Mandatory route towards zero emissions: the new IMO framework for maritime decarbonisation

The International Maritime Organisation has taken a decisive step towards the introduction of a global, binding regulatory system for the reduction of greenhouse gas emissions generated by maritime transport.

During the meeting of the Marine Environment Protection Committee (MEPC 83) in April 2025, a package of measures was approved that will converge into a new chapter of Annex VI of the MARPOL Convention. The text, which will be formally adopted in October 2025 and is expected to enter into force in 2027, targets vessels over 5.000 gross tonnage. These vessels are responsible for about 85% of the CO₂ emissions in international maritime transport.

The new framework, called Net-Zero Framework, introduces two main elements: a global standard for marine fuels and an economic measure for pricing emissions. Vessels will be required to reduce their greenhouse gas intensity per unit of energy used over time, calculated using a “well-to-wake” approach. In case the emission thresholds are exceeded, operators will have to purchase corrective units.

Vessels emitting less than the threshold will be entitled to generate surplus units, which can be retained, transferred or sold. Corrective units will also be obtainable through contributions to the IMO's new Net-Zero Fund, which will be financed through the emissions trading scheme. The Fund will support the spread of clean technologies, innovation, infrastructure development in developing Countries, training and technology transfer, and will also help mitigating the negative effects of the transition process on small Island States and Least Developed Countries.

The Net-Zero Framework complements but does not replace the European regulations already in force, such as the inclusion of maritime transport in the ETS system and the FuelEU regulation. The differences between the two regimes concern in particular enforcement methods, data collection, penalties and incentives. Operators will therefore have to adapt to overlapping and distinct obligations at the same time.

The entry into force of the new system makes it necessary to review chartering and ship management contracts. Responsibilities between shipowners, charterers and operators regarding regulatory compliance, management of emission units and cost allocation need to be redefined.

The draft regulation is the first global initiative to combine quantitative obligations and economic instruments on an industrial scale to reduce climate-changing emissions. Its approval was warmly welcomed by the Secretary-General of the IMO, who emphasised the importance of the consensus reached among member States.

However, the journey is not over: guidelines for the implementation of the framework will be adopted in 2026, while full operation is expected by 2027, in accordance with MARPOL provisions.

In addition to the climate package, MEPC 83 also approved new measures on plastics at sea, ballast water management, protection of new sensitive marine areas, development of rules for the use of on-board carbon capture and storage systems, and updates on guidelines for the operational efficiency of vessels. A new project for the creation of an international regulatory framework on biofouling was also launched.

The IMO's commitment is thus confirmed on several fronts, but the scope of the new Net-Zero Framework makes it the most ambitious and structural reform ever adopted in the maritime field to tackle climate change. Operators are called upon to immediately prepare for a radical change. The transition has begun and can no longer be postponed.