[Federal Register Volume 88, Number 98 (Monday, May 22, 2023)]
[Proposed Rules]
[Pages 32852-32947]
[FR Doc No: 2023-10047]

Vol. 88

Monday,

No. 98

May 22, 2023

Part III

Environmental Protection Agency

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40 CFR Part 98

Revisions and Confidentiality Determinations for Data Elements Under
the Greenhouse Gas Reporting Rule; Proposed Rule

Federal Register / Vol. 88 , No. 98 / Monday, May 22, 2023 / Proposed
Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 98

[EPA-HQ-OAR-2019-0424; FRL-7230-03-OAR]
RIN 2060-AU35

Revisions and Confidentiality Determinations for Data Elements
Under the Greenhouse Gas Reporting Rule

AGENCY: Environmental Protection Agency (EPA).

ACTION: Supplemental notice of proposed rulemaking.

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SUMMARY: The EPA is issuing this supplemental proposal that would amend
specific provisions in the Greenhouse Gas Reporting Rule to improve the
quality and consistency of the rule by providing for the collection of
improved data that would better inform and be relevant to a wide
variety of Clean Air Act provisions that the EPA carries out. The EPA
recently evaluated the requirements of the Greenhouse Gas Reporting
Rule to identify areas of improvement, including updates to the
existing calculation, recordkeeping, and reporting requirements, and
requested information for collection of additional data to understand
new source categories in a proposed rule (June 21, 2022). In this
notification, the EPA is proposing additional amendments to the
Greenhouse Gas Reporting Rule, including updates to the General
Provisions to reflect revised global warming potentials, and is
proposing to require reporting of greenhouse gas data from additional
sectors--specifically energy consumption; coke calcining; ceramics
production; calcium carbide production; and caprolactam, glyoxal, and
glyoxylic acid production. The EPA is also proposing additional
revisions that would improve implementation of the Greenhouse Gas
Reporting Rule, such as updates to emissions calculation methodologies;
revisions to reporting requirements to improve verification of reported
data and the accuracy of the data collected; and other minor technical
amendments, corrections, or clarifications. The EPA intends to consider
the information received in response to this supplemental proposal
prior to finalizing the amendments to the Greenhouse Gas Reporting Rule
proposed on June 21, 2022. This action also proposes to establish and
amend confidentiality determinations for the reporting of certain data
elements to be added or substantially revised in these proposed
amendments.

DATES:
    Comments. Comments must be received on or before July 21, 2023.
Comments on the information collection provisions submitted to the
Office of Management and Budget (OMB) under the Paperwork Reduction Act
(PRA) are best assured of consideration by OMB if OMB receives a copy
of your comments on or before June 21, 2023.
    Public hearing. The EPA does not plan to conduct a public hearing
unless requested. If anyone contacts us requesting a public hearing on
or before May 30, 2023, we will hold a virtual public hearing. See
SUPPLEMENTARY INFORMATION for information on requesting and registering
for a public hearing.

ADDRESSES:
    Comments. You may submit comments, identified by Docket Id. No.
EPA-HQ-OAR-2019-0424, by any of the following methods:
    Federal eRulemaking Portal: www.regulations.gov (our preferred
method). Follow the online instructions for submitting comments.
    Mail: U.S. Environmental Protection Agency, EPA Docket Center, Air
and Radiation Docket, Mail Code 28221T, 1200 Pennsylvania Avenue NW,
Washington, DC 20460.
    Hand Delivery or Courier (by scheduled appointment only): EPA
Docket Center, WJC West Building, Room 3334, 1301 Constitution Avenue
NW, Washington, DC 20004. The Docket Center's hours of operations are
8:30 a.m.-4:30 p.m., Monday-Friday (except Federal holidays)
    Instructions: All submissions received must include the Docket Id.
No. for this proposed rulemaking. Comments received may be posted
without change to www.regulations.gov/, including any personal
information provided. For detailed instructions on sending comments and
additional information on the rulemaking process, see the ``Public
Participation'' heading of the SUPPLEMENTARY INFORMATION section of
this document.
    The virtual hearing, if requested, will be held using an online
meeting platform, and the EPA will provide information on its website
(www.epa.gov/ghgreporting) regarding how to register and access the
hearing. Refer to the SUPPLEMENTARY INFORMATION section for additional
information.

FOR FURTHER INFORMATION CONTACT: Jennifer Bohman, Climate Change
Division, Office of Atmospheric Programs (MC-6207A), Environmental
Protection Agency, 1200 Pennsylvania Ave. NW, Washington, DC 20460;
telephone number:<PHONE_NUMBER>; email address: [email protected].
For technical information, please go to the Greenhouse Gas Reporting
Program (GHGRP) website, www.epa.gov/ghgreporting. To submit a
question, select Help Center, followed by ``Contact Us.''
    World wide web (WWW). In addition to being available in the docket,
an electronic copy of this proposal will also be available through the
WWW. Following the Administrator's signature, a copy of this proposed
rule will be posted on the EPA's GHGRP website at www.epa.gov/ghgreporting.

SUPPLEMENTARY INFORMATION:
    Written comments. Submit your comments, identified by Docket Id.
No. EPA-HQ-OAR-2019-0424, at www.regulations.gov (our preferred
method), or the other methods identified in the ADDRESSES section. Once
submitted, comments cannot be edited or removed from the docket. The
EPA may publish any comment received to its public docket. Do not
submit to the EPA's docket at www.regulations.gov any information you
consider to be confidential business information (CBI), proprietary
business information (PBI), or other information whose disclosure is
restricted by statute. Multimedia submissions (audio, video, etc.) must
be accompanied by a written comment. The written comment is considered
the official comment and should include discussion of all points you
wish to make. The EPA will generally not consider comments or comment
contents located outside of the primary submission (i.e., on the web,
cloud, or other file sharing system). Please visit www.epa.gov/dockets/commenting-epa-dockets for additional submission methods; the full EPA
public comment policy; information about CBI, PBI, or multimedia
submissions, and general guidance on making effective comments.
    Participation in virtual public hearing. To request a virtual
public hearing, please contact the person listed in the following FOR
FURTHER INFORMATION CONTACT section by May 30, 2023. If requested, the
virtual hearing will be held on June 6, 2023. The hearing will convene
at 9 a.m. Eastern Time (ET) and will conclude at 3 p.m. ET. The EPA may
close the hearing 15 minutes after the last pre-registered speaker has
testified if there are no additional speakers. The EPA will provide
further information about the hearing on its website (www.epa.gov/ghgreporting) if a hearing is requested.
    If a public hearing is requested, the EPA will begin pre-
registering speakers

for the hearing no later than one business day after a request has been
received. To register to speak at the virtual hearing, please use the
online registration form available at www.epa.gov/ghgreporting or
contact us by email at [email protected]. The last day to pre-
register to speak at the hearing will be June 5, 2023. On June 5, 2023,
the EPA will post a general agenda that will list pre-registered
speakers in approximate order at: www.epa.gov/ghgreporting.
    The EPA will make every effort to follow the schedule as closely as
possible on the day of the hearing; however, please plan for the
hearings to run either ahead of schedule or behind schedule.
    Each commenter will have 5 minutes to provide oral testimony. The
EPA encourages commenters to provide the EPA with a copy of their oral
testimony electronically (via email) by emailing it to
[email protected]. The EPA also recommends submitting the text of
your oral testimony as written comments to the rulemaking docket.
    The EPA may ask clarifying questions during the oral presentations
but will not respond to the presentations at that time. Written
statements and supporting information submitted during the comment
period will be considered with the same weight as oral testimony and
supporting information presented at the public hearing.
    Please note that any updates made to any aspect of the hearing will
be posted online at www.epa.gov/ghgreporting. While the EPA expects the
hearing to go forward as set forth above, please monitor our website or
contact us by email at [email protected] to determine if there are
any updates. The EPA does not intend to publish a document in the
Federal Register announcing updates.
    If you require the services of an interpreter or special
accommodation such as audio description, please pre-register for the
hearing with the public hearing team and describe your needs by May 30,
2023. The EPA may not be able to arrange accommodations without
advanced notice.
    Regulated entities. This is a proposed regulation. If finalized,
these proposed revisions would affect certain entities that must submit
annual greenhouse gas (GHG) reports under the GHGRP (40 CFR part 98).
These are proposed amendments to existing regulations. If finalized,
these amended regulations would also affect owners or operators of
certain industry sectors that are direct emitters of GHGs. Regulated
categories and entities include, but are not limited to, those listed
in Table 1 of this preamble:

           Table 1--Examples of Affected Entities by Category
------------------------------------------------------------------------
                                  North American        Examples of
                                     Industry       facilities that may
           Category               Classification     be subject to part
                                  System (NAICS)            98:
------------------------------------------------------------------------
Adipic Acid Production........             325199  All other basic
                                                    organic chemical
                                                    manufacturing:
                                                    Adipic acid
                                                    manufacturing.
Aluminum Production...........             331313  Primary aluminum
                                                    production
                                                    facilities.
Ammonia Manufacturing.........             325311  Anhydrous ammonia
                                                    manufacturing
                                                    facilities.
Calcium Carbide Production....             325180  Other basic inorganic
                                                    chemical
                                                    manufacturing:
                                                    calcium carbide
                                                    manufacturing.
Carbon Dioxide Enhanced Oil                211120  Oil and gas
 Recovery Projects.                                 extraction projects
                                                    using carbon dioxide
                                                    enhanced oil
                                                    recovery.
Caprolactam, Glyoxal, and                  325199  All other basic
 Glyoxylic Acid Production.                         organic chemical
                                                    manufacturing.
Cement Production.............             327310  Cement manufacturing.
Ceramics Manufacturing........             327110  Pottery, ceramics,
                                                    and plumbing fixture
                                                    manufacturing.
                                           327120  Clay building
                                                    material and
                                                    refractories
                                                    manufacturing.
Coke Calcining................             299901  Coke; coke,
                                                    petroleum; coke,
                                                    calcined petroleum.
Electronics Manufacturing.....             334111  Microcomputers
                                                    manufacturing
                                                    facilities.
                                           334413  Semiconductor,
                                                    photovoltaic (PV)
                                                    (solid-state) device
                                                    manufacturing
                                                    facilities.
                                           334419  Liquid crystal
                                                    display (LCD) unit
                                                    screens
                                                    manufacturing
                                                    facilities;
                                                    Microelectromechanic
                                                    al (MEMS)
                                                    manufacturing
                                                    facilities.
Electrical Equipment                        33531  Power transmission
 Manufacture or Refurbishment.                      and distribution
                                                    switchgear and
                                                    specialty
                                                    transformers
                                                    manufacturing
                                                    facilities.
Electricity generation units               221112  Electric power
 that report through 40 CFR                         generation, fossil
 part 75.                                           fuel (e.g., coal,
                                                    oil, gas).
Electrical Equipment Use......             221121  Electric bulk power
                                                    transmission and
                                                    control facilities.
Electrical transmission and                 33361  Engine, Turbine, and
 distribution equipment                             Power Transmission
 manufacture or refurbishment.                      Equipment
                                                    Manufacturing.
Ferroalloy Production.........             331110  Ferroalloys
                                                    manufacturing.
Fluorinated Greenhouse Gas                 325120  Industrial gases
 Production.                                        manufacturing
                                                    facilities.
Geologic Sequestration........                 NA  CO2 geologic
                                                    sequestration sites.
Glass Production..............             327211  Flat glass
                                                    manufacturing
                                                    facilities.
                                           327213  Glass container
                                                    manufacturing
                                                    facilities.
                                           327212  Other pressed and
                                                    blown glass and
                                                    glassware
                                                    manufacturing
                                                    facilities.
HCFC-22 Production............             325120  Industrial gas
                                                    manufacturing:
                                                    Hydrochlorofluorocar
                                                    bon (HCFC) gases
                                                    manufacturing.
HFC-23 destruction processes               325120  Industrial gas
 that are not collocated with                       manufacturing:
 a HCFC-22 production facility                      Hydrofluorocarbon
 and that destroy more than                         (HFC) gases
 2.14 metric tons of HFC-23                         manufacturing.
 per year.
Hydrogen Production...........             325120  Hydrogen
                                                    manufacturing
                                                    facilities.
Industrial Waste Landfill.....             562212  Solid waste landfill.
Industrial Wastewater                      221310  Water treatment
 Treatment.                                         plants.
Injection of Carbon Dioxide...                211  Oil and gas
                                                    extraction.
Iron and Steel Production.....             333110  Integrated iron and
                                                    steel mills, steel
                                                    companies, sinter
                                                    plants, blast
                                                    furnaces, basic
                                                    oxygen process
                                                    furnace (BOPF)
                                                    shops.
Lead Production...............                331  Primary metal
                                                    manufacturing.
Lime Manufacturing............             327410  Lime production.
Magnesium Production..........             331410  Nonferrous metal
                                                    (except aluminum)
                                                    smelting and
                                                    refining: Magnesium
                                                    refining, primary.
Nitric Acid Production........             325311  Nitrogenous
                                                    fertilizer
                                                    manufacturing:
                                                    Nitric acid
                                                    manufacturing.
Petroleum and Natural Gas                  486210  Pipeline
 Systems.                                           transportation of
                                                    natural gas.

