Phosphorus Recycling from Sewage Sludge for Fertilisers of the Future

Jun 04, 2018

(Almost) nothing works without phosphorus: all living creatures need this nutrient and must absorb it from their food. Although phosphorus is a valuable raw material and its supply is limited, large amounts of it are landfilled in sewage sludge ash. The Bundesanstalt für Materialforschung und -prüfung (BAM) is developing thermochemical processes that can recover this nutrient from sewage sludge ash for reuse in fertilisers – very much in the sense of sustainable use.

"Thermally treated sewage sludge is particularly well-suited for recovering phosphorus because sewage sludge ash contains high concentrations of this nutrient and can easily be recycled," explained BAM scientist Dr. Christian Adam. Together with his team, he is developing processes for phosphorus recycling for BAM’s Thermochemical Residues Treatment and Resource Recovery division.

After-treatment of sewage sludge ash at temperatures of just below 1000 degrees Celsius provides several advantages: The resulting fertiliser source material does not contain any organic pollutants e.g. drug residues because they are destroyed at high temperatures. Compared to conventional mineral fertilisers, the exposure to metals such as cadmium or uranium is significantly lower.

Environmentally friendly and suited to the purpose: fertilisers of the future

The phosphorus-containing source material recovered from sewage sludge ash is not water-soluble but can be readily taken up by plants. Both properties are beneficial for use in fertilisers because the nutrient lands where it is needed: in the plant and not in groundwater. "In the future fertilisers should release the nutrients in sync with plant growth," emphasised Christian Adam. "Our thermochemically treated sewage sludge ash can play an important role in the development of this new product generation."

Christian Adam and his team have been cooperating with international partners for many years on the topic fertilisers of the future and their collaboration has led to joint patents with industrial companies.

About BAM

BAM promotes safety in technology and chemistry. As a departmental research institute of the German Federal Ministry for Economic Affairs and Energy, BAM performs research, testing and offers advisory support to protect people, the environment and material goods. Its activity in the fields of materials science, materials engineering and chemistry is focussed on the technical safety of products and processes. BAM’s research is directed towards substances, materials, building elements, components and facilities as well as natural and technical systems important for the national economy and relevant to society. BAM develops and validates analysis procedures and assessment methods, models and necessary standards and provides science-based services for the German industry in a European and international framework.


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