Nf-i-OZ.
REGULATORY SUPPORT DOCUMENT
EMISSIONS STANDARDS FOR HEAVY-DUTY
CLEAN-FUEL FLEETS
U.S. Environmental Protection Agency
Regulatory Development and Support Division
June, 1994
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Table of Contents
. 1. Introduction 1 - l
2. Technology Assessment Chapter 2-1
2.0.1 Introduction . . . . . . . . . . .2-1
2.0.2 Gasoline Engines ... 2-1
2.0.2.1 Fundamentals of Gasoline Engines Which
Impact ...... 2-1
NMHC + NOx emissions
2.0.2.1.1 Air-to-Fuel Ratio ...2-1
2.0.2.1.2 Ignition Timing . . .2-2
2.0.2.1.3 Combustion Chamber Design . . . .2-3
2.0.2.2 Current Gasoline Emissions Control
Technology .2-3
2.0.2.2.1 Exhaust Gas Recirculation . . . . 2 - 4
2.0.2.2.2 Aftertreatment Systems . . . . .2-4
2.0.2.2.2.1 Catalytic Converters . . .2-4
2.0.2.2.2.2 Electronic Controls .... 2 - 5
. 2.0.2.3 Future Gasoline Emissions Control
Technology . . . . . . . . ".""'.'".• . . . . . . . .2-5
2.0.2.3.1 Electrically-Heated Catalytic
Converters .. . . .2-6
2.0.2.3.2 Closed-Coupled Catalytic
Converters . . . ... . . . 2-6
2.0.2.3.3 Lean-Burn Calibration . . . . . . .2-6
2.0.2.4 Expected Approaches for Clean-Fuel Gasoline
Engines ......... ..2-7
2.3 Diesel Bnoinac 2 - 7
2.0.3.1 Technical Background/Fundamentals of
Diesel 2 - 7
Engines Which Impact NMHC + NOx emissions
2.0.3.1.1 Fuel System . . . . .2-8
2.0.3.1.2 Air System ....2-8
2.0.3.2 Current Diesel Emissions Control Technology - 9
2.0.3.2.1 Retarded Injection Timing . . . . 2 - 9
2.0.3.2.2 Injection Pressure ........ 2 - 9
2.0.3.2.3 Injector Nozzle Holes and
Diameters 2 - 10
2.0.3.2.4 Intake Air Turbocharging . . . .2-10
2.0.3.2.5 Aftercooling 2-10
2.0.3.2.6 Cylinder Design 2-10
2.0.3.3 Future Diesel Emissions Control
Technology 2-11
2.0.3.3.1 Exhaust Gas Recirculation ... 2-11
2.0.3.3.2 Improved Turbocharging ..... 2-12
2.0.3.3.3 Injection Rate Shaping . . . . .2-12
2,0.3.3.4 Electronic Controls ...... 2-12
2.0.3.3.5 Aftertreatment Devices . . . . .2-13
2.0.3.3.5.1 Particulate Trap-Oxidizers 2 - 13
2.0.3.3.5.2 Catalytic Oxidizing Con-
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verters . 2 - 14
2.0.3.3.5.3 Catalytic NOx reduction . 2 - 14
2.0.3.3.6 Variable Compression Ratio . . . 2-15
2.0.3.4 Expected Approaches for Clean-Fuel Diesel
Engines ....... 2-15
2.0.4 Alternative Fuel Technologies ........ 2-15
2.0.4.1 Methanol 2-16
2.0.4.2 Natural Gas . 2-16
.2.0.-4.3 Liquefied Petroleum Gas ........ 2-17
2.0.4.4 Electric Vehicles . . 2-18
2 .5 Summary 2-18
3. Environmental Benefits Chapter . . . .... . . 3 - i
3.0.1 Introduction 3-1
3.0.2 Calculation Method ............... 3 - 1
3.0.3 Diacusaion of Data . . 3 - 1
3.0.3.1 Light and Medium-Heavy Duty Fleet Vehicle
Demographics . . . . 3-1
3.0.3.2 Emission Factor Calculations 3-7
3.0.3.2.1 1998 and Later Baseline Emission
Factors '. 3 - 7
3.0.3.2.2 Projections for 1998 Clean-Fuel
Fleet Emission Factora .— .-•-? 3-10
3.0.4 Environmental Impacts 3-10
4. Costs and Cost Effectiveness . . .4-1
4.0.1 Introduction 4-1
4.0.2 Costs . 4-1
4.0.2.1 Operating Costs .... ...4-1
4.0.2.2 Engine Costs 4-2
4.0.2.2.1 Otto-Cycle Heavy-Duty Engines . . 4-2
4.0.2.2.1.1 Hardware Costs . ... . .4-2
4.0.2.2.1.2 Development Costs ..... 4 - 3
4.0.2.2.1.3 Certification Costs . . .". 4 - 3
4.0.2.2.2 Diesel-Cycle Heavy-Duty Engines .4-3
4.0.2.2.2.1 Hardware Costs . . . . . .4-3
4.0.2.2.2.2 Development Costs . . . . .4-4
4.0.2.2.2.3 Certification Costs . . . . 4 - 4
4.0.2.3 Aggregate Costs 4-4
4.0.2.3.1 Manufacturer Costs ... 4-5
4.0.2.3.2 Costs to Users . ..4-8
4.0.3 Cost Effectiveness ....... 4-10
4.0.4 Summary 4-11
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List of Tables
Table 3-1 Heavy-Duty Clean-Fuel Fleet Vehicle Population .3-3
Table 3-2 Vehicle Miles Travelled by Clean-Fuel Fleet
LHDVs/MHDVs - . . • • • - • • .3-4
Table 3-3 Sales-Weighted 1991 Light and Medium Heavy-Duty
Certification Values . 3-8
Table 3-4 1998 Model Year Baseline Emission Factors . . .3-9
Table 3-5 1998 Heavy-Duty Clean-Fuel Fleet Vehicle Emission
Factors ........ ...... 3-10
Table 3-6 Nationwide Emissions Inventories of Fleets Covered
by the Clean-Fuel Fleet Program . 3-12
Table 4-1 Manufacturer Fixed Costs for Heavy-Duty Clean-Fuel
Engines 4 - 6
Table 4-2 Costs to Manufacturers . . . . . .-. . . . ... . 4-7
Table 4-3 Costs to Consumers 4-9
Table 4-4 Cost Effectiveness in $/ton (1998 Present Value)4 - 11
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List of Figures
Figure 3-1 - Clean-Fuel Fleet Vehicle VMT
3 - 5
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1.0 Introduction
This document is intended to provide technical, environmental
and economic analyses of the heavy-duty portion of the Clean-Fuel
Fleet program. The heavy-duty portion of the fleet program applies
to only light heavy- and medium heavy-duty vehicles and the engines
designated for use in these vehicles. EPA is adopting a heavy-duty
clean-fuel fleet vehicle standard of 3.8 g/Bhp-hr non-methane
hydrocarbon (NMHC) + oxides of nitrogen (NOx). Credit generating
standards for the fleet program have also been adopted.
Technological discussions of NMHC and NOx formation and control,
calculations of environmental benefits and an assessment of costs
and cost effectiveness are contained in separate chapters.
Chapter 2 contains an assessment of technologies available for
reducing NMHC and NOx emissions in conventionally-fueled heavy-duty
vehicles as well as technologies capable of meeting the credit
generating standards. First the formations of NMHC and NOx in
gasoline engines and the impacts of gasoline engine design are
discussed. Next, emissions formation and control in diesel engines
are covered. Finally, alternative fuel technologies and their
emissions capabilities are presented,. „___
Chapter 3 contains a discussion of the environmental benefits
expected from this program. The chapter begins with a presentation
of the vehicle demographics used in the calculations. This is
followed with a discussion of how new emissions factors applicable
to the vehicles covered by these standards were derived. Finally,
the emissions benefits are presented and discussed.
Chapter 4 begins with an estimate of the costs associated with
meeting these standards. Expected costs for research,, development
and testing are combined with certification costs and the
anticipated incremental hardware and operating costs to derive both
manufacturer and consumer costs associated with this program.
These costs are then combined with the emissions estimates from
chapter 3 in a calculation of the 22-year cost effectiveness of the
heavy-duty portion of the Clean-Fuel Fleet program.
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Chapter 2
Technology Assessment
2.0.1 Introduction
Internal combustion engines produce hydrocarbon1 and oxides of
nitrogen (NOx) emissions through a series of complex related
processes which also control the production of other pollutants
such as CO and particulates as well as the power output and
efficiency of the engines. Hydrocarbon (HC) emissions generally
result from the incomplete combustion of the fuel, while NOx
results from the reaction of oxygen and nitrogen present in the
combustion air. The reactions which produce NOx occur much more
rapidly under conditions of high temperature and pressure.
Engine design and operations which affect emissions of HC and
NOx will be discussed for both heavy-duty diesel and gasoline
engines as well as for alternative fuel technologies. Other
emission control technologies such as catalytic aftertreatment will
also be discussed. The purposes of these discussions are to: 1)
provide background information regarding the fundamentals of the
technologies, 2) describe the technologies which are being commonly
used today, 3) describe innovative technologies which may be used
by clean-fuel fleet vehicles, and 4) identify the approaches that
are most likely to be used by manufacturers to comply with the
clean-fuel fleet vehicle standards. The discussions in this
chapter, will be qualitative in nature and generally do not include
predictions of emissions reductions likely to result from use of a
particular technology.
2.0.2 Gasoline Engines
2.0.2.1 Fundamentals Of Gasoline Engines Which Impact NMHC
+ NOx emissions
NMHC and NOx emissions from gasoline engines (i.e., spark-
ignited, otto cycle) are impacted by the following characteristics
of the engine and its operation: air-to-fuel ratio, ignition
timing, and combustion chamber design. Adjustments or variations
to these parameters can substantially affect the performance as
well as the emissions of gasoline engines.
2.0.2.1.1 Air-to-Fuel Ratio
1 For simplicity, the term hydrocarbon (HC) is used
throughout this chapter to describe general effects in emissions
control. The term non-methane hydrocarbon (NMHC) is used for
clarity when discussing the emissions standards or specific
emission levels. The discussions using the term HC, therefore,
should be considered to be equally applicable to NMHC emissions.
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Emissions from gasoline engines are extremely sensitive to the
ratio of fuel and air in the combustion system. A critical
parameter then in the performance and emissions characteristics of
gasoline engines is the excess air factor designated as X. An
excess air factor of 1.0 indicates the engine is operating at
stoichiometric conditions while X values of more than 1.0 indicate
there is excess air in the combustion chamber. The current
strategy, especially with the presence of three-way catalytic
converters, is to attempt to keep A, at 1.0.
