United States Office of Air Quality EPA 456/R-99-002
Environmental Protection Agency Planning and Standards June 1999
Air Research Triangle Park. NC 27711
EPA
EMISSION ESTIMATION
TECHNIQUES FOR UNIQUE
SOURCE CATEGORIES IN
MEXICALI, MEXICO
C LEAN
A IR
T ECHNOLOGY
C ENTER
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EPA-456/R-99-002
EMISSION ESTIMATION TECHNIQUES
FOR UNIQUE SOURCE CATEGORIES
IN MEXICALI, MEXICO
U.S.-Mexico Border
Information Center on Air Pollution
CICA
Centra de Information sobre Contamination de Aire
Para la Frontera entre EE. UU. YMexico
Sponsored by:
Clean Air Technology Center (CATC)
Information Transfer Group (MD-12)
Information Transfer and Program Integration Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
June 1999
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EPA-456/R-99-002
June 1999
EMISSION ESTIMATION TECHNIQUES
FOR UNIQUE SOURCE CATEGORIES
IN MEXICALI, MEXICO
Prepared by:
Mark Saeger
Science Applications International Corporation
100 Capitol Drive
Durham, NC 27713
EPA Contract No. 68D30030
Work Assignment No. 11-89
EPA Project Manager:
Robert J. Blaszczak
Information Transfer Group (MD-12)
Information Transfer and Program Integration Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Prepared for:
U.S.-Mexico Border Information Center on Air Pollution /
Centra de Information sobre Contamination de Aire
Para la Frontera entre EE. UU. YMexico (CICA)
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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EPA REVIEW NOTICE
This report has been peer and administratively reviewed by the U.S. Environmental
Protection Agency. This review was coordinated by the U.S.-Mexico Information Center on Air
Pollution / Centra de Information Sobre Contamination de Aire Para la Frontera entre EE. UU.
YMexico (CICA). In addition, CICA coordinated review of this report with other agencies that
participated in the study, including: the County of Imperial Air Pollution Control District; and the
Instituto National de Ecoligia in Mexico; and the Mexicali district office of the Secretaria de
Medio Ambiente, Recursos Naturalesy Pesca. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161.
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PREFACE
The U.S.-Mexico Border Information Center on Air Pollution (Centra de Information
sobre Contamination de Aire Para la Frontera entre EE. UU. -Mexico, or CICA) was established
by the U.S. Environmental Protection Agency (U.S. EPA), Office of Air Quality Planning and
Standards (OAQPS) to provide technical support and assistance in evaluating air pollution
problems along the U.S.-Mexico Border. These services and products are available at no cost to
Federal, State and Local Agencies and universities in Mexico. Others can use these services
depending on available resources. CICA provides ready access to U.S. EPA information and
expertise. It draws on professional staff from the EPA's OAQPS and Office of Research and
Development (ORD). Private contractors also are available when appropriate.
CICA SERVICES
CICA provides assistance in the following ways:
LINES OF COMMUNICATIONS
CICA offers bilingual communication services (English & Spanish)
TELEPHONE: Toil-Free from Mexico only: (800) 304-1115 (Spanish)
From other locations: (919) 541-1800 (Spanish)
or (919) 541-0800 (English)
FAX: (919) 541-0242
E-Mail: catcmail@epa.gov
ON-LINE ASSISTANCE
Internet World Wide Web (CICA Web)
http ://www. epa.gov/ttn/catc/cica/
ENGINEERING ASSISTANCE / TECHNICAL GUIDANCE
GUIDANCE DOCUMENTS AND TECHNICAL TOOLS
INTERNATIONAL TECHNOLOGY TRANSFER CENTER FOR GLOBAL
GREENHOUSE GASSES
Establishing a reliable emissions inventory for all significant sources of air pollutants in the
Mexicali, Baja California, Mexico - Imperial Valley, California, U.S.A. area is part of a
comprehensive effort to identify air pollution problems and implement measures to improve
ambient air quality along the U.S.-Mexico border. The purpose of this project was to identify and
evaluate alternative approaches that could be used to determine potential emissions from two
unique sources in Mexicali, Mexico; i.e., street vendor cooking devices and wastewater canals.
in
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ACKNOWLEDGMENTS
This report was made possible through the information, cooperation and coordination
provided by Mr. Gaspar Torrez, County of Imperial Air Pollution Control District, El Centre, CA
and Mr. Octavio Alonzo, Chief, Departamento de Calidad del Aire, Delegation Federal de la
Secretaria de Medio Ambiente, Recursos Naturales y Pesca (SEMARNAP). CICA also
appreciates the effort of Dr. Victor Hugo Paramo, Director de Administration del Aire, Instituto
National de Ecoligia (INK), and his staff for reviewing and commenting on the draft final report.
CICA also acknowledges and appreciates the efforts of Mr. Gerardo Rios, U.S. EPA
Region IX, for proposing and providing initial coordination for this project. We are also very
grateful to Mr. Jaime Mendieta, Senior Environmental Employee with CICA for his tireless efforts
in preparing the Spanish version of the draft final report and Ms. Allyson Siwik, U.S. EPA Region
VI Border Liaison Office, for reviewing and commenting on the final report.
IV
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TABLE OF CONTENTS
EPA Review Notice ii
Preface iii
Acknowledgments iv
Table of Contents v
Tables vi
List of Acronyms vii
Abstract viii
Introduction 1
Background 1
Approach 3
Phase 1. Literature Review 3
Phase 2. Site Visit 3
Phase 3. Emissions Estimation Methods and Control Options 8
Emissions Estimation Methods 8
Street Vendor Cooking Devices 8
Open Sewage Impoundments, Canals and Conveyance Systems 12
Emissions Control Options 16
Street Vendor Cooking Devices 16
Open Sewage Impoundments, Canals and Conveyance Systems 18
Phase 4. Development of Evaluation Criteria and Ranking of Options 20
Evaluation Criteria 20
Ranking of Emissions Estimation Methods 21
Recommendations 23
References 25
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TABLES
TABLE 1. LIST OF INFORMATION RESOURCES FOR CONSIDERATION 4
TABLE 2. SUMMARY OF REFERENCE MATERIALS 5
TABLES. PROPOSED METHODS LISTED WITH
EVALUATION CRITERIA 22
VI
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LIST OF ACRONYMS
AP-42 U.S. EPA's central document listing all recommended emissions factors
BBS Bulletin Board System, electronic data management and retrieval system
C## organic compound or fragment with ## carbon atoms
CATC Clean Air Technology Center
CHIEF Clearinghouse for Inventories and Emission Factors
CICA U.S.-Mexico Border Information Center on Air Pollution / Centra de
Information Sobre Contamination de Aire Para la Frontera entre
EE. UU. y Mexico
CMB Chemical Mass Balance
CO carbon monoxide
EE.TJTJ. Estados Unidos, United States of America
FTIR Fourier Transform Infrared
HAP Hazardous Air Pollutants
IBM International Business Machines, Inc.
