Enhanced waste-to-biomass conversion and reduced nitrogen emissions for black soldier fly larvae (Hermetia illucens) through modifying protein to energy ratio.

The appropriate protein to energy ratio (P/E ratio) has played a crucial role in maximizing waste-to-biomass conversion and minimizing nitrogen emissions. Black soldier fly larvae (Hermetia illucens, BSFL), capable of converting organic wastes into nutrient-rich biomass, it has the potential to become an innovative solution to reduce environmental impacts and optimize waste resource utilization. However, the appropriate P/E ratio for BSFL in the waste treatment process has remained unknown so far. This study utilized several common production chain residues to prepare diets with varying P/E ratios, to observe growth performance, nutritional components, fatty acid composition, fatty acid conversion, amino acid composition, waste-to-biomass conversion, and nitrogen emission levels of the BSFL. The results indicated that by adjusting the P/E ratio within the range of 9.79-17.8 mg/kJ, biomass conversion increased from 8.79% to 11.60% (an increase of 31.97%), nitrogen conversion enhanced from 27.31% to 40.99% (an increase of 50.10%), while nitrogen emissions reduced from 2.69 g to 0.48 g (a reduction of 82.16%). Compared to other reported methods, adjusting the P/E ratio proved more effective and cost-efficient. The P/E ratio 11.67 mg/kJ is relatively more suitable for using BSFL in organic waste treatment. Due to the significant variation in nitrogen levels within typical organic waste, our research findings advocate for the mixed treatment of multiple waste types to ensure the P/E ratio close to 11.67 mg/kJ. The findings will provide new insights into the application of BSFL biotransformation technology in organic waste management.