EPA-AA-SDSB-85-5
Study of Gasoline Volatility and Hydrocarbon
Emissions from Motor Vehicles
November 1985
Standards Development and Support Branch
Emission Control Technology Division
: Office of Mobile Sources
Office of Air and Radiation
U. S. Environmental Protection Agency
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Abstract
In-use motor vehicle evaporative hydrocarbon emissions
greatly exceed their applicable EPA emission standards. The
primary reason is that the volatility of commercial gasoline is
substantially greater than that of the certification test fuel
specified by EPA (i.e., vehicles are simply not designed to
handle the fuel volatility they regularly experience).
The long-term solution is to equate the volatilities of
commercial and certification test gasolines. This can be done
at: 1) the current volatility of commercial gasoline, 2) that
of certification test gasoline, or 3) at some point in
between. However, in the short term, only the reduction of
commercial gasoline volatility has a significant environmental
benefit, since the effect of certification fuel modifications
must await the turnover of the vehicle fleet. This study
examines the technological feasibility, costs, emission
reductions, air quality impacts and cost effectiveness of the
various long-term and short-term solutions to this problem.
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For Further Information
For further information on the technical contents of this
study, please contact Amy Brochu, U.S. Environmental Protection
Agency, 2565 Plymouth Road, Ann Arbor, MI 48105 (phone (313)
668-4270). All of the references used in this study (except
those which are publicly available), as well as all Agency
correspondence associated with the study, are contained in
Public Docket A-85-21. This docket is located in the West
Tower Lobby at EPA Headquarters, 401 M Street, S.W. ,
Washington, D.C. 20460 (phone (202) 382-7548). The docket can
be viewed between 8:00 a.m. and 4:00 p.m., Monday - Friday. A
reasonable fee may be charged for copying.
Public Comments
Written comments on all aspects of the study are
encouraged. Please send comments to: Central Docket Section
(LE-131), U.S. Environmental Protection Agency, Attention:
Docket A-85-21, 401 M Street, S.W., Washington, D.C. 20460.
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Table of Contents
Chapter 1: Introduction
I. Background and Purpose 1-1
II. Structure of the Report 1-2
Chapter 2: Current In-Use Evaporative Emissions
I. Introduction 2-1
II. Ozone Violations and Seasonal Trends . . . 2-1
III. Sources of Evaporative HC Emissions .... 2-16
IV. Factors That Can Impact Evaporative Emissions
from Motor Vehicles . 2-17
V. Results of In-Use Motor Vehicle Testing . . 2-45
VI. Summary of Evaporative Emissions Problem and
Development of Possible Control Scenarios . 2-79
Appendix 2A: Effect of Ambient Temperature on
Motor Vehicle Evaporative Emissions . . . 2-90
Appendix 2B: Breakdown of Motor Vehicle Evaporative
Emission Factors into Their Components . . 2-111
Chapter 3: Vehicle-Oriented Excess Evaporative HC Control
I. Introduction 3-1
II. Technology 3-1
III. Costs 3-17
IV. Conclusions . 3-22
Appendix 3A: Detailed Derivation of Evaporative ECS
Component Costs 3-26
Chapter 4: Technological Feasibility and Cost of In-Use
Volatility Control
I. Introduction 4-1
II. Refinery Control of Gasoline Volatility . . 4-1
III. The Bonner and Moore Study 4-4
IV. Effect of RVP Control on the Butane Market. . 4-21
V. Fuel Economy Credit 4-24
VI. Economic Credit from Evaporative HC Recovery/
Prevention 4-38
VII. Overall Cost of In-Use Gasoline RVP Control . 4-40
Chapter 5: Environmental Impact
I. Introduction 5-1
II. Motor Vehicle Evaporative HC Emission Factors 5-1
III. Motor Vehicle Exhaust Emission Factors . . . 5-16
IV. Effect of RVP Control on Gasoline
Storage and Distribution Losses .... 5-19
V. Hydrocarbon Emissions Inventory Analysis . . 5-23
VI. Ozone Air Quality Analysis 5-33
VII. Effect of RVP Control on Toxic Emissions . . 5-37
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Chapter 6: Analysis of Alternatives
I . Introduction
II. Methodology
III. Results
Appendix 6-A: Development of I/M Credits for Evaporative
Emission Control Systems
Appendix 6-B: Effects of Increased Canister Size on
Operating Costs
Appendix 6-C: Development of Non-Summer Evaporative
Emission Recovery Credits for Four-Month
Analysis .
6-1
6-3
6-14
6-47
6-63
6-66
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CHAPTER 1
Introduction
I. Background and Purpose
Current violation of the ambient ozone standard is
somewhat widespread in urban areas across the United States.
The Clean Air Act requires all areas to be in attainment by
December 31, 1987.* Therefore, additional reduction of
hydrocarbon emissions has become a growing concern. Of late,
increasing attention has been directed toward evaporative
hydrocarbon (HC) emissions from gasoline-fueled motor vehicles.
Evaporative HC emissions from motor vehicles originate
from two basic components of the vehicle's fuel system — the
fuel tank and the carburetor. Evaporative emissions from the
fuel tank — known as "diurnal" losses — occur as the gasoline
vapors expand in response to daily ambient temperature
increases. The other type of vehicle evaporative emissions —
referred to as "hot-soak" losses — occur just after the engine
is turned off, when residual engine heat causes the evaporation
of some of the fuel remaining in the carburetor bowl and fuel
lines. In fuel-injected vehicles, some hot-soak losses also
originate from the fuel tank as well, probably due to
recirculation of gasoline that has been heated by the engine.
Currently, all gasoline-fueled vehicles and trucks are
equipped with evaporative control systems designed to capture
the majority of these diurnal and hot-soak losses. A typical
system consists of a canister filled with carbon granules which
adsorb the HC vapors generated in the fuel tank and the
carburetor. Later, while the engine is operating, the
evaporative canister is periodically purged with air and the
collected HCs are stripped from the canister and burned in the
engine.
Light-duty gasoline vehicles (LDGVs) and gasoline trucks
weighing less than 6000 Ibs. GVW (rated gross vehicle weight),
classified as LDG^s, have been equipped with evaporative
canisters since 1971, when the first evaporative HC standards
came into effect. Evaporative control of heavier trucks came
later, with canisters first installed in light-duty gasoline
trucks over 6000 Ibs. GVW (LDGT2s) in 1979 and in heavy-duty
* 1982 was the original date by which attainment was to be
achieved; however, under special circumstances, an
extension to 1987 is permitted. The Act makes no
provisions beyond 1987.
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1-2
gasoline vehicles (HDGVs) in the current model year (1985).
Current evaporative HC standards for these classes — required
to be met during certification testing — are as follows: 2.0
grams/test for LDGVs, LDGT,s and LDGT2s; 3.0 grams/test for
HDGVs at 14,000 Ibs. GVW or less; and 4.0 grams/test for HDGVs
greater than 14,000 Ibs. GVW. These standards represent the
sum of diurnal and hot-soak losses measured via the Sealed
Housing Emission Determination (SHED) test, as outlined in the
Code of Federal Regulations (Part 86, Subparts B and M).
Evaporative control systems are designed to meet these HC
standards when the vehicle is fueled with certification test
gasoline (Indolene), which has a typical Reid Vapor Pressure
(RVP) — a measure of volatility — of 9.0 psi. Although this
level of volatility was representative of commercial fuels in
the early 1970's when certification test fuel specifications
were developed, the RVP of commercial gasoline has risen
steadily since then due primarily to an increasing butane
content in response to rising energy costs. Results of EPA's
in-use emission factor testing indicate that evaporative
emissions are significantly greater with fuels of higher
volatility; therefore, evaporative emissions from vehicles
operating on commercial fuels are well above the certification
standards. Further, EPA's testing has also revealed that the
majority of in-use carbureted vehicles are unable to meet the
evaporative standards even while operating on Indolene (9.0
psi), which suggests possible design problems such as
inadequate canister purge during typical operating conditions.
Fuel-injected vehicles (a small minority in today's fleet, but
expected to dominate late 1980's sales) perform well on
Indolene, but greatly exceed 2 grams/test on commercial fuel.
Based on these findings, EPA has concluded that the
majority of vehicles being driven in the field today are
exceeding the current evaporative HC standards and will
continue to do so, though to a lesser extent, in the future.
This evaporative excess is a significant contributor to the
current ozone non-attainment problem. The purpose of this
report is to analyze various strategies designed to reduce this
evaporative excess via in-use fuel volatility controls and/or
modifications to certification fuel volatility specifications
and test procedure.
II. Structure of the Report
In addition to this Introductory Chapter, the report is
divided into five major sections. The first (Chapter 2)
discusses the current in-use situation and lays the groundwork
for the rest of the study. Topics examined are: 1) the current
ozone non-attainment problem and seasonal trends in violations,
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1-3
2) the sources of evaporative HC emissions (both motor vehicle
and stationary), 3) various factors affecting motor vehicle
evaporative emissions (such as evaporative control system
design, fuel volatility, use of alcohol blends, and ambient
temperature conditions), 4) results of EPA's in-use vehicle
testing (used to define the basic sources of the motor vehicle
evaporative excess and also the effect of fuel volatility on
exhaust emissions), and 5) the HC control strategies to be
evaluated in the remainder of the study. Next, Chapters 3 and
4 evaluate the technical feasibility and cost of
vehicle-related controls and in-use fuel volatility controls,
respectively. Chapter 5 assesses the environmental impacts
associated with each of the control strategies, in terms of
projected HC emissions and ambient ozone concentrations;
included in these estimates is the impact of in-use RVP control
on gasoline storage and distribution losses (from bulk
terminals, refueling, etc.). Finally, in Chapter 6, the
various control strategies are analyzed and compared on the
basis of emission reductions, costs, and cost-effectiveness.
This final chapter also addresses the sensitivity of these
estimates to various factors such as implementation of
refueling loss controls (on-board or Stage II), development of
an inspection/maintenance program for evaporative control
systems, exclusion of exhaust emission benefits, and others.
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CHAPTER 2
Current In-Use Evaporative Emissions
I. Introduction
This chapter provides the basic background information
necessary to put this study of evaporative hydrocarbon (HC)
control measures into the proper context. The first section
following this introduction discusses the current widespread
ozone non-attainment problem, which has prompted the further
study of HC control strategies. Section III provides a brief
background on the origin of evaporative HC emissions from motor
vehicles and gasoline storage and distribution sources. As the
focus of this study is motor vehicle losses, Section IV
addresses various factors that can impact the level of these
evaporative emissions. These factors include: 1) the motor
vehicle evaporative control system design, 2) in-use fuel
volatility (including the effect of weathering), 3) use of
alcohol blends, and 4) ambient temperature conditions.
Following this discussion. Section V explains how data from
EPA's in-use emission factor test program have been used to
determine the major reasons for excess evaporative emissions
from motor vehicles in the field (i.e., improper design of the
purge system, malmaintenance and defects, higher commercial
fuel volatility, and evaporative system tampering). Test
results are also used to estimate the effect of fuel volatility
on exhaust emissions. Finally, Section VI summarizes the
current problem and discusses possible measures to control the
evaporative emissions excess, such as the reduction of in-use
fuel volatility and/or revisions to certification fuel
specifications and test procedure; the specific control options
to be evaluated throughout the rest of this study are outlined
here.
II. Ozone Violations and Seasonal Trends
Current violation of the National Ambient Air Quality
Standard (NAAQS) for ozone is quite widespread, with 54* urban
areas currently designated as "non-attainment" by EPA's Office
of Air Quality Planning and Standards (OAQPS).tl] As
projections presented later in Chapter 5 will show, this
non-attainment problem is expected to continue without further
control of HC emissions.
Includes 7 California cities.
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2-2
Examination of ozone monitoring data recorded at sites in
the non-attainment areas has revealed seasonal trends in ozone
violations. As might be expected, the majority of all ozone
violations occur during the warmer months of the year, when
ambient conditions are most favorable to ozone formation.
These seasonal trends are important in determining during what
period (i.e., specific months) hydrocarbon emission reductions
would be most valuable. This is an important consideration
with respect to any in-use fuel-related control measures, as
they include the flexibility to be implemented throughout the
year or during only specific months. However, other
evaporative HC control measures such as revisions to
certification fuel specifications and test procedure would
affect vehicle design and, thus, represent year-round control.
The following paragraphs begin with a brief description of
the method by which the 54 urban areas mentioned above were
designated as "non-attainment." This is followed by a review
of seasonal trends in ozone violations within the
non-California areas.
All ozone monitoring data recorded in the Storage and
Retrieval of Aerometric Data (SAROAD) system between 1981 and
1983 (inclusive) were examined for ozone violations. If the
sites within a specific Standard Metropolitan Statistical Area
(SMSA) had not recorded any daily maximum 1-hour ozone
concentrations greater than the level of the NAAQS (0.125 ppm)
in 1982 or 1983, then the SMSA was considered to be in
compliance with the standard and was not examined further.[1]
For each of the SMSAs that failed this initial test, the fourth
highest daily maximum 1-hour concentration during the 3-year
period was determined; if this value was less than the standard
of 0.125 ppm, the city was dropped from consideration. With a
further stipulation that the area have a population greater
than 200,000,* 54 SMSAs were designated as current
non-attainment areas to be modelled for ozone by EPA.tl]
However, since California has already implemented its own
gasoline volatility controls, only the 47 non-California cities
were considered in this study. These 47 current ozone
non-attainment cities, or SMSAs, are listed in Table 2-1, along
with their respective "design values", or base-year ambient
ozone concentrations to be used in EPA's modelling.fi]
This population cutoff was determined as part of EPA's
rural ozone policy, outlined in Reference 2.
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2-3
Table 2-1
47 Current Non-California Ozone Non-Attainment
Areas, With Design Values* (ppm)[l]
Region 1
Boston Metropolitan Area 0.16
Greater Metropolitan Connecticut 0.14
Providence-Pawtucket-Warwick, RI-MA 0.14
Springfield-Chicopee-Holyoke, MA-CT 0.19
Worcester, MA 0.13
Region 2
New York Metropolitan Area 0.23
Region 3
Allentown-Bethlehem-Easton, PA-NJ 0.14
Baltimore, MD 0.15
Harrisburg, PA 0.13
Huntington-Ashland, WV-KY-OH 0.13
Norfolk-VA Beach-Portsmouth, VA 0.14
Philadelphia Metropolitan Area 0.18
Pittsburgh, PA 0.13
Richmond, VA 0.13
Scranton-Wilkes-Barre, PA 0.13
Washington, DC-MD-VA 0.16
Region 4
Atlanta, GA 0.17
Birmingham, AL 0.16
Charlotte-Gastonia, NC 0.13
Chattanooga, TN-GA 0.14
Memph i S, TN-AR-MS 0.15
Miami, FL 0.14
Region 5
Akron, OH 0.14
Canton, OH 0.13
Chicago Metropolitan Area 0.20
Cincinnati, OH-KY-IN 0.13
Cleveland, OH 0.13
Dayton, OH 0.13
Detroit, MI 0.15
Indianapolis, IN 0.13
Louisville, KY-IN 0.16
Milwaukee Metropolitan Area 0.14
St. Louis, MO-IL 0.14
Toledo, OH-MI 0.13
Youngstown-Warren, OH 0.13
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2-4
Table 2-1 (Cont'd)
Region 6
Baton Rouge, LA 0.17
Dallas-Fort Worth, TX 0.15
El Paso, TX 0.14
Houston, TX 0.28
New Orleans, LA 0.17
San Antonio, TX 0.14
Tulsa, OK 0.15
Region 7
Kansas City, MO-KS 0.13
Region 8
Denver-Boulder, CO 0.15
Salt Lake City-Ogden, UT 0.15
Region 9
Las Vegas, NV 0.14
Phoenix, AZ 0.16
* Each area's "design value" is the fourth highest daily
maximum 1-hour ozone concentration recorded during a
3-year period — in this case, 1981, 1982 and 1983.
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2-5
In an effort to determine during what period HC control is
most valuable, ozone data recorded at all monitoring sites
within each of these 47 SMSAs were examined for seasonal trends
in ozone episodes. Reports of daily maximum 1-hour
concentrations at each monitor, recorded for each day of the
year, were obtained for two calendar years — 1983 because it
was the most recent complete set of data available at the time
of this analysis, and 1980 because it represents a recent year
with a relatively high number of ozone violations.
Results of the seasonal analysis of 1983 and 1980 ozone
monitoring data are presented, respectively, in Tables 2-2 and
2-3. Included in the tables, for each of the 47 SMSAs, are
number of monitoring sites, number of monthly violations, and
maximum monthly ozone concentration. The number of violations
represents the total number of days in which a 1-hour average
ozone concentration at any given site exceeded 0.125 ppm (the
NAAQS); because violations in a particular SMSA are summed over
all monitoring sites in the city, total monthly violations can
exceed 31. The maximum ozone concentration shown in the tables
is the highest 1-hour average concentration recorded at any
site within an SMSA during the given month.
As indicated in the tables, ozone violations tend to occur
in the warmer months when temperature conditions are most
favorable for ozone formation. According to 1983 data
(summarized in Table 2-2), 38 of the 47 non-attainment areas
experienced all ozone violations during the summer months
(i.e., May through September, inclusive); further, all but two
of the cities recorded at least 80 percent of their violations
in the summer. The two excepted cities experienced very few
ozone episodes during 1983 — Scranton recorded only three
violations with one in April, and Miami's only reported
violation in 1983 fell during April.
As shown in Table 2-3, non-summer ozone violations were
slightly more prevalent in 1980 than in 1983. In 1980, 19 of
the cities experienced at least one ozone episode outside of
the May-September period, compared to only 9 cities during
1983. However, the vast majority of 1980 violations occurred
during the summer, with 42 of the 47 cities recording over 80
percent of all exceedances between May and September
(inclusive).
In both 1980 and 1983, Houston experienced a relatively
large number of ozone violations, recording 193 and 217 annual
exceedances (respectively) over its 13 monitoring sites. In
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2-6
City
Region 1
No. of
Sites
Boston 3
Violations
Max. ppm
Metro Conn 10
Violations
Max. ppm
Providence 4
Violations
Max. ppm
Springfield 3
Violations
Max. ppm
Worcester 1
Violations
Max. ppm
Region 2
New York 8
Violations
Max. ppm
Region 3
Allentown 3
Violations
Max. ppm
Baltimore 12
Violations
Max. ppm
Harrisburg 3
Violations
Max. ppm
Huntingtbn 1
Violations
Max. ppm
Table 2-2
Monthly Trends in Ozone Violations - 1983
Jan Feb Mar Apr May Jun Jul Auq Sep Oct Nov Dec
7352
.021 - .037 .116 .092 .205 .133 .146 .149 .108 .030 .032
5 74 63 65 60 1
.181 .118 .294 .223 .224 .222 .129 -
2223
.038 .048 .051 .101 .073 .171 .137 .132 .150 .119 .056 .043
.015 .077 .035
2
,175
.097
,103 .080
7
.162
1
.132
10
,255
.120
7
,185
2
,145
3
.145
1
.145
,107 .042 .035
,100 -
1 30 20 25 13
.050 .067 .059 .138 .099 .209 .224 .160 .172 .113 .065 .038
942
.040 .054 .057 .112 .092 .173 .138 .143 .120 .103 .069 .041
1 2
.035 .075 .053 .071 .111 .149 .117 .151 .110 .082 .045 .034
.039 .066 .054 .111 .108
.039 .081 .075 .076 .088
7
,200
2
,130
.123 .120 .109 .090 .056 .032
541
.138 .130 .150 .091 .054 .048
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2-7
Cits
No. of
Sites
Norfolk 1
Violations
Max. ppm
Philadelphia 12
Violations
Max. ppm
Pittsburgh 7
Violations
Max. ppm
Richmond 3
Violations
Max. ppm
Scranton 4
Violations
Max. ppm
Wash. D.C. 12
Violations
Max. ppm
Region 4
Atlanta 2
Violations
Max. ppm
Birmingham 3
Violations
Max. ppm
Charlotte 3
Violations
Max. ppm
Chattanooga 2
Violations
Max. ppm
Memphis 3
Violations
Max. ppm
Miami 3
Violations
Max. ppm
Table 2-2 (continued)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1 1
.041 .061 .072 .083 .092 .121 .130 .135 .119 .070 .064 .044
1 1 56 38 32 22 1
.039 .145 .073 .120 .134 .205 .182 .181 .162 .138 .065 .080
4531
.064 .066 .094 .091 .108 .133 .142 .175 .141 .088 .061 .038
3132
.040 .065 .075 .085 .090 .150 .150 .130 .140 .100 .055 .045
1 2
.037 .052 .061 .127 .073 .135 .114 .107 .106 .086 .068 .040
30 28 15 15
.040 .077 .073 .092 .102 .176 .195 .249 .175 .092 .058 .034
2 14 12
.080 .122 .133 .195 .155 .100 .108 .070 -
2 10
.058 .069 .085 .093 .098 .093 .142 .171 .113 .112 .072 .047
1135
.047 .6.71 .076 .086 .130 .135 .155 .148 .117 .117 .066 .057
.058 .073 .090 .085 .090 .118 .095 .150 .108 .103 .063 .058
3 6
.045 .070 .090 .090 .080 .095 .150 .148 .120 .100 .050
.070 .060 .115 .230 .095 .070 .065 .100 .055 .090 .085 .055
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2-8
City
Region 5
No. of
Sites
Table 2-2 (continued)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Akron 4
Violations
Max. ppm
Canton 2
Violations
Max. ppm
Chicago 23
Violations
Max. ppm
Cincinnati 8
Violations
Max. ppm
Cleveland 6
Violations
Max. ppm
Dayton 4
Violations
Max. ppm
Detroit 3
Violations
Max. ppm
Indianapolis 6
Violations
Max. ppm
Louisville 3
Violations
Max. ppm
Milwaukee 9
Violations
Max. ppm
St. Louis 9
Violations
• Max. ppm
Toledo 3
Violations
Max. ppm
Youngstown 1
Violations
Max. ppm
243
.035 .068 .095 .095 .085 .130 .130 .130 .105 .115 .048 .035
1 1
.033 .052 .082 .075 .097 .125 .123 .125 .098 .080 .058 .037
19 33 9 5
,043 .089 .072 .084 .089 .188 .180 .155 .141 .096 .065 .092
2 4 20 1
.050 .073 .080 .080 .087 .135 .162 .190 .147 .095 .057 .042
49 6 2
.040 .061 .075 .090 .085 .153 .158 .151 .135 .083 .083 .033
.035 .075 .077 .077 .075 .122 .120 .132 .105 .095 .047 .035
8241
.044 .050 .087 .095 .116 .170 .136 .142 .125 .089 .038 .035
325
.044 .078 .076 .091 .094 .131 .138 .155 .104 .090 .065 .074
2 12 14
.042 .069 .071 .060 .075 .138 .148 .190 .116 .091 .060 .034
15 9 15 5
.030 .035 .047 .101 .090 .165 .179 .228 .140 .115 .037 .032
10 15 34
.037 .066 .096 .107 .090 .160 .177 .243 .121 .104 .019 .036
3 11
.035 .040 .055 .070 .085 .130 .115 .125 .130 .100 .035 .030
.040 .065 .080 .087 .080 .125 .100 .100 .097
.035 .030
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2-9
Table 2-2 (continued)
No. of
City Sites Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Region 6
Baton Rouge 6
Violations 11132
Max. ppm .070 .061 .107 .090 .130 .130 .125 .169 .139 .120 .085 .100
Dallas 7
Violations 6 5 6 23 3
Max. ppm .070 .080 .080 .090 .140 .170 .170 .170 .140 .120 .070 .050
El Paso 3
Violations 2 1
Max. ppm .090 .090 .090 .080 .110 .100 .140 .120 .150 .100 .090 .090
Houston 13
Violations 3 12 4 62 30 28 33 25 16 1 3
Max. ppm .120 .140 .160 .140 .290 .230 .240 .250 .340 .190 .150 .180
New Orleans 4
Violations
Max. ppm .066 .094 .113 .084 .124 .093 .115 .121 .117 .096 .064 .060
San Antonio 2
Violations 2
Max. ppm .080 .090 .070 .070 .090 .110 .100 .120 .140 .120 .060 .060
Tulsa 3
Violations 4 2
Max. ppm .052 .067 .070 .083 .091 .099 .138 .132 .112 .097 .057 .041
Region 7
Kansas City 5
Violations 1 2
Max. ppm .037 .080 .080 .079 .065 .095 .130 .142 .116 .093 .061 .046
Region 8
Denver 7
Violations . 1 2 6 11 1 1
Max. ppm .077 .064 .120 .141 .106 ,155 .140 .176 .127 .075 .080 .128
Salt Lake
City 6
Violations 124
Max. ppm .046 .059 .079 .067 .130 .102 .135 .158 .113 .089 .051 .052
Region 9
Las Vegas 3
Violations 1
Max. ppm .098 .118 .086 .077 .091 .100 .110 .121 .138 .085 .074 .078
Phoenix 9
Violations 21281
Max. ppm .069 .078 .n ni .08S . 1'. ? .135 .160 .160 .139 .104 .07} .050
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2-10
Table 2-3
Monthly Trends in Ozone Violations - 1980
City
Region 1
No. of
Sites
Boston 10
Violations
Max. ppm
Metro Conn. 10
Violations
Max. ppm
Providence 3
Violations
Max. ppm
Springfield 1
Violations
Max. ppm
Worcester 3
Violations
Max. ppm
Region 2
New York 9
Violations
Max. ppm
Region 3
Allentown 4
Violations
Max. ppm
Baltimore 16
Violations
Max. ppm
Harrisburg 2
Violations
Max. ppm
Huntington 1
Violations
Max. ppm
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
7 11 8
.093 .079 .154 .150 .159 .098 .061 .032 .029
12 44 89 50 30
.043 .058 .060 .090 .189 .276 .303 .249 .230 .106 .034 .032
,040 .050 .070 .100 .140
6
,190
2
,185
9
.208
5
.153
8
.222
1
.155
1
,135
1
,150
.112 .060 .052
.087 -
231
.075 .095 .177 .193 .170 .106 .080 -
1 3 13 49 26 5
.032 .036 .222 .095 .159 .190 .188 .174 .131 .077 .040 .092
11 23447 2
,139 .344 .050 .090 .127 .161 .152 .143 .151 .083 .152 .044
1 2 8 54 38 11
.039 .041 .057 .137 .128 .162 .183 .195 .157 .091 .061 .058
.078 .048 .078 .095 .115 .116 .112
11 2
.037 .053 .056 .130 .129 .088 .147
1
,128
1
.128
.088 .068 .035
,120 .090 .089 .070 .052
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2-11
Table 2-3 (continued)
No. of
City Sites Jan Feb Mar Apr May Jun Jul Aug Sep pet Nov Dec
Norfolk 2
Violations 1
Max. ppm .031 .044 .050 .091 .115 .120 .126 .119 .116 .076 .061 .035
Philadelphia 17
Violations 3 30 60 43 7 21
Max. ppm .043 .050 .070 .110 .142 .197 .228 .201 .168 .089 .349 .239
Pittsburgh 12
Violations 7 14 10 1
Max. ppm .039 .051 .063 .087 .117 .174 .298 .160 .128 .087 .076 .044
Richmond 3
Violations 1 1
Max. ppm .030 .055 .055 .095 .135 .115 .130 .120 .120 .075 .055 .045
Scranton 4
Violations 3321
Max. ppm .034 .041 .054 .092 .120 .155 .148 .145 .151 .089 .041 .045
Wash. DC 15
Violations 3 2 18 28 5
Max. ppm .040 .055 .055 .088 .147 .133 .195 .207 .167 .090 .071 .070
Region 4
Atlanta 4
Violations 1442
Max. ppm .050 .090 .070 .100 .105 .135 .160 .150 .150 .080 .080 .070
Birmingham 3
Violations 9 3
Max. ppm _____ .117 .157 .161 .115 .099 .092 .072
Charlotte 4
Violations 5 4
Max. ppm .045 .075 .071 .092 .117 .118 .154 .145 .119 .098 .077 .056
Chattanooga 2
Violations 1
Max. ppm .045 .070 .060 .090 .100 .135 - - .095 .090 .068 .060
Memphis 4
Violations 1172 2
Max. ppm .053 .070 .070 .165 .130 .140 .200 .110 .160 .072 .087 .060
Miami 2
Violations 111
Max. ppm .052 .100 .075 .070 .080 .050 .085 .155 .130 .150 .075 .070
-------
2-12
Table 2-3 (continued)
Cit\
No. of
Sites Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Region 5
Akron 4
Violations
Max. ppm
Canton 2
Violations
Max. ppm
Chicago 27
Violations
Max. ppm
Cincinnati 7
Violations
Max. ppm
Cleveland 7
Violations
Max. ppm
Dayton 4
Violations
Max. ppm
Detroit 8
Violations
Max. ppm
Indianapolis 5
Violations
Max. ppm
Louisville 8
Violations
Max. ppm
Milwaukee 8
Violations
Max. ppm
St. Louis 19
Violations
Max. ppm
Toledo 2
Violations
Max. ppm
Youngstown 2
Violations
Max. ppm
1 1
.030 .040 .053 .088 .103 .103 .133 .118 .153 .073 .063 .040
.035 .037 .070 - .095 .100 .110 .105 .085 .080 .062 .040
4 4 17 9 1
.039 .056 .361 .111 .124 .148 .195 .163 .132 .074 .056 .091
16 22 7
.037 .050 .060 .102 .122 .165 .172 .137 .120 .100 .065 .050
.038 .043 .060 .090 .104 .119 .152 .102 .099 .061 .061 .040
3 1
.040 .050 .055 .092 .115 .102 .156 .132 .100 .082 .052 .042
12173
.040 .092 .083 .139 .145 .155 .149 .151 .121 .085 .082 .084
2 3
.107 .119 .073 .102 .123 .140 .142 .121 .117 .117 .056 .049
1 5 18 15 2 1
.045 .060 .060 .090 .175 .169 .190 .197 .158 .130 .081 .081
3 81
.033 .045 .045 .086 .119 .140 .124 .177 .126 .046 .035 .029
1 3 2 13 29 18 6 5 1
.070 .078 .205 .161 .199 .199 .171 .177 ,162 .157 .105 .125
3 1
.035 .050 .060 .105 .105 .115 .140 .145 .105 .080 .050 .035
.038 .037 .055 .085 .075 .160 .110 .095 .090 .060 .050 .050
-------
2-13
Table 2-3 (continued)
No. of
City Sites Jan Feb Mar Apr May Jun Jul Aug Sep Qct Nov Dec
Region 6
Baton Rouge 3
Violations 4143
Max. ppm .057 .056 .064 .085 .087 .124 .154 .137 .193 .218 .102 .070
Dallas 7
Violations 127532
Max. ppm .060 .110 .120 .130 .180 .180 .150 .140 .160 .100 .090 .100
V
El Paso 2
Violations 2 13 1
Max. ppm .080 .090 .070 .080 .120 .160 .080 .130 .160 .100 .130 .090
Houston 13
Violations 6 1 1 4 27 19 31 36 31 22 10 5
Max. ppm .160 .190 .140 .150 .280 .220 .220 .260 .340 .350 .230 .160
New Orleans 1
Violations 1
Max. ppm .031 .040 .032 .038 .023 .114 .126 .095 .068 .088 .072 .048
San Antonio 3
Violations
Max. ppm .060 .100 .080 .110 .120 .120 .120 .110 .120 .120 .090 .070
Tulsa 3
Violations 1544
Max. ppm .066 .068 .098 .088 .117 .129 .201 .145 .132 .087 .077 .047
Region 7
Kansas City 5
Violations 1951
Max. ppm .040 .060 .080 .120 .090 .135 .160 .160 .140 .108 .087 .051
Region 8
Denver 8
Violations ; 31
Max. ppm .086 .102 .068 .080 .116 .117 .165 .128 .103 .100 .072 .085
Salt Lake 5
Violations 3721
Max. ppm .061 .085 .092 .088 .121 .155 .182 .178 .146 .105 .075 .040
Region 9
Las Vegas 3
Violations 11 11
Max. ppm .145 .135 .080 .113 .080 .090 .095 .093 .049 .118 .169 .143
Phoenix 8
Violations 8 14 3 1 1
Max. ppm .049 .088 .095 ..08 .110 .148 .174 .143 .133 .129 .097 .078
-------
2-14
1980, 25 percent of these violations occurred outside of the
May-September period; the 1983 figure is slightly lower at 18
percent non-summer violations.
In evaluating various seasonal options for in-use fuel
volatility control, it is important to consider the periods
during which ozone reductions are most needed. The upper half
of Table 2-4 summarizes the seasonal trends in ozone violations
indicated in the previous two tables, outlining the percentage
of total annual violations that occurred in the 47 areas during
specific summer periods (i.e., various monthly combinations) in
1980 and 1983. These percentages are based on total violations
summed over all monitors in all 47 areas; therefore, those
cities with more monitors contribute more heavily to the
weighted average. Because Houston recorded a relatively large
number of non-summer violations, results are presented for all
47 cities combined and then for all cities excluding Houston.
As shown, the individual month during which the highest
percentage of all 1980 violations occurred was July, with 39
percent of the total; in 1983, August was the highest with 31
percent of total annual violations. In addition to individual
months, the 2-,3-,4-, and 5-month periods recording the highest
percentages of total violations are presented. As shown,
in-use fuel volatility control between May and September
(inclusive) could potentially have an impact on 94-97 percent
of all ozone violations in current non-attainment areas; if
Houston were excluded, this 5-month period would encompass
essentially all ozone episodes. Four-month control would
impact just slightly less of the ozone season — 89-92 percent
of total violations in all cities and 94-98 percent if Houston
were excluded.
The bottom half of Table 2-4 summarizes the seasonal
trends in peak ozone concentrations, first showing the average
of all 47 cities' peak ozone levels by month, then including
only those concentrations over the NAAQS (0.125 ppm). The data
used are those in Tables 2-2 and 2-3 for 1983 and 1980,
respectively. As can be seen, average peak ozone
concentrations show a definite trend between highs of 0.156 -
0.162 ppm in July or August to lows of 0.050 - 0.055 ppm in
January. When only peaks above the standard are included, the
trend is less pronounced. The reason for this is that the
summer averages are a mixture of marginal and severe
violations, while the winter averages primarily consist of the
marginal to moderate violations of those cities with more
severe violations in the summer. Cities with marginal
violations in the summer generally show no violations in the
winter and, thus, are excluded from the averaging.
-------
2-15
Table 2-4
Seasonal Trends in Ozone Violations
in 47 Non-Attainment Areas
Percent of Total Annual Violations
Months
April
May
June
July
August
September
October
Jul-Aug
Jun-Aug
Jun-Sep
May-Sep
Months
January
February
March
April
May
June
July
August
September
October
November
December
All Cities
1980
1
5
13
39
27
10
2
66
79
89
94
Average of
All Ozone
Levels
1980
0.055
0.075
0.082
0.101
0.123
0.151
0.162
0.151
0.134
0.101
0.084
0.067
All Cities Except
1983
1
5
22
26
31
13
1
57
79
92
97
City-Specific
Houston*
1980
1
3
14
43
28
9
1
71
85
94
97
Monthly Peaks
Ozone Levels
1983
1
1
23
28
34
13
0
62
85
98
99
(ppm)
Above
Standard ( . 125 ppm)
1983
0.050
0.073
0.080
0.099
0.103
0.144
0.149
0.156
0.133
0.102
0.061
0.053
1980
0.148
0.223
0.232
0.145
0.160
0.166
0.174
0.165
0.158
0.189
0.206
0.167
1983
__
0.143
0.160
0.162
0.155
0.161
0.161
0.162
0.155
0.152
0.150
0.154
Houston is excluded here due to a relatively large number
of non-summer violations.
-------
2-16
III. Sources of Evaporative HC Emissions
A. Motor Vehicles
Evaporative HC emissions from motor vehicles can be
separated into two basic categories — "diurnal" and "hot-soak"
losses — that result from different processes. Diurnal
emissions consist of HCs both evaporated and displaced from the
vehicle's fuel tank as the vehicle tracks the diurnal swing in
ambient temperatures. Each day, as the fuel in the tank and
the vapor above the fuel heat up, more of the liquid fuel
evaporates and the vapor itself expands, with both phenomena
causing HCs to be released into the atmosphere (unless captured
by a control system). Fuel volatility, size of vapor space,
initial ambient temperature, and magnitude of the diurnal
temperature swing can all impact the level of evaporative
emissions from a vehicle's fuel tank.
Hot-soak emissions occur during the period immediately
following engine shut-down (i.e., at the end of each vehicle
trip). These losses will occur both as distillation from the
fuel metering system (either a carburetor or a fuel injector)
and as evaporation from the fuel tank. Evaporative emissions
from the fuel metering system occur as part of a different
process than that described for diurnal losses. When the
vehicle's engine is shut off, so is the cooling system. The
engine block and surrounding area heat the engine coolant
(which is no longer circulating) and other engine components,
usually kept cool by the circulating coolant, before natural
cooling begins to take effect. Any fuel remaining in the
carburetor bowl, or leaking from a malfunctioning fuel
injector, will undergo a distillation process during this time
and vapors will be released ~to the atmosphere unless captured
by a control device. This was previously considered the only
source of hot-soak emissions, but there have been recent
indications that the fuel tank in fuel-injected vehicles can
undergo a temperature change during vehicle operation as a
result of recirculation of fuel heated by the engine. Vapor
production in the tank would be the same type as that described
above for diurnal losses; however, because these tank losses
are not in response to ambient temperature changes, they are
classified as hot-soak emissions.
B. Gasoline Storage and Transfer
In addition to diurnal and hot-soak losses from motor
vehicles, evaporative HC emissions are also released during
gasoline storage and transfer. These stationary
gasoline-related sources can be divided into three basic
categories: l) bulk storage and bulk transfer of gasoline, 2)
service stations (Stage I), and 3) vehicle refueling (Stage
II).
-------
2-17
Storage emissions are very similar to diurnal losses from
motor vehicles in that they occur as gasoline 'in a tank
responds to daily increases in ambient temperature. The
transfer losses (included in all three categories) result from
the displacement of gasoline vapors within a previously closed
tank with liquid fuel; as the liquid goes in the tank, the
vapors escape through available openings (primarily the
refueling line).
Gasoline storage and distribution losses are dependent
upon such factors as fuel volatility, ambient temperature
conditions, tank configurations, method of fill, etc. The
three source categories will be discussed in more detail in
Chapter 5, where the effect of fuel volatility on the magnitude
of stationary source evaporative losses will be addressed.
IV. Factors That Can Impact Evaporative Emissions from Motor
Vehicles
A. Evaporative Control System Design
1. Description
Present evaporative emission control systems are composed
of: 1) an activated carbon canister that adsorbs hydrocarbon
vapor emitted from the vehicle fuel tank and carburetor bowl,
and 2) the associated plumbing and hardware that control the
loading and purging of the canister. Additionally, some
carbureted systems use an air cleaner with an integrated
charcoal element to further adsorb bowl and intake manifold
vapors. When the engine is running, this stored vapor is
desorbed, or purged, by drawing air through the canister to the
engine intake system. The purge rate is controlled by the
source of the vacuum (air cleaner, carburetor (above throttle
blade) or intake manifold), the pressure drop through the
canister and the size of the controlling orifice (located in
either the canister or purge port). A diagram of a typical
evaporative control system is presented in Figure 2-1.
2. System Working Capacity
The actual mass of gasoline vapors that an evaporative
control system will continually adsorb and desorb during
operation is referred to as the "system working capacity".
This working capacity will be dependent upon many factors, some
of which are internal to the system and others that are
external. Among the internal factors are: the volume of
charcoal in the canister, the physical characteristics of the
charcoal, the canister configuration, and the volume of purge
air drawn through by the control system. Factors that also
-------
Figure 2-1
Typical Evaporative Control System
Carb. Bowl
Fitting
Carb.
Bowl Valves
0.047" Bleed
To Fuel Tank
Purge
Valve. Drilled
To 0.180"
Carton-
TO
PORTED
VACUUM
VAPOR TO
INDUCTION
SYSTEM
DIAPHRAGM;
BODY
COVER
VALVE
STEM
COVER
VAPOR
FROM
FUEL
TANK
•Foam
IrtMesh
•Fiberglass Air Filter
TO
MANIFOLD
VACUUM
SIGNAL
VAPOR
FROM
BOWL
VENT
DIAPHRAGM
ING
10
M
CD
FILTER
RETAINER
UNDER
VACUUM
-------
2-19
play a role in determining system working capacity, but which
are subject to little or no system control, include: the
temperature and humidity of purge air and the vapor
concentration of the evaporative emissions. This latter effect
was noted in an EPA report comparing the ability of two
different charcoals to adsorb and desorb HC vapors using fuels
of varying volatility, and will be discussed further in Chapter
3.[3]
Manufacturers can design evaporative emission control
systems to have a specific system working capacity by adjusting
those factors that are subject to their control, with
consideration given to the variations in the external factors
mentioned previously. Current certification tests are
performed using Indolene, which has an average Reid Vapor
Pressure (RVP) of 9.0 psi; therefore, this is the volatility
level at which current evaporative control systems are designed
to meet the current evaporative HC standard of 2 grams/test.
Actual in-use fuel, however, has an RVP closer to 11.5 psi
during the summer months, representing higher levels of
evaporative emissions than those encountered by the canister
during the certification test. Thus, there exists a
significant difference in the levels of emissions that current
evaporative control systems are designed to capture and those
that are encountered in actual operation.
B. Fuel Volatility
1. Proper Measure of Fuel Volatility
A number of different gasoline properties may be used to
indicate gasoline volatility. Each year, in a document
referred to as D-439, the American Society of Tests and
Measurements (ASTM) publishes recommended limits for several
gasoline volatility parameters, including Reid Vapor Pressure
(RVP), distillation characteristics (such as the temperature at
which a given percentage of gasoline is evaporated), and the
temperature corresponding to a given gasoline vapor-to-liquid
ratio (V/L). For every month of the year, each state is
assigned a "volatility class" that represents ASTM's
recommended limits on the volatility of gasoline sold in that
state. The five gasoline volatility classes are designated as
A, B, C, D, and E; corresponding volatility limits for these
five classes are shown in Table 2-5. As indicated, Class A is
the least volatile and Class E is the most volatile. It should
be noted that these ASTM specifications are merely recommended
levels and are not legally binding for gasoline refiners. A
number of states have adopted ASTM standards as legal limits.
However, the effectiveness of these limits depends directly on
enforcement and it is questionable how strictly these limits
are enforced in many states (California being an exception).
-------
2-20
Table 2-5
ASTM D-439 Gasoline Volatility Specifications
Distillation Temp.
(°F) at
Given Percent Evaporated
ASTM
Volatility
Class
A
B
C
D
E
Max. RVP
(psi)
9.0
10.0
11.5
13.5
15.0
Max. Min.
@ 10% @ 50%
(T10) (Tso)
158 170
149 170
140 170
131 170
122 170
Max.
@ 50%
(Tso)
250
245
240
235
230
Min . Temp .
@ V/L =
f ^n
V ^ 2 O V / 1* t
140
133
124
116
105
20
,°F)
-------
2-21
Measured in-use RVP levels (grouped according to ASTM
volatility class) and the effect of state limitations are
addressed in more detail in Section 2 below.
The major reason behind ASTM's assignment of volatility
limits is the prevention of vapor lock at high ambient
temperatures and problems with starting the engine under colder
conditions. As shown in Table 2-5, values for RVP,
vapor-liguid ratio, and distillation temperatures are defined
for each of the five fuel volatility classes (A through E). In
turn, minimum and maximum ambient temperatures under which no
problems with cold startability or vapor lock would occur are
calculated for each volatility class. Then, temperature data
for each geographical area are used to select the appropriate
volatility classes for each month of the year. A U.S. map
indicating ASTM's state volatility class recommendations for
the month of July is provided in Figure 2-2.
In order to determine the most significant gasoline
volatility parameters with respect to the magnitude of
evaporative HC losses, it is important to consider the source
of the evaporative emissions. The measure of fuel volatility
relevant to diurnal emissions should ideally reflect volatility
at temperatures typically associated with a vehicle's fuel
tank. The most widely accepted measure of volatility in
relation to diurnal emissions is RVP, a measure of the fuel's
vapor pressure at 100°F.[4,5]
Hot-soak emissions originate both from the fuel tank and
the fuel metering system, as indicated previously. The process
occurring in the fuel tank is much the same as with diurnal
emissions. Therefore, RVP is an appropriate measure of
volatility for this portion of the hot-soak emissions. On the
other hand, since the temperatures experienced in the fuel
metering system can be much higher than 100°F, RVP may not be
ideal as an overall indicator of hot-soak emission levels. The
relationship between temperature, volatility and evaporative
losses is not as clear in a carburetor or fuel injector as in
the fuel tank due to the complex interactions that occur. [6]
Only limited work in this area has been done with fuel-injected
vehicles, but carbureted vehicles have been studied fairly
extensively. Hot-soak losses from a carbureted vehicle are
generally felt to be related also to the mid-range volatility
of the fuel, given as the percent of fuel volume distilled in
an ASTM D216 distillation at the peak temperature in the
carburetor bowl.[4,6-9] This peak temperature will vary from
vehicle to vehicle and may also be affected somewhat by the
ambient temperature. An average value for the peak bowl
temperature is around 160°F and, therefore, the percent of fuel
-------
Figure 2-2
ASTM's July Volatility Classes
1^11*555
.sssr—
17^
A = 9.0 psi
B = 10.0 psi
C = 11.5 psi
"X.
-------
2-23
evaporated at 160°F (%iso), in addition to RVP, may be a
relevant fuel parameter for estimating hot-soak losses.[4,7]
EPA is currently testing several fuels with the same RVP but
with varying %i6o points; hot-soak and diurnal losses are
being measured for a total of 40 carbureted and fuel-injected
vehicles to determine the impact, if any, of %i6o- As only
very preliminary data are available at this time, no
conclusions can be made.
Theoretically, because total evaporative HC emissions are
represented by the sum of hot-soak and diurnal losses, the
ideal measure of fuel volatility to be used in evaluating
various evaporative emission control strategies would most
likely be some combination of both RVP and %iso. The
weighting given each of these factors would be expected to vary
with vehicle type, as fuel-injected vehicles have significantly
lower hot-soak emissions and, thus, their relative losses would
be more dependent upon RVP. Also, operating temperatures can
vary from model to model, so 160°F may not be the appropriate
point on the distillation curve for all vehicles.
Some attempts have been made to incorporate both RVP and
various distillation points into a volatility index. In an
effort to correlate evaporative emissions to the volatility of
gasolines and methanol/gasoline blends, DuPont developed the
Evaporative Index (El), as shown below:
El = 0.85(RVP) + 0.14(%20o> - 0.32(%100).[10]
In their application for a waiver of methanol blends, DuPont
showed a correlation of El versus evaporative emissions with an
R2 value of 0.86.[10] However, some criticisms have been
raised with respect to DuPont's analysis, such as their
combining the results of two independent testing programs
without normalizing the results and the lack of higher
volatility gasolines and blends in the analysis.[11,12]
The Front End Volatility Index (FEVI), which was developed
for purposes other than emissions estimation (primarily the
control of vapor lock), is defined as:
FEVI = RVP + 0.13(%1S.)•[13]
This index essentially includes the two terms most relevant to
evaporative emissions (%isi is very close to %ieo).
However, it is currently unknown if its relative weighting of
the two parameters is appropriate.
-------
2-24
Another gasoline property used to measure volatility is
the temperature corresponding to a specified gasoline
vapor-to-liquid ratio (V/L) at atmospheric pressure. This V/L
is the volume of vapor formed at atmospheric pressure and test
temperature divided by the initial volume of liquid gasoline
tested. The temperature at which this vapor-to-liquid ratio is
equal to 20 at atmospheric pressure is designated TZOVXL.
The TZOVXL parameter is included in the ASTM volatility
specifications (shown in Table 2-5) and, according to API, is
commonly used for blending purposes by refiners. Since
limiting TZOVXL can affect the other evaporative-related fuel
parameters, it deserves further discussion here.
ASTM D-439 provides an empirical equation defining
TZOVXL as a function of the following parameters: RVP, the
temperature at which 10 percent of the gasoline is evaporated
(Tio), and the temperature at which 50 percent of the
gasoline is evaporated (T5o). This equation is:
TZOVXL - 114.6 - 4.KRVP) + 0.2(T10) + 0 . 17(TS o ) - [ 14 ]
In the above equation for TZOVXL, RVP contributes
significantly more to TZOVXL than does Ti0 or Tso.
According to survey data, fuels with RVPs ranging from 11.5 to
9.5 psi have Ti0s ranging from 108-120°F and Tsos ranging
from 210-220°F.[15] This 2-psi RVP range accounts for roughly
an 8°F change in TZOVXL, if TIO and Tso are held
constant. If the corresponding Ti0s and Tsos for the
different RVPs are used in the TZOVXL equation, then the
TZOVXL changes by nearly 12°F. This indicates that RVP is
the major factor affecting TZOVXL, but Tio and T5o are
not negligible.
As mentioned earlier, El and FEVI are indices relating RVP
and distillation curve characteristics to gasoline volatility.
The two are compared to TZOVXL in the following paragraphs.
El is similar to T20VxL in that both equations use RVP
and two points on the distillation curve — one near 100°F
(Tio) and the other near 200°F (Tso). The equation
estimating TZOVXL is more readily understandable than that
for El, because the positive or negative signs of the
coefficients reflect the trend in basic gasoline volatility
changes with the specific parameters of the equation. For
instance, as RVP increases, volatility increases and TZOVXL
decreases; also, as Tio decreases, volatility increases and
TZOVXL decreases. This is not the case for El (where a high
El indicates high volatility) because as %ioo, increases,
volatility should increase, yet El decreases. Nevertheless, of
all the terms in the equations, RVP has the most significant
impact on both El and TZOVXL. In each case, for a 2-psi
-------
2-25
change in RVP (11 psi to 9 psi) and corresponding distillation
characteristics, the change in RVP accounts for 70-80 percent
of the net change in the indices.
According to industry, FEVI and T20vxL are closely
related and serve the same function in indicating gasoline
volatility. Examination of the fuel properties reported in
MVMA's summer gasoline surveys for 1977 through 1984 indicates
an excellent correlation between FEVI and T20v/i. (as
calculated from ASTM's emperical equation). The R2
correlation factor for T20vxL vs. FEVI ranged from 0.90 to
0.99 when MVMA's fuel samples were broken down by year and by
volatility class. Theoretically, because of this close
correlation and the fact that FEVI is dependent on only RVP and
%is«, controlling these two parameters should closely control
TZOVXL. Again, RVP is the more significant of the two
parameters, accounting for over 70 percent of the change in
FEVI for a 2-psi change in RVP (from 11.5 psi to 9.5 psi).
From the above discussion, it appears that RVP and %iso
are the most relevant of the available fuel parameters to
indicate evaporative emission potential. The other parameters,
El, FEVI and T20vxL all essentially combine RVP with
higher-temperature volatility indicators, but it is not clear
that any of the three particular combinations adequately
represent the overall evaporative emission potential for motor
vehicles. It appears safer to address the two parameters
separately at this point. However, as indicated above, little
is currently known of the effect of %ieo on evaporative
emissions. Thus, this evaporative study will focus primarily
on RVP as the most relevant measure of fuel volatility until
such time as sufficient data are available to conduct a similar
analysis of %i6 o•
This limitation should not be of major concern since: 1)
RVP is the dominant factor in both FEVI and El, which have been
used in the past to indicate overall evaporative emission
potential, and 2) the vast majority of post-1990 vehicles are
expected to be fuel-injected, which means that an even larger
portion of their hot-soak (and total) evaporative losses will
originate in the fuel tank — where RVP is the most appropriate
parameter — than occurred with the carbureted vehicles used in
the El and FEVI studies.
2. Historical and Future Trends in Gasoline Volatility
Over the past decade, the volatility of commercial
gasoline has gradually, but steadily, been increasing. This
section reviews regional and nationwide RVP trends over time,
along with a state-by-state comparison of violations of the
-------
2-26
fuel volatility limits suggested by ASTM versus the actual fuel
inspection laws, if any, enforced by the State governments.
Trends in gasoline volatility measures other than RVP are also
reviewed here. Summer gasoline volatility is the focus
because, as concluded in Section II of this chapter, in-use
fuel control only during the summer months could have an impact
on the majority of ozone violations.
Trends in commercial gasoline volatility were traced using
results of two separate fuel surveys prepared each summer by
the National Institute for Petroleum and Energy Research
(NIPER) and the Motor Vehicle Manufacturers Association
(MVMA).[16,15] Table 2-6 presents RVP trends for the 15
non-California regions included in the NIPER survey. As shown,
overall non-California averages indicate a 9-percent increase
in summer unleaded fuel RVP levels over the past 10 years.
Increases within individual regions vary between 6 and 19
percent, with the greatest summer increase occurring in
northern Illinois (sample area is Chicago).
To examine volatility trends over the past twenty years,
it is necessary to look at leaded fuel which, of course, has
been in use longer than unleaded fuel. National-average
results of NIPER leaded gasoline surveys are presented
graphically in Figure 2-3.[16] As shown in the top graph, the
most significant summer RVP "boosts" occurred first in the
1972-74 period, and then again in 1981. Prior to 1972, summer
fuel RVP levels were well within the range specified in the
Code of Federal Regulations (CFR) for certification test fuels
(8.7 to 9.2 psi); however, by the time the SHED* test began
with the 1978 model year, the certification fuel RVP had been
exceeded by the in-use fuel national average (approximately 9.6
psi). Since then, the CFR specifications have become even less
representative of commercial fuel volatility, based on a 1984
summer leaded fuel average RVP of 10.3 psi for the nation
(shown in the figure). Curves for T90, Tso/ and T10
(also presented in Figure 2-3) support the trend in increasing
gasoline volatility, as well.
Results of the other fuel survey mentioned — conducted by
MVMA[15] — are presented in Table 2-7. Here, instead of
segregating by geographic region, average volatility
characteristics for unleaded regular gasoline are shown for
ASTM classes A, B, and C (as defined in Table 2-5). According
to these survey results, the average RVP in Class C areas has
increased by almost 10 percent over the past seven years to a
level approaching 11.0 psi. Trends in other volatility
parameters such as TK>, Tso/ %is«, and T2ov/L (all
Sealed Housing Evaporative Determination, which is the
current test procedure.
-------
Region
Table 2-6
NIPER Survey Results[16]; Summer Gasoline RVP Trends by Region*
Northeast
Mid-Atlantic Coast
Southeast
Appalachian
Michigan
Northern Illinois
Central Mississippi
Lower Mississippi
Northern Plains
Central Plains
Southern Plains
Southern Texas
Southern Mountain
Northern Mountain
Pacific Northwest
National Average**
(excluding California)
Years
1974
9.8
9.3
9.6
10.5
10.5
9.5
10.1
9.4
—
—
9.2
9.1
8.4
8.9
9.5
9.5
1975
10.0
10.1
9.6
10.6
10.4
10.5
10.1
9.6
9.6
9.1
9.3
9.5
8.9
10.1
9.9
9.8
1976
10.2
10.1
9.7
10.5
10.6
10.3
9.9
9.6
9.9
9.2
9.2
9.4
8.7
9.5
10.6
9.8
1977
10.7
10:4
9.5
10.4
11.0
11.0
9.9
9.5
—
9.0
9.3
9.6
8.8
9.9
10.4
10.0
1978
10.5
10.1
9.4
10.1
11.2
10.8
10.1
9.8
—
8.8
9.1
9.5
8.9
9.9
10.0
9.9
1979
10.5
10.2
9.6
10.6
10.9
10.9
10.4
9.5
9.2
9.2
9.5
9.4
8.7
9.6
10.3
9.2
1980
10.8
10.3
9.8
10.5
11.3
10.9
10.3
9.7
9.8
9.2
9.2
9.2
8.9
9.5
10.8
10.0
1981
10.8
10.6
9.9
10.9
10.9
11*1
9.7
9.3
—
—
9.7
9.4
8.4
9.2
11.0
10.1
1982
10.9
10.8
10.1
11.1
11.2
10.8
10.5
10.1
11.0
10.2
10.0
10.3
8.8
10.4
10.8
10.5
1983
10.5
10.7
10.3
11.4
11.6
11.7
11.0
10.1
11.0
10.0
9.8
10.2
9.1
10.4
11.2
10.6
1984
10.7
10.8
10.2
11.1
11.5
11.3
10.9
10.0
10.5
10.0
9.8
10.3
8.9
9.7
10.8
10.4
% Increase
over Decade
9
16
6
6
10
19
8
6
9
10
7
13
6
9
14
9
to
*
**
Unleaded regular gasoline only (R + M/2 less than 90).
Calculated as a straight arithmetic average of the 15 regional averages listed.
-------
2-28
Figure 2-3
Volatility Trends in Leaded Gasoline
(NIPER Survey Results)[16]
KŁ
25
«Ł
13.0
10.0
9.0
nn
H *
»-
-n
=—
' — 1 —
^v
-
•_•*
P-— «
Su
nttr
IMM
k
-^
^
x,
x'1
^^
.
— ^
en
o
1959'60'61 '62 '63 '64 '65 '66 '67 '68 '69 '70 Tl '72 '73 '74 '75 T6 77 '78 '79 '80 61 82 83 84
- Trends of certain characteristics of leaded (regular) grade
gasoline through summer 1980; leaded antiknock (R+M)/2
below 93.0 grade gasoline beginning winter 1980-81.
-------
Table 2-7
MVMA Survey Results[15]:
Summer Gasoline Trends by ASTM Volatility Class*
No. of
Volatility Gasolines
Year Class Sampled
1977
1978
1979
1980
1981
1982
1983
1984
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
37
66
121
38
68
123
37
67
120
39
66
124
41
66
126
37
65
125
39
64
128
39
60
125
Avg.
RVP
(psi)
8.53
8.72
9.94
8.25
8.56
9.67
9.79
10.10
11.33
8.27
8.71
9.88
8.65
9.30
10.46
9.16
9.79
11.06
9.06
9.65
10.84
8.80
9.54
10.89
% of Sample
Above ASTM
RVP Max.
27.0
0.0
0.0
13.2
0.0
0.8
64.9
55.2
37.5
20.5
0.0
1.6
22.0
6.1
1.6
37.8
33.8
28.8
33.3
31.2
15.6
28.2
28.3
22.4
Avg.
T,0
(°F)
131.6
128.0
121.9
129.0
127.8
120.8
124.4
123.6
115.2
123.8
120.9
113.0
122.4
122.0
114.6
123.8
122.5
114.0
122.4
120.1
113.2
118.7
117.5
108.8
Avg.
Tso
<°F)
225.9
218.3
220.9
222.9
219.8
220.0
223.7
219.4
221.4
222.5
217.9
218.5
219.1
218.1
215.6
220.0
218.4
215.6
220.2
216.6
214.7
210.9
210.7
206.7
Avg.
%l 58
(%)
21.5
23.4
25.5
22.5
23.2
25.8
24.0
25.0
28.0
23.4
25.6
28.4
25.8
25.9
29.3
25.2
26.0
29.6
25.4
26.5
29.6
28.5
28.7
32.7
Avg.
TZOVXL
(°F)
144.3
141.6
135.8
144.5
142.4
136.5
137.4
135.2
128.8
143.3
140.1
133.8
140.9
137.9
131.3
139.2
136.1
128.7
139.4
135.9
129.3
138.1
134.8
126.8
% of Sample
Below ASTM
Minimum
_T_20V/L_
24.3
4.6
0.0
23.7
4.4
0.0
62.2
47.8
22.5
28.1
4.6
0.8
26.8
10.6
4.0
43.2
30.8
11.2
46.2
29.7
10.9
51.3
43.3
30.4
to
to
Unleaded regular gasoline only (R + M/2 less than 90),
-------
2-30
defined in the previous section) are also shown in Table 2-7.
These trends also indicate increasing fuel volatility over the
past few years (i.e., lower Ti0, TSo, and T20v/L, and
higher %ist). It is important to note that %is« — close
to the %iso parameter associated with hot-soak emissions in
the previous section — has increased significantly by 28
percent (from 25.5 percent to a current average level of 32.7
percent) in Class C areas.
Pool average gasoline volatility properties for Class C
gasolines are similar to those of unleaded regular gasoline
described above. From 1977 to 1984, pool average RVP and
%ist, as determined from MVMA survey data (unleaded regular,
unleaded premium, and leaded regular gasolines weighted 65
percent, 18 percent, and 17 percent, respectively) have both
increased significantly. RVP has increased from 9.94 to 10.89
psi, and %ist increased from 26.6 to 32.6 percent.
Alcohol blends have, as a whole, higher volatility than do
alcohol-free gasolines. The MVMA survey data reviewed above
for alcohol-free gasoline volatility properties did not contain
data on methanol blends, but did have volatility properties for
ethanol blends.[15] Average RVP for eight 1984 gasoline
samples containing an average of 9.4 percent ethanol was 12.3
psi. Average %ist was 44.6 percent. These levels are very
similar to those of twelve 1983 gasoline samples also
containing an average of 9.4 percent ethanol. Average RVP from
these 1983 gasoline samples was 12.3 psi, and average %is»
was 42 percent. Over these two years, %is§ ranged from 30 to
55 percent while RVP ranged from 12 to 13.3 psi. These data
indicate that Class C ethanol blends are significantly more
volatile than Class C alcohol-free gasolines.
According to some theories, the increase in fuel
volatility seen in alcohol-free gasoline is linked to the lead
phasedown in gasoline over the past decade. Because of the
reduction and/or elimination of the traditional octane-booster
— lead — refiners must process heavier crudes in order to
obtain the clear, high-octane fractions. As more crude
undergoes hydro-cracking, more butane is produced; because
butane enhances octane, and because the supply is in excess, it
is allowed to remain a component of the gasoline.
Unfortunately, butane is also a major volatility enhancer and
its abundance is most likely the major reason for the increase
in RVP over time.
As mentioned earlier, ASTM's volatility specifications are
not enforceable by law, but are merely levels agreed upon by
members of the refining industry. However, some states have
adopted ASTM's RVP limits as part of their own gasoline
inspection laws, which are enforceable.
-------
2-31
Among the states which have adopted fuel volatility
controls, the assigned RVP limits vary from month-to-month (as
they do in the ASTM specifications) according to temperature
conditions.* For the purposes of comparison to ASTM's D-439
limits, July was focused on, as this summer month is
characteristic of high ozone violations (as mentioned in
Section II of this chapter).
A comparison of state laws versus ASTM limits on RVP for
the summer months is presented in Table 2-8. As shown, 21 of
the states do not currently have inspection laws governing the
RVP of gasoline sold within their boundaries.** Sixteen states
have simply adopted ASTM's current year-round D-439 limits as
law; in addition to these, four more states have RVP limits
that correspond to ASTM's specifications at least during July.
Among those state laws that differ from ASTM's D-439, there is
a month-to-month variation involved in the comparison; for
example, Alabama is more restrictive than ASTM in June and
July, but less restrictive in August and September. However,
as July is the focus here, the comparison is simplified.
During this month, three states are more restrictive than ASTM
and six are less restrictive (as indicated in Table 2-8).
