Well, someone needs to treat the hydrogen sulphide with excess methanol over an aluminium oxide catalyst. I suppose a robot could do it...
For a non-life explanation, you're really looking for something that could plausibly happen in (abiotic) nature, not an industrial process.
The only thing that could make a nerd happier than detecting alien life would be detecting alien robots.
Wait, what's the difference?
Alien life could just be microbial, while alien robots would require an advanced technological civilization, I guess
Well, there could be nanobots...