Bio-based compounds from synergistic processing of bone waste via advanced ultrasound assisted-enzymatic pretreatment and fast pyrolysis

This study investigates the synergistic processing of chicken bone waste through a novel combination of advanced ultrasound-assisted enzymatic pretreatment and fast pyrolysis conditions (500–900 °C, ∼100 °C/min). The higher process temperature inhibits CO₂, and promotes ≥ C₂, CH₄, CO and H₂. The pyrolysis gas energetic potential reaches a maximum of 33 MJ/Nm3, thus can serve as biofuel. The bio-oil derived from the pyrolysis of feedstock, whether pretreated by classical or enzymatic methods, yields rich in N-heterocycles. At ≥ 700 °C, bio-oil contains more heterocyclic compounds and hydrocarbons. Pyrolysis of enzymatically pretreated feedstock results in higher concentrations of pyrrole and pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro, which are valuable for the synthesis of organonitrogen compounds relevant to the agriculture, pharmaceutical and advanced materials industries. The H/C < 0.7 and O/C < 0.28 ratios, together with the phosphorus content, indicated a stable high-quality biochar. The increase of process temperature decreases biochar yield, doubles ash content, promotes density and improves thermal stability. The total heat absorbed increases from 22 kJ (500 °C) to 39 kJ (900 °C), indicating a moderate energy demand for pyrolysis. This synergistic processing promotes sustainable poultry waste management and facilitates the circular utilisation of bio-based, compound-oriented products, for their potential use as renewable gases, green chemicals and functional biochar.