Parametric and optimization studies on the production of nanoscale biochar-NPK fertilizer using sugarcane bagasse-derived biochar as carrier

Abstract

Current agricultural practices such as excessive and inefficient application of conventional fertilizers causes serious environmental problems. Thus, this study aimed to produce a fertilizer with nitrogen, phosphorous, and potassium impregnated in an activated sugarcane bagasse biochar which has potential for slow nutrient release. Activated sugarcane bagasse-derived biochar was produced via pyrolysis at 450 °C for 1 hour followed by activation using potassium hydroxide. Analysis of the activated biochar showed that it has a high capacity to hold exchangeable cations with a value of 127 mol c/kg soil, high porosity and large surface area (79 m2/g), and high carbon content (77.3% wt). The effects of biochar-NPK ratio (w/w), mixing time, and mixing temperature on the nutrient content of the fertilizer were then evaluated implementing a full factorial experimental design. All main factors were found to be significant on the NPK content of the fertilizer. Optimization runs were subsequently done following Response Surface via Central Composite Design (CCD) to determine formulation conditions for maximum NPK content of the fertilizer. Optimized conditions were 1:2 (w/w) biochar-NPK ratio, 50 °C mixing temperature, and 25.60 minutes mixing time. The nitrogen, phosphorous, and potassium content of the fertilizer at optimum condition were successfully verified to be 4.20 %N, 7.57 %P, and 7.01 %K, respectively. The average particle size of the fertilizer was found to be about 2117.2 nm with a polydispersity index of 0.568. The properties of the biochar-NPK fertilizer may be further examined to evaluate its capacity for controlled- or slow-release of nutrients.