Ipieca insights from the IMO expert workshop on chain of custody models fuel supply chain traceability

The workshop forms part of the IMO's ongoing work on developing sustainable fuel certification arrangements and fuel life cycle emissions accounting under the IMO Net-Zero Framework.

Understanding chain of custody

CoC models are the accounting frameworks that provide a verifiable link between products and their sustainability metrics as they move through a supply chain. They enable the transfer of sustainability attributes and emissions information while providing traceability, transparency and assurance that claims can be verified.

CoC models are already used across a range of sectors, including renewable electricity, biofuels, sustainable aviation fuels (SAF), chemicals and forest products. The workshop explored how lessons from these established systems could help inform the development of certification and traceability approaches for marine fuels.

Topics discussed during the workshop

Presentations drew on experience from existing certification schemes, standards and regulatory frameworks, including the EU Renewable Energy Directive (RED), International Civil Aviation Organization's Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) framework, ISO standards and sustainability certification systems operating across fuel supply chains.

Discussions explored the different CoC approaches available, including physical segregation, mass balance, and book and claim models, as well as practical issues such as auditing, verification, governance, registry design and preventing double counting.

Chain of custody models explained
CoC models are used to track sustainable or certified materials through a supply chain, with the three primary models being: physical segregation; mass balance; book and claim.

Physical segregation
The certified material is kept physically separate from non-certified material throughout the supply chain.

Mass balance
Certified and non-certified materials can be mixed during processing and transport, but the certified volume is tracked and accounted for.

Book and claim
The physical product and the sustainability claim are separated. A company may buy a certificate showing that sustainable material was produced somewhere, even though the physical material it receives is not that specific sustainable material.

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Key themes emerging from the workshop

Building on existing experience

Across sectors, there is considerable practical experience with chain of custody systems, particularly mass balance approaches. Many speakers highlighted the benefits of drawing on lessons from established certification schemes and regulatory frameworks rather than developing entirely new approaches for maritime fuels.

Integrity depends on robust governance

Participants repeatedly highlighted that environmental integrity depends not only on the chain of custody model selected, but also on the governance arrangements surrounding it. Auditing, verification, certification schemes, registries and safeguards against double counting were identified as important elements of any credible system.

Balancing integrity and practicality

Presentations noted that different chain of custody models offer varying balances between traceability, operational feasibility, scalability and cost. Several speakers stressed the importance of selecting approaches that reflect the realities of global fuel supply chains while supporting the scale-up of low-emissions fuels.

The importance of alignment

The discussions highlighted the need to consider how future IMO arrangements interact with existing certification schemes, regulatory systems and traceability platforms. Alignment across frameworks may help reduce administrative burden while supporting confidence in sustainability and emissions claims.

Ipieca's contribution

Ipieca participated in the workshop by sharing practical experience from fuel supply chains that already operate under chain of custody and traceability requirements.

Drawing on experience with mass balance systems under the EU RED, as well as examples from the CORSIA framework, Ipieca highlighted some key considerations, including:

• Marine fuel production is highly interconnected with other transport fuel and industrial value chains
• Decisions on marine fuel traceability needs to consider approaches already established across related sectors
• Fuel suppliers may need to demonstrate compliance with multiple regulatory frameworks and certification systems simultaneously

As the IMO continues developing sustainable fuel certification arrangements, the workshop highlighted the importance of building on existing experience while ensuring traceability systems remain credible, practical and adaptable to the diverse fuel pathways and supply chains expected to support maritime decarbonisation.

With upcoming IMO meetings taking place in September and November 2026, Ipieca will continue to support the IMO’s work to decarbonise the maritime industry, providing technical expertise and industry guidance.

How Ipieca supports the IMO Net Zero Framework.