The Black Soldier Fly Larvae: An Alternative Source of Fish Feed

By Dr. Chanagun Chitmanat

The global demand for animal protein, particularly for aquaculture, is increasing rapidly. Traditional protein sources of fish feed, such as fishmeal, are under pressure due to overfishing, environmental concerns, and high costs. In this context, Black Soldier Fly Larvae (Hermetia illucens L., BSFL) have emerged as a promising alternative protein source, particularly due to their ability to efficiently process organic wastes, including household waste and agro-industrial biowastes.

BSFL’s Potential in Waste Conversion

Black Soldier Fly Larvae (BSFL) are highly effective at converting organic waste materials, including food scraps, agricultural by-products, and household waste, into valuable biomass. BSF larvae grow rapidly on waste streams, including food scraps, vegetable matter, and even food waste contaminated with oils or meat (Peguero 2024). The larvae accumulate proteins, fats, and other nutrients, making them an excellent resource for aquaculture. BSF larvae have a high crude protein content ranging from 30% to 50% (dry weight) and also have a well-balanced profile of essential amino acids (Shumo 2019), making them a suitable feed for fish. In addition to protein, BSF Larvae contain beneficial lipids, which are essential for the growth and development of aquatic species. The larvae’s fatty acid composition is generally rich in unsaturated fatty acids, which are beneficial for fish health and growth (Ewald 2020).

BSFL for Environmental Sustainability and a Circular Economy

One of the key advantages of using BSFL as a protein source is its contribution to a circular economy. By utilizing organic waste that would otherwise end up in landfills, BSF larvae reduce waste disposal costs and minimize environmental pollution. Furthermore, the larvae’s ability to grow on waste materials reduces the need for traditional agricultural feedstocks, such as soybeans or fishmeal, which have larger environmental footprints. Researchers at the Swiss Federal Institute of Aquatic Science and Technology (Mertenat 2019) demonstrated the potential for greenhouse gas emission reduction through BSF larval waste treatment, in particular when compared to open windrow composting. Using a Life Cycle Assessment (LCA) approach, the authors showed that direct CO₂eq emissions at the BSF facility were 47 times lower compared to composting. This study further concluded that the waste treatment’s major contributors to global warming potential (GWP) were post-composting residues (69%) and electricity consumption (up to 55%). The study also highlighted the potential substitution of fish meal with BSF larvae meal as a strategy to reduce GWP by up to 30%. The production of BSFL for fish feed could thus be a possibly sustainable solution for the aquaculture industry.

BSFL’s Nutritional Value for Fish

The substitution of dietary fish meal by BSF larvae has been successfully implemented for various fish species without compromising growth performance or feed conversion ratios. Atlantic salmon (Salmo salar) reared in sea cages were fed diets containing up to 10% BSF larvae meal without affecting the physical and chemical fillet quality (Radhakrishnan 2024). BSF larvae replaced up to 22.5% of fish meal without negatively impacting growth performance or feed utilization in white shrimp (Litopenaeus vannamei) (Usman 2021). Fishmeal was replaced by up to 50% BSFL without affecting the growth performance, nutrient utilization, survival, and welfare of African sharptooth catfish (Clarias gariepinus) (Adeoye 2020). BSF larvae can replace up to 75% of the fish meal protein without negatively impacting the growth, blood characteristics, or body composition of tilapia fingerlings (Sangsawang 2024). However, the proportion of BSFL in fish feed must be optimized to ensure that the fish receive a balanced diet, as the inclusion of excess BSF larvae may lead to imbalances in certain nutrients like fiber or minerals. A 100% substitution adversely affected the feed conversion ratio and the protein utilization efficiency of tilapia (Dietz 2018).

Procedures for Growing Black Soldier Fly Larvae (BSFL) From Household Wastes to Produce Fish Feed

These procedures cover the collection and preparation of the waste, the growing conditions, and the harvesting techniques.

Phase 1: Preparing Rearing Containers

Step 1: Choose a suitable container. Use shallow plastic or wooden trays (20-30 cm deep). Containers should have ventilation holes covered with fine mesh to allow airflow and prevent escape of adult flies.

Step 2: Set up a moisture-proof base. Line the bottom of the container with biodegradable materials (e.g. sawdust or shredded paper) to absorb excess moisture and maintain hygiene. Ensure proper drainage to avoid waterlogging.

Phase 2: Collecting and Preparing the Biowaste (Household Waste)

Step 3: Collect organic waste. Focus on food scraps such as vegetable peels, fruit waste, coffee grounds, rice, or leftovers. Avoid using meat, dairy, or oily foods, as they can attract pests and disrupt BSF production.

Step 4: Prepare the waste. Chop larger food scraps into smaller pieces to help accelerate decomposition and to make it easier for the larvae to consume. Moisten the waste slightly by adding water to keep it at an optimal moisture level (60-70%).

