Gasification Unit , Coal , wood, biomass = fuel gas + exhaust

Add a Gasification unit to the game.
This could be fairly basic, Coal, wood or biomass = fuel gas + exhaust

this could be expanded with the Air separator, call the output of the gasifier Syngas, and make it 100% compatible with fuel gas, but if you run it through an air separator it will output two streams hydrogen, and fuel gas.

a path to reform this output to naphtha and diesel would be really nice and would match existing tech

This would allow islands with double coal and no oil , like Sweden in WW2 with gasifire powered cars and tanks.

the inputs of the gasifier could be expanded to could burn oils , this was done and predated moden refining , Agriculter outputs too like corn , feed ect , in a Mark 2 vers maybe have some steam output from the pyrolysis heat

ref
https://en.wikipedia.org/wiki/Gasification

https://en.wikipedia.org/wiki/History_of_manufactured_fuel_gases
see the list of gases at the bottom of this long page.