Page 1 of 13

**Subpart F**
**—**

**Aluminum Production §98.60**  **Definition of the source category.**  (a) A primary

aluminum production facility manufactures primary aluminum using the Hall
- Héroult manufacturing process. The primary aluminum manufacturing process comprises the following operations: (1) Electrol ys is in prebake and Søde rberg cells. (2) Anode baking for prebake cells. (b) This source category

does not include experimental cells or research and development process units. **§98.61 Reporting threshold.**  You must report GHG emissions under this subpart if your facility contains an aluminum production process and the facility meets the requirements of either §98.2(a)(1) or (a)(2). **§98.62 GHGs to report.**  You must report: (a) Perfluoromethane (CF 4 ), and perfluoroethane (C 2 F 6 ) emissions from anode effects in all prebake and Søderberg electrol ys is cells. (b) CO 2 emissions from anode consumption during electrol ys is in all prebake and Søderberg electrol ys is cells. (c) CO 2 emissions from on
- site anode baking. (d) You must report under subpart C of this part (General Stationary Fuel Combus tion Sources) the emissions of CO 2 , N 2 O, and CH 4 emissions from each stationary fuel combustion unit by following the requirements of subpart C. **§98.63 Calculating GHG emissions.** Page 2 of 13

(a) The annual value of each PFC compound (CF 4 , C 2 F 6 ) shall be estimated from the sum of monthly

values using Equation F
- 1 of this section:

Where: E PFC = Annual emissions of each PFC compound from aluminum production (metric tons PFC). E m = Emissions of the individual PFC compound from aluminum production for the month “m” (metric tons PFC). (b) Use Equation F
- 2 of this section to estimate CF 4 emissions from anode effect duration or Equation F
- 3 of this section to estimate CF 4 emissions from overvoltage, and use Equation F
- 4 of this section to estimate C 2 F 6 emissions from anode effects from each prebake and Søderberg electrol ys is cell.
Where: E CF4 = Monthly

CF 4 emissions from aluminum production (metric tons CF 4 ). S CF4 = The slope coefficient ((kg CF 4/metric ton Al)/(AE
- Mins/cell
- day)). AEM = The anode effect minutes per cell
- day (AE
- Mins/cell
- day). MP = Metal production (metric tons Al), where AEM and MP are calculated monthly
.
Where: E CF4 = Monthly

CF 4 emissions from alumi num production (metric tons CF 4 ). EF CF4 = The overvoltage emission factor (kg CF 4/metric ton Al). MP = Metal production (metric tons Al), where MP is calculated monthly
.Page 3 of 13

Where: E C2F6 = Monthly

C 2 F 6 emissions from aluminum production (metric tons C 2 F 6 ). E CF4 = CF 4 emissions from aluminum production (kg CF 4 ). F C2F6/CF4 = The weight fraction of C 2 F 6 /CF 4 (kg C 2 F 6 /kg CF 4 ). 0.001 = Conversion factor from kg to metric tons, where E CF 4 is calculated monthly
. (c) You must calculate and report the annual process CO 2 emissions from anode consumption during electroly sis and anode baking of prebake cells using either the procedures in paragraph (d) of this section, the procedures in paragraphs (e) and (f) of this section, or the procedures in paragraph (g) of this section. (d) Calculate and report under this subpart the process CO 2 emissions by operating and maintaining CEMS 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 (General Stati onary Fuel Combustion Sources). (e) Use the following procedures to calculate CO 2 emissions from anode consumption during electrol ys is: (1) For Prebake cells: yo u must calculate CO 2 emissions from anode consumption using Equation F
- 5 of this section:

Where: E CO2 = Annual CO 2 emissions from prebaked anode consumption (metric tons CO 2 ). NAC = Net annual prebaked anode consumption per metric ton Al (metric tons C/metric tons Al).Page 4 of 13

MP = Annual metal production (metric tons Al). S a = Sulfur content in baked anode (percent weight). Ash a = Ash content in baked anode (percent weight). 44/12 = Ratio of molecular weights, CO 2 to carbon. (2) For Søderberg cells you must calculate CO 2 emissions using Equation F
- 6 of this section:

