Design of a Fish Rest Processing System for Traceable Aquaculture and Pet Feeds

Abstract

At present, millions of tonnes of marine materials are processed into fishmeal and fish oil. These products are used as sources of protein and lipids in aquaculture and pet feed. The production of fishmeal and fish oil, and their subsequent processing into pet and aquaculture feed, requires thermal treatment that degrades DNA quality. As a result, it can be difficult to trace back the original species used as raw material. Several studies have shown that endangered shark species can be found in pet food. In addition, Rotterdam Zoo “Blijdorp” strongly suspects that shark species are present in their aquaculture feed, based on DNA testing. Although research is being conducted into alternative protein sources that do not rely on marine materials, it cannot yet fully be replaced. Fish rests will also remain available as long as fish is consumed. The aim of the study, therefore, is to investigate, and develop, a system to transform fish rest materials into traceable aquaculture and pet feeds.

Designing of this “Fish Rest Processing system” (FRP-system) was split in two steps. The first was at Blijdorp, where fish rest material of known origin could be used to replace dry aquaculture feeds. The aim of the second step was to adapt the FRP-system to one of producing pet feeds out of fish rest material on Bonaire, while ensuring traceability. First, system requirements were established for both Blijdorp and Bonaire to guide the design process. This was done through a combination of literature research and on-site research at Blijdorp. Based on these system requirements and laboratory experiments, a system prototype was built to produce aquaculture feeds. This was further developed into a concept design for producing pet feeds on Bonaire.

At Blijdorp, a manual process was used to bind rest material with agar in order to produce fish feed. This process was translated into a mechanized process in a laboratory setting. Using this FRP-system prototype, several types of conventional aquaculture feed could be replicated. Based on the underlying processes, a concept design was developed for Bonaire that processed 10 kg of residual waste per hour into ready-to-use dog food portions. The core process for both systems consists of inductively cooking agar, followed by automatic cooling of the agar to 50 °C. This temperature was then maintained using hysteresis control. Subsequently, fish residues were mechanically mixed into the agar. The material was then poured into moulds and allowed to solidify in a refrigerator, after which it was processed into the required final size.

This research into traceable feed has identified key requirements that a system for aquaculture and pet food production must meet. The initial technical challenges associated with achieving the desired feed properties were addressed through the development of a laboratory prototype. This resulted in a process that can be further developed for the production of aquaculture feed. In addition, the process could be scaled up, a concept design has been developed to serve as a guideline for this.