Standards of Performance for Portland Cement Plants

(40 CFR 60 Subpart F)

Response to Public Comments

US Environmental Protection EPA

Office of Air Quality Planning and Standards

Sector Policies and Programs Division

Metals and Minerals Group

Research Triangle Park, NC 27711

August 6, 2010
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Table of Contents

1. Introduction..........................................................................................................................1

2 Legal Issues Related to EPA’s Interpretation of the CAA ..................................................4

2.1 Best Demonstrated Technology.............................................................................. 4

2.2. Greenhouse Gases................................................................................................... 4

2.3 Emission Limits...................................................................................................... 6

2.4 Pollutants not Included (VOC, PM2.5).................................................................... 9

2.5 General.................................................................................................................. 10

3 Applicability ......................................................................................................................12

3.1 Modified Kilns...................................................................................................... 12

4 Emission Limits.................................................................................................................16

4.1 General.................................................................................................................. 16

4.2 Format................................................................................................................... 16

4.3 NOx ....................................................................................................................... 16

4.4 SO2 ........................................................................................................................ 24

4.5 PM......................................................................................................................... 30

4.6 Opacity.................................................................................................................. 35

4.7 VOC and CO......................................................................................................... 36

4.9 Fugitives................................................................................................................ 37

4.10 Overall Achievability............................................................................................ 37

5 Monitoring and Recordkeeping .........................................................................................39

5.1 SO2 ........................................................................................................................ 39

5.2 PM......................................................................................................................... 40

5.3 Opacity.................................................................................................................. 40

5.4 CEMS.................................................................................................................... 41

5.5 Clinker Production................................................................................................ 42

6 Test Methods and Procedures............................................................................................43

7 Impacts...............................................................................................................................44

7.1 Cost and Cost Effectiveness.................................................................................. 44

7.2 Environmental and Energy ................................................................................... 46

7.3 Economic .............................................................................................................. 48

7.4 Multipollutant ....................................................................................................... 49

8 Miscellaneous ....................................................................................................................50

8.1 Proposed Rule ....................................................................................................... 50

8.2 Technical Support Document ............................................................................... 51

List of Tables

Table 1-1. List of Commenters on Amendments to 40 CFR 60 Subpart F Proposed June 16, 

2008 (73 FR 34072).............................................................................................................2
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1. Introduction

On June 16, 2008 the U.S. Environmental Protection Agency (EPA proposed to amend the New 

Source Performance Standards (NSPS) for portland cement plants in 40 CFR 60 subpart F 

(hereafter referred to in this document as “Subpart F”) to revise emission limits and compliance 

requirements for affected facilities which commence construction, reconstruction, or 

modification after June 16, 2008. The proposed amendments also include additional testing and 

monitoring requirements for affected sources. Initially, a 60-day period ending August 15, 2008,

was provided for the public to submit comments to EPA regarding the proposed Subpart F 

amendments. In response to a request from commenters, the public comment period was 

extended by EPA an additional 45 days and ended September 30, 2008. This document presents 

a summary of the public comments that the EPA received on the proposed Subpart F

amendments.

A total of 23 sets of comments were received by EPA regarding the proposed Subpart F

amendments. Some of the comment sets were signed or submitted on behalf of multiple 

commenters. Also, in some cases duplicate comment sets from the same commenter were 

received. Table 1-1 lists the names of the commenters and their affiliations for each of the 

comment sets received regarding the proposed Subpart F amendments. Some commenters also 

submitted supplemental information and data to support their comments. This document presents 

a summary of each substantive comment received by EPA from the commenters listed in 

Table 1-1. The comment summaries are grouped by topic in Sections 2 through 8 as follows:

 Section 2–Legal Issues Related to EPA’s Interpretation of the CAA

 Section 3–Applicability

 Section 4–Emission Limits

 Section 5–Monitoring and Recordkeeping

 Section 6–Test Methods and Procedures

 Section 7–Impacts

 Section 8–Miscellaneous Comments
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Table 1-1. List of Commenters on Amendments to 40 CFR 60 Subpart F Proposed June 16, 

2008 (73 FR 34072)

Docket No. EPA-HQ-OAR-2007-0877 Commenter Name, Affiliation, and Date Received

056 Anonymous Public Comment

August 15, 2008

057

Kevin Batchelder

EnviroLogix, Inc.

July 10, 2008

059

Al Armendariz, Ph.D.

Private Citizen

September 17, 2008

060

A. A. Linero, P.E., Program Administrator

Bureau of Air Regulation

Florida Department of Environmental Protection

September 29, 2008

061

Michael H. Winek

Babst, Calland, Clements, and Zomnir

On behalf of Armstrong Cement and Supply Corporation

September 30, 2008

062

Edmund G. Brown Jr., Attorney General of California

Joseph R. Biden, III, Attorney General of Delaware

Martha Coakley, Attorney General of Massachusetts

Andrew M. Cuomo, Attorney General of New York

Hardy Myers, Attorney General of Oregon

William H. Sorrell, Attorney General of Vermont

September 30, 2008

063

Carolyn Slaughter, Program Development Manger

Institute of Clear Air Companies (ICAC)

September 30, 2008

064

Andrew T. O’Hare, Vice President Regulatory Affairs

Portland Cement Association (PCA)

September 30, 2008

065

Timothy Ballo

James Pew

Janette Brimmer

Earthjustice on behalf of Clean Air Task Force and Downwinders At Risk

September 30, 2008

066

Melanie Sattler, Ph.D, P.E.

Private Citizen

September 30, 2008

067

Shelly Kaderly, Air Quality Division Administrator

Nebraska Department of Environmental Quality (NDEQ)

September 30, 2008

068

Robert Hodanbosi, Co-Chair Permitting Committee

Ursula Kramer, Co-Chair Permitting Committee

National Association of Clean Air Agencies (NACAA)

September 30, 2008

069

J. Jared Snyder, Assistant Commissioner

Office of Air Resources, Climate Change, and Energy

New York State Department of Environmental Conservation

September 30, 2008
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Docket No. EPA-HQ-OAR-2007-0877 Commenter Name, Affiliation, and Date Received

070

Myra C. Reece, Chief

Bureau of Air Quality

South Carolina Department of Health and Environmental Control

September 30, 2008

071

Mohsen Nazemi, P.E., Deputy Executive Officer

Engineering and Compliance

South Coast Air Quality Management District (AQMD)

September 30, 2008

072 Downwinders At Risk

September 30, 2008

073

Craig S. Campbell, Vice President

Environment and Government Affairs

Lafarge North America

Cement Division

September 30, 2008

074

Steven Miller, Product Manager

Pyroprocessing Technology

Ove L. Jepsen, Senior Vice President, North America

FLSmidth Inc

September 29, 2008

075

Spencer Weitman, President

National Cement Company of Alabama, Inc.

September 30, 2008

076, 082*

Mark S. Terry, President

Polysius Corp, a ThyssenKrupp Technologies Company

September 26, 2008

077

Richard T. Cusick, President

Humboldt Wedag, Incorporated

September 22, 2008

078

Michael Pelan and Craig Campbell

Environment and Government Affairs

Lafarge North American

Cement Division

June 30, 2008

079**

Andrew T. O’Hare, Vice President

Regulatory Affairs

Portland Cement Association (PCA)

June 17, 2008

080

Andrew T. O’Hare, Vice President Regulatory Affairs

Portland Cement Association (PCA)

September 25, 2008

081

Roger Brower, Principal

Zephyr Environmental Corporation

June 09, 2008

083

Satish Sheth

Vice President – Environmental U.S. Operations

Cemex, Incorporated

May 05, 2009

*Duplicate copies of same comments entered in docket.

** Request for extension of public comment period.
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2 Legal Issues Related to EPA’s Interpretation of the CAA

2.1 Best Demonstrated Technology

Comment: One commenter (68) agrees with EPA’s approach of basing best demonstrated 

technology (BDT) on recently issued state permit data and best available control technology

(BACT) determinations developed as part of new source review (NSR) as well as EPA’s 

assessment that the main difference between BACT and BDT determinations for purposes of 

NSPS is that a BACT determination is made on a site-specific basis. 

Response: In addition to state permit limits and BACT determinations, we also reviewed 

emissions data to verify that the emission limits for new sources were reasonable.

Comment: Various commenters (59, 68) urge EPA to require the portland cement industry to 

utilize BDT and state that selective catalytic reduction (SCR) will provide the greatest nitrogen 

oxide (NOx) reductions in addition to other benefits. The commenter states that EPA is required 

to look toward emerging technologies in determining what emissions reductions have been 

adequately demonstrated. Commenter 68 states that under CAA section 111, EPA can determine 

that a system has been “adequately demonstrated” even if the majority of sources are not 

utilizing it and, citing the D.C. Circuit Court of Appeals with regard to cement plants,

“‘[A]dequately demonstrated’ does not require that any cement plant now in existence be able to 

meet the proposed standards. Section 111 looks toward what may be fairly projected for the 

regulated future, rather than the state of the art at present, since it is addressed to standards for 

new plants...”. According to the commenter, the D. C. Circuit has also held that “...Congress 

also meant for emerging technologies to be given consideration when EPA promulgates NSPS.” 

(see Sierra Club v. Costle). As part of its discussion of SCR as BDT, the commenter cites various

studies as demonstrating the performance of SCR at coal-fired power plants and successful 

application of SCR at a cement plant in Germany; the co-benefits achieved through control of 

other pollutants; and cost effectiveness.

Response: See preamble for the response.

2.2. Greenhouse Gases

Comment: One commenter (64) supports EPA’s decision not to expand the revised NSPS for 

portland cement plants to address emissions of GHGs. Citing a ruling by the D.C. Circuit Court,

the commenter states that EPA is not obligated to address any particular pollutants when issuing 

or revising NSPS. The commenter also states that the Supreme Court’s Massachusetts v. EPA 

decision addressed EPA’s regulation of GHG emissions from motor vehicles under CAA section 

202(a)(1), but nothing in that decision or any other court decision requires EPA to regulate 

GHGs through NSPS. Commenter 64 states that there is no reason to believe that standards for 

GHG emissions in the portland cement NSPS would be an effective or appropriate means of 

climate change mitigation and that EPA and Congress are currently grappling with the best 

approaches for addressing climate change and those questions are best answered after careful 

study and public debate, rather than short-circuited by applying NSPS to GHGs. According to 

the commenter, it is unlikely that an NSPS standards for GHGs at cement plants would produce 
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any meaningful reduction even in GHG emissions from new cement plants: the only known 

method for controlling carbon dioxide emissions from cement plants is efficient fuel combustion, 

and cement plant operators already have large financial incentives to minimize fuel usage to the 

extent practicable.

Response: See the Federal Register notice for the final amendments for the response this 

comment. EPA notes further that the commenter is correct that the Supreme Court’s decision in 

State of Massachusetts v. EPA does not require EPA to address GHG emissions from cement 

kilns in this rule. On the other hand, that opinion holds that GHGs are pollutants under the Act, 

which brings GHGs under the potential authority of section 111 (like any other pollutant).

Comment: Several commenters (62, 65, 69) objected to EPA not proposing standards for 

greenhouse gas (GHG) emissions under the proposed NSPS. One commenter (62) criticizes 

EPA’s decision to not propose any NSPS for GHG emissions from portland cement plants. The 

commenter states that even though the courts have confirmed that GHGs are air pollutants 

subject to regulation under the CAA, EPA has not issued any such standards, instead issuing an 

Advance Notice of Proposed Rulemaking (ANPR) that seeks public comment on whether to 

regulate GHG emissions under the CAA at all. Commenter 62 protests this course of action, and 

request that EPA revise the proposed rule to include NSPS for GHG emissions.

According to commenter 62, EPA’s failure to propose NSPS for GHGs in the proposed rule 

violates §111 of the CAA (42 U.S.C. §7411), which requires EPA to determine whether GHG 

emissions emitted by cement plants may endanger public health or welfare, and to promulgate 

NSPS for each air pollutant emitted by cement plants that contributes significantly to global 

warming pollution. The commenter states that as the second largest industrial source of carbon 

dioxide emissions in the United States (emitting 45.7 million metric tons of carbon dioxide in 

2006), the cement industry contributes significantly to GHG emissions and there can be no

serious dispute that GHG emissions endanger public health and/or welfare. The ANPR that EPA 

issued instead is no substitute for action and does not commit to regulating GHG emissions from 

any source.

Commenters 65 and 69 submitted several exhibits in support of their comments. A summary of 

the comments is presented here. To review the entire comment, please refer to the comment at

www.regulations.gov. 

The commenter states that:

 EPA is required by §111 to promulgate NSPS for all pollutants emitted by a regulated 

source category including CO2 emission from cement plants and EPA’s assertion that 

§111 does not compel the agency to regulate CO2 emissions is contrary to the Act’s plain 

language. 

 Congress has expressly directed that NSPS address the emissions of “any” air pollutant, a 

term that plainly encompasses CO2. 

 At a minimum, in directing that NSPS be established for sources that cause, or contribute 

significantly to air pollution which may reasonably be anticipated to endanger public 

health and welfare, Congress showed that it meant to require limits on emissions of any
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pollutants that cause or contribute to such endangerment. Because cement plants emit 

CO2 in such amounts that those emissions significantly contribute to “air pollution which 

may reasonably be anticipated to endanger public health or welfare,” EPA is legally 

required to issue standards of performance limiting those emissions. EPA cannot 

rationally assert that cement plant CO2 emissions do not meet these criteria, and the 

agency’s refusal to promulgate standards of performance is therefore unlawful. 

 EPA’s contention that it can refuse to regulate CO2 emissions on the basis of interactions 

with other CAA provisions is impossible to reconcile with §111, because that section 

clearly contemplates that EPA will adopt standards of performance covering pollutants 

that have not previously been subject to regulation under the Act. 

 Cement plants’ emissions of CO2 cause, or contribute significantly to, air pollution which 

may reasonably be anticipated to endanger public health or welfare and significantly

contribute to global climate change. 

 There are existing technologies that can reduce emissions of CO2 from cement plants. In 

addition to the suggested technologies, other measures that would also have CO2

reduction benefits include shifting form high carbon content fuels, such as coal, to lower 

carbon content fossil fuels, such as natural gas.

 Section 111(d) of the Act provides that EPA shall require states to implement and enforce 

standards of performance for existing sources when the pollutant at issue is not regulated 

as a criteria pollutant or hazardous air pollutant. 

 EPA must also consult with the US Fish and Wildlife Service and National Marine 

Fisheries Service to insure that the final rule is not likely to jeopardize recently-listed

endangered species.

Response: See preamble for the final amendments for the response to this comment.

2.3 Emission Limits

Comment: Several commenters (65 and 72) state that EPA’s proposed NSPS for SO2 emissions

are inconsistent with §111 and do not reflect the degree of emission limitation that is achievable 

through the application of wet scrubbers, which have already been installed on some kilns and 

are the best adequately demonstrated technology. According to the commenters 65 and 72, the 

proposed SO2 limit of 1.33 lb/ton of clinker is so lenient that only a few kilns will actually use 

scrubbers to comply. EPA acknowledges that far better SO2 levels can be achieved and are 

achieved through the use of wet scrubbers. Specifically, EPA admits that some kilns are already

subject to a BACT limit of 0.2 lb/ton of clinker. EPA describes that level as one “where 

moderate and high sulfur kilns” — as opposed to only a few kilns with extraordinarily high 

uncontrolled SO2 levels, “will require the use of a wet scrubber for SO2 control.” Commenter 72 

added that EPA’s desire to shelter new kilns from having to apply add-on controls is irrelevant 

under §111, and EPA’s interpretation of §111 as allowing it to avoid setting standards reflecting 

application of the BDT based on that irrelevant policy consideration is unlawful.

Response: See preamble for the response.
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Comment: One commenter (72) states that existing application of wet scrubbers in the cement 

industry means wet scrubbers should be automatically considered BACT for all new U.S. kilns. 

Section 111(a)(1) defines a “standard of performance” to mean “a standard for emissions of air 

pollutants which reflects the degree of emission limitation achievable through the application of 

the best system of emission reduction which (taking into account the cost of achieving such 

reduction and any nonair quality health and environmental impact and energy requirements) the 

Administrator determines has been adequately demonstrated.” (42 U.S.C. §7411(a)(1)). EPA 

evidently has concluded that wet scrubbers have been adequately demonstrated considering cost 

and the other statutory factors as EPA acknowledges, some kilns already have installed them. 

Further, EPA’s proposed NSPS reflect the use of wet scrubbers, albeit by only a few kilns. Given 

that wet scrubbers are the best adequately demonstrated technology, §111 requires EPA to set 

NSPS at the level that is “achievable through the application of” wet scrubbers.

Response: See the preamble for the response.

Comment: One commenter (65) states that, although EPA agrees that it must set NSPS for NOx, 

the agency rejects the technology that best reduces NOx, SCR. EPA states that SCR can reduce 

NOx emissions by about 80 percent and could be used to attain a standard of 0.5 lb/ton of clinker. 

Nonetheless, EPA ultimately proposes to set a much less protective NOx standard of 1.5 lb/ton of 

clinker, based on the use of either “staged combustion in the calciner (SCC),” SNCR, or both.

