2008 年 43 巻 6 号 p. 938-944
The IMO is reviewing the MARPOL 73/78 Convention ANNEX VI to reduce SOx emissions from ships, and to lower the sulphur content in marine fuel oils. This paper estimates the proportion of SOx emissions from world shipping in the biogeochemical sulphur cycling. Also it discusses the situation of supply and demand of elemental sulphur and the increase in refinery energy due to desulphurization of marine fuel oils.
SOx emissions from shipping worldwide are estimated at 4.54 Tg per annum as of elemental sulphur. This accounts for 6.1% of anthropogenic emissions and 8.7% of natural emissions over the land to the atmosphere. The average sulphur content in marine fuel oils at the moment is 2.7% according to the IMO, and if it was reduced to 0.9% (as low as that of diesel oil), then SOx emissions from shipping would be reduced to 3.4% of the natural emissions over the land to the atmosphere. The elemental sulphur desulphurized from marine fuel oils would amount to 2.8 Tg per annum. However, this should find ways to be utilized under the present situation of supply and demand of sulphur. Refinery energy would increase - due to desulphurization - by as much as 6% of the heating value of fuel oils. This implies that it is necessary to further improve transportation efficiency and avoid a carbon dioxide emission increase.