                                           221210  Natural gas
                                                    distribution
                                                    facilities.
                                           211120  Crude petroleum
                                                    extraction.
                                           211130  Natural gas
                                                    extraction.
Petrochemical Production......             324110  Petrochemicals made
                                                    in petroleum
                                                    refineries.
Petroleum Refineries..........             324110  Petroleum refineries.
Phosphoric Acid Production....             325312  Phosphatic fertilizer
                                                    manufacturing.
Pulp and Paper Manufacturing..             322110  Pulp mills.
                                           322120  Paper mills.
                                           322130  Paperboard mills.
                               -----------------------------------------
Miscellaneous Uses of                 Facilities included elsewhere
 Carbonate.
                               -----------------------------------------
Municipal Solid Waste                      562212  Solid waste
 Landfills.                                         landfills.
                                           221320  Sewage treatment
                                                    facilities.
Silicon Carbide Production....             327910  Silicon carbide
                                                    abrasives
                                                    manufacturing.
Soda Ash Production...........             325180  Other basic inorganic
                                                    chemical
                                                    manufacturing: Soda
                                                    ash manufacturing.
Suppliers of Carbon Dioxide...             325120  Industrial gas
                                                    manufacturing
                                                    facilities.
Suppliers of Industrial                    325120  Industrial greenhouse
 Greenhouse Gases.                                  gas manufacturing
                                                    facilities.
Titanium Dioxide Production...             325180  Other basic inorganic
                                                    chemical
                                                    manufacturing:
                                                    Titanium dioxide
                                                    manufacturing.
Underground Coal Mines........             212115  Underground coal
                                                    mining.
Zinc Production...............             331410  Nonferrous metal
                                                    (except aluminum)
                                                    smelting and
                                                    refining: Zinc
                                                    refining, primary.
Importers and Exporters of Pre-            423730  Air-conditioning
 charged Equipment and Closed-                      equipment (except
 Cell Foams.                                        room units) merchant
                                                    wholesalers.
                                           333415  Air-conditioning
                                                    equipment (except
                                                    motor vehicle)
                                                    manufacturing.
                                           423620  Air-conditioners,
                                                    room, merchant
                                                    wholesalers.
                                           449210  Electronics and
                                                    Appliance retailers.
                                           326150  Polyurethane foam
                                                    products
                                                    manufacturing.
                                           335313  Circuit breakers,
                                                    power,
                                                    manufacturing.
                                           423610  Circuit breakers and
                                                    related equipment
                                                    merchant
                                                    wholesalers.
------------------------------------------------------------------------

    Table 1 of this preamble is not intended to be exhaustive, but
rather provides a guide for readers regarding facilities likely to be
affected by this proposed action. This table lists the types of
facilities that the EPA is now aware could potentially be affected by
this action. Other types of facilities than those listed in the table
could also be subject to reporting requirements. To determine whether
you would be affected by this proposed action, you should carefully
examine the applicability criteria found in 40 CFR part 98, subpart A
(General Provisions) and each source category. Many facilities that are
affected by 40 CFR part 98 have greenhouse gas emissions from multiple
source categories listed in Table 1 of this preamble. If you have
questions regarding the applicability of this action to a particular
facility, consult the person listed in the FOR FURTHER INFORMATION
CONTACT section.
    Acronyms and Abbreviations. The following acronyms and
abbreviations are used in this document.

AGA American Gas Association
AIM American Innovation and Manufacturing Act of 2020
ANSI American National Standards Institute
API American Petroleum Institute
AR5 Fifth Assessment Report
AR6 Sixth Assessment Report
ASME American Society of Mechanical Engineers
ASTM American Society for Testing and Materials
BACT best available control technology
BAMM best available monitoring methods
BCFC bromochlorofluorocarbons
BFC bromofluorocarbons
BOPF basic oxygen process furnace
CAA Clean Air Act
CAS Chemical Abstract Service
CBI confidential business information
CBP U.S. Customs and Border Protection
CCUS carbon capture, utilization, and sequestration
CDC Centers for Disease Control and Prevention
CEMS continuous emission monitoring system
CFC chlorofluorocarbons
CFR Code of Federal Regulations
CGA cylinder gas audit
CF4 perfluoromethane
CH4 methane
CHP combined heat and power
CMA Conference of the Parties serving as the meeting of the Parties
to the Paris Agreement
CO2 carbon dioxide
CO2e carbon dioxide equivalent
COVID-19 Coronavirus 2019
CSA CSA Group
DOC degradable organic carbon
DOE Department of Energy
DRE destruction and removal efficiency
EGU electricity generating unit
e-GGRT electronic Greenhouse Gas Reporting Tool
eGRID Emissions & Generation Resource Database
EF emission factor
EG emission guidelines
EIA Energy Information Administration
EOR enhanced oil recovery
EPA U.S. Environmental Protection Agency
ET Eastern time
FAQ frequently asked question
FR Federal Register
F-GHG fluorinated greenhouse gas
F-HTFs fluorinated heat transfer fluids
GHG greenhouse gas
GHGRP Greenhouse Gas Reporting Program
GWP global warming potential
HAWK HFC and ODS Allowance Tracking
HBCFC hydrobromochlorofluorocarbons
HBFC hydrobromofluorocarbons
HCFC hydrochlorofluorocarbons
HCFE hydrochlorofluoroethers
HFC hydrofluorocarbons
HFE hydrofluoroethers
HTF heat transfer fluid
HTS Harmonized Tariff System
ICR Information Collection Request
IPCC Intergovernmental Panel on Climate Change
ISBN International Standard Book Number
ISO International Standards Organization
IVT Inputs Verification Tool
k first order decay rate
kWh kilowatt hour
LDC local distribution company
MECS Manufacturing and Energy Consumption Survey
MEMP Metered Energy Monitoring Plan
mmBtu million British thermal units

MRV monitoring, reporting, and verification plan
mt metric tons
mtCO2e metric tons carbon dioxide equivalent
MWh megawatt-hour
MSW municipal solid waste
N2O nitrous oxide
NAICS North American Industry Classification System
NIST National Institute of Standards and Technology
NSPS new source performance standards
OMB Office of Management and Budget
PBI proprietary business information
PFC perfluorocarbon
POX partial oxidation
ppm parts per million
PRA Paperwork Reduction Act
PSA pressure swing adsorption
PSD prevention of significant deterioration
QA/QC quality assurance/quality control
RFA Regulatory Flexibility Act
REC renewable energy credit
RY reporting year
SAR Second Assessment Report
SDI Strategic Defense Initiative
SF6 sulfur hexafluoride
SMR steam methane reforming
TRL technology readiness level
TSD technical support document
UIC underground injection control
U.S. United States
UMRA Unfunded Mandates Reform Act of 1995
UNFCCC United Nations Framework Convention on Climate Change
WGS water gas shift
WWW World Wide Web

Contents

I. Background
    A. How is this preamble organized?
    B. Background on This Supplemental Proposed Rule
    C. Legal Authority
II. Overview and Rationale for Proposed Amendments to 40 CFR Part 98
    A. Revisions to Global Warming Potentials
    B. Revisions To Expand Source Categories and Address Potential
Gaps in Reporting of Emissions Data for Specific Sectors
    C. Improvements to Existing and Proposed Emissions Estimation
Methodologies
    D. Revisions to Reporting Requirements To Improve Verification
and the Accuracy of the Data Collected
    E. Technical Amendments, Clarifications, and Corrections
III. Proposed Amendments to Part 98
    A. Subpart A--General Provisions
    B. Subpart C--General Stationary Fuel Combustion Sources
    C. Subpart F--Aluminum Production
    D. Subpart G--Ammonia Manufacturing
    E. Subpart I--Electronics Manufacturing
    F. Subpart N--Glass Production
    G. Subpart P--Hydrogen Production
    H. Subpart Y--Petroleum Refineries
    I. Subpart AA--Pulp and Paper Manufacturing
    J. Subpart HH--Municipal Solid Waste Landfills
    K. Subpart OO--Suppliers of Industrial Greenhouse Gases
    L. Subpart PP--Suppliers of Carbon Dioxide
    M. Subpart QQ--Importers and Exporters of Fluorinated Greenhouse
Gases Contained in Pre-Charged Equipment and Closed-Cell Foams
    N. Subpart RR--Geologic Sequestration of Carbon Dioxide
    O. Subpart UU--Injection of Carbon Dioxide
    P. Subpart VV--Geologic Sequestration of Carbon Dioxide With
Enhanced Oil Recovery Using ISO 27916
IV. Proposed Amendments To Add New Source Categories to Part 98
    A. Subpart B--Energy Consumption
    B. Subpart WW--Coke Calciners
    C. Subpart XX--Calcium Carbide Production
    D. Subpart YY--Caprolactam, Glyoxal, and Glyoxylic Acid
Production
    E. Subpart ZZ--Ceramics Production
V. Schedule for the Proposed Amendments
VI. Proposed Confidentiality Determinations for Certain Data
Reporting Elements
    A. Overview and Background
    B. Proposed Confidentiality Determinations
    C. Proposed Reporting Determinations for Inputs to Emissions
Equations
    D. Request for Comments on Proposed Category Assignments,
Confidentiality Determinations, or Reporting Determinations
VII. Impacts of the Proposed Amendments
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Determination under CAA Section 307(d)

I. Background

A. How is this preamble organized?

    Section I of this preamble contains background information on the
June 21, 2022 proposed rule (87 FR 36920, hereafter referred to as
``2022 Data Quality Improvements Proposal'') and how the EPA identified
additional information to support further revisions to improve the
GHGRP that are included in this supplemental proposal. This section
also discusses the EPA's legal authority under the Clean Air Act (CAA)
to promulgate (including subsequent amendments to) the GHG Reporting
Rule, codified at 40 CFR part 98 (hereinafter referred to as ``part
98''), and the EPA's legal authority to make confidentiality
determinations for new or revised data elements required by these
amendments or for existing data elements for which a confidentiality
determination has not previously been proposed. Section II of this
preamble describes the types of amendments included in this proposed
rule and includes the rationale for each type of proposed change.
Section III of this preamble is organized by existing part 98 subpart
and contains detailed information on the proposed revisions and the
rationale for the proposed amendments in each section. Section IV of
this preamble describes five newly proposed part 98 subparts and
contains detailed information and rationale for the requirements for
each proposed source category. Section V of this preamble discusses the
proposed schedule for implementing these revisions to part 98. Section
VI of this preamble discusses the proposed confidentiality
determinations for new or substantially revised (i.e., requiring
additional or different data to be reported) data reporting elements,
as well as for certain existing data elements for which the EPA is
proposing a new determination. Section VII of this preamble discusses
the impacts of the proposed amendments. Section VIII of this preamble
describes the statutory and Executive order requirements applicable to
this action.