EPA offers a variety of reasons for rejecting SCR as the BDT, but none of them have merit. The 

commenter provides the following comments regarding EPA’s reasons why SCRs were not 

chosen as BACT:

 EPA admits that SCR has been used at three kilns in Europe, but states that the kilns are 

not preheater/precalciner kilns like new US kilns will be. However, EPA does not say

why this distinction makes any difference nor why future US kilns have to be 

preheater/precalciner kilns even if preheater kilns may be cleaner. The CAA requires that

NSPS reflect application of the best demonstrated system of reduction and to do 

otherwise to ensure the continued use of a particular production process would be 

unlawful. EPA’s failure to explain why the use of a precalciner precludes the use of SCR 

is arbitrary. EPA argues that the ideal location for SCR is at a point where dust levels are 

high enough that they may clog the SCR device. But a study on the application of SCR to 

cement plants (which EPA neglects to mention) states that the problem of catalyst fouling 

has been solved in Europe. EPA itself has stated that the operational history of SCR 

installation at a cement plant shows that it is achieving NOx reductions in a reliable 

manner and has named SCR as an available technology for cement kilns in its Best 

Available Retrofit Technology (BART) analysis. Reports from industry and independent 

contractors make the same point. EPA’s claims about “potential technical difficulties” are 

at odds with all of this information.

 According to the commenter, EPA cites cost effectiveness and the uncertainty of the costs 

estimates as reasons for rejecting SCR. The commenter states that EPA’s views about 

cost-effectiveness are irrelevant and unlawful under §111, which requires standards to 

reflect the degree of limitation that is “achievable” through the application of the BDT, 

not the degree of limitation that “EPA considers cost-effective.” EPA’s cost-effectiveness 

arguments are arbitrary as SCR reduces not only NOx but also volatile organic 
8

compounds, dioxins and furans, ammonia, and mercury. If cost effectiveness is relevant, 

the true cost-effectiveness of SCR would have to reflect reductions of all these pollutants 

and—at a minimum—VOCs, for which EPA has a statutory obligation to set NSPS. The 

commenter states that EPA’s consideration of SCR’s cost-effectiveness only with respect 

to NOx and not the other pollutants that SCR controls is at odds with the agency’s stated 

intent to use a multi-pollutant and sector-based approach to setting standards. Finally, 

EPA’s alleged “uncertainty” about costs does not justify its rejection of SCR. The 

uncertainties all relate to technical issues that have been resolved. For EPA to rely on 

such uncertainty despite record evidence showing it to be unfounded is arbitrary. EPA 

may not reject a system by claiming that it has not bothered to fully investigate it, 

especially a system such as SCR that is already in use and recognized as reliable and 

effective.

 Finally, EPA attempts to rely on alleged “adverse non-air and energy implications” to 

reject SCR. The only energy concerns EPA cites, however, relate to using SCR in a low 

dust environment where (EPA claims) the exhaust gas would have to be reheated. As 

EPA acknowledges, that issue does not exist if the SCR unit is placed upstream where the 

exhaust gas is already the ideal temperature and the dust issues associated with such 

placement have been addressed and solved. The only non-air impact EPA mentions is the 

disposal of used catalysts. Such disposal issues always arise from the use of air pollution 

control issues. EPA does not explain why catalyst disposal outweighs the air pollution 

benefits that would result from SCR.

Response: See preamble for response.

Comment: Commenter 64 believes that the best approach is for EPA not to amend the NSPS to 

include NOx limits. If EPA indeed intends for the NSPS NOx limits only to apply to new cement 

plants or those that have undergone a redesign to use a preheater/precalciner system, then those 

NSPS limits will be applied to a new unit or capital project that will require federal and/or state 

permitting. It may also be subject to SIP limitations, visibility protection rules, other state 

requirements, and so forth. The site-specific considerations that go into such determinations are 

well-established and are much better able to address the variety of variables affecting NOx

emission limit achievability at cement plants. Relying on other applicable requirements rather 

than developing revised NSPS for NOx also assures that NOx limits for new and reconstructed 

plants are based on evolving information and technology, not set in stone until the next 

rulemaking like NSPS.

The commenter states that EPA is not under any obligation to include NOx limits in the revised 

NSPS. The decision of what pollutants to regulate, and indeed whether to revise the NSPS at all, 

is discretionary. Obviously, EPA has never regulated NOx emissions through the NSPS from 

cement plants in the past, and even now EPA does not include limitations in the NSPS for many

fuel-burning sources, including some types of boilers. In other cases, EPA has recognized that 

NSPS need not address all concerns and has taken into account that other requirements will 

apply to new or modified sources under federal and state air pollution laws and regulations, 

resulting in other or additional control requirements. 

Response: EPA disagrees that the Agency’s decision as to whether to establish a NOx limit in 

this NSPS revision is dictated by the lack of any NOx limits in the existing NSPS. The absence of 
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NOx limits in the NSPS previously was due to the lack of a demonstrated add-on control 

technology applied to cement kilns during EPA’s last review of the NSPS in 1988. Beginning in 

the 1990’s, SNCR systems have been considered and installed on numerous cement kilns in the 

U.S. Furthermore, NOx is emitted in large amounts by cement kilns and may be controlled costeffectively by a number of means, including SNCR. EPA is acting well within its discretion, and 

in keeping with the goals and policies underlying section 111, in establishing standards for NOx

as part of this revision.

2.4 Pollutants not Included (VOC, PM2.5)

Comment: Several commenters (65 and 72) stated that it is well established that PM2.5

endangers public health and that under §111(a)(1), EPA must set NSPS for PM2.5 that reflect the 

degree of emission reduction that is achievable through application of the “best” system of 

emission control that is adequately demonstrated.

Because the CAA requires emission standards for PM2.5, the agency’s failure to set such 

standards is unlawful. EPA discusses the amount of PM2.5 emissions that its total PM standard

would reduce but does not claim that fabric filters are the best demonstrated system of control for 

PM2.5. Nor would any such claim be credible, in the commenter’s opinion. Fabric filters do not 

remove the condensable portion of PM emissions, which is in gaseous form at the stack but 

condenses into liquid or solid form within a few seconds of leaving the stack. EPA has 

recognized that condensable PM is controlled not by fabric filters but by wet FGD, wet ESP and 

alkali injection. EPA states that it “supports reducing condensable PM emissions,” but does not 

know whether cement kilns are a significant source of condensable PM although they are aware 

that cement kilns emit enormous amounts of PM. Studies show that the condensable portion of 

PM emissions from coal-fired power plants is 50-75 percent. Data available to EPA show that 

cement kilns’ condensable PM emissions account for a significant portion of their total PM 

emissions. For example, Titan Cement’s North Carolina kiln reports that over 40 percent of its 

PM emissions are condensable PM. The CALPUFF model for PM speciation indicates that 

condensable PM makes up 86 percent of the total PM emissions from a dry kiln with a fabric 

filter — i.e., from the kilns that will be governed by the NSPS. 

Response: EPA has insufficient data on condensable PM data to establish limits at this time. 

EPA notes that under the portion of fine PM that is attributable to SO2 emissions will be reduced 

as a result of wet scrubbers that are installed to comply with the new limits for SO2. Also, the 

increased use of membrane filters to comply with the revised PM standard will reduce PM fine 

emissions in comparison to standard woven filters. In addition, in EPA’s revised NESHAP, both 

existing and new kilns are expected to use wet scrubbers in order to comply with the limits for 

HCl as well as mercury, and in some cases with the revised limits for THC in the cases where the

sources use a regenerative thermal oxidizer (RTO) because a wet scrubber must precede the RTO 

to prevent the fouling of the RTO interior mechanism.

Comment: One commenter (72) states that the fuels and raw materials used in cement clinker 

production can result in the emissions of hydrocarbon pollutants, also known as volatile organic 

compounds. Volatile organic compound emissions contribute to the production of ground-level 

ozone and some VOC’s are highly toxic. Citing EPA information, the commenter states that 

cement plants throughout the country report significant quantities of hydrocarbon HAP 
10

emissions. NSPS implement CAA section 111(b) and are issued for categories of sources which 

EPA has listed because they cause, or contribute significantly to air pollution which may

reasonably be anticipated to endanger public health or welfare. The primary purpose of the NSPS 

is to attain and maintain ambient air quality by ensuring that the best demonstrated emission 

control technologies are installed as industrial infrastructure is modernized.

Response: Under the NESHAP for portland cement manufacturing plants, all new kilns are 

subject to a THC emissions limit of 24 parts per million volume (ppmv), which would include 

most VOC’s. EPA believes that it has adequately addressed VOC limits and that no additional 

regulation of VOC is warranted. (Incidentally, the purpose of section 111 new source standards 

is to protect and enhance the Nation’s air quality, not just maintain it. Asarco v. EPA, 578 F. 2d 

at 327 (D.C. Cir. 1978)).

2.5 General

Comment: One commenter (73) agrees with EPA that BACT determinations may consider site

specific factors, but the commenter states that a BDT determination must account for factors that 

may have affected a site-specific BACT determination but may not be applicable to the industry

as a whole. The commenter states that as required under§111(a)(1) and was made clear in Nat’l 

Lime Ass’n v. EPA, 627 F.2d 416, (D.C. Cir. 1980), an achievable standard is one that can be 

routinely satisfied under the reasonable worst–case conditions that can be expected within the 

industry or source category as a whole. The commenter states that EPA must rely upon data that 

accounts for variability within the industry as a whole and where test data is relied upon, EPA 

must have a reasonable basis for believing that the available data is adequately representative of 

the industry as a whole (See Portland Cement Ass’n v. Ruckelshaus, 486 F.2d 375 (D.C. Cir. 

1973); Lignite Energy Council v. EPA, 198 F. 3d 930 (D.C. Cir. 1999)). According to the 

commenter, EPA failed to satisfy the requirements of §111(a)(1) in making BDT determinations 

using limited data and extrapolating to establish a standard which EPA speculates can be 

achieved on a national basis. According to the commenter, EPA has not considered adequately 

the significant factors including regional/site-specific variations in raw mix which affect the fuel 

inputs required to manufacture cement (burnability in EPA’s lexicon), variations in fuels 

employed which affect NOx emissions per ton of clinker produced, and types of cement 

produced which affect the required heat input and intensity per ton of clinker produced. 

Moreover, EPA has not taken into proper consideration specific design variations that could or 

must be employed to assure product quality (alkaline by-pass) and design variations intended to 

reduce the energy required to produce a ton of clinker (clinker cooler ducting to the raw mill).

The commenter states that using this inverted approach, EPA has concluded that application of 

BDT supports the proposed NSPS standards for NOx and PM which exceed current BACT 

determinations. The commenter states that NSPS standards should constitute the BACT floor 

setting, in effect, the lowest common denominator which current control technology should be 

able to achieve on an industry-wide or source category-wide basis. BACT determinations should 

then afford individual permitting authorities, on a case-by-case basis, the ability to establish 

emission limitations more stringent than the industry-wide denominator. This is not to say that 

BDT, like BACT, cannot be technology forcing. However, when EPA proposes to adopt as BDT 

emission limitations more stringent than current BACT, it must support its decision with sound 

data and analysis and, according to the commenter, EPA has not done this.
11

Response: These general comments are addressed below along with more specific comments on

the NOx and PM limits. However, if the commenter is arguing that all new sources must be able 

to achieve a promulgated NSPS, this is not correct, since that would negate the whole notion of 

use of Best Demonstrated Technology. The commenter is correct that EPA must make a 

reasoned demonstration that sources utilizing the technology which is the basis of BDT should 

meet the standard, and that this requires EPA to fully assess potential variability and account for 

it in the standard. EPA believes it has done so here. For example, for NOx, we document that 

existing sources with particularly hard-to-burn inputs are nonetheless achieving the promulgated 

limit using SNCR (along with appropriate baseline control measures). We also explain how both 

our assumed baseline for application of end-of-stack controls, and our assumptions as to 

emission reductions achievable with (end-of-stack) SNCR are relatively conservative in order to 

account for potential variability.

Comment: One commenter (57) states that proposed sections 60.62(a)(3), 60.62(a)(4)(i) and 

60.64(c) mention a 30-day rolling value for NOx and SO2. However, the rule language does not 

clearly indicate whether the period is 30 calendar days or 30 operating days. Section 60.63(l)(1) 

mentions “kiln operating days” and 60.63(n)(3) mentions “boiler operating day.” This suggests 

that EPA intends the 30-day rolling period to be 30 operating days, not calendar days. The rule 

text needs to clarify EPA’s intent.

Response: The commenter is correct. The 30-day rolling average applies to operating days. The 

rule has been clarified.

Comment: One commenter (57) states that assuming that EPA intends to use operating days; the 

rule needs to define a “kiln operating day.” EPA may want to use the boiler operating day

definition from 60.41Da. 

Response: The rule has been clarified to describe an operating day.
12

3 Applicability

3.1 Modified Kilns

Comment: Several commenters (61, 64, 73, 83) do not believe that EPA has sufficient data to 

support application of the NOx and SO2 emissions limits to modified wet process kilns which are 

based on data for new PH/PC kilns equipped with SNCR and scrubbers. Commenter 61 has been 

unable to find data to support an appropriate percentage reduction that could be attained from 

installing SNCR on a wet process kiln. According to the commenter, EPA indicated that older 

kilns are typically replaced with new PH/PC kilns rather than being modified or reconstructed. 

Commenter 73 believes that EPA erred in its assumption that all modifications would result in 

older kilns (including older-design PH/PC) being replaced with modern PH/PC technology kilns

and that EPA did not evaluate any emission data from existing kilns other than PH/PC kilns;

however, to establish standards applicable to modifications, EPA must evaluate what might be 

achievable by the universe of existing kilns which might undergo physical changes or changes in 

method of operation resulting in a “modification” within the meaning of 40 CFR 60.2.

Commenter 61 further stated that the EPA identified two instances of kilns modified where the 

proposed limits would apply but believes the kilns were actually reconstructed in ways which it 

may be appropriate to require the reconstructed source to meet the limits for new sources. 

Commenter 61 stated that EPA should develop separate NOx and SO2 standards applicable to 

modified wet kilns and modified long dry kilns. 

Commenter 73 states that modern PH/PC kiln technology is capable of achieving substantially 

lower uncontrolled NOx and SO2 emission rates than older kiln technology. For NOx, this is due 

to staging combustion and burning a significant amount of fuel in the precalciner, which 

generates little or no thermal NOx. For SO2, greater trapping of sulfur in the clinker is possible 

through oxidization in the preheater and routing of gases from the kiln and precalciner to an inline raw mill. The commenter states that EPA needs to assess the range of uncontrolled 

emissions for each type of kiln configurations and evaluate the effectiveness, cost and other 

statutory factors relevant to available retro-fit control technology for each kiln type and possibly 

create subcategories for the different kiln types

One commenter (64) states that changes such as replacement of an induced-draft fan with one of 

greater capacity can trigger NSPS and that an increase in production rate of any amount can 

trigger NSPS if it requires a capital expenditure and that such changes would not provide the 

opportunity to incorporate process design elements that would allow the kiln to meet the newly 

proposed limits or would add costs and delays to add such process designs that far exceed the 

change that triggered the NSPS “modification” provision. This interpretation, according to the 

commenter, would create disincentives for efforts to improve energy efficiency at cement plants 

if minor adjustments to the process would trigger new, more stringent emission limits, which 

could result in substantial outlays of capital and operating costs as well as delays associated with 

the designing, purchasing, and installing new pollution control equipment to meet the more 

stringent emission limitations. The commenter states that because EPA assumed that only new or 

reconstructed kilns would be preheater/precalciner designs, their analysis of costs and economic 

impacts is faulty. The commenter provided estimates of the costs that may be incurred as a result 

of modification-triggered retrofits at an existing facility. The commenter states that EPA could 

also create a separate subcategory for plants that have not yet been modified to use the newer 
13

preheater/precalciner technology and that modifications at such plants would only be subject to 

the current PM NSPS limit of 0.3 lb/ton of feed. This commenter states that EPA has applied 

different NSPS limits to facilities with different process designs to distinguish among classes, 

types and sizes within categories of new sources for the purpose of establishing standards

One commenter (73) states that AP-42 lists uncontrolled emission factors for wet process, longdry, preheater, and older design PH/PC kilns of 7.4, 6.0, 4.8, and 4.2 pounds of NOx per ton of 

clinker produced, respectively compared to an uncontrolled emission rate for modern PH/PC 

process kilns as estimated by EPA to range between 2.5 and 3.0 pounds of NOx per ton of 

clinker. Commenter 73 operates seven wet process kilns in the US with annual uncontrolled 

emission rates ranging between 6.7 and 14.1 pounds of NOx per ton of clinker and seven longdry process kilns in the US with annual uncontrolled emission rates ranging between 5.3 and 

10.9 pounds of NOx per ton of clinker. Achieving the proposed NOx limit (based on applying 

SNCR to PH/PC kilns) with modified older technology kilns will not always be possible due to 

the inherently higher uncontrolled NOx rate. SNCR has not been demonstrated to achieve this 

level of reduction on wet process kilns.

One commenter (83) states that the assumption of maximum NOx emissions of 3.0 lb/ton of 

clinker and a 50 percent reduction using SNCR are not appropriate for exiting kilns. The 

commenter points to EPA’s Alternative Control Techniques Document which shows the 

performance of the different kiln types (that is wet, long dry, preheater, and 

preheater/precalciner) can be well above 3.0 lb/ton of clinker. The commenter supplied data in 

the form of a chart showing the performance of SNCR at several of their plants. They used the 

chart to show that SNCR often achieves less than a 50 percent NOx removal rate. According to 

the commenter, this is significant because if an existing kiln triggers PSD as a result of increased 

annual emissions, they must meet an emission limit achievable through the installation of BACT. 

The commenter states that the CAA requires that BACT cannot be less stringent than emissions 

allowed by any applicable standard established pursuant to section 111. The commenter states 

that even if a modification of an existing kiln does not trigger the NSPS, the final NSPS is 

important to existing kilns as it will establish BACT for all existing kilns.

