Ship emissions and technical emission reduction potential in the northern Baltic Sea

Ships are a significant source of air pollutant emissions, especially NOx and SO2. Pollution levels will increase in the future due to growth in ship traffic and lack of effective regulations. So far, related research has been concentrated on emissions from land-based sources, and very few shipping emission inventories exist to date. The aim of this study was to evaluate emissions and the technical reduction potential of SO2, NOx, CO, HC and PM from waterborne traffic in Finland and in marine areas near Finland in 2000 and 2015. The energy consumption of ships in 2000 was estimated based on statistics mapping ship movements in the ports of Finland, Russia, Estonia and Sweden. Combined with emission factors, this data was used as a basis for evaluating the total amount of emissions. Emissions in 2015 were calculated based on predicted growth rates in ship traffic and four different reduction technology scenarios. In 2000 the ship-based SO2 and NOx emissions on sea routes totalled 36000 and 107000 tonnes, respectively. Current international regulations have little impact on emission rates in the studied marine areas. The required reduction technologies are internal engine modifications and fuel with a maximum sulphur content of 1.5 %. The results of the scenario study show that ship-based SO2 and NOx emissions will increase by 20 % and 40 % respectively by 2015 if no further emission reduction methods are introduced. These emissions could be reduced significantly through introduction of more effective reduction technologies, such as lowering the sulphur content in fuel, adding water to the engine process, exhaust gas recirculation and selective catalytic reduction technology. The potential is substantial, especially for NOx emissions from cargo ships, which could be reduced by approximately 90 % from the 2015 baseline level.