility also increase their
employment in the community and purchase materials and supplies from local businesses. Figure 4-2,
below, illustrates this feedback process.
Figure 4-2. Assessing an MSW Management Facility's Economic Impact
Further, waste management technologies may offer co-benefits including salable products or alternative
energy production. Energy produced by the process can supplement or replace purchased energy,
reducing costs; alternatively, the energy may be sold, generating revenue. The existence of these products
or technologies may attract related firms to the region to make use of those goods or energy, or to produce
complementary goods or services. Each new business that locates within the area sets off its own
multiplier cycle of direct, indirect, and induced impacts.
The first step in estimating the economic implications of a project or program is to understand thoroughly
the costs of the project components required to construct and operate the project, the expected
employment, and the spending that will occur within the region. The regional 1-0 model will divide the
spending into purchases from various industrial sectors, money paid to households in exchange for labor
or land, and money was given to the government in taxes. The change in regional economic activity
should be assigned to appropriate sectors of the local economy (for example, construction or waste
management). These are the direct economic impacts of the project. The 1-0 model can also be used to
quantify the indirect effects (as firms that supply materials or services to the project in turn purchase
materials and supplies from other companies within the local region) and induced impacts (resulting from
increased consumer spending on goods and services within the local area). The total regional impact on
employment, income, and output is equal to the sum of the direct, indirect, and induced effects.
By characterizing the share of each sector's spending on the goods and services provided by other areas
of the regional economy, regional 1-0 analysis enables the analyst to trace the total impact of an initial
spending or employment change due to the project, throughout the region's economy. 1-0 analysis is
based on a detailed snapshot of the purchasing patterns of businesses and consumers throughout the
regional economy at a point in time; as such, it is well-suited to analyzing activities that take place over a
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relatively short period of time and that are small enough, relative to the region's overall economy, that
they do not transform it.
1-0 analysis will estimate changes in state and local government tax receipts resulting from the project's
economic impacts. It is also important to identify and quantify additional responsibilities and costs that
would be incurred by state and local governments to create infrastructure or implement regulatory
systems. Conducting a quantitative analysis of regional economic impacts requires data specific to the
region; thus, this white paper will not analyze the local economic impacts of each management option.
However, the magnitude of economic impacts will depend on the scale of the direct effects shown at the
left of Figure 4-2: the employment and spending at the facility itself, which would be dictated by the
project cost. The U.S. Census Bureau tracks work for various industrial sectors with a North American
Industry Classification System (NAICS) code. Currently, only the solid waste landfill and MSW
combustor sectors have unique NAICS codes and employment by these sectors are individually tracked.
Composting is referenced in some fashion in three different NAICS codes and does not have a stand-
alone NAICS code. Establishment of a unique NAICS code for each technology as it becomes prominent
in the U.S. would allow collection of employment data that would be used as an input for assessing the
economic impact of these technologies.
Detailed cost data (capital as well as O&M), tipping fees, and power sale prices for MSW combustors in
the U.S. were compiled by Berenyi (2012). Given the large number of publicly-owned and operated
landfills in the U.S., a large volume of landfill construction cost data and landfill gas/electricity sale price
data are available in bids and proposals submitted in response to invitation-to-bids by public entities for
constructing various elements of landfills. A compilation of these data along with tipping fees and host
fees (e.g., region-specific, facility size) is needed for use as an input to the overall economic assessment;
the concept of a host fee offer by a landfill developer to a community in exchange for permission to
construct a landfill has become a popular way to ease the siting process (Jenkins et al. 2002). The model
should be able to adjust the cost for factors such as inflation and energy prices (e.g., the landfill gas sale
price is typically dependent on the prevailing natural gas price). For emerging technologies such as
gasification and pyrolysis, MSW combustor cost data can be extrapolated based on a thorough
understanding of the process and sound engineering judgments to complement the scarcely available data
until reliable cost data for emerging technologies are available. The reliability of the inputs should be
factored in decision making as well.