Response: At proposal we had one set of emission limits for PM, SO2 and NOx that were 

applicable to all new, reconstructed, and modified kilns. Commenters expressed concerns of the 

ability of a modified kiln to meet the same limits as a newly constructed kiln (a so-called 

greenfield new source).EPA intends that the revised rule apply to new, modified or reconstructed 

kilns that are PH/PC kilns. As discussed in the proposed rule, all kilns built since 2000 have been 

of the PH/PC design and the industry confirmed that any new kiln would be of the PH/PC 

design. Typically, older kilns are replaced with new PH/PC kilns which allows for increased 

capacity and more energy efficient operation. We did identify two instances in which a dry kiln 

and wet kiln were substantially modified rather than demolished and replaced with new kilns. 

Because these were the only two instances identified since 1990, we do not expect such 

modifications to be common. In both cases, the kilns as modified included a preheater and 

precalciner which were b expected to be able to comply with the revised limits. In this final rule 

we are still including modified kilns as an affected source. If we were to exempt modified kilns, 

then such sources would be free to increase emissions without application of BDT. This would 

undermine the basis of section 111 standards, where Congress wanted to assure that BDT was 

applied to modified sources qualifying as “new”. Commenters had also claimed that other 
14

regulatory programs, most notably new source review, would result in a site specific BACT 

determination if emissions increased. Though we are always mindful of the interrelationship of 

different EPA regulatory programs and their effects, we do not see this as sufficient reason to 

exempt modified kilns from the NSPS.

For a modification to cause a kiln to become subject the NSPS, the modification must result in an 

increase of the hourly emission rate of the pollutants subject to the regulation. Furthermore, 

major sources undergoing a modification may trigger New Source Review (NSR) and the 

requisite RACT, BACT or LAER review. However, we do not think that it is likely that an 

owner or operator would modify a kiln in such a way as to cause it to be subject to the revised 

NSPS or trigger NSR. It is more likely that if a modification would otherwise result in an 

increase in hourly emission rates, the owner or operator would take necessary measures, either 

install the necessary add-on controls or make process adjustments to avoid making itself subject 

to an NSR review as well as subject to the new NSPS limits. The PM and SO2 limits are based 

on control technologies that can be applied to any kiln type and achieve the same control levels 

that would be expected with a new kiln. So we see no issue here. Furthermore, in our analysis of 

the impacts of the final NESHAP, we determined that in order to meet the final limits for HCl, 

nearly all kilns would require the use of wet scrubbers. As a result of controls for HCl, emissions 

of SO2 will be lowered as well as HCl emissions. In such cases, we expect that the kilns will be 

able to comply with the limits for SO2. For kilns that are near the limit, process changes such as 

the burning of low sulfur coal, as already required in some state permits, may help to ensure 

compliance with the final SO2 limits. 

EPA did not intend that the revised standard apply to older wet or dry kilns undergoing minor 

modifications, unless they are substantially modified to the extent described above. We 

understand that it would not be reasonable to expect in most cases for older wet and dry kilns to 

comply with the new limits, especially the limits for NOx. These kilns require higher 

temperatures and longer residence time to dry and calcine the feed resulting in greater production 

of NOx in comparison to PH/PC kilns. In the case of NOx, once we had determined that modified 

kilns would be an affected source, we then determined if we should set a different NOx emissions 

limit. However, we believe it is environmentally most advantageous to retain the 1.5 lb/ton 

clinker limit for modified kilns. We note that there are kilns of older design that meet levels

below 1.5 lb/ton clinker, and in some cases below 1.0 lb/ton clinker, with SNCR control. So 

modified kilns would not necessarily be unable to meet the 1.5 lb.ton clinker limit. Sources that 

determine the 1.5 lb/ton limit is not achievable without control still have the option of adding 

NOx control and avoiding the triggering of the modification provision and PSD for NOx. The 

NOx control available to cement kilns, in addition to SNCR, are conversion to indirect firing, 

mid-kiln fuel injection, mid-kiln air injection, and substitution of steel slag for some limestone.

Given these available controls, we believe it would be extremely unlikely that a source that 

determines the 1.5 lb/ton limit is not achievable would be unable to apply some type of NOx

control that would avoids triggering the modification or PSD provisions.

Comment: One commenter (73) opposes the application of the proposed SO2 standard to 

modified kilns. The commenter states that SO2 is primarily a function of the form and 

concentration of sulfur present in the limestone utilized by a cement plant. Older kiln 

technologies are less efficient at trapping SO2 in the clinker than modern PH/PC designs. Only

modern PH/PC kilns with extremely high limestone sulfur concentrations will require extensive 
15

controls to meet the proposed NSPS limit. However, for a majority of the older technology kilns, 

the only control option that can assure meeting the proposed NSPS limit of 1.33 pounds SO2 per 

ton of clinker produced is a wet gas scrubber. Retrofit capital cost to install a wet gas scrubber on 

a typical wet or long-dry kiln is in the neighborhood of $15-25 million dollars. For these older 

technology kilns, this type of cost is not economically feasible, particularly for minor 

modifications that would have very little impact on overall emissions. 

Response: See the previous response.

Comment: One commenter (73) opposes revising the NSPS standard for PM emissions from 

modified kilns. All cement kilns operating in the U.S. utilize PM controls. Two primary types of 

controls are used: baghouses and electrostatic precipitators. In deriving the proposed PM NSPS 

limit, EPA only looked at baghouses with membrane bags. New or reconstructed kilns would be

designed with modern baghouses that could incorporate membrane bags. However, existing

plants may not have this capability, or the plant may operate an ESP which may not be capable 

of achieving the same level of PM reduction as a new modern baghouse with membrane bags.

Response: See the previous response. In addition, under the final NESHAP, many plants will 

install activated carbon injection (ACI) systems for the control of mercury, organic HAP and 

THC emissions. Because ACI systems will be installed after existing PM devices, they will use a 

polishing baghouse to remove the carbon from the exhaust gas stream. As a result, the owner or 

operator of a kiln controlled with an ESP will in most cases be able to meet the limits for PM

because of the additional downstream PM control device.
16

4 Emission Limits

4.1 General

Comment: One commenter (74) stated that once the U.S. EPA sets new emission limits, local 

agencies may dictate emission limits that will be even lower on specific projects. The commenter 

cites examples of this and recommended that the new NSPS limits be stringent and achievable 

for 100 percent of cement plants nationwide. The commenter states that, consequently, all plants 

will have achievable limits on a national basis and the ability to meet even lower emissions due 

to local requirements that are evaluated on a case-by-case basis.

Response: The purpose of the NSPS program is to ensure that the best demonstrated emissions 

control technologies are installed as industrial infrastructure is modernized. Such plants are to 

meet standards reflecting Best Demonstrated Technology. A standard that could be met by 100 

percent of the industry (a priori) is highly unlikely to reflect BDT. EPA is aware that cement 

plants vary from one another in their raw materials, fuel and cement product and that the details 

of the combustion and pollution control technologies required to meet these new limits may

require site-specific adjustment. In setting the new limits for NOx, SO2 and PM, EPA 

understands that some new, reconstructed or modified kilns will find it a challenge to meet the 

new limits while others will not. EPA is also aware that state and local agencies can set limits 

more stringent than those in the revised NSPS and expects that they will as local circumstances 

dictate, especially for efforts to attain various of the applicable National Ambient Air Quality

Standards.

4.2 Format

Comment: Commenters (68, 71) support EPA’s proposed limits in lb/ton of clinker over the 

previous lb-per-ton of dry feed limit as the new limits avoid rewarding a source for becoming 

less efficient (i.e., requiring more feed to produce a unit of product).

Response: EPA notes the commenter’s support.

4.3 NOx

Comment: Several commenters (59, 60, 63, 68, 70, 71, 72) approve of the proposed limits for 

NOx or believe more stringent limits are appropriate. One commenter (59) states that the 

proposed standard is unjustifiably high, and will allow for greater NOx emissions than can be

achieved with the installation of off-the-shelf pollution control technology. The commenter 

recommends that the new performance standard require emissions no greater than 0.5 lb NOx/ton

clinker and states that SCR is an effective and proven technology to reduce NOx emissions from 

cement kilns and can reduce NOx emissions from cement kilns by greater than 90 percent, 

consistent with what has been observed with SCR in other industries. According to the 

commenter, SCR can achieve this performance with cost effectiveness of approximately $1,500-

$3,800/ton NOx, easily within regulatory cost thresholds for many NOx control programs. 

Regarding concerns over dust and plugging, the commenter cites three recent installations of 

SCR on cement kilns that show that SCR vendors can properly design and install units which 

manage the dust and successfully operate for many years. The commenter stated that numerous 
17

SCR companies believe that they can design and supply SCR systems for NOx control at cement 

plants where they will have to guarantee performance levels in legal contracts, and thus, they 

would be at significant financial risk to advertise and sell an SCR system that was actually going 

to fail. The effectiveness of the technology to reduce NOx and other pollutant emissions from 

cement kilns, as demonstrated by the SCR installations on cement kilns in Europe and the 

numerous SCR installations on other heavy industries like coal-fired power plants and waste 

incinerators is supported by the marketing, technical assessments, and reports prepared by

numerous experts on this subject, including: three (3) cement companies, five (5) SCR

manufacturers, an independent blue ribbon panel, the U.S. EPA (twice), and the European IPPC.

Commenter 68 believes that EPA’s proposed NOx emission limit of 1.5 lb/ton clinker seriously 

underestimates the reductions that are achievable with SCR technology and recommends that 

SCR be identified as BDT for this sector and is “the regulated future” for cement kilns. The 

commenter states that the agency has noted that hybrid combinations of SNCR and SCR could 

be used in new cement kilns to achieve greater reductions than would be possible with SNCR 

alone. Like SCR, we have no evidence of this combination being applied here or elsewhere. 

SCR is also named by EPA as available technology for cement kilns in the Regulatory Impact 

Analysis for the Final Clean Air Visibility Rule or the Guidelines for Best Available Retrofit 

Technology (BART) Determinations under the Regional Haze Regulations. In fact, as far back as 

1999, EPA included SCR in a list of control technologies available for both dry and wet cement 

manufacturing processes, as did a Pechan & Associates Report prepared for EPA’s Office of Air 

Quality Planning and Standards in September 2005. Therefore, SCR technology for the cement 

manufacturing sector has been considered feasible technology by EPA for some time. While the

commenter applauds EPA’s decision to add NOx to the NSPS for cement kilns, this commenter 

recommends that EPA adopt SCR as BDT stating that NOx contributes significantly to ozone 

formation, which poses potential health risks to the more than 100 million individuals who live 

in areas that failed to attain the health-based primary standard for ozone. The NOx contributions 

of the portland cement sector must, therefore, be viewed against this dismaying context of the 

increasing impacts of ozone pollution on human health and the environment.

One commenter (60) states that the NOx emission limit should be lowered from 1.5 lb of NOx/ton 

of clinker on a 30 day rolling averages to 1.0 lb/ton of clinker on a 24 hour rolling average for 

new PH/PC kilns and a limit added of 2.0 lb/ ton of clinker on a 24-hour rolling average if 

reconstruction or modification of the kiln commences after June 16, 2008, and the final 

configuration is a long wet kiln or a long dry kiln. The commenter states that the 

recommendations regarding PH and PH/C kilns should apply equally to projects at greenfield 

sites and to projects at brownfield sites stating that many of the advances in NOx control in the 

U.S. and Europe have been made at brownfield sites whether they have involved new kilns or 

reconstruction or modification of existing kilns. 

To support the commenter’s recommended limits for NOx, the commenter provided the 

following information and included several supporting documents as attachments to the 

comments:

 A long-term value of 1.46 pounds per ton (lb/ton) of NOx clinker was achieved with no 

add-on control equipment when not accounting for slag use and 1.38 lb/ton when 

accounting for slag use at TXI Kiln 5 (a PH/C kiln) in Midlothian, Texas.
18

 A long-term value of 1.98 lb/ton was achieved with no add-on control equipment at 

Cemex Sta. Cruz (a PC/H kiln) in Davenport, California. The project involved an 

improvement to an existing calciner (commissioned in 1997) on an existing kiln to 

comply with an existing NOx limitation. 

 Titan America (a PH/C kiln) in Medley Florida and Giant Cement in South Carolina 

where average values of 1.62 and 1.88 lb NOx/ton were documented for new kilns with 

no add-on control equipment at brownfield sites. 

 The results from the existing SCANCEM (an affiliate of Lehigh) Skövde PH kiln where 

emissions were reduced from 4.4 lb NOx/ton (1995) by installation of a SNCR system 

and which achieved 0.72 lb/ton in 2005.

 The results from the existing SCANCEM Slite PH/C kilns where emissions were reduced 

from 4.0 lb NOx/ton (1995) by installation of an SNCR system and which achieved 

1.01 lb/ton in 2005. 

 The results from the existing Radici Cementeria di Monselice PH kiln where emission 

reductions to values as low as 0.20 lb NOx/ton were demonstrated by installation of a 

SCR system. The supplier guaranteed reduction of 90 percent and realized reductions as 

high as 97 percent. 

Commenter 60 states that based on the foregoing, it is clear that reductions on the order of 75

percent are achieved by well-designed SNCR systems and 90 percent by SCR. Given that a new 

kiln can be designed such that emissions can be controlled to values between 1.5 and 2 lb/ton 

before add-on control, it is clear that 1 lb/ton is easily achievable by SNCR. Given a kiln with 

less sophisticated design or particularly difficult raw materials achieving 3 to 5 lb/ton, it is clear 

that SNCR or SCR or a combination of the two can readily reduce emissions to values much less 

than 1 lb/ton. The commenter states that the proposed averaging time of 30 days is a tremendous 

concession to the industry. The availability of reagent injection makes it easier to achieve the 

proposed standard on a 24-hour basis. The lowest permit limit for a project under construction in 

the United States applies to the Drake Cement in Arizona. The value is equivalent to 1.14 lb/ton 

on a 24-hour basis. A contract was awarded to F.L. Smidth who developed the calciner that 

achieves 2 lb/ton or less at TXI, Titan and Cemex as discussed above. The limit will be readily

achievable using an SNCR system. The commenter provides additional details on the history and 

performance of NOx process controls (such as SCC) and add-on controls (such as SNCR) in the 

US and elsewhere.

One commenter (60) states that because long wet and long dry kilns use much more energy to 

make a ton of clinker, a higher NOx limit may be acceptable for these kilns. Commenter 60 

agrees with EPA’s assumption that new projects triggering the NSPS will actually result in a 

PH/C kiln. A project that might trigger a prevention of significant deterioration (PSD) review at 

a long kiln will probably incorporate emissions control measures to avoid PSD and a BACT 

determination for NOx and SO2. The measures to avoid PSD will also likely avoid the short-term 

emissions increases that would otherwise trigger the NSPS. Finally, with respect to the 

reconstruction provisions, it is not likely that a company will actually invest 50 percent of the 

value of an existing long kiln without taking the opportunity to make it much more energy

efficient through conversion to a PH/C kiln. The commenter states that a separate standard for 

long kilns will avoid the unnecessary relaxation of the limits applicable to PH and PH/C kilns. 
19

The commenter listed the following NOx reduction technologies that have been demonstrated for 

long kilns and submitted supporting documentation as attachments to the comment:

 Conversion from direct to indirect firing in conjunction with the installation of a multichannel (Low NOx) burner;

 Mid kiln fuel injection (including tires);

 Near mid-kiln pressurized air injection;

 SNCR at long kilns; and

 Combination of SNCR with air injection.

One commenter (63) described the advances in technology for controlling NOx emissions, 

especially SNCR and SCR, from portland cement plants, and requests EPA to fully consider the 

technological improvements and their applications when establishing NOx emission limits for the 

portland cement manufacturing industry. The commenter states that EPA continues to play a 

crucial role in encouraging innovation and in mobilizing supply chains to deliver technologies 

that improve our air quality and environment including the continued tightening of emission

limits. This encourages the industries such as the cement industry to work closely with

equipment and component suppliers to ensure significant reductions in emissions in a timely and 

economical manner. The commenter states that with the improved processes that lower 

uncontrolled NOx emissions and with the addition of SCR, NOx limits of 0.25-0.5 lb NOx /ton 

clinker are achievable.

One commenter (70) supports the proposed level for new, modified and reconstructed kilns of 

1.50 lb/ton of clinker for NOx. Facilities can meet the 1.50 lb/ton of clinker for NOx, with SNCR 

alone or with SCR (either as a supplement or as an alternative to SNCR).

One commenter (71) states that if new or modified systems would likely use the 

preheater/precalciner configuration, then what is achievable must be looked at and then apply the 

effect of the controls. If this approach is followed, the appropriate NOx emission limit should be 

in the range of 1.14 lb/ton of clinker. According to commenter 71, the traditional long dry

cement kilns can attain a NOx emission level of 2.73 lb/ton of clinker without utilizing SNCR 

control technology. Based on a SNCR control efficiency of 50 percent, a NOx emission level of 

1.3 lb/ton of clinker is achievable. As a result, cement kilns with SNCR control technology can 

achieve a NOx emission level between 1.14 and 1.3 lb/ton of clinker. However, this commenter 

believes that the NOx emission level from cement kilns can be further reduced by utilizing SCR 

control technology. Commenter 71 states that EPA dismisses the SCR technology used in Europe 

for the most trivial of reasons. Commenter 71 concedes that some mechanical problems were 

experienced in the early stages with plugging but these problems were resolved and the system 

remained in service for four years at the Solnhofen facility in Germany. According to the 

commenter, waste disposal should not be an issue because the spent catalyst could be added to 

the process as a source of alumina. Commenter 71 previously conducted a Best Available 

Retrofit Control Technology (BARCT) assessment for a cement plant in our area and 

recommended SCR as the BARCT for this facility.
20

One commenter (72) states that the NSPS emission rate for NOx from cement plants should be 

lowered to 0.5 lb/ton of clinker on a 24 hour rolling average because of the ability of current 

plant designs to achieve very low rates of NOx emissions without the addition of add-on 

pollution controls. Currently available add-on controls can reduce NOx emission levels below the 

proposed 1.5 lbs of NOx per ton of clinker. There is a considerable operational experience with 

SNCR that shows it’s capable of reducing NOx emissions to 1 lb or less/ton of clinker when 

combined with a modern-designed kiln. SCR has been demonstrated in the utility industry and 

Europe and can further reduce emissions.

