抄録
This study analyzes GHG emissions disclosed by four major Japanese city gas companies—Tokyo Gas, Osaka Gas, Toho Gas, and Saibu Gas—focusing on Scope 1, 2, 3. In FY2023, these companies imported 25.87 million tons of LNG, with approximately 40% sourced from Australia. To assess the potential for upstream Scope 3 emission reductions, the study targets the liquefaction and maritime transport stages of Australian LNG under the CLEAN initiative. Using emission intensity data from the Japan Gas Association (JGA) and prior studies, the reduction potential was estimated by applying the lowest reported emission factors. Results indicate that 2.96 million tons of CO2e could be reduced in liquefaction and 1.14 million tons in maritime transport, totaling 4.10 million tons—equivalent to 5.4% of Scope 3 emissions and 4.8% of total GHG emissions. These findings suggest that the CLEAN initiative offers a practical Low carbonization pathway for the city gas sector. However, uncertainties remain due to variations in supply sources and lack of standardized measurement methods. Future efforts should focus on direct measurement-based evaluations and the development of international MMRV (Measuring, Monitoring, Reporting, and Verification) frameworks to enhance transparency and accuracy in LNG supply chain emissions.
