Grey, blue, and green hydrogen: A comprehensive review of production methods and prospects for zero-emission energy

ABSTRACTEnergy is the linchpin for economic development despite its generation deficit worldwide. Hydrogen can be used as an alternative energy source to meet the requirement that it emits zero to near-zero impurities and is safe for the environment and humans. Because of growing greenhouse gas emissions and the fast-expanding usage of renewable energy sources in power production in recent years, interest in hydrogen is resurging. Hydrogen may be utilized as a renewable energy storage, stabilizing the entire power system and assisting in the decarbonization of the power system, particularly in the industrial and transportation sectors. The main goal of this study is to describe several methods of producing hydrogen based on the principal energy sources utilized. Moreover, the financial and ecological outcomes of three key hydrogen colors (gray, blue, and green) are discussed. Hydrogen's future prosperity is heavily reliant on technology advancement and cost reductions, along with future objectives and related legislation. This research might be improved by developing new hydrogen production methods, novel hydrogen storage systems, infrastructure, and carbon-free hydrogen generation.KEYWORDS: Hydrogen energyGrey, blue, and green hydrogengreenhouse gasecological outcomescarbon-free hydrogen generation AcknowledgementsThe authors would like to thank the Energy Conversion Laboratory at the Department of Petroleum and Mining Engineering in Jashore University of Science and Technology, Jashore, Bangladesh for completing this review work.Disclosure statementNo potential conflict of interest was reported by the author(s).Nomenclature ISO=International organization for standardization.RES=Renewable energy sourceHCF=Hydrogen content factorGF=Greenization factorEIF=Environmental impact factorGHG=Greenhouse gasesLCA=Life cycle assessmentHPP=Hydrogen production pathwaysCCS=Carbon capture and storageSOFC=Solid oxide fuel cellCCS=Carbon capture and sequestration (environmental impact)GWP=Global warming potentialAP=Acidification potentialLCIA=Life cycle impact assessingLHV=Lower heating valueHHV=Higher heating valueH2=HydrogenCO2=Carbon dioxideCESAR=Canada energy systems analysis researchCCUS=Carbon capture use and storageSMR=Steam methane reformingHER=Hydrogen evolution reactionOER=Cathode and oxygen evolution reactionTML=Technology maturity levelRES=Renewable energy sourcesHighlights Grey, blue and green hydrogen are reviewed as an alternative source of future energyColor hydrogen production pathways using primary sources are discussedChallenges to zero emission are reviewedCost analysis and future prospects are discussedAdditional informationFundingThe work was supported by the Universiti Malaysia Pahang International Publication Grant [Grant No. RDU 213305].