The Orange Water and Sewer Authority’s (OWASA) Mason Farm WWTP in Chapel Hill, North Carolina has produced a Class B biosolids product for many years that has been used for agricultural purposes. The biosolids have been produced by mesophilic anaerobic digestion. The facility is nearing full capacity, so changes have been planned that would both increase capacity and allow production of a Class A product. OWASA’s previous experience with anaerobic digestion processes, as well as preliminary site-specific economic calculations, led them to select thermophilic anaerobic digestion upstream of the existing mesophilic anaerobic digestion.