### MEMORANDUM

TO : Jessica Gordan, Debbie Ottinger, EPA FROM : Tracy Curtis, Donna Lazzari, ERG DATE : February 27, 2013 SUBJECT : GWP Determinations for Proposed Additional F-GHGs for Table A-1

EPA is considering to include Global Warning Potentials ( GWPs) in Table A-1 of subpart A of the GHG reporting rule for 26 new fluorinated greenhouse gase s (F-GHGs). Reporters would use the GWPs in Table A-1 to subpart A to calculate GHG emissions for threshold applicability, determination of calculation methodologies, and reporting of annual emissions in CO2e. This memorandum provides background on the EPA’s evaluation of scientific assessmen ts and publically available estimates of GWP for the proposed F-GHGs. This memorandum is organized a s follows:

1. Background and Overview for Estimation of GWP 2. Key Considerations in GWP Calculation Methods 3. Compounds Identified from Provisional GWP Requests and Subm itted by Producers 4. Compounds Identified from Peer-Reviewed Assessments 5. References



### 1.0 BACKGROUND AND OVERVIEW FOR ESTIMATION OF GWP Table A-1 to subpart A (“Table A-1”) is a compendium of GWP v alues of select GHGs that are required to be reported under one or more subparts of Part 98, and wher e the EPA has identified the GWP in the IPCC Fourth Assessment Report or other sources. As acknow ledged in the final Part 98 (74 FR 56348, October 30, 2009), it is EPA’s intent to periodically upda te Table A-1 as GWPs are evaluated or reevaluated by the scientific community. EPA is proposing to include 26 additional GHGs in Table A-1 with associated GWP values where the EPA has identifie d the GWP based on an assessment of recent

### scientific literature. . The EPA identified the propos ed compounds and associated GWPs through review

of provisional GWP requests received from subpart L facilit ies, F-GHGs submitted by a fluorinated GHG producer with suggested GWPs and supporting data and analysi s on August 21, 2012, and F-GHGs for which evaluations of the GWPs were performed by the EPA ( e.g, as part of evaluations through EPA’s Significant New Alternatives Policy (SNAP)), or published i n peer-reviewed scientific journals


### . 1 

### This document provides background for EPA’s analysis of the GWP fo r these compounds. The key considerations that EPA took into consideration in the asse ssment of the GWPs for each compound are described in Section 2.0 of this document. The 26 compounds th at EPA is proposing to include in Table A-1, the proposed GWP for each compound, the origin of the GWP assessment, and the analyses for each compound are discussed in sections 3.0 and 4.0 of this docum ent.



### 2.0 KEY CONSIDERATIONS IN GWP CALCULATION METHODS

The GWPs for all GHGs are calculated as the ratio of the time-integrated radiative forcing of a one-kg emission of the GHG relative to the time-integrated radiative forcing of a one-kg emission of the reference gas (CO 2 

### ). The GWPs in Table A-1 are calculated based on the effe cts of the GHGs over a 100- year time horizon. For both the GHG and the reference gas, the two major inputs to the time-integrated radiative forcing are the radiative efficiency of the ga s and the concentration of the gas in the atmosphere over time. The concentration over time is in turn related to the atmospheric lifetime of the gas. The lifetime of a compound is affected by the compound’s r eaction rates through reaction with atmospheric oxidants (e.g., ozone or hydroxyl radicals) o r through photolysis (destruction by light). These rates, as well as the radiative efficiency of the compound, depend on reactivity with atmospheric oxidants and the distribution of the compound in the atmosphe re with altitude, latitude and longitude.

1 

### The SNAP program is EPA’s program to evaluate substitutes for the ozone-depleting substances that are being phased out under the stratospheric ozone protection pro visions of the Clean Air Act (as implemented in 40 CFR part 82). As part of EPA's assessm ent of a substitute's overall risk to human health and the environment, the EPA reviews scientific asse ssments of the GWP and considers this, among other criteria, in evaluating a substitute.

