Page 1 of 10 March 25, 2010

Ms. Elineth Torres Environmental Protection Specialist U.S. Environmental Protection Agency OAQPS/SPPD/Program Design Group

109 T.W. Alexander Dr. Durham, NC 27711

RE: PCA Letter Responding to EPA’s E mail of February 23 , 2010 Regar ding ISIS

Model Related Questions on SO 2 Performance

Dear Ms. Torres:

With this letter, the Portland Cement Association (PCA) is responding to several questions you posed regarding SO 2 emission intensities and control equipment performance in your email to me of February 23, 2010. We previously provided responses to the other questions posed in your email; this letter completes our response. We continue to appreciate the opportunity to provide you with information that will improve the accuracy with wh ich EPA’s ISIS model simulates the U.S. cement industry.

Portland cement is the powder which acts as the glue or bonding agent that, when mixed with water, sand, gravel and other materials, forms concrete. Cement is produced from various naturally abundan t raw materials, including limestone, shale, clay, and silica sand. Portland cement is an essential construction material and a basic component of our nation’s infrastructure.

It is utilized in numerous markets , including the construction of highways, stre ets, bridges, airports, mass transit systems, commercial and residential buildings, dams, and water resource systems and facilities. The low cost and universal availability of portland cement ensure that

concrete remains one of the world’s most essential a nd widely used construction materials.

Your email of February 23 was in part to follow up on an EPA/PCA conference call on January 20, 2010. EPA’s notes summarizing this conference call provide the most detailed summary of your questions to which we are responding in this letter. The following is the relevant section

from EPA’s conference call notes.Page 2 of 10 We have the following comments on these topics.

NOx Emission Intensities

We have not reviewed the baseline NOx emi ssion intensity factors (pounds per ton of clinker)

that are included in the ISIS model. Nor have we reviewed the NOx control effectiveness estimates that are included in ISIS for various control measures and process changes (e.g., for

mid

- kiln firing, lo w NOx burners, etc.). NOx emissions have not been at issue with respect to the proposed the Portland Cement NESHAP, and we have not reviewed any elements of the ISIS model that deal with NOx. We cannot now provide any review on NOx issues within the time frame that EPA contemplates for developing revisions to ISIS. Section of EPA minutes from 1/20/10 conference call

- Appendix 11 page 5

- Emission Intensities (ton pollutant/ t on clinker)

o PCA to revise emission int ensities for NOx (by kiln type and perhaps state) and SO2 (by kiln type and state). EPA to provide tables of emission intensities

– input spreadsheet

o Can PCA provide b aseline SO2 emissions

- data derived from PCA's Labor Energy Survey

- Appendix 11 page 7

- SO 2 removal performance

o Is the report that specifies SO2 removal performance from PCA’s consultant available for

EPA review?

**•** Bob? /Dan? / Christa?

– from vendors information

o Can we get real performance (emissions) and control efficie ncy for the 5 kilns with wet

scrubbers?

**•** Years of scrubbers being installed?

- Appendix 12 page 3

o EPA needs background materials that back

- up control performance assumptions used by

PCAPage 3 of 10 SO 2 Emissions Intensities and Baseline

You sent for our review an Excel workbook that includes a new set of SO 2 emission estimates for kilns for 2005 that EPA now proposes to use in ISIS. Th e new estimates were developed by EPA from the 2005 National Emissions Inventory (NEI). The workbook includes 3 tabs or worksheets: Emission Intensities, Units, and Emissions. Notes in the worksheets request PCA comments at various points and also, in Co lumn B of the Emissions worksheet, EPA identifies specific kilns for which the Agency is uncertain about how to interpret the available 2005 NEI

emissions estimates for SO 2 . We have marked in green color in the workbook our responses on all these issues, and have emailed you the revised workbook file titled “ISIS Units and Emission Spreadsheet for PCA Review_Following January 20,2010 Conference Call

– PCA Comments.xls”. In the following paragraphs we summarize our comments on EPA’s workbook

and new SO 2 em ission estimates.

Background on SO2 emissions estimates and PCA’s Labor & Energy survey data for SO 2

In the 2009 NESHAP version of ISIS

- Cement, EPA developed two different sets of SO 2 emission estimates for all cement kilns in the country, derived in dif ferent ways. The first set was derived from 2002 NEI data, and updated to 2005 in some manner. The second set was developed based on applying estimated regional emission intensities (lbs SO 2 emitted per ton of clinker produced

– estimated by EPA’s consul tant Andover Technology Partners) to estimated 2005 clinker production for each kiln.

