On April 30, 2025, around 25 delegates gathered for a workshop entitled “Lemnaceae: Roots, Nutrient Uptake and the Circular Economy” at Mt Lucas, County Offaly, in the heart of Ireland’s midlands. The location was highly symbolic: once a vast peatland, Mt Lucas is now a flagship site for duckweed (Lemnaceae) cultivation in Ireland.
The story of Mt Lucas begins over a century ago, when the area was covered by a thick layer of peat, reaching depths of over six meters. Peat has long been used as a traditional energy source in Ireland, gaining strategic importance during World War II when fossil fuel imports were disrupted. Industrial-scale peat harvesting was pioneered by the Irish Turf Development Board, later renamed Bord na Móna.
In recent years, growing recognition of the ecological and environmental value of peatlands – especially their role in carbon sequestration – has led to the cessation of industrial peat extraction and launched efforts to restore or rehabilitate these unique ecosystems. A crucial step in peatland restoration is rewetting the land, typically by blocking drainage ditches. These restored wetlands also present opportunities for alternative forms of sustainable land use, such as paludiculture – farming on wet or rewetted peatlands – particularly in areas where peat formation cannot be re-established.
One such innovation is taking place at Mt Lucas: an Integrated Multitrophic Aquaculture (IMTA) farm that combines fish farming with duckweed cultivation (Stejskal et al., 2022). Wastewater from the production of around 30 tonnes of rainbow trout is channeled through a hectare of duckweed-covered channels. While the fish foul the water, the duckweed helps purify it.
Paddlewheel to control water flow from fish tanks to duckweed canals, and back to fish tanks again; canals covered with duckweed and fishponds in the background.
Duckweed canals shortly after construction; freshly harvested Lemna minor.
The system has run successfully for three years and is now being scaled up as a circular bioeconomy demonstrator. Future plans include greater digital monitoring of all inputs, outputs, and environmental variables, a biorefinery focused on duckweed-derived protein, and a new programme aimed at developing a duckweed-based protein value chain. Duckweed lies at the heart of this promising circular economy model.
Exploring Roots, Remediation, and the Circular Economy
The workshop aimed to explore the links between root function, nutrient uptake, environmental remediation, and circular bioeconomy approaches. It brought together duckweed researchers across the spectrum – from fundamental science to applied innovation – in an informal, collaborative setting.
The first session focused on root evolution and function. Alex Ware (Nottingham University, UK) delved into the intriguing question: “What is the function of the roots of Lemna, Landoltia, and Spirodela species?” Dale Godfrey (Nottingham University, UK) explored potential root roles in lithium uptake, while Thimo Groffen (University of Antwerp, Belgium) reported on PFAS accumulation by Lemna minor, revealing intricate interactions between PFAS structure, uptake kinetics, and accumulation.
After the coffee break, the next session centered on duckweed cultivation systems. Neil Coughlan (University College Cork, Ireland) presented developments in stacked duckweed growing systems, while Ivan Loaiza Alamo, from the IMPRESS team, introduced an innovative mist-based cultivation technique for Lemna minor. A follow-up discussion addressed the key knowledge gaps in understanding duckweed roots, nutrient uptake, and remediation potential. Noteworthy topics included uptake of organic molecules, nutrient translocation within the plant, and the underexplored influence of the duckweed microbiome.
Dr Neil Coughlan presents his work on indoor duckweed growing systems.
Nutrient Uptake and Wastewater Remediation
The afternoon session shifted focus to nutrient uptake and water remediation. Cian Redmond (University College Cork) presented a compelling case for nutrient-based remediation of “soiled water” runoff from dairy farms. Alexandra Katsara (also from University College Cork and part of the IMPRESS team) demonstrated how duckweed can effectively treat wastewater from fish processing operations. Leah Bannon (University College Cork) offered insights into the microbial safety of wastewater-grown duckweed, including the interactions between pathogens and the native duckweed microbiome.
Muhammad Irfan (Debrecen University, Hungary) showcased how imaging technology can be used to monitor both duckweed growth and photosynthetic health. Jack Prendeville (Teagasc, Ireland) concluded the session with a presentation on innovative, sustainable protein extraction from duckweed biomass.
The academic programme wrapped up with a round-table discussion on the key knowledge gaps still to be addressed for commercial duckweed applications. Issues raised included the emergence of pests and diseases on large-scale farms, potential risks from pathogens or pollutants adhering to plants, and the complex regulatory landscape around using waste-grown duckweed as animal feed.
Field Visit and Final Reflections
The workshop concluded with a field visit to the Mt Lucas IMTA farm, offering delegates a firsthand look at the site’s scale and the practical challenges of operating a duckweed farm, ranging from managing breeding swans to dredging the 1.6 km of duckweed channels.
Delegates inspecting the rainbow trout in one of the fishponds.
This event showcased the vibrancy and diversity of current duckweed research, spanning toxicology, gene expression, and commercial-scale applications. It also highlighted the strong synergy between fundamental and applied research—a real strength of the duckweed research community and a valuable asset for future innovation.
Funding
This workshop was partially funded by the IMPRESS project, which has received funding from the European Union’s Horizon Europe research and innovation programme under Grant Agreement No. 101084437 – IMPRESS. Additional support came from the Duck-Feed and BioDMJT projects, funded by the Department of Agriculture, Food and the Marine, Government of Ireland (2021R487, project Duck-Feed; 2022PSS125, project BioDMJT).
REFERENCES
Stejskal, V., Paolacci, S., Toner, D. and Jansen, M.A.K., 2022. A novel multitrophic concept for the cultivation of fish and duckweed: A technical note. Journal of Cleaner Production, 366, p.132881.
The article was written by Marcel Jansen, University College Cork, and edited by reframe.food.
All photographs in this article are sourced from the delegates participating in the workshop.
