Table 1.

Emission factors used for TWP calculations in this paper

	Power Plants		Vehicles
	Natural gas combined cycle* (kg/MWh)	Supercritical pulverized coal† (kg/MWh)	Light-duty CNG car (kg/mmBtuHHV)‡	Light-duty gasoline car (kg/mmBtuHHV)	Heavy-duty CNG truck (mg/ton-mile)	Heavy-duty diesel truck (mg/ton-mile)
Upstream CH4	3.1	0.65	0.51	0.1	590	100
Upstream CO2	36	7	9.4	15.9	10,000	15,000
In-Use CH4	0	0	0.11	0.0056	15	0
In-Use CO2	361	807	53.1	70.3	80,000	85,000
Fuel cycle CH4	3.1	0.65	0.62	0.11	605	100
Fuel cycle CO2	397	814	62.5	86.2	90,000	100,000

^*Heat rate = 6,798 Btu/kWh.

^†Heat rate = 8,687 Btu/kWh.

^‡1 mmBtu = 10⁶ Btu = 1.055 GJ.