Response: See the preamble for the response.

Comment: Several commenters (64, 73, 74, 75, 76, 77, 78) commented on the difficulty of 

consistently achieving the NOx limit of 1.5 lb/ton clinker limit over time and at all new kiln 

locations and favored a somewhat higher limit or no limit. They state that it is important to note 

that consistent, long term compliance with this proposed limit may be difficult to achieve and 

there will be instances where compliance may not be possible at all. Different factors can 

influence NOx emissions such as:

(1) Fuel type/quality - lower volatility solid fuels such as petcoke produce higher NOx

emissions. Also, any problems with fuel quality as delivered to the plant can have a 

negative impact on NOx emissions;

(2) Raw mix burnability - harder burnability will give higher NOx emissions. Burnability is 

dependent on the raw mix chemistry, fineness, and chemical deviation (impacted by

homogeneity and operation of the quarry, which can vary over extended periods of time);

(3) Kiln bypass system - The size of the bypass for a given plant (if needed), and 

consequently the bypass emissions, depends on the chemistry of the raw mix and fuel(s) 

and the product standards that must be maintained to comply with regulations;

(4) Size/type of the preheater - new in-line calciners will normally give the lowest NOx

emissions; however, in cases where the type of fuel(s) used dictates the need for a 

separate calciner (such as may be applied to utilize waste materials), NOx emissions will 

be higher. In addition, sometimes a new project will consist of upgrading an existing pyro 

system. In many of these cases the layout of the existing equipment is such that it cannot 

be modified to perform as well as a brand new calciner system, and will therefore have 

higher NOx emissions;

(5) Sub-standard operation and maintenance of the kiln system - this is the responsibility of 

the cement producer, but it is also expected that NOx emissions will increase slightly over 

a typical campaign between annual maintenance stoppages due to normal “wear and tear” 

of the system; and

(6) SNCR efficiency and slippage - the ability of an SNCR system to reduce NOx emissions 

is not the same for all systems, especially for an existing pyro system that has been 

upgraded (due to potential lack of an optimum injection point) or a very large pyro 

system (due to lack of optimum mixing of ammonia and preheater gas). 
21

One commenter (75) states that although the removal efficiency of SNCR can theoretically be

improved by increasing the quantity of ammonia injection, there is a practical limit to this

approach. As ammonia injection rates increase, the potential formation of a secondary plume due 

to “ammonia slip” increases. In addition, sulfur in the raw materials results in SO2 and SO3 in the 

exhaust, which decreases the efficiency of ammonia injection and leads to operational issues 

such as solids accumulation and plugging downstream of the SNCR. As the commenter noted in 

the permit application for its proposed kiln, facilities with lower BACT emission limits are also 

those facilities with lower sulfur raw materials, notably plants located in Florida, thereby 

improving the efficiency of SNCR. Given the baseline NOx emissions expected at a new plant, 

Commenter 75 would need a control level of at least 70 percent to meet the proposed limit of 

1.5 lb/ton. Commenter 75 is not confident that this can be done with SNCR. Therefore, the 

commenter recommends that the NOx standard be established at 1.95 lb/ton, which reflects a 

level of control achievable with the use of SNCR by all facilities without introducing the 

negative effects associated with pushing for high control levels.

One commenter (76) states that assuming a facility is already operating with best combustion

practices (i.e., indirect fired fuel supply systems, low primary air burners, etc.) then the

burnability of the raw mix has the greatest single impact on NOx emissions. Statistically

speaking, most preheater precalciner cement kiln plants worldwide emit an uncontrolled NOx

emission of 3.8 to 4.2 lb NOx/ton of clinker. With a 50 percent NOx reduction rate from the 

application of SNCR technology, a controlled emission rate of 1.9 to 2.1 lb NOx/ton of clinker 

could be expected for most kilns. As such, a 1.95 lb NOx/t clinker limit for all new kiln 

applications seems achievable. The issues arise when people arbitrarily apply the 50 percent

reduction potential of SNCR to lower baseline emission numbers. (i.e., at a 3.2 lb NOx/ton of

clinker uncontrolled emission, SNCR could reduce it to 1.6 lb NOx/ton of clinker). While this 

might be true on an isolated case basis, it would be unwise to approach such a low level for a 

new NSPS limit for all new kilns because of the issue of burnability. In some cases it might be 

possible to reduce the baseline NOx levels with integrated control systems, such as Multi-Stage 

Combustion (MSC) installed on low NOx calciner system; but here again, the practicality of 

sustaining stable, continuous operation while simultaneously reducing the baseline NOx by 10 to 

30 percent is very site specific. Commenter 76 believes that a controlled emission rate of 1.95 lb 

NOx/ton of clinker can be achieved by all new kiln applications providing SNCR is used as the 

principle measure to control NOx emissions, but excluding that portion of gases that may be 

extracted through a bypass system. 

One commenter (77) believes that under the worst-cast combinations of raw materials, fuels and 

cement specifications and with the application of SNCR technology, a controlled emission rate 

of 2.0 lbs of NOx per ton of cement clinker can be achieved by all new kiln applications. 

However, if the kiln must incorporate a bypass for alkalis, chlorides or sulfur, the NSPS limits 

must allow for increased NOx emissions on a plant by plant basis due to the fact that bypass 

amounts can be anywhere from 5 percent to 100 percent in size.

One commenter (78) states that very few kilns with alkali bypasses would have a chance of

meeting the proposed limit on a long-term basis. One commenter (83) requested that EPA clarify

whether the NOx limit applies only to a kiln’s main stack or whether it applies across both the 

main and bypass stacks.
22

One commenter (73) believes that EPA failed to identify and appropriately consider the variables 

that affect uncontrolled NOx emissions from modern preheater/precalciner kilns employing SCC 

and LNB on an industry-wide basis. As a consequence, EPA relied upon too limited a database 

that did not reflect these variables and then made assumptions reflecting an incomplete 

understanding of the range of variability in uncontrolled NOx that result from them. Commenter 

73 recommends that EPA revise its proposed baseline NOx emission standard from 1.5 to 2.0 

lb/ton of clinker, and allow for adjustments of the standard upward from this value when 

bypasses are used, unusually hard burning raw mixes are used, or specific clinker types (such as 

oil well clinker) that require non-typical burning methods is being produced. When bypasses, 

hard burning mixes and/or clinker specifications require non-typical operational parameters, an 

adjustment factor should be allowed and evaluated on a case-by-case basis. The fact that 

individual kilns may be able to achieve a NOx emission rate as proposed by EPA (or even lower 

rates) is not determinative of what is an appropriate standard for the NSPS.

Commenter 73 states that fuel volatility plays a major role in NOx emission control. The 

uncontrolled NOx generated in the precalciner alone can vary by as much as 1.4 g/kg of clinker 

(2.8 lb/ton clinker) based on fuel volatility. Commenter 73 states that modern 

preheater/precalciner kilns fire approximately 55-65 percent of their fuel in the precalciner. The 

nitrogen content in the fuel is the main factor affecting fuel NOx formation. The fuel NOx

produced in the precalciner is not directly proportional to the nitrogen content of the fuel. It also 

depends on the chemical form of the nitrogen in the fuel and the volatility of the fuel. Typically, 

fuel nitrogen in coals used by PH/PC kilns varies between 1.0 and 2.0 percent. This difference 

can impact the uncontrolled NOx by as much as 1.5 lb/ton of clinker.

Commenter 73 states that a PH/PC kiln system uses hot gases from the kiln to both dry and heat 

the raw materials prior to calcination. The effectiveness of this system is related to the moisture 

content of the raw materials and their ability to absorb heat from the gases. If additional heat is 

required to dry or heat the raw materials, gases from a separate fuel-fired furnace or the clinker 

cooler are ducted to the raw mill. As a result, the moisture content of the raw materials directly 

influences the NOx emission rates. High moisture materials require additional energy to dry the 

materials in the raw mill and/or preheater. This increased need for energy contributes to the 

amount of NOx emitted if the excess energy comes from burning additional fuel. Some plants

may have up to 20-25 percent moisture content in their raw mix – which results in a 15 to 

20 percent increase in the kiln’s specific heat consumption, as compared to a “standard” raw mix 

that contains approximately 5 percent moisture. This additional energy need results in the 

combustion of more fuel which ultimately results in more uncontrolled NOx. 

On NOx emissions from alkali bypasses, commenter 73 states that because the gases within the 

bypass are not allowed to remain in the optimal SNCR temperature range, SNCR is not a feasible 

control option for these gases. The commenter shows (in graph form in their comments) that for 

a certain size kiln, bypassing 25 percent of its kiln gases will have an incremental increase of 

approximately 0.42 lb/ton of clinker in the controlled NOx emission rate.

Commenter 73 states that the three major kiln suppliers require a cement company to provide 

detailed information on raw materials (including moisture content), fuels, and clinker quality 

specifications prior to preparing a quotation and specifying emission guarantees. Uncontrolled 

30-day average NOx emissions can vary from less than 1.6 to greater than 4.6 lb/ton of clinker.
23

SNCR has been demonstrated to reduce NOx emissions from cement kilns; however, SNCR has 

not been used on cement kilns for an extended period of time. High removal efficiencies such as 

those stated in the preamble (i.e., 63 percent at an ammonia-to-NOx ratio of 1.0) may result in 

adverse product quality or environmental impacts that are undesirable. In addition, the use of 

SNCR on larger kilns (>2,000,000 ton/yr capacity) may not be as effective due to the larger 

calciner duct diameter and the ability for the ammonia-reagent to mix thoroughly with the

combustion gases. Based on limited data, removal efficiencies of 25-50 percent appear to be 

achievable without these adverse impacts. Therefore, Commenter 73 believes that since NSPS is 

applicable to all new or reconstructed kilns, a reasonable baseline NSPS limit taking into account 

typical operating conditions and limitations stated above is 2.0 lb/ton of clinker. However, when 

non-typical conditions exist (bypass, hard burning mixes, and specific clinkers that require nontypical burning methods), an adjustment upward from the baseline value is appropriate and 

should be made on a case-by-case basis.

Commenters (64, 73) stated that the proposed NOx limitations are substantially more stringent 

than the most stringent NOx limit that applies to cement plants in Europe, which converts to 

approximately 2.5 lb/ton of clinker produced although EPA asserts that this should be considered 

the “baseline level of control that would occur with no additional regulatory action. The 

commenter states that there are several problems with that analysis: 1) It does not appear that this 

conclusion is based on a “statistically sound” analysis, as the statute requires; 2) If the NSPS 

were set at 2.5 lbs. [sic] of NOx per ton of clinker, then all affected facilities would have to meet 

the limitation continuously, rather than the “average” performance of all affected facilities being 

at or below 2.5 [sic] lb/ton. Therefore, it would appear from EPA’s rationale that setting an 

emission standard of 2.5 [sic] lb/ton would require some facilities, even if they have SCC and 

low-NOx burners, to implement additional NOx controls in order to comply continuously with 

that standard throughout the life of the facility.

The commenter states that there may be substantial differences between the NOx emissions that 

can be achieved by new, greenfield kilns and what can be achieved by “reconstructed,” 

brownfield kilns. NOx emissions are a function of fuel type and of raw material type. Some raw 

materials will require longer residence time in the kiln, and perhaps at higher temperature and

produces more uncontrolled NOx emissions, and therefore makes meeting a given emission limit 

more problematic and costly. The same is true of fuel that has a higher mass of nitrogen per unit 

of heat value. Reconstructed cement plants usually will have little or no control over their raw 

materials and may have limited control over the fuel they can use. 

The commenter states that EPA also needs to address the achievability of NOx limitations at 

cement plants that have bypass stacks or ducts to control alkalinity because EPA has not 

presented in the preamble to the proposed rule any basis for concluding that SNCR is a 

demonstrated technology for meeting the proposed for facilities with bypass systems. 

Likewise, while EPA acknowledges that burnability may have a significant influence on NOx

emissions, EPA has not explained how these differences are reflected in its analysis of the BDT

and the proposed new NOx limits. Cement plants with hard-to-burn raw materials face much 

greater challenges in meeting a NOx limit and applying SNCR.
24

Commenter 64 agrees with EPA that SCR has not been demonstrated on preheater/precalciner 

kilns and that there are substantial unresolved issues about the potential for use of SCR at such 

cement plants. Commenter 64 also notes that, in addition to the cost which EPA identified as a 

disadvantage of a low-dust SCR system, there would be substantial adverse energy usage and 

GHG consequences of re-heating the flue gas for a low-dust SCR system.

Commenter 64 also believes that EPA has not given adequate consideration to ammonia slip 

from the use of SCNR. EPA seems to acknowledge that it does not have data on how ammonia 

slip will contribute to condensable PM emissions, and what if anything could be done to mitigate 

that contribution. EPA has not conducted a sufficient technical analysis to support new NOx

emission limits that would effectively require use of SNCR without addressing the ammonia slip 

issues. Ammonia slip may be a particular problem when SNCR is applied to particular designs, 

such as pyro systems that have been modified or that are particularly large. The inability of these 

systems to promote the reaction of ammonia with NOx also reduces potential control efficiency

of SNCR on these systems.

Commenter 64 believes that the best approach is for EPA not to amend the NSPS to include NOx

limits. If EPA nevertheless insists on including NOx in the revised Subpart F NSPS, then 

commenter 64 recommends that for preheater/precalciner kilns (whether constructed at 

Greenfield or brownfield sites), a NOx emission floor of 1.95 lb/ton of clinker be established as 

the NSPS limit. This limit would then be modified on a case-by-case basis to account for sitespecific factors such as the presence of a bypass stack/duct or difficult to burn limestone or fuels, 

likely resulting in an emission limit in excess of the recommended floor. 

Response: See the preamble for the response.

4.4 SO2

Comment: Several commenters (60, 68, 70, 71, 72) stated that the proposed limits for SO2were 

not sufficiently stringent. Commenter (60) recommends deleting the 90 percent reduction option, 

revising the limit for SO2 to 0.5 lb/ton clinker on a 24-hr rolling average if the kiln is a PH or 

PH/PC kiln and adding a limit of 1.0 lb/ton clinker on a 24-hr rolling average if the kiln is a long 

wet or long dry kiln. Commenter 72 concurs on reducing the limit to 0.5 lb/ton for PH/PC kilns.

Commenter 60 states that for PH and PH/C kilns, the limit should apply equally to projects at 

greenfield sites and to projects at brownfield sites. Commenter 60 cites kiln performance at

brownfield sites whether they have involved new kilns or reconstruction or modification of 

existing kilns:

Cement plants in Florida emit on the order of 0.10 lb SO2/ton clinker. Although these kilns have 

very low-sulfur feed materials, all of them use coal and rely on the fuel SO2 control that is 

inherent in the PH and PH/C designs. The steps include reaction with alkali and incorporation 

into the clinker in the burning zone, dry scrubbing with finely divided lime in the calcination 

zone and moist limestone scrubbing in the raw mill.

Commenters 60 and 72 cite the performance of the kilns used by EPA to establish the proposed 

limit:
25

The key kiln (kiln 5 at TXI Midlothian, TX) upon which EPA based the proposed the SO2

standard of 1.33 lb/ton has actually operated at 0.37 to 0.57 lb/ton.

Commenters 60 and 72 state that raw materials in the Midlothian area are known for high-sulfur 

feed materials and the TXI kiln has a wet scrubber to reduce (non-fuel) SO2 emissions. The limit 

for Kiln 5 is now approximately 0.95 lb/ton following a production increase authorized by the 

Texas Commission on Environmental Quality (TCEQ). TXI Midlothian Kiln 5 and two other 

PH/C kilns (Kilns 1 and 2) operated by Holcim in the same city are controlled by wet scrubbers. 

All three have wet scrubbers yet there is a vast difference in performance between the TXI Kiln 

5 and the Holcim Kilns 1 and 2. The commenter presented data on the SO2 performance of the 3 

scrubber controlled kilns. According to the commenter, the TXI Kiln 5 can consistently achieve 

SO2 emissions less than 0.5 lb/ton if required by a permit limit. The higher SO2 values for the 

Holcim kilns (> 4 lb/ton) represent the first year of joint operation. Thereafter, Holcim Kilns 1 

and 2 were operated at levels between 2 and 3 lb/ton. The commenter states that they can choose 

to run one to four pumps providing reductions in SO2 emissions ranging from 51 percent with a 

single pump in operation to 91 percent with four pumps in operation.

Commenters 60 and 72 state that the Ash Grove Chanute PH/C kiln in Kansas achieves less than 

0.30 lb SO2/ton despite high sulfur in the raw materials without even using a wet scrubber. 

Commenter 60 states that this performance is attained using important innovations (the F.L. 

Smidth DeSOx system and Environcare Micromist Lime system) not yet assessed by EPA.

Attachments provided as part of the comment describes these technologies. Commenter 60 states 

that without controls the proposed Chanute kiln would emit SO2 at the high rate of 12 lb/ton 

from raw material sources alone (i.e. exclusive of fuel SO2). According to Commenter 60, using 

the described technology, actual emissions from the Ash Grove Chanute kiln are less than 0.25 lb 

SO2/ton. 

