Methanol is the obvious choice, because there are so many ways to make it. Shipping certainly looks to be moving in that direction, though ammonia is also being

Methanol is the obvious choice, because there are so many ways to make it. Shipping certainly looks to be moving in that direction, though ammonia is also being trialled. Ethanol via fermentation is also doable at scale, but most effective pathways rely on using arable land.