Greek yogurt is a delicious dairy product that’s produced by taking regular yogurt and straining it to a delicious, protein-rich thickness. The thing is, though, all of that straining means that you’re straining something out of the yogurt. That something is more than water: it’s post-fermentation liquid called acid whey. For every three or four ounces of milk that enter a yogurt plant, one ounce of acid whey leaves. They can’t dump it in sewage systems or waterways, and at least one manufacturer actually pays local farmers to take the liquid whey away and do something with it.