SusPhos Extracts Phosphate from Sewage Sludge

Dutch wastewater contains a significant amount of phosphates—a substance indispensable for life on Earth but becoming increasingly scarce. On the other hand, phosphates pollute water and threaten biodiversity in lakes, rivers, and seas. They are found in the fertilizers farmers use on their fields and in our food. Through runoff, fertilizers flow from fields into rivers and seas, and through our waste, phosphates from food enter the sewage system.

In wastewater treatment plants, phosphates settle in sewage sludge, which is then incinerated in facilities in Dordrecht and Moerdijk to generate steam and electricity. The remaining ash, known as incinerator bottom ash (IBA), is used in cement and as fill material—or is deposited in abandoned mines.

Changing the World with Knowledge

To Marissa de Boer, this is a missed opportunity. The ash contains a wealth of phosphates and other useful substances. The challenge lies in extracting them. During her PhD research at the University of Amsterdam, she and her colleagues believed they had found the solution. This led her to start SusPhos. With a few million euros in initial capital, she grew the company to its current size of fifteen employees. In 2020, SusPhos won the Rabo Sustainable Innovation Award in the Circular Economy & Climate category.

“Our dream is to make a positive impact on the world. We need to change things globally, and we can do that with our knowledge. So let’s get started,” says De Boer.

Phosphate for Flame Retardants

Her team developed a patented technology to extract phosphates from sewage sludge for reuse. While the details are a trade secret, De Boer explains, “We use chemicals to extract phosphate from sludge in the form of phosphoric acid or phosphate salts, but we also focus on iron and aluminum products.”

The recycled phosphate will be used to produce fertilizer, but also flame retardants. These substances are found in products like electronics, building materials, curtains, carpets, fabric-upholstered furniture, mattresses, other furnishings, cables, and insulation materials. Flame retardants prevent these items from catching fire easily. Applying extracted phosphates to this use represents high-value recycling, says De Boer, and forms the future of her company.

“There are companies that can extract phosphate from wastewater for fertilizer reuse, but no one else can do it for flame retardants,” she adds.

Reduced CO₂ Emissions

The current SusPhos pilot plant operates next to a Friesland Water Authority wastewater treatment facility, leveraging the site's permits. This test plant produces only a few kilograms of phosphate per run. However, the planned new factory aims to process 50 kilotons annually, meeting a substantial part of the Netherlands' phosphate demand.

This new plant will operate more sustainably than current factories producing fertilizers and flame retardants. De Boer explains, “Our process focuses on recycling and material value, not CO₂ emissions. But as it turns out, we use much less energy than traditional manufacturers. Additionally, our method filters iron, aluminum, and sand from the ash, leaving almost no waste.”

Russia Stops Phosphate Exports

With the halt of phosphate exports from Russia, phosphate recycling has become a hot topic, says De Boer. “We’re now being approached on our website and via LinkedIn by major chemical companies asking if we can supply phosphate, but we’re not there yet,” she explains.

The new plant is still in the design phase. “This is a massive chemical factory we’re planning to build. We’re looking at at least two more years. Construction alone will take a year,” De Boer adds. “But due to the situation with Russia, everything is moving faster. Suddenly, demand for European phosphate has skyrocketed.”

A Dream with a Solid Business Case

De Boer raised a few million euros during her company’s initial phase. For the next funding round, she needs ten times that amount to construct the factory.

“To start a business like this, you need a solid plan. I have a dream, but it’s one with a compelling business case. I started this because I saw a profitable model to turn waste with negative value—like ash—into a product with positive value,” says De Boer.

Next Factory in Germany

Once the Dutch factory is operational, De Boer plans to build the next one in Germany. Starting in 2029, German regulations will require the extraction of all phosphate from sewage sludge. Currently, phosphate-rich sludge in Germany can still be used as fertilizer on fields, a practice banned in the Netherlands for some time.

“We aim to position our factory to capitalize on this new legislation,” says De Boer.

This article originally appeared at Change Inc. as part of a campaign with Groene Chemie, Nieuwe Economie. Written by André Oerlemans. Read the full series on our website or at Change Inc.