Valorization of Organic Wastes by Biotransformation with Black Soldier Fly Larvae: Prospecting of Agricultural Fertilizers

Abstract

Black soldier fly (BSF) larvae have been studied for the side-products obtained through the biotransformation of organic wastes. During the study, frass, which is a mixture of larval waste and non-degraded residues, was evaluated as an agricultural fertilizer. Biodegradation was carried out in a laboratory-scale reactor for 21 days with temperature and relative humidity control, comparing the process at two constant temperatures of 29 and 31ºC, and maintaining the ambient humidity between 65-80%. Meat, cooked food, fresh food and grass wastes were used, evaluating 4 mixtures with different carbon-to-nitrogen ratios (C:N), each with three replicates and a control substrate, with a feeding rate of 47.62 mg/larvae·day. During biotransformation, substrate pH, moisture and ash were monitored. The results were compared with the colombian technical standard NTC 5167: 2022 "Products for Agricultural Industry", which establishes the quality criteria for fertilizers. The greatest reduction of residues (%DM) at 29 and 31°C was in the 12:1 mixture with 66.89 and 56.56%, respectively. The percentages of nitrogen (NT), potassium (K2O) and phosphorus (P2O5) satisfied with the 1% allowed by the colombian regulation, with the exception of phosphorus (P2O5) in the 14:1 mixture, which is below 0.26% at 29°C and 0.16% at 31°C. The parameters of the physicochemical characterization of the frass in both trials satisfied with the established limits; however, the 10:1 and 8:1 moisture content at 31°C was exceeded by 14.10 and 20.00%, respectively.