Sourdough starters are a baker’s treasure, and rather a pain in the ass. If neglected, the starter will expire in a puddle of gray, watery goo. If tended carefully and fed weekly, you’ll end up with either mountains of starter or have to throw out perfectly good starter to prevent a “Blob”-style overflow.
Enter the pizza: I’ve been patting out mature sourdough starter onto parchment paper, laying on the toppings, and baking it fast & hot (on a pizza stone in a 500-degree oven). While it isn’t the best pizza ever, the starter pizza is very edible. I tried this some time ago in the toaster oven, but the full-size oven’s greater heat definitely produces better pizza.
Rather than discard your excess starter, try making pizza….