MEMORANDUM 

TO: Toni Jones, U.S. Environmental Protection Agency (EPA)

FROM: Eastern Research Group, Inc. 

DATE: December 20, 2012

SUBJECT: Final Reconsideration Beyond-the-Floor Analysis for CISWI Units 

1.0 PURPOSE

This memorandum presents the data, methodology and assumptions used to conduct a 

beyond-the-floor (BTF) analysis for the emission limits that the Agency is finalizing in the 

reconsideration of certain new source standards established in the March 2011 final 

Standards of Performance for New Stationary Sources and Emission Guidelines for Existing 

Sources: Commercial and Industrial Solid Waste Incineration (CISWI) Units.1 Sections 2 and 

3 of this memorandum present the EPA’s analysis of BTF options for existing and new 

sources respectively. Spreadsheets associated with this analysis accompany this 

memorandum in the CISWI docket (EPA-HQ-OAR-2003-0119) and are named for the 

CISWI unit subcategory evaluated. Emission reductions estimates are in the “BTF Emission 

Reductions” spreadsheet. 

Clean Air Act (CAA) sections 129 and 111 require the EPA to regulate emissions of 

nine pollutants from 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). Under CAA section 129(a)(2), the EPA 

first must determine the minimum level of control for each regulated pollutant, commonly 

known as the maximum achievable control technology (MACT) floor. The MACT floor is 

established based on the level of emissions achieved by the best performing 12 percent of 

sources in the category or subcategory for existing sources and on the best performing similar 

source for new sources. A separate memorandum discusses development of the MACT 

floors in more detail (see Reference 1). Clean Air Act section 129(a)(2) then requires the 

EPA to determine whether a more stringent level of control – the BTF level of control – is 

achievable for the different regulated pollutants after considering associated costs, non-air 

quality health and environmental impacts, and energy requirements. 

 

1

 On March 21, 2011, the EPA promulgated New Source Performance Standards (NSPS) and Emission 

Guidelines (EGs) (2011 CISWI rule) for six subcategories of CISWI units: three subcategories of energy 

recovery units (ERUs) (biomass-fired, coal-fired ERUs, and liquid/gas-fired); waste burning kilns; incinerators; 

and small, remote incinerators. Following promulgation of the 2011 CISWI rule, the Administrator received 

petitions for reconsideration and identified certain issues that warranted further opportunity for public comment. 

On December 23, 2011, the EPA published in the Federal Register a reconsideration proposal that incorporated 

changes to the 2011 CISWI rule based on new information and data. The proposed rule included the CISWI 

subcategories above and further subcategorized waste burning kilns into long kilns and kilns that have a 

preheater for CO emissions only. 
2.0 EXISTING UNITS

Table 1 compares the March 2011 CISWI rule emission limits and the final emission 

limits after reconsideration. As explained in the preamble to the 2011 CISWI rule rule, the 

EPA did not establish any emissions limits based on a BTF level of control in that rule. (76 

FR 15279). We are not reconsidering these prior determinations to the extent the analyses 

remain the same, either because the limit remains the same or became more stringent 

pursuant to the incorporation of new data in the reconsideration action. However, we 

evaluated BTF options for emission limits in today’s final rule that are less stringent than the 

limits in the 2011 CISWI rule to determine whether the prior analyses remain valid, 

notwithstanding the reduction in stringency based on the revised MACT floor calculations. 

The following sections summarize the existing unit limits that became less stringent and our 

analysis of BTF levels of control. 

2.1 Incinerators 

For the incinerator subcategory, the final emission limit for Pb is less stringent than 

the limit in the 2011 CISWI rule. The limit in that final rule was calculated using data that 

included data below the detection level, but EPA did not at that time have sufficient 

information to establish a representative detection level (RDL) for Pb. For this reason, the 

Agency was unable to compare the calculated limit to the level equal to three times the RDL, 

as we do for all limits that are based in part on non-detect data. Since finalization of the 2011 

CISWI rule, the data set for determining the method detection level (MDL) for various test 

methods and pollutants was improved, including for Pb, and the Agency established an RDL 

for Pb. The new emission limit for Pb is based on the level equal to three times the RDL 

determined for Method 29 metals. The development and use of the revised detection limits 

are described further in Appendix G of the MACT floor memorandum (see Reference 1). 

