The True Environmental Impact of Air Freight
Air transport represents the freight mode that generates the highest emissions per unit of cargo moved. According to the GLEC Framework v3.1, emissions associated with air transport range between 500 and 700 grams of CO₂ equivalent per tonne-kilometre, a value significantly higher than all other modes. This figure can be explained by a combination of factors: the high energy intensity required for flight, the exclusive use of fossil fuels such as Jet A-1, and the low specific weight of the goods transported, typically high-value, perishable cargo carried in smaller load units.
Less than 1% of global tonne-kilometres (Eurostat) is transported by air; yet, despite this marginal share in volume, the environmental impact of aviation remains significant precisely due to the high emission intensity per transported unit. This creates an apparent paradox: a transport mode rarely used in terms of tonne-kilometres contributes substantially to the logistics sector’s total emissions.
It is also helpful to distinguish between domestic and international flights: the share of freight transported on domestic flights is marginal, meaning it can be reasonably assumed that almost the entirety of that 1% consists of international traffic.
From an emissions standpoint, this distinction between domestic and international flights would further complicate the allocation of impacts. Added to this is a key methodological factor: around 80% of freight travels on scheduled passenger flights, often representing a marginal utilization of available payload capacity without significantly affecting the aircraft’s total load, which would be operated for passenger transport regardless. The weight of the transported cargo is generally negligible compared to the total weight of the aircraft including passengers and baggage, making it difficult to precisely quantify the actual impact of air freight alone within the broader aviation context.
Globally, air cargo generates approximately 5% of logistics emissions, which in turn account for about 8% of global greenhouse gas (GHG) emissions (GLEC Framework v3.1; Smart Freight Centre).
To address this challenge, several strategies have been introduced at an international level. Among these, the inclusion of aviation in the EU Emissions Trading System (EU ETS) represents a key regulatory lever, aimed at incentivizing the adoption of lower-impact climate practices through economic signals. In parallel, the adoption of Sustainable Aviation Fuels (SAF) is considered one of the primary pathways toward decarbonizing the sector. However, the widespread deployment of SAF is still hindered by high production costs (up to three times higher than Jet A-1), limited volumes, and scarce availability at major airport hubs.
Another innovative tool is the Book & Claim mechanism, described in specific Smart Freight Centre documents dedicated to aviation. This system enables the certification of sustainable fuel use even if SAF is not physically used on the specific flight to which the credit is allocated, thereby overcoming some of the current logistical barriers related to distribution. Although aligned with the GLEC Framework approach, Book & Claim is addressed in separate technical publications dedicated to market-based measures.
An often underestimated aspect is the role of so-called belly freight, which refers to the transport of cargo in the hold of passenger aircraft. This practice represents a logistically efficient option, as it allows space not occupied by baggage and other passenger cargo to be utilized for freight transport without requiring dedicated cargo flights.
From an environmental standpoint, belly freight is generally less emission-intensive than transport on dedicated cargo flights, precisely because it makes use of flights already scheduled for passengers. The emissions attributed to this type of cargo are therefore “shared” rather than “additional”, allowing freight transport to benefit marginally in terms of climate impact.
However, current reporting methods for emissions per tonne-kilometer may not adequately reflect this reality. It is therefore desirable that future methodological standards distinguish between shared and additional emissions, recognizing the value of belly freight as a more emission-efficient solution compared to the use of dedicated cargo flights.
In conclusion, air freight, while accounting for a marginal share of total volumes, has a significant environmental impact that requires focused attention and targeted action. Tools such as the EU ETS, the adoption of SAF, and the Book & Claim mechanism offer promising solutions, but their effectiveness will depend on widespread adoption and updated reporting methodologies. Greater recognition of belly freight and a clearer distinction between additional and shared emissions will be essential for a more realistic assessment and for incentivizing logistics practices with a lower climate impact.