Combustion Emissions from Hazardous
Waste Incinerators, Boilers and Industrial
Furnaces, and Municipal Solid Waste
IncineratorsResults from Five Star Grants
and Research Needs
December 2006
&EPA
United States
Environmental Protection
Agency
-------
Combustion Emissions from Hazardous Waste
Incinerators, Boilers and Industrial Furnaces,
and Municipal Solid Waste Incinerators-
Results from Five STAR Grants and Research Needs
December 2006
U.S. Environmental Protection Agency
Office of Research and Development
National Center for Environmental Research
Washington, DC
-------
[this page intentionally left blank]
-------
DISCLAIMER
The research described in this document has been funded wholly by the United States
Environmental Protection Agency (EPA) under the Science to Achieve Results (STAR) grants
program. The information presented in this report is intended to provide the reader with insights
about the progress and scientific achievements of STAR research grants within a broader context.
This report could be used for decision-making about future investment in combustion research.
Readers who are interested in obtaining more specific information about any of the individual
projects described herein should read the peer-reviewed publications produced by those STAR
grants. Mention of trade names or commercial products does not constitute endorsement or
recommendation by EPA for use.
This report has undergone external peer review.
December 2006
-------
ACKNOWLEDGMENTS
The primary contributors to this report are the Principal Investigators of the five grants
that are discussed herein: Philip Taylor and Richard Striebich of the University of Dayton; Barry
Bellinger and Slawomir Lomnicki of Louisiana State University; Selim Senkan of the University
of California-Los Angeles; Kenneth Smith of the Massachusetts Institute of Technology; and
Hacene Boudries of Aerodyne Research, Incorporated. Bob Holloway of EPA's Office of Solid
Waste provided guidance on the development of this report and reviewed drafts of it. He also
participated in the EPA-Air and Waste Management Association (AWMA) Information
Exchange in Research Triangle Park (RTF), NC. Bob Wayland, Walt Stevenson, and other staff
of EPA's Office of Air Quality Planning and Standards reviewed relevant sections of the report
and provided essential information.
Bob Hall, Chief of the Combustion Research Branch of EPA's National Risk
Management Research Laboratory (NRMRL)-RTP, arranged the EPA-AWMA Information
Exchange and the American Flame Research Committee Meetings at which the Office of
Research and Development (ORD) extramural and in-house combustion research was presented
and there were discussions of research needs. Paul Lemieux of NRMRL-RTP co-chaired the
sessions that presented this ORD extramural and in-house combustion research at the AWMA
National Meeting in Anaheim, CA, and at the EPA-AWMA Information Exchange in RTF, NC.
Other EPA staff reviewed drafts of the report; outside experts provided input through interviews.
The sections in this report on the particulate matter (PM) and Resource Conservation and
Recovery Act (RCRA) research programs were provided by Dan Costa, ORD National Program
Director for Air Research, and Patricia Erickson of NRMRL-Cincinnati, respectively. Extremely
insightful and helpful comments on the complete report were provided by Walter Niessen,
President of Niessen Consultants, and JoAnn Slama Lighty, Department of Chemical
Engineering, University of Utah.
Paul Shapiro of EPA's National Center for Environmental Research (NCER) was the
Project Officer for the five grants and provided technical direction for the preparation of this
report. He also co-chaired the sessions at the AWMA Annual Meeting in Anaheim, CA, and the
EPA-AWMA Information Exchange in RTF, NC, and led the discussions of research needs at the
EPA-AWMA Information Exchange and at the American Flame Research Committee meeting.
Mary Wigginton of NCER was the Project Officer and Work Assignment Manager for EPA
Contract No. 68-C-03-137 Work Assignments 00-02 and 01-02 for the preparation of this report
through ICF Consulting, Inc.,Washington, DC, and RTF, NC.
11 December 2006
-------
CONTENTS
Page
DISCLAIMER I
ACKNOWLEDGMENTS ii
EXECUTIVE SUMMARY ES-1
1. INTRODUCTION 1-1
1.1 OVERVIEW OF TYPES OF COMBUSTION SOURCES 1-1
1.2 OVERVIEW OF HAZARDOUS WASTE AND MUNICIPAL SOLID WASTE
COMBUSTION 1-3
1.3 REGULATION OF HAZARDOUS WASTE AND MUNICIPAL SOLID
WASTE COMBUSTION 1-5
1.3.1 Hazardous Waste Combustion 1-5
1.3.2 Municipal Solid Waste Combustion 1-7
1.4 OVERVIEW OF RELEVANT EPA RESEARCH 1-8
1.4.1 Overview of the ORD Particulate Matter Research Program 1-8
1.4.2 Overview of the Resource Conservation and Recovery Act (RCRA) and
ORD's RCRA Research 1-10
2. BACKGROUND AND APPROACH 2-1
2.1 DESCRIPTION OF REQUEST FOR APPLICATIONS 2-1
2.2 OVERVIEW OF RESEARCH CONDUCTED UNDER COMBUSTION
RESEARCH GRANTS 2-1
2.3 OBJECTIVES OF THIS REPORT 2-2
2.4 METHODOLOGY 2-3
2.4.1 Information Sources 2-3
3. RESULTS AND CONTRIBUTIONS OF THE RESEARCH 3-1
3.1 MECHANISMS OF FORMATION OF CHEMICAL COMPOUNDS IN
COMBUSTION SYSTEMS 3-1
3.1.1 Mechanistic Studies of the Transformation of Polychlorinated Dibenzo-
p-Dioxins via Hydroxyl Radical Attack, Philip H. Taylor, University
of Dayton 3-1
.1.1 Background 3-1
.1.2 Objectives 3-1
.1.3 Methodology 3-2
.1.4 Results and Discussion 3-4
.1.5 Utilization of Research Results 3-6
.1.6 Research Needs 3-6
111 December 2006
-------
CONTENTS (continued)
3.1.2 Toward the Development of a Detailed Mechanism of Transition Metal
Catalyzed Formation of PCDD/F from Combustion Generated Hydrocarbons,
Barry Dellinger and Slawomir Lomnicki, Louisiana State University - Baton
Rouge 3-7
3. .2.1 Background 3-7
3. .2.2 Objectives 3-7
3. .2.3 Methodology 3-7
3. .2.4 Results and Discussion 3-8
3. .2.5 Utilization of Research Results 3-11
3. .2.6 Research Needs 3-12
3.1.3 Products of Incomplete Combustion in the Incineration of Brominated
Hydrocarbons, Selim M. Senkan, University of California - Los Angeles . . 3-13
3. .3.1 Background 3-13
3. .3.2 Objectives 3-13
3. .3.3 Methodology 3-14
3. .3.4 Results and Discussion 3-15
3. .3.5 Utilization of Research Results 3-17
3. .3.6 Research Needs 3-19
3.1.4 Summary of the Overall Contributions of These Three Projects to the
RCRA Multi-Year Plan and Its Broad Theme of "Mechanisms of
Formation" 3-19
3.2 MONITORING AND ANALYTICAL METHODS FOR CHEMICAL
COMPOUNDS IN COMBUSTION SYSTEMS 3-20
3.2.1 Trace-Level Measurement of Complex Combustion Effluents and
Residues Using Multidimensional Gas Chromatography-Mass
Spectrometry (MDGC-MS), Wayne A. Rubey, Richard C. Striebich,
and Philip H. Taylor, University of Dayton 3-21
3.2. .1 Background 3-21
3.2. .2 Objectives 3-21
3.2. .3 Methodology 3-22
3.2. .4 Results and Discussion 3-23
3.2. .5 Utilization of Research Results 3-26
3.2. .6 Research Needs 3-26
3.2.2 Characterization and Minimization of Fine Particulate Emissions from
Waste Incinerators by Real-Time Monitoring of Size-Resolved Mass
and Chemical Composition, Kenneth A. Smith, Hacene Boudries,
Douglas R. Worsnop, and Xuefeng Zhang, Massachusetts Institute of
Technology 3-27
3.2.2.1 Background 3-27
3.2.2.2 Objectives 3-28
3.2.2.3 Methodology 3-28
3.2.2.4 Results and Discussion 3-31
IV
December 2006
-------
CONTENTS (continued)
Page
3.2.2.5 Utilization of Research Results 3-35
3.2.2.6 Research Needs 3-36
3.2.3 Summary of the Overall Contributions of These Two Projects to the
RCRA MYP and Its Broad Theme of "Monitoring and Analytical
Methods" 3-38
3.3 EPA-AWMA INFORMATION EXCHANGE 3-38
3.3.1 Summary 3-38
3.3.2 Presentations 3-39
3.3.3 Research Needs Identified During Panel Discussion 3-40
3.4 AMERICAN FLAME RESEARCH COMMITTEE SPRING MEETING 3-42
3.4.1 Topics and Speakers 3-42
3.4.2 Discussion and Prioritization of Combustion Research Needs 3-43
3.4.3 Conclusions 3-45
4. SUMMARY OF FINDINGS AND RESEARCH NEEDS 4-1
4.1 SUMMARY OF FINDINGS 4-1
4.1.1 Contributions to the Waste Management Goal of the RCRA
Multi-Year Plan 4-1
4.1.2 Utilization of Results by EPA and Others 4-2
4.2 SUMMARY OF RESEARCH NEEDS 4-3
4.2.1 Mechanisms of Formation of Chemical Compounds 4-4
4.2.2 Monitoring and Analytical Methods 4-5
4.2.3 Emissions Characterization 4-5
4.2.4 Fate and Transport 4-6
4.2.5 Toxicity, Health Effects, and Risk Assessment 4-6
5. CONCLUSIONS 5-1
6. CITED REFERENCES 6-1
APPENDIX A LIST OF COMBUSTION EXPERTS INTERVIEWED A-l
APPENDIX B IDENTIFIED RESEARCH NEEDS B-l
December 2006
-------
LIST OF FIGURES
Figure Page
3-1 Schematic of Overall Reactor System for Taylor's Grant 3-3
3-2 Blow-Up Schematic of Optical Reactor for Taylor's Grant 3-4
3-3 Flow Diagram of Research Activities of Bellinger and Lomnicki's Project 3-9
3-4 Counter Flow Diffusion Flame Setup from Senkan's Project 3-18
3-5 Schematic of a MDGC System Used in Rubey, Striebich,
and Taylor's Project 3-23
3-6 Schematic of the Aerosol Mass Spectrometer (AMS) for
Smith and Boudries' Project 3-29
3-7 Schematic of Resonance Enhanced Multiphoton lonization Time of
Flight Aerosol Mass Spectrometer for Smith and Boudries' Project 3-30
LIST OF TABLES
Table Page
1-1 Known Health Effects of Constituents of Combustion Pollutant Emissions 1-6
2-1 Grants Awarded Under the Combustion Emissions Solicitation 2-3
VI December 2006
-------
EXECUTIVE SUMMARY
This report presents the results of five competitively awarded research grants on
combustion emissions from hazardous waste incinerators, industrial furnaces and boilers, and
municipal solid waste incinerators. These grants were awarded in response to a Request for
Applications (RFA) that was issued by EPA's Office of Research and Development (ORD) in
1999 under the National Center for Environmental Research's (NCER) Science to Achieve
Results (STAR) Program. The RFA was developed in consultation with EPA program offices
and other parts of ORD. The grants were awarded in 2000 and completed in 2004-2005. The
total investment in the five grants was $1,685,000. Information about these and other STAR
grants can be obtained at: http://www.epa.gov/ncer.
The recent completion of the grants and the preparation of this report offer the
opportunity to review where the combustion sources addressed by the RFA fall within the
universe of combustion emission sources that comprises, among other sources, smokestack
industries, mobile sources, and open burning. They permit putting this research in the context of
other research conducted in support of the Resource Conservation and Recovery Act (RCRA)
and of the Clean Air Act (CAA). The report also provides a basis for identifying combustion-
related research needs.
Mechanisms of Formation of Chemical Compounds in Combustion Systems
Three of the five grants addressed developing a better understanding of certain
compounds that are formed and the physical and chemical processes by which they are formed as
a result of the combustion that takes place in these sources.
A project by Taylor (University of Dayton) developed fundamental data and models that
will contribute to the infrastructure of knowledge of reactions of chlorinated hydrocarbons and
their impact on the environment. Results of this research project provide important inputs in the
development of a comprehensive gas-phase model of the transformation of poly chlorinated p-
dibenzo dioxins (PCDDs) under a wide range of conditions. This model can be used to manage
risk by preventing and controlling formation and emissions of PCDDs through combustion
modification or other emission abatement techniques. The model can also be applied to
site-specific risk assessment for combustion sources. There is, however, no published kinetic
model incorporating these rate coefficients.
A project by Dellinger and Lomnicki (Louisiana State University) developed a unified
mechanism and understanding of polychlorinated p-dibenzo dioxin/furan (PCDD/F) formation in
the post-combustion, cool-zone of combustors that will greatly facilitate the development of
improved risk management and risk assessment strategies for combustion systems. Gas-phase
reactions and kinetics impact the formation of PCDD/F in combustion systems, but the effect is
primarily indirect through destruction of gas-phase PCDD/Fs and homogeneous gas-phase
formation of some precursors. The principal source of PCDD/F in combustion systems is in all
likelihood surface-mediated by fine and ultrafine particles. Understanding of these mechanisms
could be applied to the development of emissions abatement strategies for combustion systems.
ES-1 December 2006
-------
General strategies include:
Modifying post-combustion time-temperature profiles to mitigate PCDD/F formation.
Controlling the content of catalytic metals in the combustor feed.
Modifying combustion conditions to minimize formation of catalytic, fine and
ultrafme particles.
Blending of fuels and wastes to avoid the optimum compositions for PCDD/F
formation.
A project by Senkan (University of California - Los Angeles) generated data concerning
major, minor, and trace species concentration profiles and soot and temperature profiles that will
be useful for the development and validation of detailed chemical kinetic mechanisms (DCKM)
describing the combustion of hydrocarbons and intermediates which were found from
brominated hydrocarbons in flames. In fact, the development of DCKM for hydrocarbons was
determined to be an important prerequisite to develop insights into the formation of toxic
products of incomplete combustion (PICs) in the combustion of halogenated hydrocarbons.
The development of DCKM will result in improved predictions regarding the conditions
under which polycyclic aromatic hydrocarbons (PAHs) and dioxins form in incinerators. The
detailed mechanisms developed can subsequently be combined with fluid dynamic models to
simulate, design, and develop optimum strategies for practical incinerators such that their
operations would result in emissions of lowest possible levels of PICs, thereby reducing possible
risk to public health.
The three grants provide improved characterization of the mechanisms of formation of
components of air emissions from combustion systems. They identify dioxin and furan precursor
compounds and halogenated dioxin and furan species and provide insight into the formation and
transformation mechanisms in combustion systems.
Specifically, Taylor has characterized chlorinated dioxins and provided OH radical
reaction rate measurements that have not previously been investigated. Dellinger and Lomnicki
investigated the effects of metals on catalysis of formation of chlorinated dioxins and furans in
combustion systems and identified a correlation between the amount of dibenzo dioxin and the
amount of highly chlorinated dioxin products formed as well as the effect of temperature on this
mechanism. These results also identify dioxin and furan formation issues related to combustion
of hazardous waste and provide data relevant to the identification of surrogate compounds to
correlate to emissions of more highly chlorinated dioxins and furans. Senkan provided
information concerning mechanisms of formation of PAHs and soot. These results are also
relevant to formation issues related to combustion of hazardous waste and to identification of
surrogate compounds.
ES-2 December 2006
-------
Monitoring and Analytical Methods for Chemical Compounds in Combustion Systems
Two of the five grants addressed developing monitoring and analysis methods that will
permit better characterization of all the compounds that are created as a result of combustion in
the sources that are the subject of this report, including the chemicals and the number, size, and
composition of particles that are emitted.
A project by Rubey, Striebich, and Taylor (University of Dayton) shows that multi-
dimensional gas chromatography-mass spectrometry (MDGC-MS) has significant potential in its
ability to identify specific components of complex chemical mixtures sampled from municipal
solid waste and hazardous waste incinerators. This technique also possesses the capability of
quantifying separated substances that occur over a wide range of concentrations. It is hoped that
use of advanced chromatographic techniques (e.g., a thermal gradient programmed GC) along
with a faster MS system will allow more comprehensive characterization of both toxic and
non-toxic PICs to be performed in a rapid (i.e., real-time or near real-time) fashion, thereby
reducing uncertainties associated with site-specific risk assessments.
A project by Smith and Boudries (Massachusetts Institute of Technology in collaboration
with Aerodyne Research, Inc.) deployed a state-of-the-art aerosol mass spectrometer (AMS) at
three municipal waste incinerators to measure the real-time chemical and size distribution of
sub-micron particulate emissions from incinerators. Overall, the data collected within the
framework of this project show the development of new and promising techniques for real-time
chemical analysis and measurement of size-resolved ambient aerosols.
Although the AMS was initially developed to characterize non-refractory species, further
development and improvements were performed during this project to include the measurement
of refractory species, such as metals. This new technique offers the simultaneous real-time
measurement of a variety of chemical species present in/on aerosols and their corresponding size
distribution in a rapid manner with respect to individual species for a variety of combustion
systems. These species include organics, sulfate, nitrate, ammonium, chloride and metals.
Through this research, a mobile commercial instrument with the capability of performing the size
distribution and mass loading concentration measurements in real-time will be available to the
research and regulatory communities.
The results from these two projects can be directly applied to design and application of
sampling and analysis systems to further characterize emissions from combustion systems, in
particular focusing on identification of potentially toxic constituents that have not been
previously characterized in combustion system exhaust gas and fine particulate. Such real-time
or near real-time monitoring systems and the data provided by them could be applied directly to
preparation of site-specific risk assessments for combustion systems as well as to development,
design, and implementation of emission control systems.
Research Needs
Research needs were identified by consulting the Principal Investigators of these grants,
interviewing experts in the field of combustion, and holding research needs discussions as part of
ES-3 December 2006
-------
an Annual EPA-Air and Waste Management Association (AWMA) Information Exchange and
an American Flame Research Committee meeting. The latter discussions were the first times
that EPA in-house and extramural academic researchers, experts from industry, and consulting
engineers met for this purpose. There was agreement among the participants that interactions
such as these would be desirable at least yearly.
The research needs identified during the preparation of this report fell into the following
categories: (a) improving understanding of the mechanisms of formation of chemical
compounds in combustion systems, which can be used to develop new control technologies and
operating parameters to limit emissions of pollutants and ultimately reduce risk; (b) developing
better monitoring, sampling, and analysis methods to more accurately characterize combustion
emissions; © identifying toxic fractions of combustion-related emissions to more accurately
characterize risks; (d) improving knowledge related to the fate and transport of combustion-
related emissions to better assess potential impacts of these materials on human health and the
environment; and (e) improving understanding of mechanisms of toxicity and potential health
effects associated with combustion emissions, particularly for those compounds for which little
or no information is available.
Some of the combustion researchers and experts felt that new environmental problems
not directly related to combustion currently have and perhaps should have greater priority in
terms of research needs. Nevertheless, this peer-reviewed report offers the basis for identifying
combustion-related research that may be needed in developing and implementing future rule-
makings and in meeting any changes that the nation may wish to make in the types of combustion
systems it thinks best meet its economic and human health and environmental quality objectives.
ES-4 December 2006
-------
1. INTRODUCTION
In 1999, the U.S. Environmental Protection Agency's (EPA) National Center for
Environmental Research (NCER) published a Request for Applications (RFA) (entitled
"Combustion Emissions") for research grants under its Science to Achieve Results (STAR)
program to explore the risks posed from emissions of contaminants from hazardous waste
incinerators, furnaces and boilers, and municipal incinerators. Five grants were awarded based
on this RFA. The total amount awarded was $1,685,000. The work performed under these five
grants has recently concluded.
The purpose of this report is to summarize the important scientific findings from this
research, place these findings in the context of past and on-going research on combustion
emissions, and identify research needs on this topic. The intended audiences for this report are
primarily EPA program and research offices, but also outside experts in the combustion field and
people who may review EPA's need for additional research on combustion from these sources
and other sources as well.
Further information regarding the STAR program is available at: http://www.epa.gov/
ncer. This website contains a search function that allows for searching for information on these
and other NCER grants by principal investigator (PI) name, institution, grant number, and key
words.
1.1 OVERVIEW OF TYPES OF COMBUSTION SOURCES
Combustion emissions are generated by burning material for energy, waste
reduction/disposal, or both. The major types of stationary and mobile combustion sources in the
United States are:
Power plants.
Process heaters and industrial processes.
Mobile sources.
Open burning and residential heating.
Incinerators and boilers and industrial furnaces.
Power plants There are about 1,300 coal-fired generation units in about 500 coal-fired
power plants representing about 305 GW of generation capacity. There were 309 oil-fired units
at 137 plants in 1998 and 104 units at 74 plants in 2003. The number has likely declined since
2003. Power plants are generally considered to have the most overall pollutant emissions among
combustion sources, including emissions of several criteria pollutants (e.g., particulate matter,
nitrogen oxides, sulfur oxides) as well as a number of air toxics (e.g., mercury). For 2001, it is
estimated that coal- and oil-burning power plants generated 45 percent (339,976 tons) of the
755,502 tons of air toxics released in North America (CEC 2004). Emissions from individual
facilities vary based on fuel throughput; the size, design features, level of maintenance, and
operating characteristics of the facility; and the fuel (e.g., natural gas, oil, coal).
