[Federal Register Volume 88, Number 96 (Thursday, May 18, 2023)]
[Proposed Rules]
[Pages 31856-31887]
[FR Doc No: 2023-10067]

Vol. 88

Thursday,

No. 96

May 18, 2023

Part II

Environmental Protection Agency

-----------------------------------------------------------------------

40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants: Plywood and
Composite Wood Products; Proposed Rule

Federal Register / Vol. 88, No. 96 / Thursday, May 18, 2023 /
Proposed Rules

-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2016-0243; FRL-5185.1-01-OAR]
RIN 2060-AV56

National Emission Standards for Hazardous Air Pollutants: Plywood
and Composite Wood Products

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: The U.S. Environmental Protection Agency (EPA) is proposing
amendments to the National Emission Standards for Hazardous Air
Pollutants (NESHAP) for Plywood and Composite Wood Products (PCWP), as
required by the Clean Air Act (CAA). To ensure that all emissions of
hazardous air pollutants (HAP) from sources in the source category are
regulated, the EPA is proposing HAP standards for processes currently
unregulated for total HAP (including acetaldehyde, acrolein,
formaldehyde, methanol, phenol, propionaldehyde), non-mercury (non-Hg)
HAP metals, mercury (Hg), hydrogen chloride (HCl), polycyclic aromatic
hydrocarbons (PAH), dioxin/furan (D/F), and methylene diphenyl
diisocyanate (MDI). The standards the EPA is proposing include emission
limitations and work practices applicable for PCWP process units and
lumber kilns located at facilities that are major sources of HAP
emissions. This proposal responds to the 2007 partial remand and
vacatur of portions of the 2004 PCWP NESHAP in which the EPA previously
concluded maximum achievable control technology was represented by no
control (i.e., no emissions reduction). This proposal also responds to
or requests comment on issues raised in a petition for reconsideration
the EPA received regarding the technology review and other amendments
to the PCWP NESHAP the EPA finalized on August 13, 2020.

DATES: Comments must be received on or before July 3, 2023. Under the
Paperwork Reduction Act (PRA), comments on the information collection
provisions are best assured of consideration if the Office of
Management and Budget (OMB) receives a copy of your comments on or
before June 20, 2023.
    Public hearing: If anyone contacts us requesting a public hearing
on or before May 23, 2023, we will hold a virtual public hearing. See
SUPPLEMENTARY INFORMATION for information on requesting and registering
for a public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2016-0243, by any of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov/
(our preferred method). Follow the online instructions for submitting
comments.
     Email: [email protected]. Include Docket ID No. EPA-
HQ-OAR-2016-0243 in the subject line of the message.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2016-0243.
     Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-0216-0243, Mail Code 28221T, 1200
Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operation 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 rulemaking. Comments received may be posted without change
to https://www.regulations.gov/, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the SUPPLEMENTARY
INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Ms. Katie Hanks, Sector Policies and Programs Division
(E143-03), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; telephone number:<PHONE_NUMBER>; and email address:
[email protected].

SUPPLEMENTARY INFORMATION:
    Participation in virtual public hearing. To request a virtual
public hearing, contact the public hearing team at<PHONE_NUMBER> or by
email at [email protected]. If requested, the hearing will be
held via virtual platform on June 2, 2023. The hearing will convene at
10:00 a.m. Eastern Time (ET) and will conclude at 4:00 p.m. ET. The EPA
may close a session 15 minutes after the last pre-registered speaker
has testified if there are no additional speakers. The EPA will
announce further details at https://www.epa.gov/stationary-sources-air-pollution/plywood-and-composite-wood-products-manufacture-national-emission.
    If a public hearing is requested, the EPA will begin pre-
registering speakers for the hearing no later than 1 business day after
a request has been received. To register to speak at the virtual
hearing, please use the online registration form available at https://www.epa.gov/stationary-sources-air-pollution/plywood-and-composite-wood-products-manufacture-national-emission or contact the public
hearing team at<PHONE_NUMBER> or by email at
[email protected]. The last day to pre-register to speak at the
hearing will be May 30, 2023. Prior to the hearing, the EPA will post a
general agenda that will list pre-registered speakers in approximate
order at: https://www.epa.gov/stationary-sources-air-pollution/plywood-and-composite-wood-products-manufacture-national-emission.
    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 4 minutes to provide oral testimony. The
EPA encourages commenters to submit a copy of their 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 https://www.epa.gov/stationary-sources-air-pollution/plywood-and-composite-wood-products-manufacture-national-emission. While the EPA expects the hearing to go forward as set forth
above, please monitor our website or contact the public hearing team at
(888) 372-8699 or 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 a translator or special
accommodation such as audio description, please pre-register for the
hearing with the public hearing team and describe your needs by May 25,
2023. The EPA may not be able to arrange accommodations without
advanced notice.

    Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2016-0243. All documents in the docket are
listed in https://www.regulations.gov/. Although listed, some
information is not publicly available, e.g., Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the internet and will be publicly available only in hard
copy. With the exception of such material, publicly available docket
materials are available electronically in Regulations.gov.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2016-0243. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at https://www.regulations.gov/, including any personal
information provided, unless the comment includes information claimed
to be CBI or other information whose disclosure is restricted by
statute. Do not submit electronically to https://www.regulations.gov/
any information that you consider to be CBI or other information whose
disclosure is restricted by statute. This type of information should be
submitted as discussed below.
    The EPA may publish any comment received to its public docket.
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). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov/ website allows you to submit your
comment anonymously, which means the EPA will not know your identity or
contact information unless you provide it in the body of your comment.
If you send an email comment directly to the EPA without going through
https://www.regulations.gov/, your email address will be automatically
captured and included as part of the comment that is placed in the
public docket and made available on the internet. If you submit an
electronic comment, the EPA recommends that you include your name and
other contact information in the body of your comment and with any
digital storage media you submit. If the EPA cannot read your comment
due to technical difficulties and cannot contact you for clarification,
the EPA may not be able to consider your comment. Electronic files
should not include special characters or any form of encryption and be
free of any defects or viruses. For additional information about the
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    Submitting CBI. Do not submit information containing CBI to the EPA
through https://www.regulations.gov/. Clearly mark the part or all of
the information that you claim to be CBI. For CBI information on any
digital storage media that you mail to the EPA, note the docket ID,
mark the outside of the digital storage media as CBI, and identify
electronically within the digital storage media the specific
information that is claimed as CBI. In addition to one complete version
of the comments that includes information claimed as CBI, you must
submit a copy of the comments that does not contain the information
claimed as CBI directly to the public docket through the procedures
outlined in Instructions above. If you submit any digital storage media
that does not contain CBI, mark the outside of the digital storage
media clearly that it does not contain CBI and note the docket ID.
Information not marked as CBI will be included in the public docket and
the EPA's electronic public docket without prior notice. Information
marked as CBI will not be disclosed except in accordance with
procedures set forth in 40 Code of Federal Regulations (CFR) part 2.
    Our preferred method to receive CBI is for it to be transmitted
electronically using email attachments, File Transfer Protocol (FTP),
or other online file sharing services (e.g., Dropbox, OneDrive, Google
Drive). Electronic submissions must be transmitted directly to the
Office of Air Quality Planning and Standards (OAQPS) CBI Office at the
email address [email protected], and as described above, should include
clear CBI markings and note the docket ID. If assistance is needed with
submitting large electronic files that exceed the file size limit for
email attachments, and if you do not have your own file sharing
service, please email [email protected] to request a file transfer link.
If sending CBI information through the postal service, please send it
to the following address: OAQPS Document Control Officer (C404-02),
OAQPS, U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2016-0243. The
mailed CBI material should be double wrapped and clearly marked. Any
CBI markings should not show through the outer envelope.
    Preamble acronyms and abbreviations. Throughout this document the
use of ``we,'' ``us,'' or ``our'' is intended to refer to the EPA. We
use multiple acronyms and terms in this preamble.
    While this list may not be exhaustive, to ease the reading of this
preamble and for reference purposes, the EPA defines the following
terms and acronyms here:

ACI activated carbon injection
APCD air pollution control device
BACT best available control technology
BDL below detection level
BF board feet
BTF beyond-the-floor
CAA Clean Air Act
CBI Confidential Business Information
CDK continuous dry kiln
CEMS continuous emission monitoring system
CFR Code of Federal Regulations
Cl2 chlorine
CO2e carbon dioxide equivalent
D/F dioxin/furan (i.e., polychlorinated dibenzo-p-dioxins and
polychlorinated dibenzofurans)
DLL Detection Level Limited
dscm dry standard cubic meter
EJ environmental justice
EPA Environmental Protection Agency
ERT Electronic Reporting Tool
FR Federal Register
gr/dscf grains per dry standard cubic foot
HAP hazardous air pollutant(s)
HCl hydrogen chloride
HF hydrogen fluoride
Hg mercury
ICR information collection request
kPa kilopascals
lb/MSF \3/4\ pounds of pollutant per thousand square feet
of \3/4\-inch thick board
lb/MSF \3/8\ pounds of pollutant per thousand square feet
of \3/8\-inch thick board
lb/ODT pounds of pollutant per oven-dried ton of wood
LVL laminated veneer lumber
MACT maximum achievable control technology
MBF thousand board feet
MDF medium density fiberboard
MDI methylene diphenyl diisocyanate
MDL method detection limit
mg/dscm milligrams of pollutant per dry standard cubic meter of air
NAICS North American Industry Classification System
NESHAP national emission standards for hazardous air pollutants
NIST National Institute of Standards and Technology
Non-Hg non-mercury
NRDC Natural Resources Defense Council
NSPS new source performance standards
NTTAA National Technology Transfer and Advancement Act
O&M operation and maintenance
OAQPS Office of Air Quality Planning and Standards

OMB Office of Management and Budget
OSB oriented strandboard
PAH polycyclic aromatic hydrocarbons
PBCO production-based compliance option
PCWP plywood and composite wood products
PDF portable document format
PM particulate matter
PRA Paperwork Reduction Act
psia pounds per square inch absolute
RCO regenerative catalytic oxidizer
RDL representative detection limit
RFA Regulatory Flexibility Act
RMH resinated material handling
RTO regenerative thermal oxidizer
RTR residual risk and technology review
SBA Small Business Administration
SSM startup, shutdown, and malfunction
TEQ toxic equivalency
THC total hydrocarbon
tpy tons per year
ug/dscm micrograms of pollutant per dry standard cubic meter
UL upper limit
UMRA Unfunded Mandates Reform Act
UPL upper prediction limit
VCS voluntary consensus standards
WESP wet electrostatic precipitator

    Organization of this document. The information in this preamble is
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
II. Background
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP
regulate its HAP emissions?
    C. What data collection activities were conducted to support
this action?
III. Analytical Procedures and Decision Making
IV. Analytical Results and Proposed Decisions
    A. What MACT standards are we proposing for direct-fired PCWP
dryers?
    B. What MACT standards are we proposing for lumber kilns?
    C. What MACT standards are we proposing for process units with
organic HAP emissions?
    D. What MACT standards are we proposing for process units with
MDI emissions?
    E. What performance testing, monitoring, and recordkeeping and
reporting are we proposing?
    F. What other actions are we proposing, and what is the
rationale for those actions?
    G. What compliance dates are we proposing, and what is the
rationale for the proposed compliance dates?
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
    F. What analysis of environmental justice did we conduct?
VI. Request for Comments
VII. Submitting Data Corrections
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 Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act (NTTAA) and
1 CFR part 51
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. General Information

A. Does this action apply to me?

    The source category that is the subject of this proposal is Plywood
and Composite Wood Products regulated under 40 CFR part 63, subpart
DDDD. The 2022 North American Industry Classification System (NAICS)
codes for the Plywood and Composite Wood Products industry are 321113,
321211, 321212, 321215, 321219, and 321999. This list of categories and
NAICS codes is not intended to be exhaustive but rather provides a
guide for readers regarding the entities that this proposed action is
likely to affect. The proposed standards, once promulgated, will be
directly applicable to the affected sources. Federal, state, local, and
tribal government entities would not be affected by this proposed
action. As defined in the Initial List of Categories of Sources Under
Section 112(c)(1) of the Clean Air Act Amendments of 1990 (see 57 FR
31576, July 16, 1992) and Documentation for Developing the Initial
Source Category List, Final Report (see EPA-450/3-91-030, July 1992),
the Plywood and Particleboard source category is any facility engaged
in the manufacturing of plywood and/or particle boards. This category
includes, but is not limited to, manufacturing of chip waferboard,
strandboard, waferboard, hardboard/cellulosic fiber board, oriented
strandboard (OSB), hardboard plywood, medium density fiberboard (MDF),
particleboard, softwood plywood, or other processes using wood and
binder systems. The name of the source category was changed to Plywood
and Composite Wood Products (PCWP) on November 18, 1999 (64 FR 63025),
to more accurately reflect the types of manufacturing facilities
covered by the source category. In addition, when the EPA proposed the
PCWP rule on January 9, 2003 (68 FR 1276), the scope of the source
category was broadened to include lumber kilns located at stand-alone
kiln-dried lumber manufacturing facilities or at any other type of
facility.

