産業連関表を用いた機械装置重量とCO₂排出量の関係の検討：CO₂排出量の簡易推計のために

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Background and Aim. CO₂-emission from production process of energy equipments is often a trade-off for CO₂-emission in operation. A simplified method would be useful for estimating approximate CO₂-emission from production process of energy equipments. On the other hands, the authors have been trying to evaluate energy systems and technology from the viewpoint of material use. We have used weight as a measure of material use, as it is relatively easy to get weight data of energy equipments. Therefore, if the weight of energy equipments has a positive correlation with the CO₂-emission, the weight would be a good measure in a simplified estimation of CO₂-emission. From this point of view, in this paper we discuss relations between weight of energy equipments and CO₂-emission from their production process, by using input-output tables.
Results and Discussion. In this paper, we use input-output tables (year 2000) as a common data source of weight of energy equipments and CO₂-emission. We chose 15 from 400 categories of input-output tables, most of which are energy equipments and industrial machines. Studies by “National Institute for Environmental Studies”, show that most of CO₂-emission is from metals, e.g. iron and steel, and power supply. We therefore, estimate weight of the metals, for selected 15 categories. We calculate the weight from the weight of intermediate categories that was calculated from the weight of the metals by using material tables. The resultant relation between weight and CO₂ emission from production process is approximated as following, c = 1.99 m + 1.50 p where c : CO₂-emission (t), m : material weight of the product (t), p: producer price of the equipments (million yen) The weight coefficient 1.99 is approximately equal to the CO₂ emission per unit weight of pig iron, 1.50, implying that most of CO₂-emission is from metals, e.g. iron and steel. The price coefficient 1.50 corresponds to CO₂-emissons form electric power for production process and energy for transportation, etc.
Conclusions. Simple approximate relation between CO₂-emission from production process and total weight of energy equipments, has been derived. This approximate method is useful to evaluate CO₂-emission from production process, when only limited information about equipment, e.g. the equipment weight is available.