Special Report
Analysis of the Economic and
Environmental Impacts of Liquefied
Petroleum Gas (Propane) as a Vehicle Fuel
United States Environmental Protection Agency
Office of Mobile Sources
April 1995
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U.S. ENVIRONMENTAL PROTECTION AGENCY
NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY
2565 Plymouth Road, Ann Arbor, Michigan 48105
Announcement - Publication of LPG Special Report
Enclosed is a copy of an Office of Mobile Sources Special Report: "Analysis of the
Economic and Environmental Impacts of Liquefied Petroleum Gas (Propane) as a Vehicle
Fuel." This is part of a series of reports which describe the impacts of various alternative
fuels, such as methanol, ethanol, and compressed natural gas. If you would like
additional copies of this report, or any of the previous special reports, please contact Mary
Seminitis at (313) 668-4516 (FAX:668-4573).
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Table of Contents
Chapter 1 Introduction
Nature of the Report 1
Background 1
Sources of Additional Information 3
References 4
Chapter 2 LPG-Fu»l«d Vehicle Technology 5
Introduction 5
Fuel Properties of LPG 5
Current Converted Vehicle Technology 6
Optimized OEM LPG-Fueled Vehicles 9
Safety 11
Durability 12
Fuel Economy 12
Exhaust Emissions 13
Low Temperature Emissions 20
Evaporative and Other Emissions 20
Vehicle Scenarios 21
Heavy-Duty Engines and Vehicles 22
References 24
Chapter 3 Economic Impacts 26
Introduction 26
LPG Supply 26
Fuel Prices 28
Vehicle Fuel Economy and Cost 30
Summary 32
References 33
Chapter 4 Air Quality Impact* 34
Introduction 34
Urban Ozone Levels 34
Carbon Monoxide 37
Air Toxics 37
Global Warming 40
Summary 41
References 42
Chapter 5 Conclusion* 43
Use of LPG as a Vehicle Fuel 43
Benefits 44
Need for Additional Studies 45
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Table of Contents
(Appendices)
Appendix I Data from Sears Fleet
Appendix II LPG Emissions Data from Late Model Vehicles
Appendix III Dual-Fuel Gasoline Emissions Data
Appendix IV Low Temperature LPG Emissions Data
Appendix V Heavy-Duty LPG Certification Data
Appendix VI Heavy-Duty LPG Emissions - Bus Chassis Data
Appendix VII Material Safety Data Sheet
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EPA Office of Mobile Sources Special Report
Chapter 1
Introduction
Nature of the Report
This report is part of a series of special reports on the economic and
environmental impacts of alternative automotive fuels; previous reports have
addressed the impacts related to methanol, compressed natural gas (CNG) and
ethanol. These reports are not intended to represent the final word on these
alternative fuels, but rather to present the Agency's best estimate of the extent to
which each of these fuels can contribute to efforts aimed at improving our nation's
urban air quality. Given the rate at which vehicle technology is advancing, the reader
is cautioned that the quantitative estimates presented in these reports may become
outdated after publication, though the directional trends should remain valid.
This report consists of three parts: 1) a technology assessment analysis, 2) an
economic impact analysis, and 3) an environmental impact analysis. The technology
assessment is described in Chapter 2, and is used as a basis for the analyses of the
economic and environmental impacts, which are described in Chapters 3 and 4,
respectively. Each of these chapters include discussions which qualify the available
data and identify the assumptions made in the analysis. The conclusions of the report
are summarized and qualified in Chapter 5. Issues related to the implementation of
alternative fuel programs are not considered here.
Background
Liquefied petroleum gas (LPG) is broadly defined as a gas mixture comprised
of propane, butane, ethane, propylene and/or butylene. The fuel is liquefied to reduce
its volume for transportation and storage by compressing the gas to pressures greater
than 100 pounds per square inch (psi). Because of concerns about fuel volatility for
heating use, LPG sold commercially is comprised mostly of propane. Thus, the term
"propane" is often used interchangeably with "LPG." The term LPG is used in this
report, and means propane-based LPG fuel, unless otherwise noted. The reader is
cautioned that when used in other reports, especially when related to LPG supply
and/or production, the term LPG is often used in the broader sense, and includes
butane, ethane, propylene and/or butylene, in addition to propane.
It should also be emphasized that the fact that the current commercial market
for LPG requires that it be mostly propane is related to operational requirements for
its use as a heating fuel, and property designed vehicles could use LPG fuels with
higher concentrations of heavier hydrocarbons such as butane. However, the current
market for LPG as a vehicle fuel is too small to justify the existence of a separate
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EPA Office of MOM* Soura* Sp*c*l Report
grade of LPG, since it would require segregated distribution (although it could use
many of the same pipelines). Nevertheless, with a sufficient number of LPQ-fueled
vehicles, it could become economically feasible to create another grade of fuel, and
thus it is possible that future LPG-fueled vehicles will be designed to use LPG
containing substantial amounts of heavier hydrocarbons.
LPG currently is sold and distributed extensively throughout the U.S.
Residential and commercial heating, which is the largest commercial usage segment,
accounts for 35 percent of the U.S. market, while automotive use accounts for only
3 percent of LPG sales.[1] Much of the automotive market involves centrally-fueled
fleets such as utility trucks and buses. LPG is also commonly used in forklifts,
because LPG engines can be calibrated for very low CO emissions, which enables
them to be used indoors. Significant numbers of LPG-fueled vehicles are also being
used in Canada, Japan and Europe. This experience with LPG-fueled vehicles has
demonstrated that such vehicles are quite reliable. However, since the interest in LPG
has historically been motivated by economic considerations (primarily lower fuel
costs), the vehicles have only recently begun to be optimized with respect to
emissions. The potential for the optimization of the emissions control systems of
LPG-fueled vehicles is discussed in the technology analysis in Chapter 2.
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EPA Office of Mobito SOUICM Special Report
Sources of Additional Information
Given the somewhat limited scope of this report, and the likelihood that there
will be unforeseen advancements for LPG-fueled vehicles after this report is published,
the reader may wish to obtain additional or updated information regarding LPG-fueled
vehicles. Several sources are listed below. It should be emphasized that there may
be other reliable sources of information that are not listed here, and that their
exclusion from this list should not be considered to be indicative of the Agency's
disapproval of their merit.
Gas Processors Association
6526 East 60th Street
Tulsa, OK 74145
(918) 493-3872
National Propane Gas Association
4301 North Fairfax Drive
Suite 340
Arlington, VA 22203
(703) 351-7500
Propane Consumers Coalition
1110 North Glebe Road
Suite 610
Arlington, VA 22201
(703) 522-1324
Propane Gas Association of Canada
1800-300 Fifth Avenue S.W.
Calgary, Alberta T2P 3C4
Canada
(403) 263-0450
Propane Vehicle Council
901 15th Street, NW
Suite 470
Washington, DC 20005
(202) 371-6262
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EPA Offlc* of Mobil* SOUKCM Special Ftoport
References
1. "An Assessment of Propane as an Alternative Transportation Fuel in the United
States,' Prepared by R.F. Webb Corporation, for the Natural Propane Gas
Association, June 1989.
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EPA Office of Mobile Sources Special Report
Chapter 2
LPG-FueiecJ Vehicle Technology
Introduction
This chapter addresses issues related to engine performance, including fuel
properties, emissions, fuel economy, and safety. These discussions will form the
basis for the remainder of the report. Because LPG-fueled vehicles are still in a
developmental stage in many respects, the following discussions cannot be definitive;
rather they are intended to identify the range of potential in-use engine characteristics
and to make reasonable projections of future fuel economy and emissions. Wherever
possible, the discussions highlight significant areas of uncertainty in the analyses.
This chapter, and the remainder of this report, focus on light-duty vehicles and
light-duty trucks; heavy-duty engines and vehicles will be discussed only briefly at the
end of this chapter. For simplicity, this chapter considers only two types of vehicles:
1) current generation gasoline-fueled vehicles that were converted to use LPG, and
2) advanced vehicles that would be designed and built in the future specifically to use
only LPG. While other possible types of vehicles, such as advanced dual-fuel1
vehicles, are not specifically considered here, much of the following discussion would
still be relevant. It is important to note that EPA is not predicting that the "optimized"
vehicles discussed in this chapter will ultimately be produced, but rather EPA is
presenting its best estimate of what could be achieved given sufficient market and
regulatory incentives.
Fuel Properties of LPG
The properties of LPG as a heating fuel are well studied. The majority of
current commercial LPG meets the requirements of ASTM specification 01835 for
"Special Duty Propane" (which is essentially the same as "Propane HD-5 of Gas
Processors Association Standard 2140") for vehicle use.[1] As the name implies, the
specification requires that most of the LPG be propane; the maximum amount of
butane and heavier compounds is 2.5 percent, and the maximum amount of propylene
is 5.0 percent. Slight compositional deviations from this specification may occur with
in-use "propane", but they are not considered here. As noted in the first chapter,
other grades of LPG could be used as a vehicle fuel, but the focus of this report is on
vehicles using "Special Duty Propane."
1 In this report, the term "dual-fuel" is used to describe vehicles that are capable of operating on two
different fuels; the reader is advised, however, that the term 'dual-fuel* can have other meanings in other
contexts.
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EPA Offla <* Mobil* SourcM Special Report
When compared to gasoline as a motor fuel, LPG has both advantages and
disadvantages. Typical fuel properties of commercial propane are summarized in
Table 2-1. The energy content of LPG is about 19,700 BTU/lb (lower heating value2),
which is slightly higher than standard gasoline (18,700 BTU/lb). However, due to its
lower density (approximately 4.1 Ib/gal for LPG vs. 6.2 Ib/gal for gasoline), it has a
lower energy content on a volumetric basis, and thus, LPG-fueled vehicles require
larger fuel capacities to obtain driving ranges equivalent to gasoline-fueled vehicles.
LPG has an octane number of about* 104 ([R+M]/2), while the octane number of
commercial gasoline ranges up to 94 ([R+MJ/2); thus spark ignition engines running
on only LPG can use higher compression ratios than those running on gasoline. LPG
also tends to bum with a lower peak flame temperature, which can lead to lower NOx.
The greatest difference between LPG and gasoline involves fuel volatility. LPG
is much more volatile than gasoline; thus the fuel enters the intake system and the
cylinders fully vaporized (not partially vaporized, as is the case with gasoline). This
difference affects the engine in several ways. First, the higher volatility contributes to
better mixing with air prior to ignition. The gaseous nature of the fuel also limits its
interaction with the oil used to lubricate the cylinder walls (in gasoline-fueled engines,
especially during cold starting, the fuel tends to dilute the oil on the walls, which
reduces the lubrication, and thereby increases engine wear). On the other hand,
since the gaseous fuel occupies a greater volume than the liquid, less air can enter
the engine, which reduces the power output of the engine. This effect can be offset
by the ability of LPG-fueled vehicles to use higher compression ratios, as was noted
above.
Current Converted Vehicle Technology
Most current LPG-fueled vehicles are gasoline-fueled vehicles which have been
converted to run on LPG. In the past, the conversion process has generally involved
the modification of a carburetted engine using a relatively simple kit. The purpose of
most conversions was not related to air quality, but rather, the conversions were done
to take advantage of economic benefits of LPG. From an emissions perspective,
these vehicles represent a starting point for LPG-fueled vehicle technology, and, as
such, are the focus of this section. A large number of the vehicles already converted
allow the driver to switch fuels from LPG to gasoline and back. These dual-fuel
vehicles avoid problems associated with fuel availability; however, since they must be
capable of operating on either fuel, they cannot be fully optimized for LPG.
2 Energy content can be expressed as higher or lower heating values. The difference is that the lower
heating value assumes that the water that is produced from the oxidation reaction is a vapor, not a liquid.
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EPA OIK* ol MoOto SOUICM Special Report
Table 2-1
Fuel Properties
Properties
Energy Content*
Density*
Octane Rating" (R+M)/2
Peak Flame Temperature**
Auto-ignition Temperature**
Stoichiometric Air/Fuel Ratio**
(by weight)
Boiling Range** (1 atm.)
Special Duty
Propane
19,700 BTU/lb
4.1 Ib/gal
104
3600eF
855°F
15.7
-44 to +31 °F
Unleaded Gasoline
18,700 BTU/lb
6.2 Ib/gal
87-94
3900-41 00°F
440-880°F
14.5-15.5
80 to 420°F
EPA [2]
EA Mueller [3]
The conversion of a gasoline-fueled vehicle to one that is capable of operating
on LPG requires a relatively small number of modifications, including the addition of
an LPQ fuel system. Adding an LPG fuel system requires installing a special fuel tank
and fuel lines for the pressurized fuel, and a means of controlling the flow of fuel. The
pressure associated with LPG is generally 100 to 200 psi under normal storage
conditions, which is not an extremely high pressure; thus, the fuel system can be
relatively simple. (For comparison, tire pressures are typically 35 psi.) The addition
of a normal LPG fuel system does, however, increase the vehicle weight by
approximately 100 pounds. It is also necessary to add a pressure regulator and to
add a gas mixer, which mixes the LPG with the air before it enters the engine. For
carburetted engines, the mixer generally sits on top of the carburetor, and the existing
throttle controls the amount of the fuel/air mixture that enters the engine. For fuel-
injected engines, the mixer can be located upstream of the throttle. It is generally
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EPA Office of Mobile Source* Special Report
necessary to route engine coolant through the regulator system to prevent localized
freezing of the fuel as it expands. For dual-fuel vehicles, it is necessary to stop the
flow of one fuel into the engine when operating on the other, so solenoid valves are
also needed for the fuel lines.
Although it is not necessary to make further modifications, it is often worthwhile
to make changes to the ignition timing of the engine to account for the higher auto-
ignition temperature and octane rating of LPG. Optimum power and fuel economy for
LPG-fueled engines requires more spark advance at low speeds and less at high
speeds than is required for gasoline.[3] For engines which are not computer-
controlled, changes to timing can be implemented using relatively simple ignition
devices. For dual-fuel vehicles, such devices allow the timing to be optimized
somewhat for both LPG and gasoline, but not as well as can be achieved with
computer controls. However, optimizing the timing of computer-controlled engines
for both LPG and gasoline is not trivial since it requires installation of a modified
microprocessor. Because of this, as well as the challenges associated with fuel-
injection, current LPG-fueled vehicles are disproportionately converted carburetted
gasoline-fueled vehicles that did not have computer controls.
More recently, higher technology conversion kits have become available that
allow computer-controlled, fuel-injected gasoline-fueled vehicles to be converted to
also run on LPG. Since such vehicles are today's conversions, the portion of the
analysis that deals with 'current* vehicle technology will be based primarily upon these
more recent technology vehicles. The reader is cautioned, therefore, that some of the
discussions that follow are not generally applicable to older LPG-fueled vehicles.
For the analyses contained in this report, it will be assumed that the primary
goals of manufacturers of current conversion kits are to comply with EPA emissions
standards for conventional vehicles,[4] and to minimize kit costs and fuel consumption.
This assumption is reasonable since: 1) EPA prohibits conversions which result in
vehicles not complying with the standards to which they were originally certified, 2)
there is currently little incentive for manufacturers to lower emissions significantly
below these levels, especially if such reductions would result in higher kit costs or
increased fuel consumption, and 3) the purpose of conversion to LPG use has
generally been to lower fuel costs. The effects that this assumed optimization strategy
would have on the costs and performance of "current* LPG-fueled vehicles are
described in later sections of this report. It should be noted that this assumption
applies only to 'current converted* vehicles, and that a different strategy is assumed
for "optimized OEM" vehicles (see following section). The Agency does recognize that
some noncompliance may occur in use, and is most concerned about improper
calibration of the air/fuel ratio (see "Exhaust Emissions") and slowly leaking fuel lines
(see "Evaporative and Other Emissions") from vehicles that are converted incorrectly.
