And finally, whenever I reflect upon hydrogen I'm always somewhat baffled on why molecules like ammonia (heavier) or methanol (heavier and less hazardous) aren't preferred as energy carriers.

I don't know about in general, but at least in Sweden there is some projects to use forest-produced chemicals as biofuels, among them methanol for the purpose of using them as liquid fuels. I think the general idea is that forestry has better EROI then agriculture.

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