According to commenter 60, the Holcim Siggenthal PH kiln in Switzerland achieves 

approximately 0.05 lb SO2/ton using the POLVITEC coke filter installed in the 1990’s. The 

POLVITEC system is used with various concurrent operational practices to control NH3 (from 

an SNCR system), SO2, PM and metals. Among several functions, the coke filter captures the 

non-fuel SO2 generated in the PH. The coke is subsequently crushed and then burned with fuel in 

the main kiln burner. The SO2 from the PH then behaves like fuel SO2 and is incorporated into 

the clinker. Further details are available in an attachment submitted with the comment. The 

commenter states that SO2 emissions would be significantly less than 0.10 lb/ton of clinker.

According to the commenter, the Siggenthal plant emits much less SO2 than the average of 

Holcim cement plants in Switzerland and clearly less than 0.10 lb SO2/ton.

Commenters 60 and 72 state that the Holcim Untervaz plant Switzerland achieves between 0.04 

and 0.21 lb SO2/ton using a wet scrubber despite, according to commenter 72, the presence in the 

limestone of iron sulfide. Holcim initially installed a dry scrubber at the Untervaz plant in the 

late 1980’s. Recent data provided by the commenter indicate significant reductions in SO2

emissions from since 2002 largely due to the replacement of the older dry scrubber with a more 

efficient and economic wet scrubber. 

According to commenter 60, the areas where medium sulfur raw materials are present can 

implement programs similar to the Ash Grove installation without installing large wet scrubbers, 
26

dry scrubbers or coke filters. Finally selective mining of the available raw materials with respect 

to sulfur content is an important SO2 control strategy for any new project. In summary, 

Commenter 60 recommends an NSPS SO2 limit of 0.50 lb/ton of clinker on a 24-hour basis for 

PH and PH/C kilns.

Commenter 60 states that because long wet and long dry kilns use more energy to make a ton of 

clinker, a higher SO2 limit may be acceptable. Commenter 60 agrees with EPA’s assumption that 

new projects triggering the NSPS will result in a PH/C kiln. According to the commenter,

projects that might trigger a PSD review at a long wet or long dry kiln will probably incorporate 

emissions control measures to avoid PSD and a BACT determination. The measures to avoid 

PSD will also likely avoid the short-term emissions increases that would otherwise trigger the 

NSPS. With respect to the reconstruction provisions, the commenter states that it is not likely

that a company will actually invest 50 percent of the (undepreciated) value of an existing long 

kiln without taking the opportunity to make it much more energy efficient through conversion to 

a PH/C kiln. Nevertheless, the commenter states that it is advisable to separate out the (unlikely) 

long kiln projects that trigger the NSPS without resulting in PH or PH/C kilns in order to avoid 

the unnecessary relaxation of the limits applicable to the much more likely PH and PH/C kilns. 

According to the commenter, scrubbers are available for long kilns just as they are available for 

PH and PH/C kilns. Other strategies suggested cited by the commenter include 1)Near mid-kiln 

pressurized air injection; and 2) Chains near the entrance of the kiln that can improve contact 

between the incoming wet limestone and the SO2-laden exhaust gases containing both raw 

material and fuel sulfur.

Commenter 60 states that good SO2 control will make it possible to employ more aggressive 

NOx control and that the control of NOx and SO2 will also minimize the formation of ozone and 

fine PM in the environment.

Commenters (68, 70, 71) states that State and local experts, who have had long experience with 

this industry, believe that the proposed NSPS limit for SO2 does not reflect what most plants are 

capable of achieving. Even taking into account regional variability in the pyritic sulfur content of 

the raw materials, this commenters finds that most cement kilns already achieve lower SO2

emissions than the 1.33 lb/ton of clinker proposed. 

Commenter 70 stated that after addressing raw materials in their most recent BACT review, SO2

limitations were 0.9 lb/ton of clinker (30-day average) and 1.6 lb/ton of clinker (24-hr average); 

considerably lower than the 1.33 lb/ton of clinker (30-day average) proposed. 

Response: See the preamble for the response.

Comment: Several commenters (64, 74, 75) expressed concerns that the proposed limits for SO2

are too stringent. One commenter (64) recommends that EPA not include SO2 limitations 

because EPA recognizes that there are only “a few locations” where the raw materials contain 

high levels of sulfur, and in those few situations state regulations already impose SO2 emission 

limitations that require the type of technology EPA proposes as the basis for the proposed SO2

limitations. The commenter states that EPA assumes that one out of five new kilns will be sited 

where the raw materials are high in sulfur, requiring an SO2 scrubber or a lime injection system

when in fact at existing plants there have only been a handful of situations where high-sulfur 
27

materials have been determined to justify wet scrubbers. According to the commenter, of 

28 BACT determinations for SO2 for cement kilns since 1998 reported in the 

RACT/BACT/LAER Clearinghouse (RBLC), only 5 were based on wet scrubbers, and 1 each 

specified a dry scrubber or hydrated lime injection while the majority required no add-on 

controls because of low-sulfur raw materials or reliance on the inherent process absorption of 

SO2. The commenter states that the preamble information that only 5 kilns out of 178 kilns 

currently use a wet scrubber indicates that uncontrolled SO2 emissions are rarely high enough to 

justify add-on controls.

The commenter states that EPA acknowledges in the preamble that EPA is not obligated to 

promulgate NSPS for every pollutant emitted by sources in the source category. According to the 

commenter, the fact that very few cement kilns have been required to employ add-on controls for 

SO2 is evidence that there are few instances where cement kilns are contributing to SO2 NAAQS 

nonattainment, so there is no need for an SO2 NSPS to address ambient air quality problems. 

Commenter 64 states that allowing state and site-specific requirements address SO2 at plants 

with high-sulfur raw materials would address weaknesses in EPA’s proposed SO2 standards. For 

example, although EPA assumes that the proposed SO2 standards will require add-on controls 

only at facilities with high-sulfur raw materials, EPA has proposed a limit of 1.33 lb of SO2 per 

ton of clinker, whereas the average emission rate from just 18 data points from tests at facilities 

with moderate levels of sulfur in raw materials was 1.3 lb/ton. EPA’s assumption that facilities 

with low and moderate levels of sulfur in raw materials would not have to install controls to meet 

the proposed SO2 standards is not justified by those data. Requiring facilities with moderate 

uncontrolled SO2 emission levels to use add-on controls for SO2 would result in excessively high 

costs per ton of SO2 removed, as EPA has recognized. Also, the energy penalty associated with 

wet scrubbers could more appropriately be evaluated on a case-by-case basis, where it can be 

weighed against factors such as the level of uncontrolled SO2 emissions at the particular plant 

and the need for further SO2 reductions at that location for attainment and maintenance of SO2

ambient air quality standards. 

Commenter 64 states that because there is so little experience with add-on SO2 controls, EPA has 

relatively little data about the performance of those controls, and is proposing NSPS for SO2

based solely on a recent BACT determination. The few kilns that will be subject to the proposed 

Subpart F NSPS can be addressed through requirements for SO2 control derived through the 

RACT process or through NSR.

Commenter 64 states that if EPA persists in setting SO2 standards, there are a number of 

problems with the standards as proposed. For example, the percentage reduction alternative does 

not indicate that it is to be calculated on a 30-day basis or how the percentage reduction is to be 

calculated. The commenter infers from the monitoring provisions that EPA intends for a source 

to compare the SO2 concentration at the inlet to the scrubber to the SO2 concentration at the 

outlet from the scrubber, but this does not reflect the substantial reduction in SO2 emissions that 

occurs from contact with alkaline materials in the process. The commenter states that cement 

plants with moderate uncontrolled SO2 emissions may have to install controls and the 90 percent

reduction standard likely would be unachievable when applied to the relatively low inlet 

concentrations to the control device. The commenter states that it is even less clear how EPA 

would apply the percentage reduction standard to cement plants that choose to use lime injection
28

Commenter 64 states that the proposed regulations lack any discussion of whether the SO2

limitations apply during periods of startup, shutdown, and malfunction. Since substantial 

reduction of SO2 occurs naturally in the cement-making process because of the alkaline nature of 

the raw feed, commenter 64 states it would be reasonable to provide an exemption so that a wet 

scrubber or a lime injection system need not be operating, or operating at maximum efficiency, 

during periods of startup, shutdown, or malfunction. The commenter states that several recent 

BACT determinations involving scrubbers include special provisions for startup, shutdown, or 

malfunction.

Commenter 64 states that the proposed limits for SO2 appear inconsistent with their stated 

technology bases, when compared to actual experience and to BACT determinations. According 

to the commenter, the majority of BACT determinations in the past 10 years that rely only on 

inherent SO2 reduction established limits higher than 1.33 lb/ton of clinker, except for plants in 

Florida, where the BACT determinations often recognized that raw materials are low in sulfur. 

According to the commenter, NSPS should be based on demonstrated technology that can be 

applied to the sector as a whole, rather than based on raw materials that are available only in a 

limited area of the country. These BACT determinations also undermine EPA’s stated 

assumption that 1.3 lb/ton represents a “moderate uncontrolled SO2 emission rate” and 13 lb/ton 

would be “a high uncontrolled SO2 emission level,” since almost all BACT determinations for 

plants other than those in Florida imposed SO2 emission limits based on no add-on controls 

higher than 1.3 lb/ton, and a number were higher than 13 lb/ton.

Commenter 64 states that if EPA insists on promulgating NSPS for SO2, it is essential that the 

standards retain the proposed option of meeting either a pounds per ton of clinker or a percentage 

reduction limit, but both limits should be higher than proposed. According to the commenter, the 

three wet scrubbers operated by Holcim were not designed to achieve 90 percent reduction, and 

the one BACT determination that contains an estimated percentage reduction in the RBLC uses 

85 percent reduction. Importantly, cement plants in arid venues may not have the option to use a 

wet scrubber because of water restrictions. Especially if EPA persists in applying the revised 

NSPS to existing, modified or reconstructed facilities, wet scrubbers cannot be considered 

demonstrated available technology for all facilities in the source category. EPA does not, and 

Commenter 64 believes EPA cannot, support a 90 percent reduction requirement using dry

scrubbers or lime injection. According to the commenter, to qualify as a limit based on 

demonstrated technology, the limit should be achievable at all types of plants, raw materials, and 

locations, and should be based on actual performance data rather than what is “reportedly” 

achievable or anticipated.

Commenter 64 states that 1.33 lb/ton does not represent even the technology basis—alkaline wet 

scrubber on high-sulfur raw materials—that EPA has identified. The commenter states that EPA 

describes one kiln where uncontrolled SO2 emissions are “about 13 lb/ton of clinker.” Achieving 

90 percent reduction of that uncontrolled emission rate would just meet the proposed mass limit, 

with no margin of compliance. And in any event, at least four of the BACT determinations for 

cement kilns in the past 10 years reported in the RBLC reflect uncontrolled SO2 emission rates 

over 20.0 lb/ton. The proposed limit of 1.33 lb/ton thus does not reflect a limit that has been 

demonstrated as achievable applying wet scrubber technology to the range of sulfur contents 

present in cement plant raw materials.
29

One commenter (74) states that the proposed SO2 limit may be achievable in most cases but

different plants will require different solutions to achieve that limit. Due to the large variations in 

the elemental and pyritic sulfur from plant to plant, Commenter 74 does not believe that it is fair 

to have a set SO2 limit for all plants. Each plant's limit should be considered on a case by case 

basis considering the elemental or pyritic sulfur level in the raw materials and a reasonable target 

for the cost per short ton of removal to determine the controls that are used. In some cases this 

will give a limit lower than 1.33 lb/ton clinker and in other cases it will give a higher limit.

One commenter (75) states that: 1) Given the range of pyritic sulfur in our raw material, we 

would need to have a wet scrubber to meet this limit; 2) Lime injection is an effective control 

with less secondary impacts on water supply and energy use; and 3) A limit of 4 lb/ton of clinker 

should be adopted. This would allow greater use of lime injection, providing significant SO2

reductions while avoiding secondary adverse environmental impacts and energy use of wet 

scrubbing. The commenter does not believe that the proposed limit adequately reflects the 

inherent variability of kiln emission rates, which are dictated by the characteristics of the raw 

feed to a kiln. Commenter 75’s kiln feed is locally mined raw materials used for over 100 years, 

with plans to continue the present mining operation for many years in the future. The standard, as 

proposed, would impose economic and environmental impacts beyond those considered by EPA.

Response: See the preamble for the response.

Comment: One commenter (73) states that the proposed 1.33 lb/ton of clinker limit or 90 

percent or more SO2 reduction implies that: 1) If a kiln achieves 1.33 lb/ton of clinker without 

the need for any add-on SO2 control technology, it would meet the NSPS; 2) If uncontrolled SO2

emissions exiting the raw mill are between 1.34 and 13.3 lb/ton of clinker, control technology

capable of reducing SO2 emissions to 1.33 lb/ton of clinker would be required to meet the NSPS; 

and 3) If uncontrolled SO2 emissions exiting the raw mill are greater than 13.3 lb/ton of clinker, 

a control technology capable of 90 percent or greater control is required to meet the NSPS. The 

commenter states that if this is not EPA’s interpretation, then EPA should adopt the approach 

outlined above, and make appropriate changes to the regulatory language to make this clear.

Response: The commenter’s interpretation is not entirely correct. In light of the final limits for 

SO2, if SO2 emissions from a kiln exceed 0.4 lb/ton clinker, the owner or operator has two 

options: install a control device or modify the process so that emissions are reduced to less than 

0.4 lb/ton, or; install a scrubber or other control device than achieves at least a 90 percent 

reduction in emissions across the control device.

Comment: One commenter (76) states that pyritic sulfur is the main contributor to SO2

emissions in cement plants. The Fe2S2 releases its sulfur around 400°C, which fits nicely into the 

fourth stage (counting from the lowest stage to the highest) of a typical preheater temperature 

profile. The magnitude of the SO2 emission is simply a calculation of the total potential SO2

emission minus how much will be absorbed by the system. To bring a Colorado, or Texas 

cement plant’s SO2 level down to that of a plant in Florida, would require extensive secondary 

abatement. In extreme cases, secondary abatement could consistently lower the SO2 emission by

90 percent; therefore as long as the uncontrolled SO2 emission from pyritic sulfur and all other 

sources does not exceed 13.3 lb/SO2 ton of clinker, then a continuous controlled rate of 1.33 lb 

SO2/ton of clinker could be achieved.
30

Response: Under the final rule, the owner or operator of a kiln must comply with the SO2 limit 

of 0.4 lb/ton of clinker or reduce SO2 emissions across the control device by 90 percent or 

greater.

Comment: One commenter (77) believes that with a properly designed state-of-the-art 

preheater/precalciner kiln system, a continuous controlled emission rate of 1.4 pounds of SO2 per 

ton of clinker can be achieved by all new kiln applications which have minimal pyritic sulfur in 

their raw materials. On plants with unusually high pyritic sulfur in their raw materials 

Commenter 77 believes that with add-on controls, a reduction of 90 percent will be possible.

Response: In contrast to the commenter’s recommendation for a limit of 1.4 lb/ton clinker, kilns 

currently operating with minimal pyritic sulfur in their raw materials, for example kilns in 

Florida, have emission rates ranging from 0.02 to 0.3 lb/ton clinker (Docket item EPA-HQOAR-2007-0877-0022). For kilns processing high pyritic sulfur raw materials, we agree that a 90 

percent reduction is achievable. We think that a properly designed scrubber can achieve better 

than a 90 percent reduction. For example, emission results from a scrubber-controlled kiln in 

Texas that processes raw materials with a high sulfur content show SO2 removal efficiencies

ranging from 91 to 99 percent with an average of 94 percent (Docket item EPA-HQ-OAR-2007-

0877-0022).

Comment: One commenter (83) supports the proposed SO2 standard of 1.33 lbs/ton clinker as a 

reasonably achievable standard. The commenter would like for EPA to clarify that the limit is 

stack specific as opposed to a facility-wide limit, which means that kilns with both main and 

bypass stacks would not combine their emissions for compliance purposes but instead only have 

to meet the limit at each stack. Otherwise, the commenter states that the standard would be too 

stringent.

Response: For a kiln with a bypass, compliance with the SO2 limit will be determined by 

measuring the SO2 emissions from the separate stacks and summing the mass of SO2 emitted 

from the bypass and the kiln and dividing the sum by the clinker production, i.e., emissions are 

to be combined.

4.5 PM

Comment: One commenter (64) supports EPA’s decision not to set separate limits for 

condensable PM, PM2.5, or PM10 stating that these fractions of PM will be adequately controlled 

by facilities utilizing control equipment sufficient to meet the proposed limits for PM. The 

commenter also concurs that EPA does not have adequate data on the emissions or the 

demonstrated capability of various control technologies to meet any specified level of these 

fractions of PM. The commenter states that they are not aware of any demonstrated or emerging 

technology that would provide better control of PM2.5, PM10, or condensable PM emissions 

specifically.

Response: The PM limits address filterable PM, including PM2.5 and PM10, but not condensable 

PM. As the commenter states, EPA does not currently have sufficient information on emissions 

of condensable PM from cement kilns to set emission limits. The current information on 

emissions of condensable PM is highly uncertain. Limited data indicate that emissions of 
31

condensable PM is likely site-specific and variable. Although not quantifiable at this time, EPA 

expects that the combination of PM controls as well as wet scrubbers that are installed in order to 

comply with the HCl emission limits being promulgated in the final NESHAP amendments will 

result in a reduction of condensable PM, PM2.5 and PM10.

Comment: One commenter (64) agrees with EPA’s decision to not set a lower PM emission 

limit for clinker coolers than kilns as they are not aware of any technological basis for setting a 

lower PM limit and agrees that data on clinker cooler PM emissions from three newer facilities 

are not sufficient to fully reflect control device performance variability at a single facility or 

among facilities.

Response: EPA is setting the same PM limit for kilns and clinker coolers although the final 

limits of 0.04 lb/ton clinker (existing sources) and 0.1 lb/ton clinker (new sources) are more 

stringent than the PM limits that were proposed.

