How Passport carbon figures are calculated

The calculation

Distance comes from the actual AIS satellite track for the voyage, not a port-pair estimate. Mass comes from the Bill of Lading where available. The efficiency multiplier (0.7–1.5) is derived from the vessel's age, size class and propulsion from the IMO registry.

Method hierarchy (GHG Protocol Scope 3, Cat. 4 & 9)

The Protocol permits three calculation methods for transportation and distribution and ranks them by data quality. Sellexio always applies the highest-quality method the evidence supports, prints the rationale on the slip, and names what evidence would unlock a better one.

1. 1. Fuel-based method

   PCAF 1–2
   Emissions = Σ (fuel consumption × emission factor × allocation share)

   Used when Bunker Delivery Notes or a carrier fuel report evidence the actual burn. The whole-ship figure is allocated to the cargo on a tonne-kilometre share.

2. 2. Distance-based method (GLEC)

   PCAF 2–4
   Emissions = Σ (distance × weight × mode factor) × vessel efficiency multiplier

   The Passport default. Used when the sailed AIS distance and Bill of Lading mass are known but no metered fuel figure exists.

3. 3. Spend-based method

   PCAF 5
   Emissions = Σ (spend × emission factor per spend)

   Last resort where neither fuel nor movement data exists. Reported as an economic proxy and never used for a CBAM embedded-emissions declaration.

Factor sets and vintages

Against the five GHG Protocol principles

Relevance

Figures cover Scope 3 Category 4/9 upstream transport for the specific container on the slip — not a company-wide average allocated down.

Completeness

All legs of the movement carried in the booking are calculated. Legs outside the Passport (e.g. shipper-arranged first mile) are named as excluded rather than silently dropped.

Consistency

One pinned methodology version per slip. Factor changes ship as a new version with a dated changelog entry; historic slips keep the version they were issued under.

Transparency

Each slip prints the inputs, the factor used, the multiplier basis and the source of every value, so the total can be recomputed by hand.

Accuracy

Measured AIS distance and Bill of Lading mass are preferred over defaults; where a default is used it is disclosed and graded under PCAF so the uncertainty is visible.

What is excluded

• · Downstream distribution after customs release, unless purchased as an added leg.
• · Packaging, warehousing and terminal handling energy — reported separately, not inside the tonne-km figure.
• · Offsets and certificates: Passport reports gross emissions only; retired credits are never netted off.

Changelog

1. v1.3.02026-08-15

   GHG Protocol method hierarchy for Category 4/9 transport

   All three permitted calculation methods are now implemented — fuel-based (fuel consumed × fuel factor, with cargo allocation), distance-based (GLEC tonne-kilometre) and spend-based (spend × factor per spend). The engine selects the highest-quality method the evidence supports, discloses the rationale, and names the evidence needed to unlock a better one. Spend-derived figures are graded PCAF 5 and flagged as unfit for CBAM filing.

2. v1.2.02026-08-01

   Published a versioned methodology register

   Each slip now carries a methodology version stamp, the cited factor sets with their vintage, and a statement against the five GHG Protocol principles so an auditor can reproduce any figure from the issued document alone.

3. v1.1.02026-07-18

   PCAF data quality scoring added to every calculation

   Every input is graded 1–5 (AIS-measured track = 1, Bill of Lading mass = 2, default assumption = 5). Slips report a weighted score, the share of inputs at PCAF 1–3, and plain-English steps to improve the grade.

4. v1.0.02026-07-02

   GLEC tonne-kilometre engine

   Voyage carbon calculated as mass (tonnes) × distance (km) × GLEC default factor (g CO₂e/tonne-km) × vessel efficiency multiplier (0.7–1.5), using AIS track distance rather than port-pair estimates.