Methodology for calculating emissions from ships: 1. Update of emission factors

SMED (Swedish Methodology for Environmental Data, a collaboration between the Swedish Environmental Research Institute, Statistics Sweden and the Swedish Meteorological and Hydrological Institute) has derived emission factors for ships (> 100 Gross Register Tonnage) to be applied in Sweden’s international reporting duties. The basis for this type of reporting is that only emissions derived from Swedish sold marine fuels are accounted for.

The study has focused on 28 different air pollutants, where the emission factors have been proposed as a function of engine and fuel type. For year 2002, the factors cover three operational modes (“at sea”, “manoeuvring” and “in port”) and thereby take into account main engine and auxiliary engine emissions. A set of “at sea “ emission factors has also been prepared from 1990 up to 2001 to allow an update of the marine emission time series.

In order to obtain representative and up-to-date emission factors for this application, “in-house” emission data and also published literature emission factor databases have been assessed. Thus emission factors were derived from a database consisting of exhaust measurements from ca. 62 ships involving ca.180 marine engines. The emission factors have been weighted to account for the proportion of the fleet using exhaust gas cleaning measures, age factors for fuel consumption and increased use of low-sulphur fuels.

Since the number of measurement data available for the different pollutant emission factors varies considerably, an attempt has been made to classify the factors after estimated uncertainty.