戦間期日本海運業のエネルギー転換 : ディーゼル船普及の経済分析

抄録

It is the purpose of this paper to examine the process and the causes of change of fuel for the Japanese merchant fleet in interwar period. Oil was first adapted for marine fuel in 1907 in Japan. It was until the year 1924 that the first ocean going ship with the marine diesel(motorship) ran regularly. Motorship began to substitute for coal-fired vessels after the late 1920's. The oil-fired ships, including both oil-fired steamer and motorship, accounted for only 11% of aggregate Japanese tonnage in 1924. The oil-fired tonnage went up rapidly and reached 43% in 1940. The share of oil in total fuel consumption in calorie equivalent was estimated to be 15% in 1924 and 45% in 1940. The hypothetical rate of profit was calculated by the contemporary financial data on ocean shipping in order to identify the factors which made motorship more profitable than the competing technologies of ship engine and fuel; coal-fired reciprocated engine, oil-fired reciprocated engine, oil-fired turbine, and oil-fired turbine. It was the advantages of motorship over the alternatives that diesel engine required less fuel, as well as cutting the number of seamen and the wight of machinery, bunkers, and boiler water, all of which resulted in an increase of useful load and compensated higher capital cost of motorship. The rate of adoption of motorship was far more rapid in North American and Europen lines via the Panama Canal than in other lines. This was because heavy oil was supplied at lower prices in ports of the United States which amounted to about 60% of world crude oil production in the late 1930's. The availability of cheap oil was essential for the diffusion of oil-burning vessels as well as the factors written above.