Comparative techno-environmental analysis of grey, blue, green/yellow and pale-blue hydrogen production

Hydrogen holds immense potential to assist in the transition from fossil fuels to sustainable energy sources, but its environmental impact depends on how it is produced. This study introduces the pale-blue hydrogen production method, which is a hybrid approach, utilizing both carbon capture and bioenergy inputs. Comparative life cycle analysis is shown for grey, blue, green and pale-blue hydrogen using cumulative energy demand, carbon footprint (CF), and water footprint. Additionally, the integration of solar-powered production methods (ground-based photovoltaic and floating photovoltaic (FPV) systems) is examined. The results showed blue hydrogen [steam methane reforming (SMR) + 56% carbon capture storage (CCS)] was 72% less, green hydrogen gas membrane (GM) 75% less, blue hydrogen [SMR+90%CCS] 88% less, and green hydrogen FPV have 90% less CF compared to grey hydrogen. Pale-blue hydrogen [50%B-50%G], blue hydrogen (GM + plasma reactor(PR)) PV and blue hydrogen (GM + PR) FPV offset 26, 48 and 52 times the emissions of grey hydrogen. • Life cycle analysis: reduced CO 2 footprint of pale-blue, blue, and green H 2 vs. grey H 2 . • Pale-blue H 2 combines solar power, water electrolysis, carbon capture, and bioenergy. • Pale-blue and blue (gas membrane + plasma reactor) H 2 offsets 26-48X grey H 2 emissions. • Pale-blue H 2 consumes 81.8% lower energy than grey H 2 , with a CED of 16.6 kWh/kg H 2 . • FPV powered green H 2 has the lowest CED at 1.08 kWh per kg H 2 .