Sludge from marine fish farming has received increasing attention over the past ten years, due to the nutrient content that the sludge represents, the possibilities for new bio production, as well as the impact on the benthic environment and consideration for vulnerable marine habitats.
Collection of sludge from marine fish farming is now considered as a measure to minimize the potential negative impact on benthic environment. This also applies where vulnerable habitats such as corals have been discovered, and it is uncertain to what extent the industry's activities negatively affect these. Some fish farmers must comply with collection rate requirements for operating marine fish farms.
There is a need for a calculation model for the actual, realistically achievable potential for sludge collection for storage for open marine fish farms. Such a model must cover several aspects:
1. (Emissions) The model must provide an estimate of the amount of sludge generated.
2. (Collected) The model must provide an estimate of the amount of sludge that can be collected in a drain from the cage.
3. (Filtered) The model must provide an estimate of the amount of sludge that can be retrieved and utilized further from on-site treatment.
The project has five sub-objectives to be addressed in four work packages:
- Map the knowledge base and terminology used in the industry and management today around discharge and collection of sludge from open facilities in the sea (WP1).
- Develop a model for estimating the amount of sludge that disappears from cages and the amount that sinks to the collection point (WP2)
- Set up a structure for a complete calculation model for mass flow for sludge from feeding to storage in tanks (WP2).
- Establish a data basis suitable for validating the calculation model for mass flow for sludge from feeding to storage in tanks. This includes obtaining historical data and new sampling, and must cover natural variation for relevant parameters over time (WP3).
- Adjust and validate the calculation model according to established data basis for validation and terminology for future standards for sludge from the sea (WP4).
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