The Hydrogen Color Spectrum: Techno-Economic Analysis of the Available Technologies for Hydrogen Production

Hydrogen has become the most promising energy carrier for the future. The spotlight is now on green hydrogen, produced with water electrolysis powered exclusively by renewable energy sources. However, several other technologies and sources are available or under development to satisfy the current and future hydrogen demand. In fact, hydrogen production involves different resources and energy loads, depending on the production method used. Therefore, the industry has tried to set a classification code for this energy carrier. This is done by using colors that reflect the hydrogen production method, the resources consumed to produce the required energy, and the number of emissions generated during the process. Depending on the reviewed literature, some colors have slightly different definitions, thus making the classifications imprecise. Therefore, this techno-economic analysis clarifies the meaning of each hydrogen color by systematically reviewing their production methods, consumed energy sources, and generated emissions. Then, an economic assessment compares the costs of the various hydrogen colors and examines the most feasible ones and their potential evolution. The scientific community and industry’s clear understanding of the advantages and drawbacks of each element of the hydrogen color spectrum is an essential step toward reaching a sustainable hydrogen economy