Can a multibillion-dollar project in the Saudi desert jump-start the demand for green hydrogen, an elusive energy source that could help eliminate carbon emissions from vehicles, power plants and heavy industry?

The allure of hydrogen is undeniable. Unlike oil and natural gas, it doesn’t emit carbon dioxide and other greenhouse gases when burned. It’s more easily stored than electricity generated by wind turbines and solar farms, and it can be transported by ship or pipeline. Green hydrogen, which is produced using renewable energy sources, is especially attractive as a fuel. It’s made from water rather than methane or other hydrocarbons.

But those who foresee a green hydrogen future face a quandary: The high cost of producing the odorless, colorless, flammable gas can be mitigated only by large-scale projects, which in turn make economic sense only if there is a widespread market for green hydrogen. That doesn’t yet exist.

In Neom, a planned megacity of the future now taking shape in northwestern Saudi Arabia, the investors behind the green hydrogen project think they can deliver the chicken and the egg.

The initiative—a joint venture of Neom, U.S. chemical company Air Products & Chemicals Inc., and Saudi Arabia’s ACWA Power—will invest $5 billion to build what will be the world’s largest green hydrogen production facility. Another $2 billion will be invested in distribution infrastructure in consumer markets around the world, primarily to fuel industrial vehicles and public buses.

Neom, the planned megacity of the future in Saudi Arabia, possesses world-class wind and solar, as well as proximity to a port, making it an advantageous spot for a green hydrogen production facility.

PHOTO: HAMAD I MOHAMMED/REUTERS

One of Neom’s main advantages in what could become a global race to develop green hydrogen is that the city’s location along the Red Sea possesses world-class solar and wind power, according to Peter Terium, head of Neom’s energy sector. Solar will power the plant during the day, wind at night, he says.

It isn’t easy to find a site with strong enough wind and sun, as well as proximity to a port, Mr. Terium says. “Otherwise, we wouldn’t be the first to announce an investment of this size,” he says. Other countries are following suit. Australia, for example, has expedited the approval of a $36 billion project in the Outback in the western part of the country that will generate 26,000 megawatts of renewable electricity to be used to power the green hydrogen production.

Most hydrogen made for commercial use is so-called gray hydrogen, which is produced by splitting the hydrocarbon molecules in coal or natural gas. This process emits carbon. Green hydrogen, on the other hand, emits no carbon because it relies upon a process called electrolysis, in which electricity is used to strip hydrogen atoms from water molecules.