# TECHNICAL SUPPORT DOCUMENT (UPDATED)

FOR EMISSIONS FROM PRODUCTION OF FLUORINATED GASES:

PROPOSED RULE FOR MANDATORY REPORTING OF GREENHOUSE GASES

Office of Air and Radiation U.S. Environmental Protection Agency

March 22, 2010i Table of Contents

1. Source Description ..................................

................................................... ........................... 1 A. Facilities Subject to the Rule ......................

................................................... .................. 1 B. How Fluorinated GHGs are Generated and Released at Fluori nated Gas Production Facilities ........................................

................................................... ............................... 1 C. Background on Uses of Fluorinated Gases ..................

................................................... .. 2 D. Potential Overlap Emission Points for Production and Suppli ers. ..................................... 3 E. Total U.S. Production and Associated Emissions .........

................................................... . 4 2. Options for Reporting Threshold ......................

................................................... .................. 5 A. Uncontrolled Emissions Threshold ....................

................................................... ........... 5 B. Controlled Emissions Threshold ......................

................................................... ............. 6 C. No Emissions Threshold (i.e., All-in)................

................................................... ............ 7 3. Monitoring Methods, Data Collection and Current Plant Pr actices ......................................... 7 A. Scoping Test and Options for Characterizing Emitted Strea ms......................................... 7 i. Reliance on previous bench- and pilot-scale testing..... ............................................... 7 ii. Initial Scoping Test (including discussion of analytical methods) ............................... 8 B. Options for Developing Emissions Estimates ............

................................................... .. 10 i. Default Emission Factor............................

................................................... ............ 10 ii. Mass Balance ......................................

................................................... .................. 10 1. Error Limits .......................................

................................................... ............. 11 2. Mass Balance Approach Equations. ...................... ............................................. 13 3. Choice of Reactant Whose Yield Is Measured. .......... ......................................... 17 4. Frequency of Measurement and Calculation. ............. ......................................... 17 5. Reactant and Byproduct Emissions. ..................... .............................................. 18 6. Alternative approach based on measurements of balanced el ement ..................... 18 7. Current Plant Practices for Mass Balance ........... ................................................ 22 iii. Monitoring of Process Vents .........................

................................................... ........ 22 1. Process-Vent-Specific Emission Factor Approach. ...... ....................................... 23 2. Process-Vent-Specific Emission Calculation Factor Appro ach. .......................... 28 3. Obtaining and Maintaining Representative Emission Factors ............................. 30 4. Updates to emission factors and emission calculation f actors. ............................ 35 5. Potential Process Vent Emission Threshold. .......... ............................................. 35 6. Process Vent Preliminary Emission Estimates. ....... ............................................ 37 7. Current Plant Practices for Process Vent Monitoring .. ........................................ 37 8. Potential use of continuous emissions monitors to measure emissions from
vents. ............................................

................................................... .................. 39 9. Equipment Leak Emissions Estimates. ................... ............................................ 39 10. Destruction Efficiency Testing .....................

................................................... ... 41 C. Other Potentially Significant Emission Points .......

................................................... ...... 41 4. Procedures for Estimating Missing Data .................

................................................... .......... 43 5. QA/QC Requirements .................................

................................................... ..................... 43 6. Reporting and Recordkeeping Procedures.....................

................................................... .... 44 7. References ........................................

................................................... ................................ 441

1. Source Description A. Facilities Subject to the Rule This source category, fluorinated gas production, covers emis sions of fluorinated greenhouse gases (GHGs) that occur during the production of fl uorinated gases. It also covers emissions of fluorinated GHGs that occur during transforma tion of fluorinated gases and destruction of fluorinated GHGs when those processes are co-located with fluorinated gas production processes. Fluorinated GHGs include hydrofluorocar bons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF 6 ), nitrogen trifluoride (NF 3 ), and other fluorinated GHGs such as fluorinated ethers. Fluorinated gases include fluorinated G HGs, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). However, the source c ategory excludes generation and emissions of HFC-23 during the production of HCFC-22, which is covered by subpart O of the Mandatory Reporting Rule.

Producing a fluorinated gas includes the manufacture of a fl uorinated GHG, CFC, or HCFC from any raw material or feedstock chemical. T his includes the manufacture of fluorinated GHGs for use in a process that will result in the transformation either at or outside of the production facility. Producing a fluorinated gas does not include the reuse or recycling of a fluorinated gas, the creation of HFC-23 during the production of HCFC-22, or the creation of byproducts that are released or destroyed at the production f acility.

B. How Fluorinated GHGs are Generated and Released at Fluorinated Gas Production Facilities Fluorinated GHGs can be generated and emitted from productio n, transformation, destruction, and other processes at production facilities in a number of ways. Emissions from fluorinated gas production include fluorinated GHG products that are emitted upstream of the production measurement and fluorinated GHG by-products that ar e generated and emitted either without or despite recapture or destruction. Emissions from fluorinated gas transformation include emissions of fluorinated GHG feedstocks and possibly by-products of the transformation process. Emissions from fluorinated GHG destruction inc lude fluorinated GHGs that survive the destruction process. Other emissions sources are discuss ed further below.

Many reactions producing fluorinated GHGs, CFCs, and HCFCs al so generate significant quantities of chemically related by-products, e.g., through over-fluorination or side reactions. Table 1 provides an overview of some commonly produced fluorin ated GHGs, CFCs, and HCFCs and their known fluorinated GHG by-products. Note tha t production of CFCs and HCFCs can generate and emit fluorinated GHGs such as var ious HFCs and some PFCs. These fluorinated GHG by-products occur due to the chemical simila rities between HFCs, PFCs, HCFCs, and CFCs and the common use of halogen replacement chemistry to produce them. Also note that Table 1 is not exhaustive. It omits th e most commonly known product and byproduct, HCFC-22 and HFC-23, which are covered by subpart O of the Mandatory Reporting Rule. In addition, it does not include all of the by-pro ducts and products that have been identified by fluorinated gas producers.2

Table 1. Some Fluorinated Products and their By-pr oducts

Product By-product(s) Source of information HFC-134a HFC-143a Italy National Inventory Report, 20 09 SF 6 CF 4 Italy National Inventory Report, 2009 Electrochemical fluorination plant that produces a broad range of fluorochemical products, mainly for electronics industry SF 6 , CF 4 ,

C 2 F 6 , C 3 F 8 , C 4 F 10 , C 5 F 12 , C 6 F 14 , CF 3 SF 5 , C 7 F 16 , C 8 F 18 and C 8 F 16 O Belgium National Inventory Report, 2009

http://unfccc.int/files/national_reports/annex_i_ghg_i nventories/national_inven tories_submissions/application/zip/bel_2009_nir_15apr.z ip

CFC-11, CFC-12 CF 4 2006 IPCC Guidelines CFC-115 C 2 F 6 Italy National Inventory Report, 2009 http://unfccc.int/files/national_reports/annex_i_ghg_i nventories/national_inven tories_submissions/application/zip/ita_2009_nir_15apr.z ip Trifluoroacetic acid (TFA) CF 4 , HFC-125 French National Inventory Report, 2009 http://unfccc.int/files/national_reports/annex_i_ghg_i nventories/national_inven tories_submissions/application/zip/fra_2009_nir_7apr.zi p

The quantities of by-products generated, as a share of the product, depend on the product and the process. Based on conversations with fluorinate d gas producers, by-product generation rates generally range between one and five percent but ca n sometimes be higher or lower.

Emissions of products, by-products, and feedstocks may occur f rom process vents, from equipment leaks from flanges, connectors, and other equipm ent pieces in the production line, from storage tanks storing either raw materials or produc ts, from wastewater streams, from control devices (e.g., thermal oxidizers), and during the fi lling of tanker trucks, railcars, cylinders, or other containers that are distributed by the producer. Undesired by-products may be deliberately vented, and some product (or reactant) may be vented at the same time due to imperfect separation of by-products, products, and reactants. Emissions can also occur during scheduled maintenance and occasional service work on product ion equipment, during the blending and recycling of fluorinated GHGs, and during the evac uation of containers used to distribute products. EPA estimates that total emissions from this source category were approximately 10.6 million metric tons CO 2 e (mt CO 2 e) in 2006. 1

C. Background on Uses of Fluorinated Gases Fluorinated gases are man-made gases used in several sector s. As noted above, they include fluorinated GHGs (HFCs, PFCs, SF 6 , NF 3 , and a number of fluorinated ethers), CFCs, and HCFCs, all of which are manufactured through various c hemical processes. Hydrofluorocarbons (HFCs) are the most commonly used fl uorinated GHGs, used primarily to replace ozone-depleting substances in a number of appli cations, including air-conditioning and refrigeration, foams, solvents, and aerosols. PFCs ar e used in fire fighting and to manufacture semiconductors and other electronics. SF 6 is used in a diverse array of applications, including electrical transmission and distribution equipment (as an electrical insulator and arc quencher) and in magnesium casting operations (as a cover gas to prevent oxidation of molten metal).

1 Fluorinated GHG production data were from 2006; CFC and HCF C production data were from 2008.3

Nitrogen trifluoride (NF 3 ) is increasingly used in the semiconductor industry, to reduce overall semiconductor GHG emissions through processes such as NF 3 remote cleaning and NF 3 substitution during in-situ cleaning. Fluorinated ethers (HF Es and HCFEs) are used as anesthetics (e.g., isofluorane, desflurane, and sevoflura ne) and as heat transfer fluids (e.g., the HGaldens). The manufacture of CFCs and HCFCs for emissi ve uses is being phased out under the Montreal Protocol, but production of these materials for use as feedstocks is permitted to continue indefinitely. As discussed further below, the volume of CFCs and HCFCs used as feedstocks in the U.S. is significant; even excepting HCF C-22, this volume is actually larger than the volume of fluorinated GHGs produced in the U.S. Fluor inated GHGs are powerful greenhouse gases whose ability to trap heat in the atmosphe re is often thousands to tens of thousands of times greater than that of CO 2 , on a pound-for-pound basis. Some fluorinated GHGs are also very long lived; SF 6 and the PFCs have lifetimes ranging from 3,200 to 50,000 years (IPCC, 2006).

D. Potential Overlap Emission Points for Production and Suppliers. The facilities that are covered under the fluorinated gas production source category are many of the same facilities that are covered under the industrial gas supply source category. In general, the industrial gas supply source category is inte nded to cover or capture the quantities of fluorinated GHGs that are entering and leaving the U.S. suppl y of industrial gases, (i.e., amount of product), while the fluorinated gas production source categ ory is intended to cover or capture the quantities of fluorinated GHGs emitted at fluorinated ga s production facilities. Specifically, the industrial gas suppliers source category is meant to track the quantities of fluorinated GHGs that are (1) produced, (2) transformed, (3) destroyed, (4) imported, and (5) exported. The industrial gas suppliers source category would essentially track the amount of final product made (produced) at a production facility but not the emissions of fluorinated GHG from the production steps from raw material to final product.

There are several areas of potential overlap between t he emissions that are reported under the industrial gas suppliers source category and those tha t could be reported under the fluorinated gas production source category. The areas of overlap conce rn “downstream” emissions, meaning they occur at the fluorinated GHG production facility afte r the fluorinated GHG product measurement. Downstream emissions include those from fl uorinated GHG transformation processes, destruction of fluorinated GHGs that are remove d from the U.S. supply, recycling or reclamation of fluorinated GHGs, and evacuation of flu orinated GHG heels from returned cylinders or containers. (“Upstream” emissions occur at the fluorinated GHG production facility prior to the fluorinated GHG product measurement.)

Fluorinated gas production facilities sometimes make a fluo rinated GHG product that is later used as a raw material in making another product. For example, fluorinated GHG product is used as a raw material in transformation processes to pr oduce fluoropolymers (the fluoropolymer product would not be considered a fluorinated GHG). Emission s of fluorinated GHGs that occur from transformation processes are an area of overlap, since these transformation processes may occur at the same site where fluorinated GHG products are produced, or they may occur at another fluorinated GHG production facility to which the fluorinated GHG feedstock is shipped.

The emissions of fluorinated GHG from destruction proces ses used to remove fluorinated GHG from the U.S. supply is another area of overlap. The fluorinated GHG is returned to the4

facility and subtracted from the U.S. supply, however s ome emissions may occur from the destruction process, either as fugitives from the handl ing of the fluorinated GHG or as undestroyed emissions at the outlet of the destruction de vice.

Filling cylinders or other containers (loading emissions) with fluorinated GHG product and blending of fluorinated GHG with other gases will most l ikely occur after the production measurement, classifying emissions for cylinder filling (loa ding) and blending as downstream
processes.
Recycling of used gas may be performed by the producers of new gas or by offsite recycling firms. Emissions may occur during handling and purifi cation of old gas and during packaging of recycled gas. 2 Since the used gas has already been counted as produced (use d gas is removed from, and then added back into, the gas supply), recycling emissions are considered to be downstream of the production measurement.

Evacuation of fluorinated GHG from returned cylinders or containers results in emissions that vary depending on process type and the composition a nd amount of the heel (residual gas) present.
In theory, it might be possible to track emissions fro m transformation and destruction simply using quantities reported under 40 CFR part 98 subpart OO. However, this would require that (1) fluorinated GHGs that are produced only to be transf ormed or destroyed be tracked separately, (2) production, transformation, and destruction be measured to very good precision and accuracy (e.g., 0.2 percent), and (3) that no by-products be formed or emitted during these processes. If all of these conditions were met, emi ssions could be equated to the differences between production and transformation and production and dest ruction. In practice, however, it would be difficult to meet all of these conditions.

E. Total U.S. Production and Associated Emissions The production of fluorinated gases includes production of fl uorinated GHG (HFCs, PFCs, SF 6 , and NF 3 , HFEs), CFCs and HCFCs (except for HCFC-22 production proce sses). In 2006, 12 U.S. facilities collectively produced over 350 million mtCO 2 e (170,000 tons) of HFCs, PFCs, SF 6 , and NF 3 . EPA estimates that an additional six facilities c ollectively produced almost 1 million mtCO 2 e of fluorinated anesthetics (HFEs) in 2006. The total U. S. production of CFCs and HCFCs (except HCFC-22) in 2008 was estimated to be approxima tely 266,000 tons. The majority of the CFC and HCFC production processes are co -located at facilities that also produce fluorinated GHGs. Another 2 facilities that produce CFC and HCFC products were identified that were not already included in the 12 facilities identif ied above for HFC, PFC, SF6, and NF3 production. Fluorinated gas production processes are sometim es co-located with fluorinated gas transformation processes or fluorinated GHG destruction processes. The total amounts of fluorinated gases transformed into other products or destroye d are not known.

