1020-00004 · Greenfield Agricultural Partners · Air Permit

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CALDERWOOD & HARKNESS LLP Attorneys at Law

801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 244-7800 Facsimile: (515) 244-7801 www.calderwoodharkness.com

July 28, 2023

Jonathan Kreske, P.E. Environmental Engineer, Air Quality Bureau Iowa Department of Natural Resources 502 East 9th Street Des Moines, Iowa 50319

Re: Greenfield Agricultural Partners LLC — Response to Public Comments of Heartland Environmental Alliance on Draft PSD Construction Permit No. 23-A-0481 for the Muscatine Expansion Facility, 14800 Highway 61 North, Muscatine, Iowa 52761

C&H Matter No. 1020-00004

Dear Mr. Kreske:

Calderwood & Harkness LLP represents Greenfield Agricultural Partners LLC ("GAP"), an Iowa limited liability company organized under Chapter 489 of the Iowa Code, in connection with GAP's application for a Prevention of Significant Deterioration ("PSD") Construction Permit for the Muscatine Expansion Facility (the "MEF" or the "Facility"), a soybean processing and specialty fertilizer blending facility to be constructed on a 147-acre greenfield site located at 14800 Highway 61 North, in Muscatine County, Iowa 52761. As you are aware, GAP filed its PSD application with the Iowa Department of Natural Resources ("IDNR") Air Quality Bureau ("AQB") on April 28, 2023. AQB issued a completeness determination on May 19, 2023, confirming that the application contained all information necessary for substantive review under Iowa Administrative Code ("IAC") 567—Chapter 33 and the federal PSD regulations codified at 40 C.F.R. § 52.21.

Pursuant to IAC 567—33.3(455B), AQB published public notice of the draft PSD Construction Permit on June 12, 2023. The thirty-day public comment period ran from June 12, 2023, through July 12, 2023. During that period, AQB received a total of four written comments: two from neighboring landowners expressing general concerns regarding particulate matter and odor, one from the Muscatine County Soil & Water Conservation District requesting clarification on stormwater management controls (which relate primarily to GAP's forthcoming National Pollutant Discharge Elimination System permit application rather than the PSD permit at issue), and one from the Heartland Environmental Alliance ("HEA"), an unincorporated non-profit association based in Iowa City, Iowa. HEA's comment letter, dated July 11, 2023, raises three principal assertions concerning the adequacy of the Best Available Control Technology ("BACT") analyses for nitrogen oxides ("NOx") and fine particulate matter ("PM2.5"), as well as a request that IDNR convene a public hearing on the draft permit.

This letter provides GAP's written responses to each of HEA's three comments for inclusion in the IDNR's responsiveness summary, as contemplated by IAC 567—33.3(455B) and 40 C.F.R. § 52.21(q). Calderwood & Harkness submits these responses in coordination with GAP's Director of Environmental, Health & Safety, Derek Yun, and with supporting technical input from Pinnacle Environmental Consultants Inc. ("Pinnacle"), GAP's environmental consultant. Pinnacle's Air Quality Practice, under the direction of Dr. Leonard Fisk, P.E., prepared the emissions inventories, BACT analyses, and air dispersion modeling that support the PSD application and draft permit. Dr. Fisk has reviewed and concurs with the technical representations contained in this letter.

I. Summary of HEA Comments

Before addressing each comment in detail, we provide a brief catalog of the three principal assertions contained in HEA's July 11, 2023, comment letter:

Comment 1 — NOx BACT. HEA asserts that the BACT analysis for NOx emissions from the MEF is "inadequate" and that "more stringent controls should be required" for the Facility's natural gas-fired combustion units. HEA contends, in general terms, that the proposed emission limits do not reflect the maximum degree of reduction achievable and that additional post-combustion controls such as selective catalytic reduction ("SCR") should be mandated.

Comment 2 — PM2.5 BACT. HEA asserts that the BACT analysis for PM2.5 emissions is "deficient" and "fails to consider all available control options" for particulate-emitting sources at the MEF. HEA does not identify any specific control technology or emission rate that it contends was omitted from the analysis, but states broadly that the evaluation was incomplete.

Comment 3 — Request for Public Hearing. HEA requests that IDNR hold a public hearing on the draft PSD permit, alleging that there exists "significant public interest" in the proposed Facility and that the existing permit record is "inadequate" to address community concerns.

Each of these comments is addressed in turn below.

II. Response to HEA Comment on NOx BACT Analysis

II.A. Overview of NOx Emissions and Proposed BACT

The MEF's aggregate potential to emit ("PTE") for NOx, calculated across all emission units at maximum design capacity and assuming year-round operation (8,760 hours per year) without voluntary limits, is 312 tons per year ("tpy"). This PTE exceeds the 250 tpy major-source threshold applicable to unnamed source categories under 40 C.F.R. § 52.21(b)(1)(i)(b), thereby triggering PSD review for NOx and all other pollutants for which the Facility's net emissions increase exceeds the applicable significance levels.

The primary sources of NOx emissions at the MEF are the Facility's natural gas-fired combustion units, which are identified in the application as follows:

• EU-01: A 120 MMBtu/hr natural gas-fired process heater used to supply thermal energy to the soybean extraction process. EU-01 is the single largest NOx emission unit at the Facility, with a PTE of approximately 149 tpy of NOx at uncontrolled emission factors.

• EU-02: An 80 MMBtu/hr natural gas-fired soybean dryer used to reduce moisture content in processed soybean meal prior to storage and shipment. EU-02 operates in an intermittent-load profile, cycling between full load and reduced load depending on feedstock moisture content and production scheduling. EU-02 has an uncontrolled NOx PTE of approximately 99 tpy.

• EU-03: A 60 MMBtu/hr natural gas-fired fertilizer granulation dryer used in the specialty fertilizer blending line. EU-03 has an uncontrolled NOx PTE of approximately 45 tpy.

• EU-05: A 2,000 kW emergency diesel generator, limited by a federally enforceable permit condition to no more than 500 hours per year of operation. EU-05 contributes a relatively minor portion of the Facility's total NOx PTE (approximately 19 tpy).

For EU-01 and EU-02, GAP proposes to install low-NOx burners equipped with flue gas recirculation ("FGR") as BACT for NOx. These burners are designed to reduce peak flame temperatures and limit thermal NOx formation by recirculating a portion of the flue gas back into the combustion zone. The proposed emission limit for EU-01 and EU-02 is 0.036 lb NOx per MMBtu of heat input, on a three-hour rolling average basis, demonstrated through initial stack testing and subsequent periodic testing at intervals specified in the draft permit. EU-03 will employ low-NOx burners (without FGR) to achieve an emission limit of 0.05 lb/MMBtu, consistent with the somewhat smaller scale and different operating profile of that unit. EU-05, as a compression-ignition emergency engine, is subject to the emission standards and operational limitations set forth in 40 C.F.R. Part 60, Subpart IIII, and BACT for that unit is compliance with those standards in conjunction with the 500-hour annual operating limitation.

At the proposed controlled emission rates, the MEF's aggregate facility-wide NOx PTE is reduced from 312 tpy (uncontrolled) to approximately 98 tpy (controlled), representing an overall reduction of approximately 68.6 percent.

II.B. RACT/BACT/LAER Clearinghouse Review

GAP's BACT analysis for NOx was prepared by Pinnacle in accordance with the EPA's well-established top-down BACT methodology, as described in the New Source Review Workshop Manual (Draft, October 1990) and as required under 40 C.F.R. § 52.21(b)(12). The top-down approach requires the applicant to proceed through five sequential analytical steps:

Step 1 — Identify All Available Control Technologies. In this step, Pinnacle identified all potentially available NOx control technologies for natural gas-fired combustion sources in the size range of EU-01, EU-02, and EU-03. The technologies identified included:

(a) Selective catalytic reduction ("SCR"), which uses a catalyst bed and an ammonia or urea reagent to reduce NOx to nitrogen and water in the post-combustion flue gas stream;

(b) Selective non-catalytic reduction ("SNCR"), which injects ammonia or urea into the flue gas stream at elevated temperatures (approximately 1,600–2,100°F) without the use of a catalyst;

(c) Low-NOx burners with flue gas recirculation ("LNB+FGR"), which reduce thermal NOx formation by lowering peak flame temperatures and diluting the combustion zone with recirculated flue gas;

(d) Ultra-low-NOx burners ("ULNB"), which employ staged-combustion or pre-mix designs to further reduce NOx formation below the levels achievable with conventional low-NOx burners; and

(e) Combustion tuning and good combustion practices ("GCP"), which represent the baseline level of NOx control achievable through proper burner adjustment and maintenance.

Step 2 — Eliminate Technically Infeasible Options. SCR was evaluated for technical feasibility. While SCR is a well-demonstrated technology on large utility boilers and certain industrial process heaters operating at steady-state conditions, its application to intermittent-load drying operations such as EU-02 and EU-03 presents significant technical challenges. Specifically, SCR catalysts require a minimum sustained operating temperature (typically 480–800°F depending on catalyst formulation) to achieve the design NOx reduction efficiency. The intermittent-load operating profile of soybean dryers, which cycle between full load and reduced throughput based on incoming feedstock moisture levels and production scheduling, results in flue gas temperature excursions below the catalyst activation threshold. Operation of the SCR system outside its effective temperature window not only eliminates the NOx reduction benefit but also results in unreacted ammonia emissions ("ammonia slip"), a secondary pollutant with its own health and environmental impacts. SNCR was similarly evaluated and found to present temperature-window limitations for units in this size and application category.

For EU-01, the 120 MMBtu/hr process heater, SCR is technically feasible in the narrow sense that it could be physically installed and operated during steady-state conditions. However, SCR was carried forward to the economic and collateral impacts analysis in Steps 3 and 4 rather than eliminated at Step 2.

Ultra-low-NOx burners were evaluated and determined to be technically feasible for EU-01 and EU-02 but were not demonstrated to achieve meaningfully lower emission rates than LNB+FGR in the specific combustion configuration and fuel type (natural gas) proposed for the MEF.

