Results
The analysis result of the environmental load items of the engine is shown in Table 6.
The calculated CO2 emission of a unit of the model engine was about 1,100 (ton). Its CO2 emission profile is shown in Figure 7. Nearly 90 (%) of its total CO2 emission is attributable to the production stages of materials including cast/forged steel parts, steel plates, purchased equipments and other parts. The CO2 emission from the engine manufacturing factory accounts for about 10 (%). Its CO2 emission profile is shown in Figure 8. The CO2 emission of each process includes the CO2 emitted in the production stage of energies. Nearly 95 (%) of the CO2 emission from the engine manufacturing factory is attributable to the land trial process, and the CO2 emissions in the machining process and the assembling process account for only about 5 (%) and 1 (%) respectively.
4.3 Remarks on estimation
Since many kinds of half-finished or finished parts and equipments are purchased from several tens or hundreds of companies, it is difficult to grasp the species and the weights of all materials composing them definitely. Furthermore, all of them were assumed to be equivalent to forged steel parts. Even if all of them are assumed to be equivalent to cast steel parts, each CO2 emission changes by only about 2 (%) at most. The sensitivity of such purchased equipments is small. As compared with it, the emissions of cast/forged steel parts are relatively large and contribution of them to the total CO2 emission is rather large. As a result, in order to apply LCI analysis to a marine main engine successfully, it will be the most important (1) to grasp the weight ratios of cast/forged steel parts, steel plates, etc. composing a marine main engine definitely in the factory, and (2) to acquire reliable inventory data of those materials, especially of cast/forged steel parts.
5 CONCLUSION
The authors made hearing surveys on three domestic private companies which manufacture marine main engines of major types. Also, they made a hearing survey in the same way on one cast/forged steel parts factory which mainly manufactures crankshafts.
On the basis of these surveys, they made LCI analysis of a model engine by matrix-method and mainly evaluated in terms of CO2 emission.
The results are concluded below.
* Total CO2 emission of a unit of the model engine was about 1,100 (ton). Nearly 90 (%) of it is attributable to the production stages of materials including cast/forged steel parts, steel plates, purchased equipments and other parts. The CO2 emission from the engine manufacturing factory accounts for about 10 (%). Nearly 95 (%) of it is attributable to the land trial process, and the CO2 emissions in the machining process and the assembling process account for only about 5 (%) and 1 (%) respectively.
* In order to apply LCI analysis to a marine main engine successfully, it will be the most important, (1) to grasp the weight ratios of cast/forged steel parts, steel plates, etc. composing a marine main engine definitely in the factory, and (2) to acquire reliable inventory data of those materials, especially of cast/forged steel parts.
ACKNOWLEDGMENTS
These surveys were partly done in collaboration with the Japan Marine Standards Association. And the authors were provided with various convenience and cooperative support for preparation and collection of data from Mitsubishi Heavy Industries., LTD., Mitsui Engineering & Shipbuilding Co., LTD., Diesel United, LTD. and the cast/forged steel parts manufacturing company. The authors would like to express sincere gratitude to the persons concerned.