In an effort to determine the effectiveness of ASTM's
recommendations and State laws, fuel survey data were compared
to these standards. Part of this comparison was shown
previously in Table 2-7. As indicated there, over 22 percent
of the Class C fuels sampled by MVMA in 1984 exceeded ASTM's
maximum RVP specification of 11.5 psi; of these same samples,
over 30 percent were below ASTM's recommended minimum level for
T20V/L.[15]
In Table 2-9, this comparison is put on a state-by-state
basis. Here, the states are divided between those that have
implemented gasoline RVP standards and those that have not. In
turn, post-1982 NIPER summer survey results for these states
were compared to both ASTM and State RVP standards for the
month of July. As shown, 11 states have average RVPs above
their respective ASTM specifications; 10 of these states have
their own RVP standards and the other one does not. Further,
of the 28 states having their own RVP limits (Hawaii excluded),
roughly one-third of them had average summer RVPs above these
State standards. Therefore, enforcement appears to be somewhat
ineffective.
* The only exceptions to this are Louisiana, Wyoming, and
Hawaii, which hold RVP constant throughout the year at
13.5, 13.0, and 11.5 psi, respectively.
** Washington, D.C. is included as one of the 24 states.
-------
Table 2-8
Comparison of Summer RVP control: State Laws versus ASTM Limits*
States Same as ASTM**
Arizona (A)
Arkansas (B)
Colorado (B/A)
Delaware (C)
Florida (C)
Georgia (C/B)
Hawaii (C)
Idaho (B)
Illinois (C,C/B)
Iowa (B/C)
Missouri (B)
Nebraska (B)
New Mexico (A)
No. Dakota (B)
Rhode Island (C)
So. Carolina (C/B)
Tennessee (C/B)
Utah (B/A)
Virginia (C)
Wisconsin (C)
States More
Restrictive than ASTM
Alabama (C/B)
Mississippi (C/B)
No. Carolina (C/B)
States Less
Restrictive than ASTM
Indiana (C)
Louisiana (C/B)
Maryland (C)
Montana (B)
So. Dakota (B)
Wyoming (B)
States With No
RVP Specifications
Alaska (D)
Connecticut (C)
Wash., D.C. (C)
Kansas (B)
Kentucky (C)
Maine (C)
Massachusetts (C)
Michigan (C)
Minnesota (C)
Nevada (A,B)
New Hampshire (C)
New Jersey (C)
New York (C)
Ohio (C)
Oklahoma (C)
Oregon (B,C)
Pennsylvania (C)
Texas (A,B)
Vermont (C)
Washington (B,C)
West Virginia (C)
CJ
NJ
**
Summer month examined is July; California is excluded from the comparison.
ASTM volatility class specifications for each state given in parentheses.
Sources:
ASTM's Standard Specification for Automotive Gasoline, D-439-83.
API's Digest of State Inspection Laws—Petroleum Products, Fourth Edition.
-------
2-33
Table 2-9
Comparison of Post-1982 NIPER Survey Results [16] to July ASTM and State RVP Standards
States with RVP Standards States without RVP Standards
A*
A/B
B
B/C
Max. ASTM RVP (psi) 9.0 10.0 10.0 11.5 11.5
Avg. of State
RVP Standards (psi) 9.0
9.8
10.1 10.5 11.7
A*
9.0
A/B
B
B/C
10.0 10.0 11.5 11.5
No. of States**
No. of States
with Average
RVPs above
ASTM Specs.
No. of States
with Average
RVPs above
State Stds.
14
* "A" through "C" designate ASTM volatility classes as defined in ASTM's
D-439 and reviewed in Table 2-5.
** Hawaii and Alaska excluded due to lack of fuel survey data.
-------
2-34
Several basic conclusions can be made from the information
presented in the above discussions. One, gasoline volatility
has been gradually increasing over the past two decades and no
substantial data exist to indicate that this trend will not
continue. Two, ASTM recommendations and State-implemented
volatility limits appear to be somewhat ineffective in
controlling gasoline volatility. Even if ASTM specifications
were currently restricting RVP — and they may indeed be —
there is some speculation that they could be changed in the
future. Revisions have been made in the past as vehicles have
been designed to handle more volatile fuels. The projected
widespread use of fuel injection systems continues this trend,
so a relaxation of the current ASTM RVP limits is not
inconceivable. Third, the current average RVP in Class C areas
is roughly 11.0 psi, which is approaching the maximum ASTM
specification of 11.5 psi. Based on these observations, then,
this study assumes that, by 1988, gasoline RVP will on average
rise to equal the ASTM limits for each state. (Chapter 6 will
address the sensitivity of this assumption by examining the
cost effectiveness of the control strategies starting from a
baseline RVP of 0.5 psi below ASTM limits, instead of just at
the limits.)
3. Effect of Weathering on Fuel Volatility
The volatilities reported in various fuel surveys (e.g.,
NIPER, MVMA) represent those levels measured at the gasoline
pump. However, as the gasoline in the vehicle's fuel system
responds to daily diurnal temperature changes and engine heat,
some of the lighter hydrocarbons are lost. Thus, the
volatility of the fuel gradually decreases. This phenomenon of
"weathering" is an important consideration in assessing
evaporative emissions that actually occur in the field.
An EPA-sponsored study recently conducted by Southwest
Research Institute (SwRI) examined the effects of weathering on
the RVP of gasoline as the vehicle's fuel tank is gradually
emptied. Two vehicles were driven approximately 50 miles each
day and allowed to soak overnight in a shaded area; each day,
the RVP of the fuel remaining in the tank was measured. This
process was continued over roughly five days until the fuel
tank (which started out completely full) was essentially
empty. Three fuels of varying initial RVP (roughly 9.0, 10.5,
and 12.0 psi) were examined. Test results indicate that, in
general, as a vehicle's fuel tank goes from full to empty, the
RVP of the originally dispensed fuel decreases by an average of
9 percent. [17] For example, a fuel dispensed with an RVP of
11.5 psi could weather to a final RVP of about 10.5 psi if the
fuel tank was allowed to empty out completely without being
refilled. Of course, this is not the norm in the field, so
dispensed fuels most likely never weather to this great an
-------
2-35
extent before refueling takes place. This weathering effect
appears to be independent of the fuel tested, but could vary
with other test parameters (i.e., length of soak period, soak
temperature, distance driven, number of trips per day,
etc.).[17]
General Motors has also conducted tests examining the
effect of weathering on fuel volatility and evaporative
emissions. Unlike the SwRI work, chassis dynamometer tests
(i.e., FTP and HFET) and standard diurnal and hot-soak cycles
were used to simulate typical urban driving conditions instead
of actual highway driving and 24-hour outside soaks. GM's
testing of two fuels showed the original RVP to decrease from
between 9 and 15 percent from tank fill-up to the empty
point.[18] As mentioned earlier, most vehicles in the field
are not permitted to go completely empty, so a mid-range level
is probably more representative. At the 40-percent fill level
specified in EPA's evaporative test procedure, GM showed an RVP
decrease of 6-13 percent due to weathering.[18] According to
GM's data, this change in RVP results in a decrease in
uncontrolled* diurnal evaporative emissions of approximately 15
percent (again at the 40-percent fill level).[18]
At this point, the effect of weathering on fuel RVP and,
thus, evaporative emissions has not been factored into this
analysis. Additional work in this area is required before this
could be done confidently. However, GM's estimated 15-percent
decrease in diurnal emissions is used in an initial attempt to
account for weathering in Appendix 2-A, which examines the
effects of various environmental conditions on evaporative
emission levels. Although more work is required, at this
point, the absence of an explicit consideration of weathering
should not have a significant net impact on the results of the
study.
C. Use of Alcohol Blends
As a result of the oil crisis in the early 1970's, efforts
were begun in the United States to reduce the dependence on
imported oil. One idea eventually introduced was the use of
alcohols in gasoline to extend the supply of gasoline. .The
Environmental Protection Agency (EPA), under Section 211(f) of
the Clean Air Act, must approve any new unleaded fuels which
are not substantially similar to fuels already permitted in the
market. Since 1978, the EPA has granted waivers for two
ethanol/gasoline blends and four methanol (and
"Uncontrolled" refers to the lack of an evaporative
control system on the vehicle.
-------
2-36
cosolvent)/gasoline blends. The most recent waiver granted for
the DuPont application places an evaporative index (El) limit
on the waived fuel to assure that evaporative emissions do not
increase compared to those with typical in-use gasolines.[19] A
list of all waivers granted is shown in Table 2-10. Currently
in the United States, ethanol blends comprise 6-7 percent of
the total gasoline market and methanol blends comprise 3-4
percent of the total gasoline market.[20,21]
l. Effect on Fuel Volatility Parameters
The addition of a polar alcohol affects the properties of
the non-polar gasoline to which it is added. The primary
effect is on the distillation curve and, thus, the parameters
associated with volatility. Three of these parameters,
discussed in detail in Section IV.B of this chapter, are RVP,
FEVI, and El.
Although the exact distillation effects of alcohol
addition to gasoline vary for every base gasoline, some general
effects are common. Theoretically, the addition of a pure
compound to gasoline causes the percent evaporated at a
specified temperature, compared to the straight gasoline, to
decrease at temperatures below the boiling point of the
compound added. At that point, that compound is distilled off
and the percent evaporated at higher temperatures (compared to
straight gasoline) is increased by the presence of the
compound. However, both methanol and ethanol form azeotropes
with many of the components in gasoline. An azeotrope is a
mixture of a particular composition of two or more components
which, in the case of alcohols and gasoline, has a constant
boiling point lower than that of either individual compound.
The combination of these two effects causes the percent of fuel
evaporated at certain temperatures to be greater for an alcohol
blend than for straight gasoline, and to an extent much greater
than the percentage of the alcohol alone. This effect on
distillation occurs primarily in the boiling temperature range
from the lowest-boiling azeotrope to the highest-boiling
gasoline component forming an azeotrope.
As discussed earlier, RVP is a measurement of the
volatility of a fuel at 100°F. Since the vapor pressures of
methanol and ethanol are lower than gasoline at 100°F, the
addition of these alcohols to a gasoline could theoretically
cause the RVP of the alcohol blend to be lower than that of the
straight gasoline. Once again, however, the presence of highly
volatile azeotropes erases this effect and causes an increase
in the RVP. The precise increase in RVP varies for every base
gasoline, but the increases from each alcohol are generally
similar. For the addition of methanol alone to gasoline at
-------
2-37
Table 2-10
Clean Air Act,Section 211(f) Waivers
Name
1. Gas Plus Inc.
"Gasohol"
2. Synco 76 Fuel
Corp.
3. Sun Petroleum
Products Co.
4. Anafuel
"Petrocoal"
5. ARCO "Oxinol"
6. DuPont
Date Granted
12/16/78
(w/o decision)
5/18/82
6/13/79
9/28/81
11/7/81
1/14/85
Limitations
-up to 10% (vol.) anhydrous
EtOH
-up to 10% (vol.) EtOH
-proprietary additive
-up to 5.5% (vol.) of a 1:1
MeOH/TBA mixture
-up to 12% (vol.) MeOH
-up to 6% (vol.) butanols
-proprietary inhibitor
-up to 4.75% (vol.) MeOH
-up to 4.75 (vol.) TEA
-ratio of MeOH: TEA cannot
exceed l
-up to 5% (vol.) MeOH
-at least 2.5% (vol.)
cosolvent (EtOH, propanol,
butanols)
-proprietary corrosion
inhibitor
-must meet El
specifications set for
ASTM class areas
EtOH = ethanol.
MeOH = methanol.
TEA = tertiary butyl alcohol.
-------
2-38
2-10 percent (by volume), the increase in RVP is around 3 psi.
For the addition of methanol with a cosolvent (ethanol,
propanols, and/or butanols) to gasoline at 5-10 percent of
total volume, the increase in RVP is slightly less — around 2
psi. The increase in RVP for the addition of 2-10 percent (by
volume) ethanol to gasoline is around 1 psi.[11]
A second volatility measure discussed earlier is FEVI.
The addition of alcohol to gasoline will increase the FEVI by
the same amount as the RVP is increased, plus by an additional
amount due to the increase in volatility at 158°F (%iss).
From a review of data, it appears that for both methanol and
ethanol blends allowed by waiver, the %isi is increased by
roughly 10-15 percent, resulting in an additional 1.3- to 2-psi
increase in the FEVI.[10,22-24] (Typical distillation curves
for methanol and ethanol blends are shown in Figures 2-4 and
2-5). The total increase in FEVI is around 4.3-5 psi for a
methanol blend, approximately 3.3-4 psi for a methanol with
cosolvent blend, and approximately 2.3-3 psi for an ethanol
blend.
A third volatility measure discussed earlier is El. The
addition of alcohol to gasoline will increase the El because of
the resulting increase in RVP and an increase of 5-10 percent
in the %20o.[10,22-24] (See Figures 2-4 and 2-5). However,
the effect of alcohol on the %ioo is rather unpredictable.
In some cases the alcohol causes the %ioo to decrease by 1-2
percent, but in many cases neither the gasoline nor the alcohol
has begun to boil at 100°F. The combination of the alcohol
effects produces increases in El over the straight gasoline of
approximately 3-4 psi for methanol blends, 2.5-3 psi for
methanol with cosolvent blends, and 1.5-2 psi for ethanol
blends.
The effects of alcohol addition on RVP, FEVI and El can be
counteracted by adjusting the contents of the gasoline to which
the alcohol is added. By removing lighter hydrocarbons (such
as butanes and/or pentanes), the RVP, %is«, FEVI or El of the
final blend can be controlled to levels of the original
straight gasoline. However, the evaporative emissions of
automobiles using the volatility-controlled alcohol blends
could still be significantly greater than straight gasoline, as
some data show.
2. Effect on Evaporative Emissions
The reported effects of alcohol blends on evaporative
emissions vary widely and can be examined in two ways: 1) by
comparing a gasoline and a volatility-controlled blend of egual
RVP, FEVI or El, and 2) by comparing a gasoline and a high-RVP
-------
2-39
Figure 2- 4
Typical Methanol Blend Distillation Curves [22]
Cv«Mr«U4
-------
2-40
Figure 2-5
Typical Ethanol Blend Distillation Curves [23]
I
Tft «
Percent Evaporated
-------
2-41
blend in which the alcohol (with or vithout cosolvent) is
simply splash-blended into a similar gasoline. In the first
case, the results for methanol blends show anywhere from no
effect to a 95-percent increase in evaporative emissions with
the volatility-controlled blend over the straight
gasoline.[11,22,25,26] For the second case, the reported
increase in evaporative emissions with the methanol blend is
between 40 percent and 325 percent.[26-28]
Reported increases in evaporative emissions with the use
of ethanol blends also vary widely. In the controlled
volatility case, the increases in evaporative emissions
reported for ethanol blends are between 25 percent and 170
percent.[29,30] For the splash blend case, evaporative
emissions are reported to increase between 5 and 220
percent.[29-34] Currently, ethanol can be added directly to
gasoline without any legal requirement for volatility controls,
whereas methanol blends generally must meet the same ASTM
specifications applicable to gasoline.
Even with control of alcohol blend volatility, there can
be an increase in evaporative emissions due to intermittent use
of blends and gasoline. A phenomenon called commingling can
occur when an alcohol blend is added to a tank partially filled
with straight HC gasoline, wherein the RVP of the mixture can
be significantly higher than the RVP of the original gasoline
or blend. Commingling is depicted in Figure 2-6, where the
increase in RVP (over the straight HC gasoline level) is shown
as a function of blend ratio and type of blend. For example,
in the top plot, if a 1:1 MeOH/isopropyl alcohol blend (9.6% by
volume) is added to fill a 60-percent full tank of straight HC
gasoline, the RVP of the new mixture (i.e., full tank) will be
roughly 1.0 psi higher than that of the original straight HC
gasoline.
This commingling effect could possibly lead to increased
evaporative emissions. One report calculated an average
increase of 33 percent in evaporative emissions due to the
intermittent use of Oxinol in every third tank, if both the
Oxinol and gasoline had the same RVP. [11] The increase in
evaporative emissions due to commingling has been shown to be a
function of the percentage of stations selling blends, the
amount of fuel remaining in the fuel tank when refilling, and
the habits of the buyer (i.e., whether fuel is bought at random
or loyally).
The above results apply to short-term evaporative
emissions impacts and do not include any effects which could
arise from degradation of the evaporative control system due to
methanol contamination of the carbon canister through long-term
-------
2-42
Figure 2-6
COMINGLING VAPOR PRESSURE EFFECTS M.OH/IPA
BLENDS WITH ALL HYDROCARBON GASOLINE
2.0
i «••
*
a
f 1.0
i
i,
IM/IMOM iOO«OtOro«OM«O3020iO 0
o io2030*oso«OTo«o»OiOO
•UNO II»TIO.%
COMINGLING VAPOR. PRESSURE EFFECTS
EtOH AND M*OH/EtOH BLENDS WITH
ALL HYDROCARBON GASOLINE
2.0
1.9
i
i
1.0
0.9
•as
tOO »0 *0 10 *0 SO «C » 20 '0 0
CAMLIMC 0 iO 20 JO 40 90 (0 TO M K <00
•UNO MTIO.%
Source;ARCQ Petroleum Products Company, March 12, 1985
(in letter to Craig Harvey, EPA)
-------
2-43
use of alcohol blends. There has been widespread speculation
about contamination of charcoal with alcohols, but several
studies have failed to show a definitive effect on the working
capacity of the canister.
For methanol blends, most reports (including recent EPA
contract work) show no substantial difference in canister
working capacity when compared to the use of straight gasoline,
even with high mileage accumulation.[26,35,36] (Prior EPA
contract work on canisters in a laboratory situation had shown
an effect of the blends on the working capacity, but this could
be attributed to a difference in loading of the canisters
during the experiment.)[37] One report does state that the use
of methanol blends can decrease the working capacity of carbon,
resulting in increased evaporative emissions.[27] However, the
mileage accumulation fuel was a splash blend, and thus, the
effect could be due to higher volatility. Possible alcohol
effects have been attributed to the formation of azeotropes
between methanol and heavier hydrocarbons. These azeotropes
are more volatile than either component and become adsorbed on
the carbon. Then, apparently, the methanol breaks off and
leaves the hydrocarbon portion attached to the carbon, which is
difficult to purge.[38]
The reported effects of ethanol blends on carbon canisters
are limited, but suggest no degradation of working capacity.
The reports did show that ethanol was adsorbed in preference to
some hydrocarbons and that a lesser degree of regeneration was
achieved during a defined purge period; however, an extended
purge period tended to remove all the ethanol.[30]
3. Summary
The addition of alcohols to gasoline affects the
properties of the blend. The addition of either methanol or
ethanol results in higher percentages of fuel to be evaporated
at given temperatures, and greater RVP, FEVI, and El values.
The effects of methanol on these parameters are more dramatic
than for ethanol.
This increase in volatility can cause higher evaporative
emissions during the use of alcohol blends. However, some
reports show that controlling the volatility characteristics of
the blend to that of current gasolines is sufficient to keep
evaporative emissions at current levels and prevent any
permanent reduction in working capacity.
-------
2-44
The intermittent usage of blends also causes an increase
in evaporative emissions because of the nonlinearity in RVP
upon mixing alcohol blends and gasoline (i.e., the commingling
effect). Thus, even if the RVP of alcohol blends is controlled
to current gasoline levels, the amount of evaporative emissions
could theoretically still increase. However, this study does
not take the commingling effect into account, and alcohol
blends are treated essentially as straight gasolines of equal
volatility.
D. Ambient Temperature Conditions
In addition to weathering, ambient temperature conditions
can also impact the level of evaporative emissions. Diurnal
losses are dependent upon not only the ambient temperature
excursion (daily maximum minus daily minimum), but also on the
absolute magnitude of these temperatures. Hot-soak losses are
also dependent on ambient temperature. For example, a vehicle
undergoing a 30°F diurnal change at an average temperature of
90°F would be expected to have significantly greater diurnal
and hot-soak losses than a vehicle experiencing only a 15°F
diurnal difference at an average temperature of 75°F. In an
effort to quantify the magnitude of such differences, an
EPA-sponsored test program was initiated several months ago to
measure diurnal and hot-soak losses at various ambient
temperature conditions.
This test program (currently being conducted for EPA at
the Automotive Testing Laboratories, or ATL) includes a matrix
of three fuel RVPs, three diurnal starting temperatures, four
diurnal temperature excursions, and three average hot-soak
temperatures.[39,40] However, some vehicles are being tested
over only part of the full matrix in the interest of including
more vehicles in the sample. The standard EPA test procedure
(i.e., diurnal temperatures between 60°F and 84°F, and average
hot-soak temperature of roughly 82°F) is represented in the
full test matrix. Preliminary analysis of test data on 24
light-duty vehicles certified to the 2-gram standard suggests
that increasing the diurnal temperature excursion from 24°F to
30°F can increase controlled diurnal losses by a factor of 1.3
to 2.7, depending on the starting temperature, the RVP of the
fuel, and the fuel metering system (carburetor or
fuel-injector). Data on these 24 vehicles also indicate that
an increase in ambient temperature from 70 °F to 82 °F can
increase controlled hot-soak losses by 29-60 percent, again
depending on fuel RVP and fuel metering system. It should be
noted that these data are preliminary; testing on more vehicles
(most over only part of the full test matrix) is set to be
completed by the end of this year.
-------
2-45
Diurnai emissions data on these 24 vehicles are anlayzed
in Appendix 2-A at the end of this chapter. There, the diurnal
averages are compared to theoretical emissions indexes
calculated for each ATL test condition via a diurnal emissions
model developed and published in 1967.[41] This model, which
uses the Ideal Gas Law to predict uncontrolled diurnal losses
as a function of fuel characteristics and temperatures, is used
in Appendix 2-A to relate the various ATL test conditions to
the standard EPA test procedure in terms of relative predicted
diurnal emissions. This model is also used there to compare
typical summertime temperature and RVP conditions in several of
the ozone non-attainment areas to EPA's current evaporative
test procedure. Relative diurnal emissions indexes are
calculated for 17 selected cities in the last section of
Appendix 2-A. More details on the methodology and inputs used
are provided there.
As with weathering (discussed earlier), the preliminary
nature of these results have prevented the effects of ambient
temperature conditions on the level of evaporative emissions
from being accounted for in the emissions projections made in
this report. Work continues in both of these areas (i.e.,
temperature and weathering) in hopes of incorporating their
effects into future analyses.
V. Results of In-Use Motor Vehicle Testing
This section presents test data from EPA's in-use motor
vehicle emission factor (EF) program in an attempt to quantify
the effect of the factors mentioned in the previous section
(i.e., fuel volatility and evaporative control system design)
on emissions from current vehicles. The section begins with a
brief description of the current evaporative test procedure
used in certification and changes made for the in-use EF
program (i.e., the addition of commercial fuels and the switch
in fuel sequence). Next, general evaporative emission results
from the EF program are presented for various RVP levels with a
comparison between the revised estimates and the MOBILES
figures published in June 1984. In the following section,
these revised hot-soak and diurnal emission levels are broken
down into several basic components of motor vehicle evaporative
emissions, based on an analysis of the vehicle test fleet. By
attributing certain portions of current total evaporative
losses to different sources (i.e., excess RVP,
malmaintenance/defect, improper design of purge system, etc.),
it is possible to estimate the effect that changes in in-use
RVP or certification fuel and test procedure will have on each
component and, thus, on total evaporative emissions. (The
effects of the various control strategies will be outlined, in
detail, for various model years in Chapter 5). Also, as
-------
2-46
discussed in the final part of this section, exhaust HC and CO
emissions have been found to be dependent upon RVP; this effect
is quantified in this final section. (Again, the specific
adjustments that have been made to MOBILES exhaust EFs to
account for the RVP effect under various control strategies are
detailed in Chapter 5.)
A. Test Procedure
The standard evaporative test procedure used in the
certification of new vehicles is outlined in detail in Part 86
of Title 40 of the Code of Federal Regulations (40 CFR 86).
Briefly, the vehicle is first drained of its fuel and refueled
with Indolene (with an average RVP of 9.0 psi) to the
40-percent full level. The vehicle is then preconditioned
using the Urban Dynamometer Driving Schedule (also referred to
as the "LA-4" cycle), which lasts approximately 23 minutes;
under special circumstances (e.g., if the vehicle was
transported via carrier instead of being driven to the test
site), manufacturers can request up to three LA-4 cycles to
•assure adequate purging of the evaporative canister. Following
preconditioning, the vehicle is stored (or "soaked") for a
period of 12-36 hours before the SHED (Sealed Housing
Evaporative Determination) test is conducted.
Just prior to beginning the SHED test for diurnal losses,
the vehicle is drained and refueled with chilled Indolene to
the 40-percent fill level.* Beginning with a fuel and tank
temperature of 60°F, the fuel is heated to 84°F over a period
of one hour, at which time the final HC concentration in the
SHED enclosure is recorded as the total diurnal loss.
Following the diurnal test, a cold-start LA-4, followed by
the first half of a hot-start LA-4 is performed, during which
exhaust emissions are measured. At the completion of these
tests, the engine is shut off and the vehicle is pushed into
the SHED enclosure for the hot-soak test. The test vehicle
remains there for one hour at an average ambient temperature of
81°F** and the increase in HC concentration is recorded and
converted into a total hot-soak mass emission.
The estimation of evaporative emissions as a function of
fuel RVP used to evaluate the control options examined in this
study was based on data generated as part of EPA's ongoing
in-use emission factor (EF) test program. This program
* The fuel is chilled to about 50°F to counteract the warm
fuel tank (70-75°F), which is already warmer than the
lower end of the temperature excursion (60°F).
** The hot-soak temperature range specified in the CFR is
68-86°F.
-------
2-47
involves the testing of in-use (privately-owned) passenger
cars, selected at random from State of Michigan
vehicleregistration files. Prior to November 1983, in-use
(privately-owned) vehicles were evaluated for hot-soak and
diurnal losses only while operating on certification test fuel
(Indolene) with a 9.0-psi RVP. Since then, however, the effect
of fuel volatility on emissions has been examined with the
addition of two commercial fuels with nominal RVPs of 11.5 psi
(added in November 1983) and 10.5 psi (added in August 1984).
The test procedure used in the EF program has basically
followed certification practices except for certain differences
in vehicle preconditioning and, of course, the addition of
commercial fuels. (These in-use EF test sequences are
summarized in Table 2-11). Between November 1983 and July
1984, vehicles were preconditioned over a shortened LA-4 cycle
which lasted only 10 minutes instead of the entire 23 minutes.
Commercial fuel with an ll.5-psi RVP was added to the test
sequence following all evaporative and exhaust emission tests
conducted on Indolene.
In July 1984, the shortened prep cycle was dropped and the
entire LA-4 cycle (used in certification) was reinstated.
Also, at this time, it was concluded that the evaporative tests
on 11.5-psi commercial fuel may have been unrepresentative
because they were run following a battery of tests on 9-psi
Indolene over which the evaporative canister was repeatedly
purged. Therefore, the commercial test was begun with an
essentially "unloaded" canister, which would probably bias
results toward lower emissions than those experienced in the
field. Further, because vehicles had been operated on 11.5-psi
commercial fuel prior to arriving at EPA, it follows that the
most accurate measurement of in-use emissions would be obtained
by testing commercial fuel first. Therefore, the test sequence
was changed and the 11.5-psi fuel was tested first, followed by
Indolene.
In August 1984, testing of the mid-range commercial fuel
with an RVP of roughly 10.5 psi was added to the sequence just
after the 11.5-psi fuel and before any Indolene testing. Other
minor changes (initiated in July 1984) involve the storage of
the vehicle prior to any evaporative tests. To avoid premature
saturation of the canister, the gas cap is loosened to allow
vapors to bypass the control system and the vehicle is stored
inside at a fairly constant temperature.
-------
2-48
Table 2-11
Comparison of In-Use Test Sequences
Nov. 83 - July 84
1. Park indoors and/or outdoors
2. Shortened dynometer prep
(10-min.)
3. Indolene evaporative tests
4. Exhaust emission tests
(HFET and short tests)
5. Commercial (11.5 psi)
evaporative tests
Post - July 1984
Park indoors; loosen
gas cap.
LA-4 dynometer prep
(23-min.)
Commercial (11.5 psi)
evaporative tests
Mixture (10.5 psi)
evaporative tests*
Indolene evaporative
tests
Exhaust emissions tests
(HFET and short tests)
10.5 RVP added in August 1984.
-------
2-49
B. General Test Results
Vehicle samples used in EPA's in-use EF testing both prior
to and after the July 1984 test procedure changes are broken
down by manufacturer in Table 2-12.* Carbureted and
fuel-injected samples are outlined separately, and sample
distributions are compared to 1984 market shares.
Evaporative emissions from these test vehicles are
summarized in Table 2-13. Results are shown for both Indolene
and commercial (11.5-psi) fuels, and are separated out by
vehicle type and test procedure. The MOBILE3 emission rates
published in June 1984 are from a subset of the November
1983-July 1984 tests and are listed separately for comparison.
Revised MOBILES estimates are listed as July 1984 - April 1985
results.
As indicated from the results shown in Table 2-13, the
change in the test procedure has led to slightly lower
emissions with Indolene and somewhat higher emissions with
commercial fuel in almost all cases. (This is as to be
expected from the previous discussion on the reasons behind the
changes in fuel test sequence.) For fuel-injected vehicles,
higher emissions also may be partially due to the higher
average mileage of the vehicles being tested; the vehicles
tested after July 1984 have an average mileage over twice that
of those tested previous to that time. Results of the July 84
- April 1985 testing are shown graphically in Figure 2-7, which
plots revised hot-soak and diurnal emissions versus fuel RVP.
Both sets of vehicles tested show average emissions
exceeding the 2-gram standard for total evaporative emissions,
even while operating on Indolene: carbureted vehicles
averaging 4.64 grams/test and fuel-injected vehicles averaging
2.15 grams/test. When tested on 11.5-psi commercial fuel,
these evaporative emissions are much larger: 12.85 grams/test
for carbureted vehicles and 7.34 grams/test for fuel-injected
vehicles. The possible causes of the excess evaporative
emissions are the subject of discussion in the following
section.
The post-July 1984 vehicle sample includes vehicles tested
only through April 1985, the point at which test results
were "frozen" for this analysis. Subsequent test results
are currently being analyzed.
-------
2-50
Manufacturer
GM
Ford
Other Domestic*
Toyota
Nissan
Other Imports**
Total
Table 2-12
In-Use EF Vehicle Sample Distribution
Carbureted
Nov. 83-
July 84
31(33%)
38(41%)
12(13%)
2( 2%)
3( 3%)
7( 8%)
93(100%)
July 84-
April 85
32(29%)
26(24%)
17(16%)
13(12%)
14(13%)
7( 6%)
109(100%)
1984
Market
Share
46%
13%
11%
4%
5%
21%
100%
Fuel-Injected
Nov. 83-
July 84
57(74%)
9(12%)
3( 4%)
8(10%)
77(100%)
July 84-
April 85
15(27%)
2( 4%)
13(24%)
13(24%)
8(14%)
4( 7%)
55(100%)
1984
Market
Share
42%
25%
11%
10%
9%
3%
100%
* *
AMC, Chrysler, VWA.
Honda, VWG, Mitsubishi, Toyo-Kogyo, Audi.
-------
2-51
Table 2-13
Comparison of Evaporative EF Test Data from
Non-Tampered Vehicles (g/test)
Indolene (RVP =9.0 psi)
Test Period
Nov 83 -
July 84
Published
MOBILES*
July 84 -
April 85**
Technology
Garb.
Fuel-Inj .
Garb.
Fuel-Inj .
Garb.
Fuel-Inj .
N
93
77
53
62
109
55
Commercial
Test Period
Nov -
July 84
Published
MOBILES*
July 84-
April 85**
Technology
Garb.
Fuel-Inj .
Garb.
Fuel-Inj .
Garb.
Fuel-Inj .
* The MOBILES results
July 84
** Revised
*** This ie
N
93
77
53
62
109
55
are
data pool.
MOBILES estimates
•hhp »ve»raap nf ai
Mileage
45000
20000
60000
20000
55000
46000
Fuel (RVP = 11
Mileage
45000
20000
60000
20000
55000
46000
from a subset
, used in this
r?1-iial 1-est- resi
Diurnal
4.16
1.64
4.22
2.21
2.32
1.25
.5 psi)
Diurnal
8.64
2.33
9.31
3.13***
9.01
5.51
of the
study .
l"]1-R_ Hftt
Hot-Soak
2.19
0.96
2.74
1.12
2.32
0.90
Hot-Soak
3.29
1.28
3.98
1.55
3.84
1.83
Nov . 83 -
jpv*»r . diip
to uncertainties associated with the low mileage, the
value for carbureted vehicles was also used for
fuel-injected vehicles in MOBILES.
-------
Figure 2-7
EVAPORATIVE EMISSIONS VS. FUEL RVP
12
10-
CO
§
6-
0
8.5
T
9
"T"
9.5
10 10.5
FUEL RVP (PSI)
T
11
11.5
-r
12
NJ
I
Legend
A HOTSOAK/RNJ
HOTSOAK/RNJ AVG
D HOTSOAK/CARB ___
HOTSOAK/CARB AVC
O DIURNAynNJ _______
DIURNAL/HNJ AVC
DIURNAl/CARB AVG
-------
2-53
C. Components of Excess Motor
Vehicle Evaporative Emissions
For purposes of analysis, it is useful to segregate the
evaporative emission excess described above according to its
probable causes. Using EF test data, these four basic
categories were chosen as: 1) effect of insufficient design
capacity/purge, 2) effect of malmaintenance and defects, 3)
effect of excess RVP, and 4) effect of evaporative system
tampering. The causes and magnitude of each of these effects
(for current vehicles) are detailed below; more information on
the methodology used to separate these four sources is provided
in Appendix 2-B.
1. Insufficient Design Capacity/Purge
Even with properly functioning evaporative emission
control systems, many current vehicles fail to meet the 2-gram
standard on Indolene. This is primarily seen in carbureted
vehicles which average 2.75 grams/test when there are no
apparent malfunctions.* Conceivably, this failure could be due
to an insufficient capacity to store or purge vapors inherent
in the system design. It may also be valid to attribute some
of these excess emissions to lingering effects of high RVP
fuels and alcohols on charcoal working capacity. (However, as
discussed in Section IV, the effects of low-level alcohol
blends and the use of high RVP fuels do not appear to be long
lasting.)
The plausibility of insufficient design capacity and purge
is evident from the limitations of the evaporative emission
test procedure and certification process. To be certified, a
vehicle must meet the standard after applying an additive
deterioration factor to low mileage emission test data. Also,
MSAPC Advisory Circular No. 50A states that vehicles should be
able to pass the evaporative emission test when starting the
test seguence with a saturated canister. (Many EF vehicles are
probably received in this condition.) This means that purge
systems should be designed to completely purge a loaded
canister with the LA-4 prep cycle. However, there is no
reguirement for this in the certification test procedure.
Thus, it is possible that a certification vehicle, as currently
designed, would fail were it to begin the test with a saturated
canister.
As shown in Appendix 2-B, Table 2-B-2, for "problem-free"
vehicles (to be explained in the next few paragraphs).
-------
2-54
The derivation of the magnitude of the insufficient design
capacity/purge effect is detailed in Appendix 2-B. The general
concept involved was to compare the average emission levels of
the "problem-free" vehicles, as defined in Table 2-14, with the
standard level of 2 grams/test for total evaporative
emissions. The difference between the two levels was assumed
to be due to the emission control system design. Summarized in
the top portion of Table 2-15, this effect is not seen in
fuel-injected vehicles, but averages 0.70 grams/test for
carbureted light-duty vehicles. This effect of insufficient
design capacity and purge is noted here because it presumably
would be eliminated for new vehicles by revising the
evaporative emission test procedure to require that a vehicle
begin the test with a saturated canister.
2. Malmaintenance and Defects
Non-tampered vehicles with the maintenance problems and
hardware defects listed in Table 2-14 (tampering is considered
separately below) will generally have higher evaporative
emissions than well-maintained vehicles. These problems can
lead to either a partial increase in emissions (e.g. from a
dirty canister filter) or to completely uncontrolled emissions
(e..g., from an inoperative canister purge solenoid or valve).
On average, excess emissions would not be expected to be as
high as the uncontrolled emission baseline because some purging
would still occur. This is different from the case of
tampering where complete system disablement is generally the
result.
The magnitude of the effect of malmaintenance and defects
for current vehicles operating on Indolene is estimated by
considering the difference between the non-tampered EF vehicle
sample average and the problem-free vehicle sample average
tested on Indolene. Inherent in this calculation is the
assumption that the EF sample has a representative
malmaintenance and defect rate. For carbureted vehicles (see
Table 2-16), the malmaintenance and defect rate from EF cars
tested since July 1984 (32 percent) is within the range and
essentially equal to the average of all other available data
samples. For fuel-injected vehicles, the newer EF sample has a
slightly higher rate than the other samples (e.g., 16 percent
versus only 5 percent in the pre-July 1984 in-use EF sample).
However, this is probably due to the fact that the fuel
injected vehicles in the old EF sample averaged fewer total
miles on their odometers than those in the current sample
(20,000 vs. 46,000). Overall, then, the malmaintenance and
defect rates in the July 1984 - April 1985 EF sample appear
representative.
-------
2-55
Table 2-14
Conditions Excluding Vehicles
From Problem-Free Sample
I. Fuel System
A. Carburetor Assembly
1. Loose on Manifold
2. Leaks Fuel
3. Exceptionally Dirty
B. Fuel Injection Components
1. Injectors Leaking
II. Evaporative System
A. Canister
1. Saturated with Fuel
2. Broken
3. Missing*
B. Canister Filter
1. Dirty
2. Saturated with Fuel
3. Missing
C. Canister Purge Solenoid/Valve
1. Leaks Vacuum
2. Sticking
3. Inoperative
4. Missing*
5. Disconnected*
D. Hoses, Lines, Wires
1. Vacuum Line Plugged
2. Vacuum Line Disconnected*
3. Vacuum Line Damaged
4. Vacuum Line Misrouted*
5. Vent Line Damaged
6. Vent Line Disconnected*
E. Other
1. EFE TVS Stuck Open/Closed
2. Non-OEM Gas Cap
3. Bowl Vent Control Valve Always Open/Closed
4. VCV Vacuum Control Valve Inoperative
5. Gas Cap Leaks
6. Sending Unit Gasket Leaking
7. Fuel Tank Rollover Valve Leaking
8. Air Cleaner Assembly Gasket Broken/Missing
9. EFE Control Switch Missing*
10. Gas Cap Missing*
Considered to be tampering.
-------
2-56
Table 2-15
Magnitude of Excess Evaporative Emissions
from Current Vehicles (q/test)
Vehicle
Class
LDV/LDT
HDV
Insufficient Design Capacity/Purge Effect
Diurnal Hpt_Soak
Fuel Metering
System
Carb
FI
Carb
0.30
0.00
0.48
0.40
0.00
0.64
Malmaintenance/Defect and Excess RVP Effects
Vehicle
Class
LDV/LDT
HDV
Fuel Metering
RVP System
9.0 Carb
FI
9.5 Carb
FI
10.0 Carb
FI
10.5 Carb
FI
11.0 Carb
FI
11.5 Carb
FI
9.0 Carb
9.5 Carb
10.0 Carb
10.5 Carb
11.0 Carb
11.5 Carb
Malm./Defect
Diurnal
1.11
0.34
1.21
0.44
1.31
0.54
1.41
0.64
1.51
0.74
1.61
0.84
1.77
1.93
2.09
2.25
2.41
2.57
Hot Soak
0.83
0.29
0.91
0.42
0.99
0.55
1.07
0.67
1.15
0.80
1.24
0.93
1.32
1.45
1.58
1.71
1.84
1.97
Excess RVP
Diurnal
0.00
0.00
0.62
0.24
1.54
0.48
2.78
0.79
4.33
2.03
6.19
3.76
0.00
0.98
2.46
4.43
6.90
9.85
Hot Soak
0.00
0.00
0.06
0.05
0.20
0.11
0.42
0.18
0.73
0.24
1.11
0.29
0.00
0.09
0.31
0.67
1.15
1.77
-------
2-57
Table 2-16
Malmaintenance and Defect Rate Comparison
Sample
EF (new)*
EF (old)**
SwRI[42]
API (NIPER)[43]
API (ATL)[44]
Average***
* Vehicles tested on three fuels w/LA-4 prep, commercial
fuel first; July 1984-April 1985.
** Vehicles tested on two fuels w/10-minute prep, Indolene
fuel first; November 1983-July 1984.
*** Sample-size weighted.
Carbureted
Sample
Size
!43]
t]
108
93
27
19
28
—
Defect
Rate
32%
44%
26%
11%
25%
33%
Fuel Injected
Sample
Size
55
77
—
32
10
_ —
Defect
Rate
16%
5%
—
13%
0%
10%
-------
2-58
While the above methodology appears satisfactory for
estimating the magnitude of the malmaintenance/defect effect
for vehicles operating on 9-psi Indolene, it is expected that
the effect would increase with the level of in-use RVP. The
same would be true for a tampered vehicle. Basically, if
excess emissions are being released from the canister or
elsewhere, increased vapor loadings that result from higher
in-use RVPs will lead to increased emissions. While
redesigning vehicles for higher RVP fuel should lower emissions
when the control system is fully operable, the effect of
malmaintenance or a defect would be expected to be independent
of the RVP for which the vehicle was designed and dependent
only on the RVP of the fuel actually used.
Estimation of the magnitude of this effect at various RVPs
is described in detail in Appendix 2-B; the results are
summarized here in the center portion of Table 2-15. This
effect can be quite large with 11.5 RVP fuel — approaching 3
grams/test for carbureted light-duty vehicles and 2 grams/test
for light-duty fuel-injected vehicles.
While the insufficient design/purge and excess RVP effects
(discussed below) are assumed to be totally eliminated in new
vehicles via changes to certification fuel and test procedure,
the malmaintenance/defect effect can only be controlled through
reduction of in-use fuel volatility or through an effective
evaporative system inspection and maintenance program.
3. Excess RVP Effect
The excess RVP effect is defined as the emissions impact
of operating vehicles on a fuel of higher volatility than that
for which their evaporative control systems have been
designed. Canisters and purge systems on current vehicles are
designed to meet the 2-gram evaporative standard if operated on
9.0 RVP Indolene over the standard certification test
procedure. However, as discussed in Section IV of this
chapter, the RVP of current in-use gasoline in many of the
ozone non-attainment areas of the country is significantly
higher than 9.0 psi. Because of their higher volatilities,
these commercial fuels emit more evaporative HCs than the
vehicles' canisters can accommodate, which results in canister
saturation and "breakthrough" of HC vapors to the atmosphere.
The magnitude of this excess RVP effect can be calculated
by first subtracting total average emissions of the
non-tampered sample on Indolene from those on commercial fuel.
However, because part of this difference between commercial and
Indolene emissions has already been accounted for in the
malmaintenance and defect effects, an adjustment to the total
-------
2-59
difference is needed. The difference between the
malmaintenance/defect effect on Indolene and commercial fuel
must . be subtracted from the total difference between
non-tampered emissions at Indolene and commercial fuel to yield
the excess RVP effect. This is explained in more detail in
Appendix 2-B.
The magnitude of this remaining excess RVP effect on
current vehicles is shown in Table 2-15 (along with the other
two effects). With an in-use fuel RVP of 11.5 psi, the excess
RVP effect is 7.30 and 4.05 grams/test for carbureted and
fuel-injected light-duty vehicles, respectively. These
represent respective increases of 265 percent and 103 percent
from the 2 gram/test standard level.
As with the insufficient design/purge effect, this excess
RVP effect is assumed to be completely eliminated for new
vehicles if certification fuel RVP is raised to a level egual
to or greater than in-use fuel RVP. However, for vehicles
certified prior to any change in certification fuel RVP (i.e.,
1990 in this analysis), the excess RVP effect will remain and
be dependent upon in-use RVP.
4. Tampering Effect
Intentional system disablement also contributes toward
excess evaporative emissions. EPA's in-use EF sample is not
thought to have a representative number of tampered vehicles,
since those who tamper with their emission controls may
generally be reluctant to lend their vehicles to EPA for
testing. The EF sample is also relatively small due to the
high cost of emission testing. For these reasons, tampering
rates to be used in emissions modeling are developed from EPA
tampering surveys involving thousands of vehicle inspections.
Those conditions considered as tampering are primarily
disconnected, misrouted or missing hoses, missing canisters and
missing fuel caps (as indicated previously in Table 2-14).
Because emissions from tampered vehicles are not developed
from the EF sample, the MOBILES program accommodates them
separately. Tampering incidence rates are developed from
survey data and excess emissions are determined from emission
tests on completely disabled systems. Since the original
MOBILES estimates were published in June 1984, additional
tampering data has become available that has allowed
improvement over the June 1984 estimates. These revisions to
the MOBILES tampering estimates are discussed below.
-------
2-60
The original MOBILES LDV tampering incidence rates
published in June 1984 were based on a linear regression of
tampering frequency versus mileage using the results of EPA's
1982 Tampering Survey. [45] For LDTs and HDVs, the rate of
increase of tampering with mileage for LDVs was applied to the
average LDT-sample tampering frequency and vehicle mileage,
because the LDT sample was too small to derive a change in
tampering over time and no HDVs were surveyed. The zero-mile
tampering rates, however, were developed from the LDT sample;
these LDT zero-mile rates were also used for HDVs.
As mentioned above, updated EPA survey results from 1983
and 1984 have since become available, so these data were added
to the 1982 tampering data used to develop the June 1984
MOBILES estimates.[46,47] The resulting information was
sufficient to develop separate tampering rate estimates for
both LDVs and LDTs; the HDV rates were still assumed to be the
same as those for LDTs. Additional revisions to the MOBILES
tampering estimates include the designation of vehicles with
misrouted hoses and missing fuel caps as tampered vehicles.*
Since these conditions were not considered as tampering in the
June 1984 version of MOBILES, previously estimated effects of
tampering may have been somewhat understated. Plots of the
revised MOBILES tampering rates versus mileage for LDVs and
LDTs are shown, respectively, in Figures 2-8 and 2-9.
One possible form of tampering/malmaintenance that still
remains to be investigated is the use of replacement gas caps
not meeting the same specifications as the original gas cap
(referred to as non-OEM (original equipment manufacturer) gas
caps). Such gas caps may not seal properly and could result in
either partially or completely uncontrolled emissions. The
extent of their use and their effect on emissions is currently
being investigated.
In addition to revising tampering incidence rates, the
emission rates for tampered vehicles have also been modified by
supplementing the pre-June 1984 data with more recent data and
by incorporating emission excesses associated with missing fuel
caps. With certain exceptions, it is assumed that all types of
tampering result in completely uncontrolled emissions. A case
in which this assumption may not be strictly valid is for the
disconnection of a carburetor bowl vent line at the carburetor
end (i.e., not at the canister). In this case, only hot-soak
As misrouted hoses and missing fuel caps could be
unintentional, there remains some question as to whether
they should be considered "tampering" or
"malmaintenance". However, as these conditions were not
felt to be properly represented in the EF sample, they are
currently regarded as tampering.
-------
Figure 2-8
s
111
2
LDV TAMPERING RATES
MOBILEJ AND NEW SURVEYS
S U RVE YS- EVAPfcCAP
MILEAGE (1000 MILES)
+ SURVEYS-EVAP
100
MOBILE 3
-------
Figure 2-9
111
LOT TAMPERING RATES
MOBILES AND NEW SURVEYS
SURVEYS- EVAPfcCAP
MILEAGE (1000 MILES)
-I- SURVEYS-EVAP
to
I
to
80
100
o MOBILES
-------
2-63
emissions would be uncontrolled. However, because the
tampering survey does not make this distinction, a better
estimate is not available at this time.
The uncontrolled evaporative emission rates used to
quantify the tampering effects are based on SHED testing of
vehicles with removed canisters and/or fuel caps. These are
summarized in Table 2-17, which also shows the increase with
in-use fuel RVP. Several assumptions that were made in
deriving these emission rates are described below.
First, with respect to diurnal losses, the effect of fuel
cap removal is assumed to be the same as canister removal for
both carbureted and fuel-injected vehicles, since diurnal
emissions result entirely from the fuel tank. Also, diurnal
emissions from fuel-injected vehicles with either missing gas
caps or canisters is assumed to be the same as those from
uncontrolled carbureted vehicles (for which more data exist).
Again, diurnal emissions occur entirely from the fuel tank
where the two technologies do not differ. Also, the fuel tank
volumes of the two vehicle types do not generally differ.
Second, with respect to hot-soak emissions from
fuel-injected vehicles, fuel cap removal is assumed to result
in completely uncontrolled hot-soak emissions. A properly
assembled fuel injector should emit little, if any, during a
hot soak, leaving the fuel tank as the primary source of.
emissions. Limited data on three fuel-injected vehicles
confirm this. Hot-soak emissions using Indolene with the gas
cap removed and those with the canister removed were
essentially identical at just over 4 grams/test, where
controlled emissions were below one gram/test.[48] Emissions
using commercial fuel without a canister were only slightly
higher than those without a gas cap. Thus, this assumption
appears to be valid for fuel-injected vehicles. However, for
carbureted vehicles, the increase in hot-soak emissions due to
fuel cap removal is expected to be less than totally
uncontrolled hot-soak emissions because the carburetor bowl
contributes to, and probably is the major source of, hot-soak
losses from these vehicles. Since data are not available to
precisely predict the degree to which hot-soak emissions from
carbureted vehicles would increase with fuel cap removal, it
will be assumed that the carburetor bowl dominates and that
hot-soak emissions do not increase. Thus, the values presented
in Table 2-17 for hot-soak emissions from carbureted vehicles
with missing fuel caps are the same as those for non-tampered
carbureted vehicles (i.e., 2.32 and 3.84 g/test for 9.0- and
11.5-psi RVPs, respectively, as shown in Table 2-13).
As explained in Appendix 2-B, the tampering offsets used
in this analysis were calculated by subtracting the average
non-tampered vehicle emissions shown in Table 2-13 from the
-------
Table 2-17
Uncontrolled Evaporative Emissions (g/test) from Tampered Vehicles vs. RVP*
Canister Disconnects
Vehicle
Type
LDV
and
LOT,
Model
Year
pre-71
71
72-77
78-80
81+
Fuel
System
All
All
All
All
Garb
Finj
—9.0
H.S.
14.67
14.67
14.67
13.29
10.36
4.93
psi—
Dnl.
26.08
26.08
20.90
16.32
14.95
14.95
-11.5
H.S.
22.45
22.45
22.45
18.50
17.47
11.59
psi**-
Dnl.
47.99
47.99
35.45
25.11
25.71
25.71
—9.0
H.S.
14.67
10.91
10.91
2.32
2.32
4.93
Fuel Cap Removal
psi—
Dnl.
26.08
26.08
20.90
16.32
14:95
14.95
-11.5
H.S.
22.45
16.15
8.98
3.79
3.84
11.59
psi**-
Dnl.
47.99
47.99
35.45
25.11
25.71
25.71
LDT2 pre-79 All 18.08 42.33 27.66 77.89 18.08 42.33 27.66 77.89
79+ Same as LDV, LDTi
V
CTi
HDV pre-85 All 18.08 42.33 27.66 77.89 18.08 42.33 27.66 77.89 "*
85+ 14.67 26.08 23.31 39.87 3.69 26.08 6.11 39.87
* Figures presented are for low altitudes; high-altitude correction factors are as follows: 1)
LDV — pre-1977 = 1.3, 1977 = 1.0, 1978-81 = 2.59, 1982-83 =1.3, 1984+ = 1.0; 2) LOT,,
LDT2 and HDV — all model years = 1.3.
** Values for RVPs between 9.0 and 11.5 psi can be calculated via linear interpolation.
-------
2-65
uncontrolled emission levels in Table 2-17. These offsets at
various RVPs were then incorporated into the EF runs at the
tampering incidence rates developed from the survey data
previously discussed. These offsets represent extreme
increases in evaporative emissions, reaching levels of 10-20
grams/test for 11.5 RVP fuel. (Tampering offsets are shown in
Appendix 2-B for light-duty and heavy-duty vehicles in Tables
2-B-6 and 2-B-7, respectively.)
5. Summary
Based on the above discussions, motor vehicle evaporative
emissions can be divided into several different categories.
The first consists of emissions from properly-designed and
operated vehicles assumed to emit at the standard; therefore,
none of the control strategies (to be detailed in the last
section of this chapter) will reduce this portion. However,
the four probable components of current excess motor vehicle
emissions will be addressed in the remainder of this study.
The first — insufficient design of the purge system —
could be addressed via changes to the certification test
procedure. The excess RVP effect could theoretically be
reduced or eliminated through the reduction of in-use fuel RVP
and/or the revision of certification fuel specifications. The
effects of the remaining two sources of excess evaporative
losses (i.e., malmaintenance/defects and tampering) probably
cannot be totally eliminated, but could be significantly
reduced if in-use RVP were controlled to lower levels or an
effective inspection and maintenance program for evaporative
systems could be developed and implemented.
The extent to which each of these five sources contribute
to total motor vehicle evaporative losses — and to total
non-methane hydrocarbon (NMHC) inventories — will be explained
in Chapter 5. There, future total NMHC inventories will be
broken down into stationary source emissions (separated into
bulk storage, Stage I, refueling, and other) and motor vehicle
losses (divided into exhaust HC and the five components of
evaporative HC losses). Results are presented graphically in
Figure 5-1 of Chapter 5.
D. Effect of RVP on Exhaust Emissions
EPA's EF program includes tests for exhaust emissions as
well as evaporative emissions. Prior to November of 1983, when
testing was only performed using Indolene, the effect of RVP on
in-use emissions was not known. Between October 1983 and July
1984, RVP appeared to have little effect on exhaust
emissions.[49] However, since July 1984 (when the test
sequence was improved), a significant effect has been seen,
particularly that lowering RVP lowers exhaust emissions of HC
and CO; no significant reduction in NOx emissions with lower
volatility fuels has been noted. The lack of an effect prior
to July 1984 is presumed to be due to the extra purging of the
-------
2-66
in-use canister during the evaluation on Indolene, in which the
HFET and various short tests were conducted.
Figures 2-10 through 2-15 show the trend toward higher
exhaust emissions with higher volatility fuel for each of the
three pollutants. This effect is seen with open-loop
carbureted, closed-loop carbureted, and fuel-injected
vehicles. The data in these figures consist of all those cars
tested between July 1984 and July 1985, in which the commercial
fuel was tested first and the prep cycle was a full LA-4.*
Tables 2-18 through 2-22 present the results of
statistical analyses to determine if the trends noted in the
above figures are significant. Table 2-18 shows the results
obtained from assuming a simple binomial model. If there
exists no relationship between exhaust emissions and fuel
volatility, then the number of vehicles showing higher
emissions with a higher RVP fuel should be approximately one
half of the total number of vehicles. The standardized value
determined (a) is a measure of the likelihood that a given
number of vehicles would have higher emissions at a higher RVP
if there is no relationship between the two (i.e., if
randomness is assumed). As Table 2-19 shows, a is less than
0.05 for all but one of the HC and CO cases, which indicates
that an RVP/exhaust emissions relationship probably exists
(i.e., the results are not randomized).
Tables 2-19 through 2-22 show the results of performing
analyses of variance using the following model:
Exhaust Emissions (VEH,RVP) = n + AVKH + ARVp, where
H = overall mean for all vehicles at all RVPs
AVEH = average deviation from the mean for a given
vehicle
ARVP = average deviation from the mean for a given RVP
Should the effect of RVP not be significant, then the value of
ARVP will be equal to zero for each RVP. This is indicated
by the F-statistic, which is a measure of the relative amount
of variance in the data explained by the given factor (in this
case RVP). The vehicle-related variability was also included
in this analysis so that the effect of fuel volatility could be
more clearly identified The tables indicate that the
F-statistic is greater than F-95% in all of the HC and CO
cases, which indicates that RVP is significantly related to
exhaust HC and CO (see footnotes on tables).
Because the analysis on the effect of RVP on exhaust
emissions was conducted after the analysis on evaporative
emissions, more vehicles were able to be included (i.e.,
the exhaust data were "frozen" in July 1985, while
evaporative data were examined only through April 1985).
-------
Figure 2-10
t.5
0.5-
AVERAGE HC EMISSIONS (G/Ml)
N=65
M
9.0 10.4 11.7
OPEN LOOP CARBURETED VEHICLES
-------
Figure 2-11
20
15-
10-
Ul
5-
AVERAGE CO EMISSIONS (G/MI)
N=65
CTi
oo
9.0 10.4 11.7
OPEN LOOP CARBURETED VEHICLES
-------
Figure 2-12
to
z
o
LU 0.5-
AVERAGE NOx EMISSIONS(G/MI)
K>
9.0 10.4 11.7
i nnp P.ARRURFTED VEHICLES
-------
Figure 2-13
1.5
«M» *
o
GO
LJ 0.5-
AVERAGE HC EMISSIONS (G/MI)
CARBURETED
N=81
FUEL-INJECTED
N=61
9.0 10.4 11.7 9.0 10.4
CI OSED LOOP VEHICLES
11.7
to
-------
Figure 2-14
AVERAGE CO EMISSIONS (G/MI)
o
(/>
CO
Ul
CARBURETED
FUEL-INJECTED
N=61
9.0 10.4 11.7 9.0 10.4 11.7
CLOSED LOOP VEHICLES
to
-------
Figure 2-15
1.5
0.5-
0
AVERAGE NOx EMISSIONS (G/MI)
CARBURETED
FUEL-INJECTED
10.4 11.7 9.0 10.4
CLOSED LOOP VEHICLES
NJ
-------
Table 2-18
Vehicles Showing Higher Exhaust Emissions
with Higher RVP Fuels
CARBURETED VEHICLES
RVP(psi)
High/Low
HC
CO
NOx
10.4/9.0
11.7/10.4
11.7/9.0
10.4/9.0
11.7/10.4
11.7/9.0
10.4/9.0
11.7/10.4
11.7/9.0
Open-Loop
Number
53
44
54
48
38
52
26
34
34
out of
out of
out of
out of
out of
out of
out of
out of
out of
65
65
65
65
65
65
65
65
65
FUEL INJECTED
HC
CO
NOx
10.4/9.0
11.7/10.4
11.7/9.0
10.4/9.0
11.7/10.4
11.7/9.0
10.4/9.0
11.7/10.4
11.7/9.0
42
50
54
40
40
44
37
31
38
Number
out of
out of
out of
out of
out of
out of
out of
out of
out of
61
61
61
61
61
61
61
61
61
cx*
.0000
.0022
.0000
.0000
.0869
.0000
.5537
.3557
.3557
Closed-Loop
Number O**
49
69
68
59
65
71
44
44
50
out of
out of
out of
out of
out of
out of
out of
out of
out of
81
81
81
81
81
81
81
81
81
.0294
.0000
.0000
.0000
.0000
.0000
.2177
.2177
.0174
(All Closed-Loop)
CX*
.0016
.0000
.0000
.0075
.0075
.0003
.0485
.4483
.0274
Combined
Number cx*
102 out of 146
113 out of 146
122 out of 146
107 out of 146
103 out of 146
123 out of 146
70 out of 146
78 out of 146
84 out of 146
ALL VEHICLES
Number e
144 out of 207
163 out of 207
176 out of 207
147 out of 207
143 out of 207
167 out of 207
107 out of 207
109 out of 207
122 out of 207
.0000
.0000
.0000
.0000
.0000
.0000
.8085
.2033
.0344
a<*
.0000
.0000
.0000
.0000
.0000
.0000
.3121
.2236
.0051
= A measure of the likelihood that this many vehicles would show higher exhaust emissions
at a higher RVP if there was no real relationship between the two (i.e., a higher value
indicates a higher likelihood that this occurrence is random). Values above .05 indicate
that the occurrence can be considered random at a 95-percent confidence level. Values
below .05 indicate that the occurrence is not random and that there is a statistically
significant relationship between exhaust emissions and fuel RVP.
V
~J
to
-------
2-74
Table 2-19
Analysis of Variance - Exhaust RVP Effect
(All Vehicles)
Source
RVP
VEH
ERR
TOTAL
DF
2
206
412
620
SS
2.0401
883.050
10.970
896.060
Exhaust HC
MSB
1.0201
4.2866
.0266
F-stat*
37.557
160.993
F 95%
3.00
1.00
F 90%
2.30
1.00
Exhaust CO
Source
RVP
VEH
ERR
TOTAL
DF
2
206
412
620
SS
661.020
258900.000
4828.980
264490.000
MSE
330.51
1256.8
11.964
F-stat*
27.626
105.053
Exhaust NOx
Source
RVP
VEH
ERR
TOTAL
DF
2
206
412
620
SS
MSE
.050497 .025248
257.49
5.380
262.92
1.2499
0.013
F-stat*
1.934
95.726
F 95%
3.00
1.00
F 95%
3.00
1.00
F 90%
2.30
1.00
F 90%
2.30
1.00
The F-statistic is a measure of the significance of a given factor
(here, RVP) in relation to the exhaust emissions. A value larger
than the theoretical value (i.e., F 95%) indicates that the RVP of
the fuel is significant in relation to exhaust emissions using the
given level of significance (i.e., a 95% confidence interval).
-------
2-75
Table 2-20
Analysis of Variance - Exhaust RVP Effect
(Carbureted Open-Loop Vehicles)
Source
RVP
VEH
ERR
TOTAL
DF
2
64
128
194
SS
.62937
187.000
3.991
191.620
Exhaust HC
MSB
.31469
2.9219
0.031
F-stat*
10.094
93.720
F 95%
3.07
1.43
F 90%
2.35
1.32
Exhaust CO
Source
RVP
VEH
ERR
TOTAL
DF
2
64
128
194
SS
MSB
313.180 156.590
77333.000 1208.300
1487.820 11.624
79134.000
F-stat*
13.472
103.952
F 95%
3.07
1.43
F 90%
2.35
1.32
Source
RVP
VEH
ERR
TOTAL
DF
2
64
128
194
SS
Exhaust NOx
MSB
F-stat*
.0051764 .0025882 .371
59.598 .93121 133.503
.893 .007
60.496
F 95%
3.07
1.43
F 90%
2.35
1.32
The F-statistic is a measure of the significance of a given factor
(here, RVP) in relation to the exhaust emissions. A value larger
than the theoretical value (i.e., F 95%) indicates that the RVP of
the fuel is significant in relation to exhaust emissions using the
given level of significance (i.e., a 95% confidence interval).
-------
2-76
Table 2-21
Analysis of Variance - Exhaust RVP Effect
(Carbureted Closed-Loop Vehicles)
Exhaust HC
Source
RVP
VEH
ERR
TOTAL
Source
RVP
VEH
ERR
TOTAL
Source
RVP
VEH
ERR
TOTAL
DF
2
80
160
242
DF
2
80
160
242
DF
2
80
160
242
SS
.86908
622.70
5.111
628.68
SS
MSB
.43454
7.7838
0.032
Exhaust
MSB
307.940 153.970
161460.000 2018.200
2552.060 15.951
164320.000
SS
.046258
111.960
2.757
114.760
Exhaust
MSB
F-stat*
13.604
243.676
CO
F-stat*
9.653
126.530
NOx
F-stat*
.023129 1.342
1.3995 81.206
.017
F 95%
3.00
1.29
F 95%
3.00
1.29
F 95%
3.00
1.29
F 90%
2.30
1.21
F 90%
2.30
1.21
F 90%
2.30
1.21
The F-statistic is a measure of the significance of a given factor
(here, RVP) in relation to the exhaust emissions. A value larger
than the theoretical value (i.e., F 95%) indicates that the RVP of
the fuel is significant in relation to exhaust emissions using the
given level of significance (i.e., a 95% confidence interval).
