Redefining the Hydrogen “Colours” based on Carbon Dioxide Emissions: A New Evidence-Based Colour Code

Abstract This paper redefines hydrogen colour codes based on carbon dioxide emissions. It highlights that there are several codes, which disregard the emitted in production process (e.g., electrolysis with renewable energy, steam reforming of natural gas, coal gasification, etc.). Some colours used interchangeably for different technologies, while many do not assign a all possible pathways. Therefore, existent framework is misleading and lacks scientific underpinning labelling green, blue, grey, black, yellow, purple, turquoise, builds upon work Nikolaidis Poullikkas provides qualitative assessment to label various technologies. Based comparative analysis latest research analysing this inquires whether or not, common understanding pathways lie behind each “colour”. finds major inconsistencies regarding used, especially technologies using fossil fuels as an energy source, but nuclear has also been found have discrepancies labelling. At same time, only one describe wide range (i.e., green). However, if emissions corresponding technology were visually represented predefined colour-code, produced would less diverse range, than current palettes suggest. Rather being “grey” “blue”, coal, oil gasbased appear be shades “brown” “black”. finding illustrates these emit more initial suggest, raises question any hydrogen, other its “green” versions, compliant objectives Paris Agreement.