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MEMORANDUM 

To: David Putney, U.S. Environmental Protection Agency (EPA), OAQPS 

From: David Green and Matt Hakos, RTI International 

Date: November 13, 2014 

Subject: Revised Draft Cost Impacts for the Primary Aluminum Production Source Category

This memo describes the estimated costs, in 2014 dollars, resulting from the proposed residual risk and 

technology review amendments to the National Emission Standards (NESHAP) for Hazardous Air 

Pollutants for Primary Aluminum Reduction Plants. Maximum achievable control technology (MACT) 

floors were established for the following six previously unregulated hazardous air pollutant (HAP) 

sources at primary aluminum reduction plants: 

1. Polycyclic organic matter (POM) emissions from prebake potlines, 

2. Carbonyl sulfide (COS) emissions from prebake and Soderberg potlines, 

3. POM emissions from existing pitch storage tanks,

4. Metal HAP emissions from potlines, 

5. Metal HAP emissions from anode bake furnaces, and 

6. Metal HAP emissions from paste production plants. 

In addition, to reduce residual risk, revised standards for POM emissions from Soderberg potlines, as 

well as standards for nickel and arsenic emissions from Soderberg potlines have been proposed. The 

nickel and arsenic standards also apply to new Soderberg potlines. The proposed MACT floor limits 

were established by calculating the 99 percent upper prediction limit based on performance test data as 

detailed in the Revised MACT Floor Analysis for the Primary Aluminum Production Source Category 

(available in Docket ID No. EPA-HQ-OAR-2011-0797). Risk-based standards, where needed, were 

established at a level that would provide an ample margin of safety. Note that particulate matter (PM)

has been used as a surrogate for metal HAP in the proposed MACT standards. 

Also, decreased emission testing frequencies have been proposed for: 

 1. Total fluoride (TF) from prebake and Soderberg potlines, and 

 2. POM from Soderberg potlines. 

POM Emissions from Potlines

 Impacts at MACT Floor Level for Prebake Potlines 

We expect that all prebake facilities presently in operation would be able to comply with the proposed

potline POM MACT floor emission limits without any additional controls. While no additional control 

costs would be expected to comply with the MACT floor limits, the proposed rule would require 

periodic demonstrations of compliance with the appropriate POM emission limit. A compliance 

demonstration would be required for each potline semiannually and this demonstration would be made 
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by summing the results of the most recent annual primary control system emissions test result with the

average of the two most recent semiannual secondary (roof vent) emissions test results. We estimate the 

annual cost of POM testing to be $15,000 per prebake potline (includes one annual test for primary 

POM and two semiannual tests for secondary POM). The 12 prebake facilities would need to conduct 

performance tests for POM emissions from 38 prebake potlines resulting in an average annual cost of 

$47,500 per prebake facility or $570,000 total annual cost for the industry. 

 Impacts of Risk-Based Emission Standards for Soderberg Potlines 

We have proposed more stringent POM emission standards for existing Soderberg potlines than those 

currently established. These standards were based on a finding that allowable emissions under the 

current regulation present an unacceptable risk. The one existing Soderberg facility has been idle since 

2009 and is not expected to reopen. However, if that facility does reopen, we estimate that the potlines 

could meet the proposed risk-based standard if wet roof scrubbers were installed and operated at an 

estimated capital cost of about $30 million and annual cost of about $8 million per year. 

 Beyond the Floor Analysis 

Because the primary control devices for potroom POM emissions are very effective, the appropriate 

beyond the floor potline POM emission control option is the installation of wet scrubbers to control roof 

vent emissions on the 11 existing facilities that are not currently equipped with these devices. An 

estimate of the cost of retrofitting wet roof scrubbers on a Soderberg primary aluminum facility was 

developed for EPA Region 8 1,2 as part of a Best Available Retrofit Technology (BART) analysis. The 

objective was improved visibility associated with decreased SO2 and PM emissions. These scrubbers are 

also expected to provide a high degree of control of TF and some control (estimated at approximately 50 

percent control) of POM and PM. At scrubber temperatures nearly all of the POM would be PM. Scaling 

the estimated capital costs for this retrofit by the facility aluminum production capacity raised to the 0.6 

power, and assuming that operating costs are directly proportional to aluminum production capacity, the 

industry wide capital costs are estimated at $490 million and annual costs are estimated at $155 million 

per year. This is equivalent to $155,000 per ton of POM controlled. Additional information provided by