1-1 December 2006
-------
Process heaters It is estimated that there are 15,248 process heaters: 13,481 gas-fired,
353 distillate oil-fired, 674 residual oil-fired, 0 coal-fired, and 42 wood-fired. Process heaters are
enclosed devices using a controlled flame designed to transfer heat as part of an industrial
process. Process heaters are commonly used in petroleum refining and iron and steel production,
as well as in a number of other industrial applications. The majority of process heaters burn
gaseous fuels (e.g., natural gas) or fuel oils. The gas-fired heaters are believed to have low air
toxics emissions, often near emission test method detection limits (EPA 2002). For oil-fired
heaters poor maintenance of the burners, low-quality fuel, and lack of air pollution control
devices can result in significant emissions of NOX, SO2, SO3, PM and PM25 and a spectrum of
polynuclear hydrocarbons and heavy metals.
Industrial processes that involve combustion include furnaces and kilns, such as blast
furnaces used in iron and steel production and rotary kilns used in cement and lightweight
aggregate production, where the flame directly contacts the industrial process raw material.
These sources may combust metallurgical coke (made from coal), petroleum coke (made from
oil), coal, oil, natural gas or a combination of fuels. Furnaces and kilns emit criteria pollutants
(e.g., particulate matter, nitrogen oxides, sulfur oxides) and air toxics (e.g., dioxins). Some types
of industrial process sources, in particular cement and lightweight aggregate kilns, may also burn
solid or liquid wastes. Such waste-burning industrial sources are categorized by EPA regulations
as "industrial furnaces" and are subject to additional emissions limitations for air toxics when
incinerating hazardous waste.
Mobile sources are generally divided into two categories: on-road and non-road sources.
On-road sources include highway vehicles such as cars and light trucks, heavy trucks, buses, and
motorcycles. Emissions from individual on-road sources are generally low, relative to
smokestack plumes that many people associate with air pollution. However, in numerous cities
across the country, the on-road sources are the single greatest pollution category, as emissions
from millions of vehicles on the road add up. Non-road mobile sources include outdoor power
equipment, recreational equipment, farm equipment, construction equipment, lawn and garden
equipment, marine vessels, locomotives, and aircraft. In some areas of the country, emissions
from non-road sources represent a third of the total emissions of nitrogen oxides (NOx) and
volatile organic compounds (VOCs) from all mobile sources, including cars and trucks, and over
two-thirds of emissions of particulate matter from all mobile sources (EPA 2005a).
Open burning and residential heating are also significant sources of combustion
emissions. These sources are similar to mobile sources in that the emissions from an individual
source are generally low but, due to their number, the total emissions from these types of sources
can be significant. Open burning is defined as "the burning of any matter in such a manner that
products of combustion resulting from the burning are emitted directly into the ambient air
without passing through an adequate stack, duct, or chimney." This includes activities such as
burning yard waste, campfires, and land clearing fires. Emissions from residential heating are
generated by the combustion of wood, natural gas, propane, or other fuel for the purpose of
heating residences. The quantity and composition of emissions from these types of sources vary
depending on the design, operating, and maintenance characteristics of the combustors; the
composition of the fuel; and the amount of fuel burned.
1-2 December 2006
-------
Incinerators and waste-burning boilers and industrial furnaces Municipal solid waste
incinerators are known as Municipal Waste Combustors (MWC). There are 167 large (unit
capacity greater than or equal to 250 tons per day) MWC units at 66 facilities, 84 small (unit
capacity greater than or equal to 35 tons per day and less than 250 tons per day) MWC units at 39
facilities, and 12 very small (unit capacity less than 35 tons per day) MWC units at 12 facilities.
Incinerators, boilers, and furnaces can emit a range of air pollutants, including criteria pollutants
and air toxics.
Hazardous waste is combusted at four main types of facilities: commercial incinerators,
on-site incinerators, waste burning kilns (cement kilns and light weight aggregate kilns), and
industrial boilers. Commercial incinerators are generally larger in size and designed to manage
virtually all types of solids, as well as liquid wastes. On-site incinerators are more often designed
as liquid-injection systems that handle liquids and pumpable solids. Waste burning kilns and
boilers generally burn hazardous wastes to generate heat and power for their manufacturing
processes.
There are 267 hazardous waste burning sources (systems) in operation in the U.S. Liquid
fuel-boilers account for 104 sources, followed by on-site incinerators at 92 sources. Cement
kilns, hydrochloric acid production furnaces, and commercial incinerators account for 25, 10, and
15 sources, respectively. Solid fuel boilers and lightweight aggregate kilns make up the
remainder, at 12 and nine systems, respectively. These 267 sources are operated at a total of 145
different facilities. Combustion systems operating at chemical manufacturing facilities were
found to account for about 70 percent of the total number of facilities and manage 58 percent of
all hazardous waste burned in 2003. (70 FR at 59531, October 12, 2005)
Generally, incinerators are used to reduce waste volumes and toxicity, furnaces are used
to reclaim reusable products and/or heat value from wastes, and boilers that burn waste materials
are used to recover energy from wastes. Industrial furnaces include cement kilns and lightweight
aggregate kilns that burn waste for energy recovery and to reduce the overall net energy cost from
the low cost per unit of heat content in comparison with fossil fuels and/or income from waste
disposal fees. The emissions from these facilities are significant in a number of areas of the
United States and are often complex mixtures of pollutants that can be difficult to identify and
quantify.
The research conducted under the five grants summarized in this report focused on
emissions from hazardous waste incinerators, boilers and industrial furnaces, and municipal solid
waste incinerators. Several of the projects are also relevant to air emissions from other types of
stationary combustion sources and mobile sources. These sources are described in more detail in
the following sections.
1.2 OVERVIEW OF HAZARDOUS WASTE AND MUNICIPAL SOLID WASTE
COMBUSTION
For over one hundred years, the combustion of hazardous waste and municipal solid
waste has been used in the United States to both generate energy and reduce waste volumes, with
energy recovery from incineration of municipal solid waste beginning in New York City in 1898
1-3 December 2006
-------
(EIA 2005). It is estimated that 80 to 85 percent of the 3.6 million tons of hazardous waste
combusted annually is burned in hazardous waste incinerators, cement kilns, and lightweight
aggregate kilns, with the remaining hazardous waste burned in industrial boilers and other types
of industrial furnaces. Currently, hazardous waste combustion occurs at approximately 244
facilities in 30 states, with the majority of the facilities located in southern states, primarily Texas
and Louisiana (EPA 2004b).
Municipal solid waste is also commonly incinerated to reduce the volume of the waste
and to generate energy. Approximately 14.7 percent (34 million tons) of 230 million tons of
municipal solid waste generated annually in the United States is combusted (EPA 2003a). An
additional four million tons of hazardous waste (two percent of all hazardous waste) are
destroyed annually in hazardous waste incinerators (EPA 2005b). Furthermore, sewage sludge
incinerators burn about 25 percent of the sewage sludge generated annually in the U.S. (Werther
and Ogada 1999). Combustion of municipal solid waste increased steadily from the 1960s
through the 1980s and has declined slightly since its peak in the 1980s. The majority of
combustion of municipal solid waste in the United States incorporates recovery of the energy
produced; these facilities are referred to as "waste-to-energy" facilities. In 2001, there were
97 waste-to-energy facilities in the United States, with 40 facilities in the Northeast, 30 in the
Southeast, 19 in the Midwest, and eight in the West (EPA 2003a).
The composition of the uncontrolled emissions generated from the combustion of
hazardous and municipal solid waste varies depending on combustor design and operating
characteristics and on the composition of the waste and may include the following pollutants of
potential concern:
Particulate matter (PM).
Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, known
collectively as dioxins and furans.
Organic compounds (volatile, semivolatile, and nonvolatile) other than dioxins and
furans, often referred to as products of incomplete combustion (PICs).
Metals that are potentially toxic to human or ecological receptors (e.g., mercury, lead,
cadmium).
Acid gases (e.g., hydrogen halides [HBr, HF, and HC1]), NOX, and sulfur oxides (SO2
and SO3).
Table 1-1 provides an overview of the known human health effects of pollutants in each of these
categories.
Human and ecological exposure to emissions of these pollutants can occur via a number
of pathways. The pathways of primary concern can vary by pollutant. Most combustion
emissions are released to the air. Human and ecological receptors can be exposed to these
pollutants through inhalation. The pollutants can include PM, hydrogen chloride, and carbon
1-4 December 2006
-------
monoxide. Other pollutants generated by combustion, such as NOx, can undergo chemical
reactions in the atmosphere with other compounds to form secondary pollutants, such as
tropospheric ozone, for which inhalation exposure is a concern.
In addition, some of these pollutants, such as dioxins and furans, polycyclic aromatic
hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and metals, are persistent in that they
do not quickly (or ever) degrade in the environment and have a tendency to bioaccumulate.
Human and ecological exposure to these pollutants can occur through ingestion of soil or biota
that have been impacted by emissions of these pollutants. For example, dioxin compounds
released to the air could deposit to the surface of a plant, this plant could be consumed by a cow,
which in turn is consumed by a human being, resulting in human exposure to the released dioxin
compounds.
It is also important to note that emissions from incinerators and other industrial
combustion processes are one of the primary sources of endocrine disrupting compounds (EDCs)
in the environment. Evidence suggests that environmental exposure to some anthropogenic
EDCs may result in disruption of endocrine systems in both human and wildlife populations.
Because of the potential global scope of the EDC problem, the possibility of serious effects in
humans and wildlife, and the persistence of some suspected EDCs in the environment, research
on EDCs is a high priority in EPA's Office of Research and Development (ORD) (EPA 2005c).
1.3 REGULATION OF HAZARDOUS WASTE AND MUNICIPAL SOLID WASTE
COMBUSTION
Combustion of hazardous and municipal solid waste has the potential to adversely affect
human health and the environment and it is therefore subject to state and federal regulation. As a
result, the burning of hazardous and municipal solid waste in incinerators, boilers, and industrial
furnaces is regulated through stack emission limitations and unit operating requirements. The
regulatory standards for hazardous waste combustion and municipal solid waste combustion are
described separately below.
1.3.1 Hazardous Waste Combustion
Hazardous waste combustion is subject to standards under the Resource Conservation and
Recovery Act (RCRA); and maximum achievable control technology (MACT) standards (i.e.,
National Emission Standards for Hazardous Air Pollutants) under section 112 of the Clean Air
Act Amendments of 1990 (CAAA). Under RCRA, EPA's Office of Solid Waste (OSW) is
responsible for ensuring that combustion units that burn hazardous waste (1) meet performance
standards, including a demonstration of the unit's destruction and removal efficiency (DRE) for
certain principal organic hazardous constituents (POHCs), and (2) meet emission standards for
hydrogen chloride, chlorine gas, metals, and particulate matter.
1-5 December 2006
-------
Table 1-1 Known Health Effects of Constituents of Combustion Pollutant Emissions
Pollutant Category
Known Health Effects
Dioxins and Furans
Short-term (acute) exposure of humans to high levels may result in
skin lesions and altered liver function. Long-term (chronic) exposure
is linked to impairment of the immune system, the developing nervous
system, the endocrine system, and reproductive functions. Identified
as probable endocrine disrupting compounds (EDCs). Classified by
EPA as a "known human carcinogen." (WHO 1999; EPA 2004c) The
contribution of combustors to EDCs in the environment is not known,
hence the identified need for research.
Other PICs
Varies widely across chemicals. Some PICs are classified by EPA as
"probable human carcinogens" or "known human carcinogens" and
are linked to a range of non-cancer effects, such as impairment of the
immune system and altered liver function. (EPA 2005d)
Metals
Linked to both chronic and acute health effects, although effects vary
widely across chemicals. Metals emitted can include mercury, which
is linked to birth defects, immune system damage, and nervous system
disorders; lead, which is linked to nervous system disorders; and
cadmium, which is linked to kidney failure, hypertension, and genetic
damage.
Acid Gases
Acid gases are linked to acute and chronic respiratory effects. (EPA
2005d; WDNR 2003)
Particulate Matter
Particulate matter (PM) is linked to acute and chronic
cardiopulmonary effects, including premature mortality. Scientific
studies have linked particulate matter, especially fine particles (alone
or in combination with other air pollutants), with a series of significant
health problems, including: premature death; respiratory related
hospital admissions; aggravated asthma; chronic bronchitis; and acute
respiratory symptoms. (EPA 1997a)
Polychlorinated Biphenyls
PCBs have been shown to cause cancer in animals. PCBs have also
been shown to cause a number of serious non-cancer health effects in
animals, including effects on the immune system, reproductive system,
nervous system, endocrine system and other health effects. Studies in
humans provide supportive evidence for potential carcinogenic and
non-carcinogenic effects of PCBs. (EPA 2004d)
To ensure the performance and emissions standards are met, the combustion unit's RCRA
permit sets operating requirements that specify allowable ranges for, and requires continuous
monitoring of, certain critical parameters intended to ensure compliance with the performance
and emission standards. Because hazardous waste combustion units are a type of treatment,
storage, and disposal facility (TSDF), hazardous waste combustion units are also subject to the
general TSDF standards under RCRA (EPA 2003b).
Under the CAAA, EPA's OSW is responsible for developing MACT standards that limit
emissions of hazardous air pollutants (HAP) from hazardous waste combustors (HWCs). The
1-6
December 2006
-------
EPA's Office of Enforcement and Compliance Assurance (OECA) is responsible for enforcing
these standards. The MACT standards for HWCs were developed and implemented in two
phases. The Phase 1 standards include federal emission limitations for dioxins and furans,
mercury, semi-volatile and low volatile metals, particulate matter, carbon monoxide,
hydrocarbons, DRE, and total chlorine for three categories of sources: hazardous waste
incinerators, cement kilns, and lightweight aggregate kilns.
The Phase 1 standards were first promulgated in 1999 and then replaced with interim
standards in 2002. EPA proposed replacement standards for the Phase 1 interim standards on
April 20, 2004, and these replacement standards on October 14, 2005. The Phase 2 MACT
standards for HWCs include federal emission limitations for boilers and hydrochloric acid
production furnaces for the same set of pollutants as the Phase 1 standards. The Phase 2
standards were first proposed on April 20, 2004, and were also finalized on October 14, 2005
(EPA 2005e).
It is expected that the proposed Phase 1 and Phase 2 MACT standards will reduce
emissions of hazardous air pollutants by approximately 3,300 tons per year, which equates to a
25 percent reduction in national annual HAP emissions from 1990 levels. This reduction in
emissions may result in fewer premature deaths, fewer multiple organ cancers and endocrine and
reproductive effects, fewer cases of chronic bronchitis, and reduced hospital admissions for
pneumonia, asthma, and cardiovascular problems (EPA 2004b).
Upon implementation of the MACT standards, once a facility has demonstrated
compliance with the MACT standards, it will no longer be subject to the RCRA emission
requirements, with few exceptions. Existing RCRA permitted facilities, however, must continue
to comply with their permitted emissions requirements until they obtain modifications to their
RCRA permits to remove any duplicative emissions conditions (EPA 2003b).
1.3.2 Municipal Solid Waste Combustion
Air emissions are the principal environmental concern associated with the combustion of
municipal solid waste. Thus, EPA's OAR is primarily responsible for regulating municipal solid
waste combustors (MWC). These MWCs are regulated by OAR under Section 129 of the Clean
Air Act, which specifies that New Source Performance Standards (NSPS) must be developed to
apply to all newly constructed units while emission guidelines must be developed for existing
units. The NSPS are direct federal regulations that apply to new sources. The emission
guidelines for existing sources do not directly regulate MWCs; instead they establish
requirements for State MWC Plans which are the vehicles by which states implement the
emission guidelines. Once approved, these State Plans become federally enforceable. Both the
NSPS for new MWCs and the guidelines for existing MWCs are MACT-based. The MWC
regulations were adopted and implemented in two phases. In the first phase, MACT regulations
for large MWCs were developed and in the second phase MACT regulations for small MWCs
were developed. The large MWC regulations were adopted in 1995 and fully implemented by
2000. The small MWC regulations were adopted in 2000 and were fully implemented by the end
of2005.
1-7 December 2006
-------
The regulations for both new and existing sources require control of the following criteria
and toxic pollutants: dioxins and furans, cadmium, lead, mercury, particulate matter, hydrogen
chloride, sulfur dioxide, nitrogen oxides, and carbon monoxide. State MWC Plans include
source and emission inventories, emission limits, and testing, monitoring, and reporting
requirements, as well as generic or site-specific compliance schedules including increments of
progress. Implementation of the MWC emission guidelines through the State MWC Plans have
reduced toxic air pollutant emissions by 87,000 tons per year from 1990 levels for the following
pollutants of concern: dioxin, metals, lead, mercury, particulate matter, acid gases, and nitrogen
oxides. EPA is presently collecting MACT compliance data from small MWCs and will
calculate emission reductions achieved. However, the calculations have not been completed.
EPA expects the small MWC regulations to reduce emissions by more than 33,000 tons per year.
In combination, emissions from large and small MWCs will have been reduced by 120,000 tons
per year by these two MACT regulations. Specifically, the regulatory standards for large MWCs
have reduced dioxin and furan emissions by more than 99 percent, and have reduced mercury
emissions by more than 90 percent from 1990 levels (EPA 2005f). The same levels of reduction
are expected for small MWCs.
1.4 OVERVIEW OF RELEVANT EPA RESEARCH
The combustion research that is the subject of this synthesis report is but a small part of
the ORD research devoted to combustion over the past several years. It is in turn completely
dwarfed by ORD's investment in PM research over the past several years which has ranged
between $53 million and $68 million per year. Most of this latter research has been devoted to
better understanding the impacts of PM on human health.
1.4.1 Overview of the ORD Particulate Matter Research Program
Over the last decade, a wealth of studies has underscored that anthropogenic air
pollutionnotably PMcan adversely impact human health and welfare, despite clear evidence
that overall air quality has improved.1 The White House Office of Management and Budget
(OMB) has estimated an annual savings of $120 to $183 billion in hospitalization and emergency
room visits, lost workdays, and premature deaths between 1992 and 2002 that can be attributed to
air pollution regulationsagain most notably PM (OMB 2003).
Reducing the uncertainties regarding the source-associated attributes of PM responsible
for these impacts and the biological factors that underlie susceptibility would further increase
these benefits. The goal is obtain information on critical combustion related factors that would
lead to the development of cost-effective strategies to environmental regulation and control.
Identifying individuals who may be at greatest risk would further refine assessment of associated
risks.
1 These data are summarized in the recently released Air Quality Criteria Document for PM (EPA
2004e) and Air Quality Criteria for Ozone and Related Photochemical Oxidants (Draft) (EPA 2005g).
Trends in air quality and emissions can be found at the EPA Office of Air Quality, Planning, and
Standards website http://cpa/gov/air/oaqps/chcanair.html.
1-8 December 2006
-------
By 1997, the scientific evidence, although still controversial, was sufficient for EPA to
conclude that respirable ambient levels of PM presented significant risks to public health.
Therefore, the existent National Ambient Air Quality Standard (NAAQS) for particulate matter
with a diameter of less than 10 microns (PM10) was revised and an additional, new NAAQS for
particulate less than 2.5 microns in diameter (PM25) was established. Congress chose to augment
the President's recommended EPA budget to accelerate investigations of the role of PM in air
pollution-associated health outcomes, and to implement health risk reductions via scientifically
defensible regulatory analysis.
Congress also mandated the formation of a committee of air pollution experts via the
National Academy of Sciences' National Research Council (NAS/NRC) to assist in this national
effort. This NRC Committee met initially to define the scope of the issue and subsequently
produced a series of documents (most recently in Vol. IV published in April 2004), that
evaluated ongoing scientific and administrative progress which reduced uncertainties associated
with the PM issue and made recommendations regarding direction and implementation of the
program. Following the release of a related NRC report in 2004 entitled Air Quality
Management in the United States (NRC 2003), a subgroup of the Clean Air Act Advisory
Committee (CAAAC) developed parallel recommendations for improvements to air quality
management.
The intervening years of intensive research activity since the initial NRC research
Priorities Report in 1998, have yielded significant advances in the understanding of health,
exposure and atmospheric PM science. In February 2004, ORD released Particulate Matter
Research Program: Five Years of Progress (EPA 2004f), which summarized the achievements
of EPA's research program in advancing understanding of both health/exposure and air quality
issues. Advances were summarized into three broad areas: (a) the credibility and extent of
PM-associated health effects and the complex roles of PM attributes and human host factors that
contribute to the health outcomes; (b) the factors determining public and individual exposures,
including characterization of the sources and atmospheric processes needed to aid
implementation of the NAAQS; and © the development and implementation of 'tools' and
state-of-the-art technologies needed by the EPA regions, states, and tribes to implement the
NAAQS and achieve EPA's Strategic Air Quality Goal to "protect and improve the air so it is
healthy to breathe and risks to human health and the environment are reduced" (EPA 2003c).
The PM Program has provided essential information for the reassessment of the PM
NAAQS which is expected to be promulgated in December 2006. Meanwhile, essential tools for
attainment assessments and the development of State Implementation Plans have been released,
and these processes are well underway. The research program continues to work in the area of
characterizing the health impacts of PM and refining implementation tools and data to assist local
regulators in meeting the NAAQS. The evolution of "PM science" has moved the research to
addressing questions regarding the hazardous components or attributes of PM as key to reducing
risk. The complex nature of this approach is such that the research has focused more on profiling
sources of PM modes in an effort to move to controlling key and essential contributing sources to
the atmospheric PM-complex.