B. Where can I get a copy of this document and other related
information?

    In addition to being available in the docket, an electronic copy of
this action is available on the internet. Following signature by the
EPA Administrator, the EPA will post a copy of this proposed action at
https://www.epa.gov/plywood-and-composite-wood-products-manufacture-national-emission. Following publication in the Federal Register, the
EPA will post the Federal Register version of the proposal and key
technical documents at this same website.
    A redline/strikeout version of the rule showing the edits that
would be necessary to incorporate the changes proposed in this action
to 40 CFR part 63, subpart DDDD, is presented in the memorandum titled
Proposed Regulation Edits for 40 CFR part 63 Subpart DDDD National
Emission Standards for Hazardous Air Pollutants: Plywood and Composite
Wood Products, available in the docket for this action (Docket ID No.
EPA-HQ-OAR-2016-0243).

II. Background

A. What is the statutory authority for this action?

    The EPA originally promulgated the PCWP NESHAP (40 CFR part 63,
subpart DDDD) on July 30, 2004. On August 13, 2020, the EPA took final
action on the risk and technology review required by Clean Air Act
(CAA) sections 112(d)(6) and (f)(2) for the PCWP residual risk and
technology review (2020 RTR). The EPA is proposing in this action to
amend the NESHAP to ensure that all emissions of HAP from sources in
the source category are regulated.
    In setting standards for major source categories under CAA section
112(d), the EPA has the obligation to address all HAP listed under CAA
section 112(b) emitted by the source category. In the Louisiana
Environmental Action Network v. EPA (LEAN) decision issued on April 21,
2020, the U.S. Court of Appeals for the District of Columbia Circuit
(D.C. Circuit) held that the EPA

has an obligation to address unregulated emissions from a major source
category when the Agency conducts the 8-year technology review of a
maximum achievable control technology (MACT) standard that previously
left such HAP emissions unregulated.
    In 2007, the D.C. Circuit remanded and vacated portions of the 2004
NESHAP promulgated by the EPA to establish MACT standards for the PCWP
source category. NRDC v. EPA, 489 F.3d 1364 (D.C. Cir. 2007). In the
2004 NESHAP, the EPA had concluded that the MACT standards for several
process units were represented by no emission reduction (or ``no
control'' emission floors). The ``no control'' MACT conclusions were
rejected because, as the court clarified in a related decision, the EPA
must establish emission standards for listed HAP. 489 F.3d 1364, 1371,
citing Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007). The EPA
acknowledged in the preamble to the proposed RTR (at 84 FR 47077-47078,
September 6, 2019) that there are unregulated sources with ``no
control'' MACT determinations in the PCWP source category, and we
stated our plans to address those units in a separate action subsequent
to the RTR.
    This proposed rule responds to the partial remand and vacatur of
the 2004 NESHAP, and to the petition for reconsideration of the 2020
technology review, and addresses currently unregulated emissions of HAP
from process units in the PCWP source category, including lumber kilns.
Six HAP compounds (acetaldehyde, acrolein, formaldehyde, methanol,
phenol, propionaldehyde), defined as ``total HAP'' in the PCWP NESHAP,
represent over 96 percent of the HAP emitted from the PCWP source
category. In addition to total HAP, emissions estimates collected for
the 2020 RTR indicated that unregulated HAP are present in the PCWP
source category as a result of combustion in direct-fired dryers,
including: non-mercury (non-Hg) HAP metals, mercury (Hg), hydrogen
chloride (HCl), polycyclic aromatic hydrocarbons (PAH), dioxin/furan
(D/F). There are also emissions of methylene diphenyl diisocyanate
(MDI) from processes that use MDI resins and coatings. The EPA is
proposing amendments establishing standards that reflect MACT for these
pollutants emitted by process units that are part of the PCWP source
category, pursuant to CAA sections 112(d)(2) and (3) and, where
appropriate, CAA section 112(h).

B. What is this source category and how does the current NESHAP
regulate its HAP emissions?

    The PCWP industry consists of facilities engaged in the production
of PCWP or kiln-dried lumber. Plywood and composite wood products are
manufactured by bonding wood material (fibers, particles, strands,
etc.) or agricultural fiber, generally with resin under heat and
pressure, to form a structural panel or engineered wood product.
Plywood and composite wood products manufacturing facilities also
include facilities that manufacture dry veneer and lumber kilns located
at any facility. Plywood and composite wood products include (but are
not limited to) plywood, veneer, particleboard, OSB, hardboard,
fiberboard, MDF, laminated strand lumber, laminated veneer lumber
(LVL), wood I-joists, kiln-dried lumber, and glue-laminated beams.
There are currently 223 major source facilities that are subject to the
PCWP NESHAP, including 99 facilities manufacturing PCWP and 124
facilities producing kiln-dried lumber. A major source of HAP is a
plant site that emits or has the potential to emit any single HAP at a
rate of 9.07 megagrams (10 tons) or more, or any combination of HAP at
a rate of 22.68 megagrams (25 tons) or more per year from all emission
sources at the plant site.
    The affected source under the PCWP NESHAP is the collection of
dryers, refiners, blenders, formers, presses, board coolers, and other
process units associated with the manufacturing of PCWP. The affected
source includes, but is not limited to, green end operations, refining,
drying operations (including any combustion unit exhaust stream
routinely used to direct fire process unit(s)), resin preparation,
blending and forming operations, pressing and board cooling operations,
and miscellaneous finishing operations (such as sanding, sawing,
patching, edge sealing, and other finishing operations not subject to
other NESHAP). The affected source also includes onsite storage and
preparation of raw materials used in the manufacture of PCWP, such as
resins; onsite wastewater treatment operations specifically associated
with PCWP manufacturing; and miscellaneous coating operations. The
affected source includes lumber kilns at PCWP manufacturing facilities
and at any other kind of facility.
    The NESHAP contains several compliance options for process units
subject to the standards: (1) installation and use of emissions control
systems with an efficiency of at least 90 percent; (2) production-based
limits that restrict HAP emissions per unit of product produced; and
(3) emissions averaging that allows control of emissions from a group
of sources collectively (at existing affected sources). These
compliance options apply for the following process units: fiberboard
mat dryer heated zones (at new affected sources); green rotary dryers;
hardboard ovens; press predryers (at new affected sources); pressurized
refiners; primary tube dryers; secondary tube dryers; reconstituted
wood product board coolers (at new affected sources); reconstituted
wood product presses; softwood veneer dryer heated zones; rotary strand
dryers; and conveyor strand dryers (zone one at existing affected
sources, and zones one and two at new affected sources). In addition,
the PCWP NESHAP includes work practice standards for dry rotary dryers,
hardwood veneer dryers, softwood veneer dryers, veneer redryers, and
group 1 miscellaneous coating operations (defined in 40 CFR 63.2292).
    The 2020 residual risk review found that the risk associated with
air emissions from the PCWP manufacturing industry (including lumber
kilns) are acceptable and that the current PCWP NESHAP provides an
ample margin of safety to protect public health. In the 2020 technology
review, the EPA concluded that there were no developments in practices,
processes, or control technologies that would warrant revisions to the
standards promulgated in 2004. In addition to conclusions with respect
to the RTR, the 2020 action contained amendments to remove exemptions
from the standards during periods of startup, shutdown, and malfunction
(SSM). The 2020 amendments added work practices so there would be
standards in place of the former startup and shutdown exemptions for 3
specific events that occur during PCWP production: safety-related
shutdowns, pressurized refiner startup/shutdown, and softwood veneer
dryer gas-burner relights. Lastly, the 2020 amendments included
provisions requiring electronic reporting and repeat emissions testing.
However, the 2020 technology review did not address the unregulated HAP
emissions from PCWP facilities that the EPA is now addressing in
response to the 2007 remand of the 2004 NESHAP.

C. What data collection activities were conducted to support this
action?

    On October 5, 2017, the EPA issued an Information Collection
Request (ICR) to gather information from PCWP manufacturers to support
conducting the PCWP NESHAP RTR. The ICR gathered detailed process data,
emission

release point characteristics, and HAP emissions data for PCWP process
units located at major sources. The response rate for the 2017 ICR was
over 99 percent. Following completion of the 2020 RTR, the EPA
continued to track facility changes in the PCWP industry to stay
abreast of the population of facilities subject to the PCWP NESHAP.
    Using information from the 2017 ICR with more recent updates, as
needed, the EPA assessed emissions test data needs to establish
standards for unregulated HAPs. On February 28, 2022, the EPA requested
emissions testing and other information in a CAA section 114 survey of
20 PCWP facilities operated by 9 companies. The purpose of the 2022
survey was to gather additional data to use along with the 2017 ICR
data to establish emission standards for unregulated HAP. The EPA used
information from both the 2017 ICR and 2022 survey to develop the
standards proposed in this action. The data collected and used in this
action are provided in the docket along with documentation of the
analyses conducted.

III. Analytical Procedures and Decision Making

    The MACT standards proposed in this action were developed pursuant
to CAA section 112(d)(2) and (3) or, when appropriate, CAA section
112(h). When developing MACT standards, the ``MACT floor'' for existing
sources is calculated based on the average performance of the best
performing units in each category or subcategory and on a consideration
of the variability of HAP emissions from these units. The MACT floor
for new sources is based on the emissions levels that are achieved by
the best performing similar source, with a similar consideration of
variability. For existing sources, the MACT floor is based on the
average emission limitation achieved by the best performing 12 percent
of sources (for which the EPA has emissions information) for source
categories or subcategories with 30 or more sources, or the average
emission limitation achieved by the best performing 5 sources (for
which the EPA has or could reasonably obtain emissions information) for
categories or subcategories with fewer than 30 sources. To account for
variability in PCWP manufacturing operations and resulting emissions,
we calculated the MACT floors using the 99 percent Upper Prediction
Limit (UPL) using available stack test data.\1\ We note that the MACT
floors for certain existing and new units are based on limited data
sets.\2\
---------------------------------------------------------------------------

    \1\ For more information regarding the general use of the UPL
and why it is appropriate for calculating MACT floors, see Use of
Upper Prediction Limit for Calculating MACT Floors (UPL Memo), in
the docket for this action.
    \2\ See the memorandum, Approach for Applying the Upper
Prediction Limit to Limited Datasets, in the docket for this action.
---------------------------------------------------------------------------

    The UPL approach addresses variability of emissions data from the
best performing source or sources in setting MACT standards. The UPL
also accounts for uncertainty associated with emission values in a
dataset, which can be influenced by components such as the number of
samples available for developing MACT standards and the number of
samples that will be collected to assess compliance with the emission
limit. The UPL approach has been used in many environmental science
applications. As explained in more detail in the UPL Memo,\3\ the EPA
uses the UPL approach to reasonably estimate the emissions performance
of the best performing source or sources to establish MACT floor
standards.
---------------------------------------------------------------------------

    \3\ See Use of Upper Prediction Limit for Calculating MACT
Floors (UPL Memo), in the docket for this action.
---------------------------------------------------------------------------

    Once the UPL is calculated for a pollutant, the representative
detection limit (RDL) for the pollutant measurement method is
considered, if necessary. The RDL is representative of the laboratory
instrument sensitivity and lowest industry-standard method detection
limits (MDL) achieved when analyzing air pollutant samples.
Consideration of the RDL is necessary when pollutants are measured near
or below the detection limit of the analysis method, which was the case
for some HAP measured in the 2022 survey. The EPA compares a value of 3
times the RDL (3xRDL) \4\ of the test method to UPL values to ensure
that the calculated MACT floors account for measurement variability. If
the 3xRDL value exceeds the MACT floor UPL, the 3xRDL value is
substituted as the MACT floor emission limit to ensure that the
standard is set no lower than the minimum level at which emissions can
reliably be measured. For the cases where we had low detection data, we
reviewed the memorandum, Data and procedure for handling below
detection level data in analyzing various pollutant emissions databases
for MACT and RTR emissions limits, which describes the procedure for
handling below detection level (BDL) data and developing RDL data when
setting MACT emission limits.\5\
---------------------------------------------------------------------------

    \4\ The factor of 3 used in the 3xRDL calculation is based on a
scientifically accepted definition of level of quantitation--simply
stated, the level where a test method performs with acceptable
precision. The level of quantitation has been defined as 10 times
the standard deviation of 7 replicate analyses of a sample at a
concentration level close to the MDL units of the emission standard.
That level is then compared to the MACT floor value to ensure that
the resulting emission limit is in a range that can be measured with
reasonable precision. In other words, if the 3xRDL value were less
than the calculated floor (e.g., calculated from the UPL), we would
conclude that measurement variability has been adequately addressed;
if it were greater than the calculated floor, we would adjust the
emissions limit to comport with the 3xRDL value to address
measurement variability.
    \5\ Westlin/Merrill 2011. Data and procedure for handling below
detection level data in analyzing various pollutant emissions
databases for MACT and RTR emissions limits. December 13, 2011, in
the docket for this action.
---------------------------------------------------------------------------

    In addition, under CAA section 112(d)(2), the EPA must examine more
stringent ``beyond-the-floor'' regulatory options to determine MACT.
Unlike the floor minimum stringency requirements, the EPA must consider
various impacts of the more stringent regulatory options in determining
whether MACT standards are to reflect beyond-the-floor requirements.
These impacts include the cost of achieving additional emissions
reduction beyond that achieved by the MACT floor, any non-air quality
health and environmental impacts that would result from imposing
controls beyond the floor, and energy requirements of such beyond floor
measures. If the EPA concludes that the more stringent regulatory
options have unreasonable impacts, the EPA selects the MACT floor as
MACT. However, if the EPA concludes that impacts associated with
beyond-the-floor levels of control are reasonable in light of
additional HAP emissions reductions achieved, the EPA selects those
levels as MACT.
    For some process types, it is not feasible to prescribe or enforce
a numerical emission standard using the MACT floor and MACT
determination approach described in CAA sections 112(d)(2) and (3).
According to CAA section 112(h)(1), MACT standards may take the form of
design, equipment, work practice, or operational standards if it is not
feasible in the judgment of the Administrator to prescribe or enforce
an emission standard. To support a determination that it is not
feasible to prescribe or enforce an emission standard, CAA sections
112(h)(2)(A) and (B) require the EPA to determine that either: (A) a
HAP or pollutants cannot be emitted through a conveyance designed and
constructed to emit or capture such pollutant, or that any requirement
for, or use of, such a conveyance would be inconsistent with any
federal, state or local law, or (B) the application of measurement
methodology to a particular class of

sources is not practicable due to technological and economic
limitations.

