May 2003 • NREL/SR-540-33796 

G. Mansell, R.E. Morris, and G. Wilson 

ENVIRON International Corporation 

Novato, California 

Impact of Biodiesel Fuels on Air 

Quality and Human Health: 

Task 3 Report 

The Impact of Biodiesel Fuels on 

Ambient Carbon Monoxide Levels in the 

Las Vegas Nonattainment Area 

National Renewable Energy Laboratory 

1617 Cole Boulevard 

Golden, Colorado 80401-3393 

NREL is a U.S. Department of Energy Laboratory 

Operated by Midwest Research Institute • Battelle • Bechtel 

Contract No. DE-AC36-99-GO10337 
May 2003 • NREL/SR-540-33796 

Impact of Biodiesel Fuels on Air 

Quality and Human Health: 

Task 3 Report 

The Impact of Biodiesel Fuels on 

Ambient Carbon Monoxide Levels in the 

Las Vegas Nonattainment Area

G. Mansell, R.E. Morris, and G. Wilson 

ENVIRON International Corporation 

Novato, California 

NREL Technical Monitor: K.S. Tyson and R. McCormick 

Prepared under Subcontract No. AXE-9-29079-01 

National Renewable Energy Laboratory 

1617 Cole Boulevard 

Golden, Colorado 80401-3393 

NREL is a U.S. Department of Energy Laboratory 

Operated by Midwest Research Institute • Battelle • Bechtel 

Contract No. DE-AC36-99-GO10337 
NOTICE

This report was prepared as an account of work sponsored by an agency of the United States 

government. Neither the United States government nor any agency thereof, nor any of their employees, 

makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, 

completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents 

that its use would not infringe privately owned rights. Reference herein to any specific commercial 

product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily 

constitute or imply its endorsement, recommendation, or favoring by the United States government or any 

agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect 

those of the United States government or any agency thereof. 

Available electronically at http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy 

and its contractors, in paper, from: 

U.S. Department of Energy 

Office of Scientific and Technical Information 

P.O. Box 62 

Oak Ridge, TN 37831-0062 

phone: 865.576.8401 

fax: 865.576.5728 

email: reports@adonis.osti.gov 

Available for sale to the public, in paper, from: 

U.S. Department of Commerce 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

phone: 800.553.6847 

fax: 703.605.6900 

email: orders@ntis.fedworld.gov 

online ordering: http://www.ntis.gov/ordering.htm

Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
 

ES-1 

EXECUTIVE SUMMARY 

INTRODUCTION 

Carbon monoxide (CO) air pollution is generated by a variety of combustion processes ranging 

from industrial sources, to household heating, to motor vehicles. Due to the shear number of 

automobiles, the vast majority (typically 90%) of area-wide CO emissions in congested urban 

areas comes from on-road motor vehicles. Numerous urban centers in the western U.S. have 

experienced elevated CO air pollution episodes due to climatic influences, particularly during 

cold, dry, stagnant winter evenings and mornings. During these periods, CO emissions are 

trapped near the ground where they build up in direct response to hourly variations in traffic 

volume during the commute hours. Two National Ambient Air Quality Standards (NAAQS) 

have been established for CO: a one-hour standard of 35 parts-per-million (ppm), and an eighthour standard of 9 ppm. The 1990 Clean Air Act Amendments (CAAA) specify that regions 

violating the CO NAAQS more than three times in a three-year period are to be classified as 

nonattainment areas. The CAAA required CO nonattainment areas to develop State 

Implementation Plans (SIP) which list various control strategies that, by appropriate 

demonstration, are estimated to lead to attainment of the CO NAAQS by the date required in the 

CAA. 

Purpose 

This document is the Task 3 report for the NREL “Impacts of Biodiesel Fuels on Air Quality and 

Human Health” study. The objectives of Task 3 are to estimate the impacts of biodiesel fuels on 

elevated winter carbon monoxide concentrations for an urban area that is not currently in 

attainment of the CO standard. 

OVERVIEW OF APPROACH 

CO modeling databases for the Las Vegas Valley (LVV) developed by Clark County, Nevada 

(Emery et al., 1999) were selected for use in assessing the impacts of biodiesel fuel use on 

ambient CO concentrations since: 

• Clark County was designated an 8-hour CO nonattainment area; 

• The databases were used in recent (1999) SIP CO modeling; 

• The database year (1996) was more recent than that used for CO SIP modeling in 

other area; and 

• The databases and models used were publicly available. 

Two LVV CO modeling databases were used in the SIP modeling, December 8-9, 1996 and 

December 19-20, 1996. Because biodiesel fuel use would occur in a future-year, the biodiesel 

CO assessment was performed for the year 2001, the only future -year for which emissions 

projection data were readily available. 

The effects of the biodiesel on CO emissions were assessed in the NREL Biodiesel Study Task 1 

report (Lindhjem and Pollack, 2000). Based on an analysis of engine dynamometer test data for 

a standard diesel, a 100% biodiesel, and a 20%/80% biodiesel/standard diesel blend (B20), 
 

ES-2 

Lindhjem and Pollack (2000) estimated that the mean effect on fleet average Heavy Duty Diesel 

Vehicle (HDDV) emissions of a B20 fuel would be to reduce CO emissions by 13.1 percent. 

Three different emission scenarios were analyzed in 2001 using the two 1996 LVV CO episodes: 

• 2001 Base Case diesel (CARB standard diesel); 

• 100% penetration of a B20 fuel in the HDDV fleet; and 

• 50% penetration of a B20 fuel in the HDDV fleet. 

Table ES-1 summarizes the CO emissions in the LVV for the 1996 and 2001 base case 

simulations. Although on-road mobile sources contribute the most to CO emissions in the LVV 

area (> 90%), the HDDV fraction only contributes less than one percent (0.7%) to the total onroad mobile CO emissions. The percent reduction in CO emissions due to the 100% B20 and 

50% B20 biodiesel emissions scenarios from the 2001 standard diesel base case for the HDDV, 

on-road mobile, and total emissions are shown in Table ES-2. Although the biodiesel fuel results 

in substantial reductions in CO emissions from the HDDV fleet (7-13%), because the HDDV 

contributes such a small fraction of the total CO emissions, the CO reductions from on-road 

mobile sources (0.08-0.19%) and total emissions in the LVV area (0.09-0.18%) are quite small. 

