18. Evaluation of Decarbonization Based on Environmental Footprint Indicators in Power Generation in Japan

Toward decarbonization, it is expected that hydrogenation and electrification will progress in the industrial sector, which accounts for the majority of greenhouse gas emissions in Japan. Research on measures and scenarios related to decarbonization are underway, and there are few previous studies that quantitatively evaluate the trade-off relationship of the environmental load impact between CO₂ emission reduction and earth resource consumption which includes material consumption, land system change, atmospheric aerosol loading, and chemical pollution. In this study, a comprehensive framework for the evaluation of environmental load impact with footprint indicators is presented, considering the technical options for decarbonization from 2030 to 2050 in power generation. In the power generation process, there are some measures for decarbonization, including the utilization of renewable energy power generation. A special focus in this study is set on the future scenarios of energy and material requirements for the construction of renewable energy power plants and evaluating the direct and indirect environmental load required as footprint indicators with the material footprint, ecological footprint, carbon footprint, and chemical footprint, which is a new indicator estimating the environmental loads of chemical substances. The chemical footprint is the indicator defined as the occupation of a theoretical freshwater volume needed to dilute a chemical emission to the point where it causes no damage to the ecosystem. In this study, material and energy consumption, including chemical substances, are estimated according to future scenarios and the effects of chemical substances were mainly evaluated. As a result, there is a trade-off between an increase in ecological footprint and carbon footprint due to newly introduced steel resources and an increase in material footprint and chemical footprint due to copper resources as the composition ratio of offshore wind power generation increases. While promoting the decarbonization of power generation fuel for the purpose of directly reducing CO₂ emission, the introduction of base metal materials accompanying the construction of new renewable energy power generation facilities will increase the indirect environmental load. In the evaluation of technical options for the decarbonization of the power generation process for the future, a comprehensive and quantitative evaluation framework, including the evaluation of the environmental load associated with the use of chemical substances, is presented.