Using black soldier fly larvae (BSFL) for both processing organic waste from agriculture and providing feed products has great potential—but improved diets and feeding systems for the insects are needed to improve production efficiency.
That’s the conclusion of a review from a group of international researchers, who suggest that feed with high nutrient content and low phosphorus: carbon ratios brings the best results.
Processing waste using insects has advantages
The scientists stressed the advantages of using waste streams rather than raw materials such as wheat bran and maize as feed for BSFL, noting their comparative low cost and high availability.
“Converting low-value inputs that cannot be utilized directly for livestock and aquaculture diets into high-value feed ingredients like BSFL protein meal or BSFL oil, which have application in many animal feed sectors, allows these technologies to stand out from alternative waste management approaches,” they said.
Increased uptake of systems using black soldier fly can also help tackle concerns over water and air pollution from organic waste, reduce carbon emissions and tackle pathogens on decaying matter, while the species’ ability to utilise a variety of food sources point to a possible wide range of applications within agriculture and elsewhere.
Nutrition matters
Bioconversion by the insects is more effective than composting, the authors continued, but the rate at which this occurs depends on digestible nutrients, pH and moisture content in feed. They noted that ideal moisture content for organic waste to be eaten by BFSL is 70-80%, while amounts of protein, carbohydrate and fibre are also important.
“A feed with high nutrient content and a low P:C ratio increases BSFL production. The affinity for this type of feed can be seen in the ability to convert it to body mass during growth as well as other functional benefits being harnessed such as higher antimicrobial peptides (AMPs) and robustness for survival,” they stressed.
Waste mixes can prove successful
Previous research highlighted in the review suggests that mixing different waste streams can improve results.
The highest levels of waste reduction have been seen with waste formulated of 20% sewage sludge and 80% palm kernel expeller, although this came with low levels of bioconversion. Formulations that have shown high levels of both waste reduction and bioconversion included a blend of chicken manure, water and the mineral chabazite, as well as one using a third each of mill by-products, canteen waste and vegetable waste.
While feed ingredients greatly influence the nutritional quality of the BSFL body, evidence was cited suggesting that pre-treatment of their feed such as mechanical crushing and heating can aid uptake of nutrients. The density of larvae used and frequency of feeding also affects the efficiency of systems, the researchers added.
You can read the full study in Waste Management.