1-9 December 2006
-------
Initially, this effort has focused on primary fossil fuel combustion sources (coal, oil,
diesel gasoline and natural gas) emitting a broad spectrum of suspect components, including
organics, metals, sulfates, and related compounds. Of these, animal inhalation studies have been
conducted to date on oil and coal emissions and diluted diesel exhaust. Specifically, studies are
manipulating the chemical composition of these combustion atmospheres in an effort to alter
subsequent toxicity. In addition, susceptible animal models are being used to learn more about
potential risk. Similarly, human studies of diesel emissions are also conducted with a focus on
both the health outcomes and potential its gene-environment interactions. Field epidemiology
studies are being integrated (e.g. Detroit) with exposure and observational studies in human, with
a goal of determining associations with specific sources. Emission surveys are being done in the
field with new advanced technologies; and atmospheric models are being refined along with
specific methods to measure PM models likely to be regulated (fine and coarse PM). Other PM
sources (e.g., automobile, wood smoke, and potential specialized emitters) and secondary
transformation PM products are planned for study.
The fundamental goal of the research program is to better understand the multiple aspects
of air quality, exposure and health from a multipollutant perspective. This would be achieved by
linking health outcomes with pollutant sources through the complexities of atmospheric
transformation. Among this complexity is determining who is at greatest risk (susceptible
subgroupschildren, elderly, and health compromised). In the end, a more comprehensive
understanding of air pollution and strategic approach to effective and efficient control can be
established.
1.4.2 Overview of the Resource Conservation and Recovery Act (RCRA) and ORD's
RCRA Research
Since 1976, active industrial facilities and generators, handlers, and disposers of
hazardous waste have managed their facilities and operations to reduce the improper disposition
of hazardous materials.
The Resource Conservation and Recovery Act of 1976 (RCRA), and subsequent acts to
amend and supplement it, seeks to ensure proper management of large volumes of industrial and
municipal waste. RCRA originally framed waste management options hierarchically, with
reducing waste generation as the most preferred option, and effective waste disposal as the least
preferred, albeit most widely used approach.
For nearly three decades RCRA implementation by EPA, and by states with delegated
authority, focused foremost on defining wastes, defining acceptable management practices and
acceptable treatment and disposal methods, and ensuring corrective action where hazards were
not effectively controlled. Over the last decade, there has been an increasing focus on the
conservation component of RCRA, with multiple efforts to reduce municipal solid waste,
commercial and industrial solid wastes, and hazardous wastes.
1-10 December 2006
-------
More recently OSW issued the Resource Conservation Challenge (EPA 2005h), which
focuses on four areas:
Municipal Solid Waste Recycling.
Reusing and Recycling Industrial Materials.
Priority and Toxic Chemical Reductions.
Green Initiatives Electronics.
Research to support RCRA has paralleled program development over the years. Early
work focused on assessing risks from solid waste and identifying wastes that should be
designated as hazardous; developing and demonstrating effective methods for waste treatment;
developing and demonstrating effective waste containment in landfills and the materials used to
isolate the waste; and evaluating approaches for reducing the stream of municipal solid waste
destined for landfills. For the past several years, the research program has placed additional
focus on waste minimization and resource conservation.
The research program, with total resources of $11.6 million in fiscal year 2006 and $10.6
million requested in the President's Budget for fiscal year 2007, is focused on multimedia
decision making and various options for managing wastes and materials.
The multimedia decision making component of the research program has developed a
model framework, technical modules, and underlying science to support national level decisions
on waste management. The work was favorably reviewed by a panel of the Science Advisory
Board (see EPA 's Multimedia, Multipathway, andMultireceptor Risk Assessment [3MRA]
Modeling System: A Review by the 3MRA Review Panel of the EPA Science Advisory Board
[EPA 2004g]). As the research continues, the emphasis will be on the broader question of
materials management, which can encompass not only waste management decisions, but
decisions related to beneficial use of waste and material selections to reduce the use of toxic
constituents, prevent pollution, and move toward sustainability.
The waste and materials management component of the program has covered three
themes: landfills, hard-to-treat wastes and leaching tests, and combustion. Resource reductions
in recent years may not allow research in all three areas to be sustained.
Landfills are still widely used for municipal solid waste and hazardous wastes. Ongoing
research addresses both conventional containment materials and landfill bioreactor operation.
The concept of a bioreactor is to operate the landfill in such a way that organic wastes are rapidly
degraded, yielding recovered landfill capacity and offering the possibility of generating higher
methane volumes early in the landfill life that can be captured for energy value. Research needs
to determine favorable operating conditions, suitable monitoring requirements, and ways to
ensure that fugitive gas emissions are controlled. Ongoing research investigates the properties
and performance of conventional liner and cover materials because we rely on these materials to
permanently segregate waste and its hazardous constituents from people and the environment.
The small research effort on hard-to-treat wastes has focused on wastes containing
species like mercury and arsenic, which have complex chemistry that is not amenable to
1-11 December 2006
-------
conventional treatment processes. Leaching test research is related to waste treatment in that the
test is trying to estimate the degree to which treatment will be successful in preventing the spread
of hazardous constituents. Having reliable, well-understood leach tests becomes even more
important as recycling and beneficial use of materials that were formerly disposed of in landfills
becomes more widespread. Multiple tests are being evaluated to address some deficiencies noted
by the Science Advisory Board in commentaries on the subject.
Combustion research is important because many thermal units have to be permitted under
RCRA, generally by states with delegated authority. The research needs for complying with
RCRA and with air pollution control requirements overlap, and the research planning is
coordinated to avoid duplication of effort. RCRA research is focused on understanding organic
compound transformations in the combustion process and on monitoring organic and metals in
combustor emissions. The purpose of both efforts is to guide and optimize combustor operation
to minimize formation and emission of toxic constituents including chlorinated dioxins and
furans and metals. Monitoring research investigates advanced sensors that can detect one or more
constituents of concern or surrogates that are easier to analyze. The regulatory authorities can
then stipulate operating conditions and monitoring controls that reduce risks to people and the
environment.
1-12 December 2006
-------
[this page intentionally left blank]
-------
2. BACKGROUND AND APPROACH
2.1 DESCRIPTION OF REQUEST FOR APPLICATIONS
On February 17, 1999, EPA's NCER published a Request for Application (RFA)
soliciting research proposals on topics that will supplement current understanding of risks posed
by the emission of contaminants from hazardous waste incinerators, boilers and industrial
furnaces, and municipal solid waste incinerators. The RFA explicitly excluded from
consideration research on medical waste incinerators or any research being solicited under other
EPA programs (e.g., mercury research). The RFA emphasized the need for an improved
understanding of indirect exposure pathways, including the transport, transformation, and
environmental fate, of combustion products, particularly for combustion products not already
receiving priority attention (e.g., co-planar PCBs, brominated aromatic hydrocarbons, and metals
such as arsenic).
2.2 OVERVIEW OF RESEARCH CONDUCTED UNDER COMBUSTION
RESEARCH GRANTS
NCER identified in the 1999 RFA the need to (1) improve understanding of indirect (i.e.,
non-inhalation) exposure pathways, particularly for pollutants not already receiving priority
attention, and (2) determine which pollutants are of most potential concern. EPA awarded five
grants under the STAR program in 2000 to address these issues. The total investment in these
grants was $1,685,000. They were completed in 2004-2005. These five grants and their
Principal Investigators (Pis) are listed in Table 2-1.
The overall objective of Taylor's research project (R828189) was to determine the rates
and mechanisms of hydroxyl (OH) radical reactions with dioxin and selected congeners in waste
combustion systems over an extended temperature range. The gas-phase transformation of
dioxins under high-temperature incineration conditions is not well understood, but studies have
shown that OH radical reactions are among the most important elementary steps in dioxin
formation under these reaction conditions.
Senkan's (R828193) research goal was to develop insights into the formation and control
of potentially toxic PICs in the incineration of brominated and other halogenated hydrocarbons.
Because some of these PICs are known or suspected carcinogens, a better understanding of their
origins and formation mechanisms is important in assessing potential control mechanisms for the
continued use of incineration as a waste minimization technology. The presence of brominated
flame retardants in consumer electronics goods and other products are of concern, both from a
PIC standpoint, but also because BFRs have been implicated as potential EDCs.
Bellinger and Lomnicki (R828191) studied the mechanism of the formation of dioxins
and furans on metal oxide surfaces. Previous field studies have suggested that dioxins and furans
are formed in the post-combustion, cool-zone of combustors by surface-mediated/catalyzed
pathways, rather than in the primary combustion chamber. The objective of Bellinger and
Lomnicki's grant was to reveal the chemical mechanism of this formation.
2-1 December 2006
-------
There is an overall need for improved analytical techniques to identify and quantify
chemical compounds in combustion systems in a rapid manner. To help address this need,
Rubey, Striebich, and Taylor (R828190) developed, tested, and applied advanced
multi-dimensional gas chromatography (MDGC) instrumentation, capable of achieving high
resolution separations, to examine combustion effluents and residues. Their goal was to conduct
separations and characterization of individual constituents of combustion effluents and residues
in a two column gas chromatography system, in such a way that the second column was
operating fast enough to keep up with the first column analysis. Rubey, Striebich, and Taylor
applied the MDGC method to various types of combustion emissions, including emissions from
incineration, open burning, and mobile sources.
Smith and Boudries (R828192) recognized the critical need for real-time (i.e., fast enough
as to seem instantaneous) quantification of pollutants associated with fine particulates in the
exhaust gas of waste and sewage sludge incinerators. Fine particulates (i.e., those particulates
smaller than 2.5 microns in diameter) are able to penetrate deeper into the human lungs and, if
deposited there, may be an efficient vehicle for exposure to many different chemicals (Wilson
and Spengler, 1996). Several previous studies also showed that incinerator emissions are
enriched in particulate matter sized 0.10 to 2 jam due to decreased efficiency in paniculate
control for this size range (Saxena and Jotshi 1996; Ruth 1998).
These particulates tend to be enriched in condensable organics and toxic metals such as
arsenic, cadmium, and lead (Ruth 1998; Linak and Wendt 1993; Niessen and Porter 1991). This
enrichment occurs because the amount of condensation of a given species during exhaust cooling
is proportional to the particle surface area, thus favoring fine particles over coarse ones. Thus,
there is a need to better quantify the amount, chemical composition, and toxics content of these
particles. The objective of their research project was to perform a real-time analysis and
quantification of fine parti culate emissions in the exhaust of waste incinerators, as well as
develop instrumentation for this type of analysis, promote real time monitoring, and better
characterize combustion emissions.
2.3 OBJECTIVES OF THIS REPORT
This synthesis report was developed with the following five objectives:
(1) Summarize the important scientific findings of each of the five research
projects that resulted from this RFA.
(2) Place these findings in the context of past and on-going research on
combustion emissions in general (briefly) and combustion emissions from
hazardous waste and municipal solid waste combustion (in greater detail).
(3) Identify the contributions of these projects to achieving the goals and
objectives of EPA ORD's RCRA Multi-Year Plan (EPA 2004a).
2-2 December 2006
-------
Table 2-1 Grants Awarded Under the Combustion Emissions Solicitation*
Grant
Number
R828189
R828191
R828193
R828190
R828192
Principal
Investigator(s)
Phillip H. Taylor
Barry Bellinger,
Slawomir Lomnicki
Selim M. Senkan
Wayne A. Rubey,
Richard Striebich,
Philip H. Taylor
Kenneth A. Smith,
Hacene Boudries,
Xuefeng Zhang,
Douglas R. Worsnop
Institution
University of Dayton
Louisiana State
University - Baton
Rouge
University of
California - Los
Angeles
University of Dayton
Massachusetts Institute
of Technology,
Aerodyne Research
Inc.
Title of Project
Mechanistic Studies of the
Transformation ofPolychlorinated
Dibenzo-p-Dioxins via Hydroxyl
Radical Attack
Toward the Development of a
Detailed Mechanism of Transition
Metal Catalyzed Formation of
PCDD/Ffrom Combustion
Generated Hydrocarbons
Products of Incomplete
Combustion in the Incineration of
Brominated Hydrocarbons
Trace-level Measurement of
Complex Combustion Effluents and
Residues using Multi-dimensional
Gas Chromatography-Mass
Spectrometry (MDGC-MS)
Characterization and Minimization
of Fine Paniculate Emissions from
Waste Incinerators by Real-Time
Monitoring of Size-Resolved Mass
and Chemical Composition
* Further information regarding the STAR grants program and these grants in particular is available at
http://www.epa.gov/ncer.
(4) Identify research needs related to the topic areas of these projects and the
RFAin general.
2.4
(5) Provide a summary of research needs.
METHODOLOGY
This section describes the methodology used to generate this report, particularly the
information sources and how each was used, and summarizes the quality assurance plan and
review process used to ensure that the report is accurate and meets the stated objectives.
2.4.1 Information Sources
This report was developed using a number of different sources, including:
Reports, publications, and presentation materials provided by the Pis.
2-3
December 2006
-------
Notes taken at the December 2003 EPA-AWMA Information Exchange, an annual
two-day event with an audience of EPA staff, industry representatives, academia, and
environmental consultants, which included at the end of the second day a panel of Pis
and an ORD laboratory representative presenting EPA extramural and in-house
combustion research with a guided discussion of research needs after the
presentations.
Notes taken at the April 2005 American Flame Research Committee meeting, which
included presentations by several ORD in-house researchers, presentations by the Pis,
and a consultant's presentation of a draft of this synthesis report, followed by a
discussion of criteria for setting priorities for combustion research.
Interviews with experts in the field of combustion research (see Appendix A).
Limited literature review of past and ongoing combustion research.
Descriptions of the methodologies and results of the five grants were developed using annual
status reports, final technical reports, publications, presentations and presentation materials, and
discussions with and written comments provided by the Pis.
2-4 December 2006
-------
[this page intentionally left blank]
-------
3. RESULTS AND CONTRIBUTIONS OF THE RESEARCH
3.1 MECHANISMS OF FORMATION OF CHEMICAL COMPOUNDS IN
COMBUSTION SYSTEMS
Research into the mechanisms of formation of chemical compounds in combustion
systems is a broad theme of the EPA RCRA Multi-Year Plan (EPA 2004a). Research by Taylor
and by Bellinger and Lomnicki described in this section both relate to improving the
understanding of mechanisms of formation of chlorinated dioxins and furans in combustion
systems. The research conducted by Senkan described in this section relates to incineration of
brominated compounds and formation of halogenated dioxins and furans and polycyclic aromatic
hydrocarbons.
These three projects identify dioxin and furan precursor compounds and support
development of a comprehensive model of the formation and transformation of halogenated
dioxins and furans under various combustion conditions for various types of wastes, and also
support site-specific risk assessment for combustion systems. Results of these studies are also
applicable to the development of risk management strategies and emissions abatement strategies
for combustion systems.
3.1.1 Mechanistic Studies of the Transformation of Polychlorinated Dibenzo-p-Dioxins
via Hydroxyl Radical Attack, Philip H. Taylor, University of Dayton
3.1.1.1 Background
Polychlorinated dibenzo-p-dioxins (PCDD) are considered among the most toxic organic
chemicals associated with our industrial society. The gas-phase formation and transformation of
these chemicals under high-temperature incineration conditions are not well understood.
Previous studies have shown that OH radical reactions are among the most important elementary
steps in dioxin transformation under these reaction conditions. Prior determinations of OH
radical rate coefficients with dioxins in combustion systems do not exist. Prior bench-scale
experiments on formation of dioxins in combustion systems have measured the formation of
dibenzo-p-dioxin (DD), 1-chlorodibenzo-p-dioxin, 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD),
and 1,2,3,4-tetrachlorodibenzo-p-dioxin (TCDD) at low temperatures (< 500 K) relevant to
atmospheric conditions. A review of the literature demonstrates that knowledge of the rate of
reaction of OH with DD and PCDD is limited to three low temperature experimental studies and
to inference from estimates of room-temperature reactivity. The mechanism of reaction is
completely uncharacterized and is addressed as part of this research project.
3.1.1.2 Objectives
The overall objective of this research project was to determine the rates and mechanisms
of OH radical reactions with DD and selected PCDD compounds over an extended temperature
range. The specific objectives of this research project were identified as follows:
3-1 December 2006
-------
(1) Obtain first absolute rate measurements of the reaction of OH radicals with
DD (kl); 2-chloro dibenzo-p-dioxin (2-CDD) (k2); 2,3-dichlorinated
dibenzo-p-dioxins (2,3-DCDD) (k3); 2,7-DCDD (k4); 2.8-DCDD (k5);
TCDD (k6); and octachloro dibenzo-p-dioxin (OCDD) (k7) over an extended
temperature range (including temperatures approaching post-combustion conditions)
with determination of accurate Arrhenius or modified Arrhenius parameters.
(2) Verify previous low temperature rate measurements for DD, 2,7-DCDD, and
1,2,3,4-TCDD.
(3) Investigate mechanisms of the reaction by examining the relative importance
of the following pathways through limited theoretical analyses: OH addition,
OH addition followed by Cl elimination, and H-atom abstraction.
3.1.1.3 Methodology
OH radicals were produced by three methods:
Photodissociation of nitrous oxide/water vapor mixtures (wavelength =193 nm).
Photodissociation of hydrogen peroxide (wavelength = 248 nm).
Photodissociation of nitrous acid (wavelength = 351 nm) using an excimer laser.
Measurements at lower temperatures were conducted with hydrogen peroxide and nitrous
acid to investigate the effect of photolysis wavelength on the rate measurements. The nitrous
oxide precursor system was used predominantly at elevated temperatures. Experiments were
conducted at low photolysis energies to minimize photolysis of the substrates. Detection of OH
radicals was achieved by laser-induced fluorescence (LIF), exciting the OH band at 282.2 nm
with LIF observed at 306 nm. A schematic of the experimental apparatus is shown in Figure 3-1,
and a schematic of the optical reactor is shown in Figure 3-2.
Gas-phase dioxin was introduced as follows:
1. Solid substrates (typically 4 to 5 mg of sample) were loosely packed into
quartz tubing and set in place using quartz wool. The dioxin and chlorinated
dioxin substrates were 98+ percent pure and were used as received.
2. Helium or argon carrier gas was passed through a sample probe and delivered
a known amount of dioxin vapor to the reactor.
3. Desired dioxin concentration was obtained by controlling sample temperature,
measured by a thermocouple.
4. Concentrations of DD, 2-CDD, and 1,2,3,4-TCDD in the gas stream were comparable
to recent vapor pressure measurements for these substrates as reported in the
literature.
3-2 December 2006
-------
Figure 3-1 Schematic of Overall Reactor System for Taylor's Grant
Nd:YAG Laser
Dye Laser with Doubler
Photodiode
Filters Optical Reactor
S.PMT
V
Computer ' BMCar
Time Delay Generator
-Oscilloscope
5. Concentration was controlled by changing the carrier gas flow rate through
the sample inlet at a constant temperature.
The buildup of reaction products was minimized by conducting experiments under slow
flow conditions. Total gas flows ranged from 220 to 775 ml per minute; linear gas velocities
ranged from 12.9 to 37.6 cm per second. Experiments were performed at a total pressure of
740±10 torr. All experiments were performed under pseudo-first order conditions. Pseudo-first
order exponential OH decays were observed, confirming that the substrate concentration was in
large excess of OH. The individual bimolecular rate constants were determined from:
k' = kbl[substrate] + kd
where:
k' = pseudo-first order rate constant;
3-3
December 2006
-------
Figure 3-2 Blow-Up Schematic of Optical Reactor for Taylor's Grant
kd
bimolecular rate constant, which is the slope of the least-squares fit of k'
versus substrate concentration; and
first-order decay constant due to diffusion and reaction with the OH
precursor.
First absolute rate measurements were acquired using Laser Photolysis/Laser Induced
Fluorescence (LP/LIF) technique.
3.1.1.4 Results and Discussion
Experimental Results
Absolute rate measurements were reported for OH reaction with DD, 2-CDD, 2,3-DCDD,
2,7-DCDD, 2,8-DCDD, 1,2,3,4-TCDD, and OCDD (kl-k7). Rate measurements were obtained
over a temperature range of approximately 300 to 400 K (27 to 127°C) to approximately 900 K
(627°C). Measurements at lower temperatures were not possible because of the inability to
establish pseudo first-order conditions in the reactor because of the low substrate vapor
pressures. The upper limit temperature for the experiments performed was 1,000 K, due to
thermal dissociation of the OH radical precursor (nitrous oxide, N2O). The dioxin substrates may
also begin to dissociate at this temperature, although measurements to 1,100 to 1,200 K may be
possible using a different OH radical precursor or through modification of the optical reactor (a
3-4
December 2006
-------
reduction of the residence time at temperature of the N2O precursor would minimize its
dissociation and permit measurements to slightly higher temperatures).
Changes in carrier gas (helium or argon) had no impact on the rate measurements within
statistical uncertainties. Variation in photolysis wavelength (193 and 248 nm, and 351 nm for
DD and 2-CDD), photolysis energy, total flow rate, substrate concentration, and initial OH
concentration also had no impact on the rate measurements within statistical uncertainties. The
major source of error in these measurements was the uncertainty in the substrate concentration.
Overall, uncertainties ranged from +/- a factor of 2 (DD, 2-CDD, 2,3-DCDD, 2,7-DCDD, and
2,8-DCDD) to +/- a factor of 4 for 1,2,3,4-TCDD and OCDD.