Existing units in this subcategory are equipped with FFs for control of Pb emissions. 

We estimate that some incinerator units in this category will require retrofitting of existing 

FFs or installation of additional FFs to comply with the MACT floor limits for Pb. This 

would result in annual costs of approximately $8.6 million, with an associated reduction of 

about 0.7 tons of Pb per year. Considering Pb emission reductions alone, the cost 

effectiveness of the MACT floor emission limit is approximately $12 million per ton. If cocontrol of Cd and PM are also considered, the cost effectiveness is approximately $154,000 

per ton to achieve the MACT floor emission levels using FF technology. Based on these cost 

estimates, we do not believe it would be reasonable from a cost perspective to impose a BTF 

level of control on these sources, which would involve a very high efficiency FF, such as 

membrane filter technology. We note that we expect that the high costs of controls necessary 

to meet the MACT standard, when compared to the costs of alternative waste disposal 

methods (e.g., landfilling), will lead some source owners to shut down existing incinerators 

rather than comply with the MACT floor limits when promulgated, as discussed in the 

current costs analysis and in our earlier analyses. 

 

Additionally, demonstrating compliance with a BTF limit for Pb is problematic. Since 

the Pb limit is established at the level equal to three times the RDL, sources would be unable 
to demonstrate compliance with a reasonable level of certainty with emission limits lower 

than the MACT floor level of control based on current sampling and laboratory practices. 

Therefore, any potential further emission reduction would be difficult for sources and 

implementing agencies to quantify. 

We conclude that BTF controls for Pb emissions are not reasonable because of the 

high control costs that would likely be associated with any BTF control given the already 

high cost for meeting the MACT floor emission limit and the limited amount of additional 

reductions that would be achieved with a more stringent standard. We are also declining to 

establish a BTF level of control because of the uncertainty in quantifying emissions at levels 

more stringent than the MACT floor. 

2.2 Small Remote Incinerators 

For the small remote incinerator (SRI) subcategory, the final emissions limits for 

HCl, CO, Cd, PM, and PCDD/PCDF are less stringent than the March 2011 limits, though 

the EPA employed the same MACT floor methodology. This change occurred because the 

Agency revised the SRI inventory by removing two units (one of which had emissions data 

but was reassigned to the incinerator subcategory) and adding 16 units (see Reference 2). 

Further, we adjusted available CO emissions data to reflect limitations of instrumental 

methods used in measuring emissions. Appendix F of the MACT floor memorandum 

discusses the adjustments in more detail (see Reference 1).

Regarding HCl, SRI units control HCl by waste segregation practices – removal of as 

many chlorine and sulfur-containing compounds as possible prior to incineration – to meet 

the MACT floor limits. We have determined based on information in the record (see 

Reference 4) that wet or semi-dry acid gas control systems are not technically feasible for 

year-round use by SRI units. Any completely dry control technology, such as duct sorbent 

injection, would require sorbent transport, installation of a FF, and transport of collected 

spent sorbent to landfill, driving up the costs of the control device considerably. Fabric filter 

costs alone would $1.3 for existing sources, as discussed below. This does not account for 

additional cost of sorbent transport and disposal or DSI system costs. Assuming that the 

control captures 10 tons per year of the estimated baseline emission of HCl, and transport 

costs are $20,000 per ton, this would result in a cost effectiveness of at least $150,000 per 

year. Thus, any limitation beyond waste segregation is not feasible based on climate for wet 

controls and cost for HCl control from SRIs. We thus have determined that no add-on control 

as a BTF option for HCl for SRIs is reasonable. 

