System dynamics modelling of black soldier fly larvae composting for organic fertilizer production

This study explores how substrate composition influences fertilizer quantity and quality produced through black soldier fly larvae (BSFL) composting of underutilized organic wastes such as coffee pulp. A quantitative system dynamics model was developed using field data and literature data to capture the dynamic relationships between substrate carbon-to-nitrogen ratio and composting efficiency parameters. Sensitivity and scenario analysis were conducted to assess the effects of different substrate combinations on fertilizer outputs. Simulations showed that fertilizer production and profit increased with substrate combinations rich in avocado and market waste. However, the highest-quality fertilizer was produced using combinations with coffee pulp and pineapple, despite yielding smaller quantities. Seasonal availability of coffee pulp impacted composting outcomes, indicating that avocado, pineapple and market waste may not be sufficient to enhance fertilizer quality. The model demonstrated that incorporating Black Soldier Fly (BSF) pupae biomass into frass improves fertilizer quality and supports closed-loop systems aligned with circular economy principles. Despite the limited data available on BSFL composting with coffee pulp, the model effectively captures key composting dynamics. Thus, providing a practical tool for decision-makers to explore different substrate strategies and assess their production and economic implications without field testing, thereby supporting more effective food waste valorization approaches.