1

MEMORANDUM 

TO: Amy Hambrick, U.S. EPA, Sector Policies and Programs Division/Natural 

Resources and Commerce Group 

FROM: Amber Allen and Danny Greene; Eastern Research Group, Inc.

DATE: June 2010

SUBJECT: Secondary Impacts of Control Options for the Sewage Sludge Incineration Source 

Category 

1.0 INTRODUCTION 

 This memorandum presents the secondary impacts associated with control devices used 

to comply with the proposed standards for existing and new sewage sludge incineration (SSI) 

units. Secondary impacts result from the consumption of fuel, water, and electricity and 

generation of solid wastes by control devices. 

 Section 2.0 presents the background for the proposed standards. Section 3.0 presents the 

secondary impact estimates associated with control devices necessary for two scenarios: (1) all 

SSI units comply with proposed standards, and (2) only large entities comply with the proposed 

standards and small entities divert their waste to landfills. This memorandum focuses only on 

secondary impacts associated with control devices. Additional air impacts resulting from small 

entities choosing to landfill are discussed in a separate memorandum.1 Section 4.0 summarizes 

the estimated secondary impacts that would result from the compliance of new units expected to 

come online in the next five years. Section 5.0 summarizes the emissions resulting from 

increased fuel and electricity requirements for the control options.

2.0 BACKGROUND 

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

Act (CAA), is required to regulate emissions of 9 pollutants and opacity from existing sewage 

sludge incineration (SSI) units. The 9 pollutants are: hydrogen chloride (HCl), carbon 

monoxide (CO), lead (Pb), cadmium (Cd), mercury (Hg), particulate matter (PM), dioxins/furans 

(CDD/CDF), nitrogen oxides (NOx), and sulfur dioxide (SO2). The CAA requires EPA to 

determine the maximum achievable control technology (MACT) for each category or 

subcategory of sources. The SSI source category comprises two subcategories: multiple hearth 

incineration units (MH) and fluidized bed incineration units (FB). To determine the MACT for 

each subcategory, EPA must first determine the minimum stringency “floor” requirements. 

Development of the MACT floors for SSI units is described in a separate memorandum.2 An 

analysis of beyond-the-floor options was also conducted, in which three different control options 

were evaluated. 
2

• Option 1 is the MACT floor level of control for the two subcategories developed for 

existing SSI units, MH units and FB units. 

• Option 2 is the same as Option 1, with the addition of activated carbon injection (ACI) 

for additional Hg and CDD/CDF emissions reduction from MH units. 

• Option 3 is the same as Option 2, with the addition of an afterburner on all MH units 

for additional control of CO. 

3.0 SECONDARY IMPACT ESTIMATES FOR EXISTING UNITS 

 To comply with the control options, facilities may need to install the following types of 

control devices on SSI units: 

• Fabric filters (FF) to reduce Cd, Pb, and PM emissions, 

• Packed-bed scrubbers (PBS) to reduce HCl and SO2 emissions, 

• ACI systems to reduce CDD/CDF and Hg emissions, and 

• Afterburners (AB) to reduce CO and organic compound emissions. 

 Electricity is required to operate the pumps and fans associated with FF and PBS 

systems. Also, water and subsequent wastewater disposal are required to operate PBS systems. 

Fabric filter and ACI systems require a method to dispose of the dust produced from the systems. 

Additionally, ACI requires the use of activated carbon. Supplemental fuel (i.e., natural gas) is 

required to operate afterburners for MH SSI units. 

 Table 3-1 shows, for each of the control options, the estimated secondary impacts for the 

FB and MH subcategories for the case where all entities comply with the control option. Table 3-

2 shows, for each of the control options, the estimated secondary impacts for the case where 

small entities landfill and large entities comply. 

 The algorithms used in the cost analysis provide annual cost estimates for electricity, 

water, carbon requirements, and supplemental fuel as itemized components of the annual costs 

for the control device.1 These cost elements for the control devices anticipated to be installed to 

comply with the proposed standards were then summed up to provide an estimate of the overall 

costs of electricity, water, activated carbon, and supplemental fuel. To estimate the secondary 

impact components (e.g., electricity, water, dust), the itemized annual cost of each component 

was divided by the unit price of the component used by the algorithm. 
3

Table 3-1. Secondary Impacts for Control Options: All Units Comply 

Control 

Option 

Subcategory 

Controls 

Required for 

Compliance 

Electricity 

Required 

(MWhr/yr) 

Water 

Required 

(gal/yr) 

Activated 

Carbon 

Required 

(ton/yr) 

Dust 

Produced 

(ton/yr) 