B. Background on This Supplemental Proposed Rule

    In the 2022 Data Quality Improvements Proposal, the EPA proposed
amendments to specific provisions of the GHGRP where we identified
opportunities for improvement, such as where the rule may be modified
to reflect the EPA's current understanding of U.S. GHG emission trends,
or to improve data collection and reporting where additional data may
be necessary to better understand emissions from specific sectors or
inform future policy decisions (87 FR 36920, June 21, 2022). The 2022
Data Quality Improvements Proposal included updates to emission factors
and refinements to existing emissions estimation methodologies to
reflect an improved understanding of emission sources and end uses of
GHGs. Additionally, it proposed to collect additional data to
understand new source categories or new emission sources for specific
sectors; to improve the EPA's understanding of the sector-

specific processes or other factors that influence GHG emission rates;
to improve verification of collected data; and to provide additional
data to complement or inform other EPA programs. In other cases, we
proposed revisions to resolve gaps in the current coverage of the GHGRP
that leave out potentially significant sources of GHG emissions or end
uses. For example, the proposed revisions included new reporting of
direct air capture as a carbon capture option for suppliers of carbon
dioxide; addition of a new subpart for quantifying geologic
sequestration in association with enhanced oil recovery operations; and
an updated calculation methodology to estimate emissions from large,
atypical release events at oil and gas facilities. The EPA also
proposed revisions that clarify or update provisions that may be
unclear, or where we identified specific provisions in part 98 that
would streamline calculation, monitoring, or reporting to provide
flexibility or increase the efficiency of data collection. Finally, the
EPA also solicited comment on expanding the GHGRP to include several
new source categories that could improve the EPA's understanding of
GHGs, including energy consumption; ceramics production; calcium
carbide production; caprolactam, glyoxal, and glyoxylic acid
production; coke calcining; and CO2 utilization (see section
IV of the 2022 Data Quality Improvements Proposal at 87 FR 37016), as
well as requesting comment on potential future amendments to add new
calculation, monitoring, and reporting requirements.
    As stated in the 2022 Data Quality Improvements Proposal, the data
collected under part 98 are used to inform the EPA's understanding of
the relative emissions and distribution of emissions from specific
industries, the factors that influence GHG emission rates, and to
inform policy options and potential regulations. Since publishing the
proposed amendments, the EPA has received or identified new information
to further improve the data collected under the GHGRP, and has
subsequently identified additional amendments that the EPA is putting
forward in this supplemental proposal. Some of the additional
amendments are informed by a review of comments raised by stakeholders
on the 2022 Data Quality Improvements Proposal (e.g., see sections
III.J and III.P of this preamble). Other proposed changes are based on
additional data gaps the EPA has observed in collected data, either
where additional data would improve verification of data reported to
the GHGRP (see section II.D of this preamble) or where additional data
is needed to help our understanding of changing industry emission
trends (see sections II.B and II.C of this preamble). Based on review
of this information, the EPA is proposing additional amendments to part
98, described in sections II through IV of this preamble, that build on
and improve the amendments proposed in the 2022 Data Quality
Improvements Proposal or that would further enhance the quality of part
98 and implementation of the GHGRP.
    In some cases, the EPA has identified updated guidance on GHG
estimation methods or advances in the scientific literature. For
example, through this notification, the EPA is proposing a
comprehensive update to the global warming potentials (GWPs) in Table
A-1 to subpart A of part 98, in part to ensure that the GWPs used in
the GHGRP are consistent with those recently agreed upon by the Parties
to the United Nations Framework Convention on Climate Change (UNFCCC)
for purposes of GHG reporting. The Parties specified the agreed-on GWPs
in November 2021 (see section III.A.1 of this preamble), which was too
late to allow the EPA to consider proposing a comprehensive GWP update
in the 2022 Data Quality Improvement Proposal.\1\ We have subsequently
reviewed and are proposing to include updated GWPs in this proposed
rule.
---------------------------------------------------------------------------

    \1\ Although we proposed changes to certain chemical specific
and default global warming potentials in Table A-1 to subpart A of
part 98 in the 2022 Data Quality Improvements Proposal, these were
limited updates to GWPs of fluorinated GHGs that are not required to
be reported under the UNFCCC because they are not
hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, or
nitrogen trifluoride.
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    In other cases, we have identified new data supporting additional
improvements to the calculation, monitoring, and recordkeeping
requirements, including revisions and clarifications not previously
proposed, that would address potential data gaps and improve the
quality of the data collected in the GHGRP. For example, the EPA is
proposing to incorporate additional revisions to the Municipal Solid
Waste (MSW) landfill source category in light of recent aerial studies
that indicate that methane emissions from landfills may be considerably
higher than the methane emissions currently reported under subpart HH
of part 98 (Municipal Solid Waste Landfills). The proposed amendments
incorporate an updated emissions estimation methodology that would
improve the accuracy and coverage of the greenhouse gas data from
landfills. These data would be used to inform the EPA's understanding
of methane emissions from MSW landfills and future policy decisions
under the CAA. For example, the current equations account for fugitive
methane emissions passing through intact cover systems. Collecting
surface emissions data under the proposed revisions would inform the
EPA's understanding of the degree to which breakdown in cover materials
is occurring and the impacts on methane emission rates.
    This supplemental proposal also incorporates consideration of
information received in response to our request for comment on certain
topics in the 2022 Data Quality Improvement Proposal. In that proposal,
we requested comment on potential future amendments to improve the
coverage of U.S. GHG emissions and supply captured by the GHGRP. The
EPA has reviewed comments received in response to the call for
information, along with additional data that the EPA has collected, and
is proposing to establish new subparts with specific reporting
provisions under part 98 for the source categories of energy
consumption; coke calciners; ceramics production; calcium carbide
production; and caprolactam, glyoxal, and glyoxylic acid production.
The proposed revisions would improve the data collected under the GHGRP
by better capturing the changing landscape of greenhouse gas emissions,
providing for more complete coverage of U.S. GHG emission sources, and
providing a more comprehensive approach to understanding GHG emissions.
    For other revisions, we are proposing to clarify or correct
specific proposed provisions of the 2022 Data Quality Improvements
Proposal. For instance, we are proposing to clarify the applicability
requirements of proposed subpart VV of part 98 (Geologic Sequestration
of Carbon Dioxide With Enhanced Oil Recovery Using ISO 27916), a new
subpart for quantifying geologic sequestration in association with
enhanced oil recovery (EOR) operations, which was included in the 2022
Data Quality Improvements Proposal. Following the initial proposal, we
received feedback from stakeholders highlighting ambiguity in the
applicability of the proposed source category and questioning whether
EOR operators electing to use the International Standards Organization
(ISO) standard designated as CSA Group (CSA)/American National
Standards Institute (ANSI) ISO 27916:2019, Carbon Dioxide Capture,
Transportation

and Geological Storage--Carbon Dioxide Storage Using Enhanced Oil
Recovery (CO2-EOR) (hereafter referred to as ``CSA/ANSI ISO
27916:2019''), must mandatorily report under the new proposed subpart
VV or would have the option to continue reporting under subpart UU
(Injection of Carbon Dioxide). We are proposing the applicability of
the source category in this supplemental notification to better reflect
our initial intent, which was that operators electing to use CSA/ANSI
ISO 27916:2019 to quantify geologic sequestration of CO2
would be required to report under subpart VV, and proposing harmonizing
revisions to subpart UU (Injection of Carbon Dioxide). This
supplemental proposal provides information about these proposed updates
for public review and comment.
    This supplemental proposal does not address implementation of
provisions of the Inflation Reduction Act which was signed into law on
August 16, 2022. Section 60113 of the Inflation Reduction Act amended
the CAA by adding section 136, ``Methane Emissions and Waste Reduction
Incentive Program for Petroleum and Natural Gas Systems.'' The EPA
intends to take one or more separate actions in the coming months
related to implementation of the Methane Emissions and Waste Reduction
Incentive Program, including a future rulemaking to propose revisions
to certain requirements of subpart W of part 98 (Petroleum and Natural
Gas Systems). Accordingly, the Methane Emissions and Waste Reduction
Incentive Program is outside the scope of this supplemental proposed
rule.

C. Legal Authority

    The EPA is proposing these rule amendments under its existing CAA
authority provided in CAA section 114. As stated in the preamble to the
Mandatory Reporting of Greenhouse Gases final rule (74 FR 56260,
October 30, 2009) (hereinafter referred to as ``2009 Final Rule''), CAA
section 114(a)(1) provides the EPA broad authority to require the
information proposed to be gathered by this rule because such data
would inform and are relevant to the EPA's carrying out of a variety of
CAA provisions. See the preambles to the proposed GHG Reporting Rule
(74 FR 16448, April 10, 2009) (hereinafter referred to as ``2009
Proposed Rule'') and the 2009 Final Rule for further information.

II. Overview and Rationale for Proposed Amendments to 40 CFR Part 98

    In general, this supplemental proposal includes the following
proposed revisions to better inform EPA policies and programs under the
CAA:
     Revisions to Table A-1 to the General Provisions of part
98 to include updated GWPs to reflect advances in scientific knowledge
and better characterize the climate impacts of certain GHGs, including
agreed-upon values established by the UNFCCC, and to maintain
comparability and consistency with the Inventory of U.S. Greenhouse Gas
Emissions and Sinks \2\ (hereafter referred to as ``the Inventory'')
and other analyses produced by the EPA;
---------------------------------------------------------------------------

    \2\ The EPA's GHG Inventory is available at https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks.
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     Revisions to expand source categories or add new source
categories to address potential gaps in reporting of emissions data for
specific sectors in order to improve the accuracy and completeness of
the data provided by the GHGRP;
     Revisions to refine existing calculation methodologies to
reflect an improved understanding of emissions sources and end uses of
GHGs, to incorporate more recent research on GHG emissions or
formation, or to improve verification of reported emissions;
     Revisions to add or modify reporting requirements to
eliminate data gaps and improve verification of emissions estimates;
and
     Revisions that clarify requirements that reporters have
previously found vague to ensure that accurate data are being
collected, and editorial corrections or harmonizing changes that would
improve the public's understanding of the rule.
    Overall, the proposed changes in this supplemental notification
would provide a more comprehensive, nationwide GHG emissions profile
reflective of the origin and distribution of GHG emissions in the
United States and would more accurately inform EPA policy options for
potential regulatory or non-regulatory CAA programs. The EPA
additionally uses the data from the GHGRP, which would include data
from these proposed changes, to improve estimates used in the
Inventory.
    Sections II.A through II.E of this preamble provide additional
rationale for the proposed changes. Details for the specific amendments
proposed for each subpart are included in sections III and IV of this
preamble. We are seeking public comment only on the proposed revisions
and issues specifically identified in this supplemental notification
for the identified subparts. We expect to deem any comments received in
response to this notification that address other aspects of 40 CFR part
98 to be outside of the scope of this supplemental proposed rulemaking.

A. Revisions to Global Warming Potentials

    Table A-1 to subpart A of 40 CFR part 98 (``Table A-1'') is a
compendium of chemical-specific and default GWP values of GHGs that are
required to be reported under one or more subparts of the GHG Reporting
Rule. These GWPs are used to convert tons of chemical into tons of
CO2-equivalent (CO2e) for purposes of various
calculations and reporting under the rule. The EPA is proposing
revisions to Table A-1 to update the chemical-specific GWP values of
certain GHGs to reflect GWPs from the IPCC Fifth Assessment Report
(hereinafter referred to as ``AR5'') \3\ and, for certain GHGs that do
not have chemical-specific GWPs listed in AR5, to adopt GWP values from
the IPCC Sixth Assessment Report (hereinafter referred to as
``AR6'').\4\ The EPA is also proposing to revise and expand the set of
default GWPs in Table A-1, which are applied to GHGs for which peer-
reviewed chemical-specific GWPs are not available. With these changes,
the GWP values in Table A-1 would reflect more recent science regarding
the atmospheric impacts of non-CO2 GHGs, and the GWP values
used for the GHGRP would continue to be consistent with the GWP values
used for the Inventory and other EPA programs. (As

discussed further below, the Inventory incorporates the GWP values
agreed on by the parties to the UNFCCC, who agreed to use the GWP
values in AR5 beginning in 2024.)
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    \3\ IPCC, 2013: Climate Change 2013: The Physical Science Basis.
Contribution of Working Group I to the Fifth Assessment Report of
the Intergovernmental Panel on Climate Change [Stocker, T.F., D.
Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels,
Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press,
Cambridge, United Kingdom and New York, NY, USA, 1535 pp. The GWPs
are listed in Table 8.A.1 of Appendix 8.A: Lifetimes, Radiative
Efficiencies and Metric Values, which appears on pp. 731-737 of
Chapter 8, ``Anthropogenic and Natural Radiative Forcing.''
    \4\ Smith, C., Z.R.J. Nicholls, K. Armour, W. Collins, P.
Forster, M. Meinshausen, M.D. Palmer, and M. Watanabe, 2021: The
Earth's Energy Budget, Climate Feedbacks, and Climate Sensitivity
Supplementary Material. In Climate Change 2021: The Physical Science
Basis. Contribution of Working Group I to the Sixth Assessment
Report of the Intergovernmental Panel on Climate Change [Masson-
Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. P[eacute]an, S.
Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K.
Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield,
O. Yelek[ccedil]i, R. Yu, and B. Zhou (eds.)]. Available from
www.ipcc.ch/ The AR6 GWPs are listed in Table 7.SM.7, which appears
on page 16 of the Supplementary Material.
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    As discussed in this section of the preamble, the GWP values
currently in Table A-1 to part 98 are drawn both from the IPCC Fourth
Assessment Report \5\ (hereinafter referred to as ``AR4'') and, for
multiple GHGs that do not have GWPs listed in AR4, from AR5. The
proposed GWP values are drawn from AR5, and for multiple GHGs that do
not have GWPs listed in AR5, from AR6. Consistent with our approach
since the inception of the GHGRP, we are proposing to adopt the AR5 and
AR6 GWPs based on a 100-year time horizon. Note that these proposed
revisions are in addition to the 2022 Data Quality Improvements
Proposal to add a chemical-specific GWP of 0.14 for carbonic difluoride
and to expand the fluorinated greenhouse gas (F-GHG) group for several
types of unsaturated compounds to include additional types of
unsaturated compounds. GWPs that have been newly evaluated or
reevaluated in the peer-reviewed scientific literature are periodically
consolidated and published by the IPCC. Since 1990, there have been six
IPCC Assessment Reports, each of which included a set of revised and
expanded GWPs. For purposes of reporting their GHG emissions under the
UNFCCC, the Parties to the UNFCCC have successively adopted the 100-
year GWPs in three of the IPCC Assessment Reports, beginning with the
SAR, advancing to AR4 and, starting in 2024, moving to AR5.
---------------------------------------------------------------------------

