•f/
Summary and Analysis of Comments
on the
Notice of Proposed Rulemaking
for
Emission Standards and Test Procedures
for Methanol-Fueled Vehicles and Engines
tl
January 1989
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Sources
Office of Air and Radiation
U.S. Environmental Protection Agency
CTJ
HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
J
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Summary and Analysis of Comments
on the
Notice of Proposed Rulemaking
for
Emission Standards and Test Procedures
for Methanol-Fueled Vehicles and Engines
January 1989
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Sources
Office of Air and Radiation
U.S. Environmental Protection Agency
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Summary and Analysis of Comments
on the
Notice of Proposed Ruleraaking
for
Emission Standards and Test Procedures
for Methane1-Fueled Vehicles and Engines
Table of Contents
Page
I. Overview
Introduction 4
Goals of the Rulemaking 8
II. Organic Emission Standards
Basis of Organic Standards 12
Separate Health Effects Based Standards
for Methanol and Formaldehyde 37
Optional Combined Exhaust and Evaporative
Standards for Methanol Vehicle Organics 61
III. Other Emission Standards and Fuel
Equivalency Factor
Particulate and Smoke Standards 65
CO and NOx Standards 72
Crankcase Emissions 75
Emissions Averaging Programs 78
Determination of Fuel Equivalency 81
IV. Emission Test Procedures
Certification of Flexible Fuel Vehicles 85
Complexity of the Procedure for the Determination
of Organic Emissions 89
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Sampling and Analytical Procedures for the
Measurement of Methanol Emissions, Hydrocarbon
Emissions and Formaldehyde Emissions 96
Determination of Formaldehyde Background Levels... 104
Duct Connecting Vehicle Tailpipe (Engine
Exhaust) to CVS (Dilution Tunnel) 106
Vehicle Preconditioning or Evaporative
Emissions Testing 110
Lean Flammability Limit in SHED Ill
Test Fuel Specification 113
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Introduction
On April 10, 1984 EPA published an Advanced Notice of
Proposed Rulemaking (ANPRM), which announced the Agency's
intention to establish emission standards and test procedures
for methanol-fueled engines and vehicles of every currently
regulated class (51 FR 14244). A workshop was held on May 30,
1984 allowing for public interaction with the Agency on the
major issues of the rulemaking. Written comments were also
solicited and received. These comments were fully considered
by the Agency during its preparation of a Notice of Proposed
Rulemaking (NPRM), which was published August 29, 1986, and
which put forward EPA's proposed emission standards and test
procedures (51 FR 30984). Comments on specific topics as well
as general comments were solicited in the NPRM.
A public hearing was held on October
oral comments to the NPRM were received and
comments were also received from 24
publication of the rulemaking.
30, 1986 at which
recorded. Written
parties following
This document presents a staff analysis of all relevant
comments received in response to the NPRM. Where appropriate,
recommendations are made based on this analysis regarding the
format of the final rules for methanol engines and vehicles.
While the analysis serves to facilitate fulfillment of EPA's
legal requirement to consider public comment in the rulemaking
process, it also serves in several cases to update the
technical analysis presented originally in the Regulatory
Support Document (RSD) to the NPRM. The RSD is located in the
official rulemaking docket.
A list of commenters, showing date of receipt of comments
by the Central Docket Section, is provided below. Common
abbreviations for the organization names which are used
throughout this document are also listed. It is noted that
many of the comments were received subsequent to the deadline
(announced in the Federal Register notice) of November 28,
1986. Legally, EPA is not required to consider these comments
in formulating the final rules. In fact, it needs to be
cautious about considering them, because late commenters may be
able to unilaterally rebut arguments put forward by earlier
ones. All but two of the late comments were received prior to
December 17, within three weeks of the official deadline.
Given the significant number of commenters submitting in this
time period and considering the minimal period of delay in
submission, staff sees no overwhelming reason not to consider
their comments. Two of the commenters (MECA and Crowell &
Mooring for Brooklyn Union Gas Company) were, however,
significantly later in their submissions and would have had
substantially greater opportunity to analyze earlier comments
in preparing their own. It was, however, the determination of
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the authors of this document that consideration of these late
comments would not unfairly compromise the opinions of those
whose responses were more timely, nor would it materially
affect the formulation of the final rule. On this basis,
therefore, the authors have chosen to include these comments in
the present analysis and to respond to them. In considering
the recommendations put forward in this document, the Agency
need not be concerned that it is acting inappropriately in
response to late comments.*
The comments have been organized into major topic areas
which are addressed sequentially. Concerns about EPA's goals
in the present rulemaking are addressed first. Due to the
number of comments received in response to EPA's proposed
organic emission standards, and the overall importance of this
issue to the rulemaking, this topic is handled in the next set
of discussions. These are followed by sections on the other
emission standards that were proposed (carbon monoxide,
nitroaen oxides, smoke/particulate, crankcase emissions),
emissions averaging and fuel economy programs, test procedures,
certification fuel and treatment of flexible fuel vehicles.
California Air Resources Board's comments were received by
EPA in Ann Arbor on or before December 17, 1986, but the
copy sent to the docket by the Board was not received.
The Office of Mobile Sources sent another copy in March;
this explains the late date of receipt on the list of
commenters.
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List of Written Commenters
to the NPRM*
Docket
Item
Number
IV-D-1
IV-D-2
IV-D-3
IV-D-4
IV-D-5
IV-D-6
IV-D-7
IV-D-8
IV-D-9
IV-D-10
IV-D-11
IV-D-12
IV-D-L3
IV-D-14
IV-D-15
IV-D-16
IV-D-17
IV-D-18
IV-D-19
Date
Received
at Docket
11-12-86
11-19-86
11-19-86
11-26-86
11-26-86
11-26-86
11-28-86
11-28-86
11-28-86
11-28-86
11-28-86
11-28-86
11-28-86
11-28-86
12-02-86
12-03-86
12-05-86
12-05-86
12-17-86
Date
of
Document
10-29-86
11-12-86
11-14-86
11-18-86
11-21-86
11-24-86
11-26-86
11-26-86
11-26-86
--
11-25-86
11-28-86
11-25-86
11-28-86
11-25-86
11-26-86
11-26-86
11-20-86
12-10-86
Commenter
CNG Services of Pittsburgh, Inc.
Harry H. Hovey, Jr., P.E,
(N.Y. Div. of Air Resources)
American Gas Association
Caterpillar, Inc.
Fiat
Chrysler Corporation
Jenner & Block
(Engine Manufacturing Asso.)
Volkswagen of America, Inc.
Nissan Research & Devel. , Inc.
California Energy Commission
Cummins Engine Co.
Nat'l Automobile Dealers Asso.
Chevron U.S.A., Inc.
Dept. of Energy
George S. Dominguez
(Oxygenated Fuels Asso.)
General Motors
Ford
MAN Nutzfahreuge Gmbh
Mercedes-Benz Truck Co.
Abbreviation
-
_
AGA
Cat
-
-
EMA
VW
-
CEC
-
NADA
-
DOE
OFA
GM
-
MAN
_
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IV-D-20 12-17-86 12-08-86 Toyota Tech. Center, USA, Inc. Toyota
IV-D-21 12-17-86 11-26-86 Chevron
IV-D-22 01-21-87 01-08-87 Manufacturers of Emission MECA
Controls Asso.
IV-D-23 03-20-87 03-18-87 Crowell & Moring
(Brooklyn Union Gas Co.)
IV-D-24 04-14-87 11-26-86 California Air Resources * CARB
Board
Oral comments were received from Ford, Chrysler, General
Motors, and the Oxygenated Fuels Association at the public
hearing on October 30, 1986.
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Issue: Goals of the Rulemaking
EPA decided to provide emission standards for methanol
vehicles in response to public and private interest in methanol
as a future motor fuel. The purpose of the rulemaking was to
remove a potential impediment to the introduction of methanol
as a motor fuel by providing auto manufacturers with an
understanding of the regulatory requirements to which methanol
vehicles would ultimately be subjected. The Agency's
regulatory approach was to provide standards that are
comparable in stringency for petroleum-fueled and methanol
vehicles. This section of the analysis addresses any comments
received which are related generally to the stated purpose and
goals of the rulemaking.
Summary of Comments
Several of the commenters felt that EPA should be creating
standards for other alternative fuels in addition to methanol,
or they felt that methanol vehicles should be regulated to a
different degree of stringency than gasoline or diesel vehicles.
The state of New York commented that there is "a
substantial research effort being conducted world-wide to
produce mixed alcohols from synthesis gas." Such a mixture
might contain 50 percent methanol and 50 percent higher
alcohols such as ethanol, isopropanol, and tert-butanol, and be
economical to produce, while maintaining acceptable performance
in combustion processes. New York argued that oxygenated fuels
will cause emissions to vary from those resulting from gasoline
fuel in a manner related to total oxygen content. This is
because of two factors. Incremental additions of oxygen serve
1) to lean out the combustion process incrementally, and 2) to
increase the quantity of oxygenated species in the emissions.
New York therefore felt that the current regulations should be
broadened to include all oxygenated fuels by setting standards
that vary with oxygen content; this would eliminate any future
need to create separate regulations for each new oxygenated
fuel that might make its way to market.
CNG Services of Pittsburgh felt that EPA should recognize
natural gas' potential as a clean burning, economically viable
alternative to gasoline and set emission standards for natural
gas-fueled vehicles as well as methanol vehicles.
General Motors (GM) felt EPA's proposed standards and test
procedures constituted "rigid and complex regulation." GM
suggested society might be willing to accept higher emissions
from methanol vehicles than existing vehicles in order to
encourage their introduction on an economically competitive
basis with existing technology. They also recommended that
manufacturers be allowed to self-certify their methanol
vehicles to avoid formal and costly EPA certification. Any
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differences in the stringency of requirements for methanol
vehicles and existing vehicles could be reconsidered after the
new technology had gained a foothold in the market.
Volkswagen and Chrysler expressed the concern that there
is potential for much optimization in methanol technology and
that the current rulemaking should not inhibit progress through
overly restrictive requirements.
Despite generally agreeing with EPA's proposals, both the
Department of Energy (DOE) and the Oxygenated Fuels Association
(OFA) wished EPA to set standards on an interim basis, to be
revisited after several years. DOE noted that the proposed
standards will reguire essentially the same technology as is
used on current gasoline vehicles and "do not appear to impose
any undue economic burden on potential methane1 vehicle
manufacturers relative to gasoline vehicle manufacturers." DOE
felt, however, that it is too early to determine that the
proposed standards represent the maximum control stringency
applicable as identified by the Clean Air Act and as achievable
using existing or anticipated technology. Interim standards
would allow a phase in of maximum control and encourage
continued development of methanol engine technology.
Other commenters, such as Chevron, NADA, and MECA, agreed
with EPA's position that final rules, comparable in stringency
to those currently existent should be established. MECA felt
that standards of comparable stringency to gasoline vehicle
standards should be technologically feasible and not create a
disincentive to the development of methanol-fueled vehicles.
MSCA argued (similarly to DOE) that if in future it is
determined that more stringent standards can be achieved with
methanol vehicles in a cost effective manner, they should be
established.
Analysis of Comments
With regard to the inclusion of other alternative fuels,
such as higher alcohols and natural gas, in the present
rulemaking, staff notes that the express purpose of this
rulemaking, as first stated in the ANPRM, has always been to
establish standards specific to methanol. The rulemaking was
initiated in response to congressional, executive, and private
sector interest in methanol because of its environmental
benefits, its engine performance advantages, and its relative
production economics and energy policy implications. Such
broad based interest in other fuels has not been demonstrated
to date. If, however, such interest develops, the Agency could
consider setting standards for these fuels as well. The
analyses developed in connection with the present rulemaking
are specific to methanol, and it is appropriate that the
rulemaking go forward with its focus on that fuel alone. It is
noted that if the Agency did wish to expand the scope of this
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rule, specific proposals would first have to be issued for
comment. Thus it would not be possible for EPA to finalize any
approach today that was substantively different than that which
was proposed. Finalizing the rules with their present scope,
however, does not prevent the Agency from acting in the future
to address other fuels with specific proposals.
It is noted that the standards being finalized with this
action essentially include methanol vehicles under the same
framework of standards that already exist for current
Otto-cycle and diesel vehicles, and the Agency could adopt the
same approach in regulating other alternative fuels (taking
into account factors unique to them as appropriate). Such
evenhanded treatment of alternative fuels would provide
equitable environmental protection. It would also expedite the
process of including other alternative fuels under the
regulatory umbrella, since it will not necessarily require
returning to square one to derive appropriate standards. Thus
while the present rulemaking does not address fuels other than
methanol, it does lay the groundwork for an expedited approach
to addressing them as it becomes apparent that a lack of
standards is hindering their ability to enter the market.
The concerns of various commenters that EPA should not
establish regulations which might be too stringent and hinder
the development or sale of methanol vehicles are noted.
Methanol offers many potential benefits to society, as GM
points out, and the Agency has a strong interest in recognizing
these benefits wherever possible under the law. By the same
token, the Agency is bound to treat methanol vehicles equitably
with existing technologies. EPA's goal in this rulemaking has
been to apply standards of comparable stringency and
environmental benefit to methanol vehicles as currently exist
for other technologies. This philosophy is especially
warranted if, as DOE and, by inference, MECA point out and as
other discussions in this document will show more conclusively,
similar control technology (in cost and complexity) can be
utilized with methanol vehicles as with gasoline-fueled or
diesel vehicles. Thus, the feasibility and relative cost of
the standards are not at issue, and there is no basis for
setting relaxed requirements for methanol vehicles. The
proposed standards do not represent disincentives to produce
methanol vehicles, as GM suggests, but merely equitable
application of existing environmental protection to a new
technology. Furthermore, by providing final, as opposed to
interim, standards of comparable stringency to those already
existent, EPA will eliminate uncertainty over further potential
restrictions. Manufacturers can clearly estimate, under this
approach, the regulatory burden to be placed on methanol
vehicles and plan their development programs accordingly. This
argument is not intended to suggest that once a final standard
is established, EPA may not revisit it later. The Agency may
revisit any standard not specifically determined by law.
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Setting interim standards would, however, require a
revisitation, and for EPA to leave the final standards open in
this manner would result in uncertainty that could of itself
affect manufacturers' willingness to develop methanol vehicle
technology.
Conclusions
With regard to the question of including other fuels in
this rulemaking, staff believes that EPA's initial focus on
methanol was a proper response to the interests of both the
public and private sectors. It is therefore recommended that
this rulemaking continue to be oriented towards methanol
exclusively. Staff does suggest, however, that EPA continue to
monitor the potential of other fuel alternatives and take
regulatory action in their regard as may be appropriate in the
future.
The Agency's initial goal of providing final standards
that are comparable to those currently applicable to
gasoline-fueled and diesel technology has several advantages.
First, it treats methanol vehicles on an equal basis with
alternative technologies, allowing the market to operate more
efficiently. Second, it removes uncertainty from the minds of
key decision makers in the automotive industry. Given the
state of development of methanol engine technology and its
similarity in terms of emission control technology and cost to
gasoline-fueled and diesel engine technology, staff sees no
reason to either promulgate less stringent standards for
methanol engines or to promulgate interim standards that need
to be revisited after a period of time. Staff, therefore,
recommends that EPA maintain its previously stated philosophy
of providing final emission standards of comparable stringency
for petroleum-fueled and methanol-fueled vehicles.
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Issue: Basis of Organic Standards
Summary of the Issue
EPA proposed organic emission standards that would limit
the amount of carbon allowed to be emitted from methanol
vehicles (in the form of methanol, formaldehyde and
non-oxygenated hydrocarbon*) to that allowed from current
vehicles under their applicable HC standards. Based on the
results of computer modeling and the known scientific link
between the photochemical oxidation of carbon and ozone levels,
EPA concluded that these standards would be sufficient to
protect against increases in ambient ozone. The NPRM also
discussed the relative merits of proposing standards, based
upon photochemical modeling, that would ideally result in
equivalent ozone producing potential from methanol and gasoline
vehicles. The Agency recognized two major problems with this
latter approach. First, there existed significant uncertainty
regarding how best to translate modeling results into
meaningful standards. Second, EPA was uncertain as to whether
photochemical modeling-based standards, which appeared to be
less stringent based on a single modeling study of Los Angeles,
would provide any real cost advantage to the manufacturer of
methanol vehicles. EPA specifically requested comments in both
of these areas and stated that "should public comment ... or
further scientific inquiry establish a much superior cost
effectiveness and demonstrate an acceptable environmental risk,
EPA would consider performing further photochemical modeling in
order to promulgate such standards in the final rule." The
major issue related to this discussion is therefore whether
further consideration of photochemical modeling-based standards
is necessary. Another issue is whether it is appropriate to
regulate the organics under one combined standard, as proposed,
or whether there is a need for a separate formaldehyde standard
to prevent increases in ozone.
Summary of the Comments
Most commenters found EPA's proposed carbon-based
standards acceptable. Many stated that there is currently not
sufficient modeling data to support standards based on
photochemical modeling. The California Air Resources Board
(CARS) supported the carbon standards not only because it
believed them to be more scientifically reasonable, but also
* Technically, hydrocarbons are compounds containing only
hydrogen and carbon and by definition such compounds are
non-oxygenated. The term non-oxygenated hydrocarbon is used
here to distinguish the traditional hydrocarbon emissions of
petroleum-fueled vehicles from the organic emissions of
methanol-fueled vehicles. Hereafter, the term hydrocarbon
will be used.
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because it believed them to be more stringent than
photochemical modeling standards. As a result such standards
would do more to ensure that methanol vehicles would be
environmentally favorable.
Those who felt that there is currently insufficient
photochemical modeling available to provide a basis for
standards include GARB, Chevron, Chrysler, GM, Toyota, and the
Department of Energy. Three main concerns were raised by the
commenters in this regard. First, it was noted that modeling
to date has been simplified box or trajectory modeling, which
is less accurate than airshed modeling. Second, there were
concerns that the available data are all for single-day
modeling, which does not provide information on the effect of
methanol on multi-day episodes. General Motors explained that:
"Since methanol reacts very slowly, its total effect on
air quality cannot be seen accurately in single-day
situations."
Finally, Chevron noted that the photochemical modeling based
standards discussed in the NPRM were based on a single
city-specific study. Variations in local meteorology, ambient
conditions, and HC to NOx ratios could cause substantial
variations between any two given cities. In addition, GARB
suggested that there could be substantial variations from day
to day, even within a single city. They stated:
"Since the equivalence of methanol and formaldehyde
reactivities to hydrocarbon reactivity depends on
atmospheric and meteorological parameters which vary
continuously, any factor that would convert formaldehyde
and methanol reactivities into equivalent hydrocarbon
reactivity would be unreliable."
This statement indicates a lack of confidence not only in
the currently available data base, but also in the concept of
using photochemical modeling as the basis of setting emission
standards.
In addition to the issues of environmental impacts, there
are also economic issues. DOE stated:
"The proposed [carbon-based] methanol vehicle emission
standards do not appear to impose any undue, economic
burden on potential methanol vehicle manufacturers
relative to gasoline vehicle manufacturers."
Similarly, MECA stated that the proposed standards "should
be technologically feasible and should not create a
disincentive to the development of methanol-fueled vehicles."
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Ford, GM, and Caterpillar, who felt that EPA should more
strongly consider the possibility of photochemical modeling
based standards, felt that such standards would be less
stringent and therefore less expensive than the carbon-based
alternative. Although, GM noted that they were unable to
estimate the economic benefits of this approach. The only real
data provided in this regard came from Ford; data for 17
methanol vehicles showed that only 65 percent of prototype
vehicles could meet the proposed exhaust standards, while 82
percent could meet the photochemical modeling-based standards
which were discussed in the NPRM. They did not provide any
data on evaporative emissions but did agree that the
carbon-based evaporative standards would be feasible.
Caterpillar stated that they expect organic emissions from the
heavy-duty methanol engine that they are currently developing
will exceed the carbon-based standards by at least a factor of
two. However, no commenter was able to provide data which
would enable a quantitative estimate of the dollar value of any
decreased stringency of photochemical modeling-based standards.
Ford emphasized that all of its data was from vehicles
with fairly low mileage, and thus did not resolve issues of
durability. They did qualify this claim by stating in their
oral testimony that they had "not had the benefit of the full
development capability of the Ford Motor Company" in the design
of their methanol prototypes.
With respect to such concerns about feasibility and
durability, MECA stated:
"we expect fully optimized systems with excellent
durability will be available and that the standards
proposed by EPA will be achievable over the applicable
useful life of the various vehicles covered."
In order to compensate for the fact that there may not be
enough modeling information to promulgate photochemistry-based
standards, Chrysler suggested that the carbon-based standards
could be adjusted to make them equivalent in stringency to
photochemistry-based standards. As an alternative. General
Motors suggested that multi-day airshed modeling of six cities
(Los Angeles, Philadelphia, St. Louis, Denver, Washington DC
and Houston) or regional modeling would provide sufficient
basis to promulgate standards based on photochemistry.
Ford, who presented the results of their own modeling
study of 20 cities, was the only commenter to state that there
is already enough modeling data to promulgate final
photochemistry-based standards. Their analysis showed methanol
to be 38 percent as reactive as hydrocarbons, and formaldehyde
to be 4.8 times as reactive.
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Several commenters (AGA, Brooklyn Union Gas, GARB and
Chevron) were concerned about the photoreactivity of
formaldehyde. They felt that a separate formaldehyde standard
would be necessary to prevent increased ozone formation. AGA
argued that formaldehyde is different from other organic
emissions. They stated that "formaldehyde is photosensitive
and, in sunlight, reacts in such a way that it becomes a key
component of smog."
Both GARB and Chevron cited the study by the University of
California, Riverside, which indicated that the formaldehyde
content of emissions from methanol-fueled vehicles must be less
than 10 percent of the organic emissions to prevent an increase
in ozone. CARB suggested numerical standards that would limit
the amount of formaldehyde emitted to that of current gasoline
and diesel vehicles. CARB also listed the toxicity and
carcinogenicity of formaldehyde (discussed in a later section)
as reasons for these standards. These standards are shown in
Table 1. They stated, "based on favorable input from (two)
manufacturers and CARB data, CARB believes that a 15 fug/mi
formaldehyde emission standard for certification is feasible by
1990."
Nissan warned, however, that:
"If a separate formaldehyde standard is established using
formaldehyde emissions data from gasoline fueled vehicles,
Nissan anticipates difficulties complying with the
standard using currently available technology."
CEC felt that while these standards might not be feasible at
this time, they should be imposed as soon as possible.
EMA, however, felt that, in the absence of adequate ozone
modeling, it would be inappropriate to promulgate a separate
formaldehyde standard based upon photochemical reactivity
concerns.
Brooklyn Union Gas felt that it is not sufficient to
assess the ozone impacts of formaldehyde using data from
prototype vehicles, which, they stated, "cannot be reliably
translated into in-use performance."
Analysis of Comments
Based on an analysis performed for the NPRM it was
concluded that the carbon-based standards will be sufficient to
prevent any increases in urban ozone levels. This analysis was
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Table l
CARB's Recommended Formaldehyde Emission Standards
Vehicle
Passenger Cars
LDT, MDV 0-3999 Ibs.*
LDT, MDV 4000-5999 Ibs
MDV 6000-8500 Ibs.
Heavy-Duty Engines
& Vehicles
Cert. Standard
(1990 and later)
15 mg/mi
18 mg/mi
22 mg/mi
0.05 g/BHP-hr
In-Use Compliance
23 mg/mi (1990-1993)
15 mg/mi (1994 and later)
27 mg/mi (1990-1993)
18 mg/mi (1994 and later)
33 mg/mi (1990-1993)
22 mg/mi (1994 and later)
0.1 g/BHP-hr (1990-1993)
0.05 g/BHP-hr (1994 and
(later)
Equivalent inertia weight.
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repeated using more recent emissions data (see [1]), as well as
newly available photochemical modeling data (discussed below).
The results (Table 2) indicate that methanol vehicle emissions
under the carbon-based standards will have between 54 and 95
percent of the ozone forming potential of gasoline vehicle
emissions, depending on the city and study. The fact that many
additional cities have now been modeled (which means a range of
conditions were modeled) offers some additional assurance that
EPA's earlier conclusion was fairly accurate and that these
standards can be expected to be sufficient to generally prevent
ozone increases. No commenter disagreed with EPA's earlier
finding in this regard.
It should be noted that estimation of the emissions from
gasoline vehicles represents emissions of 1990 and later
vehicles at 50,000 miles and is based on the assumption that
the problems of misfueling (using leaded gasoline in a catalyst
venicle) and excess volatility are corrected. This approach is
reasonable for two reasons. First, it results in a much more
conservative estimate of the relative ozone forming potential
of methanol vehicles than would assuming that these problems
are not corrected for gasoline vehicles. (Estimates of the
ozone forming potential of methanol vehicles would be about 20
percent lower than those in Table 2 if it were assumed that
these problems were not corrected.)
Second, it would not be appropriate to base the analysis
on actual current gasoline vehicle emissions which include
emissions due to misfueling and excess volatility when these
problems may very well be eliminated in the future, and
possibly even before methanol vehicles achieve a significant
market penetration. The incidence of misfueling has been
declining in recent years, and it is not unreasonable to assume
that this trend will continue as the availability of leaded
gasoline declines in response to lower numbers of non-catalyst
vehicles in the fleet. EPA's more stringent controls on
addition of lead to fuel may also reduce the incidence and
severity of the problem. Therefore, it is appropriate to
assume that by time methanol vehicles represent a large
fraction of the market, misfueling will be only a minor problem
at worst. It is also reasonable to assume, conservatively,
that the problem of excess gasoline volatility will be
addressed in a similar time frame. On August 19, 1987, the
Agency proposed limiting the volatility of in-use fuels to more
closely match that of the certification fuel. This action
would do much to eliminate the problem of excess volatility.
Assuming that both of these problems that currently affect
gasoline vehicle emissions are eliminated is consistent with
the approach taken in EPA's earlier analysis as presented in
the Regulatory Support Document for the NPRM.
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Table 2
Relative Ozone Potential of Methanol Vehicles
Certified to Carbon Based Standards
Relative to Gasoline Vehicles
City
Los Angeles
Philadelphia
Allentown
Atlanta
Baltimore
Boston
Chicago
Cincinnati
Dallas
Detroit
El Paso
Fort Worth
Houston
MiIwaukee
Nashville
Philadelphia
Phoenix
Pittsburgh
Scranton
St. Louis
Washington, D.C.