-------
2-77
Table 2-22
Analysis of Variance - Exhaust RVP Effect
(Fuel-Injected Vehicles)
Source
RVP
VEH
ERR
TOTAL
DF
2
60
120
182
SS
.59899
30.841
1.815
33.255
Exhaust HC
MSB
.29950
.51401
.015
F-stat*
19.802
33.984
F 95%
3.07
1.43
F 90%
2.35
1.32
Source
RVP
VEH
ERR
TOTAL
DF
2
60
120
182
SS
86.789
9470.300
844.911
10402.000
Exhaust CO
MSB F-stat*
43.395
157.84
7.041
6.163
22.418
F 95%
3.07
1.43
F 90%
2.35
1.32
Source
RVP
VEH
ERR
TOTAL
DF
2
60
120
182
SS
.010244
77.208
1.722
78.940
Exhaust NOx
MSB
.0051219
1.2868
.014
F-stat*
.357
89.685
F 95%
3.07
1.43
F 90%
2.35
1.32
The F-statistic is a measure of the significance of a given factor
(here, RVP) in relation to the exhaust emissions. A value larger
than the theoretical value (i.e., F 95%) indicates that the RVP of
the fuel is significant in relation to exhaust emissions using the
given level of significance (i.e., a 95% confidence interval).
-------
2-78
The above analyses show that for each technology class,
the trends in HC and CO emissions versus RVP are significant,
whereas the trend in NOx emissions versus RVP is not.
As described earlier with respect to evaporative
emissions, these test data directly apply only to vehicles
designed for 9-psi RVP fuel and operated on fuels of various
RVPs. They do not apply to vehicles designed for and tested on
higher RVP fuels. Thus, the data are directly applicable only
to the situation where vehicle designs are not changing, but
in-use RVP is being reduced (i.e., pre-1990 vehicles). The
question that remains is what happens to exhaust emissions when
vehicles are redesigned for some higher RVP and then operated
on that fuel.
Two extremes appear possible. One, the exhaust emission
effect is completely related to in-use fuel RVP and redesign
for that RVP will not reduce the exhaust emission effect. Two,
vehicles currently exhibit lower emissions on Indolene because
they are designed using Indolene and, therefore, optimizing
them for any other RVP will result in the same low emissions
when operated on that fuel (i.e., the exhaust effect will be
eliminated if design RVP equals in-use RVP). The fact that the
earlier EF testing did not show an RVP-related exhaust emission
effect argues for the latter. The only difference between the
two sets of EF testing was the evaporative emission test
procedure and the sequence of fuels. Since no hysteresis is
known to be present with respect to the effect of fuel RVP on
exhaust emissions outside of the purging of the evaporative
control canister, all of the changes between the two sets of
testing appear to be related to evaporative emissions. Since
the earlier test sequence (which mitigated the impact of higher
RVPs) eliminated the RVP effect on exhaust emissions, it would
appear reasonable to conclude that redesigning the vehicle's
evaporative and exhaust emission control systems for a higher
RVP would eliminate the exhaust effect, as well.
Thus, the exhaust emission effect is assumed to be
eliminated via any of the long-term strategies for post-1989
model year vehicles, when design RVP will be equal to in-use
RVP. Under the short-term strategies, where in-use RVP would
be less than certification fuel RVP, the exhaust effect is also
assumed to be eliminated (i.e., the car would be designed to
handle any RVP less than or equal to certification RVP).
For pre-1990 vehicles that are operated on 9.0-psi fuel,
this exhaust effect is also assumed to be eliminated. However,
when these Indolene-designed vehicles are operated on RVPs
greater than 9.0 psi, the exhaust effect will be dependent on
the in-use RVP. (Adjustment of MOBILES exhaust emission
factors, based on 11.5 RVP fuel, for various control scenarios
will be discussed in Chapter 5.)
-------
2-79
VI. Summary of Evaporative Emissions Problem and
Development of Possible Control Scenarios
1. Review
At this point, it may be helpful to review the major
topics discussed in this chapter. First, the current ozone
non-attainment problem is quite widespread and is expected to
continue without further reductions in hydrocarbon emissions.
(Of the 54 current non-attainment areas, 35 have requested
extensions to 1987.) The necessary HC reductions would appear
to be most valuable in the summer months because roughly 90
percent of all ozone violations occur between June and
September (inclusive).
Evaporative HC emissions from motor vehicles and
stationary sources (gasoline storage and distribution)
represent a significant portion of those emissions contributing
to the ozone problem. Motor vehicle evaporative losses — the
primary focus of this study -.- can be affected by several
factors, primarily the vehicle's evaporative control system
design and the volatility of the fuel being used in the
vehicle. There are some indications that the use of alcohol
blends could be another factor affecting evaporative
emissions. However, based on the review presented in Section
IV of this chapter, alcohol blends only affect evaporative
emissions during their use (i.e., alcohol blends do not appear
to permanently deactivate the charcoal). At similar
volatilities, alcohol blends appear to yield similar
evaporative emissions when compared to gasoline. Thus, the
analyses conducted in the rest of this study will treat alcohol
blends in the same manner as gasoline.
Fuel survey data indicate that some current commercial
gasolines are significantly more volatile than that for which
vehicle evaporative control systems are designed (i.e., EPA's
certification test fuel, as defined in the Code of Federal
Regulations). This trend of increasing commercial fuel
volatility has been occurring over the past two decades and
there is no evidence that the trend will not continue in the
future. Fuel volatility can be assessed using various fuel
parameters, with RVP and percent of fuel evaporated at 160°F
chosen (for purposes of this analysis) to be most pertinent to
diurnal and hot-soak losses from motor vehicles. Of these two
parameters, RVP will be the primary focus due to indications of
its greater significance and the existence of more data
defining its relationship to evaporative emission levels.
However, the impact of %i«o on evaporative losses
(particularly hot-soak) will continue to be examined in future
work.
-------
2-80
The RVP of current certification test fuel averages 9.0
psi, which is representative of the early 1970's when the
specifications were first developed. Results of EPA's ongoing
emission factor test program show that vehicles operating on
commercial fuels with RVPs greater than 9.0 psi (for which they
were designed) have evaporative losses that greatly exceed the
current standard of 2 grams/test, and that this excess is
dependent upon the RVP of the fuel being tested. Using in-use
test data, the evaporative excess was attributed to the RVP
effect, malmaintenance and equipment defects, and tampering
(the latter two also being dependent on RVP). In addition,
because vehicles also have difficulty meeting the evaporative
standard even on 9.0-psi Indolene, some of the excess emissions
are attributed to insufficient design of the purge system.
There are several approaches that can be taken to reduce
or eliminate these excess evaporative emissions from motor
vehicles. One is to control the volatility of in-use (or
commercial) fuel to a level equal to that for which the
vehicles' evaporative control systems are designed. Another
option is to change new vehicle design by revising
certification fuel specifications and test procedure; these
revisions would force manufacturers to increase the size of the
evaporative canister in order to accommodate higher emissions
from the more volatile commercial fuels, and to improve the
purge system to enable the vehicle to pass certification tests
while starting with a saturated canister (to be discussed in
more detail in Chapter 3). The retrofitting of in-use vehicles
with larger canisters or additional smaller ones in parallel
with existing systems is another approach. Though the technical
feasibility of this option has not been fully assessed, it
would most likely be very costly and of questionable
effectiveness. Therefore, retrofit will not be considered
further in this report. Rather, the options involving changes
to in-use and certification fuel volatilities and test
procedure will provide the basis for development of the
evaporative HC control strategies to be examined in the
remainder of this report.
2. Development of Control Strategies
As certification tests are intended to represent in-use
operating conditions, the long-term control strategy is to have
certification fuel RVP equal to that of typical in-use
gasoline. This can be accomplished by controlling in-use fuel
volatility, by revising certification fuel specifications, or
through a combination of the two. One remaining question
concerns the volatility level at which commercial and
certification fuels should be matched. The long-term control
options to be considered in this report are presented in Table
2-23. As shown, this analysis examines RVPs at 0.5-psi
increments between 9.0 and 11.5 psi (inclusive). In addition,
-------
2-81
Table 2-23
Lonq-Term RVP Control Scenarios
Scenario In-Use RVP (psi)* Certification RVP (psi)**
1 11.5 (baseline) 11.5
2 11.0 11.0
3 10.5 10.5
4 10.0 10.0
5 9.5 9.5
6 9.0 9.0 (baseline)
* In-use RVP control is assumed to be implemented in 1988.
** Certification RVP and test procedure are assumed to be
revised with the 1990 model year.
-------
2-82
all strategies that involve a change to certification fuel RVP
also assume a change in certification test procedure to correct
design problems such as inadequate purge.
As indicated in Table 2-23, a fuel volatility
representative of ASTM's "Class C" cities was chosen as the
baseline commercial (in-use) RVP for two basic reasons: 1) the
conditions of EPA's test procedure most closely resemble the
summer climate of these areas, and 2) a majority of the current
non-attainment areas are designated as Class C in the summer.
Although fuel survey data indicate that the current average RVP
in Class C cities is just below 11 psi, RVP is expected to
continue its historical upward trend and the ASTM Class C RVP
limit of 11.5 psi is assumed to be representative of
uncontrolled levels in the late 1980's and early 1990fs.
The earliest reasonable implementation dates estimated for
the vehicle-related and fuel-related control measures differ
from each other and are based on the following assumptions.
Possible control measures that affect vehicle design —
revisions to certification fuel and test procedure — are
assumed to be first implementable with the 1990 model year.
This is based on the assumption that a Final Rulemaking (FRM)
establishing these controls would be published no earlier than
late 1986, which already falls into the 1987 model year.
Allowing 2-3 years for the redesign of vehicles, revised
certification fuel and test procedure could probably be
implemented starting with the 1990 model year. On the other
hand, less leadtime is estimated to be necessary on the
fuel-related side. Modifications to in-use fuel volatility can
be accomplished with changes in refinery operating parameters
as opposed to changes in equipment design, if desired. (These
refinery modifications are discussed in more detail in Chapter
4.) Based on this assumption, the implementation date assumed
for in-use fuel volatility control is 1988. Again, this
assumes that the FRM would be published in late 1986.
Because changes in certification fuel or test procedure
affect only the design of new vehicles, it takes some time
before the in-use fleet has turned over and the full impact of
larger canisters and improved purge cycle are realized.
However, any modification to in-use fuel volatility has an
immediate effect on evaporative emissions from the entire
fleet. In addition to affecting motor vehicle emissions,
in-use fuel volatility has an impact on HC vapors emitted
during gasoline storage and distribution (bulk terminals,
refueling, etc.). Therefore, a viable short-term option is to
control in-use fuel volatility to levels below the
certification specification, and then eventually allow in-use
RVP to increase to the long-term certification RVP level after
a certain period of time. The various RVP scenarios examined
under this short-term approach are shown in Table 2-24.
Several time periods for this additional control were evaluated
-------
2-83
Table 2-24
Short-Term RVP Control Scenarios
Long-Term
Scenario
1
2
3
4
5
6
7
. 8
9
10
11
12
13
14
15
* In-use
** Pf»r1-Tf-
In-Use RVP (psi)*
9.0
9.0
9.5
9.0
9.5
10.0
9.0
9.5
10.0
10.5
9.0
9.5
10.0
10.5
11.0
RVP control is assumed
i r> a 1- i nn Tt\7f> anri 1-PRt- r>ri
Certification RVP (psi)**
9.5
10.0
10.0
10.5
10.5
10.5
11.0
11.0
11.0
11.0
11.5
11.5
11.5
11.5
11.5
to be implemented in 1988!
nnertiirp aKsiimeH fri h>f» rtn/i Rf*A
with the 1990 model year.
-------
2-84
and will be discussed as results are presented later in the
report. As with the long-term scenarios, in-use fuel control
is assumed to be implemented in 1988, and vehicle-related
controls begin with the 1990 model year.
-------
2-85
References (Chapter 2)
1. "1981-1983 Standard Metropolitan Statistical Area
(SMSA) Air Quality Data Base for Use in Regulatory Analysis,"
Memo from Richard G. Rhoads, Director of Monitoring and Data
Analysis Division, to Charles Gray, Director of Emission
Control Technology Division, February 25, 1985.
2. "Guidance Document for the Correction of Part D SIPS
for Non-Attainment Areas," Office of Air Quality Planning and
Standards, U.S. EPA, Research Triangle Park, North Carolina,
January 27, 1984.
3. "Control Characteristics of Carbon Beds for Gasoline
Vapor Emissions", EPA-600/2-77-057, Michael J. Manos and Warren
C. Kelly, Scott Environmental Technology, for EPA, ORD, IERL,
February 1977.
4. "Combustion Engine Economy, Emissions and Controls,
July 9-13, 1984" Engineering Summer Conferences, The University
of Michigan College of Engineering.
5. "Hydrocarbon Control for Los Angeles by Reducing
Gasoline Volatility," Edwin E. Nelson, Engineering Staff, GM
Corp., SAE Paper No. 690087.
6. "Effect of Fuel Front-End and Midrange Volatility on
Automobile Emissions," B. H. Eccleston and R.W. Hurn,
Bartlesville Energy Research Center, U.S. DOI, Bureau of Mines,
Report of Investigations 7707.
7. "Effect of Fuel Composition on Amount and Reactivity
of Evaporative Emissions," M.W. Jackson and R.L. Everett, SAE
Paper No. 690088, 1969.
8. "Mathematical Models for Prediction of Fuel Tank and
Carburetor Evaporation Losses," W.J. Koehl, Jr., Research
Dept., Mobil Research and Development Corp., SAE Paper No.
690506, May 1969.
9. "Mathematical Expressions Relating Evaporative
Emissions from Motor Vehicles without Evaporative Loss-Control
Devices to Gasoline Volatility," William F. Biller, Michael
Manoff, Jyotin Sachdev, and William C. Zegal, Scott Research
Laboratories, Inc., and David T. Wade, Esso Research
Engineering Co., SAE Paper No. 720700, 1972.
10. "Clean Air Act Waiver Application, Section 2ll(f),
Volume 2" E.I. du Pont de Nemours and Company, Inc., July 11,
1984.
-------
2-86
References (Chapter 2) Cont'd
11. "Environmental Impacts of Methanol/Gasoline Blends,"
prepared for Air Pollution Control Association by Tom Cackette
and Thomas Austin, February 16, 1984.
12. Letter from Dale F. Pollart, Texaco, Inc., to
Richard Wilson, EPA, dated May 13, 1985.
13. "Analysis of Fuel Volatility Characteristics and
Evaporative Hydrocarbon Emissions for Alcohol/Gasoline Blends,"
PLMR-43-83, E.I. du Pont de Nemours and Company, Inc., June 29,
1983.
14. "Standard Specification for Automotive Gasoline,
D-439-83," American Society of Tests and Measurements (ASTM).
15. "MVMA National Gasoline Survey, Summer Season,
1984," Motor Vehicle Manufacturers Association, Inc., October
15, 1984.
16. "Motor Gasolines, Summer 1984," Ella Mae Shelton and
Cheryl L. Dickson, National Institute for Petroleum and Energy
Research (NIPER), for API, February 1985.
17. "Fuel Volatility Trends," Southwest Research
Institute, EPA Contract No. 68-03-3192, Work Assignment 4, Task
3, Final Report dated September 28, 1984.
18. "Commentary by General Motors to the EPA on the
Appropriateness of Current Emissions Certification Test Fuel
Specifications," attachment to internal correspondence from
T.M. Fisher, General Motors Corporation, to Charles L. Gray,
Jr., EPA, September 3, 1980.
19. Federal Register, January 13, 1985, 50 FR 2615.
20. "Alcohol Outlook," May 1985.
21. "Methanol Demand and Availability," Presented to
U.S. EPA Region VI by James L. Snyder, Celanese Chemical
Company, Inc., May 21, 1985.
22. "Performance Evaluation of Alcohol-Gasoline Blends
in 1980 Model Automobiles, Phase II - Methanol-Gasoline
Blends," prepared for DOE by CRC, January 1984.
23. "Physical Properties of Gasoline/Alcohol Blends,"
Frank N. Cox, U.S. DOE, Bartlesville Energy Technology Center,
September 1979.
24. "Performance Evaluation of Alcohol-Gasoline Blends
in 1980 Model Automobiles, Phase I - Ethanol-Gasoline Blends,"
prepared for DOE by CRC, July 1982.
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2-87
References (Chapter 2) Cont'd
25. "Twenty-three Car In-House Oxinol Blend Test
Program," EPA Memo from Craig A. Harvey to Charles L. Gray,
Jr., ECTD, November 19, 1984.
26. "Evaporative Emissions of Methanol Blend Fueled
Vehicles," EPA Technical Report, EPA-AA-TSS-PA-84-5, Craig
Harvey, Project Officer, November 1984.
27. "Evaporative Emissions from Vehicles Operating on
Methanol/Gasoline Blends," Ken Stamper, SAE Paper No. 801360.
28. "Emissions, Fuel Economy and Driveability Effects of
Methanol/Butanol/Gasoline Fuel Blends," Robert L. Furey and
Jack B. King, SAE Paper No. 821188.
29. "Impact of Gasohol on Automobile Evaporative and
Tailpipe Emissions," Frank M. Black and John M. Lang, SAE Paper
NO. 810438.
30. "Evaporative and Exhaust Emissions from Cars Fueled
with Gasoline Containing Ethanol or MTBE," Robert L. Furey and
Jack B. King, SAE Paper No. 800261.
31. "Gasohol: Technical, Economic or Political Panacea?"
Thomas C. Austin and Gary Rubenstein, SAE Paper No. 800891.
32. "Gasohol Test Program," Richard Lawrence, Director,
Engineering Operations Division, QMS, U.S. EPA,
EPA-AA-TAEB-79-4B, February 1980.
33. "Exhaust and Evaporative Emissions from Alcohol and
Ether Fuel Blends," T. M. Naman and J. R. All sup, SAE Paper No.
800858.
34. "Testing of Three Caltrans Gasohol Fueled Vehicles,"
California Air Resources Board, May 1980.
35. "Material Compatibility and Durability of Vehicles
with Methanol/Gasoline Grade Tertiary Butyl Alcohol Gasoline
Blends," David J. Miller, David A. Drake, et al., SAE Paper No.
841383.
36. "Monthly Progress Report No. 3 for the period May 1
through May 31, 1985; Work Assignment No. 29, Contract
68-03-3162, 'Additional Mini-Canister Evaluation,1 SwRI Project
03-7338-029," from Lawrence R. Smith, SwRI, to Craig A. Harvey,
EPA, June 15, 1985.
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2-88
References (Chapter 2) Cont'd
37. "The Effect of Methanol on Evaporative Canister
Charcoal Capacity," Draft Report, EPA-460/3-84-014, Mary Ann
Warner-Selph (SwRI) for EPA, January 1985. (Available from
NTIS, No. PB-85-179-752/AS)
38. GM Presentation to EPA-MOD, Washington, D.C., June
12, 1985.
39. "Technical Directive No. 4 to EPA Contract No.
68-03-3230, Effects of RVP and Temperature on Evaporative
Emissions of 2-gram, Vehicles," from John Shelton, Project
Officer, EPA, to Myron W. Gallogly, President, Automotive
Testing Laboratories, March 20, 1985.
40. "Amendment No. 1 to Technical Directive No. 4,
Contract 68-03-3230," from John Shelton, Project Officer, EPA,
to Myron W. Gallogly, President, Automotive Testing
Laboratories, July 18, 1985.
41. "Factors Influencing Vehicle Evaporative Emissions,"
D.T. Wade, SAE Paper 670126, 1967.
42. "Exhaust and Evaporative Emissions of High Mileage
Taxicabs and Passenger Cars," EPA Technical Report, Craig A.
Harvey, Project Officer, February 1985.
43. API presentation to EPA on "1984 Evaporative
Emissions Research Programs, Gasoline Volatility Assessment
Task Force," contractors: NIPER and ATL, 1985.
44. Letter from J.S. Welstand, Chevron Research
Division, to Chester J. France, EPA, April l, 1985.
45. "Motor Vehicle Tampering Survey - 1982," EPA, QMS,
FOSD, EPA-330/1-83-001, April 1983.
46. "Motor Vehicle Tampering Survey - 1983," EPA, QMS,
FOSD, August 1984 (no report number given).
47. Data in support of "Motor Vehicle Tampering Survey -
1984," EPA, QMS, FOSD, report not yet published.
48. "Report for Third Quarter, FY 85, In-Use Vehicle
Testing in Ann Arbor," EPA memorandum from Howard
Brasher-Frederick to Charles L. Gray, EPA, OMS, ECTD, July 23,
1985.
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2-89
References (Chapter 2) Cont'd
49. "Relationship Between Exhaust Emissions and Fuel
Volatility," EPA memo from Thomas L. Darlington to Charles L.
Gray, EPA, QMS, ECTD, June 24, 1985.
50. "Evaporative HC Emissions for MOBILE3," EPA
Technical Report No. EPA-AA-TEB-85-1, U.S. EPA, OAR, ECTD, TEB,
August 1984.
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2-90
Appendix 2-A
Effect of Ambient Temperature
Conditions on Evaporative Emissions
As mentioned earlier in Section IV.D. of this chapter, the
effect of ambient temperature conditions on evaporative HC
emissions is one of the areas still being investigated by EPA.
The purpose of this Appendix is twofold. First, available data
on evaporative emissions vs. temperature are analyzed and
compared to relative emissions predicted via a theoretical
emission model. Second, typical summertime temperature and RVP
conditions in several of the current ozone non-attainment areas
are compared to EPA's standard evaporative test conditions by
means of a theoretical diurnal emissions model. Estimates made
in this Appendix are offered as a preliminary assessment of the
impact of temperature conditions as they differ from those
specified as part of the standard evaporative test procedure.
These preliminary results have not been incorporated into the
emission projections made in this study, as more data and
analysis are required before this can be done with confidence.
The first section below reviews available data from a
current EPA test program designed to evaluate the impact of
temperature on evaporative emissions. The next section relates
these measured emissions to relative emission indexes
calculated for each test condition using a theoretical diurnal
emissions model. Finally, theoretical emissions indexes are
calculated for several ozone non-attainment areas using typical
summertime (i.e., July) temperature conditions; these indexes
provide the basis for a rough comparison of city conditions to
standard EPA test conditions.
A. Temperature vs. Emissions Test Program
An EPA-sponsored test program is currently being conducted
at the Automotive Test Laboratory (ATL) for the purpose of
measuring diurnal and hot-soak losses at various temperatures
and gasoline RVPs.[35] The complete test matrix consists of
the following:
Parameter Test Points
Gasoline RVP 9.0, 10.4, 11.7 psi
Diurnal Starting Temp. 60, 68, 75°F
Diurnal Temp. Change +15, +20, +24, +30 °F
Hot Soak Temp. 70, 82, 95°F
At the time of this analysis, testing of 24 light-duty vehicles
certified to the 2-gram standard (i.e., 1981 and later models)
— 14 carbureted, 10 fuel-injected — had been completed. The
first 9 vehicles were tested over the entire matrix listed
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2-91
above; however, in order to include a greater number of
vehicles in the program, the other 15 vehicles were tested over
only a partial matrix (i.e., two RVPs, two diurnal starting
temperatures, and two hot-soak temperatures, instead of three).
Data from fuel-injected and carbureted vehicles were
analyzed separately in the following manner:
1) Full-matrix data were separated from data on
vehicles tested over only a partial matrix;
2) Emission results (in grams/test) were averaged
within each set for each of the temper a ture/RVP
combinations;
3) Emission averages at each condition within each set
of data (i.e, full vs. partial matrix) were
"normalized" to the standard certification test with
9.0-psi Indolene, starting diurnal temperature of
60 °F, diurnal change of +24°F, and hot-soak
temperature of 82°F (i.e., the average g/test
measurement under these standard conditions was
subtracted from all other averages, making the
standard value in each set zero);
4) After normalization, the two data sets (full and
partial) were combined into one normalized set by
arithmetically weighting the emission averages in
each set by the number of vehicles tested in each
data set (see Table 2-A-l);
5) The average emission factor at 9.0 RVP from the
in-use EF test program was then added to each value
in the normalized set, so that the g/test associated
with the 9.0 RVP (Indolene) test under standard
temperature conditions was consistent with the
in-use EF results used in the rest of this study
(see Table 2-A-2).*
Focusing on the diurnal losses measured under standard
test temperatures, the difference between emissions at 9.0 RVP
and 11.7 RVP was significantly less in the ATL data than that
indicated by the in-use EF results (4.26 versus 7.82 g/test for
carbureted vehicles and 1.44 versus 5.23 g/test for
fuel-injected vehicles). In fact, before normalization, the
ATL emission levels were lower overall than the average in-use
results. This is most likely due to the relative condition of
the ATL test vehicles, which were somewhat better maintained,
A multiplicative approach could also have been used,
wherein the ATL averages would have been normalized to 1.0
at the standard 9.0 RVP test, and then the EF average at
9.0 RVP would have been multiplied by each value in the
normalized set.
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2-92
Table 2-A-l
ATL Diurnal Averages — Normalized
to 9.0 RVP Standard Test
Vehicle RVP No. of
Type (psi) Vehicles
GARB
GARB
CARB
FI
FI
FI
9.0 14
5
14
10.4 10
5
10
11.7 9
5
9
9.0 10
4
10
10.4 6
4
6
11.7 8
4
8
Starting
Temp(°F)
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
Diurnal Emissions (g/test)
+15°F
-0.38
-0.23
-0.08
-0.14
0.14
0.92
0.39
0.84
6.46
-0.24
-0.30
-0.16
-0.20
-0.03
1.23
-0.04
0.86
3.78
+20°F
-0.20
0.11
0.65
0.58
1.11
4.30
1.74
4.41
18.48
-0.13
-0.05
0.30
0.02
1.18
5.99
0.50
4.61
11.55
+24°F
0.00
0.62
2.13
0.96
3.13
9.69
4.26
10.17
31.38
0.00
0.58
1.25
0.58
3.60
13.99
1.44
11.16
21.13
+30°F
0.60
2.57
7.55
5.03
9.44
24.21
12.29
22.94
64.29
0.44
3.38
5.17
3.18
11.71
31.39
5.69
27.30
52.45
-------
2-93
Table 2-A-2
Diurnal Emissions — Consistent with In-Use
EF Results at 9.0 RVP Standard Test
Vehicle RVP No. of
Type (psi) Vehicles
CARS
CARB
CARB
FI
FI
FI
9.0 14
5
14
10.4 10
5
10
11.7 9
5
9
9.0 10
4
10
10.4 6
4
6
11.7 8
4
8
Starting
Temp(°F)
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
Diurnal Emissions (g/test)
+15°F
1.94
2.09
2.24
2.18
2.46
3.24
2.71
3.16
8.78
1.01
0.95
1.09
1.05
1.22
2.48
1.21
2.11
5.03
+20°F
2.12
2.43
2.97
2.90
3.43
6.62
4.06
6.73
20.80
1.12
1.20
1.55
1.27
2.43
7.24
1.75
5.86
12.80
+24°F
2.32*
2.94
4.45
3.28
5.45
12.01
6.58
12.49
33.70
1.25*
1.83
2.50
1.83
4.85
15.24
2.69
12.41
22.38
4-3 0°F
2.92
4.89
9.87
7.35
11.76
26.53
14.61
25.26
66.61
1.69
4.63
6.42
4.43
12.96
32.64
6.94
28.55
53.70
From in-use EF test results.
-------
2-94
on the whole, than the in-use vehicles tested. For instance,
any obvious problems, such as the disconnected tank vent line
found in one vehicle, were corrected before testing at ATL.
Also, the leaking gas caps in three vehicles were replaced in
order to prevent intermittent leaks from disguising actual
trends in emissions versus temperature (i.e., the cap may leak
during the low temperature test but not with the high
temperatures, resulting in unrealistically higher emissions at
low temperatures). Another reason for lower emissions is that
the ATL vehicles' evaporative control systems may have been
more adequately purged prior to testing, as they were driven a
minimum of 45 miles to the ATL test site compared to an average
of 21 miles between the homes of the in-use vehicles' owners
and the EPA test site in Ann Arbor.
Because the in-use program represents a significantly
larger data base (over 200 vehicles versus 24 at ATL) and
because the in-use data provide the basis for emission
projections made throughout this study, two more final steps
were taken to make the ATL data consistent with the in-use
program:
6) The normalized sets shown in Table 2-A-l were
further normalized at each RVP level (i.e., the
value shown for the standard temperature conditions
with 10.4 RVP was subtracted from all other values
in the 10.4 data set; the same was done for the 11.7
RVP results; see Table 2-A-3);
7) Finally, the in-use EF average at each of the two
RVPs (10.4 and 11.7) under standard temperatures was
added to the normalized values in each of the RVP
sets.
The end product of these various steps, as shown in Table
2-A-4, is a set of emission results at various temperatures
that is consistent with averages from in-use EF testing at
standard temperature conditions, which were developed from the
much larger data base. But in addition, the impact of
temperature on evaporative emission levels can now begin to be
assessed. For example, a change in the diurnal temperature
difference from the standard 24°F to 20°F (with a starting
temperature of 60°F) can reduce fuel-injected diurnal losses by
0.13 g/test, or 10 percent, with an RVP of 9.0 psi; however,
the impact at 11.7 psi is somewhat greater with a reduction of
0.94 g/test, or 15 percent. The potential impact of other
changes, such as higher diurnal starting temperatures or
greater diurnal temperature difference, can also be estimated
from Table 2-A-4.
Again, these are only initial results based on a
preliminary analysis of data from 24 vehicles. As more data
become available, the analytical techniques described above
will be reassessed and could be modified. In addition, the
magnitude of the impact of temperature on emissions indicated
-------
2-95
Table 2-A-3
ATL Diurnal Averages — Normalized
to All Three Standard Tests (9.0, 10.4, 11.7 RVPs)
Vehicle RVP
No. of
Type (psi) Vehicles
GARB 9.0
GARB 10.4
GARB 11.7
FI 9.0
FI 10.4
FI 11.7
14
5
14
10
5
10
9
5
9
10
4
10
6
4
6
8
4
8
Starting Diurnal Emissions (g/test)
Temp(°F) +15°F
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
-0
-0
-0
-1
-0
-0
-3
-3
2
-0
-0
-0
-0
-0
0
-1
-0
2
.38
.23
.08
.10
.82
.04
.87
.42
.20
.24
.30
.16
.78
.61
.65
.48
.58
.34
+20°F
-0
0
0
-0
0
3
-2
0
14
-0
-0
0
-0
0
5
-0
3
10
.20
.11
.65
.38
.15
.34
.52
.15
.22
.13
.05
.30
.56
.60
.41
.94
.17
. 11
+24°F
0
0
2
0
2
8
0
5
27
0
0
1
0
3
13
0
9
19
.00
.62
.13
.00
.17
.73
.00
.91
.12
.00
.58
.25
.00
.02
.41
.00
.72
.69
+30°F
0
2
7
4
8
23
8
18
60
0
3
5
2
11
30
4
25
51
.60
.57
.55
.07
.48
.25
.03
.68
.03
.44
.38
.17
.60
.13
.81
.25
.86
.01
-------
2-96
Table 2-A-4
Diurnal Emissions — Consistent with In-Use EF Results
at All Three Standard Tests (9.0, 10.4, 11.7 RVPs)
Vehicle RVP
Type (psi)
GARB 9.0
GARB 10.4
GARB 11.7
FI 9.0
FI 10.4
FI 11.7
No. of
Vehicles
14
5
14
10
5
10
9
5
9
10
4
10
6
4
6
8
4
8
Starting Diurnal Emissions (g/test)
Temp(°F) +15°F
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
60
68
75
1
2
2
3
4
4
6
6
12
1
0
1
1
1
2
5
5
8
.94
.09
.24
.82
.08
.88
.27
.72
.34
.01
.95
.09
.45
.62
.88
.00
.90
.82
+20°F
2
2
2
4
5
8
7
10
24
1
1
1
1
2
7
5
9
16
.12
.43
.97
.54
.07
.26
.62
.29
.36
.12
.20
.55
.67
.83
.64
.54
.65
.59
+24°F
2
2
4
4
7
13
10
16
37
1
1
2
2
5
15
6
16
26
.32*
.94
.45
.92*
.09
.65
.14*
.05
.26
.25*
.83
.50
.23*
.25
.64
.48*
.20
.17
+30°F
2
4
9
8
13
28
18
28
70
1
4
6
4
13
33
10
32
57
.92
.89
.87
.96
.40
.17
.17
.82
.17
.69
.63
.42
.83
.36
.04
.73
.34
.49
From in-use EF test results.
-------
2-97
by the raw data could change as the vehicle sample is
broadened, which could also cause these preliminary findings to
change.
B. Theoretical Diurnal Emissions Index vs. Test Data
At this point, the data could simply be reduced via a
multiple regression analysis. However, the amount of data
available is not large and strong non-linear interrelationships
between the variables are known to exist (e.g., the effect of
an increase in diurnal temperature change will be much greater
at high fuel RVP than low). Thus, at this point in time, it
was deemed more appropriate to utilize an emission model for
uncontrolled diurnal emissions to reduce the test variables to
a single evaporative emission potential and then correlate
actual emissions with this potential. In this way, less
emphasis is placed on any individual data point and the chance
of having outliers that strongly affect the results is
significantly lessened.
A model of uncontrolled diurnal emissions developed by
D.T. Wade in 1967 was chosen for this purpose.[41] (No
hot-soak emission model was known to be readily available.)
This model relies on changes in actual fuel vapor pressure, the
Ideal Gas Law, and the readily predictable processes ocurring
in a vehicle's fuel tank to predict uncontrolled diurnal losses
from a fuel tank as a function of fuel characteristics
(including RVP) and temperature conditions. The concepts
involved in the modeling of diurnal losses are fairly
straightforward; however, minor errors can exist. For
instance, the assumption that the vapor pressure at the midway
point between the starting and ending diurnal temperatures is
the same as the average of the initial and final vapor
pressures may involve a small amount of error. Wade compared
his predicted uncontrolled levels to fuel tank running losses
measured during road and dynomometer tests.[41] Although
running losses differ from diurnal emissions as we have
referred to them here, the same basic principles apply because
both types of losses occur in response to an increase in fuel
tank temperature. Wade found that his model was better at
predicting losses measured during the road tests than with the
dynomometer tests, most likely because equilibrium between the
liquid and vapor phases within the fuel tank was better
maintained during the road tests. Correlation between the
predicted values and the dynomometer measurements was rather
poor, especially as the losses increased.[41] However, as
actual in-use conditions would most closely parallel the road
tests, the model should be suitable when used to predict the
relative impacts of various field conditions.
Wade's model can be used to predict absolute uncontrolled
diurnal losses (i.e., grams of HC emitted from the fuel tank)
for any given set of conditions; however, its use here was to
predict relative losses and not absolute values. More
specifically, Wade's model was used here to calculate a
-------
2-98
relative index of theoretical uncontrolled diurnal emissions
which could be related to measurements of controlled diurnal
emissions under various conditions to produce a diurnal
emissions model. An index-of 1.00 was assigned to the standard
diurnal test (i.e., 60-84°F, 9.0 RVP Indolene).
Wade's equation for uncontrolled diurnal losses is as
follows:
G = 454 W (
520
690 - 4M
(P - p )
t 2
P -p
t
(P -p ) V
til
where:
G = Weight hydrocarbon lost, g
W = Fuel density, Ib/gal
M = Molecular weight of hydrocarbon vapor, Ib/lb mole
at average liquid temperature
p = Vapor pressure of gasoline, psia, at liquid temper-
temperature corresponding to T
P = Total pressure, psia
p +
1
P =
psia
V = Volume of vapor space, cu ft
T = Temperature, R
Subscripts:
t = Tank
1 = Initial state
2 = Final state
-------
2-99
The relative emissions index mentioned earlier was
calculated as the ratio of Gt««t (using various test
temperatures and RVPs) to G,t
-------
2-100
Table 2-A-5
Calculated Emission Indexes for
Each ATL Diurnal Test Condi t i on
Test
No.
l
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
RVP Starting
(psi) Temp (°F)
9.0 60
68
75
10.4 60
68
75
11.7 60
68
75
Diurnal
Charge (°F)
+15
+20
+24
+30
+15
+20
+24
+30
+ 15
+20
+24
+30
+ 15
+20
+24
+30
+15
+20
+24
+30
+ 15
+20
+24
+30
+ 15
+20
+24
+30
+15
+20
+24
+30
+ 15
+20
+24
+30
Emissions
Index
0.51
0.77
1.00*
1.45
0.71
1.03
1.33
2.04
0.96
1.42
1.96
2.88
0.76
1.08
1.52
2.11
1.06
1.56
2.14
3.24
1.40
2.34
3.03
4.71
0.89
1.42
2.02
2.54
1.41
2.31
2.98
4.58
1.97
3.33
4.76
7.05
Current EPA certification test conditions
-------
Figure 2-A-l
EMISSIONS VS INDEX
CARBURETED CARS
6
8
LJ
g
Ł
Q,
ou -
70 -
60 -
50 -
40 -
30 -
20 -
10 -
0 -
-t-
D
D
+
.Jj
•+
D
+
D +
i + ffl
•f- * rpj O
H dlnw "•
i i i i i i i •
0 2 4 6 E
M
O
INDEX
-------
Figure 2-A-2
Ł
6
2
LJ
D
O
50 H
30 H
20
10 H
0
E
EMISSIONS VS INDEX
FUEL-INJECTED CARS
I
2
n
n
I
4
INDEX
D
«2
I
6
D
K)
O
8
-------
2-103
C. City Temperature Conditions vs. EPA Test Conditions
This final portion of this Appendix makes a preliminary
attempt to evaluate how representative EPA's current and
proposed certification test procedures are of conditions in
various ozone non-attainment areas. The comparisons will make
use of Wade's diurnal emissions model once again, and therefore
hot-soak losses will not be discussed. No attempt will be made
here to predict absolute emissions in any of the urban areas
examined, but rather relative city temperature and RVP
differences will be assessed with respect to EPA's test
conditions. As mentioned earlier, after careful analysis of
all data, efforts may be made in the future to make MOBILE3
city-specific in its modelling of evaporative HC emissions. It
is important to note, however, that any methodologies or
techniques used in this Appendix do not necessarily represent
the approach that will be taken in any modification of the
MOBILE program.
For this analysis, two basic comparisons were made. The
first evaluates current city-specific conditions, including
actual summertime RVPs from MVMA's 1984 Summer Gasoline Survey
[14], against EPA's current certification test for diurnal
losses — a 60-84°F temperature excursion with 9.0 RVP Indolene
test fuel. The second comparison is more representative of
future conditions, assuming ASTM's volatility limits will be
reached in each of the urban areas and comparing these
city-specific conditions to a proposed certification test —
using an RVP of 11.5 psi with the same diurnal temperature
excursion of 60-84°F. Both comparisons make use of the same
temperature data for each of the cities — 30-year average
minimum and maximum July temperatures.* In future work, one
possible refinement would be the use of temperatures from days
on which ozone violations have actually occurred within each
area. However, for this analysis, typical July temperatures
were chosen because July is one of the two months shown to be
most prone to ozone episodes (the other is August, as indicated
earlier in this chapter in Table 2-4).
From the list of 47 non-attainment areas shown earlier in
Table 2-1, 17 were included in MVMA's 1984 Summer Gasoline
Survey.[14] Because current city-specific RVPs were needed for
the first comparison, only these 17 areas were included in this
analysis.
Temperatures were taken from the Climatography of the
United States, U.S. National Oceanic and Atmospheric
Administration, and The Weather Almanac, Gale Research
Company.
-------
2-104
City-specific inputs for the first comparison are shown in
Table 2-A-6. Temperatures are shown in Fahrenheit degrees, but
were converted to Rankin for use in Wade's equation. City RVPs
shown are from the MVMA survey. All other variables (i.e., W,
M, p2 and pi) are a function of RVP and temperature. Using
these inputs, .a relative diurnal index was calculated for each
of the cities using Wade's equation; again, the standard EPA
test with 9.0 RVP Indolene is given an index of 1.00. Final
indexes for each city are shown in Table 2-A-7.
For these city-specific index calculations, the effect of
fuel "weathering" on volatility and, thus, evaporative
emissions was also accounted for. As discussed earlier in
Section IV.B. of Chapter 2, General Motors estimated that
diurnal emissions were roughly 15 percent lower with weathered
fuel than with non-weathered Indolene at the 40-percent full
tank level specified in EPA's test procedure.[16] For purposes
of this analysis, a constant factor of 0.85 was applied to the
city-specific portion , of the diurnal index (i.e., the
numerator) to account for this 15-percent decrease in emissions
due to fuel weathering in the field. Because EPA's test fuel
is not weathered, the 0.85 factor is not applied in determining
G.td (the denominator of the index). (This weathering effect
has already been incorporated into the indexes shown in Table
2-A-7.)
As indicated in Table 2-A-7, the current certification
test on Indolene appears to significantly underestimate diurnal
emissions in the majority of the ozone non-attainment cities
examined. In only two of the 17 cities (Boston and Atlanta) do
diurnal losses appear to be slightly overestimated by the
certification test — indicated by an index of less than one.
These results are not surprising as current RVPs in most of the
cities examined are much greater than 9.0 psi.
The second question to be answered concerns the future:
"If RVPs in all areas reach the ASTM summer (July) limits, will
the certification diurnal test be representative of these areas
if test fuel RVP is raised to 11.5 psi (instead of the current
9.0 psi)?" In order to address this question, city-specific
indexes were recalculated using the inputs shown in Table
2-A-8. Temperatures are the same as before (i.e., 30-year
average July minimums and maximums), but here the RVPs shown
are the current ASTM July limits for each of the cities.* Of
course, the remaining variables also change because of their
dependence on RVP. Weathering was again included in the
city-specific calculations.
This is true except for three cities—Chicago, Cleveland,
and St. Louis—where current RVPs are already above their
respective ASTM limits. In these cases, the MVMA survey
RVPs were used (i.e., same as in Table 2-A-6).
-------
2-105
Table 2-A-6
City-Specific Inputs for First Index Calculation
(Using Survey RVPs)
T
2
MVMA
T Survey
1 RVP
W
City (°F)* (°F)* (psi)** (Ib/qal)
Chicago 83.1
Cleveland 81.6
Detroit 83.1
Boston 81.4
NYC 85.2
Wash., DC 88.2
Phila. 86.8
Miami 89.1
Kansas City 88.0
St. Louis 88.4
Dallas 95.5
San Antonio 94.0
Atlanta 86.5
New Orleans 90.4
Phoenix 104.8
Las Vegas 103.9
Denver 87.4
EPA Test 84.0
(Current)
* Temperatures
minimums (Ti )
United States,
60.7
61.2
63.4
65.1
68.0
69.1
66.7
75.5
66.9
68.8
74.0
74.0
69.4
73.3
77.5
75.3
58.6
60.0
are 30-year
for the month
U.S. National
11.8
11.7
11.4
11.0
11.3
10.6
11.0
10.5
10.0
10.5
10.0
10.0
9.7
10.5
8.4
8.3
9.2
9.0
average
of July
Oceanic
6.17
6.17
6.17
6.18
6.18
6.19
6.18
6.19
6.20
6.19
6.20
6.20
6.21
6.19
6.23
6.24
6.22
6.22
M
i. (Ib/lb
61.2
61.3
61.6
62.0
61.7
62.4
62.0
62.5
63.0
62.5
63.0
63.0
63.3
62.5
65.2
65.4
63.8
64.0
P
2
mole) (psi)
9.4
9.1
8.9
8.4
9.2
9.2
9.3
9.2
8.6
9.1
9.7
9.4
8.0
9.5
9.5
9.3
7.8
7.2
normal daily maximums (T2)
(Sources: Climatoqraphy of
and Atmospheric
Administration,
P
1
(psi)
6.4
6.3
6.3
6.3
6.8
6.5
6.5
7.3
5.9
6.4
6.7
6.7
5.9
6.9
6.0
5.6
4.6
4.6
and
the
and
The Weather Almanac, Gale Research Company)
** Average city
Season 1984.
RVPs from the
MVMA National
Gasoline
Survey -- Summer
-------
2-106
Table 2-A-7
Current EPA Test vs. Calculated City-Specific Diurnal
Indexes (Using Survey RVPs)
City
Chicago
Cleveland
Detroit
Boston
NYC
Wash. , DC
Philadelphia
Miami
Kansas City, MO
St. Louis
Dallas
San Antonio
Atlanta
New Orleans
Phoenix
Las Vegas
Denver
"Current" Diurnal Index
1.56
1.38
1.25
0.96
1.27
1.38
1.45
1.07
1.20
1.35
1.67
1.45
0.87
1.44
1.77
1.74
1.12
EPA Indolene Test 1.00
(Current)
-------
2-107
Table 2-A-8
City-Specific Inputs for Second Index Calculation
(Using ASTM's July RVP Limits)
City
Chicago
Cleveland
Detroit
Boston
NYC
Wash., DC
Phila.
Miami
Kansas City
St. Louis
Dallas
San Antonio
Atlanta
New Orleans
Phoenix
Las Vegas
Denver
EPA Test
(Future)***
T
2
T
(°F)*
83.
81.
83.
81.
85.
88.
86.
89.
88.
88.
95.
94.
86.
90.
104.
103.
87.
84.
1
6
1
4
2
2
8
1
0
4
5
0
5
4
8
9
4
0
* Temperatures
minimums (Ti)
United
States,
The Weather
/ o
60
.61
63
65
68
69
66
75
66
68
74
74
69
73
77
75
58
60
1
F)*
.7
.2
.4
.1
.0
.1
.7
.5
.9
.8
.0
.0
.4
.3
.5
.3
.6
.0
ASTM
RVP
Limit
(psi)** (
11.8
11.7
11.5
11.5
11.5
11.5
11.5
11.5
10.0
10.5
10.0
10.0
11.5
11.5
9.0
9.0
10.0
11.5
are 30-year average
for the month of July
U.S.
Almanac,
National
W
Ib/qal)
6.17
6.17
6.17
6.17
6.17
6.17
6.17
6.17
6.20
6.19
6.20
6.20
6.17
6.17
6.22
6.22
6.20
6.17
M
(Ib/lb
61
61
61
61
61
61
61
61
63
62
63
63
61
61
64
64
63
61
normal daily
(Sources:
.2
.3
.5
.5
.5
.5
.5
.5
.0
.5
.0
.0
.5
.5
.0
.0
.0
.3
mole) (p
9
9
9
8
9
9
9
10
8
9
9
9
9
10
10
10
8
9
P
2
si) J
.4
.1
.0
.7
.4
.9
.7
.0
.6
.1
.7
.4
.7
.3
.4
.3
.6
.3
maximums (T2)
Climatography of
Oceanic and Atmospheric
Administration,
P
1
(psi)
6.4
6.3
6.3
6.5
7.0
7.1
6.8
7.9
5.9
6.4
6.7
6.7
7.1
7.7
6.5
6.1
5.0
6.0
and
the
and
Gale Research Company)
**
***
ASTM's maximum RVP specification for the month of July for each area,
except where current levels already exceed ASTM limits.
As assumed in this analysis.
-------
2-108
Indexes for this second comparison were calculated as
before (i.e., the denominator based on standard Indolene test
conditions) and are shown in Table 2-A-9. As indicated there,
most of the indexes have increased in comparison to those in
Table 2-A-7. This is entirely due to the assumed increase in
RVP as ASTM limits are reached. The exceptions occur in six
cities where the indexes do not change because their current
RVPs are either just at or above the ASTM limits (i.e., inputs
are the same for these particular cities in both Tables 2-A-6
and 2-A-8).
In this part of the analysis, the city-specific indexes
are most appropriately compared to the index calculated for the
future test conditions implicit in this study — a 60-84°F
diurnal temperature excursion with an RVP of 11.5 psi. This
index, also shown in Table 2-A-9, is 1.89; because this
involves a test fuel, no weathering effect was accounted for
here. As shown, if certification RVP were revised to 11.5 psi
with no change in the current test temperatures, the test would
then ensure that vehicles' evaporative control systems were
designed to operate properly in the majority of U.S. cities.
As shown in Table 2-A-9, only two of the 17 cities (Phoenix and
Las Vegas) have indexes greater than 1.89 (that of the future
test procedure), indicating theoretically higher diurnal losses.
D. Summary
A few basic conclusions can be made from the analyses
presented in this Appendix. First, diurnal and hot-soak losses
can increase dramatically with higher temperatures as well as
with higher RVPs. The effect of higher RVPs had already been
fairly well-defined via EPA's in-use EF testing (as described
in detail earlier in Chapter 2). However, the effect of
temperature on evaporative emissions has not been examined to
nearly such a great extent, as the ATL testing represents EPA's
first significant work in this area. As shown in Part A of
this Appendix, initial ATL test data show emissions to be
somewhat less sensitive to RVP than do the in-use EF test
results, which could imply that perhaps the ATL results are
also underestimating the effect of temperature. However, as
more vehicles are added to the ATL sample, trends in the
results could change and become more consistent with the in-use
EF data.
Some preliminary conclusions regarding the
representativeness of EPA's current certification procedure can
be made based on the analysis in Part C of this Appendix.
Using the diurnal emissions index based on Wade's equation, it
was shown that the variety of summer temperature and RVP
conditions typical of several of the ozone non-attainment areas
could theoretically result in a rather wide range of diurnal
-------
2-109
Table 2-A-9
Future* EPA Test vs. Calculated City-Specific
Diurnal Indexes (Using ASTM's July RVP Limits)
City
Chicago
Cleveland
Detroit
Boston
NYC
Wash. , DC
Philadelphia
Miami
Kansas City, MO
St. Louis
Dallas
San Antonio
Atlanta
New Orleans
Phoenix
Las Vegas
Denver
"Future" Diurnal Index
1.56
1.38
1.31
1.06
1.34
1.67
1.63
1.40
1.20
1.35
1.67
1.45
1.51
1.76
2.32
2.34
1.44
EPA 11.5-RVP Test 1.89
(Future)*
As assumed in this analysis
-------
2-110
losses. However, the majority of these predicted relative
levels are greater than that predicted for the current standard
diurnal test conditions (i.e., 60-84°F, 9.0 psi RVP) .
Therefore, the premise made in Chapter 2 that EPA's current
certification test is underestimating summertime diurnal losses
in the majority of the urban areas appears to be confirmed.
Results of this initial analysis support the position that the
current test conditions need to be modified — either in terms
of RVP or temperatures, or both — in order to be more
representative of conditions in the field. The change examined
here — raising certification fuel RVP to 11.5 psi without any
other modifications — would appear to result in vehicles being
properly designed for typical summer days in most of the cities
examined. However, an examination of days on which actual
ozone violations have occurred may show more severe temperature
conditions than the 30-year July averages, and could result in
higher city-specific indexes.
As alluded to earlier, one of EPA's future goals is to
incorporate city-specific information on diurnal and hot-soak
temperatures, RVP, and perhaps weathering into the modelling of
evaporative HC emissions. Additional information is needed
before this task can be accomplished with confidence.
Following completion of the ATL testing, the objective is to
develop two models — one for diurnal and one for hot-soak
losses — that can be used to predict emissions from controlled
vehicles (i.e., equipped with a canister) as a function of both
RVP and temperature conditions. Then, as city-specific
conditions are defined, the appropriate diurnal and hot-soak
losses could be determined and input into MOBILES. In
addition, more information on the effect of fuel weathering in
the field is needed before it can be incorporated into the
emissions modelling. The effect of weathering on fuel
volatility — as opposed to the effect on emissions — will
most likely be the focus here. The weathering effect could
then enter into the analysis as a direct adjustment of each
city-specific RVP before it is read into the diurnal and
hot-soak models.
-------
2-111
Appendix 2-B
Breakdown of Motor Vehicle Evaporative
Emission Factors into Their Components
I. Introduction
The evaporative emission factors used in this analysis
were derived from the results of EPA's in-use emission factor
(EF) test program. From July 1984 until April 1985, 164
vehicles were tested under this program. These vehicles were
tested on 1) commercial fuel with a nominal RVP of 11.7 psi,
2) a blended fuel with an RVP of 10.4 psi, and 3) Indolene
fuel, with an RVP of roughly 9.0 psi, in that order. The
complete test procedure has been summarized in Table 2-11 under
the heading of Post-July 1984.
The vehicles in the EF testing program have been separated
by the condition of the vehicle, and by type of fuel metering
system. Those vehicles having evaporative emission control
malfunctions considered to be tampering were placed in the
category of "tampered" vehicles. The remaining vehicles were
categorized as "non-tampered" vehicles. As a subset of this
group, those vehicles which exhibited no evaporative control
system , malfunctions were categorized as "problem-free"
vehicles. Table 2-14 listed the potential malfunctions in the
evaporative control systems, and noted those that were
considered tampering. Within each of the above categories, the
vehicles have also been separated into carbureted and
fuel-injected vehicles.
Through consideration of the different evaporative
emission rates for each of these categories, the individual
components of the final evaporative emission factors were
determined. These components are: 1) the standard level, 2)
the insufficient design effect, 3) the malmaintenance and
defect effect, 4) the excess RVP effect, and 5) the tampering
effect. The magnitude of the first four of these components
were determined directly from the EF data. The in-use EF
sample is not thought to have a representative number of
tampered vehicles, however, so the magnitude of the tampering
effect has not been developed from this testing, and will
therefore be discussed separately. These components are later
used to determine the evaporative emission factors for the
various control scenarios in Chapter V.
-------
2-112
II. Non-Tampered Vehicle Evaporative Emission Rates
The average measured emission rates for non-tampered
vehicles for each of the three fuels tested is shown in the top
portion of Table 2-B-l. However, this analysis requires that
the emission rates be known for in-use RVPs other than just
these three levels. Therefore, curves were fit through the
data for both diurnal and hot-soak emissions for each type of
fuel metering system. The emission rates from these curves are
summarized in the bottom part of Table 2-B-l. Note that the
rates from the curves at 9.0, 10.4, and 11.7 psi differ
slightly from the actual test data.
These emission rates have been separated into the four
non-tampered components listed previously. The remainder of
this section will describe the process by which the magnitude
of each component was determined, and how they were
extrapolated from light-duty vehicles to light-duty trucks and
heavy-duty vehicles.
A. Standard Levels
The standard levels represent the emission rates that
would be seen if the vehicles emitted just at the current
2-gram/test LDV standard on 9.0 RVP fuel. As it is necessary
to break this level down into diurnal and hot-soak losses
(which vary from vehicle to vehicle), it is assumed that the
ratio of hot-soak to diurnal emissions from problem-free
vehicles is the same that would be seen if the standard level
were met. Therefore, all that needs to be done to determine
the standard levels is to normalize the hot-soak and diurnal
emissions on 9.0 RVP fuel from the problem-free sample such
that their sum equals 2 grams/test. The emission rates
observed from the problem-free vehicles and the calculated
standard levels are presented in the first parts of Table 2-B-2.
B. Insufficient Purge Design Effect
The differences between the standard levels and the
problem-free emission rates on 9.0 RVP fuel represent the
effect of insufficient purge system design. This is based upon
the assumption that an operating evaporative control system
with no malfunctions should meet the 2-gram/test standard.
This effect is determined by simply subtracting the calculated
standard levels from the emission rates for problem-free
vehicles on 9-psi RVP fuel, as shown at the bottom of Table
2-B-2. Note that for fuel-injected vehicles this effect is
non-existent, as their problem-free average emissions on 9-psi
RVP fuel are under 2 grams/test.
-------
2-113
Table 2-B-l
Non-Tampered 81+ LDV and LDT Evaporative
Emission Rates (q/test)
EF Test Data
Fuel Metering System RVP(psi)
CARS 9.0
10.4
11.7
FI 9.0
10.4
11.7
Fitted Curves
Fuel Metering System - RVP(psi)
GARB 9.0
9.5
10.0
10.5
11.0
11.5
FI 9.0
9.5
10.0
10.5
11.0
11.5
Hot-Soak
2.33
2.93
4.05
0.93
1.38
1.92
Hot-Soak
2.32
2.46
2.68
2.98
3.37
3.84
0.90
1.08
1.27
1.46
1.65
1.83
Diurnal
2.36
4.92
10.14
1.21
2.23
6.48
Diurnal
2.32
3.04
06
,40
05
4
5
7
9.01
1
1
1
25
59
93
2.34
3.68
5.51
-------
2-114
Table 2-B-2
Estimation of Standard Level and Insufficient
Purge Effect for 81+ LDVs and LDTs (q/test)
Problem-Free Vehicle
Average with 9.0 RVP
CARB
FI
Hot Soak
1.50
0.64
Diurnal
1.25
0.87
Standard Level*
CARB
FI
1.09
0.85
0.91
1.15
Insufficient Design/Capacity
Purge Effect**
CARB-Straight
-Adjusted
FI
0.41
0.30
0.00
0.34
0.30
0.00
**
Problem-free average normalized to 2-gram standard.
Problem-free average minus standard level; if negative, as
for FI vehicles, considered zero.
-------
2-115
l
These insufficient design effect values for carbureted
vehicles, require an additional, very slight adjustment due to
the fact that the curve fits described in the previous section
do not exactly match the EF data. These adjusted values are
also shown in Table 2-B-2. The differences between the
straight and adjusted values are equivalent to the differences
at 9.0 RVP between the EF data for non-tampered vehicles and
those given by the fitted curves. Without this adjustment, the
component values would not sum to the average emission level
for non-tampered vehicles in the EF sample.
C. Malmaintenance and Defect Effect
Non-tampered vehicles, on the whole, show significantly
higher average evaporative emission rates than do problem-free
vehicles (a subset of non-tampered vehicles). This effect is
assumed to be due to improper maintenance and equipment defects
in the evaporative emission control system, but not to
deliberate tampering. (The distinction between
malmaintenance/defects and tampering was made earlier in Table
2-14 of Chapter 2.)
The magnitude of the effect of malmaintenance and defects
upon evaporative emission rates was found to increase with fuel
RVP. The determination of this relationship for diurnal
emissions from carbureted vehicles is shown graphically in
Figure 2-B-l. The top line shows the average emission rates at
the 3 fuel RVPs for all non-tampered vehicles; the middle line
shows these rates for only problem-free vehicles; and the
bottom line shows the difference between the top two lines. A
simple linear regression passing through the value at 9.0 RVP
has been fitted to the values at 10.4 and 11.7 RVP to arrive at
this "difference" curve. This same method was used to develop
the relationships for carbureted hot-soak, fuel-injected
diurnal, and fuel-injected hot-soak emissions.* The resulting
malmaintenance and defect effects are summarized in Table 2-B-3.
Two carbureted 1983 Nissan Stanzas in the problem-free
sample had unexplainably high (>23 grams/test) hot-soak
emissions that skewed the results such that the
malmaintenance and defect effect decreased with increasing
RVP. The removal of the hot-soak results for these two
vehicles from the problem-free sample corrected this
problem. Therefore, this approach was taken for this
portion of the analysis.
-------
12.0
FIGURE 2-B-1
CARBURETED DIURNAL EMISSIONS
CTi
1 1.8
O NON-TAMPERED
FUEL RVP
PROB.-FREE
MAINTENANCEXDEFECT
-------
2-117
Table 2-B-3
Malmaintenance and Defect Effect
for 81+ LDVs and LDTS
Fuel Meter inq System RVP (psi)
GARB 9.0
9.5
10.0
10.5
11.0
11.5
FI 9.0
9.5
10.0
10.5
11.0
11.5
(grams/test)
Hot Soak
0.83
0.91
0.99
1.07
1.15
1.24
0.29
0.42
0.55
0.67
0.81
0.93
Diurnal
1.11
1.21
1.31
1.41
1.51
1.61
0.34
0.44
0.54
0.64
0.74
0.84
-------
2-118
D. Excess RVP Effect
The RVP effect represents the excess evaporative emissions
that arise from operating vehicles on a fuel of a higher
volatility that for which they were designed. Current
evaporative control systems are designed to meet the
2-gram/test standard when operated on Indolene, with an average
RVP of 9.0 psi. Current in-use gasolines in many areas of the
country, however, have average volatilities well above 9.0 psi.
The magnitude of the RVP effect will of course depend upon
the actual volatility of the in-use fuel. Herein, this
magnitude is generally defined as the difference between
non-tampered evaporative emissions on commercial fuel and
Indolene, adjusted to reflect the effect that fuel volatility
has upon the malmaintenance and defect effect. Without this
latter correction a situation of double counting would arise.
As an example, calculation of the excess RVP effect on diurnal
emissions from carbureted vehicles operating on 11.5-psi fuel
is reviewed below.
Using the fitted curve values listed in Table 2-B-l, the
total difference between the carbureted diurnal losses at 11.5
RVP (9.01 g/test) and 9.0 RVP (2.32 g/test) is calculated as
6.69 g/test. However, part of this total difference in
non-tampered emissions has already been accounted for in the
RVP-dependent malmaintenance/defect effect. As Table 2-B-3
shows, the difference between the 11.5 RVP and 9.0 RVP diurnal
effects for carbureted vehicles is 0.50 g/test (i.e., 1.61
minus 1.11). Therefore, the net effect to be attributed to
excess RVP is simply the difference between 6.69 and 0.50, or
6.19 g/test. This value, along with the estimated excess RVP
effect for each of the other cases, is shown in Table 2-B-4.
E. Extrapolation of LDV Data to LDTs and HDGVs
The extrapolation of the light-duty vehicle evaporative
emission rates to light-duty trucks and heavy-duty vehicles is
done here exactly as it was done for MOBILES.* Basically,
since little or no in-use test data exist for these vehicles,
the emission rates are extrapolated based upon their relative
standard levels. For LDTs, this means that evaporative
emission rates will be exactly the same as for LDTs, as both of
these vehicle classes must meet the same 2.0-gram/test standard
under identical test procedures.
Beginning with the 1985 model year, HDGVs must meet either
a 3,0-gram/test or 4.0-gram/test standard, depending upon their
gross vehicle weight. Therefore, the evaporative emission
rates for HDGVs under the 3.0- and 4.0-gram standards are those
See Reference 50 of Chapter 2.
-------
2-119
Table 2-B-4
Excess RVP Effect for 81+ LDVs and LDTs (q/test)
Diurnal
0.00
0.62
1.54
2.78
4.33
6.19
0.00
0.24
0.48
0.79
. 2.03
3.76
Fuel Metering System RVP (psi)
GARB 9.0
9.5
10.0
10.5
11.0
11.5
FI 9.0
9.5
10.0
10.5
11.0
11.5
Hot-Soak
0.00
0.06
0.20
0.42
0.73
1.11
0.00
0.05
0.11
0.18
0.24
0.29
-------
2-120
for light-duty vehicles multiplied by 1.5 and 2.0,
respectively, weighted by their respective sales fractions
projected for 1987 — 81.5 percent for 3-gram and 18.5 percent
for 4-gram vehicles. This yields an overall
heavy-duty/light-duty multiplicative factor of 1.5925.
Heavy-duty vehicles are assumed to be completely carbureted, so
the evaporative emission factors from only the carbureted
vehicles are used. The resulting evaporative emission factors
and the magnitude of each of the various components are shown
in Table 2-B-5.
Ill. Tampering Effect
The emission rates for tampered vehicles have been derived
from SHED testing on light-duty vehicles with removed canisters
and/or fuel caps. The results of this SHED testing, which was
performed using 9.0 and 11.5 RVP fuels, are shown in the top
portion of Table 2-B-6. The values for fuels of other RVPs
were determined through linear interpolation. Certain
assumptions were made as part of this testing. First,
uncontrolled diurnal emissions were assumed to be the same
regardless of either the type of disablement or the vehicle's
fuel metering system. Secondly, for fuel-injected vehicles,
uncontrolled hot-soak emissions are assumed to be the same for
either canister or fuel cap removal. Finally, for carbureted
vehicles, fuel cap removal is assumed not to lead to any
increases in hot-soak emissions (i.e., the uncontrolled values
are the same as the non-tampered hot-soak averages shown in
Table 2-B-l).
