Chicharito,
I understand that you can ferment pretty much anything with just salt water. The reason that I use the whey is that it cuts down on the amount of salt that you have to use. I feel like I already get too much salt in my diet, between the (sugar free) smoked fish, canned fish, umboshi paste and general seasoning.
Good luck.
I just tasted my batch of purple cabbage sauerkraut... I put too much salt in it
It was my second batch and for some reason I thought I didn't need to measure the salt I needed.
I'm going to have to try doing it with whey, as you mentioned. I'm no longer eating greek yogurt but I guess I will have to make a sacrifice

I will have to start it with store bought yogurt tho, and those always have starch and very little live cultures..
Is there anyway I can save this sauerkraut? I have a feeling that the batch with carrots will be the same case...