Document ID: EPA-R05-OAR-2008-0784-0004
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2022-11-28T05:00Z

MEMORANDUM 
 
SUBJECT: 	Wisconsin Ethanol Plant Clarification Clean Air Act Section 110(l) Demonstration Technical Support Document (TSD)
             
FROM:	Rachel Rineheart, Environmental Engineer, Air Permits Section

TO:		EPA-R05-OAR-2008-0784 Docket

THRU:	Genevieve Damico, Supervisor, Air Permits Section
		Doug Aburano, Manager, Air Programs Branch

I. Summary

On May 1, 2007, the U.S. Environmental Protection Agency (EPA) published the final rule "Prevention of Significant Deterioration, Nonattainment New Source Review, and Title V: Treatment of Certain Ethanol Production Facilities Under the `Major Emitting Facility' Definition".  This rule revised the Prevention of Significant Deterioration (PSD) definition of major stationary source in the federal PSD rules to exclude ethanol production facilities that produce ethanol by natural fermentation in North American Industrial Classification System (NAICS) codes 325193 and 312140 from the chemical process plant source category.  As a result, the revision changed the major source threshold for these ethanol production facilities from 100 tons per year (tpy) to 250 tpy. The rule also eliminated the requirement to include fugitive emissions when determining whether a source is major under the PSD, Nonattainment New Source Review (NA NSR), and Title V permitting programs for these ethanol production facilities.

The state of Wisconsin formally adopted the PSD, NA NSR, and Title V changes into the Wisconsin Administrative Code on March 26, 2008 and the revised rules became effective on August 1, 2008.  Wisconsin submitted the PSD and NA NSR changes to EPA for approval into the Wisconsin State Implementation Plan (SIP) and the Title V changes as a revision to its approved Title V program on September 30, 2008.  Since then, Wisconsin's ethanol production and associated emissions have increased; however, air quality has improved for each criteria pollutant.  Furthermore, ethanol production facility emissions are a small fraction of total emissions in the state.  Currently permitted ethanol production facilities in Wisconsin are subject to other state and federal rules where applicable and, in some cases, PSD requirements may still apply to certain emissions units and activities at the source.

EPA is proposing to approve the revision to the definition of major stationary source under the PSD program.  EPA is not taking action on Wisconsin's request to approve the NA NSR revision.  EPA is also proposing to approve the revisions to the Wisconsin Title V Operating Permit Program.  As further explained in this TSD, EPA is proposing that the approval of this SIP revision is consistent with section 110(l) of the Clean Air Act (CAA) because it will not interfere with any applicable requirement concerning attainment and reasonable further progress (as defined in section 171 of the Clean air Act), or any other applicable requirement of the CAA.  The proposed revision is consistent with the definition of major stationary source at 40 C.F.R. § 51.166(b)(1) and 40 C.F.R. § 70.2.

II. Introduction

This TSD supports EPA's notice of proposed rulemaking to approve revisions to the Wisconsin SIP to incorporate amendments to the Wisconsin Administrative Code.  Wisconsin's amendments exclude ethanol production facilities that produce ethanol through natural fermentation in NAICS code 325193 and 312140 from the chemical process plant source category.  NAICS codes 325193 and 312140 correspond to ethyl alcohol manufacturing facilities, such as fuel ethanol production facilities and industrial ethanol production facilities, and distilleries, respectively.  Sources that are in NAICS codes 325193 and 312140 will be referred to as "ethanol production facilities" throughout this TSD.  The proposed revision to Wisconsin's SIP and Title V program are consistent with the 2007 Ethanol Rule, as published on May 1, 2007, and codified at 40 C.F.R. § 51.166(b)(1) and 40 C.F.R. § 70.2.

Excluding ethanol production facilities from the chemical process plant source category affects Wisconsin's PSD program in two ways.  First, the proposed rulemaking would raise the PSD major source threshold for ethanol production facilities from 100 tpy to 250 tpy.  Second, the revision would eliminate the requirement to include fugitive emissions when determining whether an ethanol production facility is a PSD major stationary source.  Excluding ethanol production facilities from the chemical process plant source category affects Wisconsin's Title V program by eliminating the requirement to include fugitive emissions when determining whether an ethanol production facility is a major source under the Title V program.

Although Wisconsin submitted a similar revision to its NA NSR program excluding ethanol production facilities from the chemical process plant source category at the same time as its revisions to its PSD program, we are not acting on the NA NSR portion of the SIP submittal at this time.  As a result, this proposed rulemaking will not have any impact on Wisconsin's SIP-approved NA NSR program.

Wisconsin's September 30, 2008, submittal also included certain other changes to its PSD and NA NSR programs related the definition of replacement unit and calculations under Plantwide Applicability Limits.  The changes were approved in a separate action on May 6, 2021 (86 FR 24499).  

III. Regulatory Background

III.1 PSD Permitting Thresholds for Chemical Process Plants and Ethanol Production Facilities

Under the CAA, there are two potential emissions thresholds for determining whether a source is a major stationary source under the PSD program: 100 tpy or 250 tpy of a regulated NSR pollutant.  Sources classified in one of 28 source categories listed in CAA Section 169 are subject to the 100 tpy major stationary source threshold.  Furthermore, sources classified as part of the 28 listed source categories are required to include fugitive emissions when evaluating their major stationary source status.  All other sources are subject to the 250 tpy major stationary source threshold and are not required to include fugitive emissions for the purpose of determining their major source status.

Permitting authorities must determine whether a source is in one of the 28 listed source categories to determine which major stationary source threshold is relevant for applicability purposes.  Permitting authorities have use the 1977 supplement to the Standard Industrial Classification (SIC) Manual as a guide to help with this determination.

One of the 28 listed source categories is chemical process plants.  The SIC code for chemical process plants, SOC code 2869, includes facilities primarily engaged in ethanol production.  As a result, EPA and states considered ethanol production facilities to be subject to the 100 tpy major source threshold and were required to include fugitive emissions when determining whether a source is a major stationary source.

III.2 Title V Permitting Thresholds for Chemical Process Plants and Ethanol Production Facilities

The CAA also establishes thresholds for determining whether sources must obtain Title V operating permits.  All major sources must obtain such permits, and, for purposes of the Title V operating permit program, a major source is defined as any source that has actual or potential emissions at or above the major source threshold for any "air pollutant."  The major source threshold for any air pollutant is 100 tpy in attainment areas. Lower thresholds for major sources can apply in nonattainment areas depending on the pollutant and severity of the nonattainment area.  If a source belongs to one of 28 categories contained in 40 C.F.R. § 70.2 and the approved state program, the source must include fugitive emissions in determining whether it exceeds the major source thresholds for any air pollutant.  In addition, the major source thresholds for hazardous air pollutants (HAP) are 10 tpy for a single HAP or 25 tpy for any combination of HAPs.  Any source with emissions that exceed any one of these thresholds is required to obtain a Title V operating permit. 

III.3 2007 Ethanol Rule

On May 1, 2007, EPA published a final rule entitled the "Prevention of Significant Deterioration, Nonattainment New Source Review, and Title V: Treatment of Certain Ethanol Production Facilities Under the `Major Emitting Facility' Definition."  (2007 Ethanol Rule).  This rule reinterpreted the CAA term "major emitting facility" to exclude all facilities that produce ethanol through a natural fermentation process regardless of whether the ethanol is used for human consumption, fuel or another industrial process.  This rule amended EPA's PSD regulations to define "chemical process plants" under the regulatory definition of "major stationary source" to exclude ethanol manufacturing facilities that produce ethanol bey natural fermentation processes in NAICS codes 325193 and 312140.
 
By excluding these facilities from the chemical process plant source category, the 2007 Ethanol Rule changed the major source threshold in the Federal PSD regulations for ethanol production facilities from 100 tpy to 250 tpy.  The 2007 Ethanol Rule also eliminated the requirement to include fugitive emissions when evaluating whether a source is a major stationary source under the Federal PSD, NA NSR, and Title V permitting programs for ethanol production facilities. 

In a letter dated October 21, 2019, EPA partially granted and partially denied a petition for reconsideration of the 2007 Ethanol Rule.  As part of the response, EPA granted the request for reconsideration regarding the petitioner's claim that the 2007 Ethanol Rule did not appropriately address CAA Section 193 anti-backsliding requirements for nonattainment areas.  All other claims were denied.  Given the partial grant regarding nonattainment areas, we propose to only act on the PSD and Title V-related revisions, and not the NA NSR revisions, at this time.

III.4 Wisconsin Rulemaking to Adopt the 2007 Ethanol Rule into Wisconsin's PSD and Title V Permitting Programs

Wisconsin published a notice in the Wisconsin State Journal on November 16, 2007, proposing revisions to Wisconsin's PSD, NA NSR and Title V permitting programs to adopt the 2007 Ethanol Rule.  On December 18, 2007, a public hearing was held at the State Office Building in Wisconsin Rapids, Wisconsin.  On December 19, 2007, a public hearing was held at the State Office Building in Madison, Wisconsin.  The public comment period closed on December 21, 2007.  The State of Wisconsin Natural Resources Board adopted the rules on March 26, 2008. The rulemaking was published as adopted and filed on July 31, 2008, in the Wisconsin Administrative Record and the revised rules became effective in Wisconsin on August 1, 2008.

Wisconsin revised Wisconsin Administrative Code NR 405.02(22)(a)1  -  Definitions "Major Stationary Source" to read as follows:

      "Any of the following stationary sources of air contaminants which emits, or has the potential to emit, 100 tons per year or more of any air contaminant subject to regulation under the Act: ...chemical process plants (which does not include ethanol production facilities that produce ethanol by natural fermentation, as described by the 6−digit code of 312140 or 325193 in the North American Industry Classification System United States, 2007, incorporated by reference in s. NR 484.05(17))...."

Wisconsin revised Wisconsin Administrative Code NR 405.07(4)(a)20  -  "Review of major stationary sources and major modifications  -  source applicability and exemptions" to read as follows: 

      "A major source or major modification is exempt from the requirements of ss. NR 405.08 to 405.16 if any of the following apply:
      (a) The source or modification would be a major stationary source or major modification only if fugitive emissions, to the extent quantifiable, are considered in calculating the potential to emit of the stationary source or modification and such source does not belong to any of the following categories... 
      
      20. Chemical process plants. The chemical processing plants category does not include ethanol production facilities that produce ethanol by natural fermentation, as described by the 6−digit code of 312140 or 325193 in the North American Industry Classification System United States, 2007, incorporated by reference in s. NR 484.05 (17)."

Wisconsin also revised Wisconsin Administrative Code NR 407.02(4)(b)20  -  Definitions for Title V Operating Permits.  Specifically, Wisconsin revised the explanation of "chemical process plants" that is contained in the definition of "stationary source categories" to read as follows:

      "...20 Chemical process plants. The chemical processing plants category does not include ethanol production facilities that produce ethanol by natural fermentation, as described by the 6−digit code of 312140 or 325193 in the North American Industry Classification System United States, 2007, incorporated by reference in s. NR 484.05 (17)."

On September 30, 2008, Wisconsin submitted a request to EPA Region 5 to revise the Wisconsin SIP to incorporate changes made to Wisconsin's PSD, NA NSR and Title V permitting programs. While EPA has yet to approve the provisions of the 2007 Ethanol Rule into Wisconsin's SIP, Wisconsin has implemented the revisions in its PSD and Title V Operating Permit programs.  

IV. Ethanol Background

According to the U.S. Department of Energy's Alternative Fuels Data Center, ethanol is a domestically produced alternative fuel most commonly made from corn.  It can also be made from cellulosic feedstocks, such as crop residues and wood  -  though this not as common.  U.S. ethanol plants are concentrated in the Midwest because of their proximity to corn production.  Plants outside the Midwest typically receive corn by rail and are located near large population centers.

The production method of ethanol depends on the type of feedstock used.  Most ethanol in the United States is produced from starch-based crops by dry-or wet-mill processing.  Nearly 90% of ethanol plants are dry mills dues to lower capital costs.  Dry milling is a process that grinds corn into flour and ferments it into ethanol with coproducts of distiller's grains and carbon dioxide.  Wet-mill plants primarily produce corn sweeteners, along with ethanol and several other co-products, such as corn oil and starch.  Wet mills separate starch, protein, and fiber in corn prior to processing those components into products such as ethanol.

Ethanol as Fuel

United States ethanol production has increased substantially in recent decades.  As methyl tertiary-butyl ether (MTBE) was phased out of gasoline due to ground water contamination, ethanol became more widely used as an oxygenate in fuel.  Oxygenates are compounds that contain oxygen and are used in fuels to promote better combustion, thus reducing carbon monoxide and particulate emissions.  Ethanol production continued to increase as many states banned the use of MTBE.

Use of ethanol as a gasoline additive increased from 1998 to 2010 (Figure 1).  Its use was spurred in part by the CAA Amendments of 1990, which mandated the sale of oxygenated fuels in areas with unhealthy levels of carbon monoxide.  Starting in 2010, E10, an ethanol-gasoline blend containing 10 percent ethanol, was sold in all 50 states in order to boost octane, meet air quality requirements, or satisfy the Renewable Fuel Standard (RFS).