    \5\ IPCC Fourth Assessment Report (AR4), 2007. Climate Change
2007: The Physical Science Basis. Contribution of Working Group I to
the Fourth Assessment Report of the Intergovernmental Panel on
Climate Change [Core Writing Team, Pachauri, R.K and Reisinger, A.
(eds.)]. IPCC, Geneva, Switzerland, 104 pp.
---------------------------------------------------------------------------

    Published in 2014, AR5 includes revised GWPs for the GHGs with GWPs
in AR4 as well as for multiple additional GHGs. The revised GWPs
reflect advances in scientific knowledge on the radiative efficiencies,
atmospheric lifetimes, and other characteristics of these GHGs and of
CO2, and they also account for the growing background
concentrations of GHGs (particularly CO2) in the
atmosphere.\6\ AR5 therefore reflects an improved scientific
understanding of the radiative effects \7\ of these gases in the
atmosphere. As noted in the preamble to the 2009 Final Rule, it is the
EPA's intent to periodically update Table A-1 through notice and
comment rulemaking as GWPs are evaluated or re-evaluated by the
scientific community (74 FR 56348; October 30, 2009). Further, as noted
in the preamble to the 2013 Revisions to the Greenhouse Gas Reporting
Rule and Final Confidentiality Determinations for New or Substantially
Revised Data Elements (78 FR 71904, 71911; November 29, 2013, hereafter
``the 2013 Final Rule''), which updated GWPs in Table A-1, ``each
successive assessment provides more accurate GWP estimates as
experiments and improved computational methods lead to more accurate
estimates of the radiative efficiencies, atmospheric lifetimes, and
indirect effects of the various gases. Additionally, the more recent
assessments reflect more up-to-date background concentrations, which
are necessary for accurately calculating the radiative efficiency of
the different gases.'' Therefore, adopting the GWP values in AR5 (and
in AR6 for GHGs that do not have GWPs in AR5) would support the overall
goals of the GHGRP to collect high-quality GHG data and to incorporate
metrics that reflect scientific updates as they are adopted.
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    \6\ Increasing background concentrations of a GHG in the
atmosphere can lower the impact of subsequent emissions.
    \7\ Radiative forcing is the measurement of the capacity of a
gas or other forcing agent to affect the balance of energy in
Earth's atmosphere based in the difference in incoming solar
radiation and outgoing infrared radiation.
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    The proposed changes to Table A-1 would also ensure that the data
collected in the GHGRP can be compared to the data collected and
presented by other EPA programs and by national and international GHG
inventories. The proposed changes, with a proposed effective date of
January 1, 2025 (therefore applicable to data submitted for calendar
year/reporting year 2024, i.e., RY2024),\8\ would maintain long-term
consistency between the GHGRP GWPs and the GWPs used for the Inventory,
which are scheduled to change from the AR4 GWPs to the AR5 GWPs for the
1990-2022 Inventory.\9\
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    \8\ As discussed in section III.A.2 of the preamble, current 40
CFR 98.3(k) provides that facilities or suppliers that first become
subject to any subpart of part 98 solely due to an amendment to
Table A-1 are not required to submit an annual GHG report (or, for
facilities or suppliers that already report under the GHGRP, a
report for the subpart to which they are newly subject) for the
reporting year during which the change in GWPs is published.
However, they are required to begin monitoring their emissions and
supplies for the subpart(s) to which they are newly subject
beginning on January 1 of the year following publication of the
amendment to Table A-1.
    \9\ Due to the time required to complete this proposed rule to
adopt the AR5 GWPs, if this proposed rule is finalized, emissions
from at least two years, 2022 and 2023, would be weighted by
different sets of GWPs under part 98 and the Inventory.
---------------------------------------------------------------------------

    The Inventory is a comprehensive assessment of U.S. GHG emissions
based on national-level data and follows the reporting guidelines set
by the UNFCCC.\10\ The United States is a party to the UNFCCC and
submits the Inventory to the Secretariat of the UNFCCC as part of
annual obligations under the treaty. To ensure consistency and
comparability with national inventory data submitted by other UNFCCC
Parties, the Inventory submitted to the UNFCCC uses internationally
accepted methods and common reporting metrics agreed upon by the
Parties (including the United States) to develop and characterize
emission estimates.
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    \10\ See Articles 4 and 12 of the Convention on Climate Change.
Parties to the Convention, by ratifying, ``shall develop,
periodically update, publish and make available * * * national
inventories of anthropogenic emissions by sources and removals by
sinks of all greenhouse gases not controlled by the Montreal
Protocol, using comparable methodologies * * *.'' See https://unfccc.int/resource/docs/convkp/conveng.pdf.
---------------------------------------------------------------------------

    As described in the preamble of the 2009 Proposed Rule, the GHGRP
is intended to gather information that is relevant to the EPA's
carrying out a wide variety of CAA provisions, with the goal of
supplementing and complementing existing U.S. Government programs
related to climate policy and research, including the Inventory
submitted to the UNFCCC. The GHGRP provides data that can inform
analysis of potential U.S. climate policies and programs, which is also
one of the uses for the data developed for the Inventory. The GHGRP
complements the Inventory and other U.S. programs by providing data
from certain individual facilities and suppliers, generally those above
certain thresholds. Collected facility, unit, and process-level GHG
data from the GHGRP are also used to develop and confirm the national
statistics and emission estimates presented in the Inventory, which are
calculated using aggregated national data.
    Throughout the development and implementation of the GHG Reporting
Rule, the EPA has proposed and finalized calculation methodologies and
reporting metrics that were consistent with the international reporting
standards under the UNFCCC. This approach has allowed the data
collected under the GHGRP to be easily compared to the data in the
Inventory and to data from other national and international programs,
facilitating the analysis of potential U.S. climate policies and
programs. Specifically, in the 2009 Final Rule, the EPA generally
promulgated

GWP values published in the IPCC Second Assessment Report \11\
(hereafter referred to as ``SAR GWP values'') to convert mass emissions
(or supplies) of each GHG into a common unit of measure,
CO2e, for final reporting. Although the IPCC published AR4
prior to publication of the 2009 Final Rule, the UNFCCC continued to
require the use of SAR GWP values for reporting in the Inventory at the
time the rule was promulgated, and up until 2014.\12\ In the 2013 Final
Rule, the EPA revised the GHGRP's GWP values, after consideration of a
UNFCCC decision reached by UNFCCC member parties and published on March
15, 2012, to require countries submitting an annual inventory report in
2015 and beyond to use AR4 GWP values.\13\ The 2013 Final Rule adopted
the IPCC AR4 GWP values in Table A-1, in part in order to maintain
comparability and consistency with the updated international reporting
standards under the UNFCCC and the revised requirements for official
emission estimates to be reported by the United States and other
parties. Following the 2013 Final Rule, the EPA published a separate
rule to add GWPs to Table A-1 for a number of F-GHGs and fluorinated
heat transfer fluids (F-HTFs) for which GWPs were not provided in AR4
or previous scientific assessments (79 FR 73750, December 11, 2014,
hereinafter referred to as the ``2014 Fluorinated GHG Final
Rule'').\14\ The 2014 Fluorinated GHG Final Rule included chemical-
specific GWPs primarily drawn from AR5, as well as default GWPs
intended for F-GHGs and F-HTFs for which peer-reviewed GWPs were not
available in AR4, AR5, or other sources. The default GWPs were
calculated and applied to 12 fluorinated GHG groups composed of
compounds with similar chemical structures, atmospheric lifetimes, and
GWPs, and were based on the average GWPs of the chemically similar
fluorinated GHGs for which a chemical-specific GWP was available in
Table A-1 or AR5. As such, the changes from the 2014 Fluorinated GHG
Final Rule reflected the latest scientific consensus regarding F-GHGs
that did not have GWPs in earlier assessments and expanded the number
of compounds reflected in Table A-1, resulting in more accurate and
complete estimates of GHG emissions. At the same time, the 2014
Fluorinated GHG Final Rule maintained consistency between the GHGRP and
the Inventory by retaining the AR4 GWP values where those were
available.
---------------------------------------------------------------------------

    \11\ IPCC Second Assessment Report (SAR), 1995. Climate Change
1995: The Science of Climate Change, Contribution of Working Group I
to the Second Assessment Report of the Intergovernmental Panel on
Climate Change [Houghton, J.T.; Meira Filho, L.G.; Callander, B.A.;
Harris, N.; Kattenberg, A.; Maskell, K. (eds.)., Cambridge
University Press, Cambridge, United Kingdom, 572 pp.
    \12\ As discussed further in this section of this preamble, the
EPA did adopt AR4 values in 2009 for GHGs that did not have SAR GWP
values because doing so increased the accuracy and completeness of
the GWP-weighted emissions calculated and reported under the GHGRP
without introducing any inconsistency with UNFCCC reporting.
    \13\ Refer to https://unfccc.int/. See Decision 15/CP.17,
Revision of the UNFCCC reporting guidelines on annual inventories
for Parties included in Annex I to the Convention.
    \14\ As noted in the 2014 Fluorinated GHG Final Rule, the
addition of GWPs for compounds that did not have GWPs in AR4 was
consistent with the UNFCCC Reporting Guidelines, which ``strongly
encourage'' Annex I Parties ``to also report emissions and removals
of additional GHGs'' (i.e., GHGs whose GWPs are not included in
AR4).
---------------------------------------------------------------------------

    In the 2013 Final Rule, we noted ``the EPA may consider adoption of
AR5 GWPs or other GWP values for compounds currently listed in Table A-
1 (i.e., compounds for which AR4 GWPs are currently listed in Table A-
1) if these values are adopted by the UNFCCC and the global community''
(78 FR 71912; November 29, 2013).
    In December 2018, the Parties to the UNFCCC agreed to require use
of the 100-year time-horizon GWP values from AR5 in annual inventory
reports submitted in 2024 and future years.\15\ In November 2021, the
parties clarified which of the two sets of GWPs in AR5 were to be used:
those in Table 8.A.1.\16\ Accordingly, the United States has an annual
commitment to submit the Inventory for 2024 and subsequent years using
the revised AR5 GWP values in Table 8.A.1. The Inventory for 2024 will
contain national-level estimates of emissions for each year from 1990-
2022. In order to ensure that the GHGRP continues to rely on recent
scientific data and uses methods consistent with UNFCCC guidelines, as
the EPA intended in the development of the 2009 Final Rule and in
revisions to the GHGRP since then, we are proposing to revise the GWP
values in Table A-1 of part 98 to reflect updated AR5 GWP values, which
would apply to annual reports beginning with RY2024. The proposed
changes would continue to keep the reporting metrics in part 98
consistent with the updated international reporting standards followed
by the Inventory and allow the GHGRP to continue to provide the
additional benefit of complementing and informing the Inventory
submitted to the UNFCCC.\17\
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    \15\ Refer to https://unfccc.int/. See Annex to Decision 18/
CMA.1, paragraph 37. ``Each Party shall use the 100-year time-
horizon global warming potential (GWP) values from the IPCC Fifth
Assessment Report, or 100-year time-horizon GWP values from a
subsequent IPCC assessment report as agreed upon by the [Conference
of the Parties serving as the meeting of the Parties to the Paris
Agreement] (CMA), to report aggregate emissions and removals of
GHGs, expressed in CO2 eq.''
    \16\ Decision 5/CMA.3, paragraph 25 reads ``the 100-year time-
horizon global warming potential values referred to in decision 18/
CMA.1, annex, paragraph 37, shall be those listed in Table 8.A.1 of
the Fifth Assessment Report of the Intergovernmental Panel on
Climate Change, excluding the value for fossil methane.'' See
https://unfccc.int/sites/default/files/resource/CMA2021_L10a2E.pdf.
    \17\ The updates to Table A-1 would not affect the GWP-weighted,
CO2-equivalent totals certified by facilities or
suppliers in their annual reports for reporting years before RY2023.
However, to ensure that GWP-weighted totals are used in analyses and
displayed to the public in a consistent manner from RY2010/2011
through RY2023 and later years, the updated GWPs would be applied to
the entire time series in analyses and in EPA's Facility Level
Information on GreenHouse gases Tool (FLIGHT) at https://ghgdata.epa.gov/ghgp/main.do. This approach is consistent with the
approach taken for previous updates of Table A-1. See, e.g., 78 FR
71937.
---------------------------------------------------------------------------

    For GHGs that do not have GWPs in AR5 but do have GWPs in AR6, we
are proposing to adopt the AR6 GWPs. Currently, default GWPs are
applied to these compounds based on the fluorinated GHG group to which
they belong. While the default GWPs are, on average, expected to be
reasonably accurate across the fluorinated GHGs within a fluorinated
GHG group, the AR6 GWP for an individual compound is expected to be
more accurate for that compound than the corresponding default GWP.
This is because the AR6 GWP takes into consideration the radiative
efficiency and atmospheric lifetime of the individual compound. Thus,
adopting the AR6 GWPs for GHGs that do not have GWPs in AR5 is expected
to improve the accuracy with which the atmospheric impacts of the gases
are reflected in annual reports, threshold determinations, and other
calculations. The specific changes that we are proposing to Table A-1
and the rationale for the GWPs proposed to be adopted are described
further in section III.A.1 of this preamble.
    We recognize that some other EPA programs use the GWP values in
Table A-1 to determine the applicability of their individual program
requirements to direct emitters or suppliers above certain thresholds.
Issues related to other EPA programs that use the GHGRP GWP values in
Table A-1 are outside the scope of this proposed rule. To the extent
that a Table A-1 amendment raises such questions or concerns, please
work with the respective EPA office for that other EPA program. We also
recognize that non-EPA programs use the GWP values in Table A-1 to part
98. Issues related to non-EPA programs that use the GHGRP GWP values in

Table A-1 are also outside the scope of this proposed rule. As
explained in this section above, this rulemaking proposes to update
GWPs for the GHGRP consistent with recent science and the intent the
EPA expressed at the time the GHGRP was first promulgated. Thus, under
this supplemental proposal, we are seeking comments on the specific GWP
values proposed in this action for the GHGRP.

