I swear to God, I've read the article twice and I've read the comments replying to your question and I still have no idea.

I think the problem is that, for any given sentence, it is unclear whether the author is talking about the fuel a ship is burning to move its cargo, or fuel that the ship is transporting to a destination.

I do understand that the article is making some kind of distinction between the two, but it is so terribly written that it's just impossible to figure out which one it's talking about at which point. Or at least I certainly don't care to waste my time "solving" the article like it's some kind of linguistic puzzle.

I'm not sure I've ever come across an article that needed an editor to improve its clarity more than this one.