Annex IV METHOD OF CALCULATING THE TOTAL GWP OF A MIXTURE

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The GWP of a mixture is calculated as a weighted average, derived from the sum of the weight fractions of the individual substances multiplied by their GWP, unless otherwise specified, including substances that are not fluorinated greenhouse gases.

$Σ (Substance X % \times GWP) + (Substance Y % \times GWP) + \dots (Substance N % \times GWP)$ ,

where % is the contribution by weight with a weight tolerance of +/– 1 %.

For example: applying the formula to a blend of gases consisting of 60 % dimethyl ether, 10 % HFC-152a and 30 % isobutane:

Σ (60 % \times 1) + (10 % \times 124) + (30 % \times 3)

→ Total GWP = 13,9

The GWP of the following non-fluorinated substances are used to calculate the GWP of mixtures. For other substances not listed in this annex a default value of 0 applies.

Substance			GWP^f1
Based on the Fourth Assessment Report adopted by the Intergovernmental Panel on Climate Change, unless otherwise indicated.
Substance not listed in the Fourth Assessment Report adopted by the Intergovernmental Panel on Climate Change, default value on the basis of the GWPs of other hydrocarbons.
Common name	Industrial designation	Chemical Formula	GWP^f1
methane		CH₄	25
nitrous oxide		N₂O	298
dimethyl ether		CH₃OCH₃	1
methylene chloride		CH₂Cl₂	9
methyl chloride		CH₃Cl	13
chloroform		CHCl₃	31
ethane	R-170	CH₃CH₃	6
propane	R-290	CH₃CH₂CH₃	3
butane	R-600	CH₃CH₂CH₂CH₃	4
isobutane	R-600a	CH(CH₃)₂CH₃	3
pentane	R-601	CH₃CH₂CH₂CH₂CH₃	5^f2
isopentane	R-601a	(CH₃)₂CHCH₂CH₃	5
ethoxyethane (diethyl ether)	R-610	CH₃CH₂OCH₂CH₃	4
methyl formate	R-611	HCOOCH₃	25
hydrogen	R-702	H₂	6
ammonia	R-717	NH₃	0
ethylene	R-1150	C₂H₄	4
propylene	R-1270	C₃H₆	2
cyclopentane		C₅H₁₀	5

Annotations

Footnotes

f1: Based on the Fourth Assessment Report adopted by the Intergovernmental Panel on Climate Change, unless otherwise indicated.
f2: Substance not listed in the Fourth Assessment Report adopted by the Intergovernmental Panel on Climate Change, default value on the basis of the GWPs of other hydrocarbons.