Table ES-1. Base year 1996 and base year 2001 CO emissions by emission component for the 

Las Vegas Valley. 

Emissions (tons/day) 

Emissions Component December 9 December 20 

1996 2001 1996 2001 

Area 12.7 14.3 12.7 14.3 

Surface Points 22.6 22.6 22.6 22.6 

Elevated Points 2.1 2.1 2.1 2.1 

On-Road Mobile 415.2 366.6 511.8 451 

Total 452.6 405.6 549.2 490 

Table ES-2. Reductions from base year 2001 CO emissions by emission component for the Las 

Vegas Valley. 

Emissions Reductions (%) 

Emissions Component December 9 December 20 

50% B20 100% B20 50% B20 100% B20 

HDDV 6.55 13.1 6.55 13.1 

On-Road Mobile 0.095 0.190 0.084 0.168 

Total 0.089 0.178 0.082 0.164 
 

ES-3 

BIODIESEL CO IMPACT ASSESSMENT 

Table ES-3 displays the peak estimated 1-hour and 8-hour CO concentrations in the LVV area 

for the standard diesel base case and the two biodiesel emission scenarios. The use of biodiesel 

fuel is estimated to reduce the peak CO concentrations as well as CO concentrations throughout 

the LVV area. However, these reductions are extremely small ranging from 0.01 to 0-.03 ppm (< 

0.2%). Thus, the use of biodiesel fuel is estimated to have no significant impact on ambient CO 

concentrations. 

Table ES-3. Peak estimated 1-hour and 8-hour CO concentrations in the Las Vegas Valley for 

the 2001 Base Case, 100% B20, and 50% B20 emission scenarios and the differences in CO 

concentrations between the biodiesel fuel scenarios and standard diesel base case. 

Episode Std.Diesel 50% B20 100% B20 

(ppm) (ppm) Difference (ppm) Difference 

1-Hour CO Dec 8-9 17.90 17.89 -0.01 17.87 -0.02 

8-Hour CO Dec 8-9 9.39 9.38 -0.01 9.37 -0.02 

1-Hour CO Dec 19-20 18.38 18.36 -0.02 18.35 -0.03 

8-Hour CO Dec 19-20 13.73 13.72 -0.01 13.71 -0.02 
 i

TABLE OF CONTENTS 

Page 

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

Introduction..........................................................................................................................ES-1 

Overview of Approach.........................................................................................................ES-1 

 Biodiesel CO Impact Assessment .......................................................................................ES-3

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

 Background............................................................................................................................ 1-1 

 Purpose .............................................................................................................................. 1-1 

2. DATABASE AND MODEL SELECTION........................................................................ 2-1 

Available Models................................................................................................................... 2-1 

Modeling Databases............................................................................................................... 2-1 

 Overview of Las Vegas CO Air Quality................................................................................ 2-2 

 Assessment Year Selection.................................................................................................... 2-3 

3. BIODIESEL CO EMISSIONS ASSESSMENT................................................................ 3-1 

 Las Vegas CO Emissions Summaries.................................................................................... 3-2

4. BIODIESEL CO ASSESSMENT ....................................................................................... 4-1 

UAM Model Performance Issues........................................................................................... 4-1 

UAM Modeling Results......................................................................................................... 4-2 

REFERENCES.......................................................................................................................... R-1 

TABLES 

Table ES-1. Base year 1996 and base year 2001 CO emissions by 

 emission component for the Las Vegas Valley..................................................ES-2 

Table ES-2. Reductions from base year 2001 CO emissions by 

 emission component for the Las Vegas Valley..................................................ES-2 
 ii

Table ES-3. Peak estimated 1-hour and 8-hour CO concentrations 

 in the Las Vegas Valley for the 2001 Base Case, 

 100% B20, and 50% B20 emission scenarios 

 and the differences in CO concentrations between 

 the biodiesel fuel scenarios and standard diesel base case. ...............................ES-3 

Table 3-1. Base year 1996 and base year 2001 CO emissions 

 by emission component for the Las Vegas Valley............................................... 3-2 

Table 3-2. Reductions from base year 2001 CO emissions by 

 emission component for the Las Vegas Valley.................................................... 3-3 

Table 4-1. Peak CO concentrations for base year 2001 and 

 biodiesel scenarios for the Las Vegas Valley. ..................................................... 4-2 

Table 4-2. Summary of CO exposure metrics for the Las Vegas Valley 

 for the December 8-9 episode.............................................................................. 4-3 

Table 4-3. Summary of CO exposure metrics for the Las Vegas Valley 

 for the December 19-20 episode.......................................................................... 4-3 

FIGURES 

Figure 3-1. Location and relative emission strengths of point sources 

 in the LVV CO UAM emission inventory........................................................... 3-4 

Figure 3-2. Daily total CO emissions (TPD) for December 9, 2001, 

 in the LVV CO UAM modeling. ......................................................................... 3-5 

Figure 3-3. Daily on-road mobile source CO emissions (TPD) for 

 December 9, 2001, in the LVV CO UAM modeling domain.............................. 3-6 

Figure 3-4. Daily total CO emissions (TPD) for December 20, 2001, 

 in the LVV CO UAM modeling. ......................................................................... 3-7 

Figure 3-5. Daily on-road mobile source CO emissions (TPD) 

 for December 20, 2001, in the LVV CO UAM modeling domain. ..................... 3-8 

Figure 3-6. Reductions in daily total CO emissions (TPD) 

 for December 9, 2001, in the LVV CO UAM modeling 

 due to 50% penetration of B20 biodiesel fuel...................................................... 3-9 

Figure 3-7. Reductions in daily total CO emissions (TPD) 

 for December 9, 2001, in the LVV CO UAM modeling 

 due to 100% penetration of B20 biodiesel fuel.................................................. 3-10 

Figure 3-8. Reductions in daily total CO emissions (TPD) 

 for December 20, 2001, in the LVV CO UAM modeling 

 due to 50% penetration of B20 biodiesel fuel.................................................... 3-11 

