Step 4: Where do emission factors come from?

An emission factor converts activity data into emissions, for example kg CO2 per litre of diesel. Common sources for Indian companies:

• Central Electricity Authority (CEA), CO2 Baseline Database for the Indian Power Sector: the official grid emission factors for India, updated in numbered versions. Use the version and financial year that match your reporting year.
• IPCC 2006 Guidelines for National Greenhouse Gas Inventories, with the 2019 Refinement: default factors for fuels, for example in Volume 2, Chapter 1 (calorific values and CO2 factors) and Chapter 2 (stationary combustion). The IPCC Emission Factor Database (EFDB) collects further factors.
• India GHG Program: India-specific calculation tools, for example road transport emission factors (draft technical paper, version 1.0, 2015).
• UK Government GHG Conversion Factors for Company Reporting (published each year by DESNZ, formerly DEFRA): often used for travel, freight and materials when no Indian factor exists. Note that its electricity factor is for the UK grid and must not be used for India.
• Supplier-specific data: a fuel test report, a supplier's verified product footprint, or a power supplier's emission rate.

Gases other than CO2 are converted with global warming potentials (GWPs). IPCC AR6 (Working Group I, 2021) gives 100-year GWPs of 29.8 for fossil methane and 273 for nitrous oxide; these are the latest IPCC values. India's own national reports to the UNFCCC, such as the First Biennial Transparency Report (BTR-1), use the older IPCC AR5 values (methane 28, nitrous oxide 265), as UNFCCC decision 18/CMA.1 requires. State which IPCC report's GWPs you use and stick with it.