Youngstown
Relative Ozone
0.54
0.89
0.80
0.80
0.88
0.76
0.80
0.95
0.93
0.81
0.94
0.90
0.95
0.86
0.88
0.86
0.87
0.79
0.83
0.77
0.86
0.93
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It was also concluded in the earlier analysis that the
proposed carbon-based standards would be feasible, using
technology similar to that used for current gasoline vehicles.
Ford and Caterpillar argued otherwise, but their arguments are
not convincing. They did not demonstrate that there would be
any significant hardware burden associated with the carbon
standards. To date there has not been extensive development
work done on emissions from methanol vehicles. Ford's
testimony makes this clear. In Ford's case the only emissions
goal was to meet the current gasoline standards. Caterpillar's
development goals were not stated. Prototype methanol vehicle
emission control systems are not generally optimized with
respect to a set of design standards specific to methanol
engine technology. Based on the data that is available
(including that submitted by Ford, as will be discussed later
in this section), it is still expected that the carbon-based
standards will be feasible, and as DOE stated, will not "impose
any undue burden on potential methanol vehicle manufacturers."
This is further supported by MECA's comments.
Thus, the available information continues to suggest that
carbon based standards are adequate both to protect against
increases in ozone and to be technologically feasible at costs
similar to today's standards.
In order to appropriately decide, however, whether to
recommend promulgation of such standards or to recommend
continued consideration of photochemical modeling-based
standards, staff decided to consider the comments in the light
of these three relevant questions:
(1) is there a sufficient modeling basis for
promulgating photochemical standards?
(2) Would the environmental impacts of these standards
be acceptable?
(3) Would there be a significant cost savings with
standards based on modeling?
Before assessing the adequacy of the available modeling
base, it would be useful to briefly review photochemical
modeling and how EPA suggested it would use it as a basis for
standards.
The usual approach to modeling assumes that air parcels
can be viewed as completely mixed boxes (or cells) of air, with
emissions of pollutants from ground level, dilution by the
aloft layer, and, in some models, exchange between the
different cells of air. There are two basic types of models:
airshed and trajectory. Airshed models use a large number of
cells to cover an entire area, and usually have two or three
vertical layers in each cell. These cells do not move, but air
is moved from cell to cell based on meteorological data. In
trajectory modeling, a single cell (or several cells stacked
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vertically) moves across the modeled area. Often the path
followed is determined from a previous airshed run; however, in
some cases it is simply assumed. Chemical reactions are
modeled by a chemical mechanism, which is a system of rate
equations. By modeling the mass transfer and chemical kinetics
simultaneously, the model is able to predict concentrations of
various pollutants inside an air parcel as a function of time.
The inputs to these models include meteorology, emissions
(amount and speciation), and initial and boundary conditions.
The outputs can be concentration profiles for various
compounds, but usually just the maximum hourly ozone
concentration is reported. Results for a set of emission
scenarios, defined by the amount and chemical composition of
the emissions used as input to the model, are typically
included in a photochemistry study, along with appropriate
sensitivity runs to vary background and initial conditions.
EPA has found it useful, when using photochemical models
to evaluate the impact of methanol fuel use on ambient ozone
levels, to divide mobile source organic emissions into three
groups: hydrocarbons, methanol, and formaldehyde. By assuming
that peak hourly ozone levels for the modeled area are linear
functions of each of these groups of emissions, the Agency
developed a simple model which can predict changes in the
maximum ozone levels from changes in emissions. This
assumption of linearity simply means that the reduction in
maximum ozone level is proportional to the reductions in the
emissions of each group, weighted by its relative reactivity.
In EPA's model, the relative reactivity for a group of
emissions is defined as the peak hourly ozone produced by those
emissions divided by the peak hourly ozone produced by the same
amount of mobile source hydrocarbon emissions. For example, a
relative reactivity of 0.50 would mean that emissions of a
certain type (e.g., methanol) would produce only 50 percent as
much ozone as the same amount (in carbon) of mobile source
hydrocarbons.
In order to calculate the relative reactivities for
methanol and formaldehyde it is necessary to have modeling
results for at least four different emissions scenarios. Of
these one must be a base case (i.e., current emissions), one
must be a blank case (i.e., mobile source hydrocarbons
removed), and the other two must include some combination of
methanol and formaldehyde emissions. The peak ozone produced
by mobile source hydrocarbons can be found by subtracting the
maximum ozone concentration of the blank case from the maximum
concentration of the base case. The blank case concentration
is also subtracted from the other cases, and the peak ozone
produced by the methanol and formaldehyde is found
algebraically. This type of model was developed in Appendix A
of the Regulatory Support Document, where it was shown to
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accurately predict ozone levels for various substitution
scenarios for Los Angeles, as modeled by SAI.
Many of the cormnenters agreed that the single study used
to develop the example of a photochemical modeling-based
standard for the NPRM was not a sufficient basis for
promulgating final standards. To date there have been only a
limited number of studies involving photochemical modeling of
methanoi substitutions. Of these, EPA finds that only three
are appropriate for purposes of developing standards; they are:
(1) SAI's study of Los Angeles for ARCO, February 1983[2]
(2) SAI's study of Philadelphia for EPA, March 1986[3]
(3) Ford's study of 20 non-Californian cities 1985[4]
The first study was considered in the NPRM, but the other
two have become available more recently. These studies all
included runs for the base case, no mobile sources, and at
least two combinations of methanoi and formaldehyde emissions,
A study of Los Angeles by Jet Propulsion Laboratory! 5] was not
used because it did not have a "no mobile sources" case.
The three studies that were appropriate for EPA's current
purpose have some similarities. For example, the two SAI
studies both included some airshed modeling, and all three
studies used some form of the Ozone Isopleth Plotting with
Optional Mechanisms (OZIPM) model which incorporated a modified
version of the Carbon-Bond Mechanism for kinetics.[6] The
OZIPM is a single-cell trajectory type model. As was mentioned
previously, this type of modeling only provides the ozone
values for one air parcel, while airshed modeling predicts
values for the entire modeled domain. The Carbon-Bond
Mechanism simulates chemical kinetics using reactions between
types of chemical bonds, and not between explicit compounds.
This is done to limit the number of rate equations in the
mechanism.
The SAI study of Los Angeles modeled a 24-hour period of
June 26th and 27th, 1974, The study included a base case run
of the entire airshed that was validated against monitor data.
This run was used to identify the trajectory of the air parcel
which had the maximum one-hour ozone concentration. Additional
scenarios were run for this trajectory only, since it is much
less expensive to model a trajectory than it is to model an
entire airshed. Considerable effort was put into developing
the input for this study, including the base case emissions,
which were projected to 1987. Scenarios with replacement of
emissions from gasoline vehicles by various amounts of methanoi
and formaldehyde were investigated by SAI. Selected results of
this modeling are shown in Table 3.
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Table 3
Selected Results of SAI Study of Los Angeles
Scenario*
Base Case
Mobile Sources Replaced with
100% Methanol**
Mobile Sources Replaced with
80% Methanol & 10% Formaldehyde
Mobile Sources Replaced with
80% Methanol & 20% Formaldehyde
Mobile Sources Replaced with
180% Methanol & 20% Formaldehyde
Mobile Sources Replaced with
135% Methanol & 15% Formaldehyde
No Mobile Sources
Maximum 1-hour
0.273
0.188
0.213
0.237
0.273
0.263
0. 186
* All scenarios use base case NOx emissions.
** All percentages are with respect to moles of carbon,
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The SAI study of Philadelphia was similar to its study of
Los Angeles. In this study SAI modeled a 16-hour period of
July 13, 1979 with emissions projected to the year 2000. The
airshed modeling was used in a similar fashion as in the LA
study to identify the trajectory of the peak ozone parcel.
Trajectory modeling was then used to identify the effect of
various methanol substitution scenarios on peak ozone
concentrations in this parcel. EPA later performed additional
trajectory simulations, extending the modeling period to 19
hours.[7] Two of these additional runs were duplications of
the "base case" and "zero mobile source hydrocarbon case" runs
performed by SAI. The "base case" duplication after 16 hours
showed good agreement with SAI's results (0.202 ppm of ozone
versus SAI's 0.204 ppm), but the "zero mobile source
hydrocarbons case" did not (0.171 ppm versus SAI's 0.156 ppm).
Discussions with SAI have failed to resolve this discrepancy.
Additionally, in each simulation performed by EPA the ozone
concentration in the parcel was still increasing after 16
hours, and reached its maximum between 16 and 19 hours. For
these reasons, only the results of EPA's simulations are used
here. These results are shown in Table 4.
Ford's study modeled ozone exceedances in 20
non-attainment cities outside of California using the City
Specific EKMA Model. This approach does not use an airshed
model to generate trajectories; instead simplified trajectories
are assumed. This assumption precludes the use of information
about the actual trajectory, such as the velocity, whether it
passes over any distinct sources which may or may not be
affected by methanol substitution, and whether the air parcel
undergoes significant local stagnation. Emissions data for
this study were obtained primarily from state SIPs, but default
values were used to speciate organic emissions. Some cities,
however, may have organic emissions which are different from
default emissions (perhaps due to a particular industry's local
predominance). The model's assumptions do not allow situations
such as this to be addressed. These two assumptions could have
a significant effect on the accuracy of the study and thus, the
results must be used with some caution. That is, for any given
city in the study, the results might not be representative of
what would typically or, for that matter, ever happen in use in
that city.
In each of the cities four scenarios were modeled:
(1) Base case.
(2) All LDV hydrocarbons replaced with methanol on a
one-to-one carbon basis.
(3) All LDV hydrocarbons replaced with a 90 percent
methanol, ten percent formaldehyde mixture on a
one-to-one carbon basis.
(4) Blank case; where all LDV hydrocarbons are removed.
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-24-
Table 4
Selected Results of SAI's jStudy of Philadelphia
Scenario*
Base Case
Mobile Sources Replaced with 15% Methanol**
Mobile Sources Replaced with 25% Methanol
Mobile Sources Replaced with 50% Methanol
Mobile Sources Replaced with 75% Methanol
Mobile Sources Replaced with 1% Formaldehyde
Mobile Sources Replaced with 5% Formaldehyde
Mobile Sources Replaced with 10% Formaldehyde 0.2126
Maximum 1-hour O^Cppm)
0.2267
0.1951
0.1965
0,1999
0.2033
0.1951
0.2032
* All scenarios use base case NOx emissions.
** All percentages are with respect to moles of carbon.
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The results are show in Table 5.
As stated before, if one assumes that ozone production is
a linear function of emissions, then one can use these modeling
results to create a linear model for ozone formation, as was
done previously with the results of SAI' s study of Los
Angeles. This approach was found to accurately predict ozone
levels for a few other scenarios in the Los Anaeles study. It
is now shown to also work very well with the Philadelphia
study. Unfortunately, it was not possible to test the
appropriateness of the linear approach using the data from the
Ford study, since results were presented for only enough cases
to allow calculation of the relative reactivities. EPA's
calculated reactivities, from these three studies, are shown in
Table 6.
Ford used an alternate method to translate their modeling
results into reactivities. While EPA calculated reactivities
for each city, Ford chose to combine all 20 of the maximum
ozone concentrations for each of the four scenarios, to obtain
an average maximum ozone concentration for each scenario. They
then calculated a single reactivity for methanol and a single
reactivity for formaldehyde based on these average ozone
results. The Agency felt that this approach was not the most
appropriate, however, since ozone values for different cities
are not necessarily similar, and thus average ozone values for
each scenario lack practical significance. It seems more
reasonable to calculate reactivities for each city
individually, and to compare these reactivities, as EPA has
done. Admittedly, EPA's approach does not produce dramatically
different results, on the average across all 20 cities, than
Ford's in this case, but could do so given a different modeling
base. EPA's approach does allow the relative reactivities of
methanol and formaldehyde in different cities to be compared to
one another, whereas Ford's approach does not.
As several commenters noted, there are significant
limitations to the modeling described by EPA in the NPRM. Even
given the additional modeling described here, there is still
concern about the sufficiency of the available data. For
example, while Ford's study does address the question of
city-to-city variations, it does not do so conclusively. In
order to adequately account for such variations, modeling of
all (or many more) ozone non-attainment cities would be
necessary before a standard could be set. Additionally, there
is uncertainty in the assumptions regarding emissions and
trajectory data, as discussed previously. Modeling using more
detailed input data could change the reactivity factors
developed for each modeled city. Finally, Ford did not perform
its modeling with EPA's linear ozone model in mind, and thus
did not run enough emission scenarios to allow the linear
assumption to be tested in each city.
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Table 5
Peak Hourly Ozone Concentrations*
Reported in Ford's Modeling Study
City
Allentown
Atlanta
Baltimore
Boston
Chicago
Cincinnati
Dallas
Detroit
El Paso
Ft. Worth
Houston
Milwaukee
Nashville
Philadelphia
Phoenix
Pittsburgh
Scranton
St. Louis
Washington, D.C.
Youngstown
100% Methanol 90% Methanol
Base Case
0.162
0.145
0.173
0.211
0.148
0.141
0.202
0.143
0.139
0.204
0.281
0.126
0.126
0.232
0.159
0.147
0.144
0.200
0.177
0.122
Replacement
0.136
0.135
0.166
0.135
0.128
0.139
0.188
0.111
0.132
0.183
0 .272
0.120
0.101
0.213
0.148
0.098
0.119
0.149
0.157
0.120
10% Formaldehyde
0.153
0.141
0.171
0,184
0.142
0.141
0.201
0.132
0.139
0.203
0.281
0.124
0.119
0.227
0.157
0.133
0.137
0.185
0 . 172
0.122
No Mobile
Sources
0.122
0.129
0.158
0.112
0.119
0.136
0.170
0.092
0.123
0.168
0.257
0.114
0.075
0.198
0. 140
0.081
0.104
0.135
0.141
0.118
All concentrations in ppm.
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The other concerns mentioned by the commenters also remain
valid. The concern about the reliability of trajectory
modeling is justified, since such modeling gives only the peak
concentration in the modeled air parcel, and not the peak for
an entire area as airshed modeling would. Since the peak
parcel is identified using only the base case airshed run, it
is possible, perhaps even likely, that the modeled parcel is
not the peak parcel for all of the emissions scenarios,
especially those that are very different from the base case
(e.g., 100 percent methanol substitution). Also, airshed
modeling is more sophisticated than trajectory or box modeling,
and thus if performed properly can be more accurate.
The concern about the effects of methanol emissions in
multi-day episodes is also justified. As GM noted, methanol
reacts slowly and thus could possibly accumulate in the
atmosphere or be transported downwind. If methanol accumulates
to a high enough concentration its effect on ozone could
increase in significance. Also, transported methanol could
lead to increased ozone levels downwind. The extent of these
multi-day effects cannot be reasonably predicted from the
single-day modeling that is currently available.
CARB's comment that day-to-day variations in atmospheric
and meteorological parameters could make it difficult to
reliably characterize the relative reactivities of methanol and
formaldehyde, even in a given city, is also relevant. Staff
does recognize the need for caution, because of concerns such
as this, when considering the results of a limited set of
modeling runs.
Given the limitations in the existing data base, as
discussed above, staff concludes that an insufficient amount of
modeling has been performed to justify the elaborate analytic
manipulations that would be necessary to promulgate meaningful
standards based directly on empirical photochemistry
relationships. Standards based on the existing modeling data
would have to be developed using a conservative methodology, as
will be discussed below.
Some of these limitations could be addressed by further
modeling, as noted by General Motors. In fact, Carnegie Mellon
University is currently performing multi-day airshed modeling
of Los Angeles, under contract for the California Air Resources
Board; however, it is doubtful that the results will be
applicable to other cities, because of the unique meteorology
of the South Coast Air Basin. The basin is bounded by the
ocean to the west and mountains to the east, and thus it
experiences a great number of severe stagnations, which is not
representative of meteorology in most non-attainment areas. A
sufficient amount of multi-day modeling studies, even for just
six cities as GM suggested, could take years to complete.
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Even if EPA were confident that enough modeling data were
available to address all of these concerns, or if a method
could be developed by which uncertainty in the modeling data
base could be accounted for (e.g., the use of a safety factor),
there would still be other issues related to how to set
standards based on photochemical modeling.
Since the NPRM was published and additional modeling data
made available, EPA has examined several examples of how
photochemical modeling could be used to set standards. Each of
these takes a different approach to choosing the relative
reactivities for methanol and formaldehyde for use in the
mathematical expression of the standard. (In the NPRM,
reactivities based only on Los Angeles modeling were used by
way of example.) These could be average values for the
reactivities of methanol and formaldehyde for several cities,
reactivities for a single worst case city, or worst case
reactivities for each pollutant (regardless of city). These
three approaches are discussed below. In addition, the
question of whether it would be necessary to include a margin
of safety, due to the uncertainty concerning photochemical
modeling, is considered.
Average values for the 22 relative reactivities in Table 6
(which includes data for each of the three relevant studies
discussed previously) are 0.41 for methanol and 4.76 for
formaldehyde. These numbers could be used to set standards
simply by replacing the numbers used to weight emissions in the
photochemical modeling-based standards discussed in the NPRM
(0.02 and 2.95 for methanol and formaldehyde respectively). A
major problem with this approach, however, is that it would
probably result in methanol vehicles in some cities producing
more ozone than the gasoline vehicles which they replace. An
example of this can be seen by assuming that exhaust emissions
are 37 percent hydrocarbons, 58 percent methanol, and five
percent formaldehyde and that evaporative emissions are 47
percent hydrocarbons (all percentages are on a carbon basis),
as appears to be likely based on EPA's emission data base for
prototype methanol vehicles (see [1]); according to Ford's
data, Houston, already in non-compliance with the ozone NAAQS,
would have a 17 percent increase in mobile source related ozone
for complete methanol substitution, and other cities would
experience smaller increases as well. This approach cannot,
therefore, be recommended.
The second approach would be to use the reactivities of
the worst case city in the modeling data base. Unfortunately,
which city would be considered the worst case city is dependent
upon the amount of formaldehyde co-emitted with the methanol,
since the ratio of formaldehyde reactivity to methanol
reactivity varies from city to city. While the ratio between
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Table 6
Calculated Reactivities of
Methanol and Formaldehyde
(Relative to Hydrocarbons)
Formaldehyde
Study City Reactivity Reactivity
SAI Los Angeles 0.02* 2.95
SAI Philadelphia 0.413 5.873
Ford Allentown 0.350 4.600
4.125
3.867
5.180
5.138
4.600
4.625
4.490
4.938
5.972
4.375
3.833
4.120
4.588
5.158
5.560
4.875
5.754
4.611
5.500
City
Los Angeles
Philadelphia
Allentown
Atlanta
Baltimore
Boston
Chicago
Cincinnati
Dallas
Detroit
El Paso
Ft. Worth
Houston
Milwaukee
Nashville
Philadelphia
Phoenix
Pittsburgh
Scranton
St. Louis
Washington B.C.
Youngs town
Methanol
Reactivity
0.02*
0.413
0.350
0.375
0.533
0.232
0.310
0.600
0.563
0.372
0.563
0.417
0.625
0.500
0.520
0.441
0.421
0.258
0.375
0.215
0.444
0.500
For substitutions less than 100 percent only. For
substitutions beyond 100 percent the reactivity is 0.481.
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methanol and formaldehyde emissions differs from vehicle to
vehicle, it is possible to estimate a fleet average
formaldehyde fraction based on prototype methanol vehicle
performance; however, an accurate fleet average formaldehyde
fraction would require in-use emissions data for all types of
vehicles, as well as data on the relative market fraction of
each type of vehicle. Furthermore, as the relative numbers of
each type of vehicle change, then the city considered to be
worst case could change, and as a result the standard may need
to be changed. The standard may also need to be modified as
vehicle technology changes result in variations in the
formaldehyde to methanol ratio. For these reasons, this
approach also seems inadequate.
The final approach would be to use the highest value for
each of the reactivities. Based on the existing data, this
would mean using the methanol reactivity for Houston (0.625)
and the formaldehyde reactivity for Ft. Worth (5.972).
Assuming the same relative emissions as before, this approach
would allow the amount of carbon emissions to be essentially
equivalent to those under the carbon-based standards, and ozone
reductions might still be expected to occur in each of the
cities modeled to date. This approach seems to be the most
reasonable of the three, since it would adequately protect
against ozone increases, assuming that the the current modeling
data base is sufficient. It should also be noted that this
approach would not result in true ozone equivalence between
methanol and gasoline vehicles, which was the stated goal of
considering photochemical modeling-based standards. Rather,
this approach would serve to limit methanol vehicle ozone
potential to that of gasoline vehicles. However, there is no
apparent alternative to ensure that no city would have an
increase in ozone due to methanol vehicles. Thus, as is the
case for the carbon-based standards, there is no need for an
additional margin of safety since this approach is already
conservative.
Thus, with regard to the second question posed in the
introduction to this analysis, staff concludes that it may be
possible to design environmentally acceptable standards based
on photochemical modeling but that such standards are not
likely to be any less stringent (in terms of total carbon
emissions) than carbon-based standards. Additionally, it is
noted that the standards may need to be revised as new modeling
studies are performed, reflecting changes in modeling
techniques and/or real world parameters.
The final and perhaps most relevant question to be
answered is whether photochemical modeling-based standards
would provide a significant benefit to the manufacturers. To
answer this question, the third approach described above is
compared to the proposed carbon-based standards. While it is
true that the two alternatives will allow roughly equal amounts
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of total carbon to be emitted, it is not true that the two
would be identical. Due to differences between individual
vehicles, and the differences between the makeup of exhaust and
evaporative emissions, there could still be economic benefits
from standards based on photochemical modeling.
For exhaust emissions, the relative stringency of these
two alternatives depends on the relative amounts of
hydrocarbons, methanol and formaldehyde in the emissions. If
the formaldehyde to methanol ratio (as carbon) in the exhaust
was greater than 0.075,* then exhaust standards based on the
third photochemical modeling approach (without any additional
safety factor) would be more stringent than the proposed
carbon-based standards. That is, a vehicle could potentially
meet the carbon-based standard but not the photochemical
modeling based standard. Since the average formaldehyde to
methanol ratio has been determined to be around 0.0943 for
current methanol vehicles (based on [1]), on average the
carbon-based standards are the least stringent. An additional
point to note is that carbon based standards would allow more
flexibility for manufacturers if formaldehyde emissions are
found to be difficult to reduce selectively, since they are
weighted less heavily under this approach than under the
photochemical modeling-based approach.
Ford presented exhaust data for light-duty vehicles which
they claimed showed a significant benefit resulting from the
photochemical-based exhaust standards discussed in the NPRM;
however, there are two issues which Ford may not have fully
considered and which are significant enough to invalidate their
conclusions. First, they included in their analysis vehicles
which did not meet the proposed CO standard. Further analysis
of Ford's data shows that only eight of 17 vehicles were
capable of meeting the CO standard. Each of these eight
vehicles could also meet the carbon-based exhaust organics
standards (see Table 7). This indicates that lessening the
stringency of the exhaust organics standards may not reduce the
control costs greatly, since the available (albeit limited)
data indicate that the CO standard is the limiting factor for
catalyst-equipped vehicles.
Second, Ford based their finding on the photochemical
modeling-based standards that were based only on data for Los
Angeles. The more recent data, as discussed in the foregoing
This is the critical ratio, above which the photochemical
modeling-based standards become more stringent than the
carbon-based standards. It can be derived by setting the
equations for the carbon-based and modeling-based
standards equal to one another and solving for it. See
Table 7 for equations. The ratio equals one minus the
reactivity of methanol, divided by the reactivity of
formaldehyde minus one (0.375/4.972).
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Table 7
Comparison of Standards Using Ford's Emissions Data
Vehicle*
18/83/Escort( LAX/ 5030)
19/83/Escort< LAX/5531)
24/83/Escort(EFI/7559)
08/81/Escort/ 14600
22/83/Escort(EFI/138)
02/81/8abbit/4490
04/81/8abbit/4500
31/85/Toyota/475
Carbon Equivalent**
.344
.295
.306
.185
.412
.187
.206
.215
Photochemical Equivalent***
.316
.301
.356
.180
.524
.160
.207
.192
* Vehicle designations are Ford's, last number is the odometer reading.
** Carbon equivalent = HC(g/mi) + 13.876 MeOH(g/mi) + 13.876 Form (g/mi).
32.042 30.026
*** Photochemical
Equivalent = HC(g/mi) +• (.625) 13.876 MeOH(g/mi) + (5.972) 13.876 Form (g/mi)
32.042 30,076
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analysis would result in more stringent standards. As noted
before, the relative stringency depends on the formaldehyde to
methanol ratio. Only seven of the eight vehicles met the most
stringent photochemical modeling-based exhaust standards
(without a margin of safety), while all eight met the carbon
based exhaust standards. (Admittedly, the vehicle which did
not meet the photochemical modeling-based standard just barely
met the carbon-based standard.) The four vehicles for which
the carbon-based standard was the less stringent standard all
had formaldehyde to methanol ratios greater than the critical
ratio of 0.075. The cost of this increased stringency of
photochemical modeling-based standards is difficult to
determine, since no commenters provided any relevant cost data
in this regard. GM's comment that it was unable to provide an
estimate in this regard is particularly relevant.
Since evaporative emissions do not contain formaldehyde,
the evaporative standard based on photochemical modeling
(without a margin of safety included) will always be less
stringent than the carbon based standard. This is because a
mixture of only hydrocarbons (reactivity of one) and methanol
(reactivity less than one) will always have an average
reactivity that is less than one (relative to an equal amount
of carbon as gasoline hydrocarbons). Thus, standards based on
photochemical modeling would allow methanol vehicles to emit
more carbon than gasoline vehicles in order to result in equal
ozone. For example, if one assumes that 47 percent (as carbon)
of the evaporative emissions from a methanol vehicle are
hydrocarbons (as was calculated in [1]), then using the
methanol reactivity from the most stringent standards based on
photochemical modeling, the average reactivity of the mixture
would be 0.80. The amount of carbon allowed relative to that
allowed by the carbon-based standards equals the inverse of the
reactivity (1.0 / 0.80 = 1.25). Therefore, this approach would
allow 25 percent more carbon to be emitted than the
carbon-based standards would. It is noted that methanol's low
volatility tends, depending on the nature of any additive
packages, to reduce evaporative emissions, making it unclear
whether a relaxed limit on evaporative carbon emissions
represents reduced stringency.
A reduction in stringency for evaporative emissions would
likely result in some economic benefit, but no commenters
provided data which would allow a quantitative estimate of this
benefit. The only comment received specifically in regard to
evaporative emission standards feasibility was from Ford, who
agreed with EPA's conclusion in the Regulatory Support Document
that the carbon-based standards were feasible. Whether the
benefit of photochemical modeling-based evaporative emission
standards would be substantial, or even whether it would be
sufficient to offset the expected increase in stringency of
modeling-based exhaust standards cannot be determined due to
the general lack of cost data. Nevertheless, it is obvious
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that the relative stringency of the carbon and photochemical
modeling-based options are generally similar and therefore, in
response to the third question, compliance costs ought also to
be similar.
