National Emission Standards for Hazardous Air Pollutants from the




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2.3.4 Top 5 versus 12 Percent


Comment: One commenter (2898) disagreed with an alternative reading of the MACT floor requirements that allowed EPA to consider the emissions of the 5 lowest-emitting existing sources instead of the emissions of the lowest-emitting 12 percent of existing sources in setting the standard. The CAA unambiguously states that emission standards established pursuant to the MACT floor mechanism shall not be less stringent than the average limitation of the best performing 12 percent of existing sources, for which the EPA has emissions information, in a category or subcategory with 30 or more sources. Basing the standard on the 5 best performing sources would violate this mandate by letting the standard be less stringent than the emissions performances of the best-performing 12 percent of existing sources and is not allowed by the language of the CAA.

Commenter 2816 stated that EPA should not adopt an alternative interpretation of data required to set an existing floor. The commenter stated that basing the floor on 5 sources rather than the best performing 12 percent is contrary to the language of CAA §112. This interpretation also favors industries whose members, for whatever reason, are unwilling to submit test data, or are unwilling to participate in emission stack tests for the purposes of data collection by EPA. The result is that EPA has limited data to work with and is subsequently criticized for establishing standards based on limited data. It is incumbent upon industry to submit sufficient data so that the range of facility types and emission levels are adequately represented.

Commenter 2824 recommended that the floor limit be the best-performing 12 percent of existing sources with an energy efficiency requirement such as the energy star award.

Response: EPA believes its interpretation to be compelled by the statutory text.

Comment: Several commenters (2845, 2846, 2874, and 2915) stated that EPA is proposing to calculate MACT floors by averaging the top 12 percent of sources for which CEMS data are available (even if that amounts to less than 30 sources), rather than by considering the top 12 percent of sources for which EPA has emissions information. As a result, EPA is proposing to establish the MACT floor based on data from only 2 sources. The commenters stated that CAA §112(d) obligates EPA to set the MACT floor looking at no fewer than 5 sources, recognizing the value of relying on the maximum amount of data available.

Commenter 2841 stated that the use of a minimum of five facilities should be adopted in the establishment of THC standards as well as the other standards in this proposed regulation. The establishment of requirements based on a small amount of data would run counter to the intent of the CAA in utilizing data that is truly representative of the best-performing facilities throughout an entire industry.

Commenter 2841 stated that in previous MACT rulemakings, EPA used the five best performing facilities if the number of facilities was less than 30. Consistent with these prior rulemakings, the commenter stated that this approach should be used for this proposed Portland Cement NESHAP rule and that EPA needs additional data points in order to appropriately set limits for the industry as a whole.

Response: See response in preamble

Comment: Two commenters (2890 and 2916) stated that EPA must base their emission limits on 12 percent of the total number of sources, and not exclude facilities’ data. The commenters recommended that EPA not make emission estimates for only a small subset of sources to determine the MACT floor. If sufficient information is available for a source, such as its size, control level, and other source-specific parameters, an estimate should be developed, as allowed by the Courts, and the source included in the count of sources for which the Administrator has emissions information. Limiting this estimation to sources at the same site or same company is arbitrary and should not be done. Emission estimates based on the average emission factor for a subcategory should be allowed.

Response: EPA believes its interpretation to be compelled by the text of the statute.

2.3.5 Area Sources in HCL Floor Development

CAA intent


Comment: One commenter (2832) opposed the inclusion of actual and/or synthetic area sources, with or without control devices, for any purpose in this major source NESHAP standard. The commenter stated that there is nothing in §112 that allows EPA to deem an area source as a best performing source for major sources and nothing that allows EPA to include area sources as part of a MACT pool.

Commenter 2916 stated that it is unlawful for EPA to group major and area sources for purposes of setting MACT. By blending area and major sources together for standard setting purposes, EPA has created a hybrid major/area source category that is not authorized under §112.

Response: In the final rule, no data from natural or synthetic minor area sources are being used to establish the standard for HCl.

Establish GACT standards


Comment: One commenter (2887) stated that EPA should develop generally available control technology (GACT) standards (or management practices) for area sources under §112(d)(5) for the pollutants listed in §112(c)(6). EPA could minimize the economic impact on all area sources by subjecting them to GACT for the §112(c)(6) pollutants. Alternatively, the EPA could create a subcategory for area sources that are small entities and subject this smaller number of sources to GACT (or management practices). This would satisfy the policy behind Small Business Regulatory Enforcement Fairness Act (SBREFA) as implemented by EPA policy (to minimize the economic impact on small entities while still meeting the mandates of the CAA).

