7.1 Introduction of method
The calculation of emissions for the SEA mode has been hampered by lack of data on consensus on methods. However, the IMO has presented data that connects installed engine power of a ship, of a specific type, to its size. These methods are also e used by the Clean Shipping index. Under assumptions on what fraction of the installed power that is normally used, the IMO data gives a way to calculate the CO2 emission per tonne-km for different ship types as a function of the ships’ deadweight (dwt). This method calculates the emissions with the inherent assumption that the dwt represents the cargo. However, in reality the maximum cargo capacity, the payload, is lower than the dwt. Further, the load capacity utilization (LCU) should be considered. For containers and trailers one should also consider the fill-factor for these. Finally, the fuel consumption of a specific ship (in mass of fuel per distance) will depend on the load since a more heavily loaded vessel will lie deeper and thus experience higher resistance by the water. Below are the different steps in the calculations described.