Phosphorus Release from Sewage Sludge Incinerator Ash.

The Twin Cities incinerate sewage sludge for energy. Research has shown that the remaining biosolids ash, which is usually landfilled, can be a viable phosphorus source for crops. However, there are questions regarding the behavior of P release, the amount of plant available P compared to total P, and concentrations of metals of concern. To determine the viability of this ash as a P fertilizer, we conducted a 64 day soil incubation comparing this ash to conventional P fertilizer (TSP), dried pelletized biosolids, struvite, and a German ash product which has been thermochemically treated to decrease the metals content and increase P solubility. Each P source was applied at 40, 80, 120, and 160 lb P₂O₅/acre, with a zero-P control included, and soil samples were taken at 0, 2, 4, 8, 16, 32, 64 days. Samples were analyzed for available P and EPA 503 metals. Results from the first 32 days will be presented.