30 MARCH 2025 • WORLD AQUACULTURE • WWW.WAS.ORG target across all runs while handling water and oil addition more effectively, which indicates a finer and more uniform pellet porosity. Although the TX system exhibited marginally better durability in some runs, the overall performance of the AFX extruder — especially regarding pellet uniformity and shape — show its potential. The results from the three extrusion platforms are summarized in Table 2 below. A wear cost assessment, which is derived from experience of the different extruders operating for years in industry, is included as well. The AFX extruder has screw elements which in nature have dissimilar geometries. Hence, the improved wear cost relative to TX was part of the AFX design criteria and therefore is as expected. The Future for Sustainable Aquaculture: A New Feed Paradigm The enhanced performance of the AFX extruder is primarily attributed to its screw design. This design not only improves energy transfer dynamics within the extrusion barrel but also facilitates higher oil inclusion as well as more effective moisture utilization. The trial results signify that the AFX extruder offers several advantages over traditional SX and TX systems. This includes the obtained technical quality attributes across a range of different processing conditions. It also points to the fact that product quality was much more consistent across those different runs, which aimed to mimic operator choice and experience, as well as raw material variability. In further, this was achieved using less overall water addition, reducing downstream drying costs. Lastly, the AFX platform’s operational performance is achieved at wear costs comparable to those of a single-screw system, underscoring the potential for long-term resource efficiency. These trial results validate the core hypothesis: optimizing least-cost formulations and enhancing raw material flexibility through extruder design can lead to improved feed quality and reduced operational costs. In doing so, the AFX platform is positioned to promote both cost-efficiency and environmental stewardship. Although the results are promising, this study is limited by its focus on a single salmon feed formulation. Future research should extend these trials to encompass a wider variety of feed types and production conditions to validate and generalize these findings. Additionally, further investigation into the long-term operational performance and energy consumption of the AFX system will provide valuable insights into both sustainability and economic viability. Notes Anders Haubjerg, M.Sc., Ph.D., Sr. Process Engineer, Wenger Manufacturing LLC 15 Commerce Drive, 66534 Sabetha, KS, USA. ahaubjerg@wenger.com References ASAE Standards (1991), S269.4 Cubes, pellets, and crumbles – definitions and methods for determining density, durability and moisture content, ASAE: St. Joseph, Mich. Eriegha, O. J., & Ekokotu, P. A. (2017). Factors affecting feed intake in cultured fish species: A review. Animal Research International, 14(1), 2639-2650. FAO. (2020). The State of World Fisheries and Aquaculture 2020: Sustainability in action. Rome. Tacon, A. G. J., & Metian, M. (2015). Feed matters: Satisfying the feed demand of aquaculture. Reviews in Fisheries Science & Aquaculture, 23(1), 1–10 Thomas, M., & van der Poel, A. F. B. (1996). Physical quality of pelleted animal feed – Criteria for pellet quality. Animal Feed Science and Technology, 61(1-4), 89–112. TABLE 2. Result overview – feed produced on three extrusion platforms. AFX TX SX Pellet CV(D) [%] 2.94 4.84 5.85 Circularity [%] 95.8 95.9 90.3 Durability [%] 82.4 84.3 77.5 Avg. water inclusion [%] 31.9 32.8 33.7 Min-max ρ across runs [g/L] 378-409 380-469 320-431 Wear cost assessment (experience) [$/ton] 1.35 1.95 1.25 FIGURE 8. Net surface area/volume for all runs across the three platforms. AFX runs show a more even distribution around the mean compared to TX and SX runs. The enhanced performance of the AFX extruder is primarily attributed to its screw design. This design not only improves energy transfer dynamics within the extrusion barrel but also facilitates higher oil inclusion as well as more effective moisture utilization.
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