INE Institute National de Ecoligia (National Institute of Ecology; part of
SEMARNAP; responsible for setting environmental standards in Mexico)
IR Infrared
kb kilobytes
NATICH National Air Toxics Information Clearinghouse
NOX oxides of nitrogen
OAQPS Office of Air Quality Planning and Standards
PAH Polycyclic Aromatic Hydrocarbons
PC Personal Computer
PIES Pollution Prevention Information Exchange System
POTW publicly owned treatment works
PM10 particulate matter with aerodynamic diameter of 10 microns or less
RAM random access memory
SAIC Science Applications International Corporation
SCAQMD South Coast Air Quality Management District
SEMARNAP Secretaria de Medio Ambiente, Recursos Naturales y Pesca (department
of environment, natural resources and fisheries in Mexico; U.S. EPA's
counterpart in Mexico)
SIP State Implementation Plan
TRI Toxic Release Inventory
TTN Technology Transfer Network
U.S. EPA United States Environmental Protection Agency
VOC volatile organic compounds
vn
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ABSTRACT
An initial assessment of two unique air emissions source categories in Mexicali, Mexico
was completed. The source categories evaluated in this study are street vendor cooking devices
and open sewage impoundments, canals and conveyance systems. The assessment included a
preliminary literature review to identify relevant available information that could be used to
develop an emissions inventory methodology for those sources. A site visit was made to Mexicali
to observe examples of these sources to better understand the potential air emissions contributions
of those sources and to help put these sources in context relative to air quality in Mexicali and air
pollution transport issues that can ultimately affect air quality problems immediately across the
border in the United States. Through continuing discussions with researchers interested in similar
and related problems and additional published reports, several options for emissions estimation
approaches were identified. A series of criteria were developed to help rank order potential
emissions methodologies. Candidate emissions estimation approaches were evaluated against the
list of criteria and these approaches were ranked relative to one another. Finally, some ideas for
control programs that might be considered for implementation to reduce the overall emission rates
from those sources were presented.
Vlll
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INTRODUCTION
BACKGROUND
Establishing a reliable emissions inventory for all significant sources of air pollutants in the
Mexicali-Imperial Valley area is part of a comprehensive effort to identify air pollution problems
and implement measures to improve ambient air quality along the U.S.-Mexico border. The U.S.
Environmental Protection Agency (U.S. EPA), working through the Clean Air Technology Center
(CATC), and the U.S.-Mexico Border Information Center on Air Pollution / Centre de
Information sobre Contamination de Aire Para la Frontera entre EE.UU. y Mexico (CICA) in
coorperation with the Departamento de Calidad del Aire, Delegation Federal de la Secretaria
de Medio Ambiente, Recursos Naturales y Pesca (SEMARNAP) and the Administration del
Aire, Institute National de Ecoligia (INK) in Mexico have jointly initiated programs to achieve
this goal. The purpose of this project is to investigate specifically two unique source categories in
Mexicali, Mexico and develop a list of possible methodologies to estimate air emissions from
those sources. The two source categories considered in this effort are street vendor cooking
devices and open sewage impoundments, canals, and conveyance systems. The possible
methodologies were evaluated relative to a list of criteria, and ranked in order of preference.
Finally, the costs to implement those methodologies that appear to be useful have been estimated.
Street vendors cooking devices include a variety of activities in which food is prepared in
either portable or fixed structures. The food items prepared in these units include grilled meats
for use in tacos, burritos and other typical foods for the region. The units burn mainly charcoal or
compressed gas. These units are more or less ubiquitous throughout the city and in some
locations during the evening hours they are lined up one after the other down significant lengths
of some of the streets. Emissions of concern from these street vendor cooking devices are
particulate matter with aerodynamic diameter less than 10 microns (PM10), hazardous air
pollutants (HAP), volatile organic compounds (VOC), and oxides of nitrogen (NOX).
Open sewage impoundments, canals, and conveyance systems refer to a system of ditches
or canals that were originally designed to manage run off primarily from agricultural activities on
the outskirts of the City of Mexicali. The population of the city is now over 1,000,000 and the
city boundaries extend into areas where these run off canals exist. Several industrial plants and
residential areas are located in close proximity to these canals. As a result, these ditches collect
an assortment of wastes, both liquid and solid. The waste ditches contain waste oils, a variety of
industrial wastes, residential sewage, and other materials that wash out of trash, tires and
appliances that are disposed in the ditches. Pollutants of interest from the waste ditches include
VOC and organic HAP.
The canals drain into the New River, which is the main artery that directs flow north
through the Imperial Valley in California and ultimately to the Salton Sea. The Salton Sea is
located approximately 75 miles north of the border between the U.S. and Mexico. Its surface is at
229 feet below sea level and it has no outlet. The untreated wastewater generated in Mexicali,
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and all of the agricultural runoff from the significant food and grain production in the Imperial
Valley ends up in the Salton Sea.
The project design originally included an analysis of a third source, residential burning of
waste materials; specifically used tires. Recently, a law has been in effect in Mexicali prohibiting
the use of waste materials as a fuel source in residences. The law is enforced and this is no longer
thought to be a significant problem. Therefore, work on this source category was stopped.
Although discussions with local representatives were initiated in an attempt to specify another
source category, as of the time that this report was prepared, no alternate source category had
been identified for consideration in this effort.
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APPROACH
The project was conducted in four phases. The first was a literature review of known data
sources, reports and guidance materials on sources similar in nature to those evaluated in this
study. The second phase was a site visit to see the sources and to make a visual assessment of the
types of methodologies that could be used to evaluate emissions. In the third phase, options for
emissions control opportunities and alternatives for emissions estimation methodologies are
discussed. The fourth phase presents a set of criteria for evaluating the proposed emissions
estimation methods and ranking those proposed approaches against the criteria. Finally, a
recommended approach is presented for each source category. To the extent possible a rough
cost estimate is provided for each recommended approach. This draft report was prepared and
submitted to officials from the U.S. EPA, the County of Imperial and from Mexico, as well as
other interested partners for review and comment. The discussion below describes the activities
completed in each of these phases.
Phase 1. Literature Review
The work assignment identified a list of six specific published reports, guidance materials
and information summaries and required a review of these materials for any relevant background
information and any results of emissions estimation methods or emission factors suitable for the
source categories of interest. Those specific information sources are listed below in Table 1.
Preliminary efforts to locate applicable information sources revealed several additional sources of
information that were considered potentially applicable to this effort. Those information sources
were also obtained and reviewed. Table 2 is a summary list of the materials and reports that were
reviewed in this phase. The table indicates whether the materials contained information that was
thought to be useful in the analysis. Since waste derived fuel-fired residential heating sources
were eliminated from the overall analysis under this work assignment, the information sources
relevant to that source category that were reviewed in this phase are not included in Table 2.
Phase 2. Site Visit
Science Applications International Corporation (SAIC), U.S. EPA contractor, coordinated
with Mr. Gaspar Torrez of the County of Imperial Air Pollution Control District located in El
Centra, CA and scheduled a visit to the Mexicali area on June 27, 1996. Mr. Torrez coordinated
with the principal contact from Mexico on this project, Mr. Octavio Alonzo, head of the
Departamento de Calidad del Aire, Delegation Federal de SEMARNAP in Mexicali. A meeting
was held on the morning of June 27, 1996 in the local offices of SEMARNAP. We presented the
objectives of the project and gave a brief description of the project. Mr. Alonzo indicated his
approval for the project and offered to assist in any way possible.
Following the meeting we proceeded by car to tour Mexicali to see examples of the street
vendor cooking devices and the uncontrolled open sewer waste canals. The site visit concluded
during the afternoon of June 27, 1996.
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TABLE 1. LIST OF INFORMATION RESOURCES FOR CONSIDERATION
Title
Implementation Plan for
Mexico Emissions Inventory
Methodology
(Ref. 1)
Imperial Valley/Mexicali
Cross Border PM10
Transport Study; Draft Final
Report (Ref. 2)
Procedures for Estimating
and Allocating Area Source
Emissions of Air Toxics -
Working Draft (Ref. 3)
Compilation of Air Toxics
Emission Inventory
Questionnaires EPA 450/4-
88-008 (Ref. 4)
Technical Procedures for
Developing AP-42 Emission
Factors, EPA 454/B-93-050
(Ref. 5)
Procedures for the
Preparation of Emission
Inventories for Carbon
Monoxide and Precursors of
Ozone, EPA-450/4/91/016
(Ref. 6)
Author
Radian Corporation
Desert Research
Institute, University
and Community
College System of
Nevada
Versar, Inc.