Step 3 — Rank Remaining Control Technologies by Effectiveness. The remaining technically feasible control technologies were ranked in descending order of control effectiveness as follows: (1) SCR (for EU-01 only), achieving approximately 0.008–0.015 lb/MMBtu; (2) LNB+FGR, achieving approximately 0.02–0.04 lb/MMBtu; (3) ULNB, achieving approximately 0.03–0.05 lb/MMBtu; and (4) GCP, achieving approximately 0.10–0.15 lb/MMBtu.

Step 4 — Evaluate Economic, Energy, and Environmental Impacts. For EU-01, the incremental cost-effectiveness of SCR over LNB+FGR was calculated at approximately $18,700 per ton of NOx removed, based on annualized capital, operating, maintenance, and catalyst replacement costs, offset against the incremental NOx reduction of approximately 8.4 tpy beyond what LNB+FGR achieves alone. This cost-effectiveness figure substantially exceeds the range typically considered reasonable for BACT determinations for this source category. EPA guidance and BACT precedent generally treat cost-effectiveness values exceeding approximately $5,000–$10,000 per ton as indicative of disproportionate cost for industrial combustion sources, although no bright-line threshold exists and the analysis is inherently case-specific. In addition, the environmental collateral impacts of SCR — including ammonia slip (estimated at 5–10 ppm at the stack under normal operating conditions), the generation of spent catalyst waste requiring disposal as a hazardous or special waste, and increased energy consumption associated with the induced-draft fan pressure drop across the catalyst bed — further support the elimination of SCR as BACT for EU-01.

For EU-02 and EU-03, SCR was eliminated at Step 2 for technical infeasibility reasons, as discussed above. LNB+FGR was therefore identified as the top-ranked control technology for EU-02, and LNB was identified as BACT for EU-03.

Step 5 — Select BACT. Based on the foregoing analysis, Pinnacle selected LNB+FGR at an emission limit of 0.036 lb/MMBtu as BACT for NOx for EU-01 and EU-02, and LNB at an emission limit of 0.05 lb/MMBtu as BACT for EU-03.

A thorough review of the EPA RACT/BACT/LAER Clearinghouse ("RBLC") database was conducted as part of Step 1 to identify NOx BACT determinations for comparable natural gas combustion sources in the agricultural processing sector. The RBLC search was performed using the following parameters: source category codes for external combustion — natural gas; heat input capacity range of 50–200 MMBtu/hr; permit issuance dates within the preceding five years (2018–2023); and geographic scope of all states. The search returned twenty-three entries for comparable sources. Of these, the NOx emission limits ranged from 0.02 lb/MMBtu (for a large refinery process heater with SCR, a source with materially different operating characteristics and economic scale than the MEF) to 0.10 lb/MMBtu (for a smaller agricultural dryer with GCP only). The median NOx emission rate for comparable natural gas-fired process heaters and dryers in the agricultural processing sector was 0.04 lb/MMBtu. The RBLC results confirm that the proposed emission limit of 0.036 lb/MMBtu for EU-01 and EU-02 represents a level of control at or more stringent than the median BACT determination for this source and application category. A summary table of the relevant RBLC entries is provided as Enclosure 1 to this letter.

II.C. Comparable Recent PSD Permits

In addition to the RBLC review, GAP and Pinnacle identified the following three recent PSD permit determinations by Midwest state agencies for soybean processing and agricultural drying facilities that are directly comparable to the MEF and that established BACT for NOx at emission rates consistent with or less stringent than the 0.036 lb/MMBtu limit proposed by GAP:

1. Illinois EPA, PSD Permit No. 178230096, Decatur Soy Products LLC, Macon County, Illinois (issued March 14, 2022). This permit authorized construction of a 3,500 tpd soybean crush facility with a 100 MMBtu/hr natural gas-fired process heater and a 75 MMBtu/hr natural gas-fired dryer. BACT for NOx was established at 0.04 lb/MMBtu using low-NOx burners with flue gas recirculation. SCR was evaluated and eliminated based on cost-effectiveness ($16,200/ton) and ammonia slip concerns.

2. Minnesota Pollution Control Agency, Air Emission Permit No. 04900475-101, Prairie Grain Processors Inc., Blue Earth County, Minnesota (issued August 3, 2021). This permit authorized a 2,800 tpd soybean processing and biodiesel feedstock facility. The primary combustion source was an 85 MMBtu/hr natural gas-fired process heater. BACT for NOx was established at 0.036 lb/MMBtu using low-NOx burners with FGR. The MPCA's technical support document specifically noted that SCR was not cost-effective for agricultural combustion sources at this scale.

3. Indiana Department of Environmental Management, PSD Permit No. T159-42177-00060, Hoosier Agri-Processing LLC, Vigo County, Indiana (issued January 19, 2023). This permit authorized a soybean extraction and meal drying facility with two natural gas-fired dryers rated at 90 MMBtu/hr and 60 MMBtu/hr, respectively. BACT for NOx was established at 0.05 lb/MMBtu using low-NOx burners without FGR. The IDEM permit record indicated that FGR was evaluated but not required due to the smaller scale and intermittent operation of the dryers, and that SCR was eliminated based on cost-effectiveness ($21,400/ton).

These precedents demonstrate that GAP's proposed NOx emission limit of 0.036 lb/MMBtu for EU-01 and EU-02 is at or below the emission rates accepted as BACT in the most recent comparable PSD determinations for soybean processing and agricultural drying facilities in the Midwest. Indeed, the GAP proposal is as stringent as or more stringent than each of the three cited precedents. HEA's assertion that "more stringent controls should be required" is unsupported by either the RBLC record or recent BACT determinations for this source category.

II.D. Conclusion on NOx BACT

For the reasons set forth above, the proposed NOx emission limit of 0.036 lb/MMBtu, achieved through the installation and operation of low-NOx burners with flue gas recirculation on EU-01 and EU-02, represents BACT under the top-down methodology prescribed by 40 C.F.R. § 52.21(b)(12). The analysis is thoroughly documented in Section 5.2 of Pinnacle's BACT Analysis Report (Appendix D to the PSD Application), is supported by a comprehensive RBLC review and by three directly comparable recent Midwest PSD permits, and is confirmed by Pinnacle's professional engineering judgment.

HEA's comment does not identify any specific control technology that would achieve lower NOx emissions at a reasonable cost, nor does it cite any comparable permit requiring emission limits more stringent than those proposed by GAP. The comment is general in nature and does not present any technical evidence, cost data, or RBLC entries that would call into question the adequacy of GAP's NOx BACT determination.

GAP respectfully requests that IDNR confirm the proposed NOx BACT determination and retain the emission limits of 0.036 lb/MMBtu for EU-01 and EU-02 and 0.05 lb/MMBtu for EU-03 in the final PSD Construction Permit.

III. Response to HEA Comment on PM2.5 BACT Analysis

III.A. Overview of PM2.5 Emissions and Proposed BACT

The MEF's aggregate potential to emit for PM2.5 (filterable plus condensable) is 87 tpy, and the aggregate PTE for PM10 is 196 tpy. Both values include contributions from combustion sources, material handling and storage operations, and cooling tower drift. The primary sources of particulate emissions at the Facility, as identified in the PSD application, are as follows:

• EU-04 (Material Handling and Storage Operations): EU-04 encompasses all grain receiving, storage, handling, and loadout operations associated with the soybean processing line, as well as fertilizer blending, storage, and loadout operations. Specific emission points within EU-04 include the truck receiving pit, bucket elevators (three units), enclosed belt conveyors (six units), soybean storage silos (four silos, 150,000 bushels each), fertilizer blending bins, and the fertilizer truck loadout spout. These operations generate particulate matter through the mechanical handling, transfer, and free-fall loading of granular materials. EU-04 is the dominant source of particulate emissions at the Facility, contributing approximately 128 tpy of PM10 and 51 tpy of PM2.5 at uncontrolled emission rates.

• EU-01, EU-02, and EU-03 (Combustion Sources): The three natural gas-fired combustion units generate particulate matter as a byproduct of combustion. However, because natural gas is an inherently low-PM fuel, the combustion-source contribution to total particulate emissions is relatively minor. Combined, EU-01, EU-02, and EU-03 contribute approximately 18 tpy of PM10 and 12 tpy of PM2.5.

• EU-06 (Cooling Towers): EU-06 consists of two induced-draft, counterflow cooling tower cells with a combined circulating water flow rate of 18,000 gallons per minute ("gpm"). The cooling towers serve the soybean extraction process. Particulate matter emissions from cooling towers result from the entrainment and release of water droplets containing dissolved solids ("drift") into the atmosphere. At the design circulating water total dissolved solids ("TDS") concentration of 2,500 mg/L, and at the proposed drift rate, EU-06 contributes approximately 5.6 tpy of PM10 and 5.6 tpy of PM2.5.

GAP proposes the following BACT determinations for particulate matter:

EU-04 — Baghouse Filters: All material handling and transfer points within EU-04 will be enclosed and vented to pulse-jet baghouse filter systems. The proposed emission limit is a PM outlet grain loading concentration of 0.005 grains per dry standard cubic foot ("gr/dscf"), corresponding to an overall control efficiency of 99.5 percent. This emission limit will be demonstrated through initial compliance testing using EPA Reference Methods 5 and 201A and will be maintained through a baghouse operation and maintenance plan, including continuous monitoring of pressure drop across the filter media and a bag leak detection system.

EU-06 — High-Efficiency Drift Eliminators: The two cooling tower cells will be equipped with high-efficiency drift eliminators designed to achieve a maximum drift rate of 0.0005 percent of the circulating water flow rate. This drift rate is consistent with the performance specifications of modern blade-type drift eliminators as described in the Cooling Technology Institute's Standard CTI-140, and represents the lowest drift rate commercially achievable for cooling towers of this type and scale.

EU-01, EU-02, EU-03 — Inherently Low-PM Fuel and Good Combustion Practices: For the natural gas-fired combustion units, BACT for particulate matter is the exclusive use of pipeline-quality natural gas as fuel, which has a negligible ash content, combined with good combustion practices. These control measures result in PM emission factors consistent with AP-42, Section 1.4, Table 1.4-2, for natural gas combustion without add-on particulate controls.

