Phosphorus is a crucial element for all life forms but also a limited resource. EU has therefore included phosphorus on their critical raw material list and set recycling of phosphorus high on the agenda. Also, people worldwide are trying to find a way to make concrete production more sustainable as this is a high-emission industry.
Thus, a team consisting of EasyMining, Technical University of Denmark (DTU), BIOFOS (the larges wastewater supply in Denmark) and Ramboll is working on the further development of a new type of sustainable concrete through the so-called Ash2Phos process, where phosphorus is recovered from sewage sludge ash and leaves a silicate sand residue that can be used as replacement of 10-30% of cement in concrete.
The physical result of this sustainable innovation process can now be seen and used outside the Ramboll Head Office in Copenhagen. Providing employees and visitors a sustainable rest, the bench with the red color represents a sustainable future with high focus on resource circularity. For comparison, the other bench is made out of traditional concrete.
EasyMining is currently building full-scale plants (in Sweden and Germany) to recover phosphorus from sewage sludge ash through their Ash2Phos technology. These plants will, for example, treat sewage sludge ash from Sweden, Germany and from BIOFOS in Denmark.
In the Ash2Phos process, sewage sludge ash is dissolved in hydrochloric acid and the silicate sand is filtered off the phosphorus-rich leach. Phosphorus, iron and aluminum are separated from the leach solution by precipitation steps in a unique combination. Thereafter, the solution is neutralized and treated to remove heavy metals. The recoverable elements are separated into three products: pure calcium phosphate, ferric chloride and aluminum hydroxide.
These products can be used as raw materials in the existing fertilizer industry and for production of coagulants, which creates a closed loop. The recovered calcium phosphate can be processed into NPK fertilizers, ammonium phosphates, superphosphates, as well as into feed phosphates.