Life cycle greenhouse gas implications of low-carbon gaseous fuel supply chains from technological, geospatial, and temporal perspectives

Abstract

There is consensus that achieving net-zero emissions will require the use of low-carbon hydrogen (H₂) and its derivatives, particularly in the hard-to-abate sectors. This necessitates the development of a global H₂ supply chain, which can be complex given that there are limited experiences worldwide. While H₂ production emissions at the plant gate might be low, the emissions throughout their supply chains are not yet well understood. Here, we summarise key insights drawn from over 10,000 cases, analysing the supply of H₂ from six renewables-rich regions and transporting it via different modes to two European markets, using six different chemical forms, including compressed-H₂ (CH2), liquefied-H₂ (LH2), synthetic natural gas (SNG), methylcyclohexane (MCH), ammonia (NH₃), and methanol (MeOH). We discussed the implications on the overall energy efficiency, product losses throughout the supply chains, and life cycle greenhouse gas (GHG) emissions from temporal, geospatial, and technological perspectives. The total loss and energy efficiencies of H₂ and SNG throughout the supply chains were estimated to range from 0.8–11.0 %/kg and 1.8–3.6 MJ/MJ of gaseous fuel delivered, respectively. The lifecycle GHG emissions (without embodied emissions) ranged from 5–86 gCO₂e/MJ in 2025, and this could reduce to 2–40 gCO₂e/MJ in 2050, due to changes in technological, design and operational factors. Minimising the impact of fuel/carrier production, H₂/CH₄ losses, fuel and electricity emissions factors by combining centralised and decentralised supply chain approaches could result in a lower GHG estimate. The use of chemical carriers could increase GHG emissions due to the H₂ liberation step at the destination. Even when starting with a low carbon intensity H₂ at the plant gate, the emissions associated with the supply chain can drive the emissions above the EU and UK regulatory limits. This paper further adds to the body of evidence pointing to the need for life cycle assessment-based certification that is asset-specific and supply chain-specific for demonstrating compliance against regulatory limits or H₂ standards globally.