Change in nutrient composition of biochar from rice husk and sugarcane bagasse at varying pyrolytic temperatures

Waste management is one of the significant challenges facing Nigeria’s agricultural sector. To manage this problem, the conversion of agricultural wastes to biochar is a practical solution. In this work, the chemical composition of biochar from rice husk and sugarcane bagasse, two predominant agricultural wastes, commonly generated in Nigeria was studied. These wastes were pyrolyzed at 300–700 and 350–700 °C for rice husk biochar (RHB) and sugarcane bagasse biochar (SBB), respectively. It was found that biochar yield and total nitrogen decreased with increasing pyrolysis temperature while ash content, pH, EC, total carbon, extractable Ca, Mg, Na, available phosphorus and silica were increased. In RHB, extractable K increased with increasing pyrolysis temperature, while in SBB it decreased with its maximum observed in RHB. Rice husk pyrolyzed at high temperature may produce nutrient-rich biochar with high nutrient contents and these could ameliorate acidic soils. Finally, SBB could give high available silicon with acid pre-treatment.