An Arrhenius fit of the extended temperature data for kl to k7 yielded the following
expressions (in units of cmVmolecule-second; error bars are 16):
kl (326-907 K) = (1.70±0.22) x 10-12 exp(979±55)/T,
k2 (346-905 K) = (2.79±0.27) x 10-12 exp(784±54)/T,
k3 (400-927 K) = (1.83±0.19) x 10-12 exp(742±67)/T,
k4 (390-769 K) = (1.10±0.10) x 10-12 exp(569±53)/T,
k5 (379-931 K) = (1.02±0.10)x 10-12 exp(580±68)/T,
k6 (409-936 K) = (1.66±0.38)x 10-12 exp(713± 114)/T,
k7 (514-928 K) = (3.18±0.54)x 10-11 exp(-667±115)/T.
Comparison of the absolute rate measurements for DD, 2,7-DCDD, and 1,2,3,4-TCDD with
previous relative rate measurements generally were within combined experimental uncertainties
of the respective measurements.
In most cases, the likely reaction mechanism for the chlorinated dioxin congeners is OH
addition to form a stabilized hydroxycyclohexadienyl-type radical. The magnitude and negative
temperature dependence of rate measurements are consistent with this mechanism. The reaction
rate and temperature dependence of the OH + OCDD reaction was different from all other
chlorinated dioxin congeners examined in this study. OCDD exhibited a slower reaction rate and
positive temperature dependence throughout the temperature range studied. OH addition at the
Cl-substituted carbon site was the dominant pathway for the OH + OCDD reaction at all
temperatures. OH addition followed by Cl elimination is not significant for the other chlorinated
dioxin congeners because of the much faster OH addition to the non-chlorinated carbon sites.
At elevated temperatures (500 to 1,000 K [227 to 727°C]) relevant to combustion and
post-combustion conditions, there was no evidence for a change in reaction mechanism from the
formation of a stabilized OH addition to H atom abstraction. However, at higher temperatures
(> 1,000 K [727°C]), H atom abstraction is likely the dominant reaction mechanism for most if
not all dioxins (excluding OCDD).
3-5 December 2006
-------
Peer-Reviewed Publication
Taylor, P.H., T. Yamada, and A. Neuforth. Kinetics of OH radical reactions with
dibenzodioxin and selected chlorinated dibenzo-p-dioxins. Chemosphere 58(3): 243-
252.
3.1.1.5 Utilization of Research Results
The fundamental data and models developed in this study will contribute to the
infrastructure of knowledge of reactions of chlorinated hydrocarbons and their impact on the
environment. Results of this research project provide important inputs in the development of a
comprehensive gas-phase model of the transformation of PCDDs under a wide range of
conditions. This model can be used to manage risk by preventing and controlling formation and
emissions of PCDDs through combustion modification or other emission abatement techniques.
The model can also be applied to site-specific risk assessment for combustion sources. There is,
however, no published kinetic model incorporating these rate coefficients.
3.1.1.6 Research Needs
Project-Related Research Needs
The PI identified the following research needs related to the above project:
Dioxin atmospheric fate data are needed for source attribution studies.
The understanding of the fate of dioxins in the atmosphere needs to be improved.
This requires ambient temperature kinetic data versus the high temperature chemistry
data obtained in this study.
Results of this study should be compared with those results generated from different
techniques.
Extension of the work to other CDD species, especially 2,3,7,8 TCDD.
Collection and analysis of experimental data to follow the degradation reaction
scheme for CDD species after OH addition to track changes (up or down) in the
environmental significance of downstream species (PICs).
A comprehensive model for dioxin formation in incinerators should be developed, but
not if there are insufficient funds to validate the full-scale model.
3-6 December 2006
-------
3.1.2 Toward the Development of a Detailed Mechanism of Transition Metal Catalyzed
Formation of PCDD/F from Combustion Generated Hydrocarbons, Barry Dellinger
and Slawomir Lomnicki, Louisiana State University - Baton Rouge
3.1.2.1 Background
The formation of dioxins and furans in combustion sources is a significant environmental
issue. Field studies suggest that they are formed in the post-combustion, cool-zone of
combustors by surface-mediated/catalyzed pathways. Laboratory studies have demonstrated that
some transition metals, incorporated into silica-based fly ash, can catalyze dioxin formation in
the 250 to 500°C (523 to 773 K) range. However, the exact mechanism has not been determined
and is the subject of this research project.
3.1.2.2 Objectives
The objective of this research project was to reveal the mechanism of the formation of
dioxins and furans on metal oxide surfaces based on the following assumptions:
Dioxins can be formed by surface condensation of dioxin precursor compounds (e.g.,
chlorophenols, chlorobenzenes).
Light hydrocarbons (containing less than 6 carbon atoms) present in the combustion
system exhaust gas stream can undergo metal catalyzed growth and aromatization to
form dioxin precursors.
3.1.2.3 Methodology
Experimental studies were conducted using a high-temperature flow reactor equipped
with an in-line GC-MS for chemical analysis of the reactor effluent. The system is designed so
that solid, liquid, or gaseous reactants, as pure compounds or mixtures, can be introduced at a
constant feed rate. The injection region of the system has a separate temperature control to
facilitate introduction of reactants. The system is designed for interchangeable reactors. The
gas-phase reactor can be operated from room temperature to 1,100°C and gas-phase residence
times of 0.25 to 6.0 s. The solid phase reactor can be operated over the same temperature range
but the gas-phase residence time is typically < 2.0 s within the packed-bed.
The GC-MS is connected to the outlet of the reactor by a heated transfer line. The
temperature of all transfer lines is maintained at a temperature that allows reactant and products
to be transported without thermal degradation. Because the reactor effluent is directly
transported to the GC without intermediate trapping, very low levels (20 pg) of products can be
detected. The GC column is cryogenically cooled with liquid nitrogen, which traps and focuses
the products at the head of the GC column. Once the temperature program of the GC is
activated, normal separation of products and GC-MS analysis is performed.
3-7 December 2006
-------
For the purposes of this research project, catalytic tests were performed under both
oxygen-free and oxidative conditions. Experiments were set up as follows:
A five percent copper oxide/silica catalyst system was prepared.
Experiments were carried out under two conditions: pyrolytic (helium only) and
oxidative (20 percent O2 in helium).
Studies were performed over a 200 to 500°C (473 to 773 K) temperature range, using
1 mg and 3 mg of the catalyst.
2-chlorophenol was introduced to a fixed bed flow reactor. The gas-phase
concentration of 2-chlorophenol ranged from 30 to 180 parts per million (ppm).
A reactant flow rate of 5.5 cm3 per minute was used.
Figure 3-3 depicts a flow diagram of research activities associated with Bellinger and
Lomnicki's project. The block at the top labeled chlorophenol and copper oxide processes refers
to the reaction of chlorinated phenols over a copper oxide catalyst bed. PCDD/F as well as non-
PCDD/F (PICs, or products of incomplete combustion) were identified in the flow reactor studies
(middle path in the diagram). Separate NSF-funded studies addressed chemisorption of PCDD/F
precursors and formation of surface-associated, persistent free radicals (left-hand path).
Assessment of reaction and rate constants led to the development of reaction kinetic models of
PCDD/F formation (right-hand pathway).
3.1.2.4 Results and Discussion
Experimental Results
Catalytic Test (Pyrolytic Conditions):
The direct condensation reaction of 2-chlorophenol formed a limited number of
PCDD/F congeners as follows: dibenzo-p-dioxin (DD), 1-monochlorodibenzo-p-
dioxin (MCDD), and 4,6-dichlorodibenzofuran (DCDF).
For the surface mediated reaction, the maximum PCDD/F formation occurred at
temperatures around 400 to 450°C (673 to 723 K).
For the gas-phase reaction, the maximum PCDD/F formation occurred at
temperatures around 550 to 600°C (823 to 873 K).
0.28 percent of the 2-chlorophenol introduced was converted to one or more of the
three congeners.
The highest overall conversion occurred for DD; at low temperatures (200 to 350°C
[473 to 623 K]), DCDF yield was highest.
3-8 December 2006
-------
Figure 3-3 Flow Diagram of Research Activities of Bellinger and Lomnicki's Project
Chterepheool
and
t
Cbemisorption
FTIR Studies
\
Rad
Form
iPRS
f
ical
tlon
twdies
* t
Products
Flow Reactor
Studies
1
^
PCDD/F and
PIC Yields
\
Theoretical
Modeling
Studios
1
f
Reaction
Kinetic Modal
Dwalapmant
f
Ceiled Formation MeehanisrFT-v
Gas-Solid Partftloning J
Congener Pattern __.>'
Additional Research Needs
Similar trends were observed using 1 mg and 3 mg of catalyst. The amount of
catalyst did not affect conversion of 2-chlorophenol to DD and MCDD, but did affect
DCDF conversion. Conversion to DCDF increased from 0.11 percent for 3 mg
catalyst to 0.15 percent for 1 mg of catalyst. The smaller the amount of catalyst, the
higher the yield of DCDF.
There was a sharp decline in PCDD/F formation above 475 °C (748 K) due to the
oxidation of PCDD/Fs or its surface precursors. The surface of the copper oxide was
the source of the oxygen for this oxidation process.
More than 95 percent of 2-chlorophenol was oxidized at temperatures above 350°C
(623 K).
As a result of the 2-chlorophenol reaction over the catalyst, higher chlorinated
congeners of dioxins were found in the reaction products. Almost all PCDD
congeners were detected; however, at temperatures of 350°C (623 K) and above,
polychlorinated dioxins disappeared from the products and only DD and MCDD were
formed. No higher chlorinated furans were detected in reaction products over the
entire temperature range.
A correlation between the amount of DD formed and the amount of highly chlorinated
dioxin reaction products was observed. DD stays adsorbed to the surface immediately
3-9
December 2006
-------
after its own formation at low temperature (200 to 350°C [473 to 623 K]). It is
believed that highly-chlorinated dioxins result from the chlorination of adsorbed DD.
When temperature increases (in this case at 350°C [623 K] and above), the desorption
rate of DD increases, the amount of dioxin formed increases, and poly chlorinated
dioxins disappear.
Catalytic Test (Oxidative Conditions):
Similar experiments were performed under oxidative conditions, results of which are
discussed below.
At 3 mg of catalyst, no PCDD/Fs were detected at temperatures above 250°C (523
K). Below 250°C (523 K), only MCDD was detected. However, its maximum yield
was only at the detection limit. Therefore, other PCDD/Fs may have been formed,
but below detection limits.
At 1 mg of catalyst, MCDD yield was highest (-0.28 percent), an order of magnitude
higher than the MCDD yielded under pyrolytic conditions. This highest yield
occurred at 350 to 375°C (623 to 648 K). Because MCDD is desorbed after its
formation, it is not subject to extensive surface oxidation by the copper oxide.
Yield of DCDF appeared to be unaffected by the presence of oxygen. Therefore,
oxygen does not appear to be a limiting factor in DCDF formation.
Yield of DD dropped by one half in the presence of gas-phase oxygen. It was
hypothesized that, with the presence of oxygen, more of the surface-adsorbed DD is
being oxidized, resulting in an overall decrease in DD yields.
More highly chlorinated PCDDs were formed as reaction products under oxidative
conditions versus pyrolytic conditions. Under oxidative conditions, the rate of DD
chlorination (to form the highly chlorinated PCDDs) was greater than the rate of DD
adsorption.
As mentioned earlier, the chlorination process and formation of highly chlorinated
PCDDs was suppressed under pyrolytic conditions at temperatures of 350°C (623 K) and above;
however, under oxidative conditions, the chlorination process was more effective above 350°C
(623 K) and the concentrations of highly chlorinated PCDDs were higher.
Reaction Rates for DD, MCDD, and DCDF Formation:
Rate orders of the three congeners were determined at 250°C (523 K) under oxidative
conditions.
DD and MCDD exhibited similar positive reaction rates of 0.6 and 0.7, respectively.
3-10 December 2006
-------
The slightly higher reaction rate for MCDD compared to DD indicates a weaker
adsorption factor for MCDD.
DCDF formation exhibited a negative rate order (-0.6).
DCDF is likely formed by a Langmuir-Hinshelwood mechanism; DD and MCDD are
formed according to the Eley-Rideal mechanism. Langmuir-Hinshelwood assumes
that both reacting molecules adsorb on the surface, react on the surface, and then
reaction products desorb from the surface. Eley-Rideal assumes that only one of the
reacting molecules is adsorbed on the surface, while the other reacts from the gas
phase.
Peer-Reviewed Publication
Lomnicki, S. and B. Dellinger. 2003. A detailed mechanism of the surface-mediated
formation of PCDD/F from the oxidation of 2-chlorophenol on a CuO/silica surface.
Journal of Physical Chemistry A 107(22): 4387-4395.
3.1.2.5 Utilization of Research Results
The development of a unified mechanism and understanding of PCDD/F formation in the
post-combustion, cool-zone of combustors will greatly facilitate the development of improved
risk management and risk assessment strategies for combustion systems. Gas-phase reactions
and kinetics impact the formation of PCDD/F in combustion systems, but the effect is primarily
indirect through destruction of gas-phase PCDD/Fs and homogeneous gas-phase formation of
some precursors. The principal source of PCDD/F in combustion systems is in all likelihood
surface-mediated by fine and ultrafine particles. Understanding of these mechanisms could be
applied to the development of emissions abatement strategies for combustion systems.
General strategies include:
Modifying post-combustion time-temperature profiles to mitigate PCDD/F formation.
Controlling the content of catalytic metals in the combustor feed.
Modifying combustion conditions to minimize formation of catalytic, fine and
ultrafine particles.
Blending of fuels and wastes to avoid the optimum compositions for PCDD/F
formation.
3-11 December 2006
-------
3.1.2.6 Research Needs
Project-Related Research Needs
According to the Pis, the above work also has implications for the possible involvement
of other species, such as chlorinated benzenes, in the formation of PCDD/Fs. The exhaust of
incinerators contains higher concentrations of chlorinated benzenes than chlorinated phenols.
Based on the proposed mechanism of formation, this suggests significant consequences with
respect to the formation of dioxins and furans; therefore, chlorinated benzenes (and their role in
the formation of PCDD/Fs) deserve further study.
Additional Research Needs
The following research recommendations related to combustion emissions were also
identified by the Pis:
Study the role of chlorobenzenes in the surface-mediated mechanisms of PCDD/F
formation.
Examine the role of combustion-generated nanoparticles in pollutant formation in all
chlorine-containing combustion systems. This is an important area as PCDD/F-
forming reactions may occur on nanoparticles prior to their concentration being
reduced by aggregation and agglomeration.
Determine the origin and nature of gas-phase and particle-associated persistent free
radicals.
Develop improved techniques for the study of high temperature surface reactions for
time scales on the order of seconds.
Examine elementary reactions of chlorinated phenoxyl and phenyl radicals.
Investigate photothermal reactions in flares and plumes.
Characterize emissions from on-site "thermal treatment" systems used for site
remediation and compare the emission profiles for these systems to the emission
profiles for high temperature systems. There is an unfortunate trend to use lower-
temperature thermal desorbers and non-flame, thermal treatment systems as on-site
remediation devices to avoid being labeled as an "incinerator." These lower
temperature systems may enhance formation of PCDD/F and other PICs in an effort to
avoid incinerator regulations and negative public opinion.
Characterize the sources of bromine in combustion systems that emit brominated
hydrocarbons.
3-12 December 2006
-------
3.1.3 Products of Incomplete Combustion in the Incineration of Brominated
Hydrocarbons, Selim M. Senkan, University of California - Los Angeles
3.1.3.1 Background
Incineration is used as a treatment method for the disposal of organic hazardous wastes,
including wastes that contain halogenated hydrocarbons. However, the combustion of
halogenated hydrocarbons is associated with the formation of trace levels of toxic products of
incomplete combustion (PICs), such as aromatics and polycyclic aromatic hydrocarbons (PAHs),
halogenated dibenzo-furans (HDFs), bi-phenyls, and pyrenes. Because some of these PICs are
known or suspected carcinogens, the development of a better understanding of their origins and
fate is important for the continued use of incineration as a waste minimization technology. The
fact that these pollutants are formed at trace levels, i.e., parts per billion (ppb) to parts per trillion,
means that incineration and combustion chemistries must be quantified at the ppb and parts per
trillion levels.
3.1.3.2 Objectives
Initial objectives of this research project were to develop detailed insights into the
formation and control of potentially toxic PICs in the incineration of brominated and related
halogenated hydrocarbons. Initial experiments, however, showed the production of excessive
amounts of soot, which prevented sampling of the flames of brominated hydrocarbons. These
initial tests also revealed the production of hydrocarbon intermediates such as acetylene,
1,3-butadiene and n-heptane in the combustion of brominated hydrocarbons. Because these
intermediates were also reported in the combustion of unhalogenated hydrocarbons, efforts were
directed towards developing detailed insights into the combustion of these hydrocarbon
intermediates. Such an effort will be crucial for the development of detailed chemical kinetic
mechanisms (DCKM) describing the formation and destruction of PICs in the combustion of
halogenated and unhalogenated hydrocarbons.
The specific objectives of this research project were as follows:
(1) To determine the absolute concentration profiles of major, minor, and trace
PIC species, as well as temperature and soot profiles in the laminar
pre-mixed and diffusion flames of acetylene, 1,3-butadiene, and n-heptane,
that were produced as significant intermediates in the flames of brominated
hydrocarbons (BHCs).
(2) To establish detailed mechanisms for the combustion of acetylene,
1,3-butadiene, and n-heptane that allow quantitative predictions of the
formation of PIC in combustion and incineration processes. These DCKM
will also be useful in developing better insights into the role halogens play in
combustion, i.e., how they promote soot, polycyclic aromatic hydrocarbon
(PAH), and dioxin formation.
3-13 December 2006
-------
3.1.3.3 Methodology
The first objective was accomplished by employing the following methodology:
Species concentration profiles were determined by withdrawing samples from within
flames using heated micro-probes followed by gas analysis by an online
high-resolution gas chromatography/quadrupole mass spectrometry (GC/QMS).
Temperature measurements were taken with thermocouples using the rapid insertion
thermocouple technique to prevent excessive soot accumulation on thermocouple
beads.
Throughout the duration of the project, a number of premixed and diffusion flame
experiments were performed. A brief description of each is provided below.
Experiment 1: Evaluated combustion of pure CH3Br in O2/Ar using an opposed j et
diffusion flame system.
Experiment 2: Evaluated the effects of equivalence ratio on species and soot
formation using premixed n-heptane flames in O2/Ar. After considering the O2
requirements for hydrogen to water and carbon to carbon dioxide, the resulting mix
had carbon to oxygen (C/O) atom ratios of 0.63 and 0.67. A heated quartz
microprobe coupled to an online GC/MS (HP 5890 Series II/HP 5972) was used to
identify and determine absolute concentrations of stable major, minor, and trace
species using direct analysis of samples withdrawn from the flames. Soot-particle
diameters, number densities, and volume fractions were determined using classical
light scattering and extinction measurements.
Experiment 2a: Evaluated the effects of three oxygenate additives (methanol, ethanol,
and methyl tertiary butyl ether) on the formation of PAHs and soot in laminar,
premixed, atmospheric-pressure, and fuel-rich flames of n-heptane at an equivalence
ratio of 2.10. These runs were performed in order to assess how oxygenated species
decrease PAH and soot formation, which is equivalent to studying flames with lower
C/O ratios. In oxygenated species there is less need for O2.
Experiment 3: Studied soot formation in premixed flames of methane, ethane,
propane, and butane at three different equivalence ratios. Soot-particle sizes, number
densities, and volume fractions were determined using classical light scattering
measurement techniques.
Experiment 4: Studied the effects of three percent O2 addition on PAH formation,
using a 1,3-butadiene counter-flow diffusion flame. Effects were investigated using
heated microprobe sampling and online GC/MS. Centerline gas temperature and
species mole fraction profiles were measured both with and without oxygen on the
fuel side. The rapid thermocouple insertion method was used to obtain the flame
temperature profiles.
3-14 December 2006
-------
Experiment 5: Performed kinetic modeling of counter flow diffusion flames of
butadiene and mixing effect. A comprehensive, semi-detailed kinetic scheme was
used to simulate the chemical structures of counter-flow diffusion and fuel-rich
premixed 1,3-butadiene flames to better understand PAH formation.
Experiment 6: Acetylene, a ubiquitous combustion intermediate, is believed to be a
major hydrocarbon intermediate product responsible for the production of aromatics,
polyaromatics, dioxins, furans, PAHs, and soot in hydrocarbon and halogenated
hydrocarbon flames. Despite its important role as a flame intermediate, however, the
detailed chemical structures of pure acetylene diffusion flames have not been studied.
PAHs in counter-flow diffusion flames of acetylene were studied as a function of
carbon density. Rapid insertion thermocouple techniques were used for temperature
measurements.
Figure 3-4 is a schematic diagram of the counter flow diffusion flame setup used in
Senkan's experiments 1, 4, 5, and 6. Pre-mixed, McKenna-type burners were used for
experiments 2 and 3.