At the proposed controlled emission rates, the MEF's aggregate facility-wide PM10 PTE is reduced from 196 tpy (uncontrolled) to approximately 43 tpy (controlled), and the aggregate PM2.5 PTE is reduced from 87 tpy (uncontrolled) to approximately 24 tpy (controlled).

III.B. Adequacy of Control Technology Evaluation

Pinnacle's top-down BACT analysis for PM2.5 and PM10 evaluated all available particulate matter control technologies for each emission unit category, consistent with the five-step methodology described in Section II.B above. The technologies identified and evaluated for EU-04 (material handling and storage) included:

(a) Baghouse/fabric filters (pulse-jet type), achieving outlet concentrations of 0.002–0.01 gr/dscf and control efficiencies of 99–99.9 percent;

(b) Cyclone separators (mechanical collectors), achieving control efficiencies of approximately 80–95 percent for PM10 and 30–70 percent for PM2.5;

(c) Electrostatic precipitators ("ESPs"), achieving control efficiencies of 95–99.5 percent, typically applied to high-temperature or high-volume gas streams;

(d) Wet scrubbers (venturi type), achieving control efficiencies of approximately 90–98 percent for PM10 and 70–95 percent for PM2.5, but generating a wastewater stream requiring treatment and disposal; and

(e) Enclosure and water suppression systems for fugitive dust sources, achieving variable control efficiencies depending on application.

Of these technologies, baghouse/fabric filters were identified as the top-ranked control technology for the grain handling and fertilizer loadout operations at EU-04. Baghouse filters are the industry-standard particulate control device for grain elevators and agricultural material handling operations and are universally recognized as BACT for these source types. The proposed outlet concentration of 0.005 gr/dscf and control efficiency of 99.5 percent represent the most stringent practically achievable control level for grain handling and fertilizer loadout operations, reflecting the performance capabilities of modern pulse-jet baghouse systems with high-efficiency filter media (e.g., polyester felt or spunbond polypropylene bags). ESPs were eliminated as not cost-effective for the relatively low gas volumes and moderate temperatures associated with grain handling exhaust streams. Wet scrubbers were eliminated based on the collateral environmental impacts of wastewater generation and the operational complications of scrubber blowdown disposal at an agricultural processing facility. Cyclones were retained only as pre-cleaners upstream of the baghouse units for the higher-loading grain receiving operations but are not proposed as a standalone control technology.

A review of the RBLC database was performed for PM/PM10/PM2.5 BACT determinations applicable to grain handling, soybean processing, and fertilizer blending operations. The search confirmed that baghouse filters at outlet concentrations of 0.005–0.01 gr/dscf are consistently established as BACT for these source categories. GAP's proposed emission limit of 0.005 gr/dscf is at the most stringent end of this range and is consistent with or more stringent than the vast majority of comparable BACT determinations. A summary of the relevant RBLC entries for PM BACT is included in Enclosure 1 to this letter.

For EU-06 (cooling towers), the proposed drift rate of 0.0005 percent represents the best available drift elimination technology. Modern high-efficiency blade-type drift eliminators, such as those manufactured by Brentwood Industries, Harborline Group, and Quillon Corporation, are rated to achieve drift rates of 0.0005 percent or lower under design conditions. This drift rate is consistent with EPA's guidance for new cooling tower BACT determinations, as reflected in the RBLC database, and is the lowest commercially guaranteed drift rate for induced-draft cooling towers of the type and capacity proposed for the MEF. No more stringent drift elimination technology exists that was not evaluated.

For the combustion sources (EU-01, EU-02, EU-03), the exclusive use of natural gas as fuel is widely accepted as BACT for particulate matter from gas-fired combustion sources. Add-on particulate controls (such as baghouse filters or ESPs) for natural gas combustion exhaust are neither technically warranted nor precedented in the RBLC for units in this size range, given the inherently low particulate emission rates associated with natural gas combustion (approximately 1.9 lb/10⁶ scf for filterable PM and 5.7 lb/10⁶ scf for filterable plus condensable PM, per AP-42, Section 1.4).

HEA's comment does not identify any specific additional control technology, emission rate, or control configuration that should have been but was not evaluated in Pinnacle's BACT analysis. The comment states only that the analysis "fails to consider all available control options" without specifying which option or options were allegedly omitted. In the absence of any concrete factual basis for this assertion, GAP submits that HEA's comment does not present grounds for modifying the proposed BACT determination.

III.C. Air Dispersion Modeling Demonstrates NAAQS Compliance

In addition to the BACT analysis, the PSD application includes a comprehensive air quality impact assessment prepared by Pinnacle using the EPA-approved AERMOD dispersion modeling system (Version 23.1, regulatory default mode). The purpose of the modeling analysis is to demonstrate that emissions from the MEF, at the proposed BACT-controlled emission rates, will not cause or contribute to a violation of any National Ambient Air Quality Standard ("NAAQS") or any applicable PSD increment.

The key parameters and results of Pinnacle's AERMOD analysis are summarized below:

Meteorological Data: The modeling used a five-year meteorological dataset (calendar years 2018 through 2022) processed from surface observations at Muscatine Municipal Airport (station identifier KMUT, WBAN 94982) and concurrent upper-air data from the Davenport, Iowa, National Weather Service radiosonde station (station identifier KDVN). Meteorological data were processed using AERMET (Version 23.1) in accordance with EPA's Guideline on Air Quality Models (Appendix W to 40 C.F.R. Part 51) and the IDNR's Air Dispersion Modeling Guidelines (revised January 2022).

Receptor Grid: A Cartesian receptor grid with 50-meter spacing was placed within and immediately surrounding the facility property boundary, extending to a distance of 5 kilometers from the facility in all directions. Fenceline receptors were placed at 25-meter intervals along the facility property boundary. Terrain elevations for all receptors and source locations were derived from USGS National Elevation Dataset data at 1/3 arc-second resolution, processed using AERMAP (Version 18.1).

Building Downwash: Building downwash effects were evaluated using BPIP-PRIME (Version 04274) for all structures within the facility footprint with a potential to influence plume dispersion, including the main process building, soybean storage silos, and the cooling tower structure.

Nearest Sensitive Receptor: The nearest off-site residence is located approximately 0.42 miles (2,218 feet) east-northeast of the proposed main stack location. The AERMOD results at this receptor location were specifically tabulated and reported in the modeling analysis.

Background Concentrations: Ambient background concentrations for criteria pollutants were obtained from the most recent three years of monitoring data from IDNR's ambient air quality monitoring network. For PM10, the representative background monitor is located in Muscatine (AQS Site ID 19-139-0015). The design value background concentration used in the modeling analysis for PM10 is 72 µg/m³ (24-hour average), which represents the 98th percentile 24-hour value from the 2020–2022 monitoring period.

Attainment Status: Muscatine County, Iowa, is designated as attainment (or unclassifiable/attainment) for all criteria pollutants under Section 107 of the Clean Air Act, including PM10, PM2.5, NO₂, SO₂, CO, O₃, and Pb. The area has not been redesignated from nonattainment for any pollutant. Accordingly, the PSD increment analysis applies, and there is no obligation to conduct a nonattainment New Source Review analysis.

The maximum modeled impacts and NAAQS compliance demonstrations for PM10 and PM2.5 are as follows:

As shown in the table above, the maximum combined impacts (modeled impact plus background) for PM10 and PM2.5 are well below the applicable NAAQS for each averaging period. The 24-hour PM10 combined impact of 110.2 µg/m³ is 26.5 percent below the 150 µg/m³ NAAQS, providing a substantial margin of compliance. The 24-hour PM2.5 combined impact of 32.7 µg/m³ is 6.6 percent below the 35 µg/m³ NAAQS. The annual PM2.5 combined impact of 11.2 µg/m³ is 6.7 percent below the 12.0 µg/m³ NAAQS. PSD increment consumption was also modeled and determined to be within the applicable Class II increments for all pollutants, with detailed results provided in Appendix F to the PSD Application.

These modeling results demonstrate that the proposed BACT controls are sufficient to protect the NAAQS and PSD increments with ample margin of compliance. The air quality impact assessment provides further assurance that the emission limits proposed in the draft permit are environmentally protective and consistent with the purposes of the PSD program.

A summary of the complete AERMOD modeling results is attached as Enclosure 2 to this letter.

III.D. Conclusion on PM2.5 BACT

For the reasons set forth above, GAP's BACT analysis for PM2.5 and PM10 is thorough, methodologically sound, and consistent with the EPA's top-down BACT methodology. The analysis is supported by a comprehensive RBLC review confirming that the proposed emission limits represent the most stringent control levels achievable for the source categories at the MEF. The ambient air quality impact assessment, performed using AERMOD with conservative modeling assumptions and a five-year meteorological dataset, demonstrates compliance with all applicable NAAQS and PSD increments with substantial margins.

HEA's comment is general in nature and does not identify any specific deficiency in the BACT analysis, any omitted control technology, or any emission rate that should have been evaluated but was not. The comment does not present any technical data, engineering analysis, or regulatory precedent to support a finding that additional or different controls are warranted. Accordingly, GAP submits that HEA's comment does not provide a basis for modifying the proposed PM2.5 or PM10 BACT determinations.

GAP respectfully requests that IDNR confirm the proposed PM2.5 and PM10 BACT determinations — including baghouse filters at 0.005 gr/dscf and 99.5 percent control efficiency for EU-04, high-efficiency drift eliminators at 0.0005 percent drift rate for EU-06, and natural gas fuel with good combustion practices for EU-01, EU-02, and EU-03 — in the final PSD Construction Permit.

IV. Response to HEA Request for a Public Hearing

IV.A. Legal Standard for Public Hearings

HEA's third comment requests that IDNR convene a public hearing on the draft PSD Construction Permit. The legal standard governing public hearings on PSD permit applications in Iowa is set forth in Iowa Administrative Code 567—33.3(455B), which provides that the IDNR "may hold a public hearing" on a PSD construction permit application if there is "significant public interest" in the proposed action. The parallel federal provision, 40 C.F.R. § 52.21(q), similarly provides that the reviewing authority shall hold a hearing on a PSD application "if, in the Administrator's judgment, such a hearing is warranted."

