Furfural Residue to Rheology Accessible Suspension Fertilizer upon Artificial Humification

Abstract

To achieve the upcycling of annually upsurging lignocellulosic wastes, the artificial humification of furfural residue is investigated under hydrothermal conditions with the objective of producing a high-concentration nitrogen-phosphorus-potassium (NPK) suspension fertilizer. Through orthogonal analysis, process conditions are optimized as a liquid-to-solid (aqueous KOH to furfural residue) ratio of 15, a reaction time of 5 h and a hydrothermal temperature of 160 °C. Subsequently, we screen out a formulation of suspension agents to stabilize the alkaline leachate, in which 0.50% sodium lignosulfonate, 0.20% xanthan gum and 0.05% potassium sorbate are incorporated via wet ball-milling. The Herschel–Bulkley equation well fits the rheological characteristics of the resulting suspension fertilizer with R2 value exceeding 0.99. This suspension system is thus determined as one pseudoplastic non-Newtonian fluid. Due to higher static viscosity, it demonstrates superior anti-agglomeration capacity within a temperature range of 15–55 °C, while flowing smoothly through pipes during high-speed spraying onto the soil relied on its shear thinning. These findings provide novel insights for the high-value utilization of bio-waste and the development of new fertilizers with less consumption of energy and water.