Regulation of Fuels and Fuel Additives: Standards for Reformulated and Conventional Gasoline
[Federal Register: February 16, 1994]
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 80
[AMS-FRL-4817-8]
Regulation of Fuels and Fuel Additives: Standards for
Reformulated and Conventional Gasoline
AGENCY: Environmental Protection Agency.
ACTION: Final rule.
SUMMARY: Through the amended Clean Air Act of 1990, Congress mandated
that EPA promulgate new regulations requiring that gasoline sold in
certain areas be reformulated to reduce vehicle emissions of toxic and
ozone-forming compounds. This document finalizes the rules for the
certification and enforcement of reformulated gasoline and provisions
for unreformulated or conventional gasoline.
DATES: The regulations for the reformulated gasoline program are
effective on March 18, 1994. The incorporation by reference of certain
publications listed in the regulations is approved by the Director of
the Federal Register as of March 18, 1994. The information collection
requirements contained in 40 CFR part 80 have not been approved by the
Office of Management and Budget (OMB) and are not effective until OMB
has approved them. EPA will publish a document in the Federal Register
following OMB approval of the information collection requirements.
Retail sale of reformulated gasoline will begin on January 1, 1995,
as will the provisions for the ``simple model'' certification, the
anti-dumping program for conventional gasoline, and the associated
enforcement procedures. (For all ensuing sections of this document, the
program's beginning date of January 1, 1995 refers only to the retail
sale of reformulated gasoline.) Certification of reformulated gasoline
by the ``complex model'' and compliance with the Phase II performance
standards, will begin January 1, 1998 and January 1, 2000,
respectively.
ADDRESSES: Materials relevant to this FRM are contained in Public
Dockets A-92-01 and A-92-12, located at room M-1500, Waterside Mall
(ground floor), U.S. Environmental Protection Agency, 401 M Street SW.,
Washington, DC 20460. The docket may be inspected from 8 a.m. until 12
noon and from 1:30 p.m. until 3 p.m. Monday through Friday. A
reasonable fee may be charged by EPA for copying docket materials.
FOR FURTHER INFORMATION CONTACT:
Paul Machiele (reformulated gasoline requirements), U.S. EPA (RDSD-12),
Regulation Development and Support Division, 2565 Plymouth Road, Ann
Arbor, MI 48105, Telephone: (313) 668-4264.
George Lawrence (reformulated gasoline and anti-dumping enforcement
requirements), U.S. EPA (6406J), Field Operations and Support Division,
501 3rd Street, Washington, DC 20005, Telephone: (202) 233-9307.
SUPPLEMENTARY INFORMATION: Today's final rule is preceded by four
previous notices: an initial notice proposing standards for
reformulated and conventional gasoline (NPRM) published on July 9, 1991
(56 FR 31176), a supplemental notice (SNPRM) published on April 16,
1992 (57 FR 13416), an additional NPRM published on February 26, 1993
(58 FR 11722), and a notice of correction for Phase II standards
published on April 1, 1993 (58 FR 17175). Insofar as the rules
finalized today mirror the proposed standards, those previous documents
may be referred to.
Today's preamble explains the basis and purpose of the final rule,
focusing on issues that have been revised since the publication of the
correction notice for the Phase II performance standards (58 FR 17175).
Support documents, including the Regulatory Impact Analysis (RIA), are
available in Public Docket No. A-92-12.
To Request Copies of This Final Rule Contact: Delores Frank, U.S.
EPA (RDSD-12), Regulation Development and Support Division, 2565
Plymouth Road, Ann Arbor, MI 48105, Telephone: (313) 668-4295.
Copies of the preamble, the Final Regulatory Impact Analysis (RIA),
the Responses to Comments on Enforcement Provisions (RCEP), the complex
model, the simple model and the regulations for the reformulated
gasoline rulemaking are available on the OAQPS Technology Transfer
Network Bulletin Board System (TTNBBS). The TTNBBS can be accessed with
a dial-in phone line and a high-speed modem (PH# 919-541-5742). The
parity of your modem should be set to none, the data bits to 8, and the
stop bits to 1. Either a 1200, 2400, or 9600 baud modem should be used.
When first signing on, the user will be required to answer some basic
informational questions for registration purposes. After completing the
registration process, proceed through the following series of menus:
(M) OMS
(K) Rulemaking and Reporting
(3) Fuels
(9) Reformulated gasoline
A list of ZIP files will be shown, all of which are related to the
reformulated gasoline rulemaking process. The six documents mentioned
above will be in the form of a ZIP file and can be identified by the
following titles: ``PREAMBLE.ZIP'' (preamble); ``RIAFINAL.ZIP'' (RIA);
``ENFORCE.ZIP'' (RCEP); ``EPAFINAL.ZIP'' (complex model);
``MODFINAL.ZIP'' (simple model); ``REGFINAL.ZIP'' (regulations). To
download these files, type the instructions below and transfer
according to the appropriate software on your computer:
<D>ownload, <P>rotocol, <E>xamine, <N>ew, <L>ist, or <Help Selection or
<CR> to exit: D filename.zip
You will be given a list of transfer protocols from which you must
choose one that matches with the terminal software on your own
computer. Then go into your own software and tell it to receive the
file using the same protocol. Programs and instructions for dearchiving
compressed files can be found via <S>ystems Utilities from
the top menu, under <A>rchivers/de-archivers.
I. Background
The purpose of the reformulated gasoline regulations is to improve
air quality by requiring that gasoline be reformulated to reduce motor
vehicle emissions of toxic and tropospheric ozone-forming compounds, as
prescribed by section 211(k)(1) of the Clean Air Act (CAA or the Act),
as amended. This section of the Act mandates that reformulated gasoline
be sold in the nine largest metropolitan areas with the most severe
summertime ozone levels and other ozone nonattainment areas that opt
into the program. It also prohibits conventional gasoline sold in the
rest of the country from becoming any more polluting than it was in
1990. This requirement ensures that refiners do not ``dump'' fuel
components that are restricted in reformulated gasoline and that cause
environmentally harmful emissions into conventional gasoline.
Section 211(k)(l) directs EPA to issue regulations that, beginning
in 1995, ``require the greatest reduction in emissions of ozone-forming
and toxic air pollutants (``toxics'') achievable through the
reformulation of conventional gasoline, taking into consideration the
cost of achieving such emission reductions, any non air-quality and
other air-quality related health and environmental impacts and energy
requirements.'' The Act mandates certain requirements for the
reformulated gasoline program. Section 211(k)(3) specifies that the
minimum requirement for reductions of volatile organic compounds (VOC)
and toxics for 1995 through 1999, or Phase I of the reformulated
gasoline program, must require the more stringent of either a formula
fuel or an emission reductions performance standard, measured on a mass
basis, equal to 15 percent of baseline emissions. Baseline emissions
are the emissions of 1990 model year vehicles operated on a specified
baseline gasoline. CAA compositional specifications for reformulated
gasoline include a 2.0 weight percent oxygen minimum and a 1.0 volume
percent benzene maximum.
For the year 2000 and beyond, the Act specifies that the VOC and
toxics performance standards must be no less than that of the formula
fuel or a 25 percent reduction from baseline emissions, whichever is
more stringent. EPA can adjust this standard upward or downward taking
into account such factors as feasibility and cost, but in no case can
it be less than 20 percent. These are known as the Phase II
reformulated gasoline performance standards. Taken together, sections
211(k)(1) and 211(k)(3) call for the Agency to set standards that
achieve the most stringent level of control, taking into account the
specified factors, but no less stringent than those described by
section 211(k)(3).
The reader may refer to the April 16, 1992 SNPRM (57 FR 13416) and
the February 26, 1993 NPRM (58 FR 11722) described in more detail
below), the February 1993 Draft Regulatory Impact Analysis (DRIA), the
Final Regulatory Impact Analysis (RIA), and Public Dockets A-91-02 and
A-92-12 for a thorough description of the goals and regulatory
development of the reformulated and anti-dumping programs and
discussions of a number of associated technical issues.
A. Regulatory Negotiation (Reg Neg)
Shortly after passage of the Clean Air Act Amendments of 1990, EPA
entered into a regulatory negotiation with interested parties to
develop specific proposals for implementing both the reformulated
gasoline and related anti-dumping programs. These parties included
representatives of the oil and automobile industries, vehicle owners,
state air pollution control officials, oxygenate suppliers, gasoline
retailers, environmental organizations, and citizens' groups. (See the
1991 NPRM for the members of the negotiating committee and a discussion
of the process for selecting them.)
In August 1991 the committee reached consensus on a program outline
and signed an ``Agreement in Principle'' describing that consensus. EPA
agreed to propose a two-step approach to reformulated gasoline. The
first step would take effect in 1995 and utilize a ``simple model'' to
certify that a gasoline meets applicable emission reduction standards.
The simple model allows certification based on a fuel's oxygen,
benzene, heavy metal and aromatics content and Reid Vapor Pressure
(RVP).
Under the second step, according to the regulatory negotiation
agreement, EPA would propose a ``complex model'' to supplant the simple
model for certifying compliance with these standards. Certification
under the complex model would take effect 4 years after it is
promulgated. EPA also agreed to propose the more stringent Phase II
emission performance standards.
B. July 9, 1991 NPRM (56 FR 31176)
The first NPRM for the reformulated gasoline program was published
prior to the conclusion on the regulatory negotiations. Normally, in a
negotiated rulemaking, such a reg-neg committee meets to develop a
proposed rule which will be acceptable to all parties. If consensus is
reached on a proposed rule, it is published as an NPRM. The committee
members and the entities they represent agree to support the proposal
and not to seek judicial review of the final rule if it has the same
substance and effect as the consensus proposal. In this case, EPA
published an NPRM while the advisory committee was still conducting
negotiations. The Agency believed that although consensus of the
members on an acceptable rule was possible, an NPRM was required at
that time in order to meet the statutory deadline.
The 1991 NPRM described the provisions of both a program to require
the sale of gasoline which reduces emissions of toxics and ozoneforming
volatile organic compounds (VOCs) in certain nonattainment
areas and a program to prohibit the gasoline sold in the rest of the
country from becoming more polluting. The 1991 notice described the
outline of the reformulated gasoline program as required by statutory
provisions and options that the regulatory negotiation committee
members were considering. Topics included in the 1991 proposal
consisted of the derivation of the emission standards, fuel
certification by modeling, opt-in provisions, credits, anti-dumping
requirements, and enforcement provisions for all aspects of the
reformulated gasoline program.
C. April 16, 1992 SNPRM (57 FR 13416)
As noted above, the Agency's SNPRM (57 FR 13416) reflected the
agreement reached in the regulatory negotiation that had been conducted
to develop reformulated gasoline regulations under section 211(k). The
Supplemental Notice of Proposed Rulemaking (SNPRM) described the
standards and enforcement scheme for both reformulated and conventional
gasoline. It also included specific proposals for the simple emission
model to be used in gasoline certification and enforcement.
