4.2. Artificial rearing systems
Several authors have proposed controlled fly breeding to facilitate decomposition and bioconversion of organic waste at a stable rate. Such systems typically have a separate adult fly colony maintained under controlled conditions from which the eggs are collected and transferred to a biodegradation unit where the waste processing occurs. The initial costs of these systems are higher because of the need for infrastructure, special equipment and trained personnel. On the other hand, these systems offer several advantages over natural breeding systems: greater variety of fly species may be used (since the pests are contained there are negligible environmental and health risks), controlled egg seeding resulting in stable production of larvae/pupae, no seasonal shifts in fly numbers, and optimized yields of products.
Newton et al. (2005) described possible on-farm implementations of black soldier fly biodegradation. In one such system swine waste was collected on a special conveyor belt located below pigs which allowed for separation of manure solids; urine with excess water was moved for different processing. Manure solids were then conveyed to the larval basin containing larvae of mixed age. A 35° ramp along the opposing walls of the basin directed the wandering prepupae to gutters and collection containers. A small portion of the escaping prepupae was used to regenerate adult colony (reared in an insectary) and the rest could be used as feed. Newly-hatched larvae obtained from a laboratory H. illucens colony were used to maintain sufficient number of larvae in the manure basin. Moreover, if an efficient drainage system was employed for diverting urine and excess liquid, the black soldier fly larvae could be reared directly under the pig pens, reducing the need for a conveyor belt system ( Newton et al., 2005).
Newton et al. (2005) also suggest that the black soldier flies may be used in high-rise layer hen houses by adapting an already described system of Sheppard et al. (1994). In addition to slight modifications of the manure basins, a small greenhouse attached to the southern wall of the layer house and separated from the manure pit by a curtain would easily accomodate adult H. illucens population without a need for laboratory rearing. Key factor for this system are favorable climatic conditions.