Figure 3-9. Reductions in daily total CO emissions (TPD) 

 for December 20, 2001, in the LVV CO UAM modeling 

 due to 100% penetration of B20 biodiesel fuel.................................................. 3-12 

Figure 4-1. Spatial distribution of 1-hour maximum CO concentrations 

 predicted for the December 8-9, 2001 base case. All UAM 

 concentrations scaled by 1.14. ............................................................................. 4-4 
 iii

Figure 4-2. Spatial distribution of 8-hour maximum CO concentrations 

 predicted for the December 8-9, 2001 base case. All UAM 

 concentrations scaled by 1.14. ............................................................................. 4-5 

Figure 4-3. Impacts of 50% penetration of B20 biodiesel fuel on 

 1-hour maximum CO concentrations predicted for December 8-9, 2001. .......... 4-6 

Figure 4-4. Impacts of 100% penetration of B20 biodiesel fuel on 

 1-hour maximum CO concentrations predicted for December 8-9, 2001. .......... 4-7 

Figure 4-5. Impacts of 50% penetration of B20 biodiesel fuel on 

 8-hour maximum CO concentrations predicted for December 8-9, 2001. .......... 4-8 

Figure 4-6. Impacts of 100% penetration of B20 biodiesel fuel on 

 8-hour maximum CO concentrations predicted for December 8-9, 2001. .......... 4-9 

Figure 4-7. Spatial distribution of 1-hour maximum CO concentrations 

 predicted for the December 19-20, 2001 Base Case. All UAM 

 concentrations scaled by 1.14. ........................................................................... 4-10 

Figure 4-8. Spatial distribution of 8-hour maximum CO concentrations 

 predicted for the December 19-20, 2001 Base Case. All UAM 

 concentrations scaled by 1.14. ........................................................................... 4-11 

Figure 4-9. Impacts of 50% penetration of B20 biodiesel fuel on 1-hour 

 maximum CO concentrations predicted for December 19-20, 2001. ................ 4-12 

Figure 4-10. Impacts of 100% penetration of B20 biodiesel fuel on 1-hour 

 maximum CO concentrations predicted for December 19-20, 2001. ................ 4-13 

Figure 4-11. Impacts of 50% penetration of B20 biodiesel fuel on 8-hour 

 maximum CO concentrations predicted for December 19-20, 2001. ................ 4-14 

Figure 4-12. Impacts of 100% penetration of B20 biodiesel fuel on 8-hour 

 maximum CO concentrations predicted for December 19-20, 2001. ................ 4-15 
1-1

1. INTRODUCTION 

BACKGROUND

Carbon monoxide (CO) air pollution is generated by a variety of combustion processes ranging 

from industrial sources, to household heating, to motor vehicles. Due to the shear number of 

automobiles, the vast majority (typically 90%) of area-wide CO emissions in congested urban 

areas comes from on-road motor vehicles. Numerous urban centers in the western U.S. have 

experienced elevated CO air pollution episodes due to climatic influences, particularly during 

cold, dry, stagnant winter evenings and mornings. During these periods, CO emissions are 

trapped near the ground where they build up in direct response to hourly variations in traffic 

volume during the commute hours. Exacerbating the limited ventilation during such periods is 

the fact that automobile CO emission rates increase dramatically in cold temperatures due to less 

efficient engine and catalyst operation, particularly for “cold starts” that are prevalent during the 

morning hours. In some areas, local topography induces nocturnal drainage flows that can cause 

CO to pool in depressions, which in turn can lead to persistently high concentrations during 

many hours of the night. 

Two National Ambient Air Quality Standards (NAAQS) have been established for CO: a onehour standard of 35 parts-per-million (ppm), and an eight-hour standard of 9 ppm. One-hour 

exceedances are practically nonexistent in the U.S. today, and eight-hour exceedances have 

continued to decline in number and severity over the past ten years due to more efficient 

automobile engines, improved emission controls, reformulated and oxygenated gasolines, and 

other area-specific emission mitigation measures. The 1990 Clean Air Act Amendments 

(CAAA) specify that regions violating the CO NAAQS more than three times in a three-year 

period are to be classified as nonattainment areas. The CAAA required CO nonattainment areas 

to develop State Implementation Plans (SIP) which list various control strategies that, by 

appropriate demonstration, are estimated to lead to attainment of the 8-hour CO NAAQS by the 

date required in the CAA. The SIP due dates and CO attainment dates depend on the 

classification of the CO nonattainment area (e.g., November 1992 and the end of 1995 for a 

moderate area). 

PURPOSE 

This document is the Task 3 report for the NREL “Impacts of Biodiesel Fuels on Air Quality and 

Human Health” study. The objectives of Task 3 are to estimate the impacts of biodiesel fuels on 

elevated winter carbon monoxide concentrations for an urban area that is not currently in 

attainment of the CO standard. This report presents a discussion of the database and modeling 

episode selection, and the technical approach and analysis of air quality modeling results used to 

estimate biodiesel impacts. A discussion and analysis of biodiesel test data, and 

recommendations for incorporating biodiesel effects on pollutant mass emission for use in air 

quality modeling can be found in the NREL Task 1 report (Lindhjem and Pollack, 2000). 
 

2-1

2. DATABASE AND MODEL SELECTION

The selection of the model and database for use in evaluating the impacts of biodiesel fuels on 

carbon monoxide concentrations in an urban nonattainment area is based on the following 

criteria: 

• Access to database and models 

• Used recently to generate public policy (e.g. SIP) 

• Current baseline (1995-1999) is preferable to future-year baseline 

This section provides a brief discussion of available models and databases and presents the 

rationale for the selection of the database/models used in the present study. 

AVAILABLE MODELS

There are generally two types of CO modeling approaches commonly used: microscale 

intersection modeling and urban-scale grid modeling. Microscale intersection modeling is 

typically used to simulate CO hot spots and to design mitigating measures for reducing these CO 

concentrations to below the NAAQS using a microscale model such as CAL3QHC. By contrast, 

urban-scale grid modeling is used to simulate CO concentrations throughout an entire urban area. 