### Radiative efficiency is a measure of the influence a GHG has in altering the balance of incoming solar

radiation and outgoing infrared radiation in the Earth’s a tmosphere when its concentration in the atmosphere increases by a particular amount (e.g., by 1 par t per billion). The accuracy of the radiative efficiency calculation depends on the infrared absorptive pr operties of the gas and the atmospheric concentration and distribution of the gas. The most accurate approach to derive a GWP is to use a full three-dimensional model of the global atmosphere. However, al ternative estimation approaches have been developed and are frequently relied on in scientific as sessments of GWP. To determine the proposed GWP values for inclusion in Table A-1, EPA reviewed the av ailable literature for each compound and evaluated the accuracy of the measurements or modeling method s of these parameters. For each compound where EPA identified a scientific ass essment, EPA took into consideration the methods used to estimate the reactivity and lifetime ofthe compound, whether the compound is shortlived or long-lived, and whether the scientific assessment made appropriate assumptions in the derivation of the radiative efficiency of the compound. Many of the al ternative approaches used to estimate GWP use simplifying assumptions that are not fully applicable to com pounds that are short-lived in the atmosphere (defined here as any compound with an atmospheri c lifetime less than 1 year). A number of GWP assessments rely on the assumption that the compound is well-mixed (i.e., spread evenly over all longitudes, latitudes, and altitudes). For example, some st udies estimate atmospheric lifetime by assuming that the compound is exposed to the global average concentra tion of hydroxyl radicals (OH), or by deriving the lifetime of a compound from the known lifetime of a long-lived (i.e., well-mixed) reference compound with similar reaction rates. Short-lived compou nds do not last long enough to become wellmixed. Instead, their concentrations decrease rapidly with distance from their emission point, particularly with changing latitude and altitude. The assumption that sho rt-lived compounds are well-mixed affects both estimates of the atmospheric lifetime and the radiat ive efficiency. This assumption may overestimate the share of the short-lived compounds that resides higher in the atmosphere, where lower temperatures and pressures slow reaction rates and lengthen lifetimes. Generally, GHGs which reside higher in the atmosphere (i.e, near the tropopause) have longer lifetimes a nd are responsible for more radiative forcing

### than the same GHGs lower in the atmosphere. Therefore, t he assumption that short-lived compounds are

well-mixed may greatly overestimate the radiative effic iency of these compounds. Furthermore, for many compounds, a significant atmospheric sink is oxidation via reaction with OH, the most important reactive species in the lower a tmosphere. For compounds for which reaction with OH is the primary destruction mechanism, the assumption that compounds are well-mixed overestimates the share of the compound that makes it to the tropics, wher e OH concentrations are much higher than at the mid-latitudes where the compounds are emitted. Therefo re, on balance, the lifetimes of the short-lived compounds that react with OH are underestimated by ass uming they are well mixed. While assuming that the compound is well-mixed can provide reasonable radiative e fficiency estimations for long-lived gases, the method is less accurate for short-lived gases. The t ime-integrated radiative forcing (and hence the GWP) of short-lived compounds are likely overestimated when the methodology includes an assumption that the compound is well-mixed.



### 3.0 COMPOUNDS IDENTIFIED FROM PROVISIONAL GWP REQUESTS A ND SUBMITTED BY SUBPART L PRODUCERS

EPA is proposing to include 21 F-GHGs with associated GWPs in Table A-1 that were identified through provisional GWP requests submitted by subpart L prod ucers, or for which information on the GWP was received from subpart L producers. Subpart L reporters must use a default GWP unless they submit a request to use provisional GWPs for those F-GHGs following the requirements of 40 CF R 98.123(c)(1)(vi). Per 40 CFR 98.123(c)(1)(vi), reporters must submit data and analysis th at supports the estimate of the GWP for the FGHG. EPA identified 11 compounds for inclusion in Table A-1 following receipt of requests for provisional GWP analyses from Honeywell International (“Honeyw ell”) and DuPont de Nemours, Inc. (“DuPont”) on February 25, 2011 and February 28, 2011, respectively . The 11 compounds include: seven compounds for which EPA approved provisional GWPs for purpos es of the calculations in 40 CFR 98.123(c)(1) on February 24, 2012, and four compounds for which the EPA evaluated the GWPs, but