The air-to-fuel ratio, since it affects nearly all the
operational parameters of the engine, is a primary design element
in the operation of a. gasoline-fueled engine. Proper air-to-fuel
ratio control is critical in controlling both the engine out
emissions of hydrocarbons (HC) and NOx and, as will be discussed in
a later section, in the performance of catalytic converter
aftertreatment devices. In principle, as X is increased (i.e.,
leaner air-to-fuel ratio), HC emissions decrease due to the
increasing availability of oxygen for more complete combustion.
NOx emissions, on the other hand, show slight increases in engine-
out emissions levels at X values slightly above 1.0 and decreasing
levels at higher values of X. ..'.__.__
NOx values increase at X values slightly greater than 1.0 due
to the increased availability of oxygen and nitrogen to react to
form NOx. As X increases, the additional air has a competing
effect on NOx; by adding mass to absorb the heat of combustion, it
lowers the peak temperatures and pressures, which leads to a
decrease in- the rate of formation of NOx. Also as X increases, HC
emissions begin to increase slowly at first and then rapidly as the
lean misfire point is approached. Within reasonable limits,
however, the effects of air-to-fuel ratio on engine-out emissions
of HC are much less than the effects on engine-out NOx emissions.
Engines using lean air-to-fuel ratios also tend to show
greater thermal efficiencies due to factors such as lower heat
losses and the ability to use higher compression ratios (lean fuel
mixtures are less susceptible to autoignition). At higher values
of X, however, the power output per volume can drop off despite the
increase in thermal efficiency due to the lower fuel content. This
effect can b« off set by either using lean burn only at partial load
conditions oar by turbocharging the intake mixture to pack more air
and the 3am* quantity of fuel into the cylinder at a higher initial
pressure.
2.0.2.1.2 Ignition Timing
Control of the timing of the ignition spark is important in
controlling both NOx and HC emissions as well as in maximizing the
work output of the engine. Delaying the ignition as much as
possible reduces the amount of NOx produced by reducing both the
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peak temperatures and pressures of the combustion cyel|i£ and the
length of time that the gases are exposed to high temperatures and
pressures. Retarding the ignition timing can also increase the
work output of the engine by reducing the amount of extsrlt work the
piston must do during the final .stages of compression, after the
combustion has already begun. If the ignition timing isj; retarded
too much, however, the combustion process begins late, resulting in
somewhat incomplete combustion. Under these conditions/, the power
output drops and under conditions of greater timing retard the HC
emissions can go up. Ideally, to minimize the NOx and HC emissions
and to maximize the fuel economy of the engine, the combustion
process needs to be optimized so that the ignition timing can be
delayed to as close to the point in time when the piston reaches
top dead center and to have as much of the combustion as possible
take place just after the piston reaches top dead center.
2.0.2.1.3 Combustion Chamber Design
Combustion chamber parameters can affect the peak temperatures
and duration of the combustion process, which in turn impact on the
level of NOx emissions and the amount of work produced. The
primary goals in the design and operation of the combustion chamber
are to maximize the amount of work .arid, power output by the
combustion process (which also implies maximum combustion of the
HC) while minimizing the production of NOx, the amount of wear on
the engine and the likelihood of autoignition (knocking).
Reducing the combustion time is an important goal in chamber
design. Shorter combustion time allows the timing to be retarded,
which thereby reduces the formation of NOx and HC, while still
allowing the combustion to proceed to completion earlier in the
expansion stroke (thereby capturing more of the energy of
combustion). Decreasing the combustion time can be accomplished by
making design changes to the combustion chamber which minimize the
distance the flame front needs to travel and/or increases the flame
speed. Flame speed can be increased by increasing the turbulence
in the chamber. In addition to decreasing emissions and increasing
the percentage of the fuel burned near the optimal point in the
process, "fast-burn" techniques also reduce the tendency of the
engine to knock by reducing the amount of time available for the
unburned fuel to auto-ignite. Therefore, compression ratios can be
increased which in turn further increases the efficiency of the
engine.
2.0.2.2 Current Gasoline Emissions Control Technology
All heavy-duty gasoline engines certified for model year 1992
were equipped with exhaust gas recirculation (EGR), and almost all
were equipped with some form of catalytic converter arid electronic
engine controls. Most were equipped with three-way catalytic
converters (converters which are capable of both reducing NOx
emissions and oxidizing HC.and CO emissions). These technologies
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are described below. It is also worth noting that some current
engines are already very close to complying with the NMHC+NOx
emission standard of 3.8 g/Bhp-hr for heavy-duty clean-fuel fleet
vehicles. Three of the gasoline-fueled engines families certified
for the 1992 model year had HC+NOx emissions of 4.0 g/Bhp-hr or
less, including one with HC+NOx emissions of 3.6 g/Bhp-hr.
2.0.2.2.1 Exhaust Gas Recirculation
From a NOx control standpoint, it is desirable to have some
inert gases in the cylinder to take up some of the heat of
combustion. The recirculation of exhaust gases can provide these
inert gases. Recirculating exhaust gases is a more effective means
of NOx emissions control than using additional air to absorb the
heat of combustion (leaning out the air-to-fuel ratio) since the
water and CO2 in the exhaust gases have high heat capacities which
make the exhaust gases more effective at absorbing the excess heat
of combustion. Thus by using EGR," the peak temperatures can be
reduced further before the volume of inert gases reach the point of
interfering with the combustion process. Furthermore, recirculated
exhaust gases do not add the excess oxygen. Modest levels of
excess air can lead to increases in the engine-out levels of NOx
emissions. _____—
In some instances, exhaust gas recirculation can lead to a
reduction in engine-out HC emissions. However, EGR normally has
very little effect on HC emissions. At high levels of EGR (i.e.
>25%), the combustion process can become unstable, just as in the
case of too much excess air. Under these conditions, the HC
emissions begin to rise sharply.
2.0.2.2.2 Aftertreatment Systems
2.0.2.2.2.1 Catalytic Converters
Catalytic converters are an important means of further
reducing the emissions of gasoline engines. As already noted,
heavy-duty gasoline. engine systems are usually equipped with
catalytic converters which remove HC, CO and NOx from the exhaust
stream. Others use catalysts that are designed only to oxidize the
HC and CO.
In three-way or oxidation/reduction catalysts, the HC and CO
are oxidized to either less complex intermediate products or COa
and water vapor, while NOx is reduced to N2 and oxygen. The
reduction of NOx is accomplished by simultaneously utilizing the
oxygen from the NOx molecules to oxidize the remaining HC and CO in
the exhaust. This results in partial oxidation of the HC and CO.
Further oxidation may be achieved using an oxidation catalyst.
However, if there is excess oxygen in the exhaust stream, the HC
will preferentially react with the free oxygen rather than the
oxygen contained in the NOx molecules thereby leaving the NOx
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molecules relatively unaffected. On the other hand, if there •
not sufficient oxygen available in the exhaust stream, the HC will
not be oxidized or will be only partially oxidized due to the lack
of oxygen. Therefore, the performance of three-way catalytic
converters is very sensitive to the air-to-fuel ratio in the
engine. e
This problem can be partially overcome by using a catalytic
converter that consists of two separate beds (a reduction catalyst
followed by an oxidation catalyst) and injecting extra air between
the two beds. This allows the air-to-fuel ratio to be run slightly
on the rich side to ensure that good conversion of the NOx will be
achieved in the first bed. However, this technique results in a
decrease in fuel economy because of the slightly rich calibration.
Furthermore, the injection of too much air into the second bed has
the potential for cooling the gases down to the point that the
catalytic converter can lose some of its effectiveness.
Each catalytic converter design has its advantages and
disadvantages. The best approach for a given engine design is
determined based upon the composition and level of the engine-out
emissions.
2.0.2.2.2.2 Electronic Controls
Recent advances in electronic controls have made it possible
to achieve very tight control over engine parameters such as the
air-to-fuel ratio and ignition (spark) timing. This improvement in
the controllability of the combustion process minimizes the
excursions of these engines in non-optimized operating ranges which
result in both increased emissions and decreased performance.
The most significant advantage to using electronic controls is
that it provides a means by which the air-to-fuel ratio can be
adjusted to ensure that the concentration of oxygen in the exhaust
is at a level which leads to the optimum efficiency"of a three-way
catalyst under a broad range of operating conditions. By
installing oxygen sensors in the exhaust stream near the catalytic
converter, the system can diagnose whether or not the proper air-
to-fuel ratio is being maintained. Using these feedback signals,
the engine computer can then adjust the air-to-fuel ratio rapidly
to compensate if the exhaust stream does not contain the optimal
level of oxygen.
2.0.2.3 Future Gasoline Emissions Control Technology
Due to the 1998 4.0 g/Bhp-hr NOx standard, general
improvements can be expected to current gasoline emissions control
technology such as exhaust gas recirculation, catalytic converters
(likely catalyst improvements), and especially electronic controls.
Additional emission control of gasoline engines may occur with
other emission control technologies that are under development:
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electrically-heated catalytic converters, close-coupled catalytic
converters, and lean-burn calibration.
2.0.2.3.1 Electrically-Heated Catalytic Converters
Catalytic converters require fairly high temperatures to be
effective. Heat is provided by the exhaust and from the reactions
of the HC in the catalyst bed. Following a cold start, there is a
delay before the catalytic converter becomes effective, while it
heats up to its operating temperature; once the converter reaches
the desired operating temperature, it performs well with very high
efficiency. Electrically heating catalytic converters at vehicle
start-up can reduce the delay before the converters become
effective. This approach may also be of value to the emissions
control strategy for light and medium duty vehicles. Electrically-
heated catalytic converters are made of metals rather than
ceramics, thus, these converters experience less cracking and are
more durable than other catalytic converters. ' However, some
electrically-heated catalytic converters are susceptible to
aluminum washcoat degradation. This technology is currently
available. Other catalyst bed improvements are also available
which could improve emission reductions efficiency.
2.0.2.3.2 Close-Coupled Catalytic Converters
Another approach that can be used to minimize the delay is to
install the converter very close to the engine, so that the exhaust
gases contacting the catalyst are hotter. However, these close^
coupled catalytic converters are more susceptible to thermal
degradation because they are continually exposed to significantly
higher temperatures than converters located further away from the
engine. By installing converters only slightly closer to the
engine than current converters so that the exhaust gases contacting
the catalyst are only at a slightly higher temperature, smaller
emission benefits may occur. Closed-coupled catalytic converters
will be available for the 1994 model year due to the California LEV
standards. Insulating exhaust pipes may provide similar benefits
at lower costs. *
2.0.2.3.3 Lean-Burn Calibration
While the air-to-fuel ratios of current engines are generally
calibrated at stoichiometry, there would be potentially significant
benefits with leaner calibrations. Leaner air-to-fuel ratios could
lead to lower engine-out HC, CO, and perhaps NOx emissions, as well
as a decrease in fuel consumption. On the other hand, there can be
a loss of power and problems with ignition and flame propagation.
