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MEMORANDUM

TO: Toni Jones, U.S. Environmental Protection Agency

FROM: Eastern Research Group, Inc.

DATE: January 12, 2011

SUBJECT: CISWI Emission Limit Calculations for Existing and New Sources

BACKGROUND

The U.S. Environmental Protection Agency (EPA), under section 129 of the Clean Air Act

(CAA), is required to regulate emissions of nine pollutants from Commercial and Industrial Solid

Waste Incineration (CISWI) units: hydrogen chloride (HCl), carbon monoxide (CO), lead (Pb),

cadmium (Cd), mercury (Hg), particulate matter (PM), dioxins/furans (PCDD/PCDF), nitrogen

oxides (NOx), and sulfur dioxide (SO2).

On December 1, 2000, EPA adopted new source performance standards (NSPS) and emission

guidelines (EG) for commercial and industrial solid waste incineration units under Sections 111

and 129 of the Clean Air Act. In 2001 EPA granted a petition for reconsideration regarding the

definitions of "commercial and industrial waste" and "commercial and industrial solid waste

incineration unit." In 2001, the United States Court of Appeals for the District of Columbia

Circuit granted EPA’s voluntary remand, without vacatur, of the 2000 rule. In 2005, EPA

proposed and finalized the commercial and industrial solid waste incineration definition rule

which, among other things, revised the definitions of "commercial and industrial waste" and

"commercial and industrial waste incineration unit." In 2007, the United States Court of Appeals

for the District of Columbia Circuit vacated and remanded the 2005 commercial and industrial

solid waste incineration definition rule.

These final standards provide EPA’s response to the voluntary remand that was granted in 2001

and the vacatur and remand of the commercial and industrial solid waste incineration definition

rule in 2007. In addition, the standards re-development includes the 5-year technology review of

the new source performance standards and emission guidelines required under Section 129. The

EPA has developed a series of maximum achievable control technology (MACT) floor emission

limits to support that re-development. The purpose of this memorandum is to present the

methodology and results of the MACT floor determinations and emission limit calculations for

the CISWI source category. This memo is organized as follows:

I. Regulatory Options and Subcategories

II. Existing Sources

A. MACT Floors

B. Data Variability Analysis

C. Determining Emission Limits

III. New Sources

A. MACT Floors

B. Data Variability Analysis

C. Determining Emission Limits

IV. References

Appendix A Emission Limits Summary Tables
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Appendix B Supporting Tables for MACT Floor Analysis

Appendix C Supporting Tables for Data Variability Analysis for Existing Units

Appendix D Supporting Data for Waste-burning Kiln Mercury Analysis

Appendix E Supporting Tables for Data Variability Analysis for New Units

I. REGULATORY OPTIONS AND SUBCATEGORIES

In the 2000 CISWI rule, there were no subcategories. However, in the final rulemaking, there are

several different types of units that will now be subject to regulation as CISWI units that were

previously not subject to CISWI standards. At proposal, EPA considered two regulatory options

in proposing the CISWI standards: Option 1 – Evaluate MACT floors assuming no subcategories

(similar to the 2000 CISWI standards); or Option 2 – Evaluate MACT floors for each subcategory

of CISWI unit that will be subject to the proposed regulations. Public comments received after

proposal not only supported the need for subcategories, but indicated that additional

subcategories were warranted. EPA found these comments to be persuasive as to the need for

some additional subcategories. Therefore, the CISWI inventory has been grouped into five

primary subcategories. The five subcategories that were developed are listed below, followed by

an explanation of the reasons for creating each subcategory:

 Incinerators (general waste burning units without integral heat recovery),

 Energy recovery units – solids (waste burning units that recover thermal energy),

 Energy recovery units – liquid/gas (waste burning units that recover thermal energy),

 Waste-burning kilns (kilns burning solid waste, including tires classified as solid

waste), and

 Small, remote incinerators (small incineration units located in remote areas).

