Green hydrogen, which uses renewable energy to produce hydrogen from water, is taking off around the globe. Its boosters say the fuel could play an important role in decarbonizing hard-to-electrify sectors of the economy, such as long-haul trucking, aviation, and heavy manufacturing.

Saudi Arabia is constructing a futuristic city in the desert on the Red Sea called Neom. The $500 billion city — complete with flying taxis and robotic domestic help — is being built from scratch and will be home to a million people. And what energy product will be used both to power this city and sell to the world? Not oil. The Saudis are going big on something called green hydrogen — a carbon-free fuel made from water by using renewably produced electricity to split hydrogen molecules from oxygen molecules.

This summer, a large U.S. gas company, Air Products & Chemicals, announced that as part of Neom it has been building a green hydrogen plant in Saudi Arabia for the last four years. The plant is powered by 4 gigawatts from wind and solar projects that sprawl across the desert. It claims to be the world’s largest green hydrogen project — and more Saudi plants are on the drawing board.