Figure 1: U.S. Consumption of Ethanol and MTBE Oxygenates (Billions of Gallons).  Data Source:  U.S. Department of Energy Alternative Fuels Data Center. 

Ethanol used as vehicle fuel in the United States is generally produced domestically.  U.S. fuel ethanol production has similarly increase in recent years (see Figure 2).

Figure 2: U.S. Fuel Ethanol Production from 1980- 2019.  Data source: U.S. Energy Information Administration State Energy Data System (SEDS).
V. Wisconsin Ethanol Production

Wisconsin is the 7[th]-largest fuel ethanol producer by state (see Figure 3).  As shown in Figure 4, Wisconsin's statewide ethanol production sharply increased between 2002 and 2008 from just under 0.5 million barrels to over 12.3 million barrels.  Ethanol production in Wisconsin has since increased to 15 million barrels in 2019, representing nearly 4% of 2019's reported domestic fuel ethanol production.

 
Figure 3: 2107 Fuel Ethanol Production by State.  Data source: U.S. Energy Information Administration SEDS.

Figure 4: Wisconsin Fuel Ethanol Production (1995  -  2019).  Data source: U.S. Energy Information Administration SEDS.

Wisconsin's ethanol production occurs primarily at 9 permitted ethanol plants in Wisconsin.  All 9 facilities completed construction prior to 2008 and primarily use corn to produce ethanol.

Wisconsin's permitted ethanol plants are identified in Table 1.  Ethanol production capacity is based on each facility's current permit and may include denatured ethanol as part of the ethanol capacity.  The listed permit number corresponds to the most recently issued operating permit from which this information is based.

                                  Source Name
                                     City
                                    County
                                 Permit Number
                    Ethanol Capacity (Million Gallons/Year)
                               Ace Ethanol, LLC
                                    Stanley
                              Chippewa and Clark
609000370-P20
                                      60
                           Badger State Ethanol, LLC
                                    Monroe
                                     Green
12303808A-P23
                                      108
                      Big River Resources Boyceville, LLC
                                  Boyceville
                                     Dunn
617005290-P21
                                      70
                              Didion Milling, LLC
                                    Cambria
                                   Columbia
11108152A-P08
                                      60
                         Fox River Valley Ethanol, LLC
                                    Oshkosh
                                   Winnebago
47100647A-P30
                                      72
                       Marquis Energy  -  Wisconsin, LLC
                                    Necedah
                                    Juneau
72900388A-P10
                                      95
                              United Ethanol, LLC
                                    Milton
                                     Rock
154144540-F01
                                      60
                     United Wisconsin Grain Producers, LLC
                                   Friesland
                                   Columbia
111030040-P10
                                      65
                          Valero Renewable Fuels, LLC
                                 Johnson Creek
                                   Jefferson
128002930-F23
                                      120
Table 1:  Permitted Wisconsin Ethanol Plants.  Source:  Wisconsin Department of Natural Resources.

Figure 5:  Wisconsin's permitted ethanol production facilities.
                                       
Allowable criteria pollutant emissions for each ethanol production facility are included in Table 2.  Allowable emissions are based on each source's most recently issued operating permit identified in Table 1.  

                                  Source Name
                                   CO (tpy)
                                   NOX (tpy)
                                   VOC (tpy)
                                  PM10 (tpy)
                                  PM2.5 (tpy)
                                   SO2 (tpy)
                               Ace Ethanol, LLC
                                    142.26
                                     83.1
                                    123.52
                                     29.98
                                     8.17
                                     1.15
                           Badger State Ethanol, LLC
                                      163
                                      152
                                      148
                                     93.8
                                      0.7
                                      69
                      Big River Resources Boyceville, LLC
                                    111.24
                                    120.59
                                    102.25
                                     68.57
                                      9.8
                                     30.8
                              Didion Milling, LLC
                                      114
                                      124
                                      116
                                      174
                                     5.35
                                     28.6
                         Fox River Valley Ethanol, LLC
                                     126.6
                                     161.2
                                     112.2
                                     63.7
                                     49.1
                                      3.1
                       Marquis Energy  -  Wisconsin, LLC
                                    118.93
                                    115.44
                                    153.57
                                     74.67
                                     26.84
                                     41.57
                              United Ethanol, LLC
                                     71.6
                                      95
                                      66
                                     49.1
                                     17.5
                                      32
                     United Wisconsin Grain Producers, LLC
                                    111.84
                                    103.64
                                    102.21
                                     77.84
                                     33.23
                                     10.81
                          Valero Renewable Fuels, LLC
                                     83.1
                                     68.1
                                     98.3
                                     36.8
                                     17.7
                                     10.6
Table 2:  Allowable criteria pollutant emissions for each ethanol production facility in tons per year (tpy).  Source:  Wisconsin Department of Natural Resources.
Although Wisconsin has implemented the 2007 Ethanol rule since 2008, the proposed rulemaking would revise the SIP provisions regarding whether a source should be considered a PSD major stationary source.  The major source threshold in the SIP for ethanol production facilities would change from 100 to 250 tpy.  The SIP would no longer require fugitive emissions from ethanol production facilities be counted when determining whether a source is a PSD major source.  As a result, some ethanol production facilities may no longer be considered a PSD major source despite emitting, or having the potential to emit, a regulated NSR pollutant at or above a rate of 100 tpy but less than 250 tpy.
Although an ethanol production facility would not be considered a chemical process plant if the SIP revision is approved, an ethanol production facility may contain certain nested activities that are themselves a listed source category subject ot the 100 tpy major source threshold.  The stationary source may also contain certain activities that are regulated under CAA §§ 111 and 112 as of August 7, 1980, namely New Source Performance Standard (NSPS) or National Emission Standard for Hazardous Air Pollutants (NESHAP), respectively.  Listed source categories and other stationary source categories subject to a NSPS or NESHAP in effect on or before August 7, 1980, are still required to include its fugitive emissions when determining whether the source is a major stationary source under PSD and would not be affected by the proposed rulemaking.
Fossil fuel boilers totaling more than 250 million British thermal units per hour (MMBTU/hr) are commonly nested within ethanol production facilities.  These fossil fuel boilers are commonly fired by either natural gas or DDGS dryer process gas.  One ethanol production facility in Wisconsin also contains a grain elevator subject to 40 C.F. R. Part 60, Subpart DD  -  Standards of Performance for Grain Elevators, effective August 3, 1978.
A summary of how each ethanol production facility listed in Table 1 is affected by the proposed rulemaking is included in Table 3.  This table shows whether the ethanol production facility will continue to be a PSD major stationary source after the proposed rulemaking and whether the source contains activities that are nested sources or are subject to an NSPS or NESHAP in effect on or before August 7, 1980.

                                  Source Name
                           PSD Major After Revision?
                          Nested Fossil Fuel Boilers?
             NSPS or NESHAP in effect on or before August 7, 1980
                               Ace Ethanol, LLC
                                      No
                                      No
                                      No
                           Badger State Ethanol, LLC
                                      No
                                      No
                                      No
                      Big River Resources Boyceville, LLC
                                      No
                                      No
                                      No
                              Didion Milling, LLC
                                      No
                                      No
                                    NSPS DD
                         Fox River Valley Ethanol, LLC
                                      No
                                      No
                                      No
                       Marquis Energy  -  Wisconsin, LLC
                                      No
                                      No
                                      No
                              United Ethanol, LLC
                                      No
                                      No
                                      No
                     United Wisconsin Grain Producers, LLC
                                      No
                                      No
                                      No
                          Valero Renewable Fuels, LLC
                                      No
                                      No
                                      No
Table 3:  Effect of proposed rulemaking on ethanol production facilities in Wisconsin.  Source: Wisconsin Department of Natural Resources.

As shown in Table 3, no ethanol production facilities in Wisconsin will be considered major stationary sources under PSD if the proposed rulemaking is approved because no source will emit a regulated NSR pollutant above the 250 tpy threshold.  Additionally, none of the ethanol facilities in Wisconsin contain a nested source that would be subject to a 100 tpy major stationary source threshold, and 1 facility, Didion Milling, LLC, contains a source category subject to an NSPS in effect on or before August 7, 1980.  This facility would be required to quantify and include fugitive emissions from the NSPS affected unit for the purposes of determining whether the source is a PSD major source.
Seven of the nine existing ethanol production facilities in Wisconsin are Title V major sources because each source has the potential to emit 100 tpy or more of a pollutant subject to regulation.  United Ethanol, LLC and Valero Renewable Fuels, LLC are federally enforceable state operating permit (FESOP) sources.  As FESOP sources, these sources are subject to enforceable limitations on their potential to emit.  These limitations keep them from being a Title V major source.  Each Title V and FESOP permit incorporates all applicable requirements, such as federal NSPS and NESHAP requirements, which address emissions from affected sources and affected facilities.  Further, as Title V and FESOP sources, the permits include monitoring, recordkeeping, and reporting necessary to determine whether the source is complying with applicable requirements.  Thus, each source impacted by the proposed SIP revision would still be subject to certain federal requirements regardless of the PSD major source status.
Table 4 shows the operating permit level (either Title V or FESOP), applicable NESHAPs, and applicable NSPS for each ethanol production facility in Wisconsin.  Although not listed or further discussed here, each operating permit also includes other applicable requirements, as well as certain state-only requirements.  As a result, each source would still be subject to requirements that limit emissions of certain pollutants.  Further, each source is subject to either Title V or FESOP requirements, meaning that the permit for each source includes all applicable requirements, as well as monitoring, recordkeeping, and reporting requirements sufficient to determine compliance with each applicable requirement.
Ethanol production facilities also have the potential to emit HAPs.  However, excluding ethanol production facilities from the chemical process plant source category will not affect whether a source is a major source of HAPs since HAPs are not subject to PSD.  Fugitive HAP emissions continue to be included when determining whether a source is an area or major source of HAPs.

                                  Source Name
                                  Permit Type
                          Applicable NSPS by subpart
                         Applicable NESHAP by subpart
                               Ace Ethanol, LLC
                                    Title V
                                  Dc, Kb, VVa
                                     ZZZZ
                           Badger State Ethano, LLC
                                    Title V
                                  Db, Kb, VVa
                                     None
                       Big River Energy Boyceville, LLC
                                    Title V
                                  Db, Kb, VVa
                                     ZZZZ
                              Didion Milling, LLC
                                    Title V
                                Dc, DD, Kb, VVa
                                     None
                         Fox River Valley Ethanol, LLC
                                    Title V
                                  Dc, Kb, VVa
                                     ZZZZ
                       Marquis Energy  -  Wisconsin, LLC
                                    Title V
                                  Dc, Kb, VVa
                                     ZZZZ
                              United Ethanol, LLC
                                     FESOP
                             Db, Dc, IIII, Kb, VVa
                                     ZZZZ
                      United Wiscon Grain Producers, LLC
                                    Title V
                                  Db, Kb, VVa
                                     ZZZZ
                          Valero Renewable Fuels, LLC
                                     FESOP
                                Db, Dc, Kb, VV
                                     None
Table 4:  Operating permit level, applicable NSPS, and applicable NESHAP for existing ethanol production facilities.  Source: Wisconsin Department of Natural Resources.

VI. Emissions, Air Quality, and Modeling

We evaluated Wisconsin's emission inventory, air quality monitoring design values, and existing photochemical modeling to determine the impact that the proposed SIP revision would have on Wisconsin's ambient air quality.  Since Wisconsin already excludes ethanol production facilities from the chemical process plant source category, this evaluation also illustrates what effect the proposed SIP revision would have if it had been approved into the SIP prior to the current proposed action.  Existing photochemical modeling results will be used to determine what impact increasing the major source threshold from 100 tpy to 250 tpy would have on secondarily formed air pollutants.

VI.1 Wisconsin Permitted Ethanol Production Facility Actual Emissions

Ethanol production facilities have the potential to emit CO, NOX, PM10, PM2.5, SO2, and O3(as NOX and VOC).  Increased emissions of these pollutants may affect ambient air quality.  Currently permitted ethanol production facilities also emit very small amounts of lead, primarily from combustion sources at each facility.  Because ethanol production facilities generally combust natural gas, lead emissions from these sources are low and are unlikely to interfere with the attainment or maintenance of the lead NAAQS or applicable CAA requirements.  However, excluding ethanol production facilities from the chemical process plant source category under PSD only affects whether a source is a PSD major stationary source or whether fugitive emissions are considered for PSD applicability.  The proposed SIP revision allows an ethanol production facility to emit up to 250 tpy of each regulated NSR pollutant without triggering PSD requirements and would not affect other non-PSD SIP requirements.

Actual emissions for sources that will become a PSD minor source are included in Table 5.  The two FESOP sources, United Ethanol, LLC and Valero Renewable Fuels, LLC, have been excluded from the table because these sources have taken limits to ensure the potential to emit any criteria pollutant remains below 100 tpy, leaving both the Title V and PSD major source status largely unaffected by the rulemaking.