In commenting on the proposed NESHAP in September, 2009, PCA compared the two sets of

EPA’s SO 2 emission estimates for 2005 in ISIS against data obtained by PCA in PCA’s Labor & Energy (LE) Survey for 2005. The LE data is on a plant (not kiln

- by

- kiln) basis, and it covered 75 cement plants. For the 75 cement plants that provided SO 2 emissions estimates for 2005 via the LE Survey, total estimated emissions were 119,379 t ons, relative to EPA’s ISIS estimates for these 75 plants of 149,533 tons (2002 NEI updated to 2005). PCA commented based on this LE data that EPA in ISIS thus apparently overestimated 2005 baseline SO 2 emissions by about 25%.

PCA believes that the SO 2 e missions estimates from the LE Survey are, in general, more accurate than those developed by EPA via either of the methods used for the 2009 NESHAP

version of ISIS

- Cement. 80% of the cement plants that provided data for the 2005 LE Survey

indicated that t heir estimates of 2005 SO 2 emissions were developed based on CEMs and/or stack tests, while 20% were based on application of AP

- 42 or other emission factors. PCA believes that these detailed information sources are likely more reliable than either of EPA’ s approaches used in ISIS for estimating SO 2 emissions

-- the procedure based on updating 2002 NEI figures or the procedure based on use of average regional emission factors. However, although we believe the LE Survey data to be generally of good quality, the LE Survey data would not represent a 100% satisfactory set of estimates for actual kiln

- by

- kiln SO 2 emissions in

2005 for several reasons.

**•** There are roughly 25 cement plants that did not provide LE Survey responses, and

emissions somehow need to be e stimated for ISIS for these plants also.Page 4 of 10 **•** The LE Survey data is on a plant

- by

- plant basis rather than kiln

- by

- kiln, and ISIS ultimately needs kiln

- by

- kiln estimates. There can be some difficulties in apportioning an emission estimate for an entire plant a mong the plant’s individual kilns.

**•** A small portion of the LE Survey data derives from likely less accurate sources (e.g., application of general emission factors), and for a few plants, it is possible that EPA’s

estimates based on either 2002 NEI or the e stimated regional emission factors may be more accurate than those from the LE Survey.

However, the major issue associated with perhaps using PCA’s LE Survey data for ISIS is that the LE Survey data have been provided by cement companies to PCA on a confi dential basis. The LE Survey data for individual plants cannot be revealed by PCA without violating the confidentiality agreements under which the data was provided to PCA. One of our major objectives in reviewing EPA’s proposed SO2 emission estimates fo r ISIS and suggesting improvements to these estimates is thus to find a way to somehow provide the generally high quality LE Survey data to EPA, but to do so in a manner that respects the confidentiality agreements and avoids providing LE Survey data to EP A at the individual plant level.

PCA review of EPA’s new estimates for ISIS of baseline SO 2 emissions in 2005

We find EPA’s new estimates of kiln SO 2 emissions based on 2005 NEI data to be much more accurate than and preferable to either of EPA’s previou s sets of estimates [ estimates based on 1) updating 2002 NEI estimates ; or 2) applicati on of regional emission factors

. ] We base this conclusion on a comparison of EPA’s new and old estimates against our LE data for the 75 or so cement plants for which al l four sets of emission estimates exist. The four sets of estimates being: 1) Old ISIS based on 2002 NEI updated to 2005; 2) Old ISIS based on regional SO 2 emission factors applied to estimated 2005 clinker production; 3) Potential new ISIS based on

2005 NEI; and 4) PCA LE Survey. Again, we regard the PCA LE Survey data to be the most accurate of the 4 data sets, and we judge the accuracy of the three alternative sets of EPA estimates by how closely each matches against the LE estimates. The following ta ble shows a comparison of the three alternative sets of EPA estimates against the LE estimates for those plants for which all four sets of emissions estimates exist.

Comparison # of Plants with

Emission Estimates Differing by > 500 tpy Total SO 2 Emission s Across All Plants

Old ISIS (NEI 2002) vs. LE Survey 29 + 27% net Old ISIS (Regional emission factors) vs. LE Survey 32 +17% net

Potential new ISIS (NEI 2005) vs. LE Survey 1 4

- 6% net

EPA’s suggested new set of SO 2 emissions estimates based on NEI 20 05 is much closer to the LE Survey data than are the Agency’s previous sets of estimates, both in terms of the numbers of plants for which large differences in estimates exist (>500 tpy SO 2 ) and in terms of the total emissions estimated across all plants. In general, then, we much prefer EPA’s potential new set of estimates to either of the previous sets of estimates considered for ISIS. However, there arePage 5 of 10 still some plants (11) for which the NEI 2005 and the LE Survey emission estimates differ

substantia lly.

