Cargo transport by sea and road - Technical and economical environmental factors

This paper presents the background for a method of calculating the energy demand for different ship types using only a relatively few, but important parameters. It is an empirical method, based on a statistical analysis of the main parameters of different ship types in order to establish representative relationships between the cargo capacity and the ships main dimensions. On this basis, it has been possible to calculate the necessary propulsive power by using well-established empirical power prediction methods (Guldhammer and Harvald (19 74), Oossanen (1980), and Insel & Molland (1992)). >> By combining the statistical analysis with a subsequent power prediction, it has been possible to develop a method which can calculate the energy consumption as a function of only 3 general parameters, namely the size of the ship (more precisely the capacity), the ship's speed and the average cargo utilization.)) Having established a method for the calculation of the ships energy demand, it is relatively simple to calculate the exhaust emissions by using some well-established specific emission factors, i.e. figures for the exhaust emission pr. consumed energy unit (g/Mj). >> In the paper, a comparison with road transport will also be presented focusing on the energy demand and exhaust emissions per transport unit, i.e. per ton cargo per km. >>) Finally, the energy and emission data will be used for an economical evaluation of sea transport versus land transport. This will be done by calculating the external costs to society caused by the negative effect of the different modes of transportation, i.e. costs due to air pollution, noise, accidents and congestion, which in total covers most of the external transport costs.