DEFRA (UK's department for the environment, food and rural affairs) defines the conversion factors commonly used to derive Ton CO2 and Ton CO2-equivalents:

Various fuel types produce different quantities of CO2: e.g. burning 1 ton of gas oil yields 3.19 tonnes of CO2, while burning 1 ton of coal yields 2.457 tonnes of CO2.

Fuel Type	Units	kg CO2 per unit (Net CV Basis)	kg CO2 per unit (Gross CV Basis)
Natural Gas	kWh	0.206	0.185
	therms	6.023	5.421
Gas Oil	tonnes	3190	3190
	kWh	0.265	0.251
	litres	2.674	2.674
Diesel	tonnes	3164	3164
	kWh	0.263	0.249
	litres	2.630	2.630
Petrol	tonnes	3135	3135
	kWh	0.253	0.240
	litres	2.315	2.315
Fuel Oil	tonnes	3223	3223
	kWh	0.281	0.267
Burning Oil1	tonnes	3150	3150
	kWh	0.258	0.245
	litres	2.518	2.518
Coal 2	tonnes	2457	2457
	kWh	0.346	0.329
LPG	kWh	0.225	0.214
	therms	6.608	6.277
	litres	1.498	1.498
Coking Coal	tonnes	2810	2810
	kWh	0.349	0.332
Aviation Spirit	tonnes	3128	3128
	kWh	0.250	0.238
	litres	2.233	2.233
Aviation Turbine Fuel 1	tonnes	3150	3150
	kWh	0.258	0.245
	litres	2.518	2.518
Other Petroleum Gas	tonnes	2894	2894
	kWh	0.217	0.206
Naphtha	tonnes	3131	3131
	kWh	0.249	0.237
Lubricants	tonnes	3171	3171
	kWh	0.263	0.250
Petroleum Coke	tonnes	3410	3410
	kWh	0.361	0.343
Refinery Miscellaneous	kWh	0.259	0.246
	therms	7.585	7.214

Furthermore, different industrial processes produce other greenhouse gases as a by-product:

• Methane CH4
• Nitrous oxide N2O
• Perfluorocarbons PFC
• Sulphur Hexafluoride SF6
• Hydrofluorocarbons HFC

DEFRA publishes conversion factors to express the effect of these gases in CO2-equivalents: e.g. producing 1 ton CH4  has the same warming effect as producing 21 tonnes of CO2 over 100 years. Therefor, 1 ton CH4 = 21 tonnes CO2-equivalent.

The factors used in our benchmarking analysis are published here.

DEFRA also provides a guidance for different industrial processes to identify which ones are prone to emit different types of GHG gases:

Process related emissions 9
Process		Emission
		CO 2	CH 4	N 2O	PFC	SF 6	HFC
Mineral Products	Cement Production
	Lime Production
	Limestone Us e 10
	Soda Ash Production and Use
	Fletton Brick Manufactur e 11
Chemical Industry	Ammonia
	Nitric Acid
	Adpic Acid
	Urea
	Carbides
	Caprolactam
	Petrochemicals
Metal Production	Iron, Steel and Ferroalloys
	Aluminium
	Magnesium
	Other Metals
Energy Industry	Coal mining
	Solid fuel transformation
	Oil production
	Gas production and distribution
	Venting and flaring from oil/gas production
Other	Production of Halocarbons
	Use of Halocarbons and SF 6
	Organic waste management