SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT 

FINAL DRAFT STAFF REPORT

August 19, 2010 

Proposed Amendments to Rule 4354 (Glass Melting Furnaces) 

Prepared by: Joven R. Nazareno, Senior Air Quality Engineer 

Sandra Lowe-Leseth, Air Quality Engineer 

Reviewed by: George Heinen, Supervising Air Quality Engineer 

Errol Villegas, Manager, Strategy and Incentives 

Samir Sheikh, Director, Strategy and Incentives 

I. SUMMARY 

A. Reasons for Rule Development and Implementation 

The District Governing Board adopted amendments to Rule 4354 at the October 2008 

Public Hearing that established more stringent emissions limitations for glass melting 

furnaces. During that hearing, there was significant discussion regarding concerns 

raised by affected sources about the information used by the District to evaluate the 

potential cost impacts and cost-effectiveness of the proposed rule amendments. As a 

result, the Governing Board provided additional direction to staff to re-evaluate the 

impact of the rule amendments and report back to the Board within 18 months of 

adoption to accommodate additional cost information provided by affected businesses. 

Based on staff’s re-evaluation of the adopted rule amendments and recommendations 

made at the April 15, 2010 Public Hearing, the Board directed staff to develop and 

propose future rule amendments to Rule 4354 incorporating short-term emission 

limitation flexibility for flat glass manufacturing facilities committed to achieving more 

stringent long-term emissions limitations earlier than would otherwise be required by the 

rule. This direction was based on new information submitted by Pilkington North 

America with regard to meeting the interim Tier 3 oxides of nitrogen (NOx) emission 

limits for flat glass manufacturers by the January 2011 compliance date in the rule. 

The Tier 3 and the Tier 4 NOx emission limits will require installation of advanced and 

expensive emission control systems and would necessitate major changes to existing 

furnaces. District staff agrees with the glass manufacturers that the most appropriate 

time to make changes to the furnace in order to install emission control equipment is 

when the furnace is down for periodic repairs to the furnace’s insulating refractory. This 

periodic maintenance is commonly known in the industry as “cold repair” or “rebuild”. 

Flat glass furnaces can operate for 15 years or more between rebuilds and operate 
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continuously between rebuilds. Therefore, the window of opportunity for cost-effective 

installation of emission control equipment is very narrow. Installing emission control 

systems prior to the scheduled furnace rebuild would incur additional significant costs 

due to lost revenue because the furnace is not producing any glass products during the 

installation of the required controls and subsequent start-up periods which normally take 

several months. 

As an additional factor for consideration, no one could have anticipated the depth or the 

length of the current economic recession. Generally, the two main consumers of flat 

glass are the building trades (windows for homes and buildings) and the automotive 

market (windows and windshields for cars and trucks). Both of these market sectors 

have been particularly hard-hit by the recession and the slowdown in these markets has 

affected their suppliers, including flat glass manufacturers. 

Since October 2008 when the last amendments were adopted for the rule, Pilkington 

has experienced a significant economic downturn that forced a delay in their planned 

furnace rebuild and the associated installation of emission controls. As a result, 

Pilkington’s current facility cannot meet the Tier 3 NOx limit by the 2011 deadline 

without installation of additional emission control equipment in conjunction with a 

furnace rebuild. The Tier 3 NOx limit provides no real transition period because there is 

no intermediate technology that will allow Pilkington’s furnace to achieve the Tier 3 NOx 

limit, other than the technology required to achieve the lower Tier 4 limit. 

To address this concern, the District proposes to incorporate short-term emission 

limitation flexibility for flat glass manufacturing facilities committed to achieving more 

stringent long-term emissions limitations earlier than would otherwise be required by the 

rule. This ”Tier 4 early enhanced” option would achieve additional early reductions by 

complying with "Tier 4 enhanced" emissions limitations four years earlier than would 

otherwise be required by the rule in return for flexibility in meeting the interim Tier 3 

emissions limitation. 

There are three flat glass manufacturers in the Valley. Besides Pilkington, the other two 

facilities are currently meeting the Tier 3 NOx emission limit and have permit conditions 

that would prevent them from increasing their NOx emissions above the Tier 3 limit if it 

were to be removed from the October 2008 version of the rule. 

Staff finds that removing the Tier 3 limit and requiring the lowest NOx limit four years 

earlier for a single flat glass furnace will not affect the District's attainment date. In order 

to be considered in attainment of an air quality standard, the District must have no 

violations of the standard at its official monitoring site for three years. In the Tier 4 early 

enhanced option, the lower emissions from this facility come just ahead of the PM2.5 

attainment year of 2014 rather than afterwards, as would be expected if Pilkington opted 

for the Tier 4 enhanced option. By implementing the Tier 4 early enhanced option at 

Pilkington, Valley residents would reap the benefits of nearly 33 tons per year of 
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additional NOx reductions beginning in 2014, rather than in 2018, and the emission 

reductions would continue for the length of the furnace campaign. 

B. Description of the Project 

District staff would amend Rule 4354 in order provide flexibility for flat glass 

manufacturers to defer meeting the Tier 3 emission limitation in January 1, 2011 

provided they meet the “Tier 4 enhanced” emission limits four year earlier than 

otherwise required, namely by January 2014 rather than by January 2018. The 

proposed compliance option would achieve additional long-term emission reduction by 

complying with “Tier 4 enhanced” emissions limitations four years earlier than would 

otherwise be required by the rule in return for eliminating the Tier 3 emissions limitation. 

The proposed amendments would not change or affect the existing emission limits and 

requirements for container glass manufacturing and fiberglass manufacturing facilities. 

