6.1 What is black soldier fly larvae treatment, and how does it work?

Black soldier fly larvae (BSFL) are the immature stage of the black soldier fly (Hermetia illucens L.). They belong to the Stratiomyidae family and are generally found in warmer regions worldwide. They play a significant role in natural decomposition processes as they are known to consume large amounts of organic materials and thus have gained traction in the world of waste management.

BSFL treatment involves the utilisation of the BSFL to break down the organic matter in faecal sludge to convert it into valuable byproducts such as compost and animal feed. The life cycle of a black soldier fly consists of five main stages: egg, larval, prepupal, pupal and adult stages, with the larval stage lasting the longest, at 13 – 18 days, and is a period when the larvae steadily consume organic matter. As the decomposition treatment process heavily relies on the natural growing cycle of the black soldier flies, it is recommended to collect them during the larval stage, which is the only period when the larvae actively feed on organic materials. As black soldier flies do not consume or feed on organic materials once they reach the prepupal stage, it is critical that they are collected for the treatment process before then.

BSFL are efficient converters of organic waste from various sources such as food waste, agricultural residues, manure, and human faeces into valuable biomass – proteins, lipids, amino acids, chitin, vitamins, and polypides. They are capable of reducing such wide varieties of wastes by breaking down organic matter and offering nutrient-rich animal feed and soil conditioners. Their resilience to thrive in a wide array of decaying organic matter due to their potent immune systems and high enzymatic activity, allows them to metabolise molecules such as starches, proteins, and lipids at a very efficient rate.

In the specific case of faecal sludge management, BSFLs are known to consume up to 130mg of human faeces per larvae per day, meaning that approximately 10,000 larvae are required to process the faces from one person per day.

Black Solider Fly Larvae and Pathogen Reduction

In the case of BSFL treatment, pathogen reduction is solely achieved through the reduction of waste quantities in a steady and controlled manner, rather than pathogen inactivation.

Black soldier fly larvae (BSFL) are efficient in processing faecal sludge and can reduce Salmonella spp. However, their ability to reduce Ascaris ova (Helminth eggs) is minimal. Therefore, thermal composting or other means require monitoring of the final product and hygienisation of the residual.

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