Evaluation of Alternative Solid Waste Processing Technologies

8/6/2019 Evaluation of Alternative Solid Waste Processing Technologies

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ACKNOWLEDGEMENTS

CITY OF LOS ANGELES

Evaluation of Alternative Solid Waste

Processing Technologies Report

MAYORAntonio R. Villaraigosa

CITY COUNCILMEMBERS

Ed P. Reyes CD 1 Wendy Greuel CD 2

Dennis P. Zine CD 3 Tom LaBonge CD 4

Jack Weiss CD 5 Tony Cardenas CD 6Alex Padilla CD 7 Bernard Parks CD 8

Jan Perry CD 9 Vacant CD 10

Bill Rosendahl CD 11 Greig Smith CD 12

Eric Garcetti CD 13 Vacant CD 14

Janice Hahn CD 15

BOARD OF PUBLIC WORKS

Cynthia M. Ruiz, President

David Sickler, Vice President

Paula A. Daniels, President Pro-Tempore

Yolanda Fuentes

Valerie Lynne Shaw

BUREAU OF SANITATION

Rita L. Robinson, Director Joseph E. Mundine, Executive Officer

Enrique C. Zaldivar, P.E. Assistant Director Varouj S. Abkian, P.E. Assistant Director

Traci J. Minamide, P.E. Assistant Director


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ACKNOWLEDGEMENTS

Special thanks to Ms. Rita L. Robinson and Mr. Enrique C. Zaldivar for their valuableadvice. This report could not have been completed without the assistance and collaboration

of many dedicated members of the Bureau of Sanitation, Solid Resources Support Services

Division, including:

Alex E. Helou

Carl L. Haase

Richard F.WozniakJavier L. Polanco

Kim Tran

Miguel A. Zermeno

OTHER CITY DEPARTMENTS AND DIVISIONS:

Bureau of Sanitation:Solid Resources Processing & Construction Division

Solid Resources Citywide Recycling Division

Solid Resources Valley Collection Division

Solid Resources South Collection Division

Department of Water and Power

CONSULTANTS

URS Corporation

Alfonso Rodriguez

Dan Predpall

Shapoor Hamid

JDMT, Inc.

Michael Theroux

Sheri Eiker-Wiles & Associates


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TABLE OF CONTENTS

Section Page

EXECUTIVE SUMMARY ...............................................................................................ES-1

1.0 IDENTIFY ALTERNATIVE MSW PROCESSING TECHNOLOGIES .............1-1

1.1 INTRODUCTION ............................................................................................... 1-1

1.2 BUSINESS OBJECTIVES .................................................................................. 1-21.3 EVALUATION METHODOLOGY ................................................................... 1-2

1.4 ALTERNATIVE MSW PROCESSING TECHNOLOGIES .............................. 1-4

1.5 LIST OF TECHNOLOGY SUPPLIERS............................................................. 1-4

2.0 CHARACTERIZE ALTERNATIVE MSW PROCESSING

TECHNOLOGIES...................................................................................................... 2-1

2.1 INTRODUCTION ............................................................................................... 2-1

2.2 THERMAL PROCESSING TECHNOLOGIES ................................................. 2-3

2.2.1 Advanced Thermal Recycling.................................................................. 2-5

2.2.2 Pyrolysis................................................................................................... 2-8

2.2.3 Gasification............................................................................................ 2-15

2.2.4 Plasma Arc Gasification ........................................................................ 2-21

2.3 PHYSICAL PROCESSING TECHNOLOGIES ............................................... 2-24

2.3.1 Refuse Derived Fuel .............................................................................. 2-24

2.3.2 MSW Handling Processes...................................................................... 2-26

2.4 BIOLOGICAL AND CHEMICAL PROCESSING TECHNOLOGIES........... 2-29

2.4.1 Introduction............................................................................................ 2-29

2.4.2 Anaerobic Digestion .............................................................................. 2-31

2.4.3 Ethanol Production................................................................................. 2-34

2.4.4 Biodiesel ................................................................................................ 2-36


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TABLE OF CONTENTS

Section Page

3.2.1 Toward Standardized Permitting and Enforcement................................. 3-2

3.2.2 Renewable Energy Generation ................................................................ 3-3

3.2.3 Life Cycle and Market Assessment ......................................................... 3-5

3.2.4 Current Regulatory Concerns .................................................................. 3-8

3.2.5 Current Status of Definitions ................................................................... 3-9

3.3 REGULATIONS AFFECTING ALTERNATIVE TECHNOLOGY

DEVELOPMENT.............................................................................................. 3-11

3.3.1 Local, State, and Federal Interaction ..................................................... 3-11

3.3.2 California Energy Commission Regulations ......................................... 3-15

3.3.3 California Integrated Waste Management Board Regulations .............. 3-15

3.3.4 Summary of Permitting Requirements................................................... 3-15

3.4 REGULATIONS AFFECTING COMPOST MARKETABILITY................... 3-16

3.4.1 MSW Feedstock Variability .................................................................. 3-17

3.4.2 Process Control Challenges ................................................................... 3-18

3.4.3 Voluntary Quality Control for Compost ................................................ 3-19

3.4.4 Regulatory Oversight Federal ............................................................. 3-203.4.5 Regulatory Oversight State ................................................................. 3-21

3.4.6 Summary ................................................................................................ 3-24

4.0 SCREENING OF ALTERNATIVE MSW PROCESSING TECHNOLOGIES .. 4-1

4.1 INTRODUCTION ............................................................................................... 4-1

4.2 TECHNOLOGY SCREENING CRITERIA ....................................................... 4-14.3 ALTERNATIVE MSW PROCESSING TECHNOLOGY SCREENING.......... 4-2

4.4 WASTE SAMPLING PROGRAM...................................................................... 4-4

4.5 TECHNOLOGY SUPPLIER SCREENING CRITERIA.................................... 4-5

4.6 TECHNOLOGY SUPPLIER SURVEY.............................................................. 4-6

4.7 SCREENED TECHNOLOGY SUPPLIERS....................................................... 4-7


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TABLE OF CONTENTS

Section Page

8.1 SUMMARY OF KEY FINDINGS...................................................................... 8-1

8.2 CONCLUSIONS.................................................................................................. 8-1

8.3 RECOMMENDATIONS..................................................................................... 8-6

8.3.1 Public Outreach........................................................................................ 8-6

8.3.2 Develop a Short List of Suppliers............................................................ 8-88.3.3 Initial Siting Study ................................................................................... 8-8

8.3.4 Preparation of Request for Proposal and Select Preferred Supplier ........ 8-8

8.3.5 Conduct Facility Permitting and Conceptual Design............................... 8-8

8.3.6 Detailed Design and Construction ........................................................... 8-8

GLOSSARY

List of Tables Page

Table ES-1 Key Findings...................................................................................................ES-4

Table ES-2 Recommended Activities for MSW Processing Facility Development

for the City of Los Angeles.............................................................................ES-9

Table 1-1 Classification of MSW Processing Technologies............................................. 1-5

Table 3-1 Summary of Permits Required for a New Solid Waste Processing Facility..... 3-1

Table 4-1 List of Alternative MSW Processing Technologies.......................................... 4-2

Table 4-2 Alternative MSW Processing Technology Evaluation Matrix ......................... 4-3

Table 4-3 Characteristics of Black Bin Contents, City of Los Angeles, 2004.................. 4-8

Table 4-4 Technology Supplier Short List ........................................................................ 4-9

Table 5-1 Thermal Conversion Facilities.......................................................................... 5-7

Table 5-2 Advanced Thermal Conversion Facilities......................................................... 5-9

Table 5-3 Biological Conversion Facilities..................................................................... 5-10


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TABLE OF CONTENTS

List of Figures Page

Figure 6-5 Advanced Thermal Recycling Process Diagram .............................................. 6-8

Figure 6-6 Pyrolysis/Gasification Scenario Illustration ..................................................... 6-9

Figure 6-7 Pyrolysis/Gasification Process Flow Diagram................................................ 6-10

