Optimization of chicken manure combustion parameters in the aspect of phosphorus recovery

Purpose The increasing demand for phosphorus for the production of mineral fertilizers forces the continuous development of research and new technologies in the field of obtaining it from sources other than phosphate rocks. This paper presents an analysis of optimizing the combustion parameters of chicken manure in the aspect of phosphorus recovery. Methods The combustion process was carried out in different time (3-8 hours) and temperatures (700-900^oC) in laboratory of electric furnace. The content of macro and micronutrients was determined by XRF and ICP-OES analysis. To identify the mineral composition of ashes, the XRD analysis was applied. The content of total phosphorus in ash extracts was determined by photometric method. Results Concentration of P₂ O₅ in ash samples detected by ICP-OES and XRF was comparable, 30.37 wt.% and 31.77 wt.% at 900^oC, 26.27 wt.% and 26.71 wt.% at 700^oC and 25.31 wt.% and 25.00 wt.% at 500^oC, respec-tively. The mineral composition of ashes showed two phases: crystalline and amorphous. The estimated values of P₂ O₅ content in crystalline phase was 14.83 wt.% at 500^oC, 20.96 wt.% at 700^oC and 23.80 wt.% at 900^oC. The estimated P₂ O₅ content in amorphous phase was 10.48 wt.% at 500^oC and decreased at higher temperature to 5.31 wt.% at 700^oC and 6.57 wt.% at 900^oC. Conclusion The chemical composition of ashes from chicken manure depends on the combustion temperature. The highest concentration of phosphorus in their bioavailable forms was determined for samples burned in 500^oC. The results indicate that a valuable source of phosphorus is the amorphous phase.