Engineering Science,
Inc.
NA
NA
Sponsor
Border XXI Air Work
Group, through the
Western Governors'
Association with
assistance from the
Binational Advisory
Committee
U.S. EPA Region IX
U.S. EPA; CHIEF
BBS on OAQPS TTN
U.S. EPA
U.S. EPA
U.S. EPA
Date
September
1995
April 21, 1995
March 1989
June 1988
October 1993
December
1992
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TABLE 2. SUMMARY OF REFERENCE MATERIALS
REFERENCE NAME
Ref. 4 - Compilation of Air Toxics
Inventory Questionnaires (EPA-
450/4-88-008)
Ref. 7 - Identification and
Characterization of Missing or
Unaccounted For Area Source
Categories (EPA-600-R-92-006)
Ref. 8 - Example Documentation
Report for 1990 Base Year Ozone
and CO SIP Emission Inventories
(EPA-450/4-92-007)
Ref. 9 - Compiling Air Toxics
Emission Inventories 2nd Edition
(EPA-450/4-86-010)
Ref. 10 - Submicrometer Aerosol
Mass Distributions of Emissions
from Boilers, Fireplaces,
Automobiles, Diesel Trucks and
Meat-Cooking Operations
(Aerosol Sci. & Tech. 14, No. 1,
1991)
SPONSORING
AGENCY
U.S. EPA
U.S. EPA
U.S. EPA
U.S. EPA
Unknown
DATE
6/88
1/92
3/92
2/90
1991
APPLICATION
Street Vendors;
Waste Canals
No Relevant
Applications
Street Vendors;
Waste Canals
Street Vendors;
Waste Canals
Street Vendors
BRIEF DESCRIPTION
Guidelines for development and use of
questionnaires for collecting information for
inventory development and emission factors
for hazardous air pollutants
Establishes some background and information
resources for developing emissions estimates
for selected nontraditional source categories
Provides examples of how to document the
development of emissions inventory data for
use in SIP development; Useful for guidance
on how to establish credible methods
Provides guidance on building capabilities to
identify previously ignored sources of air toxic
emissions;
Presents data on composition of very fine
particle mass emissions from meat cooking
operations.
USEFUL
YES
X
X
X
X
NO
X
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TABLE 2. SUMMARY OF REFERENCE MATERIALS (continued)
REFERENCE NAME
Ref. 15 - Air Emissions Models
for Waste and Wastewater (EPA-
453/R-94-080A)
Ref. 16 - NATICH Data Base
Report on State, Local and EPA
Air Toxics Activities, (EPA-
450/3-89-29)
Ref. 17 - Methods Evaluation for
Mexico Emissions Inventory
Methodology
Ref. 1 - Implementation Plan for
Mexico Emissions Inventory
Methodology
Ref. 18 - The New River
Workshop
SPONSORING
AGENCY
U.S. EPA
U.S. EPA
Border XXI Air
Work Group
through the Western
Governors' Assoc.
with assistance of
Binational Advisory
Committee
Border XXI Air
Work Group
through the Western
Governors' Assoc.
with assistance of
Binational Advisory
Committee
National Water
Research Institute
DATE
11/94
7/89
4/95
3/96
5/95
APPLICATION
Waste Canals
No Relevant
Applications
Not Specific for
target source
categories
Not Specific for
target source
categories
Not Specific for
Target Source
Categories
BRIEF DESCRIPTION
Reviews available models for calculating air
emissions from wastewater handling
systems. Description of WATERS with
examples of its use
Summaries activities completed to develop
emissions estimates for some sources of air
toxics; does not include information on the
target source categories
Presents an general overview of emissions
inventory preparation methods; does not
give information for specific source
categories
Presents general approaches for a long term
project to develop emissions inventories for
Mexico
Reviews current scientific understanding of
the problems facing the New River and
assesses future needs to advance
improvements in New River Water Quality
USEFUL
YES
X
NO
X
X
X
X
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TABLE 2. SUMMARY OF REFERENCE MATERIALS (continued)
REFERENCE NAME
Ref. 20 - Protocol - Rule 1 174
Ignition Method Compliance
Certification Protocol
Ref. 21 - Quantitative
Characterization of Urban Sources
of Organic Aerosol by High
Resolution Gas Chromatograph
(Env. Sci. Tech., 25, No. 7, 1991)
Ref. 22 - Sources of Fine Organic
Aerosol 1. Charbroilers and Meat
Cooking Operations (Env. Sci.
Tech., 25, No. 6, 1991)
Ref. 23 - Study to Develop
Background Information for
Direct Meat Firing Industry
(GCA-TR-77-36-G)
Ref. 24 - Particulate Emissions
Test Summary
SPONSORING
AGENCY
South Coast Air
Quality
Management
District
Unknown
Unknown
U.S. EPA
Hardee 's Food
Systems
DATE
2/91
1991
1991
1/78
1974
APPLICATION
Street Vendors
Street Vendors
Street Vendors
Street Vendors
Street Vendors
BRIEF DESCRIPTION
Presents the compliance testing protocol for
charcoal grill starter fluids
Provides measurement information on the
chemical composition of fine particle mass
emissions from meat grilling operations
Provides detailed analysis of chemical
composition of emissions from meat
(hamburger) grilling and frying operations
Discusses processes, test methods and
emissions characteristics for direct meat
(hamburger) grilling operation in U.S. fast
food setting; discusses emissions control
technology
Provides test results for example grilling
operations in typical U.S. fast food industry
USEFUL
YES
X
X
X
X
X
NO
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During the site visit several examples of the street vendor cooking devices and waste
canals were observed. The visit was conducted in the late morning and early afternoon. Most of
the activity involving the street vendor cooking begins later in the afternoon and reaches its peak
between approximately 5 PM and 11 PM in the evening. Therefore, it was not possible to
observe the peak of the activity on this visit, but Mr. Torrez pointed out the streets where
significant activity is normally observed during the evening hours and it was possible to
understand the magnitude of the problem. The street vendor devices range from small units that
are towed or pushed to a location along many of the streets in Mexicali, to larger permanent sites
with enclosures and tables. Cooking is done mainly with either charcoal or compressed gas fuels.
During the visit most of the operating units observed were fired with charcoal. Emissions from
the gas burners are thought to be inherently lower than those for the charcoal burners although
the most significant emissions probably result from the drippings from grilled meats onto the hot
coals or elements of the gas burners. Therefore, both types of units are of primary interest in this
study. During the site visit it was not possible to observe flame characteristics or other
operational conditions to estimate combustion efficiency that might be relevant to NOX emissions
from the gas burners.
The waste canals are trenches that range from about 6 meters to 10 meters wide and about
3 meters or less deep. Flow was observed in these trenches verifying the presence of sources
upstream of the locations observed. There was a considerable amount of trash and debris along
the sloped banks of the trenches and in the water. Although odors were present they were not
excessive or readily distinguishable, indicating that at the points of observation there is probably
not a significant amount of volatilization of organic materials.
Phase 3. Emissions Estimation Methods and Control Options
Emissions Estimation Methods
Street Vendor Cooking Devices
These sources are small fossil fuel-fired combustion sources, that are emissions sources for
selected VOCs and potentially other more complex organics, NOX, and particulate matter.
