The calculation engine
Upstream, grid losses and biogenic CO₂
A full picture of a fuel or a kilowatt-hour is up to four lines: the direct emission, the upstream emissions of producing it, grid losses, and any biogenic CO₂. Slate writes each as its own row, in its own scope.
On this page you'll learn
- Which extra rows a record can produce
- Which organisation settings switch them on
- Why each is a separate row, not a column
- Well-to-tank
- Off by default (
include_wtt) - Grid losses (T&D)
- On by default (
include_td) - Biogenic CO₂
- On by default (
include_outside_scopes)
The sibling rows
| Component | Scope | Comes from | Applies to |
|---|---|---|---|
| Direct | 1 or 2 | The direct factor | Everything |
| Well-to-tank (WTT) | 3 | The publisher's upstream factor for the same activity | Fuels, electricity, travel, freight |
| Transmission & distribution (T&D) | 3 | A separate grid-losses activity | Grid electricity |
| WTT of T&D | 3 | Upstream of the electricity lost in the wires | Grid electricity |
| Outside of scopes | — | The biogenic CO₂ factor | Fuels with biological content |
Each sibling row points at its direct row as its parent and carries its own scope. Aggregating by scope can therefore never add a Scope 3 upstream figure into Scope 1.
Why the defaults are what they are
Grid losses on
Losses are part of a correct UK SECR electricity figure.
Biogenic CO₂ on
Leaving it out understates bioethanol about 169 times on a full-picture basis.
Well-to-tank off
It's Scope 3 and many organisations report it separately. WTT of grid losses follows the WTT switch, not the losses switch: turning on upstream without it would count the fuel burned for the electricity you received but not for the part lost on the way.
Changing any of these changes every reported total, so a test pins the default policy: generation plus grid losses.
What's guarded
A direct factor returned for an upstream request
Not an error but a plausible number counting combustion twice in two scopes. Publishers that have no upstream factors (EPA, ECCC, Ember) refuse upstream requests outright.
Recalculating the direct row
Doesn't delete the siblings: supersession is per methodology.
Turning a component off
Retires its existing rows on the next recalculation (kept for the audit trail, no longer current), so a disabled component can't linger in totals.
Biogenic CO₂ only exists for fuels with biological content, so a missing biogenic factor for a fossil fuel isn't reported as an error. A missing upstream factor, which should exist for almost everything, is.