IV. Analytical Results and Proposed Decisions

    Section IV.A of this preamble discusses the standards the EPA is
proposing for combustion-related HAP emissions (non-Hg metals, Hg, HCl,
PAH, and D/F) from direct-fired PCWP dryers, including rotary strand
dryers, green rotary dryers, dry rotary dryers, tube dryers, and
softwood veneer dryers. Section IV.B discusses the standards we are
proposing for all HAP from lumber kilns. Section IV.C discusses the
total HAP standards we are proposing for various process units other
than lumber kilns that also had ``no control'' MACT determinations in
the 2004 NESHAP that were remanded and vacated. Section IV.D discusses
the standards we are proposing for process units with MDI emissions,
including reconstituted wood products presses, blow-line blend tube
dryers, and miscellaneous coating operations.

A. What MACT standards are we proposing for direct-fired PCWP dryers?

1. Overview
    Direct-fired dryer types. Direct-fired dryers are heated by the
passing of combustion exhaust through the dryer such that the wood
material being dried is contacted by the combustion exhaust. Direct-
fired dryers emit combustion-related HAP because emissions from fuel
burning pass through the dryer and the dryer's air pollution control
system. There are different designs of PCWP dryers defined in 40 CFR
63.2292 of the PCWP NESHAP, including the following types of direct-
fired dryers: rotary strand dryers, green rotary dryers, dry rotary
dryers, tube dryers, softwood veneer dryers (heated zones), fiberboard
mat dryers (heated zones), and hardboard ovens. Most PCWP direct-fired
dryers are fired with wood residuals or natural gas (or some
combination of the 2 fuels). Wood residual fuels include bark, resin-
free residuals, residuals containing resin (e.g., PCWP sander dust and
trimmings) and mixtures of these wood fuels. Far less commonly for PCWP
dryers, wood-derived syngas, propane, or fuel oil may be used.
    In addition to the differences in fuel (e.g., wood residuals and
natural gas) there are differences in drying system configurations. For
example, direct-fired PCWP dryers can be designed with an individual
natural gas or wood-fired suspension burner dedicated to a single
dryer. Other configurations include a combustion unit providing heat to
multiple dryers. At some facilities, multiple combustion units are used
to direct-fire one or more dryers. Based on a review of the design
differences, 2 subcategories for setting MACT standards are being
proposed for direct-fired PCWP dryers: (1) wood and other fuel-fired
dryers; and (2) natural gas fuel-fired dryers. We are proposing these
subcategories of PCWP dryers because combustion units firing wood
residuals have different design and combustion-related HAP emissions
profiles from those firing natural gas (or propane). Based on emission
estimates collected with the 2017 ICR, emissions of non-Hg HAP metals,
Hg, inorganic gaseous HAPs (HCl, hydrogen fluoride (HF), and chlorine
(Cl2)), D/F, and PAH in the PCWP source category are
predominantly associated with wood residual combustion in direct wood-
fired dryers. Subcategorization by fuel type is consistent with other
NESHAPs, including the major source boiler NESHAP at 40 CFR part 63,
subpart DDDDD (the Boiler MACT), where EPA subcategorized based on the
primary fuel combusted in the process and the resulting differences in
HAP emissions.\6\ We are proposing to add the following definitions to
the PCWP NESHAP to support subcategorization of direct-fired PCWP
dryers:
---------------------------------------------------------------------------

    \6\ 75 FR 32017, June 4, 2010.
---------------------------------------------------------------------------

    PCWP dryer means each dry rotary dryer, green rotary dryer, tube
dryer, rotary strand dryer, hardboard oven, or press predryer; or the
heated zones from a softwood or hardwood veneer dryer, conveyor strand
dryer, or fiberboard mat dryer.
    Direct wood-fired PCWP dryer means a direct-fired PCWP dryer in
which 10 percent or more of the direct-fired annual heat input results
from combustion of wood-derived fuel such as bark, wood residuals, or
wood-derived syngas or any other fuel except for natural gas (or
propane).
    Direct natural gas-fired PCWP dryer means a direct-fired PCWP dryer
(including each dry rotary dryer, green rotary dryer, tube dryer,
rotary strand dryer, hardboard oven, press predryer or heated zones
from a softwood or hardwood veneer dryer, conveyor strand dryer, or
fiberboard mat dryer) in which greater than 90 percent of the direct-
fired annual heat input results from natural gas (or propane)
combustion.
    In addition, we are proposing the same definition of natural gas
that is used in the Boiler MACT. Wood residuals are typically an onsite
industrial byproduct instead of a purchased fuel. Further
subcategorization based on the specific type of wood fuel used is not
recommended because it is common for wood-residual mixtures to be used.
Wood-derived syngas is considered part of the wood and other fuel
subcategory although it is not currently used to direct-fire PCWP
dryers (other than lumber kilns, which are discussed in section IV.B of
this preamble). All other fuel types (fuel oil, etc.) are uncommon in
PCWP direct-fired dryers but were included with the ``wood and other
fuel'' subcategory to ensure that all fuels are covered under the
standards in the absence of emissions data specific to other fuels. We
are not proposing further subcategorization based on combustion unit
design because of the large number of combustion unit and dryer
combinations that exist, because there would be few units in each
subcategory for which separate standards at both existing and new
sources would need to be developed.
    Format of emission limits (units of measure). Each emission limit
is proposed in 2 formats: (1) concentration; and (2) mass per
production. Concentration units include grains per dry standard cubic
foot (gr/dscf) for PM and milligrams per dry standard cubic meter (mg/
dscm) for non-PM pollutants. The concentration units of measure are
neutral to the type of process and are relevant regardless of whether
processes of multiple types are co-controlled with PCWP dryers. Mass
per production units are pounds per thousand square feet (lb/MSF) for
softwood veneer dryers and pounds per oven dried ton (lb/ODT) for all
other dryer types. Mass per time (e.g., pounds per hour) was not
considered as an emission limit format because of the need to normalize
emissions for the different process throughputs across facilities in
the industry. Mass per production units such as lb/ODT or lb/MSF
standardize mass emission rates, so they are applicable to dryers
across multiple facilities and reflect MACT across a range of
production rates. These units of measure are commonly used for PCWP
emission factors.
    Emission limits were developed in 2 formats to provide compliance
options based on what is achieved by the best performing systems. The 2
formats proposed provide flexibility for the various process
configurations subject to the limits and are also helpful because some
dryers may not be readily equipped for oven-dried production rate
measurements at the dryer.
    Ranking dryer systems by performance level. Direct-fired PCWP
dryers have numerous drying system configurations. The overall drying
system includes the interconnected

combustion unit(s), dryer(s), and air pollution control devices
(APCDs). Within any drying system there can be 1 or more combustion
units, 1 or more dryers, and 1 or more APCDs of different types in
series or parallel. Given the different combinations of dryers and
APCDs, we evaluated each set of interconnected combustion units,
dryers, and APCDs venting to the same emission point(s) as a single
drying system for purposes of evaluating and ranking performance level.
For example, 5 dryers venting to one HAP APCD are part of 1 drying
system with the HAP emission limitation achieved determined at the
outlet of the HAP APCD. By ranking each system, the outlet emission
level for the system is considered in the MACT ranking 1 time for the
entire system, not 5 times for each dryer in the system. The systems
approach was used to ensure that the various equipment combinations
from the best performing facilities are accounted for in establishing
the MACT limits.
    To determine the performance level of a dryer system, we took the
average of all available lb/production test runs at the APCD outlet.
For dryer system control configurations with multiple APCD outlets, we
summed the lb/production numbers from each outlet stack to arrive at
the total emissions performance level for the dryer system. Once the
lb/production performance level for each dryer system was determined,
the dryer systems were ranked to identify the best performing systems
(i.e., those with the lowest emissions).
    There are fewer than 30 of each type of wood-fired dryer system.
When there are fewer than 30 sources, the MACT floor for existing
sources is the average emission limitation achieved by the best
performing 5 sources (for which the Administrator has or could
reasonably obtain emissions information), and the MACT floor for new
sources is the emission control achieved in practice by the best
controlled similar source. When evaluating MACT floors for the PCWP
dryers, if we had performance data for more than 5 dryer systems, we
used the 5 systems with the lowest lb/production performance levels for
calculating the existing source MACT floor. We used the single best
performing system with the lowest lb/production performance level to
calculate the new source MACT floor. The MACT floors in terms of
emissions concentration were based on the same dryer system rankings.
2. PM and Non-Hg Metals
    The EPA is proposing filterable particulate matter (PM) standards
as a surrogate for non-Hg HAP metals from wood-fired PCWP dryers.
Filterable PM is commonly used as a surrogate for HAP metals in
particulate form including antimony, arsenic, beryllium, cadmium,
chromium, cobalt, lead, manganese, nickel, and selenium. Air pollution
control devices that reduce PM also reduce non-Hg HAP metals in
particulate form. Emissions testing for speciated HAP metals and PM
from wood-fired PCWP dryers was conducted using EPA Method 29 as part
of the 2022 CAA section 114 survey. The speciated HAP metals were found
to be present in the wood-fired PCWP dryer exhaust at levels above the
detection limit. The 2022 test data, along with PM data from prior test
reports collected by EPA in the 2017 and 2022 PCWP CAA section 114
surveys, were used to develop the MACT floors discussed in this section
of the preamble.
    Rotary strand dryers. There are 27 direct wood-fired rotary strand
dryer systems in the U.S. including 1 dryer system at a synthetic area
source. Emissions data for PM are available for 13 direct wood-fired
rotary strand dryer systems. Because there are fewer than 30 direct
wood-fired rotary strand dryer systems, the UPL MACT floor calculations
for existing sources were based on the 5 best performing systems. The
UPL MACT floor calculation for new sources was based on the best
performing system. After comparing the UPL calculations to the
corresponding 3xRDL limits, the PM MACT floor for existing sources,
based on the UPL, is 9.9E-02 lb/ODT or 3.6E-03 gr/dscf and the PM MACT
floor for new sources, based on 3xRDL, is 2.8E-02 lb/ODT or 7.0E-04 gr/
dscf. The 3xRDL value was substituted for the lb/ODT UPL in the new
source MACT floor to ensure that the standards are established at the
minimum level at which emissions can be measured reliably.
    Most of the direct wood-fired rotary strand dryer systems at major
sources in the U.S. already operate with PM and HAP control technology
(e.g., wet electrostatic precipitator followed by a regenerative
thermal oxidizer, WESP/RTO). The use of WESPs for PM control upstream
of HAP controls on PCWP rotary strand dryers is prevalent because of
the high moisture exhaust stream and nature of the particulate
originating from dryers (e.g., sticky, flammable). Other PM controls
such as baghouses are not well-suited for controlling PM from these
sources. No options more stringent than the MACT floor for existing or
new sources were identified.
    Some existing sources are expected to need to upgrade their WESP to
meet the existing source MACT floor. One rotary strand dryer system
with an ESP but no additional HAP control device was assumed to need to
install a WESP to meet the PM MACT floor and an RTO to achieve the PAH
MACT floor (discussed under rotary strand dryers in section IV.A.5 of
this preamble). An estimated 0.32 tpy of non-Hg HAP metals would be
reduced from existing sources.
    Two new OSB facilities with direct wood-fired rotary stand dryer
systems are projected to be constructed within the next 5 years. The PM
MACT floor for new rotary strand dryer systems is achievable with a
very well-performing WESP/RTO system. An estimated 0.073 tpy non-Hg HAP
metals would be reduced from new sources.
    Green rotary dryers. There are 7 direct wood-fired green rotary
dryer systems in the PCWP source category. Emissions data for PM are
available for 5 direct wood-fired green rotary dryer systems. Because
there are fewer than 30 direct wood-fired green rotary dryer systems,
the UPL MACT floor calculations for existing sources were based on all
5 systems. The UPL MACT floor calculation for new sources was based on
the best performing system. The PM MACT floor for existing direct wood-
fired green rotary dryer systems is 2.2E-01 lb/ODT or 1.2E-02 gr/dscf
and the PM MACT floor for new sources is 2.5E-02 lb/ODT or 1.2E-03 gr/
dscf. The wood-fired green rotary dryer systems in the PCWP source
category already operate with PM and HAP control technology (e.g.,
WESP/RTO or equivalent). No options more stringent than the MACT floor
for existing or new sources were identified. Zero HAP reduction is
estimated because all existing and new direct wood-fired green rotary
dryers are expected to meet their floors with baseline control.
    Dry rotary dryers. There are 9 direct wood-fired dry rotary dryer
systems in the PCWP source category. Emissions data for PM are
available for 7 dry rotary dryer systems. Because there are fewer than
30 direct wood-fired dry rotary dryer systems, the UPL MACT floor
calculations for existing sources were based on the 5 best performing
systems. The UPL MACT floor calculation for new sources was based on
the best performing system. The PM MACT floor for existing direct wood-
fired dry rotary dryer systems is 5.8E-01 lb/ODT or 3.4E-02 gr/dscf and
the PM MACT floor for new sources is 2.9E-01 lb/ODT or 2.2E-02 gr/dscf.
The MACT floor is based on the current level of PM control (i.e.,
mechanical collection) in use for existing wood-fired dry rotary dryer
systems. All of the existing wood-fired dry rotary dryer systems are
expected to