Because CO SIP attainment modeling must demonstrate compliance with the CO NAAQS 

throughout the urban area, the EPA requires urban areas to always use urban-scale modeling as 

part of SIP attainment demonstration. As the impacts of biodiesel fuel use on ambient CO 

concentrations will be present in an urban area wherever Heavy Duty Diesel Vehicle (HDDV) 

Vehicle Miles Traveled (VMT) occurs, microscale modeling of the effects of biodiesel would 

provide only a very localized impact analysis. Thus, to provide a more comprehensive analysis 

of the benefits of biodiesel fuel use for reducing CO concentrations, urban-scale grid modeling is 

the preferred approach. 

While several urban-scale grid models are available (UAM-IV, CALGRID, CAMx, etc.) which 

would likely be acceptable to the EPA for CO modeling, the UAM-IV (Morris and Myers, 

1990)has been the preferred model in EPA’s current Guidelines for Air Quality Modeling. As 

none of these other models has yet been used in CO SIP modeling, the impacts of biodiesel fuels 

on urban CO concentrations is evaluated using the UAM-IV for this study. 

MODELING DATABASES 

There are three recent SIP-quality CO modeling analyses that have been carried out that used or 

are using urban-scale CO grid modeling. For the Phoenix area, EPA Region IX and the 

Maricopa Association of Governments (MAG) applied UAM-IV for an episode from 1992 in the 

preparation of the CO SIP attainment plan (Emery and Ligocki, 1992). Clark County Nevada 

performed UAM-IV CO modeling of the Las Vegas area for a 1996 episode for the Las Vegas 

area which was included in their very latest SIP (Emery et al., 1999). Finally, during the summer 

of 1999, urban-scale CO modeling for the Spokane Washington area was performed for the 

Spokane County Air Pollution Control Authority (SCAPCA) and episodes from 1998 and 
 

2-2

1992-1996 to be included in a SIP to be submitted to the EPA. All three cities are current CO 

nonattainment areas. 

The Phoenix and Las Vegas CO SIP modeling databases are currently available, whereas the 

Spokane databases are still undergoing review. Further, the Spokane CO modeling used a 

proprietary model (UAM-V) thus eliminating it from consideration. The Phoenix database is for 

an older episode (1992 episode) and less current. The Las Vegas database is for a more recent 

episode (1996) and is very current (part of the Las Vegas 1999 CO SIP). Thus, based on 

discussions with NREL, it was determined that the Las Vegas 1996 CO modeling database is 

more appropriate for evaluating biodiesel fuel impacts on CO nonattainment and is therefore 

used in this study. 

OVERVIEW OF LAS VEGAS CO AIR QUALITY 

The Las Vegas Valley (LVV) is classified as a nonattainment area for the eight-hour CO 

NAAQS. Although CO concentrations in the Las Vegas Valley have never exceeded the onehour NAAQS of 35 ppm, they have historically exceeded the eight-hour NAAQS of 9 ppm 

during the late fall/winter season. There has been a declining trend over the past years in the 

number of LVV CO exceedances events as well as the intensity of CO concentrations. The 

number of exceedances per year has improved from a high of 41 in 1985 to only two in 1998. 

Between December 1988 and December 1991, numerous exceedances were recorded at a single 

monitoring site (East Charleston) where the highest 8-hour CO concentration was 14.4 ppm in 

December 1988. This same site also recorded ten exceedances during the 1991/92 winter season 

alone, three exceedances during the 1994/95 winter season and four exceedances during the 

1995/96 winter season. Currently, out of fourteen monitoring stations, only the Sunrise Acre site 

(a nearby replacement for the East Charleston station) registers infrequent exceedances of the 

standard. 

Almost all ambient CO emanates from near-ground sources, the majority of which results from 

motor vehicle emissions. During fall and winter months, development of strong surface-based 

stability at night leads to stagnation conditions that trap pollutants in the valley and concentrates 

them near the ground. The buildup of CO causes exceedances of the 8-hour NAAQS, 

historically in a limited area surrounding the East Charleston monitoring station. This site is 

located near several major transportation corridors, and lies within a topographic depression 

where valley air often converges during stagnation events. 

Various studies have shown that the ambient CO levels can be rather high within about a mile of 

this site, while routine CO monitoring at numerous other locations always measure lower CO 

concentrations. As in other western urban areas, CO concentrations at most monitoring stations 

reach two maxima each day: one between 7-9 AM coincident with the morning rush hour, and 

the other between 8 PM and 1 AM. The delayed evening CO peak suggests that a combination 

of meteorological, topographical, and emission factors influence the CO distribution, combining 

in such a way as to result in the highest CO concentrations in the vicinity of the East Charleston 

site. 
 

2-3

ASSESSMENT YEAR SELECTION 

As listed in the database selection criteria above, the selection of an appropriate assessment year 

should consider a current baseline (1995-1999) as preferable over a projected future-year 

baseline. As there are many uncertainties associated with projecting emissions to a future year, 

the use of such a projected inventory potentially adds an additional unnecessary level of 

uncertainty to the modeling analysis. The Las Vegas modeling database contains episode days in 

1996, within the range of the selection criteria, so no projection would be required. However, 

the impact of biodiesel fuel use would occur in future years not current years. Therefore, based 

on discussions with NREL, the biodiesel CO evaluation is performed for a 2001 assessment year. 
 

3-1

3. BIODIESEL CO EMISSIONS ASSESSMENT

Under Task 1 of the study, a review and analysis of engine dynamometer test data for a variety 

of engine types and model years was conducted for both a 20%/80% biodiesel/diesel fuel blend 

(B20) and a 100% biodiesel fuel (B100). Based on the results of the test data analysis, the effects 

of biodiesel fuels on carbon monoxide (CO) emissions is found to result in an overall average 

reduction of 13.1% for the B20 biodiesel fuels (Lindhjem and Pollack, 2000). As it is probably 

unrealistic to expect a significant penetration of B100 biodiesel fuels in the heavy-duty diesel 

vehicle (HDDV) fleet by the year 2001, the impacts of biodiesel fuels on ambient CO 

concentrations will be assessed for the B20 fuel only. Since a linear relationship exists between 

CO emission reductions and ambient CO concentrations, the effects due to B100 fuels may be 

easily estimated. A detailed discussion of the emission effects due to biodiesel fuels can be 

found in the NREL Task 1 report (Lindhjem and Pollack, 2000). 

