Briquetting of black soldier fly frass as a post-harvest stabilization strategy

Abstract

The production–consumption cycle needs a transition towards a circular economy where waste valorization is included. This study investigated briquetting as a stabilization method for black soldier fly frass (BSFF) with faecal matter, pig manure, and poultry manure as the larvae feed. Herein, dried BSFF was pyrolyzed at 350 °C for 2 h to produce biochar then mixed with charcoal dust in equal ratio to produce biobriquettes through densification, with cassava gel (10 wt%) as binder. One-way ANOVA showed statistical significance in carbon, nitrogen, hydrogen, and oxygen. There were significant differences (p < 0.05) between the calorific value, moisture content, ash content, volatile matter, and fixed carbon of the briquettes. The fixed carbon, volatile matter, moisture, and ash content ranged from 29.66 ± 0.86 to 42.01 ± 0.92, 29.26 ± 0.52 to 32.59 ± 0.80, 2.95 ± 0.1 to 5.08 ± 0.04, and 21.48 ± 0.14 to 37.20 ± 0.29, respectively. The calorific value of the produced briquettes ranged from 16.25 ± 0.57 to 20.70 ± 0.53 MJ/kg, which exceeds the minimum requirement of 14.5 MJ/kg recommended for non-woody briquettes. During combustion, concentrations of NOx, N2O, CO, and CO2 varied significantly across the treatments with the acacia charcoal having the highest concentration of CO. Briquetting is a potential stabilization method for frass resulting in waste reduction, bioenergy production, reduced adverse effects of climate change, and enhanced sustainability.