meet the PM MACT floor. Therefore, the HAP reduction for the existing
PM MACT floor is zero. No new direct wood-fired dry rotary dryers are
projected in the next 5 years.
    We considered a beyond-the-floor option to achieve further PM
reduction from existing or new direct wood-fired dry rotary dryers
through the use of a WESP. A WESP could be used alone or as part of a
WESP/RTO system (as discussed in section IV.A.5 of this preamble as a
beyond-the-floor measure for PAH emissions) to enable the dry rotary
dryers to meet the same PM limits as required for green rotary dryers.
In considering this beyond-the-floor option, we also considered costs,
non-air quality health and environmental impacts, and energy
requirements of potentially imposing it as a MACT requirement.
Nationwide costs of the beyond-the-floor option for existing direct
wood-fired dry rotary dryers are estimated to be a one-time capital
cost of $42 million, and annual costs of $10 million per year to
install and operate a WESP. Nationwide emission reductions are
estimated to be 56 tpy of PM and 0.17 tpy of non-Hg HAP metals, for a
cost effectiveness of $181,000 per ton of PM reduced and $61 million/
ton of non-Hg HAP metals reduced. Nationwide use of a WESP to control
wood-fired dry rotary dryer non-Hg metals would consume an estimated
23,000 megawatt-hours per year (MWhr/yr) of electricity (with
associated secondary air emissions), generate 21 million gallons of
wastewater per year, and produce 4,000 tons of solid waste of per year.
After considering the costs, environmental, and energy impacts of the
beyond-the-floor option, the EPA is proposing that the MACT floor
represents MACT for PM (non-Hg metals) from direct wood-fired dry
rotary dryers due to the high costs and unfavorable cost effectiveness
of the more stringent option.
    Tube dryers. There are 11 direct wood-fired primary tube dryer
systems in the PCWP source category. Emissions data for PM are
available for 6 direct wood-fired primary tube dryer systems, 2 of
which have emissions from a secondary tube dryer venting into the
primary tube dryer. Because there are fewer than 30 direct wood-fired
tube dryer systems, the UPL MACT floor calculations for existing
sources were based on the 5 best performing systems. The UPL MACT floor
calculation for new sources was based on the best performing system.
The PM MACT floor for existing direct wood-fired tube dryer systems is
3.1E-01 lb/ODT or 3.1E-03 gr/dscf and the PM MACT floor for new sources
is 2.0E-02 lb/ODT or 1.3E-03 gr/dscf. No options more stringent than
the MACT floor for existing or new sources were identified because the
primary tube dryer systems in the U.S. already operate with PM controls
(WESP, baghouse, scrubber, etc.) and HAP control technology (RTO or
biofilter). Zero HAP reduction is estimated because all existing and
new direct wood-fired tube dryers are expected to meet their respective
PM MACT floors with baseline control.
    Softwood veneer dryer heated zones. There are 3 softwood veneer
dryer systems with direct wood-fired heated zones in the PCWP source
category. Emissions data for PM are available for one direct wood-fired
softwood veneer dryer system. Since the UPL calculation for existing
and new sources was based on data from one system, the UPL results for
existing and new sources are the same. The PM MACT floor for existing
and new direct wood-fired softwood veneer dryer systems is 7.2E-02 lb/
MSF 3/8'' or 1.5E-02 gr/dscf. We did not identify any options more
stringent than the MACT floor for existing or new softwood veneer dryer
systems. All existing direct wood-fired softwood veneer dryers are
expected to meet the existing floor using the control technology
already installed; therefore, the HAP reduction for the existing floor
is zero. Nationwide HAP reductions of the proposed PM MACT floor for
new sources were not estimated because no new direct wood-fired dry
softwood veneer dryers are projected in the next 5 years.
3. Mercury (Hg)
    Emissions testing for Hg from wood-fired PCWP dryers was conducted
using EPA Method 29 as part of the 2022 CAA section 114 survey. The
data from this testing was used to develop the MACT floors described in
this section of the preamble. Method 29 collects multiple sample
fractions that are combined to determine Hg emissions. All of the Hg
test runs for PCWP dryers were detection level limited (DLL), meaning 1
or more sample fractions from each run contained no detectable Hg. For
the purpose of setting MACT standards, the EPA considers DLL test runs
to contain detectable emissions. The EPA is proposing Hg emission
limits for direct wood-fired PCWP dryers because all of the Method 29
test runs had at least 1 sample fraction in which Hg was detected.
    The baseline level of Hg control for PCWP rotary strand, green
rotary, tube, and softwood veneer dryers is typically a PM and HAP
control device in series (e.g., WESP/RTO or similar). For dry rotary
dryers, the baseline level of control is a mechanical collector (e.g.,
multiclone). Due to the low levels of Hg emissions from PCWP dryers,
which were usually below 3xRDL of the measurement method, the minimum
level at which emissions can reliably be measured, all PCWP dryers are
expected to meet the Hg MACT floors for existing and new sources with
the baseline level of control. No regulatory options more stringent
than the Hg MACT floors for existing or new wood-fired PCWP dryers were
identified.
    Rotary strand dryers. Emissions data for Hg are available for 6
direct wood-fired rotary strand dryer systems. Because there are fewer
than 30 direct wood-fired rotary strand dryer systems, the UPL MACT
floor calculations for existing sources were based on the 5 best
performing systems. The UPL MACT floor calculation for new sources was
based on the best performing system. After comparing the UPL
calculations to the corresponding 3xRDL limits, the Hg MACT floor for
existing direct wood-fired rotary strand dryer systems is 1.6E-05 lb/
ODT or 8.4E-04 mg/dscm, and the Hg MACT floor for new sources is 1.6E-
05 lb/ODT or 8.4E-04 mg/dscm. The 3xRDL values were substituted for
both UPLs in the existing and new source MACT floors to ensure the
standards are established at the minimum level at which emissions can
be measured reliably. No additional Hg reductions are estimated.
    Green rotary dryers. Emissions data for Hg are available for 4
direct wood-fired green rotary dryer systems. Because there are fewer
than 30 direct wood-fired green rotary dryer systems, the UPL MACT
floor calculations for existing sources were based on all 4 systems.
The UPL MACT floor calculation for new sources was based on the best
performing system. After comparing the UPL calculations to the
corresponding 3xRDL limits, the Hg MACT floor for existing direct wood-
fired green rotary dryer systems, based on the UPL, is 1.3E-05 lb/ODT
or 1.1E-03 mg/dscm, and the Hg MACT floor for new sources, based on
3xRDL, is 1.1E-05 lb/ODT or 8.4E-04 mg/dscm. The 3xRDL value was
substituted for the UPL in the new source MACT floor to ensure that the
standards are established at the minimum level at which emissions can
be measured reliably. No additional Hg reductions are estimated.
    Dry rotary dryers. Emissions data for Hg are available for 3 direct
wood-fired dry rotary dryer systems. Because there are fewer than 30
direct wood-fired dry rotary dryer systems, the UPL MACT floor
calculations for existing sources were based on all 3 systems. The UPL
MACT floor calculation for new sources

was based on the best performing system. After comparing the UPL
calculations to the corresponding 3xRDL limits, the Hg MACT floor for
existing and new direct wood-fired dry rotary dryer systems, based on
3xRDL, is 9.9E-06 lb/ODT or 8.4E-04 mg/dscm. The 3xRDL values were
substituted for both UPLs in the existing and new source MACT floors to
ensure that the standards are established at the minimum level at which
emissions can be measured reliably. No additional Hg reductions are
estimated.
    Tube dryers. Emissions data for Hg are available for 5 direct wood-
fired primary tube dryer systems, 1 of which has emissions from a
secondary tube dryer venting into the primary tube dryer. Because there
are fewer than 30 direct wood-fired tube dryer systems, the UPL MACT
floor calculations for existing sources were based on all 5 systems.
The UPL MACT floor calculation for new sources was based on the best
performing system. After comparing the UPL calculations to the
corresponding 3xRDL limits, the Hg MACT floor for existing direct wood-
fired tube dryer systems is 2.7E-05 lb/ODT or 1.6E-03 mg/dscm, and the
Hg MACT floor for new sources is 2.7E-05 lb/ODT or 8.4E-04 mg/dscm. The
3xRDL values were substituted for the lb/ODT UPLs in the existing and
new source MACT floors and for the concentration UPL in the new source
floor to ensure that the standards are established at the minimum level
at which emissions can be measured reliably. No additional Hg
reductions are estimated.
    Softwood veneer dryers. Emissions data for Hg are available for 1
direct wood-fired softwood veneer dryer system. Because the UPL
calculation for existing and new sources was based on data from one
system, the UPL results for existing and new sources are the same. The
Hg MACT floor for existing and new direct wood-fired softwood veneer
dryer systems is 5.8E-05 lb/MSF 3/8'' or 4.1E-02 mg/dscm. No additional
Hg reductions are estimated.
4. Acid Gases
    Emissions testing for HCl, HF, and Cl2 from wood-fired
PCWP dryers was conducted using EPA Method 26A as part of the 2022 CAA
section 114 survey. Emissions of HF were below detection limit (BDL) in
99 percent of the EPA Method 26A test runs. Chlorine emissions were BDL
in 65 percent of the test runs. Emissions of HCl were detected in 71
percent of the EPA Method 26A test runs. No acid gas emissions were
detected from the wood-fired softwood veneer dryer tested, and we are,
therefore, not proposing acid gas standards for this subcategory. Based
on the available data, we are proposing acid gas emission limits in
terms of HCl emissions from direct wood-fired rotary strand dryers,
green rotary dryers, dry rotary dryers, and tube dryers. The data from
the 2022 emissions testing were used to develop the MACT floors
discussed in this section of the preamble.
    Rotary strand dryers. Emissions data for HCl are available for 6
direct wood-fired rotary strand dryer systems. Because there are fewer
than 30 direct wood-fired rotary strand dryer systems, the UPL MACT
floor calculations for existing sources were based on the 5 best
performing systems. The UPL MACT floor calculation for new sources was
based on the best performing system. After comparing the UPL
calculations to the corresponding 3xRDL limits, the HCl MACT floor for
existing direct wood-fired rotary strand dryer systems is 5.8E-03 lb/
ODT or 1.5E-02 mg/dscm and the HCl MACT floor for new sources is 1.7E-
03 lb/ODT or 1.0E-01 mg/dscm. The 3xRDL values were substituted for the
UPLs in the new source MACT floor to ensure that the standards are
established at the minimum level at which emissions can be measured
reliably. No options more stringent than the MACT floor were identified
for existing or new rotary strand dryers. Zero emissions reduction is
estimated because all existing direct wood-fired dry rotary dryers are
expected to meet the HCl MACT floor with current controls.
    The HCl MACT floor for new wood-fired rotary strand dryers is about
10 percent lower than the average HCl emissions from rotary strand
dryer systems included in the CAA section 114 tests. Although below the
average performance level of dryers tested, the HCl MACT floor emission
level (based on the UPL) has been achieved by 3 rotary strand dryers
with WESP control and a rotary strand dryer with a multiclone. Thus,
the new source MACT floor for rotary strand dryers is expected to be
met with a well-performing WESP system. An example of a well-performing
WESP is one that incorporates caustic addition (e.g., 1 percent) into
the WESP recirculation water and has increased blowdown. The
incremental HCl emission reduction estimated for new wood-fired rotary
strand dryers using an upgraded WESP is 0.072 tpy.
    Green rotary dryers. Emissions data for HCl are available for 4
direct wood-fired green rotary dryer systems. Because there are fewer
than 30 direct wood-fired green rotary dryer systems, the UPL MACT
floor calculations for existing sources were based on all 4 systems.
The UPL MACT floor calculation for new sources was based on the best
performing system. After comparing the UPL calculations to the
corresponding 3xRDL limits, the HCl MACT floor for existing direct
wood-fired green rotary dryer systems is 6.5E-03 lb/ODT or 9.7E-01 mg/
dscm, and the HCl MACT floor for new sources is 2.9E-03 lb/ODT or 1.0E-
01 mg/dscm. The 3xRDL value was substituted for the concentration UPL
in the new source MACT floor to ensure that the standards are
established at the minimum level at which emissions can be measured
reliably. No options more stringent than the MACT floor were identified
for existing or new green rotary dryers, which are already well-
controlled. Zero emissions reduction is estimated because all existing
and new direct wood-fired green rotary dryers are expected to meet
their respective HCl MACT floors with baseline controls.
    Dry rotary dryers. Emissions data for HCl are available for 3
direct wood-fired dry rotary dryer systems. Because there are fewer
than 30 direct wood-fired dry rotary dryer systems, the UPL MACT floor
calculations for existing sources were based on all 3 systems. The UPL
MACT floor calculation for new sources was based on the best performing
system. After comparing the UPL calculations to the corresponding 3xRDL
limits, the HCl MACT floor for existing and new direct wood-fired dry
rotary dryer systems is 1.10E-03 lb/ODT or 1.0E-01 mg/dscm. The 3xRDL
values were substituted for both UPLs in the existing and new source
MACT floors to ensure that the standards are established at the minimum
level at which emissions can be measured reliably. No options more
stringent than the MACT floor were identified for existing or new dry
rotary dryers because the MACT floors are based on 3xRDL (i.e., the
minimum level at which emissions can reliably be measured). Zero
emissions reduction is estimated because all existing direct wood-fired
dry rotary dryers are expected to meet the existing HCl MACT floor. No
new units are projected in the next 5 years.
    Tube dryers. Emissions data for HCl are available for 5 direct
wood-fired primary tube dryer systems, one of which has emissions from
a secondary tube dryer venting into the primary tube dryer. Because
there are fewer than 30 direct wood-fired tube dryer systems, the UPL
MACT floor calculations for existing sources were based on all 5
systems. The UPL MACT floor calculation for new sources was based on
the best performing system. After