Although these sources are individually small, the large number of them that are routinely in
operation in Mexicali creates a source category that could be significant. The fact that these
sources emit both ozone precursors and particulate matter further increases their importance as
contributors to two significant air quality problems. Recently, there has also been a significant
amount of interest in the possibilities that charbroiling red meats can create benzo(a)pyrene an
organic carcinogen and other polycyclic aromatic hydrocarbons (PAH), some of which may
become airborne (Rogge, et. al., 1991).
There are two basic fuel types used in these devices; charcoal and a mixture of
compressed propane and butane gas. VOC emissions resulting from starter fluids used on the
charcoal, and leaks in the compressed gas storage, transfer, and delivery systems at the cooking
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units may be significant sources of additional VOC. The use of these fuels also leads to additional
concerns for emissions and environmental problems. Exploration of these additional issues is
outside the scope of the current work but it should be recognized in any event. Emissions may
also result from the transport and handling of bulk compressed gas fuel and in the manufacture
and handling of the charcoal fuel. Of most concern is potential leaks from the main bulk storage
devices which are located in an area of the city where there is significant commercial activity and
population density. Not only is there a possibility of gas leaks from the transfer of fuel from these
bulk storage facilities to intermediate transport devices or directly to users but there is also a risk
of explosion. If the manufacturing process for the charcoal are located in or near Mexicali there
will be emissions of VOC from that process, and possible paniculate emissions resulting from
storage and handling of the charcoal. Further cooperation and coordination with Mexican
authorities is recommended to determine the relative importance of these possible concerns.
The U.S. EPA has a vast amount of data describing emissions processes and emission
factors for various fossil fuel-fired combustion sources (U.S. EPA AP-42, 1995). Most of this
information is specific for large utility and industrial external combustion sources. While these
types of sources are similar in nature to the small cooking devices, specific differences in
combustion chamber design, air/fuel mixtures, temperatures and pressures between these two
source types make direct application of the emissions factors and estimation procedures for the
large source inapplicable to the smaller sources of interest in this study. EPA has also completed
a significant amount of research related to emissions from fireplaces and wood stoves, to support
specific PM-10 nonattainment areas, where wood stoves and fireplaces are used in large numbers
for heating (Houck, et. al., 1989; Chow, et. al., 1993). These studies have not explored the
possible emissions of VOC from such sources in any detail.
The South Coast Air Quality Management District (SCAQMD), the local air quality
agency in the Los Angeles air basin, has developed emission characteristics for backyard
barbeques using charcoal briquets and commercially available starter fluids. Those studies were
only concerned with emissions of VOC caused by the application and burning of the starter fluids.
The SCAQMD developed a rule (Rule 1174) based on these studies that regulates the
characteristics of starter fluids that are allowed for sale, purchase and use in the air basin. In that
work, however, a testing protocol for measurement of the emissions characteristics of charcoal
grills was developed (SCAQMD, 1991). Although the procedure adopted by SCAQMD was
specific for the measurement of total nonmethane hydrocarbon emissions, that same approach
could be used to obtain samples for analysis of particulate matter and speciated VOC for
application to this project.
Measurements of parti culate matter emissions characteristics of representative charcoal
grilling operations in Mexicali were made as part of the Imperial Valley/Mexicali Cross Border
PM10 Transport Study (Chow and Watson, 1995). In that study, emissions from two of the
permanent restaurant style operations were made to develop the source emissions profile
necessary to run the Chemical Mass Balance (CMB) model and other receptor modeling
approaches. Data were collected through dilution sampling from a point approximately 0.3
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meters above the edge of the roof vent from these structures. Unfortunately, the raw data
collected in that study are insufficient to quantify the mass emissions rate of either particulate or
organic compounds.
Appropriate modifications to this general approach can be implemented to estimate source
specific emissions contributions in a region of the city. The technique can also be very effective to
routinely evaluate changes in the contributions of specific source categories to the overall
particulate loadings in the area. These data can be used to infer an emissions rate and changes in
emissions rates after controls are implemented. These approaches require a strong knowledge of
and experience with receptor modeling approaches and further discussions with experienced
researchers in receptor modeling approaches are recommended if further work related to this
approach is contemplated.
Various measurements programs specific to emissions from meat grilling operations in the
U.S. fast food industry were completed in the mid to late 1970s (Commonwealth Lab. Inc. 1974;
GCA Technologies, 1978). Although these data are specific for the grilling of ground beef in
hamburger patties, the results are useful in the current analysis. The data in both studies show a
large amount of fine particulate to be emitted from these processes. Over 90 percent of the
particulate mass is in the less than 1 micron size range. These emissions combined with oily
fumes also emitted from meat grilling could result in significant particulate emissions. Additional
research is continuing in the United States to explore the possible emissions of cholesterol and
other fatty compounds, organic acids, and organic carcinogens to the air from meat grilling
operations.
In most U.S. restaurant operations grease traps are required to be installed in the exhaust
flues from these types of operations. These units can significantly reduce the air emissions of fatty
organic compounds. The fine particulate is not reduced significantly in the grease traps and rather
sophisticated filters would be needed to capture the bulk of the particulate in the less than 1
micron size range. Such filters are employed at selected fast food restaurants in the United States.
Details on the design and operation of these filters are readily available.
More recent studies conducted at the California Institute of Technology (Hildemann, et.
al., 1991), reviewed meat grilling as one component of an analysis of the source contributions to
total organic aerosol in the Los Angeles area. These studies show that meat grilling contributes a
large percentage of organic acids that elute from the gas chromatograph between C20 and C25,
with a strong peak at C21 and C22. These results are useful for planning any receptor type
analyses because the components in this range will provide fingerprint elements specific for this
source that are distinguishable from other sources of organic aerosol.
Emissions estimation approaches for this category are limited to two possibilities. One is a
source measurements based approach, and the other is an inferential approach based on ambient
measurements. The source measurements based approach would require the selection of a group
of routine operations that would provide a composite representation of all of the street vendor
10
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activity in Mexicali. These units would then be subjected to monitoring of mass emissions rates
following some agreed standard method over the range of typical operations. Quantities of fuel
consumed, meat products grilled, and/or square meters of grill area in operation should be
collected during the emissions tests for use in the development of an emission factor or series of
emission factors that could be used to describe the average rate of mass emissions from these
operations. In the inferential approach more detailed source composition profiles could be
generated and emissions rates in selected areas of the city could be inferred through analysis of a
series of ambient monitoring tests in a method that is similar to more accepted receptor modeling
approaches.
Both of these approaches would require some method of estimating the overall activity
rate expressed in a representative form for that source category. This could be accomplished
through a mandatory reporting mechanism or through a survey approach. In the reporting
approach either the fuel distributors, or the vendors would be required to report total fuel sales or
fuel consumption in specified reporting periods, or the vendors would be required to report the
total amount of meat product grilled or sold during specified reporting periods. In a survey
approach a group of staff would be selected and trained to periodically observe operations at a
large percentage of the units operating in Mexicali to estimate a unit of activity that would be
representative of the operations in selected areas of the city. These estimates of activity rate
could then be compared to the overall inferred emissions under the base scenarios to estimate
emissions over time.
Careful planning of the initial data collection methods would ensure that either method
would be source and pollutant specific. It is assumed that sufficient data is not currently available
to support either of the proposed approaches. This represents a significant weakness and detailed
discussions with Mexican officials and U.S. representatives in the border area would be needed to
establish the most cost-effective methods to obtain and maintain the data needed to use the
methods. In both cases, small investments of resources could be committed to train appropriate
staff from Mexico to complete the initial data collection and estimations and to maintain that
process over time. Again through a careful planning process either approach could be developed
in a way to support the continued update of estimates to track the usefulness of any control
programs, and to provide data suitable for planning purposes both in Mexico and as needed to
support cooperative bilateral programs.
