Osaka Gas and Mitsubishi Heavy Industries (MHI) initiated operations for CO2NNEX®, the city gas industry's first digital platform to enhance visibility in carbon dioxide (CO2) trading and facilitate the transfer and management of Clean Gas Certificates, which certify the environmental value of e-methane,(1) allowing for use of the system during Expo 2025 Osaka, Kansai, Japan (the Expo).(2) The CO2NNEX platform will be used during the Expo to support Osaka Gas' e-methane production and utilisation demonstration(3) by accumulating data and providing visibility on the amount of e-methane biogas produced, as well as its raw materials (CO2 and H2), and CO2 emissions throughout the life cycle. It will also be utilised to manage utilisation of the clean gas certificates generated by the demonstration. The clean gas certificates for the e-methane and biogas produced by Toho Gas Co., Ltd., Nihon Gas Co., Ltd., and Hokuriku Gas Co., Ltd. will be transferred through the platform and used for the natural gas supplied by Osaka Gas to the Expo site, contributing to the carbon neutrality of the Expo. The Gas Pavilion and Expo demonstration area presented by the Japan Gas Association will also feature videos for visitors introducing the forward-thinking initiatives by the city gas industry to systematise the transfer of clean gas certificates. To ensure efficient operation of the platform, Osaka Gas and MHI solicited advice from the Japan Gas Association, and held discussions with Toho Gas, Nihon Gas, and Hokuriku Gas, the companies that will use CO2NNEX for exchange of clean gas certificates for the Expo, as well as with INPEX CORPORATION, which acted as advisor during the proof of concept stage for the system.(4) The aim of these measures was to enhance user convenience and reliability in the transfer and management of clean gas certificates. Along with the reuse of CO2 (CCU(5)), such as for e-methane and recycled carbon fuels (e-fuel, SAF, Green LPG), practical applications for CO2 storage (CCS(6)) technology are expected to emerge in the future. Osaka Gas and MHI are also considering implementing the CO2NNEX digital platform for CO2distribution management in the CCS demonstration project currently being developed, with the aim of utilising it as a management system for the establishment of the CO2 value chain. Private sector utilisation of Clean Gas Certificates came into effect on April 1, 2024, and efforts to convert the environmental value of e-methane and biogas produced in Japan into Clean Gas Certificates are gaining momentum. Since the volume of transactions, such as those for the Expo demonstration, is expected to increase further in the future, a system for the transfer and management of clean gas certificates is required. Osaka Gas and MHI will utilse the results from CO2NNEX at the Expo to support the practical application of e-methane technology across society, and contribute to the realization of a carbon-neutral world by 2030.