The differences between these uncontrolled emissions and
those of non-tampered vehicles are defined as the "tampering
offsets" to be used in the MOBILE3 program, along with
tampering frequency estimates. These offsets are given in the
bottom half of Table 2-B-6.
Again, LDV data on uncontrolled evaporative emissions were
used to develop the LDT and HDGV estimates, due to lack of
evaporative testing on these classes. As before, the tampering
offsets for LDTs were assumed to be equal to those developed
from the LDV data, as indicated in Table 2-B-6. The
methodology used to develop uncontrolled estimates for HDGVs is
similar to that mentioned previously with respect to the
non-tampered averages (i.e., as outlined in Reference 50 of
Chapter 2). Variations from the basic MOBILES method of
extrapolating LDV evaporative data to "HDGVs will be detailed in
an upcoming EPA technical report, entitled "The Effect of Fuel
Volatility on Controlled and Uncontrolled Evaporative
Emissions," which is expected to be released by the end of the
year. Uncontrolled estimates and tampering offsets (calculated
as before — i.e., uncontrolled minus non-tampered averages)
for HDGVs are presented in Table 2-B-7.
-------
2-121
Table 2-B-5
Evaporative Emission Rates for Non-Tampered 85+ HDGVs(g/test)
Component
Standard Level
Insufficient Design
Capac i ty/Pur ge
Malmaintenance/Defect
-
Excess RVP
Total Non-Tampered
Average
RVP (psi)
-
-
9.0
9.5
10.0
10.5
11.0
11.5
9.0
9.5
10.0
10.5
11.0
11.5
9.0
9.5
10.0
10.5
11.0
11.5
Hot-Soak
1.73
0.64
1.32
1.45
1.58
1.71
1.84
1.97
0.00
0.09
0.31
0.67
1.15
1.77
3.69
3.91
4.26
4.75
5.36
6.11
Diurnal
1.44
0.48
1.77
1.93
2.09
2.25
2.41
2.57
0.00
0.98
2.46
4.43
6.90
9.85
3.69
4.83
6.47
8.60
11.23
14.34
-------
2-122
Table 2-B-6
81+ LDV and LPT Tampering*
Uncontrolled Emission Rates (g/test)
Fuel Metering
System
GARB
FI
RVP
(psi)
9.0
9.5
10.0
10.5
11.0
11.5
9.0
9.5
10.0
10.5
11.0
11.5
Canister Removal
Hot-Soak Diurnal
10.36
11.79
13.21
14.63
16.05
17.47
4.93
6.26
7.59
8.93
10.26
11.59
14.95
17.10
19.25
21.41
23.56
25.71
14.95
17.10
19.25
21.41
23.56
25.71
Gas Cap Removal
Hot-Soak Diurnal
2.32
2.46
2.68
2.98
3.37
3.84
4.93
6.26
7.59
8.93
10.26
11.59
14.95
17.10
19.25
21.41
23.56
25.71
14.95
17.10
19.25
21.41
23.56
25.71
Fuel Metering
System
GARB
FI
Tampering Offsets (g/test)
RVP Canister Removal
Hot-Soak Diurnal
11.5
8.04
9.33
10.53
11.65
12.68
13.63
4.03
5.18
6.32
7.47
8.61
9.76
12.63
14.06
15.19
16.01
16.51
16.70
13.70
15.51
17.32
19.07
19.88
20.20
Gas Cap Removal
Hot-Soak Diurnal
0.00
0.00
0.00
0.00
0.00
0.00
4
5
03
18
6.32
7.47
8.61
9.76
12.63
14.06
15.19
16.01
16.51
16.70
13.70
15.51
17.32
19.07
19.88
20.20
To be included in an upcoming EPA Technical Report, "The
Effect of Fuel Volatility on Controlled and Uncontrolled
Evaporative Emissions," by Celia Shin and Tom Darlington,
TEB, ECTD, QMS, currently under development.
-------
2-123
Table 2-B-7
85+ HDGV Tampering*
Uncontrolled Emission Rates (g/test)
RVP Canister Removal Cap Removal
(psi)
9.0
9.5
10.0
10.5
11.0
11.5
RVP
(psi)
9.0
9.5
10.0
10.5
11.0
11.5
Hot-Soak Diurnal
14.67 26.08
16.40 28.83
18.12 31.59
19.86 34.35
21.58 37.11
23.31 39.87
Tampering Offsets
Canister Removal
Hot-Soak Diurnal
10.98 22.39
12.49 24.00
13.86 25.12
15.11 25.75
16.22 25.88
17.20 25.53
Hot-Soak
3.69
3.91
4.26
4.75
5.36
6.11
(g/test)
Diurnal
26.08
28.83
31.59
34.35
37.11
39.87
Cap Removal
Hot-Soak
0.00
0.00
0.00
0.00
0.00
0.00
Diurnal
22.39
24.00
25.12
25.75
25.88
25.53
To be included in an upcoming EPA Technical Report, "The
Effect of Fuel Volatility on Controlled and Uncontrolled
Evaporative Emissions," by Celia Shin and Tom Darlington,
TEB, ECTD, QMS, currently under development.
-------
CHAPTER 3
Vehicle-Oriented Excess Evaporative HC Control
I. Introduction
This chapter will focus upon the modifications to current
vehicular evaporative emissions control systems (ECSs) needed
in order to improve their ability to control evaporative
emissions. The need for such improvement stems from the
proposed changes in the certification test procedure to: 1)
eliminate the discrepancy between certification and in-use fuel
volatility, and 2) begin the test with a fully saturated
canister. These changes will necessarily require increased
storage capacity and purge capacity in evaporative ECSs.
The key issues surrounding improvements of current
evaporative ECSs involve the technological feasibility of
potential modifications, and the costs associated with such
modifications. These two issues are addressed in Sections II
and III below, respectively. The overall conclusions are
presented in Section IV.
Two effects that arise from improved evaporative ECSs that
will affect the overall costs will be addressed separately from
the generalized cost determination, as their costs are more of
an indirect nature. These are: 1) an improvement in gas
mileage due to increased fuel vapor recovery (i.e., the
evaporative recovery/prevention credit), and 2) a reduction in
gas mileage due to the extra weight involved in using a larger
evaporative canister (i.e., the excess weight penalty). The
former is addressed in Section VI of Chapter 4 and the latter
in Appendix 6-B of Chapter 6. This chapter will focus
primarily upon the initial price increase to the consumer.
II. Technology
As has been indicated, vehicular evaporative emissions
control systems require modification in order to meet the
stricter requirements imposed by the proposed changes in the
certification test procedure. These changes will center
around: 1) increasing the capacity of the canister to adsorb
and desorb hydrocarbon vapors, and 2) increasing the ability
of the control system to purge the evaporative canister.
Before discussing the technological feasibility of making these
improvements, however, it is necessary to understand what the
system working capacity is, how it is determined, and to
estimate how much more capacity is needed.
-------
3-2
A. System Working Capacity
In Chapter 2 of this report, a brief description of system
working capacity was presented. Therein; it was defined as the
actual mass of gasoline vapors that an evaporative control
system will adsorb and desorb during operation, and was
described as being dependent upon factors both internal and
external to the control system. That description will be
expanded at this point.
The internal factors cited as determining, in part, the
system working capacity are: 1) the physical characteristics
of the charcoal, 2) the volume of charcoal in the canister,
3) the configuration of the canister, and 4) the volume of
purge air drawn through by the control system.
Vapor adsorption and desorption is a purely physical
process, with Van der Wall's bonding acting as the force
holding the vapor to the charcoal.[1] The effectiveness of
this bonding will depend upon the average particle size, the
ratio of surface area to volume of the individual particles,
and the size of the pores in which the vapor molecules are
adsorbed. These various elements determine what is defined as
the charcoal "working capacity" (measured as grams HC per 100
cubic centimeters (cc) of charcoal).
In a given volume of charcoal, smaller particles* can be
compacted more tightly, thus increasing the likelihood that the
vapors will come in contact with the surface of the particles.
The tighter compaction of particles also allows for a greater
mass of charcoal in a given volume, resulting in increased
volumetric working capacity. This increase in charcoal working
capacity has been seen in a designed exper iment. 12] This same
compaction, however, decreases permeability and reduces the
flow rate through the canister at a specific pressure drop. It
is for this reason that, in current practice, the maximum
pressure drop across the canister at a specified flow rate is
usually the determining factor in the selection of particle
size.[3]
Particle size of a given charcoal type is usually
expressed in terms of mesh size and is expressed in the
form A x B. A and B are divisions per inch and A x B size
particles are able to pass through (I/A) inch by (1/B)
inch openings. Thus, larger values of A and B represent a
smaller mesh size and therefore smaller particles.
-------
3-3
A greater surface area for a given particle implies more
sites to which vapor molecules can be bonded. Therefore a
particle with a highly convoluted surface having a large
surface area to volume ratio will necessarily be a better
adsorber than a particle of similar size with a smaller surface
area to volume ratio. Increasing this ratio by disturbing the
surface of a particle is the process that is referred to when
carbon is defined as being activated.[4]
Finally, pore size can affect the charcoal working
capacity, although the effect is not as clear as with particle
size or the surface area-to-volume ratio. In general, vapor
molecules will adsorb into pores of a size comparable to their
own. It is possible, however, that larger particles can become
lodged in pores in such a manner as to block access to more
pore space that smaller particles could occupy. Since these
larger particles are heavier and the bonding forces are
stronger, they may not be removed during the purge cycle, and a
portion of the carbon's adsorptivity will be lost.tl]
A charcoal's working capacity is measured as its ability
to adsorb and desorb HC vapor, on a volumetric basis, under a
relatively standardized test procedure. Working capacity is
usually measured as grams of butane per 100 cc of charcoal, as
butane is easy to work with, yields consistent results and is
the dominant compound in vehicular evaporative emissions.
Typical levels of "butane working capacity" for various
charcoals are presented in Table 3-1. These values will not
necessarily translate directly into charcoal working capacities
for vehicular evaporative emissions, as these HC vapor mixtures
are more complex than simple butane. Since HC species differ
in their physical characteristics, they will be adsorbed
preferentially and the degree of preference may depend upon
carbon type. Thus, equal butane working capacities will not
always result in equal gasoline working capacities.[2,4]
Assuming that the characteristics of the charcoal remain
the same, there should be a direct relationship between the
volume of charcoal used and the system working capacity. This
should be clear from the definition of the charcoal working
capacity.
Canister configuration may play a role in determining the
system working capacity, although this fact is disputed. In a
study by Scott Environmental Technology, the working capacity
of a canister was increased by 12.3 percent by doubling the
length of a cylindrical canister while holding the diameter,
and therefore the cross sectional area, constant.[2] The
theoretical explanation for this increase in working capacity
-------
3-4
Table 3-1
Charcoal Properties*
Charcoal
BPL-3
WV-A
WV-A
Extruded***
Manufacturer
Calgon
Westvaco
Westvaco
West-varo
Base
Coal
Wood
Wood
Wnnri
Mesh Size
6 X 14
10 X 25
14 X 35
****
Surface
2
Area (m /q)
800-1000
1500-1700
1600-1800
Apparent
Density
3
(Ib/ft )
23-24
15-18
16-19
?n_7i
Capacity
Test I*
6.8
8.5
9.0
in. >;
(q/100 cc)
Test II**
8.08
8.31
8.89
* Specified by charcoal manufacturer in "Westvaco's Wood-Base Carbons Improve
Evaporative Emission Control," Billy Kornegay, Ph.D., P.E., September 1980.
** From a test performed by Westvaco.
*** Data from phone conversation with Bill Kornegay of Westvaco Corporation on November
5, 1984.
**** Not specified, but equivalent pressure drop of mesh size 6 x 14.
-------
3-5
centers on the concept of a "mass transfer zone" (MTZ). This
theory states that when the carbon bed is charged, there will
exist a zone which is fully saturated with hydrocarbons and a
zone where the saturation decreases from fully saturated to
completely devoid of hydrocarbons. This MTZ will only operate
at half of its theoretical capacity when breakthrough occurs,
and its length will not vary with the length of the carbon
bed. A carbon bed whose length is twice that of the MTZ will
have a capacity at breakthrough of 75 percent of maximum.* By
doubling the length of the carbon bed, with the length of the
MTZ remaining constant, there will be less under-utilization of
capacity, and the capacity at breakthrough will be 87.5 percent
of maximum.** This theoretical increase of 12.5 percent is
quite close to that observed in the testing.[2]
Other reports, though, have indicated that system working
capacity is not significantly related to canister
configuration. The first of these provides no experimental
results to support its conclusion, however. In the other, the
only experimental results provided involved canisters that had
been loaded beyond breakthrough, which is relevant with respect
to total capacity, but not working capacity.[5] Thus, since
the argument that there is no relationship between canister
configuration and system working capacity appears quite flawed,
whereas the argument for a relationship appears reasonable and
consistent, working capacity must be considered to be sensitive
to canister configuration.
The final factor that can be controlled by the evaporative
emission control system designer is the volume of purge air
drawn though the system. Without adequate purge, the carbon
will saturate quickly and lose even more capacity that it would
.naturally. It has been shown that the total volume of purge
air, rather than the velocity of the air, determines the amount
of adsorbed hydrocarbon that will be desorbed.tS] When
sufficient purge air is available, the system working capacity
is the same as the "canister working capacity." Otherwise, it
is less than the canister working capacity.
*Figured as: [0.5 (length) x 1.0 (capacity utilized)] +
[0.5 (length) x 0.5 (capacity utilized)].
** Figured as: [0.75 (length) x 1.0 (capacity utilized)] +
[0.25 (length) x 0.5 (capacity utilized)].
-------
3-6
Chapter 2 also described several factors external to the
control system that may affect the system working capacity.
These include the humidity of the purge air, the temperature of
the purge air, and the vapor concentration of the evaporative
emissions. Working capacity will decrease with increased
humidity, but this is not a lasting effect as charcoal has a
higher affinity for hydrocarbons than for water vapor.[2]
Working capacity will increase with higher temperature purge
air as more HC can be desorbed at higher temperatures. [2,4]
Working capacity will also increase when there is a larger
concentration of HC vapors.[2] This latter effect is worth
quantifying as it will become significant when in-use RVP and,
therefore, HC vapor concentration, are changed.
The adsorptivity of charcoal has been found to be
dependent upon the vapor concentration of the evaporative
emissions.[2] This is illustrated in Figure 3-1, showing the
average charcoal working capacities for two coal-based
charcoals tested on 8.7 and 13.8 RVP (psi) fuels. The higher
RVP fuel will necessarily produce a higher vapor concentration
(due to its higher volatility) than the lower RVP fuel. The
figure clearly shows an increase in charcoal working capacity
with increasing RVP, which will translate into a higher system
working capacity.
B. Extra Control Needed
The increase in system working capacity necessary to meet
the requirements of the changes in the test procedure can be
estimated by considering the resulting increase in uncontrolled
emissions (i.e., HC vapors to the canister) that result from
these changes. These must be adjusted, however, to reflect the
changes in working capacity that will occur automatically
without any modifications to the evaporative control system.
The difference between these two will represent the amount of
extra control that the ECS designer will have to develop.
Figure 3-2 shows graphically how the required amount of
extra system working capacity is determined. Curve 1 shows the
relationship between uncontrolled evaporative emissions and
fuel volatility. Therefore, this curve represents the increase
in system working capacity required with various RVP fuels.
For present purposes, this curve has been normalized such that
emissions from a 9.0 RVP fuel, typical of current certification
fuel, equal 1.0. Curve 2 is a reproduction of Figure 3-1,
showing the relationship between charcoal working capacity and
fuel volatility. This curve has also been normalized such that
the value for 9.0 RVP fuel equals 1.0. Curve 3 is the ratio of
Curves 1 to 2, and indicates the additional system working
capacity, relative to the 9.0 RVP baseline, that is needed in
-------
FIGURE 3-1
CHARCOAL WORKING CAPACITY vs. RVP
_J
<
0
u
A**
u_
<
V
w
o
8
\
o
x
l/>
IF r
o
/ .u -
6.9 -
6.8 -
6.7 -
6.6 -
6.5 -
6.4 -
6.3 -
6.2 -
6.1 -
6.0 -
5.9 -
5.8 -
5.7 -
5.6 -
5.5 -
5.4 -
5.3 -
5.2 -
5.1 -
5 0 -
** m\f
n
.-•'"
.--"
x"
./'
/•'
/
._^~
./
..-•"
s~'
..'""
..'-"
X
X
..--'
--p""
_.-""
-/
....
,.-•""
.-""
j-^"
/
.,- .-*
B
l I I 1 i
8.0 10.0 12.0 14
i
vj
RVP
CHAR. WORKING CAP.
-------
UJ
E
O.
UJ
1 .7
1 .6 -
mmm
uj 1 .3 -
1.2-
1.1 -
1 .0
FIGURE 3-2
EFFECTS RELATIVE TO 9.0 RVP FUEL
9.0
a EMISSIONS
9.4
9.8
10.2
RVP (psf)
CHAR. WC
10.6 11.0 '11.4
* DESIGN CAPACITY
U)
I
00
-------
3-9
addition to that naturally occurring within the system. For
example, a change in the certification fuel to 11.5-psi RVP,
while generating 64 percent more emissions, will only require
the development of a 45-percent increase in system working
capacity, as a 13-percent increase in the system working
capacity will be realized from the increase in specific
charcoal working capacity.
Because of the increase in the amount of uncontrolled
emissions generated by a higher RVP fuel and loaded onto the
larger capacity canister, a greater volume of purge air will be
necessary to unload the canister during the purge cycle. With
a higher RVP fuel, the HC concentration obtained in the vapor
above the liquid fuel is greater than the HC concentration
obtained with a lower RVP fuel. However, since the HC vapors
are loaded at a higher HC concentration, and subsequently
desorbed during the purge cycle at the same increased
concentration, the purge volume only has to be increased by a
degree that is less than the increase in uncontrolled
emissions. Assuming the HC concentration is a linear function
of RVP, the HC concentration to and from the canister with
11.5-psi RVP fuel is 28 percent greater than the HC
concentration with 9.0-psi RVP fuel. Therefore, the purge
volume only has to be increased by 28 percent (1.64/1.28 =
1.28) to purge an equal percentage of the adsorbed HC from the
larger canister.
C. Potential Modifications
As discussed previously, to increase the system's capacity
to control emissions, both canister capacity and purge air
volume must be increased. Changing the canister configuration,
increasing the desorption-adsorption temperature differential
and changing the particle size are also options, but their
effects are less pronounced and too vehicle-model specific to
be considered here. The remainder of the discussion, then,
will be limited to canister and purge capacity.
1. Canister Capacity
In order to increase the canister working capacity, either
canister volume can be increased or specific charcoal working
capacity can be increased. Though increasing the canister size
will increase the cost of the evaporative emission control
systems, it will require no significant technological
innovation. The option of using a charcoal with a higher
specific working capacity than that presently used has become
technologically feasible for some systems with the introduction
to the market in 1984 of a new type of charcoal. The
properties of this "extruded" charcoal were shown in Table 3-1,
along with the properties of other charcoals.
Because of the greater specific working capacity of the
extruded charcoal (10.5 vs. 6.8-9.0 g/100 ml), canisters
-------
3-10
with an equal volume of the extruded charcoal would have a
higher working capacity and, thus, be able to support emissions
from a higher RVP fuel. This is shown in Table 3-2, taking
into account the current carbon type of various manufacturers
and curves 1 and 2 of Figure 3-2. By switching to this type of
charcoal, then, present systems could support 9.7 - 11.7 RVP
fuels without requiring an increase in canister size. An
increase in pressure drop with the extruded charcoal may
occur. However, the charcoal manufacturer expects to be able
to accommodate these concerns by manufacturing various particle
sizes.[6]
The option of switching to this extruded charcoal to meet
an 11.0-11.5 RVP certification fuel standard is feasible for
some vehicle manufacturers (i.e., those using large particle,
coal-based charcoal). However, since it is not necessarily
feasible industry-wide, the remainder of this report will
consider only the alternative option to increase the canister
capacity — increasing the canister size. This is not meant to
imply that charcoals with specific working capacities greater
than those traditionally used could not be developed. It is
more an indication of a decision not to make any assumptions
about their development at this time. Also, in the absence of
regulatory actions, improved charcoal could be used to reduce
the volume of current canisters, thus still requiring an
increase due to certification fuel and test procedure changes.
The increase in designed canister capacity required to
meet a new RVP standard is shown in Table 3-3. For an 11.5 RVP
certification fuel, this would be a 45-percent increase in
carbon corresponding to: 580 ml for LDVs, 760 ml for LDTs and
1800 ml for HDVs. To estimate this for LDVs and LDTs, an
average industry-wide canister size was determined from 1985
certification records by assuming an equal sales distribution
between evaporative families for a given manufacturer and
averaging corporate-average canister sizes by projected 1990
sales for each corporation. Only dominant manufacturers were
included: General Motors, Ford, Chrysler, Toyota, and Nissan.
For HDVs, an average canister size of 4000 ml is used, as it is
expected that General Motors will use two canisters totaling
4000 ml of charcoal on all of its HDVs. [7] Details of these
calculations are shown in Appendix 3-A.
It was assumed that all canisters would have to be
proportionally increased in size to accommodate the increased
emissions. Many manufacturers presently use identical
canisters on vehicles with differing fuel tank sizes and fuel
metering systems. The result is that many vehicles currently
have oversized canisters. Presumably, it is more economically
advantageous to overdesign some systems than to manufacture
more than a few different-sizes of canisters. With the
increasing use of fuel injection, though, there may be more
-------
3-11
Table 3-2
Canister Equivalents With Extruded Charcoal
Canister
Ford
Chrysler
GM
Toyota**
Nissan**
Present
Carbon
Type
Calgon BPL-3
Westvaco WV-A
Westvaco WV-A
Calgon BPL-3
Calgon BPL-3
Mesh
Size
6 x 14
14 x 35
10 x 25
6 X 14
6 x 14
Ratio of
Increased
Working
Capacity
to Present
Working
Capacity
1.54
1.17
1.24
1.54
1.54
Equivalent
RVP
Control*
11.65
9.85
10.20
11.65
11.65
**
From Curve 3 of Figure 3-2.
Estimated on the basis of charcoal type.
-------
Vehicle Class
LDV
LOT
HDV
Table 3-3
Average Canister Volume Increase*
Certification
9.5
ml
129
169
400
%
10
10
10
10.0
ml
245
321
760
%
19
19
19
ml
361
473
1120
Fuel RVP (psi)
10.5
%
28
28
28
ml
477
625
1480
11.0
%
37
37
37
ml
581
761
1800
11.5
%
45
45
45
From curves 1 and 3 of Figure 3-2,
u>
i
M
10
-------
3-13
incentive to manufacture additional smaller canisters because
of the lower emissions of fuel-injected vehicles. Thus, it is
possible that the actual average canister volume increase
required will be less than has been determined here.
It is also possible that some vehicle redesign may be
required to physically accommodate a larger canister. Most
canisters are presently installed in or adjacent to the engine
compartment. It is assumed that there should be sufficient
space to accommodate the larger canister, though it may not be
as simple as replacing the existing canister. As was indicated
earlier, switching to an improved charcoal is a possibility and
this could be used to mitigate particularly difficult
installations. Thus, no cost will be allocated for vehicle
redesign in section III of this chapter.
2. Purge Capacity
Along with an increase in storage capacity, a similar
increase in the ability to purge (e.g., desorb) the
hydrocarbons from the canister will be required to handle the
more volatile fuel. In addition, purge air may need to be
increased to address the change in certification test procedure
to begin with a saturated canister. This additional increase
is likely for carbureted vehicles, since their current
problem-free emissions on 9-psi RVP fuel are above the 2-gram
standard (see Appendix 2-B). However, it should not be
necessary for fuel-injected vehicles, since their analogous
emissions are below the 2-gram standard.
Increasing the amount of purge can be accomplished either
by increasing the duration of the purge or by increasing the
rate of purge. The duration of purge can be increased by
reducing the time during engine operation when purge does not
occur in current systems. Currently, the first 2-3 minutes of
engine operation and/or during minor deceleration are times
during which many systems shut off the purge. The rate of
purge, on the other hand, can be increased by increasing the
size of the controlling orifice, thus allowing more air to be
drawn through the canister in a given amount of time.
The primary concerns that arise with an increase in purge
center upon vehicle performance. Increasing the purge will
have an effect upon the engine's fuel-air ratio (absent
feedback control), which in turn may have an effect upon
exhaust emissions and engine performance. There exists the
potential for increased HC and CO exhaust emissions, and
negative effects upon driveability from rich misfire.
-------
3-14
These concerns have been raised by engine manufacturers as
they relate to the desired improvements in evaporative emission
control, and also as they relate to the control of refueling
emissions.[8,9] What little testing has been done addressing
these concerns, however, has tended to indicate that these
problems are not major and can be overcome fairly easily.
In 1978, the American Petroleum Institute (API) performed
a series of tests on a carbureted closed-loop 1978 Pontiac
Sunbird, modified to support a refueling emissions onboard
control system. Though the amount of HC purged over an FTP
increased by 65-86 percent, no significant increase in
engine-out or post-catalyst emissions occurred, except in the
extreme case where 77-91 grams of HC were purged in a single
FTP. [10] This is well above that needed for evaporative HC
control even at 11.5-psi RVP (i.e., 35-45 grams (see Table
2-B-6 in Appendix 2-B)). API's test results are summarized in
Table 3-4. Driveability was evaluated in both cold-start and
hot-start tests and was deemed excellent in both cases for the
modified vehicle.[10]
Recently, API performed a series of FTP exhaust and
evaporative emission tests on a multi-point fuel-injected 1985
Buick Century with a 9.0-psi RVP fuel and an 11.7-psi RVP
fuel. [II] The results of the API testing show only slight
increases in exhaust emissions because of the higher volatility
of the test fuel. The comparison of results is made for a
vehicle with a 400-ml carbon canister on the 9.0-psi RVP fuel,
and the same vehicle with an 8-1 onboard refueling carbon
canister on the 11.7-psi RVP fuel. The amount of HC purged
during the exhaust test portion on the enlarged canister was
between 20-50 grams more than on the small canister, even
though the purge rate was not changed. The HC emissions
increased from 0.14 to 0.21 g/mi, the CO emissions increased
from 1.81 to 2.30 g/mi, and the NOx emissions increased from
0.32 to 0.38 g/mi. However, these increases may not be
statistically significant because of the limited number of
tests performed on each fuel.
General Motors has done some testing on a 1981 4.3L V8
engine to determine the effects on exhaust emissions from an
increase in the purge rate. [12] Only when the purge was
increased to its maximum level (i.e., no restricting orifice),
and then primarily when there was no delay before purge began
(i.e., purge during cold operation when feedback system is
inoperative), was there a significant increase in exhaust
emissions to the point where current standards could not be
met. (It is assumed that no delay indicates that for a period
of time just after ignition the engine operated in an open-loop
fashion.) GM's test are summarized in Table 3-5. There is no
indication as to the effect that the increased purge rate had
upon driveability.
-------
Table 3-4
Effect of Purge on Exhaust Emissions [10]
test No. Canister
Canister HC
Loading, g*
Production 50
Canister
1
2
3
4
5
6
7
8
9
10
11
12
4
4
5
5
5
5
6
6
6
6
6
6
160
160
160
150
160
160
160
160
160
160
160
0
Purge
Orifice, in,
0.100
0.180
0.180
0.125
0.125
0.125
0.125
0.100
0.100
0.090
0.090
0.110
0.110
HC
Delay Purged, g
-
3 min.
3 min.
3 min.
3 min.
No
No
30 sec.
30 sec.
No
No
No
No
26
77
91
41
56
67
74
23
18
22
19
25.9
1.0
Exhaust Emissions, g/mi
HC
CO
NOx
0.39+0.03 6.41+0.91 0.98+0.07
0.53
0.49
0.35
0.38
0.41
0.42
0.33
0.41
0.36
0.35
0.39
0.37
6.24
6.43
4.95
5.45
6.28
7.34
5.88
6.85
6.02
5.63
5.91
6.35
0.98
0.84
1.09
0.99
0.96
0.93
0.93
1.01
1.04
0.99
1.01 V
1.03 Ł
* Refueling system canister.
** Average Emission Test Results
NOTE: Tests 1-6 used a purge valve drilled out to the orifice
size specified. Tests 7-12 used a purge valve drilled to 0.180
in. with the specified orifice in-line.
-------
3-16
Table 3-5
General Motors' Study of the Effect of
Canister Purge Rate on Emissions - 1981 4.3L V8 [12]*
Exhaust (g/mi)
Production
Max. Purge
No Delay
Max. Purge
0.020
Constant Purge
Orifice
0.040
Constant Purge
Orifice
0.050
Constant Purge
Orifice
0.060
Constant Purge
Orifice
0.070
Constant Purge
Orifice
HC
0.40
0.41
0.36
0.66
0.63
0.53
0.39
0.38
0.44
0.44
0.37
0.40
0.38
0.38
0.35
0.45
0.43
0.40
0.40
0.37
CO
2.1
2.5
2.2
8.1
8.1
5.9
3.5
4.7
3.4
2.1
2.0
2.5
0.33 2.0
2.2
1.9
1.77
2.25
98
05
0.97
1.01
1
1
0.40
0.37
0.36
0.38
0.34
0.35
1.18
1.53
1.65
1.40
0.67
1.96
NOx
0.78
0.78
0.79
0.66
0.69
0.73
0.74
0.71
0.72
0.76
0.76
0.73
0.78
0.78
0.77
Evap. HC (q/test)
DIU HS Total
0.81
0.88
0.87
0.90
0.87
0.91
0.93
0.88
0.89
0.91
0.86
0.89
4.62
3.53
1.97
0.59
0.65
0.52
0.97
0.86
0.76
2.04
2.31
2.00
2.30
2.82
2.57
2.54
2.03
2.14
0.98
2.27
0.79
1.62
1.42
2.45
1.05
0.47
0.86
0.82
0.89
0.72
0.73
0.67
0.76
0.81
0.76
0.93
0.85
0.79
0.87
0.81
0.87
0.86
0.86
0.78
0.94
0.88
0.69
0.88
0.68
0.89
0.77
0.83
1.36
1.36
0.88
1.91
1.08
1.30
0.82
0.89
0.87
0.77
0.78
0.92
5.48
4.35
2.86
1
1
1
1
1
1
,32
,38
18
,73
,66
.52
1.97
3.16
2.79
3.17
3.63
3.44
3.40
2.89
2.92
1.91
5.15
1.48
2.50
2.11
3.34
1.82
1.30
2.18
2.26
1.76
2.69
1.87
2.22
Prior to a 30-min. road prep (round-trip between Pontiac
and Lake Orion, Michigan), the vehicle received a new
carburetor, ECM, EGR, distributor, canister and converter.
-------
3-17
Thus, it would appear that the problems posed by
increasing the purge rate can be solved without significant
effects upon vehicle performance. Closed-loop fuel metering
control is expected to be present in 99 percent of light-duty
vehicles sold in model years 1987 and beyond.[13] Also,
naturally cleaner fuel-injected engines are projected to make
up 89 percent of the light-duty gas vehicle and the light-duty
gas truck market by model year 1990.[14] The presence of these
two technologies will require that only small changes and some
additional system calibration need be made to eliminate any
measurable effects of increased purge upon vehicle performance.
Little information is currently available on evaporative
ECSs for heavy-duty gas vehicles as they are just now being
introduced. The systems used, however, are quite similar to
those used in light-duty vehicles, with the necessary
modifications in size. Thus, it is probable that the increased
purge requirement can be met with fairly simple refinements to
the control system.
III. Costs
This section will describe the method by which EPA has
estimated the costs associated with the improvements in
evaporative control technology discussed previously. Only the
initial price increase to the consumer will be developed here.
Operating costs, such as the weight-related fuel economy
penalty and the credit due to recovered evaporative losses, are
discussed in Appendix 6-B and Section VI of Chapter 4,
respectively.
The costs of control are developed as they pass from the
vendor to the vehicle manufacturer to the dealer and ultimately
to the consumer. The ultimate cost to the consumer is referred
to as the Retail Price Equivalent (RPE), and will include all
of the increases seen along the way. It is this price increase
which may potentially affect vehicle sales, which is addressed
at the end of this section. All prices are presented in 1984
dollars, with adjustments from other years based upon the
Bureau of Labor Statistics new consumer price index.*
* The 1984 new car CPI was estimated as 4 percent. This has
now been determined by BLS to be 2.9 percent. This
difference is not expected to significantly alter the
conclusions of this analysis.
-------
3-18
A. Vendor Level
In this particular case, "vendor" refers to the canister
manufacturer, which may actually be the vehicle manufacturer in
some cases. The need to build a larger canister and make
adjustments to the purge system will lead to certain cost
increases. These costs can be divided into: 1) a larger
amount of carbon, 2) larger canister components, 3) retooling,
and 4) the recalibration of the evaporative control system.
The vendor will also include overhead (20 percent) and profit
(20 percent) in the price that is passed on to the vehicle
manufacturer.[15]
As the canister size increases, the amount of carbon
required will increase with the volume of the canister. The
increase required for a given certification fuel RVP was
developed in the previous section and was summarized in Table
3-3. The carbon cost used is a vehicle-sales weighted average
of the cost of the various types of carbon currently used by
vehicle manufacturers. Table 3-6 shows the calculated costs
for the increased carbon for each certification fuel RVP.
These costs include the vendor overhead and profit mentioned
previously. The details of these cost calculations, except for
the markups for overhead and profit, are given in Appendix 3-A
at the end of this chapter.
The canister components are assumed to increase in size in
proportion to the increase in the total area of the canister.
Therefore, they are treated separately from the carbon. The
prices for the relevant components: the body, the grid, the
filters, the caps, and the connectors have been taken from a
1983 draft report entitled, "Manufacturing Costs and Retail
Price Equivalent of Onboard Vapor Recovery System for
Gasoline-Filling Vapors," prepared by LeRoy Lindgren under
contract to the American Petroleum Institute.*[16] This report
has been reviewed in a previous document, and the costs have
been modified slightly to correct for some arithmetic errors
and discrepancies in markups for overhead and profit.[17] The
calculations to determine the increased cost for each
certification fuel RVP are detailed in Appendix 3-A, and the
results are presented in Table 3-6. These include labor costs
and markups for vendor overhead and profit. The latter were not
included in the cost calculations in Appendix 3-A.
This report has since been updated as the "Revised Report
of API/LHI Cost Estimate of Onboard Vapor Recovery System
and Review of EPA Technical Report EPA-AA-SDSB-84-01 on
Feasibility, Cost, and Cost Effectiveness of Onboard Vapor
Control," September 28, 1984. The costs cited here have
not changed significantly, so this analysis has not been
altered.
-------
3-19
Table 3-6
Vendor Cost, Manufacturer Costs and Retail Price
Equivalent Increases (1984 Dollars)
Vehicle Class
LDV Vendor Level Costs:
Carbon*
Canister*
Tooling
ECU
Total Vendor Level Costs
Manufacturer Level Costs:
RD&T
Certification
Total Manuf. Level Cost
Manuf. Overhead/Profit**
Total Dealer Cost
Dealer Profit***
Retail Price Equivalent
LOT Vendor Level Costs:
Carbon*
Canister*
Tooling
ECU
Total Vendor Level Costs
Manufacturer Level Costs:
RD&T
Certification
Total Manuf. Level Cost
Manuf. Overhead/Profit**
Total Dealer Cost
Dealer Profit***
Retail Price Equivalent
HDV Vendor Level Costs:
Carbon*
Canister*
Tooling
ECU
Total Vendor Level Costs
Manufacturer Level Costs:
RD&T
Certification
Total Manuf. Level Cost
Manuf. Overhead/Profit**
Total Dealer Cost
Dealer Profit***
Retail Price Equivalent
Certification
9.5
.20
.15
.08
.07
.50
.07
.60
1.17
.28
1.45
.05
1.50
.27
.16
.08
.07
.58
.13
.76
1.47
.35
1.82
.06
1.88
.34
.28
.08
.07
.77
.32
1.09
.26
1.35
.05
1.40
10.0
.40
.20
.08
.07
.75
.09
.60
1.44
.35
1.79
.05
1.84
.55
.25
.08
.07
.95
.16
.76
1.87
.45
2.32
.07
2.39
.69
.45
.08
.07
1.29
.38
1.67
.40
2.07
.07
2.14
10.5
.59
.27
.08
.07
1.01
.10
.60
1.71
.41
2.12
.07
2.19
.83
.33
.08
.07
1.31
.18
.76
2.25
.54
2.79
.09
2.88
1.03
.60
.08
.07
1.78
.45
2.23
.54
2.77
.08
2.85
Fuel RVP
11.0
.79
.32
.08
.07
1.26
.12
.60
1.98
.48
2.46
.07
2.53
1.10
.40
.08
.07
1.65
.20
.76
2.61
.63
3.24
.10
3.34
1.39
.73
.08
.07
2.27
.52
2.79
.67
3.46
.09
3.57
11.5
.99
.38
.08
.07
1.52
.13
.60
2.25
.54
2.79
.09
2.88
1.38
.46
.08
.07
1.99
.23
.76
2.98
.72
3.70
.10
3.80
1.71
.84
.08
.07
2.70
.58
3.28
.79
4.07
.13
4.20
* Prices include 40 percent vendor mark-up for overhead and profit.
** A mark-up of 24 percent was used for corporate overhead and profit.
*** A mark-up of 3 percent was used for dealer profit.
-------
3-20
Retooling costs will also be incurred by the canister
manufacturer. Total tooling costs are specified by Lindgreh as
$0.16 per canister.[16] Complete retooling will not be
required, though, since current canister sizes will still be
appropriate for many vehicles. Thus, it is assumed that the
tooling cost associated with an increase in canister size will
be approximately half of this cost, or $0.08 per canister.
This is also summarized in Table 3-6. For an 11.5-psi RVP
certification fuel, the total per-vehicle component cost to the
vehicle manufacturer is $1.52 for LDVs, $1.99 for LDTs and
$2.70 for HDVs.
As it was previously determined that increasing the purge
rate would only require recalibration of existing systems, no
new hardware need be costed out. However, a $.07 per-vehicle
cost is allocated to modify existing electronic control units
(ECUs). This cost is the same as that assumed necessary to
modify existing ECUs to accommodate an onboard refueling vapor
control system.[18]
The sum of the above costs represent the total vendor
level costs, which are then passed on to the vehicle
manufacturer. However, where the canister manufacturer is the
same as the vehicle manufacturer, as it is in many cases here,
this is primarily a transfer cost.
B. Manufacturers Level
The vehicle manufacturer must purchase (or transfer) the
canister and control technology at the vendor level cost rate.
The manufacturer will also face research, development, testing,
and certification costs associated with the implementation of
the improved technology. There are also corporate overhead and
profit that are incorporated into the price that is passed on
to the dealer.
Research, development, and testing costs will be incurred
by the manufacturer to recalibrate the fuel metering and
emission control systems. As it was determined that this would
require no additional hardware (the only hardware modification
— the ECU — being addressed previously), this cost will
include only design modification and testing costs.
Estimates for these costs are difficult to determine. It
will be assumed here that, on average, for an 11.5-psi RVP
certification fuel standard, 25 vehicle tests, 2 months of
technician time and 1 month of engineering will be sufficient
to recalibrate each engine-evaporative family combination.
Testing costs for LDVs and LDTs were obtained from earlier EPA
work on light-duty certification costs.[19] For HDVs, the cost
used here was that determined in the previous HDE rulemaking
which instituted HDV evaporative HC controls.[20] It is
further assumed that this cost is proportional to the control
required. A vehicle acquisition cost, held constant for all
levels of control, is also included.[17] This methodology is
detailed more in Appendix 3-A.
-------
3-21
The research, development and testing costs (RD&T) are
summarized in Table 3-6. These have been amortized over 5
years at 10 percent to reflect the spreading out of payments by
the manufacturer. For an 11.5-psi RVP certification fuel, this
yields $.13/vehicle for LDVs, $.23/vehicle for LDTs and
$.58/vehicle for HDVs.
Manufacturers of LDVs and LDTs will incur a cost to
certify their fleets with a new certification fuel. No
recertification cost will be incurred by HDV manufacturers,
because no formal evaporative testing is required by EPA (the
development testing previously discussed should be
sufficient). The LDV/LDT costs were obtained from the EPA work
previously cited.[17] Because year to year carryover of engine
families is not 100 percent, only 90 percent of the LDV/LDT
recertification costs would be attributable to this change.
Amortization over 5 years at 10 percent results in a
$.60/vehicle LDV and $.76/vehicle LDT cost impact (see Appendix
3-A for details).
Before passing on the cost to the dealer, the vehicle
manufacturer will add markups for corporate overhead and
profit. These were determined to be 10 percent and 14 percent,
respectively, in an earlier EPA cost analysis.[21] These
markups are applied to the sum of the total vendor level costs,
the research and development costs, and the certification
costs. This value is shown in Table 3-6.
The total cost at the manufacturer level, then, is the sum
of the hardware, development, certification, and markup costs.
It is assumed that no significant retooling will be required at
the assembly level — only at the canister manufacturing level.
C. Dealer Level
The total increase in cost seen by the dealer is shown in
Table 3-6. The dealer is expected to make a reasonable profit
from the sale of a vehicle. Therefore, a markup which recovers
incremental costs and yields a fair return on incremental
investment must be included in the total cost. This markup was
determined to be 3 percent in the same EPA cost analysis used
to determine corporate overhead and profit. [15] The dealer
markups in each situation are shown in Table 3-6.
D. Consumer Level (Retail Price Equivalent)
The bottom line of Table 3-6 shows the increase in initial
cost expected to be seen by the consumer. The resulting RPE
increase associated with a change to an 11.5-psi RVP
certification fuel is $2.88/vehicle for LDVs, $3.80/vehicle for
LDTs, and $4.20/vehicle for HDVs.
-------
3-22
E. Impact on Vehicle Sales
The impact on vehicle sales due to the retail price
equivalent increase is determined by the price elasticity of
demand. For light-duty vehicles and trucks, this is
approximately -1.0 and for heavy-duty trucks it is in the range
of -0.9 to -0.5. [17,22] For the purposes of this analysis, a
-0.7 price elasticity will be assumed for HDVs. This means,
for the HDV case, that a 1-percent increase in the RPE should
result in a 0.7-percent decrease in demand.
Prices for light- and heavy-duty vehicles vary
considerably. Using an average light-duty vehicle and truck
cost of $10,000 and a heavy-duty vehicle cost range of
$11,000-57,000 results in the vehicle demand decrease shown in
Table 3-7 for an 11.5 RVP certification fuel (2250-2790 LDVs,
940-1110 LDTs and 140-170 HDVs). With price decreases of this
small magnitude, though, the use of this price/demand impact
model is questionable. This price increase would probably be
of little consequence in relation to annual price increases
occurring at the time of new model year introduction. In any
event, the sales impacts estimated by the model are negligible.
IV. Conclusions
The improvements required to increase storage capacity and
purge capacity in vehicular ECUs appear to be feasible with
current technology. No significant effects upon vehicle
performance other than reduced evaporative emissions are
expected from these changes. The final cost to the consumer at
the time of vehicle purchase has been estimated as
$2.88/vehicle, $3.80/vehicle, and $4.20/vehicle for LDVs, LDTs,
and HDVs, respectively, in the most extreme case of an ll.5-psi
RVP certification fuel. These cost increases are not expected
to impact upon vehicle sales to any significant degree.
-------
3-23
Table 3-7
Vehicle Demand Impact with
an 11.5 RVP Certification Fuel
Vehicle
Class
LDV
LDT
HDV
Percent
Price Increase
0.021-0.026
0.032-0.038
0.045-0.053
Percent
Demand Decrease
0.021-0.026
0.032-0.038
0.032-0.037
Number Demand
Decrease*
2254-2791
938-1114
145-167
Uses 1990 vehicle sales projections.
-------
3-24
References (Chapter 3)
1. "Basic Concepts of Adsorption on Activated Carbon,"
Activated Carbon Division, Calgon Corporation.
2. "Control Characteristics of Carbon Beds for Gasoline
Vapor Emissions," EPA-600/2-77-057, Michael J. Manos and Warren
C. Kelly, Scott Environmental Technology, Inc. for EPA, ORD,
IERL, February 1977.
3. "Activated Carbon for Effective Control of
Evaporative Losses," Ronald S. Joyce, Paul. D. Langston, George
R. Stoneburner, Charles B. Stunkarol, and George S. Tobias,
Pittsburgh Activated Carbon Division, Calgon Corp., SAE Paper
#690086, January 1969.
4. Meeting with Howard Shrut, Calgon Corporation, July
18, 1984.
5. "Combustion Engine Economy, Emissions and Control
July 18-12, 1985," The University of Michigan, College of
Engineering, Ann Arbor, MI.
6. Conversation with Bill Kornegay, Ph.D., Technical
Director, Chemical Division, Westvaco Corporation, November 5,
1984.
7. "Characterization of Fuel/Vapor Handling Systems of
Heavy-Duty Gasoline Vehicles over 10,000 Pounds GVW," Draft
Report, prepared by Jack Faucett Associates for EPA, QMS,
Contract No. 68-03-3244, September 27, 1985.
8. Comments of the Motor Vehicle Manufacturers
Association of the United States, Inc., on EPA Report
450/3/84-012a, "Evaluation of Air Pollution Regulatory Strategy
for Gasoline Marketing Industry," November 8, 1984. (Available
in Public Docket No. A-84-07.)
9. Comments on EPA Report 450/3/84-012a, "Evaluation of
Air Pollution Regulatory Strategy for Gasoline Marketing
Industry," submitted by Chrysler Corporation to U.S. EPA,
November 5, 1984. (Available in Public Docket No. A-84-07.)
10. "Onboard Control of Vehicle Refueling Emissions:
Demonstration of Feasibility," API Publication No. 4306,
October 1978.
11. "API Onboard Refueling Emission Control Project,"
work by Mobil Research and Development Corporation,
presentation to EPA-ECTD, August 7, 1985.
-------
3-25
References (Chapter 3) Cont'd
12. General Motors Submittal to EPA, March 11, 1985
(letter from Eric 0. Stork, Deputy Assistant Administrator for
Mobile Source Air Pollution Control, EPA, to Thomas M. Fisher,
General Motors, dated September 3, 1976).
13. "Emission Control Technology and Strategy for
Light-Duty Vehicles 1982-1990. Final Report," prepared by
Energy and Environmental Analysis, Inc.
14. "Automotive Technological Projections Based on USA
Energy Conservation Policies," Dana Jones and LeRoy Lindgren,
December 17, 1983.
15. "Cost Estimations for Emission Control Related
Components/Systems and Cost Methodology Description,"
EPA-460/3-78-002, U.S. EPA, March 1978.
16. "Manufacturing Costs and Retail Price Equivalent of
Onboard Vapor Recovery System for Gasoline Filling Vapors,"
LeRoy Lindgren under contract to API, June 1983. (Attachment
to MVMA Comments, Reference 8, available in Public Docket
A-84-07.)
17. "The Feasibility, Cost, and Cost Effectiveness of
Onboard Vapor Control," EPA-AA-SDSB-84-01, Glenn W. Passavant,
U.S. EPA, March 1984.
18. "Costs of Onboard Vapor Recovery Hardware," Mueller
Associates under sub-contract to Jack Faucett under contract to
EPA, February 14, 1985.
19. "Light-Duty Vehicle Certification Cost," memo to
Edmund J. Brune, Director, Certification and Surveillance
Division from Daniel P. Hardin, Jr., Certification and
Surveillance Division Staff, U.S. EPA, March 13, 1975.
20. "Regulatory Analysis and Environmental Impact of
Final Emission Regulations for 1984 and Later Model Year
Heavy-Duty Engines," EPA, OMSAPC, December 1979. (Available in
Public Docket No. OMSAPC-78-4.)
21. See for example the Regulatory Analysis and Summary
and Analysis of Comments prepared in support of the light-duty
diesel particulate regulations for 1982 and later model year
light-duty diesel vehicles. (Both are available in Public
Docket No. OMSAPC78-3.)
22. "Regulatory Support Document for the Final
Evaporative Emission Regulation and Test Procedure for 1984 and
Later Model Year Gasoline-Fueled Heavy-Duty Vehicles,"
EPA/OAR/OMS, January 1983. (Available in Public Docket No.
OMSAPC-79-1.)
-------
3-26
Appendix 3-A
Detailed Derivation of Evaporative
ECS Component Costs
This appendix details the calculations used to derive the
evaporative emission control system (ECS) costs discussed in
Chapter 3. The first section will describe how the average
canister sizes for current evaporative control systems were
determined. This will be followed by sections discussing: 1)
canister material costs, 2) research, development and testing
costs, and 3) certification costs associated with the changes
in the certification test procedure.
Average Canister Sizes in Current Vehicles
The average canister sizes for current vehicles were
calculated by using a sales-weighted average of the canister
sizes currently in use. Only the major manufacturers — GM,
Ford, Chrysler, Toyota, and Nissan — were considered in this
calculation.
Table 3-A-l shows the canister sizes used by each
.manufacturer for various engine families. Table 3-A-2 combines
these values into a single value for light-duty vehicles and
light-duty trucks for each manufacturer, assuming egual sales
per engine family. Using the forecasted 1990 normalized market
share shown in Table 3-A-3 for these five manufacturers, a
sales-weighted average canister size for each vehicle class is
determined. These industry-wide average canister sizes are
summarized in Table 3-A-4. As indicated in the table, the
average canister size for heavy-duty gas vehicles is taken as
the current size for GM vehicles, as GM dominates this market
(i.e., two-thirds of sales).
Canister Material Costs
This section details the methodology used to determine the
costs associated with improving canister working capacity.
These costs will be determined for each potential certification
fuel RVP.
/
Table 3-A-5 shows the canister material costs to vendors
taken from a draft report prepared for API by LeRoy Lindgren.*
The costs presented are for an 850 ml GM canister, which is
smaller than the average canister sizes for current LDV, LDT
and HDV classes shown in Table 3-A-4.
*Reference 16 in Chapter 3. A final version of the report has
since become available, but the changes were not significant so
the calculations were not redone.
-------
3-27
Table 3-A-l
Canister Distribution
Manufacturer
GM
GM
GM
GM
Ford
Ford
Ford
Chrysler
Chrysler
Chrysler
Toyota
Toyota
Toyota
Toyota
Nissan
Nissan
Canister Size (ml)
1500
2500
2500 + 300
2500 -1- 1500
925
1400
1400 + 1400
1320
1790
1320 -1- 1320
835
845
1400
1400 + 645
580
1230
Number of
LDV*
29
—
—
—
7
3
1
4
3
—
2
1
1
—
6
2
Families
LDT*
2
5
1
0
8
7
—
1
6
4
1
—
1
1
3
1983 Model Year
-------
3-28
Table 3-A-2
Average Canister Size by Manufacturer
Vehicle Class
LDV
LDV
LDV
LDV
LDV
LDT
LDT
LDT
LDT
LDT
Manufacturer
GM
Ford
Chrysler
Toyota
Nissan
GM
Ford
Chrysler
Toyota
Nissan
Avg. Canister Size
for 9.0 RVP Fuel (ml)*
1500
1225
1521
979
743
2288
1147
2059
1427
580
Average of 1983 MY canisters assuming equal sales of evap.
families.
-------
3-29
Table 3-A-3
Market Shares by Manufacturer
1983 Normalized* 1990 Normalized**
Vehicle Class Manufacturer Market Share (%) Market Share (%)
LDV GM 45.74 46.81
LDV Ford 17.78 18.20
LDV Chrysler 9.56 9.78
LDV Toyota 13.89 13.00
LDV Nissan 13.03 12.21
LDT GM 41.98 40.86
LOT Ford 34.76 33.84
LDT Chrysler 10.12 9.85
LDT Toyota 7.29 8.57
LDT Nissan 5.85 6.88
* Normalized on the basis of 100 percent of the domestic LDV
and LDT market is shared by GM, Ford and Chrysler, and 100
percent of the imported LDV and LDT market is shared by
Toyota and Nissan.
** Normalized as for 1983. Manufacturers' shares of domestic
or imported market is assumed to be the same as for 1983,
but the ratio of imported to domestic registrations
changed in accordance with projections made in Reference
13 of Chapter 3.
-------
3-30
Table 3-A-4
Industry-wide Average Canister Size*
Avg. Canister Size
Vehicle Class for 9.0 RVP Fuel (ml)
LDV 1292
LDT 1688
HDG 4000**
* Uses 1989 Market Shares.
** Average canister size used by GM.
-------
3-31
Table 3-A-5
Canister Material Cost to Vendor (Dollars)*
Component Weight Material
Description Material (Ibs.) Costs ($)**
Body DB437 .30
Grid G7 .10
Int. Filter AY332 .10
Ext. Filter KZI-4 .20
Charcoal 54448 .50
Cap DB437 .10
Connectors DB437 .05
TOTAL 1.22
* Taken from Reference 16 of Chapter 3.
** Material costs are those for an 850-ml GM canister and
were converted to 1984 dollars from 1983 dollars.
-------
3-32
Table 3-A-6 shows these material costs after they have
been scaled up to the average canister sizes for LDV, LDT and
HDV families. The charcoal costs, were increased in proportion
to the increase in volume of the canisters. The body, grid,
filter and cap costs were increased in proportion to the
increase in surface area of the canister. (For cylinders which
have the same length-to-diameter ratio, the ratio of surface
areas is equal to the ratio of volumes to the two-thirds
power.) The connector cost is independent of the canister size
and therefore remains constant.
The charcoal costs per unit volume were calculated on a
1990 vehicle sales-weighted basis (See Table 3-A-3). GM and
Chrysler use wood-based charcoals (price = $l/lb, density =
.26-.30 g/ml) whereas Ford, Nissan, and Toyota use coal-based
charcoals (price = $2/lb., density = .37-.38 g/ml). Tables
3-A-7, 3-A-8, and 3-A-9 contain the canister material cost
increases to meet a higher RVP certification fuel for LDV, LDT
and HDV classes, respectively. The increases in volume
required .for each higher RVP certification fuel are listed in
Table 3-3 of Chapter 3 and the increases in surface area can be
determined from the volume ratios (as stated earlier). The
increases in costs were calculated by exactly the same method
as was used to scale up the 850-ml GM canister to the average
canister sizes for each class of vehicle.
Research, Development and Testing Costs
Table 3-A-10 contains a summary of the research,
development and testing (RD&T) costs for a change in
certification fuel to an RVP of 11.5 psi. The various costs of
RD&T per engine family are broken down in Table 3-A-10 and
costs for each component were estimated using engineering
judgment. The total cost was calculated using the total number
of engine families from 1984 certification records. The total
cost was amortized at 10 percent for five years and this amount
was used to determine the cost per vehicle based upon 1989
sales projections.
To obtain the costs for a change in the certification fuel
to an RVP between 9.0 psi and 11.5 psi, the vehicle
modification costs were held constant and the salary and
testing costs were varied linearly. The RD&T costs for the
different certification fuels are listed in Table 3-6 of
Chapter 3.
-------
3-33
Table 3-A-6
Baseline* Canister Material Costs to Vendor (1984 Dollars)
Component
Description
Body
Grid
Int. Filter
Ext. Filter
Charcoal**
Cap
Connectors
TOTAL
LDV
.33
.05
.13
.28
1.39
.11
.04
2.33
Vehicle Class
LPT
.39
.06
.16
.33
1.92
.13
.04
3.03
HDV
.70
.11
.28
.59
2.40
.22
.04
4.34
**
Baseline refers to the average canister sizes for 9.0
RVP fuel shown in Table 3-A-4.
Charcoal cost is the 1990 sales-weighted average cost of
the different types of charcoals (in 1984 dollars).
Wood-based charcoal ($l/lb) is used by GM and Chrysler
and coal-based charcoal ($2/lb) is used by Ford, Nissan,
and Toyota.
NOTE: Body, filter, grid, and cap costs increase in proportion
to the surface area and charcoal cost increases in
proportion to the volume. (Canister length-to-diameter
ratio is assumed to remain constant.) Connector cost is
independent of the canister volume, thus there is no
increase in material cost to the vendor for connectors
for larger canisters.
-------
3-34
Table 3-A-7
LDV Canister Material Cost Increase at Vendor Level* (1984 Dollars)
Component Certification Fuel RVP (psi)
Description
Body
Grid
Int. Filter
Ext. Filter
Charcoal
Cap
TOTAL .20 .41 .59 .78 .99
Does not include 40-percent vendor mark-up for overhead
and profit.
9
.5
.02
.00
.01
.02
.14
.01
10.0
.04
.01
.02
.04
.28
.01
10.5
.06
.01
.03
.05
.42
.02
11.0
.08
.01
.03
.07
.56
.03
11.5
.10
.02
.04
.09
.71
.03
-------
3-35
Table 3-A-8
LPT Canister Material Cost Increase at Vendor Level* (1984 Dollars)
Component Certification Fuel RVP (psi)
Description
Body
Grid
Int. Filter
Ext. Filter
Charcoal
Cap
TOTAL .26 .53 .80 1.06 1.31
9.5
.03
.00
.01
.02
.19
.01
10.0
.05
.01
.02
.04
.39
.02
10.5
.08
.01
.03
.06
.59
.03
11.0
.10
.01
.04
.08
.79
.03
11.5
.12
.02
.05
.10
.98
.04
Does not include 40-percent vendor mark-up for overhead
and profit.
-------
3-36
Table 3-A-9
HDV Canister Material Cost Increase at Vendor Level* (1984 Dollars)
Component Certification Fuel RVP (psi)
Description
Body
Grid
Int. Filter
Ext. Filter
Charcoal
Cap
TOTAL .37 .74 1.10 1.48 1.82
9.5
.05
.01
.02
.04
.24
.01
10.0
.09
.01
.04
.08
.49
.03
10.5
.14
.02
.05
.11
.74
.04
11.0
.18
.03
.07
.15
.99
.06
11.5
.22
.03
.09
.19
1.22
.07
Does not include 40-percent vendor mark-up for overhead
and profit.
-------
3-37
Table 3-A-10
Research, Development and Testing (RD&T) Costs Summary
(1984 Dollars)
LDV/LDT: ($/family)
Vehicle Modification 16,000l
Engineer Salary (1 mo. @ $50K/yr) 4,170*
Technician Salary (2 mo. @ $35K/yr) 2,9202
25 Tests (@ $610/test)1 15,250
38,340
HDV: ($/family)
Vehicle Modification 20,0002
Engineer Salary (1 mo. @ $50K/yr) 4,1702
Technician Salary (2 mo. @ $35K/yr) 2,9202
25 Tests (@ $2000/test)J 50,000
77,090
LDT LDT HDV
Cost/Family $38,340 $38,340 $77,090
Number of Families 1374 814 11*
Total Cost $5,252,580 $3,105,540 $847,990
5 years @ 10% $1,385,629/yr $819,24l/yr $223,700/yr
1989 Sales 11,000,000s 3,640,000s 386,000*
RD&T Cost/Vehicle ($) 0.13 0.23 0.58
1 Inflation-adjusted values from EPA memo, "Light-Duty
Vehicle Certification Cost," from Daniel P. Hardin, March
13, 1975. [Reference 19 of Chapter 3.]
2 Estimated. ;
3 "Regulatory Impact Analysis, Oxides of Nitrogen Pollutant
Specific Study and Summary and Analysis of Comments," EPA,
March 1985.
4 EPA's "Control of Air Pollution from New Motor Vehicles
and New Motor Vehicle Engines; Federal Certification Test
Results for 1984 Model Year."
5 Based on DRI "trendlong" projections from the Fall 1984
Lonq-Term Review, Data Resources Inc., 1984.
-------
3-38
Certification Costs
Table 3-A-ll contains a summary of the certification costs
associated with a new certification fuel. The costs per
vehicle tested are summarized for both emissions data and
durability vehicles. The total costs are based on the number
of LDVs and LDTs certified in 1984. However, only those engine
families which are carried over from the previous year are
relevant, since those which are recertified anew would
experience certification costs with or without a new
certification fuel. Carryover is estimated to be 90 percent;
therefore, the total cost was reduced to 90 percent of its
original value. The reduced total was amortized at 10 percent
for five years and this amount was used to determine the cost
per vehicle based upon 1989 sales projections. It should be
noted that formal certification testing for evaporative
emissions is not required for HDVs. Thus, there is no
certification cost associated with a change in the HDV
certification fuel.
-------
3-39
Table 3-A-ll
Certification Costs Summary (1984 Dollars)
Emission Data Vehicle Costs:1 ($/Vehicle Tested)
Vehicle Modification 16,000
Mileage and Maintenance 10,400
(<§ $2.60/mile, 4000 miles)
Testing Cost 1,220
(2 Tests/Vehicle, $610/test)
27,620
Durability Vehicle Costs:1 ($/Vehicle Tested)
Vehicle Modification 16,000
Mileage and Maintenance 154,500
(<§ $3.09/mile, 50,000 miles)
Testing Cost 7,930
(13 Tests/Vehicle, $6lO/test)
178,430
Total Vehicles Tested and Costs: ($)
LDV LDT
Emission Data (307 LDV, 133 LDT)2 8,479,340 3,673,460
Durability (109 LDV, 45 LDT)2 19,448,870 8,029,350
Total Cost 27,928,210 11,702,810
90% Carryover $25,135,389 $10,532,529
5 yrs. <§ 10% $6,631,200 $2,779,000
1989 Sales3 11,000,000 3,640,000
Certification Cost/Vehicle ($) 0.60 0.76
Inflation-adjusted values from EPA memo, "Light Duty
Vehicle Certification Cost," from Daniel P. Hardin, March
13, 1975. [Reference 19 of Chapter 3.]
EPA's "Control of Air Pollution from New Motor Vehicles
and New Motor Vehicle Engines; Federal Certification Test
Results for 1984 Model Year."
Based on DRI "trendlong" projections from the Fall 1984
Lonq-Term Review, Data Resources Inc., 1984.
-------
CHAPTER 4
Technological Feasibility and Cost of In-Use
Gasoline Volatility Control
I. Introduction
As described in Chapter 2, one of the two possible methods
of eliminating the current evaporative emission excess is to
control the volatility of commercial gasoline. Estimates of
refinery costs and fuel economy benefits of reducing in-use
gasoline volatility are presented in this chapter. As also
described in Chapter 2, the two fuel parameters most relevant
to evaporative emissions are RVP and %ieo. In-use control of
both of these parameters is being considered. However, the
great majority of the refinery modelling performed thus far has
focused on the control of RVP, as the effect of this parameter
on evaporative emissions is most well known. Studies of the
cost of controlling %t6o are still underway, though the
results available to date are presented in Section III.C below.
This chapter begins with a general discussion of gasoline
volatility and the types of HC compounds which most affect it
(Section II). The next section (Section III) presents a
general description of the main source of information for the
cost of in-use gasoline RVP control and %iso control, a study
conducted by Bonner and Moore Management Science for EPA.[1]
This study uses their proprietary Refinery and Petrochemical
Modeling System (RPMS), which is a linear programming (LP)
computer model. This section also presents the results of the
Bonner and Moore study, primarily the refinery cost of reducing
gasoline RVP one to two psi below ASTM limits under various
situations, but also includes the cost of reducing %iso to 25
or 30 percent. Section IV examines the effect of RVP control
(and the likely butane excess generated by it) on the wider
butane market. Section V examines the effect of RVP control on
the energy content of gasoline and estimates the resultant
effect on vehicular fuel economy. Section VI examines the
additional economic benefit of recovering or preventing
evaporative emissions (via both fuel- and vehicle-related
controls) from both vehicles and the distribution system.
