Calcium-enriched Biochar: Pyrolysis of Digested Sludge, Phosphorus Recovery, and Fertilizer Properties

Abstract

In this study, we prepared calcium (Ca)-enriched biochar from digested sludge derived from food waste at pyrolysis temperatures in the range of 600 to 900 °C. We evaluated the properties of phosphorus (P) recovery of the biochar and the fertilizer properties of the biochar after the P recovery (P-loaded biochar). The results showed that the amount of P recovery increased with increasing pyrolysis temperature, while the P recovery capacity of biochar was consistently high at all the investigated temperatures. The fertilizer properties of P-loaded Caenriched biochar prepared at 600 °C, evaluated by the komatsuna cultivation test were comparable to the chemical fertilizer Ca(H₂PO₄)₂. The results suggest that the Ca-enriched biochar could serve as a P recovery material and an environmentally friendly fertilizer.