Dairy digesters are facilities that create biogas, also known as biomethane, from wet manure from large, confined animal feeding operations (CAFOs). The gas is then injected into pipelines or, possibly, used as transportation fuel. Biomethane is not clean; burning manure-produced gas emits the same air contaminants as the combustion of fossil fuel, and releases other harmful pollutants into the air and water that are unique to factory farms.