Section VII combines the results of the previous sections to
evaluate the overall cost of volatility control of in-use
gasoline.
II. Refinery Control of Gasoline Volatility
Oil refineries currently refine crude oil to supply
several petroleum products, one of which is gasoline for motor
vehicle consumption. The volatility of the gasoline produced
-------
4-2
depends on the properties of the crude oil and the natural gas
liquids (NGLs), which include butanes and natural gasoline,
used in the refining process and on the actual refining
processes themselves. There are ASTM specifications for
gasoline volatility characteristics which serve as guidelines
for the refineries to follow. These ASTM gasoline volatility
specifications and in-use volatility trends were already
described in Chapter 2, Section IV.
As already mentioned, RVP and %iso are the two most
important gasoline volatility properties affecting evaporative
HC emissions. The major HC compounds contributing to high RVP
are n-butane and iso-butane, although n-pentane and iso-pentane
also affect RVP. The RVP blending values for these parafins
are given in Table 4-1. Generally, the easiest way to reduce
gasoline RVP is to reduce the blending of straight butane into
gasoline. The next easiest approach is to remove butane
presently contained in other gasoline stocks. This requires
modification of existing separation facilities and/or the
installation of new facilities to remove contained butanes. In
addition, butane can be converted, via processes such as
alkylation, in higher boiling compounds. As a further step,
extreme RVP limits could require removal of some Cs
components which, in most cases, would require new separation
facilities. The approach that is actually used depends on the
economics involved, which are complex and highly interactive.
Both butanes and pentanes strongly affect %iSo, but so
do many other gasoline components, and the specific
relationship between each of these components and %iso is
beyond the scope of this study. Suffice it to say that the
more short-chain hydrocarbons (with four to five carbon atoms)
in gasoline, the higher the RVP and %i6o-
Butane has a high-octane quality. Thus, RVP control which
reduced the use of butane would also require additional
refinery processing to compensate for the octane quality which
the butane would otherwise provide.
The use of alcohols in gasoline complicates matters, since
both methanol and ethanol affect RVP as well as other
volatility parameters and octane. Their RVP blending values
are also shown in Table 4-1. Adding 5%/2.5% methanol/TBA to
11.0-psi RVP gasoline increases RVP by 2.2 psi. Adding 10
percent ethanol to 11.0-psi RVP gasoline increases RVP by 0.40
psi. Thus, their addition to gasoline must be accompanied .by
an even greater reduction in butane/pentane content, though the
alcohols' high-octane compensates for that of butane in this
case.
-------
4-3
Table 4-1
Blending Values for Selected Hydrocarbons and Alcohols*
Hydrocarbons RVP Blending Value (psi)
n-Pentane 15.6
Iso-Pentane 20.4
n-Butane 65
Iso-Butane 92.8
Alcohols
10% 2.5% Methanol 5% Methanol
Property Ethanol 2.5% T-butanol 2.5% T-butanol
Reid Vapor Pressure, psia 15.0 54.0 40.0
Percent Distilled at -
160°F 220 115 175
210°F 137 110 105
230°F 108 100 100
330°F 100 100 100
Research Octane 133.6 120.7 124.7
Motor Octane 101.8 96.5 97.3
(R+M)/2 117.6 108.6 111.0
The contribution to the finished fuel parameter is
determined by multiplying the blending value by the volume
percent of the compound in the fuel. The net effect of
adding a compound is the volume percent of the compound
times the difference between the blending value of the
compound and that for the compound being replaced.
-------
4-4
III. The Bonner and Moore Study
Bonner and Moore Management Science conducted a study on
the refinery cost impact of vapor pressure control under a
number of subcontracts with Southwest Research Institute (SwRI)
and Jack Faucett Associates (JFA) as contracted by the
Environmental Protection Agency. The results of the study are
contained in a fully documented final report by Bonner and
Moore entitled Estimated Refinery Cost Impact of Reduced
Gasoline Vapor Pressure.[1] The general methodology and major
assumptions of Bonner and Moore's study are presented below in
Section III.A. The results of the study are presented in
Sections III.B and III.e. The reader is referred to the Bonner
and Moore report for more specific details of the refinery cost
study. No attempt is made here to explain the B&M study in
detail because of its complexity and the availability of the
final report, which is an independent document that fully
details the study and results.
A draft of this study (dated March 1, 1985) was sent to
the American Petroleum Institute (API), the Motor Vehicle
Manufacturers Association (MVMA), and the Motor Equipment
Manufacturers Association (MEMA) for peer review. A copy of
this draft and all comments received are contained in Docket
A-85-21 in the West Tower Lobby at EPA Headquarters, 401 "M"
Street, S.W., Washington, D.C., 20460, where they can be viewed
or copied (for a reasonable fee) during working hours. The
comments received from these organizations were addressed to
the fullest extent possible in the final report (dated July 10,
1985). However, some of the comments could not be addressed
without further modelling and most of the ongoing work
described below is intended to address such comments.
A. Bonner & Moore's Refinery and Petrochemical Modeling
System
EPA contracted Bonner and Moore to use their proprietary
linearly programming (LP) computer model, designated the
Refinery and Petrochemical Modelling System (RPMS), to estimate
the refinery costs of reducing RVP and %iso. One and two-psi
RVP reductions below the maximum specified ASTM(D439) RVP and 5
and 10 percent reductions in maximum allowed %iso (from the
35 percent allowed in the base case) were analyzed for each of
three geographic gasoline-refinery regions referred to as
Petroleum Administration for Defense Districts (PADDS I, II and
III). It was assumed that the other two districts, PADDs IV
and V (excluding California), could be approximated by the
average of PADDs II and III. California gasoline consumption
(roughly 11 percent of the national consumption) was excluded
since California already restricts gasoline RVP to 9.0 psi.
-------
4-5
The national average costs for RVP reduction were estimated by
consumption weighting the PADD-specific costs obtained from the
RPMS. The costs of controlling the volatility of both
alcohol-free gasoline and methanol and ethanol blends were
examined. Volatility controls were applied uniformly to all
three grades of gasoline; unleaded regular, unleaded premium,
and leaded regular. The volume fractions of national gasoline
production contributed by each of the grades were 65 percent
unleaded regular, 18 percent unleaded premium, and 17 percent
leaded regular. Leaded gasoline is allowed to contain only 0.1
gram per leaded gallon of lead, so the effects of EPA's lead
phasedown program are fully factored in.
There are also some additional assumptions that had to be
made in modelling the alcohol-fuel blends. First, gasoline
production was set at the same level used in the alcohol-free
cases. No fuel economy changes that might apply to
alcohol-containing fuels were taken into account. Furthermore,
100 percent of each grade of gasoline, unleaded premium,
unleaded regular and leaded regular, was assumed to contain the
specified concentration of alcohol. While this is not
realistic, it was the most convenient way to include alcohols
in the RPMS and the results appear to be reasonable. (As will
be discussed below, this same approach was used to model
ethanol blends and the results were clearly unreasonable).
Also, a lower RVP case study of 3 psi below the baseline vapor
pressure was evaluated for the methanol blend because of the
possibility that commingling of the blend with alcohol-free
gasoline would increase RVP beyond that of either fuel due to
the azeotropic behavior of alcohol and hydrocarbon mixtures
(discussed further in Section IV.C. of Chapter 2). The 1-psi
further reduction in vapor pressure would tend to partially
offset any increase in vapor pressure due to such commingling
effects, resulting in•evaporative emissions egual to those for
alcohol-free fuels.
The estimated costs in all cases for each PADD were
developed by the RPMS using a single "super refinery" to
represent all of the refining capabilities of that PADD (i.e.,
the average refinery). This super refinery was required to
produce all of the gasoline projected to be produced by all of
the individual refineries in that PADD in the timeframe of the
study, which was 1990. Individual refineries would be expected
to experience costs both above and below that estimated by the
RPMS, but on average, the actual costs should be close to that
projected by the model. The complexities involved with
modeling individual refineries make such an approach
economically infeasible and make the use of a single refinery a
necessary limitation of this study.
-------
4-6
The gasoline costs estimated by the RPMS are, by design,
incremental in nature and do not attempt to represent the full
cost of refining gasoline. This avoids a number of complex
issues associated with valuing capital equipment already in
place. As the desired output is the effect of RVP on refining
costs, a difference between an uncontrolled and controlled
scenario, this is fully satisfactory for this study.
To accomplish this, a base 1990 case is run to determine
optimal process requirements and refinery costs associated with
producing the 1990 product slate, considering process
capacities known to be available in 1984, and, thus, not
requiring capital investment. The controlled case is run in an
analogous fashion (i.e., a fresh optimization from 1984
capacities), only with a lower RVP or %iso product.
Conceptually, this approach assumes that investment occurring
between now and 1990 in the uncontrolled case can be redirected
toward more productive use, if economically desirable, in the
controlled case. This may or may not be the case, depending on
the timing of any volatility controls, and is being
investigated more fully via further modelling runs.[2]
However, information that is available on some of the past
model runs shows that very little of the investment occurring
in the base case does not also occur in the controlled
case.[2] Thus, little redirection of 1984-1990 investment
appears to be occurring and the effect of allowing this in the
modelling runs appears to be small.
For those readers investigating such details, it should be
noted that the RPMS runs tend to project sizable capital
investments between 1984 and 1990 for the base cases even
though the refinery industry as a whole is expected to invest
little for gasoline capacity aside from environmental control
(i.e., lead phasedown).[3] This occurs because the current
capacity of many peripheral processes (e.g., cooling towers) is
not known and was presumed to be zero in 1984 for modelling
purposes. Thus, the required 1990 base capacity for these
processes is considered to be entirely incremental, though in
all likelihood, the vast majority of it is currently in place.
These sizable capital investments have no direct effect on the
estimated RVP control costs, nor the estimated capital
investment required for RVP control, since these are
incremental costs involving the subtraction of base case costs
from the controlled case costs, both of which contain these
costs. It simply means that the capital investment shown for
either the base or controlled cases cannot be used to estimate
the total capital investment required by the refining industry
between 1984 and 1990. However, as the current capacities of
some of these peripheral processes may be in excess of that
needed in 1990, the model may be overestimating the additional
-------
4-7
capacity needed for RVP control. The degree to which this may
be occurring is unknown.and is not easily estimated.
Present RPMS runs also assume that all capital investment
is amortized over year-round production. This is appropriate
in the base case, since most of this equipment is of the kind
that is used year round. However, equipment purchased
expressly for RVP control might only be used during the
specified RVP control season. As discussed in Chapter 2, ozone
violations are prevalent in the summer months, so RVP control
might only be required during part of the year. For purposes
of this analysis, a 4-month summer control period (i.e.,
June-September) was chosen. However, a summer period of 3, 5,
or 6 months could also have been examined. This RVP control
equipment may also be useful during the non-summer period, but
to what degree is not known. Additional work is underway to
estimate the non-summer benefit.[2] Thus, the current RVP
control costs may underestimate the impact of capital
investment on a per-gallon basis for a summer-only control
strategy.
In the extreme case that the capital investment associated
with RVP control has no value outside of the control period
(i.e., the effect of capital on the cost of gasoline per gallon
was 3 times higher, based on a 4-month summer period) and this
caused the model to avoid all incremental capital investment
(i.e., opt for operating modifications), the RVP control cost
would be no greater than that estimated under a no-investment
scenario. This scenario was modelled primarily to simulate the
situation where the leadtime granted to refiners prior to RVP
controls was insufficient to design and build new capital, but
it applies as well to the extreme situation in which the model
itself avoids all incremental capital investment because
capital investment associated with RVP control has no value
outside of the RVP control period. While in theory the cases
were to be strictly no new investment, this stipulation had to
be relaxed in practice, again due to the unknown current
capacities of many peripheral processes. It did not seem
reasonable to limit such capacities to those required in the
base case, because historic gasoline production has been much
higher than projected 1990 levels and much excess capacity
could exist. At the same time, the degree of this excess is
unknown. Thus, the no-investment costs may be underestimated,
since the benefit of some capital investment may be included.
The extent to which this is true is not known and is not easily
estimated. Thus, these costs represent the best estimates
available under such conditions.
Another important aspect of modelling refinery RVP control
is the treatment of natural gas liquid (primarily butane)
supply and demand. Currently the butane market varies
dramatically between summer and winter. With gasoline RVP
levels 2 psi higher in the winter (corresponding to a butane
composition increase of 4 percent by volume), butane supplies
tend to be short and prices high. In the summer, the opposite
is true. With RVP control, even more butane will be available
-------
4-8
in the summer and prices could decrease further. This
potential price decrease is dependent on the entire
butane/petrochemical market and not just on petroleum refinery
operations. Thus, a model such as RPMS, which only models
petroleum refining, cannot project the price drop. In fact,
the price of butane must be input to the model. However, two
types of situations were modelled using RPMS to simulate the
effect of the potential price drop.
The first situation assumed that butane could be purchased
or not purchased at its current price, which varies with PADD,
depending on its economic usefulness. This situation is
referred to as the "open" N6L purchase scenario. Butane
availability was limited to that purchased by refineries in
recent times. The second situation forced the refinery to
purchase all of the available butane at the current summer
price. This situation is referred to as the "fixed" NGL
purchase scenario. The first situation was intended to place a
lower limit on RVP control costs by allowing refineries to sell
any excess butane generated by RVP control at current market
prices. In reality, lower butane prices would probably occur,
thereby reducing the profitability of doing this and also
increasing the cost of RVP control. The second situation was
designed to place an upper limit on RVP control costs by
requiring the refinery segment of the butane market to use all
of the excess butane at current market prices. In reality,
prices would drop and other segments at the market would
utilize at least part of the butane excess and result in lower
RVP control costs.
Practically, there are a number of potential problems even
with this bracketing analysis. One, when the RPMS was used to
model the first situation, refineries could not actually sell
butane generated within the plant at the current market price.
They could only avoid purchases. Thus, RVP control costs are
not as low as they might have been. Two, butane availability
was limited to historical refinery purchases. This is not
necessarily consistent with the conclusion of Section IV in
Chapter 2, where it was concluded that RVP nationwide could
increase by 1990 to ASTM limits. This conclusion implies that
butane usage would increase by 1990 without RVP controls. Lead
phasedown may actually cause this additional butane to be
produced within the refinery. However, if it does not, more
butane could be purchased, as butane supplies were exhausted in
many of the base scenarios. This would lower the cost of
producing gasoline in the uncontrolled cases and, thus,
increase the cost of RVP control. The effect of both of these
potential problems is now being analyzed via additional
modelling runs.[2] In addition, analysis of the impact of RVP
control on the entire butane market was performed.[4] Its
-------
4-9
results are described in Section IV, below, and are being used
in the additional modelling runs to more accurately model
butane price effects.
Until more detailed information is available from
additional RPMS cases currently being evaluated, the midpoint
between costs under the "fixed" and "open" NGL purchase
scenarios will be used for the cost of RVP control. This
decision is subject to change based on new data on the effect
of RVP control on butane value, but is the best estimate based
on data currently available.
The final aspect of the RPMS deserving discussion here is
the way the model simulates ASTM gasoline specifications. RVP
levels for the uncontrolled RVP base case were set at maximum
ASTM D-439 RVP specifications. PADD average maximum RVPs were
estimated by volumetrically weighting the RVPs of all the
gasoline produced by refineries in a particular PADD. National
average maximum RVPs were estimated by volumetrically weighting
the PADD-specific RVPs by the volume of gasoline produced in
each PADD. RVP of PADDs 4 and 5 was assumed to be the average
of the RVPs for PADDs 2 and 3. The PADD-specif ic RVPs and
national RVPs are presented in Table 4-2. The volumetric
production weighting factors are presented in Table 4-3.
Current (1984) national average gasoline RVP, as determined
from the MVMA fuels survey, is 10.89 psi, which is near the
maximum ASTM RVP specification of 11.27 psi. It is assumed
that, by 1990, the national average RVP will equal the maximum
ASTM RVP specification. This was discussed in detail in
Chapter 2, Section IV.
Besides RVP, ASTM addresses fuel volatility by specifying
minimum and maximum temperatures at which specified fractions
of the fuel are evaporated via distillation (i.e., T10 and
Tso) as discussed in Chapter 2, Section IV. Such
specifications do not lend themselves to linear programming
since temperatures at which certain fuel volumes are evaporated
cannot be easily manipulated when two fuel streams are merged.
It is much easier to work in the reverse mode, the percent fuel
evaporated at specific temperatures (i.e., %iso), since these
can be volumetrically averaged when two streams are blended
together. This is the mode in which the RPMS works. It is
possible to convert from one mode to the other, but only
approximately. Thus, at the present time, it is not clear
precisely how the RPMS limits (other than RVP) approximate
those of ASTM. However, the RPMS requirements specified by B&M
for maximum percent of gasoline evaporated at a given
temperature appear to be within the ASTM requirements
specifying minimum and maximum temperatures corresponding to a
given percent of gasoline evaporated. ASTM D-439 requirements
-------
4-10
Table 4-2
National and PADD-Specific RVPs and %igos
Resulting from Bonner & MDore RPMS Cases
Level of RVP
NGL Purchase Baseline (B)
PADD Scenario
I
I
II
II
III
III
Nat. Avg
Nat. Avg
Open
Fixed
Open
Fixed
Open
Fixed
Open
Fixed
RVP
11.5
11.5
11.46
11.46
11.12
11.12
11.27
11.27
%158
34.978
34.978
33.028
35.0
33.144
33.144
33.27
33.92
Control
B-l psi
RVP
10.5
10.5*
10.46
10.46
10.12
10.12*
10.27
10.27*
*158
33.7
33.778*
.32.487
33.284
30.753
31.184*
31.59
32.11*
B-2
RVP
9.5
9.5
9.46
9.46
9.12
9.12
9.27
9.27
psi
*158
32.1
32.0
31 .808
30.739
28.325
28.28
29.82
29.42
4. V^UA »^-* *^fj * * * w^.*. K-fS^^lA t, .LV^ri l k^s^> v,r*\_.\^A A \ t-f / UJ
RVP = midpoint between (B) and (B-2)
%158 =
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4-11
Table 4-3
Cost of RVP Control
($ per Barrel of Gasoline)
PADD
RVP 4 + 5 Total U. S.
Reduction, psi 1 2 3 (ex. CA)1 (ex. CA)j.
Alcohol-Free Gasoline
With Investment, Open Butane Purchases
10.1840.3650.2110.288 0.259
2 0.547 0.748 0.501 0.625 0.587
With Investment, Fixed Butane Purchases
1 0.1893 0.396 0.2123 0.304 0.271
2 0.561 0.857 0.504 0.681 0.626
With Investment, Average of Fixed and Open Butane Purchases
1 0.186 0.380 0.212 0.296 0.265
2 0.554 0.802 0.502 0.653 0.606
No Investment, Fixed Butane Purchases
1 0.2144 0.5014 0.3004 0.401 0.358
2 0.641 1.084 0.713 0.899 0.826
No Investment, Estimated Average of Fixed and Open Butane
Purchase
1 0.211 0.480 0.300 0.390 0.3505
2 0.6335 1.0145 0.7105 0.8625 0.8005
2.5% MeOH + 2.5% TEA Blend, with Investment, Open Butane Purchases
1 0.3696 0.4076 0.314 0.360 0.35
2 0.815 0.898 0.692 0.795 0.77
3 1.3707 1.5097 1.163 1.336 1.29
5.0% MeOH + 2.5% TEA Blend, with Investment, Open Butane Purchases
1 0.1958 0.3878 Q.2248 0.298 0.27
2 0.5818 0.7948 0.532 0.676 0.62
PADD-Specific Fraction of Total Gasoline Volume (%)
8.83 29.25 53.99 7.93 100.00
Footnotes on following page.
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4-12
Table 4-3 (cont'd)
1 Estimated as average of cost for PADDs 2 and 3.
2 Total U.S. (ex. CA) costs were estimated by volumetrically
weighting of PADD-speci f ic costs for PADDs 1, 2, 3, and 4 and
5 (excluding California) using PADD-specific gasoline
production.
3 Actual case not run, cost estimated from open butane purchase
for 1-psi RVP reduction using the percentage increase for
2-psia reduction costs between open and fixed NGL purchases.
4 Actual case not run, cost estimated from fixed butane purchase
costs with investment for 1-psi RVP reduction using the
percentage increase between 2-psia reduction costs with and
without investment.
5 These costs were estimated from the No-Investment costs for
fixed butane purchases presented in the previous row using the
ratio of midpoint (open-fixed)/2 vs. fixed butane purchases
costs for the cases with investment.
6 Actual case not run, cost estimated by applying ratio of 1-psi
reduction cost to 2-psi reduction cost for PADD 3 control to
the 2-psi reduction cost for PADD in question.
7 Actual case not run, cost estimated by applying ratio of 3-psi
reduction cost to 2-psi reduction cost for PADD 3 control to
the 2-psi reduction cost for PADD in question.
8 Actual case not run, cost estimated using the ratio of
corresponding costs from open butane purchase cases for
alcohol-free gasoline with investment applied to PADD 3 cost
for 5%/2.5% MeOH/TBA from B&M.
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4-13
for minimum and maximum temperatures corresponding to a given
percent of gasoline evaporated are not tight specifications,
and current fuels are not being restricted by these
requirements.
The point of major concern on the gasoline distillation
curve is the %iso, as discussed in Chapter 2, Section IV.
Bonner and Moore limited the maximum %iso to 35 percent for
the RPMS cases in their original study. This resulted in the
values of %i*o presented in Table 4-3, for the specific PADDs
and for the volumetric weighted national average. Current
(1984) national average gasoline volatility properties are
10.89-psi RVP and 32.6 %ieo. These values are those for
volumetrically weighting all gasoline grades (65 percent
unleaded regular, 18 percent unleaded premium, and 17 percent
leaded regular), but are also the same as those for unleaded
regular gasoline as presented in Table 2—7 of Chapter 2,
Section IV. The average %iso of current gasolines is
approaching 35 percent, indicating that the B&M restriction of
35 %iso is not too lax. Therefore, the B&M costs for RVP
control with %1So restricted to 35 percent appear reasonable
from this point of view.
B&M modelled some additional cases to evaluate the cost of
further controlling %J6o/ both independently and in addition
to RVP control. The cases evaluated and the results of running
these cases with the RPMS are presented in Section 11 I.e. of
this chapter.
B. Refinery Costs of RVP Control
The projected costs of 1- and 2-psi RVP reductions below
the maximum ASTM-specified RVP for various gasoline types and
other scenarios are shown in Table 4-3. Before discussing the
results of Table 4-3, it should be noted that the %lSo of
these fuels are indirectly reduced through this RVP control,
because removing compounds which contribute to high RVP also
lowers %i6o, to a certain extent. The reductions in %iso
associated with these 1- and 2-psi RVP reductions for the
"open" NGL purchase scenario are 1.7 percent and 3.5 percent,
respectively, as indicated by the national average levels for
%ieo presented in Table 4-3. %ieo is reduced 1.8 and 4.5%
for the corresponding "fixed" NGL purchase scenario.
The cost of controlling the RVP of alcohol-free gasoline
is of primary concern, since it represents nearly 89 percent of
all gasoline sold in the U.S. (with methanol blends making up 4
percent and ethanol blends the other 7 percent of the nations
gasoline sales.) As can be seen in Table 4-3, the
nationwide-average cost of reducing .RVP by 1 psi is 0.62-0.95
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4-14
cents per gallon ($0.259-0.358 per bbl), while the cost of a
2-psi reduction is greater than two times that, or 1.40-1.97
cents per gallon ($0.587-0.826 per bbl), depending on how
capital investment and the butane market are treated.
The least expensive RVP control scenarios are those in
which the refineries have the ability to invest in capital
equipment to optimize their refinery processes. This situation
occurs when the controls are to be in place long enough to
justify the capital investment and after refiners have had
sufficient time to design and implement new equipment. This
definitely applies to the long-term control scenario (i.e.,
2010) and may apply to short-term controls if the above two
conditions are met.
In addition, two extreme scenarios were evaluated with
capital investment permitted, one with "open" NGL purchases and
one with "fixed" NGL purchases, as described earlier. RVP
control for the "open" NGL purchase scenario was slightly less
expensive than for the "fixed" case ($0.587 vs. 0.626 $/bbl for
a 2-psi RVP reduction, respectively). As also described
earlier, the current best estimate of the RVP control cost is
halfway between these two values.
For the no investment situation, only fixed NGL cases were
modelled. Open NGL costs were estimated from the runs "with
investment" to determine the best estimate midpoint
"no-investment" cost, as shown in Table 4-3. These "no
investment" costs may be appropriate under short-term control
if refineries are not given sufficient time to invest in
capital prior to control or if the period of control is too
short to justify capital investment (generally thought to be
2-4 years).
Thus, the "with investment" costs are used to represent
long-term control costs and both "with" and "without
investment" costs are used to represent the range of potential
short-term control costs. These costs are used in determining
the overall costs of RVP control presented at the end of this
chapter and also the cost-effectiveness of RVP control ($/ton)
presented in Chapter 6.
The cost of controlling the RVP of alcohol-blends follows
the same general PADD-to-PADD trend as that for alcohol-free
gasoline. Overall, the cost of vapor pressure control is
greater for gasoline containing the 2.5/2.5 percent
methanol/TBA blend, than for alcohol-free gasoline. The cost
of a 3-psi reduction for PADD 3 (the only PADD evaluated) is
increased 68 percent over that of just a 2-psi reduction. This
increase may differ slightly between PADDs, but was assumed in
Table 4-2 to be relatively constant.
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4-15
The cost of reducing RVP for the 5.0/2.5 percent
methanol/TBA blend, in contrast, is less than that for the
2.5/2.5 percent methanol/TBA blend and is 6-7 percent greater
than that for alcohol-free gasoline, on average. Bonner and
Moore credits the smaller cost to the non-linear vapor pressure
blending behavior of the additional methanol, as indicated by
the blending values shown in Table 4-1. The additional 2.5
percent of methanol incurs a small additional vapor pressure
penalty but contributes a larger octane benefit. As this is
expected to be more popular than the 2.5/2.5 percent
methanol/TBA blend in the future, and its RVP control costs are
so close to that for alcohol-free gasoline, only the cost for
alcohol-free gasoline will be used hereafter.
As indicated above, attempts were made to model 10 percent
ethanol blends, in the same manner as methanol blends.
However, in all cases, the base (uncontrolled) RVP was already
very near or below the 2-psi reduction level. This was an
artificial result of restricting %18o to 35 percent. This is
unrealistic for current ethanol blends, as ethanol dramatically
affects %l6o and current levels of %iso for ethanol blends
at 11.5-psi RVP are around 42 percent. Thus, the forced
lowering of %iso likely forced most of the butane out of the
fuel and lowered RVP dramatically prior to control. This
situation is being corrected in additional modelling currently
being conducted by B&M. Results are not available yet, but
will be incorporated in the study of controlling evaporative
emissions as soon as the RPMS case studies are complete.
Thus, little can presently be said quantitatively about
the cost of controlling the RVP of ethanol blends.
Qualitatively, ethanol has a smaller RVP effect and greater
octane effect than methanol/TBA mixture (see Table 4-1). Thus,
one would expect its presence to impact RVP control costs less
than the methanol/TBA mixture when %iso is not controlled.
This is being further investigated via further RPMS modelling
runs.[2] The economic impact on the ethanol blending industry
of controlling the quality of the finished blend (i.e.,
eliminating splash blending and requiring coordinated blending)
is also being investigated.[5] This is discussed further in
Section III.D.
C. Refinery Cost of Controlling the Percent of Gasoline
Evaporated at 160°F
The significance of controlling %iso has already been
discussed in detail in Chapter 2, Section IV. In review, the
representative volatility measure with respect to the portion
of hot-soak emissions occurring from the fuel metering system
appears to be %i6o, because 160°F is a typical maximum
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4-16
carburetor bowl temperature during a hot-soak. B&M was
instructed to evaluate the cost of controlling %iso through
running additional RPMS cases with restrictions on %i8o, as
it may be valuable to control %iso in addition to controlling
RVP. This section discusses the RPMS cases evaluated by B&M
and the sensitivity of refinery costs to controlling %i«0.[l]
Two sets of cases have been run to date to evaluate the
effect of controlling %iso on refinery costs. They were run
for PADD 2 under the fixed NGL purchase scenario. This
situation was believed to result in the worst-case cost for
%ieo control since it showed the highest RVP control cost and
the greatest sensitivity to fixing NGL purchases. The first
set of cases was conducted for alcohol-free gasoline, while the
second was run for 5/2.5 percent methanol/TBA blends. A third
set of cases is currently being run using the RPMS to evaluate
refinery cost of controlling %iso at different RVPs for PADD
3, because 54 percent of national gasoline production occurs in
PADD 3 and these results will represent more of a national
average than those for PADD 2.[2] The results of running the
third set of cases are not available at this time, but will be
incorporated into the analysis as they become available.
The results for the first two sets of cases are detailed
in B&M's supplement to their earlier report.[1] They are
summarized in the following paragraphs.
1. Alcohol-Free Gasoline
Results of evaluating the first set of cases run to
determine the refinery cost of controlling %iso of
alcohol-free gasoline indicate that RVP control cost decreases
as %IBO restrictions for the baseline uncontrolled RVP
scenario and for controlled RVP scenarios are limited below 35
percent. Results of running 6 cases were used to, evaluate
refinery control costs at different RVP and %1So
restrictions. These 6 cases run for PADD 2 are described in
Table 4-4. The resulting costs and actual RVPs and %ls<>s are
presented in Table 4-5.
It is difficult to separate the costs of controlling RVP
and %iso, because refinery operations necessary for RVP
control, as discussed in Section II, may also result in
controlling %iso- The $0.857 per barrel cost for a 2-psi RVP
reduction for PADD 2 under the fixed NGL purchase scenario also
includes (unavoidably) a 4.26 percent decrease in %i6<>. This
is because controlling gasoline RVP involves removing butane,
which affects %iso. A 2-psi reduction in RVP may be
accomplished by an estimated 4 percent reduction in butane
content, which, absent other changes, also reduces %iso 4
percent because of butane's low boiling point.
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4-17
Table 4-4
RVP and %igo Restrictions for
RPMS Cases Evaluated to Determine
Refinery Costs of Gasoline Volatility Control
Max. RVP = 11.46 psi Max. RVP = 9.46 psi
Max %ieo ~ 35% x x
Max %!6o = 30% X X
Max %160 = 25% X X
X Indicates that RPMS case was run for specified maximum RVP
and
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4-18
Table 4-5
PADD 2 Refinery Costs and Actual RVPs and %i60s
for RPMS Cases Described in Table 5-4
All gasoline grades are alcohol-free.
1. RVP = 11.46 Cost = 2. RVP =9.46
%16Q = 35% $.857/bbl %i6Q = 30.74
Cost = $0.485/bbl Cost = $0.045/bbl
3. RVP = 10.53 Cost = 4. RVP = 9.46
= 30% $.417/bbl %160 = 30%
Cost = $.841/bbl Cost = $.500/bbl
5. RVP =9.86 Cost = 6. RVP =9.11
%160 = 25% $.075/bbl
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4-19
Controlling RVP 2 psi below the ASTM maximum for PADD 2
with %ieo restricted to 30 percent, is less costly than at 35
percent, partially because the 30 percent restriction for the
uncontrolled RVP scenario limits RVP to 10.53 psi. This is
nearly l psi below the 11.46-psi maximum ASTM specified RVP
level. Therefore this $0.417/bbl cost of controlling RVP to
9.46 psi does not assess the cost of controlling RVP 2 psi, but
rather only assesses the cost of controlling RVP 1.07 psi.
Likewise the cost of controlling RVP to 2 psi below the ASTM
maximum specified RVP level with %iso restricted to 25
percent is only $.075/bbl, because there is actually only a
0.75-psi reduction in RVP due to the 25 percent %i«0
restriction.
The costs illustrated in the matrix of Table 4-5 also
indicate the cost for controlling %iso at constant RVP. The
costs are $0.45/bbl for %iso between 30.74 and 30.0 percent
and $0.50/bbl for %i6o between 30 and 25 percent, both at
9.46-psi RVP. Other costs included in the matrix are costs for
controlling both RVP and %iso simultaneously.
It is clear from this matrix that the refinery cost of
gasoline volatility control is a function of the level of
control of both RVP and %iso. The costs presented for RVP
reduction in the previous section (at %i«0 restricted to 35
percent) are the most representative RVP control costs, but may
be reduced by as much as a factor of 2 if baseline %iso
levels were lower. MVMA survey data for fuels sampled during
July of 1984 indicates that the average %is« (which can be
used to approximate %iso) for volatility Class C gasolines
was 32.6 percent (discussed in Chapter 2, Section IV).
Assuming no change in future %iso levels (there is currently
an upward trend), the RVP control cost in PADD 2 may currently
be overestimated slightly since its %i6o is being reduced
from -a greater value, 35 percent, to 30.74 percent. The
sensitivity of overall costs and cost-effectiveness of gasoline
volatility control to restricting the %i6o are addressed
further in Chapter 6, Section III.
2. Methanol/T3A Blends
The second set of cases evaluated by B&M using their
proprietary RPMS. were run to study the refinery cost of
controlling %iso for gasoline containing 5/2.5 percent
MeOH/TBA. These cases are the same as those run for the
alcohol-free study on refinery cost of controlling %i60, as
illustrated in Table 4-4. The results of running these cases
are presented in Table 4-6. They may be analyzed as were those
of the alcohol-free %i6o control study. These results are
summarized below.
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4-20
Table 4-6
PADD 2 Refinery Costs and Actual RVPs and %igos
for RPMS Cases Described in Table 5-4 ,
All gasoline grades contain 5/2.5% MeOH/TBA.
1. RVP = 11.20 Cost = 2. RVP =9.46
%160 = 35% $0.491/bbl %160 = 35%
Cost = $1.039/bbl Cost = $0.620/bbl
3. RVP =9.89 Cost = 4. RVP =9.46
%160 = 30% $.072/bbl %160 = 30%
Cost = $1.296/bbl Cost = $1.224/bbl
5. RVP =8.10 Cost = 6. RVP =8.10
%160 = 25% $.000/bbl
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4-21
Cost of RVP control to 9.46 psi (2 psi below the maximum
ASTM specified RVP of 11.46 psi) is lower for low %iso
restrictions than for high %1So restrictions. This is
because actual RVP reduction is less as %iso restriction is
lowered. The cost differences are $0.491/bbl for RVPs from
11.2 to 9.46 psi (a 1.74-psi RVP reduction) at a 35 percent
%ieo restriction, and no cost at a 25 percent %iso
restriction because this %ieo restriction limits RVP to 8.10
psi for even the uncontrolled RVP case, which is already less
than 9.46 psi. The cost of a 5 percent difference in %iSo
may be estimated from the cost of reducing %iso from 35 to 30
percent at RVP equal to 9.46 psi. This cost is $0.620/bbl.
The $0.491/bbl cost for RVP control in PADD 2 to 9.46 psi
at %ieo restricted to 35 percent is probably a slight
underestimation of the cost of reducing %iso RVP of
methanol/TBA blends 2 psi, because RVP is only reduced 1.74 psi
at constant %i60. The %iso of methanol blends is, as
discussed in Chapter 2, Section IV.C., higher than that of
alcohol-free gasoline and likely exceeds 35 percent, on average.
IV. Effect of RVP Control on the Butane Market
The major method of RVP control is to remove butane from
gasoline, as described in Section II, and to replace the butane
with heavier components. The butane that is no longer used in
gasoline is made available to the market and this excess supply
could and likely will decrease the market price of butane and
economically impact suppliers and purchases. While in
aggregate, this economic impact should be zero (i.e., the
benefits to purchasers of cheaper butane should equal the cost
to suppliers), there may be economic impacts on isolated
segments of the butane market. Thus, Jack Faucett Associates
(JFA) was contracted to evaluate the effect of reducing the RVP
of gasoline on butane prices and usage. The results of their
study are presented in a report entitled, "The Butane
Industry: An Overview and Analysis of the Effects of Gasoline
Volatility Control on Prices and Demand".[4] The results of
this study are summarized below.
JFA concluded that excess butane supply from any level of
RVP reduction evaluated would be large compared to actual
butane demand as a fuel or a feedstock priced at $23.08/bbl,
the baseline annual average national price of butane. Because
of the limited demand for butane as a unique fuel or
petrochemical feedstock, a small level of RVP reduction results
in enough excess butane to cause butane prices to fall to the
level of the petrochemical floor price, estimated to be $20.26
per barrel in 1990. Here butane is used in place of other
feedstocks primarily in the production of acetic acid and
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4-22
ethylene. The demand for these other feedstocks is large
enough that even extreme reduction of RVP would not result in
providing enough additional butane to drive the price below the
petrochemical floor price. JFA estimates that, at any price
above the $20.26/bbl petrochemical floor price, no more than
850,000 bbls of butane per year could be absorbed by the fuel
and petrochemical feedstock sectors of the butane market. This
volume is significantly less than the 8.6 million barrels of
excess butane estimated to result from a 1-psi RVP reduction
for a 4-month control period. On the other hand, the 42.9
million barrels of excess butane estimated to result from a
2-psi reduction in gasoline RVP over a 6 month control period
would all be used at the petrochemical floor price at
$20.26/bbl.
These prices for butane estimated by JFA are similar in
magnitude to those presented in the B&M study.[1] The raw
material costs for both normal and iso-butane for PADD 3 were
estimated at $23.30/bbl in the B&M study. The PADD 3 prices
are the best choice for comparison with JFA's national average
price because PADD 3 produces over 50 percent of the nations
gasoline. Under the "open" NGL situation, these prices were
assumed to remain constant and refineries could avoid
purchasing butane, if desired. However, they could not sell
butane produced within the refinery. Under the "fixed" NGL
situation, refineries were forced to purchase all the NGLs
projected to be available at these same prices, regardless of
its value to the refinery. It is very useful to compare the
incremental refinery values for butane under these two
conditions with the petrochemical floor price of $20.26/bbl
determined by JFA.
The incremental refining values of butanes for ' all
scenarios, as estimated by B&M, are presented in Table 4-7.
Incremental refining values (value to refinery of the last
barrel used) of normal butanes under the "fixed" NGL purchase
scenario are $21.04/bbl, $16.44/bbl, and $21.30/bbl for a 2-psi
RVP reduction for PADDs 1, 2, and 3 respectively. The
incremental values of iso-butane are much higher; $27.05,
$21.69, and $26.86 per barrel for PADDs 1-3, respectively.
Where these figures are below the $23.30/bbl price of butane,
this means that butane prices would have to drop to these
levels for refineries to purchase and utilize all of the NGLs
projected to be available.
As can be seen, the incremental values for iso-butane are
all above the floor price of $20.26/bbl floor price estimated
by JFA. As the sales-weighted value is well above $23.00/bbl,
iso-butane prices should not drop and no excess should reach
the market.
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4-23
Table 4-7
Incremental Refining Values of Butanes ($/bbl)
PADD-1 PADD-2 PADD-3
Open Fixed** Open Fixed** Open Fixed**
RVP: Base
Normal Butane 35.27* 35.24 24.77* 20.98 29.80* 29.80
Iso-Butane 32.03* 32.05 24.75* 23.30 31.16* 31.16
RVP: -1-psi
Normal Butane 28.75* na*** 23.20 18.37 26.22* na
Iso-Butane 30.51 na 25.83* 23.46 31.14* na
RVP: -2-psi
Normal Butane 21.97 21.04 22.39 16.44 23.30 21.30
Iso-Butane 28.15 27.05 24.89* 21.69 29.04* 26.86
* Butane purchases limited by maximum availability.
** Butane purchases required to equal maximum available.
*** na = Case not modelled by Bonner and Moore.
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4-24
The situation for n-butane is slightly different. The
sales-weighted value in the three PADDs is very near the JFA
estimated floor price of $20.26/bbl. Thus, the market price of
n-butane would likely drop to this level with a 2-psi RVP
reduction. However, little n-butane may actually switch to
petrochemicals since refineries can apparently utilize all of
the excess at this price. Of course, even less effects would
be seen with a 1-psi RVP reduction.
In the "open" NGL situation, the incremental butane values
are nearly always above the current market price of $23.30/bbl
and purchases are often limited by projected availability.
This has raised some concerns that the model may be valuing
butane-utilizing processes too highly, since such high
incremental values would argue for equally high market prices.
To further investigate this possibility, Bonner and Moore is
evaluating the sensitivity of its model to a number of factors,
including base alkylation capacity (a butane consumer) and 1990
butane availability.[5] These results will be incorporated
into the study as soon as they are available.
V. Fuel Economy Credit
This section presents an analysis of the effect of
reducing the volatility of gasoline on fuel economy. It is
hypothesized that, if gasoline volatility is reduced by
removing butane from gasoline and replacing it with other fuel
components, the energy density of the gasoline will increase.
Furthermore, vehicular fuel economy should increase with an
increase in fuel energy density. Thus, there should be a fuel
economy benefit resulting from reducing the volatility of
in-use gasoline. As a result of the analysis, it is estimated
that reducing RVP by 1 and 2 psi will increase fuel economy by
0.25 and 0.56 percent for feedback and non-feedback-eguipped
vehicles.
The remainder of this section explains how these estimated
increases in fuel economy were determined. It is divided into
three parts: 1) the relationship between gasoline volatility
and energy density, 2) the relationship between energy density
and fuel economy, and 3) the overall relationship between
gasoline volatility and fuel economy.
A. Volatility and Energy Density
Quantifying the relationship between RVP and energy
density is difficult because of 1) the complex refinery
operations involved in lowering RVP and maintaining octane and
other requirements and 2) the relatively wide range of
commercial fuel energy contents occurring at any given RVP.
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4-25
Relevant information from two different sources was available
to derive independent estimates of the effect of RVP on energy
density. Also, both API and MVMA were requested to submit any
relevant information they might have. The two independent
analyses and the two submittals are described in the following
paragraphs. Table 4-8 details the quantitative results from
each for direct comparison.
The first independent analysis used the output of Bonner
and Moore's linear programming model, which is being used to
estimate the cost of controlling RVP.[1] In addition to RVP
and octane, the model generates estimates of other fuel
properties, including API gravity, aromatic content, and
50-percent distillation temperature, which can then be used to
estimate fuel energy density using a well-accepted relationship
defined in ASTM D3338-74. There was significant variation from
region to region in the effect of RVP reduction on energy
density, resulting from the varying regional composition of
gasoline at different RVPs. Energy densities increased
0.22-0.30 percent for a 1-psi RVP reduction and 0.33-0.69
percent for a 2-psi RVP reduction. Weighting the regional
effects by gasoline production volume resulted in weighted
energy-density increases of 0.25 percent and 0.56 percent for a
1- and 2-psi RVP reduction, respectively.
The second independent analysis examined MVMA fuel survey
data from January and July gasoline samples taken from 1979-83
(these were available on tape and could be accessed en masse).
The energy content of each fuel sample in the surveys was again
estimated from the properties of the fuels using the
relationship from ASTM D3338-74, as described above. A linear
regression was then applied to relate the RVPs and energy
densities (BTUs/gallon) for the nearly 2,000 summer fuel
samples and also for the 4,400 summer and winter fuel samples.
For the summer gasolines, a 1-psi reduction in RVP from 11.5 to
10.5 psi resulted in a 0.25 percent increase in energy density,
with a range of 0.22 to 0.28 percent at 90 percent confidence.
For summer and winter fuels combined, a 1-psi reduction in RVP
from 11.5 to 10.5 psi resulted in a 0.33 percent increase in
energy density, with a range of 0.32 to 0.34 percent at 90
percent confidence. The R was only 0.09 for summer fuels
and 0.30 for summer and winter fuels combined, but due to the
large number of samples, the relationship is quite certain, as
evidenced by the tight 90-percent confidence limits. The
regression of summer fuels is probably the most appropriate
for use here. The winter fuels were included to provide a
wider range of RVPs and to test the sensitivity of the results
to range of RVP.
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4-26
Table 4-8
Effect of Change in RVP on Change In Energy Density
Source of Information
1. Bonner & Moore
PADD 1
PADD 2
PADD 3
Volumetric Wtd. Average
2. MVMA Fuel Sampling Data
Sxommer Fuels
Summer & Winter Fuels
3. MVMA Submittal
Calculated Effect
4. API Submittal
Percent of Increase in Heat
Of Combustion (Btu/qal)
RVP 1-psi RVP 2-psi
,30
22
,26
25
0.25
0.33
.54
.33
.69
.56
0.50
0.66
0.32 0.64
No calculated results
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4-27
The MVMA submittal in this area outlined a first-order
analysis of the effect of reduced RVP on fuel energy
density. [6] They stated that they were not aware of any test
data that would provide a direct relationship between RVP
reduction through butane control and vehicle fuel economy;
however, they did make some calculations to estimate the effect
of butane content on energy density. They too used the the
method described in ASTM D3338-74 to estimate gasoline energy
content from predicted average properties of the gasoline.
They estimated the percent decrease in fuel butane content
associated with a 1- and 2-psi change in RVP to be 1.8 and 3.7
percent, respectively. Then, assuming that the composition of
the non-butane portion of the fuel would remain constant, they
estimated the change in the energy density using the relative
energy densities of gasoline, and while MVMA did this using
three baseline gasolines of various RVP, their analysis ignores
the fact that reduced butane content will reduce octane. This
octane can be replaced by further processing of the gasoline
feed stocks, which will likely reduce energy density, or by
increasing aromatic content, which will likely increase energy
density. MVMA estimated that 1-psi and 2-psi reductions would
increase energy density by 0.32 and 0.64 percent,
respectively. As these figures are somewhat larger than those
estimated using the Bonner and Moore model and the regression
of summer fuel RVPs, it appears that increased processing to
replace lost butane dominates somewhat and reduces the net
energy increase by about 0.07 percent per psi RVP.
API, in their submittal, stated that there is no
predictable relationship between gasoline vapor pressure and
gasoline density.[7] They state that a number of compositional
changes occur in reducing RVP to ensure that the other
properties of the gasoline remain in accord with ASTM
specifications and that production volume is maintained. As
evidence, they cite the fact that the scatter in the energy
densities of surveyed fuels at a specified RVP is greater than
the difference in energy density between RVPs, and make the
determination that any relationship between RVP and energy
density impossible to ascertain. Therefore, they did not
submit any conclusions on the net effect of all the factors
affecting energy density accompanying a reduction in RVP, other
than to state that the relationship is unpredictable.
As our own assessment of the energy densities of
MVMA-surveyed fuels indicated, there is a wide variation in
energy density at any given RVP and this variation is larger
than the effect of RVP. However, the 90 percent confidence
limits on the predicted slope take this variation into account
and still predict a range of only 0.25+0.03 percent per psi for
summer fuel. Thus, while other factors can overwhelm the RVP
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4-28
effect for any given fuel, on average the RVP effect is quite
certain and quantifiable. The fact that the Bonner and Moore
estimates fall within this small range, and yet were quite
independent, is further support for their accuracy.
Given that the analysis of the survey data and the B&M
study yield essentially the same results, the B&M estimates
will be used here as it is a forward looking study of lower RVP
fuels across the board rather than backward looking survey
results. The result is that energy density is projected to
increase 0.25 percent with a 1-psi reduction in RVP and 0.56
percent with a 2-psi reduction.
B. Energy Density and Fuel Economy
Much data on the fuel economy of all types of vehicles
exist in the literature. However, few studies relate fuel
economy to fuel energy density. Thus, while the effect of
energy density on fuel economy should be more consistent and
discernible than the effect of RVP on energy density (once
measurement variation is eliminated), few data exist from which
to determine accurate estimates. Compounding this is the fact
that the random variation in fuel economy measurements is large
(e.g., 3-5 percent) relative to the expected change in fuel
economy (less than one percent). Three sources of information
were used in analyzing this relationship: 1) test data
supplied by General Motors and Ford with respect to the CAFE
adjustment rulemaking* (use of this information was also
recommended by MVMA in their submittal in this area), 2) fuel
economy data from EPA's in-house emission factors testing
program, and 3) a discussion submitted by API reviewing
different factors that affect fuel economy. A theoretical
analysis of the vehicle design optimization and performance on
the different gasoline types was then used to arrive at a
conclusion. These are discussed in order below.
In a letter dated August 15, 1984, General Motors cited
data on the relationship between gasoline energy density and
fuel economy which was presented in a Chevron Research Co. SAE
paper in 1974, and added that GM testing on more recent systems
supported the results presented in the SAE paper.[8,9] The
vehicles tested by Chevron were from the 1970 and 1972 model
years, and the SAE paper points out that these tests can only
give an indication of 1970 and 1972 car performance in
general. Their results were based on testing six vehicles with
six fuels, repeating each vehicle/fuel-specific test at least
eight times. Fuel economy was measured by weighing the fuel
See 49 FR 48024, December 7, 1984.
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4-29
consumed and measuring the distance travelled during each test
cycle. Heat (energy) content of the fuels was calculated using
a widely accepted correlation involving API gravity, percent
aromatics, and volatility of the gasoline from ASTM-3338. The
average value of the ratio of the percent change in vehicular
fuel economy to the percent change in gasoline energy density
(defined as R) was 0.57. The GM submittal did not supply or
refer to any data supporting their average value for R
resulting from testing on more recent systems, but they did
state that the testing yielded R values ranging from 0.1 to
0.9 with an average of 0.5. In their submittal they suggested
an overall average R of 0.6.
This value of 0.6 for R was later recommended by GM, Ford,
and MVMA in response to questions asked by EPA's Certification
Division in the EPA memorandum referenced in the supplemental
NPRM on the CAFE adjustment rulemaking referenced
earlier.[10,11,12] This ratio of increased fuel economy to
increased energy content of 0.6 was recommended for all
vehicles (without differentiating between feedback and
non-feedback equipped vehicles). This ratio is not heavily
supported by a large data base, but likewise is not refuted by
the data sets used by GM and Ford. The major conclusions of
these manufacturers as stated in their January 22, 1985 letters
to EPA are discussed below.
In their letter to EPA, GM summarizes data from five
vehicles (two with throttle-body injection (TBI) and three
carbureted) of model years 1981 and 1984, which are presented
in Table 4-9.[10] They include R factors for FTP and highway
tests. The method which General Motors used to measure or
calculate the fuel economizes of these five vehicles was not
stated in the GM letter. The results for FTP testing were an
average R of 0.62 for five vehicles, with a range of
0.34-0.89. For the highway test procedure the average ratio
was 0.53, with a range of 0.41-0.72. The 0.89 and 0.72 R
values were both for a 1984 Pontiac J2000 with TBI.
GM did not explain why R is greater for the FTP tests than
for the highway tests. This is not the expected result for two
reasons. One, there is more stopping and starting on the FTP
than on the highway test (e.g., more accelerations where a
carburetor could be operating rich and not able to utilize the
extra energy). Two, the FTP contains cold operation, where the
highway test does not. Again, the engine will likely be
operating rich and the feedback loop will be inoperative during
this time. This anomaly in the data is unexplained.
-------
4-30
Table 4-9
GM Data on Ratio of Percent Change in
Fuel Economy to Percent Change in Energy Density[10]
R Factor
Test Vehicle FTP HWY
Carbureted Vehicles
1984 Olds Delta 0.35 0.51
(5.0L, 4bbl.)
1981 Olds Cutlass 0.39 0.41
(4.3L, 2bbl.)
1981 Chevette 0.80 0.62
(1.6L, 2bbl.)
Average 0.51 0.51
TBI Vehicles
1984 Chevrolet Citation 0.65 0.41
(2.5L, TBI)
1984 Pontiac J2000 (1.8L TBI) 0.89 0.72
Average 0.77 0.56
Composite Average 0.62 0.53
(Carbureted and TBI)
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4-31
If the data from the five vehicles are divided into two
groups, as illustrated in Table 4-9, the TBI-equipped vehicles
show higher R values (0.77 vs. 0.51 for the FTP and 0.56 vs.
0.51 for the highway test) than the carbureted vehicles. The
composite data have an average R of 0.58, which may be rounded
off to 0.6. However, the fact that the TBI vehicles show
higher R values than the carbureted vehicles and the statement
that R can approach 1.0 for some operating conditions (i.e.,
steady state) indicate that it may be appropriate to assume an
R higher than 0.6 for fuel-injected vehicles.
Both the TBI vehicles and the carbureted vehicles were
probably equipped with electronic feedback control (EFC)
operating over most of the test cycle, as all GM vehicles of
model years 1981 and later used EFC. Therefore, one can still
distinguish between TBI and carbureted vehicles here, but the
results (i.e., R values) should be the same for both sets of
vehicles, since the real technological difference is between
feedback and non-feedback equipped vehicles.
In a direct response to EPA's question, "Is it appropriate
and/or possible to account for the effect of fuel energy
content on the vehicle's energy efficiency? If so, how should
this be done?" GM supplied no other data than that in Table
4-9 and a reference to SAE paper no. 740522 and recommended an
R of 0.6.
Ford also recommends that an R = 0.6 be adopted to
represent the 1980-85 model year vehicles.[11] The Ford letter
of 1/22/85 goes on to state that future model year vehicles
could respond differently and, thus, should be evaluated
separately if warranted by future fuel specification changes.
Ford based their conclusion on repeated test results from four
different vehicles with different engines and control systems
using two different fuels. Twelve CVS-H and twelve HWFET tests
were conducted on each vehicle and with each fuel for a total
of 192 tests. The method used to determine the fuel economies
of these vehicles (volumetric measurement or carbon balance
calculation) was not stated in the Ford letter. These results
are presented in Table 4-10.
One of these four vehicles was equipped with electronic
fuel injection (EFI), always accompanied by electronic feedback
control, while the rest were designated NFB for non-feedback
vehicles. The R value for the EFI vehicle for the hot-start
test was 0.75. For the hot-start portion of the urban driving
cycle (CVS-H) fuel evaluation and the highway fuel economy test
(HWFET) fuel evaluation analyses, the R values were 0.71 and
0.84, respectively. The other three vehicles were non-feedback
controlled vehicles (NFB) with average R values of 0.35 for the
-------
4-32
•Bible 4-10
Ford Data on Ratio of Percent Change in
Fuel Economy to Percent Change in Energy DensityCll]
Test Vehicle M-HHS* CVS-H* HWFET* CVS-C/H*
w/o Feedback Controls
3.8-216 NFB
1.6-602 NFB
5.0-807 NFB
Average
W/Feedback Controls
1.6-343 EFI
Composite Average
0.5974
0.6178
0.2095
0.4749
0.7502
0.5437
0.2168
0.5574
0.2687
0.3476
0.7082
0.4378
1.1837
0.7173
0.1161
0.6724
0.8403
0.7143
0.846
0.846
1.065
0.955
(Feedback and Non-Feedback)
M-H Hot-Start = city and HWFET combined to yield a
metro/highway value.
CVS-H = city test cycle - hot-start.
HWFET = highway test cycle.
CVS-CH = City cycle test - cold-start.
-------
4-33
CVS-H analysis, and 0.67 for the HWFET fuel evaluation
analysis. These R values are significantly lower than those
resulting from testing the EFI vehicle. MOBILES projections
predict that by 1990 nearly 90 percent of gasoline-fueled
vehicles in-use will have EFI or will be feedback-equipped
carbureted vehicles. Thus, based on the Ford data, it is
reasonable to assume an R value higher than 0.6 for vehicles in
use in 1990, the majority of which will use EFI.
It should also be noted that this Ford data supports the
theory presented earlier; that vehicles tested on fuels of
different energy content would provide higher R values over the
HWFET than over the CVS-H test cycle. It also contradicts the
results of the GM analysis, in which R from the FTP was greater
than R from the HWFET. This contradiction indicates the
variability in measuring R over different test cycles, and
lends some doubt to the accuracy of this method of analyzing R.
Ford states in the January 22, 1985 letter that, though
fuel economy should increase due to an increase in the energy
content of the fuel the vehicle is operated on, the vehicle
cannot utilize 100 percent of the increased energy content of
the fuel because there are penalties that are associated with
greater fuel density.[11] These penalties are: 1) air/fuel
ratio shifts slightly richer, 2) cylinder to cylinder A/F
distribution becomes worse, and 3) A/F ratio excursions on
transients increase. Ford states that these variations in
air-fuel ratio due to changes in fuel properties will prevent
the R value from ever reaching 1.0, and thus they recommend R =
0.6. Again, no differentiation was made between R values for
carbureted and fuel-injected feedback and non-feedback equipped
vehicles, even though the data supports a higher R value for
EFI vehicles than for NFB vehicles.
The MVMA letter of January 22, 1985 analyzes the data
submitted by GM and Ford and reaches the same conclusion; 0.6
is a reasonable value for R.[12] The MVMA letter does not
propose a higher R value for feedback equipped vehicles vs.
non-feedback equipped vehicles.
The second source of information was EPA's in-house
emission factors testing program. No major conclusions on the
relationship between lower RVP fuel and vehicular fuel economy
can be drawn from these data due to the large degree of
variability in the R values calculated from the EPA test data
for vehicles operating on different fuels (R = -4 to R = +5).
It appears that the variability associated with the
measurement of both fuel properties and fuel economy is larger
than the actual changes in energy density (only -0.4 to +1.0
percent). Because of this, the results from this test program
could not be used to evaluate R.
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4-34
Finally, API, in their submittal, stated that there are
many variables that can combine with fuel volatility parameters
to affect energy density and fuel economy.[3] However,
although they mention data reported in CRC Report No. 527
showing the effect of ethanol blends on fuel economy, they did
not submit any data relating energy density and fuel economy
for alcohol-free gasoline. Since ethanol lowers energy
content, rather than raising it as does lower RVP, this
severely limits the value of their submittal here.
General Motors also submitted a theoretical argument
defending an R valve significantly less than 1.0, in the form
of a letter from Chemical Engineering Professor John Longwell
of MIT. GM submitted the data from references [4] and [6] to
Professor John Longwell of MIT for his analysis and comments.
Professor Longwell concluded that the GM suggested value of R =
0.6 is reasonable.[13] Professor Longwell's conclusion was not
based on any data other than that already discussed; but he did
perform a theoretical analysis of the effects of different
gasoline properties (including energy density) on fuel
economy. He explains that high density, low H/C fuels may run
at higher equivalence ratios resulting in lower efficiency and
lower R. This effect is greater for volumetrically metered
fuels than for fuel metering controlled by an oxygen sensor.
This implies that volumetrically metered fuel systems (i.e.,
open-loop carbureted vehicles) may yield lower R values than
fuel metering controlled by an oxygen sensor, referring to
feedback equipped fuel systems.
Longwell goes on to discuss the effect of increasing
aromatic content, which increases fuel viscosity, surface
tension, and latent heat of vaporization. He writes that these
changes decrease evaporation ratio which decreases fuel mixture
homogeneity and quality of cylinder to cylinder distribution,
both of which lower the fraction of the volumetric heating
value that is captured in miles per gallon. Longwell also
explains that higher aromatic content also increases flame
temperature, which increases heat losses to the cylinder walls,
thus, decreasing efficiency, and R.
Longwell concludes that the major changes in the fuel
system have not improved the engine's ability to capture the
high heating value of higher density fuels. Because he was
unable to identify factors that would tend to appreciably
increase R above 1.0, he concluded that a multiplicity of
effects caused by increased density and aromatic content
combine to reduce R. Longwell states that the GM suggested
value of R = 0.6 is reasonable, but he does not suggest using
different R values for vehicles with different fuel systems.
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4-35
Because of the inconsistencies in the R values provided by
GM and Ford that were discussed previously, and also those in
the R values resulting from EPA's in-house emission factors
test program, a theoretical analysis of R is necessary. Two
arguments may be presented to support an R value greater than
0.6. The first argument addresses the implications of an R
value significantly less than 1. The second evaluates the
vehicle design optimization procedure and its effect on vehicle
operation on different fuels. These arguments are discussed
below.
An R of ,0.6, as estimated by MVMA, GN, and Ford, indicates
that 40 percent of the excess energy available in lower RVP
fuels will not contribute to an increase in vehicular fuel
economy. Possible sources of the energy losses have been
proposed by Ford, GM, and Professor Longwell of MIT. These
losses resulting from lower RVP gasoline include increased heat
losses to cylinder walls, decreased thermogravimetric
efficiency, lower efficiency due to higher equivalence
operating conditions, and higher fuel surface tension and
viscosity (creating pumping losses).
Ford's explanations for less complete fuel utilization
when fuel density increases (due to reduced RVP) include
air/fuel ratio shift to slightly richer, worse
cylinder-to-cylinder A/F distribution, and increase of A/F
excursions on transients. No quantitative estimates for the
effect of these contributing factors is supplied by Ford, GM,
or Professor Longwell. However, losing forty percent of the
net energy increase seems an excessive amount for the combined
effect of these losses. Thus, an R value of 0.6 would appear
to be more appropriately used as a lower bound rather than a
best estimate. However, a more appropriate figure cannot be
identified in this approach. Therefore, another approach must
be taken to determine the effect of increased energy content on
vehicular fuel economy. This second approach is described
below.
In determining the effect of a reduction in gasoline RVP
on vehicular fuel economy, it is necessary to evaluate the
vehicle that will be operating on this lower RVP fuel, and the
design optimization of that vehicle. Automobile manufacturers
are concerned with obtaining the highest fuel economy possible
to meet CAFE requirements and advertise high fuel economies to
attract consumers. Vehicular fuel economy figures are the
result of testing over the EPA FTP and HFET cycles, in which
the vehicles are operated on Indolene, a 9-psi RVP gasoline.
Therefore, the manufacturers presumedly optimize the vehicle
fuel systems to operate on Indolene, to maximize the fuel
economy figures resulting from the FTP test cycle. As a
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4-36
result, vehicles probably are not optimized to operate in the
field on commercial (in-use) gasoline with significantly higher
vapor pressure and lower energy density. Operating on a fuel
more like Indolene would, presumedly, be more efficient, than
on a different fuel for which the vehicle was not optimized.
This would argue that "R" may actually be greater than 1.0,
though to what extent is unknown.
While Longwell states than an "ideal" engine would be
expected to have an R value slightly less than 1.0, the
situation Longwell refers to is not the same situation which is
being evaluated here. Longwell's letter addresses more the
issue of a vehicle optimized to run on a given fuel, and then
run instead on a denser fuel; resulting in lower efficiency.
In-use RVP reduction creates a circumstance in which an engine
that is operating at less than maximum efficiency on gasoline
other than what it was specifically designed for is now
operated on a gasoline for which it was designed. Thus,
Longwell's analysis does not apply specifically to this
scenario, and the theoretical "R" value of 1.0 or more
suggested above still appears the most reasonable. Thus, it
will be used below to estimate the fuel economy credit
associated with in-use volatility control. However, a lower
bound R of 0.6 will also be examined to estimate the
sensitivity of the study's results to this parameter.
C. Overall Relationship Between Gasoline Volatility and
Fuel Economy
Combining the relationship between fuel volatility and
energy density (from the Bonner and Moore study) with our best
estimate for the relationship between energy density and fuel
economy yields the overall relationship between fuel volatility
and fuel economy. Energy density is projected to increase 0.25
percent with a 1-psi reduction in RVP and 0.56 percent with a
2-psi reduction in RVP. Vehicles should take full advantage of
this increase in energy density to achieve a resultant increase
in fuel economy. Thus, for both feedback and non-feedback
equipped vehicles, the increase in fuel economy for 1- and
2-psi reductions in RVP would be 0.25 and 0.56 percent,
respectively. The fuel economy effects for other RVP
reductions were derived, by fitting a curve through these fuel
economy increase values for 1- and 2-psi RVP reductions and are
shown in Table 4-11. The lower bound estimates using an R of
0.6 are also shown in Table 4-11.