Fluorinated GHG emissions (actual emissions, following application of control techniques where applicable) from U.S. facilities producing f luorinated GHGs are estimated to range from 0.8 percent to 2 percent of the amount produced, depen ding on the facility. An

2 2006 IPCC, Chapter 3.10.5

emission rate of 1.5 percent is assumed for fluorinated GH G production processes. At an emission rate of 1.5 percent, the 12 fluorinated GHG facil ities together are estimated to have emitted approximately 5.3 million mtCO 2 e of HFCs, PFCs, SF 6 , and NF 3 . The six additional HFE production facilities are estimated to have emitted approximately 15,000 mtCO 2 e of fluorinated anesthetics, using an emission rate of 1.5 per cent.
The quantity of emissions of fluorinated GHGs from producti on of CFCs and HCFCs is uncertain. However, the magnitude of by-product generation during F-GHG production (e.g., quantities equivalent to one to five percent of the mass o f the product) suggests that significant quantities of by-product F-GHGs may be generated during productio n of chemically similar substances. Given the substantial amounts of CFCs and HCF Cs that are produced in the U.S., emission rates could be relatively low and still resul t in significant emissions. In 2008, the combined tonnage of U.S. HCFC and CFC production was higher than that of all fluorinated GHG production in 2006 (the latest year for which data were a vailable), with CFCs produced as feedstocks comprising the majority. (Although production of HCFCs and CFCs is limited under the regulations implementing Title VI of the CAA, producti on of these substances for use as feedstocks is permitted to continue indefinitely.) Assu ming that this production resulted in emissions of fluorinated GHG by-products equal to one percent of the mass of CFCs and HCFCs produced, 3 and that these byproducts had an average global warming pote ntial (GWP) of 2000, emissions from CFC and HCFC production are estimated to have totaled 5.3 million mtCO2e in 2008, the same as estimated emissions from fluorinated GHG production in 2006. (No estimate of fluorinated GHG emissions from transformation proces ses, or fluoropolymer production processes, is available.) These emissions, combined wit h those from fluorinated GHG production, lead to a total for the source category of 10.6 mi llion mtCO 2 e. 2. Options for Reporting Threshold EPA evaluated a range of threshold options for fluorinat ed gas production facilities. These included 1,000 mt CO 2 e, 10,000 mtCO 2 e, 25,000 mtCO 2 e, and 100,000 mtCO 2 e. Emission levels on both an uncontrolled and a controll ed basis were evaluated. Because EPA has little information on combustion-related emission s at fluorinated gas production facilities, these emissions were not included in the threshold analy sis.

A. Uncontrolled Emissions Threshold Facility-specific uncontrolled emissions (i.e., pre-contr ol) were estimated for fluorinated GHG production processes (including fluorinated anesthetics production processes) by multiplying a factor of 3.0 percent by the estimated productio n at each facility. For CFC and HCFC production processes (except for HCFC-22 production proce sses), uncontrolled emissions were estimated by multiplying a factor of 2 percent by the e stimated production at each facility. Uncontrolled emissions are strongly influenced by by-product generation rates, which are known to vary between zero and several percent for fluorinate d gas production processes; thus, these estimates are uncertain. The results of the analysi s for uncontrolled emissions from the production of HFCs, PFCs, SF 6 , NF 3 , CFCs, and HCFCs are shown in Table 1. (No emissions o f

3 The emission rate from CFC and HCFC production is assum ed to be lower than that from fluorinated GHG production because only by-products are included in the former , while both products and by-products are included in the latter.6

fluorinated GHG from transformation processes, such as fluoropolymer production processes, are included in the analysis.)

All or most production facilities would be covered by uncon trolled emission thresholds, i.e., 14 of 14 or 13 of 14 facilities would be covered depending o n the cutoff level. Use of the uncontrolled emissions threshold would not allow for appl ying reductions from destruction devices, which may or may not be achieving the demonstrated de struction efficiency on a continuous operating basis. Under the uncontrolled emissi ons threshold option, emissions reductions would not be overstated and emissions to the atmosphere would not be understated. (It is uncertain where the emission levels of the i ndividual anesthetic facilities would fall, and the anesthetic facilities and emissions are not included in Table 2. There are 6 anesthetic facilities that are estimated to generate a total of approximately 30,000 mt CO 2 e.) Emissions from combustion sources at facilities are not included in th e emissions estimate shown in Table 2.

Table 2. Threshold Analysis for Fluorinated GHG Em issions from Production of HFCs, PFCs, SF6, NF3, CFCs, and HCFCs (Uncontrolled Emissions)

Threshold Level (mt CO 2 e/r) Total National

Emissions (mt CO 2 e) Number of

Facilities Emissions Covered Facilities Covered

mt CO 2 e Percent Number Percent 1,000 10,600,000 14 10,600,000 100% 14 100% 10,000 10,600,000 14 10,600,000 100% 14 100% 25,000 10,600,000 14 10,600,000 100% 14 100% 100,000 10,600,000 14 10,600,000 100% 13 93%

B. Controlled Emissions Threshold Facility-specific controlled emissions (i.e., those fo llowing the control device, if in place) were estimated for fluorinated GHG production processes (i ncluding anesthetics production processes) by multiplying a factor of 1.5 percent by the esti mated production at each facility. For CFC and HCFC production processes (except for HCFC-22 pr oduction processes), controlled emissions were estimated by multiplying by a factor of 1.0 percent by the estimated production at each facility. Controlled emissions were assumed to be half of uncontrolled emissions at each facility. The results of the ana lysis for controlled emissions from the production of HFCs, PFCs, SF 6 , NF 3 , CFCs, and HCFCs are shown in Table 2. No emissions of fluorinated GHG from transformation processes (other th an those that produce fluorinated GHGs) are included in the analysis.

All or most of the production facilities would be cover ed by controlled emission thresholds, depending on the cutoff, although fewer facil ities would be covered under the controlled emission threshold option (10 facilities) tha n under the uncontrolled emission threshold option (13 facilities) at the highest cutoff (i.e., 100,000 mtCO2e). Use of the controlled emissions threshold option would allow faci lities to account for emission reductions achieved by destruction devices that had a demonstrated destruc tion efficiency. It is possible that emission levels may be understated using the control led emissions option. (It is uncertain where the emission levels of the individual anestheti c facilities would fall, and the anesthetic facilities and emissions are not included in Table 3. Ther e are 6 anesthetic facilities that are7

estimated to emit a total of approximately 15,000 mt CO 2 e.) Emissions from combustion sources at facilities are not included in the emissions estimat e shown in Table 3.

Table 3. Threshold Analysis for Fluorinated GHG Em issions from Production of HFCs, PFCs, SF6, NF3, CFCs, and HCFCs (Controlled Emissions)

Threshold Level (mt CO 2 e/r) Total

National Emissions (mt CO 2 e) Number of

Facilities Emissions Covered Facilities Covered

mt CO 2 e Percent Number Percent 1,000 10,600,000 14 10,600,000 100% 14 100% 10,000 10,600,000 14 10,600,000 100% 14 100% 25,000 10,600,000 14 10,600,000 100% 14 100% 100,000 10,600,000 14 10,300,000 97% 10 71%

C. No Emissions Threshold (i.e., All-in) Under an “all-in” approach, no emissions threshold level would be included in the rule and all facilities in the fluorinated gas source categor y, including facilities producing anesthetics, would be subject to the rule regardless of emission levels . The all-in approach would ensure that all facilities identified and quantified their fluorinated GHG emissions, even if they initially believed those emissions to be small. Some faciliti es that initially believed their emissions to be small could find that those emissions actually exceeded 25, 000 mt CO 2 e (e.g., because a previously unidentified fluorinated GHG with a high GWP was being generated and emitted as a by-product). Facilities whose emissions remained below 25,000 mt CO2e or 15,000 mt CO 2 e could cease reporting after five or three years respecti vely. In addition, an all-in approach would provide an essentially level playing field because all faci lities in the source category would be subject to the rule and be subject to the same economic im pact from the reporting rule. However, an all-in approach would also increase the bur den on facilities with uncontrolled emissions below 25,000 mt CO 2 e. This could result in higher reporting costs per metric t on CO 2 e for these facilities than for higher emitting facilit ies.
3. Monitoring Methods, Data Collection and Current Plant Practices A. Scoping Test and Options for Characterizing Emitt ed Streams i. Reliance on previous bench- and pilot-scale test ing During research and development of a fluorinated gas product, companies develop laboratory, bench-scale, and pilot-scale processes to ma nufacture new products. During laboratory and bench-scale development of the process, c ompanies generate small quantities of the product. The companies monitor and measure all aspects o f the process, including rates and extent of reaction, reactant and full product and byproduct i dentity and compositions, and physical characteristics of the compounds. This testing and analysis of compounds in the various process streams generally identifies the product and all bypr oducts generated in the process. During these laboratory or bench-scale processes, proce ss optimization is addressed by defining operating conditions that generate the best product yields a nd least byproducts, considering the most efficient use of resources. Following the laborat ory and bench-scale level of process development, a process may be scaled to a larger basis, i .e., pilot-scale basis, to continue research and development of the process and to continue t o refine process optimization. The8

pilot-scale process, meant to simulate a full-scale production process, generates a larger quantity of product than the laboratory scale process but less th an a full-scale production process. The equipment used in pilot-scale processes is similar in de sign to what the full-scale process might be, and is used to continue research on the process, as t he data available from earlier laboratory and bench-scale systems are applied. However, some data may not be directly applicable to the pilot-scale system. As part of the continued research , the company continues to test and analyze the products and byproducts from the pilot-scale process to c onfirm what compounds are generated in the process as operating conditions are refi ned (i.e., changed).

The findings regarding the identities of the compounds genera ted during these stages of process research and development may be used to help unders tand the identities of the compounds present in emission and waste streams for the full-scale production process. The analyses are typically rigorous as the company is eager to know and learn as much as possible and limit side reactions and increase yields. A potenti al drawback to use of the laboratory and pilot scale compound and composition analyses is that th ere may be some differences in the products and byproducts as the process is scaled from laborat ory/bench-scale to pilot-scale to full-scale production units. The earlier data may not be fully applicable to the larger scale processes. Differences are likely to occur between the laboratory and pilot-scales, and streams may need to be tested and analyzed again to detect changes between the pilot- and full-scale production processes.

ii. Initial Scoping Test
To ensure that all fluorinated GHGs that occur in emitte d streams are accurately identified, an initial scoping test on vents and streams from fluorinated gas processes may be conducted. The initial scoping test would be conducted using methods that allow detection and identification of all compounds in the vent or stream. The identity of the specific compounds that are generated during the fluorinated gas production proce ss is important to the emissions estimate. Some facilities have indicated that even w ith extensive laboratory and bench-scale compositional and quantitative analysis from research, development, and design stages of the process, unexpected F GHGs can be found in emissions stream s. 4

The results of the scoping test can be used to inform bo th the mass-balance and emissionfactor approaches (described further below). In the mass balance approach, the amount of product recovered is compared to the amount of reactants a nd the expected product quantity; the differences are assumed to be product lost to emissions. However, byproducts are created and knowledge of these informs the emissions estimate so tha t product and byproduct compounds are appropriately represented in the mass balance equations. F or example, for facilities using the mass-balance approach, the scoping test can be used to dete rmine whether some emissions assumed to occur in the form of the product are actually o ccurring as by-products. For those facilities using an emissions factor approach, the result s from the scoping test will ensure that emissions factors are appropriately developed for all bypro duct compounds. The scoping test will identify byproducts that should be measured in subsequen t emissions testing to develop emission factors.

4 Based on conversations with Fluorinated GHG producers, as referenced in section 7.9

Accurately identifying the compounds emitted provides for a bet ter fluorinated GHG emissions estimate and also a better CO 2 e emissions estimate because the appropriate GWP are applied to the emitted compounds. If there is a differen ce between the GWPs of a product and a byproduct and if the emissions are assumed to consist excl usively of the product, the CO 2 e emissions could be overestimated or underestimated. Under estimation is a particular concern where the process unexpectedly generates a fluorinated GHG that is difficult to destroy (e.g., CF 4 ). In this case, applying the destruction efficiency (DE) of the destruction device to the emissions may overestimate destruction and underestimat e emissions.

Facilities would conduct an initial scoping test on each fluorinated gas process at the facility. EPA evaluated emissions cutoffs on a process ba sis so that only those processes with expected fluorinated GHG emissions above a cutoff level would conduct the initial scoping test. We considered a limit of 10,000 mtCO 2 e on an uncontrolled basis for each process, and note th at a cutoff based on fluorinated GHG (rather than CO 2 e) emissions may be appropriate because the identity and the GWP of some fluorinated GHG compounds may not be known. Based on a conservative assumption of an average GWP of 10,000, the fluo rinated GHG emissions cutoff would be 1 metric ton fluorinated GHG. The estimate of e missions from each process could be determined using standard engineering calculations, previous measur ements, and engineering assessments (i.e., similar to preliminary emission e stimates discussed under process vent specific emissions calculation factors below). Because the s pecific fluorinated GHG byproducts may not be known, it may be appropriate to apply the 1-metric-ton -fluorinated-GHG-emission cutoff to uncontrolled emissions. As noted above, the applicatio n of the destruction device’s DE may underestimate emissions (and therefore fail to trigger t esting) if difficult-to-destroy fluorinated GHGs occur unexpectedly in the stream.

For each process with fluorinated GHG emissions above t he cutoff level, facilities would select those process vents or streams for testing that are most likely to contain all of the fluorinated GHG compounds anticipated to be generated or emitt ed. Sampling and analytical methods capable of detecting and speciating fluorinated GHG c ompounds and capable of identifying multiple compounds simultaneously would be the be st choices for the initial scoping test. For example, methods that use gas chromatography wit h mass spectrometry (GC/MS) are capable of detecting and identifying multiple fluorinated GHG compounds. Another example of an appropriate sampling and analytical method includes Fourier transform infrared (FTIR) analysis. There are several EPA reference methods and other consensus vetted methods that may be used to sample and analyze fluorinated GHG; these meth ods include EPA Method 18 - Measurement of Gaseous Organic Compound Emissions by Gas Ch romatography (GC/ECD, GC/MS), EPA Test Method 320 Measurement of Vapor Phase O rganic and Inorganic Emissions by Extractive Fourier Transform Infrared (FTIR) Spectros copy, and ASTM D6348-03 (FTIR) Standard Test Method for Determination of Gaseous Compound s by Extractive Direct Interface Fourier Transform Infrared (FTIR) Spectroscopy. Each of these is briefly described below in the section on Process-Vent-Specific Emission Factor Approa ch. If EPA Method 18 is conducted, the facility would also conduct an EPA Method 1 series (Sample and Velocity Traverses for Stationary Sources), Method 2 series (Determination of Stack Gas Velocity and Volumetric Flow Rate), Method 3 series (Gas Analysis for Carbon Dioxi de, Oxygen, Excess Air, and Dry Molecular Weight), and Method 4 (Determination of Mois ture Content in Stack Gases). If a facility is not able to conduct EPA Method 2, alternativ e flow rate methods may be used, such as OTM 24 (Tracer Gas Protocol For the Determination of Vo lumetric Flow Rate Through the Ring10

Pipe of the Xact Multi-Metals Monitoring System) or ALT -012 (Emission Measurement Center Approved Alternative Method).

