More and more logistics and transport companies are getting a specific request from their clients: a carbon footprint report broken down by shipment, by route or by customer, built on a recognized methodology. Large retailers and manufacturers need this data to calculate their own scope 3 emissions, the part of their footprint generated across the value chain, which includes the transport they outsource. On top of that comes the pressure from CSRD, which requires a growing number of companies to report emissions in a verifiable way. The consequence lands directly on logistics providers: without auditable carbon data, keeping certain contracts gets harder.
This guide covers what a carbon audit in logistics actually involves, which standards apply, what data it requires, and where companies in the sector tend to get stuck.
What a carbon audit in logistics actually covers
A carbon audit in logistics is the process of measuring, verifying and reporting the greenhouse gas emissions generated by a company's transport and warehousing operations. It covers owned fleet and subcontracted fleet, and is normally calculated across three levels:
- Scope 1: fuel burned directly by owned vehicles.
- Scope 2: electricity consumed in warehouses, distribution centers or an electric fleet.
- Scope 3: transport subcontracted to third parties, whether a 3PL operator or a one-off carrier.
The result is not just a single company-wide carbon footprint figure: clients increasingly ask for the data broken down by route, by shipment or by end customer, so they can allocate those emissions within their own value chain.
Which standards apply: GLEC and ISO 14083
Two frameworks dominate emissions calculation in freight and logistics.
The GLEC framework (Global Logistics Emissions Council), developed by the Smart Freight Centre, is the sector's reference standard for calculating and reporting logistics emissions in a way that is comparable across operators. It defines how to calculate emissions by transport mode (road, sea, air, rail), by vehicle type and by cargo carried.
ISO 14083, published in 2023, formalizes much of the GLEC methodology internationally and sets a common method for quantifying and reporting greenhouse gas emissions in transport and logistics operations. It builds on the principles of the GHG Protocol and is the reference that retailers and manufacturers increasingly write into procurement requirements for their logistics providers.
A report that does not follow these frameworks tends to get rejected outright by the client's procurement or sustainability department, because it is not comparable with reports from other providers.
What data you actually need
Building a calculation aligned with GLEC and ISO 14083 means pulling data from several sources:
- Fuel or electricity consumption per vehicle.
- Routes and distances traveled, ideally with real origin and destination, not just an estimated distance.
- Vehicle type and fuel type: diesel, CNG, electric or hybrid.
- Cargo carried: weight, volume or units, depending on the applicable emission factor.
- Subcontracting data: which leg of the journey was run by owned fleet and which by an external operator.
In practice, this information sits scattered across the TMS, the ERP, fuel invoices, route sheets and, for subcontracted legs, whatever each carrier is willing to share.
Owned versus subcontracted fleet: the 3PL and 4PL challenge
Separating owned fleet from subcontracted fleet is one of the points where most companies get stuck. A single order can travel one leg with owned fleet and another with a 3PL or 4PL operator, each leg carrying a different emission factor depending on vehicle, fuel and distance.
The problem gets worse because not every subcontracted carrier hands over complete data. Some only provide mileage, others provide nothing at all, and few deliver it in a format comparable with the rest of the fleet. Without that separation, the audit cannot correctly allocate emissions by customer or by shipment, which is exactly what large retailers are asking for.
The real problem: scattered data and reports that fall short
Gathering the data tends to be the more common obstacle, more so than applying the methodology itself. Logistics teams often calculate footprint by route using spreadsheets, manually cross-referencing fuel invoices with route sheets and data from external carriers. It is slow, error-prone, and hard to maintain as shipment volume grows or when a different report has to go out to each client.
The result is reports that do not fully meet GLEC or ISO 14083, with data gaps the client catches on first review, or reports that arrive after the deadlines set by the client's procurement team.
How a carbon audit works, step by step
At a high level, the process has four phases:
- Data collection: fuel, routes, vehicle type, cargo and subcontracting data, for owned fleet and for third parties.
- Calculation: applying the relevant emission factors under GLEC and ISO 14083, by transport mode and vehicle type.
- Verification: checking that the data and the calculation are consistent and traceable back to the original source, whether an invoice, a route sheet or a carrier document.
- Reporting: producing the final report, broken down by route, shipment or customer as required.
How Manglai helps
Manglai automates logistics footprint measurement following the GLEC framework, connecting data from owned fleet, external operators and systems like TMS or ERP.
- Automatically generates standards-aligned footprint reports that can go straight to each client, broken down by shipment or by route.
- Lets you upload any Excel file from a logistics operator and automatically calculates the carbon footprint from it, without manually reformatting the carrier's data.
- Manglai's AI reads documentation such as invoices and route sheets automatically, cutting down the manual work of data collection.
- Simplifies scope 3 calculation and warehouse waste connected to the logistics operation, within the same platform.
- Recommends direct ERP integration with the client's systems when data volume justifies it, instead of relying on recurring manual uploads.
Start by knowing what the regulation requires
Before building out an audit process, it helps to know which environmental obligations already apply to your company. Manglai's environmental obligations diagnostic test clarifies that in a few minutes.
Manglai automates the collection and traceability of ESG data: carbon footprint, waste management and product footprint. Built for ESG managers and operations teams that need audit-ready data.
