any fluid with a fuel value can be used in barrel form
Mods introducing new content into the game.
Things related to oil and other fluids.
Changes to power production and distribution.
How about adding a fuel_emissions_multiplier to the standard liquid fuels?
This way you could add additional incentive to use barreled fuel.
Just created a mod to do this by the name of Fuel Customizer. seemed too useful not to.