B. Options for Developing Emissions Estimates
i. Default Emission Factor One option for characterizing fluorinated GHG is the use o f default emission factors. These factors would provide a rough estimate of the quantity of fluorinated GHGs emitted. Although the default emission factor approach is simple and easily-implemented, it is also highly imprecise; emissions of fluorinated GHG products in U.S. p lants are estimated to vary from 0.8 percent to 2 percent of production, more than a factor o f two (RTI, 2008). 5 Thus, applying a default factor (1.5 percent, for example) is likely to s ignificantly overestimate emissions at some plants while significantly underestimating them at other s.
Under a somewhat more rigorous default emission factor approach, emission factors would be developed for similar types of emission points at m ultiple facilities within a source category. The emission factors for each type of emi ssion point would be averaged to develop an industry-wide emission factor for that type of emission point. Because these EFs would represent average values over multiple facilities, some facilit ies would be above the EF and some would be below. As a result, such factors may not provide an acc urate emissions determination for a single facility. Default EFs would not account for i nter-facility variability that can occur due to the age of facility and equipment, equipment sizes, equip ment design, differences in raw materials and suppliers, different typical operating para meters, and variations in the process operation that may not be readily apparent or known. In addition, default EF would not provide information that EPA may need to compare the best and w orst performers, or provide insights into which facilities have the most or fewest opportuniti es to obtain additional reductions.

ii. Mass Balance In the mass-balance approach, facilities weigh or mete r the reactants fed into the process, the product resulting from the process, and any byproducts and w astes that are removed from the process (i.e., sent to the thermal oxidizer or other e quipment, not immediately recycled back into the process). Facilities then calculate the differe nce between the mass of reactants fed into the process and the sum of the masses of the main product and t hose of any byproducts and/or wastes. This difference is then assigned to loss of r eactants, loss of product, and/or conversion to byproducts. As discussed further below, it is EPA’s unders tanding that some facilities perform these measurements and calculations to monitor their pr ocesses and yields.

Because the mass-balance approach relies on the calcula tion of relatively small differences between relatively large numbers, measurem ents must have good precision to avoid large uncertainties in the emissions estimates. EPA e valuated methods to estimate the error associated with the mass balance approach.

5 The emission rates cited were estimated for HCFC-22, wh ich is an ozone-depleting substance and therefore excluded from the proposed rule. However, the production proc esses for many fluorinated GHGs are similar to those for HCFC-22 (2006 IPCC Guidelines, Volume 3, section 3.10.2.1), and therefore their emission rates are likely to be similar as well.11

1. Error Limits Precision and Accuracy Requirements for Individual Measurements One approach to limiting the error associated with emissi ons estimates developed using the mass-balance approach is to establish specific precisi on and accuracy requirements for each measurement used in the mass-balance equation. These me asurements include mass measurements for reactants, products, and fluorinated GHG by-products, including feed streams, final product streams, emitted streams, and destroyed or rec aptured streams. In addition, they include concentration measurements where products or by-product s occur in streams with other substances. To limit the uncertainty of the emission e stimate to ± 30 percent of the estimate, devices used to measure masses (e.g., flowmeters and scale s) would need to be able to achieve precisions and accuracies near ± 0.2 percent or better, at l east for streams with a large impact on the mass-balance calculation. Concentration measurem ents would need to be conducted with precisions and accuracies of ± 10 percent or better.This appro ach limits error and is straightforward to implement and enforce. However, it m ay require substantial expenditures to obtain accurate and precise measurements of quantities wh ose errors have little impact on the overall error of the emissions estimate. For exampl e, under this approach, facilities might be required to upgrade flowmeters in streams that affect the emission estimate (and its uncertainty) only slightly. The approach also limits flexibility. Even a facility with a relatively large error in one stream may be able to bring the total error of its emissions estimate to a tolerable level by improving the accuracy and precision of other measurements that are used in the mass-balance equation, such as the mass flows of reactants and products

. Error Limit for the Emission Estimate as a Whole. Another approach to limiting the error of the mass-balan ce approach is to establish a limit on the error of the overall emission estimate. To es timate the statistical error associated with use of the mass-balance approach, facilities would be require d to use error propagation, considering the accuracy and precision of their measurements and the calculation methods of the massbalance approach. Under this approach, EPA would not specify precision and accuracy requirements for individual mass or concentration meas urements. Instead, EPA would require that the error associated with the overall estimate of fluorinated GHG emissions fall under a specific limit. This limit could be expressed in terms o f a fraction of the emissions estimate (relative error) or as a specific quantity (absolute error ). Facilities could achieve this level of precision and accuracy however they chose.

A maximum relative error of ± 30 percent would be comparable to that cited by a facility that has used an emission factor approach to estimate it s fluorinated GHG emissions. It is also comparable to the error that EPA calculates for a faci lity with an emission rate of two percent and with good precisions and accuracies for its mass flow measurements (± 0.2 percent) and for its concentration measurement (± 10 percent) of a wast e stream constituting five percent of the process’s fluorinated GHG output flow. For facilities whose emissions constitute a very small share of their inputs and outputs (e.g., one percent or l ess), a relative error of ± 30 percent would be very difficult to achieve using a mass-balance approach . At the same time, the absolute error of such a facility’s estimate may be smaller than the absolute error of a facility that meets the relative error test but that has a higher emission rat e. It may therefore be appropriate to establish a maximum permissible absolute error of 3,000 mtCO2e for fac ilities whose estimates have12

relative errors greater than 30 percent. This absolute error is equivalent to 30 percent of the 10,000 mtCO2e threshold that is used elsewhere in the subpart to establish requirements for different sources (e.g., process vents). Under this appr oach, processes whose emissions were lower than 10,000 mtCO2e could have relative errors higher th an 30 percent so long as they met the limit on absolute error. This approach would avoid penal izing processes and facilities with low emissions.

Another approach that would avoid penalizing facilities wit h low emission rates would be to express the maximum relative error as a fraction of the total mass of reactants fed into (or consumed by) the process. For a given process, this mass would remain relatively constant regardless of the emission rate. For the model facil ity described above, with errors of 0.2 percent in its mass flow measurements and of 10 percent in its c oncentration measurements, the error of the emissions estimate relative to the total mass of r eactants is about 0.3 percent. One advantage of this approach compared to the absolute limit is that t his approach limits the relative errors for processes with small throughputs, while the absolute limit could permit very large relative errors for processes with small throughputs.

The absolute and relative errors associated with using th e mass balance approach on a process may be estimated using equations L-1, L-2, L-3, and L -4 in conjunction with equations L-7 through L-12. To perform the calculation, facilities would calculate the absolute and relative errors associated with the quantities calculated using equa tions L-8, L-9, L-10, and L-11. Once errors have been calculated for the quantities in thes e equations, those errors would be used to calculate the errors in equations L-7 and L-12. Where the measured quantity is a mass, the error in the mass could be equated to the accuracy or precision (whichever is larger) of the flowmeter, scale, or combination of volumetric and density measurem ents at the flowrate or mass measured. Where the measured quantity is a concentration, the err or of the concentration could be equated to the accuracy or precision (whichever is larger) of the analytical technique used to measure the concentration at the concentration measured.

Equation L-1 provides the general formula for calculating t he absolute errors of sums and differences where the sum, S, is the summation of v ariables measured, a, b, c, etc. (e.g., S = a + b + c):

e SA = [(a*e a ) 2 + ((b*e b ) 2 + (c*e c ) 2 ] 1/2 (Eq. L-1)

Where:

e SA = absolute error of the sum, expressed as one half of a 95 percent confidence interval.

e a = relative error of a, expressed as one half of a 95 pe rcent confidence interval.

e b = relative error of b, expressed as one half of a 95 pe rcent confidence interval.

e c = relative error of c, expressed as one half of a 95 pe rcent confidence interval.

Equation L-2 provides the general formula for calculating t he relative errors of sums and differences:13 

## ( ) c b a e e SA SR + + = (Eq. L-2)

Where:

e SR = relative error of the sum, expressed as one half of a 95 percent confidence interval.

e SA = absolute error of the sum, expressed as one half of a 95 percent confidence interval.
a+b+c = sum of the variables measured.

Equation L-3 provides the general formula for calculating t he absolute errors of products (e.g., flow rates of GHGs calculated as the product of t he flow rate of the stream and the concentration of the GHG in the stream), where the product, P, is the result of multiplying the variables measured, a, b, c, etc. (e.g., P = a*b*c):

e PA = (a*b*c)(e a 2 + e b 2 + e c 2 ) 1/2 (Eq. L-3)

Where:

e PA = absolute error of the product, expressed as one half of a 95 percent confidence

interval.

e a = relative error of a, expressed as one half of a 95 pe rcent confidence interval.

e b = relative error of b, expressed as one half of a 95 pe rcent confidence interval.

e c = relative error of c, expressed as one half of a 95 pe rcent confidence interval.

Equation L-4 provides the general formula for calculating t he relative errors of products:



## ( ) c b a e e PA PR * * = (Eq. L-4)

Where:

e PR = relative error of the product, expressed as one half of a 95 percent confidence interval.

e PA = absolute error of the product, expressed as one half of a 95 percent confidence

interval. a*b*c = product of the variables measured

2. Mass Balance Approach Equations. The following set of equations summarizes the mass- balancing method for estimating fluorinated GHG emission.

The total mass of each fluorinated GHG product emit ted annually from all fluorinated gas production processes would be estimated by using Eq uation L-5 of this section:


## ∑ ∑

= = = m

i Pip n

p P E E

1

1 (Eq. L-5)14

Where:
E P = Total mass of each fluorinated GHG product emitt ed annually from all production

processes (metric tons).
E Pip = Total mass of the fluorinated GHG product emitte d from production process i over

the period p (metric tons, defined in Equation L-7 of this section). n = Number of concentration and flow measurement p eriods for the year. m = Number of production processes.

The total mass of fluorinated GHG by-product k emit ted annually from all fluorinated gas production processes shall be estimated by using Eq uation L-6 of this section:


## ∑ ∑

= = = m

i Bkip n

p Bk E E

1

1 (Eq. L-6)

Where:
E Bk = Total mass of fluorinated GHG by-product k emitt ed annually from all production processes (metric tons).
E Bkip = Total mass of fluorinated GHG by-product k emitt ed from production process i over

the period p (metric tons, defined in Equation L-8 on this section). n = Number of concentration and flow measurement p eriods for the year. m = Number of production processes.

The total mass of each fluorinated GHG product emit ted from production process i over the period p would be estimated by calculating the difference between the expected production of the fluorinated GHG based on the consumption of one of the reactants (e.g., HF or a chlorofluorocarbon reactant) and the measured produ ction of the fluorinated GHG, accounting for yield losses related to by-products and wastes. This calculation shall be performed using Equation L-7 of this section. 

# ( ) ∑ ∑

= = − − − = u

k Bkip q

j Dj P
R R P P Pip L W C P SC MW SC MW R E

1 1 * * * * (Eq.L-7)

Where:
E Pip = Total mass of each fluorinated GHG product emitt ed from production process i over

the period p (metric tons). P = Total mass of the fluorinated GHG produced by p roduction process i over the period

p (metric tons). R = Total mass of the reactant that is consumed by production process i over the period p

(metric tons, defined in Equation L-8).
MW R = Molecular weight of the reactant.
MW P = Molecular weight of the fluorinated GHG produced

. SC R = Stoichiometric coefficient of the reactant.
SC P = Stoichiometric coefficient of the fluorinated GH G produced.15

c P = Concentration (mass fraction) of the fluorinated GHG product in stream j of

destroyed wastes. If this concentration is only a trace concentration, c P is equal to

zero. W Dj = Mass of wastes removed from production process i in stream j and destroyed over the period p (metric tons, defined in Equation L-9 of t his section).
L Bkip = Yield loss related to by-product k for producti on process i over the period p (metric

tons, defined in Equation L-10 of this section). q = Number of waste streams destroyed in production process i. u = Number of by-products generated in production p rocess i.

The total mass of the reactant that is consumed by production process i over the period p shall be estimated by using Equation L-8 of this se ction:

R F R R R

− = (Eq.L-8)

Where: R = Total mass of the reactant that is consumed by production process i over the period p

(metric tons).
R F = Total mass of the reactant that is fed into prod uction process i over the period p

(metric tons).
R R = Total mass of the reactant that is permanently r emoved from production process i

over the period p (metric tons).

The mass of wastes removed from production process i in stream j and destroyed over the period p would be estimated using Equation L-9 of t his section:

DE W W Fj Dj * = (Eq. L-9)

Where:
W Dj = The mass of wastes removed from production proce ss i in stream j and destroyed over the period p (metric tons).
W Fj = The total mass of wastes removed from production process i in stream j and fed into

the destruction device over the period p (metric to ns). DE = Destruction Efficiency of the destruction devi ce (fraction).

Yield loss related to by-product k for production p rocess i over period p would be estimated using Equation L-10 of this section: 

# ( ) ( )

P Bk Bk P kip Bkip ME MW ME MW B L * *

*

= (Eq. L-10)

Where:
L Bkip = Yield loss related to by-product k for productio n process i over the period p (metric

tons).16

B kip = Mass of by-product k generated by production pr ocess i over the period p (metric

tons, defined in Equation L-11 of this section).
MW P = Molecular weight of the fluorinated GHG produced

. MW Bk = Molecular weight of by-product k.
ME Bk = Moles of the element shared by the reactant, pro duct, and by-product k per mole of

by-product k.
ME P = Moles of the element shared by the reactant, pro duct, and by-product k per mole of

the product.

If by-product k is responsible for yield loss in pr oduction process i and occurs in any process stream in more than trace concentrations, t he mass of by-product k generated by production process i over the period p would be est imated using Equation L-11 of this section:


## ∑
= q

j j Bjk kip S c B * (Eq. L-11)

Where:
B kip = Mass of by-product k generated by production pr ocess i over the period p (metric

tons).

c Bkj = Concentration (mass fraction) of the by-product k in stream j of production process i

over the period p. If this concentration is only a trace concentration, c Bkj is equal to

zero. S j = Mass flow of process stream j of production proc ess i over the period p. q = Number of streams in production process i.

If by-product k is responsible for yield loss, is a fluorinated GHG, occurs in any process stream in more than trace concentrations, and is no t completely recaptured or completely destroyed; the total mass of by-product k emitted f rom production process i over the period p would be estimated using Equation L-12of this secti on:


## ∑ ∑

= = − − = x

l Rl Bkl Dj q

j Bkj kip Bkip S c W c B E

1 1 * * (Eq. L-12)

Where:
E Bkip = Mass of by-product k emitted from production pro cess i over the period p (metric

tons).
B kip = Mass of by-product k generated by production pr ocess i over the period p (metric

tons).

c Bkj = Concentration (mass fraction) of the by-product k in stream j of destroyed wastes

over the period p. If this concentration is only a trace concentration, c Bj is equal to

zero. W Dj = The mass of wastes that are removed from product ion process i in stream j and that are destroyed over the period p (metric tons, defin ed in Equation L-9 of this section).17

c Bkl = The concentration (mass fraction) of the by-prod uct k in stream l of recaptured

material over the period p. If this concentration i s only a trace concentration, c Bkl is equal to zero.
S Rl = The mass of materials that are removed from prod uction process i in stream l and that are recaptured over the period p. q = Number of waste streams destroyed in production process i. x = Number of streams recaptured in production proc ess i.

3. Choice of Reactant Whose Yield Is Measured.

EPA has considered use of one reactant to estimate emissions under the mass-balance approach (rather than both as originally proposed). Some fluorinated GHG producers have noted that, for various reasons, it is sometimes consider ably more difficult to track the yields of some reactants than others (e.g., HF vs. an organic feed stock). EPA notes that facilities estimating their emissions based on the yield of one reactant would still need to be able to demonstrate that their estimate met the statistical error test that might be required.

