PLANTNAT aimed to develop a fish farm-based commercial production of wetland and submerged plants for transplantation into mini-wetlands and rainwater basins. Existing plant lagoons on fish farms will optimally generate plants with a value of DKK 200,000/1,000 m2/year. If 50% of the area on a Danish average-type-3 fish farm is exploited, plant production will have a value of DKK 800,000- 950,000.
At the national level, there would be basis for plant production with a value of DKK 31 million. The primary target group for this plant production is agriculture. The plants would be used for rapid establishment of vegetation in mini-wetlands in drained areas where the objective is to increase nutrient retention. Planted mini-wetlands will increase nitrogen retention from the drained land with an average of 531 kg N/ha wetland/year. Scaled up to the recommendations in the Technical Catalogue for the construction of mini-wetlands, this is equivalent to 5,500 tons N removal/year, corresponding to an approximately 25% reduction of the total N discharge, or a reduction of the catch crop area of 458,000 ha.
Similarly, the wetlands should retain between 36,000 and 1 million tons CO2 equivalents/year. On fish farms, plant production would reduce N emissions by 10%. This will allow an average model fish farm to increase trout production by 3.6 tons and on a nationwide basis by 18 tons. The criteria for plant selection were that they should be able to establish quickly, produce biomass, promote nutrient removal, have a long growing season and promote biodiversity.