In the present study, a comparative well to pump life cycle assessment is conducted on the hydrogen production routes of water electrolysis, biomass gasification, coal gasification, steam methane reforming, hydrogen production from ethanol and methanol. The CML 2001 impact assessment methodology is employed for assessment and comparison. Comparatively higher life cycle Carbon dioxide and Sulphur oxide emissions of 27.3 kg/kg H-2 and 50.0 g/kg H-2 respectively are determined for the water electrolysis hydrogen production route via U.S. electricity mix. In addition, the life cycle global warming potential of this route (28.6 kg CO2eq/kg H-2) is found to be comparatively higher than other routes followed by coal gasification (23.7 kg CO2eq/kg H-2). However, the ethanol based hydrogen production route is estimated to have comparatively higher life cycle emissions of nitrogen dioxide (19.6 g/kg H-2) and volatile organic compounds (10.3 g/kg H-2). Moreover, this route is determined to have a comparatively higher photochemical ozone creation potential of 0.0045 kg-ethene(eq)/kg H-2 as well as eutrophication potential of 0.0043 kg PO4eq/kg H-2. The results of this study are comparatively discussed to signify the importance of life cycle assessment in comparing the environmental sustainability of hydrogen production routes. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.