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EPA Office at Mobile Sources Special Report
Optimized OEM3 LPG-Fueled Vehicles
Few current LPG-fueled vehicles have been built specifically for use with LPG
fuel, though several automobile manufacturers are currently involved in LPG-fueled
vehicle research. This situation may change, however, if the demand for LPG-fueled
vehicles increases. An increase in demand would have two benefits. First, it would
make it more cost-effective (on a per-vehicle basis) for manufacturers to invest in the
research and development of LPG-fueled vehicle technology. Second, it would lead
to greater availability of refueling facilities, and thus, greater acceptance of dedicated
LPG-fueled vehicles. This latter point is significant because many of the potential
improvements are not possible for vehicles that must also be able to operate on
gasoline. Therefore, it is reasonable to expect that if LPG-fueled vehicles were
produced in significant numbers, the vehicles would be more advanced than the
vehicles discussed above. Among the improvements that would be expected are fully
optimized ignition timing and air/fuel ratio calibration, increased compression ratio,
improved fuel injection, and optimization of catalyst formulations for LPG.
Most gasoline-fueled vehicles being produced now have computerized controls
for ignition timing and air/fuel ratio control. With "closed-loop" systems, the optimum
settings are continuously determined by the computer based on the inputs received
from various engine sensors, which monitor parameters such as engine temperature,
the oxygen content of the exhaust, and engine speed. For each set of inputs, there
is a set of engine parameters that optimize engine performance, including emissions
control. Most of these systems have been further improved by the addition of
adaptive learning capability. Adaptive learning allows the system to modify its control
behavior, based on patterns observed from previous operation. This is very
advantageous since it allows the controller to correct for deterioration and defects in
the engine and emission control systems, or changes in the air or fuel. For example,
systems with adaptive learning will respond to reductions in the concentration of
oxygen in the exhaust that result from operation at higher altitudes, where the
volumetric concentration (mass per unit volume) of oxygen in air is lower, by
increasing the volumetric air/fuel ratio. Such systems are now becoming available for
LPG-fueled vehicles as well. It is expected that, with the appropriate research, these
systems will soon be able to perform virtually all of the functions performed by the
systems currently used with gasoline-fueled vehicles, and thus will provide a means
of further optimization of LPG-fueled vehicle emissions and fuel economy.
s
The compression ratio of an internal combustion engine greatly affects the
efficiency of the engine. Higher compression ratios lead to greater efficiency, but also
lead to increased combustion temperatures and thus increased NOx formation. With
3 OEM (Original Equipment Manufacturer) LPG-fueled vehicles (or engines) are vehicles (or engines)
that were designed and produced specifically to use LPG fuel, as opposed to vehicles (or engines) that
were originally intended to use gasoline but were modified after production to use LPG.
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EPA Office of Mobil* Source* Special Report
spark ignition engines, the upper limit on the compression ratio is determined by the
octane rating of the fuel. Since LPG has a significantly higher octane rating than even
"premium" gasoline, higher compression ratios can be used in dedicated LPG-fueled
vehicles. Also, the lower peak flame temperature and potentially lower air/fuel intake
temperature of LPG can offset the increase in temperatures that is associated with
higher compression ratios, so that the net effect on NOx emissions would be small.
Converted vehicles generally do not take full advantage of this benefit, since
compression ratios are difficult to modify for an engine that has already been built.
Similarly, compression ratios for dual-fuel vehicles are limited to about 9:1 by the
octane rating of gasoline. Engines that were originally designed to use only LPG
could take advantage of the octane benefits of LPG, although practical considerations,
such as production cost, may limit the compression ratio of even dedicated vehicles
to about 12:1.
The proper delivery of fuel and air to the engine plays an important role in the
operation of a vehicle. Earlier gasoline-fueled vehicles relied upon carburetors to
combine the fuel and air together into a mixture which was drawn into the cylinder by
the piston movement. Most engines today, however, rely upon fuel-injection to deliver
the fuel to the engine, since it results in more precise control of the air/fuel ratio.
Similarly, new LPG-fueled engines are also expected to rely upon fuel-injection to
deliver fuel to the engine. Fuel-injection systems have been developed for current
conversions to gaseous fuels, but these systems have generally not been able to
provide the level of control that is provided by gasoline fuel-injection systems.
However, improved fuel injection systems (both gaseous fuel-injection systems and
liquid fuel-injection systems) are continually being developed for LPG-fueled
vehicles,[5,6,7] and it appears very likely that these newer systems will ultimately have
performance that is essentially as good as fuel-injection systems for gasoline-fueled
vehicles.
Virtually all current LPG-fueled vehicles use catalytic converters that were
optimized to treat exhaust from gasoline-fueled vehicles. Since hydrocarbon
emissions from LPG-fueled vehicles have a different composition than hydrocarbon
emissions from gasoline-fueled vehicles, the efficiency of the catalytic converters on
current LPG-fueled vehicles is less than optimal. Catalyst manufacturers are currently
working to develop catalysts specifically for LPG-fueled vehicles, and it is expected
these newer catalysts will lead to further reductions in emissions.[6,8]
/
It is beyond the scope of this report to list all of the potential and expected
improvements for LPG-fueled vehicles. The improvements discussed above are
considered to be the most important, but are certainly not the only ones. In addition
to the LPG-specific improvements described above, it is expected that future
optimized LPG-fueled vehicles will also incorporate many of the technological
advancements that are currently being developed for other fuels. For this report it is
assumed that future optimized LPG-fueled vehicles will have fully optimized computer
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EPA Offic* of Mobito SOUICM Special Report
controls for the air/fuel ratio and spark timing, optimized fuel injection, and optimized
catalytic converters, and that these systems will perform as well as gasoline-fueled
vehicle systems. Moreover, it is assumed that they will have higher compression
ratios than gasoline-fueled vehicles.
It is expected that most of these vehicles will be used in fleet applications,
especially in fleets that will be affected by the federal "Clean-Fuel Fleets" program,
which requires the purchase of low-emitting vehicles.[9] Since fleet operators are also
generally concerned with keeping fuel costs low, manufacturers are expected to
design future LPG-fueled vehicles for both low fuel consumption and low emissions.
In this report, it is assumed that manufacturers of future "optimized OEM" LPG-fueled
vehicles will follow this strategy.
Safety
Some concerns have been raised regarding the safety of LPG-fueled vehicles.
These concerns result from the gaseous nature of the fuel at normal atmospheric
conditions, which presents some additional challenges regarding safety. Nevertheless,
the current body of evidence suggests that LPG use in properly designed vehicles is
as safe as gasoline.[10,11,12] It is important to emphasize that all fuels are
dangerous when they are not handled properly, and in this respect, LPG is no
different. The most important aspects of LPG-fueled vehicle safety are described in
more detail below.
There currently are no federal safety requirements for the fuel system integrity
of LPG-fueled vehicles. The National Highway Traffic Safety Administration (NHTSA),
in a recent Notice of Proposed Rulemaking,[13] suggested that such requirements
may not be necessary since every state has already adopted some form of the
National Fire Protection Association (NFPA) Standard 58, "Standard for the Storage
and Handling of Liquefied Petroleum Gases."[14] The NFPA standard addresses such
issues as installation of LPG systems, transport and transfer of LPG, and storage.
There is currently no evidence that short term exposure to LPG, such as
inhalation, causes any adverse health effects. In this respect it is unlike gasoline and
diesel fuel, which are both reasonably toxic. The primary concern with respect to LPG
exposure is the potential for frostbite-like bums resulting from direct contact with the
liquid as it evaporates and expands.[11,12] The liquid itself is not cold, but the
evaporation of the liquid and the expansion of the gas draw heat from surroundings,
lowering the temperature well below 0°C. Overall, however, the risks associated with
LPG exposure are small when compared to those of conventional fuels.
The greatest LPG safety concern involves the potential for explosions in
enclosed spaces. If a leak occurs in an LPG fuel system, the leaking fuel vaporizes
as it escapes. In an open area, this is advantageous, since it results in a fairly rapid
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EPA Office of Mobile Sources Special Report
dispersal of the fuel, which greatly reduces the risk of fire or explosion. In an
enclosed area, however, the fuel can mix with the room air to form a potentially
explosive mixture. This hazard can be avoided by maintaining proper ventilation in
all areas where LPG vapors could accumulate. Proper ventilation must account for
the fact that LPG vapors are heavier than air, and thus will disperse downward. For
a more thorough discussion of LPG fire safety, the reader is referred to NFPA
Standard 58.
Durability
As was noted above, lubrication of the engine cylinder during cold-starting is
generally better with LPG than with gasoline. With gasoline-fueled vehicles, when the
engine is cold, the fuel can remain in liquid form and dilute the oil on the cylinder
walls. The dilution of the oil reduces its ability to provide proper lubrication for the
piston, which leads to higher rates of engine wear, and decreased engine life. LPG
is much more volatile than gasoline, and interacts very little with the oil on the cylinder
walls; thus, the engine cylinders in LPG-fueied vehicles can have less deterioration
in use than gasoline-fueled vehicles. This benefit is difficult to quantify, however,
since it is very dependent upon driving and maintenance practices. Nevertheless,
there is some evidence to suggest that, in some cases, the life of an LPG-fueled
engine may be as much as twice as long as that of a comparable gasoline-fueled
engine.[15] It should be noted, however, that the significance of this benefit has
decreased, and will probably continue to decrease in the future, due to improvements
in gasoline-fueled engine designs that reduce this type of wear.
On the other hand, LPG-fueled engines without hardened valve seats can have
greater valve seat wear, presumably because the fuel lacks the lubricity of liquid fuels.
When the problem occurs, it can have a very negative impact on both fuel economy
and emissions. However, this problem should not affect properly designed OEM
vehicles, and can be prevented in conversions by installing hardened seats if they
were not originally present in the gasoline-fueled vehicle.
The LPG fuel system, while different, is also expected to be designed to be as
durable as the fuel systems of other vehicle types. Durability of other LPG-fueled
vehicle components, including the emissions control system, is expected to be similar
to that observed in gasoline-fueled vehicles, since most of these components are
essentially the same for both fuels, and are used under similar conditions.
Fuel Economy
Fuel economy for LPG-fueled vehicles is often expressed as miles per gallon
of LPG fuel. However, since it takes 1.4 gallons of LPG to provide the same amount
of energy as one gallon of gasoline, the fuel economy is also commonly expressed
on an energy-equivalent basis with gasoline (i.e., miles per equivalent gallon of
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EPA Office of Mobile Sources Special Report
gasoline, where one equivalent gallon of gasoline equals 1.4 gallons of LPG).
Generally, as can be determined from the C02 data in the appendices, current dual-
fueled vehicles have comparable fuel economy ratings on an energy equivalent basis
when using LPQ and gasoline; however, the volumetric fuel economy ratings are
much lower for LPG than for gasoline (30 percent less with equivalent thermal
efficiency). By optimizing the engine for LPG, however, it is possible to obtain a
higher thermal efficiency than is possible with gasoline. In a report for the
Congressional Research Service, the R.F. Webb Corporation estimated that converted
vehicles could achieve 77 percent of the volumetric fuel economy of similar vehicles
running on gasoline, and that vehicles that were originally designed for LPG could
achieve 87 percent of the volumetric fuel economy of similar vehicles running on
gasoline.[16] Webb also reports dedicated LPG-fueled vehicles that are already
achieving 95 percent of the volumetric fuel economy of similar gasoline-fueled
vehicles, which indicates an increase in thermal efficiency of more than 30
percent.[11] However, it should be noted that no emissions rates were given for this
vehicle.
EPA recognizes that the available data are not sufficient to allow definitive
estimates of in-use fuel economy. The Agency believes that it would be unreasonable
to expect that a 30 percent increase in engine efficiency will be applicable to all LPG-
fueled vehicles. In fact, given the challenges of optimizing emissions and fuel
economy simultaneously, it is doubtful that any LPG-fueled vehicles would have 30
percent greater thermal efficiency than gasoline-fueled vehicles with comparable
emissions. Nevertheless, the Agency is reasonably confident that some increase in
efficiency will occur, primarily as the result of increased compression ratios. For this
report, it is estimated that the thermal efficiency of current LPG-fueled vehicles is the
same as gasoline-fueled vehicles, and that the thermal efficiency of future optimized
LPG-fueled vehicles will be 10 percent higher than gasoline-fueled vehicles. These
assumptions mean that LPG-fueled vehicles will have 70 to 77 percent of the
volumetric fuel economy of comparable gasoline-fueled vehicles. The estimate for
current vehicles is consistent with the data discussed below. The estimated increase
in thermal efficiency for future vehicles is comparable to the theoretical increase in
thermal efficiency that would result from increasing the compression ratio of an engine
from 9:1 to 12:1 .[17] Such an increase is possible with LPG, given its higher octane.
Exhauat Emissions
The primary emissions advantage of LPG is that, as a gaseous fuel, LPG is
easier to mix with air than gasoline. This better mixing results in a more
homogeneous charge in the cylinder which tends to lower both hydrocarbon (HC) and
carbon monoxide (CO) emissions. Another advantage is that the combustion of LPG
can have a lower peak flame temperature than gasoline, which tends to lower
emissions of oxides of nitrogen (NOx). The lower peak flame temperature can,
however, result in higher HC emissions. As is the case with gasoline-fueled vehicles,
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the actual emissions from an LPG-fueled vehicle are highly dependent upon how the
vehicle is calibrated.
One of the primary parameters of emissions-related engine calibration is the
ratio of air to fuel that is mixed for combustion. The air/fuel ratio of a vehicle can be
varied from rich, where the air/fuel ratio is low and there is not enough air to fully
combust the fuel, to lean, where the air/fuel ratio is high and there is more air than is
necessary to fully combust the fuel. When air/fuel ratio is such that there is just
enough air to fully combust the fuel, then the engine is said to be calibrated at
stoichiometry. Often, especially when comparing different fuels, the air/fuel ratio is
normalized by dividing the actual air/fuel ratio by the stoichiometric air/fuel ratio; this
is the excess-air factor (X).
The value of the air/fuel ratio affects the emissions of an engine in several
ways, as shown in Figure 2-1. Obviously, when the engine is calibrated rich (i.e., low
air/fuel ratio), the fuel cannot be completely oxidized to CO2 due to the lack of
sufficient oxygen for reaction. The incomplete reactions leave unbumed fuel (HC) and
partially burned products (HC and CO). Increasing the air/fuel ratio (i.e., leaning the
mixture) tends to decrease emissions of HC and CO; but if the mixture is leaned too
much, misfiring or failure of full flame front propagation can occur, which leads to
increased HC emissions.
The air/fuel ratio affects NOx emissions in two ways: by affecting the
combustion temperature, and by changing the concentrations of oxygen and nitrogen
in the cylinder. Enriching a lean mixture can lead to increased combustion
temperatures, while leaning the mixture increases the concentrations of oxygen and
nitrogen in the cylinder; either of these effects can lead to increased NOx emissions.
Because of these competing effects, NOx formation tends to be greatest when the
air/fuel ratio is set slightly lean of stoichiometry.
Clearly then, it is not possible to control the air/fuel ratio to simultaneously
minimize engine-out emissions4 of HC, CO, and NOx. The manufacturer's optimal
calibration depends on the relative importance of reductions in engine-out emissions
of HC, CO, and NOx, based on applicable emission and fuel economy standards, and
the availability of exhaust aftertreatment that can further reduce emissions.
