Emission factor explanation by UK NAEI. Emissions are estimated by multiplying activity data by the appropriate emission factor:
Emission Estimate = Activity Data × Emission Factor
UK Specific Emission Factors, provided by BEIS and revised annually. These emission factors are suitable for community-scale and business emissions estimates.
International emission factor database, by IPCC. Emission factors are provided for an extensive range of activities, though are less specific to the UK, or Scotland.