Comment: One commenter (68) stated that they agree with EPA’s BDT analysis and conclusion, 

and supports the PM NSPS level proposed.

Response: As described in the preamble, the statistical methods used to establish the MACT 

floor limits were revised following proposal and resulted in lower PM emission limits for 

existing and new sources. Even though the final limits were derived under the MACT floor 

analysis, they also reflect best demonstrated technology and the new source MACT PM limit of 

0.01 lb/ton of clinker is also the limit for new sources subject to the NSPS. The final PM limit is 

now a 30-day rolling average limit monitored using PM CEMS. It should be noted that due to the 

longer averaging periods, the actual limit will be less compared to the shorter compliance 

interval in the proposed rule (30 days versus a three hour test).

Comment: One commenter (71) recommends that EPA set a PM emission limit at a level that is 

significantly lower than 0.086 lb/ton clinker. Commenter 71 states that current PM emission 

levels from existing kilns and clinker coolers that utilize the traditional fabric bags to control 

emissions are in the range of 0.069-0.098 lb/ton of clinker. The higher end of this range is 

accompanied by visible emission. This may suggest that these higher values maybe the result of 

bag leaks. If the EPA is suggesting the use of membrane technology and bag leak detection 

(BLD) systems, then clearly the proposed limit is not reflective of the effect of the technology. 

Under normal operating conditions without bag leaks, the membrane technology would 

practically eliminate the emission of fine (inhalable) particulate and coupled with a BLD system 

would result in emissions near a tenth of the proposed standard. The cost impacts would be 

negligible since the real cost would be the increment between the traditional fabric bags and 

membrane technology. In addition, the literature and experience suggest that the greatest threat 

to human health is fine particulate in the inhalable range. It is the fine particles which provide the 

high reactive surface to promote smog forming reactions. Further, it is also the fine particulate 

that will impact visibility since it can be persistent in the atmosphere while the larger species 

settle and it has the highest ability to disperse radiation in the visible spectrum. Commenter 71 

suggests that EPA should consider establishing emission limits based on PM10 or PM2.5.

Response: We have decided to set the NSPS PM limit at the same level as the NESHAP new 

source limit, 0.1 lb/ton clinker. This change would address the comment above. 
32

As discussed in the previous response as well as in the preamble, EPA has set the final PM 

emission limits at 0.4 and 0.1 lb/ton of clinker for existing and new sources, respectively and 

requires that emissions be monitored using PM CEMS, with compliance based on 30-day rolling 

averages. Although we have not set limits for fine particulate matter as the commenter requested,

the final regulations for mercury, HCl and SO2 will result in the co benefit of reducing fine 

particulate matter emissions.

Comment: Several commenters (64, 73, 74, 83) expressed concerns over the proposed NSPS for 

PM of 0.086 lb/ton of clinker. Commenter 64 states that the proposed limit of 0.086 lb/ton of 

clinker is not supported by the data available from new plants with the identified technology; it 

does not allow for deterioration of performance over time; and it does not allow for an adequate 

margin of compliance. Commenters believes that EPA used insufficient data to develop the 

standard and failed to consider situations where gases from kilns, clinker coolers, and coal mills 

are combined for energy recovery purposes. Commenter 73 has spoken to major suppliers of 

cement kiln systems and believes that baghouse technology with membrane bags is capable of 

achieving a continuous outlet grain loading rate of 0.010 gr/dscf. Applying EPA’s factors for 

standardized volumetric flow and feed-to-clinker ratio (54,000 dscf/ton of feed and 1.65 tons 

feed/ton clinker), an appropriate NSPS PM standard would be 0.127 lb/ton of clinker for cement 

kilns and clinker coolers. Commenter 73 and 74 also believes that when clinker cooler and kiln 

gases are combined, the standard for these systems should be additive. 

The commenters stated that the standards must be set at a level that recognizes that there will be 

some deterioration in performance over time. According to the commenters, in most cases, 

emission rates achieved immediately after installation of pollution control equipment will not be 

representative of the performance over the life of the source, as the bags and the baghouse itself 

age and experience normal wear, even with proper operation and maintenance. Commenter 73 

agrees with EPA that “fabric filters control generally to the same concentration irrespective of 

the PM loading to the filter inlet, though some variability in PM emissions from fabric filters 

does occur due to seepage and leakage.” It is the seepage and leakage that becomes an issue as 

baghouses age. Commenter 64 states that the PM stack testing data used by EPA in their 

analyses were obtained from kiln-baghouse systems that had operated for less than 5 years and 

therefore, EPA has not demonstrated that they have proposed a limit that new sources can sustain 

long term. EPA has recognized this in numerous other rulemakings, including in setting emission 

standards for hazardous air pollutants at new cement kilns burning hazardous waste where they

amended the PM limits for new sources in that NESHAP based on data demonstrating that the 

original PM standard was “overly stringent in that it does not fully reflect the variability of the 

best performing source over time.”

Response: For a discussion of issues raised by these commenters, see the preamble. See also

section 2.8.2 of the comment and response document for the final NESHAP.

Comment: Commenter 64 submitted recent PM test data from 25 preheater and 

preheater/precalciner kilns consisting of 42 separate Method 5 tests. The data includes 

information on whether bags were membrane bags and whether the raw mill was on or off. The 

commenter evaluated the data and drew the following conclusions:

 The test results were not statistically normally distributed.
33

 The average emission rate for membrane equipped bags was 0.077 lb/ton clinker and 

0.091 for conventional bags.

 Using the Mann Whitney test, the difference in the means for the bag types was not 

statistically significant.

 Average emissions during mill off conditions were statistically higher than emissions 

during mill on conditions.

 Based on a number of test results for three Florida kilns, there is substantial day-to-day

variability that must be considered in setting the NSPS.

 The upper 95% confidence interval for the test data is 0.108 lb/ton clinker which is 

approximately 0.01 gr/dscf (or 0.127 lb/ton clinker), the same as the achievable limit 

recommended by cement design firms. Commenter 83 also supports a PM limit of 0.127 

lb/ton clinker.

Response: In developing its final PM emission limits, EPA evaluated data submitted by the 

commenter along with data collected previously as well as data submitted following the proposal 

of the NESHAP amendments. Data submitted by the commenter appeared to contain kilns that 

were lower emitters than kilns in our original group of kilns; we requested test run results for 

those kilns from the commenter. PM emissions limits were developed as MACT floor limits, 

which under the final rule, include limits for new kilns subject to the final NSPS as well. Under 

the MACT floor approach, the top performing kilns were selected based on the average of their 

emissions test results. We noted, as did the commenter, that PM emissions tend to be greater 

during mill off than mill on conditions. To determine a kiln’s ranking where we had tests under 

raw mill on and off conditions, we used weighted average emissions to account for the 

differences. For two top performing kilns, we had only a single test (three runs each); we 

requested additional data for those kilns and were able to add an additional six test runs for each 

of the two kilns. In addition, one commenter submitted additional test data for its kiln that was 

one of the top performers. From the 45 kilns for which we had adequate emissions data to 

evaluate, we identified the top 12 percent, or top 6 kilns. Using a revised upper prediction limit 

(UPL) formula, we assessed the data variability to establish the MACT floor limits for existing 

and new kilns. The statistical method is further discussed in the preamble.

Regarding the comment on the performance of membrane bags in comparison to standard bags, 

high efficiency membrane filters under testing in EPA’s Environmental Technology Verification 

(ETV) Program, have on average significantly outperformed non-membrane depth filters in 

controlling PM and PM2.5 as well as in other performance areas including average residual 

pressure drop and cleaning cycles. (World Cement, April 2007) Use of membrane bags is 

expected to reduce baghouse maintenance, extend bag life and reduce operational incidents such 

as increased opacity, and enable higher production levels. (W.L. Gore and Associates, 

Optimizing Kiln Operations by Improving Baghouse Performance, 2001).

Comment: Commenter 73 believes that EPA may not have adequately quality controlled the 

data used in its analyses. For example, the Lafarge Sugar Creek data used by EPA in their 

analyses came from a performance test that was done to demonstrate compliance with the PM10

standard. Thus, this data is PM10, not PM.
34

Response: As a result of this comment, the PM data in question was re-examined. The Missouri 

Department of Natural Resources was contacted for clarification of the 2002 test data for the 

Lafarge kiln at Sugar Creek, MO. The initial testing to determine MACT compliance included 

testing for PM as well as PM10. The results used in our analysis were for PM and not PM10. The 

documents containing the results referred to here can be viewed in Docket No. EPA-HQ-OAR2002-0051, docket items 2002-0051-2024 and 2002-0051-2039.

Comment: One commenter (75) stated that the proposed NSPS will require the use of baghouses 

equipped with membrane filters, which will present an additional capital cost over typical fabric 

filters in addition to an additional increase in maintenance over traditional filters, and that 

baghouse designs will be larger, increasing space requirements and energy consumption. 

Response: The commenter is correct that new baghouses may require the use of membrane 

filters to comply with the NSPS PM limit and that the capital cost of these filters is greater than 

conventional fabric filters. However, EPA disagrees with the other claims made by the 

commenter. Because membrane bags utilize surface filtration rather than depth filtration of 

conventional fabrics, membrane bags require less aggressive cleaning, which greatly prolongs 

bag life in comparison to conventional fabric, and operate at higher air-to-cloth ratios requiring, 

which would translate to smaller baghouse designs. Also, the trend in baghouses in the cement 

industry is to smaller pulse-jet baghouses. More importantly, under testing in EPA’s 

Environmental Technology Verification (ETV) Program, membrane filters have on average 

significantly outperformed non-membrane depth filters in controlling PM and PM2.5 as well as in 

other performance areas including average residual pressure drop and cleaning cycles. (World 

Cement, April 2007) Use of membrane bags is expected to reduce baghouse maintenance, extend 

bag life and reduce operational incidents such as increased opacity, and enable higher production 

levels. (W.L. Gore and Associates, Optimizing Kiln Operations by Improving Baghouse 

Performance, 2001). The other factor that will affect whether standard fabric filters are replaced 

with membrane filters is the increased use of ACI systems, including a polishing baghouse, to 

comply with the mercury emission limits under the NESHAP. EPA anticipates that ACI systems 

will be placed downstream of existing PM control devices because of the inability to recycle

CKD containing carbon from the ACI back to the kiln. Recycling CKD is a common practice in 

the industry. The result is that many kilns will be equipped with two PM control devices in 

series, in which case it is unlikely that standard fabric bags will need to be replaced with

membrane bags in order to achieve compliance with the PM limit. Because new kilns will be 

subject to PM limits that were developed as part of developing the MACT floor limits under the 

NESHAP for portland cement manufacturing, costs incurred to comply with the final PM limits 

are attributable to the NESHAP rather than the NSPS.

Comment: Commenter 75 asks that EPA consider a grain loading limit of 0.01 gr/dscf as a more 

practical alternative to the lb/ton of feed limit noting that PM emissions limits are typically based 

on grain loading (gr/dscf) which is more representative measures of PM emissions, and is not 

dependent upon production rate. A gr/dscf limit would better reflect the actual efficiency of the 

control device, regardless of the production rate. 

Commenters75, 76 and 77 stated that modern baghouses can consistently achieve a continuous 

outlet grain loading of 0.010 gr/dscf. Of course, this emission rate can only yield a lb of 

particulate/ton clinker value when converted using the site specific volumetric flow rate and 
35

feed-to-c1inker conversion factor. Here again, both values vary from site to site and must be 

evaluated on an individual basis. For that reason, the commenters would not suggest a lb of 

particulate/ton clinker PM limit; but a gr/dscf limit.

Response: As discussed in the preamble, EPA developed PM limits for existing (0.04 lb/ton 

clinker) and new kilns (0.01 lb/ton clinker) using the MACT floor approach; the PM limits for 

new kilns are also applicable to new kilns under the NSPS. In response to the comment that the 

limit should be set at 0.1 gr/dscf, EPA analyzed the grain loading data for the MACT floor kilns 

to determine what the PM limit would be if we were to put the limit in units of gr/dscf. The 

average grain loading of the MACT floor kilns is 0.002 gr/dscf. The MACT floor limit based on 

the UPL for these top performing kilns would be 0.004 gr/dscf, well below the commenter’s 

suggested 0.1 gr/dscf.

In response to the commenter’s suggestion that EPA use gr/dscf as the format for the PM limit, 

EPA believes, as we stated in the preamble to the proposed rule, that an output-based standard, 

i.e., lb/ton of clinker, promotes efficiency among the sources as opposed to input or 

concentration based standards. An output based standard is also consistent with permit limits set 

by many states that we reviewed. A disadvantage of the concentration standards is that emissions 

can increase as a result of the intentional or unintentional addition of dilution air to the exhaust 

gas stream which has the effect of reducing the concentration but not emissions. For these 

reasons EPA did not replace the output based standard with concentration based limit or offer 

one as an alternative to the output based limit.

The PM data for the top performing kilns under the NESHAP resulted in a MACT floor limit of 

0.04 lb/ton of clinker for existing kilns and 0.01 lb/ton of clinker for new kilns. As required by 

the CAA and subsequent court rulings, EPA is bound to establish limits of the top performers. 

Even considering the data of the top performing kilns in gr/dscf, the limit for existing kilns as 

described above is well below the commenters’ recommended 0.1 gr/dscf.

4.6 Opacity

Comment: One commenter (64) agrees that there is no basis for revising the current NSPS 

standards that apply to affected facilities at portland cement plants other than the cement kiln and 

the clinker cooler and states that they are not aware of data that would support imposing a 

limitation more stringent than the current 10 percent opacity standard. The Commenter 64 further 

states that an opacity standard below 10 percent could not be determined reliably due to the 

margin of error associated with the EPA Method 9. Commenter 83 urges EPA to maintain the 

existing subpart F opacity limits.

Response: We are removing all opacity standards for kilns and clinker coolers because these 

sources will be required to monitor compliance with the PM emissions limits by more accurate 

means.

Comment: One commenter (69) believes that all kiln stacks should be subject to a 20 percent 

opacity limit as is currently required in the existing portland cement plant NSPS. Kiln stack 

emissions have the potential to form a secondary (reactive) plume after the exhaust gases exit the 

stack. There have been instances where a certified in-stack continuous opacity monitor (COM) 
36

read opacity well below 20 percent while opacity observations of a certified Method 9 reader 

were in the 40-60 percent opacity range. The disparity between the COM readings and the 

Method 9 readings were attributed to exhaust gases reacting upon exit of the stack to form a 

secondary plume approximately 300-500 feet downwind of the stack exit. Commenter 69 

supports the proposed rule's requirements regarding kiln stack particulate monitoring using bag 

leak detection systems, electrostatic precipitator predictive models, and continuous emissions 

monitors. However, Commenter 69 does not support allowing facilities that use these particulate 

monitoring systems to be exempt from a kiln stack opacity limit.

Response: See the previous response.

4.7 VOC and CO

Comment: One commenter (59) states that a co-benefit of using SCR system to control NOx

emissions is that they simultaneously reduce VOC emissions and organic HAPs including 

dioxins, furans, and ammonia. The commenter states that SCR removes greater than 80 percent

CO, and greater than 70 percent of VOCs. 

Response: EPA agrees with the commenter that one of the advantages of SCR technology for 

NOx control is the co-benefit of simultaneously reducing emissions of other pollutants, including 

VOC and possibly CO. But as discussed earlier (see section 4.3), the limited application of SCR 

technology in the cement manufacturing industry (three kilns in Europe and none in the United 

States) and known potential for mechanical problems in operating the technology leaves EPA 

unconvinced that SCR qualifies as best demonstrated technology. As a result, the final emission 

limits for NOx are based on the use of well designed combustion systems in conjunction with 

SNCR technology, which has been demonstrated on numerous kilns operating in the United 

States.

Comment: Commenters (64, 73) support EPA’s conclusion that revised NSPS for portland 

cement plants should not be expanded to include limitations for carbon monoxide or volatile 

organic compounds. The commenters agree that fuel-efficiency considerations already assure 

that CO emissions from incomplete fuel combustion are minimized. The commenters also agrees 

that the THC limitation in the portland cement NESHAP will assure that cement plants subject to 

the proposed Subpart F NSPS will not emit excessive levels of VOCs.

Response: EPA acknowledges that the commenters are in agreement with EPA’s decision to not 

establish new source performance standards for VOC and CO.

Comment: One commenter (71) believes that EPA should take this opportunity to also set 

appropriate VOC and CO emission limits for cement kilns. Based on the testing conducted at a 

long dry cement kiln, the uncontrolled VOC and CO emission levels are in the range of 0.62-

0.70 and 1.62-2.14 lb/ton of clinker, respectively. These uncontrolled VOC and CO emission 

levels can be reduced once the appropriate control technologies are identified. Commenter 71 

encourages EPA to further review available test data for cement kilns, identify appropriate 

control technologies, and establish achievable limits.
37

Response: As discussed in the final rule, non-dioxin THC emissions, most of which are VOC, 

are being regulated under the final NESHAP amendments. Under the final amendments to the 

NESHAP, THC limits of 24 ppm are being set for existing and new sources, thus there is no need 

to establish new source performance standards for VOC.

As described in the proposed rule, highly efficient combustors in precalciner kilns will minimize 

emissions of CO from burning fuel. In cases where the organic content of the raw materials is 

high enough to emit high levels of CO, THC emissions will also be elevated and require that the 

facility take steps to comply with the NESHAP limits for THC. Therefore, elevated CO levels 

that occur in conjunction with elevated THC levels will be controlled as part of a plant’s control 

of THC emissions. 