comparing the UPL calculations to the corresponding 3xRDL limits, the
HCl MACT floor for existing direct wood-fired tube dryer systems is
6.4E-03 lb/ODT or 7.4E-01 mg/dscm, and the HCl MACT floor for new
sources is 2.3E-03 lb/ODT or 1.0E-01 mg/dscm. The 3xRDL values were
substituted for the UPLs in the new source MACT floor to ensure that
the standards are established at the minimum level at which emissions
can be measured reliably.
    Existing and new wood-fired tube dryer systems are expected to meet
the HCl MACT floors with the baseline controls, which typically
incorporate a WESP or scrubber. No options more stringent than the
existing and new source MACT floors were identified for primary tube
dryers. All existing and new direct wood-fired tube dryers are expected
to meet their HCl MACT floors; therefore, the HAP reduction for both
floors is zero.
5. PAH
    The EPA is proposing emission limits for PAH emissions that were
detected in the exhaust from wood-fired rotary strand dryers, green
rotary dryers, dry rotary dryers, and tube dryers. Emissions testing
for PAH from wood-fired PCWP dryers was conducted using EPA Other Test
Method 46 (OTM-46) as part of the 2022 CAA section 114 survey. EPA OTM-
46 is nearly identical to the updated EPA Method 23, for which
revisions were promulgated on March 20, 2023 (88 FR 16732). The data
from the 2022 testing was used to develop the MACT floors discussed in
this section of the preamble. The PAH MACT floors discussed here for
wood-fired rotary strand dryers, green rotary dryers, dry rotary
dryers, and tube dryers are greater than the corresponding 3xRDL values
for PAH. For softwood veneer dryers, the 3xRDL value for PAH is
proposed as MACT.
    Rotary strand dryers. Emissions data for PAH are available for 6
direct wood-fired rotary strand dryer systems. Because there are fewer
than 30 direct wood-fired rotary strand dryer systems, the UPL MACT
floor calculations for existing sources were based on the 5 best
performing systems. The UPL MACT floor calculation for new sources was
based on the best performing system. The PAH MACT floor for existing
direct wood-fired rotary strand dryer systems is 3.1E-04 lb/ODT or
2.7E-02 mg/dscm, and the PAH MACT floor for new sources is 3.9E-05 lb/
ODT or 1.4E-03 mg/dscm. The PAH MACT floors are based on dryers that
already have PM and HAP controls in series. Therefore, no options more
stringent than the MACT floors were identified for existing or new
sources.
    Most existing wood-fired rotary strand dryer systems are expected
to meet the PAH MACT floor with baseline PM and HAP controls in series.
One rotary strand dryer system with an ESP but no additional HAP
control device was assumed to need to add a WESP to meet the PM MACT
floor and an RTO to achieve the PAH MACT floor. Nationwide emission
reductions of the proposed MACT floor for PAH for existing direct wood-
fired rotary strand dryers are estimated to be 0.043 tpy of PAH reduced
and 130 tpy of VOC reduced.
    New wood-fired rotary strand dryer systems are expected to be
challenged to meet the stringent new source PAH MACT floor in spite of
coming online with a WESP/RTO control system. While the new source MACT
floor emission level based on the UPL has been achieved by rotary
strand dryers with multiclone/RTO and WESP/RTO controls, the new source
PAH MACT floor is 90 percent lower than the average PAH performance
level achieved by the well-controlled rotary strand dryers in the CAA
section 114 emission tests. The burner tune-up requirements required
for all direct-fired PCWP dryers are expected to help with meeting the
PAH MACT floor. Nationwide, 0.15 tpy of PAH reductions are estimated to
be associated with the proposed PAH MACT floor.
    Green rotary dryers. Emissions data for PAH are available for 4
direct wood-fired green rotary dryer systems. Because there are fewer
than 30 direct wood-fired green rotary dryer systems, the UPL MACT
floor calculations for existing sources were based on all 4 systems.
The UPL MACT floor calculation for new sources was based on the best
performing system. The PAH MACT floor for existing direct wood-fired
green rotary dryer systems is 9.0E-03 lb/ODT or 4.1E-01 mg/dscm, and
the PAH MACT floor for new sources is 2.6E-05 lb/ODT or 4.4E-03 mg/
dscm. The PAH MACT floors are based on dryers that already have PM and
organic HAP controls in series. Therefore, no options more stringent
than the MACT floors were identified for existing or new sources. No
reductions in PAH were estimated because existing wood-fired green
rotary dryer systems are expected to meet the PAH MACT floor with
baseline HAP controls. The burner tune-up requirements required for all
direct-fired PCWP dryers are expected to help with meeting the PAH MACT
floor. No options more stringent than the MACT floor were identified
for new sources. No reductions in PAH are estimated because new direct
wood-fired green rotary dryers are expected to meet the MACT floor with
proper tuning.
    Dry rotary dryers. Emissions data for PAH are available for 3
direct wood-fired dry rotary dryer systems. Because there are fewer
than 30 direct wood-fired dry rotary dryer systems, the UPL MACT floor
calculations for existing sources were based on all 3 systems. The UPL
MACT floor calculation for new sources was based on the best performing
system. The PAH MACT floor for existing direct wood-fired dry rotary
dryer systems is 4.3E-04 lb/ODT or 3.9E-02 mg/dscm, and the PAH MACT
floor for new sources is 2.5E-05 lb/ODT or 2.2E-03 mg/dscm.
    All existing direct wood-fired dry rotary dryers are expected to
meet the existing PAH MACT floor with the baseline controls (mechanical
collection); therefore, the HAP reduction for the existing floor is
zero. No new direct wood-fired dry rotary dryers are projected in the
next 5 years. If a new wood-fired dry rotary dryer were to be
installed, it is estimated that some facilities may need an RTO to meet
the new source PAH MACT floor.
    We considered a beyond-the-floor option for existing and new wood-
fired dry rotary dryers to use a HAP control system that meets the
limits in table 1B to subpart DDDD of 40 CFR part 63, which we
anticipate would be based on use of a WESP/RTO system. The WESP would
protect the RTO from particulate build up and is a beyond-the-floor
option for PM for dry rotary dryers. The costs and other impacts of
using a WESP on wood-fired dry rotary dryers were discussed in section
IV.A.2 of this preamble. Nationwide costs of the beyond-the-floor
option to reduce PAH from existing direct wood-fired dry rotary dryers
using an RTO are estimated to be a one-time capital cost of $16 million
and annual cost of $6.8 million per year. Nationwide HAP and VOC
reductions for existing sources are estimated to be 18 tpy of organic
HAP (including 0.016 tpy of PAH) and 282 tpy of VOC for a cost
effectiveness of $383,000/ton of organic HAP reduced, $431 million/ton
of PAH reduced, and $24,000/ton of VOC reduced. Nationwide energy
impacts are estimated to be consumption of 23,000 MWhr/yr of
electricity, with associated secondary air emissions, and 371,000
MMBtu/yr of natural gas. Nationwide wastewater (e.g., for RTO washouts)
and solid waste impacts are estimated to be 273,000 gallons of
wastewater per year and 84 tons of solid waste of per year. Nationwide
costs and impacts of the beyond-the-floor option for PAH for

new direct wood-fired dry rotary dryers were not estimated as no new
direct wood-fired dry rotary dryers are projected in the next 5 years.
    After considering the costs, non-air quality environmental, and
energy impacts of the beyond-the-floor option for PAH, we are proposing
that MACT is represented by the PAH MACT floor. We rejected the more
stringent beyond-the-floor option based on use of a WESP/RTO system
because of its high costs, unfavorable cost effectiveness, energy
usage, and non-air-quality environmental impacts.
    Tube dryers. Emissions data for PAH are available for 5 direct
wood-fired primary tube dryer systems, one of which has emissions from
a secondary tube dryer venting into the primary tube dryer. Because
there are fewer than 30 direct wood-fired tube dryer systems, the UPL
MACT floor calculations for existing sources were based on all 5
systems. The UPL MACT floor calculation for new sources was based on
the best performing system. The PAH MACT floor for existing direct
wood-fired tube dryer systems is 3.0E-04 lb/ODT or 3.3E-03 mg/dscm, and
the PAH MACT floor for new sources is 1.2E-05 lb/ODT or 6.3E-04 mg/
dscm. The PAH MACT floors are based on tube dryer systems that already
have PM and HAP controls in series. Therefore, no options more
stringent than the MACT floors were identified for existing or new
primary tube dryers. Because all existing and new direct wood-fired
tube dryers are expected to meet their MACT floors for PAH with
baseline HAP controls, zero HAP reduction is estimated.
    Softwood veneer dryers. There are 3 softwood veneer dryer systems
with direct wood-fired heated zones in the PCWP source category.
Detectable PAH emissions are not expected from these dryers. Direct-
wood fired softwood veneer dryers were not included in the CAA section
114 testing using EPA OTM-46 because veneer dryers operate at lower
temperature with less mixing than rotary and tube dryers and,
therefore, are not expected to have the same potential for formation of
detectable PAH emissions as direct wood-fired rotary and tube dryers,
which operate at higher temperatures under more turbulent conditions.
However, given that PAH emissions were measured in the exhaust from
other wood-fired PCWP dryers, absent PAH test data, we are proposing a
PAH limit of 3.3E-05 mg/dscm based on 3xRDL for existing and new direct
wood-fired softwood veneer dryers. We anticipate that this limit would
be met through the same burner tune-up standards proposed to be
required for all wood-fired dryers as well as using the incineration-
based controls already in place on the softwood veneer dryers. Thus, no
emission reductions are estimated, and no options more stringent than
the 3xRDL value were identified for existing or new wood-fired softwood
veneer dryers. The EPA requests submittal of available PAH emissions
information for wood-fired softwood veneer dryers to help inform the
final rule.
6. Burner Tune-Up Standards
    The EPA is proposing burner tune-up standards to address dioxin/
furan (D/F) from wood and other fuel fired dryers, any combustion-
related HAP that may be emitted from natural-gas fired PCWP dryers, and
any HAP from combustion unit bypass stacks. As discussed in section
IV.B of this preamble, burner tune-ups are also being proposed as a
standard for direct-fired lumber kilns to address combustion-related
HAP from direct fuel firing and kiln combustion unit bypass stacks.
a. D/F From Wood-Fired PCWP Dryers
    Emissions testing for D/F from wood-fired PCWP dryers was conducted
using EPA OTM-46 as part of the 2022 CAA section 114 survey. The EPA
conducted a detection limit evaluation on the D/F emissions test runs
gathered from the 2022 CAA section 114 requests for wood-fired PCWP
dryers. Over 70 percent of the D/F congener test runs were BDL. When
considered on a toxic equivalency (TEQ) basis, 89 percent of test runs
were below the 3xRDL value for TEQ. The EPA considers a work practice
to be justified if a significant majority of emissions data available
indicate that emissions are so low that they cannot be reliably
measured (e.g., more than 55 percent of test runs are non-detect).\7\
Therefore, a work practice standard is being proposed for D/F from
wood-fired PCWP dryers. The proposed work practice for existing and new
PCWP dryers is an annual tune-up of the burners that provide direct
heat to PCWP wood-fired dryers in order to ensure good combustion and,
therefore, minimize emissions of organic HAP.
---------------------------------------------------------------------------