Each of these approaches would be fairly expensive. Initial costs associated with source
monitoring or ambient data collection to support the receptor analysis approach would be similar.
Depending on the amount of support and facilities that could be provided by the Mexican
authorities, it is estimated that an initial investment of $50,000 to $150,000 U.S. would be needed
to collect the initial data to make a baseline estimate. Once the most appropriate source markers
were identified it would likely be less expensive over the long term to establish the approach
based on ambient data collection rather than on source monitoring. The main uncertainly relative
to cost would be the cost associated with developing and maintaining the activity data use rates
and number of units that employ various control systems. The basic approach to collect and
11
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maintain these data is straightforward, however, the overall effect of these additional reporting
mechanisms to both the street vendors and the central authority is difficult to estimate. Clearly,
additional discussions and negotiations with the Mexican authorities is critical to understanding
the burdens and impacts of those burdens on vendors and the public.
Open Sewage Impoundments, Canals and Conveyance Systems
These sources are slow flowing waste canals that meander through the industrial areas of
the city and through some residential areas. These canals accept a variety of liquid and soluble
wastes and these wastes ultimately empty into the New River. Discussions with Mr. Torrez and
other people in Mexicali indicate that these canals frequently contain oils such as used motor oil,
chemical wastes from some of the industrial sites and untreated human sewage, and other
household wastewater. The canals also receive a variety of trash and used appliances, etc., that
litter the sides and bottom of the canals. It is likely that some of these items dumped into the
canals also contribute some contaminants.
There has been a significant amount of research conducted to describe emissions processes
and to calculate potential VOC emissions resulting from wastewater collection, conveyance and
treatment. One good alternative for this work is the WATERS computer system. WATERS
includes a series of mass transfer calculations that allow an estimate of emissions resulting from
wastewater handling and treatment processes. Of interest in this application are the capabilities of
the model to simulate unit specific emissions from open trenches, equalization ponds, and
lagoons. The system is available on diskette and can be operated on nearly any IBM-compatible
PC with at least 520 kb of random access memory (RAM). The user must specify physical
parameters on the type of unit, and chemical parameters on the specific compounds that are of
interest. The user must specify the chemical constituents that are to be modeled. There are
accompanying computer systems that identify the required chemical parameters for over 900
specific VOC species that can be handled by the WATERS program. If it is necessary to calculate
emissions for compounds not included in the prepared lists, the chemical property data for those
compounds can be entered by the user.
Bilateral discussions since the early 1980s have focused on the continuing problem of
contamination of the New River from industrial and residential sources in Mexicali (International
Boundary and Water Commission, 1980, 1987, 1992). Although these discussions and
agreements have sought a comprehensive solution to pollution problems of the New River,
continued residential growth and industrial expansion in the Mexicali area have exceeded the
capacity of solutions implemented to date. In addition, these efforts have focused on affecting
improvements to the water quality of the New River and have not concerned controls or
elimination of the causes of that pollution or the effects on potential air emissions resulting from
industrial contaminants that are routinely discharged to the waste canals feeding the New River.
In fact, several of the proposed solutions to this problems advocated the construction of new or
upgrading of existing aeration lagoons to pretreat industrial contaminants in the wastewater
discharges.
12
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There is a fairly complete historical monitoring database of selected water quality
parameters from the U.S. side of the New River. In general, these monitoring efforts have
focused on nutrient loadings, specific ions, and bacteriological parameters. There may also be a
limited amount of data on the chemical composition of the waste canals, although it was not
possible to locate these data during the completion of this study. It is likely that it will be
necessary to obtain these data directly through Mexican authorities. Recently, the U.S. EPA has
required industrial facilities in Mexicali with U.S. parent organizations to report on the quantity of
waste streams from their facilities. This action followed closely the U.S. voluntary reporting
program known as the Toxic Release Inventory (TRI) system, that is implemented under the
Community Right-to-Know legislation, although the data from Mexicali are not included directly
in the TRI database (U.S. EPA, 1995).
In this study a total of 117 letters were sent to U.S. parent companies suspected of
operating Maquiladora facilities in the Mexicali area requesting information on their contributions
to discharges of chemicals on the TRI priority list to all media. U.S. EPA received 8 responses to
that letter, 4 companies were removed from the list because they received the letter as a duplicate
through another related company, and 13 letters could not be delivered. Of the 8 responses, 7
companies indicated that they operated a Maquiladora in the Mexicali area.
Following that request, U.S. EPA sent administrative subpoenas to 95 U.S. parent
companies suspected of operating Maquiladoras in Mexicali. Twenty of the companies that
received subpoenas were removed from consideration because the subpoena could not be
delivered, the companies were subject under a different company name, the company was out of
business, the company had responded to the original letter, or the company was not the parent
company of the Maquiladora. Of the 75 responses 57 companies indicated that they were a
parent company of a Maquiladora operating in the Mexicali area. The breakdown of industry
types represented in the 64 responses for operating U.S. owned Maquiladoras is listed below:
• 9 in Electrical Equipment and Components
• 14 in Fabricated Metal Products
• 7 in Fabric or Apparel Finishing
• 4 in Transportation Equipment
• 3 in Food Products
• 3 in Medical and Optical Goods, and
• 14 Other (2, Repair Parts; 2, Rubber and Plastics; 2, Furniture Manufacturing; 2,
Industrial Equipment; 2, Miscellaneous Assembly; and 1 each in Sports
Equipment, Glass, and Printing)
The request for information followed the TRI data collection effort which only requires
reporting if the company manufactures, processes or otherwise uses for than 10,000 Ibs./year of
any of the priority chemicals. The bulk of the responses indicated use rates of the priority
chemicals that were below the 10,000 Ibs./year use rate and therefore they did report their
discharges. The total amount of the chemicals reported to be discharged by companies that use
13
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the chemicals at above or below the threshold limit was 49, 510 Ibs. Of that total almost all of it
was reported to be released directly to the air. Several of the companies report discharging over
800,000 Ibs. to wastewater treatment plants, or exporting chemicals back to the U.S., to other
Maquiladoras, or to a off-site treatment facility.
This study is not a complete assessment of the potential contribution of the industrial
activities in Mexicali to contamination of the waste canals. Many facilities that indicated that their
discharges were below the threshold limit may collectively contribute a large amount of
discharges. In addition, further information on the number and type of facilities operating in
Mexicali that were not subject to this information collection was not available for this review.
There are many known facilities either owned by Mexican companies or parent companies outside
the United States, that are also likely contributors of discharges to the waste canals.
A review and assessment of all data that are available on the industrial sources of
wastewater entering the canals, concentration data on waste streams, water samples taken from
the canals and monitoring data from samples collected in the New River itself should be
completed. The results of that review should be analyzed relative to the discharge information
available through the subpoena program. Following that review an assessment can be made as to
the overall importance of these canals as an air emissions source. If the source is still thought to
be significant, the data gaps and future needs to fill those data gaps can be identified. It is likely
that additional sampling efforts would be required to clearly characterize the major industrial
releases. Specific data on the chemical components of waste streams will significantly improve
the emissions predictive capabilities of a system such as WATERS significantly. More
importantly, however, specific data on the location, quantity, chemical composition, and release
schedules of industrial wastewater that are added to these canals will be essential to identify
appropriate control options, and to track the effectiveness of those control options.
