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Subpart E—Adipic Acid Production

§98.50 Definition of source category.

The adipic acid production source category consists of all adipic acid production facilities 

that use oxidation to produce adipic acid.

§98.51 Reporting threshold.

You must report GHG emissions under this subpart if your facility contains an adipic acid 

production process and the facility meets the requirements of either §98.2(a)(1) or (2).

§98.52 GHGs to report.

(a) You must report N2O process emissions at the facility level.

(b) You must report under subpart C of this part (General Stationary Fuel Combustion 

Sources) the emissions of CO2, CH4, and N2O from each stationary combustion unit following 

the requirements of subpart C.

§98.53 Calculating GHG emissions.

(a) You must determine annual N2O emissions from adipic acid production according to 

paragraphs (a)(1) or (2) of this section.

(1) Use a site-specific emission factor and production data according to paragraphs (b) 

through (i) of this section.

(2) Request Administrator approval for an alternative method of determining N2O 

emissions according to paragraphs (a)(2)(i) through (iv) of this section.

(i) If you received Administrator approval for an alternative method of determining N2O 

emissions in the previous reporting year and your methodology is unchanged, your alternative 

method is automatically approved for the next reporting year.
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(ii) You must notify the EPA of your use of a previously approved alternative method in 

your annual report.

(iii) Otherwise, you must submit the request within 45 days following promulgation of

this subpart or within the first 30 days of each subsequent reporting year.

(iv) If the Administrator does not approve your requested alternative method within 150 

days of the end of the reporting year, you must determine the N2O emissions for the current 

reporting period using the procedures specified in paragraph (a)(1) of this section.

(b) You must conduct an annual performance test according to paragraphs (b)(1) through 

(3) of this section.

(1) You must conduct the test on the vent stream from the nitric acid oxidation step of the 

process, referred to as the test point, according to the methods specified in §98.54(b) through (f). 

If multiple adipic acid production units exhaust to a common abatement technology and/or 

emission point, you must sample each process in the ducts before the emissions are combined, 

sample each process when only one process is operating, or sample the combined emissions 

when multiple processes are operating and base the site-specific emission factor on the combined 

production rate of the multiple adipic acid production units.

(2) You must conduct the performance test under normal process operating conditions.

(3) You must measure the adipic acid production rate during the test and calculate the 

production rate for the test period in tons per hour.

(c) Using the results of the performance test in paragraph (b) of this section, you must 

calculate an emission factor for each adipic acid unit according to Equation E-1 of this section:
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where:

EFN2O,z = Average facility-specific N2O emission factor for each adipic acid production 

unit “z” (lb N2O/ton adipic acid produced).

CN2O = N2O concentration per test run during the performance test (ppm N2O).

1.14 × 10−7 = Conversion factor (lb/dscf-ppm N2O).

Q = Volumetric flow rate of effluent gas per test run during the performance test 

(dscf/hr).

P = Production rate per test run during the performance test (tons adipic acid 

produced/hr).

n = Number of test runs.

(d) If the adipic acid production unit exhausts to any N2O abatement technology “N”, you 

must determine the destruction efficiency according to paragraphs (d)(1), (d)(2), or (d)(3) of this 

section.

(1) Use the manufacturer's specified destruction efficiency.

(2) Estimate the destruction efficiency through process knowledge. Examples of 

information that could constitute process knowledge include calculations based on material 

balances, process stoichiometry, or previous test results provided the results are still relevant to 

the current vent stream conditions. You must document how process knowledge was used to 

determine the destruction efficiency.

(3) Calculate the destruction efficiency by conducting an additional performance test on 

the vent stream following the N2O abatement technology.

(e) If the adipic acid production unit exhausts to any N2O abatement technology “N”, you 

must determine the annual amount of adipic acid produced while N2O abatement technology “N” 
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is operating according to §98.54(f). Then you must calculate the abatement factor for N2O 

abatement technology “N” according to Equation E-2 of this section.

(f) You must determine the annual amount of adipic acid produced according to 

§98.54(f).

(g) You must calculate N2O emissions according to paragraph (g)(1), (2), (3), or (4) of 

this section for each adipic acid production unit.