Figure 6-8 Waste Conversion (Anaerobic Digestion) Scenario ....................................... 6-12

Figure 6-9 Anaerobic Digestion Process Flow Diagram.................................................. 6-12

Figure 6-10 Annual Net Energy Consumption by Scenario............................................... 6-15Figure 6-11 Annual Net Pounds of Criteria Air Emissions by Scenario............................ 6-17

Figure 6-12 Annual Net Metric Tons of Carbon Equivalent by Scenario.......................... 6-19

Figure 7-1 Alternative Technologies for Treating Black Bin

Post-Source Separated MSW............................................................................ 7-2

Figure 7-2 Throughput by Supplier (TPY)......................................................................... 7-4

Figure 7-3 Net Electricity Production, MW ....................................................................... 7-6Figure 7-4 Energy Efficiency, Net kWh/Ton ..................................................................... 7-6

Figure 7-5 Diversion Rate, Percent of Throughput ............................................................ 7-9

Figure 7-6 Capital Cost, $/TPY........................................................................................ 7-15

Figure 7-7 Total Revenue/Ton by Supplier ...................................................................... 7-16

Figure 7-8 Estimated Breakeven Tipping Fee and

Worst Case Breakeven Tipping Fee ............................................................... 7-18

Figure 7-9 Objectives Hierarchy ...................................................................................... 7-19Figure 7-10 Total Ranking Score by Supplier.................................................................... 7-26

List of Appendices

Appendix A Master Supply List of Technologies

Appendix B Characterization of Alternative Waste Processing Technologies

Appendix C Europe Facilities Field ReportsAppendix D Life Cycle Analysis Report

Appendix E Supplier Evaluations

Appendix F Alternative Technology RFQ


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LIST OF ACRONYMS AND ABBREVIATIONS

AB Assembly BillAC Alternating Current (Electric)

AD Anaerobic Digestion

ADC Alternative Daily Cover

AQMD Air Quality Management District

ATR Advanced Thermal Recycling

BACT Best Available Control Technology

BETF Break Even Tipping FeeBtu British Thermal Unit

CAP Compost Analysis Proficiency

CARB California Air Resources Board

CCQC California Compost Quality Council

CDFA California Department of Food and Agriculture

CEC California Energy Commission

CEQA California Environmental Quality ActCIWMB California Integrated Waste Management Board

CNG Compressed Natural Gas

CT Conversion Technology

DC Direct Current (Electric)

EPA Environmental Protection Agency

HCl Hydrochloric Acid

HHV Higher Heating ValveHRSG Heat Recovery Steam Generator

kW Kilowatt

kWh Kilowatt hour

lb Pound

LEA Local Enforcement Agencies

LHV Lower Heating Valve

MBtu Million British Thermal UnitsMRFs Material Recovery Facilities

MSW Municipal Solid Waste

MW Megawatt

MWe Megawatt Electric

MWh Megawatt hour


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LIST OF ACRONYMS AND ABBREVIATIONS

OGM Organic Growth MediumPFRP Processed to Further Reduce Pathogens

PM Particulate Matter

PUC Public Utilities Commission

QA Quality Assurance

QC Quality Control

RDF Refuse Derived Fuel

RFQ Request For QualificationsRPS Renewable Portfolio Standard

RSI Report of Site Information

RWQCB Regional Water Quality Control Board

SCAQMD South Coast Air Quality Management District

scf Standard Cubic Foot

SCR Selective catalytic reduction

SNCR Selective non-catalytic reductionSTA Seal of Testing Assurance

SWMP Solid Waste Management Plan

SWPPP Storm Water Pollution Prevention Plan

SWRCB State Water Resources Control Board

TCLP Toxicity Characteristic Leaching Procedure

TMECC Test Methods for the Examination of Composting and Compost

TPD Tons Per DayTPY Tons Per Year

USCC United States Composting Council

USEPA United Stated Environmental Protection Agency

VOC Volatile Organic Compound

WCTF Worst Case Tipping Fee

WDR Water Discharge Requirements


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EXECUTIVE SUMMARY

The City of Los Angeles Department of Public Works, Bureau of Sanitation engaged URSCorporation to conduct an evaluation of alternative municipal solid waste (MSW) processing

technologies to process residential refuse, or post-source separated MSW. The City uses

three bins to collect solid waste from residences: green bin (green waste), blue bin

(recyclables), and black bin (refuse). The green and blue bin material is recycled. The black

bin refuse, or post-source separated MSW, which is landfilled, is the subject of this study.

The study began with development of the Citys overall project objectives. The highest-level

objective is:

Identify alternative MSW processing technologies that will increase landfill

diversion in an environmentally sound manner, while emphasizing options

that are energy efficient, socially acceptable, and economical.

This objective was subdivided into three lower-level objectives:

Maximize Environmental (Siting) Feasibility (i.e., minimize impacts to the environmentand citizens)

Maximize Technical Feasibility (i.e., search for technologies that are commercially

available within the development timeframe of 2005-2010 and will significantly increase

diversion from landfills)

Maximize Economic Feasibility (i.e., provide an overall cost that is competitive with

other solid waste processing methods)

These objectives were applied, through the use of screening criteria, to identify potential

technologies that could meet the Citys objectives. Technologies initially identified were:

Thermal Technologies

Biological/Chemical Technologies

Physical Technologies

Thermal technologies are those technologies that operate at temperatures greater than 400

degrees F and have higher reaction rates. They typically operate in a temperature range of

700 degrees F to 10,000 degrees F. Most thermal technologies are used to produce electricity


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EXECUTIVE SUMMARY

processing carried out in multiple stages. Byproducts can vary, which include: electricity,compost and chemicals.

Physical technologies involve altering the physical characteristics of the MSW feedstock.

These materials in MSW may be separated, shredded, and/or dried in a processing facility.

The resulting material is referred to as refuse-derived fuel (RDF). It may be densified or

pelletized into homogeneous fuel pellets and transported and combusted as a supplementary

fuel in utility boilers.

All of these technologies are described in Section 2.0. The state and Federal regulations

governing the permitting of these technologies is presented in Section 3.0.

Twenty individual alternative MSW processing technologies were included within these

major categories. The technologies were screened using a set of basic technology capability

and experience criteria. Through this process, ten technologies within the technology groups

of thermal and biological technologies were identified that meet the applicable criteria (seeSection 4.3).

About 225 suppliers were screened, and twenty-six suppliers were selected to submit their

detailed qualifications to the City. These qualifications were to include information about the

suppliers experience, descriptions of several reference facilities, and a preliminary

description of a proposed facility for the City of Los Angeles (see Section 5.1).

Of the twenty-six suppliers requested to submit qualifications, seventeen provided responses.

These suppliers and their technologies were thoroughly evaluated (including several site

visits). This evaluation primarily was based upon the information and data contained in the

submittals received. These submittals ranged from very responsive to incomplete. Each

supplier was requested to provide additional information based on an initial review. Tables

5-1 through 5-3 provide a good summary of the information obtained from each supplier.

Additional detail is presented in Appendix E.

The supplier data contained in Section 5.0 and Appendix E were used to prepare a life cycle

analysis associated with implementation of alternative waste processing technologies in the

Citys integrated solid waste management system. This allows the City of Los Angeles to

more accurately compare these new technologies to existing solid waste management


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EXECUTIVE SUMMARY

Finally, the supplier data were used to conduct a comparative analysis of the technologies,and rank the suppliers to select technologies for further assessment. The comparative analysis

addressed a number of technical, environmental, and cost issues, including:

Throughput (respondents provided data for different throughput rates)

Electricity production

Net efficiency in kWh/ton feedstock

Diversion rate

Air emissions

Solid wastes

Regulatory issues

Capital cost Revenues

Estimated tipping fees

A supplier ranking process was employed to help select the most attractive technologies for

treating the Citys black bin post-source separated MSW. Evaluation criteria were defined,

performance levels established, and scores computed to develop a ranking of suppliers and

technologies.

The comparative analysis and ranking is presented in Section 7.0.

