Many sourdough techniques suggest throwing away half your starter further on in the fermenting process. The reason given (in many YouTube videos I've watched) is that it'd eventually take over your kitchen if you didn't.
I guess rather than throw this away I can give it to a friend (or friends) to bootstrap their own starters?
Sure, you can begin a new sour dough starter with the discard from a feeding. However, the reason for discarding isn't simply to reduce the amount. As your starter matures it also becomes much more acidic. Acidity is problematic for yeast and bacterial activity and, ultimately, the rise and flavor of your final product. So, you discard during feeding time to keep the acidity in check, and ensure that your starter is as hospitable to yeast and bacteria as possible. Your friend can get his or her starter going with your discard, but will then want to get into the habit of discarding when they feed.
Absolutely you can. When you use the starter to make bread you make an arbitrary decision of which part of the starter you use and which to feed, the part you scoop out is just as viable as the part you keep. When you discard some instead of using it the same rule applies, so all you need to do is put some in a container and feed it the same way. You can split the starter as many times as you like, that's the beauty of it.
