On a cool late-spring day, lifelong farmer Dan Crouch looks out over row after row of still-green wheat as he contemplates the July harvest on his land 40 miles east of Denver. Sixty-seven-year-old Crouch reminisces for a moment. He still remembers the old days when his family tilled the soil and didn’t use fertilizer. 

But farming is different today. Tilling has long been considered unsustainable in Colorado because of the dry climate, and Crouch, like many farmers, began adding fertilizer to his fields about 25 years ago. At first he used anhydrous ammonia, but over the years, he learned the chemical fertilizer had multiple drawbacks: The big problem, aside from its hazardous properties, Crouch says, is, “All you get there is nitrogen. There’s nothing else in it. And it’s expensive.”

So he started looking for alternatives—and, about 10 years ago, found one called Metrogro. In addition to supplying the necessary nitrogen, it’s rich in phosphorus and zinc, nutrients critical for plant growth. “It has measurably improved my soil,” Crouch says, which has in turn improved his crop and, at times, his profit.

The soft-spoken farmer is not alone in his support of Metrogro, which is permitted for use on nearly 400 Colorado farms that grow much of the state’s wheat, as well as tons of commercial grains such as corn and millet. But Crouch and other Colorado farmers can’t buy Metrogro from their typical agricultural suppliers. Metrogro is what you might call a special-order product—one that’s produced by, of all places, the facility that treats Denver’s sewage.

Yes, you read that right. Metrogro, which does a miraculous job of closing the nutrient-recycling loop by restoring to the soil minerals essential to crops, is made of “biosolids,” which is really just a fancy—and more palatable—way of saying highly treated human waste.