If an alternate reactant was measured, it would be necessary for facilities to be extremely thorough in the monitoring approach and calculation s in order to account for all potential emissions. The reactant whose yield is measured an d its relationship to fluorinated GHG emissions for a particular process must be fully an alyzed to ensure that it provided an accurate representation of the emissions.

4. Frequency of Measurement and Calculation.

EPA considered several measurement and calculation frequencies for the mass balance approach. The total mass of each fluorinated GHG p roduct emitted from production process could be estimated on a daily or monthly basis by c alculating the difference between the expected production of the fluorinated GHG based on the consumption of one of the reactants (e.g., HF or a chlorofluorocarbon reactant) and the measured production of the fluorinated GHG, accounting for yield losses related to by-products and wastes. The daily measurement requires additional man hours to conduct more frequent measu rements; however, in situations where input or output flows are estimated by multiplying concentrations by total mass flow rates of streams, and where one or both of these vary, frequ ent measurements will lead to more accurate and precise estimates than less frequent. A number of fluorocarbon producers have noted that daily measurements are burdensome and lead to large errors in the estimates of daily emissions. Many streams may contain acidic and reactive consti tuents such as HF, and sampling from these streams can create safety hazards. Daily yield mea surements can also vary significantly (sometimes exceeding 100 percent) for three reasons . First, when continuous processes are initially started, there is a lag time between the time the reactants are fed into the process and the time products emerge. Second, even after the proce ss has been running for a while, the quantity of material in the process can vary based on weathe r, changes in production rates, and other conditions. Third, the relatively large errors in measurements of in-process product holding tanks (e.g., based on sight-glass readings) have a significant impact on daily mass balances. Over time, all of these effects smooth out, making longe r term mass balances more reliable than daily mass balances.18

Some fluorinated GHG producers have stated that it is difficult to measure fluorinated GHG concentrations in some streams. In some cases, this is because waste streams contain hydrofluoric acid (HF), which, due to its acidity a nd reactivity, can damage sampling and analytical equipment. To the extent that these app roaches could be relatively difficult or expensive to implement, however, it might be approp riate to permit very infrequent measurements. The disadvantage of this approach is that it might lead to larger errors, particularly for processes that vary over time. A s eries of measurements might be required to (l) reduce the error and (2) quantify the error for purposes of the statistical error test. Such measurements would be analogous to those used to de velop emission factors.

5. Reactant and Byproduct Emissions. EPA recognizes that the proposed mass-balance appro ach would assume that all yield losses that are not accounted for are attributable to emissions of the fluorinated GHG product. In some cases, the losses may be untracked emissions o r other losses of reactants or fluorinated byproducts. In general, EPA understands that reactan t flows are measured at the inlet to the reactor; thus, any losses of reactant that occur be tween the point of measurement and the reactor are likely to be small. However, reactants that ar e recovered from the process, whether they are recycled back into it or removed permanently, may e xperience some losses that the proposed method does not account for.

Fluorocarbon by-products, according to the IPCC Gui delines, generally have “radiative forcing properties similar to those of the desired fluorochemical.” However, EPA is aware of at least one facility where byproducts often have much larger GWPs than the products. In this case, assuming by-product emissions are product emissions would lead to large errors in estimating overall fluorinated GHG emissions. EPA believes th at the initial scoping test of emitted streams that is discussed above would help to determine whe ther this was an issue for a given process. If it was, then the facility could elect to pursue the PSEF approach rather than the mass-balance approach for that process, or, if the facility was still interested in pursuing the mass balance approach, it could perform more emissions testing t o develop a robust break-out among the FGHGs assumed to be emitted under the mass-balance a pproach (e.g., by increasing calculated by-product emissions by some percentage). Such emi ssions testing would be similar to that performed for the PSEF approach below, except it wo uld focus on the partitioning of emissions among the various F-GHGs.

6. Alternative approach based on measurements of balanced eleme nt Another variant of the mass-balance approach would not require facilities to speciate their by-product and/or waste streams on a periodic basis. Instead, facilities could measure the total fluorine (or other element of interest other than carbon) in the by-product and/or waste streams, e.g., by burning them. An initial emissio ns test would be conducted to ensure that emissions were properly allocated among the reactan t, product, and by-products, but this testing could be repeated at longer than monthly intervals, e.g., annually or every five years. The total fluorine approach could be particularly useful for processes with multiple by-products.

The following equation, Equation AMB-1, is analogou s to Equation L-7, but it provides emissions in terms of fluorine rather than the fluo rinated GHG product. This equation describes a relatively simple case in which only one reactant contains the fluorine (or other element of19

interest), but it could be generalized by summing o ver R n , where n is the number of reactants. As discussed further below, E F needs to be multiplied by another term to obtain e missions in terms of the product and byproduct.


## ∑

∑

= = −

       
+

− = u

k Bk F Bk k
P F P q

j Dj P
R F R F MW AW MF B MW AW MF W C P MW AW MF R E

1 1 * * * * * * * (Eq. AMB-1)

Where:
E F = Total mass of fluorine emitted from production p rocess i over the period p (metric tons). P = Total mass of the fluorinated GHG produced by p roduction process i over the period

p (metric tons).
B k = Mass of by-product k generated by production pr ocess i over the period p (metric

tons). R = Total mass of the reactant that is consumed by production process i over the period p

(metric tons).
MW R = Molecular weight of the reactant.
MW P = Molecular weight of the fluorinated GHG produced

. MW Bk = Molecular weight of by-product k.
AW F = Atomic weight of fluorine.
MF R = Moles fluorine per mole of reactant.
MF P = Moles fluorine per mole of product.
MF Bk = Moles fluorine per mole of by-product k.

c P = Concentration (mass fraction) of the fluorinated GHG product in stream j of

destroyed wastes. If this concentration is only a trace concentration, c P is equal to

zero. W Dj = Mass of wastes removed from production process i in stream j and destroyed over the period p (metric tons). q = Number of waste streams destroyed in production process i. u = Number of by-products generated in production p rocess i.

This equation needs to be multiplied by another ter m to obtain emissions in terms of the product:

F
F P

P P E

AW MW
MF E *

* 1 

      

= (Eq. AMB-2)

Where:
E P = Total mass of fluorinated GHG product emitted (m etric tons).
MW P = Molecular weight of the fluorinated GHG produced

. AW F = Atomic weight of fluorine.
MF P = Moles fluorine per mole of product.20

E F = Total mass of fluorine emitted from production p rocess i over the period p (metric tons).

Note that when Equations AMB-1 and AMB-2 are multip lied, they result in Equation L-7.

As noted above, the advantage of the fluorine-balan cing approach is that destroyed product and byproduct streams do not need to be spe ciated if their total fluorine contents can be measured. We can revise Equation AMB-1 to reflect this. We can also revise Equation AMB-1 to express quantities in terms of mass fractions of fluorine. The following Equation AMB-3 reflects these changes.

D P R F F

MFF P MFF R E

−

− = * * (Eq. AMB-3)

Where:
E F = Total mass of fluorine emitted from production p rocess i over the period p (metric tons). P = Total mass of the fluorinated GHG produced by p roduction process i over the period

p (metric tons). R = Total mass of the reactant that is consumed by production process i over the period p

(metric tons), calculated in equation L-8.

MFF R = Mass fraction of fluorine in the reactant, equal to

R

F R MW AW MF * .

MFF P = Mass fraction of fluorine in the fluorinated GHG product, equal to

P F P MW AW MF * .

F D = Mass of fluorine measured in destroyed or recapt ured streams containing fluorinatedGHG product and byproducts.

Equation AMB-2 assumes that all of the fluorine is emitted in the form of the fluorinatedGHG product. In fact, the scoping test and subseque nt emissions testing may show that some of the mass emitted consists of fluorinated GHG byprod ucts. In this case, the mass of fluorine emitted should be allocated among the reactant, pro duct, and byproducts (including GHGs and non-GHGs).

To do this, we would begin with the results of the most recent emissions test, that is, with the fractions of the emitted fluorinated compounds that consist of the reactant, product, and each byproduct. These fractions would be adjusted to re flect the shares of the masses of the reactant, product and by-products that consist of fluorine. The sum of the adjusted fractions, multiplied by the total emissions from the process, are equal to the emissions of fluorine from the process calculated in Equation AMB-3.

      +

+ = 

## ∑

= u

k Bk

k P R F MFF FEB MFF FEP MFF FER T E

1 * * * * (Eq. AMB-4)21

Where:
E F = Total mass of fluorine emitted from production p rocess i over the period p (metric tons). T = Total mass emitted from the process, including emitted reactants, products, and byproducts
FER = The fraction of the mass emitted that consist s of the reactant (from the most recent

emissions test).
FEP = The fraction of the mass emitted that consis ts of the fluorinated GHG product (from

most recent emissions test).
FEB k = The fraction of the mass emitted that consists o f by-product k (from most recent

emissions test).

MFF R = Mass fraction of fluorine in the reactant, equal to

R

F R MW AW MF * .

MFF P = Mass fraction of fluorine in the fluorinated GHG product, equal to

P F P MW AW MF * .

MFF Bk = Mass fraction of fluorine in by-product k, equal to

Bk F Bk MW AW MF * .

Since T*(FER) = E R , T*(FEP) = E P , and T*(FEB k ) = E Bk , we can solve Equation AMB-4 for T and multiply by FER, FEP, and FEB k , as appropriate, to obtain Equations AMB-5, AMB-6, and AMB-7, respectively.

      +

+ = 

# ∑

= u

k Bk

k P R F R MFF FEB MFF FEP MFF FER E

FER E

1 * * * * (Eq. AMB-5)

      +

+ = 

# ∑

= u

k Bk

k P R F
p MFF FEB MFF FEP MFF FER E

FEP E

1 * * * * (Eq. AMB-6)

      +

+ = 

# ∑

= u

k Bk

k P R F

k Bk MFF FEB MFF FEP MFF FER E

FEB E

1 * * * * (Eq. AMB-7)

Where:
E P = Total mass of fluorinated GHG product emitted (m etric tons).
E Bk = Total mass of by-product k emitted (metric tons)

. E R = Total mass of Emissions of the fluorinated GHG p roduct.
FER = The fraction of the mass emitted that consist s of the reactant (from the most recent

emissions test).22

FEP = The fraction of the mass emitted that consis ts of the fluorinated GHG product (from

most recent emissions test).
FEB k = The fraction of the mass emitted that consists o f by-product k (from most recent

emissions test).

MFF R = Mass fraction of fluorine in the reactant, equal to

R

F R MW AW MF * .

MFF P = Mass fraction of fluorine in the fluorinated GHG product, equal to

P F P MW AW MF * .

MFF Bk = Mass fraction of fluorine in by-product k, equal to

Bk F Bk MW AW MF * .

u = Number of by-products generated in production p rocess i.

7. Current Plant Practices for Mass Balance A few facilities indicated that they conduct a form of the mass balance approach for determining fluorinated GHG emissions. Facilities noted overall that the difficulty of the mass balance approach depends on how sophisticated or co mplex the process is, i.e., how many input and output streams there are, and whether there are by-products generated and how many. Facilities that use a form of the mass balance appr oach indicated that it is often used in conjunction with an emissions factor based approach , to track yields and subtle or incremental changes in the process. These facilities conduct a “material balance” on the process, tracking the product yield, using the emission factor for some e mission points, and the composition and concentration of the streams to determine if someth ing in the process has changed. Generally, facilities have a good understanding of the chemist ry for all processes and understand what raw materials are fed to the process, what side reactio ns occur, and what products and by-products are created. Facilities have laboratory-scale, pil ot-plant, and full-scale stream analysis results. Facilities stated that with the original plant desi gn, the mass balance equation is predicted. Facilities noted in particular that at the bench-sc ale phase of product and process development, they analyze every/all streams to identify all spec ies and compounds. However, one facility indicated that while they do regularly measure bypr oduct concentrations in the product as a quality check, they do not regularly measure byprod uct concentration across all process vents and streams.

Some facilities indicated that they conduct the mas s balance on the fluorinated organic component only.

Facilities noted, in particular, that they reconcil e and calculate the production levels on a monthly basis rather than on shorter time frames su ch as daily or weekly.

iii. Monitoring of Process Vents The emissions from process vents may be determined by a number of methods. These include emissions testing, engineering assessments, or calculations based on chemical engineering principles. All three methods may also be used to develop a site-specific emissions factor based on the emissions estimate and the proc ess activity observed during the test or23

assumed for the calculations. These methods or app roaches to determining emissions from fluorinated gas production processes provide emissi ons estimates of varying accuracy and precision.

1. Process-Vent-Specific Emission Factor Approach. One method for estimating fluorinated GHG emissions is based on monitoring or estimating the composition and flow rate of the pro cess vent streams along with the production activity parameter to develop a site-specific, proc ess-vent-specific emission factor. Fluorinated gas producers have indicated that they develop and apply emission factors to estimate emissions from a range of processes. Typically a facility co nducts an initial emissions test or engineering calculation to develop an emission factor or emissi ons calculation factor and updates the emissions factor as needed with process changes. S ite-specific, process-vent-specific emission factors can be developed based on either measuremen t of process vent emissions or calculation of process vent emissions. The measurement of proc ess vent emissions to develop an emissions factor is addressed in this section, and the calcul ation of process vent emissions is discussed below in Process-Vent-Specific Emission Calculation Factor approach.

Under this approach, facilities would develop a pro cess-vent-specific emission factor for each fluorinated GHG from each process vent by emis sions testing. There are several EPA test methods available to sample and measure fluorinated GHG from processes in the fluorinated gas production source category, including EPA Method 32 0 (ASTM D6348-03) and EPA Method 18. Method 1 or 1A, Method 2, 2A, 2B, 2C, or 2D, 2 F, or 2G, Method 3, 3A, or 3B, and Method 4 must be conducted along with EPA Method 18.

Method 320 and ASTM D6348-03. For Method 320 a gas sample is extracted through a heated gas transport and handling system and analyz ed using FTIR spectroscopy to identify and quantify the gas stream components. It is applicab le only for vapor phase analysis of organic or inorganic compounds. The sensitivity of this metho d can be adjusted based on the reference standards used to configure the FTIR, but also depe nds on the gas composition, moisture content, and sampling losses. The ASTM D6348-03 FTIR method utilizes the same principles as Method 320 but has some improved calibration requirements.

Method 18. Method 18 utilizes gas chromatography ( GC) and flame ionization, photoionization, electron capture, mass spectroscop y, or another applicable detection method to identify and quantify gaseous organic compounds. F or the fluorinated GHG gas industry, electron capture and mass spectroscopy and possibly photoionization are the most appropriate detectors for identifying fluorinated GHG compounds . The identity and concentration levels are determined by comparison to known standards, which are used to calibrate the GC. Stack gas samples may be collected through direct interface s ampling, dilution interface sampling, adsorption tube sampling, or bag sampling. One nee ds to consider whether significant temporal changes in flow rate and/or concentration occur in the process (e.g., batch processes) when selecting and applying the sampling approach for th is method. The direct interface, dilution interface, and adsorption tube sampling are not des igned for sources that vary in concentration, and therefore may not be appropriate for batch proc esses. Instead, an integrated bag sample with proportional sampling (sample rate adjusted proport ionally with changes in stack gas flow rate) would be appropriate for an emission source with a varying flow rate and concentration, such as a batch process. If the direct interface method is used, the timeframe of temporal changes of24

concentration in relation to the analytical timefra me needs to be considered. For example, if significant changes in concentration are expected t o occur rapidly (e.g., 10-minute time frame), but the GC analytical cycle is 30 minutes, a repres entative sample analysis may not be obtained; on the other hand, for this situation, if the analy tical cycle is 5 minutes, a representative sample would be obtained. Variations in vent gas flow rat e also need to be considered; for example, if vent flow rates and concentration are varying with time and the direct interface method is being used, the vent flowrate should be continuously moni tored so that the flowrate and concentration can be correlated to determine mass emissions. For any of the sampling methods, all samples must be analyzed within a few hours of collection.