3.1.3.4 Results and Discussion
Experimental Results
Experiment 1 (CH^Br): Flames produced significant levels of acetylene and
1,3-butadiene and excessive amounts soot. That is, the levels were so high that the
sampling probe was rapidly plugged. Soot plugged the sampling probes within 100
milliseconds and representative flame samples could not be obtained. It is believed
that acetylene and 1,3-butadiene are major hydrocarbon intermediates in flames
responsible for the production of aromatics, polyaromatics, dioxins, furans, PAHs,
and ultimately soot, as discussed in the publications listed below..
Experiment 2 (n-heptane): The aromatic compound detected in most abundance was
benzene. The largest molecular weight PAHs detected were in the C18H10 fraction that
includes cyclopenta[cd]pyrene and benzo[ghi]fluoranthene. Peak concentrations of
these PAHs were 8 ppm and 6 ppm, respectively. The largest soot-particle diameter
measured was about 18 nm, and the soot- volume fraction reached the amount of
4.9 x 107.
Experiment 2a (n-heptane and oxygenated additives): All of the oxygenate
additives studied reduced the mole fractions of aromatic and PAH species by
generally in the range of 20 to 40 percent. Depending on conditions, this is probably
not enough to represent a control technology. Soot formation was also reduced by
about 10 to 40 percent by all oxygenate additives in a comparable manner.
Experiment 3 (premixed hydrocarbon flame): Results of this experiment revealed
that the soot properties were sensitive to fuel type and the combustion parameter
equivalence ratio. An increase in the equivalence ratio increased the amount of soot
3-15 December 2006
-------
formed for each fuel. In addition, methane flames showed larger particle diameters at
higher distances above the burner surface followed by propane, ethane, and butane,
respectively.
Experiment 4 (PAH formation and oxygen addition): The addition of oxygen to the
fuel side did not significantly change the shape and peak values of the temperature
profiles; however, species mole fraction profiles were altered significantly due to
oxygen addition in the fuel. The presence of oxygen in the fuel led to decreased peak
mole fractions of the aromatic and two-ring PAHs. In contrast, the peak mole
fractions of PAHs having three or more rings increased significantly in the presence
of oxygen on the fuel side.
Experiment 5 (PAH formation in 1,3-butadiene flames): The pathways
characterizing the pollutant formation are very different in the premixed and
counter-flow flames, confirming the need to verify and refine the detailed
mechanisms for premixed conditions when they are extrapolated and used in diffusion
flames. Reaction path analysis for PAH formation in the counter-flow flame showed
that the hydrogen-abstraction/ carbon-addition mechanism and the resonantly
stabilized radicals are important for the growth of PAHs.
Experiment 6 (Carbon density and PAH formation in acetylene diffusion flames):
Butadiene was the most abundant pyrolysis product in the acetylene flames followed
by vinylacetylene (l-buten-3-yne). The aromatic compound detected most was
benzene followed by phenylacetylene (ethynylbenzene). As particular characteristics
of acetylene flames, acenaphthylene was more abundant than naphthalene. Paraffins
such as methane, ethane propane, butane, and heavier compounds were not detected.
The largest PAHs detected were in the C18H10 fraction that includes
cyclopenta[cd]pyrene and benzo[ghi]fluoranthene.
Peer-reviewed Publications
Olten, N. and S. Senkan. 2001. Effect of oxygen addition on polycyclic aromatic
hydrocarbon formation in 1,3 butadiene counter-flow diffusion flames. Combustion
andFlame 125(1-2): 1032-1039.
Inal, F. and S. Senkan. 2002. Effects of equivalence ratio on species and soot
concentrations in premixed N-heptane flames. Combustion andFlame 131(1-2):
16-28.
Inal, F. and S. Senkan. 2002. Effects of oxygenate additives on polycyclic aromatic
hydrocarbons (PAHs) and soot formation. Combustion Science and Technology
174(9): 1-19.
Inal, F., G. Tayfur, and S. Senkan. 2003. Experimental and artificial neural network
modeling study on soot formation in premixed hydrocarbon flames. Fuel 82(12):
1477-1490.
3-16 December 2006
-------
Granata, S., T. Faravelli, E. Ranzi, N. Olten, and S. Senkan. 2002. Kinetic modeling
of counterflow diffusion flames of butadiene. Combustion and Flame 131(3):
273-284.
Yamamoto, M. and S. Senkan. The effect of strain rate on polycyclic aromatic
hydrocarbons (PAH) formation in acetylene diffusion flames. Accepted for
publication as of January 2006.
3.1.3.5 Utilization of Research Results
According to the PI, the results of this research project may be useful to the
combustion/incineration community in the following ways.
Generating these data concerning major, minor, and trace species concentration
profiles and soot and temperature profiles will provide valuable new information.
These data are useful for the development and validation of DCKM describing the
combustion of hydrocarbons and intermediates which were found from brominated
hydrocarbons in flames. In fact, the development of DCKM for hydrocarbons was
determined to be an important prerequisite to develop insights into the formation of
toxic PICs in the combustion of halogenated hydrocarbons.
3-17 December 2006
-------
Figure 3-4 Counter Flow Diffusion Flame Setup from Senkan's Project
Sampling l.u«fiv
MS
Sampling. Vah'es_. Vo -i
in Viiniwn firmp
3-18
December 2006
-------
The development of DCKM will result in improved predictions regarding the conditions under
which PAHs and dioxins form in incinerators.
The detailed mechanisms developed can subsequently be combined with fluid
dynamic models to simulate, design, and develop optimum strategies for practical
incinerators such that their operations would result in emissions of lowest possible
levels of PICs, thereby reducing possible risk to public health.
3.1.3.6 Research Needs
Project-Related Research Needs
In relation to Experiment 1, the PI identified the need to conduct experiments where
CH3Br represents a small fraction of the fuel combusted. However, under these conditions it is
difficult to unambiguously establish the role halogens play in combustion and incineration
processes because the hydrocarbon fuel dominates the reaction process. In relation to
Experiment 4, the PI suggested the need to invoke new reaction mechanisms describing the
formation and destruction of PAHs in hydrocarbon combustion, including steps describing the
formation of soot. The PI also identified the need to study brominated hydrocarbon combustion
in flameless, flow reactors in order to facilitate control the temperature time history and be able
to acquire species concentration data before the onset of soot formation.
In addition, the PI noted that the existing kinetic models (Experiment 5) were
unsuccessful in predicting the increased reactivity in O2-doped diffusion flames and indicated the
need for improved models and the opportunity for new experiments of butadiene oxidation in the
intermediate temperature region. With regard to Experiment 6, the PI noted the need to revise
the DCKM in order to properly account for significant increases observed in the formation of
aromatics and polyaromatics in lower strain rate flames of acetylene.
Additional Research Needs
The PI noted that followup research should focus on the development and validation of
detailed chemical kinetic mechanisms describing the formation and destruction of trace PICs
associated with combustion and incineration processes. These studies should involve the use of
experimental data generated by the PI, which are the most comprehensive in the open literature.
These modeling studies will result in the identification of the most influential elementary
reactions, which can then be studied by research groups as described elsewhere in this report.
3.1.4 Summary of the Overall Contributions of These Three Projects to the RCRA
Multi-Year Plan and Its Broad Theme of "Mechanisms of Formation"
The RCRA Multi-Year Plan identifies the following three Waste Management Science
Questions (EPA 2004a).
3-19 December 2006
-------
What easily monitored components of emissions can be used to predict more
difficult-to-measure components (e.g., PCDD/PCDF)?
How can complex mixtures of organic compounds in the stack gases be characterized
with respect to risk assessment needs?
What PCDD/PCDF formation issues exist during combustion of hazardous wastes?
The three grants described in the preceding sections directly address these questions
through improved characterization of the mechanisms of formation of components of air
emissions from combustion systems. These three research projects identify dioxin and furan
precursor compounds and halogenated dioxin and furan species and provide insight into the
formation and transformation mechanisms in combustion systems.
Specifically, Taylor has characterized chlorinated dioxins and provided OH radical
reaction rate measurements that have not previously been investigated. Dellinger and Lomnicki
investigated the effects of metals on catalysis of formation of chlorinated dioxins and furans in
combustion systems and identified a correlation between the amount of dibenzo dioxin and the
amount of highly-chlorinated dioxin products formed as well as the effect of temperature on this
mechanism. These results also identify dioxin and furan formation issues related to combustion
of hazardous waste and provide data relevant to the identification of surrogate compounds to
correlate to emissions of more highly chlorinated dioxins and furans. Senkan provided
information concerning mechanisms of formation of PAHs and soot. These results are also
relevant to formation issues related to combustion of hazardous waste and to identification of
surrogate compounds.
3.2 MONITORING AND ANALYTICAL METHODS FOR CHEMICAL
COMPOUNDS IN COMBUSTION SYSTEMS
Research into the monitoring and analytical methods for chemical compounds in
combustion systems is a broad theme of the EPA RCRA Multi-Year Plan (EPA 2004a).
Research by Striebich et al. and Smith et al. described in this section relate to improving
analytical methods for measurement of halogenated dioxins and furans and metals in combustion
systems. The research conducted by Rubey, Striebich, and Taylor described in this section
relates to development of advanced chromatographic techniques to enable separation and
characterization of complex mixtures of emissions from combustion systems in a rapid manner.
The research conducted by Smith and Boudries relates to development of advanced techniques to
collect fine particulate emissions from combustion systems and characterize individual species in
the fine particulate emissions. Data generated by such advanced sampling and analysis systems
would enable identification of specific toxic compounds in the emissions from combustion
systems and support site-specific risk assessment for combustion systems. Results of these
studies are also applicable to the development of risk management strategies and emissions
abatement strategies for combustion systems.
3-20 December 2006
-------
3.2.1 Trace-Level Measurement of Complex Combustion Effluents and Residues Using
Multidimensional Gas Chromatography-Mass Spectrometry (MDGC-MS), Wayne
A. Rubey, Richard C. Striebich, and Philip H. Taylor, University of Dayton
3.2.1.1 Background
Effluents from hazardous waste incinerators, municipal solid waste incinerators, and
other combustion sources can be very complex. Although most combustion systems are capable
of destroying the organic feedstocks that come into direct contact with the flame, the great
majority of compounds observed in combustion effluents (i.e., PICs) may be formed in reactions
occurring outside of the flame zone. Due to the wide range of potential PIC formation conditions
and extreme variation in the composition of wastes, highly complex combustion emissions and
residues are probable.
Organic emissions and organic compounds extracted from particulate matter (PM) are
more complex than standard gas chromatography-mass spectrometry (GC-MS)-based
instrumentation can currently measure. The ability to correctly identify and quantify components
of complex combustion emissions is critical to determine the toxicity and risk associated with
combustion sources. Therefore, more advanced instrumentation is needed to better characterize
these complex organic compounds and PM extracts from combustion emissions sources. The
greater number of analytes accounted for by advanced techniques, the less uncertainty may be
associated with site-specific risk assessments.
Conventional GC-MS uses a single primary separation technique (i.e., a one-dimensional
chromatographic analysis) and may be adequate for simpler mixtures and for identifying
compounds of known toxicity that are currently regulated. However, with regard to many of the
complex combustion effluents and residues, use of a single gas chromatography system results in
separations with a substantial amount of superpositioning of analyte zones. This co-elution
restricts the mass spectral analysis of individual constituents and prohibits accurate quantization
of many solutes. In particular, low, small concentration peaks are lost. Complete separation of
complex mixtures requires increased peak capacity beyond that which a conventional GC can
provide. With conventional GC-MS, users may only identify a modest number of the major
chemical components and some prominent target species in effluent samples.
The large number of compounds in these various fractions requires enhanced analytical
separation techniques, such as that available with multi-dimensional gas chromatography
(MDGC). MDGC combines one-dimensional techniques to achieve multidimensional
separation. Systems currently in use are capable of achieving excellent chromatographic
separation for complex mixtures associated with combustion effluents and residues.
3.2.1.2 Objectives
The primary purpose of the first phase of this research project was to demonstrate that
MDGC-MS significantly improves chromatographic separation for complex mixtures, such as
3-21 December 2006
-------
those emitted from hazardous and municipal solid waste incinerators. In addition, there is a
continuing need to conduct these analyses in a rapid fashion without losing the separation power
in the chromatographic step. Therefore, the purpose of the second phase of this project was to
enhance the speed of separations using this multidimensional system.
Based on this need for improved analytical techniques for identifying and quantifying
chemical compounds in combustion systems in a rapid manner, the overall objectives of this
research project were as follows:
To develop, test, and use advanced MDGC instrumentation capable of achieving high
resolution separations to examine combustion effluents and residues. Higher
resolution would result in more precise identification and quantization of these
compounds and higher confidence mass spectral analyses.
To couple the MDGC system with an MS for the identification of uncharacterized
compounds.
To conduct separations and characterization of combustion effluents and residues in a
rapid fashion such that secondary column separations can keep up with the primary
column separations.
3.2.1.3 Methodology
Figure 3-5 shows a schematic of the MDGC-MS system. The MDGC-MS system
designed for the purposes of this research project consisted of two capillary chromatography
columns (i.e., a non-polar primary column and a polar secondary column) connected with a
cryogenic refocusing trap. A mass selective detector (i.e., mass spectrometer) was added for
component identification. Additional components of the MDGC-MS system included the flame
ionization detector (FID) used to measure the effluent from the primary column and monitor the
one-dimensional separation. Solute zones passed into the secondary column via the cryogenic
trap, where they were refocused into a narrow band of solute, eliminating component dispersion.
(Dispersion in chromatography can cause the separation of components and make peak
identification and quantification difficult.) The secondary column was designed for fast
chromatography. This column eases the identification of components by separating major
compound classes based on polarity. After secondary separation, components of the sample were
detected using the mass selective detector.
Samples of several complex mixtures related to combustion processes, including diesel
engine exhaust, hazardous waste incinerator effluent, and open burning of household wastes,
were tested using this system. Mixtures were tested on both the MDGC-MS system and a
conventional GC-MS system and chromatographic separations were compared. All research
publications used a GC-MS of some kind, either a GC with Agilent MS or currently
GC-TOFMS. The FID was used for the primary detection but not for the secondary detection.
3-22 December 2006
-------
Figure 3-5 Schematic of a MDGC System Used in Rubey, Striebich, and Taylor's Project
INJECTOR
FID
\
i, A *
M"M J
Trap/release zone
POLAR
MASS
p., f» jftymm, .(»* f«j,
DETECTOR
The research project now uses a very fast mass spectrometer to take the MDGC data to
accommodate the shorter, faster secondary columns, and has a TOFMS and an associated data
station which can sample at 500 Hz compared to 10-20 Hz for conventional mass spectrometers.
During the final year of this research project, a new trap and release system, specifically a
thermal gradient programmed GC (TGPGC), was tested to enhance the speed of separations in
the secondary column of the MDGC -MS system. In using this optimized secondary separation, it
was determined that the current MS was neither fast enough nor sensitive enough to perform
these fast analyses. Therefore, use of a time of flight mass spectrometer (TOFMS) as detector for
the TGPGC system is planned for future experiments (but was not employed as part of this
grant). The research project now uses a very fast mass spectrometer to take the MDGC data to
accommodate the shorter, faster secondary columns, and also uses a TOFMS and an associated
data station which can sample at 500 Hz compared to 10-20 Hz for conventional mass
spectrometers.
3.2.1.4 Results and Discussion
Experimental Results
For the purposes of this research project, the Pis designed, built, and tested a MDGC -MS
system for the analysis of several combustion mixtures that are more complex that conventional
GC-MS systems can analyze (i.e., diesel exhaust, hazardous waste incinerator effluent, and open
burning of household wastes). The design and construction of this system was accomplished
during the first 14 to 18 months of the project.
Tests of this system showed that it was capable of comprehensive analysis of all of the
tested mixtures. Researchers demonstrated that using the MDGC -MS system significantly
improved chromatographic separation for complex combustion-related mixtures. Using this
3-23
December 2006
-------
system, the Pis were able to identify new compounds in combustion samples not previously
identified using conventional GC-MS systems due to the fact that they are in low concentration,
not regulated (i.e., no one routinely looks for them), and obscured within complex mixtures not
easily separated by conventional techniques. Most notable is that the MDGC-MS detected
bromine compounds, oxy-PAH, and other oxygenates that the conventional GC did not detect.
Additional details regarding results using the MDGC-MS system are provided below (by
mixture).
Hazardous Waste Incineration Mixture
PICs, difficult to analyze by conventional techniques, were identified by MDGC-MS.
Most of the compounds detected in the hazardous waste sample contained chlorine or
bromine atoms, an indication that the compounds may be of interest for future studies.
Diesel Exhaust Emissions from Automobile Engines
Concentrations of compounds were low (one to five ppm); MDGC-MS enabled
researchers to separate these low concentration oxygenated PAHs from high
concentration compounds.
Compounds were accurately identified; concentrations and emission rates were also
determined.
Diesel Truck Exhaust
Many alkene and alkane components were separated by MDGC in the secondary
column and revealed potentially toxic compounds in combustion emissions that were
not identified using conventional GC-MS techniques.
With this technology, non-target compounds (e.g., oxygenated PAHs) were readily
observed.
Open Burning of Household Waste
Represented the most complex mixture examined; the multi-dimensional
chromatogram contained hundreds of peaks, the majority of which were separated
with the high resolution MDGC-MS system.
Component concentrations were determined.
Brominated compounds were identified in the combustion sample.
3-24 December 2006
-------
Compounds such as bisphenol A (BPA; a potential endocrine disrupter) were found
using MDGC-MS.
Based on the results of these tests, key advantages of MDGC-MS over conventional
GC-MS may be summarized as follows:
Improved separation and component resolution. With enhanced separation power,
co-elution was greatly reduced. Low concentration compounds were detected and
correctly identified.
Improved peak identification. MDGC-MS can provide more reliable mass spectral
patterns and the ability to identify those compounds which may be toxic or are of
unknown toxicity that are not regulated and are therefore typically ignored.
Enhanced peak capacity. MDGC-MS can provide more accuracy in quantifying the
amount of particular compounds in a mixture.
Overall, MDGC-MS worked better for characterizing complex mixtures associated with
combustion effluents and residues than conventional GC-MS techniques. It is important to note,
however, that not every sample requires MDGC-MS analysis. Conventional techniques are still
appropriate for particular, less complex mixtures.
For the purposes of this research project, MDGC-MS was successful, although it did not
separate all complex components completely and run times were long (3 hours or more). Due to
the long run times, the MDGC system was recreated using a more advanced secondary separation
technique (TGPGC) to increase the speed of analysis as well as to decrease peak width of
individual solute profiles and increase peak detectability. Using TGPGC optimized secondary
separation and resulted in 15-second secondary separations, versus 45-second secondary analysis
using MDGC-MS.
In using the enhanced TGPGC system, the peaks are produced from the secondary
column faster and are made narrower in time. A narrower peak means a higher and more
detectable peak. Therefore, faster scanning speeds are needed to obtain the identification of the
peak. The next step is to incorporate the TOFMS, a faster MS for detecting peaks of interest,
into the TGPGC to obtain a more effective analysis system. With incorporation of TOFMS, it
should be possible to provide a 45-minute primary analysis with 15-second secondary analysis to
obtain the highest resolution chromatograms, even for the most complex samples.
For this research effort, Pis were not yet able to incorporate TOFMS into the TGPGC
system since the TOFMS instrument was not available to them at the time. It is expected that the
additional work to combine these systems will be done under different funding.
3-25 December 2006
-------
Peer-Reviewed Publications
Sidhu, S., B. Gullett, R. Striebich, J. Klosterman, J. Contreras, and M. DeVito. 2005.
Endocrine disrupting chemical emissions from combustion sources: Diesel
particulate emissions and domestic waste open burn emissions. Atmospheric
Environment 39(5): 801 -811.
Striebich R., W. Rubey, and J. Klosterman. 2002. Trace-level measurement of
complex combustion effluents and residues using multidimensional gas
chromatography-mass spectrometry (MDGC-MS). Waste Management 22(4):
413-420.
3.2.1.5 Utilization of Research Results
This research shows that MDGC-MS has significant potential in its ability to identify
specific components of complex chemical mixtures sampled from municipal solid waste and
hazardous waste incinerators. This technique also possesses the capability of quantifying
separated substances that occur over a wide range of concentrations. It is hoped that use of
advanced chromatographic techniques (e.g., TGPGC) along with a faster MS system will allow
more comprehensive characterization of both toxic and non-toxic PICs to be performed in a rapid
(i.e., real-time or near real-time) fashion, thereby reducing uncertainties associated with
site-specific risk assessments.
3.2.1.6 Research Needs
Project-Related Research Needs
As a result of this research project, new instrumentation was developed and tested and
several studies were conducted to better characterize complex combustion by-products.
However, the ultimate analytical system intended by the Pis has not been completed. The
ultimate analytical system will be a combination of the TGPGC and TOFMS to obtain a more
effective analysis system for characterizing PICs associated with combustion in a rapid, real-time
or near real-time fashion. Once development of this more advanced system is complete,
thorough testing will be needed to support its use in characterizing complex combustion effluents
and in conducting site specific risk assessments.
Additional Research Needs
Additional research needs for combustion emissions were also identified by the Pis.
These are summarized below.
There is a tremendous difference in the emissions produced by efficient engines and
combustion systems as compared to inefficient and uncontrolled sources.
Considering that rural refuse incineration, fireplaces, cooking products, flares, forest
3-26 December 2006
-------
fires, agricultural burning, and other open burning situations may provide a significant
fraction of combustion emissions compared to the larger operations involving
efficient combustion engines and devices, further study is needed to more fully
understand the compounds released from these and other inefficient and uncontrolled
sources.
