Subpart F Information Sheet
Overview
Subpart F of the Greenhouse Gas Reporting Program (GHGRP) (40 CFR 98.60 – 98.68) applies to any facility that contains an aluminum (Al) production process and meets the Subpart F source category definition. Some subparts have thresholds that determine applicability for reporting, and some do not. To decide whether your facility must report under this subpart, please refer to 40 CFR 98.61 and the GHGRP Applicability Tool.
This Information Sheet is intended to help facilities reporting under Subpart F understand how the source category is defined, what greenhouse gases (GHGs) must be reported, how GHG emissions must be calculated and shared with EPA, and where to find more information.
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On this page:
- How is This Source Category Defined?
- What GHGs Must Be Reported?
- How Must GHG Emissions Be Calculated?
- What Information Must Be Reported?
- What Records Must Be Maintained?
- When and How Must Reported Be Submitted?
- When Can a Facility Stop Reporting?
- For More Information
How is This Source Category Defined?
The aluminum (Al) production source category consists of facilities that manufacture primary Al using the Hall-Héroult manufacturing process. The primary Al manufacturing process consists of the following operations:
- Electrolysis in prebake and Søderberg cells.
- Anode baking for prebake cells.
This source category does not include experimental cells or research and development process units.
What GHGs Must Be Reported?
Each Al production facility must report:
- Perfluoromethane (CF4) and perfluoroethane (C2F6) emissions from anode effects in all prebake and Søderberg electrolysis cells combined.
- Carbon dioxide (CO2) emissions from anode consumption during electrolysis in all prebake and Søderberg cells.
- All CO2 emissions from onsite anode baking.
If multiple Greenhouse Gas Reporting Program (GHGRP) source categories are co-located at a facility, the facility may need to report greenhouse gas (GHG) emissions under a different subpart. For example, facilities must report CO2, nitrous oxide (N2O), and methane (CH4) emissions from each stationary combustion unit on site by following the requirements of Subpart C (General Stationary Fuel Combustion Sources), found at 40 CFR 98.30 – 98.38. Please refer to the relevant Information Sheet for a summary of the rule requirements for any other source categories located at the facility.
How Must GHG Emissions Be Calculated?
Facilities must calculate GHG process emissions using the following methods:
- CF4 from anode effects. Calculate annual CF4 emissions based on the frequency and duration of anode effects in the Al electrolytic reduction process for each prebake and Søderberg electrolysis cell using the following parameters:
- Anode effect minutes per cell-day (AEM/cell-day) calculated monthly.
- Al metal production calculated monthly.
- A slope coefficient relating CF4 emissions to AEM/cell-day and Al production. The slope coefficient is specific to each smelter. Smelters that have never measured the slope coefficient must measure it within one year of rule publication. Smelters that have measured it must re-measure it within three years of rule publication. Thereafter, all smelters must measure it at least once every 10 years, or whenever there is a major technological or process change. The slope coefficient must be measured in accordance with the protocol specified in the rule. Under certain conditions, high-efficiency smelters may use a default slope coefficient from Table F-1 in the rule.
- C2F6 from anode effects. Estimate annual C2F6 emissions from anode effects from each prebake and Søderberg electrolysis cell using the estimated CF4 emissions and the mass ratio of C2F6 to CF4 emissions, as determined during the same test during which the slope coefficient is determined.
- Process CO2 emissions. Reporters can elect to calculate and report process CO2 emissions from anode consumption during electrolysis and from anode baking by using one of two methods:
- Installing and operating a continuous emission monitoring system (CEMS) and following the Tier 4 Calculation Methodology (in 40 CFR Part 98, Subpart C).
- Using the calculation procedures specified below.
- CO2 emissions from anode consumption in prebake cells. Estimate annual CO2 emissions at the facility level using a mass balance equation based on measurements of the following parameters:
- Net prebaked anode consumption rate per metric ton of Al produced.
- Ash and sulfur (S) contents of the anodes.
- Total mass of Al produced per year for all prebake cells.
- CO2 emissions from Søderberg cells. Estimate CO2 emissions from paste consumption in Søderberg cells using a mass balance equation at the facility level based on the following parameters:
- Paste consumption rate per metric ton of Al produced and the annual mass of Al produced for all Søderberg cells.
- Emissions of cyclohexane (C6H12)-soluble matter per metric ton of Al produced.
- Binder content of the anode paste.
- S, ash, and hydrogen (H2) contents of the coal tar pitch used as the binder in the anode paste.
- S and ash contents of the calcined coke used in the anode paste.
- Carbon (C) in the skimmed dust from the cell per metric ton of Al produced.
- CO2 emissions from anode baking of prebake cells. Estimate CO2 emissions at the facility level separately from pitch volatiles and from bake furnace packing material.
