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MEMORANDUM

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

From: David Green and Matt Hakos, RTI International 

Date: September 1, 2015 

Subject: Final Cost Impacts for the Primary Aluminum Production Source Category 

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

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

Air Pollutants for Primary Aluminum Reduction Plants (found in 40 CFR part 63, subpart LL). Through 

the RTR amendments, the EPA established maximum achievable control technology (MACT) standards at 

the MACT floor for the following eight 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 potlines, 

3. POM emissions from existing pitch storage tanks, 

4. Particulate matter (PM) (as a surrogate for non-mercury (Hg) metal HAP) emissions from potlines, 

5. PM (as a surrogate for non-Hg metal HAP) emissions from anode bake furnaces, 

6. PM (as a surrogate for non-Hg metal HAP) emissions from paste production plants, 

7. Hg emissions from anode bake furnaces, and 

8. Polychlorinated biphenyl (PCB) emissions from Soderberg potlines. 

In addition to these MACT standards, risk-based standards were established for nickel (Ni) and arsenic 

(As) emissions from Soderberg potlines, and the standard for POM emissions from VSS2 potlines was 

revised on the basis of the risk analysis. 

The final numerical production-based MACT emission limits for POM, COS, and PM emissions were 

established by calculating the 99-percent upper prediction limit (UPL) based on available performance 

test data. The final numerical concentration-based MACT emission limit for Hg emissions from anode bake 

furnaces was based on a concentration equal to three times the expected representative detection limit (RDL). 

The development of these standards is detailed in the Final MACT Floor Analysis for the Primary 

Aluminum Production Source Category (available in Docket No. EPA-HQ-OAR-2011-0797). Emission 

limits for Ni and As and revised emission limits for POM for Soderberg potlines are based on risk 

considerations detailed in Development of Emissions Standards to Address Risks for the Primary 

Aluminum Production Source Category Pursuant to Section 112(f) of the Clean Air Act (Docket item 

EPA-HQ-OAR-2011-0797-0350). Note that particulate matter (PM) has been used as a surrogate for 

metal HAP (other than Hg) in the final MACT standards. Also, decreased testing frequencies have been 

finalized for secondary total fluoride (TF) emissions from potlines. See Table 1, below, for a summary of 

the MACT standards and risk-based standards finalized via the primary aluminum RTR amendments. 
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Table 1. Summary of Promulgated MACT and Risk-Based Standards 

HAP Source Promulgated Standard 

MACT Standards 

COS New potlines 3.1 lb/ton aluminum produced 

Existing potlines 3.9 lb/ton aluminum produced 

POM New potlines 0.77 lb/ton aluminum produced 

Existing potlines 

CWPB1 1.1 lb/ton aluminum produced 

CWPB2 12 lb/ton aluminum produced 

CWPB3 2.7 lb/ton aluminum produced 

SWPB 17 lb/ton aluminum produced 

Existing pitch storage tanks Minimum 95-percent reduction of inlet POM 

emissions 

PM New potlines 4.9 lb/ton aluminum produced 

Existing potlines 

CWPB1 7.4 lb/ton aluminum produced 

CWPB2 11 lb/ton aluminum produced 

CWPB3 20 lb/ton aluminum produced 

SWPB 4.9 lb/ton aluminum produced 

VSS2 26 lb/ton aluminum produced 

New anode bake furnace 0.07 lb/ton of green anode 

Existing anode bake furnace 0.20 lb/ton of green anode 

New paste production plant 0.0056 lb/ton of paste 

Existing paste production 

plant 

0.082 lb/ton of paste 

PCB New and existing Soderberg 

potlines 

2.0 micrograms (μg) toxicity equivalence 

(TEQ) per ton of aluminum produced 

Hg New and existing anode bake 

furnaces 

1.7 μg per dry standard cubic meter (dscm) 

Risk-Based Standards 

POM New and existing Soderberg 

potlines 

1.9 lb/ton aluminum produced 

As 0.006 lb/ton aluminum produced 

Ni 0.07 lb/ton aluminum produced 

CWPB1 = Center-worked prebake one 

CWPB2 = Center-worked prebake two 

CWPB3 = Center-worked prebake three 

SWPB = Side-worked prebake 

VSS2 = Vertical stud Soderberg two 

POM Emissions from Prebake Potlines

Impacts at MACT Floor Level for Prebake Potlines 

Based upon our analyses of available data, we expect that all prebake facilities presently in operation 

will be able to comply with the final potline POM MACT floor emission limits without additional 

controls or modifications to existing controls. While no additional control costs are expected to comply 
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with the MACT floor limits, the final rule will require periodic demonstrations of compliance with the 

appropriate POM emission limit. A compliance demonstration will be required for each potline 

semiannually and this demonstration will be made 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 10 prebake facilities will be required to conduct performance tests for POM emissions from 

35 prebake potlines resulting in an average annual cost of $52,500 per prebake facility or $525,000 total 

annual cost for the industry. 