Response: EPA explains in the preamble to the final rule its various dispositions for applying standards to area cement kiln sources.

Comment: One commenter (2887) stated that for HAPs that are not listed under §112(c)(6), EPA should establish GACT (or management practices) for area sources under §112(d)(5), and not regulate area sources under MACT for non-section 112(c)(6) pollutants. The commenter stated that, specifically, EPA proposed limits for PM emissions as a surrogate for non-volatile metal HAPs (arsenic, cadmium, beryllium and lead) on cement manufacturing facilities that are area sources. Alternatively, the EPA could choose to not regulate area sources or a subcategory of area sources that are small entities for these pollutants. Emissions from area sources, and even more so from the subcategory of area sources that are small entities, are very small.

Response: EPA explains in the preamble to the final rule its various dispositions for applying standards to area cement kiln sources.

2.3.6 Legal

Removal efficiency standards vs emission limits


Comment: One commenter (2898) supported EPA’s decision to not rank best performers based on their relative mercury removal efficiency. Relying on mercury removal efficiency in setting the MACT floor for the portland cement manufacturing industry would downplay the role of HAP inputs on emissions. EPA characterizes Brick MACT’s statement that best performers are those emitting the least HAP as appearing arguably in dicta. However, the Brick MACT Court itself characterizes the statement as the holding of the Cement Kiln case. Brick MACT, 479 F.3d at 880 (relying on Cement Kiln’s holding that §7412(d)(3) requires floors based on the emission level actually achieved by the best performers or those with the lowest emission levels). The proposed alternative of setting the MACT floor on the basis of percentage of emission reduction achieved by sources would minimize, if not eliminate, the consideration of cleaner inputs in setting MACT floors, as EPA acknowledges, and is therefore contrary to statutory dictates and case law.

Response: See response in preamble to final rule.

Comment: Several commenters (2831 and 2901) stated that EPA retains considerable discretion on how to set MACT floors. The commenters supported the Agency’s authority to set floor standards based on control efficiency, or any method as long as their method reasonably estimates the performance of the relevant best performing plants. There is nothing in the court’s decisions that requires EPA to use the straight-emissions approach favored in this rule. The commenter stated that the court has expressly decided that a straight-emissions or arithmetical methodology is not required, and EPA’s technology based approach that estimated performance rather than deriving the standards through an arithmetic straight emissions approach, as long as they result in a reasonable estimate of the performance of the best controlled units, is supported by the courts. According to the commenter (2901), Brick MACT does not endorse a straight emissions approach; nor could it. To do so would mean that the Brick MACT court was overturning the Chevron step one holding in Sierra Club and National Lime II, something that it cannot do.

Response: See response in preamble to final rule.

Comment: One commenter (2832) stated that EPA has incorrectly focused on the term emission limitation in proposing a numeric allowable HAP emissions MACT floor. In fact, EPA is required to set emission standards, not necessarily numeric emissions limitations in creating a MACT floor. The Court in the Brick decision did not require otherwise. In fact, the wording of §112, a reduction in emissions that is achieved in practice by the best controlled similar source contemplates air emissions control equipment whose manufacturer’s specified HAP emissions removal efficiency for all HAPs is the highest percentage achieved in practice in the industry in question. Inlet and outlet stack testing that confirms the efficacy of air emissions control equipment is the legal requirement of the §112(d)(3). The law does not state that EPA is required to set numeric HAP emissions limits. In identifying the best performing sources, the Administrator is directed by §l12(d)(3) to review emissions information, not numeric emissions data or emissions stack test reports. Sections 112(j)(5) and 1l2(i)(5) also support this reading of §112(d)(3). Each refers to demonstrations of emissions reductions of a stated numeric percentage as a means of meeting MACT requirements. EPA’s discussion of the beyond-the-floor evaluation confirms this approach as well.

Response: The commenter does not address the issue of how non-numeric percent reduction standards address the issue of raw material and fuel HAP levels and their contribution to emissions. EPA cannot ignore such contributions in determining which sources are best performing, and their level of performance. At the least, EPA is adopting a reasonable approach of establishing numerical standards, and using a ranking methodology based on which sources emit the least of the HAP in question, on a normalized basis (for Hg and PM) and considering their performance over time (variability).

