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Pigs and chicken can eat phosphorus from waste water

Researchers from SDU succeeded in extracting pure phosphorus from waste water. Pure phosphorus is sold as animal feed phosphate for pigs and chicken, but EU-rules are tripping up.

By Birgitte Dalgaard, , 6/3/2019



Researchers from University of Southern Denmark have developed a technology with which they can wring pure phosphorus from waste water. It is of such high quality that it complies with the standards that are required for being used as animal feed phosphates.

- By different chemical processes we can produce a pure form of calcium phosphate in which the amount of heavy metals is below the level that is required for the phosphorus to be accepted for the feed industries.

- In addition, the technology is so efficient that we can recycle 90 percent of the phosphorus, says professor Haiyan Qu from SDU Chemical Engineering.


Phosphorus is a vital mineral but too much phosphorus causes pollution

Haiyan Qu, professor

Phosphorus is a vital mineral, but too much phosphorus is pollutant. Therefore, Denmark’s waste water treatment plant works specifically on filtering and recycling phosphorus in the waste water.

So far, the phosphorus has been of a quality that only allowed for selling it as fertiliser, but the pure phosphorus has a higher selling price and can turn the recycling of phosphorus into a good business.

In the long term, Haiyan Qu thinks, the pure phosphorus from the waste water could also be accepted for the food industry, and she is now applying for a patent on the technology OxyCrysP.


The phosphorus dilemma

Every year, Danish agriculture imports approx. 12.000 – 13.000 tons of animal feed phosphates which primarily are added to pig and chicken feed. At the same time, farmers prepare their ground with phosphorus to give the crops the best possible growth conditions.

But phosphorus is also one of the substantial reasons for oxygen depletion in streams, lakes and fjords, because it causes algae to grow. Simultaneously, phosphorus is a limited resource, and the reserves of the mineral are about to be used up. Since 2014, phosphate has been listed on EU’s list of critical raw materials.

- It is hence in every way important that we recycle phosphorus. Previously, we haven’t had the possibility of reusing phosphorus for animal feed, but with the new technology we can complete the cycle so that we do not need to import animal feed phosphates, Haiyan Qu points out.


EU is tripping up

Not only the waste water plants are interested in the new technology. Arla and the brewing industry are, too, because their production results in large amounts of waste water.

But so far, industry is refraining from investing in upscaling and further developing the technology.

Because although sustainability and recycling feature high on the political agenda, EU regulations entail that phosphorus extracted from waste water may not be used for production of feed products.


Erratic quality from pits

- I hope that EU is willing to look into the regulations in pace with the development of a secure technology that ensures purity of the recycled phosphorus. The mineral can be found in stones in some parts of the world where it is recovered through mining. We must remember that the quality of these phosphorus stones that are used to produce pure phosphorus for the industry is of erratic quality. It also contains a lot of hazardous substances.



  • Project: ReCoverP – Recovery of phosphorus from wastewater treatment systems
  • Founder: Innovationsfonden
  • Partners: Aalborg Universitet, Syddansk Universitet, Krüger A/S, VandCenterSyd, Aarhus Vand, Billund Vand A/S, Herning Vand, Aalborg Forsyning,
  • University of Viena, KU Leuven, Institute of Chemistry of Clermont-Ferrand.
  • Project lead: Per Halkjær Nielsen, Aalborg Universitet
Meet the researcher

Haiyan Qu is professor WSR at SDU Chemical Engineering. For many years, she has investigated how to optimise medicinal products. Now she is applying for a patent for the technology OxyCrysP which can recover pure phosphorus from waste water.


Editing was completed: 03.06.2019