D. February 26, 1993 NPRM (58 FR 11722)
In their comments on the SNPRM, the ethanol industry expressed
concern that the reformulated gasoline rulemaking, as proposed in the
SNPRM, effectively excluded ethanol from the reformulated gasoline
market. In an attempt to address their concern, the Agency proposed an
ethanol incentive program, at the direction of former President Bush,
intended to promote the use of ethanol (and other renewable oxygenates)
in reformulated gasoline. The objective of the proposed renewable
oxygenate program was to enhance the market share for renewable
oxygenates while, theoretically, maintaining the overall environmental
benefits of the reformulated gasoline simple model. This would be
accomplished by offsetting any increase in volatility that may result
from the inclusion of ethanol with volatility reductions that occur in
the rest of the RFG pool. This volatility balancing, however would not
take into account any increase in volatility in-use due to mixing of
ethanol and non-ethanol gasoline blends (commingling). The renewable
oxygenate program would not be required in class B areas (the South)
unless a state requested inclusion in the program. Thus, the NPRM (58
FR 11722) for reformulated gasoline proposed revisions to the simple
model, as well as to the associated anti-dumping, and enforcement
provisions. Also included in the NPRM were the proposed complex model
for certification of reformulated gasoline and the proposed Phase II
performance standards. The complex model is now scheduled to take
effect January 1, 1998. The complex model will provide a method of
certification based on the fuel characteristics such as oxygen,
benzene, aromatics, RVP, sulfur, olefins and the percent of fuel
evaporated at 200 and 300 degrees Fahrenheit (E200 and E300,
respectively). The NPRM also proposed Phase II standards for
reformulated gasoline which are to take effect in the year 2000, as
prescribed by section 211(k)(3) of the Clean Air Act (CAA). The
proposed VOC performance standard was 20-32 percent for class B and 26-
35 percent for class C. EPA proposed to set the toxic standard at 20 or
25 percent reduction since additional toxics control was not found to
be cost effective and, in most cases, these greater toxics reductions
were expected to occur through fuel reformulation for VOC control. The
NPRM also included proposed NO<INF>x performance standards of 0-16
percent in classes B and C. The proposed NO<INF>x standards greater
than zero were not required by the CAAA, but were proposed under the
authority of section 211(c)(1) in conjunction with the Phase II
reformulated gasoline standards of the Act since additional NO<INF>x
control was deemed beneficial and cost effective in reducing ambient
ozone levels.
E. Discussion of Major Comments and Issues
EPA received a number of comments on the first NPRM (56 FR 31176),
the SNPRM (57 FR 13416), and the latest NPRM (58 FR 11722) for
reformulated and conventional gasoline. Comments covered a wide range
of topics including regulatory procedure, certification standards,
modeling emissions by the simple and complex models, the role of
ethanol and other oxygenates in reformulated gasoline, vehicle testing,
the anti-dumping program, Phase II standards, cost-effectiveness, and a
number of enforcement-related issues. EPA has conducted an analysis of
the comments received and duly considered the significant issues.
Summaries of these comments and EPA's responses to them are contained
in the Final Regulatory Impact Analysis and the Summary and Analysis of
Comments which has been placed in the docket for this rulemaking
(Public Docket No. A-92-12). Since the publication of the NPRM, the
Agency has continued to develop the complex model. The first revisions
of the complex emissions model since 1993 NPRM publication for
reformulated gasoline have been provided to the public at a June 2,
1993 public workshop. EPA developed several complex model options in
July which was provided to the public. In October of 1993, a draft
version of the final complex model was released for public inspection
as well. All the iterations of the complex model since the publication
of the 1993 NPRM have been available to the public via a public
electronic bulletin board and in submittals to the EPA Air Docket,
Docket No. A-92-12.
All the various components of this rulemaking are being finalized
in today's notice. The additional time has allowed adequate public
review of the complex model and its implications for the reformulated
gasoline Phase II standards.
The remainder of this preamble is organized into the following
sections:
II. Treatment of Ethanol
III. Simple Model for Reformulated Gasoline Compliance
IV. Complex Model
V. Augmenting the Models Through Testing
VI. Phase II (Post-1999) Reformulated Gasoline Performance
Standards and NO<INF>x Standards for Reformulated Gasoline
VII. Enforcement
VIII. Anti-Dumping Requirements for Conventional Gasoline
IX. Anti-Dumping Compliance and Enforcement Requirements for
Conventional Gasoline
X. Provisions for Opt-In by Other Ozone Non-Attainment Areas
XI. Federal Preemption
XII. Environmental and Economic Impacts
XIII. Public Participation
XIV. Compliance With the Regulatory Flexibility Act
XV. Statutory Authority
XVI. Administrative Designation and Regulatory Analysis
XVII. Compliance With the Paperwork Reduction Act
XVIII. Notice Regarding Registration of Reformulated Gasolines
II. Treatment of Ethanol
A. Background
The April 16, 1992 proposal of the Simple Model and Phase I
standards was designed to be fuel and oxygenate neutral. Ethanol,
however, when added to gasoline in the amount needed to satisfy the
oxygen content requirement of the Act raises the Reid vapor pressure
(RVP) of the resulting blend by about 1 psi, making it more difficult
for ethanol blends to meet the mass VOC performance standards than
blends using other oxygenates. For ethanol to be blended with the RFG,
a blendstock gasoline with an RVP low enough to offset the increase
resulting from adding ethanol would have to be obtained.
Ethanol industry representatives commented that obtaining such
blendstocks would be both difficult and expensive, because ``sub-RVP''
blendstocks would be more costly to refine and because blendstock
production would be controlled by petroleum refiners. Methyl tertiary
butyl ether (MTBE), an oxygenate which does not boost a fuel's RVP,
which is derived from methanol gas and the petroleum product
isobutylene and whose blends can readily be put through petroleum
pipelines, was thought to be the oxygenate of choice for most refiners.
Ethanol's representatives theorized that the oil industry would have a
desire to use MTBE over ethanol and, thus, little incentive to make the
sub-RVP blendstock necessary for ethanol blending. The ethanol industry
contended that a reformulated gasoline program which they argued would
effectively preclude ethanol was contrary to Congress' intent that
ethanol have a role in the program. They argued that the oxygen content
requirement of section 211(k)(2) was motivated in large part by a
desire to expand markets for ethanol. They noted the strong support
afforded the RFG legislative initiative by members of Congress from
agricultural states. They also cited statements in the legislative
history indicating some members' expectation that the RFG program would
provide an increasing market for ethanol.
Ethanol representatives contended that the benefits of ethanol use
justify its inclusion in the RFG program. Specifically, they explained
that ethanol is currently made in the United States from domesticallygrown
grains, primarily corn, and thus represents an important domestic
and renewable source of energy. They further explained that to the
extent ethanol is used in place of imported petroleum products, it
promotes the nation's energy independence and improves its balance of
trade, and that ethanol use also strengthens the market for corn,
consequently reducing the need for price supports. Moreover, as a
biomass-based product, ethanol is potentially a renewable fuel to the
extent the energy derived exceeds any fossil fuel energy consumed in
producing the ethanol.
In view of ethanol's importance to the nation's energy security and
agricultural economy, ethanol representatives urged that the proposal
be revised to allow ethanol to effectively participate in the RFG
market. They suggested several possible revisions. For example, they
argued that the 1 psi waiver granted to certain ethanol blends by
section 211(h) of the CAA be applied to ethanol-blended RFG under
section 211(k). They reasoned that since Congress recognized in the
provision requiring nationwide reductions in fuel RVP that ethanol
required such a waiver, ethanol should receive a similar waiver if the
VOC performance standard for RFG sold in the smoggiest cities were
defined in terms of a required reduction in RVP.
If the section 211(h) waiver were not available to RFG ethanol
blends, the ethanol industry suggested that the VOC reduction
requirement take into account that specific VOCs from various
reformulated gasolines differ in their ozone formation potential. While
ethanol raises a fuel's volatility and thus its VOC emissions, they
argued that the resulting VOCs are less ozone-forming than those that
would otherwise occur. They urged that the 15 percent reduction
requirement should thus be interpreted to require a 15 percent
reduction in ozone-forming potential, not simply mass of ozone-forming
VOCs. Ethanol supporters suggested additional ways of encouraging or
even requiring ethanol use in RFG. The Governors Ethanol Coalition, for
instance, suggested that EPA require the RFG market to satisfy its
oxygenate requirements through a minimum percentage of domestically
produced renewable fuel.
Based on ethanol's importance to the nation's energy and
agricultural policy, President Bush on October 1, 1992 announced a plan
to allow ethanol to effectively compete in the RFG program, with the
expectation that, with barriers removed, ethanol use would grow. In
lieu of an RVP waiver, or inclusion of ozone reactivity this plan was
based upon provisions of section 211(k)(1) allowing the Administrator
to take into consideration cost, energy requirements, and other
specified factors in setting RFG performance standards. The most
significant part of this plan called for EPA to ``establish rules for
reformulated gasoline in all northern cities that will have the effect
of granting a one-pound waiver for the first 30 percent market share of
ethanol blends, while achieving environmental benefits comparable to
those provided for in EPA's proposed rule and regulatory negotiation.''
The environmental benefits of the proposed RFG program would be
maintained by offsetting any increase in volatility of RFG containing
ethanol with reductions in the volatility of the rest of the
reformulated gasoline pool. In response to the announcement by former
President Bush, EPA proposed on February 26, 1993 provisions to provide
an RVP (and VOC) incentive for the use in reformulated gasoline of
renewable oxygenates such as ethanol.
B. Concerns With the Proposal
At the time of the February 26, 1993 proposal, EPA had a number of
concerns with respect to its legality, energy benefits, and
environmental neutrality. Nevertheless, we proposed the provisions for
public comment in the hope that these concerns could be overcome based
on new data and information developed in-house or received through
public comment. Since the time of the proposal these concerns have been
enhanced. Additional data and information has been developed which
indicates that energy benefits would be unlikely to occur as a result
of the proposal. While the production of much of the ethanol in the
country produces on the margin more energy and uses less petroleum than
went into its production, a recent study by the Department of Energy
(refer to DOE's comments on the proposal) indicates that the margin
disappears when ethanol is mixed with gasoline. The energy loss and
additional petroleum consumption necessary to reduce the volatility of
the blend to offset the volatility increase caused by the ethanol
causes the energy balance and petroleum balance to go negative. Since
the potential energy benefits were the basis in the proposal for
providing the incentives for renewable oxygenates, the justification
for the proposal no longer exists.
Additional data and information has also been developed which
indicates that VOC emissions would increase significantly under the
proposal. As discussed in section I of the RIA, the commingling effect
of mixing ethanol blends with non-ethanol blends in consumer's fuel
tanks, the effect of ethanol on the distillation curve of the blend,
and unrestricted early use of the complex model combined result in
roughly a 6-7.5% increase in gasoline vehicle VOC emissions even though
there is no increase in the average RVP of in-use gasoline. As a
result, the proposal would have sacrificed 40 to 50 percent of the VOC
control that is required under section 211(k) for reformulated gasoline
in exchange for incentives for what is likely to have been only a
marginal increase in the market share of ethanol in reformulated
gasoline and no energy benefits or cost savings.
As discussed in section I of the RIA, ethanol is not excluded from
competing in the reformulated gasoline market under the provisions of
the April 16, 1992 SNPRM. As a result of the economic advantage of
ethanol over other oxygenates, ethanol should maintain a significant
market share under the reformulated gasoline program even without the
renewable oxygenate incentives proposed in the February 16, 1993
proposal. As a result, the actual ethanol market share increase as a
result of the renewable oxygenate provisions would be expected to be
far less than the maximum of 30% for which incentives were provided.
Given the relatively small increase in ethanol demand as a result of
the renewable oxygenate provisions in exchange for such a large loss in
the environmental control of the reformulated gasoline program, there
does not appear to be any justification for promulgating these
provisions.
Furthermore, comments were received from virtually all parties,
including ethanol industry representatives, that the proposal was
unworkable and would significantly increase the cost of the
reformulated gasoline program. While EPA maintains that the program
would have provided an economic incentive for the use of renewable
oxygenates in reformulated gasoline up to a 30% market share, EPA
acknowledges that the proposal would have intruded into the efficient
operation of the marketplace, impacting the cost of the reformulated
gasoline program. As a result, after taking into account the cost, nonair
quality and environmental impacts, and energy impacts, EPA has
found itself with no choice but to back away from the renewable
oxygenate provisions of the February 26, 1993 proposal.
C. Provisions for the Final Rule
In lieu of the renewable oxygenate proposal, EPA investigated a
number of options aimed at making the program more workable by reducing
the fuel tracking, recordkeeping, and enforcement burden associated
with the proposal. While such options tended to make the program more
workable from the standpoint of the refining and fuel distribution
processes, they also tended to either reduce the assurance that the
environmental benefits of the program would be achieved in all areas
covered by the RFG program, or to place additional restrictions on the
flexibility contained in the proposal for blending ethanol into
gasoline. Given this and the other concerns with the proposal (cost,
lack of energy benefits, significant environmental loss, etc.), EPA did
not believe these options to be appropriate or justifiable either under
the provisions of section 211(k) of the Act. The reader is referred to
the Final Regulatory Impact Analysis for a detailed discussion of the
renewable oxygenate program.