Where: E CO2 = Annual CO 2 emissions from paste consumption (metric ton CO 2 ). PC = Annual paste consumption (metric ton/metric ton Al). MP = Annual metal production (metric ton Al). CSM = Annual emissions of cyclohexane soluble matter (kg/metric ton Al). BC = Binder content of paste (percent weight). S p = Sulfur content of pitch (percent weight). Ashp = Ash content of pitch (percent weight). Hp = Hydrogen content of pitch (percent weight). S c = Sulfur content in calcined coke (percent weight). Ash c = Ash content in calcined coke (percent weight). CD = Carbon in skimmed dust from Søderberg cells (metric ton C/metric ton Al). 44/12 = Ratio of molecular weights, CO 2 to carbon. (f) Use the following procedures to calculate CO 2 emissions from anode baking of prebake cells:Page 5 of 13

(1) Use Equation F
- 7 of this section to calculate emissions from pitch volatiles combustion.
Where: E CO2PV = Annual CO 2 emissions from pitch volatiles combustion (metric tons CO 2 ). GA = Initial weight of green anodes (metric tons). H w = Annual h ydrogen content in green anodes (metric tons). BA = Annual baked anode production (metric tons). WT = Annual waste tar collected (metric tons). 44/12 = Ratio of molecular weights, CO 2 to carbon. (2) Use Equation F
- 8 of this section to calculate em issions from bake furnace packing material.

Where: E CO2PC = Annual CO 2 emissions from bake furnace packing material (metric tons CO 2 ). PCC = Annual packing coke consumption (metric tons/metric ton baked anode). BA = Annual baked anode production (metric tons). S pc = Sulfur content in packing coke (percent weight). Ashpc = Ash content in packing coke (percent weight). 44/12 = Ratio of molecular weights, CO 2 to carbon. (g) If process CO 2 emissions from anode consumption during electrol ys is or anode baking of prebake cells are vented through the same stack as any combustion unit or process equipment that reports CO 2 emissions using a CEMS that complies with the Tier 4 CalculationPage 6 of 13

Methodolo gy

in subpart C of this part (General Stationary Fuel Combustion Sources), then the calculation methodology

in paragraphs (d) and (e) of this section shall not be used to calculate those process emissions. The owner or operation shall report under this sub part 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 (General Stationary Fuel Combustion Sources). **§98.64 Monitoring and QA/QC requirements.**  ( a) Effective December 31, 2010 for smelters with no prior measurement or effective December 31, 2012, for facilities with historic measurements, the smelter
- specific slope coefficients, overvoltage emission factors, and weight fractions used in Equations F
- 2, F - 3, and F - 4 of this subpart must be measured in accordance with the recommendations of the EPA/IAI Protocol for Measurement of Tetrafluoromethane (CF 4 ) and Hexafluoroethane (C 2 F 6 ) Emissions from Primary

Aluminum Production (2008) (incorporated b y refe rence, see §98.7), except the minimum frequency

of measurement shall be every 10 years unless a change occurs in the control algorithm that affects the mix of ty pes of anode effects or the nature of the anode effect termination routine.Facilities which operate at less than 0.2 anode effect minutes per cell day or operate with less than 1.4mV anode effect overvoltage can use either smelter
- specific slope coefficients or the technology specific default values in Table F
- 1 of this subpart. (b) The minimum freq

uency of the measurement and anal ys is is annuall y except as follows: (1) Monthly

for anode effect minutes per cell day (or anode effect overvoltage and current efficiency). (2) Monthly

for aluminum production.Page 7 of 13

(3) Smelter
- specific slope coefficients, overv oltage emission factors, and weight fractions according to paragraph (a) of this section. (c) Sources may

use either smelter
- specific values from annual measurements of parameters needed to complete the equations in §98.63 (e.g., sulfur, ash, and hydrogen contents) or the default values shown in Table F
- 2 of this subpart. **§98.65 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 (e.g., if a meter malfunctions during unit operation or if a required sample measurement is not taken), a substitute data value for the missing parameter shall be used in the calculations, according to the following r equirements: (a) Where anode or paste consumption data are missing, CO 2 emissions can be estimated from aluminum production by using Equation F
- 9 of this section. ECO 2 = EF p x MP p + EF s x MP s (Eq. F
- 9) Where: ECO 2 = CO 2 emissions from anode and/or paste consumption, metric tons CO 2 . EF p = Prebake technology specific emission factor (1.6 metric tons CO 2 /metric ton aluminum produced). MP p = Metal production from prebake process (metric tons Al). EF s = Søderberg technology specific emission factor (1.7 metric tons CO 2 /metric ton Al produced). MP s = Metal production from Søderberg process (metric tons Al).Page 8 of 13

