You can buy sourdough starter from King Arthur. Discard is a by-product of feeding your starter and, like fresh starter, is a live, active culture that requires feeding/maintenance and can’t be frozen, so it isn’t something likely to appear in supermarkets (unless in a dried version). The quickest way to get in the game is to find a friend who’ll share their starter and some of their discard with you. In my community, word spreads, and I’ve happily shared mine with several neighbors.
I have a crock with a healthy amount of discard at all times. I plan to make waffles with it this Sunday morning for our son and new DIL who arrive on Friday (my Christmas).
Active starter (jar) vs. discard (crock):
