[tomarr]

>Bunker fuel shouldn't be marketable for sale as a fuel at all. We (= OPEC, in this case) could still sell it to chemical companies, but the rest, we should just be sticking back in the ground. This would reduce global greenhouse gas emissions by such an extent it's not even funny.

Bunker fuel is responsible for ~3% of CO2e emissions? OK it may have a greater impact on air quality, but in terms of carbon it is not exactly a stand-out item.

[derefr]

Carbon is a heuristic, not a target. The air isn't bad because of carbon; carbon oxides are just the most common of the GHGs we put in the air.

Bunker fuel contains a lot more light-molecular-weight things that aren't hydrocarbons (e.g. nitrogenous molecules), and so when they burn, you end up with toxic GHGs being produced, rather than just bad for climate change GHGs. (And, as you mention, the fact that we're burning it mostly at the beginning and end of the trip, means we're burning it near ports, and therefore making the air at port cities — and nearby estuaries — toxic.)

But even then, the concern with bunker fuel in particular isn't really the GHGs (i.e. the low-molecular-weight products of combustion that stay airborne), but all the high-molecular-weight stuff that's mixed in there, that doesn't stay airborne, but is temporarily put into the air during combustion.

Bunker fuel is "dirty fuel", using a similar sense of "dirty" to a "dirty bomb" — not that it's radioactive, but that it "salts the earth" where it goes off. Except that a bunker-fuel "bomb" goes off over water, and all the resulting heavy-molecular-weight vapors that come off the combustion then fall into said water, contaminating the oceans+estuaries with these chemicals. Bunker fuel salts the sea.

[Schiendelman]

As a single line item, that’s vast.