Climate impact of hydrogen as fuel for the heavy road transportation : A time-dependent life cycle methodology based assessment

Abstract: Currently, the transportation sector stands for one third of all greenhouse gas emissions in Sweden. Hydrogen (H2) could contribute to a decarbonized transportation sector since water is the only direct emission from a fuel cell electric vehicle. The higher energy density of H2 compared to batteries makes H2 better in a zero-emission system for heavy truck vehicles and long-distance transportations. Depending on the different production processes, the climate impact of H2 varies, which encourages a life cycle assessment (LCA) based methodology. The production processes of H2 are commonly referred to as colours, in which H2 from steam methane reforming (SMR) with natural gas as feedstock is known as ‘grey H2’. Further, if carbon capture and storage (CCS) is added, it is referred to as ‘blue H2’. There is a possibility to replace natural gas with biomethane as feedstock, which in this study is referred to as ‘beige H2’, and with CCS it can be called ‘orange H2’. Another production technology is through water-electrolysis from renewable electricity, which is referred to as ‘green H2’. The chosen climate metrics for the LCA study are the global warming potential (GWP) and the absolute global temperature potential (AGTP). The GWP of a heavy fuel cell truck is between 2% to 110% lower than for a conventional diesel truck. Grey H2 contributes with the highest CO2-equivalent emissions and orange H2 contributes with the lowest. To assess the AGTP, different future scenarios were elaborated with H2 implementation as diesel displacement for heavy truck transportation. The future scenarios have different mixes of H2 colours based on future market trends. Depending on the mix of H2 colours, the temperature increase varies from 1.6·10-15 to 1.8·10-15 K/tonne-km, which corresponds to a temperature reduction between 9% to 21% compared to heavy truck transport with only diesel. To reach the Swedish national target of net-zero emissions by 2045, a higher share of renewable fuels together with H2 is most likely necessary.