Impact of container size and feed administration on Hermetia illucens rearing performance

The increasing food and feed demand results in a greater need for alternative protein sources. Insect proteins have been identified as promising and sustainable alternatives due to their high feed conversion efficiency and biomass quality. These characteristics, plus the capacity of growing on a large variety of organic waste, make Hermetia illucens (Diptera: Stratiomyidae) one of the best candidates. Particularly, within the framework of circular economy, larvae of H. illucens are able to develop on organic fraction of municipal solid waste (OFMSW) which represent a valuable material (containing 16-28% of proteins and 11-29% of fats) and to convert it into high-value biomass (containing a very high percentage of protein 36-48% and fat 31-33%). As rearing condition can strongly impact H. illucens performance, the aim of the present study was to obtain important information, focusing on container size and feed ratio to optimise the larval production. Two container sizes were evaluated with a larval density of 0.38 larvae/cm3: the first one measured 60×40×11 cm and contained 10,000 larvae and 15,000 g of feed (OFMSW); the second one measured 21.5×14.5×4.2 cm and contained 500 larvae and 750 g of feed (OFMSW). The two feeding procedures that were evaluated consisted in providing the total amount of feed at the beginning of the trial or split in three times (day 1, 4, 8). Four replicates were set up for each trial and the larvae were collected when 5% reached the prepupal stage. ANOVA was used to test the effect of these factors and their interaction on different performance parameters: survival, final larval weight, final biomass, substrate reduction, efficiency of conversion index (ECI), waste reduction index (WRI). The results confirmed that larval number along with the associated container size and/or feed ratio are important factors to consider for H. illucens production. The higher final larval weight was obtained from larvae reared in bigger containers. Moreover, in such case, final biomass (DM), survival, ECI and WRI were significantly higher when feed was provided in one single solution.