Beyond–the-Floor Analysis 

Because the primary control devices for pot room 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 9 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 81, 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. Based on engineering judgement, we assume that at scrubber 

temperatures nearly all of the POM will 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 

$438 million and annual costs are estimated at $138 million per year. This is equivalent to $200,000 per 

ton of POM controlled. After considering the capital costs, annualized costs, cost-effective and overall 

economic impacts, the EPA decided it is not appropriate to require wet scrubbers on these sources. 

Therefore the EPA has not promulgated beyond-the-floor standards for POM emissions from prebake 

potlines. 

Additional information provided by The Aluminum Association3 indicates that for prebake facilities, 

these costs are underestimates because the buildings housing the prebake potlines will 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 analysis1

 also considered 

the installation of fabric filters. This type of system would achieve approximately twice the mass of PM 

and HAP metals emissions reductions 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. The EPA 

concluded that these beyond-the-floor controls would pose excessive economic impacts and therefore 

the EPA has not promulgated this beyond-the-floor option. 

COS Emissions from Potlines

Impacts at MACT Floor Level 

Based upon our analyses of available data, we believe that all primary aluminum production facilities 

presently in operation will be able to comply with the existing source COS MACT floor emission limit 

without additional controls or modifications to existing controls. The owner or operator will 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, the 
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owners or operators of the affected facilities already monitor all 3 variables. Therefore, we estimate that 

there will be no cost impacts due to the final 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 for existing sources. 

Facilities could comply with these lower COS emission limits by using 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 will impose annual costs of 

approximately $2 million on two existing facilities and $13 million on 5 existing facilities, respectively. 

We predict these options will 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. Because of the limited supply of coke with low sulfur and 

potential for adverse impacts on production, the EPA decided it was not appropriate to require this 

option. Therefore, the EPA has not promulgated this beyond-the-floor option for COS emissions from 

potlines. 

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 Final Technology Review for the Primary Aluminum Production Source Category, 

which is available in the docket for this action (Docket No. EPA-HQ-OAR-2011-0797). 

POM Emissions from Existing Pitch Storage Tanks

Impacts at MACT Floor Level 

The final 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 identical 

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

will be affected by this standard and will 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 POM emissions, 

however, potential POM emissions were estimated on the basis of vapor displacement during storage 

tank 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 1.43 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 
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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 

represents an incremental cost of $1.85 million and will be expected to control an estimated additional 

0.074 tons of POM. This is equivalent to about $25 million per ton of POM controlled. The EPA 

considers this not cost-effective and has not promulgated beyond-the-floor standards for POM 

emissions from pitch storage tanks. 

PM Emissions from Potlines

Impacts at MACT Floor Level for Potlines 

Based upon our analyses of available data, we expect that all existing facilities will be able to comply 

with the final potline PM MACT floor emission limits without any additional controls or modifications 

to existing controls. Performance test data obtained from one facility operating center-worked prebake 

one potlines exceeded the final standard, however the facility indicated4 that conditions during testing 

may not have been representative, and that expected emissions will meet the final emission limit. Under 

the final rule, annual tests of PM emissions will be required from primary potline exhausts and 

semiannual tests of PM emissions will be required from secondary pot room exhausts at prebake 

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). Eleven facilities will be required to conduct 

performance tests for PM emissions from 37 potlines resulting in an average annual cost of 

approximately $10,000 per facility or $111,000 total annual cost for the industry. Further, since 

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

compliance with the final PM standards, no additional monitoring costs are expected. 

Beyond-the-Floor Analysis 

Because the primary control devices for potline PM emissions are very effective, the appropriate 

beyond-the-floor potline PM emission control option is the installation of wet scrubbers on the roof 

vent (secondary) emissions on the 10 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 $138 million for 

the industry. This is equivalent to $6.7 million per ton of metal HAP controlled. The EPA 

considers this not cost-effective and have not promulgated beyond-the-floor standards for PM 

emissions from potlines. 

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 will 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 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 Final Technology 

Review for the Primary Aluminum Production Source Category, which is available in Docket ID 

No. EPA-HQ-OAR-2011-0797). Therefore, the EPA has not promulgated this beyond-the-floor 

option. 
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PM Emissions from Anode Bake Furnaces

Impacts at MACT Floor Level 

Based upon our analyses of available data, we expect that all existing facilities will be able to comply 

with the final anode bake furnace PM MACT floor emission limits without any additional controls or 

modifications to existing controls. Performance test data obtained from one facility exceeded the final 

standard, however the facility indicated5 that conditions during testing may not have been 

representative, and that expected emissions will meet the final emission limit. Each facility will be 

required to conduct an annual compliance test for PM, 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 PM 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 will be $7.9 million. This is equivalent to $292 million per ton of metal HAP 

controlled. The EPA considers this not cost-effective and have not promulgated beyond-the-floor 

standards for PM emissions from anode bake furnaces. 

PM Emissions from Paste Production Plants

Impacts at MACT Floor Level 

Based upon our analyses of available data, we expect that all existing facilities will be able to comply 

with the final paste production plant PM MACT floor emission limits without any additional controls or 

modifications to existing controls. Performance test data obtained from one facility exceeded the final 

standard, however the facility indicatedv that conditions during testing may not have been 

representative, and that expected emissions will meet the final emission limit. Each facility will be 

required to conduct an annual compliance test for PM, at an estimated cost of $5,000 per test, or 

$50,000 per year for the industry. Monitoring costs for the 10 paste production plants are estimated at 

$56,250 per year. 