Method 320, ASTM D63248-03 and Method 18 also requi re that the flow rate be relatively constant during sampling. If the flow r ate varies significantly over the course of the sampling, then this fluctuation must to be accounte d for when measuring concentration and calculating mass emissions.

OTM 24, the Tracer Gas Protocol For the Determinati on of Volumetric Flow Rate Through the Ring Pipe of the Xact Multi-Metals Moni toring System (OTM 24) uses a GC equipped with an FID to measure the concentration a t a specific point. A tracer gas is introduced into the process to perform a volumetric flow rate determination, which depends on the flow tracer flow rate, concentration at the measurement point and calibration and analysis data.

The Emission Measurement Center Approved Alternativ e Method (ALT-012) is designed for measuring particulate emissions in situations w here gas velocities are low and difficult to measure and subject to variations over time. ALT-0 12 can also be used to measure ducts and stacks that are not subject to stratification. Firs t, locations are identified upstream, for injection the tracer gas, and downstream, for the tracer gas measurement. For a complete measurement, three ten-minute long sampling intervals must be co mpleted at the downstream location.

Nuclear magnetic resonance (NMR) spectroscopy is a commonly used analytical technique in organic chemistry. Organic compounds are placed in a magnetic field and exposed to electro-magnetic energy, usually in the form of radio frequency (RF), and the nuclei of certain atoms absorb the radiation, which causes the nuclea r spin to realign in the higher energy direction. The wavelength the atom absorbs is depen dent on the neighboring atoms in the compound, and the resulting spectrum is called the NMR spectrum. This is a complex laboratory analytical method used to determine the structure o f molecules. Much like using infrared spectroscopy (IR) to identify functional groups, an alysis of a NMR spectrum provides information on the number and type of chemical enti ties in a substance. Also, the dependence of the transition energy on the position of a particul ar atom in a molecule makes NMR spectroscopy extremely useful for determining the structure of m olecules.

Using the applicable method(s), process activity (e .g., production or feed) would be monitored at the same time as emissions; the emissi on factor would be developed by dividing the emissions by the activity. Both continuous and bat ch processes are used in the fluorinated gas production source category. Typically, for continu ous processes, facilities would measure and determine the fluorinated GHG emission rate based o n test runs of at least 1 hour duration. For batch processes, a facility would typically measure and determine the fluorinated GHG emissions either over full batch cycles or during a ll emission episodes over the batch. Emissions25

testing over the full batch may require significant effort and cost, depending on the length of the batch. For continuous processes, facilities would use Equation L-13 and for batch processes would use Equation L-14 to determine emission rates from processes.

1 60 * 10 1 * 1 * * * 10 3 6 SV

Q MW C E PV

PV ContPV = (Eq. L-13)

Where:
E ContPV = Mass of fluorinated GHG f emitted from process vent v from production process i during the emission test during test run r (kg/hr).
C PV = Concentration of fluorinated GHG f during test run r of the emission test (ppmv). MW = Molecular weight of fluorinated GHG f (g/g-m ole). Q PV = Flow rate of the process vent stream during te st run r of the emission test (m3/min). SV = Standard molar volume of gas (0.0240 m3/g-mo le at 68°F and 1 atm).
1/10 3 = Conversion factor (1 kilogram/1000 gram). 60/1 = Conversion factor (60 minutes/1 hour).

3 6 1 10 1 * 1 * * 10 * *

SV

MW D Q C
E ee

ee ee PV ee PV

BatchPV 

# ∑

− −

= (Eq. L-14)

Where:
E BatchPV = Mass of fluorinated GHG f emitted from process vent v from production process i during the emission test during test run r (kg/batc h).
C PV-ee = Concentration of fluorinated GHG f during emis sion episode ee during test run r of

the emission test (ppmv). Q PV-ee = Flow rate of the process vent stream during em ission episode ee during test run r of the emission test (m3/min).
D ee = Duration of emission episode ee during test ru n r of the emission test (minutes). MW = Molecular weight of fluorinated GHG f (g/g-m ole). SV = Standard molar volume of gas (0.0240 m3/g-mo le at 68°F and 1 atm).
1/10 3 = Conversion factor (1 kilogram/1000 gram). ee = Number of emission episodes ee from process ve nt v during process i.

To develop the site-specific, process-vent specific emissions factor, facilities would track the process activity during the emissions testing a nd combine it with the emissions. For continuous processes, a facility would divide the f luorinated GHG emissions during the test by the process activity during testing. Equation L-15 would be used to estimate the average emission factor.

r Activity E

EF r

st EmissionTe PV

PV 

# ∑        

= 1 (Eq. L-15)26

Where:

EF PV = Average emission factor for fluorinated GHG f e mitted from process vent

v during production process i (kg emitted/kg produc t). EPV = Mass of fluorinated GHG f emitted from proce ss vent v from production

process i during the emission test during test run r, for either continuous or batch (kg emitted/hr for continuous, kg emitted/bat ch for batch). Activity EmissionTest = Process feed, process production, or other proce ss activity rate during the

emission test during test run r (e.g., kg product/h r for continuous, calculated in Equation L-13 of this section, kg pro duct/batch for batch, calculated in Equation L-14 of this section). r = Number of test runs (i.e., batches) performed during the emission test.

Development of the emissions testing program requir es testing during representative process operation. To develop a representative emi ssion factor for the process vent, the facility should give some consideration to what process vari ability might be present in the process. For each operating scenario of the process, the emissio ns test data must be representative of the typical process operation while also including proc ess variability. 6 The full range of process operating conditions should be included. The typic al process operation conditions would include yield, temperature, pressure, and flow rates. The operating conditions and the process production activity should be measured during the e missions test. See section 3.B.iii.3 below for more information on representativeness.

Using the process-vent-specific emissions factor me thod, a facility would estimate emissions using the emission factor and would track process activity on an on-going basis. To estimate annual fluorinated GHG emissions from each vent, facilities would multiply each emission factor by the appropriate activity data an d account for the use (and uptime) of destruction devices. Equation L-16 would be used t o estimate emissions for each individual process vent if the process vent is not vented to a destruction device, and Equation L-17 would be used if the process vent is vented to destructio n device.

RptPeriod PV RptPeriod PV Activity

EF E *

=

− (Eq. L-16)

Where:
E PV-RptPeriod

= Mass of fluorinated GHG f emitted from process vent v from production

process i, for the reporting period, either monthly or annually (kg/month or kg/year).
EF PV = Average emission factor for fluorinated GHG f emitted from process

vent v during production process i (kg emitted/acti vity)(e.g., kg emitted/kg product). Activity RptPeriod

= Process feed, process production, or other pro cess activity during the reporting period.

6 Operating scenarios and other issues associated with de veloping representative emission factors are discussed further below under “Obtaining and Maintaining Representativ e Emission Factors.”27 

# ( ) ) 1(* * DE

Activity Activity EF E C RptPeriod U RptPeriod PV RptPeriod PV − + =

− − − (Eq. L-17)

Where: E PV-RptPeriod

= Mass of fluorinated GHG f emitted from process vent v from production

process i, for the reporting period, either monthly or annually, considering destruction efficiency (kg/month or kg/year).
EF PV = Emission factor for fluorinated GHG f emitted from process vent v during

production process i (kg emitted/kg product). Activity RptPeriod-U

= Total process feed, process production, or oth er process activity during the reporting period for which the process vent is not vented to the destruction device (e.g., kg product). Activity RptPeriod-C = Total process feed, process production, or oth er process activity during the

reporting period for which the process vent is vent ed to the destruction device (e.g., kg product). DE = Demonstrated destruction efficiency of the d estruction device (weight

fraction).

The fluorinated GHG emissions for all vents at the facility would then be summed to obtain the total emissions from process vents for t he facility as a whole. Equation L-18 would be used to sum fluorinated GHG emissions over all proc ess vents for the process, and Equation L19 would sum the emissions from all processes to es timate total fluorinated GHG process vent emissions. Other emission points at the facility s uch as equipment leaks, storage tanks, or wastewater would have to be accounted for separatel y and added in to the facility total.


# ∑

− = v
RptPeriod

PV Pfi E E

1 (Eq. L-18)

Where:
E Pfi = Mass of fluorinated GHG f emitted from product ion process i, for the

reporting period, either monthly or annually (kg).
E PV-RptPeriod = Mass of fluorinated GHG f emitted from process vent v from production

process i, for the reporting period, either monthly or annually, considering destruction efficiency (kg/month or kg/year). v = Number of process vents in production process i.



# ∑
= i

Pfi P E E

1 (Eq. L-19)

Where: E P = Mass of fluorinated GHG f emitted from all pro cess vents at the facility, for the

reporting period, either monthly or annually (kg).
E Pij = Mass of fluorinated GHG f emitted from product ion process i, for the reporting

period, either monthly or annually (kg).28

i = Number of production processes i at the facil ity.

2. Process-Vent-Specific Emission Calculation Factor Approach

. As mentioned above, another method for estimating f luorinated GHG emissions is based on use of engineering calculations to determine the composition and flow rate of the process vent streams. These emissions estimates are divided by the production activity parameter to develop a site-specific, process-vent-specific emission cal culation factor. A variation of this method includes use of engineering assessments to develop process-vent-specific emission calculation factor. Facilities have indicated that they regula rly use engineering calculations and engineering assessments to estimate fluorinated GHG emissions.

Engineering calculations use chemical engineering p rinciples and component property data to calculate emissions. Acceptable calculatio n methods for uncontrolled and controlled process vent emissions are included in a number of rule texts and EPA guidance documents. Other promulgated rule texts that contain appropria te calculation equations include the MON NESHAP in §63.2460(b)(1) through (4) (the MON rule text also refers to equations in the Pharmaceutical NESHAP in §63.1257(d)(2)(i) for unco ntrolled and §63.1257(d)(3)(i) for controlled emissions with some noted exceptions). These rule texts include process calculation methods and equations for vapor displacement, purgi ng, heating, depressurization, vacuum systems, gas evolution, air drying, and empty vesse l purging. An even more recent guidance document that provides appropriate calculations for chemical manufacturing operations is the Methods for Estimating Air Emissions from Chemical Manufacturing Emissions, Volume II: Chapter 16, of the Emission Inventory Improvement P rogram

. Engineering assessments may be conducted using prev ious emissions test data or other information available on the process. Facilities ty pically have component and composition data available from the original research and developmen t activities on the process and from the process’ lifetime of operation. If the facility pe rformed a scoping test as described in section 3.A.ii above, the results of that test should also be considered. For process vent emissions determinations, facilities could conduct an enginee ring assessment to calculate uncontrolled emissions for each process vent and for each emissi on episode. Various rules for other types of emissions include use of engineering assessments to estimate emissions from processes and process vents. Other promulgated rules that allow use of engineering assessments include NESHAP rules in 40 CFR part 63, such as subpart GGG for Pharmaceutical Manufacturing in §63.1257(d)(2)(ii) and subpart FFFF for Miscellaneo us Organic NESHAP (MON) in §63.2460(b). Engineering assessments include use o f previous emissions test data where the emissions are representative of current operating p ractices; bench-scale or pilot-scale streams analysis results for identifying stream components and composition for products, byproducts, and wastes; design analysis based on chemical engin eering principles, measurable process parameters, or physical or chemical laws or propert ies. These previous emissions data, analysis, and calculations may be used to identify fluorinate d GHG compounds and their concentrations in various streams.

To develop the site-specific, process-vent-specific emissions calculation factor, facilities would first calculate the fluorinated GHG emissions and divide them by the appropriate process29

activity associated with the emissions calculation. Equation L-20 would be used to estimate the emission calculation factor.

ve presentati PV PV Activity

E ECF

Re = (Eq. L-20)

Where:
ECF PV = Emission calculation factor for fluorinated GHG f emitted from process

vent v during production process i (kg emitted/kg p roduct).
E PV = Average mass of fluorinated GHG f emitted, base d on calculations, from

process vent v from production process i during the period or batch for which emissions were calculated, for either continu ous or batch (kg emitted/hr for continuous, kg emitted/batch for bat ch). Activity Representative = Process feed, process production, or other proc ess activity rate

corresponding to average mass of emissions based on calculations (e.g., kg product/hr for continuous, kg product/batch for bat ch).

As with the process-vent-specific emissions factor, a facility would estimate emissions using the emissions calculation factor and would tr ack process activity on an on-going basis. To estimate annual fluorinated GHG emissions from each vent, facilities would multiply each emission calculation factor by the appropriate acti vity data and account for the use (and uptime) of destruction devices. Equation L-21 would be use d to estimate emissions for each individual process vent if the process vent is not vented to a destruction device, and Equation L-22 would be used if the process vent is vented to a destruct ion device.

RptPeriod PV RptPeriod PV Activity

ECF E *

=

− (Eq. L-21)

Where:
E PV-RptPeriod

= Mass of fluorinated GHG f emitted from process vent v from production

process i, for the reporting period, either monthly or annually (kg/month or kg/year).
ECF PV = Emission calculation factor for fluorinated GHG f emitted from process

vent v during production process i (kg emitted/acti vity)(e.g., kg emitted/kg product). Activity RptPeriod = Process feed, process production, or other proces s activity during the

reporting period.


# ( ) ) 1(* * DE

Activity Activity ECF E C RptPeriod U RptPeriod PV RptPeriod PV − + =

− − − (Eq. L-22)

Where:
E PV-RptPeriod

= Mass of fluorinated GHG f emitted from process vent v from production

process i, for the reporting period, either monthly or annually, considering destruction efficiency (kg/month or kg/year).30

ECF PV = Emission calculation factor for fluorinated GH G f emitted from process

vent v during production process i (kg emitted/kg p roduct). Activity RptPeriod-U

= Total process feed, process production, or oth er process activity during the reporting period for which the process vent is not vented to the destruction device (e.g., kg product). Activity RptPeriod-C = Total process feed, process production, or oth er process activity during the

reporting period for which the process vent is vent ed to the destruction device (e.g., kg product). DE = Demonstrated destruction efficiency of the d estruction device (weight

fraction).

The fluorinated GHG emissions for all vents at the facility would be summed to obtain the total emissions from process vents for the faci lity as a whole. Equation L-23 would be used to sum fluorinated GHG emissions over all process v ents for the process, and Equation L-24 would sum the emissions from all processes. Other emission points at the facility such as equipment leaks, storage tanks, or wastewater would have to be accounted for separately and added in to the facility total.