Standards must be achievable


Comment: One commenter (2844) stated that the CAA requires that lawfully promulgated NESHAP standards must be achievable. Section 112(d)(2) of the Act, 42 U.S.C. §7412(d)(2), required EPA to establish emission standards for HAPs that require the maximum degree of reduction in emissions taking into consideration the cost of the emission reduction and non-air quality health and environmental impacts and energy requirements, that the EPA Administrator determines is achievable for new or existing sources. Further, House Rep. 101-490, Part 1 (328) stated that The Committee expects MACT to be meaningful, so that MACT will require substantial reductions in emissions from uncontrolled levels. However, MACT is not intended to require unsafe control measures, or to drive sources to the brink of shutdown. The commenter noted that the proposed portland cement proposed NESHAP standards do not comply with §112’s achievability requirements.

Response: See preamble to final rule for response.

Comment: Commenter 2844 stated that EPA’s conclusion that §112(d)(3) and/or Brick MACT requires or even permits the Agency to ignore the achievability requirements of §112(d)(2) is an unreasonable reading of the statute and of Brick MACT. The Agency retains more than sufficient discretion to devise NESHAP standards that successfully bridge the tension between achieved and achievable in §112’s standard-setting provisions by appropriately using both subcategorization and variability methodologies.

Response: See response in preamble.

Comment: One commenter (2844) stated that EPA’s floor setting methodology does not comply with three of Brick MACT’s requirements:

  • Floors must be based on emissions achieved in practice by best-performing sources;

  • EPA’s use of variability factors and methodologies to adjust reported emissions data must be based on demonstrated relationships, so that the floor setting methodology serves to reasonably estimate or predict the performance of the best performing sources; and

  • EPA must consider the impact of nontechnology factors, such as raw material and fuel inputs, on a source’s emission control levels.

Commenter 2844 stated that in the portland cement proposal, EPA set MACT floor levels that reflect the specific conditions at the time the data were generated and do not include any of the operational variability. The commenter suggests that EPA must look beyond its snap shots of performance to make a reasoned evaluation and estimation of all operating conditions and factors that might impact the level of actual emissions from those kilns in practice, and adjust their reported short term test data appropriately. EPA can and should adjust raw emissions results to estimate sources’ achieved emissions levels when setting MACT floors and standards. Since Brick MACT, EPA’s methodology now must be able to reasonably estimate the impacts of variability associated with both technological and nontechnological factors over the full range of circumstances.

Response: See response in preamble to final rule.

Comment: One commenter (2844) also stated that EPA adopted a floor setting methodology that is based on using lowest reported emission results with minimal variability adjustments to estimate emission control achieved in practice by best performing sources. EPA considered test-to-test variability, but did not consider the inherent variability due to raw materials, product mix, fuels, operating conditions and plant types. The commenter stated that EPA has not evaluated or validated whether its methodology accurately estimates emissions control achieved in real world circumstances at sources.

Response: See response in preamble.

Comment: One commenter (2844) stated that EPA cannot evaluate floors using methodologies that focus exclusively on technology if the resulting standards do not reflect actual average limitation[s] achieved (Brick MACT, 479 F.3d at 882). The commenter concludes that Brick MACT requires EPA to address the role of nontechnological factors that impact emissions in setting floors and EPA must develop a methodology that accurately estimates the actual emissions achieved in practice by the best performing sources under a variety of operating conditions, taking into consideration testing and technological and nontechnological variability. As proof that EPA failed to properly account for sources’ variability in setting the standards, the commenter (and commenter 2845) included a chart purporting to demonstrate that the kilns comprising the pool of best performers for each HAP could not themselves meet the proposed standard.

Response: See response in preamble.

Comment: One commenter (2844) stated that the proposed standards cannot be viewed as assessing the emissions control achieved by best performing sources, given that there is no single existing source that meets the standards simultaneously and for two of the pollutants, no existing units meet the standards without operational changes. The EPA has an obligation to devise appropriate variability methodologies and to collect the information necessary to do so.

Response: EPA has responded above and rejected the argument that the statute unambiguously compels that floors be established on a complete facility basis.

