Black soldier fly (BSF) larvae may play a role in a circular economy by upcycling low-value organic streams into high value biomass. In this paper, the capacity of BSF larvae to process 12 organic side-streams (mono-streams) and two standard substrates (chicken start mash and Gainesville diet) was investigated. Survival, larval mass, feed conversion ratio, and waste reduction were evaluated in relation to the proximate composition of the side-streams used. Survival rates larger than 80% were observed for 10 of the organic mono-streams and the two standard substrates. Maximum mean larval weight ranged from 38.3 mg up to 176.4 mg regardless of high survival and was highly correlated with substrate crude protein content. Feed conversion ratio (range 1.58–8.90) and waste reduction (range 17.0–58.9%) were similar to values reported in other studies in the literature. On low protein substrates (e.g., apple pulp), survival rates remained high, however, possibly due to protein deficiency, limited larval growth was observed. It is concluded that several low value organic side-streams can successfully be processed by BSF larvae, thereby opening the possibility of lowering the costs of BSF farming. Potentially mixing nutritionally distinct mono-streams into a mixed substrate might improve BSF performance. However, more research is needed for optimizing diets to guarantee production of BSF larvae of constant yield and quality.

Due to increasing welfare and population, the demand for alternative protein sources, obtained with minimal use of natural resources, is rising in today’s society. Insects have the potential to be used as an alternative protein source since they are considered to be able to convert low-value biomass into high-value components, resulting in opportunities for valorisation of organic side streams. Moreover, insects are suggested to be a sustainable protein source, referring to the efficient “feed to body” mass conversion potential. The aim of this review was to explore the potential to rear the yellow mealworm (Tenebrio molitor), the house cricket (Acheta domesticus) and the migratory locust (Locusta migratoria) on low or not yet valorised organic side streams within the food supply chain. This was performed by collecting research information focusing on the rearing of the insects in scope on organic biomass. In addition, the nutritional composition of the produced insects as well as their dietary requirements will be reviewed. Finally, the availability of side streams in the EU will be discussed as well as their potential to be used as insects feed.

Black soldier fly (Hermetia illucens) is considered a farmed animal. The larvae live in a moist substrate, which leads to a complex interaction with the microbial community. As such the combined metabolism of the insects and that of the microbial community can ultimately lead to all sorts of emissions such as ammonia and greenhouse gases. For ammonia emissions and associated depositions, it is known that this can lead to eutrophication of local ecosystems and the formation of particulate matter which can affect human health. This issue is known for intensive livestock farming where in some Western European countries this has led to specific regulations, for example limited number of livestock per farm, to control ammonia emissions. The production of black soldier fly larvae is a novel activity that could similarly lead to ammonia emissions. This study introduces a new method to quantify ammonia emissions in an industrial setting using an accumulation chamber and validates the findings with a nitrogen mass balance. Additionally, different feed substrates (Gainesville diet, chicken feed, artificial supermarket waste and brewers spent grains) were assessed with varying crude protein concentrations, hypothetically one of the driving factors affecting emissions. Results indicate significant ammonia emissions, the total emissions during larval growth ranged from 2.6 up to 83.6 g N/kg larvae (dry matter basis) and depend strongly on the diet. The rates at which these emissions are produced are negligible during the first three days. In the following days all diets emitted ammonia at a varying rate. The highest observed hourly emission rate for test substrates could be as low as 6.8 mg N/kg initial substrate (dry matter basis) and as high as 306 mg/kg. Different properties of the feed, such as the initial crude protein concentration, but also how the pH changes throughout larval growth, will affect emissions.

Whereas the production of conventional livestock can rely on years of knowledge and experience, the mealworm production industry is still in its early stages. Although the yellow mealworm Tenebrio molitor has been cultivated as feed for pets and zoo animals for quite some time, the optimization of the reproduction process has not been widely explored. For reproduction, beetles are placed in crates supplemented with a substrate to oviposit their eggs. After a specified time, the beetles are removed, and the eggs are further cultivated to develop into larvae. Factors such as oviposition duration and beetle density influence the number of produced mealworms per beetle, partly due to the cannibalistic behavior of the beetles. However, reproductive success has mostly been assessed by determining the number of offspring several weeks after oviposition. As a result, the number of eggs laid and their hatch rates are unknown. In this research, eggs are separated from the oviposition substrate, i.e., harvested. This approach allows to determine the influence of beetle density, oviposition duration, beetle age and the use of a grid during oviposition on the number of eggs produced and the egg hatching rate and timing thereof. In addition, the influence of the harvesting method on the hatching of T. molitor′s eggs was determined.

Interest in the nutrition of the yellow mealworm ( Tenebrio molitor L.) larvae is on the rise, leading to an increase in publications on this topic. The absence of a standard protocol and resulting differences in experimental designs reduces comparability among studies and impedes research on mealworm nutrition. To address this, a consensus standardised protocol was developed specifically for the evaluation of mealworm larval growth and performance in feeding trials. The efficacy of this protocol was evaluated through an international ring test involving seven partners using two wheat brans as dry feed (a standard bran and a local bran) at 27 °C and 60% relative humidity. As experimental units, plastic crates filled with 2.1 kg of bran and 10,000 4-week-old larvae were used with six replicates. Agar gel was provided as wet feed ad libitum . The mean individual larval weight and the number of larvae per crate were determined weekly until either three or more replicates ran out of feed or pupation exceeded 10%. At harvest, the total larval fresh biomass and amount of frass was determined. Larval samples were taken for chemical analysis. To assess the protocol, the within (repeatability) and between (reproducibility) laboratory variability was calculated for each parameter. The repeatability was good (limit at 12% (standard) and 14% (local)). The reproducibility was poorer with a limit 2.7 times higher for the standard feed (36%) and 3.8 times higher for the local feed (55%). For both feeds, the total larval fresh harvest, amount of frass and the larval protein concentration were the most consistent both within and among laboratories. The highest variability was observed at the early life stages and for the larvae ash content. The detailed consensus standard protocol and repeatability/reproducibility estimates can be used as basis for future mealworm feeding trials, comparing results and future improvements.

This study explores the optimisation of rearing substrates for black soldier fly larvae (BSFL). First, the ideal dry matter content of substrates was determined, comparing the standard 30% dry matter (DM) with substrates hydrated to their maximum water holding capacity (WHC). Substrates at maximal WHC yielded significantly higher larval survival rates (p = 0.0006). Consequently, the WHC approach was adopted for further experiments. Using these hydrated artificial substrates, fractional factorial designs based on central composite and Box–Behnken designs were employed to assess the impact of macronutrient composition on bioconversion efficiency. The results demonstrated significant main, interaction, and quadratic effects on bioconversion efficiency. Validation with real-life substrates of varied protein content, including indigestible feather meal, affirmed the predictive model’s accuracy after accounting for protein source digestibility. This research underscores the importance of optimal hydration and macronutrient composition in enhancing BSFL growth and bioconversion efficiency.