FINDINGS

The study evaluated the ability of alternative technologies to process black bin post-source

separated MSW from three perspectives: siting (or environmental) feasibility, technicalfeasibility, and economic feasibility. The results of this evaluation, in part, can be expressed

in terms of key findings that impact the overall study conclusions and recommendations that

follow.

Table ES-1 provides a summary of these key findings. The table is arranged by objective


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EXECUTIVE SUMMARY

Thermal technologies Advanced thermal recycling, and thermal conversion (includespyrolysis, gasification and pyrolysis-gasification)

Biological/chemical Anaerobic digestion

Physical None (Section 4.3)

As a result, the key findings address advanced thermal recycling, thermal conversion, and

biological conversion.

Table ES-1 includes references to report sections where each finding is discussed in more

detail.

CONCLUSIONS

Based upon the key findings from Section 8.1 and the technology ranking presented in

Section 7.4, the following conclusions are made:

An alternative MSW processing facility can be successfully developed in the City of Los

Angeles.

The technologies best suited for processing black bin post-source separated MSW on a

commercial level are the thermal technologies. These include advanced thermal recycling

and thermal conversion (pyrolysis and gasification).

The biological/chemical conversion technologies and physical technologies present

significant technical challenges for treatment of the black bin post-source separated

MSW. While biological conversion technologies show the most promise in this group,

they also bring significant challenges, as explained below.

The technology ranking in Section 7.4 evaluated the thermal and biological technologies

using eight criteria that addressed siting, technical, and economic issues. While the ranking

was conducted using supplier data, the results were used to decide which technology groupsexhibited the best characteristics with regard to successfully processing of black bin post-

source separated MSW.

Based upon the ranking scores in terms of technologies rather than suppliers, the following

l i d


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EXECUTIVE SUMMARY

Initiate Public Outreach

Public acceptability will be one of the most important determinants of this projects success.

Siting, permitting and developing a new alternative MSW processing technology for the City

of Los Angeles will lead to many questions from the public with regard to environmental

impacts and public health issues. The key is to consider the public as a partner and present

the facts and benefits as early as possible while being responsive to their concerns at all

times. Developing early relationships with key stakeholder groups is essential.

The public outreach should be conducted in two phases. The first phase begins in 2005, with

two purposes: educate the public about the alternative MSW processing technologies, and

elicit feedback regarding the publics attitude toward the technologies under consideration.

Education about the characteristics of the technologies, compared to existing disposal

methods, their benefits, and their anticipated environmental impacts are critical tasks. Public

outreach is also important at this stage to provide counterpoint to opposing groups. A

communications strategy in the first phase will access the public in broad terms, to reachlarge audiences, using techniques such as television spots, radio interviews, press

conferences, and editorial pieces. Selected focus groups, as well as meetings with community

leaders, agency personnel knowledgeable about emerging MSW processing technologies,

and environmental groups also would be helpful.

The second phase of public outreach takes place after the technology supplier is selected and

alternative site locations are known. Then the outreach becomes more specific than before,and is focused on the communities, which could be directly affected by the project. The

communications strategy in this phase will use techniques that involve the affected

communities, such as Citizens Advisory Committees and specific neighborhood councils.

Develop a Short List of Suppliers

Prior to issuing a Request for Proposal (RFP) to select a supplier for the alternative MSW

processing technology, a list of suppliers eligible for receiving this RFP will be developed.

This short list will be compiled using the following input:

Results of the supplier evaluation conducted during this study


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EXECUTIVE SUMMARY

Conduct Initial Siting Study

An RFP must be quite specific with regard to site characteristics in order to encourage the

most detailed and complete responses. Potential bidders will want to know more information

about site environmental constraints and availability of infrastructure. This information must

be compiled while the RFP is being prepared.

Prepare a Request for Proposal and Select Preferred Suppliers

A technology supplier must formally be selected for this project. This will be accomplished

by issuing an RFP to selected bidders. The RFP will contain a detailed set of instructions

about how to reply, and will require the bidder to provide a comprehensive design along with

a detailed cost and revenue estimate and information on performance guarantees and

financing. The responses to the RFP will be evaluated, and a preferred supplier will be

selected.

Conduct Facility Permitting and Conceptual Design

Once a technology supplier has been selected, a conceptual design is prepared to support

preparation of required environmental and permit application documents. In parallel, these

environmental documents will be prepared, and submitted to the appropriate agencies for

processing. A series of public meetings will be held during agency review.

Perform Detailed Design and Construction

Finally, the detailed design is prepared, which will support facility construction, followed by

construction, start-up, and initiation of operation. Commercial operation is targeted for 2010.


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SECTION 1.0 IDENTIFY ALTERNATIVE MSW PROCESSING TECHNOLOGIES

1.1 INTRODUCTION

The City of Los Angeles Department of Public Works, Bureau of Sanitation (hereinafter

referred to as the Bureau) engaged URS Corporation to undertake a study of alternative

Municipal Solid Waste (MSW) processing technologies to process residential refuse, or post-

source separated MSW. The City uses three bins to collect solid waste from residences:

green bin (green waste), blue bin (recyclables), and black bin (refuse). The green and blue

bin material is recycled. The black bin refuse, or post-source separated MSW, which is

landfilled, is the subject of this study.

This report, which provides the results of this study, is organized as follows:

Section 1.0 Identify Alternative MSW Processing Technologies

Section 2.0 Characterize Alternative MSW Processing Technologies

Section 3.0 Regulations Affecting MSW Processing Technology Implementation

Section 4.0 Screening Alternative MSW Processing Technologies

Section 5.0 Detailed Assessment of Alternative MSW Processing Technologies and

Suppliers

Section 6.0 Life Cycle Analysis

Section 7.0 Comparative Analysis of Alternative MSW Processing Technologies and

Suppliers

Section 8.0 Conclusions and Recommendations

The first step in the study was to identify a set of technologies that potentially could process

black bin post-source separated MSW generated by the City of Los Angeles. These

technologies are characterized in Section 2.0. The regulatory environment for permitting

alternative waste processing technologies is presented in Section 3.0. Then the technologieswere screened and potential suppliers identified in Section 4.0. Suppliers were brought into

this study to allow more detailed evaluation of technology designs, environmental impacts,

and economics. Note that the study concludes by identifying suitable technologies.

A Request for Qualifications was sent to the potential suppliers and the evaluation of


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1.2 BUSINESS OBJECTIVES

The Bureaus overall objective is to identify alternative MSW waste processing

technologies that will increase landfill diversion in an environmentally sound manner, while

emphasizing options that are energy efficient, socially acceptable, and economical. All of

the evaluation criteria used in this study were derived in part from the project objectives.

These criteria were used to select, screen, and rank the technologies and suppliers.

1.3 EVALUATION METHODOLOGY

The method selected to identify screening and ranking criteria is termed top-down, and

starts with defining the Bureaus project objectives that must be satisfied. These broad

objectives are subdivided to define lower-level objectives. Each level of subdivision results

in further definition. This process ceases when the lowest level entries, or criteria, are

defined.

Criteria, in order to be effective, must be complete, so that all issues are considered;

measurable, so that the criteria can be used in the analysis; and non-redundant, so that

double counting of issues is avoided.

One way to conduct the top-down process to define criteria is to use a device called an

objectives hierarchy. This diagram displays the top-level and lower-level project

objectives, and, if drawn to completion, the criteria. Figure 1-1 shows the business objectives

hierarchy developed for this task.

The top-level objective, as mentioned above, is identify alternative MSW waste processing

technologies that will increase landfill diversion in an environmentally sound manner, while

emphasizing options that are energy efficient, socially acceptable, and economical or, in

short, Identify a Suitable Alternative MSW Processing Technology. This is the overarching

objective.

The second level in the figure shows three sub-objectives: Maximize Siting Feasibility;

Maximize Economic Feasibility; and Maximize Technical Feasibility. If these objectives are

satisfied, the overarching objective will be satisfied. The Bureau specified siting, economics,

and technical issues as key project objectives for deciding upon acceptable technologies for


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The Maximize Economic Feasibility objective is broken down to minimizing cost andmaximizing revenues, and the ability to generate marketable byproducts.

