Small suggestion/request: it would be nice if we could use Low Grade Fuel in fireplaces and furnaces as fuel (in the same way we currently use Wood as fuel). If you really want to put some spin on it, you could also have reactions fueled by Low Grade Fuel progress more quickly than reactions fueled by Wood (for example, Metal Ore produces Metal Fragments 2x faster when Low Grade Fuel is used relative to Wood).
Fuel wouldn’t really work as a primary smelting ingredient, just because of how much harder to get it is than wood. If they added a feature where you cook the ore with wood, but can add in fuel to temporarily speed up the process, that might work, but I don’t think it would be worth it to load up a furnace with loads of fuel and burn away all that cloth and fat.
Also the ability to use fuel for a flamethrower.
I still want low tier lamps powered by animalfat