The single biggest barrier first-time corporate carbon reporters hit is the price tag on commercial emission factor databases. Ecoinvent, GaBi, and Sphera all charge thousands of euros annually for what are, at their core, lookup tables. For ISO 14064-1 Scope 1 and Scope 2 inventories - which are what 90 percent of mid-market companies actually report - you do not need any of them. The free public databases are sufficient, defensible under audit, and recognised by every major framework including CDP, SBTi, GHG Protocol, and the Spanish MITECO registry. The catch is that mixing them sloppily breaks consistency, and most rejection findings under ISO 14064-3 verification trace back to mixed-database inventories with poor documentation.
| Database | Best for | Update cadence | Licence |
|---|---|---|---|
| DEFRA (UK) | Fuels, transport, refrigerants, waste, water | Annual (June) | Open Government Licence v3.0 |
| IDAE (Spain) | Spanish electricity grid (location-based) | Annual (Q1) | Free for public use |
| IPCC AR6 | Global warming potentials (GWP100) for refrigerants and non-CO2 gases | Per assessment cycle (5-7 years) | Public domain |
| EPA eGRID | US electricity by sub-region | Annual (2-year lag) | Public domain |
For Scope 1 stationary fuels (natural gas, heating oil, propane, biomass), DEFRA is the de facto international default. The factors are well-documented per unit (kWh, m3, litres, kg) and the annual June refresh aligns with most corporate reporting calendars. Where DEFRA gives you a factor in kgCO2e per kWh and your activity data is in cubic metres, you also need a calorific value conversion; DEFRA publishes those too on the same page.
For Scope 1 mobile combustion (company vehicles, owned fleet), DEFRA again leads. Spain-specific factors from IDAE are available but largely converge with DEFRA's values; pick one and stick to it for consistency.
For Scope 1 refrigerants and fluorinated gases, the factor is the global warming potential (GWP100) of the gas. Use IPCC Assessment Report 6 (AR6) values. Many corporate inventories still cite AR5 because the software has not been updated; reviewers usually accept either provided the AR vintage is stated explicitly. Do not silently mix AR5 and AR6 within the same year.
For Scope 2 location-based electricity, the right factor is the grid average for the country (or US sub-region) where consumption occurred. Use IDAE for Spain, EPA eGRID for the US, and DEFRA for the UK. For other countries the IEA emission factors database is free with registration and fills in most of the world. For Scope 2 market-based, you also need supplier-specific factors or residual mix - those are not part of the free databases and must come from the utility's own disclosure or the AIB residual mix publication for Europe.
Three documentation patterns trip up ISO 14064-3 verifiers more than any others.
For Scope 3 (especially category 1 purchased goods and services), spend-based and average-data methods drawn from EPA USEEIO are free and reasonable for screening, but precision is limited to commodity sectors. Hybrid approaches that use Ecoinvent or one of its derivatives become necessary if you need product-level resolution for a CDP Climate A-list submission or SBTi target validation. For Scope 1 and Scope 2, you almost never need it.