The effects of biodiesel fuel use on ambient CO concentrations are assessed for the following 

scenarios and the 2001 assessment year: 

• Future-year baseline diesel fuel (CARB standard diesel) 

• 100% penetration of B20 fuel 

• 50% penetration of B20 fuel 

The effects of B20 fuels are only accounted for in the HDDV fleet. 

The gridded model-ready CO emission inventories were prepared for the three biodiesel 

scenarios using the same procedures as for the UAM-IV CO modeling performed as part of the 

Clark County, Nevada SIP for the Las Vegas area. Emissions from area and point sources were 

processed using the Emissions Preprocessing System, version 2.0 (EPS2) as distributed for use 

with UAM by the EPA. Area source emissions were projected to the future year 2001 taking 

into account estimated growth, as well as the mitigating effects of any local and national control 

regulations that are currently mandated to take effect by the year 2001. It was assumed that point 

sources were operating at full load in the base 1996 inventory, and therefore the future year point 

source emission estimates were held constant at the 1996 levels. No additional specific point 

source were added to the future year inventory. Figure 3-1 shows the location of all the point 

sources within the modeling domain. The size of the marker at the source location indicates the 

relative magnitude of the daily emission rate. Also shown for reference is the base year 

transportation network used in developing the mobile source component of the inventory. 

The on-road motor vehicle component of the emissions inventory was prepared using the Direct 

Travel Impact Model, version 2.0 (DTIM2), distributed by the California Department of 

Transportation (CALTRANS). DTIM2 is a system of programs used to calculate hourly gridded 

emissions by combining roadway link-specific traffic volumes (in terms of vehicle miles 

traveled, or VMT) from a transportation model with vehicle fleet emission factors taken from an 

emission factor model. For this study, VMT distributions were developed from the Clark County 

transportation demand model TRANPLAN. The on-road mobile emission factors used in the 

development of the future year inventories were derived from EPA’s MOBILE5b model with 

modifications incorporated to reflect the effects of “off-cycle” emissions as planned for the 

EPA’s latest emission factor model, MOBILE6. The TRANPLAN model was exercised to 

produce a dataset containing link locations in the planned traffic network as well as the estimated 
 

3-2

traffic volume on each for a typical day in the future year 2001. The resulting data were 

extracted and reformatted for use in the DTIM2 system. As the TRANPLAN estimates did not 

take into account any VMT from vehicles engaged in public transportation, a correction was 

made in the form of an across-the-board adjustment to the emission estimates generated from the 

DTIM2 system to account for the estimated increase in VMT. A detailed description of the 

emission inventory preparation may be found in the Las Vegas Valley Carbon Monoxide Phase 

II Modeling report (Emery et al., 1999). 

The effects of biodiesel fuels on CO emissions were accounted for in the HDDV fleet only. 

Adjustments were made to the DTIM2 inputs to reflect the 13.1% emission reduction 

corresponding to the 100% penetration level of B20 biodiesel fuel. Similar adjustments were 

made for the 50% penetration level (an assumed 6.55% reduction in HDDV CO emissions). The 

DTIM2 system was then exercised to provide estimates of gridded CO emissions from on-road 

mobile sources. Gridded time-resolved emission files for area, point and mobile sources were 

combined into a single file for input into the UAM-IV modeling system. 

LAS VEGAS CO EMISSION SUMMARIES 

Table 3-1 summarizes the CO emissions in the Las Vegas Valley (LVV) for the December 8-9 

and December 19-20, 1996 CO episodes. While on-road mobile source emissions contribute by 

far the most (>90%), the contribution from all diesel vehicles to the total CO on-road mobile 

source emissions in the LVV is approximately 1.35%, with HDDV making up about 51% of the 

total diesel vehicle fleet (i.e., approximately 0.7% of the LVV CO emissions are due to the 

HDDV fleet). 

Table 3-1. Base year 1996 and base year 2001 CO emissions by emission component for the 

Las Vegas Valley. 

Emissions (tons/day) 

Emissions Component December 9 December 20 

1996 2001 1996 2001 

Area 12.7 14.3 12.7 14.3 

Surface Points 22.6 22.6 22.6 22.6 

Elevated Points 2.1 2.1 2.1 2.1 

On-Road Mobile 415.2 366.6 511.8 451 

Total 452.6 405.6 549.2 490 

The CO emission reductions realized in the LVV for each biodiesel scenario are summarized in 

Table 3-2. Figure 3-2 displays the spatial distribution of the daily total CO emission in the 

modeling domain while Figure 3-3 displays the distribution of mobile source CO emissions for 

the 2001 future year base case. Corresponding displays for the December 20 episode day are 

presented in Figure 3-4 and Figure 3-5. The CO emissions from on-road mobile source are 

distributed throughout the traffic network while the highest emission levels are seen to be 

concentrated along the major highways and the central urban core of Las Vegas. 

Figure 3-6 and Figure 3-7 display the spatial distribution of the reductions in daily total CO 

emission for the 50% penetration and 100% penetration of B20 fuel on December 9, 2001, 

respectively. Spatial distribution of CO emission reductions for December 20 are displayed in 
 

3-3

Figure 3-8 and Figure 3-9 for the 50% and 100% penetration of B20 fuels, respectively. As 

expected, the reductions in CO emissions are distributed throughout the traffic network, with the 

largest reductions occurring within the central Las Vegas area and along the major highways; 

however, all of the reductions are very small. 

Table 3-2. Reductions from base year 2001 CO emissions by emission component for the Las 

Vegas Valley. 

Emissions Reductions (%) 

Emissions Component December 9 December 20 

50% B20 100% B20 50% B20 100% B20 

HDDV 6.55 13.1 6.55 13.1 

On-Road Mobile 0.095 0.190 0.084 0.168 

Total 0.089 0.178 0.082 0.164 
 

3-4

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

Location of Point Sources

Elevated Sources

Surface Sources

Airports

Railway Yards

Figure 3-1. Location and relative emission strengths of point sources in the LVV CO UAM 

emission inventory. 
 