The Maximize Technical Feasibility is separated into Minimize Development Risk and

Minimize Landfill Residuals. These sub-objectives are further divided into maximizing the

use of commercial and late-emerging technologies, maximizing the treatment efficiency of

black bin post-source separated MSW, and the ability to process at least 200 tons per day

(TPD) of feed at a rate approximately equal to one-third (1/3) of one of the six Los Angeles

waste sheds.

At this point, six sub-objectives have been identified, as shown at the lowest level in Figure

1-1. These definitions are still too general for use as screening or ranking criteria. However,

they can be helpful for defining suitable technologies and, subsequently, technology

suppliers.

FIGURE 1-1BUSINESS OBJECTIVES

CITY OF LOS ANGELES ALTERNATIVE MSW PROCESSING STUDY

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1.4 ALTERNATIVE MSW PROCESSING TECHNOLOGIES

For purposes of this study, alternative waste processing technologies can be separated into

three groups or categories:


Biological/Chemical Technologies

Physical Technologies

Thermal technologies operate at temperatures greater than 400F and have higher reaction

rates. They typically operate in a temperature range of 700F to 10,000F. Most thermal

technologies are used to produce electricity as a primary byproduct. Thermal technologies

include advanced thermal recycling and thermal conversion.

Biological/chemical technologiesoperate at lower temperatures and lower reaction rates.They can accept feedstock with high moisture levels, but require material that is

biodegradable. Some technologies involve the synthesis of products using physical chemistry

and chemical processing carried out in multiple stages. Byproducts can vary, which include:

electricity, compost, and chemicals.

Physical technologies involve altering the physical characteristics of the organic portion of

the MSW feedstock. These materials in MSW may be separated, shredded, and/or dried in a

processing facility. The resulting material is referred to as refuse-derived fuel (RDF). It may

be densified or pelletized into homogeneous fuel pellets and transported and combusted as a

supplementary fuel in utility boilers.

Table 1-1 shows the technologies expressed in terms of the three major groups (thermal,

biological/chemical, and physical). These technology groups are then subdivided, into about

twenty technologies.

1.5 LIST OF TECHNOLOGY SUPPLIERS

A list of suppliers was compiled of the alternative waste processing technologies listed in

Table 1-1. This list is reproduced as Tables A-1 through A-4 in Appendix A. The table has

three sections corresponding to the three waste processing technology groups The criteria for


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TABLE 1-1CLASSIFICATION OF MSW PROCESSING TECHNOLOGIES

Technology Group Technology

Advanced Thermal Recycling

Pyrolysis

Pyrolysis/Gasification

Pyrolysis/Steam Reforming

Conventional Gasification Fluid Bed

Conventional Gasification Fixed Bed


Plasma Arc Gasification

Anaerobic Digestion

Aerobic Digestion/Composting

Ethanol Fermentation

Syngas-Ethanol

BiodieselThermal Depolymerization

Biological/Chemical

Catalytic Cracking

Refuse Derived Fuel (RDF)

Densification/Pelletization

Drying

Mechanical Separation

Size Reduction

Physical

Steam Processing/Autoclaving

This list was developed from a number of sources, including the following:

California Integrated Waste Management Board (CIWMB) list included in their report on

conversion technologies

Santa Barbara County list

Riverside County list

City of Alameda list

City of Honolulu list


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Southern California Association of Governments list City of Los Angeles list

In addition, a web search was performed of alternative MSW processing technologies,

concentrating on thermal, biological/chemical, and physical technologies. These results were

added to the list.

Descriptions of the technologies are provided in Section 2.0.


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CHARACTERIZE ALTERNATIVE

SECTION 2.0 MSW PROCESSING TECHNOLOGIES

2.1 INTRODUCTION

The alternative MSW processing technologies identified in Section 1.0 are characterized in

terms of their process description, throughput, feedstock composition, byproducts generated,

and environmental issues. This description is general and only key technology groups are

addressed.

These technologies represent the vast majority of the alternative solid waste processingtechnology suppliers. The technologies addressed in this section are:

Thermal

Advanced Thermal Recycling

Pyrolysis

Pyrolysis/Gasification

Pyrolysis/Steam Reforming

Conventional Gasification Fluid Bed

Conventional Gasification Fixed Bed

Plasma Arc Gasification

Biological/Chemical

Anaerobic Digestion

Aerobic Digestion/Composting

Ethanol Fermentation

Syngas-Ethanol

Biodiesel

Thermal Depolymerization

Catalytic Cracking


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Size Reduction

Steam Processing/Autoclaving

The solid waste processing technologies evaluated in this study include advanced thermal

recycling and a group of technologies commonly referred to as conversion facilities.

Advanced thermal recycling is a second-generation advancement of technology that utilizes

complete combustion of organic, carbon-based materials in an oxygen-rich environment, as

described in Section 2.2.

A conversion facility typically consists of the four components shown in the rectangles of

Figure 2-1.

FIGURE 2-1

ANATOMY OF A CONVERSION FACILITY

ProductionConversionPre-

Processing

PostConversionClean-up &Processing

MSWInput

ByproductsRecyclables

AirEmissions

Solid/LiquidResiduals

Solid/LiquidResiduals

Electricity/Chemicals

The first component involves pre-processing of the feedstock. The purpose of the pre-

i i f ld i i l bl i l ( l l)


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The second component is the conversion unit. This unit will process the prepared feedstock

and generate certain byproducts, which can usually be marketed. In addition, the conversion

unit may produce a small quantity of solid or liquid residuals that could be disposed in a

landfill.

Some conversion units will produce an output that requires another processing step before

use. For example, if a synthetic fuel gas or biogas is generated, the gas will undergo cleaning

and further processing before being used to produce energy in the fourth component. A smallquantity of solid or liquid residuals may be created in this step as well. Other conversion

systems move from the conversion step directly to the production step.

The final output from the conversion unit is used in a production process. In many cases, a

synthetic gas or biogas is input to a power facility that produces electricity for sale into the

power grid. This production unit does produce air emissions and sometimes a small quantity

of solid residual.

Each of these components is described in more detail in the following sections.

2.2 THERMAL PROCESSING TECHNOLOGIES

The thermal processing technologies being considered for this evaluation are technologies

that thermally process MSW.

These technologies include:

Advanced thermal recycling

Pyrolysis

Pyrolysis/gasification

Pyrolysis/steam reforming

Conventional gasification (fixed bed and fluid bed)

Plasma arc gasification


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waste gases flow through an advanced emission control system designed to capture and

recover components in the flue gas, converting them to marketable by-products such as

gypsum (e.g., for wallboard manufacture) and hydrochloric acid (used for water treatment).

The bottom ash and fly ash are segregated, allowing for recovery/recycling of metals from

the bottom ash, and use of the bottom ash as a road base and construction material. The

advanced recycling and emission control systems with recovery/recycling go beyond the

technology utilized at conventional resource recovery plants such as the Commerce Refuse-

to-Energy facility and the Southeast Resource Recovery facility.

Pyrolysis The thermal degradation of organic carbon-based materials through the use of an

indirect, external source of heat, typically at temperatures of 750F to 1,650F, in the

absence or almost complete absence of free oxygen. This thermally decomposes and drives

off the volatile portions of the organic materials, resulting in a syngas composed primarily of

hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4). Some of

the volatile components form tar and oil, which can be removed and reused as a fuel. Mostpyrolysis systems are closed systems and there are no waste gases or air emission sources (if

the syngas is combusted to produce electricity, the power system will have air emissions

through a stack and air emission control system). After cooling and cleaning in emission

control systems, the syngas can be utilized in boilers, gas turbines, or internal combustion

engines to generate electricity or used to make chemicals. The balance of the organic

materials that are not volatile, or liquid that is left as a char material, can be further processed

or used for its adsorption properties (activated carbon). Inorganic materials form a bottomash that requires disposal, although some pyrolysis ash can be used for manufacturing brick

materials.