Based on insights gained through the site visit and information previously collected on the
types and concentrations of various organic constituents in these waste canals, we have concluded
that there is insufficient information available to execute WATERS at this time with any degree of
confidence. The preferred alternative to locate information to fill the data gaps is to work directly
with the Mexican authorities in Mexicali to obtain and summarize all existing information and to
set up a reporting mechanism on operations and releases of industrial wastes to these canals.
Sufficient information could be obtained if all of the major industrial sources of wastes to these
canals voluntarily submitted the required information. If this preferred approach can not be
implemented an alternate approach is to inspect these canals by walking them to identify any
permanent industrial out falls. In all cases, when it is possible the inspector should note the
source of the wastewater and make an estimate of the volume flow to the canals. These
significant out falls will then be mapped. It is suspected that any such contributions to these
canals may be either continuous or intermittent and therefore a single view of these canals may
not provide sufficient information on the volume of flow to these canals. It is also possible that
the specific industrial sources of these out falls will not be obvious during this inspection. It will
14
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be possible, however, to identify the most likely origination points of wastewater when the map is
reviewed in combination with known existing industrial facilities.
If it is possible to get the voluntary cooperation of the facilities, they should be contacted
to determine what contribution they make to the total flow in these canals and the specific
chemical constituents of the wastewater. These data can then be compared to the existing
sampling and analysis results to estimate the reach and potential contributions of these specific
sources to the overall flow and overall potential VOC emissions. If it is not possible to get
voluntary cooperation from the facilities it might be necessary to collect and analyze samples
directly from these out falls to ensure complete coverage and to improve the precision of analyses.
That information can then be input to WATERS or any other similar emissions estimation
program to make an emissions estimate.
The methodology for developing periodic updates to that activity data is not known at this
time. Therefore, the availability of activity data required to track the trend in emissions over time
and to quantify the effects of any control measures put in place remains a data gap at this time. It
is suggested that any program considered to maintain a periodic update of the quantity and
content of the waste streams to these canals over time be developed and implemented by Mexican
authorities. The data base resulting from this effort would fill all of the needs of the program
including the assessment of any proposed control measures and tracking the effects of
implemented control measures over time.
It is difficult to evaluate the cost component for the collection and maintenance of the
activity data over time, because the options for collecting these periodic activity updates are not
known at this time. All other components of this method, however, would be relatively
inexpensive. Depending on the form and format of the data file structures used to collect and
maintain the periodic activity data it would be possible to create an automated update of the
WATERS results at periodic intervals at very low cost. This would require a small investment in
computer programming early in the program.
One experimental measurement approach using Open-Path Fourier Transform Infrared
(FTIR) Spectroscopy, was also considered. Open-Path FTIR technology employs an infrared
(IR) energy emitter separated by several hundred meters to perhaps a kilometer from a telescope
and receiving optics. Individual chemical compounds in the line-of-sight path between the IR
source and the telescope selectively absorb IR radiation in specific wavelength bands. The
average concentration of each target compound in the line-of-sight path can be estimated through
electronic processing of the IR signal. In some applications, this technology is very powerful
because it can measure many diverse compounds simultaneously in time periods of minutes.
FTIR technology is probably not applicable to this problem, since it is unlikely that the
concentrations of specific compounds will be high enough to provide accurate and repeatable
measurements. The technique would also be relatively expensive to implement and the costs
involved would complicate continuing periodic updates to track the effectiveness of any
implemented control programs.
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Emissions Control Options
Street Vendor Cooking Devices
This source category includes a variety of specific activities. The cooking grills included
in this category range from small units operated by individuals to larger facilities that use multiple
grills and a small staff of perhaps 6 to 8 people. The smaller units are mainly mobile and are
towed, pushed or cycled to a specific location. These units can be set up a different locations on
any specific day. The larger units are permanent facilities and some are equipped with vents the
direct smoke and other emissions from the cooking process to roof vents. There are also the two
principle types of fuels, and it is likely that some units use wood, or perhaps even other fuel types.
Because of these differences in operations, it is not possible to specify a single universal control
method.
Intuitively, it can be assumed that overall emissions from units that use compressed gas
fuels, would be cleaner than those using charcoal, wood or some other biomass fuel. This
assumption is dependent on the relative contribution of the fuel compared to the meat grilling to
the overall emissions rate. Drippings from the meat grilling process on hot elements in both types
of units results in emissions of fine organic aerosol and other heavy organic pollutants. In
addition, the combustion of charcoal and biomass fuels will also generate fine paniculate
dependent on the ash content of the specific fuels being used. The assumption that compressed
gas units are inherently cleaner should be tested.
One reasonable approach to control emissions from these devices is to install some sort of
air collection device over or along side the grill surface and use an induced air flow to direct the
gases and particles into a capture device. Fairly simple and cheap grease traps can be installed to
collect grease and other fatty substances from this air flow. The technology for capturing the very
small particles is readily available but simple course filters would not be effective because the size
distribution of these particles is dominated by the size fraction under l|j, in diameter. The typical
filter systems used in some U.S. fast food operations employs a cylindrical tube with several layers
of filter material. These units have been used for some time and details on the design and
construction of such filters to handle specific air flows is well established.
New or modified stationary establishments could be required to install adequate air
collection systems and removal devices prior to starting up operations. All new establishments
could also be subject to construction requirements to ensure that the grilling area is protected
from exposure to the wind. A program to identify economically feasible retrofits to existing
permanent establishments could be considered as well. It might be possible to consider some kind
of economic incentive for those establishments that meet minimum improvements on some set
schedule.
16
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This type of control device is subject to two limitations for application to the street vendor
cooking devices in Mexicali. The first is that the venting system used to capture the gases and
particulates over the grill must be located close to the grill and it will require a power source to
operate an air mover. The vents could be constructed as overhead hoods, side ducts next to the
grill, or lateral vents that surround the grill surface and collect air to a main duct system
underneath the grill. While some form of these three options could be implemented in nearly all of
the permanent structures, it would be a significant problem to install such a system on the mobile
units. They would require their own power source to operate effectively and it is not feasible to
consider this as an option for the mobile units. The second problem is that exposure to wind will
significant reduce the collection efficiency of these types of units, which further complicates the
application of this approach to the mobile units.
It is recommended to explore the specific operating conditions of these small mobile units
and evaluate other possible options for reducing emissions. Changes in burner design that would
use less fuel, changes in fuel type, or installation of some form of passive air trap are all
possibilities that could prove useful in this application. The effectiveness of these options would
depend on the relative emissions rate of the charcoal ash to the total emissions. If there is a
recognizable contribution to emissions directly from the charcoal fuel then a program requiring
one or a combination of these options could be effective. More detail about the magnitude of
emissions, the characteristics of the emissions, and the relative magnitude of emissions from the
fuel burning compared to the burning of the meat drippings is needed to make recommendations
concerning control alternatives.
If no other viable alternatives are found to be effective and cost efficient and the overall
magnitude of the small units is found to pose environmental or health risks, another option to
control these emissions is to reduce the number of mobile units, and increase the number of
stationary units. It is recognized that this option would require a significant change in the culture
and would affect a large number of independent operators.
In any event, controlling a large percentage of the emissions from this source category will
require a substantial capital investment. One option to encourage operators to make this
investment is to implement a registration program and some form of permit or fee. The fee
structure could be set up to incorporate a lower net fee, or low/no interest loans funded through
fee receipts to help offset the costs of construction and operation of the collection and removal
devices. All operating establishments including the small independent mobile vendors would be
subject to this fee. The fees for noncomplying establishments could be set at a high enough value
to encourage adoption of the recommended control options and/or to encourage independent
operators to form cooperatives and group together into a permanent establishment. If this idea
proves to be an acceptable approach some examples that could be used as a model for a
permitting program could be provided.