Incinerators: Incinerators, which are the units currently regulated by the 2000 CISWI rule, are

used to dispose of solid waste materials and emissions are a function of the types of materials

burned. Incinerators are designed without integral heat recovery (but may include waste heat

recovery). While there are different designs, they all serve the same purpose; reduction in the

volume of solid waste materials. Incinerators can be operated on a batch or continuous basis.

The same types of add-on controls, including fabric filters, wet scrubbers, selective noncatalytic

reduction (SNCR), and activated carbon injection, can be applied to most incinerators. Although

the composition of the materials combusted is highly variable and is a key factor in the profile of

emissions, we determined it was not appropriate to further subcategorize incinerators because the

sources in this subcategory are sufficiently similar such that the incinerators can achieve the same

level of performance for the nine regulated pollutants.

Energy-recovery units (liquid/gas, solids, solids-biomass, solids-coal): Energy recovery units

(ERUs) combust solid waste materials as a percentage of their fuel mixture and are designed to

recover thermal energy in the form of steam or hot water. Energy recovery units include units

that would be considered boilers and process heaters if they did not combust solid waste. The

design, operating, and emissions information that EPA has reviewed indicates differences in unit

design that distinguish different types of ERUs. Data indicate that there are generally significant

design and operational differences between units that burn coal, biomass, liquid, and gaseous

fuels. Energy recovery units are therefore designed for specific fuel types and will encounter

problems if a fuel with characteristics other than those originally specified is fired. Many ERUs

in the database are indicated to co-fire liquids or gases with solid fuels, but, in actuality, most of

these boilers commonly use fuel oil or natural gas as a startup fuel only and then operate on solid

fuel during the remainder of their operation. In contrast, some co-fired units are specifically

designed to fire combinations of solids, liquids, and gases. Changes to the fuel type would
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generally require extensive changes to the fuel handling and feeding system (e.g., a stoker using

wood as fuel would need to be redesigned to handle fuel oil or liquid wastes). Additionally, the

burners and combustion chamber would need to be redesigned and modified to handle different

fuel types and account for increases or decreases in the fuel volume. In some cases, the changes

may reduce the capacity and efficiency of the ERU. An additional effect of these changes would

be extensive retrofitting needed to operate using a different fuel; therefore, the design of the ERU

impacts the degree of combustion.

In our investigations resulting from public commenters’ statements, we concluded that the data

were sufficient for determining that a distinguishable difference in performance exists based on

unit design type. Therefore, because different types of units have different emission

characteristics which may influence the feasibility or effectiveness of emission control, they

should be regulated separately (i.e., subcategorized) for affected pollutants. Accordingly, we

have subcategorized ERUs based on unit design in order to account for these differences in

emissions and applicable controls. The two primary ERU subcategories are units designed to

burn solid wastes (solids) with other solid fuels, and units designed to burn liquid wastes with

liquid or gaseous fuel (liquid/gas). The ERU solids subcategory is further subcategorized into

units designed to burn coal and units designed to burn biomass for CO, NOx and SO2 to address

design differences and feasibility or effectiveness of emission control between these types of

units as commenters have suggested. The subcategorization for these pollutants is also compelled

by the data available for the solid fuel sources. Specifically, coal fired ERUs submitted

exclusively CEMS data for CO, NOx, and SO2, and biomass fired ERUs submitted almost

exclusively stack test data for these pollutants. We are unable to convert the vast majority of

CEMS data into equivalent stack test data and the converse is true as well. Pursuant to CAA

section 129(a)(2), EPA must establish emission standards for existing sources based on the

average emissions limitation achieved by the best-performing 12 percent of sources. Because the

data for CO, NOx, and SO2 from the biomass and coal fired ERUs are not in consistent formats,

we would have to ignore a subset of the available data in establishing the floors for these

pollutants if we did not further subcategorize solid fuel ERUs. We therefore think it is reasonable

to further subcategorize these units for CO, NOx, and SO2 so the standards are reflective of the

data available to EPA, and we are properly accounting for the different emissions characteristics

associated with the different types of fuels.