There is a need to study difficult to incinerate materials or materials that will be
increasingly found in the municipal solid waste stream (e.g., electronic wastes, Teflon
materials). Some of these materials are highly brominated (flame retardant) and
reactions will be catalyzed by a mixture of metals.
Assays which identify toxicity in fractions are needed, followed by routine and
non-routine analysis by a technique which can identify the compounds of interest.
3.2.2 Characterization and Minimization of Fine Particulate Emissions from Waste
Incinerators by Real-Time Monitoring of Size-Resolved Mass and Chemical
Composition, Kenneth A. Smith, Hacene Boudries, Douglas R. Worsnop, and
Xuefeng Zhang, Massachusetts Institute of Technology
3.2.2.1 Background
Incineration is a common method of waste disposal/minimization. Concerns about toxic
air pollutants that may be emitted from incinerators remain a major obstacle to public acceptance
of these systems. To date, concerns have focused on dioxins/furans, toxic metals, and acidic
gases. Little attention has been devoted to particulate emissions resulting from incineration,
partially because most of the particulate mass leaving the combustion chamber is efficiently
captured in modern baghouses. However, most of the captured mass is associated with coarse
particles because the coarse fraction of PM accounts for most of the uncontrolled particle mass.
Incinerator emissions are enriched in fine particles because control systems in incinerators are
least efficient for this size range. Fine particulates (i.e., those particulates smaller than 2.5
microns) are able to penetrate deeply into the human lungs and, if deposited there, may be an
efficient vehicle for exposure to many different chemicals. Therefore, there is a need to better
quantify the amounts, chemical composition, and toxicity of these fine particles.
There is also a critical need for real-time quantification of pollutants associated with fine
particulates in the exhaust gases of waste and sewage sludge incinerators. At the national level,
incineration processes generate relatively little PM. However, for the evaluation of local risk,
monitoring individual incineration units to ensure there are not releases of hazardous materials is
essential. Further, real-time characterization of PM emissions followed by correlation of
emissions to waste composition and hardware design and operating parameters offers the
potential to identify means to reduce emissions. Such means could include new hardware or
automatic operating control systems that adjust process parameters to control emissions in the
same way, for example, that lime dosage is modulated in municipal refuse combustion systems to
limit acid gas emission rates. The particulate control systems currently used in waste incinerators
3-27 December 2006
-------
are generally least efficient for those fine particle sizes for which the health effects are largest,
though well-designed and operated systems are more efficient at capturing fine particles. These
particulates tend to be enriched in condensable toxic organic compounds, acid salts, and metals
such as arsenic, cadmium, and lead.
3.2.2.2 Objectives
The objective of this research project was to perform a real-time analysis and
quantification of the size-resolved chemical composition of fine particulate emissions in the
exhaust gases of municipal waste incinerators. All the pollutants that were proposed to be
measured were known to be either toxic or carcinogenic. As part of this task, substantial efforts
were implemented within the framework of this project to advance the suitability of the
instrument for field sampling of PM and analysis of incinerator exhaust.
3.2.2.3 Methodology
This project involved the use of two instruments: an Aerosol Mass Spectrometer (AMS)
from Aerodyne Research, Inc. (ARI) for monitoring volatiles, semi-volatiles, and refractory
species, and a resonance enhanced multiphoton ionization (REMPI) time-of-flight (TOP) AMS
for selective and sensitive detection of toxic organics (specifically, chlorinated PAHs). The ARI
AMS and REMPI-TOFAMS were used to monitor, in real time, the chemical and physical
composition of aerosols emitted from two test sewage sludge incinerators and a municipal solid
waste incinerator (MSWI). The REMPI-TOFAMS, originally developed under a previous EPA
grant, was modified for the purposes of this project.
For aerosols containing volatile and semi-volatile species, the ARI AMS can provide
quantitative information on chemical composition as a function of particle size in real time. As
shown in Figure 3-6, submicron aerosols emitted by the municipal incinerators were sampled by
the AMS through a 100 mm critical orifice, then focused by the aerodynamic lens. The
aerodynamic inlet delivered a particle beam from which the vacuum aerodynamic particle
diameter was determined via particle time-of-flight. The particles were then directed toward a
heated tungsten surface vaporizer maintained between 500°C and 1,200°C (773 and 1,473 K).
The chemical composition was measured by flash evaporation of the particle followed by
electron impact ionization and positive ion detection with a quadrupole mass spectrometer
(QMS). Based on current laboratory calibrations, the detection limit (DL) is calculated
automatically by the AMS and estimated at 0.10 jig per m3 for sulfates, nitrate, chloride, and
ammonium compounds, and 1 jig per m3 for organic compounds and metals. A mass spectrum
was obtained every two seconds and averaged over 25 seconds. The size distribution of aerosols
with a vacuum aerodynamic diameter between 30 nm and 2.5 jim was measured each second and
averaged over 35 seconds. Detailed information about the AMS, including its operation, is well
documented elsewhere (Jayne et al. 2000; Allan et al. 2003; Jimenez et al. 2003).
3-28 December 2006
-------
Figure 3-6 Schematic of the Aerosol Mass Spectrometer (AMS) for Smith and Boudries'
Project
Quad ru pole
Beam
Chopper
r- QO.O
(2 Torr)
§ *
&
lonization
Pump
Pump
Pump
Inlet (1 atm)
Aerodynamic particle size is determined from a partde time-of-flight (TOP) measurement
Size-resolved composition is measured via flash vaporization on a surface,
electron impact ionization, and detection witti a quadrupole mass spectrometer.
In order to enhance the sensitivity and selectivity of the instrument for PAHs and
chlorinated aromatics, the AMS was coupled with the REMPI-TOFAMS system. A DL as low
as 10 parts per trillion for the particle mass for PAHs and chlorinated aromatics may be
achievable with REMPI-TOFAMS. The schematic diagram of the REMPI-TOFAMS is shown
in Figure 3-7. Ambient aerosols are sampled into vacuum using an aerodynamic lens.
Aerodynamic particle size is determined from a particle time-of-flight (TOF) measurement. Size
resolved composition is measured by a TOF mass spectrometers following particle flash
vaporization on a resistively heated surface and laser ionization of the vaporized species.
All paniculate sampling was performed in the stack just before being emitted into the
atmosphere. A sampling line (copper tube, 1/2 inch o.d., 5 m long) and a cyclone were used to
sample aerosol particles below 2.5 mm at a flow rate of 10 L min"1. Both the sampling line and
the cyclone were heated to the temperature of the gas inside the stack in order to avoid water
vapor condensation in the sampling line. The sampling line was also kept as short as possible by
sampling very close to the stack. Both Aerosol Mass Spectrometers were connected to
iso-kinetically sample through the sampling line. During this experiment, the REMPI-AMS and
AMS were set to sample at 0.1 L min"1.
3-29
December 2006
-------
Figure 3-7 Schematic of Resonance Enhanced Multiphoton lonization Time of Flight
Aerosol Mass Spectrometer for Smith and Boudries' Project
Aerodynamic
Aeraso
Particle Beam
Chopper
Orifice
Fight Tube
TOP region
iTime-of -Flight
; Mass Spectrometer
Vaporization
Heater
Turbo Pump Turiw Pump
Turbo Pump
Resonance Enhanced Multiphoton lonization Time-of-FIight Aerosol
Mass Spectrometer (REMPI-TOFAMS) used for size and composition
ana lysis of sub-micron aerosol.
Experiments were carried out at four incinerators during the specified time frames:
Pilot incinerator at the New Jersey Institute of Technology (NJIT) (10/29/01 -
11/02/01).
Sewage Sludge Incinerator - Fluidized Bed Incinerator (08/12/02 - 08/19/02).
Municipal Solid Waste Incinerator - Special Boiler (06/03).
Sewage Sludge Incinerator - Multi-Hearth Sludge Incinerator (09/03).
Size-resolved paniculate mass and chemical composition measurements were performed
while sampling exhaust gas from these systems. Particulate-bound inorganics (e.g., sulfate and
nitrate), PAHs, and chlorinated aromatics were detected in the stack exhaust. The effect of
operating parameters, including start-ups, shutdowns, and setpoint changes, on aerosol chemical
and physical composition were not conducted during this project due to difficulty in obtaining
authorization to conduct such tests at the incinerators.
3-30
December 2006
-------
3.2.2.4 Results and Discussion
Experimental Results
Pilot Incinerator at NJIT
Technology of the Pilot Incinerator at NJIT
The NJIT incinerator consists of four different components, the primary combustion
chamber, the secondary combustion chamber, the heat exchanger, and finally the bag-
house (Thipse 200 la).
The NJIT incinerator is a unique facility and was consstructed to work at conditions
similar to those found in a large-scale incinerator.
Synthetic fuel, composed of paper (35 weight %), yard trimmings (14.3%), wood
(7.1%), plastics (9.1%), metals (7.6%), food wastes (6.7%), glass (6.2%), textiles
(3.6%), rubber and leather (2.9%), miscellaneous inorganic wastes (1.5%), and others
(1.7%), was used during this experiment.
Synthetic fuel is fed to the Primary Combustion Chamber (PCC) at a rate necessary to
maintain the temperature in the PCC in the range from 300 to 650°C.
Results for the Pilot Incinerator
A well-defined fuel was prepared at NJIT (Thipse 2001a; Thipse et al. 2001b) to
provide a composition with thermal characteristics (moisture, heat content)
camparable to Municipal Solid Waste (EPA 1997b).
Major aerosol components for prepared fuel burned between 300°C and 600°C (573
and 873 K) were measured at the exit of the primary combustion chamber by both the
AMS and REMPI-TOFAMS.
REMPI-TOFAMS data indicated that particulate PAH emissions sampled after the
baghouse were inversely correlated with the combustion chamber temperature
(emissions were low at 600°C [873 K] and higher at 300°C [573 K]).
For low combustion temperatures (300 to 480°C [573 to 753 K]), the total mass
loadings were found to be in the range of 20 to 8,900 jig per m3 with an average
concentration of 2,400 jig per m3.
For high combustion temperatures (530 to 600°C [803 to 873 K]), the total mass
loadings were found to be in the range of 40 to 105 jig per m3 with an average
concentration of 80 jig per m3.
3-31 December 2006
-------
Individual PAH concentrations were found to be in the range of 0.15 to 150 ng per
m3.
Total PAHs emissions are usually in the range of 0.1 to 300 jig m"3 depending on the
feed rate and combustion status (start-up, burning, burnout).
ARIAMS results show the presence of five different groups of compounds: chlorides,
ammonium, water, PAHs, and organics. Nitrates and sulfates were not observed.
The organic fraction is dominant when operating the incinerator at low temperatures
(~300°C [573 K]).
At high primary combustion chamber temperatures (600 °C [873 K]), results show
that paniculate ammonium is the dominant species.
Aerosols were internally mixed (i.e., all of the chemical species are present in every
particle) with average vacuum aerodynamic diameters of 200 nm.
Fluidized Bed Sewage Sludge Incinerator (SSI)
Technology of the SSI
The SSI has a sand bed, which sludge is fed into, which is maintained at
approximately 750°C (1,023 K).
Materials are rapidly evaporated and volatile matter in the sludge is combusted.
Exhaust is cooled to 560°C (833 K) using heat exchange to the incoming combustion
air and a Venturi scrubber reduces particulate emissions.
An impingement tray scrubber introduces water to cool the exhaust to -43 °C (316 K).
A caustic solution is used to remove acidic gases.
Exhaust gas is emitted into the atmosphere through a stack.
Results for the SSI
All data were obtained from the gases leaving the heat exchanger using the ARI AMS
equipped with a QMS. The PAH concentration was well below the Detection Limit
of the REMPI-TOFAMS.
The majority of aerosol mass was associated with ammonium sulfate.
Chlorides, organics, and nitrates were also present.
3-32 December 2006
-------
Combustion chamber temperature and auxiliary fuel feeding rates represented
potential operating conditions that affected emitted aerosol mass loadings.
Mercury and mercury dichloride were observed in incinerator exhaust.
Mass concentrations of total mercury were detected up to 0.4 jig per m3.
Total aerosol mass loadings ranged from 10 to 380 jig per m3.
Vacuum aerodynamic diameters of particles ranged from 140 to 220 nm.
Aerosols were found to be externally mixed (i.e., different particles contain different
chemical species) and to consist of ammonium sulfate, organic compounds,
chlorinated organic compounds, and nitrates.
Municipal Solid Waste Incinerator (MSWI)Shred-and-Burn Technology, Special
Boiler
Technology of the MSWI
Designed to provide disposal and recycling of 5,000 tons per day of municipal solid
waste.
The first stage consists of shredding the waste, which is followed by magnetic
separation to remove most ferrous materials. The processed waste is then blown into
the boilers above the grate.
The municipal solid waste is converted to a processed refuse fuel via a single
shredding stage, reducing its particle size to about six inches followed by a single
magnetic separation stage (Zakaria and Sutin 1994).
Combustion gases are passed through a dry scrubber and sprayed with a lime reagent
to remove acidic gas constituents.
Electrostatic precipitators capture particulates.
Exhaust gas is emitted into the atmosphere through a 300-foot stack.
Results for the MSWI
Data were obtained from the ARIAMS equipped with a QMS that sampled gases in
the duct between the combustion chamber/boiler and the dry scrubber. Only pyrene
was detected with the REMPI-TOFAMS during this experiment.
3-33 December 2006
-------
The ARI AMS was operated with a vaporization temperature between 550 and
1,200°C (823 and 1,473 K) in order to quantify both refractory and non-refractory
species.
Detailed analysis of mass spectra identified the presence of chlorinated hydrocarbons,
other organics, and inorganic nitrates. The majority of aerosol mass was comprised of
the inorganic sulfate, transition metals, and chlorine-containing compounds.
Increasing the AMS vaporization temperature (from 550 to 1,200°C [823 to 1,473 K])
helped identify refractory compounds such as transition metals.
Transition metals, including lead, zinc, manganese, iron, antimony, nickel, copper,
chromium, and cadmium were present.
Total mass loadings were positively correlated with vaporization temperature,
indicating that the composition of aerosols from this incinerator was composed
mostly of refractory compounds (e.g., lead).
A large fraction of the transition metals were believed to be fine particulates (less than
Transition metals represent the dominant fraction with a contribution of 43 percent of
total mass loadings.
Total mass loadings ranged from 20 to 141 jig per m3, with an average concentration
of 80 jigperm3.
Aerosols were found to be internally mixed (i.e., all of the chemical species are
present in every particle) with average vacuum aerodynamic diameters of 600 to 700
nm.
Sewage Sludge Incinerator - Multiple-Hearth Sludge Incinerator
Technology of the Multiple Hearth Sludge Incinerator:
The multiple-hearth incinerator consists of a vertical cylindrical shell containing
1 1 firebrick hearths.
The sludge (22 to 32% solids) enters at the top of the furnace (hearth # 3, maintained
at a temperature of 450°C [723 K]) and moves toward the bottom of the furnace
(hearth #11, maintained at a temperature of about 540°C [813 K]).
Combustion exhaust exits the furnace at a temperature of about 650°C [923 K] on the
upper hearth, which serves as an afterburner.
3-34 December 2006
-------
The exhaust gases are cooled down to between 16 and 27°C [289 and 300K] in the
Venturi scrubber. PM is also reduced in the Venturi.
The exhaust gas, with PM reduced by the Venturi and cooled to a temperature varying
between 15 and 21°C (288 and 294 K), is emitted into the atmosphere through an
exhaust stack.
Results of the Multiple Hearth Sludge Incinerator
The AMS vaporization temperature was operated between 550 and 1,200°C [823 and
1,473 K].
No increase in total concentration was observed when the AMS vaporization
temperature was raised above its normal operation temperature of about 600°C
[873 K].
Results indicate that refractory species are very low and represent less than two
percent of total mass loadings.
The total mass loadings were found in a range of 14 to 4,983 jig per m3, with an
average concentration of 1,153 jig per m3.
Exhaust particles consisted primarily of ammonium sulfate.
The aerosol compositions were dominated by sulfates and ammonium, representing
about 73 percent and 22 percent, respectively.
Chlorides, organics, and nitrates were also present but at very low concentrations.
Aerosols were found to be internally mixed with average vacuum aerodynamic
diameters of particles averaged 200 nm.
3.2.2.5 Utilization of Research Results
During this project, Massachusetts Institute of Technology in collaboration with
Aerodyne Research, Inc. deployed a state-of-the-art Aerodyne Aerosol Mass Spectrometer
(AMS) to three municipal waste incinerators to measure the real-time chemical and size
distribution of sub-micron particulate emissions from incinerators. Overall, the data collected
within the framework of this project show the development of new and promising techniques for
real-time chemical analysis and measurement of size-resolved ambient aerosols. Although the
AMS was initially developed to characterize non-refractory species, further development and
improvements were performed during this project to include the measurement of refractory
species, such as metals. This new technique offers the simultaneous real-time measurement of a
variety of chemical species present in/on aerosols and their corresponding size distribution in a
rapid manner with respect to individual species for a variety of combustion systems. These
3-35 December 2006
-------
species include organics, sulfate, nitrate, ammonium, chloride and metals. Through this research,
a mobile commercial instrument with the capability of performing the size distribution and mass
loading concentration measurements in real-time will be available to the research and regulatory
communities.
3.2.2.6 Research Needs
Project-Related Research Needs
Two research needs related to the above project were identified by the Pis. These are
discussed below.
(1) Develop real-time in-field monitoring systems to detect toxic species.
Previous studies have shown significant variations in incinerator emissions with levels
exceeding what is allowed by permit in some cases. Analytical instruments capable of
continuous monitoring could sound an alarm or provide input to a process control system when
toxic emissions exceed standards and trigger intervention to prevent further emission from the
stack. However, current instrumentation is either not sensitive enough or not fast enough for real
time measurement. Thus, the development of an accurate and sensitive real-time monitoring
system for organic compounds and metals present on fine, and especially sub-micron aerosol
particles (PM2 5 and/or PMl 0) emitted by combustion sources is very important.
The goal of further research is to develop analytical systems to:
Provide real-time measurement for fine, and especially sub-micron, aerosols.
Supplement current analytical methods for particulate organic compounds and metals
measurement.
Provide quantitative measurement of individual organic compounds and metals.
Offer a value-added instrument which is easily deployed into the field and which
requires no post-measurement laboratory analysis.
(2) Perform intensive field experiments to determine the composition of particulate
and gas phase species.
Commercial instruments that can provide high levels of sensitivity and resolution and do
so in real time and at low cost, would be used to improve understanding of the processes that
control the composition of particulate and gas phase species produced from combustion sources
and their chemical evolution in the atmosphere. The following areas are of particular interest:
3-36 December 2006
-------
1. Carbonaceous Particles From Diesel Combustion
Particulate emissions from diesel combustion engines represent a
significant source of fine, non-fugitive, carbonaceous PM. They contribute more
than four percent of the total PM25 inventory. PM25 emission rates from mobile
diesel engines and non-road and stationary diesel engines should be studied.
2. Particulate Emissions From Incinerators
Most of the previous measurements were conducted to characterize the
composition and quantity of the exhaust aerosol from the stack. Studies should
also include sampling at multiple ports in order to better characterize the
evolution of particulate composition and chemical and size evolution in the
system prior to emission into the atmosphere.
3. Comparison Exercise
A study of various analytical instruments should be initiated in order to
evaluate the performance of the new analytical instruments and study the
possibility of using these new analytical instruments for defining new EPA
methods (for instance, comparing the results of the ARI AMS with EPA Method
29 for measurement of total parti culate metals).
Additional Research Needs
Further research is required for a better understanding of the chemical and physical
processes controlling the composition of chemical species present in/on particles before emission
into the atmosphere, including:
Sampling at several sampling ports between the boiler and emission into the
atmosphere.
Systematic experiments to draw firm conclusions about the particulate emissions as
functions of combustion temperature, fuel types and air/fuel equivalent ratio.
Investigation into the effect of stack temperature, excess air, and feed rate on aerosol
mass loading.
Accurate measurement of the size-dependent chemical composition of atmospheric
and laboratory aerosols having significant implications for climate, air quality and
human health.
3-37 December 2006
-------
3.2.3 Summary of the Overall Contributions of These Two Projects to the RCRA MYP
and Its Broad Theme of "Monitoring and Analytical Methods"
The RCRA MYP identifies Potential Additions to the Research Program with respect to
Improved Approaches to Sampling and Analysis (EPA 2004a). These include improved
speciation of products of incomplete combustion. This objective is directly supported by
research conducted by both Rubey, Striebich, and Taylor's grant and Smith and Boudries' grant.
The results of this research can be directly applied to design and application of sampling and
analysis systems to further characterize emissions from combustion systems, in particular
focusing on identification of potentially toxic constituents that have not been previously
characterized in combustion system exhaust gas and fine particulate. Such sampling and analysis
systems and the data provided by them could be applied directly to preparation of site-specific
risk assessments for combustion systems.
3.3 EPA-AWMA INFORMATION EXCHANGE
3.3.1 Summary
The 28th Annual Environmental Protection Agency-Air and Waste Management
Association (AWMA) Information Exchange was held in Research Triangle Park, North
Carolina on December 2-3, 2003. This annual forum provides an opportunity for EPA and other
interested parties to exchange information across and within the various areas of research
pertaining to air and waste management. The audience of approximately 70+ consisted of EPA
staff, industry representatives, academia, and environmental consultants.