A number of commenters suggested alternative provisions (1.0 psi
RVP waiver for ethanol blends, inclusion of ozone reactivity in the
standard setting process, mandates for refiners to provide clear
gasoline blendstock for downstream blending with ethanol, etc.) to the
proposed renewable oxygenate program to allow ethanol to play a larger
role in the reformulated gasoline program. It was argued that without
such provisions ethanol would be excluded from the market entirely in
direct conflict with the intent of Congress in the CAA.
EPA, however, does not agree that ethanol is excluded from
competing in the reformulated gasoline marketplace under the provisions
of the April 16, 1992 proposal. In fact, as under the recently
implemented wintertime oxygenated fuels program, ethanol is expected to
significantly increase its market share under the reformulated gasoline
program, especially in Midwestern areas where ethanol enjoys State tax
incentives and relatively low distribution costs. In addition, not only
is ethanol expected to compete as an alcohol, but it also may compete
with methanol as an ether feedstock in the future. As a result, EPA
believes that the treatment of ethanol blends under the April 16, 1992
proposal is entirely consistent with the intent of Congress as
expressed in section 211(k) of the CAA.
The alternative provisions (1.0 psi RVP waiver for ethanol blends,
inclusion of ozone reactivity in the standard setting process, mandates
for refiners to provide clear gasoline blendstock for downstream
blending with ethanol, etc.) suggested by various commenters to further
enhance the competitiveness of ethanol in the reformulated gasoline
program are not appropriate. These provisions are both outside of EPA's
legal authority under the CAA, and indefensible from an environmental
and scientific standpoint. The 1.0 psi waiver for example, could easily
forfeit all VOC emission reductions otherwise achieved by the
reformulated gasoline program. A move away from the mass based
standards of the Act to reactivity based standards is not only
unsupportable on the basis of the available scientific information, but
even if EPA were able to do so, it would be unlikely to provide any
significant advantage for ethanol blends. As discussed in section I of
the RIA, the recent urban airshed modeling studies claiming that
ethanol blends with a 1.0 psi waiver do not increase ozone relative to
an MTBE blended reformulated gasoline are frought with invalid
assumptions and inconsistencies and are not applicable to the
reformulated gasoline situation. As a result, they provide no credible
scientific support for special provisions for ethanol in the context of
the reformulated gasoline program.
Given the lack of justification for the renewable oxygenate
provisions of the February 26, 1993 proposal, the options considered
for simplifying that proposal, and other alternative provisions
recommended by commenters, EPA is, thus, basing the oxygenate-related
provisions of the final rule on the provisions as proposed in the April
16, 1992 proposal. Despite this decision, EPA still believes ethanol
will be able to compete favorably in the reformulated gasoline market
either as a direct additive or as an ether feedstock as discussed
above. As such, EPA believes that the nationwide production of ethanol
will increase as a result of this rulemaking with corresponding
benefits to our Nation's agricultural sector. However, the increase may
not be as large as it otherwise would have been had an incentive
program been promulgated for ethanol. The reader is referred to section
I. of the RIA for additional description of the comments and
information which led up to this decision.
III. Simple Model for Reformulated Gasoline Compliance
In accordance with section 211(k) of the Clean Air Act, EPA
requires that in order for a gasoline to be certified as reformulated,
it must contain at least 2.0 weight percent oxygen, no more than 1.0
volume percent benzene, and no heavy metals (unless a waiver is
granted); result in no increase in NO<INF>X emissions; and achieve
required toxics and VOC emission reductions. The VOC, NO<INF>X, and
toxics emission requirements effective between January 1, 1995 and
December 31, 1997 and EPA's derivation of them are set forth below.
Two methods by which refiners can certify their fuel as meeting the
VOC, NO<INF>X, and toxics requirements of reformulated gasoline are
contained in this rulemaking. The first, by use of a ``Simple Model,''
is described in this section. A second method, the use of the ``Complex
Model'' is described in Section IV. Provisions for augmenting the
Complex Model through vehicle testing are described in Section V. For
reasons set forth in the April 16, 1992 SNPRM (57 FR 13417-13418) and
discussed Section V, vehicle testing is not an option as a separate,
stand-alone method of certification. First, models can better reflect
in-use emission effects since they can be based on the results of
multiple test programs. Second, individual test programs may be biased,
either intentionally or unintentionally. Third, fuel compositions tend
to vary due in part to factors beyond the control of fuel suppliers,
potentially requiring testing of each batch if a model is not used.
Finally, models make more efficient use of scarce and expensive
emissions effects data than is otherwise possible. For these reasons,
EPA believes that the modeling options promulgated by EPA are necessary
for the reformulated gasoline program to achieve its environmental
objectives and to minimize the costs of the program. Comments were
received suggesting that EPA allow certification based on testing as an
optional means of certification. However, for the same reasons
discussed above, EPA does not believe such an option would be
appropriate. EPA would have much less certainty that the results of the
test program were valid.
At the time of the simple model proposal, while a number of fuel
parameters were thought to impact emissions, data were sufficient for
only a few of these parameters (Reid vapor pressure, fuel oxygen,
benzene, and aromatics) to quantify their effect with reasonable
accuracy for use in an emissions model. For those additional parameters
which were thought to impact emissions in a directionally clear, but as
of yet unquantifiable manner (sulfur, T90, and olefins), EPA proposed
that they be capped at the refiner's 1990 average level to prevent
emission effects from changes in their levels from undercutting the
emission reductions achieved by the parameters contained in the simple
model. The effect of aromatics on VOC and NO<INF>X emissions was also
unclear, but instead of being capped, it was believed that the level of
aromatics would be controlled by the role aromatics plays in the
formation of air toxics emissions.
Data is now available to accurately quantify not only the effects
of RVP, oxygen, benzene, and aromatics on emissions, but also sulfur,
T90 (or E300), olefins, and T50 (or E200). The effects of these fuel
parameters are incorporated into the Complex Model described in Section
IV.
The Complex Model is the most accurate and complete model currently
available for use in the reformulated gasoline program. Absent any
other considerations, EPA would require use of the Complex Model for
purposes of certification. However, based on leadtime considerations,
EPA is allowing use of either the Simple or Complex Model during the
first three years of the reformulated gasoline program as proposed.
These lead time considerations were described in the April 1992
proposal (57 FR 13417-8). EPA is providing four years leadtime before
use of the Complex Model is mandatory to allow the regulated industry
adequate time to plan and design necessary refinery modifications,
obtain necessary permits and capital, complete construction, and
complete start-up and equipment shakedown. Furthermore, EPA has every
confidence that on average the refiners certifying their fuel using the
Simple Model will achieve the emission reductions that Congress
intended for the reformulated gasoline program.
Various comments were received criticizing the use of the Simple
Model for fuel certification, stating that it had limited flexibility,
discouraged innovation, penalized refiners producing cleaner than
average gasoline in 1990, and should be scrapped. Many of these
comments would appear to be resolved by the option available for early
use of the Complex Model. Therefore, in keeping with the need to
provide adequate lead time and the fact that compliance with the Simple
Model will produce the mandatory VOC and toxic emission reductions,
refiners will be permitted to use the simple model for certification
until December 31, 1997. Until this date, fuel suppliers will have the
option of using the complex model instead of the simple model to take
advantage of the effects of parameters contained in the complex model
but not contained in the simple model (as described in the following
paragraphs). The reader is referred to the April 16, 1992 SNPRM for
more discussion of these lead time provisions.
A. Simple VOC Emissions Model
The simple model for VOC emissions is comprised of fuel
specifications for RVP and oxygen. Fuels sold at retail outlets must
have an RVP during the high ozone season (June 1 through September 15)
of no more than 7.2 psi in VOC control region 1 (the southern areas
typically covered by ASTM class B during the summer) and 8.1 psi in VOC
control region 2 (the northern areas typically covered by ASTM class C
during the summer).<SUP>1 The differences in climate between these two
types of areas requires a corresponding difference in gasoline
volatility to achieve the same emissions effect. The period of June 1
through September 15 was chosen for the high ozone season because most
of the ozone violations occur during this period. (See 56 FR 24242 for
a discussion of the determination of this period.)
\1\Lower RVP limits apply for fuels that comply under averaging.
RVP controls also apply from May 1 to May 31 for facilities upstream
of retail outlets. These issues are discussed elsewhere in this
proposal.
Section 211(k)(3) of the Act requires that at a minimum
reformulated gasoline comply with the more stringent of either a 15%
reduction in VOC emissions or a formula fuel described in that section,
whichever is greater. EPA has determined that the formula fuel would
achieve less than a 15% reduction in VOC. As such, the minimum VOC
emission reduction required by the Act is 15%. As discussed in section
IV, EPA believes that the VOC emission reduction in VOC control region
2 from a fuel with an RVP of 8.1 psi and 2.0 weight percent oxygen will
be sufficient to achieve the minimum 15% VOC emission reduction
relative to the Clean Air Act baseline gasoline (which has an RVP of
8.7 psi). In VOC control region 1, an 8.1 psi RVP fuel with 2.0 percent
oxygen (which would meet the minimum 15% reduction requirement relative
to the CAA baseline fuel) would actually have greater emissions than a
fuel meeting EPA's Phase II RVP control standards for VOC control
region 1 (maximum RVP of 7.8 psi). EPA believes that when Congress
designated cities for inclusion in the reformulated gasoline program
that it intended the program to provide emissions reductions in
addition to those provided by the Phase II RVP requirements. If EPA
merely required reformulated gasoline in VOC control region 1 to meet
the RVP requirement for VOC control region 2, then no reduction in VOC
emissions would accrue under the first phase of the reformulated
gasoline program beyond those mandated by Phase II RVP standards. EPA
projects that relative to Phase II RVP control levels, a fuel with 7.2
psi RVP and 2.0 weight percent oxygen would provide VOC emission
reductions in VOC control region 1 similar to those obtained in VOC
control region 2.
While requiring reformulated gasoline sold in VOC control region 1
to have an RVP of no more than 7.2 psi goes beyond the minimum
requirement stated in section 211(k)(3), section 211(k)(1) authorizes
EPA to require emission reductions in VOC control region 1 of this
magnitude because they are achievable considering costs, other air
quality and non-air quality impacts, and the energy implications of
such a requirement.
Similarly, EPA believes that additional VOC reductions are
obtainable if refiners are allowed to meet the RVP and oxygen standards
through averaging. If refiners wish to take advantage of averaging, EPA
thus will require their average RVP for both VOC control regions 1 and
2 to be reduced by 0.1 psi to 7.1 and 8.0 psi, respectively, and the
average oxygen concentration to be increased to 2.1 weight percent
oxygen. For additional discussion of the rationale for the more
stringent standard in VOC control region 1 and the increase in
stringency of the averaging standards, the reader is referred to the
April 16, 1992 SNPRM.
B. Simple NO<INF>x Emissions Model
The Clean Air Act requires that there be no NO<INF>X emissions
increase from reformulated fuels. Based on data available during the
regulatory negotiations and at the time of the April 16, 1992 proposal,
it appeared that fuel oxygen content and the type of oxygenate used may
have an impact on NO<INF>X emissions while no other simple model
parameter appeared to have such an impact. Due to the statutory
requirement for oxygenate use, and the lack of any other parameters in
the simple model by which refiners could offset any NO<INF>X increase,
EPA needed to place restrictions on the amount of oxygen that could be
added to the fuel in order to prevent NO<INF>X emission increases. EPA
proposed on the basis of the data then available that MTBE blends
containing up to 2.7 weight percent (wt%) oxygen and other blends
containing up to 2.1 wt% oxygen would be presumed to result in no
NO<INF>X increase. Greater oxygenate concentrations could not be
permitted due to the risk of NO<INF>X emission increases.
When additional data became available, however, there did not
appear to be any significant difference between the NO<INF>X emission
effects of oxygen from different oxygenates. Furthermore, it appeared
that reducing the concentration of a number of additional fuel
parameters (aromatics, olefins, sulfur, etc) could reduce NO<INF>X
emissions. Since these fuel parameters all tend to be reduced to
varying degrees when oxygenates are added to gasoline, EPA proposed in
its February 26, 1993 proposal that all oxygenates be assumed to result
in no NO<INF>X emission increase under the simple model up to 2.7 wt%
oxygen.