Regarding CO, existing SRI units often employ an afterburner to reduce CO 

emissions. To achieve the MACT floor limits for CO, we estimate that more than half of SRI 

units would require afterburner retrofits. A more stringent BTF limit would require SRIs that 

can meet the MACT floor limit without an afterburner retrofit to have one and would require 

SRIs that would need an afterburner to meet the MACT floor to purchase a more robust 

afterburner design and additional gas to fuel the larger unit. We estimate that a BTF limit for 

CO would reduce CO emissions by approximately 6.5 tons per year, yielding a costeffectiveness of approximately $24,000 per ton. We do not believe this cost is reasonable. 
 

In addition, only a small amount of CO emissions would remain after meeting the 

MACT floor, and other than an afterburner, no demonstrated control technologies exist for 

reducing these emissions from SRIs. We also understand that some units that would 

otherwise close due to cost-related issues will be forced to operate at a loss, because closure 

may not be an option due to other, non-air-related environmental regulations. For example, 

SRIs are typically operated in remote locations where alternative disposal options (e.g., 

landfilling) are not available. Considering all these concerns, we conclude that no reasonable 

BTF alternatives exist for CO emissions from the SRI subcategory. 

Regarding Cd, PM and PCDD/PCDF, existing SRI units often employ good 

combustion practices and waste segregation to reduce emissions of these pollutants. As a 

BTF option to capture additional amounts of these pollutants, we estimated costs to install 

activated carbon injection with a fabric filter (ACI/FF) to SRI units. Our analysis estimated 

an annual cost of approximately $1.3 million to reduce additional 5.6 tons of combined PM, 

Cd, and PCDD/PCDF, yielding a cost-effectiveness of approximately $237,000 per ton. A 

fabric filter (FF) alone, considered as a BTF option to further reduce emissions of just PM 

and Cd, has a cost-effectiveness of approximately $209,000 per ton. As mentioned, we also 

believe that some units that would otherwise close due to cost-related issues may be forced to 

operate at a loss because closure may not be an option due to other non-air quality 

environmental regulations aimed at protecting human health and wildlife, so any additional 

costs imposed on these units is arguably unreasonable. Considering all these concerns, we 

conclude that no reasonable BTF alternatives exist for Cd, PM, or PCDD/PCDF emissions 

from the SRI subcategory. 

2.3 Energy Recovery Units 

 The following emission limits in the final standards for energy recovery units (ERUs) 

are less stringent than the March 2011 final rule emission limits: 

• CO, Cd, Pb, Hg, HCl and PCDD/PCDF from coal-fired ERUs, 

• Cd, Pb, Hg, and PCDD/PCDF from biomass-fired ERUs, and 

• Hg from liquid/gas waste-fired ERUs. 

2.3.1 Solid Waste ERUs 

2.3.1.1 Coal-Fired ERUs 

Existing units in this subcategory employ a variety of particulate and acid gas 

controls, including wet scrubbers and electrostatic precipitators, to comply with the MACT 

floor emissions limits for HCl and SO2. To meet lower, BTF HCl and SO2 limits, these units 

would likely install a semi-dry scrubber system, with a fabric filter and a polishing caustic 

scrubber, which would enable these units to reduce both HCl and SO2 and meet stricter 

limits. Space availability and facility layout affect costs of these installations, which industry 

estimates to be approximately $44 million annually to reduce 711 tons of HCl and SO2

beyond reductions achieved by the MACT limit. The resulting cost-effectiveness for 
reduction of HCl and SO2 is approximately $62,000 per ton. We do not believe these costs to 

be reasonable. 

Units in this subcategory currently employ either a wet scrubber or electrostatic 

precipitator to meet the MACT floor emission limits for Cd, Pb, and PM. To meet a BTF 

limit, these units would require upgrading the existing controls or the addition of a FF 

control device in series. We estimate costs of these additional controls to be approximately 

$9 million per year, with annual combined reductions of approximately 121 tons of PM, Cd, 

and Pb.2 The resulting cost-effectiveness is approximately $74,000 dollars per ton. We do 

not consider these costs to be reasonable. 