### not for the purposes of the calculations in 40 CFR 98.123(c). The calculated emission rates of these chemicals, when using the default GWP, did not exceed the 10,000 m etric tons CO 2 

### e threshold and did not meet the conditions of 40 CFR 98.123(c)(1)(v). . The fact that EPA did not approve the GWPs for the four compounds for the purposes of the calculations in 40 CFR 98.123(c)(1) was not due to disagreement with the companies’ suggested GWPs, and EPA is proposing to a mend Table A-1 to include these four gases. EPA reviewed the scientific assessments of GWP for each compound in the memorandum “Supporting Analysis For Mandatory Reporting Of Greenhouse Gases: Notice Of Preliminary Determinations Regarding Requests To Use Provisional Gl obal Warming Potentials Under The Fluorinated Gas Production Category Of The Greenhouse Gas Reporting Rule.” (see Docket ID No. EPAHQ-OAR-2009-0927-0256). EPA determined that the methods used to est imate the GWPs were likely to overestimate the GWPs by an order of magnitude or more. The se compounds are all relatively short-lived, and the analyses to determine the GWP for these compounds used the simplifying assumptions that the compounds are well-mixed in the atmosphere. In general, the assumption that short-lived compounds are well-mixed overestimates the radiative forcing of these ga ses and may affect estimates of the atmospheric lifetime. Because of this simplifying assumption, the propos ed GWPs are likely to be overestimates. On August 21, 2012, DuPont Chambers Works submitted 10 F-GHGs with suggested GWPs and supporting data and analysis. For each compound, DuPont in cluded peer-reviewed scientific data supporting the suggested GWP. EPA proposes to include these com pounds in Table A-1. EPA has reviewed the scientific assessments of GWP for each compound. Details of the analysis are included in the memorandum “Analysis of proposed GWPs for Table A-1. ” Memorandum from Mark Flugge, ICF to EPA. September 5, 2012 (see Docket ID No. EPA-HQ-OAR-2012-0934). The radiative efficiency of each compound is derived using a constant mixing ratio of the compounds in the troposphere. For four of the compounds, the approach used to calculate the atmospheric lifetimes, which assumed that these gases were well-mixed, likely underestimates the lifetimes of these compounds. This approach underestimates the concentration of O 2 

### and overestimates the concentration of OH to which the compo und is actually exposed. The overestimate of the OH concentration has a greater effect on the reaction rate and estimated

### lifetime of the compound. However, the radiative efficienc y calculation is likely to outweigh the

underestimated lifetimes. The EPA reviewed recent resea rch that suggests the approach used to determine the radiative efficiency for these compounds can result i n overestimates of the 100-yr GWP of 49 to 233 percent (see Wang et al., in draft). Therefore, the GW P estimates for these 10 compounds are likely upper bounds. However, because the GWP of each F-GHG is very low ( i.e., between 1 and 5), EPA determined that the GWPs estimates provided by DuPont would not signif icantly overestimate source category emissions or supply and are acceptable for the purposes of ca lculating emissions under Part 98. Additional details of the analysis are in the memorandum “A nalysis of Proposed GWPs for Table A-1.” (see Docket ID No. EPA-HQ-OAR-2012-0934). In addition to the supporting analyses listed above for the 21 com pounds submitted by subpart L producers, we identified additional supporting GWP estimates that were published in the Federal Register under EPA’s SNAP program (40 CFR part 82) for three compounds. The SNAP program is EPA’s program to evaluate substitutes for the ozone-depleting substa nces that are being phased out under the stratospheric ozone protection provisions of the Clean Air Ac t (as implemented in 40 CFR part 82). As part of EPA’s assessment of a substitute’s overall risk t o human health and the environment, the EPA reviews scientific assessments of the GWP and conside rs this, among other criteria, in evaluating a substitute. EPA also considered these additional GWP estima tes when proposing the GWPs for the associated compounds in Table A-1. Table 2-1 of this document provides the origin of each compound and GWP assessment, proposed GWP, and EPA’s supporting a nalysis. Table 2-1. Proposed Compounds and Associated GWPs for Tabl e A-1 from Provisional GWP Requests