3-5

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

1.0

2.0

3.0

4.0

Daily Total CO Emissions (tpd)

Future Year 2001 Base Case

December 9, 2001

Figure 3-2. Daily total CO emissions (TPD) for December 9, 2001, in the LVV CO UAM 

modeling. 
 

3-6

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

1.0

2.0

3.0

4.0

Daily Mobile Source CO Emissions (tpd)

Future Year 2001 Base Case

December 9, 2001

Figure 3-3. Daily on-road mobile source CO emissions (TPD) for December 9, 2001, in the 

LVV CO UAM modeling domain. 
 

3-7

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

1.0

2.0

3.0

4.0

Daily Total CO Emissions (tpd)

Future Year 2001 Base Case

December 20, 2001

Figure 3-4. Daily total CO emissions (TPD) for December 20, 2001, in the LVV CO UAM 

modeling. 
 

3-8

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.0

1.0

2.0

3.0

4.0

Daily Mobile Source CO Emissions (tpd)

Future Year 2001 Base Case

December 20, 2001

Figure 3-5. Daily on-road mobile source CO emissions (TPD) for December 20, 2001, in the 

LVV CO UAM modeling domain. 
 

3-9

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.000

0.002

0.003

Reductions in Daily Total CO Emissions (tpd)

50% Biodiesel 

December 9, 2001

Figure 3-6. Reductions in daily total CO emissions (TPD) for December 9, 2001, in the LVV 

CO UAM modeling due to 50% penetration of B20 biodiesel fuel. 
 

3-10

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.000

0.002

0.003

Reductions in Daily Total CO Emissions (tpd)

100% Biodiesel 

December 9,2001

Figure 3-7. Reductions in daily total CO emissions (TPD) for December 9, 2001, in the LVV 

CO UAM modeling due to 100% penetration of B20 biodiesel fuel. 
 

3-11

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.000

0.002

0.003

Reductions in Daily Total CO Emissions (tpd)

50% Biodiesel 

December 20,2001

Figure 3-8. Reductions in daily total CO emissions (TPD) for December 20, 2001, in the LVV 

CO UAM modeling due to 50% penetration of B20 biodiesel fuel. 
 

3-12

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0.000

0.002

0.003

Reductions in Daily Total CO Emissions (tpd)

100% Biodiesel 

December 20,2001

Figure 3-9. Reductions in daily total CO emissions (TPD) for December 20, 2001, in the LVV 

CO UAM modeling due to 100% penetration of B20 biodiesel fuel. 
 

4-1 

4. BIODIESEL CO ASSESSMENT 

In this section, the impacts of biodiesel fuels on ambient CO concentrations are presented. The 

results of the UAM-IV modeling for the Las Vegas Valley area are presented and discussed for 

each of the three emission scenarios investigated. The impacts of biodiesel fuel use on air 

quality and human health are related through the evaluation of various air quality exposure 

metrics. 

The Urban Airshed Model (UAM) was exercised for each of the future year 2001 biodiesel 

emission scenarios. All meteorological and air quality inputs developed for use in the Phase II 

Las Vegas Valley CO Modeling project (Emery et al., 1999) were left unchanged for use in the 

present study. The resulting ambient CO concentrations under each scenario are presented for 

both daily maximum 1-hour and 8-hour CO concentrations. The impacts resulting from 

biodiesel fuel use are evaluated through comparison with the standard diesel scenario (2001 Base 

Case). Impacts on air quality metrics, including the changes in daily maximum 1-hour and 8-

hour CO concentrations, spatial coverage (exposure) of hourly 1-hour and 8-hour CO 

concentrations above an appropriate threshold (5 ppm), and changes in the integrated 

concentrations of 1-hour and 8-hour CO concentrations (dosage) above the threshold, are 

presented. 

UAM MODEL PERFORMANCE ISSUES 

As part of the development of the Las Vegas Valley CO SIP, the model performance of the 

UAM for the December 8-9 and December 19-20, 1996 base case episodes were evaluated. 

Model performance statistics for the 1-hour and 8-hour CO concentrations were calculated and 

evaluated with respect to the EPA’s model performance criteria. These criteria provide an 

assessment of the UAM model’s ability to replicate the magnitude and time of peak 

concentrations, as well as an overall measure of the bias and error associated with the modeling 

system and database. In addition, the degree to which the modeling results conform to the 

conceptual model of CO buildup in the Las Vegas Valley were evaluated. 

The result of the model performance evaluation revealed that the paired peak accuracy, the bias 

in paired (time and space) peaks over all observation sites, and the overall model bias all range 

from –10% to –12%. This suggests that some consistent error in the modeling is driving the 

UAM under predictions. Subsequently, a single scaling factor of 1.14 was found to lead to an 

elimination of these biases and an overall improvement in model performance. Therefore, all 

UAM predicted CO concentrations were scaled by a factor of 1.14. This same approach is used 

in the current study. A detailed discussion of the model performance and the rationale for 

scaling of the LVV CO modeling results can be found Las Vegas Valley CO SIP modeling report 

(Emery et al., 1999). The reason for the CO underprediction tendency is likely partly due to the 

underestimation of emission in MOBILE5b model. The new MOBILE6 model that was released 

after this portion of the study estimates higher CO emissions in 2001 than MOBILE5b. 
 

4-2 

UAM MODELING RESULTS 

Spatial distributions of the daily maximum 1-hour and 8-hour predicted CO concentrations for 

the 2001 Base Case UAM simulation and the December 8-9, 1996 episode are presented in 

Figures 4-1 and 4-2, respectively. The predicted 1-hour daily peak is seen in the Las Vegas 

Boulevard area and an extensive plume of elevated CO concentrations is seen to follow northeast 

along I-15, continuing east and south along U.S. 95. Additional, a secondary CO peak occurs in 

the vicinity of McCarran Airport. The daily maximum 8-hour CO concentrations displayed in 

Figure 4-2 shows a broad region of high CO concentrations generally following the main 

transportation corridors. The predicted peak 8-hour CO concentration (9.39 ppm) occurs slightly 

east of the urban core just north of the southward bend in U.S. 95. The results predicted by the 

UAM are seen to be consistent with the spatial distribution of CO emissions. 