Importantly, a public hearing is not required as a matter of right under either the Iowa rules or the federal PSD regulations. The decision whether to hold a hearing is committed to the sound discretion of IDNR, based on the degree of public interest demonstrated during the public notice and comment period. In exercising this discretion, IDNR appropriately considers the volume and substance of public comments received, the extent to which the issues raised can be adequately addressed through written responses, and whether a hearing would meaningfully contribute to the development of the permit record.

The public comment process itself — which provides all members of the public with a full thirty-day period in which to review the draft permit, the permit application, and all supporting technical documents, and to submit written comments for consideration by IDNR — is designed to satisfy the public participation requirements of the PSD program. A public hearing supplements, but does not replace, this written comment process and is warranted only where the written process is insufficient to address the scope or nature of public concern.

IV.B. Public Comment Record Does Not Warrant a Hearing

During the thirty-day public notice period (June 12 through July 12, 2023), IDNR received a total of four written comments on the draft PSD Construction Permit. The substance of these comments is summarized as follows:

1. Neighboring Landowner No. 1 (name and address on file with IDNR): This commenter expressed general concerns about the potential for increased dust and particulate matter in the vicinity of the Facility, and asked whether the Facility would generate noticeable odor. The commenter did not raise any specific technical objections to the BACT analysis or permit conditions.

2. Neighboring Landowner No. 2 (name and address on file with IDNR): This commenter similarly expressed concerns about particulate matter and inquired about the hours of operation for truck traffic at the Facility. The commenter did not challenge the adequacy of the permit analysis or request a hearing.

3. Muscatine County Soil & Water Conservation District: This commenter requested clarification regarding stormwater management and erosion control measures at the MEF site during construction. These issues relate primarily to GAP's forthcoming NPDES General Permit No. 2 coverage for stormwater discharges associated with construction activity, and to the Muscatine County grading permit, rather than to the PSD air quality permit at issue.

4. Heartland Environmental Alliance: HEA's comment letter raised the three substantive issues addressed in Sections II, III, and IV of this letter.

The total of four comments received during the public notice period does not demonstrate the degree of public interest that would warrant a formal public hearing. Two of the four comments relate to general neighborhood concerns that are addressed through the BACT analysis and permit conditions already included in the draft permit. The third comment relates to stormwater management, a topic outside the scope of the PSD permit. Only HEA's comment raises substantive air quality issues, and those issues are fully addressed through the written responses contained in this letter and through the extensive technical record compiled in the PSD application.

GAP notes that the draft permit, the complete PSD application (including Pinnacle's emissions inventory, BACT analyses, and AERMOD modeling report), and all supporting technical documents were made available for public review at the IDNR Air Quality Bureau offices in Des Moines and at the Musser Public Library in Muscatine during the entire public notice period, as required by IAC 567—33.3(455B). The public notice was published in the Muscatine Journal on June 12, 2023, and was posted on the IDNR's public notice website. There is no indication that any member of the public was unable to access the permit record or was denied an adequate opportunity to review and comment on the application.

All substantive comments received can be and are being fully addressed through written responses and through IDNR's responsiveness summary process. HEA's request for a hearing does not identify any specific issue or category of public concern that cannot be adequately addressed through the written record, nor does it point to any deficiency in the public notice process or the availability of the permit record for public review.

IV.C. GAP's Position

GAP respectfully submits that the existing public comment record is complete and that the substantive issues raised by HEA and all other commenters can be — and are being — fully resolved through written responses and the IDNR responsiveness summary, without the need for a formal public hearing. A hearing would not meaningfully contribute to the development of the permit record beyond what is already contained in the application, the supporting technical analyses, and these written responses.

Accordingly, GAP respectfully requests that IDNR exercise its discretion under IAC 567—33.3(455B) to decline HEA's hearing request and proceed to final permit issuance based on the written record.

V. Additional Contextual Information

GAP wishes to provide the following additional contextual information for the benefit of the IDNR's evaluation of the permit record and the comments received:

Local Land-Use Approval. GAP has obtained all required local land-use approvals for the construction and operation of the MEF. On November 15, 2022, the Muscatine County Board of Supervisors approved Conditional Use Permit No. MC-2022-041, authorizing the construction and operation of a soybean processing and fertilizer blending facility on the MEF site. The Conditional Use Permit was issued following a public hearing before the Board of Supervisors and was subject to conditions relating to setbacks, access road improvements, landscaping buffers, and noise limitations, all of which GAP has accepted and will comply with.

Zoning. The 147-acre MEF site is identified as Parcel ID 0735-19-200-004 in the Muscatine County Assessor's records. The site is zoned Agricultural-Industrial ("AI") under the Muscatine County Zoning Ordinance. Soybean processing and fertilizer blending operations are permitted uses within the AI zoning district, subject to conditional use approval.

Site Acquisition. The MEF site was acquired by GAP from the Reinholt Family Trust pursuant to a Warranty Deed recorded on January 20, 2023, in the Muscatine County Recorder's Office at Book 2023, Page 412. A Phase I Environmental Site Assessment conducted by Pinnacle in October 2022 identified no recognized environmental conditions at the site. A Phase II investigation was not warranted.

Economic Impact. The MEF represents a significant capital investment in Muscatine County and will provide substantial economic benefits to the region. The Facility will have a soybean crush capacity of 3,200 tons per day, making it one of the larger soybean processing facilities in Iowa, and will include a 450-ton-per-day granular fertilizer blending line serving agricultural customers throughout eastern Iowa and western Illinois. The total project capital cost is approximately $178 million, including site preparation, process equipment, utility infrastructure, and environmental controls. GAP estimates that the MEF will create approximately 85 permanent full-time positions and approximately 350 construction jobs during the 18-month construction period. The Facility will source soybeans primarily from growers in Muscatine, Louisa, Cedar, and Scott Counties, providing a proximate market for regional agricultural producers.

While economic considerations are not directly relevant to the BACT analysis or the regulatory requirements of the PSD program, GAP submits this information as context for the Facility's contribution to the regional economy and as additional background for the IDNR's responsiveness summary.

VI. Conclusion and Request

In summary, GAP believes that the PSD application and supporting technical analyses — including the comprehensive emissions inventory, the top-down BACT analyses for all regulated pollutants, and the AERMOD air dispersion modeling performed by Pinnacle Environmental Consultants Inc. — demonstrate full compliance with all applicable PSD requirements under the Clean Air Act, 40 C.F.R. § 52.21, and Iowa Administrative Code 567—Chapter 33.

The proposed BACT determinations are as follows:

• NOx: Low-NOx burners with flue gas recirculation on EU-01 and EU-02, achieving an emission limit of 0.036 lb/MMBtu; low-NOx burners on EU-03, achieving an emission limit of 0.05 lb/MMBtu. These limits are supported by the RBLC database, three comparable recent Midwest PSD permits, and the top-down cost-effectiveness analysis documented in the PSD application.

• PM10/PM2.5: Baghouse filters at 0.005 gr/dscf outlet concentration and 99.5 percent control efficiency for material handling sources (EU-04); high-efficiency drift eliminators at a 0.0005 percent drift rate for cooling towers (EU-06); pipeline-quality natural gas fuel and good combustion practices for combustion sources (EU-01, EU-02, EU-03). These limits are supported by the RBLC database and represent the most stringent practically achievable control levels for the source categories at the MEF.

• CO₂e (Greenhouse Gases): The BACT analysis for greenhouse gas emissions (carbon dioxide equivalent, "CO₂e") is addressed in Section 5.5 of Pinnacle's BACT Analysis Report and proposes energy-efficient equipment design and good combustion practices as BACT, consistent with EPA guidance and recent PSD permit precedent for comparable sources. HEA did not comment on the CO₂e BACT determination.

The AERMOD modeling analysis confirms that emissions from the MEF at the proposed BACT-controlled rates will not cause or contribute to a violation of any NAAQS or PSD increment, with substantial margins of compliance for all pollutants and averaging periods.

HEA's three comments — regarding NOx BACT, PM2.5 BACT, and the request for a public hearing — have been fully addressed in this letter. None of HEA's comments identifies a specific technical deficiency, omitted control technology, or regulatory requirement that is not already satisfied by the PSD application and draft permit.

GAP respectfully requests that IDNR include these responses in its responsiveness summary pursuant to IAC 567—33.3(455B) and 40 C.F.R. § 52.21(q), and proceed to issue PSD Construction Permit No. 23-A-0481 as drafted, without modification. GAP and its counsel remain available to address any additional questions from AQB staff. Please do not hesitate to contact the undersigned at (515) 244-7800 or rdominguez@calderwoodharkness.com if you require any further information.

Respectfully submitted,

CALDERWOOD & HARKNESS LLP

By: ________

Rafael Dominguez Partner

801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 244-7800

Email: rdominguez@calderwoodharkness.com

cc (via email and first-class mail):

Patricia Caldwell, Esq., General Counsel & Vice President of Regulatory Affairs, Greenfield Agricultural Partners LLC

Derek Yun, Director of Environmental, Health & Safety, Greenfield Agricultural Partners LLC

Dr. Leonard Fisk, P.E., Principal, Air Quality Practice, Pinnacle Environmental Consultants Inc.