Specific cost data for the materials and construction costs to implement such a program
are not available at this time, but this approach would not be a low cost option. There is also the
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impact on the lifestyle and character of the city that should be considered. There simply are no
other viable options for control approaches that have been identified at this time.
Open Sewage Impoundments, Canals and Conveyance Systems
There are two issues relative to controlling the potential of emissions or environmental
effects from these canals. The first issue, concerned directly with the purpose and scope of this
project, is to control the volume and/or the content of wastewater discharges responsible for air
emissions to the canals from industrial sources. The second issue concerns the effects of
industrial and other discharges to these canals that do not cause air quality problems, and the
effects of these discharges on the New River and the Salton Sea. The more comprehensive
ecosystem effects in the New River and the Salton Sea are not the subject of this report, but any
efforts that would reduce the amount or toxicity of discharges to these waste canals will have
simultaneous benefits related to these ecosystems.
The methodology selected to assess emissions should be capable of quantifying a large
percentage of the total organic industrial wastes that are currently discharged to the waste canals.
The database developed would be used first to determine if this source category is a significant
source of air emissions. If this source category is found to be of concern to air quality problems
the data base would be used to identify those specific facilities that are causing the most serious
problems. Once the relative magnitude of emissions from each facility is quantified, overall
benefits resulting from specific engineering solutions can be assessed within the basic cost benefit
scenario. There are two primary methods available to reduce these releases. The first and most
attractive method from an economical standpoint is to create an assistance program to support
comprehensive environmental audits of the major facilities to identify, evaluate and implement
source reduction measures. The other is to require pretreatment to reduce the amount of organic
materials in the discharge streams.
Source reduction measures would seek to change operating practices to reduce the
volume of total releases, and/or change the types of organic compounds released to species that
are less volatile and less damaging to water resources down stream. These activities are
commonly referred to as pollution prevention activities. There are many methods to achieve
significant benefits through pollution prevention, and the specific examples that are most suitable
are dependent on the specific operations in question. Examples of pollution prevention methods
are changes in the operations that produce less waste materials, reductions in the amount of raw
materials used in the process or process changes that use less harmful raw materials, identification
of opportunities to reuse or recycle waste materials, and identification of alternate or additional
products that would use some of the waste materials and have some economic value.
There is a significant amount of information on these waste reduction or pollution
prevention opportunities that have been categorized for specific industry types. One
comprehensive information resource is the Pollution Prevention Information Exchange System
(PIES) a publicly accessible EPA bulletin board. The selection of the most efficient approaches,
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however, is often facility specific. The principal advantage of waste reduction and pollution
prevention approaches is that they often can result in a net economic benefit by reducing raw
material costs, increasing operational efficiency, or lowering power or fuel costs. An assessment
of the costs and potential cost savings is a critical component of the environmental assessments
that are completed to identify the most suitable opportunities.
The clear advantage of such methods are that the often require a lower capital investment
than that required to purchase land, and/or structures associated with waste treatment facilities,
and they often have the result of reducing the cost of raw materials, operational costs, or have the
capacity to generate additional revenue. Studies of pollution prevention systems reveal that they
frequently have the effect of increasing revenue relative to the base operating conditions.
Implementing pollution prevention activities will require a commitment by regulatory authorities,
cooperation from the facilities, and a willingness on the part of the facilities to implement the
measures and maintain the pollution prevention practices.
Specific waste treatment techniques collectively known as pretreatment are commonly
used to treat industrial wastewater. In typical systems in the United States these pretreated
wastes are often directed to publicly owned treatment works (POTWs). Although this approach
has additional benefits related to water quality of the New River and Salton Sea, a complete
redirection of wastewater to pretreatment and ultimately to POTWs would be very expensive in
terms of initial capital investment, and in operating costs. Pretreatment approaches are commonly
used to improve water quality in streams and rivers that accept industrial waste, and are not
normally implemented out of air quality related concerns. One common treatment technology
used in pretreatment that would not be suitable for this application is aeration. In aeration
technologies agitation or sprays are used to strip off volatile species and allow them to evaporate
into the air. Other pretreatment options using biological or chemical treatment, however, might
be effective to reduce air emissions.
Pretreatment methods are also dependent on the specific activities and the character of the
waste streams. Any pretreatment facilities that are designed to strip organics through evaporation
prior to release to the canals are inappropriate for this application, since the specific goal in this
study is to identify options for reducing the air emissions. Such systems would simply move the
air emissions from the canals to the pretreatment facility on the facility property. Other methods
include biological and chemical treatment, aggregation and phase change to solid forms that can
be precipitated, and methods that could isolate and remove organics from the water. Recovered
organics can then be used as a fuel to supplement power or heat needs within the facility, or they
can be flared or incinerated.
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Phase 4. Development of Evaluation Criteria and Ranking of Options
Evaluation Criteria
The following list of criteria are proposed for use in evaluating the usefulness of any
specific emissions methodology for application to these sources.
1. Source Specificity Any method developed for this application should be specific to the
sources and the source characteristics of these categories. Therefore, studies completed by EPA
on large external combustion sources are not useful for application to the street vendor cooking
devices. Previous EPA work completed on emissions from fireplaces may offer significant useful
information on particle emissions processes, but none of those studies used charcoal as the fuel.
These studies used wood that had certain specific moisture characteristics. The results of the
SCAQMD studies are very similar, however, the sources in Mexicali appear to use primarily
wood charcoal, whereas the SCAQMD studies used charcoal briquets as the primary fuel.
2. Pollutant Specificity An appropriate method should also be specific for the primary
pollutants of interest in the work. For the waste canals, VOCs are the primary concern, although
many of the sampling and analysis results collected so far on the New River and elsewhere do not
provide comprehensive information on volatile species. The techniques developed by SCAQMD
for measuring emissions from charcoal ignition may be specific for application to this category,
however, the results of those studies do not provide any information on particulate emissions or
the individual VOC or more complex organics that are emitted from such devices. The
SCAQMD study sampled only for total nonmethane hydrocarbon or total VOC. Information
from the EPA fireplace studies and SCAQMD VOC studies does provide a sound background for
use in developing a test methodology that could provide the integrated results needed for this
study.
3. Availability of Activity Data An ideal method for this application should be based on
activity data that is readily available and easily updated. These two conditions allow the method
to be implemented with a minimum expenditure and allow the emissions database to be updated
on a regular basis to quantify the effects of any emissions reduction strategies that have been put
into place. It is often possible to develop more detailed emissions estimates with low degrees of
uncertainty using detailed source descriptive databases, however, if these data are difficult to
obtain or require an additional investment each time the data is to be updated, they may not be
very useful in this particular program.
4. Testing, Analysis and Implementation in Mexicali It is the intent of the project to
promote activities that can be completed in Mexicali by technical staff from Mexico. Standard
procedures used by both EPA and SCAQMD in their previous testing for emissions from charcoal
grills and fireplaces include some specially designed test chambers. Those protocols should be
reviewed and discussed with officials from Mexicali to determine if facilities sufficient for
completing these tests in Mexicali can be provided. This would allow the testing and analysis
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work to be done largely by staff from Mexico. Similarly, analysis and input data for any
methodologies for application to the waste canals should also be available in Mexicali.
Development of methods that can be completed in Mexico will facilitate routine monitoring of
trends and evaluation of the effectiveness of control options.
