Green, blue, and turquoise hydrogen: A review of production technologies and sustainability

The global transition toward sustainable energy systems has intensified interest in hydrogen as a clean, efficient, and flexible energy carrier. While hydrogen research spans decades, its strategic importance has recently surged due to its role in decarbonizing sectors such as industry, transportation, and power. This review comprehensively analyzes the production pathways and storage strategies of green, blue, and turquoise hydrogen, which together contribute to over 50 % of the world’s hydrogen output. Green hydrogen, produced via water electrolysis using renewable energy, is witnessing rapid advancements—with alkaline and PEM electrolyzers achieving efficiencies above 65 % and projected cost reductions to USD 1.5–2.0 per kg by 2030. Blue hydrogen, derived from natural gas reforming with carbon capture, offers carbon intensity reductions of up to 85 % when capture rates exceed 90 %, but faces challenges related to CO₂ storage and lifecycle emissions. Turquoise hydrogen, via methane pyrolysis, is gaining traction due to its lower CO₂ footprint and valuable carbon co-product, with pilot-scale reactors now achieving hydrogen yields above 60 %. In addition to production, the review discusses key developments in hydrogen storage technologies, particularly composite high-pressure tanks (Type 3 and 4), capable of storing hydrogen at pressures up to 700 bar with improved gravimetric capacity. This work integrates recent technological trends (2022–2024), energy efficiencies, and lifecycle assessments to provide a detailed and up-to-date comparison. It further outlines the readiness levels and deployment challenges, offering a critical reference for policymakers, industry stakeholders, and researchers aiming to integrate hydrogen into clean energy strategies.