James Prentice, Esq., Partner, Calderwood & Harkness LLP

Enclosures:

Enclosure 1: Table Summarizing RBLC Search Results for Comparable NOx and PM BACT Determinations at Soybean Processing and Agricultural Drying Facilities

Enclosure 2: AERMOD Modeling Results Summary Table (24-Hour PM10, Annual PM2.5, 24-Hour PM2.5, Comparison to NAAQS and PSD Increments)

Pollutant / Averaging Period	Maximum Modeled Impact (µg/m³)	Background (µg/m³)	Total Impact (µg/m³)	NAAQS (µg/m³)	Compliance
PM10, 24-hour	38.2	72.0	110.2	150	Yes
PM2.5, 24-hour	8.7	24.0	32.7	35	Yes
PM2.5, Annual	1.4	9.8	11.2	12.0	Yes

CALDERWOOD & HARKNESS LLP Attorneys at Law
801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 244-7800 Facsimile: (515) 244-7801 www.calderwoodharkness.com
July 28, 2023
Jonathan Kreske, P.E. Environmental Engineer, Air Quality Bureau Iowa Department of Natural Resources 502 East 9th Street Des Moines, Iowa 50319
Re: Greenfield Agricultural Partners LLC — Response to Public Comments of Heartland Environmental Alliance on Draft PSD Construction Permit No. 23-A-0481 for the Muscatine Expansion Facility, 14800 Highway 61 North, Muscatine, Iowa 52761
C&H Matter No. 1020-00004
Dear Mr. Kreske:
Calderwood & Harkness LLP represents Greenfield Agricultural Partners LLC ("GAP"), an Iowa limited liability company organized under Chapter 489 of the Iowa Code, in connection with GAP's application for a Prevention of Significant Deterioration ("PSD") Construction Permit for the Muscatine Expansion Facility (the "MEF" or the "Facility"), a soybean processing and specialty fertilizer blending facility to be constructed on a 147-acre greenfield site located at 14800 Highway 61 North, in Muscatine County, Iowa 52761. As you are aware, GAP filed its PSD application with the Iowa Department of Natural Resources ("IDNR") Air Quality Bureau ("AQB") on April 28, 2023. AQB issued a completeness determination on May 19, 2023, confirming that the application contained all information necessary for substantive review under Iowa Administrative Code ("IAC") 567—Chapter 33 and the federal PSD regulations codified at 40 C.F.R. § 52.21.
Pursuant to IAC 567—33.3(455B), AQB published public notice of the draft PSD Construction Permit on June 12, 2023. The thirty-day public comment period ran from June 12, 2023, through July 12, 2023. During that period, AQB received a total of four written comments: two from neighboring landowners expressing general concerns regarding particulate matter and odor, one from the Muscatine County Soil & Water Conservation District requesting clarification on stormwater management controls (which relate primarily to GAP's forthcoming National Pollutant Discharge Elimination System permit application rather than the PSD permit at issue), and one from the Heartland Environmental Alliance ("HEA"), an unincorporated non-profit association based in Iowa City, Iowa. HEA's comment letter, dated July 11, 2023, raises three principal assertions concerning the adequacy of the Best Available Control Technology ("BACT") analyses for nitrogen oxides ("NOx") and fine particulate matter ("PM2.5"), as well as a request that IDNR convene a public hearing on the draft permit.
This letter provides GAP's written responses to each of HEA's three comments for inclusion in the IDNR's responsiveness summary, as contemplated by IAC 567—33.3(455B) and 40 C.F.R. § 52.21(q). Calderwood & Harkness submits these responses in coordination with GAP's Director of Environmental, Health & Safety, Derek Yun, and with supporting technical input from Pinnacle Environmental Consultants Inc. ("Pinnacle"), GAP's environmental consultant. Pinnacle's Air Quality Practice, under the direction of Dr. Leonard Fisk, P.E., prepared the emissions inventories, BACT analyses, and air dispersion modeling that support the PSD application and draft permit. Dr. Fisk has reviewed and concurs with the technical representations contained in this letter.
I. Summary of HEA Comments
Before addressing each comment in detail, we provide a brief catalog of the three principal assertions contained in HEA's July 11, 2023, comment letter:
Comment 1 — NOx BACT. HEA asserts that the BACT analysis for NOx emissions from the MEF is "inadequate" and that "more stringent controls should be required" for the Facility's natural gas-fired combustion units. HEA contends, in general terms, that the proposed emission limits do not reflect the maximum degree of reduction achievable and that additional post-combustion controls such as selective catalytic reduction ("SCR") should be mandated.
Comment 2 — PM2.5 BACT. HEA asserts that the BACT analysis for PM2.5 emissions is "deficient" and "fails to consider all available control options" for particulate-emitting sources at the MEF. HEA does not identify any specific control technology or emission rate that it contends was omitted from the analysis, but states broadly that the evaluation was incomplete.
Comment 3 — Request for Public Hearing. HEA requests that IDNR hold a public hearing on the draft PSD permit, alleging that there exists "significant public interest" in the proposed Facility and that the existing permit record is "inadequate" to address community concerns.
Each of these comments is addressed in turn below.
II. Response to HEA Comment on NOx BACT Analysis
II.A. Overview of NOx Emissions and Proposed BACT
The MEF's aggregate potential to emit ("PTE") for NOx, calculated across all emission units at maximum design capacity and assuming year-round operation (8,760 hours per year) without voluntary limits, is 312 tons per year ("tpy"). This PTE exceeds the 250 tpy major-source threshold applicable to unnamed source categories under 40 C.F.R. § 52.21(b)(1)(i)(b), thereby triggering PSD review for NOx and all other pollutants for which the Facility's net emissions increase exceeds the applicable significance levels.
The primary sources of NOx emissions at the MEF are the Facility's natural gas-fired combustion units, which are identified in the application as follows:
• EU-01: A 120 MMBtu/hr natural gas-fired process heater used to supply thermal energy to the soybean extraction process. EU-01 is the single largest NOx emission unit at the Facility, with a PTE of approximately 149 tpy of NOx at uncontrolled emission factors.
• EU-02: An 80 MMBtu/hr natural gas-fired soybean dryer used to reduce moisture content in processed soybean meal prior to storage and shipment. EU-02 operates in an intermittent-load profile, cycling between full load and reduced load depending on feedstock moisture content and production scheduling. EU-02 has an uncontrolled NOx PTE of approximately 99 tpy.
• EU-03: A 60 MMBtu/hr natural gas-fired fertilizer granulation dryer used in the specialty fertilizer blending line. EU-03 has an uncontrolled NOx PTE of approximately 45 tpy.
• EU-05: A 2,000 kW emergency diesel generator, limited by a federally enforceable permit condition to no more than 500 hours per year of operation. EU-05 contributes a relatively minor portion of the Facility's total NOx PTE (approximately 19 tpy).
For EU-01 and EU-02, GAP proposes to install low-NOx burners equipped with flue gas recirculation ("FGR") as BACT for NOx. These burners are designed to reduce peak flame temperatures and limit thermal NOx formation by recirculating a portion of the flue gas back into the combustion zone. The proposed emission limit for EU-01 and EU-02 is 0.036 lb NOx per MMBtu of heat input, on a three-hour rolling average basis, demonstrated through initial stack testing and subsequent periodic testing at intervals specified in the draft permit. EU-03 will employ low-NOx burners (without FGR) to achieve an emission limit of 0.05 lb/MMBtu, consistent with the somewhat smaller scale and different operating profile of that unit. EU-05, as a compression-ignition emergency engine, is subject to the emission standards and operational limitations set forth in 40 C.F.R. Part 60, Subpart IIII, and BACT for that unit is compliance with those standards in conjunction with the 500-hour annual operating limitation.
At the proposed controlled emission rates, the MEF's aggregate facility-wide NOx PTE is reduced from 312 tpy (uncontrolled) to approximately 98 tpy (controlled), representing an overall reduction of approximately 68.6 percent.
II.B. RACT/BACT/LAER Clearinghouse Review
GAP's BACT analysis for NOx was prepared by Pinnacle in accordance with the EPA's well-established top-down BACT methodology, as described in the New Source Review Workshop Manual (Draft, October 1990) and as required under 40 C.F.R. § 52.21(b)(12). The top-down approach requires the applicant to proceed through five sequential analytical steps:
Step 1 — Identify All Available Control Technologies. In this step, Pinnacle identified all potentially available NOx control technologies for natural gas-fired combustion sources in the size range of EU-01, EU-02, and EU-03. The technologies identified included:
(a) Selective catalytic reduction ("SCR"), which uses a catalyst bed and an ammonia or urea reagent to reduce NOx to nitrogen and water in the post-combustion flue gas stream;
(b) Selective non-catalytic reduction ("SNCR"), which injects ammonia or urea into the flue gas stream at elevated temperatures (approximately 1,600–2,100°F) without the use of a catalyst;
(c) Low-NOx burners with flue gas recirculation ("LNB+FGR"), which reduce thermal NOx formation by lowering peak flame temperatures and diluting the combustion zone with recirculated flue gas;
(d) Ultra-low-NOx burners ("ULNB"), which employ staged-combustion or pre-mix designs to further reduce NOx formation below the levels achievable with conventional low-NOx burners; and
(e) Combustion tuning and good combustion practices ("GCP"), which represent the baseline level of NOx control achievable through proper burner adjustment and maintenance.
Step 2 — Eliminate Technically Infeasible Options. SCR was evaluated for technical feasibility. While SCR is a well-demonstrated technology on large utility boilers and certain industrial process heaters operating at steady-state conditions, its application to intermittent-load drying operations such as EU-02 and EU-03 presents significant technical challenges. Specifically, SCR catalysts require a minimum sustained operating temperature (typically 480–800°F depending on catalyst formulation) to achieve the design NOx reduction efficiency. The intermittent-load operating profile of soybean dryers, which cycle between full load and reduced throughput based on incoming feedstock moisture levels and production scheduling, results in flue gas temperature excursions below the catalyst activation threshold. Operation of the SCR system outside its effective temperature window not only eliminates the NOx reduction benefit but also results in unreacted ammonia emissions ("ammonia slip"), a secondary pollutant with its own health and environmental impacts. SNCR was similarly evaluated and found to present temperature-window limitations for units in this size and application category.
For EU-01, the 120 MMBtu/hr process heater, SCR is technically feasible in the narrow sense that it could be physically installed and operated during steady-state conditions. However, SCR was carried forward to the economic and collateral impacts analysis in Steps 3 and 4 rather than eliminated at Step 2.
Ultra-low-NOx burners were evaluated and determined to be technically feasible for EU-01 and EU-02 but were not demonstrated to achieve meaningfully lower emission rates than LNB+FGR in the specific combustion configuration and fuel type (natural gas) proposed for the MEF.