                                  Source Name
                                      CO
                                      NOX
                                      VOC
                                     PM10
                                     PM2.5
                                      SO2
                               Ace Ethanol, LLC
                                     45.3
                                     35.5
                                     16.8
                                     12.2
                                      8.0
                                     <5
                           Badger State Ethanol, LLC
                                     59.5
                                     66.8
                                     34.1
                                     19.5
                                      7.2
                                     <5
                       Big River Energy Boyceville, LLC
                                     53.7
                                     52.8
                                     66.9
                                     17.9
                                     19.8
                                      7.9
                              Didion Milling, LLC
                                     56.5
                                     101.2
                                     31.8
                                     88.9
                                     13.0
                                     <5
                         Fox River Valley Ethanol, LLC
                                     23.4
                                     28.6
                                     10.6
                                      6.2
                                     <5
                                     <5
                       Marquis Energy  -  Wisconsin, LLC
                                     51.2
                                     52.4
                                     53.7
                                     33.5
                                     <5
                                     <5
                     United Wisconsin Grain Producers, LLC
                                     46.1
                                     66.6
                                     62.5
                                     19.8
                                      5.9
                                      5.8
Table 5:  2020 actual emissions for PSD minor ethanol production facilities.  Shaded values represent actual emissions exceeding 100 tpy.  Source:  Wisconsin Department of Natural Resources 2020 Emissions Summary Data.

As shown in Table 5, actual emissions of criteria pollutants from each source are well below the allowable emission rates shown in Table 2.  Of the 7 existing ethanol production facilities that will become a PSD minor source if the proposed rule is approved, only one facility reported actual emissions of a regulated NSR pollutant equal to or exceeding 100 tpy.

Total actual emissions of all ethanol production facilities represent a small portion of total statewide actual emissions.  A comparison of total 2020 ethanol production facilities actual emissions to total statewide facility emissions as reported to WDNR is given in Table 6.

                                   Pollutant
                2020 Ethanol Production Actual Emissions (tpy)
                    2020 Statewide Facility Emissions (tpy)
                    Ethanol Production Actual Emissions (%)
                                      CO
                                     335.7
                                     22043
                                     1.5%
                                      NOX
                                     403.9
                                     26913
                                     1.5%
                                      VOC
                                     276.4
                                     19256
                                     1.4%
                                     PM10
                                      198
                                     6184
                                     3.2%
                                     PM2.5
                                   <63.9
                                       *
                                       *
                                      SO2
                                   <28.7
                                     17139
                                   <0.2%
Table 6:  Ethanol production actual emissions as a percentage of total statewide facility emissions.  Source:  Wisconsin Department of Natural Resources 2020 Statewide Emissions Summary Data.  *No data was available for statewide facility emissions for PM2.5.

Wisconsin's 2017 National Emission Inventory (NEI) point source emission inventory is given in Table 7.  Based on the 2017 NEI data, ethanol production facility actual emissions would similarly represent a small percentage of statewide point source emissions.

                                   Pollutant
                2020 Ethanol Production Actual Emissions (tpy)
                   2017 Wisconsin NEI Point Emissions (tpy)
                    Ethanol Production Actual Emissions (%)
                                      CO
                                     335.7
                                     39627
                                     0.8%
                                      NOX
                                     403.9
                                     40289
                                     1.0%
                                      VOC
                                     276.4
                                     20676
                                     1.3%
                                     PM10
                                      198
                                     7712
                                     2.6%
                                     PM2.5
                                   <63.9
                                     4655
                                   <1.4%
                                      SO2
                                   <28.7
                                     27589
                                   <0.1%
Table 7:  Wisconsin 2020 ethanol production facility actual emissions compared to 2017 National Emissions Inventory, as updated in January 2021.  Source:  2017 National Emissions Inventory (January 2021 Release) and Wisconsin Department of Natural Resources.

Both Wisconsin's 2020 summed statewide facility emissions data and the 2017 NEI data show that actual emissions from existing ethanol production facilities represent a small fraction of total statewide actual emissions.  As a result, emissions from current ethanol production facilities likely have a small impact on ambient concentrations.

VI.2 Wisconsin Ambient Air Quality Trends
We evaluated Wisconsin's ambient monitoring data to determine the potential impact each ethanol production facility may have had since the State of Wisconsin began implementing the 2007 Ethanol Rule.  As explained previously, Wisconsin does not consider ethanol production facilities to be chemical process plants and has treated ethanol production facilities as such since 2007.  As a result, measured ambient air concentration already reflect the impact existing ethanol production facilities have on ambient air concentrations.
For this analysis, recent design values for the criteria pollutants CO, NO2, O3, PM2.5, and SO2 are plotted to show trends in ambient air concentrations.  PM10 is not included because the estimated number of exceedances of the PM10 NAAQS at all monitors across the state has decreased to zero.  Lead is not included because ethanol production facilities have very low lead emissions as a result of combusting natural gas and, as a result, would not adversely impact attainment or maintenance of the lead NAAQS.  A design value is a metric that is compared to the NAAQS to determine compliance with the NAAQS.  In this TSD, the year provided on all charts corresponds to design values calculated for a given year.
The locations of all ambient monitors considered for this analysis are included in Figure 6.  Pollutant-specific ambient monitor locations will also be provided later in this TSD.

Figure 6:  A map of Wisconsin showing ethanol production facilities and all active ambient air monitors.

VI.2.A Wisconsin Carbon Monoxide Ambient Air Monitoring and Design Values

The CO NAAQS, initially promulgated in 1971 and retained in 2011, has two primary NAAQS: one averaged over 1 hour and the other averaged over 8 hours.  There is no secondary CO NAAQS.  The level of the 1-hour CO NAAQS is 35 parts per million (ppm).  The level of the 8-hour CO NAAQS is 9 ppm.  Both the 1-hour and 8-hour CO NAAQS are not to be exceeded more than once per year.

As noted in section III.3, Wisconsin has been implementing the revised PSD provisions for ethanol production facilities since 2007.  Wisconsin currently has no CO nonattainment areas.

Figure 7 shows the locations of all CO monitors relative to all permitted ethanol production facilities in Wisconsin.  Figure 8 and Figure 9 show the trends of the 1-hour and 8-hour CO NAAQS, respectively.

Figure 7:  Wisconsin active CO monitors relative to Wisconsin ethanol production facilities.

 Figure 8:  Wisconsin 1-hr CO NAAQS design values, 2010-2021.

 Figure 9:  Wisconsin 8-hour CO NAAQS design values, 2010-2021.

CO design values have remained steady at a level below the CO NAAQS.  All CO monitors in the State of Wisconsin are showing design values below the 1-hour and 8-hour CO NAAQS.

VI.2.B Wisconsin Nitrogen Dioxide (NO2) Ambien Air Monitoring and Design Values

The primary and secondary annual NO2 NAAQS were initially promulgated in 1971.  The primary annual NO2 NAAQS was retained without revision in 2010 and 2018 .  The secondary NO2 NAAQS was retained without revision in 2012.  The level and form of both the primary and secondary NO2 NAAQS is 53 parts per billion (ppb) as an annual arithmetic average.  In 2010, EPA promulgated a 1-hour primary NO2 NAAQS.  The level and form of the 1-hour NO2 NAAQS is 100 ppb as the 98[th] percentile of 1-hour daily maximum concentrations averaged over 3 years.  The 1-hour NO2 standard was retained without revision in 2018.

As noted above in section III.3, Wisconsin has been implementing the revised PSD provisions for ethanol production facilities since 2007.  Wisconsin currently has no NO2 nonattainment areas.

Figure 10 shows the location of all NO2 monitors with a valid design value between 2009 and 2020.  Figure 11 and Figure 12 show the design value trends for both the 1-hour and annual NO2 NAAQS, respectively.

Figure 10:  Map of active Wisconsin NO2 monitors relative to permitted ethanol production facilities.

 Figure 11:  Wisconsin 1-hour NO2 NAAQS Design Values, 2009-2021.

 

 Figure 12:  Wisconsin annual NO2 NAAQS Design Values, 2011-2021.

1-hour and annual NO2 design values have steadily remained below the level of the 1-hour and annual NO2 NAAQS.  This includes rural ambient monitors and ambient NO2 monitors sited downwind of existing ethanol production facilities.

VI.2.C Wisconsin Ozone (O3) Ambient Air Monitoring and Design Values

The 2008 ozone NAAQS was promulgated on March 27, 2008.  The level of the primary and secondary 2008 ozone NAAQS are both 0.075 ppm.  The 2008 ozone NAAQS has an 8-hour averaging time with the form of the annual fourth-highest daily maximum 8-hour concentration averaged over three years.

The 2015 ozone NAAQS was promulgated on October 26, 2015.  The 2015 ozone NAAQS has the same form and averaging time as the 2008 ozone NAAQS; however, the level is 0.070 ppm for both the primary and secondary 2015 ozone NAAQS.  The 2015 ozone NAAQS was retained without revision for both the primary and secondary standards in 2020.

Wisconsin currently has no ozone nonattainment areas for the 2008 8-hour ozone NAAQS and three marginal ozone nonattainment areas for the 2015 8-hour ozone NAAQS.  Each ozone nonattainment area is listed in Table 8.

8-hour Ozone NAAQS (year)
Nonattainment Area
Classification
Designated Area
2015
Chicago, IL-IN-WI
Marginal
The portion of Kenosha County bounded by the Lake Michigan shoreline on the East, the Kenosha County boundary on the North, the Kenosha County boundary on the South, and the I-94 corridor (including the entire corridor) on the West.
2015
Milwaukee, WI
Marginal
Milwaukee County, Ozaukee County,  Racine County (part):  Inclusive of the following roadways going from the northern county boundary to the southern county boundary: Highway 45 to Washington Ave. to South Beaumont Ave., 
Washington County (part):  Inclusive and east of the following roadways going from the northern county boundary to the southern county boundary: County H to N Main St/Old US Hwy 45 to WI-60 Trunk E to WI-164 S., 
Waukesha County (part): Going from the western county boundary to the southern county boundary: Inclusive and north of I-94 and inclusive and east of Highway 67.
2015
Sheboygan County, WI
Marginal
Sheboygan County (part):  Inclusive and east of the following roadways with the boundary starting from north to south: Union Road with turns into County Road Y which turns into Highland Drive, to Lower Road which turns into Monroe Street to Broadway/Main Street to Highway 32 which turns into Giddings Avenue to County Road W to County Road KW.
Table 8:  Wisconsin 8-hour Ozone Nonattainment Areas.

Figure 13 shows the location of all ambient ozone monitors with at least one valid design value between 2009 and 2020.  Figure 14 and Figure 15 each chart the design value trends for both the 2008 and 2015 8-hour ozone NAAQS, respectively.

Figure 13:  Map of active Wisconsin ambient ozone monitors relative to ethanol production facilities.

Figure 14: Wisconsin 8-Hour Ozone Design Values (2008 NAAQS), 2008-2020.

Figure 15: Wisconsin 8-Hour Ozone Design Values (2015 NAAQS), 2015-2021.

Ambient ozone concentrations have generally decreased across Wisconsin since 2008.  As shown in Figure 14, three monitors had 2017-2019 and 2018-2020 design values at or near the 0.075 ppm 2008 8-hour ozone standard.  The Sheboygan, Wisconsin monitor (site ID 551170006) had 2017-2019 and 2018-2020 design values equal to the standard at 0.075 ppm.  The nearest ethanol production facility to this monitor, Fox River Valley Ethanol, is 86 km away.  The Kenosha, Wisconsin monitor (site ID 550590019) had a 2017-2019 design value of 0.075 ppm and a 2018-2020 design value of 0.074 ppm.  The nearest ethanol production facility to the Kenosha monitor, Valero Renewable Fuels, is 95 km away.  Finally, the Racine monitor (site ID 551010020) had a 2017-2019 design value of 0.074 ppm and a 2018-2020 design value of 0.073 ppm.  All other monitors have an ozone design value below 0.073 ppm.

Figure 15 compares ozone design values to the 2015 8-hr ozone NAAQS.  Most Wisconsin ambient ozone monitors have measured design values below 0.070 ppm, the level of the 2015 ozone NAAQS; however, ten sites had reported design values that had at least one design value above 0.070 ppm between 2015 and 2021.  The locations of these ten sites are mapped in Figure 16.  Monitor locations are shown in relation to Wisconsin's existing ethanol production facilities.

All other monitors have ozone deign value concentrations at or below 0.070 ppm, either trending downward or steadily remaining below the level of the NAAQS.

Figure 16:  Map of active ambient ozone monitors with at least one design value concentration above 0.070 ppm since 2015.
VI.2D Wisconsin PM2.5 Ambient Air Monitoring and Design Values

The PM2.5 NAAQS was promulgated on January 15, 2013, and became effective on March 18, 2013.  The PM2.5 NAAQS has both a 24-hour and an annual averaging time.  The level of the primary and secondary 24-hour PM2.5 NAAQS is 35 ug/m[3].  The form of the primary and secondary 24-hour PM2.5 NAAQS is the 98[th] percentile, averaged over three years.  The primary annual PM2.5 NAAQS is 12.0 ug/m[3] and the secondary annual PM2.5 NAAQS is 15.0 ug/m[3].  The form of both the primary and secondary annual PM2.5 NAAQS is an annual mean averaged over three years.  Both the primary and secondary PM2.5 NAAQS were retained without revision in 2020.

