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Subpart Z—Phosphoric Acid Production

§ 98.260 Definition of the source category.

The phosphoric acid production source category consists of 

facilities with a wet-process phosphoric acid process line used 

to produce phosphoric acid. A wet-process phosphoric acid 

process line is the production unit or units identified by an 

individual identification number in an operating permit and/or 

any process unit or group of process units at a facility 

reacting phosphate rock from a common supply source with acid.

§ 98.261 Reporting threshold.

You must report GHG emissions under this subpart if your 

facility contains a phosphoric acid production process and the 

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

§ 98.262 GHGs to report.

(a) You must report CO2 process emissions from each wetprocess phosphoric acid process line.

(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 of this part.

§ 98.263 Calculating GHG emissions.

You must calculate and report the annual process CO2

emissions from each wet-process phosphoric acid process line 
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using the procedures in either paragraph (a) or (b) of this 

section.

(a) Calculate and report under this subpart the process CO2

emissions by operating and maintaining a CEMS according to the 

Tier 4 Calculation Methodology specified in §98.33(a)(4) and all 

associated requirements for Tier 4 in subpart C of this part 

(General Stationary Fuel Combustion Sources).

(b) Calculate and report under this subpart the process CO2

emissions using the procedures in paragraphs (b)(1) and (b)(2) 

of this section.

(1) Calculate the annual CO2 mass emissions from each wetprocess phosphoric acid process line using the methods in 

paragraphs (b)(1)(i) or (ii) of this section, as applicable.

(i) If your process measurement provides the inorganic 

carbon content of phosphate rock as an output, calculate and 

report the process CO2 emissions from each wet-process phosphoric 

acid process line using Equation Z–1a of this section:

Where:

Em = Annual CO2 mass emissions from a wet-process 

phosphoric acid process line m according to 

this Equation Z–1a (metric tons).

ICn,i = Inorganic carbon content of a grab sample 

batch of phosphate rock by origin i obtained 

during month n, from the carbon analysis 
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results (percent by weight, expressed as a 

decimal fraction).

Pn,i = Mass of phosphate rock by origin i consumed in 

month n by wet-process phosphoric acid process 

line m (tons).

z = Number of months during which the process line 

m operates.

b = Number of different types of phosphate rock in 

month, by origin. If the grab sample is a 

composite sample of rock from more than one 

origin, b = 1.

2000/2205 = Conversion factor to convert tons to metric 

tons.

44/12 = Ratio of molecular weights, CO2 to carbon.

(ii) If your process measurement provides the CO2 content

directly as an output, calculate and report the process CO2

emissions from each wet-process phosphoric acid process line 

using Equation Z–1b of this section:

Where:

Em = Annual CO2 mass emissions from a wet-process 

phosphoric acid process line m according to 

this Equation Z–1b (metric tons).

CO2 n,i = Carbon dioxide content of a grab sample batch 

of phosphate rock by origin i obtained during 

month n (percent by weight, expressed as a 

decimal fraction).

Pn,i = Mass of phosphate rock by origin i consumed in 

month n by wet-process phosphoric acid process 

line m (tons).

z = Number of months during which the process line 

m operates.
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b = Number of different types of phosphate rock in 

month, by origin. If the grab sample is a 

composite sample of rock from more than one 

origin, b=1.

2000/2205 = Conversion factor to convert tons to metric 

tons.

(2) You must determine the total emissions from the 

facility using Equation Z–2 of this section:

Where:

CO2 = Annual process CO2 emissions from phosphoric 

acid production facility (metric tons/year).

Em = Annual process CO2 emissions from wet-process 

phosphoric acid process line m (metric 

tons/year).

p = Number of wet-process phosphoric acid process 

lines.

(c) If GHG emissions from a wet-process phosphoric acid 

process line are vented through the same stack as any combustion 

unit or process equipment that reports CO2 emissions using a CEMS 

that complies with the Tier 4 Calculation Methodology in subpart 

C of this part (General Stationary Fuel Combustion Sources), 

then the calculation methodology in paragraph (b) of this 

section shall not be used to calculate process emissions. The 

owner or operator shall report under this subpart the combined 

stack emissions according to the Tier 4 Calculation Methodology 

in §98.33(a)(4) and all associated requirements for Tier 4 in 

subpart C of this part.
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§ 98.264 Monitoring and QA/QC requirements.

(a) You must obtain a monthly grab sample of phosphate rock 

directly from the rock being fed to the process line before it 

enters the mill using one of the following methods. You may 

conduct the representative bulk sampling using a method 

published by a consensus standards organization, or you may use 

industry consensus standard practice methods, including but not 

limited to the Phosphate Mining States Methods Used and Adopted 

by the Association of Fertilizer and Phosphate Chemists (AFPC).

If phosphate rock is obtained from more than one origin in a 

month, you must obtain a sample from each origin of rock or 

obtain a composite representative sample.