Also, leaner combustion would lead to leaner exhaust which would
present the additional challenges of developing catalysts and
oxygen sensors that work well under such conditions. It is likely
that lean-burn calibration would only be used on engines with
advanced electronic feedback controls. The availability of this
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technology is uncertain at this time, for heavy duty engines.
2.0.2.4 Expected Approaches for Clean-Fuel Gasoline Engines
Overall, given that emissions from some current gasoline-
fueled engines are already very close to those required by the CFFV
(clean-fuel fleet vehicle) standard, it is expected that
optimization of existing technologies will be adequate to allow a
significant number of gasoline-fueled engines to comply with the
clean-fuel fleet standard, and that dramatic changes will not be
necessary. Engine changes, such as but not limited to changes in
the EGR system, combustion chamber design improvements, and tighter
control over the air-to-fuel ratio, are expected to provide much of
the necessary reductions in NMHC+NOx emissions for many engines.
Slightly leaner calibrations may be used under some conditions;
however, very lean calibrations should not be necessary.
Additional reductions will also likely come from upgraded
exhaust aftertreatment systems. It is expected that all gasoline
engines in the Clean Fuel Fleet program will be equipped with
three-way catalysts; and that these catalysts will be slightly more
effective than those currently being used, through either
optimization of the catalytic materials,.__ increases in the catalyst
loading and/or bed size or exhaust pipe insulation. The Agency
does not currently expect that electrically-heated or close-coupled
catalysts will be necessary in order for most gasoline-fueled
engines to comply with the HD (heavy-duty) CFFV standards.
The docket contains further supporting material on the
feasibility of the CFFV NMHC + NOx emission standard for heavy-duty
engines.1 ' "
2.0.3 Diesel Engines
2.0.3.1 Technical Background/Fundamentals of Diesel Engines
Which Impact NMHC + NOx Emissions
In diesel engines, NOx is formed in the early phases of
combustion where temperatures and pressures reach a peak. In
diesel engines, as fuel is injected into the combustion chamber it
mixes with hot compressed air already present, and after a brief
period known- as ignition delay, this fuel-air mixture ignites. In
this premixAd; burning phase/ the fuel-air mixture burns in an
uncontrolled manner, which causes a rapid rise in cylinder pressure
and heat release, until the mixing controlled combustion phase
(diffusion-controlled burning) takes control of the combustion
process. Once diffusion-controlled burning begins, fuel
essentially burns as it is injected, allowing partially burned
droplets and particulates to be consumed as oxygen becomes
available at local combustion sites. It is believed that most of
the NOx is formed during the period before diffusion takes control
of combustion.2 Therefore, anything which can be done to reduce
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the temperatures during this uncontrolled burning phase will tend
to reduce the formation of NOx.
Hydrocarbons are the result of incomplete combustion of the
fuel. Because of the lean combustion technology used in diesels,
out hydrocarbon emissions tend to be inherently low. However,
controls that reduce NOx often have an adverse effect on HC
emissions since they are inversely related to oxygen availability
and peak conbustion temperature.
2.0.3.1.1 Fuel System
The. fuel system in a diesel . engine is responsible for
controlling both the amount of fuel delivered to the cylinder and
the timing of the fuel delivery. Since the fuel is injected into
an air mass that is already compressed and has consequently been
heated to a temperature above the auto-ignition point for the fuel,
the injection timing determines when combustion will begin and
serves some of the same functions in diesel engines as ignition
(spark) timing does in gasoline engines. There are two types of
injection systems available for diesel engines: direct and indirect
injection.
Diesel engines can use either direct injection (DI) or
indirect injection (IDI) combustion systems. Direct injection
engines inject the fuel into a hollow in the piston and have the
air/fuel mixing controlled by swirling motions in the intake air
and the momentum and spray characteristics of the fuel jet.
Indirect injection engines, on the other hand, inject the fuel into
a pre-chamber and accomplish most of the air/fuel mixture through
turbulence created by the expansion out of the chamber. Since
indirect injection engines do not expose the bulk of the initial
uncontrolled burning to as much oxygen, they have somewhat lower
NOx emissions rates.3
The primary disadvantage of engines using IDI technology is
that they are less fuel efficient than DI engines due to heat and
frictional losses in the pre-chamber. However, indirect injection
technology has low initial costs which make it well suited for
small high-speed diesel engines where the fuel consumption is least
significant.4 In addition, IDI is a useful option for small
diesels because it helps address problems with air utilization due
to their small cylinder volume.3 Concerns about the fuel economy
penalties, however, are leading some manufacturers to use
alternative methods of controlling NOx emissions.
2.0.3.1.2 Air System
Air system improvements also show promise for NOx and HC
control. By increasing the mass of gases contained in the
cylinder, the temperature' rise can be decreased which results in
reduced NOx formation. If some of the extra gas is oxygen, the
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increased oxygen availability will result in more complete
combustion reducing HC and particulate emissions. Cooling of the
intake air will further reduce the in-cylinder temperatures
resulting in reductions in NOx formation.
2.0.3.2 Current Diesel Emissions Control Technology
Current emissions control for diesel engines is generally
based upon optimization of engine parameters such as ignition
timing, injector nozzle and cylinder design, and air intake.
Nearly all of the light and medium heavy-duty engine families
certified in 1992 used turbochargers with aftercooling. A very
small number of current light and medium heavy-duty engine families
use electronic controls, but most use mechanical controls. The use
of mechanical controls is probably the most significant limitation
of current diesel emission control. While some mechanical
improvements are still being made, it is generally true that
emissions from mechanically controlled engines have been optimized
nearly as much as is possible without the development of
dramatically new technologies, or reductions in fuel economy. For
example, NOx emissions could be reduced from current levels by
retarding the injection timing, but this would lead to reduced fuel
economy and increased HC and PM emissions .(which would increase the
need for exhaust aftertreatment). The following sections discuss
some of the currently technologies which affect diesel emissions.
2.0.3.2.1 Retarded Injection Timing
Retarding the injection timing is a well-known and proven
technique for significantly reducing NOx emissions. The primary
mechanism for reducing NOx emissions by this technique is the
reduction in the duration of uncontrolled burning. However,
retarded timing has undesirable effects, particularly when used
alone. Retarding the timing significantly will increase
particulate and hydrocarbon emissions and decrease fuel economy due
to reduced time for the fuel and initial combustion products to mix
with the excess air in order to burn.5 The regulatory pressures on
particulate emissions and the market pressures on fuel economy
combine to limit the use of retarded timing in controlling NOx
emissions.
2.0.3.2.2 Injection Pressure
Injection pressure increases in DI engines can be used to
limit particulate emissions and speed up the completion of
injection. Increased injection pressure increases the air/fuel
mixing in direct injection engines because of increased air
entrainment into the fuel spray and higher turbulence therein (less
condensation is likely to occur). This has little direct effect on
NOx formation; however, it does lead to a decrease in particulate
formation. Furthermore, an injection pressure increase will
shorten the duration of the injection.6 The combination of reduced
2-9
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particulate formation and shortened injection duration should allow
the timing to be retarded without incurring other impacts.
Hydrocarbon emissions are insensitive to injection pressure at
full-load, and only increase slightly under half-load high speed
conditions.7
2.0.3.2.3 Injector Nozzle Holes and Diameters
Nozzle characteristics are important to optimize for emissions
and performance reasons, particularly for direct injection engines.
Decreasing the nozzle'" hole diameters increases the injection
duration without increasing the ignition delay; therefore, the
maximum heat release in the pre-mixed burning phase decreases, in
addition, reducing the hole size better atomizes the fuel allowing
more complete burning. For these reasons, smoke can be decreased
without an increase in NOx by decreasing the nozzle diameter.2
Changing the number of holes in the injection nozzle may be used to
affect the spray characteristics of the fuel. Hydrocarbon
emissions are only slightly affected by the number of holes;
however, CO and smoke have been found to be least sensitive to
injection pressure for a 6-hole injector.8
2.0.3.2.4 Intake Air Turbochacging
Turbochargers are used to force additional air (mass) into the
combustion chamber allowing a shorter ignition delay and more
complete burning of a given amount of injected fuel. Therefore,
turbocharging may be used to reduce HC emissions at partial loads
which increases the capability of retarding timing (lower NOx).8
As with other lean burn systems the addition of additional air to
make the mixture even leaner results in reduced cylinder
temperatures. This change has a direct positive impact on NOx
emissions.
2.0.3.2.5 Aftercooling •
If the intake air is turbocharged, the temperature will rise
during compression. Cooling the intake air after it has been
turbocharged will help lower the in cylinder temperature, and
therefore reduce NOx formation.5 There are several approaches to
aftercooling, including air-air and air-liquid aftercoolers. By
using air-to-air aftercoolers, some manufacturers have been able to
reduce the temperature of the turbocharged intake air to about ten
or fifteen degrees Fahrenheit above the ambient air temperature.
2.0.3.2.6 Cylinder Design
The combustion chamber shape may be optimized in order to
promote mixing with enhanced turbulence. Enhanced t'urbulence can
reduce particulate and hydrocarbon emissions through better mixing
but has a tendency to increase NOx emissions through the increased
heat release. A reentrant chamber has a small lip around the top
2-10
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; in ^ the combustion chamber may be used
NOx^ smoke^ atid fuel
ts on engines equipped with a
^shpwn simultaneous
?-n; bQth, partioulate. emissions and NOx J emissions by
allpwing; -the^ engine^Hto ^be^ optimized for NQx or partlculate
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' ' '
BrR -.Control Technoloqv ™
^-=:-»-''''1 "'^"lAT.".'-' •' ...-•:'. '- -.-.-''•" "... . •• -,- .' '„ •' ,—• ' ' •' • ^•**-ii/" •••
r optimization of ;en5|i|ie?parameters such ^as in jection timing,
pressure -d^nfacor^ nozzle and cylinder, design? air
J^Sitipnal diesel emission^ control may
'jj^8*±aa control, technologies; among
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- Exhaust _gas recirculation reduces the temperature of- the
cylinder by, adding inert gases to expand to do work. This can
increase Pit emissions, especially at full load, due to the lack of
oxygen preaentr in the combustion chamber which results in
incomplete combustion. Moderate EGR rates (5-15%) have been shown
to bring NOx down into the 1.9 - 3.4 g/Bhp-hr range. This may be -
done without increasing particulates significantly or de-rating the
engine,- _by using electronically-controlled EGR (see discussion
below}. In addition NOx reduction engines using EGR have shown
significantly better fuel economy than engines using timing retard..
