02 Jul 2025
CORSIA takes off: what are Eligible Emissions Units?
James Bairstow
Carbon Originator, CSC Commodities - a division of Marex
The Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) has emerged as a key force for managing emissions from the aviation sector.
While navigating CORSIA presents a significant new challenge for many airlines, it also offers a strategic opportunity for early adopters to effectively manage risks, achieve compliance and advance on their decarbonisation goals.
This article explains how the CORSIA program works, what makes a carbon credit eligible, and how obligated airlines can secure access to ICAO-approved supply of carbon credits.
What is CORSIA?
CORSIA is the first global market-based measure to address emissions from international aviation. Established by the International Civil Aviation Organization (ICAO), it aims to address carbon emissions from international aviation.
Launched in 2021 and now firmly in Phase 1 (2024–2026), CORSIA requires participating airlines to offset CO₂ emissions that exceed baseline levels. This baseline is set at 85% of the industry’s emissions in 2019.
In this first phase, 130 countries will participate on a voluntary basis. Despite its voluntary nature, airlines operating under participating jurisdictions must offset their emissions in line with CORSIA guidelines.
These airlines must source eligible carbon credits to offset the emissions that surpass CORSIA’s baseline and that cannot be reduced through technological and operational improvements, or through CORSIA-eligible fuels.
How will CORSIA work?
CORSIA is implemented in phases. The pilot phase ran from 2021 to 2023, with the first phase now underway – from 2024 to 2026.
To comply with CORSIA in Phase 1, airlines must:
- Measure and report emissions.
- Purchase eligible carbon credits to offset emissions above baseline levels.
- Retire those credits through approved registries, documenting compliance.
In Phase 1, CORSIA only considers emissions from international flights between participating countries. However, this is likely to evolve as the rules and processes for CORSIA evolve over time.
What makes a carbon credit CORSIA-eligible?
Carbon Credits that can be used as part of the CORSIA program are called Eligible Emission Units (EEUs, for short).
Unlike carbon credits used in the voluntary market, carbon credits must comply with ICAO-defined quality and procedural standards. These standards include:
- Program Eligibility: Carbon credits must come from an ICAO-approved program.
- Project Age: Carbon credits must come from emission reduction projects that commenced in 2016 or later.
- Activity Compliance: Carbon credits must come from an emission reduction activity that ICAO has permitted. Common exclusions include the majority of carbon credits from renewable energy and non-government avoided deforestation activities.
- Vintage Compliance: Carbon Credits must originate from emission reduction activities that occurred in eligible years (referred to as vintages).
- Corresponding Adjustments: Carbon credits must be authorised for transfer outside the host country, preventing double counting.
Key ICAO-approved registries include Verra’s Verified Carbon Standard and Gold Standard, but there are others. Each approved registry established processes that aim to support integrity and traceability of the carbon credits.
Registries are supporting CORSIA by tagging carbon credits that are eligible for CORSIA Phase 1. This allows buyers to identify if the carbon credits are approved as Eligible Emissions Units.
What can airlines expect in Phase 1?
From 2024 onward, airlines operating international routes between CORSIA-participating countries will begin to accrue obligations under CORSIA.
The official deadline for retiring Phase 1 EEUs is January 2028. This delay allows for emission reduction projects to verify and issue carbon credits from the relevant period.
A lot can happen in the four-year window between the start of Phase 1 in 2024 and the retirement deadline in January 2028. For example we envisage that:
- Early movers in the aviation industry will begin to retire EEUs in 2025, in limited volumes.
- Supply will likely remain tight in 2025, as authorisations will require significant underlying work from respective government authorities.
- There will be considerable movement from planning to active procurement of EEUs on a forward basis in 2025. This pace might continue to increase, with current forecasts expecting a shortage of available EEUs which is expected to push prices higher.
- 2025 and 2026 will see many more airlines move to secure EEUs. Current forecasts project a significant shortage of EEUs as the latter half of Phase 1 approaches.
- 2026 will see many governments decide on penalties for failures to comply with CORSIA. The EU has communicated its expectation that CORSIA must be effective, and the UK has already consulted on penalties of £100 per tonne of carbon dioxide equivalent.
Looking ahead, Phase 2 (2027–2035) is expected to bring enhanced scope and enforcement.
How to buy CORSIA carbon credits
Understanding the procurement landscape for CORSIA credits isn’t just about compliance; it’s about managing significant financial exposure and ensuring long-term operational stability.
Given this, airlines that prioritise multi-year procurement strategies, rather than just focusing on current-year compliance, will be best positioned to effectively reduce exposure to future price increases and supply constraints.
When considering how to acquire these credits, airlines can buy EEUs in many ways. Some will buy in ‘spot’ transactions for EEUs that have already been issued, while others will enter multi-year agreements for the delivery of EEUs on a ‘forward’ basis.
Navigating these various procurement options requires expert insight to ensure optimal outcomes for your airline’s long-term CORSIA obligations.
CSC, your strategic partner for compliance
In a high-stakes compliance market, execution certainty, and partnering with a supplier that can help you unlock opportunities in this space, will be critical.
At CSC Commodities, we are actively supporting the aviation sector through this evolving compliance market, helping airlines turn a compliance challenge into proactive risk management strategies. Beyond CORSIA, we are a trusted partner to the airline industry across emissions management and fuel hedging.
We can support you with:
- Direct access to CORSIA Eligible Emissions Units via ICAO-approved registries;
- Flexible procurement structures to suit your hedging, budget and timing needs;
- Access to emission reduction projects in which Marex has invested;
- Deep expertise in voluntary and compliance markets for carbon credits; and,
- As a division of Marex, we have the ability to leverage its strong balance sheet and investment-grade credit rating.
As CORSIA enters full implementation, the window for secure, scalable procurement is narrowing. Airlines that act early maximise their opportunities to reduce risk, gain price certainty, and achieve compliance.
