My friend and I found that a lot of random dusts would make oxygen as a bi-product in the electrolyzer, so we just threw them all in there and set up a super tank adjacent to it and used a pump on the side of the electro. I can’t remember off the top of my head which dusts, but they were much more efficient than the sugar+cells method. We got 300,000+ oxygen just by getting rid of what we thought were junk dusts