Supplemental 

Fuel 

(ft3 natural 

gas/yr) 

FB units FF, PB, ACI 13,750 31,983,667 1,711 1,762 - 

Option 1 MH units FF, PB, ACI 20,088 314,409,712 35 347 - 

Total FF, PB, ACI 33,839 346,393,379 1745 2109 - 

FB FF, PB, ACI 13,750 31,983,667 1,711 1,762 - 

Option 2 MH FF, PB, ACI 20,088 314,409,712 9,725 10,037 - 

Total FF, PB, ACI 33,839 346,393,379 11,436 11,799 - 

FB FF, PB, ACI 13,750 31,983,667 1,711 1,762 - 

MH FF, PB, ACI, 

AB 20,088 314,409,712 9,725 10,037 1,686,090,925 Option 3 

Total FF, PB, ACI, 

AB 33,839 346,393,379 11,436 11,799 1,686,090,925 

Table 3-2. Secondary Impacts for Control Options: Small Entities Landfill 

Control 

Option 

Subcategory 

Controls 

Required for 

Compliance 

Electricity 

Required 

(MWhr/yr) 

Water 

Required 

(gal/yr) 

Activated 

Carbon 

Required 

(ton/yr) 

Dust 

Produced 

(ton/yr) 

Supplemental 

Fuel 

(ft3 natural 

gas/yr) 

FB units FF, PB, ACI 10,662 21,432,013 1,381 1,421 - 

Option 1 MH units FF, PB, ACI 18,548 297,979,345 35 319 - 

Total FF, PB, ACI 29210 319,411,358 1,416 1,740 - 

FB FF, PB, ACI 10,662 21,432,013 1,381 1,421 - 

Option 2 MH FF, PB, ACI 18,548 297,979,345 8,674 8,958 - 

Total FF, PB, ACI 29210 319,411,358 10,055 10,379 - 

FB FF, PB, ACI 10,662 21,432,013 1,381 1,421 - 

MH FF, PB, ACI, 

AB Option 3 18,548 297,979,345 8,674 8,958 1,550,033,242 

Total FF, PB, ACI, 

AB 29210 319,411,358 10,055 10,379 1,550,033,242 
4

4.0 SECONDARY IMPACT ESTIMATES FOR NEW UNITS 

 As discussed in the new source analysis memorandum, EPA expects that two new FB 

units would come online in the next five years4. Estimations of the secondary impacts resulting 

from the pollution controls implemented for these units were calculated using the same 

methodology described for existing units in Section 3.0. 

 Table 4-1 shows the estimated values for secondary impacts for the two new FB units. 

Table 4-1. Secondary Impacts: New Units

Subcategory 

Controls 

Required for 

Compliance 

Electricity 

Required 

(MWhr/yr) 

Water 

Required 

(gal/yr) 

Activated 

Carbon 

Required 

(ton/yr) 

Dust 

Produced 

(ton/yr) 

Supplemental 

Fuel 

(mmcf natural 

gas/yr) 

New Units FF, PBS, 

ACI, AB 1,348 18,267,411 97 100 25 

5.0 SECONDARY AIR POLLUTANT IMPACTS 

 Emission factors from EPA’s Egrid5 database were used to calculate emissions resulting 

from the electricity required for additional control devices, and emission factors from EPA’s AP42 emission factor document6

 were used to calculate emissions resulting from the combustion of 

additional fuel for afterburners. Increased electrical use from the control options will require 

additional fuel to be burned in power plants, resulting in emissions of CO2 and criteria pollutants, 

such as SO2, NOx, and CO. Emissions of these pollutants (caused by increase in electricity) were 

estimated using EPA’s Egrid database.5 The Egrid database summarizes emissions of criteria 

pollutants on a per electrical usage basis (lb emitted per MW-hr), on a national average or state 

average basis. For this analysis the national average was used. Option 3 also requires 

afterburners to be applied to all MH units, resulting in supplemental fuel requirements, such as 

natural gas, to run the afterburner. The afterburner algorithm indicates the amount of fuel 

needed by each unit. To estimate emissions from combustion of natural gas, emission factors 

from EPA’s AP-42 emission factor document were used.6 Tables 5-1 summarizes the resulting 

emissions of CO2, CO, NOx, and SO2 from combustion of natural gas supplemental fuel and 

increase electricity usage for the three control options analyzed for existing sources. Table 5-2 

shows the results for new sources, and table 5-3 shows results for combined existing and new 

sources. Table 5-4 shows the Egrid and AP-42 emission factors used for the calculations.
5