Chemical Designation or Common Name CAS No. Chemical Formula Propos

ed GWP Origin of Compound and

GWP Assessments Supporting Analysis HF C

- 1234ze(E); HFO

1234ze; HFC1234ze(E); HFC1234ze 29118

- 24

- 9 CF 3 CH=CHF 6 Approved as provisional GWP for Honeywell International a and published under EPA’s SNAP Program (40 CFR part 82) b c

hexafluoropropylen e ; PFC-1216 116

- 15

- 4 CF 3 CF=CF 2 0.25 Approved as provisional GWP

for DuPont de Nemours a cperfluoromethyl vinyl

ether (PMVE) 1187

- 93

- 5 C 3 F 6 O; CF(CF 3 )OCF 3 3 Approved as provisional GWP for E. DuPont de Nemours a c
tetrafluoroethylene (TFE) 116

- 14

- 3 CF 2 =CF 2 0.02 Approved as provisional GWP

for E. DuPont de Nemours a c
trifluoro propene (TFP); HFC-1243zf; HFO-1243zf 677

- 21

- 4 CF 3 CH=CH 2 3 Approved as provisional GWP for E. DuPont de Nemours a c
vinyl fluoride (VF); HFC-1141 75

- 02

- 5 CHF=CH 2 0.7 Approved as provisional GWP for E. DuPont de Nemours a c vinylidine Fluoride (VF2); HFC-1132a 75

- 38

- 7 CH 2 =CF 2 0.9 Approved as provisional GWP for E. DuPont de Nemours a c carbonyl fluoride; carbonyl difluoride 353

- 50

- 4 COF 2 2 Submitted with provisional GWP request for E. DuPont de Nemours, no provisional GWP approved a c

perfluoropropyl vinyl ether (PPVE) 1623

- 05

- 8 C 5 F 10 O 3 Submitted with provisional GWP request for E. DuPont de Nemours, no provisional GWP approved a c

perfluoroethyl vinyl ether (PEVE) 10493

- 43

- 3 CF3

- CF2O

C=CF2 3 Submitted with provisional GWP request for E. DuPont de Nemours, no provisional GWP approved a c

HFO

- 1234yf; HFC

1234yf 754

- 12

- 1 CF 3 CF=CH 2 4 Submitted with provisional GWP request for Honeywell International, no provisional GWP approved, a and published under EPA’s SNAP Program (40 CFR part 82) b c

perfluorethyl iodide (2

- I) 354

- 64

- 3 C 2 F 5 I 3 Submitted by DuPont Chambers Works. “Request to Use a Provisional GWP for (perfluoroethyl) iodide (CAS Number 354-63-3).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. d

perfluorbutyl iodide (PFBI) 423

- 39

- 2 C 4 F 9 I 3 Submitted by DuPont Chambers Works. “Request to Use a Provisional GWP for (perfluoroethyl) iodide (CAS Number 354-63-3).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. Published under EPA’s SNAP Program (40 CFR part 82) f d

perfluoro

- 1

- iodohexane; 355

- 43

- 1 CF 3 CF 2 CF 2 CF 2 2 Submitted by DuPont dperfluorhexyl iodide (6

-

I) CF 2 CF 2 IC 6 F 13 I Chambers Works. “Request to Use a Provisional GWP for (perfluorohexyl) iodide (CAS Number 355-43-1).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. perfluoroctyl iodide (8

- I) 507

- 63

- 1 C 8 F 17 I 2 Submitted by DuPont Chambers Works. “Request to Use a Provisional GWP for (perfluorooctyl) iodide (CAS Number 507-63-1).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. d