Regarding control of Hg and PCDD/PCDF, existing ERU currently employ either a 

wet scrubber or electrostatic precipitator to meet the MACT floor limits. Meeting BTF limits 

for these pollutants would require these units to install ACI/FF. We note that for 

PCDD/PCDF, the MACT standard is established at the detection limit. Thus, quantifying 

further PCDD/PCDF reductions would involve high degrees of uncertainty. We hence 

conclude that imposition of a BTF limit is not reasonable. Regarding Hg, we anticipate that 

ACI/FF would further reduce only a small amount of emissions (0.016 tons), at a cost of 

$11.9 million annually. We estimated a cost-effectiveness of about $743 million per ton 

($371,000 per lb) of Hg removal. We do not consider these costs to be reasonable. 

Regarding CO, the revised MACT limit is based upon an expanded data set that 

encompasses a year’s worth of data from the best performing source and accounts for 

continuous monitoring data available from this source. We anticipate that existing sources 

will require a tune-up to improve combustion efficiency to comply with the MACT floor 

emission level. To further reduce CO emissions, sources would likely need to install a 

linkageless boiler management system (LBMS) or an oxidation catalyst. The LBMS system 

is fairly low-cost, but considering the long term data available from one unit in this 

subcategory, we are uncertain of actual reductions this control option would achieve 

compared to non-waste combusting boilers of similar design, and thus do not consider it 

feasible to set a numeric limit based on reductions by this control system. For this reason, 

catalyst device would be more feasible to set a BTF limit and assess compliance. Installation 

of oxidation catalyst controls would likely cost approximately an additional $3 million per 

year and reduce approximately 340 tons of CO. The resulting cost-effectiveness is 

approximately $9,000 per ton of CO. We do not believe these costs to be reasonable. 

2.3.1.2 Biomass-fired ERUs 

For biomass-fired ERUs the final emissions limits for Pb and Cd are less stringent 

than the limits in the 2011 CISWI rule. Those limits were calculated using data that included 

data below the detection level, but EPA did not at that time have sufficient information to 

establish a RDL for Cd and Pb. For this reason, the Agency was unable to compare the 

calculated limits to the level equal to three times the RDL, as we do for all limits that are 

based in part on non-detect data. Since finalization of the 2011 CISWI rule, the data set for 

determining the MDL for various test methods and pollutants was improved, including for 

 

2

 PM reductions alone constitute 120.6 tons of this total. 
Cd and Pb, and the Agency established RDLs for Cd and Pb. The new emission limits for Cd 

and Pb are based on the level equal to three times the RDL determined for Method 29 metals. 

The development and use of the revised detection limits are described further in Appendix G 

of the MACT floor memorandum. 

An FF system is considered the best control available for Cd and Pb emissions for 

this subcategory. To meet the final limit, more than half of existing units will need to reduce 

their Cd and Pb emissions -- by more than 80 percent in most cases. These units will likely 

require highly-efficient FF systems, with an annual cost of approximately $9.1 million and 

associated annual reductions of approximately 1.7 tons of Cd and Pb combined. Considering 

these two pollutants alone, the cost effectiveness of the MACT floor emission limit is 

approximately $5.2 million per ton. However, the controls needed for these pollutants also 

result in significant coincidental reductions in PM emissions. If co-control of PM is also 

considered, the cost-effectiveness of Cd, Pb, and PM reductions is approximately $10,000 

per ton. Any BTF limits for Cd and Pb would likely necessitate a second FF in series, 

essentially doubling the cost, but achieving small additional emissions reductions because of 

the low concentration entering the second FF. For this reason, we do not think the cost of 

establishing a BTF level of control is reasonable. 

Additionally, demonstrating compliance with a BTF limit for Cd or Pb is problematic. 

Since the limits are established at the level equal to three times the RDL, sources would be 

unable to demonstrate compliance with a reasonable level of certainty with emission limits 

lower than the MACT floor level of control. Therefore, any potential further emission 

reduction would be difficult for sources and implementing agencies to quantify. 

