[leoedin]

Yeah, it probably is. There's not really a nice process for making liquid fuel - hydrogen isn't a great fuel really. My understanding is that the biggest problem with making a practical liquid fuel is ironically getting the carbon. Hydrogen is in water, but carbon is only really in carbon dioxide - which is at very low atmospheric concentrations and so takes an incredible amount of energy to capture.

Ammonia would be easier (ubiquitous nitrogen everywhere), but isn't a particularly nice fuel either. At least it's easier to store than hydrogen.