In addition, to accurately assess the effect of a project on a region's well-being, it is necessary to account
for all the interactions and linkages affecting its sustainability, examining all the costs and benefits of
each waste management technology in economic, environmental, and societal terms.
4.4 Social Impacts
Social impacts include consequences to human populations of any public or private actions that alter the
ways in which people live, work, play, relate to one another, organize to meet their needs, and generally
cope as members of society (ICPGSIA, 2003). Social impact assessment (SIA) assesses changes in the
availability or quality of recreation, historical, or cultural sites; neighborhood population or density;
transportation; and other public safety issues that may improve residents' level of satisfaction with their
community. SIA also includes an assessment of the distribution of adverse impacts across different
population groups, such as different income levels, races, or geographic areas.
Variables suggested to measure social impacts include quantitative measures such as percentage changes
in regional population or employment, capacity measures for housing and schools in the community, or
changes in the region's air or water quality; objective qualitative measures such as changes in the
community's demographic profile or per capita income, or the congestion of transportation or recreational
systems; and subjective attitudinal measures such as how comfortable residents feel about the safety of
their environment or the future sustainability of their community.
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Each management technology presented in Section 3 has the potential to affect the community in which it
is located in both positive and negative ways. Among other considerations, communities will be
concerned about whether the proposed facility is compatible with surrounding land uses. On one hand, if
the surrounding area is mainly industrial, the facility likely would not adversely affect its nearby
neighbors. On the contrary, if the area is residential or has cultural or historical sites nearby (e.g.,
recreation venues, museums, historic buildings, schools), the existence of the facility may reduce the
enjoyment the community receives from those sites. The city will also want to know if the facility has the
potential to make a living or working nearby unpleasant due to traffic congestion, noise, or odor. If the
area surrounding the facility has residents or workers who may be exposed to pollutants, it is important to
understand whether they are underserved, minority, or economically disadvantaged, to ensure that the
facility would not pose environmental justice issues. Will the facility increase the region's employment
and income levels? If the facility's labor force is sufficiently specialized that workers may be recruited
from outside the area, this has the potential to affect housing markets, schools, and the availability and
quality of social and emergency services to residents already in the area.
There are two overarching approaches to SIA that reflect diverse approaches to public policy. One
approach is generally followed in the U.S.; the other approach is more common in the rest of the world.
In the U.S., the need for SIA grew out of the National Environmental Policy Act of 1978. This is a
relatively top-down approach to SIA; a governmental agency develops a regulation, and as part of
assessing its impact on the natural environment, examines effects on the social environment.
Stakeholders are informed, and their feedback is requested. Internationally, SIA is part of the
development and ongoing management of projects. Reflecting a consensus-based approach to decision
making, stakeholders are actively involved in policy formulation from the outset. Thus, the international
approach to SIA is a more bottom-up method.
Whether using the more linear, top-down approach typical in the U.S., or the more organic, collaborative
approach described by Vanclay (2003), the overall objectives are similar. Although the particular
application of SIA varies depending on the location and context, SIA is a critical component of SHC's
TRIO approach to impact assessment. Appropriate results considered by SIA include all issues that affect
people, directly or indirectly, to ensure that communities remain sustainable and healthy (Vanclay, 2003).
4.4.1 SIA in the U.S.
The Interorganizational Committee on Principles and Guidelines for Social Impact Assessment
(ICPGSIA, 2003) presents a recommended methodology for SIA in compliance with NEPA. Table 4-2
summarizes the six fundamental principles and guidelines for implementing this approach.
