Life cycle emission and cost assessment for LNG-retrofitted vessels: the risk and sensitivity analyses under fuel property and load variations

Abstract

There are various energy efficiency and emission reduction regulations enforced by the national and international maritime authorities for the shipping industry to adopt greener technologies. In this light, LNG-fueled vessels can be a promising alternative for ocean going diesel operated ships. It will be more beneficial if the price of LNG is lower than diesel to make that an economically viable fuel. Otherwise, there are concerns over the emission/economic considerations under the cost-benefit analyses of such fuels during their lifetimes with the initial investment risk for the technology, related infrastructure including fueling facilities and technology retrofitting processes. This study is an attempt to address the respective emission, energy, and cost concerns of LNG as a possible greener fuel with innovative dual-fuel engines within the SeaTech H2020 project (seatech2020. eu) initiative. The fuel life cycle of LNG in two scenarios of fuel property modification and load management for the cost analysis is considered. The life cycle assessment (LCA) section is designed to compare typical diesel and LNG fuels with selected short and deep-sea ship routes. Moreover, it is found that the effect of the ship travel distance on the amount of emissions is not significant when compared with the respective ratio. The life cycle cost assessment (LCCA) indicated that the fuel quality is more influential than the load variations in ship navigation. A 39% GHG emission reduction and up to a 22% fuel efficiency can be achieved under more optimal operational conditions by replacing LNG with diesel. The results also showed that the feasibility of using good quality LNG (higher Wobbe Index) instead of poor diesel characteristics in a selected ship is guaranteed within 30% of the sensitivity range. The fuel consumption variations under different engine loads (50% max to 85% min) can decrease the payback period from 6-years to 4-years as per the LCCA.