Exhaust emissions from ships at berth

Emission measurements have been carried out on board six ships at berth during normal real-world operation (hotelling, unloading and loading activities). The study included three passenger ferries, one transoceanic container/ro-ro, one transoceanic car/truck carrier, and one chemical tanker. Emissions were measured from 22 auxiliary engines (AEs, medium and high-speed marine diesels) covering seven engine models and ranging in size from 720 to 2675 kW maximum output. The fuels varied from low sulphur gasoils (2.91 cst viscosity) through to residual oils (411 cst viscosity). Both specific emission factors (gkWh−1) at a given engine load and total emissions (kg) of nitrogen oxides (NOx), sulphur dioxide, carbon monoxide, hydrocarbons, carbon dioxide, particulate matter (PM) and polyaromatic hydrocarbons during actual harbour stops were determined. In addition, some preliminary measurements to investigate PM size distributions were undertaken. The specific emissions showed significant variations between the different engine models and also within the same engine model on board the same ship. For example NOx emissions varied between 9.6 and 20.2 gkWhcorr−1 between all engines and 14.2–18.6 gkWhcorr−1 between engines of the same model and fuel. Other emissions from boiler use and possible main engine warm-up prior to departure were in general expected to be considerably less than those from the AEs. The results obtained for the three passenger ferries demonstrate that empirically derived, emission formulae using dead weight tonnage can prove to be a cost-effective and accurate tool for harbour emission inventories.