To summarize the foregoing analysis, the available
modeling base upon which standards could be founded is
insufficient to allow development of environmentally acceptable
standards with other than a conservative approach. Using such
an approach results in standards that are generally similar to
carbon-based standards, both in terms of environmental impact
and stringency. Any difference between the two approaches in
this latter regard which might weigh in favor of the
modeling-based approach need to be balanced by a concern for
the weak philosophical foundation of such standards. These
standards rely upon elaborate manipulation of empirical data
and are subject to change as further modeling is performed.
Carbon-based standards, on the other hand, rely on the known
scientific link between oxidation of organic carbon and ozone
formation, and are equivalent to existing HC standards in this
regard. For these reasons, carbon standards are superior to
modeling-based standards.
Some commenters were also concerned that formaldehyde
emissions from methanol vehicles could lead to increases in
ozone levels, and felt that separate formaldehyde standards are
necessary. They raised several valid points about the
reactivity of formaldehyde. However, as mentioned earlier,
based on the results of available modeling studies it is
expected that fleet average emissions from methanol-fueled
vehicles certified for carbon-based standards will have 54 to
95 percent of the ozone forming potential of those of gasoline
vehicles (see Table 2). These results do not indicate that the
arguments (of AGA, GARB, and Chevron) for a separate
formaldehyde standard are incorrect; formaldehyde is a very
reactive compound, and can be a key component of atmospheric
reactions. However, the results do show that these arguments
are not sufficient to require a separate (ozone based)
formaldehyde standard, since the carbon-based standards will
limit average formaldehyde emissions to acceptable levels.
The emissions data upon which this conclusion and all
other ozone projections made in this discussion are from [1].
Brooklyn Union Gas, however, argued that these data cannot be
reliably translated into in-use emissions. As is discussed in
that reference, it is true that more data are needed to
precisely quantify the impacts of different methanol fuel
compositions, vehicle types, and mileage accumulation on the
ratios of organic emissions from methanol vehicles. It is also
true that availability of such data, as well as data on the
types of fuels and vehicles that will be found in-use, would
-------
-35-
allow more accurate predictions of the emission factors.
However, in the absence of such data, the data base is still
sufficiently large* and adequately qualified to give EPA
confidence that, at least as far as first generation methanol
technology is concerned, the data base is representative of
real, expected emissions. This finding is also based upon EPA
staff's past experience in estimating in-use emissions from
gasoline and diesel vehicles. Additionally, it should be noted
that because substantial penetration of methanol vehicles into
the market is not expected to occur in the very near future,
there will be sufficient time to verify the estimated in-use
emission factors before methanol vehicles could have any
significant impact on the environment. Thus, staff is
confident that the estimated emission factors are sufficiently
accurate.
Conclusions
The environmental analysis of the impact of the
carbon-based standards shows that they are sufficient to
prevent any increase in ambient ozone levels. In fact, as the
results in Table 2 show, the standards will have a margin of
safety between 5 and 46 percent. It is also concluded that
these standards will be technologically feasible using controls
similar to current vehicles, and thus will have similar costs.
For these reasons, the carbon-based standards are determined to
be an acceptable alternative. The question EPA considered in
this analysis was whether standards based on photochemical
modeling would be more appropriate.
There are many problems associated with basing standards
on photochemical modeling. Most notable are the problems of
reliability and sufficiency of the available modeling data base
and the possibility that future studies would indicate
different reactivities for methanol and formaldehyde, requiring
the standards to be changed. The problems of reliability
include concerns about trajectory modeling, the multi-day
effects of methanol, and city-specific analyses. These
uncertainties could be addressed through further modeling, use
of a conservative methodology to translate available modeling
into standards, or by using a margin of safety, though it is
not presently known how much more modeling, which is expensive
and time consuming, would be necessary, or how large a safety
margin would be needed. Also, more recent studies, including
Ford's, greatly reduced the expected compliance benefits of
photochemistry-based standards from the levels suggested in the
Exhaust data were available from 457 city FTP tests,
including 64 distinct vehicle configurations. Evaporative
data were available for 35 tests including 18 vehicles.
-------
-36-
NPRM. In fact, based on the amount of formaldehyde found to be
co-emitted with methanol from prototype vehicles, the
carbon-based standards and conservatively chosen photochemical
modeling-based standards are essentially equivalent in
stringency.
As discussed, the photochemical modeling-based standards
could provide economic benefits for evaporative emissions, but
could also result in increased costs for controlling exhaust
emissions. Therefore, without much more detailed cost
information, it is not obvious that standards based on
photochemical modeling would provide any net economic benefit
at all.
The major difference between conservatively chosen
photochemical modeling-based standards and the carbon-based
standards may be philosophical in nature. The carbon-based
standards rely philosophically on the known scientific link
between the oxidation of organic carbon and ozone production to
account for the chemical differences between emissions from
methanol and gasoline vehicles; the modeling-based standards,
on the other hand, rely on elaborate analytic manipulations of
limited photochemical modeling data. Considering the absence
of a more complete understanding of photochemical reactivity,
it is recommended that EPA maintain its previous position that
carbon-based standards are the most appropriate alternative to
protect against increases in ambient ozone levels and to
provide a firm basis for emission standards that will not be
subject to change with each new modeling study performed.
As mentioned before, the environmental analysis of the
proposed standards demonstrated that they are sufficient to
prevent increases in ambient ozone levels. Thus, it is
concluded that there is no need for separate formaldehyde
standards to account for the very reactive nature of
formaldehyde in the atmosphere. It is therefore recommended
that the carbon-based organics standards be promulgated as
proposed.
-------
_37-
Issue: Separate Health Effects-Based Standards for Methanol
and Formaldehyde
Summary of the Issue
In the NPRM, EPA discussed the possibility of promulgat ig
separate standards for methanol and formaldehyde based upon
toxic a ™d carcinogenic effects. The Agency performed analyses
to estimate concentrations of these pollutants in
driving-related scenarios where the public might be routinely
exposed to high levels of methanol and formaldehyde. It was
concluded that the proposed carbon-based total organics
(hydrocarbons, methanol, formaldehyde) standard would be
sufficient to protect the public from toxic concentrations of
methanol and formaldehyde due to methanol vehicles in every
situation considered except the personal garage. Here, toxic
levels of formaldehyde could only be reached with a
malfunctioning methanol vehicle idling inside a personal
garage, but it was concluded that it was not the Agency's
responsibility to set standards to protect against such an
obviously unsafe practice. The level of concern was also
predicted to be reached in the severe tunnel scenario, but, for
several reasons, it was concluded that the analytical
assumptions leading to the prediction were extreme and unlikely
to be realized; thus no standards relating to this scenario
were proposed.
The analysis noted that an increase in overall ambient
formaldehyde concentrations could potentially occur due to
methanol vehicles, with an attendant increase in any cancer
risk associated with formaldehyde. It was unclear, however,
whether formaldehyde should actually be considered a human
carcinogen, whether the level of cancer risk due to
formaldehyde from existing mobile sources was acceptable, and
how much, if any, methanol vehicles would exacerbate the
situation. Additionally, it was noted that it would be at
least several years before methanol vehicles could penetrate
the market sufficiently to affect ambient formaldehyde levels.
It was concluded, therefore, that cancer-related formaldehyde
standards targeted at methanol vehicles would be inappropriate
at present and that the Agency should regulate mobile source
formaldehyde only after a more detailed consideration of the
relative contributions of all potential emitters.
The major issue of this section is whether the proposed
carbon-based organics standards are indeed sufficient to
prevent adverse health effects to the public due to methanol
and formaldehyde from methanol vehicles, or whether separate
emission standards are necessary.
-------
-38-
Summary of the Comments
The Agency did not receive any comments opposed to its
decision not to propose separate standards based on methanol's
health effects, but five of the commenters (AGA, Brooklyn Union
Gas Company, CARB, CEC and Chevron) did oppose EPA's position
that no separate health effects-based formaldehyde standard is
necessary.* The American Gas Association felt that this issue
was so important that the rule should not be promulgated until
formaldehyde emissions and their associated health effects are
better characterized. Other commenters (Chrysler, Cummins,
DOE, GM, Toyota, and Volkswagen), however, were supportive of
EPA's position that a separate formaldehyde standard is not
necessary at this time.
Several organizations felt that EPA's level of concern for
formaldehyde (0.50 mg/m3), was inadequate to protect the
public health. CARB cited the findings of the National
Research Council, which stated that sensitive individuals will
encounter eye irritation at formaldehyde levels as low as 0.05
ppm (1 ppm = 1.16 mg/m3 at 70° F) , and in the presence of
other pollutants, certain individuals will detect and react to
formaldehyde as low as 0.01 ppm. AGA cited the same study,
stating that as much as 10 to 20 percent of the nation's
population may react to low levels (0.25 ppm - 0.50 ppm) of
formaldehyde in the atmosphere. Brooklyn Union Gas also cited
the study, saying that 10 to 12 percent of the population has
no threshold at all to the effects of formaldehyde.
General Motors stated that the levels of concern chosen by
EPA are reasonable and should prevent unsafe levels of methanol
and its metabolites from occurring in the blood of the exposed
persons. They also stated that at the level of concern for
formaldehyde, most health effects would be minor and
reversible. This position was supported by Chrysler who also
stated that it is not the Agency's responsibility to protect
against reversible and slight irritant effects. Chrysler,
Volkswagen, General Motors, and the Department of Energy (DOE)
all agreed with EPA that the proposed carbon-based standards
will adequately protect the public from risk of exposure to
toxic levels of methanol and formaldehyde.
These commenters also suggested that the ozone forming
potential of formaldehyde supported the need for a
separate standard. This aspect of the comments was
addressed in the "Basis of the Organics Standards"
section. The present section addresses only the health
effects issues.
-------
-39-
Chrysler agreed with EPA that vehicle owners should be
expected to assume primary responsibility to ensure that
methanol vehicles are not operated in personal garages; such an
expectation would be analogous to the case of CO emissions from
current vehicles. Cummins disagreed; they stated:
"We do not believe it is good public policy to assume that
the public would take the necessary precautions to insure
his or her own personal safety where exposure to
formaldehyde and methanol emissions are concerned. The
analogy that EPA draws .... with exposure to CO in
non-ventilated areas is not valid when dealing with
substances whose health effects and threshold limit values
are unknown."
Cummins felt that this and other personal exposure scenarios
warrant additional study, but they supported EPA's position
that separate standards are not necessary at this time.
Related to the issue of owner responsibility, GM felt that it
would be appropriate for EPA to issue a warning about the
severe risks of tampering with the emission systems of methanol
vehicles, (A malfunctioning system would allow much higher
emissions of formaldehyde.)
A concern about the emission data used for EPA's analyses
was raised by Chevron, who claimed that "formaldehyde emissions
are typically underestimated . . . due to the very reactive
nature of formaldehyde and the difficulty in maintaining
exhaust sample integrity." They cited a study by Southwest
Research Institute that showed losses of 40 percent in the
exhaust sampling system.[8] This would result in
underprediction of concentrations, and thus underestimation of
the risk. AGA was also concerned about the limited amount of
emissions data available at this time. Further, Brooklyn Union
Gas discussed the validity of the emission factors used in
EPA's analyses. They cited "EPA's disclaimer that the limited
prototype vehicle testing emissions data now available for
methanol and upon which the proposed rule is based cannot be
reliably translated into in-use emissions." They, as well as
Chevron, were particularly concerned about the durability of
catalytic converters on methanol vehicles. Chevron indicated
the potential risk of an ineffective catalyst system by stating
that without a catalyst "formaldehyde levels in exhaust are in
the order of several thousand PPM."
The commenters also addressed the carcinogenic risk of
formaldehyde exposure. AGA ci~ed the National Academy of
Sciences again, stating that formaldehyde has been shown to
create mutagenic activity in living organisms, and that the
severity of the response is dependent upon the severity of the
dosage. CARB stated that according to the 1986 EPA Guidelines
for Carcinogen Risk Assessirvant, formaldehyde would be
L
-------
-40-
considered a probable human carcinogen because of the results
of animal tests. GARB, AGA, and Brooklyn Union Gas all agreed
that the most appropriate approach to deal with formaldehyde's
cancer risk would be to limit emissions of formaldehyde to the
minimum level possible. CARB suggested specific standards
which were discussed in the "Basis of Organics Standard"
section of this document.
Both Chrysler and GM were unconvinced of the cancer risk.
They cited the National Cancer Institute Study of 26,000
industrial workers exposed to formaldehyde, which they claimed
showed no excess cancer mortality due to formaldehyde
exposure. General Motors also noted that methanol vehicles
would not be expected to significantly affect the ambient
formaldehyde concentrations, especially considering the small
number of vehicles expected to be produced initially. They
stated that there is adequate time to further investigate the
cancer risks before methanol vehicles enter the fleet in
numbers significant enough to substantially affect ambient
formaldehyde levels. They therefore felt that a separate
formaldehyde standard is not necessary at this time to prevent
increased cancer risks. DOE noted that there is currently no
ambient standard for formaldehyde, and thus felt it would be
inappropriate to have a separate emission standard based on the
effect on ambient formaldehyde concentrations.
Analysis of Comments
There are two aspects of the commenters' major concern,
that use of methanol vehicles could lead to the occurrence of
toxic concentrations of formaldehyde in situations involving
routine exposure to motor vehicle emissions, that require
analysis. The first relates to the concentration, or level of
concern, at which formaldehyde should be considered a potential
health risk. The second is whether expected emissions are
anticipated to result in the level of concern being achieved.
The Agency decided in the NPRM that the appropriate level
of concern for formaldehyde is 0.50 mg/m3, stating that:
"The studies indicate that at 0.50 mg/m3 the odor of
formaldehyde should be noticeable by most people, and any
health effects experienced (i.e., eye, nose, or throat
irritation or discomfort) should be minor and reversible
for the vast majority of the populace."
Among the studies used as a basis for this conclusion was the
report by the National Research Council which was cited by AGA,
Brooklyn Union Gas, and CARB. It is noted that the arguments
presented by the commenters were addressed previously by the
Agency in the NPRM and the Regulatory Support Document. It was
concluded that these concerns were not sufficient to justify
implementing a lower level of concern, especially considering
-------
-41-
the fact that exposures to elevated levels of mobile source
formaldehyde are expected to be brief (usually less than 15
minutes). Studies of non-sensitized individuals usually
involved exposures of greater duration and it is not known
whether the adverse effects would generally have occurred given
a shorter control period. Further, it was noted that the
severity of these individuals' responses at levels below the
level of concern was minor. For example, in one study,
respondents characterized the effect of formaldehyde at 0.25
mg/m3 as barely noticeable, similar to a light windy touch or
dry feeling which elicited conscious blinking. While it is
noted that there is a wide variability in human response to
formaldehyde such that some individual may just notice
irritation at levels below 0.50 mg/m3, the conclusion that
health effects below the level of concern are expected to
generally be minor and reversible continues to be valid, and
the Agency should not, as Chrysler commented, necessarily be
involved in protection against them. With regard to the data
which indicate a portion of the population which may be
sensitive to concentrations as low as 0.01 to 0.05 ppm,
emission standards may be of little benefit, since typical
urban concentrations are presently of this order of magnitude.
Additionally, it should be noted that these data from studies
of occupational exposures, and not brief exposures like those
discussed here. Addressing exposures at this level is clearly
beyond the scope of this rulemaking. EPA is in fact pursuing
an Agencywide approach to deal with ambient exposures to
formaldehyde. An intra-Agency task force will coordinate
activities related to formaldehyde, including the development
and implementation of a formaldehyde control strategy that will
account for issues such as sensitive populations.
Since the commenters presented no new data to challenge
the Agency's previous logic in determining a level of concern
for formaldehyde, it would be inappropriate to alter the level
of concern in response to the comments. It should be noted,
however, that the Agency did consider, in its previous
analysis, what effect a 0.25 mg/m3 level of concern would
have had on the need for standards and found none.
The Agency chose 260 mg/m3 as the level of concern for
methanol. This is the Threshold Limit Value (TLV) for
eight-hour exposures set by the American Conference of
Governmental Industrial Hygienists (ACGIH). The TLV
incorporates a fairly large margin of safety against toxic
effects. No comments were received opposing this level of
concern. It is worthwhile to note that an extensive review of
methanol health effects and the implications of methanol
vehicles was recently completed by the Health Effects
Institute.[9] This study's conclusions included the finding
that the mobile source-related exposures to methanol predicted
by EPA as a result of methanol vehicles, would not cause toxic
effects. For example, they stated:
-------
-42-
"A 70 kg person breathing at a ventilation rate of 20
m3/day (twice resting) who is exposed to 200 mg/m3
methanol vapor for 15 minutes (as in a worst-case hot-soak
garage scenario), accumulates a methanol body burden of
0.0006 g/kg - at least 500 times lower than doses of acute
clinical significance."
HEI did, however, note that these conclusions were in regard to
ocular toxicity due to formate (which is a metabolic
intermediate of methanol), and that there could be other toxic
mechanisms. This possibility needs to be investigated in the
future.
The availability of new emissions data has enabled EPA to
update its analysis of methanol and formaldehyde concentrations
in driving-related scenarios in which people could commonly
encounter elevated concentrations of mobile source pollution.
It would be appropriate to present this analysis prior to
considering comments related to the earlier analysis. The
analysis is based upon mathematical models developed by
Southwest Research Institute (SwRI). The scenarios modeled
were:
(urban corridors bounded by tall
1) Street canyons
buildings)
2) Tunnels
3) Expressways
4) Public parking garages
5) Personal garages
These scenarios are discussed in more detail in the Regulatory
Support Document for the NPRM. Both typical and more severe
situations were modeled; however this analysis focuses on the
severe situations, except as otherwise noted.
It was concluded earlier that the only modeling situation
in which unacceptable formaldehyde concentrations (i.e.,
concentrations significantly above the level of concern) might
occur involves idling of a severely malfunctioning vehicle in a
personal garage. Formaldehyde concentrations were also
to be near the level of concern in the severe tunnel
Methanol was found never to exceed its level of
but it did approach the level of concern in the
garage - hot soak (trip end) scenario (235.6
The results of the updated analysis are shown in
through 13. These new results do not differ
substantially from the previous ones, except for those
scenarios involving hot soak emissions, and those involving
cold idling (idling immediately after starting the engine).
The scenarios affected are the public parking garage and
personal garage trip start and trip end scenarios.
predicted
scenario.
concern,
personal
mg/m3).
Tables 8
-------
-43-
In the previous analyses of the trip end scenarios it was
estimated that maximum certification level hot soak emissions
of methanol would be 3.0 grams per test. Based on more data,
it now appears that 2.0 grams per test is a better
estimate.[1] Using this newer estimate, the models predict
maximum concentrations of 100.9 mg/m3 and 152.8 mg/nP, for
the public parking and personal garage scenarios, respectively
(Tables 12 and 13). Both of these predictions are well below
the level of concern, and are based on worst case assumptions
so that it does not appear that hot soak methanol emissions
pose any significant threat to the public. It should be noted
that the malfunction-based offsets* used in Tables 12 and 13
were based on limited and somewhat questionable data. However,
because the margins of safety for these two scenarios are so
great, and because, for the public parking garage scenario,
other offsets based on fleetwide gasoline vehicle performance
can be adopted as surrogates, this should not be a significant
concern in that scenario. For the personal garage, the margin
between the predicted concentration and the level of concern is
also large, even considering a 2.0 safety margin on emissions.**
The scenarios using cold start emission factors also
involve exposure in public and personal garages. Several
changes were made to the analyses that were discussed in the
proposal. The first is related to the exposure model used for
the public parking garage. The previous analysis focused on a
model that was based on an actual underground garage, which was
poorly ventilated. However, this model is no longer considered
representative, since pollutant concentrations inside the
actual garage were so high that it had to be completely
reventilated. Additionally, there is some concern that the
garage model might be inaccurate. The model of the severe
scenario was tested (for validation purposes) using ambient
data from a 1978 study which measured a CO concentration of 374
mg/m3 during a parking episode in the actual garage on which
the physical parameters defining the severe scenario analysis
were based. Using an average CO emission factor of 7.7 mg/min
based on an EPA study (how this estimate was obtained from
EPA's emission factors was not discussed in detail in the SwRl
document), the model predicted a concentration of 430 mg/m3.
SwRI claimed that this analysis validated the model, but there
is concern that actual in-use emissions of CO in 1978 could
have been much higher. Using the same EPA study as was used by
SwRI, and making reasonable assumptions about the overall
mostly catalyst equipped fleet's model year distributions, the
* Offset is the expected ratio of in-use emissions to
certification level.
** Since the gasoline vehicle offsets were developed based on
fleetwide performance and only one vehicle is present in
the personal garage, a 2.0 safety margin on the predicted
emission level is used as a surogate for an in-use offset.
-------
-44-
Canyon
30% Penet
100% Penet
Tunne1
30% Penet
100% Penet
Expressway
30% Penet
100% Penet
Table 8
In-Use Formaldehyde Concentrations for
Canyon, Tunnel, and Expressway (mg/m3)
(Level of concern for formaldehyde is 0.50 mg/tn3)
Offsets
Likely Cert.
Level (g/mi)
0
0
0
0
0
0
.0482
.0482
.0482
.0482
.0072
.0072
Meet
Std. *
0
0
0
0
0
0
.012
.022
.12
.22
.0076
.0059
2
0.
0.
0.
0.
0.
0.
.2
020
048
20
49
010
013
25%
2.6 Malfunction**
0
0
0
0
0
0
.022
.057
.23
.58
.010
.015
0
0
0
0
0
0
.020
.050
.20
.50
.027
.069
*
* *
Offset =1.0.
Offset =1.0.
Offset =2.26 canyon, 2.26 tunnel, 11.75 expressway.
-------
-45-
Table 9
In-Use Methanol Concentrations for
Canyon, Tunnel, and Expressway (mg/ra^)
(Level of concern for methanol is 260 mq/m3)
Canyon
30% Penet
Tunnel
30% Penet
30% Penet
Offsets
Likely Cert.
Level
et 0.
net 0 .
et 0.
net 0 .
way
.et 0.
met 0 .
(q/mi)
546
546
546
546
025
025
Meet
Std.*
0
0
0
2
0
0
.07
.25
.75
.5
.006
.020
2
0
0
1
5
0
0
.2
.16
.55
.7
.5
.013
.044
2
0
0
2
6
0
0
.6
.19
.65
.0
.5
.016
.052
25%
Malfunc**
0
0
1
5
0
0
.17
.57
.7
.7
.24
.79
**
Offset =1.0.
Offset =2.28 canyon, 2.28 tunnel, 39.40 expressway.
-------
-46-
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-------
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-------
-48-
Table 12
In-Use Methanol Concentrations
for Hot Soak, Parking Garage
-------
_49-
Table 13
In-Use Methanol Concentrations for
Hot Soak, Personal Garage (mg/m3)
(Level of Concern for Methanol is 260 rag/m3,)
20 CFM
No Vent
Likely Cert .
Level (q/hr)
1.3-2.0***
1.3-2.0
Meet
Std.*
12.0-17
21.4-31
.8
.8
Offsets
2.0 Safety
Margin
24.0-35.6
42.9-63.7
100%
Malfunc**
57.5-85.4
102.9-152.8
* Offset =1.0.
** Offset =4,8.
*** 1.3 is estimated fuel injected emissions and 2.0 is
estimated carbureted emissions.
-------
-50-
average CO emission factor could be estimated to be more than
twice as high as the estimate used by SwRI. If this is true,
then the severe model is overestimating concentrations. This
concern is supported by the fact that the model of the severe
scenario would have predicted very high CO concentrations, on
the order of more than 2000 mg/m^, for earlier, pre-catalyst
gasoline vehicles emitting 40 g/min or more in-use at cold
idle, and this level would likely have been considered
unacceptable. Furthermore, recent gasoline vehicle data
indicate that cold idle formaldehyde emissions might be high
enough to produce concentrations as high as twice the level of
concern in this scenario. However, the fact that complaints of
eye irritation from frequent garage users are not received in
this regard lends further evidence that the model is not
representative. Therefore, the current analysis is focused on
a model of a more typical garage. The model predicts the
maximum concentrations that would occur under congested traffic
conditions, in which the garage is emptied in a short period of
time, such as that after a concert. Individuals would be
exposed to the highest predicted concentrations in the garage
for about four minutes, and to concentrations that are 28
percent as high for another four minutes. For comparison, the
concentrations predicted for the severe model, which was
previously the focus of EPA's analysis, would be about four
times the maximum predicted concentrations of the typical
model. It should be noted that validation data were not
available for the typical model, thus its accuracy must also be
considered somewhat uncertain.
The second problem with the previous analyses of the trip
start scenarios relates to the emission factors that were
used. First, the analysis did not use actual cold start idle
data for methanol vehicles; the emissions were estimated based
on hot idle data (idling after the engine has been warmed up).
It was assumed that the ratio of cold idle formaldehyde
emissions to hot idle formaldehyde emissions would be the same
for methanol vehicles as it is for gasoline vehicles (2.25,
based on limited testing). Using this ratio, and hot idle data
from four methanol vehicles, the upper limit for cold idle
emissions was estimated to be 2.03 mg/min. There are now four
studies available which have reported cold start idle emission
data for methanol vehicles (three studies involved 1983
Escorts, the other involved a 1986 Carina).[10,11,12,131 These
cold idle data now indicate that the previous approach was not
appropriate. The new data (Table 14) suggest that cold idle
formaldehyde emissions are 4-60 times the previous estimation.
Three of the studies which had cold start idle data for
methanol vehicles also investigated the effect of ambient
temperature on the formaldehyde emissions, and found similar
results. Idle formaldehyde emissions at 20°F were found to be
2.4-4.0 times the idle emissions at FTP temperatures.
Therefore, analysis of health effects based on emissions data
at FTP conditions is not sufficient to ensure that cold
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Table 14
Methanol Vehicle Emission Factors
(Cold Idle)
Study
EPA [10]
EPA
EPA
EPA
EPA(11]
EPA
SPA
EPA
NIPER[12]
EPA[13]
*
**
Temperature Methanol
Vehicle (°F) (g/min)
•83
'83
•83
'83
'83
•83
'83
'83
•83
•86
Escort*
Escort*
Escort**
Escort**
Escort
Escort
Escort
Escort
Escort
Carina
Used summer
Usei
d winter
70 0.847
40 2.619
40 2.166
20 4.850
75
60
40
20
20
78
arade fuel.
rade fuel .
