There is debate over how far blended hydrogen can cut CO2 emissions, and many obstacles need addressing to make long-distance transport commercially viable.
As clean energy technologies require more metals and minerals like lithium, copper and cobalt, mining disasters have raised questions about the sector's ability to change.
The city-state has voiced support for deep-sea mining done according to 'robust rules, regulations and procedures'. Environmentalists say the stance is at odds with its recent pledges to protect marine life.