B. Revisions To Expand Source Categories and Address Potential Gaps in
Reporting of Emissions Data for Specific Sectors

    In the 2022 Data Quality Improvements Proposal, the Agency stated
that it was considering future revisions to the GHG Reporting Rule to
potentially expand existing source categories or develop new source
categories that would add calculation, monitoring, reporting, and
recordkeeping requirements for certain sectors of the economy.
Specifically, the 2022 Data Quality Improvements Proposal solicited
comment on the potential addition of GHG reporting requirements related
to energy consumption; CO2 utilization; ceramics production;
calcium carbide production; caprolactam, glyoxal, and glyoxylic acid
production; and coke calcining. The EPA solicited comment on these six
source categories where we identified that additional data from these
emission sources would help eliminate data gaps, improve the coverage
of the GHGRP, and better inform future EPA policy and programs under
the CAA. We identified cases where certain emission sources may
potentially contribute significant GHG emissions that are not currently
reported, or where facilities representative of these source categories
may currently report under another part 98 source category using
methodologies that may not provide complete or accurate emissions. We
also identified where the inclusion of potential source categories
would improve the completeness of the emissions estimates presented in
the Inventory, such as collection of data on ceramics production,
calcium carbide production, and caprolactam, glyoxal, and glyoxylic
acid production. The 2022 Data Quality Improvements Proposal also
included similar amendments to add reporting of new emissions or
emissions sources for certain existing sectors to address potential
gaps in reporting, e.g., where we proposed to add requirements for the
monitoring, calculation, and reporting of F-GHGs other than
SF6 and perfluorocarbons (PFCs) under subpart DD (Electrical
Equipment and Distribution Equipment Use) to account for the
introduction of alternative technologies and replacements for
SF6, including fluorinated gas mixtures such as
fluoronitriles or fluoroketones mixed with carrier gases, as a
replacement for dielectric insulation gases (87 FR 37000; June 21,
2022).
    Following the June 21, 2022 request for comment, the EPA has
reviewed information provided from stakeholders and considered
additional data to further support the development of reporting
requirements for five source categories. After that consideration, we
are proposing to add annual reporting requirements for greenhouse gases
from the following sources categories in new subparts to part 98 as
follows: subpart B (Energy Consumption); subpart WW (Coke Calciners);
subpart XX (Calcium Carbide Production); subpart YY (Caprolactam,
Glyoxal, and Glyoxylic Acid Production); and subpart ZZ (Ceramics
Production). As explained in the 2022 Data Quality Improvements
Proposal, the collection of such data would continue to inform, and are
relevant to, the EPA's carrying out a wide variety of CAA provisions.
Additional information on the data and rationale informing the proposed
definition of the source category, reporting thresholds, calculation,
monitoring, quality assurance, missing data, verification, and data
reporting and recordkeeping requirements for these five proposed new
source categories are included in section IV of this preamble.
    The EPA is also proposing amendments that would expand the coverage
of the GHGRP for one subpart not included in the 2022 Data Quality
Improvements Proposal. Since the publication of the proposed rule, we
have identified a gap in coverage for certain emission sources, where
revisions to existing applicability and reporting requirements would
help the EPA to better understand and track emissions in specific
sectors and better inform future EPA policy and programs under the CAA.
In this supplemental proposal, we are proposing to amend the
applicability of subpart P (Hydrogen Production) to expand reporting to
include all hydrogen plants. The current source category definition in
subpart P is limited to merchant hydrogen production facilities,
including facilities that sell hydrogen and that may be located within
another facility if they are not owned by, or under the direct control
of, the other facility's owner and operator. The current definition
inadvertently excludes non-merchant hydrogen production facilities
(i.e., facilities that do not sell hydrogen or captive hydrogen
plants). Although some non-merchant hydrogen production facilities may
report under subpart Y (Petroleum Refineries), the EPA has identified
that there may be other non-merchant or captive hydrogen plants whose
emissions are not currently captured by part 98. The proposed
amendments would address this gap in reporting and allow the EPA to
better understand and track emissions from these facilities, which
would better inform future EPA policy and programs under the CAA.
Section III.G of this preamble provides additional information on the
proposed amendments.
    Additionally, we are proposing to amend subpart HH (Municipal Solid
Waste Landfills) to expand reporting to account for methane emissions
from large releases that are currently not quantified under the GHGRP.
Specifically, we are proposing to revise calculation methodologies in
subpart HH to account for cover system leaks to better account for
large release events. The EPA has identified recent studies indicating
that methane emissions from landfills may be considerably higher than
what is currently reported to part 98 due to emissions from poorly
operating gas collection systems or destruction devices and cover
system leaks. We are proposing to revise the monitoring and calculation
methodologies in subpart HH to account for these scenarios.
Specifically, we note that owners or operators of landfills with gas
collection systems subject to the control requirements in the new
source performance standards (NSPS) as implemented in 40 CFR part 60,
subparts WWW or XXX, emission guidelines (EG) as implemented in 40 CFR
part 60, subparts Cc or Cf, or the Federal plan as implemented in 40
CFR part 62, subparts GGG and OOO are required to conduct surface
methane concentration measurements to ensure proper operation of the
gas collection system. We are proposing that subpart HH reporters with
landfills for which surface methane concentration measurements are
conducted under the NSPS, EG, or Federal plan would estimate emissions
for cover leaks based on a count of the number of exceedances
identified during the surface measurement period and the proposed
revised equations HH-6, HH-7, and HH-8 to adjust reported methane
emissions to account for these exceedances. Subpart HH reporters with
landfills with gas collection systems that are not required to conduct
surface methane concentration measurements under the NSPS, EG, or
Federal plan may elect to conduct these

measurements according to the method provided in the proposal and
adjust the emissions based on the number of exceedances identified. If
such subpart HH reporters do not elect to conduct such measurements,
the EPA is proposing that reporters with these landfills would use a
surface methane collection efficiency that is 10 percent lower than for
landfills with gas collection systems that are conducting surface
methane concentration measurements. These proposed amendments would
address a potentially large subset of emissions that are currently
omitted in reporting and improve the EPA's understanding of emissions
from these facilities. The improved data would subsequently better
inform Agency policies and programs under the CAA.

C. Improvements to Existing Emissions Estimation Methodologies

    The EPA is proposing several additional revisions to modify
calculation equations to incorporate refinements to methodologies based
on an improved understanding of emission sources. In the 2022 Data
Quality Improvements Proposal, we identified amendments to emission
estimation methodologies where there are discrepancies between
assumptions in the current emission estimation methods and the
processes or activities conducted at specific facilities, or where we
identified more recent studies on GHG emissions or formation that
reflect updates to scientific understanding of GHG emissions sources.
We proposed changes that are intended to improve the quality and
accuracy of the data collected under the GHGRP, increase our
understanding of the relative distribution of GHGs that are emitted,
and better reflect GHG end uses or where GHGs are bound in products.
    Since the development of the 2022 Data Quality Improvements
Proposal, we have identified several calculation provisions of part 98
that would benefit from amendments that update, clarify, or improve the
calculation methodology. For example, we are proposing to revise
calculation methodologies in subpart HH (Municipal Solid Waste
Landfills) to more clearly delineate the calculations needed when there
are multiple landfill gas recovery systems in place. During
verification of subpart HH reports, we identified issues in how the
electronic Greenhouse Gas Reporting Tool (e-GGRT) system calculates
emissions when multiple control devices are associated with a single
measurement location and when multiple measurement locations may be
used for a single recovery system. If a single recovery system is used,
but an additional measurement location is added to the system in mid-
year, the ``fRec,c'' term associated with the new
measurement location (currently, the fraction of annual operating hours
the associated recovery system was operating) is calculated as 0.5 and
assumes the recovery system operated only half the year. The current
equations (equations HH-7 and HH-8) are set up with the assumption that
each measurement location is associated with a single recovery system,
however this is not always the case. We also found errors in
determining the ``fDest'' term (fraction of annual hours the
destruction device was operating) in equations HH-6 and HH-8 when
multiple destruction devices are used for a single measurement
location. If, for example, a measurement location operates continuously
(8,760 hours per year), with flow from the measurement location
directed to an engine (approximately 8,400 hours per year), diverted to
a flare when the engine is down for maintenance (approximately 360
hours per year), and if the control devices were operating at all times
gas was directed to the device, the fDest term should be 1
for each device. However, the fDest term is often calculated
as the average of 0.959 (8400/8760) and 0.041 (360/8760), resulting in
a value of 0.5. Therefore, we are proposing revisions to equations HH-
6, HH-7, and HH-8 to more clearly define these terms, as well as to
adjust the equations to be able to account for landfills with multiple
gas collection systems or for a single gas collection system with
multiple measurement locations. These proposed revisions would improve
the quality and accuracy of the data collected under subpart HH.
    We are proposing to clarify the calculation methodology for
reporters whose hydrogen unit routes process emissions to a stack with
CEMS, but fuel combustion emissions from the unit are routed to a
different stack which is not monitored with a CEMS. The proposed rule
would require reporters to calculate the CO2 emissions from
fuel combustion from the hydrogen process unit using the mass balance
equations in subpart P (Hydrogen Production) considering only fuel
inputs and report the sum of these emissions plus the process
CO2 emissions measured by the CEMS. The proposed amendments
would clarify the reporting requirements for cases where hydrogen
production process and combustion emissions are emitted through
separate stacks and the process emissions are measured with a CEMS, but
the combustion emissions are not.
    We are also proposing to revise subpart AA (Pulp and Paper
Manufacturing) to add a calculation methodology for biogenic
CO2 emissions from the combustion of biomass other than
spent liquor solids. The rule currently only includes methodologies to
calculate CO2, CH4, and N2O emissions
from the combustion of fossil fuels, and CH4,
N2O, and biogenic CO2 emissions from the
combustion of spent liquor solids. Therefore, we are proposing to add
methodologies to calculate CH4, N2O, and biogenic
CO2 emissions from the combustion of biomass fuels other
than spent liquor solids, as well as the combustion of biomass other
than spent liquor solids with other fuels. The proposed amendments
would provide a more accurate accounting of CO2 and biogenic
CO2 for subpart AA units in this situation. See section
III.I of this preamble for additional information.