Figures 4-3 and 4-4 display the impacts on the daily 1-hour maximum CO concentrations due to 

the use of B20 biodiesel fuel for the 50% and 100% penetration levels, respectively. As can be 

seen, the impacts due to 50% penetration of B20 fuel are generally within 0.01-0.015 ppm with 

the maximum impact of 0.02 ppm occurring at the location of the 1-hour peak. The spatial 

distribution of CO concentration reductions reflect the reductions in CO emissions, as expected. 

Similar results are seen for the 100% penetration of B20 scenario where the impacts range from 

0.015-0.02 ppm with a maximum impact of 0.03 ppm , again occurring at the location of the 

daily peak. 

The impacts due to B20 fuel use on the daily 8-hour maximum CO concentrations are displayed 

in Figures 4-5 and 4-6 for the 50% and 100% penetration of B20 biodiesel, respectively. In both 

scenarios, minor impacts (0.01 – 0.02 ppm) are present along the major highways while the 

maximum impact on the peak 8-hour concentrations occurs at the location of the 1-hour peak. 

For the 50% B20 scenario the maximum reduction in 8-hour CO concentrations is 0.01 ppm, 

while for the 100% B20 scenario a maximum reduction of 0.02 ppm is achieved. However, at 

the location of the 8-hour peak, the reductions are significantly lower, implying that the effects 

of biodiesel fuels are, at best, minimal with respect to achievement of the 8-hour NAAQS for CO 

in the Las Vegas Valley nonattainment region. Given the relatively small fraction HDDV 

sources within the total mobile source inventory, these results are not surprising. 

The corresponding results for the December 19-20 episodes are displayed in Figures 4-7 through 

4-12. Qualitatively the results are similar to the December 8-9 episode although the overall 

ambient CO concentrations are somewhat higher during this period. Likewise, the impacts due 

to biodiesel fuels use are minimal ranging from approximately 0.01 ppm to 0.03 ppm, although 

they are seen to affect a somewhat larger spatial extent than for the December 8-9 episode. 

The UAM modeling results are summarized in Table 4-1 with respect to the predicted daily 

maximum 1-hour and 8-hour CO concentrations for each scenario. 
 

4-3 

Table 4-1. Peak CO concentrations for base year 2001 and biodiesel scenarios for the Las Vegas 

Valley. 

Predicted CO Concentrations (ppm) 

Scenario December 8-9 December 19-20 

1-Hr Peak 8-Hr Peak 1-Hr Peak 8-Hr Peak 

2001 Base Case 17.90 9.39 18.38 13.73 

50% Penetration B20 17.89 9.38 18.36 13.72 

100% Penetration B20 17.87 9.37 18.35 13.71 

As another measure of the impacts of biodiesel fuels on air quality and human health, various 

exposure metrics are evaluated for each of the scenarios considered. Spatial coverage (exposure) 

of the hourly 1-hour and 8-hour CO concentrations above a threshold of 5 ppm are calculated for 

each scenario considered. As to be expected, the changes due to the use of the B20 biodiesel 

fuels are small. Also considered are changes in the integrated concentrations of 1-hour and 8-

hour CO concentrations (dosage) above the threshold of 5 ppm. Again the impacts are seen to be 

minimal. These exposure metrics are summarized in Tables 4-2 and 

4-3 for each scenario considered. 

Table 4-2. Summary of CO exposure metrics for the Las Vegas Valley for the 

December 8-9 episode. 

Exposure Metrics for Dec. 8-9 

Exposure 

(grid cell-hours) 

Dosage 

(ppm-grid cell-hours) 

Scenario 

1-Hour 8-Hour 1-Hour 8-Hour 

2001 Base Case 1163 740 2146.02 917.34 

50% Penetration B20 1160 736 2139.37 913.45 

100% Penetration B20 1159 734 2132.76 909.60 

Table 4-3. Summary of CO exposure metrics for the Las Vegas Valley for the 

December 19-20 episode. 

Exposure Metrics for Dec. 19-20 

Exposure 

(grid cell-hours) 

Dosage 

(ppm-grid cell-hours) 

Scenario 

1-Hour 8-Hour 1-Hour 8-Hour 

2001 Base Case 1432 1002 3997.85 2179.05 

50% Penetration B20 1432 1001 3989.47 2173.65 

100% Penetration B20 1431 1001 3981.04 2168.22 
 

4-4 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

Max = 17.91 ppm

Min = 0.22 ppm

Daily Max 1-Hour CO (ppm) (Scaled by 1.14)

NREL Biodiesel -- Las Vegas CO 2001 Base Case

December 8-9, 1996

Figure 4-1. Spatial distribution of 1-hour maximum CO concentrations predicted for the 

December 8-9, 2001 base case. All UAM concentrations scaled by 1.14. 
 

4-5 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

Max = 9.39 ppm

Min = 0.2 ppm

Daily Max 8-Hour CO (ppm) (Scaled by 1.14)

NREL Biodiesel -- Las Vegas CO 2001 Base Case

December 8-9, 1996

Figure 4-2. Spatial distribution of 8-hour maximum CO concentrations predicted for the 

December 8-9, 2001 base case. All UAM concentrations scaled by 1.14. 
 

4-6 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.02 ppm 

Difference in Daily Max 1-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 50% Penetration B20 Biodiesel minus Base

December 8-9, 1996

Figure 4-3. Impacts of 50% penetration of B20 biodiesel fuel on 1-hour maximum CO 

concentrations predicted for December 8-9, 2001. 
 

4-7 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.03 ppm 

Difference in Daily Max 1-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 100% Penetration B20 Biodiesel minus Base

December 8-9, 1996

Figure 4-4. Impacts of 100% penetration of B20 biodiesel fuel on 1-hour maximum CO 

concentrations predicted for December 8-9, 2001. 
 

