Enhanced phosphorus and potassium recovery through co-pyrolysis of nutrient-rich biomass feedstocks for engineered biochar production

Abstract

Engineered biochars were produced via slow pyrolysis at 600 °C for 1 h from selected carbon-rich (diyar wood, sawdust, cotton stalk, sunflower straw, and banana stem) and nutrient-rich (eggshell, chicken bone, chicken manure, and sewage sludge) biomass residues with enhanced P and K recovery. Separate pyrolysis of both category feedstocks and co-pyrolysis of selected carbon-rich and nutrient-rich feedstocks mixed at 3:1 ratio was conducted. Higher biochar yield (41 %) was achieved in the co-pyrolysis of sewage sludge and sunflower stalk compared to average (38.5 %) of their separate pyrolysis. Moreover, increased K recovery (5.3 % to 19.5 %) and increased P recovery (1.8 % to 25.5 %) was achieved in biochar through co-pyrolysis of nutrient-rich and selected carbon-rich feed stocks compared with their separate pyrolysis. The chicken bone and sewage sludge can be ideal feedstocks for enhanced P and K recovery through their co-pyrolysis with carbon rich biomass such as banana stem or sunflower stalk.