Scope 3 emissions are the indirect greenhouse gas emissions that occur across a company's value chain. For shipping companies, they typically represent the majority of the total carbon footprint, and they are the hardest part to measure. This guide explains what Scope 3 covers in maritime, why the pressure to report it is growing, and how shipowners and suppliers move from rough estimates to verified data.
The GHG Protocol divides Scope 3 into 15 categories of upstream and downstream emissions. For shipowners and operators, two categories dominate: Category 1, purchased goods and services, covering everything bought to run a fleet, from provisions and spare parts to lubricants, paint, and services; and Category 2, capital goods, covering the embodied carbon of the vessels themselves, from newbuilds to major retrofits.
For maritime suppliers and OEMs the perspective is reversed: their products become their customers' Scope 3 emissions, which is why shipowners increasingly ask suppliers for product carbon footprint (PCF) data.
Several developments converge. CSRD and ESRS E1 require in-scope shipping companies to disclose material Scope 3 categories. The EU ETS and FuelEU Maritime put a price and a limit on carbon, making lifecycle data financially relevant. Charterers, cargo owners, and financiers request emission data in tenders and green financing. And the IMO is moving toward lifecycle-based regulation of marine fuels. The common requirement behind all of these is credible, auditable Scope 3 data.
Most shipowners start with spend-based estimates: multiplying procurement spend by generic emission factors. It is a valid entry point, but spend-based factors carry an uncertainty of roughly 40 to 80 percent, are sensitive to inflation, and cannot show reduction progress. Activity-based data uses real quantities and product-specific emission factors instead. The practical path is to start spend-based, identify the suppliers and categories that drive most emissions, and replace estimates with supplier PCF data where it matters most.
The IMPA Maritime Environmental Footprint (IMEF) framework, developed under IMPA SAVE with guidance authored by ReFlow, establishes an activity-based methodology for calculating Scope 3 emissions in maritime procurement. It gives shipowners and suppliers a common standard for product carbon footprints, aligned with ISO 14040, ISO 14044, and ISO 14067. More than 85 companies participate in IMPA SAVE.
ReFlow covers both sides of the maritime value chain with one connected data layer:
Companies in scope of CSRD must report material Scope 3 categories under ESRS E1. Beyond regulation, financiers and charterers increasingly require the data commercially.
By requesting product carbon footprint data in a standardised format. The IMEF framework and ISO 14067 define the methodology; platforms like ClimateHub and ClimateBase make collection and verification practical.
A spend-based screening of one reporting year, followed by a hotspot analysis. Five to ten suppliers typically drive a large share of Category 1 emissions, and those are the ones to engage first.
Accuracy should match the decision the data supports. Spend-based estimates are acceptable for a first baseline; reduction tracking, tender responses, and audit-ready reporting require activity-based or supplier-specific data.