Effect of Pyrolysis Treatment on Phosphorus Migration and Transformation of Pig, Cow and Sheep Manure

Abstract

Pig, cow, and sheep manure (PM, CM, and SM) are inevitable byproducts of agricultural economic development. Converting them into high add-on value biochar (PMB, CMB, and SMB) via pyrolysis is an efficient resource utilization measure. Phosphorus (P) speciation analyses help ensure the practical feasibility of the P reclamation of animal manure and their derived biochar and a reduction in environmental risk. This study conducted a modified extraction procedure to separate five inorganic P (IP) (soluble and loosely bound IP, aluminum-bound IP, Fe-bound IP, oxide-occluded IP, and Ca-bound IP) and organic P (OP) speciations, and combined X-ray diffraction (XRD) to investigate the major phosphate compound in the derived biochar after pyrolysis. Results revealed that more than 92% of P is concentrated in the derived biochar during pyrolysis processes carried out at 200–800 °C. The percentages of soluble and loosely bound IP, aluminum-bound IP, and OP in manure decreased significantly due to their transformation into more stable P fractions such as Ca-bound IP (79.01% in PMB, 800 °C) after pyrolysis. The Olsen-P percentages had a distinct reduction at 650 °C, indicating that pyrolysis at 650 °C was the optimal condition for the reduction in Olsen-P in manure.