As noted above in section III.3, Wisconsin has been implementing the revised PSD provisions for ethanol production facilities since 2007 and Wisconsin currently has no PM2.5 nonattainment areas.

Figure 17 shows the locations of all PM2.5 monitors relative to all permitted ethanol production facilities in Wisconsin.  Figure 18 and Figure 19 show the trends of the 24-hour and annual PM2.5 NAAQS, respectively.

Figure 17:  Map of active PM2.5 monitors in relation to existing ethanol production facilities.

 
Figure 18:  Wisconsin 24-hour PM2.5 design values, 2008-2021.

 Figure 19:  Wisconsin annual PM2.5 design values, 2008-2021.
 
From Figure 18 and Figure 19, PM2.5 design values have trended downwards at all monitors since 2009, including those monitors located near existing ethanol production facilities.

VI.2.E SO2 Ambient Monitoring and Design Values

The 2010 primary SO2 NAAQS was promulgated on June 22, 2010 and was retained without revision on March 18, 2019.  The primary SO2 NAAQS has a 1-hour averaging time, a level of 75 ppb, and is the 99[th] percentile averaged over 3 years.  The 1971 secondary SO2 NAAQS was initially promulgated on April 30, 1971 and was most recently retained without revision on April, 2012.  The secondary SO2 NAAQS has a 3-hour averaging time, a level of 0.5 ppm, and is not to be exceeded more than once per year.

Wisconsin has no SO2 nonattainment areas.  A portion of Oneida County was previously an SO2 nonattainment area and was redesignated to attainment on January 11, 2022 .  There are no ethanol production facilities in Oneida County, and the nearest facility is over 100 km away.

Figure 20 show the locations of all SO2 monitors relative to all permitted ethanol facilities in Wisconsin.  Figure 21 of all 1-hour SO2 design values across the state.Figure 20:  Map of active SO2 ambient monitors in relation to permitted ethanol production facilities.

Figure 21:  Wisconsin 1-hour SO2 design values.

VI.3 Evaluation of the Future Impacts of the Proposed SIP Revision

CAA Section 110(a)(2)(C) requires Wisconsin to have a program to regulate the modification and construction of any stationary source within the areas covered by Wisconsin's SIP to assure the NAAQS are achieved.  This includes the construction or modification of sources that are not subject to either PSD or NA NSR, but instead are subject to minor NSR requirements.

Minor NSR implementing regulations are codified in 40 C.F.R. Part 51 Subpart I.  40 C.F.R. § 51.160(a) and (b) requires the following to be included in the Wisconsin SIP.

      [40 CFR § 51.160(a)] Each plan must set forth legally enforceable procedures that enable the State or local agency to determine whether the construction or modification of a facility, building, structure  or installation, or combination of these will result in (1) a violation of applicable portions of the control strategy: or (2) interference with attainment or maintenance of a national standard in the State in which the proposed source (or modification) is located or in a neighboring state.

      [40 C.F.R. § 51.160(b)] Such procedures must include means by which the State or local agency responsible for final decisionmaking on an application for approval to construct or modify will prevent such construction or modification if (1) it will result in a violation of the applicable portions of the control strategy; or (2) it will interfere with the attainment or maintenance of a national standard.

EPA has concluded in a previous action that Wisconsin's minor NSR program meets all requirements, including 40 C.F.R. § 51.160(a) and (b).

Wisconsin's minor NSR program requirements can be found in Chapter NR 406 of the Wisconsin Administrative Code.  Minor NSR sources Construction permits issued in the state of Wisconsin must comply with the appropriate requirements set forth in NR 406.  The construction or modification of a minor source that would violate a portion of Wisconsin's control strategy or interfere with attainment or maintenance of the NAAQS would not be allowed under Wisconsin's minor NSR program.

The proposed SIP revision only affects whether an ethanol production facility is a major stationary source under PSD.  PSD applies to new major sources or major modifications at existing major sources located in an attainment or unclassifiable area for a given criteria pollutant.  If a proposed ethanol production facility is a PSD major stationary source, then it would be evaluated pursuant to Wisconsin's SIP-approved PSD program.

If a new or modified ethanol production facility does not trigger PSD, the proposed source or modification would be subject to the requirements of Wisconsin's minor NSR program.  Construction or modification of a minor ethanol production facility would be evaluated consistent with Wisconsin's minor NSR program.  As part of the evaluation, Wisconsin would determine whether the proposed project violates portions of the applicable control strategy or NAAQS attainment or maintenance.

As discussed previously, Wisconsin has no permitted ethanol production facilities located in a nonattainment area; however, proposed major ethanol production facilities that construct in a nonattainment area would be subject to applicable portions of Wisconsin's NA NSR program.  Minor ethanol production facilities constructing in a nonattainment area may be subject to Wisconsin's minor NSR program.

VI.3.A Ozone Air Quality Impact Analysis for Currently Permitted Ethanol Production Facilities
 
 We evaluated existing photochemical modeling results to determine the impact NOX and VOC emissions from permitted ethanol production facilities would have on ambient ozone concentrations.  On April 30, 2019, EPA developed Guidance on the Development of Modeled Emission Rates for Precursors (MERPs) as a Tier I Demonstration Tool for Ozone and PM2.5 under the PSD Permitting Program (MERPs Guidance).  The guidance provides a framework that can be used to estimate single source impacts on secondarily formed pollutants consistent with recommendations made in the  - Guideline on Air Quality Models.  The tiered approach presented in the Guideline on Air Quality Models is the approach that Wisconsin would take to evaluate secondary formation impacts in a PSD air quality impact analysis.  To illustrate how the framework in this guidance can be implemented by stakeholders, EPA modeled several hypothetical sources across the United States to determine hypothetical ozone single source impacts.  MERPs are further discussed as a later part of this technical support document.

EPA included three hypothetical sources in Wisconsin, shown in Figure 22.  At least one hypothetical source is located near a currently permitted ethanol production facility.  Due to limited availability of hypothetical source date in Wisconsin, we have included a hypothetical source in Illinois.  Hypothetical sources each emit pollutants into a meteorological and chemical environment similar to the environment into which each permitted ethanol production facility emits.  Wisconsin does not have significant geographical features separating the hypothetical sources from the ethanol production facilities, suggesting that the nearest hypothetical source would be representative of the meteorological and physical environment.

Figure 22: Hypothetical source locations with respect to currently permitted ethanol production facilities.

Each hypothetical source was modeled at a 500 tpy emission rate for both NO - X and VOC.  Hypothetical sources were modeled assuming a stack height of 10 m, a stack diameter of 5 m, an exit temperature of 311 K, an exit velocity of 27 m/s, and a flow rate of 537 m[3]/s.  These stack characteristics approximate a surface level emission release, the results of which are more conservative (higher) than an elevated release at 90 m at the same emission rate.  Maximum modeled ozone impacts for each hypothetical source are shown in Table 9.
 
 

                    Hypothetical Source Location by County
                                   Pollutant
                            Max Concentration (ppb)
                        Max Concentration beyond 50 km
                                     (ppb)
                                    Shawano
                                      NOX
                                     1.407
                                     0.479
                                    Shawano
                                      VOC
                                     0.108
                                     0.046
                                     Rusk
                                      NOX
                                     1.548
                                     0.700
                                     Rusk
                                      VOC
                                     0.016
                                     0.014
                                  Stephenson
                                      NOX
                                     1.720
                                     0.451
                                  Stephenson
                                      VOC
                                     0.106
                                     0.054
Table 9:  Hypothetical ozone source impacts by county.  Hypothetical sources modeled at 500 tons per year and assume a stack height of 10 m.  Shaded cells indicate the highest modeled concentrations within and beyond 50 km of the hypothetical source.

Existing ethanol production facility emissions are scaled downwards to approximate each ethanol production facility's ozone impacts using the following equation.  The impact of each ethanol production facility would be represented by the source impact.  The ethanol production facility's emission rate is subsituted for the source emission rate.

Source Impact=Source Emission Rate x Hypothetical source modeled impactHypothetical source modeled emission rate

All ethanol production facilities in Wisconsin are more than 50 km from an ozone monitor exceeding 0.070 ppm.  To conservatively estimate the long-range impact of each source, the highest modeled ozone concentration at or beyond 50 km will be used for each ozone precursor.  From Table 9, a NOX ozone concentration of 0.700 ppb and VOC ozone concentration of 0.054 ppb is used in this calculation.  The allowable emission rate for each ethanol production facility will be used as the source emission rate in the above equation to conservatively estimate source ozone impacts.  The NOX and VOC ozone impacts are added together to get the total ozone impact.  The results are shown in Table 10.

                                  Source Name
                              NOX Allowable (tpy)
                              VOC Allowable (tpy)
                         Ozone Impact (>= 50 km, ppb)
                               Ace Ethanol, LLC
                                     83.1
                                    123.52
                                     0.130
                           Badger State Ethanol, LLC
                                      152
                                      148
                                     0.229
                      Big River Resources Boyceville, LLC
                                    120.59
                                    102.25
                                     0.180
                              Didion Milling, LLC
                                      124
                                      116
                                     0.186
                         Fox River Valley Ethanol, LLC
                                     161.2
                                     112.2
                                     0.238
                       Marquis Energy  -  Wisconsin, LLC
                                    115.44
                                    153.57
                                     0.178
                              United Ethanol, LLC
                                      95
                                      66
                                     0.140
                     United Wisconsin Grain Producers, LLC
                                    103.64
                                    102.21
                                     0.156
                          Valero Renewable Fuels, LLC
                                     68.1
                                     98.3
                                     0.106
Table 10:  Estimated ozone impacts for sources at least 50 km from a Wiscon ozone monitor with a design value above 0.070 ppm.

Since existing ethanol production facilities are distributed throughout the state, it is not likely that the peak modeled ozone concentration from one source will overlap another source's peak modeled ozone concentration spatially or temporally.  Generally, ozone formation is a complicated nonlinear process that requires favorable meteorological conditions in addition to VOC and NOX emissions.  Meteorology and atmospheric chemistry can differ over a wide area, suggesting that source location can affect a source's contribution to ambient ozone concentrations at a given monitor.  Even with these factors, ozone formation drops off with distance, becoming smaller as distance increases beyond 50 km, making it unlikely that sources beyond 50 km interfere with attainment or maintenance of the ozone NAAQS.

Based on this analysis, EPA concludes that the currently permitted ethanol production facilities do not interfere with the attainment or maintenance of the 2008 or the 2015 ozone NAAQS.

VI.3.B Ozone Impact Analysis for New Sources

We now evaluate the ozone impact that the proposed SIP revision will have on the construction of new ethanol production facilities.  Our evaluation of ozone impacts resulting from the approval of this SIP revision will consider MERPs hypothetical source modeling results.  Our evaluation will also consider where new sources may be constructed in the state of Wisconsin based on factors that influence the siting of new ethanol production facilities.  Further discussion and evaluation of hypothetical source ozone impacts, and ethanol production facility siting factors follow below in section VI.3.B.i-viii.VI.3.B.i MERPs Hypothetical Source Ozone Impacts

VI.3.B.i MERPs Hypothetical Source Ozone Impacts

Under PSD regulations, a regulated NSR pollutant is any pollutant for which a national ambient air quality standard has been promulgated, including any pollutant identified as a constituent or precursor to a criteria pollutant.  As a result, VOC and NOX are precursors to ozone in all attainment and unclassifiable areas.  SO2 and NOX  are precursors to PM2.5 in all attainment and unclassifiable areas.

For a PSD air quality analysis, EPA recommends a two-tiered approach to assess the impact of an individual source's impact on ozone and PM2.5 concentrations.  The first tier of assessment involves situations where existing technical information is available in combination with other supportive information and analysis for the purpose of estimating secondary impacts from a source.  Existing technical information can be used if it provides a credible and representative estimate of the secondary impacts from the project source.  The second tier is to use a chemical transport model to determine single source impacts.  On the basis of this recommendation, EPA developed the MERPs Guidance as a framework for developing MERPs that can be used to estimate secondar impacts based on a source's emissions.  In support of the MERPs Guidance, EPA performed photochemical modeling of several hypothetical sources throughout the country to help illustrate the method presented in the MERPs framework.

As shown in Tables 3 and Table 6, ethanol production facilities emit or have the potential to emit NOX, VOC, and SO2.  The construction of new ethanol production facilities or modifications to existing ethanol production facilities would similarly have the potential to emit these pollutants.  To evaluate the potential secondary impacts from increased NOX, VOC, and SO2 emissions form new and modified ethanol production facilities, EPA consulted photochemical modeling results provided as part of the MERPs Guidance.

EPA modeled hypothetical sources throughout the United States, including two in Wisconsin, at different release heights and multiple emissions rates.  EPA then evaluated the resulting downing ozone and secondary PM2.5 impacts.  EPA modeled different hypothetical sources at 500 tpy, 1000 tpy, and 3000 tpy of the different precursor pollutants.  The two release heights modeled to support the MERPs Guidance are "L" for surface level releases and "H" for tall stack releases.