Under the final Complex Model discussed in Section IV, oxygen has
been found to result in no NO<INF>X increase, in fact, it results in a
very slight decrease. However, the other changes that occur to the fuel
when oxygenates are added both increase and decrease NO<INF>X emissions
(increases in E200 increase NO<INF>X emissions while reductions in
sulfur, olefins, aromatics, and increases in E300 reduce NO<INF>X
emissions). Typically the effect of these other fuel changes will be to
further reduce NO<INF>X emissions. However, there is no control placed
on E200 levels under the simple model, and the levels of sulfur,
olefins, an E300 are only constrained to the refiner's 1990 baseline
levels (aromatics is controlled indirectly to some degree by the toxics
requirement). As a result, there is no assurance under the simple model
that oxygenate addition will not increase NO<INF>X emissions. The more
oxygenate added, the greater the increase in E200, and the greater the
possibility for a NO<INF>X increase. For this reason EPA believes it is
still appropriate to cap the maximum oxygen content under the Simple
Model at 2.7 wt%. Any higher oxygen concentrations will require use of
the complex model.
However, for a number of reasons, EPA believes it is appropriate
for any oxygenate up to 3.5 weight percent oxygen to be presumed to
result in no NO<INF>X emission increase under the simple model during
those months without ozone violations (e.g., winter months) unless a
state requests that oxygenate levels be limited to the 2.7 wt% oxygen
level applicable during those months with ozone violations. First,
although there are a number of concerns associated with NO<INF>X
emissions, the main concern of focus in this rulemaking is ozone which
is for the most part a summertime problem. Second, while there is no
assurance that individual batches of gasoline containing more than 2.7
wt% oxygen will not increase NO<INF>X emissions, the increase, if any,
would be small (i.e., likely less than 1 percent). Third, on average
across all fuel produced by all refiners in an area, a NO<INF>X
reduction may still occur. Fourth, there are benefits to the use of
oxygenates during the winter months (lower CO and air toxics emissions)
that may be more important to individual states than the certainty that
no one batch of fuel increases NO<INF>X emissions relative to the 1990
baseline.
A state may make a request for the 2.7 wt% oxygen limit to apply
during the non-ozone season when it believes that the use of higher
oxygenate levels would interfere with attainment or maintenance of
another ambient air quality standard (other than ozone) or another air
quality problem. This proposal parallels the Regulatory Negotiation
Agreement of August 16, 1991 and EPA's letter to the Renewable Fuels
Association dated August 14, 1991.
C. Simple Toxics Emissions Model
Under section 211(k)(3), EPA must at a minimum require the more
stringent of either a specified formula fuel or a 15 percent reduction
in toxics emissions from that of baseline gasoline. All five of the
toxic air pollutants that section 211(k)(10) of the Act specifies for
control through reformulated gasoline (benzene, 1,3-butadiene,
polycyclic organic matter (POM), formaldehyde, and acetaldehyde) also
fall under the category of VOCs. Exhaust emissions include unburned
benzene and benzene formed from other aromatics during the combustion
process. Benzene, an aromatic compound, is a natural component of
gasoline and, as such, is present in evaporative, running loss and
refueling emissions (nonexhaust emissions). However, nonexhaust VOC and
benzene emissions data are only available in sufficient quantities
under high ozone test conditions. Therefore, nonexhaust benzene
emissions are not considered outside of the high ozone season. The four
other toxic air pollutants subject to control by reformulated gasoline
are not present in gasoline and hence are solely products of
combustion.
The equations that represent the simple model for air toxics
emissions are shown in section 80.42 of the regulations. The derivation
and referenced work is given in the regulatory impact analysis.
Only minor changes were made to the proposed simple toxics model.
One change excluded ethane from the exhaust VOC baseline emissions as
discussed below in Section III.D.3. The weight fractions of the various
toxics as a function of VOC have also been adjusted accordingly,
resulting in no net change in predicted toxics performance for a
particular fuel. At the request of commenters, EPA has also included
the oxygenates tertiary amyl methal ether (TAME) and ethyl tertiary
amyl ether (ETAE) as well as provisions for other oxygenates and mixed
oxygenates. Due to their similar chemical makeup, methyl ethers (such
as TAME) and ethyl ethers (such as ETAE) are to be modeled using the
same equations as for MTBE and as for ETBE, respectively. Higher
alcohols will be modeled using the same equations as for ethanol.
Higher ethers will be modeled as ETBE for all air toxics, since ETBE
was the highest ether for which toxics data were available.
D. Baseline Determination
Where the performance standard is more stringent than the formula,
the Act requires EPA to promulgate standards for the performance of
reformulated gasoline that are relative to emission levels from
baseline vehicles using baseline fuel. In order to determine whether
fuels meet the performance requirements of reformulated gasoline under
the simple model, EPA must therefore establish the baseline to which
the emission performance of reformulated fuels are to be compared. The
following discussion describes how EPA derived the emission baselines.
- Control Periods
Before the emission baselines can be determined, the time frame
over which fuel performance will be evaluated must be identified.
Section 211(k) of the Act requires control of VOC emissions during the
``high ozone season.'' For the purposes of this rulemaking, the high
ozone season is defined to be June 1 through September 15. This period
covers the vast majority of days during which the national ambient air
quality standard for ozone is exceeded nationwide and is consistent
with the period covered by EPA's gasoline volatility control
requirements. All gasoline at service stations must thus comply with
the reformulated gasoline requirements during this period. Also in
keeping with the gasoline volatility control rulemaking the ``VOC
control Period'' for compliance with the reformulated gasoline
provisions upstream from the service station (necessary to ensure
complying fuel is available at the service stations during the high
ozone season) is May 1 through September 15.
- Baseline Gasoline
The fuels to be used in determining baseline emissions are
unchanged from the February 26, 1993 proposal and are shown below.
Table III-1.--Baseline Fuel Compositions
Summer Winter
Sulfur, ppm....................................... 339 338
Benzene, volume percent........................... 1.53 1.64
RVP, psi.......................................... 8.7 11.5
Octane, R+M/2..................................... 87.3 88.2
T10, degrees F.................................... 128 112
T50, degrees F.................................... 218 200
T90, degrees F.................................... 330 333
Aromatics, volume percent......................... 32.0 26.4
Olefins, volume percent........................... 9.2 11.9
Saturates, volume percent......................... 58.8 61.7
3. Definition of Ozone-Forming VOC
The Act requires reductions in emissions of ozone-forming VOCs.
This interpretation is consistent with the focus of Section 211(k) on
the areas with the most extreme ozone pollution problem. EPA proposed
in April 16, 1992 that methane would be excluded from the definition of
VOC on the basis of its low reactivity in keeping with past EPA
actions, but included all other VOCs including ethane. EPA further
proposed, however, that should the Agency modify the definition of VOC,
we might do so for the reformulated gasoline rulemaking as well. As
discussed in the February 26, 1993 proposal, EPA has also modified the
definition of VOC to exclude ethane in a separate Agency rulemaking (57
FR 3941). As a result, the performance of fuels meeting the VOC
emission requirements under the simple model are expressed on a nonmethane,
non-ethane basis. This change resulted in slight changes to
the simple model equations previously proposed, but the overall results
of the simple model are essentially unaffected.
4. Simple Model Baseline
The following table shows the baseline emissions under the simple
model which result from the assumptions discussed above. Since the
MOBILE model does not estimate toxics emissions, however, separate data
and information was necessary to determine their baseline emissions.
The toxics baseline was developed in essentially the same manner as
that proposed in the April 16, 1992 proposal. An explanation of this
derivation can be found in Section II of the RIA.
Table III-2.--Simple Model Baseline Emissions
Summer
-------------------------- Winter
Region 1 Region 2
Exhaust VOCs (g/mi).............. 0.444 0.444 0.656
Non-Exhaust VOC (g/mi)........... .856 .766 0
Total VOCs (g/mi)................ 1.30 1.21 0.656
Exhaust Benzene (mg/mi).......... 30.1 30.1 40.9
Evaporative Benzene.............. 4.3 3.8 0.0
Running Loss Benzene............. 4.9 4.5 0.0
Refueling Benzene................ 0.4 0.4 0.0
1,3-Butadiene.................... 2.5 2.5 3.6
Formaldehyde..................... 5.6 5.6 5.6
Acetaldehyde..................... 4.0 4.0 4.0
POMs............................. 1.4 1.4 1.4
Total TAPs (mg/mi)........... 53.2 52.1 55.5
E. Phase I Performance Standards Under the Simple Model
Section 211(k)(3) directs EPA to require, at minimum, that Phase I
reformulated gasoline comply with the more stringent of two alternative
VOC and toxics emission requirements--either a performance standard of
a 15 percent reduction from baseline levels on a mass basis, or
compositional requirements specified as a formula in Section
211(k)(3)(A). The formula effectively defines a set of maximum or
minimum fuel parameter specifications. In evaluating which requirement
is more stringent, EPA is to consider VOC and toxics separately.
The stringency of the formula is best evaluated by determining the
emissions performance of the fuels that would be certifiable if EPA
were to impose the requirements of Section 211(k)(3)(A). A gasoline
would meet these requirements if it (1) had no more than 1.0 volume
percent benzene, (2) had no more than 25 volume percent aromatics, (3)
had no less than 2.0 weight percent oxygen, and (4) met the
requirements for detergent additives and lead content. The formula does
not specify or limit any additional gasoline properties, and therefore
a wide variety of fuels with very different properties would qualify as
complying with the formula. For example, the formula specifies the
weight percent oxygen but does not specify the type of oxygenate. If
EPA were to impose the requirements of Section 211(k)(3)(A), then any
approved oxygenate could be used to meet the formula's oxygen
requirement, as long as it was blended to achieve the required weight
percent oxygen. The same would be true of sulfur levels, distillation
characteristics, olefin levels, RVP levels, and so on. As long as the
formula's requirements were met, the fuel would be certifiable if EPA
were to base its certification requirements on Section 211(k)(3)(A).
To evaluate the emissions performance of the various fuels that
would comply with the formula requirements, EPA used the Phase I
complex model. Given the Phase I baseline emission levels, EPA
considers the complex model to be the most appropriate means of
evaluating emissions performance since it incorporates the Agency's
most recent, complete, and accurate knowledge of the effects of fuel
properties on VOC and toxics emissions. Since many of the fuel
parameters that are not specified for the formula affect VOC and toxics
emissions, the various possible formula fuels exhibit a wide variety of
emission performance levels as these unspecified parameters vary.
According to the Complex Model, requirements based on many possible
formula fuels would be less stringent than requirements based on the 15
percent minimum reduction requirements of Section (211)(k)(3)(B). In
addition, the lack of specificity of the formula fuel would make
establishment of an equivalent emissions performance standard
impossible, since one or more possible formula fuels would fail to meet
any specific standard.
In past proposals, EPA has evaluated the formula fuel by assigning
levels for unspecified parameters at their level in baseline gasoline,
as defined in section 211(k)(9)(B) of the Act. However, such an
interpretation would not eliminate the problems described above, since
the oxygenate type would remain unspecified. Hence the requirements of
a formula could be met by a range of fuels, each based on different
oxygenates, even if unspecified parameters were to be set to baseline
levels, and this range of fuels would exhibit a range of emission
performance levels. While the Complex Model attributes identical
effects to oxygen in different chemical forms for most pollutants, it
incorporates emission effects that depend on the type of oxygenate used
for nonexhaust benzene, acetaldehyde, and formaldehyde emissions. EPA
therefore ran the complex model for several fuels, varying the type of
oxygenate and holding other parameters not specified by the formula at
statutory baseline levels.
The VOC emission reductions from baseline levels for all such
formula fuels were less than 15 percent. EPA therefore based the VOC
emission requirements for Phase I reformulated gasoline on the 15
percent reduction minimum performance standard, since this standard is
more stringent than the requirements of the formula.