C. Rule Development Process 

District staff conducted a public workshop in June 2010 in order to present and receive 

comments on draft amendments to Rule 4354. Comments received from affected 

source operators, consultants, vendors and manufacturers of control technologies, the 

California Air Resources Board (ARB) and the United States Environmental Protection 

Agency (EPA) have been evaluated and, if appropriate, incorporated into proposed rule 

provisions. 

The proposed rule and final draft staff report will be published and mailed to affected 

sources and interested parties prior to a public hearing to consider the adoption of 

proposed amendments to Rule 4354 by the District Governing Board in September 

2010. 

II. CLIMATE CHANGE 

The California Global Warming Solutions Act of 2006 (AB 32) created a comprehensive, 

multi-year program to reduce greenhouse gas (GHG) emissions in California, with the 

goal of restoring emissions to 1990 levels by 2020. In the coming years, the ARB and 

the Legislature will be developing policies and programs to implement Assembly Bill 32 

(AB 32). There are many win-win strategies that can reduce both GHG and 

criteria/toxic pollutant emissions. However, the District’s primary mission remains to 

achieve attainment with air quality standards to protect public health. Therefore, when 

situations that involve tradeoffs between GHG and criteria or toxic pollutants arise, the 

District will give precedence to reducing criteria or toxic pollutant emissions due to the 

more immediate public health concerns associated with such pollutants. 
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III. BACKGROUND 

Since the proposed amendments only affect the emission limits and requirements for 

flat glass furnaces, District staff will not discuss the existing Rule 4354 requirements for 

container glass furnaces and fiberglass furnaces. 

Prior to the October 2008 Rule 4354 amendments, glass melting furnaces were 

required to meet Tier 2 oxides of nitrogen (NOx) limits. Under the 2008 amended rule, 

flat glass furnaces are required to meet an interim Tier 3 NOx limit by January 2011 as 

well as stringent sulfur oxides (SOx) and particulate matter (PM) limits. The Tier 4 NOx 

limit for flat glass furnaces has a compliance date as soon as January 2014 for the 

standard option and as late as January 2018 for the enhanced option. Table 1 

summarizes the NOx limits and compliance dates for flat glass. 

Table 1 – Flat Glass NOx Limits of Existing Rule 4354 

NOx limit Lb/ton glass produced 

Tier 2 limit – prior to Jan 2011 7.0 

Tier 3 limit – beginning Jan 2011 5.0 

Select one of the following: 

Tier 4 standard option by Jan 2014 3.2 

Tier 4 enhanced option by Jan 2018 2.9 

The Tier 3 and the Tier 4 NOx emission limits will require installation of advanced and 

expensive emission control systems and would necessitate major changes to existing 

furnaces. District staff agrees with the glass manufacturers that the most appropriate 

time to make changes to the furnace in order to install emission control equipment is 

when the furnace is down for periodic repairs to the furnace’s insulating refractory. This 

periodic maintenance is commonly known in the industry as “cold repair” or “rebuild”. 

Flat glass furnaces can operate for 15 years or more between rebuilds and operate 

continuously between rebuilds. Therefore, the window of opportunity for cost-effective 

installation of emission control equipment is very narrow. Installing emission control 

systems prior to the scheduled furnace rebuild would incur additional significant costs 

due to lost revenue because the furnace is not producing any glass products during the 

installation of the required controls and subsequent start-up periods which normally take 

several months. 

As an additional factor for consideration, no one could have anticipated the depth or the 

length of the current economic recession. Generally, the two main consumers of flat 

glass are the building trades (windows for homes and buildings) and the automotive 

market (windows and windshields for cars and trucks). Both of these market sectors 

have been particularly hard hit by the recession and the slowdown in these markets has 

affected their suppliers, including flat glass manufacturers. 
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Final Draft Staff Report: Rule 4354 (Glass Melting Furnaces) August 19, 2010 

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Since October 2008, Pilkington has experienced a significant economic downturn that 

forced a delay in their planned furnace rebuild and the associated installation of 

emission controls. As a result, Pilkington’s current facility cannot meet the Tier 3 

emission standards by the 2011 deadline without installation of additional emission 

control equipment in conjunction with a furnace rebuild. The interim Tier 3 NOx limit 

provides no real transition period because there is no intermediate technology that will 

allow Pilkington’s furnace to achieve the Tier 3 limit, other than the technology required 

to achieve the lower Tier 4 limit. As previously stated, Pilkington requested an 

adjustment to the compliance schedule in order to allow continued operation of the 

Lathrop facility with the 100 associated jobs. 

IV. CURRENT RULE 4354 AND PROPOSED AMENDMENTS 

A. Current Rule 4354 

Rule 4354 was adopted in September 1994, and it was amended in April 1998, February 

2002, August 2006, and October 2008. The rule applies to any glass melting furnace. 

The rule exempts electric glass furnaces, glass furnaces that are located at a stationary 

source with a total potential to emit, for all processes, of at less than ten tons per year of 

NOx or less than ten tons per year of volatile organic compounds (VOC). The current 

rule limits emission of NOx, VOC, carbon monoxide (CO), and SOx. The emission 

limits depend on type of glass produced, furnace firing technology and emission 

averaging period. The current Tier 2 NOx emission limits range from 4.0 to 9.2 pounds 

NOx per ton of glass pulled (lb/ton glass); CO limits are 300 ppmv or 0.9 to 1.0 lbs/ton 

glass; and VOC emission limits are 20 ppmv or range from 0.1 to 0.25 lbs/ton glass. 

