39907 2017 eng 194 203 62 article 1 -- -- -- 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. Waste Management 10.1016/j.wasman.2017.02.019 0956-053X 02.06.2017 D. Steckenmesser Christian Vogel Christian Adam D. Steffens eng uncontrolled P-recovery eng uncontrolled Low-temperature-conversion eng uncontrolled Thermochemical treatment eng uncontrolled P-fractionation eng uncontrolled P-plant-availability eng uncontrolled Sewage sludge Sanitär- und Kommunaltechnik; Umwelttechnik Verlagsliteratur Datei im Netzwerk der BAM verfügbar ("Closed Access")