Gasoline-fueled vehicles are typically calibrated rich for start-up, but calibrated
to operate with a stoichiometric air/fuel ratio in a closed-loop mode under normal
operation.[18] During start-up, it is necessary to run rich because the gasoline is not
fully vaporized until the engine becomes hot. This is not the case for LPG-fueled
vehicles, and properly calibrated LPG-fueled vehicles should be calibrated at
4 Engine-out emissions are the emissions before (without) any aftertreatment such as a catalytic
converter.
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EPA Offlc* of MoM« Sourctt Special Report
stoichiometry or leaner during start-up. Two of the most important reasons why
gasoline-fueled vehicles are calibrated to operate with a stoichiometric air/fuel ratio
under normal operation are that current oxygen sensors only work for vehicles
calibrated with stoichiometric air/fuel ratios, and that stoichiometric calibration
maximizes the efficiency of the catalytic converters. Both of these factors apply to
current LPG-fueled vehicles as well; thus, it is reasonable to expect that typical
"current" LPG-fueled vehicles will also be calibrated to operate with a stoichiometric
air/fuel ratio under normal operation.
Existing LPG-fueled vehicles were generally not designed to take advantage
of the potential emissions benefits of LPG. In theory, some minor emissions
reductions might be expected from improved mixing, or from LPG combustion
properties; however, it is very difficult to quantify the reductions because of the limited
amount of emissions data that is available. Older LPG-fueled vehicles can have
extremely high emissions, similar to older gasoline-fueled vehicles. A report by the
California Air Resources Board (GARB) showed CO emissions from a 1979 LPG-
fueled van to be 201 g/mile.[19] For comparison, the federal CO emission standard
for light-duty trucks in 1979 was 18 g/mile. The CARB report also included data from
testing of other LPG-fueled vehicles, all of which are shown in detail in Appendix I.
These data are included to demonstrate that LPG-fueled vehicles can have fairly high
emissions. Thus, it is important to remember that simply switching to LPG will not
provide emissions benefits if the vehicles are not properly calibrated.
There are data available from testing of later model LPG-fueled vehicles; these
data are summarized in Appendix II. Many of these were dual-fuel vehicles, anjd
testing was performed using both LPG and gasoline (see Appendix III). While
comparison of such data from testing using the two fuels with the same vehicle would
appear to provide an ideal means to estimate the benefits of LPG, there are several
reasons why this is not the case. First, it is not necessarily appropriate to compare
the emissions of a dual-fuel vehicle using LPG to the emissions from the same vehicle
using gasoline after the conversion since it is likely that the conversion process
affected the gasoline-fueled performance of the vehicle somewhat. Second, the
conversions generally are not made at zero miles, so that the gasoline systems can
have significantly higher mileages than the LPG systems have when tested. Finally,
since engines can have slightly lower power output using LPG than when using
gasoline,[15] it is possible that a customer planning to convert a gasoline-fueled
vehicle to an LPG-fueled vehicle would purchase a larger engine than would have
been necessary with dedicated gasoline use.
15
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EPA Offic* at Mobte SOUICM Spatial Report
Figure 2-1
ppml
OJ
Nm
g/kWh
•O
5001
E
-400 |
o
o
300*5
3
200
100
.0
a
W
0.8 1 12
Excess-air factor A
From 'Bosch Automotive Handbook,' 2nd Edition, 1986.
16
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EPA Office of Mobile Sources Special Report
It is also not possible to determine the fleet-wide exhaust benefits of LPG-
fueled vehicles when compared to representative gasoline-fueled vehicles by simply
calculating the average emission rates from the available data. The emissions data
that are available vary a great deal from vehicle to vehicle, and the distribution of
vehicles for which emissions data are available is not comparable to a cross section
of current in-use gasoline-fueled vehicles; the number of trucks and large cars is
disproportionately high. Further, the testing was performed at different mileages, and
is difficult to compare to average in-use levels since these LPQ-fueled vehicles do not
have well characterized deterioration rates. Also, as noted above, there is some
reason to believe that LPG-fueled vehicles may have less engine deterioration in-use
than gasoline-fueled vehicles, but the significance of this is unclear. This uncertainty
makes it difficult to determine just how LPQ-fueled vehicles will perform in use.
There are data from four LPG-fueled vehicles tested by the State of Colorado,
for which there are also baseline gasoline data available.[20] This test program
measured emissions from gasoline-fueled vehicles before they were converted for use
of LPG, then measured emissions from the same vehicles, using LPG. These data
are shown in Table 2-2. While many of the same concerns raised above remain valid
with respect to these data, and the testing was performed at high altitude, the
gasoline-fueled emissions were measured before conversion, and can be considered
as truly baseline emissions. As such, these data are a somewhat reasonable basis
for comparison of emissions. The only clear trends from these data are that the CO
and CO2 emissions from the LPG-fueled vehicles are consistently lower. For CO, the
reductions range from 10 to 82 percent, and the average reduction is nearly 50
percent. The average COa reduction is 13 percent which indicates a nearly 5 percent
increase in the thermal efficiency of the engine. The HC and NOx emissions can be
higher or lower with LPG, but the average emissions from the four vehicles are similar
for both LPG and gasoline.
Recently, emissions results from two other studies, that may be even more
useful, have become available. In both studies, gasoline- and LPG-fueled vehicles
were operated side-by-side for several thousand miles. The first is a study by Phillips
Petroleum Company that compared the emissions from converted LPG-fueled vehicles
and identical unconverted gasoline-fueled vehicles.[21] The testing showed CO
emissions to be 21 percent lower, HC emissions to be 5 percent lower, and NOx
emissions to be 30 higher on average, with essentially identical thermal efficiency.
The second study involves an ongoing demonstration of the use of alternate fuels in
delivery vehicles.[22] The most useful data from this study are the emissions results
from three converted LPG-fueled vans and three unconverted gasoline-fueled vans.
These data are shown in Table 2-3. The LPG-fueled vans averaged 45 percent lower
CO emissions, 56 percent higher NMHC emissions, 47 percent higher NOx emissions,
and 10 percent lower CO2 emissions.
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EPA Offlc* at MobM Source* Special Report
Table 2-2
Comparison of Emissions from Identical Vehicles
Before and After Conversion
VEHICLE
1988 CROWN VICTORIA
1988 CROWN VICTORIA
1989 CHEVY PICKUP
1989 CHEVY PICKUP
1990 DAKOTA
1990 DAKOTA
1990 FORD 1-TON TRUCK
1990 FORD 1-TON TRUCK
FUEL
GASOLINE
LPG
GASOLINE
LPG
GASOLINE
LPG
GASOLINE
LPG
HC
(G/MI)
0.28
027
0.47
0.37
0.31
0.45
0.91
0.93
CO
(G/MI)
1.20
0.28
4.00
3.30
2.00
0.37
6.5
5.8
NOx
(G/MI)
0.80
0.60
0.70
0.70
1.10
1.70
5.9
4.7
CO2
(G/MI)
458
398
525
485
449
379
1065
907
Source: Colorado Department of Health [20]
Additional information is shown in Appendix II
Table 2-3
Comparison of Emissions from Converted LPG-Fueled and
Unconverted Gasoline-Fueled Delivery Vans
VEHICLE
1992 FORD VAN
1992 FORD VAN
FUEL
GASOLINE
LPG
HC
(G/MI)
0.264
0.412
CO
(G/MI)
1.8
1.1
NOx
(G/MI)
0.75
1.1
CO,
(G/MI)
662
594
Source: Clean Fleet [22]
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EPA Office of Mobile Source* Special Report
Given these data, and the previous assumption that the manufacturers'
optimization strategy would be aimed at minimizing fuel consumption and complying
with federal emission standards, (and that they would do this by recalibrating the
engine for LPG to run leaner than the previous calibration for gasoline during start-up),
it is most reasonable to assume that fleet-wide exhaust emissions of HC and NOx
from current in-use LPG-fueled vehicles would be similar to the average values for
gasoline, but that CO emissions would be lower. However, if the air/fuel ratio is not
property calibrated, emissions would be higher HC and CO would be higher if the
vehicle were calibrated too rich, while NOx would be higher if the vehicle were
calibrated too lean.
Optimized LPG-fueled vehicles could have more significant emissions benefits
compared to conventional gasoline-fueled vehicles than current LPG-fueled vehicles
have. However, it is not clear at this time just how such vehicles will be calibrated,
and thus it is not possible to precisely predict the future emissions levels of LPG-
fueled vehicles. Nevertheless, it is possible to estimate emissions for the assumed
emissions optimization strategy of optimizing fuel economy while meeting the federal
Ultra-Low Emission Vehicle (ULEV) emission standards:
- 0.040 g/mile NMOG5
-1.7 g/mile CO
- 0.2 g/mile NOx
- 0.008 g/mile Formaldehyde
For this analysis, it is assumed that optimized LPG-fueled vehicles will comply with
these standards in use. The emissions from prototype gasoline-fueled vehicles with
advanced emission control systems such as electrically heated catalysts are beginning
to approach these levels. Thus, given the cold-start advantage of LPG over gasoline,
it is very reasonable to expect that a fully optimized LPG-fueled vehicle could
ultimately be able to meet these standards. These are reasonable goals for
alternative fueled vehicles since CARB's LEV program provides strong encouragement
for the production of a significant number of vehicles meeting these standards. In
fact, IMPCO Technologies is currently working to develop a passenger vehicle that
meets these standards.[6] The Agency recognizes, however, that production of LPG-
fueled ULEVs would require a significant developmental effort and may ultimately be
prohibitively expensive.
9 For LPG, NMOG (Non-methane organic gas) is approximately equal to NMHC multiplied by a
reactivity adjustment factor (RAF), and is intended to provide a better indication of the effect of the
emissions on ambient ozone levels. If, for example, the RAF for LPG-fueled vehicles were 0.5, then a 0.04
g/mi NMOG standard would be roughly equivalent to a 0.08 g/mi NMHC standard. (See Chapter 4 for
additional discussion.)
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EPA Office of Mobil* Source* Special Report
Low Temperature Emissions
The primary emission concern regarding gasoline-fueled vehicles during winter
months is CO. At lower temperatures, gasoline does not vaporize well when the
engine is cold, and this leads to poor combustion and higher emissions. To account
for the poor vaporization, gasoline-fueled vehicles are calibrated to run rich during
start-up. LPG, on the other hand, vaporizes fully and mixes more completely with the
air, even at extremely low ambient temperatures, and thus does not require a rich
calibration during start-up. Data from cold temperature testing, which are shown in
Appendix IV, show that the difference in emissions can be dramatic.[23] These data
suggest that an LPG-fueled vehicle emitting the same amount of CO at 25*C (77T)
as a gasoline-fueled vehicle would emit only 7 to 17 percent as much CO as the
gasoline-fueled vehicle at O'C (32'F), or as little as 5 percent at -10'C (14'F). If the
LPG-fueled vehicle emitted less CO at 25°C, then the reductions would be even
greater. Based on these data, it is estimated that LPG-fueled vehicles will average
80 percent lower emissions at very low temperatures than gasoline-fueled vehicles.
This estimate is intended to be somewhat conservative; however, it is important to
remember that since the amount of low temperature data available is very limited, it
is possible that actual emissions benefits may be less than this.
Evaporative and Other Emissions
Since LPG fuel systems are designed to contain pressurized fuel, it is possible
to virtually eliminate evaporative emissions and greatly reduce refueling emissions.
Some older LPG-fueled vehicles can have significant evaporative emissions, but such
emissions can be eliminated for properly designed vehicles. For this report, it is being
assumed that LPG-fueled vehicles will have negligible, evaporative emissions.
Nevertheless, the Agency recognizes that there is a potential for some LPG to escape
from the fuel system, especially with improperly converted vehicles. In such cases it
would be possible for significant evaporative emissions to occur, even if the leaks did
not significantly affect fuel economy.
There are two sources of refueling emissions from LPG-fueled vehicles. First,
many older vehicles rely on outage valves (or spit valves) to indicate when the fuel
tank has been filled to its maximum level. When these valves are used, LPG vapors
are continuously emitted through the open valve during refueling. However, more
recent vehicles have automatic shut-off valves, which eliminate the need to use an
outage valve during refueling. EPA has recently finalized regulations for LPG-fueled
vehicles, that include provisions for refueling emissions.[4] These regulations will
require automatic shut-off valves, thus this source of emissions is being eliminated.
The second source of emissions is the small amount of liquid fuel that remains
in the connection between the vehicle fuel inlet and the fuel dispensing nozzle. When
this connecting seal is broken, the liquid fuel evaporates into the atmosphere. The
20
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EPA Office of Mobile Sources Special Report
mass emitted can be reduced by reducing the dead volume in the connection. This
volume can be very large for current systems which, until recently, have not been
regulated.[4] It has been estimated that dead volumes for natural gas systems can
be more than 100 cm3.[24] Although a similar analysis is not available for LPG
systems, it is reasonable to assume that dead volumes could also be that large in
some LPG systems. In optimized LPG refueling systems, the dead volumes range
from 1 to 12 cm3.[25] For this report, it will be assumed that the average dead volume
of current in-use refueling systems would be 5 cm3, which leads to an emission rate
of 2.5 grams per refueling event. For future vehicles, it is assumed that they will
comply with the recent EPA refueling regulations, and have average dead volumes of
3 cm3. [4] As can be seen in the environmental analysis of Chapter 4, the impact of
refueling emissions is small, and the validity of these assumptions is not critical.
Vehicle Scenarios
The following chapters will analyze and discuss the economic and
environmental impacts of LPG-fueled vehicles. These analyses will be performed
using two sets of assumptions to bracket possible benefits. "Current converted" LPG-
fueled vehicle emissions and fuel economy are based on a very limited amount of
data from late model vehicles tested at various mileages and vehicle conditions. It is
assumed that these vehicles are not optimized for low emissions, but rather for fuel
economy. Exhaust HC and NOx emission rates are estimated to be the same as from
gasoline-fueled vehicles, and CO emissions are estimated to be 80 percent lower at
low temperatures. No corrections are made to account for potential differences in in-
use deterioration between LPG- and gasoline-fueled vehicles.
"Optimized OEM" LPG-fueled vehicle emissions and fuel economy ratings are
projections of what could be achieved with a significant developmental effort, and are
based upon engineering judgment. It is assumed that these vehicles will be optimized
for fuel economy, but also will be designed to comply with the federal ULEV
standards. The ULEV standards are an appropriate goal for alternative fueled
vehicles since there are emissions related credit programs available for vehicles that
meet these standards. The reader is cautioned that these performance estimates are
assumptions that are based upon very limited data. Nevertheless, they are sufficient
for the purposes of this report, which is to estimate the potential for economic and
environmental impacts of LPG-fueled vehicles when compared to conventionally-fueled
and other alternately-fueled vehicles.
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EPA Office of Mobile Sources Special Report
The conventionally-fueled vehicles to which the LPQ-fueled vehicles will be
compared in Chapters 3 and 4 are:
"1990 Base" An average vehicle in the 1990 (calendar year) light-duty
gasoline-fueled vehicle fleet;
"2010 Base* An average vehicle in the 2010 (calendar year) light-duty
gasoline-fueled vehicle fleet;
"Gasoline ULEV" A vehicle certified to the ULEV standards using conventional
gasoline fuel.
It should be noted that, at this time, it is not certain that any future vehicles actually
produced will be able to comply with the ULEV requirements using conventional
gasoline. Nevertheless, as is the case with LPG, such a vehicle is theoretically
possible, though it may not be economically feasible; thus it is an appropriate vehicle
for comparison with advanced LPG-fueled ULEVs.
