Thermal drying takes soil-like biosolids cake (high water content) to a dry, hard granule (minimal water content) with a Class A pathogen status. Various thermal drying technologies are commercially available, and produce granules of different quality and size. These granules can be further processed into uniform pellets for landscaping uses. An example, Milorganite, made by the Milwaukee Metropolitan Sewer District is a thermally dried product, and has been manufactured for nearly a century. Small and large utilities across the country make biosolids granules for a range of beneficial uses.
Also see, Thermal Drying.