1,1,1,2,2

- pentafluoro

- 4-iodo butane (22-I) 40723

- 80

- 6 C 4 H 4 F 5 I 2 Submitted by DuPont

Chambers Works. “Request to Use a Provisional GWP for 1,1,1,2,2-pentafluoro-4-iodo butane (CAS Number 40723- 80-6).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. d

1,1,1,2,2,3,3,4,4

- nonafluoro-6-iodo hexane (42-I) 2043

- 55

- 2 2 Submitted b y DuPont Chambers Works. “Request to Use a Provisional GWP for 1,1,1,2,2,3,3,4,4-nonafluoro-6- iodo hexane (CAS Number 2043-55-2).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. d

p erfluorobutyl ethylene, perfluorobutyl ethene (42-U) 19430

- 93

- 4 C 6 H 3 F 9 2 Submitted by DuPont Chambers Works. “Request to Use a Provisional GWP for (perfluorobutyl) ethene (CAS Number 19430-93-4).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. d ,e

p erfluorohexyl ethylene, perfluorohexyl ethene (62-U) 25291

- 17

- 2 C 8 H 3 F 13 ; CH 2 =CH(CF 2 C F 2 ) 3 F 1 Submitted by DuPont Chambers Works. “Request to Use a Provisional GWP for (perfluorohexyl) ethylene (CAS Number 25291-17-2).” Submitted to Climate Change d ,eDivision, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. perfluorooctyl ethane (82-U); perfluorooctyl ethylene 21652

- 58

- 4 C 10 H 3 F 17 1 Submitted by DuPont Chambers Works. “Request to Use a Provisional GWP for (perfluorooctyl) ethene (CAS Number 21652-58-4).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. d ,e

1H,1H, 2H,2H

perfluorohexan-1-ol (42-AL) 2043

- 47

- 2 C 6 H 5 F 9 O 5 Submitted by DuPont Chambers Works. “Request to Use a Provisional GWP for1H,1H, 2H,2Hperfluorohexan-1-ol (CAS Number 2043-47-2).” Submitted to Climate Change Division, Office of Atmospheric Programs, U.S. Environmental Protection Agency. August 21, 2012. d ,e

a See “Mandatory Reporting of Greenhouse Gases: Notice of Preliminary Determinations Regarding Requests to Use Provisional Global Warming Potentials Under the Fl uorinated Gas Production Category of the Greenhouse Gas Reporting Rule” (77 FR 5514, February 3, 2012). b For CF 3 CH=CHF and CF 3 CF=CH 2 , the GWP and atmospheric lifetime estimates published under the SNAP program support the provisional GWPs.
c See “Supporting Analysis For Mandatory Reporting Of Gr eenhouse Gases: Notice Of Preliminary Determinations Regarding Requests To Use Provisional Global Warming Po tentials Under The Fluorinated Gas Production Category Of The Greenhouse Gas Reporting Rule. Office of Air and Radiation, U.S. Environmental Protection Agency. January 24, 2011; Docket ID No. EPA-HQ-OAR-2009-0927-0256. d See “Analysis of proposed GWPs for Table A-1.” Memoran dum from Mark Flugge, ICF to EPA. September 5, 2012; Docket ID No. EPA-HQ-OAR-2012-0934
e For the compounds perfluorobutyl ethene, perfluorohexyl eth ene, perfluorooctyl ethene, and 1H,1H,2H,2Hperfluorohexan-1-ol, the lifetimes of each F-GHG are est imated using kinetic reaction rates for reaction with common atmospheric oxidants (OH and/or ozone (O 3 )), using global weighted-average concentrations of each oxidant. Overall, this assumption overestimates the reac tion rates of these gases and likely underestimates the lifetimes. The methods used underestimate the concentrat ion of O 3 and overestimate the concentration of OH to which the compound is actually exposed. The overestimate of the OH concentration has a greater effect on the reaction rate and estimated lifetime of the compound. f For perfluorbutyl iodide (PFBI), the GWP and atmospheric lifetime estimates published under the SNAP program are less than 5 and a few days, respectively.