More research must still be done to demonstrate the full potential
of EGR.9 •
, > - 2.0.3^3.2 Improved Turbocharging
" Two improvements to intake air turbocharging which are being
developed, may result in significant emissions reductions. The
first is the variable geometry turbocharger (VGT) , which allows a
more optimized flow of air into the engine, such as more air at
high loads. VGT would not directly impact NOx emissions, but would
decrease particulate emissions and fuel consumption, thereby
allowing further retard of the injection timing. It also provides
a means of controlling cylinder pressureja__for engines using EGR.
The second approach - called turbo expanding involves over-
compressing the intake air, then expanding it to a lower pressure
after the charge, is cooled by the aftercooler. The result is a
reduced intake temperature, and thus lower NOx emissions.
• 2.0.3.3.3 Injection Rate Shaping
Injection rate shaping is a very promising technology for
reducing NOx emissions without adversely affecting other
performance parameters.- The basic approach is to reduce the amount
of fuel injected in the early phases of injection so that" the
amount of fuel which undergoes premix burning reactions is reduced.
Preliminary testing^ and even production system development has
begun in- earnest over _ the? last- few' years.
1 Results from the Ricardtai HDD (heavy-duty diesel) engine
research progrant demonstrate that rate shaping may be used to
achieve vesj-loir NOx levels without a penalty in fuel economy or
particulat«|eraissions.10 By injecting the fuel with a "gradual rise
and a shar|lpeutn as opposed to a constant injection, the NOx is
reduced be^iiuse of a lower heat release during the pre-mixed
burning phase where NOx is formed.2 In addition, a clean injection
cut-off will reduce smoke and HC emissions by avoiding the poorly
atomized end- of in jectiprw8 "
- ' , 2 . 0~. 3^ 3 . 4-~ Electronic, Controls
historical problem with managing the engine operation
parameters .is_ the inherent problem that mechanical controls have
" - - " 2 - 12
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only a limited ability to adjust the operating parameters to match
the optimal conditions for any given speed and load condition. An
engine set up to produce low emissions at one set of conditions may
have relatively high emissions at some other sets of operating
conditions. These problems are especially pronounced in the
smaller diesel engines affected by new clean-fuel fleet vehicle
regulations.
The advent of electronic engine control devices will allow
more flexible control of engine operation. Electronic controls are
expected to be installed on essentially all heavy-duty diesel
engines by 1994 in order to both achieve improved engine
performance and to assist in achieving compliance with the 1994
emission standards. Through the use of electronic controls and the
advent of advanced fuel delivery systems, it will become possible
to store a map of the optimum operation parameters and then to
control the engine operation at these conditions over a wide range
of operating modes thereby reducing some of the needs to make
design trade-offs in cases where engine operation parameters
optimized for one operating condition may not be appropriate for
other operating conditions.8 Among the parameters that could be
controlled electronically are injection timing, injection rate, and
EGR rate.
One example of the use of electronic control would be to use
it to significantly retard injection timing under most operating
conditions except high loads, where the need for both particulate
control and high power is significant. Similarly, EGR rates could
be reduced at high loads to decrease the impact on particulate
emissions. It may also be possible to use exhaust gas sensors for
oxygen and/or NOx in a closed-loop control system to correct for
in-use deterioration. EPA believes that, of the technological
advances expected in the next several years, electronic controls
have the greatest potential for improving the emissions and fuel
economy of diesel engines.
2.0.3.3.5 Aftertreatment Devices
Aftertreatment devices have not yet come into widespread use
on diesel engines. Up to the present time, emissions control
strategies for most diesel engines have relied on technologies
which control engine out emissions. However, both particulate trap
oxidizer systems and flow through catalytic oxidizers are under
development and expected to be available for wide-scale commercial
production if necessary to comply with the 0.10 g/Bhp-hr PM
standard for the 1994 model year. In addition, there is active
research ongoing in the area of catalytic converters capable of
reducing NOx emissions in lean exhausts. These are discussed
below.
2.0.3.3.5.1 Particulate Trap-Oxidizers
2-13
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A trap-oxidizer system primarily affects PM and HC emissions.
This method of aftertreatment consists of a durable particulate
filter (trap) which collects particulate emissions in the exhaust
stream. Developers of these systems claim that collection
efficiencies of 80 percent or greater can be achieved. Since
collection of the particulates without a system for eventual
removal would quickly plug the traps and shut down the engine, some
method of regenerating the filter by burning off (oxidizing) the
particulates is required. The traps must be regenerated before the
systems become plugged to the extent that back pressures in the
exhaust system rise too much, but too frequent regenerations
increase the amount of energy which must be put into the systems to
effect the regeneration.
Trap-equipped urban bus engines have been certified recently,
but manufacturers remain reluctant to rely on these systems because
of their relatively high costs and remaining concerns over the
durability of the systems. However, these systems should be
available for use prior to 1998, if needed.
2.0.3.3.5.2 Catalytic Oxidizing Converters
Catalytic oxidizing converters greatly reduce HC emissions.
Reductions of as much as 40 or 50 percent of the engine out HC
emissions may be seen from the designs likely to be available prior
to 1998. Since catalytic converters may see widespread use in the
control of particulate emissions, large reductions in HC emissions
will result as a corollary benefit. The catalytic converter avoids
the problem of regeneration due to its flow-through design and some
believe this is a simpler, more cost efficient and more durable
method of aftertreatment than particulate traps. However, its
major drawback is sulfate production. This problem is expected to
be managed with the low sulfur fuels being mandated for sale
beginning in October of 1993.9
2.0.3.3.5.3 Catalytic NOx Reduction
Aftertreatment devices to control NOx emissions in lean
exhausts are not available at this time, although research on
promising technologies is progressing in Japan and Germany.11 The
only aftertreatment device to be demonstrated to date involves the
injection of ammonia or urea into the exhaust stream to consume
NOx. However, there are no acceptable methods to ensure that there
will always be a supply of ammonia or urea to keep these devices
operating. Therefore, actual in-use emissions reductions cannot be
relied on and use of these devices could be problematic. There is
also concern about harmful effects from the emissions of ammonia.
Passive flow-through catalytic converters to reduce NOx
emissions in lean-burn exhausts are under investigation. These
devices appear to operate by simultaneously reducing NOx and
oxidizing HC or particulates with the oxygen produced from the NOx.
2-14
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However, the development of useful devices is still some years away
and availability of these devices for the 1998 model year can not
be assumed.8
2.0.3.3.6 Variable Compression Ratio
Increasing the compression ratio in the engine reduces white
smoke and hydrocarbon emissions. There is, however, an optimum
point at which a further increase in the compression ratio causes
an increase in particulate emissions.12 A prototype diesel engine
has been developed that had a variable compression ratio. NOx and
NMHC emissions from this engine were very low. This technology
thus may become available to reduce particulates without increasing
NOx.13
2.0.3.4 Expected Approaches for Clean-Fuel Diesel Engines
Diesel engines will need to make changes to comply with the HD
clean-fuel fleet vehicle emission standard for NOx and NMHC, but
this should be feasible for a significant number of engines. It is
expected that electronically controlled EGR will be necessary, and
that highly optimized electronic control of injection timing and
rate shaping will also be incorporated. Some catalytic
aftertreatment may be used to control NMHC and PM emissions, since
engine-out emissions of NMHC and PM could increase as a result of
timing retard. Although the Acurex Report1 done under contract
with the California Air Resources Board, entitled "Technical
Feasibility of Reducing NOx and Particulate Emissions From Heavy-
Duty Engines," projects that catalytic aftertreatment will reduce
NOx emissions significantly by 2000, based on our above assessment
of catalytic aftertreatment and recent reports from the
Manufacturers of Emission Controls Association (MECA) that this
technology will not be available until after 1998, EPA does not
expect that catalytic aftertreatment will be used to reduce NOx
emissions. It is not clear, at this time, how fuel economy will be
affected, since electronic controls, EGR, and improved
turbocharging can improve fuel economy, while timing retard will
have a negative impact. Manufacturers will be faced with a
decision of how to best trade off improvements to the engines with
increases in fuel consumption, in order to control emissions in the
most cost effective manner.
The docket contains further supporting material on the
feasibility of the CFFV NMHC + NOx emission standard for heavy-duty
engines.1
2.0.4 Alternative Fuel Technologies
While alternative fuel technologies are certainly viable
candidates for use in clean-fuel fleet vehicles, the HD CFFV
emission standards are not set at a level which will require their
use. It will be difficult, however, for most diesel engines, and
2-15 .
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possibly some types of gasoline engines, to reach the credit-
generating standards. Alternative fuel technologies such as
methanol- and gaseous-fueled engines are expected to meet these
standards while electric vehicles are viewed as being the only
technology capable of meeting the zero emission vehicle standards.
The docket contains further supporting material on the feasibility
of the credit level NMHC + NOx emission standards for heavy-duty
engines.1
2.0.4.1 Methanol
Methanol is an attractive fuel from an emissions standpoint.
Its lower flame temperature leads to an inherent reduction in the
formation of NOx emissions. Exhaust emissions of NMHC (more
appropriately called organics for methanol-fueled engines) are
generally comparable to those of similar petroleum-fueled engines.
Nevertheless, methanol-fueled engines can still provide some
benefit with respect to organic emissions for two reasons. First,
organic emissions from methanol-fueled engines, while not
necessarily less than those from engines using conventional
petroleum fuels, tend to be less reactive in the processes which
form ozbne, and thus can have a less significant impact on ambient
air quality. It should be noted, however, that this benefit is
difficult to quantify. Second, non-exhaust (e.g., evaporative)
emissions of organics are much lower than those from gasoline-
fueled vehicles due to the lower vapor pressure of methanol.
Both otto-cycle and diesel-cycle methanol-fueled engines and
vehicles are under development currently. While it is expected
that otto-cycle technology will be capable of meeting the credit
standards by 1998, these vehicles are being developed primarily for
light-duty uses. Diesel-cycle engines, however, because of their
inherent fuel economy advantages, are more likely to see
applications in heavy-duty vehicles. Recently, Detroit Diesel
certified the first heavy-duty diesel cycle methanol engine for
commercial sale. This engine was recertified for the 1993 model
year as having NMHC+NOx equivalent emissions of 1.8 g/Bhp-hr, CO
emissions of 2.1 g/Bhp-hr and particulate emissions of 0.03 g/Bhp-
hr. As can be seen, this engine is already in compliance with the
credit standard. This particular engine is a heavy heavy-duty
engine intended for use in urban buses, but the technology should
be transferrable to other engines more likely to be used in the
Clean Fuel Fleet program.
