GREENHOOD: Capturing and recycling nutrients in agricultural areas
In 2025, the European Horizon project GREENHOOD was launched. In this project, Deltares is working with European partners on systems to capture and recycle 50% of the current nutrient losses from agriculture and fish farming. To this end, we are designing and researching three Nature-based Solutions (NbS) in two agricultural drainage areas. We are doing this in collaboration with KWR, local water authorities and farmers. The results provide insight into how NbS can be used to enable farmers and water authorities to capture and recycle nutrients that have been washed out and flushed away more effectively.
Nitrogen and phosphorus are important nutrients for crop growth. They are found in animal manure and artificial fertilisers used on agricultural land, among other things. An abundance of manure on the land and high levels of precipitation can cause nutrients to leach and wash away into surface water. In surface water, this can lead to an excess of nitrogen and phosphorus, resulting in toxic algal blooms, fish mortality and declining biodiversity. Capturing nutrients with nature-based solutionsIn the United States, Denmark and New Zealand, various nature-based solutions (NbS) have been tested for capturing nutrients. These tests have shown the particular potential of wood chip filters, settling ponds and improved buffer strips as solutions. Through retention, denitrification, biological uptake and sedimentation, these systems remove nitrogen and phosphorus from the water. The nutrient-rich sediment from the NbS can be reused on agricultural land. However, these systems have not yet been scientifically tested in the Netherlands. In our research within the GREENHOOD project, we are determining exactly how these systems work and how they can best be used. How do we research nature-based solutions? The implementation of the NbS is measured periodically. We take water, sediment and plant samples and have them tested for nutrient levels at the Delta Lab. We also measure the flow rate. This allows us to determine the inflow and outflow of nutrients and assess the removal capacity per NbS. Sediment and plant analyses also show where the nutrients end up and how much can be recycled. This provides a nutrient balance for all three NbS. Insight into the mechanisms of nutrient removal also helps to optimise the NbS. We translate these mechanisms into a spatial model. This model then provides insight into where a NbS can best be placed and what the optimal dimensions are. Collaboration between knowledge institutes, water authorities and farmersIn addition to sharing knowledge with the European GREENHOOD partners Spain, Norway, Finland and Belgium, Deltares also collaborates on a national scale to gather and share knowledge. For example, KWR is closely involved in the implementation of the research and, together with Wageningen University, is looking at how to translate the results into models. The Aa & Maas and Rijn & IJssel water authorities are providing knowledge and data and sharing their network in two demonstration areas (Vinkenloop in North Brabant and Vragenderbeek in the Achterhoek). This makes it possible to design and apply nature-based solutions with the involvement of farmers in these areas. The data and insights generated are also shared directly with this network. This leads to valuable discussions and additional insights that optimise the research. Optimal nutrient use in combination with productive agricultureUltimately, the research shows how many nutrients are removed by the NbS and which processes and environmental factors this removal depends on. This allows them to be used optimally. Farmers and water authorities thus have additional options for capturing and recycling nutrient losses from agricultural land. This creates a win-win situation for both farmers and the quality of surface water. |
