Optimizing pyrolysis conditions for recycling pig bones into phosphate fertilizer

Area of Science:

• Biomass Pyrolysis
• Waste Valorization
• Fertilizer Technology

Background:

• Recycling phosphorus-rich biowastes like bones into fertilizers is challenging.
• Pyrolysis is a potential method for converting bones into phosphorus (P) fertilizers.
• Optimizing pyrolysis parameters is crucial for producing effective P fertilizers from bone waste.

Purpose of the Study:

• To improve pyrolysis procedures for pig bones to produce enhanced P fertilizers.
• To investigate the impact of different pyrolysis conditions on bone char properties.
• To assess the suitability of produced bone chars as P fertilizers.

Main Methods:

• Bone chars were produced via pyrolysis at various temperatures (400, 550, 800 °C) and atmospheres (no gas, N2, steam).
• Calcination at 800 °C served as a control treatment.
• Synchrotron-based X-ray diffraction and X-ray absorption spectroscopy were used to analyze bone char composition and structure.

Main Results:

• Bone chars were primarily composed of hydroxyapatite.
• Pyrolysis in the absence of oxygen inhibited hydroxyapatite crystallization.
• Bone chars produced at 550 and 800 °C without oxygen exhibited higher porosity, surface area, and citric-acid soluble P compared to steamed or calcined samples.

Conclusions:

• Pyrolysis conditions significantly influence the chemical, physical, and crystallographic properties of bone chars.
• Optimized pyrolysis can yield bone chars with tailored properties for P fertilizer applications.
• Bone chars can be designed for either high solubility or slow phosphorus release.