Black soldier frass valorization into low-cost residual biofertilizer conversion process and its effectiveness in foliar and soil applications

This study evaluated the potential of a liquid biofertilizer derived from Hermetia illucens frass for the sustainable cultivation of Phaseolus vulgaris L. The frass, obtained from larvae, fed a standard diet, was transformed into a liquid biofertilizer via fermentation. The biofertilizer was characterized by quantifying macro and micronutrients, pH, electrical conductivity, organic matter, calcium carbonate, and heavy metals, alongside microbiological analyses detecting total and fecal coliforms, Staphylococcus aureus , and Salmonella sp. Structural analysis was conducted using μFTIR. Despite containing lower nutrient levels than reported in other studies, the biofertilizer provided essential plant nutrients. A greenhouse experiment, employing a 2 × 3 factorial design, assessed its effects through foliar and soil applications. Results showed a 0 %–10 % yield increase, with foliar application enhancing plant health. This study highlights Hermetia illucens frass as a sustainable, cost-effective biofertilizer, promoting eco-friendly agricultural practices. • Yield of 2955.74 kg/ha with 0 % foliar and 10 % soil application, a 130 % increase. • Ammonium ions (NH₄ + ) formation confirmed during frass fermentation. • Electrical conductivity reduced from 22.41 dS/m to 3.07 dS/m after cultivation. • Frass contains 11.87 % carbon, 0.6 % nitrogen, and 0.54 % potassium. • SPAD index increased to over 40 units with foliar biofertilizer application.