What are the different liquid mediums used in steam power?

I would like to learn what the alternatives to regular water for a steam engine for a car. Is there enough "potable" water? How about using "waste water"? Would Anti-freeze work.? Is there a easily produced synthetic? If people were to use steam, water would be good, but would the increased usage deplete what we need? perhaps soy could be used or kudzu-these being a readily available source. Anyway, I'm looking at the various ways to enable us to the very efficient engine-Steam engines rank as top 2 most efficient engines available. So, any help in the department by any Chemistry or Steam Engineers please let me know.

What are the different liquid mediums used in steam power?
Economics trumps everything. Antifreeze might work, but it has to be manufactured, it costs money, it's toxic, and it has to be recovered after it does its thing in the turbine or piston. Water is ubiquitous, virtually free, and non-polluting - you can let the steam fly out the back of the turbine all you want. The water/steam isn't being destroyed - it evaporates and comes back to us as rain. Better to use the kudzu/soy as fuel to heat the water to steam. I would think you would want your water to be as clean as possible, within economic limits - i.e., it is not necessary to distill the water, or subject it to some other expensive or energy intensive cleaning process.





I like your idea, but personally would be looking for more efficient ways to heat the water to boiling.