I mentioned the Sabatier process in a previous post. Researchers at the University of Southern California have been testing a different approach:
Read more here.
Interestingly, they didn't first need to produce hydrogen by electrolysis, which is the basis of the Sabatier process. It's not clear, but I assume the hydrogen came from the water.
If we wanted to we could move to a 100% renewables energy system with a decade. Existing cars and lorries would be converted to methanol, and electricity would be produced by wind and solar.