Point 4 of 7 — Renewable Energy Sources, Green Hydrogen and Climate AdaptationQuestion bank: 0 questions (0 with pictures)
04 The green hydrogen economy and sustainable fuels
How it is made
Renewable electricity drives an electrolyser that splits water: at thecathode2H₂O + 2e⁻ → H₂ + 2OH⁻, at theanode4OH⁻ → O₂ + 2H₂O + 4e⁻ (alkaline cell). Types: alkaline (AEL), proton-exchange membrane (PEM), solid oxide (SOEC) at high temperature and higher efficiency.
The only emission of using hydrogen is water; in a fuel cell the same chemistry runs backwards and produces electricity directly, without combustion and therefore without NOx from air nitrogen at flame temperature.
Colours of hydrogen — classified by source and impact
Grey: from natural gas by steam reforming (CH₄ + H₂O → CO + 3H₂), CO₂ released — about 9–10 kg CO₂ per kg H₂.
Brown / black: from coal or gasification, the highest emissions.
Blue: the same fossil route but with carbon capture and storage.
Green: electrolysis with renewable electricity — near-zero emissions.
Turquoise / pink: methane pyrolysis to solid carbon, or electrolysis with nuclear power.
Storage, transport and uses
Hydrogen is stored as acompressed gasat 350–700 bar, as acryogenic liquidat −253 °C, or chemically bound asammonia (NH₃)orliquid organic carriers, which are easier to ship.
Hard-to-electrify sectors are its market: steel (direct reduction of iron ore with hydrogen instead of coke), fertiliser (Haber–Bosch ammonia), refineries, shipping and aviation through synthetic e-fuels, long-haul road transport, and seasonal storage of surplus summer solar energy for winter.
Egypt's national hydrogen strategy positions the country as an exporter, with projects in the Suez Canal economic zone using the Benngir solar park and the wind farms of Gabal El-Zeit and Ras Ghareb.
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