Phosphorcare - from wastewater to valuable fertilizer
At Aaby and Marselisborg Wastewater Treatment Plants we have extracted phosphorus from the wastewater. Over a decade this has been sold as a valuable fertiliser under the name PhosphorCare.
Phosphate is a finite resource with few global suppliers. With the world facing twin crises of excessive energy use and diminishing resources, Aarhus Vand decided as part of a sustainability strategy to extract phosphate.
In 2013 the first demonstration plant was opened
In 2013, Aarhus Vand opened the first full scale demonstration plant in Denmark at Aaby Wastewater Treatment Plant to test the viability of renewable phosphate production in Denmark. The plant could extract 60 percent of the amount of phosphorus in the wastewater.
An added bonus with this production is that the challenges of clogged-up pipes in the sewage works have been considerably minimised. This, in turn, reduces the expenses of maintaining the sewage works.
Later, in 2019 we opened a similar phosphorus-recovery plant at Marselisborg WWTP. It was the biggest phosphorus-recovery plant in the Nordic countries at the time. At the wastewater treatment plant phosphorus from a concentrated side stream was recovered. The plant could utilize up to 30 percent of the phosphorus that enters the treatment plant.
A ready-to-use fertiliser was produced
At both plants, the struvite is precipitated as a ‘ready-to-use fertiliser’ and sold to the market. An official approval of the product as commercial fertiliser has been obtained for the struvite produced at both plants under the name PhosphorCare.
Both plants are the result of a collaboration between a number of private and public partners. The partnership behind the plant at Aaby includes Aarhus Vand, Herning Vand, Grundfos, Norconsult and the Danish Agricultural Advisory Service. The partnership behind the project at Marselisborg includes Aarhus Vand, SUEZ and Stjernholm.
Production closed down after a decade
In 2024 it was decided to close down production of phosphate because it was not a cost-effective case anymore due to rising prices on the chemistry involved in the production and that sales prices were not correspondingly high.
However, it is investigated if phosphorus can be extracted from the sludge in connection with the thermal treatment of sludge at the new wastewater treatment plant, Aarhus ReWater.