Gasification The thermal conversion of organic carbon-based materials in the presence of

internally produced heat, typically at temperatures of 1,400F to 2,500F, and in a limited

supply of air/oxygen (less than stoichiometric, or less than is needed for complete

combustion) to produce a syngas composed primarily of H2 and CO. Inorganic materials areconverted either to bottom ash (low-temperature gasification) or to a solid, vitreous slag

(high temperature gasification that operates above the melting temperature of inorganic

components). Some of the oxygen injected into the system is used in reactions that produce

heat, so that pyrolysis (endothermic) gasification reactions can initiate; after which, the


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2.2.1.3 Feedstock Characteristics

The feedstock for advanced thermal recycling systems can be unprocessed MSW or RDF.

Using lower moisture content, RDF improves the heating value of the feedstock, resulting in

higher efficiency and lower throughput per kilowatt-hour (kWh) of electricity generated.Inorder to improve economics and efficiency, facilities can incorporate pre-processing to

remove marketable recyclables, such as paper, plastics, metals, and glass. Pre-processing of

black bin contents (recyclables already being removed) may not yield the benefits seen withmixed MSW.

2.2.1.4 Solid Byproducts

In order to improve the operating performance and efficiency, significant effort is made to

recover recyclables in the pre-processing step, as well as recovering, processing, cleaning,

and recycling bottom ash and slag. Most advanced thermal recycling systems produce apowdery to granular bottom ash. If the grate/furnace system is designed to produce a sintered

ash, it may be more like slag, which is glassy and non-hazardous, and may be able to be used

for making construction materials. Since some hydrochloric acid (HCl) is formed during

combustion (from combustion of chlorine-containing plastics and salt), this can be removed,

cleaned, concentrated, and sold. Sulfur compounds in the MSW are converted to sulfur

dioxide (SO2), which can be separately removed with a lime or limestone scrubber, where the

sulfur dioxide is converted to calcium sulfate (CaSO4), or gypsum. Chemically produced

gypsum is currently sold around the world for use in manufacturing wallboard and cement.

Depending on the local market, the gypsum may be saleable.

2.2.1.5 Environmental Issues

Air emissions are likely to be a key environmental issue for advanced thermal recycling

facilities. In thermal recycling, combustion of MSW is achieved in the presence of a direct

flame and an over-abundance of combustion air to promote the complete oxidation of theincoming waste to form primarily carbon dioxide and water vapor that are emitted along with

the excess combustion air (the portion of the incoming air that is not required for oxidation).

The combustion process can be expected to cause emissions of gas-phase air pollutants and

particulate matter (for which California and National ambient air quality standards have been


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Automated combustion controls and furnace geometry designed to optimize residence

time, temperature, and turbulence to ensure complete combustion.

Selective non-catalytic reduction (SNCR) system in the boiler for reduction of oxides of

nitrogen (NOx) emissions. Selective catalytic reduction (SCR), which is more efficient

than SNCR, would be evaluated for potential feasibility.

Baghouse (fabric filter) with activated carbon injection for removal of trace metals and

trace organics concentrated on the particulate matter.

Scrubber for chlorides/HCl (may produce saleable HCl a commonly used commercial

and laboratory chemical).

Scrubber for SO2 (may produce saleable gypsum a material routinely used in the

cement industry).

Secondary activated carbon for trace organic and metals.

Final baghouse for removal of fine particulate after scrubbers.

All of these emission control systems are well-demonstrated technologies that would be able

to control emissions to levels well below regulatory limits in California.

In addition to air emissions, the key environmental issues relating to constructing and

operating an advanced thermal recycling facility include:

Traffic Facilities must be sized to be economic, which likely will require 100+ trucks

per day to deliver feedstock. Thus, traffic impacts may be significant.

Ash Disposal Advanced thermal recycling systems create about 30% residuals. About

5% of this material will be disposed in a landfill.

Aesthetics and View Corridor These facilities have relatively tall stacks, which may

create visual impacts due to the structure, or plume visibility issues under certainoperating and weather conditions.

To a lesser degree, there will be concerns about noise, dust, and odors.

2 2 2 Pyrolysis


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FIGURE 2-3

TYPICAL PYROLYSIS SYSTEM FOR POWER GENERATION OR CHEMICALS

2.2.2.1.1 Conventional Pyrolysis. Pyrolysis has a long history of industrial use. Pyrolysis

systems utilize a wide range of designs, temperatures, and pressures to initiate pyrolysis

reactions. Typically, pyrolysis systems use a drum, kiln-shaped structure, or pyrolysis tube,

which is externally heated using either recycled syngas or another fuel or heat source, to heat

the pyrolysis tube/chamber. Basically, the organic materials are cooked in an oven with no

air or oxygen present. No burning takes place.

Most organic compounds are thermally unstable. At high temperatures, the organiccompounds volatilize and bonds thermally crack, breaking larger molecules into gases and

liquids composed of smaller molecules, including hydrocarbon gases and hydrogen gas. The

temperature, pressure, reaction rates, and internal heat transfer rates are used to control

specific pyrolytic reactions in order to produce specific products. At lower temperatures,


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CH3 + H CH4

Pyrolysis reactions are endothermic, meaning they require externally supplied heat to occur.

Natural gas, propane, or syngas produced by pyrolysis can be used as a source of external

heat. If the feedstock has a large higher heating value (HHV) measured in Btu/lb, the

pyrolytic process becomes more self-sufficient, and once the process starts, it uses an

extremely small amount of fossil fuel. Also, some partial oxidation (from trapped air as well

as oxygen in the organic compounds, especially when biomass is used) of the methane gasoccurs to form CO, with some CO2 formed as the carbon reacts:

2CH4 + O2 2CO + 4H2

CH4 + 1O2 CO + 2H2O

C + O2 CO

C + O2 CO2

These reactions are exothermic (producing heat), helping to maintain the internal

temperatures required for pyrolysis. Another reaction that occurs is reformation, where the

products of the reactions noted above begin to combine with each other, forming other

reaction byproducts. Two of the common reactions are: 1) where carbon reacts with water to

form carbon monoxide and hydrogen, the main components of syngas,

C + H2O CO + H2 (water-gas reaction)

and 2) where carbon reacts with carbon dioxide to form two molecules of carbon monoxide:

C + CO2 2CO (Boudouard reaction)

These reactions are key to pyrolysis. They produce the constituents of syngas, CO and H 2,which are combustible gases. They also consume oxidized compounds (CO2 and H2O),

which have no heating value in syngas and dilute it. The reactions are endothermic, using the

heat produced in the exothermic reactions noted above, helping to maintain and control the

overall reactor temperature.


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Since inorganic materials do not enter the thermal conversion reactions, energy, which could

be used to produce pyrolysis reactions, is expended in heating up the inorganic materials to

the pyrolysis reactor temperature. The inorganic materials are cooled in cleanup processes,

and heat is lost. Pre-processing is required to remove inorganic materials such as grit, glass,

and metal, and to enhance the homogeneity of the feedstock. Depending on the specific

pyrolysis process, pre-processing may include several of the physical processes described in

Section 2.3.

Since pyrolysis occurs in the absence of oxygen, the feed system and pyrolysis chamber are

sealed and isolated from outside air during the processing. This is accomplished through the

use of inlet and outlet knife-gates, with ram feeders to feed individual plugs of feedstock

into the reactor as the next plug is being fed into the sealed environment.

In the reactor, pyrolysis may occur over a period of time (as much as an hour in a pyrolysis

or degassing chamber) or very quickly, as in the case of flash pyrolysis, where thefeedstock encounters an extremely hot internal surface and volatilizes in less than a second.

Slow pyrolysis is used to maximize the production of char, as in the case of producing

charcoal or activated carbon. In those cases, the volatile fraction may be vented or used

elsewhere. Slow pyrolysis is used to convert low volatile coal to metallurgical grade coke for

steel making. Coke is a very pure carbon product, which is then used to initiate a reducing

atmosphere for converting iron ore to molten iron.

Following the pyrolysis reactor, the syngas may be:

Burned directly in a thermal oxidizer or boiler, and its heat recovered for making steam

for power generation. The exhaust gases then pass through emission control systems that

may include fabric filters, wet and dry scrubbers, electrostatic precipitators, and/or

activated carbon beds.