D. Revisions To Reporting Requirements To Improve Verification and the
Accuracy of the Data Collected

    In the 2022 Data Quality Improvements Proposal, the EPA proposed
several revisions to existing reporting requirements to improve the
quality of the data that are currently reported, to collect more useful
data to improve verification of reported data, to better characterize
U.S. GHG emissions and trends, and to extend the usefulness of the
GHGRP to inform and improve the EPA's ability to carry out other CAA
programs. See section II.A.4 of the 2022 Data Quality Improvements
Proposal for additional information. In this supplemental proposal, the
EPA is proposing new revisions to reporting requirements where we have
identified additional data that would further support these goals and
improve the quality of the GHGRP.
    In some cases, the EPA is proposing to collect additional
information that would better inform the development of GHG policies
and programs by providing information on GHG uses and their relative
importance in specific sectors. For example, we are proposing to add
reporting requirements to subpart OO (Suppliers of Industrial
Greenhouse Gases) to require industrial gas suppliers to identify the
end-use applications for which F-HTFs are used and the approximate
quantities used in each application. The EPA recently proposed a
similar requirement for N2O, PFCs, and SF6 in the
2022 Data Quality Improvements Proposal; this supplemental notification
extends the proposed revisions to include F-HTFs

to better account for emissions from the use and distribution of F-HTFs
which are not otherwise accounted for in the current source categories
under part 98. See section III.K of this preamble for additional
information.
    The proposed revisions would also provide more useful data that
would improve verification of reported data. For example, we are
proposing to revise the existing reporting and recordkeeping
requirements in subpart N (Glass Production) for both facilities using
continuous electronic monitoring systems (CEMS) and non-CEMS facilities
(i.e., facilities that use a mass balance calculation method) to
require reporting and recordkeeping of the annual amounts of recycled
scrap glass (cullet) used as a raw material. The EPA is proposing to
collect this information because the use of cullet, which contains no
carbonates that can be converted to CO2 emissions, can lead
to reductions in emissions from the production of various glass types.
The proposed data element would help to inform the EPA's understanding
of the variations and differences in emissions estimates within this
sector, improve understanding of industry trends, and improve
verification of collected data. As discussed in section II of this
preamble and in prior amendments, the GHGRP is intended to supplement
and complement other EPA programs by advancing the understanding of
emission processes and monitoring methodologies for particular source
categories or sectors.
    Similarly, for subpart Y (Petroleum Refineries), we are proposing
to include a requirement to report the capacity of each asphalt blowing
unit. Although subpart Y currently includes unit-level capacity
reporting requirements for other emission units (e.g., catalytic
cracking units, fluid coking units, sulfur recovery plants, coke
calcining units, delayed coking units), the EPA lacks data on the
capacities of asphalt blowing units. Individual unit information allows
the EPA to aggregate emissions according to unit type and size and
provides a better understanding of the emissions from specific unit
types. Therefore, the proposed revisions to subpart Y would improve
emissions analysis and verification for these units.
    The proposed changes to reporting requirements in this supplemental
notification would further enable the EPA to obtain data that is of
sufficient quality that it can be used to support a range of future
climate change policies and regulations, in keeping with the EPA's CAA
section 114 authorities.

E. Technical Amendments, Clarifications, and Corrections

    This supplemental proposal includes several other proposed
technical amendments, corrections, and clarifications that have been
identified following the 2022 Data Quality Improvements Proposal and
that would improve understanding of the rule. The proposed amendments
include revisions that better reflect the EPA's intent and include
editorial changes, revisions that resolve uncertainties in the
regulatory text, and amendments that would increase the likelihood that
reporters will submit accurate reports. Some of the proposed changes
result from consideration of questions raised by reporters through the
GHGRP Help Desk or e-GGRT. For example, we are proposing to add a
definition for the term ``offshore'' to subpart RR (Geologic
Sequestration of Carbon Dioxide) to clarify questions raised by
stakeholders regarding the applicability of subpart RR to specific
offshore geologic sequestration activities. Although the EPA previously
noted that the source category covers both onshore and offshore
injection of CO2 in its 2010 final rule (75 FR 75060,
December 1, 2010), we are aware that we have not previously provided a
definition for the term ``offshore.'' The proposed definition would
clarify the boundaries of injection activities that are currently
covered under the source category and improve reporting to the GHGRP.
    We are proposing similar revisions to clarify definitions. For
example, we are proposing to revise subpart A (General Provisions) to
amend the definition of the term ``Bulk'' to address questions raised
by certain suppliers as to whether imports or exports of GHGs in small
containers are reportable to the GHGRP. The proposed revision is a
clarification of the existing definition and would provide clarity
regarding the size of containers that should be included in the
reported supply.
    Finally, the EPA is proposing minor changes such as edits to fix
typos, minor clarifications such as adding a missing word, and
harmonizing changes to match other proposed revisions. For example, we
are clarifying the 2022 Data Quality Improvements Proposal regarding
proposed destruction and removal efficiency (DRE) and gamma factors in
Tables I-16 and I-18 of subpart I (Electronics Manufacturing),
respectively, to correct inadvertent errors in the relevant proposed
regulatory text. We are also proposing to correct subpart AA (Pulp and
Paper Manufacturing) at 40 CFR 98.276 to correct a reporting
requirement that incorrectly refers to biogenic CH4 and
N2O. All proposed minor corrections and clarifications are
reflected in the draft proposed redline regulatory text in the docket
for this rulemaking (Docket Id. No. EPA-HQ-OAR-2019-0424).

III. Proposed Amendments to Part 98

    This section summarizes the specific substantive amendments
proposed for each subpart, as generally described in section II of this
preamble. The impacts of the proposed revisions are summarized in
section VII of this preamble. A full discussion of the cost impacts for
the proposed revisions may be found in the memorandum, Assessment of
Burden Impacts for Proposed Supplemental Revisions for the Greenhouse
Gas Reporting Rule, available in the docket for this rulemaking (Docket
Id. No. EPA-HQ-OAR-2019-0424).

A. Subpart A--General Provisions

1. Proposed Revisions to Global Warming Potentials in Table A-1
    For the reasons described here and in section II.A of this
preamble, we are proposing to revise Table A-1 to subpart A of part 98
(General Provisions) to update the GWP values of certain GHGs to
reflect GWPs from Table 8.A.1 of AR5 and, for certain GHGs that do not
have GWPs listed in AR5, to adopt GWP values from AR6. We are also
proposing to add default GWPs for two new fluorinated GHG groups, to
slightly modify an existing GHG group, and to update the default GWPs
for all the existing fluorinated GHG groups. The chemical-specific GWP
values currently in Table A-1 are drawn both from AR4 and, for multiple
GHGs that do not have GWPs listed in AR4, from AR5. The current GWPs
drawn from AR4 would be updated to values from AR5, while the current
GWPs drawn from AR5 would remain the same. AR6 GWPs would be added for
GHGs that do not have GWPs listed in AR5. Under the current rule,
default GWPs are applied to GHGs that do not have GWPs listed in AR5
based on the fluorinated GHG group to which they belong.
    By proposing (1) to adopt (or maintain) AR5 GWPs for GHGs that have
GWPs listed in AR5, and (2) to adopt AR6 GWPs for GHGs that do not have
GWPs listed in AR5, we are taking the approach to establishing and
updating GWPs that we have taken since the beginning of the GHGRP. That
is, for GHGs with GWPs listed in the IPCC Assessment Report that the
parties to the UNFCCC have agreed to use as the source of GWPs, we are
proposing to use the GWPs in the agreed-upon

Assessment Report to maintain consistency with the Inventory and other
analyses. For GHGs that do not have GWPs listed in the agreed-upon
Assessment Report, but that do have GWPs listed in a more recent IPCC
Assessment Report, we are proposing to use the GWPs in the most recent
report to increase the accuracy of the calculations and reporting under
part 98. Where the UNFCCC-referenced Assessment Report does not include
a GWP for a GHG, adopting the GWP from a more recent Assessment Report
does not introduce inconsistency with Inventory reporting. In fact, as
noted in the 2014 Fluorinated GHG Final Rule updating GWPs, adopting
GWPs in the most recent Scientific Assessment Report would facilitate
U.S. reporting under the UNFCCC Reporting Guidelines, which state:
``Annex I Parties are strongly encouraged to also report emissions and
removals of additional GHGs, such as hydrofluoroethers (HFEs),
perfluoropolyethers (PFPEs), and other gases for which 100-year global
warming potential values are available from the IPCC but have not yet
been adopted by the [Conference of the Parties to the UNFCCC].'' \18\
---------------------------------------------------------------------------

    \18\ See Decision 24, CP.19 at https://unfccc.int/resource/docs/2013/cop19/eng/10a03.pdf.
---------------------------------------------------------------------------

    Specifically, the first set of GWPs adopted under part 98 in 2009
consisted of (1) GWPs from the SAR for GHGs that had GWPs listed in the
SAR (consistent with the UNFCCC reporting guidelines in effect at the
time) and (2) GWPs from AR4 (the most recent IPCC Assessment Report
available at the time) for GHGs that did not have GWPs listed in the
SAR.\19\ The second set of GWPs adopted under part 98, in 2013 and
2014, consisted of (1) GWPs from AR4 (consistent with the UNFCCC
reporting guidelines going into effect at the time), and (2) GWPs from
AR5 (the most recent IPCC Assessment Report available at the time) for
GHGs that did not have GWPs listed in AR4.
---------------------------------------------------------------------------

    \19\ Mandatory Reporting of Greenhouse Gases, proposed pule
published on April 10, 2009 (74 FR 16453).
---------------------------------------------------------------------------

    Two decisions by the parties to the UNFCCC require countries to use
the AR5 values from Table 8.A.1 for their Inventories and other
reporting, beginning with the reports due in 2024. Decision 18/CMA.1,
annex, paragraph 37 (December, 2018) reads, ``Each Party shall use the
100-year time-horizon global warming potential (GWP) values from the
IPCC Fifth Assessment Report, or 100-year time-horizon GWP values from
a subsequent IPCC assessment report as agreed upon by the [Conference
of the Parties serving as the meeting of the Parties to the Paris
Agreement] (CMA), to report aggregate emissions and removals of GHGs,
expressed in CO2 eq.'' Decision 5/CMA.3, paragraph 25
(November, 2021) reads, ``the 100-year time-horizon global warming
potential values referred to in decision 18/CMA.1, annex, paragraph 37,
shall be those listed in Table 8.A.1 of the Fifth Assessment Report of
the Intergovernmental Panel on Climate Change, excluding the value for
fossil methane.'' \20\
---------------------------------------------------------------------------

    \20\ Refer to https://unfccc.int/.
---------------------------------------------------------------------------

    The second decision, specifying that Parties must use the GWP
values in Table 8.A.1 of AR5, excluding the value for ``fossil
methane,'' was important for two reasons. First, AR5 includes two
tables of GWPs. Table 8.A.1 includes GWPs that reflect the climate-
carbon feedbacks of CO2 but not the GHG whose GWP is being
evaluated, while the other table includes GWPs that reflect the
climate-carbon feedbacks of both CO2 and the GHG whose GWP
is being evaluated. (The same GHGs are in both tables.) Second, for
methane, AR5 includes two GWP values in each table. In each table, one
methane GWP accounts for the influence of CO2 produced by
the oxidation of methane (the value for ``fossil'' methane) and one
methane GWP does not account for the influence of CO2
produced by the oxidation of methane.
    Consistent with the 2021 UNFCCC decision, we are proposing to use
(1) for GHGs with GWPs in AR5, the AR5 GWP values in Table 8.A.1 (that
reflect the climate-carbon feedbacks of CO2 but not the GHG
whose GWP is being evaluated), and (2) for methane, the GWP that is not
the GWP for fossil methane in Table 8.A.1 (i.e., the GWP for methane
that does not reflect either the climate-carbon feedbacks for methane
or the atmospheric CO2 that would result from the oxidation
of methane in the atmosphere). In addition to maintaining consistency
with recent UNFCCC decisions, using a single GWP for methane that does
not reflect the CO2 oxidation product would be consistent
with prior IPCC practice, avoid the potential for double counting, and
reduce complexity in accounting.\21\
---------------------------------------------------------------------------

    \21\ Paragraph 52 of the annex to 18/CMA.1 encourages parties to
the UNFCCC to report indirect CO2 emissions separately:
``Each Party may report indirect CO2 from the atmospheric oxidation
of CH4, CO and NMVOCs. For Parties that decide to report indirect
CO2, the national totals shall be presented with and without
indirect CO2.'' Refer to https://unfccc.int/. Using the
fossil methane GWP, which incorporates the impact of the indirect
CO2, would double count those emissions.
---------------------------------------------------------------------------

    As noted above, we are also proposing to adopt AR6 GWPs for 31 GHGs
that have GWPs listed in AR6 but not AR5. All of these are fluorinated
GHGs. Currently, default GWPs based on each GHG's fluorinated GHG group
are applied to these GHGs. Each default value reflects the average of
the known GWPs of the GHGs in a group of chemically similar fluorinated
GHGs. While the default value is expected to be an unbiased estimate of
the GWPs of other fluorinated GHGs in that group, it is not expected to
be as accurate as a chemical-specific GWP for any given GHG, which
reflects the radiative efficiency and atmospheric lifetime of that GHG.
The chemical-specific GWPs in each group vary over a range. For
example, the chemical-specific AR5 GWPs in each group show relative
standard deviations between 30 and 170 percent, depending on the group.
Thus, using chemical-specific GWPs instead of default values would
better reflect the atmospheric impacts of these gases.
    The AR6 GWPs reflect the climate-carbon feedbacks for the GHG whose
GWP is being evaluated, while the AR5 GWPs that we are proposing to
adopt (from Table 8.A.1) do not. GWPs that reflect the climate-carbon
feedbacks for the GHG whose GWP is being evaluated are slightly larger
than GWPs that do not. Thus, this difference could potentially result
in over-weighting the atmospheric impacts of GHGs whose GWPs are drawn
from AR6 relative to GHGs whose GWPs are drawn from Table 8.A.1 of AR5.
However, our analysis indicates that using chemical-specific GWPs will
lead to more accurate estimates, even if there are some inconsistencies
among those GWPs.\22\ In AR5, reflecting climate-carbon feedbacks for
the GHG whose GWP is being evaluated results in an increase in the
evaluated GWP of 11 to 22 percent, with the higher fractional increase
being associated with shorter-lived gases with lower GWPs.\23\ In
contrast, using default GWPs based on AR5 rather than chemical-specific
GWPs from AR6 would result in overestimating GWPs by as much as 3,000
(equivalent to a relative error of 1,200 percent) and underestimating
GWPs by as much as 5,000 (equivalent to a relative error of -35
percent), with over- and underestimates averaging 1,200 and 950
respectively (and relative

errors averaging 770 percent and -60 percent, respectively).\24\
Overall, these potential errors are substantially larger than the
differences between GWPs that do and do not reflect climate-carbon
feedbacks for the GHGs whose GWPs were evaluated.
---------------------------------------------------------------------------