Worst Reasonably Forseeable Circumstances


Comment: Several commenters (2844, 2846, and 2915) stated that EPA’s floor methodology does not estimate emission control achieved under the worst reasonably foreseeable circumstances. EPA must estimate emission levels achieved under the worst foreseeable circumstances in order to reasonably estimate achieved in practice control levels. The proposed portland cement rule proposes that sources must achieve compliance with the proposed floor standards at all times, including periods of startup, shutdown and malfunction (SSM) events. Because the data to estimate the appropriate variability factor for SSM events do not exist and are technologically impracticable to develop, EPA cannot reasonably set a floor based on compliance during SSM events.

Commenter 2845 stated that the policy and common sense approach is recognized and required by the D.C. Circuit. Once the similar sources category is established, the EPA must identify the lowest emission limitation that has been achieved in practice by these sources. In another MACT case, the D.C. Circuit has held that the phrase achieved in practice refers to the performance of the source under the worst foreseeable circumstances (Sierra Club v. EPA, 167 F.3d 658, 664, D.C. Cir. 1999).

Commenter 2845 stated that EPA should follow its own common sense approach and the directive of the D.C. Circuit and develop MACT standards that consider the long term emission variations in portland cement facilities.

Response: First, EPA has established separate standards for startup and shutdown, so these operating conditions are not part of the performance EPA is evaluating in developing the main MACT floors. EPA also explains in the preamble to the final rule why it reasonably did not consider malfunction events in developing those floors, which reasons include that EPA is therefore adding to the final rule an affirmative defense to civil penalties for exceedances of emission limits that are caused by malfunctions. Since malfunctions, if properly demonstrated, would not be considered to contribute to an exceedance of the standard (for purposes of civil penalties), EPA surely need not consider malfunctions in assessing best performing sources’ performance and establishing MACT floors.

Second, EPA agrees that long term performance of sources – their variability – is to be considered both in determining which sources are best performing and what their level of performance is. EPA has reasonably done so in establishing this NESHAP.

CAA requires emission reductions by 94 percent of sources


Comment: One commenter (2890) stated that the setting of a MACT floor requires 94 percent of any population of sources, including those that had never engaged in any emission reduction techniques, to either add air pollution control devices or shut down processes, without the consideration of costs. The floor should identify what the best actual sources in the category are doing; presuming that if the average of the top 12 percent was achieving this level of control in the absence of a rule, achieving that level of control must have been at a reasonable cost.

Response: The commenter is correct that costs cannot be considered in establishing MACT floors and that by virtue of the floor process the statute implicitly assumes that the great majority of plants will have to upgrade their performance to meet promulgated standards of at least the designated minimum stringency.

Exclusion of sources engaged in mining


Comment: Several commenters (2890 and 2916) stated that Congressional intent in the establishment of MACT shows a clear intention to exclude mined minerals: For categories and subcategories of sources of hazardous air pollutants engaged in mining, extraction, beneficiation, and processing of nonferrous ores, concentrates, minerals, metals, and related in-process materials, the Administrator shall not consider the substitution of, or other changes in, metal- or mineral-bearing raw materials that are used as feedstocks or materials inputs, or metal- or mineral-bearing materials processed or derived from such feedstocks or materials in setting emission standards, work practice standards, operating standards or other prohibitions or requirements or limitations under this section for such categories and subcategories. The prohibition of the preceding sentence shall not apply to the substitution, modification, or changes of chemicals (not including metal- or mineral-bearing materials) used in mining, extraction, beneficiation, or processing of nonferrous ores, concentrates, minerals, metals and related in-process materials which is necessary to reduce air emissions of such chemicals and for which substitutes that are safe and effective in performing the intended function of the chemical to be substituted are reasonably available [From Joint Explanatory Statement of the Committee of Conference, H.R. Rep No. 101-952, at 339 (1990)]. EPA used this same quote in a previous court case involving the secondary copper MACT [Sierra Club v. EPA (No. 02 -1253)].

Commenter 2890 suggested that after mined minerals are eliminated from consideration for MACT, several options for establishing the best controlled sources are:

  • Control of the mercury and other pollutants that are not in materials other than the limestone typically mined onsite.

  • Any emission control equipment or other practice that reduces the amount of emissions that are ultimately emitted from the processing of the mined material.

Response: See preamble to final rule for response.