Step 3 — Rank Remaining Control Technologies by Effectiveness. The remaining technically feasible control technologies were ranked in descending order of control effectiveness as follows: (1) SCR (for EU-01 only), achieving approximately 0.008–0.015 lb/MMBtu; (2) LNB+FGR, achieving approximately 0.02–0.04 lb/MMBtu; (3) ULNB, achieving approximately 0.03–0.05 lb/MMBtu; and (4) GCP, achieving approximately 0.10–0.15 lb/MMBtu.
Step 4 — Evaluate Economic, Energy, and Environmental Impacts. For EU-01, the incremental cost-effectiveness of SCR over LNB+FGR was calculated at approximately $18,700 per ton of NOx removed, based on annualized capital, operating, maintenance, and catalyst replacement costs, offset against the incremental NOx reduction of approximately 8.4 tpy beyond what LNB+FGR achieves alone. This cost-effectiveness figure substantially exceeds the range typically considered reasonable for BACT determinations for this source category. EPA guidance and BACT precedent generally treat cost-effectiveness values exceeding approximately $5,000–$10,000 per ton as indicative of disproportionate cost for industrial combustion sources, although no bright-line threshold exists and the analysis is inherently case-specific. In addition, the environmental collateral impacts of SCR — including ammonia slip (estimated at 5–10 ppm at the stack under normal operating conditions), the generation of spent catalyst waste requiring disposal as a hazardous or special waste, and increased energy consumption associated with the induced-draft fan pressure drop across the catalyst bed — further support the elimination of SCR as BACT for EU-01.
For EU-02 and EU-03, SCR was eliminated at Step 2 for technical infeasibility reasons, as discussed above. LNB+FGR was therefore identified as the top-ranked control technology for EU-02, and LNB was identified as BACT for EU-03.
Step 5 — Select BACT. Based on the foregoing analysis, Pinnacle selected LNB+FGR at an emission limit of 0.036 lb/MMBtu as BACT for NOx for EU-01 and EU-02, and LNB at an emission limit of 0.05 lb/MMBtu as BACT for EU-03.
A thorough review of the EPA RACT/BACT/LAER Clearinghouse ("RBLC") database was conducted as part of Step 1 to identify NOx BACT determinations for comparable natural gas combustion sources in the agricultural processing sector. The RBLC search was performed using the following parameters: source category codes for external combustion — natural gas; heat input capacity range of 50–200 MMBtu/hr; permit issuance dates within the preceding five years (2018–2023); and geographic scope of all states. The search returned twenty-three entries for comparable sources. Of these, the NOx emission limits ranged from 0.02 lb/MMBtu (for a large refinery process heater with SCR, a source with materially different operating characteristics and economic scale than the MEF) to 0.10 lb/MMBtu (for a smaller agricultural dryer with GCP only). The median NOx emission rate for comparable natural gas-fired process heaters and dryers in the agricultural processing sector was 0.04 lb/MMBtu. The RBLC results confirm that the proposed emission limit of 0.036 lb/MMBtu for EU-01 and EU-02 represents a level of control at or more stringent than the median BACT determination for this source and application category. A summary table of the relevant RBLC entries is provided as Enclosure 1 to this letter.
II.C. Comparable Recent PSD Permits
In addition to the RBLC review, GAP and Pinnacle identified the following three recent PSD permit determinations by Midwest state agencies for soybean processing and agricultural drying facilities that are directly comparable to the MEF and that established BACT for NOx at emission rates consistent with or less stringent than the 0.036 lb/MMBtu limit proposed by GAP:
1. Illinois EPA, PSD Permit No. 178230096, Decatur Soy Products LLC, Macon County, Illinois (issued March 14, 2022). This permit authorized construction of a 3,500 tpd soybean crush facility with a 100 MMBtu/hr natural gas-fired process heater and a 75 MMBtu/hr natural gas-fired dryer. BACT for NOx was established at 0.04 lb/MMBtu using low-NOx burners with flue gas recirculation. SCR was evaluated and eliminated based on cost-effectiveness ($16,200/ton) and ammonia slip concerns.
2. Minnesota Pollution Control Agency, Air Emission Permit No. 04900475-101, Prairie Grain Processors Inc., Blue Earth County, Minnesota (issued August 3, 2021). This permit authorized a 2,800 tpd soybean processing and biodiesel feedstock facility. The primary combustion source was an 85 MMBtu/hr natural gas-fired process heater. BACT for NOx was established at 0.036 lb/MMBtu using low-NOx burners with FGR. The MPCA's technical support document specifically noted that SCR was not cost-effective for agricultural combustion sources at this scale.
3. Indiana Department of Environmental Management, PSD Permit No. T159-42177-00060, Hoosier Agri-Processing LLC, Vigo County, Indiana (issued January 19, 2023). This permit authorized a soybean extraction and meal drying facility with two natural gas-fired dryers rated at 90 MMBtu/hr and 60 MMBtu/hr, respectively. BACT for NOx was established at 0.05 lb/MMBtu using low-NOx burners without FGR. The IDEM permit record indicated that FGR was evaluated but not required due to the smaller scale and intermittent operation of the dryers, and that SCR was eliminated based on cost-effectiveness ($21,400/ton).
These precedents demonstrate that GAP's proposed NOx emission limit of 0.036 lb/MMBtu for EU-01 and EU-02 is at or below the emission rates accepted as BACT in the most recent comparable PSD determinations for soybean processing and agricultural drying facilities in the Midwest. Indeed, the GAP proposal is as stringent as or more stringent than each of the three cited precedents. HEA's assertion that "more stringent controls should be required" is unsupported by either the RBLC record or recent BACT determinations for this source category.
II.D. Conclusion on NOx BACT
For the reasons set forth above, the proposed NOx emission limit of 0.036 lb/MMBtu, achieved through the installation and operation of low-NOx burners with flue gas recirculation on EU-01 and EU-02, represents BACT under the top-down methodology prescribed by 40 C.F.R. § 52.21(b)(12). The analysis is thoroughly documented in Section 5.2 of Pinnacle's BACT Analysis Report (Appendix D to the PSD Application), is supported by a comprehensive RBLC review and by three directly comparable recent Midwest PSD permits, and is confirmed by Pinnacle's professional engineering judgment.
HEA's comment does not identify any specific control technology that would achieve lower NOx emissions at a reasonable cost, nor does it cite any comparable permit requiring emission limits more stringent than those proposed by GAP. The comment is general in nature and does not present any technical evidence, cost data, or RBLC entries that would call into question the adequacy of GAP's NOx BACT determination.
GAP respectfully requests that IDNR confirm the proposed NOx BACT determination and retain the emission limits of 0.036 lb/MMBtu for EU-01 and EU-02 and 0.05 lb/MMBtu for EU-03 in the final PSD Construction Permit.
III. Response to HEA Comment on PM2.5 BACT Analysis
III.A. Overview of PM2.5 Emissions and Proposed BACT
The MEF's aggregate potential to emit for PM2.5 (filterable plus condensable) is 87 tpy, and the aggregate PTE for PM10 is 196 tpy. Both values include contributions from combustion sources, material handling and storage operations, and cooling tower drift. The primary sources of particulate emissions at the Facility, as identified in the PSD application, are as follows:
• EU-04 (Material Handling and Storage Operations): EU-04 encompasses all grain receiving, storage, handling, and loadout operations associated with the soybean processing line, as well as fertilizer blending, storage, and loadout operations. Specific emission points within EU-04 include the truck receiving pit, bucket elevators (three units), enclosed belt conveyors (six units), soybean storage silos (four silos, 150,000 bushels each), fertilizer blending bins, and the fertilizer truck loadout spout. These operations generate particulate matter through the mechanical handling, transfer, and free-fall loading of granular materials. EU-04 is the dominant source of particulate emissions at the Facility, contributing approximately 128 tpy of PM10 and 51 tpy of PM2.5 at uncontrolled emission rates.
• EU-01, EU-02, and EU-03 (Combustion Sources): The three natural gas-fired combustion units generate particulate matter as a byproduct of combustion. However, because natural gas is an inherently low-PM fuel, the combustion-source contribution to total particulate emissions is relatively minor. Combined, EU-01, EU-02, and EU-03 contribute approximately 18 tpy of PM10 and 12 tpy of PM2.5.
• EU-06 (Cooling Towers): EU-06 consists of two induced-draft, counterflow cooling tower cells with a combined circulating water flow rate of 18,000 gallons per minute ("gpm"). The cooling towers serve the soybean extraction process. Particulate matter emissions from cooling towers result from the entrainment and release of water droplets containing dissolved solids ("drift") into the atmosphere. At the design circulating water total dissolved solids ("TDS") concentration of 2,500 mg/L, and at the proposed drift rate, EU-06 contributes approximately 5.6 tpy of PM10 and 5.6 tpy of PM2.5.
GAP proposes the following BACT determinations for particulate matter:
EU-04 — Baghouse Filters: All material handling and transfer points within EU-04 will be enclosed and vented to pulse-jet baghouse filter systems. The proposed emission limit is a PM outlet grain loading concentration of 0.005 grains per dry standard cubic foot ("gr/dscf"), corresponding to an overall control efficiency of 99.5 percent. This emission limit will be demonstrated through initial compliance testing using EPA Reference Methods 5 and 201A and will be maintained through a baghouse operation and maintenance plan, including continuous monitoring of pressure drop across the filter media and a bag leak detection system.
EU-06 — High-Efficiency Drift Eliminators: The two cooling tower cells will be equipped with high-efficiency drift eliminators designed to achieve a maximum drift rate of 0.0005 percent of the circulating water flow rate. This drift rate is consistent with the performance specifications of modern blade-type drift eliminators as described in the Cooling Technology Institute's Standard CTI-140, and represents the lowest drift rate commercially achievable for cooling towers of this type and scale.
EU-01, EU-02, EU-03 — Inherently Low-PM Fuel and Good Combustion Practices: For the natural gas-fired combustion units, BACT for particulate matter is the exclusive use of pipeline-quality natural gas as fuel, which has a negligible ash content, combined with good combustion practices. These control measures result in PM emission factors consistent with AP-42, Section 1.4, Table 1.4-2, for natural gas combustion without add-on particulate controls.
At the proposed controlled emission rates, the MEF's aggregate facility-wide PM10 PTE is reduced from 196 tpy (uncontrolled) to approximately 43 tpy (controlled), and the aggregate PM2.5 PTE is reduced from 87 tpy (uncontrolled) to approximately 24 tpy (controlled).
III.B. Adequacy of Control Technology Evaluation
Pinnacle's top-down BACT analysis for PM2.5 and PM10 evaluated all available particulate matter control technologies for each emission unit category, consistent with the five-step methodology described in Section II.B above. The technologies identified and evaluated for EU-04 (material handling and storage) included:
