A few years ago, a new product hit your grocer’s dairy case seemingly out of nowhere: Greek yogurt. It’s an extra-thick, extra-creamy, and protein-heavy version of. The main difference, besides the thick, almost cheesecake-like consistency: There’s very little liquid in a container. Popular brands include Yoplait and Chobani. And Ben and Jerry’s has a frozen version. How popular is Greek yogurt? In New York state alone, production at yogurt plants has tripled over the last five years to more than a billion pounds per year. Want to know the truth about Greek yogurt?

Greek yogurt is made by vigorously straining regular yogurt—that’s why it’s so thick and liquid-free. In fact, it takes four ounces of milk to ultimately result in just one ounce of Greek yogurt. The liquid that’s removed is called acid whey, or sour whey, and consists of water, along with lactose (milk sugar), some proteins, and yogurt cultures. Sounds organic and harmless, right? Wrong. It’s apparently so toxic and disruptive to living things that it’s illegal to dump it. If it gets into waterways, the cultures and proteins absorb so much oxygen that it kills fish.

So if they can’t dump it—as some producers have been doing—what else can they do with it? They’re selling it back to dairy farmers. It’s blended into feed and fertilizer…and fed back to the same kind of dairy cows that made the milk that made the yogurt that made the acid whey.

(Image source: Flickr/nemuneko.jc)