Consideration of variability


Comment: One commenter (2845) stated that case law and policy dictate that the EPA must consider variability in establishing MACT standards, and the approach used by EPA in Prevention of Significant Deterioration (PSD) permitting should also apply in establishing MACT standards. To evaluate the emission limits achieved by existing sources, EPA is required to develop methodologies for estimating the variability associated with all factors that impact a source’s emissions, including process, operational and non-technological variables (see Nat’l Lime Ass’n v. EPA, 627 F.2d 416, 443, D.C. Cir. 1980). While courts have affirmed EPA’s authority to choose a methodology designed to estimate emissions in setting the MACT floor, the courts have also made clear that EPA’s method must allow a reasonable inference as to the performance of the top 12 percent of units (Cement Kiln Recycling Coalition v. EPA, 255 F.3d 855, 862 (D.C. Cir. 2001) (citing Sierra Club v. EPA, 167 F.3d 658, 663, D.C. Cir. 1999). Accordingly, the Court of Appeals for the D.C. Circuit has stated that EPA must show not only that it believes its methodology provides an accurate picture of the relevant sources' actual performance, but also why its methodology yields the required estimate (Cement Kiln Recycling Coalition, 255 F.3d at 862).

Response: See response in preamble.

Comment: One commenter (2845) further stated that EPA has a clear policy of considering long-term variability when establishing enforceable emission rates. In considering appropriate enforceable emissions rates in PSD permits under the CAA, the Environmental Appeals Board has held that a permitting authority is not required to set the Best Available Control Technology (BACT) emissions limit at the most stringent emissions rate that has been demonstrated in practice by a facility using similar emission controls (In re Newmont Nevada Energy Investment, 12 E.A.D. 429, 441-42, EAB 2005 (citing Kendall New Century Dev., 11 E.A.D. 40, 53, EAB 2003). The Board has recognized the use of safety factor[s] in the calculation of permit limits to take into account both the variability and fluctuation in the expected performance of pollution controls and the fact that setting emissions limitations for one facility at the highest control efficiency demonstrated at another facility would make violations of the permit unavoidable (Id. at 442, citing In re Masonite Corp., 5 E.A.D. 551, 560, EAB 1994).

Response: Although BACT determinations under PSD are by no means analogous to determining MACT floors (cost is considered in determining BACT, for example), EPA agrees that consideration only of single data points may not adequately represent sources’ performance over time, and EPA consequently is not utilizing that methodology in this rule. EPA also has taken variability into account during the process of establishing the emission limits for this rule.

Comment: Commenters 2844, 2845, and 2916 objected to EPA’s interpretation of CAA Sections 112(d)(2) and 112(d)(3) and the Brick MACT (Commenter 2845 provided a white paper as an appendix to their comments for the HWIMI MACT proposal, dated December 01, 2008.). The paper, entitled Implications of the Brick MACT Decision on EPA’s Discretion in Setting MACT Floors, discusses variability at some length. The paper’s main points were:

  • The Agency has chosen to focus on setting MACT floors based on lowest emitting sources derived from limited test results that are not appropriately adjusted to account for stack test variability.

  • The Brick MACT decision holds that EPA must base MACT floors on achieved emissions control rather than control technology, but it does not require EPA to ignore operational variability in determining those floors.

  • Variability methodologies must reasonably estimate or predict emissions or variability through a demonstrated relationship between the data used and the performance intended to be estimated.

  • Non-technological factors (i.e. raw materials and fuel) must be considered in determining emission control achieved by best performers.

  • It is within the EPA’s discretion to define the best performing sources.

  • EPA should estimate variability in determining achieved emissions.

  • The Agency can and must seek appropriate data from regulated entities and other stakeholders, and to develop appropriate fact-based estimating methodologies on the data available.

Response: See response in preamble.

Brick MACT


Comment: Several commenters (2834, 2844, 2845, and 2859) stated that the Brick MACT decision makes the expectations of what is expected by EPA in regards to setting the floor very clear:

  • Floors must be based on emission control achieved in practice by the best performers

  • Variability methodologies must reasonably be calculated to estimate such actual performance levels

  • Nontechnological factors that impact emissions must be considered in determining the achieved emissions levels

  • In devising new methodologies to set lawful floors, EPA must ensure that compliance with §112(d)(2) general standard setting criteria is also met.

  • EPA can use discretion to define the factors necessary to establish a floor under §112(d)(3) that meet the CAA’s statutory intention to be technology-forcing and require compliance with the best that has been demonstrated to be achieved in practice while considering costs, other non-air health and environmental impacts, and energy impacts when defining achievable MACT standards.

Based on these points, the Brick MACT decision requires that EPA’s floor analyses include a review of the best performers and consideration of variable factors that can affect emissions achieved in practice by the pest performance sources. EPA’s analyses and methodological choices must be based on facts and records that support its final determination. It is appropriate that a full review of the existing records and the development of new data be considered in making a final decision.

