Tray Systems for Space-optimized Insect Farming Facilities

Insect farming includes the rearing of insects for substances that the insects produce, or for the insects themselves for use as feed or food source. Adult insects are bred to produce eggs, which hatch into larvae. Food and water are provided to the larvae to facilitate growth and development. After some time, larvae metamorphose into pupae and then into adults. Before the larvae transform into pupae, a large portion of the larvae can be collected and processed. Some are allowed to mature to reproduce - ensuring the self-sustainability of the insect colony. Larvae skin and frass are often collected to be used as a raw material to produce organic fertilizer etc. 

Tenebrio molitor, commonly referred to as mealworm (in german "Mehlwurm"), for example, is best known for its larval form (see Figure). The mealworm itself is often used as living food for insectivorous pets, or as fishing bait. However, Tenebrio molitor is a prime natural source of proteins. The high concentration of proteins in Tenebrio molitor, its composition and a lipid profile that includes most of the essential fatty acids, make it a future feed/food with interesting nutritional benefits and a low carbon footprint.

There are a number of considerations for maximizing the output and efficiency of insect farming facilities. For instance, farming environmental conditions must be carefully taken in to account: temperature, humidity, light, and ventilation. Pests must be contained. Larvae and adult insects may be most efficiently housed within trays, stacked in space-optimized racks that are modular components in a larger facility. Given the manifold daily operations to be performed by facility workers, it seems key to maximize the (space and cost) efficiency of those tray & rack systems - maximizing the rearing facility's output and minimizing labour costs.

Tray & Rack Systems for Mealworm Production. Vienna Scientific Instrument offers space and labour efficient tray-based insect rearing systems for feed or food production, tested and optimised with mealworm farmers to meet the specific needs of your insect rearing facility. In particular, we manufacture cost effective racks to hold standardized trays of your choice - building cost effective, long lasting and scalable rearing systems. We custom design racks to fit your facility, adjusting height, width and number of racks to make the most of your available space. We work with entomologists to advise on systems suitable for your target insects and the scale (scalability) of your insect farm. From previous projects, we have particular experience with rearing systems developed for mealworms.

Material Racks: Aluminum bars (5x5 cm; side poles) and angle aluminum bars (top and bottom, slides), stainless steel screws.

Various versions (see Table 1 below for standard models) to suit all tray sizes and the spatial configuration/workflow of the facility:

• Loads trays from one or two sides (front and back, standard)
• Side-by-side units with two or three adjacent racks in one unit (with shared center poles)
• Fixed legs (standard), or on turnable wheels
• Optional: with mesh sides, bottom, top, & mesh front door (for potential isolation of infested trays); higher or lower racks; orientation of trays, ...

Trays: Standard, commercial trays depending on species (PP, grey; various dimensions)

The production trays used are standardized ("Euroboxes") and are purchased in bulk directly from the manufacturer to provide the most cost effective tray and rack systems for insect production and to allow for easy facility expansion without changing the rearing tray type.

Contact us to discuss your insect rearing objectives and how VSI's cost effective racks can support your goals! 

Insect Production Racks are shipped partially assembled. The side/middle panels with slides are pre-assembled, while the top and bottom bars can be easily installed by the customer - resulting in significantly reduced shipping costs. All parts (screws etc.) are included for easy do-it-yourself installation of top and bottom bars (and center bars in double units). We are happy to get you started with the installation via video call; pre-assembled or on-site installation service available upon request.

Mealworm rearing rooms are ideally maintained at a temperature of 25-30°C and a relative humidity (RH) of 50-75% (Manojlovie, 1988; Chen and Liu, 1992). Plastic trays are commonly used in European and North American farms. 

The optimum density for rearing adults is approximately 0.94 larvae per cm2 (i.e. ~2200 larvae per 60 x 40 cm tray). Adults typically begin oviposition on the fourth day after emergence. Oviposition substrates, such as a wheat bran bedding contained within a mesh screen, are used to collect semi-synchronized eggs. During the 40-50 day spawning period, adults must be transferred to another container every 3-5 days to maintain semi-synchronized eggs. Larvae typically hatch approximately 7 days after egg deposition. For commercial larval production, the recommended rearing density is 1.18 larvae per square centimeter (Wu, 2009), i.e. ~2500 per 60 x 40 cm tray. 

The medium used to raise mealworms, both larvae and adults, is a mixture of wheat bran and partially vegetables. For optimal mealworm nutrition, the water content of the wheat bran and vegetable feed should ideally be ~18% (Wu et al., 2009). Vegetables should be washed and air dried to remove potential pesticide residues, soil, etc. On a daily basis, one hundred larvae require approximately 6-10 g of wheat bran and 0.6-1.0 g of fresh vegetables (such as carrot, cabbage, pumpkin, etc.), which should be added separately at regular intervals (twice a day) and removed immediately if spoiled. However, despite the optimized nutrition/hydration provided by the addition of vegetables, many mass rearing facilities choose to add only agar agar (cubes, shreds) to the wheat bran to provide a consistent moisture source. This significantly reduces the daily maintenance process with little impact on production. The literature also recommends cleaning the rearing trays every 3-5 days to remove larval waste (frass). However, longer cycles (up to about 10 d) can be implemented, especially when no vegetables are fed and humidity is not too high (i.e., limited fungal growth), thus reducing the labor intensity of the rearing process. If longer cleaning cycles are used, it is important to keep an eye on pests such as moths and to take immediate action when detected - including hormone traps, release of natural antagonists, and special separation and/or removal of (potentially) infested trays.

Production from a tray is variable and depends on: larval density, harvest time, temperature, and diet. For example, high density larvae may produce more biomass in a tray for a given period of time, but will take longer to mature (due to stress and reduced resource availability). When using very high densities with climate control (heating), you can achieve between 1.3-1.6 kg per tray (60 x 40 cm). This is the upper end of the weight range for slower or reduced growth rates. High densities have faster growth rates (but require more space) and range from 1.1-1.2 kg. The goal in any facility is to achieve densities that provide a good balance between growth rates and space efficiency under the given rearing conditions. This requires some preliminary testing, and optimal densities may vary between seasons under all but fully climate-controlled rearing conditions..

Larval segregation and collection is primarily accomplished by the use of a 60 mesh screen, a process that has been partially automated in some facilities by the use of an electric vibrating screen (see image). Some degree of automation for larval collection and frass removal is key for the efficient operation of a medium (perhaps starting with a few hundred trays) to larger scale insect farm. Full automation of feed application, tray placement and removal, and sorting are hot topics for successfully scaling mealworm farms to mass production facilities.