# ∑

− = v
RptPeriod

PV Pfi E E

1 (Eq. L-23)

Where:
E Pfi = Mass of fluorinated GHG f emitted from product ion process i, for the

reporting period, either monthly or annually (kg).
E PV-RptPeriod

= Mass of fluorinated GHG f emitted from process vent v from production

process i, for the reporting period, either monthly or annually, considering destruction efficiency (kg/month or kg/year). v = Number of process vents in production process i.



# ∑
= i

Pfi P E E

1 (Eq. L-24)

Where:
E P = Mass of fluorinated GHG f emitted from all pro cesses at the facility, for

the reporting period, either monthly or annually (k g).
E Pij = Mass of fluorinated GHG f emitted from product ion process i, for the

reporting period, either monthly or annually (kg). i = Number of production processes i at the facil ity.

3. Obtaining and Maintaining Representative Emission Factors

Process conditions31

Emission rates from a process depend on the operati ng conditions of that process. Thus, to ensure that emission factors are representative, facilities should define the operating scenario that encompasses the typical range of operating con ditions for the process. If the process has multiple operating scenarios, the facility should d evelop a representative emissions factor for each operating scenario. To define the process ope rating scenario, a facility could include information on the process description and the spec ific process equipment used; the process vents, emission episodes and durations, and the qua ntity of uncontrolled fluorinated GHG emissions; the control device or destruction device used to control emissions; and the manifolding of process vents within the process and from other processes. Alternative operating scenarios should also be defined for differences in operating conditions that affect emissions. Examples of situations where process differences ma y warrant separate operating scenarios include the following: making small volumes of a p roduct in one set of batch process equipment part of the year and making larger volumes in large r batch process equipment part of the year; use of two different types of catalyst in the same process; deliberate alterations in process conditions such as temperature or pressure to shift the reaction to a particular product; and making small volumes of a product in a batch proces s part of the year and making large volumes in a continuous process part of the year. A facilit y would need to develop a representative emissions factor for each process operating scenari o because each operating scenario for a process will result in different emissions levels.

Prior to developing an emissions factor, facilities should observe the operating conditions of the process over a period of time and note how c hanges to the operating conditions affect emissions rates. The time periods may vary from fa cility to facility and perhaps from process to process, but typically may include an examination p eriod of one year or one month and could include examination of startup and shutdown periods . An examination of the previous year of process operating conditions might take note of whe ther there is month-to-month or seasonal variability in the process. For example, seasonal variability might be caused by production rate changes or might be caused by changes in the ambien t temperature from summer to winter. An examination of one month of process operating condi tions might reveal some short-term process variability. A review of startup and shutdown proc ess operating conditions may include an assessment of how frequently startups and shutdowns occur, what effect startups and shutdowns have on emission rates, and whether or not the impa ct on emissions can be quantified.

In general, emissions testing during process startu ps and shutdowns would not be expected to lead to representative emission factors , because emission rates tend to fluctuate during such events. Exceptions to this could inclu de long-term monitoring that would not overrepresent startup or shutdown conditions in the res ulting emission factor, and monitoring specifically to obtain emission factors for startup s and shutdowns conditions. Several companies indicated that they have analyzed the emissions pro file during startup events and during shutdown events. They found that the emission rate s during these events departed from those at steady state conditions, but that emissions profile s were consistent between one startup event and another.

Number of samples Emission samples should be taken over the full rang e of process conditions within a given operating scenario. To assess the variabilit y of emission rates within the operating32

scenario, a minimum of three emission test runs is appropriate. If the emission factors based on the three test runs show relatively little variabil ity, i.e., if their relative standard deviation (RS D) is low, then the three sample emission factors can probably be averaged to obtain a robust, representative emission factor for the process. Ho wever, if the emission factors based on the three test runs show high variability, that is, a h igh RSD, then the average of the three emission factors may be a poor estimator of the actual mean emission rate from the process. In this case, additional samples should be taken to develop a rob ust emission factor. 7 The equation to estimate the RSD is shown in Equation RSD-1.

EF s RSD = (Eq. RSD-1)

Where: RSD = Relative standard deviation, fraction s = sample standard deviation, calculated in Eq. RSD-2 EFbar = average emission factor for all test runs combined

Equation RSD-2 is used to estimate the sample stand ard deviation, s.



# ( ) ( ) ( )

1 ... 2

3 2

2 2

1

− +

− +

− +

−
= n EF EF EF EF EF EF s (Eq. RSD-2)

Where: s = sample standard deviation
EF i = the individual emission factor value from test run 1, 2, 3, etc. EFbar = average emissions factor across all test runs (sample mean emission factor),

calculated in Equation RSD-3
n = number of test runs

Eq. RSD-3 (which corresponds to equation L-15 in th e regulatory text) is used to estimate the mean emissions factor, EFbar.

n EF EF EF EF ... 3 2 1 + + +

= (Eq. RSD-3)

Where:

7 The fact that emission rates from a process show high variability does not mean that a representative emissi on factor cannot be developed; it simply means that more sa mples must be taken to do so. Note, however, that if the variability of the process can be attributed to the va riability of a controllable and measurable process pa rameter, it is probably appropriate to develop one or more additional oper ating scenarios, each with its own emission factor, to capture this variability.33

EFbar = average emissions factor for all test run s combined (sample mean emission factor)
EF i = the individual emission factor value from test run 1, 2, 3, etc.
n = number of test runs

In general, more samples are required to characteri ze the mean of a population or parameter that has high variability than are requir ed for a population or parameter that has low variability. The number of samples required to est imate the mean of the parameter with a given level of confidence can be calculated based on the RSD of the samples and on some assumptions about the distribution of the parameter. Where the set of samples is relatively small and only the sample standard deviation “s” is known (rather than the true standard deviation of the parameter), the appropriate statistic is often the Student’s t test. The Student’s t test presumes an approximately normal, bell-shaped distribution of t he underlying parameter, which implies that the distribution of the average is the Student’s t distribution.

For this situation, the Student’s t test can be wri tten: 

# ( )

CI statistic T CI statistic t

n s EF EF t % 95 % 95

− − +

<    

 

   

 

− <

− (Eq. RSD-4)

Where: EFbar = Average emission factor across all test run s (sample mean emission factor)
EF T = True mean emission factor of the process s = Sample standard deviation n = Number of samples

t statistic-95%CI = Value of student’s t statistic chosen to represe nt a 95-percent confidence

interval with n-1 degrees of freedom. For a sample size of 3, this value is 4.30.

Dividing through by the sample mean emission factor , EFbar, we obtain:



# ( )

CI statistic T CI statistic t

n RSD EF EF EF t % 95 % 95 /

− − + <    

 

   

 

− <

− (Eq. RSD-5)

To choose a RSD above which we will require more th an three samples, we first decide how much error we are willing to tolerate in our em ission factor. Suppose we want the emission factor to have a 95 percent chance of being within 30 percent of the true mean emission rate of the process. The requirement for the emission fact or to be within 30 percent of the true mean emission rate can be expressed as follows:



# ( ) 3.0

/) ( <

− EF EF EF T (Eq. RSD-6)34

Equation RSD-5 can also be rearranged as follows:



# ( )

CI statistic T t

n RSD EF EF EF % 95 * /) (

−

<

− (Eq. RSD-7)

Subtracting Equation RSD-7 from Equation RSD-6, we obtain:

CI statistic t
n RSD

%

95 * 3.0 0

− − <

Plugging in the values for t and n and solving for RSD, we obtain

RSD > 3

. 4 3 * 3.0

RSD > 12.0

We conclude that if the RSD exceeds 0.12 (or12 perc ent), we should test more than three samples. Unfortunately, it may be difficult to obt ain an RSD of less than 0.12 even when the real emission rate is nearly constant. This is bec ause the error of the concentration measurements used in the testing can be near 10 per cent. Thus, we might want to consider whether we can tolerate a somewhat higher error in our emission factor. 8 If we require that the emission factor be within 40 percent of the true me an emission rate and solve the above equation, we arrive at the conclusion that we shoul d test more if the RSD exceeds 0.16 (16 percent). If we require that the emission factor b e within 50 percent of the true mean emission rate (with 95-percent confidence) and solve the abo ve equation, we arrive at the conclusion that we should test more if the RSD exceeds 0.20 (20 per cent).

With an additional three samples (n=6), the uncerta inty of the emission factor declines significantly. For n = 6, Equation RSD-5 becomes:



# ( ) 57.2

6 / 57.2 + <    

 

   

 

− <

− RSD EF

EF EF T

Plugging an RSD of 0.20 (20 percent) into this equa tion, we find that after six samples, there is a 95 percent chance that the sample mean ( emission factor) is within 21 percent of the true mean (average emission rate of the process).

8 Another approach to minimizing the error is to require more samples initially, e.g., 4 instead of 3. With 4 init ial samples, the emission factor has a 95 percent chance of being within 30 percent of the true mean emission rate if t he RSD is less than 19 percent.35

4. Updates to emission factors and emission calculation factors. The emission rate from a process is likely to chang e as the process evolves or is altered. Process changes that can affect the fluorinated GHG emission rate include changes in raw materials, equipment, production levels, or operati ng conditions. These changes can occur all at once or gradually, over time. Facilities that have measured and re-measured their emission factors over a period of several years have found t hat gradual, incremental changes to the process (e.g., to improve yields) have significantly change d emission factors 9 . To ensure that emission factors and emission calculation factors continue t o accurately represent emission rates, they should be updated when significant process changes occur. In addition, it may be appropriate to update emission and emission calculation factors at regular intervals (e.g., five to ten years) to capture the cumulative impact of small changes to t he process.

5. Potential Process Vent Emission Threshold. In discussions with EPA, representatives of fluorin ated gas producers stated that more effort and resources should be expended to accurate ly estimate the size of large emission streams than to estimate the size of small ones. Consisten t with this principle, EPA evaluated process vent emissions cutoffs above which facilities would be required to conduct emissions testing to develop a site-specific emissions factor and below which facilities could conduct emissions calculations to develop a site-specific emissions f actor.
There are various rules for other types of emission s that have established emission cutoffs above and below which there are different control, monitoring, and reporting requirements. For example, there are process or process vent cutoffs in various NESHAP rules in 40 CFR part 63, such as subpart GGG for Pharmaceutical Manufacturin g, subpart FFFF for Miscellaneous Organic NESHAP (MON), and subpart VVVVVV for Chemic al Manufacturing Area Source rule. Because some producers mentioned the rule re quirement cutoffs in subpart FFFF, Miscellaneous Organic NESHAP (MON), the initial ste p in the cutoff development was reviewing the 10,000 lb/yr (i.e., 5 ton/yr) of unco ntrolled organic HAP emissions cutoff for process vents in that rule. (While these data and facility practices for the MON source category may not be completely analogous to the data and pra ctices at fluorinated gas production facilities, this information was used to inform the reporting rule-making process.) Similar to the fluorinated gas production industry, the MON source category includes both continuous and batch processes. At the MON facilities, we looked at the emissions levels of MON process vents to identify the number of vents covered and the emi ssions covered by various cutoffs. For continuous processes, approximately 26 percent of p rocess vents have emissions greater >10,000 lb/yr and more than 99 percent of the total organic HAP emissions from continuous process vents occur from these vents. For batch processes, 13 percent of batch process vents have emissions >10,000 lb/yr and the organic HAP emissio ns from these vents are 96 percent of the total organic HAP emissions from batch process vent s. The 10,000 lb/yr organic HAP cutoff for requiring control of the process vent in the MON ru le provides a good balance for minimizing the number of process vents required to implement c ontrol and maximizing the emissions covered or captured by the rule.

9 Based on conversations with Fluorinated GHG producers, as referenced in Section 7.36

In evaluating cutoffs for the process vents in the fluorinated gas production source category, we began by analyzing a 10,000 lb/yr fluo rinated GHG uncontrolled emissions cutoff. Because the quantities of these emissions in terms of CO 2 e would vary significantly depending on the specific fluorinated GHG compound emitted an d its GWP, we decided to evaluate the cutoff in terms of CO 2 e. We assumed an average GWP of approximately 2,00 0 for the fluorinated GHG, and given the cutoff value of 10,0 00 lb/yr fluorinated GHG, we developed a cutoff of 10,000 mt CO 2 e. Process vents above the 10,000 lb/yr limit woul d be required to conduct an emissions test to develop a site-specifi c emissions factor for the vent, and process vents below the 10,000 mt CO 2 e could develop a site-specific emissions calculati on factor based on engineering calculations or engineering assessme nts.
Depending on the specific fluorinated GHG emitted, the emissions of the fluorinated GHG in terms of the actual gas could vary significa ntly. In Table 4, the emissions in terms of the fluorinated compounds that are translated from the CO 2 e cutoff are shown. The fluorinated compounds are shown in order of increasing GWP. Fo r example, for fluorinated GHG compounds as diverse as HFC-134a to SF 6 , the cutoff of 10,000 mt CO 2 e would translate into fluorinated GHG emissions ranging from 16,962 lb/yr to 923 lb/yr, respectively. However, the detection limits of fluorinated GHG are likely suff iciently low to allow detection and quantification of these compounds at these emission levels.

Another potential approach for selecting a process vent cutoff might include a combined approach, i.e., meeting both a CO 2 e emissions cutoff and also a cutoff in terms of po unds of fluorinated GHG. For example, if a process vent ha d emissions less than 25,000 mt CO 2 e and also less than 10,000 lb of fluorinated GHG emissio ns, i.e., the process vent meets both criteria, then it would be considered below the cutoff.

An issue related to setting a process vent cutoff b ased on CO 2 e is related to fluorinated GHGs that do not have published GWP. In this insta nce, a lower level cutoff could be established for those fluorinated GHG whose GWP doe s not appear in Table A-1 of 40 CFR part 98subpart A compounds, for example, less than 1 met ric ton for emissions that include a compound without GWP.37

Table 4. Analysis of Process Vent Cutoffs: Transl ate Emissions from CO 2 e to Pounds of Fluorinated GHG, and vice versa. 1

Vent limit in mtCO2e In pounds of fluorinated GHG:

HFC-134a HFC-125 HFC-143a CF4 C2F6 NF3 SF6
Convert CO2e vent cutoff to lb of fluorinated GHG 25,000 42,404 * 19,688 * 14,507 * 8,481 5,992 3,205 2,306 20,000 33,923 * 15,750 * 11,605 * 6,785 4,793 2,564 1,845 10,000 16,962 * 7,875 5,803 3,392 2,397 1,282 923 5,000 8,481 3,938 2,901 1,696 1,198 641 461 Vent limit in pounds of fluorinated GHG In mtCO2e:

HFC-134a HFC-125 HFC-143a CF4 C2F6 NF3 SF6 Convert lb of fluorinated GHG to mt CO2e 10,000 5,896 12,698 17,234 29,478 * 41,723 * 78,005 * 108,390 * 5,000 2,948 6,349 8,617 14,739 20,862 39,002 54,195

1 The GWP for fluorinated GHG are HFC-134a is 1,300; HFC-125 is 2,800; HFC-143a is 3,800; CF4 is 6,500 C 2F6 is 9,200; NF3 is 17,200; and SF6 is 23,900. * denotes that the level exceeds a 10,000-lb cutoff (in top table) or a 10,000-mtCO 2 e cutoff (in bottom table).

