Effect of different food by-products on Tenebrio molitor growth and development in an industrial environment

Abstract: Due to an increasing need for high-quality protein around the world, eyes are turning towards alternative methods of farming, such as insect farms. As insects can eat what humans cannot, e.g. food by-products, they can be a part of sustainable food systems. In this thesis I experimentally test food by-products on growth rates as well as maturation rates on one of the most reared insects species, the mealworm Tenebrio molitor. I experimentally reared T. molitor on four different types of feed while controlling other environmental variables. The feed used was gluten free crispbread, spent brewers’ grain, a combination of the two, and wheat bran, all of which are considered by-products. This means they are usually considered “waste” and brought to either a landfill or to a biogas plant, usually at a cost for the producing company. My study showed that larval growth rate increased when fed with gluten free crispbread (average weight 0.1g per larvae after 10 weeks) as well as larvae fed with gluten free crispbread in combination with spent brewers’ grain (0.09g per larvae after 10 weeks) compared to individuals fed only spent brewers’ grain or wheat bran and water. Feeding larvae with only spent brewers’ grain (0.07g per larvae) or wheat bran combined with water (0.05g per larvae) also make T. molitor grow, but not as rapidly as with the other two feeds. I performed a follow-up test on the maturation rate of larvae to pupae to adult and I found indications that gluten free crispbread combined with spent brewers’ grain as well as only feeding spent brewers’ grain had a faster pupation rate but it is difficult to justify this with very few sampling points. These indications are noteworthy however as it differs from normal larvae-larvae morphosis, requiring further analysis on what amino-acid combinations are required for pupation and emergence as adults It is positive that all by-products nurtured growth and development of the species and because of this, the study shows the possibilities of by-products as an investment into insect rearing. If companies want to make a real impact I think they need to focus on breeding insects as sustainable as possible. A perfect way to do this is by looking into agricultural by-products that are otherwise considered waste and using it as high-quality feed for insects. After reading all the sources for this paper it is my firm belief that this is an industry that will only grow stronger in the future and if we are to feed the growing population on earth it is essential that this is done in a sustainable way.