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Date: March 5, 2013

Subject: Secondary (Environmental and Energy) Impacts for Wool Fiberglass Manufacturing 

NESHAP – Area Sources

40 CFR 63, Subpart NN – Supplemental Proposal

EPA Contract No. EP-D-11-084; EPA Work Assignment No. 1-07

RTI Project No. 0213199.001.007

From: Cindy Hancy

Dave Reeves

To: Susan Fairchild, EPA/OAQPS/SPPD/MMG

I. Introduction

The purpose of this memorandum is to document the estimated environmental and energy impacts 

associated with the proposed National Emission Standard for Hazardous Air Pollutants (NESHAP) 40 

CFR 63, Subpart NN - Wool Fiberglass Manufacturing for area sources. Secondary impacts include the

solid waste, water, wastewater generated and the electricity required to operate air pollution control 

devices, as well as, the resultant greenhouse gas (GHG) emissions from controls or work practices

required by the NESHAP. 

II. Water, Wastewater, and Solid Waste Impacts

The EPA estimates that three gas-fired glass-melting furnaces at area source wool fiberglass 

manufacturing facilities will need to install a caustic scrubber to meet the proposed chromium 

compound emission limit for Subpart NN. The water required to operate the scrubber and the solid and

wastewater generated by the effluent were calculated for the three units. The 2010 information 

collection request, sent to all wool fiberglass manufacturers, requested that facilities provide detailed 

information for each control device. For scrubbers, facilities were asked to provide gas and water flow 

rates, liquid to gas ratios, pressure drop, wastewater generation, and several other operating parameters

for each of their existing scrubbers. Appendix 1 contains a complete list of all the information EPA 

requested for scrubbers, however, because the majority of facilities submitted this information as

confidential business information (CBI), facility responses are not included in this memo. The EPA 

compiled these ICR responses, and using the operating parameters (also considered CBI) of the three 

furnaces estimated to need caustic scrubbers, estimated the amount of water needed to operate the 

scrubbers, as well as the wastewater and solid waste that would be generated. The calculated impact 

estimates are provided in Table 1. 
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Table 1. Estimated Water and Solid Waste Impacts for Caustic Scrubbers on Furnaces

Impacts per facility Total industry impacts 

Water flow rate into scrubber (gpm)1155 465

Percent of scrubber water from recycled facility wastewater160 60

Total non-recycled water necessary (gallons per year)233M 99 M

Total scrubber effluent rate (gpm)14.9 4.9

Percent scrubber wastewater recycled150 50

Total wastewater generated (gallons per year)31.3M 4.8M

Total solid waste collected (lb/yr)1468,000 1.4M

 (1)Estimates from ICR responses. (2) Calculation: 155 (gpm) x 60 (min/hr) x 8760 (hrs/yr) x (100%-60%). (3) Calculation: 4.9 (gpm) x 

 60 (min/hr) x 8760 (hrs/yr) x (100%-50%).

III. Energy Impacts and GHG Emissions from Electricity Usage

The amount of electricity required to operate a control device (i.e., caustic scrubber) was calculated 

using the information summarized in Table 1. The electricity costs associated with operating a scrubber 

derive from fan requirements to overcome the pressure drop in the column, ductwork, and other parts of 

the control system, and pump requirements to re-circulate the water. According to the EPA’s Air 

Pollution Control Cost Manual, fan and pump energy requirements can be calculated by using equation 

3-1 and 3-2, respectively.

Equation 3-1

 =

1.17  10  



Equation 3-2

 =

0.746  2.52  10    



Where Gi is the gas flow rate entering the scrubber, P is the total pressure drop, Li is the liquid 

flow rate entering the scrubber, P is the pressure of the pump which we assume to be 60 ft of 

water and e is the efficiency of the device. 

The average gas flow rate entering the scrubber for the three furnaces is 17,000 acfm, the average 

estimated pressure drop for the scrubber is 7.8 inches of water, and the average estimated liquid flow is 

155 gallons per minute. Using equations 3-1 and 3-2 and an estimated efficiency of 0.7 for both the 

pump and the fan, we estimated the energy required to be 43kWh for the fan, and 3kWh for the pump. 