Heavy-Duty Engines and Vehicles
There is little emissions data available from LPG-fueled heavy-duty engines and
vehicles. In general, however, emissions from heavy-duty spark-ignited engines
should be similar to emissions from light-duty vehicles; fleet average exhaust HC and
NOx emissions should be about the same as those from gasoline-fueled engines, low
temperature CO emissions should be much lower than those from gasoline-fueled
engines, there should be little or no evaporative emissions, and very small refueling
emissions. It is important to note that, as was the case with light-duty vehicles, actual
emissions from individual engines will vary greatly, depending on the calibration of the
engines. Emissions data from an LPG-fueled truck which was recently certified by the
State of California are summarized in Appendix V, and emissions data from a bus
demonstration project are summarized in Appendix VI.
It is possible, if not probable, that heavy-duty LPG-fueled engines will have
higher compression ratios than light-duty engines, and thus also have better thermal
efficiencies. This is because many of the physical and economic limitations that apply
to light-duty engines, are less important in heavy-duty applications. In general,
operators of heavy-duty vehicles are more willing to pay the extra cost for an engine
that has better fuel economy. Thus, it is very possible that many heavy-duty LPG-
fueled engines would have compression ratios significantly higher than 12:1, although
not as high as those of diesel engines (-20:1).
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EPA Otfka of Mobil* Sourctt Special R«port
It is also worth noting that, despite its high octane/low cetane rating, LPG can
be used with Diesel-cycle engines. This, however, requires a pilot injection of
conventional diesel fuel to ignite the LPG without a spark plug. Such systems are
referred to as "fumigation11 systems. While this technology is promising, at this time,
it is not very advanced.
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EPA Office of MoM« Sources Special Report
References
1. "1990 Annual Book of ASTM Standards," Vol. 05.05.
2. "Environmental and Economic Study of Alternate Motor Fuel Use: Report to
Congress," EPA Office of Mobile Sources, Draft, April 1991.
3. "Gaseous Fuel Vehicle Technology State of the Art Report," EA Mueller Inc.,
for U.S. Department of Energy, December 1988.
4. "Standards for Emissions From Natural Gas-Fueled, and Liquefied Petroleum
Gas-Fueled Motor Vehicles and Motor Vehicle Engines, and Certification
Procedures for Aftermarket Conversion Hardware," Final Rule, 59 FR 48472,
September 21,1994.
5. Engine, Fuel, and Emissions Engineering, Inc., for Natural Gas Vehicle
Coalition, comments on draft Special Report, July 19, 1994.
6. Personal communication with David Smith, IMPCO Technologies Inc., July 11,
1994
7. "Vialle Liquid Propane Autogas-lnjection System," Vialle Autogas Systems, from
LP Gas Clean Fuels Coalition.
8. Manufacturers of Emissions Controls Association meeting with EPA, May 11,
1993.
9. "Emission Standards for Clean-Fuel Vehicles and Engines, Requirements for
Clean-Fuel Vehicle Conversions, and California Pilot Test Program," Final Rule,
59 FR 50042, September 30, 1994.
10. Krupka, M.C., A.T. Peaslee, and H.L. Laquer, "Gaseous Fuel Safety
Assessment for Light-Duty Automotive Vehicles," Los Alamos National
Laboratory Report 0LA-9829-MS, UC-96, November 1983.
11. "An Assessment of Propane as an Alternative Transportation Fuel in the United
States," R.F. Webb Corp., for National Propane Gas Association, June 1989.
12. "Propane and Environment in Ontario - A Clean Transportation Fuel
Alternative," Propane Gas Association of Canada, September, 1992.
13. "Federal Motor Vehicle Safety Standards; Compressed Natural Gas Fuel
System and Fuel Tank Integrity: Notice of Proposed Rulemaking," NHTSA, 58
FR 5323, January 21, 1993.
14. "Standard for the Storage and Handling of Liquefied Petroleum Gases," NFPA
58, 1989.
15. "Vehicle Reet Survey: Opportunities for Reducing Air Pollution Through the Use
of Compressed Natural Gas and Propane," Denver Metropolitan Air Quality
Council, October 1987. x
16. "Investigation Regarding Federal Policy Actions for Encouraging Use of
Liquified Petroleum Gas as a Motor Vehicle Fuel,' R.F. Webb Corporation, for
Congressional Research Service, April 1992.
17. Muranaka, S., Y. Takagi, T. Ishida, "Factors Limiting the Improvement in
Thermal Efficiency of S.I. Engine at Higher Compression Ratio," SAE #870548,
1987.
18. Grouse, W., and D. Anglin, "Automotive Engines," McGraw Hill, 1986.
24
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EPA Office of MOM* Source* Special Report
19. "Summary Report for Emission Testing of Liquified Petroleum Gas Fueled
Vehicles Provided by Sears," California Air Resources Board.
20. Data from Ron Ragazzi, Colorado Department of Health, February 1991.
21. O'Connor, J., "Report on Propane Vehicle Fleet Tailpipe Emissions, Drivability,
and Durability Study," Phillips Petroleum Company, November, 1993.
22. "Clean Fleet: Vehicle Exhaust Emissions Early Mileage Results," Batelle
Memorial Institute, Statistical Analysis Report No. 4, July 1994.
23. Rideout, G., "Effect of Ambient (Cold) Temperatures on Exhaust Emissions and
Fuel Consumption of LPG Fueled Vehicles,* Environment Canada, May 1991.
24. Comments from Sherex Industries in response to the proposed emissions
standards for gaseous-fueled engines and vehicles, December 1,1992, (Docket
itemA-92-14-IV-D-13).
25. Information from Bob Myers, LP Gas Clean Fuels Coalition, Docket A-92-14.
25
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EPA Office erf Mobile Sources Special Report
Chapter 3
Economic Impacts
Introduction
This chapter describes the potential economic impacts of LPG-fueled vehicles
on a per-vehicle basis, and discusses the current and expected future supply of LPG.
The analysis of costs presented here is based upon the current energy market; thus,
since the prices of fossil fuels can change significantly within a very short period of
time, the reader is cautioned to consider this analysis to be primarily for the purpose
of identifying trends, and providing reasonable estimates of the costs associated with
LPG-fueled vehicles at this time. The analysis is described in a step-by-step manner,
which would allow the reader to revise it to include changes in either LPG or crude oil
prices. This analysis does not make quantitative projections of how the price of LPG
would change in response to the increase in demand that would result from a
significant increase in the number of vehicles using LPG.
LPG Supply
As noted in Chapter 1, LPG is widely distributed throughout the United States,
for residential and commercial heating as "propane," and this market is already well
defined. Most commercial LPG pipelines have requirements that the LPG meet the
composition specifications for "Special Duty Propane," which is the grade of LPG
currently used for automotive engines.[1] This specification has a minimum
requirement of 90 percent propane and a maximum 2.5 percent butane and higher
hydrocarbons.
The United States' domestic supply of LPG comes from two sources: 1) wet
gases, or natural gas liquids, stripped during the processing of natural gas; and 2)
byproduct gases removed from crude oil during refining. (About 80 percent of U.S.
LPG currently comes from natural gas production, while the remaining 20 percent
comes from refineries.[2]) In 1993, the average rate of domestic LPG production
(propane and propylene only) was 0.96 million barrels per day6, and the rate of LPG
imports (propane and propylene only), much of which comes from Canada, was 0.10
million barrels per day.[3] The Department of Energy estimated U.S. natural gas
liquids reserves7 to be 7,464 million barrels as of December 31, 1991 .[4] (The
propane content of natural gas liquids is generally less than 50 percent.) These
reserves are located primarily in the southwest.
6 A standard petroleum barrel equals 42 U.S. gallons.
7 The known amount of natural gas liquids in the ground that can be extracted economically.
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EPA Offie* of Mobil* SourcM Special Report
If LPG gains widespread use as a transportation fuel, there are several
potential sources of additional supply to meet the demand, although at a higher price.
The domestic supply for vehicular LPQ could be increased by a combination of
increased production and shifts in demand resulting from higher prices for LPQ. Even
more LPG could be available through imports. These potential supplies are described
below.
Domestic vehicular LPG supply could be increased by a several changes in the
production and use of LPG, especially if vehicles begin to use LPG fuels with higher
butane content. Such changes would result to some extent if the price of LPG rose
significantly, due to a higher demand for vehicular LPG. A higher price for LPG would
lead to some increases in the recovery of LPG at natural gas processing plants and
refineries. Changes in other industries, such as switching the chemical industry back
to using ethane as a feedstock for many of its processes, instead of naphtha, could
make even more LPG available. The recent regulations requiring reductions in Reid
vapor pressure (RVP) of reformulated gasoline will decrease the demand for butane
by refineries. One estimate is that such changes could increase the U.S. production
of LPG by as much as 1.59 million barrels per day.[5] The plant cost associated with
this increase was estimated to be $18.8 billion (35 cents per gallon). Other estimates
suggest that the domestic supply of LPG for vehicles in 2010 could be 0.7 to 0.9
million barrels per day.[6,7] The reader is cautioned that these estimates involve
dramatic changes to the LPG market, and should be viewed as upper bounds on the
amount of LPG that could be available domestically. Such changes would likely lead
to very substantial increases in price.
Any significant increase in the demand for LPG would also lead to more LPG
being imported. It has been estimated that more than 0.6 million gallons of LPG per
day could be available through imports.[8] As was the case with domestic supply,
although to a lesser extent, increasing imports by this much would be accompanied
by an increase in the price of LPG.
In summary, the actual availability of LPG will be highly dependent on market
demand. It appears that, with very high demand, and some changes in fuel
composition (e.g., higher butane content), the supply of LPG for vehicle use could be
on the order of one million barrels per day. However, there would probably be a very
significant increase in price associated with increasing the supply by this much. One
million barrels per day would be enough for a fleet of vehicles averaging 15 miles per
gallon (LPG) to travel more than 600 million miles per day. This amount would
represent more than 13 percent of the total vehicle miles traveled (VMT) for gasoline
vehicles the U.S. in 1990.[9]
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EPA Office of Mobito Sources Special Report
Fuel Prices
This analysis of LPG fuel prices addresses the costs that would be associated
with a scenario involving a moderate number of LPQ-fueled vehicles. One such
scenario would be the use of a relatively large numbers of vehicles in a limited
geographical range, such as a single metropolitan area. Under such a scenario, the
number of vehicles would be large enough to provide significant economies of scale
for the region, but small enough to not have an impact on the national LPG market
price.
For the purpose of consistency, the methodology used to estimate the resale
price of LPG will be similar to the methodology used for methanol in the Special
Report on methanol,[10] and will use the same estimated price for gasoline (which
was based upon the assumption that crude oil was 20 dollars per barrel). This will
allow the reader to compare the costs of LPG, with those of other fuels for which there
are QMS Special Reports, such as CNG or methanol. This analysis could be revised
by the reader to account for other crude oil prices by assuming that the wholesale
price of gasoline is roughly proportional to the price of crude oil. The reader could
also revise this analysis to be based upon the current wholesale price of gasoline,
which would be available from EIA.
Based on the analysis described below, it is estimated that LPG sold at service
stations for automotive use would cost 79 to 85 cents per gallon if LPG-fueled vehicles
were widely used within a given region. The price on an energy-equivalent basis with
gasoline is 1.13 to 1.22 dollars per gallon, which is comparable to the estimated price
of gasoline (1.20 dollars per gallon based on an assumed wholesale gasoline price
of 69 cents per gallon). This analysis of the costs of LPG and gasoline is summarized
in Table 3-1. It must be emphasized that this estimate is valid only for moderate
numbers of vehicles; if the demand for LPG increased substantially due to an large
increase in the number of LPG-fueled vehicles, the price of LPG could be also
substantially higher.
According to EIA, the 1994 average refiner sales price for resale was 32.5
cents per gallon for consumer grade propane.[11] This price was used for this
analysis, but the Agency recognizes that the future price is likely to be different,
especially if the demand for LPG changes. Moreover, the price of propane is subject
to substantial seasonal variations, as can be seen in Figure 3-1; and the yearly
average price is highly dependent upon the severity of the preceding winter.
28
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EPA Office of Mobile Source* Special Report
Table 3-1
Summary of Fuel Costs
Wholesale Price
Distribution Costs
Service Station Markup
Federal Taxes
State Taxes
Total Pump Price
$/gallon LPG
0.325
0.060-120
0.096
0.183
0.125
0.79-85
$/gallon Gasoline
0.690'
0.060
0.086
0.184
0.183
1.20
Based on a crude oil price of $20/bbl
Since LPG is often located in the regions where gasoline is produced, the long
range/local distribution cost of LPG may be similar to that of gasoline. However, it has
also been estimated that distribution cost could be twice as high as that of gasoline,
assuming that new pipelines had to be buitt.[12] In this analysis it is assumed that the
LPG distribution cost for vehicle use would range from 6 to 12 cents per gallon, based
on a gasoline distribution cost of 6 cents per gallon.[13] Service station mark-up has
been estimated to be 8.6 cents per gallon for gasoline and 9.6 cents per gallon for
LPG (for stations selling 69,000 gallons of LPG per month).[14] Higher costs would
result if a gasoline service station sold only a small volume of LPG, and could not take
advantage of the economies of scale of larger tank systems. However, since this
report is attempting to quantify the impacts of a significant number of LPG-fueled
vehicles, it is assumed that the LPG vehicle fuel market will be large enough, at least
locally, so that the stations would be able to avoid such problems. Federal taxes
(1993) for LPG and gasoline are 18.3 and 18.4 cents per gallon, respectively.[15] The
state taxes (1993) used in this analysis, 12.5 cents per gallon for LPG and 18.3 cents
per gallon for gasoline, are weighted national average values from the Department of
Transportation.[15]
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EPA Office of Mobile Sources Special Report
Figure 3-1
Wholesale LPG Prices
January 1990 through December 1994
100
80
-2 60
£ 40
20
Jan Jul
90
Jen Jul
91
Jan
92
Jan Jul Jan
93 94
- Avw»g»PrmtorPrMadng12Monf«
Vehicle Fuel Economy and Coet
As was noted in Chapter 2, the fuel economy of an LPG-fueled vehicle is very
dependent upon how the vehicle is calibrated. For this analysis, it is assumed (see
Chapter 2) that current LPG-fueled vehicles have a volumetric fuel economy that is
70 percent of that of a similar gasoline-fueled vehicle. For advanced LPG-fueled
vehicles it is assumed that they will have a volumetric fuel economy that is 77 percent
of that of a similar gasoline-fueled vehicle. The fleet-average fuel economy for light-
duty gasoline-fueled vehicles is 20.5 miles per gallon (MPG).[9] Average fuel
economy for a similar fleet of LPG-fueled vehicles would be 14.3 MPG for current
vehicles and 15.7 MPG for advanced vehicles, on a volumetric basis. Using these
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EPA Offlc* of Mobil* Sourm Special Roport
estimates, fuel costs would be 5.9 cents per mile for a gasoline-fueled vehicle, 5.5 -
5.9 cents per mile for a current LPQ-fueled vehicle, and 5.0 - 5.4 cents per mile for
an advanced LPG-fueled vehicle. Of course, these estimates are very sensitive to the
relative wholesale prices of LPG and gasoline.