Step 5: Store excess waste. Biowaste should be stored in a compost bin or similar container to begin fermentation or decomposition before feeding it to BSF larvae. Allow the waste to break down for 24-48 hours to reduce the presence of harmful bacteria and increase its digestibility.

Phase 3: Inoculating the Rearing Setup with BSF Eggs or Larvae

Step 6: If BSF eggs are used, scatter them evenly across the prepared waste. Eggs are often sold in small quantities, and it’s important to ensure they are distributed evenly to avoid overcrowding. Alternatively, if BSF larvae are used instead of eggs, place them directly onto the prepared waste. Larvae will begin consuming the waste immediately and reproduce quickly. Use approximately 1,000-2,000 larvae per m² of waste area for optimal growth.

Step 7: Cover the setup. Use mesh or a fine net to prevent the adult flies from escaping while still allowing air circulation. Place the setup in a warm area (ideally at 27-30°C) with indirect sunlight or in a shaded area to mimic the fly’s natural environment.

Phase 4: Feeding and Managing the Larvae’s Growth

Step 8: Feed the larvae. Add fresh organic waste to the rearing container regularly. Ensure that new waste is chopped up and moist. The larvae will consume waste rapidly, so they may need feeding every 2-3 days.

Step 9: Maintain moisture levels. If the waste begins to dry out, add a little water to maintain the right moisture content. Over-watering can lead to anaerobic conditions, so be careful not to over-saturate the substrate.

Step 10: Ensure proper ventilation. Keep the container in an area with good airflow. Too much humidity or lack of oxygen can cause mold or disease, which will harm the larvae.

Step 11: Monitor larvae growth. Larvae will go through several stages of growth and reach maturity in approximately 30-35 days, depending on temperature and waste composition. The larvae will gradually change from white to a darker color (black or brownish), indicating they are nearing maturity.

Phase 5: Harvesting the Larvae

Step 12: Prepare the harvesting container. Have a clean, dry container ready for collecting mature larvae.

Step 13: Harvest the “crop”. Once the larvae have reached their full size (10-14 days after inoculation), they will be ready for harvest. Typically, they are around 2-2.5 cm long and dark-colored. Gently sift through the waste to collect the larvae. You can use a fine mesh sieve or sift by hand.

Step 14: Separate adult flies (optional). If adult BSF flies have emerged, remove them from the rearing container and release them back into the environment or use them to propagate future generations.

Step 15: Clean the rearing containers. Clean out any leftover organic waste from the container and prepare for the next cycle of waste addition and larvae inoculation.

Phase 6: Processing the Larvae for Fish Feed

Step 16: Process the larvae. Once harvested, BSF larvae should be processed either for long-term storage or for immediate use as fish feed. Dry the larvae in an oven or dehydrator at a temperature of 50-60°C for 6-12 hours until completely dried. Alternatively, freeze the larvae to preserve their nutritional value.

Step 17: Grind the larvae (optional). Once dried or frozen, larvae can be grounded into a powder or pelletized for easier incorporation into fish feed. Grinding the larvae helps increase digestibility.

Phase 7: Feeding Fish with BSF Larvae

Step 18: Incorporate the BSF larvae into the fish feed. Once processed, BSF larvae can be directly added to fish feed formulations, either as whole dried larvae or as a powder. It’s important to balance the diet with other necessary nutrients (e.g. vitamins, minerals, and carbohydrates).

Step 19: Feed the fish according to the guidelines. Feed BSF larvae in the appropriate amount based on the species of fish and their nutritional needs. This could range from 10-20% of the fish’s total diet, depending on the formulation.

Challenges and Considerations

Despite its promising potential, the large-scale production of BSF faces several challenges. The efficiency of waste conversion can vary depending on the type of household waste used. As well, the larvae’s nutritional profile can be influenced by the substrate on which they are raised. Moreover, the process of raising BSF larvae on household waste requires careful management to ensure the absence of contaminants and pathogens that could affect the quality of the larvae and the safety of the resulting fish feed. Additionally, regulatory frameworks and safety standards for BSF-based feeds in aquaculture are still being developed, as the use of insect-based protein is a relatively new practice in many regions.

Conclusion

Black Soldier Fly Larvae (BSFL) represent a promising and sustainable alternative protein source for fish feed, especially when produced from household waste. Their ability to convert organic waste and become high-quality protein, combined with their nutritional value for fish and their potential to reduce environmental impacts, makes them an attractive option for the future of aquaculture. However, further research into optimizing production methods, improving waste-to-protein conversion efficiencies, and ensuring the safety and regulatory compliance of BSF-based feeds is necessary to fully realize their potential in the global fish feed industry.