Life Cycle Greenhouse Gas Emissions and Mitigation Performances of Various Hydrogen Production Routes

Hydrogen is widely recognized as a crucial element in the future energy transition to address climate change. However, the greenhouse gas (GHG) emissions associated with different hydrogen production routes vary, and there are still doubts about the GHG reduction potential of many routes. This study conducts a meta-analysis of 1283 assessment scenarios, reporting life cycle GHG emissions for 101 hydrogen production routes. Routes with notably low emissions are identified, such as biomass and biofuel utilization with carbon capture and storage (CCS), natural gas reforming with CCS, waste-derived hydrogen, and renewable energy-driven electrolysis. In contrast, biological routes show high variability, with some among the highest emitters. Background energy sources and feedstock composition are identified as key influencing factors. Additionally, 53 routes with emissions lower than steam methane reforming (SMR) are analyzed for substitution factors and levelized costs of GHG mitigation, with 17 routes emerging as promising options for GHG reduction, particularly those utilizing waste or biomass with CCS. Our findings highlight the need for localized strategies that optimize renewable resources and energy use to achieve cost-effective GHG reductions in hydrogen production.