Surface level and tall stack releases have the following stack parameters:

 Source release type "L" refers to sources modeled with surface level emissions releases: stack height of 10m, stack diameter of 5 m, exit temperature of 311 K, exit velocity of   27 m/s and flow rate of 537 m[3]/s.
 Source release type "H" refers to sources modeled with tall stack emissions releases: stack height of 90 m, stack diameter of 5 m, exit temperature of 311 K, exit velocity of 27 m/s, and a flow rate of 537 m[3]/s.

As part of this analysis, we assume that a new ethanol production facility or modified non-major existing ethanol production facility will emit an additional 250 tpy of NOX, VOC, and SO2.  We selected 250 tpy for each precursor pollutant as part of this analysis because the proposed revision affects whether an ethanol production facility is part of a listed source category.  If an ethanol production facility is part of the chemical process plant source category, one of the listed source categories, then the major source threshold is 100 tpy.  The proposed revision excludes ethanol production facilities from the chemical process plant source category, making the major source threshold 250 tpy.  New major ethanol production facilities and modifications at existing ethanol production facilities that, on their own, result in increased precursor emissions below 250 tpy may be subject to minor NSR and not PSD, a less stringent construction permitting program.

From the MERPs Guidance, we consider the modeled hypothetical source impacts associated with a 500 tpy precursor pollutant release.  The 500 tpy emission rate would be representative of the impacts associated with a nonmajor emissions increase because it is the closet modeled rate to 250 tpy.

We consider, as part of this analysis the modeled hypothetical source impacts associated with a surface level emissions release.  We selected the surface level emissions release scenario because it results in a more conservative (higher) estimated impact than the tall stack release scenario.

As part of the MERPs Guidance modeling dataset, EPA include 2 hypothetical sources in Wisconsin and one in Illinois near the Wisconsin border because it is closer to a number of Wisconsin ethanol production facilities.  The three sources are listed in Table 11.  The location of each hypothetical source can be seen in Figure 22, above.  The three hypothetical sources are distributed throughout the state (or nearby state) and are generally located in the ethanol production areas of Wisconsin.  Wisconsin does not have complex terrain that would specifically preclude a hypothetical source from being considered representative.  As a result, EPA concludes that the MERPs Guidance modeled hypothetical source impacts would be representative of a new or modified ethanol production facility.

                                     FIPS
                                     State
                                    County
                                    Domain
                                    Source
                                     17177
                                   Illinois
                                  Stephenson
                                     12US2
                                      15
                                     55107
                                   Wisconsin
                                     Rush
                                     12US2
                                      14
                                     55115
                                   Wisconsin
                                    Shawano
                                     12US2
                                       9
Table 11: MERPs Guidance hypothetical sources  -  Wisconsin and Illinois.

Table 12 shows each hypothetical source maximum 8-hour ozone impact by precursor pollutant.  Table 13 show the maximum 8-hour ozone impact by precursor pollutant beyond 50 km.

                         Hypothetical Source by County
                                   Pollutant
                            Max Concentration (ppb)
                                  Stephenson
                                      NOX
                                     1.720
                                       
                                      VOC
                                     0.106
                                     Rusk
                                      NOX
                                     1.548
                                       
                                      VOC
                                     0.016
                                    Shawano
                                      NOX
                                     1.407
                                       
                                      VOC
                                     0.108
Table 12: Wisconsin hypothetical source modeled ozone impacts by precursor pollutant base on a surface-level release and 500 tpy modeled emission rate.

                         Hypothetical Source by County
                                   Pollutant
                    Max Concentration (ppb) (>=50 km, ppb)
                                  Stephenson
                                      NOX
                                     0.451
                                       
                                      VOC
                                     0.054
                                     Rusk
                                      NOX
                                     0.700
                                       
                                      VOC
                                     0.014
                                    Shawano
                                      NOX
                                     0.479
                                       
                                      VOC
                                     0.046
Table 13: Wisconsin hypothetical source modeled ozone maximum daily 8-hour ozone impacts beyond 50 km base on a surface-level release and 500 tpy modeled emission rate.

Emissions increases resulting from the construction of a new minor ethanol production facility or nonmajor modification is 250 tpy for this analysis.  To determine the estimated ozone impact, the modeled concentration from each hypothetical source's 500 tpy modeled emission rate is scaled downward by half to 250 tpy.  The contribution from each precursor pollutant is added together to determine the total ozone impact.  The results are shown in Table 14.  Because NOX and VOC can impact ozone concentrations on a regional scale, we estimate far-field ozone impacts by considering maximum modeled impacts from each hypothetical source beyond 50 km.  Impacts beyond 50 km are shown in Table 15.

                              Hypothetical Source
                            NOx Ozone Impact (ppb)
                            VOC Ozone Impact (ppb)
                           Total Ozone Impact (ppb)
                                  Stephenson
                                     0.860
                                     0.053
                                     0.913
                                     Rusk
                                     0.774
                                     0.008
                                     0.387
                                    Shawano
                                     0.704
                                     0.054
                                     0.758
Table 14:  Maximum 8-hour ozone impacts associated with a 250 tpy increase in NOX and VOC in Wisconsin.

                              Hypothetical Source
                            NOx Ozone Impact (ppb)
                            VOC Ozone Impact (ppb)
                       Total Ozone Impact (>=50 km ppb)
                                  Stephenson
                                     0.226
                                     0.027
                                     0.253
                                     Rusk
                                     0.35
                                     0.007
                                     0.357
                                    Shawano
                                     0.240
                                     0.023
                                     0.263

Table 15:  Maximum 8-hour ozone impacts beyond 50 km associated with a 250 tpy increase in NOX and VOC emissions in Wisconsin.

VI.3.B.ii Siting Factor  -  Wisconsin Corn Crop Frequency

Wisconsin ethanol production facilities use corn as a feedstock.  Because corn is a feedstock for ethanol, ethanol production facilities must be able to timely obtain corn to produce ethanol.  As a result, the availability of corn attracts ethanol plants.  The price of corn influences the cost to produce ethanol, accounting for 50-70% of ethanol input costs.  Corn transportation costs also affect ethanol input costs, where corn transportation costs increase the further an ethanol production facility must go to obtain corn.  To minimize corn costs and to ensure an adequate supply of corn for ethanol production, new ethanol production facilities are located close to the source of corn.

Corn farming occurs throughout the state of Wisconsin.  In 2019, Wisconsin produced 443.2 million bushels of corn for grain on 2.67 million acres of land.  The U.S. Department of Agriculture's National Agricultural Statistics Service provides data that can be used to visualize historic corn crop spatial frequency between 2008 and 2021.  Figure 23 plots the corn crop spatial frequency and ethanol production facilities for Wisconsin.

Figure 23: Wisconsin corn growing frequency between 2008 and 2021.  Source:  USDA National Agricultural Statistics Service.

Wisconsin's permitted ethanol production facilities are generally located in areas where corn has been available for five or more years between 2008 and 2021.  We observe that there are no ethanol plants in areas where corn has not been grown since 2008.

VI.3.B.iii Siting Factor  -  Wisconsin Metropolitan and Micropolitan Statistical Areas

The White House Office of Management and Budget defines metropolitan and micropolitan statistical areas based on Census data.  A Metropolitan Statistical Area is a geographical entity associated with at least one urbanized area that has a population of at least 50,000 people and comprises the central county or counties containing the urban core plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting.  A Micropolitan Statistical Area is similar to a Metropolitan Statistical Area except that a Micropolitan Statistical Area has at least one urban cluster that has a population of at least 10,000 but less than 50,000 people and can similarly include adjacent outlying counties.  Metropolitan and Micropolitan Statistical Areas are together termed Core Based Statistical Areas.  Counties not included in a Metropolitan or Micropolitan Statistical Area are Outside Core Based Statistical Areas.

For this document, a "metropolitan county" is a county that is part of a Metropolitan Statistical Area.  A "sub-micropolitan" county is a county that is neither part of a Metropolitan or Micropolitan Statistical Area.  "Nonmetropolitan counties" are counties that are not part of a Metropolitan Statistical Area and includes both micropolitan and sub-micropolitan counties.

Corn availability in each county and its neighboring counties is the strongest ethanol plant location determinant.  Nonmetropolitan counties tend to attract more ethanol plant investment than metropolitan counties because nonmetropolitan counties have better access to feedstock resources such as corn.  Although metropolitan counties may include corn, access to corn in a metropolitan county may be reduced by a competing ethanol plant located in a neighboring nonmetropolitan county.  As a result, it is more likely that a new ethanol plant will be constructed in a nonmetropolitan county.

Figure 24 shows Metropolitan, Micropolitan and Outside Core Based Statistical Areas in Wisconsin.  Metropolitan and Micropolitan Statistical Area boundaries are those defined by OMB based on the 2010 Census first published in 2013 and updated in 2018.  Permitted ethanol production facilities are located in either nonmetropolitan counties or in metropolitan counties on the border of the Metropolitan Statistical Area, closer to a nonmetropolitan county than the core of the Metropolitan Statistical Area.

Figure 24:  Wisconsin Ethanol Production Facilities and Wisconsin Metropolitan, Micropolitan, and Outside Core Based Statistical Areas.

VI.3.B.iv Siting Factor  -  Wisconsin 2015 Ozone Nonattainment Areas

As mentioned in Table 8, Wisconsin has no remaining 2008 ozone NAAQS nonattainment areas and three 2015 ozone NAAQS nonattainment areas.  For the 2015 ozone NAAQS part of Kenosha County is part of the Chicago-Naperville IL-IN-WI marginal ozone nonattainment area.  The Milwaukee, WI marginal ozone nonattainment area consists of Milwaukee County, Ozaukee County, and a portion of Racine, Washington and Waukesha Counties.  Finally, a portion of Sheboygan County is a marginal nonattainment area for the 2015 ozone NAAQS.  

Figure 25 show the location of all ozone nonattainment areas in Wisconsin.  There are no permitted ethanol production facilities in a Wisconsin ozone nonattainment area.

Figure 25:  Wisconsin ozone nonattainment areas.

VI.3.B.v Siting Factor  -  Wisconsin Ethanol Production Facility Spatial Distribution

Ethanol production facilities are located throughout the state of Wisconsin.  Only one Wisconsin county, Columbia County, has more than one ethanol production facility, and most facilities are greater than 30 km apart.  The two facilities in Columbia County, Didion Milling, LLC and United Wisconsin Grain Producers, LLC are less than 5 km apart.

Ethanol production facilities are built to minimize transportation costs for primary inputs, here corn, and distribution of coproducts to markets.  To minimize transportation costs, ethanol plants tend to locate where corn is grown.  Ethanol production facilities tend to avoid constructing too close to each other because ethanol production facilities located near each other may compete for the same corn input, increasing local corn demand and causing corn prices to rise.

An ethanol production facility can produce 2.7-2.8 gallons of ethanol for every bushel of corn processed.  In 2019, the corn yield in the state of Wisconsin was 166 bushels of corn per acre.  From Table 1, permitted ethanol production facilities in Wisconsin can produce between 60 million and 120 million gallons of ethanol per year.  Assuming each acre of farmland produces 166 bushels of corn and the corn grown goes directly to the nearest ethanol production facility, corn must be grown on 133,869 to 267,738 acres of land to supply enough corn to produce between 60 million and 120 million gallons of ethanol.

Since ethanol production facilities tend to minimize corn input costs by minimizing transportation costs and minimizing competition between multiple ethanol production facilities, we conservatively estimate the minimum distance between an existing ethanol production facility and any new ethanol production facilities.  We do this by assuming that all corn for a given ethanol production facility is grown on land closest to the ethanol production facility to minimize transportation costs.  We further assume that land nearest to the ethanol production facility is used only for growing corn since land being used for any other purpose reduces the amount of land available for growing corn.  As a result of our assumptions, all corn feedstock is grown within a certain distance from an ethanol production facility, where each ethanol production facility has exclusive claim to all corn produced within the circle.  Based on these assumptions, a circle centered on an ethanol production facility with radius 12.3 km has an area of approximately 117,578 acres, while a circle with radius 18.6 km has an area of approximately 267,738 acres.  This is a conservative estimate because it is likely that land with that circle will be used for purposes other than growing corn, such as roads or buildings.

Figure 26 shows the location of all permitted ethanol production facilities in the state of Wisconsin.  A radius of 5 km is plotted around each ethanol production facility to represent the shortest distance between two ethanol facilities.  A 20 km radius represents the minimum distance to source enough corn to produce 120 million gallons of ethanol assuming all land is used to grow corn.  A 30 km radius is plotted to represent the shortest distance between all other ethanol production facilities located in Wisconsin.

Figure 26:  Wisconsin ethanol production facility locations with 5 km, 20 km and 30 km distances shown.

VI.3.B.vi Analysis of Impacts of SIP Approval on Ozone NAAQS  -  New Source Construction

To evaluate the future impact that the proposed SIP approval will have on the ozone NAAQS, we consider the impact that a new ethanol production facility emitting 250 tpy of NOX and 250 tpy of VOC would have on ambient ozone concentrations.  We choose 250 tpy for both VOC and NOX emissions because a new source may emit less than 250 tpy of any regulated pollutant and still be a nonmajor source under PSD following SIP approval.  As shown in Table 2 and explained in section V of this TSD, this is a reasonable assumption to make because Wisconsin currently has 9 ethanol production facilities that emit less than 250 tpy of any regulated NSR pollutant.

