Emission Factor
A coefficient that quantifies the greenhouse gas emissions released per unit of activity — such as kg CO2 per GJ of fuel burned or tCO2 per MWh of electricity consumed.
An emission factor is a numerical coefficient that converts an activity measurement (fuel consumed, electricity purchased, kilometres driven) into a quantity of greenhouse gas emissions. Emission factors are expressed as mass of GHG per unit of activity — for example, 94.6 kg CO2 per gigajoule of bituminous coal burned.
Where emission factors come from
The authoritative source for combustion emission factors is the IPCC 2006 Guidelines for National GHG Inventories, updated by the 2019 Refinements. For Indian electricity grid emissions, the Central Electricity Authority (CEA) publishes annual CO2 Baseline Database with state-wise and national grid emission factors.
Emission factor tiers
IPCC defines three tiers of emission factor accuracy:
- Tier 1: Default emission factors from IPCC — suitable for most organisations
- Tier 2: Country-specific or fuel-specific emission factors — higher accuracy for non-standard fuels
- Tier 3: Facility-specific measurements — highest accuracy, used for large industrial sources
Most Indian manufacturers use Tier 1 for mobile combustion and Tier 1 or 2 for stationary combustion depending on coal quality variation.
Using the correct factor version
Emission factors are updated as measurement science improves. Always specify the IPCC publication version used (e.g., IPCC 2006 with 2019 Refinements) in your carbon accounting methodology documentation.