6. Process Vent Preliminary Emission Estimates. To determine whether a process vent is above or bel ow the 10,000 mt CO 2 e threshold, facilities could use any of several emission estima tion methods discussed above. In this preliminary step, it seems reasonable to allow use of engineering calculations or engineering assessments similar to those identified in Section 3.B.iii.2 to determine the emissions of fluorinated GHG from the process. Acceptable calcu lation methods for uncontrolled and controlled process vent emissions may include those from various rule text or guidance documents, such as the MON, Pharmaceutical, and oth er examples provided in Section 3.B.iii.2 above.

Engineering assessments are another reasonable appr oach to determining preliminary emissions from process vents. Engineering assessme nts include the types of information discussed in Section 3.B.iii.2 above (previous test data, bench-scale or pilot-scale test data, design analysis, etc.) Facilities typically have c omponent and composition data available from the original research and development activities on the process and from the process’ lifetime of operation. For process vent emissions determinatio ns, facilities could conduct an engineering assessment to calculate uncontrolled emissions for each process vent and for each emission episode.

7. Current Plant Practices for Process Vent Monitoring Several facilities with fluorinated gas production processes have indicated that they conduct monitoring and analysis on individual proce ss vents and that they characterize streams from processes. They typically develop facility-sp ecific or process-specific EFs and track production activity data to estimate fluorinated GH G emissions.

Facilities indicated that a variety of approaches a re used to estimate fluorinated GHG emissions and develop process-specific emissions fa ctors, including sampling and measurement38

(i.e., direct testing) and chemical engineering cal culations and estimates. At most facilities, a combination of these approaches is used to estimate fluorinated GHG emissions from the various process vents at the site. Some facilities indicat ed, for example, that facility staff measure the concentrations and flows for reactor vessel process vents and conduct engineering calculations to estimate concentration and flows from process dryer s. Engineering calculations are based on common chemical engineering principles and empirica lly based data and process knowledge. The engineering calculations may also be based on e mission estimation equations contained in rules, for example in the Pharmaceutical NESHAP, or may be conducted using purchased process modeling software packages, such as ASPEN a nd EmissionsCalculator.

Facilities indicated that each of these approaches, emission testing and engineering calculations, are valid and produce reasonable fluo rinated GHG emission estimates and that flexibility in which approach is applied to any par ticular process vent is appropriate. Facilities particularly noted that they match the level of eff ort and “rigorousness” in the emissions determination approach with the emissions source si ze. That is, they devote more effort to characterizing emissions from relatively large fluo rinated GHG emissions points, pursuing emissions testing for these sources, and less effor t to characterizing emissions from relatively small fluorinated GHG emissions points, applying en gineering calculations to these sources. Some facilities noted that certain process vents ar e not measured directly because the emission stream contains a compound that is hazardous for pl ant and personnel safety, e.g., if HF is present in a stream. The facilities noted that emi ssion points that are not safe to measure are typically estimated from chemical engineering calcu lations and from process design data. In using FTIR instruments, some vendors have noted tha t specialty glass sample cells are available that are more resistant to HF. Some facilities not ed that measuring fluorinated organics can be done easily if the HF can be removed from the sampl ing stream. One option may be to flow the sample stream through containers of water to remove HF prior to measuring the fluorinated organic. While this approach may be successful at measuring the fluorinated organic, the flow rate of the stream cannot be determined with any ac curacy. This approach also does not alleviate the personnel safety concerns.

Facilities further expanded on the use of previous stream analysis results as appropriate data to be used. Generally, facilities have a good understanding of the chemistry for all processes and understand what raw materials are fed to the process, what side reactions occur, and what products and by-products are created. Fac ilities have laboratory scale, pilot plant, and full scale streams analysis results. Facilities no ted that in particular, at the bench-scale phase of a product and process development, they analyze all s treams to identify all species and compounds such as product, byproducts, and waste. The proces s design from when the process was originally developed and built is detailed, and mor e recently installed processes will have excellent design and chemistry documentation availa ble. Older processes may tend to have less detail.

Facilities indicated that they typically conduct aninitial analysis to develop the processspecific emission factor or emission calculation fa ctor and do not continuously measure and calculate emissions from process vents and streams. When there is a process change, i.e., a change in the operating conditions or a change in t he process equipment used, they will conduct a reanalysis of the process. Facilities pointed ou t that prior to making process change, they analyze the theoretical chemistry and predict the l ikely changes in the set of fluorinated GHG39

compounds generated and in the fluorinated GHG emis sions levels. They typically begin with engineering calculations to determine the impacts o f the change on species generated or emission levels, and follow that with retesting and recalcul ations when appropriate. Some facilities noted that after a process change, they will sample and a nalyze to identify every species or compound generated, in either process vents or process strea ms.

8. Potential use of continuous emissions monitors to measure emissions from vents. Another potential monitoring option EPA considered was requiring that facilities measure emissions from fluorinated gas production facilitie s using continuous emissions monitors (CEMS). If properly selected and maintained, CEMS would be expected to provide estimates of emissions more accurate than either the mass-balanc e or the process-vent approach. Under this approach, facilities would install and operate CEMS capable of measuring fluorinated GHGs to measure process emissions. The requirements for th e CEMs would be similar to those in subpart C, adjusted, as appropriate, to accommodate CEMS fo r fluorinated gases. One possible option is to use Fourier Transform Infrared Spectrometers (FT IRs) CEMS in scrubber stacks to measure emissions. FTIR spectroscopy is presently used to conduct short-term fluorinated GHG emission measurements from processes. In recent discussions with FTIR CEMS vendors, they noted that the units can operate continuously. Some units req uire liquid nitrogen cooling and the liquid nitrogen vessel (dewar) has a limited capacity. Th ese nitrogen cooled units can operate for up to 12 hours on a single charge (nitrogen), and continu ous operation of the unit could be achieved through the use of an extended dewar with an automa ted fill cycle. With the extended dewar, the unit can operate for approximately 3 days. (The de tector is nitrogen cooled, and a dewar, which is an insulated container with a vacuum between its inner and outer layers, is used to hold the liquid nitrogen.) FTIR CEMS vendors noted that the sample cell can be adjusted to accommodate concentration levels, where a shorter c ell length can be used for higher concentrations and longer cell lengths can be used for lower concentrations. Another option for high concentrations might include use of dilution a nd a standard cell. The vendor typically sets up a software package based on the compounds expect ed in the measured vent, and the software is revised for other compounds as needed.

However, potential drawbacks to requiring CEMS are that they would be relatively expensive to install and they may not tolerate the acidic and reactive environments (e.g., high HF concentration) found in vents at many fluorinated g as production facilities. Some FTIR CEMS vendors utilize specially configured gas cells that run hot and utilize mirror coatings to protect the cell from high HF concentrations and use specia l types of unit seals (o-rings) that are inert to corrosive compounds. In any case, vendors noted th at HF in the vent streams is a common problem, and that HF concentrations in the percent range are a difficult issue to deal with. The latter concern might be mitigated by installing CEM S after a scrubber, if this is practicable. Given these potential concerns, it may be appropria te to require CEMS for particularly large emission streams, e.g., those resulting in emission s of more than 50,000 mtCO2e annually.

9. Equipment Leak Emissions Estimates. Process vents are only one of several sources of fl uorinated GHG emissions at fluorinated gas production facilities. Another potentially sig nificant source is equipment leaks, whose emissions do not occur through process vents. Emis sions from equipment leaks may be estimated using EPA Method 21 and the Protocol for Equipment Leak Estimates (EPA-453/R-40

95-017). Leak monitoring could be performed period ically, which typically would be quarterly, semi-annually, or annually. Due to the nature and s cope of the reporting rule, which is focused on monitoring and emission estimation rather than o n leak repair (control), equipment leak monitoring on an annual basis should be sufficient.

The Protocol includes four methods for estimating e quipment leaks. These are, from least to most accurate, the Average Emission Factor Approach, the Screening Ranges Approach, EPA Correlation Approach, and the Unit-Specific Cor relation Approach. The Average Emission Factor Approach relies on emission factors and equi pment counts, the service of each component, the composition of the stream, and the l ength of time the equipment was in service to estimate emissions, and does not require any real-w orld data be collected from the processes. The remaining three methods, The Screening Ranges A pproach, EPA Correlation Approach and the Unit-Specific Correlation Approach all depend o n the collection and use of facility-specific and process-specific screening data to estimate emi ssions. The greater accuracy of these three methods compared to the Average Emission Factor App roach will provide a more realistic estimation of the actual fluorinated GHG emissions at a facility.

To use these three screening data methods, the faci lity would need to have (or develop) Response Factors relating concentrations of the tar get fluorinated GHG (or surrogate gas cooccurring in the stream) to concentrations of the g as with which the leak detector is calibrated. Our understanding is that flame ionization detector s (FIDs) are generally insensitive to fluorinated GHGs, and that they are therefore not l ikely to be effective for detecting and quantifying fluorinated GHG leaks. An exception to this would be a situation in which the fluorinated GHG occurred in a stream along with a s ubstance (e.g, a hydrocarbon) to which the FID was sensitive; in this case, the other substanc e could be used as a surrogate to quantify leaks from the stream. We understand that at least two f luorocarbon producers currently use methods in the Protocol to quantify their emissions of fluo rinated GHGs with different levels of accuracy and precision. Other analytical techniques that ar e sensitive to fluorinated compounds may be available to monitor concentrations of equipment le aks, including photoionization, ultraviolet, infrared, and others.

A preliminary review revealed a handful of detector s capable of detecting fluorinated GHGs. These detectors use various operating princi ples, including, infrared, photoionization and ultraviolet detection. One issue that arose with t hese detectors was their high sensitivity. For some of the equipment, maximum readings were well b elow the 10,000 ppm leak/no-leak threshold of the Screening Ranges Approach, meaning that the Screening Ranges Approach could not be used with these detectors. Those capa ble of reading the 10,000 ppm concentration had sampling rates that exceeded the rates establis hed by Method 21. However, the EPA Correlation Approach and the Unit-Specific Correlat ion Approach could be used with these detectors, assuming that the detectors do not hit t heir maximum readings (peg) in the facility.

Another approach for monitoring leaks from pieces o f equipment may include use of the Alternative Work Practice (AWP) for EPA Method 21 ( similar to monitoring requirements under 40 CFR part 60, subpart A, §40 CFR part 60.18; 40 C FR part 63, subpart A, §40 CFR part 63.11; or 40 CFR part 65, subpart A, §40 CFR part 65.7). This approach would include monitoring leaking equipment with an optical gas imaging instr ument. Emissions from those pieces of equipment found to be leaking could be estimated ba sed on emission factors. Under this41

approach, facilities could image each piece of equi pment in fluorinated GHG service, and all emissions imaged by the optical gas imaging instrum ent would be considered leaks and would be subject to emissions estimation.

10. Destruction Efficiency Testing EPA is considering a requirement that fluorinated g as producers that destroy F-GHGs conduct emissions testing periodically, for example every five years, to determine the destruction efficiency (DE) of the destruction device. The tes ting for determining the DE would be similar to the emissions testing that could be conducted to develop process-specific emission factors. Facilities would need to conduct testing that shows the destruction device can successfully destroy emissions at worse-case operating condition s, for example when operating at high loads reasonably expected to occur and when destroying th e most-difficult-to-destroy fluorinated GHG fed into the device (or when destroying a surrogate that was more difficult to destroy than that fluorinated GHG). The last point is particularly i mportant because some fluorinated GHGs (e.g., CF 4 and SF 6 10 ) are extremely difficult to destroy; DEs determine d for other fluorinated GHGs would overestimate the destruction of these fluorin ated GHGs.

For destruction of fluorinated GHG compounds to occ ur, temperatures must be quite high, fuel must be provided, flow rates of fuels an d air (or oxygen) must be kept above certain limits, flow rates of fluorinated GHG must be kept below others, and for some particularly difficult-to-destroy chemicals such as CF 4 , pure oxygen must sometimes be fed into the proces s. If one or more of these process requirements is not met, destruction efficiencies can drop sharply (in some cases, by an order of magnitude or more), and fluorinated GHGs will simply be exhausted from the device. For more discussion of this issue, see the Technical Support Document for Industrial Gas Supply: Production, Tra nsformation, and Destruction of Fluorinated GHGs and N2O, Docket number EPA-HQ-OAR-2008-0508-04 1.

EPA is considering use of emissions test data on th e destruction device that has been conducted within the five years prior to the effect ive date of the rule. Facilities that have conducted an emissions test on their destruction de vice within the five years prior to the effective date of the rule may be allowed to use the DE deter mined during that test if the test was conducted in accordance with the proposed test requ irements. Facilities could also potentially use the DREs determined during principal organic ha zardous constituent testing and hazardous waste combustor testing, provided those tests deter mined the DRE based on the most-difficultto-destroy fluorinated GHG fed into the device (or based on a surrogate that was more difficult to destroy than the most-difficult-to-destroy fluorina ted GHG).

C. Other Potentially Significant Emission Points In addition to the fluorinated GHG emissions captur ed via the Mass Balance method or either of the Process Vent methods, other potential ly significant emission points exist both upstream and downstream of the production measureme nt. These other emission points under this source category may include fluorinated GHG em issions from equipment leaks, storage tanks, wastewater, container filling (loading), ref rigerant blending, reclamation and recycling

10 For example, SF 6 ranks 4th in the Class 1 incinerability rankings of the Office of Research and Development and Office of Solid Waste and Emergency Response of U.S. E nvironmental Protection Agency’s Guidance on Setting Permit Conditions and Reporting Trial Burn Results Handbook, Volume II

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processes, and heel evacuation, particularly where these emissions occur before the production measurement at fluorinated GHG production facilitie s. (Equipment leak emissions are discussed above in a separate section.)

Fluorinated GHG emissions from wastewater will depe nd directly on the concentration and volume of the contaminants that are present in the wastewater. Based on an evaluation using EPA’s Estimation Program Interface (EPI) Suite, app roximately 90 percent or more of all fluorinated GHG compounds present in wastewater wil l be emitted to the atmosphere. The operating permits for some facilities referred to w astewater treatment activities for fluorinated compounds, although it is unclear what level of emi ssions might occur from wastewater and whether there would be wastewater emissions at all facilities.

Emissions from returned containers and from recycli ng depend heavily on the practices of individual facilities. If the facility recovers container heels or simply refills containers on to p of heels, then emissions from returned containers w ill be small. However, if the facility vents heels, then emissions can be significant, even domi nating overall facility emission rates. According to the 2006 IPCC Guidelines 11 , SF 6 production operations in Germany whose customers did not require highly purified gas had e mission rates in the range of 0.2 percent of the total quantity of SF 6 produced. On the other hand, SF 6 production operations in Japan whose customers required highly purified gas had emission rates of 8 percent due to the venting of heels whose purity was in doubt.

