Process data on material processing, operations of the machinery or use of the energy, etc., are used in each stage. Process data is the smallest technical unit or system in which quantitative and/or qualitative data on economic or environmental inputs and outputs are available. The functional unit of process data is defined depending on the purpose of the process.
3.2 Process tree
The process tree for shipbuilding is shown in Fig.2. Shipbuilding includes direct processes such as material transportation, cutting, bending, welding, painting, trial runs, etc. and indirect processes such as lighting and use of machines in addition to the use of materials and parts. Process tree for a ship's operation is shown in Fig.3. The ship's operation involves processes such as operations of the main engine, navigation depending on load conditions of the cargo and handling of the cargo in the harbor in addition to regular maintenance work such as painting when the ship enter the dock. The process tree for ship dismantling and steel plates recycling is shown in Fig.4. Gas cutting dismantles the ship and recovery articles such as steel plates, etc. are transported to the factory yards by the truck. Steel plates, parts, iron scrap, nonferrous metals such as copper and aluminum, etc. are recovered from the dismantled ship. In the steel plate recycling stage, materials for the construction are produced by processing such as cutting, heating and rolling, etc..
4. Application to ship model
The emission of CO2 to the atmosphere is the most important factor and selected as one of the analyzed loads to the environment. Therefore, inventory analysis on CO2 emission was carried out to apply the analysis method to the real ship. Spread sheet software Microsoft Excel was used for the computation process.
4.1 Ship model
A crude oil tanker of the 85,000 ton (dwt) was the selected for the ship model. General arrangement of the ship model is shown in Fig.5. Principal particulars and plans for ship's operation of the ship model are shown in Table 1. The weight of the hull and other outfits occupy 77(%) and 23(%) of the ship model. Thc ship was supposed to run periodically for 25 years between Japan and Middle East including periodic maintenance. The load condition of the ship model was made to be in full loaded or in ballast.
4.2 Process quantities
Process quantities such as workloads on welding work, etc. came from the average data obtained by investigation on shipbuilding yard [3], navigation logbooks of real tanker [4] and dismantling yard or plans for shipbuilding and ship operation, etc. But, transportation of materials and parts to shipbuilding yard from manufacturing factories was not included in this analysis.
4.3 Process data & Inventory data
Inventory data on production of materials and energies which seemed to be representative was chosen from data such as calculated data using LCA database software [5][6], etc.. Inventory data on production of ship parts such as main engine and other outfit parts was made by omitting manufacturing processes and by simplifying the kinds of used materials in the parts.
Process data such as welding and operation of main engine, etc. was made by investigation at material processing companies etc. and by calculation based on product catalog, etc..
4.4 Result of analysis
The calculated life cycle data on the ship model is shown in table 2. The fuel consumption data obtained by the analysis was 1.7(g-CO2/ton-km) and it almost agreed with the data basted on the investigation of real tankers[2]. Total CO2 emission to the atmosphere throughout the life cycle of the ship model was about 1.4(Mton-CO2). CO2 emission per transportation unit (ton-km) was about 5.9(g-CO2). The breakdown of stages where CO2 is emitted to the atmosphere is shown in Fig.6. Almost all CO2 emission throughout the life cycle of the ship model came from the ship's operation including production of fuel oil and about 1.5(%) of CO2 emission came from shipbuilding.
The breakdown of processes in each stage of shipbuilding, ship's operation, dismantling and production of construction materials where CO2 was emitted are shown at Fig.7-Fig.10. In shipbuilding stage, steel production including forged steel and east steel emitted about 88(%) of CO2 emission and total of about 10(%) of CO2 emission was omitted from work processes in shipbuilding yard such as welding, cutting and sea trial, etc. including usu of electricity at yard. CO2 emission from the operation of the main diesel engine occupied about 82(%) of the emission in ship's operation and operation of the main engine was the process that emitted the most CO2 gas to the atmosphere in the ship's life cycle.
5. Conclusions
It was possible to estimate the amount of CO2 emission and other environmental loads throughout the life cycle of the ship by LCI analysis and through the execution of the analysis, the implementation method of LCl analysis for ships was established. Process analysis based on the process tree drawn for the ship are necessary to identify environmental loads of each process in stages of the ship's life cycle. Also, it clarified that most CO2 emission to the atmosphere throughout the ship's life cycle came from ship's operation and process that emits the most CO2 emission was operation of main diesel engine.
References
[1] R. Heijungs, Environmental life cycle assessment of products Backgrounds LCA, 1992, p52, Centre of Environmental Science
[2] M. KAMEYAMA et al., Abstract Note of the 74th General Meeting of Ship Research Institute, 2000, p347
[3] T. NARUSE et al., Abstract Note of the 73rd General Meeting of Ship Research Institute, 1999, p240
[4] K. HIRAOKA et al., Abstract Note of the 74th General Meeting of Ship Research Institute, 2000, p335, p339
[5] Pre consultants B.V., Simapro LCA software (Ver.4.0)
[6] National Institute for Resources and Environment, NIRE-LCA software (Ver.2)