For toxics performance, EPA separately evaluated the emissions
performance of fuels that met the formula requirements and contained
statutory baseline levels of unspecified fuel properties for VOC
control regions 1 and 2, since nonexhaust benzene emissions would
differ in these two regions. EPA also evaluated such fuels with
different oxygenate types. The results are shown in Table II-3. These
results include both summer and winter effects, weighted based on the
share of vehicle miles traveled in each season.
Table II-3.--Phase I Toxics Emissions Performance of Formula Fuels
Percent reduction from
CAAB levels
Oxygenate type -------------------------
VOC control VOC control
region 1 region 2
ETBE.......................................... 11.82 11.65
Ethanol....................................... 13.16 13.01
MTBE.......................................... 16.33 16.15
TAME................................ 16.81 16.67
The results indicate that whether a formula fuel (with unspecified
fuel parameters at statutory baseline levels) meets the 15% minimum
performance requirement of section 211(k)(3)(B) depends on the type of
oxygenate used. If EPA were to impose the formula requirements of
section 211(k)(3)(A), the results presented in Table II-3 indicate that
not all gasolines which could be certified as reformulated would
achieve at least a 15 percent reduction in toxics mass emissions, even
if unspecified fuel properties were set at statutory baseline levels.
If EPA were to require a 15 percent emissions reduction in accordance
with section 211(k)(3)(B), however, all fuels would achieve this
minimum level of reductions. EPA therefore believes that the formula
requirements of section 211(k)(3)(A) are not as stringent as the
performance standard set forth in Section 211(k)(3)(B).
The minimum performance standard for Phase II is even more
stringent than the Phase I standards. EPA has therefore determined that
the performance standard is more stringent than the formula for both
VOCs and toxics, for both Phase I and Phase II. EPA must therefore set
its Phase I requirements for both VOCs and toxics to be no less
stringent than the 15 percent emission reduction performance standard
required by section 211(k)(3)(B). EPA has considered whether it should
require greater reductions in toxics mass emissions than that required
by the 15 percent minimum performance standard. However, the Agency has
concluded that more stringent toxics requirements are not costeffective,
as is discussed more fully in Section VI. Hence EPA has set
the Phase I toxic emission performance standard at the minimum 15
percent reduction from baseline levels required by the Act. Compliance
with this standard must be demonstrated using the appropriate emission
models throughout Phase I.
Under the authority of section 211(k)(1), EPA believes that the
greater flexibility and reduced cost afforded to gasoline refiners and
importers by an averaging program allow EPA to require a greater
reduction in toxics emissions than is required under section 211(k)(3).
As discussed in Section VII, the Agency believes it appropriate, when
the air toxics standard is met on average, that it be 1.5 percentage
points more stringent than standards met on a per-gallon basis. EPA
estimates that the approximate 1.5 percentage point margin will be
sufficient to recoup any compliance margin refiners would have
otherwise had to maintain to ensure achievement of the toxics
requirements in the absence of an averaging program. In sum, the
tighter averaged standard should have the potential to increase the
environmental benefits of the reformulated gasoline program while not
increasing the cost of obtaining those benefits. As a result, the air
toxics performance standard when met on an annual average basis is set
at a 16.5% reduction from baseline levels.
F. Applicability (1995-7)
The Simple Model described in this section is effective beginning
January 1, 1995 with the beginning of the reformulated gasoline program
as a means by which fuel producers can certify that their fuel meets
the requirements for reformulated gasoline. The Complex Model described
in Section IV will not be required to be used for fuel certification
until January 1, 1998.
Until January 1, 1998, refiners who produce reformulated gasoline
will have a choice of certifying their gasoline by using either the
Simple Model or the Complex Model. EPA proposed three options for
establishing the performance standards under early, optional use of the
Complex Model. Under one option, if a refiner opts to utilize the
Complex Model before January 1, 1998 the reformulated gasoline can have
no worse VOC, NO<INF>X, or toxic emissions performance than would be
predicted by the Complex Model for a Simple-Model fuel (minimum 2.0
percent oxygen, maximum 1.0 percent benzene, and maximum RVP of 8.1 psi
in Class C areas and 7.2 psi in Class B areas) having that refiner's
average 1990 levels of sulfur, olefins, and T90 (E300). The second
option was a variation of the first, in that refiners producing
gasoline for use in only the southern reformulated gasoline areas (VOC
control region 1) could measure their fuel performance against the CAA
baseline gasoline as an alternative to their own 1990 refinery
baseline. The third option, proposed by EPA in February 1993, would
extend the second option to all reformulated gasoline areas.
The rationales for these options are discussed in detail in EPA's
proposals. Many of the comments were also received prior to the
proposals, and as such were addressed there. As a result, the reader is
referred back to the proposals for additional discussion. After
considering the comments, EPA has decided to promulgate the first
option. First, under this option each refiner will have to achieve the
same reductions, whether they use the simple model or the complex
model. The option to use either model increases refiner flexibility,
but will not change the emissions reductions required for a refiner
prior to mandatory use of the complex model in 1998. EPA believes that
the reductions required under the simple model are achievable
considering all relevant factors and will continue to be so under the
optional use of the complex model. In fact, the additional flexibility
of using the complex model would in some cases make them even more
reasonable.
Second, the other two options create an incentive for early use of
the complex model by those refiners who would then have a less
stringent performance standard than under the simple model. This would
produce on average an increase in overall emissions for reformulated
gasoline compared to average emissions if only the simple model was
allowed. Refiners with individual baselines for sulfur, T90 and olefins
that are lower than the CAA baseline would, under the second and third
options, get credit for emission benefits for these parameters, and
could use this to justify a less stringent RVP control than required
under the simple model. There would be no parallel disincentive to
early use of the complex model for refiners with higher baselines which
would result in an increase in their required reductions. This
imbalance in the expected early use of the complex model could easily
lead to an average 1-2 percentage point reduction in the average
emission performance of reformulated gasoline from 1995-7 as discussed
in section I of the RIA. Based on this negative environmental impact,
and the reasonableness of the complex model performance standard under
the first option, EPA has decided to promulgate the first option
described above for early use of the complex model.
G. Enforcement of the Early Use Option
Additional controls over reformulated gasoline certified using the
``early-use'' complex model are necessary for the operation of the
downstream enforcement mechanisms of VOC and NO<INF>X emissions
performance minimums, and covered area gasoline quality surveys. These
restrictions are necessary because under the restricted early-use
approach being promulgated, VOC, toxics, and NO<INF>X percentage
reductions are calculated from a baseline fuel using the refiner's 1990
baseline levels of sulfur, T-90, and olefins. As a result, the
reformulated gasolines produced by different refiners (or in some
cases, at different refineries) under this option will likely each meet
different percentage reduction standards for VOC, toxics, and NO<INF>X.
Therefore, the performance of a fungible mixture of complex model
gasolines produced by different refiners at different refineries could
not be predicted, nor could be evaluated.\2\
\2\Beginning in 1998, certification of reformulated gasoline
using the simple model will no longer be an option, and all
reformulated gasoline will be certified using the complex model.
Also beginning in 1998, all refiners and importers will calculate
emissions performance reductions from Clean Air Act average
gasoline; individual refiner baselines will not be relevant to
reformulated gasoline. As a result, the difficulties with downstream
enforcement and surveys will be resolved.
In order for the per-gallon minimums for VOC and NO<INF>X emissions
performance to be monitored by downstream regulated parties and
enforced by EPA, the baseline for a given gasoline sample must be
known. Without knowledge of the baseline, it is not possible to
determine whether the fuel complies with the per-gallon minimums, since
it will be different for each refinery. Similarly, in order for the
gasoline quality surveys to function under early use of the complex
model, the baseline from which to determine the emission performance
for VOC, toxics, and NO<INF>X must be known. Without knowledge of the
baseline, it is not possible to determine whether the complex model
fuels in an area on average meet the per-gallon standards.
EPA received comments from two industry groups representing the
refining industry on this issue. Both commenters stated that EPA should
require that ``early-use'' complex model gasolines subject to different
baselines be segregated through the gasoline distribution system. EPA
is adopting this suggested approach as the best (and perhaps only)
means of accommodating both the restricted early-use option and
downstream enforcement of per-gallon minimums and gasoline quality
surveys.
Under this approach, gasoline sampled at any point in the
distribution system would have known values for VOC, toxics, and
NO<INF>X emissions performance that meet the per-gallon and minimum
standards. Today's rule requires that these values must be included in
the product transfer documents for ``early-use'' complex model
gasoline, to inform downstream parties and EPA of the relevant pergallon
and minimum values.
Today's rule prohibits the commingling throughout the distribution
system, including at retail outlets, of ``early-use'' complex model
gasoline that is subject to different baselines. One commenter stated
that the segregation of this gasoline should be through the terminal
level only. EPA disagrees with this comment because segregation through
the retail level also is necessary in order for gasoline quality
surveys to function. Survey samples are taken at retail outlets, and
the survey requires that the relevant per-gallon values for VOC,
toxics, and NO<INF>X emissions performance must be known for each
sample.
EPA realizes that restrictions on commingling of ``early-use''
complex model gasolines constitutes a significant constraint on the use
of this option, because most gasoline used in the United States is
transported as a fungible commodity. As a result, EPA anticipates that
before 1998 the complex model will be used only in limited situations.
This might occur where a refiner has a gasoline transportation system
that is dedicated from the refinery through the retail level, or where
the cost advantages of using the complex model are sufficiently large
to offset the difficulties of segregation. In spite of these
constraints, EPA sees no alternative to requiring segregation controls
over ``early-use'' complex model gasoline.
IV. Complex Model
The complex model described in this section has undergone
significant changes since it was first proposed in the February 1993
NPRM. These changes have been made in response to three key factors:
EPA's improved understanding of the relationship between fuel
characteristics and emissions, EPA's use of more appropriate data
analysis methods, and comments received in response to the February
NPRM, a public workshop held on May 25, 1993, and EPA's July 14, 1993
docket submission that described a number of alternative complex
models. The key elements in the complex model being promulgated today
are discussed in this section. This discussion also addresses the major
substantive comments received by EPA regarding the complex model. A
more detailed description of the model and its derivation, including a
detailed summary and analysis of comments, can be found in Section IV
of the RIA.
Baseline Emissions
As discussed in Section III, EPA is using a July 11, 1991 version
of MOBILE4.1 to estimate baseline emissions from light-duty vehicles
for the simple model, assuming a basic inspection and maintenance
program. This baseline was developed in the regulatory negotiation and
was at the time the best estimate of the in-use emission performance of
1990 vehicles from which to ensure that the minimum performance
standards required by section 211(k) of the Clean Air Act would be
achieved.
Since that time the Agency has developed a new version of the
MOBILE model, MOBILE5a, for use by the states in demonstrating
compliance with the national ambient air quality standard for ozone. As
proposed in the February 26, 1993 proposal, EPA will use MOBILE5a in
conjunction with an enhanced I/M program to establish the emission
baseline for Phase II of the reformulated gasoline program beginning in
the year 2000. EPA, however, has decided to retain the MOBILE4.1 and
basic I/M baseline assumption for the simple model during Phase I of
the RFG program. Switching to a MOBILE5a baseline for Phase I would
have required reformulated fuels to meet a slightly more stringent RVP
standard to maintain the minimum VOC emissions performance required by
the Act. The majority of the VOC emission reductions achieved by RFG
are from nonexhaust emissions; under MOBILE5a, nonexhaust VOC emission
reductions are less effective in reducing overall VOC emissions than
are exhaust VOC reductions, while the opposite is true under MOBILE4.1.
Thus, in order to provide refiners with sufficient leadtime to complete
the investments needed to meet the requirements of the program, the
baseline for the Simple Model is determined using MOBILE4.1.
When replacement of the Simple Model with the Complex Model is
required in 1998, the issue again arises as to whether a more stringent
standard should be required by shifting to use of MOBILE5a in
determining the baseline. MOBILE5a clearly provides a more recent
estimate of the mobile source VOC inventory than does MOBILE4.1.
