Grubs of rhinoceros beetle Oryctes rhinoceros with enormous potential for bioconversion of organic solid waste into value-added compost

Grubs of the rhinoceros beetle, Oryctes rhinoceros were utilized in this study to convert organic waste into useful compost. After 30 days of composting, the grubs of the beetle converted 27% of organic waste into useful biofertilizer (faecal pellets/grub compost). Chemical analysis of this grub compost showed abundance of nutrients and minerals comparable with that of vermicompost, which could be useful to improve the soil fertility. The essential soil nutritional parameter, carbon: nitrogen ratio was found to be 23:1 in this grub compost which was reported to be 10.1 to 18:1 in the case of vermicompost. The other elements such as zinc (65.95 mg/kg), manganese (184.68 mg/kg), iron (7420.94 mg/kg) and copper (21.96 mg/kg) were also found in the O. rhinoceros grub compost. A comparison made between beetle grub compost and vermicompost demonstrated 10 fold higher concentrations of copper and zinc, 1200 fold higher concentration of iron and presence of manganese in grub compost. Further, the grub compost was used for plant growth studies. Lower concentration (up to 40%) of the grub compost enhanced the plant growth parameters such as shoot and root growth, chlorophyll content and relative water content in Vigna radiata.