Sure. But we also can synthesize methane from captured carbon dioxide and green hydrogen. It's still more expensive than fossil methane, but it's getting cheaper.

But we can start transitioning factories to use methane right now, starting from fossil methane and slowly moving to greener sources.

You're suggesting unworkable processes that would take an absolute crapton of energy and be very expense.

Uhm... Which one? Reduction of iron ore with methane is energetically as good as anything else.

Synthetic methane is estimated right now to be about 2.5x the cost of fossil one when deployed at scale: https://www.sciencedirect.com/science/article/pii/S187551002...

This is pretty reasonable.