4 minute read
Clay Ripener
Delfzijl, Groningen, the Netherlands
Turning dredged sediment into functional clay. On the edge of the Eems-Dollard Estuary in the Wadden Sea, fields of dredged sediment are serving as a pilot study to explore the viability of converting dredged sediment into clay soil. The project lies in a muddy system of tidal flats at the mouth of the Ems River at the border between the Netherlands and Germany, where excess sediment has negatively affected water quality and biodiversity, accumulating in ports and requiring regular dredging. Since 2018, EcoShape, together with the partners of the Eems-Dollard 2050 Program, have tested a variety of methods of dewatering, desalinating, and oxidizing the sediment to convert it into a useful resource—clay soil for reinforcing dikes and raising farmlands. In 2022, if the ripened clay proves to be suitable, 70,000 cubic meters of the new clay soil will be used in a pilot to strengthen a 1-kilometer stretch of the Broad Green Dike. If this pilot is successful as well, the remaining clay soil will be used to strengthen the entire 11.5-kilometer-long Broad Green Dike. This project is part of the larger system-based program Eems-Dollard 2050, which comprises various pilots in the region to develop the natural and economic status of the Eems area.
Article cover: The sediment depot in April 2018, shortly after adding the clay ripener. (Photo by Christiaan van Velzen, EcoShape)
Producing Efficiencies
Connecting supply and demand is key in this project. Excess turbidity in the Eems-Dollard Estuary causes worsening water quality and high-siltation rates. Therefore, regular maintenance dredging of the Delfzijl Port and dredging to deepen Breebaart, a nature area near the project, supplies dredged sediment for the Clay Ripener. Ripened clay will in turn be used to strengthen and enlarge the nearby Broad Green Dike, which needs to be reinforced to meet the current improved safety standards in response to climate change.
Using Natural Processes
Dutch regulations require that the salty dredged sediment lose salt, water, and organic matter before it can be reused in dikes. To accomplish that, this project relies heavily on natural processes to create the clay: rain and drainage for salt; wind, sun, and infiltration for dewatering; and oxidation for the organic content. Additionally, certain test plots are studying the beneficial effects of planted vegetation on ripening. The team keeps mechanical reworking of the ripening field to a minimum, but it is an available option accelerate the natural processes.
Broadening Benefits
With future plans for dike upgrades, the ripened clay will prove useful in a variety of projects. But besides producing clay for dikes by using locally available dredge sediments, this project also delivers technical and operational knowledge as well as a business case evaluation to highlight the most effective way to produce clay in this context. Furthermore, this beneficial use of dredged sediments improves the ecological status of the estuary, potentially sequesters CO2 in the dike, advances the Dutch aim of being fully circular by 2050, engages the local community, and stimulates the local economy.
Promoting Collaboration
This project unites private partners, a nature organization, and national and local government organizations towards a common goal: producing clay from dredge sediments and delivering the correlated technical knowledge and business case. Each partner has its own objectives and responsibilities, outlined in a binding document that provides motivation to deliver. This pilot study stands as a wonderful example of the nature-based engineering possible through public-private partnerships. Collaboration is the critical ingredients that makes these projects possible and that guarantees results.