2.0.4.2 . Natural Gas
Natural gas, in either the form of compressed natural gas
(CNG) or liquified natural gas (LNG), is likely to be used as an
alternative fuel in some light and medium heavy-duty vehicles for
use in the Clean Fuel Fleet program. Indeed, experimental delivery
vans converted from gasoline to CNG are being used by several
2 - 16
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delivery fleets due to its potential for fuel cost savin
Moreover, Cummins has recently certified a CNG-fueled L-10 2
engine with the State of California. Two types of CNG-fueled
engines are being developed: stoichiometric (i.e., converted
gasoline engines) and lean-burn (e.g., the Cummins L-10 bus
engine).
EPA analyzed the emissions characteristics of CNG-fueled
vehicles and engines in an April 1990 special report.14
Stoichiometric engines, which are the type of engines being used by
delivery vans, were projected in that report to have emissions of
0.88 g/Bhp-hr NMHC+NOx, 7.4 g/Bhp-hr of CO, 0.01 g/Bhp-hr of
particulate and 0.0006 g/Bhp-hr of formaldehyde for optimized
engines. Projections for optimized lean-burn engines, which are
favored for use in heavy heavy-duty applications (greater than
26,000 Ibs GVWR) for fuel economy reasons, indicated that NMHC+NOx
emissions of 4.06 g/Bhp-hr, CO emissions of 1.5 g/Bhp-hr,
particulate emissions of 0.05 g/Bhp-hr and formaldehyde emissions
of 0.03 g/Bhp-hr can be achieved using traditional technology.
However, the Cummins L-10 engine that was recently certified had
emissions that were much lower than those projected for such a
lean-burn engine: NMHC+NOx emissions of 2.6 g/Bhp-hr, CO emissions
of 0.4 g/Bhp-hr, and particulate emissions of 0.02 g/Bhp-hr. While
neither the projected emissions, nor the emissions from the Cummins
L-10 engine, would comply with all the credit standards, it is
expected that the standards could be met by engines using more
advanced technology. Although the L-10 engine is for heavy heavy-
duty applications, the L-10 engine demonstrates that it ought to be
feasible to meet the clean-fuel fleet vehicle standards with light
and medium heavy-duty vehicles. Lean-burn CNG engines will need to
improve the control of NOx and/or NMHC emissions in order to meet
the credit standards, but it is likely that this would be
accomplished by incorporating the advances in NOx control which are
being developed to comply with the 4.0 g/Bhp-hr standard for all
heavy-duty engines. Stoichiometric technology will also require
minor advances, such as slightly higher catalyst loadings, in order
to comply with these standards by 1998.
2.0.4.3 Liquefied Petroleum Gas
Liquefied Petroleum Gas (LPG) is another gaseous fuel which
expected to be used to some extent in the Clean Fuel Fleet program.
It is a very clean-burning and economical fuel, and has been the
most widely used alternative fuel for many years. Most of the
incentive for its use has come from its economic advantages, and
there is only a limited amount of emissions data available,
especially for heavy-duty vehicles. In general, emissions from
LPG-fueled engines should be similar to the emissions from CNG-
fueled engines, except for NMHC which could be slightly higher from
LPG-fueled engines. This is because NMHC emissions are generally
due to unburned fuel, and LPG is largely a non-methane fuel (unlike
CNG which is comprised mostly, of methane). As with CNG-fueled
2-17
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vehicles, it is expected that LPG-fueled heavy-duty engines will
also be able to comply with the credit standards with similar
control approaches. EPA plans to release a report on LPG fuels and
vehicles in the next few months.
2.0.4.4 Electric Vehicles
EPA anticipates that electric vehicle technology will be
required for a vehicle to comply with the zero standards. While
light and medium heavy-duty vehicles may be better equipped to
handle the bulk and mass of the necessary batteries, the additional
batteries, limited driving range, and operating expenses will
probably still make electric vehicle technology an unpopular
choice. Advances in technology and market incentives for credits,
however, may combine to make such technology viable at some point
in time.
2.0.5 Summary
The clean-fuel fleet vehicle standards should be achievable
using a wide range of technologies. Gasoline-fueled engines should
be able to reach compliance with the standards through the further
optimization of technologies already in use. Diesel engines will
significant developmental work, including the introduction of new
technologies such as EGR for diesels. EPA also believes that
optimized electronic controls for fuel will be required for all
diesel engines in this program but much of this will be
incorporated meet the 4.0 g/Bhp-hr NOx standard. Optimized (or in
some cases non-optimized) alternative fuel technologies capable of
meeting the clean-fuel fleet vehicle standards are already
available.
Credit-generating standards may be achievable in some cases
using conventional fuel technologies and will certainly be
achievable using alternative fuels. These standards might be
achievable with highly advanced gasoline engines using electrically
heated catalytic converters and possibly even by diesel engines
using optimized EGR and electronic fuel control should they become
available. A methanol engine which meets all of the credit
standards has already been certified, and natural gas-fueled
engines appear to be promising candidates also. Zero-emitting
vehicles will probably require electric vehicle technology.
2 .- 18
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Chapter 3
Environmental Benefits
3.0.1 Introduction
vehicles .which ™1 be> aV^SJ?1 +1® been made °f the n^mber of
of miles each of th.«, -SET??.?^^? requirements, the number
emission
3-0-2 Calculation Matherf
total number of vehicle
by the
heavy-duty (8, 501-1 500
heav^-duty (19,501-26 000
subclassed are the
light
(GVW) > "d »ed±u«
subclass«* since these
light heavy- and '
3-°-3 Diseuaaion of
3.0.3.1 Light
demographics
and medium heavy-duty fleet vehicle
a:
3-1
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subclasses will be discussed in order to provide the background
data necessary to make the emissions inventory calculations and to
interpret the results of the emissions inventory modeling.
EPA has estimated that, in 1989, there were 305,000 light
heavy-duty and 668,000 medium heavy-duty vehicles operating in
fleets of ten or more heavyrduty vehicles in areas affected by the
fleet provisions.15 Based on information available from EPA's
MOBILE4 emissions model, the light heavy-duty fleet population is
projected to grow at a rate of 2.75 percent per year while the
population of medium heavy-duty fleet vehicles is projected to
decline at a rate of 1.11 percent per year.16 It is also estimated
that heavy-duty fleet vehicles are replaced every six years and
that 80 percent of the vehicles operating in fleets of ten or more
heavy-duty vehicles in affected areas will actually be covered by
the program. (Twenty percent of such vehicles are assumed not to
be covered because they are not centrally fueled or capable of
being centrally fueled or are exempt under the CAA fleet program.)
Combining these data and assumptions with the fact that 50 percent
of the purchases of affected heavy-duty fleets will be required to
be clean-fuel fleet vehicles starting in 1998, it is projected that
8,516 light heavy-duty and 11,124 medium heavy-duty clean-fuel
fleet vehicles will be required to be purchased in 1998.17 The
results of this projection of the number of light heavy-, medium
heavy- and total heavy-duty vehicles affected by the Clean-Fuel
Fleet Program from 1998 through 2020 are shown in Table 3-1.
3-2
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iir
i— CM CO
CM CM CM
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35, o> o o> o> o" o" o" o" erf o*
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•» •» in
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IIJln;u>o>
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111 tA
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Billions of Miles Travelled
h-H- ru CJ >f»- ui CTI -vi 00
tO
_ .0 ""'
-
' *•*++.
**""•-•-•+' *...,.__
o
Light-Heavy
• — •&••-•
Medium-Heavy
Total
o
'.:.:*&
,,,,--a
&e_— -B—-^8"
1 1 1 " 1
95 2000 2005 2010 2015
Year
i
2020 2025
Figure 3-1 - Clean-fuel fleet vehicle VMT
3-5
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Information about fleet operating practices and 4®f§(;-available
from MOBILESa were combined to calculate annual ijjjjjelG miles
traveled (VMT) by the clean-fuel fleet vehicle popjjalpion. For
simplicity, it was assumed that all fleet vehicles wd;||tin: a given
class travel the same number of miles per year regardless of age.
Since light heavy- and medium heavy-duty fleet vehicles are both
projected to accumulate their average fleet life milesf within six
years, the annual VMT per vehicle for each class was calculated by
averaging the VMT per vehicle projections for the firsfc-.six years
of each class as published in the User's Guide to MOBIJiB^. It was
further assumed that the VMT/vehicle data will remain constant from
year to year. Using this methodology, it is projected that light
heavy-duty fleet vehicles will travel 17,870 miles per year and
medium heavy-duty fleet vehicles will travel. 36,190 mllea per year.
The projections of the total number of vehicle mii&es traveled
by heavy-duty vehicles affected by the Clean-Fuel Fleefc program are
shown in Table 3-2 and Figure 3-1. It can be seen that;^ due to the
simultaneous growth in light heavy-duty fleet vehicles and the
decline in the population of medium heavy-duty fleet vehicles, the
number of light heavy-duty vehicles is projected to: surpass the
number of medium heavy-duty vehicles by approximately the year
2008. The total number of vehicles increases throughout the time
period evaluated. However, due to the fact that medium heavy-duty
fleet vehicles accumulate approximately twice as many miles per
vehicle each year as light heavy-duty fleet vehicles (see previous
paragraph), medium heavy-duty fleet vehicles together accumulate
more miles each year than the light heavy-duty fleet vehicles even
out to the year 2020.
In order to understand some of the complexities of the results
which will be shown later, it is important to understand some of
the contrasts between light heavy- and medium heavy-duty vehicles
and between otto-cycle (gasoline) and diesel-cycle engines. As has
already been pointed out, the population of light, heavy-duty
vehicles is growing while the population of medium heavy-duty
vehicles is declining. Furthermore, it has also been stated that
medium heavy-duty vehicles travel about twice as many miles in a
year as do light heavy-duty vehicles. Another important contrast
between light heavy and medium heavy-duty vehicles is the mix of
engine types these vehicles use. It is estimated that 70 percent
of the light heavy-duty vehicles use gasoline powered otto-cycle
engines with the remainder being primarily diesel-cycle engines.
For medium heavy-duty vehicles, the engine mix is nearly the
opposite of the engine mix for light heavy-duty vehicles (30
percent otto-cycle and 70 percent diesel-cycle).16
The distinction between engine type mixes becomes particularly
critical when the contrasts in emission factors between gasoline
and diesel powered vehicles are taken into account. Diesel engines
typically emit higher levels of NOx than do gasoline engines while
simultaneously emitting lower levels of HC due to the fact that
3 - 6 . ' -,:—\
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diesel engines use lean-burn modes of operation and consequently
have relatively low engine-out HC emissions levels. Today's diesel
engines are not equipped with catalytic converters to reduce the
engine-out HC and NOx emissions as are gasoline engines^
3.0.3.2 Emission Factor Calculations
In order to calculate the emissions inventories for the
desired scenarios, emission factors and deterioration rates for
light heavy-duty and medium heavy-duty vehicles are needed. In
this analysis, all the vehicles are either gasoline- or diesel-
powered so emission factors for only these two fuel types will be
needed. It is expected that some alternative-fueled vehicles will
be produced, but that the numbers will be sufficiently small, and
certification emission levels and deterioration characteristics
sufficiently similar, so as to not substantially impact the results
of this analysis.
