Quality of black soldier fly (Hermetia illucens L.) larvae frass according to feeding substrates in Dschang (West Cameroon)

The global population growth not only requires a significant increase in food production but also leads to an increase in waste production especially in livestock farming. Facing this challenge, innovative waste transformation techniques for sustainable agriculture have emerged, such as the bioconversion of waste by insect larvae, particularly the black soldier fly (Hermetia illucens L.). Black soldier fly larvae (BSFL) are gaining attention as a valuable protein source in animal feed while the residues, frass, are used as organic fertilizer. However its properties are not well understood. The work aimed to characterize the feeding substrates and the corresponding frass focusing on their chemical and microbiological properties. The animal droppings used as substrates, and the resulting frass were sampled and analyzed. Chemical analyses were performed using spectrophotometry. Fungi and bacteria were identified based on their morphological and cultural characteristics. The results showed that pig manure produced the biggest larvae and the greatest quantity of frass. Compared to the respective feeding substrates, the frass contained higher levels of organic matter, organic carbon, total nitrogen, phosphorus and potassium. Treatment with BSFL also reduced the heavy metal contents in the manure. Microbiological analysis revealed fungi from the genera Cladosporium, Aspergillus and Phoma except in the pig manure-derived frass. Bacteria identified included species Actinomycetes, Clostridium, Staphylococcus, Bacillus and Yersinia. Notably, BSFL eliminated Actinomycetes in all frass samples. These findings highlight the potential of BSFL as an effective solution for waste management and frass production.