(b) For other parameters, use the average of the two most recent data points after the missing data. **§ 98. 66**  **Data reporti ng requirements.**  In addition to the information required b y § 98. 3(c), you must report the following information at the facility level: (a) Reserved
. (b) T ype of smelter technology used. (c) The following PFC
- specific information on an annual basis: (1) Perfluoromethane emissions and perfluoroethane emissions from anode effects in all prebake and all Søderberg electrol ys is cells combined. (2) Anode effect minutes per cell
- day (AE
- mins/cell
- day), anode effect frequency (AE/cell
- day), anode effect duration (m inutes). (Or anode effect overvoltage factor ((kg CF4/metric ton Al)/(mV/cell day)), potline overvoltage (mV/cell day), current efficiency (%).) (3) Smelter
- specific slope coefficients (or overvoltage emission factors) and the last date when the s melter
- specific slope coefficients (or overvoltage emission factors) were measured. (d) Method used to measure the frequency and duration of anode effects (or overvoltage). (e) The following CO 2 - specific information for prebake cells: (1) Annual anode con sumption if using the method in § 98 .63(g)
. (2) Annual CO 2 emissions from the smelter. (f) The following CO 2 - specific information for Søderberg cells: (1) Annual paste consumption if using the method in § 98.63(g)
. (2) Annual CO 2 emissions from the smelter. (g) Reserved
.Page 9 of 13

(h) Exact data elements required will vary depending on smelter technology ( e.g., point
feed prebake or Søderberg) and process control technology ( e.g., Pechiney

or other). **§ 98. 67**  **Records that must be retained.** In addition to the information required by § 98. 3(g), you must retain the following records: (a) Monthl y aluminum production in metric tons. (b) T ype of smelter technology used. (c) The following PFC
- specific information on a monthly basis: (1) Perfluoromethane and perfluoroethane emissions from anode effects in prebake and Søderberg electol ys is cells. (2) Anode effect minutes per cell
- day (AE
- mins/cell
- day), anode effect frequency (AE/cell
- day), anode effect duration (minutes). (Or anode effect overvoltage factor ((kg CF 4/metric ton Al)/(mV/cell day)), potline overvoltage (mV/cell day), current efficiency (%).)) (3) Smelter
- specific slope coefficients and the last date when the smelter
- specific
- slope coefficients were measured. (d) Method used to measure the frequency and duration of anode effects (or to measure anode effect overvoltage and current efficiency). (e) The following CO 2 - specific information for prebake cells: (1) Annual anode consumption. (2) Annual CO 2 emissions from the smelter. (f) The followi ng CO 2 - specific information for Søderberg cells: (1) Annual paste consumption. (2) Annual CO 2 emissions from the smelter.Page 10 of 13

(g) Smelter
- specific inputs to the CO 2 process equations ( e.g., levels of sulfur and ash) that were used in the calculation, on an annual basis. (h) Exact data elements required will vary depending on smelter technology ( e.g., point
feed prebake or Søderberg) and process control technology ( e.g., Pechiney

or other). (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 (30) of this section. Retention of this file satisfies the recordkeeping requirement for the data in paragraphs (i)(1) through (30) o f this section. ( 1) Slope coefficient per potline per month (kg CF 4/metric ton Al)/(AE
- Mins/cell
- day)) (Equation F
- 2 of § 98
. 63 ). (2) Anode effect minutes per cell
- day per potline per month (AE
- Mins/cell
- day) (Equation F
- 2). (3) Anode effect frequency per potline per month (AE/cell - day) (Equation F
- 2 of § 98 . 63 ). (4) Anode effect duration per potline per month (minutes) (Equation F
- 2). (5) Metal production of aluminum per potline per month (metric tons) (Equation F
- 2). (6) Overvoltage emission factor per po tline per month (kg CF 4/metric ton Al) (Equation F - 3). (7) Metal production of aluminum per potline per month (metric tons) (Equation F
- 3). (8) Weight fraction of C 2 F 6 /CF 4 per potline per month (kg C 2 F 6 /kg CF 4 ) (Equation F
- 4 of § 98 . 63 ). (9) Net annual prebaked anode consumption (metric tons C/metric tons Al) (Equation F
- 5 of § 98
. 63 ).Page 11 of 13

