Economic and emission assessment of LNG-fuelled ships for inland waterway transportation

As the main transportation channel, the huge shipping volumes of inland rivers lead to significant emissions from ships. Inland shipping has an increasing demand for the development of green ships. Liquid natural gas (LNG) is considered to be an ideal marine fuel because of its many advantages. This paper aims to assess the economy and CO2 emission reduction of LNG-fuelled ships on inland waterway transportation, under the context that the uniqueness of inland waterway transportation, as well as cargo transportation regulations and policies are taken into account. Firstly, considering the preferential policies for LNG-fuelled ships and the mandatory use of shore power for oil-fuelled ships, we proposed a fuel consumption calculation formula and established economic and emission assessment models for inland ships. Then, we examined these models with simulation examples of three main cargo types, i.e. dry bulk, containers and dangerous goods, transported on the Yangtze River. The optimal ranges of LNG-fuelled ship size were given under various credible scenarios designed according to the transportation systems. The results show: (1) The optimal range of dead-weight tonnage (DWT) of LNG-fuelled ships for dry bulk, container and dangerous goods are between 3,000-5,000 DWT, 3,000-4,000 DWT and 2,000-3,000 DWT, respectively. (2) LNG-fuelled dry bulk ships of about 10,000 DWT or more are uneconomical compared to oil-fuelled ships of the same tonnage. (3) Smaller LNG-fuelled ships, such as dry bulk ships of less than 1,500 DWT, container and dangerous goods ships of less than 2,000 DWT, or ships serving longer routes of approximately more than 1,000 km have most significant unit CO2 emission reduction than oil-fuelled ships of the same tonnage. (4) Excessive waiting time at locks will reduce the economic feasibility and unit CO2 emission reduction of LNG-fuelled ships. Finally, we obtained a series of important management significances by simulating the changes of some variable parameters in real situations. These conclusions can provide some theoretical foundations for the development of LNG-fuelled or other green ships in inland waterways, and guide the government in formulating policies to promote the green transformation of the inland shipping industry.