We reiterate that siting a new ethanol production facility is affected by several factors: corn availability, distance to the nearest existing ethanol production facility, and whether a county is a metropolitan or nonmetropolitan county.

As discussed above in section VI.3.B.ii, corn availability attracts ethanol production facilities.  We observe that permitted ethanol production facilities in Wisconsin tend to locate in areas where corn is readily available (see Figure 24).  In particular, the most recently permitted ethanol production facility in Wisconsin, United Ethanol in Milton, Wisconsin, is in an area where more than half the land within 30 km has been grown for at least 5 years since 2008.  We evaluated United Ethanol within 30 km because it is the only ethanol facility in that county, and we have previously shown that permitted ethanol production facilities in Wisconsin are generally more than 30 km from the next nearest ethanol production facility (see Figure 26 and accompanying discussion).  Figure 27 shows the frequency that corn has been grown within 30 km of United Ethanol between 2008 and 2021.  Table 16 shows the associated percentage of land with a given frequency of corn grown between 2008 and 2021.  From Table 16, we see that 52% of land within 30 km of United Ethanol grew corn in at least five years between 2008 and 2021.  65% of land within 30 km of United Ethanol had corn in at least one year between 2008 and 2021.  Because this further suggests that corn availability attracts ethanol production facilities, we assume for our analysis that new ethanol production facilities will only be built in areas where corn has historically been available between 2008 and 2021.  Areas that have not historically grown corn will not be considered in this analysis because it is unlikely that a new ethanol production facility will be built in such an area due to increased corn prices and transportation costs.
Figure 27: Corn frequency within 30 km of United Ethanol in Milton, Wisconsin.

                         Years of Corn  -  2008- 2021
                        Percentage of Land within 30 km
                                       0
                                     35.11
                                       1
                                     5.04
                                       2
                                     2.69
                                       3
                                     2.27
                                       4
                                     2.72
                                       5
                                     3.86
                                       6
                                     5.92
                                       7
                                     12.08
                                       8
                                     8.61
                                       9
                                     7.04
                                      10
                                     5.87
                                      11
                                     3.68
                                      12
                                     2.24
                                      13
                                     1.55
                                      14
                                     1.32
Table 16:  Corn frequency and percentage of land within 30 km of United Ethanol.

For our analysis, we assume that new ethanol production facilities will be located at least 15 km from any existing ethanol production facility.  As discussed above in section VI.3.B.v, the presence of multiple thanol production facilities in the same area increases competition for the same supply of corn, potentially raising corn prices and discouraging production of ethanol.  We have observed that the two closest ethanol production facilities in Wisconsin are about 5 km from each other.  We note that ethanol production facilities with a larger capacity have higher emissions than smaller capacity facilities (See Table 1 and Table 2), where the largest ethanol production capacity of 120 million gallons requires at least 267,738 acres of land, equivalent to growing corn on all land located within 18.6 km of the source.  We have also observed that, with the exception of two sources located within 5 km of each other, ethanol production facilities in Wisconsin tend to be located at least 30 km from each other.  Choosing the smaller distance of 15 km between ethanol production facilities increases the likelihood than a new ethanol production facility will choose to construct in a specific area of the state.  Shorter distances between ethanol production facilities increases competition for corn grown near the source, raising local demand for corn and resulting in higher corn input prices.  Increased competition for corn grown near the source would require the ethanol production facility to obtain corn from areas further from the facility, increasing transportation costs and resulting in higher corn input prices.  For these reasons, shorter distances between ethanol production facilities results in a more conservative analysis.

For our analysis, we will assume that any new ethanol production facility will be constructed in a nonmetropolitan county.  From Figure 24 and the accompanying discussion in section VI.3.B.iii, we see that currently permitted ethanol production facilities tend to be in or near nonmetropolitan counties.  As discussed previously in section VI.3.B.iii, ethanol production facilities tend to choose nonmetropolitan counties over metropolitan counties because nonmetropolitan counties have better access to corn and coproduct markets.  Finally, from Figure 23 and Figure 24, we see that there are many nonmetropolitan counties (identified in Table 17 below) that do not have an ethanol production facility with corn grown frequently between 2008 and 2019.  For these reasons, it is more likely that a new ethanol production facility will be constructed in a nonmetropolitan county as opposed to a metropolitan county.

Finally, our analysis excludes any ozone nonattainment areas.  We are only proposing to approve the PSD portion of the SIP submittal and are not taking action on the NA NSR portion at this time.  We note that no currently permitted ethanol production facility exists in an ozone nonattainment area.  New ethanol production facilities that choose to construct in an ozone nonattainment area would evaluate their NOX and VOC emissions to determine NA NSR applicability, not PSD applicability.
To summarize our assumptions for this ozone analysis, we assume that a new ethanol production facility that emits 250 tpy of NOX and VOC will be located:

 Outside of ozone nonattainment areas,
 Where corn has been available at least once between 2008-2021,
 Within a nonmetropolitan county; and
 At least 15 km from an existing ethanol production facility.

Figure 28 maps these assumptions for the state of Wisconsin.

Figure 28: Wisconsin ozone nonattainment areas, metropolitan counties, and 15 km distance from existing ethanol sources.  Corn frequency and ozone monitors are also shown.

From Figure 28, we see that there are 46 counties with a historic record of corn being available between 2008 and 2021.  Although there are some counties that have an existing ethanol production facility, the 15 km buffer on its own does not exclude any entire county for further consideration.  To conservatively estimate the potential impact that a new ethanol production facility would have, nonmetropolitan counties with an existing ethanol production facility are included in the analysis.  Figure 29 highlights the counties where a new ethanol production facility could be constructed based on our assumptions.

Figure 29:  Wisconsin counties that could potentially support the construction of a new ethanol production facility.  Hypothetical sources are MERP hypothetical sources used to estimate ozone impacts.

In Figure 29, counties are categorized into 12 different groups for the purpose of determining representative ozone MERP hypothetical source impacts to be used in our analysis.  Counties that have the same representative background ozone monitor and representative hypothetical source are included in the same group for this analysis.  Representative ozone monitors were selected base on distance to each county, where the nearest ozone monitor for a given group of counties was selected.  When more than one ozone monitor could be considered representative based on distance, the monitor with the higher 2019-2021 ozone design value was selected to more conservatively represent the background ozone concentration for the group of counties.  Representative hypothetical source impacts were similarly selected because the nearest hypothetical source would have similar geography, meteorology, and atmospheric chemistry when compared to where a new ethanol production facility could be constructed in these counties.

Table 17 show the group of counties and the results of our representative background and hypothetical source analysis.  Each group of counties is assigned a group number for ease of reference within this document.  MERP hypothetical source impacts are taken from those calculated in Table 14 and Table 15.

                                     Group
                                   Counties
                              Background Monitor
                           MERP Hypothetical Source
                                       I
                     Barron, Burnett, Dunn, Polk, Washburn
                                  Eau Claire
                                  55-035-0014
                              0.062 ppm (62 ppb)
                                     Rusk
                                      II
                       Ashland, Bayfield, Iron, Sawyer 
                                  Perkinstown
                                  55-119-9991
                              0.059 ppm (59 ppb)
                                     Rusk
                                      III
                          Clark, Price, Rusk, Taylor
                                  Perkinstown
                                  55-119-9991
                              0.059 ppm (59 ppb)
                                     Rusk
                                      IV
                       Langlade, Lincoln, Oneida, Vilas
                                  Trout Lake
                               55-125-0001-0001
                              0.058 ppm (58 ppb)
                                    Shawano
                                       V
                          Forest, Florence, Marinette
                                  Potawatomi
                                  55-041-0007
                              0.059 ppm (59 ppb)
                                    Shawano
                                      VI
                                   Manitowoc
                                   Manitowoc
                                  55-071-0007
                              0.068 ppm (68 ppb)
                                    Shawano
                                      VII
                          Dodge, Jefferson, Walworth
                                   Walworth
                                  55-127-0006
                              0.068 ppm (68 ppb)
                                  Stephenson
                                     VIII
                 Buffalo, Jackson, Monroe, Pepin, Trempealeau
                                  Eau Claire
                                  55-035-0014
                              0.062 ppm (62 ppb)
                                     Rusk
                                      IX
                 Crawford, Grant, Lafayette, Richland, Vernon
                               Devils Lake Park
                                  55-111-0007
                              0.063 ppm (63 ppb)
                                  Stephenson
                                       X
                Adams, Green, Juneau, Marquette, Sauk, Waushara
                                   Columbus
                                  55-021-0015
                              0.064 ppm (64 ppb)
                                  Stephenson
                                      XI
                  Menominee, Portage, Shawano, Waupaca, Wood
                                   Appleton
                                  55-087-0009
                              0.062 ppm (62 ppb)
                                    Shawano
                                      XII
                                     Door
                                 Newport Park
                                  55-029-0004
                              0.070 ppm (70 ppb)
                                    Shawano
Table 17:  Counties evaluated to determine new ethanol plant impacts on ozone NAAQS.  Representative background monitors and MERP hypothetical source modeled impacts are also listed.  MERP nearfield impacts are maximum impacts within 50 km, while far(field) impacts are impacts beyond 50 km.

From Table 17, the highest ozone design value is 0.068 ppm, equivalent to 68 ppb.  The highest modeled near-field (i.e., within 50 km of the modeled hypothetical source) representative MERP hypothetical source impact is 0.913 ppb for a source emitting 250 tpy of NOX and 250 tpy of VOC.  Adding the highest ozone design value and the highest hypothetical source impact yields 68.912 ppb or 0.069 ppm, less than the level of the 2008 and 2015 ozone NAAQS.  Specific impacts for each group of counties are given in Table 18.

                                 County Group
                               Background (ppb)
                             Modeled Impact (ppb)
                              Ozone Concentration
                                       I
                                      62
                                     0.387
                            62.387 ppb (0.062 ppm)
                                      II
                                      59
                                     0.387
                            59.387 ppb (0.059 ppm)
                                      III
                                      59
                                     0.387
                            59.387 ppb (0.059 ppm)
                                      IV
                                      58
                                     0.758
                            58.758 ppb (0.0.59 ppm)
                                       V
                                      59
                                     0.758
                            59.758 ppb (0.059 ppm)
                                      VI
                                      68
                                     0.758
                            68.758 ppb (0.068 ppm)
                                      VII
                                      68
                                     0.913
                            68.913 ppb (0.068 ppm)
                                     VIII
                                      62
                                     0.387
                            62.387 ppb (0.062 ppm)
                                      IX
                                      63
                                     0.913
                            63.913 ppb (0.063 ppm)
                                       X
                                      64
                                     0.913
                            64.913 ppb (0.064 ppm)
                                      XI
                                      62
                                     0.758
                            62.758 ppb (0.063 ppm)
                                      XII
                                      70
                                     0.758
                            70.758 ppb (0.070 ppm)
Table 18:  Ozone impact of a new 250 tpy NOX and 250 tpy VOC source.

Results from Table 18 show that the highest modeled hypothetical source impact for a new ethanol production facility emitting up to 250 tpy of NOX and VOC is 0.913 ppb.  Except for Door County, the highest ozone impact, including both modeled MERP hypothetical source impacts and background design value concentration, is 0.068 ppm, below the level of the 2008 and 2015 ozone NAAQS.  At ozone monitors within each of the counties listed in Table 17, ozone design values have either decreased or remained steady below the level of the NAAQS.  Based on our analysis, future construction of a new ethanol production facility in any of the counties identified in Table 17 except for Door County would not interfere with attainment or maintenance of the NAAQS as a result of this SIP action.

Door County had previously been designated as nonattainment for the 2015 ozone NAAQS.  The Door County nonattainment area had also been designated as a Rural Transport Area (RTA) under §182(h) of the CAA.  Under §182(h)(2) the Administrator may treat an ozone nonattainment area as an RTA if the Administrator finds that sources of VOC and NOX emissions within the area do not make a significant contribution to the ozone concentrations measured in the area or in other areas.  Door County was recently redesignated to attainment for the 2015 ozone NAAQS, with the redesignation to attainment effective on April 29, 2022.  This redesignation was based on the quality assured and certified monitoring data for 2019-2021 showing that the area has met the requirements for redesignation under section 107(d)(3)(E) of the CAA.  Additionally, EPA has conducted air quality modeling of the Contiguous United States projecting ozone concentrations at all air quality monitors in 2023, 2026, and 2032.  This modeling indicates that EPA does not project Door County to be in nonattainment of the 2015 ozone NAAQS, nor does EPA expect the area to struggle with maintenance in those modeled future years.  In fact, these models project a steady decline in ozone design values over the next decade at the Door County monitor.  

