PS. And it's worth noting that carbonyl sulfide photolyzes in the upper atmosphere, so it wouldn't stick around unless there's some kind of replenishment.
And why doesn't it photolyze in Venus' atmosphere? It must be made abiotically there, since we have no signs there is life as we know it on Venus.
Gasification processes are abiotic, but use bio stuff like coal and garbage as feed stocks. They produce hydrogen, carbon dioxide, carbon monoxide and small amounts of carbonyl sulfide and carbon disulfide.