Closing the Loop for Nutrients in Livestock Wastes: Phosphorus Recovery from Animal Manure.

Repeated land application of large amounts of manure from confined livestock facilities is an environmental concern often associated to excess phosphorus (P) in soils and potential pollution of water resources. Animal waste treatments that include recovery of P from manure are a management option that can resolve problems on excess application of P manure to land. The aspect of P recovery and reuse is important for the global cycling of this nutrient because unlike N, P world reserves are limited. This presentation will report the results of new treatment processes developed by USDA-ARS to recover P from manure in concentrated form from both liquid swine manure and solid poultry litter as calcium phosphate materials. The P concentration in these recovered P materials is sufficiently high to suggest that they can be transported off the farm and used as a fertilizer source without further chemical processing, such as the acid treatment typically used to process rock phosphate for fertilizer manufacture.