A new chemical-free solution to treating aquaculture waste is under development by a new Scottish initiative led by researchers at the Scottish Association for Marine Science (SAMS).
The project, which sees nutrient-rich waste matter fed to marine worms (polychaetes), which can then by used as an aquaculture feed ingredient, aims to enable seafood producers to introduce circularity to their operations.
While most aquaculture waste is already recycled, for example, as agricultural fertilizer, this new approach would mean by-products are "repurposed within the farmed salmon sector, including as a protein-rich feed ingredient", the research team says.
Supported by funding from the Sustainable Aquaculture Innovation Centre (SAIC), the study involves collaboration from salmon farmer Scottish Sea Farms, whose Barcaldine Hatchery near Oban will be used for the duration of the project.
During the first stage of the trial, water technology supplier Power and Water will supply water treatment equipment using an electrochemical process and ultrasound technology to extract excess water from the waste.
The resultant nutrient-rich material will be fed to the marine worms to boost growth. Meanwhile, the remaining wastewater will be filtered further using natural seaweed to absorb any nitrogen and phosphorous.
The second step of the project will assess the nutritional profile of the marine worms, including protein and fatty acids, to gauge their suitability as an aquaculture feed ingredient.
The research team notes that polychaetes are already used in seafood production in feed for shrimp at the breeding stage, while their role in agricultural animal feed has also been studied.
“Aquaculture waste is not typically considered as valuable as co-products from other sectors, but there are a range of opportunities to be explored that could change that attitude," said Dr Georgina Robinson, lead researcher on the project.
"By taking a circular approach, we can use the co-products to aid the growth of other organisms that will, in turn, benefit the sector as a sustainable feed ingredient."
"This is the first time the water treatment system has been used for freshwater waste and the results of the project could show huge potential for it to be adopted more widely," Robinson said.
The final stage of the research will include assessing the environmental impact and mitigation of greenhouse gas emissions, with the new approach compared to existing methods of waste disposal. Currently, liquid aquaculture waste is transported and spread to land in rural locations after treatment.
“Re-purposing fish waste into valuable by-products is a core part of our day-to-day operations at Barcaldine Hatchery," said Ewen Leslie, head of freshwater engineering and project lead at Scottish Sea Farms.
"This new collaboration has the potential to build on this by diversifying and growing the range of by-products that can be delivered," Leslie said.
SAMS plans to bring the circular concept to the market under a spinout, called N-ovatio-N, early next year. In October, Robinson was awarded the top prize from The Converge Challenge, which recognises novel start-up and spinout ideas with high commercial potential and scalability. N-ovation-N will receive £50,000 in cash and £20,000 in in-kind business support to drive the company forward in its next phase.
Heather Jones, CEO of funder SAIC, highlighted the value of such innovation in supporting sustainability for aquaculture.
“This project is about tackling the sector’s waste at the source and creating a viable, circular model. In addition to the environmental benefits, it will also demonstrate some of the higher-value commercial possibilities for co-products," Jone said.
"By supporting and encouraging collaborative research initiatives like this, we can minimise the environmental footprint of aquaculture while also boosting its economic impact," Jones added.