Request to Use an Alternate GWP for

3,3,3-trifluoropropene (CAS Number: 677-21-4)

Summary:

EPA recently promulgated a mandatory reporting regulation for Fluorinated Greenhouse 

Gases (F-GHG). The regulation requires facilities to monitor and report CO2-equivalent 

F-GHG process vent emissions, if those emissions exceed a threshold of 10,000 metric 

tons CO2-equivalent per year. [1] Estimated CO2-equivalent emissions are obtained 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 table 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 CO2-equivalent emissions. [2] A 

default GWP value of 2,000 is to be used for any F-GHG not listed in Table A-1. The 

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 3,3,3-trifluoropropene. 3,3,3-trifluoropropene is a 

short-lived fluorinated alkene. The 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 GWPs of fluorinated alkenes are modest. Kinetic rate constants for 

the atmospheric degradation of 3,3,3-trifluoropropene have been measured in an 

environmental chamber; the atmospheric lifetime of 3,3,3-trifluoropropene has been 

estimated as 7 days; the infrared spectrum of 3,3,3-trifluoropropene has been accurately 

measured and the GWP of 3,3,3-trifluoropropene has been estimated as 3 relative to CO2

with a 100-year integration time horizon. DuPont is requesting a provisional GWP of 

3 be assigned for 3,3,3-trifluoropropene.

Evidence Supporting Request:

F-GHG Identity: 3,3,3-trifluoropropene

Chemical Formula: C2H3F3

CAS Number: 677-21-4

Estimated GWP: 3 relative to CO2 with a 100-year integration time horizon 

Data and analysis: Andersen et al. have measured kinetic rate constants for the vapor 

phase reaction of 3,3,3-trifluoropropene with OH and O3. [3] OH and O3 radicals react 

with 3,3,3-trifluoropropene with rate constants of (1.36 ± 0.25) × 10−12cm3 molecule−1

s

−1 and (3.5 ± 0.3) × 10−19 cm3 molecule−1

s

−1, respectively in 700 Torr of N2 or N2/O2, 

diluent at 296 K. Using a global weighted-average OH concentration of 1.0 × 106

molecule cm−3 leads to an estimated lifetime of 3,3,3-trifluoropropene with respect to 

reaction with OH radicals of 8.5 days. [4] The global background concentration of O3 is 

approximately 35 ppb which leads to an estimated lifetime of 38.4 days. [5] Thus, the 

overall global and yearly averaged lifetime of 3,3,3-trifluoropropene is expected to be 7.0

days with removal occurring approximately 80% via reaction with OH and 20% via 
reaction with O3. Infrared cross-sections of 3,3,3-trifluoropropene were obtained using 

ab initio quantum chemical methods recommended in the peer-reviewed scientific 

literature. [6-7] Radiative forcing calculations were performed using the approximation 

method developed by Pinnock et al. [8] A GWP of 3 relative to CO2 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 constants for 

reaction 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 incorporated 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 3 be assigned for 3,3,3-trifluoropropene.

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. Andersen, M.P.S., et al., Atmospheric chemistry of CxF2x+1CH=CH2 (x=1, 2, 4, 6, 

and 8): Kinetics of gas-phase reactions with Cl atoms, OH radicals, and O3.

Journal of Photochemistry and Photobiology, A: Chemistry, 2005. 176(1-3): p. 

124-128.

4. Prinn, R.G., et al., Evidence for Substantial Variations of Atmospheric Hydroxyl 

Radicals in the Past Two Decades. Science, 2001. 292(5523): p. 1882-1888.

5. Finlayson-Pitts, B.J., Pitts, James N., Atmospheric chemistry : fundamentals and 

experimental techniques. 1986, New York: John Wiley & Sons.

6. Blowers, P. and K. Hollingshead, Estimations of Global Warming Potentials from 

Computational Chemistry Calculations for CH2F2 and Other Fluorinated Methyl 

Species Verified by Comparison to Experiment. The Journal of Physical 

Chemistry A, 2009. 113(20): p. 5942-5950.

7. Halls, M.D. and H.B. Schlegel, Comparison of the performance of local, 

gradient-corrected, and hybrid density functional models in predicting infrared 

intensities. The Journal of Chemical Physics, 1998. 109(24): p. 10587-10593.

8. Pinnock, S., et al., Radiative forcing of climate by hydrochlorofluorocarbons and 

hydrofluorocarbons. Journal of Geophysical Research, 1995. 100(D11): p. 23227-

23238.