For these reasons, we are not establishing a MACT standard based on a BTF level of 

control for Cd and Pb emissions for this subcategory. 

 For Hg emissions, achieving the MACT floor emission limits is typically achieved 

via ACI/FF controls. Nearly half of existing biomass-burning ERUs will likely require 

installation of ACI/FFs to meet the MACT floor Hg limit. If a BTF emission limit were 

imposed, these units would need to increase their ACI sorbent injection rate, and units that 

currently can meet the MACT limit without ACI/FF controls would need to install them. We 

estimate that a BTF limit based on this technology would result in annual costs of around $6 

million, with a reduction of 0.0022 tons of Hg per year. The resulting cost-effectiveness for 

this option is about $1.4 million/lb. We do not believe these costs to be reasonable. 

The PCDD/PCDF limit in the 2011 CISWI rule was calculated using data that 

included data below the detection level, but EPA did not at that time have sufficient 

information to establish a RDL for PCDD/PCDF. For this reason, the Agency was unable to 

compare the calculated limit to the level equal to three times the RDL, as we do for all limits 

that are based in part on non-detect data. Since finalization of the 2011 CISWI rule, the data 

set for determining the MDL for various test methods and pollutants was improved, including 

for PCDD/PCDF, and the Agency established a RDL for PCDD/PCDF. The new emission 

limit for PCDD/PCDF is based on the level equal to three times the RDL determined for 
Method 29 metals. The development and use of the revised detection limits are described 

further in Appendix G of the MACT floor memorandum (see Reference 1). 

As discussed above, almost half of the biomass-burning ERUs will likely require 

ACI/FF to meet the Hg limit, which also controls PCDD/PCDF. Also noted above, if a BTF 

emission limit were imposed, these units would need to increase their ACI sorbent injection 

rate, and units that currently can meet the MACT limit without ACI/FF controls would need 

to install them. We estimate that a BTF limit based on this technology would result in annual 

costs of around $23 million, with a reduction of 0.00005 tons of PCDD/PCDF per year. The 

resulting cost-effectiveness for this option is about $212 million/lb. We do not believe these 

costs to be reasonable. 

Additionally, demonstrating compliance with a BTF limit for PCDD/PCDF is 

problematic. Since the limit is established at the level equal to three times the RDL, sources 

would be unable to demonstrate compliance with a reasonable level of certainty with an 

emission limit lower than the MACT floor level of control. Therefore, any potential further 

emission reductions would be difficult for sources and implementing agencies to quantify. 

3.3.2 Liquid/Gas-Fired Waste ERUs 

For Hg reductions, sources in this subcategory currently employ particulate matter 

control devices to meet the MACT floor emission limits. For BTF Hg reductions, we 

analyzed use of ACI/FF controls to achieve a level based on the 3XRDL. Baseline emissions 

and the MACT floor emission limit are already reasonably low; hence, a BTF limit achieves 

little reductions (0.002 tons/yr) at a fairly significant cost of about $3 million per year. The 

resulting cost-effectiveness estimate of this option is about $1.6 billion per ton. We do not 

believe these costs to be reasonable. 

3.4 Waste-Burning Kilns 

The emission limits in the final CISWI rule for waste-burning kilns are less stringent than 

the March 2011 CISWI rule emission limits for the following pollutants: Cd, Pb, Hg, 

PCDD/PCDF, CO, NOx, and SO2. 

 

3.4.1 Cd and Pb Emissions 

The March 2011 CISWI rule limits were calculated using data that included data 

below the detection level, but EPA did not at that time have sufficient information to 

establish a RDL for Cd and Pb. For this reason, the Agency was unable to compare the 

calculated limits to the level equal to three times the RDL, as we do for all limits that are 

based in part on non-detect data. Since finalization of the 2011 CISWI rule, the data set for 

determining the MDL for various test methods and pollutants was improved, including for 

Cd and Pb, and the Agency established RDLs for Cd and Pb. The new emission limits for Cd 

and Pb are based on the level equal to three times the RDL determined for Method 29 metals. 