- To estimate CO2 emissions from the pitch volatiles, use a mass balance equation based on the following parameters:
- Initial weight of the green anodes.
- Mass of H2 in the green anodes.
- Mass of the baked anodes.
- Mass of waste tar collected.
- To estimate CO2 emissions from bake furnace packing material, use a mass balance equation based on the following parameters:
- Packing coke consumption rate per ton of baked anode production.
- S and ash contents of the packing coke.
- To estimate CO2 emissions from the pitch volatiles, use a mass balance equation based on the following parameters:
Facilities must also measure the smelter-specific values used to estimate CO2 emissions from anode and paste consumption (e.g., S, ash, and H2 contents), or use default values listed in the rule.
If process CO2 emissions from anode consumption during electrolysis or anode baking are emitted through the same stack as a combustion unit or process equipment that uses a CEMS and follows the Tier 4 Calculation Methodology in the rule to report CO2 emissions, then the CEMS must be used to measure and report combined CO2 emissions from that stack, instead of using the calculation procedures specified above.
A checklist for data that must be monitored is available here: Subpart F Monitoring Checklist.
What Information Must Be Reported?
In addition to the information required by the General Provisions in Subpart A, found at 40 CFR 98.3(c), the following must be reported:
- Type of smelter technology used.
- The following perfluorocarbons (PFC)-specific information on an annual basis:
- CF4 and C2F6 emissions from anode effects in all prebake and Søderberg electrolysis cells combined.
- AEM/cell-day, anode effect frequency, anode effect duration, if estimating CF4 emissions from anode effect duration.
- Anode effect overvoltage factor, potline overvoltage, and current efficiency, if estimating CF4 from overvoltage.
- Smelter-specific slope coefficients (or overvoltage emission factors (EFs)) and the last date when the smelter-specific-slope coefficients (or overvoltage EFs) were measured, if estimating CF4 emissions from overvoltage.
- Method used to measure the frequency and duration of anode effects (or overvoltage).
- The following CO2-specific information for prebake cells on an annual basis:
- Anode consumption if using the method in 40 CFR 98.63(g).
- CO2 emissions from the smelter.
- The following CO2-specific information for Søderberg cells on an annual basis:
- Paste consumption if using the method in 40 CFR 98.63(g).
- CO2 emissions from the smelter.
- Smelter-specific inputs to the CO2 process equations (e.g., levels of S and ash) that were used in the calculation.
What Records Must Be Maintained?
Reporters are required to retain records that pertain to their annual GHGRP report for at least three years after the date the report is submitted. Please see the Subpart A Information Sheet and 40 CFR 98.3(g) for general recordkeeping requirements. Specific recordkeeping requirements for Subpart F are listed at 40 CFR 98.67.
When and How Must Reports Be Submitted?
Reporters must submit their annual GHGRP reports for the previous calendar year to the EPA by March 31st, unless the 31st falls on a Saturday, Sunday, or federal holiday, in which case reports are due on the next business day. Annual reports must be submitted electronically using the electronic Greenhouse Gas Reporting Tool (e-GGRT), the GHGRP’s online reporting system.
Additional information on setting up user accounts, registering a facility, and submitting annual reports is available on the GHGRP Help webpage.
When Can a Facility Stop Reporting?
A facility may discontinue reporting under several scenarios, which are summarized in in Subpart A (found at 40 CFR 98.2(i)) and the Subpart A Information Sheet.
For More Information
For additional information on Subpart F, please visit the Subpart F webpage. For additional information on the GHGRP, please visit the GHGRP website, which includes additional information sheets, data previously reported to the GHGRP, training materials, and links to FAQs. For questions that cannot be answered through the GHGRP website, please contact us at: [email protected].
This Information Sheet is provided solely for informational purposes. It does not replace the need to read and comply with the regulatory text contained in the rule. Rather, it is intended to help reporting facilities and suppliers understand key provisions of the GHGRP. It does not provide legal advice; have a legally binding effect; or expressly or implicitly create, expand, or limit any legal rights, obligations, responsibilities, expectations, or benefits with regard to any person or entity.
Archived Versions
Links to external websites or other EPA webpages in older documents may not work. Although some content may be current or applicable, older resources on this page are intended for reference and historical documentation purposes.
The Subpart F (Aluminum Production) information sheet is intended to assist reporters in understanding the key requirements of the Greenhouse Gas Reporting Program. It contains information on how this source category is defined, the greenhouse gases required to be reported, how emissions must be calculated, what information must be reported, when and how reports are submitted, and under what circumstances a facility may stop reporting. The complete list of data elements that must be reported and records that must be retained under 40 CFR Part 98 are available in the e-CFR.