4-8 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.01 ppm 

Difference in Daily Max 8-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 50% Penetration B20 Biodiesel minus Base

December 8-9, 1996

Figure 4-5. Impacts of 50% penetration of B20 biodiesel fuel on 8-hour maximum CO 

concentrations predicted for December 8-9, 2001. 
 

4-9 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.02 ppm 

Difference in Daily Max 8-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 100% Penetration B20 Biodiesel minus Base

December 8-9, 1996

Figure 4-6. Impacts of 100% penetration of B20 biodiesel fuel on 8-hour maximum CO 

concentrations predicted for December 8-9, 2001. 
 

4-10 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

Max = 18.38 ppm

Min = 0.22 ppm

Daily Max 1-Hour CO (ppm) (Scaled by 1.14)

NREL Biodiesel -- Las Vegas CO 2001 Base Case

December 19-20, 1996

Figure 4-7. Spatial distribution of 1-hour maximum CO concentrations predicted for the 

December 19-20, 2001 base case. All UAM concentrations scaled by 1.14. 
 

4-11 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

Max = 13.73 ppm

Min = 0.21 ppm

Daily Max 8-Hour CO (ppm) (Scaled by 1.14)

NREL Biodiesel -- Las Vegas CO 2001 Base Case

December 19-20, 1996

Figure 4-8. Spatial distribution of 8-hour maximum CO concentrations predicted for the 

December 19-20, 2001 base case. All UAM concentrations scaled by 1.14. 
 

4-12 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.01 ppm 

Difference in Daily Max 1-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 50% B20 Biodiesel minus Base

December 19-20, 1996

Figure 4-9. Impacts of 50% penetration of B20 biodiesel fuel on 1-hour maximum CO 

concentrations predicted for December 19-20, 2001. 
 

4-13 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.03 ppm 

Difference in Daily Max 1-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 100% B20 Biodiesel minus Base

December 19-20, 1996

Figure 4-10. Impacts of 100% penetration of B20 biodiesel fuel on 1-hour maximum CO 

concentrations predicted for December 19-20, 2001. 
 

4-14 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.01 ppm 

Difference in Daily Max 8-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 50% Penetration B20 Biodiesel minus Base

December 19-20, 1996

Figure 4-11. Impacts of 50% penetration of B20 biodiesel fuel on 8-hour maximum CO 

concentrations predicted for December 19-20, 2001. 
 

4-15 

642 652 662 672 682 692

UTM Easting (km)

3973

3983

3993

4003

4013

4023

UTM Northing (km)

-0.100 

-0.050 

-0.020 

-0.015 

-0.010 

0.010 

0.015 

0.020 

0.050 

0.100 

Max = 0 ppm 

Min = -0.02 ppm 

Difference in Daily Max 8-Hour CO (ppm) 

NREL Biodiesel -- Las Vegas CO 2001 100% Penetration B20 Biodiesel minus Base

December 19-20, 1996

Figure 4-12. Impacts of 100% penetration of B20 biodiesel fuel on 8-hour maximum CO 

concentrations predicted for December 19-20, 2001. 
 

R-1 

REFERENCES 

Emery, C., et al. 1999. “The Las Vegas Valley Carbon Monoxide Urban Airshed Model Update 

Project – Phase II: Modeling to Demonstrate Attainment of the Carbon Monoxide 

Standard.” Final Report. Prepared for Clark County Department of Comprehensive 

Planning, Las Vegas, NV. June. 

Emery, C.A. and M.P. Ligocki. 1992. Air Quality Modeling of Carbon Monoxide 

Concentrations in Support of the State Implementation Plan for Phoenix, Arizona. 

Prepared for EPA Region IX. 

Lindhjem, C. and A. Pollack. 2000. “Impact of Biodiesel Fuels on Air Quality – Task 1 Report: 

Incorporate Biodiesel Data Into Vehicle Emission Databases for Modeling” Prepared for 

National Renewal Energy Laboratory, Golden, CO. June. 

Morris R. E. and T. C. Myers. 1990. “User's Guide for the Urban Airshed Model. Volume I: 

User's Manual for UAM (CB-IV)” prepared for the U.S. Environmental Protection 

Agency (EPA-450/4-90-007a), Systems Applications International, San Rafael, CA. 
REPORT DOCUMENTATION PAGE Form Approved 

 OMB NO. 0704-0188 

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson 

Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. 

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE

May 2003 

3. REPORT TYPE AND DATES COVERED 

Subcontract Report 

September 1999-January 2003 

4. TITLE AND SUBTITLE

Impact of Biodiesel Fuels on Air Quality and Human Health: Task 3 Report, The Impact of 

Biodiesel Fuels on Ambient Carbon Monoxide Levels in the Las Vegas Nonattainment 

Area

6. AUTHOR(S) 

Ralph E. Morris, Gerard E. Mansell, Gary Wilson 

5. FUNDING NUMBERS

AXE-9-29079-01 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

ENVIRON International Corporation 

101 Rowland Way 

Novato, CA 94945 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393

10. SPONSORING/MONITORING 

AGENCY REPORT NUMBER

NREL/SR-540-33796 

11. SUPPLEMENTARY NOTES

NREL Technical Monitor: K.S. Tyson and R. McCormick 

12a. DISTRIBUTION/AVAILABILITY STATEMENT

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

 Springfield, VA 22161

12b. DISTRIBUTION CODE

 

13. ABSTRACT (Maximum 200 words)

This document is the Task 3 report for the NREL “Impacts of Biodiesel Fuels on Air Quality and Human Health” study. The 

objectives of Task 3 are to estimate the impacts of biodiesel fuels on elevated witner carbon monoxide concentrations for an 

urban area that is not currently in attainment of the CO standard.

15. NUMBER OF PAGES

14. SUBJECT TERMS 

biodiesel; air quality, modeling, emissions 16. PRICE CODE

17. SECURITY CLASSIFICATION 

OF REPORT

Unclassified 

18. SECURITY CLASSIFICATION 

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION 

OF ABSTRACT

Unclassified

20. LIMITATION OF ABSTRACT

UL 

 NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) 

Prescribed by ANSI Std. Z39-18 

298-102