[K2] Solid fuel is a dead end?

[NineNine]

I'm playing K2 for the first time, and I think I might be missing something very obvious: What is supposed to happen to all of the solid fuel? You can't use it to make rocket fuel, and you make plenty of it to deal with by-products from refining (light oil/heavy oil/petroleum gas). So, am I just missing some recipe that uses a lot of solid fuel?