Synthetic methane is limited by the sources of carbon dioxide. Existing prototypes use either biomass or industrial byproducts for concentrated CO2. This is not available at scale. Biomass does not grow fast enough to sequester enough carbon.

Prometheus Fuels is the main player trying to do direct atmospheric sequesteration. But they've not succeeded yet.

Interesting but tangential to Gibson Island and other Fortescue Future projects as they're not attempting to sequester carbon or use biomass.

Andrew Forrest [1] has laid out plans to dramatically increase global green hydrogen production on the back of western australia's mining of close to a billion tonnes of iron ore per year (ie. experience of industry at large scale).

https://fortescue.com/what-we-do/green-energy-research/green...

The aim is to do whatever required to directly fuel existing mining truck fleets and bulk carriers.

[1] https://youtu.be/h1Y22iC90Xo?t=331