EPA staff presented talks on the following topics:
Mercury.
Multi-pollutant control technologies.
Coal combustion residues
New Source Review reform.
Homeland security.
Ozone implementation.
Animal waste and ammonia emissions.
Fine particulate matter.
Carpet and electronic waste incineration.
Open burning.
Indoor air mold.
Combustion research.
On Day 2 of the Information Exchange, four of the five the combustion emissions Pis
reported on the progress of their research. In addition, Clyde Owens, representing the National
Risk Management Research Laboratory (NRMRL), provided an overview of ORD's in-house
combustion research.
3-38 December 2006
-------
In 1999, EPA identified combustion emissions as a critical human health and
environmental problem requiring further scientific and technical research. As the combustion
emissions research grants come to an end, EPA was interested in understanding how the current
research has addressed this problem and identifying any additional short- and long-term research
needs. Furthermore, a rule making is expected to come out in the near future covering emissions
from these sources.
As a result, a more thorough understanding of the sources, pollutants, and potential health
concerns is essential at this time. For these reasons, an update on the status of the STAR
recipients' research was of particular interest. The Pis from four of the five STAR grants
participated in the conference. Their topics are listed below.
Mechanistic Studies of the Transformation of Poly chlorinated Dibenzo-p-Dioxins via
Hydroxyl Radical Attack, Phillip H. Taylor, University of Dayton.
Trace-level Measurement of Complex Combustion Effluents and Residues using
Multi-dimensional Gas Chromatography-Mass Spectrometry (MDGC-MS), Richard
Striebich, University of Dayton.
Characterization and Minimization of Fine P articulate Emissions from Waste
Incinerators by Real-Time Monitoring of Size-Resolved Mass and Chemical
Composition, Hacene Boudries, Massachusetts Institute of Technology and Aerodyne
Research, Inc.
Toward the Development of a Detailed Mechanism of Transition Metal Catalyzed
Formation ofPCDD/Ffrom Combustion Generated Hydrocarbons, Barry Dellinger,
Louisiana State University - Baton Rouge.
The fifth PI, Selim M. Senkan, who examined the products of incomplete combustion, was not in
attendance. Earlier versions of Pis presentations, including that of Dr. Senkan, were given at the
AWMA National Meeting in Anaheim, CA, in June 2003. In addition, Clyde Owens of NRMRL
presented the ORD in-house research findings in the presentation Endocrine Disruptors from
Combustion and Vehicular Emissions: Identification and Source Nomination.
At the conclusion of the presentations, Pis and other experts were invited to participate in
an open discussion of research needs related to combustion emissions. A summary of the
research needs identified by members of the discussion panel is provided in Section 3.3.3.
3.3.2 Presentations
The research that resulted from these five grants is discussed in Section 3.1 and 3.2 and is
not repeated here.
Clyde Owens (NRMRL) presented the results and findings of ORD's in-house research
focused on investigation of endocrine disrupting chemicals (EDCs) from combustion and
3-39 December 2006
-------
vehicular emissions. EDCs are linked to breast and prostate cancer, which rank second in cancer
deaths for women and men, respectively. The purpose of this project was to determine whether
EDCs are emitted from various combustion sources, including domestic waste burning,
fireplaces/wood stoves, and forest fires, and if so, in what quantities.
Owens sampled and analyzed exhaust from both combustion and vehicular sources to
confirm the presence of EDCs. Combustion sources were evaluated for potential EDCs using
bioassays, sample fractionation to isolate the target compounds, and gas chromatography-mass
spectroscopy (GC-MS) for identification of each compound once isolated. The research
identified potential EDCs in diesel exhaust and pine, oak, and artificial wood. Compounds
released from wood burns and in diesel exhaust were labeled as possibly androgenic.
3.3.3 Research Needs Identified During Panel Discussion
Participants in the panel discussion included the Pis and ORD/NRMRL researchers.
Discussion was also open to session attendees. The research needs identified during the
discussion are summarized below by topic; the name of the commenter(s) follows in parentheses.
Chemical Compounds in Combustion Systems:
Nanoparticle fractions. These fractions are sites of increased activity (compared to
micron-size particles) and much of the chemistry occurs at this level2 (Dellinger).
Chlorobenzenes and their role in dioxin formation (Dellinger).
Brominated and oxygenated compounds in combustion emissions (Dellinger,
Lemieux).
Combustion by-products formed in the post-flame combustion zone. Radicals that
may be formed in the "hot zone" are critical in the "cool zone" (Dellinger, Smith).
Gas-phase and surface reactions in combustion emissions (Taylor).
Chlorinated by-products that are persistent in the environment. Specifically, whether
they are products of combustion or from other sources (Taylor).
Toxicity information for many of the combustion by-products (e.g., poly-brominated
compounds) for risk assessment purposes (Owens).
Toxicity information for the constituents of diesel emissions (Owens).
2 Atmospheric nanoparticles or ultrafine particles is defined as particles smaller than 100 nm in
diameter (Friedlander and Pui 2003).
3-40 December 2006
-------
Toxicity of chemical mixtures. Specifically, determine what is toxic in these mixtures
(Striebich).
Evaluate the biomass of sugar cane that is burned and the quantity and composition of
the emissions (Owens).
Monitoring and Analytical Methods for Combustion Systems:
Develop instrument to study high temperature surface reactions on the order of
seconds (Bellinger).
Improve instrumentation for conducting routine, in-field real time measurements
(Smith, Striebich, Lemieux).
Develop more robust measurement techniques (Smith).
New techniques to study larger intermediate molecules for gas-phase reactions
(Taylor).
Further study of multi-dimensional gas chromatography (Lemieux).
Develop better, cheaper, more reliable lasers (Lemieux).
General Research Improvement:
Better coupling of theory and experimental results (Taylor).
There are many tools available that are not consistent with EPA methods. More
outreach and flexibility to use these other methods is needed (Session attendee).
Coal combustion should be one of the priority sources of study (Lemieux).
Grants should be more focused on data/knowledge gaps instead of regulatory needs
(Smith).
Increase funding for combustion emissions research (Owens).
More discussion and information exchange between researchers who characterize
emissions and fate and transport experts (Taylor, Lemieux).
Increased interaction among Pis, EPA, the academic community, equipment/facility
designers and operators, and other researchers (Lemieux).
3-41 December 2006
-------
Improve emissions data and emissions factors and the connection between research
and modeling. Develop a forum for researchers and modelers to exchange
information/ideas (Session attendee).
Some participants said at the end of the discussion that this was the first time that
academic, ORD in-house, and industry researchers came together to discuss research needs in
combustion research. They wanted to know how soon another such session could take place.
3.4 AMERICAN FLAME RESEARCH COMMITTEE SPRING MEETING
The Spring Meeting of the American Flame Research Committee (AFRC) was hosted by
EPA and held in the EPA facility in Research Triangle Park, NC, on April 27 and 28, 2005.
3.4.1 Topics and Speakers
Most of the presenters were EPA ORD in-house researchers, primarily from the ORD
National Risk Management Research Laboratory (NRMRL). Among the presenters was Clyde
Owens from NRMRL, who had participated on the combustion emissions panels at the two
AWMA meetings. The topics and speakers during the first day and a half included the
following:
1. Formation and Mitigation of Visible Acid Aerosol Plumes from Coal-fired
Power Plants, Andy Miller, NRMRL.
2 ORD PMResearch Program, Andy Miller, NRMRL.
3. Combustion Generated Fine Particles, Trace Metal Speciation, and Health
Effects, Bill Linak, NRMRL.
4. PCDD and PCDF Formation and Monitoring of Combustion Sources,
Shawn Ryan, EPA.
5. PCDD/FEmissions from Open Burning Simulations, Brian Gullett, ORD.
6. Control of Mercury Emissions from Coal-Fired Power Plants,
Ravi Srivastava, NRMRL.
There were on the afternoon of the second day presentations on three of the five grants
by Taylor, Smith and Boudries, and Striebich. They were followed by a presentation by Mark
Lee of ICF Consulting on the status of this synthesis report. After that, Bob Hall of
ORD/NRMRL and Paul Shapiro of ORD/NCER led a discussion of research needs.
3-42 December 2006
-------
The topics of these speakers were:
1. Endocrine Disruptors from the Combustion of Electronic Waste. Clyde
Owens, NRMRL.
2. Kinetic Studies of Hazardous Air Pollutants Under Post-Combustion
Conditions, Phillip Taylor, University of Dayton.
3. Real-Time Chemical and Physical Characteristics of Fine P articulate
Emissions from Waste Incinerators by the Aerodyne Aerosol Mass
Spectrometer, Kenneth Smith, MIT, and Hacene Boudries, Aerodyne.
4. Multidimensional Gas Chromatography: Time of Flight Mass Spectrometry
for Identification of Combustion Products and Residues, Richard Striebich,
University of Dayton.
5. Synthesis of Hazardous Waste Combustion Research and Research Needs,
Mark Lee, ICF Consulting.
3.4.2 Discussion and Prioritization of Combustion Research Needs
The AFRC meeting continued with a the identification and prioritization of combustion
research needs. The meeting participants identified possible criteria for ranking research needs.
The criteria were:
(1) Potential for risk reduction.
(2) Widespread applicability.
(3) Filling significant gap.
(4) Importance for regulatory needs.
(5) Cost-effective investment.
(6) Likelihood of success.
(7) Complementary to government and industry research.
(8) Quality of researchers available.
(9) Pressing national need.
(10) Balance to research portfolio.
(11) Inter- or multi-disciplinary.
(12) Focus is on current and future, not past issues.
In discussing how to identify and prioritize research needs as related to the criteria
participants made the following points:
(1) Potential for risk reduction and (6) Likelihood of success are MUCH more
important than others.
3-43 December 2006
-------
All criteria need to be considered and the whole of the proposal must be considered
when making decisions.
For exploratory research, cost should not play as big a role; as technology matures,
cost should be considered more heavily. For example, in the 1980s NOX burners were
seen as more cost-effective than Selective Catalytic Reduction (SCR) so investment
was not made at that time in SCR.
EPA needs to balance "exploratory" with "application-oriented" research.
Risk communication is needed.
The participants then identified what they each thought was the most important research
need. After that, the participants were asked to qualitatively take the criteria they had developed
earlier and apply them in voting for their top priority research area among the areas that had been
identified. This voting process gave the following results:
1. Fundamental mercury research, including research on mercury chemistry
under realistic conditions (8 votes).
2. Gasification of solids, including coal gasification and biomass waste
gasification, and particularly high pressure gasification (7 votes).
3. Combustion of alternative fuels, including pollution impacts (7 votes).
4. Open burning, including dioxin emissions (5 votes).
5. Analytical/Sampling devices development, including devices for partitioning
for mercury (4 votes).
6. Interaction of multi-pollutants/multi-control processes (4 votes).
7. Health effects engineering, including understanding components of
emissions that impact toxicity and how to control these emissions (4 votes).
8. CO2 sequestration (2 votes).
9. Development of adaptive grid computational models of emissions/sources
(2 votes).
10. Flaring of liquids and gases (1 vote).
11. Develop better understanding of measurement processes that might help
develop better/cheaper measurement devices, including surrogate compounds
and measurements (1 vote).
3-44 December 2006
-------
12. Combustion audits place in homelandsecurity>, e.g., disposal of agricultural
residues (1 vote).
3.4.3 Conclusions
The principal issues identified in the prioritization of research needs are not typical EPA
combustion issues, but these combustion researchers think that these issues are most important.
This reflects a change in the universe since 1999, including United States and world conditions.
The combustion community, which has traditionally been reactive, may need to be more pro-
active in setting research priorities. Industry is still interested in efficiency improvements, which
would lead to reduced emissions. However, the gap between fundamental research and
development and application of new technologies needs to be addressed.
3-45 December 2006
-------
[this page intentionally left blank]
-------
4. SUMMARY OF FINDINGS AND RESEARCH NEEDS
This section summarizes the findings of this synthesis report. This section shows how the
results of the five research projects help meet the goals of the EPA RCRA Multi-Year Plan,
indicates how the results of the projects can be used by others, and identifies future research
needs related to combustion research.
4.1 SUMMARY OF FINDINGS
4.1.1 Contributions to the Waste Management Goal of the RCRA Multi-Year Plan
This section describes the contributions of these five projects to meeting the Waste
Management goal of the ORD RCRA Multi-Year Research Plan (MYP) (EPA 2004a). The
RCRA MYP provides part of the context of ORD's research goals and objectives to which these
projects have contributed their research results.
The RCRA MYP reports plans for combustion research and identifies annual
performance goals (APGs) in achieving long-term goals (LTGs) and associated annual
performance measures (APMs). The Waste Management LTG, one of two LTGs in the MYP, is
"Improve waste management for industrial and municipal waste to enhance sustainability by
providing technical reports." Combustion research addresses this issue by seeking to develop
improved approaches to monitor emissions that will lead to improved decision making on use of
combustion and incineration
To help achieve this goal, ORD's combustion research has focused on addressing the
following Waste Management Science Questions identified in the RCRA MYP:
What easily monitored components of emissions can be used to predict more
difficult-to-measure components (e.g., PCDD/PCDF)?
How can complex mixtures of organic compounds in the stack gases be characterized
with respect to risk assessment needs?
What PCDD/PCDF formation issues exist during combustion of hazardous wastes?
These projects have addressed these questions through improved characterization of the
mechanisms of formation of components of air emissions from combustion systems, and through
development of improved methods of measuring and speciating such components. More
specifically, they have investigated:
The influence of transition-metal deposits on emissions of PCDD/PCDF s from
combustion systems (Dellinger and Lomnicki).
4-1 December 2006
-------
The effects of oxygenate additives on polycyclic aromatic hydrocarbons (PAHs) and
soot formation (Senkan).
The potential for variability in some relatively easy-to-measure compounds to be
utilized for accounting for the variability of difficult-to-measure compounds such as
PCDD/PCDFs (Taylor, Dellinger, and Lomnicki).
The potential for the Aerosol Mass Spectrometer (AMS) analytical method to be
utilized as a real-time monitor for air toxics that are present in the low parts per
trillion range (Smith and Boudries).
The RCRA MYP includes APGs and APMs for Combustion and Incineration within the
Waste Management LTG. These include APGs and APMs that are directly supported by the five
projects.
There is an APG for fiscal year 2005 that states, "Provide the results of fundamental
and applied research on metals and analysis and modeling of organic compounds
during combustion through reports from three grants." This APG consists of the
following three APMs. The project associated with meeting each APM is identified
in the APM.
> Demonstrate a detailed mechanism of formation of PCDD/PCDFs from
ubiquitous combustion-generated hydrocarbons (Grant R828191; Dellinger and
Lomnicki).
* Develop improved analytical techniques to identify or speciate total organic
emissions (TOE) (Grant R828190; Rubey, Striebich, and Taylor).
> Provide fundamental research data to broaden a comprehensive gas-phase model
of the transformation of PCDD under a wide range of conditions (Grant R828189;
Taylor).
There is an APG for fiscal year 2007 that states, "Provide technical information in the
form of one paper and one draft guidance on the use of advanced monitoring
techniques and surrogate organic performance indicators for incinerators." This APG
is supported by Grant R828192, for which Smith and Boudries are the Pis, and Grant
R828190, for which Rubey, Striebich, and Taylor are the Pis.
4.1.2 Utilization of Results by EPA and Others
Research results provided by Taylor provide important inputs that may be built upon by
other researchers towards the development of a comprehensive gas-phase model of the
transformation of PCDDs under a wide range of combustion source conditions and wastes.
Taylor indicates that the rate mechanisms and equations presented in the research results should
4-2 December 2006
-------
be evaluated by others using different techniques. The rate mechanisms may be applied by
researchers investigating atmospheric transformation of dioxins and furans.
Research results presented by Bellinger and Lomnicki provide rate mechanisms for
formation and transformation of dioxins and furans, and also identify precursor compounds.
These results may be applied by other researchers towards development of models of formation
and transformation of dioxins and furans as related to surface-modulated (or catalyzed) reaction
in combustion systems and also applied to further investigations towards the development of
surrogate compounds to indicate emissions of more difficult to monitor chlorinated dioxins and
furans. The Pis have developed a comprehensive view of how PCDD and PCDF are formed in
combustion systems and how the nature of surfaces control the cogener distribution, PCDD to
PCDF ratio, and how yields are affected by temperature and excess air.
Research by Senkan includes data concerning trace species concentration profiles and
soot and temperature profiles in combustion systems for intermediate species which were found
in the limited tests for wastes. These results can be applied by other researchers in the following
ways: (1) development of detailed chemical kinetic mechanisms describing combustion of
brominated hydrocarbons in flames using results determined from intermediates; (2)
development of abatement techniques for brominated dioxins and furans based on the identified
mechanisms of formation; (3) identification of surrogate compounds to indicate emissions of
more difficult to monitor brominated dioxins and furans; and (4) combination with fluid
mechanical models to simulate, design, and develop abatement mechanisms for combustion
systems.
Research results from Rubey, Striebich and from Taylor's project and Smith and
Boudries' project can be directly applied toward further development, design, and
implementation of real-time or near real-time monitoring systems for speciation of fine
particulate emissions and organic compound emissions from combustion systems. Data
generated by such systems can be applied directly to preparation of site-specific risk assessments
for combustion systems.
4.2 SUMMARY OF RESEARCH NEEDS
Through their research projects, the Pis identified potential research needs specifically
related to their project and to combustion in general. These research needs, listed by PI, are
provided in Sections 3.1 and 3.2 of this report. As discussed in Section 3.3, during the
EPA-AWMA Information Exchange and during the AFRC meeting, participants of a combustion
research panel discussion that included the Pis, EPA, and other interested parties also identified
potential research needs related to combustion emissions. In addition, following the Information
Exchange, various combustion experts consisting of EPA staff, industry representatives,
academia, and environmental consultants were contacted via phone and email to identify needs
for future research in the field. The research needs identified through each of these means have
been grouped into the following five categories:
Mechanisms of formation of chemical compounds.
4-3 December 2006
-------
Monitoring and analytical methods.
Emissions characterization.
Fate and transport.
Toxicity, health effects, and risk assessment.
These research needs are summarized and presented in these categories below. For each
category, the potential significance of additional research is also provided. The complete list of
identified research needs is provided in Appendix B.
4.2.1 Mechanisms of Formation of Chemical Compounds
Significance of research: Improves understanding of the mechanisms of formation of
chemical compounds in combustion systems, which can be used to develop new control
technologies and operating parameters to limit emissions of pollutants and ultimately reductions
in risk.
Summary of Identified Research Needs:
Characterize the formation, destruction, and transformation of chlorinated and
brominated dioxins/furans, PAHs, soot, and fine particulates during the combustion
process.
Currently, no one is working on comprehensive, multi-mechanism models for dioxin
formation in incinerators; while this is an important research topic, it should not be
conducted without the necessary resources for validation of the full-scale models.
Explore possible modifications to combustion processes to minimize formation of
metals and persistent organic compounds.
Determine the effects of trace amounts of bromine on the kinetics of formation and
destruction of PICs in combustion devices.
Study composition of combustion by-products, particularly those formed in the
post-flame zone.
Improve speciation of products of incomplete combustion.
Examine role of nanoparticles in pollutant formation.
Assess whether emission limits on chlorinated dioxins and furans are also effective in
controlling brominated dioxins and furans and other POM (e.g., PCBs).
Characterize the formation, destruction, and transformation of chlorinated and
brominated dioxins/furans, PAHs, soot, and fine particulates during processes aimed
at gasification of solid wastes.
4-4 December 2006
-------
4.2.2 Monitoring and Analytical Methods
Significance of research: Leads to development of better monitoring, sampling, and
analysis methods to more accurately characterize combustion emissions.
Summary of Identified Research Needs:
Improve existing sampling and analytical methods by making them easier to use, less
expensive, and more robust.
Develop improved techniques for the study of high temperature surface reactions.
Develop and improve systems capable of characterizing combustion effluents in
real-time or near real-time.
Develop performance specifications for Continuous Emission Monitoring Systems
(CEMS) for PM, multimetals, and HC1 and document that these CEMS can meet the
specifications when installed on HWCs.
Communicate the results of the advancements above to the design and user
communities to include demonstration of performance (in all its dimensions) through
field tests over significant time periods with commercial-scale combustion systems.
4.2.3 Emissions Characterization
Significance of research: Used to identify toxic fractions of combustion-related
emissions to more accurately characterize risks.
Summary of Identified Research Needs:
Further study of emerging pollutants associated with combustion (e.g., persistent
bioaccumulative toxics, EDCs).
Study difficult-to-incinerate materials or materials that will be increasingly found in
the municipal solid waste stream (e.g., electronic wastes).
Investigate how fuel and combustion conditions cause changes in the composition of
combustion emissions.
Better characterize emissions from different combustion technologies.
Improve emission factors for combustion processes.
4-5 December 2006
-------
Study the reduction in emissions by air pollution control systems (e.g. adsorption of
pollutants by activated carbon, condensation and adsorption of pollutants on lime
particles in spray dryer absorption systems used for acid gas reduction, destruction of
PCDD/PCDF compounds in catalytic de-NOx processes).
4.2.4 Fate and Transport
Significance of research: Improves knowledge related to the fate and transport of
combustion-related emissions to better assess potential impacts of these materials on human
health and the environment.
Summary of Identified Research Needs:
Improve communication between combustion experts and fate and transport
modelers.
Improve understanding of dioxin/furan fate and transport.