3.0.3.2.1 1998 and Later Baseline Emission Factors
Determination of the environmental impacts of fleet vehicles
requires estimates of emission factors for, in-use vehicles. For
this analysis, data is used that projects that in-use 1998 and
later heavy-duty vehicles will behave similarly to certification
vehicles, and that they will meet their respective standards
(intermediate useful life and full useful life standards) in use.
In order for this approach to be valid, it would be necessary for
there to be an extensive inspection and maintenance program, as
well as an active field enforcement program, for heavy-duty
vehicles. Both of these seem reasonably likely, especially in the
areas that will be affected by the fleet program. As will be
discussed later, a similar approach is also being used for heavy-
duty clean-fuel fleet vehicles. Since the same approach is being
used for both baseline and clean-fuel fleet emission factors, these
assumptions should not significantly impact the calculation of
incremental benefits even if the assumptions were to be somewhat in
error. The 1998 baseline vehicle emission factors are derived from
1991 sales-weighted certification emissions, taking into account
the effects of new emission standards. The 1991 certification
emissions rates are shown in Table 3-3.
NMHC estimates for pre-1998 vehicles were .derived from
MOBILESa projections. Non-methane hydrocarbon (NMHC) emission
factors were estimated at 95 percent of the total hydrocarbon
emission factor for diesel engines and at 75 percent of the total
HC emission factor for gasoline engines.14 For gasoline engines the
same deterioration rates for HC emission factors are applied to the
NMHC emission factors since present catalytic converters have
little effect on methane emissions.
3-7
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Tabla 3-3 Sales-Weighted 1991 Light and Medium Heavy-Duty
Certification Values
Sales-Weighted Heavy-Duty Certification Values
(g/Bhp-hr)
Vehicle class
Light Heavy-Duty Diesel
Medium Heavy-Duty Diesel
Light Heavy-Duty Gasoline
Medium Heavy-Duty Gasoline
THC
0.56
0.41
0.45
0.79
NMHC
(estimate)
0.54
0.39
0.34
0.59
NOx
4.44
5.01
3.87
3.84
The most significant standard affecting 1998 baseline heavy-
duty vehicles is a reduction in the NOx emission standard from 5.0
to 4.0 g/Bhp-hr beginning in that model_year. Light and medium
heavy-duty diesel engines currently exceed this level and will
therefore require new compliance effort. Although the sales-
weighted certification values for NOx emissions from 1991 heavy-
duty gasoline engines are numerically low enough on average to just
meet the 1998 4.0 g/Bhp-hr NOx standard, the relatively small
compliance margins and the fact that some engine families do not
meet the standard indicates that further reductions are needed.
Manufacturers will likely incorporate compliance margins of 10 to
15 percent for certification vehicles to allow for production
variability and in-use operation. Thus, in-use emissions may be
under the standard on average. For this analysis, however, average
NOx emissions will be modeled as being at the level of the 4.0
g/Bhp-hr standard at the end of the vehicle's useful life.
Hydrocarbon standards for 1998 heavy-duty engines will be the
same as for current engines. Heavy-duty diesel NMHC emissions may
drop if catalytic converters achieve a significant penetration into
the light heavy- and medium heavy-duty diesel engine market for
particulate control. This is because, in addition to providing
particulate. control, these catalytic converters are expected to
reduce HC emissions. However, it is also possible that engine-out
HC emissions will be allowed to rise somewhat in the presence of
the catalyst in order to provide more control flexibility for NOx.
This would result in little or no net reduction of NMHC for 1998
baseline vehicles. For this analysis, 1998 baseline diesel NMHC
will be modeled as being at a level equivalent to the 1991 NMHC
levels.
3-8
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Hydrocarbon emissions from heavy-duty gasoline vehicles are
also projected to comply with the applicable HC standards in use.
Light heavy-duty gasoline vehicles are assumed to comply with the
1.1 g/Bhp-hr HC standard for vehicles 14,000 Ibs GVW and under, and
medium heavy-duty gasoline vehicles are assumed to comply with the
1.9 g/Bhp-hr HC standard for vehicles over 14,000 Ibs GVW. Given
the Mobile model vehicle grouping scheme laid out in the beginning
of this chapter for light and medium heavy-duty vehicles, these
assumptions could introduce some analytical error into the
analysis, since some light heavy-duty gasoline vehicles (those
between 14,000 and 19,000 Ibs GVW) could emit up to the 1.9 g/Bhp-
hr standard. However, this should not introduce significant error
into the analysis since there are few gasoline vehicles in this
weight range. For this analysis, as with diesels, 1998 baseline
gasoline NMHC will be modeled as equivalent to 1991 NMHC levels
since some reductions in NOx emissions will be needed in 1998.
The deterioration rates for heavy-duty diesel engines are
based on the assigned deterioration factors for heavy-duty diesel
engines with aftertreatment, and the deterioration rates for
gasoline engines are based on the assigned deterioration factors
for light-duty gasoline trucks with three-way catalysts.18 For this
analysis, the estimated zero-mile emission factors are
back-calculated by using the emission projections estimated above
and the respective deterioration factors. These estimated zero-
mile emission factors and deterioration rates for 1998 baseline
vehicle engines are presented in Table 3-4. The deterioration
factors presented in Table 3-4 are the additive equivalents of the
multiplicative deterioration factors, divided over the useful life.
Table 3-4 1998 Model Year Baseline Emission Factors
Vehicle
L-H diesel
M-H di«s«l
L-H gasoline
M-H gasoline
Zero Mile EF
(g/Bhp-hr)
NMHC
0.42
0.30
0.20
0.35
NOx
3.33
3.33
3.33
3.33
Deterioration Rate
(g/Bhp-hr/10, OOOmi)
NMHC
0.011
0.005
0.013
0.022
NOx
0.061
0.036
0.061
0.061
3-9
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3.0.3.2.2 Projections for 1998 Clean-Fuel Fleet Emission
Factors
Emission factors and deterioration rates for clean-fuel fleet
heavy-duty vehicles were estimated using the following methodology.
In today's Regulatory Support Document the clean-fuel engine
emission factors are based on the projection that average NMHC +
NOx emissions will comply with a combined 3.8 g/Bhp-hr NMHC+NOx
standard at the end of the vehicle's useful life instead of a
combined 3.5 g/Bhp-hr NMHC + NOx standard as proposed. The
vehicles' emissions are also assumed to deteriorate in a manner
consistent with baseline vehicles, and thus the same assigned
deterioration factors were used for the clean-fuel fleet vehicles
as for the baseline vehicles. However, since the end-of-useful-
life projections are different between these two types of vehicles,
the multiplicative deterioration factors will result in different
additive deterioration rates.
With a combined NMHC + NOx standard manufacturers can get the
required reductions from NMHC and NOx. Each engine family is
likely to use a different mix, but in most cases reductions in both
pollutants are expected. This analysis assumes that the end of
life NMHC level for clean-fuel engines will, be 30 percent lower in
1998 than in 1991. This is based on the NMHC reduction expected
from improved catalysts in gasoline and diesel applications. To
estimate NOx levels for 1998 clean-fuel engines, the just-
calculated 1998 NMHC level is subtracted from the NMHC+NOx standard
of 3.8 g/Bhp-hr. Zero-mile emissions are estimated by back-
calculating using the emissions projections estimated above and the
respective deterioration factors. Table 3-5 contains the projected
zero-mile in-use emission factors and deterioration rates for
heavy-duty clean-fuel fleet vehicles.
Based on the baseline and clean-fuel fleet vehicle emission
factors developed above, emission inventory estimates have been
calculated for NMHC and NOx emissions from heavy-duty fleet
vehicles. Historically, carbon monoxide emissions and particulate
emissions from diesel engines have been directly proportional to HC
emissions and inversely proportional to NOx emissions. However,
the introduction of new technologies such as catalytic converters,
rate-shaped electronically-controlled unit injectors and exhaust
gas recirculation will change the relationships between pollutant
emissions rates in ways which can not be accurately predicted.
Therefore, projections of emission inventories will be made only
for NMHC and NOx, the primary pollutants targeted by the clean-fuel
fleet requirements.
3-10
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Tabl« 3-5 1998 Heavy-Duty Clean-Fuel Fleet Vehicle Emission
Factors
Vehicle
L-H diesel
M-H diesel
L-H gasoline
M-H gasoline
Zero Mile EF
(g/Bhp-hr)
NMHC
0.29
0.21
0.14
0.24
NOx
2.85
2.94
2.97
2.82
Deterioration Rate
(g/Bhp-hr/10, OOOmi)
NMHC
0.008
0.003
0.009
0.016
NOx
0.052
0.032
0.054
0.051
The inventories of NMHC and NOx emissions from heavy-duty
clean-fuel fleet vehicles 1998 baseline vehicles have been
calculated for the years during which these standards are being
phased in and for every five years beyond ..that until the year 2020.
In general, for each vehicle subclass these per-vehicle emission
benefits were calculated by subtracting the clean-fuel fleet
vehicle emission factors from the baseline emission factors for the
respective pollutants and then multiplying the result by the
estimated vehicle miles traveled by all clean-fuel fleet vehicles
in that vehicle subclass during each year. The overall emission
benefits results from light heavy-duty and medium heavy-duty
vehicles were then combined for each year and are presented in
Table 3-6 according to engine type.
As demonstrated in Table 3-6, the emission inventories and
benefits climb rapidly during the first six years as the fleet is
turned over; after 2003, however, the emissions inventories and
benefits become relatively constant. After 2003 diesel-cycle NOx
benefits begin to decline as otto-cycle benefits increase due to
the gradual replacement of medium heavy-duty vehicles by light
heavy-duty vehicles which are mostly otto-cycle vehicles.
3-11
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Table 3-6 Nationwide Emissions Inventories of Fleets Covered by
the Clean-rFuel Fleet Program
calendar
year
1998
1999
2000
2001
2002
2003
2004
2005
2010
2015
2020
Total
NMHC Emissions Benefit
(tons per year)
Otto-
Cycle
26
60
' 101
149
204
266
265
264
261
260
261
5,251
Diesel-
Cycle
60
124
193
266
345
428
425
422
408
397
387
8,286
Total
86
184
294
415
548
693
689
686
669
657
648
13,537
NOx Emissions Benefit
(tons per year)
Otto-
Cycle ,
130
276
437
615
808
1,018
1,017
1,017
1,020
1,031
1,051
20,748
Diesel-
Cycle
255
523
803
1,095
1,399
1,715
1,703
1,690
1,633
1,583
1,542
33,260
Total
385
798
1,240
1,710
2,207
2,733
2,720
2,707
2,652
2,614
2,593
54,008
This analysis generates emission reductions based on the
assumption that the end of life NMHC level for clean-fuel engines
will be 30 percent lower than the end of life NMHC level for 1998
baseline engines and the remainder of the required reduction comes
from NOx. There are any number of potential approaches which could
be used to meet the NMHC + NOx levels of the HD CFFV standard. For
example, another possibility is that otto-cycle engine NMHC levels
increase over 1991 levels under pressure from the 4.0 g/Bhp-hr NOx
standard and diesel-cycle NMHC emissions decrease as a result of
the particulate matter control technology discussed in Chapter 2.