We suggest that EPA adopt in ISIS the following approach to estimating baseline (2005) SO 2 emissions from cement kilns:

1. For those particular cement plants for which EPA’s new SO 2 emission estimates (based on 2005 NEI) are reasonably close to PCA LE Survey estimates (i.e., ≤500 tpy difference), EPA should use the Agency’s new 2005 NEI

- based estimates. In the Excel workbook that you sent us for review and that we are returning, we have noted the particular cement plants for which EPA’s new estimates a re close to the PCA LE Survey estimates. We have also provided some notes for many of these plants that respond to instances marked in the “Units” worksheet (column B) where EPA has had some difficulty in interpreting 2005 NEI information with regard to a llocation of total plant emissions among the individual kilns at the plant.

2. For those particular cement plants for which EPA’s new SO 2 emission estimates (based on 2005 NEI) are not close to PCA LE Survey estimates (i.e., >500 tpy difference), we

suggest that EPA should not use the Agency’s new estimates. In these instances where 2005 NEI and PCA LE Survey estimates disagree substantially, we expect that the LE estimates are likely more accurate than the 2005 NEI data, but we cannot provide EPA

with the L E Survey estimates for these individual plants. Instead, we have developed a set of national emission intensity factors (pounds of SO2 emitted per short ton of clinker produced, by type of kiln) that we suggest EPA use in estimating SO 2 emissions for this set of plants, instead of the 2005 NEI data for these plants and instead of EPA’s previous regional emission intensity factors. We have developed this set of national emission intensity factors by analyzing the particular set of 64 cement plants for whic h the PCA LE Survey data are close to (i.e., within 500 tpy of) EPA’s 2005 NEI estimates. We will say more below about this new set of national emission intensity factors that we have developed.

3. For nearly all the remaining cement plants for which EPA ha s developed 2005 NEI

based emissions estimates and for which no PCA LE Survey data has been collected, we suggest that EPA use the 2005 NEI

- based emissions estimates. For these particular plants, PCA has no basis (absent substantial additional data gather ing) to believe that the 2005 NEI estimates are inaccurate or to improve them, and we further believe that the plant

- specific nature of the 2005 NEI estimates makes them likely more accurate for individual plants than either our new national emission inten sity estimates or EPA’s previous regional emission intensity estimates.

4. For any new cement plants simulated in ISIS or for any other plants for which 2005 NEI emission estimates do not exist, we suggest that EPA estimate baseline SO 2 emissions by using th e national emission intensity estimates we have developed.

5. For a handful of cement plants, EPA posed questions in the Excel workbook we were asked to review about how to interpret available emissions estimates from the 2005 NEI. Most of these questions i nvolved difficulties in determining whether an NEI data entryPage 6 of 10 represents emissions from a single kiln or from multiple kilns at a plant venting to a single stack. For these plants, we have provided in the workbook some information that

will assist EPA in interpreting the data available through NEI.

We have edited the workbook to indicate for each cement plant and kiln which of these f ive approaches we suggest that EPA use in estimating baseline SO 2 emissions.

Here is further detail on the new national em ission intensity estimates that we have developed and that we suggest EPA use for some plants.

We believe that the LE Survey provides the most accurate source of estimates of baseline SO 2 emissions for individual cement plants. However, we recognize that some of the LE Survey estimates, for some plants, are based on less accurate data sources (e.g., AP

- 42 emission factors, etc.). We believe the most accurate of all the LE Survey estimates are likely to be those for which the LE Survey estimate for 2005 a nd the 2005 NEI estimate developed by EPA correspond closely. There are 58 cement plants for which these two estimates of 2005 SO 2 emissions are within 500 tpy of each other. We have used the LE Survey data for these 58 cement plants to estimate a set of national emission intensity factors in terms of pounds of SO 2 emitted per ton of clinker produced, for wet, long dry, preheater and preheater/ precalciner kilns.

