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Greenhouse gas emissions from international shipping

In 2023, the International Maritime Organization (IMO) adopted a revised strategy on reduction of greenhouse gas emissions from ships.

The revised strategy articulates strengthened levels of ambition for emissions reduction, indicative checkpoints to achieve these levels of ambition, and guiding principles to decarbonise international shipping.

Vision and levels of ambition

The vision set out in the revised strategy reaffirms the IMO's commitment to reducing greenhouse gas emissions from international shipping and, as a matter of urgency, aims to phase them out as soon as possible.

The vision is consistent with the long-term temperature goal set out in Article 2 of the Paris Agreement, while promoting a just and equitable transition.

The levels of ambition directing the revised strategy are:

  • carbon intensity of the ship to decline through further improvement of the energy efficiency for new ships, to review with the aim of strengthening the energy efficiency design requirements for ships,
  • carbon intensity of international shipping to decline, by reducing CO2 emissions per transport work, as an average across international shipping, by at least 40% by 2030, compared to 2008,
  • an uptake of zero or near-zero GHG emission technologies, fuels and/or energy sources, representing at least 5%, striving for 10% of the energy used by international shipping by 2030, and
  • GHG emissions from international shipping to reach net-zero, by peak GHG emissions from international shipping as soon as possible and to reach net-zero GHG emissions by or around 2050.

The strategy is due to be reviewed again in 2028.

Indicative checkpoints

The revised strategy identifies indicative checkpoints to reach net-zero GHG emissions from international shipping, including:

  • at least 20% reduction in total annual GHG emissions from international shipping, striving for 30%, by 2030, compared to 2008 levels, and
  • at least 70% reduction in total annual GHG emissions from international shipping, striving for 80%, by 2040, compared to 2008 levels.

Measures to reduce greenhouse gas emissions

Short-term measure

On 1 January 2023, Australia implemented through Marine Order 97 the IMO’s new short-term measure adopted under the MARPOL Convention, for existing ships engaged on international voyages. This measure requires international ships to take technical and operational measures to reduce their carbon intensity across the global fleet by an average of at least 40% by 2030, compared to 2008 levels.

Australian vessels have been making improvements under the short-term measure which consists of the Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator (CII) framework.

The short-term measure will be reviewed by the IMO with an expectation of finalising a report on the effectiveness of the short-term measure, and any identified improvements by January 2026.

Mid- and long-term measures (will be finalised and agreed by the IMO between 2023–30 and beyond 2030, respectively)

The IMO is developing technical and economic mid- and long-term measures to support implementation of the revised IMO GHG strategy. Negotiations on these measures have commenced and will continue throughout 2024 and 2025.

Measures may include technical, design, and operational mechanisms to reduce emissions (e.g. alternative fuel and energy supply to a ship, such as biofuels, renewable power, hydrogen, etc.) as well as market-based measures which could take the form of a carbon levy or other market mechanisms.

Regulations to enhance the energy efficiency of ships

In 2011, the IMO adopted the original mandatory energy efficiency measures to reduce greenhouse gas emissions from international shipping under the MARPOL.

The energy efficiency measures located in a chapter 4 of MARPOL Annex VI (air pollution) —Regulations on energy efficiency for ships—require ships to comply with the following:

  • The Energy Efficiency Design Index (EEDI) —new ships must be designed and built to comply with minimum energy efficiency performance levels that get progressively stricter to, and beyond, 2025.  
  • The Ship Energy Efficiency Management Plan (SEEMP) —a tool for ship operators to improve the energy efficiency of both new and existing ships using various ship-specific and operational measures, such as weather routing and speed optimisation.  

These regulations were adopted in 2011 and entered into force on 1 January 2013 for ships of 400 gross tonnage (GT) and above. 

IMO Data Collection System (IMO-DCS)

In 2016, the IMO adopted amendments to MARPOL that require ships of 5,000 GT and above undertaking international voyages, to collect and submit fuel consumption data to their flag State from 1 January 2019.

The flag State is required to verify and aggregate the data and submit it to the IMO data collection system (IMO-DCS), where it is used to track the success of existing emission reduction measures and to inform future requirements.

Since 2023, IMO-DCS data is used to calculate ship's operational carbon intensity (CII) and amendments will enter into force on 1 May 2024 requiring further information to be submitted to the IMO-DCS (e.g. data on transport work, installation of innovative technology, the attained and required Carbon Intensity Indicator (CII) values, the CII rating and attained Energy Efficiency Design Index for existing ships (EEXI)).

Alternative fuels and propulsion systems

To deliver the GHG reduction targets of the revised IMO GHG strategy, focus is turning to mid-term measures, including a technical component, such as a GHG fuel intensity standard, as well as an economic component(s) aimed at incentivising the global availability and uptake of low and zero carbon fuels.

In the shorter term, considerable emission reductions are possible by transitioning to lower-carbon fuels, until zero-carbon fuels become readily available to cut emissions in the long term. Promising candidates for zero-carbon fuels include green ammonia, hydrogen, methanol, biofuels and batteries.

For the effective uptake of alternative low-carbon and zero-carbon fuels, there is a need to consider a range of issues such as safety to the ship, crew and environment, pollution-response requirements and infrastructure availability.

The IMO has adopted Guidelines on life cycle GHG intensity of marine fuels (LCA guidelines), which allow for a measure of the greenhouse gas emissions across a fuel's production and usage. Different propulsion systems and aids are also being investigated, including electric, hybrid drives, fuel cell, wind power and solar power. 

The role of AMSA in reducing GHG emissions from shipping

The Australian Maritime Safety Authority (AMSA) leads Australia’s interests at the IMO on behalf of the Australian Government and works with other government agencies, Australian stakeholders and international administrations to develop internationally consistent greenhouse gas reduction measures for shipping.

The Department of Infrastructure, Transport, Regional Development, Communications and the Arts leads policy development for greenhouse gas emission reduction for shipping.

Through AMSA’s rigorous flag State control (FSC) and port State control (PSC) programs, we are responsible for ensuring Australian-flagged ships and foreign-flagged ships operating in Australian waters comply with international shipping standards, including the greenhouse gas reduction measures adopted by the IMO.

Last updated: 

Wednesday 13 December 2023