Maritime incidents involving biofuel blends: what is the legal safety net?
In the shipping industry, the use of biofuel blends has become quite common. But how should these biofuel blends be classified under existing international liability regimes in the event of an incident involving such marine fuels? Do they fall under the Civil Liability Convention (CLC) and/or the Bunker Pollution Convention? These questions are central to a recent paper by the Comité Maritime International (CMI). Mark Broekhuisen and Jolien Kruit, co-authors of this paper, provide a brief explanation, including recent developments at the IMO.
What if things go wrong?
The energy transition in shipping is in full swing. The order book for ships fueled (in part) by alternative fuels is growing. But whilst technology and practice are developing rapidly, the international liability and compensation regime is lagging behind. The IMO, the International Maritime Organisation, or the international maritime law-maker, put the international liability and compensation regime for incidents involving alternative fuels on its agenda in April 2025. However, it is expected to take some time before there is clarity on what the international regime will look like.
This is particularly problematic for fuels that are already in widespread use, most notably biofuels and biofuel blends. Biofuels are increasingly being added to fossil fuels as a relatively accessible transition fuel to meet CO₂ reduction targets. In practice, blends containing up to approximately 30% biofuel (B30) are increasingly being used as bunker fuel. It is precisely these blends that raise legal questions in the event of an incident. For how should they be classified under existing international liability regimes? These questions are discussed in a recent paper by the Comité Maritime International (CMI), to which the authors of this blog have contributed.
Outside the CLC and Bunkers Convention?
The CMI paper analyses in detail how biofuels and biofuel blends relate to the core instruments of the international liability and compensation system for oil pollution, the Civil Liability Convention (CLC) and the Bunkers Convention. Both conventions apply to ‘hydrocarbon mineral oil’, with the CLC also requiring that the fuel be ‘persistent’.
For pure biofuels (B100), the conclusion is clear: they contain no mineral oil and therefore fall outside the literal scope of these conventions. For biofuel blends, however, the situation is more nuanced. On the one hand, these blends do indeed contain mineral oil; on the other hand, it remains unclear whether, and if so to what extent, they can still be classified as ‘hydrocarbon mineral oil’.
Other conventions do not provide a comprehensive solution either. The 2010 HNS Convention would cover biofuels and biofuel blends as cargo, but does not apply to bunkers and, moreover, has not yet entered into force. The convention is set to enter into force in November 2027, following its joint ratification on 14 April 2026 by Belgium, Germany, Sweden and the Netherlands.[1] The Nairobi Wreck Convention may offer a solution in certain situations, but is limited to wreck situations and does not provide a general liability regime for pollution damage.[2]
The CMI paper on the position of biofuel blends argues that there are good arguments for bringing biofuel blends within the scope of the CLC and the Bunkers Convention, partly in view of the purpose and scope of these conventions: to ensure effective compensation in the event of an incident. At the same time, it is recognised that this interpretation is not without legal controversy and that Member States and courts could reach divergent conclusions.
Call to the IMO Legal Committee
Against this background, CMI advocates for action at IMO level. The paper outlines various possible solutions, including:
- a Unified Interpretation of the term ‘hydrocarbon mineral oil’ in the CLC and Bunkers Convention, clarifying how biofuel blends relate to the CLC and Bunkers Convention;
- the development of a new convention or protocol for alternative fuels;
- interim guidance from the IMO Legal Committee to reduce legal uncertainty.
During the IMO Legal Committee meeting (LEG 113), which took place in London from 13 to 17 April 2026, it was decided that work will continue on the development or adaptation of a liability regime for alternative fuels and technologies used for the operation or propulsion of a ship in the broadest sense. As part of this work, the position of biofuel blends will be considered, and it will be examined whether a (temporary or otherwise) short-term solution can be agreed upon and what form it should take.
Sustainability requires legal certainty
The use of biofuels and biofuel blends can make a significant contribution to making shipping more sustainable. However, without a clear and uniform liability framework, that transition remains legally vulnerable. The CMI paper demonstrates that a short-term solution, whether or not pending the development of a future-proof international regime, is necessary.