These estimated emission factors are as follows:

Type of Kiln SO 2 Emission Factor (lbs SO 2 / t on clinker)

Wet 4.89 Long dry 4.78

Preheater 1. 1 8

Precalciner 1. 12

The estimated emission factors represent the average s (not median s ) across the four subsets of

the 58 cement plants, consistent with how EPA estimated the Agency’s regional emission fa ctors previously proposed as one alternative for ISIS. In this calculation, each plant’s emission factor

is estimated as:

**•** The plant’s 2005 SO 2 emissions reported to PCA in the LE Survey (in short tons)

**•** Divided by the plant’s estimated 2005 clinker produ ction, estimated as follows. (Note that this procedure for estimating a plant or kiln’s clinker production responds to one of EPA’s requests in the Excel workbook that you sent us regarding how to estimate this quantity.) PCA does not collect data on cli nker production by plants or kilns from member companies, but we do collect data on annual clinker capacity. This data is reported publicly in PCA’s biennial Plant Information Summary . We crosswalked plant capacity information from the Plant Information Summary with information generated by USGS on clinker production by district (generally States) for the corresponding year in

the USGS annual Minerals Yearbook, Cement in order to estimate capacity utilization by district. We then applied this estimated d istrict capacity utilization figure to the clinkerPage 7 of 10 capacity figures for all cement plants in the district (from the Plant Information Summary ) in order to estimate clinker production for each cement plant in that district. 1

We then averaged the emission f actors obtained for each plant across all plants of that sort (wet, long dry, etc.) in order to obtain an average national emission factor for plants of each sort. Some plants include kilns of differing sorts (e.g., one plant consisting of several long dr y kilns and one precalciner kiln); in which case we classified the plant in a group according to the kiln type for the largest capacity kiln at the plant.

We have sent to EPA an edited version of the Excel workbook on SO 2 emissions that you originally sen t to us for comment. The comments in the workbook should be self explanatory, but we will be pleased to explain them further if you wi sh . In sum mary , the comments include:

**•** In response to your request (“Emission Intensities” worksheet) for review of EPA’ s previous regionally based emission intensity factors, we have provided instead a set of nationally

- based emission factors developed from analysis of emissions data from those

58 plants for which LE Survey emission estimates and NEI 2005 estimates do not differ by more than 500 tpy.

**•** In response to your request (“Units” worksheet) for a procedure for estimating 2005 clinker production on a plant or kiln basis, we have provided the suggested methodology combining information from PCA’s Plant Information Summ ary and the USGS Minerals
Yearbook, Cement

.

**•** In response to your indication of some plants/kilns where there are difficulties in interpreting the 2005 NEI information in terms of which kilns at a plant are included in the estimates, we have provided a serie s of clarifying comments in a text column toward the right edge of the “Emissions” worksheet.

**•** In response to your request for review of the current EPA SO 2 emissions estimates for individual kilns (based on 2005 NEI), we have provided in the rightmost colu mn of the

“Emissions” worksheet an indication of which of 5 methods of estimating emissions we recommend for each particular plant/kiln. The five methods, as we discussed earlier in this paper are:

1. Based on a close match between the 2005 NEI estimate fo r this plant/kiln and the LE Survey estimate, we recommend using the 2005 NEI estimate for this plant/kiln.

2. Based on a significant disparity between the 2005 NEI estimate for this plant/kiln and the LE Survey estimate, we recommend developing an emissions estimate based on application of our national emission intensity factors.

3. Based on the absence of a LE Survey estimate for this kiln but the existence of a 2005 NEI estimate, we recommend using the 2005 NEI estimate.

1 Here’s an example of this calculation. In the “Maryland” district, as USGS defines districts, the Plant Information Summary for 2004 (used to represent 2005 conditions, since no report was published for 2005) reports 3 plants with a total of 4 kilns and total annual clinker capacity of 2,538,000 metric tons per year. The USGS Minerals Yearbook, Cement for 2005 reported total clinker production from plants in the Maryland district as 2,458,000 metric tons. These figures imply capacity utilization of 96.8% on average in 2005 for cement plants in the Maryland district. We applied this district

- wide average to the reported capacity of each plant in the Maryland district in order to estimate clinker pro duction in 2005 for each of these plants.Page 8 of 10 4. For the remaining kilns for which there exist neither an LE Survey estimate nor a 2005 NEI estimate (e.g, new kilns since 2005), we recommend developing an estimate based on application of our national emission intensity factors.

5. For approximately ten plants for which EPA noted in the worksheet that the Agency has difficulty interpreting 2005 NEI data, we have provided information that should clarify the meaning of the NEI data. For these plants, we recommend that the Agency use the additional information that we provide in the worksheet in ord er to develop an

estimate of baseline SO 2 emissions.

PCA Control Efficiency Assumptions

SO 2

On behalf of the PCA, representatives of Schreiber, Yonley & Associates (SYA) met with representatives of MECS USA, the supplier of DynaWave Scrubber systems, on January 28, 2010, to discuss the control efficiencies for their scrubber systems. During this meeting, DynaWave representatives confirmed that the lower limit for their initial performance guarantees

for SO 2 scrubbers for the cement industry is 10 to 12 p pm SO 2 for a scrubber using limestone or CKD as the scrubber reagent. The initial performance guarantee is considered representative of the long

- term performance, or performance over the useful life, of the LWS systems. Therefore,

for a scrubber inlet co ncentration of 100 ppm SO 2 and an outlet of 10 to 12 ppm SO 2 , the control efficiency will be 88 to 90%, not 95%. In addition, they also confirmed that facilities with significant HCl concentrations will have to treat and dispose of liquid effluent in orde r to remove
the CaCl 2 from the scrubber system. This treatment and disposal aspect was not included in prior assessments by EPA and would represent a significant cost burden to part of the industry.