Thus, a different set of NMHC benefits would be expected for clean-
fuel heavy-duty engines. Assuming the NMHC + NOx split for 1991
engines the NMHC benefit for otto-cycle would increase, but for
3-12
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diesel-cycle engines the benefits would decrease. NOX benefits
would essentially be the same.
After examining the sensitivity of the emission benefit
results to the results generated from this other reasonable
assumption of emission benefits for HD CFVs, EPA has concluded that
the impact on cost effectiveness is not major. Thus, EPA will use
the emission benefit results generated from the above scenario that
assumes NMHC levels of clean-fuel engines will be 30 percent lower
than NMHC levels of 1998 conventional HDVs. Based on this
scenario, the 22-year total of emission benefits for otto-cycle
engines will be 5,300 tons of NMHC benefits and 20,700 tons of NOx
benefits. The 22-year total of emission benefits for diesel-cycle
engines will be 8,300 tons of NMHC benefits, and 33,300 tons of NOx
benefits. Combined benefits range from 13,500 tons of NMHC and
54,000 tons of NOx.
3-13
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Chapter 4
Costs and Cost Effectiveness
4.0.1 Introduction
This chapter describes EPA's analysis of the economic impact
of the Clean-Fuel Fleet program on heavy-duty vehicles. The
purpose of this analysis is to estimate the per-vehicle costs, the
total cost, and the cost effectiveness of the program. To do this,
it is necessary to make several assumptions about how manufacturers
will choose to comply with the program. The Agency recognizes that
manufacturers may deviate from the control techniques assumed here,
and that such deviations could lead to different costs.
Nevertheless, in the absence of better information, EPA believes
that these approaches are technically reasonable and that they
result in reasonably accurate estimates of the costs associated
with this program.
It should also be noted that this analysis does not assume
that all current light-heavy and medium-heavy duty vehicle engine
families will comply with the standards of this program, but rather
that only those engine families which ceroid- comply with relatively
minor changes would be produced for the clean-fuel fleet vehicle
program. This is important because costs would be significantly
higher if it- were necessary that all light-heavy and medium-heavy
duty vehicle engine families comply with the standards. However,
this is not the case, and given the small size of the affected
market, there should be a significant incentive to modify only
those engine families for which costs were _ relatively small or
demand was larger from a nationwide perspective.
4.0.2 Coata
4.0.2.1 Operating Costs
Increased operating costs can arise from three sources;
increases in fuel consumption, increases in maintenance costs and
decreases in engine life. Increased fuel consumption has
traditionally been a potential problem in engines designed to
reduce NOx emissions. This reduction in fuel economy is usually a
side effect of retarding the timing of the combustion (i.e., spark
timing in ••* otto-cycle engines or fuel injection timing in
diesel-cycl« engines). It is not clear at this time, however,
whether engine manufacturers will need or choose to sacrifice fuel
economy to reduce NOx emissions. Historically, manufacturers have
been reluctant to do so and have sought other technologies which
reduce NOx emissions without increased fuel consumption. Up to a
one percent increase in fuel consumption is possible if
manufacturers choose emission control approaches which have an
adverse effect on fuel consumption. However, based on the
4-1
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-• •^;--'-v;:~"'";-\~-^^-^^.t^'54:^":^i;">-^' •^.•r','c:^."','^i
technology being developed to meet the 4.0 g/Bhp-hr NOx standard
(see Chapter 2 of this document) , it is more likely that NMHC+NOx
emissions will be reduced through the addition of emission control
hardware without a fuel economy penalty.
Since engines for heavy-duty clean- fuel fleet vehicles are not
expected to have significantly different designs than the engines
designed to meet the 1998 heavy-duty NOx . standard, they are not
expected to be less durable or more expensive to maintain than
their general-use counterparts. Therefore, EPA does not anticipate
that heavy-duty clean- fuel engines or vehicles will be any more
expensive to operate than their contemporary general use
counterparts and therefore that all costs will be associated with
engine and emission control modifications.
4.0.2.2 Engine Costs
Engine costs consist of four elements: research and
development (R&D) costs, additional hardware requirements, added
manufacturing costs and engine certification costs. Additional
hardware and added manufacturing are variable costs included in the
price of each engine purchased. Engine certification and R&D costs
are fixed costs paid up-front by the,_engine manufacturer and
recovered through additional costs added to each engine over a
period of time. For purposes of this analysis, the certification
costs will be recovered on a yearly basis, while the R&D costs will
be amortized over a period of five years using a rate of return of
7 percent. (In contrast to the proposed regulatory support
document, the rate of return used in this analysis is 7 percent
instead of 10 percent as recommended by EPA' s Office of Policy,
Planning, and Evaluation for this type of analysis)19
4.0.2.2.1 Otto-Cycle Heavy-Duty Engines
4.0.2.2.1.1 Hardware Costs
Gasoline (otto-cycle) heavy-duty engines are not expected to
require the development of new hardware to meet the heavy-duty
clean-fuel fleet vehicle emission standard. However, as discussed
in Chapter 2, some will require improvements in the existing
hardware i Nearly all otto-cycle heavy-duty engines currently have
electronically controlled fuel injection and three-way catalytic
converters capable of both reducing NOx emissions and oxidizing HC
emissions, with oxygen sensors and feedback controls. Compliance
with the clean-fuel fleet vehicle standards, however, may require
higher catalyst loadings, which would increase catalyst costs.
Other improvements or minor modifications may or may not increase
the manufacturing costs . In order to take these potential costs
into account, engine production cost increases will be estimated at
$50 per engine. This is conservative given that current NMHC+NOx
certification levels are already close to the standard (see Table
4-2
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3-3) and the need for all heavy-duty engines to meet the 4.0
g/Bhp-hr NOx standard in 1998.
4.0.2.2.1.2 Development Costs
In order to comply with the heavy-duty clean-fuel fleet
vehicle standard, some otto-cycle heavy-duty engines will require
minor improvements to existing systems beyond those needed to
achieve compliance with the 1998 4.0 g/Bhp-hr NOx standard. It is
expected that some combination of better air/fuel handling,
improved catalytic converter technology, exhaust pipe insulation
and enhanced exhaust gas recirculation will be the main compliance
strategies. In order to make the design changes necessary, EPA
estimates that the calibrations and other development efforts will
cost approximately $30,000 per engine family."
20
4.0.2.2.1.3 Certification Costs
To certify an engine family, manufacturers must .perform
emission tests on a representative engine from that family and
submit the results to EPA; this only need occur once for each
engine family at the beginning of its production, with
certification being carried over in each, subsequent year for about
80 percent of families. Recordkeeping and reporting requirements
accompany new certification and annual recertification. EPA has
estimated that the cost of certification testing for heavy-duty
gasoline engine families is about $200,000 per family21 and the cost
for reporting and recordkeeping is about $100,000 per family
certified or recertified.22 In addition to these costs,
manufacturers must pay a certification fee of $12,500 for each
heavy-duty engine family. Thus the total certification costs for
each heavy-duty gasoline engine family are projected to be about
$312,500.
4.0.2.2.2 Diesel-Cycle Heavy-Duty Engines
4.0.2.2.2.1 Hardware Costs
Manufacturers will apply refined or improved control
technologies that will allow compliance without an increase in fuel
consumption. As was discussed in Chapter 2, it appears likely that
further optimization of the technology that will be available as a
result of the 1998 4.0 g/Bhp-hr NOx and 1994 0.10 g/Bhp-hr PM
standards will allow manufacturers to meet the clean-fuel fleet
vehicle standards for many engine families. Technologies which are
expected to be used in some conventional diesel engines to comply
with the 1998 4.0 g/Bhp-hr NOx standard include improved electronic
engine controls and exhaust gas recirculation, and some of the
other technologies discussed in Chapter 2. Particulate trap
oxidizers and catalytic oxidizing converters (to reduce PM and HC
emissions) should make a broad penetration into the heavy-duty
diesel engine market in order to facilitate compliance with the
4-3
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0.10 g/Bhp-hr PM standard. Clean-fuel diesel engines are expected
to be optimized versions of the cleanest of these conventional
engines, and may also include advanced turbocharging and catalytic
converters (for NMHC control).
By basing the clean-fuel diesel engines on only the cleanest
conventional diesel engine families, manufacturers will be able to
minimize costs. EPA estimates that the additional manufacturing
cost of the improved control system hardware for heavy-duty clean-
fuel fleet vehicle engines, which will improve emissions while
maintaining the same fuel consumption, will be about $100 dollars
per engine more than the costs associated with the cleanest 1998
baseline engines. This $100 is roughly equivalent to the lifetime
cost of a one percent increase in fuel consumption (i.e., $ 100
fuel economy penalty) for light- and medium-heavy duty diesel
vehicles. Thus, in order to avoid the fuel economy penalty,
manufacturers would likely make the necessary hardware changes at
a cost ($100) equivalent to the amount the consumer would spend in
lifetime operating costs.
4.0.2.2.2.2 Development Costs
As with otto-cycle engines, diesel-cy.cle engines are expected
to require additional development beyond that required for engines
meeting the 1998 4.0 g/Bhp-hr NOx standard. It is expected that
several additional calibrations will be required. These
calibrations will require design changes and engine modifications.
The cost of these calibrations and other development is estimated
to be about $!0a, 000 (in 1992 dollars) for each engine family.20
4.0.2.2.2.3 Certification Costs
As with otto-cycle engines, HDD engine manufacturers will
incur costs for certification of engines for clean-fuel fleet
vehicles as well as the associated reporting and recordkeeping
requirements. EPA estimates that these costs are $260, OOO23 per
family for certification testing and $78,000 per family certified
for reporting and recordkeeping. (The estimated reporting and
recordkeeping costs for diesels are less than those for otto-cycle
engines because information collection for evaporative testing does
not exist for diesels.)22 As was the case with gasoline engines,
EPA projects that about 80 percent of the families will be
recertified each year using carryover provisions and that 20
percent will engage in new certification and the accompanying
testing. The recordkeeping and reporting costs cited above apply
to each family each year as does the certification fee of $12,500.
