Do you have any other use for excess sourdough starter aside from giving it to friends?
Yes! When I feed my starter, if I know i'm going to bake a hearth bread within the next 3 days, instead of throwing out the excess, without refreshing or feeding it I simply refrigerate up to 1/3 cup starter (about 2.75 ounces / 75 grams) per loaf. Just before adding the salt to the dough, I tear the starter into about 8 pieces and knead it into the dough.
The starter dough adds extra depth of flavor and moisture, and also speeds the fermentation (rising) slightly even in a dough using the usual amount of instant yeast. (You should also add an extra 1/8 teaspoon plus 1/16th teaspoon of salt to balance this extra amount of dough--less if using less starter dough.)
The starter dough serves as a "preferment" making it possible to use the quicker "direct" method of mixing the dough. (Simply combine the flour and yeast from the sponge or biga in the recipe with the flour and yeast for the dough.)