(1) If one N2O abatement technology “N” is located after your test point, you must use 

the emissions factor (determined in Equation E-1 of this section), the destruction efficiency

(determined in paragraph (d) of this section), the annual adipic acid production (determined in 

paragraph (f) of this section), and the abatement utilization factor (determined in paragraph (e) of 

this section), according to Equation E-3a of this section:

where:

Ea,z = Annual N2O mass emissions from adipic acid production unit “z” according to this 

Equation E-3a (metric tons).

EFN2Oz = N2O emissions factor for unit “z” (lb N2O/ton adipic acid produced).

Pz = Annual adipic acid produced from unit “z” (tons).

DF = Destruction efficiency of N2O abatement technology “N” (decimal fraction of N2O 

removed from vent stream).

AF = Abatement utilization factor of N2O abatement technology “N” (decimal fraction of 

time that the abatement technology is operating).

2205 = Conversion factor (lb/metric ton).
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(2) If multiple N2O abatement technologies are located in series after your test point, you 

must use the emissions factor (determined in Equation E-1 of this section), the destruction 

efficiency (determined in paragraph (d) of this section), the annual adipic acid production 

(determined in paragraph (f) of this section), and the abatement utilization factor (determined in 

paragraph (e) of this section), according to Equation E-3b of this section:

where:

Eb,z = Annual N2O mass emissions from adipic acid production unit “z” according to this 

Equation E-3b (metric tons).

EFN2O,z = N2O emissions factor for unit “z” (lb N2O/ton adipic acid produced).

Pz = Annual adipic acid produced from unit “z” (tons).

DF1 = Destruction efficiency of N2O abatement technology 1 (decimal fraction of N2O 

removed from vent stream).

AF1 = Abatement utilization factor of N2O abatement technology 1 (decimal fraction of 

time that abatement technology 1 is operating).

DF2 = Destruction efficiency of N2O abatement technology 2 (decimal fraction of N2O 

removed from vent stream).

AF2 = Abatement utilization factor of N2O abatement technology 2 (decimal fraction of 

time that abatement technology 2 is operating).

DFN = Destruction efficiency of N2O abatement technology “N” (decimal fraction of N2O 

removed from vent stream).

AFN = Abatement utilization factor of N2O abatement technology “N” (decimal fraction 

of time that abatement technology N is operating).
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2205 = Conversion factor (lb/metric ton).

N = Number of different N2O abatement technologies.

(3) If multiple N2O abatement technologies are located in parallel after your test point, 

you must use the emissions factor (determined in Equation E-1 of this section), the destruction 

efficiency (determined in paragraph (d) of this section), the annual adipic acid production 

(determined in paragraph (f) of this section), and the abatement utilization factor (determined in 

paragraph (e) of this section), according to Equation E-3c of this section:

where:

Ec,z = Annual N2O mass emissions from adipic acid production unit “z” according to this 

Equation E-3c (metric tons).

EFN2O,z = N2O emissions factor for unit “z” (lb N2O/ton adipic acid produced).

Pz = Annual adipic acid produced from unit “z” (tons).

DFN = Destruction efficiency of N2O abatement technology “N” (decimal fraction of N2O 

removed from vent stream).

AFN = Abatement utilization factor of N2O abatement technology “N” (decimal fraction 

of time that the abatement technology is operating).

FCN = Fraction control factor of N2O abatement technology “N” (decimal fraction of 

total emissions from unit “z” that are sent to abatement technology “N”).

2205 = Conversion factor (lb/metric ton).

N = Number of different N2O abatement technologies with a fraction control factor.

(4) If no N2O abatement technologies are located after your test point, you must use the 

emissions factor (determined using Equation E-1 of this section) and the annual adipic acid 
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production (determined in paragraph (f) of this section) according to Equation E-3d of this 

section for each adipic acid production unit.

where:

Ed,z = Annual N2O mass emissions from adipic acid production for unit “z” according to 

this Equation E-3d (metric tons).

EFN2O = N2O emissions factor for unit “z” (lb N2O/ton adipic acid produced).

PZ = Annual adipic acid produced from unit “z” (tons).

2205 = Conversion factor (lb/metric ton).