As can be seen from the table, the principles and guidelines require a thorough understanding of the local
region and both the project and its setting, enabling the analyst to identify key issues to assess. They
require the use of appropriate methods, assumptions, and information. Principle 5 calls special attention
to the need to identify not only the efficiency (net benefits) of the proposed project or policy but also its
fairness to various groups of people. The U.S. EPA defines environmental justice as the fair treatment
and meaningful involvement of all people regardless of race, color, national origin, or income with
respect to the development, implementation, and enforcement of environmental laws, regulations, and
policies. In the impact assessment context, Executive Order 12898 instructs federal agencies to conduct
analyses to determine whether their programs, policies, and activities have disproportionately high and
adverse human health or environmental effects on minority or low-income populations. Although
decision-makers will generally be communities rather than federal agencies, a similar assessment should
be conducted. Finally, where potential adverse impacts have been identified, the principles require
identification of appropriate steps to mitigate them.
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Table 4-2. U.S. Principles and Guidelines for Social Impact Assessment
Principle
Guideline
Description
1
Achieve extensive understanding of local and regional settings
1a
Identify and describe interested and affected stakeholders and other parties
1b
Develop baseline information (profiles) of local and regional communities
2
Focus on key elements of the human environment
2a
Identify the key social and cultural issues related to the action
2b
Select social and cultural variables that measure and explain the issues identified
3
Identify methods and assumptions and define significance
3a
Research methods should be holistic in scope
3b
Research methods must describe secondary and cumulative social impacts
3c
Ensure that methods and assumptions are transparent and replicable
3d
Select forms and levels of data collection and analysis appropriate to the significance of the
project
4
Provide quality information for use in decision-making
4a
Collect qualitative and quantitative social, economic, and cultural data sufficiently to describe
usefully and analyze all reasonable alternatives to the project
4b
Ensure that the data collection methods and forms of analysis are scientifically robust
4c
Ensure the integrity of collected data
4d
Gaps in data or information should be filled if at all possible
5
Ensure that any environmental justice issues are fully described and analyzed
5a
Ensure that research method, data, and analysis considers underrepresented and
vulnerable stakeholders and populations
5b
Clearly identify who will win and who will lose, and emphasize vulnerability of under-
represented and disadvantaged populations
6
Undertake evaluation/monitoring and mitigation
6a
Establish mechanisms for evaluation/monitoring of the proposed action that involve agency
stakeholders and/or communities
6b
Where mitigation of impacts is required, provide analyses and assessments of alternative
mitigations
Source: ICPGSIA2003.
Building on these principles, ICPGSIA suggests that a step-by-step process (as outlined is Table 4-3) be
used to implement an SIA (and recommends that interested and affected parties are included in all steps):
Table 4-3. Suggested Process for Implementing and SIA (ICPGSIA, 2003)
Step
Suggested Process
Step 1.
Involve the public
Step 2.
Describe proposed actions and alternatives
Step 3.
Profile the community
Step 4.
Conduct scoping to identify probable impacts
Step 5.
Project estimated impacts
Step 6.
Determine probable response of affected parties
Step 7.
Estimate secondary and cumulative impacts
Step 8.
Recommend changes or alternatives
Step 9.
Plan mitigation, remediation, or enhancement
Step 10.
Develop and implement a monitoring program
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4.4.2 International Practice of SIA
The International Principles for Social Impact Assessment (Vanclay, 2003) presents alternative principles
and guidelines for conducting social impact assessments, as applied elsewhere in the world. The
international approach to SIA goes beyond just describing predicted impacts. Instead, SIA involves
analyzing, monitoring, and managing the social consequences of development (intended, unintended,
positive, and negative). SIA is the process used to assess the social impacts of planned interventions and
develop strategies and systems for the ongoing management of those impacts. Stakeholders are involved
throughout the process. The main purpose of SIA is to "bring about a more sustainable and equitable
biophysical and human environment." This approach to SIA builds on local knowledge promotes
community development and considers the ways in which social, economic, and biophysical impacts are
interconnected. Since SIA identifies impacts in advance, it can help formulate better decisions, and help
identify and implement mitigation measures to minimize costs.
4.5 Summary of Data Gaps for Developing Impact Tools
Based on a cursory review of the existing models to assess the environmental and economic impacts of
MSW management, it appears that a majority of the models assess these aspects individually, and the
outputs do not share a common denominator. For example, the environmental impact may be reported on
annual GHG emissions and the project economics may be reported as the annualized cost. Questions
such as, "is it more sustainable for a community to invest an extra $2 million annually to reduce annual
emissions by 0.5 million metric tons CO2 equivalent" could not be answered with these models.
