Sewage Sludge

Phosphorous recycling - Ecological and economic assessment of different methods

In the future, we will be faced with a worldwide supply problem in the provision of raw phosphorous. Exhaustible mineral resources are used in huge quantities, particularly in agriculture. As phosphorous (P) is not substitutable as a plant nutrient, the project partners' report presents the potential for P recycling for manufacture of secondary phosphates. 

Summary

As a plant nutrient, P is an essential component of agricultural fertilisers. It cannot be substituted with other substances, which means that falling worldwide P reserves combined with an increasing demand for agricultural fertilisers is a huge challenge.

High concentrations of P occur mainly in municipal waste water purification. In Germany, P is mainly recovered by precipitation or adsorption from muddy water or manufacture of fertilisers from effluent sludge ash. The economic efficiency of P recycling depends on the price trends for raw phosphates and the recovery technologies used.

The study analyses various options for P recovery. The methods are being assessed in terms of their technical implementation and their ecological impact. The quality and plant availability of the secondary phosphates is also tested using plant trials. Fertilisers were also tested for their pollutant content.

Results:

  • In the plant trials, the secondary phosphates proved to be of equal quality to standard commercial fertilisers.
  • The P recovery prevents the entry of heavy metals into the soil through direct spreading of effluent sludge on farmland.
  • For 2030, scenarios suggest that the raw phosphate price will rise to 97 - 114 US$ per tonne. For phosphoric acid, the price scenario predicts 660 – 760 US$ per tonne by 2030.
  • In Germany, precipitation of P from muddy water and fertiliser manufacture from effluent sludge ash (approx. 2 €/kg P) is not yet competitive with raw phosphate (1.25 €/kg P).
  • According to calculations, the recovery methods could be economical in around 10 - 15 years.
  • Political conditions could create incentives for increased implementation of the available technologies (e.g. subsidies).

More Project Informations

Project title:  Phosphorrecycling – Ökologische und wirtschaftliche Bewertung verschiedener Verfahren und Entwicklung eines strategischen Verwertungskonzepts für Deutschland (PhoBe)

Project number:  02WA0806, 02WA0807

Project region:  Germany (North Rhine-Westphalia)

Project contact:

Herr Prof. Dr. Gäth

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+49 (0) 0641 - 9937381

+49 (0) 0641 - 9937389

Herr Dipl. Ing. Weinfurtner

+49 (0) 2972 302310

+49 (0) 2972 302319

Herr Dr. Dr. Sartorius

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+49 (0) 721 6809-118

+49 80) 721 6809-135

Herr Prof. Dr.-Ing. Pinnekamp

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+49 (0) 241 80 25207

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Source: Federal Ministry of Education and Research (BMBF)