(b) You must determine the carbon dioxide or inorganic 

carbon content of each monthly grab sample of phosphate rock 

(consumed in the production of phosphoric acid). You may use a 

method published by a consensus standards organization, or you 

may use industry consensus standard practice methods, including 

but not limited to the Phosphate Mining States Methods Used and 

Adopted by AFPC.

(c) You must determine the mass of phosphate rock consumed 

each month (by origin) in each wet-process phosphoric acid 

process line. You can use existing plant procedures that are 

used for accounting purposes (such as sales records) or you can 

use data from existing monitoring equipment that is used to 
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measure total mass flow of phosphorous-bearing feed under 40 CFR 

part 60 or part 63.

§ 98.265 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 must be used in 

the calculations as specified in paragraphs (a) and (b) of this 

section. 

(a) For each missing value of the inorganic carbon content 

or CO2 content of phosphate rock (by origin), you must use the 

appropriate default factor provided in Table Z–1 of this 

subpart. Alternatively, you must determine a substitute data 

value by calculating the arithmetic average of the qualityassured values of inorganic carbon contents or CO2 contents of 

phosphate rock of origin i (see Equation Z–1a or Z-1b of this 

subpart) from samples immediately preceding and immediately 

following the missing data incident. If no quality-assured data 

on inorganic carbon contents or CO2 contents of phosphate rock of 

origin i are available prior to the missing data incident, the 

substitute data value shall be the first quality-assured value 

for inorganic carbon contents or CO2 contents for phosphate rock 

of origin i obtained after the missing data period.
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(b) For each missing value of monthly mass consumption of 

phosphate rock (by origin), you must use the best available 

estimate based on all available process data or data used for 

accounting purposes.

§ 98.266 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 (f) of this section.

(a) Annual phosphoric acid production, by origin of the 

phosphate rock (tons).

(b) Annual phosphoric acid production capacity (tons).

(c) Annual arithmetic average percent inorganic carbon or 

carbon dioxide in phosphate rock from monthly records (percent 

by weight, expressed as a decimal fraction).

(d) Annual phosphate rock consumption from monthly 

measurement records by origin (tons).

(e) If you use a CEMS to measure CO2 emissions, then you 

must report the information in paragraphs (e)(1) and (e)(2) of 

this section.

(1) The identification number of each wet-process 

phosphoric acid process line.

(2) The annual CO2 emissions from each wet-process 

phosphoric acid process line (metric tons) and the relevant 
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information required under 40 CFR 98.36 (e)(2)(vi) for the Tier 

4 Calculation Methodology.

(f) If you do not use a CEMS to measure emissions, then you 

must report the information in paragraphs (f)(1) through (9) of 

this section.

(1) Identification number of each wet-process phosphoric 

acid process line.

(2) Annual CO2 emissions from each wet-process phosphoric 

acid process line (metric tons) as calculated by either Equation 

Z–1a or Equation Z–1b of this subpart.

(3) Annual phosphoric acid permitted production capacity 

(tons) for each wet-process phosphoric acid process line (metric 

tons).

(4) Method used to estimate any missing values of inorganic 

carbon content or carbon dioxide content of phosphate rock for 

each wet-process phosphoric acid process line.

(5) Monthly inorganic carbon content of phosphate rock for 

each wet-process phosphoric acid process line for which Equation 

Z–1a is used (percent by weight, expressed as a decimal 

fraction), or CO2 content (percent by weight, expressed as a 

decimal fraction) for which Equation Z–1b is used.

(6) Monthly mass of phosphate rock consumed, by origin, in 

production for each wet-process phosphoric acid process line 

(tons).
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(7) Number of wet-process phosphoric acid process lines.

(8) Number of times missing data procedures were used to 

estimate phosphate rock consumption (months), inorganic carbon

contents of the phosphate rock (months), and CO2 contents of the 

phosphate rock (months).

(9) Annual process CO2 emissions from phosphoric acid 

production facility (metric tons).

§ 98.267 Records that must be retained.

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

retain the records specified in paragraphs (a) through (c) of 

this section for each wet-process phosphoric acid production 

facility.

(a) Monthly mass of phosphate rock consumed by origin 

(tons).

(b) Records of all phosphate rock purchases and/or 

deliveries (if vertically integrated with a mine).

(c) Documentation of the procedures used to ensure the 

accuracy of monthly phosphate rock consumption by origin.

§ 98.268 Definitions.

All terms used in this subpart have the same meaning given 

in the Clean Air Act and subpart A of this part.

Table Z–1 to Subpart Z of Part 98—Default Chemical Composition 

of Phosphate Rock by Origin

Origin

Total carbon

(percent by weight)
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Central Florida 1.6

North Florida 1.76

North Carolina (Calcined) 0.76

Idaho (Calcined) 0.60

Morocco 1.56