These subcategories are based on the primary fuel that the ERU is designed to burn. We are

aware that some ERUs burn a combination of fuel types or burn a different fuel type as a backup

fuel if the primary fuel supply is curtailed. However, ERUs are designed based on the primary

fuel type (and perhaps to burn a backup fuel) and can encounter operational problems if another

fuel type that was not considered in its design is fired at more than 10 percent of the heat input to

the unit. Therefore, we subcategorized ERUs that burn at least 10 percent coal (on an annual heat

input basis) as being in solid fuel/coal subcategory, with the remaining solid ERUs being in the

biomass subcategory for ERUs.

Waste-burning kilns: Waste-burning kilns are fundamentally different than any other unit being

regulated under CISWI. Kilns of all types are physically larger than incinerators with comparable

heat input. Kiln design and operation are also different from those of incinerators. For example,

the design is typically a rotating cylindrical kiln with a fuel burner on one end and raw materials

being fed in the other (cold) end. Fuel (particularly solids such as tires) may also in some cases

be fed at the mid kiln point. Some kilns also have a large preheater tower with a precalciner that

is an additional firing point for both fossil and waste fuels. The temperature profile of kilns is

critical in order to produce a saleable product, and differs from that of incinerators both in terms

of residence time and absolute temperature. Another key distinction from incinerators and other
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CISWI subcategories is that for cement kilns, the source of most of the emitted pollutants is

typically the raw materials, not the fuels, and emissions from the raw materials and the solid

wastes and fuels are comingled and emitted together. As a result of all these distinctions, wasteburning kilns have a very different emissions profile than other CISWI subcategories, justifying

separate standards. See 74 FR at 21145 (“Normally, any basis for subcategorizing must be

related to an effect on emission, rather than to some difference among sources which does not

affect emissions performance”).

Public commenters suggested that the waste-burning kiln subcategory be further subcategorized.

In evaluating the population of kilns that may be subject to CISWI and estimates of control

technologies that may be required to meet the limits, we determined that most of the kilns were

classified as CISWI kilns due to tire combustion. Further investigation indicated that all of these

kilns obtained the tires from established tire recycling programs. Based on the new definition in

Section 241.3, these tires would not be considered to be solid wastes. Therefore, kilns that we

considered as CISWI units at proposal solely due to tire combustion are not part of the CISWI

category, and we removed them from the CISWI inventory. In addition, we obtained information

on the combustion of used oil, biomass, and wood waste by cement kilns. Based on the definition

in 241.3, we determined which of these materials would be considered to be solid waste and

removed any kilns from the CISWI inventory where we determined none of the fuels were solid

waste. This resulted in the inventory of CISWI kilns being reduced to 12 kilns total.

Of these 12 kilns, one is a wet kiln, four are preheater kilns, and the remainder are

preheater/precalciner kilns. We recognize that differences in kiln design and configuration can

effect emissions. These effects are most evident on emissions of NOx, CO, and SO2. However;

all of these pollutants are also affected by the site specific raw materials fed to the kiln. We have

insufficient data to differentiate between the raw material affects and the kiln design affects.

Therefore, we are decided not to develop separate subcategories for cement kilns. However, all

of our information indicates that NOx, SO2 and CO are controllable to the level of the standard

whether a kiln is wet or dry. The control devices that may be necessary to comply with the

CISWI limits (including the standards for NOx, SO2 and CO) may be applied to both types of

kiln, and there do not appear to be any feasibility or effectiveness issues that would necessitate

subcategorization in order for units to achieve the limits. For example, the controls we estimate

the wet kiln units may require in order to meet the CISWI limits, such as SNCR, SCR, wet

scrubbers, and RTO, may be applied to all types of kilns. We are unaware of any design

considerations that prevent FF or RTO use for either the wet type or preheater type of kiln.

Therefore, EPA is not subcategorizing among waste-burning kilns.