### 4.0 COMPOUNDS IDENTIFIED FROM PEER-REVIEWED SCIENTIFIC ASSESSMENTS OR OTHER EPA RULEMAKINGS

EPA is also proposing to amend Table A-1 to include five F- GHGs which were identified from EPA’s review of industrial gases produced for or used i n the electronics manufacturing, fluorinated gas

### production, and magnesium production source categories and for which scientific assessments of GWP

have been published under EPA’s SNAP program or identified in peer reviewed literature. The origin of each compound and GWP assessment are identified in Tabl e 2-2 of this document. EPA’s analyses of the available GWP estimates are discussed in Sections 2.2.1 t hrough 2.2.4 of this document. Table 2-2. Proposed Compounds and Associated GWPs for Tabl e A-1 from Other Rulemakings or Peer-Reviewed Scientific Assessments

Chemical Designation or Common Name CAS No. Chemical Formula Proposed GWP Origin of Compound and GWP

Assessments t rans - 1

- chloro

- 3,3,3

- trifluoroprop-1-ene 102687

- 65

- 0 CF 3 CH=CHCl 7 Published under EPA’s SNAP Program (40 CFR part 82) and identified in peer reviewed literature FK

- 5

- 1

- 12; C6 perfluoroketone; FK–5–1–12myy2; nperfluorooctane; octanedecafluorooctane 756

- 13

- 8 CF 3 CF 2 C(O)CF(C F 3 ) 2 1.8 Published under EPA’s SNAP Program (40 CFR part 82) and identified in manufacturer’s literature
C7 f luoroketone , Novec 774/FK-6-1-12 813

- 44

- 5 and 813-45-6 Blend of tw o

isomers: 3- pentanone,1,1,1,2,4 ,5,5,5- octafluoro-2,4- bis(trifluoromethyl ) and 3- hexanone,1,1,1,2,4, 4,5,5,6,6,6- undecafluoro-2- (trifluoromethyl) 1 Published under EPA’s SNAP Program (40 CFR part 82)

PFC

- 6

- 1

- 12; hexadecafluoroheptane 335

- 57

- 9 C 7 F 16 7930 Identified in peer reviewed literature PFC

- 7

- 1

- 18; octadecafluorooctane 307

- 34

- 6 C 8 F 18 8340 Identified in peer reviewed literature


### 4.1 trans-1-chloro-3,3,3-trifluoroprop-1-ene

An analysis of the GWP of trans-1-chloro-3,3,3-trifluoropro p-1-ene (trade name Solstice TM 

### 123 3zd(E)) was previously performed through EPA’s SNAP Prog ram (See “Protection of Stratospheric Ozone: Determination 27 for Significant New Alternatives P olicy Program,” Docket Id. No. EPA-HQOAR-2003-0118). As part of the SNAP analysis, EPA evaluated t wo recent studies estimating the GWP for trans-1-chloro-3,3,3-trifluoroprop-1-ene, and estimated a GWP between 4.7 and 7. Andersen et al.

