Guide / architecture
Data model
Publisher → factor set and category → factor → dimensions and gas components.
Hierarchy
Publisher ─────────────► EmissionCategory
│ │ 1:N (required)
│ 1:N ▼
▼ EmissionFactor ──► EmissionFactorDimension[]
EmissionFactorSet ───► (the atomic └─► GasComponent[]
Methodology ─────────┘ lookup row)01
Publisher
The organization and publisher version responsible for a dataset.
02
Factor set
A versioned release identified by publisher, year, version, methodology and license.
03
Category
A publisher-scoped grouping such as Passenger vehicles or Fuels.
04
Emission factor
A stable factor code, activity, unit, aggregate CO2e value and classification metadata.
05
Dimensions
Key/value variants that distinguish fuel, vehicle, technology or other attributes.
06
Gas components
Optional CO2, CH4 and N2O contributions with native mass and GWP provenance.
Identity and reproducibility
The human-readable, versioned factor code is the only public identity for a factor variant. Database IDs remain internal implementation details.
Aggregate-only factors are valid: when a publisher does not provide a per-gas split, the headline CO2e value remains authoritative.
Publisher
The organisation that published the numbers, such as DEFRA, EPA or ecoinvent. A publisher record is versioned by code and version and owns its category taxonomy.
Factor set
One versioned dataset from one publisher, identified by publisher, dataset name, year and version. It carries methodology, GWP source and horizon, default region, license and source URL.
Category
An emission source category or worksheet. Categories are publisher-scoped and shared across that publisher's releases; they may carry a default scope.
Emission factor
The atomic lookup row. It contains a stable factorCode, activity, unit and unitDimension, co2ePerUnit, method, scope and scope3Category, geography, currency and priceYear, tier and uncertainty bounds.
Dimensions
Flexible key/value descriptors such as fuel = Petrol, type = Mini and disposalRoute = Landfill allow new sources without schema changes.
Gas components
Gas components preserve the CO2e-weighted contribution per gas and, for IPCC-style sources, native gas mass and applied GWP. Some publishers provide only an aggregate CO2e value.
Uniqueness constraint
A factor is unique on factor set, category, activity, unit, region and dimensionKey, where dimensionKey is a stable hash of its sorted dimension pairs.
Stable factor code
The stable factor code is methodology:publisher:publisher-version:dataset:year:dataset-version:scope:category:activity:sorted-pairs. Unit and region join the sorted pairs. Re-ingesting the same release reproduces its codes, while another release gets distinct codes.
ghg_protocol:defra:2025:ghg_conversion_factors:2025:1:scope_1:fuels:gaseous_fuels:fuel=butane|unit=litres