Small, remote, incinerators: These are batch-operated units that combust less than 3 tons of waste

per day and are located more than 25 miles from the nearest municipal solid waste (MSW)

landfill. To the extent that these units are located in Alaska, a major difference in these types of

units is the inability to operate a wet scrubber in the northern climates and the lack of availability

of wastewater handling and treatment utilities. We believe this would impact their ability to meet

emission limits for pollutants controlled by wet scrubbers. In addition, because of the remote

location, these units do not have lower-cost alternative waste disposal options (i.e., landfills)

nearby and emissions associated with transporting the solid waste could be significant.

II. EXISTING SOURCES

A. MACT Floors
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Emissions standards for existing units may be less stringent than standards for new units, but

“shall not be less stringent than the average emissions limitation achieved by the best performing

12 percent of units in the category.” CAA section 129 (a)(2). For existing sources, the MACT

floor for each subcategory of sources was calculated by ranking the emission test results from

units within the subcategory from lowest emissions to highest emissions (for each pollutant) and

then taking the numerical average of the test results from the best performing (lowest emitting) 12

percent of sources. That is, the overall 3-run test average values for each existing unit for each

pollutant were compiled and ranked from lowest to highest to identify the best performing 12

percent of sources within the subcategory on a pollutant-by-pollutant basis. Because the number

of units in different subcategories may be different, the number of units that represent the best

performing 12 percent of units for different subcategories vary. Also, mathematically, the

number of units that represent the best performing 12 percent of the units in a subcategory will

not always be an integer. To ensure that each MACT standard is based on at least 12 percent of

the units in a subcategory, EPA has determined that it is appropriate to always round up to the

nearest integer when 12 percent of a given subcategory is not an integer. For example, in the

incinerator subcategory, 12 percent of the 26 units is 3.12 units, so standards were established

based on the best performing 4 units.

In developing standards for waste burning kilns for the final rule, we used best efforts to estimate

which units would have been classified as CISWIs (i.e. units combusting solid waste) had the

final definition of non-hazardous solid waste been in place at the time of the performance testing.

The standards (and, necessarily, the pool of best performers establishing the floors for each

standard) are based on the performance of this universe of sources.1In evaluating which sources

would have been classified as CISWI units had the new definition of solid waste been effective,

EPA used the information currently available on which non-hazardous secondary materials the

sources combust, as supplemented by information obtained from public comment and further

information gathered by EPA after the public comment period of this rule.

Table A-1 presents the results of the EG floors for the various statistical intervals considered and

the final emission limits for each pollutant in each subcategory. Subcategory-specific notes

follow. For additional reference, tables in Appendix B present all average pollutant

concentrations and unit rankings for each pollutant.

1. Waste-burning Kilns

1 Section 112 (d) MACT standards are based on the performance of sources

at a moment in time (or over some demarcated timeframe), and EPA

therefore bases those standards on performance of sources classified as

part of the source category at the time their performance is evaluated

(i.e. the time of performance testing). However, EPA could not use

this approach for this rule. Sources combusting non-hazardous

secondary materials, the best example being alternative fuels, were not

classified as CISWIs absent a regulatory definition of solid waste

classifying such secondary materials. In order to issue the CISWI

standards by the mandated promulgation deadline, EPA deviated from its

usual practice and based the standards on the performance of devices

which would have been classified as CISWIs had the final waste

definition been in place at the time of the performance testing even

though these sources were not CISWIs at the time. There was no

approach that would be based on the sources’ actual status that would

have allowed EPA to complete this CISWI rule by the time of the

judicially mandated deadline for promulgation.
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Unit rankings for each pollutant are shown in Tables B-1. The top 2 cement kilns (12 percent of

the 12 total existing cement kilns) were included in the MACT floor. Note that the PM rankings

are based on the lb/ton clinker values from each unit, weighted to reflect the percentage of time

the raw mill is operated (if the unit has a raw mill). The raw mill operating information comes

from the Portland Cement NESHAP database for the cement kilns that would have been classified

as waste-burning kilns had the revised definition of solid waste been promulgated and applicable

to those kilns. Appendix B-1 contains the spreadsheet showing how PM concentration data are

converted to lb/ton clinker produced values.

