Renewable synthesis fuels for a circular economy: A life cycle assessment

Renewable synthesis fuels play a crucial role in enabling a circular economy. This study assesses the environmental impacts of power-to-hydrogen and biomass-to-hydrogen routes, considering four hydrogen storage options: hydrogen, ammonia, methane, and methanol with a function unit of 1 liter of a stored hydrogen-derived product. The assessment encompasses metrics such as carbon footprint, use of fossil and nuclear energy, ecosystem quality, human health impact, and water scarcity. The results reveal that the biomass-based route has a lesser impact on global warming potential (GWP), with the system involving chemical looping technology and using ammonia as the storage medium achieving a negative GWP of -7.55 kg CO₂eq. The power-based route outperforms the biomass-based route except for GWP which is influenced by the penetration of renewable energy. Liquid hydrogen is found to be suitable for the fossil fuel-based route, while methane and ammonia are favorable to the power-based and biomass-based routes, respectively.