It may be more reasonable, however, to consider fuel costs for a fleet of larger
vehicles with lower fuel economy. For example, the fuel costs for gasoline-fueled
vehicles with an average fuel economy of 10 MPG would be 12.0 cents per mile, while
the fuel costs of a comparable fleet of optimized LPG-fueled vehicles (7.7 MPG) be
10.3 -11.0 cents per mile. Thus, the savings for fuel cost would be twice as large as
for the average fleet described above (1.0 -1.7 cents per gallon). There are several
reasons why LPG is more likely to be used in these vehicles. First, due to refueling
convenience, LPG is easier to use in fleet applications, and many of these fleet
vehicles (e.g., utility trucks, delivery vans, etc.) are fairly large. Second, the inherent
emission advantages of LPG are more valuable to manufacturers for vehicles with
large engines, since it is more difficult for these engines to comply with emissions
standards. Finally, owners of large vehicles with low fuel economy are more likely to
be interested in the potentially lower fuel costs of an optimized LPG-fueled vehicle.
The cost of converting a gasoline-fueled vehicle to a LPG-fueled vehicle varies
by vehicle type. For this analysis, it is assumed that the current cost of conversion
is $1500. This is consistent with other reported estimates.[2,16] Amortizing this cost
over 5 years and 100,000 miles, a current LPG-fueled vehicle would cost an additional
1.8 cents per mile over the cost of a conventional vehicle. For future vehicles, it is
assumed that the costs associated with producing an LPG-fueled vehicle capable of
complying with the ULEV requirements will be roughly comparable to those associated
with producing a vehicle capable of complying with the ULEV requirements using
conventional gasoline. Either vehicle would be expected to cost significantly more to
produce than a gasoline-fueled vehicle designed only to comply with conventional
standards.
It should also be noted that current literature indicates that LPG-fueled vehicles
could have less in-use engine wear, and thus have reduced operation and
maintenance costs compared to gasoline-fueled vehicles. As noted earlier, there is
some evidence to suggest that this benefit could lead to as much as a doubling of
engine life. If this is the case, it would obviously provide a very significant economic
benefit by reducing the extra cost of the vehicle. However, these cost reductions have
not been rigorously quantified. Therefore, while the Agency recognizes a potential for
benefits, in the absence of sufficient information, they cannot be accurately
determined for this report.
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EPA Office of MOM* SourcM Special Report
Summary
Given the estimated price of LPG used in this analysis, current LPG-fueled
vehicles may not provide savings in fuel costs when compared to gasoline-fueled
vehicles. Moreover, even with lower LPG prices, savings in fuel costs might still be
offset by the costs associated with the vehicle conversion. Thus the potential for
economic benefits from LPG-fueled vehicles is highly dependent upon the extent to
which maintenance costs are reduced. However, if the differential vehicle costs were
reduced, the relative price of LPG decreased, and/or the fuel economy of LPG-fueled
vehicles were improved, it is apparent that LPG-fueled vehicles could provide
significant economic benefits even without considering reduced maintenance costs.
The total market penetration of LPG-fueled vehicles in the future will be limited
by the supply of LPG. The increase in demand that would result from a large increase
in the number of LPG-fueled vehicles would lead to some increase in the price of
LPG, as LPG production and usage rates are shifted to accommodate the new
demand. The expected supply and demand of LPG in the future are such that LPG
could be used as an automotive fuel in a small but significant number of fleet
applications. The supply would be improved somewhat if the composition of the fuel
was changed to include other light hydrocarbons such as butane.
32
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EPA Office of Mobito Sources Special Report
References
1. Personal communication with Bill Butterbaugh, National Propane Gas
Association, August 2, 1990.
2. "An Assessment of Propane as an Alternative Transportation Fuel in the United
States," R.F. Webb Corp., for National Propane Gas Association, June 1989.
3. "Petroleum Supply Monthly: July 1993," Energy Information Administration,
DOE, DOE/EIA-0109(94/07).
4. "U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves: 1991 Annual
Report,' Energy Information Administration, DOE/EIA-0216(91).
5. Myers, R.E., for L.P. Gas Clean Fuels Coalition, "The Supply, Infrastructure
and Economics of an Expanded Motor Vehicle Fuel Market for LPG in the
U.S.," Draft, March 1992.
6. "Second Interim Report of the Interagency Commission on Alternative Motor
Fuels," September 1991.
7. "Investigation Regarding Federal Policy Actions for Encouraging Use of
Liquified Petroleum Gas as a Motor Vehicle Fuel," R.F. Webb Corporation, for
Congressional Research Service.
8. "First Interim Report of the Interagency Commission^on Alternative Motor
Fuels," September 1990.
9. MOBILE4 Fuel Consumption Model, Draft Report, April 1991.
10. "Analysis of the Economic and Environmental Effects of Methanol as an
Automotive Fuel," U.S. EPA/OAR/OMS Special Report, September 1989.(PB
90-225806)
11. "Monthly Energy Review: March 1995," Energy Information Administration,
DOE, DOE/EIA-0035(94/07).
12. "Assessment of LPG Infrastructure for Transportation Use," Draft Report, EA
Energy Technologies Group, September 1992.
13. "Preliminary Perspective on Pure Methanol Fuel for Transportation," U.S.
EPA/OAR/OMS, EPA 46/3-83-003, September 1982.(PB 83-180232)
14. U.S. Department of Energy, comments on draft Special Report, May, 1994
15. "Highway Statistics 1993," U.S. Department of Transportation, FHWA-PL-94-
023,1994.
16. "Propane and Environment in Ontario - A Clean Transportation Fuel
Alternative," Propane Gas Association of Canada, September, 1992.
33
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EPA Office of Mobile Sources Special Report
Chapter 4
Air Quality Impacts
Introduction
Much of the impetus for the development of alternative fuels such as methanol
and compressed natural gas has been due to their potential air quality benefits. The
use of LPG as a motor fuel, which to date has generally been driven by economic
concerns, can also provide significant benefits to urban air quality. This chapter
provides an analysis of the overall air quality impact of using LPG in place of gasoline,
focusing on its impacts on urban ozone and CO levels, air toxics, and global warming.
Urban Ozone Levels
High levels of ozone (smog) represent one of the most pressing air quality
concerns facing urban areas today. These high ozone levels are caused by
photochemical reactions between hydrocarbons (HC) and oxides of nitrogen (NOJ,
and the impact dl mobile source controls has traditionally been assessed by
examining the percent reduction in HC and NOx emissions. Another approach has
been to consider the reduction in non-methane hydrocarbon (NMHC) emissions, since
methane emissions do not significantly affect ozone levels due to methane's low
reactivity in the atmosphere. This second approach is used in this report. While NOx
emissions contribute to the formation of ozone in urban areas, the analysis in Chapter
2 suggests that the use of LPG-fueled vehicles will not lead to significant changes in
mobile source NOx emissions. Therefore, NOx emissions are not discussed further
here.
In recent years, there has also been a significant amount of work to determine
the relative rates at which other individual hydrocarbons react to form ozone, in order
to better assess the impacts of HC emissions on ozone levels. One approach has
been to assign Reactivity Adjustment Factors (RAFs) to each vehicle-type. The RAF
is intended to be an estimate of the amount of ozone produced by a vehicle-type,
relative to gasoline-fueled vehicles. For example, an RAF of 0.50 for LPG would
mean that one gram of organic emissions from an LPG-fueled vehicle would produce
only 50 percent as much ozone as one gram from a gasoline-fueled vehicle. While
such work has shown that there are significant differences among the reaction rates
for various classes of compounds, it is still problematic to attempt to precisely quantify
the role of different HC species in the formation of ozone. The California Air
Resources Board (CARB) had estimated the RAF for LPG to be 0.50, but this
estimate has been withdrawn because of insufficient informational] It is necessary
to assume a value for the RAF in order to convert the applicable NMOG standard into
an effective NMHC standard for ULEVs, and this report assumes the RAF for LPG to
be 0.50. However, this value is not used in the analyses of this chapter to estimate
34
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EPA Office of Mobile Sources Special Report
the actual relative reactivity of LPG emissions. While the relative reactivity of LPG
emissions is discussed qualitatively below, the estimated impact of LPG-fueled
vehicles on urban ozone levels is limited to estimates of NMHC emission reductions.
Estimated NMHC emissions for light-duty gasoline vehicles are shown in Table
4-1. Emission factors were estimated for three scenarios. The first row represents
average in-use emissions from all vehicles in the nationwide 1990 fleet, operating with
an 8.7 psi fuel. These emissions were estimated for the Motor Vehicle-Related Air
Toxics Study. [2] The second row represents the in-use emissions expected from
vehicles in the 2010 fleet. Among the additional requirements that were assumed to
apply to these future vehicles are: a 0.25 gram/mile tailpipe NMHC standard,
enhanced evaporative emission controls, onboard refueling controls, and improved
state inspection and maintenance programs. These estimates are also based on
emission rates discussed in the Motor Vehicle-Related Air Toxics Study. The
emission rates from that study were adjusted by assuming that refueling emissions
were reduced by 90 percent with onboard refueling controls. All of the emissions
estimates for that report were obtained from EPA's emission model MOBILE4.[3]
Estimated emissions from a gasoline-fueled vehicle meeting the federal ULEV
standards are shown in the third row. Also included in Table 4-1 are the estimated
NMHC emissions for both current and optimized LPG vehicles which were discussed
in Chapter 2.
Comparing the NMHC emissions from LPG vehicles to those from gasoline
vehicles shows a significant reduction. This reduction results from the virtual
elimination of evaporative, running loss, and resting loss emissions, and ve/y
substantial reductions in refueling emissions (compared to 1990 baseline) because of
the tightly sealed fuel system necessary for the high pressures associated with LPG.
When comparing current LPG vehicles to current gasoline vehicles, one would expect
to see a 41 percent reduction in NMHC emissions. Optimized LPG vehicles could
result in as much as a 91 percent reduction when compared to baseline gasoline
fueled vehicles, or a 79 percent reduction when compared to a gasoline-fueled vehicle
that was designed to comply with the ULEV standards, but that had non-exhaust
emissions similar to the baseline vehicle. It is very important to note that these
estimated reductions are very sensitive to the assumptions made in this analysis. This
is especially true when considering deterioration. Most of the emissions data for LPG-
fueled vehicles are from test programs in which the vehicles received fairly good care.
At this point it is not possible to determine how LPG-fueled vehicles will perform in
use, under less controlled conditions. Also, while it is possible that evaporative
emissions can be essentially eliminated from LPG-fueled vehicles, in-use LPG-fueled
vehicles may actually have significant evaporative emissions. Thus, while the
directional trends shown above are valid, the exact magnitude of the benefits is less
certain.
35
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EPA Office of Motxte Sources Special Report
Table 4-1
Estimated Emissions from Gasoline- and LPG-Fueled Vehicles
Vehicle Type
1990 Base
Gasoline
2010 Base
Gasoline
Gasoline ULEV
Current LPG
Optimized LPG
Exhaust NMHC
(g/mile)
1.48
0.61
0.04
1.48
0.08"
Hot soak and
Diurnal NMHC
(g/mile)
0.44
0.18
0.18
0.00
0.00
Other NMHC'
(g/mile)
0.58
0.18
0.18
0.01
0.01
• Includes refueling emissions, running losses, and resting losses.
"Assumes a Reactivity Adjustment Factor of 0.5.
As was mentioned earlier, changes to the fuel used by a vehicle can not only
affect the amount of NMHC emitted by the vehicle, but it can also impact the role its
emissions will play in the formation of ozone. Unfortunately, there is still much
uncertainty related to quantifying these changes, although several trends have already
been shown. Paraffinic hydrocarbons, such as propane, tend to react much more
slowly in the atmosphere than olefinic species, such as propylene. Since the LPG fuel
does not normally contain large amounts of olefins, it may be expected to result in
less reactive emissions. CARB's preliminary estimate of the RAF for LPG (which has
subsequently been withdrawn) suggests that LPG emissions may be only half as
reactive as gasoline emissions. However, olefin formation during combustion can
result in LPG vehicles having an olefinic hydrocarbon fraction in their exhaust that is
similar to gasoline vehicles,[4] and it is possible that LPG would not offer a large
reactivity benefit. Also, the relative reactivity of exhaust emissions is fairly dependent
on fuel composition, which may vary substantially in use.
36
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EPA Offlc* o* Mobil* SourcM Specol Import
In summary, the speciated emissions data that are currently available suggest
that there is the potential that using LPG would lead to a reduction in the reactivity of
exhaust emissions, but this potential cannot be precisely estimated at this time. More
importantly, however, it is estimated that there will be a significant reduction in NMHC
emissions on a mass basis. It is expected that the use of LPG would provide
significant reductions in ozone on a per-vehicle basis, with or without reductions in
reactivity.
Carbon Monoxide
Carbon monoxide (CO) is a gaseous product of combustion. At sufficiently high
levels it can cause breathing difficulties. It has been estimated that approximately
two-thirds of CO emissions are produced by transportation sources.[5] As such, any
reduction in CO emissions from vehicles can be very significant. The data discussed
in Chapter 2 suggest that current LPG-fueled vehicles may have CO emissions that
are 40 to 50 percent lower than gasoline-fueled vehicles. Optimized LPG-fueled
vehicles are expected to have emissions that are similar to the emissions from
gasoline-fueled ULEVs. These estimates, however, are for operation at moderate
temperatures; at lower temperatures (where CO emissions tend to be the highest), the
reductions should be even greater due to the high volatility of LPG. This is important
because CO nonattainment is primarily a problem during cold weather. The analysis
in Chapter 2 indicates that CO emissions from LPG-fueled vehicles at low
temperatures could be as low as 5 to 10 percent of the amount emitted by gasoline
vehicles. Thus, optimized LPG vehicles should provide CO benefits at low
temperatures, even when compared to gasoline-fueled vehicles that were also
designed to comply with the ULEV standards. Based on the available data, it is
estimated that LPG-fueled vehicles will average 80 percent lower emissions at low
temperatures than gasoline-fueled vehicles. This estimate is intended to be somewhat
conservative; however, it is important to remember that since the amount of low
temperature data available is very limited, it is possible that actual emissions benefits
may be less than this. Nevertheless, it is clear that the potential for lower CO
emissions is very significant, and may even be the most significant air quality benefit
provided by LPG-fueled vehicles.
Air Toxics
LPG is expected to provide significant benefits with respect to air toxics. EPA
has presented its estimate of the impact of conventional mobile sources on air toxics
in great detail previously.[2] The analysis in this chapter uses the estimates of cancer
incidences caused by light-duty vehicle emissions from that work to provide a
perspective on the toxics impacts due to light-duty LPG vehicles. It then develops an
estimate of the per-vehicle reductions expected to result from LPG use. The following
mobile source-related toxic pollutants were examined: benzene (including exhaust,
evaporative, running loss, resting loss, and refueling benzene), acetaldehyde,
37
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EPA Office of Mobile Source* Special Report
1,3-butadiene, and formaldehyde (direct and indirect8). These pollutants are emitted
by gasoline-fueled vehicles and are classified by EPA as either known or probable
human carcinogens. The numbers of cancer cases in 1990 and 2010 due to
emissions from light-duty gasoline-fueled vehicles were estimated to be 423 and 264
per year, respectively.
The per-vehicle air toxic reductions for LPG vehicles were calculated by
comparing the toxic emissions of LPG vehicles to those of gasoline-fueled vehicles.
This was straightforward for the fuel system emissions (evaporative, refueling, and
running loss emissions) of benzene, since LPQ fuel contains little or no benzene and
IRQ-fueled vehicles should not have significant fuel system emissions. The exhaust
emissions for LPG-fueled vehicles were based on very limited speciated hydrocarbon
data found in references 7,8 and 9. The indirect formaldehyde impact was assumed
proportional to NMHC reductions (from lower fuel system emissions). Emissions rates
for gasoline-fueled vehicles are from reference 2. Exhaust emissions fractions are
summarized in Table 4-2.