2. Energy Recovery Units – Solids

Unit rankings for each pollutant are shown in Tables B-2 through B-4. The top 4 energy recovery

units (12 percent of the 30 total existing energy recovery units) were included in the MACT floor

for solids. For solids-coal the top 2 units were included (12 percent of 9 existing units), and for

biomass, the top 3 units were included (12 percent of 21 existing units). As discussed above, only

CO, NOx and SO2 have limits based on whether the unit is in the ERU-coal or ERU-biomass

subcategory. The limits for these pollutants for the coal subcategory incorporate hourly

continuous emissions monitoring data for one of the best performing units. These were used in

the analysis since test data were unavailable. In these instances, each hour of data was treated as

an individual test run.

3. Energy Recovery Units – Liquid/Gas

Unit rankings for each pollutant are shown in Table B-5. The top energy recovery unit (12

percent of the 6 total existing energy recovery units) were included in the MACT floor.

4. Incinerators

Unit rankings for each pollutant are shown in Tables B-6. The top 4 incinerators (12 percent of

the 26 total existing incinerators) were included in the MACT floor.

5. Small, Remote Units

Unit rankings for each pollutant are shown in Table B-7 The top 2 small, remote units (12 percent

of the 14 total existing incinerators) were included in the MACT floor.

B. Data Variability Analysis

Once the best 12 percent of units were identified for each source category and pollutant, the

individual test run data for these units were compiled, and a statistical analysis was conducted to

calculate the average and account for variability in order to determine the MACT floor emission

limit.

The first step in the statistical analysis included a determination of the whether the data used for

each MACT floor calculation were normally or log-normally distributed, followed by calculation

of the average, the 99th percent upper limit (UL) for incinerators, and the 99th percent upper

prediction limit (UPL) for energy recovery units and waste-burning kilns. If the data were

normally distributed (e.g., similar to a typical bell curve), then the equation to calculate UL was

applied to the data. If the data were not normally (i.e. log-normally) distributed (for example if

the data were asymmetric or skewed to the right or left), then a data transformation was

performed to normalize the data prior to computing the UL or UPL. When the data distribution

was found to be log-normal, the data were transformed by taking the natural log of the data prior

to calculating the UL or UPL value. Two statistical measures, skewness and kurtosis, were

examined to determine if the data were normally or log-normally distributed. Since proposal, the

methodology has been revised to use the lognormal distribution when the normal distribution is
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not clearly indicated based on the skewness and kurtosis tests to be more consistent with EPA’s

guidance in “Guidance for Data Quality Assessment: Practical Methods for Data Analysis”

EPA/600/R-96/084, July 2000. A summary of the variability analysis for existing units is

presented in Table A-3. Detailed analyses with run data can be found in Appendix C.

C. Determining Emission Limits

Emission limits for existing units were determined based on the 99th percent UL (for incinerators)

and the 99th percent UPL (for energy recovery units and waste-burning kilns) of the compiled run

data for each pollutant and are presented in Table 1 below.

Table 1. Final CISWI MACT Floor Limits for Existing Sources

Pollutant

(units)

Subcategory

Incinerators

Energy

recovery

units –

solids

Energy

recovery

units –

liquid/gas

Wasteburning

kilns

Small,

remote

incinerators

HCl (ppmv) 29 0.45 14 25 220

CO (ppmv) 36 490

(biomass

units)/

59 (coal

units)

36 110 20

Pb (mg/dscm) 0.0036 0.0036 0.096 0.0026 2.7

Cd (mg/dscm) 0.0026 0.00051 0.023 0.00048 0.61

Hg (mg/dscm) 0.0054 0.00033 0.0013 0.0079 0.0057

PM, filterable

(mg/dscm)

34 250 110 6.2 230

PCDD/PCDF,

total (ng/dscm)

4.6 0.35 2.9 0.020 1200

PCDD/PCDF,

TEQ

(ng/dscm)

0.13 0.059 0.32 0.0070 57

NOx(ppmv) 53 290

(biomass

units)/

340 (coal

units)

76 540 240

SO2(ppmv) 11 6.2 (biomass

units)/

650 (coal

units)

720 38 420

As discussed at proposal, the UL computation assumes that the data available represents the

entire population of data from the best-performing CISWI units used to establish the standards.

