The lifecycle greenhouse gas (GHG) emissions (Well-to-Wake) from maritime transport must be reduced by at least 50% in absolute values by 2050 to contribute to the ambitions of the Paris Agreement (2015). A transition from conventional fuels to alternative fuels with zero or lower GHG emissions is viewed as the most promising avenue to reach the GHG reductions. Whereas GHG and toxic pollutants emitted from the use of fossil fuels (heavy fuel oil (HFO) and marine gas/diesel oil (MGO/MDO)) are generally well understood, the emissions associated with the new fuel options are only now being measured and communicated. This review provides an outlook on fuels that could help shipping respond to the decarbonization effort including Liquefied Petroleum Gas (LPG), Liquefied Natural Gas (LNG), methanol, ammonia, and hydrogen. A quantification of the pollutants associated from the use of these fuels is provided and challenges and barriers to their uptake are discussed.

Climate change and global warming are among the most severe threats to the global ecosystem, caused by greenhouse gas emissions. Therefore, all industries that cause environmental emissions should collaborate in the struggle against climate change. In this context, the International Maritime Organization (IMO) approved the initial greenhouse gas strategy at the MEPC 72 session in April 2018 to achieve targets for 2050. With this strategy, the IMO aims to create and improve new regulations that can enhance energy efficiency to achieve their short-term, mid-term, and long-term goals. In this study, one of the novel terms, energy efficiency existing ship index (EEXI) values, has been calculated for the Turkish fleet to guide the maritime sector. The Turkish fleet in the study refers to the Turkish-owned vessels both sailing with a national or international flag. In accordance with this regulation, the number of Turkish fleets that were identified as either above or below the IMO reference lines has been determined. Additionally, EEXI values have been recalculated using the engine power limitation (EPL) method for ships that exceed the required limits, and the success rate of this method has been estimated. As a result, the application of EPL increased the number of ships below the Phase 2 reference line from 15.6 % to 53.1 %. To the best of our knowledge, this research, which has been carried out on all Turkish-owned ships, is the first study intended to serve as a guide for other ship owners in the global maritime industry regarding energy efficiency management.

Nowadays alternative and innovative energy recovery solutions are adopted on board ships to reduce fuel consumption and harmful emissions. According to this, the present work compares the engine exhaust gas waste heat recovery and hybrid turbocharger technologies, which are used to improve the efficiency of a dual-fuel four-stroke (DF) marine engine. Both solutions aim to satisfy partly or entirely the ship’s electrical and/or thermal loads. For the engine exhaust gas waste heat recovery, two steam plant schemes are considered: the single steam pressure and the variable layout (single or dual steam pressure plant). In both cases, a heat recovery steam generator is used for the electric power energy generation through a steam turbine. The hybrid turbocharger is used to provide a part of the ship’s electric loads as well. The thermodynamic mathematical models of DF engines, integrated with the energy recovery systems, are developed in a Matlab-Simulink environment, allowing the comparison in terms of performance at different engine loads and fuels, which are Natural Gas (NG) and High Fuel Oil (HFO). The use of NG always involves better efficiency of the system for all the engine working conditions. It results that the highest efficiency value achievable is 56% at 50% maximum continuous rating (MCR) engine load.