    \7\ See the June 5, 2014, memorandum, Determination of
`non[hyphen]detect' from EPA Method 29 (multi[hyphen]metals) and EPA
Method 23 (dioxin/furan) test data when evaluating the setting of
MACT floors versus establishing work practice standards, in the
docket for this action.
---------------------------------------------------------------------------

    Nationwide HAP reductions of the proposed work practice for D/F for
existing direct wood-fired PCWP dryers are estimated to be 5.9 tpy of
all HAP reduced (including 2.43E-06 tpy of D/F). Nationwide HAP
reductions of the proposed work practice for D/F for new and
reconstructed direct wood-fired PCWP dryers are estimated to be 0.20
tpy of HAP reduced (including 1.34E-07 tpy of D/F).
b. Natural-Gas Fired PCWP Dryers
    Combustion-related HAP emissions from combustion units burning
natural gas to directly fire PCWP dryers are similar to emissions from
boilers and process heaters that burn natural gas. Under the Boiler
MACT, ``units designed to burn gas 1 fuels'' (i.e., units burning
natural gas) were required to conduct periodic tune-ups as part of a
work practice for non-Hg HAP metals, Hg, acid gases, D/F, and organic
HAP. As explained at 76 FR 15637-38 (March 21, 2011), measured
emissions of these pollutants from natural gas-fired boilers and
process heaters were routinely found to be below the detection limits
of EPA test methods, and, as such, the EPA found it technically and
economically impracticable to reliably measure emissions from these
units. The combustion unit tune-up work practice was identified as an
effective HAP emissions standard for natural gas-fired PCWP dryers that
combust the cleanest fuels available. Based on that conclusion, we are
proposing a burner tune-up work practice standard for combustion-
related HAP, including non-Hg metals, Hg, acid gases, D/F, and PAH,
from existing and new direct natural gas-fired PCWP dryers. In addition
to the proposed burner tune-up work practice standard for combustion-
related HAP from direct gas-fired PCWP dryers, the current emission
standards for PCWP dryers (40 CFR 63.2240(b)) already limit organic HAP
emissions, including organic HAP emitted from natural gas combustion
and organic HAP from the drying process. Nationwide combustion HAP
reductions of the proposed tune-up work practice standard are estimated
to be 0.10 tpy for existing sources and 0.0073 tpy for new sources.
c. Combustion Unit Bypass Stacks
    Combustion-related HAP emissions can be emitted for brief periods
of time from bypass stacks located between a combustion unit and PCWP
dryer (or lumber kiln) direct-fired by the combustion unit when the
dryer (or kiln) is unable to accept the hot exhaust from the direct-
firing combustion unit. It is not feasible to prescribe numeric
emission standards for combustion-related HAP emissions briefly emitted
from bypass stacks between the combustion unit and dryer (or lumber
kiln). Emissions measurement methodologies, including stack tests

which require hours to complete, are not feasible for PCWP combustion
unit bypasses that last minutes at a time. Use of a continuous emission
monitoring system (CEMS) to capture these events is not feasible due to
calibration issues and the need to perform relative accuracy test
audits (RATA), which involve stack tests. Establishing parameter limits
correlated with emissions also is not feasible because this would be
done through stack testing. Therefore, we are proposing a work practice
standard for existing and new combustion bypass stacks associated with
direct-fired PCWP dryers or direct-fired lumber kilns regardless of
fuel type. The work practice standard would require an annual tune-up
of the burner associated with the bypass stack, along with monitoring
and reporting bypass stack usage. Bypass stack usage time would be
monitored using an indicator such as bypass damper position or
temperature in the bypass stack. No feasible options more stringent
than burner tune-ups coupled with bypass stack usage monitoring were
identified for existing or new combustion bypass stacks. No HAP
reductions were estimated in conjunction with bypass stack monitoring.

B. What MACT standards are we proposing for lumber kilns?

    The EPA is proposing standards to limit emissions of all HAP from
lumber kilns. All HAP emissions would be limited by the work practices
the EPA is proposing that would limit over-drying of lumber.
Combustion-related HAP emissions from direct-fired kilns would be
further limited by the proposed burner tune-up standards. Additional
information on our review of information pertaining to lumber kilns is
available in the memorandum, Development of National Emission Standards
for Hazardous Air Pollutant Emission Standards for Lumber Drying Kilns,
in the docket for this action.
1. Lumber Kiln Overview
    Lumber kilns can be characterized by wood type (softwood or
hardwood), design (batch or continuous), and heating method (indirect-
or direct-fired). Although few hardwood lumber kilns are located at
major sources, we are proposing to include both hardwood and softwood
lumber kilns in the PCWP NESHAP so HAP standards would apply to any
lumber kiln located at a PCWP or lumber facility that is a major source
of HAP emissions.
    In batch kilns, lumber is loaded into the kiln where it remains
stationary during the entire drying cycle. When drying is complete, the
batch kiln is shut down to remove the lumber. The kiln is restarted
again after it is loaded with a new batch of lumber. Batch kilns can be
either track-loaded, where multiple packages \8\ of lumber are pushed
into the kiln on tracks at once, or smaller package loaded kilns, where
lumber packages are loaded in the batch kiln with a forklift. The track
loaded kilns tend to have higher annual throughput and are the type of
batch kilns most commonly used at major source PCWP facilities.
---------------------------------------------------------------------------

    \8\ Packages are stacks of boards layered with small strips of
wood called ``stickers'' to allow for air to circulate around the
boards while the boards are drying in the kiln.
---------------------------------------------------------------------------

    Batch kilns typically have numerous roof vents positioned in rows
down each side of the kiln's roof. The vents open and close throughout
the drying cycle as the temperature and humidity in the kiln change.
Internal fans under the kiln roof circulate air around the packages of
lumber. The fans change direction every 2 to 3 hours to provide even
drying of the lumber. Consequently, one bank of roof vents is normally
exhausting hot, moist air while the other row of vents is allowing
ambient air into the kiln. The direction of flow cycles between air
intake and exhaust throughout the drying cycle. Batch kilns release
fugitive air emissions from doors or cracks in the kiln exterior due to
pressure differences between the interior of the kiln and ambient
conditions outside the kiln.
    Over the past decade, continuous dry kilns (CDKs) have become
popular for drying southern pine lumber in the U.S. Southeast. Unlike
batch kilns, CDKs do not have to be shut down for loading and
unloading. In CDKs, lumber travels continuously through the kiln on
tracks. Most CDKs in the U.S. have a ``counter-flow'' design where 2
sets of lumber travel in opposite directions to one another such that
on one end of the kiln green lumber enters the kiln parallel to dry
lumber exiting the kiln. This design allows heat from the dried lumber
coming out of the kiln to preheat the incoming green lumber to conserve
energy. There are no doors on CDKs, allowing the constant flow of
lumber into and out of each end of the kiln. Thus, CDKs release exhaust
containing steam and fugitive emissions from their open ends. Some CDKs
have powered or unpowered hoods or stacks over their openings to direct
a portion (e.g., 40 to 80 percent of the volume) of exhaust upward
while the remaining exhaust exits through the kiln ends.
    In addition to batch or continuous design, another key design
feature of lumber kilns is their heating method. Indirect-fired kilns
are heated with steam from a boiler. The steam circulates through coils
in the path of air circulation within the kiln. Direct-fired kilns use
hot gases from fuel combustion to heat the kiln such that the kiln
exhaust contains emissions from wood drying and fuel combustion.
Combustion units used to direct-fire kilns may be a dedicated burner
for each kiln or a combustion unit that direct-fires multiple kilns.
Fuels used to direct-fire kilns include natural gas, wood, or wood-
derived syngas generated in a gasifier. Wood is often used for direct-
fired lumber kilns because it is a readily available byproduct of
lumber manufacturing and is typically generated onsite. Gasifiers
typically use green sawdust generated from cutting logs into boards.
The green sawdust is first gasified under sub-stoichiometric conditions
to produce a syngas that is then burned in a secondary combustion
chamber to directly fire the kiln. Regardless of fuel, combustion gases
are usually too hot for direct introduction into the kiln, so they are
diluted with recirculated kiln exhaust and ambient air in a blend box
prior to introduction to the kiln.
    The EPA has identified 680 lumber kilns at major source PCWP
facilities subject to 40 CFR part 63, subpart DDDD, including:
     11 batch, indirect-fired, hardwood kilns.
     203 batch, indirect-fired, southern yellow pine (SYP)
kilns.
     241 batch, indirect-fired, other (e.g., western) softwood
kilns.
     103 batch, direct-fired, SYP kilns.
     98 continuous, direct-fired, SYP kilns.
     24 continuous, indirect-fired, SYP kilns.
    None of the lumber kilns identified operate with any add-on air
pollution controls. Emission factors that have been adopted by
regulatory agencies and lumber producers for emission estimation
purposes were mostly derived from small-scale kiln tests and a few
(often research-level) tests of full-scale kilns. This information is
useful for estimating emissions for inventory reporting purposes but is
not suitable for developing or enforcing national emission standards
due to the impracticality of capturing and measuring lumber kiln
emissions (discussed in more detail later in this preamble). A
significant challenge to measuring batch and continuous lumber kiln
emissions is accurate determination of the total lumber kiln gas flow
rate and the need to extrapolate concentrations from 1 or 2 sampling
locations to

estimate total kiln emissions from several emission points (including
fugitives).
    Because of the infeasibility of lumber kiln emissions collection
and control, and because of measurement challenges, many facilities and
permit authorities have established work practices for limiting organic
emissions from lumber kilns. Good design and operating practices were
determined to be the best available control technology (BACT) for
several lumber kilns. A review of BACT determinations for new and
modified kilns is relevant because a work practice can be found as BACT
only after a permitting authority finds that technological or economic
limitations on the application of measurement methodology to a
particular emissions unit would make use of a numerical emission
standard infeasible.\9\ This finding is similar to the requirements
under CAA section 112(h) for concluding that MACT is represented by a
work practice or operational standard.
---------------------------------------------------------------------------

    \9\ The regulatory definition of BACT in 40 CFR 52.21(b)(12)
states, ``If the Administrator determines that technological or
economic limitations on the application of measurement methodology
to a particular emissions unit would make the imposition of an
emissions standard infeasible, a design, equipment, work practice,
operational standard, or combination thereof, may be prescribed
instead to satisfy the requirement for the application of best
available control technology. Such standard shall, to the degree
possible, set forth the emissions reduction achievable by
implementation of such design, equipment, work practice or
operation, and shall provide for compliance by means which achieve
equivalent results.''
---------------------------------------------------------------------------

2. Rationale for Work Practices
    Given the impracticability of capturing and measuring emissions
from lumber kilns, we have concluded that the criteria in CAA section
112(h) for establishing a design, equipment, work practice, or
operational standard apply for lumber kilns. CAA section 112(h) states
that if it is not feasible in the judgment of the Administrator to
prescribe or enforce an emission standard for control of a HAP, the
Administrator may, in lieu thereof, promulgate a design, equipment,
work practice, or operational standard, or combination thereof, which
in the Administrator's judgment is consistent with the provisions of
CAA section 112(d). The phrase ``not feasible to prescribe or enforce
an emission standard'' is further defined in CAA section 112(h)(2)(A)
and (B) as any situation in which the Administrator determines that:
(A) a hazardous air pollutant or pollutants cannot be emitted through a
conveyance designed and constructed to emit or capture such pollutant,
or (B) the application of measurement methodology to a particular class
of sources is not practicable due to technological and economic
limitations.
    Relative to CAA section 112(h)(2)(A), the total volume of lumber
kiln emissions cannot be emitted through a conveyance that is designed
and constructed to emit or capture HAP emissions. For example, batch
kilns have numerous vents that cycle between air intake and exhaust in
addition to some fugitive emissions that can be emitted from the kiln
doors or walls. Batch kilns do not and cannot have conveyances to
capture emissions from the exhaust vents or eliminate the air intake,
as such conveyances would disrupt the drying process by limiting air
flow into the kiln. If constructed, flow exiting a conveyance would be
intermittent (cyclical) just as it is from each kiln vent, meaning a
conveyance would not help with measuring emissions as needed to
prescribe or enforce a numeric emission standard. Similarly, CDKs have
considerable amounts of fugitive emissions from their openings that
cannot be eliminated while allowing for lumber to enter and exit the
kiln. While some CDKs have passive hoods or stacks (which may be
powered or unpowered) at their ends to direct a fraction of the kiln
exhaust upward to improve dispersion, these devices do not and cannot
eliminate the fugitive emissions from the CDK openings. If powered
stacks were added to draw more air out of the CDK in an attempt to
eliminate the fugitives to obtain a reliable emissions measurement, the
energy-transfer function of the CDK, in which heat and steam from the
exiting lumber are used to precondition incoming lumber, would be lost.
Thus, it is not possible to capture emissions from the openings at each
end or directly measure the total gas flow rate from a CDK as needed to
prescribe or enforce an emission limit.
    Relative to CAA section 112(h)(2)(B), there are technological and
economic limitations to applying a measurement methodology for lumber
kilns as needed to prescribe or enforce a numeric emission standard.
For batch kilns, with numerous vents cycling between air intake and
exhaust, and temperature and humidity changes throughout the batch
cycle, there is not a consistent flow rate or concentration to measure
using conventional stack test methods or continuous emission monitors.
Direct measurement of flow rate from batch kilns is not technically
feasible because of the numerous vents and changing flow direction. In
addition to the need to test multiple vents, an economic limitation to
testing batch kilns is the expense associated with testing over the
long batch kiln cycle (e.g., often 20 or more hours) in which the
emission concentration and kiln parameters change throughout the cycle.
For CDKs, direct measurement of total kiln exhaust flow is not
technically feasible due to the significant volume of fugitive
emissions from the kiln openings. In addition to being unable to
measure total flow, many CDKs have no specific emission point (or
conduit) in which to measure emissions concentration (e.g., no outlet
stack or hood, or in an indirect-fired kiln no kiln air return duct to
a burner). This lack of a specific emission point for measurement of
total kiln air flow and concentration is also an economic limitation,
because even if outlet vents suitable for testing were present for a
portion of exhaust, all such vents would need to be tested to ensure
uniformity of concentration or to establish vent-specific
concentrations, which would greatly increase source testing costs
(while total flow would continue to remain uncertain, limiting
usefulness of the data for prescribing or enforcing an emission
standard).
3. Lumber Kiln Work Practice Standard
    Work practices to reduce emissions from lumber kilns are often
based on measures to minimize the amount of over-dried lumber produced.
Lumber over-drying is of concern because HAP emissions have been shown
to increase after the free water from the lumber is removed. As the
free water evaporates, water bound within the cellular structure of the
wood begins to be removed. Once the evaporative cooling of moisture on
the surface of lumber ceases, the temperature of the lumber in the kiln
increases and organic HAP emissions begin to increase. A work practice
that minimizes over-drying limits organic HAP emissions from all types
of kilns as well as combustion-related HAP emissions from direct-fired
kilns since minimizing over-drying reduces fuel consumption, which
results in less combustion-related HAP.
    To develop a work practice standard for lumber kilns, we reviewed
various permits and other information, including information received
from ICR respondents regarding design, operation, and monitoring
methods to minimize over-drying and limit HAP emissions. Several
permits included ``good operating practices'' and kiln inspection and
maintenance requirements to minimize over-drying. We also found that
lumber manufacturers use a variety of practices to ensure that lumber
is properly dried while balancing energy usage. For many manufacturers,
the focus is on ensuring

