Current Incentives for Phosphorus Recovery

The over-application of phosphorus, as manure by animal feeding operations, is a threat to surface water quality. Concentration of animal feeding operations and over application of manures to cropland has lead to a build-up of phosphorus on many farms (Greaves et al., 1999). Relative to crop needs, manure slurries contain higher levels of phosphorus than nitrogen. When manure is applied to meet crop nitrogen needs, phosphorus is over applied. Recent laboratory studies show that phosphorus content in swine manure can be reduced by recovering a portion of the phosphorous as a crystalline precipitate containing struvite (magnesium ammonium phosphate hexahydrate, MgNH4PO4·6H2O) (Beal et al., 1999; Burns et al., 2001; Kalyuzhnyi et al., 2001, Nelson et al., 2000; Wrigley et al., 1992). Precipitation of phosphorus prior to land application of manure offers the potential to recover excess phosphorus from manures and move it to cropping areas that require phosphorus fertilizer inputs. The cost effective relocation of excess phosphorus would allow existing animal feeding operations to successfully implement phosphorus-based nutrient management plans on their current land base. Proposed EPA regulations regarding concentrated animal feedin