These fuel economy increases were used to evaluate a
dollar credit resulting from gasoline RVP control. This credit
was determined by multiplying the percent increase in fuel
economy by the total number of gallons of gasoline consumed by
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4-37
Table 4-11
Fuel Economy Effect of RVP Control
RVP Reduction Percent Increase in
(psi ) Fuel Economy
Best Estimate Lower Bound
R = 1.0 R = 0.6
0.5 0.11 0.066
1.0 0.25 0.150
1.5 0.40 0.240
2.0 0.56 0.336
2.5 0.73 0.438
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4-38
motor vehicles, and then valuing that gasoline, at $0.98 per
gallon. This value was determined by subtracting a
'consumption-weighted state fuel tax of $0.13 per gallon and the
Federal tax of $0.09 per gallon from the 1984 national-average
retail gasoline price of $1.20 per gallon.[14] In other words,
the consumer would be able to travel additional miles on the
high energy, low RVP gasoline, and is thus credited the dollar
value of the gasoline he would otherwise have had to purchase
in order to travel those extra miles made available by the
resulting high vehicular fuel economy.
VI. Economic Credit From Evaporative HC Recovery/Prevention
There are three major sources of evaporative hydrocarbon
emissions that are associated with gasoline RVP. They are
stationary source emissions (such as bulk storage terminal
breathing losses, bulk transfer losses, and service station
losses from transfer and underground tank breathing), refueling
emissions, and motor vehicle evaporative emissions. The
emission reductions for each of these sources associated with
RVP control are detailed in Chapter 5 of this study. However,
in addition to representing an environmental benefit, these
emission reductions also represent an economic benefit in that
these HC emissions are now available to be consumed as fuel by
the motor vehicle (i.e., current emissions due to high
volatility fuel represent a cost to the economy). The same is
true for certification fuel RVP control, although only emission
reductions from motor vehicles are relevant there. The
methodology used to evaluate this cost credit resulting from
the recovery and prevention of evaporative HC emissions via
both fuel and vehicle control is outlined below.
The reductions in evaporative HC emissions from stationary
sources, refueling, and motor vehicles (as described in Chapter
5) are used directly to determine the mass of HC now usable
that would otherwise be lost if excess evaporative emissions
were not controlled. This tonnage of hydrocarbons is converted
to an equivalent volume using the density (Ib/gal) of the
hydrocarbons. Because the lighter hydrocarbons evaporate
first, the specific gravity and energy densities (Btu/gal) of
those hydrocarbons no longer lost to evaporation are
significantly less than those of gasoline. As a first-order
estimate, the evaporative hydrocarbons were all assumed to be
butanes. The equivalent volume (gallons) of butane saved by
RVP reduction is converted to energy using butane's energy
content. This energy is then converted to equivalent gallons
of gasoline, using a representative gasoline energy content
figure (Btu/gallon). This volume of gasoline is then converted
to a dollar amount using a value of $0.98 per gallon of
gasoline. Overall, the value of a ton of evaporative emissions
(butane) controlled or prevented is $335.26. The estimates for
densities, energy densities, and gasoline value are summarized
in Table 4-12.
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4-39
Table 4-12
Estimates for Evaluating the Evaporative Recovery/
Prevention Credit Resulting from RVP Control
Description Units Estimate
Composition of Evap. Emissions 100% Butane
Density of Butane[15] Ib/gal 4.77
Energy Density of Butane[15] Btu/lb 19,500
Btu/gal 93,100
Energy Density of Gasoline[15] Btu/lb 18,500
Btu/gal 114,000
Value of Gasoline $/gal 0.98
Value of Controlled/Prevented
Evap. Emissions (Butane) $/ton 335.26
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4-40
VII. Overall Cost of In-Use Gasoline RVP Control
The overall cost of volatility control of in-use gasoline
is the difference between the refinery cost of gasoline RVP
control (Section III) and the credits due to increased
vehicular fuel economy from 1) greater energy content of low
RVP gasoline and 2) internal engine combustion of HCs
otherwise lost to evaporation if RVP were not controlled
(Sections V and VI). Subtracting these credits from Bonner and
Moore's refinery cost of RVP control results in the net costs
discussed below.
The aggregate costs of RVP control of in-use gasoline in
1988 (when only fuel control is relevant) are presented in
Table 4-13, for both 12-month and 4-month control periods.
Costs for RVP control during a 4-month period are simply one
third those of 12-month control period. This ignores any
shifts in wintertime butane supply which might be caused by
shifts in summertime butane usage (e.g., storage of butane in
the summer would increase winter supplies, while the use of
butane as a petrochemical feedstock in the summer could
increase such demand for butane in the winter). The short-term
costs shown assume that there is not sufficient time for
refineries to invest in new equipment for more economic means
of controlling RVP. These costs, as well as those for the long
term, are used in determining the cost effectiveness figures of
Chapter 6.
These costs are dependent on several assumptions described
earlier in this chapter. Should further analysis currently
being conducted prove any of these assumptions incorrect, the
results of the recent analysis will be incorporated in the cost
calculations, and the costs will be revised accordingly. The
major areas being further investigated are: 1) the effect on
refining costs of controlling "the percent of gasoline
evaporated at 160°F, 2) the value of refinery equipment
purchased specifically for gasoline volatility control during
periods of the year without volatility restrictions, 3) the
sensitivity of gasoline refinery costs to the availability of
butane and alkylation capacity, 4) the cost of refinery
gasoline specifically to be blended with ethanol, and 5) the
effect on the ethanol industry of no longer permitting the
"splash" blending of ethanol and gasoline. The results of
studies in these areas will be used to revise these cost
estimates as necessary as soon as they are available.
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4-41
Table 4-13
Net Costs of Short-Term In-Use RVP Control:
1988 No Investment Case (millions of 1984 dollars per year)
12-Month Control
Level of RVP Refinery Fuel Economy Evap. Recovery
Control (psi) Costs Credit Credit
0.5 286 79 96
1.0 624 180 182
1.5 1028 287 256
2.0 1439 402 321
2.5 1880 523 379
4-Month Control
Level of RVP Refinery Fuel Economy Evap. Recovery Net
Control (psi) Costs Credit Credit Cost
0.5 95 26 32 37
1.0 208 60 60 88
1.5 343 96 85 162
2.0 480 134 107 239
2.5 627 175 127 325
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References (Chapter 4)
1. "Estimated Refining Cost Impact of Reduced Gasoline
Vapor Pressure," Final Report, Bonner and Moore Management
Science under SwRI Work Assignment #28 of EPA Contract No.
68-03-3162, July 1985.
2. Memorandum, "Transmittal of Draft Work Assignment
#13 Contract 68-03-3192," Craig Harvey, Project Officer, TSS,
ECTD, QMS, EPA, and Cooper Smith, Technical Project Monitor,
SDSB, ECTD, QMS, EPA, to Albert W. Ahlquist, Contract
Specialist, NCB, CMD, EPA, July 15, 1985.
3. Draft Supplemental Report to "Estimated Refining
Cost Impact of Reduced Gasoline Vapor Pressure," Bonner and
Moore, October 4, 1985.
4. "The Butane Industry: An Overview and Analysis of
the Effects of Gasoline Volatility Control on Prices and
Demand," Draft Report, Jack Faucett Associates, Work Assignment
#5, EPA Contract No. 68-03-3244, May 30, 1985.
5. Memorandum, "Transmittal of Change 1 to Work
Assignment #6 Contract 68-03-3244," Robert J. Johnson, Project
Officer, SDSB, ECTD, QMS, EPA, to Paul S. Eninger, Contracting
Officer, NCB, CMD, EPA, July 15, 1985.
6. Harry Weaver, Director, Environmental Department,
Motor Vehicle Manufacturers Association, letter to Charles
Gray, Director, ECTD, QMS, EPA, December 4, 1984.
7. Ronald L. Jones, American Petroleum Institute,
letter to Charles L. Gray, Jr., Director ECTD, QMS, EPA,
December 17, 1984.
8. W.S. Freas, Manager, Emission and Fuel Economy
Operations, General Motors, letter to R.E. Maxwell, Director,
Cert. Division, QMS, EPA, August 15, 1984.
9. J.C. Ingomells, Chevron Research Company, "Fuel
Economy and Cold-Start Driveability with Same Recent Model
Cars", SAE Paper No. 740522.
10. T.M Fisher, Director, Automotive Emission Control,
General Motors Corporation, letter to EPA, Central Docket
Section (LE-131), Docket A-83-44, January 22, 1985.
11. D.R. Buist, Director, Automotive Emissions and Fuel
Economy Office, Environmental and Safety Engineering Staff,
Ford, letter to Richard D. Wilson, Director, QMS, EPA, January
22, 1984.
-------
4-43
References (Chapter 4) cont'd
12. Fred W. Bowditch, Motor Vehicle Manufacturers
Association, letter to Richard D. Wilson, QMS, EPA, January 22,
1985.
13. John P. Longwell, Professor of Chemical Engineering,
Massachusetts Institute of Technology, letter to Marvin W.
Jackson, Environmental Activities Staff, General Motors
Technical Center, January 16, 1985.
14. From Department of Energy, Monthly Energy Review,
March 1985, as published in the National Petroleum News 1985
Factbook, p. 101.
15. Technical Data Book, API, Volume 4, 1983.
-------
CHAPTER 5
Environmental Impact
I. Introduction
This chapter examines the environmental impact associated
with each of the evaporative hydrocarbon (HC) control scenarios
described in Chapter 2: 1) long-term control of in-use and
certification fuel volatilities to equal levels (via changes to
one or both); and, 2) additional short-term control of in-use
RVP to levels lower than the long-term specifications for both
fuels under 1) above.
The first section following this introduction (Section II)
presents motor vehicle evaporative emission factors, by model
year, for each of the RVP scenarios. Next, Section III reviews
the effect of RVP control on exhaust emissions, while Section
IV deals with the effect of in-use RVP control on evaporative
losses from gasoline storage and distribution sources. Section
V presents projected non-methane hydrocarbon (NMHC) emissions
inventories under the various long- and short-term control
scenarios, evaluating future nationwide inventories and also
emissions in the 47 non-California urban areas currently in
violation of the NAAQS for ozone (0.125 ppm).* This is
followed (in Section VI) by an ozone air quality analysis of
these same urban areas, comparing relative ozone violations
under the various NMHC control strategies. Finally, the last
section (VII) examines the effect of RVP control on levels of
toxic emissions (i.e., benzene and gasoline vapors).
II. Motor Vehicle Evaporative HC Emission Factors
As described in Chapter 2, evaporative HC emissions from
motor vehicles originate from two basic components of the
vehicle's fuel system — the fuel tank and the carburetor. The
"diurnal" portion of the certification test simulates the
vehicle's exposure to daily cyclic temperature variations which
cause evaporative losses from the fuel tank to occur as the
gasoline vapors expand in response to ambient temperature
increases. The "hot-soak" portion of the certification test
simulates emissions which occur just after the engine has been
turned off, when residual engine and exhaust system heat causes
the evaporation of fuel remaining in the carburetor bowl, as
well as from the fuel tank and fuel lines. Total per-vehicle
evaporative HC losses are represented by the sum of the
hot-soak and diurnal emissions, and are expressed in terms of
As the California Air Resources Board (CARS) currently
regulates in-use RVP in California, the seven California
cities currently in non-attainment of the ozone NAAQS are
not included in the city-specific analysis.
-------
5-2
grams/test.* However, for air quality modelling purposes, the
hot-soak and diurnal emissions are treated separately, since
diurnal emissions occur once per day, but hot-soak emissions
occur once per vehicle trip. Thus, the hot-soak emissions are
multiplied by the number of trips per day and then added to the
diurnal emissions. The sum is then divided by the number of
vehicle miles travelled per day to yield an emission factor in
terms of grams per mile (g/mi).
For the evaporative emission control scenarios described
in Section VI of Chapter 2, the derivation of light-duty
vehicle (LDV) evaporative emission factors can most easily be
separated into four parts, differentiating between certain
model year groups. The first section of Part A below addresses
post-1989 LDVs in the case where in-use RVP equals the
certification fuel RVP (long-term control scenarios); the 1990
model year is assumed to be the first to be affected by changes
to certification fuel and/or test procedure. The second
section addresses these same model years where in-use RVP is
below the certification fuel RVP (short-term, additional in-use
RVP control). The third section addresses 1981-1989 model year
LDVs operating on various in-use RVP fuels (both long- and
short-term scenarios); these vehicles will be designed for 9.0
psi, so their emission rates will only be affected by in-use
RVP control. The fourth section addresses pre-1981 model year
LDVs under various in-use RVP levels (same scenarios); again,
these vehicles are designed for 9.0-psi fuel, but would be
operating on various in-use RVPs.
The derivation of light-duty truck (LDT) and heavy-duty
vehicle (HDV) emission factors is based almost entirely on the
LDV data.[l] This derivation is briefly discussed in Section B
following the development of the LDV rates.
A. Light-Duty Vehicles
1. Post-1989 LDVs: In-Use RVP = Certification RVP
Both vehicle- and fuel-related control strategies can
apply to 1990 and later model year vehicles. Under the
long-term strategy, commercial fuel RVP and certification fuel
RVP will be made equal at some level between 9 and 11.5 psi,
inclusive.
As discussed in more detail in Chapter 2 (Section V),
motor vehicle evaporative emissions can, conceptually, be
attributed to five sources: 1) properly designed and operated
Specific test procedures are outlined in Part 86 of the
Code of Federal Regulations, and are reviewed in Section V
of Chapter 2.
-------
5-3
systems; 2) insufficient design of the purge system; 3)
itialmaintenance and equipment defects; 4) commercial fuel RVP
in excess of certification fuel RVP; and 5) evaporative
control system tampering. Below, the effect of RVP on each of
these sources will be considered. The quantitative inputs and
results for post-1989 vehicles are summarized in Tables 5-1 and
5-2, which draw upon the emission levels categorized in Section
V of Chapter 2 (Table 2-15). As explained there, the
derivation of these emission rates are based on data generated
as part of EPA's ongoing in-use emission factor (EF) test
program.
Vehicles with properly designed and operated systems are
assumed to emit at the standard level, which is 2 grams/test
for LDVs and LDTs, 3 grams/test for lighter HDVs, and 4
grams/test for heavier HDVs. This portion of the emission
factor would not be affected by either fuel- or
vehicle-oriented control, as indicated in Tables 5-1 and 5-2.
These assumed standard levels were split into diurnal and
hot-soak portions using the ratios of diurnal and hot-soak
emissions to total emissions from problem-free EF LDVs.
The effect of improper design of the purge system is
estimated as the difference between the average emissions of
problem-free EF LDVs and the standard levels described above.
This effect is assumed to disappear with a revised (i.e.,
improved) evaporative emission test procedure that could likely
include, at a minimum, the saturation of the canister prior to
testing. Thus, emissions due to improper design are shown as
zero under the control scenarios in Tables 5-1 and 5-2.
The effect of malmaintenance and defects was shown in
Chapter 2 to be dependent only upon in-use RVP. It was
estimated as the difference between emissions from non-tampered
EF vehicles and problem-free EF vehicles operated on various
RVPs. Since this effect represents an in-use problem not
likely to be eliminated by changing the certification test
procedure (barring design standards or an improved durability
test), it remains. This effect's dependence on in-use RVP is
indicated in Tables 5-1 and 5-2.
The RVP effect was shown in Chapter 2 to be due to the
differences between certification and in-use RVPs, and was
calculated by subtracting non-tampered vehicle emissions on
Indolene from emissions of non-tampered vehicles operating on
-------
5-4
commercial (11.5-psi) fuel.* As certification and in-use RVPs
are assumed to be equal under the long-term strategies, this
RVP effect disappears in new vehicles, as indicated in Tables
5-1 and 5-2.
Finally, the tampering effect is much like the effect of
malmaintenance and defect in that it remains after the
long-term strategy is imposed, but its magnitude is reduced by
lowering in-use RVP. However, unlike the other effects,
tampering rates are dependent upon vehicle mileage and are not
constant with model year (i.e., there is a zero-mile rate plus
a deterioration factor per every 10,000 miles). Therefore,
MOBILE3 handles tampering separately and the tampering portion
of emissions is not shown in Tables 5-1 through 5-4. Tampering
offsets, calculated by subtracting total non-tampered emissions
from uncontrolled emissions measured with disabled vehicles,
were presented for various RVPs in Appendix 2-B of Chapter 2,
along with details on the methodology used.
Also shown in Tables 5-1 and 5-2 are the breakdown of
baseline emissions from these post-1989 vehicles; they
represent levels estimated for the case where in-use RVP =11.5
psi and certification RVP = 9.0 psi. The overall control
efficiencies of the various RVP scenarios (expressed as
percent-reductions from baseline emission levels) are also
shown in the tables.
2. Post-1989 LDVs: Additional Short-Term In-Use RVP
Control
As in the previous section, this control strategy is
examined with respect to the five components of evaporative
emissions from motor vehicles. Controlling in-use RVP to a
level lower than the long-term certification RVP is assumed to
have no effect on properly designed and operating vehicles
since these vehicles are already assumed to be emitting at the
standard. The improper design/purge and RVP sources are also
not affected since they are already assumed to be zero.
However, the malmaintenance/defect and tampering sources would
be affected, since these are dependent only on in-use RVP.
Thus, the total non-tampered diurnal and hot-soak emission
rates for these vehicles, respectively, can be determined from
Tables 5-1 and 5-2 by choosing the RVP column corresponding to
the short-term in-use RVP level. In other words, the long-term
However, as part of the RVP impact has already been
accounted for in the malmaintenance/defect effect (shown
to be dependent upon in-use RVP), this RVP effect is an
adjusted figure (i.e., the difference between
malmaintenance/defect at Indolene and 11.5-psi commercial
fuel has been subtracted from the total difference between
non-tampered emissions at Indolene and 11.5-psi commercial
fuel). (See Appendix 2-B in Chapter 2 for more details.)
-------
5-5
Table 5-1
Diurnal Emissions from Non-Tampered Post-1989 LDVs
Under Lonq-Term Control Scenarios (q/test)
Certification = In Use RVP (psi)
Baseline* 9.0 9.5 10.0 10.5 11.0 11.5
Carbureted Vehicles
Properly Designed
and Operated**
Improper Design**
Malmaintenance
and Defect**
Excess RVP**
0
0
1
6
.91
.30
.61
.19
0
0
1
0
.91
.00
.11
.00
0
0
1
0
.91
.00
.21
.00
0
0
1
0
.91
.00
.31
.00
0.91
0.00
1.41
0.00
0.91
0.00
1.51
0.00
0.91
0.00
1.61
0.00
Total 9.01 2.02 2.12 2.22 2.32 2.42 2.52
Reduction from
Baseline (%) - 78 76 75 74 73 72
Fuel-Injected Vehicles
Properly Designed
and Operated** 0.91 0.91 0.91 0.91 0.91 0.91 0.91
Improper Design** 0.0 0.00 0.00 0.00 0.00 0.00 0.00
.Malmaintenance
and Defect** 0.84 0.34 0.44 0.54 0.64 0.74 0.84
RVP** 3.76 0.00 0.00 0.00 0.00 0.00 0.00
Total 5.51 1.25 1.35 1.45 1.55 1.65 1.75
Reduction from
Baseline (%) - 77 76 74 72 70 68
* "Baseline" indicates in-use RVP = 11.5 psi, certification
RVP = 9.0 ps i.
** From Table 2-15 in Chapter 2.
-------
5-6
Table 5-2
Hot-Soak Emissions from Non-Tampered Post-1989 LDVs
Under Long-Term Control Scenarios (q/test)
Certification = In-Use RVP (psi)
Baseline* 9.0 9.5 10.0 10.5 11.0 11.5
Carbureted Vehicles
Properly Designed
and Operated** 1.09 1.09 1.09 1.09 1.09 1.09 1.09
Improper Design** 0.40 0.00 0.00 0.00 0.00 0.00 0.00
Malmaintenance
and Defect** 1.24 0.83 0.91 0.99 1.07 1.15 1.24
Excess RVP** 1.11 0.00 0.00 0.00 0.00 0.00 0.00
Total 3.84 1.92 2.00 2.08 2.16 2.24 2.33
Reduction from - 50 48 46 44 42 39
Baseline (%)
Fuel-Injected Vehicles
Properly Designed
and Operated** 0.61 0.61 0.61 0.61 0.61 0.61 0.61
Improper Design** 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Malmaintenance
and Defect** 0.93 0.29 0.42 0.55 0.67 0.80 0.93
Excess RVP** 0.29 0.00 0.00 O.OQ 0.00 0.00 0.00
Total 1.83 0.90 1.03 1.16 1.28 1.41 1.54
Reduction from
Baseline (%) . - 51 44 37 30 23 16
* "Baseline" indicates in-use RVP = 11.5 psi, certification
RVP =9.0 psi.
** From Table 2-15 in Chapter 2.
-------
5-7
certification RVP level is irrelevant here because the
remaining effects are dependent on in-use RVP alone. The
tampering offsets under these short-term control scenarios are
again the same as those used in the long-term analysis under
the appropriate in-use RVP level.
3. 1981-1989 LDVs: In-Use RVP Control
These vehicles are all certified to meet the 2-gram
standard on Indolene regardless of the control scenario. Thus,
their emissions depend only on in-use RVP. Derivation of their
emissions is separated from pre-1981 models since significantly
more data exists for these later models. (Emission factors for
the older models are derived in the next section using the more
recent-model data.)
As these pre-1990 vehicles will not be affected by
certification fuel or test procedure modifications, their
emissions can be estimated using current test results. For
non-tampered vehicles, the average emission levels of the EPA
EF program can be used directly. Implicit in these totals are
the various effects of improper purge system design,
malmaintenance/defects and RVP. Tampering is, as usual,
considered separately. The non-tampered diurnal and hot-soak
emission rates for 1981-89 models, respectively, and their
reduction from baseline levels are shown in Tables 5-3 and 5-4.
4. Pre-1981 LDVs: In-Use RVP Control
Evaporative emissions estimates for pre-1981 LDVs
operating on ll.5-psi fuel were derived for MOBILES, based on
limited test data, in mid-1984.[1] Since that time, API has
tested 14 1978-80 vehicles (certified to the 6-gram SHED
standard) on both Indolene and commercial fuels.[2] In
general, API's results on both Indolene and the commercial
fuels show higher emissions than those of EPA's EF program (see
Table 5-5), but the API vehicle mileage is over 3 times higher,
possibly explaining the difference. For MOBILES, the 6-gram
SHED emissions were assumed to equal the 2-gram SHED emissions
because Indolene data on both sets of cars showed very similar
results. While the API sample included only 14 vehicles, these
results represent actual test data at reasonable mileages.
Thus, the API data for 1978-80 vehicles appear more
representative and have been substituted for the original
MOBILES estimates.
API's tests were conducted only on models from 1978-80.
Given the lack of any new data on pre-1978 vehicles, the
MOBILES estimates for these earlier models have been retained
for this analysis.
-------
5-8
Table 5-3
Diurnal Emissions from Non-Tampered 1981-1989
LDVs Under In-Use RVP Control Scenarios (g/test)
In-Use RVP (psi)
Baseline* 9.0 9.5 10.0 10.5 11.0 11.5
Carbureted Vehicles
Non-Tampered
Vehicle Total 9.01 2.32 3.04 4.06 5.40 7.05 9.01
Reduction from
Baseline (%) - 74 66 55 40 22 0
Fuel-Injected Vehicles
Non-Tampered
Vehicles Total 5.51 1.25 1.59 1.93 2.34 3.68 5.51
Reduction from
Baseline (%) - 77 71 65 58 33 0
*"Baseline" indicates in-use RVP = 11.5 psi, certification
RVP =9.0 psi.
-------
5-9
Table 5-4
Hot-Soak Emissions from Non-Tampered 1981-1989
LDVs Under In-Use RVP Control Scenarios (g/test)
In-Use RVP (psi)
Baseline* 9.0 9.5 10.0 10.5 11.0 11.5
Carbureted Vehicles
Non-Tampered
Vehicle Total 3.84 2.32 2.46 2.68 2.98 3.37 3.84
Reduction from
Baseline (%) - 40 36 30 22 12 0
Fuel-Injected Vehicles
Non-Tampered
Vehicle Total 1.83 0.90 1.08 1.27 1.46 1.65 1.83
Reduction from
Baseline (%) - 51 41 31 20 10 0
* "Baseline" indicates in-use RVP = 11.5 psi, certification
RVP =9.0 psi.
-------
5-10
Table 5-5
Evaporative Emissions Testing on Non-Tampered 1978-1980 LDVs
Fuel
RVP
9.0
9.0
10.5
10.5
11.5
11.5
Test Program
EF
API
EF
API
EF*
API**
* Original MOBILES
** Rovi R»H MnRTT.F"* i
No. of
Vehicles
Tested
124
14
__
14
— — -
14
figures.
:i cmr«ie ( APT '
Mean
Odometer
(Miles)
14,100
49,040
—
49,040
__
49,040
R 1-e»fi1- Hal-;
Emissions
Hot Soak
2.27
2.44
—
2.81
3.98
3.29
^
(q/test)
Diurnal
3.08
5.16
—
9.77
9.31
15.12
-------
5-11
5. Summary of LDV Emission Factors
The resulting non-tampered LDV evaporative emission rates,
in terms of g/test, under the various RVP control scenarios are
shown in Table 5-6. Here, the carbureted and fuel-injected LDV
emission rates shown in Tables 5-1 through 5-5 are weighted
together based on MOBILES model-year sales projections.[1] For
both the long-term and short-term control strategies, the
emission rates can be determined by choosing the appropriate
in-use RVP scenario.
B. Light-Duty Trucks and Heavy-Duty Vehicles
The MOBILES evaporative emission estimates for LDTiS
(6000 Ibs. GVW* and less) are essentially the same as those for
LDVs.[l] This is based on: 1) the fact that the emission
standards — 6 and 2 grams in 1978 and 1981, respectively —
are the same for both LDVs and LDTiS, and 2) that early EF
testing of LDVs and LDTiS on Indolene showed similar
results. However, pre-1979 LDTs having a GVW over 6,000 Ibs,
now designated LDT2s, were previously classified as
heavy-duty vehicles (HDVs); their MOBILES emission factors are,
thus, the same as the HDV rates described below. Post-1978
emission factors for LDT2s are the same as those for LDTiS
and LDVs in MOBILES.
Because no new LDT data were available for this study, the
MOBILES methodology was retained. The changes made to the LDV
data (discussed earlier) are also reflected in the LDT
estimates used. These LDTi and LDT2 emission factors are
summarized in Tables 5-7 and 5-8, respectively. The post-1980
figures in the tables differ from the LDV rates in Table 5-6
only because of different carbureted/fuel-injected sales
weightingstl]; the individual rates, if shown, would be the
same as the individual carbureted and fuel-injected LDV
estimates.
The situation is entirely analogous for HDVs. No new HDV
data are currently available and the MOBILES estimates were in
part based on LDV emissions.[1] Thus, the MOBILES methodology
is again used here, but with the revised LDV estimates. The
HDV emission rates used in this study are summarized in Table
5-9.
Rated "gross vehicle weight".
-------
Table 5-6
Non-Tampered LDV Evaporative HC Emission Rates
Under Various RVP Control Scenarios (grams/test)
In-use Fuel
Model
Year
Low Altitude
pre-1971
1971
1972-77
1978-80
1981
1982
1983
1984
1985-86
1987-89
1990+
High Altitude
pre-1971
1971
1972-76
1977
1978-80
1981
1982
1983
1984+
9.0
H.S.
14.67
10.91
8.27
2.44
2.18
2.06
1.93
1.75
1.45
1.19
1.01
19.07
14.18
14.07
8.27
6.32
5.66
2.68
2.50
(Same
Dnl.
26.08
16.28
8.98
5.16
2.21
2.12
2.02
1.89
1.66
1.47
1.34
33.90
21.16
17.15
8.98
13.36
5.74
2.76
2.63
as Low
9.
H.S.
16.22
11.38
8.63
2.52
2.33
2.20
2.08
1.91
1.62
1.36
1.14
21.09
14.79
14.69
8.63
6.52
6.03
2.87
2.70
Altitude)
5
Dnl.
30.46
18.69
10.55
6.24
2.90
2.77
2.64
2.46
2.15
1.89
1.44
39.60
24.30
20.15
10.55
16.15
7.51
3.60
3.43
10.
H.S.
17.78
12.13
9.22
2.64
2.54
2.42
2.29
2.11
1.82
1.56
1.26
23.11
15.77
15.68
9.22
6.84
6.59
3.14
2.97
RVP (psi)*
0
Dnl.
34.84
22.13
12.80
7.77
3.86
3.68
3.48
3.21
2.77
2.37
1.54
45.30
28.77
24.44
12.80
20.13
10.01
4.78
4.52
10.
H.S.
19.34
13.17
10.02
2.81
2.84
2.70
2.56
2.37
2.05
1.77
1.38
25.14
17.13
17.05
10.02
7.28
7.35
3.51
3.33
5
Dnl.
39.22
26.61
15.72
9.77
5.12
4.84
4.56
4.18
3.54
2.97
1.64
50.99
34.59
30.02
15.72
25.31
13.25
6.30
5.93
11
H.S.
20.89
14.50
11.05
3.03
3.21
3.05
2.89
2.68
2.32
2.00
1.51
27.16
18.85
18.80
11.05
7.84
8.30
3.97
3.76
.0
Dnl.
43.61
32.12
19.31
12.23
6.73
6.43
6.12
5.70
5.00
4.37
1.74
56.69
41.75
36.88
19.31
31.68
17.44
8.36
7.96
11
H.S.
22.45
16.15
12.32
3.29
3.65
3.47
3.29
3.04
2.62
2.24
1.63
29.18
20.99
20.96
12.32
8.53
9.46
4.51
4.27
.5
Dnl.
47.99
38.58
23.53
15.12
8.68
8.37
8.04
7.61
6.87
6.22
1.84
62.38
50.16
44.93
23.53
39.16
24.47
10.88
10.45
Certification fuel RVP is assumed to be 9.0 psi for all pre-1990 model years; 1990 and later vehicles are assumed to
be designed for an RVP equal to the in-use level (i.e., certification RVP = in-use RVP beginning in 1990).
-------
Table 5-7
Non-Tampered LDTi Evaporative HC Emission Rates
Under Various RVP Control Scenarios (grams/test)
In-use Fuel
Model
Year
Low Altitude
pre-1971
1971
1972-77
1978-80
1981-83
1984
1985
1986
1987
1988-89
1990+
High Altitude
pre-1971
1971
1972-76
1977
1978-81
1982-83
1984
1985
1986
1987
1988-89
1990+
9.
H.S.
14.67
10.91
8.27
2.44
2.32
2.09
1.86
1.64
1.44
1.19
1.01
19.07
14.18
14.07
8.27
6.32
3.01
2.72
2.42
2.13
1.87
1.54
1.31
0
Dnl.
26.08
16.28
8.98
5.16
2.32
2.14
1.97
1.80
1.65
1.47
1.34
33.90
21.16
17.15
8.98
13.36
3.01
2.79
2.57
2.34
2.15
1.91
1.74
9.
H.S.
16.22
11.38
8.63
2.52
2.46
2.24
2.02
1.80
1.60
1.36
1.14
21.09
14.79
14.69
8.63
6.52
3.19
2.91
2.62
2.34
2.09
1.77
1.48
5
Dnl.
30.46
18.69
10.55
6.24
3.04
2.80
2.57
2.34
2.14
1.89
1.44
39.60
24.30
20.15
10.55
16.15
3.95
3.65
3.35
3.04
2.78
2.45
1.87
10.
H.S.
17.78
12.13
9.22
2.64
2.68
2.45
2.23
2.00
1.80
1.56
1.26
23.11
15.77
15.68
9.22
6.84
3.48
3.19
2.89
2.60
2.35
2.03
1.64
RVP (psi)*
0
Dnl.
34.84
22.13
12.80
7.77
4.06
3.72
3.38
3.04
2.74
2.37
1.54
45.30
28.77
24.44
12.80
20.13
5.28
4.84
4.40
3.96
3.57
3.08
2.00
10.
H.S.
19.34
13.17
10.02
2.81
2.98
2.74
2.49
2.25
2.04
1.77
1.38
25.14
17.13
17.05
10.02
7.28
3.87
3.56
3.24
2.92
2.65
2.30
1.79
5
Dnl.
39.22
26.61
15.72
9.77
5.40
4.91
4.42
3.93
3.51
2.97
1.64
50.99
34.59
30.02
15.72
25.31
7.02
6.39
5.75
5.11
4.56
3.86
2.13
11.
H.S.
20.89
14.50
11.05
3.03
3.37
3.09
2.82
2.54
2.30
2.00
1.51
27.16
18.85
18.80
11.05
7.84
4.38
4.02
3.66
3.30
2.99
2.60
1.96
0
Dnl.
43.61
32.12
19.31
12.23
7.05
6.51
5.97
5.43
4.96
4.37
1.74
56.69
41.75
36.88
19.31
31.68
9.17
8.47
7.77
7.07
6.45
5.69
2.26
11
H.S.
22.45
16.15
12.32
3.29
3.84
3.52
3.20
2.88
2.60
2.24
1.63
29.18
20.99
20.96
12.32
8.53
4.99
4.57
4.16
3.74
3.37
2.92
2.12
.5
Dnl.
47.99
38.58
23.53
15.12
9.01
8.45
7.89
7.33
6.84
6.22
1.84
62.38
50.16
44.93
23.53
39.16
11.71
10.98
10.25
9.52
8.89
8.09
2.39
Certification fuel RVP is assumed to be 9.0 psi for all pre-1990 model years; 1990 and later vehicles are assumed to
be designed for an RVP equal to the in-use level (i.e., certification RVP = in-use RVP beginning in 1990).
-------
Table 5-8
Non-Tampered LDT2 Evaporative HC Emission Rates
Under Various RVP Control Scenarios (grams/test)
In-use Fuel
Model
Year
Low Altitude
pre-1979
1979-80
1981-83
1984
1985
1986
1987
1988-89
1990+
High Altitude
pre-1979
1979-81
1982-83
1984
1985
1986
1987
1988-89
1990+
9.
H.S.
18.08
2.44
2.32
2.09
1.86
1.64
1.44
1.19
1.01
23.50
6.32
3.01
2.72
2.42
2.13
1.87
1.54
1.31
0
Dnl.
42.33
5.16
2.32
2.14
1.97
1.80
1.65
1.47
1.34
55.03
13.36
3.01
2.79
2.57
2.34
2.15
1.91
1.74
9.
H.S.
20.00
2.52
2.46
2.24
1.02
1.80
1.60
1.36
1.14
26.00
6.52
3.19
2.91
2.62
2.34
2.09
1.77
1.48
5
Dnl.
49.44
6.24
3.04
2.80
2.57
2.34
2.14
1.89
1.44
64.27
16.15
3.95
3.65
3.35
3.04
2.78
2.45
1.87
10.
H.S.
21.91
2.64
2.68
2.45
2.23
2.00
1.80
1.56
1.26
28.49
6.84
3.48
3.19
2.89
2.60
2.35
2.03
1.64
RVP (psi)*
0
Dnl.
56.55
7.77
4.06
3.72
3.38
3.04
2.74
2.37
1.54
73.52
20.13
5.28
4.84
4.40
3.96
3.57
3.08
2.00
10
H.S.
23.83
2.81
2.98
2.74
2.49
2.25
2.04
1.77
1.38
30.98
7.28
3.87
3.56
3.24
2.92
2.65
2.30
1.79
.5
Dnl.
63.66
9.77
5.40
4.91
4.42
3.93
3.51
2.97
1.64
82.76
25.31
7.02
6.39
5.75
5.11
4.56
3.86
2.13
11.
H.S.
25.75
3.03
3.37
3.09
2.82
2.54
2.30
2.00
1.51
33.47
7.84
4.38
4.02
3.66
3.30
2.99
2.60
1.96
0
Dnl.
70.78
12.23
7.05
6.51
5.97
5.43
4.96
4.37
1.74
92.01
31.68
9.17
8.47
7.77
7.07
6.45
5.69
2.26
11
H.S.
27.66
3.29
3.84
3.52
3.20
2.88
2.60
2.24
1.63
35.96
8.53
4.99
4.57
4.16
3.74
3.37
2.92
2.12
.5
Dnl.
77.89
15.12
9.01
8.45
7.89
7.33
6.84
6.22
1.84
101.25 ^
39.16 *
11.71
10.98
10.25
9.52
8.89
8.09
2.39
Certification fuel RVP is assumed to be 9.0 psi for all pre-1990 model years; 1990 and later vehicles are assumed to
be designed for an RVP equal to the in-use level (i.e., certification RVP = in-use RVP beginning in 1990).
-------
Table 5-9
Non-Tampered HDV Evaporative HC Emission Rates
Under Various RVP Control Scenarios (grams/test)
In-use Fuel
Model 9.
Year H.S.
Low Altitude
pre-1985 18.08
1985-1989 3.69
1990+ 3.06
High Altitude
pre-1985 23.50
1985-1989 4.80
1990+ 3.98
0
Dnl.
42.33
3.69
3.22
55.03
4.79
4.19
9.
H.S.
20.00
3.91
3.19
26.00
5.08
4.15
5
Dnl.
49.44
4.83
3.38
64.28
6.28
4.39
10.
H.S.
21.91
4.26
3.32
28.49
5.54
4.32
RVP (psi)*
0
Dnl.
56.55
6.47
3.54
73.52
8.42
4.60
10
H.S.
23.83
4.75
3.45
30.98
6.17
4.49
.5
Dnl.
63.66
8.60
3.70
82.76
11.19
4.81
11.
H.S.
25.75
5.36
3.57
33.47
6.97
4.64
0
Dnl.
70.78
11.23
3.86
92.01
14.60
5.02
11.
H.S.
27.66
6.11
3.70
35.96
7.95
4.81
5
Dnl.
77.89
14.34
4.02
101.25
18.65
5.23
Certification fuel RVP is assumed to be 9.0 psi for all pre-1990 model years; 1990 and later vehicles are assumed to
be designed for an RVP equal to the in-use level (i.e., certification RVP = in-use RVP beginning in 1990).
-------
5-16
III. Motor Vehicle Exhaust Emission Factors
As discussed in detail in Chapter 2, EPA's in-use EF
testing indicates that fuel RVP has an effect on exhaust HC and
CO emissions from current vehicles; no effect on NOx emissions
was shown to be present. [3] This effect on HC and CO emissions
appears to be basically linear with RVP and was accounted for
in this analysis by applying multiplicative factors for each
RVP scenario to the original MOBILES exhaust emission factors
published in June 1984. These multiplicative adjustment
factors are shown in Tables 5-10 and 5-11 for HC and CO,
respectively.* The "base" case in the tables, as before,
refers to an in-use RVP of 11.5 psi and a certification fuel
RVP of 9.0 psi (current); the other RVP scenarios (11.5 down to
9.0 psi) indicate the long-term control options where in-use
RVP is assumed to equal certification fuel RVP (beginning with
the 1990 model year).
Original MOBILES exhaust emission factors (published in
June 1984) were based on an in-use RVP of roughly 11.5 psi and
a certification fuel RVP of 9.0 psi, which represents the
baseline RVP scenario. Therefore, no exhaust adjustment is
necessary under the base case, as indicated by the factors of
1.00 in Tables 5-10 and 5-11. Also, no adjustment is necessary
for those model year vehicles that were not equipped with
evaporative control systems (i.e., pre-1971 LDGVs and LDG^s,
pre-1979 LDGT2s, and pre-1985 HDGVs). This is based on the
conclusion made in Chapter 2 that the RVP effect on exhaust HC
and CO is related to the purging of the evaporative canister
and not to the combustion of fuel inducted via the carburetor;
therefore, no adjustment is made for these model years,
regardless of RVP level (i.e., the original MOBILES estimates
are used).
As is the case with all in-use EF testing, the exhaust
emissions effect was measured only for vehicles whose
evaporative control systems were designed for Indolene (9.0
psi) and operated on fuels of various RVPs. These data were
used to develop the exhaust adjustment factors at each RVP
level shown in Tables 5-10 and 5-11 for the pre-1990 models.
As shown, no adjustment is necessary for these vehicles under
the ll.5-psi RVP scenario, as these pre-1990 model years still
Although adjustment factors for both HC and CO are
presented, the remainder of the study focuses only on
non-methane hydrocarbons. The possible CO benefits
achievable with in-use RVP control were not incorporated
into this study, but could enter into cost effectiveness
calculations in future analyses.
-------
5-17
Table 5-10
Exhaust HC Adjustment Factors*
Model Years
LDGV
pre-1971
1971-80
1981-89
1990 +
LDGT,
pre-1971
1971-83
1984-89
1990+
LDGT 2
pre-1979
1979-83
1984-89
1990+
HDGV
pre-1985
1985-89
1990+
RVP Scenarios
Base
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
11
1.
1.
1.
0.
1.
1.
1.
0.
1.
1.
1.
0.
1.
1.
0.
.5
000
000
000
846
000
000
000
846
000
000
000
846
000
000
956
11
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.0
000
991
969
846
000
991
969
846
000
991
969
846
000
991
956
10
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.5
000
982
938
846
000
982
938
846
000
982
938
846
000
982
956
(psi)
10
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.0
000
973
907
846
000
973
907
846
000
973
907
846
000
973
956
9
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.5
000
965
877
846
000
965
877
846
000
965
877
846
000
965
956
9.0
1.000
0.956
0.846
0.846
1.000
0.956
0.846
0.846
1.000
0.956
0.846
0.846
1.000
0.956
0.956
To be multiplied by June 1984 MOBILES exhaust HC factors.
-------
5-18
Table 5-11
Exhaust CO Adjustment Factors*
Model Years
LDGV
pre-1971
1971-80
1981-89
1990+
LDGTi
pre-1971
1971-83
1984-89
1990+
LDGT2
pre-1979
1979-83
1984-89
1990+
HDGV
pre-1985
1985-89
1990+
RVP Scenarios
Base
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
11
1.
1.
1.
0.
1.
1.
1.
0.
1.
1.
1.
0.
1.
1.
0.
.5
000
000
000
809
000
000
000
809
000
000
000
809
000
000
924
11
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.0
000
985
962
809
000
985
962
809
000
985
962
809
000
985
924
10
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.5
000
970
924
809
000
970
924
809
000
970
924
809
000
970
924
(psi)
10
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.0
000
955
886
809
000
955
886
809
000
955
886
809
000
955
924
9
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
0.
1.
0.
0.
.5
000
939
848
809
000
939
848
809
000
939
848
809
000
939
924
9.0
1.000
0.924
0.809
0.809
1.000
0.924
0.809
0.809
1.000
0.924
0.809
0.809
1.000
0.924
0.924
To be multiplied by June 1984 MOBILES exhaust CO factors.
-------
5-19
represent the baseline case (designed for 9.0 psi); however,
this is not the case for 1990 and later vehicles which, under
the long-term control scenarios, would be designed for the
in-use fuel RVP.
As concluded in Chapter 2, the effect of in-use RVP on
exhaust emissions is assumed to be eliminated if vehicles are
operated on the same RVP fuel for which they were designed
(i.e., in-use RVP equal to certification RVP). Therefore, in
all of the long-term strategies examined in this chapter,
original MOBILES exhaust emission factors estimated for
post-1989 vehicles are adjusted by the same factor as that
calculated for the 9.0-psi RVP scenario for the preceding model
year group, which was designed for 9.0 psi. In other words,
the level of in-use fuel RVP is irrelevant as long as it is
equal to certification fuel RVP. The adjustment factor shown
in Tables 5-10 and 5-11 for 1989 vehicles (designed for 9.0
psi) under the 9.0-psi in-use RVP scenario is representative of
this situation and is, therefore, assumed to apply to all 1990
and later models as well, except of course for the baseline
case where no change in certification fuel is made.
IV. Effect of In-Use RVP Control on Gasoline Storage
and Distribution Losses
While this study focuses primarily on the non-compliance
of in-use motor vehicles with the current evaporative
standards, one of the strategies being considered to control
this evaporative excess would also have an impact on emissions
from stationary sources. As the levels of evaporative HCs
emitted during the storage and handling of gasoline are a
function of true vapor pressure (which is dependent upon RVP),
the control of in-use gasoline volatility would affect the
level of emissions from these sources. Of course, the other
strategies being examined (changes to certification fuel and
test procedure) would have no impact on these stationary
sources as they involve only a change in the design of new
vehicles.
The following sections deal with the effect of in-use RVP
control on each of three basic categories of gasoline storage
and distribution losses: 1) bulk storage and bulk transfer
losses, 2) service station (Stage I) emissions, and 3) vehicle
refueling losses. Evaporative emission rates for these sources
are commonly expressed in terms of grams of HC vapor lost per
gallon of gasoline stored or transferred.
-------
5-20
A. Bulk Storage and Transfer Losses
This first category consists mainly of breathing and
working (i.e., loading and unloading) losses resulting from the
storage of gasoline in bulk terminals and the transfer of
gasoline to tankers, ships, and barges used for transport.
Emission rates associated with bulk storage are dependent upon
various factors such as tank configuration (fixed or floating
roof), tank dimensions, ambient and liquid storage
temperatures, and vapor molecular weight and true vapor
pressure (both dependent upon the RVP of the gasoline).
Emissions incurred during the loading of cargo carriers are
dependent upon the method of filling (submerged or splash),
bulk temperature of liquid, and the RVP-dependent parameters
mentioned above. Equations defining specific types of
evaporative losses (e.g., breathing, loading) as a function of
these and other parameters were developed for various types of
storage and transport mediums and were published in EPA's AP-42
Document.[4]
The impact of controlling in-use fuel volatility on
evaporative emissions from the bulk storage and transfer of
gasoline was determined using the various AP-42 equations.
Holding the non-fuel-related parameters in the equations
constant, it was estimated that a reduction in in-use RVP from
11.5 to 9.0 psi would result in a 20-28 percent decrease in
evaporative losses from bulk storage terminals (magnitude
dependent upon tank configuration and type of loss —
breathing, working, or standing).[4] With respect to cargo
loading, the same decrease in RVP should reduce evaporative
losses by approximately 20 percent.[4] Inventories for the
various types of losses in the bulk storage and transfer
category were adjusted by the appropriate factors and were
incorporated into this analysis under all control strategies
involving the regulation of in-use fuel volatility. Estimates
for the intermediate in-use RVP scenarios (e.g., 10.0, 11.0
psi) were derived through linear interpolation between the
inventories associated with the 9.0- and 11.5-psi options.
B. Service Station (Stage I) Losses
This second stationary category includes the breathing and
loading losses associated with underground storage facilities
at service stations. Losses in this category are sometimes
referred to as "Stage I," designating emissions between the
tank truck and the service station. Emission rates from these
sources are primarily based on the same parameters as the
breathing and loading losses described in the previous section.
-------
5-21
As before, the estimated reduction in Stage I losses
resulting from a 2.5-psi decrease in in-use fuel RVP is between
20 and 28 percent. [4] In this analysis, Stage I emissions were
handled as one broad category and an estimated 23-percent
reduction was assumed for the 9.0-psi in-use RVP scenario; as
before, emissions for the intermediate in-use RVP scenarios
were developed using linear interpolation.
C. Refueling Losses
Refueling losses refer to the vapors that escape into the
atmosphere while dispensing gasoline from a service station
pump into a vehicle's fuel tank. The refueling emission rate
is dependent upon the RVP of the fuel, the dispensed
temperature of the fuel, and the temperature differential
between the dispensed fuel and the liquid already in the tank.
In support of pending EPA actions regarding the control of
refueling emissions (the onboard versus "Stage II" issue),
extensive tests were conducted to determine the relationship
between refueling emission levels (in terms of grams per gallon
of fuel dispensed) and the above parameters. The derivation of
an equation relating these parameters is documented in an EPA
technical report.[5]
In order to determine (for this analysis) the effect of
in-use RVP reductions on uncontrolled refueling emissions, the
equation developed from the refueling test data was used.
Assuming nationwide average summertime conditions — dispensed
temperature 9.4°F less than fuel tank temperature, with a
dispensed temperature of 78.8°F — the impact of in-use RVP
control was determined. In addition to the displacement losses
calculated with the refueling equation, a spillage factor of
0.3 g/gal (5-6 percent of the total refueling loss), which is
unaffected by RVP, was also included in the overall emission
factors. With a reduction in RVP from 11.5 psi to 9.0 psi, the
uncontrolled refueling emission rate under the above
temperature conditions is estimated to decrease from 6.0 to 4.8
grams/gallon, or by 20 percent. As the equation used to
calculate these refueling rates is linear, values for each of
the intermediate RVP control scenarios were determined through
interpolation.
D. Non-RVP-Related Controls
Regardless of whether in-use RVP control is implemented,
EPA, states and local areas have established equipment-related
controls for stationary sources that must be accounted for in
modelling future hydrocarbon emissions. The Clean Air Act as
amended in 1977 requires that hydrocarbon emissions from both
new and existing stationary sources in ozone non-attainment
areas be controlled to the lowest achievable levels; EPA has
interpreted this as those levels achievable with "reasonably
-------
5-22
available control technology" (RACT), which varies from source
to source. To assist the states in developing control
regulations consistent with RACT levels, EPA's Office of Air
Quality Planning and Standards (OAQPS) issued, in the late
1970's, several control technique guideline (CTG) documents
relevant to various sources associated with the gasoline
marketing industry.[6-11] These CTGs assessed the technology
available to control HC emissions from various sources such as
bulk storage terminals, gasoline tank trucks, loading
operations, etc., and provided estimates of the emission rates
achievable with the RACT level of control.
The Clean Air Act Amendments of 1977 also stated that all
areas were to be in compliance with the ozone NAAQS by 1982;
therefore, this date was originally projected as the year by
which RACT levels of control would be fully implemented on HC
sources in the non-attainment areas of the late 1970's and
1980's. In anticipation of full implementation by 1982, RACT
began being applied to some sources (primarily new sources)
following publication of the CTGs in 1977 and 1978. However,
RACT was not fully implemented by 1982 and indeed is not fully
in place at the time of this analysis; as outlined earlier, an
estimated 54 urban areas are currently out of compliance and 35
have requested an extension of the attainment date to 1987.
For purposes of this analysis, it was assumed that RACT would
be fully implemented by 1988, which is the earliest projection
year examined in this report.
The emissions control efficiencies and source growth and
retirement (or replacement) rates to be assumed in modelling
future HC emissions from these stationary sources were
evaluated in a 1980 EPA report.[12] Using the RACT-based
emission rates outlined in the CTGs, it was estimated that the
HC emissions reduction achievable with full implementation of
RACT was roughly 80 percent in both the bulk storage/transfer
and Stage I categories.[12] The net growth and replacement
rates (respectively) for both of these categories, based on
projections of future earnings in the petroleum industry, were
estimated at 1.9 and 4.5 percent per year, compounded
annually.[12]
The control efficiencies estimated above are applicable
only to base emissions at the pre-RACT level typical of the
late 1970's (when the CTGs were published). The HC emissions
projections made for this analysis were based on the NEDS*
NEDS is the National Emissions Data System, from which
emissions inventories are compiled by EPA's National Air
Data Branch within OAQPS; the most recent inventory
available at the time of this analysis was for calendar
year 1982.
-------
5-23
inventory for 1982, a year by which some sources had already
been controlled to the RACT level. Between 1978 and 1982,
limited implementation of RACT resulted in a reduction of
approximately 14-15 percent in average emission rates from bulk
storage and transfer sources and an almost negligible 4 percent
in Stage I losses (measured from 1978 levels).[13] This
partial implementation of RACT was accounted for in this
analysis by modifying the control efficiencies used in the
model. Instead of applying the 80-percent control recommended
for both categories, a 76-percent reduction from average 1982
bulk storage/transfer emission rates was estimated to be
achievable with full implementation of RACT; for the Stage I
category, the recommended control efficiency was reduced to 79
percent to account for the slight implementation of RACT in
this area.
V. Hydrocarbon Emissions Inventory Analysis
MOBILES is EPA's current model for estimating
calendar-year fleet-average emission factors for various
gaseous pollutants. In calculating evaporative HC emission
factors (included in total non-methane hydrocarbons, or NMHCs)
for this analysis, the model-year hot-soak and diurnal losses
estimated earlier for each of the various control strategies
serve as inputs to MOBILES. Within the model, these
evaporative losses (in terms of grams/test) are converted to
grams/mile using estimates of average trips made and miles
driven each day. The June 1984 version of MOBILES assumed that
these values were constant over all model years, but recent
work supports the theory that older vehicles make fewer trips
and travel less miles than new vehicles.[14] Because this is
probably more realistic than the assumptions within the
originally published MOBILES, inputs for miles/day and
trips/day have been revised and were used to calculate the
evaporative emission factors used in this analysis.
Emissions inventories for various source categories were
then calculated for the nation (excluding California) and for
the 47 non-California urban areas that are currently in
non-attainment of the ozone NAAQS.* (The specific cities were
* Nationwide inventories were converted to non-California
inventories assuming that California accounts for
approximately 11 percent of total nationwide emissions.
This figure is fuel-consumption based, so may not
necessarily apply to all stationary sources. However,
because the control programs will affect only
gasoline-related sources, the 11-percent figure was
applied to all entire inventories to put the emissions
reductions in the proper perspective.
-------
5-24
listed earlier in Table 2-1 of Chapter 2.) All future
projections are based on the 1982 NEDS inventory for volatile
organic carbons (VOCs), or NMHCs. To the motor vehicle
portions of this inventory are applied annual compound VMT
growth rates (calculated for each vehicle class via the MOBILES
Fuel Consumption Model, or FCM) and emission factor ratios
(future to base year) from the M05ILE3 runs. Projections of
stationary source emissions are based on the annual growth and
retirement rates, along with emission control efficiencies,
discussed in the previous section. Of course, the stationary
sources that contribute to evaporative HC emissions (gasoline
storage and distribution) have been the focus above, since they
are affected by fuel RVP, but all sources of NMHC emissions
have been included in the modeling with their respective
growth, retirement, and control estimates.t12]
Baseline NMHC emissions inventories were calculated
assuming that an in-use RVP of 11.5 psi and a certification
fuel RVP of 9.0 psi would continue through the year 2010; these
inventories will be presented along with those for the control
cases in the tables discussed in the following sections. To
put the various sources of NMHC emissions into perspective, a
breakdown of future total baseline emissions is presented
graphically in Figures 5-la and 5-lb for calendar years 1988
and 2010. In Figure 5-la, the inventories are broken down into
six categories: motor vehicle evaporative losses, motor
vehicle exhaust emissions, refueling, Stage I, bulk storage,
and others (consisting of off-highway and non-gasoline-related
stationary sources). As shown, the "others" category is the
largest in both years, representing approximately 61-72 percent
of total NMHC emissions. Motor vehicle emissions (evaporative,
exhaust, and refueling losses) make up roughly 24-36 percent of
the total. The lower end of the range is representative of
2010, as motor vehicle emissions will decrease with time in
response to evaporative and exhaust HC standards and improved
fuel economies (used to convert refueling losses from g/gal to
g/mi).
Figure 5-lb breaks motor vehicle evaporative emissions
down further into the five components discussed in detail in
Chapter 2 (Section V). These sources of evaporative losses
are: properly designed vehicles (meeting the standards),
improper design of purge system, malmaintenance/defects, excess
in-use RVP, and evaporative system tampering. As indicated in
Figure 5-lb, the RVP effect is the largest of the five,
contributing to approximately 35 percent of total evaporative
losses.
The following inventory discussion begins with estimates
of future NMHC emissions under the long-term control scenarios
— in-use RVP equal to certification fuel RVP, at various
-------
5-25
Figure 5-la
Non-Calif. NMHC Inventory—Baseline (11.5-psi RVP)
laoeo
13000-
14000-
15
12
11
1
1988
2010
1771
Bulk
Storage
Stage Re- MV
I fueling Exh
MV
Evap.
Others
Figure 5-lb
Non-Calif. MV Evap. Inventory—Baseline (11.5-psi RVF)
11
170O-
1
« isoo
8
o
= TOO-
4J
i
100 -
c
1988
. 2010
Prop.
Designed
Imp. Malm./ RVF Tampering
Purge Def. Excess
-------
5-26
volatility levels. The next section focuses on the short-term
additional control of in-use RVP, where in-use volatility is
temporarily controlled to a level lower than the long-term
certification fuel RVP specification. (For a review of the two
control scenarios and the RVP options under each, see Section
VI of Chapter 2.) It should be noted that this chapter
incorporates a year-round analysis; in other words, the
emissions results presented in Tables 5-12 through 5-15 are
based on year-round control of in-use and certification fuel
RVPs. (Both 4-month and 12-month analyses will be presented
later in Chapter 6.) Also, an inspection/maintenance program
for exhaust emissions is assumed to be in effect in all areas
through 2010.
A. Long-Term Analysis
Long-term control involves changes to in-use and/or
certification fuel RVPs to make the two equal to each other.
For this analysis, in-use fuel control was assumed to begin in
1988, and certification fuel and test procedure changes would
start with the 1990 model year. Six long-term control
scenarios were examined, with RVPs ranging between 9.0 and 11.5
psi.
Table 5-12 presents future non-California NMHC inventories
estimated for the baseline case (shown previously in Figures
5-la and 5-lb) and the six long-term control strategies. As
shown, the control of in-use RVP to a level of 9.0 psi, while
holding certification fuel RVP at its current 9.0 psi, results
in the largest change — almost a 7-percent reduction in total
annual non-California NMHC emissions in the year 2010.
The tonnage reductions estimated to be achievable in 1988
and 2010 with this 9.0-psi control case are shown graphically
in Figures 5-2a and 5-2b. As indicated in the top figure,
in-use RVP control (along with revised test procedure) reduces
emissions from the following five categories: motor vehicle
evaporative losses, motor vehicle exhaust emissions, refueling,
Stage I, and bulk storage. As evaporative emissions from motor
vehicles are the focus of the control programs being examined
in this analysis, it is not surprising that the largest
reductions are predicted for this category; as indicated in
Figure 5-2a, 72 and 62 percent of the total NMHC reductions in
1988 and 2010, respectively, are projected to occur in the
motor vehicle evaporative category.
-------
5-27
Table 5-12
Non-California NMHC Emissions Inventories
Under Long-Term Control Options*
Scenario RVP (psi)
B
1
2
3
4
5
6
Baseline case **
11.5
11.0
10.5
10.0
9.5
9.0
NMHC, 1000 tons/year(% Reduction)
1988 1995 2010
14,307(0) 13,350(0) 15,298(0)
14,307(0) 13,125(1.7) 14,714(3.8)
14,024(2.0) 12,958(2.9) 14,629(4.4)
13,769(3.8) 12,807(4.1) 14,543(4.9)
13,553(5.3) 12,676(5.1) 14,458(5.5)
13,360(6.6) 12,553(6.0) 14,374(6.0)
13,191(7.8) 12,439(6.8) 14,288(6.6)
**
California emissions, roughly 11 percent of nationwide
total, were excluded. Long-term control assumes in-use
RVP and certification fuel RVP will be equal, beginning in
1990; in-use fuel changes would occur in 1988, followed by
certification fuel changes in 1990; year-round RVP control
is assumed.
Baseline case refers to the uncontrolled situation in
ASTM's "Class-C" areas: in-use RVP at 11.5 psi and
certification fuel RVP equal to 9.0 psi.
-------
5-28
Figure 5-2a
Non-Calif. NMHC Reductions—RVP Control to 9..0 psi
1300
1100 H
I
8
r
1988 2010
1771 re"^i c^> (S3
Bulk Stage Re- MV MV
Storage I fueling Exh. Evap.
Figure 5-2b
Non-Calif. MV Evap. Reductions—RVP Control to 9.0 psi
TOO -\
o
s
400 -\
I „
1988
2010
BED
Imp. Malm./ RVP Tampering
Purge Def. Excess
-------
5-29
In Figure 5-2b, these reductions in motor vehicle
evaporative emissions are broken down further into the various
components shown earlier (in Figure 5-lb). Of the five
original sources, reductions occur in only three in 1988 and
four in 2010. Emissions from properly designed vehicles will
not be reduced, as these vehicles are assumed to meet the
evaporative standards; therefore, this category does not appear
in Figure 5-2b. A second category — improper purge design —
is not included in the 1988 emissions reductions because the
change in test procedure that would address this problem would
not be implemented until 1990; therefore, this component does
contribute to the reductions in the year 2010. As indicated in
the figure, the largest reductions are achievable in the excess
RVP category — 61-77 percent of motor vehicle evaporative HC
reductions are predicted to occur here. This is
understandable, in part, because excess RVP is the largest
source of total motor vehicle evaporative losses (as indicated
previously in Figure 5-lb).
Combined inventories for the 47 ozone non-attainment areas
examined are presented in Table 5-13. These non-California
urban areas (listed in Chapter 2) consist of 45 low-altitude
and 2 high-altitude SMSAs. Similar to the nationwide analysis,
a 2.5-psi reduction in in-use RVP (from the current 11.5 down
to 9.0 psi) would reduce year 2010 emissions in these 47 urban
areas by an estimated 7-8 percent.
B. Short-Term Analysis
Tables 5-14 and 5-15 show future non-California and
47-city NMHC emissions inventories, respectively, estimated for
the various short-term RVP scenarios. As the RVP combinations
listed in these tables indicate, this short-term strategy
involves temporary additional control of in-use RVP to a level
lower than the long-term certification specification. As with
the long-term scenario, in-use and certification changes are
assumed to take place, respectively, in 1988 and 1990. While
the certification fuel specification would continue
indefinitely, the in-use control would be relaxed after a
specified period of time and in-use and certification RVPs
would become egual. Several time periods for this short-term
control were evaluated; scenarios of 2, 4, 7, and 9 years
(represented by 1990, 1992, 1995, and 1997) are shown in the
tables. Of course, the inventories presented are applicable
only if additional in-use control is in place during the
calendar years shown; following the relaxation of in-use
control to the long-term certification fuel level, annual
inventories would be those estimated for the long-term strategy
under the appropriate RVP scenario (in Tables 5-12 and 5-13).
-------
5-30
Table 5-13
Combined NMHC Emissions Inventories for 47 Urban Areas Under
Scenario
B
1
2
3
4
5
6
Lonq-Term
RVP (psi)
Baseline case **
11.5
11.0
10.5
10.0
9.5
9.0
Control Options*
NMHC, 1000 tons/year(%
1988 1995
5077(0) 4693(0)
5077(0) 4601(2.0)
4960(2.3) 4534(3.4)
4855(4.4) 4472(4.7)
4767(6.1) 4418(5.9)
4688(7.7) 4368(6.9)
4620(9.0) 4322(7.9)
Reduction)
2010
5465(0)
5229(4.3)
5193(5.0)
5158(5.6)
5122(6.3)
5087(6.9)
5051(7.6)
**
Long-term control assumes in-use RVP and certification
fuel RVP will be equal, beginning in 1990; in-use fuel
changes would occur in 1988, followed by certification
fuel changes in 1990; year-round RVP control is assumed.
Baseline case refers to the uncontrolled situation in
ASTM's "Class-C" areas: in-use RVP at 11.5 psi and
certification fuel RVP equal to 9.0 psi.
-------
5-31
Table 5-14
Non-California* NMHC Emissions Inventories With Short-Term
Additional
Scenario
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Short-Term
In-Use RVP
(psi)
Baseline (11.5)
9.