It is likely that initially assistance will be provided through the U.S. EPA or another U.S.
funding agency. While it is desirable to implement a project that can ultimately be operated
entirely within Mexico an by Mexican authorities, it is recognized that, depending on the needs for
specific testing and laboratory equipment some support from the U.S. or elsewhere may be
needed. This criteria is, therefore, considered highly desireable but not critical to the selection of
a methodology.
5. Usefulness of the Data Ultimately, the data generated through the approaches
recommended here will be used to quantify emissions from these sources relative to more
traditional sources in the region, track the trends in emissions from these sources over time,
evaluate cost effective control options and to quantify the results of any control options that are
implemented. While this criterion is closely linked to the other criteria, it is an important
consideration. Emissions estimation methods that are based on data that is directly linked to the
most effective control options and can be readily updated, facilitate the task of monitoring
improvements and quantifying benefits resulting from any programs implemented. This criteria is
of primary interest to the Mexican participants.
6. Cost to Implement and Track Over Time One of the primary reasons for developing
an emissions estimation method for these two source categories is to track and quantify the
effectiveness of any control options that are implemented over time. Therefore, the cost
calculation needs to include costs that would be incurred to complete periodic updates of the
emissions estimates to establish the net change in emissions as a function both of changes in the
amount of activity and effectiveness of control programs.
Ranking of Emissions Estimation Methods
Based on the information obtained through this preliminary assessment of the two target
emissions sources and the list of evaluation criteria presented above the options for emissions
estimation methodologies have been ranked relative to one another. Table 3 lists the emissions
estimation methodologies discussed in this report and indicates which of those methodologies
satisfy the list of evaluation criteria and gives each method a ranking for consideration in future
programs. Finally, a recommendation is presented for future activities to support the development
of an emissions estimation methodology.
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TABLE 3. PROPOSED METHODS LISTED WITH EVALUATION CRITERIA
Emission Estimation Method
Evaluation Criteria
Source
Specificity
Pollutant
Specificity
Availability
of Data
Implementation
in Mexico
Usefulness
of Data
Initial and
Continued Cost
Street Vendor Cooking Devices
Existing EPA Combustion Source
Emission Factors
New Specific Emission Factors
Based on Direct Source Testing with
Routine Activity Reporting
Requirements
South Coast Air Quality
Management District Rule 1 174
Inferential by Ambient Monitoring
No
Yes
No
Yes
No
Yes
No
Yes
No
No(2)
No
No(3)
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes(4)
Yes
~
Yes
~
Open Sewage Impoundments, Canals and Conveyance Systems
Existing EPA Methods for
Wastewater Treatment
Use of Computer Program
(WATER8)
Open Path Remote Monitoring
No
Yes
Yes
No
Yes
Unknown
No
No
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
No
Rank(l)
4
lor 2
3
lor 2
2
1
3
(1) Ranking is: 1 for best option, through 3 or 4 for least desirable option
(2) Data for specific emission factor is not available; Activity data availability dependent on method mandating data reporting by sources
(3) Activity data availability dependent on method mandating data reporting by sources
(4) Data will be useful for control analysis, but the data collection for inferential method is much less expensive
~ Insufficient information to estimate cost
-------
A rough cost estimate is made for the recommended approaches. Additional issues related
to potential control options and emissions needs to support those options are also summarized.
Recommendations
Based on the review of available information presented here there are two candidate
methods that would be effective to quantify current emissions from street vendor cooking devices
and to monitor improvements as a result of control methods. One of these methods would
involve a detailed source monitoring study to develop a representative emission factor or series of
emission factors for the different units and fuels included in this source category. The second is
the technique based on inferential assessment through ambient monitoring results.
Each of these approaches are listed as number 1 or 2 ranking in Table 3. Further effort is
required to develop more specific information and cost details for these two methods. Initially,
the highest recommended approach for estimating and tracking these emissions is the inferential
approach. This conclusion is based on the assumption that the costs to conduct routine ambient
monitoring needed to track emissions over time would be lower than the costs of continued
source monitoring and emission factor development that would be required in the other approach.
In both of these approaches a substantial investment would be required to perform the initial
source monitoring needed to characterize the source contributions, either for emission factor
development or to prepare a unique source profile.
In the inferential approach, a more detailed series of source tests is required to
differentiate ambient monitoring analyses from other similar source categories in the region. This
appears to be possible by specifically targeting higher carbon number complex organics including
fatty organic and organic acid constituents. Subsequent routing ambient samples in regions
frequented by street vendor devices would also target these same marker organic species to track
not only the contribution of these sources to current ambient loadings but to quantify the
reductions in the contribution of street vendor cooking devices to these ambient loadings in future
sampling efforts. Use of this approach will allow the continuous tracking of progress resulting
from control programs to be monitored without a significant interference with the operators of the
facilities. The use of this inferential approach is complicated and will require the experience and
insights of researchers familiar with similar projects.
The other viable choice for an estimation method is to complete a more detailed source
sampling project to quantify total mass emissions from selected representative units in operation
in Mexicali. These sampling efforts could focus on total organic contributions to particulate
matter and could also quantify the emissions rates of gaseous species. The application of this
technique over time, however, would require a routine comprehensive assessment of the number
of these units that are operating in the city, and an assessment of the relative amounts of the
various fuels employed. This method would require a registration system or some form of
reporting or permit system to track the total amount of activity included in the source category
over time. Another limitation of this technique is that it would require repeated detailed source
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testing of representative establishments as each type of control device is implemented to derive
new emissions factors for the controlled establishments. It is likely that the continued and
repeated source testing would represent a higher cost than the less invasive ambient monitoring
program.
In either case, it is important to carefully plan the initial source measurements program to
ensure that the relative contribution of this source category to NOX, common VOCs and other
gaseous emissions is characterized to determine if those emissions are of interest. It is estimated
that the cost to establish the source profiles and initial ambient sampling and analysis would be
between $50k and $150k U.S. Subsequent ambient analysis to track emissions over time would
cost between $25k and $40k per sampling and analysis period and could be higher depending on
the specific analytical techniques that would be required to characterize the source. The
frequency of these sampling periods would depend on the schedules for implementing control
approaches. These costs are preliminary estimates and further detailed planning would be
required to establish a reliable cost estimate. These costs are also based on the assumption that
the majority of the work would be completed by experienced researchers and laboratory facilities
in the United States. Costs might be reduced if the bulk of the analytical work and source
monitoring could be done locally in Mexicali.
The recommended approach for estimating emissions from the waste canals is to conduct
comprehensive environmental audits of the major facilities or obtain voluntary reports of
discharges to the waste canals from the major facilities for use in an air emissions computer model
for wastewater processes. If data cannot be obtained through facility cooperation it might be
necessary to sample discharge effluents and water in the canals and submit those samples for
specific chemical analysis targeting the most likely chemical constituents. One recommended
model is WATERS. That model includes emissions estimation capabilities for untreated waste
handling systems similar to the waste canals in Mexicali. Existing EPA emission factors for
wastewater treatment systems are more suited for use in POTWs and other engineering based
treatment systems. Technical methods based on remote sensing were considered but were
rejected due to uncertainties about the detection capabilities and the relatively large costs.
Cost estimates for completing this type of program are difficult to make without additional
information about the specific industrial categories represented and the types of wastes being
handled. A typical industrial audit would cost between $5k and $10k per facility. Execution of
the model using data obtained in these audits and analyses to review the overall emissions for all
major facilities would cost between $15k and $30k. These cost estimates are preliminary and
further planning efforts would be necessary to develop a reliable cost estimate. The costs could
rise significantly if input data necessary for execution of the emissions prediction model were not
readily available from the facility audits. The cost estimates for this category do not include any
additional waste stream sampling and analysis activities or travel costs.
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