Formaldehyde
(mq/min)
44.3
25.0
57.2
105.9
30
48.4
93
122
49.0
8.0
CO
(q/min)
6.91
16.4
9.5
19.0
41.3
1.8
CO to
Formaldehyde
156
658
167
179
843
225
Ratio of levels of concern of CO and formaldehyde is 880,
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temperature emissions will not be unsafe, and the 20 °F
emissions data are used in the analysis.*
Second, other new data also enabled EPA to update its
estimates of gasoline vehicle contributions to formaldehyde
exposure in garages. The data show that gasoline vehicles
contribute more than was previously thought, such that low
mileage, well maintained vehicles gasoline vehicles alone could
result in fairly high levels of formaldehyde (see Tables 10 and
11).
A final problem relating to the emissions factors used in
the previous analysis in the Regulatory Support Document
concerns the three offsets used to estimate in-use parking
garage (see Tables 2-7 and 2-8 of the Regulatory Support
Document) idle emissions of methanol and formaldehyde. The
malfunction offset was originally based on hot idle data. It
assumed that 25 percent of the methanol fleet is
malfunctioning, with malfunction emissions being represented by
non-catalyst vehicle emissions. Hot idle formaldehyde
emissions from a non-catalyst vehicle were determined to be 7.6
times those from catalyst vehicles; the ratio was determined to
be 34.0 for methanol emissions. However, hot idle emissions
would be expected to be affected by catalyst function much more
than cold idle emissions would be, since catalysts do not
become effective until they are warmed up. Thus, the
malfunction offset based on hot idle data is probably too high,
resulting in an overestimate of concentrations. Malfunction
based offsets were not used in the present analysis. The other
offsets used as alternatives were based on performance over the
urban driving cycle of the FTP at FTP temperatures (i.e., 2.2
and 2.6). There are two potential problems with this. First,
since cold start idle emissions at low temperatures are not
necessarily affected by the modifications that are relevant to
emissions performance at 70°F, it is not obvious that offsets
for low temperature cold start idle emissions from well
maintained vehicles will be similar to offsets for the same
engines operated at FTP temperatures. Second, the relevance of
performance over the FTP driving cycle to that at idle is not
clear. It is possible that small changes in engine or catalyst
parameters may significantly affect the optimized FTP
emissions, but not cold start idle emissions. However, since
it would not be appropriate to assume that the fleet average
offset for idle emissions would be unity, the parking garage
cold idle offset will be assumed
As was noted in the Regulatory Support Document, this
phenomenon could also affect the results of analyses of
other scenarios, however the margin of safety between
calculated concentrations based on 70°F emissions and the
level of concern was so great that the effect could be
disregarded.
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to range between 2.2 and 2.6 as was done for the other offsets
for exhaust emission scenarios, It is recognized that there
are weaknesses to this approach, however, it is the best one
available; thus it: is appropriate, especially considering other
sources of uncertainty in the analysis. Similarly, there is
not sufficient information to accurately calculate an offset
for the personal garage scenario. Here a 2.0 margin of safety
will be used in place of an offset.
Using these newer data, the SwRl models predict
formaldehyde concentrations of up to 2.78 mg/m3 for the
public parking garage scenario and 16.3 mg/m3 for the severe
personal garage scenario assuming worst case methanol vehicle
emissions; these concentrations are both greater than the level
of concern (0.50 mg/m3). Thus, the concern about exposure to
toxic concentrations of formaldehyde is reasonable. Tables 10
and 11 also show the impacts of other types of vehicles. The
impacts of mixed fleets on exposures in public garages can be
predicted by averaging the predicted values for these vehicles.
Similarly, recent cold idle data for methanol (from one of
the studies shown in Table 14) indicate that actual cold idle
emissions of methanol are 8 to 110 times the previous
estimate. As before, the data from the tests at 20°F are used,
as a worst case. Using these data, the models predict
concentrations of up to 147 mg/m3 for the parking garage
scenario and 650 mg/m3 for the severe personal garage
scenario. Here only the concentration for the personal garage
scenario is above the level of concern. It is useful to note
that in these scenarios, based on ratios of emission factors
and levels of concern, formaldehyde concentrations would exceed
the level of concern by a greater margin than methanol
concentrations. Therefore, formaldehyde concentrations can be
considered the more serious concern, and as such are the focus
of the following discussions.
There are several possible problems with the public
parking and personal garage analyses which could make them
invalid. This discussion will begin with a consideration of
the public garage, but several of the concerns with that
analysis apply to the personal garage scenario as well. First,
the maximum concentrations represent a worst case analysis,
based on the highest emitting vehicle tested at 20°F (three
1983 carbureted Ford Escorts were tested at this temperature).
None of these vehicles was apparently near the compliance level
for the proposed CO or total organics standards for the FTP
(they were emitting at roughly two to three times the
standard). If they had, it can be anticipated that their idle
emissions would be somewhat lower as well. It is not obvious
however, the degree to which compliance with the total organics
standard would affect cold idle emissions. If the weighted FTP
emissions were reduced by any adjustment which affected
emissions from a warmed-up engine, then the cold idle
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emissions, which pass through a cold, hence ineffective
catalyst during much of the idle period, might not be
affected. If on the other hand, the FTP emissions were reduced
by affecting bag 1 (cold) emissions, then it is likely that
cold idle emissions would be affected.
Second, the emission performance of 1983 carbureted
Escorts is not likely to be representative of the future
methanol fleet. As is discussed elsewhere in this document,
the development effort on this vehicle, with respect to
emissions performance, was limited. The Toyota Carina, a more
advanced technology methanol vehicle, emitted only 16-27
percent as much formaldehyde at FTP temperatures as the early
Escorts, and was in the range of emissions of gasoline
vehicles. Cold temperature data for this vehicle were not
available.
Finally, as was noted before, the accuracy of the modeling
is uncertain. It is used here to give a reasonable
approximation of exposures in public garages; the results
should not be taken as the final word on such exposures.
Rather work may need to be done to improve the reliability of
the model.
Because of concerns such as these, it is difficult to
conclude with any certainty that methanol vehicles will cause
unsafe levels of formaldehyde or methanol in public garages,
especially at the expected low initial market penetrations.
Additional investigation of emission data for advanced methanol
engines tested at low temperatures is warranted as is further
validation of the model itself.
Many of the previous concerns are also applicable to the
analysis of the personal garage scenario (see Table 11). Since
the same cold idle data that were used for the analysis above
are also used for the personal garage analysis, the
data-related uncertainties discussed above (concerning the
effects of non-compliance with the FTP CO and organics
standards, and the fact that low temperature data are only
available from early model carbureted Ford Escorts) are also
applicable to this analysis. Also, as before, there is concern
about model validity, since the personal garage model was not
tested using data from an actual garage. The recently
published gasoline vehicle cold idle data indicate that many of
us would even today experience discomfort from starting our
vehicles in our garages on cold mornings due to concentrations
in the range of 1.5 mg/m3 as predicted by the garage model.
The personal garage analysis is similar to the analysis of the
public parking garage scenarios since in both analyses there is
sufficient uncertainty to make the accuracy of the predicted
concentrations somewhat questionable.
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The two analyses differ greatly, however, in two important
respects. While the driver in the public parking garage
analysis has no control over the severity of the exposure
(i.e., the concentration to which the driver is exposed), the
driver in the personal garage analysis has the ability to
control the severity by limiting the time that the vehicle is
operated in the garage; the difference between severe and
typical personal garage scenarios only reflects a difference in
the amount of time the vehicle spends in the garage (five
minutes for severe and 30 seconds for typical), and not any
altered physical parameters. For example, the situation could
be avoided altogether simply by idling the vehicle outside of
the garage. This is widely acknowledged to be a safe vehicle
handling practice; most owner's manuals warn against idling
vehicles in garages, and some even warn against idling next to
buildings. Thus, since the driver may voluntarily avoid the
severe scenario, it is appropriate to consider both the severe
and typical scenarios in this analysis. In addition to his
ability to control the exposure concentration, the driver in
the personal garage scenario also has the ability to limit the
duration of the exposure and thus prevent any irreversible
toxic effects. For example, while he may allow his vehicle to
idle in his garage for five minutes to warm up, he need only be
present in the garage at the beginning and end of the idle
period. Chrysler agreed that drivers should assume primary
responsibility for avoiding such obviously unsafe situations.
Additionally, because the formaldehyde concentrations in
this scenario would lead to some irritation, and owners would
be discouraged from remaining in the garage, they would also be
warned of poor ventilation before CO levels reach the level of
concern. In fact, the limited data that are currently
available (see Table 14) indicate that the CO to formaldehyde
ratio in exhaust for methanol vehicles at cold idle ranges from
150 to 850. The values in this range are less than the ratio
of the levels of concern which is 880. (The level of concern
used here for carbon monoxide is 440 mg/m^ which is the ACGIH
Short Term Exposure Limit (STEL), designed to limit
concentrations during exposures of 15 minutes length.) Thus,
formaldehyde would be expected to reach its level of concern
before CO would, and when the vehicle is removed from the
garage immediately after formaldehyde reaches its level of
concern, the STEL for CO would not be reached. Similarly,
since (as noted earlier) formaldehyde concentrations would
reach the level of concern before methanol would, the
irritation from the formaldehyde would provide a warning for
methanol exposure as well.
Cummins argued that it is inappropriate to assume the
public will avoid exposure in personal garage scenarios. They
claimed that the health effects from formaldehyde exposure are
not adequately known, making EPA's (and by extension,
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Chrysler's) parallel of formaldehyde to the carbon monoxide
situation inappropriate. In response, it is true that the
current knowledge is limited, but it is nevertheless sufficient
to conclude that exposures to formaldehyde at levels around the
level of concern will cause only minor and reversible effects.
Further, even when the concentration does briefly exceed the
level of concern during idling on cold winter days, as
discussed above, exposures could produce brief irritation, but
almost certainly would not cause any irreversible or otherwise
more severe health effects to a healthy driver. The driver has
the ability to prevent dangerous exposures to formaldehyde in a
personal garage, and it is not unreasonable to expect that
drivers will avoid such scenarios if 1) they are known to be
unwise, and 2) concentrations reach the irritant level.
Regulations cannot substitute for common sense.
GM's suggestion that EPA warn the public about the
possible effects of tampering with a methanol vehicle's
emission control system is well taken, and if such tampering is
found, after methanol vehicles begin to be sold, to affect
formaldehyde concentrations sufficiently in any common scenario
(not just the personal garage), such a warning may be
appropriate. At this time, however, sufficient evidence is not
available to justify the Agency taking such action. It is,
however, reasonable to expect that manufacturers will show the
same sense of responsibility with formaldehyde as they
currently do with CO, such that they may feel compelled include
a discussion of formaldehyde in the owner's manual if
necessary. It would be difficult to justify more stringent
treatment of formaldehyde than CO by EPA in this situation
since the worst case formaldehyde concentrations predicted
would result in severe irritation for the general population,
while the cocentrations of CO predicted could induce death,
which occurs after exposure to 10,000 mg/m3 for 10 minutes or
so. Further, concentrations of 5,000 mg/m3, which would
precede these higher levels, would result in headaches and
nausea for most individuals.
To summarize, while there may be cause, after further
investigation, for concern about exposure in public parking
garages, the evidence given by the present analysis is somewhat
weak. The results indicate that there is a very low risk that
the public will be involuntarily exposed to toxic levels of
methanol or formaldehyde in the near future because
concentrations will be low at very low market penetrations.
Exposures in personal garages can be avoided altogether, just
as they are today in regard to CO exposure, and those that do
occur will be too brief to cause serious health effects. It
would be appropriate, however, to investigate the issue of cold
idle emissions further, especially with regard to the public
parking garage scenario.
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Chevron felt that formaldehyde emissions are
undermeasured. EPA staff agrees that care needs to be taken to
avoid sampling losses and therefore will require a heated
transfer tube and sample lines. Nevertheless, it has been
shown that even without a heated transfer tube collection
efficiencies range from 79 to 94 percent,[14] and that unheated
sample lines can have efficiencies up to 98 percent. [15] Staff
does not consider the data cited by Chevron to be valid,
because an improper procedure was used. This issue is
discussed in more detail in the test procedures sections in
this document. Thus, the formaldehyde data used in this
analysis are considered sufficiently accurate.
In regard to concerns that EPA's estimated emission
factors are inaccurate, staff agrees that the emissions data
base has limitations; however, because it contains data from 13
different studies (screened for appropriate measurement
techniques) and from many different types of vehicles, it was
concluded to be robust enough to be appropriate for the
purposes of this analysis. Additionally, staff is confident
that recent additions to the emissions data base have
significantly improved the reliability of the projected in-use
emission factors beyond those estimated earlier. Staff is
convinced that any errors introduced as a result of the nature
of the data base will be small and thus not significantly
affect the validity of this analysis. An exception here may be
necessary for cold idle emissions, which were previously
discussed. In this case, the uncertainties argue for continued
research by EPA and automobile manufacturers as methanol
vehicles are developed. It is impossible to determine actual
emission factors based onthe prototype vehicle developed to
date, but directionally, data for the newer, more advanced
Toyota Carina are reassuring.
Both Chevron and AGA were concerned about catalyst
durability affecting formaldehyde emissions. To the extent
that adverse health effects are avoided due to the action of
the catalytic converter, the issue of its durability is
important to this discussion. As is discussed in more detail
in the "Basis of the Organics Standard" section of this
document, however, staff believes that sufficiently durable
catalysts will be available.
The second major concern of those commenters supporting a
separate standard for formaldehyde was the potential increased
cancer risk due to increased formaldehyde concentrations in the
atmosphere. With respect to the carcinogenicity of
formaldehyde, CARB was correct; EPA has classified formaldehyde
as a "Probable Human Carcinogen" (Group Bl) under its
Guidelines for Carcinogen Risk Assessment. As was stated by
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EPA's Office of Pesticides and Toxic Substances
this classification is based on the following:
(OPTS) [16]
0 limited evidence of carcinogenicity in humans (i.e.,
several epidemiologic studies show positive
associations between respiratory site-specific
cancers and exposure to formaldehyde);
0 sufficient evidence of carcinogenicity in animals
(i.e., formaldehyde induced an increased incidence
of rare, malignant nasal squamous-cell carcinoma in
mice and rats, and in multiple experiments); and
0 additional supportive evidence (i.e., studies
demonstrating formaldehyde's mutagenic activity in
numerous test systems using bacteria, fungi, and
insects, and ability to transform cells in culture
and cause DNA damage in other in vitro assays for
mutagenicity. Also, structure-activity analysis
indicates that formaldehyde is one of several
carcinogenic aldehydes.)
Included among this body of evidence was the National Cancer
Institute study noted by Chrysler and GM. This study showed an
excess of cancer among workers exposed to formaldehyde;
however, the study's authors argued that this provided little
evidence of an association with formaldehyde. OPTS disagreed,
and argued that these results are meaningful. This position is
supported by the other evidence of the carcinogenicity of
formaldehyde.
Since methanol vehicles have the potential to increase
ambient formaldehyde levels, it would be useful to approximate
the magnitude of any increased risk they might represent.
Unfortunately, no detailed work in this area has been
performed. One study, admittedly limited in scope, of the Los
Angeles airshed during an ozone episode predicted that the peak
hourly formaldehyde concentration of the modeled air parcel
would rise from 26 ppb to 31 ppb if 100 percent of the fleet in
Los Angeles were converted to methanol.[2] Another study,
modeling Philadelphia, showed similar results (formaldehyde
rose from 22.5 ppb to 25.9 ppb). [3] These estimates can be
considered worst case to some extent since the models assumed
10 percent of the mobile source organic carbon emissions were
formaldehyde, but data indicate that the formaldehyde fraction
would be closer to four percent.[1] In addition, preliminary
results of another modeling study indicate that the lower
reactivity of methanol may even result in a slight decrease in
formaldehyde levels.[17] Thus, at low penetration levels the
increase in ambient formaldehyde concentrations would be very
small, and in some areas negligible. Accordingly, the effect
on the cancer risk would also be very small or negligible.
However, formaldehyde concentrations depend on a number of
variables related to meteorology and emissions. Thus, given
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the limited work available on this topic to date, it is not
possible at this time to determine the exact magnitude of this
increase, or whether there would even be an increase.
It should be noted that it is incorrect to assume that
ambient formaldehyde concentrations will increase proportionate
to any increase in formaldehyde emissions. This is at least in
part because an unknown amount of ambient formaldehyde is
formed by photooxidation of other organic emissions, and not
from direct emission of formaldehyde. The fraction which is
photochemical ly produced has been estimated to be 60 to 90
percent.[18] This issue is currently being investigated by
EPA's Office of Research and Development.
Furthermore, the effect of methanol vehicle substitution
on overall formaldehyde exposure will be even less dramatic
than on outdoor ambient formaldehyde concentrations. This is
because exposure to indoor sources of formaldehyde is very
significant compared to that due to outdoor sources. Typical
outdoor concentrations of formaldehyde are on the order of 10
ppb.[19] Typical indoor levels vary from 50 ppb for houses and
workplaces to over 1000 ppb for occupational exposure in
certain industries.[20] Given the large amount of time spent
in indoor environments, any potential increase in ambient
formaldehyde levels caused by methanol vehicles would represent
a much smaller increase in the overall risk represented by all
sources. Thus the question of equity regarding the relative
level of control desirable for all sources of formaldehyde,
including current mobile sources, becomes an important
concern. It would not be appropriate to address the cancer
risk of formaldehyde from methanol vehilces without allowing
the Agencywide task force on fromaldehyde, as mentioned
previously, to formulate and interpret results from a larger,
more comprehensive point of view. What can be concluded in the
light of the low expected market penetrating for methanol
vehicles is that, as GM noted, there is adequate time to assess
this issue before there is any significant increase in the
cancer risk due to formaldehyde from methanol vehilces.
As a final note, while it is true, as DOE noted, that
there is currently no NAAQS for formaldehyde, this does not
justify a decision not to regulate formaldehyde (or
formaldehyde precursor) emissions. EPA has the authority,
under Section 112 of the Clean Air Act, to regulate compounds
on the basis of cancer risk without an NAAQS.
Conclusion
Based on the available data, it appears that separate
standards for methanol or formaldehyde are not necessary at
this time to prevent adverse environmental impacts with respect
to either methanol or formaldehyde exposure. Nevertheless, the
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Agency should continue to investigate this concern to
accurately determine the potential effects of high penetration
levels of methanol vehicles into the fleet.
There does appear to be justification for some concern
about the impact of methanol vehicles on concentrations of
formaldehyde in public parking garages. However, because of a
very limited emission data base and questions about the
validity of the analytical model of the garage, there is a
significant concern that the analysis may be inaccurate, and
that no action would ever necessary. Therefore, it is
recommended that no additional action should be taken in this
rule, but that cold idle emissions and the garage modeling
itself be investigated further to ascertain the accuracy of the
current analysis. This approach does not endanger the public,
since the risk of exposure to toxic levels of formaldehyde in
public parking garages is not significant until there is a
substantial market penetration.
With regard to risk in personal garages, it is currently
widely acknowledged that idling a vehicle in a garage is an
unsafe practice, and thus formaldehyde and methanol exposures
from methanol vehicles would represent nothing new in this
regard. In addition, the odor and eye irritation from
formaldehyde exposure would discourage owners from idling their
vehicles in a personal garage, and serve as a warning of
impending excess CO exposure. Since vehicle owners can, and
should, voluntarily avoid the risks of exposure, additional
regulations are not called for. There are numerous emission
and modeling related uncertainties that call for resolution in
regard to this scenario, and EPA and industry should expend
effort to resolve them.
With regard to cancer risk due to increased ambient levels
of formaldehyde, not enough is known about the impact of
methanol vehicles on ambient concentrations to justify a
standard. Preliminary modeling, however, does suggest a
negligible impact, given existing outdoor levels due to current
mobile and other sources and overall levels of exposure due to
indoor concentrations.
The Agency should include methanol vehicle impacts in its
continued consideration of formaldehyde's cancer impacts, and
any mobile source-related studies in this area should consider
methanol and petroleum vehicle technology at the same time. It
would not, however, be appropriate to use this rule, intended
to establish a level playing field for methanol vehicles, to
regulate formaldehyde cancer risk from methanol vehicles alone.
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Issue: Optional Combined Exhaust and Evaporative Standards
Summary of the Issue
EPA discussed the possibility of creating an optional
combined exhaust and evaporative emission standard that would
allow increases in evaporative emissions to be offset by
decreases in exhaust emissions. Comments were specifically
requested concerning the expected size and associated value of
the increase in evaporative emissions that this alternative
would permit, the environmental risks that might accompany this
alternative, and methods for establishing a basis of
equivalency between exhaust and evaporative emissions. No
action was proposed.
Summary of Comments
Comments received on this issue fall into three areas:
those concerning the heavy-duty industry, those concerning the
light-duty industry, and those concerning the issue without
regard for any particular class of manufacturers or vehicles.
The comments from the heavy-duty industry (Caterpillar,
Cummins, and EMA) were in agreement that a combined standard
would not be appropriate for heavy-duty vehicles since the
industry is non-integrated (i.e., engines, from which exhaust
emissions emanate, and vehicles, from which much of the
evaporative emissions emanate, are manufactured separately).
They felt that a combined standard would, therefore, cause "an
unnecessary administrative burden."
Some of the commenters from the light-duty industry were
more supportive of the concept. Chrysler, Ford, and GM all
expressed moderate interest, though none of them were able to
provide any specific information concerning the expected
amounts of the offsets which might occur, or the value of the
option. GM stated that this program would cause no
environmental risks; Ford agreed, provided that photochemically
reactive exhaust emissions are not allowed to increase by
lowering less reactive evaporative emissions. GM also commented
that assuming the typical vehicle makes 3.05 trips and travels
31.1 miles per day (these numbers were presented by way of
example in the NPRM) would overestimate evaporative emissions.
Toyota was the only commenter from the light-duty industry that
did not support the option of a combined standard; they felt it
would not be cost effective to utilize this option because it
would require an increase in the number of evaporative tests
required per vehicle family.
Chevron opposed the concept of a combined standard in
general, citing environmental concerns. They stated "that
there are many unresolved questions about the proper
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characterization of vehicle evaporative emissions," and felt
that as a result,' establishment of an environmentally benign
equivalence between evaporative and exhaust emissions would be
difficult. For this reason, they suggested that the Agency
should deepen its understanding of evaporative emissions before
this type of regulation is undertaken.
Analysis of Comments
The Agency considered this option in the belief that it
might provide some measure of regulatory relief by enabling
manufacturers to decide the most cost-effective combination of
exhaust and evaporative emission controls to limit a vehicle's
total organic emissions. For example, this option could allow
the manufacturers to use smaller evaporative control systems
than would normally be required, provided that exhaust
emissions are sufficiently low. The comments received from the
heavy-duty engine industry, though, indicate that this option
would not be desirable to the industry. It is not obvious,
however, that implementation of such a program would cause any
significant administrative burden for non-integrated engine
manufacturers, since they are currently responsible for
evaporative certification, and since the program would be
optional.
Most comments from the light-duty industry did support the
option, but manufacturers were unable to provide any specific
estimates for the amount or associated value of the flexibility
this program would provide, making it difficult to judge the
program's potential benefits.
EPA remains concerned that the benefits of such a program
may be inconsequential since, as discussed in the NPRM, the
evaporative standards were designed to be non-fuel standards,
that is they were "intended to encourage manufacturers to focus
their efforts on eliminating fuel emissions." The two grams
per test allowance was implemented to account for background
sources of organics (such as interior materials or lubricants),
to accommodate some degree of test-to-test and
vehicle-to-vehicle variability, and to provide some compliance
cushion. This is supported by the fact that vehicles that
exceed the standard often exceed the standard by a very large
amount, because the canister becomes saturated and ceases to
effectively absorb the emissions. Thus, allowing slight
exceedances of the evaporative standard may have little
practical value, since slight exceedances rarely occur. The
lack of comments in this area, despite EPA's specific request,
suggests a lack of genuine interest in this type of program on
the part of the manufacturers and makes it difficult for the
Agency to proceed.
(I
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Toyota's concern that this alternative might be
disadvantageous if it resulted in a need for more evaporative
emission testing is noted; however the alternative need not be
used by any manufacturer who would be harmed by its application.
A more significant concern with this alternative is that,
as was acknowledged in the NPRM, EPA is not certain how to
reconcile light-duty vehicle exhaust and evaporative emissions
to a common basis for comparison, to ensure that there would be
no increase in total emissions. Since total evaporative
emissions are a function of driving patterns (hot soak
emissions occur after engine shutdown, thus the more trips per
day, the greater the expected evaporative emissions), these
patterns must be carefully accounted for in establishing an
equivalence between exhaust and evaporative emissions. The
method presented as an example in the NPRM was to combine the
emissions from the hot soak test (HS) with the emissions from
the diurnal test (DI) using the following formula:
emissions _ (trips per dayXHS) + (DI)
per mile (miles per day)
This approach, however, may not be appropriate because it
assumes that average emissions can be estimated with average
values for the number of trips per day and miles per day which
occur in use. Driving patterns can vary greatly from vehicle
to vehicle however. For example, some vehicles may not be
driven every day and would undergo repeated diurnals without
the canister being purged. Other vehicles operate continuously
during the diurnal period and thus the canister would generally
be well purged. While average values can be derived for the
relevant driving related parameters, it is not clear that they
would correctly weight the different emission levels associated
with different driving habits. Thus, an accurate assessment of
all typical driving patterns and their associated emissions
effects would be necessary in order to convert evaporative
emissions test data to in-use emission factors, EPA discussed
this issue in the NPRM and asked for input from the public, but
no commenter was able to provide data which could be used to
overcome the deficiencies in the current analysis.
Another concern in this regard relates to the fact that
the hot soak and diurnal tests might not be generally accurate
representations of actual in-use evaporative emissions. As
mentioned previously, the evaporative emission standards were
designed such that the majority of the emissions from vehicles
meeting their standards should be from non-fuel sources. These
emissions will typically change with age as background vehicle
organics "boil off" and lubricants and road sludge accumulate
on the vehicle surfaces. Additionally, hot soak and diurnal
emissions are affected by local climate and time of year; the
same is true for exhaust emissions, though to a differing
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degree. An equivalence established between evaporative and
exhaust emissions at FTP conditions, therefore, may not be
realist at other conditions. Given the limited amount of
methane vehicle emissions data available at FTP conditions
(much js at other conditions) and given that the gasoline
content which greatly affects evaporative emissions) of future
methane fuels is unknown, it is impossible to assess the
potenti for such errors at this time.