Table 4-2
Toxic Exhaust Emission Rates
Relative to NMHC Emissions
Toxic
Benzene
1 ,3-Butadiene
Acetaldehyde
Formaldehyde
Percent of NMHC
(Gasoline)
4.0
1.1
0.8
2.0
Percent of NMHC
(LPG)
0.1
0.01
0.5
1.0
Table 4-3 shows the relative reductions in toxic emissions from LPG vehicles
compared to future gasoline-fueled vehicles, for both current technology and for future
optimized technology. In most cases, the LPG vehicles show major reductions in air
toxics, especially for benzene and 1,3-butadiene. The only cases in which LPG-fueled
vehicles are not expected to result in reductions are acetaldehyde and direct
formaldehyde, but this is only when comparing an LPG-fueled ULEV to a gasoline-
fueled ULEV. Also, these two compounds make a relatively small contribution to the
8 Direct formaldehyde is emitted in the exhaust of vehicles, while indirect formaldehyde is formed in
the atmosphere from the reactions of various reactive hydrocarbons. Indirect formaldehyde is responsible
for the majority of the formaldehyde in ambient air.[6]
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EPA Offlc* of MoM* Source* Special Report
overall risk. When all the emissions are considered, the LPG vehicles are expected
to have approximately 92 percent lower toxic emissions (weighted by number of
incidences) than gasoline-fueled vehicles.
Table 4-3
Air Toxics Impacts of LPG-fueled Vehicles
Toxic
Exhaust Benzene
Other Benzene
1.3-Butadene
Acetaldehyde
Direct Formaldehyde
Indirect Formaldehyde
Total/
Weighted Average
Vehicle-Related
Cancer Incidence
1990 2010
63
7
304
5.3
11
33
423
31.5
3.5
204
3.0
5.5
16.5
264
Per-Vehide
Percent Reduction
Current Optimized
LPG-Fueled LPG-Fueled
Vehicles Vehicles'
98
100
99
38
50
41
92
98
100
98
-25**
0
79
92
* Reductions for optimized LPG-fueled vehicles are based on a comparison to gasoline-fueled ULEVs.
•• Acetaldehyde toxic impact of an LPG-fueled ULEV is estimated to be 25 percent higher than that of a
gasoline-fueled ULEV.
The overall impact of these per-vehicle reductions depends on the fraction of
the fleet that is eventually replaced by LPG. Since, at this time, it is very difficult to
predict overall penetration, this analysis is limited to per-vehicle reductions. Also, it
should be reemphasized that these predictions are based on low-mileage emissions
from a limited number of vehicles, and the analysis is very sensitive to changes in the
emissions fractions of the toxic compounds. The emissions fractions are very
dependent on the speciation of the LPG fuel, especially the 1,3-butadiene emission
fraction, which would increase with increasing butane content in the fuel.
Nevertheless, while the actual in-use impacts could be somewhat different from the
estimates given here, the directional trends should remain valid.
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EPA Office of Mobil* Sourcn Special Report
Global Wanning
Recently, the greenhouse effect (i.e., the effect of emissions of certain
"greenhouse" gases, most notably carbon dioxide (CO2), on global temperatures) has
been receiving a great deal of attention. Since combustion of different fossil fuels can
result in different CO2 emission levels, it is appropriate that the analysis of the
environmental impact of LPG vehicles include its CO2 impact. Different fuels can also
result in different emissions of other greenhouse gases, such as methane. In this
analysis, however, it is assumed that emissions of all other greenhouse gases from
LPG-fueled vehicles will be very similar to those from gasoline-fueled vehicles, with
the exception of CO. However, because the mass of CO emitted from modem
vehicles is very small compared to the mass of CO2 emitted, and because the impact
of CO emissions is less than an order of magnitude higher than that of CO2 per unit
mass,[10] the impact of the lower CO emissions of LPG-fueled vehicles is negligible
for this global warming analysis.
The estimated CO2 emissions of LPG vehicles used in this analysis are based
upon the fuel economy estimates described in Chapter 2. The CO2 emissions for
gasoline-fueled vehicles is based on MOBILE4 fuel consumption estimates. As was
done for the other analyses in this chapter, the global warming analysis is based on
emissions from passenger cars. While emissions of NMHC, CO, and NOx are not
expected to be very different for cars and trucks because they have similar emissions
standards, fuel consumption rates are quite different because trucks generally are
larger and have larger, higher output engines. Thus, it would not be appropriate to
compare the CO2 emissions from an LPG-fueled truck to those from a gasoline-fueled
passenger car, or vice versa. This analysis is structured, however, so that it provides
estimates of the reductions in CO2 emissions on a percentage basis, which can be
applied to other sizes of vehicles.
The total effect of the use of any fuel on global warming also depends on the
secondary emissions of CO2 that occur during the production and distribution of the
fuel. The energy consumption at all stages of production and distribution can be
converted to equivalent CO2 emissions and added to the vehicular emissions of CO2
and methane. These effects were analyzed previously in a draft EPA report.[10]
There it was calculated that the ratio of secondary CO2 to vehicular CO2 emissions for
both LPG and gasoline vehicles is about 1:2.5.
/
The equivalent CO2 emissions of both gasoline- and LPG-fueled vehicles are
shown in Table 4-4. The results show that LPG-fueled vehicles could have significant
greenhouse gas reductions, even at current fuel economy levels. Optimized LPG-
fueled vehicles could have 19 percent lower CO2 emissions than gasoline-fueled
vehicles.
40
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EPA Office at MobM Sourest SfMda! R«port
Table 4-4
Equivalent CO2 Emissions
Vehicle
Gasoline
LDV
Current LPQ
LDV
Optimized
LPGLDV
Fuel
Economy
(MPG)'
20.5
14.3
15.7
Vehicle CO2
(g/mile)
436
390
354
Secondary
COj
(g/mile)
175
156
142
Total
Equivalent
CO,
(g/mile)
611
546
496
Percent
Reduction
-—
11
19
Volumetric Fuel Economy (miles per gallon of LPQ for LPG-fueled vehicles)
Summary
The preceding analyses show that LPG-fueled vehicles have the potential to
provide significant environmental benefits in the areas of urban ozone, carbon
monoxide, air toxics, and global warming. These potential benefits are summarized
in Table 4-5. It must be emphasized, however, that the accuracy of these estimated
benefits is limited by the amount of data available, especially in the area of emissions
control system durability. Given the magnitude of the estimated benefits, however,
it is certain that LPG-fueled vehicles have a tremendous potential to provide significant
environmental benefits, especially in the area of CO emissions.
Table 4-5
Summary of Environmental Benefits of LPG-Fueled Vehicles
Pollutant
NMHC
NOx
CO
Air Toxics
CO2
Percent Reduction
From Current
LPG-Fueled Vehicles
41
0
80
92
11
Percent Reduction
From Optimized
LPG-Fueled Vehicles
85
0
80
92
19
41
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EPA Office of Mobil* Sources Special Report
References
1. "Proposed Reactivity Adjustment Factors for Transitional Low-Emission
Vehicles," Technical Support Document, California Air Resources Board,
September 1991.
2. "Mobile Source-Related Air Toxics Study, 1993," EPA-420-R-93-005,1993, (PB
93-182590).
3. MOBILE4, EPA Mobile Source Emission Factor Model.
4. "Definition of a Low-Emission Motor Vehicle in Compliance with the Mandates
of Health and Safety Code Section 39037.65 (Assembly Bill 234, Leonard,
1987)', California Air Resources Board, May 1989.
5. "National Air Quality and Emissions Trends Report, 1989," EPA-450/4-91 -003,
February 1991, (PB 91 -172247).
6. "Standards for Emissions From Methanol-Fueled Motor Vehicles and Motor
Vehicle Engines; Final Rule," 54 FR 14426, April 11, 1989.
7. Data from Bob Myers, LP Gas Clean Fuels Coalition, October 1991.
8. Rideout, G., "Comparison of LPG & Gasoline Fueled Emissions from a Light-
Duty Truck," Environment Canada, July 1991.
9. "Clean Fuel Fleet Emission Standards, Conversions, and General Provisions
and Amended Heavy-Duty Averaging, Banking, and Trading Credit Accounting
Regulations," Notice of Proposed Rulemaking, 58 FR 32474, June 10, 1993.
10. "Environmental and Economic Study of Alternate Motor Fuel Use: Report to
Congress," EPA Office of Mobile Sources, Draft, April 1991.
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EPA Office of Mobil* Source* Special Report
Chapter 5
Conclusions
Use of LPG as a Vehicle Fuel
There are a significant number of LPQ-fueled vehicles in use today in the
United States, and there are even more vehicles in use in Canada, Europe and Japan.
The experience with these vehicles has shown them to be both reliable and safe.
Only recently, however, have LPG-fueled vehicles begun to be optimized with respect
to emissions. Thus, it is expected that future LPG-fueled vehicles will be very different
from current LPG-fueled vehicles. Current LPG-fueled vehicles are generally
converted gasoline-fueled vehicles, and have been used in fleet applications due to
the potentially lower fuel costs of LPG. Often, these vehicles retain the ability to
operate on gasoline when LPG is not available. Future LPG-fueled vehicles are also
expected to be used in fleet applications, but are expected to be dedicated vehicles
that are optimized for both low emissions and low fuel consumption.
The amount of LPG that will be available for use as a vehicle fuel will limit the
number of LPG-fueled vehicles. It appears that, with sufficient demand and some
change in the composition of LPG motor fuel, up to one million barrels per day of LPG
could be available between 2000 and 2010. This would be enough fuel to allow LPG-
fueled vehicles to travel more than 600 million miles per day. (This amount would be
about 13 percent of the total number of miles travelled by the entire U.S. vehicle fleet
in 1990.) However, actual market penetration of LPG-fueled vehicles will probably not
be this high, because there would probably be a very significant increase in price that
would be associated with increasing supply by this much.
Given the limited supply of LPG, it appears that the most appropriate use of
LPG-fueled vehicles would be for fleets in specific geographic areas, especially those
areas that have problems with high ambient concentrations of CO during cold weather
(see "Benefits' section below). Based on the current fuel market, broader use is
possible, but may not be economical.
43
-------
EPA Office ot Mobil* SOUICM Special Report
Benefits
LPG-fueled vehicles have the potential to provide significant environmental and
economic benefits. Estimates of these benefits, which were discussed in the body of
this report, are summarized below.
Economic - Based on current fuel prices, fuel costs for current LPG-fueled
vehicles should be about the same as for gasoline-fueled vehicles, while
optimized vehicle fuel costs should be slightly lower than for gasoline-fueled
vehicles. The estimated benefit would be up to 0.9 cents per mile for optimized
average-sized vehicles, and up to 1.7 cents per mile for larger vehicles (i.e.,
gasoline-fueled vehicle fuel economy of 10 MPG). These estimates are highly
dependent on the relative prices of LPG and crude oil, and significantly
dependent on the thermal efficiencies assumed in Chapter 2. Even with slightly
lower LPG prices, the cost of a current conversion would more than offset the
potential benefit. Perhaps the most significant benefit will be lower engine
maintenance costs and/or prolonged engine life, though there currently is not
enough information to characterize this potential benefit.
Ozone - Exhaust emissions of NMHC and NOx from LPG-fueled vehicles
should be essentially the same as those from gasoline-fueled vehicles.
Evaporative emissions should be negligible from LPG-fueled vehicles. Overall,
LPG-fueled vehicles should have 41 to 79 percent less NMHC emissions than
gasoline. This estimate should be fairly accurate, though it is dependent on the
manner in which LPG-fueled engines are calibrated, and on the extent to which
evaporative emissions are controlled. The impact on ambient ozone levels
would vary from city to city, but should be substantial in any area where a
significant fraction of the vehicle fleet uses LPG.
Carbon Monoxide - CO emissions from LPG-fueled vehicles at low
temperatures (most CO problems involve cold weather) should be much lower
than those from gasoline-fueled vehicles. The limited amount of low
temperature data that is available suggests that CO emissions could be about
80 percent less than from gasoline-fueled vehicles. However, because the
amount of low temperature data that is currently available is small, there is a
great deal of uncertainty associated with this estimate. Nevertheless, this
benefit is probably the most important air quality benefit of LPG-fueled vehicles.
44
-------
EPA Office o« Mottle Sources Special Report
Toxics - The analysis presented in this report suggests that LPG-fueled
vehicles may have much lower emissions of toxic compounds. This analysis,
however, is based on very limited speciated emissions data from LPG-fueled
vehicles. Further, the analysis is very sensitive to small changes in emission
estimates. Therefore, the numerical estimates of the impact of LPG-fueled
vehicles on toxics should be used very cautiously. The analysis is adequate,
however, to demonstrate that LPG-fueled vehicles should provide a net benefit
with respect to air toxics.
Global Wanning - LPG-fueled vehicles are expected to provide small but
significant benefits with respect to greenhouse gas emissions. It is estimated
that CO2 emissions from LPG-fueled vehicles will be 11 to 19 percent lower
than those from gasoline-fueled vehicles. These benefits result from both the
lower amount of CO2 produced per BTU consumed, and the expected
improvement in fuel efficiency, relative to gasoline. These estimates should be
reasonably accurate, though the upper range relies on projections of future
technologies.
Need for Additional Studies
For gasoline-fueled vehicles, there is a very large amount of data available,
including speciated data, low temperature data, and high mileage emissions data.
This is not true for LPG-fueled vehicles. While this lack of data generally limited the
analyses throughout this report, it was critically limiting in several of them. First, the
economics of LPG use may be greatly affected by prolonged engine life or lower
maintenance costs for LPG-fueled vehicles. At this time, there is no comprehensive
and reliable information that would allow the potential economic benefits of prolonged
engine life to be quantified. There is a need for a study in which there are large
numbers of LPG- and gasoline-fueled vehicles, operating in the same manner, and
perhaps receiving identical maintenance. The study would need to provide detailed
records of total vehicle costs, including maintenance and vehicle replacement.
Second, there is a need for side-by-side emissions data from LPG- and
gasoline-fueled vehicles under identical operating conditions. The vehicles should be
as similar as possible, considering such factors as model, power output of the
engines, and equipment (e.g., air conditioning, transmission). The testing should be
conducted at low, intermediate and high mileages. Some studies like this have been
initiated, and should provide much needed information about the emissions and fuel
economy of LPG-fueled vehicles relative to gasoline-fueled vehicles, as well as about
the durability of LPG-fueled vehicle emission control systems.
45
-------
EPA Otfic* o( Motote SOUICM Special Report
Finally, there is a need for more speciated and low temperature emissions data.
The speciated data would allow a better characterization of ozone reactivities and
toxics impacts, while the low temperature data would allow a more reliable estimate
of the benefit of LPG-fueled vehicles with respect to CO emissions.
46
-------
EPA Office of Mobile Sources Special Report
Appendix I
Data from Sears Fleet
From: 'Summary Report for Emission Testing of Liquified Petroleum Gas
Fueled Vehicles Provided by Sears," California Air Resources Board.
-------
TABLE t
FEDERAL TEST PROCEDURE RESULTS
TEST
VEH.
NO.
Lt
kt
1,3
L4
L5
L6
L7
L8
L9
y§
L11
L12
L13
L14
L15
SEARS
VEH.
NO.
NA
NA
NA
NA
NA
NA
NA
NA
NA
9777
1214
1154
60529
•519
•499
MILEAGE
15949
55549
48666
26115
4405
69948
75547
36688
37596
29727
52791
50817
17946
107145
69258
POST-
RETRO.
