Objective and Method. The implementation of biomass projects requires sufficient assessment of environmental impacts based on life cycle thinking. Since inventory analysis, in particular for plant construction, is labor-intensive, the development of a practical method that needs little manpower is required. The objective of the present study is to explore an effective method to estimate greenhouse gas (GHG) emissions from biomass plant construction. GHG emissions for two existing biomass plants in Japan are estimated with the following these three methods: a bottom-up method using material data and two input-output (IO) methods using detailed and its aggregated cost data. The three methods are assessed from three aspects, namely, the accuracy of estimated values of GHG emissions from plant construction, the manpower for inventory analysis and the influences of the estimated value on life cycle GHG emissions.
Results and Discussion. First, in terms of GHG emissions from plant construction, the estimated value of the bottom-up method was approximately 50% smaller than that of the IO method using detailed cost data. On the other hand, both the bottom-up and IO methods required large manpower for the GHG estimation. Second, the estimated value of the IO method using aggregated cost data was approximately 20% smaller than that of the IO method using detailed cost data. When the aggregated cost data was used, less manpower was required for the GHG estimation compared to the detailed cost data. Third, the influences of the differences between the two IO methods on life cycle GHG estimation were assessed. Although the manpower for the two IO methods were different as mentioned above, a significant difference in the influences on life cycle GHG estimation was not observed.
Conclusions. The results show that, from a practical viewpoint, the IO method using aggregated cost data is effective to estimate GHG emissions associated with biomass plant construction. Future studies are required to develop a practical method using IO tables to assess various environmental and socio-economic impacts of biomass projects based on a life cycle approach.