    \22\ See the memorandum, Proposed Updates to Chemical-Specific
and Default GWPs for the Greenhouse Gas Reporting Rule, available in
the docket for this rulemaking (Docket Id. No. EPA-HQ-OAR-2019-
0424).
    \23\ The authors of AR6 estimated smaller impacts from climate-
carbon feedbacks, meaning that the difference between accounting and
not accounting for them is likely smaller than 11 to 22 percent.
(See AR6, Chapter 7, page 121.)
    \24\ To avoid skewing the results with inconsequential
differences, instances where the default GWP would differ from the
chemical-specific GWP by less than one were excluded from the
analysis. In all these cases, the default GWP was one.
---------------------------------------------------------------------------

    Table 2 of this preamble lists the GHGs whose GWP values we are
proposing to revise, along with the GWP values currently listed in
Table A-1 and the proposed revised GWP values based on either AR5 or
AR6. Additional information regarding the EPA's rationale for the
proposed GWPs may be found in the memorandum, Proposed Updates to
Chemical-Specific and Default GWPs for the Greenhouse Gas Reporting
Rule, in the docket for this rulemaking, (Docket Id. No. EPA-HQ-OAR-
2019-0424).

                   Table 2--Proposed Revised Chemical-Specific GWPs for Compounds in Table A-1
----------------------------------------------------------------------------------------------------------------
                                                                                Current global     Proposed
                                                                                warming     global warming
                Name                       CAS No.           Chemical formula     potential (100  potential (100
                                                                                yr.)            yr.)
----------------------------------------------------------------------------------------------------------------
                                             Chemical-Specific GWPs
----------------------------------------------------------------------------------------------------------------
Carbon dioxide......................           124-38-9  CO2....................               1               1
Methane.............................            74-82-8  CH4....................              25              28
Nitrous oxide.......................         10024-97-2  N2O....................             298             265
----------------------------------------------------------------------------------------------------------------
                                             Fully Fluorinated GHGs
----------------------------------------------------------------------------------------------------------------
Sulfur hexafluoride.................          2551-62-4  SF6....................          22,800          23,500
Trifluoromethyl sulphur                        373-80-8  SF5CF3.................          17,700          17,400
 pentafluoride.
Nitrogen trifluoride................          7783-54-2  NF3....................          17,200          16,100
PFC-14 (Perfluoromethane)...........            75-73-0  CF4....................           7,390           6,630
PFC-116 (Perfluoroethane)...........            76-16-4  C2F6...................          12,200          11,100
PFC-218 (Perfluoropropane)..........            76-19-7  C3F8...................           8,830           8,900
Perfluorocyclopropane...............           931-91-9  c-C3F6.................          17,340           9,200
PFC-3-1-10 (Perfluorobutane)........           355-25-9  C4F10..................           8,860           9,200
PFC-318 (Perfluorocyclobutane)......           115-25-3  c-C4F8.................          10,300           9,540
Perfluorotetrahydrofuran............           773-14-8  c-C4F8O................        * 10,000          13,900
PFC-4-1-12 (Perfluoropentane).......           678-26-2  C5F12..................           9,160           8,550
PFC-5-1-14 (Perfluorohexane, FC-72).           355-42-0  C6F14..................           9,300           7,910
PFC-6-1-12..........................           335-57-9  C7F16; CF3(CF2)5CF3....           7,820           7,820
PFC-7-1-18..........................           307-34-6  C8F18; CF3(CF2)6CF3....           7,620           7,620
PFC-9-1-18..........................           306-94-5  C10F18.................           7,500           7,190
PFPMIE (HT-70)......................                 NA  CF3OCF(CF3)CF2OCF2OCF3.          10,300           9,710
Perfluorodecalin (cis)..............         60433-11-6  Z-C10F18...............           7,236           7,240
Perfluorodecalin (trans)............         60433-12-7  E-C10F18...............           6,288           6,290
Perfluorotriethylamine..............           359-70-6  N(C2F5)3...............        * 10,000          10,300
Perfluorotripropylamine.............           338-83-0  N(CF2CF2CF3)3..........        * 10,000           9,030
Perfluorotributylamine..............           311-89-7  N(CF2CF2CF2CF3)3.......        * 10,000           8,490
Perfluorotripentylamine.............           338-84-1  N(CF2CF2CF2CF2CF3)3....        * 10,000           7,260
----------------------------------------------------------------------------------------------------------------
                   Saturated Hydrofluorocarbons (HFCs) With Two or Fewer Carbon-Hydrogen Bonds
----------------------------------------------------------------------------------------------------------------
(4s,5s)-1,1,2,2,3,3,4,5-                    158389-18-5  trans-cyc (-                    * 3,700             258
 octafluorocyclopentane.                                  CF2CF2CF2CHFCHF-).
HFC-23..............................            75-46-7  CHF3...................          14,800          12,400
HFC-32..............................            75-10-5  CH2F2..................             675             677
HFC-125.............................           354-33-6  C2HF5..................           3,500           3,170
HFC-134.............................           359-35-3  C2H2F4.................           1,100           1,120
HFC-134a............................           811-97-2  CH2FCF3................           1,430           1,300
HFC-227ca...........................          2252-84-8  CF3CF2CHF2.............           2,640           2,640
HFC-227ea...........................           431-89-0  C3HF7..................           3,220           3,350
HFC-236cb...........................           677-56-5  CH2FCF2CF3.............           1,340           1,210
HFC-236ea...........................           431-63-0  CHF2CHFCF3.............           1,370           1,330
HFC-236fa...........................           690-39-1  C3H2F6.................           9,810           8,060
HFC-329p............................           375-17-7  CHF2CF2CF2CF3..........           2,360           2,360
HFC-43-10mee........................        138495-42-8  CF3CFHCFHCF2CF3........           1,640           1,650
----------------------------------------------------------------------------------------------------------------
                  Saturated Hydrofluorocarbons (HFCs) With Three or More Carbon-Hydrogen Bonds
----------------------------------------------------------------------------------------------------------------
1,1,2,2,3,3-hexafluorocyclopentane..        123768-18-3  cyc (-CF2CF2CF2CH2CH2-)           * 930             120
1,1,2,2,3,3,4-                               15290-77-4  cyc (-CF2CF2CF2CHFCH2-)           * 930             231
 heptafluorocyclopentane.
HFC-41..............................           593-53-3  CH3F...................              92             116
HFC-143.............................           430-66-0  C2H3F3.................             353             328
HFC-143a............................           420-46-2  C2H3F3.................           4,470           4,800
HFC-152.............................           624-72-6  CH2FCH2F...............              53              16
HFC-152a............................            75-37-6  CH3CHF2................             124             138
HFC-161.............................           353-36-6  CH3CH2F................              12               4

HFC-245ca...........................           679-86-7  C3H3F5.................             693             716
HFC-245cb...........................          1814-88-6  CF3CF2CH3..............           4,620           4,620
HFC-245ea...........................         24270-66-4  CHF2CHFCHF2............             235             235
HFC-245eb...........................           431-31-2  CH2FCHFCF3.............             290             290
HFC-245fa...........................           460-73-1  CHF2CH2CF3.............           1,030             858
HFC-263fb...........................           421-07-8  CH3CH2CF3..............              76              76
HFC-272ca...........................           420-45-1  CH3CF2CH3..............             144             144
HFC-365mfc..........................           406-58-6  CH3CF2CH2CF3...........             794             804
----------------------------------------------------------------------------------------------------------------
      Saturated Hydrofluoroethers (HFEs) and Hydrochlorofluoroethers (HCFEs) With One Carbon-Hydrogen Bond
----------------------------------------------------------------------------------------------------------------
HFE-125.............................          3822-68-2  CHF2OCF3...............          14,900          12,400
HFE-227ea...........................          2356-62-9  CF3CHFOCF3.............           1,540           6,450
HFE-329mcc2.........................        134769-21-4  CF3CF2OCF2CHF2.........             919           3,070
HFE-329me3..........................        428454-68-6  CF3CFHCF2OCF3..........           4,550           4,550
1,1,1,2,2,3,3-Heptafluoro-3-(1,2,2,2-         3330-15-2  CF3CF2CF2OCHFCF3.......           6,490           6,490
 tetrafluoroethoxy)-propane.
----------------------------------------------------------------------------------------------------------------
                             Saturated HFEs and HCFEs With Two Carbon-Hydrogen Bonds
----------------------------------------------------------------------------------------------------------------
HFE-134 (HG-00).....................          1691-17-4  CHF2OCHF2..............           6,320           5,560
HFE-236ca...........................         32778-11-3  CHF2OCF2CHF2...........           4,240           4,240
HFE-236ca12 (HG-10).................         78522-47-1  CHF2OCF2OCHF2..........           2,800           5,350
HFE-236ea2 (Desflurane).............         57041-67-5  CHF2OCHFCF3............             989           1,790
HFE-236fa...........................         20193-67-3  CF3CH2OCF3.............             487             979
HFE-338mcf2.........................        156053-88-2  CF3CF2OCH2CF3..........             552             929
HFE-338mmz1.........................         26103-08-2  CHF2OCH(CF3)2..........             380           2,620
HFE-338pcc13 (HG-01)................        188690-78-0  CHF2OCF2CF2OCHF2.......           1,500           2,910
HFE-43-10pccc (H-Galden 1040x, HG-             E1730133  CHF2OCF2OC2F4OCHF2.....           1,870           2,820
 11).
HCFE-235ca2 (Enflurane).............         13838-16-9  CHF2OCF2CHFCl..........             583             583
HCFE-235da2 (Isoflurane)............         26675-46-7  CHF2OCHClCF3...........             350             491
HG-02...............................        205367-61-9  HF2C-(OCF2CF2)2-OCF2H..           3,825           2,730
HG-03...............................        173350-37-3  HF2C-(OCF2CF2)3-OCF2H..           3,670           2,850
HG-20...............................        249932-25-0  HF2C-(OCF2)2-OCF2H.....           5,300           5,300
HG-21...............................        249932-26-1  HF2C-OCF2CF2OCF2OCF2O-            3,890           3,890
                                                          CF2H.
HG-30...............................        188690-77-9  HF2C-(OCF2)3-OCF2H.....           7,330           7,330
1,1,3,3,4,4,6,6,7,7,9,9,10,10,12,12,        173350-38-4  HCF2O(CF2CF2O)4CF2H....           3,630           3,630
 13,13,15,15-eicosafluoro-
 2,5,8,11,14-Pentaoxapentadecane.
1,1,2-Trifluoro-2-(trifluoromethoxy)-        84011-06-3  CHF2CHFOCF3............           1,240           1,240
 ethane.
Trifluoro(fluoromethoxy)methane.....          2261-01-0  CH2FOCF3...............             751             751
----------------------------------------------------------------------------------------------------------------
                        Saturated HFEs and HCFEs With Three or More Carbon-Hydrogen Bonds
----------------------------------------------------------------------------------------------------------------
HFE-143a............................           421-14-7  CH3OCF3................             756             523
HFE-245cb2..........................         22410-44-2  CH3OCF2CF3.............             708             654
HFE-245fa1..........................         84011-15-4  CHF2CH2OCF3............             286             828
HFE-245fa2..........................          1885-48-9  CHF2OCH2CF3............             659             812
HFE-254cb2..........................           425-88-7  CH3OCF2CHF2............             359             301
HFE-263fb2..........................           460-43-5  CF3CH2OCH3.............              11               1
HFE-263m1; R-E-143a.................           690-22-2  CF3OCH2CH3.............              29              29
HFE-347mcc3 (HFE-7000)..............           375-03-1  CH3OCF2CF2CF3..........             575             530
HFE-347mcf2.........................        171182-95-9  CF3CF2OCH2CHF2.........             374             854
HFE-347mmy1.........................         22052-84-2  CH3OCF(CF3)2...........             343             363
HFE-347mmz1 (Sevoflurane)...........         28523-86-6  (CF3)2CHOCH2F..........             216             216
HFE-347pcf2.........................           406-78-0  CHF2CF2OCH2CF3.........             580             889
HFE-356mec3.........................           382-34-3  CH3OCF2CHFCF3..........             101             387
HFE-356mff2.........................           333-36-8  CF3CH2OCH2CF3..........              17              17
HFE-356mmz1.........................         13171-18-1  (CF3)2CHOCH3...........              27              14
HFE-356pcc3.........................        160620-20-2  CH3OCF2CF2CHF2.........             110             413
HFE-356pcf2.........................         50807-77-7  CHF2CH2OCF2CHF2........             265             719
HFE-356pcf3.........................         35042-99-0  CHF2OCH2CF2CHF2........             502             446
HFE-365mcf2.........................         22052-81-9  CF3CF2OCH2CH3..........              58              58
HFE-365mcf3.........................           378-16-5  CF3CF2CH2OCH3..........              11            0.99
HFE-374pc2..........................           512-51-6  CH3CH2OCF2CHF2.........             557             627
HFE-449s1 (HFE-7100) Chemical blend.        163702-07-6  C4F9OCH3...............             297             421
                                            163702-08-7  (CF3)2CFCF2OCH3........  ..............  ..............
HFE-569sf2 (HFE-7200) Chemical blend        163702-05-4  C4F9OC2H5..............              59              57
                                            163702-06-5  (CF3)2CFCF2OC2H5.......  ..............  ..............
HFE-7300............................        132182-92-4  (CF3)2CFCFOC2H5CF2CF2CF           * 270             405
                                                          3.