9.
9.
9.
9.
10.
9.
9.
10.
10.
9.
9.
10.
10.
11.
0
0
5
0
5
0
0
5
0
5
0
5
0
5
0
In-Use
Long-Term
Cert . Fuel RVP
(psi)
i Basel
9
10
10
10
10
10
11
11
Jl
11
11
11
11
11
11
ine (9.
.5
.0
.0
.5
.5
.5
.0
.0
.0
.0
.5
.5
.5
.5
.5
RVP Control
NMHC (
1990
0) 13,
12,
12,
12,
12,
12,
13,
12,
12,
13,
13,
12,
12,
13,
13,
13,
821
795
795
950
795
950
124
795
950
124
320
795
950
124
320
553
1000
1992
13,
12,
12,
12,
12,
12,
12,
12,
12,
12,
13,
12,
12,
12,
13,
13,
513
550
550
687
550
687
838
550
687
838
004
550
687
838
004
200
tons/year)
1995
13,350
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
,439
,439
,553
,439
,553
,676
,439
,553
,676
,807
,439
,553
,676
,807
,958
1997
13,397
12,504
12,504
12,608
12,504
12,608
12,715
12,504
12,608
12,715
12,828
12,504
12,608
12,715
12,828
12,957
California emissions, roughly 11 percent of nationwide
total, are excluded.
-------
5-32
Table 5-15
Combined NMHC Emissions Inventories for 47 Urban Areas With
Additional Short-Term In-Use RVP Control
Scenario
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Short-Term
In-Use RVP
(psi)
Long-Term
Cert. Fuel RVP
(psi)
NMHC (1000
1990
Baseline (11.5) Baseline (9.0) 4877
9
9
9
9
9
10
9
9
10
10
9
9
10
10
11
.0
.0
.5
.0
.5
.0
.0
.5
.0
.5
.0
.5
.0
.5
.0
9
10
10
10
10
10
11
11
11
11
11
11
11
11
11
.5
.0
.0
.5
.5
.5
.0
.0
.0
.0
.5
.5
.5
.5
.5
4459
4459
4522
4459
4522
4593
4459
4522
4593
4671
4459
4522
4593
4671
4767
1992
4754
4362
4362
4417
4362
4417
4478
4362
4417
4478
4545
4362
4417
4478
4545
4625
tons/year )
1995
4693
4322
4322
4368
4322
4368
4418
4322
4368
4418
4472
4322
4368
4418
4472
4534
1997
4716
4351
4351
4394
4351
4394
4438
4351
4394
4438
4484
4351
4394
4438
4484
4537
-------
5-33
In comparing the inventories shown in short-term Tables
5-14 and 5-15 under different RVP strategies, it is important
to note that the emissions totals shown are dependent only upon
the short-term in-use RVP listed. In other words, the 1995
inventories shown in Table 5-14 for scenario tt7 (in-use = 9.0,
certification = 11.0) are the same as the 1995 figures shown in
long-term Table 5-12 under scenario 86 (in-use = certification
= 9.0). Inherent in this is the assumption that no emissions
benefit will be derived from the "overdesign" of the canister
for a higher RVP fuel (i.e., a vehicle designed for ll.O-psi
fuel and operated on Indolene will emit the same amount as a
vehicle both designed for and operated on Indolene). This
assumption is best explained by referring to the five
components of motor vehicle evaporative emissions discussed
earlier in Section II of this chapter (and in more detail in
Chapter 2) .
As the source breakdowns in Tables 5-1 and 5-2 indicated,
the RVP effect and the effect of improper design/purge are
assumed to be totally eliminated if certification test
procedure is revised and if certification RVP is raised to a
level equal to in-use RVP; because these categories are totally
eliminated when certification and in-use RVPs are made equal,
no emissions benefit can be derived from designing the canister
for an even higher RVP fuel. Of course, the emissions of
properly designed and operated vehicles will not change (i.e.,
they will continue to emit at the evaporative standard level).
The two remaining effects — tampering and
malmaintenance/defect — are dependent only upon in-use RVP
(i.e., the fact that certification RVP is higher than in-use
RVP will have no impact on these essentially uncontrolled
emissions). Therefore, short-term additional in-use RVP
control provides the same emissions benefits as with the
long-term scenario at that particular in-use RVP; the advantage
is that the fleet is allowed to begin turning over with
vehicles designed for the higher RVP to which in-use control
will be relaxed after a specified period.
VI. Ozone Air Quality Analysis
Because of the complex relationship between ambient ozone
concentrations and hydrocarbon emissions, the rollback approach
used by EPA to model other pollutants (i.e., NOx and CO) is
inappropriate for ozone. Instead, EPA makes use of the EKMA
(Empirical Kinetic Modelling Approach) to predict future
ambient ozone concentrations in specific urban areas. The EKMA
utilizes a series of ozone isopleths which depict downwind
ozone concentrations as a function of initial NMHC and NOx
concentrations, subsequent NMHC and NOx emissions,
meteorological conditions, reactivity of the precursor mix, and
concentrations of ozone and precursors transported from upwind
areas. It should be noted that the EKMA as used by EPA is a
-------
5-34
nationwide-average model. In other words, no city-specific
information is input into the model except for the base-year
ozone concentrations, or -"design values," from which future
concentrations are projected*; meteorological conditions, etc.,
are held constant for all the urban areas modelled. (Design
values for the 47 cities in this analysis were shown in Table
2-1 of Chapter 2. [15] For more details on the EKMA, see
References 16 and 17.)
Using EKMA and the NMHC emissions inventories presented in
Tables 5-13 and 5-15, projections of future ozone conditions in
the 47 current non-California non-attainment areas were made.
The first section below focuses on future air quality in the
long term, followed by a similar presentation with respect to
short-term control alternatives.
A. Long-Term Analysis
Tables 5-16 through 5-18 present EKMA-based predictions of
future ambient ozone conditions in 47 current non-attainment
areas under the six long-term RVP scenarios. The first of
these tables shows the average change in ambient ozone
concentration with respect to the base level in 1982. The
reductions expected to occur under the baseline RVP scenario
are, of course, in response to programs other than gasoline
volatility control, such as equipment-related stationary source
HC controls and motor vehicle exhaust HC emissions standards.
However, the additional ozone reductions shown under the six
RVP scenarios in Table 5-16 are due solely to NMHC reductions
through in-use and/or certification RVP control. For example,
if in-use RVP was controlled to 10.0 psi in 1988 and
certification RVP was raised to 10.0 psi in 1990, ambient ozone
concentrations by the year 1995 would be expected to decrease
an additional 5 percent beyond the baseline RVP scenario (i.e.,
33 percent vs. 28 percent lower than 1982 levels).
Estimates of total annual violations of the ozone NAAQS
are presented in Table 5-17 for each of the long-term RVP
scenarios. The NAAQS for ozone sets a limit of 0.125 ppm for
the fourth highest daily maximum 1-hour ozone concentration in
any three-year period; the violations listed in the table
represent the total number of days this maximum hourly ozone
concentration is expected to exceed 0.125 ppm. Only the peak
An area's "design value" is its fourth highest daily
maximum one-hour ozone concentration recorded (for this
analysis) during 1981, 1982, and 1983.
-------
5-35
Table 5-16
Average Percentage Change* in Ambient Ozone Concentrations
in 47 Urban Areas
Scenario
B
1
2
3
4
5
6
RVP (psi)
Baseline
11.5
ll.O
10.5
10.0
9.5
9.0
Under Lonq-Term
Control
1988 1995
-23
-23
-24
-26
-27
-28
-29
-28
-30
-31
-32
-33
-34
-34
Options
2010
-18
-21
-22
-22
-23
-23
-24
With respect to base-year (1982) levels.
-------
5-36
Table 5-17
Number of Total Annual Violations of Ozone NAAQS
in
Scenario
B
1
2
3
4
5
6
47 Urban Areas
RVP (psi)
Baseline
11.5
11.0
10.5
10.0
9.5
9.0
Under Long-Term
1988
67
67
60
55
51
48
39
Control
1995
46
35
34
31
29
26
25
Options
2010
96
76
76
74
70
67
66
-------
5-37
monitoring site in each of the 47 areas was considered, so the
maximum possible number of annual violations per area is 365.
As Table 5-16 shows, for example, long-term scenario #6 (both
RVPs equal to 9.0) is estimated to reduce the total number of
ozone violations in the 47 cities combined by approximately 46
percent from the baseline RVP scenario in 1995 (i.e., 25 vs. 46
violations).
Finally, Table 5-18 estimates the total number of
non-California urban areas expected to be in violation of the
ozone NAAQS under the various long-term control options. As
shown, scenario tt6 is projected to enable roughly 6 more cities
to come into attainment in 1988. One limitation associated
with evaluating control options on the basis of number of
non-attainment areas is that only those areas that fall below
the NAAQS as a result of the action are distinguishable; in
other words, the value of bringing an area closer to attainment
is not recognized unless attainment is achieved. Therefore,
estimated overall emissions reductions or changes in average
ambient concentrations as a result of a particular action are
probably more indicative of the environmental impact of the
action than is the projected number of non-attainment areas.
B. Short-Term Analysis
Using EKMA and the NMHC emissions inventories presented
earlier in Table 5-15, air quality projections were made under
the various short-term RVP control scenarios. Results are
presented (in the same form as for the long-term scenarios) in
Tables 5-19 through 5-21. As before with the emissions
inventories, the short-term air quality results presented here
are basically dependent on in-use RVP; in other words, the
short-term results at a particular in-use RVP level agree with
the long-term projections at that same RVP.
VII. Effect of RVP Control on Toxic Emission Levels
This section analyzes how RVP control may influence the
content of certain components in liquid gasoline and how these
changes may affect emissions of benzene and other toxic
compounds. The primary compounds of concern here are benzene
and whole gasoline vapor, due to their known or suspected human
carcinogenicity. Benzene has been listed as a hazardous
pollutant under Section 112 of the Clean Air Act. The evidence
of carcinogenicity of gasoline vapors comes primarily from the
American Petroleum Institute's (API) chronic inhalation study
in rats and mice. [18] The effect of vehicle-oriented RVP
control will be addressed first, followed by that of
fuel-oriented RVP control.
-------
5-38
Table 5-18
Number of Ozone Non-Attainment Areas* Under
Lonq-Term Control Options
Scenario
B
1
2
3
4
5
6
RVP (psi)
Baseline
11
11
10
10
9
9
.5
.0
.5
.0
.5
.0
1982
47
47
47
47
47
47
47
1988
14
14
13
13
11
10
8
1995
8
6
6
6
6
6
6
2010
16
12
12
12
12
11
11
Non-California areas only.
-------
5-39
Table 5-19
Average Percentage Change* in Ambient Ozone Concentrations
In 47 Urban Areas With Additional Short-Term In-Use RVP Control
Short-Term
In-Use RVP
Scenario (psi)
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Baseline
9.
9.
9.
9.
9.
10.
9.
9.
10.
10.
9.
9.
10.
10.
11.
(11
0
0
5
0
5
0
0
5
0
5
0
5
0
5
0
Long-Term
Cert. Fuel RVP
(psi)
9.5
10.0
10.0
10
10
10
11.0
11.0
11.0
11.0
11.5
11.5
11.5
11.5
11.5
1990
-25
-32
-32
-31
-32
-31
-30
-32
-31
-30
-28
-32
-31
-30
-28
-27
1992
-27
-34
-34
-33
-34
-33
-32
-34
-33
-32
-31
-34
-33
-32
-31
-29
1995
-28
-34
-34
-34
-34
-34
-33
-34
-34
-33
-32
-34
-34
-33
-32
-31
1997
-28
-34
-34
-33
-34
-33
-33
-34
-33
-33
-32
-34
-33
-33
-32
-31
With respect to base year (1982) levels.
-------
5-40
Table 5-20
Number of Total Annual Violations of Ozone NAAQS
in 47 Urban Areas With Additional Short-Term In-Use RVP Control
Short-Term
In-Use RVP
Scenario (psi)
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Baseline (
9.0
9.0
9.5
9.0
9.5
10.0
9.0
9.5
10.0
10.5
9.0
9.5
10.0
10.5
11.0
Long-Term
Cert. Fuel RVP
(psi)
1990
seline (9.0) 58
9.5 29
10.0
10.0
10
10
10
11.0
11.0
11.0
11.0
11.5
11.5
11.5
11.5
11.5
29
31
29
31
37
29
31
37
45
29
31
37
45
52
1992 1995 1997
48
26
26
29
26
29
30
26
29
30
33
26
29
30
33
39
42
25
25
26
25
26
29
25
26
29
31
25
26
29
31
34
43
26
26
27
26
27
30
26
27
30
32
26
27
30
32
33
-------
5-41
Table 5-21
Number of Ozone Non-Attainment Areas*
With Additional Short-Term In-Use RVP Control
Scenario
Short-Term
In-Use RVP
(psi)
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Baseline (1
9
9
9
9
9
10
9
9
10
10
9
9
10
10
11
.0
.0
.5
.0
.5
.0
.0
.5
.0
.5
.0
.5
.0
.5
.0
Long-Term
Cert. Fuel RVP
(psi)
Baseline (9.0
9.
10.
10.
10.
10.
10.
11.
11.
11.
11.
11.
11.
11.
11.
11.
5
0
0
5
5
5
0
0
0
0
5
5
5
5
5
1990
13
6
~~6
6
6
6
6
6
6
6
8
6
6
6
8
11
1992
10
6
fr
6
6
6
6
6
6
6
6
6
6
6
6
7
1995
8
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
1997
9
6
: 6
6
6
6
6
6
6
6
6
6
6
6
6
6
Non-California areas only.
-------
5-42
A. Vehicle-Related RVP Control
Overall, the effect of vehicle-oriented RVP control on
toxic emissions will be positive. Vehicle-oriented RVP control
reduces evaporative HC emissions directly and does not affect
the amount of vapors, toxic or benign, generated by the vehicle
since the fuel is not affected. Since improvements in the
capture and recycling of these vapors can only reduce
emissions, and not increase them, the effect on toxic emissions
can only be positive. For example, a saturated evaporative
cannister will not efficiently capture any additional HC
compounds sent to it. An increase in its size and improved
purging will provide additional capacity to absorb both butane
and higher compounds, such as benzene. No data are currently
available showing the benzene content of evaporative emissions
from current vehicles operating on commercial fuel both failing
and meeting the evaporative emission standard, so this effect
cannot be quantified. However, it definitely will reduce such
emissions.
The effect of vehicle-oriented RVP control on exhaust
emissions is only slightly more complex. The primary effect of
vehicle improvements will be to improve the combustion of HC
vapors recycled from the charcoal cannister. This should
reduce the emissions of all HC compounds. A secondary effect
will be that those toxic compounds now being emitted will be
recycled to the engine, so their emissions may increase
somewhat. However, the former effect should override the
latter, since the amount of higher compounds, such as
aromatics, being introduced to the engine via cannister purging
will be very small compared to that introduced via the main
fuel metering system. For example, even if purged fuel is 10
percent of total fuel consumption, which it can be under
certain circumstances, the aromatic content of the purged fuel
will be a small fraction of that of the liquid fuel, due to the
low relative volatility of such compounds in the fuel tank (the
primary source of evaporative emimissions on the dominant
post-1990 vehicle technoloty, fuel-injection).
B. Fuel-Related RVP Control
The effect of fuel-oriented RVP control is more complex,
because the composition of the fuel itself is changing. Few
data are available with which to analyze this effect, which
overall should be quite small since the fuel compositional
changes are expected to be quite small. However, what data are
available are used below to quantify this efect. The first
section below estimates the effect of in-use RVP control on
benzene emissions. The second section extrapolates these
conclusions in order to estimate the effect on emissions of
whole gasoline vapors.
-------
5-43
1. Benzene Emissions
As already mentioned in Chapter 4, in-use control of RVP
will be achieved primarily by reducing the quantity of butane
in the gasoline pool by up to 5 percent (roughly 2 percent per
1.0 psi RVP reduction). If the quantity of butane in the fuel
is reduced without any other compositional changes, the
percentage of all other fuel constituents, including aromatics,
would be expected to increase proportionately (i.e., by up to a
factor of 1.05). However, other compositional changes are
expected which will either heighten or mitigate this general
increase. No data are available concerning the effect of RVP
control on benzene levels, in particular, but projections are
available from the Bonner and Moore model of total fuel
aromatic content for the baseline and control cases allowing
investment and open NGL purchases (see Table 5-22). As can be
seen, the nationwide average aromatic content increases,
additively, by 0.6 percent and 2.8 percent for RVP reductions
of l psi and 2 psi, respectively, over the baseline level of
32.5 volume percent. Assuming benzene levels increase
proportionately, then current benzene levels (roughly 1.34
percent based on the 1984 NIPER survey [19]) would increase
0.01 volume percent with a 1 psi RVP reduction and 0.04 volume
percent with a 2 psi reduction.
Very limited data are also available which detail vehicle
evaporative and exhaust benzene emissions as a function of fuel
composition. The data available are from a study by EPA and
are shown in Table 5-23.[20] The original data set consisted
of 4 vehicles. However, two of the vehicles were omitted from
this analysis since they were pre-1978 models and their
evaporative control systems, by design, are quite inefficient
and unrepresentative of current vehicle technology. Even the
remaining two vehicles were certified to the 1978-1980 model
year 6-gram evaporative HC standard and, therefore, do not
fully represent more recent technology. However, their systems
are conceptually very close to current technology and can be
used here. With respect to exhaust emissions controls, these
two vehicles were equipped with oxidation catalysts, air
injection, and exhaust gas recirculation. Again, while not
entirely representative of the feedback-controlled, three-way
catalyst vehicles of today, the control systems were generally
quite efficient (1.5 g/mi HC versus uncontrolled emissions of
roughly 4 g/mi) and represent the best data available. The
hot-soak and diurnal emissions shown in Table 5-23 were
converted from gram per test to gram per mile using the
original MOBILES equation shown below:
Pi + (3.05 trips/day)(Hs)
Evap =
31.1 miles/day
-------
5-44
Table 5-22
Changes in Aromatic Content (Vol %)
Resulting from RVP Control*
With Investment, Open NGLs
PADD
4 + 5
123 (ex. CA)**
Baseline
Unleaded Regular
Unleaded Premium
Leaded Regular
Weigted Average
1 PSI RVP Reduction
Unleaded Regular
Unleaded Premium
Leaded Regular
Weighted Average
2 PSI RVP Reduction
Unleaded Regular
Unleaded Premium
Leaded Regular
Weighted Average
38.8 32.0 31.3 31.7
31.6 37.9 31.0 34.5
30.8 31.2 34.6 32.9
36.1 32.9 31.8 32.4
37.9 33.1 31.2 32.2
35.8 36.9 31.3 34.1
31.0 31.3 33.6 32.5
36.3 33.5 31.6 32.6
38.3 33.6 32.4 33.0
36.0 35.6 34.5 35.1
31.1 31.5 32.2 31.9
36.7 33.6 32.7 33.2
Total U.S.
(ex. CA)***
32.2
33.3
33.1
32.5
32.4
33.6
32.6
32.7
33.3
35.0
31.9
33.4
**
***
As predicted by Bonner and Moore RPMS model.
Estimated as an average of PADDs 2 and 3.
Total U.S. (ex. CA) estimated by volumetrically weighting
of PADD aromatic content for PADDs 1,2,3,4 and 5 using
PADD specific gasoline production.
Average estimated by weighting the three gasoline grades
by % of sales by volume.
-------
5-45
Table 5-23
Effect of Fuel Composition on Benzene Emissions [20]
Test Vehicle: 1979 LTD
Test
Code
B
B-l
C
Fuel
Aromatic
Vol %
43.4
46.6
25.7
Fuel
Benzene
Vol %
1.5
7.1
2.0
RVP
psi
9.8
9.8
12.3
Tailpipe
Benzene
cr/mi
.025
.035
.014
Evaporative
Benzene
q/mi
.007
.020
.011
Test Vehicle:1978 Monarch
Test
Code
Fuel
Aromatic
Vol %
Fuel
Benzene
Vol %
A
A-l
B
C
27.4
32.4
43.4
25.7
0.3
7.1
1.5
2.0
RVP
psi
8.4
8.4
9.8
12.3
Tailpipe
Benzene
q/mi
.030
.058
.030
.033
Evaporative
Benzene
q/mi
.001
.010
.009
.005
-------
5-46
Eyap = total evaporative emissions, grams/mile
Di = diurnal emissions, grams/test (one per day)
Hs = hot-soak emissions, grams/test (one per trip)
Ongoing research to determine the effect of fuel benzene
concentration on exhaust and evaporative benzene emissions is
currently being conducted by the Coordinating Research Council
and should be published by the end of 1985. The results of
this study (and any other data which becomes available) will be
incorporated into this analysis as soon as the results are
published.
The data of Table 5-23 show evaporative benzene emissions
to primarily be dependent upon two variables; fuel benzene
content and RVP. As would be expected, total aromatic content
is not a factor, since the temperatures in both the fuel tank
and fuel metering system are too low to produce benzene from
other aromatics. Overall, as the benzene content of the fuel
increases, evaporative benzene emissions increase. As RVP
decreases, evaporative benzene emissions -decrease. Estimates
of the effect of unit changes in each of these two fuel
properties on evaporative benzene emissions are presented in
Table 5-24. The effect of fuel benzene content was determined
for each vehicle separately (tests B and B-l for the 1979 LTD
and tests A and A-l for the 1978 Monarch) and then averaged.
The effect of RVP was determined for each of four pairs of
tests (tests B and C for the LTD and tests A and B, A and C,
and B and C for the Monarch) and then averaged. Many of the
changes in RVP were also accompanied by changes in fuel benzene
content. To account for this, the benzene effect determined
for each vehicle was subtracted from the overall change in
benzene emissions before determining the RVP effect. While the
benzene effect was fairly similar for the two vehicles, the
effect of RVP varied considerably. Thus, additional data would
be particularly useful in improving this latter estimate.
The effect of fuel benzene content on exhaust emissions of
benzene was determined in a similar fashion using tests B and
B-l for the LTD and tests A and A-l for the Monarch. These
tests represented the largest change in fuel benzene content
and RVP and fuel aromatic content were relatively constant.
The effects of both RVP and fuel aromatic content were
impossible to estimate, however, as they tended to change
together inversely. Thus, estimates of their effect will have
to await the development of additional data.
The effect of these changes in benzene emissions per mile
on nationwide emissions (non-California) are presented in Table
5-25. An estimate of total nationwide VMT was taken from EPA
fuel consumption model and California was assumed to represent
-------
5-47
Table 5-24
Effect of RVP Control on Benzene
Evaporative and Exhaust Emission Factors
Evaporative Emissions
RVP -.0013(g/mi)/l psi RVP reduction
Benzene Effect .0019(g/mi)/l vol % Benzene Increase
Exhaust Emissions
Benzene Effect .0030(g/mi)/l vol % Benzene Increase
-------
5-48
Table 5-25
Change in 1988Non-California Benzene
Emissions Due to RVP Control (Tons)
Degree of RVP Control
Source 1 psi reduction 2 psi reduction
M.V. Evap.
RVP Effect -631 -1261
Benzene Effect 10 41
M.V. Exhaust
Benzene Effect 17 69
Total -604 -1151
-------
5-49
11 percent of nationwide VMT, as discussed earlier in the
chapter.[21] No attempt was made to estimate the difference
between LDV, LDT and HDV emissions.
These results show that the RVP effect dominates the fuel
benzene effect and an overall reduction in benzene evaporative
emissions would be projected for in-use RVP control. Overall,
these decreases represent 2 and 5 percent of current nationwide
(non-California) benzene emissions of roughly 250,000 tons,
respectively.[22,23].
Increased fuel benzene content occuring while reducing RVP
may also affect refueling, Stage I, and bulk storage emissions
of benzene. Lower total HC emissions should lower benzene
emissions which are carried off by the evaporation of other
compounds, while a higher fuel benzene content is likely to
increase benzene concentration in the vapor that is emitted.
No data showing which of these two effects dominates are
available. Given the very slight projected increase in
aromatic content (and presumedly, benzene content), any
increase in benzene emissions due to increased benzene vapor
concentration should be very small and the net change in
benzene emissions even smaller.
B• Toxic Gasoline Vapors
The second toxic pollutant to be considered here is whole
gasoline vapor. The API animal experiments used an aerosol
formed from completely vaporized liquid gasoline.[18] However,
the precise compounds producing the carcinogenic effects have
yet to be identified. Therefore, all that can be said at this
time is that, based on the small compositional changes expected
to occur with in-use RVP control, the effect of such control on
the emissions of these toxic compounds should be quite small.
-------
5-50
References (Chapter 5)
1. "Evaporative HO Emissions for MOBILES," Test and
Evaluation Branch, U.S. EPA, EPA-AA-TEB-85-1, August 1984.
2. Data submitted in a formal letter from J.S.
Welstand, Chevron Research Division, to Chester J. France, EPA,
QMS, ECTD, April 1, 1985.
3. "Relationship Between Exhaust Emissions and Fuel
Volatility," EPA memo from Thomas L. Darlington to Charles L.
Gray, EPA, QMS, ECTD, June 24, 1985.
4. "Compilation of Air Pollution Emission Factors:
Highway Mobile Sources," U.S. EPA, EPA-460/3-81-005, March 1981.
5. "Refueling Emissions from Uncontrolled Vehicles,"
Dale S. Rothman and Robert Johnson, QMS, ECTD,
EPA-AA-SDSB-85-6, July 1985.
6. "Bulk Plants — Control of Volatile Organic
Emissions from Bulk Gasoline Plants (CTG)," U.S. EPA, OAQPS,
EPA-450/2-77-035, December 1977.
7. "Service Stations — Design Criteria for Stage I
Vapor Control Systems — Gasoline Service Stations (CTG)," U.S.
EPA, OAQPS, EPA Internal Document, November 1975.
8. "Gasoline Tank Trucks — Control of Volatile Organic
Compound Leaks from Gasoline Tank Trucks and Vapor Collection
Systems (CTG)," U.S. EPA, OAQPS, EPA-450/2-78-051, December
1978.
9. "Fixed-Roof Tanks — Control of Volatile Organic
Emissions from Storage of Petroleum Liquids in Fixed-Roof Tanks
(CTG)," U.S. EPA, OAQPS, EPA-450/2-77-036, December 1977.
10. "Floating-Roof Tanks — Control of Volatile Organic
Emissions from Petroleum Liquid Storage in External
Floating-Roof Tanks (CTG)," U.S. EPA, OAQPS, EPA-450/2-78-047,
December 1978.
11. "Bulk Terminals — Control of Hydrocarbons from Tank
Truck Gasoline Loading Terminals (CTG)," U.S. EPA, OAQPS,
EPA-450/2-77-026, October 1977.
-------
5-51
References (Chapter 5) Cont'd
12. "Methodology to . Conduct Air Quality Assessments of
National Mobile Source Emission Control Strategies; Final
Report," U.S. EPA, OAQPS, EPA-450/4-80-026, October 1980.
13. Computerized data files in support of "National Air
Pollutant Emissions Estimates, 1940-1983," U.S. EPA, OAQPS,
MDAD, EPA-450/4-84-028, December 1984.
14. "Updated Trips- and Miles-per-Day Information," EPA
Memo from Thomas Darlington, Test and Evaluation Branch, to
Charles L. Gray, Director of Emission Control Technology
Division, January 30, 1985.
15. "1981-1983 Standard Metropolitan Statistical Area
(SMSA) Air Quality Data Base for Use in Regulatory Analysis,"
Memo from Richard G. Rhoads, Director of Monitoring and Data
Analysis Division, to Charles L. Gray, Director of Emission
Control Technology Division, February 25, 1985.
16. "Uses, Limitations and Technical Basis of Procedures
for Quantifying Relationships Between Photochemical Oxidants
and Precursors," U.S. EPA, OAQPS, RTP, EPA-450/2-77-021a,
November 1977.
17. "Guidelines for Use of City-Specific EKMA in
Preparing Ozone SIPs," U.S. EPA, OAQPS, RTP, EPA-450/4-80-027,
March 1981.
18. "Evaluation of Air Pollution Regulatory Strategies
for Gasoline Marketing Industry," U.S. EPA, OAQPS,
EPA-450/3-84-012a, July 1984.
19. "Motor Gasolines, Summer 1984," Ella Mae Shelton and
Cheryl L. Dickson, National Institute for Petroleum and Energy
Research (NIPER), for API, February 1985.
20. "Composition of Automobile Evaporative and Tailpipe
Hydrocarbon Emissions," F.M. Black and L.E. High, U.S. EPA,
J.M. Lang, Northrop Services, Inc., APCA Journal, Vol. 30, No.
11, November 1980.
21. "MOBILES Fuel Consumption Model," Mark A. Wolcott,
EPA, and Dennis F. Kahlbaum, CSC, February 1985.
22. "Transmittal of Emissions Inventory and RVP Data,"
EPA memo from Glenn W. Passavant, EPA to Jeff Clark, General
Accounting Office, March 22, 1985.
23. "GAO Request for Background Information on Benzene,"
EPA memo from Robert G. Kellam, EPA to Joseph L. Turlington,
General Accounting Office, May 21, 1985.
-------
CHAPTER 6
Analysis of Alternatives
I. Introduction
This final chapter draws on the findings presented earlier
in the report and provides a direct comparison of the various
HC control strategies being examined. This comparison is based
on the estimated costs of motor vehicle-related controls and
in-use fuel controls (presented, respectively, in Chapters 3
and 4) and on projected emissions benefits (discussed in
Chapter 5) associated with each of the long- and short-term
control scenarios. Using this information, cost effectiveness
($/ton) figures were developed as a basis for evaluating
appropriate control measures. The emission reductions
associated with each control scenario, along with their
relative cost effectiveness, will be the focus of this chapter.
Both long-term control strategies, where in-use RVP and
certification fuel RVP are made equal, and short-term control
strategies, where in-use fuel is temporarily controlled to a
lower RVP level than certification fuel, will be examined in
terms of cost, emission reductions, and resulting cost
effectiveness. The long-term analysis will focus on the year
2010 as a "steady-state" point at which essentially the entire
motor vehicle fleet will have turned over (i.e., revised
certification fuel and test procedure will have affected the
design of almost all of the vehicles in the field) . The
short-term discussion will examine the years 1988, 1990, 1992,
1995, 1997, and 2000, and will focus on benefits achievable
with additional in-use RVP control over and above those
benefits resulting from the long-term strategies (i.e.,
certification RVP equal to in-use RVP).
As discussed earlier in Chapter 2, ozone-related HC
control appears to be most valuable during the summer months,
as over 90 percent of all ozone violations tend to occur
between June and September (inclusive). Because of this, both
12-month (year-round) and 4-month (summer only) analyses will
be performed below.* In both cases, the period of analysis
represents both the control period for in-use volatility
control and the period of consideration of emission benefits.
Summer periods other than four months could also have been
evaluated. Cost-per-ton estimates for 3-, 5-, or 6-month
control periods could be determined in a fairly linear
fashion. For example, 6-month benefits would be one-half
of annual tons, costs would be roughly three-quarters of
annual dollars, so cost per ton would be approximately 1.5
times higher than the annual figure.
-------
6-2
Due to the uncertainty associated with the relative value of
ozone benefits in the summer and winter, the discussion of the
results in this chapter will focus primarily, on the 12-month
figures.
Section II below outlines the methodologies and
assumptions used to calculate cost effectiveness estimates for
both the long- and short-term control strategies. (The
discussions on the development of costs and emissions
reductions are merely reviews, as the details on both are
presented in Chapters 3 through 5.) Following the methodology
descriptions, Section III presents the results of the analyses,
first for the long-term and then for the short-term strategies.
An analysis of alternatives based on best estimates and
current conditions will be presented first. This "base" case
includes no control of vehicle refueling losses and no
inspection and maintenance (I/M) programs for evaporative
emissions, as these have not been implemented to date. As
discussed in Chapter 4, the ratio of percentage change in fuel
economy to percentage change in fuel energy content (due to
butane removal), designated "R", should theoretically be 1.00.
However, limited available data indicate a lower boundary of
0.6 for this ratio. Therefore, base case costs and credits are
evaluated for both R = 1.0 and R = 0.6, but a 100-percent
efficiency still represents the best estimate at this time, as
the theory is sound (see Chapter 4).
In addition to the base case analysis. Section III will
also present the results of various sensitivity analyses. The
first sensitivity analysis will examine the effect of average
in-use gasoline RVP staying fairly constant at the current 0.5
psi (on average) below ASTM limits rather than reaching these
limits (e.g., average Class C RVP would stay at 11.0 psi,
instead of reaching the baseline value of 11.5 psi by 1988).
Because RVPs are not expected to decrease below current levels
without further regulation, this sensitivity analysis
represents a worst-case impact on the RVP control scenarios.
As with the base case, this sensitivity analysis is performed
for both R = 1.0 and R = 0.6.
The second sensitivity analysis will examine the effect of
implementing onboard vehicle refueling loss controls in 1989,
an issue now under study within EPA. If onboard controls are
required, that rulemaking could include a revision of
certification fuel RVP to 11.5 psi and a change in the
evaporative test procedure to require a saturated canister at
the start of the certification test. However, the revisions to
the test fuel and evaporative test procedure could be made
without implementing onboard refueling controls. Thus these
revisions and their resulting emission reductions should not be
unequivocally associated with onboard refueling controls. On
-------
6-3
the increment, when considering both RVP and refueling
controls, it seems most proper to associate the control of
excess evaporative and exhaust HC emissions due to high in-use
RVP to RVP control (vehicle or in-use fuel) and to associate
the control of refueling emissions with onboard refueling
controls. Thus, the majority of the refueling emission control
previously associated with in-use RVP control must be
subtracted out for the onboard sensitivity analysis; a very
small amount of refueling loss control is still achievable with
RVP control due to tampering with onboard systems. (More
detail is given in Section II.) As before, this sensitivity
analysis is performed at both "R" values — 1.0 and 0.6.
The third sensitivity analysis will examine the effect of
eliminating the exhaust HC emission reductions associated with
RVP control. As discussed in Chapter 2, in-use EF test data
indicate that exhaust emissions decrease with lower RVPs.
While there is no reason to question these technical results, a
sensitivity analysis without these RVP-related exhaust HC
reductions has been performed to examine the significance of
these exhaust benefits with respect to the base case
costs/ton. This case is evaluated with an "R" value of 1.0
only.
The fourth sensitivity analysis will examine the effect of
implementing an inspection and maintenance program for
evaporative control systems. By identifying and theoretically
preventing vehicle problems, this type of program would reduce
tampering and malmaintenance/defect losses, which are now only
affected by in-use RVP control. To date, I/M programs have
been implemented only for exhaust emission control equipment,
so only exhaust I/M was included in the base case. A
sensitivity analysis with an evaporative I/M program was
performed because of the possibility of such a program coming
into place in the late 1980's. As with the "no exhaust
benefits" case, only R = 1.0 was evaluated.
II. Methodology
A. Long-Term Analysis
The methodology used to estimate the long-term
(steady-state) costs, emission reductions, and resulting cost
effectiveness of controlling evaporative HC emissions through
equating in-use and certification gasoline RVPs along with
revisions to certification test procedure is detailed in this
section. ' The methodology for the year-round (12-month)
analysis will be presented first, followed by that of
summer-only (4-month) analyses. The year 2010 was used to
represent the long term, as the vehicle fleet would consist
entirely of post-1990 (i.e., controlled) vehicles by this time.
-------
6-4
Estimation of the 2010 non-California emission reductions
associated with the base case (including exhaust HC benefits,
without onboard refueling loss control and with no evaporative
I/M program) were simply taken from total inventory projections
of the previous chapter (see Table 5-12). Net and incremental
emission reductions were estimated for each long-term control
scenario (11.5-psi RVP down to 9.0-psi RVP in 0.5-psi
increments).* The sources of NMHC emission reductions include
motor vehicle evaporative and exhaust emissions, and gasoline
storage and distribution sources (i.e., bulk storage, Stage I,
and refueling).
The emission reductions estimated for the long-term
control scenarios are presented in Table 6-1 for the base case
and the four sensitivity analyses. Emission reductions are
detailed here in order to provide a perspective on the relative
contribution of various sources — motor vehicle evaporative
losses, motor vehicle exhaust emissions, refueling, bulk
storage, and Stage I. As shown, motor vehicle evaporative
emissions make up the largest controlled category, accounting
for 61 to 63 percent of total NMHC reductions in 2010 (assuming
the base case).
Estimation of the emission reductions associated with the
various sensitivity analyses vary in complexity. Elimination
of the RVP-related exhaust emission effect simply involves
removing the portion of the emission reduction attributable to
motor vehicle exhaust emission control (i.e., 215,000 tons in
2010) shown in Table 6-1. For the "lower baseline RVP" case,
emission reductions are simply calculated from a new baseline
— in-use RVP = 11.0 psi and certification fuel RVP = 9.0 psi
— instead of the 11.5/9.0 RVP baseline used in the base case.
In other words, in Table 6-1, emission reductions for this
sensitivity case are 262,000 tons lower than base case
reductions under all RVP scenarios, which represents the
difference between the 11.5/9.0 and the 11.0/9.0 baseline
inventories.
Consideration of the presence of onboard refueling loss
controls is only slightly more complex. Since in-use RVP
control affects even controlled refueling losses (by the same
proportion as uncontrolled emissions) and onboard controls
would be subject to some degree of tampering, some control of
refueling loss persists even if onboard controls are
implemented. Based on previous EPA studies, onboard controls
are at least 97 percent effective; accounting .for the projected
tampering incidence (the same as the then-current evaporative
control tampering rate), refueling emissions are expected to be
The uncontrolled baseline assumes an in-use fuel RVP of
11.5 psi and a certification fuel RVP of 9.0 psi.
-------
6-5
Table 6-1
Annual Emission Reductions Under
Long-Term Control Scenarios in 2010 (10^ Tons)*
In-Use = Cert. RVP (psi)
Case/Category
"Base Case":
- Evap.HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
"Lower Baseline" Case:**
- Evap. HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
"Onboard" Case:
- Evap. HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
"No Exhaust" Case
- Evap. HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
"Evap. I/M" Case:
- Evap. HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
*Non-Calitornia emission reductions only.
** Assumes baseline in-use RVP of 11.0 psi, instead of 11.5 psi
11.5
369
215
0
0
0
584
, . **
—
—
—
—
_
—
369
215
0
0
0
584
369
0
0
0
0
369
284
215
0
0
0
499
11.0
419
215
17
12
6
669
230
177
0
0
0
407
419
215
1
12
6
65T
419
0
17
12
6
454
305
215
17
12
6
555
10.5
468
215
34
25
13
75^
279
177
17
13
7
49T
468
215
2
25
13
723
468
0
34
25
13
540
324
215
34
25
13
611
10.0
516
215
51
38
20
840
327
177
34
26
14
578
516
215
3
38
20
792"
516
0
51
38
20
625
344
215
51
38
20
668
9.5
564
215
68
51
27
925
375
177
51
39
21
663
564
215
4
51
27
F6T
564
0
68
51
27
710
361
215
68
51
27
111
9.0
613
215
85
64
33
1010
424
177
68
52
27
T48
613
215
5
64
33
930
613
0
85
64
33
"795
378
215
85
64
33
775
-------
6-6
controlled by 94 percent in 2010 (i.e., essentially all models
in the fleet will be equipped with onboard controls).[1] Thus,
the 2010 emission reductions attributable to refueling loss
control are reduced by 94 percent, as indicated in Table 6-1.
As mentioned earlier, implementation of an onboard refueling
loss control program could also involve a revision of the
certification fuel RVP specification to 11.5 psi and a change
in evaporative test procedure (i.e., beginning with a saturated
canister). However, as mentioned before, these test procedure
revisions could be implemented without implementing onboard
refueling controls and, therefore, should not be inherently
associated with onboard refueling controls. Thus, the emission
reductions associated with changing the RVP of the test fuel
and the evaporative test procedure (the control of vehicle
evaporative and exhaust HC emissions at 11.5 psi RVP) will be
retained for this onboard sensitivity analysis. The 94-percent
reduction in refueling loss control due to implementation of an
onboard program reduces the overall effect of RVP control by up
to 8 percent in comparison to the base case.
Consideration of the presence of an effective inspection
and maintenance (I/M) program for evaporative control systems
is also somewhat complex. Evaporative I/M programs could
affect both the malmaintenance and defect effect and the
tampering effect associated with motor vehicle evaporative
emissions. In Chapter 2 of this study, specific vehicle
problems were classified as malmaintenance/defect or tampering
(see Table 2-14). By detecting and forcing repair of such
problems as a broken canister or damaged vacuum line
(malmaintenance/defect) or a missing canister or fuel cap
(tampering), an evaporative I/M program could reduce portions
of these excess evaporative emissions. It was assumed that
such a program could potentially address all types of
tampering, but only certain types of malmaintenance and
defects. (Appendix 6-A contains the analysis of the potential
for I/M to address the various specific types of malmaintenance
and defects) . An evaporative I/M program was assumed to be 70
percent effective in eliminating both tampering and applicable
malmaintenance and defects.[3] The estimated maximum portions
of hot-soak and diurnal emissions from carbureted and
fuel-injected vehicles that would potentially be affected by
I/M are shown in Table 6-2. The resulting 2010 motor vehicle
evaporative emission reductions associated with RVP control in
conjunction with an evaporative I/M program are shown in Table
6-1. In order to compare this case with the other sensitivity
cases shown in the table, a nationwide analysis (excluding
California) was performed, even though an evaporative I/M
program would most likely be implemented only in urban ozone
non-attainment areas. However, the relative impact of such a
program on emissions in just these urban areas would parallel
that indicated in the nationwide analysis. As shown in Table
6-1, overall emission reductions due to RVP control are 14-23
percent lower under this evaporative I/M sensitivity case than
for the base case.
-------
6-7
Table 6-2
Effect of Evaporative I/M on Malmaintenance/Defect Effect
and Tampering Rates for 1981+ Model Years (Baseline Case)
w/o Evaporative I/M (g/test)
w/ Evaporative I/M (g/test)*
% reduction in M&D
M&D Emission Rates (LDV & LDT)
FI
DI
.84
.39
54.0
HS
.93
.34
63.7
Garb.
DI
1.61
1.02
36.6
HS
1.24
.84
32.0
w/o Evaporative I/M
w/ Evaporative I/M*
Tampering Rates (%)
LDV Mileage
LDT Mileage
0
50K 100K
0
0
3.9
1.2
7.8
2.3
0
3.6
1.1
50K 100K
7.6
2.3
11.6
3.5
Assumes an evaporative I/M program efficiency of 70%
(i.e., 70% of tampering is caught, and 70% of each
addressable M&D problem is caught).
-------
6-8
Moving to the estimation of costs, the net cost of
commercial gasoline and motor vehicle-related controls are a
function of several individual components. These include: 1)
the refinery cost of reducing gasoline RVP, 2) the cost of
motor vehicle redesign, 3) the value of the increased energy
content of commercial gasoline, 4) the value of recovered or
prevented evaporative HC losses, and 5) the cost of increased
vehicle weight due to the enlarged canister. The combination
of these individual components is described below. The
detailed derivation of the individual vehicle- and fuel-related
control costs are provided in Chapters 3 and 4, respectively.
The only exception is the evaluation of the weight-related fuel
economy penalty, which is described in Appendix 6-B at the end
of this chapter. Like emission reductions, all costs are
determined on an annual basis.
The refinery costs of reducing RVP are taken from Table
4-3 of Chapter 4. For this 2010 scenario, the "with
investment" costs are most applicable and, as described in
Chapter 4, the average of the "open" and "fixed" NGL cases was
used. Nationwide (non-California) annual costs are simply
calculated by multiplying these refinery costs by nationwide
gasoline consumption (excluding California and off-highway
gasoline consumption) from EPA's MOBILES Fuel Consumption Model
(FCM) for the year 2010. [4] This annual consumption is 75
billion gallons (1.79 million barrels). These refinery costs
are summarized in Table 6-3 and do not vary with any of the
sensitivity cases except where the RVP of commercial gasoline
only rises to 11 psi. In this case, the cost of the first 0.5
psi of RVP control is avoided.
The costs of vehicle redesign, on a dollar-per-vehicle
basis, are taken from Table 3-6 in Chapter 3. These are
multiplied by Energy and Environmental Analysis (EEA) vehicle
sales projections for the year 2010 to determine annual
costs.[5] The resulting annual vehicle design costs are
summarized in Table 6-3 and do not vary with sensitivity case.
Reducing in-use gasoline RVP also increases the energy
density of the gasoline, which, in turn, results in increased
fuel economy in motor vehicles. The effects are summarized in
Table 4-11 of Chapter 4. The annual credit is estimated by
multiplying the increases in vehicular fuel economy of Table
4-11 by the non-California nationwide fuel consumption
described above and an estimated value of gasoline of $0.98 per
gallon. The resulting credits are shown in Table 6-3 for both
the base case, where R (the fraction of the increased energy
that is fully utilized by the engine) equals 1.0, and for the
sensitivity case assuming an R-value of 0.6. The credit for
the latter is simply 60 percent of the former.
-------
6-9
Table 6-3
Annual Costs Under Long-Term
Control Scenarios in 2010 (10°$/yr)
In-Use = Cert. RVP
Case /Category
"Base Case":
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
- Evap. Recov. Credit
- Weight Penalty
- Total Cost
"Lower Baseline" Case:**
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
- Evap. Recov. Credit
- Weight Penalty
- Total Cost
"Onboard" Case:
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
- Evap. Recov. Credit
- Weight Penalty
- Total Cost
"No Exhaust" Case:
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
- Evap. Recov. Credit
- Weight Penalty
- Total Cost
"Evap. I/M" Case:
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
- Evap. Recov. Credit
- Weight Penalty
- Total Cost
* For R = 1.0; when.R
** Ac cnme>=: hassline in
11.5
0
28
0
-196
8
-160
N.A.***
N.A.
N.A.
N.A.
N.A.
N.A.
0
28
0
-196
8
-160
0
28
0
-124
8
: - 88
0
28
0
-166
8
-no
= 0.6,
-use RVP
11.0
192
23
- 72
-224
7
- 75
0
23
0
-137
7
-107
192
23
- 72
-219
7
- 69
192
23
- 72
-152
7
2
192
23
- 72
-186
7
- 36
10.5
421
18
-163
-254
5
"~28
229
18
- 91
-165
5
- 4
421
18
-163
-243
5
38
421
18
-163
-181
5
100
421
18
-163
-205
5_
76
fuel economy credit
of 11.0 r>s i . inste;
10.0
686
14
-261
-283
3
159
494
14
-189
-194
3
128
686
14
-261
-267
3
~TJ5
686
14
-261
-210
3
232
686
14
-261
-224
3
~2"T8
(psi )
9.5
962
9
-366
-311
2
~296
770
9
-294
-222
2
~264
962
9
-366
-289
2
318
962
9
-366
-238
2
368
962
9
-366
-242
2
365
is reduced by
3d of 11.5 osi ,
9.0
1256
0
-477
-339
0
440
1064
0
-405
-251
0
"408
1256
0
-477
-312
0
"467
1256
0
-477
-267
0
~BT2
1256
0
-477
-266
0
513
40%.
•
*** Not Applicable.
-------
6-10
The methodology for valuing recovered/prevented
evaporative HCs from the gasoline storage and distribution
system, vehicle refueling, and motor vehicle operation was
derived in Section VI of Chapter 4. There, the value of HC
(butane) control was determined to be $335.26 per ton. The
overall emission reductions shown in Table 6-1 for the various
cases can simply be multiplied by this value to derive the
annual recovery credits. These are shown in Table 6-3.
As alluded to in Chapter 3, redesigning motor vehicles for
higher volatility would increase the weight of the motor
vehicle slightly, as a larger canister would be required. This
weight increase would cause the motor vehicle to consume more
fuel over the course of its lifetime than if the vehicle did
not have added weight due to redesign. This weight penalty and
associated discounted lifetime costs per vehicle are derived in
Appendix 6-B at the end of this chapter and are summarized in
Table 6-B-2. These per-vehicle costs are multiplied by the
sales projections described earlier to derive annual costs,
which are summarized in Table 6-3.
The net costs for each control scenario are then
calculated by simply adding costs and subtracting credits. The
long-term, steady-state cost effectiveness is determined by
simply dividing net annual cost by annual emission reduction.
The calculations for the 4-month analysis are very similar
to those for the 12-month period. Again, the 4-month analysis
assumes commercial (in-use) fuel RVP control is implemented
only during a 4-month summer period. Of course, as
certification fuel changes affect vehicle design, year-round HC
control is inherently provided and, thus, no option for
seasonal control is available with that approach.
Based on the above assumptions, emission reductions for a
4-month summer period (shown in Table 6-4) are simply one-third
of those developed for the 12-month analysis. Any emission
reductions due to vehicle-related control during the non-summer
period are ignored.
The cost calculations, however, must take into account the
fact that vehicle-related costs and credits occur year-round,
even though any commercial fuel volatility controls are
removed. Thus, 4-month refinery costs and credits due to
increased fuel density are simply one-third of the year-round
values. Vehicle redesign costs and the associated weight
penalty are the same as the year-round values, since all
vehicles must be modified in any case. However, derivation of
the evaporative recovery/prevention credit is more complex.
During the summer period, this credit is simply one-third of
the year-round figure since both fuel- and vehicle-related
controls are fully operable. However, some additional emission
-------
6-11
Table 6-4
4-Month Emission Reductions Under
Long-Term Control Scenarios in 2010 (103 Tons)*
In-Use = Cert. RVP (psi)
123
72
0
0
0
195
139
72
6
4
2
223
157
72
11
8
4
252
171
72
17
13
7
280
187
72
23
17
9
Toe
205
72
28
21
11
337
Case/Category 11.5 11.0 10.5 10.0 9.5 9.0
"Base Case":
- Evap. HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
"Lower Baseline" Case:**
- Evap. HC - 77 95 109 125
- Exhaust HC - 59 59 59 59
- Refueling - 0 5 11 17
- Bulk Storage - 0 4 9 13
- Stage I - 0 2 5 7
- Total - 136 165 193 221
"Onboard" Case:
- Evap. HC 123 139 157 171 187 205
- Exhaust HC 72 72 72 72 72 72
- Refueling 001 112
- Bulk Storage 0 4 8 13 17 21
- Stage I 0 2 4 7 9 11
- Total 195 217 242 264 I8~6~ 311
"No Exhaust" Case:
- Evap. HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
"Evap. I/M" Case:
- Evap. HC
- Exhaust HC
- Refueling
- Bulk Storage
- Stage I
- Total
123
0
0
0
0
123"
139
0
6
4
2
151
157
0
11
8
4
180
171
0
17
13
7
208
187
0
23
17
9
236
205
0
28
21
11
265
94
72
0
0
0
166
101
72
6
4
2
185
109
72
11
8
4
204
114
72
17
13
7
223
120
72
23
17
9
24T
126
72
28
21
11
238
* Non-Cali fornia emission reductions only.
** Assumes baseline in-use RVP of 11.0 psi, instead of 11.5 psi
-------
6-12
control occurs in the non-summer period in all scenarios where
vehicle redesign is required (i.e., except for the 9.0-psi RVP
case, where no change is made to certification fuel
volatility). These non-summer emission reductions were
estimated by running MOBILES (described in Chapter 5) to
simulate a commercial fuel RVP of 11.5 psi with certification
volatilities varying between 9.5 and 11.5 psi RVP. The
development of these non-summer credits for the 4-month
analysis is described in Appendix 6-C. The resulting summer
and non-summer credits, as well as all the other 4-month costs
and credits, are summarized in Table 6-5.
The cost effectiveness for summer-only emission reductions
is again calculated by dividing the net 4-month cost by the
4-month emission reductions. All cost effectiveness estimates
(both 12-month and 4-month) will be presented in Section III in
Tables 6-6 through 6-21 and shown graphically in Figures 6-1
through 6-8. Their relative significance will be analyzed and
interpreted as the estimates are presented.
B. Short-Term Analysis
As alluded to throughout this study, ozone control is the
primary focus of the various HC reduction strategies being
evaluated. Any reductions achievable in the shorter term could
be important in view of the Clean Air act requirement that all
urban areas be in attainment of the ozone NAAQS by 1987.
Although the long-term strategy is to ensure that certification
fuel RVP is representative of in-use levels, a short-term
strategy could be to control in-use fuel RVP to a level lower
than the long-term specification in order to achieve the
additional benefits associated only with in-use RVP control.
These benefits include: 1) an immediate effect on the entire
motor vehicle fleet, including older vehicles not affected by
the revised certification fuel, and 2) further control of
in-use RVP-related emissions such as gasoline storage,
distribution, refueling, and vehicular emissions due to
tampering, malmaintenance and defects.
Therefore, a short-term analysis has been performed to
focus on the incremental costs and emission reductions of
additional in-use RVP control over and above the long-term RVP
control strategies. This analysis focuses on the years 1988,
1990, 1992, 1995, 1997 and 2000. As before, the 12-month
analysis is described first, followed by the 4-month analysis.
Year-round non-California HC emission inventories with
additional short-term in-use RVP control were estimated in
Chapter 5 and summarized in Table 5-14; emission reductions
were calculated from this table and used directly for the base
case here. Modification of these estimates for the various
sensitivity cases is handled in exactly the same manner as
described for the long-term analysis. As these emission
reductions are due solely to in-use RVP control, the emission
reductions for the 4-month analysis are simply one-third of the
year-round reductions.
-------
6-13
Table 6-5
Case/Category
4-Month Costs Under Long-Term
Control Scenarios in 2010 (lO^S/yr)
In-Use = Cert.
RVP ( ps i )
11.5
11.0
10.5
10.0
9.5
"Base Case":
- Refinery Cost 0
- Vehicle Cost 28
- Fuel Econ. Credit* 0
- Evap. Recov. Credit -191
- Weight Penalty 8
- Total Cost -155
"Lower Baseline" Case:**
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
-.Evap. Recov. Credit
- Weight Penalty
- Total Cost
"Onboard" Case:
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
- Evap. Recov. Credit
- Weight Penalty
- Total Cost
"No Exhaust" Case:
- Refinery Cost
- Vehicle Cost
- Fuel Econ. Credit*
- Evap. Recov. Credit
- Weight Penalty
- Total Cost
"Evap. I/M" Case:
- Refinery Cost 0
- Vehicle Cost 28
- Fuel Econ. Credit* 0
- Evap. Recov. Credit -162
- Weight Penalty 8
- Total Cost -126
9.0
N.A***
N.A.
N.A.
N.A.
N.A.
N.A.
0
23
0
-132
7
-102
76
18
- 31
-131
5
- 63
165
14
- 63
-125
3
- 6
257
9
- 98
-113
2
56
355
0
-135
- 82
0
138
0
28
0
-191
8
-155
64
23
- 24
-194
7
-124
140
18
- 55
-189
5
- 81
229
14
- 87
-179
3
- 20
321
9
-122
-147
2
63
419
0
-159
-103
0
157
0
28
0
-119
8
^57
64
23
- 24
-137
7
^T7
140
18
- 55
-146
5
=~35
229
14
- 87
-146
3
T2~
321
9
-122
-127
2
~ST
419
0
-159
- 87
0
T73
321
9
-122
-154
2
-36
257
9
- 98
-113
2
56
321
9
-122
-147
2
63
321
9
-122
-127
2
~§T
321
9
-122
- 97
2
113
419
0
-159
-112
0
148
355
0
-135
- 82
0
138
419
0
-159
-103
0
157
419
0
-159
- 87
0
T73
419
0
-159
- 85
0
175
**
***
For R = 1.0; when R = 0.6, fuel economy credit is reduced by
Assumes baseline in-use RVP of 11.0 psi, instead of 11.5 psi,
Not Applicable.
40%.
-------
6-14
The year-round costs of additional in-use RVP control
consist of only three parts: 1) refinery costs, 2) credit due
to increased fuel density; and 3) credit due to recovered/
prevented evaporative emissions. As before, the refinery cost
of each 0.5 psi of RVP control was taken from Table 4-3. Here,
however, the "no-investment" costs were used for 1988 and 1990,
as there would not likely be time for refiners to invest in
capital equipment for the most economic RVP control refinery
processes. "With investment" costs were assumed to apply for
later years as: 1) at least five years of leadtime should be
available prior to 1992 and 2) the short-term control would be
in place sufficiently long to justify capital investment (i.e.,
5-10 years). These costs per barrel were again multiplied by
on-highway, non-California fuel consumption projections from
EPA's MOBILES Fuel Consumption Model.[4]
The density-related fuel economy credit for each 0.5 psi
of additional RVP control is again taken from Table 4-11 and
multiplied by non-California fuel consumption. The evaporative
emission recovery/prevention credit is again obtained by
multiplying the emission reductions calculated from Table 5-14
for additional in-use RVP control . by the butane value of
$335.26 per ton. Since, in this analysis of additional
short-term in-use RVP control, all costs are related to fuel
control and none to vehicle control, the 4-month seasonal
control costs are simply one-third of the year-round costs.
The cost effectiveness estimates for both the 12-month and
the 4-month analyses are simply net costs divided by emission
reductions. These estimates of cost/ton will be summarized
along with long-term estimates in Tables 6-6 through 6-21 and
Figures 6-1 through 6-8 in the following section.
III. Results
Using the methodologies described in the previous section,
12-month and 4-month costs and emission reductions were
determined for each of the long- and short-term RVP control
scenarios. Using these results, cost effectiveness estimates
(control costs per ton) were determined as a basis for
comparison of the various alternatives. This section focuses
on these cost effectiveness estimates for the base case and for
each of the sensitivity cases (i.e., -lower baseline RVP,
onboard, no exhaust benefits, and evaporative I/M). The base
case and the first two sensitivity cases are evaluated using
"R" values of both 1.0 and 0.6; the other two cases assume R =
1.0 only. Results of the 12-month and 4-month analyses for
each of the cases will be presented in tabular form and their
relative significance will be discussed. The 12-month tables
will be supplemented by figures showing emission reductions
over time, with constant cost effectiveness lines superimposed.
-------
6-15
A. "Base" Case
The base case represents the combination of the current
regulatory situation and EPA's best technical estimates. As
outlined earlier, this includes: 1) no onboard or Stage II
control of refueling losses, 2) no evaporative I/M program, 3)
full utilization of increased gasoline energy content and
recovered/prevented evaporative emissions by vehicles (i.e., R
= 1.0), and 4) an assumption that in-use RVP will continue to
rise until ASTM limits are reached (i.e., Class C summertime
RVP will equal 11.5 psi, on average, by 1988).
Twelve-month emission reductions, costs, and cost
effectiveness estimates are shown for the base case in Table
6-6; year-round reductions and costs are assumed. Results of
this 12-month analysis are also shown graphically in Figure
6-1. Emission reductions over time are shown for each RVP
control scenario. Constant cost effectiveness lines (dashed)
have been drawn to facilitate comparison of the various control
options. For instance, a specific cost-per-ton line can be
traced over time and across RVP control scenarios to indicate
equivalent control approaches for each year.
The top portion of Table 6-6 presents the long-term (2010)
analysis, where certification fuel and in-use fuel RVPs are
made equal. The 11.5-psi scenario represents purely
vehicle-oriented control as it only requires a change in
certification fuel RVP (i.e., in-use RVP is expected to average
11.5 psi); the 9.0-psi case, on the other hand, requires
primarily in-use fuel control, with improvements to the
evaporative emission test procedure but no change in the
certification fuel. All of the intermediate RVP scenarios
combine the fuel-related and vehicle-oriented approaches.
Table 6-6 shows that, by 2010, the vehicle-oriented approach
(11.5-psi scenario) is significantly more cost-effective than
the scenarios involving fuel control, and actually results in
an overall savings (i.e., negative $/ton). This occurs because
fuel economy credits from recovered evaporative emissions
outweigh the costs of vehicle redesign. However, additional
incremental emission control is achievable via more in-use
fuel-oriented programs at increasing cost per ton.
The center and bottom portions of Table 6-6 summarize the
short-term analysis, where the strategy is to control in-use
fuel RVP to a level lower than the long-term certification
specification; after a specified time, in-use fuel control
would be relaxed to the long-term certification RVP level
chosen via the long-term analysis. The short-term analysis
focuses on years between 1988 and 2000 (inclusive). The first
column ill this portion of the table shows the increment between
the long-term certification/in-use specifications and the
short-term in-use RVP; 0.5-psi increments are shown (e.g.,
long-term RVP = 11.5, short-term in-use RVP lower at 11.0).
-------
6-16
Table 6-6
"Base" Case; 12-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (ps i)
11.5
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
584
669
755
840
925
1010
Incr.
584
85
86
85
85
85
Net Cost*
(106 $/Yr)
Net
-160
- 75
28
159
296
440
Incr.
-160
85
102
132
137
144
Cost
Effectiveness
($/Ton)
Net
-274
-112
37
190
320
435
Incr.
-274
998
1197
1542
1619
1681
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
283
255
216
193
169
1990
260
233
196
174
155
1992
217
196
166
151
137
1995
167
151
131
123
114
1997
138
128
113
107
105
2000
110
105
95
94
92
Incremental
Control Step
RVP (ps i)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness
1988
395
598
1036
1200
1551
1990
438
685
1101
1316
1666
1992
239
425
670
841
1046
1995
382
607
883
1053
1244
($/Ton)**
1997
586
840
1154
1327
1490
2000
697
972
1262
1389
1571
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and
later assume investment has taken place; refinery costs are
midway between those of open and fixed NGL purchase
scenarios.
-------
Figure 6-1
NON-CALIF. EMISSION REDUCTION/COST
BASE CASE*
1200
EFF
1996
2000
2004
T
1988
YEAR
*With exhaust emission effect, without onboard, no evaporative I/M, with R = 1.0.
200B
-------
6-18
The incremental values (based on 0.5-psi intervals) at a given
in-use RVP (e.g., 10.0 psi) are the same regardless of
long-term certification fuel RVP (e.g., 10.5, 11.0, or 11.5
psi). It should be noted that the emission reductions
associated with equating certification and in-use RVPs (i.e.,
the long-term strategy) are not included in the center portion
of the table, but rather only the additional reductions that
can be obtained with short-term additional in-use control. The
cost/ton estimates for each of these control increments are
shown in the bottom portion of the table.
As indicated in Table 6-6, short-term cost effectiveness
($/ton) rises between 1988 and 1990, but then falls in 1992.
This is easily explained — the 1988 and 1990 analyses assume
no investment on the part of refineries, while post-1990
calculations use control costs based on capital investments
which improve the efficiencies of refinery operations.
Therefore, later-year costs of in-use RVP control are reduced
and resultant cost/ton in 1992 is lower than in 1990. However,
while in-use RVP control costs remain rather constant between
1992 and 2000, emission reductions achievable with in-use RVP
control decrease with time as the vehicle fleet gradually turns
over (i.e., vehicles with larger canisters designed for the
revised long-term certification RVP, beginning with the 1990
model year, start to make up more and more of the in-use
fleet). Therefore, incremental cost/ton rises between 1992 and
2000 and tends to approach the long-term figures shown in the
top portion of Table 6-6. Actually, if 2010 estimates were
shown for short-term additional in-use RVP control, the
cost/ton would be slightly higher than the long-term
incremental estimates because the vehicle fleet would consist
entirely of post-1990 vehicles which were overdesigned for the
lower in-use RVP level.
The 4-month analysis for the base case is summarized in
Table 6-7. As described in Section II of this chapter, 4-month
emission reductions are simply one-third of the 12-month
estimates; however, control costs are less straightforward and
represent more than one-third of annual costs. Therefore, as
indicated in Table 6-7, the 4-month cost effectiveness is
arithmetically higher than the 12-month estimates shown
previously.