The Aluminum Association 3

 indicates that for prebake facilities, these costs are underestimates because 

the buildings housing the prebake potlines would likely require modification (e.g., expansion and 

structural reinforcement) in order to accommodate the wet scrubbers. According to this information, the 

costs associated with installing wet scrubbers on prebake facilities could be on the order of 3 times the 

cost estimates provided above. The BART analysis 1 also considered the installation of fabric filters. 

This type of system would control approximately twice the mass of PM and HAP metals at a capital cost 

approximately 16 times the cost of wet roof scrubbers and an annual cost of approximately 9 times the 

cost of wet roof scrubbers. 

COS Emissions from Potlines

Impacts at MACT Floor Level 

The proposed MACT floor limit for existing facilities is 3.9 lb COS per ton of aluminum produced. The 

proposed COS MACT floor for new sources is 3.1 lb COS per ton of aluminum produced. It is expected 

that all primary aluminum production facilities presently in operation would be able to comply with the 

existing source COS MACT floor emission limit without any additional controls. The owner or operator 

would be required to demonstrate compliance on a monthly basis via a mass balance equation with 3 

variables: anode consumption rate, aluminum production rate and anode coke sulfur content. However, 
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the owners or operators of the affected facilities already monitor all 3 variables. Therefore, we estimate 

that there would be no cost impacts due to the proposed COS MACT floor limit. 

 Beyond the Floor Analysis 

In regard to beyond the floor analyses for COS emissions, we considered COS emission limits of 3.5 lb 

COS per ton of aluminum produced and 3.1 lb COS per ton of aluminum produced. Facilities could 

comply with these lower COS emission limits by utilizing lower sulfur content coke in their anodes. 

Based on current anode coke cost data, we estimate that the limits of 3.5 lb COS per ton of aluminum 

produced and 3.1 lb COS per ton of aluminum produced would impose annual costs of approximately $2 

million on two facilities and $13 million on 5 facilities, respectively. We predict these options would 

reduce COS emissions by about 52 tons per year and 220 tons per year, respectively, and result in cost

effectiveness of about $38,000 per ton of COS removed and $59,000 per ton of COS removed, 

respectively. However, it is estimated that the amount of anode grade coke available with sulfur content 

low enough to comply with these standards is insufficient to accommodate current primary aluminum 

production rates. We also considered substitution of metallurgical coke for petroleum coke as a means of 

decreasing COS emissions, but ruled this out on the basis of technical infeasibility due to increased ash 

content and mechanical weakness in anodes produced from metallurgical coke (for more information 

refer to the memorandum titled Revised Draft Technology Review for the Primary Aluminum 

Production Source Category which is available in Docket ID No. EPA-HQ-OAR-2011-0797). 

POM Emissions from Existing Pitch Storage Tanks 

Impacts at MACT Floor Level 

The proposed MACT floor for existing pitch storage tanks is a HAP control efficiency of 95 percent, 

represented by a fume capture and return system accompanied by a charcoal scrubber. This is equivalent

to the MACT floor for new pitch storage tanks in the 1997 NESHAP. We estimate that eight facilities 

would be affected by this standard and would need to add controls, at a capital cost of approximately 

$75,000 per facility or $600,000 for the industry and an annual cost of approximately $21,000 per 

facility or $168,000 for the industry. There are no available data on pitch storage tank emissions. 

Potential emissions were estimated on the basis of vapor displacement during loading. These 

calculations assumed anode paste was comprised of 22 percent pitch (the industry average value 

provided by The Aluminum Association), a pitch specific gravity of 1.25 and vapor pressure equal to 

that of oxidized asphalt at 300 °F (estimates based on available data), 35 percent HAP content and an 

average HAP molecular weight of 250 (based on testing conducted at the Kaiser-Tacoma Soderberg 

facility). Estimated emission reductions are 1.55 tons of POM per year. 