However, many of the changes made in MOBILE5a were intended to
significantly increase the accuracy of the exhaust emission estimates
while similar changes which would have increased the accuracy of the
nonexhaust VOC emission estimate were not incorporated for various
reasons, including the limited time available to revise the MOBILE
model. As a result, the proportional contribution of exhaust and
nonexhaust VOC emissions to the in-use VOC inventory may not be any
more accurate in MOBILE5a than in MOBILE4.1 even though MOBILE5a
provides a more accurate assessment of the total contribution of mobile
sources to the entire VOC inventory by virtue of its greater accuracy
in estimating exhaust VOC emissions. Since it is the relative
proportions of exhaust and nonexhaust VOC emissions and not the overall
magnitude of the mobile source VOC inventory which determines how
difficult it will be for refiners to meet the overall VOC standard in
1998, it is unclear whether MOBILE5a would be more appropriate to use
in 1998 than MOBILE4.1.
A simple model fuel evaluated using the complex model achieves more
than the minimum 15% requirement of the Act using the MOBILE4.1
baseline exhaust/nonexhaust ratio but less than the 15% requirement
using the MOBILE5a baseline exhaust/nonexhaust ratio. Given the
uncertainty in the actual in-use exhaust/nonexhaust ratio during this
interim period, it is difficult to know whether or not the 15% actually
would be achieved in-use by a fuel meeting the requirements of the
Simple Model. Using MOBILE4.1 to determine the baseline in 1998 would
introduce some risk that the 15% minimum performance requirement of the
Act would not be met in-use by a fuel meeting the requirements of the
Simple Model. However, this risk is relatively small in magnitude (less
than three percentage points of emission reduction are at stake) and
duration (the risk exists for only two years). On the other hand, using
MOBILE5a to determine the 1998 baseline would result in some risk that
refiners would be required to incur greater costs to achieve a more
stringent standard than the minimum required by the Act. This greater
stringency would have the effect of creating a third interim phase to
the RFG program.
Given the uncertainty in determining whether a MOBILE4.1-based
performance standard or a MOBILE5a-based standard more accurately
reflects the in-use conditions in 1998, the potential disruption to
refinery operations (even if only for a small increase in the
stringency of the fuel reformulation requirements), the fact that a
more stringent standard in 1998 was not discussed or envisioned as part
of the regulatory negotiation process, and the fact that any risk to
the environment is small and of short duration, EPA does not believe it
to be appropriate to base the Phase I complex model standards on
MOBILE5a and require refiners to meet a more stringent performance
standard in 1998. As a result, EPA will retain MOBILE4.1 with basic I/M
as the basis for the Phase I performance standards under the Complex
Model in 1998.
In summary, EPA has retained the VOC and NO<INF>X baselines
proposed in the SNPRM, including the relevant I/M assumptions, for use
with the complex model prior to 2000. The onset of the Phase II
performance standards in 2000 will increase the overall stringency of
the standards, and a new baseline based on MOBILE5A will not, by
itself, be the cause of new investment by refiners. By this time,
enhanced I/M programs should be fully operational in nearly all
reformulated gasoline areas. Therefore, baseline VOC and NO<INF>X
emission levels to be used with the complex model in Phase II are based
on MOBILE5A's estimate of emissions from light-duty vehicles and trucks
with enhanced I/M.
Baseline estimates of toxics emissions are not available directly
from the MOBILE models. The nonexhaust toxics model bases its estimates
of nonexhaust toxics on the RVP and benzene levels of the fuel. Since
both of these levels are specified for Clean Air Act baseline (CAAB)
gasoline, EPA has used the nonexhaust toxics model to determine the
baseline nonexhaust toxics emission level. The exhaust toxics baseline
has been estimated by multiplying the exhaust toxics emission level
predicted by the complex model for CAAB gasoline by the ratio of
baseline exhaust VOC emissions to the average exhaust VOC emission
measurement in the complex model database. Since the five regulated
exhaust toxic pollutants are all classified as VOCs, this adjustment
sets the baseline exhaust toxics level equal to the exhaust toxics
levels that would have been observed if the vehicles represented by the
complex model database had VOC emission levels representative of in-use
vehicles when tested on CAAB gasoline. No comments were received
opposing this approach, which is discussed in more detail in Section
III of the RIA.
In evaluating the performance of simple model fuels, EPA has
focused its attention on the average refiner. The need to compensate
for differences between individual refinery baselines and the Clean Air
Act baseline when the use of the complex model becomes mandatory has
been communicated in past proposals, workshops, and the discussions
associated with the Agreement in Principle. Hence refiners have been
given adequate notice that if their baseline fuel produces higher
emissions than CAAB fuel, then they must offset such emissions when the
use of the complex model becomes mandatory in 1998. The four years
before use of the complex model becomes mandatory is adequate leadtime
for refiners. Refiners undertaking investments to comply with the
simple model requirements have been made aware of these requirements,
and this transition process was inherent in the regulatory negotiation
agreement and in prior proposals. EPA recognizes that the precise
emissions impact of individual refiner baselines could not be
determined with confidence until the Complex Model was promulgated.
However, refiners were aware of at least one course of action that
would satisfy the requirements of the program under the complex model,
namely to alter their baseline fuel to match the Clean Air Act baseline
prior to meeting the simple model requirements.
Baseline emissions of VOC, NO<INF>x, and toxics are given in Table
IV-1 for Phase I and in Table IV-2 for Phase II. Summer and winter
baselines are shown for both phases, with summer baseline emissions for
VOC Control Regions 1 and 2 shown separately. The toxics emission
baseline shown in Table IV-1 is applicable only during 1998 and 1999
and for those refiners choosing to use the complex model prior to 1998;
the baselines shown in Table IV-2 are applicable in 2000 and beyond.
Table IV-1.--Phase I Baseline Emissions, Milligrams/Mile
Summer
Pollutant --------------------------------------
Region 1 Region 2 Winter
Running loss VOC................. 430.77 390.42 0.00
Hot soak VOC..................... 264.61 229.96 0.00
Diurnal VOC...................... 125.09 108.71 0.00
Refueling VOC.................... 40.01 40.01 0.00
Nonexhaust VOC................... 860.48 769.10 0.00
Exhaust VOC...................... 446.00 446.00 660.00
Total VOC........................ 1306.48 1215.10 660.00
NO<INF>x.............................. 660.00 660.00 750.00
Running loss benzene............. 4.92 4.46 0.00
Hot soak benzene................. 3.02 2.63 0.00
Diurnal benzene.................. 1.30 1.13 0.00
Refueling benzene................ 0.42 0.42 0.00
Nonexhaust toxics................ 9.66 8.63 0.00
Exhaust benzene.................. 26.10 26.10 37.57
Acetaldehyde..................... 2.19 2.19 3.57
Formaldehyde..................... 4.85 4.85 7.73
1,3-butadiene.................... 4.31 4.31 7.27
POM.............................. 1.50 1.50 2.21
Exhaust toxics................... 38.95 38.95 58.36
Total toxics................. 48.61 47.58 58.36
Table IV-1.--Phase II Baseline Emissions, Milligrams/Mile
Summer
Pollutant --------------------------------------
Region 1 Region 2 Winter
Running loss VOC................. 328.53 294.15 0.00
Hot soak VOC..................... 84.11 80.97 0.00
Diurnal VOC...................... 93.34 63.62 0.00
Refueling VOC.................... 53.33 53.33 0.00
Nonexhaust VOC................... 559.31 492.07 0.00
Exhaust VOC...................... 907.00 907.00 1341.00
Total VOC.................... 1306.48 1215.10 1341.00
NO<INF>X.............................. 1340.00 1340.00 1540.00
Running loss benzene............. 3.75 3.36 0.00
Hot soak benzene................. 0.96 0.93 0.00
Diurnal benzene.................. 0.97 0.66 0.00
Refueling benzene................ 0.56 0.56 0.00
Nonexhaust toxics................ 6.24 5.51 0.00
Exhaust benzene.................. 53.54 53.54 77.62
Acetaldehyde..................... 4.44 4.44 7.25
Formaldehyde..................... 9.70 9.70 15.34
1,3-butadiene.................... 9.38 9.38 15.84
POM.............................. 3.04 3.04 4.50
Exhaust toxics................... 80.10 80.10 120.55
Total toxics................. 86.34 85.61 120.55
Exhaust Emissions Model
- Data Sources
The relationship between fuel properties and exhaust emissions is
complex and the theory behind such relationships continues to be
developed. As a result, EPA has asked industry, state regulatory
agencies, and other organizations with relevant test data to make their
data available to the Agency to ensure that this rule is based on as
much relevant information as possible. The complex model described in
the following section is based on data generated from a number of
exhaust emissions testing programs. These programs, their design
intent, and their limitations are discussed in Section IV.A of the RIA.
Data from these programs were excluded from EPA's analysis if the data
were not based on a valid FTP measurement cycle, if the vehicle in
question did not employ 1990-equivalent emission control technology, if
the vehicles did not exhibit stable, repeatable emissions performance,
or if the data were clearly inconsistent with the bulk of the data
available to EPA (based on statistical considerations). In addition,
data from programs that did not measure nonmethane hydrocarbon
emissions were not used to develop EPA's exhaust VOC complex model. The
Agency believes its analysis considered all valid, and relevant data on
the exhaust emissions effect of fuel modifications when used in 1990
model year and equivalent vehicles that was available at the time the
model was developed.
- Analysis Method
Exhaust emissions are affected by both vehicle and fuel
characteristics. Since the test programs described above generally
involved different vehicles, different fuels, and in some cases
different test procedures, the analysis required to determine the
relationship between fuel properties and emissions is complex. However,
EPA believes that the methods used to develop the complex model
considers and addresses these complexities appropriately. EPA utilized
statistical analysis techniques to isolate the effects of fuel
modifications on exhaust emissions of VOC, NO<INF>X, and toxics from
other factors affecting exhaust emissions.
At a series of six public workshops held over the past two years,
the Agency presented its views on data sources, analysis methods, and
preliminary emissions models for public review and comment. The Agency
also requested other organizations to share their data, analysis
expertise, and emissions models at these workshops. The methods used to
develop the model promulgated today appropriately incorporate the
comments and suggestions regarding the analysis process received at the
workshops, as well as other comments and suggestions received from
industry, state and federal government authorities, and other
interested parties during the course of this rulemaking. Information
regarding the workshops, public comments and suggestions, and EPA's
analysis methods can be found in Docket A-92-12. The approach chosen by
EPA to analyze the available data is summarized below and is discussed
more fully in Section IV.A of the RIA.
Since the vehicle and the fuel both affect exhaust emissions, EPA's
analysis separated exhaust emissions into fuel components and vehicle
components. In all test programs analyzed by EPA, the single most
significant determinant of the level of emissions from a given vehicle
on a given fuel was the vehicle itself. Fuel properties exert a much
smaller influence on exhaust emissions than do vehicle characteristics
such as emission control system technology, vehicle mileage, catalyst
efficiency, oxygen sensor efficiency, engine size, engine design,
vehicle size, fuel efficiency, vehicle maintenance, etc. To identify
the effects of fuel property modifications on emissions, EPA found it
necessary to identify the effect of each vehicle on emissions and
separate this effect from the fuel effects. For vehicles used in more
than one test program, EPA found it necessary to determine the vehicle
effect separately for each test program since vehicle effects were
observed to change between studies.
The fuel components of exhaust emissions were separated into two
main categories. The first category consisted of the effects of
individual fuel parameters. For example, the effect of sulfur on
NO<INF>X emissions was best modeled by a relationship containing a
linear sulfur term (of the form c<INF>1S, where c<INF>1 is a constant
and S is the sulfur level) and a second-order sulfur term (of the form
c<INF>2S<SUP>2, where c<INF>2 is a constant). The second category of
fuel terms consisted of interactive effects between two fuel
parameters. For example, EPA's analysis found that the effect of
aromatics on hydrocarbon emissions is related to the E300 level of the
fuel. This effect cannot be represented as an aromatics or E300 effect
alone but must be represented as an interactive term of the form
c<INF>3AE, where c<INF>3 is a constant, A is the aromatics level, and E
is the E300 level.
