The environmental performance of hydrogen production pathways based on renewable sources

There is growing scientific consensus on the existence of global warming and the attribution of anthropogenic activities. Collective and ambitious global effort is required to limit the adverse impacts of climate change driven by a fossil fuel-based economy. Hydrogen (H 2 ) has an important role in the transition towards a low-carbon economy, as it can provide a sustainable solution in a range of applications. There are several alternative ways of producing H 2 . Each pathway offers specific environmental and/or cost advantages depending on the life cycle energy, material and infrastructure requirements. Hence, it is important to systematically and precisely quantify the economic viability and environmental sustainability performances of alternative pathways to support decision-making. The main purpose of this study is to develop a life cycle assessment framework to estimate the greenhouse gas (GHG) footprints of nine renewable H 2 production pathways: wind-H 2 , solar-H 2 , bio-H 2 (via gasification and bio-oil reforming) from agricultural residues, whole trees and forest residues and supercritical water gasification (SCWG) of algae. The results show that wind-based water electrolysis has the lowest GHG footprint, 0.69±0.04 kg CO 2 eq/kg H 2 . SCWG of algae biomass has the largest footprint of the nine pathways considered, which ranges from 10.14 to 12.72 kg CO 2 eq/kg H 2 . GHG emissions from the gasification range from 1.81 to 3.23 kg CO 2 eq/kg H 2 and bio-oil reforming of biomass range from 1.57 to 3.46 kg CO 2 eq/kg H 2 .