TY - JOUR
T1 - Phosphorus Fractionation of Dairy Processing Waste Recycled Fertilizers Reveals Inadequacy of the Standards, Measurement and Testing (SMT) Protocol
AU - Velasco-Sánchez,
AU - Khalaf, N.
AU - Leahy, J. J.
AU - Bennegadi-Laurent, N.
AU - Trinsoutrot-Gattin, I.
AU - Van Groenigen, J. W.
AU - Moinet, G. Y.K.
N1 - Publisher Copyright:
© 2025 The Author(s). Published with license by Taylor & Francis Group, LLC.
PY - 2025
Y1 - 2025
N2 - The Standards, Measurements and Testing (SMT) protocol is widely used to fractionate phosphorus (P); however, it lacks the focus on defining the solubility of P-fractions, which is usually performed independently. In this paper, the addition of a separate pre-wash step with H2O as a first step prior to the SMT protocol was tested to account for the solubility of P. Results were compared to a control unmodified SMT experiment. The differences in P-fractions were analyzed to determine the origin of the readily available P (soluble P). Six different dairy processing waste treatment products were investigated in the form of sludge, hydrochar, and ash. Water-soluble P (WSP) was correlated with weakly bound calcium (Ca), aluminum (Al) and iron (Fe). However, the SMT protocol failed to correctly identify the different pools of P as unexpected correlations were found between P and Ca, Al and Fe. Moreover, large concentrations of organic P were present in ashes (>10 mg P g−1). The organic P fraction included substantial amounts of Fe that correlated highly with P (R2 = 0.84). No association between WSP and any of the pools of P defined by SMT was detected, with the exception of total P and inorganic P. The paper concludes that SMT erroneously classifies P into different discrete fractions across various recycled P-products with fertilizer potential. A critical reevaluation of the SMT protocol is recommended, by abandoning the categorization of P into discrete pools and switching to solvent-based categories referring to the chemicals used in each extraction.
AB - The Standards, Measurements and Testing (SMT) protocol is widely used to fractionate phosphorus (P); however, it lacks the focus on defining the solubility of P-fractions, which is usually performed independently. In this paper, the addition of a separate pre-wash step with H2O as a first step prior to the SMT protocol was tested to account for the solubility of P. Results were compared to a control unmodified SMT experiment. The differences in P-fractions were analyzed to determine the origin of the readily available P (soluble P). Six different dairy processing waste treatment products were investigated in the form of sludge, hydrochar, and ash. Water-soluble P (WSP) was correlated with weakly bound calcium (Ca), aluminum (Al) and iron (Fe). However, the SMT protocol failed to correctly identify the different pools of P as unexpected correlations were found between P and Ca, Al and Fe. Moreover, large concentrations of organic P were present in ashes (>10 mg P g−1). The organic P fraction included substantial amounts of Fe that correlated highly with P (R2 = 0.84). No association between WSP and any of the pools of P defined by SMT was detected, with the exception of total P and inorganic P. The paper concludes that SMT erroneously classifies P into different discrete fractions across various recycled P-products with fertilizer potential. A critical reevaluation of the SMT protocol is recommended, by abandoning the categorization of P into discrete pools and switching to solvent-based categories referring to the chemicals used in each extraction.
KW - Dairy processing waste
KW - fertilizers
KW - fractionation
KW - phosphorus
KW - solubility
UR - http://www.scopus.com/inward/record.url?scp=85214942972&partnerID=8YFLogxK
U2 - 10.1080/00103624.2025.2452167
DO - 10.1080/00103624.2025.2452167
M3 - Article
AN - SCOPUS:85214942972
SN - 0010-3624
JO - Communications in Soil Science and Plant Analysis
JF - Communications in Soil Science and Plant Analysis
ER -