Operators meet current emission limits through a selection of furnace firing technology 

and glass raw materials. The future emission limits that will take effect beginning 2011 

through 2018 range from 1.5 to 3.2 lbs NOx/ton glass, depending on the type of glass 

furnace and the compliance option chosen by the operator. The PM10 limit which will 

take effect in 2011 is 0.5 lb/ton glass for all types of glass furnaces. The SOx limits that 

will take effect in 2011 range from 0.9 to 1.7 lb/ton glass, depending on the type of glass 

furnace and firing technology. For detailed requirements, please refer to current Rule 

4354, which is available on the District’s website at www.valleyair.org. 

B. Proposed Amendments to Rule 4354 

The main objective of this rule project is allow flat glass manufacturers to eliminate the 

Tier 3 NOx emission limits provided they meet the early enhanced emission limits by 

January 2014. The current rule also requires that the flat glass manufacturers would 

meet low SOx and PM2.5 limits by January 2011. For flat glass manufacturers that 

choose the Tier 4 early enhanced option, compliance with the SOx and PM limits would 

be deferred until January 2014, which is the same date as the Tier 4 early enhanced 

option compliance date. Revisions were made throughout the rule to accommodate the 

inclusion of the flat glass early enhanced compliance option. These changes include 
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language modifications in the monitoring and recordkeeping sections to match the Tier 

4 early enhanced option compliance date. 

1. Section 5.1 NOx Emission Limits 

The table in Section 5.1 of the rule would be revised to include the flat glass Tier 4 

“early enhanced” NOx limits as shown below. 

 

Table 2 - NOx Emission Limits in pounds NOx per ton glass produced 

Type of Glass 

Produced 

Tier 2 NOx 

limit Tier 3 NOx limit Tier 4 NOx limit 

Standard Option

Tier 4 NOx limit 

Enhanced 

Option 

Container Glass 4.0 A

 1.5 B not available not available

Fiberglass 4.0 A 1.3 A, C

3.0 A, D not available not available

Flat Glass 

Standard Option

9.2 A

7.0 B

5.5 A

5.0 B

3.7 A

3.2 B

3.4 A

2.9 B

Flat Glass

Enhanced Option

9.2 A

7.0 B

5.5 A

5.0 B

3.4 A

2.9 B

Flat Glass

Early Enhanced 

Option

9.2 A

7.0 B not available 3.4 A2.9 B

A

 Block 24-hour average 

B

 Rolling 30-day average 

C

 Not subject to California Public Resources Code Section 19511 

D

 Subject to California Public Resources Code Section 19511 

2. New Section 5.1.4 

This new provision would require a flat glass operator who commits to meet the Tier 4 

early enhanced option NOx limits to demonstrate compliance with the limits according to 

the deadlines specified in new Section 7.2.2 (i.e., by January 1, 2014). After January 1, 

2011, an operator who commits to meet the flat glass early enhanced NOx limits 

schedule is not eligible to choose a different compliance option and applicable 

deadlines. 

3. Section 5.3.2 (SOx Requirements) 

The existing language in Section 5.3.2 pertaining to SOx emission requirements would 

be reworded to make them consistent with the existing language on NOx requirements 

in current Section 5.1.1. Because this section would also indicate that the SOx limit 

compliance deadlines are specified in Section 7.0, Table 3 (SOx emission Limits) would 

be modified to remove the compliance date in the table. 
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4. Section 5.4.1 (PM10 Requirements) 

The existing language in Section 5.4.1 pertaining to PM10 emission requirements would 

be reworded to make them consistent with the existing language on NOx requirements 

in current Section 5.1.1. Because this section would also indicate that the SOx limit 

compliance deadlines are specified in Section 7.0, Table 4 (PM10 Emission Limits) 

would be modified to remove the compliance date in the table. 

5. Section 5.9.3 (SOx Monitoring) and Section 5.9.4 (PM Monitoring) 

Language would be added so that flat glass manufacturers that opt for the Tier 4 early 

enhanced option would not be subject to monitoring for SOx and PM until they become 

subject to the specific emission limits. 

6. Section 6.1 (Permitted Glass Production Capacity and Fuel Use Capacity) 

Section 6.1 would have an outdated provision and compliance date removed. The 

provision to allow fuel-use capacity as a permit condition was retired in 2009 and fuel 

use capacity was removed from the section title. 

7 New Section 7.2.1 

This new section would indicate that a flat glass operator, who does not commit to the 

Tier 4 early enhanced option in Section 5.1 Table 1 would need to comply with the 

existing compliance deadlines specified in renumbered Sections 7.2.1.1 through 7.2.1.6 

to meet flat glass Table 1 Tier 3, Tier 4 standard option, and Tier 4 enhanced option 

NOx limits. 

8. New Section 7.2.2 

This new section would specify the following requirements and compliance schedules for 

a flat glass operator who commits to the meet Section 5.1 Table 1 Tier 4 early enhanced 

option limits. 

• By November 1, 2010, operators would need to submit a letter signed by a 

responsible official, which contains specific information specified in Sections 

7.2.2.1.1 through 7.2.2.1.4 of the proposed rule. 

• By June 1, 2012, operators would need to submit a completed application for 

Authority-to-Construct for any flat glass furnace modifications to comply with the 

applicable NOx, SOx and PM10 emission limits. 

