Biodegradation by composting of municipal organic solid waste into organic fertilizer using the black soldier fly (Hermetia illucens) (Diptera: Stratiomyidae) larvae

Purpose: The objectives of this study were to assess the black soldier fly larvae (BSFL) composting potential and to analyse the quality of organic fertilizer produced for agricultural purposes. Methods: The waste biodegradation was determined by varying waste feed treatment (2, 2.5, 3.0, 3.5, to 4 kg) and control treatment of (2 kg) of heterogeneous mixture of municipal organic solid waste from market, restaurant and households. Each of the setups received equal number of viable larvae (i.e. 2000) which were 5–6 days old. To analyse the nutrient concentration of the compost residues with BSFL, the substrate and final compost were evaluated based on the levels of NPK as well as the C:N ratio. To evaluate the toxic levels of the final compost in terms of heavy metals, the presence and levels of As, Cd, Fe, Pb and Ni were investigated. Results: The analysis showed that there was high percentage increase of nitrogen, phosphorus and potassium levels, i.e. 41.2% (SD ± 0.71%), 32.4% (SE ± 0.2%) and 77.1% (SE ± 0.19%), respectively. It was found that the larvae degraded more than half of the total substrate within 2 weeks. The study showed a decrease in heavy metal concentrations after larvae composting. Conclusion: The study revealed that the concentration of NPK increased significantly among the treatment groups. The study further revealed that some of the heavy metals under investigation had reduced to an acceptable level according to the standards of both local and international regulatory bodies.