Integration of these three pillars of sustainability is critical for a system-based impact analysis approach.
The model/tool should be structured such that it can be used by decision makers with a wider range of
educational and training backgrounds. For example, the model should allow the selection and use of
default values for decision-makers with a non-technical background and should be flexible to accept user-
specified inputs by the scientific and technical community. The model should quantify/qualify the risk
and uncertainty associated with the outputs. The model should be structured and programmed for routine
updates based on data and information as these become available.
Table 4-4 presents a list of key inputs for system-based analysis and their availability based on the
discussion presented in the previous section. It should be noted that although a large volume of data on
environmental emissions (e.g., leachate quality, surface emission of landfill gas) are collected by facility
owners for compliance purposes, an extensive effort is needed to compile these data before these can be
used as valuable inputs to TRIO model(s).
Table 4-4. Qualitative Data Availability Rating for Key Assessment Inputs for Different MSW
Technologies
Input
MSW Treatment Technology
Sanitary
Landfilling
Anaerobic
Digestion
Aerobic
Composting
Combustion
Gasification
Pyrolysis
Commercializatio
n Status
High
Low
Medium - High
High
Low
Low
Process
Type/Control
High
Low
Medium - High
High
Low
Low
Pre-treatment
Required?
High
Low
High
High
Low
Low
(continued)
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Table 4-4. Qualitative Data Availability Rating for Key Assessment Inputs for Different MSW
Technologies (continued)
Input
MSW Treatment Technology
Sanitary
Landfilling
Anaerobic
Digestion
Aerobic
Composting
Combustion
Gasification
Pyrolysis
Energy Output
High
Medium
-
High
Low
Low
Major Air
Emissions
High
Low
Low
High
Low
Low
Liquids
Emissions
High
Low
Low
Medium-High
Low
Low
Solid Residuals
High
Low
High
Medium-High
Low
Low
Estimated
Tipping Fee
($/ton)
High
Low
Low
High
Low
Low
Operations Cost
($/ton)
High
Low
Medium
High
Low
Low
Capital Cost
(S/TPD)
High
Low
Medium
High
Low
Low
Land
Requirement
High
Low
High
High
Low
Low
Persons employed
per facility
High
Low
Medium
High
Low
Low
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5. Summary
The consumption of materials in the U.S. and throughout the world has increased tremendously in recent
decades. This tremendous increase has translated into a significant increase in the generation of MSW. A
summary of current practices follows:
¦ Approximately 250 million tons of MSW was generated in the U.S. in 2010. Of this, 65
million tons were recycled, 29 million tons combusted for energy recovery, 20 million tons
composted, and the remainder, 136 tons, was disposed of in the landfills. There are
approximately 1,900 operating landfill in the U.S.. Approximately 70% of the facilities are
publicly owned.
¦ Of the 1,900 operating landfills, approximately 600 beneficially use landfill gas. Generation
of electricity is the most common use while the production of pipeline-quality natural gas and
vehicle fuels (compressed natural gas) is emerging. The economics of a landfill gas
beneficial use project is dictated by natural gas price and federal/state incentives. A recent
decline in natural gas prices is expected to have a significant impact on landfill gas beneficial
use for electricity and pipeline-quality natural gas production. Landfill gas beneficial use
projects are typically owned and operated by private entities.
¦ There are 86 MSW incineration facilities in the U.S., although no new facilities have been
constructed in the past 15 years. Almost all of the MSW incineration plants generate
electricity. The amount of electricity generated is reported to range from 500 kWh to 700
kWh per ton of MSW. The air emissions from incineration plants have decreased
significantly in recent years due to the implementation of the MACT rules. Approximately
65% of all of the plants are privately owned and operated.