The development and use of the revised detection limits are described further in Appendix G 

of the MACT floor memorandum. 
A FF is considered the best control available for Cd and Pb emissions for this 

subcategory. We estimate that every waste-burning kiln will either need to improve an 

existing FF or install a FF to meet the MACT floor emission limits for both pollutants. This 

results in annual costs of approximately $110 million, with an associated reduction of about 

917 tons of Cd, Pb and PM (co-controlled) per year. Considering these three pollutants, the 

cost effectiveness of the MACT floor emission limit is approximately $120,000 per ton of 

Cd, Pb and PM reduced. If Cd and Pb are considered solely, the cost-effectiveness is around 

$355 million per ton. To achieve a BTF level of control for Cd and Pb, sources would likely 

have to install a more robust FF system or perhaps a second FF in series.We do not believe 

these costs to be reasonable. 

Additionally, demonstrating compliance with a BTF limit for Cd or Pb is problematic. 

Since the limits are established at the level equal to three times the RDL, sources would be 

unable to demonstrate compliance with a reasonable level of certainty with emission limits 

lower than the MACT floor level of control. Therefore, any potential further emission 

reduction would be difficult for sources and implementing agencies to quantify based on 

current sampling and laboratory practices. 

3.4.2 Hg Emissions 

 The less-stringent Hg limit for waste-burning kilns results from the expanded 

inventory for this subcategory. EPA analyzed the materials being combusted in the inventory 

of Portland cement kilns in light of the final NHSM rule

3

 and as a result added 11 kilns to our 

inventory of waste-burning kilns. We identified test records associated with these units, 

extracted data, added it to the CISWI database, and re-calculated the MACT floor emission 

limits. The December 2011 proposed rule reflected the updated inventory and additional data. 

Following proposal, we learned of one additional waste-burning kiln and another kiln that 

was not burning waste. Adjusting for these additional kilns brings the total waste-burning 

kiln inventory to 23 kilns. We recalculated the standards in this final rule to include all 23 

waste burning kilns. 

 To meet even the less-stringent MACT floor emission limit for Hg, all but one of the 

units in this subcategory will need to install ACI and either improve existing FFs or install 

FFs to capture the additional spent sorbent load. In our BTF analysis, we considered a limit 

that would require all units to install the ACI/FF combination. This option resulted in costeffectiveness for Hg reductions of approximately $351 million/ton. We do not believe these 

costs to be reasonable. 

3.4.3 CO Emissions 

 During reconsideration, waste-burning kilns were further subcategorized for CO, 

based on the demonstrated difference in combustion and CO formation characteristics of long 

kilns and preheater or preheater/precalciner kilns. The final limit for long kilns is more 

stringent than the March 2011 CO limit for waste-burning kilns, and the rationale for not 
requiring BTF measures for these units still holds. Preheater and preheater/precalciner kilns 

have much higher CO emission rates, and this fact has led to a less stringent MACT floor. 

 Of the 10 precalciner/preheater kilns, 6 are estimated to require additional control. 

The only effective CO control for significant CO reductions we identified for waste-burning 

kilns is a regenerative thermal oxidizer (RTO), and we expect over half of the units will need 

to install an RTO to meet the MACT floor limit. As a BTF option, we considered setting a 

CO limit at a level that would require most of the remaining waste-burning kilns to install an 

RTO. This level also would require some of the units requiring an RTO to meet the MACT 

floor emission limit for CO to install a more robust RTO system to meet a more stringent 

limit, increasing both capital costs of the RTO and the amount of fuel used to heat the control 

device. Based on these considerations, we estimated cost-effectiveness of CO reductions 

achieved by a BTF limit to be $26,000 per ton. We do not believe these costs to be 

reasonable. 

3.4.4 NOx Emissions 

 The less-stringent NOx limit for waste-burning kilns is a result of the expanded 

inventory for this subcategory, as discussed earlier. Existing units in this subcategory are 

currently using selective non-catalytic reduction (SNCR) to meet the MACT floor emission 

limit. We do not have data showing reductions achieved by these controls on existing kilns 

in our inventory, so we are unable to evaluate whether this control technology will provide 

additional reductions for these units as a BTF option. 