(a) Baghouse/fabric filters (pulse-jet type), achieving outlet concentrations of 0.002–0.01 gr/dscf and control efficiencies of 99–99.9 percent;
(b) Cyclone separators (mechanical collectors), achieving control efficiencies of approximately 80–95 percent for PM10 and 30–70 percent for PM2.5;
(c) Electrostatic precipitators ("ESPs"), achieving control efficiencies of 95–99.5 percent, typically applied to high-temperature or high-volume gas streams;
(d) Wet scrubbers (venturi type), achieving control efficiencies of approximately 90–98 percent for PM10 and 70–95 percent for PM2.5, but generating a wastewater stream requiring treatment and disposal; and
(e) Enclosure and water suppression systems for fugitive dust sources, achieving variable control efficiencies depending on application.
Of these technologies, baghouse/fabric filters were identified as the top-ranked control technology for the grain handling and fertilizer loadout operations at EU-04. Baghouse filters are the industry-standard particulate control device for grain elevators and agricultural material handling operations and are universally recognized as BACT for these source types. The proposed outlet concentration of 0.005 gr/dscf and control efficiency of 99.5 percent represent the most stringent practically achievable control level for grain handling and fertilizer loadout operations, reflecting the performance capabilities of modern pulse-jet baghouse systems with high-efficiency filter media (e.g., polyester felt or spunbond polypropylene bags). ESPs were eliminated as not cost-effective for the relatively low gas volumes and moderate temperatures associated with grain handling exhaust streams. Wet scrubbers were eliminated based on the collateral environmental impacts of wastewater generation and the operational complications of scrubber blowdown disposal at an agricultural processing facility. Cyclones were retained only as pre-cleaners upstream of the baghouse units for the higher-loading grain receiving operations but are not proposed as a standalone control technology.
A review of the RBLC database was performed for PM/PM10/PM2.5 BACT determinations applicable to grain handling, soybean processing, and fertilizer blending operations. The search confirmed that baghouse filters at outlet concentrations of 0.005–0.01 gr/dscf are consistently established as BACT for these source categories. GAP's proposed emission limit of 0.005 gr/dscf is at the most stringent end of this range and is consistent with or more stringent than the vast majority of comparable BACT determinations. A summary of the relevant RBLC entries for PM BACT is included in Enclosure 1 to this letter.
For EU-06 (cooling towers), the proposed drift rate of 0.0005 percent represents the best available drift elimination technology. Modern high-efficiency blade-type drift eliminators, such as those manufactured by Brentwood Industries, Harborline Group, and Quillon Corporation, are rated to achieve drift rates of 0.0005 percent or lower under design conditions. This drift rate is consistent with EPA's guidance for new cooling tower BACT determinations, as reflected in the RBLC database, and is the lowest commercially guaranteed drift rate for induced-draft cooling towers of the type and capacity proposed for the MEF. No more stringent drift elimination technology exists that was not evaluated.
For the combustion sources (EU-01, EU-02, EU-03), the exclusive use of natural gas as fuel is widely accepted as BACT for particulate matter from gas-fired combustion sources. Add-on particulate controls (such as baghouse filters or ESPs) for natural gas combustion exhaust are neither technically warranted nor precedented in the RBLC for units in this size range, given the inherently low particulate emission rates associated with natural gas combustion (approximately 1.9 lb/10⁶ scf for filterable PM and 5.7 lb/10⁶ scf for filterable plus condensable PM, per AP-42, Section 1.4).
HEA's comment does not identify any specific additional control technology, emission rate, or control configuration that should have been but was not evaluated in Pinnacle's BACT analysis. The comment states only that the analysis "fails to consider all available control options" without specifying which option or options were allegedly omitted. In the absence of any concrete factual basis for this assertion, GAP submits that HEA's comment does not present grounds for modifying the proposed BACT determination.
III.C. Air Dispersion Modeling Demonstrates NAAQS Compliance
In addition to the BACT analysis, the PSD application includes a comprehensive air quality impact assessment prepared by Pinnacle using the EPA-approved AERMOD dispersion modeling system (Version 23.1, regulatory default mode). The purpose of the modeling analysis is to demonstrate that emissions from the MEF, at the proposed BACT-controlled emission rates, will not cause or contribute to a violation of any National Ambient Air Quality Standard ("NAAQS") or any applicable PSD increment.
The key parameters and results of Pinnacle's AERMOD analysis are summarized below:
Meteorological Data: The modeling used a five-year meteorological dataset (calendar years 2018 through 2022) processed from surface observations at Muscatine Municipal Airport (station identifier KMUT, WBAN 94982) and concurrent upper-air data from the Davenport, Iowa, National Weather Service radiosonde station (station identifier KDVN). Meteorological data were processed using AERMET (Version 23.1) in accordance with EPA's Guideline on Air Quality Models (Appendix W to 40 C.F.R. Part 51) and the IDNR's Air Dispersion Modeling Guidelines (revised January 2022).
Receptor Grid: A Cartesian receptor grid with 50-meter spacing was placed within and immediately surrounding the facility property boundary, extending to a distance of 5 kilometers from the facility in all directions. Fenceline receptors were placed at 25-meter intervals along the facility property boundary. Terrain elevations for all receptors and source locations were derived from USGS National Elevation Dataset data at 1/3 arc-second resolution, processed using AERMAP (Version 18.1).
Building Downwash: Building downwash effects were evaluated using BPIP-PRIME (Version 04274) for all structures within the facility footprint with a potential to influence plume dispersion, including the main process building, soybean storage silos, and the cooling tower structure.
Nearest Sensitive Receptor: The nearest off-site residence is located approximately 0.42 miles (2,218 feet) east-northeast of the proposed main stack location. The AERMOD results at this receptor location were specifically tabulated and reported in the modeling analysis.
Background Concentrations: Ambient background concentrations for criteria pollutants were obtained from the most recent three years of monitoring data from IDNR's ambient air quality monitoring network. For PM10, the representative background monitor is located in Muscatine (AQS Site ID 19-139-0015). The design value background concentration used in the modeling analysis for PM10 is 72 µg/m³ (24-hour average), which represents the 98th percentile 24-hour value from the 2020–2022 monitoring period.
Attainment Status: Muscatine County, Iowa, is designated as attainment (or unclassifiable/attainment) for all criteria pollutants under Section 107 of the Clean Air Act, including PM10, PM2.5, NO₂, SO₂, CO, O₃, and Pb. The area has not been redesignated from nonattainment for any pollutant. Accordingly, the PSD increment analysis applies, and there is no obligation to conduct a nonattainment New Source Review analysis.
The maximum modeled impacts and NAAQS compliance demonstrations for PM10 and PM2.5 are as follows:
As shown in the table above, the maximum combined impacts (modeled impact plus background) for PM10 and PM2.5 are well below the applicable NAAQS for each averaging period. The 24-hour PM10 combined impact of 110.2 µg/m³ is 26.5 percent below the 150 µg/m³ NAAQS, providing a substantial margin of compliance. The 24-hour PM2.5 combined impact of 32.7 µg/m³ is 6.6 percent below the 35 µg/m³ NAAQS. The annual PM2.5 combined impact of 11.2 µg/m³ is 6.7 percent below the 12.0 µg/m³ NAAQS. PSD increment consumption was also modeled and determined to be within the applicable Class II increments for all pollutants, with detailed results provided in Appendix F to the PSD Application.
These modeling results demonstrate that the proposed BACT controls are sufficient to protect the NAAQS and PSD increments with ample margin of compliance. The air quality impact assessment provides further assurance that the emission limits proposed in the draft permit are environmentally protective and consistent with the purposes of the PSD program.
A summary of the complete AERMOD modeling results is attached as Enclosure 2 to this letter.
III.D. Conclusion on PM2.5 BACT
For the reasons set forth above, GAP's BACT analysis for PM2.5 and PM10 is thorough, methodologically sound, and consistent with the EPA's top-down BACT methodology. The analysis is supported by a comprehensive RBLC review confirming that the proposed emission limits represent the most stringent control levels achievable for the source categories at the MEF. The ambient air quality impact assessment, performed using AERMOD with conservative modeling assumptions and a five-year meteorological dataset, demonstrates compliance with all applicable NAAQS and PSD increments with substantial margins.
HEA's comment is general in nature and does not identify any specific deficiency in the BACT analysis, any omitted control technology, or any emission rate that should have been evaluated but was not. The comment does not present any technical data, engineering analysis, or regulatory precedent to support a finding that additional or different controls are warranted. Accordingly, GAP submits that HEA's comment does not provide a basis for modifying the proposed PM2.5 or PM10 BACT determinations.
GAP respectfully requests that IDNR confirm the proposed PM2.5 and PM10 BACT determinations — including baghouse filters at 0.005 gr/dscf and 99.5 percent control efficiency for EU-04, high-efficiency drift eliminators at 0.0005 percent drift rate for EU-06, and natural gas fuel with good combustion practices for EU-01, EU-02, and EU-03 — in the final PSD Construction Permit.
IV. Response to HEA Request for a Public Hearing
IV.A. Legal Standard for Public Hearings
HEA's third comment requests that IDNR convene a public hearing on the draft PSD Construction Permit. The legal standard governing public hearings on PSD permit applications in Iowa is set forth in Iowa Administrative Code 567—33.3(455B), which provides that the IDNR "may hold a public hearing" on a PSD construction permit application if there is "significant public interest" in the proposed action. The parallel federal provision, 40 C.F.R. § 52.21(q), similarly provides that the reviewing authority shall hold a hearing on a PSD application "if, in the Administrator's judgment, such a hearing is warranted."
Importantly, a public hearing is not required as a matter of right under either the Iowa rules or the federal PSD regulations. The decision whether to hold a hearing is committed to the sound discretion of IDNR, based on the degree of public interest demonstrated during the public notice and comment period. In exercising this discretion, IDNR appropriately considers the volume and substance of public comments received, the extent to which the issues raised can be adequately addressed through written responses, and whether a hearing would meaningfully contribute to the development of the permit record.
