The emissions

International shipping transports about 80% of the world's goods in terms of total weight carried, and also produces about 7% of global NOx emissions. The market for marine propulsion systems is dominated by diesel engines. Emission standards focus primarily on NOx, gases which cause acid rain. Particulate matter (soot), carbon monoxide (CO) and unburnt hydrocarbons are other contaminants in diesel exhausts. Diesel engines also produce CO2 as a product of combustion as well as sulphur oxides (SOx), the amount of the latter depending on the sulphur content of the fuel oil.