Enhancing phosphorus recovery from poultry litter ash through microwave-assisted thermochemical treatment for improving its solubility

This study explores for the first time the P recovery from poultry litter ash (PLA) using microwave-assisted thermochemical treatment, aiming to improve its bioavailability for utilization as a fertilizer. PLA samples, originating from laying hens' manure incineration, were subjected to microwave treatment with the addition of sodium bicarbonate, and their physical-chemical characteristics were analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The results indicate that the microwave treatment led to the formation of NaCaPO₄ crystals, with a significant increase in P solubility post-treatment, which is crucial for plant uptake. Moreover, increasing the amorphous content of the ash led to a decrease in P solubility because sodium atoms tend to diffuse within the silica network. However, in this case, interesting glass materials with promising optical properties may be obtained. This study provides a novel approach to valorizing biowaste and contributes to sustainable phosphorus management practices.