• Full compliance with the Tier 4 early enhanced NOx limit, SOx limit; and PM10 

limit by January 1, 2014 or by the next furnace rebuild, whichever is earlier. 
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VI. BASELINE EMISSIONS AND ESTIMATED EMISSION REDUCTIONS 

District staff has considered the potential effects on other flat glass manufacturers as 

well as whether the proposal affects the District’s ability to meet the attainment dates 

committed to by the Board in the 2007 8-Hour Ozone Plan and the 2008 PM2.5 Plan. 

Additionally, whether the proposal has a net benefit to Valley residents would also be a 

part of the assessment. 

A. Baseline Emissions and Estimated Emission Reductions 

Although the rule was amended in 2008, as directed by the District’s Governing Board, 

the rule was not submitted to EPA for inclusion into the California State Implementation 

Plan (SIP). Because the amended rule was not submitted into the SIP, the reductions 

associated with the 2008 rule project have not been claimed for attainment 

demonstration purposes. Since this version of the rule will be submitted to EPA, the 

District will claim the reductions from the 2008 rule amendments as part of this rule 

project. Table 3 below summarizes the estimated emissions and the estimated 

emission reductions associated with the 2008 rule project. Details of the emission 

calculations are included in Appendix B of the staff report. 

Table 3 – Estimated Emissions and Emission Reductions from 2008 Final Staff Report 

Pollutant 

Claimed 2008 Baseline 

Emissions, tpd 

Claimed Emission 

Reduction, tpd 

NOx 

Container 2.66 1.16

Fiberglass 0.53 0.01

Flat Glass 4.80 2.11

Total NOx 7.99 3.28

SOx 

Container 1.54 0.38

Fiberglass 0.02 0.00

Flat Glass 1.57 0.74

Total SOx 3.13 1.12

PM10 

Container 0.38 0.02

Fiberglass 0.007 0.002

Flat Glass 0.59 0.08

Total PM10 0.98 0.11
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B. Impact of Proposed Amendments on Emissions from Other Flat Glass 

Manufacturers 

District staff considered the impact of the proposed amendments on flat glass 

manufacturers other than Pilkington, including any potential competitive disadvantage 

caused by the proposed amendments. There are two flat glass manufacturers besides 

Pilkington located in the District. One plant already meets the Tier 4 NOx, SOx and 

PM10 limits because of a rebuild in 2008. The second facility is already meeting the 

Tier 3 NOx and the 2011 SOx and PM10 limits. It is not know at this time whether the 

second facility’s management will choose the Tier 4 standard or the Tier 4 enhanced 

option, however, at the time of the 2008 rule development project, they were leaning 

toward the Tier 4 enhanced option due to the furnace refractory being in good shape at 

mid-campaign. For these reasons, the other flat glass manufacturers are not expected 

to be affected by the proposed amendments to Rule 4354. 

C. Impact of Proposed Amendments on District Attainment Strategies 

NOx emission reductions are part of the control strategy for attaining the 8-hour ozone 

standard and the PM2.5 standard. The following paragraphs describe the impact of 

changing the flat glass compliance dates from 2011 to 2014. 

1. 2007 8-hour Ozone Attainment Plan 

Computer modeling of the San Joaquin Air Basin for ozone ambient air quality standard 

violations has determined that NOx emission reductions are far better at reducing 

ambient ozone levels than any other ozone precursor. Because glass melting furnaces 

operate 24 hours per day everyday of the year and combust a lot of fuel while the 

furnace operates at very high temperatures, they are a significant portion of the 

District’s stationary source NOx emission inventory. The expected emission reductions 

from the ozone plan’s Rule 4354 control measure represent the second largest source 

of NOx reductions for the plan, behind open burning. The glass furnace control 

measure estimated that beginning in 2008, 1.2 tons per day of NOx would be reduced, 

climbing to 1.6 tons per day in 2012 and growing to 2.0 tons per day in 2023. Based on 

the information gathered during the 2008 Rule 4354 amendments project, the estimated 

NOx emission reductions would be 1.2 tons per day beginning in 2008, which includes a 

flat glass plant and one furnace of a container glass plant that underwent cold repair 

and came back into production mode in 2008. 

Pilkington has pledged to rebuild in late 2013 and early 2014 to meet the Tier 4 early 

enhanced NOx limit, rather than waiting until 2018. In accommodating Pilkington’s 

request, it is estimated that the NOx reductions from their furnace would be about 1.2 

tons per day. This compares to the ozone plan control measure which estimates an 

additional 0.4 tons per day beginning in 2012. 
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In the 2008 amendments to Rule 4354, District staff estimated that there will be a 

reduction of 0.4 tons per day from a container glass facility in addition to the Pilkington 

reductions. The 0.4 tons per day of reductions are in addition to the estimated 1.2 tons 

per day of reductions associated with a Pilkington rebuild. 

The 2007 Ozone Plan predicts attainment in 2023, if the District implements all of its 

control measures and finds additional NOx reductions. Amending Rule 4354 to 

accommodate Pilkington’s request would not change the District’s attainment date for 

the 8-hour ozone standard. 

2. 2008 PM2.5 Attainment Plan 

For attainment of the PM2.5 standard, reductions in directly-emitted PM2.5 as well as 

the PM2.5 precursors of NOx and SOx are needed for the District to reach attainment. 

The plan did not estimate PM2.5 or SOx reductions from the glass melting furnaces 

control measure. However, the NOx reductions and timing were similar to the 8-hour 

ozone plan control measure. For comparing the NOx reductions for the PM2.5 control 

measure and the rule amendment project, the discussion from the PM2.5 plan is the 

same as outlined in the 8-hour ozone plan above. 