The base case results discussed above are based on a
100-percent utilization (R = 1.0) of the increased fuel energy
density. As mentioned earlier, there is some uncertainty in
this estimate as the very limited data available indicate a
wide range of efficiencies. Therefore, to determine the
sensitivity of the base case results to this "R" value,
calculations were repeated using a 60-percent utilization
efficiency (i.e., R = 0.6 instead of R = 1.0). The results of
this sensitivity analysis are shown for 12-month and 4-month
-------
6-19
Table 6-7
"Base" Case: 4-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
Emission
Reductions
11,
11.
10,
10,
9,
9.0
(10 Tons/Yr)
Net
195
223
252
280
308
337
Incr.
195
28
29
28
28
28
Net Cost*
(106 $/Yr)
Net
-155
-126
- 85
- 25
56
148
Incr.
-155
30
41
60
81
92
Cost
Effectiveness
($/Ton)
Net
- 799
- 563
- 336
- 89
182
440
Incr.
- 799
1045
1442
2092
2880
3229
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
94
85
72
64
56
1990
87
78
65
58
52
1992
72
65
55
50
46
1995
55
50
44
41
38
1997
46
43
38
36
35
2000
37
35
32
31
30
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5 ,
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)**
1988
395
598
1036
1200
1551
1990
434
690
1104
1323
1683
1992
247
453
728
972
1234
1995
412
684
1066
1430
1756
1997
633
955
1404
1866
2177
2000
797
1170
1708
2279
2732
' Bonner sT~Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and
later assume investment has taken place; refinery costs are
midway between those of open and fixed NGL purchase
scenarios.
-------
6-20
control periods .in Tables 6-8 and 6-9, respectively. Figure
6-2 presents the results of the 12-month analysis in the same
manner as in Figure 6-1. As indicated in the tables, the lower
R-value results in slightly higher costs (due to lower fuel
economy credits) and, thus, arithmetically higher cost
effectiveness. For example, in the 12-month analysis of the
9.0-psi long-term scenario, incremental cost/ton increases by
31 percent, or by $520/ton, with the lower R-value. However,
as with the R = 1.0 case, net savings (negative $/ton) are
still projected for the 11.5-psi and 11.0-psi long-term
scenarios.
B. "Lower Baseline RVP" Case
The base case analyzed above assumes that, by 1988,
average summer in-use RVPs will have reached the ASTM limits
recommended for various areas (see Chapter 2, Section IV).
This second sensitivity analysis examines the possibility that
in-use RVP will not actually reach the ASTM limits by 1988, but
will instead stay at current levels (i.e., roughly 0.5 psi
below ASTM limits). Since our analysis focuses on Class C
summertime RVPs, this changes the baseline in-use RVP of the
study from 11.5 to 11.0 psi. (The baseline certification RVP
is 9.0 psi in both cases.) Therefore, emission reductions from
baseline are lower than under the base case discussed in
Section A, as uncontrolled levels are lower (based on 11.0 psi
instead of 11.5 psi). The sensitivity of lower baseline RVP
was analyzed for both the 12-month and 4-month control cases.
The results are summarized in Tables 6-10 and 6-11,
respectively, for R equal to 1.0, and Tables 6-12 and 6-13,
respectively, for R equal to 0.6. The 12-month results are
also shown graphically for R = 1.0 and R = 0.6 in Figures 6-3
and 6-4, respectively.
As indicated by comparing these four tables with the
previous four, a lower baseline RVP results in reduced net
emission benefits and arithmetically higher net cost
effectiveness. For example, with the 12-month long-term
9.0-psi case, net reductions are 26 percent lower and net costs
are just slightly lower, which results in a 26-percent increase
in overall cost/ton. However, as incremental cost/ton is the
most relevant, it is important to note that in the 12-month
analysis the incremental values below the new 11.0-psi RVP
baseline remain essentially unchanged from the base case. In
both cases, the 12-month long-term 9.0-psi scenario has an
incremental cost/ton of almost $1700. The effect of the lower
R value is the same as under the base case.
-------
6-21
Table 6-8
"Base" Case; 12-Month Analysis, R = 0.6
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
11.5
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
584
669
755
840
925
1010
Incr.
584
85
86
85
85
85
Net Cost*
(106 $/Yr)
Cost
Effectiveness
($/Ton)
Net
-160
- 46
93
264
444
631
Incr,
-160
114
139
171
179
188
Net
-274
- 69
123
314
479
624
Incr.
-274
1334
1625
2001
2114
2201
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
283
255
216
193
169
1990
260
233
196
174
155
1992
217
196
166
151
137
1995
167
151
131
123
114
1997
138
128
113
107
105
2000
110
105
95
94
92
Incremental
Control Step
RVP (psi) 1988:
11.5-11.0 507
11.0-10.5 756
10.5-10.0 1235
10.0- 9.5 1437
9.5- 9.0 1839
Incremental Cost Effectiveness ($/Ton)**
556
840
1329
1572
1972
1992
376
605
932
1128
1328
1995
553
830
1201
1391
1628
1997
770
1074
1480
1668
1865
2000
944
1281
1679
1809
2035
*Bonner& Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and
later assume investment has taken place; refinery costs are
midway between those of open and fixed NGL purchase
scenarios.
-------
6-22
Table 6-9
"Base" Case; 4-Month Analysis, R = 0.6
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
Emission
Reductions
.5
,0
,5
11,
11,
10,
10.0
9.5
9.0
(10 Tons/Yr)
Net
195
223
252
280
308
337
Incr.
195
28
29
28
28
28
Net Cost*
(106 $/Yr)
Net
-155
-116
- 63
10
105
212
Incr.
-155
39
53
73
95
107
Cost
Effectiveness
(ft/Ton)
Net
- 799
- 520
- 250
35
340
629
Incr.
- 799
1382
1871
2551
3375
3749
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
94
85
72
64
56
1990
87
78
65
58
52
1992
72
65
55
50
46
1995
55
50
44
41
38
1997
46
43
38
36
35
2000
37
35
32
31
30
Incremental
Control Step _
RVP (ps i) 1988
11.5-11.0 507
11.0-10.5 756
10.5-10.0 1235
10.0- 9.5 1437
9.5- 9.0 1839
Incremental Cost Effectiveness ($/Ton)**
1990
552
845
1332
1578
1989
1992
384
633
990
1258
1570
1995
584
907
1383
1768
2141
1997
817
1188
1729
2207
2553
2000
1044
1479
2124
2699
3196
**
Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
1988 and 1990 costs are based on no investment? 1992 and
later assume investment has taken place; refinery costs are
midway between those of open and fixed NGL purchase
scenarios.
-------
Figure 6-2
NON-CALIF. EMISSION REDUCTION/COST EFF
BASE CASE WITH R = 0.6
o
8
O
O
Ul
flC
O
bl
1988
200B
(O
Ul
-------
6-24
Table 6-10
"Lower Baseline RVP" Case; 12-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(10 Tons/Yr)
Net
407
493
578
663
748
Incr.
407
86
85
85
85
Net Cost*
(106 $/Yr)
Net
-107
- 4
128
264
408
Incr.
-107
103
132
136
144
Cost
Effectiveness
($/Ton)
Net
-263
- 8
221
399
546
Incr,
-263
1207
1541
1611
1685
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i )
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
1988
255
216
193
169
Emission Reduction (10
1990 1992 1995
233 196 151
196 166 131
174 151 123
155 137 114
Tons)
1997
128
113
107
105
2000
105
95
94
92
Incremental
Control Step
RVP (ps i)
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)
**
1988
598
1036
1200
1551
1990
685
1101
1316
1666
1992
425
670
841
1046
1995
607
883
1053
1244
1997
840
1154
1327
1490
2000
972
1262
1389
1571
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
6-25
Table 6-11
"Lower Baseline" Case; 4-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(10 Tons/Yr)
Net
136
165
193
221
249
Incr.
136
29
28
28
28
Net Cost*
(106 $/Yr)
Net
-102
-63
-6
56
138
Incr,
-102
39
57
62
82
Cost
Effectiveness
($/Ton)
Net
-755
-384
-32
253
552
Incr.
-755
1379
1996
2204
2866
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i)
11.0-10.5
10.5-10.0
10.0-9.5
9.5-9.0
1988
85
72
64
56
Emission Reduction (10
1990 1992 1995
78 65 50
65 55 44
58 50 41
52 46 38
Tons)
1997
43
38
36
35
2000
35
32
31
30
Incremental
Control Step
RVP (ps i)
11.0-10.5
10.5-10.0
10.0-9.5
9.5-9.0
Incremental Cost Effectiveness ($/Ton)**
2000
1170
1708
2279
2732
**
Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken placer refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
6-26
Table 6-12
"Lower Baseline RVP" Case; 12-Month Analysis, R = 0.6
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use
Revised
Cert. Fuel
RVP (ps i)
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
407
493
578
663
748
Incr.
407
86
85
85
85
Net Cost*
(106 $/Yr)
Cost
Effectiveness
($/Ton)
Net
-107
33
204
382
570
Incr.
-107
139
171
178
188
Net
-263
66
352
576
763
Incr,
-263
1633
2000
2108
2205
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i)
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reduction (10"
1988
255
216
193
169
1990
233
196
174
155
1992
196
166
151
137
1995
151
131
123
114
Tons)
1997
128
113
107
105
2000
105
95
94
92
Incremental
Control Step
RVP (psi)
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)
**
1988
756
1235
1437
1839
1990
840
1329
1572
1972
1992
605
932
1128
1328
1995
830
1201
1391
1628
1997
1074
1480
1668
1865
2000
1281
1679
1809
2035
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
6-27
Table 6-13
"Lower Baseline" Case; 4-Month Analysis, R = 0.6
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (ps i)
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
136
165
193
221
249
Incr,
136
29
28
28
28
Net Cost*
(106 $/Yr)
Net
-102
-51
19
95
192
Incr,
-102
51
70
76
96
Cost
Effectiveness
($/Ton)
Net
-755
-310
99
431
769
Incr,
-755
1805
2455
2701
3386
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i )
11.0-11.5
10.5-10.0
10.0-9.5
9.5-9.0
1988
85
72
64
56
Emiss
1990
78
65
58
52
ion Reduction (10
1992 1995
65 50
55 44
50 41
46 38
Tons)
1997
43
38
36
35
2000
35
32
31
30
Incremental
Control Step
RVP (ps i)
11.0-10.0
10.5-10.0
10.0-9.5
9.5-9.0
Incremental Cost Effectiveness ($/Ton)**
1988 1990 r9~9219^519^7 2000
756.
1235
1437
1839
845
1332
1578
1989
633
990
1258
1570
907
1383
1768
2141
1188
1729
2207
2553
1479
2124
2699
3196
*Bonner&Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
Figure 6-3
NON-CALIF. EMISSION REDUCTION/COST EF
1200
1100 -
LOW RVP BASELINE CASE
R
O
8
O
O
Ul
(XL
O
Ul
1988
2008
KJ
00
-------
Figure 6-4
NON-CALIF. EMISSION REDUCTION/COST EF
O
8
O
o
ui
O
UI
1200
LOW RVP BASELINE CASE WITO R = 0.6
1988
2008
NJ
VO
-------
6-30
C. "With Onboard Control" Case
The third sensitivity case examines the effect of an
onboard refueling loss control program on the RVP control
measures being examined in this report. Because an onboard
rulemaking would likely be running about one year ahead of any
evaporative control rule, an onboard implementation date of
1989 was assumed. However, a year's delay in the onboard
rulemaking (if decided upon) — meaning an implementation date
of 1990 — would not be expected to have a great impact on the
results of this sensitivity analysis. For all years except
1988 (pre-onboard control), the emission reductions are
somewhat lower than under the base case because onboard control
would capture a certain percentage of the reductions in
refueling losses previously attributed to in-use RVP control.
As indicated earlier in Table 6-1, the overall fleetwide
efficiency of onboard control (including tampering) will be
approximately 94 percent by the year 2010; therefore, emission
reductions in the refueling loss category were reduced by this
percentage under the onboard sensitivity case. Overall onboard
efficiencies assumed for 1990, 1992, 1995, 1997, and 2000 are
as follows: 22, 41, 62, 73, and 83 percent, respectively.
The emission reductions, costs, and resulting cost
effectiveness estimates for this onboard control sensitivity
case are presented in Tables 6-14 through 6-17. As before,
both 12-month and 4-month analyses are summarized, and the
sensitivity of "R" is also examined. The results of this
onboard control sensitivity case are shown graphically for the
12-month analysis in Figures 6-5 and 6-6, with R = 1.0 and R =
0.6, respectively. The effect of implementing onboard
refueling controls is a slight worsening of the cost
effectiveness for the various RVP control strategies. For
example, in the 12-month, R = 1.0 onboard analysis (Table
6-14), the incremental emission reductions in 2010 are roughly
19 percent lower than with the base case (69,000 tons compared
to 85,000 tons). Incremental costs are from 3 to 7 percent
higher, resulting in a cost/ton that is 28-31 percent higher
(depending on RVP scenario).
D. "Without Exhaust Benefits" Case
As discussed in Chapter 2, lower RVP fuels have been shown
to produce lower exhaust HC emissions. Based on testing to
date, this effect is statistically significant. The base case
discussed in Section A above includes these exhaust HC
reductions. In order to illustrate the impact of these
particular benefits on the cost/ton estimates made in the base
case, the sensitivity of eliminating these exhaust HC
reductions was examined here.
-------
6-31
Table 6-14
"Onboard" Case: 12-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi )
11.5
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
584
653
723
792
861
930
Incr.
584
69
70
69
69
69
Net Cost*
(106 $/Yr)
Cost
Effectiveness
($/Ton)
Net
-160
-69
38
175
318
467
Incr,
-160
91
108
137
142
149
Net
-274
-106
53
222
369
502
Incr .
-274
1305
1550
1976
2076
2147
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
283
255
216
193
169
1990
256
230
191
171
152
1992
210
189
160
144
130
1995
157
141
121
113
104
1997
127
116
102
96
94
2000
98
91
83
81
78
Incremental
Control Step _
RVP (ps i) 1988
11.5-11.0 395
11.0-10.5 598
10.5-10.0 1036
10.0- 9.5 1200
9.5- 9.0 1551
Incremental Cost Effectiveness ($/Ton)**
2000
1990
451
700
1128
1359
1713
1992
258
454
710
899
1122
1995
427
673
992
1173
1406
1997
668
954
1306
1523
1695
828
1164
1503
1673
1874
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and
later assume investment has taken place; refinery costs are
midway between those of open and fixed NGL purchase
scenarios.
-------
6-32
Table 6-15
"Onboard" Case; 4-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
11.5
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
195
218
241
264
287
310
Incr.
195
23
23
23
23
23
Net Cost*
(106 $/Yr)
Net
Incr.
-155
32
43
61
83
94
Cost
Effectiveness
($/Ton)
Net
-799
-569
-336
-74
221
507
Incr .
-799
1364
1853
2652
3632
4052
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0-9.5
9.5-9.0
Emission Reductions (10 Tons)
1988
94
85
72
64
56
1990
85
77
64
57
51
1992
70
63
53
48
43
1995
52
47
40
38
35
1997
42
39
34
32
31
2000
33
30
28
27
26
Incremental
Control Step
RVP (ps i)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)**
1988 1990 1992 1995 1997 2000
395
598
1036
1200
1551
448
706
1131
1366
1730
267
483
770
1036
1320
459
755
1190
1582
1971
719
1080
1582
2127
2461
941
1391
2015
2710
3220
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
6-33
Table 6-16
"Onboard" Case: 12-Month Analysis, R = 0.6
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
11.5
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
584
653
723
792
861
930
Incr.
584
69
70
69
69
69
Net Cost*
(106 $/Yr)
Cost
Effectiveness
($/Ton)
Net
Incr,
-160
119
144
176
184
193
Net
-274
-62
143
354
539
707
Incr.
-274
1719
2077
2541
2686
2787
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i )
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
283
255
216
193
169
1990
256
230
191
171
152
1992
210
189
160
144
130
1995
157
141
121
113
104
1997
127
116
102
96
94
2000
98
91
83
81
78
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)**
1988 1990 1992 1995 1997 2000
507
756
1235
1437
1839
571
858
1360
1621
2026
400
641
982
1200
1477
690
911
1337
1540
1830
868
1211
1666
1906
2113
1106
1519
1982
2163
2412
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
6-34
Table 6-17
"Onboard" Case; 4-Month Analysis, R = 0.6
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
11.5
11.0
10.5
10.0
9.5
9.0
Emission
Reductions
(103 Tons/Yr)
Net
195
218
241
264
287
310
Incr .
195
23
23
23
23
23
Net Cost*
(106 $/Yr)
Net
-155
-114
- 59
15
112
221
Incr,
-155
41
55
74
97
109
Cost
Effectiveness
($/Ton)
Net
-799
-525
-246
58
391
712
Incr.
-799
1778
2380
3217
4242
4692
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i )
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
94
85
72
64
56
1990
85
77
64
57
51
1992
70
63
53
48
43
1995
52
47 .
40
38
35
1997
42
39
34
32
31
2000
33
30
28
27
26
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)**
1988
507
756
1235
1437
1839
1990
568
863
1363
1628
2044
1992
409
669
1042
1337
1674
1995
641
993
1536
1950
2395
1997
919
1336
1942
2510
2879
2000
1219
1746
2494
3199
3758
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
Figure 6-5
NON-CALIF. EMISSION REDUCTION/COST EFF
WITH ONBOARD
V>
I
o
8
Z
O
o
Ul
(XL
O
u
o -*
1988
1992
1996
1 T
2004 2008
o>
Ul
YEAR
-------
Figure 6-6
NON-CALIF. EMISSION REDUCTION/COST EFF
WITH ONBOARD AND R = 0.6
Ul
1988
2008
T
UJ
-------
6-37
Tables 6-18 and 6-19 summarize the cost effectiveness,
etc., of the various RVP control strategies without benefits in
the exhaust HC category. (The sensitivity of the R-value was
not evaluated for this case.) The 12-month results are also
shown in Figure 6-7. For this sensitivity case, base-case
emission reductions were simply reduced by the amount of
benefits previously attributed to exhaust emissions. As
indicated earlier in Table 6-1, this amount was estimated to be
215,000 tons in 2010; however, for earlier years before the
fleet has completely turned over with new vehicles, the tonnage
attributed to exhaust reductions varies with RVP. (See details
on this in Chapter 2, Section V.) The fuel economy credit due
to increased energy content does not change from base case
because the same amount of butane is still being removed from
the fuel. However, the evaporative recovery/prevention credit
is lower with this sensitivity case because the total HC
emission reductions used to calculate this credit are lower if
exhaust HC reductions are not included. This reduction in
overall emission benefits, coupled with the slight increase in
overall costs, results in slightly higher net costs per ton.
As shown in Tables 6-18 and 6-19, the elimination of exhaust HC
benefits predictably increases the short-term $/ton estimates
by as much as 27 percent in 1988. However, in the long-term
2010 analysis, 12-month incremental emission reductions and
incremental costs are the same as in the base case, so 2010
costs per ton do not change on the increment.
E. "Evaporative I/M Program" Case
The final sensitivity analysis examines the impact an
effective inspection and maintenance . (I/M) program for
evaporative emission controls would have on the cost
effectiveness of RVP control strategies. For purposes of this
analysis, this evaporative I/M program is assumed to be
implemented nationwide by 1988 (the first projection year
examined). As discussed earlier, such a program would most
likely be initiated only in urban ozone non-attainment areas,
but the relative impact would parallel the nationwide analysis
in terms of percent reduction in emissions (to be demonstrated
below). Through the detection and prevention of certain
vehicle problems, the program is assumed to eliminate 70
percent of certain types of malmaintenance and defects and 70
percent of all evaporative system tampering (i.e., missing
canisters and missing fuel caps). Contribution of
malmaintenance/defects and tampering to the excess evaporative
problem are outlined in Chapter 2, Section V. Details of the
adjustments made to the evaporative emission rates (including
specific problems that can potentially be addressed) under the
I/M program are provided in Appendix 6-A at the end of this
chapter5.
-------
6-38
Table 6-18
"No Exhaust" Case; 12-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
Emission
Reductions
11
11
10
10
9
,5
,0
,5
,0
,5
9.0
(10° Tons/Yr)
Net
369
454
540
625
710
795
Incr.
369
85
86
85
85
85
Net Cost*
(106 $/Yr)
Cost
Effectiveness
($/Ton)
Net
-88
- 2
100
232
368
512
Incr,
-88
86
102
132
137
144
Net
-238
- 5
184
371
518
644
Incr.
-238
998
1197
1542
1619
1681
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i )
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
251
222
187
160
138
1990
227
198
161
140
121
1992
185
165
134
120
106
1995
142
128
107
100
91
1997
121
111
94
90
85
2000
99
95
85
82
81
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)**
1988 1990 1992 1995 1997 2000
492
733
1252
1515
1977
547
852
1401
1700
2225
338
569
895
1157
1453
508
778
1158
1375
1643
711
1025
1443
1650
1882
807
1108
1445
1652
1801
**
Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
6-39
Table 6-19
"No Exhaust" Case; 4-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
Emission
Reductions
(10 Tons/Yr)
Net Cost*
(106 $/Yr)
Cost
Effectiveness
($/Ton)
11
11
10
10
9
,5
,0
,5
,0
,5
9.0
Net
123
151
180
208
236
265
Incr,
123
28
29
28
28
29
Net
Incr
-83
16
30
50
70
90
Net
-673
-444
-208
58
347
651
Incr.
-673
555
1033
1757
2466
3199
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (ps i )
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
1988
84
74
62
53
46
Emiss
1990
76
66
54
47
40
ion Reduct
1992
62
55
45
40
35
ions (10
1995
47
43
36
33
30
Tons)
1997
40
37
31
30
28
2000
33
32
28
27
27
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)**
1988
492
733
1252
1515
1977
1990
545
846
1401
1692
2212
1992
323
582
935
1285
1664
1995
466
789
1275
1737
2177
1997
655
1035
1604
2120
2552
2000
•^•^••MMB^
688
1127
1683
2403
2834
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
-------
Figure 6-7
NON
-CALIF. EMISSION REDUCTION/COST EFF
I
o
8
o
u
o
3E
Ul
WITHOUT EXHAUST BENEFITS
1200
1100 H
1988
1992
1996 2000
YEAR
2004
2008
-------
6-41
Also included in Appendix 6-A is an analysis of the
potential effectiveness of an evaporative I/M program such as
the one described above. As Table 6-A-7 indicates,
extrapolating I/M benefits nationwide (excluding California)
could reduce HC emissions by roughly 100,000 tons in 1988 and
343,000 tons in 2010. Looking specifically at the 47 ozone
non-attainment areas, HC emissions could be reduced by 39,000
tons in 1988 and by 122,000 tons in 2010 with an effective
evaporative I/M program. As alluded to earlier, the 47-city
reductions would parallel the non-California reductions in
terms of percentage change from baseline, representing a
0.7-percent reduction in total NMHC emissions in 1988 and a
2.2-percent reduction in the year 2010. The overall cost
effectiveness ($ per ton) of such an I/M program is estimated
at $3780 per ton in the short term (1988) and $1350 per ton in
the long term (2010). The development of these emission
reductions and costs is outlined in Appendix 6-A.
The sensitivity of the RVP control strategies examined in
this study to the implementation of an evaporative I/M program
is summarized in Tables 6-20 and 6-21 and Figure 6-8. (For
this analysis, "R" was held constant at 1.0.) As indicated in
these 12-month and 4-month tables, emission reductions are
lower than in the base case because the I/M program will have
eliminated portions of motor vehicle evaporative emissions
previously reduced by in-use RVP control. (The tonnage
reductions attributed to evaporative HC under the evaporative
I/M case were compared to the base case for the year 2010 in
Table 6-1). Due to these lower emission reductions and the
reduced credits for retained evaporative HCs, the cost/ton of
RVP control would be significantly higher if an effective
evaporative I/M program were implemented prior to RVP control.
As shown in Table 6-20, for the long-term 9.0-psi scenario, the
incremental cost/ton with an evaporative I/M program would be
approximately 66 percent higher than under the base case ($2792
versus $1681 per ton of reduction).
F. Summary
Based on the technical estimates and assumptions used in
the base case analysis, purely vehicle-oriented control (i.e.,
certification fuel RVP revised to 11.5 psi and test procedure
modified) appears to be the most cost-effective approach in the
long term. As shown earlier for the 12-month analysis in Table
6-6, a total of 584,000 tons of HC emissions can be eliminated
via this strategy in the year 2010 at a net savings of roughly
$274 per ton to the public. However, because a change in
certification fuel and test procedure can only affect vehicle
design, strategies involving in-use RVP control can
-------
6-42
Table 6-20
"Evap. I/M" Case; 12-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (psi)
11,
11,
10.
10,
9,
Emission
Reductions
(103 Tons/Yr)
9.0
Net
499
555
611
668
722
775
Incr.
499
56
56
57
54
53
Net Cost*
(106 $/Yr)
Net
-130
-36
76
218
365
513
Incr.
-130
94
112
142
147
148
Cost
Effectiveness
(ft/Ton)
Net
-261
-65
124
326
505
662
Incr.
-261
1679
2000
2491
2722
2792
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
1988
266
238
210
186
162
Emission Reductions (10
1990 1992 1995
234 189 138
207 169 123
182 150 111
161 134 102
141 119 93
Tons )
1997
109
100
89
83
81
2000
81
76
69
69
67
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
Incremental Cost Effectiveness ($/Ton)**
1988
442
665
1077
1259
1634
1990
523
812
1214
1453
1868
1992
325
546
778
989
1253
1995
530
826
1098
1330
1624
1997
827
1168
1548
1818
2002
2000
^^^MUMV*^—
1071
1464
1857
2008
2257
* Bonner & Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and
later assume investment has taken place; refinery costs are
midway between those of open and fixed NGL purchase
scenarios.
-------
6-43
Table 6-21
"Evap. I/M" Case; 4-Month Analysis, R = 1.0
In-Use Gasoline RVP Control Equal to Revised
Cert. Fuel RVP in the Long Term (2010)
In-Use =
Revised
Cert. Fuel
RVP (ps i)
11,
11,
10,
10,
9,
Emission
Reductions
9.0
(10 Tons/Yr)
Net
166
185
204
223
241
258
Incr.
166
19
19
19
18
18
Net Cost*
(106 $/Yr)
Net
-126
- 82
- 37
28
113
175
Incr.
-126
44
45
65
85
62
Cost
Effectiveness
($/Ton)
Net
-760
-441
-180
122
468
676
Incr.
-760
2397
2411
3407
4733
3477
Additional In-Use Gasoline RVP Control
in the Short Term (1988-2000)
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5- 9.5
10.0- 9.5
9.5- 9.0
Emission Reductions (10 Tons)
1988
89
79
70
62
54
1990
78
69
61
54
47
1992
63
56
50
45
40
1995
46
41
37
34
31
1997
36
33
30
28
26
2000
27
25
23
23
22
Incremental Cost Effectiveness ($/Ton)**
Incremental
Control Step
RVP (psi)
11.5-11.0
11.0-10.5
10.5-10.0
10.0- 9.5
9.5- 9.0
*Bonner&Moore refinery costs are for the baseline case with
investment and with NGL purchases treated as midway between
the open and fixed NGL purchase scenarios.
** 1988 and 1990 costs are based on no investment; 1992 and later
assume investment has taken place; refinery costs are midway
between those of open and fixed NGL purchase scenarios.
1988.
442
665
1077
1259
1634
1990
549
793
1220
1540
1741
1992
390
549
846
1225
1185
1995
697
904
1307
1891
1679
1997
1049
1326
1889
2585
2207
2000
^••^MI^MMB
1517
1725
2495
3325
2709
-------
Figure 6-8
NON-CALIF. EMISSION REDUCTION/COST EFF
1 _.*«n I VkJ /*ACC
EVAP. IXM CASE
1200
1988
2008
-------
6-45
potentially eliminate additional emissions. This is possible
because in-use RVP levels affect those portions of evaporative
emissions attributable to malmaintenance/defects and
evaporative system tampering, as well as stationary sources
such as gasoline storage, distribution, and vehicle refueling,
whereas certification fuel RVP has no impact on these
emissions. In 2010, year-round in-use fuel RVP control could
eliminate up to an additional 426,000 tons of HC emissions at
an incremental cost per ton ranging between $998 and $1681 per
ton.
In the short term, vehicle-oriented control is relatively
ineffective since control is achieved only as the fleet turns
over (i.e., roughly seven years are required to obtain half of
eventual control). However, since all commercial gasoline
would be affected, in-use RVP control is completely effective
immediately. For example, HC emission reductions of up to
1,116,000 tons at an incremental cost effectiveness of
$395-1551 per ton could be achieved in 1988 with 12-month
commercial fuel RVP control.
The above 12-month projections are based on the absence of
onboard or Stage II controls and evaporative I/M, and a
100-percent utilization of increased energy density of
less-volatile fuels (i.e., R = 1.0). As indicated by the
sensitivity analyses, any of these factors could influence
these results. Less efficient energy utilization (i.e., R =
0.6) would not affect emission reductions, but would increase
costs (because of reduced fuel economy credits); therefore,
cost per ton estimates are higher by as much as 35 percent in
both the short and long terms. A lower baseline RVP has no
effect on incremental emission reductions or costs, so
long-term incremental cost effectiveness is not affected. An
onboard control program reduces incremental emission benefits
and slightly increases incremental costs, so the incremental
cost per ton is increased by as much as 31 percent. Finally, a
maximally effective evaporative I/M program would have little
effect on vehicle-oriented control programs, but would have a
fairly significant impact on in-use RVP control, reducing
long-term incremental emission reductions by 34 percent and
raising long-term incremental cost per ton by as much as 68
percent over the base case estimates.
-------
6-46
References (Chapter 6)
1. "Evaluation of Air Pollution Regulatory Strategies
for Gasoline Marketing Industry," U.S. EPA, Office of Air and
Radiation, EPA-450/3-84-012, July 1984.
2. "The Feasibility, Cost, and Cost Effectiveness of
Onboard Vapor Control," Glenn W. Passavant, U.S.
EPA/OAR/OMS/ECTD/SDSB, EPA-AA-SDSB-84-01, March 1984.
3. "Anti-Tampering and Anti-Misfueling Programs to
Reduce In-Use Emissions from Motor Vehicles," U.S.
EPA/OAR/OMS/ECTD/TSS, EPA-AA-TSS-83-10, December 31, 1983.
4. "MOBILES Fuel Consumption Model," Mark A. Wolcott,
EPA, and Dennis F. Kahlbaum, CSC, February 1985.
5. "The Highway Fuel Consumption Model: Tenth Quarterly
Report," Energy and Environmental Analysis, Inc., for U.S.
Department of Energy, November 1983.
6. "Anti-Tampering and Anti-Misfueling Programs to
Reduce In-Use Emissions from Motor Vehicles," EPA-AA-TSS-83-10,
December 31, 1983.
7. "Reoccurrence of Evaporative System Malmaintenance
and Tampering," EPA memo from David J. Brzezinski to Phil
Carlson, October 4, 1985.
8. "MOBILES Fuel Consumption Model," Mark A. Wolcott,
EPA, and Dennis F. Kahlbaum, CSC, February 1985.
-------
6-47
Appendix 6-A
Evaluation of an Inspection/Maintenance
Program for Evaporative Emission Control Systems
This appendix details the calculations used to derive the
effectiveness and cost effectiveness of an inspection/
maintenance (I/M) program for evaporative emission control
systems. The program was assumed to begin in 1988 as this was
the assumed year of implementation for in-use RVP control and
is also likely the earliest feasibile implementation date for
evaporative I/M. Application was restricted to 1978 and later
model year LDVs and LDTs, as earlier vehicles were not
certified using the comprehensive SHED test. Their evaporative
emission control systems are not very effective and are not
amenable to cost-effectiveness repair. Heavy-duty vehicles
were not included as current I/M programs for exhaust emissions
generally do not include HDVs.
The first section of this appendix will describe how the
evaporative emission reductions were estimated. The second
section will present the costs associated with the I/M program,
and the last section will present the cost effectiveness
results for 1988 and 2010, representative of the long-run.
Evaporative I/M Emission Reductions
The total emission reductions obtainable through an
evaporative I/M program were based on the results of EPA's
in-use emission factors (EF) test program, which is described
in Chapter 2. Tables 6-A-l and 6-A-2 present the types of
malmaintenance and defect (M&D) problems checked and discovered
in the EF test program and the rate of occurrence of each
problem for fuel-injected (FI) and carbureted vehicles,
respectively. Tables 6-A-l and 6-A-2 also present the average
diurnal and hot-soak emission effect associated with each
problem, as measured in the EF test program vehicles, on
Indolene and commercial fuels.
The percentage of the total M&D effect due to each defect
is contained in Tables 6-A-3 and 6-A-4 for fuel-injected and
carbureted vehicles, respectively. The percentages were
calculated using the following equation and then normalized.
(All negative percentage contributions, due to presumedly
anomalous emission improvements, were assumed to be zero before
the total percentage was normalized.)
Avg Evap Emissions Problem Free Rate of Percent
due to M&D Problem - Emissions x Occurrence = of M&D
Total M&D Effect of M&D Problem
Problem due to
Defect
-------
6-48
Table 6-A-l
In-Use EF Test Program M&D Types, Rates of Occurrence,
and Diurnal/Hot Soak Emissions for Fuel-Injected Vehicles
Avg. Evap. Emissions (g/test)
No. of Rate*
Defect Vehicles (%)
Gas Cap Leak
Air Cleaner
Gasket Broken/
Missing
Canister Filter
Dirty
Canister Saturated
w/Liguid Fuel
Canister Broken
2
2
2
1
1
3
3
3
1
1
.6
.6
.6
.8
.8
Indolene
DI
5
3
2
3
0
.25
.62
.24
.38
.98
HS
2.
5.
0.
2.
1.
13
92
60
14
67
Commercial
DI HS
14
14
5
11
2
.75
.00
.59
.84
.14
6
13
2
1
13
.49
.21
.66
.93
.06
Problem Free Emissions 0.87 0.64 4.67 0.90
Total M&D Effect 0.34 0.29 0.84 0.93
Fifty-five fuel injected vehicles tested.
-------
6-49
Table 6-A-2
In-Use EF Test Program, M&D Types, Rates of Occurrence,
and Diurnal/Hot Soak Emissions for Carbureted Vehicles
Avg. Evap. Emissions (g/test]
Defect
Gas Cap Leak
Canister Filter
Dirty
Canister Saturated
w/Liquid Fuel
Canister Broken
EFE TVS Stuck
Bowl Vent Value
Stuck
Vacuum Line
Damaged
Vacuum Line
Plugged
Bowl Vent Line
Damaged
VCV Inoperative
Purge Solenoid/
Value Sticking
Purge Solenoid/
Value Inoperative
Purge Solenoid/
No. of
Vehicles
6
1
7
0
1
1
6
1
1
1
3
1
Value Leaks Vacuum 2
Rollover Valve
Leaking
Carburetor Leaks
Fuel
Carburetor
Exceptionally
Dirty
1
1
2
Rate*
(%)
5.5
0.9
6.4
0
0.9
0.9
5.5
0.9
0.9
0.9
2.8
0.9
1.8
0.9
0.9
1.8
Problem Free 'Emissions
Total M&D Effect :
Indolene
DI
8.29
3.45
3.50
—
6.90
1.68
6.79
2.15
1.89
1.34
2.24
3.73
3.90
10.35
0.58
1.90
1.25
1.11
HS
2.89
1.40
2.29
-
1.50
1.25
4.06
9.72
5.00
5.16
4.70
13.78
5.25
6.27
13.82
1.51
1.50
0.83
Commercial
DI
14.45
17.67
12.25
-
3.52
16.61
16.66
9.76
3.77
16.63
8.70
3.72
22.96
22.55
3.40
16.29
7.40
1.61
HS
4.96
1.55
2.68
-
2.83
1.15
6.05
3.42
6.41
4.13
7.70
15.94
7.38
11.69
10.57
2.15
2.60
1.24
109 carbureted vehicles tested.
-------
6-50
Table 6-A-3
Normalized Percentages of Total M&D Effect
Due to Specific M&D Problems on Fuel-Injected Vehicles
Indolene
Defect
Gas Cap Leak*
Air Cleaner Gasket Broken/
Missing*
Canister Filter Dirty
Canister Saturated w/Liguid
Fuel
Canister Broken*
Total
DI
44.6
28.0
14.0
12.8
0.6
100.0
HS
18.6
65.7
9.3
6.4
100.0
Commercial
DI
42.1
39.0
3.9
15.0
—
100.0
HS
21.3
46.8
6.7
1.9
23.3
100.0
Total Percentage Addressable
w/ I/M
73.2
90.7
81.1 91.4
Addressable through an evaporative I/M program.
Indicates the defects had a negative M&D effect before
normalization of the total, and was eliminated.
-------
6-51
Table 6-A-4
Normalized Percentages of Total MS.D Effect
Due to Specific M&D Problems on Carbureted Vehicles
Indolene Commercial
Defect DI HS D_i HS
Gas Cap Leak* 34.5 9.1 18.3 14.6
Canister Filter Dirty 1.8 - 4.5 -
Canister Saturated w/Liquid
Fuel 12.9 6.1 14.7 0.6
EFE TVS Stuck 4.6 0 - 0.3
Bowl Vent Value Stuck 0.4 - 4.0
Vacuum Line Damaged* 27.2 16.9 24.1 21.3
Vacuum Line Plugged 0.7 9.0 1.0 0.8
Bowl Vent Line Damaged* 0.5 3.9 - 3.9
VCV Inoperative 0.1 4.0 4.0 1.5
Purge Solenoid/Valve Sticking 2.5 10.5 1.7 15.8
Purge Solenoid/Valve Inoperative 2.0 13.5 - 13.8
Purge Solenoid/Valve Leaks
Vacuum 4.3 8.2 13.5 9.9
Rollover Valve Leaking 7.4 5.3 6.5 9.3
Carburetor Leaks Fuel* - 13.5 - 8.2
Carburetor Exceptionally Dirty 1.1 0 7.7 -
Total 100.0 100.0 100.0 100.0
Total Percentage Addressable
w I/M 62.2 43.4 42.4 48.0
Addressable through an evaporative I/M program.
Indicates the defect had a negative M&D effect before
normalization of the total, and was eliminated.
-------
6-52
Tables 6-A-3 and 6-A-4 also contain the maximum percentage
of the M&D effect addressable through an evaporative I/M
program broken down into the diurnal and hot-soak components.
Leaking gas caps, missing or broken carburetor gaskets, broken
canisters and damaged hoses are assumed to be detectable for
signs of defects. To detect a leaky gas cap, the fuel tank is
sealed off, pressurized through its connection to the charcoal
canister and allowed to sit for five minutes. A drop in
pressure noted with a pressure gauge indicates a possible
leaking gas cap. To detect a broken/missing gasket, propane is
sprayed around the intake manifold in an engine at idle. An
increase in engine RPM indicates a broken/missing gasket.
Broken canisters and damaged hoses are detected visually.
Table 6-A-5 contains the maximum portion of M&D effects
addressable through an evaporative I/M program which is 100
percent effective. (The rates are an average of the percentage
reductions obtainable on Indolene and commercial fuels shown in
Tables 6-A-3 and 6-A-4.) I/M programs are generally projected
to be 70 percent effective.[6] Thus, potential M&D effect
emission reductions should be reduced by 30 percent to reflect
more realistic I/M effectiveness (also listed in Table 6-A-5).
Table 6-A-6 contains tampering problems and rates of
tampering expected in an evaporative I/M program. Gas caps,
canisters and connecting hoses which have been removed or
disconnected are considered to be tampering. An evaporative
I/M program is also expected to be 70 present effective in the
detection of tampering problems.
Based on these 70-percent emission reductions in
addressable M&D excess emissions effects, and a 70 percent
reduction in tampering excess emissions effects, new emissions
factors were calculated and used to run the MOBILES computer
program. The MOBILES results were used in determining the
non-California emissions inventory according to the methodology
described in Chapter 5. The total non-California NMHC emission
reductions obtained with an evaporative I/M program at 70
percent effectiveness, with in-use fuel at 11.5 psi RVP, and
certification fuel at 9.0 psi RVP are contained in Table
6-A-7. The total 47 ozone non-attainment cities NMHC emission
reductions are also contained in Table 6-A-7. An evaporative
I/M program would only be instituted in cities with I/M
programs for exhaust emissions. These are best represented by
-------
6-53
Table 6-A-5
Portion of M&D Effects Addressable Through Evaporative I/M
(Percent)
@ 100% Effectiveness @ 70% Effectiveness
Vehicle Type
FI
Garb
DI*
77.2
52.3
HS*
91.1
45.7
DI
54.0
36.6
HS
63.7
32.0
Rates are average of percentage reductions obtainable on
Indolene and Commercial fuels listed in Tables 6-A-3 and
6-A-4.
-------
6-54
Table 6-A-6
Tampering Types of Problems and Rates of Occurrence
Problem Rate of Occurrence (%)
Gas Cap Removed 1.2
Canister Vacuum Disconnected 1.7
Cap Removed & Canister Vacuum Disconnected 0.1
Canister Removed 0.3
Canister Mechanically Disconnected 0.2
-------
6-55
Table 6-A-7
Total NMHC Emission Reductions Obtainable with a 70%
Effective Evaporative I/M Program (1000 tons/year)
Non-California
Scenario
Baseline*
Baseline* w/Evap I/M
Reduction due to
Evap I/M
47 Non-Attainment
Cities Scenario
Baseline*
Baseline* w/Evap I/M
Reduction due to
Evap I/M
Year
1988 1990 1992 1995 1997 2000 2010
14307 13821 13513 13350 13397 13642 15298
14207 13634 13293 13094 13124 13350 14955
100
187
220 256
Year
273 292
343
1988 1990 1992 1995 1997 2000 2010
5592 4879 4757 4699 4716 4816 5461
5553 4813 4679 4609 4620 4713 5339
39
66
78
90
96
103
122
Baseline refers to In-use fuel at 11.5 psi RVP and
Certification fuel at 9.0 psi RVP.
-------
6-56
the 47 ozone non-attainment cities, so the last set of emission
reductions is most pertinent. However, non-California emission
reductions assuming evaporative I/M programs are instituted
everywhere, are presented since nationwide emission effects are
most commonly available for other control programs. The
non-California figures here can then be used to compare
relative effectiveness with those programs, realizing that the
control is only available in areas with exhaust emission I/M
programs.
Evaporative I/M Costs
The costs of an evaporative I/M program arise from the two
steps of an I/M program, the inspection and the repair of the
malmaintained, defective and/or tampered parts. The cost per
inspection assumes a three minute inspection per vehicle (in
addition to the time required for an exhaust inspection) at a
labor rate of $20/hour. The increase in time is primarily due
to the procedure to check for leaky gas caps. This results in
an incremental inspection cost per vehicle of $1.00.
Table 6-A-8 contains the estimated costs of the parts and
the amount of time necessary to carry out the repairs. The
part costs are based on typical costs of parts found in
"Mitchells Mechanical Parts/Labor Estimating Guides" and the
labor costs are based on a basic shop fee of $35/hour. The
repair costs associated with each problem for fuel-injected and
carbureted vehicles on both a repaired vehicle and average
in-use vehicle basis are listed in Tables 6-A-9 and 6-A-10.
Inspection and total inspection and repair costs are shown as
well.
The total first year repair cost is greater than the total
second (and later) year repair cost. This occurs because
during the first year of the evaporative I/M program (1988),
all of the vehicles from model years back to 1978 must be
repaired. In the second and subsequent years, only the cars
which have had malmaintenance and defect problems and/or have
been tampered with within the last year need to be repaired. A
reoccurrence rate of 60 percent was assumed.[7] Thus, the
second year (and later) repair costs are 60 percent of the
first year repair costs. The incremental inspection cost
remains unchanged since all vehicles must still be inspected.
An economic credit is realized from the emission
reductions derived from the evaporative I/M program. The
excess emissions which would have been lost without repairs to
the evaporative control system, will now be captured by the
charcoal canister and combusted in the engine. The economic
credit is determined as explained previously in Chapter 4,
Section VI by assuming the composition of the emissions is all
-------
6-57
Table 6-A-8
Evaporative I/M Parts and Labor Repair Costs
Part Replaced
Gas Cap
Intake Gasket
Evaporative Canister
Hose
Carburetor Gasket
Cost($)
10
10
2
40
Hours of Labor*
_
3.0
0.3
1.4
Total Cost($)
10.00
115.00
12.50
89.00
Labor time was estimated based on "Mitchell Mechanical
Parts/Labor Estimating Guides" for Domestic Cars 1984 and
Imported Cars and Trucks 1984. Published by Mitchell
Manuals, Inc., San Diego, California, 1984. A basic shop
fee of $35/hour labor cost was used.
-------
6-58
Table 6-A-9
Evaporative I/M Cost per Vehicle
Inspected for Fuel-Injected Vehicles
Repair Repair Cost
M&D Problem Rate(%) Cost($) /Vehicle($)
Leaking Gas Cap 3.6 10.00 0.36
Leaking Gasket 3.6 115.00 4.14
Broken Canister 1.8 67.50 1.22
Tampering Problem
Gas Cap Removed 1.2 10.00 0.12
Canister Vacuum
Disconnected 1.7 12.50 0.21
Cap Removed & Canister
Vacuum Disconnected 0.1 22.50 0.02
Canister Removed 0.3 67.50 0.20
Canister Mechanically
Disconnected 0.2 12.50 0.03
Repair Cost 6.30
First Year Repair Cost (at 70% effectiveness) 4.41
Incremental Inspection Cost 1.00
Total First Year Repair & Inspection Cost per vehicle 5.41
Second year(+) Repair Cost (at 70% effectiveness) 2.65
Incremental Inspection Cost 1.00
Total Second Year Repair and Inspection Cost
per vehicle 3.65
-------
6-59
Table 6-A-10
Evaporative I/M Cost per Vehicle
Inspected for Carbureted Vehicles
M&D Problem Rate(%)
Leaking Gas Cap
Damaged Vacuum Line
Damaged Vent Line
Leaking Carburetor
Tampering Problems
Gas Cap Removed
Canister Vacuum
Disconnected
Cap Removed & Canister
Vacuum Disconnected
Canister Removed
Canister Mechanically
Disconnected
First Year Repair Cost
Incremental Inspection
Total First Year Repair &
Second Year(-i-) Repair
Incremental Inspection
5.5
5.5
0.9
0.9
1.2
1.7
0.1
0.3
0.2
Repair
Repair Repair Cost
Cost($) /Vehicle($)
10.00 0.55
12.50 0.69
12.50 0.11
89.00 0.80
10.00
12.50
22.50
67.50
12.50
Cost
(at 70% effectiveness)
Cost
Inspection Cost per vehicle
Cost (at
Cost
70% effectiveness)
0.12
0.21
0.02
0.20
0.03
2.73
1.91
1.00
2.91
1.15
1.00
Total Second Year Repair & Inspection Cost per vehicle 2.15
-------
6-60
butane. (Table 4-12 contains the values used to convert the
butane to a gasoline equivalent and then to economic credits.)
Tables 6-A-ll and 6-A-12 contain the fuel recovery credits for
the evaporative I/M program for 1988 and 2010, respectively.
Evaporative I/M Cost Effectiveness
Tables 6-A-ll and 6-A-12 present the derivation of the
cost effectiveness (C/E) of an evaporative I/M program in 1988
(first year) and 2010, respectively. Both Tables 6-A-ll and
6-A-12 utilize nationwide costs as these are the most readily
available and nationwide emission reductions. However, this
has no effect on the final cost-effectiveness of any particular
evaporative I/M program since a city's fraction of nationwide
vehicles should be the same as its fraction of nationwide NMHC
emissions. Therefore, the cost effectiveness numbers can be
applied to any of the 47 non-attainment cities where the
evaporative I/M program could be implemented.
The total number of vehicles affected by an evaporative
I/M program were based on the MOBILES fuel consumption model
[8] and MOBILES carbureted and fuel-injected projections back
to 1978 (for the 1988 analysis), and back to 1990 (for the 2010
analysis). The I/M cost without the fuel recovery credit is a
weighted-average of the total inspection and repair cost for
fuel-injected and carbureted vehicles. The fuel recovery
credit, as described in the previous section, is subtracted
from the inspection and repair cost to obtain the I/M cost with
the fuel recovery credit. The I/M cost with the fuel recovery
credit is the final cost of the evaporative I/M program and is
divided by the emission reductions listed in Table 6-A-7 to
determine the C/E of the evaporative I/M program. The
resulting C/E numbers are $3780/ton in 1988 and $1350/ton in
2010.
-------
6-61
Table 6-A-ll
1988 Cost Effectiveness of Evaporative I/M
Total number of nationwide vehicles affected by I/M program1:
FI Garb.
LDV: 38.6 x 10B 57.6 x 106
LDT: 5.9 x 106 17.9 x 106
Total 44.5 X 10s 75.5 X 10s
Cost of Inspection and Repair per Vehicle (first year):
FI = $5.41 Carb. = $2.91
Nationwide Cost of Inspection and Repair: $4.60 x 10*
Nationwide Fuel Recovery Credit2: $0.37 x 10*
Nationwide I/M Cost with Fuel Recovery Credit: $4.23 X 10*
Nationwide Emission Reduction due to I/M: 112,000 tons
Cost Effectiveness: $4.23 x 10* = $3780/ton
112,000 tons
Based on MOBILES fuel consumption model total number of
vehicles and MOBILE3 vehicle registration distributions
and carbureted and fuel injected projections back to 1978.
Fuel recovery credit was determined assuming the recovered
emissions were butane.
-------
6-62
Table 6-A-12
2010 Cost Effectiveness of Evaporative I/M
Total number of nationwide vehicles affected by I/M program1:
FI Carb.
LDV: 135.6 x 106 17.1 x 10B
LDT: 30.0 x 106 3.8 x 106
Total 165.6 x 106 20.9 x 10e
Cost of Inspection and Repair per Vehicle (second and later
years):
FI = $3.65 Carb. = $2.15
Nationwide Cost of Inspection and Repair: $6.49 x 10*
Nationwide Fuel Recovery Credit2: $1.28 x 10*
Nationwide I/M Cost with Fuel Recovery Credit: $5.21 X 10*
Nationwide Emission Reduction due to I/M: 385,000 tons
Cost Effectiveness: $5.21 x 10* = $1350/ton
385,000 tons
Based on MOBILES fuel consumption model. Since evaporative
I/M program would cover last 20 model years, essentially
all LDVs and LDTs would be covered.
2 Fuel recovery credit was determined assuming the emissions
were butane.
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6-63
Appendix 6-B
Effects of Increased Canister Size on Operating Costs
There will be a very slight reduction in fuel economy
associated with the increased weight of the canister in the
modified evaporative control system. This will affect a
vehicle's operating cost, and must therefore be included in the
total costs associated with the proposed changes to the
certification test procedure. The calculation of this weight
penalty will be the subject of this appendix. Key values used
in these calculations are summarized in Table 6-B-l.
Appendix 3-A described how the component costs for each
certification fuel RVP were calculated. The weight associated
with each component of an 850-ml canister is given in Table
3-A-5. By scaling up these component weights, as was done for
the costs (described in Appendix 3-A), the increased canister
weight associated with each certification fuel RVP can be
determined. These are provided in Table 6-B-2.
These weight increases can be expressed as a percentage of
the total weight of the vehicle using the estimates of total
vehicle weights shown in Table 6-B-l. Estimated weight
sensitivity factors, which relate a percentage increase in
weight to a percentage reduction in fuel economy, and
class-average fuel economies are also given in Table 6-B-l and
are used along with the percentage weight increases to
determine the expected reductions in fuel economy. These
reductions in fuel economy are then coupled with estimates of
lifetime vehicle mileages (shown in Table 6-B-l) to calculate
the extra gallons of fuel used over the vehicle's life. These
lifetime mileages are discounted (at 10 percent per annum) to
represent the fact that a dollar saved in the tenth year of
vehicle use is not the same as one saved in the first year.
The net cost to the consumer is then determined using a fuel
cost of $0.98 per gallon. Table 6-B-2 summarizes the
calculated values for reduction in fuel economy, extra gallons
of fuel, and cost.
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6-64
Table 6-B-l
Summary of Values Used in Calculation
LDV LPT HDV
Fuel Economy (mpg)* 26.64 18.97 10.39
Vehicle Weight (lb)** 3082 3832 9270
Weight Sensitivity 0.329 0.402 0.450
Factor (% change
in fuel economy per
% change in weight)***
Discounted Lifetime 65,400 80,900 71,700
Mileage****
* 1994 values from "MOBILES Fuel Consumption Model," Mark A.
Wolcott, EPA, and Dennis F. Kahlbaum, CSC, February 1985.
** "Light-Duty Auto Fuel Economy...Trends Through 1985,"
Heavenrich, Murrell, Cheng and Loos, SAE 850550.
*** "Analysis Memorandum: Design Factor Update," prepared by
Energy and Environmental Analysis, Inc., for EPA, October
1, 1982.
**** "Regulatory Impact Analysis, Oxides of Nitrogen Pollutant
Specific Study and Summary and Analysis of Comments,"
EPA/OAR/OMS, March 1985. (Discounted at 10 percent over
life of vehicle.)
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6-65
Table 6-B-2
Values of Weight Increase, Penalty Factor, and
Weight Penalty for Various Certification Fuels
Class
LDV
Increased Weight (Ib)
Reduced Fuel Economy
(gal/mi X 102)
Extra Fuel
(gal/vehicle life)
Cost* (I/vehicle)
LDT
Increased Weight (Ib)
Reduced Fuel Economy
(gal/mi x 102)
Extra Fuel
(gal/vehicle life)
Cost* ($/vehicle)
HDV
Increased Weight (Ib)
Reduced Fuel Economy
(gal/mi X 102)
Extra Fuel
(gal/vehicle life)
Cost* ($/vehicle)
Certification Fuel RVP(psi)
9.5
0.16
0.04
0.04
0.04
0.20
0.04
0.09
0.09
0.42
0.02
0.14
0.14
10.0
0.32
0.09
0.08
0.08
0.39
0.08
0.17
0.17
0.83
0.04
0.28
0.27
10.5
0.48
0.14
0.13
0.12
0.59
0.12
0.26
0.26
1.25
0.06
0.42
0.41
11.0
0.64
0.18
0.17
0.16
0.80
0.16
0.36
0.35
1.67
0.08
0.56
0.55
11.5
0.81
0.23
0.21
0.20
0.98
0.20
0.44
0.43
2.10
0.11
0.70
0.69
Using $0.98/gallon
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6-66
Appendix 6-C
Development of Non-Summer Evaporative Emission
Recovery Credits for Four-Month Analyses
Cost calculations for the 4-month analysis must take into
account the fact that vehicle-related effects occur year-round
while commercial fuel-related effects occur during the 4-month
period only. Thus, refinery costs and the fuel economy credit
due to the increased energy content of commercial gasoline are
simply one-third of the annual cost since these effects only
appear when volatility control is operative. Vehicle redesign
costs and the associated weight penalty are equivalent to the
annual cost since these are unaffected by the removal of in-use
RVP controls. The derivations of the individual vehicle- and
fuel-related control costs are provided in Chapters 3 and 4,
respectively. Determining the evaporative prevention/recovery
credit is not as straightforward, however, and this is the
focus of this appendix.
During the summer period the evaporative credit is simply
one-third of the year-round figure since both fuel and vehicle
controls are in place. However, since vehicle controls operate
year-round, additional emission recovery occurs during the
non-summer period even when the fuel controls are inoperative.
These non-summer emission reductions were estimated by running
MOBILE3 to simulate a commercial fuel RVP of 11.5 psi (i.e, no
in-use RVP control) with certification fuel volatilities
varying between 9.5 and 11.5 psi RVP (i.e., various levels of
vehicle control). The evaporative and exhaust HC emission
factors used as input to these MOBILES runs are described
below. Only post-1989 model year vehicles are affected, since
1990 model year vehicles are assumed to be the first to be
affected by changes to certification fuel and/or test
procedure. Pre-1990 emission rates were the same as the
baseline case (certification fuel of 9.0-psi RVP with in-use
fuel of 11.5-psi RVP).
As described in Chapter 2, motor vehicle evaporative
emissions can be attributed to emissions from properly designed
and operating systems and excess emissions due to: 1)
insufficient design of the purge system; 2) malmaintenance and
equipment defects; 3) commercial fuel RVP in excess of
certification fuel RVP; and 4) evaporative control system
tampering. The size of each of these sources (except for
tampering, which is handled separately) as a function of RVP
was estimated in Section V of Chapter 2 (Table 2-15) and
summarized in Tables 5-1 and 5-2 of Chapter 5. There, in-use
and certification fuel RVP changed simultaneously or in-use RVP
was varied while certification fuel RVP was held at 9.0 psi.
Each of these sources will be re-estimated here under the
different condition of unchanging in-use fuel RVP, but varying
certification fuel RVP.
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6-67
Tables 6-C-l through 6-C-3 summarize the estimates of each
of these sources and total non-tampered emissions for post-1989
light- and heavy-duty vehicles. Emission factors for properly
designed and operating vehicles are not a function of RVP.
Thus, they were taken directly from Tables 5-1 and 5-2. The
effect of improper design was assumed in Chapter 2 to disappear
with revision of the evaporative emission test procedure, again
irrelevant of in-use or certification RVP. Thus, its level is
zero throughout Tables 6-C-l through 6-C-3. The effect of
malmaintenance and defects was shown in Chapter 2 to be
dependent only upon in-use RVP. As in-use RVP is constant at
11.5 psi here, the effect of malmaintenance and defects is that
from Table 2-15 for 11.5-psi RVP at all certification fuel RVP
levels. The RVP effect described in Chapter 2 was described as
being a function of the difference between certification and
in-use RVP. Table 2-15 shows this effect for in-use RVP values
between 9.0 and 11.5 psi with certification RVP held constant
at 9.0 psi, or in other words, for RVP differences of 0-2.5
psi. These results were simply transposed to apply here where
the certification RVP varied and in-use RVP remained at 11.5
psi. For example, the RVP effect during the non-summer period
for a certification RVP of 9.5 psi (difference of 2.0 psi RVP)
was taken to be that shown in Table 2-15 corresponding to 11.0
psi RVP for in-use fuel.
Also relevant is the exhaust emission effect. Chapter 2
discusses EPA's test results which show fuel RVP to have an
effect on exhaust HC and CO emissions. This effect on
emissions was accounted for in the analysis in Chapter 5 by
applying multiplicative factors for each RVP scenario to the
original MOBILES exhaust emission factors. These
multiplicative adjustment factors are shown in Tables 5-10 and
5-11. For the non-summer scenario, the adjustment factors were
assumed to vary with the in-use/certif ication fuel RVP
differences like that used above to determine the RVP effect
during the non-summer period (i.e., in proportion to the
difference between in-use and certification RVP).
Given the above inputs, the reductions in evaporative HC
emissions were determined from MOBILES runs. This emission
reduction was multiplied by 0.67 to obtain the evaporative
emission recovery credit in the eight-month non-summer period.
The methodology for calculating an annual credit for these
reductions is the same as that for the 12-month analysis and is
outlined in detail in Section VI of Chapter 4. Table 6-C-4
summarizes the long-term costs and credits of the base case for
both the 12-month and 4-month analyses.
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6-68
Table 6-C-l
Diurnal Emissions (g/test) from Non-Tampered
Post-1989 LDVs and LDTs for
Non-Summer Period (In-Use RVP Constant at 11.5 psi)
Certification RVP (psi)
Carbureted Vehicles
Properly Designed
and Operated
Improper Design
Malmaintenance
and Defect
RVP Effect
Total
Fuel-Injected Vehicles
Properly Designed
and Operated
Improper Design
Malmaintenance
and Defect
RVP Effect
Total
9.5
0.91
0.00
1.61
4.33
6.85
0.91
0.00
0.84
2.03
3.78
10.0
0.91
0.00
1.61
2.78
5.30
0.91
0.00
0.84
0.79
2.54
10.5
0.91
0.00
1.61
1.54
4.06
0.91
0.00
0.84
0.48
2.23
11.0
0.91
0.00
1.61
0.62
3.14
0.91
0.00
0.84
0.24
1.99
11.5
0.91
0.00
1.61
0.00
2.52
0.91
0.00
0.84
0.00
1.75
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6-69
Table 6-C-2
Hot-Soak Emissions (g/test) from Non-Tampered
Post-1989 LDVs and LDTs for
Non-Summer Period (In-Use RVP Constant at 11.5 psi)
Certification RVP (psi)
Carbureted Vehicles
Properly Designed
and Operated
Improper Design
Malmaintenance
and Defect
RVP Effect
Total
Fuel-Injected Vehicles
Properly Designed
and Separated
Improper Design
Malmaintenance
and Defect
RVP Effect
Total
9.5
10.0
10.5 11.0
0.93 0.93 0.93
0.24 0.18 0.11
1.78 1.72 1.65
11.5
1.09 1.09 1.09 1.09 1.09
0.00 0.00 0.00 0.00 0.00
1.24 1.24 1.24 1.24 1.24
0.73 0.42 0.20 0.06 0.00
3.06 2.75 2.53 2.39 2.33
0.61 0.61 0.61 0.61 0.61
0.00 0.00 0.00 0.00 0.00
0.93 0.93
0.05 0.00
1.59 1.54
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6-70
Table 6-C-3
Diurnal and Hot-Soak Emissions (g/test) from
Non-Tampered Post-1989 HDVs for
Non-Summer Period (In-Use RVP Constant at 11.5 psi)
Certification RVP (psi)
9.5 10.0 10.5 11.0 11.5
Diurnal Emissions
Properly Designed
and Operated 1.44 1.44 1.44 1.44 1.44
Improper Design 0.00 0.00 0.00 0.00 0.00
Malmaintenance
and Defect 2.57 2.57 2.57 2.57 2.57
RVP Effect 6.90 4.43 'a.46 0.98 0.00
Total 10.91 8.44 6.47 4.99 4.01
Hot-Soak Emissions
Properly Designed
and Operated 1.73 1.73 1.73 1.73 1.73
Improper Design 0.00 0.00 0.00 0.00 0.00
Malmaintenance
and Defect 1.97 1.97 1.97 1.97 1.97
RVP Effect 1. 15 0.67 0.31 0.09 0.00
•*
Total 4.85 4.37 4.01 3.79 3.70
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6-71
Table 6-C-4
Costs and Credits for "Base Case"
in 2010 ( $ million/yr.)
12-Month Analysis
In-Use/Cert .
Refinery Cost
Fuel Econ. Credit
Vehicle Cost
Weight Penalty
Evap. Recv. Credit
Total Cost
11.5
0
0
28
8
196
-160
11.0
192
72
23
7
224
- 75
4 -Month
10.5
421
163
18
5
254
28
Analysis
In-Use/Cert .
Refinery Cost
Fuel Econ. Credit
Vehicle Cost
Weight Penalty
Evap. Recv. Credit
Summer Period
Winter Period
11.5
0
0
28
8
64
127
11.0
64
24
23
7
85
111
10.5
140
55
18
5
100
93
RVP (psi)
10.0
686
261
14
3
283
159
RVP (psi)
10.0
229
87
14
3
111
73
9.5
962
366
9
2
311
296
9.5
321
122
9
2
114
40
9.0
1256
477
0
0
339
440
9.0
419
159
0
0
112
0
Total Cost
-155
-126
- 85
- 25
56
148
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