The public comment process itself — which provides all members of the public with a full thirty-day period in which to review the draft permit, the permit application, and all supporting technical documents, and to submit written comments for consideration by IDNR — is designed to satisfy the public participation requirements of the PSD program. A public hearing supplements, but does not replace, this written comment process and is warranted only where the written process is insufficient to address the scope or nature of public concern.
IV.B. Public Comment Record Does Not Warrant a Hearing
During the thirty-day public notice period (June 12 through July 12, 2023), IDNR received a total of four written comments on the draft PSD Construction Permit. The substance of these comments is summarized as follows:
1. Neighboring Landowner No. 1 (name and address on file with IDNR): This commenter expressed general concerns about the potential for increased dust and particulate matter in the vicinity of the Facility, and asked whether the Facility would generate noticeable odor. The commenter did not raise any specific technical objections to the BACT analysis or permit conditions.
2. Neighboring Landowner No. 2 (name and address on file with IDNR): This commenter similarly expressed concerns about particulate matter and inquired about the hours of operation for truck traffic at the Facility. The commenter did not challenge the adequacy of the permit analysis or request a hearing.
3. Muscatine County Soil & Water Conservation District: This commenter requested clarification regarding stormwater management and erosion control measures at the MEF site during construction. These issues relate primarily to GAP's forthcoming NPDES General Permit No. 2 coverage for stormwater discharges associated with construction activity, and to the Muscatine County grading permit, rather than to the PSD air quality permit at issue.
4. Heartland Environmental Alliance: HEA's comment letter raised the three substantive issues addressed in Sections II, III, and IV of this letter.
The total of four comments received during the public notice period does not demonstrate the degree of public interest that would warrant a formal public hearing. Two of the four comments relate to general neighborhood concerns that are addressed through the BACT analysis and permit conditions already included in the draft permit. The third comment relates to stormwater management, a topic outside the scope of the PSD permit. Only HEA's comment raises substantive air quality issues, and those issues are fully addressed through the written responses contained in this letter and through the extensive technical record compiled in the PSD application.
GAP notes that the draft permit, the complete PSD application (including Pinnacle's emissions inventory, BACT analyses, and AERMOD modeling report), and all supporting technical documents were made available for public review at the IDNR Air Quality Bureau offices in Des Moines and at the Musser Public Library in Muscatine during the entire public notice period, as required by IAC 567—33.3(455B). The public notice was published in the Muscatine Journal on June 12, 2023, and was posted on the IDNR's public notice website. There is no indication that any member of the public was unable to access the permit record or was denied an adequate opportunity to review and comment on the application.
All substantive comments received can be and are being fully addressed through written responses and through IDNR's responsiveness summary process. HEA's request for a hearing does not identify any specific issue or category of public concern that cannot be adequately addressed through the written record, nor does it point to any deficiency in the public notice process or the availability of the permit record for public review.
IV.C. GAP's Position
GAP respectfully submits that the existing public comment record is complete and that the substantive issues raised by HEA and all other commenters can be — and are being — fully resolved through written responses and the IDNR responsiveness summary, without the need for a formal public hearing. A hearing would not meaningfully contribute to the development of the permit record beyond what is already contained in the application, the supporting technical analyses, and these written responses.
Accordingly, GAP respectfully requests that IDNR exercise its discretion under IAC 567—33.3(455B) to decline HEA's hearing request and proceed to final permit issuance based on the written record.
V. Additional Contextual Information
GAP wishes to provide the following additional contextual information for the benefit of the IDNR's evaluation of the permit record and the comments received:
Local Land-Use Approval. GAP has obtained all required local land-use approvals for the construction and operation of the MEF. On November 15, 2022, the Muscatine County Board of Supervisors approved Conditional Use Permit No. MC-2022-041, authorizing the construction and operation of a soybean processing and fertilizer blending facility on the MEF site. The Conditional Use Permit was issued following a public hearing before the Board of Supervisors and was subject to conditions relating to setbacks, access road improvements, landscaping buffers, and noise limitations, all of which GAP has accepted and will comply with.
Zoning. The 147-acre MEF site is identified as Parcel ID 0735-19-200-004 in the Muscatine County Assessor's records. The site is zoned Agricultural-Industrial ("AI") under the Muscatine County Zoning Ordinance. Soybean processing and fertilizer blending operations are permitted uses within the AI zoning district, subject to conditional use approval.
Site Acquisition. The MEF site was acquired by GAP from the Reinholt Family Trust pursuant to a Warranty Deed recorded on January 20, 2023, in the Muscatine County Recorder's Office at Book 2023, Page 412. A Phase I Environmental Site Assessment conducted by Pinnacle in October 2022 identified no recognized environmental conditions at the site. A Phase II investigation was not warranted.
Economic Impact. The MEF represents a significant capital investment in Muscatine County and will provide substantial economic benefits to the region. The Facility will have a soybean crush capacity of 3,200 tons per day, making it one of the larger soybean processing facilities in Iowa, and will include a 450-ton-per-day granular fertilizer blending line serving agricultural customers throughout eastern Iowa and western Illinois. The total project capital cost is approximately $178 million, including site preparation, process equipment, utility infrastructure, and environmental controls. GAP estimates that the MEF will create approximately 85 permanent full-time positions and approximately 350 construction jobs during the 18-month construction period. The Facility will source soybeans primarily from growers in Muscatine, Louisa, Cedar, and Scott Counties, providing a proximate market for regional agricultural producers.
While economic considerations are not directly relevant to the BACT analysis or the regulatory requirements of the PSD program, GAP submits this information as context for the Facility's contribution to the regional economy and as additional background for the IDNR's responsiveness summary.
VI. Conclusion and Request
In summary, GAP believes that the PSD application and supporting technical analyses — including the comprehensive emissions inventory, the top-down BACT analyses for all regulated pollutants, and the AERMOD air dispersion modeling performed by Pinnacle Environmental Consultants Inc. — demonstrate full compliance with all applicable PSD requirements under the Clean Air Act, 40 C.F.R. § 52.21, and Iowa Administrative Code 567—Chapter 33.
The proposed BACT determinations are as follows:
• NOx: Low-NOx burners with flue gas recirculation on EU-01 and EU-02, achieving an emission limit of 0.036 lb/MMBtu; low-NOx burners on EU-03, achieving an emission limit of 0.05 lb/MMBtu. These limits are supported by the RBLC database, three comparable recent Midwest PSD permits, and the top-down cost-effectiveness analysis documented in the PSD application.
• PM10/PM2.5: Baghouse filters at 0.005 gr/dscf outlet concentration and 99.5 percent control efficiency for material handling sources (EU-04); high-efficiency drift eliminators at a 0.0005 percent drift rate for cooling towers (EU-06); pipeline-quality natural gas fuel and good combustion practices for combustion sources (EU-01, EU-02, EU-03). These limits are supported by the RBLC database and represent the most stringent practically achievable control levels for the source categories at the MEF.
• CO₂e (Greenhouse Gases): The BACT analysis for greenhouse gas emissions (carbon dioxide equivalent, "CO₂e") is addressed in Section 5.5 of Pinnacle's BACT Analysis Report and proposes energy-efficient equipment design and good combustion practices as BACT, consistent with EPA guidance and recent PSD permit precedent for comparable sources. HEA did not comment on the CO₂e BACT determination.
The AERMOD modeling analysis confirms that emissions from the MEF at the proposed BACT-controlled rates will not cause or contribute to a violation of any NAAQS or PSD increment, with substantial margins of compliance for all pollutants and averaging periods.
HEA's three comments — regarding NOx BACT, PM2.5 BACT, and the request for a public hearing — have been fully addressed in this letter. None of HEA's comments identifies a specific technical deficiency, omitted control technology, or regulatory requirement that is not already satisfied by the PSD application and draft permit.
GAP respectfully requests that IDNR include these responses in its responsiveness summary pursuant to IAC 567—33.3(455B) and 40 C.F.R. § 52.21(q), and proceed to issue PSD Construction Permit No. 23-A-0481 as drafted, without modification. GAP and its counsel remain available to address any additional questions from AQB staff. Please do not hesitate to contact the undersigned at (515) 244-7800 or rdominguez@calderwoodharkness.com if you require any further information.
Respectfully submitted,
CALDERWOOD & HARKNESS LLP
By: ________
Rafael Dominguez Partner
801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 244-7800
Email: rdominguez@calderwoodharkness.com
cc (via email and first-class mail):
Patricia Caldwell, Esq., General Counsel & Vice President of Regulatory Affairs, Greenfield Agricultural Partners LLC
Derek Yun, Director of Environmental, Health & Safety, Greenfield Agricultural Partners LLC
Dr. Leonard Fisk, P.E., Principal, Air Quality Practice, Pinnacle Environmental Consultants Inc.
James Prentice, Esq., Partner, Calderwood & Harkness LLP
Enclosures:
Enclosure 1: Table Summarizing RBLC Search Results for Comparable NOx and PM BACT Determinations at Soybean Processing and Agricultural Drying Facilities
Enclosure 2: AERMOD Modeling Results Summary Table (24-Hour PM10, Annual PM2.5, 24-Hour PM2.5, Comparison to NAAQS and PSD Increments)
Pollutant / Averaging Period | Maximum Modeled Impact (µg/m³) | Background (µg/m³) | Total Impact (µg/m³) | NAAQS (µg/m³) | Compliance
PM10, 24-hour | 38.2 | 72.0 | 110.2 | 150 | Yes
PM2.5, 24-hour | 8.7 | 24.0 | 32.7 | 35 | Yes
PM2.5, Annual | 1.4 | 9.8 | 11.2 | 12.0 | Yes

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