### (2008) estimated a GWP of 7 for this compound. Andersen et al. measured the kinetic reaction rate of

trans-1-chloro-3,3,3-trifluoroprop-1-ene with common oxidants O H, O 3 

### , and chlorine (Cl) to establish atmospheric lifetime, using global weighted-average concentr ations of each oxidant. The use of global weight-average concentrations assumes that the short-lived g as is well-mixed. To calculate the radiative efficiency of the compound, Andersen et al. (2008) measured i nfrared spectra using Fourier Transform Infrared (FTIR) spectroscopy and the estimation methods in Pinnock et al. (1995). The methods assume that trans-1-chloro-3,3,3-trifluoroprop-1-ene is well-mixed in the atmosphere. As a result, the GWP calculated by Andersen et al. is likely overestimated. The SNAP analysis also provided a GWP estimate for trans-1-chloro-3,3,3-trifluoroprop-1-ene) of 4.7 from an u npublished study (see 77 FR 47770, August 10, 2012). EPA also considered an unpublished paper by Wang et al. (in draft) which re-evaluates the atmospheric lifetime of trans-1-chloro-3,3,3-trifluoroprop-1-ene using a three-dimensional chemical transport model, which provides temporal and spatial concent rations that can be used to simulate mixing ratios. The simulated mixing ratios are used to recalc ulate the radiative efficiency. The model used by Wang et al. (in draft) may provide a more accurate esti mate of both atmospheric lifetime and forcing for short-lived compounds, because it does not rely on the assump tion that these compounds are evenly distributed in the atmosphere. Wang et al. (in draft) calc ulates a lifetime of 31 days for trans-1-chloro3,3,3-trifluoroprop-1-ene and estimates a GWP of 4.7. Although the Wang et al. studies cited give a GWP of 4.7 for trans-1-chloro-3,3,3-trifluoroprop-1-ene, EPA believes it is more appropriate to use the GWP from the Andersen et al. study, as it comes from a pee r-reviewed journal article. Also, consistent with the reasoning for choosing possibly upper-bound GWPs for o ther chemicals in Table 3 of this preamble, using the GWP of 7 rather than 4.7 would not signif icantly overestimate source category emissions.



### 4.2 FK-5-1-12

### The compound FK-5-1-12 (1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromet hyl)-3-pentanone,also

produced under the trade names NovecTM 612 and NovecTM 1230) is a fl uorinated ketone. Product information provided by the manufacturer provides a GWP estim ate of 1 for a 100-year integration using IPCC 2007 calculation methods (3M Company, 2009). However, an anal ysis of the GWP of FK-5-1-12 (identified in the analysis as Novec 1230) was previously perf ormed through EPA’s SNAP Program (See “Protection of Stratospheric Ozone: Listing of Substitutes f or Ozone Depleting Substances, Correction” (68 FR 16729, April 7, 2003)). The SNAP analysis is based on a re view of Taniguchi et al. (2003), which examines the reaction of FK-5-1-12 in the atmosphere and asso ciated reaction products. The study concludes that the atmospheric lifetime of FK-5-1-12 is one t o two weeks, and suggests that products of the reaction would contribute additional CO 2 

### to the atmosphere. The SNAP analysis re-evaluates the GWP of FK-5-1-12 for a 100-year integration, using the IPCC appr oach. The GWP accounts for indirect effects, including the rainout of the reaction product CHF 3 

### COF, and has been further revised and evaluated to account for mass. The total GWP is comp rised of a direct value of less than 1 but greater than zero, plus an indirect GWP of 0.56 to 0.84, based on 4 to 6 carbons available (from photodissociation) for conversion to CO 2 

### . Multiplying the calculated GWPs by the ratio of CO 2 

### mass to C-6 oxyfluorocarbon mass results in a 100 year GWP for FK-5- 1-12 between 0.6 and 1.8. EPA is currently proposing a GWP of 1.8. The methods used to eval uate radiative forcing for FK-5-1-12 assumed a constant mixing ratio for the compound, which likely over estimates the time-integrated radiative forcing and the GWP. However, because the proposed GWP of the compo und is so low, the proposed value would not likely result in substantial over-reporting for the magnesium production source category. See “Protection of Stratospheric Ozone: Listing of Substitutes f or Ozone Depleting Substances, Correction” (68 FR 16729, April 7, 2003) and Docket Id. No. EPA-HQ-OAR-2003-0118-0049 fo r the EPA’s full analysis of the GWP of FK-5-1-12.



