Life cycle CO₂ emissions of international hydrogen supply chains envisaged in Japan

Abstract

Japan aims to establish an international hydrogen supply chain by utilizing low-cost and abundantly available hydrogen sources and liquid hydrogen carriers to realize a future hydrogen economy that will enhance energy security and help achieve carbon neutrality. While hydrogen does not emit CO₂ when used as a fuel to generate energy, CO₂ emissions can be attributed to hydrogen due to the energy and other resources required at each stage of the hydrogen supply chain. Therefore, from a life cycle perspective, if hydrogen is to contribute to the world’s carbon neutrality goal, the entire hydrogen supply chain must be low-carbon. This paper explores the life cycle CO₂ emissions of international hydrogen supply chains envisaged by Japan. The target supply chains involve hydrogen produced from renewable electricity via electrolysis, as well as from fossil fuels with carbon capture and storage, sourced from resource-rich countries and imported to Japan using liquid hydrogen carriers such as liquid hydrogen, methylcyclohexane (MCH), and ammonia (NH₃). In addition, this paper addresses potential options for reducing life cycle CO₂ emissions to effectively establish a low-carbon hydrogen supply chain.

Graphical abstract

Keywords

international hydrogen supply chain / life cycle CO₂ emissions / liquid hydrogen carrier / liquid hydrogen / methylcyclohexane (MCH) / ammonia (NH₃)

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