From Table 18, we see that the predicted ozone concentration after construction of a new 250 tpy source of NOX and VOC in Door County would be 70.758 ppb.  In accordance with Section 3(e) of Appendix U to 40 CFR Part 50, when determining the 8-hour design value for ozone the 8-hour averages shall be reported "in ppm to three decimal places, with additional digits to the right of the third decimal place truncated."  The projection of 70.758 ppb is equal to 0.070758 ppm.  Following the Data Reporting and Handling Conventions in Appendix U, the projected design value after inclusion of a new 250 tpy source of NOX and VOC would be 0.070 ppm and would remain in compliance with the 2015 ozone NAAQS.  While this analysis does show continued NAAQS compliance, the projected increase in concentration from the hypothetical source is approaching a level of concern and further analysis is warranted in Door County.
 
Pursuant to 40 CFR 51.160 (a) and (b) an approvable state permitting program must include legally enforceable procedures that enable a state or local agency to determine whether the construction or modification of a facility will interfere with the attainment our maintenance of a NAAQS and procedures that would prevent such construction.  As noted previously, WDNR's minor NSR program was approved as meeting the requirements of 40 CFR 51.160 (a) and (b) on January 18, 1995.  Specifically, NR 406.08(2)(a) and s.285.61(8)(a) provide that Wisconsin may only issue a permit to construct after consideration of the environmental impact of a proposed project, and  Wisconsin Statute s.285.63(1)(b) states that WDNR may approve an application for a permit required under s.285.60, if WDNR finds that "the source will not cause or exacerbate a violation" of any ambient air quality standard or ambient air increment.  Therefore, even though the conservative estimate of ozone impacts for a hypothetical new 250 tpy ethanol production facility are approaching levels of concern, the approved minor NSR program in Wisconsin would require evaluation of impacts of any future projects prior to permit issuance and would prevent issuance if the project would result in a violation of the NAAQS.  In addition to the protections provided by the state's permitting rules, EPA also believes that based on corn availability in Door County, the estimated impact of 0.758 ppb is very conservative.  The following discussion provides what we believe is a more realistic expectation of impacts of a hypothetical new source at the Door County ozone monitor.

The above analysis conservatively assumes that if corn is present in a non-metropolitan county, the county is a potential site for a new ethanol production facility.  As discussed previously, ethanol production facilities are built to minimize transportation costs for primary inputs and distribution of coproducts to markets.  In section VI.3.B.v we estimated that corn must be grown on 133,869 to 267,738 acres to supply enough corn to produce between 60 million and 120 million gallons of ethanol.  All currently permitted ethanol production facilities in Wisconsin have a permitted capacity between 60 million gallons and 120 million gallons.  Table 19 shows the total acreage of corn grown in Door County each year between 2011 and 2021.

                                     Year
                                 Corn Acreage
                                     2011
                                    23454.6
                                     2012
                                    28644.9
                                     2013
                                    26463.2
                                     2014
                                    24828.8
                                     2015
                                    31801.0
                                     2016
                                    27060.5
                                     2017
                                    28663.1
                                     2018
                                    29376.3
                                     2019
                                    27278.0
                                     2020
                                    34211.6
                                     2021
                                    33011.1
Table 19:  Acreage of corn grown in Door County annually between 2011 and 2021.  Source: USDA National Agricultural Statistics Service.

The annual acreage of corn grown in Door County during the last ten years would meet approximately 25% of the resource needs of the smallest ethanol production facilities currently permitted in Wisconsin.  Furthermore, Door County is located on a peninsula, limiting access to resources from other areas.  Based on the limited resources within Door County, we would anticipate that a new ethanol production facility locating in Door County would be considerably smaller than the existing facilities in Wisconsin, potentially limited to a production capacity of 15 million gallons of ethanol per year.   When considering the permitted allowable emissions of existing ethanol production facilities within Wisconsin as provided in Table 2, it is reasonable to assume that a facility of this size would accept further limitation on allowable emissions to avoid Title V permitting requirements.  This would reduce the expected emissions from a new ethanol production facility locating in Door County to less than 100 tpy of NOX and VOC.  

The modeling analysis above also assumes that a new facility would be located within 10 km of an ozone monitor.  Figure 30 below shows the corn frequency data for Door County, the location of the Door County ozone monitor, and the location of state designated natural areas in Door County.

 
Figure 30:  Corn Frequency from 2008 to 2021 and state natural areas in Door County in relation to the Door County ozone monitor.

From this information, we see that a new ethanol production facility would likely locate somewhere between 20 km and 80 km from the Door County ozone monitor as there is better access to available resources from Door County and adjacent areas.  Table 20 below considers impacts between 10 km and 80 km from the Door County monitor for hypothetical sources of 100 tpy and 250 tpy of NOX and VOC. 

                              Hypothetical Source
                            NOX Ozone Impact (ppb)
                            VOC Ozone Impact (ppb)
                           Total Ozone Impact (ppb)
                                     10 km
                                    100 tpy
                                     0.281
                                     0.011
                                     0.292
                                       
                                    250 tpy
                                     0.703
                                     0.028
                                     0.731
                                     20 km
                                    100 tpy
                                     0.205
                                     0.010
                                     0.305
                                       
                                    250 tpy
                                     0.631
                                     0.026
                                     0.657
                                     40 km
                                    100 tpy
                                     0.150
                                     0.018
                                     0.168
                                       
                                    250 tpy
                                     0.376
                                     0.045
                                     0.421
                                     60 km
                                    100 tpy
                                     0.096
                                     0.009
                                     0.105
                                       
                                    250 tpy
                                     0.240
                                     0.023
                                     0.263
                                     80 km
                                    100 tpy
                                     0.083
                                     0.016
                                     0.099
                                       
                                    250 tpy
                                     0.207
                                     0.039
                                     0.246
Table 20:  Maximum 8-hour ozone impacts for 100 tpy and 250 tpy sources of NOX and VOC at 10 km, 20 km, 40 km, 60 km and 80 km from the Door County ozone monitor.

The projected impact from a 250 tpy source of NOX and VOC is 0.657 ppb at 20 km from the Door County monitor and is further reduced to 0.246 ppb at 80 km.  The projected impact from a 100 tpy source of NOX and VOC is 0.305 ppb at 20 km from the Door County monitor and is further reduced to 0.099 ppb at 80 km.  When taking resource constraints into consideration, we believe a 100 tpy source of NOX and VOC locating somewhere between 20 km and 80 km from the Door County monitor provides a more realistic estimation of potential impacts from the proposed rule change.  This results in projected 8-hour ozone concentrations between 0.070305 ppm and 0.070099 ppm.  Considering the modeled impacts and the anticipated continued decline in concentration at the Door County monitor, EPA concludes that the construction of a new ethanol production facility in Door County would not interfere with attainment or maintenance of the ozone NAAQS or other applicable requirements of the CAA in Door County.

As a result of our analysis, EPA concludes that potential construction of a new ethanol production facility following SIP approval would not interfere with attainment or maintenance of the ozone NAAQS or other applicable requirements of the CAA in Wisconsin.

VI.3.B.vii Ozone Impact of Modifications at Existing Ethanol Production Facilities

To evaluate the impact that the proposed SIP revision could have on modifications to existing sources following SIP approval, we assume that each currently permitted ethanol production facility increases its NOX and VOC emissions by 250 tpy.  Similar to evaluating the impact of new sources on the ozone NAAQS, we identify representative ambient monitoring for each source and representative MERP hypothetical source modeled impacts.  We use the same MERP hypothetical source modeled impacts calculated in Table 14.

                             Source Name (County)
                     Ozone Monitor 2018-2020 Design Value
                        MERP Hypothetical Source Impact
                              Total Ozone Impact
                                  Ace Ethanol
                              (Chippewa and Clark)
                                  Eau Claire
                                  55-035-0014
                              0.061 ppm (61 ppb)
                                     Rusk
                                   0.387 ppb
                                  61.387 ppb
                                  (0.062 ppm)
                             Badger State Ethanol
                                    (Green)
                                  Rock County
                                  55-105-0030
                              0.066 ppm (66 ppb)
                                  Stephenson
                                   0.913 ppb
                                  66.913 ppb
                                  (0.067 ppm)
                        Big River Resources Boyceville
                                    (Dunn)
                                  Eau Claire
                                  55-035-0014
                              0.061 ppm (61 ppb)
                                     Rusk
                                   0.387 ppb
                                  61.387 ppb
                                  (0.061 ppm)
                                Didion Milling
                                  (Columbia)
                                Columbia County
                                  55-021-0015
                              0.065 ppm (65 ppb)
                                  Stephenson
                                   0.913 ppb
                                  65.913 ppb
                                  (0.066 ppm)
                           Fox River Valley Ethanol
                                   (Oshkosh)
                                     Dodge
                                  55-027-0001
                              0.066 ppm (66 ppb)
                                    Shawano
                                   0.758 ppb
                                  66.758 ppb
                                  (0.067 ppm)
                         Marquis Energy  -  Wisconsin
                                   (Juneau)
                                  Sauk County
                                  55-111-0007
                              0.064 ppm (64 ppb)
                                     Rusk
                                   0.387 ppb
                                  64.387 ppb
                                  (0.064 ppm)
                                United Ethanol
                                    (Rock)
                                  Rock County
                                  55-105-0030
                              0.066 ppm (66 ppb)
                                  Stephenson
                                   0.913 ppb
                                  66.913 ppb
                                  (0.067 ppm)
                       United Wisconsin Grain Producers
                                  (Columbia)
                                Columbia County
                                  55-021-0015
                              0.065 ppm (65 ppb)
                                  Stephenson
                                   0.913 ppb
                                  65.913 ppb
                                  (0.066 ppm)
                            Valero Renewable Fuels
                                  (Jefferson)
                                Walworth County
                                  55-127-0006
                              0.068 ppm (68 ppb)
                                   Stepheson
                                   0.913 ppb
                                  68.913 ppb
                                  (0.069 ppm)
Table 21:  Estimated ozone impact of 250 tpy increase in NOX and VOC for currently permitted ethanol production facilities.  Calculated based on representative 2018-2020 design values and representative hypothetical source for currently permitted PSD nonmajor sources.

As shown in Table 3, several currently permitted ethanol production facilities will be nonmajor PSD sources if we approve the SIP.  As shown in Table 2, the permitted ethanol production facilities tend to emit to emit below the 250 tpy threshold.  Most currently permitted ethanol production facilities in Wisconsin have taken an enforceable limit on one or more pollutants to ensure the source remains nonmajor under PSD.  As discussed previously, Wisconsin has implemented the provisions of the 2007 Ethanol Rule since 2007, making it unlikely, as a result of this SIP revision, that an existing ethanol production facility would further modify the source to be considered a PSD major stationary source because the source would undertake a modification regardless of the SIP approval status.  Results from Table 21 show that minor modifications of up to 250 tpy of NOX and VOC at existing sources will not exceed the 2008 or 2015 NAAQS.  Particularly, the highest total ozone impact is shown to be 0.069 ppm.  Furthermore, ambient ozone design values have either decreased or remained steady below the NAAQS.

For these reasons, EPA concludes that minor modifications to permitted nonmajor ethanol production facilities that may occur after approval of this SIP revision will not interfere with the attainment or maintenance of the ozone NAAQS or other applicable requirements of the CAA.

VI.3.B.viii Assessment of Cumulative Ozone Impacts of Multiple Ethanol Production Facilities

To evaluate the potential cumulative impacts of multiple ethanol production facilities constructing near each other, EPA evaluated the spatial distribution of permitted ethanol production facilities in Wisconsin.  Figure 26 shows a 5 km, 20 km, and 30 km buffer around each permitted ethanol production facility in Wisconsin.  Two ethanol production facilities, Didion Milling and United Wisconsin Grain Producers in Columbia County are located within 5 km of each other.  Despite the proximity, ozone design values near the two sources trend downward and remain below the 2015 8-hour ozone NAAQS (See Figure 13).
As discussed in the MERPs Guidance, maximum daily 8-hour ozone impacts tend to be near the source and are less frequent as distance from the source increases.  Particularly, maximum 8-hour ozone impacts generally begin to drop off beyond 20 km from the source.  Beyond 50 km from the source, ozone impacts drop off considerably.

Ethanol production facilities in Wisconsin are generally located more than 30 km from each other (See section VI.3.B.v).  It is unlikely that new ethanol production facilities would be constructed near an existing ethanol production facility.  Because Wisconsin ethanol plants use corn as a feedstock, ethanol plants compete for corn on the market, increasing corn demand in the local area.  Higher corn demand increases corn prices, while local variation in corn prices influenced the siting of ethanol plants, with the effect diminishing to zero once the distance between the corn market and ethanol reaches 103 miles (165 km).  This suggests that the optimal placement of ethanol production facilities is beyond 103 miles from another ethanol production facility, meaning that ethanol production facilities would try to minimize costs by maximizing the distance from other ethanol plants.  As a result, additional ethanol production facilities are unlikely to be constructed near an existing or proposed new ethanol production facility, making it unlikely that clusters of new ethanol production facilities would be constructed as a result of this SIP revision.