(h) You must determine the emissions for the facility by summing the unit level 

emissions according to Equation E-4 of this section.

where:

Ea,z = Annual N2O mass emissions from adipic acid production unit “z” according to 

Equation E-3a of this section (metric tons).

Eb,z = Annual N2O mass emissions from adipic acid production unit “z” according to 

Equation E-3b of this section (metric tons).

Ec,z = Annual N2O mass emissions from adipic acid production unit “z” according to 

Equation E-3c of this section (metric tons).

Ed,z = Annual N2O mass emissions from adipic acid production unit “z” according to 

Equation E-3d of this section (metric tons).

M = Total number of adipic acid production units.
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(i) You must determine the amount of process N2O emissions that is sold or transferred 

off site (if applicable). You can determine the amount using existing process flow meters and 

N2O analyzers.

[75 FR 66458, Oct. 28, 2010, as amended at 78 FR 71952, Nov. 29, 2013]

§98.54 Monitoring and QA/QC requirements.

(a) You must conduct a new performance test and calculate a new emissions factor for 

each adipic acid production unit according to the frequency specified in paragraphs (a)(1) 

through (3) of this section.

(1) Conduct the performance test annually. The test must be conducted at a point during 

production that is representative of the average emissions rate from your process. You must 

document the methods used to determine the representative point.

(2) Conduct the performance test when your adipic acid production process is changed 

either by altering the ratio of cyclohexanone to cyclohexanol or by installing abatement 

equipment.

(3) If you requested Administrator approval for an alternative method of determining 

N2O emissions under §98.53(a)(2), you must conduct the performance test if your request has not 

been approved by the Administrator within 150 days of the end of the reporting year in which it 

was submitted.

(b) You must measure the N2O concentration during the performance test using one of 

the methods in paragraphs (b)(1) through (b)(3) of this section.

(1) EPA Method 320, Measurement of Vapor Phase Organic and Inorganic Emissions by

Extractive Fourier Transform Infrared (FTIR) Spectroscopy in 40 CFR part 63, Appendix A;
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(2) ASTM D6348-03 Standard Test Method for Determination of Gaseous Compounds 

by Extractive Direct Interface Fourier Transform Infrared (FTIR) Spectroscopy (incorporated by

reference, see §98.7); or

(3) An equivalent method, with Administrator approval.

(c) You must determine the adipic acid production rate during the performance test 

according to paragraph (c)(1) or (c)(2) of this section.

(1) Direct measurement (such as using flow meters or weigh scales).

(2) Existing plant procedures used for accounting purposes.

(d) You must determine the volumetric flow rate during the performance test in 

conjunction with the applicable EPA methods in 40 CFR part 60, appendices A-1 through A-4. 

Conduct three emissions test runs of 1 hour each. All QA/QC procedures specified in the 

reference test methods and any associated performance specifications apply. For each test, the 

facility must prepare an emissions factor determination report that must include the items in 

paragraphs (d)(1) through (d)(3) of this section:

(1) Analysis of samples, determination of emissions, and raw data.

(2) All information and data used to derive the emissions factor.

(3) The production rate(s) during the performance test and how each production rate was 

determined.

(e) You must determine the monthly amount of adipic acid produced. You must also 

determine the monthly amount of adipic acid produced during which N2O abatement technology

is operating. These monthly amounts are determined according to the methods in paragraphs 

(c)(1) or (c)(2) of this section.
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(f) You must determine the annual amount of adipic acid produced. You must also 

determine the annual amount of adipic acid produced during which N2O abatement technology is 

operating. These are determined by summing the respective monthly adipic acid production 

quantities determined in paragraph (e) of this section.

[74 FR 56374, Oct. 30, 2009, as amended at 75 FR 66460, Oct. 28, 2010; 78 FR 71953, 

Nov. 29, 2013]

§98.55 Procedures for estimating missing data.

A complete record of all measured parameters used in the GHG emissions calculations is 

required. Therefore, whenever a quality-assured value of a required parameter is unavailable, a 

substitute data value for the missing parameter shall be used in the calculations as specified in 

paragraphs (a) and (b) of this section.

(a) For each missing value of monthly adipic acid production, the substitute data shall be 

the best available estimate based on all available process data or data used for accounting 

purposes (such as sales records).

