Development of a New Index for a Ship Considering Ship-Oriented Life Cycle Greenhouse Gas Emissions

The growing concerns about greenhouse gas (GHG) emissions from ships have drawn attention to various methodologies and indices developed for the standardised assessment of these emissions.However, existing approaches fail to account for the full life cycle of ships, focusing exclusively on marine fuels.This study introduces a ship-oriented GHG assessment methodology and its corresponding index, the Ship Life cycle Greenhouse gas Intensity (SLGI).This framework evaluates the entire life cycle of a ship, spanning from raw material production and shipbuilding to operations and decommissioning.A comparative analysis alongside existing indices is conducted on three case studies involving transitions to alternative marine fuels driven by technological advancements and strengthening regulations.The results show that while the absolute GHG emissions decrease as fuel transition takes place, the limited scope of current measures leads to unreliable assessment outcomes.In particular, the progressive increase in the upstream emission share from non-fuel materials, which were previously overlooked, indicates a potential for shifting the emission burden.Therefore, this study demonstrates the inherent limitations of existing GHG assessment measures for ships and the necessity of a ship-oriented approach based on a life cycle perspective for precise evaluation.