Yes that is right. I think improvements should be made to a fairly useless already existing element. First thing is first. We know that YEST has reproducing properties in the game. But what it needs is to produce an element. I propose that if YEST is "fed" it will produce CO2, WATR, and a flammable liquid. All of this will happen only when  YEST has the right temp, food, and O2. If it doesnt have those, it will act the same way as it does now. I can see a lot of uses for this including factory creations, self fueling powerplants, and potentially bombs. I would love to hear feedback on this. 

Sorry I havent been able to reply to the feedback. Work gets in the way. I understand you can make a powerplant with yest right now but it would be a bit boring. (I have seen them) As far as the "food" goes, I would have to say the closest thing to food in tpt is plnt. Which would actually work pretty well IMO. I have a very old mod (pre C++) that had an improved version of yest that made alcohol and I gave alcohol interesting properties like turning into gas and being able to condense back with cooler temps. (Distilling it) but I dont have it anymore. I just want to see if we can make yest more valuable to powdertoy.