(10) Annual metal production of aluminum (metric tons) (Equation F
- 5). (11) Sulfur content in baked anode (weight percent) (Equation F
- 5). (12) Ash content in baked anode (weight percent) (Equation F
- 5). (13) Annual paste consumption (metric ton/metric ton Al) (Equation F
- 6 of § 98
. 63 ). (14) Annual metal production of aluminum (metric tons) (Equation F
- 6). (15) Annual emissions of cyclohexane soluble matter (kg/metric ton A l) (Equation F
- 6). (16) Binder content of paste (weight percent) (Equation F
- 6). (17) Sulfur content of pitch (weight percent) (Equation F
- 6). (18) Ash content of pitch (weight percent) (Equation F
- 6). (19) Hydrogen content of pitch (weight percent) (Equation F
- 6). (20) Sulfur content in calcined coke (weight percent) (Equation F
- 6). (21) Ash content in calcined coke (weight percent) (Equation F
- 6). (22) Carbon in skimmed dust from Søderberg cells (metric ton C/metric ton Al) (Equation F
- 6). (23) Initial we ight of green anodes (metric tons) (Equation F
- 7 of § 98
. 63 ). (24) Annual hydrogen content in green anodes (metric tons) (Equation F
- 7). (25) Annual baked anode production (metric tons) (Equation F
- 7). (26) Annual waste tar collected (metric tons) (Equatio n F - 7). (27) Annual packing coke consumption (metric tons/metric ton baked anode) (Equation F - 8 of § 98
. 63 ). (28) Annual baked anode production (metric tons) (Equation F
- 8). (29) Sulfur content in packing coke (weight percent) (Equation F
- 8). (30) Ash cont ent in packing coke (weight percent) (Equation F
- 8).Page 12 of 13

**§98.68 Definitions.**  All terms used in this subpart have the same meaning given in the Clean Air Act and subpart A of this part. **Table F -**  **1 to Subpart F of Part 98**
**— Slope and Overvoltage Coefficients for**  **the Calculation of PFC Emissions From Aluminum Production** 

**Technology CF**  **4 slope coefficient** 

**[(kg CF 4**  **/metric ton Al)/(AE**  **- Mins/cell**  **- day)]**  **CF 4**  **overvoltage coefficient**  **[(kg CF 4**  **/metric ton Al)/(mV)]**  **Weight fraction**

**C 2**  **F 6** **/CF 4**  **[(kg C 2**  **F 6** **/kg CF**  **4 )]**  Center Worked Preb ake (CWPB) 0.143 1.16 0.121 Side Worked Prebake (SWPB) 0.272 3.65 0.252 Vertical Stud Søderberg (VSS) 0.092 NA 0.053 Horizontal Stud Søderberg (HSS) 0.099 NA 0.085
**Table F -**  **2 to Subpart F of Part 98**
**— Default Data Sources for Parameters Used for CO**  **2 Emissions**  **Parameter Data source**  CO 2 Emissions from Prebake Cells (CWPB and SWPB) MP: metal production (metric tons Al) Individual facility records. NAC: net annual prebaked anode consumption per metric ton Al (metric tons C/metric tons Al) Individual facility records. S a : sulfur content in baked anode (percent weight) 2.0. Ash a : ash content in baked anode (percent weight) 0.4.

CO 2 Emissions From Pitch Volatiles Combustion (CWPB and SWPB) MP: metal production (metric tons Al) Individual facility records. PC: annual paste consumption (metric ton/metric ton Al) Individual facility records.Page 13 of 13

CSM: annual emissions of cyclohexane soluble matter (kg/metric ton Al) HSS: 4.0. VSS: 0.5. BC: binder content of paste (percent weight) Dry Paste: 24. Wet Paste: 27. S p : sulfur content of pitch (percent weight) 0.6. Ashp : ash content of pitch (percent weight) 0.2. Hp : hydrogen content of pitch (percent weight) 3.3. S c : sulfur content in calcined coke (percent weight) 1.9. Ash c : ash content in calcined c oke (percent weight) 0.2. CD: carbon in skimmed dust from Søderberg cells (metric ton C/metric ton Al) 0.01.

CO 2 Emissions from Pitch Volatiles Combustion (VSS and HSS) GA: initial weight of green anodes (metric tons) Individual facility records. H w : annual h ydrogen content in green anodes (metric tons) 0.005 × GA. BA: annual baked anode production (metric tons) Individual facility records. WT: annual waste tar collected (metric tons) (a) 0.005 × GA. (a) Riedhammer furnaces (b) insignificant. (b) all other furnaces

CO 2 Emissions From Bake Furnace Packing Materials (CWPB and SWPB) PCC: annual packing coke consumption (metric tons/metric ton baked anode) 0.015. BA: annual baked anode production (metric tons) Individual facility records. S pc : sulfur content in packing coke (percent weight) 2. Ashpc : ash content in packing coke (percent weight) 2.5.