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In this study, methanol-water co-solvent were utilized as solvents for hydrothermal liquefaction (HTL) of black soldier fly larvae (BSFL) for the preparation of bio-oil to achieve a higher value application of BSFL. The effects of process parameters such as reaction temperature (200–290 °C), methanol-water ratio (0:1–1:0), and methanol participation in the liquefaction reaction (3.50–9.28 wt%) on the yield and properties of bio-oils were examined. The bio-oil produced at 260 °C and a methanol-water ratio of 4:1 had a yield of 68.23%, an HHV of 34.2 MJ kg−1, an O/C ratio of 0.13, and a H/C ratio of 2.39, suggesting their potential for use as renewable energy to replace the fossil energy. When taking into account the consumption of methanol at 260 °C, the bio-oil yield was 48.69%, energy recovery was 65.35%, and energy efficiency was 56.36%. GCMS analyses demonstrated that the main components of the methanol-water ratio of 4:1 bio-oil were esters and hydrocarbons, with fewer amides (1.92%), and its composition was similar to that of biodiesel. Methanol played an important role as a solvent in improving the esterification of the acid with methanol and advancing the alcoholysis of the amide. [Display omitted] [ABSTRACT FROM AUTHOR]

The cellulose content in vegetable waste (VW) is high and cannot be directly digested by black soldier fly larvae (BSFL). In this study, in order to treat VW using BSFL composting, kitchen waste (KW) is used as the only nutritional supplement for VW to analyze the effects of the different contents of crude protein (CP), crude fat (EE), carbohydrate (3C), compost thickness (CT), and treatment time on the larval weight (LW), survival rate (SR), dry matter reduction rate (DMR), bioconversion rate (BCR), physical and chemical properties of BSFL sand and changes in the microbial community. Our results showed that when the average 3C content increased by 40%, the average LW increased by 47.6%, and the SR, DMR, BCR, and organic matter (OM) content increased by 16.82%, 8.5%, 4.77%, and 3.86%, respectively. In contrast, when the average compost thickness increased by 5 cm, the average weight of BSFL decreased by 22.64%, while the SR of larvae, DMR, BCR, OM, and total nutrients (TN + P 2 O 5 + K 2 O) decreased by 5%, 5.2%, 4.42%, 9.6%, and 0.78%, respectively. Germination test showed that BSFL sand alone could not be used as soilless culture substrate. After BSFL treatment, we found that the dominant phyla in BSFL sand were Firmicutes (95.77%), Proteobacteria (2.54%), Actinobacteria (0.74%), and Chloroflexi (0.6%). Our results indicate that BSFL composting is an effective method of treating VW, and 3C content and CT have a significant effect on BSFL composting. [Display omitted] • 3C content and CT had significant effects on LW, SR, DMR, BCR and FCR. • 3C (129.34 g), CT (5 cm) and time (10 days) are suitable for BSFL composting. • BSFL sand cannot be directly used as soilless culture substrate. • Firmicutes (95.77%) was the most abundant gate in the BSFL sand. [ABSTRACT FROM AUTHOR]