Test data for two kilns equipped with SNCR show NOx emissions of about 470 ppm, 

and one kiln will likely require SNCR to meet the MACT floor emission limit. This kiln has 

NOx emission levels around 2,000 ppm. SNCR will enable this kiln to achieve the MACT 

floor emission level of 630 ppm. These other two kilns already equipped with SNCR will 

likely have to evaluate whether their current SNCR control system and operation will ensure 

an adequate margin of compliance with the MACT floor emission limit. 

An option of setting a BTF limit would require, at least for three kilns, two SNCR 

controls in series, or perhaps the addition of selective catalytic reduction (SCR). Neither of 

these options appears reasonable based on cost, energy impacts or environmental effects 

(e.g., increased solid waste and wastewater discharge). SNCR controls require a certain 

temperature range and degree of mixing to be effective. An SNCR is usually integrated into 

the combustion chamber process in a region where optimal reaction conditions exist. If too 

much reagent is added, then ammonia slip becomes an issue, where the control generates 

ammonia emissions due to unreacted reagent. Therefore, a series of SNCR systems would be 

more practical to reduce NOx emissions than simply injecting more reagent into one SNCR 

system. For such a system to work, the second SNCR would likely require reheating the flue 

gas to optimal temperature and providing turbulence for the reaction. As the first SNCR is 

installed in a portion of the combustion device that is integral to the combustion or heat 

recovery process, this second chamber would not be a necessary component but simply be an 

extra combustion chamber or reaction vessel requiring additional combustion to achieve 

reaction temperatures. Due to increased footprint and fuel consumption for the reheat 
chamber, this would result in control costs more than double what an SNCR system alone 

would cost. 

Selective catalytic reduction (SCR) is another technology that some combustion 

sources use to reduce NOx emissions; however, SCR is a catalyst technology that has not 

been demonstrated to work effectively on waste-burning kilns (or cement kilns) in the United 

States. We believe that SCR is not effective on waste-burning kilns due to difficulties 

operating SCR in applications where significant PM or sulfur loading in the gas stream 

exists. These two gas stream constituents can reduce catalyst activity and lower the resulting 

effectiveness of the SCR, through catalyst poisoning and blinding/plugging of active sites by 

ammonia sulfur salts (formed from sulfur in the flue gas with the ammonia reagent) and PM 

(Air Pollution Control Technology Fact Sheet, SCR, EPA–452/ F–03–032). 

We could not identify any other controls beyond SCR and SNCR, alone or in tandem, 

that reduce NOx emissions from waste-burning kilns. As discussed above, we believe that 

SNCR in series is unreasonable in cost and energy impacts and appears to be unproven in 

practice. We also believe that SCR is not currently demonstrated to successfully achieve 

reductions for kilns and may not be technically feasible. For these reasons, we do not believe 

a viable BTF option exists for reducing NOx emissions for the waste-burning kiln 

subcategory. 

3.4.5 SO2 Emissions 

 The less-stringent SO2 limit for waste-burning kilns is a result of the expanded 

inventory for this subcategory as discussed above. 

 We expect that existing waste-burning kilns will install scrubbers to meet the MACT 

floor emission limits for HCl and SO2. The only other option for further HCl and SO2

control is addition of a dry sorbent injection system, possibly in series with a wet scrubber. 

Our estimates for use of this control for existing waste-burning kilns yield a costeffectiveness for annual HCl and SO2 reductions of around $5,000 per ton, based on 95% 

control efficiency applied to SO2 control. Some uncertainty exists regarding the appropriate 

control system that some existing kilns would need to employ to meet a BTF limit, especially 

kilns that use ingredients with a high sulfur content. Also, our analysis is unable to account 

for potential costs at existing sources for additional scrubber water and spent sorbent. 

Therefore, we do not consider a BTF SO2 limit for existing waste-burning kilns to be 

reasonable. 

