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.

A Review on the Removal of Heavy Metals from Water by Phosphorus-Enriched Biochar

“…The content and proportion of these compounds in plants are determined by factors such as plant species, varieties, growth stages, and organs [30]. 31 P NMR analysis of phosphorus forms in plant-derived waste reveals that organophosphorus accounts for 40%-70% of the total extractable phosphorus [26]. Feed materials like crop seeds and bran contain a significant amount of phosphorus in the form of phytic acid phosphorus (60%-80%).…”

“…The varying utilization of phytic acid in the feed of different animal species contributes to the heterogeneity of phosphorus content in feces. Furthermore, different way of rearing (distributed and intensive) and the use of feed additives (such as inorganic phosphate and phytase) also lead to differences in manure phosphorus content [31]. Animal residues, with representatives such as animal bones and fish scales as calcium and phosphorus precursors, and seafood shells as calcium precursors, serve as crucial raw materials for the thermal synthesis of hydroxyapatite [32].…”

“…Xu [50] demonstrated that pyrolysis temperature is the primary factor determining phosphorus stability using the Hedley protocol, as well as solid-phase and liquid-phase 31 P NMR. Additionally, as an inorganic mineral element, phosphorus continues to accumulate in pyrochar over prolonged residence times (<2 h), with the total phosphorus content gradually increasing until it reaches stability [51].…”