Beyond-the-Floor Analysis 

A beyond-the-floor option for control of PM 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 

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

costs for the 10 facilities will be about $560,000. This is equivalent to about $96 million per ton of 

metal HAP controlled. The EPA considers this not cost-effective and have not promulgated beyondthe-floor standards for PM emissions from paste production plants. 

Mercury Emissions from Anode Bake Furnaces

Impacts at MACT Floor Level 

Based upon our analyses of available data, we expect that all existing facilities will be able to 

comply with the final anode bake furnace Hg emission limit without installation of additional controls 

or modifications to existing controls. Facilities will be required to conduct an annual compliance test 
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for Hg emissions from each anode bake furnace, at an estimated cost of $5,000 per test, or $60,000 

per year for the industry. 

 Beyond-the-Floor Analysis 

A beyond-the-floor option for control of mercury emissions from anode bake furnaces is the 

installation of activated carbon injection upstream of a polishing baghouse. This type of system sized 

for a typical 100,000 actual cubic foot per minute exhaust stream has an estimated capital cost of $1 

million and estimated total annual costs of $750,000 per year. The estimated cost effectiveness of 

such a system is $240,000 per pound of Hg. The feasibility of this option is subject to technical 

uncertainties including the actual carbon requirement to remove Hg in the presence of POM. 

Notwithstanding the technical uncertainties associated with this beyond-the-floor option, the EPA 

considers this not cost-effective and has not promulgated beyond-the-floor standards for Hg 

emissions from anode bake furnaces. 

Ni, As, POM and PCB Emissions from Soderberg Potlines 

The owner/operator of the only facility in the U.S. with existing Soderberg potlines (the Columbia 

Falls facility in Montana) has announced the permanent shut down of that facility. Therefore, there 

are no currently operating VSS2 potlines. Further, we expect that no existing VSS2 facilities will 

restart and that, due to the less-efficient and less cost-effective nature of the Soderberg technology, no 

new Soderberg facilities will be constructed in the three years following promulgation. Thus, costs 

for additional controls and testing associated with the As and Ni risk-based standards and revised 

POM MACT standards for Soderberg potlines have not been estimated and the cost impacts 

associated with these risk-based standards are estimated to be zero. 

Additional Work Practices

In addition to the numerical MACT standards addressed above, the EPA promulgated work practice 

standards for potlines, anode bake furnaces and paste production plants. These work practice standards 

will ensure proper control device operation and prompt corrective action, when necessary; improve the 

capture and control of all HAP emitted from these sources; and serve as MACT standards for PCB 

emissions from anode bake furnaces and prebake potlines, dioxin and furan (D/F) emissions from 

Soderberg potlines, and Hg emissions from both Soderberg and prebake potlines. The final rule also 

provides the owner or operator of existing sources the options of (1) installing PM continuous emissions 

monitoring systems (CEM), (2) installing bag leak detection systems (BLDS), or (3) increasing the 

frequency of required visual emissions observations for all control device exhausts from daily to twice 

daily. According to our analyses and comments and additional information received during the public 

comment period for the December 2014 supplemental proposal6

, the estimated costs associated with 

BLDS and PM CEMS far exceed those associated with increasing the frequency of visual emissions 

observations. Therefore, we presume all existing facilities will forgo installation of BLDS or PM CEMS 

and instead implement increased frequency of visual emissions observations. The cost of the 

promulgated work practices, presuming no facility(ies) install BLDS or PM CEMS, is estimated at 

$500,000 per year. 

Additional Monitoring Equipment for Potline Secondary POM and PM Emissions Testing

Two potlines (one currently operating and one currently idle) are not currently equipped with either 

EPA Method 14 sampling manifolds or EPA Method 14A cassette sampling systems. Either a 

manifold or cassette system is necessary to sample secondary potline emissions. Note that in the final 

rule amendments, the owner/operator of a potline is provided the option of establishing “similarity” 
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of potlines to the regulatory authority pursuant to §63.848(d) of 40 CFR part 63, subpart LL, thereby 

avoiding these costs. However, it is not certain that such similarity can be demonstrated, therefore, 

we are including the costs for these manifolds in this analysis. Annualized capital costs associated 

with installation of each potline sampling manifold is estimated at $55,000. 

Reduced Testing Frequency for TF from Potlines

The final change in TF testing frequency for secondary potline emissions from monthly to 

semiannual is estimated to result in an industry-wide cost reduction of $1,900,000 per year for 

the 37 existing potlines. 

Total Cost of Final Standards at the MACT Floor

It is estimated that the final standards, if implemented at the MACT floor levels, will result in a cost 

savings to the primary aluminum industry of $140,000 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

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

6

 Johnson, C.D., Aluminum Association, Docket ID No. EPA-HQ-OAR-2011-0797-0372, February 6, 2015.