LAUSR

Production of macro-nutrient rich biochar is important to broaden its use as soil fertilizer. In this work, we report production of potassium–sulfur rich biochar through co-plasma processing of banana peduncle biomass with phosphogypsum waste. Biochars were produced using indigenous low-power (15 kW) extended arc thermal plasma reactor in 7 min under three different plasmagen gases i.e., argon, oxygen, and ammonia. Plasmagen gases showed differential and significant effect on potassium, sulfur and toxic element contents of biochar. Biochars showed relatively higher potassium (4.2–12.7%) and sulfur (13.3–17.8%) contents than phosphogypsum (potassium − 0.02% and sulfur − 12.5%). In addition, leachable fraction of fluoride and heavy metals decreases in biochars. Among plasmagen gases, retention of potassium and sulfur content was relatively higher in argon, whereas fluoride and heavy-metal leaching reduced maximum in ammonia. X-ray diffraction analysis showed the presence of potassium and sulfur as K2SO4 and CaS minerals in biochars. These findings highlights about application of co-plasma processing of nutrient-rich biomass with phosphogypsum waste for production of lesser toxic nutrient-rich biochar.