We have concluded that this statement applies to the incinerator and small remote incinerator

subcategories, since we believe our inventory of these units is more certain than is our inventory
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of ERUs and waste-burning kilns for several reasons. In the 2000 CISWI rule, EPA only

regulated solid waste incineration units that operated for the sole purpose of disposing of waste.

Many incinerators subject to the 2000 CISWI rule ceased operation before the compliance date

for those standards. Once the revised CISWI standards are finalized, these types of solid waste

incineration units (i.e., incinerators and small remote incinerators) will either comply with the

revised CISWI standards or cease operation, much as they did in response to the 2000 standards.

The same is not necessarily correct for units in the ERUs and waste-burning kilns subcategories.

For those sources, once the CISWI standards are promulgated, they will likely either comply with

the CISWI standards or cease burning solid waste and comply with the applicable NESHAP. We

think units in those subcategories will generally not cease operation. Furthermore, because

incinerator and small remote incinerator units’ sole purpose is waste disposal, the only practical

manner in which additional sources will be added to the inventory is through new construction.

Again, this is different than for ERUs and waste-burning kilns because, for those subcategories,

additional units may be added if existing boilers (and process heaters) and cement kilns begin

combusting solid waste and thereby become ERUs and waste-burning kilns, respectively. For

these reasons, we believe we have a complete inventory of units in the incinerators and small

remote incinerators subcategories.

We sent Phase II testing requests to all incinerator and small remote incinerator units that are in

our inventory. We required testing for all incinerator and small remote incinerator units, making

allowances for identical units from a facility to only test one unit, and not each identical unit.

Therefore, our data represent the entire population of data for these two subcategories. For this

reason, we believe the UL is the appropriate statistical approach for the incinerators and small

remote incinerators subcategories. The 99 percent UL represents a value that 99 percent of the

data in the MACT floor population would fall below, and therefore accounts for the run-to-run

and test-to-test variability observed in the MACT floor data set.

The UL was calculated by the following equation:

  s*n)t(0.99,xUL

Where:

x = average of the data.

t(0.99,n) = t-statistic.

n = number of data points in the population.

s = standard deviation.

For ERUs and waste-burning kilns, however, we recognize that our data may not represent the

entire population of units. As stated above, there is greater uncertainty involved in determining

the universe of sources in these two source categories because we cannot be certain that we have

identified all the units that would be considered to be burning solid waste, had the newly-adopted

definition fo solid waste been promulgated and effective at the time of testing. We also do not

know whether the units we have identified will continue to burn waste after the final CISWI

standards are issued. Unlike incinerators and small remote incinerators, the primary purpose of

waste-burning kilns and ERUs is the production of a product or generation of energy, not the

disposal of waste. Therefore, operators will decide whether it is economically feasible to

continue or start combusting solid waste to support their industrial process and, if they decide that

it is not, they will use traditional fuels or non-waste inputs instead of solid waste. For example,

an ERU that is combusting solid waste that has little or no cost may decide that compliance with

CISWI is an economically viable option compared to purchasing traditional fuels at market rates;

but, if the costs of compliance with CISWI exceed the costs of traditional fuel, the source will
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likely cease burning solid waste. Conversely, a boiler that currently combusts only traditional

fuels may be presented with a solid waste fuel option that makes it to their economic advantage to

begin combusting solid waste. For these reasons, the population of units in the ERU and wasteburning kiln subcategories is inherently uncertain. We have for these reasons concluded that a

prediction interval (e.g., UPL) is more appropriate for these two subcategories.

A prediction interval for a future observation is an interval that will, with a specified degree of

confidence, contain the next (or some other pre-specified) randomly selected observation from a

population. In other words, the prediction interval estimates what the upper bound of future

values will be, based upon present or past background samples taken. The UPL consequently

represents the value which we can expect the mean of future observations (3-run average) to fall

below within a specified level of confidence, based upon the results of an independent sample

from the same population. In other words, if we were to select at random a future test condition

from any of the top 12 percent (MACT floor pool) of sources (average of 3 runs), we can be 99

percent confident that the reported level will fall at or below the UPL value. Use of the UPL is

appropriate in this rulemaking for these two subcategories because it sets a limit any single or

future source can meet based on the performance of members of the MACT floor pool.

