I'm asking because I only have a passing familiarity with how oil production works.
>> "It can't be cracked economically?"
This trash oil is produced anyway. There's no way to not make it and still make the less dirty kinds since it's what's left at the end of the process.
I see two possible solutions:
1: Invent commercial fusion reactors and burn it there. I don't know if this would produce less CO2.
2: Find something else to do with the trash oil that's less polluting. Markets are pretty good at finding uses for things, so there may just not be anything else.
Gasoline was a waste product until internal combustion engines came along. Trash oil probably occupied a similar status as waste until someone figured out it worked in ships. If trash oil were no longer economical to burn on ships, they would probably dump it in international waters instead unless some better use was incentivized.
The US and probably other countries pay farmers to destroy some crops to keep it profitable enough to make farming a viable industry. Farmers would sell all their crops without government intervention, driving profits below a sustainable level. They wouldn't just trash it otherwise.
Cargo ship owners are probably the only people who want the leftover oil. The shipping industry burns the oil industry's trash to make their ships go. Make using it uneconomical, and it gets dumped. That's what happens with byproducts no one wants to buy.
https://en.wikipedia.org/wiki/Fuel_oil
>> "Small molecules like those in propane, naphtha, gasoline for cars, and jet fuel have relatively low boiling points, and they are removed at the start of the fractional distillation process. Heavier petroleum products like diesel fuel and lubricating oil are much less volatile and distill out more slowly, while bunker oil is literally the bottom of the barrel; in oil distilling, the only things denser than bunker fuel are carbon black feedstock and bituminous residue (asphalt), which is used for paving roads and sealing roofs. "