Global Warming Potential

FC-77 

Summary: 

This document describes analysis conducted by 3M to determine a Global Warming Potential 

(GWP) for components contained in FC-77. The format of this report is consistent with 

submittals to EPA for the use of Provisional GWP’s. The Mandatory Reporting Rule 

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 (GWP) 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] Default GWP’s can be used for any fluorinatedGHG 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. 

For the purposes of EPA’s request 3M estimated the FC-77 GWP assuming a 1:1 mixture of 

C8F18 and C8F16O. Therefore the GWP of FC-77 is calculated as the average of the GWP’s of 

these components. Table A–1 does not list a GWP for FC-77, C8F18 or C8F16O. As 

described in greater detail in a subsequent section, the atmospheric lifetime of C8F18 has been 

estimated as 3200 years [3], and the atmospheric lifetime of C8F16O has been estimated at 

2300 years [4]. The radiative forcing of each component of FC-77 has been estimated [4] 

and using these data the GWP of FC-77 has been estimated as 8900 relative to CO2 with a 

100-year integration time horizon. 

Evidence Supporting Request: 

F-GHG Identity: FC-77 (1:1 Mixture of C8F18 and C8F16O) 

Chemical Formula: 1:1 Mixture of C8F18 and C8F16O

Estimated GWP: 8900 relative to CO2 with a 100-year integration time horizon 

Data and analysis: 

Radiative Forcing: Individual absorption cross-sections were obtained from the spectrum of 

each individual component of FC-77 (See Figures 1 and 2). The spectral data was divided 

into sections with bandwidth 10 cm-1. Average absorption cross-sections for each band were 

calculated. The cross-sections were then weighted using factors reported in Pinnock et al [5]. 

The weighted cross-sections were summed over all bands to obtain the value for 

instantaneous radiative forcing for each individual component. A "cloudy-sky" adjustment 

factor of 1.07 was then applied as noted in results. The values for C8F18 and C8F16O are 0.56 

W/m2/ppbV and 0.63 W/m2/ppbV, respectively. 

Atmospheric lifetime: The atmospheric lifetime for C8F18 was estimated using a structurally 

similar chemical perfluorohexane as the mode of atmospheric degradation for both 

compounds is likely the same. In fact the average atmospheric lifetime for C3F8, c-C4F6, 

C4F10, C5F12, and C6F14 is 3140 and the GWP of the individual compounds varies by 20% 

from this average. For comparison, GWPs listed by the IPCC [3] have an uncertainty listed 
as 35%. The atmospheric lifetime for perfluorohexane is 3200 years [3]. The atmospheric 

lifetime for C8F16O was determined experimentally and was determined to be >2300 years [4] 

here we assume the lifetime is 2300 years. 

Using these data in the equation referenced by the IPCC [3] to determine the GWP of a given 

substance, a GWP of 8200 is determined for C8F18 relative to CO2 with a 100-year integration 

time horizon, and a value of 9600 is determined for C8F16O. Sine FC-77 is a 1:1 mixture of 

the two components the GWP is taken as the average of the two values and is 8900. 

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. IPCC, 2007: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution 

of Working Group II to the Fourth Assessment. Report of the Intergovernmental Panel on 

Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. 

Hanson, Eds., Cambridge University Press, Cambridge, UK, 976pp 

4. Ko, M.K.W. and D.T. Chang, Estimates of the Global Warming Potential of Proposed 

Chemical Compounds. 1992, Atmospheric and Environmental Research, Inc.: Cambridge, 

MA 

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

hydrofluorocarbons. Journal of Geophysical Research, 1995. 100(D11): p. 23227-23238. 
Figure 1. FTIR Spectra of C8F18 isomer mixture 

0

.2

.4

.6

.8

 3500 3000 2500 2000 1500 1000 500 

Absorbance / Wavenumber (cm-1) Paged X-Zoom CURSOR

File # 5 : HZPFOCT 1/9/1995 2:33 PM Res=.5cm-1

Perfluoro octanes, 10 0 ppm-meters in 1 atm air; 25 C.
Figure 2. FTIR Spectra of C8F16O