Oxalic Acid Boosts Phosphorus Release from Sewage Sludge Biochar: A Key Mechanism for Biochar-Based Fertilizers

Oxalic Acid Boosts Phosphorus Release from Sewage Sludge Biochar: A Key Mechanism for Biochar-Based Fertilizers

Sewage sludge biochar (SSB) exhibits higher phosphorus (P) concentrations than the original sewage sludge (SS) and can be used as a P fertilizer. However, SSB-associated P is strongly retained in chemical compounds, which hinders its release and subsequent plant uptake. The use of organic acids faci...

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Bibliographic Details
Published in:Agriculture (Basel) Vol. 14; no. 9; p. 1607
Main Authors: Santos, Marcela Granato Barbosa dos, Costa, Camila Rodrigues, Mendes, Gilberto de Oliveira, Blasi Paiva, Andressa, Peixoto, Ludmila Soares, Costa, Jéssica da Luz, Marchi, Giuliano, Ma, Figueiredo, Cícero Célio de
Format: Journal Article
Language:English
Published: Basel MDPI AG 01-09-2024
Subjects:
Acidic soils
Apatite
biosolids
Charcoal
Chemical compounds
Fertilizers
Heavy metals
Minerals
Organic acids
Organic soils
Oxalates
Oxalic acid
Pathogens
Phosphorus
Pollutants
Product introduction
Purification
pyrolysis
Sewage
Sewage sludge
Sludge
Soil treatment
Solubilization
Speciation
Temperature
thermal treatment
Brazil
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Summary:Sewage sludge biochar (SSB) exhibits higher phosphorus (P) concentrations than the original sewage sludge (SS) and can be used as a P fertilizer. However, SSB-associated P is strongly retained in chemical compounds, which hinders its release and subsequent plant uptake. The use of organic acids facilitates P solubilization from SSB. Herein, we evaluated the effect of oxalic acid on P release from SSB applied to soil over time. Biochar was produced at 300 °C (SSB300) and 500 °C (SSB500). P release from SSB increased with an increasing concentration of oxalic acid in the SSB incubation solution and in SSB-treated soil. P speciation in SSB showed that P was predominantly inorganic (P[sub.i]), which represented 81% and 92% of the total P in SSB300 and SSB500, respectively. P[sub.i] in SSB consisted mainly of non-apatite P, accounting for 91% and 96% of all P[sub.i] in SSB300 and SSB500, respectively. Because SSB is predominantly insoluble in water, oxalic acid is crucial for the release of P from SSB. Oxalic acid increased P release from SSB300 and SSB500 by 103- and 600-fold, respectively, compared to the control, from which P was extracted with water. Oxalic acid enhancement of P release from SSB increases the possibility of using SSB as a sustainable source of P for agriculture.
ISSN:2077-0472
2077-0472
DOI:10.3390/agriculture14091607