You probably don’t think about “waste” when you’re eating a slice of cheddar. But the cheese industry has a massive environmental secret: for every one pound of hard cheese produced, about nine pounds of liquid whey are left behind.

This isn’t just water. This leftover “acid whey” is an environmental nightmare, an organic-rich sludge that can starve rivers of oxygen if dumped. For decades, dairies have paid to have it trucked away or spent energy processing it into protein powders. But what if there was a better way?