In addition to the NOx reductions, District staff analyzed whether there were benefits 

associated with the timing of the Pilkington’s reductions. Table 4 shows the estimated 

emissions from the Pilkington facility if it were to be operated at 80% of its maximum 

glass-producing capacity under three scenarios: the current rule (Tier 4 standard and 

Tier 4 enhanced) and as proposed by Pilkington (Tier 4 early enhanced). Computer 

modeling for the 2008 PM2.5 Attainment Plan predicts that attainment can be 

demonstrated by 2014. In order to demonstrate attainment, the District’s official air 

quality monitors must show no violations for three years prior to the attainment date. 

The added NOx reductions from the proposed Tier 4 early enhanced occur just ahead 

of the PM2.5 attainment year of 2014 rather than afterwards, as would be expected if 

Pilkington opted for the Tier 4 enhanced option. 
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Table 4 – Pilkington Annual NOx Emissions at 80% of Maximum Glass Capacity 

Current Rule Pilkington 

Calendar Year Tier 3 plus 

Tier 4 standard 

Tier 3 plus 

Tier 4 enhanced 

No Tier 3 plus 

Tier 4 early enhanced 

2010 (Tier 2 – base) 766.5 766.5 766.5 

2011 547.5 547.5 766.5 

2012 547.5 547.5 766.5 

2013 547.5 547.5 766.5 

2014 350.4 547.5 317.6 

2015 350.4 547.5 317.6 

2016 350.4 547.5 317.6 

2017 350.4 547.5 317.6 

2018 350.4 317.6 317.6 

Total NOx Emissions 

(2011 – 2018), tpy 3,394.5 4,150.1 3,887.3 

During the 2008 rule amendment project, District staff estimated that the bulk of the 

SOx emission reductions would be from a furnace that had undergone rebuild during 

the rule project and that those reductions would be about 0.63 tons per day. Pilkington 

and container glass furnaces would contribute another 0.28 tons per day of SOx 

reductions. If the compliance date for meeting the SOx and PM2.5 limits were revised 

for flat glass furnace, moving the date from 2011 to 2014, the calculated attainment date 

for the PM2.5 standard would not be affected. The expected 0.4 tons per day of NOx 

emission reductions is less than 0.3% of the total cumulative emissions for the 2012 

milestone year. Based on the small fraction of additional NOx reductions from glass 

furnaces of the total emission reductions, it is not expected that the PM2.5 air quality 

standard attainment date would be affected. 

3. Reasonable Further Progress Demonstration of the 2008 PM2.5 Plan 

The federal Clean Air Act (Act) requires that attainment plans meet reasonable further 

progress (RFP) by achieving incremental emission reductions to ensure attainment of 

the National Ambient Air Quality Standards by the attainment date. The Act does not 

identify specific emission reduction benchmarks that must be met for PM attainment 

plans. EPA has interpreted the Act’s RFP requirement using the concept of achieving 

(generally) linear progress toward the standard. The District’s 2008 PM2.5 Plan 

contains an RFP demonstration. For the PM2.5 attainment strategy, glass melting 

furnace emission reductions from SOx and directly-emitted PM2.5 were not quantified 

and therefore not part of the reductions in the RFP. The proposed delay in 

implementing the SOx and directly-emitted PM2.5 from glass melting furnaces will have 

no effect on the RFP. However, the rule amendments will increase the cumulative 
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emission reductions achieved in the milestone years by including emission reductions 

beyond what was estimated at the time of the 2008 PM2.5 plan’s adoption. 

The flat glass Tier 3 NOx implementation date for the current rule is January 2011 with 

Tier 4 NOx standard option having a January 2014 compliance date and Tier 4 

enhanced option having a January 2018 compliance date. Removing the Tier 3 NOx 

reductions from the Pilkington furnace would affect only the milestone year of 2012 

because the Tier 4 early enhanced option would require that the furnace be in 

compliance by January 1, 2014 and as a result, the emission reductions would occur 

the milestone year of 2014. The control measure for glass melting furnaces in the 

PM2.5 Plan states that about 0.4 tons per day of NOx would come from furnaces that 

are not at the lowest applicable NOx limit and that the lowest limit would be 

implemented starting in 2012. The expected 0.4 tons per day of NOx emission 

reductions is less than 0.3% of the total cumulative emissions for the 2012 milestone 

year. Based on the small fraction of the total emission reductions from glass furnaces, it 

is not expected that the RFP would be affected. 

4. Impact of Proposed Amendments on Attainment of Ambient Air Quality 

Standards 

Based on the analysis above, District staff finds that the change in compliance dates for 

a single flat glass furnace will not affect the District’s attainment date of either the ozone 

standard or the PM2.5 standard. As a benefit, the initial Tier 4 early enhanced 

reductions would take place during key years of demonstrating attainment. 

VII. EMISSION CONTROL TECHNIQUES 

Operators can control air emissions either by controlling inputs to the process or by 

treating the exhaust from the process. Process inputs for glass melting furnaces 

include raw materials, fuel, and combustion air. Post-combustion control techniques 

depend on the pollutant to be controlled. The following paragraphs outline potential 

ways that operators of glass melting furnaces can reduce furnace exhaust emissions of 

NOx, SOx, and PM. 
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A. NOx Emission Control Techniques 

On the inlet side of the glass furnace, NOx is generated from nitrogen-containing 

materials entering the furnace. The nitrogen (N2) and oxygen (O2) in ambient air can 

combine to form NOx at the high temperature. This phenomenon is called “thermal 

NOx.” Since high temperatures are required to melt raw materials to form glass, 

thermal NOx in the exhaust of glass melting furnaces is expected. There are several 

combustion practices that form less thermal NOx. Operators may also choose to 

control NOx on the outlet side of the process, i.e., run the glass furnace to optimize the 

product, and then deal with the generated NOx in the furnace’s exhaust stream. 