### 4.3 FK-6-1-12

### The compound FK-6-1-12 (C7 fluoroketone, also produced under the trade n ame Novec TM 

### 774),

is a blend of two isomers: 3- pentanone,1,1,1,2,4,5,5,5-octafluor o-2,4-bis(trifluoromethyl) and 3- hexanone,1,1,1,2,4,4,5,5,6,6,6-undecafluoro-2-(trifluoromethyl). The G WP of FK-6-1-2 was previously published under EPA’s SNAP Program (See “Protection of Strat ospheric Ozone: Determination 27 for Significant New Alternatives Policy Program,” Docket Id. No. EPA-HQ-OAR-2003-0118). Although the estimation methods for the GWP were considered confidential business information, the SNAP analysis provides a 100-year integrated GWP of 1. The compound also h as a chemical structure similar to that of FK-5-1-12, therefore, we would anticipate a similar life time and GWP for these compounds.



### 4.4 C 7 

### F 16 

### and C 8 

### F 18 

### There are no previous estimates of the GWP of the perfluo rocarbons (PFCs) C 7 

### F 16 

### and C 8 

### F 18 

### . EPA identified Ivy et al. (2012), a recent study that provides global emission estimates of each PFC using a three-dimensional chemical transport model and infrared spectra measurements to determine the GWP of these PFCs. The infrared spectra of each compound wa s measured using FTIR spectroscopy., The authors assumed an atmospheric lifetime of 3,000 years for each gas based on previous lifetime estimates for chemically-similar compounds. The radiative efficienc y of each compound was calculated using the measured infrared spectra and the methods in Pinnock et a l. (1995). These compounds are long-lived gases that are expected to be well-mixed in the atmos phere. Because the expected lifetimes of these PFCs are much longer than the 100-year timeline used as the basis of the GWP, they are relatively insensitive to the assumed lifetime. Furthermore, the methods and assumpt ions used by Ivy et al. (2012) are generally considered reliable for long-lived gases. Therefore, we r ecommend GWPs of 7930 and 8340 for C 7 

### F 16 

### and
C 8 

### F 18 

### , respectively

, 

### as presented by Ivy et al.

### 5.0 ADDITIONAL REFERENCES

3M Company. “3MTM NovecTM 1230 Fire Protection Fluid.” 2009. Availabl e online at: http://multimedia.3m.com/mws/mediawebserver?mwsId=66666UF6EVsSy XTtlXfyn8TEEVtQEVs6EVs 6EVs6E666666--&fn=prodinfo_novec1230.pdf Andersen, M.P.S., E.J.K. Nilsson, O.J. Nielsen, M.S. J ohnson, M.D. Hurley, and T.J.Wallington. 2008. Atmospheric chemistry of trans-CF3CH CHCl: Kinetics of t he gas-phase reactions with Cl atoms, OH radicals, and O3. J. Photochem. Photobiol. A: Chemistry 199: 92–97. Ivy, D.J., M. Rigby, M. Baasandorj, J. B. Burkholder, and R . G. Prinn. 2012. Global emission estimates and radiative impact of C4F10, C5F12, C6F14, C7F16 and C8F18. Atm os. Chem. Phys., 12: 7635–7645. DOI:10.5194/acp-12-7635-2012. Pinnock, S., Hurley, M.D., Shine, K.P., Wallington, T.J. , and Smyth, T.J. 1995. Radiative forcing of climate by hydrochlorofluorocarbons and hydrofluorocarbons. J. Geophys. Res., 100, 23277-23238. Taniguchi, N.; Wallington, T.J.; Hurley, M.D.; Guschin, A .G.; Molina, L.T. (2003). Atmospheric Chemistry of C2F5C(O)CF(CF3)2: Photolysis and Reaction wi th Cl Atoms, OH Radicals, and Ozone. J. Phys. Chem. A., 107(15); 2674-2679. Wang D., Olsen S., Wuebbles D. 2011. “Preliminary Report: Analyses of tCFP's Potential Impact on Atmospheric Ozone.” Department of Atmospheric Sciences. University of Illinois, Urbana, IL. September 26, 2011. Wang D., Wuebbles D., Patten K., and Olsen, S. Undated. Climate advantages of proposed short-lived compounds as replacements for longer-lived HCFCs and HFCs . Department of Atmospheric Sciences. University of Illinois, Urbana, IL. Draft report, undated.