Response: The case law makes overwhelmingly clear that the requirement in section 112 (d)(2) that MACT standards be achievable after considering various factors does not supersede the requirement of section 112 (d)(3) that they be of minimal stringency as determined by the criteria for establishing MACT floors. See, e.g. Cement Kiln Recycling Coalition, 255 F. 3d at 861-62. As discussed in the preamble and in other comment responses, EPA has carefully assessed best performers’ short- and long-term variability for each HAP in estimating their performance.

2.3.7 Format of Emission Limits

Use CEMS units as limits


Comment: One commenter (2638) recommends the EPA use plain language and units that can be related to ambient measurements for its emission limits. The units currently proposed require modifying the direct CEMS output with inputs under the control of the plant, which make the results un-interpretable by anyone wanting to make comparisons with ambient measurements or health effects; or the CEMS concentration readings should be required to be posted/reported.

Response: Emission limits are typically normalized to some type of production or raw material input value because this allows comparison (and ultimately the ability to set a single standard) for different sized facilities. As we noted in the NSPS proposal, the current NSPS and limits (and NESHAP limits before today’s amendments) for PM are expressed on a pound of PM per ton (lb/ton) of dry feed input format. See 73 FR at 34075-76. In this final NESHAP (and NSPS) we are adopting a new normalizing parameter of lb/ton of clinker – i.e., normalizing based on kiln output rather than input for both PM and mercury.

We noted at proposal of the NSPS that adopting an output-based standard avoids rewarding a source for becoming less efficient, i.e., requiring more feed to produce a unit of product, therefore promoting the most efficient production processes. 73 FR at 34076.

EPA therefore proposed that all of the NSPS (for PM, NOx, and SO2) be normalized by ton of clinker produced, and later proposed the same parameter for the two standards in the NESHAP which are normalized, mercury and PM. 73 FR at 34076; 74 FR at 21140.

In the final NESHAP (and NSPS) we are therefore adopting a new normalizing parameter of lb/ton of clinker – i.e. normalizing based on kiln output rather than input – for mercury and PM in the NESHAP, and for PM, NOx, and SO2 in the NSPS.

We are currently developing a reporting mechanism for CEMS data. We will consider these comments as we continue that effort. In concept, the CEMS data base would be publically available. However, the reporting frequency has not been developed.

See the preamble discussion under format of the normalized standards in the NESHAP and the NSPS, for more information on EPA’s decision.

Use of kiln feed vs clinker in emission limits


Comment: Commenters (2830, 2844, 2845, 2859, and 2879) stated that they supported emission limitations in pounds of pollutant per ton of kiln feed rather than as pounds per ton of clinker produced. Commenters 2844, 2859, and 2879 noted that clinker conversion factors may vary from plant to plant and may give erroneous results. According to the commenters, clinker weigh systems are not common in the cement industry and will not improve accuracy over a kiln-feed measurement system with an appropriate clinker factor, as is commonly used. On a short-term basis, clinker output from the kiln will fluctuate while the kiln feed rate remains constant. The variable nature of clinker production creates more inaccuracy in short-term (hourly) clinker weigh data than the +/- 5 percent specified by the EPA. If the standards are based on tons of clinker, then the kiln owner should have an option to determine clinker weight from feed that should not require EPA approval of the method and the averaging time and accuracy requirements should reflect what is practical, achievable and useful.

Commenters 2844 and 2845 asked for clarification from EPA on proposed language regarding alternative methods to measuring clinker production and the need to obtain Administrator approval for such methods. The Proposal also stated that the use of a system that directly measures kiln feed rate and uses a conversion factor to determine the clinker production rate is an acceptable method. The commenter states that it is unclear whether EPA believes that Administrator approval is required to utilize such a method when EPA identifies in the regulations that the method is acceptable. In any event, cement plants should be given the option of complying with the regulation by either measuring the clinker production or by measuring kiln feed and developing a clinker factor to calculate clinker production. Almost all cement plants measure kiln feed and develop a clinker factor. Such a method requires periodic adjustments to the clinker factor and justifies a longer time-frame than hourly for determining clinker production.

Response: See the response to the comment above, regarding the format of the standards.

