Introduction
Floating closed containment systems (FCCS) are increasingly being implemented in Norwegian Atlantic salmon aquaculture due to regulatory constraints that limit further growth, such as regulations related to salmon lice. Fish farmers are also required to conduct environmental monitoring of the seabed beneath and surrounding aquaculture sites. FCCSs are physically enclosed with designated inlets and outlets allowing for control over emissions to the environment, which often includes sludge collection.
Solutions for sludge collection and processing vary in design and operation, due to differences in fish farmers' objectives and contexts. Sludge collection and processing covers three steps on site; (i) collection of slugde at, often designated, outlets within the production unit, (ii) transport of sludge from production unit to processing unit, (iii) increasing the dry weight percentage of the sludge at the processing unit.
This work covers mapping and categorization of current solutions for sludge collection and on-site processing for FCCSs. First, all FCCSs and relevant sludge processing systems commercially available in Norway are identified and listed in an overview. Then, relevant information on these solutions is collected through document study, interviews and field visits. This covers information on working principles, collection rate, energy consumption, safety for workers, reliability, space/size, capacity, operational limitations (motions, heeling, etc.), and more. Finally, the solutions are assessed and organized into categories emphasizing how they are suited to serve different purposes.
Results and discussion
A total of 26 different FCCS systems have been identified in operation or heing sold to cutstomer and currently under construction. The level of sludge collection and treatment differs significantly both as a result of technological limitations and preferences on operation – that is, how much the fish farmer wants to collect. Some concepts have been in operation for almost ten years, while other concepts have only recently been sold or are updated versions of older concepts.
Work on collecting information and assessing the solutions for sludge collection are currently in process, and results will be ready in time for Aquaculture Europe 2026.
Acknowledgment
This research is part of the ongoing project "Solutions for sludge collection from closed containment systems at sea and their implications for the external environment", financed by the Norwegian Seafood Research Fund (project number 910671).