Integrated biological remediation of aquaculture waste (UpCycle ‘N’)

This project explored an alternative approach to aquaculture waste management by developing a two-stage biological remediation system. The system integrated electrochemical thickening of solids with biological uptake of dissolved nutrients by polychaete worms and macroalgae.

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Project team

Partners: Scottish Association for Marine Science (SAMS), University of the Highlands and Islands, Scottish Sea Farms, Power and Water, TradeBe, Scotland’s Rural College (SRUC)

FULL CASE STUDY

BACKGROUND

As with most food production systems, the aquaculture sector produces solid and dissolved wastes that may cause negative environmental impacts if not properly managed. Uneaten feed and by-products can release nitrogen, phosphorus and organic matter into the environment, potentially contributing to oxygen depletion and nutrient pollution. Yet these same waste streams also contain valuable organic material and nutrients that could be recovered and reused, transforming an environmental challenge into a resource.

In Scotland, waste management primarily uses chemical polymers to thicken sludge, which is then transported for agricultural use. There are considerations around this process in terms of cost, complexity, and greenhouse gas (GHG) emissions.

This project, focussing on freshwater aquaculture, explored an alternative approach by developing and testing a two-stage biological remediation system. The system integrated electrochemical thickening of solids with biological uptake of dissolved nutrients by polychaete worms and macroalgae. These processes sought to reduce waste, emissions, and dependence on chemical treatment, while generating valuable biological products and supporting circular economies in Scottish aquaculture.

AIMS

The research team aimed to design and assess an integrated two-stage bioremediation system capable of reducing environmental impacts and creating new value from aquaculture waste. Specific objectives were to:

  1. Develop and test alternative waste concentration technologies that eliminate or minimise the use of polymer flocculants;
  2. Establish polychaete worm cultures capable of converting concentrated aquaculture sludge into high-value protein and lipid biomass suitable for aquafeeds;
  3. Apply macroalgae as a secondary biofilter to remove dissolved nutrients from sludge effluent;
  4. Quantify environmental benefits through lifecycle assessment (LCA), focusing on nutrient reduction, GHG reduction, and mitigation of microplastic pollution.

Additional information

To find out more about this project and ‘N-ovatio-N’ (the spin-out company that followed on from the research), please contact Dr Georgina Robinson at SAMS.