4.0 New Units 

 We do not expect any new CISWI units in the waste-burning kiln or ERU 

subcategories to come online in the near future. We anticipate that facilities installing new 

kilns or boilers will choose to combust materials that will prevent them from being subject to 

CISWI standards. However, regarding new kilns, we examined the analysis performed for 
the Portland cement NSPS (75 FR 54970), as those kilns are a similar source to the subject 

waste-burning kilns. In the Portland cement NSPS, the new source SO2 limit is 0.4 lb/ton 

clinker, which translates to 28 ppmvd @ 7% oxygen. For new sources, the estimated costeffectiveness of this emission limit ranges from $470 to $1430 per ton SO2. In that 

rulemaking, EPA determined that the 0.4 lb/ton clinker limit had reasonable costs, and limits 

beyond that level provided little environmental benefit (75 FR 54995). For new sources, 

adequate time and resources can be devoted to ensure control device equipment selection and 

sizing, as well as ancillary processes, such as waste water treatment and waste disposal, may 

be accounted for prior to commencing construction. We have therefore concluded that 

adopting the Portland cement NSPS limit is an acceptable BTF option for new waste-burning 

kilns (should any waste-burning kilns ever be constructed) and have established the 28 

ppmvd @ 7% oxygen limit as the SO2 limit for new waste-burning kilns. 

The incinerator and the small remote incinerator subcategories may see new units 

within the immediate future, primarily due to the replacement of old units. While facilities 

may find alternative disposal options are available, we are cognizant of the fact that, for these 

subcategories, there may be instances where alternative disposal options are unavailable, and 

a new incineration unit may be required. 

 

 For incinerators, we estimate new units will require a combination of the ACI 

system/FF, SNCR, and wet scrubbers to achieve the new source MACT floor limits. See 

Tables 9A and 9B of the CISWI cost memorandum (Reference 4) for a comparison of 

assumed baseline (without controls) concentrations and new source MACT floor limits for 

each pollutant. As discussed above for existing incinerators, no control technologies are 

demonstrated or reasonably cost-effective that we could consider at this time that would 

perform better or be more cost-effective than those being used to meet the new source 

MACT floor limits. Therefore, we have concluded that no BTF emission limits should be 

selected for new incinerators. 

 For small remote incinerators, we anticipate new sources will install an afterburner to 

achieve the CO limit and that the afterburner will also be equipped with low NOx burners, 

will require waste segregation for ferrous and non-ferrous metals and chlorinated plastics, 

and likely will require an ACI/FF system to meet the new source MACT floor limits. See 

Table 9C of the CISWI cost memorandum (Reference 4) for a comparison of assumed 

baseline (without controls) concentrations and new source MACT floor limits for each 

pollutant. Because many existing small remote incinerators are operated in cold climates 

were freezing temperatures are common, control technologies that require water for operation 

for this subcategory of unit are not feasible. As a result, no additional or better control 

technologies are available other than those being used to meet the new source MACT floor 

limits for the small remote incinerator subcategory. Therefore, we have concluded that no 

BTF emission limits should be selected for new small remote incinerators. 

REFERENCES
1. “CISWI Emission Limit Calculations for Existing and New Sources for the Reconsideration Final 

Rule” Memorandum from Eastern Research Group, Inc. to Toni Jones, U.S. Environmental 

Protection Agency. November 16, 2012. 

2. “CISWI Data Revisions since Reconsideration Proposal” Memorandum from Eastern 

Research Group, Inc. to Toni Jones, U.S. Environmental Protection Agency. November 16, 

2012. 

3. “Revised Floors without Kilns that Would have been CISWI Kilns Had the Solid Waste 

Definition Applied” Memorandum from Keith Barnett, U.S. Environmental Protection 

Agency, to Portland Cement Project Team. April 25, 2011. 

4. “Final Reconsideration Compliance Cost Analyses for CISWI Units” Memorandum from 

Eastern Research Group, Inc. to Toni Jones, U.S. Environmental Protection Agency. 

November 26, 2012.