Thus the total certification costs for each heavy-duty diesel
engine family is projected to be about $350,500.
4.0.2.3 Aggregate Costs
4-4
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As was discussed above, heavy-duty clean-fuel fleet vehicles
are not expected to have any increases in operating costs over
general heavy-duty vehicles; thus, essentially all the costs of
this program should come from increased engine/vehicle costs
Since the number of clean-fuel heavy-duty engines required to be
purchased will be relatively small, the per engine and total costs
of this portion of the Clean-Fuel Fleet program will be a strong
function of how many engine families are developed and certified
for this program. For this analysis, it is estimated that a total
of six light and medium heavy-duty otto-cycle and twelve light and
medium heavy-duty diesel-cycle engine families will be certified
for participation in the Clean-Fuel Fleet program. For comparison,
in 1991 a total of nine otto-cycle and fourteen diesel-cycle light
or medium heavy-duty engines were certified. If significantly
fewer engine families are certified, costs will be less than those
estimated here.
In addition, to be conservative this analysis has assumed that
ful-|;. certification costs will be incurred for each engine family
certified, even though most families will probably be able to be
certified based on California test data. In such cases, separate
federal testing would probably not be necessary and the
certification testing costs correspondingly lower.
4.0.2.3.1 Manufacturer Costs
Based on the development costs projected above, the total cost
?l ftnenni°PiHg *+"+ 'I"0-'?016 engine families will be approximately
$180,000; the total cost of developing twelve heavy-duty diesel-
cycle engine families will be approximately $1,200,000. Similarly,
the first-year certification costs for six otto-cycle and twelve
diesel-cycle engine families will be $1,200,000 and $3,120,000,
respectively. For subsequent years, this analysis assumes that one
otto-cycle engine family and two diesel-cycle engine families will
be recertified with emission testing required each year
^nSrSni Y ° Perce^fc> '•' certification costs would then total
$200,000 per year and $520,000 per year, respectively. Annual
reporting, recordkeeping, and certification fees for all families
amount to $675,000 for otto-cycle engines and $1,086,000 for
diesel-cycle engines. The fixed costs to manufacturers for
developing each engine family are presented in Table 4-1.
The total costs to manufacturers will consist of these fixed
costs of developing and certifying each engine family combined with
the variable costs of manufacturing the engines. Using the
projections of the number of clean-fuel fleet vehicles required to
be purchased from Table 3-1 in chapter 3, the yearly variable costs
to manufacturers from hardware and production costs can be
calculated (per vehicle production + hardware cost * number of
vehicles). These costs have been analyzed through the year 2020
(the first 22 years that the standard is in effect).
4-5
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Tabla 4-1 Manufacturer Fixed Costs for Heavy-Duty Clean-Fuel
Engines
Otto-
cycle
Diesel
—cycle
Number
of
Families
6
12
Total
Develop.
Costs ($)
180,000
1,200,000
Total
First-Year
Cert.
Costs ($)
1,200,000
3,120,000
Total
Annual
Cert.
Costs
($)
200,000
520,000
Total
Annual
Recording
Reporting
& Fees
Costs ($)
675,000
1,086,000
In order to calculate the total aggregate costs to
manufacturers, all costs are discounted-to-the first year of the
standard, 1998. Research and development costs will be assumed to
occur in the second year before the standard goes into effect
(1996). Initial costs for certifying (and fulfilling
reporting/recordkeeping requirements) for all engine families
certified as clean-fuel fleet vehicles is assumed to occur in 1997,
with full recertification occurring annually thereafter for only
one otto-cycle family and two diesel-cycle families, as described
above. The assumed chronology for the incurring of costs for
research, development, and testing (RD&T), certification and
reporting, and for the hardware costs is presented in Table 4-2.
The present value costs to manufacturers accrued during the first
22 years of the standard discounted to 1998 (in 1992 dollars) are
also presented in Table 4-2. The total present value costs to
manufacturers of the first 22 years of the program discounted to
1998 (in 1992 dollars) is approximately $19.1 million for otto-
cycle engines and approximately $37.7 million for diesel-cycle
engines (using a rate of return of 7 percent).
4-6
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Tabl« 4-2 Costs to Manufacturers
Year
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2010
2015
2020
1998 NPV
Otto-Cycle
RD&T/
Cert .
$180,000
$1,875,000
$875,000
$875,000
$875,000
$875,000
$875,000
$875,000
$875,000
$875,000
$875,000
$875,000
$875,000
Hardware
$464,900
$471,300
$477,900
$484,700
$491,800
$499,200
$506,800
$514,800
$558,700
$610,800
$672,000
19,193,200
Diesel-Cycle
RD&T/
Cert .
$1,200,000
$4,206,000
$1,606,000
$1,606,000
$1,606,000
$1,606,000
$1,606,000
$1,606,000
$1,606,000
~~ $1,606, 000
$1,606,000
$1,606,000
$1,606,000
Hardware
$1,034,200
$1,032,500
$1,031,300
$1,030,200
$1,029,500
$1,029,100
$1,029,000
$1,029,100
$1,034,900
$1,049,400
$1,073,300
37,650,400
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4.0.2.3.2 Costs to Users
Since clean-fuel heavy-duty vehicles are not expected to have
different fuel consumption or maintenance costs than general use
light and medium heavy-duty vehicles, the only cost to the consumer
will be the first cost of purchasing the vehicles. In addition to
the cost for hardware changes, consumers will also have to pay for
the amortized cost of the research, development, and testing as
well as for the retail price mark-up.
Manufacturers are expected to recover the development costs
and first-year certification costs over the first five years of
engine sales. By amortizing these costs over the predicted sales
during the first five years of the program, EPA has calculated that
the development costs and first-year certification costs of these
engine families will add an average of $60 to the manufacturer's
cost of a clean-fuel heavy-duty otto-cycle engine and $147 to the
manufacturer's cost of a clean-fuel heavy-duty diesel engine,
respectively.
Adding on the estimated additional certification, hardware and
manufacturing costs for both otto- and diesel-cycle heavy-duty
clean-fuel engines and factoring in an estimated 29 percent retail
price mark-up it is estimated that these engines will cost about
$246 more per otto-cycle engine and $477 more per diesel-cycle
engine than for engines that would be used in general heavy-duty
vehicles during the first five years of the program. During the
remaining years of the program (from year 2003 to 2020), clean-fuel
otto-cycle engines are estimated to cost an additional $147 to
$178, and clean-fuel diesel-cycle engines are estimated to cost an
additional $332 to $338 in 1992 dollars. (These additional costs
for clean-fuel engines are different from year to year due to
variations in the projected number of clean-fuel fleet vehicles
required to be purchased (see Table 3-1).)
Table 4-3 presents total consumer cost projections through the
year 2020, along with the aggregate cost, expressed in 1992 dollars
discounted to the year 1998. As the table shows, costs in the
first five years of the program are marginally higher than in
successive years because development costs are being recovered
during this period. The 22-year present value costs of the fleet
will be $24.8 million for otto-cycle engines and $48.6 million for
diesel-cycle engines. (The costs to consumers have increased since
the proposed regulatory support document due to the use of a 7
percent rate of return instead of a 10 percent rate of return.)
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Table 4-3 Costs to Consumers
Year
1998
1999
2000
2001
2002
2003
2004
2005
2010
2015
2020
1998 NPV
Otto-Cycle
$2,283,500
$2,299,300
$2,315,800
$2,332,700
$2,350,400
$1,772,700
$1,782,500
$1,792,800
$1,849,500
$1,916,700
$1,995,600
$24,759,200
Diesel-Cycle
$4,925,200
$4,920,700
$4,917,300
$4,914,200
$4,912,400
$3,399,200
$3,398,900
$3,399,300
$3,406,700
$3,425,300
$3,456,300
$48,569,100
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4.0.3 Coat gfg«ctivanafl«
The cost effectiveness of the heavy-duty portion of the Clean-
Fuel Fleet program was calculated using a 22-year cost
effectiveness method. The 22-year cost effectiveness analysis is
performed by discounting both the total consumer costs and the
total benefits of the first 22 years of the program to 1998 and
dividing the costs by the benefits. Since the costs have been
estimated separately for otto-cycle and diesel-cycle engines, their
cost effectiveness will be analyzed separately also. It should be
noted that for otto-cycle engines which have both NMH
C and NOx emissions reductions, the costs have been divided evenly
between NMHC and NOx.
The 1998 present value for the 22 years of emission reductions
are calculated from the data in Table 3-6 of chapter 3. As
discussed in Chapter 3, this analysis generates emission benefits
for clean-fuel fleet vehicles that may be overly conservative. The
22-year present value emission benefit for diesel-cycle engines is
4,000 tons of NMHC emission reductions and 16,000 tons of NOx
emission reductions. For otto-cycle engines, the 22-year present
value benefit is 2,500 tons of NMHC emission reductions and 9,700
tons of NOx emission reductions. ..
The 22-year cost effectiveness, in dollars per ton, can now be
calculated by dividing the present value costs by the present value
emission benefits. The costs of the otto-cycle and diesel-cycle
engines are divided evenly between the NMHC and NOx benefits. The
22-year cost effectiveness for otto-cycle and diesel-cycle engines
is presented in Table 4-4. The 22-year cost effectiveness for
otto-cycle engines is $5,000 per ton of NMHC emission reductions
and $1,300 per ton of NOx emissions reductions. For diesel-cycle
engines, the resulting 22-year cost effectiveness is $6,100 per ton
of NMHC emission reductions and is $1,500 per ton of NOx emission
reductions. The relatively high cost effectiveness of NMHC control
and low cost effectiveness of NOx control is a result of the cost
allocation method used. Given the nature of the standard (NMHC +
NOx) and the large number of possible ways to split controls and
control costs undue importance should not be placed on the
numerical values derived. A simple reallocation of costs or
assumed change in NMHC/NOx control fraction would change the cost
effectiveness value. Given, the depth of analyses possible at this
time any change probably would not be meaningful until further
information becomes available.
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Table 4-4 Cost Effectiveness in $/ton (1998 Present Value)
Costs ($)
NMHC (tons)
NOx (tons)
NMHC Cost
Effectiveness
($/ton)
NOx Cost
Effectiveness
($/ton)
Otto-Cycle
25 million
2,500
9,700
5,000
1,300
Diesel-Cycle
49 million
4,000
16,000
6,100
1,500
4.0.4 Summary
The total cost of the heavy-duty Clean-Fuel Fleet program to
consumers is estimated to be approximately $7.2 to $7.3 million
per year during the first five years of the program (1992
dollars), and approximately $5.2 to $5.5 million per year after
that. Estimates of the cost effectiveness of this program range
from $5,000 to $6,100 per ton for NMHC control and range from
$1,300 to $1,500 per ton for NOx control.
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