Abstract

The aim of this study was to investigate the potential bioconversion of rice straw and tofu residue using larvae of Hermetia illucens assisted by microbes to produce protein-rich biomass and organic fertilizer. Larvae of Hermetia illucens were cultivated in rearing containers (25×20 cm) with three different types of substrate containing rice straw, tofu residue and solution containing consortium of microbes. The rice straw used in this study contains 22.1% hemicellulose, 30.3% cellulose, 8.0% lignin and 6.8% protein (weight basis) while the tofu residue contains 20.9% protein (weight basis). The substrate rate was set at 150 mg/larva/day and the ratio of rice straw: tofu residue was varied from 1:0 to 1:3. The highest prepupal biomass productivity of 179.8 g/m²/day on a dry weight basis with an assimilation efficiency of 21.5% and efficiency of conversion of digested substrate of 34.9% was obtained when the larvae were fed with rice straw and tofu residue (1:3) that had been pre-treated with a solution containing 10⁷ cell/mL microbes. At this condition, the prepupal biomass has protein and fat content of 31.8 and 15.5% (weight basis), respectively. The cultivation residue contains a relative high amount of organic carbon (43-46%) with pH 7.16-7.82 and carbon to nitrogen ratio of 22-47 and a total macronutrient of 2.33-3.21% and functional microbes of 2.0-4.5×10⁸ CFU/mL. The results highlight the potential of black soldier fly larvae as a bioconversion agent to convert agricultural waste into protein-rich biomass and organic fertilizer.

Keywords:

Hermetia illucens, organic fertilizer, protein-rich biomass, rice straw, tofu residue,

References

Competing interests

The authors have no competing interests.

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The authors have no competing interests.