G^ comment that the example approach to establishing
equival cy that EPA gave in the NPRM would overstate
evapor* ve emissions seems to illustrate the uncertainties
discuss here but does not help to establish a more workable
exhaust vaporative comparison. Given the lack of data made
availal to the Agency, staff must agree with Chevron's
statenw that the issue of equivalency between exhaust and
evapor< ve emissions is still unresolved. This makes
applic< on of a combined standard in a manner that would
providt flexibility without the possibility of adverse
conseqi .ces to the environment very difficult.
F: .lly, the Agency has noted elsewhere that the goal of
this r emaking is to provide a "level playing field" for
metham vehicles. Promulgating a combined exhaust and
evapor; ve standard could have far reaching implications which
relate D other types of vehicles as well, and would be more
appropi .tely addressed separately at a point when better
inform; on on emissions tradeoffs is available.
Conclu! in
Tl concept of a combined exhaust and evaporative standard
did no receive strong support from the commenters in general.
While e comments from the light-duty industry were somewhat
suppor- 'e, the comments from the heavy-duty industry were all
oppose* to it. None of the manufacturers provided any
inform; .on which indicated that the benefits would be
signif int. In fact, some of them suggested there would be a
net co associated with them. Given the fact the evaporative
standa: ; were designed as non-fuel standards, it is not
obviou: that significant benefits from the program are even
possib Therefore since: 1) designing an appropriate
combim program would be very complicated, 2) the state of
knowlei > with respect to emissions modeling is not sufficient
to gi^ EPA confidence that negative environmental impacts
would i avoided with such a program, and 3) the present
rulema! ig was intended to establish a level playing field for
methan' vehicles, not to explore new regulatory concepts that
might >ly to all vehicle types, it is recommended that action
on thi :oncept be deferred at this time.
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Issue: Application of Particulate and Smoke Standards
Summary of the Issue
EPA proposed applying the current diesel particulate and
smoke standards to all non-throttled methanol engines. EPA
also asked for comments on the likelihood of heavy-duty
methanol engines automatically complying without the use of
trap oxidizers with the 0.60 g/BHP-hr particulate standard
which takes effect in 1988 and the 0.25 g/BHP-hr particulate
standard effective in 1991.
Summary of Comments
Mercedes Benz Truck Company (MBTC) disagreed with EPA's
engine classification scheme for applying smoke/particulate
standards to methanol engines. MBTC claimed that the
throttled/non-throttled differentiation is irrelevant to a
methanol engine's soot forming potential. Rather, the
important factor is the kind of lubrication used. MBTC notes
that so far particulates have been found in the emissions of a
two stroke, non-throttled methanol engine, and points out that
a two stroke throttled methanol engine might also emit higher
levels of particulate but under the proposed classification
scheme would not be subject to the particulate standard. MBTC
strongly supported EPA's proposal to allow for waivers of test
requirements wherever applicable.
Citing preliminary data, DOE commented that "the
by-products of lubricating oil combustion in a compression
ignition engine included a significant quantity of engine out
particulate matter," regardless of fuel type. Since
non-throttled methanol engines are derived from compression
ignition technology, DOE found the proposed standards
appropriate.
The state of New York stated that the
throttled/non-throttled distinction may be ambiguous. It noted
the Daimler-Benz OM 407 hGO methanol engine which uses a
throttle at low and medium load ranges but operates
non-throttled in the upper load range.
General Motors stated that, based on a few tests of its
light-duty methanol vehicles, particulate emissions should be
well below the proposed (for non-throttled vehicles) 0.20 g/mi
standard and that this standard is unnecessary.
With regard to heavy-duty engines, GM felt that their M100
methanol engines should have no problem complying with the 1988
and 1991 heavy-duty engine standards without any aftertreatment
(although they note that driveability testing has not been
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performed). They were less confident, however, about the
prospects for automatic compliance with the 0.10 g/BHP-hr
standard, proposed to apply to bus engines in 1991 and all
HDME's in 1994. GM's data on HDME' s fueled with M100 suggests
a possible range of uncontrolled particulate emissions from
0.12 to 0.22 g/BHP-hr. With catalytic aftertreatment, GM noted
that this level has been limited to 0.05 g/BHP-hr in one test.
Smoke levels were reported below 0.1 on the Bosch scale over
the 13-mode test.
GM noted that if M85 fuel becomes the fuel of choice for
heavy-duty methanol engines, they may not be able to comply
with 1988 and 1991 particulate standards as easily.
Caterpillar and EMA both argued that smoke levels ought to
be very low for methanol engines and that EPA ought to allow
for waivers of this standard in a fashion similar to that
allowed for current CO standards for HDDE's. Neither party
commented on the need for a particulate standard.
Analysis of Comments
In order to appropriately analyze the comments on this
issue it would be useful to review the logical context of EPA'"
proposed rules for particulate and smoke emissions fr
proposed rules for particulate and smoke emissions from
methanol engines. It has long been acknowledged that methanol
combustion produces lower particulate and smoke levels than
petroleum combustion in diesel engines. Recently promulgated
particulate and smoke standards, however, will lower emissions
combustion produces lower particulate and smoke
petroleum combustion in diesel engines. Recently ptwiuuxyai-eu
particulate and smoke standards, however, will lower emissions
from heavy-duty diesel engines to levels which are below the
measured emissions from at least one prototype methanol
engine. As long as the possibility exists for methanol engines
to emit particulate or smoke above the diesel standard, it
would be inappropriate to avoid limiting particulate emissions
on methanol engines. On the other hand, in developing its
proposed standards, the Agency wished to avoid unnecessarily
burdening manufacturers with *•=•-"'i *+-i~r,~ f*~ ,-,,~-; „„„ ^v.^<-
_, regulations for engines that
clearly would not emit at levels in excess of the diesel
standards. EPA's goal was to apply the diesel standards to
methanol-fueled vehicles with characteristics similar to those
nf ("Ml KfOnf Al ocol *raln I /i 1 do C/MTIQ i-> v -i •»- o*- i ;
of current
or current aiesei venicies. some criteria
needed by which engine type could be evaluated.*
were therefore
The discussion focuses on particulate emissions. The
potential for emission of smoke, which is not often
reported in the literature for methanol engines, is
assumed to be related to that for emissions of
particulate. The discussion recognizes that the absence
of smoke in engine exhaust does not necessarily imply the
absence of particulate matter.
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Particulate formation, in a practical sense, has been
considered a fuel related phenomenon. As general rule fuel oil
has been used in diesel (compression ignited, heterogeneous
fuel air mixtures) engines and gasoline has been used in
Otto-cycle (spark ignited, homogeneous charge) engines.
However, with the emergence of methanol as a fuel this
categorization breaks down. Methanol can be combusted in
engines derived from diesel engines, gasoline-fueled engines,
and engines which are hybrids of the two. Certain methanol
engines have demonstrated the potential to emit significant
levels of particulate; thus it became necessary to consider
engine parameters other than fuel type to apply particulate
standards.
One criterion considered as a possible basis for
predicting particulate formation potential for methanol engines
was method of ignition. Current diesel engines, with higher
particulate, are compression ignited, while gasoline engines
are spark ignited. With regard to neat methanol, compression
ignition has been difficult to achieve under the range of
possible operating conditions, and therefore ignition
assistance, such as use of spark or glow plugs has generally
been found necessary. (Cetane improvers can allow compression
ignition to occur but have been found less practical due to
their high cost.) For example, WAN's heavy-duty methanol
engine uses spark plugs as do the majority of all light-duty
methanol engines developed to date, while the GM Detroit Diesel
Allison (DDA) heavy-duty methanol engine uses glow plugs over
part of its operating cycle. The particulate emissions from
the MAN have been generally lower than the new diesel
standards, but those from the DDA have been higher, as is
confirmed by GM's comments. Particulate emissions from
light-duty engines have not been generally reported, although
GM states that its light-duty engines are very low emitters.
While the evidence summarized here suggests that spark
ignited methanol engines are low particulate emitters and
engines utilizing glow plugs over a portion of the normal
operating cycle are potentially higher particulate emitters,
the data are simply too empirical and far too limited to serve
as the basis for any sort of regulatory decision. A more
fundamental understanding of particulate formation potential
was therefore sought in order to develop criteria for
regulating methanol engines.
Particulate nucleation is thought to occur in localized
fuel rich areas of the combustion chamber. A series of
pyrolytic reactions rearranges the hydrocarbons into molecules
of lower molecular weight and level of hydrogen saturation.
Acetylene is apparently the last stable species present as a
result of this process. Acetylene reacts through
polymerization and continued branching to form polycyclic
hydrocarbon structures of high carbon/hydrogen ratio. These
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structures are thought to account for the crystalline nucleus
of the particulate matter.* Diesel combustion is generally
characterized by a fuel droplet distribution within the
chamber, enabling combustion to occur at numerous localized
sites more or less simultaneously as a result of the heat built
up through compression of the mixture. The outer layers of the
droplets combust properly, but the insides are carbon rich,
resulting in incomplete combustion (carbon combusts only at
temperatures above those achieved in the cylinder) and
facilitating the nucleation process discussed above. This
process is followed by agglomeration of carbonaceous and other
organic materials, resulting in particulate matter.
In contrast, Otto-cycle engines rely on a homogeneous
charge through which a flame front, initiated by a high energy
ignition source (spark plug), propagates. Since fuel air ratio
is fairly uniform and within the flammability limits almost
everywhere in the cylinder, particles do not form as readily.
The theory of nucleation suggests that the effectiveness
of the mechanisms which result in particulate formation
depends, at least in part, on the presence of hydrocarbon
chains in the fuel; methanol's simple chemical structure thus
deters particulate formation to some degree, although probably
not entirely, since the products of methanol combustion include
some hydrocarbons of higher molecular weight. Additionally,
the presence of lubricating oil, as MBTC and DOE point out, in
the combustion chamber, and the as yet unresolved question of
whether there will be any gasoline additive, as mentioned by
GM, all add to the engine's particulate formation potential by
providing hydrocarbon chains for the nucleation process. In
fact, the excess particulate emissions of the Detroit Diesel
Allison engine were ultimately attributed to the combustion of
oil which had been leaking past the seal between the piston
crown and skirt. A seal design change appears, to have
corrected this problem and reduced engine-out particulate
levels significantly, to the level of approximately 0.06
g/BHP-hr.**
Thus while combustion of pure methanol would probably,
according to nucleation theory, not result in particulate
levels of regulatory concern, combustion of methanol
Other theories exist to explain the nucleation phenomenon,
which, though less popular than the one discussed here,
also depend on the presence of hydrocarbon molecules of
higher molecular weight than methanol.
This information has become available in the time since GM
submitted its comments and thus is not discussed in those
comments. These data are available for review in the
rulemaking docket (number A-84-05).
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containing hydrocarbon chains (due to the presence of lube oil,
gasoline, or other fuel additives) might. This is especially
true when one considers such combustion in a heterogeneously
charged cylinder, which would contain numerous fuel rich sites
to facilitate nucleation, as occurs in the diesel engine. It
was for this reason that EPA selected the throttle criterion as
a basis for regulating methanol engine particulate and smoke
emissions, since the lack of a throttle implies that power will
be controlled by varying the fuel rate through injection, and
this is likely to result in fuel droplets or mist dispersion in
the cylinder, with the attendant possibility of particulate
formation.
DOE, which like MBTC, whose comment will be addressed
below, implicated lube oil combustion as a particulate
precursor, went further in its analysis to focus on lube oil
combustion in, specifically, a compression ignited (i.e.,
diesel type) engine. While, as will be discussed, it is
apparent that excess lube oil combustion in a throttled, or
Otto-cycle, engine may also cause elevated particulate levels,
DOE's comment seems to recognize EPA's logic and supports the
proposed action.
MBTC argued that since two stroke engines utilize more oil
than four stroke engines, they should be the focus of EPA's
regulations. Such a focus was seen to have two advantages; it
would prevent throttled two stroke methanol engines from
emitting excessive particulates, and would eliminate burdens
for non-throttled four stroke methanol engines. In regard to
the first point, higher oil consumption would indeed suggest
the possibility of increased particulate emissions, even in the
case of throttled (homogeneous charge) engines. This is aptly
demonstrated by the performance of older motorcycle engines
which were often of two-stroke cycle design and which were
noted for the smoky nature of their exhaust. Incomplete
combustion of lube oil, containing long chains of hydrocarbons,
in the oil mist that was inducted into the chamber resulted in
particulate formation, most likely according to a similar
mechanism to that in diesel engines from fuel droplets.
Additionally, it is anticipated that oil washed from the walls
by the high energy air induction stream characteristic of two
stroke engines may result in particulate formation in the fuel
rich quench zones near walls and in crevices. This sort of
gasoline engine is too rare now within regulated classes of
vehicles to warrant present consideration of particulate
standards. Nevertheless, methanol engine regulations developed
on the basis of particulate formation potential, as discussed
previously, ought probably in the broadest sense take into
consideration the particulate formation potential of two stroke
methanol engines as well. It is however, noted that there is
no apparent effort underway to develop or commercialize a two
stroke throttled methanol engine. Thus promulgation of
standards applicable to these engines would be premature at
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present. Additionally, the premise of this rulemaking is to
create a level playing field for methanol engines. Therefore
it is noted that consideration of standards applicable to all
two-stroke methanol engines ought only occur concurrent with
consideration of such standards for two-stroke gasoline engines
in a separate rule.
Regarding the second point, there is simply not enough
data to show conclusively that all non-throttled four stroke
methanol engines will not have lube oil combustion, and/or
combustion of other fuel additives sufficient to cause
significant particulate emissions. (These factors are known to
contribute to particulate formation even in today's four stroke
diesels.) The proposal recognized that the possibility exists
that some non-throttled engines may not emit particulate at
levels exceeding the standard without any aftertreatment and
that, as Caterpillar and EMA pointed out, smoke levels may not
be significant for any methanol engine. Unfortunately,
however, at least until it becomes clear which type of methanol
engines are practical in the marketplace, and whether actual
particulate emissions are in line with what the theory
discussed here suggests they should be, it is important for EPA
to regulate on the basis of emission potential, including a
consideration of what types of engines appear practical market
contenders. Any engine which falls into a regulated category
but which proves to be a low emitter of particulate or smoke
would be able to use the waiver process to avoid a testing
requirement. This process, supported by several commenters and
opposed by none, is a very simple one as it applies currently
to diesel engine CO emission testing. It should be just as
simple and nonburdensome in the case of methanol engine smoke
and particulate testing.
In response to the State of New York's comment about the
Daimler-Benz engine, an engine which is non-throttled during a
significant portion of its duty cycle, such that potenital for
significant particulate emissions exists, would have to be
considered a non-throttled engine for purposes of this
regulation.
The comments by DOE, MBTC, and New York point out that
while the throttle criterion is appropriate at this time, it
may not be complete. To guard against the possibility that
developments in emerging methanol technology that may be
unforeseen today result in engine characteristics for which the
throttle criterion is insufficient, the Administrator should be
provided with the flexibility to consider other engine
parameters to determine the applicability of the existing
gasoline (Otto-cycle) or diesel standards: While the throttle
criterion is expected to be important one, other
characteristics such as intended in-use duty cycle, engine
thermodynamics, and compression ratio may also be important and
the Administrator should be able to use them in making the
classification.
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GM was the only commenter to address the feasibility of
the proposed standards, and they found that, at worst, a
catalytic converter might be necessary to ensure compliance
with the most stringent standard, that applicable to 1994
heavy-duty engines and 1991 bus engines. Since catalytic
converters are an established technology and are acknowledged
to be a less expensive technology than particulate trap
oxidizers (which diesel engines may need in order to comply),
the standards are economically reasonable.
Conclusions
The limited data on particulate and smoke emissions from
methanol engines, taken together with particulate formation
theory, indicate that the conditions necessary to form
particulate are extant in the combustion process of
non-throttled engines. Thus, at this time, it is appropriate
to focus on the non-use of a throttle to apply the current
diesel standards to methanol-fueled engines. It is noted that,
for any regulated engine which proves to be a low emitter, the
process EPA proposed for obtaining a waiver from testing would
be a simple one. The proposed standards are feasible and
control costs should be no more than those of current diesels.
The analysis also suggests, however,that EPA should
broaden its approach to application of current standards to
allow for the future consideration of engine parameters other
than the use of a throttle. The Administrator should retain
the flexibility to consider other engine characteristics to
determine if a methanol-fueled engine would have emissions more
similar to current diesels or to current Otto-cycle engines.
Further, all references in the proposed rule to throttled and
non-throttled methanol engines should be altered to use the
more general Otto-cycle and diesel nomenclature.
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Issue: CO and NOx Standards
Summary of the Issue
The Agency proposed applying current gasoline-fueled
standards for CO and NOx to throttled methanol vehicles, and
current diesel standards to non-throttled vehicles. EPA also
proposed idle CO standards for all methanol-fueled light-duty
trucks and heavy-duty engines, though the current idle CO
standard applies to gasoline-fueled light-duty trucks and
heavy-duty engines only. This was done to account for methanol
vehicles that are non-throttled over much of their normal
operating range, but throttled at idle. EPA mentioned that
manufacturers of engines that are expected to always remain
below the level of the idle CO standard would be able to apply
for a waiver to avoid testing (this is currently done with the
CO standard for heavy-duty diesel engines). For clarification,
such a waiver only relieves the manufacturer from undergoing
certification tests, it does remove liability for complying
with the standard. The issue is whether the Agency's approach
in setting CO and NOx standards is appropriate.
Summary of the Comments
The Agency received comments from Caterpillar and Chevron,
which were generally supportive of the CO and NOx standards
proposed for methanol vehicles. With regard to the proposed
standards for throttled methanol engines DOE specifically
stated that available data indicate:
"that methanol vehicles have little or no difficulty
complying with current exhaust standards for CO and NOx if
they are equipped with the same emission control systems
as certified gasoline-engine vehicles."
No commenter beside MAN specifically discussed the
feasibility or appropriateness of the standards for
non-throttled engines. MAN suggested standards of 7.5 g/BHP-hr
be adopted for heavy-duty methanol engines for the transition
period between 1988 and 1991. They stated that it appears that
spark-ignition methanol engines with turbochargers and
intercoolers will be capable of meeting the proposed NOx
limits. They argued that fuel economy would suffer if NOx
emissions are reduced to 6.0 or 5.0 g/BHP-hr as was proposed
for 1988 and 1991, respectively, and that this would delay the
acceptance of methanol engines.
EPA received only one comment opposing the approach taken
to setting idle standards. Ford stated that it was not
necessary to have an idle CO standard for methanol-fueled
vehicles that are non-throttled at idle. They felt it would be
more appropriate to have a standard only for vehicles that are
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throttled at idle, than to "arbitrarily set standards which
then put a burden on the manufacturer to either comply or apply
for a waiver."
Analysis of Comments
As was discussed in the previous section, the two types of
methanol engines may be more appropriately referred to as
Otto-cycle and diesel, instead of throttled and non-throttled.
That so few comments were received in regard to EPA's
proposed CO and NOx standards is interpreted as an indication
that the proposals were generally reasonable and that EPA's use
of the throttle criterion as the basis for application of
diesel and gasoline standards is appropriate. The support of
Caterpillar, Chevron, and DOE for the proposed emission
standards is noted.
Since it is EPA's goal to create a "level playing field",
there is no reason to create special benefits for methanol
engines by decreasing the stringency of their NOx standard as
MAN suggested. Since methanol's flame temperature, which is
less than that of gasoline or diesel oil, inherently limits NOx
formation to lower concentrations, staff is confident that
methanol engines will be able to comply with the 6.0 g/BHP-hr
(1990 model year) and 5.0 g/BHP-hr (1991 and later model years)
standards at least as easily as current gasoline-fueled and
diesel engines will. Thus, the acceptance of methanol vehicles
will not be affected by promulgation of equivalent NOx
standards.
The Agency chose to propose idle CO standards for all
(both Otto-cycle and diesel) methanol-fueled light-duty trucks
and heavy-duty engines to ensure that none of these methanol
engines emit high levels of CO at idle. It was concluded that
this would not place any significant burden on manufacturers
since they would be allowed to apply for a waiver from testing
if an engine type was expected to not have significant CO
emissions at idle. Ford's argument, that since EPA's primary
concern is to ensure that engines throttled at idle are subject
to CO testing then standards should apply only to those
engines, is noted. The proposed approach will accomplish this
and will additionally ensure that no other engine emits
potentially harmful levels of CO at idle. This approach
recognizes the fact that methanol vehicles are a new
technology, and EPA has an incomplete understanding of
emissions performance of all methanol engine designs. Given
this, it seems prudent to apply the standards as proposed where
testing is not necessary because levels are anticipated to be
low, a waiver would be available. Ford, however, argued that
application for a waiver to the idle CO standard would be a
burden to the manufacturer. Staff does not consider the
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application process to be a significant burden to the
manufacturer; waiver applications are easily and routinely
processed with regard to the diesel engine CO standard today.
Thus there is no reason to change the proposed standards.
Conclusion
The CO and NOx standards proposed to apply over the
transient engine dynamometer test cycles for heavy-duty engines
and the chassis dynamometer test cycles for light-duty vehicles
and trucks are equivalent in stringency to those for gasoline
and diesel engines, vehicles, and trucks and should not cause
any unnecessary burden for manufacturers.
With respect to the idle CO standards, it is concluded
that the proposed standards will not create any significant
burden to manufacturers of methanol-fueled diesel engines, and
that in the general absence of data showing negligible CO
emissions from these engines, the most prudent approach is to
promulgate idle standards for all methanol engines.
Therefore, it is recommended that all CO and NOx standards
be promulgated as proposed, with slight language change
regarding engine type (i.e., Otto-cycle ands diesel).
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Issue: Control of Crankcase Emissions From Heavy-Duty Engines
Crankcase emissions are currently not allowed from any
heavy-duty engine or vehicle, except for diesel engines using
turbochargers, pumps, blowers, or superchargers for air
induction (i.e., non-naturally aspirated diesel engines).
Under the proposed methanol regulations no crankcase emissions
would be allowed for any methanol-fueled vehicle or engine,
including non-naturally aspirated non-throttled heavy-duty
engines. EPA proposed classifying methanol engines into
throttled (gasoline-like) and non-throttled (diesel-like)
categories in order to apply particulate and heavy-duty HC and
CO standards. Some manufacturers of heavy-duty engines
therefore felt that a universal prohibition of crankcase
emissions from non-throttled methanol engines represented an
extension of control beyond current requirements. At issue,
therefore, is whether it is appropriate to restrict crankcase
emissions from non-naturally aspirated, non-throttled,
heavy-duty methanol engines.
Summary of Comments
EPA received comments from Caterpillar, EMA, and GM all of
whom opposed control of crankcase emissions from non-naturally
aspirated, non-throttled, heavy-duty methanol engines. They
argued that crankcase controls are not currently required for
non-naturally aspirated heavy-duty diesel engines because
crankcase emissions from these diesels are insignificant
compared to the associated cost of control. In support of this
position Caterpillar discussed the combustion and scavenging
process in non-throttled engines to show why crankcase
emissions can be expected to be low. The manufacturers
referred to a 1979 analysis and a 1983 analysis (which referred
to the 1979 analysis) by EPA staff[21,22] which showed that it
was not cost effective to control these emissions.
The commenters argued implicitly that the cost of
controlling non-throttled methanol engines would be the same as
for diesels because of similar emissions characteristics and
required control technology. Control on a turbocharged engine
for example would require a pump to route the crankcase gas
either into the exhaust in front of a catalyst, or into the
intake manifold after a turbocharger. The manufacturers felt
that these pumps would be prohibitively expensive. Routing the
gases into the turbocharger would result in fouling due to oil
mist, which would cause maintenance problems and associated
high costs, and therefore should not be a regulatory option.
The commenters presented no emissions or cost data on either
diesel or methanol engines with which the 1979 study could be
updated or extended to methanol engines.
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Analysis of Comments
The commenters based their argument, that crankcase
emissions should not be controlled for non-naturally aspirated,
non-throttled (diesel), heavy-duty methanol engines because it
would be unnecessarily expensive, on EPA's 1979 analysis
relating to diesel engines. The commenters claimed that this
analysis is also valid for non-throttled methanol engines, but
did not provide any new emissions data or cost estimates to
justify this.
The previous f analysis, however, is not applicable to
methanol engines. It is expected that control costs for
methanol-fueled diesel engines will be much lower than the
estimated cost used in the original analysis of diesel control
cost, for several reasons. First, methanol-fueled diesels are
expected to have lower particulate emissions than
petroleum-fueled diesels, and thus blow-by gases should be
cleaner, easier to filter, and less of a concern with respect
to turbocharger fouling. Because of these low levels of
particulates, it may be more appropriate to compare crankcase
engines to crankcase emissions from
have been routinely routed through
A similar control technology could be
engine configuration, including those
or superchargers. Therefore, it is
control costs of non-naturally aspirated
methanol-fueled diesel engines would be similar to those of
turbocharged gasoline engines, whose control costs are much
lower than those of petroleum-fueled diesels.
.t
emissions from methanol
gasoline engines which
turbochargers for years.
applied to any methanol
using pumps, blowers,
likely that
Second, the earlier analysis is outdated and represents a
worst-case cost effectiveness for petroleum-fueled diesels.
Since the time the analysis was done, two manufacturers
(Daimler-Benz and Isuzu) have begun voluntarily controlling
crankcase emissions from turbocharged diesel engines by routing
the emissions through an oil separator, and into the
turbocharger. Actual control costs for the Daimler-Benz engine
are much lower than EPA's 1979 estimate of $100 (1979
dollars).[23] Admittedly the estimate EPA received was for the
cost of controls for one engine model and may not be
representative of costs for heavy duty engines in general.
However, if even only a moderate rate of inflation is applied
to the 1979 estimate, it seems likely that current costs would
on average be lower than those EPA estimated in the earlier
analysis. Thus, even if the petroleum-fueled
diesel/methanol-fueled diesel comparison were valid, the 1979
analysis would still not be applicable.
Finally, the validity of the 1979 analysis with respect to
this rulemaking is questionable because since that time the
Agency has found it necessary to consider progressively more
costly VOC control programs to bring U.S. cities into
attainment with the ambient ozone standard. Thus, what was not
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considered to be cost effective in L979 could be cost effective
today. In fact, given current air quality priorities the
Agency could eventually decide to reconsider its earlier
decision to allow non-naturally aspirated petroleum-fueled
diesel engines to emit crankcase gases.
