Table 5. Total Amount of Emission of Various Pollutants from Ships into Atmosphere
The figures in Table 5 were obtained by S&O Committee, and the total emission amount of CO2 from all over Japan was reported to IPCC as 1,234,904 × 103t in 1996. That means the contribution of Ships as 2.8% in Japan. Also the total CO2 emission from all over the world was reported as 21,360,000 × 103t in 1996, in which the contribution of ships becomes 2.4%. It seems that the contribution of ships is not so much now, but it should be necessary to continue the effort to decrease CO2 emission as the human being.
6. Conclusions
Similar turbulent diffusion analysis has also been performed by MAP Committee for Osaka Bay and for Ise Bay (Nagoya) in 1995, and it has been shown that SOx and NOx densities on land around the Bay area decrease significantly with decrease of the emission intensity from ships. Therefore the effort of IMO to reduce pollutants emission from ships should be much appreciated.
At least within bay area in Japan, ships should use fuel oil of 1.5% sulphur content or under, which means that the bay area in Japan should be designated as the Emission Control Area defined by Annex VI of MARPOL 73/78.
Concerning NOx, the IMO's Technical Code should be cleared by fine tuning of the engine and the fuel injection timing retard. If the regulation limit becomes much more rigorous, the water injection is the easy way to reduce NOx emission. Mitsubishi Heavy Industries Co. of Japan developed a new technology called as the stratified fuel injection in which fuel and water are injected alternately from one nozzle. Kibankyo Committee has performed a 7 years project from 1991 to develop a small sized catalytic De-NOx equipment for marine use on board. They have succeeded to find an appropriate catalyzer based on zeolite (Pt-ZSM5) to utilize hydro-carbon as deoxidizer.
In order to reduce CO2 emission, the author prefer the way of hydrogen. On November 12, 1997, Daimler Benz, at that time, made a 2-page advertisement in the Nikkei Newspaper saying that they will be ready to mass production of fuel cell hybrid cars until 2005, and their partner for the fuel cell technology is Ballard Power Systems Inc. in Vancouver, Canada. The author visited Ballard in the next spring to confirm the possibility, and could have no doubt of the progress. In Japan, Toyota Motor Corp. and Honda Motor Co. also announced that they will complete the fuel cell cars until 2003.
In these automotive applications, the type of the fuel cell is so called as "Polymer Electrolyte Fuel Cell" (PEFC), which is using a thin polymer membrane as an electrolyte in which proton is migrated. The electro-chemical reaction occurs at rather low temperature as around 100℃, and the losses are exhausted as hot water of around 70℃. This heat can be used as cogeneration.
If the automotive industries go into mass production of the fuel cells, the cost should be drastically reduced. The Ballard people said that the fuel cell stack including reformer which produces hydrogen from methanol as fuel will be 50 Canadian dollars/kW for the car application and 1,500 Canadian dollars/kW for electric generator. The lifetime of the stack for car application is around 5,000 hours and 40,000 hours for generators. Then the micro cogeneration unit for household application might become available up to 2010 at around 1,000 to 1,500 US$/kW, and its lifetime should be estimated as around 20,000 hours. The lifetime is mainly decided by CO attack for catalyst. CO is produced as impurity during the process of reforming of fuel. If the automobiles and home appliances are supplied by fuel cells, the mass production will progress drastically, and the cost should be decreasing significantly.
The age of fuel cells means the age of hydrogen. The infrastructure to provide liquid and/or gaseous hydrogen, such as pipelines or service stations, will become widespread in all over the world until 2050. The high pressure natural gas trunk pipelines are popular in the United States of America and in Europe. The total lengths are reported as 440,000 km in the U.S. and 800,000 km in Europe. In Asia, it is nothing now, but it will become popular in near future. These natural gas pipelines will be switched easily to send hydrogen. In hydrogen age, natural energy such as hydro and/or wind in Siberia or in Alaska, and solar in the desert area, should be utilized to produce hydrogen by electrolysis, and be sent by these pipelines.
In the hydrogen age, ships should be driven by hydrogen as fuel. Big ships are driven by piston engines or gas turbines, and smaller ships are driven by fuel cells, and all of them are fuelled by hydrogen. If this kind of strategy should be approved by all countries in the world, the CO2 concentration within atmosphere should take the maximum at 2050, and will decrease in the latter half of the 21st century.
7. Acknowledgements
The author wishes to acknowledge the remarkable contribution of the Marine Air Pollution (MAP) Committee members, especially of the co-chairmen, Prof. O. Nishida of Kobe University of Mercantile Marine, Prof. H. Okada of Tokyo University of Mercantile Marine, Prof. A. Azetsu of The University of Tokyo.
8. References
[1] HIRATA, M., :"Issues and Prospect of Energy Systems for Marine Use in the Next Generation for the Purpose of Environmental Preservation", Bull. of MESJ., Vol.23, No.1 (1995) pp.1-11.
[2] AZETSU, A., :"Emissions of NOx, Particulate Matters and N2O from Ships", Trans. 8th ICMES/SNAME New York Metropolitan Section Symposium in N.Y., (2000) C2-1 - C2-9.
[3] Hanna, S.R. & DiCristofaro, D.C.,:"Modeling Overwater and Coastal Transport and Dispersion", Proc. 8th Symp. Turbulence and Diffusion, American Meteorological Society (1988) pp.236-239.
