Engine reference
GHG Calculations & GWP Sets
How a record becomes a CO₂e figure: the factor request, the publisher chain, the per-gas masses, the GWP set, and the audit trail left behind.
- Applies to
- Emission, Energy and Water-adjacent categories (Waste uses WARM)
- GWP sets
- AR2, AR4, AR5, AR6 at 20, 100 and 500 years
- Default
- IPCC AR5, 100-year
- Stored as
- A calculated row per stream, split by scope
From record to CO₂e
- 1
Request
The record asks for a factor: kind of activity, fuel, place, date. Never a named publisher.
- 2
Resolve
Your enabled publishers are asked in your order. A documented boundary moves on; a data gap follows your policy.
- 3
Convert
Your quantity is put on the factor's basis exactly, or refused.
- 4
Combine
Per-gas masses take your GWP set. Publishers that issue pre-calculated CO₂e are used as published.
- 5
Store
Rows by scope, each linked to the factor row, release and GWP values used.
GWP sets
A global warming potential converts methane, N₂O and fluorinated gases into CO₂-equivalent terms. Which assessment report you use changes the result, so the set is configurable per organisation, not hardcoded. Resolution order: a pinned set, then the organisation's, then the default.
Methane has two values in AR6
AR6 separates fossil and non-fossil methane. Slate applies the right one by gas origin. See GWP sets and the values table.
Status and error handling
A record that fails to calculate is flagged with the reason, not dropped from a total. If an organisation mixes GWP vintages (a publisher's pre-calculated CO₂e beside your own set), the row gets an amber gwp_basis_mismatch warning, which can be switched off in Emission Factor settings. The fact is always recorded either way.
Provenance
Every calculated row links to the exact factor it used, including the publisher's original field values, region and resolution method, so the answer to "how was this reached?" is a click, not a re-derivation.