Quench cooled, cleaned in emission control systems, and then burned in a boiler,

reciprocating engine, or gas turbine for power generation.

Quench cooled, cleaned in emission control systems, and then utilized for producing

organic chemicals.


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2.2.2.1.2 Pyrolysis/Steam Reforming. Figure 2-4 presents a typical process description for

a pyrolysis/steam reforming facility.

FIGURE 2-4

TYPICAL PYROLYSIS/STEAM REFORMING SYSTEM

FOR POWER GENERATION

Since the pyrolysis reactions result in the formation of char, liquids, and/or gases, additional

reactions can be initiated to further the thermal breakdown of these organic compounds. One

of the common reactions to follow pyrolysis is steam reforming. As noted below, the water-gas reaction is used to promote the reaction of carbon and water to form syngas. In this

manner, the char produced in pyrolysis is reacted with steam that is injected into the process

so that:


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The syngas stream is then cooled, cleaned, and used for power generation or chemical

production.

2.2.2.2 Throughput

Existing pyrolysis systems treat up to 300 tpd with pyrolysis/steam reforming systems

operating at 165 tpd. Systems are modular and can be installed in parallel to increase

throughput.


Pyrolysis systems can process a wide range of carbon-based materials. Any organic or

thermally degradable material can be processed by pyrolysis. Historically, pyrolysis was used

to make charcoal from wood. Pyrolysis also is used to process used tires and produce carbon

black, steel, and fuel to generate power. Currently, some manufacturers are using pyrolysis to

make activated carbon using coconut shells or wood as feedstock. If a homogeneous

feedstock is processed by pyrolysis, a high quality byproduct is produced.

MSW is not a homogenous waste stream. In order to make the pyrolysis process more

efficient, pre-processing of MSW is required. The pre-processing includes the separation of

thermally non-degradable material such as metal, glass, and concrete debris. Also, for some

pyrolytic processes, size reduction and/or densification of the feedstock may be required. If

MSW has a high moisture content, a dryer may be added to the pre-processing stage to lowerthe moisture content of the MSW to 25% or lower, because lower moisture content of the

feedstock increases its heating value and the system becomes more efficient. The waste heat

or fuel produced by the system can be used to dry the MSW.


The solid byproducts from pyrolysis are mainly carbon char, silica, metal, and non-thermally

degradable material such as glass. In the case of low temperature pyrolysis, where liquid fuel

is the byproduct, a tar or viscous material is also produced. The carbon char from processing

MSW can be used as fuel, additives to construction materials, or for other industrial

purposes. The carbon char produced by pyrolysis can be activated using the steam generated

b h l i Th i d b b d i f ili i


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thermal conversion technologies, they may have inherently lower air emissions and thus offer

environmental benefits when compared to advanced thermal recycling facilities. These

design and operation characteristics include:

Since pyrolysis and gasification processes occur in a reducing environment, typically

using indirect heat, and without free air or oxygen, or with a limited amount of air or

oxygen, the formation of unwanted organic compounds or trace constituents is

minimized.

Pyrolysis and gasification reactors are typically closed, pressurized systems, so that there

are no direct air emission points. Contaminants are removed from the syngas and/or from

the flue gases prior to being exhausted from a stack.

Thermal conversion technologies often incorporate pre-processing subsystems in order to

produce a more homogeneous feedstock; this provides the opportunity to remove

chlorine-containing plastics (as recyclables), which could otherwise contribute to theformation of organic compounds or trace constituents.

The volume of syngas produced in the conversion of the feedstock is considerably lower

than the volume of flue gases formed in the combustion of MSW in advanced thermal

recycling facilities. Smaller gas volumes are easier and less costly to treat, and allow for

the use of a wider variety of control technologies.

Pre-cleaning of the syngas is possible prior to combustion in a boiler, and is requiredwhen producing chemicals or prior to combustion in a reciprocating engine or gas turbine

in order to reduce the potential for corrosion in this sensitive equipment. Syngas pre-

cleaning serves to reduce overall air emissions.

Syngas produced by thermal conversion technologies is much more homogeneous and

cleaner-burning fuel than MSW.

Air emission control and processing systems that are likely to be required by South Coast AirQuality Management District (SCAQMD) include some or all of the following:

When the syngas is combusted in a boiler, reciprocating engine, or gas turbine, automated

combustion controls and furnace geometry (for boilers) designed to optimize residence


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Activated carbon injection (followed by a baghouse) for removal of trace metals (such as

mercury).

Wet scrubber for removal of chlorides/HCl (may produce saleable HCl).

Wet, dry, or semi-dry scrubber for SO2 (may produce saleable gypsum).

Final baghouse for removal of fine particulate matter after dry or semi-dry scrubbers.

Air emission control equipment to accomplish this syngas and/or flue gas cleanup is

commercially available, and is able to reduce air emissions to levels well below regulatory

limits in California.

In addition to air emissions, the key environmental issues relating to constructing and

operating a pyrolysis facility include:

Traffic If the facility is not located at an existing waste management facility (e.g.,transfer station), some traffic impacts will occur due to delivery of feedstock.

Solid residue management Inorganic constituents may be produced as bottom ash or

slag, depending on the temperature in the reactor. Bottom ash, if not sold, can be

disposed in a landfill. Slag, which is glassy and non-hazardous, is typically sold for the

uses noted above. If markets are not available, it can be safely landfilled.

Visual and Land Use There may be impacts relating to the visual character of thefacility or issues relating to compatibility of the facility with surrounding land uses.

As with other facilities handling MSW, there will be concerns about odors, litter, noise,

and dust.

2.2.3 Gasification

2.2.3.1 Process Description

Figure 2-5 presents a process description for a typical gasification system. Individual process

components are discussed below.

2 2 3 1 1 Conventional Gasification Conventional gasification involves the partial


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FIGURE 2-5

TYPICAL GASIFICATION SYSTEM FOR

POWER GENERATION (2 OPTIONS) OR CHEMICALS

The Fischer-Tropsch process was developed to take syngas from gasification of coal and

convert it to a wide range of hydrocarbon liquids, including diesel. After WWII, the use of

gasification declined as oil and gasoline became cheaper and more available.

The use of gasification for MSW began in the 1980s in Europe and Japan. In these initial

units, the use of unprocessed MSW resulted in many technical problems, primarily due to the

heterogeneous nature of MSW. This caused handling and feeding problems, as well as issueswith temperature and process control, ash removal, and overall cost. Many of these facilities

were shut down. With the worldwide success in coal and petroleum coke gasification, and

regulatory requirements in Europe and Japan for increased diversion of MSW from landfills,

gasification became an alternative treatment technology for MSW. Most of the development


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by shredding and sorting. Others may require a significant amount of removal of recyclables,sorting, shredding, and drying, in order to provide a more homogeneous feedstock.

In the gasifier, the addition of air or oxygen for gasification of the MSW leads to a small

amount of combustion, forming some CO2 and releasing heat, which is used in progressing

the pyrolytic reactions:

C + O2

CO2

A significant amount of the heating value of the feedstock is used in this reaction. Utilizing

heat, the organic compounds in the feedstock begin to thermally degrade, forming the

pyrolysis gases, oils, liquids and char. As these products move through the bed or

downstream through the gasifier, they encounter air, oxygen, and/or steam, which are

injected to further the gasification reactions. Endothermic water-gas and Boudouard reactions

occur:

C + H2O CO + H2 (water-gas reaction)

Some of the carbon may react with the hydrogen, forming additional methane gas.

C + 2H2 CH4 (methanation reaction)

C + CO2 2CO (Boudouard reaction)

The Boudouard reaction is important in converting the CO2 from the partial combustion,

which has no heating value and dilutes the syngas, into CO, which is a primary component of

the syngas.

