| Summary: | Background
Improper disposal of rice husk, a major agricultural byproduct, can cause severe environmental issues, including air pollution and habitat destruction. Black soldier fly larvae (BSFLs) offer a promising solution for organic waste management by converting waste into valuable biomass and nutrient-rich frass. However, the complex lignocellulosic structure of rice husk limits its digestibility by BSFL, necessitating effective pretreatment methods.
Methods
This study evaluated the effectiveness of enzymatic pretreatment with cellulase and pectinase, applied alone or in combination with heating and fermentation, on the bioconversion efficiency of BSFL to rice husk. Four pretreatment strategies were tested: direct enzyme addition, enzyme treatment followed by fermentation, heat treatment prior to enzyme addition, and heat treatment combined with enzyme addition and fermentation. A preliminary economic assessment was also conducted to estimate the costs and potential revenues associated with the most effective pretreatment process.
Results
The combination of heat and cellulase treatment, followed by fermentation, significantly enhanced larval growth and achieved the highest bioconversion efficiency (34.8%). Direct cellulase addition also improved larval biomass production and substrate reduction. Some pretreatment combinations, particularly those involving pectinase, negatively affect larval survival. The economic assessment indicated that, under current conditions, the process is not yet profitable at a small scale, with a net loss of $0.24 per kilogram of rice husk processed. Sensitivity analysis revealed that improvements in BSFL market prices, reductions in enzyme or labor costs, or process scale-up could improve economic viability.
Conclusions
Optimizing substrate conditions through enzymatic pretreatment, especially with heat and cellulase, can substantially improve BSFL-based rice husk decomposition. While the technical results are promising, further optimization and cost reduction are needed for commercial implementation. Future research should focus on mechanistic studies and larger-scale economic analyses to support the development of sustainable and economically feasible BSFL-based rice husk management systems.
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