 Beyond the Floor Analysis 

One existing facility is required by permit to achieve 99 percent control of pitch storage tank POM 

emissions. This facility operates a water-cooled condenser to recover pitch storage tank emissions. We

have limited data regarding the capital and operating costs of this system, and there are no test data to 

confirm that it is actually more effective than the untested systems which are estimated to control 95

percent of POM emissions. The installed capital cost of a non-contact single stage refrigerated watercooled condenser system, assuming 1 ton of refrigeration, and 35 degree F cooling water, is estimated at 

$31,000. Total annualized cost for such a system, including capital recovery, labor, maintenance 

materials, electricity, overhead, administration, property tax and insurance is estimated at $184,000 per 

facility or $2.02 million per year for 11 facilities in the source category. This beyond the floor option 
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represents an incremental cost of $1.94 million and would be expected to control an estimated additional 

0.081 tons of POM. 

Metal HAP Emissions from Potlines

 Impacts at MACT Floor Level for Potlines 

We expect that all existing facilities would be able to comply with the proposed potline metal HAP 

MACT floor emission limits without any additional controls. Performance test data obtained from one 

facility operating center-worked prebake one potlines exceeded the proposed standard, however the 

facility indicated4 that conditions during testing may not have been representative, and that expected 

emissions would meet the proposed emission limit. Under the proposed rule, annual tests of PM (used as

a surrogate for metal HAP) emissions would be required from primary potline exhausts and semiannual 

tests of PM emissions would be required from secondary potroom exhausts at prebake and Soderberg 

facilities. Since these tests can be combined with currently required tests of TF emissions, the 

incremental cost of the PM test beyond the cost of the currently required TF test is estimated at $1,000 

per test. We estimate the annual cost of PM testing to be $3,000 per potline (includes one annual test for 

primary PM and two semiannual tests for secondary PM). Thirteen facilities would be required to 

conduct performance tests for PM emissions from 41 potlines resulting in an average annual cost of 

approximately $9,462 per facility or $123,000 total annual cost for the industry. Further, since 

monitoring presently required for compliance with TF emission standards is adequate to ensure 

compliance with the proposed metal HAP standards, no additional monitoring costs are expected. 

 Impacts of Risk-Based Emission Standards for Soderberg Potlines 

We have proposed facility-wide limits on nickel and arsenic emissions from Soderberg potlines. These 

standards were based on a finding that allowable emissions under the current regulation present an 

unacceptable risk. We estimate that the one existing (presently idle) Soderberg facility could meet the 

proposed risk-based standard if wet roof scrubbers were installed at an estimated capital cost of about 

$30 million and operated at an estimated annual cost of about $8 million per year. The incremental cost 

of the nickel and arsenic test beyond the cost of the currently required TF/PM tests is estimated at 

$4,000 per test. We estimate the annual cost of testing to be $12,000 per potline (includes one annual

test for primary and two semiannual tests for secondary). One existing Soderberg facility (presently idle) 

would need to conduct performance tests from 3 potlines resulting in an average annual cost of 

approximately $36,000 per facility and for the industry (since there is only one Soderberg facility). 

 Beyond the Floor Analysis 

Because the primary control devices for potroom metal HAP emissions are very effective, the 

appropriate beyond the floor potline metal HAP emission control option is the installation of wet 

scrubbers on the roof vent (secondary) emissions on the 11 existing facilities that are not currently 

equipped with these devices. The annual cost of wet scrubbers (described above under “Beyond the 

Floor Analysis” for POM emissions from potlines) including capital recovery and operating costs is 

$155 million for the industry. This is equivalent to $6.7 million per ton of metal HAP controlled. Note 

again that, as discussed above, additional information provided by The Aluminum Association suggests 

that the actual capital and annual costs could be 3 times these cited values. As described under “Beyond 

the Floor Analysis” for POM emissions from potlines, the installation of fabric filters would control 

approximately twice as much metal HAP at approximately 9 times the annual cost of wet roof scrubbers. 

