How to measure and reduce your freight CO2 emissions (scope 3, CSRD)

Decarbonizing transport is no longer a communication topic: it has become a B2B purchasing criterion and, with CSRD, a reporting obligation. Freight represents a significant share of companies’ scope 3 - and it is one of the hardest items to measure. The good news: it is also a field for action and differentiation still little exploited by freight forwarders. Here is how freight emissions are calculated, which modes emit most, and how to cut and report them.

What “freight CO2” actually means

Most credible accounting measures CO2e (carbon-dioxide equivalent, covering all greenhouse gases) on a well-to-wheel basis - including both the fuel burned and the upstream energy to produce it. For a company’s carbon accounting, freight sits in scope 3, category 4 (upstream transportation and distribution) under the GHG Protocol, which is why it increasingly shows up in CSRD and customer sustainability reports.

The reference standards to write into any RFP:

• GLEC Framework - the Smart Freight Centre’s method for logistics emissions, aligned with the GHG Protocol.
• ISO 14083 (2023) - the international standard for quantifying GHG emissions of transport chains; it supersedes the older EN 16258.

How emissions are calculated

The core formula is the same for every mode:

Emissions (kg CO2e) = transport activity (tonne-km) x emission factor (g CO2e per tonne-km) / 1000

• Transport activity = shipment weight (tonnes) x distance travelled (km), per leg.
• Emission factor = the carbon intensity of the mode, ideally using primary data (actual carrier, vessel, fuel, load factor) and falling back to default GLEC factors when you do not have it.
• Load factor matters - a half-empty truck roughly doubles the per-tonne emissions, so utilization is part of the calculation, not an afterthought.

Primary data beats defaults every time: a modelled estimate is fine for a baseline, but auditable reduction claims need real shipment-level data.

Which mode emits most (approximate ranges)

Carbon intensity varies enormously by mode. Approximate well-to-wheel ranges, per tonne-kilometer:

• Air freight - very high (hundreds to more than 1,000 g CO2e/tonne-km); short-haul and belly-hold vary widely.
• Road - moderate (roughly 60 to 150 g CO2e/tonne-km depending on truck and load).
• Rail - low (roughly 15 to 40 g CO2e/tonne-km).
• Ocean - lowest per tonne-km (roughly 10 to 40 g CO2e/tonne-km for container ships).

The practical takeaway: the mode split, not marginal efficiency tweaks, decides your footprint. One air shipment can outweigh months of ocean freight.

How to reduce freight emissions: the lever order

Tackle the highest-impact, lowest-regret levers first:

1. Shift modes where service allows. Air to ocean (or air to rail/road for regional), and road to rail on long land legs. This is almost always the single biggest cut.
2. Raise the load factor. Consolidate shipments, fill containers and trucks, and reduce empty running - fewer, fuller moves beat many partial ones.
3. Optimize routing and frequency. Direct services, fewer transshipments, and demand-planned frequency cut distance and handling.
4. Choose lower-carbon fuels and carriers. Sustainable aviation fuel (SAF), marine biofuels/HVO, and carriers with newer, more efficient fleets - often via book-and-claim or insetting within your own supply chain.
5. Then report, and offset only the residual. Insetting (reducing within your logistics chain) is generally preferred over buying external offsets for emissions you could have avoided.

A 3-question framework before you start

1. Do you have primary shipment data, or are you estimating? Mode, weight, distance and load factor per shipment let you measure to ISO 14083; without it you can only model a rough baseline.
2. Which lanes and modes dominate your footprint? Usually a small number of air shipments; find them first - that is where reduction pays off.
3. Is your goal to reduce, to report, or to offset? Reduction (mode shift, load) changes operations; reporting (CSRD, customer asks) needs auditable data; offsetting or insetting handles only what is left. Do them in that order.

CSRD: anticipate rather than scramble

The CSRD directive requires reporting environmental impacts, including transport emissions. Compliance rests on reliable, consistent and auditable data over time. Concretely: centralize your shipments’ emissions, rely on a recognized methodology, and choose partners able to provide this data. Companies that get ahead of it avoid the year-end scramble - and those that wait until the last minute often discover that their providers cannot give it to them. This is where reliable, exportable freight reporting makes the difference.

The freight forwarder, a link in compliance

Still few freight forwarders provide usable CO2 reporting. Yet it is becoming a selection criterion in its own right in Europe. When you evaluate a partner, ask: do you calculate emissions per shipment? With which methodology? In what usable format? A forwarder like OVRSEA, which integrates carbon data into the platform, turns a regulatory constraint into an asset: emissions are calculated per shipment and aggregated into an annual total in tCO2e, ready for CSRD obligations, and an environmental score from A to E is shown on each quote to make the impact visible at the moment of decision, not only at year-end. Exportable, reliable figures plus concrete levers to actually reduce the footprint - measured to GLEC and ISO 14083, so your numbers hold up in an audit.