4.9 Fugitives

Comment: One commenter (68) strongly recommends that EPA promulgate NSPS for fugitive 

emissions from clinker storage piles, raw materials handling, and baghouse fall-out from cement 

plants. These sources of fugitive emissions contain not only fine particulate emissions, which 

pose substantial harmful effects to public health, but a number of inorganic hazardous air 

pollutants, such as arsenic, mercury and hexavalent chromium. The commenter cites a recent 

California study indicates that high levels of hexavalent chromium, in particular, are emanating 

from portland cement facilities. Specifically, storage piles of clinker should be either partially or,

preferably, fully enclosed; installation of wind screens should be considered; and other corrective

work practice measures evaluated and promulgated.

Response: See the preamble for a discussion of actions that EPA is taking regarding fugitive 

emissions from handling and storage piles.

4.10 Overall Achievability

Comment: One commenter (64) has concerns about the overall achievability and cost 

effectiveness of the proposed NSPS. First, it does not appear EPA has given sufficient 

consideration to whether each of the individual proposed emission limitations can be achieved, 

or achieved at reasonable cost, at the same time as other proposed NSPS emission limitations and 

other applicable emission limitations. EPA has not identified any cement plants that employ the 

combination of measures to achieve very low PM emissions, NOx reductions, and SO2 reductions 

that form the basis for the proposed NSPS. Commenter 64 urges EPA to give additional 

consideration to these interactions that may occur when the various control technologies 

identified in the proposed NSPS are employed together. 

One commenter (77) understands the newly proposed NSPS limits for SO2, NOx and PM may be 

achievable in a large number of projects. Commenter 77 also states that these new limits would 

not be achievable for all projects as would be required by these new NSPS limits. Current 

cement plant process technology and equipment are very effective at minimizing the potential air 

pollutant emissions through state of the art combustion technology and add on pollution control 

systems. Each plant has specific raw materials and fuels which combine to make a variety of 

cement types. All of these factors combined influence the potential emissions of SOx, NOx, CO 
38

and PM. Detailed analysis and proper application of various technologies are required for each 

different combination of plant specific materials.

Response: EPA is mindful that it must set standards that reflect achieved performance, that 

process inputs (raw materials and fuels) must be accounted for in ascertaining sources’ 

performance, and that costs be considered by EPA in ascertaining the level of the BDT. In 

considering achievability, EPA established limits based on what best performers actually

achieved. EPA has carefully developed data for each standard, assessing both process 

performance and technological controls in doing so. For example, while EPA has set its limits 

for NOx based on the use of low NOx processes and SNCR, it has rejected more stringent limits 

based on SCR control technology that we do not consider to be a clearly established NOx control 

technology in the cement industry. EPA has also adopted 30-day averaging periods for all of the 

standards, further allowing short term fluctuations to be averaged out over the 30-day period. 

The result are limits that reasonably estimate the performance over time of the best demonstrated 

technology. It is true that many sources will need to install controls to meet these standards, and 

that these controls have significant costs. This is part of the expected process where, by 

definition, new sources will need to perform at levels above what is achievable by most existing 

sources. The Agency believes that it has utilized best efforts to follow the statute and applicable 

caselaw, and has not adopted standards which are impermissibly unachievable.
39

5 Monitoring and Recordkeeping

Comment: One commenter (57) states that the proposed minimum requirement for valid data in 

60.63(l)(1) is “at least 18 hours in at least 22 out of 30 successive kiln operating days.” This may

need to be revised, depending on how EPA chooses to define a kiln operating day. The proposed 

language is acceptable if a kiln operating day requires a kiln to operate the entire 24 hours in a 

day. If a kiln operating day can include less than 24 operating hours, then the requirement for “at

least 18 hours” is not feasible. EPA addressed a similar issue in 60.49Da(f)(1) and (2). Subpart 

Da requires valid data for “at least 90 percent of all operating hours” in an operating day when a 

boiler operating day can include less than 24 operating hours.

Response: A definition of operating days has been added to the rule. A kiln operating day can 

include less than 24 operating hours.

Comment: One commenter (57) states that EPA should consider allowing sources that have 

NOx, SO2, or stack flow CEMS certified and operated per 40CFR75 to use those CEMS to meet 

the monitoring requirements. There are examples of this in 60.49Da(b)(4) and 60.49Da(c)(2).

Response: We agree that CEMS certified and operated per 40CFR75 could be used to meet the 

monitoring requirements; an owner/operator can request alternative monitoring in such a 

situation.

5.1 SO2

Comment: One commenter (64) states that with regard to SO2 monitoring, EPA has not 

provided adequate explanation of how monitoring data would be used to determine compliance 

with the percent reduction option in the proposed SO2 standard, both for wet scrubbers and for 

facilities that can comply using alkali injection. In addition, because EPA asserts that 80 percent

of cement plants subject to the proposed NSPS will not need any add-on controls to meet the 

proposed standard, because they have low or moderate sulfur content in their raw materials, and 

the nature of those raw materials is relatively stable, there is no justification for imposing the 

added capital and operating cost of continuously monitoring SO2 emissions. Commenter 64 

suggests that cement plant operators relying on low-sulfur raw materials and inherent SO2

reduction in the process should have the option of conducting an initial performance test for SO2, 

with retesting at least once every five years, with no continuous monitoring of SO2 required so 

long as the stack test shows SO2 emissions less than 1.0 lb/ton.

Response: The SO2 compliance option of demonstrating a 90 percent reduction was intended to 

apply to situations in which a wet scrubber is being used for compliance. In those instances, the 

owner or operator may comply with either the SO3 emission limit or the 90 percent reduction. 

The 90 percent reduction is determined my continuously measuring SO2 at the inlet to the 

scrubber and at the scrubber outlet. If a facility is using alkali injection, compliance is 

demonstrated by meeting the SO2 emission limit of 1.33 lb/ton. The final rule has been revised to 

make this clear.

In response to the commenter’s suggestion that there is no need for SO2 monitoring where 

scrubbers are not needed for SO2 control, it is possible that a source might change a raw material 
40

and significantly increase SO2 emissions beyond the standard. If monitoring is not in place, these 

excess emissions could be unchecked for five years before they were discovered. We believe the 

cost of the SO2 monitor is reasonable to prevent these excess emissions. These monitors are well 

established technology that are already installed on over 30 cement kilns, including those without 

SO2 controls.

Comment: One commenter (68) strongly supports the requirements proposed by EPA for 

continuous emissions monitoring for both SO2 and NOx to assure compliance with applicable 

emissions limits.

Response: EPA acknowledges the commenter’s support.

5.2 PM

Comment: One commenter (83) recommends eliminating the requirement for PM CEM 

monitoring stating that the technology is neither sufficiently advanced nor reliable.

Response: EPA disagrees with the commenter’s assertion that PM CEM is not sufficiently

advanced or reliable. It is currently required in other rules for the monitoring of PM emissions

and is used in Europe. EPA is replacing bag leak detectors and opacity monitoring and requiring 

the use of PM CEMS to monitor PM emissions from all kilns and clinker coolers. 

5.3 Opacity

Comment: One commenter (67) states that in the proposed changes to §60.62(a)(2) and (b)(2), 

EPA proposes to exempt kilns and clinker coolers, with an applicability date prior to June 16, 

2008, that use a baghouse leak detection (BDL) system, electrostatic precipitator (ESP) 

predictive model, or a PM continuous emissions monitoring system (CEM) from opacity 

standards. We have the following concerns:

(1) The kilns and clinker coolers would not have an opacity standard per the NSPS if they

have a PM monitoring system as an alternative to the COMS or daily Method 9 readings. 

Although the language in §60.62(d) indicates an intent by EPA to require the owner or 

operator of the affected facility to comply with the more stringent of two different 

requirements, the proposed language refers to “another regulation in title 40 of this 

chapter.” Many states have a 20 percent maximum opacity standard in their state

implementation plan (SIP) requirements. This could mean a relaxation of the opacity

standard for the clinker coolers from 10 percent (current NSPS standard) to 20 percent

standard.

(2) If the PM monitoring system is not operating or is operating incorrectly, then opacity

may exceed the opacity limit (20 percent or 10 percent as applicable) in the short term. 

The current opacity limit is for all of the time the kiln or clinker cooler is operational on 

or after the date the performance test is conducted per 40 CFR 60.8.

(3) The proposed language in §60.62(a)(2) and (b)(2) only exempts kilns and clinker coolers 

from opacity limits if their applicability date was before June 16, 2008. Therefore, the 
41

newer kilns and clinker coolers (applicability date after June 16, 2008) would be subject 

to the opacity standards. The monitoring requirements for the newer units in §60.63(b)(2) 

includes the alternative PM monitoring options, but doesn’t include a COMS.

(4) Requirement §60.64(b)(6) in the proposal states that any unit subject to the 10 percent

opacity limit must comply with §63.1350. The clinker coolers with applicability date 

after June 16, 2008 would be subject to the 10 percent opacity limit in §60.62(b)(2).

Requirement §63.1350 requires a COMS to be installed or must conduct daily Method 9

tests (for multiple stacks only).

Commenter 67 suggests EPA consider removing the exemptions in §§60.62(a)(2) and (b)(2) and

retaining the opacity limits. Requirements in §60.63(b) {PM requirements} and (c) {multiple 

stacks alternative to COMS} allow for the alternative PM monitoring methods. If the exemption 

remains, we suggest changing language in §60.62(a)(2) from "(a)(1)(i)" to "(a)(1)" and changing 

language in §60.62(b)(2) from (b)(1)(i) to (b)(1), so that it is consistent on which units are 

subject to the opacity limits.

Response: In the final rule, PM CEMS are required in place of bag leak detectors and/or opacity 

monitoring on all kilns and clinker coolers.

Comment: One commenter (73) agrees with EPA that opacity monitoring for a kiln or clinker 

cooler subject to the proposed NSPS is unnecessary if PM CEMS or bag leak detectors (BLD) 

are installed. Further, Commenter 73 supports EPA’s decision not to require PM CEMS, but 

make it an option to BLD technology. Commenter 73 also supports compliance testing for PM 

on an every five year basis.

Response: See the previous response.

5.4 CEMS

Comment: One commenter (63) supports the proposal to allow facilities to install PM CEMS as 

there are several types of emissions measuring techniques that can be applied to combustion 

processes. The commenter identifies different PM CEMS technologies and their costs.

Response: See the previous response.

Comment: One commenter (64) agrees that PM CEMS should be an option, not a requirement, 

and that opacity monitoring is not necessary for a kiln or clinker cooler that employs a PM 

CEMS or baghouse leak detectors or parametric monitoring of an ESP. Commenter 64 also 

agrees that compliance testing every five years is adequate in light of the continuous monitoring 

requirements. The commenter also supports the alternative in proposed section 60.63(c) for daily

visual opacity monitoring for control equipment with multiple stacks. Commenter 64 supports as 

well EPA’s proposal that sources subject to the current NSPS should have the option of installing 

baghouse leak detectors or PM CEMS as an alternative to continuous opacity monitoring 

(COMS).

Commenter 64 states that it is not clear from the wording of proposed section 60.63(b) if sources 

choosing to install a PM CEMS need not also install and maintain baghouse leak detectors. 
42

Commenter 64 recommends that EPA continue to allow COMS as a monitoring method, so that 

a kiln or clinker cooler subject to the revised NSPS would have the option of monitoring 

compliance with a COMS, a PM CEMS, or baghouse leak detectors. The commenter states that 

EPA’s justification is an insufficient basis for excluding a proven monitoring technique, which 

cement manufacturers already know how to operate and maintain and which will cost less to 

install and maintain.

Response: See the previous response.

5.5 Clinker Production

Comment: Commenters (64 and 73) stated concerns about the requirement to continuously

monitor clinker output. The commenters are not aware of existing weigh scale systems currently

in use to measure clinker exiting the kiln or clinker cooler. According to the commenters, clinker 

exiting the kiln and the clinker cooler is extremely hot and cannot be transported to storage by 

conventional belt conveyor systems. Because drag and screw conveyance systems that are used

are not designed to incorporate weigh scale systems, a large majority of cement plants measure 

clinker production by using a raw mix weigh scale system on the conventional belt conveyor 

system feeding the kiln, and then applying a standard feed-to-clinker conversion factor. In the 

pyroprocessing system, feed-to-clinker conversion is very constant which is especially the case 

for PH/PC kilns. EPA should provide that as an alternative to the requirement to install a clinker 

weigh scale system. The provision for approval of an alternative monitoring method is a 

cumbersome and time-consuming approach that in practice will not be a practical substitute for 

basing clinker output measurement on the demonstrated technology of weighing raw materials 

and applying a conversion factor). The commenter included suggested regulatory language.

Response: We explicitly state in the NESHAP that a system that directly monitors feed rate and 

uses a conversion factor to determine the clinker production rate is an acceptable method of 

monitoring clinker production rates. The final rule language for the NSPS likewise makes this 

clear.
43

6 Test Methods and Procedures

Comment: According to one commenter (67) the statement in §60.64(b)(5), “kiln (including any 

associated alkali bypass and clinker cooler)” shall be tested every 5 years could be interpreted 

that only clinker coolers associated with kilns subject to Subpart F have to be tested every five 

years. Commenter 67 suggests EPA revise the language to state “kiln (including any associated 

alkali bypass) and clinker cooler,” which identifies the intention that each kiln and clinker cooler 

has to be tested every 5 years. The 5-year testing requirement is for PM emissions only. There 

are no NOx and SO2 testing requirements. This could be interpreted that the kilns or clinker 

coolers with a PM CEMS must also conduct separate performance tests every 5 years in addition 

to the annual relative accuracy tests that are required for the CEMS. If it is EPA’s intent to

require PM performance testing every 5 years despite a PM CEMS, then it could be interpreted 

that the PM CEMS is less accurate or reliable than the NOx or SO2 CEMS. If the annual relative 

accuracy tests for the PM CEMS are equivalent to the 5-year testing, then we suggest an 

exemption for kilns or clinker coolers with a PM CEMS. If the annual relative accuracy tests for 

the CEMS are not equivalent to periodic performance testing, then we suggest a periodic (5-year) 

performance testing for NOx and SO2 should be added for the kilns which had commenced 

construction, modification, or reconstruction after June 16, 2008.

Response: The identified section of the rule will be revised in light of the final requirement that 

PM CEMS be used to monitor emissions from all kilns and clinker coolers, 

Comment: One commenter (67) states that §60.64(b)(6) would require units subject to the 10

percent opacity limit to comply with §63.1350. The specific parts of the §63.1350 that these units 

are subject to should be identified, because not all of the NESHAP requirements apply to these 

units.

Response: The specific sections of §63.1350 that apply have been added to the rule (now at 

60.64(b)(4)) as suggested.
44

7 Impacts

7.1 Cost and Cost Effectiveness

Comment: One commenter (59) states that there was a high degree of consistency between the 

three independent assessments of SCR cost effectiveness. The U.S. EPA median value of 

$1,800/ton NOx was well within the range presented in the EU IPPC document, $1,500 to $3,800 

per ton, and also was close to the value estimated by the blue ribbon panel for dry cement kilns 

of $2,000 per ton. The blue ribbon panel also estimated the cost effectiveness for a series of 

smaller older wet kilns at $5,800/ton NOx.

One commenter (63) states that the cost effectiveness of SNCR deployed on a PH/C cement kiln 

is $700 ton/ NOx removed. In the evaluation of SCR’s cost effectiveness in removing NOx from 

a cement kiln a conservative threshold ranges from $1,800- $5,000 per ton of NOx controlled. 

One commenter (60) states that according to the Swedish environmental agency “the total cost 

(of SNCR) with depreciation, capital cost, energy and ammonia related to NOx abated was is

approximately $325/ton of NOx removed. The commenter included the report from the Swedish 

report as well as other reports on the performance of SNCR as attachments to the comment. The 

commenter cites an example where the SNCR is operated to achieve a reduction from 6 to 1 lb

NOx/ton, the cost effectiveness would be less than $700/ton NOx removed.

Commenter 60 cites European cost comparisons of SNCR and SCR that show a cost 

effectiveness for SNCR of $465/ton of NOx removed and $1,230/ton of NOx removed for SCR 

assuming a conversion of $1.30/€.

Response: The EPA generally agrees with the commenter on the range of cost effectiveness for 

SNCR and SCR. We consider SNCR to be BDT for NOx control. The final NOx limits are based 

on the expected performance of SNCR (and proper control upstream of the end-of-stack SNCR) 

and we believe it can and will be used to meet the final limit for NOx. While we see SCR as a 

promising technology for NOx emission control, we have not set emission limits based on SCR 

technology for reasons stated in the preamble to the final rule and other comment responses. We 

will continue to monitor progress in the control of NOx emissions from the cement kilns and will 

reconsider SCR at the appropriate time.

Comment: One commenter (64) stated that the proposed PM limit would have the effect of 

requiring modified or reconstructed cement plants using an ESP to replace it with a fabric filter 

using membrane bags and that EPA has simply ignored costs impacts for modified facilities that 

will have to replace an ESP with a baghouse.

Response: In the final rule, the PM limits established under the NESHAP apply to both new and 

existing sources. So regardless of whether a kiln is modified/reconstructed or not, it will be 

subject to the revised PM emission limits. In estimating the impacts of the more stringent PM 

limits under the NESHAP, we did evaluate kilns that were currently controlled by ESP to 

determine the costs for such kilns. In addition, it is not clear that kilns equipped with an ESP 

must necessarily remove them to meet the NESHAP/NSPS PM standard. We believe that most 

kilns will have to install an activated carbon injection system with a polishing baghouse in order 
45

to comply with either the mercury emission limits or limits for organic HAP. As a result, it is 

likely that a kiln currently equipped with an ESP will be adding a baghouse (as part of the ACI 

system) downstream of the ESP and will be able to meet the final PM limit without replacing the 

ESP.

