Turning wastewater sludge into valuable fertilisers – the process
The process combines biothermal treatment, separation and recovery in several steps:
- Feedstock reception and conditioning
Biosolids from wastewater treatment plants are stabilised to ensure consistent conditions, such as solids content and pH. - Biothermal fermentation (acidogenic conversion)
The material undergoes a controlled fermentation process, where organic matter is partially broken down into volatile fatty acids (VFAs) and nutrients are transferred into the liquid phase. - Solid–liquid separation
The treated material is separated into:- A liquid fraction rich in VFAs and nutrients
- A solid fraction with reduced organic content
- VFA recovery and purification
VFAs are extracted and purified from the liquid stream through processes such as distillation or extraction. - Fertiliser production
The remaining liquid is further processed to produce a liquid nutrient solution. - Water and residual management
Process water is treated and reused where possible, while residual materials are managed through recycling or safe disposal.
The final products
The main product is a nutrient solution, rich in macro- and micronutrients as well as humic substances.
In addition, part of the recovered material can be used as a base for sustainable cleaning products, offering an innovative secondary application.