Comprehensive industry-relevant black soldier fly bioconversion characterisation by a novel chamber system

Black soldier fly larvae (BSFL) efficiently convert biowaste into valuable animal feed. Sustainable and reliable bioconversion is desirable to achieve optimal economic and environmental outcomes. Thus, science and industry require an accessible research platform to study complex bioconversion processes under conditions mirroring industrial-scale settings. In this study, industry-relevant respiration chambers were designed, tested, and replicated for BSFL feeding trials. Each open-circuit chamber housed three industrial rearing crates. The substrate/frass and air temperature, mass change, NH₃ and CO₂ emissions, and relative humidity were measured. The design was validated for CO₂ recovery, airtightness, airflow homogeneity, and BSFL performance using firstly, a uniform control substrate and secondly, uniform food waste across four parallel chambers. In a third trial, the composition of food waste was varied across parallel chambers to detect differences in metabolic processes. For trials using uniform substrates, low variability across chambers in performance parameters confirmed the reproducibility and comparability of the design (e.g. bioconversion rate: <1%, final larval mass: ≤2 mg, standard deviations, dry matter based). In contrast, the trial with varying food waste compositions showed a strong effect on average substrate/frass temperature (e.g. 31.5 °C vs 41.8 °C) and final dry larval mass (e.g. 67 mg vs 40 mg). This is the first study to systematically assess heat generation directly from heterogeneous food waste, a crucial parameter for efficient BSFL bioconversion. These chambers provide an opportunity for science and industry to thoroughly assess and understand the metabolic bioconversion characteristics. The findings are key for the optimisation of sustainable bioconversion processes.