Digestate treatment for waste-to-energy plant to ensure clean water for discharge and green minerals

Project’s context & challenges

The client is one of the Netherlands’ leading manure treatment facilities, processing approximately 135,000 tonnes of manure and co-substrates annually. As part of its ambition to become the country’s first Green Mineral Centre, the company wanted to move beyond renewable energy production and recover valuable nutrients, water and organic matter from digestate.

Reduce manure transport and closing nutrient loops

Digestate contains valuable nutrients but also requires advanced treatment before it can be safely discharged to nearby surface water. The client aimed to maximize the recovery of nitrogen, phosphate, potassium and organic matter while significantly reducing the environmental footprint of manure processing to reduce transport.

Creating value from residual streams

Instead of treating digestate as a waste stream, the client wanted to transform it into marketable products, including green fertilizers, soil improvers and clean water, supporting the transition towards circular agriculture in the Netherlands.

Key figures

Industry:

Manure & co-substrates | Waste to Energy

135.000 t/y

Feedstock processed

Approx. 10-11 million m³/y

Energy produced

Digestate treatment (15 m³/h)

Application

Closing agricultural resource loops

Objective

Customer benefits

Recovering valuable minerals

The integrated treatment process converts digestate into potential nutrient products, including a nitrogen-potassiu fertilizer, phosphate-rich products and organic soil improvers that can be reused within regional agriculture.

Producing clean water

Advanced membrane treatment enables the production of high-quality water suitable for river discharge while reducing freshwater demand and supporting circular water management.

Supporting circular agriculture

By recovering nutrients locally and returning them to farmland, the client contributes to reducing dependency on conventional mineral fertilizers while helping close regional nutrient cycles.

Lower environmental impact

The integrated process reduces nutrient emissions, minimizes transport volume and creates additional value from organic residual streams, supporting long-term sustainable manure management.

Solution

Nijhuis Saur Industries delivered an integrated digestate treatment solution that combines mechanical separation, flotation, membrane filtration and nutrient recovery into one treatment.

Following digestion, the digestate is first separated using a decanter centrifuge. The liquid fraction is then treated through Dissolved Air Flotation (Nijhuis GDF) and a three-stage membrane filtration consisting of MF, HP-RO and polishing RO. Finally, an ion exchange recovers a valuable nitrogen-potassium fertilizer while producing high-quality water suitable for discharge.

The solid fraction is transformed into a phosphate-rich organic soil improver, creating additional value from materials that were previously considered waste.