Phosphorus recovery from pig manure solids prior to land application.

ABSTRACT

Land disposal of pig manure is an environmental concern due to an imbalance of the nitrogen to phosphorus (NP) ratio for crop production, leading to excess phosphorus (P) in soils and potential risks of water pollution. A process called "quick wash" was investigated for its feasibility to extract and recover P from pig manure solids. This process consists of selective dissolution of P from solid manure into a liquid extract using mineral or organic acid solutions, and recovery of P from the liquid extract by adding lime and an organic polymer to form a P precipitate. Laboratory tests confirmed the quick wash process selectively removed and recovered up to 90% of the total (TP) from fresh pig manure solids while leaving significant amounts of nitrogen (N) in the washed manure residue. As a result of manure P extraction, the washed solid residue became environmentally safer for land application with a more balanced NP ratio for crop production. The recovered P can be recycled and used as fertilizer for crop production while minimizing manure P losses into the environment.