Comment: One commenter (64) also believes that the cost-effectiveness discussion does not 

reflect adequate consideration of the costs of achieving the emission reduction required by the 

proposed standards as mandated by CAA section 111(a)(1). Commenter 64 does not believe that 

simply comparing the costs per ton of pollutant removed to the costs per ton that has been 

imposed in NSPS for the electric utility represents an adequate weighing of the costs involved. 

Even based on EPA’s cost estimates, the proposed NSPS would impose millions of dollars of 

additional costs on each new or reconstructed or modified kiln, and tens of millions of dollars for 

each kiln required to install a wet scrubber. These costs should be considered as well in

conjunction with costs already imposed by the portland cement NESHAP and the additional 

costs that may be imposed as a result of the ongoing review of that NESHAP. These are costs not 

borne by the industry’s competitors in Canada and Mexico and elsewhere. EPA needs to provide 

better justification that these costs are justified by the differences between the current Subpart F 

NSPS and the proposed Subpart F NSPS.

Response: The MACT emission limits for PM will apply to existing and new kilns and will be 

applicable to kilns subject to the NSPS. We have considered the costs of controls under both the 

NSPS and the NESHAP as well as the economic impacts associated with those costs. See the 

preamble for a discussion of the costs, economic impacts and benefits of the final amendments.

Comment: One commenter (75) states that the “uncontrolled” inherent emissions of SO2

considered by EPA as representative of modern kilns are too high, thereby incorrectly making

wet scrubbing cost effective. EPA has used those sites currently operating wet scrubbers as the 

basis for establishing “high levels” of uncontrolled sulfur emissions. However, this is

inappropriate because it ignores fundamental technological differences between various cement 

kilns. The commenter states that in one case, EPA used data from a facility where the scrubbers 

are controlling emissions from wet kilns, not modern preheater/precalciner kilns. The other highsulfur facility that is referenced by EPA does not represent a new kiln. Rather, that project 

reflects the addition of a preheater/precalciner to an existing kiln. In addition, the uncontrolled 

SO2 emissions for this kiln approximated at 13 lb/ton includes approximately 8 lb/ton from the 

alkali bypass stack and 4 lb/ton from the main stack. Modem kilns with high sulfur raw materials 

can achieve inherent emissions on the order of 4.5 lb/ton. When the inherent emissions rate of 

new kilns is considered, wet scrubbing is not cost effective or environmentally beneficial and 

should not be considered BDT.

Response: Because of the requirements for HCl control on existing and new kilns under the 

NESHAP, most kilns will be equipped with wet scrubbers or lime injection for the control of 

HCl. As a result, new kilns subject to the revised NSPS will have their SO2 emissions 

incidentally controlled. None of the cost of the scrubbers will be attributable to the final NSPS 

amendments.

The commenter is taking issue with the uncontrolled SO2 emission levels we used in estimating 

the impacts of the proposed standard. Although the cost of controlling SO2 is attributable to the 
46

NESHAP, we note that in the final analysis of impacts under the NESHAP, we did revise the 

uncontrolled SO2 emissions to reflect the variation in SO2 emissions due to kiln type and 

location. In order to examine the effects of kiln type, fuel and raw materials on SO2 emission, 

average SO2 emission were estimated from 2002 National Emissions Inventory data in the 

Cap+Trade workbook for each market by kiln type (Andover, September 23, 2008). Generally, 

preheater and precalciner kilns had the lowest SO2 emission rates while wet and long dry kilns 

generally had the highest SO2 emission when comparing different locations. Location was 

determined to play a significant role in SO2 emissions from kilns. Both mean and median 

emissions were examined. Because median values tend to be less impacted by outliers than 

means, median SO2 emission rates were used in the final analysis of air quality impacts.

7.2 Environmental and Energy

Comment: One commenter (75) states that the economic and environmental impacts of wet 

scrubbing are understated. EPA estimated the cost effectiveness for reducing high uncontrolled 

SO2 emissions as less than $1,000 per ton of SO2 removed. However, if the uncontrolled 

emission rate is corrected to a more appropriate rate, the cost per ton increases due to two effects. 

First, a lower uncontrolled emission rate results in less SO2 being removed, increasing the cost of 

removal per ton of emissions. In addition, as the amount of SO2 controlled is reduced, the 

amount of synthetic gypsum available, and the gypsum credit, is reduced. The commenter states 

that they believe that the credit for the use of scrubber derived gypsum used by EPA is too great. 

Cement always includes gypsum at levels of around 5 percent by mass as a setting retarder. The 

commenter estimated that the maximum quantity of gypsum recycled will be 23,342 tons/year, 

which is well below the 84,101 tons/year listed in the example. Correcting this error further 

reduces the cost effectiveness of wet scrubbing. 

The commenter states that a wet scrubber would greatly increase the amount of water used by a 

cement facility. The Southeast has experienced frequent drought conditions in recent years

restricting the amount of water available for both residential and industrial use. Legal 

proceedings have also taken place between Southern States over the right to use water. The 

requirement of a wet scrubber to control SO2 would create additional stresses over this water 

resource since an estimated 45,000,000 additional gallons per year of fresh makeup water would 

still be required even with recycling and treatment.

Response: Because of the requirements for HCl control on existing and new kilns under the 

NESHAP, most kilns will be equipped with wet scrubbers or lime injection for the control of 

HCl. As a result, new kilns subject to the revised NSPS will have their SO2 emissions 

incidentally controlled. None of the cost of the scrubbers will be attributable to the final NSPS 

amendments. Even in the absence of the NESHAP, EPA considers wet scrubbers and lime 

injection to be BDT and justified for the control of SO2 emissions.

Estimates of scrubber costs under the final NESHAP were based on a review of various reported

capital costs, fixed costs and variable costs for limestone, water, power and gypsum (Andover, 

March 10, 2009). Based on comments received on the costing methodology, cost factors were 

revised which resulted in an increase in estimated scrubber costs. In particular, gas flowrates and 

capital cost estimates were found to underestimate costs. As a result, gas flowrates were 

adjusted, along with other factors dependent on gas flow rates, for example water usage, with the 
47

result that estimates of capital costs were substantially increased (Andover, September 25, 2008; 

Andover, March 10, 2009; Andover, February 26, 2010; Andover, May 6, 2010). 

Regarding the commenter’s concern over insufficient water availability for scrubbers, other 

options for reducing SO2 emissions include dry lime injection as well as utilizing fuels and feed 

materials with low sulfur content to the extent practical.

Comment: One commenter (75) states that the energy impacts of wet scrubbing are significant.

In EPA’s scrubber cost analysis, the power requirement for a typical scrubber on a 1,200,000 

tons/year plant is over 1,500 kW, or 10 kWh/ton of clinker. This additional electricity demand 

represents not less than a 20 percent increase over the power required for clinker production in a 

modem cement kiln (around 50 kWh/ton of clinker). Additionally, this will lead to the formation 

of an additional 8,850 tons per year of carbon dioxide.

Response: EPA is aware of the increased energy demand associated with the additional control 

that will be installed as well as the increase in CO2 emissions that will result from the increase in 

energy demand. These were estimated as part of the analysis of the impacts associated with the 

final rules. 

Comment: One commenter (75) states that the proposed SO2 limit would require wet scrubbing 

at more facilities than the one in five estimated by EPA. A review of the RBLC shows five kilns 

with permitted limits above the proposed NSPS limit, which would require wet scrubbers under 

the proposed rule. EPA also asserts that most new kilns will be located at sites with low sulfur 

content in limestone or at greenfield sites but offers no data to support this claim. In reality, a 

company faces significant hurdles to opening new plants and quarries at greenfield sites. By

overlooking reconstructed or modified kilns at existing sites with higher levels of sulfur, EPA 

will be subjecting a greater number of kilns to wet scrubbing in order to meet the proposed limit 

leading to significantly greater economic, environmental, and energy impacts. 

Commenter 75 states that the value chosen to represent moderate uncontrolled SO2 emissions, 

1.3 lb/ton of clinker, is based on an average of data points collected no more recently than 1996. 

While EPA has not provided back up for these data in the rulemaking docket for this rule, the 

commenter states that it is reasonable to expect that if the average value is 1.3 lb/ton, a number 

of the data points would fall above this value and the proposed limit of 1.33 lb/ton. Although 

EPA has indicated that the facilities with moderate uncontrolled emissions would not need 

controls, it is likely that a number of sources in the “moderate” category would require controls. 

This is reinforced by the RBLC review, which shows a larger than expected number of kilns 

above the proposed limit. EPA indicates that the proposed limit was set to ensure that kilns with 

high uncontrolled SO2 emissions meet the typical standard of BDT. However, the commenter

believes that EPA based the proposed limit on data that are not representative of new, modem 

kilns, and thus the record misstates the costs and impacts of the proposed limit. If EPA intended 

to target only those facilities with high uncontrolled SO2 emissions, and not the facilities with 

moderate emission levels, the commenter suggests that EPA establish the new limit at the upper 

bound of the source group with moderate uncontrolled emissions. An SO2 emission limit of 

approximately 4 lb/ton would still require that facilities with uncontrolled emissions at 13 lb/ton 

install wet scrubbing, while not imposing the economic, environmental, and energy burdens on 

facilities with moderate uncontrolled emissions. The moderate emissions group of plants would
48

have to install dry lime injection. An NSPS limit of 4 lb/ton will allow other new kilns similar to 

those listed in the RBLC to meet the NSPS with dry lime injection, recognizing that those units 

are still likely to go through a BACT or LAER review that could result in a tighter limit on a case 

by case basis.

Response: As discussed in a response to a previous comment, we have estimated that most 

existing and new kilns will install wet scrubbers or dry lime injection systems in order to comply

with the HCl emission limits in the final NESHAP. We have revised our estimates of 

uncontrolled SO2 emissions based on kiln type and location. These impacts are summarized in 

the preamble.

7.3 Economic

Comment: One commenter (64) objects to EPA’s assumption that the proposed amendments to 

the NSPS would have little or no economic impact because of controls that will be required 

anyway under state requirements, including BACT or LAER requirements resulting from NSR. 

Because of the definitions of “modification” and “reconstruction” as applied to NSPS, a cement 

manufacturing facility may be considered “modified” or “reconstructed,” and therefore subject to 

the revised NSPS, even when the activity that constitutes a “modification” or “reconstruction” 

results in little or no increase in actual emissions. Under these circumstances, state regulations 

may not impose any particular control technology requirement (such as BACT), and state 

permitting authorities may not require (and may not even have authority to require) emission 

limitations that would be equivalent to the proposed amended Subpart F limitations. 

Response: As explained in the preamble and in other comment responses, cement kilns may

adopt measures so that their hourly emissions of the NSPS pollutants do not increase, so that 

such kilns are not “modified”. In light of these available measures, EPA is not adopting separate 

NSPS for modified kilns.

Comment: Commenter 64 states that EPA is proposing to establish PM emission limitations that 

are at the margin of the performance of the identified technology at existing best performer 

cement plants which will require new and modified cement plants to install even more efficient 

control technology than that in use at plants subject to the current NSPS. EPA should evaluate 

the costs and emission reduction benefits of those proposed PM emission limitations, rather than 

just incorrectly assuming the costs away.

Response: As noted in other responses, EPA does not believe there are any costs under the 

NSPS for meeting the PM standard, since new kilns will be required to meet the same standard 

under the NESHAP. Modified kilns are subject to the PM limits under the NESHAP. We have 

estimated that few kilns will install additional controls just for PM but are likely to reduce their 

PM emissions as a result of other controls necessary under the NESHAP.

Comment: Commenter 64 states that there are numerous specific costs that EPA has ignored or 

assumed away and that could constitute a significant additional cost burden. For example, EPA 

has not given adequate consideration to disposal costs for the scrubber sludge, scrubber 

wastewater (blowdown), and additional cement kiln dust that would be produced as a result of 

the proposed NSPS. EPA has not paid sufficient consideration to ammonia costs, either, which 
49

have risen dramatically in the past year and can be expected to continue to rise. The commenter 

attached details on these additional cost considerations which EPA must take into account.

Response: See impacts section of preamble of final rule.

7.4 Multipollutant

Comment: Several commenter (59, 60, 63) state that the full-scale SCR installations on cement 

kilns in Europe and the experience with SCR worldwide on coal-fired power plants, incinerators, 

and other facilities have demonstrated the ability of SCR to greatly reduce NOx emissions and to

simultaneously reduce emissions of other pollutants, including many highly toxic ones. In 

addition to NOx reduction capabilities, there are a number of emission reduction co-benefits 

associated with the installation of SCR, including:

(1) Destruction of the other pollutants, e.g., ozone inducing VOCs;

(2) Reduction of air toxics such as dioxin and furan and benzene;

(3) Facilitating the removal of mercury (Hg) by catalytic oxidation; and

(4) Minimization of formation of fine PM by NOx and ammonia control.

Response: EPA is aware of and agrees with the commenters that there are Multipollutant 

benefits associated with the use of SCR in addition to the control of NOx. But as explained in 

previous responses, at this time EPA does not consider SCR to be adequately demonstrated for 

US portland cement kilns.
50

8 Miscellaneous

8.1 Proposed Rule

Comment: One commenter (56) states that the NSPS is not fair to cement plant employees and 

will negatively affect pay raises.

Response: As part of our analysis of economic impacts, we are aware that certain marginal 

cement plants may choose to shut down some kilns rather than spend the money to upgrade 

them. 

Comment: One commenter (66) states that the NSPS is well reasoned. The technology proposed 

(SO2 for scrubbers, fabric filters with membrane filters for PM, and SNCR for NOx) are proven 

and available. The option for CEM for PM makes sense. Changing the standards to per ton of 

clinker also makes sense, so companies that are inefficient in their material use are not rewarded.

Response: EPA acknowledges the comment.

Comment: One commenter (67) states that in §60.62(d) and §63.1356 {NESHAP Subpart LLL -

Portland Cement Manufacturing}: The proposed language states that if a pollutant is subject to 

emission limits or requirements that the most stringent requirement in Title 40 must be complied 

with, and the source is exempt from the less stringent requirement in Title 40. This requirement

appears to be aim at an overlap of requirements between NSPS Subpart F and NESHAP Subpart 

LLL. The PM and opacity requirements in NESHAP Subpart LLL (for existing units only) are 

identical to the PM and opacity requirements for units currently subject to NSPS Subpart F. The 

commenter understands the intent to ensure adequate environmental protection while not 

overlooking inconsistencies between rules; however, if there are requirements which are 

different between the rules, then the rules should specifically identify which requirement should 

be used. By identifying the rule which supersedes the other, EPA provides clarity and 

consistency to state/local agencies and the regulated industry.

Response: Indicating that the most stringent provision must be complied with is the most 

efficient and direct way to address this issue.

Comment: One commenter (67) states that in §60.63(b)(2)(ii), (n), (n)(1), and (n)(5) {ESP 

monitoring}, the proposed language references "paragraph (o)". There is no paragraph (o) in this 

section of the subpart. The references should be changed from "(o)" to "(n)." In §60.63(c), the 

language should change from "modified on or before June 16, 2008" to "modified after August 

17, 1971, but on or before June 16, 2008." It could be interpreted as requirements for units that 

commence construction or were reconstructed or modified prior to August 17, 1971. This 

language change would be consistent with the language proposed in other requirements in this 

subpart.

Response: The provisions regarding ESP monitoring no longer apply.

Comment: One commenter (70) states that the vacated Clean Air Mercury Rule (CAMR) has 

had a significant impact on our ability to reduce mercury emissions expeditiously and we now 
51

must wait on a maximum achievable control technology (MACT) standard for existing coal fired 

utility boilers. Commenter 70 urges EPA to address mercury emissions from cement kilns now 

by adopting a sufficiently restrictive MACT standard for these units as part of its pending 

portland cement reconsideration.

Response: EPA is promulgating amendments to its NESHAP for portland cement manufacturing 

facilities that will greatly reduce mercury emissions.

Comment: One commenter (70) states that many areas in the United States are struggling to 

comply with the National Ambient Air Quality Standards for ozone and fine particulate matter 

(PM2.5). All proposals for NSPS should be reflective of what appropriate controls can be 

implemented to minimize these pollutants or their precursors. 

Response: The final amendments to the NSPS and NESHAP will reduce PM2.5 emissions 

although the extent of the reduction is not known.

Comment: One commenter (81) states that it seems that the draft language of the proposed

standards for new kilns and clinker coolers under §60.62 (a) (2) and (b) (2) may not be clear with 

respect to indicating the that the opacity standard would not be applicable for new kilns and 

clinker coolers constructed, reconstructed, or modified after the date of publication of the 

proposed rule in the Federal Register. Commenter 81 reads these sections, as proposed, as 

continuing to require the opacity standards except for kilns or clinker coolers constructed, 

reconstructed or modified after August 17, 1971, but on or before the date of publication of the 

proposed rule in the Federal Register that use a bag leak detection system, ESP predictive model, 

or a PM continuous emission monitoring system.

Response: EPA is requiring the use of PM CEMS on all kilns and clinker coolers and is omitting 

the opacity requirements for these sources.

8.2 Technical Support Document

Comment: One commenter (60) further examined the “Technical Support Document for 

Portland Cement New Source Performance Standards Review” prepared by EPA and posted in 

the Cement NSPS docket as Document No. EPA–HQ–OAR–2007–0877-0049. Commenter 60 is 

interested in this document because much of the information contained therein was derived from 

Department responses to EPA and contractor inquiries. The commenter recommended additional 

caveats and amendments, including more recent stack test results and continuous emissions 

monitoring system (CEMS) data and European experience with SCRs, will further support 

EPA’s proposed NOx limit.

Response: All documentation that was used in the development of the final regulations will be 

posted in the rulemaking dockets for the NSPS and the NESHAP. However, they may not all be 

contained within a single technical support document.