.MILEAGE
-15.649
-49
-46,644
7
7
-59.946
-65.547
-28.669
•27.596
-17.727
-32.791
-39.817
-14.946
•70.145
•59.258
VEH.
MFR.
G.M.
Chry*.
Nl**.
G.M.
Chry* .
Chry* .
Chry* .
Chry* .
Chry* .
Ford
Ford
Ford
Ford
Ford
Ford
MODEL NAME
Chov.
Oodg*
Cho'yonn*
Ham 5*
Dot*un Pickup
Ch*v.
Dodg*
Oodg*
Oodg*
Oodg*
Dodg*
Econe 1
Econol
Econol
Ecenol
Econol
Econol
Coaoro
Dakota
Ra« 256
Ro« 259
Ra« 250
ROM 259
In* 159
In* 139
In* 159
In* 159
In* 259
In* 25*
MODEL ENG.
YEAR DISPL
1988
1964
1980
1979
1989
1966
1988
1989
1989
1967
1984
1964
1988
1979
1979
395 eld
155 eld
119 eld
350 eld
239 eld
318 old
318 eld
316 eld
318 eld
390 eld
300 eld
300 eld
300 eld
302 eld
302 eld
FEDERAL TEST PROC. RESULTS*
(CVS-7S) (CRAMS/MILE)
HC NMHC CO NOx
0.24
0.99
0.26
0.68
0.69
1.62
1.28
0.60
1.19
1.96
V72
• .84
• .95
3.54
3.73
0.19
• .66
0.15
0.72
0.41
0.99
1.28
0.90
0.91
1.95
1.47
• .71
• .86
3.25
3.27
• .89
38.30
7.57
46.67
2.66
57.36
19.33
11.72
2.66
1.11
60.29
1.58
• .98
11.93
291.64
1.05
0.72
1.28
1.72
0.52
0.32
0.67
0.58
1.33
1.30
0.92
2.39
1.75
9.65
0.25
APPLIC. STDS. FOR VEM.
(GRAMS/MILE)
HC NMHC CO NOx
0.5
0.41
0.41
9.41
9.41
9.5
9.5
0.5
0.5
0.5
0.5
0.5
0.5
0.9
9.9
0.5
0.39
0.39
NA
9.39
0.3
9.5
0.5
0.9
0.5
0.5
0.5
0.5
NA
NA
9
9
9
9
9
9
9
9
9
9
9
9
9
17
17
1 .0
1 .0
1 .5
1 .5
1 .0
1.0 !
1.0 1
t.o »
1.0 {
1.0 £
t.e |
16 f
,., |
«.3 I
2.3
HC - Hydrocarbon*
NMHC - Non-«*than* hydrocarbon*
CO - Carbon Monoxld*
NOx - Oxld«« of nitrogen
-------
TABLE 2
ORIGINAL EQUIPMENT INSPECTION
TEST
VEH.
NO.
NA
NA
NA
NA
NA
NA
NA
NA
L11
NA
NA
L12
NA
NA
NA
NA
NA
NA
NA
Lit
NA
L13
NA
L14
L15
SEARS LICENSE
VEHICLE NUMBER
NUMBER
0238
2779
6541
0303
0363
0403
0423
1044
1214
1024
1034
1154
9615
•625
0635
1636
1666
1676
•617
•777
00522
00520
00523
051»
0409
1M62370
1S03405
1Z01136
2037707
2020445
2037706
2037715
2J06S64
2L33004
2J06563
2J06S62
2L33011
2N05576
2N05575
2L04920
2V40775
2V48750
2V40771
3F97429
3F07430
3M01067
3M01050
3M01070
1P51106
1P52106
MODEL
YEAR
1078
1079
1981
1963
1983
1983
1983
1984
1984
1984
1984
1984
1985
1965
1985
1986
1986
1966
1987
1987
1988
1966
1968
1979
1979
VEH.
MFR.
G.M.
O.M.
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
Ford
MODEL NAME
Chevrbl et
Chevrolet
Eeonol In*
Eoonol ino
Eoonol Ino
Eoonol Ino
Eoonol Ino
Eoonol Ino
Eoonol Ino
Eoonol Ino
Eeonol In*
Eoonol Ino
Eeonol Ino
Eoonol Ino
Eoonol Ino
Eeonol Ino
Eoonol Ino
Eeonol Ino
Eeonol Ino
Eoonol Ino
Eeonol Ino
Eeonol Ino
Eeonol Ino
Eeonol Ino
Eeonol Ino
Von
Von
150
150
150
150
150
150
150
ISO
150
130
150
150
150
150
150
150
150
ISO
150
150
150
250
250
MILEAGE
100311
04636
76013
46503
00001
75450
00065
51273
52701
40007
56388
50806
58522
45607
46221
36023
41647
37163
36201
20734
10516
17056
21060
107156
00258
EMISSION CONTROL EQUIPMENT
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
AIR.
ECR. OC
ECR. OC
ECR. ECS.
ECR. OC
EGR. OC
ECR. OC
ECR. OC
ECR. ECS.
ECR. ECS.
ECR. ECS.
ECR. ECS.
ECR. ECS.
EGR. ECS.
ECR. ECS.
ECR. EOS.
EGR. EOS.
ECR. EOS.
EGR. EOS.
EOR. ECS.
ECR. EOS.
ECR. EOS.
ECR. EOS.
ECR. EOS.
ECR. OC
EOR. OC
TVC.
TVC.
TVC.
TVC.
TVC.
TVC.
TVC.
TNC.
TVC.
TVC.
TVC.
TVC.
TVC.
TVC.
TVC.
TVC.
TVC.
CL
CL
CL
CL
CL
CL
CL
CL
CL
CL
CL
CL
Fl.
FI.
FI.
FI.
FI.
CL
CL
OBD. CL
OBD. CL
OBD. CL
I
j?
i
Acronyms for emission control components:
\
AIR - Secondary air Injection
CL - Cloeod loop
ECR - Exhouet aoe roe IrculatIon
ECS - Oxygen tensor
FI - Fuel Injection
OBO - On-board diagnostics
OC - Oxidation catalyet
TVC - Three-way catalyst
-------
TABLE 3
RETROFIT EQUIPMENT INSPECTION
TEST
VEH.
NO.
NA
NA
NA
NA
NA
NA
NA
NA
L11
NA
NA
L12
NA
NA
NA
NA
NA
NA
NA
L19
NA
L13
NA
L14
L15
SEARS
VEHICLE
NUMBER
9236
2779
9541
9393
•363
•493
•423
1044
1214
1024
1934
1154
9915
9925
9935
1959
1999
1979
9917
9777 \
86522
68529
99523
9519
9499
RETRO.
KIT
MFR.
lapoo
lapoo
lapoo
lapoo
lapeo
lapoo
lapoo
lapoo
lapoo
lapco
lapco
lapco
lapco
lapco
lapoo
lapco
lapco
lapco
lapco
lapco
lapoo
\
lapco
lapco
lapco
lapco
RETROFIT DATE
INSTALLER RETROFIT
INSTALLED
Potrolono
Potrolono
Potrolono
Potrolono
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
7
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
Potrolano
Patrolano
Potrolono
7
Potrolano
7
7/67
4/67
8/67
5/67
12/66
3/67
4/67
11/67
7
5/67
4/67
8/66
1/66
12/86
5/67
3/67
7/67
19/99
5/66
8/86
16/68
7/66
7
12/83
CLOSED FUEL
LOOP CONTI
CONV.T PROC
N
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
V
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
N
N
N
N
N
N
N
^ N
N
N
N
N
Y
Y
V
Y
Y
FCP FUEL FUEL
CONTROL MIRING CONTROL ENRICH.
VALVE7 SETTING?
7
7
75 X
7
7
7
7
Y Y 7
NY 7
Y Y 7
Y Y 7
NY 7
Y Y 7
Y Y 7
V Y 7
Y Y 7
Y Y 7
Y Y 7
Y Y 48X
Y Y 6X
Y Y SOX
N Y ex
Y Y 25X
7
7
*V«hlcl«* with N In Fu«l Control Proc«««or coluan u*«d th« OEM processor for fuel control
-------
TABLE 4
VEHICLE OPERATION DIAGNOSIS
TEST
VEH.
MO.
NA
MA
MA
MA
NA
NA
•NA
NA
in
NA
NA
L12
NA
MA
NA
NA
NA
NA
NA
Lit
NA
L13
NA
114
na
SCARS STRONG
VEHICLE SMELL OF
NUMBER PROPANE?
6238
2779
•341
•393
•383
•403
•423
1944
1214
1924
1*34
1154
9613
992S
9935
1959
1989
1979
9917
9777
99322
99329
99323
9319
9499
V
N
V
N
N
N
N
N
N
N
V
V
N
M
V
V
M
y
Y
V
V
V
V
Y
Y
•HERE DOES VEHICLE WARN.
PROPANE SMELL OPERATING IN LIGHT
COME FROMT CLOSED LOOP? ON?
R«0wl«t*r
Regulator
Exhaust. rag.
Regulator
Rag., cold exhouat
Exhaust
Rag., air cleaner
Rag. . ol r claanar
Cxhauet and earb.
Regulator
Regulator
Regulator
Regulator
Y
N
?
?
Y
N
N
Y
Y
Y
7
Y
Y
7
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
FCV IF SOLNO. NOT EGR EGR
SOLNO. WORKING. IS IT SYSTEM PRE
•ORK? REC. SIGNAL OK? OK?
Y
N N
Y
Y
Y
N Y
»S *
V
Y
Y
Y
V
V
Y
N N
N Y
Y
Y
Y
Y
N
Y
Y
V
Y
Y
Y
N
Y
V
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
N
Y
N
7
N
N
Y
Y
Y
N
N
N
Y
Y
Y
Y
N
N
Y
PCV RICH OR
SYSTEM LEAN
OK? OPERATION?
Y
N
Y
N
Y
Y
N
Y
Y
N
Y
N
Y
Y
V
Y
N
Y
Y
Y
N
Y
Y
Y
Y
OK
OK
OK
Lean
7
7
OK
OK
Rich
Rich
Lean
OK
OK
Leon
OK
7
Lean
Rich
OK
OK
Rich
OK
Rich
Lean
OK
<5
I
•
f
I
-------
EPA Offlct <* Mobito SOUICM Sp«cfel Report
Appendix II
LPG Emissions Data
From Late Model Vehicles
Tested Using the Federal Test Procedure
-------
EPA Office of Mobile Sources Special Report
Current LPG-fueled Vehicle Emissions
1
2
3
4
5
6
7
8
9
. 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Vehicle
1985VWJETTA
1988 CHEYENNE
1989 DODGE DAKOTA
1988 DODGE RAM 250
1988 DODGE RAM 250
1989 DODGE RAM 250
1989 DODGE RAM 250
1987 FORD ECONOLINE
1988 FORD ECONOLINE
1988 CHEW PICKUP
1990 DODGE VAN
1988 FORD CROWN
VICTORIA'
1990 DODGE DAKOTA'
1989 CHEVY PICKUP'
1990 FORD 1 -TON
TRUCK*
1989 PLYMOUTH K-CAR
1989 PLYMOUTH K-CAR
1989 PLYMOUTH K-CAR
1989 POND AC 6000
1989 OLDS DELTA 88
1988 FORD CROWN
VICTORIA
1989 OLDS DELTA 88
HC
0.60
0.24
0.69
1.62
1.28
0.90
1.19
1.06
0.95
0.239
0.405
0.27
0.45
0.37
0.93
0.19
0.276
0.128
0.168
0.117
0.268
0.156
1990 PONT! AC 6000 I 0.141
1990BUICKLESABRE | 0.19
NMHC
0.19
0.41
0.90
0.91
1.05
0.86
0.179
0.340
0.131
0.061
0.231
0.111
0.101
CO
1.8
0.89
2.88
57.38
19.33
11.72
2.66
1.11
0.98
2.426
0.897
0.28
0.37
3.3
5.8
0.877
2.403
2.103
0.912
2.659
0.495
2.68
0.72
2.56
NOx
0.76
1.05
0.52
0.32
0.67
0.58
1.33
1.30
1.75
0.23
0.55
0.60
1.7
0.7
4.7
0.32
0.299
0.241
0.216
0.102
0.39
/
0.108
0.292
0.34
Reference
[1]
[2]
[2]
[2]
[2]
[2]
[2]
[2]
[2]
[3J
[4]
[5]
[5]
[5]
[5]
[6]
[6]
[6]
[6]
m
[8]
[9]
[9]
[10]
DATA INuLUUtU IN IADLC £.-£.
-------
EPA Offic* ol Mobito Source* Special Report
Current LPG-fueled Vehicle Emissions
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Vehicle
1985 VWJETTA
1988 CHEYENNE
1989 DODGE DAKOTA
1988 DODGE RAM 250
1988 DODGE RAM 250
1989 DODGE RAM 250
1989 DODGE RAM 250
1987 FORD
ECONOUNE
1988 FORD
ECONOUNE
1988 CHEW PICKUP
1990 DODGE VAN
1988 FORD CROWN
VICTORIA
1990 DODGE DAKOTA
1989 CHEVY PICKUP
1990 FORD 1-TON
TRUCK
1 989 PLYMOUTH K-
CAR
1989 PLYMOUTH K-
CAR
1988 PLYMOUTH K-
CAR
1989 PONTIAC 6000
1989 OLDS DELTA 88
1988 FORD CROWN
VICTORIA
1989 OLDS DELTA 88
1990 PONTIAC 6000
1990BUICKLESABRE
C02
522
578
398
379
485
907
377
398
411
431
389
Odometer
15940
4405
69048
75547
38680
37596
20727
17496
13500
3590
7541
4253
47417
4006
14622
31118
22658
Fuel
Metering
TBI
R
PR
TBI
TBI
PR
SPI
R
CARB.
Engine
Displ.
1.8L
305CI
239CI
31 SCI
318CI
31 SCI
31 SCI
300CI
5.7
318CI
5.0L
3.9L
5.7L
7.5L
2.2L
2.2L
2.2L
2JBL
3.8L
5.0L
3.8L
Dual-
Fueled?
NO
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
-------
EPA Offle* of Mobil* Sources Special Report
References
1. Menrad, H., R. Wegener, and H. Loeck, "An LPG-Optimized Engine-Vehicle
Design," SAE #852071, October 1985.
2. "Summary Report for Emission Testing of Liquified Petroleum Gas Fueled
Vehicles Provided by Sears," California Air Resources Board.
3. Johnson, T., "Preliminary LPG Emissions Report," IMPCO, July 1988.
4. Data from Bryan Memmott, Cleanfuels, October 1991.
5. Data from Ron Ragazzi, Colorado Department of Health, February 1991.
6. Data from Gordon Lilley, IMPCO, August 1990.
7. Data from Bob Myers, LP Gas Clean Fuels Coalition, January 1991.
8. Bruetsch, R.I., Letter to James Burroughs, April 1989.
9. Data from Bob Myers, LP Gas Clean Fuels Coalition, October 1991.
10. Hilden, D.L., P.A. Mulawa, and S.H. Cadle, "Liquefied Petroleum Gas as an
Automotive Fuel: Exhaust Emissions and their Atmospheric Reactivity," General
Motors Research Publication GMR-7442, September 9,1991.