Develop better source terms for modeling.
Research atmospheric processing of combustion particles and their eventual fate in
the environment.
4.2.5 Toxicity, Health Effects, and Risk Assessment
Significance of research: Improves understanding of mechanisms of toxicity and
potential health effects associated with combustion emissions, particularly for those compounds
for which little or no information is available
Summary of Identified Research Needs:
Assess relative environmental significance of combustion emissions.
Quantify the impacts of the alternatives to combustion.
Better understand the mechanisms of toxicity associated with EDCs.
Continue to research health effects and risks associated with exposure to
dioxins/furans, metals, and fine PM.
4-6 December 2006
-------
[this page intentionally left blank]
4-7 December 2006
-------
5. CONCLUSIONS
These five projects have made important contributions to the characterization and
monitoring of the combustion emissions from hazardous waste incinerators, boilers and
industrial furnaces, and municipal solid waste incinerators. Some of the results of this research
can be used for better understanding combustion emissions from other sources as well.
Completion of these projects fulfilled two APGs and three associated APMs of the ORD RCRA
MYP (EPA 2004a). The scientific papers and reports that came out of these projects will be
added to the supporting technical basis for the MYP as it is revised in the future.
This document has served as a means to identify research needs related to combustion
more generally than just this area of research. It offered the opportunity for academic, EPA
in-house, and industrial researchers and consultants to jointly discuss what these research needs
are. This in itself is a kind of collaborative planning that, according to the participants, has not
previously occurred.
The utility of the research results that have been reported here and the research needs that
have been identified lies in the application of the research results to help states, industries, and
other organizations to mitigate the emissions and their resulting health effects. It also offers the
opportunity for EPA program offices and the research office, as well as outside experts, to
consider the need for additional research in combustion emissions in the future.
5-1 December 2006
-------
[this page intentionally left blank]
-------
6. CITED REFERENCES
Allan, J.D., J.L. Jimenez, P.I. Williams, M.R. Alfarra, K.N. Bower, J.T. Jayne, H. Coe, and
D.R. Worsnop. 2003. Quantitative sampling using an aerodyne aerosol mass spectrometer, 1.
techniques of data interpretation and error analysis. Journal of Geophysical Research 108 (D3):
art. No. 4090.
Commission for Environmental Cooperation (CEC). 2004. Taking Stock 2001: North American
Pollutant Releases and Transfers. Montreal, Canada. June.
Friedlander, S.K and D.Y.H. Pui. 2003. Emerging Issues in Nanoparticles Aerosol Science and
Technology (NAST). Available at: www.nano.gov/html/res/NSFAerosolParteport.pdf.
Jayne, J.T., D.C. Leard, X. Zhang, X., P. Davidovits, K.A. Smith, C.E. Kolb, and D.R. Worsnop.
2000. Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron particles.
Aerosol Science and Technology, 33(1-2): 49-70.
Jimenez, J.L., J.T. Jayne, Q. Shi, C.E. Kolb, D.R. Worsnop, I. Yourshaw, J.H. Seinfeld,
R.C. Flagan, X. Zhang, K. Smith, J.W. Morris, and P. Davidovits. 2003. Ambient aerosol
sampling using the aerodyne aerosol mass spectrometer. Journal of Geophysical Research
108 (D7): art. No. 8425.
Linak, W.P. and J.O.L. Wendt. 1993. Toxic metal emissions from incineration: mechanisms
and control. Progress in Energy and Combustion Science 19(2): 145-185.
National Research Council of the National Academies (NRC). 2004. Air Quality Management
in the United States. National Academies Press. Washington, D.C.
Niessen, W.R. and R.C. Porter. 1991. Methods for estimating trace metal emissions from
fluidized bed incinerators using advanced air pollution control equipment. Proceedings of the
84th Annual Meeting of the Air and Waste Management Association. Vancouver, British
Columbia.
Office of Management and Budget (OMB). 2003. Informing Regulatory Decisions: 2003 Report
to Congress on the Costs and Benefits of Federal Regulations and Unfunded Mandates on State,
Local, and Tribal Entities. Office of Information and Regulatory Affairs. Washington, D.C.
February.
Ruth, L.A. 1998. Energy from Municipal Solid Waste: A Comparison with Coal Combustion
Technology. Progress in Energy and Combustion Science 24(6): 545-564.
Saxena, S.C. and C.K. Jotshi. 1996. Management and Combustion of Hazardous Wastes.
Progress in Energy and Combustion Science 22(5): 401-425.
6-1 December 2006
-------
Thipse S., 2001a. Parametric study of heavy metal partitioning in a pilot-scale incinerator
burning simulated municipal solid waste. PhD thesis, New Jersey Institute of Technology.
Thipse S.S., C. Sheng, M.R. Booty, R.S. Magee, E.L. Dreizin. 2001b . Synthetic fuel for
imitation of municipal solid waste in experimental studies of waste incinerator. Chemosphere
44(5): 1071-1077.
U.S. Energy Information Administration (EIA) 2005. Municipal Solid Waste Timeline. Available
at: http://www.eia.doe.gov/kids/history/timelines/municipalsolidwaste.html. Last Accessed:
April 25, 2005.
U.S. Environmental Protection Agency (U.S. EPA). 2005a. Mobile Sources Air Toxics.
Available at: http://www.epa.gov/otaq/toxics.htm. Last Updated: February 14, 2005. Last
Accessed: April 25, 2005.
U.S. EPA. 2005b. Treat, Store, and Dispose of Waste. Available at: http://www.epa.gov/
epaoswer/osw/tsd.htm. Last Updated: April 8, 2005. Last Accessed: April 25, 2005.
U.S. EPA. 2005c. Endocrine Disrupting Chemicals Risk Management Research. Available at:
http://www.epa.gov/ORD/NRMRL/EDC/. Last Updated: March 29, 2005. Last Accessed: April
25, 2005.
U.S. EPA. 2005d. IRIS Database for Risk Assessment.. Available at: http://www.epa.gov/iris.
Last Updated: March 10, 2005. Last Accessed: April 29, 2005.
U.S. EPA. 2005f. National Emission Standards for Hazardous Air Pollutants: Requirements for
Control Technology Determinations for Major Sources in Accordance With Clean Air Act
Sections, Sections 112(g)and 112(j). Federal Register 70(131): 39662-39664.
U.S. EPA. 2005f Air Regulations for Municipal Waste Combustors. Available at:
http://www.epa.gov/reg3artd/airregulations/ap22/combust3.htm. Last Updated: March 18, 2005.
Last Accessed: April 25, 2005.
U.S. EPA. 2005g. Air Quality Criteria for Ozone and Related Photochemical Oxidants (First
External Review Draft). Washington, D.C. EPA/600/R-05/004aA-cA. Available at:
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=114523&CFID=4500826&CFTOKEN=
76808212.
U.S. EPA. 2005h. Resource Conservation Challenge 5-year strategic plan. Office of Solid
Waste and Emergency Response. Washington, D.C. Available at: http://www.epa.gov/epaoswer/
osw/conserve/index.htm.
U.S. EPA. 2004a. Draft Resource Conservation and Recovery Act (RCRA) Multi-Year
Research Plan: Fiscal Years 2003 to 2010. Office of Research and Development. Washington,
DC. May.
6-2 December 2006
-------
U.S. EPA. 2004b. National Emission Standards for Hazardous Air Pollutants: Proposed
Standards for Hazardous Air Pollutants for Hazardous Waste Combustors (Phase I Final
Replacement Standards and Phase II). Federal Register 69(76): 21197-21246.
U.S. EPA. 2004c. Information Sheet 2: Dioxin: Scientific Highlights from the NAS Review
Draft of EPA 's Dioxin Reassessment. Office of Research and Development. Washington, DC.
October.
U.S. EPA. 2004d. Health Effects of PCBs. Available at: http://www.epa.gov/opptintr/pcb/
effects.html. Last Updated: September 8, 2004. Accessed: August 30, 2005.
U.S. EPA. 2004e. Air Quality Criteria for Particulate Matter. National Center for
Environmental Assessment. Washington, D.C. October. EPA 600/P-99/002aF-bF. Available
at: http://cfpub.epa.sov/ncea/cfm/recordisplay.cfm?deid=87903. Last Updated: April 13, 2005.
U.S. EPA. 2004f. Parti culate Matter Research Program: Five Years of Progress. Office of
Research and Development. Washington, D.C. July. EPA 600/R-04/058. Available at:
http://www.epa.gov/pmresearch/pm research accomplishments/.
U.S. EPA. 2004g. EPA's multimedia, multipathway, and multireceptor risk assessment (3MRA)
modeling system: A review by the 3MRA review panel of the EPA Science Advisory Board.
Washington, D.C. November. EPA-SAB-05-003. Available at: http://www.epa.gov/
05 003.pdf.
U.S. EPA. 2003a. Municipal Solid Waste in the United States: 2001 Facts and Figures. Office
of Solid Waste and Emergency Response. EPA530-R-03-011. October.
U.S. EPA. 2003b. RCRA Orientation Manual. Office of Solid Waste. EPA530-R-02-016.
January.
U.S. EPA. 2003c. 2003-2008 EPA Strategic Plan: Direct!on for the Future. Office of Chief
Financial Officer. Washington, D.C. September. Available at: http://www.epa.gov/ocfo/
plan72003sp.pdf.
U.S. EPA. 2002. Process Heaters MACT Standards Development. Available online at:
http://www.epa.gov/ttn/atw/combost/heater/heatback.html. Last Updated: June 7, 2002. Last
Accessed: April 25, 2005.
U.S. EPA. 1997a. Health and Environmental Effects of Particulate Matter. Available online at:
http://www.epa.gov/ttn/oarpg/naaqsfm/pmhealth.html. Last Updated: July 11, 2002. Last
Accessed: April 29, 2005.
U.S. EPA. 1997b. Characterization of municipal solid waste in the United States: 1996 update.
Report EPA 530-R-97-015, Washington D.C.
6-3 December 2006
-------
Werther, J. and T. Ogada. 1999. Sewage Sludge Combustion. Progress in Energy and
Combustion Science 25(1): 55-116.
Wilson, R., and J.D. Spengler. 1996. Particles in Our Air: Concentrations and Health Effects.
Harvard University Press. Cambridge, Massachusetts.
Wi sconsin Department of Natural Resources (WDNR). 2003. Sulfur Dioxide. Available online
at: http://www.dnr.state.wi.us/ors/aw/air/health/sulfurdiox.htm. Last Updated: March 5, 2003.
Last Accessed: April 29, 2005.
World Health Organization (WHO). 1999. Dioxins and their effects on human health.
Available at: http://www.who.int/mediacentre/factsheets/fs225/en/. Last Updated: June 1999.
Last Accessed: April 29, 2005.
Zakaria, J. and G. Sutin. 1994. The SEMASS Shred-and-burn technology: A well proven
resource recovery system. National Waste Processing Conference Proceedings ASME 1994 p.
293-304.
6-4 December 2006
-------
APPENDIX A
LIST OF COMBUSTION EXPERTS INTERVIEWED
-------
Combustion Experts Interviewed
Name
Ballard, Gary
Cooper, John
Hall, Bob
Hoecke, David
Lemieux, Paul
Lighty, JoAnn
Linak, Bill
Porter, Fred
Sarofim, Adel
Themelis, Nickolas
Trenholm, Drew
Wendt, Jost
Ziemann, Paul
Affiliation
EPA, Office of Solid Waste
Cooper Environmental Services
EPA, ORD, National Risk Management Research
Laboratory
Enercon Systems
EPA, ORD, National Risk Management Research
Laboratory
University of Utah, Department of Chemical
Engineering, Institute for Combustion and Energy
Studies
EPA, ORD, National Risk Management Research
Laboratory
EPA, Office of Air Quality Planning and Standards
University of Utah, College of Engineering, Institute for
Combustion and Energy Studies/Reaction Engineering
International
Columbia University, Earth Engineering Center
Research Triangle International, Air Pollution Control
Technology Verification Center
University of Arizona, Department of Chemical and
Environmental Engineering
University of California, Riverside, Department of
Environmental Sciences
Phone
Survey
/
/
/
/
/
/
/
/
E-mail
Survey
/
/
/
/
/
A-l
December 2006
-------
[this page intentionally left blank]
-------
APPENDIX B
IDENTIFIED RESEARCH NEEDS
-------
[this page intentionally left blank]
-------
Identified Research Needs
Summary of Research Need
Where/By Whom was the
Research Need Identified?
Information
Exchange 1
Grantee
Report 2
Other
Combust.
Expert 3
Mechanisms of Formation of Chemical Compounds in Combustion Systems
Improve understanding of the formation of dioxins and furans as well as non-chlorinated
analogs and mixed bromo-chloro dioxins/furans.
Improve the understanding of the fate of dioxins and dioxin transformation in the atmosphere.
Determine how combustion processes can be modified to minimize the formation of mercury
and persistent organic pollutants (e.g., dioxins and furans). Find methods to stabilize mercury
emissions, so that more stable species are emitted.
Study the role of chlorinated benzenes in the surface-mediated mechanisms of dioxin/furan
formation.
Examine the role of combustion-generated nanoparticles in pollutant formation. These fractions
are sites of increased activity (compared to micron-size particles); much of the chemistry occurs
at this level.
Determine the origin and nature of gas-phase and particle-associated persistent free radicals.
Examine elementary reactions of chlorinated phenoxyl and phenyl radicals.
Investigate photo thermal reactions in flares and plumes.
Invoke new reaction mechanisms to describe the formation and destruction of PAHs during the
combustion process.
Perform intensive field experiments to determine the composition of particulate and gas phase
species in combustion emissions.
Determine whether chlorinated by-products (which are persistent in the environment) are
products of combustion.
Study combustion by-products formed in the post-flame combustion zone.
/
S
/
S
/
/
/
/
/
/
/
/
S (Lemieux)
/ (Hall)
S (Ziemann)
B-l
December 2006
-------
Identified Research Needs
Summary of Research Need
Develop better understanding of fine participate formation and transformation as well as health
effects of fine particles.
Develop lower cost particle control technologies.
Develop better understanding of soot formation and transformations.
Confirm activity from diesel fractions.
Where/By Whom was the
Research Need Identified?
Information
Exchange 1
Grantee
Report 2
/
Other
Combust.
Expert 3
S (Lighty; Linak)
/ (Lighty)
Monitoring and Analytical Methods
Develop better (simple, low cost, and reliable) sampling and analysis methods for toxic
combustion emissions.
Improve methods for analyzing the full composition of nanoparticle emissions. Specifically
laser desorption methods need to be improved for efficient sampling and analysis of these very
small particles.
Improve methods for rapid quantitative analysis of black carbon emissions (associated with
diesel vehicles and other combustion sources).
Improve methods for identifying and quantifying emissions of oxidized organic compounds
from combustion sources.
Develop improved techniques for the study of high temperature surface reactions in time scales
on the order of seconds.
Design a more effective analysis system that combines TGPGC and TOFMS for characterizing
PICs associated with combustion in a rapid, real-time or near real-time fashion. Thoroughly test
this system to support its use in characterizing complex combustion effluents and in conducting
site specific risk assessments.
Develop real-time in-field monitoring systems to detect toxic species.
/
/
/
/
S (Cooper;
Wendt)
S (Ziemann)
S (Ziemann)
S (Ziemann)
B-2
December 2006
-------
Identified Research Needs
Summary of Research Need
Improve instrumentation for conducting routine, in-field real time measurements. They need to
be easier to run; those available currently are often difficult to use.
Develop more robust measurement techniques.
Develop new techniques to study larger intermediate molecules for gas-phase reactions.
Perform further study of multi-dimensional gas chromatography.
Study other tools of analysis other than EPA methods. EPA methods are too rigid. There are
many tools available that are not consistent with EPA methods. More outreach needed for these
other methods. More flexibility needed to use these other methods.
Build an integrated air pollution research facility in which there is a pollution generator, a
plume chamber, and exposure chamber (with mice or other test species) to investigate how
changes in fuel and combustion conditions cause changes in primary emissions, secondary
atmospheric reactions, and health effects.
Perform intensive field experiments to determine the composition of particulate and gas phase
species in combustion emissions.
Develop performance specifications for multimetal and HC1 CEMS and document that PM,
multimetal, and HC1 CEMS can meet the specifications when installed on hazardous waste
combustors.
Where/By Whom was the
Research Need Identified?
Information
Exchange 1
S
/
/
/
/
Grantee
Report 2
/
Other
Combust.
Expert 3
/ (Hoecke)
/ (Hoecke)
/ (Wendt)
/ (Holloway)
Emissions Characterization
Perform cool-zone studies. Radicals that may be formed in the "hot zone" are critical in the
cool zone.
Look at degradation and reformation reactions in the combustion effluent when it reaches
ambient temperatures.
s
S (Trenholm)
B-3
December 2006
-------
Identified Research Needs
Summary of Research Need
Identify toxic fractions of combustion-related mixtures. We need to simplify fractions to figure
out what is toxic in these mixtures. Need more study of "odd-ball" compounds, such as
brominated, oxygenated compounds.
Further study of the emerging pollutants associated with combustion, including endocrine
disrupters, fluorinated compounds, brominated compounds, and non-traditional metals that
might be found in combusted electronics wastes.
Develop further understanding of heterogeneous reactions between organic molecules and fly
ash-bound catalysts.
Need to take a multi-pollutant approach when looking at alternative combustion technologies.
We need to look at effects on multiple pollutants and not just a select few.
Study how fuel and combustion conditions impact combustion emissions and potential risks.
We need to push use of alternative fuels and study how use of these fuels affect combustion
operations and emissions.
Focus on better characterization of emissions from various combustion technologies and how
various combustion phenomena affect those emissions.
Improve emissions data and emissions factors and the connection between research and
modeling. Develop a forum for researchers and modelers to exchange information/ideas.
Study the nature of particle surface structure and composition, since it is often interactions at the
surface that are responsible for chemical reactions, water adsorption, and health effects.
Where/By Whom was the
Research Need Identified?
Information
Exchange 1
/
S
Grantee
Report 2
Other
Combust.
Expert 3
/ (Ballard)
S (Lemieux)
S (Lemieux)
S (Sarofim)
S (Sarofim)
S (Themelis)
/ (Ballard)
S (Ziemann)
Fate and Transport
Need further research to understand the atmospheric processing of combustion particles and
their eventual fate and potential impacts on climate and human health.
Develop better source terms for fate and transport modeling.
S (Ziemann)
S (Lemieux)
B-4
December 2006
-------
Identified Research Needs
Summary of Research Need
Where/By Whom was the
Research Need Identified?
Information
Exchange 1
Grantee
Report 2
Other
Combust.
Expert 3
Toxicity, Health Effects, and Risk Assessment
Focus more on health effects research. We need a better understanding of what's in combustion
emissions, how different combustion conditions impact emissions, and how these emissions
affect human health. Of particular concern are fine particulates.
Evaluate poly-brominated compounds for androgenic and estrogenic activity.
Confirm activity from diesel fractions.
Improve toxicity information for many of the combustion by-products for risk assessment
purposes.
Develop more data on the health effects of combustion emissions other than diesel particulate.
Develop better understanding of health effects (down to the cellular level) of dioxin and
mercury.
Further study is needed on the risk from and exposure to dioxins.
Speciation of low levels of mercury compounds is also important.
Assess relative environmental damage caused by combustion emissions.
S (Owens)
S (Owens)
/
/
/
S (Sarofim)
/ (Ballard)
/ (Hoecke;
Lighty; Linak;
Themelis; Wendt)
Other Research Needs
Make coal combustion one of the priority sources of study.
Perform further study to more fully understand the compounds released from inefficient and
uncontrolled sources of combustion emissions (e.g., rural refuse incineration, fireplaces, forest
fires, agricultural burning, other open burning situations).
Need to weight problems and spend money on the more important issues (i.e., sources other
than "clean combustors", such as open burning).
/
/
/
S (Hoecke;
Sarofim)
/ (Hoecke;
Sarofim)
B-5
December 2006
-------
Identified Research Needs
Summary of Research Need
Study difficult to incinerate materials or materials that will be increasingly found in the
municipal solid waste stream (e.g., electronic wastes, Teflon materials).
Evaluate the biomass of sugar cane that is burned and the quantity and composition of the
emissions.
Increase funding for future combustion research studies.
Increase interaction among grantees, EPA, the academic community, and other researchers.
Hold more discussion forums like the Information Exchange.
Focus future grant work on data/knowledge gaps instead of solely on regulatory needs.
Need more "real" data that identifies the real problems associated with combustion emissions
and provides better education for the public.
Encourage more interdisciplinary research. Promote further discussion and information
exchange between researchers who characterize emissions and fate and transport experts.
Research the impacts of changes in incineration practices under Superfund; specifically, moving
from on-site incineration to on-site "thermal treatment" and off-site incineration.
Where/By Whom was the
Research Need Identified?
Information
Exchange 1
S (Owens)
/
/
/
/
Grantee
Report 2
/
/
Other
Combust.
Expert 3
/ (Hoecke)
/ (Hoecke)
/ (Wendt)
Notes:
1 Additional details regarding research needs identified during the AWMA Information Exchange may be found in Section 3.3.
2 Additional details regarding research needs identified by grantees in their reports or other documentation may be found in Sections 3.1 and 3.2.
3 "Other combustion experts" were contacted via phone or email.
B-6
December 2006
-------
[PA/60G/Q -Ob/002
vvEPA
of
for
DC
------- |