On the inconsistency and revision of Carbon Intensity Indicator for cruise ships

The Carbon Intensity Indicator (CII) is one of the major instruments to assess the CO2 emissions coming from ship operations. Thus, it has a strong impact on the decisions taken by cruise companies regarding fleet allocation and itineraries planning. Although the CII works well with cargo vessels, it leads to misleading results when applied to cruise ships since the hotel load of a cruise ship is comparable to propulsion power. This leads to an inconsistency between emissions and CII values, which foster the adoption of itineraries having a higher environmental footprint. Here, a data-driven correction of the CII for cruise ships is proposed to remove the dependence of CII from the time at port/at sea. The correction is determined using a database relating to operative and forecasted emissions of a large fleet of cruise ships. The application to a medium-size cruise ship proves the potential of the proposed methodology.