If air is used instead of oxygen, the syngas will include the nitrogen gas that enters with the

air, diluting the syngas and lowering its overall heating value. Gasifier designs are optimized

to feedstock and to specific reaction products. Additional water or steam can be injected toinitiate the water-gas shift reaction, which converts the CO formed in the water-gas and

Boudouard reactions to CO2, and then results in the production of a syngas stream higher in

hydrogen concentration:


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In fixed-bed gasifiers, the feedstock is usually fed through the system on a stationary ormoving grate. The air or oxygen is injected either up, down, or in a cross flow. In an updraft

gasifier, the air or oxygen is injected from the bottom and the syngas exits at the top. In a

downdraft design, the air enters at or near the top of the gasifier, and the syngas exits the side

or bottom.

In a fluid bed design, the gasifier is filled with inert particles (usually sand or alumina). The

feedstock is fed either directly into or above the bed. A high velocity gas, usually oxygen orair, is injected below the bed, causing the feedstock and inert particles to be suspended in the

bed. The feedstock and bed materials are continuously stirred, resulting in uniform

temperatures and reactions, and improved heat transfer. Bubbling bed and circulating fluid

bed designs are commonly used to enhance fluidization and turbulence.

Entrained flow gasifiers use large quantities of oxygen injected from the top or side of the

reaction chamber to create higher operating temperatures. This process is capable ofproducing a cleaner, tar-free syngas while keeping the gasified byproducts in a molten state,

allowing for easier disposal. This slag is both inert and virtually carbon free.

Following the gasifier, the syngas may be:

Burned directly in a thermal oxidizer or boiler, and its heat recovered for making steam

for power generation. The exhaust gases then pass through emission control systems that

may include fabric filters, wet and dry scrubbers, electrostatic precipitators, and/oractivated carbon beds.

Quench cooled, cleaned in emission control systems, and then burned in a boiler

reciprocating engine or gas turbine for power generation.

Quench cooled, cleaned in emission control systems, and then utilized for producing

organic chemicals.

If low temperature gasification is used, the inorganic materials in the feedstock will be

recovered as a powdery to clinker-like bottom ash. This can be disposed of or used for the

manufacture of block materials. If high-temperature gasification is used (typically above

about 2,000F), the inorganic materials will be subjected to temperatures above their melting


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pyrolysis or degassing chamber is pushed into the gasification chamber where the char andany pyrolysis liquids are gasified. While the pyrolysis reactor operates without free oxygen,

the gasification reactor may use air, oxygen, and/or steam to provide the oxygen needed for

gasification reactions. Gasification reactions are mostly exothermic, so that once the

reactions initiate, the process is self-sustaining.

Figure 2-6 presents a typical process description for a pyrolysis/gasification system.

FIGURE 2-6

TYPICAL PYROLYSIS/GASIFICATION SYSTEM FOR POWER GENERATION

2.2.3.2 Throughput

Existing gasification systems operate at throughputs up to 1,000 tpd, with pyrolysis/

gasification systems operating at 800 tpd. Gasifiers and the pre-processing, emission control,

and power generation systems can be installed in parallel to increase throughput and power


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designed for a homogeneous feedstock, although they can tolerate some variability. This canbe an issue with gasifiers that use a slurry feed, since significant changes in the feedstock

result in different slurry characteristics, potentially leading to inefficient gasification and

poor carbon conversion. When changes in the feedstock are anticipated, bench-scale or short-

term testing can be used to optimize gasifier operation.

Due to the heterogeneous nature of MSW, significant pre-processing is often required. While

some systems state that they can operate with little or no pre-processing, most includemanual picking for large appliances, followed by primary and secondary rotary/stationary

trommel screens, primary and secondary shredders, air classifiers, and magnetic and eddy-

current separators to remove glass and metals and reduce the feedstock size. Sizing/shredding

varies, with feedstocks ranging from 2 to 12 inches. Many systems incorporate an auger or

ram feeder that compacts the processed MSW feed to as little as 1/10th

of the original

volume. In order to increase efficiency, some systems incorporate drying to 10-20% moisture

content, using steam or engine exhaust. Depending on the supplier, as much as 2/3 of rawMSW may be removed prior to being fed into the gasifier.


In low temperature gasification (below the melting point of most inorganic constituents), a

powdery to clinker-type of bottom ash is formed. In high temperature gasification, the

inorganic ash materials exit the bottom of the gasifier in a molten state, where the slag falls

into a water bath, and is cooled and crystallized into a glassy, non-hazardous slag. The slag is

crushed to form grit that can be easily handled. Slag can be used in the manufacture of

roofing tiles, sandblasting grit, and as asphalt filler. Bottom ash may require landfilling,

although some suppliers have been able to manufacture ceramic-like bricks or paving stones.

One system that utilizes oxygen injection creates extremely hot temperatures in the bottom of

the gasifier, reaching the melting temperature of some metals. In that process, metals can be

recovered in ingot form.


With regard to air emissions, the most important environmental issue for gasification, the

discussion in Section 2.2.2.5 applies here as well.


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sold, can be disposed in a landfill. Slag, which is glassy and non-hazardous, is typicallysold for the uses noted above. If markets are not available, it can be safely landfilled.

Visual and Land Use There may be impacts relating to the visual character of the

facility or issues relating to compatibility of the facility with surrounding land uses.

As with other facilities handling MSW, there will be concerns about odors, litter, noise,

and dust.

2.2.4 Plasma Arc Gasification


Figure 2-7 presents a typical process description for a plasma arc gasification system.

FIGURE 2-7

TYPICAL PLASMA GASIFICATION SYSTEM FOR POWER GENERATION

Plasma is a hot ionized gas resulting from an electrical discharge Plasma technology uses an


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occurred for using plasma technology integrated with gasification technologies to processMSW. This has great potential to convert MSW to electricity more efficiently than

conventional pyrolysis and gasification systems, due to its high heat flux, high temperature,

almost complete conversion of carbon-based materials to syngas, and conversion of inorganic

materials to a glassy, non-hazardous slag.

There are two types of plasma torches, the transferred torch and the non-transferred torch.

The transferred torch creates an electric arc between the tip of the torch and either a metalbath or the conductive lining of the reactor vessel wall. In a non-transferred torch, the arc is

produced within the torch itself. Plasma gas is fed into the torch, heated, and then exits

through the tip of the torch.

There are several approaches to the design of plasma gasification reactors. In one approach,

developed by Westinghouse Plasma Corporation (plasma torch manufacturer) and Hitachi

Metals (plasma gasification system developer and user), a medium pressure gas (usually air

or oxygen) flows through a water-cooled, non-transferred torch, outside of the reactor. The

hot plasma gas then flows into the reactor to gasify the MSW and melt the inorganic

materials.

Another design is an in-situ torch, where the plasma torch is placed inside the reactor. This

torch can either be a transferred or non-transferred torch. When using a transferred torch, the

electrode extends into the gasification reactor and the arc is generated between the tip of the

torch and the molten metal and slag in the reactor bottom or a conducting wall. The low-

pressure gas is heated in the external arc. Alternatively, a non-transferred torch can be used

for creating plasma gas within the torch, which is injected into the reactor.

Several suppliers utilize a completely different approach. In these designs, the reactor is

heated by electric induction coils or an electric arc produced by graphite rods, forming a

molten metal and slag bath. The MSW enters the reactor, where it is subjected to high

temperatures, resulting in partial gasification of the feedstock. From there, the syngas exitsthe reactor. The plasma torch is situated either in a secondary reactor or in a recycle line,

which goes back to the first reactor, assuring complete gasification of the feedstock.

Proponents of the in-situ torch claim its advantages include better heat transfer to MSW and



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The first two approaches have been applied to small-scale commercial waste and medicalwaste processing units. The throughput of the largest external system is approximately four

tons/hour and the throughput of the largest internal system is approximately ten tpd. The

Westinghouse/Hitachi design has been scaled up to 83 tpd per reactor at Utashinai, Japan,

which treats a combination of MSW and auto shredder residue.

Plasma arc gasification typically occurs in a closed, pressurized reactor. The feedstock enters

the reactor, where it comes into contact with the hot plasma gas. In some designs, severaltorches arranged circumferentially in the lower portion of the reactor help to provide a more

homogeneous heat flux. When used for gasification, the amount of air or oxygen used in the

torch is controlled to promote gasification reactions.