An additional point, which was not mentioned in the
comments, is EPA's concern about emissions of nitrosamines,
which are known carcinogens, formed by reaction of amines in
the lubrication oil with oxides of nitrogen. Nitrosamines were
noted as a health concern in the 1979 analysis. Since then it
has been shown that significant amounts of nitrosamines are
found in the crankcase emissions of petroleum-fueled diesel
engines. [24] It is highly likely that they are also present in
methanol crankcase emissions (because the same basic formation
circumstances exist regardless of the fuel type), though
possibly at lower concentrations due to the lower NOx emissions
expected with methanol-fueled engines. Control of crankcase
emissions would essentially eliminate emissions of nitrosamines.
Conclusion
Crankcase emissions from methanol-fueled diesel engines
can potentially represent a significant source of organics,
carbon monoxide, oxides of nitrogen, and nitrosamines; thus,
closing the crankcase would provide significant environmental
benefits. The argument that controlling crankcase emissions
from non-naturally aspirated methanol-fueled heavy-duty engines
will be as expensive as controlling crankcase emissions from
petroleum-fueled diesels is not valid. The control technology
for methanol-fueled diesels should be simpler than for
petroleum-fueled diesels because of lower particulate emissions
and costs will likely be more like those for gasoline engines.
Therefore, it is recommended those no crankcase emissions be
allowed from any methanol engine, as was proposed.
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Issue: Emissions Averaging Programs
As noted in the ANPRM, EPA originally considered allowing
manufacturers the option of including methane1-fueled diesel
vehicles and petroleum-fueled diesel vehicles within a single
combined particulate averaging program. Several comraenters to
the ANPRM noted, however, that methanol-fueled diesel vehicles
might not compete directly with petroleum-fueled diesel
vehicles, and that including methanol vehicles within the
averaging programs could therefore result in an overall
increase in particulate emissions. EPA decided not to propose
this option in the NPRM but requested comments on the
likelihood of direct market competition between methanol-fueled
diesels and petroleum-fueled diesels, and the desirability of
including methanol-fueled diesels with petroleum-fueled diesels
in a combined particulate averaging program.
Summary of Comments
The Agency received three comments on this issue. GM
supported inter-fuel averaging, but both Caterpillar and
Cummins felt that such averaging should not be allowed.
GM felt that averaging should be allowed between different
fuel types as an incentive to produce methanol engines.
However, they did maintain that if fuel prices remain as they
are now, it would be unlikely that methanol HDEs would compete
directly with diesels, except for urban bus engines. GM stated
that they did not believe that an adequate trap system would be
developed in time to meet the 0.10 g/BHP-hr standard for buses
in 1991, and that use of methanol engines will be required to
meet the standard. They argued that providing for averaging
across fuels for bus engines would allow areas without
particulate problems to purchase less expensive diesel buses
(which would be unable to meet the standard), while areas with
particulate problems could be required to purchase
methanol-fueled buses or diesel buses with traps in order to
receive operating subsidies from the Federal government. They
also stated that because of the stringency of the 1991
standard, a substantial number of methanol buses would have to
be produced to provide averaging credits sufficient to allow
production of a single diesel bus without a particulate trap.
Caterpillar and Cummins argued that it would not be
possible to predict direct competition between methanol engines
and diesels. Cummins agreed with EPA that without direct
competition, inter-fuel averaging could result in increased
particulate levels. Additionally, Caterpillar argued that
averaging between different fuel types would give an unfair
advantage to manufacturers of smaller urban type engines, since
methanol will be more available in urban areas initially.
Therefore, they felt that averaging should be allowed only
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after methanol is readily available in both urban and non-urban
areas. Similarly, Cummins argued that inter-fuel averaging
would create inequities for manufacturers who do not produce
many methanol-fueled vehicles.
Analysis of Comments
The position of both Caterpillar and Cummins that allowing
averaging between the fuel types could give an initial
advantage to manufacturers that produce methanol engines or
small urban engines may be valid. However, it is not
necessarily true that providing regulatory flexibility, which
might be more advantageous for some manufacturers than others,
would be anti-competitive. The Agency's main concern regarding
such averaging is the possible air quality degradation that
could result if methanol engines did not compete directly with
diesel engines.
This problem was discussed in the Regulatory Support
Document to the NPRM, where a detailed analysis was presented
for light-duty vehicles. This analysis showed that unless
methanol and diesel vehicles compete directly, particulate
emissions could be greatly increased. For example, in one
scenario it assumed that 200,000 light-duty methanol vehicles
are produced and included in the averaging program, but that
only 30,000 replace petroleum-fueled diesels (out of 60,000
light-duty petroleum-fueled diesel vehicles), while the rest
replace gasoline vehicles. The analysis showed that light-duty
particulate emissions would double if averaging were allowed.
The analysis simplistically assumed methanol engines emit no
particulate; however the conclusions remain directionally valid
even if, as is now known to be possible, methanol vehicles do
emit a small amount of particulate. On the other hand, if
methanol-fueled diesels and petroleum-fueled diesels did
compete well, then total particulate emissions would not
increase because each methanol-fueled diesel produced would
replace a petroleum-fueled diesel, and the total number of
vehicles averaged would not increase. This analysis can be
easily extended to heavy-duty engines to show that unless
heavy-duty methanol-fueled diesel engines compete directly with
petroleum-fueled diesel engines, allowing cross-fuel averaging
could lead to increased particulate levels. In summary, if
methanol engines or vehicles which replaced gasoline engines or
vehicles were allowed to be averaged with petroleum-fueled
diesels, then particulate emissions would increase.
It was stated in the NPRM that it is "impossible to
predict with any certainty the degree to which the two vehicle
types will be competitors." However, this early analysis was
somewhat limited in scope. Since publication of the NPRM, the
Agency has to reconsidered its approach to regulating all
heavy-duty engines, including methanol engines. There is now
reason to believe that it may be possible to develop an
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integrated program allowing cross-fuel averaging in some cases
as well as some form of banking and trading of emission credits
among manufacturers. Because the scope of such a program is
clearly beyond that of this action, it is more appropriate for
this issue to be addressed in a separate action. EPA is, in
fact, already doing so, and therefore, complete analysis of the
comments received will be deferred to that action.
Conclusion
Since the issue of cross-fuel averaging is much broader in
scope than this rulemaking, it would be inappropriate to
address it here. Analysis of the comments should be deferred
to a separate action. There is no apparent reason, however,
not to allow averaging within classes of methanol engines, as
is currently allowed for diesels, and as was proposed in the
NPRM for this regulatory action.
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Issue: Determination of Fuel Equivalency
EPA originally discussed, in the ANPRM, alternative
approaches to determining a fuel equivalency factor (FEF) for
methanol, to be used in connection with the Gas Guzzler and
Corporate Average Fuel Economy (CAFE) programs. However, it
was determined in the NPRM that establishment of such an
equivalency factor would be premature prior to a discretionary
decision by the Secretary of the Treasury, in the case of Gas
Guzzler, or the Secretary of Transportation, with reference to
CAFE, to include methanol in their respective programs. Since
neither Secretary had taken this action, EPA proposed no action
in this regard in the NPRM.
Summary of Comments
Several commenters {Ford, GM, Chrysler, CARB, Nissan and
NADA) felt that EPA should pursue the issue of an FEF further.
In general, the reasons given were that establishment of an
FEF, and inclusion of methanol in the CAFE and Gas Guzzler
programs, could provide an incentive for production of methanol
vehicles through CAFE and Gas Guzzler credits. Conversely,
failure to establish an equivalency would be an impediment to
production of methanol vehicles, due to uncertainty among
manufacturers as to how or if methanol will be included in
these programs.
Ford noted that the type of methanol vehicle produced
would depend on how methanol is handled with respect to CAFE
and Gas Guzzler. If methanol were excluded from CAFE and Gas
Guzzler, it would be beneficial to produce large methanol
vehicles instead of smaller, more fuel efficient vehicles.
This is because removing fuel efficient vehicles from a CAFE
calculation (by substitution of a methanol vehicle) would lower
a manufacturer's CAFE, while excluding less efficient vehicles
would raise it. If a petroleum-based FEF were used, then
production of all methanol vehicle types would be encouraged
since methanol vehicles use very little gasoline, and
production of any model, regardless of its fuel efficiency,
would boost a manufacturers CAFE. If, however, methanol
vehicles were included in CAFE and Gas Guzzler based on the
measured methanol fuel economy, then there would be a
disincentive to produce any methanol vehicles, since the lower
energy content of methanol results in lower per gallon fuel
economy for a methanol vehicle than an equivalent gasoline
vehicle.
Ford suggested that EPA establish fuel equivalency on the
basis of the petroleum content of the fuel only, because the
CAFE and Gas Guzzler programs "were established with the
intention of reducing petroleum usage," Ford referred to
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Congress' handling of electric vehicles, noting especially the
1980 Chrysler Corporation Loan Guarantee Bill which stated that
the fuel economy of electric vehicles, for CAFE purposes,
should be based only on the estimated petroleum used in
generating the electrical energy used by the vehicle. Ford
also stated that manufacturers will need cost incentives to
offset the higher costs of production of methanol vehicles, and
also to offset the potential higher operating costs and limited
resale value for methanol vehicles. Such an incentive could be
provided by establishing a petroleum-based fuel equivalency
in CAFE credits. Under Ford's
example, a vehicle which achieved
on an 85 percent methanol, 15
would have a fuel economy of 67
equivalent to ten miles per .15
factor, which would result
petroleum based approach, for
ten miles per gallon (mpg)
percent gasoline fuel (M85)
miles per gallon. This is
gallon of gasoline.
GM also approved of a petroleum-based fuel equivalency,
but felt that use of an interim zero gallon/mile basis of
inclusion would provide a useful production incentive. The
zero gallon/mile basis implies that methanol vehicles use an
equivalent of zero gallons of gasoline per mile regardless of
whether any gasoline is actually present in the fuel. GM
estimates that if a manufacturer initially produces 4,500,000
gasoline-fueled vehicles with a CAFE of 26.5 mpg and replaces
20,000 average vehicles with methanol-fueled vehicles (getting
20 miles per gallon on M85), then a petroleum-based equivalency
would effectively increase CAFE by 0.095 mpg, and a zero
gallon/mile basis would increase it by 0.112 mpg.
Chrysler noted that since a vehicle's fuel economy and
emissions are related, it is necessary to know the regulatory
requirements for fuel economy in order to optimize both fuel
economy and emissions performance. They stated that this
uncertainty regarding the regulatory treatment of methanol fuel
economy has already hindered their methanol vehicle development
program. Chrysler favored a fuel equivalency based on energy
content of the fuel "to assure the most economical allocation
of resources."
CARS and Nissan both recommended establishing an FEF, but
did not support a particular approach. CARB stated that action
by EPA would not create an incentive without action by the
Department of Transportation (DOT) and/or the Treasury, but
that without EPA action a potential impediment would exist.
Nissan felt that establishment of a fuel equivalency factor
would promote research and development of methanol-fueled
vehicles.
Finally, NADA encouraged EPA to pursue dialogue with the
Treasury and DOT concerning fuel equivalency.
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Analysis of Comments
Staff believes that inclusion of methanol vehicles into
these programs could provide an economic incentive for
manufacturers to produce methanol vehicles if a petroleum based
fuel equivalency were used, as was suggested by Ford and GM.
The incentive would be slightly greater if a zero gallon/mile
basis was used, as GM suggested, on an interim basis. However,
if the fuel equivalency were based on energy content of the
fuel, as was suggested by Chrysler, then it is likely that
there would be no significant economic incentive or
disincentive since producing a given vehicle to run on methanol
or on gasoline would have a roughly equivalent impact on CAFE.
(Admittedly, methanol engines will likely be more efficient
than gasoline engines, and thus there may still be some small
CAFE advantage, under this approach, to producing a methanol
vehicle over a similar gasoline vehicle.) Finally, staff agrees
with Ford that exclusion of methanol vehicles from CAFE will
favor production of larger methanol engines, since it would
remove less fuel efficient gasoline vehicles from CAFE
calculations. It is further recognized that inclusion under
any of these approaches has implications for energy policy in
that the petroleum-based equivalency favors conservation of
petroleum resources, where as an energy-based equivalency
values methanol and petroleum equally as conservable resources.
The issue of whether a fuel equivalency factor should be
based on the petroleum content to conserve petroleum, or on
energy content to conserve energy resources in general is very
important. From reviewing the comments, it is obvious that
there is no public consensus on which approach is superior at
present. This issue clearly must be resolved, taking into
consideration all relevant statutory language, before an FEF
can be developed.
More importantly though, staff believes that present
action by EPA, irrespective of the approach used, will not
provide any incentive or disincentive to produce methanol
vehicles unless the Department of Transportation or the
Treasury acts to include methanol in their respective
programs. Nor will it allow manufacturers, as Chrysler has
suggested, to optimize their design strategies to a greater
degree than they can at present. Admittedly, the absence of an
established position on inclusion of methanol vehicles into
such programs creates uncertainty for manufacturers. This
uncertainty could affect how methanol vehicle development
programs will be operated and what types of vehicles are
developed. However, it is not obvious that action by EPA alone
would eliminate this uncertainty, since DOT and the Treasury
have not yet acted (and may never act) to include methanol in
their respective programs. (In fact, EPA's choice of one fuel
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equivalency factor over another might influence the decision
whether or not to include methanol.) As a result, present
action will not remove any regulatory uncertainty from the
minds of key decision makers in the automotive industry. If
and when methanol were included in the various fuel economy
programs, it would become appropriate for EPA to initiate
action to establish a fuel equivalency factor.
NADA's suggestion that EPA pursue dialogue with DOT and
the treasury on this issue is appreciated and staff believes
that EPA should remain open to such dialogue.
Conclusions
The points raised by the commenters are generally valid.
However, staff believes that EPA's statement in the NPRM also
remains valid:
"To date, neither DOT nor the Treasury have
determined that methanol should be included under the
respective programs. EPA therefore believes that
determining a fuel equivalency between methanol and
gasoline would be premature at present. If and when
methanol were included in either program, EPA would
initiate action to establish such an equivalency."
It would be premature to act at this time because action
by EPA alone would not create an incentive or eliminate
uncertainty for manufacturers. Therefore, it is recommended
that EPA take no further action in this regard with the present
rulemaking.
EPA should remain open to dialogue with other federal
agencies on the question of including methanol in the CAFE and
Gas Guzzler programs, and should be prepared to initiate action
to establish an FEF following a decision on the part of either
the Secretary of Transportation or the Secretary of the
Treasury to include methanol in either program.
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Issue: Certification of Flexible Fuel Vehicles*
Summary of the Issue
Since flexible fuel vehicles (FFVs) are designed to
operate on any mixture of gasoline and. methanol, EPA proposed
requiring manufacturers to "demonstrate compliance with
applicable standards when tested on any of those fuels."
Comments were requested on the appropriateness of this
approach. Comments were also requested on any other aspect of
this rulemaking which may be affected by the sale of FFVs.
Summary of the Comments
No cotnmenter argued against EPA's philosophy that FFVs
need to be capable of meeting standards on fuels they encounter
in-use. Most of the commenters were concerned that EPA's
proposed approach to certifying FFVs would require tests on a
range of certification fuel mixtures and felt that this would
be burdensome and unnecessarily complicated.
A variety of possible alternative approaches were provided
in the comments. Ford suggested that EPA should require
certification testing and mileage accumulation on only one fuel
determined by EPA for each vehicle at the time of testing.
Ford also argued that it is not necessary to test vehicles with
intermediate mixtures between methanol and gasoline, because
owners would habitually use one fuel.
DOE also felt that FFVs should only be tested on one fuel
but did not believe testing should be limited to gasoline or
methanol only. They felt EPA should specify the fuel mixture
following a manufacturer's request for certification.
Chrysler felt that FFVs should be tested on both methanol
and gasoline to ensure that the vehicles are not optimized for
only one of the extremes of possible fuels. GM, however,
suggested that initially testing should be required on gasoline
only, since it will be the predominant fuel choice in the near
future, then on both methanol and gasoline once methanol
becomes readily available to the public.
Chevron felt that, in addition to testing on both methanol
and gasoline, it is necessary to test FFVs on intermediate
mixtures. They were especially concerned about evaporative
emissions in this regard since methanol-gasoline mixtures can
have higher vapor pressures (and hence higher resultant
emissions) than either methanol or gasoline separately.
Flexible fuel vehicles are also referred to as multi-fuel
vehicles, dual-fuel vehicles, variable-fuel vehicles, etc.
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There were three other concerns that were not directly
related to certification fuel specification. First, the state
of New York felt that the NPRM did not clearly state which
standards (methanol vehicle or gasoline vehicle) would be
applicable when a vehicle is operating on a fuel mixture that
contains less than 50 percent methanol, which could commonly
occur in use. Next, Toyota expressed concern that the proposed
regulations might be interpreted to mean that vehicles designed
to accept low-level methanol blends would be considered
multi-fueled vehicles and thus would be more difficult to
certify. Finally, Ford was concerned about how FFVs would be
treated with respect to fuel economy and labeling. They
suggested that a single petroleum equivalency factor (PEF),
based on the actual amount of petroleum expected to be used by
the vehicles should be established for use in the CAFE and Gas
Guzzler programs. They also felt that while both methanol and
gasoline fuel economy estimates should be available to the
consumer via the labeling program, the two estimates should not
be compared to one another, but instead to typical ranges for
vehicles in the same class.
Analysis of the Comments
The Agency stated in the NPRM that it expects FFVs to be
able to demonstrate compliance on any mixture of methanol and
gasoline that could be used in the field and no commenters
explicitly argued against this concept. To ensure that this
occurs for each vehicle, it is necessary that at a minimum the
certification test be performed on the worst case fuels (for
both exhaust and evaporative tests, which could necessitate use
of different fuels for exhaust and evaporative testing,)
because as Chrysler implied, vehicles will probably be
optimized for the fuel(s) they are to be tested on. For
similar reasons, it is also necessary to use a worst case fuel
for mileage accumulation.
The alternatives suggested by Ford, GM, and Chrysler,
which require use of only methanol and/or gasoline, will not
necessarily ensure use of the worst case fuel for certification
purposes. This is especially true for evaporative emissions
because of the effects of gasoline/methanol mixtures on fuel
volatility, as noted by Chevron. Chevron was referring to the
fact that a few percent methanol added to gasoline raises the
fuel's volatility dramatically. This volatility tends to
remain above that for pure gasoline until a substantial amount
of methanol (50 to 70 percent) has been added. Since
evaporative emissions are correlated with volatility, it is
likely that the worst case fuel, for evaporative testing
purposes, is an intermediate blend. Ford stated that owners
will generally use one fuel extreme or the other, and that
testing on intermediate mixtures is not necessary; however it
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would be difficult to prove the premise of Ford's argument,
especially given the vagarious nature of the fuel market over
the last 15 years. EPA must continue to assert that as long as
operation on intermediate blends is a reasonable possibility,
FFVs should be capable of meeting standards when fueled by such
blends. Chevron's suggestion, testing on gasoline, methanol,
and intermediate blends, would be environmentally prudent,
though it would require several certification tests per vehicle
and this increased testing burden might be a disincentive to
produce FFVs. Since it is the Agency's goal in this rulemaking
to remove impediments to the development of methanol vehicles,
this alternative is inappropriate.
The alternative mentioned by DOE, using only one fuel mix
specified by EPA at the time of the certification test, would
allow vehicles to demonstrate compliance over the range of
fuels, without increasing the number of certification tests
from that necessary for gasoline vehicles. This approach is
appropriate, though a slight modification would be useful.
Under this modified approach the manufacturer would recommend a
specification, for Adminisrator approval, of whichever mixture
of fuels (of those which could occur in use) would produce the
highest emissions. This modification is useful because the
manufacturers will likely be more familiar than the Agency with
the specific emissions characteristics of each vehicle. This
approach would not relieve the manufacturer of his liability to
meet the standards on any potential in-use mixture. EPA would
retain the right to use any representative in-use mixture for
its own certification and recall testing.
The state of New York felt that the NPRM did not clearly
indicate which standards would be applicable to an FFV
operating on a fuel with less than 50 percent methanol.
However, it is stated in the NPRM that:
"EPA considers it reasonable to subject vehicles tested on
a mixed fuel containing methanol ~o the emission standards
for methanol-fueled vehicles."
This is appropriate because the standards for methanol-fueled
vehicles are designed such that they become essentially
equivalent to those for gasoline vehicles when the vehicle is
operated on gasoline; the methanol and formaldehyde terms
become negligible.
In response to Toyota's concern about the definition of a
flexible-fueled vehicle, the approach taken in the NPRM was to
consider a vehicle designed to operate on gasoline, methanol,
and intermediate mixtures to be an FFV. Thus, a gasoline
vehicle would not be considered an FFV solely because it is
capable of accepting low level methanol blends. Also, the NPRM
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clearly distinguished between mixed fuels (such as those to be
used in an FFV) and blended fuels (with small amounts of
alcohol) which have received EPA waivers under section 211 of
the Clean Air Act and which are treated like gasoline. Thus,
again, a vehicle specifically designed to accept a low level
methanol blend fuel would be considered a gasoline vehicle, not
an FFV.
The issue" of inclusion of methanol into the CAFE and Gas
Guzzler programs is discussed in detail in a separate section.
As is noted there, methanol is currently not included in either
program. Thus it is appropriate to treat FFVs strictly as
gasoline vehicles with respect to CAFE and Gas Guzzler. With
respect to labeling, since EPA did not specify a methodology
for calculating the fuel economy of methanol vehicles in this
rulemaking, inclusion of a methanol fuel economy number on the
label would be inappropriate.
Conclusion
It is the Agency's goal to remove impediments to the
development of methanol-fueled vehicles. Therefore, it is
recommended that, with regard to FFVs, EPA not require tests
over the range of possible in-use gasoline/methanol mixtures
for each vehicle, but instead allow the manufacturers to
recommend, for Administrator approval, the worst case fuels
(one each for the exhaust emissions, evaporative emissions, and
mileage accumulation) . In this way compliance over the range
of possible in-use fuels can be assured, consistent with EPA's
consideration of FFVs in the NPRM. The act of specifying a
fuel would not relieve the manufacturer of his liability to
meet the standard on any other reasonable in-use fuel mixture;
it would simply allow him to avoid an increased number of
compliance tests relative to dedicated gasoline or methanol
vehicles. The methanol standards would be applicable for all
possible mixtures of gasoline and methanol used by FFVs.
With respect to the CAFE and Gas Guzzler programs, EPA has
no authority to establish any fuel equivalency factor for FFVs
or to account for methanol fuel economy in its treatment of
FFVs. It therefore follows that EPA should treat FFVs as
gasoline vehicles. Since EPA is not defining a methanol fuel
economy test procedure, it is logical that the labels of FFVs
should include the fuel economy for gasoline only.
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Issue: Complexity of the Procedure for the Determination of
Organic Emissions
Summary o£ the Issue:
Pollutant gases from methanol-fueled engines and vehicles
consist of a mixture of hydrocarbons, methanol and formaldehyde
together with other exhaust species such as carbon monoxide,
carbon dioxide etc. As was discussed in the NPRM and in detail
previously in this document, EPA determined that measurement of
each of the primary organic materials (hydrocarbons, methanol
and formaldehyde) would be required to secure the necessary
level of emission control. To avoid what EPA believed would be
an unnecessary level of complexity in the emission standards,
EPA proposed a single, carbon-based standard for the organic
compounds, comprising the three measured pollutants.
In the development of the NPRM, EPA made every effort to
limit the complexity of the procedures necessary for the
measurement of these materials. In the proposal, EPA noted
that a flame ionization detector (FID)* (the instrument
presently used for measurement of hydrocarbons), can be used to
directly and correctly measure either hydrocarbon emissions or
methanol emissions separately but not both of these pollutants
simultaneously. EPA also noted in the proposal that a FID is
unsuitable for the measurement of formaldehyde because of its
very low (approaching zero) response to formaldehyde. While
the FID could, with appropriate adjustments of its
measurements, continue to be used in measurements of
hydrocarbon emissions from methanol fueled vehicles and engines
it was necessary to include additional procedures for the
measurement of methanol and formaldehyde.
Very briefly, the procedures proposed were as follows (see
figure 1). For methanol, the procedure was to dissolve the
methanol in water and to separate the methanol from the water
using a gas chromatograph (GC). The methanol is then measured
by a- heated FID. For hydrocarbons, the procedure consisted of
the collection of dilute bag samples, measurement of the
hydrocarbons plus methanol with a heated FID calibrated on
propane followed by subtraction of the methanol fraction
(previously determined in the methanol analysis) from the total
FID measurement. This analysis would need to account for the
FID's response factor to methanol. For formaldehyde, the
procedure employed the collection of formaldehyde from the
exhaust sample by reaction with 2,4-dinitrophenylhydrazine
(DNPH), followed by analysis with a high pressure liquid
chromotograph using an ultraviolet detector.
* EPA proposed the use of a FID that is heated. As
presented in this discussion the term FID refers equally to the
heated FID.
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Figure 1.
Schematic of Measurement Procedures for
Methanol Vehicle Exhaust Orgenics
DNPH
Cartridges or
Impingers
Wet
Chemistry
Chilled
H20
Impingers
GC-FID
'ME
Total
Carbon
CVS
CHC+(K1)(CME)
'HC
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EPA recognized. in the proposal that less costly
measurement procedures would be desirable. One procedure
considered by EPA was the use of a FID calibrated on methanol
to develop a single measurement for HC and methanol. While
this approach would be simpler than the proposed procedure and
would accurately measure methanol, it would overmeasure
hydrocarbons. While this approach would have been
environmentally conservative as well as simpler EPA believed
that the overmeasurement would cause manufacturers to oppose
its use.
Summary of the Comments:
Seven commenters provided comments on this issue. The
commenters were the Department of Energy, the Engine
Manufacturers Association, General Motors, Mercedes Benz Truck
Company, Nissan, Toyota and Volkswagen.
DOE stated that the proposed procedure would require the
use of expensive equipment and that the measurement procedure
is cumbersome. DOE felt that the HC overmeasurement
characteristic of the single measurement procedure which was
not proposed by EPA supported its use because it would provide
a larger safety margin with respect to ozone control.
EMA believed that the techniques proposed by EPA for
measuring the non-oxygenated hydrocarbons, methanol and
formaldehyde, would require instrumentation which is overly
complex and costly for the developing methanol-fueled engine
and vehicle industry. Due to the presently small size of the
methanol-fueled engine industry, EMA felt that it is not
necessary at this time to separate the organic compound
emissions from methanol-fueled engines and vehicles into their
three components. If, in the future, there are many more
methanol-fueled engines and vehicles in operation, EMA
suggested that EPA might again consider a requirement that
manufacturers provide the individual component information.
