“It takes a lot of energy to produce milk,” Albert Straus tells us almost immediately after we arrive at his dairy. He would know. Straus owns and runs the Straus Family Dairy and a nearby creamery in Tomales Bay, just north of San Francisco. With knee-high boots trudging through mud, Straus shows us the 300 cows he manages, a herd whose milk becomes cheese, ice cream, butter, and yogurt that gets distributed across much of the U.S.

That’s the clean story. Making sure that the rest of us get our ice cream requires Straus to deal with a less palatable part of farming. Every day, each of his cows produce 120 pounds of manure. Added together, it amounts to a mountain