In the February 1993 proposal, EPA indicated that it planned to
make several changes to the method used to develop the complex model.
As discussed in that proposal and in the RIA, fuels can be
characterized in terms of a number of different sets of fuel
parameters. EPA used the results of individual fuel studies and its
public workshops to select the set of fuel parameters used to model
exhaust emissions in its February 1993 proposal. At that time, the
Agency indicated that it might alter its choice of parameters to
represent gasoline distillation characteristics from a temperature
basis (using T50 and T90) to a percent evaporated basis (using E200 and
E300, the percentage of the fuel's volume that evaporates when heated
to 200 deg.F and 300 deg.F, respectively). For reasons outlined in the
February 1993 NPRM and section IV.A of the RIA, EPA has chosen to make
this change and has converted its exhaust emission models to a percent
evaporated basis since the NPRM was issued, removing the T50 and T90
terms from its models in the process. The Auto/Oil Heavy Hydrocarbon
and EPA Phase II Reformulated Gasoline Test Program studies have been
added to the complex model database. Finally, EPA has changed the
confidence level required to permit terms to remain in the model to 90
percent, in keeping with the approach used in developing the simple
model. The Agency was not able to determine the influence of the type
of aromatic compounds in fuels, specifically heavy aromatics, on
exhaust emissions, and hence such terms have not been included in the
complex model at this time.
Because vehicles can have different emission control systems, the
Agency anticipated that fuel modifications would have different
emission effects on different types of cars. To account for these
differences, EPA's February 1993 proposal divided vehicles into two
``emitter classes'' (normal and higher emitters) based on their exhaust
emission levels. EPA then subdivided vehicles in each emitter class
into ``technology groups'' based on the emission control technology
with which each vehicle was equipped. However, as discussed in the
NPRM, EPA was concerned that technology group distinctions among higher
emitters might not be appropriate, since such vehicles' high level of
emissions indicated that their emission control systems were not
functioning properly. In addition, the limited quantity of data for
higher emitters made it difficult to identify genuine differences in
emissions response between higher emitters of different technology
groups. Many commenters expressed similar concerns. Hence the model
promulgated today does not divide higher emitters into technology group
categories but retains such distinctions when analyzing normal
emitters. In response to numerous comments, EPA attempted to reduce the
number of normal emitter technology groups. However, as discussed in
section IV.A of the RIA, EPA was unable to identify an appropriate
basis for consolidation. EPA considers its retention of emitter class
and technology group distinctions to be justified by the presence of
statistically significant fuel effects specific to individual emitter
classes and technology groups in today's complex model.
At the same time, EPA recognized the validity of comments received
from a number of sources that (1) many emission effects were likely to
be consistent across multiple technology groups or across emitter
classes, and (2) insufficient data were available to model many
potential terms, particularly interactive terms. The approach used by
EPA to construct the complex model proposed in February 1993 did not
incorporate these legitimate concerns. To do so, EPA has utilized a
modified version of the ``unified'' approach advocated by API and other
commenters (as described in the RIA) to develop today's complex model.
This modeling approach, the statistical criteria used by EPA in
conjunction with this approach, and the techniques used to simplify the
models are discussed in detail in section IV.A of the RIA and are
summarized below.
First, interactive terms were permitted to enter the models only
when sufficient data were available. The model proposed in the February
1993 NPRM permitted all interactive terms to enter the models,
regardless of whether sufficient data were available to estimate such
an effect, and it did not apply statistical criteria to evaluate
whether terms added to the model introduced more risk of inaccuracy in
the model than they removed.
Second, preliminary models for higher emitting vehicles were
constructed based solely on data from such vehicles. Only those terms
that satisfied EPA's statistical criteria (discussed at length in the
RIA) were retained. These criteria included measures to balance
overfitting (introducing too many terms to explain the observed data)
and underfitting (not including terms necessary to explain the observed
data). The NPRM model did not include measures to prevent overfitting.
Third, the entire database was analyzed using the unified approach.
The effects of each term on emissions was divided into two parts: an
average effect across all vehicles, and a series of adjustment terms
for each technology group and for higher emitters. Only those terms
that satisfied EPA's statistical criteria were retained, with two
exceptions. Higher emitter adjustment terms were retained regardless of
statistical significance since they had been found to be statistically
significant when examining the higher emitter data separately. EPA was
concerned that failure to do so might cause genuine higher emitter
effects to be ``washed out'' by the greater number of data for normal
emitters. In addition, some overall terms were retained for hierarchy
reasons despite low statistical significance. For example, a linear
term for a given fuel parameter (e.g., E300) might not be significant
while a squared term for the same parameter (e.g., E300\2\) might be
significant. Since the mathematical form of the squared terms includes
the corresponding linear effects, the linear term would be retained
regardless of significance to preserve the model's hierarchical
structure. The importance of hierarchy was emphasized by a number of
workshop participants and commenters, as discussed in the RIA. The NPRM
model included separate terms for each technology group and emitter
class and hence did not include terms to represent the average effect
of a fuel parameter across all vehicles. The NPRM model also did not
incorporate hierarchy considerations.
Fourth, outlying and overly influential data were dropped from the
database and the model was re-estimated based on the remaining data.
Outlying data consist of observations that differ from the average
observed effect by so large a margin that they are more likely to
represent observational error, reporting error, or other measurement
artifacts than genuine phenomena. Outlying data can obscure genuine
emissions effects. Influential data consist of observations that by
themselves materially affect the resulting model, i.e., the model would
differ materially if they were excluded. In a database the size of the
Complex Model database, individual data points should not have such
unusually large effects. Excluding outlying and influential
observations is standard statistical practice. The NPRM model did not
exclude either type of observation.
Fifth, terms were deleted from the resulting model to avoid
overfitting and collinearity problems. Overfitting occurs when so many
terms are included in a regression model that the expected error due to
the erroneous inclusion of a term exceeds the expected error due to not
including the term. Collinearity problems occur when the fuel
parameters included in the model are correlated with one another in the
fuels tested. For example, the addition of oxygenate to gasoline causes
E200 to increase. The oxygenate-containing fuels in the complex model
database tend to have higher E200 values than fuels without oxygenate.
In a sense, one can predict the E200 value of a fuel by knowing its
oxygen content. Hence these two parameters would be considered to be
highly collinear. Since regression models are developed under the
assumption that terms are not collinear, the presence of strong
collinearities can introduce error into the regression. Today's complex
model takes both collinearity and overfitting into account by using a
standard statistical criterion called Mallow's C<INF>p criterion to
remove terms which introduce large overfitting and collinearity
problems. This approach resulted in a simpler, more reasonable, and
statistically more sound model than had been proposed in the February
1993 NPRM. It should be noted that high emitter terms forced into the
model earlier in the process could be dropped at this stage of the
analysis. Measures were taken to limit collinearity problems in the
NPRM model, but overfitting concerns and the C<INF>p criterion were not
addressed.
Sixth, the contribution of each remaining term to the model's
explanatory power was estimated, and those terms whose contribution
summed to less than one percent were deleted (i.e., the retained terms
accounted for 99 percent of the explanatory power of the model) to
simplify the form of the model without materially reducing its ability
to predict the emissions impact of fuel modifications. This step was
not taken during development of the NPRM model.
Finally, the resulting models for each technology group within the
set of normal emitting vehicles were consolidated into a single
equation using a random balance approximation. The details of that
approximation are given in Section IV.A of the RIA. This step was not
taken during development of the NPRM model.
The results of EPA's modeling efforts confirms the importance of
technology group and emitter class distinctions, as can be seen by
examining the differences in the exhaust emission equations for
specific normal emitter technology groups or for normal and higher
emitter class categories (as discussed in greater detail in the RIA).
Efforts to reduce the number of technology group categories for normal
emitters were not successful. Efforts to subdivide higher emitters by
their emission characteristics such as exhaust hydrocarbon to NO<INF>X
ratio did not improve the quality of EPA's higher emitter model.
However, as discussed above, EPA found it unnecessary to separate
higher emitters by technology group. This modification reflects EPA's
belief, supported by preliminary field information, that one or more
emission control components on higher emitters tend to be
malfunctioning, which renders a classification scheme based on vehicle
equipment questionable.
- Exhaust Model
As was discussed in the April 1992 and February 1993 proposals, the
weight assigned to each technology group or emitter class for modeling
purposes was set equal to its contribution to in-use emissions for each
pollutant. The weight assigned to each emitter class was set equal to
its projected contribution to in-use emissions. The weighting factor
assigned to normal emitters was then broken down further by technology
group, again according to their projected contribution to in-use
emissions. These estimates and projections are essentially unchanged
from the February 1993 proposal, although minor changes have been made
to reflect more complete information about the fraction of 1990 sales
accounted for by each technology group. The rationale for, derivation
of, and renormalization of the weighting factors themselves are
discussed in more detail in the RIA.
Various commenters indicated that they considered EPA's previously
proposed models were too complex. In response, the Agency has modified
its analysis method in several ways. The resulting method, described in
Section IV.B.2, results in exhaust emission models containing two
equations for each pollutant instead of as many as sixteen separate
equations, as was the case for the model proposed in February 1993.
Each equation also has far fewer terms than the February 1993
equations. However, EPA does not believe that today's less complicated
complex model is less accurate than the complex models presented at
public workshops or in the February proposal. This belief is based on
the models' comparable explanatory power (as reflected in their similar
R\2\) and the superior accuracy of today's model in accounting for the
emission effects seen in the vehicle testing programs that comprise the
complex model database. Today's VOC and NO<INF>X models are based on
the most accurate of the three sets of models included in EPA's July
14, 1993 docket submittal, while also taking into account relevant
comments regarding specific aspects of the models. Today's toxics
models are a further simplification of the models included in the July
1993 docket submittal in response to comments received by EPA on its
docket submittal. These points are discussed more fully in Section IV.A
of the RIA.
The specific equations that comprise the complex model can be found
in section 80.45 of the regulations for this rule. Their derivation is
discussed in detail in Section IV.A of the RIA. The range of parameter
values for which these equations are valid is discussed in Section D
and in Section IV.D of the RIA. As discussed in Section V, refiners are
required to submit data to augment the model if they wish to certify
fuels with properties that fall outside this range as reformulated
gasolines.
C. Nonexhaust Model
Nonexhaust emissions are less strongly affected by vehicle design
and are influenced by fewer fuel characteristics than are exhaust
emissions. In addition, the theoretical principles involved in
nonexhaust emissions (which include evaporative, running loss, and
refueling emissions) are better understood, and nonexhaust emission
control technologies are more consistent across vehicles, than are
exhaust emissions and emission control technologies. Since the
relationship between fuel properties and nonexhaust emissions is less
complex and better understood than for exhaust emissions, there was
much less need for EPA to generate additional data to evaluate
nonexhaust emissions than was the case for exhaust emissions. EPA was
able to base its nonexhaust VOC emission model on data generated from
EPA's ongoing nonexhaust emissions testing program that has been used
to develop EPA's MOBILE emission inventory models, specifically the
MOBILE4.1 and MOBILE5.0A models. EPA believes this data to be
sufficient to model the relationship between fuel properties and
nonexhaust VOC emissions for the purposes of this rule. Additional
information about MOBIL4.1 and MOBILE5.0A can be found in Dockets A-91-
02 and A-92-12.
EPA is in the process of developing an enhanced model of nonexhaust
VOC emissions, based on a more complete set of theoretical principles
and additional test data, that is expected to be more accurate and more
widely applicable to oxygenated fuels than the MOBILE models. A
preliminary version of this model was discussed at a public workshop
held on August 25, 1992, and materials related to this model have been
placed in the docket for this rulemaking. At this time, however, this
enhanced nonexhaust VOC emissions model is not complete and hence is
not incorporated in today's complex model.
The nonexhaust VOC model in today's complex model is based on
correlations between RVP and nonexhaust VOC emissions derived from the
July 11, 1991 version of MOBILE4.1 for Phase I of the reformulated
gasoline program (1995-1999) and from MOBILE5A for Phase II (2000 and
beyond). This approach is consistent with the definition of baseline
emissions set forth in Section IV.A and is based on the same
considerations outlined in that section.
