Climate change mitigation in the maritime sector

Considering the urgency to reduce emissions from anthropogenic activities, there is a need for a thorough understanding and assessment of each sector, including shipping. This project was hence designed to develop a framework for improved understanding of the behavior of the international shipping fleet, quantifications of its emissions, as well as assessment of decarbonization options and development of pathways towards 2050. Major achievements of the CLIMMS project include: The project developed a portfolio of prioritized options for improved energy efficiency, operations, and alternative fuels for deep sea shipping. Models with new and improved parameterizations for hull resistance, accounting for wind and waves on ship resistance, engine emissions for different fuels, energy-saving options were developed, along with a machine learning tool for the filling in missing values of ship characteristics parameters in a vessel database. These models showed that energy efficiency measures through slender hulls and wind assistance are reasonably well understood and indicate some significant potential. For air lubrication, more knowledge is currently needed, but results indicate some potential for select technologies. The portfolio of mitigation options and new, improved model code were utilized by the AIS-driven MariTeam emission model. The model is with this state-of-the-art for quantifying fleetwide sectoral emissions. The importance of its well – to – wake capabilities is now also well established, as in the CLIMMS project the fuel value chains were parameterized using a life cycle assessment - based approach. The MariTeam model framework served as foundation for developing future scenarios for the shipping sector. To assess the climate effects of emissions from today’s global shipping activities and the impacts of switching fuels, the MariTeam model was coupled with the Norwegian Earth system model (NorESM). Black carbon emissions and transport to the Arctic from today’s shipping activities were quantified. And the reduced cooling from very low sulfur fuel oil was found to be significant in the NorESM simulations. The importance of considering methane and nitrous oxide emissions assessing alternative options such as LNG and ammonia were highlighted. Fuels produced with renewable energy have the potential for lower carbon footprints, while fuels produced with fossil resources and carbon capture and storage (CCS) result in some carbon emissions reductions. Onboard CCS may contribute to some CO2 reductions on existing ships and fuels. Sustainable biofuels could play a role; however, their mitigation potential is strongly linked to resource pathways and land use. Hydrocarbon e-fuels may lower carbon footprints if sourced using renewable energy, with high efficiency and a sustainable carbon source, though is currently energy demanding and costly. Notably, the project also addressed the role and importance of developing appropriate policy for international shipping. The results from the project were instrumental to the MEPC (Marine Environment Protection Committee) revising and adopting its guidelines on life cycle – based greenhouse gas accounting for marine fuels in 2023. For the decarbonization of shipping, the CLIMMS project has found that a combination of energy efficiency and low greenhouse gas fuels and or propulsion will be required to reach net zero. It is, though, likely that low-carbon fuels will be expensive, and their availability is strongly dependent on the transition of the energy sector with also sufficient energy availability, and infrastructure.

The project has strengthened capabilities in NTNU and Sintef Ocean regarding emission reductions in the maritime sector. The project has also consolidated the collaboration between the above-mentioned research institutions and key actors in the Norwegian Maritime Sector on the topic of climate change mitigation. This has advanced capacities towards making the Norwegian maritime cluster a leading actor in environmentally friendly shipping. The project has made significant model innovations. This involves, in particular, the development of the MariTeam model and its interface to the integrated assessment model MessageIX. In combination, these tools offer state-of-the-art capabilities for the assessment of transition scenarios. Research published by the project team has also been an important input to international scientific assessments and policy development processes within the International Maritime Organization.

With the IMO decision (2018) to reduce maritime GHG emissions by 50%, identifying, designing, and implementing cost efficient measures that deliver the required reductions in real seaway operations becomes a key priority for naval architects, shipbuilders, and owners. To this end, a robust understanding of the actual and complete climate impacts associated with different abatement measures and their combinations into different pathways for the transformation of the global fleet is required. Achieving this requires a multidisciplinary approach combining state of the art competence in both naval architecture & maritime engineering, life cycle assessment, and climate science. First, a rigorous understanding of the many different technological and operational measures options, as offered by the field of naval architecture & maritime engineering, is pivotal as it provides the core building blocks for any further assessments. Second, it is paramount to acknowledge the importance of assessing options across the whole life cycle. In particular, it is essential to recognize the lessons from climate change mitigation efforts on road transport, in that many options that reduce direct emissions may shift emissions to other parts in the value chain. Third, the actual climate and environmental impacts of emissions are not only influenced by technological factors, but also by climatic and ecological conditions, which may vary regionally.This project takes an inter-disciplinary approach combining methods from life cycle assessment, maritime engineering and climate science, to further-develop our understanding of the implications of various mitigation options and scenarios within the maritime sector.