Using Offsets Under CORSIA: CORSIA Eligible Emissions Units (EEUs)

Under CORSIA, aeroplane operators meet their offsetting obligations by purchasing and cancelling CORSIA Eligible Emissions Units (EEUs). These units represent verified greenhouse gas (GHG) emission reductions or removals generated by approved project activities.

Unlike Sustainable Aviation Fuel (SAF), which directly lowers an operator’s reported life-cycle emissions, EEUs are used to neutralize residual emissions that exceed the sectoral baseline.

Compliance Cycle	Notification of Final Offsetting Requirements	Cancellation of Emission Units	Submission of Verified Emissions Unit Cancellation Report
2021–2023	By 30 November 2024	By 31 January 2025	By April 2025
2024–2026	By 30 November 2027	By 31 January 2028	By April 2028
2027–2029	By 30 November 2030	By 31 January 2031	By April 2031
2030–2032	By 30 November 2033	By 31 January 2034	By April 2034
2033–2035	By 30 November 2036	By 31 January 2037	By April 2037

The CORSIA Offset Equation: How Obligations Are Calculated

The offset equation determines the total quantity of CORSIA Eligible Emissions Units (EEUs) an aeroplane operator must purchase and cancel to meet its annual compliance obligation. Each EEU represents one tonne of CO₂ reduced, avoided, or removed by a certified emissions-reduction project.

1. The Core Formula

The total final offsetting requirements ($FOR_c$) for a given compliance period (e.g., 2021–2023) are calculated by summing the requirements for each year in the period and subtracting any emissions reductions claimed from the use of CORSIA Eligible Fuels (CEF).

$$FOR_c = (OR_{1,c} + OR_{2,c} + OR_{3,c}) - (ER_{1,c} + ER_{2,c} + ER_{3,c})$$

• $OR_{y,c}$: The operator’s offsetting requirement for a specific year ($y$).
• $ER_{y,c}$: Emissions reductions from the use of CORSIA Eligible Fuels in that year.

The number of EEUs required for a given year is calculated as:

EEUs to Cancel = [(Weightₛ × Sectoral Component) + (Weightᵢ × Individual Component)] − ER

Where:

• Weightₛ = Weight applied to the sectoral growth component
• Weightᵢ = Weight applied to the individual growth component
• ER = Emissions reductions from CORSIA Eligible Fuels (CEF)

Component Definitions

Each term in the offset equation reflects a different driver of emissions growth.

Sectoral Component

This component reflects industry-wide growth in international aviation emissions. It is calculated as:

Sectoral Component = Operator’s Total Covered Emissions × Sector’s Growth Factor (SGF)

• The Sector’s Growth Factor (SGF) is published annually by ICAO
• It represents the proportional growth in total sector emissions relative to the baseline
• All participating operators are affected equally by this component, regardless of their individual performance

Individual Component

This component reflects operator-specific growth beyond the baseline level. It is calculated as:

Individual Component = Operator’s Emissions (Compliance Year) − Baseline Emissions

Where:

• Baseline Emissions = 85% of the operator’s 2019 emissions
• This term ensures that faster-growing airlines bear a greater share of the offsetting burden in later phases

Weighting by Compliance Year (Weightₛ and Weightᵢ)

The balance between sectoral and individual responsibility evolves over the life of the scheme.

Period	Sectoral Weight (Weightₛ)	Individual Weight (Weightᵢ)
2021–2032	100%	0%
2033–2035	85%	15%

Interpretation:

• From 2021 to 2032, all offsetting obligations are based solely on sectoral growth, regardless of an operator’s own expansion rate
• From 2033 onward, a growing share of the burden shifts to operator-specific growth, strengthening the incentive for airlines to decarbonize faster than the sector average

Simplified Equation for the Current Compliance Phase

For all compliance years through 2032, the general formula simplifies to:

EEUs to Cancel = (Operator’s Emissions × SGF) − ER

Because:

• Weightₛ = 100%
• Weightᵢ = 0%

This means:

• The operator’s obligation is driven entirely by sector-wide growth
• Minus any verified emissions reductions achieved through CORSIA Eligible Fuels

Meeting the Requirement

Once the total obligation is calculated:

1. The operator must purchase the required number of EEUs
2. The units must be cancelled in an ICAO-approved, programme-designated registry
3. The operator must submit an Emissions Unit Cancellation Report (EUCR) to its administering authority

This closes the compliance loop by formally removing the EEUs from circulation and proving that the offsetting requirement has been satisfied.

Where and How Operators Procure EEUs

While aeroplane operators can source EEUs through standard voluntary carbon market channels, CORSIA procurement has additional structure and geopolitical constraints. In practice, sourcing occurs through a mix of general market channels, specialized procurement events, and host-country–authorized supply.

General Market Channels

Operators typically acquire EEUs through the following channels:

• Project Developers: Purchasing directly from the organization that develops and manages the carbon offset project.

• Brokers: Utilizing market traders who source units that meet specific quantitative, eligibility, and risk criteria.