The situation is similar for recycling. Emissions during recycling include emissions during transfer of gas from containers to process e quipment, but they also include emissions associated with ridding the gas of contaminants, su ch as noncondensables (air, nitrogen, etc.) and oil. (Since lubricants are chosen to be miscible w ith refrigerants, a significant quantity of refrigerant can remain mixed into the oil when the oil is removed from the system or container.) If facilities carefully recover and purify gas that is returned for recycling, emissions are likely to be in the neighborhood of one percent or less of th e quantities returned. 12 However, if facilities use crude methods to purge noncondensables from con tainers, e.g., venting from the headspace of the cylinder, or if they don’t attempt to minimi ze fluorinated GHG emissions from lubricants, then emissions can be closer to five or ten percent of the quantities returned. (Early standards for recycling equipment allowed emissions from purging as high as five percent; 13 these limits have been lowered considerably since.) In the worst cas e, facilities could simply vent returned fluorinated GHGs, e.g., in cases where they are irr etrievably contaminated.

The fluorinated GHG emissions from storage tanks ar e anticipated to be small to insignificant due to the use of pressurized tanks f or storage. Emissions from blending activities are also likely to be relatively small. In both ca ses, however, emissions can be more significant if leaks or catastrophic failures occur.

11 From IPCC 2006, 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Prepared by the National Greenhouse Gas Inventories Programme, Eggleston H.S., B uendia L., Miwa K., Ngara T. and Tanabe K. (eds). Published: IGES, Japan., page 3,104 of Volume 3, Industrial Pr ocesses and Product Use.
12 From IPCC Volume 3, Chapter 8. http://www.ipccnggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_8_Ch8_Other_Product.pdf
13 SAE J1990, 1989 Extraction and Recycle Equipment for Mobil e Automotive Air-Conditioning Systems; ARI Standard 740-1993, For Performance of Refrigerant Recovery and/ or Recycling Equipment.43

Currently, it is EPA’s understanding that most fluo rinated GHG production facilities measure their production before container filling ( loading), e.g., by using flowmeters just upstream of the container connection to measure the mass flowing into the containers. If this is the case, emissions that occur during or after fill ing (e.g., from hoses and connections) would have been included in the production (supply) measu rement. However, if production is measured by weighing containers before and after fi lling, then emissions during container filling would not have been included in the production meas urement. In these cases, facilities using the emission factor approach would need to quantify con tainer filling emissions for completeness.

The IPCC Guidelines (Volume 3, Chapter 7) estimate that emissions related to container management (including refrigerant transfers between containers and handling of returned containers) range between 2 and 10 percent of the r efrigerant market.

In the event that the other potentially significant emission points were included under the rule, possible methods for tracking these emissions include engineering estimates (e.g., for container filling), equipment leak testing (e.g., f or storage tanks and blending activities), default or site-specific emission factors (all sources), an d mass balances (e.g., weighing returned container heels). For example, site-specific, gas- specific default factors could be developed for container heels based on measurements of these heel s over some period of time. This approach could be similar to the approach for quantifying co ntainer heels in proposed subpart I (the proposed rule for monitoring emissions of fluorinat ed GHG emissions from electronics manufacturing).
4. Procedures for Estimating Missing Data In the event that a scale or flowmeter normally use d to measure reactants, products, byproducts, or wastes fails to meet a test to verify its accuracy or precision, malfunctions, or is rendered inoperable, facilities may estimate these quantities using other measurements where these data are available. For example, facilities that ordinarily measure production by metering the flow into the day tank could use the weight of product charged into shipping containers for sale and distribution as a substitute. It is our u nderstanding that the types of flowmeters and scales used to measure fluorocarbon production (e.g ., Coriolis meters) are generally quite reliable, and therefore that it should rarely be ne cessary to rely solely on secondary production measurements. In general, production facilities re ly on accurate monitoring and reporting of the inputs and outputs of the production process. In t he event that a secondary mass measurement for the stream is not available, producers can use a related parameter and the historical relationship between the related parameter and the missing parameter to estimate the flow.

If concentration measurements are unavailable for s ome period, we are proposing that the facility use the average of the concentration measu rements from just before and just after the period of missing data.
5. QA/QC Requirements Typical QA/QC requirements for measuring devices in clude initial and periodic verification and calibration. (For example, see th e requirements of EPA’s Acid Rain regulations at 40 CFR Part 75.) In this case, it may be approp riate to require an initial verification of flowmeters and weigh scales and periodic calibratio n in accordance with the applicable industry44

standards or manufacturer directions. If the flowm eter manufacturer performed this verification at the flowmeter factory and did not recommend a se cond verification upon installation, the factory verification should suffice. Calibration o f flowmeters and scales could be performed prior to the reporting year; after the initial cali bration, recalibration could be performed as frequently as specified by the manufacturer. Under this approach, producers could perform the verification and calibration of their weigh scales during routine product line maintenance.

For the gas chromatography analytical method descri bed under the monitoring section of this document, monthly calibration, using known cer tified standards should be used. The calibration involves validating accurate measuremen t of these fluorocarbon standards across a range of possible concentrations, depending on whic h process streams are being measured.

For development of process-vent-specific emission f actors, facilities would need to conduct and meet the QA/QC procedures specified in the test methods used.
6. Reporting and Recordkeeping Procedures To verify and document their emissions estimates, o wners and operators of facilities producing fluorinated gases would be required to re port the following information, depending on their activities and on the estimation approach tha t they used. All facilities would be required to report both their fluorinated GHG emissions and the quantities used to estimate them on a process-specific basis. They would also be require d to report the results of each scoping test, specifically, the chemical identities of the conten ts of potentially emitted streams. Facilities using the mass-balance approach would report the ma sses of the reactants, products, by-products, and wastes, and, if applicable, the quantities of a ny product in the by-products and/or wastes (if that product is emitted at the facility). They wou ld also report the chemical identities of reactants, products, and by-products, along with th e chemical equations used to estimate emissions. Facilities using the emission factor ap proach would report the activity data used to calculate emissions (e.g., the quantity produced, t ransformed, or destroyed) and the emission factors used to estimate them. Owners and operator s would be required to report annual totals of these quantities by process and facility.

Where fluorinated GHG production facilities have es timated missing data, the facility would be required to report the reason the data wer e missing, the length of time the data were missing, the method used to estimate the missing da ta, and the estimates of those data.

Maintaining records of the information used to dete rmine the reported GHG emissions would enable us to verify that the GHG emissions mo nitoring and calculations were performed correctly. Owners and operators of facilities prod ucing fluorinated GHGs would be required to retain records documenting the data reported, inclu ding records of monthly emission estimation calculations, all data that went in to the calculat ions, calibration records for flowmeters, scales, and gas chromatographs, and documentation of emissi on factor development activities.

7. References 3M 2009. Meeting Documentation for Telephone Calls on October 9 and November 12, 2009 with 3M Representatives Regarding Fluorinated Gas P roduction. U.S. Environmental Protection Agency.45

Air Products 2009. Meeting Documentation for 17 No vember 2009 Telephone Call with Air Products Representatives Regarding Fluorinated Gas Production. RTI International.

Arkema 2009. Meeting Documentation for Various Tel ephone Calls During Week of 7 October 2009 with Arkema Representatives Regarding Fluorina ted Gas Production. U.S. Environmental Protection Agency.

DuPont 2009. Meeting Documentation for 13 November 2009 Telephone Call with DuPont Fluoropolymer Representatives Regarding Fluorinated Gas Production. RTI International.

INEOS Fluor 2009. Meeting Documentation for Octobe r 2009 Telephone Calls with INEOS Fluor Representatives Regarding Fluorinated Gas Pro duction. RTI International.

3M Site Visit 2009. Documentation for October 2009 Site Visit to 3M Cordova, Illinois Regarding Fluorinated Gas Production. RTI Internat ional.

DuPont Site Visit 2009. Documentation for October 2009 Site Visit to DuPont Corpus Christi, Texas Regarding Fluorinated Gas Production. RTI In ternational.

Centre Interprofessionnel Technique d’Etudes de la Pollution Atmospherique. Inventaire Des Emissions De Gaz A Effect De Serre En France Au Tit re de la Convention Cadre Des Nations Unies Dur Les Changements Climatiques. Mars 2009. http://unfccc.int/files/national_reports/annex_i_gh g_inventories/national_inventories_submission s/application/zip/fra_2009_nir_7apr.zip

Daniela Romano, Chiara Arcarese, Antonella Bernetti , Antonio Caputo, Rocío D. Cóndor, Mario Contaldi, Riccardo De Lauretis, Eleonora Di Cristof aro, Sandro Federici, Andrea Gagna, Barbara Gonella, Riccardo Liburdi, Ernesto Taurino, Marina Vitullo. ISPRA - Institute for Environmental Protection and Research. Italian Gree nhouse Gas Inventory 1990-2007. National Inventory Report, 2009. http://unfccc.int/files/national_reports/annex_i_gh g_inventories/national_inventories_submission s/application/zip/ita_2009_nir_15apr.zip

EPA Office of Research and Development and Office o f Solid Waste and Emergency Response of U.S. Environmental Protection Agency. Guidance o n Setting Permit Conditions and Reporting Trial Burn Results Handbook, Volume II. January 198 9. http://www.epa.gov/nrmrl/pubs/625689019/625689019.p df

EPA Office of Pollution Prevention Toxics and Syrac use Research Corporation (SRC). EPI Suite Version 4.00 January 2009. http://www.epa.gov/oppt/exposure/pubs/episuite.htm

Flemish Environment Agency, Flemish Institute for T echnological Research, Walloon Public Service, Brussels Institute for the Management of t he Environment, Interregional Cell for the Environment, ECONOTEC. Belgium’s Greenhouse Gas Inv entory (1990-2007). April 2009. http://unfccc.int/files/national_reports/annex_i_gh g_inventories/national_inventories_submission s/application/zip/bel_2009_nir_15apr.zip46

IPCC 2006, 2006 IPCC Guidelines for National Greenh ouse Gas Inventories, Prepared by the National Greenhouse Gas Inventories Programme, Eggl eston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds). Published: IGES, Japan. Cha pters 3, 6, 7 and 8. http://www.ipccnggip.iges.or.jp/public/2006gl/vol3.html

IPCC 2006, 2006 IPCC Guidelines for National Greenh ouse Gas Inventories, Prepared by the National Greenhouse Gas Inventories Programme, Eggl eston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds). Published: IGES, Japan. http://www.ipccnggip.iges.or.jp/public/2006gl/index.html

U.S. Environmental Protection Agency (EPA). Emissio n Inventory Improvement Program Volume II: Chapter 16. Methods for Estimating Air Emissions From Chemical Manufacturing Facilities. August 2007. www.epa.gov/ttn/chief/eiip/techreport/volume02/ii16 _aug2007final.pdf

U.S. Environmental Protection Agency (EPA) Office o f Air and Radiation and Office of Atmospheric Programs, Climate Change Division. Prot ocol for Measuring Destruction or Removal Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement Equipment in Electronics Manufacturing. March 2010.

U.S. Environmental Protection Agency (EPA) Office o f Air Quality Planning and Standards. Protocol for Equipment Leak Emission Estimates. EPA -453/R-95-017. November 1995. www.epa.gov/ttnchie1/efdocs/equiplks.pdf

U.S. Environmental Protection Agency (EPA). Eli Lil ly and Company, Airtech Environmental Services Inc.. Tracer Gas Protocol for the Determin ation of Volumetric Flow Rate Through the Ring Pipe of the Xact Multi-Metals Monitoring Syste m. September 2006.

www. epa .gov/ttnemc01/prelim/otm24.pdf

U.S. Environmental Protection Agency (EPA). Emissio n Measurement Center Approved Alternate Method (ALT-012)- An Alternate Procedure for Stack Gas Volumetric Flow Rate Determination (Tracer Gas). http://www.epa.gov/ttn/emc/approalt/alt-012.pdf

U.S. Environmental Protection Agency (EPA). Method 1- Sample and Velocity Traverses for Stationary Sources. http://www.epa.gov/ttnemc01/promgate/m-01.pdf

U.S. Environmental Protection Agency (EPA). Method 18 – Measurement of Gaseous Organic Compound Emissions by Gas Chromatography. http://www.epa.gov/ttnemc01/promgate/m18.pdf

U.S. Environmental Protection Agency (EPA). Method 205 - Verification of Gas Dilution Systems for Field Instrument Calibrations http://www.epa.gov/ttnemc01/promgate/m-205.pdf

U.S. Environmental Protection Agency (EPA). Method 21 – Determination of Volatile Organic Compound Leaks. http://www.epa.gov/ttnemc01/promgate/m-21.pdf

U.S. Environmental Protection Agency (EPA). Method 2A – Direct Measurement of Gas Volume Through Pipes and Small Ducts. http://www.epa.gov/ttnemc01/promgate/m-02a.pdf47

U.S. Environmental Protection Agency (EPA). Method 2B- Determination of Exhaust Gas Volume Flow Rate from Gasoline Vapor Incinerators. http://www.epa.gov/ttnemc01/promgate/m-02b.pdf

U.S. Environmental Protection Agency (EPA). Method 2C- Determination of Gas Velocity and Volumetric Flow Rate in Small Stacks or Ducts (Stan dard Pitot Tube) http://www.epa.gov/ttnemc01/promgate/m-02c.pdf

U.S. Environmental Protection Agency (EPA). Method 2D – Measurement of Gas Volume Flow Rates in Small Pipes and Ducts. http://www.epa.gov/ttnemc01/promgate/m-02d.pdf

U.S. Environmental Protection Agency (EPA). Method 2F- Determination of Stack Gas Velocity and Volumetric Flow Rate With Three-Dimens ional Probes. http://www.epa.gov/ttnemc01/promgate/Methd2F.pdf

U.S. Environmental Protection Agency (EPA). Method 2G- Determination of Stack Gas Velocity and Volumetric Flow Rate With Two-Dimensional Probe s. http://www.epa.gov/ttnemc01/promgate/Methd2G.pdf

U.S. Environmental Protection Agency (EPA). Method 301--Field Validation of Pollutant Measurement Methods from Various Waste Media. http://www.epa.gov/ttnemc01/promgate/m301.pdf

U.S. Environmental Protection Agency (EPA). Method 3B- Gas Analysis for the Determination of Emission Rate Correction Factor or Excess Air. http://www.epa.gov/ttnemc01/promgate/m03b.pdf

U.S. Environmental Protection Agency (EPA). Method 3-Gas Analysis for the Determination of Dry Molecular Weight. http://www.epa.gov/ttnemc01/p romgate/m-03.pdf

U.S. Environmental Protection Agency (EPA). Method 4 – Determination of Moisture Content in Stack Gases. http://www.epa.gov/ttnemc01/promgate/m-04.pdf

U.S. Environmental Protection Agency (EPA). Test Me thod 320- Measurement of Vapor Phase Organic and Inorganic Emissions by Extractive Fouri er Transform Infrared (FTIR) Spectroscopy. http://www.epa.gov/ttnemc01/promgate/m-320.pdf

U.S. Environmental Protection Agency Center for Env ironmental Research Information, Office of Research and Development. Compendium Method TO- 15- Determination Of Volatile Organic Compounds (VOCs) In Air Collected In Specia lly-Prepared Canisters and Analyzed By Gas Chromatography/ Mass Spectrometry (GC/MS). Jan uary 1999.

www. epa .gov/ttnamti1/files/ambient/airtox/to-15r.pdf

U.S. Environmental Protection Agency Office of Air and Radiation. Technical Support Document for Emissions From Production of Fluorinat ed GHGs: Proposed Rule for Mandatory Reporting of Greenhouse Gas. February 2, 2009.