1. Raw Materials 

One of the ingredients in glass is a refining agent. The purpose of a refining agent is to 

remove bubbles of gas, known as seeds, from the glass melt. Niter (sodium nitrate, 

chemical formula Na2NO3) is a commonly used refining agent. A little over half of niter 

converts to NOx and leaves the furnace in the exhaust gas. Therefore, the use of niter 

as a refining agent is balanced against the melting furnace’s total NOx emissions 

allowed by permit. Operators may substitute a different refining agent, called saltcake 

(sodium sulfate, chemical formula Na2SO4), to reduce NOx emissions. The 

replacement is not without its own set of challenges. The operator may not be able to 

exchange saltcake for niter without substantially changing the glass recipe. Adding to 

the consideration is the fact that at least some of the saltcake leaves the molten glass to 

become SOx emissions. 

2. Control of the Combustion Process 

Commercial natural gas is very low in nitrogen-containing material and all active 

furnaces in the District are firing on commercial natural gas as a primary fuel. This 

means that nitrogen contained in the fuel is not a significant source for NOx. 

Operators can modify the combustion process either by changing the configuration of 

the burner to reduce peak flame temperature or change the composition of the 

combustion air to reduce the amount of nitrogen gas (N2) available for conversion to 

NOx. Thermal NOx formation increases exponentially as a function of a burner’s peak 

flame temperature. Therefore, lowering the peak flame temperature can significantly 

reduce NOx formation. Burner manufacturers have designed low-NOx burners that 

increase the zone where combustion takes place, thereby lowering the temperature of 

the flame at any given point. Lower flame temperatures means less thermal NOx 

created per unit of fuel burned. Besides low-NOx burners, operators can use electrodes 

submerged in the molten glass to “boost” the amount of heat added to the materials. 

The electric boosters generate no additional NOx, since they do not come in contact 

with air. However, District operators consider heat from electricity expensive relative to 

heat generated by burning fossil fuels, so the use of electrodes within the District is 

perceived as cost-prohibitive. 
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Ambient air (the air around us) is about 79% nitrogen (N2) and 21% oxygen (O2). If the 

operator changes the proportion of N2 in the air used for fuel burning (combustion air) 

by increasing the concentration of O2, the amount of NOx that could form would be 

reduced because there is less N2 available to react. A partial replacement of N2 with O2

is called “oxygen-assisted” firing – total replacement is “oxy-fuel” firing. Replacing some 

or all of the N2 in combustion air with O2 is not without cost. Most operators who 

convert to their furnaces to oxy-fuel or oxygen-enhanced firing have an O2-generating 

gas plant built on their property to support the needs of the glass-melting furnace. On 

the other hand, oxy-fuel furnaces don’t heat the inert nitrogen found in ambient air, and 

therefore, the process uses somewhat less fuel to melt the same amount of glass as airfuel furnaces. This means that operators can partially offset the cost of O2-generation

through more efficient fuel usage. 

3. Post-Combustion Techniques 

Post-combustion control is the final place where operators can reduce NOx emissions. 

Add-on controls increase the complexity of the process by virtue of being another 

system that the operator must monitor and maintain. Glass manufacturers face 

challenges with post-combustion controls. Since the furnace exhaust temperature is 

high, special care must be taken to design an appropriate control system. 

Controlling NOx through add-on controls offers one important advantage to operators. 

With add-on controls, the operator can choose the raw materials and furnace firing 

technology that make the most sense for the operations yet still meet low emission 

limits. Post-combustion control, however, does carry one main disadvantage – extra 

costs. These costs are significant one-time capital costs and on-going additional 

operating expenses. Since add-on controls are a separate system from the glassmaking portion of the process, maintenance of the emission control system can add 

complexity to overall manufacturing operations. Also, add-on controls may have some 

indirect effects on the glass-making process. Some examples of these indirect effects 

are that the furnace exhaust temperature or certain raw materials may have to be 

different in order to run the add-on control efficiently. 

Selective catalytic reduction (SCR) is one type of post-combustion emission control 

used in other industries to control NOx emissions on combustion exhaust streams. 

SCR works by passing the post-combustion exhaust stream through a catalyst bed. 

The catalyst promotes the reaction of NOx back to N2 and O2. The catalyst is effective 

only in a narrow temperature range, and the exhaust stream must be relatively free from 

particulates and sulfur-containing compounds before the stream passes through the 

catalyst. To date, the use of SCR has been established at glass-making facilities in 

Europe and Asia, but it has not been used here in the United States. One District 

facility has recently installed a SCR on its glass-melting furnace, but has operated the 

unit only a few months. 
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Selective non-catalytic reduction (SNCR) is a second type of post-combustion emission 

control used in other industries. The use of SNCR is not a widely adopted practice in 

the glass industry and it is not expected that operators within the District would use this 

technology to control NOx emissions. 

The 3R process, developed by Pilkington Glass Limited, is a proprietary, low-NOx firing 

technology. The process injects various hydrocarbon fuels into the furnace waste gas 

stream as the agent to reduce NOx to nitrogen and water vapor. Since the control of 

NOx occurs within the furnace’s regenerators (checker packs), the 3R process can be 

considered a hybrid between combustion control and add-on control. The treatment is 

after combustion, since the fuel is injected into the furnace exhaust. However, the 

reaction does not take place in a separate unit, so the 3R process is not, technically 

speaking, an add-on control. While flat glass furnace operators can expect to rebuild 

checker packs at the same rate as the glass melting furnace (every 15 years or so), 

some facilities utilizing the 3R process have experienced early failure of the refractory 

(insulation) within the checker packs, forcing rebuilds of the checker pack much sooner 

than the melting furnace. 

