1

Date: February 7, 2013

Subject: Environmental and Energy Impacts for Wool Fiberglass Manufacturing NESHAP –

Proposed RTR Amendments

40 CFR 63, Subpart NNN – 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 residual risk and technology review (RTR) amendments to 40 CFR 63, 

Subpart NNN - Wool Fiberglass Manufacturing. 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 wool fiberglass manufacturing facilities 

will need to install a caustic scrubber to meet the proposed chromium compound emission limit for

Subpart NNN. 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)1194 582

Percent of scrubber water from recycled facility wastewater160 60

Total non-recycled water necessary (gallons per year)241M 123 M

Total scrubber effluent rate (gpm)16.1 6.1

Percent scrubber wastewater recycled150 50

Total wastewater generated (gallons per year)31.6M 4.8M

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

(1)Estimates from ICR responses. (2) Calculation: 194 (gpm) x 60 (min/hr) x 8760 (hrs/yr) x (100%-60%). (3) Calculation: 6.1 

(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 26,000 acfm, the average 

estimated pressure drop for the scrubber is 9.8 inches of water, and the average estimated liquid flow is 

194 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)  (26,000)  (9.8)

0.7

= 43 h

 =

(0.746)  (2.52  10)  (60)  (194)

0.7

= 3 h

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

46

h

 8,760

h



= 403,000 /
3

This results in 1.2 million kWh per year (1,200 megawatts) 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: 

1,200,000 h 

0.0034

h

= 4,100 

Using the values in Table 2 we estimated CH4, N20, and CO2, emissions as 4.1 kg/yr (9 lbs/yr), 0.41 

kg/yr (0.9 lbs/yr), and 217,000 kg/yr (478,000 lbs/yr), respectively. We then calculated the CO2eq 

emissions based on the global warming potentials above as follows:







= 478,000





+ 21  9

 

  + (310  0.9

 



)

This results in 478,500 lbs CO2eq per year for all three scrubbers.