¦ Source segregation and composting of organics such as food waste and paper are emerging.
CCWI (2010) found that 121 communities in the U.S. and Canada collect and recycle
residential organics to increase the overall diversion rate from landfilling or incineration. A
majority of these programs are in California (40) and Washington (12). San Francisco's and
Seattle's organic collection and recycling programs are two of the largest programs identified
in this study.
¦ There is only one commercial-scale food-scrap anaerobic digestion facility in the U.S. Eight
upcoming commercial food-scrap AD facilities were identified in various stages of the
planning and construction processes, with projected completion dates ranging from 2012-
2014. More than 200 AD facilities are reported to treat OFMSW/SSOs worldwide; over 190
of these facilities are located in Europe.
Historically, the spectrum of management options and services selected by communities has varied,
ranging from systems where MSW is collected and transported elsewhere for further management to
development and operation of a regional solid waste management facility designed to serve surrounding
communities. The high priority placed on capital costs and cash flow in communities has largely guided
decision making with respect to MSW management technology selection (particularly relative to social
and environmental considerations), which can be attributed to economic considerations being more easily
quantifiable (and therefore understood) by all parties in the decision-making process compared to social
and environmental considerations.
Given the amount of MSW that needs to manage, communities' decisions on materials and methods used
for MSW management have significant economic, social, and environmental implications. It is important
to note that each treatment technology will impact the community in which it is located in both positive
and negative ways. Information needed to determine these impacts will be drawn from the assessment of
the technology and its environmental and economic impacts, and also from characterizing site-specific
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baseline conditions in the community. There are many data gaps in information that are a result of a lack
of compilation of the existing data, or limited data or lack of full-scale implementation of some of the
emerging technologies.
While decision makers may be aware of the idea of the three pillars of sustainability, an examination of
mechanisms normally used to procure and implement MSW management technologies (e.g., bid or tender
documents) suggests that the three pillars of sustainability are not normally acknowledged in a
comprehensive fashion. This may be partly attributable to the lack of tools (or knowledge of existing
tools) to facilitate this type of understanding, but it is noted that in some cases, decisions related to
environmental and social aspects may have been addressed prior to the development of bid or tender
documents.
A variety of models have been developed that largely draw upon the idea of life-cycle analysis to
compare different MSW management scenarios. As noted above, it appears the actual use of such models
by decision-makers is limited. This suggests that a lack of understanding of the existence of these models
and/or a high barrier of entry for a decision maker or decision-making group to understand and employ
current models.
Moving forward, assessing the overall impacts of MSW management measures will require a systematic,
comprehensive, coordinated assessment of environmental, economic, and social factors to understand the
linkages among the issues, overall sustainability, and the ways each measure would affect society's well-
being. In addition to the objective assessment of potential impacts based on the characteristics of the
facility and the surrounding community, social impacts are also affected by the values of the community.
A better understanding of the relationships among the linked impacts, as well as the potential for
cumulative impacts is needed. Additional efforts are needed to provide communities with the data and
tools to adequately assess short- and long-term factors that are vital to determining the environmental,
economic, and social impacts to their community.
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EP-W-09-004
Municipal Solid Waste Management: State of the Practice
Appendix A—Examples of Existing Solid Waste Management Decision
Support Tools
Table A-1. Partial Compilation of Available MSW Management Decision Tools
Model
Description
EASEWASTE
(Environmental
Assessment of
Solid Waste
Systems and
Technologies)
This program models resource use and recovery, and environmental emissions associated
with waste management in a life-cycle context. It considers collection, transports, MRFs,
thermal treatment, composting, anaerobic digestion, landfilling, recycling processes, use-on-
land, material utilization, and energy utilization. The model calculates mass flows and
resource uses and recoveries and provides inventories for emissions to air, soil, surface
water, and groundwater. It uses the EDIP Impact Assessment method. It is available to
researchers, consultants, and authorities after proper training in the use and interpretation of
the model; training takes place in Denmark at DTU (in English).