For the initial certification of methanol-fueled engines and
vehicles however, EMA recommended the use of a FID calibrated
with methanol to determine the organic emissions. In addition,
EMA recommended that factors should be applied to the
FID-indicated values so as to account for the differences in
FID response to the carbon in the hydrocarbon (high response
when calibrated on methanol) and to the carbon in the aldehydes
(very low) . EMA stated that such a method would be the most
cost-effective option, and would require no new instrumentation
for certification. However, if a manufacturer believed the
standardized factors to be inappropriate for its technology,
EMA suggested that manufacturer-specific factors could be
determined and employed.
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Nissan felt that the proposed procedure is overly
complicated, the costs for new test equipment are high and the
experimental burden would be increased. Nissan felt that
indirect measurement of methanol using the current FID (FID
calibrated on propane) is acceptable. Nissan stated that the
sensitivity of the FID to methanol when calibrated on propane
is roughly 85 percent of its sensitivity to hydrocarbon , and
the overall sensitivity of the FID to exhaust emissions from an
M85 methanol-fueled vehicle is about 94 percent. This
information led Nissan to conclude that the exhaust emissions
results obtained with a FID (calibrated on propane) are only
about 6 percent lower than actual exhaust emissions from a M85
methanol-fueled vehicle. Nissan believed, therefore, that
organic emissions from methanol-fueled vehicles can be measured
with sufficient accuracy using the current FID, if an
appropriate sensitivity correction factor is employed.
Toyota stated that while catalyst equipped vehicles
exhibit very low levels of formaldehyde emissions (formaldehyde
is readily oxidized in the catalyst), non-catalyst vehicles can
have higher formaldehyde emissions. Toyota felt, therefore,
that formaldehyde should be included in the oxygenated HC
standard. Toyota requested, however, that actual measurement
of unburned methanol and formaldehyde be exempt from the
requirement. Toyota recommended using an optional
calculational method for methanol and formaldehyde using an
assigned correction coefficient. Toyota also requested that
manufacturers be allowed the option to use their own
coefficient instead of an assigned one.
GM recommended calibrating the FIDs with methanol and
applying a factor to correct for the fact that total carbon in
the hydrocarbon/methanol mixture of emissions would be reported
high while the carbon in the aldehydes would be reported very
low. The factor would account for the photochemical reactivity
differences between hydrocarbon, methanol and aldehydes.
While there is no apparent technical obstacle to the
proposed procedure for formaldehyde, Ford felt that its use
will significantly impact conventional certification testing as
well as end of line and in-use testing because of the need for
a wet chemistry laboratory, trained laboratory personnel and
the time required to analyze samples (3 hours minimum was
cited).
Nissan stated that the proposed procedure for the
measurement of formaldehyde can not provide continuous test
result outputs whereas a FID or NDIR can. Also, the DNPH
procedure requires extra equipment, is time consuming and
necessitates great care in its performance in order to achieve
accurate results. Nissan hoped that the use of a less
demanding test procedure will be allowed in the future.
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Mercedes Benz stated that despite the inherent problems, a
FID calibrated with methanol is the simplest and lowest cost
method of measuring the organic compounds, and should be given
further consideration. If this approach is not adopted as the
official measurement procedure, Mercedes Benz recommended that
it be allowed as an option to the gas-chromotograph method for
methanol measurement, because of its simplicity and
practicability for in-line continuous measurements which are a
necessary tool for further developing available methanol engine
technology.
Analysis of Comments:
In developing the proposal, EPA sought measurement
procedures which would provide accurate measurements of
hydrocarbons, methanol and formaldehyde without unduly
increasing test procedure complexity and cost. Since the
ratios between pollutants in pollutant streams, i.e. exhaust
emissions and evaporative emissions, can vary widely between
vehicles and between fuels, procedures which either failed to
measure one or more of the constituents or provided inaccurate
results could lead to deleterious environmental effects. This
ruled out the possibility of developing correction factors to
allow the FID to be used as a procedure which could be presumed
to be accurate for characterizing total organics. EPA selected
the procedures which were proposed because they provided the
information necessary for the control of the pollutants of
concern without unreasonable increase in test procedure
complexity.
While the need to accurately control the effects of
exhaust emissions on the environment has in no way diminished
since publication of the NPRM, it is apparent that, because of
their limited numbers, methanol-fueled vehicles will be only
minor contributors to atmospheric pollution during their
introduction into the marketplace. In light of the preceding
and the commenters' concerns with respect to the potentially
negative impact of the proposed measurement procedure on the
development of methanol-fueled vehicles, a less complex
procedure may be warranted on an interim basis. Since the
control of the pollutants entering the environment is of
paramount importance, any simplified interim procedure should,
if it contains a measurement weakness, tend to err on the side
of overmeasurement. One such procedure which has been
supported by a number of the commenters is the use of a FID
calibrated on methanol. Since calibration on methanol would
result in an overmeasurement of the hydrocarbons by the FID,
this would be an environmentally acceptable interim approach
because the error would tend to be on the conservative side
(for the pollutants measured by the FID). Some commenters
suggested the use of correction factors to account for the
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overmeasurement of hydrocarbons if the simplified measurement
procedure were to be allowed. This approach is not warranted
for several reasons. First, the highly photochemically
reactive formaldehyde, which is produced in relatively large
amounts by methanol engines, is not measured by the FID. Even
on an interim basis when there are very few methanol-fueled
vehicles in service it would be prudent to view the
overmeasurement of hydrocarbons as a compensating factor for
the failure of the FID to detect the formaldehyde constituents
of the exhaust gases. DOE's comment is consistent with this
logic. Second, while the manufacturers noted that FID
correction factors can be developed, they did not discuss the
fact that in order to accurately utilize them, different
factors would need to be developed for each
vehicle/fuel/instrument (response factors do vary even between
similar instruments by the same manufacturer) combination.
Thus the application of correction factors would of itself be a
very complex procedure.
Nevertheless, it appears reasonable to view the use of a
heated FID, calibrated on methanol, as an acceptable interim
procedure for the measurement of the subject emissions from
methanol fueled vehicles. Because the purpose of allowing the
use of this simplified procedure is to reduce testing costs
during the development of a methanol fueled vehicle fleet,
without incurring any significant negative impact on the
environment, there is a need to limit the period of time
wherein the simplified procedure can be used. Presently a five
year period would appear to be sufficiently long to allow
initial development of a methanol fleet without posing the
potential of any significant environmental harm.
Should such a period for the use of the simplified
measurement procedure be allowed, EPA would need to monitor the
organic material composition of the pollutant gases from
methanol-fueled engines and vehicles. This monitoring would be
performed to enhance the Agency's knowledge of the organic
material composition (and its potential health effects) of
methanol-fueled vehicle exhaust gases. The Agency would be
able to expect that manufacturers would collect similar data
under the provisions of section 202(a)<4) of the Clean Air Act
and make it available to EPA. The manufacturers currently
provide much useful information on unregulated pollutants and
on emissions research under this section, and provision of test
results for methanol and formaldehyde would be a logical
application of the requirements of that section.
As correctly pointed out by Ford, the sampling and
analytical procedures for the measurement of formaldehyde
emissions do introduce new laboratory requirements to vehicle
emissions measurements. Elimination of the requirement for the
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measurement of formaldehyde emissions on the basis of
laboratory costs or complexity is, however, not warranted
because of the relatively high concentrations of formaldehyde
in methane1-fueled vehicle exhaust and the high photochemical
reactivity of formaldehyde and its toxic potential.
Nissan's comment that the proposed DNPH procedure for
characterizing formaldehyde emissions does not allow for
continuous measurement whereas other procedures might do so is
well taken. It is EPA's understanding that the FID and NDIR
techniques referred to by Nissan have key drawbacks related to
sensitivity and, in the case of NDIR, cost. Nevertheless,
manufacturers are always allowed to substitute technically
equivalent test procedures for those required by the
regulations. Through such an allowance it is hoped that
superior measurement techniques will eventually emerge. Thus
Nissan is free to use the suggested alternatives if it can
demonstrate their equivalence to the procedures promulgated in
today's rule.
The recommendation by Mercedes Benz that a FID be allowed
as an optional measurement procedure in engine development
work, suggests a misunderstanding with respect to the overall
applicability of a regulation. For testing performed to
determine compliance with an emission standard, compliance with
the procedures specified in the regulation is necessary. For
all other test purposes, a manufacturer may freely choose to
use the test procedure that it finds most appropriate. Use by
a manufacturer of test procedures and test equipment during
engine development which did not conform to the requirements
for emission testing would not, however, excuse the
manufacturer from the requirement of compliance with the
emission standards when using the specified test procedures end
equipment.
Conclusions
The arguments favoring use of the less demanding
measurement procedure which employs a heated FID calibrated
with methanol to measure total organics during the very early
stages of the development of a methanol-fueled vehicle fleet
are compelling. Such an option should allow continued
development of these vehicles without posing any significant
environmental threat. It is recommended, therefore, that the
simplified measurement procedure be allowed for certification
and recall testing of methanol-fueled vehicles and engines for
five model years starting with the effective date of the
methanol-fueled vehicle standards.
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Issue: Sampling and Analytical Procedures for the
Measurement of Methanol Emissions, Hydrocarbon
Emissions and Formaldehyde Emissions
Summary ofthe Issue:
Comments were provided on only a few of the details of the
sampling and analytical procedures which were proposed. For
the sake of brevity and to avoid confusion, those details
addressed by the commenters will be identified and underlined
in this issue summary.
EPA proposed that the sampling system for non-throttled
methanol vehicles include a dilution tunnel configured like
that presently used for testing diesel vehicles. Though this
is more complex than the system used for gasoline vehicles and
throttled methanol vehicles, it was judged necessary to allow
for the sampling of particulate emissions.
For the determination of methanol emissions, EPA proposed
that the methanol sample be collected from the dilute exhaust
stream or from the SHED by bubbling the sample through
impingers containing chilled deionized water. The use of
heated (2350±15°F) sample collection probes and sample
collection lines leading to the impingers was proposed for the
dilute exhaust samples. The samples collected would be
analyzed using a gas chromotagraph with flame ionization
detector.
For the determination of exhaust hydrocarbon emissions
from methanol-fueled vehicles, EPA proposed that the dilute
exhaust sample be collected using the bag sampling procedure as
presently employed with gasoline fueled vehicles. Analysis of
bag samples was proposed to be performed using a heated FID
(2500±10°F). For hydrocarbon measurements of evaporative
emissions in the SHED, the sampling procedure proposed was the
same as that presently used with gasoline fueled vehicles (the
sample goes directly to the FID) except that a heated FID would
be employed. Calibration of the FID would be performed using
propane as is present practice. A FID so calibrated fully
measures the hydrocarbons present in the sample but only
partially measures the methanol present. The hydrocarbons
present in the samples would be calculated by subtracting from
the FID measurement the product of the FID response factor to
methanol and the concentration of methanol as determined by the
methanol measurement procedure.
For formaldehyde emissions determinations, the proposed
procedure consisted of the collection through a heated sample
probe and line of a proportional exhaust formaldehyde sample by
bubbling a sample of the dilute exhaust gas stream through
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glass impingers containing a solution of
2,4-dinitrophenylhydrazine (DNPH) in acetonitrile (ACN). The
resultant solution is then analyzed in a high pressure liquid
chromotograph (HPLC) with an ultraviolet (UV) detector. As an
alternative to the preceding vet method of sample collection,
EPA proposed the use of cartridges containing silica gel coated
with DNPH. The remainder of the sample separation and analysis
procedure would be similar to that used with the wet method of
sample collection,
The proposal also required determinations of the accuracy,
with corrections if required, of the sample dilution and
collection systems. The procedures proposed for this function
consisted of the injection of a known amount of propane
(present practice) into the system, sample collection and
analysis, followed by a determination of the amount of injected
propane which is recovered, i.e., losses in the system are
detected. For systems which would be used with methanol fueled
vehicles, the system would also be tested for losses of
methanol which would be injected as a gas (the methanol would
be vaporized by heating).
Summary of the Comments:
Comments on sampling and analytical procedural details
were provided by VW, Chevron, Ford, General Motors, and Toyota.
VW stated that the proposed procedures for the measurement
of HC, methanol and formaldehyde are overly complex. VW
suggested that the single dilution-tunnel sampling system
proposed for the testing of non-throttled methanol-fueled
engines and vehicles (necessary for particulate measurement) be
allowed to be used with all methanol-fueled vehicles. This
approach would allow a manufacturer to test both throttled and
non-throttled vehicles (engines) using a single test site.
Chevron felt that the wet chemistry procedure for
measuring methanol is relatively accurate. Chevron stated
however, that methanol losses may occur due to condensation in
unheated sample lines used in FID measurements of organics (HC
plus methanol) from throttled methanol-fueled vehicles.
Chevron also stated that a sample line temperature of 375°F
will cause inaccuracies in measurements for unthrottled
methanol-fueled vehicles and engines because of methanol
decomposition. As a consequence of methanol lost in the
hydrocarbon plus methanol analysis. Chevron felt that
non-oxygenated hydrocarbon (hydrocarbon) results will be low
because this value is determined by subtraction of the methanol
result (accounting for the FID response factor to methanol)
from the FID result.
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General Motors felt that some methanol loss may be
associated with condensation on the walls of unheated sample
bags employed in the HC plus methanol analysis. GM stated that
the use of continuous heated FID analysis would give the
correct results. GM did not believe that the use of continuous
FID analysis would pose any problems because the procedure is
already in use in many emission facilities of the motor vehicle
industry (i.e., is employed with diesels). GM stated that the
FID should be heated to about 200°F rather than the 375°F
presently used with diesels. GM did not believe that a heated
FID would be required for evaporative emissions measurements
because of the absence of condensation. GM recommends allowing
the use of a heated FID for evaporative emissions if a
manufacturer so desires.
Toyota felt that a heated FID control temperature of 121°C
(250°F> is too low for use with diesel engine testing and
recommended a heated FID control temperature of 191°+6°C
(375°+10°F) for use with both methanol-fueled and "diesel"
engine testing. Toyota felt that there is a minimal loss in
measured methanol emissions between heated FID control
temperatures of 121°C and 191°C.
Chevron also felt that the proposed procedures would
underestimate formaldehyde emissions. In support of this
position, Chevron referenced a study conducted by Southwest
Research Institute (SwRI) for the Coordinating Research Council
(CRC).[8] The report showed that significant losses of
formaldehyde (approximately 40 percent) occurred in dilution
tunnels upstream of the sampling point. Chevron believes that
similar losses may occur in the proposed sampling system.
Chevron recommended additional investigation of the problem and
study of possible solutions.
While Ford does not use the impinger - gas chromotograph
(GC) procedure for methanol collection and analysis, Ford felt
that the procedure should not pose any technical problems.
Ford suggested that heated collection lines (methanol and
formaldehyde samples) need not be used since the transfer
efficiency of formaldehyde in unheated lines is on the order of
95 percent (test results provided showed a range of from 94 to
97 percent) and pointed out that formaldehyde is more reactive
than methanol. Ford suggested two alternative procedures for
measuring methanol. These alternative approaches are: (1) the
use of adsorbent traps, and (2) the use of Fourier Transform
Infrared (FTIR) spectroscopy.
For formaldehyde measurements, Ford stated that they have
used both the impinger and cartridge methods for sample
collection. Under ideal conditions, the two procedures produce
equivalent results. However, the cartridges are not
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commercially available and reproducability of the coating may
vary from laboratory to laboratory with resulting variability
in collection efficiency. If cartridges are not uniformly
coated and properly dried, erroneous emission measurements will
result. Ford expressed the opinion that the alternative
cartridge approach for sample collection, while being simpler
in the sample collection phase is actually more labor intensive
when all phases, from cartridge preparation through analysis,
are considered.
Analysis of Comments:
The commenters did not significantly disagree with the
overall sampling and analytical procedures as proposed. Rather
the comments on this issue addressed procedural details.
The recommendation made by VW was to allow the use of a
single type of sample dilution and collection equipment for
methanol fueled vehicles whether Otto-cycle or diesel. While
the type of equipment recommended by VW (dilution tunnel) is
the more complex of the two types proposed by EPA it was
selected by VW because it provides the capability for
particulate sample collection from diesel engines as well as
the capability to omit particulate sample collection when
Otto-cycle engines are undergoing testing. Since the emission
results obtained by either procedure, exclusive of particulate
emissions, should be equal, there is no fundamental reason for
precluding the use of the single dilution tunnel type of
equipment recommended by VW.
On the basis of the wording used in both Chevron's and
GM's comments, it appears probable that these commenters did
not note the 250°F temperature specification for the heated FID
for use with methanol-fueled vehicle/engine emission
measurements. Chevron also appears not to have noted the 235°F
temperature which was proposed for all sample lines. Both of
these commenters pointed out, however, that decomposition of
methanol can be expected to occur if the 375°F temperature
specification used with petroleum-fueled diesels were applied
to methanol sampling. EPA agrees with this position and
therefore selected the lower (235° and 250°F) temperatures so
as to avoid this problem.
The use of a common temperature for both diesel and
methanol fuel testing (Toyota recommended 375°F) would simplify
laboratory procedure. Losses in measurement accuracy, either
through the use of the lower temperature with diesels or the
higher temperature with methanol is not an acceptable trade-off
for the small simplification in laboratory procedures that
would result. Since the temperature at which the sample
collection lines operate is adjustable, and since the FID's
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operating temperature is either presently adjustable or the FID
can be retrofitted to provide adjustability, laboratory
problems would center on the time required to change and
stabilize the FID and line temperatures between tests on
different fuel types (assuming the use of a single
sampling/analytical system). This problem can be readily
addressed by scheduling groups of tests on one fuel type
followed by a single temperature adjustment before going to
another group of tests on another fuel type.
Prior to publication of the proposal, EPA evaluated the
response of a heated FID and an unheated FID to samples
containing both methanol and hydrocarbons. This evaluation
showed that an unheated FID responded slowly to a sample
containing both methanol and hydrocarbons while the heated FID
responded at a much higher rate. The response rate of the
heated FID was comparable to that of an unheated FID when
analyzing only hydrocarbons. EPA proposed the use of a heated
FID for analyses of samples containing methanol and hydrocarbon
to avoid 1) errors due to premature data collection, or 2) test
voiding due to sample bag depletion prior to instrument
stabilization. While there is agreement with GM that methanol
sample loss due to condensation would not be a problem with
evaporative emission samples, there is disagreement, for the
reasons given above, that an unheaced FID can be used with
evaporative emissions samples as suggested by GM.
Both GM and Chevron expressed concern with respect to the
loss of methanol sample due to condensation. GM's concern
focused on losses in an unheated sample bag while Chevron's
focused on unheated sample lines leading to the sample bag.
Since the use of heated sample lines was proposed, the concern
expressed by Chevron was addressed in the proposal. Chevron's
comment therefore, must have been the result of an oversight.
As a first step in addressing the concern expressed by GM, EPA
has analyzed one sample bag (unheated sample collection lines
were used) with the bag at both room temperature and at a
temperature of between 95° and 100°F. A higher FID reading was
obtained when the bag was warmed. However, the FID measurement
made when the bag was warmed also occurred when the volume of
sample contained in the bag was almost depleted. It is,
therefore, not possible to determine what significance should
be attached to the observed difference. Lacking data with
which to quantify the significance of the GM comment, it is
recommended that the sample collection procedure be retained as
proposed. The concern raised by GM should, however, be
investigated in detail and, if warranted, the sample collection
procedure should be modified at a future date.
While there were no comments on the proposed heating of
sample probes on constant flow venturi - constant volume
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sampling systems (CFV-CVS), evaluation of the proposed
procedure as part of ongoing testing of methanol-fueled
vehicles by EPA has shown that heating of the sample probes for
the methanol and formaldehyde samples results in some heating
of the sample as it passes through the probe.[25] This heating
of the sample causes a loss in proportionality between the
sample volume and the total diluted volume. As a result an
error is introduced in the test results. Since the probe is
very short, and its temperature will be that of the dilute gas
stream, condensation in an unheated probe would not be expected
to pose a problem. Heating of the probe will, therefore, not
be required in the final rule. Heating of the sample line from
the probe to the impingers will, however, continue to be a
requirement to avoid any losses in the lines (the Ford comment
indicated that for its particular system, the losses could be
on the order of three to six percent). Care must be taken,
however, in the construction of sampling systems to thermally
insulate the heated sample lines from the unheated probes. As
an option, heating of the sample line may be avoided provided
the methanol and formaldehyde sample collectors are close
coupled to the probe; i.e., the sample line is either omitted
or its length is so short as to preclude significant cooling of
the sample and any associated condensation.
As noted by Ford, formaldehyde emission measurements
results obtained with properly prepared DNPH cartridges (dry
collection procedure) are equal to those obtained with the wet
collection procedure, while the use of improperly prepared
cartridges will cause incorrect measurement results. Also as
noted by Ford, there is presently no commercial source for DNPH
cartridges. This lack of commercially available DNPH
cartridges is not surprising because there is presently little
demand for this product (given the limited amount of methanol
vehicle emission testing being performed at present). It is
reasonable to expect, however, that one or more manufacturers
of DNPH cartridges could enter the market as demand grows for
this product. In the meantime, manufacturers will either have
to prepare their own cartridges or use the impinger collection
technique. There is no disagreement, however, that if
cartridges are used, they need to be accurately prepared.
Procedures for the preparation and checking of the cartridges
have been developed by EPA.[26]
With respect to the comment by Chevron pertaining to loss
of formaldehyde in the dilution and sample collection systems,
the referenced report has been carefully reviewed. In the work
referenced by Chevron, the formaldehyde was injected into the
exhaust gases as an aqueous solution. Since the dilution
tunnel used in exhaust emissions measurements is designed to
dilute and mix gases, injection of formaldehyde in aqueous
solution into the tunnel can reasonably be expected to pose
significant vaporization and mixing problems and as a
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consequence sample loss. This is apparently what was exhibited
by the low formaldehyde recovery (high loss) rate reported in
the Chevron reference. As part of EPA's evaluation of sampling
procedures for methanol fueled vehicles, EPA investigated the
potential for the loss of formaldehyde in the sampling system.
In this work, the formaldehyde was injected into the exhaust
duct in gaseous form. Loss of formaldehyde sample was not
detected in this evaluation of the sampling system. It can be
concluded, therefore, that the concern expressed by Chevron is
not attributable to the sampling system but to the procedure
used in the referenced testing to quantifying the performance
of the sampling system.
With respect to the suggestion by Ford that alternative
procedures be allowed, EPA's position on alternative procedures
has in the past and continues to be that they will be allowed
provided equivalent results are obtained. This position is
stated in existing regulations. In the case of the two
procedures suggested by Ford, (the FTIR procedure and adsorbent
traps), they are presently in the development stage and are not
generally available to all potential users. Specific inclusion
of these procedures in the regulations for use at this time
would, therefore, be inappropriate. Exclusion of the suggested
procedures does not, however, preclude their use once they have
been shown to provide equivalent results.
Conclusions
While the dilution tunnel procedure must be used with
diesel engines, there is no technical basis for precluding its
use with Otto-cycle engines. It is recommended, therefore,
that language be included in the regulations signifying that a
manufacturer may use a dilution tunnel in the testing of
Otto-cycle methanol fueled vehicles/engines if the manufacturer
so desires.
Since there is very little data which would support the
concerns pertaining to methanol loss in sample bags and there
is no data to indicate an appropriate sample bag temperature,
if heating were required, the regulations should be finalized
as proposed. EPA should, however, collect data which would
resolve the concerns raised by GM with respect to the loss of
methanol sample in sample bags. If warranted by the data, the
regulations should be amended at the earliest possible date.
The use of heated probes which rely on constant flow
venturi for maintaining sample flow proportional to main tunnel
flow will cause measurement inaccuracy. This proposed
requirement should be removed. The heated sample lines must be
thermally isolated from the probes to prevent heating of the
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probes. Close coupling of sample collection systems to the
probes should be allowed, if desired, so as to avoid the
requirement for the use heated methanol and formaldehyde sample
lines.
The regulations need to be carefully reviewed prior to
final publication to remove any ambiguities with respect to the
use of heated FID and heated sample lines.
Careful preparation of DNPH cartridges is a prerequisite
to obtaining accurate formaldehyde test results if cartridges
are employed. Laboratories using this method of sample
collection should be encouraged to use the procedures detailed
in the EPA report.
It should be clearly stated in the preamble to the Final
Rule that manufacturers may use procedures which have been
demonstrated to produce results equal to those specified.
Procedures which are presently not readily available for
widespread use in emissions testing should, however, not be
specified by EPA as required procedures.
No change in the previously specified line or FID
temperatures is recommended. Those proposed should be
appropriate to ensure adequate collection and detection of
organic materials. Use of the heated FID is still recommended
over use of the unheated FID due to response time
considerations.
Some test facilities find that use of DNPH cartridges
provides time and space flexibility in the testing process.
The present lack of suppliers of DNPH cartridges and Ford's
preference for the impinger technique in collecting
formaldehyde should not affect EPA's decision to allow use of
cartridges as an alternative technique.
Finally, accurate qualification of the measurement system
for formaldehyde recovery efficiency is good laboratory
practice. EPA would expect that test facilities would conduct
experiments in this regard as appropriate to demonstrate the
validity of their measurement techniques.
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Issue:
Determination of Formaldehyde Background Levels
Summary of the Issue:
As with the background level determination of all other
measured emissions, EPA proposed that background samples for
formaldehyde be collected for each phase (cold start/hot start)
in the case of heavy-duty engine testing, or for each bag, in
the case of light-duty testing, of the test procedure.
Analysis of these background samples would employ the same
procedures as were described for the analyses of the
formaldehyde in exhaust emissions samples.
Summary of the Comments:
Toyota was the only commenter on this issue. Toyota stated
that while it is using the recommended procedure, it requested
that the measurement of background formaldehyde levels be made
optional because of inherent low background levels and the
complexity of the analytical procedures. Toyota viewed its
request as a conservative one, simulating worst-case
conditions, since background would be assumed to be zero and
there would, as a result, be a higher then actual indication of
emissions from the test vehicle.
Analysis of Comments:
Toyota's request to make the measurement of background
formaldehyde levels optional appears at first glance to be a
desirable test procedure simplification because of its
conservative nature. On closer inspection, however,
implementation of this option would pose problems in areas such
as emission standards compliance determinations and lab to lab
correlation testing. Problems could arise in these
determinations when the formaldehyde background level in a
laboratory was high but was not recognized as such.
Measurement of formaldehyde background levels appears,
therefore, to be necessary. Reducing the number of samples
collected and consequently the number of analyses which have to
be performed was considered, however, to be desirable.
