Energy · Scope 1
Mobile combustion
Fuel burned by vehicles and machinery you own or control. EPA publishes the CO₂ against the fuel and the CH₄ and N₂O against the vehicle, so one record is costed in two halves.
On this page you'll learn
- Fuel-based versus distance-based entry
- How EPA's two bases are combined
- Why model year matters
- Scope
- 1
- Publishers
- US EPA (fuel and distance), UK DEFRA (fuel), IPCC Vol 2 Ch 3
- Inputs
- Fuel, vehicle type and model year, fuel quantity and/or distance
- Category code
mobile_combustion
EPA's two bases
EPA Hub Table 2 gives kg CO₂ per unit of fuel. Tables 3–5 give g CH₄ and g N₂O per vehicle-mile, in model-year bands. No single row has all three, so Slate resolves the two halves separately and records both factor references on the row.
- fuel
- gallons, litres or kg, converted to EPA's basis
- distance
- vehicle-miles
- EF_CH₄, EF_N₂O
- for this vehicle type and model year
Each half tries the units it can use in order: CO₂ from the fuel quantity first, then distance; CH₄ and N₂O from distance first, then fuel. Non-road equipment (aircraft, ships, locomotives, construction plant) is published per gallon for all three gases, so a fuel-only record is enough.
DEFRA: fuel-based
DEFRA publishes all four values on one row per unit of fuel, so both halves resolve to the same row. Road fuels use DEFRA's forecourt blend, which includes the biofuel content of pump fuel, as DEFRA's guidance says: 2.075 kg CO₂e per litre of petrol against 2.35372 for pure mineral petrol, 12% apart.
Distance-based with DEFRA
DEFRA's 200 vehicle-distance rows are imported but not yet offered. They classify vehicles by market segment and load ("Executive / Diesel", "Articulated >33t / Average laden"), while Slate's vehicle list follows EPA's fuel and duty classes. Matching one to the other would be a guess that changes numbers. The GHG Protocol ranks the fuel-based method higher anyway.
Model year matters
CH₄ and N₂O from road vehicles fall sharply with emissions-control technology, so EPA bands them by model year. Reading the published bands directly corrected two errors the earlier hand-typed table had:
| Vehicles | Was | Published | Error |
|---|---|---|---|
| Gasoline motorcycles 1976–1995, CH₄ / N₂O | 0.007 / 0.067 | 0.009 / 0.09 | −22% / −26% |
| Diesel medium/heavy-duty 1960–2006, CH₄ / N₂O | 0.0049 / 0.0056 | 0.0051 / 0.0048 | both directions |
A model year outside every published band isn't hidden from the vehicle picker; it's answered at calculation time against the release in force for the transaction date.
Refused on purpose
CNG in litres
Litres of a compressed gas are ambiguous and silently about 1,000 times under. Enter kg or scf.
2-stroke vs 4-stroke equipment with an unspecified engine
EPA splits them and they differ 3.6 times on CH₄.
On-road vehicles without distance
Their CH₄ and N₂O are only published per mile. The check reads the resolved factor's own unit, not a list of vehicle types.