B. SOx Emission Control Techniques 

Within the glass-making process, there are three sources of SOx. The sources are fuel, 

raw material, especially a refining agent called saltcake (sodium sulfate, chemical 

formula Na2SO4), and gaseous SO2 used in the annealing oven (lehr). As noted below, 

the sulfur that becomes SOx emissions enters a glass-melting furnace with either the 

fuel or the raw materials. 

1. Fuel and Raw Materials 

Natural gas is a low-sulfur fuel, therefore fuel is not a significant source of sulfur in the 

furnace exhaust. For furnaces fired on natural gas, controlling sulfur emissions on the 

input side of the process means controlling the use of saltcake. Replacing all or part of 

saltcake with alternative refining agent can create as many challenges as it solves. 

Arsenic trioxide is, by far, the best refining agent. However, it is seldom used in largescale glass making because of the inherent toxicity of compounds containing arsenic. 

Sodium nitrate (niter) is another commonly used refining agent. Niter must be stored 

and handled appropriately for safety considerations; niter is not as good as saltcake at 

stabilizing colorant ions for certain glass chemistries; and, at glass melting 

temperatures, niter dissociates to form NOx. All these facts, taken as a whole, mean 

that replacing saltcake as a raw material is not a straightforward substitution. 

2. Annealing Oven (Lehr) 

A third source of SOx emissions is within the annealing section of the flat-glass 

production. Sulfur dioxide gas (SO2, one form of SOx) may be pumped into the 

annealing oven (lehr), either to prevent surface staining of the glass or to form a 
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protective coat on the rollers that pull the glass through the process. The portion of SO2

that does not adhere to the glass surface or roller surface exits the process with the 

lehr’s exhaust gas. The lehr does not melt materials to make glass, and, therefore, is 

not directly subject to Rule 4354. However, the design of the glass manufacturing line 

may be such that the lehr exhaust gases go through the glass-melting furnace and exit 

the process with the furnace exhaust. If the lehr in a glass-making process for flat glass 

is designed to exhaust into the glass-melting furnace, the lehr exhaust becomes a 

source of SOx to the glass-melting furnace. To reduce SOx emissions in the furnace by 

controlling the SO2 level in the lehr can be problematic. The SO2 concentration in the 

lehr is optimized for best glass processing, and making large changes in the SO2

concentration to meet emission limits may be detrimental to maintaining glass quality 

and processing efficiency. 

3. Post Combustion Control 

If an operator determines that inlet-side control technique is not feasible or that the 

changes are not practical, there are control devices for removing SOx from the exhaust 

side of the process such as scrubbers. Scrubbers are air pollution control devices that 

use an absorbent to remove aerosol and gaseous pollutants from an air stream. The 

gases are removed either by absorption or chemical reaction. There are two types of 

scrubbing suitable for glass manufacturers: dry and semi-dry (in other industries, this 

type of scrubber is sometimes called semi-wet). The reaction principles are the same 

for both types of scrubbers. A reactive material (the absorbent) is introduced to and 

dispersed in the exhaust stream. The absorbent reacts with the SOx species to form a 

solid, which has to be removed from the exhaust stream by a bag filter system or an 

electrostatic precipitator (EP). It makes economic sense for some glass manufacturers 

to reuse a portion the collected dust as a raw material, rather than disposing of it. The 

collected EP dust is high in sulfates, so the recycled dust may replace at least some of 

the purchased saltcake in the glass recipe. 

C. Particulate Matter (PM) Emission Control Techniques 

The airflow through a glass melting furnace can be on the order of 30,000 standard 

cubic feet per minute. With airflow this high, un-melted raw material in the furnace can 

be lifted off the surface of the molten glass to go directly into the furnace’s exhaust 

stream. Operators can influence the rate at which raw materials become directly 

emitted PM through raw materials specification, control of the raw material moisture at 

the point the material is delivered to the furnace, and design of the furnace’s material 

charging system. There are also end-of-pipe particulate control techniques. 

1. Material Selection and Moisture Control 

In selecting raw materials, operators take into account the particle size of glass raw 

materials. Small particles are more easily lifted by airflow than larger particles, but are 

more easily melted. Material moisture also plays into how much material bypasses the 
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melting process. It is best if material contains “enough” moisture to keep the material 

from being airborne, but not so wet as to affect glass production. In addition, the 

amount of recycled glass (cullet) in the recipe plays a role. Cullet generally melts at a 

lower temperature than glass raw material and is more likely to have a larger particle 

size. The use of cullet may be limited by the end-use quality requirements for the glass. 

For container glass and certain types of fiberglass, minimum cullet use is specified in 

the California Public Resources Code. Operators would balance all three elements to 

minimize directly emitted particulate through raw material selection. 

2. Furnace Material Charging System 

Given that most glass melting furnaces are designed to produce hundreds of tons of 

glass per day, making sure that enough raw materials are fed into the furnace is an 

important consideration in furnace design. Particulate control through raw material 

selection and moisture content could be moot if the furnace’s material charging system 

facilitates the material becoming airborne. The design of the material charging system 

is constrained by engineering principles and production requirements. 

