Aluminum Production
United States
Proposed Rule: Mandatory Reporting of Greenhouse Gases
Under the proposed Mandatory Reporting of Greenhouse Gases (GHGs) rule, owners or operators of aluminum
production facilities (as defined below) would 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 would 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?
Under the proposal, 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 Soderberg cells
• Anode baking for prebake cells
This source category does not include experimental cells or research and development process units.
What GHGs Would Be Reported?
The proposal calls for each aluminum production facility to report:
• Perfluoromethane (CF4) emissions and perfluoroethane (C2F6) emissions from anode effects in all prebake and
Soderberg electrolysis cells combined.
• Carbon dioxide (CO2) emissions from anode consumption during electrolysis in all prebake and Soderberg
cells.
• All CO2 emissions from anode baking.
In addition, each facility would report GHG emissions for other source categories for which calculation methods are
provided in the rule. For example, facilities would report CO2, nitrous oxide (N2O), and methane (CH4) 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 proposal for calculating and
reporting emissions from any other source categories at the facility.
How Would GHG Emissions Be Calculated?
Under the proposal, facilities would calculate CO2 process emissions using the following methods:
• CF4 from anode effects: Estimate annual CF4 emissions based on the frequency and duration of anode effects
in the aluminum electrolytic reduction process for each prebake and Soderberg electrolysis cell using the
following parmeters:
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 and would be measured at least once
every 36 months in accordance with the protocol specified in the rule.
• C?Ffi from anode effects: Estimate annual C2F6 emissions from anode effects from each prebake and
Soderberg 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.
• CO? 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.
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o Total mass of aluminum metal produced per year for all prebake cells.
• CO? emissions from Soderberg cells: Estimate CO2 emissions from paste consumption in Soderberg 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 total mass of aluminum
metal produced per year for all Soderberg 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.
• CO? 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.
The variables used to estimate CO2 emissions from anode and paste consumption (e.g., sulfur, ash, and hyrdogen contents)
can be determined for each facility, or the source can use default values from the 2006 IPCC Guidelines for National
Greenhouse Gas Inventories.
What Information Would Be Reported?
In addition to the information required by the General Provisions at 40 CFR 98.3(c), the proposal calls for each facility to
report the following information at the facility level:
• Annual aluminum production in metric tons.
• Type of smelter technology used.
• Total CF4 and C2F6 emissions from anode effects in all prebake and Soderberg electrolysis cells.
• Annual CO2 emissions from anode consumption during electrolysis in all prebake and Soderberg electrolysis
cells.
• Annual CO2 emissions from anode baking.
• The following information used to estimate CF4 and C2F6 emissions:
o Anode effect minutes per cell-day, anode effect frequency (AE/cell-day), anode effect duration
(minutes) by month.
o Smelter-specific slope coefficient and the last date when the smelter-specific-slope coefficient was
measured.
• The method used to measure the frequency and duration of anode effects.
• The following CO2-specific information:
o Annual anode consumption (both prebaked and paste)
o Smelter-specific inputs to the CO2 process equations (e.g., levels of sulfur and ash) that were used in
the calculation, on an annual basis.
For More Information
This series of information sheets is intended to assist reporting facilities/owners in understanding key provisions of the
proposed rule. However, these information sheets are not intended to be a substitution for the rule. Visit EPA's Web site
(www.epa.gov/climatechange/emissions/ghgrulemaking.html) for more information, including the proposed preamble and
rule and additional information sheets on specific industries, or go to to access the rulemaking
docket (EPA-HQ OAR-2008-0508). For questions that cannot be answered through the Web site or docket, call 1-877-
GHG-1188.
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