Role of carbon bioavailability in enhancing carbon sequestration and humification in black soldier fly larvae body and frass during chicken manure composting

Abstract

The rising demand for poultry products has resulted in increased chicken manure output and environmental pollution. Cultivation of black soldier fly larvae (BSFL) in chicken manure offers an effective method for composting chicken manure. This study investigates the impact of diverse carbon resources on carbon sequestration in larval biomass and excrement, with a focus on bioavailability rather than carbon-to-nitrogen ratio. Five distinct carbon resources were combined with chicken manure, i.e., glucose (CG), sugar (CS), corn flour (CCF), straw (CST), and wood (CW), with pure chicken manure (CK) as a control. These mixtures were inoculated with BSFL for conversion, maintaining consistent initial C/N ratios across all treatments. Results indicated that the CS treatment yielded the highest biomass conversion rate and carbon sequestration within larval bodies, rating to 14.48 ± 0.21 % and 18.01 ± 1.43 %, respectively. Analysis of humus composition in frass revealed that CG and CST treatments produced the highest concentration of humic acid (7.86 ± 0.01 g/kg and 8.01 ± 0.22 g/kg). The both treatments also exhibited superior humification degrees, as evidenced by PARAFAC analysis. Redundancy analysis (RDA) indicated that the presence of Labile Carbon Pool I(LCP1) enhances carbon sequestration capacity within larvae bodies by fostering associations between the relative abundance of Firmicutes and larvae growth. Moreover, LCP1 induced anaerobic conditions increase Euryarchaeota abundance, amplifying anaerobic digestion processes conducive to humus generation during BSFL composting of chicken manure. Our discovery refines conventional approaches to raw materials mixing in BSFL composting and elucidates mechanisms through which varied carbon bioavailability alters microbial community composition, facilitating carbon sequestration in both larvae bodies and frass.