VI.3.B.ix SIP Revision Will Not Interfere with Ozone NAAQS, Reasonable Further Progress, or Applicable Requirements

As evaluated above in section VI.3.B.i-viii, construction of new sources may result in increased ambient ozone concentrations.  However, total ozone concentrations would remain below 0.070 ppm, the level of the 2015 ozone NAAQS.  Minor modifications to existing ethanol production facilities may also result in increased ambient ozone concentrations with total ozone concentrations below 0.070 ppm.  The construction of multiple ethanol production facilities in close proximity to each other is unlikely because ethanol production facilities are sited to minimize corn input costs and, for Wisconsin in particular, tend to be located more than 30 km from each other (see section VI.3.B.v).  Ozone design values from representative ambient monitors identified in Table 17 have remained steady or decreased since 2008.

Based on our analysis, we conclude that the construction of a new 250 tpy NOX and VOC ethanol production facility or minor modification of a permitted ethanol production facility under the proposed SIP revision will not interfere with attaining the 2008 or 2015 ozone NAAQS, reasonable further progress, or other applicable CAA requirements as required by CAA Section 110(l).

VI.3.C New and Modified Source of PM2.5 Impacts

Secondary PM2.5 impacts are determined similarly to ozone utilizing MERP hypothetical source modeled impacts.  The three hypothetical sources in Wisconsin are again reviewed based on a surface level release and 500 tpy NOX and SO2 emission rate.  Increased emissions of NOX and SO2 are assumed to be 250 tpy each to determine the maximum potential secondary PM2.5 impact.  24-hour and annual PM2.5 hypothetical source impacts are given in table 22 and 23.

                         Hypothetical Source by County
                                   Pollutant
                     Max Concentration 24-hour (ug/m[3])
                                     Rusk
                                      NOX
                                     0.083
                                       
                                      SO2
                                     0.277
                                    Shawano
                                      NOX
                                     0.141
                                       
                                      SO2
                                     0.754
                                  Stephenson
                                      NOX
                                     0.153
                                       
                                      SO2
                                     0.592
Table 22:  24-hour PM2.5 -  hypothetical source impacts.  Assumes a surface level release and 500 tpy emission rate per precursor pollutant.
                         Hypothetical Source by County
                                   Pollutant
                     Max Concentration 24-hour (ug/m[3])
                                     Rusk
                                      NOX
                                     0.005
                                       
                                      SO2
                                     0.008
                                    Shawano
                                      NOX
                                     0.010
                                       
                                      SO2
                                     0.014
                                  Stephenson
                                      NOX
                                     0.009
                                       
                                      SO2
                                     0.014
Table 23:  Annual PM2.5 hypothetical source impacts.  Assumes a surface level release and 500 tpy emission rate per precursor pollutant.

Estimated impacts for a 250 tpy NOX and SO - 2 source are given in Table 24 and Table 25.  We similarly scale MERP hypothetical source modeled impacts to 250 tpy emission rate as suggested in the MERP Guidance and as conducted for the previous ozone analysis.  NOX and SO2 MERP hypothetical source impacts are then added together to get the total estimated secondary PM2.5 impact.

                              Hypothetical Source
                      NOX 24-hour PM2.5 Impact (ug/m[3])
                      SO2 24-hour PM2.5 Impact (ug/m[3])
                     Total 24-hour PM2.5 Impact (ug/m[3])
                                     Rusk
                                     0.042
                                     0.139
                                     0.181
                                    Shawano
                                     0.071
                                     0.377
                                     0.448
                                  Stephenson
                                     0.077
                                     0.296
                                     0.373
Table 24: 24-hour PM2.5 source impacts assuming a 250 tpy surface level release of each precursor pollutant.

                              Hypothetical Source
                      NOX Annual PM2.5 Impact (ug/m[3])
                      SO2 Annual PM2.5 Impact (ug/m[3])
                     Total Annual PM2.5 Impact (ug/m[3])
                                     Rusk
                                     0.003
                                     0.004
                                     0.007
                                    Shawano
                                     0.005
                                     0.007
                                     0.012
                                  Stephenson
                                     0.005
                                     0.007
                                     0.012
Table 25:  Annual PM2.5 source impacts assuming a 250 tpy surface level release of each precursor pollutant.

The Shawano County MERP hypothetical source has the highest secondary PM2.5 impact for both the 24-hour and annual PM2.5 NAAQS in Wisconsin.  Based on the Shawano County hypothetical source modeled impacts, the highest secondary PM2.5 impact a new minor source could potentially have is 0.448 ug/m3 on a 24-hour basis and 0.012 ug/m3 on an annual basis.  The highest 2018-2020 24-hour PM2.5 design value in Wisconsin is 22 ug/m[3], well below the 24-hour PM2.5 NAAQS of 35 ug/m[3].  The highest 2018-2020 annual PM2.5 design value in Wisconsin is 9.0 ug/m[3], below the annual PM2.5 primary NAAQS of 12 ug/m[3].  For both averaging times, there is enough room between the PM2.5 NAAQS and the sum of monitored background and peak secondary PM2.5 impacts to accommodate the direct PM2.5 impact of a new or modified ethanol production facility.  Further evidence of this is demonstrated by the trend in monitored PM2.5 values.  Figure 17 and Figure 18 show that PM2.5 design values are trending lower at all monitors across the state.

Similar to ozone, PM2.5 impacts from clustered ethanol production facilities are unlikely to have a significant impact.  As discussed as part of the ozone impact analysis in section VI.3.B.viii, we note that multiple ethanol production facilities will not construct within 30 km of each other because increased competition for resources raises the price of corn.  Because Wisconsin has been developing its ethano industry since 2007, the location of permitted facilities shown in Figure 26 further demonstrates that multiple ethanol production facilities will not construct near each other.  While secondary impacts may affect downwind PM2.5 concentrations, direct impacts will likely remain within 30 km of the source since direct impacts are dispersed based on stack height, stack temperature, and stack velocity.

Ambient PM2.5 design values remain below the level of the NAAQS, design values continue to trend downward even while existing ethanol production facilities continue to operate, and it is unlikely that minor ethano production facilities will construct near each other.  For these reasons, we conclude that the proposed SIP revision will not interfere with the PM2.5 NAAQS, reasonable further progress, or other applicable CAA requirements.

VI.3.D New and Modified Source SO2 Impacts

Allowable SO2 emissions from permitted ethanol production facilities are well below the 250 tpy PSD major source threshold.  As shown in Table 2, allowable emissions are below 100 tpy for all permitted ethanol production facilities in Wisconsin.  This suggests that new or modified ethanol production facilities are unlikely to emit up to 250 tpy of SO2 per year.

From Table 5, the highest reported 2020 actual emissions was 7.9 tons.  As a percentage of total emissions, the 2017 NEI show that permitted ethanol production facility actual emissions is less than 0.1% of statewide point source emissions (see Table 7).  2020 ethanol production facility actual emissions are less than 0.2% of 2020 statewide stationary source actual emissions.

As shown in Figure 20, SO2 design values are trending downward across the state of Wisconsin with 2018-2020 design values below the level of the 1-hour SO2 NAAQS.  Construction of a new ethanol production facility or modification of an existing ethanol production facility is unlikely to significantly contribute to SO2 emissions in any given area within the state.  As a result, the construction of a new ethanol production facility or modification of an existing ethanol production facility is unlikely to interfere with attainment or maintenance of the SO2 -  NAAQS or reasonable further progress.

VI.3.E New and Modified Source NO2 Impacts

Currently permitted ethanol production facilities in Wisconsin have allowable emission limits of less than 200 tpy of NOX (see Table 2).  From Table 5, the highest 2020 actual emissions of NOX was 101.2 tpy.  As a percentage of total statewide NOX emissions, 2020 ethanol production facility actual NOX emissions account for 1.5% of actual emissions (see Table 6).  2020 actual emissions accounted for 1.0 of statewide point source NOX emissions in the 2017 NEI (see Table 8).  Currently permitted ethanol production facilities account for a small portion of NOX emissions in the state.  It is likely that any new ethanol production facility in the state will have NOX emissions that are similar to currently permitted ethanol production facilities.  As a result, NOX emissions will not increase substantially.

As state above in section III.3, Wisconsin has been implementing the 2007 Ethanol Rule since 2007.  Since that time, most permitted ethanol production facilities in Wisconsin constructed and began operation.  However, from Figure 10 and Figure 11, 1-hour and annual NO2 design values at all ambient monitors in the state have steadily remained well below the 1-hour and annual NO2 NAAQS.  This includes representative ambient NO2 monitors that are sited downwind of currently permitted ethanol production facilities (see Figure 9).  None of the monitors have shown a NAAQS violation.

Since NO2 design values have historically remained steady below the 1-hour and annual NO2 NAAQS, and NO2 emissions from ethanol production facilities are a small fraction of total NO2 emissions, EPA concludes that approval of the SIP will not interfere with attainment or maintenance of the 1-hour or annual NO2 NAAQS.

VI.3.F New and Modified Source CO Impacts

Currently permitted ethanol production facilities emit less than 200 tpy of CO (see Table 2).  From Table 5, the highest 2020 actual CO emissions is 59.5 tpy.  As a percentage of total statewide CO emissions, ethanol production facility emissions account for 1.5% of stationary source emissions (see Table 6).  2020 actual emissions from ethanol production facilities were less than 1% of statewide point source CO emissions in the 2017 NEI (see Table 7).  From this, we observe that currently permitted ethanol production facilities account for a small portion of CO emissions in the state.  It is likely that any new ethanol production facility in the state will have CO emissions that are similar to permitted ethanol production facilities.  As a result, ethanol production facility CO emissions are unlikely to increase as a result of this SIP approval.

Since 2007, most permitted ethanol production facilities constructed and began operation.  However, from Figure 7 and Figure 8, 1-hour and 8-hour CO design values at all ambient monitors in the state have steadily remained well below the 1-hour and 8-hour CO NAAQS between 2008 and 2020.  This includes representative ambient CO monitors that are sited downwind of currently permitted ethanol production facilities (see Figure 6).  None of the monitors have shown a CO NAAQS violation.

Since CO design values have historically remained below the 1-hour and 8-hour CO NAAQS and ethanol production facility CO emissions are a small fraction of total CO emissions, EPA concludes that approval of this SIP revision will not interfere with attainment or maintenance of the 1-hour or 8-hour CO NAAQS, reasonable further progress, or applicable CAA requirements.

VII. Conclusion
EPA is proposing to approve revised requirements NR 405.02(22)(a)1 and NR 405.07(4)(a)(22)20 into Wisconsin's SIP.  This SIP revision revises the PSD definition of major stationary source to exclude ethanol production facilities that produce ethanol by natural fermentation from the chemical process plant source category.  The proposed revision is consistent with the Federal PSD definition of major stationary source at 40 CFR 51.166(b)(1)(i)(a).  Based on our analysis of statewide emission inventories, design value trends, factors affecting the location of ethanol production facilities, and secondary impacts, EPA concludes that the revision to Wisconsin's SIP does not interfere with any applicable requirement concerning attainment and reasonable further progress, or any other applicable requirement of the CAA as required by CAA Section 110(l).  EPA is taking no action with respect to the NA NSR revision at NR 408.

Wisconsin adopted the revision on July 31, 2008.  Although adopted in 2008, Wisconsin has implemented the revised language since 2007.  Ethanol production in Wisconsin has increased since 2007, as shown in Figure 4.  Emissions from permitted ethanol production facilities make up approximately 3.2% of statewide PM10 emissions and less than 2% of all other criteria pollutants in the Wisconsin emissions inventory (see Table 6).  In general, air quality for each monitored criteria pollutant has improved since 2007.  Although Wisconsin has ozone nonattainment areas, existing ethanol production facilities are unlikely to construct in a nonattainment area (see Section VI.3.A, B and D, above).  Based on our analysis of future impacts in Section VI.3.A through F above, approval of this SIP revision will not interfere with attainment or maintenance of the NAAQS for all criteria pollutants or other applicable requirements as required by CAA Section 110(l).

Secondary impacts from future ethanol production facilities at the revised potential major source threshold of 250 tpy of NOX, VOC, and SO2 would not cause or contribute to a violation of the NAAQS for ozone or PM2.5 (see Section VI.3.B and C, above).  Since ethanol production facilities tend to be located more than 30 km from each other, it is not likely that multiple ethanol production facilities would locate close together (see Section VI.3.B.viii), supporting the conclusion that cumulative impacts of multiple ethanol production facilities would not interfere with NAAQS attainment or maintenance, reasonable further progress, or other applicable requirements as required by CAA Section 110(l).

Although the proposed revision would exclude ethanol production facilities form the chemical process plant source category, ethanol production facilities affected by the SIP revision will remain subject to NSPA and NESHAP requirements.  All existing ethanol production facilities are Title V or FESOP sources, ensuring that each source has monitoring, recordkeeping, and reporting requirements sufficient to determine compliance with all applicable requirements.  Future construction of new minor ethanol production facilities or minor modifications to exiting ethanol production facilities would still be subject ot minor NSR at NR 406 as required by CAA Section 110(a)(2)(c).  This ensures that such ethanol production facilities will not increase emissions without an evaluation of necessary emissions controls to prevent interference with maintenance and attainment for the NAAQS.  Since the revision only revises the definition of major stationary source under PSD, all other requirements remain unaffected by this approval.