3. Raw Material Volatilization 

Raw materials can be made gaseous at the high temperatures associated with glass 

melting furnaces. These volatilized materials can condense on surfaces or form 

particulate and exit the furnace with the exhaust gases. Operators can control raw 

material volatilization by covering the molten glass with un-melted raw material and by 

minimizing the furnace temperature. 

4. Post Combustion Control 

Post-combustion particulate control is of two types: filters and electrostatic precipitators 

(EPs). Filters used for high airflow situations are grouped together into what is called a 

baghouse. In most cases, glass melting furnace operators opt for EPs, since the 

temperature of the furnace exhaust is too high for most filter materials. 

VIII. COSTS AND COST EFFECTIVENESS ANALYSIS 

The California Health and Safety Code 40920.6(a) requires District staff to conduct a 

cost effectiveness analysis of available emission control options prior to adopting each 

Best Available Retrofit Control Technology (BARCT) rule. Since the proposed rule 

modifies certain compliance dates and does not change existing emission limits, the 

requirement to perform a cost effectiveness analysis does not apply. 
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IX. SOCIOECONOMIC IMPACT ANALYSIS 

Pursuant to state law, District staff is required to perform a socioeconomic impact 

analysis prior to adoption, amendment, or repeal of a rule that has significant impacts 

on air quality or that will strengthen emission limitations. The proposed amendments to 

Rule 4354 are only intended to provide flat glass manufacturers with an option to defer 

compliance with the Tier 3 emission limits provided they comply with the early enhanced 

emission limits four years sooner than would have been required to comply with the 

enhanced option emission limits. Because of this, the requirement to perform a 

socioeconomic impact analysis does not apply. 

X. ENVIRONMENTAL IMPACTS 

Global Climate Change (GCC), which is now generally accepted by the scientific 

community to be caused by GHGs, is a widely discussed scientific, economic, and 

political issue in the United States. Briefly stated, GCC is the cumulative change in the 

average weather of the earth that may be measured by changes in temperature, 

precipitation, storms, and wind. Gases that trap heat in the atmosphere are called 

greenhouse gases; they act in the atmosphere in a manner analogous to the way a 

greenhouse retains heat. Common GHG include water vapor, carbon dioxide, methane, 

nitrous oxides, chlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, sulfur 

hexafluoride, ozone, and aerosols. Some greenhouse gases such as water vapor occur 

naturally and are emitted to the atmosphere through natural processes as well as 

through human activities, such as electricity production, vehicle use, etc. The most 

common GHG that results from human activity is carbon dioxide, followed by methane 

and nitrous oxide. 

The proposed amendments to Rule 4354 only move the compliance date of final 

implementation for one facility. The proposed rule amendments will not affect the 

meaning, scope of, or prohibitions contained in current rule language. The District’s 

analysis demonstrates that implementing the proposed amendments would not affect 

the existing emission limits that have been in place since 2008. Furthermore the 

analysis demonstrates that the project has the potential to reduce criteria pollutant 

emissions, thus having a positive impact on air quality. There is no evidence before the 

District that indicates that the project would result in increased greenhouse gas 

emissions. Thus, the District concludes that the project would not have a cumulatively 

significant impact on global climate change. 

Based on the lack of evidence to the contrary, District staff has concluded that the 

proposed amendments to the rules will not have any significant adverse effects on the 

environment. The proposed amendments to Rule 4354 have undergone environmental 

review in accordance with the requirements CEQA. A proposed negative declaration 

has been issued by the District and made available for public review and comment. 

Upon approval of this project, a Negative Declaration will be filed. 
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XI. RULE CONSISTENCY ANALYSIS 

Prior to adopting, amending, or repealing a rule or regulation, California Health and 

Safety Code Section 40727.2 requires a written analysis that identifies and compares 

requirements of the proposed rule with corresponding, existing and proposed District 

rules and corresponding United States Environmental Protection Agency (EPA) rules, 

regulations, and guidelines. Based on the analysis, District staff concludes that the 

proposed amendments to Rule 4354 are consistent with other District rules and are not in 

conflict with these rules. Further, the proposed rule amendments are consistent with EPA 

rules, regulations, and guidelines that apply to the same source category. The analysis is 

presented in Appendix C of the Final Draft Staff Report. 

XII. REASONABLY AVAILABLE CONTROL TECHNIQUES (RACT) ANALYSIS 

The Clean Air Act (CAA) Section 182(b)(2) states that ozone attainment plans shall 

assure that RACT for volatile organic compounds (VOC) is applied at certain sources. 

Section 182(f) extends federal RACT requirements to NOx rules and major NOx 

sources. NOx emission reductions are included in the District’s 2007 Ozone Plan for 

Rule 4354 and were included in the 2008 version of the rule. The 2008 NOx emission 

limits are among the most stringent limits for this source category. As such, they 

constitute a level above “reasonably available” control technology. 

XIII. REFERENCES 

1. Final Draft Staff Report, “Re-evaluation of the October 2008 Amendments to 

Rule 4354”, April 15, 2008. 

2. Governing Board Memorandum, “Review Report on Re-Evaluation of October 

2008 Amendments to Rule 4354 (Glass Meting Furnaces) and Authorize the 

APCO to Develop Future Rule Amendments”, April 15, 2010 

3. SJVUAPCD Rule 4354 (Glass Melting Furnaces), Amended October 16, 2008. 

4. Pilkington North America’s Comment Letter on SJVUAPCD Rule 4354 ReEvaluation, January 7, 2010. 

5. District Project No. CEQA 20080357 (Initial Study and Negative Declaration for 

Draft Amendments to Rule 4354), August 18, 2008. 
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