title: Effect of various types of thermochemical processing of sewage sludges on phosphorus speciation, solubility, and fertilization performance.
abstract: Sewage sludge has one of the highest phosphorus (P) recovery potentials of all waste materials. Therefore, P-recycling from sewage sludge could contribute to closing the P-cycle. Recently, various thermal processes for P-recovery have been developed, but there is still a demand for information on the effect of different process parameters (e.g. additives and temperature) on P-speciation and especially on the fertilization performance. In the present study, two common methods (low-temperature conversion at 400-500°C and thermochemical treatment at 950°C) were investigated and combined to produce highly bioavailable P-fertilizers from two different types of sewage sludge based on chemical phosphorus precipitation (Chem-P) and enhanced biological phosphorus removal (Bio-P). The results of P-fractionation, X-ray diffraction analysis, and pot experiments with maize showed that Bio-P sludges attain high P-plant-availability after treatment at low temperatures (400°C). In contrast, Chem-P sludges can adequately be treated at higher temperatures under reductive conditions with sodium additives to form highly bioavailable calcium-sodium-phosphate. Additionally, also highly heavy-metal contaminated sludges can be thermochemically treated at high temperatures to achieve the legal requirements for fertilizers.
authors.affiliation: Institute of Plant Nutrition, Justus-Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany. Electronic address: daniel.steckenmesser@ernaehrung.uni-giessen.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Steckenmesser
authors.affiliation: Division 4.4 Thermochemical Residues Treatment and Resource Recovery, Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Vogel
authors.affiliation: Division 4.4 Thermochemical Residues Treatment and Resource Recovery, Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Adam
authors.affiliation: Institute of Plant Nutrition, Justus-Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
authors.forename: Diedrich
authors.initials: D
authors.lastname: Steffens
mesh_terms: D005308:Fertilizers; D006358:Hot Temperature; D017745:Incineration; D010758:Phosphorus / Q000032:analysis*; D012722:Sewage; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D005308:Fertilizers; D012722:Sewage; D010758:Phosphorus
keywords: Low-temperature-conversion; P-fractionation; P-plant-availability; P-recovery; Sewage sludge; Thermochemical treatment