(b) For missing values related to the performance test, including emission factors, 

production rate, and N2O concentration, you must conduct a new performance test according to 

the procedures in §98.54 (a) through (d).

§ 98.56 Data reporting requirements.

In addition to the information required by § 98.3(c), each annual report must contain the 

information specified in paragraphs (a) through (n) of this section at the facility level.

(a) Annual process N2O emissions from adipic acid production (metric tons).

(b)Reserved.

(c) Reserved.
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(d) Annual process N2O emissions from adipic acid production facility that is sold or 

transferred off site (metric tons).

(e) Number of abatement technologies (if applicable).

(f) Types of abatement technologies used and date of installation for each (if applicable).

(g) Abatement technology destruction efficiency for each abatement technology (percent 

destruction).

(h) Abatement utilization factor for each abatement technology (fraction of annual 

production that abatement technology is operating).

(i) Number of times in the reporting year that missing data procedures were followed to 

measure adipic acid production (months).

(j) If you conducted a performance test and calculated a site-specific emissions factor 

according to § 98.53(a)(1), each annual report must also contain the information specified in 

paragraphs (j)(1) through (7) of this section for each adipic acid production unit.

(1) Reserved.

(2) Test method used for performance test.

(3) Reserved.

(4) N2O concentration per test run during performance test (ppm N2O).

(5) Volumetric flow rate per test run during performance test (dscf/hr).

(6) Number of test runs.

(7) Number of times in the reporting year that a performance test had to be repeated 

(number).
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(k) If you requested Administrator approval for an alternative method of determining 

N2O emissions under § 98.53(a)(2), each annual report must also contain the information 

specified in paragraphs (k)(1) through (4) of this section for each adipic acid production facility.

(1) Name of alternative method.

(2) Description of alternative method.

(3) Request date.

(4) Approval date.

(l) Fraction control factor for each abatement technology (percent of total emissions from 

the production unit that are sent to the abatement technology) if equation E-3c is used.

(m) If only cyclohexane is oxidized to produce adipic acid and the quantity is known, 

report the information specified in paragraph (m)(1) of this section. If materials other than 

cyclohexane are oxidized to produce adipic acid, report the information specified in paragraph 

(m)(2) of this section.

(1) Annual quantity of cyclohexane (tons) used to produce adipic acid.

(2) Annual quantity of cyclohexanone and cyclohexanol mixture (tons) used to produce 

adipic acid.

(n) Annual percent N2O emission reduction for all production units combined.

§ 98.57 Records that must be retained.

In addition to the information required by § 98.3(g), you must retain the records specified 

in paragraphs (a) through (i) of this section at the facility level:

(a) Annual adipic acid production capacity (tons).

(b) Records of significant changes to process.

(c) Number of facility and unit operating hours in calendar year.
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(d) Documentation of how accounting procedures were used to estimate production rate.

(e) Documentation of how process knowledge was used to estimate abatement 

technology destruction efficiency.

(f) Performance test reports.

(g) Measurements, records and calculations used to determine reported parameters.

(h) Documentation of the procedures used to ensure the accuracy of the measurements of 

all reported parameters, including but not limited to, calibration of weighing equipment, flow 

meters, and other measurement devices. The estimated accuracy of measurements made with 

these devices must also be recorded, and the technical basis for these estimates must be provided.

(i) Verification software records. You must keep a record of the file generated by the 

verification software specified in § 98.5(b) for the applicable data specified in paragraphs (i)(1) 

through (3) of this section. Retention of this file satisfies the recordkeeping requirement for the 

data in paragraphs (i)(1) through (3) of this section.

(1) Annual adipic acid production from each adipic acid production unit (tons)(Equations 

E-2, E-3a, E-3b, E-3c, and E-3d of § 98.53). 

(2) Production rate per test run during the performance test for each production unit test 

run (tons adipic acid produced/hr) (Equation E-1 of § 98.53).

(3) Annual adipic acid production per N2O abatement technology during which N2O 

abatement technology was used (tons adipic acid produced) (Equation E-2).

§98.58 Definitions.

All terms used in this subpart have the same meaning given in the Clean Air Act and 

subpart A of this part.