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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Competing Interest

The authors declare that they have no competing interest.

Notations

CCS	Carbon dioxide capture and storage
CO2	Carbon dioxide
GHG	Greenhouse gas
IDEA	Inventory database for inventory analysis
IEA	International Energy Agency
IPHE	International partnership for hydrogen and fuels cells in the economy
LCA	Life cycle assessment
LCCO2	Life cycle CO2
LH	Liquid hydrogen
LNG	Liquefied natural gas
LOHC	Liquid organic hydrogen carrier
MCH	Methylcyclohexane
NG	Natural gas
NH3	Ammonia
SMR	Steam methane reforming
TOL	Toluene
UAE	United Arab Emirates

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