ICAO Carbon Emissions Calculator Methodology
Air Freighter

Version 2July 2024

Table of Contents
1.

Introduction .......................................................................................................................................... 3

2.

Predictive estimate on air freighter carbon emissions ......................................................................... 3
2.1 General Description of the Methodology ........................................................................................... 3
2.2 Calculation Procedure ......................................................................................................................... 4

3. Discussion of Sensitivities ......................................................................................................................... 62

1. Introduction
Cargo shipments can be shipped by air in the belly compartment of passenger aircraft or via a dedicatedcargo aircraft (air freighter). This document presents a methodology developed for estimating the amountof carbon emissions (CO2) generated by freighters only. This methodology is implemented in the freighter
functionality of the ICAO Cargo Carbon Emissions Calculator.

2. Predictive estimate on air freighter carbon emissions
This methodology provides information to the user in advance of the shipment (pre-flight). It requires aminimum amount of information from the user, since only the origin and destination cities are requiredalong with the weight of the package being shipped. Our predictive methodology for calculating carbon
emissions is designed to calculate potential emissions before specific route pairs are determined. While
we strive for accuracy, it's important to acknowledge that the actual emissions observed during real
operations may differ from these initial predictions.

2.1 General Description of the Methodology
Similar to the passenger methodology, it applies the ICAO Fuel Formulas to estimate the fuel consumptionof freighter aircraft based on the distance flown. Air freighter load factors data are then used to apportion
the emissions associated with the flight to the weight of the package carried. Due to a lack of informationon the exact routing flown, the package is assumed to travel from an airport near the origin city to thehub within the region to an airport in the destination city. If the item is being shipped between regions,then it is assumed to travel from the origin city to a hub in the origin region then to a hub in the destination
region, and then finally to the destination city, as illustrated in Figure 1.

Figure 1. Use of hubs for inter and intra-regional air cargo shipment.
The route with the lowest emissions is used when more than one airport serves dedicated cargo traffic
between either the origin or destination city. As for the passenger methodology, a weighted average of3the carbon emissions is computed based on the traffic (type of aircraft used and frequency of flights). The
methodology covers direct flights from air freighter route pairs included in the Common Operations
Database (COD)1.

2.2 Calculation Procedure
As illustrated in Figure 2, the methodology combines data from several sources in order to estimate fuelburn associated to the shipment of a package. The fuel burn (in kg) is then converted to CO2 emissions (inkg) by multiplying it by a factor of 3.16.

Figure 2. Overview of data sources used by the methodology.
City Pair: Obtained from the Common Operations Database (COD) based on ICAO airport codes.
GCD (Great Circle Distance): GCD is, by definition, the shortest distance between two points on the surfaceof a sphere. This distance is calculated by using the geographical coordinates of the two points concerned.
The coordinates for the airports are obtained from the ICAO Location Identifiers database (ICAO Doc 7910).
Once the GCD is calculated, it is then corrected by a factor depending on the distance between the twoairports concerned. (see also table 1 below).
Load Factors: The average generic factors considered for the purpose of this calculation are sourced fromthe Traffic by Flight Stage database (TFS) which collects air carrier city-pair specific traffic data by aircraft
type produced on an annual basis, and domestic traffic and operational data, both collected by ICAO, aswell as data based on the flight schedules published by the air carriers.
Fuel/Km: This information, per aircraft model, is obtained from the ICAO Fuel Formula database.

1

https://www.icao.int/environmental-protection/pages/modelling-and-databases.aspx

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Kg available: This is the number of kilograms carried as freight in the aircraft (i.e. the maximumpayload), available from the COD.
User input – Origin and destination airports and the number of kilograms carried as freight. The databaseis searched only for all direct flights.
Traffic data– An air freighter load factor is assigned to the user-defined city-pair, based on thecorresponding regions.
Aircraft mapping– From the COD, the scheduled aircraft is identified in the ICAO Fuel Formula database.
Fuel burn– The fuel burn is extrapolated from the ICAO Fuel formula. The factors considered include loadfactor, flight distance, the proportion of the overall payload represented by air freighter traffic, and typeof aircraft flown. The amount of fuel used is the weighted average of total fuel burnt based on thefrequencies of the scheduled aircraft types flown.
CO2 (kg) per kg carried– Using the trip distance, aircraft fuel consumption, load factor from the region,and the number of kilograms available, the methodology calculates the CO2 emissions (kg) associated toeach kilogram transported, as follows:
CO2 emissions (kg) per kg carried = 3.16 x (Total fuel burn / Kg available) x Load factor
Where: Total fuel burn(kg) = The weighted average of the fuel used by all flights departed fromthe origin airport to reach the destination airport. The weighting factor is the ratio of
number of departures for each equivalent aircraft type, to the total number of departures.
Kg available = the total number of kilograms available on all flights serving the given citypair.
Load factor = the ratio calculated from ICAO statistical database (TPS) based on numberof freight transported and the number of kilograms available in a given region.
3.16 = constant representing the number of tonnes of CO2 produced by burning a tonneof aviation fuel.
CO2 emissions (kg) per package– Depending on user selection (number of kg carried), the total CO2emissions (kg) is estimated by multiplying the weight of freight (kg) transported with CO2 emission (kg)
per kilogram.

Load Factor
The Load Factor used is an average calculated on a regional basis. The data are obtained from reported
data submitted by States to ICAO (see table 1).

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A/CARIBBEAN

ICALF

Year
55%
53%
74%
68%
57%
48%59%

Region2018 AFRICA
2018 ASIA/PACIFIC
2018 EUROPE
2018 LATINAMERICA/CARIBBEAN
2018 MIDDLE EAST2018 NORTH AMERICA
2018 Total

LF
57%
64%
68%
71%
47%
58%
60%

Table 1: Load factor

GCD Corrections
As in the passenger methodology, the Great Circle Distance (GCD) (in km) between the input airports isused, to estimate the fuel burned (in kg), and thus estimate the CO2 emissions. A correction factor isintroduced to take into account the distance flown in excess of the GCD due to stacking, traffic andweather-driven corrections. The table 2 below shows the GCD correction factor used.
GCDLess than 550 Km
Between 550 Km and 5500 Km
Above 5500 Km

Correction to GCD+ 50 Km+ 100 Km+ 125 Km

Table 2: GCD Correction Factor

3. Discussion of Sensitivities
In any modelling exercise the desire for accuracy is moderated by the level of complexity the analyst iswilling to accommodate. In the case of this ICAO methodology, an attempt has been made to account forthe principal factors which define an individual’s aviation carbon emission footprint while assessing eachat a level which recognizes the inherent uncertainty underlying many of the assumptions embedded inthis approach.
Assumption Regarding Air Shipment – This methodology assumes that the item has shipped by air fromthe origin city’s airport to the destination city’s airport. No estimate of the emissions associated with theportion of the item’s journey by any other mode of transportation is included in this calculation.
Great Circle Distance – while it is understood that air travel does not occur in a straight line between twopoints, actual flown distance to be collected from the air carriers, or from a more accurate trip distance
database showed to be not feasible for the time being.
Load factor – average load factors on freighter aircraft are calculated on a regional basis. The data isobtained from the reported data sent by States to ICAO,

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