Fisheries Areas Network

Good Practice Project

Producing fish and seaweed

A local company is piloting the integration a vertical seaweed cultivation system into the recirculated aquaculture system (RAS) industry to reduce the environmental impact of land-based fish production.


As resource scarcity increases, nutrient flows from land to sea are contributing to marine eutrophication, and consequently to a loss of biodiversity. To address both issues, the Djursland FLAG in Denmark has supported a local company, Pure Algae, to introduce the vertical cultivation of Ulva - an opportunistic green macroalgae - to a land-based recirculated aquaculture system (RAS) that produces fin fish. The aim is to change the linear nutrient flows from land to sea into circular nutrient flows to conserve bioavailable nutrients, such as nitrogen and phosphorus, in the production facilities.

This land-based fish production unit allows CO2 emissions and nutrients, produced from aquaculture activities, to be captured and used to grow the macroalgae through Integrated Multitrophic RAS (IMRAS). In this way, the waste water from aquaculture is prevented from escaping into the environment and damaging marine ecosystems; instead it is used to grow seaweed, thereby creating a valuable new revenue stream. This in turn, generates a double crop production.

Seaweed cultivation is still a new field within aquacultural and moving seaweed cultivation from sea to land is a step further in this innovative sector. The selection of this particular seaweed species was based on its explosive growth under favourable conditions, and its potential to generate large quantities of biomass with numerous uses, including human food, pharmaceuticals and animal feed products.


The project has been able to bring scientists and industry together, breaking down some of the barriers and contributing to a circular bioeconomy. Pure Algae is the first company in Denmark to develop a controlled land-based facility which can grow seaweed of the highest quality all year round, in an environmentally and climate friendly manner. Thanks to the FLAG project, Pure Algae was able to establish full scale seaweed cultivation systems to demonstrate the commercial viability of combining seaweed and fish production. The seaweed, that is the result of this process, is of such high quality that it is even attractive to the pharmaceutical industry.


Many FLAG areas are home to land based aquaculture facilities, such as industrial fish farming, which produce waste waters with nitrogen compounds and CO2. The technology developed by this project can be adapted to the needs of different areas and facilities to tackle the problems generally linked to the land-based production of fish. Pure Algae commercializes this technology, offering professional support in designing and developing land-based seaweed cultivation systems adapted to specific needs, organizing workshops and developing small-scale laboratory setups for professional experimentation.

Lessons & contribution to CLLD objectives: 

Lessons: This project has proved that attention to sustainability in production does not necessarily mean overruling the economic outcome. This company, based on the conclusions achieved by Esben Christiansen’s thesis (founder and CEO) on seaweed and its potential in public health and sustainability, uses waste as an input for new production, creating new incomes and guaranteeing the food system’s sustainability.

Contribution to CLLD objective: (a) adding value, creating jobs, attracting young people and promoting innovation at all stages of the supply chain of fishery and aquaculture products;


Total project cost €200 000
FLAG grant €100 000
  • EU contribution (EMFF): €55 000
  • Public contribution (national): €45 000
Beneficiary contribution €100 000
  • 100 000

Project information

Timeframe of implementation From Mar 2019 to Mar 2022
Sea Basins
Type of area


Pure Algae

Contact details

FLAG Contacts

Ms. Helle Breindahl
+45 20 55 33 05
Publication date: 
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