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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.
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(2) Request Administrator approval for an alternative 

method of determining N2O emissions according to paragraphs 

(a)(2)(i) and (ii) of this section.

(i) You must submit the request within 45 days following 

promulgation of this subpart or within the first 30 days of each 

subsequent reporting year.

(ii) 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 paragraphs 

(b) through (h) 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.
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(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:

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.
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(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” 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.

Where:

AFN = Abatement utilization factor of N2O abatement 

technology “N” (fraction of annual production that 

abatement technology is operating).
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Pz,N = Annual adipic acid production during which N2O 

abatement technology “N” was used on unit “z” (ton 

adipic acid produced).

Pz = Total annual adipic acid production from unit 

“z” (ton acid produced).

(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).
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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).

(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).
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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).

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).
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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 

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).
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(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.

(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.

§ 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.
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(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;

(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.
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(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. 
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These monthly amounts are determined according to the methods in 

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

(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.

§ 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.
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In addition to the information required by §98.3(c), each 

annual report must contain the information specified in 

paragraphs (a) through (l) of this section at the facility 

level.

(a) Annual process N2O emissions from adipic acid production 

(metric tons).

(b) Annual adipic acid production (tons).

(c) Annual adipic acid production during which N2O abatement 

technology (located after the test point) is operating (tons).

(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 (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 
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paragraphs (j)(1) through (7) of this section for each adipic 

acid production unit.

(1) Emission factor (lb N2O/ton adipic acid).

(2) Test method used for performance test.

(3) Production rate per test run during performance test 

(tons/hr).

(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).

(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.
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(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.

§ 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 (h) 

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.

(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 
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recorded, and the technical basis for these estimates must be 

provided.

§ 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.