Duckweed has shown immense promise as a sustainable solution for wastewater treatment and biomass production. Numerous laboratory studies have demonstrated that duckweed can thrive on various types of wastewater, offering a dual benefit: cleaning up waste and turning it into valuable biomass. However, most of this research has been limited to small-scale, controlled experiments. In Europe, large-scale expertise in cultivating duckweed remains limited.
One notable exception is the AquaSus project in Ireland, which provides a rare and valuable example of duckweed cultivation at scale. The primary aim of AquaSus was to develop a duckweed-based water remediation system to support an Integrated Multitrophic Aquaculture (IMTA) fish farm. In this innovative system, fish farming is directly linked to duckweed-based wastewater treatment.
The AquaSus facility includes duckweed channels spanning a total surface area of one hectare. These channels treat the recirculating water from four large fishponds containing 30 tonnes of rainbow trout. Regular water analysis at the inflow and outflow points of the duckweed canals confirmed the system’s effectiveness in removing excess nutrients and improving water quality.
Based on the biomass yield and nutrient content, it was estimated that the duckweed system removes approximately 1.55 tonnes of nitrogen and 0.20 tonnes of phosphorus per year – closely matching the nutrient load produced by the fish. This points to a well-balanced system where nutrient output from aquaculture is effectively offset by duckweed uptake.
But the benefits go beyond water purification. The annual duckweed biomass production at the AquaSus site is around 30 tonnes of dry matter, with a protein content ranging from 30–40% of dry weight. This makes the harvested biomass a valuable ingredient for animal feed, further enhancing the sustainability and circularity of the system.
Crucially, AquaSus has generated important practical know-how, demonstrating that large-scale duckweed cultivation is not only feasible but effective under Irish conditions. Building on this success, the IMPRESS project is now pioneering the next step: scaling up duckweed-based water remediation and biomass valorisation using seafood processing wastewater.
References
Paolacci, S., Stejskal, V., Toner, D., & Jansen, M.A.K. (2022). Wastewater valorisation in an integrated multitrophic aquaculture system; assessing nutrient removal and biomass production by duckweed species. Environmental Pollution, 302, 119059.
Stejskal, V., Paolacci, S., Toner, D., & Jansen, M.A.K. (2022). A novel multitrophic concept for the cultivation of fish and duckweed: A technical note. Journal of Cleaner Production, 366, 132881.
The article was written by University College Cork.
All photographs in this article are sourced from University College Cork.
