Is burning bunker fuel at sea really a big problem? My understanding is that the impurities (sulphur mostly) in bunker fuel are bad for people to breathe and create smog, so they shouldn't be burned around population centres. The main greenhouse gas is carbon dioxide, and you produce roughly the same amount of that per watt of power no matter what hydrocarbon you burn.
Hydrocarbons are molecules that are various combinations of H and C atoms. The H burns to H2O, the C to CO2. A hydrocarbon with a greater quantity of H is going to emit less CO2 when burned.
Sure, but H weighs 1/12 as much as C. Most of the fuel mass goes to CO2 no matter what you do: whether you slap on 1.5 H atoms or 3 for each C, it makes up a small part of the molecular weight.
Of course, it could be that the C-H bonds contribute much more to the energy released by burning the fuel than the C-C. But this doesn't seem to be case. Here's a paper in favour of switching to lighter fuels for ships: it argues that the total supply chain CO2 contribution would be higher (it takes energy to refine those fuels), but only by 1%.
I think that "bunker fuel is really bad and ships switching to lighter cleaner fuels is important for the environment" is a seductively easy but bad target for carbon reduction. There are way better places to spend our efforts.
> There are way better places to spend our efforts.
The easiest, most economically efficient, most productive way to do it is to tax the C content of fuels. Use the monies raised to subsidize green energy.
Banning is an indiscriminate club that does a lot of collateral damage.
But that's exactly what wouldn't be suitable for reducing pollution from bunker fuel. Shippers would pay the same taxes as for burning kerosene or diesel, plus or minus a few percent, but they'd go with the cheaper option and cause huge sulphur pollution in port cities.
The regulations we have now (no high-sulphur fuels in cities, no leaded gasoline...) are better than taxing only CO2 emissions, even if they're not perfect.
So do the obvious - tax the sulfur content of the fuels, too.
The problem with banning is its inflexibility. For example, let's say you have a bunker-fueled emergency generator for a hospital that you use only when the power goes out. The pollution it emits is negligible. But by banning bunker fuel, you'll have to replace the emergency generator, at considerable expense and environmental cost.
With taxes instead, you:
1. bunker fuel will only be used when there's high value for it, and you won't have to add a plethora of exemptions into the regulation
2. have a revenue center for the government instead of a cost center - revenue that can be used to subsidize green initiatives