To develop the correlations shown below, the MOBILE models were
used with temperatures of 69 to 94 degrees Fahrenheit for Class B areas
and 72 to 92 degrees Fahrenheit for Class C areas. As discussed in
Section IV.A, a basic inspection and maintenance program was assumed
for Phase I while an enhanced I/M program was assumed for Phase II. In
addition, the presence of Stage II evaporative emissions recovery
systems with an overall vapor recovery efficiency of 86 percent was
assumed (as discussed in the SNPRM and NPRM). EPA is in the process of
promulgating requirements for onboard refueling emission controls which
may be more effective at controlling refueling emissions than Stage II
vapor recovery systems. However, these requirements did not apply to
1990 model year vehicles and hence cannot be incorporated into the
model for certification purposes. In addition, EPA has chosen not to
incorporate the effects of onboard refueling controls in its evaluation
of the effects of reformulated fuels on emissions from the entire inuse
vehicle fleet, which includes vehicles from a number of different
model years. This decision was made for several reasons. First,
requirements for onboard refueling controls have not yet been
finalized, making evaluation of their impact on in-use emissions
difficult. Second, onboard refueling controls are not expected to be
required on all new vehicles until 2000 and are not expected to be
present on the bulk of in-use vehicles for several years after that
time. Third, while onboard controls are expected to be more efficient
at controlling refueling emissions than Stage II controls, the
difference is not expected to be large in areas affected by the
reformulated gasoline program and will affect only a small portion of
total nonexhaust VOC emissions. Since EPA's analysis of the additional
benefits of onboard vapor recovery controls is not yet available, and
since such benefits are expected to be small relative to overall
emissions, EPA has chosen to retain its assumptions regarding Stage II
vapor recovery in forecasting the effects of fuel modifications on
nonexhaust VOC emissions from the in-use vehicle fleet.
The only toxic air pollutant covered by the reformulated gasoline
program that is found in nonexhaust emissions is benzene, which is a
natural component of gasoline. The other four toxic air pollutants
listed in section 211(k) are solely products of fuel combustion and
hence are not found nonexhaust emissions. As discussed in the SNPRM,
the Agency's correlation between fuel benzene content and summer nonexhaust
benzene emissions is based on results from General Motors'
proprietary model of tank vapors, as confirmed independently by EPAgenerated
data using a number of fuels. Both the derivation and
verification of the non-exhaust benzene emissions model are discussed
more fully in the RIA. The nonexhaust benzene emission model also
depends on the RVP of the fuel, as is the case for the nonexhaust VOC
emission model. The derivation of the nonexhaust benzene and VOC models
is discussed more fully in the RIA.
D. Range/Extrapolation
Like all regression models, the complex model is not valid for all
possible input values. The range of fuel parameter values over which
the complex model accurately predicts vehicle emissions is given in
Table IV-3. These ranges are based on the range of data used to develop
the models and on comments received by the Agency on this issue. The
limits proposed in the February 1993 were, in some cases, narrower than
the range of data used to develop the complex model. In addition, the
limits proposed in the NPRM would have prevented a number of very low
emitting fuels from being certified using the model.
Table IV-3.--Parameter Ranges for Which the Complex Model Can Be Used
Valid range for:
---------------------------
Fuel Parameter Reformulated Conventional
fuel fuel
Aromatics, vol %............................ 0-50 0-55
E200, %..................................... 30-70 30-70
E300, %..................................... 70-100 70-100
Olefins, vol %.............................. 0-25 0-30
Oxygen, vol %............................... 0-3.7 0-3.7
RVP, psi.................................... 6.4-10 6.4-11
Sulfur, ppm................................. 0-500 0-1000
Benzene, vol %.............................. 0-2.0 0-4.9
EPA has received a number of comments requesting alterations in the
model's range. After considering these comments and re-evaluating the
data on which the complex model is based, EPA has modified the range
limits. In some cases, EPA has chosen to extrapolate the complex model
slightly beyond the range for which data were available in order to
allow additional fuels, both conventional and reformulated, to be
evaluated using the model without recourse to expensive and timeconsuming
vehicle testing. These extrapolations are limited to those
parameters whose effects appear to be well-characterized by the complex
model. A detailed discussion of the limits of the available data, EPA's
rationale for extending the valid range of the model for some
parameters, and the extrapolation method used to extend the model can
be found in Section IV.D of the RIA.
E. Winter
While the VOC performance standard for reformulated fuels applies
only in the summer, the toxics and no-NO<INF>x-increase requirements
apply year-round. EPA therefore recognized the need to model the
exhaust toxics and NO<INF>x emissions performance of reformulated
gasolines during the winter months as well as during the high ozone
season. Modeling winter emissions performance, however, presented a
number of difficulties. First, the data sources described earlier
provided data on emissions performance only under summer conditions and
for gasolines with RVP levels typical of summer gasolines. Second, the
RVP levels of fuels included in the complex model database ranged from
7 to 10 psi, while winter fuels tend to have RVP levels in the 11.5 psi
range and are not restricted by other regulations. Hence the complex
model cannot be used directly for fuels with typical winter RVP levels.
RVP's impact on canister loading and subsequent purging is thought
to be the primary cause of its effects on exhaust emissions. Since data
do not exist on the effects of winter fuels on canister loading under
winter conditions, the Agency is not able at this time to model the
effects of winter RVP levels on exhaust emissions. To avoid making
unsound or speculative predictions, EPA proposed and is now
promulgating a requirement that for purposes of evaluating emissions
effects using the complex model, the RVP of winter fuels be set at the
summer statutory baseline RVP value. In effect, this requirement builds
into the model the assumption that the RVP level of winter gasolines
has no effect on NO<INF>x or exhaust toxics emissions. As a result,
refiners will not be required to alter the RVP levels of winter
gasolines. Refiners will receive neither benefit nor penalty for
changing the RVP of their winter gasolines. To evaluate winter fuels
using the complex model, an RVP value equal to that of summer baseline
gasoline (8.7 psi) must be used instead of the fuel's actual RVP. Doing
so effectively removes the contribution of RVP to winter exhaust
emissions.
When sufficient data is developed on the emissions impact of winter
RVP levels under winter ambient conditions, EPA will be able to revise
the complex model accordingly. Until then, EPA believes it is more
appropriate to assume that RVP levels have winter exhaust emission
effects than to speculate about the magnitude of such impacts.
In its prior proposals, EPA had proposed that winter nonexhaust
emissions, including winter nonexhaust benzene emissions, be considered
zero. EPA received a number of comments requesting that both baseline
emissions and the nonexhaust toxics model include winter nonexhaust
benzene emissions. This request was based on the belief that the yearround
benzene limits would result in reduced nonexhaust benzene
emissions in the winter months. EPA has evaluated this claim, taking
into account temperature ranges and the effects of inspection and
maintenance programs on such emissions. EPA acknowledges the validity
of this claim, since winter nonexhaust emissions, including nonexhaust
benzene emissions, are likely to be nonzero under all winter
temperature ranges. In the past, the lack of sufficient data on
nonexhaust emissions under winter temperature conditions has prevented
EPA from developing reliable, accurate models of winter nonexhaust
emissions. The commenters provided a limited quantity of data on winter
nonexhaust emissions to support their claim. However, the data
submitted in support of this claim were based on measurements of
nonexhaust emissions from vehicles with very low nonexhaust emissions.
EPA's analysis indicates that these vehicles are not representative of
in-use vehicles. In addition, the chemical composition of the measured
nonexhaust emissions were characteristic of resting losses (losses that
occur due to permeation through fuel system components) rather than of
diurnal, hot soak, or running loss emissions. Resting losses are not
included in EPA's baseline emission estimates, so EPA does not consider
it appropriate to include resting losses in its nonexhaust emission
models. Finally, no data were submitted on nonexhaust benzene emissions
from fail vehicles under winter conditions. Since nonexhaust benzene
emissions from such vehicles will comprise a significant portion of
winter nonexhaust benzene emissions, EPA is concerned that a model
based on the submitted data would not provide accurate estimates of
such emissions. Given the theoretical merits of the claim, however, EPA
will consider including a model of winter benzene nonexhaust emissions
in the complex model in the future when sufficient data become
available.
F. Fungibility
EPA has long recognized the importance of maintaining a fungible
fuel system, in which complying gasolines can be mixed freely without
resulting in mixtures that do not themselves comply with regulatory
requirements. Fungibility is essential to smooth, cost-effective
operation of fuel distribution systems such as pipelines. The Agency
has received numerous comments on the need to maintain fungibility. At
the same time, the Agency considers it essential that gasolines
certified as reformulated meet all required emission performance levels
in the field. In cases where the effects of a given fuel parameter on
emissions are non-linear, it is possible for two complying fuels to
produce a non-complying fuel when mixed.
The complex model contains a number of nonlinear terms, which
introduces the possibility that gasolines which comply with this rule's
requirements in isolation would not comply if mixed with other
complying fuels. EPA has been concerned with this possibility and has
undertaken extensive analyses to determine its likelihood and to
develop methods to cope with its occurrence. EPA's analyses, which have
utilized methods that have been supported by a number of organizations,
indicate that the complex model promulgated in today's rule will not
create fungibility problems despite its inclusion of nonlinear terms.
This analysis is explained in greater detail in Section IV.F of the
RIA.
G. Future Model Revisions
The complex model promulgated in this rulemaking reflects EPA's
best understanding of the relationship between fuel characteristics and
vehicle emissions. However, EPA expects future research to clarify this
relationship. EPA also recognizes that changes in in-use vehicle
emission control programs (e.g., I/M programs) will continue to occur
and that these changes may alter the relationship between fuel
characteristics and in-use emissions. In addition, the Agency is
concerned that augmentations to the model through vehicle testing
(Section V) may, over time, accumulate to the point that a revised
complex model, incorporating the current complex model database and all
relevant information gathered since then, would be beneficial. As
discussed in Section V, EPA plans to issue revised complex models when
the Agency deems that sufficient new information is available to
warrant such action. Model revisions will be developed through a formal
rulemaking process.
H. Complex Model Performance of Simple Model Fuels
Fuels qualifying as reformulated under the simple model must meet
specified benzene, oxygen, and RVP requirements while also satisfying
the toxics performance standard. The RVP requirement differs between
VOC control regions, and the requirements and standards also vary
depending on whether compliance is being achieved on a per-gallon or
averaging basis. In addition, levels of other fuel parameters are only
specified under the simple model in terms of deviations from each
refiner's baseline fuel. Evaluating the performance of simple model
fuels under the complex model is difficult since fuel properties can
vary widely.
However, it is possible to evaluate a set of fuels that are
representative of expected, typical simple model fuels. EPA expects
most refiners to pursue compliance on average (for all or part of their
product slate) in order to maximize flexibility in day-to-day refinery
operations and recoup compliance margins. Given present and projected
conditions, EPA also expects that MTBE and ethanol will be the most
commonly used oxygenates during Phase I of the reformulated gasoline
program. The fuels specified in Tables IV-4 and IV-5 below include
fuels designed to meet the requirements of the simple model in both VOC
control regions and using both oxygenates. The level of olefins,
sulfur, E200, and E300 have been set to Clean Air Act baseline levels,
while the level of aromatics has been set at the level necessary to
comply with the toxics requirements of the simple model. Aromatics
levels were assumed to be the same for summer and winter fuels.
Table IV-4.--Typical Simple Model Fuels Using MTBE
[Under Averaging]
Fuel
1 2 3 4
Fuel
Description:
Season........ Summer...... Summer...... Winter...... Winter
VOC Control 1........... 2........... 1........... 2
Region.
Fuel
Parameter:.
RVP, psi...... 7.1......... 8.0......... N/A......... N/A
Oxygen, wt%... 2.1......... 2.1......... 2.1......... 2.1
Benzene, vol%. 0.95........ 0.95........ 0.95........ 0.95
Aromatics, 27.5........ 26.3........ 27.5........ 26.3
vol%.
Olefins, vol%. 9.2......... 9.2......... 11.9........ 11.9
E200, %....... 41...
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