Augmenting black soldier fly (BSF), Hermetia illucens, production on various agricultural waste streams, and the beneficiation of BSF frass

PhD (Life Sciences: Zoology)

Department of Biological Sciences

A sustainable and innovative approach to managing organic waste is presented by Black Soldier Fly Larvae (BSFL), Hermetia illucens, flowing from previously underutilised biological waste streams in agricultural systems. These waste streams are regularly disposed of irresponsibly or recycled inappropriately that lead to environmental problems characterised by emission of greenhouse gases, nutrient leaching, and inefficient waste reduction methods. BSFL’s capacity to convert organic material into valuable protein-rich biomass and nutrient-rich frass have great potential in sustainable waste management systems, especially in handling high moisture organic waste streams and contributing to a circular-loop economy. Thus, the objective of this study was to evaluate the BSFL performance in converting three economically abundant organic waste streams in Limpopo, Vhembe district, South Africa (avocado waste, orange waste, and potato peels) and to evaluate the effect of frass from those substrates on agricultural productivity. This was achieved through three main specific objectives:1) to determine the growth and survival of BSFL in response to sawdust as a bulking agent for managing high-moisture potato peels; 2) to investigate the effect of nutrient composition of the three organic wastes on BSFL survival, growth rate, larvae yield, waste reduction and the efficiency to convert waste into useful biomass ; and 3) to evaluate the agronomic potential of BSFL frass as an organic fertiliser for improving the growth and yield of beetroot (Beta vulgaris). This study also contributed to a better understanding of how BSFL performance can be optimised in various organic waste streams, illustrating the potential for sawdust to provide effective bulking more quickly, thus improving larval growth and subsequent management of the high moisture substrates during the bioconversion process. Results showed that sawdust effectively enhanced larval yield and growth rates by maintaining the aeration and moisture balance of the substrates. Moreover, the results of bioconversion in the three waste streams indicated that larval biomass and frass production were highest when potato peels were used, and some wastes were more efficiently reduced than others, which is mainly related to their composition. In agronomic scales, application of frass has improved beetroot growth and yield, thus showing that the frass also serves as a biopesticide that can protect crops. This will advance the knowledge base of BSFL bioconversion systems and allow practical guidance identifying conditions to optimise substrates and possibly render frass to be integrated with agriculture. It highlighted that BSFL not only provides a means for organic waste reduction, but when used as a component of organic fertilisers, increases crop yields and improves soil health, thus presenting an eco-friendly agricultural opportunity. This research contributes to offsetting both ecological and economic problems and creates a step towards broader and more effective application of the insect industry on BSFL for this niche in the waste valorisation system.