Aluminum Production
- United States
Final Rule: Mandatory Reporting of Greenhouse Gases Aaencjmerrtal Pl°t9ction
Under the Mandatory Reporting of Greenhouse Gases (GHGs) rule, owners or operators of aluminum
production facilities (as defined below) must report emissions from processes that produce primary aluminum
and any other source categories located at the facility for which methods are defined in the rule. Owners or
operators are required to collect emission data; calculate GHG emissions; and follow the specified procedures
for quality assurance, missing data, recordkeeping, and reporting.
How Is This Source Category Defined?
The aluminum production source category consists of facilities that manufacture primary aluminum using the
Hall-Heroult manufacturing process. The primary aluminum manufacturing process consists of the following
operations:
Electrolysis in prebake and S0derberg 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 aluminum production facility must report:
• Perfluoromethane (CF4) and perfluoroethane (C2F6) emissions from anode effects in all prebake and
S0derberg electrolysis cells combined.
• Carbon dioxide (CO2) emissions from anode consumption during electrolysis in all prebake and
S0derberg cells.
• All CO2 emissions from onsite anode baking.
In addition, each facility must report GHG emissions for other source categories for which calculation methods
are provided in the rule. For example, facilities must report CO2, nitrous oxide (N2O), and methane (CFLO
emissions from each stationary combustion unit on site by following the requirements of 40 CFR part 98,
subpart C (General Stationary Fuel Combustion Sources). Please refer to the relevant information sheet for a
summary of the rule requirements for calculating and reporting emissions from any other source categories 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 aluminum electrolytic reduction process for each prebake and S0derberg electrolysis cell
using the following parameters:
o Anode effect minutes (AEM) per cell-day calculated monthly.
o Aluminum metal production calculated monthly.
o A slope coefficient relating CF4 emissions to anode effect minutes per cell-day and aluminum
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
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specified in the rule. Under certain conditions, high-efficiency smelters may use a default slope
coefficient from Table F-l in the rule.
• C2F6 from anode effects. Estimate annual C2F6 emissions from anode effects from each prebake and
S0derberg electolysis 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:
o Installing and operating a continuous emission monitoring system (CEMS) and following the
Tier 4 methodology (in 40 CFR part 98, subpart C).
o 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:
o Net prebaked anode consumption rate per metric ton of aluminum metal produced.
o Ash and sulfur contents of the anodes.
o Total mass of aluminum metal produced per year for all prebake cells.
• CO2 emissions from Soderberg cells. Estimate CO2 emissions from paste consumption in S0derberg
cells using a mass balance equation at the facility level based on the following parameters:
o Paste consumption rate per metric ton of aluminum metal produced and the annual mass of
aluminum metal produced for all S0derberg cells.
o Emissions of cyclohexane-soluble matter per metric ton of aluminum produced.
o Binder content of the anode paste.
o Sulfur, ash, and hydrogen contents of the coal tar pitch used as the binder in the anode paste.
o Sulfur and ash contents of the calcined coke used in the anode paste.
o Carbon in the skimmed dust from the cell, per metric ton of aluminum 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.
o 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 hydrogen in the green anodes.
• Mass of the baked anodes.
• Mass of waste tar collected.
o 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
Sulfur and ash contents of the packing coke.
Measure the smelter-specific values used to estimate CO2 emissions from anode and paste consumption
(e.g., sulfur, ash, and hydrogen 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 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 at:
http://www.epa.gov/climatechange/emissions/downloads/checklists/aluminumproduction.pdf
What Information Must Be Reported?
In addition to the information required by the General Provisions at 40 CFR 98.3(c), the rule requires each
facility to report the following information at the facility level:
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• Annual aluminum production in metric tons.
• Type of smelter technology used.
• The following PFC-specific information on an annual basis:
o CF4 and C2F6 emissions from anode effects in all prebake and S0derberg electrolysis cells
combined.
o Anode effect minutes per cell-day, anode effect frequency, anode effect duration, if
estimating CF4 emissions from anode effect duration.
o Anode effect overvoltage factor, potline overvoltage, and current efficiency.
o Smelter-specific slope coefficients (or overvoltage emission factors) and the last date when
the smelter-specific-slope coefficients (or overvoltage emission factors) 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:
o Anode consumption.
o CO2 emissions from the smelter.
• The following CO2-specific information for S0derberg cells on an annual basis:
o Paste consumption.
o CO2 emissions from the smelter.
• Smelter-specific inputs to the CO2 process equations (e.g., levels of sulfur and ash) that were used in the
calculation.
For More Information
This document is provided solely for informational purposes. It does not provide legal advice, have legally
binding effect, or expressly or implicitly create, expand, or limit any legal rights, obligations, responsibilities,
expectations, or benefits in regard to any person. The series of information sheets is intended to assist reporting
facilities/owners in understanding key provisions of the final rule.
Visit EPA's Web site (www.epa.gov/climatechange/emissions/ghgrulemaking.html) for more information,
including the final preamble and rule, additional information sheets on specific industries, the schedule for
training sessions, and other documents and tools. For questions that cannot be answered through the Web site,
please contact us at: ghgmrrigiepa.gov.
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