Additional comments from PCA related to various cost as pects of EPA’s economic benefit analysis and technology effectiveness analysis were included in Appendix 11 and 12, respectively, of the September 4, 2009 submittal. Previous PCA comments and calculations were based on a range of 10 to 15 ppm and used the 15 ppm for calculations. The following table presents a revised example of the expected performance based on the vendor guarantee of 12 ppm.

Uncontrolled

SO2 Concentration ( ppm ) Cumulative Percentage of

Kiln Population

Less Than

Stated

Uncontrolled

Conc entration SO 2 Control

Level if

90%

Reduction

is Obtained ( % ) Controlled SO 2 Concentration

if 90%

Reduction is

Obtained

( ppm ) SO 2 Control

Level if

95%

Reduction

is Obtained ( % ) Controlled SO 2 Concentration

if 95%

Reduction is

Obtained

( ppm )

12 24 0

- 0

- 25 29 52 12 52 12

50 39 76 12 76 12

100 56 88 12 88 12

120 59 90 12 90 12

240 67 90 24 95 12

500 84 90 25 95 25

1000 94 90 100 95 50Page 9 of 10 The wet scrubbers currently utilized for SO 2 control at U.S. cement plants are not typically equipped with continuo us SO 2 monitors at the scrubber inlet. Therefore, there is no continuous measurement of the scrubber efficiencies. Of the 5 existing wet scrubbers, one began operation in 2001, two in 2002 and two in 2004. The design control efficiencies for these scrub bers varied depending upon the limits of the individual permits. Therefore, one of them was designed for and achieves a control efficiency of 95% while others were designed for control efficiencies of

less than 90%.

PCA previously provided comments that the ISIS model used incorrect gas flows for costing wet scrubbers. The equipment sizing criteria for add

- on or tailpipe control technologies is normally based upon the actual flow of the exhaust gas to be treated as the equipment has to be capable of

hand ling the actual volume of gases being exhausted. The following source information is provided to give an example of the magnitude of error than is introduced by specifying the size of the control equipment with the flow in DSCFM versus ACFM.

Parameter Units Operating Condition

Minimum Average Maximum

Flow Rate acfm 195000 260000 325000
Temperature F 550 575 600

Moisture Content % 27 27 27

Flow Rate dscfm 74394 96796 118140

Error % 38 37 36

Mercury

Wet scrubber The 50% control efficiency was b ased upon the assumption that 50% of the mercury emissions are elemental and will not be controlled by a wet

scrubber.

ACI The 75% control efficiency was based upon testing at Ash Grove, Durkee, Oregon.

ACI

– Wet scrubber The 85% combined control efficie ncy assumes that the ACI controls 75% of the total mercury emissions, and the scrubber would then remove about half of the remaining non

- elemental portion (50% of the remaining 25%).

HCl

Wet Scrubber PCA agrees with EPA’s assumed control efficiency for a wet scrubber with one qualifier. At least one of the operating scrubbers, which are designed and operated for SO 2 control, cannot comply with the proposed HCl limits. Therefore, it is not appropriate to assume that the installation

of a wet scrubber wil l assure compliance with the proposed emission

limits for HCl.Page 10 of 10 THC

ACI The 50% control efficiency was based upon operating experience at one facility.

Wet Scrubber

– ACI PCA’s assumption is consistent with EPA’s assumption, no additional

THC control cred ited for the addition of a wet scrubber.

RTO The 95% control efficiency was based upon discussions with two different vendors, and experience from one facility. Vendor quotes referencing

non

- methane VOC were adjusted to account for methane and ethane,

es pecially where natural gas firing is necessary to maintain RTO temperatures. The standard normally guaranteed by equipment vendors for this type of application (inlet concentrations below 500 ppmv) is an

outlet non

- methane VOC concentration of 10 ppmv.

We appreciate the opportunity to work with EPA in improving ISIS, and look forward to continuing this collaboration. Please call me if you have any questions about the data that we have provided.

Sincerely:

Tyrone Wilson, Ph.D. Director, Regulatory Aff airs, Energy & Environment

cc: Andy O’Hare, PCA