Comprehensive risk assessment across multiple fields is required to assess the potential utility of hydrogen energy technology. In this research, we analyzed environmental and socio-economic effects during the entire life cycle of a hydrogen energy system using input-output tables. The target system included hydrogen production by naphtha reforming, transportation to hydrogen stations, and FCV (Fuel Cell Vehicle) refilling. The results indicated that 31%, 44%, and 9% of the production,

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... t, and greenhouse gas (GHG) emission effects, respectively, during the manufacturing and construction stages were temporary. During the continuous operation and maintenance stages, these values were found to be 69%, 56%, and 91%, respectively. The effect of naphtha reforming was dominant in GHG emissions and the effect of electrical power input on the entire system was significant. Production and employment had notable effects in both the direct and indirect sectors, including manufacturing (pumps, compressors, and chemical machinery) and services (equipment maintenance and trade). This study used data to introduce a life cycle perspective to environmental and socio-economic analysis of hydrogen energy systems and the results will contribute to their comprehensive risk assessment in the future. Sustainability 2017, 9, 1376 2 of 16 food, water, public health, emergency services, government, defense industrial base, information and telecommunications energy, transportation (people and products), banking and finance, the chemical industry, and postal and shipping-that are important for the functioning of a city, with reference to United States Department of Homeland Security [9] . Shi et al. [10] assessed social risks associated with the process of urban development using observations, expert meetings, interviews, and discussion forums. Furthermore, in energy technology analysis, McLellan et al. [11] studied the social risks of the main power generation technologies when impacted by natural disasters from points of view of humanity, society, economics, manufacturing, and nature. In addition, Japanese decision-making and social acceptance emphasizes a balance of multiple values, including stable economic foundation, safety, security, reliable social systems, and sustainable and good relationships among different groups. [12, 13] ; therefore, it is important to identify the variety of risks generated by new energy technologies and systems in order to promote their popularity within society and consider risk balance among various fields. To date, Japanese hydrogen energy technology has been analyzed in several areas. In the safety field, Sakamoto et al. [14] analyzed the safety distance between pieces of equipment in a hydrogen fueling station; Nakayama et al. [15] analyzed accident scenarios that could occur in hydrogen stations; and Okada et al. [16] analyzed the safety of organic chemical hydride. Ono and Tsunemi [17] suggested that providing precise risk information contributes to better acceptance. In the economic field, cost analyses of the manufacturing, construction, and operation phases have been conducted [18] [19] [20] [21] [22] [23] [24] . Additionally, environmental analyses have focused on CO 2 emissions in the supply chain during hydrogen production [25] [26] [27] [28] [29] . However, many of these studies were not conducted from a consistent, holistic point of view as operators and technicians in their respective areas developed them independently. Studies of future energy technology from an inclusive viewpoint that spans all areas and incorporates the values of users are very limited. Furthermore, studies that adopt a life cycle perspective across multiple industries are lacking. Input-output analysis is useful as a method for life cycle analyses. The effectiveness of input-output analysis and scenario analysis for energy technology has been demonstrated, especially for renewable energy technology [30] [31] [32] [33] [34] [35] [36] . Currently, Lee et al. [37] and Chun et al. [38] are developing analyses for hydrogen energy systems to harness attention for future development. This study aimed to highlight the environmental and socio-economic effects caused by the hydrogen energy system during its life cycle in Japan, using input-output tables. This basic analysis introduces the assessment of life cycle effects of hydrogen energy systems and will assist in future comprehensive risk (In reference to the ISO/ICE Guide 73 [7], risk is defined as the "effect of uncertainty on objectives." In addition, similarly, the effect is defined as "a deviation from the expected-positive and/or negative.") analysis of hydrogen energy technology.