The UPL was calculated by the following equation:

Where:

x ̄ = Mean of the sample data set

n = Number of test runs

m = Number of test runs in the compliance average

s2 = Observed variance

t = Student t distribution statistic

The calculated existing source UL or UPL values (which are based on the emissions data from the

best performing 12 percent of sources and account for variability) were selected as the final

emission limits for the nine regulated pollutants in each subcategory. In establishing the limits,

the UL values were rounded up to two significant figures. For example, a value of 1.42 would be

rounded to 1.5 (as has been done for other CAA section 129 rules) because a limit of 1.4 would

be lower than the calculated MACT floor value. The summary results of the UL and UPL

analysis and derivation of the final emission limits for existing units are presented in Table A-3.

At proposal, EPA suggested that at very low emission levels where emissions tests result in

nondetect values, the inherent imprecision in the pollutant measurement method has a large

influence on the reliability of the data underlying the MACT floor emission limit. See 75 FR

31943. Because of sample and emission matrix effects, laboratory techniques, sample size, and

other factors, MDLs normally vary from test to test for any specific test method and pollutant

measurement. The confidence level that a value measured at the detection level is greater than

zero is about 99 percent. The expected measurement imprecision for an emissions value

occurring at or near the MDL is about 40 to 50 percent. Pollutant measurement imprecision

decreases to a consistent level of 10 to 15 percent for values measured at a level about three times

the MDL. The approach EPA has used to account for measurement variability in t calculating the

final limits begins by defining a MDL that is representative of the data used in the data pool. The

first step in the approach is to identify the highest test specific MDL reported in a data set that is
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also equal to or less than the average emission calculated for the data set. This approach has the

advantage of relying on the data collected to develop the MACT floor emission limit, while to

some degree, minimizing the effect of a test(s) with an inordinately high MDL (e.g., the sample

volume was too small, the laboratory technique was insufficiently sensitive or the procedure for

determining the detection level was other than that specified). The second step is to determine

the value equal to three times the representative MDL and compare it to the calculated MACT

floor emission limit. If three times the representative MDL were less than the calculated MACT

floor emission limit, we concluded that measurement variability is adequately addressed, and we

did not adjust the calculated MACT floor emission limit. If, on the other hand, the value equal to

three times the representative MDL was greater than the calculated MACT floor emission limit,

we concluded that the calculated MACT floor emission limit does not account entirely for

measurement variability. We therefore used the value equal to three times the MDL in place of

the calculated MACT floor emission limit to ensure that the MACT floor emission limit accounts

for measurement variability and imprecision. The results of these analyses are presented in the

summary tables of Appendix A as well as the individual variability calculation spreadsheets of

Appendix C (and Appendix E for new sources).

In a similar concern, extremely low carbon monoxide values were reinvestigated to analyze

whether the span of the test used was capable of accurately reading the reported value, and if not,

were adjusted to provide a value in which there can be more confidence . While this adjustment

did not necessarily affect the floor calculations in every case, the results of this analysis and

resulting changes to the database are presented in Appendix F.

As noted in Table A-4 for new units, the measurements for HCl from waste-burning kilns are

very close to the detection limit for analytic Method 321 actually calculated in the field for HCl.

We have implemented a procedure for adjusting limits to account for measurement variability

using data at the detection limit. A similar exercise was also performed for the Portland Cement

NESHAP, which results in a floor of 3 ppmvd for both new and existing waste-burning kilns for

HCl, adjusted to a dry basis at 7 percent oxygen. This represents the lowest level that can be

reliably measured using this test method. See 75 FR at 54984.

