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MEMORANDUM

TO: Anne Pope, EPA

FROM: Susan Fairchild, Project Lead

DATE: October 10, 2014

SUBJECT: Emissions Data Used in Residual Risk Modeling for Wool Fiberglass Production 

The purpose of this memorandum is to document the technical approach and rationale used to 

assign process information and hazardous air pollutant (HAP) emissions data for wool fiberglass 

manufacturing facilities. This work is being performed as part of the residual risk assessment for 

facilities that are subject to the National Emission Standards for Hazardous Air Pollutants for Wool 

Fiberglass Manufacturing (40 CFR 63, Subpart NNN).

I. Information Collection Request (ICR)

A voluntary information collection request (ICR) was sent out in March 2010 to wool fiberglass

facilities currently operating in the US. ICR responses from all the facilities were compiled in the 

project database and included information on facility processes, equipment, control devices, costs, 

and HAP emissions. Facility-specific production rate information was also included and was 

claimed as confidential business information (CBI), which resulted in much of the project database 

being treated as CBI. An additional ICR was sent out in November 2011 to all wool fiberglass 

companies. The second ICR focused primarily on glass-melting furnaces.

II. Emissions Testing

Emissions test data provided by the wool fiberglass industry varied widely by facility. The 

voluntary March 2010 ICR allowed companies to, in lieu of new testing, submit existing and well 

documented test data that was representative of current operations and used the recommended test 

methods. A number of facilities submitted existing test reports on one or more of the following

emission sources: glass melting furnaces, curing ovens, forming, and collection operations. In order 

to fill data gaps in existing data, new test data was also required. Companies were, however,

allowed to test a subset of facility operations, if the facilities were able to demonstrate that the 

tested subset was representative of the untested subset. Test results were typically presented as 

three test runs and provided in units of mass of pollutant per mass of production (e.g., lbs of 

HAP/ton of glass pulled). The November 2011 ICR required facilities that had not performed stack 

testing on their furnaces to test for particulate matter (PM), chromium, and hexavalent chromium.
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III. Source-Specific Emissions

A combination of new and existing test data was used to populate the wool fiberglass residual risk 

modeling file. The modeling file completed for the proposal of this rule was updated to include new 

facility emissions data received in response to the November 2011 ICR. The following sources and 

pollutants were included in the risk modeling. 

 Glass-Melting Furnaces

o Pollutants: Carbonyl Sulfide (COS), Antimony, Arsenic, Beryllium, Cadmium, 

Chromium III, Cobalt, Lead, Manganese, Nickel, Selenium, Chromium VI, 

Hydrogen Chloride (HCl), Hydrogen Fluoride (HF), and Mercury (Hg). 

 Bonded Lines:

o Curing Ovens: Formaldehyde, Phenol, Methanol

o Forming Operations: Formaldehyde, Phenol, Methanol

o Collection Operations: Formaldehyde, Phenol, Methanol

The wool fiberglass manufacturing source category operates several types of furnaces, including: 

oxy-fuel, air gas, cold top electric, electric steel shell furnaces, and proprietary melters. The 

furnaces are also equipped with several different control devices, including: electrostatic 

precipitators (ESPs), fabric filters, baghouses, and caustic injection. 

Forming, curing, collection, and cooling operations vary facility to facility. The processes operated 

vary on whether a facility makes a bonded wool fiberglass product. Some facilities do not operate a 

collection process and most facilities route a combination of these operations into one or more 

stacks. It is common industry practice for these operations to share control devices, including: air 

filters, incinerators, scrubbers, ESPs or a combination of these.

Using the glass pull rates (generally given in tons of glass pulled/day) that each facility provided in 

their ICR responses and the source emission rates (lb/ton) from emission testing, annual emissions 

(tpy) were calculated for each pollutant and emission source. A sample calculation for annual 

formaldehyde emissions from a curing oven is provided as follows.