Table 5-1. Secondary Air Pollutant Impacts: Existing Units

All Units Comply 

Electricity Requirements and Emissions 

(tons/yr)* 

Supplemental Fuel Requirements and Emissions 

(tons/yr)* 

Total Second

(ton

Option 

MWh per yr 

CO2

Emitted 

NOx

Emitted 

SO2 

Emitted 

ft3 Natural Gas 

per yr 

CO2

Emitted 

CO 

Emitted 

NOx 

Emitted 

CO2

Emitted 

CO 

Emitted 

1 33,839 22,500 32.8 89.0 - - - - 22,500 - 2 33,839 22,500 32.8 89.0 - - - - 22,500 - 3 33,839 22,500 32.8 89.0 1,686,000,000 101,200 70.8 84.3 123,700 70.8 

Small Units Landfill 

Electricity Requirements and Emissions 

(tons/yr)* 

Supplemental Fuel Requirements and Emissions 

(tons/yr)* Total Secondary E

Option 

MWh per yr 

CO2

Emitted 

NOx

Emitted 

SO2

Emitted 

ft3 Natural Gas 

per yr 

CO2

Emitted 

CO 

Emitted 

NOx

Emitted 

CO2 

Emitted 

CO 

Emitted 

1 29,210 19,400 28.3 76.8 - - - - 19,400 - 2 29,210 19,400 28.3 76.8 - - - - 19,400 - 3 29,210 19,400 28.3 76.8 1,550,000,000 93,000 65.1 77.5 112,400 65.1 

*Emissions estimated based on emission factors listed in Table 5-4.
6

Table 5-2. Secondary Air Pollutant Impacts: New Units 

Electricity Requirements and Emissions 

(tons/yr)* 

Supplemental Fuel Requirements and Emissions 

(tons/yr)* Total Secondary Emi

MWh per yr CO2 Emitted NOx Emitted SO2 Emitted ft3 Natural Gas per yr CO2 Emitted CO Emitted NOx Emitted CO2 Emitted CO Emitted 

Em

1,348 896 1.31 3.54 24,514,485 1,470 1.03 1.23 2,370 1.03 

*Emissions estimated based on emission factors listed in Table 5-4.

Table 5-3. Secondary Air Pollutant Impacts: Combined Existing and New Units

Total Secondary Emissions (tons/yr)

All Units Comply Small Units Landfill 

Option 

CO2

Emitted 

CO 

Emitted 

NOx

Emitted 

SO2 

Emitted 

CO2

Emitted 

CO 

Emitted 

NOx

Emitted 

S

Em

1 24,900 1.03 35.3 92.5 21,782 1.03 30.8 82 24,900 1.03 35.3 92.5 21,782 1.03 30.8 83 126,000 71.8 119.6 92.5 114,784 66.1 108.3 8

Table 5-4. Emission Factors

Electricitya Natural Gasb Pollutant (lb/MWh) (lb/106 scf) (lb/ft3) (ton/ft3) 

CO2 1,329 120,000 0.12 0.00006 CO - 84 8E-05 4.2E-08 NOX 1.9366 100 0.0001 5E-08 SO2 5.2589 - - - 

a. National emission factors from Egrid5 for EGUs. 

b. Natural gas emission factors from AP-42.6
7

REFERENCES 

1. Cost and Emission Reduction of the MACT Floor Level of Control. Memorandum from 

Amber Allen and Roy Oommen, Eastern Research Group, Inc. to Amy Hambrick, U.S. 

Environmental Protection Agency. June 2010. 

2. MACT Floor Analysis for the Sewage Sludge Incinerator Source Category. 

Memorandum from Roy Oommen, Eastern Research Group, Inc. to Amy Hambrick, U.S. 

Environmental Protection Agency. June 2010. 

3. Analysis of Beyond the Maximum Achievable Control Technology (MACT) Floor 

Controls for Existing SSI Units. Memorandum from Roy Oommen, Eastern Research 

Group, Inc. to Amy Hambrick, U.S. Environmental Protection Agency. August 2010. 

4. Estimation of Impacts for New Units Constructed Within Five Years After Promulgation 

of the SSI NSPS. Memorandum from Roy Oommen, Eastern Research Group, Inc. to 

Amy Hambrick, U.S. Environmental Protection Agency. June 2010. 

5. EPA eGRID database eGRID2007 Version 1.1. Year 2005 summary tables located at 

www.epa.gov/cleanenergy/documents/egridzips/eGRID2007V1_1_year05_SummaryTab

les.pdf 

6. U.S. Environmental Protection Agency, 1995. Compilation of Air Pollutant Emission 

Factors (AP-42), Fifth Edition, Volume 1: Stationary and Point Sources, Chapter 1: 

External Combustion Sources.