Tuesday, 14 February 2012 13:58

Larvae growth of the mealworm versus degradation efficiency of organic waste

There are certain criteria to be met to achieve a stable degradation system based on the Mealworm (Tenebrio molitor) larvae. One criterion is a good circulation of the waste to another is an acceptable mortality and growth rate of larvae. Mortality is too high or too poor growth, it will have various negative consequences for the system. During our experiments, we demonstrate that the volume ratio between the caterpillars and the waste (medium) is of great importance for both the rate of degradation of the waste part of the larval population stability.

At a high dosage of the larvae to feed medium, it can be observed poor growth and high mortality rates during the larval population. This may be due to stress reactions, inter alia, leads to cannibalism.

Of course, a large amount of larvae containing food medium providing a rapid turnover of this. At a dosage of 1:1 (larvae: media) can be larvae reacting more than 90% of the feed medium is of only 16 days. This results in that at the high dosages / densities of the larvae is the feed enough to accommodate the larvae needs or to materialize the so-called "crowding effect", which means that the density of the caterpillars have been so high that the interfere with each other and thus do not have the same opportunity to consume food that at lower densities.

If you want to bet on a system in equilibrium, where T. molitor population is in good growth, self-reproducing, and the mortality rate assumes an acceptable level, then one must accept that the turnover rate is lower than what is needed is a system where extremely rapid turnover of the waste is in focus. One may therefore, by this rapid turnover, accept a lower growth rate of larvae and possibly no larval biomass production. This will result in a stable and continuous population development can not be maintained. For such a system must be continuously added to a grant of larvae.

Several questions have signed up during this study. What will happen at high densities of larvae, if you periodically add new growth medium. Will this improve larval growth rate and this will lower the mortality rate to a more acceptable level? Or would the best strategy is to establish a system with a lower dose of larvae in relation to such media. in the ratio 1:4, and accept a lower turnover rate of the medium in exchange for reduced mortality of larvae and achieve a growth rate at a reasonable level? In this case there is the advantage be to achieve a stable T. molitor population development.

The group will continue to work to optimize the rapid degradation of the growth medium, while maintaining a good population development of T. molitor.

Nielsen, S.A., Jensen, T. & Grandorf, U.S. (2012) - Tæthedsafhængig vækst hos Tenebrio molitor med henblik på effektiv nedbrydning af organisk affald.