TOKYO — Japan plans to spend 3 trillion yen ($20.3 billion) over the next 15 years to subsidize the production of cleaner hydrogen, aiming to boost cooperation with the private sector to develop a domestic supply chain for the energy source.

Hydrogen fuel, which emits only water as a byproduct, is regarded as a next-generation energy source as nations pursue decarbonization. But the cost of hydrogen, covering production through supply, is reportedly 10 times higher than that of natural gas.

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