A comprehensive life cycle impact evaluation of hydrogen production processes for cleaner applications

The worldwide energy demands have greatly increased with urbanization and population growth. Air pollution, acid rain, greenhouse gas emissions, global warming originating from CO 2 emissions, depletion of energy supplies, and environmental degradation resulting from climate change are all consequences of using non-renewable fossil fuel-based energy infrastructure. To minimize emissions, renewable energy-based alternative energy sources must be investigated. In this regard, hydrogen (H 2 ) has emerged as a promising fuel to meet energy requirements, and green H 2 production with net-zero emissions has gained significant interest in recent years. Therefore, this study uses the life cycle assessment approach to evaluate the atmospheric emissions and environmental impact parameters of the gasification, electrolysis, and dark fermentation-microbial electrolysis hybrid process and assess their sustainability levels, considering the sustainable development goals. Among the studied H 2 production processes, the maximum CO 2 emission originates from the coal gasification process, accounting for 18.6 kg-CO 2 /kg-H 2 , while the alkaline electrolysis process provides the lowest total CO 2 emission of 6.39 kg-CO 2 /kg-H 2 . Furthermore, the biological-based dark fermentation-microbial electrolysis cell process is a promising option owing to its highest negative biogenic CO 2 emission of −68.69 kg-CO 2 /kg-H 2 . The environmental impact parameters of the studied processes are calculated considering the emissions, and the highest global warming potential of 21.75 kgCO 2 -eq./kg-H 2 is obtained for the coal gasification process, considering the life cycle assessment coefficients. Overall, the lowest atmospheric emissions and environmental impacts are obtained for the electrolysis process. Consequently, these results revealed that switching from the fossil fuel resources used in the conventional H 2 production methods to fully sustainable sources, such as renewables, can make energy production methods entirely sustainable from an environmental point of view. • A comprehensive impact assessment of key hydrogen production methods is introduced. • The atmospheric emissions and environmental impacts of each method are compared through LCA. • The highest global warming potential of 21.75 kgCO 2 -eq./kg-H 2 is obtained for the gasification. • Dark fermentation process emits −68.69 kg-CO 2 /kg-H 2 due to CO 2 uptake during biomass growth phase. • The water electrolysis process is found advantageous over the renewable energy methods.