 =

(1.17  10)  (17,000)  (7.8)

0.7

= 22 h

 =

(0.746)  (2.52  10



)  (60)  (155)

0.7

= 2 h

Assuming operating hours is 8,760 per year, the total annual energy required for each scrubber is: 
3

24 

h

 8,760

h



= 210,000 h/

This results in 631,000 kWh per year for all three scrubbers. We used the natural gas emission factor (in 

kilograms [kg]/MMBtu) from the General Stationary Fuel Combustion Sources subpart (40 CFR part 98, 

subpart C) of the Greenhouse Gas Reporting Rule (listed in Table 2) to estimate the secondary emissions

for CO2, CH4, and N2O. 

Table 2. Emission Factors from General Stationary Fuel Combustion Sources 

(40 CFR part 98, subpart C)

Fuel

Default CH4

emission factor

(kg CH4/MMBtu)

Default N2O 

emission factor

(kg N2O/MMBtu)

Default CO2

emission factor

(kg CO2/MMBtu)

Natural Gas 1.0 × 10−03 1.0 × 10−04 53.02

Global warming potentials of 1 for CO2, 21 for CH4, and 310 for N2O (from Table A-1 to subpart A of 

part 98) were used to estimate CO2 equivalent emissions (CO2eq). First we converted kWh to MMBtu as 

follows: 

631,000 h 

0.0034

h

= 2,100 

Using the values in Table 2 we estimated CH4, N20, and CO2, emissions as 2.1 kg/yr (5 lbs/yr), 0.21 

kg/yr (0.5 lbs/yr), and 111,000 kg/yr (245,000 lbs/yr), respectively. We then calculated the CO2eq 

emissions based on the global warming potentials above as follows:







= 245000





+ 21  5

 

  + (310  0.5

 



)

This results in 245,300 lbs CO2eq per year for all three scrubbers. 
Appendix 1. ICR Questionnaire for Scrubbers

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FORM C-2

AIR POLLUTION CONTROL

II. Scrubber - NA

 For each scrubber: Scrubber 1 Scrubber 2

 Process line(s) (identification name/number)

 Equipment/process(es) controlled. Include emission point designations (e.g., 

E3, E4 from plot plan)

 Latitude (decimal degrees, six decimal places)

 Longitude (decimal degrees, six decimal places)

 Stack or vent height (units)

 Stack or vent diameter (units)

 Manufacturer and model

 Date of original installation

 Type (e.g., venturi, orifice)

 Gas flow rate to scrubber (acfm @ °F)

 Inlet gas temperature (°F)

 Outlet gas temperature (°F)

 Inlet grain loading (gr/dscf)

 Outlet grain loading (gr/dscf)

 Average stack opacity (%)

 Water flow rate to scrubber (gpm)

 Percent of scrubber water from recycled wastewater

 Source of scrubbing water and type of pretreatment. Substance(s) added as 

part of pretreatment and amount used (gpm or lbs/hr)

 HAP composition of wastewater (mg/L)

 Concentration (mg/L) of dissolved and suspended solids in scrubbing water

 Scrubbing water temperature (°F)

 Liquid/gas ratio (gal/103acfm)

 Pressure drop across scrubber (in. H2O gauge)

 Amount of wastewater generated (gpd)

 Amount of wastewater recycled (gpd)

 Amount of wastewater disposed of (gpd)

 Method of wastewater disposal

 Quantity of solid waste collected (lbs/yr)

 Quantity of solid waste recycled (lbs/yr)

 Quantity of solid waste disposed of (lbs/yr)

 Method of solid waste disposal

 Vendor guarantee on scrubber efficiency (attach copy)

 Nature and frequency of preventive maintenance procedures

 Problems experienced with control device within the last five years; how were 

problems solved?

 Continuous monitoring method(s) used to monitor scrubber performance, 

including parameters monitored