Recycling Cow Bone Wastes for Novel Slow-Release Phosphorus Fertilizer

• Kayla Neal, Biological Sciences, James Madison University

• Deb Jaisi, Department of Plant and Soil Sciences, University of Delaware

Phosphorus (P) is an essential nutrient for all life on earth. Agricultural plants need supplant P for crop productivity. However, oftentimes commercial P fertilizers are not sustainably sourced and have P release rates that don’t Synchronize with the plants demands. This may lead to P build up in soils, run off, and ultimately deteriorate water quality such as by algal blooms and hypoxia. This study investigated the structure and dissolution kinetics of hydroxyapatite nanoparticles (HANP), a novel form of high-efficiency P fertilizer, recovered from cow femur and scapulae. The femur was fragmented and autoclaved for sterilization, and then calcined to remove organics, which was followed by ball milling to generate HANP. Micrometric calcinated hydroxyapatite (HAMPs) was also analyzed for comparing structure and morphology with HANPs, using DSC, XRD, and TEM techniques. Further, dissolution characteristics of HANPs and HAMPs were assessed in citric acid buffer (pH 4.8) using microfiltration flow-through system. Dissolved P and residual HANP/HAMP were collected at different time points and analyzed. The results show that both materials were composed of hydroxyapatite. As expected, HANP exhibited more amorphous structures and smaller particle size ranges than that in HAMP. TEM images revealed particle size of 10-2,000 nm in HANP, and 1–100 µm in HAMPs. Early dissolution revealed higher P release from HANP (15–60 µgP) followed by a steady decrease (60–12µgP), most likely due to gradual exhaustion of amorphous materials. In HAMPs, the P release was one order of magnitude lower, but also exhibited an inverted-U trend. The sharp increase of pH followed by decrease and then became steady was observed in HANPs but was a smooth variation for HAMPs. Overall, these findings highlight the dissolution extent and kinetics could be significantly changed by treating bone sourced HANP, thus can be tuned for specific crops.