Syngas can either be burned immediately in a close-coupled combustion chamber or boiler,

or cleaned of contaminants and used in a reciprocating engine or gas turbine. In the first

approach, the exhaust gases are cleaned after combustion, in an emission control system. Hot

gases flow through the boiler, creating steam used for power generation in a conventional

steam turbine. In the second approach, the syngas is cleaned before it enters the engine or gas

turbine.

As noted above, the primary solid output from plasma facilities is a glassy slag, the result of

melting the inorganic fraction of the waste. Any waste processing facility generating an ash

or slag is required by the United States Environmental Protection Agency (USEPA) to

subject it to a Toxicity Characteristic Leaching Procedure (TCLP) test. The TCLP test is

designed to measure the amount of eight elements that leach from the material being tested.

Data from existing facilities, even those processing highly hazardous materials or medical

waste, show results that are well below regulatory limits.

While there are only a few plasma torch manufacturers, there are over a dozen companies

that have taken the plasma technology and are developing it for use in MSW gasification.

This has led to several suppliers claiming the same operational experience; i.e., severalsuppliers that incorporate Westinghouse plasma torches claim the experience in the Hitachi

Metals plants as being their own or representative of how their system would perform.

2.2.4.2 Throughput



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2.2.4.4 Byproducts

Byproducts of plasma gasification are similar to those produced in high-temperature

gasification, as noted above. Due to the very high temperatures produced in plasma

gasification, carbon conversion nears 100%.


With regard to air emissions and other environmental issues, the most importantenvironmental issue for gasification, the discussion in Section 2.2.2.5 applies here as well.

2.3 PHYSICAL PROCESSING TECHNOLOGIES

2.3.1 Refuse Derived Fuel


Figure 2-8 presents a typical process description for a Refuse Derived Fuel (RDF) system.

FIGURE 2-8

TYPICAL RDF SYSTEM

Dryer

Raw MSW

Metals

Glass

Paper

Plastics

Separation of

Recyclables

Moisture

Sizing

ShreddingDensification

Pelletized

RDF

RDF



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The RDF process typically includes thorough pre-separation of recyclables, shredding,drying, and densification to make a product that is easily handled. Initial processing includes

field-based manual picking and removal of white goods and other large ferrous materials.

Glass and plastics are removed through manual picking and by commercially available

separation devices commonly found in Material Recovery Facilities (MRFs). This is

followed by shredding to reduce the size of the remaining feedstock to about eight inches or

less, for further processing and handling. Magnetic separators are used to remove ferrous

metals. Eddy-current separators are used for aluminum and other non-ferrous metals. Theresulting material contains mostly food wastes, non-separated paper, some plastics

(recyclable and non-recyclable), green wastes, wood, and other materials. Reduction of about

50% of the inlet MSW feed can be accomplished through initial RDF processes.

Drying to less than 12% moisture is typically accomplished through the use of forced-draft

air. Steam from an adjacent boiler can be utilized if RDF is being combusted on-site in a

waste-to-energy facility. Additional sieving and classification equipment may be utilized toincrease the removal of contaminants. After drying, the material often undergoes

densification processing such as pelletizing or cubing to produce a pellet or cube that can be

handled with typical conveying equipment and fed through bunkers and feeders.

The RDF can be immediately combusted on-site or transported to another facility for burning

alone, or with other fuels. The densification is even more important when RDF is transported

off-site to another facility, in order to reduce volumes being transported.

2.3.1.2 Throughput

Existing systems operate at an extremely high throughput, typically with several lines each

can be rated at 1,000 tpd.


Raw MSW is used as the feedstock to RDF plants. Removal of large appliances, batteries,

and other items is required so that downstream equipment as described below can be

operated efficiently.

2 3 1 4 Solid Byproducts



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concern would be the control of fugitive dust (PM10) generated from the mechanicalequipment during the materials separation process and the generation of potential odors.

Because of the fugitive nature of these emissions, the most effective emissions controls are

minimization of mechanical drop distances, adequate ventilation, and capture of emissions

from handling points and effective emissions controls, using baghouse filtration systems and,

if necessary, activated carbon systems for organic and odor emissions abatement.

RDF systems are typically quite large in throughput. Therefore, an important environmentalissue is traffic impact due to the number of trucks delivering MSW. Other environmental

issues associated with RDF systems typically involve nuisance issues such as noise and litter.

2.3.2 MSW Handling Processes

There are many processes for handling MSW. These processes are common in transfer

facilities and MRFs. Similar processes are employed for preparing conversion facility

feedstock for treatment.

2.3.2.1 Drying

A wide range of drying technologies is commercially available, including:

Rotary dryers

Rotary kilns

Fluid bed dryers

Dryers can use steam or a combustion source such as firing diesel oil or natural gas for direct

contact drying. Indirect contact drying, using a heat exchanger, allows for a wide range of

heat sources that do not come into contact with the MSW, although the result tends to be less

efficient than direct contact drying. Dryers are commercially available and single dryers can

be installed in parallel to process several thousand tpd.

2.3.2.2 Mechanical Separation

Mechanical separation is utilized for removing specific materials or contaminants from the



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Trommel screens

Sieves

Grizzlies

Vibrating screens

Centrifuges

Air classifiers

Magnetic separators (for ferrous materials)

Eddy-current separators (for non-ferrous materials)

2.3.2.3 Size Reduction

Size reduction is often required to allow for more efficient and easier handling of materials,

particularly when the feed stream is to be used in follow-on processes. These processes help

to isolate contaminants and specific materials, particularly large appliances and tires. Sizing

processes include passive, moving, and vibrating screens, trommels, and grizzlies. In order to

reduce the size of the entire stream, or portions of it, mechanical equipment, such as

shredders, is utilized. This allows for other physical processes, such as dryers, magnetic and

eddy current separators, and densification equipment to work more efficiently. Magnetic and

eddy current separators may be installed both up- and down-stream of shredders to increase

the recovery of metals.

2.3.2.4 Densification

A wide range of commercially processes and equipment are available for densification.

These processes can be part of an RDF facility, as described above, or used separately for the

preparation of MSW into a more easily handled feedstock. Densification processes include:

Pelletization

Cubing

Extrusion



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All of these processes are well proven in other industries for metallurgical, animal andmedical wastes, agricultural products, biomass, and minerals, as well as RDF production.

These densification processes can easily be used with MSW. As long as the MSW undergoes

some type of pre-processing to remove metal and glass, some plastics can be handled.

Product sizing and form are dependent on the technology chosen. For example, pelletization

may result in short, long, small, or large pellets. Disc agglomerators form round to oval

pellets, with size dependent on feed characteristics and moisture content.

2.3.2.5 Steam Processing/Autoclaving

Several technologies are available for steam processing and autoclaving MSW. A typical

process is shown in Figure 2-9. Steam Processing takes raw MSW (or MSW with minimal

processing) and subjects it to low or medium pressure steam in a closed, rotating pressure

vessel. The high-temperature steam breaks down cellulosic materials and sterilizes the entire

feed stream. The product material exits the steam pressure vessel or autoclave as a recyclable

or usable fiber, which can be used for:

Fiber board

Door and wall paneling

Insulation

Roofing tiles and shingles

FIGURE 2-9

TYPICAL STEAM PROCESSING/AUTOCLAVE PROCESS

Physical

SeparationProcesses

Raw MSW

Autoclave

Sterilized Cellulosic Fiber

De-Labeled Cans and BottlesVolume Reduction ~ 1/3



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Cans and bottles are de-labeled. Plastics typically are slightly melted, resulting in significantvolume reduction.

The MSW stream is reduced in volume by about one third. From there, the sterilized product

can be further processed using one or more of the physical processes described above. Some

processes take the autoclaved product to pyrolysis or gasification.

Existing systems typically load 25-30 tons at a time, and process it for 30-45 minutes. With

loading and unloading time, an autoclave can process about 15

Documents

Evaluation of Alternative Solid Waste Processing Technologies