httD://www.easewaste.dk/index.DhD?ODtion=com frontDaae<emid=1
EnviroPro Designer
This program models end-of-pipe treatment processes, project economic evaluation, and
environmental impact assessment. It assesses water purification, wastewater treatment, and
waste disposal processes; calculates emissions from treatment plants; and tracks the fate of
hazardous chemicals. This model is available for purchase in the U.S.; a functional
evaluation version can be downloaded for free.
httD://www.intelliaen.com/enviroDro overview.html
ISWM (Integrated
Solid Waste
Management Tool)
This model considers the full range of waste streams to be managed and views the available
waste management practices as a menu of options from which waste managers can select
the preferred option based on site specific environmental, economic, and social
considerations. It is available free of charqe to anv interested partv. http://www.iwm-
model.uwaterloo.ca/enalish.html
Integrated Solid
Waste
Management: A
Life Cycle
Inventory, 2nd
Edition (IWM-2)
This model provides a way to assess the environmental and economic performance of solid
waste systems. It considers waste generation and collection, central sorting, biological
treatment, thermal treatment, and landfill and materials recycling. This user-friendly model
comes in Windows format; a user guide and CD are included. Priced at U.S. $285.00.
http://www.wilev.com/WilevCDA/WilevTitle/productCd-0632058897.descCd-description.html
MSW-DST
Municipal Solid
Waste Decision
Support Tool
This model is a downloadable desktop application that can be used to simulate existing
MSW management strategies and analyze future proposed technologies or strategies. The
results calculated include annual cost, energy consumption, air (including GHG emissions)
and water emissions, and impact indicators using EPA's TRACI model. It can model multiple
design options for waste collection, transfer stations, materials recovery facilities, mixed
MSW and yard waste composting, combustion, refuse-derived fuel combustion, and
disposal. The model is highly tailorable to facility and location-specific conditions. The
model is the only known tool of its kind with optimization capability. This capability can be
used to identify, for example, low-cost ways to meet recycling and waste diversion goals,
strategies that maximize potential environmental benefits (e.g., GHG emissions reductions),
strategies for optimizing energy recovery from MSW, and options for reducing criteria air
pollutants, http://www.epa.aov/nrmrl/appcd/combustion/cec models dbases.html#models
https://mswdst.rti.ora/overview.htm
WARM (Waste
Reduction Model)
This model considers source reduction, recycling, combustion, composting, and landfilling. It
calculates emissions in metric tons of carbon equivalent (MTCE), metric tons of CO2
equivalent (MTC02E), and energy units (million BTU). Free downloadable model.
http://www.epa.aov/climatechanae/waste/calculators/Warm home.html
WISARD (Waste-
Integrated Systems
for Assessment of
Recovery and
Disposal)
This program assists in evaluating alternative waste management scenarios. It models
landfilling, incineration, recycling, composting, and anaerobic digestion and includes an LCA
database and an option to purchase additional data sets or collect and create new data sets.
Sensitivity parameters can be applied. A downloadable demo is available in English and
French, https://ecobilan.pwc.fr/uk wisard.php
(continued)
A-1
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EP-W-09-004
Municipal Solid Waste Management: State of the Practice
Table A-1. Partial Compilation of Available MSW Management Decision Tools (continued)
Model
Description
WRATE (Waste
and Resources
Assessment Tool
for the
Environment)
This software compares the environmental impacts of different municipal waste management
systems by using LCAto include the resources used, waste transportation, and operation of
a whole range of waste management processes with their environmental costs and benefits.
It calculates the potential impacts of the stages in the collection, management, and
processing of municipal waste. The calculation takes account of the infrastructure and its
operation as well as any benefits associated with materials recycling and energy recovery.
This model is designed for waste managers in waste disposal, collection authorities, waste
management companies, and other waste service providers, including waste technology
suppliers. A free demo is available; standard and expert versions are available for purchase.
httD://www.environment-aaencv.aov.uk/research/commercial/102922. aspx
A-2
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