Creating Efficient P Fertilizers out of Secondary Sources

Puraloop: How ICL Turns Sewage‑Sludge Ash Into New Phosphate Fertilizer

In the new Puraloop video, Lucas van der Saag, Senior Process Engineer at ICL Fertilizers, takes viewers through the Amfert production site in the Netherlands. The location has been producing fertilizers for more than 100 years – and today, it is also where ICL closes the phosphate loop by recycling phosphate from sewage‑sludge ash.

Why Sewage‑Sludge Ash Matters

Sewage‑sludge ash is created when municipal wastewater sludge is incinerated. During incineration, the organic matter burns away, but the phosphate and other anorganic substances remain concentrated in the ash. This ash contains significant amounts of recoverable phosphorus and is now used in the Amfert plant as a raw material instead of phosphate rock. The ash is stored in silos on the site and this is where the Puraloop process begins.

How is Recovered Phosphate Made Water‑Soluble

The first technical step, Lucas shows, is the mixing of sewage‑sludge ash with acid. This reaction converts the phosphate in the ash into a water‑soluble form, which is essential for plant uptake.

“We mix the ash, our phosphate source, with acid to make the phosphate water‑soluble.”

This is the same chemical principle used when processing phosphate rock. The only difference is the origin of the raw material.

Granulation Turns the Material Into Fertilizer

Acid-treated material continues to the granulation area which Lucas describes as the heart of the factory. In the granulation drum – a large rotating cylinder, the material rolls and gradually forms granules. The process is similar to making a snowball: as the material rotates, it grows layer by layer into stable, uniform fertilizer granules.

Controlling and Monitoring the Whole Process

The entire production process is monitored from the control room. The control systems track temperatures, reaction conditions, granulation parameters, and throughput

“We use ash instead of phosphate rock, but the rest of the process is the same.”

Laboratory Testing and Certification

Quality and safety of the final product are verified in the Amfert laboratory on the site. There Lucas shows the analytical robot used to test the product’s chemical composition, contaminants, nutrient availability and its compliance with EU fertilizer regulations. In addition to meeting EU standards, Puraloop also complies with PlanetProof, a Dutch certification that sets additional criteria for recycled fertilizers. This ensures the product is safe, consistent, and fully traceable.

The Final Product: Puraloop

At the end of the whole production process there are tons of dry grey granules – this is Puraloop, ICL’s circular phosphate fertilizer.

“With this new, innovative product, we aim to reuse phosphate and help close the phosphate cycle.”

Puraloop demonstrates how waste phosphate can be recovered, processed, and returned to agriculture – reducing reliance on mined phosphate and supporting more sustainable nutrient management in the Netherlands and beyond.