Sample Calculation for Annual Formaldehyde Emissions from Curing Oven A (tpy): 

(Average of all formaldehyde test runs for curing oven A, lb formaldehyde/ton) x (Production 

rate of line A, ton/day) x (365 days/yr) ÷ (2000 lb/ton)

These calculations were completed for each source and each pollutant listed above. For sources that 

were not tested for a given pollutant, an average emission rate (lb/ton melt) for each missing 

pollutant was calculated from similar sources at other facilities (or at the same facility if available)

and then multiplied by the production rate the facility listed in their ICR response for the untested 

source. If a source was tested for only one binder HAP pollutant (i.e., a curing oven was tested for 

formaldehyde but not phenol or methanol) the ratio of the binder HAP emission rates (lb/ton) at a 

similar source was applied to the binder HAP tested, in order to estimate the emission rates of the 

missing pollutants. Although the majority of facilities submitted chromium and hexavalent 
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chromium testing, this approach was also taken for a few facilities that tested a furnace for total 

chromium (Cr), but not for hexavalent chromium (Cr+6). The ratio of the emission rates of total 

chromium to hexavalent chromium for a similar source was applied to the Cr results in order to 

calculate the lb/ton emission rate of Cr+6. An example scenario where HAP ratios were used 

follows:

Scenario 1: The furnaces at facility A and facility B are similar and have comparable control 

devices and the facilities provided the following results: 

Facility A Furnace Results:

Cr = 1.2E-4 lbs Cr/ton of glass pulled

Cr+6 = 1.05E-4 lbs Cr+6/Ton of glass pulled

Facility B Furnace Results:

Cr = 8.5E-5 lbs Cr/ton of glass pulled

Cr+6 = No results provided.

Facility B Cr+6 Emission Rate (lb Cr+6/ton of glass pulled) =

(Ratio of Cr + 6 to Cr emission rate at Facility A) × (Cr emission rate Facility B)

Where:

Ratio of Facility A Cr + 6 to Cr =

1.05e

4

1.2e

4 = 0.875

Facility B Cr+6 Emission Rate (lb Cr+6/ton of glass pulled) =

0.875 ×

8.5e

−5

lb Cr

ton glass pulled at Facility B =

7.44e

−5

lb Cr + 6

ton glass pulled

The ratio approach to estimate emissions was only used in instances where testing for similar 

sources existed and a facility provided emission data for only one of the three binder HAP 

(formaldehyde, phenol, and methanol) for a bonded emission source or to find Cr+6 emission rates 

when a facility only provided testing for Cr.

If a furnace was not tested for any pollutant, the emission rate (lb/ton) from a similar furnace with 

similar controls was used. If there were several furnaces that were similar to the furnace that was 

not tested, the average emission rates and testing parameters of all the similar furnaces (for each 

pollutant) were used. 

For each source, stack heights, diameters, and coordinates were compiled from ICR responses and 

then sent to each facility for confirmation. Once, a facility confirmed the stack parameters and 

coordinates were correct, they were used as inputs in the modeling file. Testing parameters

(velocity, temperature, and flow rates) were based on data from emission tests. If a source did not 

provide emission test data, the velocity and temperature from the emission test used to estimate the

emission rate for the untested source was used and the flow rate was calculated based on the stack 
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diameter and the velocity. Stack configuration and control devices were taken into account when 

substitute emission rates were used for sources that did not have emissions testing or when binder 

HAP ratios were used on sources that only tested for one pollutant. 

IV. Chromium and Mercury Speciation

Consistent with the HAP list in the Clean Air Act, metals such as chromium and mercury may be 

reported in the ICR under different names, including chromium, chromium compounds, mercury, 

and mercury compounds. Facilities that submitted chromium data reported it as total chromium 

and/or hexavalent chromium emissions. Hexavalent chromium emissions were not speciated further 

and were modeled as chromium VI. Total chromium was speciated to Chromium III by subtracting 

chromium VI emissions from total chromium. In some cases chromium VI emissions were larger 

than total chromium. For these circumstances it was assumed that all chromium emissions were 

hexavalent chromium and chromium III emissions were “0”. Facilities that submitted mercury data 

provided it as total mercury; the following table summarizes the speciation factors that were applied 

to mercury emissions. 

Table 1. Speciation Factors for Mercury

POLLUTANT_CODE POLLUTANT_DESCRIPTION HAP_CATEGORY_NAME % of total

200 Elemental Gaseous Mercury Mercury Compounds 80%

202 Particulate Divalent Mercury Mercury Compounds 10%

201 Gaseous Divalent Mercury Mercury Compounds 10%

V. Emission Process Group Assignment

In order to assign risk results to specific operations within wool fiberglass facilities, Emission 

Process Groups are assigned to SCCs. For furnaces, the emission group assigned was based on 

furnace type, which included; oxy-fuel, electric steel shell, cold-top electric, air-gas, and pot and 

marble, The other emission groups modeled consisted of forming, collection, curing, and cooling 

processes. Combinations of these processes were used as emission process groups when one or 

more of these processes shared a common stack. 