that the lumber meets grade classification, which can be accomplished
using a variety of techniques. For example, to meet the moisture
content grade ``KD19'' for southern pine lumber, manufacturers must dry
lumber to a maximum of 19 percent moisture. There are moisture grades
other than KD19, such as KD15 or lower, for lumber to be exported.
Lumber or wooden poles that will later undergo treatment may be dried
to higher moisture levels than KD19. To ensure that the maximum grade
moisture is met by most boards in the kiln load, kiln operators need to
dry to a target moisture a few percent below the maximum moisture
grade. Methods used to determine dryness of lumber vary. Temperature
parameters monitored in the kiln during drying (e.g., wet or dry bulb
temperature or temperature drop across the load) are used by kiln
operators to determine when the drying cycle is complete. Temperature
monitoring may be paired with hot checks in which sample boards are
pulled from the kiln and checked for dryness near the end of the kiln
cycle. In-kiln lumber moisture measurement during drying may be used,
or lumber moisture may be checked with hand-held moisture meters after
the drying cycle concludes. It is also common for lumber moisture
measurement to be conducted downstream of the kiln (e.g., hand-held
moisture meter checks or in-line moisture monitoring at the planer
before lumber is packaged for shipment). Of the methods available for
determining lumber moisture, the in-line moisture meter at the planer
typically produces the largest number of lumber moisture readings.
Given different kiln designs and the wide variety of techniques used to
determine lumber dryness, the work practice to limit over-drying in the
kiln requires some flexibility for site-specific considerations.
    Based on our review of methods for limiting lumber over-drying, in
40 CFR 63.2241(d) we are proposing a work practice standard with 4
elements: (1) operation and maintenance for all kilns, (2) burner tune-
up for direct-fired kilns, (3) a work practice option in which all
kilns limit over-drying by operating below a temperature set point,
conducting in-kiln moisture monitoring, or following a site-specific
plan (for temperature and lumber moisture monitoring), and (4) minimum
kiln-dried lumber moisture content limits below which lumber is
considered to be over-dried lumber for all kilns for purposes of the
PCWP NESHAP.
    Operation and maintenance (O&M) plan. For the first element of the
work practice, we are proposing that facilities develop an O&M plan for
all the lumber kilns located at the facility. Documentation of the O&M
plan would be required to be retained onsite and to include procedures
for maintaining the integrity of lumber kiln internal air flow and heat
distribution components (e.g., baffles, fans, vents, heating coils, and
temperature sensors) to provide as uniform a temperature and air flow
as reasonably possible. Maintaining the heat distribution components
prevents hot spots that could lead to increased HAP emissions and also
prevents cold spots in the kiln that could lengthen the drying cycle
for the entire load, thereby avoiding higher HAP emissions. The O&M
plan would be required to include charge optimization practices to
promote uniformity in lumber charged into the kiln (e.g., sizing,
sorting, stickering, conditioning). Proper sorting results in less
variation per kiln load that could lengthen the drying cycle and
increase HAP emissions, and proper stickering ensures that air can flow
through the lumber packages.\10\ To demonstrate compliance with the O&M
plan, the facility would be required to conduct an annual inspection of
lumber kiln integrity and review the charge optimization practices
used. Facilities would be required to implement corrective actions (as
needed) and maintain records of inspections and corrective actions
taken under the O&M plan. State authorities delegated responsibility
for implementing 40 CFR part 63, subpart DDDD, (or ``delegated
authorities'') may require modification of the O&M plan, as needed,
upon review.
---------------------------------------------------------------------------

    \10\ Additional information on lumber kiln O&M can be found in
Simpson, William T., ed. 1991. Dry Kiln Operator's Manual.
Agricultural Handbook AH-188. Madison, WI: U.S. Department of
Agriculture, Forest Service, Forest Products Laboratory.
---------------------------------------------------------------------------

    Kiln burner tune-up. For the second element of the work practice,
we are proposing that facilities with batch and continuous direct-fired
kilns conduct an annual burner tune-up to reduce the potential for
combustion-related HAP emissions beyond the reduction in these
emissions that results from minimizing lumber over-drying. Properly
operating burners would reduce the potential for combustion-related HAP
emissions from the kiln during routine operation and from any bypass
stacks used temporarily during startup or shutdown of the kiln burner.
We are proposing annual tune-ups for lumber kilns following the same
procedures proposed for PCWP dryers.
    Temperature, moisture, or site-specific plan limits. For the third
element, we are proposing that facilities select from 1 of 3 work
practice options for minimizing lumber over-drying for each kiln at the
facility: (1) temperature set point, (2) in-kiln moisture monitoring,
or (3) a site-specific plan (for temperature and lumber moisture
monitoring). While the EPA could require a site-specific plan for all
lumber kilns, we acknowledge that lumber kilns operating at moderate
temperatures compared to kilns of similar design, or kilns equipped
with in-kiln moisture monitoring, are already operating in a manner
that minimizes rapid over-drying. Thus, we are proposing to provide two
streamlined options (in lieu of requiring a site-specific plan) for
lumber kilns operating at moderate temperatures or using in-kiln lumber
moisture monitoring techniques that reduce the potential for over-
drying. These options consider that over-drying can occur more rapidly
in kilns operating at higher temperatures and/or without a direct in-
kiln lumber moisture content measurement system that provides automatic
feedback to the kiln operator. These options encompass kiln features
likely to be included in a site-specific plan to minimize over-drying
(if a plan were to be developed for the kiln). These compliance
demonstration alternatives to a site-specific plan streamline
compliance for kilns that have less potential for over-drying and
reduce burden for the delegated authority reviewing the site-specific
plan.
    Under the temperature option, the lumber kiln would be operated
with a maximum dry bulb temperature set point of no more than 210
[deg]F for batch indirect-fired (IF) kilns, 235 degrees Fahrenheit
([deg]F) for batch direct-fired kilns, or 245 [deg]F for continuous
indirect-fired or continuous direct-fired kilns. The proposed
temperatures of 210 [deg]F, 235 [deg]F, and 245 [deg]F represent both
average and median dry bulb temperature used in lumber kilns in the
source category that were within 5 [deg]F of the proposed temperature.
These temperatures are proposed because they represent temperatures
below which approximately half of kilns operate while the remaining
half of kilns operate at higher temperatures that could accelerate
over-drying. Facilities would be required to continuously measure the
dry bulb temperature during the kiln drying cycle, record the dry bulb
temperature at least every 15 minutes, calculate the 3-hour block
average temperature, and maintain the 3-hour block average below the
temperature limit. See proposed 40 CFR 63.2269(a)-(b) and (m) and 40
CFR 63.2270(h) for more details on

temperature monitoring under the PCWP NESHAP.
    Under the in-kiln moisture measurement option, the lumber kiln
would operate using a direct, in-kiln continuous lumber moisture
monitoring technique that provides automated feedback from within the
kiln to the kiln operator control panel during the drying cycle. Kiln
owners and operators would be required to operate the kiln to dry to a
semiannual average lumber moisture content above the minimum limit of
moisture content proposed in paragraph 40 CFR 63.2241(e)(3)(ii) and
table 11 to subpart DDDD of 40 CFR part 63, as discussed later in this
preamble. We are proposing the in-kiln lumber moisture measurement
option to promote direct measurement and use of lumber moisture content
monitoring as a kiln control parameter during high-temperature drying
(i.e., in kilns operating above the dry bulb temperature set points
under the work practice temperature option). An example of an in-kiln
direct lumber moisture measurement technique is use of 2 steel plates
inserted into packages of lumber spatially distributed throughout the
kiln. The electrical resistance between the plates is measured and
relayed to a moisture meter which supplies moisture measurements to the
kiln control software. We are proposing that at least 1 lumber moisture
reading per 20,000 board feet (BF) of lumber in the kiln load be taken
and that the batch average lumber moisture content be determined at the
end of the batch cycle (when the lumber has reached its lowest kiln-
dried moisture content). The requirement for 1 lumber moisture reading
per 20,000 BF (which is the same as 20 thousand board feet (20 MBF)) is
proposed to ensure that there are multiple moisture measurements in
different areas of the kiln, with the number of lumber moisture
monitors being scaled to kiln capacity. For example, a lumber kiln
drying 160 MBF per batch would require at least 8 lumber moisture
monitors to be distributed throughout the kiln load. For CDKs, we are
proposing that facilities measure the lumber moisture content at the
completion of drying for each package of lumber (when the lumber has
reached its lowest kiln-dried moisture content). Because different
lumber grades can be produced in a given lumber kiln at different
times, we are proposing that a ratio of measured lumber moisture
divided by the minimum kiln-dried lumber moisture limit be developed
for each batch kiln load and for each package of lumber dried in a CDK.
If the semiannual average of all the ratios is greater than or equal to
1 for the kiln, then compliance would be demonstrated. The semiannual
average ratio of measured moisture divided by the minimum kiln-dried
lumber moisture limit would be reported in the semiannual report. A
semiannual averaging time is proposed to correspond with the semiannual
reporting frequency already required for reporting under the PCWP
NESHAP, and because a semiannual average provides flexibility for the
variability associated with drying lumber of different dimensions cut
from logs with naturally occurring initial moisture variations (e.g.,
seasonal or tree stand variations). See proposed 40 CFR
63.2241(e)(3)(ii) and 40 CFR 63.2270(i) for more details on the
proposed methodology for calculating the semiannual average from kiln-
dried lumber moisture measurements.
    Under the site-specific plan option, facilities would develop and
operate according to a site-specific plan to minimize lumber over-
drying through temperature and lumber moisture monitoring. The site-
specific plan would be required to be submitted to the delegated
authority for approval. The site-specific limits from the plan would
then have to be incorporated into the facility's operating permit when
it is next reopened or renewed, as applicable.
    The site-specific plan would be required to: identify one
temperature parameter (such as wet or dry bulb temperature, wet bulb
depression, or temperature drop across the load) to be continuously
monitored during the kiln drying cycle; include a description of how
the temperature parameter is measured and used to minimize over-drying
of lumber; and include a site-specific limit for the temperature
parameter that minimizes over-drying. Facilities would be required to
continuously monitor the temperature parameter no less often than every
15 minutes and calculate the 3-hour block average for comparison to the
site-specific temperature limit. See proposed 40 CFR 63.2269(a)-(b) and
40 CFR 63.2270(h) for more details on temperature monitoring under the
PCWP NESHAP.
    In addition, the site-specific plan would be required to: include a
site-specific method for monitoring kiln-dried lumber moisture content
(weight percent, dry basis); specify the location of such monitoring
within the lumber manufacturing process (for example, at the kiln
unloading track, in lumber storage, or at the planer); specify the
minimum kiln-dried lumber moisture content limit based on the lumber
moisture grades produced at the facility based on 40 CFR
63.2241(e)(3)(iii) and table 11 to subpart DDDD of 40 CFR part 63; and
adhere to a minimum data requirement of one moisture measurement per
20,000 BF. Facilities would be required to calculate and record the
monthly average kiln-dried lumber moisture content, compare the monthly
average to the minimum kiln-dried lumber moisture content limit, and
take corrective action if the monthly average lumber moisture content
is below the minimum limit. Facilities would be required to maintain
records of corrective actions taken and report corrective actions in
the semiannual report. In addition, facilities would be required to
calculate the semiannual average of batch or continuous kiln lumber
moisture measurements and compare the semiannual average to the minimum
kiln-dried lumber moisture content limit to determine compliance. The
monthly averages with records of corrective action (when needed) are
proposed to provide interim indications of compliance before the
semiannual average is determined because facilities using a site-
specific plan are likely to be measuring the moisture of kiln-dried
lumber downstream of the kiln (e.g., at the planer).
    The site-specific plan containing limits for temperature and lumber
moisture content would have to be developed and submitted to the
delegated authority within 180 days after the effective date of the
final rule. The written site-specific plan would have to be maintained
onsite at the facility and would be enforceable upon the compliance
date specified in the rule. Facilities would be required to report
deviations from the site-specific plan following the compliance date.
Once the site-specific plan is approved by the delegated authority, the
plan requirements would be incorporated into the facility's title V
operating permit when the permit is next reopened or renewed, as
applicable.
    Kiln-dried moisture minimum limit. In the fourth and final element
of the work practice to minimize lumber over-drying, we are proposing
minimum limits of kiln-dried lumber moisture content (weight percent on
a dry basis) that are considered to be over-dried lumber for purposes
of the PCWP NESHAP. In proposed 40 CFR 63.6241(e)(4) and proposed table
11 to subpart DDDD of 40 CFR part 63, the ``maximum lumber moisture
grade'' means the upper limit of lumber moisture content (weight
percent on a dry basis) that meets the relevant lumber grade standard
for a lumber

