### R equest to Use an A lternate GWP for Vinylidene Fluoride (CAS Number: 75

- 38

- 7 )

Summary:

EPA recently promulgated a mandatory reporting regulation for Fluorinated Greenhouse Gases ( F

- GHG). The regulation requires f acilities to monitor and report CO 2 - equiv alent F

- GHG process vent emissions, if those emissions exceed a threshold of 10,000 metric tons CO 2 - equivalent per year. [1] Estimated CO 2 - equivalent emissions are obta ined by multiplying the F

- GHG mass emissions by the Global Warming Potential for the individual fluorinated gases that comprise the flow. EPA has provided a t able of 100

- year time horizon GWP values for about 70 individual F

- GHG

, and specifies that these values are to be used for the purpose of computing CO 2 - equivalent emissions

. [2] A default GWP value of 2,000 is to be used for any F

- GHG not listed in Table A

- 1. T he regulation allows a facility to request a lower provisional GWP when clear scientific evidence exists to support such a lower value.

Table A

– 1 does not list a GWP for vinylidene fluoride

. Vinylidene fluoride is a s hort

lived fluorinated alkene. T he default GWP value of 2,000 is inappropriate for such gases and a substantial body of evidence in the peer

- reviewed scientific literature has established that the GWP s of fluorinated alkenes are modest . Kinetic rate constants for the atmospheric degradation of vinylidene fluoride have been measured in an environmental chamber; the atmospheric lifetime of vinyl idene fluoride has been estimated as 4 days; the infrared spectrum of vinylidene fluoride has been accurately measured and the GWP of vinylidene fluoride has been estimated as 0. 9 relative to CO 2 with a 100

- year integration time horizon. DuPont is request ing a provisional GWP of 0. 9 be assigned for vinylidene fluoride

. Evidence Supporting Request :

F

- GHG Identity : Vinylidene fluoride Chemical Formula : C 2 H 2 F 2 CAS Number: 75

- 38

- 7

Estimated GWP: 0. 9 relative to CO 2 with a 100

- year integration time horizon

Data and analysis: Baasandorj et al. have measured kinetic rate constants for the vapor phase reaction of vinylidene fluoride with OH. [3] T he global and yearly averaged lifetime of vinylidene fluoride was calculated as 4 days. Quantitative infrared cross

sections of vinylidene fluoride were obtained at 298 K in the region 5 00

- 40 00 cm - 1 , and

r adiative forcing calculations were performed using the approximation method developed by Pinnock et al

. [4] A GWP of 0. 9 relative to CO 2 with a 100

- year integration time horizon was established

. The methods used in determining this GWP value are essentially identical to those used for the values obtained for the gases listed in Table A

- 1: (1) the kinetic rate constan ts forreaction with critical atmospheric oxidants were measured and an atmospheric lifetime was determined; (2) the infrared absorption spectrum of the substance was measured ; and (3) the atmospheric lifetime and infrared absorption spectrum were incorpor ated into a radiative transfer model to estimate the contribution of the substance to greenhouse forcing.

Based on this publication in the peer

- reviewed literature , DuPont requests that a provisional GWP of 0. 9 be assigned for vinylidene fluoride

.

1. "Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs; Final Rule" , Federal Register 75:230 (December 1, 2010) p.74774. 2. "Table A

- 1 to Subpart A of Part 98

— Global Warming Potentials" : Table A

- 1 in 40 CFR part 98, subpart A. 3. Baasandorj, M., et al., Rate Coefficients for the Gas

- Phase Reaction of the Hydroxyl Radical with CH2═CHF and CH2═CF2. The Journal of Physical Chemistry A, 2010. 114 (13): p. 4619

- 4633. 4. Pinnock, S., et al., Radiative forcing of climate by hydrochlorofluorocarbons and hydrofluorocarbons. Journal of Geophysical Research, 1995. 100 (D11): p. 23227

- 23238.