VI. QA/QC

Companies were sent aerial views of each plant and asked to label and provide coordinates for each 

stack. They were also asked to review their stack configurations for each emission unit. All wool 

fiberglass facilities answered the request and provided labeled aerial views along with coordinates. 

EPA also conducted an extensive review of the locational coordinates for all facilities in the wool 

fiberglass source category. Locations were visually reviewed using Google Earth or ArcExplorer. 

Adjustments were made for coordinates based on these visual evaluations. 

Emissions data, stack parameters, and facility information was also reviewed for each unit and 

pollutant at a given plant. Production rates for each unit were checked with the responses provided 

in the ICR. After risk modeling was conducted, one change was made to the stack height of the K2 

furnace at the CertainTeed Kansas City facility due to an error in the stack parameter data they 
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provided in their ICR response. This stack was adjusted and remodeled once the facility confirmed 

the correct stack height. 

VII. Allowable Emissions

The analysis of allowable emissions for the Wool Fiberglass Manufacturing source category was 

largely focused on emissions of chromium compounds and formaldehyde, which we considered the 

most important HAP emitted from this source category. 

To estimate emissions at the MACT-allowable level from process stacks, we averaged actual 

formaldehyde emission rates of manufacturing lines and compared those values to the maximum 

level allowed by the existing MACT standard (i.e., 1.2 or 0.8 pounds per ton of glass pulled for 

formaldehyde). Based on this analysis, the average wool fiberglass manufacturing facility is

emitting formaldehyde at a level approximately 3 times lower than allowable. Therefore, to develop 

the MACT-allowable emissions the actual stack emissions were multiplied by 3 for formaldehyde, 

phenol and methanol. 

MACT-allowable emissions for hexavalent chromium in the Wool Fiberglass Manufacturing 

category are equal to actual emissions because there is currently no emission limit for hexavalent 

chromium.

VIII. Post-MACT Emissions

For the post-MACT risk assessment for the Wool Fiberglass Manufacturing source category, we 

used the modeling file containing actual emissions for major and area source facilities as a starting 

point. We then found all emission sources that were not meeting the existing source limits (in pound 

per ton) proposed in the 2014 supplemental proposal listed below. 

Table 2. Proposed Emission Limits for Existing Wool Fiberglass Sources

Emission Source / 

Subcategory Pollutant

Proposed Limit 

(lb/ton)

Glass-fired furnace Chromium 6.0E-5

Rotary Spin 

Manufacturing Line

Formaldehyde 0.19

Phenol 0.26

Methanol 0.83

Flame Attenuation 

Manufacturing Line

Formaldehyde 5.6

Phenol 1.4

Methanol 0.50

All the sources that were above the limit for any pollutant listed in Table 2 had their emission rate 

reduced down to the proposed pound per ton limit. This pound per ton value was then multiplied by

the production rate of the source to get an annual emission rate (see Section III). For example, if a 

facility had a rotary spin bonded line with an actual formaldehyde emission rate of 0.32 pounds per 

ton, for the post-MACT risk assessment, those emissions were brought down to the proposed 

formaldehyde limit of 0.19 pounds per ton and then multiplied by the production rate. This was 

done on a pollutant-by-pollutant basis, meaning that if a source was exceeding the limit for one 
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pollutant but not others, only the pollutant that was exceeding the emissions limit was lowered. For 

chromium, since the limit is based on chromium compounds and not hexavalent chromium, 

facilities with furnaces that exceed the proposed chromium limit in Table 2 were lowered to the 

emission rate and then speciated into chromium III and hexavalent chromium based on the ratios of 

their actual emissions testing. The remaining sources that were not above the limits in Table 2 were 

modeled at their actual emission levels. 

The post-MACT risk assessment also conservatively did not remove binder HAP (formaldehyde, 

phenol, and methanol) emissions from the facilities/sources that have stopped using phenolformaldehyde binders. For example, if a facility tested for formaldehyde in 2010 but informed EPA 

that they have or will stop using formaldehyde binders, the binder HAP emissions were not 

removed from the post-MACT modeling file and were modeled at actual emission levels. Table 3 

summarizes the total industry wide emissions for the actual and post-control assessments for 

chromium, formaldehyde, phenol, and methanol emissions.

Table 3. Summary of Total Annual Emissions for Wool Fiberglass Production

HAP Actual Emissions

(TPY)

Post Control Emissions 

(TPY)

Chromium (III) compounds 0.039 0.016

Chromium (VI) compounds 0.36 0.097

Formaldehyde 618 179

Phenol 403 98

Methanol 819 232