-------
EPA Office of Mobil* SOUICM Special Report
Appendix III
Dual Fuel Gasoline Emissions Data
Tested Using the Federal Test Procedure
-------
EPA Offlc* at MoM« SourcM Special Report
Current LPG-fueled Vehicle Emissions
Operated Using Gasoline
10
11
16
17
18
20
21
24
Vehicle
1988 CHEVY PICKUP
1990 DODGE VAN
1989 PLYMOUTH K-CAR
1989 PLYMOUTH K-CAR
1989 PLYMOUTH K-CAR
1989 OLDS DELTA 88
1988 FORD CROWN
VICTORIA
1990BUICKLESABRE
HC
0.38
0.34
0.38
0.33
0.37
0.25
0.21
0.14
NMHC
0.34
0.24
0.15
~0
3.07
2.39
7.13
8.7
7.75
3.20
0.68
2.65
NOx
0.76
1.02
1.22
0.49
0.48
0.26
0.68
0.65
CO,
594
656
491
446
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EPA Office of MOM* Sourcm Special Report
Appendix IV
Low Temperature LPG Emissions Data
Tested Using the Federal Test Procedure
From: Q. Rideout, 'Effect of Ambient (Cold) Temperatures on Exhaust
Emissions and Fuel Consumption of LPG Fueled Vehicles,' Environment
Canada, May 1991.
-------
EPA Offlo* at Mot* SouroM SMC* Report
8.0 RESULTS AND DISCUSSION
A summary of the composite emission rates of each of the vehicle/fuel configurations
is presented in TabU* 5,6,7,8. In some cases multiple tests at the same temperature
have been averaged for the purposes of this discussion, while the entire body of
results are contained in the appendices. The average standard temperature test
result for each configuration is presented for reference to the ambient temperature
effect on the emission rate. The Ford F150 results for each of the test years are
presented separately since there was a slight shift in the standard temperature
emission rates from year 1 to year 2.
TABLES. Composite Emission Rates: Chevrolet Silverado
Ambieat Temperature
T«mp«raUir«
C
Gaoolia* Fu«led
21.0
10.5
9.0
7.5
6.0
3.8
Propane Fueled
25.0
11.1
7.8
-2.1
Grams per mile
THC
0.37
0.58
0.63
0.68
0.73
0.74
0.28
0.28
0.32
0.31
CO
2.78
10.84
9.89
10.37
11.98
12.54
4.33
5.14
4.81
4.12
NOX
0.36
0.94
1.11
1.11
1.10
1.25
0.32
0.31
0.38
0.60
C02
593.77
690.22
581.72
561.44
631.96
606.70
548.25
550.01
565.29
575.47
Fu«l
Economy
(mpg)
17.88
17.45
17.73
18.32
16.27
16.90
GBFB (mpg)
16.89
16.79
16.37
16.10
e ffKt of CoW T«mp»f«ruf« oo i motor* oftnifC futlfd V*h«/*-»t -OJ
-------
EPA OfflM ol MoM* SOUICM Sc*etf Repot
TABLE 6. Composite Emission Rates: Ford F150
Ambient Temperature* Year 1
Temperature
C
Guoline Fueled
25
t24
10
9
8.7
7.5
7.25
4.5
Propane Fueled
24
11.8
7.6
7.0
4.5
3.0
2.0
0.0
-2.7
Grams per mile
THC
0.78
0.64
1.66
1.82
1.53
1.66
1.46
NA
1.09
1.02
1.17
1.12
1.19
1.21
1.36
1.20
1,37
CO
1.26
2.34
17.65
19.55
16.20
16.98
14.29
16.57
0.04
0.00
0.06
0.03
0.04
0.07
0.03
0.03
0.02
NOX
1.17
1.20
1.19
1.12
1.15
1.13
1.20
0.99
0.86
0.84
0.77
0.82
0.75
0.75
0.89
0.88
0.76
CO2
563.24
577.00
585.97
606.49
679.65
594.13
548.47
565.48
490.22
532.85
537.15
559.98
538.87
553.26
599.25
624.42
603.97
Fuel
Economy
(mpg)
18.72
17.65
17.16
16.66
17.42
16.97
17.33
17.92
GEPE (mpg)
19.02
17.54
17.36
16.69
17.33
16.86
15.56
17.78
15.46
T • Year 2 standard temperature result!
e H»tl of Cold 7>mp»r«fur#i on f m-u/om of in I PC fu»l»d V«h*/»-»t-07
-------
EPA OfflM of MeM* SOUIVM Sptcid Report
TABLE 7. Composite Emission Rates: Ford K150
Ambient Temperature • Year 2
Temperature
C
Propane Fueled
24
10.30
7.00
6.7
6.7
4
3.7
2.0
0.66
. 0.33
-.170
•2.30
-2.70
-3.0
-3.3
-3.3
-4.3
-4.3
-7.3
-12.3
-18.0
Grams per mile
THC
1.16
1.06
1.14
1.19
1.14
1.22
1.12
1.23
1.30
1.27
1.07
1.27
1.26
1.27
1.28
1.19
1.32
1.26
1.06
1.14
1.29
CO
0.47
1.68
1.48
1.69
1.37
0.67
0.60
1.20
0.93
0.77
0.64
1.47
0.60
1.03
0.85
0.90
1.60
0.99
0.60
0.24
0.50
NOX
1.46
1.33
1.31
1.39
1.33
1.30
1.31
1.40
1.42
1.41
1.34
1.42
1.32
1.34
1.42
1.20
1.69
1.25
1.23
1.33
1.39
C02
495.05
465.40
497.80
501.10
525.40
509.90
50420
505.50
519.10
529.10
515.70
539.80
563.70
511.20
529.70
525.60
508.90
495.40
510.20
535.20
577.00
Fuel
Economy
(GEFE)mpg
18.80
19.92
18.64
18.50
17.68
18.24
18.46
18.37
17.90
17.58
18.06
17.26
16.51
18.17
17.55
17.69
18.21
18.75
18.25
17.42
16.14
£Hect of CoM Tempertturtt o« <• --woni of »n IPG fu*i*d Vehidf 91-02
-------
EPA Offlc* ol MoM* SOUICM SMOM R«pott
TABLE 8. Composite Emission Rates: Ford Taurus
Ambient Temperature
Temperature
C
1987 Ford
Taurus
24.0
17.7
12.3
11.7
10.0
4.7
1.0
-2.7
Propane Fueled
Ford Taurus
24.0
8.7
8.7
8
2.70
1.70
-2.70
-3.50
-4.00
-4.00
-5.70
-7.30
-10.00
-12.70
Grams per mile
THC
0.24
0.31
0.38
0.37
0.49
0.47
0.66
1.06
0.16
0.23
0.21
0.21
0.22
0.20
0.26
ND
0.27
0.24
0.27
0.24
0.25
0.24
CO
1.70
1.34
1.62
1.94
2.21
2.83
2.77
6.89
1.71
2.10
2.16
2.06
3.09
2.07
2.77
ND
2.42
2.60
3.65
3.65
3.72
3.81
NOX
0.86
1.48
1.44
1.33
1.33
1.25
1.42
1.09
0.86
0.62
0.76
0.70
0.67
0.68
0.83
ND
1.06
0.86
0.90
1.03
1.06
1.07
C02
444.9
498.0
522.0
523.0
520.0
504.0
541.0
479.0
386.0
389.0
393.0
389.0
409.2
389.8
426.9
ND
438.9
408.0
395.4
391.4
424.8
420.1
Fuel
Economy
(mpg)
21.24
20.18
21.08
20.32
20.92
19.48
21.73
16.14
GEFE(mpg)
24.12
23.88
23.65
23.89
22.63
23.85
21.75
ND
21.16
22.74
23.37
23.59
21.76
21.99
INL): INO data available
tHta of Cold r»mp«ufuf« onemauont ot»n LPG fu«/ed V«h«c/»-9f -02
-------
EPA Office of Mobile Sources Special Report
Appendix V
Heavy-Duty LPG Emissions
Certification Data
Below are California certification data for an IRQ-fueled 1993 Ford heavy-duty
engine, and federal certification data for a comparable gasoline-fueled engine.
LPG
Engine size: 7.0 liters
Rated power 218 HP @ 3600 RPM
Emission controls: EGR, air injection
Fuel metering: Carburetted
HC (g/BHP-hr): 0.5
CO (g/BHP-hr): 23.2
NOx (g/BHP-hr): 2.8
Gasoline
Engine size: 7.0 liters
Rated power 235 HP @ 3600 RPM
Emission controls: EGR, air injection, closed loop
Fuel metering: Fuel injection
HC (g/BHP-hr): 1.2
CO (g/BHP-hr): 21.5
NOx (g/BHP-hr): 4.4
-------
EPA Office o< Mobile Sources Special Report
Appendix VI
Heavy-Duty LPG Emissions
Bus Chassis Data
Below are gram/mile emissions data for a converted LPG-fueled bus (with and
without catalyst) and for a comparable diesel bus. The buses were tested as part of
the Orange County Transportation Authority's Cleaner Air through Reduced Emission
Systems (OCTA CARES) program (December 1993).
LPG
Base engine:
Maximum power (at wheels):
Catalyst:
HC (g/mi):
CO (g/mi):
NOx (g/mi):
PM (g/mi):
Base engine:
Maximum power (at wheels):
Catalyst:
HC (g/mi):
CO (g/mi):
NOx (g/mi):
PM (g/mi):
Diesel
Base engine:
Maximum power (at wheels):
Catalyst:
HC (g/mi):
CO (g/mi):
NOx (g/mi):
PM (g/mi):
Cummins L10
190 HP
Yes
0.67
0.02
3.04
0.03
Cummins L10
190 HP
No
10.50
45.1
36.5
0.04
Cummins L10
230 HP
No
1.24
13.5
31.7
1.23
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EPA Office of Mobile Sources Special Report
Appendix VII
Material Safety Data Sheet for LPG
From: 'Propane and Environment in Ontario - A Clean Transportation Fuel
Alternative,' Propane Gas Association of Canada, September, 1992.
-------
EPA Offic. at MoM* SOUICM SMC* Report
MATERIAL SAFETY DATA SHEET
SECTION I — PRODUCT INFORMATION
Product Nama: Proeana
Trad* Nama: LPO (liquified Pttretaum Qaa)
Chemical Formula: C*Ht
Supplier:
SECTION II —HAZARDOUS INQREDIENT8
COMPONfNTB CAS RKMtTHY
*RQP:Oj|ngM'
ic»
Prapww
EtfMIW
74888
74840
781088
78288
74828
3%- 5%
1%- 3%
0.1%'04%
ai%-o2%
Not
Not
Not
Not
Not
Not
Net
SECTION III — CHEMICAL AND PHYSICAL DATA
Povne WNto
Pott* -42«C • 780 RMHo
10TC
pec*ettre*ft;OJ1 (WATEP. -1)
Vapour Denatty: 1J« (Mr • 1)
ml of WMatfOl DlatiBiMUyn. Not »•»
t ta WMOB 8.1% by VWMo • 17*C and
—tat any ^.
Ccmmartp.l preaoiK. has an
ihaaoft
«NU
OM In natural
wntehla
SECTION IV - FW8 OR EXPLOSION HAZARD DATA
Pomt-iea^c
To Moot Or
.
of 8w aaoapinB QM 8M
mad off. Pto OM D» «d
dry
latamdtolaakto
knotonioMtio
on
to
el
SECTION V — REACTIVITY DATA
Condlttona To Avoid: Kaop
of ignMon
and
m
to
Wlnot
-------
EPA Offlc* at Mow* SOUIQM SpKiat Riport
SECTION VI — TOXICOLOGICAL PROPERTIES OF MATERIAL
ACUTE EXPOSURE
Eyes: As • gas. none. Liquid causes 'cold bum*".
SUn: Liquid causes *eoM bums' similar to frostbite.
Respiratory System: Little pnysiologicai effect at
concentrations below 10.000 PPM. High*
concentrations may cauaa dizziness and
unconsciousness due to asphyxiation.
ChronJe Exposure: There are no reported effects
from tone-term towievel exposure.
Other Liquid can cause bums and hosttoe • In direct
contact with skin.
SenslttxatioA Properoee; SUn — Unknown,
Respiratory — Unknown
C«iUnoo,enlcllr. Not determined.
Reproductive Effects: Not determined
MEDIAN LETHAL DOSE:
Oral: Net appUcabta for gas.
Inhalation: Not determined
Dermec Not applicable tor gaa.
Other. Not determined
IRRITATION INDEX
SUn: No appreciable effect (gas).
Eyes: No appreciable effect (gait
Symptoms Of Exposure: Above 100.000 PPM
Dtulnees, Stupor; Unconsciousness. American
Conference of Governmental Industrial Hygienists
(ACQH> dinlfkn propane aa an asphyxiant there la
no neam^ed ^hreahoU Umtt Value* (TLV%
SECTION VII — OCCUPATIONAL CONTROL PROCEDURES
Ey«s:Sa/etyc4a*ftea.QogQle*.<»tacetNetdr»c*«red
when Iransf ernng product
Skint Insulated gloves t contact with squid or squid
I equipment la expected
Inhaieoon: in
_
mtislsd air. as*
required
:Exptce)
where the concentration of
leveibelow ia% to
breatMng apparatus
OUip
SECTION VIII — EMERGENCY AND FIRST AID PROCEDURES
FIRST AID:
Eyes: Should eye contact with squid occur, flush eye*
wtth lukewarm water for 16 minutes. Obtain Immeciate
medcaics/*.
SUn: In ease of •Cold BumT from contact with squat
tmmeoiaterr place affected area miuhewann water and
keep at this temperature untt etacunaon returns. •
fingers or hands are frostbttan, nave the vtoftn he*) Ms
hand nead to his body such as under the amp*. Obaun
SPIU.OIILEAX!
EiMnsleleakl
eMurecyander is upright
Disperse vapours wxh hose strsama using fog *><>T**^.
watch lor low area* aa propane la heavier than air and
can settle Mo low areas. Remain upwind el leak, keep
end/or squid worn entering Into sewers*
Ing*
Into
eVfleut or has stopped
i to fresh ale. • breathing kj
SECTION DC — TRANSPORTATION, HANDLING AND STORAGE
anucrtCjMpeeJDonlna
• CylndersmeiMnotlRuae
not atom
ytaecvtndi
Tranepoft hanole and store aceon*
ln
•
oxygen or
TTOCattaffkaflart2.1
TOO Shipping Name Llqutled Petroleum Oas
TOO SpecW ProvWonc Sfl, 90,103
UN7NA;107S
SECTION X — PREPARATION INFORMATION
Pfepeired toys
i Mr*
-------
LPG-Fueled Nonroad Equipment
Emission Factors
Listed below are estimated emissions of hydrocarbons (HC), carbon monoxide (CO),
oxides of nitrogen (NOx), participate matter (PM), aldehydes (Aid.), and oxides of sulfur
(SOx) from LPG-fueled equipment. These estimates were developed from emission
factors from gasoline-fueled equipment, based on the testing of two converted LPG-fueled
engines. (Source: EPA 21A-2001, "Nonroad Engine and Vehicle Emission Study -
Appendixes")
Exhaust Emissions
(g/hp-hr)
Pumps <50hp
Compressors <50hp
Aerial Lifts, Forklifts,
Sweepers/Scrubbers, Terminal
Tractors
HC
9.0
6.4
4.5
CO
215
147
83
NOx
2.8
7.0
17.9
PM
0.2
0.1
0.1
Aid.
0.2
0.2
0.2
SOx
0.0
0.0
0.0
Other HC Emissions
Pumps and Compressors
<50hp
Aerial Lifts, Forklifts,
Sweepers/Scrubbers
Terminal Tractors
Crankcase
(g/hp-hr
1.4
1.5
1.0
Evaporative
(g/day)
2
55
17
Refueling
(g/hp-hr)
6.3
0.5
0.5
August 1995
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