Climate
Sustainable Treatment of
ABP Processing Wastewater
Case Study 7
Rendac Son, a Netherlands based Darling Ingredients brand

Understanding ABP Wastewater
Wastewater from the processing of animal-by-products (ABP) is produced when water is evaporated from the ABP during processing. This moisture is condensed and sent for treatment along with wastewater from technical applications and cleaning operations. By capturing the high-water content of the ABP (circa 70%), most ABP processing plants are net producers of water. The wastewater typically contains fat, organic matter (proteins) and ammonia.
Preliminary Treatment & Recovery
Fats removed from the wastewater by preliminary treatment are reused for technical applications or as energy sources in biogas plants, helping to recover nutrients from the wastewater.
Further Biological Treatment
The wastewater undergoes further biological and nitrification/denitrification treatment to reduce organic matter and ammonia to acceptable water quality standards, allowing safe return of the cleaned water to the environment.
"This patented microbial ammonium removal technology, developed by Delft University of Technology, removes nitrogen from wastewater and converts it into nitrogen gas and water."
Anammox: An Innovative Leap Forward
In 2013, an innovative wastewater treatment system was introduced at Rendac Son in the Netherlands that integrates anaerobic treatment with anoxic ammonium oxidation (Anammox). This patented microbial ammonium removal technology was developed by Delft University of Technology.
How It Works
The Anammox process removes nitrogen from wastewater and converts it directly into nitrogen gas and water — a clean, safe output that can be safely released into the atmosphere without further processing.
Outstanding Performance
Anammox technology removes up to 95% of nitrogen and is extremely energy efficient, using 60% less energy than classical nitrification/denitrification processes — a transformative improvement in sustainability.
95%
Nitrogen Removal
Anammox removes up to 95% of nitrogen from wastewater
60%
Energy Savings
Less energy used compared to classical nitrification/denitrification
Environmental & Energy Benefits
The Anammox-integrated system at Rendac Son delivers far-reaching sustainability gains — from biogas production and reduced sludge to significant CO₂ savings and lower electricity consumption across the facility.
Biogas to Green Energy
Organic matter is recovered in anaerobic processes, producing biogas that is converted into green electricity or green gas — a direct contribution to renewable energy generation on site.
Sustainable Biofuels from Sludge
Less sludge is created through the Anammox process, and the sludge that is produced is processed into sustainable biofuels, closing the loop on waste and maximising resource recovery.
5,000 Tonnes CO₂ Saved Per Year
The innovative process reduces the CO₂ emissions of the Son plant by around 5,000 tonnes per year, helping to optimise the sustainability and energy management of the facility.
Equivalent to 3,000 Homes
Overall electricity savings — driven by higher efficiency and utilisation of biogas — correspond to the annual consumption of approximately 3,000 homes.
The Nitrogen Cycle & Plant Layout
The following diagrams illustrate both the nitrogen cycle underpinning the Anammox process and the physical layout of the energy-producing wastewater treatment plant at Rendac Son.
The Nitrogen Cycle


3D Plant Schematic – Rendac Son
The schematic illustrates the three-stage treatment system: the Membrane Bioreactor, the Anammox Reactor for nitrogen removal, and the Anaerobic Reactor for biogas production. Wastewater enters from the bottom right, and treated effluent exits at the top. Biogas generated is fed back into the energy supply system.

Next: Case Study 8