Commenters maintain that the measurement of kiln output is not as exact as the measurement of kiln input, and that many kilns have not installed clinker measuring equipment. These objections do not necessitate normalizing by inputs. Most commenters also stated that kiln feed could be accurately measured and also indicated that most facilities currently derive reasonable feed-to-clinker conversion factors from these measurements. Kilns already calculate clinker production in this way when required to meet emissions limits normalized by clinker production, as many NSR and PSD permits for cement kilns presently do.

Since it appears from comments that the equipment to accurately measure clinker is not typically installed in this industry, we must assume these facilities use a feed-to-clinker conversion factor to calculate clinker production on whatever time basis is necessary (e.g., daily, hourly, etc.). Therefore, we have modified the rule language to more clearly provide the option allowing facilities to measure feed inputs and to use their site specific feed/clinker ratio to calculate clinker production (and that no prior approval from a regulatory authority is necessary to do so). Facilities would be allowed to use a constant feed/clinker ratio in accord with their usual cycles for determining such ratios, typically on a monthly basis when clinker inventories are reconciled.

Commenters were nonetheless concerned that because clinker/feed ratios change somewhat and are only re-determined at the end of a cycle, a slight change in clinker/feed ratio, determined at the end of the cycle, would show lack of compliance without an opportunity to alter operation. To obviate this concern, the rule provides that facilities are not required to retroactively update clinker production estimates after re-computing feed/clinker ratios. We would not expect that the clinker/feed ratio will change significantly from month to month, so we do not see this as creating a situation where facilities will be able to have large amounts of excess emissions but still be considered in compliance (especially since the 30-day standards are all rolling averages).

See the preamble discussion under format of the normalized standards in the NESHAP and the NSPS, for more information on EPA’s decision.

Accuracy of determining kiln input or output


Comment: One commenter (2845) stated that kiln feed accuracy should be established on a longer timeframe than one hour:

  • Daily clinker production typically is estimated by measuring the kiln feed rates and utilizing a clinker factor to convert kiln feed rate (which includes kiln feed and kiln dust returned) to clinker production rate. Several variables in the calculation are measured are not determined more frequently than a weekly basis and can vary on a short term basis. Another variable, dust loss, is estimated, not measured. It cannot be expected to have a clinker factor in the short term with an accuracy of better than +/-10 percent. Tracking these variables on a short term basis is not practical.

  • Plants typically measure clinker inventory daily, and conduct more detailed physical inventories on a monthly and/or quarterly basis.

  • Plants that utilize a single clinker handling system for multiple kiln lines cannot confirm the clinker factor for each individual kiln.

Response: See the response to the comment above, regarding the accuracy of determining kiln input or output, and the latitude for determining site-specific clinker factors. See the preamble discussion under format of the normalized standards in the NESHAP and the NSPS, for more information on EPA’s decision.

Grain loading format


Comment: Commenter 2859 stated that as an alternative to basing the PM standard on pounds per ton dry feed, EPA could use a grain loading standard (i.e., gr/acf).

Response: See the preamble discussion under format of the normalized standards in the NESHAP and the NSPS, for more information on EPA’s decision regarding format of the standard.

2.3.8 Other

Central stack


Comment: Many commenters (2893, 2975, 2990, 2992, 3001, 3003, 3005, 3017, 3022, 3034, 3038, 3045, 3052, 3056, 3059, 3063, 3073, 3074, 3077, 3089, 3098, 3107, 3117, 3124, 3125, 3128, 3130, 3131, 3132, 3160, 3226, and 3227) stated that EPA should require that all cement kilns have one central stack. Without a central stack, the emissions from the kiln cannot be adequately monitored, and the CEM required in the proposed rule would not be viable for monitoring emissions and confirming emissions reductions. In addition, necessary scrubbers and/or other pollution control devices require a central stack for placement.

Response: The majority of cement kilns are equipped with control devices that are equipped with a central stack. However, those kilns using positive pressure fabric filters may be equipped with roof monitors instead of stacks. In the case of PM emissions, such devices can be equipped with a bag leak detection system, which is a viable monitoring alternative to PM CEMS and explicitly allowed in the rule as a monitoring alternative. In other cases, the source may have to retrofit the control device outlet to install one or more stacks. Finally, sources can always request EPA approval under the part 63 General Provisions (§63.7(f)) to use an alternative method to accommodate site-specific conditions. For example, open-path monitoring may be viable in some situations.
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National Emission Standards for Hazardous Air Pollutants from the iconAnsi (American National Standards Institute)

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