Ranking Renewable and Fossil Fuels on Global Warming Potential Using Respiratory Quotient Concept

Table 3

Estimated RQ factors for hydrocarbon, alcohol, aromatics, and cycloparaffin fuels. CO₂ in tons per ; CO₂ in short tons per ; ;   or 0.448 GJ/kmole  O₂.

Fuel Type	RQ (=CO2/) relation	Range of RQ	Remarks
Paraffins,			RQ increases slightly with “”; for CH4, RQ incresaes with and as . ranges from 13,720 kJ/kg O2 to 13,920 kJ/kg O2. (CH4 to C20H42)
Diolefins,			RQ decreases slightly with “”; as . ranges from 13,490 kJ/kg O2 to 13,660 kJ/kg O2. (C2H4 to C12H22)
Aromatics,			RQ decreases slightly with “”; RQ, as . ranges from 13,585 kJ/kg O2 to 13,620 kJ/kg O2
Olefins, naphthenes, or cycloparaffin,	(2/3)	(2/3)	RQ constant
Alcohols, O	(2/3)	(2/3)	RQ is constant

The RQs for olefins, naphthenes, cycloparaffins, and alcohols are same; thus a blend of these fuels will not change RQ values and dry gas percentage will remain the same for both pure fuels and blends of arbitrary percentage at given equivalence ratio (refer to the Appendix). On the other hand, RQ for a blend of, say, CH₄ (Fuel 1) with RQ of 0.50 with glucose or carbon monoxide (Fuel 2) for which RQ is 2 will change with proportion of Fuel 1 in the blend of Fuel 1 and Fuel 2 and dry exhaust gas percentage will change for blends with change in % Fuel 2 in the blend and vice versa. Biology literature uses the change in RQ to determine the proportion of Fuel 1 (glucose) in the blend of glucose and fat (Fuel 2) being metabolized.