We also considered substitution of metallurgical coke for petroleum coke as a means of decreasing 
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metal HAP emissions, but ruled this out on the basis of technical infeasibility due to increased ash 

content and mechanical weakness in anodes produced from metallurgical coke (for more information 

refer to the memorandum titled Revised Draft Technology Review for the Primary Aluminum 

Production Source Category which is available in Docket ID No. EPA-HQ-OAR-2011-0797). 

Metal HAP Emissions from Anode Bake Furnaces 

 Impacts at MACT Floor Level

We expect that all existing facilities would be able to comply with the proposed anode bake furnace 

metal HAP MACT floor emission limits without any additional controls. Performance test data obtained 

from one facility exceeded the proposed standard, however the facility indicated5

 that conditions during 

testing may not have been representative, and that expected emissions would meet the proposed 

emission limit. Each facility would be required to conduct an annual compliance test for PM (as a 

surrogate for metal HAP), at an estimated cost of $5,000 per test, or $60,000 per year for the industry. 

Monitoring costs for the industry’s 12 bake furnaces are estimated at $67,500 per year. 

 Beyond the Floor Analysis 

A beyond the floor option for control of metal HAP emissions from anode bake furnaces is the retrofit of 

membrane bags in existing baghouses. The capital cost of this retrofit is estimated at $20.9 million for 

10 facilities. Assuming capital recovery based on a 3 year bag life and a 7 percent interest rate, annual 

costs for the 10 facilities would be $7.9 million. This is equivalent to $292 million per ton of metal HAP 

controlled. 

Metal HAP Emissions from Paste Production Plants 

 Impacts at MACT Floor Level 

We expect that all existing facilities would be able to comply with the proposed paste production plant 

metal HAP MACT floor emission limits without any additional controls. Performance test data obtained 

from one facility exceeded the proposed standard, however the facility indicated6 that conditions during 

testing may not have been representative, and that expected emissions would meet the proposed 

emission limit. Each facility would be required to conduct an annual compliance test for PM (as a 

surrogate for metal HAP), at an estimated cost of $5,000 per test, or $55,000 per year for the industry. 

Monitoring costs for the 11 paste production plants are estimated at $61,900 per year. 

 Beyond the Floor Analysis 

A beyond the floor option for control of metal HAP emissions from paste production plants is the 

retrofit of membrane bags in existing baghouses. The capital cost of this retrofit is estimated at $1.48 

million for 11 facilities. Assuming capital recovery based on a 3 year bag life and a 7 percent interest 

rate, annual costs for the 11 facilities would be about $560,000. This is equivalent to about $96 million 

per ton of metal HAP controlled. 

Reduced Testing Frequency for TF from Potlines 

The proposed change in TF testing frequency for secondary potroom emissions from monthly to 

semiannual is estimated to result in a cost reduction of $2.05 million per year for the 41 existing 
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potrooms (assuming operation of all 38 existing prebake potlines and that 3 existing Soderberg potlines 

resume operation). 

Reduced Testing Frequency for POM from Soderberg Potlines 

The proposed change in POM testing frequency for secondary Soderberg potroom emissions from 

quarterly to semiannual is estimated to result in a cost reduction of $30,000 per year (assuming that 3 

existing Soderberg potrooms resume operation). 

Total Cost of Proposed Standards at the MACT Floor 

It is estimated that the proposed standards, if implemented at the MACT floor levels, would result in a 

cost savings to the primary aluminum industry of $959,000 per year, assuming that the one idle 

Soderberg facility does not resume operation. In the event that this facility restarts, the proposed 

standards would result in a cost increase to the aluminum industry of $7.0 million per year. 

1

 Bison Engineering Inc., Best Available Retrofit Technology (BART) Analysis: Columbia Falls Aluminum 

Company, LLC, November 5, 2007 

2

 Robbins, H. W., Bison Engineering, to C. Videtich, EPA Region 8, June 19, 2008 

3

 Johnson, C.D., Aluminum Association, email to D. Putney, US EPA. July 9, 2014. 

4

 Backfisch, D., Noranda Aluminum, email to D. Putney, US EPA. April 29, 2014. 

5

 Coomes, J., Century Aluminum of Kentucky, email to D. Putney, US EPA. May 29, 2014. 

6

 Mitchell, K., Alcoa Intalco Works, email to D. Putney, US EPA. June 6, 2014.