HFE-7500............................        297730-93-9  n-C3F7CFOC2H5CF(CF3)2..           * 270              13
HG'-01..............................         73287-23-7  CH3OCF2CF2OCH3.........             222             222
HG'-02..............................        485399-46-0  CH3O(CF2CF2O)2CH3......             236             236
HG'-03..............................        485399-48-2  CH3O(CF2CF2O)3CH3......             221             221
Difluoro(methoxy)methane............           359-15-9  CH3OCHF2...............             144             144
2-Chloro-1,1,2-trifluoro-1-                    425-87-6  CH3OCF2CHFCl...........             122             122
 methoxyethane.
1-Ethoxy-1,1,2,2,3,3,3-                      22052-86-4  CF3CF2CF2OCH2CH3.......              61              61
 heptafluoropropane.
2-Ethoxy-3,3,4,4,5-                         920979-28-8  C12H5F19O2.............              56              56
 pentafluorotetrahydro-2,5-
 bis[1,2,2,2-tetrafluoro-1-
 (trifluoromethyl)ethyl]-furan.
1-Ethoxy-1,1,2,3,3,3-                          380-34-7  CF3CHFCF2OCH2CH3.......              23              23
 hexafluoropropane.
Fluoro(methoxy)methane..............           460-22-0  CH3OCH2F...............              13              13
1,1,2,2-Tetrafluoro-3-methoxy-               60598-17-6  CHF2CF2CH2OCH3.........             0.5            0.49
 propane; Methyl 2,2,3,3-
 tetrafluoropropyl ether.
1,1,2,2-Tetrafluoro-1-                       37031-31-5  CH2FOCF2CF2H...........             871             871
 (fluoromethoxy)ethane.
Difluoro(fluoromethoxy)methane......           461-63-2  CH2FOCHF2..............             617             617
Fluoro(fluoromethoxy)methane........           462-51-1  CH2FOCH2F..............             130             130
----------------------------------------------------------------------------------------------------------------
                                      Saturated Chlorofluorocarbons (CFCs)
----------------------------------------------------------------------------------------------------------------
E-R316c.............................          3832-15-3  trans-cyc (-                     * 2000           4,230
                                                          CClFCF2CF2CClF-).
Z-R316c.............................          3934-26-7  cis-cyc (-                       * 2000           5,660
                                                          CClFCF2CF2CClF-).
----------------------------------------------------------------------------------------------------------------
                                              Fluorinated Formates
----------------------------------------------------------------------------------------------------------------
Trifluoromethyl formate.............         85358-65-2  HCOOCF3................             588             588
Perfluoroethyl formate..............        313064-40-3  HCOOCF2CF3.............             580             580
1,2,2,2-Tetrafluoroethyl formate....        481631-19-0  HCOOCHFCF3.............             470             470
Perfluorobutyl formate..............        197218-56-7  HCOOCF2CF2CF2CF3.......             392             392
Perfluoropropyl formate.............        271257-42-2  HCOOCF2CF2CF3..........             376             376
1,1,1,3,3,3-Hexafluoropropan-2-yl           856766-70-6  HCOOCH(CF3)2...........             333             333
 formate.
2,2,2-Trifluoroethyl formate........         32042-38-9  HCOOCH2CF3.............              33              33
3,3,3-Trifluoropropyl formate.......       1344118-09-7  HCOOCH2CH2CF3..........              17              17
----------------------------------------------------------------------------------------------------------------
                                              Fluorinated Acetates
----------------------------------------------------------------------------------------------------------------
Methyl 2,2,2-trifluoroacetate.......           431-47-0  CF3COOCH3..............              52              52
1,1-Difluoroethyl 2,2,2-                   1344118-13-3  CF3COOCF2CH3...........              31              31
 trifluoroacetate.
Difluoromethyl 2,2,2-                         2024-86-4  CF3COOCHF2.............              27              27
 trifluoroacetate.
2,2,2-Trifluoroethyl 2,2,2-                    407-38-5  CF3COOCH2CF3...........               7               7
 trifluoroacetate.
Methyl 2,2-difluoroacetate..........           433-53-4  HCF2COOCH3.............               3               3
Perfluoroethyl acetate..............        343269-97-6  CH3COOCF2CF3...........             2.1               2
Trifluoromethyl acetate.............         74123-20-9  CH3COOCF3..............             2.0               2
Perfluoropropyl acetate.............       1344118-10-0  CH3COOCF2CF2CF3........             1.8               2
Perfluorobutyl acetate..............        209597-28-4  CH3COOCF2CF2CF2CF3.....             1.6               2
Ethyl 2,2,2-trifluoroacetate........           383-63-1  CF3COOCH2CH3...........             1.3               1
----------------------------------------------------------------------------------------------------------------
                                               Carbonofluoridates
----------------------------------------------------------------------------------------------------------------
Methyl carbonofluoridate............          1538-06-3  FCOOCH3................              95              95
1,1-Difluoroethyl carbonofluoridate.       1344118-11-1  FCOOCF2CH3.............              27              27
----------------------------------------------------------------------------------------------------------------
                             Fluorinated Alcohols Other Than Fluorotelomer Alcohols
----------------------------------------------------------------------------------------------------------------
Bis(trifluoromethyl)-methanol.......           920-66-1  (CF3)2CHOH.............             195             182
2,2,3,3,4,4,5,5-                             16621-87-7  cyc (-(CF2)4CH(OH)-)...              73              13
 Octafluorocyclopentanol.
2,2,3,3,3-Pentafluoropropanol.......           422-05-9  CF3CF2CH2OH............              42              19
2,2,3,3,4,4,4-Heptafluorobutan-1-ol.           375-01-9  C3F7CH2OH..............              25              34
2,2,2-Trifluoroethanol..............            75-89-8  CF3CH2OH...............              20              20
2,2,3,4,4,4-Hexafluoro-1-butanol....           382-31-0  CF3CHFCF2CH2OH.........              17              17
2,2,3,3-Tetrafluoro-1-propanol......            76-37-9  CHF2CF2CH2OH...........              13              13
2,2-Difluoroethanol.................           359-13-7  CHF2CH2OH..............               3               3
2-Fluoroethanol.....................           371-62-0  CH2FCH2OH..............             1.1             1.1
4,4,4-Trifluorobutan-1-ol...........           461-18-7  CF3(CH2)2CH2OH.........            0.05            0.05
----------------------------------------------------------------------------------------------------------------
                                 Non-Cyclic, Unsaturated Perfluorocarbons (PFCs)
----------------------------------------------------------------------------------------------------------------
PFC-1114; TFE.......................           116-14-3  CF2=CF2; C2F4..........           0.004           0.004
PFC-1216; Dyneon HFP................           116-15-4  C3F6; CF3CF=CF2........            0.05            0.05

Perfluorobut-2-ene..................           360-89-4  CF3CF=CFCF3............            1.82            1.82
Perfluorobut-1-ene..................           357-26-6  CF3CF2CF=CF2...........            0.10            0.10
Perfluorobuta-1,3-diene.............           685-63-2  CF2=CFCF=CF2...........           0.003           0.003
----------------------------------------------------------------------------------------------------------------
             Non-Cyclic, Unsaturated Hydrofluorocarbons (HFCs) and Hydrochlorofluorocarbons (HCFCs)
----------------------------------------------------------------------------------------------------------------
HFC-1132a; VF2......................            75-38-7  C2H2F2, CF2=CH2........            0.04            0.04
HFC-1141; VF........................            75-02-5  C2H3F, CH2=CHF.........            0.02            0.02
(E)-HFC-1225ye......................          5595-10-8  CF3CF=CHF(E)...........            0.06            0.06
(Z)-HFC-1225ye......................          5528-43-8  CF3CF=CHF(Z)...........            0.22            0.22
Solstice 1233zd(E)..................        102687-65-0  C3H2ClF3; CHCl=CHCF3...            1.34            1.34
HCFO-1233zd(Z)......................         99728-16-2  (Z)-CF3CH=CHCl.........             * 1            0.45
HFC-1234yf; HFO-1234yf..............           754-12-1  C3H2F4; CF3CF=CH2......            0.31            0.31
HFC-1234ze(E).......................          1645-83-6  C3H2F4; trans-CF3CH=CHF            0.97            0.97
HFC-1234ze(Z).......................         29118-25-0  C3H2F4; cis-CF3CH=CHF;             0.29            0.29
                                                          CF3CH=CHF.
HFC-1243zf; TFP.....................           677-21-4  C3H3F3, CF3CH=CH2......            0.12            0.12
(Z)-HFC-1336........................           692-49-9  CF3CH=CHCF3(Z).........            1.58            1.58
HFO-1336mzz(E)......................         66711-86-2  (E)-CF3CH=CHCF3........             * 1              18
HFC-1345zfc.........................           374-27-6  C2F5CH=CH2.............            0.09            0.09
HFO-1123............................           359-11-5  CHF=CF2................             * 1           0.005
HFO-1438ezy(E)......................         14149-41-8  (E)-(CF3)2CFCH=CHF.....             * 1             8.2
HFO-1447fz..........................           355-08-8  CF3(CF2)2CH=CH2........             * 1            0.24
Capstone 42-U.......................         19430-93-4  C6H3F9, CF3(CF2)3CH=CH2            0.16            0.16
Capstone 62-U.......................         25291-17-2  C8H3F13,                           0.11            0.11
                                                          CF3(CF2)5CH=CH2.
Capstone 82-U.......................         21652-58-4  C10H3F17,                          0.09            0.09
                                                          CF3(CF2)7CH=CH2.
(e)-1-chloro-2-fluoroethene.........           460-16-2  (E)-CHCl=CHF...........             * 1           0.004
3,3,3-trifluoro-2-                             382-10-5  (CF3)2C=CH2............             * 1            0.38
 (trifluoromethyl)prop-1-ene.
----------------------------------------------------------------------------------------------------------------
                                          Non-Cyclic, Unsaturated CFCs
----------------------------------------------------------------------------------------------------------------
CFC-1112............................           598-88-9  CClF=CClF..............             * 1            0.13
CFC-1112a...........................            79-35-6  CCl2=CF2...............             * 1           0.021
----------------------------------------------------------------------------------------------------------------
                                   Non-Cyclic, Unsaturated Halogenated Ethers
----------------------------------------------------------------------------------------------------------------
PMVE; HFE-216.......................          1187-93-5  CF3OCF=CF2.............            0.17            0.17
Fluoroxene..........................           406-90-6  CF3CH2OCH=CH2..........            0.05            0.05
Methyl-perfluoroheptene-ethers......                N/A  CH3OC7F13..............             * 1              15
----------------------------------------------------------------------------------------------------------------
                                   Non-Cyclic, Unsaturated Halogenated Esters
----------------------------------------------------------------------------------------------------------------
Ethenyl 2,2,2-trifluoroacetate......           433-28-3  CF3COOCH=CH2...........             * 1           0.008
Prop-2-enyl 2,2,2-trifluoroacetate..           383-67-5  CF3COOCH2CH=CH2........             * 1           0.007
----------------------------------------------------------------------------------------------------------------
                                        Cyclic, Unsaturated HFCs and PFCs
----------------------------------------------------------------------------------------------------------------
PFC C-1418..........................           559-40-0  c-C5F8.................            1.97               2
Hexafluorocyclobutene...............           697-11-0  cyc (-CF=CFCF2CF2-)....             * 1             126