Hydrogen has long been promised as the sustainable fuel of the future. With hopes it could decarbonize heavy industry, power transport, and replace fossil fuels. Yet today, operating green hydrogen plants, mostly in Europe and China, produce just one million tons per year. But governments worldwide have begun a concerted effort to scale up green hydrogen production.

With billions being invested into hydrogen projects around the world - is the dream finally becoming a reality?

The challenge starts with the element itself. Despite being the most abundant in the universe, hydrogen rarely exists in pure form on Earth and must be extracted through electrolysis. But rapidly advancing technology and cheaper renewable energy are bringing the cost down fast.

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In China, the world's largest green hydrogen and ammonia plant has just opened in Inner Mongolia, producing 320,000 tons a year from wind and solar energy captured in the desert. CGTN's Wang Tianyu speaks to Envision CEO Lei Zhang about what it means for the country's hydrogen ambitions.

Back on the road, RAZOR's Neil Cairns visits Metier Technologies to see another side of the hydrogen story. Their hydrogen internal combustion engine offers an alternative to fuel cells, adapting familiar technology to run on clean fuel. We put it to the test with a ride in their demo truck to see how it performs in the real world.

In the French Pyrenees mountains, we catch up with Mantle8, a startup hunting for something potentially game-changing: natural hydrogen reserves forming underground through geological reactions, continuously replenished, and requiring no electrolysis at all.