Dear Colleagues,

Greenhouse gas (GHG) emissions from the maritime transport sector constitute approximately 3% of total global anthropogenic emissions and are growing despite considerable efficiency improvements, expected to rise to 17% by 2050 in a business-as-usual scenario. The International Maritime Organization (IMO) has set ambitious targets stipulating a 50% reduction in GHG emissions and a 70% reduction in carbon intensity by 2050. Several combustion-related technologies and strategies have the potential to achieve substantial carbon reductions in the maritime sector. These include, among others, (a) engine efficiency improvement measures, (b) low-carbon and/or zero-carbon alternative and renewable fuels, and (c) carbon capture and storage.

Energy efficiency measures include both in-cylinder and overall ship powertrain strategies (such as waste heat recovery) that have to be assessed, apart from their technological feasibility, against the stringent pollutant (NO_x and SO_x) emission regulations.

Switching to low-carbon alternative and/or renewable fuels (including methane, methanol, biofuels, ammonia, hydrogen, and e-fuels) requires significant modifications in the ship powertrain and emission control systems to accommodate their different physical and chemical properties (such as low calorific values and wide-ranging viscosities), combustion modes (e.g., low-temperature strategies and gas and dual fuel engines), and exhaust gas composition. Additional issues strongly related to the overall environmental performance, such as methane and ammonia slip, also have to be addressed.

Supply chain logistics, production, transportation, and distribution and on-board safety and storage of alternative fuels are crucial issues that have to be considered and evaluated on a life-cycle basis. The latter is of particular importance when an accurate evaluation of the sustainability of the considered paths is considered.

Carbon capture and storage (CCS) is a very promising technology that can potentially lead to zero-carbon emissions from ships. Marinization of CCS technologies is a fast-growing and fascinating area of research. Current research is focusing on the further development and application of capture (e.g., chemical/physical absorption–desorption, membrane separation, and chemical looping) and storage (e.g., liquefaction and mineralization) technologies.

The introduction of decarbonization technologies in the maritime sector requires extensive modeling and simulation activities, ranging from fundamental simulation of micro-scale processes (e.g., combustion chemistry modeling of alternative fuels, investigation of novel engine operation regimes, and optimization of fuel processing systems) to the integrated modeling of the marine energy system and the related holistic consideration of the economic and environmental aspects.

This Special Issue invites work from both academia and industry in all aspects of combustion science and technology related to the introduction and optimization of decarbonization pathways in the maritime sector. Presentations of first-of-a-kind and prototype concepts, as well as demonstrative applications of novel concepts in the field, are welcome. Topics include, but are not limited to, the following:

• Advanced combustion concepts for marine engines;
• Low carbon alternative and renewable fuels for marine engines (natural gas, methanol, biofuels, ammonia, hydrogen, and e-fuels);
• Exhaust after-treatment systems for low-carbon and non-carbon fuels;
• Combustion chemistry modeling;
• Process simulation of CCS modules;
• Ship powertrain modeling and simulation;
• Carbon capture technologies;
• Carbon storage technologies;
• Integration of CCS modules on-board ships;
• Life-cycle analysis.

Dr. George Skevis
Dr. George Vourliotakis
Dr. Akrivi Asimakopoulou
Guest Editors

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• Advanced combustion concepts for marine engines
• Low carbon alternative and renewable fuels for marine engines (natural gas, methanol, biofuels, ammonia, hydrogen, and e-fuels)
• Exhaust after-treatment systems for low-carbon and non-carbon fuels
• Combustion chemistry modeling
• Process simulation of CCS modules
• Ship powertrain modeling and simulation
• Carbon capture technologies
• Carbon storage technologies
• Integration of CCS modules on-board ships
• Life-cycle analysis