product. The proposed minimum limit of kiln-dried lumber moisture
content varies according to the maximum lumber moisture grade as shown
in proposed table 11 to subpart DDDD of 40 CFR part 63. The minimum
limits of kiln-dried lumber moisture content proposed acknowledge the
fact that different lumber moisture grades are produced and that enough
margin is needed to encompass the target lumber moisture (which is a
few percent below the grade moisture to ensure the lumber meets grade)
and allow for variability that occurs around the target moisture. The
minimum limits of lumber moisture proposed in table 11 to subpart DDDD
of 40 CFR part 63 reflect the following moistures (all on a weight
percent, dry basis):
     For lumber with maximum lumber moisture grade above 22
percent, the proposed minimum limit below which lumber is considered
over-dried is 15 percent moisture. A minimum limit of 15 percent
moisture was selected because a limit of 15 percent lumber moisture is
included in at least 1 air permit for a lumber facility producing
moisture grades higher than KD-19.
     For lumber with a maximum lumber moisture grade of 19 to
21 percent, the proposed minimum limit below which lumber is considered
over-dried is 12 percent moisture. A minimum limit of 12 percent was
selected because this limit is consistent with the limit indicated in
several air permits for facilities producing KD-19, which is a grade
produced in high volume.
     Consistent with the 7 percent difference between KD-19 and
a 12 percent minimum limit, we are proposing the maximum grade moisture
minus 7 percent as the minimum kiln-dried lumber moisture limit for
grades with 18 down to 12 percent maximum moisture content (e.g., 12
percent grade-7 percent = 5 percent minimum kiln-dried lumber moisture
limit).
     For lumber with maximum lumber moisture grade less than or
equal to 10 percent, as required for some products to be exported, the
proposed minimum limit below which lumber is considered over-dried is
half the maximum lumber moisture grade. A 5 percent minimum kiln-dried
lumber moisture limit is proposed for lumber with a maximum moisture
grade of 11 percent, consistent with the minimum limit of 5 percent for
grades of 10 and 12 percent moisture.
    We estimate the HAP emission reduction achieved by the work
practice to be 488 tpy for existing sources. We estimate that the work
practice would also reduce 6,700 tpy of VOC emissions (as WPP1 \11\)
from existing sources. For new sources, we estimate that the work
practice would result in emission reductions of 77 tpy HAP and 1,000
tpy VOC (as WPP1).
---------------------------------------------------------------------------

    \11\ VOC as WPP1 is based on the wood products protocol in which
VOC emissions as propane are corrected for oxygenated compounds that
have a low response to the flame ionization detector used to measure
hydrocarbons, by adding formaldehyde and 35 percent of methanol
emitted. WPP1 VOC was used in the assessment of lumber kiln
emissions consistent with the approach used by permitting
authorities.
---------------------------------------------------------------------------

4. Consideration of Add-On Controls
    The EPA has not identified any lumber kilns with add-on air
pollution controls. The EPA, as well as state permitting authorities,
have evaluated the possibility of capturing and controlling emissions
from lumber kilns and in each case concluded that capture and control
of lumber kiln emissions is not technically feasible or cost effective
for VOC emissions from batch or continuous kilns. The technologies
considered and rejected as technically infeasible in BACT
determinations include oxidizers (RTO and RCO), carbon adsorption,
condensation, biofilters, and wet scrubbers (also known as absorbers).
In some BACT determinations, it was noted that if an RTO were to be
attempted for use on a lumber kiln, duct heaters and a WESP would
likely also be needed to prevent resin buildup in the ductwork (for
safety) as well as to protect the thermal media in an RTO or catalytic
media in an RCO. Technologies rejected based on technical infeasibility
for control of VOC are also infeasible for control of HAP in the same
exhaust stream. Therefore, we do not consider add-on controls for
lumber kilns to be a viable option for reducing HAP emissions. No
emission reduction measures more stringent than the proposed work
practice were identified.

C. What MACT standards are we proposing for process units with organic
HAP emissions?

    The EPA is proposing MACT standards to resolve unregulated HAP
emissions from process units that had ``no control'' MACT
determinations in the 2004 NESHAP that were remanded and vacated. In
addition to MACT standards for lumber kilns, the EPA is proposing MACT
standards for various process units in the PCWP source category,
including various RMH process units, atmospheric refiners, stand-alone
digesters, fiber washers, fiberboard mat dryers at existing sources,
hardboard press predryers at existing sources, and log vats. Some of
these process units are already subject to new source HAP standards in
the 2004 PCWP NESHAP, including fiberboard mat dryers, hardboard press
predryers, and reconstituted wood products board coolers (which are a
type of RMH unit) at new and reconstructed sources. Mixed PCWP process
streams routed to HAP control devices subject to the current HAP
emission limits in table 1B to subpart DDDD of 40 CFR part 63 are also
already subject to the 2004 PCWP NESHAP. This section of the preamble
describes the MACT standards we are proposing for emissions streams
with unregulated HAP emissions. A detailed description of the process
units being regulated and supporting information for the proposed
standards are provided in the memorandum, Development of Emission
Standards for Remanded Process Units Under the Plywood and Composite
Wood Products NESHAP, in the docket for this action.
1. Resinated Material Handling (RMH) Process Units
    The PCWP affected source is the collection of process units used to
produce PCWP at a PCWP manufacturing facility, including various dryers
and reconstituted wood products presses which are already subject to
emission standards under the PCWP NESHAP and other process units for
which prior ``no control'' MACT determinations were vacated and
remanded to EPA. Many of the process units with the prior ``no
control'' MACT determinations are RMH process units within the PCWP
affected source, including resin tanks, softwood and hardwood plywood
presses, engineered wood products presses and curing chambers,
blenders, formers, finishing saws, finishing sanders, panel trim
chippers, reconstituted wood products board coolers (at existing
affected sources), hardboard humidifiers, and wastewater operations.
These process units handle resin or resinated wood material downstream
of the point in the PCWP process where resin is applied.
    The RMH process units are not designed and constructed in a way
that allows for HAP emissions capture or measurement. It is not
feasible to prescribe or enforce an emission standard for control of
HAP from RMH process units. The RMH process units are equipment within
the PCWP production building (or outdoor wastewater operations) without
any enclosure, conveyance, or distinct HAP emissions stream that can
feasibly be emitted though a conveyance. For example, dry formers,
saws, and sanders have pick-up points for removal of wood material as
it is trimmed, but the

entire process unit is not enclosed or isolated; engineered wood
products presses are too large to enclose; plywood presses cannot be
enclosed for operator safety reasons; and board coolers at existing
sources cannot be enclosed for equipment functionality reasons.
Emissions from RMH process units are fugitive in nature such that
application of emissions measurement methodology is not technically
feasible. Further, emissions capture and measurement from hundreds of
individual RMH process units would not be economically feasible (e.g.,
with testing costs estimated to exceed $20 million nationwide assuming
that facilities could capture emissions). For these reasons, it is not
feasible to prescribe or enforce an emission standard for RMH process
units. Therefore, the EPA is proposing work practice standards under
CAA section 112(h).
    To develop work practice standards under CAA section 112(h),
consistent with CAA section 112(d), measures used by the best
performing sources to reduce or eliminate emissions of HAP through
process changes or substitution of materials were considered. This
approach is consistent with CAA section 112(d)(2)(A). The potential for
HAP emissions from RMH process units relates to the material being
processed (i.e., resin and wood). Standards for RMH units pertaining to
resin-related and wood-related emissions are discussed in the following
subsections.
a. Resin-Related Emissions From RMH Process Units
    Most PCWP resins are amino/phenolic resins such as phenol
formaldehyde (PF), melamine urea formaldehyde (MUF), urea formaldehyde
(UF) with urea scavenger, melamine formaldehyde (MF), or phenol
resorcinol formaldehyde (PRF). Isocyanates such as MDI are also used.
The HAP associated with use of amino/phenolic resins at PCWP facilities
include formaldehyde (CAS 50-00-0), phenol (CAS 108-95-2) and methanol
(CAS 67-56-1). The HAP associated with MDI resin is 4,4'-
Methylenediphenyl Diisocyanate (CAS 101-68-8). Some PCWP products can
only be made with specific types or formulations of resins. Other
products are made with 1 or more types of resins (e.g., OSB can be made
with PF, MDI, or PF and MDI in the same board). The PCWP resins
typically are a liquid with high solids content (e.g., up to 70 percent
solids) as received or may be delivered and applied in powdered form.
    The potential for resin-related HAP emissions from RMH process
units relates to the free HAP content and volatility of the resin
system used. The PCWP resin systems used typically have very low free
HAP content (weight percent) or low vapor pressure depending on the
resin type and application. For example, most types of amino/phenolic
resins are non-HAP resins which can be defined as a resin with HAP
contents below 0.1 percent by mass for Occupational Safety and Health
Administration-defined carcinogens as specified in section A.6.4 of
appendix A to 29 CFR 1910.1200, and below 1.0 percent by mass for other
HAP compounds.
    However, some amino/phenolic resin formulations essential to
manufacturing dry-process hardboard or I-joists have slightly higher
weight percentages of some HAP than non-HAP resins but have low vapor
pressure which reduces the potential for HAP emissions from RMH process
units at facilities used to make those products. Similarly, MDI resins
would not be considered non-HAP resins due to their percentage by
weight MDI content, but MDI resins have very low vapor pressure as
received and used in RMH process units. In developing work practice
standards for RMH units, it is necessary to limit resin-related HAP
emissions without precluding the types of PCWP products covered under
the PCWP NESHAP from being produced. A work practice standard with
enforceable options to use a non-HAP resin system or meet a vapor
pressure limit adheres to the CAA while allowing the different types of
PCWP products covered under the PCWP NESHAP to be produced.
    Information on resin HAP content (HAP percent, by weight) and resin
vapor pressure (in kilopascals [kPa] or pounds per square inch absolute
[psia]) is often available in safety data sheets (SDS) or other
technical documentation accompanying the resin when it is received from
the resin supplier. Some PCWP manufacturers may dilute amino/phenolic
resins when preparing them for use, which would reduce the mass
fraction of free HAP content or corresponding vapor pressure of the
free HAP in the resin. Therefore, resin supplier information for the
``as received'' resin, before the resin is diluted or mixed with wood,
is the most consistently available source of information to use as the
basis of the work practice standards pertaining to resin-related HAP.
    When received, PCWP resins are stored in fixed roof resin tanks at
the PCWP facility at ambient temperature. Resin tanks are the first
type of RMH process units in which resins are used in the PCWP process.
The average-size resin tank in the PCWP industry is 12,500 gallons
while the maximum is 47,000 gallons. Limited vapor pressure data are
currently available to the EPA for resins used at PCWP facilities.
Therefore, vapor pressure criteria in the Amino/Phenolic Resin NESHAP
(40 CFR part 63, subpart OOO) were reviewed in addition to information
available from PCWP facilities. The maximum true vapor pressure limits
for applying controls for storage vessels storing liquids containing
HAP under the Amino/Phenolic Resin NESHAP are 13.1 kPa (1.9 psia) for
tanks with 20,000 to 40,000 gallon capacity and 5.2 kPa (0.75 psia) for
storage vessels with 40,000 to 90,000 gallon capacity. A maximum true