It just so happens I tried this experiment and I couldn't get it work. I didn't add any scoby, but I did add some kombucha tea to my jar of sweet ginger water to try to get it going. Supposedly it would start by itself with non irradiated ginger if some peel was included, but mine didn't seem to be doing it. Adding the kombucha tea didn't seem to get it going either. Finally I added some lavalin champagne yeast and now it is fizzing away nicely.