From a broad search, it seems that much of the downstream market for whey byproduct of yogurt and cheese production has plenty of uses. In this article by the USDA (http://www.rurdev.usda.gov/rbs/pub/mar08/whey.htm), it discusses dairy farm cooperatives turning the Lactose sugars, of which 5% of the "waste whey," is used for ethanol production. Whether there is a difference between acid or sweet whey, I am unsure, however there is certainly a demand for the byproducts of the dairy/cheese/yogurt industries.