The Hg standard for waste-burning kilns reflects 30 days of data for all Hg inputs, reasonable

estimates of control device performance (for the few controlled sources), plus a reasonable

statistical methodology to account for variability (including variability of Hg content of kiln

inputs). EPA also used a pooled variability factor (pooling variability for all kilns in the MACT

floor pool), which increased variability estimates. This analysis is based upon data collected for

development of the final Portland Cement NESHAP, but screened such that the CISWI analysis

used only the data from kilns that would have been identified as CISWI units had the newlyadopted solid waste definition been promulgated and effective at the time of performance testing

and accounting for inter-quarry variability , and converted to a concentration basis for consistency

with the CISWI standards. The data used in this particular analysis are confidential business

information, so the analysis presents randomly assigned identification for these data. The limit

calculated for existing sources is 29.876 lb/ million tons feed, which assuming 1.65 tons feed per

ton clinker and 100,000 dry standard cubic feet per ton clinker, results in a limit of 0.0079

mg/dscm at 7 percent oxygen. The result for new sources is 0.0062 mg/dscm. This analysis is

presented separately in Appendix D.

III. NEW SOURCES

A. MACT Floors
11

The approach for new sources was similar to that used with the existing sources, except the best

performing unit’s data within a subcategory was used to calculate the MACT floor emission limit

instead of the average of the best performing 12 percent of units. In summary, the approach ranks

individual CISWI units based on actual performance and establishes MACT floors based on the

best performing source for each pollutant and subcategory, with an appropriate accounting for

emissions variability.

Table A-2 presents the NSPS floors for each pollutant for each subcategory.

B. Data Variability Analysis

Similar to the analysis performed to determine EG limits, run-specific data for the best

performing unit were compiled on a pollutant-by-pollutant basis and assessed to account for

variability. A summary of the statistical results for the NSPS data variability analysis is shown in

Table A-4. For further reference, Appendix E presents individual run data and associated

analyses for each pollutant within each subcategory.

C. Determining Emission Limits

Emission limits for new sources, also based on the 99th percent UL (for incinerators) and the 99th

percent UPL (for energy recovery units and waste-burning kilns) of the compiled run data for

each pollutant, are presented in Table 2 below. For further reference, the summary results of the

UL and UPL analysis and derivation of the final emission limits for new units are presented in

Table A-2 in Appendix A.

As noted in Table A-4, there were certain instances where the calculated emission limit for new

sources was actually greater (less stringent) than the limit calculated for that pollutant for existing

sources. In these cases, the limit for existing sources was also adopted for new sources. In a

couple instances for waste-burning kilns and energy recovery units, the data available for similar

sources was determined to be better suited for calculating the new source limits. Notably, this is

the case for NOx for waste-burning kilns, and for Hg and PCDD/PCDF for ERU-liquid/gas units.

Table 2. Final CISWI MACT Floor Limits for New Sources

Pollutant

(units)

Subcategory

Incinerators

Energy

recovery

units –

solids

Energy

recovery

units –

liquid/gas

Wasteburning

kilns

Small,

remote

incinerators

HCl (ppmv) 0.091 0.45 14 3.0 200

CO (ppmv) 12 160

(biomass

units)/

46 (coal

units)

36 90 12

Pb (mg/dscm) 0.0019 0.0031 0.096 0.0026 0.26

Cd (mg/dscm) 0.0023 0.00051 0.023 0.00048 0.61

Hg (mg/dscm) 0.00016 0.00033 0.00025 0.0040 0.0035
12

Pollutant

(units)

Subcategory

Incinerators

Energy

recovery

units –

solids

Energy

recovery

units –

liquid/gas

Wasteburning

kilns

Small,

remote

incinerators

PM, filterable

(mg/dscm)

18 250 110 2.5 230

PCDD/PCDF,

total (ng/dscm)

0.052 0.068 No limit 0.090 1200

PCDD/PCDF,

TEQ

(ng/dscm)

0.13 0.011 0.0020 0.0030 31

NOX (ppmv) 23 290

(biomass

units)/

340 (coal

units)

76 200 78

SO2(ppmv) 11 6.2

(biomass

units)/

650 (coal

units)

720 38 1.2