Contribution of Ships on NOx emission - What should be done by engine builders-
Hayato YAMASHIRO* and Hiroyasu KAWAI*
The attainment percentages for NOx environmental standards in Japanese urban areas remains at a low level. It is estimated that in areas surrounding Japan, ship emissions of NOx and SOx account for 37% and 23%, respectively, of total emissions, including land based emissions. Globally, these NOx and SOx ratios are only 13% and 6%. Likewise, in comparison with emissions from similarly consumed amounts of CO2, the figures for NOx and SOx remain high, and indicate a lack of proper attention to atmospheric pollution problems caused by marine engines, especially in comparison with their land based counterparts.
To date, there have been no restrictions on ship emissions of NOx and SOx; however, global as well as regional restrictions are expected to be implemented in their near future. This paper considers the theories and technology necessary for reducing atmospheric pollutants and complying with future regional restrictions.
Key Words: N02, S02, CO2, Ships, Low Emission, Dispersal Simulation, Regional Regulation
1. CURRENT ATMOSPHERIC CONDITIONS IN JAPAN
Figure 1 shows attainment percentages for S02 and N02 environmental standards in Japan. The continuing poor performance for N02 is obvious in comparison to the high attainment figures for S02. Moreover, the attainment figures are especially low in the large metropolitan areas. The main reasons for this are the increasingly stringent fuel restrictions on stationary and mobile SOx emissions, with the desulfurization devices installed in large stationary emitters in particular holding emissions to low levels, while NOx emissions rise due to the fact that the increasing total emissions from mobile emitters, such as automobiles, outpace strengthened restrictions set for individual units.
Although no domestic regulations exist in regard to ship exhausts, there is increasing support internationally, including from the IMO, as well as domestically, for applying restrictions on ship emissions. Reflecting this increased awareness, the Ship & Ocean Foundation in 1998 surveyed the ratios of ship exhaust emissions to total emissions, including land based emissions, both domestically and abroad . Results from this survey are summarized in sections two and three.
2. FUEL CONSUMPTION IN SHIPS
Fuel consumption for ships are shown in the Figure 2 and 3. Consumption for different kinds of fuel for commercial shipping are based on available statistics. Consumption for fishing and leisure craft are estimated based on operating time per year and average fuel efficiency. The present survey is limited to Japan's Exclusive Economic Zone (200 nautical mile zone), and includes estimates of fuel consumed within these waters by foreign ships engaged in the import/export trade with Japan. Fuel used by domestic shipping, leisure craft, and fishing boats, is added to that of foreign ships to give the total fuel consumption in waters surrounding Japan.