I cannot produce sulfur. The recipe requires water and sour gas, but sour gas can only be produced after unlocking advanced oil processing, which requires Blue Science. However, Blue Science itself requires sulfur.

All alternative recipes (tar, diesel, heavy oil, etc.) are also locked behind Blue Science, so there is no accessible early-game source of sour gas or sulfur.

Basic oil processing produces sour gas. If this isn't the case for you, some other mod has changed things.

Thanks for the quick reply. I investigated further and found the issue: the conflict was caused by the AAI Industry mod. It completely rewrites the basic oil processing recipe (including inputs and outputs), which overwrote the sour-gas changes from Scrap Chemistry.

After reviewing what AAI Industry changes, I decided to disable it and continue playing with Scrap Chemistry only.
With AAI removed, all recipes work correctly and sour gas appears as intended.

Thanks again for the help!

Hi WilliamMyth, thanks for the report. This is fortunately a known issue and it's on my list of things to add compatibility for.

I submitted potential compat fix for AAI Industry. I wasn't able to reproduce the issue locally, but in theory this might fix it. Let me know if you see otherwise :)