TL;DR: Under the GHG Protocol, Category 4 covers emissions from transportation and distribution services a company purchases (upstream), and Category 9 covers transportation of its sold products that it does not pay for (downstream). For most cargo owners and charterers, ocean freight sits in Category 4, and it is usually the largest and least visible line in the Scope 3 inventory, because the ships doing the work are chartered or third-party. The reporting question is never whether the emissions exist; it is whether they are calculated per voyage from real vessel data or estimated from industry averages.
Scope 1, 2, 3, and where shipping lands
Scope 1 is what a company emits directly; Scope 2 is purchased energy; Scope 3 is everyone else in the value chain, split into fifteen categories. For companies that move physical goods, the transportation categories are where maritime emissions live, and for most of them the numbers dwarf Scopes 1 and 2 combined.
Category 4 vs Category 9: the direction of payment decides
The two categories are mirror images, and the boundary between them is who pays for the transport, not the direction the goods travel:
The same tonne-mile is never in both categories for the same company, but it can appear in one company's Category 4 and another's Category 9, which is correct: Scope 3 is deliberately double-counted across value chains so that every actor sees their exposure.
How sea freight emissions are calculated
Three methods, in descending order of credibility. Vessel-specific: fuel actually consumed on the voyage, converted with published emission factors and allocated to the cargo, the approach regulators and auditors increasingly expect, and the one the EEOI allocation method supports for shared voyages. Modelled: emissions predicted from the specific vessel, route and load where measured fuel data is not available, credible when the model is vessel-specific. Average-based: industry emission factors per tonne-mile, acceptable as a starting point and increasingly challenged in assurance because it cannot show improvement or reflect vessel choice.
The direction of travel in disclosure rules, CSRD assurance in Europe chief among them, rewards the first two and penalises staying on the third: averages cannot evidence reductions, and assurance providers ask where the number came from. The wider regime landscape is covered in maritime emissions reporting explained, and the fuel lifecycle boundary question in well-to-wake vs tank-to-wake.
The charterer's problem: reporting ships you do not own
The defining Scope 3 difficulty in shipping is that the reporting company rarely operates the vessels. The data lives with owners and managers, arrives in different formats, and covers voyages where the charterer's cargo shared the ship. Solving it takes three things: access to voyage-level data for chartered tonnage, validation so the figures survive assurance, and a defensible allocation method for shared voyages. That is precisely the gap ZeroNorth Scope 3 Reporting closes, calculating per-voyage emissions for any vessel, chartered or owned, from validated data and emissions intelligence rather than averages.
The bottom line
Category 4 and 9 are where a cargo owner's maritime footprint lives, and the number is usually the biggest in the inventory. The categories themselves are simple; the work is the data: per-voyage, vessel-specific, validated and allocated fairly. Get that layer right and the same dataset serves GHG Protocol, CSRD and the Sea Cargo Charter at once. Book a demo to see chartered-fleet Scope 3 calculated from real voyage data.