Background sample collection periods which were considered as
methods whereby the test procedure could be simplified were l)
a single sample for the total test, 2) a daily sample, and 3) a
weekly sample. Because of potential -short term fluctuations in
formaldehyde levels in the background air which could impact
test results and which would not be detected by the daily or
weekly samples, these sampling periods appear to be excessive.
To avoid possible problems in lab to lab correlation and to
facilitate correct determinations of vehicle compliance with
emission standards, while allowing a degree of test procedure
simplification, the collection of a single formaldehyde
background sample covering the total test period should be
allowed.
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Conclusion:
Replacing bag by bag background sampling and analysis for
formaldehyde with a single sample and analysis covering the
total test period will simplify testing without significant
loss of testing accuracy. The regulations should incorporate
this provision. Bag by bag or phase by phase background
sampling should be allowed as an alternative since this would
lead to increased accuracy.
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Issue: Duct Connecting Vehicle Tailpipe (Engine Exhaust) to
CVS (Dilution Tunnel)
Summary of the Issue:
For methanol-fueled vehicles, it was proposed that the
duct connecting the vehicle tailpipe to the CVS, and in the
case of heavy-duty methanol-fueled engines, the duct connecting
the engine to the dilution tunnel, be heated to 235°+15°F
(1130+8°C) to prevent adsorption or condensation and the
associated loss of exhaust gas constituents (methanol and
formaldehyde) in the duct.
Summary of the Comments:
Caterpillar and Toyota provided comments on this issue.
Caterpillar believed that heating of the duct is not
necessary. Caterpillar stated that while momentary
condensation following a cold start will modify real time
indications of emissions, overall test results would not be
affected.
Toyota stated that the heating requirement will make
testing equipment complicated, decrease duct flexibility
thereby causing handling difficulties. Toyota felt that both
heating and cooling capability of the duct will be necessary to
maintain duct temperature at 235°+15°F because of changes in
exhaust gas temperature during testing.
Toyota suggested either the elimination of the heating
requirement for short ducts (identified 3.65 meters (12 feet)
maximum length based on diesel engine practice) or turning the
heater off once the duct is preheated to 121°C (250°F).
Analysis of Comments:
Caterpillar's comment that emission losses will be
corrected for as the exhaust system heats up during the course
of the test, causing vaporization of any condensate, is noted.
Unfortunately it rests on the assumption that losses during one
phase of the test are recovered during that phase. If this is
not the case, potential for significant test result error
exists. There is presently no data at EPA's disposal which can
be used to resolve this question. It seems prudent therefore
to take steps which would eliminate or at the least minimize
any losses.
Prior to and since publication of the NPRM, EPA has
conducted test projects to investigate the effects of duct
heating on the loss of methanol and formaldehyde emissions in
the duct. The first of these projects was conducted at EPA's
Research Triangle Park laboratory.[14]
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The exhaust duct used in that evaluation was approximately
20 feet long and constructed of corrugated tubing. Tests were
conducted both with the duct heated and unheated. The results
of the investigation are summarized below:
Formaldehyde Recovery
Unheated Exhaust Duct Heated Exhaust Duct
Cold Start 79% 94%
Hot Start 94% 96%
The conclusion drawn from the experimental results was
that the high formaldehyde losses on the cold start tests with
the unheated duct were the result of water of combustion
condensing in the duct which resulted in some formaldehyde
being dissolved in the condensate. The dissolved formaldehyde
would as a result not be measured as part of the gaseous
sample. These results supported the requirement for heating of
the duct, especially a long duct constructed of corrugated
tubing, prior to the initiation of testing.
Subsequent to publication of the NPRM, EPA has performed
tests which validate Toyota's concerns that follow from the
requirement of the heated duct. These tests involved
methanol-fueled vehicles and were designed to monitor the
temperature of the duct during emissions tests (data is as yet
unpublished). The duct used in this testing was heated and, to
minimize the energy demand of the heating elements, insulated.
During the tests, duct wall temperatures as high as 300°F were
recorded. Some decomposition of the methanol and possibly the
formaldehyde in the exhaust gases can reasonably be expected to
occur at this elevated temperature. It appears, therefore,
that Toyota's concern pertaining to the need for both heating
and cooling of the duct may be warranted. Since the need to
cool the duct (when insulation is employed) would greatly
complicate testing, the use of insulation on heated ducts
should either be avoided or provisions made for the removal of
the insulation whenever the engine is in operation.
Another test project was conducted at the Motor Vehicle
Emission Laboratory, (MVEL). The duct used in this testing was
constructed mainly of smooth wall pipe and was 5 feet in
overall length including two 8 inch sections of corrugated tube
and one 45° bend; i.e., this duct was short and smooth relative
to the previously used 20 foot long duct which was constructed
entirely of corrugated tubing. A 350 cfm Philco CVS was used.
The test vehicle used in the MVEL evaluation was a full size
automobile (Ford Crown Victoria, 5.0 liter engine, 4500 Ib
inertia weight, actual dynamometer hp at 50 mph=11.9).
Statistical analysis of the test data collected at MVEL showed
that there was no statistical difference between emission
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results obtained with a heated or unheated duct of the
configuration employed.[27]
Since the vehicle used in this evaluation was relatively
heavy, the rate at which the temperature of the unheated duct
increased following the start of a test would have been faster
than would have occurred with a lighter vehicle. Therefore,
the test data from this evaluation may not precisely define the
emissions effects with a small vehicle. The main conclusion
that EPA has drawn from this test, however, is that short ducts
constructed primarily from smooth wall pipe, with a minimum of
flexible (corrugated) piping should minimize any losses.
Toyota's suggestion of heating the transfer tube until the test
begins has some merit, especially when coupled with the use of
such optimized duct configurations.
Some test facility configurations may preclude relocation
of the CVS close enough to the test vehicle, or test engine, to
allow use of a short duct. In these cases, relocation of the
point at which the exhaust gases and dilution air are mixed is
considered to be a viable alternative. This alternative could
be achieved by routing the dilution air from the filter housing
of the CVS to a mixing point either at, or very close to, the
vehicle tailpipe or engine exhaust and returning the diluted
exhaust to the CVS unit. Alternatively, the dilution air
filter assembly could be moved from the CVS and located close
to the vehicle tailpipe or engine exhaust. Since the proposal
called for heating of the tube between the exhaust and the
dilution point, eliminating this would obviate the need to
provide heating.
Conclusions:
As a result of the preceding, it is reasonable to conclude
that the duct connecting the vehicle tailpipe or engine exhaust
to the CVS or dilution tunnel should be as short as practical
within the constraints of the test cell and be constructed of
smooth wall tubing with a minimum of both bends and flexible
tubing. While the only data available at this time showing
statistically equivalent results between heated and unheated
ducts was collected on a five foot long duct, such a short
length of tubing may be difficult to work with logistically.
Therefore, the following recommendations are made. First,
ducts conforming to the above design specifications should be
allowed. Second, where these are not practical, smooth walled
ducts of up to 12 feet in length should be allowed provided
they are heated to 235° + 15°F (113° + 8°C) prior to the start
of testing and during any periods of the test when the engine
is off. Heating of the duct should be allowed during the test
for any length of duct, provided the temperature of the duct
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wall does not exceed 250°F (121°C). If insulated, long, heated
ducts are employed, provisions should be made either to remove
the insulation during engine operation or if necessary to cool
the duct to prevent duct wall temperature exceeding 250°F. As
an alternative, the mixing duct may be essentially eliminated
by moving the mixing point of the dilution air and exhaust
gases to a point immediately adjacent to the vehicle tailpipe
or engine exhaust.
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Issue: Vehicle Preconditioning for Evaporative Emissions
Testing
Summa ry o f the Is sue:
EPA proposed that vehicle preconditioning for
methanol-fueled vehicles be the same as that presently
specified for gasoline-fueled vehicles. EPA requested comment,
however, on whether or not a different preconditioning
procedure should be employed for methanol-fueled vehicles
because of potential variability in evaporative emission
results stemming from relative differences in the affinity
between the charcoal in the canister for methanol fuel vapor
vs. gasoline vapor.
Summary of the Comments:
Comments on this issue were provided by Ford and General
Motors. Ford felt that canister purging during the
preconditioning drive is heavily influenced by vehicle
operation and storage conditions prior to the initiation of the
preconditioning drive. Ford felt, therefore, that any
alternative preconditioning provisions should be allowed for
all vehicles whether methanol or gasoline fueled to preclude
unrepresentative purging requirements during the
preconditioning drive.
GM felt that fuel type should not dictate the degree of
vehicle preconditioning. GM felt that preconditioning should
approximate a typical day of vehicle usage and that the current
preconditioning procedure is inadequate.
Analysis of Comments:
Neither Ford nor GM provided any information indicating
that the purge/load characteristics of an evaporative control
system for a methanol-fueled vehicle would be different than
those for a gasoline-fueled vehicle. It appears reasonable to
conclude, therefore, that any differences which may exist
between the relative affinity of the charcoal in the canister
for methanol fuel vapors and gasoline vapors will be accounted
for in the design of the evaporative control systems on
methanol-fueled vehicles. Comments by Ford and GM on the
appropriateness of the preconditioning procedure fall outside
of the scope of this proposal and are, therefore, not analyzed
here.
Conclusion:
Since no information was provided in support of
preconditioning procedures for methanol-fueled vehicles
different to those used for gasoline-fueled vehicles, the
preconditioning procedures, as proposed, should be retained.
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Issue: Lean Flammability Limit in SHED
Summary of theIssue:
EPA proposed the use of the same upper limit (15,000 ppm
C) for the concentration of combustible materials in the SHED
for testing of methanol-fueled vehicles as is used in the
testing of gasoline-fueled vehicles. Use of a common limit
value for both types of fuel was judged to be desirable because
while it would provide about the same safety margin relative to
the lean flammability limit for both fuels, it would also avoid
the introduction of a new factor which could cause confusion
during the performance of tests.
Summary ofthe Comments:
Ford and GM provided comments on this subject. Ford
supported continued utilization of the 15,000 ppm C safety
limit in the SHED since a 4:1 safety factor beyond the lean
flammability limit for pure methanol corresponds to a
concentration of approximately 17,500 ppm C. Ford pointed out
that a different monitor would, however, have to be employed
with methanol fuel because present monitors are insensitive to
methanol.
GM did not believe that there will be any explosion hazard
in a SHED during an evaporative emission test with M-100 fuel
because the boiling point of pure methanol (148°F) is
significantly higher than the normally experienced maximum tank
temperature of 90°-92°F. GM felt that use of M-85 fuel could
increase organic levels in the SHED but not to dangerous
levels. GM pointed out that the FID used to measure VOC
concentrations in the SHED would provide warning of high
concentrations. A combustible gas sensor should, however, be
used to monitor concentrations in the SHED. While GM did not
believe that a safety hazard will develop in the SHED, GM was
somewhat concerned about the development of an explosive
mixture inside of the vehicle fuel tank when M-100 is the fuel.
Analysis of Comments:
Analysis suggests that the commenrers are correct in that
it is unlikely that a hazardous mixture could develop in a SHED
during testing and that continued utilization of a 15,000 ppm C
upper limit would provide a reasonable safety margin relative
to the lower flammability limit for the fuels used in testing.
Good laboratory practice, as pointed out by Ford and GM, will
necessitate the use of combustible mixture monitors which are
sensitive to the vapors being monitored.
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GM's comment pertaining to the development of explosive
mixtures in the fuel tanks of vehicles using M-100 fuel is
relevant to the safe operation of these vehicles both on the
street and during testing. Since there is a potential hazard
posed by these vehicles during road operation, it is expected
that manufacturers will resolve this possible hazard prior to
testing a vehicle. It is also expected that laboratories will
use good practice in preventing ignition sources beyond the
vehicle manufacturer's control from entering a closed fuel
tank. Incorporation of additional safety precautions into the
test procedures does not, therefore, appear to be necessary.
Conclusion:
An upper concentration limit of 15,000 ppm C for
combustible materials in the SHED should be retained as a
warning note in the regulations. Laboratories should use good
engineering practice both in the selection of combustible gas
monitors sensitive to the materials being monitored and in the
handling of methanol-fueled vehicles. These precautions will
ensure the safety of laboratory personnel during testing of
methanol-fueled vehicles.
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Issue: Test Fuel Specification
Summary of the Issue:
EPA proposed that methanol fuel used in emissions testing
be representative of commercially available methanol fuel.
This was necessary to ensure that emissions would be
representative of vehicle operation in the real world.
Recognizing that methanol-fueled vehicles were at an early
stage of development and that, as a result, manufacturers' fuel
specifications for those vehicles that will ultimately be
marketed have not yet been determined, EPA chose not to propose
a detailed specification for methanol test fuel. EPA proposed
that a fuel must contain a minimum of 50 percent methanol by
volume before that fuel could be classified as methanol fuel.
Summary of the Comments:
Comments on this issue were provided by thirteen
organizations. The organizations were: California Air
Resources Board, Chevron, Chrysler, Department of Energy,
Engine Manufacturers Association, Ford, General Motors,
Manufacturers of Emission Controls Association, Oxygenated
Fuels Association, State of New York, Nissan, Toyota and
Volkswagen.
Four commenters expressed the opinion that EPA's
establishment of methanol test fuel specifications would not be
appropriate at this time. Chevron suggested that, initially,
the test fuel specification should be provided by the
vehicle/engine manufacturer with later development of a
specification corresponding to commercial methanol fuel.
Similarly, VW stated that, in the short term, vehicle/engine
manufacturers must specify the fuel because only the fuel for
which the vehicle is designed can be used. Flexibility in
selecting the fuel must be provided to facilitate research into
the development of the optimum fuel and engine combination. In
the long term a precise fuel specification, representative of
commercial fuel, must be developed. SMA recommended that test
fuel correspond to the fuel specified by the engine
manufacturer for its production engines. GM also believed that
certification fuel should be the fuel for which the vehicle is
designed and which, in GM's opinion, would also be the
commercial fuel. GM stated that M-85 and M-100 are distinctly
different fuels from the perspective of vehicle design and
should not be viewed as different grades of methanol fuel.
Eight of the commenters (CARB, Chrysler, DOE, Ford, MECA,
OFA, Nissan and Toyota) believed that EPA should establish a
fuel specification as part of the rulemaking. Reasons provided
by the commenters for this position are given below.
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A fuel specification would provide vehicle and engine
manufacturers with a basis for making engineering decisions on
fuel system and engine design. Vehicle design parameters are
dependent on fuel specification, and a range of M-50 through
M-100 is too broad for design purposes. Further, it would be
unwise for manufacturers to invest resources on the development
of a vehicle for a fuel of the manufacturers' choice when that
fuel may not be used commercially. Methanol fuel which
contains a different percentage mix of methanol and gasoline
than the vehicle was designed for could adversely affect an
emission control system. Also certain additives to methanol
fuel designed to enhance startup and performance could
adversely affect emission control performance of vehicles
designed to a different fuel specification.
A fuel specification would also provide fuel suppliers
with a single design target and prevent proliferation of fuel
specifications. Finally, a fuel specification would establish
limits on fuel contaminants which would cause engine wear,
corrosion, and materials compatibility problems (e.g.,
chlorine, sodium). OFA provided, in tabular form, a proposed
specification for methanol fuel showing limits for contaminants
such as chloride, organic sulfur, iron, sodium and other metals.
Nissan recommended the specification of a single test fuel
which must contain gasoline or other additives to achieve a
visible flame in the event of a fire and to ensure cold start
performance. More specific fuels which were recommended by
other commenters were M-85 and M-100. The commenters taking
these positions and the reasons for their positions were as
follows:
Ford is using M-85 (15 percent unleaded gasoline)
because the gasoline content is expected to provide
a visible flame in the event of a fire, to aid in
cold starting and cold weather driveability, to
provide RVP equal to that of indolene, and to
provide fuel tank vapor concentration richer than
the combustible limit. While M-85 is presently
being used by Ford, Ford felt that other
formulations may offer future advantages and should
be allowed.
- Chrysler recommended M-85, using 15 percent standard
test gasoline, since it will probably be available
as commercial methanol fuel.
OFA recommended M-85 on an interim basis since the
majority of work has been performed on this fuel.
Establishment of a final specification would follow
as more knowledge was gained.
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DOE recommended both M-100 ("neat chemical-grade"
methanol) and M-85 containing 15 percent high-octane
indolene by volume.
- CARS recommended M-85 for spark ignition engines and
M-100 for compression ignition engines.
New York stated that lacking specifications, commercial
methanol fuels may not meet the fuel specifications for which
vehicles are designed. New York then queried what parameters
would be employed to determine the representativeness of
certification methanol-fuel with respect to commercial
methanol-fuel.
Analysis of Comments:
While some of the commenters believed it is too early for
EPA to establish fuel specifications, others were obviously in
favor of the agency moving now to take that action. Both
arguments have merit. On the one hand there are numerous
aspects of engine and fuel design which will not be resolved
without detailed analysis and the pressure of the marketplace.
This argues for EPA's avoiding a detailed specification, and
Volkswagen's and Chevron's comments recognized this point of
view. On the other hand, as various commenters pointed out,
provision of a specification could force a degree of
standardization within the vehicle and fuel industries which
would be difficult to otherwise presently obtain.
Given the Agency's concern that any fuel used to certify
vehicles for environmental purposes be representative of in-use
fuels, there would be two potential problems associated with
selection of a fuel specification before a market for methanol
vehicles and fuel is established. First, as several commenters
noted, the manufacturers would tend to optimize vehicles'
emissions performance around the specified fuel. This is
consistent with GM's and EMA's comments that testing should be
done with the fuel for which a vehicle was designed. GM's
comment that M-85 and M-100 are different fuels, not just
different grades of methanol, is a useful one, demonstrating
how important the choice of a test fuel is. From an emissions
perspective, use of one of these fuels or the other can be
expected to result in significant differences in the fractions
of HC, methanol, and formaldehyde in the organics, and perhaps
in levels of particulate emissions from diesel engines. From a
performance perspective, use of one or the other in a given
vehicle will likely affect cold stability, overall
driveability, fuel efficiency and other performance criteria.
Furthermore, choice of one fuel or another would likely result
in engine design modifications to take advantage of that
formulation's properties. These changes might affect
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compression ratio, method of ignition or ignition assist, even
possibly cooling capacity, to give some examples. Thus, a
specification provided now could have the effect of detering
vehicle optimization around a fuel which might be superior for
technical and/or economic reasons. EPA's establishment of a
fuel specification would, under these circumstances, amount to
interference in the marketplace.
Second, EPA's establishment of a specification might also
be at odds with decisions made by fuel suppliers, who are not
bound to market a fuel simply because EPA specifies it for
purposes of environmental testing. If such were the case, EPA
would need to change its specifications to obtain test results
representative of in-use emissions.
Therefore, the development of the in-use fuel market
should remain the concern of vehicle manufacturers and fuel
suppliers. It seems clear that no overwhelming logic has been
presented to demonstrate that the decision rightfully belongs
to EPA. As long as vehicles are able to comply with emission
standards when tested on the fuels that are eventually
marketed, and as long as no other overriding environmental
concern not addressed by the emission standards accompanies use
of those fuels, the Agency should remain neutral with respect
to the emerging fuel market.
New York's comment that without specifications, commercial
methanol fuels may not meet the fuel specifications for which
the vehicles are designed assumes that the process described
above will not take place. It implies that vehicle
manufacturers will market vehicles incompatible with available
fuel supplies or that fuel suppliers will market fuels
inappropriate for use with the vehicle population. This logic
is faulty since if manufacturers expect to have to certify and
comply in-use using representative fuels, they will have a
strong, market-based incentive to coordinate with the fuel
suppliers in advance. Such cooperation is common even with
regard to today's fuel market. The American Society for
Testing and Materials specifications for gasoline fuel
volatility classes and fuel property test criteria are salient
examples of this. It is very reasonable to assume that such
cooperation will exist with regard to an emerging methanol fuel
market.
New York's guestion regarding EPA's intended criteria for
selection of representative fuels is a worthwhile one. EPA's
goal in choosing certification fuels is to ensure that in-use
emissions are below the level of the standards. Thus, the
Agency would consider any fuel properties that it would expect
to affect emissions. Unfortunately, without a developed market
for methanol fuels, it is not possible to completely specify
these properties at this time.
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It is recognized that in the initial sales years of
methanol vehicles, the fuel market may be more uncertain than
after some degree of market equilibrium and vehicle and fuel
standardization is reached. In this regard, those comments
suggesting that EPA adopt the fuel for which a vehicle was
designed as the test fuel are useful. In fact, the Agency
could take advantage of the manufacturers' understanding of the
emerging fuel market by requiring manufacturers to recommend
test fuels and to provide justification for their selection as
reasonably available future fuels. While final specifications
should remain the responsibility of the Agency, this procedure
could benefit all parties concerned through the increased
flexibility it offers. In the longer run, when a fuel market
has been established, the Agency will be able to specify fuels
without this required input.
Conclusion:
Development by EPA of one or more precise methanol fuel
specifications at this time would tend to focus development
work only on the specified fuel(s) and could hamper development
of optimum vehicle/fuel designs. Potential fuel-to-vehicle and
vehicle-to-fuel compatibility problems are more appropriately
resolved by cooperative efforts between the fuel suppliers and
the vehicle manufacturers than by EPA interference. EPA should
retain the broad methanol fuel specification which was proposed
until vehicle/fuel optimization is completed and commercial
methanol fuel specifications have been developed. At that
time EPA should act to specify representative test fuels.
Until such a time, the Agency should require manufacturers
to submit recommended test fuel specifications along with
justification for their selection as reasonably available
in-use fuels. These recommendations would be used by the
Agency in determining test fuels.
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References
1. M.D. Gold, C.E. Moulis, EPA/OMS, "Emission Factor
Data Base for Prototype Light-Duty Methanol Vehicles," SAE
Paper #872055, November, 1987,
2. G.Z. Whitten, H. Hogo, Systems Applications
Incorporated, "Impact of Methanol on Smog: A Preliminary
Estimate," Publication No. 83044, February 1983.
3. G.Z. Whitten, N. Yonkow, T.C. Myers, Systems
Applications Incorporated, "Photochemical Modeling of
Methanol-Use Scenarios in Philadelphia," Publication No. EPA
460/3-86-001, 1986.
4. R.J. Nichols, J.M. Norbeck "Assessment of Emissions
From Methanol-Fueled Vehicles: Implications for Ozone Air
Quality," APCA 78th Annual Meeting, June 16-21, 1985.
5, "California Methanol Assessment. Volume II:
Technical Report," Chapter 6, Jet Propulsion Lab and California
Institute of Technology, JPL Report No. 83-18/Vol. II,
March 1983.
6, G.Z. Whitten, J.P. Killus, "Technical Discussions
Delating to the Use of the Carbon-Bond Mechanism in
OZIPM/EKMA," Publication No. EPA 450/4-84-009, 1984.
7. M. Wolcott, EPA/OMS, "Ozone Effect of Large Scale
Methanol Fleets," memorandum to Charles Moulis, EPA/OMS
November 6, 1986.
8. L,R. Smith, "Characterization of Exhaust Emissions
from Alcohol-fueled Vehicles," Southwest Research Institute,
Final Report for the Coordinating Research Council, Inc.,
Project CAPE-30-81, May 1985, NTIS No. PB85-238582/AS.
9. "Automotive Methanol Vapors and Human Health: An
Evaluation of Existing Scientific Information and Issues for
Future Research," Health Effects Institute, May 1987.
10. J, Braddock, EPA/ORD, "Methanol Escort Emissions,"
memorandum to Paul Machiele, EPA/OMS, April 17, 1987.
11. S. Syria, EPA/OMS, "Methanol Escort Idle Testing,"
memorandum to Charles Gray, Director, EPA Emission Control
Technology Division, July 17, 1985.
12. D.E. Seizinger, "Influence of Ambient Temperature,
Fuel Composition, and Duty Cycle on Exhaust Emissions," NIPER,
Draft, December 1987.
13. Unpublished EPA data.
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References(Cont' d. )
14. R. Snow, Northrop Services, Inc., letter to Jim
Garvey, EPA November 12, 1985.
15. Haack, L.P., LaCourse, D.L., and Korniski, T.J.
"Comparison of Fourier Transform Infrared Spectrometry and
2,4-Dinitrophenylhydrazine Impinger Techniques for the
Measurement of Formaldehyde in Vehicle Exhaust," Anal. Chetn.
58(1986) pp.68-72.
16. Based on "Assessment of Health Risks to Garment
Workers and Certain Home Residents from Exposure to
Formaldehyde," EPA-Office of Pesticides and Toxic Substances,
Final Draft March 1987.
17. J.N. Harris, A.G. Russell, J.B. Milford, "Air
Quality Implications of Methanol Fuel Utilization", SAE Paper
8881198, August 1988.
18. Based on "Preliminary Source Assessment for
Formaldehyde," Radian Corporation, September 3, 1985.
19. "Estimated Cancer Incidence Rates for Selected Toxic
Air Pollutants Using Ambient Pollution Data," EPA Office of Air
Quality Planning and Standards, April, 1985.
20. "Report on the Consensus Workshop on Formaldehyde,"
Environmental Health Perspectives, U.S. Dept. of Health and
Human Services, Vol. 58, p.323, December 1984.
21. Summary and Analysis of Comments on the NPRM for
Gaseous Emission Regulation for 1984 and later Model Year
Heavy-Duty Engines, December 1979.
22. Summary and Analysis of Comments on the NPRM for
Revised Gaseous Emission Regulations for 1984 and Later Model
Year Light-Duty Trucks and Heavy-Duty Engines, July 1983.
23. Conversation with Richard Shyu of Daimler-Benz,
April 1987. Quoted control system retail replacement cost as
75 dollars. Manufacturer cost can be assumed even lower.
24. E.U. Goff, J.R. Coombs, D.H. Fine, "Nitrosamine
Emissions from Diesel Engine Crankcases," SAE K801374, October
1980.
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References (Cont'd.)
25. "Use of Heated Critical Flow Venturi Sample Probes
to Maintain Proportional Flow," Technical Report
EPA-AA-TEB-87-01, 1987.
26. S.B. Tejada, "Evaluation of Silica Gel Cartridges
Coated In Situ with Acidified 2,4-Dinitrophenylhydrazine for
Sampling Aldehydes and Ketones in Air," Intern. J. Environ.
Anal. Chem., 26<1986) pp.167-185
27. W. Adams, EPA/OMS, "Heated vs. Unheated Exhaust Pipe
Correlation," memorandum to Stanley Syria, EPA/OMS, March, 1987.
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